Biomedical subjects

S W Rabkin

Publications and source records attributed to S W Rabkin.

At least 19 recordsLinked to original sources

PubMed2002

Lovastatin does not accentuate but is rather additive to palmitate-induced apoptosis in cardiomyocytes.

Fatty acids such as palmitate have been observed to induce apoptosis in cardiomyocytes but the mechanism of this cytotoxicity is unresolved. The present study sought to determine whether an aspect of fatty acid metabolism is responsible for palmitate-induced apoptosis in cardiomyocytes. As palmitate metabolism increases acetyl CoA production via increased beta oxidation within the mitochondria, we hypothesized that increased acetyl CoA entering the cholesterol biosynthesis pathway might produce intermediates or end products that would be toxic to the cell. To test this hypothesis, cardiomyocytes from embryonic chick cardiomyocytes were treated with the 3-hydroxy-3-methylgutaryl CoA (HMG-CoA) reductase inhibitor lovastatin that inhibits the cholesterol biosynthesis pathway downstream of the acetyl CoA trimerization into HMG-CoA. Lovastatin did not inhibit palmitate-induced apoptosis. Rather, lovastatin induced significant apoptosis itself and when combined with palmitate, the level of apoptosis was equal to the sum of palmitate alone and lovastatin alone. This observation suggests that palmitate and lovastatin are inducing apoptosis by two independent mechanisms. A role for mitochondrial metabolism via carnitine palmitoyl transferase (CPT) in palmitate-induced apoptosis was suggested since capric acid, a fatty acid that is metabolized within the mitochondria but does not utilize CPT-1, did not induce apoptosis. Palmitate-induced apoptosis was further related to the metabolism of saturated fatty acids as the unsaturated fatty acid oleic acid did not induce apoptosis. These data suggest that a unique feature about palmitate metabolism independent of its role in cholesterol biosynthesis is responsible for palmitate-induced apoptosis and the effects of palmitate are additive to those of lovastatin to induce cardiac apoptosis.

Acridine Orange↗

PubMed2001

Prevention of staurosporine-induced cell death in embryonic chick cardiomyocyte is more dependent on caspase-2 than caspase-3 inhibition and is independent of sphingomyelinase activation and ceramide generation.

Apoptosis was induced in embryonic chick cardiomyocytes by staurosporine. Treatment of cardiomyocytes with the preferential caspase-2 inhibitor, z-VDVAD-fmk (100 microM), produced a significant (P < 0.05) although small reduction in the amount of cell death. Ac-DVED-cmk (100 microM), which preferentially inhibits caspase-3 but inhibits to a lesser extent caspase-6, -7, -8, and -10, produced a minimal decrease in cell death. The combination of the caspase-3 and -2 inhibitors produced an additive reduction in cell death after staurosporine (1 microM for 6 h) from 80.4 +/- 0.7 to 54.6 +/- 1.3%. The ability of staurosporine to activate caspase-3 was confirmed in these cardiomyocytes by measurement of caspase-3 activity. A role for ceramide formation, from sphingomyelin to induce caspase activation was unlikely, as there were no changes in cellular ceramide or sphingomyelin after staurosporine treatment of cardiomyocytes when sphingomyelin was labeled by [(3)H]palmitate for 24 h. Neither were there any changes in sphingomyelinase activity. While staurosporine effectively suppressed PKC activity, phorbol 12-myristate 13 acetate did not alter staurosporine-induced cell death or DNA fragmentation. These results demonstrate that, in this model of cardiac cell death, caspase-2 inhibition is of considerable importance, caspase-3 inhibition is of lesser significance but may produce additional effects in the combination with caspase-2 inhibition, and ceramide production from sphingomyelin is not operative in the pathway leading to caspase activation and cell death.

Animals↗

PubMed2000

Palmitate-induced apoptosis in cardiomyocytes is mediated through alterations in mitochondria: prevention by cyclosporin A.

Palmitate, a C16 fatty acid found in high concentrations in the blood in acute myocardial infarction, induces apoptotic cell death. To more completely define the nature and mechanism underlying palmitate-induced cell death, cardiomyocytes were cultured from embryonic chick heart and were treated with palmitate. Concentration-dependent loss of cell viability was established by loss of the ability of palmitate-treated cells to exclude propidium iodide (PI), metabolize 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and retain fluorescein diacetate (FDA). Dual staining with PI and FDA and subsequent analysis by FACS established that palmitate-induced cell death was predominantly necrosis whereas apoptosis occurred in 13% of all dead cells. The low proportion of palmitate-induced apoptosis was confirmed by evaluation of the DNA content or PI fluorescent staining of the DNA of permeabilized cardiomyocytes. A critical role for mitochondria in the pathogenesis of palmitate-induced cell death was demonstrated, for the first time, based on palmitate-induced reduction of mitochondrial activity as assessed by the mitochondrial-selective dye chloromethyl-X-Rosamine and the presence of a greater amount of the mitochondrial marker cytochrome C in the cytosol of palmitate-treated cardiomyocytes than in control cells. Further, cyclosporin that inhibits the development of mitochondrial transition pores blocked palmitate-induced alteration in mitochondrial function and palmitate-induced cell death. We further demonstrated the selectivity of cyclosporin A for the prevention of apoptotic cell death in the heart as there was no alteration in necrotic cell death produced by palmitate with cyclosporin pretreatment. Our data demonstrate the nature of palmitate-induced cell death in cardiomyocytes (both apoptotic and necrotic), propose a mitochondrial basis for its pathogenesis and show that cyclosporin A prevents palmitate-induced apoptotic cardiomyocyte cell death.

Animals↗

PubMed2000

Nifedipine does not induce but rather prevents apoptosis in cardiomyocytes.

The potential of Ca(2+) channel antagonists, particularly nifedipine, to cause apoptotic cell death has been controversial and is of considerable importance for cardiomyocytes as loss of these cells is an important component of the pathophysiology leading to heart failure. To examine the hypothesis that nifedipine induces cell death and modulates calcium-induced apoptosis, cardiomyocytes in culture from embryonic chick hearts, that readily manifest apoptosis, were studied. Apoptosis was evaluated by fluorescent activated cell sorting (FACS) analysis and by quantitative analysis of DNA fragmentation by an enzyme-linked immunosorbent assay (ELISA) specific for histone-associated DNA fragments of mono- and oligonucleosome size. Cell death was evaluated by using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay. Cardiomyocytes were treated with various concentrations of nifedipine over a concentration range relevant to serum concentrations in man. Nifedipine, 1 to 100 microM, did not produce cell death in cardiomyocytes. There was no evidence of apoptosis on FACS analysis of cardiomyocytes stained with fluoresceine diacetate or propidum iodide (PI). Neither was there any evidence of apoptotic nuclei on PI staining of permeabilized cardiomyocytes treated with nifedipine. In contrast, DNA fragmentation consistent with apoptosis was induced in a significant (P<0.05) concentration-dependent manner, by increases in extracellular Ca(2+) concentration ([Ca(2+)](o)). Importantly, nifedipine reduced DNA fragmentation produced by increased [Ca(2+)](o). Furthermore, nifedipine blocked calcium-induced cell death as high [Ca(2+)](o) significantly (P<0. 05) reduced cell viability. These data indicate that nifedipine does not induce apoptosis in cardiomyocytes rather apoptosis in cardiomyocytes is under regulatory control by Ca(2+) and nifedipine can antagonize Ca(2+)-mediated apoptotic cell death.

Animals↗

PubMed2000

Angiotensin II does not induce apoptosis but rather prevents apoptosis in cardiomyocytes.

The ability of angiotensin II (ang II) to produce apoptosis is controversial. Cardiomyocytes, isolated from 7-day embryonic chick hearts and maintained in culture for 72 h, were treated with ang II. There was no evidence of ang II-induced apoptosis consistently demonstrated by six different techniques: electrophoretic separation of fragmented DNA, staining with TUNEL, enzyme-linked immunosorbent assay specific for fragmented DNA, dual staining of cells with fluorescein diacetate and propidium iodide with analysis by flow cytometry, staining of nuclei with propidium iodide and cell microscopy. In contrast, apoptosis was readily induced by camptothecin or staurosporine or serum deprivation. The absence of ang II-induced cell death was also demonstrated in neonatal mouse cardiomyocytes in culture. We further sought to answer the question whether ang II Type 1 receptor blockade by antagonizing the potential beneficial effects mediated through this receptor and producing more ang II binding to the ang II Type 2 receptors, would lead to cardiac apoptosis. There was no evidence of ang II-induced apoptosis in the presence of the ang II Type 1 receptor antagonist losartan in embryonic chick cardiomyocytes. Rather ang II prevented serum deprivation-induced apoptosis. In summary, in these cardiomyocytes ang II does not induce but rather prevents apoptosis.

Angiotensin II↗

PubMed2000

Nitroprusside induces cardiomyocyte death: interaction with hydrogen peroxide.

We examined the hypothesis that sodium nitroprusside (SNP) produces cell death in cardiomyocytes through generation of H(2)O(2). Embryonic chick cardiomyocytes in culture were treated with SNP, and cell viability was assessed by trypan blue, MTT assay, and fluorescent activated cell sorting (FACS) analysis. SNP for 24 h induced a significant (P < 0.001) dose-dependent loss of cell viability. On MTT assay, the half-maximal effective concentration was 0.53 mM (confidence interval 0.45-0.59 mM). SNP-treated cardiomyocytes displayed characteristic microscopic features of apoptosis: reduced cell size, nuclear disintegration, and membrane bleb formation. FACS analysis demonstrated SNP-induced apoptosis as well as cell changes consistent with necrosis. The proportion of cells with nuclear changes of apoptosis, identified by propidium iodide (PI) staining of permeabilized cells, increased significantly (P < 0.05) after 0.5 mM SNP for 24 h. The proportion of apoptotic cells, characterized by dual staining of intact cardiomyocytes with fluorescein diacetate and PI, was significantly (P < 0.05) increased after treatment with 0.5 mM SNP for 24 h. SNP metabolism and NO production was suggested by the significant (P < 0.05) increase in nitrite generation in the media with 0.5 mM SNP compared with control. SNP-mediated H(2)O(2) production was implicated in the mechanism of SNP-induced cell death. First, SNP produced a significant (P < 0.05) increase in H(2)O(2) detected in the media after 6 or 24 h of SNP treatment. Second, catalase completely blocked the reduction of cell viability induced by 0.1 mM SNP and significantly (P < 0.05) blunted the effect of 0.5 mM SNP. In contrast, the iron chelator deferoxamine did not alter SNP-induced loss of cell viability. FACS analysis showed that the combination of low concentrations of H(2)O(2) (10(-8) M) that did not alter cell viability augmented SNP-induced apoptosis. In contrast, the amount of necrotic cell death was unchanged by the combination of H(2)O(2) and SNP. H(2)O(2) plus SNP produced a dramatic alteration in cell structure with greater membrane bleb formation, shrunken cells, and more intense cytosolic acridine orange staining and nuclear fragmentation than either agent alone. These data indicate the vulnerability of cardiomyocytes to SNP and suggest the involvement of H(2)O(2) in the pathogenesis of SNP-induced cardiomyocyte cell death. Establishing apoptosis as a component of the type of cell death induced by SNP permitted the recognition that SNP-induced apoptosis was increased by chronic treatment with low (subtoxic) concentrations of H(2)O(2).

Animals↗

PubMed1999

Factors associated with implementation of preventive care measures in patients with diabetes mellitus.

BACKGROUND: There is only limited information on the extent to which physicians' characteristics affect the level of care and implementation of guidelines in patients with diabetes mellitus. OBJECTIVE: To identify physician characteristics associated with implementation of measures for preventive care in patients with diabetes mellitus and the distribution of implementation of these measures among them. PATIENTS AND METHODS: A retrospective chart audit of 519 patients eligible for health maintenance organization insurance on December 31, 1994, representing patients with diabetes receiving care from 22 primary care physician-providers of a managed care medical group in suburban North Los Angeles, Calif, and seen by physicians between January 1993 and December 1994. A short retroactive questionnaire for participating physicians was also used. The outcome measures were (1) measurement of serum high-density lipoprotein cholesterol; (2) urinalysis for the detection of proteinuria; and (3) ophthalmology referral for dilated fundus examination. RESULTS: Over a period of 2 years 78% of the patients had a high-density lipoprotein cholesterol determination, 80% had a test for proteinuria, and 62% were referred to an ophthalmologist. After adjustment for patient pool differences, physicians who were perceived by the administration of the medical group as "fast," based on a blinded evaluation of their number of patient encounters per unit time, had an odds ratio of 0.60 (95% confidence interval [CI], 0.37-0.95; P=.03) to obtain a high-density lipoprotein cholesterol determination in their patients and an odds ratio of 0.53 (95% CI, 0.32-0.87; P=.01) to test their patients for proteinuria. In patients requiring insulin, of fast physicians, the odds ratio for a referral for ophthalmology screening was 0.25 (95% CI, 0.07-0.85; P= .03). Duration of time in practice of over 15 years and disagreement with practice guidelines were associated with better outcomes. There was no association between physician sex, internal medicine training, or number of patients with diabetes in the practice and the implementation of outcomes. There was a highly significant association between the implementation of an outcome and the implementation of the other 2, resulting in a nonhomogeneous distribution of health care delivery. Physicians' estimate of their rate of implementation of outcomes, as assessed by the questionnaires, overestimated their actual performance while being in proportion with the documented rates. Most physicians took responsibility for the nonimplementation, accepting that it was an oversight on their part as opposed to an encounter with patient resistance. CONCLUSIONS: Most physicians believe that the lack of implementation of the measures for preventive care in patients with diabetes mellitus is an oversight. The oversight is more prevalent in the practices of busy physicians. The result is a nonhomogeneous distribution of health care. Computer reminders might be the solution.

Diabetes Complications↗

PubMed1999

Canadian hypertension society guidelines for ambulatory blood pressure monitoring.

The Canadian Hypertension Society has developed guidelines for the use of ambulatory blood pressure (BP) monitoring in clinical practice. Published articles with the best available levels of evidence were used to support the following recommendations: Physicians should only use ambulatory BP monitoring devices that have been validated independently using established protocols. A decision to withhold drug therapy based upon the ambulatory BP should take into account normal values for 24-h and awake ambulatory BP. Based upon studies on prognosis and a clinical trial based upon BP control as an outcome, ambulatory BP monitoring should be considered for untreated patients whenever an office-induced increase in BP is suspected. Ambulatory BP monitoring should be considered for treated patients suspected of having an office-induced increase in BP, including individuals with apparent resistance to drug therapy, symptoms suggestive of hypotension, and fluctuating office BP readings. Based upon studies on prognosis, changes in nocturnal BP should be taken into account in any decision to withhold drug therapy based upon the ambulatory BP. Further studies are required to determine whether the clinical benefit of antihypertensive therapy is more closely related to ambulatory or office BP.

Blood Pressure↗

PubMed1999

Modulation of palmitate-induced cardiomyocyte cell death by interventions that alter intracellular calcium.

The objective of this study was to investigate whether palmitate-induced cell death in cardiomyocytes was dependent on alterations of intracellular calcium ([Ca2+)I). Specifically, we sought to determine whether palmitate might produce a cellular calcium overload by increasing calcium influx into the cell or by altering sarcoplasmic reticulum (SR) calcium transport. We also determined whether palmitate's effects might be modulated by agents that alter [Ca2+]l. Treatment of chick embryonic cardiomyocytes in culture with palmitate (100 uM) produced a significant (P < 0.05) and 42.9 +/- 5.3% reduction in cell survival or increase in cell death. As determined by FURA-2 measurement of [Ca2+]I, the cytotoxicity of palmitate on cardiomyocytes did not appear to be mediated through acute increases in [Ca2+]l. In contrast, the unsaturated fatty acid, arachidonic acid increased [Ca2+]l. The calcium ionophore ionomycin significantly (P < 0.05) increased palmitate-induced cardiomyocyte cell death. The effects of ionomycin and palmitate, however, were additive, suggesting palmitate and ionomycin acted in an independent manner to induce cell death. Furthermore, in contrast to palmitate, an ionomycin-induced increase in [Ca2+]l was demonstrated in these cells. Inhibition of SR calcium reuptake by thapsigargin, which acutely increases [Ca2+]I, also significantly (P < 0.05) increased palmitate-induced cardiomyocyte death. Again, these two agents most likely acted in an independent manner because of the additive nature of the effect of palmitate and thapsigargin on cell viability. Palmitate-induced cardiotoxicity was not mediated through release of [Ca2+]I from SR or through voltage-operated channels on plasma membranes, as neither SR calcium depletion by low concentrations of ryanodine nor blockade of the voltage-operated calcium channel with nifedipine significantly altered palmitate-induced cardiomyocyte death. These data suggest that palmitate-induced cardiac cell death is enhanced by increases in [Ca2+]I and highlights the potential adverse effect of a combination of palmitate with conditions that increase [Ca2+]I in cardiomyocytes.

Animals↗

PubMed1999

Palmitate induces structural alterations in nuclei of cardiomyocytes.

The objective of this study was to examine the hypothesis that the alterations of cardiac nuclei, that has been noted in some cardiomyopathies, can be produced by palmitate, a saturated fatty acid present in high circulating concentrations in patients with conditions associated with a high probability of developing cardiomyopathy. Cardiomyocytes isolated from embryonic chick ventricle were maintained in culture for 72 h and then treated with palmitate, 100 microM for 24 h. Cells were stained with acridine orange or Giemsa and examined microscopically. Cell size and nuclear size were examined by forward light scatter during flow cytometry. Cells were permeabilized and their nuclei were stained with propidium iodide and examined by flow cytometry on populations of 10,000 cells. Cardiomyocytes treated with palmitate displayed changes in nuclear appearance as nuclei were larger, relative to cell size, with more intense acridine orange staining in a peripheral location. Nucleoli were often disrupted. Palmitate produced a significant (P < 0.001) and 17% increase in nuclear size compared to untreated cells using flow cytometry analysing forward light scatter to estimate nuclear and whole cells size. There were no significant changes in the size of the whole cell and ratio of nucleus to whole cell was significantly (P < 0.01) increased compared to control cells. Fluorescent activating cell sorting analysis of propidium iodide stained nuclei demonstrated that the nuclear enlargement was not due to cell mitosis as the proportion of nuclei in Go/G1, S or M was not changed by palmitate. In summary, these studies identify that palmitate can induce structural abnormalities of cardiomyocytes nuclei by producing increased nuclear size and nucleolar destruction.

Animals↗

PubMed1999

Thapsigargin enhances camptothecin-induced apoptosis in cardiomyocytes.

Topoisomerase I inhibitors are promising new chemotherapeutic agents for the treatment of certain malignancies. The present study investigated the impact of the topoisomerase I inhibitor camptothecin on cell death in cardiomyocytes and sought to determine whether the sesquiterpene gamma-lactone--thapsigargin, that alter sarcoplasmic reticulum calcium flux, modulates the effect of camptothecin on the cardiomyocyte. Camptothecin-induced cell death was demonstrated in cardiomyocytes maintained in culture, from 7 day old embryonic chick hearts, by the trypan blue and the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay, two independent indicators of the loss of cell viability. The type of cell death was attributed to apoptosis based on cell structure, DNA fragmentation and flow cytometry studies. Camptothecin-treated cardiomyocytes were shrunken with membrane blebs and nuclear fragmentation. Camptothecin produced a dose-dependent increase in DNA fragments of 180 base pairs, or multiples thereof, which are characteristic of apoptosis. A two-fold increase in this type of DNA fragmentation was produced by camptothecin (10 microM) compared to control (diluent-treated) cells. Flow cytometry analysis of populations of 10,000 cardiomyocytes stained with propidium iodide demonstrated a significant increase in the proportion of the population with alterations of DNA content consistent with apoptosis. Pretreatment of cells with thapsigargin, which selectively inhibits sarcoplasmic reticulum and endoplasmic reticulum Ca+2-dependent ATPase, significantly augmented camptothecin-induced apoptosis. Exploring further the role of calcium in camptothecin-induced cell death, we found that the Ca+2 chelator EGTA decreased camptothecin-induced DNA fragmentation. These data indicate the potential for cardiotoxicity from camptothecin through the process of apoptosis and suggest that agents which affect cellular calcium regulation enhance camptothecin-induced apoptosis.

Animals↗

PubMed1998

Comparison of angiotensin II type-1 and type-2 receptor antagonists on angiotensin II-induced IP3 generation in cardiomyocytes.

1. Angiotensin II (ang II) produced significant (P<0.01) increases of inositol 1,4,5-mono-, -di- and -triphosphates (IP1, IP2 and IP3) within 1 min of treatment of cardiomyocytes prepared as primary culture from 7-day-old chick embryo hearts. 2. The ang II receptor type 1 (AT1-R) antagonist losartan blocked ang II-stimulated production of IP3; however, the inhibition was not complete even at 10(-5) M. 3. The ang II receptor type 2 (AT2-R) antagonist PD123319 blocked ang II-induced IP3 production but to a lesser extent than losartan. At 10(-5) M, losartan reduced ang II-induced formation of IP3 by 71%, whereas PD123319 reduced IP3 formation by ang II by 40%. 4. Neither losartan nor PD123319, 10(-5) M, affected IP3 formation in cardiomyocytes that were not treated by ang II. 5. The combination of both antagonists, at concentrations that each partly reduced IP3, completely inhibited IP3 formation. Thus AT1 and AT2 receptor blockade may be necessary to completely block the effects of ang II mediated by the IP3 signal transduction pathway.

Angiotensin II↗

PubMed1997

Report of the Canadian Hypertension Society Consensus Conference: 2. Nonpharmacologic management and prevention of hypertensive disorders in pregnancy.

OBJECTIVE: To provide Canadian physicians with comprehensive, evidence-based guidelines for the nonpharmacologic management and prevention of gestational hypertension and pre-existing hypertension during pregnancy. OPTIONS: Lifestyle modifications, dietary or nutrient interventions, plasma volume expansion and use of prostaglandin precursors or inhibitors. OUTCOMES: In gestational hypertension, prevention of complications and death related to either its occurrence (primary or secondary prevention) or its severity (tertiary prevention). In pre-existing hypertension, prevention of superimposed gestational hypertension and intrauterine growth retardation. EVIDENCE: Articles retrieved from the pregnancy and childbirth module of the Cochrane Database of Systematic Reviews; pertinent articles published from 1966 to 1996, retrieved through a MEDLINE search; and review of original randomized trials from 1942 to 1996. If evidence was unavailable, consensus was reached by the members of the consensus panel set up by the Canadian Hypertension Society. VALUES: High priority was given to prevention of adverse maternal and neonatal outcomes in pregnancies with established hypertension and in those at high risk of gestational hypertension through the provision of effective nonpharmacologic management. BENEFITS, HARMS AND COSTS: Reduction in rate of long-term hospital admissions among women with gestational hypertension, with establishment of safe home-care blood pressure monitoring and appropriate rest. Targeting prophylactic interventions in selected high-risk groups may avoid ineffective use in the general population. Cost was not considered. RECOMMENDATION: Nonpharmacologic management should be considered for pregnant women with a systolic blood pressure of 140-150 mm Hg or a diastolic pressure of 90-99 mm Hg, or both, measured in a clinical setting. A short-term hospital stay may be required for diagnosis and for ruling out severe gestational hypertension (preeclampsia). In the latter case, the only effective treatment is delivery. Palliative management, dependent on blood pressure, gestational age and presence of associated maternal and fetal risk factors, includes close supervision, limitation of activities and some bed rest. A normal diet without salt restriction is advised. Promising preventive interventions that may reduce the incidence of gestational hypertension, especially with proteinuria, include calcium supplementation (2 g/d), fish oil supplementation and low-dose acetylsalicylic acid therapy, particularly in women at high risk for early-onset gestational hypertension. Pre-existing hypertension should be managed the same way as before pregnancy. However, additional concerns are the effects on fetal well-being and the worsening of hypertension during the second half of pregnancy. There is, as yet, no treatment that will prevent exacerbation of the condition. VALIDATION: The guidelines share the principles in consensus reports from the US and Australia on the nonpharmacologic management of hypertension in pregnancy.

Female↗

PubMed1997

Report of the Canadian Hypertension Society Consensus Conference: 1. Definitions, evaluation and classification of hypertensive disorders in pregnancy.

OBJECTIVES: To provide Canadian physicians with a standard definition of hypertension in pregnancy, recommendations for laboratory investigations and tests for the assessment and management of hypertensive disorders in pregnancy, and a classification of such disorders. OPTIONS: To improve or not improve Canadian uniformity and standardization in the investigation and classification of hypertensive disorders in pregnancy. OUTCOMES: 1) Accuracy, reliability and practicality of diagnostic clinical criteria for hypertensive disorders in pregnancy. 2) Laboratory tests useful to determine severity and prognosis of disorders as measured by maternal and neonatal adverse outcomes. 3) A classification of disorders for use by Canadian physicians to facilitate uniformity and diffusion of research through a common language. EVIDENCE: Articles on hypertensive disorders in pregnancy published from 1966 to 1996, retrieved through MEDLINE search, related to definitions, tests, diagnostic criteria and classification, as well as documents on diagnosis and classification from authorities in the United States, Europe and Australia and from special interest groups. VALUES: High priority was given to the principle of preventing adverse maternal and neonatal outcomes through the provision of diagnostic criteria for severity and prognosis and through dissemination of reliable and pertinent information and research results using a common language. BENEFITS, HARMS AND COST: Higher degree of vigilance in diagnosing hypertensive disorders in pregnancy, allowing for earlier assessment and intervention, and more efficient dissemination of comparative information through common language. No harm or added cost is perceived at this time. RECOMMENDATIONS: (1) A diastolic blood pressure of 90 mm Hg or more should be the criterion for a diagnosis of hypertension in pregnancy and should trigger investigation and management. Except for very high diastolic readings (110 mm Hg or more), all diastolic readings of 90 mm Hg or more should be confirmed after 4 hours. (2) A regularly calibrated mercury sphygmomanometer, with an appropriate-sized cuff, is the instrument of choice. A rest period of 10 minutes should be allowed before taking the blood pressure. The woman should be sitting upright and the cuff positioned at the level of the heart. (3) Both Korotkoff phase IV and V sounds should be recorded, but the phase IV sound should be used for initiating clinical investigation and management. (4) A urine protein level of more than 0.3 g/d should be the criterion for a diagnosis of proteinuria; 24-hour urine collection should be the standard method for determining proteinuria. (5) Edema and weight gain should not be used as diagnostic criteria. (6) Hypertensive disorders diagnosed during pregnancy should be classified as pre-existing hypertension; gestational hypertension with or without proteinuria; pre-existing hypertension with superimposed gestational hypertension with proteinuria; and unclassifiable antenatally but final classification 42 days after delivery. VALIDATION: Except for expert opinions and reviews solicited for this project, these recommendations need to be field tested and validated in Canada. Guidelines endorsed by the Canadian Hypertension Society and the Society of Obstetricians and Gynaecologists of Canada.

Blood Pressure Determination↗

PubMed1997

Risk factor correlates of body mass index. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To examine the association of obesity, as reflected by body mass index, with other cardiovascular risk factors specifically blood pressure, smoking, physical inactivity, plasma lipid levels and diabetes mellitus. DESIGN: Population-based, cross-sectional surveys. SETTING: Ten Canadian provinces between 1986 and 1992. PARTICIPANTS: A probability sample of 29,855 men and women aged 18 to 74 years was selected from the health insurance registration files of each province and invited to participate. Anthropometry was performed on 19,841 (66%) of these adults. OUTCOME MEASURES: Body mass index (BMI, kg/m2), systolic and diastolic blood pressure, smoking status, level of leisure-time physical activity, self-reported diabetes, levels of plasma total cholesterol, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL) and triglycerides (TRIG). RESULTS: The prevalence of high blood pressure increased with increasing BMI. The gradient of increase was steepest for younger (18-34 years) men and women compared with older (55-74 years) groups. The prevalence of physical inactivity in women tended to increase with increasing BMI except in the lowest BMI category. The J-shaped relationship, although weaker, was also seen in men. The prevalence of self-reported diabetes mellitus was greater with higher BMI categories at all ages and for both sexes except for the youngest group of men. The prevalence of dyslipidemia was related to BMI, as LDL and TRIG levels were higher and HDL levels lower in those with higher BMI. BMI was strongly related to blood pressure, diabetes mellitus and lipid abnormalities. CONCLUSION: These data suggest a central role for obesity in cardiovascular risk and the potential importance of intervention strategies aimed at reducing population obesity in the management of other cardiovascular risk factors.

Adult↗

PubMed1997

The association of cardiovascular disease risk factors with abdominal obesity in Canada. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To assess the degree of association of abdominal obesity with blood pressure and plasma lipid levels and to determine which anthropometric measures of obesity are most closely associated with these cardiovascular risk factors. DESIGN: Population-based, cross-sectional surveys. SETTING: Five Canadian provinces (Alberta, Manitoba, Ontario, Quebec and Saskatchewan) between 1989 and 1992. PARTICIPANTS: A probability sample of 16,007 men and women aged 18 to 74 was selected using health insurance registration files in each province and invited to participate. A complete set of measurements was available for 8974 (56%) adults. OUTCOME MEASURES: Initially, simple correlation analyses by age and sex were performed between the anthropometric variables-body mass index, waist circumference (WC), hip circumference (HC), ratio of waist to hip circumference (WHR)- and cardiovascular disease risk variables-systolic blood pressure (SBP), diastolic blood pressure (DBP), levels of total cholesterol (TC), low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides (TRIG) and the TC/HDL ratio. Canonical correlation analyses were performed to determine the multivariate associations between the anthropometric and risk variables. RESULTS: The simple correlations between anthropometric variables and cardiovascular disease risk variables were highest for SBP; moderate for DBP, HDL, TRIG and TC/HDL; and lowest for LDL and TC. Of the anthropometric variables, WC demonstrated the greatest correlations with the risk variables. The first canonical correlations were significant (p < 0.0001) in men (0.58) and women (0.61) of all ages. Of the anthropometric variables, WC consistently demonstrated the highest loading values in the first canonical variable in men (0.56) and women (0.59). Of the risk variables in both sexes, the loadings of TRIG were generally the largest, those of HDL, SBP, DBP intermediate and those of LDL the smallest. In men, the strength of these associations generally decreased with age, whereas in women they peaked in the 35-54 year age group. CONCLUSION: Considerable association was seen between measures of abdominal obesity and blood pressure and plasma lipid levels. WC is the measure of abdominal obesity most highly correlated with these cardiovascular disease risk factors.

Abdomen↗

PubMed1997

Reduction of angiotensin II-induced activation of mitogen-activated protein kinase in cardiac hypertrophy.

Mitogen-activated protein (MAP) kinases play a role in cell growth and are activated in the heart by cardiac stretch and various growth factors, but their role in signal transduction pathways once the heart has undergone hypertrophy is uncertain. To investigate the regulation of MAP kinases in the heart in response to angiotensin II (ang II), once cardiac hypertrophy has become established, ventricular and skeletal muscle explants were studied from Dahl S salt-sensitive and Dahl R salt-resistant rats that were on a high (6% NaCl) salt supplement in their diet. Cardiac hypertrophy was produced in the Dahl S but not R rat through NaCl-induced hypertension. MAP kinases were assayed by myelin protein phosphotransferase activity in MonoQ fractions of cell extracts. Ang II increased MAP kinases mainly in extracts from nonhypertrophic ventricles of Dahl R rats on a high-salt diet. Immunoblots revealed predominantly p44ERK1 with lower amounts p42MAPK in rat ventricle, and no apparent changes with hypertrophy. In hypertrophied hearts, ang II-induced MAP kinase activity was less markedly increased and more rapidly fell to baseline levels in comparison to the response in nonhypertrophied hearts. Prolonged ang II exposure did not produce the same effect on MAP kinase activity in ventricles from Dahl S rats on a low-salt diet, or skeletal muscle from salt-fed Dahl R and S rats. The ability of phorbol myristate acetate to simulate MAP kinase and ang II to simulate translocation of protein kinase C from the cytosole to the membrane was similarly compromised in hypertrophied ventricles. These results are consistent with a disturbance in the regulation of cell-signalling pathways in cardiac hypertrophy in which the MAP kinase response to ang II is dramatically altered.

Angiotensin II↗

PubMed1997

Angiotensin II-induced inositol phosphate generation is mediated through tyrosine kinase pathways in cardiomyocytes.

The objective of this study was to determine whether the G-protein-linked angiotensin II receptor mediated inositol phosphate production involves a tyrosine phosphorylation (tyr phos) dependent pathway in the heart. Cardiomyocytes, in culture, from 7-day-old chick embryonic hearts were incubated with myo [3H] inositol for 18-24 h. Cells were incubated with LiCl to inhibit inositol 1-phosphate phosphatase and allow accumulation of inositol phosphates with angiotensin II (ang II) treatment. Inositol fractions were separated on column chromatography. Ang II produced significant (p < 0.01) increases of InsP1, InsP2, and InsP3, within 1 min of treatment of cardiomyocytes. Tyrosine kinase inhibition with genistein significantly (p < 0.05) reduced ang II induced inositol phosphate production. This did not occur with the analogue diazdien that is a very weak inhibitor of tyrosine kinase. The ability of ang II to induce tyr phos was demonstrated in whole cell lysates of cardiomyocytes immunoprecipitation with anti-P-Tyr antibodies. Genistein blunted this action of ang II. The rapid activation of a tyr phos dependent pathway by ang II was demonstrated by the similar time course of tyr phos of two different cardiac proteins, 70 and 195 kDa, and peak inositol phosphate production. Tyr phos of these cardiac proteins was mediated predominantly but not exclusively through the AT1 and II receptor subtype as it was completely blocked by the AT1 antagonist losartan, while the AT2 receptor antagonist PD123319 blunted ang II-induced tyr phos. These results demonstrate a novel role for a tyr phos dependent pathway in the heart for ang II-induced inositol phosphate production and strengthens the concept of the interaction of G-protein coupled receptors with tyrosine kinases.

Angiotensin II↗