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Biomedical subjects

L Johnston

Publications and source records attributed to L Johnston.

At least 19 recordsLinked to original sources
PubMed1995

Increased fetal plasma prostaglandin E2 concentrations during fetal placental embolization in pregnant sheep.

OBJECTIVE: The purpose of this study was to examine the effect of chronic fetal placental embolization on fetal plasma prostaglandin E2 concentrations. STUDY DESIGN: Fourteen pregnant sheep were studied (seven embolized and seven controls) for 10 days between 0.84 and 0.91 of gestation. Daily injections of nonradioactive microspheres were made to decrease fetal arterial oxygen content by 30% to 35% of preembolization values. RESULTS: In response to repeated embolization, fetal plasma prostaglandin E2 concentrations increased significantly on day 1, declined to near control levels on days 2 to 6, but were significantly elevated again after day 7. Maternal prostaglandin E2 levels remained unchanged throughout the study. Fetal plasma prostaglandin E2 levels increased significantly with decreasing fetal oxygenation when fetal arterial oxygen content was < 2.0 mmol/L. CONCLUSION: We conclude that there is increased production of prostaglandin E2 by the placenta during progressive fetal hypoxemia induced by fetal placental embolization. We speculate that the progressive increase in prostaglandin E2 may be an important hormonal adaptive mechanism to maintain fetal homeostasis during the development of placental insufficiency.

Animals↗
PubMed1995

Alterations in fetal and placental deoxyribonucleic acid synthesis rates after chronic fetal placental embolization.

OBJECTIVE: Fetal growth and development are closely related to normal placental growth and function. We performed a study to determine the effect of a 10-day period of fetal hypoxemia induced by umbilical-placental hypoperfusion on tissue deoxyribonucleic acid synthesis rates in the 0.84 to 0.91 of gestation ovine fetus and placenta. STUDY DESIGN: Daily fetal placental embolization was performed in four chronically catheterized sheep fetuses until fetal arterial oxygen content decreased by approximately 30% compared with preembolization values. Five control fetuses received vehicle only. On experimental day 10, the deoxyribonucleic acid synthesis rate was determined by injecting tritiated thymidine (1 mCi/kg) intravenously approximately 8 hours before the end of the study. RESULTS: Fetal arterial oxygen decreased from 3.2 +/- 0.1 (SEM) mmol/L preembolization to 2.2 +/- 0.2 mmol/L on day 10 (p < 0.001) and remained unchanged in controls. On day 10 deoxyribonucleic acid synthesis rates were significantly reduced in embolized fetuses compared with controls, by 38% in cotyledons (83.0 +/- 15.1 vs 133.7 +/- 9.9 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05), 28% in the left ventricular wall (36.8 +/- 3.7 vs 51.0 +/- 4.7 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05), and 45% in the quadriceps muscle (15.4 +/- 4.0 vs 28.1 +/- 3.0 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05). Tritiated thymidine autoradiography demonstrated that cotyledonary deoxyribonucleic acid synthesis occurred exclusively in the fetal trophoblasts cells. CONCLUSION: We concluded that a reduction in cotyledonary, quadriceps muscle, and left ventricular myocardium deoxyribonucleic acid synthesis rates are the earliest adaptive mechanisms of fetal growth associated with development of umbilical-placental insufficiency. We speculate that alteration in the myocardial deoxyribonucleic acid synthesis rate could be a major contributing factor in the deterioration of fetal myocardial function associated with increased placental vascular resistance.

Analysis of Variance↗
PubMed1994

Quality of life of people with psychiatric disabilities 1 and 3 years after discharge from hospital.

We interviewed 43 clients 1 and 3 years following discharge from a psychiatric rehabilitation programme. The Clients' Quality of Life Interview and Uniform Client Data Instrument examined several domains of clients' life situations. Quality of life measures of living situation, social and community living skills, and recreation improved from 1988 to 1990, and other measures were stable. Findings suggest that clients' living circumstances and functioning continue to improve in the 3 years following discharge from psychiatric hospital.

Adult↗
PubMed1994

Fetal endocrine responses to chronic placental embolization in the late-gestation ovine fetus.

OBJECTIVE: The purpose of this study was to examine the effect of chronic fetal placental embolization on the fetal corticotropin, cortisol, and catecholamines concentrations and on myometrial contractility pattern. STUDY DESIGN: Fourteen fetal sheep were studied (seven embolized, seven controls) for 10 days between 0.84 and 0.91 of gestation. Daily injections of nonradioactive microspheres were performed to decrease fetal arterial oxygen content by 30% to 35% of the preembolization value. Umbilical artery Doppler flow velocity waveforms were measured daily. RESULTS: Chronic fetal placental embolization produced progressive fetal hypoxemia (p < 0.001) with changes in umbilical artery Doppler flow velocity waveforms indicative of a 25% increase in placental vascular resistance (p < 0.01). In response to chronic fetal hypoxemia there was a progressive increase in baseline fetal plasma norepinephrine concentration (p < 0.001). There was a transient fourfold to fivefold increase in baseline fetal plasma cortisol levels concomitant with a significant decrease in baseline immunoreactive corticotropin between days 7 and 9 of embolization (both p < 0.05), with a return to control values by day 10. There was a 57% increase in myometrial contracture frequency in the embolized group when compared with controls (p = 0.001). CONCLUSIONS: During repetitive chronic placental damage that led to fetal hypoxemia, the fetal endocrine environment changed with time in a direction that would prevent the onset of premature activation of the hypothalamic-pituitary-adrenal axis and premature delivery.

Adrenocorticotropic Hormone↗
PubMed1994

Low cholesterol and impaired cardiac function following heart transplantation.

1. During follow-up of 59 cardiac transplant recipients over 2 or more years, a small group of subjects was observed who displayed an unpredictable, relatively marked, reduction in plasma cholesterol. 2. A significant proportion of these subjects were subsequently observed as having experienced a marked decline in left ventricular function at the time of routine radionuclide ventriculography. 3. While the mechanism for this fall in cholesterol is unclear, the observation of such an unexpected reduction in total cholesterol, late after heart transplantation should be considered significant and prompt further investigation including an assessment of allograft function.

Cholesterol↗
PubMed1993

Prevalence of self-induced vomiting and laxative/medication abuse among female adolescents: a longitudinal study.

In order to assess the prevalence and stability of weight reduction techniques utilized by adolescent females, three comprehensive samples of middle school and high school students (ages 12-18) were surveyed in the springs of 1984, 1989, and 1992. All participants were enrolled in the same school district to ensure that the groups were demographically equivalent. The results demonstrated a significant decrease in the use of appetite suppressants among high school students. However, middle school females reported a significant increase in medication use and self-induced vomiting during the same 7-year period. Laxative abuse has persisted unchanged for a small segment of both populations.

Adolescent↗
PubMed1993

Persistence of sham feeding after intragastric meals in rats.

In rats on a stringent deprivation schedule and at reduced body weight, an intragastric load of liquid diet that equals or exceeds normal meal size has no effect at all on subsequent sham feeding of milk diet or of glucose. Removing the acute deprivation period and reversing, or preventing, severe weight reduction has no effect on this "persistence" of sham feeding: a full intragastric meal may leave sham feeding quite unaffected, even if that meal follows the previous meal at a physiological interval, in rats at normal weight. These data contrast with graded, dose-dependent effects of other manipulations by other investigators. Perhaps such effects depend on conditioned or anticipatory controls of feeding, whereas our findings apply to unconditioned controls.

Animals↗
PubMed1992

Susceptibility testing of bacteria recovered from patients with peritonitis complicating continuous ambulatory peritoneal dialysis.

Antagonism of antibiotic activity by peritoneal dialysate has been postulated to be a cause of failure of treatment of peritonitis complicating continuous ambulatory peritoneal dialysis. We evaluated by a case-control study whether unexpected treatment failure could be attributed to such antagonism. Bacteria isolated from 34 patient episodes of peritonitis treated with the same regimen of ciprofloxacin monotherapy were studied. Ciprofloxacin was significantly less active in dialysate than in Iso-Sensitest broth (IB). The median MIC in IB was 0.5 microgram/ml, increasing to 2.0 micrograms/ml for both fresh dialysate (FD) (P = 0.003) and pooled dialysis effluent (PDE) (P = 0.03); the median MBC in IB was 8.0 micrograms/ml, increasing to 128.0 micrograms/ml in FD (P = 0.0002) and 64.0 micrograms/ml in PDE (P = 0.02). However, no significant differences were found in the results for patients suffering unexpected treatment failure (relapse of peritonitis) compared with the results for patients whose infection resolved without sequel. In IB the median MICs for relapsers and nonrelapsers were 1.0 and 0.5 microgram/ml, respectively (P = 0.88); median MBCs were 32.0 and 4.0 micrograms/ml (P = 0.19). In FD median MICs for relapsers and nonrelapsers were 2.0 and 1.0 micrograms/ml (P = 0.06); median MBCs were 128.0 micrograms/ml for both groups (P = 0.84). In PDE the median MICs were 2.0 micrograms/ml for both groups (P = 0.78); median MBCs were 256.0 and 64.0 micrograms/ml (P = 0.17). We therefore found no evidence to suggest that antagonism of antibiotic activity by dialysate is a cause of treatment failure or that conventional methods for laboratory susceptibility testing in peritonitis complicating continuous ambulatory peritoneal dialysis should be abandoned in favor of testing in media containing dialysate.

Ciprofloxacin↗
PubMed1992

Compliance with a nonrecapping needle policy.

Compliance with nonrecapping needle policies is poor. Accidental needlestick injuries account for up to 80% of reported occupational needle exposures, and 45% of needlestick injuries occur at recapping. To determine the degree of compliance with in-house nonrecapping and needle disposal policies, the authors undertook an unannounced survey of needles disposed in designated sharps disposal containers and, via a questionnaire, surveyed attitudes to policies. The results show between 46 and 77% of needles were being recapped with 9 to 20% of bloodstained needles recapped before disposal. Recapping devices were rarely used and two-handed recapping techniques predominated. Highest rates of recapping were seen in intensive care, intermediate care and medical care units. Common reasons for recapping include inability to dispose immediately of needles properly, and sharps containers being too far away. Awareness of the risks of recapping was widespread with over 90% of respondents having been instructed in proper needle disposal techniques. While few health care professionals disagreed with non-recapping and needle disposal policies, many--for various reasons--persist in hazardous needle disposal practices.

Health Knowledge, Attitudes, Practice↗
PubMed1990

Identification of a seventh operon on plasmid RK2 regulated by the korA gene product.

Broad-host-range IncP plasmids possess a series of operons involved in plasmid maintenance, whose expression is coordinated by a series of regulators, most of which are encoded in a central regulatory operon. The nucleotide sequence of a new monocistronic operon located between coordinates 55.0 and 56.0 kb on the genome of the IncP alpha plasmids RK2 and RP4 is presented. The operon encodes a 34 kDa protein which has a net negative charge. Transcription of the operon, designated by us kfrA (korF-regulated), is repressed not only by the product of the previously described korA gene but also by the product of a gene which we have designated korF and which has not been described previously. The korF gene is encoded downstream from korB within the key korA/korB regulatory operon. We propose that K or F binds to a novel inverted repeat overlapping the promoter for the kfrA operon.

Amino Acid Sequence↗
PubMed1989

Remember when...? Using mnemonics to boost memory in the elderly.

Memory loss associated with normal aging is frequently confused with dementia. Self-perceived memory loss can lead to social withdrawal, which can contribute to an ongoing pattern of memory impairment. Memory instruction utilizing mnemonic techniques can lead to improvement in both memory and self-esteem in the elderly. A simple, four-session mnemonics instruction program can provide an effective intervention to assist older persons in coping with memory problems.

Aged↗
PubMed1987

Ciprofloxacin for eradication of methicillin-resistant Staphylococcus aureus colonization.

Ciprofloxacin (750 mg orally twice a day) was used to treat 22 episodes of methicillin-resistant Staphylococcus aureus (MRSA) colonization among 20 patients. Most patients had serious, progressive underlying medical diseases and had multiple sites of colonization. Eleven had previously received parenteral vancomycin therapy. Duration of ciprofloxacin therapy was from seven to 28 days. Therapy was discontinued in eight patients because of minor adverse reactions (two patients) or serious events attributed to underlying diseases (six patients). These serious events included seizures in two patients with known seizure disorders. Of the remaining 14 courses of therapy, 11 (79 percent) were associated with eradication of MRSA colonization. For the 18 patients who received at least two weeks of therapy, results of cultures from 47 of the 56 colonized sites became negative. Recolonization with MRSA occurred in four patients within one month. Increased resistance to ciprofloxacin was observed in seven of the 22 treatment episodes; this was associated with treatment failure in three patients and successful therapy in one patient; therapy was discontinued for other reasons in three patients. For comparison, medical records of 31 patients whose clinical specimens revealed MRSA but who did not receive ciprofloxacin were reviewed. MRSA colonization (as opposed to infection) was not eradicated in any patient who received only a single drug or no specific therapy directed against MRSA; four of seven patients given combination therapy had colonization eradicated. Although there is the potential for increased resistance, ciprofloxacin is an important new option that can be used as a single agent for eradication of MRSA colonization. Additional study is needed to define the optimum use of ciprofloxacin as a single agent and in combination therapy for MRSA colonization and infection.

Adult↗
PubMed1987

Impact of prolonged incubation on disk diffusion susceptibility test results for Staphylococcus aureus.

Because strains of Staphylococcus aureus that are resistant to penicillinase-resistant penicillins may be difficult to detect in the clinical laboratory, a variety of changes in methodology have been suggested to increase their detection. In 1984, the West Los Angeles Veterans Administration Medical Center experienced an increase in clinically significant strains of oxacillin-resistant S. aureus. To insure that such strains would not be missed by the disk diffusion test methods employed for routine testing, changes in methodology were insituted. These included interpreting zone diameters around oxacillin disks at 48 h of incubation. We collected 139 isolates from patients thought to have oxacillin-resistant S. aureus based on these test results and later retested the isolates using microdilution MIC testing. Only 85 isolates (61%) had microdilution oxacillin MICs of greater than or equal to 8.0 micrograms/ml, whereas 54 (39%) had oxacillin MICs of less than or equal to 2.0 micrograms/ml. A review of medical records revealed that in 1 year there were 98 patients with isolates appearing resistant by disk diffusion but not confirmed by microdilution MICs; many patients were placed in isolation and treated with specific antimicrobial agents. We conclude that incubation of oxacillin disk diffusion tests for longer than 24 h in conjunction with disregard for resistance to other classes of antimicrobial agents may result in an unacceptably high degree of false resistance results. Because the resistance of S. aureus has important therapeutic and infection control implications, it is necessary to recognize problems that may result in ambiguous or inaccurate susceptibility results.

Humans↗
PubMed1986

Decreased production of interferon-gamma by human neonatal cells. Intrinsic and regulatory deficiencies.

Human neonatal lymphocytes produced little macrophage activation factor in response to mitogens. This correlated with decreased production of interferon-gamma (IFN gamma): adult lymphokines contained 894.2 +/- 177.1 U/ml, whereas neonatal cord and peripheral lymphokines contained 66.9 +/- 17.0 and 116.7 +/- 29.6 U/ml by bioassay. Results by radioimmunoassay (RIA) for IFN gamma were similar. In contrast, the interleukin 2 content of cord lymphokines was greater (P less than 0.01) and that of neonatal peripheral blood lymphokines similar to that of adults. Interleukin 1 production and interleukin 2 receptor expression and affinity were similar for adult and neonatal cells. Interleukins 1 and 2 in amounts comparable to those in adult lymphokines did not increase production of macrophage activation factor or IFN gamma by neonatal cells. Neonatal cells did not contain intracellular IFN or degrade exogenous IFN. Excess suppressor activity was not found in neonatal cultures. Addition of IFN alpha, 10,000-50,000 U/ml of interleukin 2 or phorbol myristate acetate (PMA) to cord mononuclear cells or of adult monocytes or PMA to cord T cells increased IFN gamma production compared to cells stimulated with concanavalin A (ConA) alone. Nevertheless, under optimal conditions (T cells + PMA + Con A), adult cells produced much more IFN gamma (1,360 +/- 261 U/ml by RIA) than cord cells (122 +/- 37 U/ml). Staphylococcal enterotoxin A (SEA) stimulated cord cell IFN gamma production at low cell densities; nevertheless, adult cells produced more IFN in response to SEA 1,341 +/- 350 U/ml) than cord cells (350 +/- 33 U/ml). Decreased production of IFN gamma by neonatal cells appears to be due both to differences in their intrinsic capacity to produce IFN gamma and to differences in regulatory mechanisms.

Concanavalin A↗
PubMed1985

Effect of intracoronary nitroglycerin on myocardial blood flow and distribution in pacing-induced angina pectoris. Quantitative assessment by single-photon emission tomography.

Changes in regional coronary flow after administration of intracoronary nitroglycerin were assessed by measuring total coronary blood flow (using coronary sinus flow catheters) and its regional distribution (by quantitative single-photon emission tomography of injected radioactive microspheres). After pacing to angina, 10 patients with coronary artery disease received serial selective left coronary injections of technetium-99m microspheres, 40 micrograms of nitroglycerin, and indium-111 microspheres. Significant changes in coronary flow distribution were determined by subtracting prenitroglycerin from postnitroglycerin tomographic profiles. Perfusion of each myocardial segment was classified as normal mildly, moderately or severely compromised, based on upstream coronary anatomy. The overall increase in coronary flow was 23% in the normal territories and 33%, 44% and 15% (p less than 0.05), in the mildly, moderately and severely compromised territories, respectively, compared with control values. Thus, intracoronary nitroglycerin increased coronary blood flow to all perfusion territories. The increase in distribution of coronary flow was greatest in the mildly and moderately compromised regions and the least in the most severely compromised regions; this is probably a reflection of the underlying coronary reserve.

Adult↗
PubMed1985

Length of stay on a short-term unit.

In this retrospective study of length of stay (LOS) and outcome on a general hospital unit, utilizing analysis of variance techniques, the authors found institutional, psychiatric, and economic factors significantly related to LOS. Patients with diagnosis of major mental illness and lower scores on The Global Assessment Scale tended to stay longer and improve more. The involvement of a private (versus staff or clinic) psychiatrist and a history of previous hospitalization were also significant, when controlled for other variables. These findings are discussed in relation to previous research showing the advantages of a brief LOS.

Adult↗
PubMed1983

Effects of gender on inpatient psychiatric hospitalization.

In this study of inpatient hospitalization, gender was found to be a significant variable. Effects of gender upon admission and discharge Global Assessment Scale scores raises the possibility of differential criteria for men and women to be admitted or discharged: a "gender bias effect." Results also support the hypothesis of a "patient gender effect" of greater responsiveness to treatment by women. As predicted, gender showed complex interactions with other variables, including diagnosis, age, marital status, and prior hospital experience. Length of stay was not found to be related to gender.

Adult↗