Biomedical subjects

E W Seely

Publications and source records attributed to E W Seely.

49 records · Page 3Linked to original sources

PubMed1992

Hypervitaminosis D associated with drinking milk.

BACKGROUND: Vitamin D has been added to milk in the United States since the 1930s to prevent rickets. We report the unusual occurrence of eight cases of vitamin D intoxication that appear to have been caused by excessive vitamin D fortification of dairy milk. METHODS: Medical records were reviewed and a dietary questionnaire was sent to eight patients who had unexplained hypervitaminosis D. Vitamin D analyses with high-performance liquid chromatography were performed on samples of the patients' serum, the dairy milk they drank, and the vitamin D concentrate added to the milk. RESULTS: All eight patients drank milk produced by a local dairy in amounts ranging from 1/2 to 3 cups (118 to 710 ml) daily. All had elevated serum 25-hydroxyvitamin D concentrations (mean [+/- SD], 731 +/- 434 nmol per liter [293 +/- 174 ng per milliliter]). Six of the eight patients had elevated serum vitamin D3 concentrations. Of the eight patients, seven had hypercalcemia and one had hypercalciuria but normocalcemia (mean serum calcium, 3.14 +/- 0.51 mmol per liter [12.6 +/- 2.1 mg per deciliter]). Analysis of the dairy's vitamin D-fortified milk revealed concentrations of vitamin D3 (cholecalciferol) that ranged from undetectable to as high as 232,565 IU per quart (245,840 IU per liter). An analysis of the concentrate that was used to fortify the milk, labeled as containing vitamin D2 (ergocalciferol), revealed that it contained vitamin D3. CONCLUSIONS: Hypervitaminosis D may result from drinking milk that is incorrectly and excessively fortified with vitamin D. Milk that is fortified with vitamin D must be carefully monitored.

Adult↗

PubMed1992

Increased platelet angiotensin II receptor number in pregnancy-induced hypertension.

Women with pregnancy-induced hypertension (PIH) are characterized by relatively greater blood pressure sensitivity to exogenous angiotensin II (Ang II) than normotensive pregnant women. Evidence suggests that this is due to an alteration in Ang II receptor sites. However, the question of whether this represents an increase in receptor number or affinity remains unanswered. To answer this question Ang II receptors on platelets from normotensive women during each trimester of pregnancy and the postpartum period were studied and compared with platelet Ang II binding in third trimester women with PIH and in postpartum women who had had a recent pregnancy complicated by PIH. We also measured plasma renin activity, Ang II, and aldosterone in blood samples from these women and sodium and creatinine in 24-hour urine collections. Normotensive pregnant women had significantly less platelet Ang II binding than nonpregnant, postpartum women (0.85 +/- 0.19 versus 2.87 +/- 0.83%, p = 0.003), reflecting a reduction in receptor number but not affinity. This probably reflects the significant increase in Ang II during pregnancy. Urinary sodium excretion was equivalent and could not explain these changes. Comparisons of third trimester women with PIH against those without PIH documented a significantly higher Ang II binding in the women with PIH (2.23 +/- 0.42 versus 0.85 +/- 0.19%) that was caused by an increase in receptor number (6.0 +/- 1.3 versus 3.0 +/- 0.8 fmol Ang II per 5.6 x 10(8) platelets, p = 0.047) but similar Ang II binding affinity. This reflected significantly lower Ang II levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Markers of sodium and volume homeostasis in pregnancy-induced hypertension.

Normal pregnancy is associated with increased levels of digitalis-like factor (DLF) and erythrocyte sodium-lithium countertransport (RBC CTT), which return to normal levels postpartum. Patients with pregnancy-induced hypertension (PIH) have greater increases in both factors than women with normotensive pregnancies. This study was designed to determine if both abnormalities are observed concomitantly in PIH, if they correlate with blood pressure, if they correlate negatively with a hormonal index of volume status (PRA), and if they differ in women with and without proteinuria. Twenty-six normotensive women and 26 women with PIH were studied in the third trimester. Thirteen of these patients were also studied 6 months postpartum. Women with PIH, compared to those who were normotensive, had higher RBC CTT (0.49 +/- 0.04 vs. 0.36 +/- 0.03 mmol Li/L cells.h; P = 0.004) and DLF (0.30 +/- 0.3 vs. 0.20 +/- 0.03 microgram digoxin equiv./L; P = 0.01) and lower PRA [4.58 +/- 0.76 vs. 7.34 +/- 0.86 ng/mL.h (1.27 +/- 0.21 vs. 2.04 +/- 0.24 ng/L.s); P = 0.001]. All three parameters correlated significantly with diastolic blood pressures (RBC CTT and DLF positively (P less than or equal to 0.02) and PRA negatively (P = 0.03). Comparisons of DLF, RBC CTT, and PRA demonstrated a significant correlation of RBC CTT and DLF for normotensive pregnant women only (r = 0.38; P = 0.05). Patients with PIH were further analyzed according to whether proteinuria (24-h urinary protein, greater than 0.30 g; urine dipstick, greater than or equal to 2+) was present or absent. There was no significant difference in diastolic blood pressure or PRA between the hypertensive subpopulations, although there was a tendency for those without proteinuria to have lower PRAs [3.85 +/- 0.80 ng/mL.h (1.07 +/- 0.02 ng/L.s)] than those with proteinuria [5.31 +/- 1.30 ng/mL.h (1.48 +/- 0.36 ng/L.s)]. RBC CTT was significantly higher (P less than 0.05) in women with PIH without proteinuria, whereas serum DLF was significantly higher in women with PIH with proteinuria (P less than 0.05). In 13 women studied 6 months postpartum, there was a significant reduction in serum DLF, RBC CTT, and PRA for all women and in blood pressure for women who had had PIH (P less than 0.01). Thus, women with PIH, compared to normotensive pregnant women, had abnormalities in a variety of factors known to be volume sensitive or indicative of salt- and volume-sensitive forms of hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1992

Lower serum ionized calcium and abnormal calciotropic hormone levels in preeclampsia.

Relative hypocalciuria has been reported in women with preeclampsia. However, there has been no systematic explanation for this finding. We measured serum and urinary calcium and serum calciotropic hormones in third trimester women with preeclampsia (n = 12, gestational hypertension and proteinuria) and with normotensive pregnancies (n = 24) to try to explain these changes. We confirmed that the women with preeclampsia have a relative hypocalciuria (2.9 +/- 0.7 vs. 6.5 +/- 0.2 mmol/day, P less than 0.01). Preeclamptic women also had lower serum ionized calcium than normotensive third trimester pregnant women (1.20 +/- 0.01 vs. 1.26 +/- 0.01 mmol/L, P less than 0.02). Intact PTH levels were significantly higher in preeclamptic women (29.9 +/- 4.3 vs. 15.4 +/- 1.3 ng/L, P less than 0.01) and a significant inverse relationship was observed between PTH and both urine calcium (r = -0.60, P less than 0.0001) and serum ionized calcium (r = -0.36, P less than 0.05). We measured vitamin D metabolites in a subgroup of both normotensive and preeclamptics. Preeclamptic and normotensive pregnant women had equivalent levels of 25-hydroxyvitamin D [25(OH)D]; however, preeclamptics had significantly lower 1,25-dihydroxyvitamin D [1,25-(OH)2D] levels (172.1 +/- 18.5 vs. 219.6 +/- 12.7 pmol/L, P less than 0.05). Lower 1,25-(OH)2D may contribute to suboptimal intestinal absorption of calcium during a time of increased calcium demand resulting in lower ionized calcium, increased PTH, and hypocalciuria in preeclampsia. Abnormalities in calcium homeostasis may contribute to the increased vascular sensitivity documented in preeclampsia.

Adult↗

PubMed1992

Interrelationships between the renin-angiotensin-aldosterone and calcium homeostatic systems.

Blood pressure is affected by both sodium and calcium intake. To determine if there is an interaction between the regulatory mechanisms for these two cations, eight normal male volunteers received the following 1-h infusions on three different days: 1) angiotensin II (AII), 2) the synthetic 1-34 amino terminal fragment of human PTH [hPTH(1-34)], and 3) AII and hPTH(1-34) together. Blood samples were obtained at t = 0 and every 20 min during each infusion and urine was collected for 3 h both before and after the start of each infusion. Infusion of AII produced an increase in intact PTH from 18 +/- 2 to 31 +/- 4 ng/L (P < 0.05), most likely in response to a small decrease in serum ionized calcium (1.25 +/- 0.01 to 1.23 +/- 0.01 mmol/L, P < 0.05). Urinary excretion of calcium was unchanged. Infusion of hPTH(1-34) at 200 U/h increased N-terminal PTH levels (18 +/- 3 to 268 +/- 42 ng/L, P < 0.05), decreased tubular reabsorption of phosphate (0.92 +/- 0.03 to 0.82 +/- 0.11, P < 0.05), and increased urinary cAMP (0.18 +/- 0.02 to 0.53 +/- 0.05 nmol/L of glomerular filtrate, P = 0.0001). hPTH(1-34) infusion suppressed endogenous intact PTH (18 +/- 3 to 14 +/- 2 ng/L, P < 0.005) and increased PRA from 0.14 +/- 0.02 to 0.32 +/- 0.05 ng/(L.s) (P < 0.05) without a change in serum ionized calcium which suggests direct effects of hPTH(1-34) on the parathyroid glands and the juxtaglomerular apparatus. The effects of AII and hPTH(1-34) were antagonistic with little change in serum ionized calcium, intact PTH, or PRA when both were infused together. These interrelationships between the major hormonal systems controlling sodium and calcium homeostasis suggest a mechanism underlying the close association of calcium and sodium in the regulation of blood pressure.

Adult↗

PubMed1990

Increased need for thyroxine during pregnancy in women with primary hypothyroidism.

BACKGROUND AND METHODS: Women with hypothyroidism have been thought not to require an increase in thyroxine replacement during pregnancy. To evaluate the effects of pregnancy on thyroxine requirements, we retrospectively reviewed the thyroid function of 12 women receiving treatment for primary hypothyroidism before, during, and after pregnancy. RESULTS: In all patients, the serum thyrotropin level increased during pregnancy. The mean (+/- SE) serum free-thyroxine index decreased from 111.0 +/- 5.8 before pregnancy to 86.5 +/- 5.2 during pregnancy (normal, 64 to 142; P less than 0.05), and the mean serum thyrotropin level increased from 2.0 +/- 0.5 mU per liter before pregnancy to 13.5 +/- 3.3 mU per liter during pregnancy (normal, 0.5 to 5.0 mU per liter; P less than 0.01). Because of high thyrotropin levels, the thyroxine dose was increased in 9 of the 12 patients. Among the three patients who did not require an increased thyroxine dose were two with low serum thyrotropin levels before pregnancy, suggesting excessive replacement at that time. The mean thyroxine dose before pregnancy was 0.102 +/- 0.009 mg per day; it was increased to 0.148 +/- 0.015 mg per day during pregnancy (P less than 0.01). The mean postpartum serum free-thyroxine index was 136.6 +/- 11.4 (P less than 0.05 as compared with values before and during pregnancy), and the mean postpartum serum thyrotropin level was 1.4 +/- 0.4 mU per liter (P less than 0.01 as compared with levels during pregnancy), demonstrating a decrease in the thyroxine requirement. The mean postpartum thyroxine dose was decreased to 0.117 +/- 0.011 mg per day (P less than 0.01 as compared with the dose during pregnancy). CONCLUSIONS: Our results indicate that the need for thyroxine increases in many women with primary hypothyroidism when they are pregnant, as reflected by an increase in serum thyrotropin concentrations. Although the effects of this modest level of hypothyroidism are not known, we think it prudent to monitor thyroid function throughout gestation and after delivery and to adjust the thyroxine dose to maintain a normal serum thyrotropin level.

Female↗

PubMed1989

Angiotensin-mediated renin suppression is altered in non-modulating hypertension.

Plasma renin activity (PRA) suppression by angiotensin II (Ang II), the "short feedback loop," has been shown to be blunted in essential hypertension. Non-modulators comprise 50% of normal- and high-renin essential hypertensive individuals and are defined by their abnormal adrenal and renal responses to infused Ang II. This study sought to determine if the abnormal Ang II suppression of PRA in essential hypertension is specific to non-modulators. We measured PRA suppression during infusion of Ang II in 22 normotensive and 32 hypertensive (16 modulators and 16 non-modulators) subjects. A significant correlation between basal PRA and the fall in PRA in response to Ang II infusion was seen in the normotensives (r = -0.934, p less than 0.001) and modulators (r = -0.831, p less than 0.001) but not in the non-modulators (r = -0.275, p = 0.304). However, after 3 days of converting enzyme inhibition therapy, the correlation between basal PRA and decrement in PRA was significant in the non-modulators (r = -0.762, p less than 0.01). Thus, the abnormal PRA suppression documented previously in hypertensive individuals is a defect specific to non-modulators and is corrected with converting enzyme inhibition therapy.

Adult↗

PubMed1989

The calcium channel blocker diltiazem lowers serum parathyroid hormone levels in vivo and in vitro.

PTH secretion is inversely related to the extracellular and cytosolic calcium (Ca2+) concentrations and, therefore, might be affected by calcium channel blockers such as diltiazem. To investigate the effects of diltiazem on parathyroid function in vivo, 15 subjects were treated with diltiazem (120-360 mg/day), and 15 subjects were treated with the nonspecific vasodilator hydralazine (75-150 mg/day). Diltiazem lowered serum PTH levels from 1.07 +/- 0.07 to 0.87 +/- 0.07 pg/L (P = 0.001), and increased urinary calcium and decreased urinary phosphate excretion (P less than 0.001 and P less than 0.01, respectively). The hydralazine-treated subjects had no significant differences in any of these parameters. To investigate this effect further, dispersed bovine parathyroid cells were incubated for 2 h with or without diltiazem. Regression analysis of PTH released vs. the concentration of diltiazem (10(-7)-10(-4) mol/L) revealed a significant negative relationship (P less than 0.01) with 40% inhibition of PTH release at 10(-4) mol/L (P less than 0.01). The cytosolic Ca2+ concentration, measured using the Ca2+-sensitive fluorescent dye fura-2, was significantly increased in the presence of 10(-4) mol/L diltiazem (P less than 0.01). In summary, diltiazem lowered PTH levels in vivo and in vitro, perhaps acting as a Ca2+ channel agonist in the parathyroid cell and inhibiting PTH release through a rise in the cytosolic Ca2+ concentration.

Adult↗

PubMed1989

Adrenocorticotropin stimulation of aldosterone: prolonged continuous versus pulsatile infusion.

Continuous iv administration of ACTH leads to a sustained stimulation of cortisol but a transient stimulation of aldosterone followed by a decline to prestimulation levels by 72 h. Since CRH and ACTH are released in a pulsatile pattern in man, this study sought to investigate whether pulsatile administration of alpha-cosyntropin-(1-24) would lead to the maintenance of aldosterone stimulation over time. Eight normal male subjects on a 10-meq sodium, 100-meq potassium diet received both a continuous and a pulsatile (0.33 U ACTH/pulse over 15 min, pulsed every 2 h) infusion of cosyntropin (4 U/24 h) for 48 h (n = 4) or 72 h (n = 4). Aldosterone and cortisol were sampled every 6 h, and PRA and angiotensin-II every 24 h. Continuous infusion led to a stimulation of aldosterone followed by a progressive decline to preinfusion levels by 72 h [preinfusion 29 +/- 5 ng/dL (810 +/- 139 pmol/L); 72 h, 38 +/- 10 ng/dL (1054 +/- 277 pmol/L); P = 0.40]. Pulsatile infusion led to a stimulation of aldosterone which was maintained up to 72 h [preinfusion 33 +/- 7 ng/dL (915 +/- 194 pmol/L); 72 h, 85 +/- 13 ng/dL (2358 +/- 361 pmol/L); P less than 0.05]. Regression analysis of aldosterone (y) over time (x) from the peak level at 18 h for the continuous infusion showed a significant negative relation (r = 0.63; P = 0.001), indicating a progressive decline in aldosterone. However, for the pulsatile infusion, there was no relation (r = 0.02; P = 0.85), indicating maintenance of aldosterone levels. There were no significant differences in sodium, potassium, PRA, angiotensin-II, or cortisol between infusions to explain these differences in aldosterone levels. Therefore, pulsatile infusion of cosyntropin maintains aldosterone secretion over time.

Adrenocorticotropic Hormone↗

PubMed1989

A single dose of lithium carbonate acutely elevates intact parathyroid hormone levels in humans.

Hyperparathyroidism has been reported in patients receiving lithium therapy, and lithium alters calcium-regulated PTH release in vitro. Previous studies in vivo have used assays which measure fragments of PTH as well as the intact hormone. To determine if lithium acutely elevates intact PTH levels, we studied 9 subjects who received a single oral dose of lithium carbonate (600 mg). Serum levels of intact PTH, ionized calcium, and lithium were measured before, 2 and 14 h after the dose of lithium. PTH levels rose significantly 2 h following the dose of lithium (before 22 +/- 5.0, post 32 +/- 7.3 ng/l, p less than 0.02). PTH levels had returned to baseline at 14 h (22 +/- 3.8 ng/l). There were no significant changes in ionized calcium levels. Therefore, a single oral dose of lithium carbonate acutely elevates intact PTH values in human subjects.

Administration, Oral↗

PubMed1988

Relationship between the concentration and rate of change of calcium and serum intact parathyroid hormone levels in normal humans.

We employed variable rates of infusion of EDTA or calcium gluconate to examine the relationships between the concentration and rate of change of serum total and plasma ionized calcium and serum immunoreactive intact PTH concentrations in normal subjects. Use of a sensitive immunoradiometric assay specific for PTH-(1-84) made it possible to determine the full range of PTH responses to perturbations in the extracellular calcium concentration. By progressively increasing the rate of administration of calcium gluconate or EDTA during rapid or slow infusions, linear rates of change in the serum calcium concentration were achieved in eight men. The slopes were 2-fold greater during the rapid infusions. Both the calcium infusions decreased serum PTH-(1-84) levels from a mean of 23.2 +/- 2.0 (+/- SE) to 6.4 +/- 1.0 and 5.6 +/- 1.0 ng/L for the rapid and slow infusions, respectively, with no obvious rate dependence. The rapid or slow EDTA infusions increased serum PTH levels to the same maximal extent (95.0 +/- 20.2 and 99.9 +/- 14.5 ng/L, respectively), also with no significant rate dependence. Thus, there was no effect of the rate of change of calcium on the PTH response, which was reflected in similar inverse sigmoidal relationships between PTH and serum total and plasma ionized calcium when the data for the slow and rapid infusions were pooled separately. Similar sigmoidal curves were found in normal women. These data suggest the feasibility of using calcium and EDTA infusions combined with an intact PTH assay to define the relationships between circulating levels of PTH-(1-84) and calcium in states of normal and deranged parathyroid physiology.

Adult↗

PubMedDate not supplied

Localization of the extracellular Ca(2+)-sensing receptor in the human placenta.

We have demonstrated using immunohistochemistry and in situ hybridization that the calcium-sensing receptor (CaR) is expressed in both villous and extravillous regions of the human placenta. CaR expression was detected in both first trimester and term placentas. In the villous region of the placenta, the CaR was detected in syncytiotrophoblasts and at lower levels in cytotrophoblasts. Local expression of the CaR in the brush border of syncytiotrophoblasts suggests a role for maternal Ca(2+) concentration in the control of transepithelial transport between the mother and fetus. In the extravillous region of the placenta, the CaR was detected in cells forming trophoblast columns in anchoring villi, in close proximity to maternal blood vessels and in transitional cytotrophoblasts. Given the importance of extravillous cytotrophoblasts in the process of uterine invasion and maintenance of placental immune privilege, the CaR represents a possible target by which the maternal extracellular Ca(2+) concentration could promote or maintain placentation. Thus, the results support hypotheses that the CaR contributes to the local control of transplacental calcium transport and to the regulation of placental development.

Adult↗

PubMedDate not supplied

Provider characteristics: impact on bone density utilization at a health maintenance organization.

OBJECTIVE: Information from bone mineral density (BMD) is relevant in guiding postmenopausal osteoporosis prevention and treatment, yet many providers do not typically order BMDs. This study was designed to identify physician characteristics associated with utilization of bone densitometry in a northeastern US health maintenance organization (HMO). DESIGN: Internal medicine primary providers in practice at a northeastern HMO between April 1997 and March 1998 were categorized by BMD utilization, based on the number of BMDs performed during that time per number of women older than 50 years in their patient panel. In one analysis, providers in the highest quintile for this parameter were considered "high utilizers" (n = 25), and those in the lowest quintile, "low utilizers." These groups were compared with respect to provider characteristics and practice composition. In a second analysis, multiple variable linear regression was used to predict the likelihood of utilization of BMD as a function of those parameters for all providers. RESULTS: The range of BMDs by provider was 0 to 190 per 1,000 women >50 years (median = 34) over this 1-year period. Providers who were high utilizers had a significantly greater number of female patients more than age 50 in their practice (p < 0.05) and were also more likely themselves to be female (62% vs. 48%; p < 0.05). There was no association between BMD utilization and age of provider or years in practice. Female provider gender (p < 0.01) and greater percentage of women more than age 50 in the practice (p < 0.05) were independent predictors of BMD utilization in a multivariate model. CONCLUSION: BMDs were infrequently utilized by the majority of providers over this 1-year period. Female provider gender was associated with a significantly greater likelihood of BMD utilization that was not simply explained by the greater number of women in these providers' practices. These findings may be relevant to identifying strategies to improve bone health care in this population.

Absorptiometry, Photon↗