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Biomedical subjects

J C Stevenson

Publications and source records attributed to J C Stevenson.

At least 145 records · Page 8Linked to original sources
PubMed1989

Serum concentrations of alkaline phosphatase isoenzymes and osteocalcin in normal pregnancy.

We measured serum alkaline phosphatase isoenzymes and osteocalcin levels in 40 healthy women at 4-week intervals throughout uncomplicated pregnancies and 6 weeks after delivery in 17 women. Serum bone alkaline phosphatase was significantly higher in the third trimester than in early pregnancy (P less than 0.001), and this elevation was still apparent at the end of the puerperium, suggesting increased bone turnover. Serum osteocalcin was not detected (less than 0.2 micrograms/L) after the first trimester in the majority of women, and it reappeared within 48 h after delivery. The disappearance of osteocalcin after the first trimester and its rapid reappearance after delivery suggest placental clearance of this peptide. We conclude that serum osteocalcin measurements cannot be used as a marker of bone metabolism during pregnancy.

Adult↗
PubMed1989

Changes in completed family size and reproductive span in Anabaptist populations.

The Anabaptist Amish, Hutterite and Mennonite peoples trace their origins to the Reformation. Although they share certain beliefs, such as adult baptism and the separation of church and state, each group is culturally unique. The Hutterite and Amish are highly fertile and their populations exhibit stable rates of growth. These demographic characteristics reflect communal living among the Hutterites and labor intensive farming practices among the Amish. The Mennonites are the most receptive Anabaptist group to outside socioeconomic influences and provide a demographic contrast to the more conservative Amish and Hutterites. Demographic data collected during a study of aging in Mennonite population samples from Goessel and Meridian, Kansas, 1980, and Henderson, Nebraska, 1981, formed the basis of a cohort analysis in order to assess fertility change over time. Completed family size has decreased significantly in all three communities since 1870. Since the early 1900's the mean age of the mother at first birth has fluctuated but the mean age of mother at the birth of the last child is decreasing significantly for the communities of Goessel and Henderson, thus effectively shortening the reproductive span. The pattern is somewhat different for Meridian, the most conservative of the three communities.

Adolescent↗
PubMed1988

Dietary intake of calcium and postmenopausal bone loss.

The use of calcium supplements to prevent postmenopausal bone loss and hence osteoporosis is widespread, but the evidence for their efficacy, either alone or in combination with other treatments, is contradictory. Skeletal measurements and dietary intake of calcium were determined in 59 healthy postmenopausal women, most of whom were within five years of the menopause. No correlation was found between current intake of calcium and either total calcium in the body or the density of trabecular or cortical bone in the forearm or vertebral trabecular bone. Dietary intake of calcium did not influence the rate of postmenopausal bone loss in the 54 women who completed 12 months of active or placebo treatment. Even when extremes of calcium intake were examined no difference was found in bone measurements between the women with the highest and lowest intakes. The results of this study suggest that the bone density of women in the early menopause is not influenced by current dietary intake of calcium.

Adult↗
PubMed1988

Calcitonin for prevention of postmenopausal bone loss.

A 2-year randomised pilot study was conducted in 70 patients to see whether the osteoclast-inhibiting effect of calcitonin would reduce postmenopausal vertebral bone loss. An oestradiol-treated group was included in the study as a positive control since oestrogens are known to be effective. Calcitonin reduced vertebral bone loss in doses above 250 micrograms human calcitonin (50 international units) a week, and at this dose was as effective as oestradiol.

Administration, Oral↗
PubMed1988

Elevated 7B2 levels during normal human pregnancy.

In a cross-sectional study the plasma concentrations of immunoreactive 7B2, a novel protein originally isolated from the pituitary gland, was measured in 60 healthy pregnant and postpartum women. The mean circulating concentration of 7B2 immunoreactive equivalents was found to be significantly increased throughout pregnancy (10 to 12 weeks, 52.2 +/- 13.1 pmol/L; 20 to 22 weeks, 74.4 +/- 20.1 pmol/L; 30 to 32 weeks, 56.0 +/- 12.9 pmol/L; and 36 to 40 weeks, 85.7 +/- 13.6 pmol/L) when compared with a group of 32 age-matched nonpregnant controls (19.7 +/- 5.0 pmol/L); (p less than 0.01). The highest 7B2 plasma concentrations were found shortly before delivery (36 to 40 weeks) and fell sharply after birth, returning to normal within 4 to 6 weeks. Fetal plasma from both umbilical artery and vein was found to have particularly high concentrations of 7B2-like immunoreactivity (396 +/- 19 and 361 +/- 24 pmol/L, respectively), and 7B2 was extractable from the placenta. Chromatographic analysis of plasma and tissue extracts showed the main peak of immunoreactivity to coincide with that originally described in the pituitary gland. Although the function of 7B2 is at present unknown, our data suggest that 7B2 immunoreactivity in fetal blood originates from the fetus and may play an important role in pregnancy.

Adolescent↗
PubMed1988

Current management of malignant hypercalcaemia.

The pathogenic mechanisms causing malignant hypercalcaemia are primarily increased bone calcium mobilisation and renal calcium retention. In some reticuloendothelial malignancies, enhanced intestinal calcium absorption may also play a role. Malignant hypercalcaemia is a life-threatening condition, and there are many patients with malignancy in whom suppression of this complication is most desirable. In such cases, successful management of the hypercalcaemia will enable the overall treatment aims, such as tumour removal or ablation, to be achieved. Acute treatment involves the rapid lowering of serum calcium from potentially fatal concentrations, and comprises the use of intravenous rehydration, calcitonin and diphosphonates. In the longer term, other measures may be introduced to maintain and control the calcium concentration while specific antitumour therapy is instituted.

Calcitonin↗
PubMed1987

Regional and total skeletal measurements in the early postmenopause.

In a cross-sectional study of 70 early postmenopausal women, regional bone measurements were compared with total body calcium (TBCa). Spinal and forearm trabecular bone were mainly related to age and time since menopause. In contrast, TBCa and forearm integral (cortical and trabecular) and cortical bone were unrelated to age, although the time since menopause also had some influence. Forearm integral and cortical bone measurements were quite well correlated with TBCa (r = 0.84 and 0.73, respectively, P less than 0.001). The correlation between spinal bone measurements and any of the forearm measurements, even purely trabecular bone, was weak (r less than 0.52, P less than 0.001). Our results show quite clearly that forearm bone measurements cannot be used to predict bone density in the vertebrae. Loss of ovarian function affects bone in general, and trabecular bone in particular. Bone measurements at specific anatomical sites are clearly necessary for studies of metabolic bone diseases and their response to treatment.

Adult↗
PubMed1986

Increased concentration of circulating calcitonin gene related peptide during normal human pregnancy.

Calcitonin gene related peptide is an extremely potent vasoactive peptide that causes profound vasodilatation in man. Its distribution in perivascular nerves suggests that one of its functions may be the regulation of peripheral vascular tone. Pregnancy is a physiological condition in which there are major haemodynamic changes. An increase in plasma volume of about 40% necessitates changes in peripheral vascular tone. In a cross sectional study plasma concentrations of immunoreactive calcitonin gene related peptide were measured throughout normal pregnancy and at five to seven days post partum. Calcitonin gene related peptide concentrations were significantly increased throughout pregnancy but fell after delivery. Calcitonin gene related peptide may participate in the physiological regulation of vasomotor tone in man.

Adolescent↗
PubMed1986

Human calcitonin gene related peptide: a potent endogenous vasodilator in man.

In addition to calcitonin and katacalcin, it is now known that the human calcitonin gene encodes a novel peptide called calcitonin gene related peptide (CGRP). In experimental animals, CGRP produces vasodilatation and complex changes in plasma calcium. We have now assessed its biological activity in man by infusing human CGRP (hCGRP) into six normal volunteers. hCGRP (545 pmol/min) caused the diastolic pressure to fall from 64 +/- 5 to 55 +/- 7 mmHg (P less than 0.05), the heart rate to increase from 61 +/- 7 to 87 +/- 5 beats/min (P less than 0.05) and the skin temperature to increase from 33.7 +/- 0.9 to 34.9 +/- 0.5 degrees C. Plasma noradrenaline increased from 481 +/- 126 to 835 +/- 65 pg/ml (P less than 0.05) and plasma adrenaline from 57 +/- 17 to 82 +/- 12 pg/ml (P less than 0.05). There were no significant changes in the albumin-corrected plasma calcium. hCGRP is thus a potent endogenous vasodilator in man and is in fact more potent than any other known vasodilator. Together with the observations that CGRP circulates in normal subjects at relatively high concentration (approximately 25 pmol/l) and that CGRP is present in perivascular nerves, this study suggests a possible role for CGRP in controlling peripheral vascular tone in man.

Adult↗
PubMed1986

Osteoporosis with hip fracture: changes in calcium regulating hormones.

It has been suggested that there are two distinct types of involutional osteoporosis in women. Loss of ovarian function causes spine and wrist fractures in middle-aged women whilst a decline in renal endocrine function and bone formation is responsible for fractures, especially of the hip, in elderly women. We have investigated calcium regulation in post-menopausal women with hip fractures in their seventh decade together with non-osteoporotic controls of similar age. The major findings were reduced secretion of calcitonin (P less than 0.01) and 1,25 dihydroxy-vitamin D (P less than 0.025) in the osteoporotics as compared with controls. No differences in plasma levels of calcium, parathyroid hormone and 25 hydroxyvitamin D were observed. Our results show some similarities with those reported in both proposed types of osteoporosis, suggesting considerable overlap between them. Secondary hyperparathyroidism does not appear to be a usual feature of osteoporotic women with hip fracture up to age 75 years. Our hormonal findings are more in keeping with marked oestrogen deficiency, suggesting that loss of ovarian function is a major determinant of the osteoporosis in these women.

Calcitonin↗