A sensitive radioimmunoassay of alpha human atrial natriuretic polypeptide using monoclonal antibody recognizing human form ring structure

A monoclonal antibody (C351) against alpha human atrial natriuretic polypeptide (alpha hANP) recognizing human form ring structure was established and applied to a radioimmunoassay of plasma alpha hANP. The minimum detectable amount in terms of 10% radioligand displacement relative to zero dose were 0.28 fmol/tube, corresponding to 0.7 fmol/ml in plasma after extraction using Sep-Pak C18 cartridges. When the mean plasma levels at recumbent position in fasted morning were compared in 10 young (less than 30 years) and 10 elderly (greater than or equal to 50 years) healthy subjects taking normal sodium diet, it was slightly higher in the latter (3.2 +/- 0.4 vs 4.7 +/- 0.5 fmol/ml, mean +/- SE, p less than 0.05). After i.v. infusion of hypertonic saline (2.5% NaCl) at a rate of 0.24 ml/kg/min for 20 min in 6 normal subjects (26 to 35 years), it was increased from 4.1 +/- 0.4 to 5.9 +/- 0.7 fmol/ml (p less than 0.01). In 6 patients with essential hypertension (34 to 57 years), it was elevated with high salt intake, i.e. 3.3 +/- 0.3, 3.9 +/- 1.03 and 7.6 +/- 1.5 fmol/ml under 34, 170 and 340 mEq NaCl/day for 7 days, respectively. From these results, the radioimmunoassay of plasma IR-alpha hANP using MAb C351 seems to be quite suitable to detect rather small changes at low plasma concentrations and to investigate a physiological importance of alpha hANP in man.     

Direct radioimmunoassay for human atrial natriuretic peptide (hANP) and its clinical evaluation

A direct radioimmunoassay for the rapid and accurate detection of human ANP from unextracted plasma is described. The sensitivity was approximately 50 pg/ml, respectively 2.5 pg/tube, the intra-assay variation 4%, and the inter-assay variation less than 12%. Rat ANP (1-28, 5-25, 5-27 and 5-28), oxydized and reduced hANP as well as plasma samples from various patients run in parallel to the 1-28 hANP standard curve. These findings imply, that the antibody primarily recognizes the mid-region (amino acids 6-25) of the intact ANP, that the C-terminal portion further increases the immunoreactivity, and that circulating plasma hANP is reliably measured. Plasma hANP ranged from 50-166 pg/ml (mean +/- SD: 98.3 +/- 44.6) in healthy individuals, there was no significant difference between samples were drawn in upright or lying position, the apparent half-life of injected hANP was 5.65 minutes. Patients with liver cirrhosis revealed significantly higher hANP levels of 244.5 +/- 173.5 pg/ml. Patients with various forms of cardiac disease had hANP concentrations ranging from 50 to 1744 pg/ml, depending at least partially on the right atrial pressure. No difference was observed if the samples were drawn from either right or left intracardial locations. Our findings with this system demonstrate that hANP is reliably measured even without prior extraction.     

X-linked hypophosphatemia: the mutant gene is expressed in teeth as well as in kidney.

Mutation at a locus (HPDR) on the X chromosome (McKusick 30780 [HPDR1]; 30781 [HPDR2]) causes impaired renal phosphate transport, hypophosphatemia, and an associated impairment in the process of mineralization in bone and teeth (X-linked hypophosphatemia [XLH]). We measured the dental pulp profile area (PRATIO [= pulp area/tooth area]) and serum phosphorus (Pi) values in uniformly treated XLH patients (six males, 81 teeth, 1,457 Pi values; 11 females, 129 teeth, 1,439 Pi values). Serum Pi values, reflecting the metabolic environment of tooth development, were obtained by repeated measurement between 1 mo and 26 years of age during treatment. PRATIO values calculated from standardized Rinn radiographs were used as outcome measurements of tooth development in XLH patients and in age-matched controls (12 males, 100 teeth; 27 females, 275 teeth). Age-dependent serum Pi values were not different in the treated XLH males and females. In teeth forming primary dentin there was no gene dosage effect on PRATIO values apparent in subjects below 15 years of age. However, in teeth forming secondary dentin a gene dosage was found in the subjects aged 15 to 25 years: XLH male teeth (n = 65) mean +/- SD = 0.163 +/- 0.046; XLH female teeth (n = 75) mean +/- SD = 0.137 +/- 0.039; control teeth (n = 209) mean +/- SD = 0.116 +/- 0.023; (higher PRATIO values mean less development or mineralization of secondary dentin); differences in these PRATIO values (males vs. female and XLH vs. control) were significant by mixed-model analysis of variance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma levels of vascular endothelial growth factor in patients with acromegaly.

Vascular endothelial growth factor (VEGF) is known to be linked to retinal ischemia-associated neovascularization. It was recently found that insulin-like growth factor-I (IGF-I) enhances VEGF gene expression. In this study we investigated whether plasma VEGF levels are increased in patients with acromegaly, a disease in which plasma IGF-I levels are elevated, and whether plasma VEGF levels are correlated with plasma IGF-I levels in these patients. We retrospectively analyzed plasma samples from 13 active acromegalic patients (7 males and 6 females) aged 33 to 66 years, with a mean age of 52.3+/-10.8 years. The results were compared with plasma VEGF levels in 16 age- and sex-matched, healthy subjects (9 males and 7 females) aged 22 to 66 years, with a mean age of 52.4+/-11.5 years. Plasma VEGF levels were not higher in the acromegalic patients than in the healthy subjects (253+/-61 vs. 197+/-30 pg/mL, P= 0.39). In 5 patients plasma VEGF levels were rather slightly increased after pituitary adenomectomy while one patient showed a reduced plasma VEGF level. In addition there was no correlation between plasma VEGF and GH or IGF-I levels. These data indicate that plasma VEGF levels are not increased in patients with acromegaly and that serum VEGF may play a less important role in the neovascularization in the carcinogenesis and/or disturbances of the cardiovascular system in patients with acromegaly.     

A possible contribution of endogenous atrial natriuretic peptide to proteinuria in patients with chronic renal failure.

Plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) were measured with a specific radioimmunoassay in 19 undialysed patients with chronic renal failure. At the beginning, an extremely high level of plasma hANP (50 fmol/ml) seen in a patient was rejected with Smirnov's test and was excluded from further statistics. The plasma IR-ANP levels in these patients were significantly higher than those of 19 normal subjects matched with age and sex (10.9 +/- 1.6 vs 5.3 +/- 0.6 fmol/ml, mean +/- SEM, p less than 0.01), and positively correlated with mean blood pressure (r = 0.44, p less than 0.05) and the cardiothoracic ratio (r = 0.65, p less than 0.01), but did not correlate with creatinine clearance (r = -0.38, n.s.). Further, a significant correlation was observed between plasma IR-ANP and urinary protein output (r = 0.47, p less than 0.05). On the other hand, urinary protein output did not correlate significantly with variables such as mean blood pressure, the cardiothoracic ratio or creatinine clearance. Since it has been suggested that ANP enhances glomerular capillary permeability, increased ANP responding to volume overload in those patients may play an important role in increasing urinary protein excretion.     

The measurement of 11 beta-hydroxy-4-pregnene-3,20-dione (21-deoxycorticosterone) by radioimmunoassay in human plasma

A specific radioimmunoassay (RIA) method is described for the determination of 21-deoxycorticosterone (21 DB) in human plasma. 21-Deoxycorticosterone-3-(O-carboxymethyl) oxime-bovine serum albumin conjugate was used to generate antisera in rabbits. Steroids which reacted significantly with the antisera were found to be progesterone, pregnenolone, corticosterone and 11-oxo progesterone. However, after extraction of plasma and column chromatography on Celite, all these steroids were separated from 21-deoxycorticosterone and consequently did not interfere with the radioimmunoassay. The intra- and interassays coefficients of variation were 8% and 11% respectively. Mean plasma 21-deoxycorticosterone level for healthy subjects was very low: 17.8 +/- 14.8 pmol/l (mean +/- SD) with no statistical difference between males and females. During the ACTH stimulation test, the 21-deoxycorticosterone levels of healthy subjects increased to 84.7 +/- 26.3 pmol/l (mean +/- SD) for males and 79.3 +/- 31.6 pmol/l (mean +/- SD) for females. Consequently high levels of plasma 21-deoxycorticosterone were found in treated patients suffering from congenital adrenal hyperplasia (CAH) with 21-hydroxylase deficiency, particularly in CAH salt-losers with high plasma renin activity (PRA), where the plasma level reached 40,545 pmol/l. Thus, 21-deoxycorticosterone may be a new marker for adrenal 21-hydroxylase deficiency.     

Radioimmunoassay of 5-androstene-3 beta,17 beta-diol in plasma and in breast cyst fluid

A simple and reliable radioimmunoassay for the determination of 5-androstene-3 beta, 17 beta-diol in peripheral plasma and in breast cyst fluid, after a chromatography on Celite microcolumn has been described and evaluated. The antiserum used was raised in rabbits injected with dehydroepiandrosterone-15 alpha-(O-carboxymethyl)-bovine serum albumin. In men below 40 years of age the levels ranged from 0.85 to 2.80 ng/ml (mean +/- SEM: 1.52 +/- 0.11; n = 24) and from 0.50 to 2.20 ng/ml (mean +/- SEM: 0.93 +/- 0.09; n = 20) in men aged between 41 and 62 years. The mean level was significantly different (P less than 0.001) between the 2 groups. A significant correlation (r = -0.56; P less than 0.01) was demonstrated between age and all male levels. In females the mean plasma level was in the follicular phase: 0.81 +/- 0.07 ng/ml (range: 0.40-1.50; n = 17; age: 19-41 years) and in the luteal phase: 0.83 +/- 0.05 ng/ml (range: 0.40-1.30; n = 29; age: 18-43 years). No cyclical change and no correlation with age could be evidenced. A significant difference (P less than 0.001) was shown between females and the young male group. In breast cyst fluid the levels ranged from 0.05 to 13.70 ng/ml (mean +/- SEM: 2.36 +/- 0.86; n = 20) whereas the sulfate concentrations ranged from 75 to 7500 ng/ml (mean +/- SEM: 1891 +/- 565; n = 15), thus demonstrating very wide inter-individual variations.     

Spontaneous growth hormone secretion and plasma somatomedin-C in children of short stature

We studied 17 short prepubertal children, aged 7.5 to 17.0 years (mean +/- SD: 11.7 +/- 2.4) more than 2.0 SD below the mean height for their age and of delayed bone age (M +/- SD: 8.1 +/- 2.3), to clarify their physiological GH secretory status. The mean concentration of GH (MCGH) was calculated and was compared with the subjects' GH responses to insulin and arginine tolerance tests (IATT) and plasma somatomedin-C (SM-C). The mean 24-h MCGH value was 3.2 +/- 1.3 ng/ml (range 1.6-5.5). The mean peak GH response to the IATT was 13.0 +/- 7.5 ng/ml (range 2.4-33.9). In addition to the two patients with abnormally low GH responses to the IATT, seven with normal responses showed low 24-h MCGH values, a small number of GH pulses and low mean GH amplitude. The mean plasma SM-C in all patients was 0.60 +/- 0.20 U/ml. This was significantly lower than that of age-matched children of normal height (p less than 0.001). The 24-h MCGH was significantly correlated with plasma SM-C levels (r = 0.51, p less than 0.05) and with that of the first three hours of sleep at night (r = 0.84, p less than 0.01). These results indicate that: 1) some short children with normal GH response to pharmacological tests secrete a low amount of GH physiologically and 2) blood sampling during the first three hours of sleep as well as 24-hour sampling is suitable in evaluating the physiological secretion of GH.     

Elevated serum leptin levels in patients with acute myocardial infarction; correlation with coronary angiographic and echocardiographic findings

ABSTRACT: BACKGROUND: To assess the relationship between serial serum leptin levels in patients with acute myocardial infarction (AMI) who received thrombolysis and the degree of coronary atherosclerosis, coronary reperfusion, echocardiographic findings, and clinical outcome. 51 consecutive patients presenting with AMI were studied. Clinical characteristics including age, sex, body mass index (BMI) and cardiovascular risk factors were recorded. Serial serum leptin levels at the time of admission and subsequently at 0, 6, 12, 24, 36, 60 hours afterwards were obtained. Coronary angiography was performed in 34 patients; the relation between serum leptin levels and evidence of coronary reperfusion as well as the extent of coronary atherosclerosis according to the coronary artery surgery study classification (CASS) were evaluated. Echocardiographic evaluation was performed in all patients. 36 matched patients were enrolled as control group who had serum leptin level 9.4 +/- 6.5 ng/ml. RESULTS: The patients mean age was 50.5 +/- 10.6 years. There were 47 males and 3 females. 37.1% were diabetics, 23.5% were hypertensive, 21.6% were dyslipidemic and 22.7% were obese (BMI [greater than or equal to] 30). Leptin concentrations (ng/ml) increased and peaked at the 4th sample (36 hrs) after admission (mean +/- SD) sample (1) =9.55 +/- 7.4, sample (2) =12.9 +/- 8.4, sample (3) =13.8 +/- 10.4, sample (4) =18.9 +/- 18.1, sample (5) =11.4 +/- 6.5, sample (6) =10.8 +/- 8.9 ng/ml. There was a significant correlation between serum leptin and BMI (r = 0.342; p =0.03). Leptin levels correlated significantly to creatine kinase level on the second day (r = 0.43, p [less than or equal to] 0.01). Significant correlation of mean serum leptin with the ejection fraction (P < 0.05) was found. No difference in timing of peak serum leptin between patients who achieved coronary reperfusion vs. those who did not (p= 0.8). There was a trend for an increase in the mean serum leptin levels with increasing number of diseased vessels. There was no correlation between serum leptin levels and outcome neither during the hospitalization nor at 9 months follow up. CONCLUSION: Serum leptin levels increase after myocardial infarction. Serum leptin level may be a predictor of the left ventricular ejection fraction and the degree of atherosclerosis but not of coronary reperfusion.     

Chronobiological pattern of growth hormone secretion in normal subjects and in retinopathic diabetics. Lack of suppression by a plurichronocorticoid drug.

Nyctohemeral variations in plasma concentrations of HGH, glucose, and FFA were studied in 22 normal subjects and 48 diabetic patients affected with retinopathy. In the normal subjects, (fourteen males and eight females, mean age 40+/-3 years; body weight less than 110% of I.B.W.) the determinations were made on blood samples drawn every hour. Seven of these normal subjects were examined before and after 10 days of administration of a new plurichronocorticoid drug (administered at 08(00) and 15(00), with a total amount of 14 mg of prednisolone and 15 mg of cortisone). In patients with diabetic retinopathy (32 male and sixteen female patients, mean age 46+/-2 years, body weight less than 110% of I.B.W.) the determinations were made on blood samples drawn every 3 hrs. All the diabetic patients were insulin treated and were under good or discrete metabolic control, and presented advanced retinopathy. Both in the normal subjects and in retinopathic diabetics, the mean HGH curve showed a characteristic elevation during the early nighttime hours (between 21(00) and 02(00). Despite higher values in plasma glucose and FFA, in diabetics the nocturnal elevation of HGH was only slightly lower than in the normals. The comparison between daytime and nighttime determinations, both in the normal subjects and in the diabetics, reveals statistically significant differences. These results suggest that in subjects with diabetic retinopathy, in the phase of good or discrete metabolic control, spontaneous HGH secretion is not increased, and that nocturnal elevation of HGH is not substantially influenced by higher plasma levels of glucose and FFA. Ten days of plurichronocorticoid treatment with a new drug which exhausts its activity before the evening, did not modify the circadian rhythm of HGH.     

Age-related differences in serum gonadotropin (FSH and LH), salivary testosterone, and 17-beta estradiol levels among Ache Amerindian males of Paraguay

Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-beta estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 +/- 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in hypothalamic-pituitary function. Significant increases in FSH (r = 0.75, P < 0.0005) and LH (r = 0.65, P < 0.01) were noted in association with aging. No significant correlation was observed between morning or evening testosterone and age. Morning and evening estradiol levels were associated with morning and evening testosterone, respectively (morning, r = 0.53, P = 0.05; evening, r = 0.63, P = 0.02). Evening estradiol was also positively associated with LH (r = 0.66, P = 0.02), suggesting testicular production to be an important source of circulating estradiol. Morning estradiol tended to rise with age, but was not significant (r = 0.39, P = 0.15). Anthropometric measurements of height, weight, body mass index, and fat percent did not change significantly with age. In contrast to testosterone, age-related differences in gonadotropin levels may be independent of energetic status, less variant, and more universal among male populations. Implications for gonadotropin function and aging on human male reproductive senescence and life histories are discussed.     

On the relationship between body dimensions and appendix length

In the last decades a lot of significant correlations between clinical and anthropometric parameters were found, e.g. the relationships between somatotypical and endocrine parameters or between body dimensions and echocardiographic heart size. During operation, surgeons often find a wide range of appendix size of patients with varying body dimensions. A goal of this work is the detection of the relationships between anthropometric characteristics (height, weight, body mass index (= BMI)), inflammation parameters (histological inflammation degree, leukocyte count and C-reactive protein (= CRP)) and the appendix length with n=167 consecutive patients (time period 1.1.2004 - 31.12.2006; range of age 7-95 years, median age 20 years; average age of men 27.7, women 26.6 years), which had to be operated because of acute appendicitis. Appendectomy was laparoscopic in 95 % of the patients and open in 5 %. The appendix length of the male patients was high-significantly longer with a mean of 7.5 cm (SD = 2.1) than those of the female patients with 6.3 cm (SD = 1.6). The following mean anthropometric values were registered: height 169.8 (SD = 15.6) cm for the males and 165.2 (SD = 9.6) cm for the females, weight 70.4 (SD = 23.4) kg for the males and 61.9 (SD = 16.1) kg for the females, BMI 24.1 (SD = 5.4) kg/m2 for the males and 22.9 (SD = 4.8) kg/m2 for the females. The mean leukocyte count was 12,700 (SD = 5500)/ml for the males and 11,600 (SD = 4900)/ml for the females, CRP was 4.3 (SD = 5.4) mg/l for the males and 4.5 (SD = 8.9) mg/l for the females. Concerning the histopathological diagnosis, n=76 patients (45.5 %) suffered from a submucous fibrosis bliteration, n 1 (12.6 ) from an acute purulent inflammation degree, n = 65 (38.9 ) from an ulcerative hlegmonous inflammation degree and n (3 ) from a perforation. While no significant Spearman's correlation coefficient between appendix length and CRP was found, the appendix length correlated highly significantly to the body weight (r = 0.25) and significantly to leukocyte count (r = 0.16), body height (r = 0.16), BMI (r = 0.17) and the histological inflammation degree (r = 0.18). Thus, the correlations found were lower than the relationships between anthropometric and endocrine or echocardiographic parameters described in literature.     

Human atrial natriuretic polypeptide in plasma of patients with anorexia nervosa

To examine the effects of chronic dehydration and starvation on plasma levels of human atrial natriuretic polypeptide (hANP) in human subjects, the basal level and saline-induced rise of plasma hANP in 7 patients with anorexia nervosa were compared with those in age-matched healthy subjects. The unstimulated level of plasma hANP was markedly high in the patients with anorexia nervosa (patients vs. control; 55.4 +/- 9.0 pg/ml vs. 11.4 +/- 6.1 pg/ml, P less than 0.01). However, no significant increase of plasma hANP in the anorectic patients was observed in response to saline-infusion, while a 3-fold increase over the basal level of plasma hANP was noted in the saline-infused normal young subjects. These results show that hANP may be secreted to an inadequate extent, hence the release would be resistant to volume-loading. The pathophysiological meaning of such a high plasma concentrations of hANP in anorexia nervosa is the subject of ongoing studies.     

Further evidence for the usefulness of the salivary testosterone radioimmunoassay in the assessment of androgenicity in man in basal and stimulated conditions

Since correct assessment of testicular function and androgenic status in humans requires multiple sampling, a sensitive and accurate radioimmunoassay (RIA) of testosterone (T) was established for male and female saliva samples. This easily collected biological fluid, which contains nonprotein-bound T, may represent an attractive alternative or a complement to total plasma T assays. In saliva samples from 5 normal males, a clear circadian rhythm was observed, and morning concentrations (135 +/- 31 pg/ml) were significantly higher (p less than 0.02) than evening samples (85 +/- 23 pg/ml). In 11 normal females, morning saliva levels were 12.8 +/- 1.8 pg/ml. The levels of T in male saliva, in response to both exogenous T administration (100 mg i.m.) and HCG stimulation (2 X 2,000 IU i.m.), accurately reflected the changes observed in plasma T, and the magnitude of increase in T levels was clearly greater in saliva than in plasma samples during the intramuscular administration of the long-acting T preparation. In males, significant correlations were observed between salivary and plasma T concentrations in morning samples (r = 0.61, p less than 0.01), following HCG stimulation (r = 0.89, p less than 0.05) and during T administration (r = 0.87, p less than 0.05). In women, the correlation at 8 a.m. was also significant (r = 0.82, p less than 0.05).     

Pharmacokinetics of synthetic alpha-human atrial natriuretic polypeptide in normal men; effect of aging

We reported that plasma human atrial natriuretic polypeptide (hANP) in healthy aged men was significantly higher than that in young men, presumably due to a diminished cellular response to endogenous hANP in the aged subjects (J. Clin. Endocrinol. Metab., 64 (1987) 81). To examine the effect of age on the metabolic clearance rate for hANP, synthetic alpha-hANP (2 micrograms/kg) was administered intravenously to healthy young (n=6) and aged (n=4) men. The plasma hANP was measured by a direct radioimmunoassay. The disappearance of alpha-hANP from plasma was characterized by a biexponential decay curve, in both groups. There was no difference of the initial phase between young and aged groups (young vs aged; 1.2 +/- 0.2 min vs 2.9 +/- 1.0 min), while the second phase of alpha-hANP disappearance in the aged group was significantly prolonged compared with that in the young individuals (young vs aged; 17.3 +/- 3.9 min vs 34.3 +/- 3.0 min, P less than 0.05). We tentatively conclude that the reduced metabolic clearance rates for hANP were responsible, in part, for the high plasma concentrations in the aged men.     

Effects of atrial natriuretic peptide infusion and its metabolism in patients with chronic renal failure.

Synthetic alpha-human atrial natriuretic peptide (hANP) was infused continuously at a rate of 80 ng/kg/min for 20 min into normal volunteers and patients with chronic renal failure (CRF) receiving hemodialysis. Blood pressure (BP) decreased significantly both in normals and in patients with CRF. The magnitude and the duration of the decrease, however, were greater in patients with CRF. The plasma aldosterone concentration (PAC) decreased significantly in normals and only minimally in patients with CRF. The half time (T1/2) of plasma hANP in patients with CRF (M +/- SE: 4.5 +/- 0.5 min) was longer than that in normals (1.8 +/- 0.2 min). Moreover, the metabolic clearance rate in patients with CRF (64 +/- 7 ml/kg/min) was less than in normals (150 +/- 20 ml/kg/min). Thus, the T1/2 in plasma of hANP in patients with CRF was noticeably longer than in a normal control group. These findings suggest that hANP suppresses PAC regardless of electrocyte imbalances and/or volume change induced by kidney dysfunction and that the kidney may be important in degrading hANP.     

Sex difference in the saturable binding of low-density lipoprotein by liver membranes in ageing rats

It is well documented that women of child-bearing age tend to have lower serum low-density lipoprotein (LDL) concentrations than men. In order to explore the metabolic basis of this sex difference, we have compared the saturable binding of 125I-labeled LDL (d 1.02-1.05 g/ml) at 37 degrees C by liver membranes from healthy male and female Wistar rats of different ages (15-213 days). Woolf plots of saturable binding curves over the concentration range 15-65 micrograms LDL protein/ml were linear and compatible with a single class of binding sites. Maximum binding capacity (Bmax) was not significantly different in male and female animals of 15-19 days of age (respectively, 0.331 +/- 0.018 vs. 0.427 +/- 0.044 micrograms LDL protein/mg membrane protein, mean +/- S.E.). Thereafter, Bmax increased in females, reaching a peak of 0.635 +/- 0.042 micrograms LDL protein/mg membrane protein at 60 days. As no increase in Bmax occurred in males, values were significantly higher (P less than 0.02) in females than in males (by a mean of 61-117%) at all ages after 30 days. During ageing, serum cholesterol concentration changed reciprocally with Bmax in females (Pearson's correlation coefficient, r = -0.761, P less than 0.01) and remained essentially constant in males. The equilibrium dissociation constant for 125I-labelled LDL binding to the hepatic membranes was unaffected by both age and sex. These results provide evidence that the sex difference in the plasma total and LDL cholesterol concentrations is related, at least in part, to a greater mean LDL receptor density in the livers of females.     

The effect of exercise on circulating immunoreactive calcitonin in men

Moderate-duration exercise increases serum catecholamine and serum calcium levels and might as a result be also expected to increase the levels of circulating serum immunoreactive human calcitonin (HCT). To explore this possibility, HCT was studied during and after moderate duration symptom-limited dynamic exercise in 13 healthy males, mean age 28 +/- 6.9 (SD) years. The mean duration of exercise using the Bruce treadmill protocol was 14.1 +/- 2.2 (SD) minutes. The mean heart rate (HR) peaked at 185 +/- 6 (SD) bpm which was 96.1% of the predicted maximal HR for age. Values for HCT, uncorrected for changes in plasma volume, showed a minimal decrease in the recovery phase, whilst HCT corrected for changes in plasma volume did not alter during exercise or recovery. The serum parathyroid hormone (PTH) also did not change. At peak exercise, uncorrected but not corrected values for plasma noradrenaline, adrenaline and dopamine had increased significantly. Corrected plasma total calcium increased during recovery. In summary, dynamic weight-bearing moderate-duration exercise did not elevate HCT in healthy males.     

Obesity and low back pain

Obesity and low back pain (LBP) are common health problems among patients attending Primary Health Care (PHC) in general practice at the United Arab Emirates (UAE). The objective of this study was to determine whether obesity is associated with low back pain. A cross-sectional face-to-face interview questionnaire survey was conducted. The questionnaire was a modified version of the Roland-Morris Scale for evaluating back disability. The interviews were conducted in Arabic by qualified nurses. A multi-stage stratified sample 1,103 UAE national aged 25-65 years, who attended PHC clinics for any reason, were invited to participate but only 802 subjects were eligible to be included for the statistical analysis. The data were analyzed using univariate and multivariate statistical methods. Of the 802 subjects, 428 (53.4%) were males and 374 (46.6%) were females. The mean age of the males was 40.5 +/- 11.5 years and females was 38.2 +/- 10.5 years (p = 0.004). The mean BMI of the males was 26.4 +/- 7.4 and females was 27.8 +/- 5.6 (p = 0.002). The overall prevalence of LBP in the present study was 64.9% (95% confidence interval, 61.0-68.8) and respectively, 56.1% in males and 73.8% in females. The results revealed that there was association between BMI and some socio-demographic variables with the respect of with low back pain. Back pain had more influence on the life style habits on females than in males. Stepwise multiple regression analysis showed that only age (p < 0.0001), educational level (p = 0.001), gender (p = 0.002), place of living (p = 0.019), BMI (p < 0.0001), and housing condition (p = 0.02) had significant effect on the presence of LBP in patients. The present study showed that obesity is moderately associated with low back pain.