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Biomedical subjects

S Hendricks

Publications and source records attributed to S Hendricks.

34 records · Page 2Linked to original sources
PubMed1977

Metabolic clearance and plasma half disappearance time of exogenous gonadotropin releasing hormone in normal subjects and in patients with liver disease and chronic renal failure.

The metabolic clearance rate (MCR) and half disappearance time (t 1/2) of gonadotropin releasing hormone (GnRH) has been measured during and after cessation of constant infusion of exogenous GnRH. Studies were performed on normal subjects and patients with severe renal and liver disease. GnRH was quantified by a sensitive and specific radioimmunoassay which does not measure GnRH fragments. The MCR of GnRH in normal subjects was 1640+/-59.7 ml/min (23.7+/-1.8 ml/min/kg), similar to values found in 4 patients with liver disease. However in chronic renal failure an MCR of only 631+/-62 ml/min (9.1+/-0.7 ml/min/kg) was obtained. The t1/2 of GnRH after infusion was linear for 8-10 min, after which a much slower component was observed. The t1/2 of the first component ranged from 5.5 to 8 min in normal subjects, 6.5-8 min in patients with liver disease but prolonged (12-16.5 min) in patients with renal failure. It would appear that GnRH is cleared rapidly in normal subjects, that moderate liver dysfunction does not alter this, but that impaired renal function significantly prolongs the t1/2 and lowers the MCR. The kidney might be an important catabolic organ for infused GnRH; alternatively, uremia might impair catabolism non-specifically.

Adult↗
PubMed1976

Free radical theory of aging: effect of dietary fat on central nervous system function.

Free radical reactions have been implicated in aging. A rise in the level of random free radical reactions in a biologic system might have a greater effect on the central nervous system (CNS) than elsewhere, partly because of the presence of glial cells and the unique connections between neurons. To evaluate this possibility, some animal experiments were conducted. The initial experiment involved old male Sprague-Dawley rats fed (since shortly after weaning) with semisynthetic diets characterized by fat differing in amount or degree of unsaturation. The number of errors made in a Hebb-Williams maze was determined and found to be higher as the amount or degree of unsaturation of the fat was increased. Likewise rats aged 6 and 9 months, fed semisynthetic diets containing 20 percent by weight of lard, oleinate, or safflower oil +alpha-tocopherol performed significantly better in a discrimination learning situation (Skinner box) than did rats fed a diet containing 20 percent by weight of safflower oil. The diets employed in these studies did not have a significant effect on the mortality rates. These results are compatible with the possibility that enhancing the level of lipid peroxidation has an adverse effect on the CNS, out of proportion to the effect on the body as a whole, as measured by the mortality rate.

Aging↗
PubMed1976

Plasma gonadotropin and gonadotropin-releasing hormone levels after intranasal administration of gonadotropin releasing hormone.

Intranasal administration of gonadotropin hormone (GnRH) in doses ranging from 2-4 mg produced a consistently prolonged LH response in patients with secondary amenorrhea. In 4 cases, a delayed secondary rise occurred. A similarly prolonged FSH response was observed in the majority of patients. Six hours after intranasal GnRH, FSH and LH values were well above basal levels and were higher than those observed at a similar interval after intravenous GnRH. Plasma GnRH levels after intranasal administration failed to achieve the high peaks found after the intravenous route but maintained elevated levels for at least an hour and often longer. Despite the much lower plasma GnRH levels, intranasal GnRH produced a sustained effect on LH and FSH secretion, greater than GnRH given by the intravenous route.

Administration, Intranasal↗
PubMed1975

A specific radio-immunoassay for gonadotrophin-releasing hormone.

A specific antiserum has been made to synthetic gonadotrophin-releasing hormone (GnRH) conjugated to keyhole limpet haemocyanin and appears to be directed against amino acids 6-8 of this decapeptide. This has allowed the development of a radio-immunoassay for GnRH sensitive to 5 picograms per tube. Although it is easily measurable in hypothalamic extracts, we have failed to detect GnRH in plasma and urine from normal subjects and menopausal women.

Animals↗
PubMed1975

Fasting blunts the TSH response to synthetic thyrotropin-releasing hormone (TRH).

Thyrotropin (TSH) responses to intravenous thyrotropin-releasing hormone (TRH) were studied in 9 men after 12 and 36-h fasts separated by more than a week and performed in random order. The TSH, basally and in response to TRH, was significantly lower after the 36-h fast compared to that after 12 h. The mechanism for this effect is not clear, but may be related to the altered hormonal or fuel status associated with prolonged fasting.

Fasting↗
PubMedDate not supplied

Intraventricular insulin suppresses the acoustic startle response in rats.

We and others have previously reported that the hormone insulin alters brain noradrenergic function at the synaptic and molecular levels. In the present study, we examined the in vivo effect of insulin (administered chronically via osmotic minipumps at a dose of 5 mU/day into the third cerebral ventricle) on the acoustic startle response. Rats receiving chronic intraventricular insulin had a significantly reduced startle response relative to vehicle-treated controls (i.e., 47 +/- 21% of baseline control startle response). Because our previous findings suggest that on an acute basis, insulin may enhance endogenous noradrenergic activity by inhibiting norepinephrine reuptake, we speculate here that the chronic effect of insulin is similar to that of the noradrenergic reuptake blocker, desipramine, which has been reported to decrease baseline startle performance.

Acoustic Stimulation↗
PubMedDate not supplied

Effect of recall on reporting of at-work injuries.

Difficulty with recall of injuries can result in underestimates of injury incidence and bias in risk estimates in surveys based on self-reports. This study examined the effect of recall on estimates of at-work injury obtained from the 1988 Occupational Health Supplement of the National Health Interview Survey, which used a 12-month reference period for injury reporting. Estimates of annual injury incidence were obtained from recall intervals of increasing time between injury date and interview date. A linear model was fitted to these data to estimate the incidence rate expected if all respondents had been interviewed within 4 weeks of injury. The incidence rate for all at-work injuries adjusted for recall was 32 percent higher than the unadjusted rate. The percent increase in the estimates differed among demographic groups and by injury severity. Rate ratios comparing risk of injury between some demographic groups were also affected by adjustment for recall. A 12-month or longer reference period is frequently used in injury surveys in order to obtain an adequate number of injuries for analysis. A shorter reference period is desirable to provide more accurate estimates; however this necessitates increasing the size of the sample used in the survey. This increased cost must be balanced against the need for accurate information on injury.

Adolescent↗