The Age Comparative Construct Validity of Speeded Cognitive Factors

The age comparative construct validity of speeded cognitive processing tasks was assessed using confirmatory factor analysis. Reaction time and card sorting tasks which varied in complexity, and which were assumed to assess aspects of memory, speed of information processing, and selective attention, were administered to 141 young (X = 24.9) and 142 elderly (X = 65.3) adults. All simultaneous models were rejected. Since the confirmatory analyses were unsuccessful, exploratory analyses were undertaken. Independent analyses yielded three factors as hypothesized for the young adults but unexpectedly five factors for the elderly adults. One extra factor for the older subjects appeared to represent strategy differences while the other may be an order artifact. Although the age comparative validity for the three primary factors seems to be supported, the results raised the possibility that speeded processing tasks with spatial content do not necessarily assess the same underlying constructs for adults at different points in the life span. These findings underscore the importance of establishing age comparative construct validity for cognitive processing tasks when the research goal is to compare the performance of diverse age groups.

Malaria on the Thai-Burmese border: treatment of 5192 patients with mefloquine-sulfadoxine-pyrimethamine

Multidrug-resistant falciparum malaria is a major health problem along the Thai-Burmese border. From July 1985 until December 1986 a total of 5192 patients with falciparum malaria (1734 males, 3458 females) from this area were given supervised treatment with the combination mefloquine-sulfadoxine-pyrimethamine (MSP). The radical cure rate, assessed 21 days after drug administration, was 98.4% for the first 1975 patients, and 98.8% when assessed at 28 days for the remaining 3217 patients. In 3.8% of cases, parasites were still detected in peripheral blood smears on day 7 after treatment but this had fallen to 0.27% by day 9. Adverse reactions among the first 1975 patients were: vertigo (7.5% of patients), vomiting (5.8%), epigastric pain (0.6%), and transient confusional state (one case). MSP is an effective and well-tolerated drug for the treatment of drug-resistant falciparum malaria; however, delayed parasite clearance may give a false impression of RII resistance.

Dual trophic effects of the alpha 1-adrenergic receptor in cultured neonatal rat heart muscle cells

The molecular signals regulating myocardial hypertrophy are unknown. We used a new model system to study this problem. Muscle cells from the neonatal rat ventricle were cultured in serum-free medium. Control cells did not change in size over time and did not show spontaneous contractile activity. Incubation with norepinephrine or epinephrine had two major trophic effects that developed over 1-2 days. The first was stimulation of muscle cell hypertrophy or increase in size. The second was induction of spontaneous contractile activity. The hypertrophic response was mediated through an alpha 1-adrenoceptor. The beating response required both alpha 1- and beta 1-adrenergic receptor stimulation. Alpha 1 stimulation alone produced enlarged cells that did not beat. Alpha 1 plus beta 1 stimulation induced contractile activity even when protein synthesis and hypertrophy were inhibited. Thus, the two alpha 1 responses could be dissociated, providing evidence for two independently-regulated cellular pathways for the dual alpha 1 trophic effects. One pathway leads to hypertrophy. The other, which requires concomitant beta 1 stimulation, controls the development of beating. Preliminary work raises the possibility that different products of inositol phospholipid hydrolysis might initiate the two alpha 1 trophic pathways. Other preliminary work suggests that the growth pathway is associated with the expression of specific genes and might reflect an action of the alpha 1-adrenoceptor on the cell nucleus. These studies define previously unsuspected trophic roles for the alpha 1-adrenergic receptor.

2-Hydroxyoestradiol acutely inhibits prolactin secretion from the superfused pituitary glands of normal female rats: evidence for a cyclical effect

Catecholoestrogens are naturally occurring metabolites of oestrogens which are found in brain tissue and for which a neuroendocrine role has been postulated. However, reports of their effects on prolactin secretion are ambiguous and as yet no defined function has been attributed to them. The effects of 2-hydroxyoestradiol (2-OHE2) and dopamine on the release of prolactin in vitro by perfused pituitary glands from normal adult female rats at different stages of the oestrous cycle have been investigated. The purity and stability of the 2-OHE2 preparation before and after exposure to pituitary tissue was confirmed by radioenzymatic assay and subsequent thin-layer chromatography. Dopamine (500 nmol/l, 100 nmol/l) was found consistently to suppress release by 60%; this effect was immediate and reversible upon removal of the dopamine. In contrast, the effects of 2-OHE2 (10 nmol/l, 100 nmol/l) were found to vary during the cycle. No effect on prolactin release was evident during either dioestrus or pro-oestrus, but during oestrus a similar, though less potent, suppression of prolactin secretion to that of dopamine was observed (35% suppression compared with controls). The cyclical variation in the suppressive effect of 2-OHE2 on prolactin secretion in the female rat is compatible with a postulated neuroendocrine role for this catecholoestrogen.

Management of obese patients with diabetes mellitus: comparison of advice education with group management

The purpose of our study was to compare the effect on diabetes control of group management with the advice-educational technique traditionally used in managing obese outpatients with poorly controlled non-insulin-dependent diabetes mellitus (NIDDM). Forty-one patients were randomly assigned to these two treatment programs, and 32 patients completed the 6-mo study. Initially, patients were seen for 1-h sessions at 1- and 2-wk intervals and later at 1-mo intervals. Patients were asked to do home blood glucose monitoring, decrease caloric intake, increase exercise, and if they were taking insulin, to adjust the dose to attain approximate euglycemia and to stabilize food and exercise patterns. The combined groups reduced mean +/- SD glycohemoglobin from 10.9 +/- 3.1 to 9.4 +/- 2.4% (P less than .05). Internal Health Locus of Control Scale was negatively and significantly correlated with initial and subsequent glycohemoglobin values (the more internal, the lower the glycohemoglobin). At the end of the study the patients in the group management program had significantly lower blood glucose levels than those given advice and education, but no significant differences in glycohemoglobin values or percentage overweight were observed. One patient had a normal initial glycohemoglobin, and only 4 patients had values in the normal range of 4-6.8% at the end of the study. Better management programs need to be developed for treating obese outpatients with NIDDM.

Oestrogen-2/4-hydroxylase activity in the rat brain during lactation and throughout the oestrous cycle

Oestrogen-2/4-hydroxylase activity was measured in whole brain, thalamus, amygdala, hypothalamus and pituitary gland of lactating rats and in whole brain of rats on different days of the oestrous cycle. Enzyme activity was increased in whole brain and in each of the brain regions examined (with the exception of the amygdala) in lactating rats. This increase in enzyme activity was associated with an increase in serum prolactin levels. During the oestrous cycle, enzyme activity in whole brain was higher on metoestrus and dioestrus than on pro-oestrus and oestrus. The decrease in enzyme on pro-oestrus was associated with an increase in both serum oestradiol and prolactin levels. These results are consistent with the hypothesis that changes in oestrogen-2/4-hydroxylase activity are associated with changes in prolactin and oestradiol secretion and may play a regulatory role in reproduction.

Severe Chlamydia psittaci sepsis in pregnancy

Two patients with severe chlamydial sepsis in pregnancy are described and compared with previously published case reports. The infections appear to have been zoonotic, the patients acquiring their infections as a result of exposure to enzootic abortion of ewes. This is an important but poorly recognised human infection which because of its severity in pregnancy deserves consideration in patients with an appropriate occupational history.

Cryopreservation of semen in men with testicular tumour or Hodgkin's disease: results of artificial insemination of their partners

After cryopreservation of semen from men with testicular tumours or Hodgkin's disease the success rate of artificial insemination of their partners was analysed. The cumulative probability of pregnancy at 6 months was 45%. The chance of pregnancy was greater when timing of ovulation was predicted with measurements of urinary luteinising hormone. Sperm density and sperm motility were also important in predicting the likelihood of pregnancy.

Plasma levels of apoprotein B in patients with diabetes mellitus: the effect of glycemic control

Patients with diabetes mellitus often exhibit abnormalities in plasma lipoprotein concentrations. We have examined the effect of glycemic control (as assessed by hemoglobin A1 levels) on the concentrations of plasma lipoproteins and apoproteins in 109 patients with type I diabetes mellitus. HbA1 levels showed positive correlations with plasma LDL-cholesterol levels (r = 0.31; P less than 0.002) and triglyceride levels (r = 0.41; P less than 0.002), but not with HDL-cholesterol levels. The strongest correlation was between HbA1 and plasma levels of apoprotein B (r = 0.57; P less than 0.001). We have also examined the effect of long-term improvement in glycemic control (achieved with insulin infusion pump therapy) on plasma lipoproteins in six patients with type I diabetes. Patients were followed for 5 to 12 months, with mean (+/- SD) HbA1c levels decreasing from 11.4 +/- 2.5 to 9.1 +/- 1.8. Most, but not all, patients showed reduction in plasma LDL-cholesterol levels and increase in plasma HDL-cholesterol levels, but these did not reach statistical significance. Only the decrease in plasma apo B levels was statistically significant (from 112 +/- 38 mg/dL before pump therapy to 91 +/- 33 mg/dL at the end of the follow-up, P less than 0.05). We conclude that glycemic control plays an important role in regulating the levels of plasma LDL-cholesterol and triglycerides in patients with type I diabetes. Apoprotein B is a particularly sensitive indicator to alterations in glycemic control. It is possible that tight glycemic control may have "antiatherogenic" effects through reduction of apo B levels.

Studies on oestrogen-2/4-hydroxylase activity in mammalian brain, using a radioenzymatic assay method

The activity of oestrogen-2/4-hydroxylase in brain tissue was studied using a radioenzymatic assay which controlled for non-specific formation of catechol oestrogen. The ontogeny of enzyme activity in male and female rat brain was examined between 1 and 70 days of age. Until 10 days of age, both sexes showed low enzyme activity. Between days 10 and 15 enzyme activity in the female significantly increased but was unchanged in the male. Male brain enzyme activity increased between days 15 and 20 whereas activity was unchanged in the female. Both males and females showed increases in enzyme activity between 20 and 25 days of age. Thereafter enzyme activity plateaued but at all ages between day 20 and day 70 male brain enzyme activity was significantly greater than in the female. A study of the distribution of the oestrogen-2/4-hydrolase in the sheep hypothalamus revealed that the stalk/median eminence had approx 10 times greater activity than either the anterior, medial or posterior hypothalamus. These findings are discussed in relation to sexual differentiation of the brain.

In vivo chloroquine-induced inhibition of insulin degradation in a diabetic patient with severe insulin resistance

We report on a 26-yr-old patient with an 11-yr history of insulin-dependent diabetes mellitus who exhibited insulin resistance with a requirement of up to 15,000 U of intravenous (i.v.) insulin/day. Attempts to diminish her insulin requirement by administration of sulfated insulin or Trasylol were unsuccessful, with the patient remaining resistant to subcutaneous (s.c.) and i.v. administration of pure pork insulin. Chloroquine phosphate therapy (500 mg twice a day) resulted in a decreased requirement for i.v. insulin (700 U/day as compared with the pretreatment requirement of 8400 U/day). Accelerated insulin degradation in s.c. fat tissue of the patient before treatment with chloroquine was demonstrated. This activity was decreased by 64% during chloroquine therapy. Inhibition of insulin degrading activity (IDA) during chloroquine therapy was associated with reductions in the leukocyte lysosomal enzymes alpha-galactosidase and hexosaminidase-A but not hexosaminidase-B and beta-glucuronidase. This study constitutes the first reported use of chloroquine for treatment of insulin resistance as a result of accelerated insulin degradation, and it provides evidence of the effectiveness of this agent in this rare condition.

Modified Forssell's operation for crib biting in the horse

Thirty-five horses with a history of crib biting or wind sucking were treated with a modification of the Forssell procedure. The technique involved bilateral neurectomy of the ventral branch of the accessory nerve combined with excision of a portion of the omohyoideus, sternohyoideus, and sternothyroideus muscles. Twenty horses became free of the vice, while in 11 there was a noticeable reduction in frequency of the vice. Four horses returned to crib biting/wind sucking at the same intensity as before surgery. The observation time following each operation was at least 12 months. Complications from wound healing were minimal, and cosmetic results were considered excellent in most horses. It was concluded that this modified surgical procedure produced a better result than neurectomy alone, without the disfigurement of Forssell's procedure.

Critical review of international standards for respiratory protective equipment - I. Respiratory protective equipment for particulate-laden atmospheres

The standards for respiratory protective equipment (R.P.E.) from eleven countries and standards organizations were grouped according to type as particulate removing, gas and vapor removing, airline (fresh air hose and compressed air types), and self-contained breathing apparatus (open circuit and closed circuit). Each group of standards was further divided into specification and performance requirements. This paper is one in a series of three that highlights and critically reviews international respirator standards; it deals specifically with R.P.E. for protection against particulate-laden atmospheres. Great Britain, Australia, European Committee for Standardization (CEN), France, South Africa, Italy, Spain, New Zealand, Scandinavia, Japan, and Germany have standards for R.P.E. against particulate-laden atmospheres. Tabular summaries and accompanying discussion of national requirements are presented in the following categories: solid and liquid aerosol removal efficiency, clogging, and rough usage. Large differences and some notable omissions exist among standards. For example, the protection capacity of the filter can be tested by using solid particulate or liquid challenge aerosols. The majority of the countries evaluate protection capacity using solid particulate aerosols, while the remainder use both solid and liquid or liquid aerosols only. Other differences in filter testing deal with the composition of the test aerosol and the characteristic of the filter measured. The initial penetration or the penetration of the filter as it is being loaded over a specified period of time can be measured. In the latter case penetration is averaged over the test period and the degree of protection is assessed only for that overall time period; information is not provided concerning the protection afforded by the filter in the earlier stages of use.

Critical review of international standards for respiratory protective equipment - II. Gas and vapor removal efficiency and fit testing

The purpose of a Respiratory Protective Equipment (R.P.E.) standard is to assure that a minimum level of performance is reached by the respirator. Standards from a number of countries and standards organizations require that certain specifications are met in construction and that respirators be evaluated by specific performance tests. This is the second of three critical review papers related to respirator standards. We here summarize in tabular form, compare and critically review how the different countries or standards organizations test respirators designed for protection against gases and vapors for leakage due to improper fitting of the respirator facepiece and gas and vapor removal efficiency of the cartridge/canister. Two general aspects as they relate to removal capacity testing are discussed. The first issue deals with the selection of test gases and vapors that best represent the sorptive behavior of a class or group of compounds. The second issue deals with the extrapolation of laboratory testing under rigidly specified conditions to conditions of actual use. Fit testing varies from country to country. The fit testing conditions specified in the various standards are summarized along with a discussion of test material selection, the test panel selection, and the range of controlled test activities.

Critical review of international standards for respiratory protective equipment - III. Practical performance tests

This paper, the third in a series of papers devoted to review of international standards for Respiratory Protective Equipment (R.P.E.), summarizes in tabular form, compares, and critically reviews standards of different countries or organizations pertaining to practical performance tests (Man Tests). There are similarities, differences and omissions in the national standards that deserve attention. Of the countries or organizations that require Man Tests on particulate and/or gas and vapor respirators, none described in detail the tests to be performed. For example, CEN requires that Man Tests be conducted on gas/vapor respirators under realistic conditions to determine imperfections that cannot otherwise be determined by other performance tests, but does not stipulate the testing procedure. With respect to fresh-air hose, compressed-air line and self-contained breathing apparatus R.P.E., only Great Britain and CEN present specific Man-testing requirements in detail. Man Tests for all types of R.P.E. have a specific purpose: to determine any imperfections in, or malfunction of the apparatus under simulated work conditions. One major difference, however, is in the kind of work simulation activities required. In the testing of fresh-air hose and compressed-air line respirators, for instance, CEN describes in great detail, a variety of activities to be conducted. Great Britain merely states that the subjects shall work in practical conditions. Another important disparity relates to the conditions under which the test is to be performed. For example, CEN requires a heavy-duty test and a cooled chamber test, as well as tests under normal and low temperature conditions. Great Britain, on the other hand, requires only the latter two tests. Still other differences lie in the kinds of medical surveillance required during testing and the evaluation criteria used for assessment.

The effects of blood glucose testing versus urine sugar testing on the metabolic control of insulin-dependent diabetic children

Glycosylated hemoglobin A1c was measured in 43 insulin-dependent diabetic children before and after training in blood glucose testing. These measurements were compared with those obtained from a group of matched controls who tested urine sugars for the same period. Mean HbA1c measurements for the blood glucose testing group were significantly improved at 6 mo after training in blood glucose testing, and were significantly lower than those measured in the urine sugar testing group. However, HbA1c levels in the blood glucose testing group were well above levels for nondiabetic persons, and were generally higher than those reported for adult insulin-dependent diabetic persons following training in blood glucose testing. Explanations for this difference were considered. It was noted that 81% of the trained children accepted and continued to use blood glucose testing for at least 9 mo after training.

Prevalence of hypertension in semi-skilled manual workers

This study demonstrates a high prevalence of hypertension (43,9%) in a population of unskilled manual workers. No differences were detected in the prevalence rates for two ethnic groups. The importance of age standardization for comparison of data with other studies of an age-linked phenomenon such as hypertension is stressed. Blood pressure was higher in workers who had worked their daily shift than in those who had not worked a shift. These findings might be explained by means of an hypothesis linking stress at work with hypertension. The literature relevant to this hypothesis is outlined.

What is the evidence for retrieval problems in the elderly?

To determine whether older adults experience particular problems with retrieval, groups of young and elderly adults were given free recall and recognition tests of supraspan lists of unrelated words. Analysis of number of words correctly recalled and recognized yielded a significant age by retention test interaction: greater age differences were observed for recall than for recognition. In a second analysis of words recalled and recognized, corrected for guessing, the interaction disappeared. It was concluded that previous interpretations that age by retention test interactions are indicative of retrieval problems of the elderly may have been confounded by methodological problems. Furthermore, it was suggested that researchers in aging and memory need to be explicit in identifying their underlying models of error processes when analyzing recognition scores: different error models may lead to different results and interpretations.

Effect of serotonin depletion induced by p-chloroamphetamine on changes in rats' activity levels-produced by lithium

The role of serotonin (5-HT) transmission in the production of changes in rats' activity levels induced by 0.15 and 1.50 mEq/kg LiCl was assessed by selectively depleting 5-HT brain levels with p-chloroamphetamine prior to chronic administration of LiCl for 21 days. While p-chloroamphetamine pretreatment decreased 5-HT levels by 56%, irrespective of the fact that the animals had been administered either saline, 0.15, or 1.50 mEq/kg LiCl for 21 days, it did not alter the effects that each LiCl dose alone that on activity levels. Both LiCl administrations produced an 18% increase in 5-HT levels in rats pretreated with saline, yet diametrically opposed effects on activity levels. A parallel is drawn between these biochemical findings and previously reported data indicating that both LiCl doses produce an improvement in selective attention, yet opposed effects on rats' activity levels. The hypothesis that 5-HT transmission might be crucially involved in mediating the dose-independent effect of lithium on selective attention is proposed for future research.

Pimozide attenuates conditioned taste preferences induced by self-stimulation in rats

Conditioned taste preferences (CTPs) were observed in rats who drank flavored water followed by a session of self-stimulation. Control groups that did not self-stimulate did not exhibit CTPs. Other taste/SS pairings conducted under the influence of the dopamine receptor antagonist pimozide (0.1 or 0.3 mg/kg, IP) resulted in dose-dependent reduction in the size of the CTPs. No evidence of any aversive effects (conditioned taste aversions) of the pimozide treatment were observed in the no-stimulation control groups. These data suggest that, in addition to its effects on responding, low doses of pimozide reduce the rewarding properties of self-stimulation.

2-hydroxyoestradiol inhibits prolactin release from the superfused rat pituitary gland

The effects of 2-hydroxyoestradiol (2OH-OE2), dopamine, oestradiol-17 beta and 2OH-OE2 plus dopamine on prolactin and LH release from the male rat pituitary gland were examined in vitro. 2-Hydroxyoestradiol reduced prolactin secretion by 51% at 10(-10) mol/l and by 34% at 10(-7) mol/l, while oestradiol-17 beta had no effect at these doses. Dopamine alone (5 x 10(-7) mol/l) decreased prolactin released by 58%, 2OH-OE2 plus dopamine produced a similar inhibition of 60%. No significant effect on LH release was observed throughout.

Diabetes responsive to intravenous but not subcutaneous insulin: effectiveness of aprotinin

Patients with diabetes that is insensitive to subcutaneous insulin but sensitive to intravenous insulin have recently been described. We have studied this phenomenon is five female diabetics (14 to 31 years of age) who required excessive amounts of insulin (2.5 to 30.0 units per kilogram of body weight per day) to avoid recurrent ketoacidosis. Known causes of insulin resistance were excluded. All patients had normal responses to conventional doses of intravenous insulin (0.35 to 0.9 unit per kilogram per day). Four patients required continuous intravenous infusion of insulin for one to six months. When a mixture of aprotinin (a protease inhibitor) and regular porcine insulin was given subcutaneously, conventional doses (0.7 to 1.4 units per kilogram per day) produced euglycemia; plasma levels of free insulin rose, and ketonuria disappeared. Four patients had episodes of spontaneous, severe hypoglycemia before and during aprotinin therapy, necessitating continuous infusion of glucose for two to 14 days. Although no insulin was administered, hyperinsulinemia (50 to 2000 muU of free insulin per milliliter [359 to 14,350 pmol per liter]) was present. These findings suggest excessive degradation or sequestration of insulin at the site of injection.

The effect of weight loss on sex steroid secretion and binding in massively obese women

We have previously reported increased testosterone and androstenedione concentrations and decreased sex hormone binding globulin (SHBG) concentrations in the plasma of massively obese women. We now report that these plasma hormone concentrations return to normal in twelve of the same women after substantial weight reduction and these changes are associated with more normal menstrual cycles. We conclude that body weight and fat are important determinants of sex steroid secretion and binding and thus influence menstrual function.

The natural history of retinopathy in insulin-dependent juvenile-onset diabetes

We determined the cross-sectional natural history of retinopathy by prospective study of 461 insulin-dependent juvenile-onset diabetics. In so doing, we compared the sensitivity of ophthalmoscopy, photography, and fluorescein angiography in detecting retinopathy. Photography was far more reliable than ophthalmoscopy in detecting early retinopathy and equivalent to angiography. Retinopathy was not present at diagnosis of diabetes. After a lag period, the prevalence of retinopathy rose in sigmoidal fashion, reaching 50% at just over seven years duration, and asymptotically approaching 90% at 17--50 years. Proliferative retinopathy was first seen at 13 years duration, and its prevalence rose to 26% at 26--50 years. From the natural history we computed the dimensions of a proposed clinical trial to test the effect of tight metabolic control in prevention of retinopathy.

Lithium increases selective attention in rats

Both 0.15 and 1.50 mEq/kg lithium chloride were found to increase inspective exploration (i.e. behaviors directed at the close examination if discrete stimuli in a new environment) in rats. In addition, 1.50 mEq/kg LiCl decreased general activity, irrespective of the characteristics of the experimental situation. The dose-independent increase in inspective exploration was interpreted as increased selective attention to salient stimuli which provide information about the environment. This hypothesis predicts that both doses of lithium should decrease distractibility by irrelevant stimuli. This prediction was confirmed in a second experiment, in which the ability of a tone to suppress drinking by thirsty rat was reduced by both doses of lithium. A two-factor model of lithium's action in rats is proposed. Lithium produces a dose-independent improvement of selective attention to stimuli which provide detailed information about the environment. In addition, lithium exerts dose-related effects on activity levels: a mild increase in activity with dose in the 0.15-0.20 mEq/kg range and a decrease in activity with doses of 0.50 mEq/kg and higher.

Lithium induces dose-related increases and decreases in activity levels in the rat

The effect of intraperitoneal lithium chloride on the activity levels of rats was measured by counting photocell interruptions in an open field. Treatment with 0.15 mEq/kg increased activity and 1.5 mEq/kg decreased activity. In a second experiment behavioral observations were added to the photocell counts of open field activity, and the increase observed with 0.15 mEq/kg LiCl in Experiment 1 was compared with the increase in open field activity produced by 0.4 g/kg ethanol. The two drugs produced similar increases in cell counts and walking, and similar decreases in sitting and sniffing. Lithium produced significantly more rearing and behavior directed at the cage than did ethanol. Following Johnson's hypothesis of lithium action, these findings are discussed within the context of lithium-induced changes in responsiveness to the environment. We suggest that, at 0.15 mEq/kg, lithium chloride might increase reactivity to the environment.

Age-related changes in the degradation of thyrotrophin releasing hormone by human and rat serum

Changes in the rate of in-vitro degradation of thyrotrophin releasing hormone (TRH) in serum as related to age have been investigated in the rat and man. In rats, no inactivation was found up to the age of 15 days but therafter an age-related increase in inactivation was detected with approximately 75% inactivation in 60 min at 40 days and reaching a maximum of 88-93% inactivation in adult male and female animals. The human serum samples studied (both male and female) showed a similar but less clear-cut pattern of inactivation of TRH compared with that found in the rat. A physiological role for these age-related changes in the degradation of TRH remains to be established but it has been concluded that the changes observed in both rat and man may be associated with growth and development, possibly by facilitating feedback control of thyrotrophin secretion through the degradation of TRH.

Further studies on the inactivation of thyrotrophin releasing hormone (TRH) by enzymes in the rat hypothalamus

Thyrotrophin-releasing hormone (TRH) is known to be inactivated by enzymes present in the rat hypothalamus. To make a further study of the enzymes' action on the tripeptide, synthetic TRH was incubated with two hypothalamic subcellular fractions. By using a direct radioimmunoassay for TRH, the tripeptide was shown to be rapidly degraded by both supernatant and particulate fractions, with higher enzyme activity in the particulate fraction. Of several biologically-active peptides tested, only luteinizing hormone-releasing hormone was found to inhibit TRH inactivation; bacitracin, a polypeptide antibiotic, was also effective in inhibiting inactivation. Enzyme activity was highest in the middle hypothalamic area and lowest in the posterior hypothalamic area. Thin layer chromatography of the products of enzyme cleavage revealed the formation of only deamidated TRH in the supernatant fraction and the constitutent amino acids (pyroGlu, His, ProNH2) and histidylproline-diketopiperazine by the particular fraction, suggesting the presence of an amidase in the supernatant and two peptidases in the particulate fractions. These properties of the enzymes inactivating TRH may indicate that the enzymes could be of importance in regulating the endocrine and other functions attributed to this hypothalamic regulatory hormone.

Abnormal sex steroid secretion and binding in massively obese women

We have measured the plasma concentrations of sex steroids and sex hormone-binding globulin (SHBG) in twenty-three massively obese women and ten age-matched lean female volunteers. In the obese women increased plasma testosterone (obese 3.2 +/- 0.5 nmol/l controls 1.7 +/- 0.5 nmol/l, P less than 0.3) and androstenedione concentrations (obese 9.7 +/- 1.2 nmol/l, controls 4.4 +/- 0.6 nmol/l, P = less than 0.01) an increased ratio of oestrone:oestradiol (obese 2.4 +/- 0.4, controls 1.0 +/- 0.1, P = less than 0.1) and decreased SHBG levels (obese 30 +/- 4 nmol/l, controls 60 +/- 8 nmol/l, P = less than 0.001) were found. Obesity differed from the polycystic ovary syndrome (in which a similar pattern of changes of sex steroid concentrations and binding are seen) in that it was associated with normal increases in serum luteinizing hormone (LH) follicle stimulating hormone (FSH) levels in response to the administration of LHRH. We conclude that the common occurrence of menstrual abnormalities in obesity results from abnormal secretion and binding of sex steroids. In addition, the unaltered secretion of LH and FSH in the presence of such changes is evidence for a disorder of hypothalamic function.

Evidence for existence of two types of massive obesity

The responses of growth hormone, cortisol, and prolactin to symptomatic hypoglycaemia during an intravenous insulin tolerance test were measured in 20 massively obese subjects and six lean volunteers. In 11 subjects, who had been obese since early childhood, an impaired growth-hormone response and an absent prolactin response were found. In the nine other obese subjects, however, the growth-hormone and prolactin responses were not significantly impaired. Seven of these subjects had become obese either as a teenager or during adult life. These findings suggest the existence of two types of human obesity similar to those found in rodent models. In one the disorder of hypothalamic function may be due to a basic, possibly genetic abnormality, while in the other it is acquired.

Ultrastructural localization of TRH-like immunoreactivity

With the peroxidase-antiperoxidase (PAP) method TRH-like immunoreactivity (TRH-LI) was observed in certain neurons of the central nervous system. Their distribution agreed well with findings previously obtained with the indirect immunofluorescence technique. At the ultrastructural level electron-dense precipitates representing TRH-LI were observed in so-called large dense core vesicles, which were localized both in the cytoplasm of some hypothalamic neuronal cell bodies, as well as in boutons in the hypothalamus and spinal cord. The boutons often seemed to form axo-somatic or axodendritic synapses.

Performance effects with repeated-response measures during pimozide-produced dopamine receptor blockade

Rats were trained to lever-press for either food reward or brain-stimulation reward on a continuous reinforcement schedule. Following training each animal was extinguished (i.e. tested with the reward omitted) under the influence of pimozide (0.25 mg/Kg or 0.5 mg/Kg). Pimozide produced a dose-dependent reduction in the mean number of responses to extinction made by rats in ecach group. In a second experiment, pimozide produced a similar dose-dependent decrease in the performance of a naturally occurring behavior (nose-poking) that had never been associated with reward. These data suggest that dopamine receptor blockade can produce a perofrmance deficit in situations which require repetitive responses, and that this deficit is unrelated to the presence or absence of reward.

HLA-DR specificities among black Americans with juvenile-onset diabetes

To study the association of histocompatibility (HLA) genes in black persons with juvenile-onset diabetes, we determined HLA-A, HLA-B, HLA-C and HLA-DR specificities in 40 black Americans with this disease and in 67 unaffected black Americans. Marked increases in the frequencies of HLA-DRw3 and HLA-DRw4 were found in the patients as compared with the unaffected persons: DRw3 was found in 72.5 per cent of patients versus 29.9 per cent of unaffected persons and DRw4 in 72.5 per cent versus 25.4 per cent (corrected P values each less than 0.0007). DRw2 was not found in any of the patients but was present in 26.9 per cent of unaffected persons (P corrected less than 0.035). There is thus a negative correlation between this specificity and juvenile-onset diabetes. By contrast, no meaningful differences were found in the frequencies of A, B, or C locus antigens. Studies in white persons with juvenile-onset diabetes have suggested that the reported HLA-B associations are due to HLA-D region specificities, and our results also support the premise that D region specificities are the primary associations with juvenile-onset diabetes.

Age-dependent changes in the inactivation of thyrotrophin-releasing hormone by different areas of rat brain

Age-dependent changes in the inactivation of thyrotrophin-releasing hormone (TRH) were investigated in two subcellular fractions prepared from hypothalamus, thalamus, cortex and cerebellum of male rats. It was found that, in both supernatant and particulate fractions from the four brain areas, enzyme activity increased to a peak at 10-25 days of age and then decreased gradually until adult levels were reached. The changes in TRH degradation observed may be related to alterations in hypothalamic TRH content with age and to maturation of the tripeptide's putative neurotransmitter/neuromodulator function.