Impaired hypothalamic control of prolactin secretion in massive obesity

Intravenous insulin tolerance tests and thyrotropin-releasing hormone (T.R.H.) stimulation tests were performed in nine massively obese women and six lean female controls and the prolactin, growth hormone, and cortisol responses were measured. A combined pituitary function test (insulin, T.R.H., and gonadotropin-releasing hormone) was performed in eleven other massively obese women. In the obese women to whom insulin was given separately there was no prolactin release, and growth hormone and cortisol responses were impaired. T.R.H. stimulation produced a prolactin response which was subnormal. These changes were not apparent in the obese women in whom a combined pituitary function test was performed. The results suggest an alteration of hypothalamic function in massive obesity.

Effects of catecholamine manipulations on three different self-stimulation behaviors

Rats with self-stimulation electrodes in the medial part of lateral hypothalamus (LH) or in the lateral part of LH were trained to bar press, to run in a continuous, square-shaped runway, and to move their tails from side to side while otherwise restrained, all using LH stimulation on an FI 2 sec schedule as the reinforcement. At low doses of pimozide (a dopaminergic blocker) or of FLA-57 (a dopamine beta-hydroxylase inhibitor) different effects on rates of responding were observed on each of the three tasks at the two electrode placements, indicating that the rate reductions were not the results of specific performance effects of the drugs. The patterns of rate changes suggested that the effects of LH stimulation on behavior in the runway were primarily, but not exclusively mediated by a dopaminergic system; that the effects of LH stimulation on tail movement were primarily, but not exclusively mediated by a noradrenergic system; and that the effect of LH stimulation on bar pressing was mediated by both, or either of these substrates. These results suggest that the reinforcement of behavior by LH stimulation is flexibly mediated by at least two different neural systems.

Effects of catecholamine manipulations on three different self-stimulation behaviors

Rats with self-stimulation electrodes in the medial part of lateral hypothalamus (LH) or in the lateral part of LH were trained to bar press, to run in a continuous, square-shaped runway, and to move their tails from side to side while otherwise restrained, all using LH stimulation on an FI 2 sec schedule as the reinforcement. At low doses of pimozide (a dopaminergic blocker) or of FLA-57 (a dopamine beta-hydroxylase inhibitor) different effects on rates of responding were observed on each of the 3 tasks at the 2 electrode placements, indicating that the rate reductions were not the results of specific performance effects of the drugs. The patterns of rate changes suggested that the effects of LH stimulation on behavior in the runway were primarily, but not exclusively mediated by a dopaminergic system; that the effects of LH stimulation on tail movement were primarily, but not exclusively mediated by a noradrenergic system; and that the effect of LH stimulation on bar pressing was mediated by both, or either of these substrates. These results suggest that the reinforcement of behavior by LH stimulation is flexibly mediated by at least 2 different neural systems.

Effect of pimozide on the improvement in learning produced by self-stimulation and by water reinforcement

When rats self-stimulate immediately after the training trial of an appetitive task their performance on a retention test is improved the next day. In the present study, this improvement was blocked by pretraining injections of pimozide, a dopaminergic blocker. In a second experiment, injections of pimozide retarded learning on the same task when the learning was reinforced by drinking water, but had no effect on learning which occurred in the absence of a reinforcer. The data made the hypotheses that the animal's behavior was a result of an action of primozide on sensory or motor mechanisms, or that the drug produced state-dependent effects, highly unlikely. We concluded that neural systems involving dopamine mediate an effect of reinforcing events on behavior.

Effects of lesions of various medial forebrain bundle components on lateral hypothalamic self-stimulation

Unilateral lesions of various medial forebrain bundle components were assessed for their effects on lateral hypothalamic self-stimulation. Damage of areas containig nigrostriatal dopaminergic or ascending noradrenergic neurons had negligible effects on bar pressing, tail moving and alley running for hypothalamic stimulation. Lesions which appeared to destroy most or all of the catecholaminergic fibers in the posterior medial forebrain bundle virtually eliminated reinforced bar pressing and tail moving, but only partially suppressed alley running. The results suggest that brain stimulation reinforcement of the bar press and tail movement tasks depends upon the integrity of neural tissue in the area of the catecholaminergic pathways of the medial forebrain bundle, but not upon specific dopaminergic or noradrenergic systems. The data further suggest that the reinforcement of alley running is at least partially mediated by different neural tissue (possibly non-catecholaminergic) at the level of the posterior medial forebrain bundle lesions.

Circulating immune complexes after repeated halothane anaesthesia

A patient developed hepatitis after receiving three halothane anaesthetics in 22 days. Twenty-four hours after the onset of jaundice she developed an acute serum sickness syndrome with polyarthralgia, proteinuria, and transient impairment of renal function. Serum concentrations of complement components C1q, C4, and C3 were substantially reduced, and immune complexes capable of activating the complement system via the classical pathway were present in the serum and synovial fluid. A metabolite of halothane was associated with these complexes. Fourteen months after exposure to halothane her lymphocytes were stimulated in vitro by this metabolite. The conditions under which stimulation occurred were unusual--namely, a 7S fraction of the serum, presumably IgG, was necessary. Our results provide strong evidence that halothane may be immunogenic and that its immunogenicity is dependent on the non-covalent binding of one of its metabolites to plasma proteins.

Painless ascites in systemic lupus erythematosus

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The reinforcing action of morphine and its paradoxical side effect

Rats were trained to run down a runway for food in the goal box, and were then tested with one trial per day for 5 days. After running in the runway and eating in the goal box each rat was injected with a drug and returned to the empty goal box for 50 min. Over the 5 trials, rats that received morphine sulphate increased their running speed approximately 400% while the amount of food they ate in the goal box decreased to about 70% of baseline values. The running speed of rats that received lithium chloride decreased to about 30%, while the amount of food they ate decreased to less than 10% of baseline. These two variables did not change for rats that received saline injections. The large increases in running speed observed in the rats that received morphine injections were attributed to an interaction (but not simple summation) between the positive reinforcing effects of morphine and food. The accompanying paradoxical decrease in amount eaten was discussed in terms of the complex pharmacological properties of morphine and it was suggested that morphine may have a reinforcing effect on behavior that is independent of its affective properties.

Effect of thyroid status on the thyrotrophin-releasing hormone-degrading activity of rat serum

The TRH-degrading activity of rat serum in vitro is five times more potent than that of human serum. In rats, it is significantly reduced in hypothyroidism (thiouracil-induced) and significantly increased in hyperthyroidism (T3 or T4-induced). This suggests a possible role in the regulation of adenohypophysial-thyroid function which is probably, in turn, dependent on thyroid hormone, rather than TSH, levels.

The role of physical dependence in animal models of human alcoholism

This paper critically examines the concept that physical dependence is a necessary attribute for animal models of human alcoholism. On the basis of a review of the literature, it is argued that, since the production of physical dependence requires the presence of continuous high blood-alcohol levels, and since the production of preference for alcohol requires intermittent presentation of alcohol, the two cannot, in principle, be established in the same organism at the same time. It is further argued that physical dependence does not play a role in the development of high alcohol intake in animals. The implications of these observations for human alcoholism are discussed.

Strength-duration analysis of the organization of reinforcement pathways in the medial forebrain bundle of rats

Strength-duration curves were determined for electrical self-stimulation of the brain in rats implanted with lateral hypothalamic electrodes. The rats self-stimulated in different behavioral situations which required them to make different responses, and the parameters of the strength-duration curves determined in each situation were compared. The comparisons suggested that two distinct groups of neurons were involved in the mediation of brain stimulation reinforcement of the bar pressing response, and that one of these groups was primarily involved in mediating the reinforcement of an alley running response, while the other group primarily mediated the reinforcement of a responses suggested that the nature of the response a rat is response a rat is required to perform determines the exact combination of neurons from the two groups which participate in mediating the brain stimulation reinforcement of the task. The possible functional significance of these two neuron groups was discussed.

Hypothalamic inactivation of thyrotrophin-releasing hormone

Following the demonstration of peptidases in the rat hypothalamus which inactivate thyrotrophin-releasing hormone (TRH), a sensitive and specific radioimmunoassay for the releasing hormone was used to investigate the presence of similar peptidases in the rabbit hypothalamus. TRH was found to be rapidly inactivated by supernatant and particulate hypothalamic fractions, with higher peptidase activity in the supernatant than in the particulate fraction. An optimum pH of 7.3 within physiological limits was obtained for the enzymes in both the fractions examined. The results obtained confirm that the rabbit hypothalamus contains enzymes capable of inactivating TRH, and since it has been found that such peptidases interfere with studies on TRH biosynthesis, it is possible that the peptidases may play a part in controlling the releasing hormone's production. The specificity of the antiserum used in the radioimmunoassay has also suggested that the peptidases may cleave the C-terminal-ProNH2,-NH2 or both from the TRH molecule to cause inactivation.

Distribution of thyrotropin-releasing hormone (TRH) in the central nervous system as revealed with immunohistochemistry

With the indirect immunofluorescence technique TRH-containing nerve terminals were found in the medial part of the external layer of the median eminence, the dorsomedial nucleus and the perifornical area, in extrahypothalmic nuclei such as nucleus accumbens, the lateral septal nucleus and in several motor nuclei of the brain stem and spinal cord. These findings suggest that TRH may act both as a hormone, released into the portal vessels, as well as a neurotransmitter or modulator, released at synapses in discrete regions of the brain and spinal cord.

Clearance and identification of thyrotrophin releasing hormone in human urine after intravenous injections

The urine clearance of TRH after intravenous injection in man has been measured by radioimmunoassay. Between 4.4 percent and 10.7 percent of the dose was excreted within 90 min, the majority within 30 min. The TRH excreted was immunochemically and chromatographically indistinguishable from synthetic TRH and was inactivated by plasma enzymes with the same kinetic characteristics. The immunoreactive TRH-like material in basal urine samples was not TRH however: chromatographically and enzymatically it behaved differently from the synthetic tripeptide.

Peptidases in the rat hypothalamus inactivating thyrotrophin-releasing hormone (TRH)

Peptidases capable of inactivating thyrotrophin-releasing hormone (TRH) have been demonstrated in the hypothalamus. With the development of a specific radioimmunoassay for TRH, this method was used to further study the enzymes acting on the releasing hormone. Whole hypothalamic homogenates from male and female rats inactivated TRH, with greater peptidase activity being found in the female animals. Separation of the homogenates into particulate (microsomal and mitochondrial) and supernatant (soluble/cytoplasmic) fractions showed approximately the same amounts of enzyme activity in both fractions, while dialysis of the fractions slightly reduced the TRH peptidase activity present, suggesting that a diffusible co-factor might be partially involved in the releasing hormone's degradation. These results confirm the presence of TRH-inactivating peptidases in the rat hypothalamus and suggest that the enzymes may be involved in some way in the mechanisms by which the brain controls thyrotrophin release by the anterior pituitary.

The inactivation of thyrotrophin releasing hormone by plasma in thyroid disease

The inactivation of immunoreactive TRH in vitro by human plasma has been investigated. In a preliminary study, 2.5 ng TRH was destroyed by 50 mul plasma at a mean rate of 1.7%/min in eight subjects. The per cent inactivation of the same amount of TRH at three plasma dose levels was measured after 60 min in seventy unselected patients attending a thyroid clinic. There was no significant difference in the results obtained in those subsequently shown to be euthyroid (forty-three patients), hyperthyroid (eighteen patients) or hypothyroid (nine subjects).

Studies on the nature of mammalian hypothalamic thyrotrophin releasing hormone using immunochemical, chromatographic and enzymic techniques

Hypothalamic extracts from three mammalian species (rat, rabbit and sheep) were found to contain several ng of immunoreactive thyrotrophin releasing hormone (TRH)-like activity. This substance chromatographed on ion exchange chromatography (carboxymethyl cellulose) as a single peak that was indistinguishable from synthetic TRH. Hypothalamic TRH was also inactivated by normal human plasma at a rate (1.21-1.46%/mul plasma/h and 1.59-1.77%/50mul plasma/min) similar to that of synthetic TRH (1.42%/mul plasma/h and 1.73%/50mul plasma/min). This combination of chromatographic and enzymic techniques can be applied to the identification of immunoreactive TRH in body fluids.

Three Skiagrams Showing a Complication of External Version for Breech Presentation

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