Gonadotropin-releasing hormone: one polypeptide regulates secretion of luteinizing and follicle-stimulating hormones

A polypeptide isolated from porcine hypothalami stimulates the release of both luteinizing hormone and follicle-stimulating hormone from the pituitaries of several species. This polypeptide has been structurally identified as (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH(2) and synthesized. The natural and synthetic materials share biological properties. It appears that this peptide represents the hypothalamic hormone regulating the secretion of both luteinizing hormone and follicle-stimulating hormone.

Decreased serotonergic receptor binding in rhombic lip-derived regions of the medulla oblongata in the sudden infant death syndrome

The sudden infant death syndrome (SIDS) is postulated to result from a failure of homeostatic responses to life-threatening challenges (e.g. asphyxia, hypercapnia) during sleep. The ventral medulla participates in sleep-related homeostatic responses, including chemoreception, arousal, airway reflex control, thermoregulation, respiratory drive, and blood pressure regulation, in part via serotonin and its receptors. The ventral medulla in humans contains the arcuate nucleus, in which we have shown isolated defects in muscarinic and kainate receptor binding in SIDS victims. We also have demonstrated that the arcuate nucleus is anatomically linked to the nucleus raphé obscurus, a medullary region with serotonergic neurons. We tested the hypothesis that serotonergic receptor binding is decreased in both the arcuate nucleus and nucleus raphé obscurus in SIDS victims. Using quantitative autoradiography, 3H-lysergic acid diethylamide (3H-LSD binding) to serotonergic receptors (5-HT1A-D and 5-HT2 subtypes) was measured blinded in 19 brainstem nuclei. Cases were classified as SIDS (n = 52), acute controls (infants who died suddenly and in whom a complete autopsy established a cause of death) (n = 15), or chronic cases with oxygenation disorders (n = 17). Serotonergic binding was significantly lowered in the SIDS victims compared with controls in the arcuate nucleus (SIDS, 6 +/- 1 fmol/mg tissue; acutes, 19 +/- 1; and chronics, 16 +/- 1; p = 0.0001) and n. raphé obscurus (SIDS, 28 +/- 3 fmol/mg tissue; acutes, 66 +/- 6; and chronics, 59 +/- 1; p = 0.0001). Binding, however, was also significantly lower (p < 0.05) in 4 other regions that are integral parts of the medullary raphé/serotonergic system, and/or are derived, like the arcuate nucleus and nucleus raphé obscurus, from the same embryonic anlage (rhombic lip). These data suggest that a larger neuronal network than the arcuate nucleus alone is involved in the pathogenesis of SIDS, that is, a network composed of inter-related serotonergic nuclei of the ventral medulla that are involved in homeostatic mechanisms, and/or are derived from a common embryonic anlage.

Decreased muscarinic receptor binding in the arcuate nucleus in sudden infant death syndrome

Muscarinic cholinergic activity in the human arcuate nucleus at the ventral medullary surface is postulated to be involved in cardiopulmonary control. A significant decrease in [3H]quinuclidinyl benzilate binding to muscarinic receptors in the arcuate nucleus is now shown to occur in sudden infant death syndrome (SIDS) infants, compared to infants dying acutely of known causes. In infants with chronic oxygenation abnormalities, binding is low in other nuclei, as well as in the arcuate nucleus. The binding deficit in the arcuate nucleus of SIDS infants might contribute to a failure of responses to cardiopulmonary challenges during sleep.

Medullary serotonergic network deficiency in the sudden infant death syndrome: review of a 15-year study of a single dataset

The sudden infant death syndrome (SIDS) is the leading cause of postneonatal infant mortality in the United States today, despite a dramatic 38% decrease in incidence due to a national risk reduction campaign advocating the supine sleep position. Our research in SIDS brainstems, beginning in 1985 and involving a single, large dataset, has become increasingly focused upon a specific neurotransmitter (serotonin) and specific territories (ventral medulla and regions of the medullary reticular formation that contain secrotonergic neurons). Based on this research, we propose that SIDS, or a subset of SIDS, is due to a developmental abnormality in a medullary network composed of (at least in part) rhombic lip-derived, serotonergic neurons, including in the caudal raphé and arcuate nucleus (putative human homologue of the cat respiratory chemosensitive fields); and this abnormality results in a failure of protective responses to life-threatening stressors (e.g. asphyxia, hypoxia, hypercapnia) during sleep as the infant passes through a critical period in homeostatic control. We call this the medullary serotonergic network deficiency hypothesis. We review the triple-risk model for SIDS, the development of the dataset using tissue autoradiography for analyzing neurotransmitter receptor binding; age-dependent baseline neurochemical findings in the human brainstem during early life; the evidence for serotonergic, rhombic lip, and ventral medullary deficits in at least some SIDS victim; possible mechanisms of sudden infant death related to these deficits; and potential causes of the deficits in the medullary serotonergic network in SIDS victims. We conclude with a summary of future directions in SIDS brainstem research.

Stimulus-secretion coupling processes in brain: analysis of noradrenaline and gamma-aminobutyric acid release

1. Brain synaptosomal fractions released both endogenous and exogenously loaded noradrenaline and gamma-aminobutyric acid (GABA) in response to calcium. Elevation of magnesium concentrations in the release media decreased the calcium-dependent release. 2. The release of noradrenaline and GABA occurred within 250 msec following the application of calcium. Following the initial response to calcium, release progressively decreased with continued application of calcium. GABA release declined more rapidly than noradrenaline release, consistent with a noradrenaline distribution having greater accessibility to the release process. 3. Sodium was required for the loading of noradrenaline and GABA into pools released by calcium. On the other hand, the presence of sodoium was not required for release from previously loaded pools. 4. Microsomal fractions did not exhibit calcium-dependent release of noradrenaline or GABA. Furthermore, exogenously loaded lysine was not released from synaptosomal fractions in response to calcium. 5. Barium and strontium, but not magnesium, stimulated noradrenaline and GABA release in the absence of calcium. The ordering of alkaline earth efficacies was barium greater than strontium greater than calcium. 6. Manganese inhibited calcium-dependent release of noradrenaline and GABA to a greater extent than magnesium. 7. Release, in response to 1 mM calcium, increased linearly with the log. [K+]0, suggesting that a voltage-dependent calcium inophore limits release. The slope of release vs. log. [K+]0 was greater for noradrenaline than for GABA. 8. For a given [K+]0 less than 55 mM, increases in external calcium concentration above 1 mM increased noradrenaline release but decreased GABA release. These data suggest that calcium can decrease its own permeation and that differences in the release process may exist for different neurotransmitters. 9. In the presence of the artificial calcium ionophore, A23187, both noradrenaline and GABA release increased linearly with the log. [Ca2+]0. The slope for noradrenaline release was greater than that for GABA release. 10. Stimulus-secretion coupling in brain is suggested to be regulated at the level of a voltage dependent calcium permeation mechanism. However, basic differences in the interaction of calcium with the release process may exist between the noradrenaline and GABA systems.

Interscalene brachial plexus block with a continuous catheter insertion system and a disposable infusion pump

Continuous interscalene brachial plexus blockade traditionally requires a hospital stay for local anesthetic infusion, and achieving consistent catheter insertion may be difficult. Incorporating long-acting pain relief from a continuous peripheral nerve block, with a reliable method of catheter insertion, and a self-contained infusion system would be a valuable asset for short-stay care. We compared the efficacy of single injection interscalene brachial plexus blockade to a continuous peripheral nerve block, with an insulated Tuohy system and a disposable infusion pump. Forty adult patients scheduled for open rotator cuff repair were entered in this randomized, double-blinded, placebo-controlled study. Patients received an interscalene brachial plexus blockade and a continuous peripheral nerve catheter as their primary anesthetic and then, were assigned to receive one of two different postoperative infusions: either 0.2% ropivacaine at 10 mL/h via a disposable infusion pump or normal saline at 10 mL/h via a disposable infusion pump (n = 18-20 per group). Visual analog pain scores and postoperative morphine consumption were measured for 24 h. The ropivacaine group showed less pain than the placebo group (P: = 0.0001) between 12 and 24 h after the initial injection of local anesthetic. In addition, initial interscalene blockade was successful in all patients and all redosed catheters were functional after 24 h with the continuous catheter insertion system. We conclude that it is possible to achieve a high rate of successful catheter placement and analgesia by using the continuous catheter insertion system and a disposable infusion pump in the ambulatory setting. This method of analgesia may offer improved pain relief after outpatient rotator cuff repair.

Cellular schwannoma. A clinicopathologic study of 57 patients and 58 tumors

The cellular schwannoma is a variety of schwannoma with a predominantly cellular growth but no Verocay bodies. Because doubt has been raised about the original assessment of this tumor as benign, the clinical and pathologic characteristics of 58 cellular schwannomas from 57 patients were reviewed. The patients were most often middle aged (63% were female), and their tumors most commonly were painless masses with a predilection for the paravertebral region of the retroperitoneum, pelvis, and mediastinum. Most tumors were solitary and encapsulated, and an associated nerve was identified for 43% of the cases. Electron microscopic and immunohistochemistry studies confirmed the tumor's Schwann cell nature. Worrisome features such as bone erosion, hypercellularity, foci of necrosis (four tumors), hyperchromasia, nuclear pleomorphism, and the presence of mitotic figures led to a malignant diagnosis for 28% of the cases. Treatment in all but one case was surgical excision. Two patients also received radiation therapy and chemotherapy. Follow-up of from 1 year to 24 years, 7 months (median of 6 years and mean of 7 years) for 61% (35 cases) of the cases reveals three patients with a local recurrence but no cases in which the tumor metastasized or the patient died of the tumor. Awareness of this tumor type is important so that the surgeon will avoid unnecessary sacrifice of functionally important nerves attached to these tumors and so that needless adjuvant radiation and chemotherapy will not be instituted.

Early developmental changes in [3H]nicotine binding in the human brainstem

Little is known about the developmental profile of nicotinic cholinergic receptors in the developing human brain, despite the potential importance of such information in understanding the pathogenesis of neurological abnormalities or increased risk for the sudden infant death syndrome in offspring exposed to nicotine in utero. In this study, we determined the distribution of [3H]nicotine binding in the developing human brainstem by quantitative tissue autoradiography. In midgestational fetuses, [3H]nicotine binding sites were heavily concentrated in tegmental nuclei related to cardiopulmonary integration, arousal, attention, rapid eye movement sleep, and somatic motor control. Over the last half of gestation, [3H]nicotine binding decreased 60-70% in the tegmental nuclei, with a significant difference in binding between midgestation and early infancy. In contrast, there was essentially no change in [3H]nicotine binding in the major cerebellar-relay nuclei (principal inferior olive and griseum pontis) between the same time-points. Tritium quenching by increasing lipid (myelin) content in tissue sections did not account for the decreases in [3H]nicotine binding in tegmental nuclei. Based upon the high levels of [3H]nicotine binding at midgestation, combined with experimental data demonstrating trophic properties for acetylcholine, we postulate that nAChRs a role in the development of the brainstem tegmentum during this period, and that once this role is fulfilled, nicotinic cholinergic binding decreases and remains low thereafter. Alternatively, nicotinic cholinergic receptors may be critical for other developmentally related functions and/or neurotransmission in the brainstem tegmentum at midgestation. The high levels of [3H]nicotine binding in the brainstem tegmentum at midgestation and its rapidly changing profile over late gestation further suggest that mid-to-late gestation is a developmental period during which this region is likely to be most vulnerable to the harmful effects of nicotine in maternal cigarette smoke. The baseline information provided in this study is potentially relevant towards understanding attention deficits and risk for the sudden infant death syndrome in offspring exposed to cigarette smoke in utero.

Biochemical correlates of GABA function in rat cortical neurons in culture

Serial biochemical studies of a rat cortical tissue culture system in which synapses regularly form showed that gamma-aminobutyric acid (GABA) is present in the cultures and increases with their maturation. The tissue GABA concentration in mature cultures is similar to that of adult rat cortex in vivo. The synthetic enzyme, glutamate decarboxylase, also increases with age as does high affinity GABA uptake. GABA uptake was blocked by L-2,4-diaminobutyrate (DABA) and had the properties of neuronal GABA uptake. Specific release by depolarizing media of both exogenous [3H]GABA and GABA synthesized from D-[U-14C]glucose was demonstrated. The GABA released by high potassium media had higher specific activity and a greater contribution from glucose (as compared to acetate) than GABA found in the medium in the absence of depolarization. Calcium dependency of evoked GABA release could be shown only after pretreatment of cultures with ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid or EGTA. Synaptosomes may exhibit greater calcium dependence of evoked transmitter release than intact cells in culture because their intracellular calcium stores are depleted during preparation. Glycine uptake by the cultures was much less in amount than was GABA uptake, and specific release of glycine could not be demonstrated. Specific binding of both a GABA agonist ([3H]muscimol) and an antagonist ([3H]bicuculline) was shown by membranes prepared from the cultures. By contrast, when [3H]muscimol binding to intact cells was studied, essentially all binding was sodium dependent and had the properties of GABA uptake binding. We conclude that the use of [3H]muscimol for receptor studies is valid only after the elimination of GABA uptake systems. Biochemical data from these studies support the concept that GABA is the transmitter for many cortical synapses. Glycine and taurine are not likely to be transmitters in these cortical cultures. When considered together with physiological data from the preceding paper, we have satisfied Werman's criteria (see ref. 36) for accepting GABA as the major inhibitory transmitter in the cortical culture system.

Depression in male and female patients undergoing cardiac surgery

The present longitudinal study was designed to determine the prevalence of depression in male and female patients undergoing cardiac surgery, and to examine what factors are associated with depression before and after surgery. One day prior to surgery (T1), and one day prior to discharge from the hospital (T2), 141 patients completed a psychometric test battery including the Center for Epidemiological Studies Depression Scale (CES-D), the State-Trait Anxiety Inventory (STAI), and the Perceived Social Support Scale (PSSS). Data were also collected on 13 physiological measures. Forty-seven per cent of patients were depressed (defined as a score of 16 or above on the CES-D) at T1. Scores on the CES-D significantly increased from T1 (M = 15) to T2 (M = 20), with 61 per cent of patients classified as depressed at T2. Factors associated with depression at T1 were female gender, higher state anxiety, and less social support. Depressed patients at T2 were characterized by higher scores on the STAI at T2 and higher scores on the CES-D at T1. The prevalence of depression in cardiac surgery patients, particularly women, may be underrecognized and warrants increased attention.

A frameshift mutation in the mouse alpha 1 glycine receptor gene (Glra1) results in progressive neurological symptoms and juvenile death

The neurologic mutant mouse, oscillator, is characterized by a fine motor tremor and muscle spasms that begin at 2 weeks of age and progressively worsen, resulting in death by 3 weeks of age. We report the localization of the oscillator mutation to the central region of mouse Chr 11, and demonstrate its allelism with spasmodic, a recessive viable neurological mutation which displays excessive startle. Oscillator is caused by a microdeletion in the gene coding for the alpha 1 subunit of the adult glycine receptor (Glra1). Glra1 assembles into a pentameric complex with the beta subunit of the glycine receptor (3 alpha (1)2 beta 5) to form a glycine-gated chloride channel. This receptor is the major adult glycine receptor, and the site of action of the poison strychnine. The oscillator deletion causes a frameshift resulting in loss of the highly conserved third cytoplasmic loop and fourth transmembrane domain of the protein. Membranes isolated from oscillator homozygote spinal cords display a 90% reduction in glycine-displaceable strychnine binding. This lack of ligand binding function confirms that oscillator is a complete loss of function allele. The oscillator mutation provides evidence that although at least four different alpha subunits exist for the glycine receptor, none of the other subunits can compensate for the loss of alpha 1 function. Mutations which impair GLRA1 function in humans have been shown to cause dominant familial startle disease. The identification of the oscillator mutation suggests that severe loss of function alleles in humans would result in prenatal or neonatal lethality.

Delay of puberty and inhibition of reproductive processes in the rat by a gonadotropin-releasing hormone agonist analog

Studies were performed in immature and mature female rats to determine the effects of chronic administration of [D-Leu6,des-Gly-NH210, Pro-ethylamide9]-gonadotropin-releasing hormone (GnRH) upon maturation and maintenance of reproductive function. Treatment of immature rats inhibited normal overian growth and maturation as evidenced by arrest of uterine growth, delay of vaginal opening, and absence of normal cycling. The primary responses in the mature animal were cessation of cycling, atrophy of the ovaries to a "prepuberal" size, and uterine weight regression. In both groups termination of treatment was followed by prompt restoration of normal ovarian mass and function, including support of breeding processes. The results presented here suggest that chronic administration of the GnRH analog inhibits ovarian steroid output either by direct action of the analog on the ovary or indirectly through qualitative or quantitative changes in levels of luteinizing hormone and follicle-stimulating hormone.

The effect of acidic amino acid antagonists on synaptic transmission in the hippocampal formation in vitro

The effects on synaptic efficacy of the putative acidic amino acid antagonists, 2-amino-4-phosphonobutyric acid (APB), 2-amino-3-phosphonopropionic acid (APP), 1-hydroxy-3-amino-pyrrolidone-2 (HA-966) and glutamic acid diethyl ester (GDEE), were tested by bath application to the hippocampal slice preparation. On the basis of previous work, we hypothesized that APB, HA-966 and GDEE might antagonize synaptic responses to either glutamate or aspartate, but APP should antagonize only synaptic responses to aspartate. APB and HA-966 reduced the amplitude of the extracellular EPSP recorded during stimulation of the perforant path fibers, but APP and GDEE were without effect. APB, APP and HA-966, but not GDEE, consistently inhibited transmission at Schaffer collateral and commissural synapses. The mossy fiber evoked extracellular EPSP was unaffected by these agents. At the concentrations used in this study (usually 2.5 mM) none of these drugs affected the amplitude of presynaptic fiber potentials or antidromic responses, indicating that they probably acted at synapses. The spontaneous activity of hippocampal pyramidal cells, but not of dentate granule cells, increased in the presence of 2.5 mM APB. The amplitude of the population spike generated by Schaffer commissural stimulation initially increased following introduction of APB into the medium and then declined in parallel with the extracellular EPSP. In addition, APB reduced the duration of recurrent inhibition during the period when pyramidal cell firing was enhanced. These results can be explained by an antagonism at the synapse between pyramidal cell and inhibitory interneuron.

Brainstem 3H-nicotine receptor binding in the sudden infant death syndrome

Maternal cigarette smoking during pregnancy has been shown to be a major risk factor for the sudden infant death syndrome (SIDS). We hypothesized that SIDS is associated with altered 3H-nicotine binding to nicotinic receptors in brainstem nuclei related to cardiorespiratory control and/or arousal. We analyzed 3H-nicotine binding in 14 regions in SIDS and control brainstems using quantitative tissue receptor autoradiography. Three groups were analyzed: SIDS (n = 42), acute controls (n = 15), and a chronic group with oxygenation disorders (n = 18). The arcuate nucleus, postulated to be important in cardiorespiratory control and abnormal in at least some SIDS victims, contained binding below the assay detection limits in all (SIDS and control) cases. We found no significant differences among the 3 groups in mean 3H-nicotine binding in the 14 brainstem sites analyzed. When a subset of the cases were stratified by the history of the presence or absence of maternal cigarette smoking during pregnancy, however, we found that there was no expected increase (upregulation) of nicotinic receptor binding in SIDS cases exposed to cigarette smoke in utero in 3 nuclei related to arousal or cardiorespiratory control. This finding raises the possibility that altered development of nicotinic receptors in brainstem cardiorespiratory and/or arousal circuits put at least some infants, i.e. those exposed to cigarette smoke in utero, at risk for SIDS, and underscores the need for further research into brainstem nicotinic receptors in SIDS in which detailed correlations with smoking history can be made.

Decreased kainate receptor binding in the arcuate nucleus of the sudden infant death syndrome

The human arcuate nucleus is postulated to be homologous to ventral medullary surface cells in animals that participate in ventilatory and blood pressure responses to hypercarbia and asphyxia. Recently, we reported a significant decrease in muscarinic cholinergic receptor binding in the arcuate nucleus in victims of the sudden infant death syndrome compared with control patients that died of acute causes. To test the specificity of the deficit to muscarinic cholinergic binding, we examined kainate binding in the arcuate nucleus in the same database. We assessed 3H-kainate binding to kainate receptors with tissue receptor autoradiography in 17 brainstem nuclei. Analysis of covariance was used to examine differences in binding by diagnosis, adjusted for postconceptional age (the covariate). Cases were classified as SIDS, 47; acute control, 15; and chronic group with oxygenation disorder, 17. (Acute controls are infants who died suddenly and unexpectedly and in whom a complete autopsy established a cause of death). The arcuate nucleus was the only region in which there was a significant difference in the age-adjusted mean kainate binding between the SIDS group (37+/-2 fmol/mg tissue) and both the acute controls (77+/-4 fmol/mg tissue) (p < 0.0001) and the chronic group (69+/-4 fmol/mg tissue) (p < 0.0001). There was a positive correlation between the density of muscarinic cholinergic and kainate binding in the SIDS cases only (R = 0.460; p = 0.003). The neurotransmitter deficit in the arcuate nucleus in SIDS victims involves more than one receptor type relevant to carbon dioxide and blood pressure responses at the ventral medullary surface.

Prolongation and enhancement of serum methotrexate concentrations by probenecid

The disappearance of methotrexate (MTX) from the serum after an intravenous bolus injection and intravenous infusion was studied over 24 hours in eight and four patients respectively. Probenecid given at the same time as the bolus injection delayed the disappearance of MTX from the serum and resulted in enhanced concentrations throughout the 24 hours studied. At 24 hours the mean concentration was four times higher than in patients not given probenecid. Overall serum concentrations were even greater than those in patients who had received MTX by intravenous infusion. We suggest that smaller doses of MTX may be given and treatment costs thereby reduced if probenecid is given in addition.