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Biomedical subjects

J D Glass

Publications and source records attributed to J D Glass.

At least 145 records · Page 8Linked to original sources
PubMed1986

Changes in the concentration of hypothalamic and hypophyseal receptors for estradiol in pregnant and postpartum ewes.

The sensitivity of the hypothalamic-pituitary axis to estradiol was evaluated by monitoring changes in the concentration of receptors for estradiol during gestation and the postpartum period of the ewe. Ewes that had been bred during anestrus so that lambing would occur during the breeding season were killed on d 50 and 140 of gestation or on d 2, 13, 22 and 35 postpartum. Total cytosolic receptors for estradiol were quantified in the anterior and posterior hypothalamus, median eminence, anterior pituitary and cerebral cortex. Concentration and total number of receptors for estradiol in the anterior and posterior hypothalamus and anterior pituitary gland during gestation through d 13 postpartum were similar but increased (P less than .05) by d 22 and 35 postpartum. Changes in the concentration of receptors for estradiol were tissue-specific because stage of reproduction did not influence the number of receptors for estradiol in the median eminence or cerebral cortex. Increases in the concentration of receptors for estradiol in hypothalamic and pituitary tissues on d 22 postpartum immediately preceded the onset of normal ovarian cyclicity in ewes. From these data we conclude that resumption of reproductive cycles in postpartum ewes occurs about the time concentrations of receptors for estradiol in the anterior pituitary gland and hypothalamus increase.

Animals↗
PubMed1984

Effects of season and sex on the distribution of cytosolic estrogen receptors within the brain and the anterior pituitary gland of sheep.

This study was undertaken to evaluate the effects of season and sex on the distribution of cytosolic estradiol-17 beta receptors (E2-receptors) within multiple regions of the ovine brain and the anterior pituitary gland. Our data confirm the existence of a saturable, high-affinity receptor specific for estradiol-17 beta (E2) in the hypothalamus and anterior pituitary gland. The concentrations of E2-receptors in tissues from castrated ewes and rams killed in December (breeding season) and May ( nonbreeding season) were determined by incubating cytosols with a saturating concentration of [3H] E2. For both sexes, the anterior pituitary gland contained the highest concentration of E2-receptor. Within the brain, the highest concentrations of E2-receptor were in the hypothalamus and preoptic area (POA), and within the hypothalamus, the median eminence-infundibular stalk (ME) contained a higher concentration of E2-receptor than the anterior and posterior hypothalamus. The numbers of E2-receptors in the anterior hypothalamus and ME of ewes were 2- 3X those for rams. In ewes, there was little seasonal difference in the numbers of E2-receptors in the POA, anterior hypothalamus and ME. In rams, there was little seasonal difference in the numbers of E2-receptors in the POA and anterior hypothalamus. For both sexes, there were fewer E2-receptors in the anterior pituitary gland and posterior hypothalamus in May than in December. Thus, during the nonbreeding season, the major neuroendocrine site of action of E2 probably is within the brain, specifically in the POA, anterior hypothalamus and ME of the ewe, and in the POA and the anterior hypothalamus of the ram. These data do not support a mechanism whereby the increased sensitivity to sex steroids during the nonbreeding season is due to enhanced numbers of E2-receptors.

Animals↗
PubMed1984

Cytosolic receptor for estradiol in the corpus luteum of the ewe: variation throughout the estrous cycle and distribution between large and small steroidogenic cell types.

This study was designed to: 1) determine the concentration of the cytosolic receptor for estradiol-17 beta (E2 receptor) in the ovine corpus luteum throughout the estrous cycle and 2) determine the contents of E2 receptor in large and small steroidogenic and nonsteroidogenic luteal cells. Our data confirm the existence of a saturable, high-affinity receptor specific for estrogen in the cytosol fraction of ovine corpus luteum. The concentration of E2 receptor was assessed in corpora lutea collected at Days 4, 6, 8, 12 and 16 postestrus; it was lowest at Day 4 (6.9 +/- 0.5 fmol/mg protein) and maximal (19.0 +/- 2.8 fmol/mg protein) at Day 8 (P less than 0.05). The concentration was decreased somewhat at Day 12 (11.8 +/- 3.1 fmol/mg protein), but was higher again at Day 16 (18.0 +/- 4.6 fmol/mg protein). The affinity constants were not different between Days 5 and 15 (P less than 0.3). The large steroidogenic cells contained a 3.5X higher concentration of cytosolic E2 receptor than did the small steroidogenic cells at Day 10 (27.7 +/- 5.8 vs. 7.9 +/- 4.0 fmol/mg protein; P less than 0.05). There was no apparent difference between the affinity constants of the E2 receptor in large and small cells. The differences in concentration of cytosolic E2 receptor throughout the estrous cycle and the higher concentrations of the E2 receptor in the large steroidogenic cells suggests that estradiol may play a role in regulating luteal function.

Animals↗
PubMed1984

Iatrogenic cardiac herniation: post mortem case.

A case is presented in which sudden cardiac death was caused by herniation of the heart through a pericardial incision following a gunshot wound to the chest, resulting in acute compression of the coronary arteries. At autopsy the heart protruded through the pericardial incision, which appeared to have elongated, and the cause of death was thought to be acute myocardial infarction secondary to coronary artery constriction.

Adolescent↗
PubMed1982

Do phenytoin and carbamazepine depress excitation and/or facilitate inhibition?

The effect of phenytoin and carbamazepine on the segmental and the periventricular inhibition was investigated in interneurons of the spinal trigeminal nucleus oralis of cats. The segmental inhibition was elicited by delivering a conditioning stimulus to the maxillary nerve 100 ms prior to the test stimulus to the maxillary nerve, and the periventricular inhibition was elicited by delivering a conditioning stimulus to the periventricular gray matter. Therapeutic serum levels of phenytoin and carbamazepine facilitated the segmental inhibition, but depressed the periventricular inhibition, while also depressing the response of trigeminal nucleus neurons to an unconditioned maxillary nerve stimulus. These results indicate that the depression of neural activity by phenytoin and carbamazepine is selective, leaving some inhibitory pathways relatively untouched and thus greatly enhancing their effectiveness. It is suggested that the anticonvulsant properties of phenytoin and carbamazepine are due to their ability to produce a relative facilitation of inhibitory feedback mechanisms.

Animals↗
PubMed1982

Pattern processing and slow waves in visual cortex of visually deprived cats.

The slow-wave response recorded from electrodes within the visual cortex of the awake cat has been shown to reflect the pattern processing activities of the visual cortex. In a cat deprived of pattern vision by monocular lid closure, the response evoked from the non-deprived eye by patterned and diffuse stimuli show differences similar to those found in a normal cat. However, when these same stimuli are presented to the deprived eye, the differences are not present. These slow-wave data confirm previous data from single unit recordings in showing that pattern processing is altered by deprivation.

Animals↗
PubMed1982

Evidence for a brain site of melatonin action in the white-footed mouse, Peromyscus leucopus.

A brain site of melatonin action has been determined for the white-footed mouse (Peromyscus leucopus). Melatonin-beeswax implants releasing small quantities of melatonin (less than 100 ng/day) caused a 50% reduction in reproductive tract weight relative to controls (p less than 0.025) with 83% of these animals having an imperforate vagina, when implanted in the anterior hypothalamic nuclei (AH) and suprachiasmatic nuclei (SCN). Subcutaneous implants had little effect. Implants in the AH and SCN also had a pronounced effect on both lipid-free interscapular brown fat and nesting behavior. Mice implanted in these regions exhibited a 59% increase in interscapular brown fat and 65% more nesting than controls (both p less than 0.01). These results suggest that melatonin acts at a region in the anterior hypothalamus which controls photoperiodic adjustments.

Adipose Tissue, Brown↗
PubMed1982

Diurnal rhythm of response to chronic intrahypothalamic melatonin injections in the white-footed mouse, peromyscus leucopus.

A pronounced diurnal change in responsiveness to intrahypothalamic melatonin injections was observed in the white-footed mouse, Peromyscus leucopus. 7 weeks of chronic daily afternoon (12 h after lights-on) injections of 500 ng melatonin into the vicinity of the suprachiasmatic nuclei (SCN) caused a 66% reduction in female reproductive tract weight relative to saline-injected controls (p less than 0.01), with 83% of these animals having an imperforate vagina, and no animals having mature follicles. Subcutaneous injections of 500 ng melatonin had little effect. Chronic morning (2 h after lights-on) injections of melatonin into the vicinity of the SCN had little effect on the maintenance of normal reproductive tract weight, with 18% of these animals having an imperforate vagina, and 71% having mature follicles. These results indicate that the daily rhythm of melatonin antigonadal action is due to change in responsiveness to melatonin of target neurons in the region of the SCN.

Animals↗
PubMed1981

Biochemical markers.

Explore the source record for details and available documents.

Clinical Laboratory Techniques↗
PubMed1981

Melatonin: identification of sites of antigonadal action in mouse brain.

Long-term implants releasing a small quantity of melatonin (45 nanograms per day) were used to determine the brain sites of the hormone's antigonadal action in a photoperiodic species, the white-footed mouse (Peromyscus leucopus). Implants in the medial preoptic and supra- and retrochiasmatic areas elicited completed gonadal regression after 7 weeks. Implants in other brain regions had little effect on the animals' reproductive state.

Animals↗
PubMed1981

Pattern processing and slow-wave activity in visual cortex of cat.

Animal models play a significant role in research on human disorders. In vision research, the recording of single-neuron activity from animals has been of great value to our understanding of pattern processing mechanisms. In humans, investigations of visual function have typically utilized slow-wave activity. We have studied in cats the relationship between pattern processing and the slow-wave evoked response recorded from cortical areas 17, 18, 19 and 4 in the awake cat. We have found that within a restricted latency range the response in 17, 18 and 19 reflects the processing of the patterness of a visual stimulus. A comparison of response components occurring prior to 50 msec poststimulus showed few significant differences (P less than 0.05) between peak amplitudes evoked by a diffuse and a checkerboard pattern stimulus. A much higher proportion of response components occurring after 50 msec but prior to 300 msec poststimulus were significantly different (P less than 0.05). The response recorded from area 4 (motor cortex) did not show significant differences as a function of the diffuse and patterned stimuli. Our findings show that the slow wave recorded from cat visual cortex can reflect the pattern processing mechanisms of visual cortex. Since slow waves are used in the study of visual functions in humans, the slow wave may have an important role to play in animal models of visual disorders in humans.

Animals↗
PubMed1981

Effect of anticonvulsant drugs on inhibitory and excitatory pathways.

A conditioning stimulus to the periventricular gray matter inhibits the response of spinal trigeminal neurons to maxillary nerve stimulation. Sodium valproate and ethosuximide decrease the periventricular inhibition without significantly affecting the response of these neurons to the unconditioned maxillary nerve stimulus. We have now found that carbamazepine and phenytoin decrease the response to the unconditioned maxillary nerve stimulus, and only depress the periventricular inhibition secondarily. These results further support the hypothesis that the ability to depress selectively inhibitory pathways in the CNS is an important characteristic of antiabsence drugs, and that absence seizures may represent paroxysmal discharges in inhibitory pathways.

Animals↗
PubMed1981

Sites and action spectra for encephalic photoreception in the Japanese quail.

Sexually mature Japanese quail, Coturnix coturnix japonica, were transferred to short environmental photoperiod for 20 days, during which they received encephalic illumination via surgically implanted optic fibers. White light delivered to discrete sites in the basal hypothalamus induced photogonadal response for testicular maintenance. There was also a strong positive response to monochromatic red, green, or blue light delivered to these areas, and this response was of equal magnitude regardless of wavelength. Illumination of sites in the median eminence and pars nervosa was also effective in inducing photogonadal response. White light delivered to the optic chiasma was effective, whereas green or blue light to this structure had no effect. Illumination of the preoptic hypothalamus or the dorsal cortex was also without effect. Our data indicate that there are photoreceptive sites in and near the basal hypothalamus that, when illuminated directly, are capable of responding to a broad range of visible wavelengths.

Animals↗
PubMed1981

Role of inhibitory mechanisms in trigeminal neuralgia.

Segmental inhibition was elicited in the spinal trigeminal nucleus of cats by delivering a conditioning stimulus to the maxillary nerve 100 msec before the test stimulus. Carbamazepine, baclofen, and phenytoin markedly facilitated this segmental inhibition, as well as depressing the response to an unconditioned maxillary nerve stimulus. Phenobarbital, on the other hand, usually depressed the segmental inhibition. These results suggest that drugs that relieve trigeminal neuralgia both facilitate inhibitory mechanisms and depress excitatory mechanisms in the spinal trigeminal nucleus. The facilitation of inhibitory mechanisms appears to be at least as important as the depression of excitatory mechanisms and suggests that a failure of inhibitory mechanisms may play a significant role in the pathogenesis of trigeminal neuralgia.

Animals↗
PubMed1980

Baclofen in trigeminal neuralgia: its effect on the spinal trigeminal nucleus: a pilot study.

Experiments with cats showed that baclofen resembles carbamazepine and phenytoin sodium in its ability to depress excitatory synaptic transmission in the spinal trigeminal nucleus. Baclofen was, therefore, given to 14 patients with refractory trigeminal neuralgia. Ten patients were relieved of the paroxysms of tic douloureux while taking 60 to 80 mg/day of baclofen. A reduction in the dosage of baclofen in six of these patients resulted in a recurrence of painful paroxysms in five patients. Seven patients have been pain-free or almost pain-free on a regimen of baclofen for four to 12 months. Our results suggest that baclofen may be a useful drug in the treatment of trigeminal neuralgia and that our experimental model may successfully predict the efficacy of a drug in the treatment of this condition.

Adult↗
PubMed1980

Bicuculline and neuronal activity in motor cortex.

We have studied the effects of bicuculline applied in microgram quantities to the precruciate gyrus (motor cortex) of cat upon visually evoked and spontaneous single-unit and slow-wave activity. The bicuculline produced an increase in both the visually evoked and the spontaneous unit activity. A surface negative component of the slow-wave response was markedly enhanced by the bicuculline. This component was associated with an intense suppression of spontaneous single-unit activity. Therefore, we have found that bicuculline has a convulsant effect upon single-unit activity as previously reported by others. However, we also found that bicuculline potentiates a process which appears associated with an enhancement of inhibition.

Animals↗
PubMed1980

Camphorquinone-10-sulfonic acid and derivatives: convenient reagents for reversible modification of arginine residues.

Camphorquinone-10-sulfonic acid hydrate was prepared by the action of selenous acid on camphor-10-sulfonic acid. Camphorquinone-10-sulfonylnorleucine was prepared either from the sulfonic acid via the sulfonyl chloride or by selenous acid oxidation of camphor-10-sulfonylnorleucine. These reagents are useful for specific, reversible modification of the guanidino groups of arginine residues. Camphorquinonesulfonic acid is a crystalline water-soluble reagent that is especially suitable for use with small arginine-containing molecules, because the sulfonic acid group of the reagent is a convenient handle for analytical and preparative separation of products. Camphorquinonesulfonylnorleucine is more useful for work with large polypeptides and proteins, because hydrolysates of modified proteins may be analyzed for norleucine to determine the extent of arginine modification. The adducts of the camphorquinone derivatives with the guanidino group are stable to 0.5 M hydroxylamine solutions at pH 7, the recommended conditions for cleavage of the corresponding cyclohexanedione adducts. At pH 8-9 the adducts of the camphorquinone derivatives with the guanidino group are cleaved by o-phenylenediamine. The modification and regeneration of arginine, of the dipeptide arginylaspartic acid, of ribonuclease S-peptide, and of soybean trypsin inhibitor are presented as demonstrations of the use of the reagents. The use of camphorquinonesulfonyl chloride to prepare polymers containing arginine-specific ligands is discussed.

Arginine↗