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Biomedical subjects

J Guy

Publications and source records attributed to J Guy.

At least 145 records · Page 8Linked to original sources
PubMed1979

Blockade of rapid axonal transport. Effect of intraocular pressure elevation in primate optic nerve.

After acute intraocular pressure (IOP) elevation, an induced disturbance of rapid axonal transport at the optic nerve head began within three hours at the IOP levels tested. The accumulation of radioactive label at the scleral lamina cribrosa increased with time of IOP elevation. There was a 60% decrease in the amount of transported material in the optic nerve, tract, and lateral geniculate body (LGN). Detailed analysis suggests that this decrease is not due to a simple slowdown of transport, but results from a total block of rapid transport in some axons, with no impairment in other axons. This total blockade of rapid transport by elevated IOP in involved axons differs from the apparent slowdown of transport in experimental papilledema, and the difference may explain the response of ganglion cells to the two conditions.

Animals↗
PubMed1979

Diarrhea and medullary carcinoma of the thyroid.

The authors present the case of a 34-year-old woman with disseminated medullary carcinoma of the thyroid to emphasize the value of calcitonin assay in the diagnosis of this condition despite the absence of a thyroid mass and negative scans. An increased concentration of serum carcino-embryonic antigen was confirmed. The diarrhea associated with the disease did not respond to indomethacin in this patient suggesting that in some cases of medullary carcinoma diarrhea is not due to excessive production of prostaglandins.

Adult↗
PubMed1978

The effect of biogenic monomines on rapid axonal transport in the rabbit optic nerve.

Since L-dopa and serotonin have been reported to increase the rate of axonal transport in rat sciatic nerve, we decided to study the effect of these monoamines on rapid orthograde transport in the rattit optic nerve. To do this, tritiated leucine was injected into the vitreous of both eyes of 56 albino rabbits, and arrival of radioactive labeled proteins at the superior colliculus was measured at various intervals by liquid scintillation counting. Rabbits were studied 24 hr after intraperitoneal injections of (1) Sinemet + L-dopa, (2) Sinemet + 5-hydroxytryptophan, or (3) pargyline. There were 14 rabbits in each group compared to 14 controls that received no monoamies. In the monoamine-treated groups, transported labeled proteins arrived at the superior colliculus earlier, and an increased amount of radioactivity accumulated during the next several hours. The maximum amount of radioactive proteins accumulating in drug-treated animals did not differ significantly from the maximum amount in control animals. As judged by autoradiographic densitometry, retinal ganglion cell synthesis was similar in control and drug-treated animals. We suspect that the rate of rapid axonal transport is increased by monoamines, although an increased rate of ganglion cell protein synthesis is another possibility.

5-Hydroxytryptophan↗
PubMed1977

Acute pulmonary toxicity of a commercial fluorocarbon--lipid aerosol.

The death of an adolescent after deliberate inhalation of the domestic fluorocarbon--lipid spray, PAM, triggered an investigation of the effects of this product on mammalian lung. Some of its constituents are known to destroy the lung-surfactant system, but death from its inhalation by earlier victims was usually attributed to the fluorocarbon's cardiac arrhythmogenic properties. In the present study, we applied methods and experimental models not previously used to study the effects of this aerosol material on the lung surfactant. We found morphological and functional acute disintegration of normal alveolar surfactant, leading to extensive alveolar collapse, with sustained and elevated surface tensions in vitro. This could result in fatal hypoxaemia at inspired concentrations of fluorocarbons insufficient to cause cardiac arrhythmias, and may explain at least partly the large number of deaths associated with inhalation of such product.

Aerosol Propellants↗
PubMed1977

A psychiatric study of women with urgency and urgency incontinence.

26 patients with frequency, urgency and urgency incontinence, without bladder or urethral abnormality, underwent psychiatric evaluation. They were divided into 2 groups according to the degree of neuroticism found. Treatment by group and individual psychotherapy showed that approximately one-third of the patients benefited considerably, one-third refused treatment or ceased prematurely and one-third improved slightly or not at all. The importance of excluding organic bladder or urethral disease prior to psychiatric assessment is stressed.

Adolescent↗
PubMedDate not supplied

Magnetic resonance angiography of vascular lesions causing neuro-ophthalmic deficits.

Magnetic resonance angiography (MRA) is a noninvasive, rapidly evolving technique for imaging the intra- and extracranial carotid and vertebrobasilar circulations. It may in some circumstances obviate conventional angiography and the accompanying risks associated with catheterization and contrast injection. MRA exploits the different physical properties between moving protons and stationary tissue to yield flow sensitive data in the form of anatomic images or velocity and flow measurements. Since patients with various vascular disorders may present exclusively with ophthalmologic signs and symptoms, it is expected that MRA will become more frequently utilized by ophthalmologists. The exact role of MRA in the workup of vascular disorders remains to be more precisely defined, pending the performance of additional well-controlled standardized studies. At present, MRA is utilized to complement the conventional spin-echo studies of patients with arterial and venous occlusion, vascular malformations, intracranial aneurysms, and neoplastic vascular invasion. With further refinements, it is expected that MRA will become a standard diagnostic tool for the evaluation of patients with vascular disorders.

Blood Flow Velocity↗
PubMedDate not supplied

Effects of neuropeptide Y (NPY) on the release of anterior pituitary hormones in the rat.

Neuropeptide Y (NPY) has been recently localized in several hypothalamic nuclei in the mammalian brain. In order to investigate the possible role of NPY on neuroendocrine function, we have investigated the effects of the peptide on the release of anterior pituitary hormones in the rat. Both intravenous (300 micrograms) or intraventricular (2 to 15 micrograms) injection of NPY produced in gonadectomized male rats a significant and long-lasting decrease of plasma LH levels. A short duration stimulating effect on prolactin plasma levels was also observed after the intravenous but not after the intraventricular injection of NPY. Plasma levels of the other pituitary hormones were not significantly modified after NPY injection. When incubated in vitro with anterior pituitary cells in monolayer culture, NPY produced no significant change in release of pituitary hormones. Thus NPY seems to exert a selective effect on LH release. Since this effect can be observed after both intravenous and intraventricular injection, it might be hypothesized that NPY could affect LHRH release in two areas which lack blood-brain barrier: the organum vasculosum of the lamina terminalis (OVLT) which contains LHRH cell bodies and NPY fibers and the median eminence which contains both LHRH and NPY fibers. The effect on prolactin release needs to be carefully evaluated in different experimental conditions.

Animals↗
PubMedDate not supplied

Localization and identification of neuropeptide Y (NPY)-like immunoreactivity in the frog brain.

The distribution of neuropeptide Y (NPY) in the central nervous system of the frog Rana ridibunda was determined by immunofluorescence using a highly specific antiserum. NPY-like containing perikarya were localized in the infundibulum, mainly in the ventral and dorsal nuclei of the infundibulum, in the preoptic nucleus, in the posterocentral nucleus of the thalamus, in the anteroventral nucleus of the mesencephalic tegmentum, in the part posterior to the torus semicircularis, and in the mesencephalic cerebellar nucleus. Numerous perikarya were also distributed in all cerebral cortex. Important tracts of immunoreactive fibers were found in the infundibulum, in the preoptic area, in the lateral amygdala, in the habenular region, and in the tectum. The cerebral cortex was also densely innervated by NPY-like immunoreactive fibers. A rich network of fibers was observed in the median eminence coursing towards the pituitary stalk. Scattered fibers were found in all other parts of the brain except in the cerebellum, the nucleus isthmi and the torus semicircularis, where no immunoreactivity could be detected. NPY-immunoreactive fibers were observed at all levels of the spinal cord, with particularly distinct plexus around the ependymal canal and in the distal region of the dorsal horn. At the electron microscope level, NPY containing perikarya and fibers were visualized in the ventral nuclei of the infundibulum, using the peroxidase-antiperoxidase and the immunogold techniques. NPY-like material was stored in dense core vesicles of 100 nm in diameter. A sensitive and specific radioimmunoassay was developed. The detection limit of the assay was 20 fmole/tube. The standard curves of synthetic NPY and the dilution curves for acetic acid extracts of cerebral cortex, infundibulum, preoptic region, and mesencephalon plus thalamus were strictly parallel. The NPY concentrations measured in these regions were (pmole/mg proteins) 163 +/- 8, 233 +/- 16, 151 +/- 12 and 60 +/- 13, respectively. NPY was not detectable in cerebellar extracts. After Sephadex G-50 gel filtration of acetic acid extracts from whole frog brain, NPY-like immunoreactivity eluted in a single peak. Reverse phase high performance liquid chromatography (HPLC) and radioimmunoassay were used to characterize NPY-like peptides in the frog brain. HPLC analysis revealed that infundibulum, preoptic area and telencephalon extracts contained a major peptide bearing NPY-like immunoreactivity. The retention times of frog NPY and synthetic porcine NPY were markedly different. HPLC analysis revealed also the existence, in brain extracts, of several other minor components cross-reacting with NPY antibodies.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Neuronal interactions between neuropeptide Y (NPY) and catecholaminergic systems in the rat arcuate nucleus as shown by dual immunocytochemistry.

Several recent studies have suggested interactions between catecholamine (CA) and neuropeptide Y (NPY) neuronal systems in the rat brain. In order to obtain morphological evidence for such CA/NPY interactions in the arcuate nucleus, we have used a double immunostaining procedure using an anti-tyrosine hydroxylase (TH) antiserum as a marker for catecholamine neurons and an anti-NPY antiserum. This double staining, where the first staining is silver-gold intensified, was detectable at both light and electron microscopic levels. In semi-thin sections, a substantial overlap and close proximity of TH-immunopositive neurons and NPY neuronal elements could be seen within the arcuate nucleus. At the electron microscopic level, direct appositions between TH- and NPY-immunoreactive structures could be detected. These appositions were of axosomatic, axodendritic or axoaxonic types without any synaptic membrane differentiation. Moreover, direct appositions between NPY-immunoreactive structures have also been observed. This morphological study showing appositions between TH and NPY neuronal systems suggest direct interactions between these two systems in the arcuate nucleus.

Animals↗
PubMedDate not supplied

Recovery of cyclic antidepressants with gastric lavage.

The role of lavage fluid volume in recovery of cyclic antidepressant with gastric lavage was determined in 13 patients treated for moderate to severe cyclic antidepressant intoxication. An orogastric tube was placed, gastric contents aspirated, and gastric lavage performed with 60 to 180 mL aliquots of tap water or 0.9% NaCl for irrigation. A volume of 12.8 +/- 4.4 liters of lavage fluid was instilled, and 97.6 +/- 6.9% of this volume was recovered. The recovered aspirate and lavage fluid were inspected for the presence of particulate matter and saved in 4 to 5 liter collections. Determination of cyclic antidepressant and metabolite concentrations was performed using gas chromatography-mass spectrometry, and the amount of cyclic antidepressant recovered was calculated. The mean total amount recovered was 110 mg and ranged from 2.4 mg to 342 mg. Of the total amount recovered, 88% +/- 13% was recovered in the first 4 to 5 liters of lavage fluid. An estimate of the dose ingested was available in 7 patients, with 8.7% (0.4% to 21.7%) of the estimated dose recovered by lavage. There were no cases of significant drug recovery in clear lavage fluid. We conclude that if gastric lavage is undertaken in cyclic antidepressant intoxications, it should utilize 5 liters initially and then continue only if particulate matter is seen.

Adolescent↗