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Biomedical subjects

G Cohen

Publications and source records attributed to G Cohen.

At least 415 records · Page 23Linked to original sources
PubMed1976

Quantitative assessment of field uniformity for gamma cameras.

Objective criteria for judging the uniformity of field floods are developed and the effects of the energy window and scatter material on uniformity are examined. There is a highly significant correlation (p = 0.99) between a 14% difference in average count among adjacent photomultiplier tube regions and observer detection of detuned areas. Similarly, a 10% average count difference is not significantly recognized as a nonuniform area. Results indicate that there is a complex interaction between uniformity, energy window (15-30% symmetrical) and 0-7.6 cm of tissue-equivalent scatter medium interposed between the flood source and the collimator. Quantitation of the flood should be performed to indicate which regions need retuning.

Radionuclide Imaging↗
PubMed1976

[Analysis of flow-volume curves in asthmatic patients and their application in pharmacodynamic tests (author's transl)].

Study of the influence of some parameters upon flow-volume curves and pressure-type body plethysmography during inhalation tests (acetylcholine; metaproterenol) in 10 asthmatic patients (5 males and 5 females). Although the specific conductance decreased when bronchoconstriction was induced and returned to values superior to those measured before provocation when a bronchodilator was administered, changes in specific conductance did not always parallel those of flow-volume curves (V/V), maximum expiratory volume/sec (VEMS) and mid-miximum expiratory flow rate (MMEFR). All the parameters of V/V used here are well correlated with VEMS and MMEFR but not so with the specific conductance. The inverse correlation between the time constants of V/V and residual/total pulmonary capacity (VR/CT) before provocation and the significant decrease after provocation, indicate that V 60 (or 70%) CT and V 75% vital capacity (CV) are most valuable for the evaluation of physiopathological ventilatory changes occurring in bronchoconstriction.

Acetylcholine↗
PubMed1976

Clinical evaluation of a newly designed contoured tooth-brush.

A newly designed contoured toothbrush was tested against the Oral B toothbrush in a single blind crossover study over a 6-month period using 78 patients. The findings were: (1) The contoured toothbrush was significantly better (P less than 0.01) than the Oral B brush for gingival index scores; (2) Plaque scores were lower for the contoured brush (P = 0.10); (3) No significant differences were observed with respect to calculus scores.

Dental Calculus↗
PubMed1976

A comparison of 6,7-dihydroxytetrahydroisoquinoline, salsolinol and tetrahydropapaveroline as inhibitors of monoamine oxidase within the adrenergic nerve plexus of the isolated mouse atrium.

Three dopamine-derived tetrahydroisoquinolines (TIQs) were tested for their ability to inhibit monoamine oxidase (MAO) within the adrenergic plexus of atria from reserpinized mice. Inhibition of MAO was shown by improved accumulation of 3H-norepinephrine with a concomitant decrease in 3H-deaminated catechols. Salsolinol was less potent than 6,7-dihydroxy-TIQ as a MAO inhibitor. Tetrahydropapaveroline did not appear to inhibit MAO in this system.

Animals↗
PubMed1976

Destruction of sympathetic nerve terminals by 6-hydroxydopamine: protection by 1-phenyl-3-(2-thiazolyl)-2-thiourea, diethyldithiocarbamate, methimazole, cysteamine, ethanol and n-butanol.

1-Phenyl-3-(2-thiazolyl)-2-thiourea (PTTU) administered i.p. to mice prevented the neurodegenerative actions of subsequently injected (1 hour later) 6-hydroxydopamine (6-OHDA) or 6-aminodopamine on peripheral adrenergic nerve terminals. Destruction of nerve terminals was studied in vitro in the left atrium by measuring the accumulation of 3H-norepinephrine (3H-HE), and in the iris by both 3H-NE accumulation and fluorescence microscopy methods. Strong protection was observed at 4, 24 and 72 hours after 6-OHDA. The degree of protection was dose-dependent and showed step-wise decrements for concentrations of PTTU below 200 mg/kg (viz., 100, 50 and 20 mg/kg) or concentrations of 6-OHDA-HBr above 7.5 mg/kg (viz., 10, 20 and 50 mg/kg). Protection also fell off at time intervals greater than 1 hour after administration of PTTU (viz., 3 and 5 hours). The appearance (fluorescence microscopy) of the nerve plexus of fully protected mice and the remaining plexus in partially protected mice was essentially normal at 24 hours, except for infrequent large swellings. PTTU proved to be a very effective scavenger of hydroxyl radicals; the formation and scavenging of these radicals was studied by gas chromatography in a system in which the hydroxyl radicals (which were generated during the autoxidation of 6-aminodopamine) gave rise to ethylene, a hydrocarbon gas. Other hydroxyl radical scavengers, namely diethyldithiocarbamate and methimazole, exhibited a protective action on sympathetic nerves in the left atrium; PTTU, diethyldithiocarbamate and methimazole are also recognized as copper chelating compounds. Ethanol, n-butanol and cysteamine, which are well known hydroxyl radical scavengers, also exhibited some degree of protection against 6-OHDA. Blockade of transport of 6-OHDA into sympathetic nerves was ruled out as a protective mechanism by the observation that none of the protective compounds inhibited the accumulation of tritium by the left atrium when 3H-NE was injected in place of 6-OHDA. The mechanism of action for these protective agents has not been definitively established, but scavenging of cytotoxic hydroxyl radicals within neurons may play a significant role.

Animals↗
PubMed1976

Reversible bilateral simultaneous papillitis with no light perception.

This 14-year-old patient with bilateral simultaneous papillitis experienced no light perception in either eye for 24 hours and had a complete recovery of central and peripheral vision 3 weeks later. Fluorescein angiography confirmed the diagnosis. Although her hospital work-up was negative except for a mildly elevated CSF protein, it seems most likely that this was a postviral syndrome based on the bilaterality, rapid recovery of vision, and the age group.

Adolescent↗
PubMed1976

The effect of pargyline and other monoamine oxidase inhibitors on blood acetaldehyde levels in ethanol-intoxicated mice.

Pargyline (100 mg/kg i.p.) administered to Swiss-Webster mice prior to the injection of ethanol (4 g/kg i.p.) elevated blood acetaldehyde levels to a mean of 20 mug/ml, compared to less than 1 mug/ml in control mice treated with ethanol alone. Elevated blood acetaldehyde was observed when ethanol was given at 15 minutes, 2 or 5 hours after pargyline; the action of pargyline had largely disappeared after 18 hours. The magnitude of the increase in blood acetaldehyde levels was dependent upon the dose of pargyline between 20 and 100 mg/kg; however, the elevation was relatively independent of the ethanol dose between 1 and 6 g/kg. Of the other monoamine oxidase inhibitors tested, Lilly 51641 showed a strong elevation in acetaldehyde (mean 13.3 mug/ml), whereas deprenyl and clorgyline gave modest elevations (2.9 and 2.6 mug/ml, respectively), and nialamide and tranylcypromine were only weakly active (1.4 and 1.2 mug/ml, respectively). Blood acetaldehyde levels in mice treated with pargyline and ethanol were strongly depressed (85%) by pyrazole, an inhibitor of alcohol dehydrogenase, and moderately to strongly depressed (49-71%) by pretreatment with phenobarbital, an inducer of liver aldehyde dehydrogenase.

Acetaldehyde↗
PubMed1975

[Myelomonocytic leukemia with Philadelphia-positive and Philadelphia-negative cell lines in early childhood (author's transl)].

The authors report on an infant with myeloproliferative syndrome of the myelomonocytic type. The findings fulfilled the criteria for juvenile chronic myeloid leukemia except that there was no increase of fetal hemoglobulin and no depression of erythrocyte carbonic anhydrase I. In one half of the bone marrow cells a Ph1-chromosome was found. During the course of the disease the Ph1-positive clone was successively replaced by cell lines with different chromosomal aberrations. The relationship between the cytogenetic mosaicism and the clinical and laboratory findings is discussed.

Adult↗
PubMed1975

Photocoagulation in venous occlusive disease.

Fifty-one eyes with branch or tributary retinal venous occlusive disease underwent photocoagulation (1970-1973) after certain criteria were met: reduced visual acutity, fluorescein angiographic documentation of vessel permeability changes, and either dye leakage into the macula or neovascularization of the retina, or both. Eighty-four percent of the eyes responded to treatment with an improvement or stabilization in visual acuity, a reduction in collateral vessel caliber and permeability, and reduced dye accumlation in the macular area and increased fluorescein transit time. Photocoagulation is an affective means of reducing macular edema resulting from vascular compensatory changes following venous occlusion and decreases the risk of vitreous hemorrhage from sites of retinal neovascularization.

Collateral Circulation↗
PubMed1975

Prevention of 6-hydroxydopamine neurotoxicity.

1-Phenyl-3-(2-thiazolyl)-2-thiourea (PTTU) prevented the neurotoxic actions of 6-hydroxydopamine on adrenergic nerves in the mouse atrium and iris. This is the first reported 6-hydroxydopamine antagonist that does not act by blocking uptake of catecholamines into nerve terminals. PTTU also prevented the diabetogenic action of alloxan.

Animals↗
PubMed1975

Dopamine-containing neurons of the substantia nigra and their terminals in the neostriatum.

Tne ultrastructural and fluorescence histochemical characteristics of the mature rabbit substantia nigra and neostriatum have been reviewed as a frame of reference for the developmental study. Biochemical investigations were reported on neostriatal dopamine concentrations and the relative uptake and accumulation of 3H-dopamine by this tissue from fetal to adult stages, to provide quantitative data for correlation with the fluorexcence information. The development of the neurons of the substantia nigra and their axons which project to the neostriatum has been presented from their appearance at day 14 of gestation to their maturation in early postnatal life. The initial bipolar neuroblasts, which develop in the midline of the caudal mesencephalon, are fluorescent as soon as they emerge from the ependymal zone. Their fluorescent axons, which form the nigroneostriatal pathway, reach the telencephalon at day 16 of gestation and ramify extensively in the putamen by day 20, but do not enter the caudate nucleus until several days later. Some of the early fluorescent axonal profiles in the putamen are extremely large. Electron microscopic study of theis stage suggests that the large fluorescent profiles may correspond to axonal growth cones or early synapses. A distinct substantia nigra, pars compacta and reticulata, can be recognized by fluorescence microscopy by day 20 of gestation. Electron microscopy reveals that the young neurons are multipolar with numerous developing dendrites, some of which exhibit early synaptic junctions. The subsequent maturaition of these cells and the neuropil is described. The fluorescent axons of the substantia nigra grow into the putamen and caudate nucleus in a nonuniform manner forming fluorescent islands throughout the neostriatum in late fetal life. Occasionally, minute beaded fluorescent axons are found. These profiles might correspond to some of the axons with varicosities "en passage" revealed by electron microscopy. In an attempt to identify further the dopamine-containing axon, the ultratructure of adult neostriatum incubated in 5-hydroxydopamine was reported. Axonal varicosities "en passage" containing a dense "tag" in the vesicles were found. Most of the tagged boutons did not exhibit synaptic contacts. The possible significance of these finding s as related to dopamine secretion are discussed.

Animals↗