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Biomedical subjects

B Cohen

Publications and source records attributed to B Cohen.

At least 361 records · Page 20Linked to original sources
PubMed1985

Intraoral carcinoma in Nigeria: a review of 137 cases.

Carcinoma of the oral cavity occurring in Africans is poorly documented. Although oral cancer is considered rare in Africa approximately 40 cases of intraoral carcinoma are seen yearly at the Maxillofacial Clinic, Kaduna. This paper reviews 137 cases of malignant disease in the oral cavity and compares the results with previously published literature. Tumours of the major salivary glands and carcinoma that could clearly be shown to originate from the antral mucosa are not included in this series. Lesions of the palate, alveolar ridge and the oral vestibule, all of which appeared to have arisen primarily from the oral mucosa, predominated. A relatively low incidence of carcinoma of the lip and tongue was recorded. The patients were considerably younger than those reported in comparable series from Europe and America.

Adult↗
PubMed1984

A human IFN-beta 1 gene deleted of promoter sequences upstream from the TATA box is controlled post-transcriptionally by dsRNA.

Induction of IFN-beta 1 RNA was studied in the mouse cell line SR117-21E transformed by a BPV episome containing the human IFN-beta 1 gene deleted of promoter sequences upstream from position -40. Nuclei isolated from these cells synthesize constitutively IFN-beta 1 RNA from the partially deleted promoter. The IFN-beta 1 RNA synthesized by nuclei of uninduced SR117-21E cells is similar to that made by nuclei of poly(rI):(rC)-induced cells, but does not accumulate and hence no IFN is produced unless the cells have been treated either by ds RNA or by cycloheximide. We conclude that the IFN-beta 1 gene has, in addition to the transcription control due to upstream promoter sequences, an additional post-transcriptional control acting on mRNA accumulation and linked to sequences close to the TATA box and RNA start site. Both controls are relieved by ds RNA.

Animals↗
PubMed1984

Methylmercuric iodide modification of lipoxygenase-1. Effects on the anaerobic reaction and pigment bleaching.

The effect of methylmercuric iodide modification of sulfhydryl groups in soybean lipoxygenase-1 on linoleate oxidation, carbonyl production and beta-carotene and chlorophyll alpha bleaching were determined under aerobic and anaerobic conditions. Linoleate oxidation at pH 9.0 was strongly inhibited by modification of the enzyme. On the other hand, pigment bleaching was enhanced with the modified enzyme. Unmodified lipoxygenase-1 was not sensitive to chlorophyll inhibition, but activity of modified lipoxygenase-1 was affected. Linoleate oxidation was inhibited up to 70% when 2.2 microM chlorophyll was present in the reaction mixture. Chlorophyll inhibition was similar with affinity chromatography-purified lipoxygenase-2 and modified lipoxygenase-1. Unmodified lipoxygenase-1 exhibited high bleaching activity under anaerobic conditions and relatively low activity under aerobic (oxygen or air) conditions. Modified lipoxygenase-1 showed a significant increase in carotene and chlorophyll bleaching under both anaerobic and aerobic conditions. Under anaerobic conditions in the presence of either pigment, both modified and unmodified lipoxygenase-1 exhibited high 285 nm absorbing material production. Antioxidants (butylated hydroxyanisole, butylated hydroxytoluene, alpha-tocopherol, propyl gallate and tertiary butylated hydroxyquinone ) were powerful inhibitors of pigment bleaching by modified lipoxygenase-1. However, only tertiary butylated hydroxyquinone and propyl gallate blocked the increase in the rate of absorbance at 285 nm.

Anaerobiosis↗
PubMed1984

Projections from the superior colliculus to a region of the central mesencephalic reticular formation (cMRF) associated with horizontal saccadic eye movements.

Radioactive wheatgerm agglutinin (WGA) and horseradish peroxidase (HRP) were injected into portions of the mesencephalic reticular formation at sites where electrical stimulation induced either small or large contralateral horizontal saccadic eye movements. We have designated this region as the Central MRF (cMRF). It contains both cells and fiber tracts, including the efferent output of the superior colliculus (SC), destined for the dorsal tegmental decussation and the predorsal bundle. Cells labelled by WGA and HRP injections were found in the intermediate and deep layers of the superior colliculus and the adjacent central gray matter on the ipsilateral side. Injections into the dorsal cMRF, at sites where small saccades were induced, caused labelling of cells in the rostral intermediate layer of SC. Injections into the ventral cMRF, at points where large saccades were elicited, caused labelling of cells in the caudal intermediate layer of SC. The deepest layers of SC and the adjacent central gray were also labelled from the small eye movement region of dorsal cMRF. We interpret these findings to indicate that the intermediate layers of SC send axonal projections to the horizontal eye movement region of the MRF in a topographic fashion. The projection from the intermediate layer is organized so that regions in SC and cMRF related to small or to large eye movements are interconnected. The results support the hypothesis that cMRF is a topographically organized area, involved, like SC, in the control of eye movements. Since both cMRF and the superior colliculus project to areas of the pons and medulla where saccadic eye movements are produced, they could give rise to parallel pathways for the generation of contralateral saccades.

Animals↗
PubMed1984

Vertical optokinetic nystagmus and vestibular nystagmus in the monkey: up-down asymmetry and effects of gravity.

Vertical optokinetic nystagmus (OKN) i.e., OKN in the sagittal plane, was asymmetrical in the monkey when it was induced with animals lying on their sides in a 90 degrees roll position. In typical monkeys the slow phase velocity of downward OKN (slow phases up) increased proportionally with stimulus velocity at close to unity gain to about 60 degrees/s and saturated at about 100 degrees/s. Upward OKN (slow phases down) increased with close to unity gain only to about 40 degrees/s and saturated at about 60 degrees/s. The slow phase velocity of upward OKN was usually irregular and its frequency was lower than that of downward or horizontal OKN. Upward and downward optokinetic after-nystagmus (OKAN) were also asymmetrical. Upward OKAN was weak or absent and when present it usually saturated at 10 degrees/s. Downward OKAN was stronger, increasing with a gain of about 0.7 with regard to stimulus velocity to a saturation velocity of about 50-60 degrees/s. This was usually about 10-30 degrees/s less than the saturation velocity of horizontal OKAN. The weak or absent upward OKAN indicates that stored activity related to slow phase eye velocity contributes little to the production of upward OKN. In agreement with this, there was little or no slow rise in slow phase velocity to a steady state level during upward OKN. Instead eye velocity rose to its peak velocity at the onset of stimulation. The lack of stored velocity information is probably largely responsible for the differences in regularity, gain and frequency between upward and downward OKN. Vertical vestibular nystagmus was induced by rotating monkeys in darkness with steps of velocity about a vertical axis, while they were lying on their sides in a 90 degree roll position. The velocities of the initial upward and downward slow phases were approximately equal. Gains of the vertical VOR ranged from about 0.5 to 0.98 for stimuli up to 150 degrees/s. Despite equivalent initial gains for upward and downward nystagmus, the vertical VOR was asymmetrical in that downward nystagmus had a higher frequency and generally lasted longer than upward nystagmus. Time constants of downward nystagmus (slow phases up) were about 15 s on average and were similar to those of horizontal nystagmus. Mean time constants of upward nystagmus (slow phases down) were about 8 s. This is only slightly longer than the average time constant of afferent activity in the semicircular canal nerves induced by steps of velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1984

Electrical effects of potassium and bicarbonate on proximal tubule cells of Necturus.

The effects of stepwise concentration changes of K+ and HCO3- in the basolateral solution on the basolateral membrane potential (Vbl) of proximal tubule cells of the doubly-perfused Necturus kidney were examined using conventional microelectrodes. Apparent transference numbers were calculated from changes in Vb1 after alterations in external K+ concentration from 1.0 to 2.5 mM (tK, 1.0-2.5), 2.5 to 10, and in external HCO3- concentration (at constant pH) from 5 to 10 mM (tHCO3, 5-10), 10 to 20, or 10 to 50. tK, 2.5-10 was 0.38 +/- 0.02 under control conditions but was sharply reduced to 0.08 +/- 0.03 (P greater than 0.001) by 4 mM Ba++. This concentration of Ba++ reduced Vb1 by 9 +/- 1 mV (at 2.5 external K+). Perfusion with SITS (5 X 10(-4)M) for 1 hr hyperpolarized Vb1 by 10 +/- 3 mV and increased tK, 2.5-10 significantly to 0.52 +/- 0.01 (P less than 0.001). Ba++ application in the presence of SITS depolarized Vb1 by 22 +/- 3 mV. In control conditions tHCO3, 10-50 was 0.63 +/- 0.05 and was increased to 0.89 +/- 0.07 (P less than 0.01) by Ba++ but was decreased to 0.14 +/- 0.02 (P less than 0.001) by SITS. In the absence of apical and basolateral chloride, the response of Vb1 to bicarbonate was diminished but still present (tHO3, 10-20 was 0.35 +/- 0.03). Intracellular pH, measured with liquid ion-exchange microelectrodes, increased from 7.42 +/- 0.19 to 7.57 +/- 0.17 (P less than 0.02) when basolateral bicarbonate was increased from 10 to 20 mM at constant pH. These data show that the effects of bicarbonate on Vb1 are largely independent of effects on the K+ conductance and that there is a significant current-carrying bicarbonate pathway in the basolateral membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1984

Regulation of the basolateral potassium conductance of the Necturus proximal tubule.

Two methods, the measurement of the response of the basolateral membrane potential (Vbl) of proximal tubule cells of Necturus to step changes in basolateral K+ concentration, and cellular cable analysis, were used to assess the changes in basolateral potassium conductance (GK) caused by a variety of maneuvers. The effects of some of these maneuvers on intracellular K+ activity (aiK) were also evaluated using double-barreled ion-selective electrodes. Perfusion with 0 mM K+ basolateral solution for 15 min followed by 45 min of 1 mM K+ solution resulted in a fall in basolateral potassium (apparent) transference number (tK), Vbl and aiK. Results of cable analysis showed that total basolateral resistance, Rb, rose. The electrophysiological effects of additional manipulations, known to inhibit net sodium reabsorption across the proximal tubular epithelium of Necturus, were also investigated. Ouabain caused a fall in tK accompanied by large decreases in aiK and Vbl. Lowering luminal sodium caused a fall in tK and a small reduction in Vbl. Selective reduction of peritubular sodium, a maneuver that has been shown to block sodium transport from lumen to peritubular fluid, also resulted in a significant decrease in tK. These results suggest that GK varies directly with rate of transport of the sodium pump, irrespective of the mechanism of change in pump turnover.

Animals↗
PubMed1984

Infectious mononucleosis-like response in common marmosets infected with Epstein-Barr virus.

Callithrix jacchus marmosets infected with Epstein-Barr virus (EBV) with or without concurrent treatment with cyclosporin A (CySA) remained healthy. Five marmosets given virus alone developed lymphocytosis and heterophile antibody. Antibody to EBV capsid antigens (VCA) appeared and remained at titers of 1:40-1:80 from 15 weeks onward. Two animals produced antibody to the R component of early antigens (EA) from six weeks onward. Five CySA-treated EBV-infected marmosets showed no increase in total lymphocyte counts; only two developed heterophile antibody. Four developed persistent antibody to the EA-R component. All developed antibody to VCA, and mean titers were higher than in animals given EBV alone. Antibody to VCA also appeared in animals given EBV into Waldeyer's ring. Because these responses to EBV resemble those of humans, C. jacchus may provide a useful model for exploring the potential of cofactors in inducing EBV-associated malignancy.

Animals↗
PubMed1984

Relationship between peritubular membrane potential and net fluid reabsorption in the distal renal tubule of Amphiuma.

Amphiuma kidneys were isolated and perfused with modified Ringer solution and peritubular and transepithelial membrane potentials (p.d.s) in distal tubules measured with micro-electrodes during rapid changes of luminal electrolyte concentrations. Peritubular membrane potential and net fluid reabsorption (split-oil-droplet method) were also measured with and without application of various drugs known to alter transport. Raising the luminal sodium concentration from 10 to 100 mM reversibly increased the peritubular p.d. The magnitude of the peritubular p.d. was a saturable function of luminal sodium concentration. In the presence of chloride in the lumen the peritubular hyperpolarization following increased luminal sodium could be inhibited by luminal amiloride (10(-4)M). Sodium-induced hyperpolarization of the peritubular p.d. could be completely inhibited by 10(-5)M-ouabain. Adding amiloride (10(-4)M) to the luminal fluid rapidly and reversibly depolarized the peritubular p.d. and inhibited fluid reabsorption. Addition of amphotericin B (20 micrograms/ml) to the luminal perfusion solution had no effect on peritubular p.d. at 100 mM-luminal NaCl but at 10 mM-NaCl, peritubular p.d. hyperpolarized. Fluid reabsorption was stimulated (with 100 mM-NaCl in the lumen). Addition of amphotericin when the tubule was perfused on both sides with solutions containing a constant potassium concentration of 78 mM and a variable sodium concentration ranging from 7.8 to 34.5 mM revealed strong dependence of the peritubular hyperpolarization on the sodium concentration. Luminal furosemide (10(-4)M) and chlorothiazide (10(-4)M) and peritubular ethacrynic acid (10(-4)M) all reduced fluid reabsorption but hyperpolarized the peritubular p.d. The data suggest the presence of an electrogenic sodium transport process in the peritubular membrane that directly contributes to the generation of the peritubular potential. In addition, chloride transport has an important role in determining this potential.

Absorption↗
PubMed1984

The influence of warm and cold ischemic time on the outcome of cadaveric renal transplantation.

The influence of warm and cold ischemic time (WIT and CIT) on renal allograft function and allograft survival rates was analyzed from the Eurotransplant data. From 1977 through 1980 renal allograft recipients were divided into three groups, according to the length of the WIT of their graft: group I, 0-10 min (n = 2,636); group II, 11-20 min (n = 108); group III, 21-35 min (n = 17). Differences in graft function or graft survival have not been observed between these groups. It is concluded that donor kidneys with a WIT up to 20 min are acceptable for transplantation. The transplantation results in group III suggest that 35 min is a safe limit for acceptance, but the small number of transplantations in this group does not justify a firm conclusion. A combined analysis of warm and cold ischemia shows that simple cold storage up to 50 h is safe and acceptable, provided that warm ischemia is kept minimal (less than 10 min). It seems advisable to keep hypothermic preservation within the limit of 30 h, when WIT exceeds 10 min.

Cold Temperature↗