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K Cooper

Publications and source records attributed to K Cooper.

At least 199 records · Page 11Linked to original sources
PubMed1990

A non-selective cation channel in rabbit corneal endothelium activated by internal calcium and inhibited by internal ATP.

The apical membrane of the rabbit corneal endothelium contains a cation selective channel of 21.7 +/- 0.4 pS conductance which is activated by internal Ca2+ and inhibited by internal ATP. Patch clamp studies show the channel to be quite selective for cations over anions but not to select between Na+ and K+. In excised patches in the inside-out configuration, the open probability increases when the internal Ca2+ is raised above 10(-4) M. ATP decreases the open probability when its internal concentration exceeds 10 microM. At 1 mM ATP, no channel openings are ever seen. AMP and ADP also inhibit at least as well as does ATP. One microM AMP-PNP, a non-hydrolyzable ATP, also inhibits gating and so phosphorylation by a PO4(-3) cleaved from ATP is not the mechanism of ATP inhibition. The channel is apparently impermeable to divalent ions since neither Ba2+ nor Ca2+ carry any detectable current. Quinidine produces a flickery, weakly voltage dependent blockade when applied to the channel's cytoplasmic surface. Both Ca2+ and ATP work at concentrations not expected to occur inside healthy cells. It is presently uncertain if this is a physiologically important channel in these cells.

Adenosine Diphosphate↗
PubMed1990

Granuloma inguinale of the cervix: a carcinoma look-alike.

Granuloma inguinale of the cervix presents as a proliferative growth and may mimic carcinoma. Over a 3 year period 18 patients with cervical granuloma inguinale were detected. Nine (50%) had a clinical diagnosis of carcinoma of the cervix on admission, five of whom had extensive investigations to exclude a malignancy. In communities where these two conditions are commonly seen it is recommended that granuloma inguinale be considered in young women with granulomatous lesions of the cervix, so as to avoid extensive and financially costly investigations, and unnecessary psychological stress for patients.

Adult↗
PubMed1990

A maxi calcium-activated potassium channel from chick lens epithelium.

The apical membrane of embryonic chick lens epithelium contains at high density, a large conductance K+ channel whose open probability is increased by Ca++ at the inner surface of the membrane and by depolarization. The conductance of the channel when it is fully open in symmetrical 150 mM K+ solutions is 214 +/- 3 pS (mean +/- std. error). The current through the channel is a function of the K+ concentration. Gating (open probability) at positive transmembrane voltages increases as the internal [Ca++] is raised above 10(-7) M. The open probability decreases monotonically as the transmembrane voltage is made more negative. The channel is at least 87 times more permeable to K+ than to Na+ or Li+ and shows appreciable permeability to Rb+ and NH4+. It has at least three subconductance levels amounting to approximately 3/4, 1/2, and 1/4 the fully open unitary conductance. The occurrence of these subconductance levels is highly variable from one patch to another. The channel is blocked by physiological levels of internal Na+ but not over a physiological voltage range. This block is partially overcome by elevated external K+. This K+ channel from chick lens epithelium is blocked by a number of compounds known to block BK channels in other tissues. Here we show that decamethonium and Ba++ are effective blockers when added to the inner bathing solution at concentrations greater than .1 mM. Tetraethylammonium, Cs+, quinine, quinidine and Ba++ are all effective blockers when applied to the outer side of the channel in the .1 mM - 5 mM range. With the exception of internal Ba++, all of these compounds produce a fast flicker-type blockade. We use a one-site model to quantify the blockade caused by these flicker producing agents. The voltage dependence of the blockade by Cs+ suggests that this channel probably allows multiple occupancy.

Animals↗
PubMed1990

Single potassium channels in corneal epithelium.

The basal cell layers of the rabbit and human corneal epithelia contain a frequently occurring ionic channel whose unitary currents can be recorded in cell-attached or excised membrane patches by use of a patch voltage clamp. The channel is highly conductive (165 pS in 150 mM K+ salts) and is very selective for K+ over Na+ (PK/PNa greater than 40:1). Its open probability is increased by the application of suction to the recording pipette although its gating is less sensitive to suction than that of many other "stretch-activated" channels reported. The current through the channel is a saturating function of the K+ concentration in the bathing solutions with half saturation occurring at 480 mM and a single-channel current at saturation (imax) of 31 pA. In the absence of applied suction, the open probability is extremely variable from patch to patch and shows little voltage dependence over the physiologic voltage range. The channel also gates frequently to several subconductance levels. It is blocked by external Cs+ and Ba+2 in the 0.1-10 mM range but not by most other K+ channel blockers. It is also partially blocked by Ca+2 at both its internal and external surfaces. Because of its novel properties (stretch activation and large conductance), it can be used to measure the input resistance and total capacitance of single dissociated cells.

Animals↗
PubMed1989

Influence of plasma triglycerides on lipoprotein patterns in normal subjects and in patients with coronary artery disease.

This study examined the correlation of plasma triglyceride levels with concentrations of intermediate, low and high density lipoproteins (IDL, LDL, and HDL, respectively) and to particle sizes of LDL in 93 normal men and 106 men with coronary artery disease. Plasma triglyceride concentrations were in the normal range for all persons in both groups. Analysis of lipoproteins of density less than 1.063 g/ml was carried out by analytical ultracentrifugation. The analytical pattern gave the peak Sf for LDL as well as an indication of heterogeneity of particle sizes in the density range of LDL. In both normal subjects and patients with coronary artery disease, a positive correlation was found between peak Sf for LDL and concentrations of plasma triglycerides. Plasma triglyceride levels also were correlated positively with concentrations of Sf 20 to 60 lipoproteins and total IDL mass, and inversely with HDL cholesterol levels. Furthermore, the value for peak Sf for LDL correlated inversely with the IDL mass concentration and IDL/LDL mass ratio, and positively with the HDL cholesterol levels. The results indicate that the lipoprotein pattern, including lipoprotein concentrations and particle sizes, is sensitive to concentrations of plasma triglycerides even when the latter are within the normal range.

Adult↗
PubMed1989

Mesenchymal hamartoma of the liver. A report of 5 cases.

Mesenchymal hamartoma of the liver is a rare benign tumour of childhood, characterised by an admixture of ductal structures within a copious loose connective tissue stroma. Less consistent features include hepatocytes and haemopoietic elements. The stroma has a propensity to accumulate fluid and to create macroscopic cystic spaces. Five cases are reported.

Child, Preschool↗
PubMed1989

Light-chain nephropathy. A report of 2 cases.

Two cases of renal impairment caused by the deposition of monoclonal immunoglobulin light-chain determinants in the glomerular mesangium and basement membranes as well as in the tubular basement membranes of the kidney are described (light-chain nephropathy). Both cases were associated with myeloma. Examinations by light microscopy, immunohistochemistry and electron microscopy are also described. Differential diagnoses on light microscopy include diabetic glomerulosclerosis (Kimmelstiel-Wilson lesions), amyloidosis and mesangiocapillary glomerulonephritis type 1.

Adult↗
PubMed1989

Low prevalence of neurological and neuropsychological abnormalities in otherwise healthy HIV-1-infected individuals: results from the multicenter AIDS Cohort Study.

Accurate description of the prevalence of neurological impairment in healthy individuals who are infected with human immunodeficiency virus type 1 (HIV-1) has relevance for public health policy, for employment issues, and for planning future health needs. Within the Multicenter AIDS Cohort Study, we determined the cross-sectional prevalence of neurological abnormalities in 270 HIV-1 seropositive homosexual and bisexual men in Centers for Disease Control Groups II and III, using a control group of 193 HIV-1 seronegative homosexual men. Utilizing a neurological and neuropsychological screening battery, we found no differences in the prevalence of neuropsychiatric symptoms or in neuropsychological performance. One hundred nineteen subjects with abnormalities on screening tests completed additional neuropsychological testing and had neurological examinations. The majority had normal results and the frequency of neurological abnormalities and impaired neuropsychological performance was not significantly increased among HIV-1 seropositive subjects. Most of the abnormalities could be attributed to causes other than HIV-1. One subject had mild HIV-1-related dementia, yielding a prevalence of 3.7:1,000 (95% confidence interval: 0.19-23.7:1,000). Magnetic resonance imaging demonstrated sulcal prominence and focal areas of high signal intensity in white matter in 63% of HIV-1 seropositive subjects and 48% of uninfected control subjects. Abnormalities in cerebrospinal fluid were noted in 23 (85%) of 27 HIV-1-infected individuals. Our studies indicate that the prevalence of dementia and other HIV-1-related neurological disorders is very low among healthy HIV-1 seropositive homosexual men. The confounding effects of factors such as substance abuse or preexisting medical conditions must be considered in the neurological evaluation of such patients.

AIDS Dementia Complex↗
PubMed1989

Membrane and junctional properties of dissociated frog lens epithelial cells.

Individual cells and cell pairs were isolated from frog lens epithelium. Individual cells were whole cell voltage clamped and the current-voltage relationship was determined. The cells had a mean resting voltage of -54.3 mV and a mean input resistance of 1.4 G omega. The current-voltage relationship was linear near the cell resting voltage, but showed decreased resistance with large depolarization or hyperpolarization. Junctional currents between pairs of cells were recorded using the dual whole cell voltage-clamp technique. The corrected junctional resistance was 15.5 M omega (64.5 nS). The junctional current-voltage relationship was linear. A combination of ATP and cAMP, in the electrodes, stabilized junctional resistance. Currents recorded when uncoupling was nearly complete, showed evidence of single connexion gating events. A single-channel conductance of about 100 pS was prominent. Dye spread between isolated cell pairs was demonstrated using Lucifer Yellow CH in a whole cell configuration. Photodamage to the cells due to the dye was apparent. Dye loaded cells, in the presence of exciting light, showed decreased resting voltages, decreased input resistances and morphological changes. Glutathione (20 mM) delayed this damage.

Animals↗
PubMed1989

Properties of single potassium-selective ionic channels from the apical membrane of rabbit corneal endothelium.

The corneal endothelium from several species contains a highly conductive, flickery potassium selective channel in the apical membrane. The channel flicker is not due to blockade. The single channel has an inwardly rectifying current-voltage relationship under symmetrical ionic conditions. Based on reversal potential measurements, it is more than 40:1 selective for potassium over sodium. It also shows subconductance levels. In bathing solutions lacking chloride and bicarbonate, its open probability is less than 0.1 and is quite independent of voltage in the physiological voltage range. Bicarbonate in the bath or DIDs in the pipette increase channel activity. The channel is blocked by external cesium in the 0.5 to 5 mM range. The steepness of the voltage dependence of this blockade is consistent with multiple occupancy.

Animals↗
PubMed1989

Aluminum induced anemia: pathogenesis and treatment in patients on chronic hemodialysis.

The baseline hematologic status of 27 patients with modest degrees of aluminum overload was examined. In addition, hematologic data were evaluated in 19 of these patients during and after treatment with DFO. Although neither severe anemia nor microcytosis was observed pretreatment, there was a significant correlation between hemoglobin level and degree of aluminum burden as determined by bone surface aluminum staining (r = -0.58; P less than 0.007). Following treatment with DFO, hemoglobin concentration increased dramatically by 1.3 to 4.4 g/dl in eight patients but did not change in the remaining eleven. Responders and nonresponders were similar with regard to the degree of aluminum overload both before and after chelation therapy but differed with regard to baseline levels of erythropoietin (higher in responders) and degree of iron overload (greater in nonresponders). Pretherapy levels of red cell ALA dehydratase were depressed in all patients (32 +/- 4 vs. 56 +/- 5 U/g Hb in normals) but did not correlate with the degree of aluminum overload and did not change with chelation therapy. Pretherapy levels of red cell protoporphyrin were elevated in 15 of 24 patients (62%) and were higher in responders than in nonresponders. Following DFO therapy, levels fell by 25 to 50% in 7 of 8 patients with elevated pretherapy values, despite the tendency in several patients to develop iron deficiency with treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1989

The safety of maximal exercise testing.

Previous reports on the safety of exercise testing have been based on surveys from different testing facilities with a variety of testing protocols and patient types. From 1971 through 1987, 71,914 maximal exercise tests conducted in a population with a low prevalence of known coronary heart disease under uniform conditions at a single medical facility resulted in six major cardiac complications including one death. No complications have occurred in the past 10 years in 45,000 maximal tests. The overall cardiac complication rate in men and women is 0.8 complications per 10,000 tests with 95% confidence intervals of 0.3-1.9 complications per 10,000 tests. Maximal exercise testing appears safer than some previously published reports have suggested and seems to be getting safer with time.

Accident Prevention↗
PubMed1989

Studies on the mechanism of benzene toxicity.

Using the 59Fe uptake method of Lee et al. it was shown that erythropoiesis in female mice was inhibited following IP administration of benzene, hydroquinone, p-benzoquinone, and muconaldehyde. Toluene protected against the effects of benzene. Coadministration of phenol plus either hydroquinone or catechol resulted in greatly increased toxicity. The combination of metabolites most effective in reducing iron uptake was hydroquinone plus muconaldehyde. We have also shown that treating animals with benzene leads to the formation of adducts of bone marrow DNA as measured by the 32P-postlabeling technique.

Aldehydes↗
PubMed1989

Dye and electrical coupling between cells of the rabbit corneal endothelium.

The corneal endothelium is known to contain gap junctions on its lateral borders. Here we show that the endothelial cells of the rabbit cornea are highly dye coupled. Lucifer Yellow CH introduced into a single cell through either an intracellular glass microelectrode or a patch electrode rapidly spreads into its neighboring cells at room temperature. We have used the analysis of Safranyos and Caveney (JCB 100:736-747, 1985) to place quantitative lower bounds on the effective diffusion coefficient of Lucifer Yellow CH iontophoresed into rabbit corneal endothelial cells. By this analysis, we obtain a value of 5.0 x 10(-8) cm2/sec. We also demonstrate that both dye and electrical coupling exists in cell pairs or small clusters of cells enzymatically dissociated from Descemet's membrane.

Animals↗
PubMed1989

Thyroid carcinosarcoma. A case report.

A thyroid carcinosarcoma--a rare neoplasm of the thyroid gland--in an elderly woman is described. On histological examination the tumour showed the characteristic biphasic pattern of follicular carcinoma and mesenchymal differentiation with a chondrosarcomatous component and osseous metaplasia. The clinical features and details of the histopathological and immunohistological examinations of this tumour are reported.

Carcinosarcoma↗