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Biomedical subjects

K A Fisher

Publications and source records attributed to K A Fisher.

At least 19 recordsLinked to original sources
PubMed1995

Nephrotic syndrome and acute renal failure associated with hepatitis A virus infection.

Acute renal failure has been documented in association with hepatitis A virus (HAV) infection. This report describes a temporal relationship between HAV infection and immune complex mesangial proliferative glomerulonephritis associated with nephrotic syndrome. Animal experimental data have already shown that this is indeed a histological lesion associated with HAV infection. This case report is the first English documentation associating HAV infection with immune complex mesangial proliferative glomerulonephritis.

Acute Kidney Injury↗
PubMed1992

Activation of proximal tubular Na(+)-H+ exchange by angiotensin II.

Stimulation of Na(+)-H+ exchange by angiotensin II (ANG II) was characterized in renal proximal tubular cells. Rabbit proximal nephron segments were incubated in the presence or absence of ANG II (5 x 10(-10) M), after which brush-border membrane vesicles (BBMV) were isolated and assayed for Na(+)-H+ antiporter activity using the acridine orange technique. Both the affinity (for sodium) and capacity of the carrier were elevated significantly (P less than 0.05) within 15 min of incubation with ANG II. To determine whether the stimulation of transport capacity involved a change in Na(+)-H+ antiporter density in the luminal membrane, binding of tritiated 5-(N-methyl-N-isobutyl)amiloride ([3H]MIA) was measured in BBMV derived from control and ANG II-treated nephron segments, following maximal stimulation. This demonstrated a significant (P less than 0.05) increase in the maximal specific binding (Bmax) of [3H]MIA binding in the ANG II-treated group compared with control, of a magnitude sufficient to account for the observed change in maximal velocity (Vmax). The data indicate that the Vmax effect is caused by an apparent increase in the number (density) of active Na(+)-H+ carriers present in the luminal membrane. Finally, to test the possibility that the observed kinetic change involves an exocytic mechanism, the effect of colchicine on ANG II-stimulated antiporter activity was examined. The increase in Vmax due to ANG II was blocked by the addition of 0.5 mM colchicine to the incubation medium, whereas colchicine alone had no significant effect on the Vmax of Na(+)-H+ kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1990

Measuring changes in membrane thickness by scanning tunneling microscopy.

We investigated the feasibility of using the scanning tunneling microscope (STM) as a morphometric tool to measure the thickness of biomembranes. Planar monolayers of oriented purple membrane (PM) were prepared, nitrogen-dried or freeze-etched, and coated with metal. PM thickness was quantified by STM and transmission electron microscopy. STM calibration and the effect of contamination-mediated surface deformation on measurements of PM thickness were evaluated. The thickness of PM attached to mica and glass and the effect of papain on PM thickness were also examined. The apparent thickness of enzymatically modified PM increased after papain treatment. The mean thickness of both nitrogen-dried PM on mica and freeze-etched PM on glass was 4.6 nm. After papain treatment PM thickness on mica increased to 4.8 nm and on glass to 5.4 nm. These results demonstrate that STM analysis of metal-coated planar membrane monolayers can be used to measure changes in average membrane thickness at sub-nanometer resolution.

Amino Acids↗
PubMed1990

Long-term neurologic outcome in psychogenic water drinkers with severe symptomatic hyponatremia: the effect of rapid correction.

PURPOSE: The purpose of our study was to ascertain the safety of rapidly correcting acute symptomatic hyponatremia in psychogenic water drinkers, particularly in regard to any delayed adverse neurologic sequelae. PATIENTS AND METHODS: We reviewed the medical records of all known psychogenic water drinkers (34) in our hospital from 1977 to 1989. Using seizure as a marker of severity, we identified 13 patients having a total of 27 episodes associated with severe hyponatremia. We evaluated the charts of those patients in detail to assess the mode of treatment, rate of correction, and long-term neurologic outcome. None of the patients experienced respiratory arrest before treatment, which was initiated within 2 hours of seizure. RESULTS: For all 27 episodes, the initial serum sodium level (mean +/- SE) was 110.9 +/- 1.2 mmol/L, and the rate of correction (mean +/- SE) was 1.65 +/- 0.2 mmol/L/hour. All but one episode were corrected "rapidly" (initial correction rate of 0.7 or more mmol/L/hour) to 120 to 130 mmol/L within 12 hours. The absolute change in the serum sodium level was 15.1 +/- 1.2 mmol/L in 12 hours, 21.6 +/- 1.4 mmol/L in 24 hours, and 25.9 +/- 1.4 mmol/L in 48 hours. In no instance did therapy induce hypernatremia. All patients recovered immediately after treatment. There was no clinical or radiologic evidence of adverse neurologic sequelae immediately after treatment or after 6 years of follow-up. CONCLUSION: In this series of male psychogenic water drinkers, early "rapid" correction of acute symptomatic hyponatremia by raising the serum sodium level 15 mmol/L in 12 hours while maintaining an absolute change in the serum sodium level of 26 mmol/L within 48 hours produced no long-term neurologic sequelae.

Adult↗
PubMed1990

Scanning tunneling microscopy of planar biomembranes.

We combined planar membrane monolayer techniques with scanning tunneling microscopy (STM) to measure the thickness of metal-coated purple membrane (PM) isolated from Halobacterium halobium. Although the metal coating precluded obtaining high-resolution lateral information, it facilitated obtaining high-resolution vertical information. For example, the apparent mean thickness of planar PM and variations in thickness of enzyme-treated PM could be detected and quantified at sub-nanometer resolution.

Cell Membrane↗
PubMed1990

Effects of hypertonic peritoneal dialysis solutions on neutrophil superoxide production.

Superoxide produced by neutrophils plays an important role in the killing of bacterial pathogens. The effects of glucose-containing peritoneal dialysis solutions on superoxide production by canine and human neutrophils were studied. A significant decrement in superoxide generation was noted with the 2.27% and 3.86% glucose solutions. The results suggest that hypertonic peritoneal dialysis solutions curtail neutrophil superoxide generation.

Animals↗
PubMed1989

Transmembrane signaling: tumor promoter distribution.

Diacylglycerol plays a critical role in transmembrane signaling by activating protein kinase C (PKC). The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) mimics that action, and in the human erythrocyte, TPA-activated PKC phosphorylates membrane proteins. Although molecular aspects of this process have been investigated, details of the interaction of TPA with plasma membranes remain elusive. Because TPA is hydrophobic, it has been assumed that it associates with the lipid bilayer. However, there is no direct evidence for its transbilayer distribution. Because knowledge of its location would limit molecular models proposed to explain its mode of action, we have used membrane-splitting techniques, based on freeze-fracture of planar cell monolayers, to quantify transmembrane partitioning of [3H]TPA. Under conditions where PKC-mediated phosphorylation was stimulated by [3H]TPA and where more than 90% of the [3H]TPA was associated with the human red cell plasma membrane, two-thirds of the TPA partitioned with the cytoplasmic leaflet after bilayer splitting. This represents the first direct topographic localization of TPA in a biological membrane and supports the hypothesis that the mechanism of TPA activation requires its association with the cytoplasmic leaflet of the bilayer.

Cytosol↗
PubMed1989

Monolayer freeze-fracture and scanning tunneling microscopy.

This article reviews research on planar monolayer methods, application of the methods to analyses of transmembrane signaling, and the combination of these methods with scanning tunneling microscopy (STM). Past research has involved the development of monolayer freeze-fracture methods. These include monolayer freeze-fracture autoradiography (MONOFARG), an electron microscopic cytochemical method to analyze in-plane distributions of radioisotopes, and double-labeled membrane splitting (DBLAMS) and single-membrane monolayer splitting (SMMS), methods to analyze transmembrane distributions of native and radiolabeled proteins and lipids. Present research has focussed on using these methods to investigate mechanisms of transmembrane signaling mediated by protein kinase C (PKC), including the transbilayer distribution of the tumor promoter TPA, a lipophilic activator of PKC, and the transbilayer distribution of peripheral membrane proteins phosphorylated by PKC. Future work will involve the combination of planar sample preparation with STM. The principles and applications of biological STM are briefly reviewed and a low-resolution STM image of a planar purple-membrane monolayer is included. The combination of planar methods and STM can provide the chemical information lacking in STM images enabling microscopists to investigate biochemical phenomena at nanometer resolution.

Autoradiography↗
PubMed1988

Topography of protein kinase C substrates analyzed by membrane splitting.

We have used the methods of planar cell and membrane monolayer formation and monolayer splitting to study structural details of the transmembrane signaling process mediated by protein kinase C. We analyzed human red cell membrane proteins phosphorylated by phorbol ester activation of protein kinase C. Planar single membrane preparations, extraction procedures, and gel electrophoresis coupled with silver staining and autoradiography confirmed that two bands in the 100 kDa region, and bands 4.1, and 4.9, were peripheral and phosphorylated by treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA also stimulated minor incorporation of [32 P]Pi into most integral membrane proteins, including band 3, glycophorin A, the band 4.5 region (glucose transporter) and band 7. Planar cell and membrane-splitting methods revealed that neither integral nor peripheral phosphorylated polypeptides were cleaved by freeze fracture, that all phosphorylated peripheral proteins partitioned intact with the cytoplasmic side of the membrane, and that the percentages of [32P]Pi-labeled peripheral proteins were the same in split membrane cytoplasmic leaflets as in intact membranes. As a unique approach to examining protein topographies membrane splitting provides strong evidence that the major phosphorylated products of the polyphosphatidylinositide pathway are topographically associated with the cytoplasmic leaflet of the human erythrocyte plasma membrane. We further conclude that TPA-induced phosphorylation of red cell peripheral proteins does not significantly alter their transbilayer partitioning patterns after membrane splitting.

Cell Fractionation↗
PubMed1987

Correlation of mammalian cell killing by heat shock to intramembranous particle aggregation and lateral phase separation using fluorescence-activated cell sorting.

Heat shock induces a dose-dependent increase in the fraction of Chinese hamster ovary cells that stain the fluorescent membrane probe N-epsilon-dansyl-L-lysine (DL). Dansyl lysine has previously been shown to select for cholesterol-free membrane domains in phospholipid liposomes. We found that the fraction of cells excluding DL could be closely correlated to cell survival as assayed by 37 degrees C incubation following heat treatment. Fluorescence-activated cell sorting indicated that essentially all of the DL-staining cells were nonviable. Freeze fracture electron microscopy of sorted cells showed that all the cells that stained with DL also had highly suggested intramembranous particle (IMP) aggregation while DL-excluding cells did not. Furthermore, IMP aggregation was shown to occur immediately after heat shock and to precede DL staining. Treatment with other membrane-active agents such as ethanol, amphotericin B, filipin, procaine, and lidocaine (i) induced DL staining that was closely correlated to survival, (ii) induced dramatic cytotoxic sensitization when combined with heat, and (iii) induced aggregated IMPs at relevant cytotoxic concentrations. Several nonmembrane-active agents were examined; none induced DL staining, dramatic cytotoxic sensitization, or IMP aggregation. These results raise the possibility that heat shock inactivates mammalian cells primarily via nonspecific aggregation and denaturation of membrane proteins resulting in a lateral phase separation of membrane components, including the generation of phospholipid domains.

Animals↗
PubMed1987

Malignant mesothelioma with occupational and environmental asbestos exposure in an Illinois community hospital.

Clinical, radiologic, pathologic, and epidemiologic data on 32 patients with diffuse malignant mesothelioma (DMM) diagnosed between 1968 and 1984 at a 427-bed community hospital in Berwyn, Ill, were reviewed. Independent pathologists' review of light microscopy, supported by electron microscopy, immunoperoxidase staining, or autopsy, confirmed 29 pleural and three peritoneal DMMs. Clinical and radiologic characteristics were similar to those in published case series. Median age at diagnosis was 67 years, and median survival after diagnosis, seven months. Fourteen patients were women. Exposure histories were obtained through 22 interviews supplemented by hospital charts and death certificates. Thirty patients (94%) had a history of asbestos exposure through work (15 [47%]) and/or residence near an asbestos facility (27 [84%]). Medical records and death certificates underreported asbestos exposure and DMM.

Adult↗
PubMed1986

Effect of membrane splitting on transmembrane polypeptides.

We investigated the effect of membrane splitting on the primary structure of human erythrocyte membrane polypeptides. Monolayers of intact, chemically unmodified cells were freeze-fractured and examined by one-dimensional SDS PAGE. Silver-stained gels revealed all major polypeptides that stain with Coomassie Blue as well as all bands that stain with periodic acid Schiff's reagent. Both nonglycosylated and glycosylated membrane polypeptides could be detected at concentrations of only a few nanograms per band. Membrane splitting had no effect on the position or number of bands. Monolayers of intact erythrocytes that had been enzymatically radioiodinated with lactoperoxidase were examined by electrophoresis, fluorography, and liquid scintillation counting. Radioactivity was quantified before and after monolayer formation and splitting, and at several stages of gel staining, drying, and fluorography. Although overexposed fluorographs revealed several minor radioiodinated bands in addition to band 3 and the glycophorins, no new bands were detected in split membrane samples derived from intact cells. These observations support the conclusion that neither the band 3 anion channel nor the glycophorin sialoglycoproteins are fragmented during freeze-fracturing. Although both band 3 and glycophorin partition to the cytoplasmic side of the membrane, preliminary quantitative observations suggest an enrichment of glycophorin in the split extracellular "half" membrane. We conclude that the process of membrane splitting by planar monolayer freeze-fracture does not cleave the covalent polypeptide backbone of any erythrocyte membrane protein, peripheral or integral.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1985

Bactericidal activity of ascitic fluid in patients with nephrotic syndrome.

Patients with nephrotic syndrome are unusually susceptible to infections, including primary peritonitis. In this study, we have evaluated nine adult patients with nephrotic syndrome and ascites for ascitic fluid bactericidal activity, complement and immunoglobulin concentrations. Eight of nine patients had diminished ascitic fluid bactericidal activity while twelve control peritoneal fluids had normal bactericidal activity. Complement (C3 and C4) and immunoglobulin (IgG and IgM) concentrations were significantly lower in nephrotic syndrome ascitic fluid than peritoneal fluid from normal subjects. These findings may explain the high occurrence rate of primary peritonitis in nephrotic patients with ascites.

Ascitic Fluid↗
PubMed1984

Two-dimensional electrophoretic analysis of human erythrocyte cylindrin.

Cylindrin, a macromolecule isolated from the human erythrocyte, and the band 7 proteins of the erythrocyte membrane were analyzed by one- and two-dimensional electrophoresis. Cylindrin was recovered from both the cytosol and cell membranes of hypotonically lysed erythrocytes, and its identity was confirmed by electrophoresis and transmission electron microscopy. Cylindrin from either source produced eight bands on one-dimensional SDS gels, and seventeen spots on two-dimensional gels, revealing a more complex composition than previously reported. It is unlikely that this complexity was due to proteolysis, since preparations of cylindrin with various protease inhibitors gave the same electrophoretic patterns. Mixing experiments showed that the polypeptide subunits of the cylindrin complex are distinct from the band 7 proteins of the erythrocyte membrane. This finding failed to support a role for the cylindrin macromolecule in the permeability disorders of the erythrocyte membrane associated with a missing band 7 protein.

Blood Proteins↗
PubMed1983

Hypertension in pregnancy.

Blood pressure; extracellular fluid volume; renal plasma flow; glomerular filtration rate; plasma concentrations of renin, angiotensin, aldosterone, desoxycorticosterone, and prostaglandins; responses to infused angiotensin; and many other factors are altered during normal and hypertensive gestation. The diagnosis of the exact disease process responsible for hypertension in pregnancy in an individual patient is extremely difficult if based solely on clinical criteria. The American College of Obstetricians and Gynecologists has suggested the following clinical classifications: (1) preeclampsia-eclampsia, (2) chronic hypertension of whatever cause, (3) chronic hypertension with superimposed preeclampsia, and (4) late or transient hypertension. The three broad categories of renal disease responsible for these clinical syndromes are: (1) preeclampsia-eclampsia, (2) hypertensive changes, and (3) various primary renal diseases. Controversy abounds regarding the aggressiveness of therapy in this syndrome. We prefer a middle-of-the-road approach, bringing blood pressure down to the range of 95 to 100 mm Hg. Hydralazine and Aldomet are the usual drugs of choice. Any intervening nervous system hyperexcitability suggests impending eclampsia and should be immediately treated with magnesium sulfate. The long-term prognosis for the mother with pure preeclampsia appears to be excellent. Most infants born of hypertensive gestations are small for date, with a prognosis that is also affected by the underlying disease of the mother.

Chronic Disease↗
PubMed1982

Spectroscopic assays for measuring quantities of erythrocyte membrane "halves".

The quantities of outer and inner"halves" produced by freeze-fracturing human erythrocyte membranes have been measured by visible and fluorescence spectroscopy. Assays have been developed that are based on the use of two membrane surface markers: hemoglobin (Hb), a native marker for the cytoplasmic side of the membrane, and fluoresceinated concanavalin A (FITC-Con-A), a marker for the extracellular side. Hb absorbance is proportional to the fraction of cytoplasmic "half" membranes, and FITC fluorescence is proportional to the fraction of extracellular "halves." A procedure is described for the preparation of surface-labeled, intact erythrocytes suitable for the formation of homogeneous, planar cell monolayers of square-centimeter dimensions on polylysine-treated glass (PL-glass). Cell monolayers were frozen and fractured, and the fractions of absorbance and fluorescence in each of the two split portions determined. The PL-glass portion of membrane contained a substantially higher ratio of fluorescence to absorbance than unsplit controls, and its paired portion, a complementary lower ratio, demonstrating that the PL-glass portion was significantly enriched in extracellular "half" membrane. Experiments investigating split membrane recovery show that the double labeled membrane splitting technique is well suited to analysis of the transmembrane distribution of membrane lipids and polypeptides using methods that do not require quantitation by electron microscopy.

Erythrocyte Membrane↗