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Biomedical subjects

G Meissner

Publications and source records attributed to G Meissner.

At least 127 records · Page 7Linked to original sources
PubMed1981

Evidence for two types of rat liver microsomes with differing permeability to glucose and other small molecules.

Radioisotope flux measurements using Millipore filtration revealed two populations of rat liver microsomes designated type A and B. Type A and B vesicle are similar in that both are essentially impermeable to sucrose yet permeable to Cl-. About 70% of the microsome (type A) are permeable to D-glucose, L-glucose, 2-deoxy-D-glucose, D-mannose, D-mannitol, uridine, glycine, L-leucine, choline+, Tris+, Rb+, K+, and Na+. Other solutes such as D-gluconate-, D-glucosamine+, N-acetyl-D-glucosamine, L-glutamate-, L-lysine+, sulfate2-, oxalate2-, and phosphate anions transverse type A vesicles with an intermediate rate. All of the above solutes except Cl- pass with a comparatively slow rate the remaining 30% type B vesicles. Both type A and B microsomes are relatively impermeable to glucose 6-phosphate and related monophosphates. Membrane potential measurements using liver microsomes and control membrane vesicles derived from rabbit skeletal muscle sarcoplasmic reticulum indicated that type A liver microsomes, despite being permeable to K+ and Na+, either lack or contain only a small number of highly conducting K+ and Na+ structures, such as the K,Na channel of sarcoplasmic reticulum. Treatment with the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid lowered the permeability of type A vesicles to several uncharged and negatively charged solutes including D-glucose and gluconate-. These results suggest that a large fraction of liver microsomes is rendered permeable to various biologically relevant solutes and ions, perhaps through the presence of one or more channels with a maximal diameter of approximately 7-8 A which select(s) against solutes on the basis of their size and charge.

Animals↗
PubMed1981

Calcium transport and monovalent cation and proton fluxes in sarcoplasmic reticulum vesicles.

ATP-dependent Ca2+ uptake by rabbit skeletal muscle sarcoplasmic reticulum vesicles has been studied in the presence and absence of artificially generated pH gradients and membrane potentials. H+ and K+ diffusion potentials were generated via the H+ and K,Na channels of sarcoplasmic reticulum by transfer of vesicles from low to high pH, or from high to low K+. Membrane potentials were measured using the voltage-sensitive fluorescent dye 3,3'-dipentyl-2,2'-oxacarbocyanine. The initial rate of Ca2+ uptake was found to be increased in the presence of a pH gradient and membrane potential (negative inside). In turn, the rates of decay of K+- or H+-induced membrane potentials were accelerated during Ca2+ transport, suggesting that active Ca2+ uptake stimulated the release of K+ and H+ from the vesicles. The ratio of K+ (or H+) release to Ca2+ transport was near two. Release of K+ did not appear to be directly catalyzed by the Ca2+-ATPase. Evidence against a directly coupled ATP-mediated 2 K+-Ca2+ or K+-Ca2+ exchange reaction was that (i) similar results were obtained when K+ was substituted by Na+ or by organic cations which could rapidly permeate through the channel of K+,Na+-permeable vesicles and (ii) Ca2+ transport did not result in an equivalent release of 86Rb+ or 22Na+ from K+,Na+-impermeable vesicles. These studies are in support of an electrogenic Ca2+ transport system in sarcoplasmic reticulum. The results further suggest that during Ca2+ transport development of a membrane potential (positive inside) is likely nullified by the countermovement of the permeant cations K+, Na+, and H+.

Adenosine Triphosphate↗
PubMed1981

Permeability of reconstituted sarcoplasmic reticulum vesicles. Reconstitution of the K+, Na+ channel.

Permeability properties of reconstituted rabbit skeletal muscle sarcoplasmic reticulum vesicles were characterized by measuring efflux rates of [3H]inulin, [3H]choline+, 86Rb+, and 22Na+, as well as membrane potential changes using the voltage-sensitive probe, 3,3'-dipentyl-2,2'-oxacarbocyanine. Native vesicles were dissociated with deoxycholate and were reconstituted by dialysis. Energized Ca2+ accumulation was partially restored. About 1/2 of the reconstituted vesicles were found to be 'leaky', i.e., permeable to choline+ of Tris+ but not to inulin. The remaining reconstituted vesicles were 'sealed', i.e., impermeable to choline+, Tris+ and inulin. Sealed reconstituted vesicles could be further subdivided according to their K+, Na+ permeability. About 1/2, previously designated Type I, were readily permeable to K+ and Na+, indicating the presence of the K+, Na+ channel of sarcoplasmic reticulum. The remaining sealed vesicles (Type II) formed a permeability barrier to K+ and Na+, suggesting that they lacked the K+, Na+ channel. These studies show that the K+, Na+ channel of sarcoplasmic reticulum can be solubilized with detergent and reconstituted with retention of activity. Furthermore, our results suggest that part or all of the decreased Ca2+-loading efficiency of reconstituted vesicles may be due to the presence of a significant fraction of leaky vesicles.

Animals↗
PubMed1981

A liquid diffraction analysis of sarcoplasmic reticulum. I. Compositional variation.

Intensities of x-ray scattering from a series of fragmented rabbit muscle sarcoplasmic reticulum (SR) samples have been measured over the range x = 0.05 to s = 0.25. By varying the relative concentrations of lipid and protein (chiefly the Mg++-dependent, Ca++- stimulated ATPase) in the membranes of this series, and by employing methods of analysis appropriate to the scattering from binary liquid mixtures, we have identified the separable contributions of protein and lipid, and the protein-lipid interaction contributions to the total scattering profiles. The shape of the protein term is consistent with scattering from a cylindrical ATPase particle 142 A in length and 35 A in diameter. These data imply that the dominant ATPase species is monomeric. The protein-lipid interaction term has been analyzed by a novel treatment based on a determination of the pair correlation function between the electrons of the protein molecule with the electrons of the lipid bilayer in terms of the asymmetry of the transbilayer disposition of the protein. Applied to our results, the analysis indicates a fully asymmetric disposition of ATPase, in which one end of the molecule is contiguous with either the lumenal or cytoplasmic surface of the bilayer.

Animals↗
PubMed1981

Biochemical and cytochemical comparison of surface membranes from normal and dystrophic chickens.

Cytochemical and biochemical characteristics of the surface membrane components of avian dystrophic muscle were examined. A Mg2+- or Ca2+-activated ("basic") adenosine triphosphate (ATPase) was localized cytochemically in fixed, intact dystrophic muscle slices in a medium containing Mg2+ or Ca2+, adenosine triphosphate (ATP), and 1 microM free Pb2+ to capture enzymatically released phosphate ions. Electron-dense staining precipitates were found to be associated with the plasmalemma and its tortuous invaginations, and the transverse components of the T-system membrane and its associated proliferated networks. Enzymatic analysis of microsomal fractions isolated from 7-day-old and 90-day-old normal and dystrophic muscle showed a complex behavior. Specific activity of "basic" ATPase decreased with maturity in normal and dystrophic animals. The specific activities of the surface membrane associated enzymes, leucyl beta-naphthylamidase, adenylate cyclase, and guanylate cyclase, remained at various elevated levels in the mature dystrophic animals, in contrast to the normal muscle, which showed decreases in the specific activity of all three enzymes with maturation. The persistent high levels in some but not all enzyme activities in 90-day-old dystrophic muscle indicates a complicated developmental pattern in the dystrophic chicken muscle.

Adenosine Triphosphatases↗
PubMed1980

Proton permeability of sarcoplasmic reticulum vesicles.

The proton permeability of rabbit skeletal muscle sarcoplasmic reticulum vesicles was investigated by means of membrane potential measurements. Diffusion potentials were generated in sarcoplasmic reticulum vesicles, rat liver microsomes, and sarcoplasmic reticulum phospholipid vesicles by transferring vesicles from low to high pH. Potentials were measured using the voltage-sensitive fluorescent dye 3,3'-dipentyl-2,2'-oxacarbocyanine. Diffusion potentials were generated readily in sarcoplasmic reticulum vesicles using H+ gradients. Generation of a similar potential in phospholipid vesicles or liver microsomes required the presence of an uncoupler of oxidative phosphorylation. H+ and K+ gradient competition experiments indicated that both K+,Na+-permeable and -impermeable sarcoplasmic reticulum vesicles were permeable to H+. These studies suggested that a mechanism of H+ transport exists in sarcoplasmic reticulum that is independent of the K,Na channel, and that transient or steady state membrane potentials may be effected by the movement of H+.

Animals↗
PubMed1980

Cytochemical localization of a "basic" ATPase to canine myocardial surface membrane.

Enzymatic properties of a canine cardiac muscle microsomal fraction were determined to localize in situ a "basic," divalent cation dependent adenosine triphosphatase (ATPase) by ultrastructural cytochemistry. The microsomal fraction had a buoyant density of 1.08--1.13 (20--30% [w/w] sucrose) and hydrolyzed adenosine triphosphate in the presence of Mg2+, Ca2+, Mn2+, or Co2+, but not in that of Sr2+ or Ni2+, under conditions that inhibited interfering (Na+ + K+)-ATPase and sarcoplasmic reticulum Ca2+-ATPase activities. "Basic" ATPase was localized in paraformaldehyde-fixed tissue in a medium containing Mg2+ or a high Ca2+ concentration (4 mM). A free Pb2+ concentration of less than 1 microM was used to capture enzymatically released phosphate anions. Electron-dense lead precipitates were present at the plasmalemma, T-system, and intercalated disc membranes with the exception of the nexus. These studies suggest that "basic" ATPase activity is associated with surface membrane structures of canine cardiac muscle.

Animals↗
PubMed1979

Particulate guanylate cyclase of skeletal muscle: effects of Ca2+ and other divalent cations on enzyme activity.

The properties of particulate guanylate cyclase (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2) from purified rabbit skeletal muscle membrane fragments were studied. Four membrane fractions were prepared by sucrose gradient centrifugation and the fractions characterized by analysis of marker enzymes. Guanylate cyclase activity was highest in the fraction possessing enzymatic properties typical of sarcolemma, while fractions enriched with sarcoplasmic reticulum had lower activities. In the presence of suboptimal Mn2+ concentrations, Mg2+ stimulated particulate guanylate cyclase activity both before and after solubilization in 1% Triton X-100. Guanylate cyclase activity was biphasic in the presence of Ca2+. Increasing the Ca2+ concentration from 10(-8) to 10(-5) M decreased the specific activity. As the Ca2+ concentration was further increased to 5 . 10(-4) M enzyme activity again increased. After solubilization of the membranes in 1% Triton X-100, Ca2+ suppressed enzyme activity. Studies utilizing ionophore X537A indicated that the altered effect of Ca2+ upon the solubilized membranes was independent of asymmetric distribution of Ca2+ and Mg2+.

Animals↗
PubMed1978

Evidence for a K+, Na+ permeable channel in sarcoplasmic reticulum.

Potassium and sodium cation permeabilities of skeletal sarcoplasmic reticulum vesicles were characterized by means of 3H-choline, 22Na+ and 86Rb+ isotope efflux and membrane potential measurements. Membrane potentials were generated by diluting K gluconate filled sarcoplasmic reticulum vesicles and liposomes into Tris or Na gluconate media, in the presence or absence of valinomycin, and were measured using the voltage-sensitive membrane probe 3,3'-dipentyl-2,2'-oxacarbocyanine. About 2/3 of the sarcoplasmic reticulum vesicles, designated Type I, were found to be permeable to Rb+, K+ and Na+. The remaining 1/3, Type II vesicles, were essentially impermeable to these ions. The two types of vesicles were impermeable to larger cations such as choline or Tris. Both were present in about the same ratio in fractions derived from different parts of the reticulum structure. Studies with cations of different size and shape suggested that in Type I vesicles permeation was restricted to molecules fitting through a pore with a cross-section of 4--5 A by 6 A or more. When vesicles were sonicated, vesicles permeable to K+ decreased more than those impermeable to K+. These data suggest the existence of K+, Na+ permeable channels which are probably randomly dispersed in the intact reticulum structure at an estimated density of 50 pores/micrometer2. The function of the channel may be to allow rapid K+ movement to counter Ca2+ fluxes during muscle contraction and relaxation.

Animals↗
PubMed1978

A co-operative numerical analysis of Mycobacterium gastri, Mycobacterium kansasii and Mycobacterium marinum.

A co-operative taxonomic study has been performed on slowly growing photochromogenic mycobacteria (Runyon Group I) and closely related organisms. Phenetic data on 54 strains, studied in seven laboratories, were collected and analysed by numerical taxonomic methods. Immunological properties and phage susceptibility patterns were analysed independently to establish correlation with numerical classification. Mycobacterium gastri, M. kansasii and M. marinum appeared as distinct well-defined clusters and the serological and phage data supported the resolution of these three species. A table of definitive properties is presented. Two strains each of M. simiae and M. asiaticum formed a loose cluster which was clearly separated from the previously mentioned three species; the small number of strains examined precluded the establishment of a list of definitive properties of these two species. It is concluded that the Runyon Groups, which provided a practical though arbitrary basis for establishment of a series of co-operative studies, have served their purpose and should now be supplanted by classification and nomenclature based on species.

Bacteriophage Typing↗
PubMed1977

Sources of Mycobacterium avium complex infection resulting in human diseases.

Human disease caused by organisms in the Mycobacterium avium complex occur virtually worldwide. A 20-year ongoing study conducted in Western Germany has been analyzed to elucidate the ecologic and epidemiologic characteristics of these infections in man. Organisms included in this investigation have been cultured from man, from domestic and wild animals and fowl, and from a variety of environmental sources. In addition to the usual taxonomic studies of these bacilli, infrasubspecific typing by seroagglutination has enabled identification of 3 distinct serogroups: the classical Mycobacterium avium strains (serovars avium 1, 2, and 3), the intermediate group (avium serovars 4, 5, 6, 8, 9, 10, and 11), and the less frequently encountered organisms, the 11 remaining avium serovars (7 and 12 through 21). Analysis of the number of strains in each of the 3 serogroups, derived, respectively, from man, from animals, and from the environment, has enabled us to draw some conclusions regarding reservoirs and sources of human infection with these agents.

Animals↗
PubMed1976

Permeability of sarcoplasmic reticulum membrane. The effect of changed ionic environments on Ca2+ release.

Permeability properties and the effects of a changed membrane potential on Ca2+ release of sarcoplasmic reticulum vesicles of rabbit skeletal muscle were investigated by Millipore filtration. The relative permeability of sarcoplasmic reticulum to solutes determined under conditions of isotope exchange at equilibrium and/or under conditions of net flow of solute and water into the vesicles was as follows: sucrose, Ca2+, Mn2+ less than gluconate-, choline+, Tris+ less than methanesulfonate- less than urea, glycerol, K+, Na+,Li+, Cl-. Transient membrane potentials were induced by rapidly changing the ionic environment of the vesicles. Knowledge of the relative permeation rates of the above ions allowed prediction of the direction and extent of membrane polarization. Osmotic effects in the polarization measurements due to the rapid influx of solute and water into the vesicles were minimized by using media containing a fast (K+ or Cl-) and a relatively slow (gluconate- or choline+) penetrating ion. 45Ca2+ efflux from vesicles derived from different parts of the sarcoplasmic reticulum structure was not appreciably changed when vesicles were made more positive inside (choline chloride leads to potassium gluconate) or more negative inside (potassium gluconate leads to choline chloride). These studies suggest that part or all of the ion-induced changes in sarcoplasmic reticulum membrane permeability, previously interpreted to indicate "depolarization" -induced Ca2+ release, may be due to osmotic effects.

Animals↗
PubMed1975

Isolation and characterization of two types of sarcoplasmic reticulum vesicles.

A purified preparation of sarcoplasmic reticulum from rabbit skeletal muscle has been found to consist of a heterogeneous population of vesicles. Isopycnic centrifugation was used to obtain "light" and "heavy" vesicles from the upper and lower ends of a 25 to 45% (w/w) linear sucrose gradient. Each fraction accounted for about 10 to 15% of the total vesicles. The remainder of the vesicles were of intermediate density and banded between the light and heavy fraction. Light vesicles were composed of about equal amounts of phospholipid and Ca-2+ pump protein which contained approx. 90% of the protein. Heavy vesicles contained in addition to the Ca-2+ pump protein (55-65% of the protein) two other major protein components, the Ca-2+ binding and M55 proteins which accounted for 20-25 and 5-7% of the protein of these vesicles, respectively. The sarcoplasmic reticulum subfractions had 32-P-labelled phosphoenzyme levels proportional to their Ca-2+ pump protein content and contained similar Ca-2+-stimulated ATPase activities. They were capable of accumulating Ca-2+ in the presence of ATP and of releasing the accumulated Ca-2+ when placed into a medium with a low Ca-2+ concentration. The vesicles differed significantly in that heavy vesicles had a greater number of non-specific Ca-2+ binding sites than light vesicles (approx. 220 vs 75 nmol of bound Ca-2+ per mg protein), in accordance with their high content of Ca-2+ binding protein. Electron dense material could be seen within the compartment of heavy but not light vesicles. Removal of Ca-2+ binding and M55 proteins from heavy vesicles resulted in empty membranous structures consisting mainly of Ca-2+ pump protein and phospholipid. Electron micrographs of sections of muscle showed dense material in terminal cisternae but not in longitudinal sections of sarcoplasmic reticulum. These experiments are consistent with the interpretation that (1) the electron dense material inside heavy vesicles may be referable to Ca-2+ binding and/or M55 proteins, and that (2) light and heavy vesicles may be derived from the longitudinal sections and terminal cisternae of sarcoplasmic reticulum, respectively.

Adenosine Triphosphatases↗
PubMed1975

Relationship between Mycobacterium simiae and Mycobacterium habana.

Strains of the species Mycobacterium simiae give a positive niacin test. On the basis of their cultural and biochemical characteristics and by seroagglutination they can be classified into 2 subspecies. (1) The strains of serotype M. simiae 1 hydrolyze urea regularly and nicotinamide and pyrazinamide irregularly. They are photochromogenic after prolonged exposure to light. (2) The strains of serotype M. simiae 2 hydrolyze urea only. Three of 4 strains are scotochromogenic; the fourth has a pale pink pigment. Two of these strains possess alpha- and beta-esterase activity. The other two are negative in this test. Strains of M. habana are culturally and biochemically identical with the serotype M. simiae 1 and show the same serologic specificity as M. simiae 1. M. habana sera, after having been absorbed by M. simiae 1, retain a small amount of agglutinins specific for M. habana. We believe that the M. habana strains belong to the species M. simiae and are closely related to the serotype M. simiae 1.

Agglutination↗