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Biomedical subjects

R Weil

Publications and source records attributed to R Weil.

At least 181 records · Page 10Linked to original sources
PubMed1975

Lifetime and rotational relaxation time of dansylgalactoside bound to the lac carrier protein.

The results presented in this paper demonstrate that the excited state lifetime, anisotropy, and rotational relaxation time of 2'-(N-dansyl)aninoethyl 1-thio-beta-D-galactopyranoside (DG2) increase when the probe is bound specifically to the lac carrier protein in "energized" Escherichia coli membrane vesicles. Although the probe also binds nonspecifically to the vesicle membrane, such binding is independent of the lac carrier protein and is unaffected by "energization" of the vesicles. The experiments provide further evidence that the dansylgalactosides are useful probes for the beta-galactoside transport system and support the hypothesis that the changes in dansylgalactoside fluorescence observed on "energization" of membrane vesicles reflect changes in the binding of the probe.

Bacterial Proteins↗
PubMed1975

Differentiation between binding and transport of dansylgalactosides in Escherichia coli.

The results presented in this paper confirm and extend previous observations which indicate that fluorescent dansylgalactsodes bind to the beta-galactoside carrier protein but do not penetrate the cytoplasmic membrane. The conclusion is supported by the following observations. (a) Although 2'-(N-dansyl)aminoethyl-beta-D-thiogalactopyranoside and 2'-(N-dansyl)aminoethyl-beta-D-galactopyranoside are competitive inhibitors of lactose transport in intact cells of Escherichia coli and induce the in vitro synthesis of beta-galactosidase, they do not induce beta-galactosidase in vivo. (b) p-Chloromercuribenzenesulfonate does not cause efflux of lactose from the intravesicular pool, but causes rapid reversal of D-lactate-induced dansylgalactoside fluorescence. (c) Dansylgalactosides inhibit dilution-induced, carrier-mediated lactose efflux.

4-Chloromercuribenzenesulfonate↗
PubMed1975

Energy-dependent binding of dansylgalactosides to the beta-galactoside carrier protein.

Fluorescent beta-galactosides (1-(N-dansyl)amino-beta-D-galactopyranoside (DG0), 2'-(N-dansyl)aminoethyl-beta-D-thiogalactopyranoside (DG2), 2'-(N-dansyl)aminoethyl-beta-D-galactopyranoside (oxy-DG2), and 6'-(N-dansyl)aminohexyl-beta-D-thiogalactopyranoside (DG6)) competitively inhibit lactose transport by membrane vesicles from Escherichia coli ML 309-225, but are not actively transported. An increase in the fluorescence of these dansylgalactosides is observed upon addition of D-lactate, imposition of a membrane diffusion potential (positive outside), or dilution-induced, carrier-mediated lactose efflux. The increase is not observed with 2'-(N-dansyl)aminoethyl-beta-D-thioglucopyranoside nor with membrane vesicles lacking the beta-galactoside transport system. Moreover, the D-lactate-induced fluorescence increase is blocked or rapidly reversed by addition of beta-galactosides, sulfhydryl reagents, inhibitors of D-lactate oxidation, or uncoupling agents. The fluorescence increase exhibits an emission maximum at 500 nm and excitation maxima at 345 nm and at 292 nm. The latter excitation maximum is absent unless D-lactate is added, indicating that the bound dansylgalactoside molecules are excited by energy transfer from the membrane proteins. Titration of vesicles with dansylgalactosides in the presence of D-lactate demonstrates that the lac carrier protein constitutes 3 to 4% oof the total membrane protein, and that the affinity of the carrier for substrate is directly related to the length of the alkyl chain between the galactosidic and the dansyl moieties of the dansylgalactosides. In addition, there is excellent agreement between the affinity constants of the various dansylgalactosides as determined by fluorimetric titration and their apparent Kis for lactose transport (KDs and/or apparent Kis are approximately 550, 3o, 40, and 5 muM FOR DG0, DG2, oxy-DG2, and DG6, respectively). Polarization of fluorescence measurements with DG2 and DG6 demonstrate a dramatic increase in polarization on addition of D-lactate which is reversed by addition of lactose or anaerobiosis. These findings provide strong evidence for the contention that the fluorescence changes observed on "energization" of the membrane are due to binding of the dansylgalactosides per se, rather than binding followed by transfer into the hydrophobic interior of the membrane

Bacterial Proteins↗
PubMed1975

Photoinactivation of the beta-galactoside transport system in Escherichia coli membrane vesicles with 2-nitro-4-azidophenyl-1-thio-beta-D-galactopyranoside.

2-Nitro-4-azidophenyl-1-thio-beta-D-galactopyranoside (azidophenylgalactoside) is a competitive inhibitor of lactose transport in membrane vesicles isolated from Escherichia coli ML 308-225, exhibiting an apparent Ki of 75 muM. The initial rate and steady state level of [3H]azidophenylgalactoside accumulation are markedly stimulated by the addition of D-lactate to vesicles containing the lac transport system, and kinetic studies reveal an apparent Km of 75 muM. Membrane vesicles devoid of the lac transport system do not take up significant amounts of azidophenylgalactoside in the presence or absence of D-lactate. When exposed to visible light in the presence of D-lactate, azidophenylgalactoside irreversibly inactivates the lac transport system. Strikingly, photolytic inactivation is not observed in the absence of D-lactate. Kinetic studies of the inactivation process yield a KD of 77 muM. Since lactose protects against inactivation and azidophenylgalactoside does not inactivate amino acid transport, it is apparent that these effects are specific for the lac transport system. The results are consistent with the proposal that the lac carrier protein is inaccessible to substrate in the absence of energy coupling.

Amino Acids↗
PubMed1975

Iliofemoral thrombophlebitis associated with central nervous system pathology.

It is very uncommon for acute thrombophlebitis to develop in children without an identifiable predisposing cause. During a ten year period at a children's hospital, central nervous system disease was observed in four of eight children with iliofemoral thrombophlebitis. This association suggests that a thorough neurologic evaluation should be carried out in any child with acute thrombophlebitis.

Acute Disease↗
PubMed1975

Neuraminidase treated homologous IgG and immune deposit rental disease in inbred rats.

Immune deposit renal disease followed intravenous or intraperitoneal injections of neuraminidase treated homologous IgG or neuraminidase alone. No alterations were associated with several groups of controls. This preliminary study suggests that one mechanism by which microogranisms may be involved in the development of immune renal disease is by chemical alteration of immunoglobulin.

Animals↗
PubMed1975

Cardiac heterotransplantation. Morphological and immunohistological studies.

A vascularized heterograft model using outbred strains of animals was developed by transplanting mouse hearts heterotopically into rats. With this species desparity rapid but not immediate graft rejection was observed, with a predictably narrow range of graft survival times. Morphological and immunohistological studies showed early deposition of fibrinogen and vascular and myocardial inflammation without prominent or consistent localization of either IgG or C3. Later more extensive changes were observed, and deposition of IgG and C3 were more prominent in the grafts. Pretreatment of the recipient with cyclophosphamide alone or cyclophosphamide plus antigen prolonged graft survival; however, no statistically significant difference was noted between these groups. Morphological and immunohistological alterations preceded clinical rejection, and tissue injury appeared to be mediated by humoral and cellular immune mechanisms and by the coagulation system. This model is potentially useful for the study of heterotransplantation.

Animals↗
PubMed1975

Cryoglobulins. III. Further studies on the nature, incidence, clinical, diagnostic, prognostic, and immunopathologic significance of cryoproteins in renal disease.

Serial serum samples from a large number of patients with immunologic renal disease, normal healthy controls, acute infections as well as non-immunological renal disease were studied for the presence, nature and properties of cryoproteins, and these correlated with serial renal functional, morphologic, immunohistologic and clinical fingings as well as serologic observations. A high incidence of cryoproteins were found in renal disease thought to be mediated by immune complexes. Cryoprecipitates were not detected in the other patients. The presence of fibrinogen in a serum cryoprecipitate was always associated with rapidly progressive disease and poor prognosis. An association between the detection of cryoproteins and the clinical and morphological activity of disease was observed. Persistence of cryoproteinemia was associated with progression and apparent disappearance with resolution or progression to end stage renal disease. In patients with hematuria or proteinuria of questionable significance cryoprotein detection was always associated with immune complex nephritis. Renal transplantation in the presence of cryoproteinemia was associated with recurrent nephritis in the graft. Cryoproteins were found to have biologic properties attributable to antigen-antibody complexes, to contain immune complexes of antigen and antibody and to have serologic factors concentrated. The detection of serum cryoglobulins was found to be a better index of clinical and morphologic activity of immune complex renal disease than was serum complement. As in our previous studies, these proteins appear to be of diagnostic and prognostic value in renal disease and provide a method of antigen identification in these disorders.

Animals↗
PubMed1975

Pancreatic transplantation in diabetic rats: renal function, morphology, ultrastructure, and immunohistology.

Serial renal morphologic, ultrastructural immunohisotlogic and functional studies were done on diabetic Lewis rats to evaluate the course of nephropathy and to study the effects of early pancreatic isografts on renal disease associated with streptozotocin diabetes. Three groups of experimental animals and one group of agematched controls were used. Group 1 consisted of 12 animals which were made diabetic with streptozotocin and which did not receive transplants. Early in the course of diabetes, these animals developed an increase in mesangial matrix, electron-dense material in themesangium, with immunoglobulin G, C3, and occasionally fibrinogen deposits in the glomerular mesangium. Alterations were progressive and mesangial bars, proximal tubular degeneration, tubular vacuolization, and myeloid figureswere present later. Progressive increase in protein excretion and increase in glomerular filtration rate were observed. Persistent glycosuria, hyperphosphaturia, andhypercalcuria. In contrast, only an occasional animal from Groups 2 and 3 with a pancreatic transplant showed renal in age-matched controls. These studies have demonstrated the evolution of renal glomerular and tubular changes in streptozotocin diabetic rats, and they have showed functional, and immunohistochemical changes.

Animals↗
PubMed1975

The human choroid plexus and autoimmune nephritis.

The choroid plexus resembles the glomerular basement membrane (GBM) and may be a site of injury or source of antigen in Goodpasture syndrome. Immunohistologic studies were performed on the choroid plexus of a patient with auto-immune nephritis and pulmonary hemorrhage. The studies showed linear deposition of host IgG, IGM, and beta1c. Antibody eluted from the diseased kidney fixed in a linear pattern to normal choroid plexus and could be absorbed by either choroid plexus or GBM. Antibody to choroid plexus fixed to GBM and the linear staining was no longer observed after absorption with GBM or choroid plexus. Antibody to GBM fixed to normal choroid plexus and was obsorbed by both choroid plexus and glomerular basement membrane. The studies suggest an immunologic relationship between choroid plexus and GBM and a role for the choroid plexus in autoimmune nephritis.

Animals↗
PubMed1975

Xenotransplantation of piscine islets into hyperglycemic rats.

Xenotransplantation of piscine islets into hyperglycemic rats usually lowers the blood sugar level of the recipient. The duration of this effect is prolonged by irradiation of the host or by enclosing donor tissue in synthetic envelopes. This prolongation appears to be related to interference with the host's ability to reject the graft; the duration of the prolongation may be limited by the host tissue reaction surrounding the envelope. The availability of anatomically separate piscine islet tissue makes it potentially useful for xenotransplantation into mammals.

Animals↗
PubMed1974

Polyoma viral DNA replicated as a nucleoprotein complex in close association with the host cell chromatin.

Polyoma viral DNA is shown to be replicated in close association with the mouse cell chromatin. Two virus-specific nucleoprotein complexes, designated complex A and B, can be dissociated from the isolated chromatin by gentle homogenization in 0.5 M NaCl. Complex A contains only replicating polyoma (Py) DNA whereas complex B contains only mature Py DNA I. The results show, furthermore, that complex A, containing viral DNA in different stages of replication, and complex B are both nucleoproteins with the same buoyant density. The data presently available suggest that newly synthesized stretches of Py DNA are immediately complexed with mouse cell histones and that complex B becomes the "core" of progeny Py virions. These results suggested that Py-induced replication of the mouse cell chromatin may be necessary to provide replicating Py DNA with histones.

Animals↗
PubMed1974

Effect of beta-propiolactone inactivation of polyoma virus on viral functions.

Polyoma virus was inactivated by treatment with beta-propiolactone. T-antigen production, polyoma-RNA synthesis, induction of host DNA synthesis (measured by incorporation of labeled thymidine into the cell culture), and in vitro transforming ability were inactivated to a similar degree by various beta-propiolactone concentrations (0.25% beta-propiolactone reduced these functions approximately 96%), whereas plaque-forming ability and the ability of the virus to replicate its DNA and to synthesize capsid antigen were inactivated by a given concentration of beta-propiolactone to a much greater degree (0.25% beta-propiolactone led to a reduction of plaque-forming ability of over 8 logs). The significance of these data and their relationship to previously published experiments are discussed.

Animals↗