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Biomedical subjects

R Scherrer

Publications and source records attributed to R Scherrer.

At least 37 records · Page 2Linked to original sources
PubMed1982

Purification and characterization of bovine rotavirus cores.

Using the chaotropic effect generated by a high concentration of CaCl2, we converted calf rotavirus particles into cores of 40 nm in diameter. These cores were purified by rate zonal centrifugation in sucrose gradients and by isopycnic gradients. They had a sedimentation coefficient of 280S +/- 20S and a density of 1.44 g/ml in CsCl. When analyzed by polyacrylamide gel electrophoresis, they contained three polypeptides (VP125, VP89, and VP78). The major internal polypeptide of the virion (VP39) was recovered in a purified and soluble form in the top fractions of the sucrose gradients. From this stepwise degradation, it appears that VP39 is the most external polypeptide of dense particles. In contrast to reovirus cores, calf rotavirus cores did not exhibit transcriptase activity. Purified VP39 also did not exhibit transcriptase activity when tested after being mixed with purified rotavirus genome RNA as a template. Transcriptase activity was partially recovered when ionic conditions were adjusted to permit the reassociation of VP39 with the cores.

Animals↗
PubMed1981

[Adaptation of an isolate of bovine enteritic coronavirus to serial growth in cell culture and characterization of the virus (author's transl)].

Coronaviruses are known to behave as pathogens in a variety of animal species. Their multiplication in the differentiated enterocytes of the intestinal tract induces a severe diarrheic syndrome which may lead to death. To study these viruses and to progress in the development of prophylactic and diagnostic methods, it is essential to succeed in adapting the agents to serial growth in cell culture. In spite of several attempts adaptation to primary cell cultures could be obtained in the past only for two isolates. The present work describes the methodology which enabled us to succeed in the adaptation of a bovine enteric coronavirus isolated in France to primary calf kidney cells, and reports results on the characteristics of this virus. Adaptation to serial growth was realized at 34 degrees C in the following way: 3 passages each lasting 8 to 10 days followed by 16 passages each lasting 6 days. From the 20th passage on the duration of incubation was reduced to 4 days. Virus growth was checked using an indirect immunofluorescence test. During the first passages only a few dispersed positive cells could be observed but later on small foci of immunofluorescent cells did appear. By the 35th passage infective titers did not exceed 1 x 10(5) TCID50/ml and cytopathic effects were always very discrete. When the susceptibility of different cell-types to this coronavirus strain (G110) was checked we found that only bovine cells and the human HRT18 cell-line were able to replicate the virus. In HRT18 cells titers as high as 5 x 10(7) TCID50/ml could be obtained at the first passage of G110 strain, previously adapted to primary calf kidney cells. As regards the antigenic properties of G110 virus no difference could be established between this strain and the Nebraska isolate (NCDCV) neither by indirect immunofluorescence test nor by indirect neutralization test. The G110 strain agglutinates rat and mouse erythrocytes. The density of purified virions in mouse gradients is 1.19 and the morphology of the particles is characteristic of a coronavirus.

Animals↗
PubMed1980

Weak susceptibility of rotavirus to bovine interferon in calf kidney cells.

Bovine, virus-induced interferon was titred in primary embryonic calf kidney cells, using three challenge viruses: Reovirus type 3, vesicular stomatitis virus (serotype Indiana), and a French isolate of bovine rotavirus (TR) adapted to grow in tissue culture. Rotavirus repeatedly displayed a very weak susceptibility to interferon as compared to the other two viruses.

Animals↗
PubMed1980

[Clinicohematologic effects of hemoglobin Altdorf (alpha 2 beta 2 135 Ala replaced by Pro)].

Hb Altdorf alpha 2 beta 2 135 Ala leads to Pro is an unstable variant occurring near Lecce in Italy. The abnormal hemoglobin does not separate from Hb A in the electrophoresis. In vitro a marked Heinz body formation is produced with phenylhydrazin. In heterozygous individuals an almost compensated hemolysis and a slight splenomegaly are found. Hemolysis can be aggravated by exogenous factors. A rather severe hemolysis was induced by a viral infection in a 3 years old girl.

Adolescent↗
PubMed1979

[Hyperventilation and airway resistance. Bronchial spasms after hyperventilation].

Airway resistance, FEV1.0 and lung volume were measured by body plethysmography before and after voluntary hyperventilation. In normal subjects, resistance increased to 130--140% of the initial value measured before hyperventilation. The same increase was observed in silicosis patients without chronic obstructive bronchitis. Asthmatic patients in an asymptomatic phase showed a rise in airway resistance to an average of 255% of the nearly normal initial values, and also a reduction in FEV1.0. In normal subjects and asthmatic patients, the administration of bronchodilators inhibits the rise in airway resistance induced by hyperventilation. The hyperventilation test can be used to identify increased susceptibility to bronchoconstriction.

Asthma↗
PubMed1979

Activation of rotavirus RNA polymerase by calcium chelation.

Two types of particles were isolated during purification of rotavirus. Dense (D) particles have a density of 1.38 in CsCl and exhibit spontaneously a fully active endogenous transcriptase. Light (L) particles (density of 1.36 in CsCl) need to be treated with chelating agents to show a polymerase activity. The activation process of L particles was studied under strictly controlled monovalent, divalent, and hydrogen ion concentrations. These experiments demonstrate that i) activation is not affected by the ionic strength ii) activation occurs only at a pH higher than 7.1 iii) a low concentration of chelating agent (40 muM EDTA) is sufficient to activate the enzyme. Treatment of particles with EGTA, which chelates selectively Ca2+, leads to unmasking even in the presence of magnesium, indicating that the concentration of free calcium ions plays a major role in the activation process. Various glycosidases, detergents, and chelating agents were tested in respect to unmasking properties. Of these compound only chelating agents turned out to be efficient. Following activation, two glycopeptides were solubilized. These glycopeptides have an apparent molecular weight of 34,000 and 31,000 daltons and react with concanavalin A. The role of Ca2+ upon the stability of virus particles, and the activation of the endogenous transcriptase in vitro and in the infected cells is discussed.

Animals↗
PubMed1979

Infantile gastroenteritis caused by rotavirus: comparison of enzyme-linked immunosorbent assay and electron microscopy for rapid diagnosis.

ELISA and negative contrast EM have used for the detection of rotavirus in one hundred stools from children, less than two years old, hospitalized for acute gastro-enteritis during the winter 1977-78. Samples obtained from the same children some months after hospitalization were also tested. A good correlation was found between the results given by EM and ELISA, but the later technique turned out to be more sensitive (12% more positive using ELISA). A rotavirus infection could be demonstrated in 73% of the patients. In the stools of 3 children we found a second virus in association with the rotavirus, and in two cases a pathogenic bacterium. When a second serum specimen was available from children previously infected by rotavirus it was always possible to detect a significant increase in CF antibodies. Several months after hospitalization a 2nd survey indicated that the rotavirus was no longer present but calicivirus, echovirus, coxsackievirus and adenovirus could be detected in those asymptomatic children.

Antibodies, Viral↗
PubMed1978

The experimental production of diarrhoea in colostrum deprived axenic and gnotoxenic calves with enteropathogenic Escherichia coli, rotavirus, coronavirus and in a combined infection of rotavirus and E. coli.

We attempted to produce diarrhoea experimentally in the newborn calf by orally injecting 17 colostrum-deprived calves with two serotypes of Escherichia coli Ent+ K99+, a rotavirus and a coronavirus. With E. coli alone, a dose of 2 x 10(8) bacteria administered 24 hours after birth causes a mild attack of diarrhoea, whereas 1 x 10(10) bacteria leads to dehydration and death. An inoculation of rotavirus is followed by diarrhoea which always contains large quantities of rotavirus. These animals were anorectic for a time, but none was dehydrated or died. With coronavirus, there were large quantities of watery diarrhoea, which led to dehydration and death. The inoculation of rotavirus, not lethal in itself, followed by a similarly non lethal inoculation of E. coli in doses of 3 x 10(8) to 2 x 10(9) led to dehydration and death. The authors conclude that dehydration and death of the animal can caused by large doses of E. coli or coronavirus or by two non-lethal doses of rotavirus and E. coli administered one after the other.

Animals↗
PubMed1977

Density, porosity, and structure of dried cell walls isolated from Bacillus megaterium and Saccharomyces cerevisiae.

Helium displacement and nitrogen adsorption techniques were used to determine the density and porosity, respectively, of freeze-dried cell walls isolated from Bacillus megaterium KM and Saccharomyces cerevisiae. The densities were 1.302 and 1.180 g/cm3, respectively, suggesting noncrystalline solids. The porosities were extremely small, indicating that the cell walls had collapsed and become essentially impervious upon lyophilization.

Bacillus megaterium↗
PubMed1976

Fine structure of the Baccilus thuringiensis spore.

The thin-sectioned spore of Bacillus thuringiensis resembles that of Bacillus cereus in fine structure. Planar inclusions occur between the exosporium and spore coat and are structured differently from the parasporal crystal outside the exosporium.

Bacillus cereus↗
PubMed1976

[In vitro culture of a rotavirus associated with neonatal calf diarrhea].

About fifty diarrheic fecal samples in which the calf rotavirus was present in variable quantities were passed in tissue cultures and the ability of the virus to replicate was analysed under different experimental conditions by means of an indirect immunoflourescent test. Several cell species were shown to be susceptible to the virus but the best results were obtained in primary or secondary cultures of embryonic calf kidney cells in presence of maintainance medium containing 2 to 4 p. 100 foetal calf serum or chick serum. The specific infectivity of this type of virus is low in tissue culture. Under the best experimental conditions about 70 p. 100 of the samples that were positive for the virus by electron microscopy, induced the appearance of specifically fluorescent cells. Cytopathic effects due to infection are extremely discreet and most often there is no evidence of transfer of infection from cell to cell. Different attempts to adapt the infective agent to grow in tissue culture finally succeeded in the selection of a virus that was able to induce fluorescnet plaques at the fifth pass.

Animals↗
PubMed1976

Reovirus-like agent (rotavirus) associated with neonatal calf gastroenteritis in France.

A reo-like virus (calf rotavirus) was shown to be associated with cases of neonatal calf diarrhea in France. The virus could be detected in more than 50 p. 100 of diarrheic fecal samples, while it was practically absent in control samples originating from healthy calves that had never had diarrhea. The results obtained by electron microscopy and immunofluorescent studies indicate that the virus is closely related or identical to the agent isolated originally in the United States.

Animals↗
PubMed1975

Studies on infectious pancreatic necrosis virus interactions with RTG-2 and FHM cells: selection of a variant virus-type in FHM cells.

Evidence is presented that adaptation of IPN virus (strain VR 299) to FHM cells entails the selection of a variant virus type that differs significantly from the parental, and most representative, RTG-2 virus type in being able to adsorb efficiently to, and form plaques in, FHM cells. The plaque titre of FHM-non-adapted virus stocks (RTG-2 viruses) was reduced by at least 99-99% in FHM cells, while FHM-adapted virus stocks (FHM viruses) produced plaques at equally high titres in both RTG-2 and FHM cells. FHM viruses and RTG-2 viruses differed also in their behavior in RTG-2 cells in respect to plaque size distribution and growth characteristics, but both virus-types were shown to be morphologically identical, and no significant difference in reactivity against specific antiserum could be detected. Analysis of virus in individual RTG-2 plaque isolates or plaque progeny shows that a mutation of relatively high frequency (10(-4) to 10(-5))robably causes the ability to infect the FHM cells efficiently. Only these mutant virus-types were found in FHM plaque isolates.

Animals↗
PubMed1974

Porosity of the yeast cell wall and membrane.

The limiting sizes of molecules that can permeate the intact cell wall and protoplast membrane of Saccharomyces cerevisiae were determined from the inflection points in a triphasic pattern of passive equilibrium uptake values obtained with a series of inert probing molecules varying in molecular size. In the phase identified with the yeast protoplast, the uptake-exclusion threshold corresponded to a monodisperse ethylene glycol of molecular weight = 110 and Einstein-Stokes hydrodynamic radius (r(ES)) = 0.42 nm. In the cell wall phase, the threshold corresponded to a polydisperse polyethylene glycol of number-average molecular weight ( M(n)) = 620 and average radius (r(ES)) = 0.81 nm. The third phase corresponded to complete exclusion of larger molecules. The assessment of cell wall porosity was confirmed by use of a second method involving analytical gel chromatographic analyses of the molecular weight distribution for a single polydisperse polyglycol before and after uptake by the cells, which indicated a quasi-monodisperse threshold for the cell wall of M(n) = 760 and r(ES) = 0.89 nm. The results were reconciled with two situations in which much larger protein molecules previously have been reported able to penetrate the yeast cell wall.

Biological Transport↗