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Biomedical subjects

F Klein

Publications and source records attributed to F Klein.

At least 19 recordsLinked to original sources
PubMed1992

Purification, sequence, and cellular localization of a novel chromosomal protein that binds to methylated DNA.

Methylation of mammalian DNA can lead to repression of transcription and alteration of chromatin structure. Recent evidence suggests that both effects are the result of an interaction between the methylated sites and methyl-CpG-binding proteins (MeCPs). MeCP1 has previously been detected in crude nuclear extracts. Here we report the identification, purification, and cDNA cloning of a novel MeCP called MeCP2. Unlike MeCP1, the new protein is able to bind to DNA that contains a single methyl-CpG pair. By staining with an antibody, we show that the distribution of MeCP2 along the chromosomes parallels that of methyl-CpG. In mouse, for example, MeCP2 is concentrated in pericentromeric heterochromatin, which contains a large fraction (about 40%) of all genomic 5-methylcytosine.

Amino Acid Sequence↗
PubMed1992

Modification of the amount of cholesterol in hepatic steatosis induced in susceptible and resistant mice infected with MHV3: a biochemical and ultrastructural study.

A mouse hepatitis virus-3 strain subcultured in our laboratory is a unique experimental model in which to study virus-induced liver steatosis. This strain produces massive lipid deposition not only in sensitive adult BALB/c mice but also (though less extensive) in virus-resistant adult A/J mice. Biochemical determinations have shown that this steatosis is characterized by an increased amount of neutral lipids (sterols and triglycerides) in infected livers of BALB/c mice and by a smaller increase in those of A/J mice. However, the relative percentage of cholesterol and triglycerides is similar in both strains. Liver phospholipid content was significantly decreased in both strains of mice. To discriminate between cytoplasmic and membrane cholesterol content in different types of liver cells, an ultrastructural study was performed with filipin, a specific cholesterol marker. This study shows on one hand an important increase in the cholesterol in the hepatocytes of BALB/c mice and a smaller increase in those of A/J mice, in agreement with biochemical data. However, marked cholesterol decrease and abnormal cholesterol distribution were observed in the endothelial liver cells of infected BALB/c mice. This decreased cholesterol content probably led to higher fluidity of these membranes, which could be related to the important drop in the number of endothelial cell fenestrae observed after mouse hepatitis virus-3 infection. Because in A/J infected mice neither a decrease in the amount and distribution of cholesterol nor decreased fenestration were observed in endothelial liver cells, these findings could be correlated with the resistance of these mice to the infection.

Animals↗
PubMed1992

Prolonged increase of corticosterone secretion by chronic social stress does not necessarily impair immune functions.

The influence of a chronic social stress upon immunity was investigated in Wistar rats, submitted for four weeks to two different behavioral situations, balanced in a factorial design: housing with three females and membership rotation. The combination of these two factor led to adrenal enlargement (43.3%), thymus involution (39.5%) and increased basal corticosterone levels, all indices of activation of the hypothalamic-hypophysis-adrenal axis. However, neither natural killer cell activity, splenocyte reactivity to mitogen nor the rate of spontaneous development of antibodies against Mycoplasma pulmonis, a common pathogen of the respiratory tract, were changed in the endocrine activated animals. Analysis of the data on kinetics of stress at 1, 7 and 28 days after the initial mixing of the animals gave the same results. These data question the immunosuppressant activity usually conferred to corticosteroids, at least when adrenal hyperactivity is induced by chronic environmental stressors.

Adrenal Glands↗
PubMed1992

Localization of RAP1 and topoisomerase II in nuclei and meiotic chromosomes of yeast.

Topoisomerase II (topoII) and RAP1 (Repressor Activator Protein 1) are two abundant nuclear proteins with proposed structural roles in the higher-order organization of chromosomes. Both proteins co-fractionate as components of nuclear scaffolds from vegetatively growing yeast cells, and both proteins are present as components of pachytene chromosome, co-fractionating with an insoluble subfraction of meiotic nuclei. Immunolocalization using antibodies specific for topoII shows staining of an axial core of the yeast meiotic chromosome, extending the length of the synaptonemal complex. RAP1, on the other hand, is located at the ends of the paired bivalent chromosomes, consistent with its ability to bind telomeric sequences in vitro. In interphase nuclei, again in contrast to anti-topoII, anti-RAP1 gives a distinctly punctate staining that is located primarily at the nuclear periphery. Approximately 16 brightly staining foci can be identified in a diploid nucleus stained with anti-RAP1 antibodies, suggesting that telomeres are grouped together, perhaps through interaction with the nuclear envelope.

Base Sequence↗
PubMed1992

Interstitial deletion and ring chromosome derived from 19q. Proximal 19q trisomy phenotype.

A small supernumerary ring chromosome has been found in a boy with overweight, dysmorphic facies and mental retardation. His mother had an interstitial deletion of the long arm of chromosome 19 and the same ring chromosome. By means of fluorescence in situ hybridization the ring chromosome was shown to be derived from the deleted chromosome, after the occurrence of two breaks: one in the centromere region, the other in the q-arm of chromosome 19.

Abnormalities, Multiple↗
PubMed1991

Meiotic chromosome synapsis in a haploid yeast.

An extensive synaptonemal complex (SC) is found at pachytene in whole mount spread preparations of a haploid yeast, Saccharomyces cerevisiae, strain. Whereas unsynapsed axial elements are present only in a few nuclei, in others non-homologous synapsis involves virtually the whole chromosome set. This suggests that homology is not an indispensable precondition for SC formation in yeast but that chromosomes engage in non-homologous synapsis if no homologous partner is available. Recent evidence that in the sporulation deficient yeast mutants rad50 and mer1 axial elements do form but remain unsynapsed in the majority of nuclei is discussed in the light of the above findings.

Chromosomes, Fungal↗
PubMed1991

Relationship between allozymes, heterozygosity and morphological characters in red deer (Cervus elaphus), and the influence of selective hunting on allele frequency distribution.

Morphological characters in red deer (Cervus elaphus), which serve as criteria for selective hunting, were examined in relation to electrophoretic variation in three populations from the Vosges in eastern France. From the polymorphic loci examined, certain alleles at Idh-2, Me-1 and Acp-1 showed significant associations with a special development of body and antler characters selected for by hunters. Idh-2(125) was associated with larger hind foot length in females and a higher number of antler points in males. Me-1(90) and Acp-1(100) were associated with small spikes. The populations studied differed from one another in the duration and intensity of selective hunting and the increase or decrease in the respective allele frequencies could be explained by selection for large body size, a high number of antler points and against small spikes in yearlings, rather than by genetic drift. Among other morphological characters examined, the length of the main beam was significantly associated with the allele Acp-2(100). In contrast, no associations could be detected between overall heterozygosity and the development or the degree of asymmetry (in paired structures) of any of the morphological traits in question. Although no obvious differences in the overall values of polymorphism or heterozygosity were found between the populations, selective hunting leads towards a change in allele frequencies and eventually to the loss of one or the other rare allele.

Alleles↗
PubMed1990

Pedigree analyses of yeast cells recovering from DNA damage allow assignment of lethal events to individual post-treatment generations.

Haploid cells of Saccharomyces cerevisiae were treated with different DNA damaging agents at various doses. A study of the progeny of individual such cells (by pedigree analyses up to the third generation) allowed the assignment of lethal events to distinct post treatment generations. By microscopically inspecting those cells which were not able to form visible colonies we could discriminate between cells dying from immediately effective lethal hits and those generating microcolonies (three to several hundred cells) probably as a consequence of lethal mutation(s). The experimentally obtained numbers of lethal events (which we call apparent lethal fixations) were mathematically transformed into mean probabilities of lethal fixations as taking place in cells of certain post treatment generations. Such analyses give detailed insight into the kinetics of lethality as a consequence of different kinds of DNA damage. For example, X-irradiated cells lost viability mainly by lethal hits (which we call 00-fixations); only at a higher dose also lethal mutations fixed in the cells that were in direct contact with the mutagen (which we call 0-fixations), but not in later generations, occurred. Ethyl methanesulfonate (EMS)-treated cells were hit by 00-fixations in a dose dependent manner; 0-fixations were not detected for any dose of EMS applied; the probability for fixation of lethal mutations was found equally high for cells of the first and second post treatment generation and, unexpectedly, was well above control in the third post-treatment generation. The distribution of all sorts of lethal fixations taken together, which occurred in the EMS-damaged cell families, was not random.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA Damage↗
PubMed1990

Comparative study of test kits for measurement of rheumatoid factors by the latex fixation test.

The performance of 14 test kits for the measurement of rheumatoid factors by the latex fixation test was investigated; all results were expressed in IU/ml. Reproducibility and properties of control sera were also studied. It was found that half of the kits did not satisfactorily detect rheumatoid factor levels lower than 25 IU/ml. Most kits performed reasonably well in practice. Positive control sera only rarely met strict requirements. The relative costs did not always have a clear correlation with the quality of the results. The variation caused by differences between kits became acceptable when the results were expressed in IU/ml.

Humans↗
PubMed1989

After a single treatment with EMS the number of non-colony-forming cells increases for many generations in yeast populations.

The course of lethal events occurring in populations of haploid Saccharomyces cerevisiae after DNA-damaging treatments was studied. After X-irradiation and after incubation with methyl methanesulfonate (MMS) populations recovered according to expectation, if one assumes successive dilution of killed cells by the proliferating survivors. However, populations treated with ethyl methanesulfonate (EMS) for many generations of proliferation contained more inviable cells than expected. This behaviour was not due to EMS or toxic reaction products remaining with the cells after treatment but to residual divisions of lethally mutated cells. In addition the data suggest that lethal fixations may occur in cells originating from later than the first generation after EMS treatment.

Dose-Response Relationship, Drug↗
PubMed1989

Sustained, multimodal outpatient group therapy for chronic psychotic patients.

Twelve predominantly psychotic patients who were at high risk for relapse and rehospitalization participated in a treatment regime that combined medication and supportive and insight-oriented group therapy. The group was studied over a 44-month period during which the same psychiatrist was present. None of the 12 group members required rehospitalization during the study period, and the quality of life and level of functioning significantly improved for most of them. Factors that possibly contributed to the patients' responses are addressed.

Adult↗
PubMed1989

Twenty-five years of renal trauma at a teaching hospital.

In a study of 535 patients with renal trauma admitted to the Medical College of Virginia Hospitals from 1962 to 1988, the authors found indications of a decrease in the rate of total nephrectomy in patients with blunt trauma, due in part to advances in diagnostic technology. In the cases of gunshot wounds, however, a persistently high rate of nephrectomy prevailed, reflecting, the authors believe, the proliferation of increasingly lethal weaponry.

Humans↗
PubMed1988

Standardisation of the quantitative determination of antinuclear antibodies (ANAs) with a homogeneous pattern.

The results of antinuclear antibody tests using the indirect immunofluorescence technique may be reported as a description of the pattern and the intensity of fluorescence obtained at a certain dilution. If quantitative results are required titration is necessary. Such titrations may vary greatly between different laboratories. The present study involving 26 laboratories shows an improvement of interlaboratory comparability for the homogeneous fluorescence pattern when a common reference serum is used. Cultured cells as substrate appear to give better quantitative agreement than rat liver sections. National reference sera should be standardised in items of the appropriate WHO reference preparation.

Antibodies, Antinuclear↗
PubMed1988

Characteristics of the mitogenic activity found in the supernatant of pokeweed mitogen stimulated human mononuclear cells.

Human peripheral blood mononuclear cells were stimulated with pokeweed mitogen (PWM), washed, and cultured in fresh mitogen-free culture medium; a second set of peripheral blood mononuclear cells was used to assess the mitogenic activity of supernatants of these cultures. The effects of this stimulation resembled those of a normal PWM stimulation, including the formation of blast cells, proliferation of lymphoid cells, and immunoglobulin synthesis. Our findings led us to perform experiments to investigate the nature of this mitogenic factor. The molecular weight of the mitogenic activity was found in the region of 700 kD. Additional experiments indicated that human alpha 2-macroglobulin was not responsible for the high molecular weight of the mitogenic factor. Protein digestion or precipitation with trichloroacetic acid only partially abolished the mitogenicity of the mitogenic supernatant. Comparison of the molecular weight of the mitogenic factor with that of the PWM in culture medium showed that the mitogenic activity in the supernatants could be caused by PWM associated with a high molecular weight component.

B-Lymphocytes↗
PubMed1987

Standardisation of serological tests for rheumatoid factor measurement.

Standardisation of quantitative data obtained by several types of rheumatoid factor test was achieved by the use of a reference serum preparation. Interlaboratory comparability improved for the latex fixation test, the Waaler-Rose test, the IgM RF test by an enzyme linked immunosorbent assay (ELISA), and for the antiperinuclear factor test. Use of a common method and latex preparation was not sufficient to improve comparability for the latex test. The comparability of IgM RF tests by immunofluorescence (IF) was not changed by reading against a common reference. It is concluded that expression in international units, as defined by the World Health Organisation (WHO), improves interlaboratory comparison of quantitative data in rheumatoid serology.

Analysis of Variance↗