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Biomedical subjects

B Sauer

Publications and source records attributed to B Sauer.

90 records · Page 5Linked to original sources
PubMed1987

Functional expression of the cre-lox site-specific recombination system in the yeast Saccharomyces cerevisiae.

The procaryotic cre-lox site-specific recombination system of coliphage P1 was shown to function in an efficient manner in a eucaryote, the yeast Saccharomyces cerevisiae. The cre gene, which codes for a site-specific recombinase, was placed under control of the yeast GALI promoter. lox sites flanking the LEU2 gene were integrated into two different chromosomes in both orientations. Excisive recombination at the lox sites (as measured by loss of the LEU2 gene) was promoted efficiently and accurately by the Cre protein and was dependent upon induction by galactose. These results demonstrate that a procaryotic recombinase can enter a eucaryotic nucleus and, moreover, that the ability of the Cre recombinase to perform precise recombination events on the chromosomes of S. cerevisiae is unimpaired by chromatin structure.

Coliphages↗
PubMed1986

Bacteriophage P1 cre gene and its regulatory region. Evidence for multiple promoters and for regulation by DNA methylation.

The bacteriophage P1 site-specific recombination system consists of two components, a site, loxP, at which recombination occurs, and a recombinase protein, Cre. In this paper, we present the DNA sequence of the cre structural gene and its upstream regulatory region. Analysis of the sequence indicates: (1) that cre encodes a protein of 343 amino acids; (2) that cre and loxP are separated by a 434 base-pair region that contains a 73 amino acid open reading frame, orf1; and (3) that cre and orf1 are oriented with their amino-terminal ends proximal to loxP. We have identified three promoters that are located upstream of the cre structural gene. Their activities range from 7 to 10% of the activity of the galactose operon promoter. The promoter furthest from cre, pR1, contains two Dam methylation sites (5'-G-A-T-C-3') in its -35 region, and is sensitive to Dam methylation. Its transcription is three- to fourfold higher in a dam- host than it is in a dam+ host. The promoter closest to cre, pR3, signals the production of an RNA transcript that functions inefficiently for Cre protein synthesis because it lacks a ribosome recognition site. None of the three cre promoters is sensitive to proteins expressed by the P1 prophage, including the c1 repressor protein. To assess the role of cre in the P1 life-cycle, we isolated cre mutants and studied their behavior in recA+ and recA- hosts. Those studies indicate that Cre is dispensable for viral vegetative growth and lysogeny in a recA+ host, but is required for both processes in a recA- host. The cre requirement for lysogeny suggests that the protein is essential for the cyclization of newly injected terminally redundant virion DNA. The requirement for vegetative growth suggests that Cre also has a role to play in the viral lytic cycle after the viral DNA has been cyclized.

Base Sequence↗
PubMed1986

A quantitative study of the cerebral cortex in Alzheimer's disease and senile dementia using an automatic image analyzing system.

The gray level index method was used in order to quantitatively differentiate the histological characteristics of a pathological population (n = 14) from those of a normal population (n = 14). An automatic image analysis system compared the laminar patterns in the straight gyrus of the cerebral cortex of deceased normal patients with those who died with Alzheimer's disease and senile dementia. In comparison to the normal control group, the cases with Alzheimer's disease and senile dementia show a significant decrease in the gray level index of lamina III.

Aged↗
PubMed1986

Brain growth in man.

25 male brains meeting the criteria for normativity and available in serial sections suitable for morphometric studies were selected from the Yakovlev Collection. Growth parameters were calculated based on the generalized logistic function. The ideal weight is 1,313 g (SD = 41), with a half value time of 387 (SD = 26) ontogenetic days and a growth factor of 4.0 (SD = 0.5). Comparison of growth parameters derived from a sample of 161 normative male brains collected at the Department of Neuroanatomy of the Medical School in Hannover revealed an ideal weight of 1,353 g (SD = 14), a half value time of 401 (SD = 10) ontogenetic days and a growth factor of 4.0 (SD = 0.2). The minor discrepancies in the corresponding parameters reflect the small sample size and a considerable lack of developmental data of the three first postnatal decades in the material derived from the Yakovlev Collection. It was, therefore, deemed necessary to analyze these data in combination with data derived from other sources of human material. A comparison of human with animal growth parameters derived from mice, cats and tree shrews reveals differences in brain development. Histological shrinkage of the 25 male brains of the Yakovlev Collection related to fixation, embedding, and staining was assessed. Fetal brains shrank by about 75%, and adult brains by about 50%. The degree of shrinkage was inversely proportional to the age of the brain and was also characterized by individual variations of up to 20%. Therefore, shrinkage had to be corrected on an individual basis in order to determine the true growth of brain regions as reflected by morphometric analysis of histological serial sections.

Adolescent↗
PubMed1986

Growth of the hippocampal formation in man.

The fresh volumes of the cortical area of the hippocampal formation were determined in 29 male, normative human brains ranging in age from 137 to 36,221 ontogenetic days inclusive of mid-gestation to the 99th postnatal year. The data were fitted by the 3-, 4-, and 5-parametric logistic functions. The ideal value P1 of the left hippocampal formation is 3 ml (SD = 0.1), the half-value time is 306 (SD = 32) ontogenetic days and the growth factor is 2.5 (SD = 0.4). The maximal daily growth rate of 8 mm3 occurs at approximately the half value time. According to the theory of Dobbing and Sands [1979], this period of rapid growth of the hippocampal formation with other brain regions suggests the existence of heterochronous development.

Adolescent↗
PubMed1985

An evaluation of cefoxitin in the prevention of postoperative infections following orthopedic surgical procedures.

An open, nonrandomized study of 25 patients was conducted to evaluate the efficacy of cefoxitin in the prevention of postoperative infection following orthopedic surgical procedures. Cefoxitin was administered in a 2 g dose preoperatively and continued postoperatively at a dose of 2 g every six hours for 72 hours. The mean peak serum level achieved ten minutes after the preoperative dose was 153.7 mcg/ml. The mean bone level in samples taken during the procedure was 10.14 mcg/ml. All patients were monitored postoperatively and at intervals of six weeks, four months and six months for signs of early or late morbidity. No signs of major morbidity were observed in the study group.

Adult↗
PubMed1983

Semi-automatic analysis of microscopic images of the human cerebral cortex using the grey level index.

A new semi-automatic method is introduced which makes possible the quantitative examination of cresyl-fast-violet stained sections of the cerebral cortex. These sections are divided into measuring fields of 20 X 20 microns in a well-defined area. A scanning procedure then automatically determines the grey level index of every single field. The image of the histological section can be compared with the grey level index data matrix by means of a plotted image, the density of the plotted points of which is proportional to the measured grey level index. By overlaying this plotted image with the original section, the boundaries of the laminae can be fixed in the data matrix. The grey level index profiles--the grey level data plot as a function of the cortical depth--after smoothing and standardization are typical of special cortical areas. The mean thickness and the mean portion of the grey level index profile of the different laminae of the striate area are compared with data from other publications.

Cerebral Cortex↗
PubMed1983

Quantitative analysis of the laminae of the striate area in man. An application of automatic image analysis.

181 cortical fields from the striate area of 11 normal, adult brains were studied using the grey level index method. The absolute and relative thickness, the relative portion of the GLI profile, and the mean absolute and relative GLI of the different laminae of the striate area were measured. The values for the laminae were analysed for correlation. Significant correlations could partly be explained by the influence of the geometrical shape of the cortex. The lamina data of one brain were examined in relation to the position in the sulcus calcarinus.

Adult↗
PubMed1982

Immunological comparison of purified DNA polymerase alpha from embryos of Drosophila melanogaster with forms of the enzyme present in vivo.

Specific antisera to purified DNA polymerase alpha from embryos of Drosophila melanogaster and to two of the four constituent subunits (alpha, beta, gamma, and delta) were prepared. These antibodies have revealed the following features of the enzyme. (i) The Mr = 148,000 alpha subunit is very likely derived by in vitro proteolysis from polypeptides with molecular weights of 185,000 and 166,000 that are present in vivo. (ii) The Mr = 60,000 beta subunit occurs in rapidly replicating embryos as both an 85,000- and a 60,000-dalton form, but predominantly as a 60,000-dalton form in more slowly replicating cultured cells. (iii) There is no detectable immunologic cross-reactivity between the four subunits. (iv) There is an abundance of antigenic material in embryos that co-migrates with the delta subunit of the purified enzyme during polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate.

Animals↗
PubMed1980

DNA polymerase alpha from Drosophila melanogaster embryos. Subunit structure.

The homogeneous DNA polymerase alpha from early embryos of Drosophila melanogaster contains four polypeptides designated alpha, beta, gamma, and delta, with molecular weights of 148,000, 58,000, 46,000, and 43,000, respectively (Banks, G. R., Boezi, J. A., and Lehman, I. R. (1979) J. Biol. Chem. 254, 9886-9892). The four polypeptides are structurally distinct from one another, as indicated by their different peptide patterns following limited proteolysis with Staphylococcus aureus protease. Furthermore, the inclusion of the protease inhibitors, leupeptin and pepstatin, in addition to phenpylmethylsulfonyl fluoride and sodium metabisulfite, which are used routinely during the purification, does not alter the pattern of polypeptides in the purified polymerase, suggesting that the four polypeptides are not a consequence of nonspecific proteolysis during purification. Thus, the alpha, beta, gamma, and delta polypeptides appear to be distinct subunits of the alpha-DNA polymerase of D. melanogaster. The alpha subunit is required for DNA polymerase activity. However, the specific activity of the isolated subunit is substantially lower than when it is associated with the beta, gamma, and delta subunits.

Animals↗
PubMed1980

Genetic analysis of bacteriophage P4 using P4-plasmid ColE1 hybrids.

A set of plasmids that contain fragments of the bacteriophage P4 genome has been constructed by deleting portions of a P4-ColE1 hybrid. A P4 genetic map has been established and related to the physical map by examining the ability of these plasmids to rescue various P4 mutations. The P4 virl mutation and P4 genes involved in DNA replication (alpha), activation of P2 helper genes (delta and epsilon), polarity suppression (psu) and head size determination (sid) have been mapped, as has the region responsible for synthesis of a nonessential P4 protein. One of the deleted plasmids contains only 5900 base pairs (52%) of P4 but will form plaques if additional DNA is added to increase its total size to near that of P4. This plasmid is also unique in that it will not form stable associations with P2 lysogens of E. coli which are recA+. P4 alpha mutants can be suppressed as a result of replication under control of the ColE1 part of the hybrid.

Chromosome Mapping↗
PubMed1975

A bacterial mutation blocking P2 phage late gene expression.

A mutant of Escherichia coli strain C has been isolated, called gro109, that blocks bacteriophage P2 propagation by interfering with late gene expression. DNA replication proceeds normally in P2+-infected gro109 cells, but late phage proteins are not made. Early P2 mRNA is made in normal amounts, but very little late mRNA can be detected. P2 mutants (P2 ogr) able to overcome the gro109 block have been isolated in which synthesis of late P2 mRNA and phage proteins Is restored. The gro109 mutation is closely linked to the cluster of ribosomal genes at 64 min and is recessive to the wild-type (gro+) allele. A P2 ogr mutation has been mapped on the left arm of the P2 genome, between the right-most known late gene (D) and the phage attachment site. P2 ogr can complement P2+ in gro109 cells, indicating that ogr codes for a diffusible product.

Coliphages↗