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Biomedical subjects

S Scherer

Publications and source records attributed to S Scherer.

At least 73 records · Page 4Linked to original sources
PubMed1997

Evidence that the homeodomain protein Gtx is involved in the regulation of oligodendrocyte myelination.

We have investigated the patterns of postnatal brain expression and DNA binding of Gtx, a homeodomain transcription factor. Gtx mRNA accumulates in parallel with the RNAs encoding the major structural proteins of myelin, myelin basic protein (MBP), and proteolipid protein (PLP) during postnatal brain development; Gtx mRNA decreases in parallel with MBP and PLP mRNAs in the brains of myelin-deficient rats, which have a point mutation in the PLP gene. Gtx mRNA is expressed in differentiated, postmitotic oligodendrocytes but is not found in oligodendrocyte precursors or astrocytes. These data thus demonstrate that Gtx is expressed uniquely in differentiated oligodendrocytes in postnatal rodent brain and that its expression is regulated in parallel with the major myelin protein mRNAs, encoding MBP and PLP, under a variety of physiologically relevant circumstances. Using a Gtx fusion protein produced in bacteria, we have confirmed that Gtx is a sequence-specific DNA-binding protein, which binds DNA sequences containing a core AT-rich homeodomain binding site. Immunoprecipitation of labeled DNA fragments encoding either the MBP or PLP promoter regions with this fusion protein has identified several Gtx-binding fragments, and we have confirmed these data using an electrophoretic mobility shift assay. In this way we have identified four Gtx binding sites within the first 750 bp of the MBP promoter and four Gtx binding sites within the first 1. 3 kb of the PLP promoter. In addition, inspection of the PLP promoter sequence demonstrates the presence of six additional Gtx binding sites. These data, taken together, strongly suggest that Gtx is important for the function of differentiated oligodendrocytes and may be involved in the regulation of myelin-specific gene expression.

Aging↗
PubMed1997

Analysis of HLA-DR split-specificity matching in cadaver kidney transplantation: a report of the Collaborative Transplant Study.

The influence of mismatches for HLA-DR "split" specificities was investigated in more than 8000 cadaver kidney transplants. HLA-DR typing was performed using DNA methodology. Among first transplants, mismatches defined by HLA-DR split specificities did not have a deleterious influence. Among retransplants, however, graft survival was significantly decreased if a mismatch was defined, considering split specificities in patients with no mismatch according to the "broad" definition (P=0.04) and also in grafts with two split mismatches, which showed only one mismatch according to the broad definition (P=0.03). Moreover, consideration of further "subsplit" specificities resulted in clinically relevant mismatches only among retransplants. These data indicate that the recognition of HLA-DR split specificity mismatches is fundamentally different in primary and regraft recipients. The results imply that recipients and donors of kidney retransplants should be typed for HLA-DR split specificities and that these specificities should be considered for organ allocation.

Alleles↗
PubMed1997

Phylogenetic relationships of fungal cytochromes c.

The CYC1 gene encoding cytochrome c in the yeast Candida albicans was cloned by complementation of a cytochrome c-deficient mutant of Saccharomyces cerevisiae, and its DNA sequence was determined. The analysis of the amino acid sequences of cytochrome c from 14 fungal species and two isoforms from S. cerevisiae revealed sequences unique to fungi, and revealed a phylogenetic relationship with a pronounced divergence between Schizosaccharomyces pombe and other ascomycetous budding yeast.

Amino Acid Sequence↗
PubMed1997

Identification of an amplified gene cluster in glioma including two novel amplified genes isolated by exon trapping.

Gene amplification, which occurs in more than 50% of malignant gliomas, is considered to play a pivotal role in tumorigenesis. There are, however, few studies aimed toward the isolation of novel genes from amplified sequences. Previously, we reported amplification of the protooncogene MET (hepatocyte growth factor receptor; 7q31) in more than 20% of glioblastomas. For an approximate size estimation of the amplification unit we analyzed three glioblastomas all of which carried an amplified MET gene, by Southern blot analysis and/or competitive polymerase chain reaction using eight DNA markers. Although the extent of the amplified domain varied, the close vicinity of the MET gene was the only region consistently amplified in these glioblastomas. A yeast artificial chromosome (YAC) contig of 900 kb was refined spanning the amplified region flanking the MET gene. The YAC inserts were subcloned into 59 cosmids, which were used for exon trapping. Eight sequences were identical to parts of the genes MET and CAPZA2 (human actin capping protein alpha-subunit). Two newly identified exons and the CAPZA2 exons were amplified in tumor TX3095, which retains an amplified MET gene. The new exons were localized close to MET and CAPZA2. Characterization of the clones, which were termed glioma-amplified sequence (GAS)7-1 and GAS7-2, showed an open reading frame and a different expression pattern in multiple human tissues. This study reports the identification of a cluster of amplified genes including two novel genes in a region amplified in more than 20% of glioblastomas.

Actin Capping Proteins↗
PubMed1997

Identification of yeasts and coryneform bacteria from the surface microflora of brick cheeses.

Coryneform bacteria and yeasts of 21 brick cheeses from six German dairies, produced by using undefined ripening cultures, were identified. Arthrobacter nicotianae, Brevibacterium linens, Corynebacterium ammoniagenes, Corynebacterium variabilis and Rhodococcus fascians were found in significant numbers. Out of 148 coryneform isolates 36 could not be identified at the species level. With the exception of a large rennet cheese, the coryneform microflora of rennet and acid cured cheeses were similar, but the cheeses had clearly different yeast populations. Debaryomyces hansenii and Galactomyces geotrichum prevailed in rennet cheeses while Kluyveromyces marxianus and Pichia membranaefaciens were the main species found in acid cured cheese. The dominance of Yarrowia lipolytica probably indicates an improper yeast population, resulting in poor cheese quality. Some of the species identified are potential candidates for designing a defined ripening culture for rennet red smear cheese.

Actinomycetales↗
PubMed1997

HLA class I DNA typing of 215 "HLA-A, -B, -DR zero mismatched" kidney transplants.

DNA typing for HLA class II improves the typing quality and this was shown previously to be relevant for kidney graft survival. In this project we addressed the question whether molecular typing for HLA class I also increases the efficacy of HLA matching in kidney transplantation. 215 HLA-A,-B,-DR zero-mismatched donor/recipient pairs as defined by serological typing were selected. Retrospective HLA-A and HLA-B typing was performed both by the PCR-SSP and the PCR-SSOP method. DNA typing for HLA-A revealed discrepant results to serology in 5.7% of the donors and 2.8% of the recipients. HLA-B typing discrepancies were found in 6.6% of the donors and 5.6% of the recipients. 10.4% of the donors and 6.5% of the recipients showed either an HLA-A or an HLA-B discrepancy Nearly one-third of the HLA-A discrepancies affected A19 splits. The most common reason for HLA-A discrepancies was the erroneous assignment of serological blanks, whereas HLA-B errors were caused mainly by the assignment of incorrect specificities. DNA typing allowed the definition of HLA-A and -B split specificities in all 118 "splitable" cases for which only broad specificities were reported based on serological typing. A total of 183 DNA class I compatible transplants had a 15% higher one-year graft survival rate than 32 transplants for which DNA typing revealed a class I incompatibility

DNA Probes, HLA↗
PubMed1997

Growth reduction of Listeria spp. caused by undefined industrial red smear cheese cultures and bacteriocin-producing Brevibacterium lines as evaluated in situ on soft cheese.

The undefined microbial floras derived from the surface of ripe cheese which are used for the ripening of commercial red smear cheeses have a strong impact on the growth of Listeria spp. In some cases, these microbial consortia inhibit Listeria almost completely. From such undefined industrial cheese-ripening floras, linocin M18-producing (lin+) (N. Valdés-Stauber and S. Scherer, Appl. Environ. Microbiol. 60:3809-3814, 1994) and -nonproducing Brevibacterium linens strains were isolated and used as single-strain starter cultures on model red smear cheeses to evaluate their potential inhibitory effects on Listeria strains in situ. On cheeses ripened with lin+ strains, a growth reduction of L. ivanovii and L. monocytogenes of 1 to 2 log units was observed compared to cheeses ripened with lin strains. Linocin M18 activity was detected in cheeses ripened with lin+ strains but was not found in those ripened with lin strains. We suggest that production of linocin M18 contributes to the growth reduction of Listeria observed on model red smear cheeses but is unsufficient to explain the almost complete inhibition of Listeria caused by some undefined microbial floras derived from the surface of ripe cheeses.

Bacteriocins↗
PubMed1997

Evaluation of luciferase reporter bacteriophage A511::luxAB for detection of Listeria monocytogenes in contaminated foods.

A511::luxAB is a recombinant derivative of a broad-host-range bacteriophage specific for the genus Listeria, transducing bacterial bioluminescence into infected cells. In this study, we have evaluated its use for rapid and easy testing of contaminated foods and environmental samples for the presence of viable Listeria cells, in comparison to the standard plating procedure. With a short preenrichment step of 20 h, the system was capable of detecting very low initial contamination rates in several foods artificially contaminated with Listeria monocytogenes Scott A cells. In ricotta cheese, chocolate pudding, and cabbage, less than one cell per g of food could be clearly identified by comparing the light emission of phage-infected samples to that of controls without lux phage. In foods having a large and complex microbial background flora, such as minced meat and soft cheese, at least 10 cells per g were necessary to produce a positive bioluminescence signal. Of 348 potentially contaminated natural food and environmental samples, 55 were found to be Listeria positive by the lux phage method. The standard plating procedure detected 57 positive samples. Some differences were observed with respect to the individual samples, i.e., the lux phage procedure detected more positive samples among the dairy products and environmental samples, whereas the plating procedure revealed more contaminated meat and poultry samples. Overall, both methods performed similarly, i.e., were equally sensitive. However, the minimum time required for detection of Listeria with the luciferase phage assay was 24 h, which is much shorter than the 4 days needed by the standard plating method. Furthermore, a most probable number technique with three parallels, based on the use of A511::luxAB for differentiation of positive and negative tubes, is described. The method enables rapid enumeration of low levels of Listeria cells in several foods tested, against the background of a competing microflora.

Animals↗
PubMed1997

Variable number of tandem repeats in clinical strains of Haemophilus influenzae.

An algorithm capable of identifying short repeat motifs was developed and used to screen the whole genome sequence available for Haemophilus influenzae, since some of these repeats have been shown to affect bacterial virulence. Various di- to hexanucleotide repeats were identified, confirming and extending previous findings on the existence of variable-number-of-tandem-repeat loci (VNTRs). Repeats with units of 7 or 8 nucleotides were not encountered. For all of the 3- to 6-nucleotide repeats in the H. influenzae chromosome, PCR tests capable of detecting allelic polymorphisms were designed. Fourteen of 18 of the potential VNTRs were indeed highly polymorphic when different strains were screened. Two of the potential VNTRs appeared to be short and homogeneous in length; another one may be specific for the H. influenzae Rd strain only. One of the primer sets generated fingerprint-type DNA banding patterns. The various repeat types differed with respect to intrinsic stability as well. It was noted for separate colonies derived from a single clinical specimen or strains passaged for several weeks on chocolate agar plates that the lengths of the VNTRs did not change. When several strains from different patients infected during an outbreak of lung disease were analyzed, increased but limited variation was encountered in all VNTR sites analyzed. One of the 5-nucleotide VNTRs proved to be hypervariable. This variability may reflect the molecular basis of a mechanism used by H. influenzae bacteria to successfully colonize and infect different human individuals.

Algorithms↗
PubMed1997

UV-B-induced synthesis of photoprotective pigments and extracellular polysaccharides in the terrestrial cyanobacterium Nostoc commune.

Liquid cultures of the terrestrial cyanobacterium Nostoc commune derived from field material were treated with artificial UV-B and UV-A irradiation. We studied the induction of various pigments which are though to provide protection against damaging UV-B irradiation. First, UV-B irradiation induced an increase in carotenoids, especially echinenone and myxoxanthophyll, but did not influence production of chlorophyll a. Second, an increase of an extracellular, water-soluble UV-A/B-absorbing mycosporine occurred, which was associated with extracellular glycan synthesis. Finally, synthesis of scytonemin, a lipid-soluble, extracellular pigment known to function as a UV-A sunscreen, was observed. After long-time exposure, the UV-B effect on carotenoid and scytonemin synthesis ceased whereas the mycosporine content remained constantly high. The UV-B sunscreen mycosporine is exclusively induced by UV-B (< 315 nm). The UV-A sunscreen scytonemin is induced only slightly by UV-B (< 315 nm), very strongly by near UV-A (350 to 400 nm), and not at all by far UV-A (320 to 350 nm). These results may indicate that the syntheses of these UV sunscreens are triggered by different UV photoreceptors.

Carotenoids↗
PubMed1997

Three Bacillus cereus bacteriophage endolysins are unrelated but reveal high homology to cell wall hydrolases from different bacilli.

The ply genes encoding the endolysin proteins from Bacillus cereus phages Bastille, TP21, and 12826 were identified, cloned, and sequenced. The endolysins could be overproduced in Escherichia coli (up to 20% of total cellular protein), and the recombinant proteins were purified by a two-step chromatographical procedure. All three enzymes induced rapid and specific lysis of viable cells of several Bacillus species, with highest activity on B. cereus and B. thuringiensis. Ply12 and Ply21 were experimentally shown to be N-acetylmuramoyl-L-alanine amidases (EC 3.5.1.28). No apparent holin genes were found adjacent to the ply genes. However, Ply21 may be endowed with a signal peptide which could play a role in timing of cell lysis by the cytoplasmic phage endolysin. The individual lytic enzymes (PlyBa, 41.1 kDa; Ply21, 29.5 kDa, Ply12, 27.7 kDa) show remarkable heterogeneity, i.e., their amino acid sequences reveal only little homology. The N-terminal part of Ply21 was found to be almost identical to the catalytic domains of a Bacillus sp. cell wall hydrolase (CwlSP) and an autolysin of B. subtilis (CwlA). The C terminus of PlyBa contains a 77-amino-acid sequence repeat which is also homologous to the binding domain of CwlSP. Ply12 shows homology to the major autolysins from B. subtilis and E. coli. Comparison with database sequences indicated a modular organization of the phage lysis proteins where the enzymatic activity is located in the N-terminal region and the C-termini are responsible for specific recognition and binding of Bacillus peptidoglycan. We speculate that the close relationship of the phage enzymes and cell wall autolysins is based upon horizontal gene transfer among different Bacillus phages and their hosts.

Amino Acid Sequence↗
PubMed1997

Angiotensin-converting enzyme genotype and renal allograft survival.

Increased activity of the renin-angiotensin system has been implicated in decreased, long-term survival of renal allografts. Recent studies suggest that a deletion variant of the angiotensin-converting enzyme, associated with increased humoral and tissue activity of this enzyme, is a risk factor for the development of diabetic nephropathy and the progression of IgA nephropathy. To determine whether the deletion variant of the angiotensin-converting enzyme gene influences the long-term outcome in renal transplant recipients, the relationship between donor and recipient angiotensin-converting enzyme genotype and clinical outcome were examined over a follow-up period up to 30 mo in a cohort of 269 Caucasian patients undergoing kidney transplantation between 1988 and 1993. In a subsequent case control study, the frequencies of the angiotensin-converting enzyme genotype were compared in a group of Caucasian patients with a graft survival of less than 3 yr (mean survival, 11 mo; n = 328) with the frequencies in patients with a graft survival of at least 3 yr (mean survival, 65 mo, n = 461). Neither in the cohort nor in the case control study was there a significant effect of recipient or donor angiotensin-converting enzyme genotype on transplant survival. Furthermore, the frequency of the angiotensin-converting enzyme deletion allele both in recipients and donors was similar to that reported in Caucasian controls. This study, therefore, does not support the hypothesis that the recipient or donor angiotensin-converting enzyme insertion/deletion polymorphism is an important determinant of transplant survival in Caucasian patients undergoing renal transplantation.

Adult↗
PubMed1996

Chromosomal localization in mouse and human of the vasoactive intestinal peptide receptor type 2 gene: a possible contributor to the holoprosencephaly 3 phenotype.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) have been shown to act on a wide range of tissue and cell types, both in the central nervous system and in the periphery. Two distinct receptors for VIP, the VIP receptor type 1 (VIPR1) and the VIP receptor type 2 (VIPR2), have recently been cloned, each of which binds PACAP and VIP with equal affinity. We report here the chromosomal mapping of the human and mouse VIPR2 genes by fluorescence in situ hybridization. The VIPR2 gene maps to the human chromosomal region 7q36.3 and to the F2 region of mouse chromosome 12. Our localization of the human gene places it in the region where the locus for the craniofacial defect holoprosencephaly type 3 (HPE3) maps. Further mapping experiments, carried out on cell lines derived from patients with HPE or HPE microforms and associated 7q deletions, have led us to redefine the distal extent of the HPE3 minimal critical region, originally characterized by Gurrieri et al. (1993, Nature Genet. 3: 247-251.) The VIPR2 gene lies within this new HPE3 minimal critical region. Our results suggest that deletion of the VIPR2 gene is not the sole factor responsible for the HPE3 phenotype. However, it is possible that monosomy at the VIPR2 locus may contribute to the phenotype observed in many cases of HPE3.

Animals↗
PubMed1996

The Ikaros gene encodes a family of lymphocyte-restricted zinc finger DNA binding proteins, highly conserved in human and mouse.

The Ikaros gene is an essential regulator in the development and homeostasis of the mouse lymphopoietic system. To study the role of the Ikaros gene in the human lymphopoietic system, we cloned and characterized human Ikaros cDNAs. In the human, as in the mouse, differential splicing of Ikaros primary transcripts generates a family of lymphoid-restricted zinc finger DNA binding proteins, highly conserved in sequence composition and relative expression to the mouse homologues. Expression of Ikaros isoforms is highly restricted to the lymphopoietic system and is particularly enriched in maturing thymocytes. The Ikaros gene maps at a syntenic locus located on the short arm of human chromosome 7 and on mouse chromosome 11 next to the epidermal growth factor receptor (Egfr). The high degree of conservation of the Ikaros gene at the genetic and expression levels strongly suggests that it plays a fundamental role in the ontogeny of the lymphopoietic system across species.

3T3 Cells↗