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B Stern

Publications and source records attributed to B Stern.

At least 19 recordsLinked to original sources
PubMed1998

Cyclin B proteolysis and the cyclin-dependent kinase inhibitor rum1p are required for pheromone-induced G1 arrest in fission yeast.

The blocking of G1 progression by fission yeast pheromones requires inhibition of the cyclin-dependent kinase cdc2p associated with the B-cyclins cdc13p and cig2p. We show that cyclosome-mediated degradation of cdc13p and cig2p is necessary for down-regulation of B-cyclin-associated cdc2p kinase activity and for phermone-induced G1 arrest. The cyclin-dependent kinase inhibitor rum1p is also required to maintain this G1 arrest; it binds both cdc13p and cig2p and is specifically required for cdc13p proteolysis. We propose that rum1p acts as an adaptor targeting cdc13p for degradation by the cyclosome. In contrast, the cig2p-cdc2p kinase can be down-regulated, and the cyclin cig2p can be proteolyzed independently of rum1p. We suggest that pheromone signaling inhibits the cig2p-cdc2p kinase, bringing about a transient G1 arrest. As a consequence, rum1p levels increase, thus inhibiting and inducing proteolysis of the cdc13p-cdc2p kinase; this is necessary to maintain G1 arrest. We have also shown that pheromone-induced transcription occurs only in G1 and is independent of rum1p.

Animals↗
PubMed1997

Fission yeast pheromone blocks S-phase by inhibiting the G1 cyclin B-p34cdc2 kinase.

Yeast pheromones block cell cycle progression in G1 in order to prepare mating partners for conjugation. We have investigated the mechanism underlying pheromone-induced G1 arrest in the fission yeast Schizosaccharomyces pombe. We find that the G1-specific transcription factor p65cdc10-p72res1/sct1 which controls the expression of S-phase genes is fully activated in pheromone, unlike the analogous control in budding yeast. In contrast, the G1 function of p34cdc2 acting after activation of the G1-specific transcription is blocked. Pheromone inhibits the p34cdc2 kinase associated with both the G1-specific B-type cyclin p45cig2 and the B-type cyclin p56cdc13 and overexpression of p45cig2 or p47cdc13delta90 overcomes the pheromone-induced G1 arrest. G1 arrest is compromised in enlarged cells. We suggest that onset of S-phase is controlled by pheromone inhibiting the B-cyclin-associated kinase in G1, and that increasing cell size contributes to the mechanism for pheromone adaptation. Thus, pheromone in fission and budding yeast acts similarly in inhibiting the G1 cyclin-dependent kinase (CDK), but differs in its effects on the G1/S transcriptional control, suggesting that inhibition of CDKs may be a more general mechanism for the control of G1 progression compared with G1/S transcriptional control.

Blotting, Northern↗
PubMed1997

Helical epitopes determined by low-stringency antibody screening of a combinatorial peptide library.

Combinatorial phage display peptide libraries are routinely used to map epitopes of specific monoclonal antibodies. In this study we illustrate that these libraries can be used in the analysis of protein structure. By screening libraries at low stringency, a collection of phages can be obtained. These are characterized by the fact that they are recognized by a given monoclonal antibody yet with various affinities. Comparing the random peptides of these phages indicates the common essential residues necessary for antibody recognition. Aligning the inserts based on the detected homology has revealed structural motifs that correspond to secondary protein structures. The envelope protein of HIV-1 has been studied using this approach. A combinatorial phage display library containing a 20 mer random peptide in protein III of the filamentous phage fd-tet has been used to analyze two different monoclonal antibodies directed against gp120. Our results provide experimental evidence that indicate that the C1 domain of gp120 contains an alpha helix.

Amino Acid Sequence↗
PubMed1996

Humoral immune response to immunocomplexed HIV envelope glycoprotein 120.

To further our understanding of the nature of HIV-1 immunogenicity, we injected mice with the virus envelope protein gp120 in different configurations: free, complexed with its receptor CD4, and as an immunocomplex with a monoclonal antibody directed against the V3 loop of the protein. Analyses of the polyclonal sera, as well as of monoclonal antibodies produced in each case, allowed us to conclude that the quality of the humoral immune response depended on the complexation state of the antigen. For the free gp120 and gp120-CD4 complex the responses were directed mainly toward conformational epitopes. However, gp120 immunocomplexed with anti-V3 loop Mab produced, in addition, numerous MAbs directed toward linear epitopes. Epitopes were mapped using immunoblots of gp120 cleaved with S. aureus V8 protease and a combinatorial epitope phage-display library. It was found that some of the linear epitopes had been previously identified as T cell epitopes. These results suggest that the immunocomplexed gp120 may be particularly well taken up by antigen-presenting cells, leading to the processing of the gp120 and the efficient presentation of T cell epitopes. Thus immunocomplexation should afford a means for enhancing the immunogenicity of gp120 and improving its presentation.

Amino Acid Sequence↗
PubMed1996

Traditional risk factors and ischemic stroke in young adults: the Baltimore-Washington Cooperative Young Stroke Study.

OBJECTIVE: To determine the association of hypertension, diabetes, and cigarette smoking with incidence of ischemic stroke in young adults. DESIGN: Case-control study. SETTING: Population-based sample of cases and controls. SUBJECTS: The study included 296 cases of incident ischemic stroke among black and white adults aged 18 to 44 years in central Maryland counties from the Baltimore-Washington Cooperative Young Stroke Study and 1220 black and white adults aged 18 to 44 years from the Maryland Behavioral Risk Factor Survey, a telephone survey of a random sample of the same region, to serve as controls. MAIN OUTCOME MEASURES: Logistic regression models were developed to determine the age-adjusted odds ratios for each risk factor. Population-attributable risk percent were computed based on the odds ratios and prevalence of each risk factor. RESULTS: The age-adjusted odds ratios (95% confidence intervals) for white men (WM), white women (WW), black men (BM), and black women (BW) were as follows: current cigarette smoking: WM, 2.0 (1.1-3.8), WW, 2.1 (1.1-4.3), BM, 3.3 (1.6-6.6), and BW, 2.2 (1.3-3.9); history of diabetes mellitus: WM, 22.9 (5.8-89.6), WW, 6.2 (1.9-20.2), BM, 4.2 (0.8-21.9), and BW, 3.3 (1.4-7.7); and history of hypertension: WM, 1.6 (0.7-3.2), WW, 2.5 (1.1-5.9), BM, 3.8 (1.8-7.9), and BW, 4.2 (2.4-7.5). The population-attributable risk percent (95% confidence intervals) were as follows: current cigarette smoking: WM, 22.6 (3.1-38.2), WW, 17.2 (4.0-34.0), BM, 40.5 (23.1-54.0), and BW, 29.1 (13.5-41.9); history of diabetes mellitus: WM, 19.0 (8.2-28.5), WW, 15.8 (3.8-26.3), BM, 13.2 (5.3-20.4), and BW, 22.1 (12.5-30.7); and history of hypertension: WM, 21.7 (6.2-34.6), WW, 21.3 (5.4-34.5), BM, 53.5 (39.0-64.4), and BW, 50.5 (37.1-61.1). CONCLUSIONS: Hypertension, diabetes mellitus, and current cigarette smoking are important risk factors in a biracial young adult population. Cigarette smoking and hypertension, the 2 most modifiable risk factors, were particularly important risk factors in young blacks.

Adolescent↗
PubMed1996

Serum antibodies from patients with primary Sjögren's syndrome and systemic lupus erythematosus recognize multiple epitopes on the La(SS-B) autoantigen resembling viral protein sequences.

The aim of this study was to investigate the epitope recognition pattern of La(SS-B) autoantibodies in sera from patients with Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE) using overlapping synthetic decapeptides on solid phase. Eighty different decapeptides with five amino acids overlap from the human La(SS-B) autoantigen were synthesized on cellulose paper using F-moc chemistry. Tests were performed with 14 SS and six SLE sera. The results showed that the immune response to the La(SS-B) oligopeptides was restricted and unique for each individual with no particular pattern typical for each of the two diseases, apart from the fact that SLE sera gave positive reaction with fewer peptides. Regions within the N- and C-termini harboured most of the positive sequences. The authors specifically addressed the possibility of a viral aetiology for disease development or autoantibody generation. In this context the most frequently recognized linear epitopes on the La(SS-B) autoantigen showed sequence similarities with proteins from a range of ubiquitous human viruses, in particular from the herpes virus group. The La(SS-B) autoantibodies may thus be generated through molecular mimicry.

Adult↗
PubMed1996

A quantitative model for the cdc2 control of S phase and mitosis in fission yeast.

In this article we consider the role of the cyclin-dependent protein kinase cdc2 in regulating progression through the fission yeast cell cycle. The onset of mitosis is governed by cdc2 in partnership with the B-type cyclin, cdc13. Recent evidence shows that the cdc2-cdc13 complex can also control the onset of S phase and, in addition, ensures that there is only one S phase per cell cycle. This leads us to propose a novel quantitative model in which different levels of cdc2 activity regulate cell-cycle progression: S phase is initiated when protein kinase activity increases from a very low to a moderate level; maintenance of this moderate level prevents re-initiation of S phase, and a further increase of activity to a high level initiates mitosis. Inactivation of the kinase activity at the end of mitosis resets the cell for a new cell cycle.

Animals↗
PubMed1995

Conserved sequence patterns in phages Mu and lambda DNA.

The genetic maps of bacteriophages Mu and lambda can be aligned with respect to the functions of their genes. We were interested to ascertain whether the congruence of gene order is reflected at the nucleotide sequence level. A sliding window analysis of sequences from the early regions of both phages revealed a substantial degree of similarity. Equally high scores, however, were found when the early region of Mu was compared to the late region of lambda and in self-comparisons of either Mu or lambda. Hence, the similarity is due to a common pattern of nucleotides rather than to sequence similarities between functionally related genes. Employing degenerated scoring matrices we could show that primarily adenine and thymine residues contribute to the high scores and that a specific clustering of these residues is the basis for the conserved pattern. Since such a similarity was not observed with control sequences of other phages. Escherichia coli or eukaryotic viruses, the data support the notion that Mu and lambda have diverged from a common phage module. In general, our approach could offer a simple and sensitive way to trace distant relationships.

Bacteriophage lambda↗
PubMed1993

Genetic analysis of the Drosophila cdc2 homolog.

We have identified mutations in the Drosophila cdc2 gene. The recessive lethality of these mutant alleles was rescued after P-element-mediated transformation with a genomic cdc2 fragment. Sequence analysis of amorphic alleles revealed non-conservative exchanges in evolutionary conserved positions. These alleles caused lethality at the larval-pupal interphase due to the absence of imaginal tissues. Embryonic lethality resulted when the maternal Dm cdc2 contribution was reduced through the use of a temperature-sensitive allele. Dm cdc2 function, therefore, is essential for cell proliferation throughout development. Dm cdc2 function is clearly required for mitosis, but no evidence for a requirement in S-phase was obtained. The reversible block of the mitotic proliferation which was observed in the PNS of mutant embryos occurred exclusively in the G2-phase. Moreover, while the mitotic proliferation of imaginal cells was blocked in the amorphic mutant larvae, non-imaginal larval cells continued to grow and endoreplicate their DNA. The Dm cdc2 mutant phenotype could neither be rescued with Dm cdc2c (encoding a cdc2-like kinase) nor enhanced by a reduction of the Dm cdc2c gene dose. These results indicate that the Dm cdc2- and Dm cdc2c-kinases control different processes.

Amino Acid Sequence↗
PubMed1992

Cyclins and cdc2 kinases in Drosophila: genetic analyses in a higher eukaryote.

Cyclin proteins and the kinases with which they associate are encoded by gene families in multicellular eukaryotes. A variety of cyclin/kinase complexes with different functions may exist. We have started a genetic dissection of this complexity in Drosophila. We have done experiments to investigate a potential functional overlap between two kinases (Dmcdc2 and Dmcdc2c) and two cyclins (cyclin A and cyclin B). No functional overlap was observed between the Dmcdc2 and the Dmcdc2c kinases. The phenotype resulting from mutations in Dmcdc2 was not affected by altering the level of Dmcdc2c. Our results concerning cyclin A and cyclin B strongly suggest that these two cyclins have largely overlapping functions. Cell proliferation was observed in the absence of either cyclin A or cyclin B, but not if both cyclins were absent. Cyclin A also has essential functions that cannot be taken over by cyclin B, but these functions appear to be required at defined developmental stages in specific tissues only.

Animals↗
PubMed1990

A comprehensive survey of graduate education and training in hazardous waste management.

The United States Department of Health and Human Services through Wayne State University (WSU) has completed a study of hazardous waste education and training in the United States. The study documents university course work and degrees as well as non-degree continuing education short courses. Major portions of the study are based on a WSU sponsored survey in which 1469 four-year degree granting institutions were contacted. Of the 732 institutions responding, 113 were identified as offering course work of some kind in hazardous waste. Information on 499 distinct non-degree short courses was also gathered and evaluated. The purpose, methodology and results of the study are summarized in this article.

Education, Graduate↗
PubMed1989

Respiratory health effects associated with ambient sulfates and ozone in two rural Canadian communities.

A cross-sectional epidemiological study investigating the respiratory health of children in two Canadian communities was conducted in 1983-1984 in Tillsonburg, Ontario, located in a region of moderately elevated concentrations of transported air pollutants, and in Portage la Prairie, Manitoba, situated in a low pollution area. There were no significant local sources of industrial emissions in either community. Seven hundred and thirty-five children aged 7-12 were studied in the first town and 895 in the second. Respiratory health was assessed by the measurement of the forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1.0) of each child, and by evaluation of the child's respiratory symptoms and illnesses using a parent-completed questionnaire. Sulfur dioxide (SO2), sulfate, and particulate nitrate levels were significantly higher in Tillsonburg than in Portage la Prairie (P less than 0.05), but nitrogen dioxide (NO2) and inhalable particles (PM10) differed little between the communities. Historical data in the vicinity of Tillsonburg indicated that average annual levels of sulfates, total nitrates, and ozone (O3) did not vary markedly in the 9-year period preceding the study. The results show that Tillsonburg children had statistically significant (P less than 0.001) lower levels of 2% for FVC and 1.7% for FEV1.0 as compared with children in Portage la Prairie. These differences could not be explained by parental smoking or education, the use of gas cooking or wood heating fuels, pollution levels on the day of testing, or differences in age, sex, height, or weight. The differences persisted when children with cough with phlegm, asthma, wheeze, inhalant allergies, or hospitalization before age 2 for a chest illness were excluded from analysis. With the exception of inhalant allergies, which occurred more frequently in Tillsonburg children, the prevalence of chronic respiratory symptoms and illnesses was similar in the two communities.

Air Pollutants↗
PubMed1989

Acute lung function responses to ambient acid aerosol exposures in children.

We examined the relationship between lung function changes and ambient acid aerosol episodes in children attending a residential summer camp. Young females (112) performed daily spirometry, and 96 were assessed on one occasion for airway hyperresponsiveness using a methacholine bronchoprovocation test. Air quality measurements were performed on site and four distinct acid aerosol episodes were observed during the 41-day study. The maximum values observed during the 41-day study were: O3 at 143 ppb; H2SO4 at 47.7 micrograms/m3; and [H+] at 550 nmole/m3. Maximum decrements of 3.5 and 7% for FEV1 and PEF, respectively, were observed to be associated with the air pollution episodes. There was some evidence of a differential lung function response to the episodes where children with a positive response to a methacholine challenge had larger decrements compared to their nonresponsive counterparts.

Acid Rain↗
PubMed1989

Evolution of the DNA invertase Gin of phage Mu and related site-specific recombination proteins.

The relationship between site-specific recombination enzymes has been studied by computer analysis of nucleotide and amino acid sequences. A phylogenetic tree for two types of these enzymes has been constructed. DNA resolvases of Tn3-related transposable elements and DNA invertases form a superfamily which can be divided into four families of resolvases and one family of invertases comprising the Gin, Cin, Pin and Hin proteins. The DNA invertase genes descend from the tnpR branch that is represented by Tn917. Although TnpR 917 and Gin are almost 50% identical in their amino acid sequence, no gin-complementing activity of Tn917 could be measured. Within the family of DNA invertases, Gin and Pin are the closest relatives. The degree of sequence relatedness of the various invertases compared to Gin correlates with the biological relatedness tested in a gin complementation assay. A relationship between the inversion enzymes FimB and FimE and the super-family of site-specific recombinases could not be detected by these methods.

Bacteriophages↗