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Biomedical subjects

B Martin

Publications and source records attributed to B Martin.

At least 199 records · Page 11Linked to original sources
PubMed1995

Role of auxilin in uncoating clathrin-coated vesicles.

Clathrin-coated vesicles transport selected integral membrane proteins from the cell surface and the trans-Golgi network to the endosomal system. Before fusing with their target the vesicles must be stripped of their coats. This process is effected by the chaperone protein hsp70c together with a 100K cofactor which we here identify as the coat protein auxilin. Auxilin binds with high affinity to assembled clathrin lattices and, in the presence of ATP, recruits hsp70c. Dissociation of the lattice does not depend as previously supposed on clathrin light chains or on the amino-terminal domain of the heavy chain. The presence of a J-domain at its carboxy terminus now defines auxilin as a member of the DnaJ protein family. In conjunction with hsp70, DnaJ proteins catalyse protein folding, protein transport across membranes and the selective disruption of protein-protein interactions. We show that deletion of the J-domain of auxilin results in the loss of cofactor activity.

Adaptor Proteins, Vesicular Transport↗
PubMed1995

Construction and evaluation of new drug-resistance cassettes for gene disruption mutagenesis in Streptococcus pneumoniae, using an ami test platform.

Although drug-resistance markers have been used frequently for gene-disruption mutagenesis in Streptococcus pneumoniae, none has yet been shown to be free of dependence on local transcription for its expression. Indeed, the erythromycin-resistance marker (erm), originating in pAM beta 1, has been used as an indicator of local transcription on several occasions. A procedure is demonstrated for evaluation of the autonomous expression of such a marker by placing it in a consistent background, at the pneumococcal ami (aminopterin resistance) locus, in combination with active or inactive alleles of the ami promotor (pA). Using this test platform, a chloramphenicol-resistance marker (cat) and a spectinomycin-resistance marker used in streptococcal gene disruption studies and derived from pJS3 and pDL269, respectively, were shown to depend on local transcriptional signals for expression when placed in the pneumococcal chromosome as single-copy genes. To overcome this limitation, new drug-resistance cassettes were designed and constructed, using pA as a model for synthetic promoters for the erm and cat genes. Both new cassettes were shown, by the same procedure, to be expressed after insertion in the pneumococcal chromosome, independent of local transcription. A new insertion-duplication vector, pEVP3, incorporating the new cat cassette and a lacZ reporter derived from pTV32, was also constructed. The ami test platform was used to demonstrate both the autonomous expression of cat and the reporter function of lacZ in chromosomal copies of pEVP3.

Amino Acid Sequence↗
PubMed1995

Immunostimulating lipopeptide, LtriP (RP 56142): comparison of the effect on hepatic cytochrome P 450 modulation and radioprotection in male and female of three mouse strains.

The sex-dependent effect of lauroyl-L-Ala-D-gamma-Glu-L,L-A2pmNH2 (LtriP, RP 56142) on hepatic microsomal cytochromes P 450 (cyt P 450) was studied in three mouse strains NMRI, C3H/OuJ and C3H/HeJ. In NMRI and C3H/OuJ, strains which are responsive to bacterial lipopolysaccharides (LPS-responsive), regardless of the sex of the mouse, significant decrease in the amount of cyt P 450 was observed after LtriP treatment, with a concomitant reduction in ethoxyresorufin-O-deethylase (cyt P 450 1A-dependent) and 7-ethoxycoumarin-O-deethylase activities. This was not seen in C3H/HeJ (LPS-hyporesponsive) mice. These effects may be related to LtriP-dependent cytokine induction, since neither LtriP nor LPS stimulated interleukin-1 (IL-1) secretion by C3H/HeJ macrophages. 11- and 12-hydroxylations (11- and 12-OH) of lauric acid were compared in C3H/OuJ and C3H/HeJ mice. LtriP depressed the total enzymatic conversion of lauric acid in the two strains without modification of the 11/12-OH ratio for C3H/OuJ or male C3H/HeJ mice. However, in females C3H/HeJ mice this decrease was particularly significant and concerned especially the 12-OH activity (a marker of cyt P450 4A family). Although males of the three strains were more sensitive to irradiation than females, LtriP exerted a sex-independent radioprotection on NMRI and C3H/OuJ mice. Its radioprotective effect was illustrated by the preservation of all the enzymatic activities studied in treated NMRI mice, contrary to irradiated control animals. In contrast, for the C3H/HeJ strain, males were not protected by LtriP treatment and, furthermore, females showed a marked sensitization to irradiation. The effects in CH3/HeJ strain implicate LtriP in the control of cyt P 450 induction and of sensitivity to irradiation independently of IL-1 induction.

Adjuvants, Immunologic↗
PubMed1995

Structure, chromosomal location, and expression pattern of three mouse genes homologous to the human MAGE genes.

The human MAGE1 gene directs the expression of an antigen recognized on a melanoma by autologous cytolytic T lymphocytes. MAGE1 belongs to a family of genes that are expressed in a number of tumors of various histological types but not in normal tissues except testis. The MAGE genes are arranged in two groups that are located within two different regions of the human X chromosome (Xq26-qter and Xp21.3). By hybridizing mouse genomic libraries with a MAGE1 probe, we identified three homologous genes. Two of these mouse genes, Smage1 and Smage2, are more than 99% identical to each other and encode the same protein of 330 aa. The 5' noncoding region of Smage2 provides the potential for regulating the expression of the gene through several different promoters located in front of alternative first exons. The third gene, Smage3, has the structure of a processed transcript. It codes for a protein with only 11 aa substitutions with respect to the Smage1/2 product. Somatic cell hybrids and interspecific backcross analysis showed that Smage3 is autosomal and that Smage1 and Smage2 are located between the Dmd and the Ar loci on the mouse X chromosome. Since this region is syntenic to the human Xp21.1-p22.1 region, we conclude that Smage1 and Smage2 are homologous to the MAGE-Xp rather than to the MAGE-Xq genes. Smage1/2 transcripts were detected in several tumor and embryonal cell lines but not in normal mouse tissues with the exception of testis. Expression of Smage3 was found in embryos from Day 11 to Day 15.

Amino Acid Sequence↗
PubMed1995

Identification of B-cell growth factors (interleukin-14; high molecular weight-B-cell growth factors) in effusion fluids from patients with aggressive B-cell lymphomas.

The molecular basis of neoplastic B-cell growth is complex and poorly understood. Cytokines have been postulated to contribute to neoplastic cell growth, and many in vitro studies have confirmed this prediction, but little is known about the in vivo role of these growth factors. We have examined the production of interleukin-14 (IL-14) (high molecular weight [HMW], B-cell growth factor [BCGF]) by aggressive intermediate (diffuse large cell) lymphomas of the B-cell type non-Hodgkin's lymphoma (NHL-B) in four patients with lymphomatous effusions. In these studies, IL-14 was detected in the effusion fluids by Western blots and IL-14 mRNA was constitutively expressed in the freshly isolated lymphoma cells that also expressed the receptor for IL-14 (IL14R). Lymphoma B cells placed at low serum and cell density proliferated in vitro to either purified IL-14 or IL-14 derived from effusion fluids. Antibodies to IL-14 removed the growth-stimulating cytokine(s) from the effusions. Cell lines developed from these patients produced IL-14 in vitro and antisense oligos to IL-14 blocked their growth in vitro. Thus, autocrine or paracrine production of IL-14 may play a significant role in the rapid proliferation of aggressive NHL-B. Interrupting this pathway could be a useful goal of therapy for patients resistant to conventional chemotherapy.

Aneuploidy↗
PubMed1995

Discriminative stimulus effects of anandamide in rats.

Anandamide (arachidonylethanolamide), a putative endogenous ligand for the cannabinoid receptor, produces a tetrad of behavioral effects in mice characteristic of psychoactive cannabinoids including catalepsy, antinociception, hypothermia, and hypomobility. The present study examined the discriminative stimulus effects of anandamide in rats trained to discriminate delta 9-tetrahydrocannabinol or the potent cannabinoid receptor ligand CP 55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)-phenyl]-trans-4-(3- hydroxypropyl)cyclohexanol)] from vehicle. Intraperitoneal injections of anandamide substituted for delta 9-tetrahydrocannabinol and for CP 55,940; however, unlike substitution dose-effect curves with the training drugs, anandamide substitution occurred at a single dose (30 or 45 mg/kg) and was accompanied by severe decreases in response rates. The results of the present study suggest that, although systemic anandamide administration may have cannabimimetic effects similar to those of delta 9-tetrahydrocannabinol and CP 55,940, some differences in the behavioral effects of anandamide and other psychoactive cannabinoids also are apparent.

Animals↗
PubMed1995

Mathematical model for repair of fatigue damage and stress fracture in osteonal bone.

This paper assembles current concepts about bone fatigue and osteonal remodeling into a mathematical theory of the repair of fatigue damage and the etiology of stress fracture. The model was used to address three questions. (a) How does the half-life of fatigue damage compare with the duration of the remodeling cycle? (b) Does the porosity associated with the remodeling response contribute to stress fracture? (c) To what extent is a periosteal callus response necessary to augment repair by remodeling? To develop the theory, existing experimental data were used to formulate mathematical relationships between loading, damage, periosteal bone formation, osteonal remodeling, porosity, and elastic modulus. The resulting nonlinear relationships were numerically solved in an iterative fashion using a computer, and the behavior of the model was studied for various loading conditions and values of system parameters. The model adapted to increased loading by increasing remodeling to repair the additional damage and by adding new bone periosteally to reduce strain. However, if too much loading was encountered, the porosity associated with increased remodeling caused the system to become unstable; i.e., damage, porosity, and strain increased at a very high rate and without limit. It is proposed that this phenomenon is the equivalent of a stress fracture and that its biological and mechanical elements are significant in the etiology of stress fractures. Additional experiments must be done to test the model and provide better values for its parameters. However, the instability characteristic is relatively insensitive to changes in model parameters.

Animals↗
PubMed1995

Chromosome 18 analysis by fluorescence in situ hybridization (FISH) in human blastomeres of abnormal embryos after in vitro fertilization (IVF) attempt.

We performed fluorescence in situ hybridization (FISH) with a chromosome 18-specific probe on human abnormal cleaved embryos, fertilized either by two spermatozoa and exhibiting three pronuclei (3 PN) or normally fertilized and exhibiting two pronuclei (2 PN) with subsequent severe fragmentation and/or blocking. The aim of the study was to evaluate the incidence of chromosome 18 anomalies among these embryos in order to evaluate the FISH efficiency on such material and to obtain more precise and complete data than those obtained with classical cytogenetic analysis. For the 3 PN cleaved embryos, FISH confirmed the frequent regulation towards diploidy (25 per cent) and the high frequency of mosaics (53 per cent). For the 2 PN blocked or damaged embryos, FISH permitted chromosome evaluation, which was otherwise impossible with classical cytogenetic techniques: we also found a high mosaic frequency (45 per cent) with these embryos. If this frequency were the same for normally developing embryos, it would be a major obstacle to the reliability of either chromosomal or genetic preimplantation diagnosis.

Blastomeres↗
PubMed1995

Involvement of regions of the 4th and 7th chromosomes in the open-field activity of mice.

Reactivity to a new environment was studied in mice, using an open-field procedure in two strains, C57BL/6By and ABP/Le, the F1 populations and the intercrosses F2 and backcross segregating populations. The analysis of the behavioral traits: peripheral and central activities, leaning, rearing and defecation in the parental strains made it possible to show that the ABP/Le strain was more reactive than C57BL/6By. In addition, the study of segregating, for four phenotypic markers, in F2 and backcross populations strongly suggested that two autosomal regions were involved in the control of open-field behavior: one in chromosomal region comprising the b locus on chromosome 4 and one in chromosomal region comprising the p locus on chromosome 7.

Analysis of Variance↗
PubMed1995

The recA gene of Streptococcus pneumoniae is part of a competence-induced operon and controls lysogenic induction.

The recently identified recA gene of the naturally transformable bacterium Streptococcus pneumoniae has been further characterized by constructing a recA null mutation and by investigating its regulation. The recA mutation has been shown to confer both DNA repair (as judged from sensitivity to u.v. and methyl methane sulphonate) and recombination deficiencies. Plasmid transformation into the recA mutant was also drastically reduced. Western blotting established that recA gene expression is increased several fold at the onset of competence for genetic transformation. Increased expression was associated with the appearance of a recA-specific transcript, approximately 5.7 kb long. This transcript indicated that recA is part of a competence-inducible (cin) operon. The major (about 4.3 kb) transcript detected from non-competent cells did not include cinA, the first gene in the operon, suggesting that this gene could be specifically required at some stage in the transformation process. Detection of small amounts of the 5.7 kb polycistronic mRNA in cells treated with mitomycin C suggested that the operon could also be damage inducible. In addition, mitomycin C treatment of a recA- lysogenic strain did not lead to prophage induction and cell lysis. This is unlike the situation of a recA+ lysogen. Together these results demonstrate that RecA controls lysogenic induction and suggest the existence of a SOS repair system in S. pneumoniae.

Bacterial Proteins↗
PubMed1995

Failure to incriminate hepatitis B, hepatitis C, and hepatitis E viruses in the aetiology of fulminant non-A non-B hepatitis.

Sporadic non-A, non-B hepatitis is the most common indication for liver transplantation in patients presenting with fulminant and subacute liver failure. This study used serological, histological, and molecular biological techniques to examine specimens from 23 consecutive patients transplanted for sporadic non-A, non-B hepatitis. No evidence was found of hepatitis C virus, hepatitis E virus, or 'cryptic' hepatitis B virus infection.

Adolescent↗
PubMed1995

Effects of long-term moderate exercise on iron status in young women.

The impact of long-term (6-month) moderate exercise on the iron status of previously sedentary women was determined by randomly assigning 62 college-age women into one of the following four groups: 1) 50 mg.d-1 iron supplement, low iron diet (N = 16); 2) Placebo, free choice diet (N = 13); 3) Meat supplement to achieve 15 mg.d-1 iron intake (N = 13); and 4) Control, free choice diet (N = 20). All groups except the Control group exercised 3 d.wk-1 at 60%-75% of their heart rate reserve. VO2max was measured at baseline and week 24. Blood was sampled at baseline and every 4 wk thereafter for 24 wk to measure iron status and to elucidate the causes for alterations in iron status. Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels (< 15 ng.ml-1). Serum iron, total iron binding capacity and transferrin saturation were not compromised with exercise. Mean hemoglobin level in the Placebo/Ex group was significantly (P < 0.05) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24. However, changes in serum albumin, haptoglobin, and erythropoietin data from the study cannot explain these changes.

Adult↗
PubMed1995

Investigation and management of cervical intraepithelial neoplasia in Canadian Inuit: enhancing access to care.

Cervical intraepithelial neoplasia (CIN) is a major cause of morbidity among Circumpolar women. Cervical cancer comprised 15% of all cancers in Canadian Inuit women from 1969-1988. The age standardized incidence for invasive cervical cancer in Canadian Inuit women is 3.1 times the rate in the general Canadian population. Management of CIN in women of remote Arctic regions has traditionally required multiple visits to specialized medical centres for diagnosis, therapy and follow-up. Such centralized care requires separation of women from their families, resulting in significant medical, emotional and economic costs for the patient, her family and community. In the Canadian Central Arctic, a program for the diagnosis and therapy of CIN has been established using colposcopy with loop electrosurgery, performed by a trained local family practitioner and visiting gynecologist. Early program evaluation has indicated reduction in medical expenditures due to travel costs, minimal procedure-related morbidity and discomfort, and improved patient satisfaction associated with reduced separation from family and community. It is hoped that the program design, which harnesses technology in order to provide improved care closer to home, will be applicable to other Circumpolar regions.

Arctic Regions↗
PubMed1994

Two silencing sub-domains of v-erbA synergize with each other, but not with RXR.

The thyroid hormone receptor (TR) and the retinoic acid receptor (RAR) induce gene expression in the presence of specific ligand and repress transcription in the absence of hormone. This repression is mediated by an active silencing mechanism rather then by interference with DNA binding activators. V-erbA, a variant form of TR which is unable to bind hormone, represents a constitutive repressor. Here we show, using fusion proteins with the GAL4 DNA binding domain, that the minimal silencing domain of v-erbA extends from amino acids 389 to 632 and that internal deletions within this domain retain at least some repression function. Co-transfection experiments of different deletion mutants indicate that the silencing domain is composed of at least two sub-domains which are non-functional when tested individually. When combined in a heterodimeric complex, they synergize such that silencing activity is regained. In contrast to the retinoic acid receptor the retinoid X receptor does not contain a silencing domain. In addition it is unable to cooperate with the repression function of TR or v-erbA in a heterodimer.

Amino Acid Sequence↗