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B Martin

Publications and source records attributed to B Martin.

At least 271 records · Page 15Linked to original sources
PubMed1990

Substrate specificity of Acanthamoeba myosin I heavy chain kinase as determined with synthetic peptides.

Phosphorylation of a single threonine (myosin IA) or serine (myosins IB and IC) in the heavy chains of the Acanthamoeba myosin I isozymes is required for expression of their actin-activated Mg2(+)-ATPase activities. We now report that the synthetic peptide Gly-Arg-Gly-Arg-Ser-Ser-Val-Tyr-Ser, which corresponds to the phosphorylated region of Acanthamoeba myosin IC, is a good substrate for myosin I heavy chain kinase: Km = 54 microM, and Vmax = 15 mumols/min.mg. The same serine is phosphorylated as in the native substrate (residue 6 in the above sequence), and kinase activity with the synthetic peptide as substrate is also stimulated by phosphatidylserine-enhanced autophosphorylation of the kinase. These results indicate that all of the essential sequence determinants of kinase specificity are contained within this 9-residue peptide. With the peptide as substrate, we found that another acidic phospholipid, phosphatidylinositol, also enhances autophosphorylation of the kinase whereas the neutral phospholipids phosphatidylcholine and phosphatidylethanolamine do not. By comparing the Km and Vmax values for a series of synthetic peptide substrates, we established that 1 basic amino acid is essential on the NH2-terminal side of the phosphorylation site, and two are preferable, and that a tyrosine is essential 2 residues away on the COOH-terminal side. There is a slight preference for arginines over lysines. All of these local sequence specificity determinants are present in the three native substrates, Acanthamoeba myosins IA, IB, and IC, and in two Dictyostelium myosin I isozymes that are putative substrates for the kinase. Similar sequences do not occur in the myosins I from intestinal brush border, which is not a substrate for the Acanthamoeba kinase.

Acanthamoeba↗
PubMed1990

In vitro binding of retinoids to the nuclear retinoic acid receptor alpha.

We describe a rapid method for measuring in vitro binding properties of new synthetic retinoids to the recently identified nuclear receptor RAR alpha. Transfection of cos-7 cells with the expression vector RAR alpha O produces a 100-fold increase in intracellular RAR alpha concentration which allows us to perform accurate determination of binding parameters of various retinoids. Cytosol and nuclear extracts obtained after freeze drying of the transfected cells are incubated with a new stable tritiated analog of retinoic acid, [3H]CD367. Complete separation between RAR alpha and endogenous cellular retinoic acid binding protein is achieved by high-performance size-exclusion chromatography. These improved techniques provide a useful method for determining binding affinities of analogs to RAR alpha.

Animals↗
PubMed1990

Concentration decrease of corticosteroid binding globulin (CBG) in plasma of the mare throughout pregnancy.

A significant decrease of CBG binding capacity in plasma of the mare throughout pregnancy was demonstrated using equilibrium dialysis and gel equilibration methods. As indicated with immunoelectrophoresis experiments, the pregnancy related fall of CBG binding capacity was linked to an actual decrease in blood CBG concentration. This result contrasts sharply with data on most other mammalian species, with the exception of the gestating rhesus monkey.

Animals↗
PubMed1990

In vivo behavior of genetically engineered herpes simplex viruses R7017 and R7020. II. Studies in immunocompetent and immunosuppressed owl monkeys (Aotus trivirgatus).

The genetically engineered herpes simplex virus strains R7017 and R7020 were tested in owl monkeys (Aotus trivirgatus) previously shown to model herpetic diseases of immunocompromised patients and neonates. In contrast to the lethal disease seen in monkeys receiving 100-1,000 plaque-forming units (pfu) of wild-type virus, inoculation of greater than or equal to 10(6) pfu of recombinant viruses produced local lesions and viral shedding but not disseminated disease. Latent recombinant viruses were recovered from some ganglia innervating the sites of inoculation. Monkeys protected from lethal infection with wild-type virus exhibit recurrent lesions that increase in frequency and severity after total lymphoid gamma irradiation (TLI). In contrast, monkeys immunosuppressed by TLI and inoculated with R7020 could not be differentiated from irradiated controls with respect to morbidity or mortality. Moreover, the virus was not transmitted from immunosuppressed infected females to normal male cage mates.

Animals↗
PubMed1990

JO 1784, a potent and selective ligand for rat and mouse brain sigma-sites.

JO 1784 ((+)-cinnamyl-1-phenyl-1-N-methyl-N-cyclopropylene) is a potent ligand for (+)-[3H]SKF 10,047 (2'-hydroxy-5,9-dimethyl-2-allyl-6,7-benzomorphan) binding sites in rat brain membrane preparations with an IC50 of 39 +/- 8 nM, which is comparable to that of haloperidol. The stereoisomer of JO 1784 is ten fold less potent. When administered to mice i.p. or p.o. JO 1784 displaced (+)-[3H]SKF 10,047 (5 muCi i.v.) from its sites in the brain with ID50 values of 1.2 and 3.5 mg kg-1, respectively. The high selectivity of JO 1784 for the sigma-binding site was assessed by its lack of significant affinity for more than 20 other sites including those for phencyclidine.

Animals↗
PubMed1990

Epstein-Barr virus types 1 and 2 differ in their EBNA-3A, EBNA-3B, and EBNA-3C genes.

The two Epstein-Barr virus (EBV) types, EBV-1 and EBV-2, are known to differ in their EBNA-2 genes, which are 64 and 53% identical in their nucleotide and predicted amino acid sequences, respectively. Restriction endonuclease maps and serologic analyses detect few other differences between EBV-1 and EBV-2 except in the EBNA-3 gene family. We determined the DNA sequence of the AG876 EBV-2 EBNA-3 coding region and have compared it with known B95-8 EBV-1 EBNA-3 sequences to delineate the extent of divergence between EBV-1 and EBV-2 isolates in their EBNA-3 genes. The B95-8 and AG876 EBV isolates had nucleotide and amino acid identity levels of 90 and 84%, 88 and 80%, and 81 and 72% for the EBNA-3A, -3B, and -3C genes, respectively. In contrast, nucleotide sequence identity in the noncoding DNA adjacent to the B95-8 and AG876 EBNA-3 open reading frames was 96%. We used the polymerase chain reaction to demonstrate that five additional EBV-1 isolates and six additional EBV-2 isolates have the type-specific differences in their EBNA-3 genes predicted from the B95-8 or AG876 sequences. Thus, EBV-1 and EBV-2 are two distinct wild-type EBV strains that have significantly diverged at four genetic loci and have maintained type-characteristic differences at each locus. The delineation of these sequence differences between EBV-1 and EBV-2 is essential to ongoing molecular dissection of the biologic properties of EBV and of the human immune response to EBV infection. The application of these data to the delineation of epitopes recognized in the EBV-immune T-cell response is also discussed.

Amino Acid Sequence↗
PubMed1990

Farmer's lung in Northern Ireland.

A total of 381 farmers in Northern Ireland were studied using a questionnaire, pulmonary function tests, and antibody levels to Micropolyspora faena to assess the incidence of farmer's lung. Twenty (4.9%) had a history of a previous diagnosis of farmer's lung by their doctor. Forty four (10.4%) had delayed onset symptoms compatible with farmer's lung, 32 (7.9%) had precipitant antibody, and 61 (15%) had raised antibody by the enzyme linked immunosorbent (ELISA) method. Restricted lungs were present physiologically in 40 (9.8%). A confirmation of delayed symptoms and precipitant antibody was present in seven (1.7%) whereas delayed symptoms and ELISA antibody was present in nine (2.2%). Using either antibody method only two (0.5%) had a combination of antibody to M faenae, delayed onset symptoms, and restricted pulmonary physiology.

Antibodies, Bacterial↗
PubMed1990

Differentiation of F9 embryonal carcinoma cells by synthetic retinoids: amplitude of plasminogen activator production does not depend on retinoid potency or affinity for F9 nuclear retinoic acid receptors.

Retinoic acid and analogues (retinoids) are able to induce the differentiation of F9 murine embryonal carcinoma stem cells into endoderm-like cells. The secretion of plasminogen activator (PA) which accompanies this differentiation is a good index of the biological response of F9 cells to retinoids. We have previously reported that the potency of a series of natural and synthetic retinoids, evaluated by the concentration which provokes half-maximal induction of PA, correlates well with the affinity of these compounds for the endogenous F9 nuclear retinoic acid receptors, but not for the cytosolic retinoic acid binding protein, CRABP. In this paper we show that various retinoids differ, not only in terms of potency, i.e. the dilution at which they are active, but also in terms of the amount of PA that they induce. This parameter, called amplitude, is used to quantify the extent of PA induction by a given retinoid relative to retinoic acid. The amplitude parameters of synthetic retinoids are found to vary over a wide range and are independent of both potency and binding affinity for F9 retinoic acid receptors. It is proposed that the amplitude of the biological response to a given retinoid is the resultant of three factors: (i) the total or partial agonist character of the retinoid; (ii) the binding spectrum of the retinoid for the various types of retinoic acid receptors; (iii) the chemical and metabolic stability of the retinoid in the test system.

Animals↗
PubMed1990

Activity of centrally administered galanin fragments on stimulation of feeding behavior and on galanin receptor binding in the rat hypothalamus.

Synthetic fragments of galanin 1-29 were administered intraventricularly or into the paraventricular nucleus of the hypothalamus for analysis of the critical amino acid sequence necessary to stimulate feeding behavior in rats. Galanin 1-29 and galanin fragment 1-16 significantly increased feeding at doses of 6 nmol microinjected into the lateral ventricles and 1 nmol microinjected into the hypothalamus. There was no significant effect of D-TRP2 galanin 1-16 microinjected into the hypothalamus, and no significant effect of galanin fragments 1-9, 10-20, 12-29, 17-29, or 21-29 microinjected intraventricularly, on food consumption. Synthetic fragments of galanin 1-29 were assayed for displacement of 125I-galanin 1-29 binding to rat hypothalamic membranes. The efficacies of the galanin fragments in the feeding paradigm were consistent with the relative affinities of these fragments for the hypothalamic galanin receptor in equilibrium binding experiments. The first 16 N-terminal amino acids appear to contain galanin agonist activity on increasing food consumption and to bind to the galanin receptor in the rat hypothalamus.

Animals↗
PubMed1990

[Long-term results of the Swanson implant for the treatment of basal joint arthrosis].

The authors present a review of Swanson's trapezium implants used in the surgical treatment of arthrosis of the basal joint of the thumb. 32 patients operated between 1970 and 1979 were invited to consultation, and 22 were examined again after an average period of 9.8 years. The clinical findings seemed to be good, with satisfactory subjective results in 95 per cent of all cases. On the contrary, radiographs showed 50 per cent of luxations and subluxations, and implant wear in 70 per cent of cases, increasing with time. In 39 per cent of cases, intracarpal cavities secondary to an adverse reaction to the silicon implant were noted. However, no second operation was needed. In spite of the good clinical results, the authors reserve Swanson's implants, considering the radiological findings, to subjects older than 65 years, because of the risks of long-term intolerance. Trapezectomy seems to be preferable in younger patients.

Female↗
PubMed1990

[Unreduced posterior luxations and fractures-luxations of the shoulder. Apropos of 30 cases].

Twenty-seven patients (30 shoulders) presenting with an unreduced posterior dislocation or fracture-dislocation were operated on and followed up for at least 2 years. The lesions were classified in 4 types, after Randelli: posterior dislocation with cephalic fracture inferior to 50 per cent (type I = 10 cases) or superior to 50 per cent (type II = 8 cases) and posterior fracture-dislocations with two fragments (type III = 6 cases) or several fragments (type IV = 6 cases). The first patients of the series underwent a resection of the humeral head (5 cases) or an open reduction (7 cases). During a second period 10 shoulders were reduced by a posterior approach and stabilized by transfer of the subscapularis tendon with or without the lesser tuberosity in the humeral defect 6 shoulders were reduced by an anterior approach together with derotation osteotomy. Lastly, one patient refused to be operated on and we performed a shoulder prosthesis to the last one. Necrosis of the humeral head (9 cases) appeared to be related to the severity of the lesion (type III and IV) and the type of surgical procedure (5 derotation osteotomy out of 6 and 3 open reductions out of 7) rather than to the approach route or the interval from injury to diagnosis. These results show that an anatomical repair may be attempted when the dislocation is less than 6 months old and when the impression defect involved less than 50 per cent of the articular surface. Otherwise and a fortiori in old posterior fracture-dislocations, an arthroplasty seems to be the best solution. Even if it may be clinically difficult, it offers the best chance for a functional shoulder in an active patient.

Adult↗
PubMed1989

The localization and sequence of the phosphorylation sites of Acanthamoeba myosins I. An improved method for locating the phosphorylated amino acid.

The actin-activated Mg2+-ATPase activities of Acanthamoeba myosins IA, IB, and IC are expressed only when a single site in their heavy chains is phosphorylated by a myosin I heavy chain-specific kinase. We show that phosphorylation occurs at Ser-315 in the myosin IB heavy chain, Ser-311 in myosin IC, and a threonine residue at a corresponding position in myosin IA whose amino acid sequence is as yet unknown. The most obvious feature common to the three substrates is a basic amino acid(s) 2 or 3 residues before the site of phosphorylation. The phosphorylation site is located between the ATP- and actin-binding sites, which corresponds to the middle of the 50-kDa domain of skeletal muscle myosin subfragment 1. The sequence similarity between the region surrounding the phosphorylation site of myosin I and subfragment 1 is much lower than the average sequence similarity between myosin I and subfragment 1. This is consistent with the hypothesis that the conformation of this region of myosin I differs from that of the corresponding region in skeletal muscle myosin and that phosphorylation converts the conformation of the actomyosin I complex into a conformation comparable to that present in actosubfragment 1 without phosphorylation. The protein sequences obtained in the course of this work led to the conclusion that the myosin I genes previously identified as myosin IB and IL (myosin-like) heavy chains actually are the myosin IC and IB heavy chains, respectively. Finally, we report a modification of the method for monitoring the appearance of 32Pi during sequencing of 32P-labeled peptides that results in almost complete recovery of the radioactivity, thus allowing unequivocal assignment of the position of the phosphorylated residue.

Acanthamoeba↗
PubMed1989

Molecular cloning of cDNA coding for kidney aldose reductase. Regulation of specific mRNA accumulation by NaCl-mediated osmotic stress.

Cells generally respond to long-term hyperosmotic stress by accumulating nonperturbing organic osmolytes. Unlike bacteria, in which molecular mechanisms involved in the increased accumulation of osmolytes have been identified, those in multicellular organisms are virtually unknown. In mammals, during antidiuresis, cells of the renal inner medulla are exposed to high and variable extracellular NaCl. Under these conditions, the cells contain a high level of sorbitol and other osmolytes which help balance the high extracellular osmolality. PAP-HT25 is a continuous line of cells derived from rabbit renal inner medulla. When medium osmolality is increased by raising the NaCl concentration, these cells accumulate sorbitol. The sorbitol is synthesized from glucose in a reaction catalyzed by aldose reductase. When the medium is made hyperosmotic, aldose reductase activity increases because of a larger increase in the amount of enzyme. This increase is produced by the accelerated rate of synthesis of aldose reductase protein. The purpose of the present studies was to examine the mechanism of this increase in aldose reductase protein by measuring the relative abundance of aldose reductase mRNA. A cDNA clone coding for rabbit kidney aldose reductase was isolated. Antisense RNA probes transcribed from this clone hybridized specifically with a 1.5-1.6 kilobase mRNA in Northern blots. Cells grown chronically in hyperosmotic medium had a relative abundance of this specific mRNA which was six times that of cells grown in isoosmotic medium. When cells grown in isoosmotic medium were switched to hyperosmotic medium, the level of aldose reductase mRNA peaked (18-fold) at 18-24 h. The induction of aldose reductase mRNA by osmotic stress was reversible. Our finding of increased abundance of a specific mRNA in direct response to hyperosmotic stress represents the first report of such an effect in animals.

Aldehyde Reductase↗