PubMed Health⌕ Search

Biomedical subjects

B Baker

Publications and source records attributed to B Baker.

At least 19 recordsLinked to original sources
PubMed1992

Structure-function relationship of myotoxin a using peptide fragments.

Myotoxin a, a small basic polypeptide isolated from the venom of prairie rattlesnake (Crotalus viridis viridis), has been shown to bind to sarcoplasmic reticulum (SR) Ca(2+)-ATPase. The attachment of myotoxin a to Ca(2+)-ATPase is believed to cause uncoupling of the calcium pump. In order to further elucidate which portion of myotoxin a is important for the uncoupling action, five peptides were synthesized and two peptide fragments were obtained by chemical cleavage. These peptides correspond to discrete portions of the primary sequence of myotoxin a. The peptides are equivalent to the primary sequence of myotoxin a from 1 to 16 residues, 7 to 22 residues, 13 to 28 residues, 19 to 34 residues, and 25 to 42 residues. Chemically produced fragments are equivalent to 1 to 28 residues and 29 to 42 residues of myotoxin a. Peptides of the sequences "YKQCHKKGGHCFPKEK" and "LGKMDCRWKWKCCKKGSG" of myotoxin a inhibited 45Ca uptake into isolated SR and bound to Ca(2+)-ATPase. The same peptides caused weak skeletal muscle vacuolization similar to that caused by native myotoxin a and increased serum creatine kinase activity. The active peptides correspond to the N-terminal and C-terminal portions of myotoxin a. The inactive or less active peptides have sequences which correspond to the middle sequence of myotoxin a. From this study, both the N-terminal and the C-terminal regions of primary sequence of myotoxin a are required to express myotoxin a's biological activity.

Amino Acid Sequence↗
PubMed1992

Medical management of inflammatory bowel disease in a spider monkey.

Inflammatory bowel disease was diagnosed in a 3-year-old, captive-born, hand-raised, female spider monkey (Ateles geoffroyi). The diagnosis was based on clinical signs, positive-contrast radiographic series, endoscopy, histologic appearance of intestinal biopsy specimens, and the monkey's response to treatment. Treatment consisted of oral administration of prednisone, sulfasalazine, and trimethoprim-sulfamethoxazole. Supportive care included a bland diet and an electrolyte solution given free choice. Although several infective agents were considered, this case illustrates that recurrent enteritis in primates may be noninfectious and may respond to anti-inflammatory agents.

Animals↗
PubMed1992

Expression of interferon-gamma receptors in normal and psoriatic skin.

Psoriatic keratinocytes have a reduced antiproliferative response to interferon (IFN)-gamma, and HLA-DR expression is usually not observed on keratinocytes in psoriatic plaques despite the presence of activated T cells. We have therefore compared the expression of IFN-gamma receptors in psoriatic skin with that of normal human skin. Using mouse monoclonal antibodies and immunoperoxidase staining on cryostat cut sections, we detected IFN-gamma receptors on keratinocytes throughout the epidermal layers except stratum corneum in normal skin (n = 11). Biopsy specimens from involved psoriatic skin (n = 17) consistently showed a staining pattern that differed from that of normal skin in that only the lower part of epidermis reacted with the antibodies to IFN-gamma receptors, whereas the upper layers showed no or minimal staining. Expression of IFN-gamma receptors in uninvolved psoriatic skin (n = 16) did not differ from that of healthy controls. Forty-five percent of the biopsies from lesional psoriatic skin displayed ICAM-1 positive keratinocytes, and only two specimens had a limited expression of HLA-DR reactive keratinocytes. The decreased binding of antibodies against the IFN-gamma receptors in the upper part of psoriatic epidermis might be secondary to abnormal maturation of psoriatic keratinocytes or a primary defect involving abnormal modulation of IFN-gamma receptors.

Adult↗
PubMed1991

Binding of myotoxin a to sarcoplasmic reticulum Ca(2+)-ATPase: a structural study.

The interaction of myotoxin alpha with intact sarcoplasmic reticulum (SR) components was investigated, and two SR proteins were identified that associated with myotoxin a. One of the proteins has an apparent molecular weight similar to the Ca(2+)-ATPase, the major SR protein responsible for calcium loading. Ca(2+)-ATPase was purified, and its interaction with myotoxin a was studied. Evidence for specific binding of myotoxin a to Ca(2+)-ATPase was established by isolating chemically cross-linked myotoxin a-Ca(2+)-ATPase complexes and further proving their association with anti-myotoxin a antibodies. The binding region of myotoxin a was further delineated by cleaving the protein with cyanogen bromide (CNBr) into two fragments, a larger N-terminal fragment of 28 residues and a smaller C-terminal fragment of 14 residues. Competition experiments with 125I-myotoxin a showed that the C-terminal fragment competed better against 125I-myotoxin a than the N-terminal fragment for SR protein binding. Two overlapping peptides covering the sequence of the N-terminal fragment were synthesized to clarify the interaction of the N-terminal fragment of myotoxin a with SR proteins. A 16-residue peptide corresponding to residues 1-16 competed strongly with 125I-myotoxin a, while a second peptide (residues 13-28) did not.

Amino Acid Sequence↗
PubMed1991

Long-term remission of chronic hepatitis B after alpha-interferon therapy.

OBJECTIVE: To evaluate whether remissions of chronic hepatitis B induced by alpha-interferon therapy are of long duration. DESIGN: Cohort study. SETTING: Clinical Center of the National Institutes of Health, a tertiary referral center. PATIENTS: Sixty-four patients with chronic hepatitis B were treated with alpha-interferon between 1984 and 1986. MAIN OUTCOME MEASURES: Patients were followed with frequent examinations and determinations of serum liver biochemical tests and hepatitis B virus (HBV) markers including hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and HBV DNA using blot hybridization and polymerase chain reaction. RESULTS: Among 64 patients with chronic hepatitis B who were treated with alpha-interferon, 23 (36%) responded to treatment with loss of HBeAg and improvement in serum aminotransferases. All 23 have been followed for 3 to 7 years (mean, 4.3 years). During follow-up, 3 of 23 patients relapsed, with reappearance of HBeAg and abnormal serum aminotransferases, all within 1 year of therapy. The remaining 20 patients continued to have no detectable HBeAg or HBV DNA (using blot hybridization) in serum and to be asymptomatic for liver disease, although 3 had minimal elevations in serum aminotransferases. Thirteen patients (65%) became negative for HBsAg between 0.2 and 6 years (mean, 3 years) after loss of HBeAg. Although no patient had HBV DNA that was detectable by blot hybridization, the 7 patients who remained HBsAg positive all had HBV DNA in serum detected by polymerase chain reaction, but only 2 of 13 HBsAg-negative patients had viral genome using this method. Testing sequential samples indicated that HBV DNA detected by polymerase chain reaction usually disappeared at or around the time that test results for HBsAg became negative. CONCLUSIONS: Remissions in chronic hepatitis B induced by alpha-interferon are of long duration and are followed, in most patients, by the loss of HBsAg and all evidence of residual virus replication.

Adult↗
PubMed1991

A computer-aided control, design and image-processing system for electron microscopes.

A computer-control system for electron microscopes is described. The aim is to reduce a complex series of vacuum-system controls to a menu-driven program that simplifies the operation of the microscope. The system also incorporates image processing, notebook, computer-aided design, and communication functions. It is designed around a commercially available computer workstation. This system has been implemented on an institute-built photoelectron microscope of ultrahigh-vacuum design.

Computer Graphics↗
PubMed1991

Ac transposition from a T-DNA can generate linked and unlinked clusters of insertions in the tomato genome.

We have investigated the distribution of transposed Acs in the tomato genome. Our approach has been to clone the regions flanking the T-DNAs and transposed Acs from two transgenic lines of tomato and place these sequences on the tomato restriction fragment length polymorphism (RFLP) map. The distribution of transposed Acs around the T-DNA and at locations unlinked to the T-DNA indicates that Ac transposes to linked and unlinked sites in tomato as it does in maize. The structure and terminal sequence of these cloned elements shows that Ac remains intact after transposition. We discuss these results and their bearing on gene tagging strategies using Ac and Ds.

Base Sequence↗
PubMed1991

Psychiatric treatment strategies for patients at risk of dying suddenly.

This paper outlines the development of psychiatric treatment approaches to certain patients with life-threatening ventricular arrhythmias which may affect outcome, both psychological and, at times, medical. Three cases sketches which illustrate psychiatric management strategies are presented. One case history indicates how lack of adherence to such treatment contributed to a negative outcome. Emphasis is placed on an integrated approach to psychiatric treatment which is individualized for each patient. The importance of close liaison with cardiologist, selective psychotherapy, stress management skills and family involvement is highlighted.

Adaptation, Psychological↗
PubMed1991

Detection of hepatitis C viral RNA in serum of a patient with acute non A, non B hepatitis.

The sequence of serologic events in a patient with acute type C hepatitis associated with intravenous drug abuse is described. Hepatitis C virus (HCV) ribonucleic acid was detectable in serum during the acute episode of hepatitis, whereas antibody to the hepatitis C virus appeared later, after the acute illness had subsided. The patient developed chronic hepatitis with persistently elevated serum aminotransferase activities. Both hepatitis C viral ribonucleic acid and antibody to hepatitis C virus persisted in serum, together with elevated serum aminotransferases. Thus, detection of HCV RNA may be useful in the diagnosis of acute type C hepatitis, particularly in the absence of detectable antibody to the hepatitis C virus.

Acute Disease↗
PubMed1990

Pertussis toxin produces differential inhibitory effects on basal, P2-purinergic, and chemotactic peptide-stimulated inositol phospholipid breakdown in HL-60 cells and HL-60 cell membranes.

P2-purinergic receptor agonists (UTP) and formylated peptide receptor agonists (FMLP) were found to be equally efficacious in eliciting rapid 6-7-fold increases in inositol polyphosphate accumulation in differentiated HL-60 granulocytes. The activation of this response by either agonist was substantially but incompletely inhibited in cells treated with pertussis toxin. Thus, in cells containing only 1-10% of the control level of non-ADP-ribosylated Gi-2/3, UTP induced rapid 2-fold increases in inositol polyphosphate accumulation whereas smaller 50% increases were observed in FMLP-stimulated cells. Washed membranes prepared from control and toxin-treated HL-60 cells were used to characterize this toxin-insensitive activation of phospholipase C further. The agonist-independent stimulation of phospholipase C by either millimolar Ca2+ or the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) was only modestly attenuated by toxin treatment. There was a 70-80% decrease in the rate and extent of phospholipase C activity stimulated by GTP per se in the absence of receptor agonists. The rate and extent of FMLP-induced potentiation of GTP-dependent phospholipase C activity were also inhibited by greater than 80% in toxin-treated membranes. Conversely, the potency and efficacy characterizing UTP-induced potentiation of GTP-dependent phospholipase C activity were only modestly attenuated (less than 20% inhibition). The results indicate that P2-purinergic receptors (and perhaps other Ca2(+)-mobilizing receptors) activate both pertussis toxin-sensitive and toxin-insensitive pathways for phospholipase C regulation in phagocytic leukocytes.

Cell Differentiation↗
PubMed1990

Amplification of genomic sequences flanking transposable elements in host and heterologous plants: a tool for transposon tagging and genome characterization.

The isolation of sequences flanking integrated transposable elements is an important step in gene tagging strategies. We have demonstrated that sequences flanking transposons integrated into complex genomes can be simply and rapidly obtained using the polymerase chain reaction. Amplification of such sequences was established in a model system, a transgenic tobacco plant carrying a single Ac element, and successfully applied to the cloning of a specific Spm element from a maize line carrying multiple Spm hybridizing sequences. The described utilization of methylation sensitive restriction enzymes (including those with degenerate recognition sequences) in the generation of templates for amplification will simplify the cloning and mapping of genomic sequences adjacent to transposable elements.

Base Sequence↗
PubMed1990

Comparisons of two expressed emotion scales with the Camberwell Family Interview.

The relationship of the Camberwell Family Interview (CFI) with two self-report scales purported to measure levels of expressed emotion was assessed. Fifteen schizophrenic patients and 22 of their relatives completed the Level of Expressed Emotion Scale (LEE) and the Influential Relationships Questionnaire (IRQ). The relatives of patients also participated in Camberwell Family Interviews (CFI). Results supported the value of the self-report measures in evaluating the affective environment of patients with schizophrenia.

Adult↗
PubMed1990

Therapy of chronic delta hepatitis with interferon alfa-2b.

In this pilot study, 12 patients with chronic delta hepatitis were studied. The diagnosis was based on the presence of antibodies to the hepatitis delta antigen in the serum and hepatitis delta virus RNA and hepatitis delta antigen in the serum and liver. All patients were also positive for hepatitis B surface antigen. The infection was presumed to have been transmitted by intravenous drug abuse in six of the patients, blood transfusion in one and by sexual contact in four (two had antibodies to human immunodeficiency virus in their serum, but did not show signs of acquired immunodeficiency syndrome). In one further patient, the source of infection was unknown. Interferon alfa-2b (INTRON A, Schering-Plough Corporation) was initiated at 5 million units per day subcutaneously for at least 4 months, being reduced by half if side effects occurred. Serum alanine aminotransferase levels, hepatitis delta virus RNA and hepatitis delta antigen were measured at monthly intervals for up to 12 months in some patients. Interferon therapy resulted in decreased serum levels of these three markers. On cessation of therapy, most patients experienced a relapse over 6 months, but alanine amino transferase levels could be normalized once more by restarting interferon therapy. In conclusion, interferon decreased hepatic inflammation by the inhibition of hepatitis delta virus replication, although relapse occurred when interferon was stopped and long-term therapy is required to achieve permanent control of the disease. Care will be required when treating patients with advanced or decompensated liver disease.

Adult↗
PubMed1990

Wheat dwarf virus Ac/Ds vectors: expression and excision of transposable elements introduced into various cereals by a viral replicon.

The maize transposon Activator (Ac) and in vitro-generated nonautonomous derivatives thereof [Ac delta or Dissociation (Ds) elements] were inserted into the genome of a geminivirus of graminaceous plants, wheat dwarf virus, at a site that does not interfere with viral replication. These recombinant viral genomes were introduced into wheat, maize, and rice protoplasts, where rapid and efficient excision of Ac was observed. Excision was detected only in vectors in which, after transfection, the virus could replicate. This result is not restricted to the autonomous Ac; excision of Ds elements was also induced by transposase activity provided in trans by plasmids expressing the cDNA of Ac. The potential of this combination of a transposon with a viral replicon for plant molecular genetic engineering is discussed.

Base Sequence↗
PubMed1990

Properties of the maize transposable element Activator in transgenic tobacco plants: a versatile inter-species genetic tool.

The maize controlling element Activator (Ac) transposes autonomously from an integrated T-DNA vector to new sites in the genomes of tobacco and other heterologous plant species. Here we demonstrate that critical functions required for transposition of Ac in maize are conserved in tobacco and that Ac transposes at high frequency for at least five generations. Ac structure and terminal sequences are conserved upon transposition and a characteristic 8-bp duplication of target sequences is generated upon integration. Ac remains unmethylated, transcriptionally active, and capable to trans-activate transposition of the nonautonomous Dissociation (Ds) element throughout several generations. In tobacco, as in maize, Ac transposes adjacent to low copy or unique DNA, and transcriptional analysis of unique target DNA provides evidence that an Ac element transposed into a gene. In maize, increasing copies of Ac delay the timing and reduce the frequency of early transposition of Ac and Ds. In tobacco, increasing copies of Ac correlate with an increased frequency of Ds trans-activation. These data firmly establish that the Ac and Ds transposable elements are versatile genetic tools well suited for use as insertional mutagens and demonstrate that thorough investigation of mechanism and regulation of transposition is facilitated in heterologous settings.

Base Sequence↗
PubMed1990

Renal function after long-term low-dose cyclosporin for psoriasis.

Two groups of patients receiving cyclosporin A (CyA) for psoriasis had their renal function assessed by measurement of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). The first group comprised 13 patients who had taken low dose (average 3 mg/kg per day) CyA for an average period of 2.5 years. Seven of the 13 had a normal GFR of 108 (77-121) ml/min (median; range). In the other six patients the GFR was low at 63 (50-77) ml/min and CyA was discontinued for periods ranging from 3 to 17 weeks. The GFR rose in all six patients, to 79 (60-91) ml/min; this change was significant (P less than 0.05). The six patients restarted CyA because their psoriasis recurred and after a mean interval of 15 weeks the GFR had fallen in all six to 63 (46-80) ml/min (P less than 0.05) and the ERPF decreased from 339 (231-414) ml/min to 244 (177-321) ml/min (P less than 0.05). In the second group of 11 patients measurements were made prior to starting CyA and after taking CyA for a mean of 9 weeks. The GFR fell in eight out of 11 subjects, the GFR for the 11 patients being 117 (72-128) ml/min before taking CyA and 97 (51-122) ml/min after CyA (P less than 0.02). The ERPF was measured in nine of the 11 patients and fell in seven of the nine. The ERPF for the nine patients before CyA was 490 (296-642) ml/min and for the 11 patients after CyA was 410 (195-543) ml/min (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Molecular cloning of murine intercellular adhesion molecule (ICAM-1).

We have previously reported a murine lymphocyte surface antigen MALA-2 of approximately 95,000 Mr which is expressed mainly on activated lymphocytes. The rat monoclonal antibody YN1/1 that detects this antigen profoundly inhibits mixed lymphocyte response. We have now purified MALA-2 and determined its partial amino acid sequence. By using non-redundant synthetic oligonucleotides as probes, based on the amino acid sequence, we have isolated two full length cDNA clones encoding MALA-2. The two clones are identical except for the 5' end sequence. Expression of MALA-2 on transfected COS cells is only achieved with one of the two cDNA clones. The nucleotide sequence as well as the deduced amino acid sequence of MALA-2 display striking homology with those of the recently reported human intercellular adhesion molecule ICAM-1. All the unique features of the human ICAM-1, including its homology with the neural adhesion molecule NCAM, its internal repeat structure and the immunoglobulin-like structure, are found in MALA-2. Furthermore, purified MALA-2 crosslinked to a solid support binds Con A blasts that express LFA-1, the putative receptor for ICAM-1, and the binding can be blocked by YN1/1 antibody or antimurine LFA-1 antibody indicating a direct interaction of these molecules in cell adhesion. Therefore, we consider MALA-2 to be the murine homolog of human ICAM-1. Since ICAM-1 is known to be of primary importance in immune responses and inflammatory reactions, having a monoclonal antibody and a mouse model will provide the opportunity to study the functional role of ICAM-1 in vivo.

Amino Acid Sequence↗