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Biomedical subjects

B J Johnson

Publications and source records attributed to B J Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1992

An association between complete and incomplete stress fractures of the humerus in racehorses.

Twenty-one horses had a complete unilateral humeral fracture during race training or racing at a California racetrack during the period 24 February 1990 to 10 July 1991. Fractures occurred approximately equally in left and right limbs, and in males and females. Most fractures occurred during training, and in 2- and 3-year-old horses. Only 5 of 16 Thoroughbred horses with known racing records had previously raced more than once, and their mean time between races was less than the time between their last race and fracture (P = 0.07). Ten of 13 humeri studied further had gross evidence of periosteal callus bridging one portion of the fracture line, indicative of a pre-existing stress fracture.

Animals↗
PubMed1992

Detection of Borrelia burgdorferi in ticks by species-specific amplification of the flagellin gene.

We developed a polymerase chain reaction (PCR) that specifically amplifies a fragment of the flagellin gene (fla) of Borrelia burgdorferi, the causative agent of Lyme disease. This fla target, amplified with nested primers, was conserved among all 80 strains of B. burgdorferi tested. Strains examined included cultures from ticks, humans, and rodents from major B. burgdorferi-endemic regions of the United States and parts of Europe and Asia. Templates from B. hermsii, B. parkeri, B. turicatae, and B. coriaceae were not amplified, nor were eukaryotic DNAs from three tick genera. Several host DNAs potentially present in a tick blood meal also were not amplified. Approximately six B. burgdorferi per PCR reaction could be detected by ethidium bromide staining of amplified DNA. Colony-raised Ixodes dammini were used to evaluate the method. One infected nymph in a pool of 40 ticks was routinely detected. The specificity of the assay for detecting B. burgdorferi-infected ticks in pools was 94% (29 of 31). This protocol should prove useful for assessing infection rates in other putative arthropod vectors.

Animals↗
PubMed1991

Attenuating mutations in the E2 glycoprotein gene of Venezuelan equine encephalitis virus: construction of single and multiple mutants in a full-length cDNA clone.

Attenuated mutants of Venezuelan equine encephalitis virus (VEE) were isolated by selection for rapid penetration of cultured cells (R. E. Johnston and J. F. Smith, 1988, Virology 162, 437-443). Sequence analysis of these mutants identified candidate attenuating mutations at four loci in the VEE E2 glycoprotein gene: a double mutation at E2 codons 3 and 4, and single substitutions at E2 76, 120, and 209. Each candidate mutation was reproduced in an isogenic recombinant VEE strain using site-directed mutagenesis of a full-length cDNA clone of VEE. Characterization of these molecularly cloned mutant viruses showed that mutation at each of the four loci in the E2 gene was sufficient to confer both the accelerated penetration and attenuation phenotypes. Inoculation of the molecularly cloned viruses into rodent models that differ in their response to VEE suggested that individual mutations affected different aspects of VEE pathogenesis. Full-length clones containing multiple mutations were produced by combining independently attenuating mutations. Molecularly cloned viruses carrying two or three mutations were more attenuated in sensitive animal models than viruses which contained any single mutation alone. However, these highly attenuated strains still retained the ability to induce an immune response sufficient to protect against a high dose challenge with virulent VEE. These results indicate that production of a molecularly cloned live virus vaccine for VEE is feasible.

Animals↗
PubMed1990

D1 and D2 receptor contributions to ingestive and locomotor behavior are altered after dopamine depletions in neonatal rats.

The effects of selective D1 and D2 antagonists on ingestive and locomotor behavior were studied in adult rats depleted of dopamine (DA) as neonates and their vehicle-treated controls. Blockade of either D1 or D2 receptors inhibited food intake and produced akinesia in control animals. Simultaneous administration of subthreshold doses of these antagonists produced similar behavioral deficits, indicating a synergism between the two receptor subtypes. In contrast, adults depleted of DA as neonates were unaffected by either D1 or D2 blockade. However, combined administration of these antagonists produced behavioral deficits comparable to those seen in controls. These data demonstrate that while activity within residual DA neurons remains critical for the expression of ingestive and locomotor behavior in rats depleted of DA as neonates, the precise nature of the interactions between the D1 and D2 receptor subtypes is altered after the depletion.

Animals↗
PubMed1990

Variants of Venezuelan equine encephalitis virus that resist neutralization define a domain of the E2 glycoprotein.

Stable neutralization (N) escape variants of Venezuelan equine encephalitis (VEE) virus were selected by anti-E2 glycoprotein monoclonal antibodies (MAbs) that neutralize viral infectivity, block viral hemagglutination, and passively protect mice. The nucleotide sequence of the E1, E2, and E3 genes of four variants revealed a clustering of single mutations in a domain spanning E2-182 to E2-207. The conformation of this short linear sequence affects antigenicity in the N domain because reduction and alkylation of virus disrupted binding of some E2 neutralizing MAbs. Serologic evidence for interaction of E2 epitopes also was obtained. Mutations in the N domain of VEE virus did not alter the kinetics of binding to Vero cells. They did, in some cases, produce attenuation of virulence in mice.

Amino Acid Sequence↗
PubMed1990

A case of Datisca glomerata poisoning in beef cattle.

Six of 175 Angus heifers died after ingesting excessive amounts of Durango root (Datisca glomerata). Animals had rumens full of Durango root, were extremely lethargic, and had diarrhea prior to death. The animals had nonspecific postmortem lesions. This case is discussed in light of previous findings from trials in which Durango root was experimentally fed to cattle.

Animals↗
PubMed1989

The full-length nucleotide sequences of the virulent Trinidad donkey strain of Venezuelan equine encephalitis virus and its attenuated vaccine derivative, strain TC-83.

Nucleotide sequence analysis of cDNA clones covering the entire genomes of Trinidad donkey (TRD) Venezuelan equine encephalitis (VEE) virus and its vaccine derivative, TC-83, has revealed 11 differences between the genomes of TC-83 virus and its parent. One nucleotide substitution and a single nucleotide deletion occurred in the 5'- and 3'-noncoding regions of the TC-83 genome, respectively. The deduced amino acid sequences of the nonstructural polypeptides of the two viruses differed only in a conservative Ser(TRD) to Thr(TC-83) substitution in nonstructural protein (nsP) three at amino acid position 260. The two silent mutations (one each in E1 and E2), one amino acid substitution in the E1 glycoprotein, and five substitutions in the E2 envelope glycoprotein of TC-83 virus were reported previously (B.J.B. Johnson, R.M. Kinney, C.L. Kost, and D.W. Trent, 1986, J. Gen. Virol. 67, 1951-1960). The genome of TRD virus was 11,444 nucleotides long with a 5'-noncoding region of 44 nucleotides. The carboxyl terminal portion of VEE nsP3 contained two peptide segments (7 and 34 amino acids long) that were repeated with high fidelity. The open reading frame of the nonstructural polyprotein was interrupted by an in-frame opal termination codon between nsP3 and nsP4, as has been reported for Sindbis, Ross River, and Middelburg viruses. The deduced amino acid sequences of the VEE TRD nsP1, nsP2, nsP3, and nsP4 polypeptides showed 60-66%, 57-58%, 35-44%, and 73-71% identity with the aligned sequences of the cognate polypeptides of Sindbis and Semliki Forest viruses, respectively. The lack of homology in the nsP3 of the viruses is due to sequence variation in the carboxyl terminal half of this polypeptide.

Amino Acid Sequence↗
PubMed1989

Potential for insect transmission of HIV: experimental exposure of Cimex hemipterus and Toxorhynchites amboinensis to human immunodeficiency virus.

Human immunodeficiency virus (HIV) was detected in bedbugs (Cimex hemipterus) up to 8 d after oral exposure to highly concentrated virus in blood meals, but no virus replication was observed. HIV did not replicate in either intraabdominally inoculated bedbugs or intrathoracically inoculated mosquitoes (Toxorhynchites amboinensis). The virus was not detected in bedbug feces. Mechanical transmission of HIV by bedbugs could not be demonstrated in an in vitro model. The persistence of HIV in an insect or on its mouthparts is one of many factors necessary for mechanical transmission in nature. The risk of insect transmission of HIV appears to be extremely low or nonexistent.

Animals↗
PubMed1988

Site-specific oligonucleotide-directed mutagenesis using T4 DNA polymerase.

A simple and efficient mutagenesis procedure is described which uses both the 3'----5' exonuclease and 5'----3' polymerase activities of T4 DNA polymerase. Different types of mutation-deletion, insertion, and substitution-can be introduced into the DNA in a single reaction. The technique uses recombinant M13 single-stranded DNA and two complementary DNA oligonucleotides to target and control the extent of deletions catalyzed by T4 DNA polymerase. The second oligonucleotide not only directs ligation, but also serves as a template for insertion or substitution of nucleotides by T4 polymerase. Mutant phages in a genetically pure form can be obtained at high efficiency, allowing their characterization directly by nucleotide sequencing without prior enrichment, plaque purification, and screening. We tested the versatility of this method by manipulating five regions of cDNA encoding the structural proteins of eastern equine encephalitis virus.

Base Sequence↗
PubMed1988

Recombinant vaccinia/Venezuelan equine encephalitis (VEE) virus expresses VEE structural proteins.

cDNA molecules encoding the structural proteins of the virulent Trinidad donkey and the TC-83 vaccine strains of Venezuelan equine encephalitis (VEE) virus were inserted under control of the vaccinia virus 7.5K promoter into the thymidine kinase gene of vaccinia virus. Synthesis of the capsid protein and glycoproteins E2 and E1 of VEE virus was demonstrated by immunoblotting of lysates of CV-1 cells infected with recombinant vaccinia/VEE viruses. VEE glycoproteins were detected in recombinant virus-infected cells by fluorescent antibody (FA) analysis performed with a panel of VEE-specific monoclonal antibodies. Seven E2-specific epitopes and two of four E1-specific epitopes were demonstrated by FA.

Antibodies, Monoclonal↗
PubMed1988

Recombinant vaccinia virus/Venezuelan equine encephalitis (VEE) virus protects mice from peripheral VEE virus challenge.

Mice immunized with recombinant vaccinia virus (VACC) expressing Venezuelan equine encephalitis (VEE) virus capsid protein and glycoproteins E1 and E2 or with attenuated VEE TC-83 virus vaccine developed VEE-specific neutralizing antibody and survived intraperitoneal challenge with virulent VEE virus strains including Trinidad donkey (subtype 1AB), P676 (subtype 1C), 3880 (subtype 1D), and Everglades (subtype 2). However, unlike immunization with TC-83 virus, immunization with the recombinant VACC/VEE virus did not protect mice from intranasal challenge with VEE Trinidad donkey virus. These results suggest that recombinant VACC/VEE virus is a vaccine candidate for equines and humans at risk of mosquito-transmitted VEE disease but not for laboratory workers at risk of accidental exposure to aerosol infection with VEE virus.

Animals↗
PubMed1987

Partial nucleotide sequence of St. Louis encephalitis virus RNA: structural proteins, NS1, ns2a, and ns2b.

cDNA clones of the St. Louis encephalitis (SLE) virus genome have been obtained and the nucleotide sequence of 4.7 kb corresponding to the 5' terminal half of the genome determined. The genome contains a 5' noncoding region of 98 nucleotides followed by a single continuous open reading frame that encodes three structural proteins in the order capsid (C), membrane precursor (prM)-membrane (M), and envelope (E). Immediately following the C-terminus of E are located nonstructural proteins NS1 through NS3. The SLE amino acid sequence homology with yellow fever (YF), Murray Valley encephalitis (MVE), West Nile (WN), and dengue-2 (DEN) viruses over the sequenced region is 39, 66, 64, and 43%, respectively. The start of each SLE protein has been assigned on the basis of N-terminal sequence data and potential proteolytic cleavage sites homologous with YF and MVE viruses. Flaviviruses have conserved glycosylation sites in prM and NS1 proteins, although only one of the two glycosylation sites in the SLE E protein is conserved in MVE and DEN viruses. An evolutionary tree showing relationships of SLE, MVE, WN, YF, and DEN-2 flaviviruses is proposed on the basis of the amino acid sequences of the C proteins.

Base Sequence↗
PubMed1986

Canary pox causing high mortality in an aviary.

In an aviary housing 200 six-month-old canaries, 165 became ill and 145 died over a 6-week period from a disease initially characterized by lethargy, ruffled feathers, open-mouth breathing, and death in 2 to 3 days. Proliferative "pox-like" lesions around the eyes and mouth were not seen until the 4th week. At necropsy, initially affected birds had cloudy air sacs and patchy pneumonia. Histologically, the lungs had proliferative necrotizing bronchitis. Birds necropsied later had proliferative skin lesions and intracytoplasmic inclusions typical of poxvirus in the epidermis and airway epithelium. A virus was isolated from an organ pool of lung, air sac, liver, and skin of affected birds and was identified by electron microscopy as poxvirus.

Animals↗
PubMed1986

AIDS: medicolegal considerations for Canadian hospitals.

Given the increasing endemicity of human immunodeficiency virus (HIV), the agent implicated in the causation of acquired immune deficiency syndrome (AIDS), in numerous sizeable subgroups of society, hospitals can expect increasing exposure to the legal implications presented by patients with AIDS. This paper reviews the duty of care owed by hospitals, both directly, through contractual obligations, and indirectly, through the acts of their employees and private contractors, to patients with AIDS, other patients and the public. Owing to the absence of case law directly related to AIDS or to HIV antibody reactivity, inferences were drawn from precedents set with other infectious diseases. Recommendations are made in the areas of confidentiality, informed consent, standards of care and vicarious liability.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Nucleotide sequence of the 26 S mRNA of the virulent Trinidad donkey strain of Venezuelan equine encephalitis virus and deduced sequence of the encoded structural proteins.

A cDNA clone containing all of the 26 S mRNA coding region of the RNA genome of Venezuelan equine encephalitis (VEE) virus, virulent strain Trinidad donkey (TRD), has been constructed and sequenced. The nucleotide and deduced amino acid sequences of the 26 S RNA of VEE virus conform to the general organization of the alphavirus subgenomic mRNA. Excluding the poly(A) tail, the VEE 26 S RNA is 3913 nucleotides long with a protein coding region of 3762 nucleotides. Codon usage in the translated region is nonrandom and correlates well with that reported for Sindbis (SIN), Semliki Forest (SF), and Ross River (RR) alphaviruses. Highly conserved sequences of 19 to 22 nucleotides representing putative replicase recognition sites occur at the 26 S RNA junction region of the 42 S genomic RNA and at the 3' terminus immediately preceding the poly(A) tail. The conserved sequence at the 26 S/42 S junction region of VEE virus differs from that of other alphaviruses in that an ochre termination codon (UAA) is substituted for a GGU (Gly) codon present in the other viruses. The 5' and 3' noncoding regions (30 and 121 nucleotides, respectively) of the VEE 26 S RNA are shorter than has been reported for several other alphaviruses. The approximate transmembrane domains of the VEE E1 and E2 envelope glycoproteins have been identified. VEE E1 contains a single asparagine-linked glycosylation site, whereas E2 has three such sites, all of which are apparently glycosylated. The deduced amino acid sequence of the VEE polyprotein shows an overall homology of 44 to 46% with the precursor polyproteins of SIN, SF, and RR viruses. VEE virus capsid, E1, and E2 structural proteins show 43 to 46%, 50 to 53%, and 36 to 41% homology, respectively, with the cognate proteins of SIN, SF, and RR viruses.

Amino Acid Sequence↗