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B J Johnson

Publications and source records attributed to B J Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1986

Thalamic control of dopaminergic functions in the caudate-putamen of the rat--II. Studies using ibotenic acid injection of the parafascicular-intralaminar nuclei.

We have investigated the role of the parafascicular-intralaminar thalamus in the regulation of dopaminergic function in the caudate-putamen by making unilateral injections of the excitotoxin, ibotenic acid, into the thalamus of the halothane-anaesthetized rat. Dopamine utilization was measured at 4 h, 18 h, and 7 days after operation in microdissected tissue from caudate-putamen, substantia nigra, and nucleus accumbens. High performance liquid chromatography with electrochemical detection was used to simultaneously determine dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid. Dopamine utilization was recorded as a ratio of metabolite to its parent amine. At 4 h following injection large bilateral increases in dopamine utilization were recorded in both medial and lateral sectors of caudate-putamen. The percentage increases found for homovanillic acid-based ratios were larger than those found for 3,4-dihydroxyphenylacetic acid-based ratios. These results probably reflect increased dopamine release resulting from the acute effects of ibotenic acid. These changes were independent of dopamine utilization ratios recorded in the substantia nigra, which showed no change either ipsilateral or contralateral to the injection. In contrast to these findings, at 7 days following injection, dopamine utilization ratios were reduced both ipsilateral and contralateral to the injection, although only the ipsilateral reductions were significant. Again, no change was found for this survival time in the substantia nigra. At 18 h survival an intermediate pattern between the 4 h and 7 day result was found. In the nucleus accumbens, ibotenic acid injection produced similar results to those found in caudate-putamen, i.e. a bilateral increase in dopamine utilization at early time intervals and a unilateral ipsilateral decrease at long intervals following injection. These results show that dopamine release in the caudate-putamen is sensitive to experimentally induced changes in neural activity and lesions of its thalamic input. Since the effect of presumed stimulation is markedly greater than lesion, it would appear that, under the conditions employed in these experiments, the thalamus is relatively silent; a suggestion consistent with other evidence. Furthermore, since the changes found occurred in the absence of changes in utilization ratios in the substantia nigra, the mechanisms whereby thalamus regulates dopamine release may be exerted via a local circuit and/or a presynaptic mechanism in the region of dopamine terminals. The anatomical routes responsible for these effects are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Molecular determinants of alphavirus neurovirulence: nucleotide and deduced protein sequence changes during attenuation of Venezuelan equine encephalitis virus.

The nucleotide and deduced amino acid sequences of the structural proteins of the TC-83 vaccine strain of Venezuelan equine encephalitis (VEE) virus have been determined from a cDNA clone containing the 26S mRNA coding region. A cDNA clone encoding the equivalent region of the virulent parent VEE virus [Trinidad donkey strain (TRD)] has been sequenced previously. Comparison of the sequences of the TC-83 and TRD cDNA clones revealed 13 nucleotide differences. Neither the organization of the structural proteins (5'-capsid-E3-E2-6K-E1-3') nor the length (3762 nucleotides) of the open reading frame coding for the viral polyprotein precursor was altered during attenuation. Of the 13 nucleotide differences between the cDNA clones of TC-83 and TRD, nine occurred in the dominant population of the respective genomic RNAs from plaque-purified viruses. Six of the nine mutations were clustered in the E2 surface glycoprotein gene. All five of the nucleotide changes which produced non-conservative amino acid substitutions in the encoded proteins were located in the E2 gene. Two mutations occurred in the E1 glycoprotein gene; one was silent and the other did not alter the chemical character of the E1 protein. One nucleotide difference was found in the non-coding region immediately preceding the 5'-end of the 26S mRNA. The E2 and non-coding region mutations are candidates for the molecular determinants of VEE virus neurovirulence.

Amino Acid Sequence↗
PubMed1986

Efficacy of glycoprotein inhibitors alone and in combination with trifluridine in the treatment of murine herpetic keratitis.

The present study examined the anti-herpetic effect of the glycoprotein inhibitors, hydroxynorvaline and 2-deoxyglucose, alone and in combination with trifluridine on murine ocular herpes. Following ocular inoculation with a large dose of HSV-1 RE strain (10(6) pfu), ICR mice were treated during the acute infection with different therapeutic regimens, and their efficacy was evaluated by ocular virus titers, clinical grading of blepharo-conjunctivitis and histological evaluation of stromal keratitis and iridocyclitis. The results following a large dose HSV-1 inoculum demonstrated that trifluridine was the best single therapeutic agent. Hydroxynorvaline and 2-deoxyglucose had no effect at all. Combination therapy of the glycoprotein inhibitors with trifluridine was no better than trifluridine alone. The mouse HSV-1 keratitis model proved to be an effective, economical alternative to the rabbit model for the evaluation of new antiviral agents.

Animals↗
PubMed1986

Intoxication of cattle by Perilla frutescens (purple mint).

Perilla frutescens or purple mint has been associated with atypical interstitial pneumonia (AIP) for a quarter of a century. The amount and the stage of the plant required to produce AIP have been much debated. A field case in which catastrophic loses occurred in cattle ingesting hay containing purple mint showed that more than the green plants have the capability of producing atypical interstitial pneumonia. In this study, Perilla frutescens produced atypical interstitial pneumonia in three of five calves to which it was given. The amount required to produce the syndrome ranged from 2.3 to 15.5 kg of green seed stage mint and 11.8 kg of mint hay. The toxic syndromes were similar in signs, but quite different in duration. Necropsy examinations showed varied amounts of pulmonary emphysema and edema. Two of the three affected animals' lungs histologically displayed a marked proliferation of Type II pneumocytes. The flowering or seed parts of perilla mint were found by high pressure liquid chromatographic analysis to contain the highest concentration of perilla ketone, considered the most toxic agent involved. This stage of plant growth was also shown to be the most toxic in our calf feeding trial. Calves fed the flowering plant developed the toxic syndrome while those fed earlier plants (collected before seed stage) and late plants (collected after frost) remained asymptomatic. The time of year when perilla reaches the seed stage often corresponds to periods when pasture grass is scarce forcing cattle to consume plants not normally eaten when ample desirable forage is available.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1984

Dirofilariasis with arteriosclerosis in a horse.

Arteriosclerosis caused by Dirofilaria immitis adult parasites was diagnosed in a 20-month-old Quarter horse stallion that died from cantharidin toxicosis. Microscopically, the pulmonary vascular changes were typical of those described as "proliferative endarteritis" in D immitis-infected dogs.

Animals↗
PubMed1984

An outbreak of poliomyelitis caused by poliovirus type I in captive black and white colobus monkeys (Colobus abyssinicus kikuyuensis) in Kenya.

In the latter part of 1982, three black and white colobus monkeys, Colobus abyssinicus kikuyuensis, from a small breeding group maintained at the Institute of Primate Research in Kenya, became paralysed within one month. Two of these cases were fatal and the third animal survived. The clinical and pathological findings suggested a poliomyelitis-like disease. This was confirmed by the isolation of wild strains of poliomyelitis virus type I from faeces, spleen, kidney, lung and central nervous system from affected animals.

Animals↗
PubMed1984

The maxicircle of Trypanosoma brucei kinetoplast DNA encodes apocytochrome b.

The region of the maxicircle of Trypanosoma brucei kinetoplast DNA which hybridizes at low stringency with the apocytochrome b gene of Saccharomyces cerevisiae has been identified and cloned. The nucleotide sequence of a 1.7 kb segment of this region is reported. This segment contains a single long open reading from capable of coding for a 350 amino acid protein with substantial homology to apocytochromes b of other species. The trypanosome protein is considerably more distantly related to other apocytochromes b than they are to each other. Several short unassigned open reading frames (300 nucleotides or shorter) also are described. If polypeptides are synthesized from these regions, they are more hydrophilic than known mitochondrially coded proteins.

Amino Acid Sequence↗
PubMed1982

The maxicircle of Trypanosoma brucei kinetoplast DNA hybridizes with a mitochondrial gene encoding cytochrome oxidase subunit II.

A restriction endonuclease fragment of the maxicircle of Trypanosoma brucei brucei kinetoplast DNA hybridizes with a cloned mitochondrial DNA sequence which encodes cytochrome oxidase subunit II of Zea mays. A cloned mitochondrial DNA sequence encoding cytochrome oxidase subunit II of Saccharomyces cerevisiae also hybridized with kDNA, but exhibits less homology with the maxicircle than does the maize gene. The hybridizing maxicircle DNA was localized to a 2.8 kbp segment which is bounded by TaqI restriction endonuclease sites and nearby HindIII and EcoRI restriction sites. The TaqI restriction fragment is conserved between T. brucei brucei, T. brucei rhodesiense and T. brucei gambiense and hybridizes with the Zea mays probe in each case.

Animals↗
PubMed1981

Synthesis of a nitrobenzeneboronic acid substituted polyacrylamide and its use in purifying isoaccepting transfer ribonucleic acids.

Highly purified isoaccepting species of transfer ribonucleic acid (tRNA) were prepared by use of a polyacrylamide substituted with nitrobenzeneboronic acid functional groups. This method exploits the well-known ability of boronic acids to complex with RNA cis-diols. tRNA isoacceptors were obtained by enzymatically acylating a mixture of tRNA species with a single amino acid and passing the mixture over a solid-state nitrobenzeneboronic acid at pH 6.5 or 7.0. Pure aminoacyl-tRNA eluted at the column liquid volume, and unacylated tRNA species were bound. The bound species were recovered by lowering the pH of the eluant to 4.5. This procedure is uncomplicated, rapid, and applicable to nearly all tRNA isoacceptors. It does not chemically modify the tRNA(s) of interest or adversely affect their ability to be aminoacylated. Since boronic acids must be ionized to complex with cis-1,2-diols, boronic acid derivatives were prepared which ionize at a pH compatible with the stability of the aminoacyl bond. Two isomeric benzeneboronic acids with pKas of 6.8 and 7.4 were synthesized by introducing electron-withdrawing nitro groups into the aromatic ring. The addition of succinyl side chains permitted the nitrobenzeneboronic acids to be coupled to aminoethylpolyacrylamide. The properties of the nitrobenzeneboronic acid substituted acrylamide were illustrated by enriching phenylalanyl-tRNA at pH 7.0 to greater than 95% purity (1.63 nmol of phenylalanine accepted per A260 unit of tRNA) and seryl-tRNA isoacceptors at pH 6.5 to essentially theoretical purity (1.58 nmol of serine accepted per A260 unit of tRNA.

Acrylic Resins↗
PubMed1980

Studies of synthetic peptide analogs of the amphipathic helix. Effect of charged amino acid residue topography on lipid affinity.

The amphipathic helix hypothesis for plasma lipoproteins was investigated using synthetic peptides. The lipid-associating properties of two potentially amphipathic model peptides and two analogs were studied by incubating synthetic peptides with small unilamellar vesicles and protein-lipid association examined by equilibrium density centrifugation, leakage of liposome-entrapped fluorescence compounds, intrinsic tryptophan fluorescence, and circular dichroism spectroscopy. The analog peptides were designed to determine the significance of the number and specific location of the charged residues in amphipathic domains of plasma lipoproteins to protein-lipid association. Based on the four procedures used to examine protein-lipid interactions, the two model peptides (18Aa, 18As) were found to associate strongly with liposomes; the two analog peptides (18As1, 18Asr), differing only with respect to the number and/or position of their charged residues, failed to demonstrate similar lipid binding properties. These findings support the earlier suggestions of the importance of the charged residues, but do not define the precise mechanisms involved. Such amino acids may help initiate the lipid-protein association by electrostatic interactions, contribute to the hydrophobicity of the nonpolar face of the helix by the acyl portion of lysine and arginine, and/or complement the charge distribution in the polar head regions of the phospholipid molecules.

Amino Acid Sequence↗
PubMed1979

Utilization of a radioiodinated bile salt for kinetic studies and hepatic scintigraphy. Studies in nonhuman mammals.

An 125I- or 131I-labeled bile salt derivative, cholylglycyliodohistamine, has been synthesized and purified. The bile salt derivative is rapidly cleared from the circulation when injected intravenously into rats and rabbits. Ten minutes after injection, approximately 50% of the recovered bile salt derivative was in the jejunum and ileum, and 36% was found in the liver. Sixty minutes after injection, 99% of the recovered radioactivity was found in the luminal gastrointestinal tract. The isotope was cleared from the circulation of rabbits with a t1/2 of approximately 2 min. Hepatic scintigraphy using rabbits demonstrated rapid uptake by the liver and excretion into the intestine. Quantitative analysis of scintigraphy showed an uptake rate of 14%/min and a subsequent excretory rate of 4.6/min.

Animals↗
PubMed1978

Mobilization of colonic kallikrein following pelvic nerve stimulation in the atropinized cat.

1. Pelvic nerve stimulation (p.n.s.) in cats induces atropine-resistant colonic vasodilatation and colonic contraction. The effects of this on cat colon are mimicked by synthetic bradykinin infusions. The present study examines the effect of p.n.s. on the activation of kallikrein, the kinin-forming enzyme present in colonic tissue and its effects on the plasma kinin system in the atropinized cat.2. Mean level (+/- S.D.) of mucosal kallikrein was found to be about 37 times higher in unstimulated colonic mucosa (300 +/- 100 ng bradykinin equivalents min(-1)g(-1)) than in the underlying muscle (8.2 +/- 6.3 ng bradykinin equiv min(-1)g(-1)).3. After a p.n.s. of 5 min, mean kallikrein level in colonic muscle was 7.3 +/- 3.5 ng bradykinin equiv min(-1)g(-1), which was not significantly different from the control muscle kallikrein. However, there was an 86% fall in mucosal kallikrein to 41.3 +/- 34.7 ng bradykinin equiv min(-1)g(-1) after 5 min p.n.s., indicating a rapid activation and secretion of mucosal kallikrein.4. Secretion of mucosal kallikrein was paralleled by specific depletion of plasma kininogen, the precursor of active kinin in blood draining the colon. The mean plasma kininogen level fell to 79 and 68% of the prestimulated value (3.1 +/- 1.1 S.D. mug bradykinin equiv per ml. plasma) after 5 and 10 min p.n.s. respectively. Total plasma protein and haematocrit remained unaltered excluding non-specific changes due to protein extravasation or haemodilution and indicating utilization of the plasma kinin precursor.5. Following 2 hr p.n.s., raised levels of kallikrein were detected in both colonic muscle (28 +/- 2.0 bradykinin equiv min(-1)g(-1)) and mucosa 434 +/- 118 ng bradykinin equiv min(-1)g(-1)). Preliminary studies using a kallikrein inhibitor indicated that the increased kallikrein levels originated from plasma.6. Direct stimulation of the parasympathetic pelvic nerve in the atropinized cat thus produced activation of the plasma kinin system in the colon and formation of free kinins may be responsible for the mucosal vasodilatation and strong motor contraction which is not blocked by large doses of atropine. The observation that prolonged stimulation causes extravasation of plasma kallikrein, a potential inflammatory mediator, into the tissues may be of clinical significance.

Animals↗
PubMed1977

Complement fixing site of human IgG1.

A number of chemical modifications were made to purified human IgG1. The effects of these modifications on the complement activity of the immunoglobulin were studied using aggregation on latex and measuring the consumption of the complement by CH50-quantitation. Tryptophan and tyrosine are implicated in the complement fixing site of this human immunoglobulin, and an arginine moiety probably provides a binding site for the complement.

Adsorption↗
PubMed1977

Lipid-protein interactions: detergent binding to L-glutamic acid dehydrogenase.

A nonionic detergent was found to bind to the enzyme L-glutamic acid dehydrogenase [L-glutamate:nicotinamide adenine dinucleotide phosphate oxidoreductase (deaminating) EC 1.4.1.3]. The amount bound was 17 moles of detergent/mole of enzyme, which, however, was not sufficient for the enzyme to be included in a detergent micelle.

Chromatography, Gel↗
PubMed1977

Interrelation between two anticomplement cobra venom factors isolated from crude Naja naja cobra venom.

Two moieties occurring in crude Naja naja cobra venom were found to possess anticomplement activity. Both materials possessed similar molecular weights and specific activities but dissimilar elution profiles upon ion-exchange chromatography. The anticomplement activities of these materials were maintained upon digestion with neuraminidase, and their elution profiles from cation-exchange chromatography became identical after this treatment. It was concluded that the differences between the two anticomplement materials were due to their different sialic acid contents.

Animals↗