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Biomedical subjects

D A Johnson

Publications and source records attributed to D A Johnson.

At least 307 records · Page 17Linked to original sources
PubMed1984

Influence of circulating catecholamines on protein secretion into rat parotid saliva during parasympathetic stimulation.

Secretion of proteins by rat parotid glands in response to parasympathetic nerve stimulation was studied in vivo during pentobarbitone anaesthesia. Parasympathetic stimulation (3-10 Hz) via the auriculotemporal nerve resulted in a copious flow of saliva low in protein. In contrast, sympathetic stimulation (5 Hz) via the cervical sympathetic trunk evoked saliva low in volume but high in protein. Nevertheless, the specific concentrations of amylase and peroxidase (mg/mg protein) and the ratio of amylase to peroxidase remained constant. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis revealed a single, rapidly migrating protein band of unknown identity in proportionately greater amounts in parasympathetic saliva than in sympathetic saliva. Bilateral adrenalectomy led to reduced amylase and peroxidase secretion in response to parasympathetic stimulation both on a mg/ml and a mg/mg protein basis. SDS gel electrophoresis also demonstrated the decrease in specific amylase concentration following adrenalectomy. The ratio of amylase to peroxidase, however, was not significantly affected. Administration of 6-hydroxydopamine 17-72 h prior to adrenalectomy caused no further reduction in the secretion of amylase and peroxidase. Chronic sympathectomy of 2.5-4 months duration resulted in an increased protein secretion (mg/ml) by the parotid gland in response to parasympathetic stimulation. This increase was only slightly reduced by bilateral adrenalectomy. However, as observed in non-sympathectomized rats, adrenalectomy caused a significant reduction in the specific concentrations of both amylase and peroxidase, but did not affect the amylase to peroxidase ratios. We conclude that parasympathetic nerve stimulation of rat parotid glands after overnight starvation causes secretion of proteins in proportions similar to, but in significantly lower concentrations than those found in sympathetic saliva. Circulating catecholamines, however, influence the amount of amylase and peroxidase secreted by the rat parotid gland in response to parasympathetic nerve stimulation and account for most of the increased secretion of these enzymes following chronic sympathectomy.

Adrenalectomy↗
PubMed1984

Fast-Growing Rhizobium japonicum That Effectively Nodulates Several Commercial Glycine max L. Merrill Cultivars.

Several isolates of fast-growing Rhizobium japonicum that nodulate the wild soybean Glycine soja have been recently described (Keyser et al., Science 215:1631-1632, 1982). We demonstrate that one of these isolates, designated PRC 440 or USDA 191, has a wider host range than that previously reported and is able to nodulate several commercial Glycine max cultivars as effectively as does slow-growing R. japonicum 61A76. Electron microscopic examination revealed no obvious differences between strain 61A76- and strain USDA 191-induced nodules.

Journal Article↗
PubMed1984

Spontaneous and induced leukemias of myeloid origin in recombinant inbred BXH mice.

BXH-2 recombinant inbred (RI) mice produce high titers of B-ecotropic murine leukemia virus beginning early in life and have a high incidence of non-T-cell leukemias that occur before 1 year of age. The leukemias that develop are in some cases associated with hind limb paralysis. In addition, a dualtropic mink cell focus-forming virus has been isolated from leukemic cells of BXH-2 mice. Immunological and cytochemical characterization of the BXH-2 leukemias showed that they are of the myeloid lineage. To assess the oncogenicity of the BXH-2 viruses, newborn mice of several BXH RI strains were inoculated at birth with biologically cloned B-ecotropic or mink cell focus-forming murine leukemia virus. These studies demonstrated that the B-ecotropic virus can induce myeloid leukemias in other BXH RI strains, whereas the dualtropic mink cell focus-forming isolates were nononcogenic in the strains tested. DNA-DNA reassociation analysis indicated that the organotropism of the B-ecotropic murine leukemia virus is confined to lymphoid tissues. Southern analysis of tumor DNAs showed that there was amplification of ecotropic virus-specific sequences in BXH-2 myeloid tumors and in all leukemias induced in other BXH RI strains by inoculation of the BXH-2 B-ecotropic virus. Although B-ecotropic virus is expressed in central nervous tissues of paralyzed BXH-2 mice, we were unable to induce the disorder in several BXH RI strains inoculated intracranially at birth with either the B-ecotropic or dualtropic virus. These results suggest that the paralysis that occurs in BXH-2 mice is due to the infiltration of leukemic cells into the central nervous system.

Animals↗
PubMed1984

Observations on the use of long-acting depot neuroleptic injections in the maintenance therapy of schizophrenia.

The advantages of both long-acting injections and oral administration of neuroleptic agents in treating schizophrenia are discussed. Problems related to patient noncompliance and other factors relevant in evaluating long-term maintenance therapy are considered, as well as variables that influence the duration of maintenance therapy. The results of discontinuation, whether initiated by patient or physician, are discussed, along with the limitations of long-term medication therapy (e.g., depression, dyskinesia, extrapyramidal symptoms). General guidelines are provided for evaluating dose requirements in maintenance therapy.

Administration, Oral↗
PubMed1984

Interaction of a fluorescent acyldicholine with the nicotinic acetylcholine receptor and acetylcholinesterase.

A fluorescent acyldicholine, bis-(choline)N-[4-nitrobenzo-2-oxa-1,3-diazol-7-yl]-iminodiprop ionate (BCNI), was synthesized and its capacity to associate with acetylcholinesterase and the nicotinic acetylcholine receptor examined. The fluorescent bisquaternary diester competitively inhibits acetylcholinesterase with a Ki of 0.46 microM. Binding is accompanied by a large decrease in BCNI fluorescence and a 40% reduction in enzyme tryptophanyl fluorescence due to spectral overlap between BCNI absorption and the fluorescence emission of tryptophanyl residues on the enzyme. BCNI titrations show a stoichiometry of one site per subunit and a dissociation constant of 0.2 microM. BCNI also inhibits the initial rate of alpha-toxin binding to the membrane-associated nicotinic acetylcholine receptor and yields a protection constant (Kp) of 0.26 microM. Prior exposure of BCNI to the receptor increases the affinity of the complex, and after equilibration Kp is found to be 0.11 microM. Fluorescence titrations reveal that BCNI binds with 1:1 stoichiometry to alpha-toxin sites on the receptor with a dissociation constant of 0.22 microM. Agonists and antagonists, but not local anesthetics, compete with BCNI binding. BCNI behaves as a competitive antagonist on receptors from the snake neuromuscular junction and from BC3H-1 cells. The 4-nitrobenzo-2-oxa-1,3-diazole fluorophore in BCNI shows a hypsochromatic shift and an enhancement of quantum yield when bound to the receptor but is quenched when associated with acetylcholinesterase. Thus, despite the similarity in dissociation constants, the fluorophore exists in very different environments when bound to the two proteins.

Affinity Labels↗
PubMed1983

Mammalian tissue trypsin-like enzymes. Comparative reactivities of human skin tryptase, human lung tryptase, and bovine trypsin with peptide 4-nitroanilide and thioester substrates.

The subsite specificity of human lung and skin tryptase (trypsin-like enzyme) has been studied at pH 7.5 using 17 amino acid and dipeptide thioester substrates and 14 tripeptide 4-nitroanilide substrates. The reactivity and specificity of the human tryptases were compared with bovine trypsin and other trypsin-like enzymes. Neither tryptase was similar to either kallikrein or factor XIIa (Hageman factor). The skin enzyme was the most reactive as measured by the specificity constant kcat/KM. The best substrate was benzyloxycarbonyl(Z)-Lys-Arg-S-CH2CH(CH3)2 which had a kcat/KM value of 59,000,000 M-1 S-1. Only a single substrate, Z-Glu-Phe-Arg-4-nitroanilide, was slightly more reactive with the lung tryptase. Both enzymes have extended substrate-binding sites and proline residues at P3 substantially decrease kcat/KM. Both enzymes preferred the tripeptide 4-nitroanilides with a P2 Gly residue over Phe, and both favored the substrate Z-Lys-Gly-Arg-4-nitroanilide over similar substrates containing six other representative amino acid residues at P3. The lung enzyme was inhibited over three times faster by p-amidinophenylmethanesulfonyl fluoride than the skin enzyme. The preference of the skin tryptase for substrates with two terminal basic residues indicates that this enzyme could process prohormones and proproteins which contain this structural feature at the cleavage site. The substrates reported in this paper should be useful for the further characterization of the physiologic function of tryptases.

Anilides↗
PubMed1983

Antibody directed to determinants of a Moloney virus derived MCF GP70 recognizes a thymic differentiation antigen.

We prepared an antiserum to a 14-amino-acid-long synthetic peptide derived from the published nucleotide sequence of a Moloney virus-derived MCF recombinant virus. This peptide is not found in the parental Moloney virus gp70 sequence or in other ecotropic viruses so far sequenced. When several tissues of the mouse were examined by Western blot analysis for related molecules, we found that thymocytes from 2-3-mo-old mice, but not splenic T cells or bone marrow cell extracts reacted with this probe. We found that the Mr 70,000 thymic glycoprotein recognized by the anti-peptide antiserum (81-TAg) was present at equivalent levels on peanut agglutinin positive thymocytes in all mouse strains tested. These results indicate that 81-TAg is a differentiation antigen that is related to the substituted portion of an MCF retrovirus.

Animals↗
PubMed1983

A procedure for the separation and quantitation of tryptophan and amino sugars on the amino acid analyzer.

Tryptophan, 5-methyl tryptophan, glucosamine, and galactosamine can be separated from each other and hydrolysis products including lysinoalanine by chromatography on a 6 X 260-mm column of W-3H resin. The column is developed at 70 degrees C for 20 min with pH 3.95 (0.4 M Na+) buffer, followed by pH 6.4 (1 M Na+) buffer for 55 min using a Beckman 119 CL amino acid analyzer. The recovery of the internal standards, 5-methyl tryptophan and galactosamine, can then be used to correct for tryptophan and glucosamine losses, respectively. The procedure uses the column and buffers normally employed for protein hydrolysate analysis and does not require additional resin columns, special buffers, or flow rate changes.

Amino Sugars↗
PubMed1983

Production of macrophage activation factors by tryptic cleavage of calf serum proteins.

Trypsin, when added to a bioassay for tumoricidal macrophages, produced killing of tumor cells. Trypsin cleaved fetal calf serum proteins to produce a protein fragment that activated macrophages to lyse tumor cells. Diisopropyl fluorophosphate-inhibited trypsin did not produce tumoricidal macrophages either by direct action on the macrophage or by action on serum proteins. The macrophage activation factors produced from serum proteins were fractionated into molecular weight ranges of 150,000, 68,000, and 30,000-5000. The effects of neutral proteinases and proteinase inhibitors on the ability of macrophages to lyse tumor cells is discussed.

Animals↗
PubMed1983

Developmental changes in synaptic membrane lipid composition and fluidity.

Synaptic membrane enriched fractions were prepared from 7 and 14 day and adult cortical nerve endings. (a) The levels of synaptic membrane phosphatidylcholine decrease 19% during development while the levels of ethanolamine phosphoglycerides increase 21%. (b) On day 7, desmosterol accounts for 33% of the total membrane sterols. With maturity, the desmosterol disappears and the molar sterol/lipid P ratio increases 56%. (c) The fatty acid composition of the membranes change during development. 16:0 decreases 36% while 18:1 increases 49%. 16:1, a minor component of adult membranes, is found in significant quantities in pup membranes. 22:6 (n-3) increases 34% during development while 22:5 (n-6) decreases 59%. (d) The microviscosity of synaptic membranes, as measured by the fluorescence depolarization technique, increases during development. This effect is observed in both intact membranes and bilayers prepared from lipid extracts of the membrane.

Aging↗
PubMed1983

Differences in basic proline-rich proteins in rat parotid saliva following chronic isoproterenol treatment or maintenance on a liquid diet.

The basic proline-rich proteins (BPRP) in the stimulated parotid saliva of rats treated for 8 days with isoproterenol and rats fed a liquid diet for 2 weeks were compared to those in the stimulated parotid saliva of untreated rats fed a stock pelleted-diet (control). In the control, the BPRP were separated into 5 groups designated Peak A (the basic proline-rich glycoprotein), SP-1, SP-2, SP-3 and SP-4. The percentage of BPRP in each group was as follows: Peak A, 6.5 per cent; SP-1, 37 per cent; SP-2, 6.5 per cent; SP-3, 32.4 per cent; SP-4, 17.6 per cent. In the parotid saliva of rats fed the liquid diet, proteins corresponding to Peak A and SP-2 were not present, the proportion of BPRP in SP-4 was increased to almost 90 per cent while the proportions of material in SP-1 and SP-3 were reduced to 3 and 8 per cent, respectively. In the saliva of rats subjected to chronic isoproterenol treatment, a protein corresponding to SP-4 was not present; proteins corresponding to Peak A, SP-1 and SP-3 were present and in amounts similar to their proportion in untreated rats although material in SP-2 increased to 36 per cent.

Amino Acids↗
PubMed1983

lambda-Transducing phages carrying transfer genes isolated from an abnormal prophage insertion into the traY gene of F.

A set of lambda-transducing phages carrying transfer (tra) genes has been isolated from an abnormal lysogen in which a lambda prophage was inserted into the traY gene of Flac. These have been characterized genetically for complementation of Flac tra and finP point mutants and for the presence of oriT. Studies of tra gene expression during lambda repression showed that tra genes on the transducing phages were expressed from the lambda PL promoter as well as from the transfer promoters when these were present. The molecular weights of the traM (14,000) and traJ (23,500) proteins were measured after infection of ultraviolet-irradiated cells with one of the phages, ED lambda 102, and overproduction of the traJ protein upon induction of an ED lambda 102 lysogen was demonstrated. A proportion of this traJ protein was located in the inner membrane and cytoplasmic fractions of the cell, the majority being in the outer membrane. Physical analysis of the DNA carried by the lambda tra phages by determination of the phage buoyant densities in CsCl, by restriction enzyme digestion and by electron microscope heteroduplex analysis, was used to define the DNA segments encoding the tra functions. Correlation of the physical and genetical data improved the positioning of the tra genes within the transfer region. These results were combined with new restriction enzyme cleavage data to construct an improved map of this region.

Attachment Sites, Microbiological↗
PubMed1983

The discontinuance of maintenance neuroleptic therapy in chronic schizophrenic patients: drug and social consequences.

In a prospective follow-up the outcome of 60 chronic schizophrenic patients who discontinued neuroleptic therapy after remaining stable 12-48 months was compared with controls continuing medication. Not only did the drug-discontinued patients have more relapses (P less than 0.001), but the form of relapse was both more severe and acute, resulting in differences of self-injury (P less than 0.05), anti-social behaviour (P less than 0.01), inpatient admissions (P less than 0.001), and the use of compulsory powers (P less than 0.01). In patients who relapsed, both social and work function was affected adversely for some months. Patients who remained relapse-free without drugs (20%) had a level of work and social function similar to medicated patients. At the end of 18 months the patients who discontinued depot maintenance therapy were found to have been prescribed one-third more neuroleptic drugs than controls, with a possible increase in the risk of long-term tardive dyskinesia.

Adult↗
PubMed1983

Tonic and reflex synaptic activity recorded in ciliary ganglion cells of anaesthetized rabbits.

We have studied patterns of synaptic activity in rabbit ciliary ganglion cells by intracellular recording in vivo, and have examined the morphology of functionally characterized neurones by intracellular injection of horseradish peroxidase. Nearly all of the neurones studied (293 of 300) received tonic synaptic input from preganglionic neurones. This tonic activity was not decreased by darkness or by acute optic nerve section. The rate of tonic synaptic activity recorded in the vast majority of neurones (94%) changed in response to retinal illumination. Most ganglion cells showed an increased rate; some cells, however, showed decreased activity during illumination. The rate of synaptic activity recorded in ciliary neurones tended to be progressively higher in neurones with more complex geometries. Neurones with similar reflex properties included cells that lacked dendrites and cells with complex dendritic arborizations; conversely, neurones with similar geometries often had different reflex characteristics. The synaptic activity arising from different preganglionic axons innervating the same ganglion cell was not temporally linked in any obvious way. The relevance of these results to the regulation of the number of axons that innervate target neurones is discussed.

Animals↗