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Biomedical subjects

L M Jones

Publications and source records attributed to L M Jones.

At least 91 records · Page 5Linked to original sources
PubMed1976

Cholinergically stimulated phosphatidylinositol breakdown in parotid-gland fragments is independent of the ionic environment.

Carbamoylcholine stimulated phosphatidylinositol breakdown in rat parotid-gland fragments incubated in either a Krebs--Ringer medium or an ion-depleted iso-osmotic sucrose medium. This suggest that phosphatidylinositol breakdown is not initiated by a change in the intracellular concentration of Na+ or of K+, and previous experiments have already indicated that it is independent of cyclic nucleotides and Ca2+. Thus it seems that this reaction may be initiated by a direct interaction at the plasma membrane between the activated muscarinic cholinergic receptor system and the enzyme that catalyses phosphatidylinositol breakdown.

Animals↗
PubMed1976

Endotoxic activity of rough organisms of Brucella species.

A rough-specific antigen extracted from the rough species Brucella ovis and lipopolysaccharide extracted from smooth Brucella abortus demonstrated equivalent levels of activity in tests for mouse lethality and limulus lysate clotting activity. Acetone-extracted whole cells of B. ovis and of B. canis and of a rough mutant of B; abortus had the same toxicity for mice, but it was not possible to extract endotoxin from B. canis by the methods used.

Animals↗
PubMed1976

A potency assay for brucella allergens in guinea pigs.

In the development of a biological potency assay for brucella allergens by skin testing of guinea pigs, it was observed that the delayed hypersensitivity reactions to a given dose depended upon (1) the method of sensitization of the guinea pigs, (2) the time interval between sensitization and skin test and (3) the total of allergen given per animal. Data illustrating these factors are presented and a method for titrating allergens is recommended.

Allergens↗
PubMed1976

Studies of Brucella lipopolysaccharide.

Brucella endotoxin differs from other gramnegative endotoxins in that it is recovered in the phenol phase rather than the aqueous phase of the Westphal hot phenol water procedure. This was the first described from this laboratory by Redfearn (1960) with phenol-killed smooth B. abortus and B. melitensis and has since been confirmed by others. Preliminary extraction of brucella cells with acetone, as called for in the original Westphal procedure, was followed by Renoux et al. (1973) who reported that the aqueous phase lacked endotoxic activity and the phenol phase had very low toxicity. In order to test the hypothesis that prior acetone extraction removes lipid A, we have repeated the Redfearn procedure with acetone extracted cells and have confirmed that the major portion of the endotoxic activity resides in the phenol phase. Acetone treatment does not remove the lipid A believed to be responsible for mouse lethality as well as necrotizing activity in guinea pig and rabbit skin. Preparations of brucella endotoxin (lipopolysaccharide) contain varying amounts of polypeptide some of which is tightly bound. The dermal response of sensitized guinea pigs to brucella LPS was shown to be a combination of reactions comprising those due to (1) innate toxicity of lipid A, (2) antibody mediated reactions due to polysaccharide portion of the molecule and (3) delayed hypersensitivity due to polypeptide portion of the molecule.

Antigens, Bacterial↗
PubMed1976

The role of living vaccines in prophylaxis.

Although strain 19 vaccine has been widely recognized as the most effective vaccine for the control of bovine brucellosis, its use in the United States has declined in the last ten years. When the national level of infection was reduced to 1%, it was believed possible to move towards complete eradication of bovine brucellosis. The continued use of strain 19 vaccine was thought to interfere with the goal of complete eradication because: 1. persistence of serum agglutination titers in some animals caused confusion in the serological diagnosis, 2. occasional persistence of strain 19 infection in adult animals caused reactions in surveillance tests which required follow-up herd tests, 3. vaccination was reported to "mask" virulent infection in a herd by prolonging the incubation period. These perceived disadvantages of strain 19 are discussed in relation to the benefits derived from its use in infected areas. In the last ten years the number of calves vaccinated with strain 19 has steadily declined, whereas the national average of infected cattle has remained stationary. The level of infection in some areas has increased however. The date for complete eradication of bovine brucellosis in the United States has had to be postponed. A retrospective examination of the brucellosis eradication program shows that in general those states which vaccinated 40% or more of their eligible calves with strain 19 were able to eradicate brucellosis. States which still have a bovine brucellosis problem, in general, have never employed wide-scale vaccination. Other factors contributing to these differences in the progress of eradication will be discussed. The important role of strain 19 in the successful eradication of bovine brucellosis in some areas of the United States has been the reduction in the level of infection to the point where eradication was economically feasible.

Animals↗
PubMed1975

The relationship of calcium to receptor-controlled stimulation of phosphatidylinositol turnover. Effects of acetylcholine, adrenaline, calcium ions, cinchocaine and a bivalent cation ionophore on rat parotid-gland fragments.

The possibility that Ca2+ ions are involved in the control of the increased phosphatidylinositol turnover which is provoked by alpha-adrenergic or muscarinic cholinergic stimulation of rat parotid-gland fragments has been investigated. Both types of stimulation provoked phosphatidylinositol breakdown, which was detected either chemically or radiochemically, and provoked a compensatory synthesis of the lipid, detected as an increased rate of incorporation of 32Pi into phosphatidylinositol. Acetylcholine had little effect on the incorporation of labelled glycerol, whereas adrenaline stimulated it significantly, but to a much lower extent than 32P incorporation: this suggests that the response to acetylcholine was entirely accounted for by renewal of the phosphorylinositol head-group of the lipid, but that some synthesis de novo was involved in the response to adrenaline. The responses to both types of stimulation, whether measured as phosphatidylinositol breakdown or as phosphatidylinositol labelling, occurred equally well in incubation media containing 2.5 mm-Ca2+ or 0.2 mm-EGTA [ethanedioxybis(ethylamine)-tetra-acetic acid]. Incubation with a bivalent cation ionophore (A23187) led to a small and more variable increase in phosphatidylinositol labelling with 32Pi, which occurred whether or not Ca2+ was available in the extracellular medium: this was not accompanied by significant phosphatidylinositol breakdown. Cinchocaine, a local anaesthetic, produced parallel increases in the incorporation of Pi and glycerol into phosphatidylinositol. This is compatible with its known ability to inhibit phosphatidate phosphohydrolase (EC 3.1.3.4) and increase phosphatidylinositol synthesis de novo in other cells. These results indicate that the phosphatidylinositol turnover evoked by alpha-adrenergic or muscarinic cholinergic stimuli in rat parotid gland probably does not depend on an influx of Ca2+ into the cells in response to stimulation. This is in marked contrast with the K+ efflux from this tissue, which is controlled by the same receptors, but is strictly dependent on the presence of extracellular Ca2+. The Ca2+-independence of stimulated phosphatidylinositol metabolism may mean that it is controlled through a mode of receptor function different from that which controls other cell responses. Alternatively, it can be interpreted as indicating that stimulated phosphatidylinositol breakdown is intimately involved in the mechanisms of action of alpha-adrenergic and muscarinic cholinergic receptor systems.

Acetylcholine↗
PubMed1975

Antibody-mediated and delayed-type hypersensitivity reactions to Brucella skin test antigens in guinea pigs.

Cutaneous hypersensitivity responses to brucella antigens of different composition were studied in guinea pigs sensitized by infection with smooth brucella or immunization with killed rough brucella in adjuvant. These animals had circulating antibodies to smooth lipopolysaccharide or protein antigens, respectively. Intradermal skin tests, active cutaneous anaphylaxis, passive cutaneous anaphylaxis, and immunodiffusion tests were performed. Delayed-type hypersensitivity reactions uncomplicated by accompanying antibody-mediated reactions were seen only in infected guinea pigs with protein antigen that was entirely free of lipopolysaccharide. In the adjuvant-immunized animals, the protein antigen evoked overlapping antibody-mediated and delayed-type reactions. Lipopolysaccharide and polysaccharide preparations contained varying amounts of protein components. In infected animals, reactions of these antigens were clearly antibody mediated, but participation of delayed-type hypersensitivity could not be excluded. In adjuvant-immunized animals, the antibody-mediated reaction to the lipopolysaccharide preparation was caused by its protein component.

Animals↗
PubMed1975

Titration of a brucella protein allergen in sheep sensitized with Brucella melitensis.

A protein allergen extracted from a rough strain of B. melitensis was titrated in sheep sensitized by vaccination with the attenuated B. melitensis strain Rev. I. Single doses of allergen were given per animal by the intradermal or palpebral routes. Doses over a 100-fold range produced delayed hypersensitivity reactions of similar magnitude by both routes. The most suitable method for application in the field was a dose of 50 mug given by the palpebral route (0.5 ml subcutaneously in the upper eyelid) with readings taken 48 hours after inoculation. Sheep vaccinated with H 38 adjuvant vaccine for 6 to 9 months showed positive reaction to the allergic test, whereas non-vaccinated non-infected sheep showed no reactions. No increase in agglutinations titers following allergic test was observed in either Rev. I or H 38 vaccinated sheep.

Allergens↗
PubMed1974

Enhanced phosphatidylinositol labelling in rat parotid fragments exposed to alpha-adrenergic stimulation.

1. Adrenergic agonists provoke a marked increase in labelling of phosphatidylinositol in fragments of rat parotid gland. 2. Adrenaline and phenylephrine (an adrenergic alpha-agonist) are effective stimulants, but isoprenaline (an adrenergic beta-agonist) is relatively ineffective. 3. The response evoked by phenylephrine or adrenaline is prevented by prior incubation of the tissue with phenoxybenzamine (an alpha-receptor blocking agent), but not by prior incubation with pindolol (a beta-receptor blocking agent). 4. Adrenergic stimulation of phosphatidylinositol metabolism in parotid gland is therefore mediated through alpha-receptors, in common with the adrenaline-induced K(+) efflux. It is not linked to enzyme secretion, which is triggered by stimulation of beta-receptors. 5. It is suggested that the stimulation of phospholipid metabolism that occurs in several other tissues in the presence of adrenaline or noradrenaline may also involve alpha-receptors.

Animals↗
PubMed1974

Breakdown of phosphatidylinositol provoked by muscarinic cholinergic stimulation of rat parotid-gland fragments.

When rat parotid fragments that had been labelled with (32)P in vivo were exposed to high concentrations of acetylcholine, radioactivity was lost from phosphatidylinositol but not from other phospholipids. Simultaneously the concentration of phosphatidylinositol in the tissue decreased. If previously unlabelled tissue was incubated with (32)P(i) an increase in incorporation of radioactivity into phosphatidylinositol was observed during this decrease in concentration. The effects of acetylcholine were blocked by atropine, but not by tubocurarine. The response to acetylcholine was rapid, with up to one-third of the tissue's phosphatidylinositol disappearing within 5min. Similar effects were evoked by stimulation with methacholine and by high concentrations of tetramethylammonium ion; these responses were also atropine-sensitive and tubocurarine-insensitive. It is concluded that the event in inositol lipid metabolism that is affected by acetylcholine stimulation is removal of the phosphorylinositol group from the molecule; this is mediated through muscarinic cholinergic receptors. This is followed by a compensatory increase in the rate of synthesis of phosphatidylinositol, which has been described in detail in the past. These observations are compared with those of previous workers and are discussed in relation to the existing hypotheses relating to the significance of stimulus-provoked phosphatidylinositol turnover.

Acetylcholine↗
PubMed1972

Studies of antigens for complement fixation and gel diffusion tests in the diagnosis of infections caused by Brucella ovis and other Brucella.

Sonically treated and saline-extracted antigens of Brucella ovis, B. canis, B. abortus, and B. melitensis were compared in gel diffusion, complement fixation, and serum absorption tests. All the sonically extracted antigens showed cross-reactions with sera from animals infected or immunized with these species, whereas the saline-extracted antigens were specific for the surface of the rough or smooth colonial phase of the species or strain. The saline-extracted antigens of B. ovis and B. melitensis were both eluted as a single peak in the void volume by Sephadex G-200 column chromatography, in gel diffusion had staining characteristics of lipoproteins, but in immunoelectrophoresis showed distinct mobility patterns. Serological activity for both gel diffusion and complement fixation tests was demonstrated in the immunoglobulin G-containing fraction of sera taken from sheep 12 to 412 days after infection with B. ovis. The gel diffusion test with saline extract of B. ovis is as sensitive as the complement fixation test for the diagnosis of ram epididymitis and is more practical.

Absorption↗