Biomedical subjects
Publications and source records attributed to G A Jones.
Under anaerobic conditions, resting cell suspensions of Coprococcus sp. Pe15 degraded 1 molecule of phloroglucinol to 2 molecules of acetic acid and 2 molecules of carbon dioxide. The organism metabolized the flavonoids rhamnetin and quercetin anaerobically in 20% rumen fluid medium but failed to grow under similar conditions at the expense of any of 39 other aromatic or flavonoid compounds tested.
Streptococcus bovis was cultured in a synthetic medium with three concentrations of sucrose. Initial viscosity of the media was 1.5 centipoise (cp). After incubation for 8 h, the viscosity of the medium with 0.5% sucrose was unchanged, that with 3% sucrose had increased to 8 cp, and that with 6% sucrose to 112 cp. Similar results were found with a rumen fluid medium. A slimy material, responsible for increased viscosity of these cultures, was digested by dextranase. The material appeared as a complex system of intercellular fibers when viewed under the electron microscope after freeze-etching. With proteins and other polymers released from lysed bacteria, this slimy material may contribute directly to increased viscosity and foam formation. In addition to these intercellular fibers, each cell was surrounded by a fibrous capsule that was not digested by dextranase. This capsule stained with lead citrate and uranyl acetate, but not with ruthenium red. The amount of capsular material produced was similar whether the media contained 0.5, 3.0, or 6% sucrose.
Digital vascular pressures, blood flow, and vascular resistances were measured in 11 control ponies and in 8 animals (7 ponies and 1 horse) affected with laminitis created by feeding a high starch ration. Animals with laminitis had increased digital blood flow, increased arterial, small vein, and large vein pressures, and decreased vascular resistances. Comparison of digital lymph flow rates and protein concentrations in animals with laminitis and control animals revealed no differences. Digital vascular responses of the 2 groups to acetylcholine, epinephrine, histamine, or serotonin also did not differ. Thus, the increased digital blood flow observed in animals with laminitis could not be attributed to altered responsivenss to the previously mentioned vasoactive agents. The studies also provided no evidence for increased capillary permeability in digits of animals affected with laminitis.
Eight strains of rumen bacteria capable of degrading phloroglucinol (1,3,5-trihydroxybenzene) under anaerobic conditions were isolated from enrichment cultures of the bovine rumen microflora established in a prereduced medium containing 0.02 M phloroglucinol. Five of the strains were facultatively anaerobic Gram-positive streptococci which were identified as Streptococcus bovis. Three strains of obligately anaerobic Gram-positive cocci were assigned to the genus Coprococcus. Anaerobic cultures of the Streptococcus bovis strains in a 40% rumen fluid medium initially containing 0.02 M phloroglucinol degraded 50-80% of the substrate within 2 days, whereas cultures of the Coprococcus strains degraded more than 80% of the substrate under the same conditions. The Streptococcus bovis strains were incapable of degrading phloroglucinol in brain heart infusion or in the medium of de Man, Rogosa, and Sharpe (MRS broth) incubated aerobically.
Inocula of rumen fluid from sheep were grown on a medium of low nitrogen content under an oxygen-free atmosphere containing N2. The cultures produced methane and carbon dioxide. Hydrogen gas was utilized and the partial pressure of N2 decreased by 24% in 48 h. Assuming this N2 to have been reduced to metabolically available nitrogenous compounds, these account for about 0.2% of the sheep's daily need.
We measured the flow rate and protein concentration of lymph collected from a digital lymphatic in eight anesthetized ponies. Additionally, we recorded systemic arterial pressure (Part), and small vein pressure (Psv). Control lymph flow averaged 0.068 ml/min, and contained 3.11 g/100 ml of protein with albumin/globulin ratio of 0.75. Twenty-minute local intra-arterial infusion of acetylcholine (10 mug/min.) elevated Psv but did not increase lymph flow rate or protein concentration. A 60-min local intra-arterial infusion of histamine (10 mug/min) produced a marked sustained increase in Psv and both lymph flow and protein concentration. Edema developed in the digit receiving histamine. These data support the conclusion that in the horse, as in other species, histamine edema is due primarily to a decreased transcapillary colloid osmotic pressure gradient rather than an increased transcapillary hydrostatic pressure gradient.
The digital circulation was isolated in 12 ponies under pentobarbital anesthesia. Blood flow was either controlled by a pump or measured under natural perfusion. The responses to rapid changes and stoppages of blood flow indicated no evidence of autoregulation or reactive hyperemia. Local administration of acetylcholine, histamine, and prostaglandins E1 and E2 decreased prevenous resistance, whereas epinephrine and serotonin caused prevenous constriction. Large doses of epinephrine and serotonin decreased venous caliber. The effects of prostaglandins A1 and F2alpha were variable. The equine digital vasculature responds to changes in flow and to vasoactive agents like the canine forelimb skin vasculature.
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