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Biomedical subjects

J K Johnson

Publications and source records attributed to J K Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1983

Liposomes replace serum for cultivation of fermenting mycoplasmas.

Cholesterol and albumin are limiting factors in the growth of Mycoplasma species. These nutrients are usually supplied in the culture medium by the addition of serum. The growth of M. pneumoniae in a serum-free medium containing an ethanolic cholesterol suspension and albumin was about one-half the level attained in serum-containing medium. M. gallisepticum and M. fermentans were not cultivable in the cholesterol suspension medium even after supplements were included. In another culture medium containing phosphatidylcholine-cholesterol liposomes and albumin as serum replacements, the growth of M. pneumoniae was approximately equal to that in serum-containing medium, and the growth of M. gallisepticum and M. fermentans was significantly greater than that in medium containing serum. M. fermentans produced even higher yields in liposome medium supplemented with arginine. These fermenting mycoplasmas readily adapted to the liposome medium and by the fifth or sixth serial passage produced thick confluent growth on the lower surface of culture bottles. To obtain maximum growth, we serially transferred the mycoplasmas at least 10 times in serum-free medium before quantitations of growth were made. This is the first report of a serum-free mycoplasma medium of high growth-promoting ability.

Blood↗
PubMed1981

Plasma angiotensin II concentrations and experimentally induced thirst.

The systemic administration of angiotensin II or its precursors will result in increased water intake. Several manipulations that result in hypovolemia and/or hypotension (extracellular thirst challenges) are known to activate the peripheral renin-angiotensin system and also produce drinking. Although there are without question multiple mediators of thirst associated with extracellular thirst challenges, one of the major factors responsible for water intake has been hypothesized to be the action of angiotensin II. In the experimental analysis of thirst, several types of hypovolemic-hypotensive manipulations have been employed. However, there is a paucity of data available that characterize the systematic changes of angiotensin II levels following such challenges. The present studies determined plasma angiotensin II levels and drinking responses after isoproterenol administration, caval ligation, and subcutaneous polyethylene glycol treatment. The experimental protocols for treatment of the animals closely approximated conditions commonly employed in the experimental analysis of thirst. The results indicated that endogenous levels of angiotensin II increase after these treatments to levels that in all likelihood are sufficient to make a substantial contribution to the drinking response.

Angiotensin II↗
PubMed1980

Cholesterol as a limiting factor in the growth of Mycoplasma pneumoniae.

Ultracentrifugation was used to separate three commercial lots of bovine serum fraction (BSF) into components designed to contain lipoproteins. Each BSF lot and component was tested for ability to support the growth of tree strains of Mycoplasma pneumoniae. In general, the level of growth-promoting activity corresponded to the amount of cholesterol present in the BSF or BSF components rather than to the amount or type of lipoprotein Cholesterol was the limiting nutritional factor of BSF with low growth-promoting activity. The addition of cholesterol and bovine serum albumin to BSF with low activity resulted in growth equal to or greater than that observed for BSF with high growth-promoting activity. When cholesterol was added to agar medium containing BSF of low activity, mycoplasma colonies were greater in number, possessed larger mean diameters, and had centers that were more distinct than those observed when this BSF was used alone. Variability in growth-promoting actions of commercial lots of BSF was eliminated by increasing their cholesterol content to an optimum level. An adjustment of the cholesterol and albumin levels of any serum product used in culture media may provide a simple convenient method to improve growth and isolation of mycoplasmas.

Animals↗
PubMed1979

Floor pen studies on the anticoccidial efficacy of arprinocid in turkeys.

Arprinocid was tested against coccidiosis in turkeys reared in floor pens. Contamination of pens with Eimeria meleagrimitis, E. adenoeides, and E. gallopavonis was accomplished by the infected seeder bird technique. Performance improved with increasing levels of arprinocid through 120 ppm, but weight gains were depressed at 180 ppm. Lesion scores were significantly and progressively reduced by treatment with 60, 90, 120, and 180 ppm of arprinocid. Control of lesion scores and performance of birds treated with 120 ppm of arprinocid were comparable to the amprolium (125 ppm) treatment. In a separate experiment, the oocyst passage of E. meleagrimitis and of E. adenoeides was progressively reduced by increasing levels of arprinocid, and sporulation rate was decreased. Sportulation was not obtained in oocysts from birds fed arprinocid at 120 ppm or higher.

Adenine↗
PubMed1979

Anticoccidial activity of narasin in battery raised broiler chickens.

The anticoccidial activity of the ionophorus antibiotic narasin was tested against six species of coccidia (Eimeria acervulina, Eimeria mivati, Eimeria maxima, Eimeria necatrix, Eimeria brunetti, and Eimeria tenella) in battery-raised broilers. Feeding ration medicated with 60, 80, or 100 ppm narasin significantly improved weight gains during the periods of D 0 to D7 and D 0 to D 14 (D 0 = day of inoculation with sporulated oocysts), compared with the weight gains in corresponding inoculated groups fed unmedicated feed. A similar protective effect of the medication was seen with feed conversion ratios (feed consumed/bird weight) and coccidiosis-induced mortality. With most species studied, 40 and 60 ppm narasin was not as efficacious as 80 or 100 ppm. The maximum numerial improvement in weight gain and feed conversion ratio was with 80 ppm narasin. Gross intestinal lesion scores were reduced by medication compared with the scores in birds fed unmedicated feed. The overall trend was for a larger reduction in lesion score with higher drug levels. Narasin at 80 or 100 ppm was generally more effective in controlling individual or mixed species infections of coccidia than 99 ppm monensin.

Animals↗
PubMed1976

Evaluation and restoration of endodontically treated posterior teeth.

The increasing acceptance and utilization of endodontic therapy for the preservation of broken-down posterior teeth presents the practitioner with many difficult restoration problems. If 25% or more of the coronal tooth structure is lost, some form of artificial dentin augmentation is required to provide adequate support and retention for the final restoration. Criteria to be used in the prerestorative evaluation of endodontically treated teeth are presented. Various methods and techniques to protect the remaining toth structure from fracture and to provide support and retention for the final restoration are described.

Composite Resins↗
PubMed1976

Effects of high environmental temperatures on cecal coccidiosis.

Maintenance of broiler or White Leghorn cockerels in a high temperature (32 C.), high humidity (90%) environment for six days following artificial infection with Eimeria tenella significantly reduced coccidiosis severity as compared to birds similarly infected and maintained in an ambient environment averaging 24.5 C., and 62% humidity. Disease severity was determined by lesion scores, fecal scores, and hematocrit readings. The heavier broiler stock maintained body temperatures of 0.7-1.6 C. higher than those birds kept at ambient temperatures for the entire six days. Body temperatures of heat-treated Leghorn cockerels were 0.9 C. higher during the first 48 hours post-inoculation (P.I.), but similar to ambient temperature controls for the last four days. Elevated body temperatures during the first two days following inoculation impaired the survival and development of some parasites while shorter periods (24 hours) of heat treatment did not affect parasite survival.

Animals↗