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Biomedical subjects

K G Johnson

Publications and source records attributed to K G Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1988

Temperature and humidity of expired air of sheep.

The temperature and humidity of expired air from three adult Merino sheep were measured at air temperatures of 20, 30 and 40 degrees C before and after the animals were shorn. Expired air was apparently always saturated with water vapour. At the higher air temperatures the temperature of expired air was close to deep body temperature; at lower air temperatures, expired air had been significantly cooled, e.g. to 32.3 degrees C in shorn sheep at 20 degrees C air temperature. Expired air was cooler from shorn than from unshorn animals at 20 and 30 degrees C air temperature, possibly due to thermally induced vasomotor changes in the upper respiratory tract. Cooling of expired air would be expected to lead to recovery of some of the water evaporated during inspiration; at 20 degrees C air temperature, this fraction was estimated to be 25% in unshorn sheep and 36% in shorn sheep.

Animals↗
PubMed1987

A phase II trial of combination chemotherapy in patients with metastatic carcinoid tumors. A Southwest Oncology Group Study.

A prospective Phase II trial of combination chemotherapy in patients with metastatic carcinoid tumors was conducted by the Southwest Oncology Group. The therapy included 5-fluorouracil, Adriamycin, cyclophosphamide, and streptozotocin (FAC-S) or the same combination without Adriamycin (FC-S) in patients with heart disease. Seventy-four patients were entered and two were ineligible. Sixty-nine of the 72 were histologically reviewed. Six patients were declared ineligible after this review. Fifty-six patients received FAC-S, and nine received FC-S (one patient was inevaluable). The response rates were 31% and 22%, respectively. The median survival of all patients was 10.8 months. The analyses of various clinical and histologic parameters indicated that responses were more common in patients with gastrintestinal carcinoids; there was also a tendency toward shorter survival in patients with tumors that had a higher mitotic rate or the atypical and/or undifferentiated histologic pattern. The FAC-S combination can produce objective responses in patients with metastatic carcinoid tumors, but these are generally partial and brief. It was also concluded that currently available chemotherapy is inadequate.

Adult↗
PubMed1987

Induction of Cellulolytic and Xylanolytic Enzyme Systems in Streptomyces spp.

Extracellular enzyme preparations from Streptomyces flavogriseus and Streptomyces olivochromogenes cultures grown on cellulose contained primarily cellulase activities, but similar preparations from cultures grown on xylan-containing materials possessed high levels of both cellulase and xylanase activities. Growth conditions that gave high endoxylanase levels also resulted in the production of enzymes involved in the hydrolysis of the nonxylose components of xylan. Specific acetyl xylan esterase activities were identified in enzyme preparations from both organisms. Both organisms also produced alpha-l-arabinofuranosidase activity that was not associated with endoxylanase activity. Other activities produced were alpha-l-O-methylglucuronidase and ferulic acid esterase. The latter enzyme was produced only by S. olivochromogenes and is an activity which has not previously been identified as a component of hemicellulase preparations.

Journal Article↗
PubMed1985

The natural history of Kaposi's sarcoma in the acquired immunodeficiency syndrome.

Kaposi's sarcoma is a multifocal systemic neoplasm histologically characterized by proliferating fibroblastic and microvascular elements. Initial signs include macules, papules, or nodules on the skin or mucosal surface. Lesions are frequently found on the trunk, arms, and head and neck. In general, sites of involvement and tumor load do not correlate with prognosis. A general decrease in the functional capacities of T and B cells is found in most patients. Kaposi's sarcoma is reported as the initial manifestation of the acquired immunodeficiency syndrome (AIDS) in approximately 30% of cases. Most cases are in men, although it has been reported in all risk groups. Kaposi's sarcoma in AIDS is more frequent among whites and homosexuals than blacks and intravenous drug abusers. Overall mortality is approximately 41%, with over 60% of patients alive at 1 year and 50% at 22 months. Overall survival is 18 months; however, some patients who have had the disease for 3 to 4 years are still doing well.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Purification and characterization of an exoglucanase from Streptomyces flavogriseus.

Streptomyces flavogriseus, a mesophilic actinomycete, produces high levels of extracellular enzymes capable of hydrolyzing cellulose and xylan. One such enzyme, an exoglucanase, has been purified to molecular homogeneity by a sequence involving DEAE Bio-Gel A chromatography, gel permeation chromatography on Bio-Gel P-60, preparative isoelectric focusing, and concanavalin A affinity chromatography. This purification sequence disclosed the presence of several distinct endoglucanase and xylanase fractions. Homogeneity of the purified enzyme was demonstrated by analytical isoelectric focusing and sodium dodecyl sulphate--polyacrylamide gel electrophoresis. The purified enzyme had a molecular weight of approximately 45 000 and an isoelectric point of 4.15. The enzyme demonstrated negligible activity with carboxymethylcellulose as the substrate. It was able to extensively hydrolyse acid-swollen cellulose; the main product of enzyme action was cellobiose.

Chromatography, Gel↗
PubMed1983

The structure of an R-type oligosaccharide core obtained from some lipopolysaccharides of Neisseria meningitidis.

The main structure of a lipopolysaccharide R-type core oligosaccharide common to a number of different strains of Neisseria meningitidis has been elucidated. Methylation analysis, specific degradations, and nuclear magnetic resonance spectroscopic analysis of the dephosphorylated cores indicated that they all have the following structure. (formula see text) The determinants responsible for the L3, L7, and L9 meningococcal lipopolysaccharide serotypes are situated in this oligosaccharide.

Lipopolysaccharides↗
PubMed1983

Human thermoregulatory behavior during a conflict between cold discomfort and money.

A conflict was contrived between thermal and non-thermal drives in humans to study the effects of varying degrees of voluntary suppression of behavioral temperature regulation. Five, young, near-nude males were paid 2, 5, 10, 20 or 40 cents per min to expose themselves to increasing cold (15 degrees to 0 degree C in 2 hours), after being instructed to terminate the exposure as soon as the cold discomfort exceeded the monetary reward. The duration of voluntary cold exposure was approximately linearly related to the logarithm of monetary reward. Reported cold discomfort was greater with high than with low rates of reward. Although V02 approached summit metabolism, the capacity for shivering did not appear to limit cold tolerance. Subjects adopted various strategies for coping with the conflict but, in general, greatest cold tolerance was recorded in subjects of large body mass and willing to tolerate low Tsk.

Adult↗
PubMed1983

Analysis of a conflict between palatability and cold exposure in rats.

Rats were trained to feed each day from 10 o'clock to 12 noon. Once a week in an environment of Ta--15 degrees C, additional food was made available 16 m from a thermoneutral refuge. The additional food offered was either shortcake, meat pâté, peanut butter, Coca-cola, all of these (cafeteria), or laboratory chow. Although laboratory chow was also always available in their thermoneutral home, rats invariably ran in the cold to the feeder, especially so when the food offered was highly palatable. With such foods, animals took as much as half their nutrient intake in the cold. For less palatable food, rats went only once or twice to the feeder, and there ate little. The attractiveness of the various foods was ranked similarly by the amount eaten, the number of excursions to the feeder, and the time spent feeding in the cold. Meal duration and speed of running to the food were not influenced by palatability. For the whole group, the preference was: shortcake, Coca-cola, meat pâté, peanut butter, and chow. There was a considerable variation between rats in their attraction to different foods. Feeding behavior in a situation of conflict could be used to measure palatability.

Animals↗
PubMed1982

Structure of the 3-deoxy-D-manno-octulosonic acid-containing polysaccharide (K6 antigen) from Escherichia coli LP 1092.

The acidic polysaccharide (K6) antigen from Escherichia coli LP 1092 contains D-ribose and 3-deoxy-D-manno-octulosonic acid in the molar ratio of 2:1, respectively. Spectroscopic data (13C- and 1H-n.m.r.), methylation analyses, and periodate oxidation indicate that the polysaccharide is composed of the foregoing components essentially in the following trisaccharide sequence: leads to 2)-beta-D-Ribf-(1 leads to 2)-beta-D-Ribf-(1 leads to 7)-alpha-D-KDO-(2 leads to. The polysaccharide also contains O-acetyl substituents (approximately 0.2-0.3 mol per KDO residue).

Carbohydrate Conformation↗
PubMed1982

Homeostatic competition between food intake and temperature regulation in rats.

Rats obliged to leave a thermoneutral box to feed at air temperatures (Ta) of 25 degrees, 5 or -15 degrees C reduced the total time spent feeding and the duration of each meal as Ta fell, but increased their food intake by eating faster. Increasing the palatability of the food offered at -15 degrees C Ta did not prolong feeding but further increased food intake and the speed of eating. The estimated maximum fall in rectal temperature during feeding at -15 degree C was small (0.48 degrees +/- 0.15 degrees C, S.E.) but skin temperatures of ears and tail tip fell to near 0 degree C. These rats were able to maintain near-normal balances of food intake and body temperature by reallocating the time spent feeding and sheltering and by altering the speed of eating; they thus resolved a conflict between hunger and cold discomfort with little evidence of a strain on homeostasis.

Animals↗
PubMed1982

Homeostatic competition in rats fed at varying distances from a thermoneutral refuge.

Rats were fed in an air temperature of -15 degrees C at distances of 1, 2, 4, 8 or 16 m from a thermoneutral refuge. As the distance between the feeder and thermoneutrality increased, the number of excursions to feed decreased from 37 +/- 5 to 7 +/- 1 during the 2-hour feeding sessions; concomitantly, the meal duration increased from 1.2 to 5.2 min. The rate of eating and total feeding time were the same at all distances. The mass of food ingested was also constant except for a slight decline at 16 m. Meal duration was strongly correlated (r = 0.9) with the time taken to reach the feeder at each distance while the estimated cost/benefit of feeding episodes increased with distance. Estimates of body temperature indicated that significant falls in skin temperature occur over even short distances, while over greater distances core temperature probably also decreases. In the range of distances studied, rats accorded their hunger drive a higher priority than thermal preference, and chose to feed while tolerating greater thermal disturbance.

Animals↗
PubMed1982

Sweating in the intact horse and isolated perfused horse skin.

1. In intact horses, heat-induced sweating occurred initially as pulses, then as a continuous, synchronously fluctuating discharge. 2. I.V. adrenaline (Adr) induced sweating immediately; isoprenaline (Isop) elicited sweating after a delay; and phenylephrine (PhE) had no sudorific effect. 3. In isolated perfused skin, PhE induced an immediate small sweat discharge, Isop a slower sustained output and Adr a biphasic discharge. alpha- and beta-adrenergic antagonists blocked the first and second phases, respectively, of Adr-induced sweating. 4. The observed sweating patterns are consistent with independent activation of alpha-adrenergic myoepithelium and beta-adrenergic secretory cells in the sweat glands. 5. Microcirculatory changes apparently also influenced sweat discharge.

Animals↗
PubMed1982

Sweating in the intact ox and isolated perfused ox skin.

1. Heated, intact oxen discharged sweat as a steady continuous output rising abruptly and synchronously approximately every 5 min. 2. I.V. adrenaline (Adr) or large doses of phenylephrine (PhE) induced sweating but isoprenaline (Isop) did not. 3. In isolated perfused skin, alpha-adrenergic drugs induced sweating which was blocked by phentolamine. 4. Vasodilator drugs reduced the sweat output induced by Adr, whereas the beta-antagonist propranolol increased it. These effects were possibly due to microvascular changes. 5. Natural fluctuations in sweat rate seem likely to be due to contraction of sweat gland myoepithelium, but it is uncertain whether myoepithelial contraction was ever induced by drugs.

Animals↗