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Biomedical subjects

M Howe

Publications and source records attributed to M Howe.

34 records · Page 2Linked to original sources
PubMed1989

Growth of an ocular strain of Chlamydia trachomatis on Chang conjunctival cells.

The most widely used cell lines for in vitro studies of Chlamydia trachomatis infections are McCoy and HeLa cells. Our understanding of the intracellular events that occur during ocular C. trachomatis infections may well be improved if such infections could be studied in a host cell that more closely approximates the natural host conjunctival cell. We report here that Chang conjunctival cells, which have been derived from human conjunctival cells, can be infected with C. trachomatis, serovar B. The optimal times for exposure of the host cells to infectious material and to cycloheximide are about 24 and 48 h, respectively. Under these conditions, the maximum number of inclusions is observed at 72 h after centrifugation.

Cells, Cultured↗
PubMed1988

Blood selenium and glutathione peroxidase activity of populations in New Zealand, Oregon, and South Dakota.

The relationship of whole blood selenium (Se) to glutathione peroxidase (GPX) activity was examined for individuals in New Zealand, Oregon, and South Dakota who represented, respectively, populations with exposure to low, medium, and high amounts of Se. The mean (respective) blood Se levels were 60, 200, and 400 ng/ml. Intergroup differences in blood Se levels were highly significant (P less than 0.001). GPX assays were performed using two variations of an enzyme-coupled procedure to assess the equivalence of the two methods. Despite a fourfold difference in absolute activities measured by these methods, the GPX activities were highly correlated (r = .86) between procedures. Average blood GPX activity was significantly lower (P less than 0.001) for the New Zealand group compared with the other two groups, but there was no difference in GPX activities between the Oregon and South Dakota groups. Linear regression of GPX vs. Se values within each group indicated a significant correlation of these parameters only in the New Zealand group (r = .46, P less than 0.01). Comparison of these parameters for combined data from all three groups also showed a significant positive correlation (r = .60, P less than 0.001). A saturation model (In GPX = k1 + k2 (Se)-1)) fits the combined data better (r = .80, P less than 0.01) than does direct comparison of the two parameters. These results suggest that GPX activity is an appropriate indicator of human Se status only in populations with below normal exposure to Se, as activity of this enzyme is saturated at relatively low levels.

Glutathione Peroxidase↗
PubMed1985

Delayed developmental sequences in rodent diabetic embryopathy.

Diabetes induced by alloxan at day 6 of gestation in Wistar rats produced decreased fetal growth, delayed skeletal ossification, decreased fetal kidney beta-glucuronidase, and an increased frequency of fetal birth defects which correlated with the degree of diabetic control. Offspring of severely diabetic mothers (mean blood glucose greater than 501 mg/dl) sacrificed at 20 days had a mean weight of 2.12 +/- 0.16 g, a mean of 1.8 +/- 0.46 caudal ossification centers, and a 28% incidence of birth defects as compared to 3.70 +/- 0.22 g, 5.9 +/- 0.42 caudal centers, and 1.1% defects for controls. Offspring of severely diabetic mothers sacrificed at 21 days had mean numbers of caudal and sternal ossification centers which did not significantly differ from controls, indicating that decreased ossification observed at 20 days of gestation is a delayed developmental sequence which is mostly corrected by 21 days. Offspring of moderately diabetic (mean blood glucose 300-500 mg/dl) and insulin-treated dams (mean blood glucose 152-168 mg/dl) had intermediate degrees of growth or ossification delay and birth defect frequency at both the 20- and 21-day sacrifices. Maternal diabetes also retards the developmental increase in fetal kidney beta-glucuronidase such than 20-day offspring of severely diabetic mothers had a mean specific activity of 1.1 nmol/min/mg compared to 3.0 nmol/min/mg for controls. The results support prior studies in rodents suggesting a progression of early growth delay, altered developmental sequences, and birth defects in diabetic pregnancy. This progression is suggested as a common teratogenic mechanism which has implications for evaluating analogous pregnancies in man.

Animals↗
PubMed1979

Orality and smoking.

This study was designed to investigate the relation of orality and smoking, smoking motivation and anticipatory pleasure in smoking. Ninety-seven male and female subjects completed questionnaires designed to elicit information about their motivation and behaviour. Results indicated that difficulty in stopping smoking was positively related to three non-nutriment oral preoccupations. Smoking for psychological as opposed to social reasons was positively related to two-nutriment oral preoccupations. Anticipation of pleasure in smoking before becoming a smoker was negatively related to nutriment orality, positively related to smoking because of a craving, and, for females only, positively to one type of non-nutriment orality. The results are discussed in relation to the role of oral ingestion and the reaction of the central nervous system to the drug.

Adult↗
PubMed1971

Control of responding by location of auditory stimuli: rapid acquisition in monkey and rat.

Monkeys require a considerably larger number of trials to bring responding under the control of the location of an auditory stimulus than cats, rats, and bats with the same experimental procedures. The present experiment sought to determine the conditions necessary for rapid acquisition of control of responding by location of noise and tone bursts in the monkey. Monkeys were run in an enclosure that contained four loudspeakers and four manipulanda. Two conditions were used in training. In the adjacent condition, a stimulus (noise or tone burst) was presented through one or other of two speakers and a response on the manipulandum adjacent to the speaker was reinforced with food. In the nonadjacent condition, a stimulus was presented through one of two speakers and a response on a manipulandum remote from the speaker was reinforced with food. Acquisition of control was measured by change in the percentage of reinforced responses during training. In the adjacent condition, responding came under control of location within zero to three sessions. In nonadjacent conditions, the animals required 14 to 20 sessions to come under control of location. These latter numbers are comparable to those reported in the literature for localization discrimination in monkeys.

Animals↗
PubMedDate not supplied

Selenium in the blood of South Dakotans.

Determinations of blood selenium levels of the normal human population in and around the state of South Dakota were made and related to known seleniferous areas. With two exceptions, the highest mean values were obtained in regions where animal selenosis has been observed, but whether any of the samples contained enough selenium to indicate a chronic toxicosis cannot be stated. Data on blood, hair, and urine of four Rapid City residents showed no seasonal differences, and the average blood concentrations were consistent with previous findings. Urine concentrations were variable within limits. Hair was found to be unreliable in evaluating the selenium status of people because of the general use of antidandruff shampoos containing the element.

Hair↗