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Biomedical subjects

M R Petersen

Publications and source records attributed to M R Petersen.

51 records · Page 3Linked to original sources
PubMed1978

Auditory thresholds and kanamycin-induced hearing loss in the guinea pig assessed by a positive reinforcement procedure.

Absolute thresholds from 125 Hz to 52 kHz are determined for six guinea pigs trained by a positive reinforcement method. Four to five hundred trials were conducted during daily testing sessions and little between- or within-subject variability was found. Two of the six animals were subsequently treated with kanamycin and the development of a hearing loss for the high frequencies was followed. Loss of outer and to a lesser extent inner hair cells was well correlated with the threshold shift observed. Contrary to the experience of previous investigators, this operant training procedure has proved as efficient as that for other species of experimental animals, such as the monkey and the chinchilla. It holds excellent promise for future auditory behavioral work with the guinea pig.

Animals↗
PubMed1978

Schedule-induced polydipsia in rats living in an operant environment.

The effect of variations in interreinforcement interval on the temporal and distributional relation between feeding and drinking was continuously monitored. Rats were housed continuously in an operant chamber in which water was freely available, but lever pressing was required to obtain food (45-mg pellets). Initially, pellets were delivered on a fixed-ratio 1 schedule of reinforcement, which was followed by testing on response-initiated fixed-interval 15-, 30-, and 60-second schedules. The total number of discrete, daily meals (a period in which several pellets were earned in succession) was slightly higher during the fixed-interval schedules than during the fixed-ratio 1, but there was no systematic effect of fixed-interval length on meal frequency. Total water consumption, in contrast, increased dramatically as the interval was lengthened: both subjects consumed two to three times as much water on the fixed-interval 60-second schedule as on the fixed-ratio 1. The increased water consumption was the result of an alteration in the distribution of drinking relative to eating. During the fixed-ratio 1 condition, drinking occurred infrequently following individual food pellets and represented the smallest percentage of total drinking; drinking occurred predominantly just before or after a meal. As the fixed interval was lengthened, however, the frequency of postpellet drinking gradually increased and eventually comprised the largest proportion of daily drinking.

Journal Article↗
PubMedDate not supplied

Health status of anthracite surface coal miners.

In 1984-1985, medical examinations consisting of a chest radiograph, spirometry test, and questionnaire on work history, respiratory symptoms, and smoking history were administered to 1,061 white males who were employed at 31 coal cleaning plants and strip coal mines in the anthracite coal region of northeastern Pennsylvania. The prevalence of radiographic evidence of International Labour Office (ILO) category 1 or higher small opacities was 4.5% in 516 men who had never been employed in a dusty job other than in surface coal mining. Among these 516 workers, all 4 cases of ILO radiographic category 2 or 3 rounded opacities and 1 case of large opacities had been employed as a highwall drill operator or helper. The prevalence of category 1 or higher opacities increased with tenure as a highwall drill operator or helper (2.7% for 0 y, 6.5% for 1-9 yr, 25.0% for 10-19 y, and 55.6% for greater than or equal to 20 y drilling). Radiographic evidence of small rounded opacities, dyspnea, and decreases in FEV1.0, FVC, and peak flow were significantly related to tenure at drilling operations after adjusting for age, height, cigarette smoking status, and exposures in dusty jobs other than in surface coal mining. However, tenure in coal cleansing plants and other surface coal mine jobs were not related to significant health effects. The apparent excess prevalence of radiographic small rounded opacities in anthracite surface coal mine drillers suggests that quartz exposures have been increased. Average respirable quartz concentrations at surface coal mine drilling operations should be evaluated to determine whether exposures are within existing standards, and dust exposures should be controlled.

Adult↗
PubMedDate not supplied

Permanent threshold shift and cochlear hair cell loss in the kanamycin-treated guinea pig.

The differential contribution of the inner hair cells (IHC) and the outer hair cells (OHC) in the mammalian cochlea to hearing sensitivity was assessed in six behaviorally-trained guinea pigs by comparing audiograms preadministration and postadministration of kanamycin, an antibiotic that predominantly destroys guinea pig OHC while leaving the IHC structurally unchanged. The results support the hypothesis that only the IHC of the cochlea responds to tones approximately 50 to 60 dB above the threshold of the intact cochlea.

Animals↗
PubMedDate not supplied

Worksite health promotion programs in the U.S.: factors associated with availability and participation.

PURPOSE: To examine how the availability of and participation in worksite health promotion programs varies as a function of individual (e.g., age), organizational (e.g., occupation), and health (e.g., high blood pressure) characteristics. Availability of worksite programs was also compared to that reported in two previous national surveys of private companies. DESIGN: Data analyzed were from the 1994 National Health Interview Survey (NHIS), a national cross-sectional probability sample of the U.S. civilian population. SUBJECTS: Five thousand two hundred nineteen NHIS respondents met the inclusion criteria of (1) being currently employed in a company of at least 50 employees, and (2) completing the NHIS section on worksite health promotion. MEASURES: Employees indicated the availability of, and their participation in, 33 different types of worksite programs. National Health Interview Survey data were also available regarding general health, blood pressure, body mass index, and medical conditions. RESULTS: Smoking cessation programs had the highest mean availability (43%), followed by health education programs (31%) and screening tests (31%). Overall, availability of worksite programs appeared comparable to that reported in a recent national survey. Participation ranged from 32% for health education programs to 5% for smoking cessation programs. Compared to availability, participation depended less on individual and organizational characteristics. Healthy employees were not consistently more likely to participate in worksite health promotion programs than nonhealthy employees. CONCLUSIONS: Although availability of worksite health promotion programs remains high, participation by employees in specific types of programs can vary widely. Attempts to increase participation should look beyond individual, health, and organizational variables, to specific features of the work environment that encourage involvement in health promotion activities.

Adult↗
PubMedDate not supplied

The effect of diffuse pulmonary fibrosis on lung mechanics.

Maximum expiratory flow-volume curves (MEFV), inflational and deflational pressure-volume curves, dynamic compliance at 20, 40, and 60 breaths per minute, closing volume (single-breath oxygen method), standard lung volumes are airway resistance measurements were made in eleven subjects with a clinical diagnosis of diffuse interstitial fibrosis (DIF) and eleven control subjects. No subject was a current cigarette smoker. Maximum flow-static recoil pressure curves (MFSR) were constructed and calculations of upstream resistance (Rus) were made. Comparison of the mean values showed no significant differences in airway resistance or FEV1/FVC% between the two groups; however, significant differences were noted in total lung capacity (TLC), forced expiratory volume in one second (FEV1) and expiratory flow rates. Nine of the diseased subjects had pressure-volume curves shifted to the right of the normal range, and a significant decrease in static expired and inspired compliance was noted in the diseased group. Six subjects with DIF showed increased Rus. The single-breath oxygen test results revealed an increased slope of phase III (delta N2/I) in the diseased group. Decreases in the static compliance may be explained by loss of lung volume in some patients with DIF. There is also evidence that the small airways may be affected by this disease process.

Adult↗