Biomedical subjects

J A Hadley

Publications and source records attributed to J A Hadley.

3 recordsLinked to original sources

PubMed1992

Effects of a simulated microgravity model on cell structure and function in rat testis and epididymis.

A tail-suspension (TS) rat model used to simulate microgravity was tested for its effects on the anatomy, cell structure, and function of the testis and epididymis in sexually mature male rats. Rats suspended for 7 days without inguinal canal ligation exhibited a significant (P less than or equal to 0.05) reduction in testis weight compared with controls (1.55 +/- 0.04 to 1.1 +/- 0.02 g). Except for the liver, epididymis, and adrenals of TS rats and TS rats allowed to recover for 7 days, no significant (P less than or equal to 0.05) change was observed in the weight of other body and accessory sex organs. A histological examination of the testes and epididymides of model animals revealed disorganized seminiferous tubules and accumulation of large multinucleated cells and spermatids in the lumen of the epididymis. A significant (P less than or equal to 0.05) increase in serum luteinizing hormone (53.1 +/- 6.7 to 66.2 +/- 10.1 ng/ml) and follicle-stimulating hormone (257 +/- 25 to 305 +/- 38 ng/ml) was observed in TS nonligated rats, whereas serum prolactin and testosterone levels were observed to decline from 8.3 +/- 1.3 to 5.1 +/- 0.29 and 7.1 +/- 1.3 to 3.8 +/- 0.25 ng/ml, respectively. Decreases in testis protein content and testosterone levels of the testis, interstitial fluid, and epididymis were also observed in model animals. These data demonstrate that the suspension procedure used in the National Aeronautics and Space Administration TS model results in the testis and epididymis translocating into the abdominal cavity, causing cellular degeneration and organ dysfunction.

Animals↗

PubMed1992

Output and retrieval interference in the missing-number task.

Three experiments are reported that represent a reexamination of the missing-number method (Buschke, 1963b) of estimating short-term memory span. The missing-number task involved presenting a random sequence of all but one of the numbers of a known reference set and asking subjects to identify the missing number. Experiment 1 introduced a modified missing-number task that included two missing items and two choices made by the subject. With a large decline in performance for the second choice relative to the first, it is possible that only the second choice was subject to output or retrieval interference. An alternative explanation is that subjects output the number with the weakest memory representation as their first response. By postcuing subjects to report their two choices in a forward or backward sequence, Experiment 2 provided evidence against the importance of output interference and support either for the importance of retrieval interference or for the "weakest-first" hypothesis. However, with a paradigm that replaced only correctly identified missing numbers, a prediction that subjects would select the number with the weakest memory representation as their first response was not confirmed in Experiment 3. Instead, retrieval interference was implicated to explain the first-choice superiority found in Experiments 1 and 3. The results were interpreted in terms of the TODAM model of Murdock (1982, 1987, in press).

Attention↗

PubMed1989

Evaluation of reproductive function of female rats exposed to radiofrequency fields (27.12 MHz) near a shortwave diathermy device.

In recent years, there has been increased concern regarding effects of operator exposure to the electromagnetic (EM) field associated with shortwave diathermy devices. The present study was designed to investigate the effects, on rats, of repeated exposure to such an EM field. Following repeated exposure for 5 wk, a reduction in fertility occurred as indicated by a reduced number of matings in exposed rats compared to sham-irradiated rats and a reduction in the number of rats that conceived after mating. The data suggest that female operators could experience reduced fertility, if they remained close to the console for prolonged periods. This has particular significant for the physiotherapy profession.

Animals↗