Teased testicular tissue with defined cell populations from experimental rats, as well as testicular tissue from normal rats, was incubated in an environment that insured the morphologic integrity of the tissue at the conclusion of the experiment. In cryptorchid animals, conversion of available substrate to various metabolites by testicular tissue comprised of Leydig and Sertoli cells was comparable to that of intact controls. Using hypophysectomized and hypophysectomized-cryptorchid rats, reliably measurable androgen metabolites were produced by testicular tissue that had specific populations of intact cell types. The reported methodology shows that defined cell populations, capable of testosterone metabolism, can be obtained in vivo by surgical procedures. Histologic monitoring of the tissue at the conclusion of the incubation has helped define the best environment for the maintenance of morphologic integrity throughout the incubation period. These techniques will allow future work on quantitative assessment of testosterone metabolism by defined cell populations of the testis.

Animals↗

PubMedDate not supplied

Development of transmembrane signaling in the fetal rat Leydig cell.

Gonadotropin binding to the adult Leydig cell activates a GTP binding protein that interacts with adenylate cyclase to increase cAMP production within the cell. The increased production of cAMP stimulates steroidogenesis and leads to an increase in testosterone production and secretion. The fetal Leydig cell responds to LH with an increase in cAMP and testosterone production as early as 15.5 days of gestation, although the specific mechanism of transmembrane signaling has not been characterized. Fetal rat testis cells from 13.5-20.5 days of gestation were treated with dibutyryl cAMP (dbcAMP), cholera toxin, and hCG to determine the onset of steroidogenesis stimulation by activation of each moiety in the transmembrane signaling system of the fetal Leydig cell. Maximal stimulation at each age from 14.5 through 20.5 days of gestation was achieved with 1 mM dbcAMP, 500 ng/ml cholera toxin, or 10 ng/ml hCG. At 13.5 days of gestation, fetal testes did not produce any testosterone. These findings indicate that a cholera toxin-sensitive, stimulatory guanine-nucleotide regulatory protein is functional in the fetal Leydig cell as early as 14.5 days of gestation. The LH receptor becomes functional in the transmembrane signaling system of the fetal Leydig cell at 14.5 days of gestation.

Animals↗

PubMedDate not supplied

Hepatic thyroxine (T4) uptake as a mechanism for regulation of triiodothyronine (T3) generation in rat liver slices.

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Animals↗

PubMedDate not supplied

The influence of acoustic and perceptual factors on perceived hypernasality in the vowel.

The purpose of this study was to examine the influence of acoustic and perceptual factors of speech on listeners' perceived hypernasality in the vowel [i]. The isolated syllable [pi] produced by 22 children with hypernasal speech and 6 noncleft children was rated by 10 listeners. These speech samples were then divided into two groups: (1) the samples (n = 14) that received inconsistent ratings from each listener or variable ratings among listeners (i.e., unreliable ratings) and (2) the samples (n = 14) that received consistent ratings from each listener and similar ratings among listeners (i.e., reliable ratings). These results suggest that the severity of hypernasality was easy to rate in some speech samples and not in others. Voice quality deviation and a particular type of spectral change that related to the severity of hypernasality could be factors that influence perceived hypernasality.

Adolescent↗

PubMedDate not supplied

Perceptual and physiologic effects of histamine challenge on nasal breathing.

The purpose of this study is to determine the effect of histamine-induced nasal congestion on nasal airflow and the perception of externally applied resistance to nasal breathing. Nasal cross-sectional area and nasal airflow during free breathing were measured in 15 adult subjects before and after histamine challenge. The threshold for perception of resistance to nasal breathing was determined using a dynamic perturbator device, with both free breathing and controlled nasal air-flow. The average threshold for perception of nasal resistance was 0.383 Pa/cm3/s at baseline. After histamine application, there was a significant decrease in nasal cross-sectional area (p = 0.0001), associated with a decrease in nasal airflow (r = 0.6). The average threshold of perception increased to 1.373 Pa/cm3/s (p < 0.0001). When nasal airflow was controlled at the baseline rate, the threshold of perception improved to 0.638 Pa/cm3/s (p = 0.024). These findings indicate that nasal congestion causes a reduction in both nasal airflow and the perception of resistance to nasal breathing. The ability to detect nasal airway impairment is improved with increased nasal airflow. An improved understanding of the physiology of the subjective perception of nasal patency may lead to innovative methods for the treatment of nasal obstruction.

Adult↗

PubMedDate not supplied

Tumor necrosis factor and interleukin-1 stimulate testosterone secretion in adult male rat Leydig cells in vitro.

The actions of two cytokines, tumor necrosis factor (TNF) and interleukin-1 (IL-1), on testosterone production by dispersed adult testis cells and purified Leydig cells in culture were studied. In one set of experiments, testis cells from adult (90-day-old) rats were enzymatically dispersed. In another set of experiments, the dispersed testis cells were placed on a Percoll density gradient and were centrifuged to yield purified (greater than 85%) Leydig cells. Both whole testis cells and purified Leydig cells were cultured in the presence of varying doses of TNF or IL-1 with or without maximally stimulating doses of human chorionic gonadotropin (hCG). Both TNF and IL-1 stimulated basal secretion of testosterone in whole testis cells, as well as purified Leydig cells. Additionally, both TNF and IL-1 augmented maximally hCG stimulated testosterone secretion. Both cytokines stimulated testosterone secretion by dispersed testis cells as early as 4 hours, and the effect continued for up to 72 hours. The cytokines slightly, but significantly, stimulated testosterone production in purified Leydig cells after 24 hours, and continued for up to 72 hours. We have concluded from this data that TNF and IL-1 stimulate the testosterone secretion by adult rat Leydig cells. While this effect might be mediated through the action of the cytokines on testicular macrophages, there might also be a direct effect on the Leydig cell since augmentation of secretion occurred in purified Leydig cells, as well as whole testis cells. Therefore, TNF and IL-1 may serve as local regulators of Leydig cell function.

Animals↗