The presence of the glucocorticoid (GC) receptor is required for GC-evoked apoptosis. However, the explicit mechanism of involvement of this receptor continues to be debated. Employing the murine (S-49) and human (CCRF-CEM) lymphoid cell lines, we demonstrated that this response requires a specialized form of the glucocorticoid receptor (GR) that resides in the plasma membrane (mGR). Our studies of mGR have been done in our stable mGR-enriched (by sequential cell separation--immunopanning, fluorescent cell sorting, soft agar cloning) S-49 and CCRF-CEM cells. Direct and indirect immunofluorescent studies of live intact cells showed GR-specific periplasma membrane staining. Immunoanalysis by flow cytometry demonstrated abundant mGR in mGR++ cells, but only barely detectable mGR in mGR-- cells. Western blot and autoradiographic analyses of immunoprecipitated membrane extracts from these cells show they contain immunoreactive and competitively labeled high Mr receptor ranging from 94 to 150 kDa. Using mGR++ CCRF-CEM cells and three synchronization procedures (double thymidine, thymidine/colcemid, and colcemid blocks), we have investigated the influence of cell cycle on regulation and function of mGR. Both mGR expression and GC-mediated lymphocytolysis appear highest at late S-G2/M. Analysis of mGR in lymphocytes of several leukemic patients indicated differences in the levels of receptor expression. These findings might provide diagnostic clues about patients' differential response to steroid therapy and potential therapeutic avenues for effective treatment of hormone-responsive leukemic patients.

Animals↗

PubMedDate not supplied

Rapid actions of estrogens in GH3/B6 pituitary tumor cells via a plasma membrane version of estrogen receptor-alpha.

The focus of our work on rapid actions of estrogens has been on the immuno-identification of a membrane version of the estrogen receptor-alpha (mERalpha) and the correlation of the presence of this receptor to the rapid secretion of prolactin in pituitary tumor cells. We demonstrated the mERalpha by both fluorescence and immuno-enzyme-cytochemistry and with both conventional and confocal microscopy in the cell line GH3/B6 and its sublines. Its presence on cells (including recently subcloned ones) is very heterogenous, unlike the nuclear ERalpha, which is present in every cell. An impeded ligand (estradiol covalently linked to BSA) binds to mERalpha and elicits the same response. A total of eight antibodies to ERalpha recognize mERalpha, making it likely that the membrane and nuclear proteins are highly related. Immuno-identification techniques have also been used to identify mERalpha on the MCF-7 human breast cancer cell line. Estradiol at very low concentrations elicits prolactin release from GH3/B6 cells within a few minutes of application. This response is bimodal, with effective concentrations in both the picomolar and nanomolar ranges. Prolactin release is also elicited or inhibited by ERalpha-specific antibodies. The characteristics of mERalpha and the membrane receptor for glucocorticoids have many similarities, suggesting that this mode of subcellular location/function alternative might be used by other members of the gene family.

Cell Membrane↗

PubMedDate not supplied

Prognostic validity of auditory brainstem evoked response screening in newborn infants.

The effectiveness of the auditory brainstem evoked response (ABR) test as a screening test for permanent hearing loss in neonates is examined in 32 published studies including 4,945 infants. Follow-up studies validating initial test failure were available for only 658 infants. Significant differences in methodology exist among these studies, and these differences may have affected their outcomes. Despite this problem, data from these studies were pooled, and they revealed that 16.5 per cent of neonates failed the initial ABR test. Of these, 5.1 per cent were later confirmed to be hearing-impaired or otherwise neurologically impaired. This implies that many of the false-positive results occurred in neonates who had transient disorders, such as conductive hearing loss or neurologic abnormalities, at the time of the screening test, or that the pass/fail criterion was too stringent. Lack of data on false-negative results or the rate of correct identification of normal infants makes it impossible to assess the sensitivity of the test accurately. Firm estimates of the prognostic validity of the neonatal ABR screening in identifying the impaired population can be achieved only when the actual impairment rate can be estimated, and when the distributions of ABR latencies and thresholds for both normal and impaired populations are known. These data could be obtained by following groups of high-risk infants longitudinally and by pooling raw ABR data from the normal and impaired populations that are collected using standardized procedures and similar equipment.

Audiometry↗

PubMedDate not supplied

Time course of auditory perceptual learning.

The time course of auditory perceptual learning can vary from one hour to more than a year, depending on the task, the complexity of the sounds, and the level of stimulus uncertainty under which the tasks are learned. Previous studies are reviewed which show that longer training is required to identify sounds than to discriminate between them, while the least time-consuming task is to learn to detect a sound's presence. The time course of each of these tasks is greatly extended for complex sounds compared to those for single tones. The learning of a speech-like code would thus be expected to require longer training than the employed in previous psychoacoustic research. The consequences of this fact for the exploitation of residual hearing are briefly discussed.

Auditory Perception↗