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Biomedical subjects

A Easton

Publications and source records attributed to A Easton.

At least 37 records · Page 2Linked to original sources
PubMed1999

Regulation of limbic motor seizures by GABA and glutamate transmission in nucleus tractus solitarius.

PURPOSE: The nucleus of the solitary tract (NTS) is a primary site at which vagal afferents terminate. Because afferent vagal nerve stimulation has been demonstrated to have anticonvulsant effects, it is likely that changes in synaptic transmission in the NTS can regulate seizure susceptibility. We tested this hypothesis by examining the influence of gamma-aminobutyric acid (GABA) ergic and glutamatergic transmission in the NTS on seizures evoked by systemic and focal bicuculline and systemic pentylenetetrazol (PTZ) in rats. METHODS: Muscimol (256 pmol), a GABA(A)-receptor agonist, bicuculline methiodide (177 pmol), a GABA(A)-receptor antagonist, kynurenate (634 pmol), a glutamate-receptor antagonist, or lidocaine (100 nl; 5%), a local anesthetic, was microinjected into the mediocaudal (m)NTS. Ten minutes later, seizure activity was induced by either a focal microinfusion of bicuculline methiodide (177 pmol) into the rostral piriform cortex, systemic PTZ (50 mg/kg, i.p.), or systemic bicuculline (0.35 mg/kg, i.v.). RESULTS: Muscimol in mNTS (but not in adjacent regions of NTS) attenuated seizures in all seizure models tested, whereas bicuculline methiodide into mNTS did not alter seizure responses. Kynurenate infusions into mNTS significantly reduced the severity of seizures evoked both systemically and focally. Anticonvulsant effects also were obtained with lidocaine application into the same region of mNTS. Unilateral injections were sufficient to afford seizure protection. CONCLUSIONS: Our results demonstrate that an increase in GABA transmission or a decrease in glutamate transmission in the rat mNTS reduces susceptibility to limbic motor seizures. This suggests that inhibition of mNTS outputs enhances seizure resistance in the forebrain and provides a potential mechanism for the seizure protection obtained with vagal stimulation.

Animals↗
PubMed1998

Effects of aging on sleep in the golden hamster.

The golden hamster (Mesocricetus auratus) has been a model organism for the study of circadian rhythmicity and, in particular, the effects of age on the circadian system. Surprisingly, nothing is known about the effects of advanced age on sleep in this species. As a first step in determining the effects of aging on sleep in the golden hamster, we recorded sleep for 24 hours in 12 young (3 months) and 18 old (17-18 months) golden hamsters entrained to a 14:10 light:dark (LD) cycle. Aged hamsters exhibited small but significant increases in overall NREM sleep time, primarily due to an increase in time the old animals spent in the NREM sleep state during the dark period relative to the young hamsters. There were no significant differences in REM sleep, median sleep episode length, or the number of arousals. The most striking differences between the sleep of young and old hamsters was in NREM delta (0.5-4 Hz) power per epoch. Old hamsters showed approximately 27% less (p=0.0004) delta power per NREM epoch than young hamsters. It is possible that increased NREM sleep time in the old hamsters may be a failed attempt to maintain cumulative delta power; ie, old hamsters may have more NREM sleep in order to make up for the lower intensity of their sleep. This decline in delta power with age parallels earlier findings in cats and humans, although has it not been previously reported in rodents.

Age Factors↗
PubMed1998

The human placenta and fetal membranes express the corticotropin-releasing hormone receptor 1alpha (CRH-1alpha) and the CRH-C variant receptor.

Placentally derived CRH plays a major role in the mechanisms controlling human pregnancy and parturition. It has been suggested that there is a CRH placental clock that is active from the early stages of pregnancy and determines the length of gestation and the timing of parturition. CRH can influence human reproductive tissue function via specific CRH receptors. Two distinct CRH receptors have been cloned (R1 and R2) that share 70% homology at the amino acid level and exist as two alternatively spliced forms (alpha and beta). In this study we investigated the presence of CRH receptor subtypes in human fetal membranes derived from spontaneous rupture and placental biopsies at term. Using RT-PCR, we identified the full length of the CRH-R1alpha subtype in placental and fetal membranes. In both tissues we also identified a spliced variant of the CRH receptor (CRH-Rc). We were unable to detect any CRH-R2 messenger ribonucleic acid in any of the biopsies. Fluorescent in situ hybridization and immunofluorescence in both tissues demonstrated that syncytiotrophoblast cells and amniotic epithelium are the major cell types expressing CRH-1alpha and CRH-Rc receptor messenger ribonucleic acid. Further studies are necessary to give a better insight into the role of CRH and its receptors in these tissues.

Extraembryonic Membranes↗
PubMed1996

Race-specific versus general stamps on African-American women's survey return rates.

This study examined cancer survey return rates in relation to race-specific versus general stamps used on self-addressed stamped return envelopes. Of the 104 race-specific stamps sent 41 (39%) were returned. Of the 108 general stamps sent 41 (38%) were returned. Thus, race-specific stamps were not effective in increasing return rates in this sample of African-American women.

Adult↗
PubMed1995

Teaching about sexual orientation by secondary health teachers.

Less than half of a random sample (N = 211) of high school health teachers formally teach about homosexuality. When taught, it most commonly is taught for less than one class period. Only one-in-four teachers perceived themselves as very competent in teaching about homosexuality. This is not surprising given the fact that teachers were most likely to identify the mass media as the most commonly used source of information regarding homosexuality. One-in-five teachers claimed students in their classes often used abusive language when describing homosexuals. One-third of health teachers indicated gay and lesbian rights are a threat to the American family and its values. However, one-third of the health teachers perceived the schools were not doing enough to help homosexual adolescents. Finally, more than half the health teachers indicated gay/lesbian support groups would not be supported by their school administrator. Perceptions and behaviors regarding adolescent homosexuality varied by the teachers' gender, age, educational level, and teaching status regarding homosexuality.

Adolescent↗
PubMed1994

Tumour necrosis factor alpha and interleukin-1 beta induce specific subunits of NFKB to bind the HIV-1 enhancer: characterisation of transcription factors controlling human immunodeficiency virus type 1 gene expression in neural cells.

In human astrocytoma and neuroblastoma cell lines tumour necrosis factor alpha (TNF alpha) and interleukin 1 beta (IL-1 beta) induced NFKB and an additional KB-specific protein of approximately 80 K to bind the HIV-1 enhancer. One nucleoprotein complex contained prototypical NFKB comprising of p50 and p65 subunits and a second contained the p65 subunit and an 80 K factor, p80. Over a 24 hr period of cytokine stimulation the p50/p65 complex of NFKB was present in the nucleus whilst the second complex declined in abundance after two hours due to the decline of p80. In unstimulated cells, DNAse I footprinting revealed a previously unidentified octamer-like binding site in the negative regulatory element (NRE) of the HIV-1 long terminal repeat (LTR) which specifically bound protein factors present in human astrocytoma, neuroblastoma and murine oligodendroglioma cell lines. A second unique motif, also in the NRE, was observed with extracts from one human neuroblastoma cell line and a murine oligodendroglioma. Footprinting analysis also confirmed that Sp1, TATA, Site A and Site B motifs of the LTR were occupied by nuclear factors present in neural cells.

Astrocytoma↗
PubMed1993

Evidence that Chlamydia pneumoniae causes pneumonia and bronchitis.

An epidemic often provides an opportunity to obtain evidence of the etiologic association of a microorganism with disease. Chlamydia pneumoniae TWAR is a newly recognized organism whose relationship to disease is not completely understood. An outbreak of C. pneumoniae infections from November 1990 to February 1991 was studied in University of Washington students. Twelve TWAR infections were identified serologically in 54 students with acute respiratory disease. The organism was isolated from 7 of the 12 and identified by the polymerase chain reaction (PCR) in 2 that were isolation-negative. The organism was not found in any of the 42 serologically negative patients or in 51 control student patients without respiratory illness cultured in 1991. There was no evidence of infection with Mycoplasma pneumoniae or respiratory viruses in the 12 patients with C. pneumoniae infection. During the 4-month outbreak, there was an increase in total pneumonia cases. These findings provide evidence for an etiologic association of C. pneumoniae with pneumonia and bronchitis.

Academic Medical Centers↗
PubMed1992

Cytokine augmentation of HIV-1 LTR-driven gene expression in neural cells.

The induction of human immunodeficiency virus type 1 (HIV-1) gene expression by cytokines was investigated in cells of central nervous system origin. These were human neuroblastoma, glioblastoma, and astrocytoma cell lines, a murine oligodendroglioma and primary murine astrocyte cultures. The cytokines used were tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), IL-6, and interferons alpha and gamma (IFN alpha, gamma). Transient transfection of cells with a chloramphenicol acetyltransferase (CAT) reporter gene under the control of the HIV-1 long terminal repeat (LTR) showed significant augmentation following treatment by particular cytokines. TNF alpha was found to augment HIV LTR-directed CAT activity in all cell types. IL-1 beta also activated the HIV LTR reporter gene in glioblastoma, astrocytoma, and astrocyte cells. IL-6 enhanced HIV gene expression in one example only, the primary astrocyte cultures. The interferons generally suppressed expression from the LTR except IFN gamma which produced a twofold rise in the murine glial cells and IFN alpha augmenting expression in one neuroblastoma cell line. No synergy was observed between pairs of activating cytokines tested. The HIV tat gene product was found to be functional in all cells, cotransfection of a tat expression vector transactivating expression from the LTR, with varying degrees of efficiency. In some cell lines the combination of an activating cytokine and tat resulted in an enhancement above that obtained by cotransfection of tat alone. In others, the level of CAT activity did not significantly change. Analysis of nuclear extracts from cytokine-treated cells further implicated the involvement of NFKB in the induction of HIV-1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗