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Biomedical subjects

G Davis

Publications and source records attributed to G Davis.

At least 109 records · Page 6Linked to original sources
PubMed1995

HIV prevention beliefs among urban African-American youth.

PURPOSE: This study investigates specific beliefs related to prevention of AIDS and HIV infection among African-American teenagers. METHODS: This study administered valid and reliable measures of HIV/AIDS risk knowledge and prevention beliefs to 150 African-American teenagers. Demographic and psychosocial data were gathered. RESULTS: Black teenagers respond in socially acceptable and undesirable ways and this ambivalence can be explained within the theory of reasoned action. These teens simultaneously believed in the importance of safe sex behaviors while expressing doubt about the viability of some safe sex behaviors. Females demonstrated higher self-efficacy and self-control beliefs while males were more likely to endorse culturally loaded suspicious beliefs about AIDS contraction and transmission. CONCLUSIONS: Those teenagers who perceived themselves as highly knowledgeable scored lower on reliable AIDS Knowledge and Prevention Beliefs measures than those who claimed moderate AIDS knowledge. Some of these "Know It All" teenagers may reflect a subculture of pseudo-confidence that requires special interventions.

Adolescent↗
PubMed1995

Beta 2-adrenoceptor densities do not correlate with growth, carcass quality, or meat quality in cattle.

Drugs that activate beta 2-adrenoceptors (beta-agonists) are known to have profound effects on growth, body composition, and meat quality. Physiologically, these adrenoceptors are activated and regulated by the hormone adrenaline. Because the response to a drug or hormone is dependent partly on the density of the tissue receptors, the potential for predicting growth, carcass quality, or meat quality from knowing beta 2-adrenoceptor density in three disparate sample sites in cattle was examined. Cell membrane fragments were prepared using samples of longissimus muscle, semitendinosus muscle, or ear obtained within 30 min of death from 48 steers. Beta 2-Adrenoceptor density (Bmax) was measured in these membrane preparations by saturating them with the radioligand [125I]iodocyanopindolol. There was no correlation between Bmax values measured in ear samples, longissimus muscles, or semitendinosus muscles. Bmax measured in samples of ear did not correlate with any growth or carcass traits, including weight gain, carcass weight, fat depth, or eye muscle area. Bmax measured in longissimus muscle only correlated weakly with meat color, and Bmax measured in semitendinosus muscle only correlated with carcass weight. We conclude that beta 2-adrenoceptor density is not a useful predictor of growth, carcass quality, or meat quality in cattle.

Adrenergic beta-Agonists↗
PubMed1995

B7-1 expression decreases tumorigenicity and induces partial systemic immunity to murine neuroblastoma deficient in major histocompatibility complex and costimulatory molecules.

Neuroblastoma may escape an immune attack by virtue of its low expression of surface accessory molecules essential in the antitumor response. Murine neuroblastoma, neuro-2a, was transduced with the retroviral vector LB7-1SN to examine the influence of B7-1 expression on the immune response directed against a low major histocompatibility class (MHC) I and class II negative, B7-2, and ICAM-1 negative tumor. Using a retroperitoneal model for implantation of neuroblastoma in its natural site, we demonstrated that expression of B7-1 by neuro-2a reduces its tumorigenicity. Coinjection of B7-1-positive and -negative cells improved survival compared with mice receiving B7-1-negative cells alone. This was dependent on the ratio of B7-1+ to B7-1- neuro-2a cells injected. CD8+ and not CD4+ T-cell depletion significantly increased tumor-induced mortality in syngeneic A/J mice, indicating that B7-1 decreases tumorigenicity primarily by direct constimulation of CD8+ T cells. Rejection of N-2a/B7-1 tumors or preimmunization with irradiated N-2a/B7-1 cells die not increase protection to challenge with unmodified neuro-2a cells over mice vaccinated with N-2a/neo. Furthermore, cytotoxic T lymphocyte (CTL) precursor frequencies were not significantly higher after in vivo priming and in vitro stimulation with irradiated N-2a/B7-1 compared with N-2a/neo, indicating that B7-1 costimulation by the tumor, in the absence of adequate antigen presentation by MHC molecules, may limit the generation of effective CTLs.

Animals↗
PubMed1995

Clinical characteristics of black asthmatic children.

A prospective study of 455 black asthmatic children (277 boys) attending the Baragwanath Hospital asthma clinic was undertaken. A history was obtained by means of a standardised questionnaire and skin tests were performed. Cough was the commonest presenting symptom and upper respiratory tract infections, exercise and cold weather the commonest symptom precipitants. The relative incidences of the other precipitants reflected the environment of the study population. Associated atopic conditions were present in 75.5% of patients and a family background in 22.2%. Other respiratory diagnoses were commonly made, particularly tuberculosis, which was diagnosed in 7.4%. Fewer than one-third had no positive skin reaction. The commonest allergens were grasses, pollen and house-dust mites. The high proportion of house-dust mite sensitivity (44.2%) contradicts beliefs that they are rare at higher altitudes.

Adolescent↗
PubMed1994

Somatosensory regulation of renal function in the stroke-prone spontaneously hypertensive rat.

1. Chloralose-urethane-anaesthetized Wistar rats and stroke-prone spontaneously hypertensive rats (SHRSP) were prepared for measuring renal function. 2. Bilateral brachial nerve stimulation for 15 min, at 1.3 Hz (15 V, 0.2 ms), increased blood pressure from 119 +/- 2 to 151 +/- 6 mmHg (P < 0.01) in Wistar rats and from 181 +/- 6 to 203 +/- 6 mmHg (P < 0.05) in SHRSP; renal perfusion pressure was mechanically regulated at prestimulus levels but renal blood flow (4.1 +/- 0.7 ml min-1 g-1 in Wistar rats and 3.4 +/- 0.3 ml min-1 g-1 in SHRSP) and glomerular filtration rate (1.18 +/- 0.09 ml min-1 g-1 in Wistar rats and 0.88 +/- 0.01 ml min-1 g-1 in SHRSP) decreased between 5 and 30% (P < 0.05-0.001). 3. During brachial nerve stimulation, urine flow (13.8 +/- 2.2 microliters min-1 g-1) and absolute and fractional sodium excretion (3.70 +/- 0.64 mumol min-1 g-1 and 2.06 +/- 0.23%) decreased by 60-70% in the Wistar rats (P < 0.01-0.001) and the responses were unaffected by vagotomy or carotid sinus denervation. In the SHRSP, urine flow rate (9.74 +/- 2.52 microliters min-1 g-1) and absolute and fractional sodium excretion (1.98 +/- 0.59 mumol min-1 g-1 and 1.41 +/- 0.28%) decreased by 15-30% (P < 0.05-0.01), decreases which were significantly (P < 0.05) smaller than those observed in the Wistar rats. Moreover, the responses were some 40-60% larger in the vagotomized and carotid sinus-denervated SHRSP. 4. The influence of vagal and carotid sinus afferent nerves on the somatosensory-induced renal responses in the Wistar rats was small, whereas in the SHRSP they appeared to exert a marked tonic inhibitory effect. It is concluded that there is excessive baroreceptor restraint on neural regulation of renal function in the SHRSP.

Animals↗
PubMed1994

Parallel detection of Kanizsa subjective figures in the human visual system.

Subjective figures, seen in the absence of luminance gradients (Fig. 1), provide a phenomenal illusion that can be related to the properties of single cells in the visual cortex, offering a rare bridge between brain function and visual awareness. It remains controversial whether subjective figures arise from intelligent cognitive mechanisms, or from lower-level processes in early vision. The cognitive account implies that the perception of subjective figures may require serial attentive processing, whereas on the low-level account they should arise in parallel at earlier visual stages. Physiological evidence apparently fits a low-level account and indicates that some types of subjective contour may be detected earlier than the conventional Kanizsa type. Here we report that even Kanizsa subjective figures can be detected without focal attention at parallel stages of the human visual system.

Humans↗
PubMed1994

Processing of the pre-beta-amyloid protein by cathepsin D is enhanced by a familial Alzheimer's disease mutation.

A major pre-beta-amyloid protein695 (APP695) processing activity from Alzheimer's disease brain extracts was identified and found to be indistinguishable from the activity of cathepsin D.APP695 processing activity cleaved APP695 into a series of fragments that reacted on immunoblots to a monoclonal antibody (C286.8a) against beta-amyloid-(1-7)-peptide and cleaved N-dansyl-APP-(591-601)-amide at the Glu-Val and Met-Asp bonds. Fragments of 5.5 kDa and 10-12 kDa were formed from the cleavage of APP695 by cathepsin D at the Glu593-Val594 bond, and had the same N-terminus as a minor form of beta-amyloid released by cells. The Lys595-->Asn and Met596-->Leu substitutions found in a pedigree of familial Alzheimer's disease, increased the cathepsin D-catalyzed rate of accumulation of 5.5 kDa and 10-12 kDa C286.8a-reactive fragments 5-10fold. This substitution also increased the rate of N-dansyl-APP-(591-601)-amide cleavage at the Xaa-Asp bond by up to 41-fold. These observations suggest a role of cathepsin D in beta-amyloid formation under certain circumstances.

Alzheimer Disease↗
PubMed1994

Baroreceptor and somatic sensory regulation of kidney function in two-kidney, one-clip Goldblatt hypertensive rats.

The aim of this investigation was to characterize the renal haemodynamic and tubular responses to somatic afferent nerve stimulation following the removal of afferent nerve input from the atria or the carotid sinuses in chloralose-urethane-anaesthetized Sprague-Dawley rats and two-kidney, one-clip Goldblatt hypertensive rats. Bilateral stimulation of the brachial nerve plexi at 15 V, 1.3 Hz for 0.2 ms resulted in an increase in systemic blood pressure in each group of 10-40%, while renal perfusion pressure was maintained at a constant level. There were significantly larger falls in left renal blood flow and combined left and right glomerular filtration rate in all groups following selective denervation of either the cardiopulmonary or the carotid sinus baroreceptors, respectively. Brachial nerve stimulation decreased urine flow rate and absolute and fractional sodium excretion from both kidneys in Sprague-Dawley intact animals by 53, 65 and 59%; in vagotomized animals by 68, 77 and 63%; and in carotid sinus denervated animals by 86, 90 and 48%, respectively. The renal response in the Goldblatt group were similar to the normotensive group, but the main contribution of the total response was from the untouched left kidney. The inhibitory influence of the vagus and carotid sinuses on the renal sympathetic nerve-mediated sodium and water resorption appeared to be enhanced in the Goldblatt hypertensive rats when compared with the normotensive rats. The renal functional responses to somatic afferent nerve stimulation appeared to be well preserved in the renovascular hypertensive rats, although there were important differences in the contributions to the responses from the left and right kidneys. Furthermore, the baroreceptors exerted a greater influence on basal renal function in the hypertensive rats.

Animals↗
PubMed1994

Cytogenetic studies in endometriosis tissue.

We analyzed 45 pelvic endometrial implants from 42 patients between the ages of 14 and 40 years to investigate whether cytogenetic abnormalities were present in these samples. Chromosomal abnormalities have been described in benign tumors of the female genital tract, such as uterine leiomyomas and endometrial polyps. Furthermore, heritable factors have been postulated to influence a woman's susceptibility to develop endometrial tissue implants outside the uterine cavity. To study whether these factors result in or are associated with chromosomal changes, endometriosis cells were analyzed cytogenetically after short-term culture. No consistent chromosome abnormalities were observed in any of the cases analyzed.

Adult↗
PubMed1994

Corneal astigmatism induced by superior versus temporal corneal incisions for extracapsular cataract extraction.

PURPOSE: We tested the hypothesis that superior corneal sections induce a shift to 'against-the-rule' astigmatism and temporal corneal sections lead to the preferred 'with-the-rule' astigmatism. METHODS: We conducted a prospective randomised trial of superior versus temporal corneal incisions in extracapsular cataract surgery in a hospital practice. Thirty nine eyes of 37 patients were included. The induced astigmatism was analysed by three methods. RESULTS: When analysed by Cravy's method of induced astigmatic cylinders, the superior incision induced a greater degree of 'with-the-rule' astigmatic cylinder prior to sutures removal on day 77 (P < 0.049). Long term, the temporal incision produced 1.44 dioptre of 'with-the-rule' astigmatism, while the superior section produced 0.08 dioptre of 'against-the-rule' astigmatism (P < 0.001). CONCLUSION: The results of this small trial indicates that the superior corneal incision produces significantly less astigmatism than the temporal incision. The temporal incision induces a moderate degree of 'with-the-rule' astigmatism.

Aged↗
PubMed1994

Effect of nitrendipine on autoregulation of perfusion in the cortex and papilla of kidneys from Wistar and stroke prone spontaneously hypertensive rats.

1. This investigation examined the autoregulatory efficiency of different vascular regions of the normotensive and stroke prone-spontaneously hypertensive rat (SP-SHR) kidney and determined how these myogenic responses were dependent upon extracellular calcium. In acute studies, renal autoregulatory blood perfusion curves for cortex and papilla were generated, autoregulatory indices (AI's) calculated as a ratio of the perfusion change divided by the ratio of the pressure difference where zero represents perfect and 1 equates to no autoregulation. The influence of a calcium channel antagonist on this AI was measured at both cortex and papilla. 2. Rats were anaesthetized with sodium pentobarbitone, the kidney exposed and cortical and papillary perfusion measured by Laser-Doppler flowmetry. Groups of rats either received no drug or nitrendipine at either 0.125 or 0.25 micrograms kg-1 min-1. 3. In the Wistar normotensive rats there was efficient autoregulation in the cortex (AI = 0.21 +/- 0.17), from 127 to 90 mmHg, but not in the papilla (AI = 0.89 +/- 0.08), while below 90 mmHg perfusion in both regions decreased with renal perfusion pressure. Nitrendipine attenuated cortical autoregulation at the higher pressure range (AI = 0.62 +/- 0.13 and 0.92 +/- 0.10 at the low and high dose, respectively) while having no effect on the papillary pressure perfusion pattern. 4. In the SP-SHR, reduction in renal perfusion pressure, from 150 to 100 mmHg, gave a cortical AI of 0.49 +/- 0.10, indicating impaired autoregulation, whereas the papilla demonstrated little myogenic response. Over the high pressure range in the presence of both doses of nitrendipine there was neither cortical (AI of 0.75 +/- 0.11 and 0.94 +/- 0.12, respectively) nor papillary autoregulation. 5. Autoregulation in the renal cortex but not papilla of the young Wistar rats is well developed. The myogenic responses are attenuated by the calcium channel antagonists suggesting that they are dependent upon the availability of extracellular calcium. Cortical autoregulation in the SP-SHR is deficient compared to the normotensive rats and is further impaired by the calcium channel antagonists.

Animals↗
PubMed1994

A randomized, double-blind, comparative trial comparing high- and standard-dose oral acyclovir for first-episode genital herpes infections.

Orally administered acyclovir ameliorates the clinical course and decreases the duration of viral shedding in patients with first-episode genital herpes infections. We investigated in a randomized, double-blind, comparative trial whether a higher (4 g) than standard (1 g) daily dose of oral acyclovir results in greater clinical benefit and influences the time to first recurrence. A total of 139 patients with first-episode genital herpes were randomized to receive orally 4 or 1 g of acyclovir daily. A total of 52 subjects were excluded from the efficacy analysis because most had recurrent disease. Of 87 eligible subjects, 28 (32%) had primary herpes simplex virus type 1 (HSV-1) infections, 48 (55%) had primary HSV-2 infections, and 11 (13%) had nonprimary HSV-2 infections. We did not find any statistically significant differences in the duration of symptoms or viral shedding between the two dose groups, nor did the median time to first recurrence differ between the two groups. Initiation of therapy with either dose within the first 3 days of the appearance of symptoms shortened the duration of the first episode. Adverse gastrointestinal effects developed in 8% of subjects receiving the higher dose, whereas no adverse reactions were observed among those receiving the standard dose (P = 0.10). We conclude that, in comparison with standard therapy, higher-dose oral acyclovir does not result in additional clinical benefit or modify the time to first recurrence. The present study may have implications for the development and efficacy of congeners of acyclovir which provide higher levels in blood than the standard dose of acyclovir.

Acyclovir↗
PubMed1994

Impact of culturally sensitive AIDS video education on the AIDS risk knowledge of African-American adolescents.

AIDS video education is a major mode of providing information about the spread and prevention of the human immunodeficiency virus (HIV). Very little has been written about the need for culturally salient messages in increasing the acquisition and retention of HIV/AIDS prevention information, even though there is considerable agreement that limited culturally sensitive information is reaching African-American youth. This investigation sought to ascertain the impact of a culturally similar AIDS video on the acquisition of AIDS knowledge and endorsement of HIV/AIDS prevention beliefs. This study randomly assigned classes of African-American teenagers to one of two treatment groups: culturally similar video (CSV) AIDS education and culturally dissimilar video (CDV) AIDS education. Results suggest that the CSV group demonstrated significant improvement in pre- to post- AIDS knowledge scores compared to the CDV group (using ANCOVA procedures). The intervention was not significant in demonstrating change in beliefs about prevention. Implications for the development of HIV/AIDS prevention programs for inner-city African-American youth are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Recombinant Chinese hamster ovary cell matrix metalloprotease-3 (MMP-3, stromelysin-1). Role of calcium in promatrix metalloprotease-3 (pro-MMP-3, prostromelysin-1) activation and thermostability of the low mass catalytic domain of MMP-3.

Recombinant human fibroblast pro-MMP-3 (prostromelysin-1) expressed in Chinese hamster ovary cells and the zymogen from cultured human dermal fibroblasts have been purified by monoclonal antibody immunoaffinity chromatography, and the role of Ca2+ in proenzyme activation and thermostability of the low mass catalytic domain of MMP-3 has been investigated. In the presence of high Ca2+ (5.0 mM), the organomercurial aminophenylmercuric acetate (APMA) initiated the stepwise removal of both NH2- and COOH-terminal domains from both recombinant and dermal fibroblast proenzymes, resulting in the generation of a heterogeneous family of nonglycosylated low mass truncated active enzyme species beginning at Phe83. However, in the presence of low Ca2+ (0.1 mM), incubation of recombinant pro-MMP-3 with or without APMA did not result in formation of either the high or low mass forms of active MMP-3 but resulted in complete autolysis of both enzyme species. The concentration of Ca2+ required for optimal pro-MMP-3 activation and stability of the low mass catalytic domain was 2.0 mM. The low mass truncated enzyme species containing the catalytic domain were remarkably heat-stable (90 min at 60 degrees C) in high Ca2+ (5.0 mM) but rapidly autolyzed when heated at 60 degrees C in low Ca2+ (0.1 mM). The thermostability properties of MMP-3 appeared to be specific for Ca2+, since no other divalent metal ions tested were able to confer thermostability to the low mass catalytic domain of MMP-3. From homology to the thermostable bacterial metalloprotease, thermolysin, two putative Ca2+ binding sites were found in the catalytic domain of MMP-3 and several other members of the MMP gene family. These putative Ca2+ binding sites are postulated to play an important role in stabilizing active MMP-3 and other members of the matrix metalloprotease gene family by protecting them against autolysis.

Amino Acid Sequence↗
PubMed1993

Beta-core fragment of human chorionic gonadotropin in cervical intraepithelial neoplasia (CIN).

A low molecular weight glycoprotein immunologically identical with the beta-core fragment of hCG (beta C-hCG) has been described in invasive tumors of the genital tract, particularly carcinoma of the cervix. A previous report has also suggested increased urinary concentrations in subjects with cervical intraepithelial neoplasia (CIN). This prospective study of 107 patients with CIN was conducted to determine concentrations of beta C-hCG in the urine compared to a reference population without CIN. All subjects underwent a cervical smear and colposcopy, with biopsy when indicated. Between 11 and 18% of patients had urinary concentrations of beta C-hCG greater than the upper limit of the reference group and these results were confirmed when corrected for urinary creatinine concentration. A substantial number of subjects (19%) also had a positive result in a C-terminal immunoassay. It is concluded that preinvasive carcinoma of the cervix may secrete hCG or beta C-hCG in the earliest stages although measurement of beta C-hCG is unlikely to prove to be a valuable diagnostic marker in CIN.

Adolescent↗
PubMed1993

Priapism of the clitoris: a case report following trazodone use.

We report a case of painful priapism of the clitoris lasting 24 hours, which was believed to be pathophysiologically associated with the administration of trazodone hydrochloride. Drug-induced unusual erectile activity in the clitoris has been described previously. However, to our knowledge this is the first reported case of drug-induced priapism of the clitoris. Management involved discontinuation of the offending agents and administration of adrenergic agonists to induce clitoral smooth muscle contraction. Clitoral function, proposed to be the ability to engorge and enable extrusion of the glans clitoris, was not obviously adversely affected by the priapistic episode.

Adjustment Disorders↗