Search PubMed⌕ Search

Biomedical subjects

J Bowers

Publications and source records attributed to J Bowers.

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

Neutron reflectivity studies of critical adsorption: the correspondence between a critical adsorption profile and specular neutron reflection.

For interfacial order parameter profiles which decay as Az(-mu), such as the composition profile of the noncritical interface of a binary liquid mixture at a critical end point, there is a reported one-to-one correspondence between the profile and the reflectivity which can be described by an analytical theory [S. Dietrich and R. Schack, Phys. Rev. Lett. 58, 140 (1987)]. Evidence for mu=0.53+/-0.02 for adsorption at the hydrophilic silicon/liquid surface of the mixture (2-butoxyethanol+deuterium oxide) near its lower critical end point, determined from neutron reflectivity measurements, is presented. This value is in good agreement with the theoretical prediction of mu=0.516+/-0.004. Further examination of the data permits the determination of the asymptotic surface enrichment scaling factor amplitude P0 approximately 0.11, which is not in agreement with the theoretical value P(0) = 0.94+/-0.05 and values determined by other experimental methods.

Journal Article↗
PubMed1996

Developing culturally sensitive HIV/AIDS and substance abuse prevention curricula for Native American youth.

In 1990, researchers and health care professionals joined with members of several southwestern Native American communities to form an HIV/AIDS and substance abuse prevention partnership. Culturally sensitive approaches to theory-based interventions were developed into highly replicable, structured, school-based and community-based intervention programs. Process evaluations indicated high levels of program acceptance and fidelity. Outcome evaluations demonstrated significant positive preventive intervention effects among participants. This article reports how NAPPASA school prevention curricula were developed and discusses three critical processes in developing these successful curricula: 1) selection of integrative theory to address the multi-dimensional antecedents of HIV/AIDS and substance abuse among Native Americans, 2) use of ethnographic methodology to obtain intensive input from target groups and community members to ensure cultural and developmental sensitivity in the curriculum, and 3) use of process and outcome evaluations of pilot and field trials to develop an optimal curriculum.

Adolescent↗
PubMed1995

The pharmacology of GR203040, a novel, potent and selective non-peptide tachykinin NK1 receptor antagonist.

1. The in vitro and in vivo pharmacology of GR203040 ((2S, 3S)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), a novel, highly potent and selective non-peptide tachykinin NK1 receptor antagonist, was investigated in the present study. 2. GR203040 potently inhibited [3H]-substance P binding to human NK1 receptors expressed in Chinese hamster ovary (CHO) and U373 MG astrocytoma cells, and NK1 receptors in ferret and gerbil cortex (pKi values of 10.3, 10.5, 10.1 and 10.1 respectively). GR203040 had lower affinity at rat NK1 receptors (pKi = 8.6) and little affinity for human NK2 receptors (pKi < 5.0) in CHO cells and NK3 receptors in guinea-pig cortex (pKi < 6.0). With the exception of the histamine H1 receptor (pIC50 = 7.5). GR203040 had little affinity (pIC50 < 6.0) at all non-NK1 receptors and ion channels examined. Furthermore, GR203040 produced only weak inhibition of Na+ currents in SH-SY5Y neuroblastoma and superior cervical ganglion cells (pIC50 values < 4.0). GR203040 produced only weak antagonism of Ca(2+)-evoked contractions of rat isolated portal vein (pKn = 4.1). The enantiomer of GR203040, GR205608 (2R, 3R)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), had 10,000 fold lower affinity at the human NK1 receptor expressed in CHO cells (pKi = 6.3). 3. In gerbil ex vivo binding experiments, GR203040 produced a dose-dependent inhibition of the binding of [3H]-substance P to cerebral cortical membranes (ED50 = 15 micrograms kg-1 s.c. and 0.42 mg kg-1 p.o.). At 10 micrograms kg-1 s.c., the inhibition of [3H]-substance P binding was maintained for > 6 h. In the rat, GR203040 was less potent (ED50 = 15.4 mg kg-1 s.c.) probably reflecting, at least in part, its lower affinity at the rat NK1 receptor. 4. In guinea-pig isolated ileum and dog isolated middle cerebral and basilar arteries, GR203040 produced a rightward displacement of the concentration-effect curves to substance P methyl ester (SPOMe) with suppression of the maximum agonist response (apparent pKB values of 11.9, 11.2 and 11.1 respectively). 5. In anaesthetized rabbits, GR203040 antagonized reductions in carotid arterial vascular resistance evoked by SPOMe, injected via the lingual artery (DR10 (i.e. the dose producing a dose-ratio of 10) = 1.1 micrograms kg-1, i.v.). At a dose 20 fold greater than its DR10 value (i.e. 22 micrograms kg-1, i.v.), significant antagonism was evident more than 2 h after GR203040 administration. 6. In anaesthetized rats, GR203040 (3 and 10 mg kg-1, i.v.) produced a dose-dependent inhibition of plasma protein extravasation in dura mater, conjunctiva, eyelid and lip in response to electrical stimulation of the trigeminal ganglion. 7. It is concluded that GR203040 is one of the most potent and selective NK1 receptor antagonists yet described, and as such, has considerable potential as a pharmacological tool to characterize the physiological and pathological roles of substance P and NK1 receptors. GR203040 may also have potential as a novel therapeutic agent for the treatment of conditions such as migraine, emesis and pain.

Animals↗
PubMed1994

Non-specific effects of the tachykinin NK1 receptor antagonist, CP-99,994, in antinociceptive tests in rat, mouse and gerbil.

We have examined the antinociceptive activity of the potent and selective tachykinin NK1 receptor antagonist, CP-99,994, and its less active enantiomer, CP-100,263, in a variety of models in rat, mouse and gerbil. Administered systemically to gerbil or mouse CP-99,994 but not CP-100,263 stereo selectively inhibited a caudally directed biting and scratching elicited by intrathecal administration of the tachykinin NK1 receptor agonist, GR73632. In contrast, both CP-99,994 (ED50 = 3 (1-6) mumol.kg-1 s.c.) and CP-100,263 (4 (2-10)), were equipotent at inhibiting acetylcholine-induced abdominal constrictions in mice. Similarly, both enantiomers were also equipotent in reducing formalin-induced licking in gerbil (CP-99,994 (10.1 (5.7-18.6)), CP-100,263 (13.8 (7.8-27.1)) and rat (100 mumol.kg-1 s.c.). Finally, in the spinalised, anaesthetised rat, CP-99,994 dose-dependently and significantly inhibited the flexion reflex evoked by noxious pinch (5.0 (3.3-7.5) mumol.kg-1 i.v.), whereas the less active enantiomer, CP-100,263, was without significant effect when tested up to 30 mumol.kg-1. Our results demonstrate that in the spinal cord, CP-99,994 exhibits a tachykinin NK1 receptor mediated antinociceptive action.

Analgesics↗
PubMed1994

The use of activated clotting times to monitor heparin therapy during and after interventional procedures.

Use of the activated clotting time (ACT) was recommended in the mid 1970s to guide administration and reversal of heparin during cardiopulmonary bypass. As the applications of cardiopulmonary bypass spread, so too did the need for more efficient techniques to assess coagulation status. This led to the development of automated ACT measurements. Today, the importance of coagulation and anticoagulation has been further highlighted by recent advances in the field of interventional cardiology. More and more cardiologists are using in-laboratory bedside coagulation monitoring to assess heparin requirements during interventional procedures such as percutaneous transluminal coronary angioplasty (PTCA). This review focuses on the development of anticoagulation monitoring and provides historic information on the clinical use of heparin. The application of ACTs in the catheterization laboratory and in other clinical situations is discussed, along with alternative methods for bedside assessment of coagulation status. No definite guidelines have been established for ACT monitoring during invasive intravascular procedures; thus its role continues to be refined. In the meantime, the ACT appears to be an extremely useful method for monitoring heparin therapy and the adequacy of anticoagulation.

Angioplasty, Balloon, Coronary↗
PubMed1993

Risk assessment for aflatoxin: an evaluation based on the multistage model.

Lifetime cancer potency of aflatoxin was assessed based on the Yeh et al. study from China in which both aflatoxin exposure and hepatitis B prevalence were measured. This study provides the best available information for estimating the carcinogenic risk posed by aflatoxin to the U.S. population. Cancer potency of aflatoxin was estimated using a biologically motivated risk assessment model. The best estimate of aflatoxin potency was 9 (mg/kg/day)-1 for individuals negative for hepatitis B and 230 (mg/kg/day)-1 for individuals positive for hepatitis B.

Adult↗
PubMed1993

Use of the activated clotting time in anticoagulation monitoring of intravascular procedures.

The activated clotting time first came into clinical use in the mid-1970s to guide the administration and reversal of heparin during cardiopulmonary bypass procedures. The explosive growth of cardiopulmonary bypass led to the development of automated techniques for measuring activated clotting times. Recent advances in the field of interventional cardiology have emphasized the importance of the coagulation cascade and the need for the prevention of thrombosis with anticoagulant drugs. The activated clotting time has emerged as an important means of monitoring and guiding heparin therapy during invasive intravascular procedures. This review focuses on the following topics: 1) the development of anticoagulation monitoring techniques; 2) current alternatives in bedside anticoagulation monitoring; and 3) the clinical application of activated clotting times outside surgery. Until prospective studies can establish appropriate "target" activated-clotting-time values for interventional procedures, procedural anticoagulation must be guided empirically. Nevertheless, the activated clotting time is extremely useful in the catheterization laboratory, for monitoring heparin therapy and the adequacy of anticoagulation.

Angioplasty, Balloon, Coronary↗
PubMed1993

Preoperative ultrasound and thallium-technetium subtraction scintigraphy in localizing parathyroid lesions in patients with hyperparathyroidism.

Clinical and biochemical evaluation of patients with hypercalcemia are today extremely accurate in identifying those with primary hyperparathyroidism. Neck exploration by an experienced parathyroid surgeon is equally likely to identify correctly the diseased gland or glands. It has been suggested that recently devised localization techniques may allow the surgeon to limit the extent of the procedure to one side of the neck. The present retrospective study was undertaken to determine the reliability with which two such imaging procedures, ultrasonography (US) and thallium-technetium subtraction scanning (TTSS) localize these lesions by specific site or side. The identity of each patient undergoing parathyroidectomy at a metropolitan medical center was determined by review of the operating room log. From the records of each subject were noted the results of any imaging studies done, the location of lesions found at surgery, and the histologic diagnosis. Accuracy and positive predictive value of US and TTSS were then calculated on the basis of precise and lateralizing localization. Seventy-four patients underwent primary neck exploration during the study period. In 69 patients US, TTSS, or both were performed preoperatively, and among these, data were complete in 65. Ultrasound correctly localized the site of a lesion in 31 of 63 subjects, and TTSS in 25 of 45. Ultrasound correctly localized the side on which the lesion lay in 35 of 62 subjects, and TTSS in 27 of 45. In 29 of 42, one or both studies correctly identified the side on which the lesion lay. In only one of 13 subjects with hyperplasia were all four glands correctly identified as hyperplastic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1992

General practitioners' reported knowledge about depression and dementia in elderly patients.

Previous studies have shown that general practitioners often fail to detect dementia and depression in their elderly patients. The present study aimed to find out how much knowledge general practitioners have of these disorders. The knowledge of 36 general practitioners was assessed and it was found that they had a limited knowledge of the symptoms and signs of dementia and depression. Furthermore, almost 60% of the general practitioners did not know that Alzheimer's disease is the most common dementing disorder.

Aged↗
PubMed1990

General practitioners' detection of depression and dementia in elderly patients.

In a study of 11 general practitioners' detection of dementia and depression in 101 elderly patients it was found that general practitioners were more accurate in their detection of dementia than depression. The general practitioners did not identify 12 of the 15 patients assessed as depressed by a Diagnostic Interview for Depression, but their assessments of dementia corresponded quite well with the results of dementia tests. The general practitioners' knowledge of the symptoms and signs of dementia and depression was limited. If the patient talked to the general practitioner about feeling depressed, sad or irritable, the depression recognition rate increased.

Activities of Daily Living↗
PubMed1989

Effect of ranitidine on gastroduodenal mucosal damage induced by nonsteroidal antiinflammatory drugs.

The effect of ranitidine in preventing mucosal damage caused by nonsteroidal antiinflammatory drugs (NSAIDs) was evaluated for eight weeks in a prospective study of 144 patients requiring NSAIDs. Patients with normal endoscopic findings were randomly assigned to receive either ranitidine 150 mg twice daily or placebo for eight weeks, along with either ibuprofen, indomethacin, naproxen, sulindac, or piroxicam. Duodenal damage was significantly less in the ranitidine group compared with the placebo group by weeks 4 and 8 (P less than or equal to 0.01). Duodenal ulcers did not develop in any patients on ranitidine (0/57) compared with 4/49 patients (8%) on placebo (P = 0.02). No significant difference was found between treatment groups with respect to gastric damage; 6/60 (10%) in the ranitidine group compared with 6/50 (12%) in the placebo group developed gastric ulcers. These findings suggest that acid suppression is of greater importance for mucosal protection in the duodenum than in the stomach, where other defense mechanisms may be operative. While ranitidine is an effective prophylaxis for NSAID-induced damage in the duodenum, further studies are needed to define specific risk groups and to assess the potential usefulness of more complete acid suppression in preventing gastric mucosal damage.

Adult↗
PubMed1987

The ovulated ovum of the horse: cytology of nonfertilized ova to pronuclear stage ova.

Fertilization and early development in the horse were studied by recovering oviductal ova at various times after postovulatory mating. Ova collected between 7 and 22 h post coitum (pc) were examined for evidence of fertilizing sperm, cellular changes accompanying fertilization, and pronuclear development. Five ova collected between 7 and 9 h pc contained a marginal metaphase plate, but had no indication of sperm components; three of these, however, showed reduced numbers of cortical granules. Two activated ova (10 and 14 h pc) were in telophase of the second meiotic division, following incorporation of the fertilizing sperm. The fertilizing sperm was situated in a slight elevation; the nucleus was expanding but lacked a nuclear envelope. The pronuclear stage in the horse began as early as 12 h pc, and lasted at least until 21 h pc. Sperm tail remnants were seen in 5 of 7 pronuclear-stage ova, although the crowding of the cytoplasm with clusters of lipid and vacuoles made discerning sperm tail remnants difficult. The spindles of the metaphase stage of the second meiotic division were oriented radially, that is, at right angles to the cell surface, in all but one ovum, so this orientation is not a response to fertilization.

Animals↗
PubMed1987

Chemotactic and phagocytic function of peripheral blood polymorphonuclear leucocytes in newborn foals.

Chemotactic and phagocytic responsiveness of peripheral blood polymorphonuclear leucocytes (PMNLs) from 11 foals were analysed immediately after birth (pre-colostral) and at different times after colostrum ingestion. The number of foal PMNLs per microscopic field that had migrated through the filter in chemotaxis and the number of yeast particles ingested per foal PMNL in phagocytosis were significantly lower when tested with foal plasma before colostrum ingestion (chemotaxis, 2.0 +/- 0.55 (s.e.m.); phagocytosis, 0.98 +/- 0.352) than in tests 4 or more days after colostrum ingestion (chemotaxis, 17.6 +/- 3.88; phagocytosis, 3.87 +/- 0.410; P less than or equal to 0.005). A similar functional deficiency was found in foal PMNLs tested with pre-colostral foal plasma when compared to tests of the same cells with mare plasma (chemotaxis, 11.6 +/- 2.91; phagocytosis, 3.94 +/- 0.269; P less than or equal to 0.005). PMNLs from neonatal foals responded with normal functions to plasma from normal adult horses. Results of both assays suggest that pre-colostral foal PMNLs are functionally mature but the expression of their chemotactic and phagocytic functions depends on the humoral source of chemotactic and opsonic factors.

Animals↗
PubMed1985

An acoustic-speech study of patients who received orthognathic surgery.

Several reports have suggested that orthognathic surgery may influence speech patterns. The purpose of this study was to examine the formant frequency changes of speech following orthognathic surgery in patients whose speech was considered perceptually normal preoperatively and postoperatively. Speech samples were obtained from five patients (three patients with Class II, Division 1 malocclusions and two patients with Class III malocclusions). Significant second-formant frequency shifts were found for the vowel 'e' (as in 'seat'); however, only minor second-formant frequency variations were found for the vowels 'a' (as in 'sat') and 'u' (as in 'suit'). The pattern of formant frequencies before and after surgical treatment suggested that the speakers adjusted their articulation to accommodate the orthognathic surgery. Overall, the data from this study indicate that speech patterns may be reorganized after orthognathic surgery even though speech remains perceptually "normal."

Adolescent↗
PubMed1984

Binaural phase differences and binaural auditory adaptation.

In order to determine the relationship between binaural phase localization and auditory adaptation, subjects were asked to perform a series of phase-based localization tasks, as well as an SDLB adaptation task. A binaurally presented 400 Hz tone was used for midplane localization tasks, and adaptation balances. The tone was presented monaurally during adaptation after binaural localization and the SDLB pre-test. Following 7 min exposure, subjects readjusted phase to centre the binaural stimulus in the midline, and then adjusted intensity to determine dB of adaptation. No consistent or statistically significant change in phase settings occurred. There was a significant decline in the balance intensity as a function of adaptation. A further re-establishment of the midline by phase manipulation also showed no localization effect. For the stimulus values used in the present study, there was no inter-effect of binaural phase localization, and SDLB auditory adaptation.

Adaptation, Physiological↗