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Biomedical subjects

G Davis

Publications and source records attributed to G Davis.

At least 37 records · Page 2Linked to original sources
PubMed2002

Variability of reported techniques for performance of the pubovaginal sling procedure.

The aim of this study was to determine the commonly used techniques for sling surgery. A questionnaire was distributed to the attendees at the 20th Annual Scientific Meeting of the American Urogynecologic Society. Techniques addressed included the type and length of the graft material, the fixation point, and the methods of sling tensioning. Type of training and monthly surgical volume was also determined. Sixty-five gynecologic and urologic surgeons responded to the survey, the majority of whom were fellowship-trained urogynecologists (68%). The median monthly operative experience was 8 anti-incontinence procedures, including 3.5 pubovaginal slings. There was wide inter-respondent variability in all techniques except fixation point. There was also large intra-respondent variability in sling technique: 42% reported the use of differing graft materials, 19% noted using differing graft lengths, and 19% employed variable tensioning methods. Type of training and operative experience did not predict surgical technique(s) or consistency. Our conclusion was that there is wide variability in the techniques of sling performance.

Biocompatible Materials↗
PubMed2002

Increased visual after-effects in migraine following pattern adaptation extend to simultaneous tilt illusion.

Much previous research into visual processing in migraine supports a model of abnormal cortical processing, in between the headache attacks, that is characterised by hyperexcitability, heightened responsiveness, a lack of habituation and/or a lack of intra-cortical inhibition. Shepherd (2001) reported two adaptation studies that challenged this view, one using the tilt after-effect, the second using the motion after-effect. Models of cortical function in migraine based on hyperexcitability and a lack of inhibition lead to specific predictions in an adaptation study: there should have been smaller after-effects in people with migraine than in people without. Both experiments, however, revealed larger after-effects in the migraine group than in the control group. Here, these results are extended to the simultaneous tilt illusion and an identical pattern of results was obtained: there were consistently larger effects in the migraine group than in the control group. The results from the three experiments are not consistent with a lack of inhibition in migraine. The results are discussed in terms of alternative models of cortical function, including a lack of excitation and reduced central energy reserves.

Adaptation, Ocular↗
PubMed2001

Effect of ischemia-reperfusion injury on the microcirculation of the steatotic liver of the Zucker rat.

BACKGROUND: Much discussion has been focused on the use of steatotic livers for transplantation due to the prevalence of steatosis in the potential donor liver pool (1). The aim of this study was to investigate the possibility that the microcirculation of steatotic liver is more sensitive to the ischemia-reperfusion (IR) injury than normal liver. METHODS: The left liver lobe of obese (n=9) and lean Zucker rats (n=9) were subjected to 40 min of warm ischemia followed by 60 min of reperfusion. Fluorescent probes rhodamine 123 (Rh123), bisbenzimide (Bis), and rhodamine 6G (Rh6G) were administered for the identification by intravital fluorescence microscopy (IVFM) of mitochondrial membrane potential, hepatocyte nuclei and leukocytes, respectively before hepatic ischemia and at 15, 30, 45, and 60 min after reperfusion. Blood samples were obtained before and after 60 min of reperfusion. Liver tissue was taken at the end of experiment for histological analysis. RESULTS: The liver of the obese rats showed prominent macro- and microvesicular fatty changes (MAFC and MIFC) and hepatocyte swelling. Under IVFM, the obese animals had significantly wider hepatic cords (23.1+/-0.8 microm) than the lean ones (15.9+/-0.5 microm) (P<0.01), whereas no significant difference in sinusoidal diameters was noted. The number of functional sinusoids significantly decreased after 30 min of reperfusion in both groups but no significant change was noted in the nucleus count throughout the experiment. Rh123 fluorescence intensity dropped significantly in the obese group after 60 min of reperfusion but not in the lean rats. Leukocyte adherence showed a significant rise after reperfusion in both groups. Plasma AST and ALT levels were 40- and 24-fold higher respectively for the obese animals after IR compared with their preischemic values, whereas the corresponding increase were 4.2- and 3.4-fold for the lean animals, respectively. CONCLUSIONS: Our results indicate that the liver of the obese Zucker rat is steatotic and presents with an abnormal microcirculation manifested by a reduced sinusoidal density. IR led to significantly greater hepatic injury in the steatotic than in the normal liver. This injury was accompanied by a significant reduction in the functional sinusoidal density and mitochondrial membrane potential as assessed by Rh123-associated fluorescence in the steatotic liver. In conclusion, the increased sensitivity of the steatotic liver to IR injury would appear to involve both alterations in blood flow in the microcirculation and to cellular changes.

Alanine Transaminase↗
PubMed2001

Specific proliferative T cell responses and antibodies elicited by vaccination with simian immunodeficiency virus Nef do not confer protection against virus challenge.

The efficacy of immunizing with a combination of simian immunodeficiency virus (SIV) Nef vaccines was evaluated. Four vaccinates received three intradermal immunizations with recombinant vaccinia virus that expressed SIV Nef, followed by three intramuscular immunizations with rDNA also expressing SIV Nef. Finally, the four vaccinates received two subcutaneous boosts with recombinant SIV Nef protein. This immunization protocol elicited anti-Nef antibodies in all of the vaccinates as well as specific proliferative responses. However, specific cytotoxic T cell responses were not detected before virus challenge. All vaccinates were challenged intravenously with 10 MID(50) of SIVmacJ5 along with four controls. All eight subjects became infected after SIV challenge and there were no group-specific differences in virus load as measured by virus titration and vRNA analysis. The results of this study support indirectly the report from Gallimore and colleagues (Nat Med 1995;1:1667) suggesting that CD8(+) T lymphocyte responses are required for Nef-based vaccines to restrict SIV infection. If Nef-based vaccines are to be beneficial in controlling infection with immunodeficiency viruses, then it will be necessary to develop more effective immunization protocols that elicit potent CD8(+) cell responses reproducibly.

Animals↗
PubMed2001

Endotelin ETA and ETB receptor antagonism during cold preservation in renal transplantation.

BACKGROUND: In this study, we investigated the effects of selective endothelin (ET) receptor antagonism during different periods of cold ischemia on glomerular and tubular function and long-term survival in renal transplantation. METHODS: Left renal transplantation was performed in Lewis rats after 2 hr of cold ischemia without (n=8) and with (n=6) ETA receptor antagonism and after 16 hr of cold ischemia without treatment (n=6), with ETA receptor antagonism (n=8) and with ETB receptor antagonism (n=6). A control group (n=8) underwent right nephrectomy and left renal denervation. The ETA and ETB receptor antagonists (BQ-610 and A-192621, respectively) were added to the preservation solution (EuroCollins). After transplantation, renal glomerular and tubular functions were monitored for up to 60 days or death. RESULTS: All animals in the control and 2-hr groups survived the follow-up protocol, with early postoperative recovery of glomerular and tubular function while the entire untreated 16-hr group died between day 3-6 postoperatively. BQ-610 treatment had no measurable effect on the renal function in the 2-hr group, however, it improved glomerular and tubular functions and led to 50% long-term survival (60 days) in the 16-hr group. A-192621 treatment had no effect on long-term survival or renal parameters. CONCLUSION: ETA receptor antagonism had protective renal effects after prolonged ischemic preservation in renal transplantation while ETB receptor antagonism had not.

Animals↗
PubMed2001

The standardization of terminology for researchers in female pelvic floor disorders.

The lack of standardized terminology in pelvic floor disorders (pelvic organ prolapse, urinary incontinence, and fecal incontinence) is a major obstacle to performing and interpreting research. The National Institutes of Health convened the Terminology Workshop for Researchers in Female Pelvic Floor Disorders to: (1) agree on standard terms for defining conditions and outcomes; (2) make recommendations for minimum data collection for research; and (3) identify high priority issues for future research. Pelvic organ prolapse was defined by physical examination staging using the International Continence Society system. Stress urinary incontinence was defined by symptoms and testing; 'cure' was defined as no stress incontinence symptoms, negative testing, and no new problems due to intervention. Overactive bladder was defined as urinary frequency and urgency, with and without urge incontinence. Detrusor instability was defined by cystometry. For all urinary symptoms, defining 'improvement' after intervention was identified as a high priority. For fecal incontinence, more research is needed before recommendations can be made. A standard terminology for research on pelvic floor disorders is presented and areas of high priority for future research are identified.

Fecal Incontinence↗
PubMed2001

Segmentation, attention and phenomenal visual objects.

Issues concerning selective attention provoke new questions about visual segmentation, and vice-versa. We illustrate this by describing our recent work on grouping under conditions of inattention, on change blindness for background events and the residual processing of undetected background changes, on modal versus amodal completion in visual search, and the differential effects of these two forms of completion on attentional processes, and on attentional modulation of lateral interactions thought to arise in early visual cortex. Many of these results indicate that segmentation processes substantially constrain attentional processes, but the reverse influence is also apparent, suggesting an interactive architecture. We discuss how the 'proto-objects' revealed by studies of segmentation and attention (i.e. the segmented perceptual units which constrain selectivity) may relate to other object-based notions in cognitive science, and we wrestle with their relation to phenomenal visual awareness.

Attention↗
PubMed2001

Effects of high copper supplements on performance, health, plasma copper and enzymes in goats.

Six growing female Nubian goats (average BW=34.8+/-0.55kg, 7-8 months of age) were randomly assigned to either a basal diet (BD, 10-15ppm Cu/DM), or to medium Cu (MC, BD+50mgCu), or to high Cu (HC, BD+100mgCu) diets for 9 weeks. This level would cause Cu toxicity in sheep, but none occurred in the goats. Therefore, Cu supplementation was then increased to 150 and 300mg per head per day, for the following 14 weeks; to 300 and 600mg per head per day, for the next 8 weeks; and to 600 and 1200mg per head per day, for an additional 4 weeks, in the MC and HC group, respectively. Body weight and vital signs were recorded and blood samples collected at different time intervals. Hematological parameters, plasma Cu, sorbitol dehydrogenase (SDH), glutamic oxaloacetic transaminase (GOT), and gamma-glutamyl transferase (GGT) were determined. At the termination of the study, tissue Cu concentration in different organs was also determined. During first 23 weeks (<300mgCu per day) of the study there were no apparent signs of Cu toxicity. Cu supplementation at 600mg per head per day in young Nubian does, had no effect on respiration rate (RR), heart rate (HR), and decreased (P<0.05) rectal temperature (RT) in the HC group only. Leukocyte counts were positively correlated with Cu supplementation (r=+0.296, P<0.02) and negatively correlated (r=-0.254, P<0.05) with RT in the HC group. Plasma SDH increased (P<0.05) when Cu supplementation was >/=300mg per head per day, thus, SDH may serve as an early indicator of Cu toxicosis in goats. Increases (P<0.05) in GOT were noted when Cu intake was >/=600mg per head per day. Contrary to the results observed for SDH and GOT, feeding goats 50mgCu per day or more, resulted in an increased plasma GGT as compared to BD goats. Levels of SDH, GOT and GGT of the BD goats were within normal range. Plasma Cu was not indicative of Cu status of animals. Copper improved ADG by 28% at the 100-150ppm level in diet. No relationship between Cu intake and hair Cu was found in the present study. Highest concentration of Cu was found in liver, followed by duodenum, rumen and brain. Results of this study indicate that goats are more resistant to Cu toxicity than sheep. This is one of the first reports documenting significant differences in Cu requirements and tolerance between goats and sheep.

Journal Article↗
PubMed2001

Outcome of bilateral lung volume reduction in patients with emphysema potentially eligible for lung transplantation.

OBJECTIVE: Between January 1993 and May 1998, we performed 200 consecutive bilateral lung volume reduction operations. After initial assessment, 99 of these patients were eligible for lung volume reduction and potentially eligible for immediate or eventual lung transplantation on the basis of age and absence of contraindications. All chose to proceed with lung volume reduction surgery. The outcomes of these 99 patients are reviewed to assess the consequences of proceeding with lung volume reduction surgery on patients potentially eligible for lung transplantation. METHODS: A retrospective study was performed with the use of a prospectively assembled computer database. RESULTS: The 61 men and 38 women were 55 +/- 7 years old at evaluation for lung volume reduction. Mean values for first second expired volume, total lung capacity, and residual volume were 24% +/- 8%, 141% +/- 19%, and 294% +/- 54% predicted. There were 4 operative deaths and 17 late deaths. Two-year and 5-year survival after evaluation for lung volume reduction are 92% and 75%. The 32 patients who have been listed for transplantation after lung volume reduction include 15 who have undergone transplantation, 14 who remain on the list, and 3 who have been removed from the list. All 15 transplant recipients survived transplantation and 3 have subsequently died of rejection or late infection. The 12 living recipients have a median post-transplantation follow-up of 1.7 years. The age at transplantation was 58 +/- 5 years with transplantation occurring 3.8 +/- 1.1 years after lung volume reduction. Sixteen of 99 patients underwent lower lobe volume reduction with an increased rate of listing (63%, P =.008) and transplantation (38%, P =.003) compared with patients undergoing upper lobe volume reduction. Patients listed for transplantation were younger, more impaired, and experienced less benefit from lung volume reduction than patients not yet listed for transplantation. CONCLUSIONS: The preliminary use of lung volume reduction in patients potentially suitable for transplantation does not appear to jeopardize the chances for subsequent successful transplantation.

Contraindications↗
PubMed2001

Can attention select only a fixed number of objects at a time?

Several previous studies have suggested that we may attend only a fixed number of 'objects' at a time. However, whereas findings from two-target experiments suggest that we can attend only one object at a time, other results from object-tracking and enumeration paradigms point instead to a four-object limit. Here, we note that in these previous studies the number of objects covaried with the overall size and complexity of the stimulus, such that apparent one-object or four-object limits in those tasks may reflect changes in the complexity of attended stimuli, rather than the number of objects per se. Accordingly, in the current experiments we employ stimuli in which the number of objects varies, while overall size and complexity are held constant. Using these refined measures of object-based effects, we find no evidence for a one-object or four-object limit on attention. Indeed, we conclude that the number of attended objects does not affect how efficiently we can attend a given stimulus. We propose and test an alternative approach to object-based attention limitations based on within-object and between-object feature-binding mechanisms in human vision.

Adult↗
PubMed2001

Evaluation of features of syndrome X in offspring of Caribbean patients with Type 2 diabetes.

OBJECTIVE: To determine whether the features of metabolic syndrome X are more common in offspring of patients with Type 2 diabetes than in control subjects without immediate family history of diabetes. MATERIALS AND METHODS: Thirty-four young offspring of patients with Type 2 diabetes and 27 healthy control subjects underwent a standard oral glucose tolerance tests (OGTT; 75 g glucose in 300 ml water). Anthropometric indices, blood pressure, plasma glucose, serum lipids and insulin levels were measured. Homeostasis model assessment (HOMA) was used to assess basal insulin resistance (IR) and sensitivity (%S). RESULTS: The offspring had significantly higher mean+/-SD BMI (p<0.01) and basal serum triglyceride (p<0.05), insulin (p<0.05), insulin/glucose ratio (p<0.01), and lower %S (p<0.001) than the control subjects, in spite of similar fasting plasma glucose concentrations. Multiple linear regression analysis showed that these differences were independent of BMI. Although, the two groups of subjects had similar serum HDL-Cholesterol, LDL-cholesterol and blood pressure levels, %S was significantly related to diastolic BP (p<0.01) and serum triglyceride levels (p<0.01). CONCLUSIONS: In comparison with the healthy control subjects, the insulin resistant offspring have higher levels of the identified syndrome X features independent of obesity. These features were quantitatively lower than the values reported in offspring of white Caucasian and African-American patients.

Adult↗
PubMed2001

Role of endothelin ET(A) receptor antagonism in the post-transplant renal response to angiotensin II in the rat.

The role of endothelins in the renal damage associated with ischaemic-reperfusion (I-R) injury during organ transplantation was determined by selective blockade of the ET(A) receptors with the receptor antagonist ABT-627. The integrity of kidney function was determined 2 and 8 weeks after transplantation by investigation of the renal response to angiotensin II. Under pentobarbitone anaesthesia (70 mg x kg(-1), I.P.), rats underwent a right nephrectomy. Transplantation of the left kidney was performed after 2 h cold ischaemia without or with ABT-627 treatment. Control animals underwent left renal denervation. The renal response to angiotensin II was measured 2 weeks later following blockade of endogenous production of angiotensin II with captopril. A further transplant group was allowed to recover for 8 weeks before the terminal study. In the control group, angiotensin II reduced renal blood flow (RBF), glomerular filtration rate (GFR), urine flow rate (UV), and fractional sodium excretion (FE(Na)) by 29 +/- 5 %, 19 +/- 4 %, 25 +/- 4 % and 32 +/- 7 %, respectively. Conversely, in the transplant group, angiotensin II left RBF unchanged and increased GFR (59 +/- 12 %) and UV (93 +/- 8 %). FE(Na) decreased by 24 +/- 9 %. In both the transplant group treated with ABT-627 and the long-term recovery group, the renal response to angiotensin II was normalised. In conclusion, renal transplantation following 2 h cold I-R injury resulted in a temporary abnormal renal response to angiotensin II, which was reversed by ET(A) receptor antagonism at the time of transplantation.

Angiotensin II↗
PubMed2001

Managing the pharmaceutical industry-health system interface.

BACKGROUND: Direct-to-consumer advertising, media, and Internet marketing to physicians and patients, as well as enticing marketing strategies, are used by the pharmaceutical industry to ensure market share growth of new drugs. Our health system adopted a strict vendor policy governing detailing and sampling activities of pharmaceutical representatives, but realized that further analysis of vendor influence in our system was needed. OBJECTIVE: An assessment of tangible benefits, ethical concerns, and financial liabilities and gains was conducted to reassess the need for further vendor restriction. CONCLUSIONS: Based on our findings, several recommendations have been made. Medical practices and health systems are encouraged to establish and enforce explicit vendor policies, measure their effectiveness, partner proactively with representatives to deliver a drug-detailing message consistent with system initiatives, monitor and regulate continuing medical education funding, and implement strategies to ensure appropriate drug use.

Advertising↗
PubMed2001

Insulin secretion in glucose-tolerant offspring of type 2 diabetes patients in Trinidad, West Indies.

BACKGROUND: Genetics and environmental factors play vital roles in type 2 diabetes. To gain insight into its pathogenesis, early study of offspring of affected patients is needed. METHODS: Thirty-four offspring of patients with type 2 diabetes and 27 nondiabetic control subjects matched for sex, height, weight, and waist-to-hip ratio had standard oral glucose tolerance tests (75 g glucose in 300 mL water). Homeostasis model assessment was used in measuring insulin resistance and sensitivity. RESULTS: Offspring had significantly higher mean fasting serum insulin (126.6 +/- 10.3 vs 87.5 +/- 6.9 pmol/L), incremental insulin at 30 to 150 minutes, and body mass index and lower insulin sensitivity than control subjects (49.9% +/- 3.1% vs. 71.9% +/- 5.6%), despite similar fasting plasma glucose concentrations. CONCLUSIONS: As in other populations, the offspring of Caribbean patients with type 2 diabetes are at greater risk for development of diabetes independent of obesity.

Adult↗