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Biomedical subjects

B Davis

Publications and source records attributed to B Davis.

At least 55 records · Page 3Linked to original sources
PubMed2000

Effect of gastrin-releasing peptide on rat hippocampal extracellular GABA levels and seizures in the audiogenic seizure-prone DBA/2 mouse.

Gastrin-releasing peptide (GRP), a selective agonist for the BB(2) subtype of bombesin receptor, is reported to depolarise GABAergic interneurons in the stratum oriens layer of the hippocampus. Such an action might lead to increased extracellular levels of GABA in the hippocampus, and result in an anti-convulsant effect with this peptide. We have tested this hypothesis by determining the effect of GRP on extracellular levels of GABA in the ventral hippocampus of the freely moving rat using in vivo microdialysis, and by intracerebroventricular (i.c.v.) administration of GRP to audiogenic seizure-prone DBA/2 mice prior to exposure to the noise of an electric bell. Following local perfusion in the ventral hippocampus by reverse dialysis GRP (10 microM) significantly raised levels of GABA in the recovered dialysates by approximately 40%. In the seizure studies, GRP (30-300 ng) increased the latency to tonic seizure, the number of mice convulsing and reduced the incidence of lethality. In both dialysis and seizure studies, the effects of GRP were blocked by the selective BB(2) receptor antagonist, [D-Phe(6), Leu-NHEt(13)]bombesin (6-13). These experiments provide further functional evidence that activation of the BB(2) receptor may modulate neurotransmission in the hippocampus, and that this action may confer anti-convulsant properties on agonists acting at the BB(2) receptor in the brain.

Animals↗
PubMed2000

Relation of low body mass to death and stroke in the systolic hypertension in the elderly program. The SHEP Cooperative Research Group.

BACKGROUND: There are scant data on the effect of body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) on cardiovascular events and death in older patients with hypertension. OBJECTIVE: To determine if low body mass in older patients with hypertension confers an increased risk of death or stroke. PATIENTS: Participants were 3975 men and women (mean age, 71 years) enrolled in 17 US centers in the Systolic Hypertension in the Elderly Program trial, a randomized, double-blind, placebo-controlled clinical trial of lowdose antihypertensive therapy, with follow-up for 5 years. MAIN OUTCOME MEASURES: Five-year adjusted mortality and stroke rates from Cox proportional hazards analyses. RESULTS: There was no statistically significant relation of death or stroke with BMI in the placebo group (P = .47), and there was a U- or J-shaped relation in the treatment group. The J-shaped relation of death with BMI in the treated group (P = .03) showed that the lowest probability of death for men was associated with a BMI of 26.0 and for women with a BMI of 29.6; the curve was quite flat for women across a wide range of BMIs. For stroke, men and women did not differ, and the BMI nadir for both sexes combined was 29, with risk increasing steeply at BMIs below 24. Those in active treatment, however, had lower death and stroke rates compared with those taking placebo. CONCLUSIONS: Among older patients with hypertension, a wide range of BMIs was associated with a similar risk of death and stroke; a low BMI was associated with increased risk. Lean, older patients with hypertension in treatment should be monitored carefully for additional risk factors.

Aged↗
PubMed2000

Comparison of Abbott LCx Chlamydia trachomatis assay with Gen-Probe PACE2 and culture.

In this study the LCx assay (a nucleic acid amplification assay) for Chlamydia trachomatis in endocervical samples was compared with the Gen-Probe PACE2 assay (a nucleic acid probe assay) for endocervical samples, and with endocervical culture. In addition, the efficacy of the LCx assay was determined for midstream clean-catch urine samples because it is often necessary to obtain such a sample for routine urine culture and it is simpler to collect only a single sample without also collecting a first-void urine for LCx. Endocervical specimens from 205 patients were tested for C. trachomatis via LCx and PACE2. Of these patients, 203 were tested by culture. Midstream clean-catch urine samples from 75 of these patients were tested by LCx. The sensitivities and specificities for these assays, after discrepant analysis, were 100 and 98.9% for LCx of endocervical samples, 52.4 and 100% for PACE2; and 71.4 and 100% for culture. The sensitivity/specificity of LCx for midstream clean-catch urines was 66.7/98.5%. The apparent prevalence of C. trachomatis in our population was 10.2%. These data indicate that among the methods tested, LCx of endocervical samples had the highest sensitivity for C. trachomatis in this population. The sensitivity of the urine LCx assay using midstream clean-catch collected urines was considerably less than that reported in other studies that used first-void urines but was higher than that of PACE2.

Adolescent↗
PubMed2000

2D CSI proton MR spectroscopy of human spinal vertebra: feasibility studies.

This report focuses on proton magnetic resonance spectroscopy (1H MRS) of spine vertebra acquired with two-dimensional chemical shift imaging (2D CSI), utilizing the stimulated echo acquisition mode (STEAM) sequence. Both validity and reproducibility studies were performed. To validate the 2D CSI method, its spectra were compared with those obtained with the single-voxel (SV) method. Five normal volunteers were scanned. The reproducibility of 2D CSI was examined by performing spectroscopy on two different occasions, on three normal volunteers. Data show that the STEAM 2D CSI technique results in MRI spectra comparable to those obtained with the STEAM SV method. 2D CSI offers significant time savings and convenient multi-voxel spectral analysis at a substantially higher signal-to-noise ratio. The 2D CSI method was then applied to a patient with a small vertebral hemangioma. The results demonstrated that the voxels containing the hemangioma exhibit different spectra than the neighboring voxels of the same vertebra. Additionally, a case of vertebral osteoporosis was investigated. Results showed a significant increase in the lipid-to-water ratio (LWR). It is suggested that 2D CSI may be powerful in identifying physiological as well as pathological changes of the bone marrow. Furthermore, covering a more extensive area of the vertebral body will maximize the chances of depicting a small focus of pathologic tissue. A more detailed bone marrow pattern was noticed in on one subject whose spectra show more lipid peaks.

Adult↗
PubMed2000

Surgical management of hereditary pancreatic cancer.

Pancreatic cancer continues to be a leading cause of cancer death in the United States. Seven genetic syndromes are now known to be associated with an increased incidence of pancreatic cancer. Other familial forms of pancreatic cancer exist although the genetic basis for this predisposition remains elusive. The similarities in the genetic and clinical manifestations of the sporadic and familial forms of pancreatic cancer suggest that pretreatment staging and management of patients with established pancreatic cancer should be similar. For carcinomas of the pancreatic head, pancreaticoduodenectomy should be performed according to current surgical practice, whereas the use of total pancreatectomy should be limited to cases in which margins are found to be positive or if the anatomy precludes a safe pancreaticojejunostomy. Total pancreatectomy may be considered in high-risk kindreds who strongly desire prophylactic surgery and in those with premalignant lesions. Identification of the precise genetic basis for inherited pancreatic cancer will someday make it possible to examine scientifically the effectiveness of specific management strategies.

Adenocarcinoma↗
PubMed2000

Regulation of negative affect during mother-child problem-solving interactions: adolescent depressive status and family processes.

Despite recent suggestions that depression can be conceptualized as a disorder of affect regulation, relatively little research has focused on affect regulation skills in depressed individuals. This paper investigated whether depressed adolescents (N = 25) differ from nondepressed adolescents (N = 25) on two indices of affect regulation (i.e., duration of negative affective states and reciprocity of maternal negative affect) as well as whether these indices are related to microsocial family interactional processes. Analyses revealed that depressed teens differed from their nondepressed peers with regard to duration of negative affective states but not in their likelihood of reciprocating negative affect. Additionally, indices of adolescent affect regulation were related to family interactional processes. Duration of depressive affect was positively associated with maternal display of facilitative behavior contingent on adolescent depressive behavior. Duration of aggressive behavior was inversely related to maternal problem-solving responses to aggressive behavior. Finally, adolescent reciprocity of maternal depressive and aggressive behaviors was strongly associated with mothers' reciprocity of adolescents' negative affective behavior.

Adolescent↗
PubMed2000

Adolescent responses to depressive parental behaviors in problem-solving interactions: implications for depressive symptoms.

The purpose of this study was to explore the relations between child responses to interparental depressive behavior and subsequent child depressive symptomatology. Data were collected on 156 two-parent families. Families completed questionnaire data and participated in problem-solving interactions, which were coded using a microsocial observational system. Three potential child responses to interparental depressive behavior were examined: facilitative, aggressive, and depressive. Results indicated that for female adolescents the displays of facilitative and depressive behavior as well as the suppression of aggressive behavior in response to interparental depressive behavior were related to increases in depressive symptomatology. For males, on the other hand, the display of aggressive and depressive behavior in response to interparental depressive behavior was related to increases in depression. Results provide preliminary support both for the examination of child responses to conflictual marital behavior and for expanding the conceptualization of conflictual marital behaviors to include depressive as well as the more traditionally examined aggressive behaviors, in order to better understand the link between conflictual marital behavior and child depressive symptomatology.

Adolescent↗
PubMed2000

Analysis of cathepsin D in human breast cancer: usefulness of the processed 31 kDa active form of the enzyme as a prognostic indicator in node-negative and node-positive patients.

The relative amounts of the precursor (52 kDa) and processed (31,27 kDa) forms of cathepsin D have been analyzed by Western blotting in biopsied breast tissue cytosols from 134 lesions from invasive breast cancer patients, 24 lesions from patients with ductal carcinoma in situ (DCIS), 227 lesions from benign breast disease patients, and 28 lesions from normal control subjects. The mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.001) in the invasive breast cancer group compared to the other three groups. In addition, the mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.05) in node-positive compared to node-negative breast cancer patients. In the benign breast disease group, patients with proliferative-type disease had a significantly increased (p = 0.02) mean relative percentage amount of the 31 kDa form of cathepsin D compared to patients with nonproliferative-type disease. Invasive breast cancer patients were followed for up to 75 months to determine if the relative percentage amount of the 31 kDa form of cathepsin D was predictive of disease-free and overall survival. Although the amount of the 31 kDa form was not predictive of disease-free survival, patients in the 'high' 31 kDa group (> 18%) were significantly (p < 0.05) more likely to die than patients in the 'low' 31 kDa group (< or = 18%). The 12 patients who died were all node-positive and in the high 31 kDa group. It thus appears that the relative amount of the processed, active 31 kDa form of cathepsin D is a useful prognostic indicator, at least in node-positive breast cancer patients.

Adult↗
PubMed2000

Lack of neuropeptide Y receptor detection in human bladder and prostate.

OBJECTIVE: To investigate the presence of functional neuropeptide Y (NPY) receptors in human bladder and prostate (both richly endowed with NPY-containing nerve fibers) using peptide YY (PYY) as the agonist. Materials and methods Binding studies were conducted using [125I]PYY as the radioligand. Organ-bath studies were performed on isolated tissue strips for direct (postjunctional) contractile effects and for (prejunctional) inhibition of field stimulation effects. Any possible degradation of PYY was determined using high-performance liquid chromatography (HPLC). RESULTS: In the radioligand binding studies no quantifiable specific [125I]PYY binding was detected in human bladder or prostate, while specific high-affinity binding was readily seen in rat cerebral cortex. In organ-bath experiments, PYY (up to 1 micromol/L) caused no contraction of human prostate or bladder, whereas noradrenaline and carbachol, respectively, were effective; the potency or efficacy of noradrenaline and carbachol were not altered by PYY. Field stimulation-induced contraction was not affected by PYY in either human bladder or prostate, but was readily inhibited in rat vas deferens. HPLC detected no relevant PYY degradation by human bladder or prostate homogenates. CONCLUSION: Human bladder and prostate express only very few if any functional NPY receptors.

Animals↗
PubMed2000

Altered hormonal responsiveness of proliferation and apoptosis during myometrial maturation and the development of uterine leiomyomas in the rat.

Uterine leiomyomas are responsive to the ovarian steroids, estrogen and progesterone; however, a mechanistic understanding of the role of these hormones in the development of this common gynecologic lesion remains to be elucidated. We have used the Eker rat uterine leiomyoma model to investigate how ovarian hormones regulate or promote the growth of these tumors. Proliferative and apoptotic rates were quantitated in normal uterine tissues and leiomyomas in response to endogenous ovarian steroids. In 2- to 4-mo-old animals, cell proliferation in the normal uterus corresponded with high serum levels of steroid hormones during the estrous cycle, and apoptosis occurred in the rat uterus in all cell types following sharp, cyclical declines in serum hormone levels. It is interesting that the responsiveness of uterine mesenchymal cells changed between 4 and 6 mo of age, with significant decreases in both proliferative and apoptotic rates observed in myometrial and stromal cells of cycling animals. Leiomyomas displayed much higher levels of proliferation than did age-matched myometrium; however, their apoptotic index was significantly decreased in comparison with normal myometrium. This disregulation between proliferative and apoptotic responses, which were tightly regulated during ovarian cycling in the normal myometrium, may contribute to the disruption of tissue homeostasis and underlie neoplastic growth of these tumors.

Aging↗
PubMed2000

Efficacy of sustained-release bupropion in neuropathic pain: an open-label study.

OBJECTIVE: The purpose of this study was to assess the analgesic potential of sustained-release (SR) bupropion for neuropathic pain. DESIGN: Open-label treatment design. SETTING: Outpatient pain clinic, University of Arizona Health Sciences Center, Tucson, Arizona. PATIENTS: Twenty-two patients with a diagnosis of neuropathic pain. INTERVENTIONS: Patients with neuropathic pain received 1 week of 150 mg SR bupropion once daily followed by 7 weeks of 150 mg SR bupropion twice daily. OUTCOME MEASURES: Treatment effects were assessed by daily ratings of pain intensity, posttreatment global ratings of pain relief, depression scores (Hamilton Depression Scale), and daily ratings of side effects. RESULTS: Fifteen patients (68%) reported that their pain relief was improved or much improved with bupropion. The mean average pain score at week 1 was 6.7, which decreased at the end of week 8 to 5.3 (paired t test, t[df = 21]3.327; p = 0.003) in all patients studied and to 3.8 (paired t test, t[df = 14]3.754; p = 0.002) in the patients who improved. Pain relief was statistically significant at week 5 (paired t test, t[df = 21]3.816; p = 0.001) and continued throughout weeks 6, 7, and 8. Most patients were not depressed, and analgesia was observed to occur without change in depression ratings in most patients who responded. Side effects were rated as mild and consisted primarily of insomnia (8 patients), tremor (3 patients), and gastrointestinal upset (2 patients). These symptoms had a tendency to recede with continuation of therapy. CONCLUSIONS: This uncontrolled pilot study suggests that bupropion may be an effective and tolerated treatment for some patients with neuropathic pain. Blockade of norepinephrine reuptake may mediate this effect. The role of dopamine reuptake blockade is uncertain. A larger randomized, double-blind, placebo-controlled study is currently underway to confirm these preliminary results.

Adult↗
PubMed2000

The accuracy and precision performance of four videokeratoscopes in measuring test surfaces.

In this study we evaluated the accuracy and precision of three placido-disk videokeratoscopes (the Keratron, Medmont and TMS) and one videokeratoscope that uses the raster-stereogrammetry technique (PAR-CTS) in elevation topography with six test surfaces. The test surfaces were a sphere, an asphere, a multicurve, and three bicurve surfaces. Each instrument performed well on certain test surfaces, but none of the instruments excelled on all of the surfaces. The results showed high accuracy of the Keratron and Medmont instruments in measuring the sphere, asphere, and multicurve surfaces, but not the bicurve surfaces. The precision of the Keratron and Medmont instruments were high. The TMS and PAR-CTS instruments showed poorer accuracy than the Keratron and Medmont instruments for the multicurve test surface but showed better performance for the bicurve surfaces. The PAR-CTS had the poorest performance in precision of the four instruments. The use of the Noryl spherical test surface instead of polymethyl methacrylate (PMMA) resulted in small differences in the accuracy performance of the placido-disk videokeratoscopes only.

Cornea↗
PubMed2000

A single intramuscular injection of recombinant plasmid DNA induces protective immunity and prevents Japanese encephalitis in mice.

Plasmid vectors containing Japanese encephalitis virus (JEV) premembrane (prM) and envelope (E) genes were constructed that expressed prM and E proteins under the control of a cytomegalovirus immediate-early gene promoter. COS-1 cells transformed with this plasmid vector (JE-4B clone) secreted JEV-specific extracellular particles (EPs) into the culture media. Groups of outbred ICR mice were given one or two doses of recombinant plasmid DNA or two doses of the commercial vaccine JEVAX. All mice that received one or two doses of DNA vaccine maintained JEV-specific antibodies 18 months after initial immunization. JEVAX induced 100% seroconversion in 3-week-old mice; however, none of the 3-day-old mice had enzyme-linked immunosorbent assay titers higher than 1:400. Female mice immunized with this DNA vaccine developed plaque reduction neutralization antibody titers of between 1:20 and 1:160 and provided 45 to 100% passive protection to their progeny following intraperitoneal challenge with 5,000 PFU of virulent JEV strain SA14. Seven-week-old adult mice that had received a single dose of JEV DNA vaccine when 3 days of age were completely protected from a 50, 000-PFU JEV intraperitoneal challenge. These results demonstrate that a recombinant plasmid DNA which produced JEV EPs in vitro is an effective vaccine.

Animals↗
PubMed2000

Normal lumbar vertebrae: anatomic, age, and sex variance in subjects at proton MR spectroscopy--initial experience.

Fifty-seven subjects underwent proton magnetic resonance (MR) spectroscopy of the second lumbar vertebra to evaluate single-voxel and multivoxel techniques. Measurements included lipid-to-water ratios, lipid fractions, and line width. These data provide information about vertebral fat content. There was an age-dependent linear increase in fat content and sex dependence. A higher fat concentration was found in men. The observed spectra provide a basis for future study to determine clinical utility of vertebral proton MR spectroscopy.

Adolescent↗
PubMed2000

The consequences of anterior femoral notching in total knee arthroplasty. A biomechanical study.

BACKGROUND: Notching of the anterior femoral cortex during total knee arthroplasty has been implicated as a cause of subsequent periprosthetic supracondylar femoral fracture. However, other than observational clinical data, no reliable association between these events has been established, to our knowledge. The purpose of the present study was to investigate the biomechanical effects of notching of the anterior femoral cortex. METHODS: The femoral component of a total knee replacement was implanted in twelve matched pairs of human cadaveric femora; one specimen in each pair had preservation of the anterior femoral cortex, and the other had a full-thickness cortical defect created just proximal to the anterior flange of the femoral component. The pairs were then subjected to either bending or torsional loading to failure. Both the fracture pattern and the quantitative load to failure were analyzed. Two matched pairs were excluded from the analysis because of inadvertent fracture during placement of the component. RESULTS: Following the application of a bending load, femora with notching of the anterior femoral cortex sustained a short oblique fracture that originated at the cortical defect proximal to the femoral component and femora without notching had a midshaft fracture. In contrast, notching of the anterior femoral cortex had no effect on the fracture pattern that was observed after the application of a torsional load. The mean load to failure was significantly reduced by notching in both testing modes. Notching decreased bending strength from 11,813 to 9690 newtons (18 percent; p = 0.0034), and it decreased torsional strength from 134.7 to 81.8 newton-meters (39.2 percent; p = 0.01). CONCLUSIONS: Biomechanical testing demonstrated that notching of the anterior femoral cortex significantly lessens the load to failure following total knee arthroplasty and influences the subsequent fracture pattern. These effects are manifested in different ways under the two loading conditions: the fracture pattern is altered under bending load, and there is a greater quantitative decrease in load to failure with torsional loading. CLINICAL RELEVANCE: Weakening of the femur by notching of the anterior cortex after total knee arthroplasty may warrant alteration in the customary postoperative regimen for these patients. Manipulation of a total knee replacement with a notched anterior femoral cortex should probably be avoided.

Aged↗
PubMed1999

Diagnostic marker cooperative study for the diagnosis of myocardial infarction.

BACKGROUND: Millions of patients present annually with chest pain, but only 10% to 15% have myocardial infarction. Lack of diagnostic sensitivity and specificity of clinical and conventional markers prevents or delays treatment and leads to unnecessary costly admissions. Comparative data are lacking on the new markers, yet using all of them is inappropriate and expensive. METHODS AND RESULTS: The Diagnostic Marker Cooperative Study was a prospective, multicenter, double-blind study with consecutive enrollment of patients with chest pain presenting to the emergency department. Diagnostic sensitivity and specificity and frequency of increase in patients with unstable angina were determined for creatine kinase-MB (CK-MB) subforms, myoglobin, total CK-MB (activity and mass), and troponin T and I on the basis of frequent serial sampling for </=24 hours. Of 955 patients with chest pain, 119 (12.5%) had infarction identified by use of CK-MB mass, and 203 (21%) had unstable angina. CK-MB subforms were most sensitive and specific (91% and 89%) within 6 hours of onset, followed by myoglobin (78% and 89%). For late diagnosis, total CK-MB activity (derived from subforms) was the most sensitive and specific (96% and 98%) at 10 hours from onset, followed by troponin I (96% and 93%), but not until 18 hours, and troponin T (87% and 93% at 10 hours). In unstable angina, CK-MB subforms were increased in 29.5%, myoglobin in 23.7%, troponin I in 19.7%, and troponin T in 14.8%. All markers were increased in 99 patients. With each marker as the diagnostic standard, CK-MB subforms and myoglobin remained the most sensitive for early diagnosis. CONCLUSIONS: The CK-MB subform assay alone or in combination with a troponin reliably triages patients with chest pain and should lead to improved therapy and reduced cost.

Angina, Unstable↗