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Biomedical subjects

B Davis

Publications and source records attributed to B Davis.

At least 199 records · Page 11Linked to original sources
PubMed1987

Phosphate content of human amniotic fluid and its relationship to bacterial growth inhibition.

A sensitive method for assay of phosphate has been adapted for use with human amniotic fluid. The presence of an antibacterial factor in amniotic fluid inactivated by phosphate suggested that measurement of free phosphate may predict antibacterial activity and hence susceptibility to intrapartum infection. The intrinsic antibacterial activity of amniotic fluid was altered by addition of large amounts of phosphate, but the intrinsic concentration of free phosphate correlated poorly with antibacterial activity and organically combined phosphates did not appear to be related to the antibacterial property.

Amniotic Fluid↗
PubMed1986

Chloride transport in human placental microvillus membrane vesicles. I. Evidence for anion exchange.

36Cl uptake by microvillus brush border membrane vesicles prepared from normal term human placenta has been studied using an ion exchange column assay and a novel method to correct for vesicle recovery. Uptake of this anion, which was largely into an osmotically active space, was time dependent with a half-time of approximately 4 min at 4 degrees C. DIDS at a maximal inhibitory concentration inhibited 36Cl uptake by approximately 40%; furosemide (10(-4)M) showed a similar degree of inhibition and the effects of the two drugs appeared not to be additive. Anions including Cl, Br, I, NO3, salicylate and SCN reduced 36Cl uptake, the latter two being the most potent; gluconate was without effect. Inhibition by maximal inhibitory concentrations of DIDS and the anions SCN and salicylate was not additive. Neither the DIDS-sensitive nor the SCN-sensitive component of 36Cl uptake was influenced by membrane potential; in contrast the inhibitor-insensitive component was increased by an inside positive membrane potential. These findings suggest that under the conditions employed an electroneutral anion exchange system is responsible for approximately half of the chloride flux across this plasma membrane.

Cell Membrane Permeability↗
PubMed1986

Suicide and parasuicide in a northern Canadian native community.

This report describes suicide and parasuicide in a small, remote northern Canadian native community for a three-year period from 1981 to 1984. The overall rate for suicide was 77 per 100,000, with a rate of 241 for male Treaty Indians age 20 - 24. Parasuicide in the form of overdose was epidemic, with a rate of 7,722 per 100,000 in Treaty Indian females age 15 - 19. None of the completed suicides had previous contact with the mental health system or previous parasuicides. The public health implications of these figures are discussed.

Adolescent↗
PubMed1986

Extended sphincteroplasty for juxtapapillary duodenal diverticulum.

The application of the sphincteroplasty in the treatment of juxtapapillary diverticulum is presented. The relative simplicity of the procedure compared with excision or diversions, or both, may allow more aggressive treatment of such diverticula in borderline situations. In addition, this approach raises the possibility that the sphincteroplasty might be accomplished endoscopically in situations in which the gallbladder has been removed and biliary tract symptoms persist.

Ampulla of Vater↗
PubMed1986

Metabolism and excretion of nitrofurothiazole bladder carcinogens.

Nitrofurothiazoles such as 2-amino-4-(5-nitro-2-furyl) thiazole (ANFT) and N-formylated ANFT (FANFT) are model compounds used in the study of chemical carcinogenesis. FANFT is a more potent uroepithelial carcinogen than ANFT but previous studies have shown extensive deformylation of FANFT to ANFT in vivo and ANFT to be the putative proximate carcinogen. To investigate this paradox, disposition of radiolabeled FANFT and ANFT was determined in rats prepared for clearance experiments. After 2 hr, 27.3 +/- 2.1% of recovered ANFT was excreted in urine compared to 44.2 +/- 1.8% of FANFT (P less than .001). In addition, approximately 20% of both FANFT and ANFT were excreted in bile after 2 hr. The disposition of nonradiolabeled FANFT and ANFT was also determined. The urinary excretion rate for ANFT with i.v. ANFT administration was 0.9 +/- 0.1 nmol/min. Following i.v. FANFT administration, the urinary excretion rate for ANFT was 49.7 +/- 8.6 nmol/min (P less than .001). The elimination half-lives were 23 +/- 3 and less than 5 min, for ANFT and FANFT, respectively. The differences in renal handling of ANFT and FANFT could not be accounted for by differences in protein binding. Large differences were found in urinary metabolite excretion between FANFT and ANFT administration. These results demonstrate deformylation dependent excretion (renal metabolic/excretory coupling) exists for FANFT resulting in much higher concentrations of ANFT reaching the urinary tract than when ANFT only is administered. Biliary excretion accounts for significant early clearance of both ANFT and FANFT. Renal metabolic/excretory coupling may explain the difference in uroepithelial carcinogenicity between FANFT and ANFT.

Animals↗
PubMed1985

Adult vitelliform macular detachment occurring in patients with basal laminar drusen.

We studied 41 young and middle-aged adults who developed innumerable, small, round, uniformly sized, yellow, subretinal nodules that were often arranged in clusters throughout the posterior fundus. Angiographically, they fluoresced discretely during the early arteriovenous phase. In middle or later life 17 of these patients developed visual loss caused by vitelliform retinal detachment in the macula of one or both eyes. Spontaneous resolution of the detachment and retention of good visual acuity occurred frequently. We found evidence indicating that the multiple, small, subretinal nodules are probably focal areas of pigment epithelial attenuation overlying nodular thickenings of the basement membrane of the pigment epithelium. The term basal laminar drusen would distinguish these nodules from those of typical drusen, which are caused by focal detachments of attenuated pigment epithelium and its usually normal-thickness basement membrane from the inner collagenous zone of Bruch's membrane.

Adult↗
PubMed1985

Pulmonary C-fibers reflexly increase secretion by tracheal submucosal glands in dogs.

Stimulation of bronchial C-fibers evokes a reflex increase in secretion by tracheal submucosal glands, but the influence of pulmonary C-fibers on tracheal gland secretion is uncertain. In anesthetized dogs with open chests, we sprayed powdered tantalum on the exposed mucosa of a segment of the upper trachea to measure the rate of secretion by submucosal glands. Secretions from the gland ducts caused elevations (hillocks) in the tantalum layer. We counted hillocks at 10-s intervals for 60 s before and 60 s after we injected capsaicin (10-20 micrograms/kg) into the right atrium to stimulate pulmonary C-fiber endings. Right atrial injection of capsaicin increased the rate of hillock formation fourfold, but left atrial injection had no significant effect. The response was abolished by cutting the vagus nerves or cooling them to 0 degree C. We conclude that the reflex increase in tracheal submucosal gland secretion evoked by right atrial injection of capsaicin was initiated as capsaicin passed through the pulmonary vascular bed, and hence that pulmonary C-fibers, like bronchial C-fibers, reflexly increase airway secretion.

Animals↗
PubMed1984

Magnetic resonance imaging in cystic fibrosis.

A clinical dilemma in patients with cystic fibrosis is the determination of the nature of linear areas of decreased aeration in the lungs. It is difficult using chest roentgenograms or even computed tomography to differentiate atelectasis, mucoid impacted bronchi, or peribronchial inflammatory disease from normal pulmonary vascularity. Magnetic resonance imaging is a noninvasive sensitive means that provides the distinction. Pulmonary vessels are easily identified, because with the spin-echo sequence that we use, the rapidly flowing blood within the vessels has no signal intensity. In contradistinction, mucoid-impacted bronchi appear as high-intensity linear branching structures. Peribronchial inflammatory disease appears as curvilinear areas of high intensity, representing inflammatory edema, around central lucencies representing bronchi.

Adolescent↗
PubMed1984

[Intratumoral regional differences in hormone receptor status of breast cancer].

Biopsy specimens of tissue were taken from 32 invasive carcinomas of the breast, in each case from the centre of the tumour, the tumour margin and the surrounding mammary gland tissue. After preparation of a frozen section for tissue identification, the concentration of oestrogen and progesteron receptors (ER and PR, respectively) was determined in each specimen by means of the dextrane-coated charcoal method. On the basis of these measured values, the receptor status of each specimen was classified either as positive (R+), borderline value (BL) or as negative (R-). Various morphological parameters were compared with the measured data. 9 (28%) of the 32 carcinomas demonstrated such high intratumoural differences in receptor concentration that the receptor status was classified quite differently in each of them. Formation of tubuli of the invasive ductal carcinomas was more marked with the R+ tumours (p = 0.005) than with the R- tumours. The quantitative ER content did not correlate with the abundance of the tissue specimen (r = 0.182). The regional differences in receptor status could not be explained, neither by the abundance in cells nor by morphological peculiarities of the tumour. - It follows from the results of this study that intratumoural regional variations in ER and PR concentrations can occur in carcinoma of the breast, and that such variations can have clinical significance.

Breast Neoplasms↗
PubMed1984

Critical assessment of antibacterial properties of human amniotic fluid.

A low molecular weight fraction of human amniotic fluid was found to be rapidly bactericidal for Escherichia coli ATCC 33908. Incubation in an atmosphere of CO2 but not N2 diminished the antibacterial effect suggesting that loss of CO2 and change in pH may be partly responsible for the observed antibacterial activity of the low molecular weight fraction of amniotic fluid. Incubation in pH 8.5 buffers did not duplicate the rapid killing of bacteria observed in the low molecular weight fraction of amniotic fluid, suggesting that elevated pH and an antibacterial factor from amniotic fluid act synergistically. The pH change in amniotic fluid which occurs in room atmosphere may account for some of the antibacterial effect which has been reported for amniotic fluid incubated aerobically.

Amniotic Fluid↗