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Biomedical subjects

B Davis

Publications and source records attributed to B Davis.

At least 217 records · Page 12Linked to original sources
PubMed1984

Identification of beta variant hemoglobins by DNA restriction endonuclease mapping.

An alternative method for identifying beta variant hemoglobins is described. Computer analysis of restriction sites was used to predict which beta variants could be detected by DNA mapping. 61 of 217 variants were shown to have changes in restriction fragment patterns which were useful markers for the abnormal hemoglobin. A further 25 could be identified by polyacrylamide electrophoresis. Implications of DNA analysis in diagnosis of variant hemoglobins are discussed.

Base Sequence↗
PubMed1984

Enhancement of the antibacterial property of amniotic fluid by hyperthermia.

The intrinsic ability of human amniotic fluid to prevent growth of Escherichia coli varies with the test strain employed, but is enhanced by increasing the temperature of incubation, as demonstrated by viable counts of test organisms in amniotic fluid compared with growth media at various temperatures. The antibacterial activity of amniotic fluid is reversed at all temperatures by the addition of potassium phosphate, but residual inhibition is seen at temperatures above 37C. When purified inhibitor preparations are tested, complete reversal by phosphate at the highest temperatures is seen. Thus, the augmented inhibition in whole amniotic fluid depends on the combined effects of phosphate-sensitive and -insensitive inhibitors. Test organisms in the presence of partially purified inhibitor were not adversely affected at 4C, indicating that bacteria must be metabolically active to be inhibited. It is concluded that temperatures above 37C enhance the antibacterial effect. This may enhance protection during pyrexia.

Amniotic Fluid↗
PubMed1983

Model students.

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Education, Nursing↗
PubMed1983

Anaplastic thyroid cancer presenting with hyperthyroidism.

Primary thyroid malignancies typically do not interfere with thyroid function. A patient is reported with anaplastic thyroid carcinoma presenting with hyperthyroidism; this is believed to be the first such case described. Prior to the onset of the thyroidal process, the patient was clinically euthyroid. It is concluded that the mechanism of thyrotoxicosis is analogous to that of subacute thyroiditis: rapid tissue necrosis with resultant release of thyroid hormone.

Carcinoma↗
PubMed1983

Vasoactive intestinal peptide stimulates tracheal submucosal gland secretion in ferret.

We studied the effect of vasoactive intestinal peptide (VIP) on the output of 35S-labeled macromolecules from ferret tracheal explants either placed in beakers or suspended in modified Ussing chambers. In Ussing chamber experiments, the radiolabel precursor, sodium [35S]sulfate, and all drugs were placed on the submucosal side of the tissue. Washings were collected at 30-min intervals from the luminal side and were dialyzed to remove unbound 35S, leaving radiolabeled macromolecules. Vasoactive intestinal peptide at 3 X 10(-7) M stimulated bound 35S output by a mean of + 252.6% (n = 14). The VIP response was dose-dependent with a near maximal response and a half maximal response at approximately 10(-6) M and 10(-8), M, respectively. The VIP effect was not inhibited by a mixture of tetrodotoxin, atropine, I-propranolol, and phentolamine. Vasoactive intestinal peptide had no effect on the electrical properties of the of the tissues. We conclude that VIP stimulates output of sulfated-macromolecules from ferret tracheal submucosal glands without stimulating ion transport. Our studies also suggest that VIP acts on submucosal glands via specific VIP receptors. Vasoactive intestinal peptide has been shown to increase intracellular levels of cyclic AMP, and we suggest that this may be the mechanism for its effect on the output of macromolecules. This mechanism may be important in the neural regulation of submucosal gland secretion.

Animals↗
PubMed1982

Serological and genotypic diversity among serogroup 5- reacting environmental Legionella isolates.

Five strains of bacteria (strains 684, 687, U7W, U8W, and MICU-B) that were biochemically and morphologically indistinguishable from Legionella pneumophila were recovered from the environment. Strains U7W, U8W, and MICU-B were antigenically identical to L. pneumophila strain Dallas 1E (serogroup 5), as determined by direct fluorescent antibody staining and immunodiffusion. Although strains 694 and 687 shared antigenic determinants with L. pneumophila Dallas 1E, they could be distinguished by immunodiffusion and differential absorption studies. However, as determined by DNA hybridization, the antigenically distinct strains 684 belong to the same DNA homology cluster as previously described authentic strains of L. pneumophila, whereas strain U7W, U8W, and MICU-B belong to a separate homology group. Therefore, two groups could be identified among these environmental isolates; one represents an antigenic subclass of serogroup 5 L. pneumophila (strains 684, and 687), and the other, although antigenically indistinguishable from serogroup 5 L. pneumophila, probably represents a new Legionella species (strains U7W, U8W, and MICU-B).

Antigens, Bacterial↗
PubMed1982

Hypoxemia reflexly increases secretion from tracheal submucosal glands in dogs.

We anesthetized dogs, ventilated their lungs via the lower trachea, and exposed the epithelial surface of the upper trachea and coated it with powdered tantalum. Secretions from submucosal gland ducts formed elevations (hillocks) in the tantalum layer; we counted the number of hillocks that appeared in a 1.2-cm2 field. In 12 dogs, during normoxemia, 12 +/- 2 hillocks/cm2 formed in 90 s; during severe hypoxemia [fractional inspired O2 concentration (FIO2) = 0.05], 40 +/- 4 hillocks/cm2 formed in 90 s. Injections of sodium cyanide (25-75 micrograms) into the arterial supply to the carotid body also stimulated tracheal submucosal gland secretion. Secretory response to hypoxemia was suppressed by 1) section of both carotid sinus body nerves in six dogs and 2) section of both superior laryngeal nerves and vagus nerves in six other dogs. During mild hypoxemia (FIO2 = 0.10 or 0.15) tracheal submucosal gland secretion still increased. We conclude that hypoxemia increases secretion from submucosal glands in canine trachea by a carotid body chemoreflex.

Animals↗
PubMed1982

Reflex tracheal gland secretion evoked by stimulation of bronchial C-fibers in dogs.

We examined the effect of stimulating bronchial C-fibers on tracheal submucosal gland secretion in anesthetized dogs with open chest and lungs ventilated through the lower trachea. We opened the upper trachea in the midline, retracted the cut edges, and sprayed powdered tantalum onto the exposed mucosa. Secretions from the ducts of submucosal glands caused elevations (hillocks) in the tantalum layer, which were viewed through a microscope and recorded on videotape with a television camera. We counted the hillocks (greater than 0.2 mm diam) in an area of mucosa (1.2 cm2) before and after injecting capsaicin (3 micrograms) into a bronchial artery to stimulate bronchial C-fibers. In the minute before capsaicin was injected 7 +/- 2 (mean +/- SE; n = 20) hillocks appeared and in the minute after 40 +/- 2 hillocks. Bradykinin (1.5 micrograms) had similar effects. Secretion was accompanied by contraction of the trachealis muscle. Effects were abolished by cooling (0 degree C) or cutting the vagus nerves. Since capsaicin and bradykinin stimulate bronchial C-fibers selectively when injected in these small doses, we conclude that bronchial C-fibers furnish the afferent arm of an airway secretory reflex.

Animals↗
PubMed1982

Assessment of density dependent flow-volume parameters in nonsmokers and smokers. Measurement with spirometry, body plethysmography and respiratory inductive plethysmography.

The purpose of this investigation was to assess the density-dependent flow-volume components of the forced vital capacity using simultaneous spirometry, respiratory inductive plethysmography, and body plethysmography in the detection of small airway disease. The forced vital capacity was measured during air, helium-oxygen and sulfur-hexafluoride breathing to provide a range of gas density influences. Combining flow measured at the mouth with volume referenced to change in alveolar gas volume as measured by body or respiratory inductive plethysmography during helium-oxygen breathing accentuated the differences between nonsmokers and smokers because of the variable degree of alveolar gas compression occurring over the second half of FVC. The volume of isoflow obtained when comparing the helium and oxygen mixture to air also effectively separated nonsmokers from smokers. The utilization of the high density gas mixture, sulfur hexafluoride-oxygen during the FVC maneuver did not provide useful diagnostic information. Therefore, density-dependent flow-volume information using helium as a test gas alone or compared to air with a variety of analyses is a good approach to detection of early lung disease in smokers.

Adolescent↗
PubMed1982

Assessment of time-volume and flow-volume components of forced vital capacity. Measurement with spirometry, body plethysmography and respiratory inductive plethysmography in nonsmokers and smokers.

The purpose of this investigation was to assess the effectiveness of the time-volume and flow-volume components of the forced vital capacity measured by simultaneous spirometry, respiratory inductive plethysmography, and body plethysmography in detecting small airway disease. Spirometry measured the exit of gas from the lungs, whereas body plethysmography measured both the exit of gas and alveolar gas compression. Respiratory inductive plethysmography, which reflected change in thoracic volume, provided semi-quantitative data f both gas exit and alveolar gas compression which generally lay between spirometry and body plethysmography. In nine nonsmokers and 12 smokers (six with small airway disease as defined by abnormal closing volumes and alveolar uniformity), analysis of forced vital capacity revealed that the only test which differentiated nonsmokers from smokers was the higher spirometric estimation of maximum expiratory flow measured at 25 percent VC in nonsmokers. Combining flow measure at the mouth with volume referenced to change in alveolar gas volume as measured by body or respiratory inductive plethysmography did not differentiate nonsmokers from smokers. Moment analysis performed of forced vital capacity with all of the three devices did not distinguish nonsmokers from smokers. The data in this study and a review of other investigations indicate that the time-volume and flow-volume components of the forced vital capacity on air breathing are not very sensitive in detecting early lung disease in smokers.

Adolescent↗