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Biomedical subjects

B L Brown

Publications and source records attributed to B L Brown.

At least 127 records · Page 7Linked to original sources
PubMed1980

Transplantation of fresh allografts (homografts) of crushed and uncrushed cartilage and bone: a 1-year analysis in rabbits.

Fresh allografts (homografts) of cartilage and bone, crushed and uncrushed, were transplanted in 53 rabbits. Each material was implanted into the auricle and concomitantly into the subdermis of the face. Postoperative assessment was every 1 to 3 days; sacrifice was at 6 weeks, 6 months, and 1 year for microscopic evaluation. Uncrushed cartilage allografts remained viable, and no significant resorption occurred. Crushed cartilage was significantly resorbed by 6 weeks but changed little after that. Resorption of uncrushed bone was moderate and appeared to be ongoing. Total resorption by 1 year occurred in the absence of contact with perichondrium or periosteum. Crushed bone, like crushed cartilage, was largely resorbed. These data document the fact that uncrushed cartilage is superior to crushed cartilage, crushed bone, or uncrushed bone for fresh allograft transplantation in the rabbit and that uncrushed cartilage is probably superior to all other fresh allografts for use in the clinical setting.

Animals↗
PubMed1980

Sinusoidal fetal heart rate pattern in association with amnionitis.

A case is reported of intrapartum sinusoidal fetal heart rate (FHR) pattern in association with intrapartum amnionitis. Fetal and maternal outcome were excellent. Sinusoidal FHR patterns have been widely associated with severe fetal asphyxia and impending fetal death. In reviewing the published experience with sinusoidal FHR patterns, it is concluded that, although it is alarming, not every sinusoidal FHR pattern is an indication for immediated delivery.

Adult↗
PubMed1980

Intrauterine meconium aspiration syndrome.

A case of presumptive intrauterine meconium aspiration is reported in which the diagnosis was made on the basis of an unexplained intrauterine fetal tachycardia and the presence of severely meconium-stained amniotic fluid. The possible pathophysiology of intrauterine meconium aspiration is discussed with special attention to animal experimentation. The importance of an early diagnosis of this condition is stressed. The clinical management of such cases may change once the antenatal diagnosis of intrauterine meconium aspiration can be made with more certainty. In addition, the legal implications of a confirmed diagnosis of intrauterine meconium aspiration are discussed as meconium aspiration is considered presently to represent a largely preventable neonatal event.

Adolescent↗
PubMed1979

Correction for the presence of cross-reactants in saturation assays: application to thyroxine cross-reactivity in 3,3',5'-(reverse)-triiodothyronine radioimmunoassay.

Cross-reaction of anti-3,3',5'-triiodothyronine (rT3) antisera with thyroxine has proved problematical in the development of radioimmunoassays for rT3. Results of experimental work with two antisera with differing specificities are presented which illustrate certain aspects of cross-reacting assay systems. The mathematical theory of a single binding-site, two ligand assay is discussed and extended by use of a multiple binding-site computer model to a two binding-site, two ligand system. It is suggested that for the practical evaluation of the nature and extent of cross-reaction, a family of response curves for the hormone should be drawn, each curve representing the addition of a fixed mass of the cross-reactant to a set of standard incubation mixtures. Such curves will reveal whether the antiserum is (a) specific, implying that assay results require no correction, (b) behaves as a single binding site system, in which case measurement of the relative potency of the two ligands at the point on the response curve generated by the serum sample will enable an algebraic correction to be made, given that the T4 concentration is known or (c) behaves as a multiple binding-site system where correction necessitates the use of a nomogram.

Binding Sites, Antibody↗
PubMed1979

Nasal polypectomy in patients with asthma and sensitivity to aspirin.

Nasal polypectomy is safe in patients with asthma and intolerance to aspirin. Asthma should be controlled before polypectomy. Patency of the nasal airway after the operation and the effect of polypectomy on asthma are independent of severity of the asthma, history of atopy, and administration of steroids. We reviewed retrospectively the courses of 101 patients with the asthma triad who had nasal polypectomies between 1970 and 1974. Before polypectomy, 39 patients were hospitalized to control active asthma: during the postoperative hospitalization, 19 had wheezing, mostly mild. Of the 62 patients with inactive asthma, three had wheezing postoperatively. Asthmatic condition at one year after polypectomy, compared with the condition at one year before, was improved in 30 patients, worse in 14, and unchanged in the rest. Nasal airways remained good for at least one year in 60% of the patients.

Adolescent↗
PubMed1979

Implants of Supramid, Proplast, Plasti-Pore, and Silastic.

Four types of synthetic materials were implanted in 54 rabbits: Supramid, Proplast, Plasti-Pore, and Silastic. Each material was implanted into the auricle and concomitantly into the subdermis of the face. Postoperative assessment was every one to three days, while killing was done at six weeks, six months, and one year postoperatively for microscopic evaluation. Supramid mesh contains black pigment, which became incorporated within the histiocytes and giant cells around the implanted mesh by six weeks; at one year, the soft tissues were pigmented microscopically. Proplast was not extruded despite an intense and persistent histiocytic and giant-cell reaction; its black color constituted a major drawback for implantation beneath thin skin. The Plasti-Pore used in these studies was rigid and somewhat difficult to sculpture, and it induced a persistent but minor cellular reaction. Silastic was easily displaced.

Animals↗
PubMed1978

Effect of TRH and dopamine on cyclic AMP levels in enriched mammotroph and thyrotroph cells.

Populations of normal anterior pituitary cells enriched in thyrotrophs or mammotrophs prepared by velocity sedimentation were used to investigate the effect of modulators of TSH and prolactin secretion on cyclic AMP accumulation. In both thyrotroph-enriched and mammotroph-enriched fractions, IBMX increased cyclic AMP accumulation. In the presence of IBMX, TRH invoked an increase in cyclic AMP suggesting that TRH modulates cyclic AMP accumulation in both of these cell types from normal pituitary glands. In the mammotroph-rich fraction, dopamine inhibited the increase in cyclic AMP induced by TRH. In contrast however, in the thyrotroph-enriched fraction dopamine lowered neither cyclic AMP concentration nor TSH secretion. Thus the inhibiting effect of dopamine on cyclic AMP appears to be specific for prolactin-secreting cells.

1-Methyl-3-isobutylxanthine↗
PubMed1978

Induced cell aggregation and mating in Streptococcus faecalis: evidence for a bacterial sex pheromone.

Recipient strains of Streptococcus faecalis produce a trypsin sensitive, heat resistant, nuclease resistant factor, designated clumping-inducing agent (CIA) which causes strains carrying certain conjugative plasmids to aggregate. RNA and protein synthesis but not DNA synthesis are required for aggregation to occur. Recipient filtrates that contain CIA activity also induce donors to mate at high frequencies. Introduction of a transferable plasmid into strains producing CIA dramatically reduces the amount of CIA activity produced by the strain but allows the strain to respond to exogenously added CIA. Our data suggest that CIA represents a bacterial sex hormone (pheromone).

Animals↗
PubMed1977

Studies on the control and dynamics of thyrotropin secretion from isolated adenohypophyseal cells.

Thyrotropin (TSH) secretion from isolated anterior pituitary cells has been studied using the technique of cell column perifusion. The consistency in secretory rate and temporal profiles of TSH output in response to stimulation illustrated that the system is suitable for studying the kinetics of stimulation and inhibition of secretion. During perfusion TSH release was stimulated in response to a variety of secretogogues, namely TRH, raised potassium concentrations and phosphodiesterase inhibitors. The onset and termination of the secretory responses were rapid and displayed a temporally biphasic pattern of secretion. Dose-related increases in TSH output in response to TRH and consistent responses to repetitive pulses of TRH (5.5 X 10-10 M) during a 4 h period were demonstrated. Studies on the dynamics of thyroid hormone feedback on TRH-stimulated TSH secretion indicated that inhibition was manifest within 1 h and reached a maximum after 2 1/2 h during continual exposure to thyroid hormones. Isobutylmethylxanthine (IBMX) potentiated the effect of raised K+ as well as that of TRH on TSH secretion, suggesting an as yet unidentified relationship between Ca2+ and cyclic AMP.

Animals↗
PubMed1977

Analysis of plasmid deoxyribonucleic acid in a cariogenic strain of Streptococcus faecalis: an approach to identifying genetic determinants on cryptic plasmids.

Streptococcus faecalis strains ND539 and OG1 have been previously shown to be cariogenic in gnotobiotic animals. Deoxyribonucleic acid analyses have revealed the presence of a single 26-megadalton plasmid designated pAM539 in the former strain, whereas the latter strain was found to be plasmid-free. By gene transfer experiments, it was possible to construct isogenic pairs of strains that differed only with regard to the presence or absence of pAM539. Comparative studies of isogenic pairs showed that the presence of pAM539 conferred bacterial sensitivity to a bacteriocin produced by S. faecalis strain 5952.

Animals↗
PubMed1977

Characterization of plasmids determining hemolysin and bacteriocin production in Streptococcus faecalis 5952.

Two plasmids designated pOB1 and pOB2 were isolated from Streptococcus faecalis strain 5952 and found to have molecular weights of approximately 46 X 10(6) and 28 X 10(6), respectively. pOB1 was found to determine hemolytic activity and was transmissible, whereas pOB2 appeared to determine a bacteriocin that is specifically inhibitory to S. faecalis strains harboring the 26-megadalton plasmid pAM539.

Bacteriocins↗
PubMed1976

Prophylactic granulocyte support in experimental septicemia.

The purpose of this study was to determine the value of prophylactic granulocyte transfusions in preventing death from sepsis. An intravenous dose of 10(9) Escherichia coli was lethal when given to granulocytopenic rats 6 days following irradiation with 750 rads. Only one of 22 irradiated animals survived the septicemia. Although normal (nonirradiated) animals experienced a transient leukopenia from this dose of organisms, it was less than LD10 for the normal host. There were no deaths in a group of animals receiving irradiation only. A group of 14 irradiated animals was given a single granulocyte transfusion 2 hr before the septic inoculum, and 57% of these animals survived (p less than 0.01). No antibiotic therapy was administered to any of these animals. Irradiated animals who received granulocytes and recovered from sepsis had earlier granulocyte reconstitution than animals irradiated but not given the septic challenge. Platelet reconstitution was the same in both groups. In the rat model, prophylactic granulocyte support of septc animals led to improved survival. It was concluded that granulocyte prophylaxis may be of value in selected patients with transient bone marrow failure who are therefore at high risk from sepsis.

Animals↗
PubMed1976

The development of adrenocorticotrophin-sensitive adenylate cyclase activity in the foetal rabbit adrenal: a correlated biochemical and morphological study.

Proliferation of the smooth endoplasmic reticulum, the site of some hydroxylating steroidogenic enzymes in foetal adrenocortical cells, is the first major change in the process of their differentiation into steroidogenic tissue. This was observed in our ultrastructural studies on foetal rabbit adrenals to begin at about day 19 of development. Morphological changes in the mitochondria, the site of production of other steroidogenic enzymes, occurred at about day 24. The elongated or rod-shaped forms of the earlier stages became flattened and rounded by this time, while the cristae were transformed from a flattened lamellar type of the earlier stages to the tubulo-vesicular form of the adult. Other changes observed included an increase in microvilli and in cell size, with a concomitant increase in thickness of the gland. Adenylate cyclase activity in foetal adrenal homogenates was assessed in response to sodium fluoride (NaF) and ACTH. All preparations responded to NaF. While good responses to ACTH were observed at days 24, 27, 28 and in the neonate, there was a lack of any significant response in the day 19 gland. Foetal ACTH was depressed by administration of cortisol, and the effects of this treatment on both the morphological changes and adenylate cyclase activity was reassessed. The response of foetal adrenals to ACTH was depressed by this treatment and differentiation of the mitochondria was arrested. These results suggest a circumscribed period for the development of ACTH-sensitive adenylate cyclase coinciding with the time at which final differentiation of the mitochondria is completed. Furthermore, both the differentiation of the mitochondria and the development of ACTH-sensitive adenylate cyclase in the foetal adrenal may be dependent on foetal ACTH secretion.

Adenylyl Cyclases↗
PubMed1975

A strategy for thyroid function tests.

The concept of decision-aiding ranges were introduced to improve diagnostic efficiency. The clinical uncertainty in distinguishing borderline cases of hyperthyroidism and hypothyroidism among 1559 consecutive requests for thyroid function tests was 47%. This was reduced to 22% by using the free thyroxine index and to under 2% by using specific tests determined by the decision-aiding ranges.

Bayes Theorem↗