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Biomedical subjects

A C Brown

Publications and source records attributed to A C Brown.

At least 73 records · Page 4Linked to original sources
PubMed1984

Activated rat neutrophils. A sequential quantitative assay for aggregation and NBT reduction.

We present here a rapid, sensitive, and convenient approach for the analysis of activated Lewis rat PMNs based on detecting separately, or in tandem, PMN aggregation and PMN reduction of nitroblue tetrazolium (NBT). These responses are quantitated using an ELISA scanner which can rapidly measure optical densities of cell cultures in microtiter plates. Aggregation induced by as little as 0.005 micrograms/ml of phorbol myristate acetate (PMA), 0.01 micrograms/ml lipopolysaccharide (LPS), or a 1:160 dilution of lymphokine-containing rat serum can be detected employing this approach. NBT reduction was induced by as little as 0.01 micrograms/ml PMA. Blocking studies employing 2-deoxyglucose, iodoacetamide, and polymyxin B gave the expected results and confirmed that these assays detect cellular responses to soluble stimuli. Using this technology the effects of PMA and LPS on rat peritoneal exudate PMNs were evaluated. Rat PMNs appeared less sensitive to LPS than human PMNs and also reduced NBT more slowly following stimulation with PMA. Because of the slowness in NBT reduction following stimulation, NBT reduction can be evaluated, in tandem, after measuring aggregation. The simplicity of this system, coupled with the speed with which large numbers of microcultures can be read and the low number of cells required, make this approach for studying responses especially attractive.

Animals↗
PubMed1984

Blood and milk lipid responses induced by growth hormone administration in lactating cows.

Nine multiparous Holstein cows (average 5.8 yr, 63 to 132 days postpartum) were in a 28-day single reversal experiment in the Beltsville open circuit respiration chambers with two 14-day injection periods (placebo versus bovine growth hormone, 51.5 IU/day). With growth hormone treatment, milk fat percentage increased 25 to 29%, milk fat yield increased 41%, and cows averaged -13.7 Mcal/day energy balance. There were small increases of triglycerides and 1,2-diglycerides, core lipids, and small decreases of cholesterol and phospholipids, the membrane lipids. Fat from growth hormone treatment had 6% less short (6:0, 8:0, 10:0) and medium (12:0, 14:0, 14:1, 15:0, 16:0) chain fatty acids and 6% more long chain 18:1 fatty acids. Plasma of cows treated with growth hormone had an increase of concentrations of free fatty acids, but no shifts were apparent among other lipid classes. Analysis of total plasma fatty acids did not show any net changes, but within individual plasma lipid classes, 18:1 increased and 18:2 decreased. Overall changes of blood and milk lipids are consistent with the concept that adipose tissue reserves were mobilized in response to hormone treatment and that these mobilized lipids were the major carbon source for the 41% increase of milk fat secretion. Increases of de novo synthesis of short and medium chain fatty acids also occurred but much less. Cows treated with growth hormone were in negative energy balance, and the mechanism may differ when cows are in positive energy balance.

Animals↗
PubMed1984

Recurrent Fusarium keratomycosis: a light and electron microscopic study.

Corneal buttons infected with Fusarium solani, were removed during penetrating keratoplasty, and studied by light and electron microscopy. Histologically, it appeared that the hyphae penetrated Descement 's membrane and the posterior stroma from the anterior chamber. Their cell wall, plasmalemma, and cytoplasm were preserved indicating that the fungi might be still active despite antifungal therapy, which may not be effective once the fungus penetrates Descemet's membrane. The other interesting feature was the total lack of phagocytic activity of macrophages on adjacent fungal hyphae indicating possible suppression of host defense responses in this cornea. Patients with fungal keratitis should be treated with antifungal drugs at an early stage, and therapeutic penetrating keratoplasty appears to be most effective, if performed before the fungus penetrates the barrier of Descemet's membrane.

Cornea↗
PubMed1983

Video-photo slit lamp.

A combination video and photographic slit lamp manufactured by Rodenstock with a special light source by Storz has been described. Primarily a research instrument because of the expense of the light source, the video system, when properly adjusted, provides useful records of certain procedures and pathology and is an excellent teaching tool. The photographic attachment provides excellent quality, high resolution 35 mm documentation of anterior segment disease and pathology.

Ophthalmoscopes↗
PubMed1983

Peripheral corneal grafts in Terrien's marginal degeneration.

Surgical treatment of two cases of Terrien's marginal degeneration is discussed. Because of the peripheral location of the corneal thinning, free-hand grafting is required. The procedure and its complications, both intraoperative and postoperative, are described in detail.

Adult↗
PubMed1982

Ocular and testicular abnormalities in alopecia areata.

Ocular abnormalities similar to those usually found in patients with vitiligo occurred in nine patients with alopecia areata and one patient with poliosis. Exophthalmos, iris color change, discrete depigmentation, and, frequently, associated pigment hyperplasia of the choroid and retinal epithelium were found in the ten patients. Four patients had had a bilateral iris color change from dark brown to blue-green. Hypogonadism, thyroid disease, and poliosis may frequently be associated with pigmentary disturbances of the eye, as well as hair loss. Testicular dysfunction with oligospermatism to aspermatism, hypoandrogyny, hyperretractable testes, and epididymal cyst is reported. Two patients had unilateral and one patient had bilateral testicular atrophy.

Adolescent↗
PubMed1982

Keratoprosthesis. Results, complications, and management.

Thirty-one cases of keratoprosthesis were followed for periods of from 1 to 84 months (average 35 months). The Cardona through-and-through device was implanted, covered with periosteum, and exteriorized through an opening in the upper lid. Visual results varied from 20/20 (1 of 31 cases) to counting fingers (5 of 31 cases). While 12 of the 31 cases achieved 20/40 or better at some point in the postoperative course, only 5 of 31 maintained this level of acuity over a long-term period. Severe complications included retroprosthetic membrane (18 out of 31), vitreitis (7 out of 31), dislocation (5 out of 31), extrusion (3 out of 31), and endophthalmitis (5 out of 31). Fifteen of the 31 patients required subsequent surgical revision. Despite the frequency and severity of complications, 17 out of 31 patients achieved sufficient improvement in visual acuity to enable them to function without assistance for periods of 1 to 7 years.

Cornea↗
PubMed1981

Time course of antirecall effect of diazepam and lorazepam following oral administration.

The time course of antirecall effect and grades of sedation after the oral administration of diazepam and lorazepam were determined in 120 patients. Three standard doses of each drug were employed. Grades of sedation following oral diazepam were dose related, with a latency of 30-60 min and duration of 120-150 min. All three doses of lorazepam produced significantly more sedation with a similar latency (30-60 min) but longer duration (more than 240 min). Peak frequencies of the antirecall effects of diazepam 10, 15, and 20 mg were 5, 20, and 30 per cent, respectively. The duration was about two hours. Peak frequencies of the antirecall effect after lorazepam 2, 3, and 4 mg were 30, 45, and 72 per cent, respectively. Latency of peak action was about 60-90 min for all the doses, but the duration, especially with 3 and 4 mg doses, was long (4 h).

Administration, Oral↗
PubMed1979

Tooth pulp-driven neurons in somatosensory cortex of primates: role in pain mechanisms including a review of the literature.

The tooth pulp of primates was stimulated electrically while searching for evoked unit potentials in the cerebral cortex. Control procedures were employed to assure that the electrical stimuli reached only tooth pulp fibers but no extrapulpal sensory fibers. In addition, an electrode was inserted in soft tissue surrounding the tooth for separate excitation of extrapulpal axons. A tooth pulp projection area was identified in the "face area" of primary somatosensory cortex. Two major neuron groups were encountered, one excited only by the extrapulpal soft tissue stimulus, the other by tooth pulp stimuli. Within the pulp-projection area, soft tissue-driven neurons were most numerous in superficial cortex of the postcentral gyrus, pulp-driven neurons dominated in deep cortex in the base of the central sulcus. The pulp-driven population divided into several functional subsets: those excited from one pulp only (conceivably capable of localizing pulpal stimuli), those excited from more than one pulp and those excited from both pulp and extrapulpal soft tissue. Within each of these 3 pulp-driven subsets, some units responded to single shock, others only to a train of shocks. Mean discharge latency was shortest for the population excited only from soft tissue, intermediate for pulp-driven units excited by single shock and longest for pulp-driven units excited only by trains of shocks. Both soft tissue and pulp stimuli evoked extensive inhibitory effects. In the Discussion, the possible role of pulp-driven neurons in pain is considered. The functional properties of some neurons are consistent with a role in stimulus localization but those of the remaining neurons suggest other roles in pain. An examination of the literature on cortex and pain suggests that normally somatosensory cortex is important for localizing painful stimuli and that it contributes to other pain mechanisms as well. After certain lesions, somatosensory cortex has the capacity for generating "central" pain just like other structures in the nociceptive pathway.

Animals↗
PubMed1979

Acceleration forces at eye level experienced with rotation on the horizontal bar.

Negative acceleration forces (-Gz) experienced at eye level have been associated with preretinal hemorrhage and headache. These signs and symptoms were found in individuals who experienced negative (toward the head) force while rotating on a horizontal bar or hanging from a trapeze. Lightweight accelerometers were used to measure -Gz experienced at eye level in children and adult gymnasts performing a single-knee backswing on a horizontal bar. Rate of onset of -Gz, peak -Gz, time experiencing -Gz, area of curve (G.second), and mean force (area/time) were calculated. There was no significant difference between the children and the adult gymnasts in any of the above parameters. The best gymnast had a maximum rate of onset of 38.15 G/s and the maximum negative force experienced was 5.52 G. The maximum rate of onset for a child was 41.56 G/s and the maximum negative force experienced was 5.73 G. Compared with -Gz tolerance curves generated on a centrifuge the best gymnast would have become symptomatic while performing this maneuver in 6 s. The best child would have become symptomatic in 25 s. These tolerance limits can be easily exceeded by gymnasts and by the monkey-bar enthusiast.

Adolescent↗