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Biomedical subjects

R L Boyd

Publications and source records attributed to R L Boyd.

At least 163 records · Page 9Linked to original sources
PubMed1983

Inhalation studies of diesel exhaust and coal dust in rats.

The preliminary 12-month data of an ongoing two-year chronic inhalation study into the effects of diesel exhaust and coat dust on rats are reported. The study design consists of four exposure regimens: coal dust, diesel exhaust, coal dust plus diesel exhaust, and filtered air (control). Total respirable particulate is being maintained at 2 mg/m3 in all exposure groups. Animals are being serially sacrificed and subjected to immunologic, biochemical, physiological, microbiological, and pathological evaluations. Extracts of diesel emissions showed marked mutagenic activities in the Ames Salmonella his reversion assay. Mutagenic compounds were not however found in the urine of the exposed animals, nor were sister chromatid exchanges detected in peripheral lymphocytes. No changes were observed in cytochrome P450 enzyme activity in lung microsomes of exposed rats. Physiological tests showed no evidence of pulmonary function impairment in any group. Light microscopic examination of the lungs showed dust deposition with the formation of macules in all exposed groups. The preliminary results revealed few pathological effects of significance and no evidence of synergism between diesel exhaust and coal dust.

Animals↗
PubMed1983

Bursal and thymic reticular epithelial cells in the chicken: induction of B- and T-lymphocyte differentiation by in vitro monolayer cultures.

The role of chicken bursal and thymic reticular epithelial cells (REp cells) in the induction of B- and T-lymphocyte differentiation has been investigated using in vitro culture of these cells. Splenic adherent cells were used as controls. Precursor populations were obtained predominantly from embryonic bone marrow or spleen and incubated with REp cell monolayers for 72 hr. Differentiation was assessed by the expression of specific membrane antigens: chicken B lymphocyte-specific antigen (CBLA) and chicken T lymphocyte-specific antigen (CTLA). Bursal REp cells specifically induced approximately 20-30% of the embryonic cells to express CBLA but had no influence on CTLA expression. Conversely, CTLA, but not CBLA, was induced in approximately 20% of the embryonic cells by the thymic REp cell cultures. No effect on the expression of either antigen was observed with the splenic adherent cells. The induced cells correspond to the first stage of B- and T-lymphocyte differentiation found in vivo. The assay system also facilitated the study of shifts in precursor content of various organs with development. Whereas embryonic bone marrow of all ages studied contained both B- and T-lymphocyte precursors, these were not demonstrable in donors after hatching. Use of 12-day embryonic bursa and thymus suspensions as sources of stem cells indicated that precommitment to the B- or T-lymphocyte lineage is irreversible.

Aging↗
PubMed1983

Bursal and thymic reticular epithelial cells in the chicken: preparation of in vitro monolayer cultures.

To study the nature of reticular epithelial (REp) cells and their role in the specific microenvironments of the chicken bursa and thymus, a method was developed for the in vitro culture of purified preparations of these cells. For comparison, similar cultures of splenic adherent cells were also performed. REp cell-rich bursa medullary follicles and mildly trypsinized thymic fragments were X-irradiated (850 rad) to eliminate remaining lymphocytes and transferred to culture flasks. In bursal cultures, after 2-4 days incubation the basement membrane (BM) encapsulating the follicles disrupted and the immediately underlying epithelial cells grew out as a monolayer. By 10 days, REp cells at the periphery developed cytoplasmic processes; occasionally these cells appeared to "bud-off" and grow as isolated dendritic cells. Thymic REp cells were generally slower to proliferate but formed a monolayer by 10-14 days. Splenic adherent cells developed extensive growth within 4 days. REp cells were distinguished from fibroblasts, when present, morphologically and by their limited phagocytic ability. The former were also periodic acid-Sciffs reagent (PAS)-positive and produced reticulin granules. Bursal REp cells were also positive for a gut-associated mucin, but this may have been bound in vivo prior to culture. Neither T nor B lymphocyte-specific antigens were detectable on the cultured REp cells or splenic adherent cells, but they were all rich in cytoplasmic actin. A major feature of REp cells to emerge in this study was the obvious presence of subpopulations of these cells, which raises important questions as to their exact nature and lineage. The accompanying paper details the ability of the bursal and thymic REp cell cultures to induce B-or T-lymphocyte differentiation, respectively, in vitro.

Animals↗
PubMed1982

Clinical assessment of injuries in orthodontic movement of impacted teeth. I. Methods of attachment.

Recent studies have indicated ankylosis, loss of attachment, and external resorption occurring as sequelae of orthodontic movement of impacted teeth when these teeth are ligated around the cervix with wire. The purpose of this study was to record the effects of two commonly employed methods of attachment to impacted teeth--the wire ligation and the direct bond. Twenty subjects who had previously undergone full-banded orthodontic treatment involving a unilateral impacted maxillary canine were studied. The contralateral non-impacted maxillary canine served as a control. In eight of the subjects the impacted canine was ligated at the cervix with wire at the time of surgical exposure. In the other twelve subjects the impacted tooth also was exposed surgically but then an orthodontic bracket was bonded directly to the tooth approximately 2 weeks after the surgical exposure. The criterion for the diagnosis of ankylosis was failure to move the tooth for at least 3 months. The diagnosis of external resorption was made from radiographs. Loss of periodontal attachment was measured by comparing the level of attachment on the previously impacted tooth with the contralateral canine 3 months after debanding. The results indicated that three of the eight patients in the group receiving wire ligation exhibited external resorption and ankylosis. Also, there was an average of 1.36 mm. greater loss of attachment in all four proximal and lingual probing measurements of teeth ligated with ligature wire but no significant differences in the direct buccal probing measurement.

Adolescent↗
PubMed1982

IgG-Fc and C3 receptors in the chicken: distribution, tissue localization and functional significance.

This paper summarizes data obtained in our laboratory on the demonstration of receptors for IgG-Fc (FcR) and complement (CR) on mononuclear cells of the fowl. A clearcut distinction of these two structures on spleen cells was achieved in rosette assays using SRBC coated with rabbit IgG as indicator cells which bind avian complement, but are not bound by the FcR. The tissue distribution and localization of FcR and CR positive cells was studied in mixed hemadsorption assays on sections of both central (bursa, thymus) and peripheral (spleen) lymphoid organs from normal chickens, as well as lymphocytic infiltrated thyroid glands from animals of the Obese strain (OS) afflicted with spontaneous autoimmune thyroiditis. The possible significance of both receptors in the pathogenesis of this autoimmune process is discussed.

Animals↗
PubMed1982

Contact-dependent expression of actin in chicken lymphocytes in vitro.

The presence of actin in chicken bursa, thymus and spleen cells has been confirmed using quantitative neutralization absorptions of anti-actin antibody (AAA) with frozen-thawed preparations of these three cell types. Spleen cells were more effective than thymus or bursa cells in reducing the AAA titre. Cell suspensions of these organs were allowed to settle onto a glass slide, air-dried and stained with AAA. Immunofluorescence was restricted to cell borders at points of contact with other cells. This staining was reversibly inhibited by cytochalasin B but not colchicine. The higher content of actin in spleen cells demonstrated by the absorption experiments was reflected in their more rapid expression of actin during smear formation, and the relative resistance of this to cytochalasin B treatment, compared to thymus and bursa preparations. These findings further support the proposition that actin expression is a function of lymphocyte maturation.

Actins↗
PubMed1982

Effector mechanisms in the spontaneous autoimmune thyroiditis of obese strain (OS) chickens: analysis of cytotoxic cells.

Different forms of cellular cytotoxicity that may constitute potential effector mechanisms in the spontaneous autoimmune thyroiditis (SAT) arising in Obese strain (OS) chickens have been investigated. A microcytotoxicity assay (MCA) employing 51Cr-labelled-, thyroglobulin (Tg) coated-chicken red blood cells (Tg-CRBC) was used to detect cells mediating Tg-specific direct cellular cytotoxicity (DCC). Tg-CRBC presensitized with anti-Tg autoantibody (Tg-AAB) obtained from high titer OS sera served as targets for antibody-dependent cell-mediated cytotoxicity (ADCC). Tannic acid-only treated CRBC (TA-CRBC) were used simultaneously as specificity controls for DCC and also as targets for cells eliciting spontaneous cellular cytotoxicity (SCC) to surface-modified normal cells. The results demonstrated that Tg-specific cytotoxic cells exist in the OS and thus represent an effector mechanism in SAT, in addition to the previously well-documented role of antibody. This DCC appears to be unrelated to the presence and titer of circulating Tg-AAb. It is present in highest levels in the peripheral blood of OS chickens, but in only 55% of the animals tested, indicating either a secondary importance to humoral immunity in the disease process or the possibility of different effector mechanisms prevailing in different birds. There were no overall differences in ADCC between OS and normal chickens when the two strains were considered as a whole. Chronological analysis, however, revealed very low ADCC in the peripheral blood of young OS birds, followed by a later elevation above that in the normal control chickens. Destruction of the gland by ADCC may be initiated via maternally-derived of in situ-produced anti-Tg antibody. No overall significant differences in SCC were observed between OS and normal chickens.

Animals↗
PubMed1982

Strain differences in pulmonary function of laboratory rats.

The effect of strain differences on pulmonary function was studied with male Sprague-Dawley and Fischer-344 rats. The larger Sprague-Dawley rats had a larger thoracic gas volume and specific thoracic gas volume (thoracic gas volume normalized for body mass) than the Fischer-344 rats. The thoracic gas volume differences corresponded to differences in static lung compliance reported in the literature for these strains of rats. The resistance of airways was less in the Sprague-Dawley rats but the specific conductance was greater in the Fischer-344 rats. These results suggested that even though the smaller Fischer-344 rats had a smaller lung volume and smaller cross sectional area of the airways, the caliber of the airways relative to lung volume was larger than that of the Sprague-Dawley rats.

Airway Resistance↗
PubMed1981

Pulmonary mechanisms of the normal ferret.

Pulmonary mechanics were measured in normal anesthetized male Fitch ferrets (200-360 g). In eight transorally intubated ferrets, pressure-volume (PV) curves for the lung and chest wall were obtained with an esophageal balloon and body plethysmograph. The lung volumes and capacities expressed as a percentage of the total lung capacity (mean, 49.8 ml) were: vital capacity, 84.7%; inspiratory capacity, 63.7%; inspiratory reserve volume, 58.2%; functional residual capacity, 33.8%; expiratory reserve volume, 16.8%; residual volume, 15.3%; and tidal volume, 8.0%. The compliance of the lung (2.93 ml . cmH2O-1), chest wall (22.42 ml . cmH2O-1) and respiratory system (2.55 ml . cmH2O-1) were determined from the PV curves. The dynamic compliance (1.6 ml . cmH2O-1), pulmonary resistance (0.024 cmH2O . ml-1 . s), frequency of breathing (43.5 breaths . min-1), and minute ventilation (195 ml . min-1) were measured during spontaneous breathing. In a second group of 10 ferrets the total airway resistance (0.116 cmH2O . ml-1 . s) and specific conductance (0.915 ml . s-1 . cmH2O . ml-1) were measured during spontaneous nasal breathing. In general the pulmonary mechanics of the ferret were similar to those of the rabbit and dog, when the data were normalized for lung volume.

Airway Resistance↗
PubMed1981

Transductal fluxes of water and monovalent ions in ferret salivary glands.

The net transductal fluxes of water and monovalent ions were measured in the parotid and submandibular salivary glands of the ferret, Mustela putorius furo, during stimulation of secretion with pilocarpine. The duct systems of these glands were found to be impermeable to water using the split-oil droplet method for stationary microperfusion of lobular and main ducts. The net transductal fluxes of Na+, K+, Cl-, and HCO3- were characterized by analysis of ductal fluid samples obtained simultaneously from the intercalated, lobular, and main ducts of these glands.

Animals↗
PubMed1981

Handling of calcium by the ferret submandibular gland.

The handling of Ca by the submandibular gland of the ferret during stimulation of salivation with pilocarpine was studied using micropuncture and microanalytical, as well as standard, physiological techniques. Concentrations of ionized Ca were measured in the fluid from the intercalated, lobular, and main ducts of the gland. The net transductal fluxes of this divalent ion were calculated.

Animals↗
PubMed1981

Secretion of monovalent ions and water in ferret salivary glands: a micropuncture study.

The acinar mechanisms of secretion of the monovalent ions, Na+, K+, Cl-, and HCO3-, and water in the parotid and submandibular glands of the ferret, Mustela putorius furo, were investigated using micropuncture and microanalytical techniques during salivation induced by pilocarpine. The osmolarity and monovalent ionic composition of the primary secretory fluid obtained from the intercalated ducts of these glands were determined.

Animals↗