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R L Boyd

Publications and source records attributed to R L Boyd.

180 records · Page 10Linked to original sources
PubMed1981

Direct measurement of loads at the temporomandibular joint in Macaca arctoides.

This paper describes a novel technique of directly measuring loads at the condyle in Macaca arctoides and provides recordings on one animal while measuring loads at the TMJ. This study is the first to actually measure loads directly at the articulating surfaces of the condyle. The data collected in this study confirm Hylander's data that the TMJ is a stress-bearing joint. With this pilot study, observations which can be made are: 1) The loads at the condyle are minimal during posterior chewing of both soft and hard foods (1-3 lb), and 2) during mastication of food the load (3-4 lb) at the condyle is larger than for posterior chewing. It was demonstrated during the calibration of the transducer that as the condyle translates forward over the articulating eminence during opening, a load is produced on it which is as large as the load present during incisal biting. Since recordings were only successfully taken on one animal, the above observations must be confirmed with further experiments.

Animals↗
PubMed1981

Representative oxygen dissociation curve and equation for the chicken.

Because of the considerable variability in the oxygen dissociation curves for chickens reported in the literature, the respiratory physiologist studying avian gas exchange is faced with the dilemma of which curve is representative for the chicken. In order to arrive at a representative curve, data from eight reported curves were compiled and adjusted to the same set of standard conditions of temperature (T), pH, and partial pressure of carbon dioxide (PCO2): T = 42 C, pH = 7.5 PCO2 = 40 torr. The mean PO2 STD (mean +/- SD) versus percent saturation of hemoglobin curve was then determined. The mean data were fitted to an equation representing the oxygen dissociation curve so that for any selected partial pressure of oxygen (PO2) the percent saturation (%SAT) of oxyhemoglobin may be computed. The P50 values for the mean literature and equation curves, respectively, were 47.4 +/- 9.8 and 45.3 Torr. The mean curve with its standard deviations provides a chicken oxygen dissociation curve representative of the literature data to which experimental data may be compared. The equation for the curve enables rapid referral to the representative curve to compute the %SAT, given the PO2 adjusted to the standard conditions.

Animals↗
PubMed1980

Non-invasive lung function tests in rats with progressive papain-induced emphysema.

Non-invasive plethysmographic methods for measurement of thoracic gas volume (TGV), airway resistance (Raw) and phase difference (PD) between flow rate at the nose and mean alveolar pressure were adapted for use in anesthetized rats. Thirty-six male Sprague-Dawley rats (200-250 g), were treated in groups of six by a single transoral, intratracheal instillation of 2 mg . kg-1 or 4 mg . kg-1 of papain in saline, or left untreated as controls. Measurements of TGV, Raw, and PD were made before treatment and at 4-day intervals after treatment for 8 or 16 days. TGV increased 65 percent by the fourth day and showed no change beyond the eighth day. Raw (0.4 +/- 0.04 cm H20 . ml-1 . sec) was not different from that of the controls. PD did not change significantly from the pretreatment value (4.7 +/0 0.41 degrees). The TGV, Raw, and PD responses were similar in the 2 mg . kg-1 and 4 mg . kg-1 papain treated rats. The TGV results suggest that the destructive effects of papain on the lungs are complete by the eighth day. The Raw results indicate that the airways are unaffected. The PD data are consistent with theoretical modeling studies for uneven distribution of compliances but neglible inequality of peripheral resistances.

Airway Resistance↗
PubMed1980

Calcium and cGMP in isolated rat parotid acinar cells.

The role of calcium ions in the activation of guanylate cyclase and in the propagation of the effects of cGMP during activation of the muscarinic cholinergic receptors was studied in isolated rat parotid acinar cells. It was demonstrated that the requirement for extracellular calcium is complete in the transduction of information from the muscarinic receptor to the guanylate cyclase, and partial in the steps beyond the synthesis of cGMP.

Acetylcholine↗
PubMed1980

Chicken oxygen dissociation curve by dynamic tonometry.

Oxygen dissociation curves were determined for blood from mature (5 male, 5 female) Single Comb White Leghorn chickens. Blood was oxygenated by bubbling with humidified 95% O2, 5% CO2, 0% N2 at 100 ml/min for 30 min, then gradually deoxygenated with 0% O2, 5% CO2, 95% N2 at 4 ml/min. During deoxygenation .5 ml samples were drawn at 7 in intervals. The PO2, PCO2, and pH were measured polarographically and the content of O2 was measured by gas chromatography. The PO2 was corrected to T = 42 C, pH = 7.5, and PCO2 = 40 Torr. The curves were determined by plotting: 1) PO2 vs. % Saicont based on O2 content of each serial sample as compared to the fully oxygenated blood O2 content, and 2) PO2 vs. duration of dynamic tonometry plots. The curves determined by the two methods of data analysis corresponded closely, the P50 values (x +/- SD) being 36.2 +/- 2.5, 34.3 +/- 3.1 Torr, respectively.

Animals↗
PubMed1978

Lymphoid antigenic determinants of the chicken. Cellular representation and tissue localization.

Antisera were prepared against a variety of chicken tissues with a view to detecting antigens specific for subpopulations of T and B cells at different maturation stages. By appropriate absorption analysis, the following antigens were defined: (a) thymus organ-specific antigen (CTOA); (b) T lymphocyte-specific antigen (CTLA); (c) B lymphocyte-specific antigen (CBLA); (d) mature B lymphocyte-specific antigen (CMBLA); (e) a foetal-associated antigen (CFAA) present on embryonic haemopoietic cells, and adult bone marrow and immature bursa cells, suggesting the cell types concerned may be at an early stage of development, possibly including precursors. For comparison with the above antigens, cells were also examined for surface Ig and IgG. T cells were found in periarteriolar sheaths in the spleen, and predominantly in the sub-epithelium and sub-mucosa of the caecal tonsil of the gut-associated lymphoid tissue (GALT). B cells were localized in periellipsoidal sheaths and germinal centres in the spleen, and in primary follicles or germinal centres in the GALT. The thymic and bursal medullas contained the mature populations of T and B lymphocytes respectively.

Animals↗
PubMed1976

Antiserum specific for reticulin of the bursa of fabricius.

Antiserum produced by immunizing rabbits with embryonic chicken spleen cells showed, after appropriate absorption with cell suspensions, specificity for fetal spleen cells in membrane immunofluorescence tests. However, when the original antiserum was absorbed with tissue homogenates and tested on cryostat tissue sections, it reacted specifically with the reticular framework which separates the cortical and medullary lymphocytes in the follicles of the adult bursa of Fabricius. It is suggested that the reticulin may influence bursal lymphoid differentiation.

Animals↗
PubMedDate not supplied

A bursal stromal derived cytokine induces proliferation of MHC class II bearing cells.

To delineate the mechanisms of early embryonic chicken bursapoiesis, we developed several virally transformed stromal cell lines. Extensive phenotyping of one of these lines, BSL.2, with a panel of mAb mapped it as deriving from the E11 bursal surface epithelium. The functional properties of BSL.2 were assessed in vitro by culture of its conditioned medium with either embryonic bursal cells (BC) or adherent cell depleted bone marrow (BM). In both these populations there was an induction of proliferation during the first 72 h of culture, followed by a subsequent loss of proliferative activity coincident with the appearance of phagocytic and non-specific esterase positive adherent cells, which remained viable in culture for up to 3 weeks. Flow cytometric analysis of the proliferating cells demonstrated an increase in the number of MHC Class II+ (B-L+) cells for both BM and BC. There was, however, an overall decrease in total viable cell number during the period of proliferation, demonstrating the stimulation of a specific subpopulation of cells. FACS separation of the unstimulated adherent depleted BM and BC populations demonstrated that only a subpopulation of the B-L+ cells proliferated in response to BSL.2 CM in addition to a subpopulation of B-L-BM. BSL.2 CM stimulated B-L+ BM and BC co-expressed the antigen detected by 68.1, which has been described as a M[symbol: see text] marker, but is also detectable on bursal lymphocytes. In ovo administration, at E11, of concentrated BSL.2 conditioned medium resulted in a significant increase, by E18, of bursal weight and Bu-1 and B-L+ cell number. There were no simultaneous alterations to the spleen. Preliminary MW analysis of the BSL.2 supernatant has revealed an active factor of approximately 90 kDa.

Animals↗
PubMedDate not supplied

In vitro characterization of a novel avian haemopoietic growth factor derived from stromal cells.

To better define the role of the chicken haemopoietic microenvironment in supporting haemopoiesis, a continuous cell line was generated by RSV transformation of avian spleen stromal cells (SSL-1). Supernatants from this line were found to contain haemopoietic growth factor activity as measured by the ability to induce proliferation and differentiation of precursor cells present in embryonic and post-hatched haemopoietic tissues. Comparison of cultures grown in the presence of cMGF and SSL-1 conditioned media (CM) revealed that both cytokine sources induced similar types of cell populations. Both sources supported the proliferation of predominantly macrophage-like cells based on colony morphology, differential staining, non-specific esterase staining, and phagocytosis activity. Interestingly, SSL-1 does not express any message for cMGF, nor does it secrete any IL-2 or interferon activities suggesting that the growth factor activities seen in SSL-1 are novel.

Animals↗
PubMedDate not supplied

Somatostatin gene expression in hypothalamus and cortex of aging male rats.

Somatostatin has been reported to decrease with age in many brain regions and these changes generally have been considered to have important implications for the regulation of both neural activity and neuroendocrine regulatory systems. The purpose of this study was to determine whether the age-related changes in somatostatin concentration in cortex and hypothalamus are attributable to alterations in the regulation of somatostatin gene expression. Hypothalamic and cortical tissue were dissected from young (3-4 month), middle-aged (12-14 month), and old (22 month) male Fischer 344 rats. Total RNA was extracted and dilutions blotted to nitrocellulose. Somatostatin cDNA in expression vector pSP65 was used to produce a 32P-labeled antisense probe for hybridization. After washing, blots were autoradiographed and analyzed by densitometry. Dilutions of total RNA were also probed with 32P-labeled oligo d(pT)16 to determine poly A +RNA levels. Data were expressed as relative somatostatin gene expression (somatostatin mRNA/poly A +RNA). Results indicated that in cortex, relative somatostatin gene expression was similar in young, middle-aged, and old animals (0.54 +/- 0.11, 0.60 +/- 0.08, and 0.51 +/- 0.04, respectively). However, somatostatin gene expression in the hypothalamus decreased consistently with age and ratios in old rats were approximately 50% of levels observed in young animals (p less than 0.05). Northern analysis of RNA revealed a single somatostatin transcript of approximately 0.65 kb in all age groups. In situ hybridization analysis of somatostatin mRNA in the hypothalamus indicated that the age-related decrease in somatostatin gene expression is a consequence of decreased expression within specific hypothalamic nuclei rather than a loss of somatostatin-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMedDate not supplied

Thymic stromal cells and positive selection.

The intrathymic differentiation events leading to the development and export of mature T cells tolerant to self yet capable of responding to foreign peptide antigen in the context of self-MHC are clearly both dynamic and complex. The changing phenotype of the developing thymocyte as it migrates through and interacts with the heterogeneous thymic microenvironment and the intracellular signalling events associated with such interactions are being extensively studied, yet many aspects remain poorly defined, such as the precise relationship between stromal cells and thymic selection. Positive and negative selection are crucial events in the development of T cells, leading to a diverse yet non-autoreactive immune system. A breakdown in either of these processes could lead to either a reduced T cell repertoire or the escape into the periphery of autoreactive T cells - both clearly having deleterious consequences for the health of the individual. This review aims to summarise the current status of research in thymic positive selection with emphasis on the role of different cell types and peptides.

Animals↗