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Biomedical subjects

J R Stevenson

Publications and source records attributed to J R Stevenson.

At least 19 recordsLinked to original sources
PubMed2005

Does continuous passive motion during keyboarding affect hand blood flow and wrist function? A prospective case report.

The purpose of this prospective case report was to evaluate the use of a keyboard platform device that uses continuous passive motion (CPM) on vascular flow to the hand for clerical employees who perform daily keyboarding tasks. Subjects were two female volunteers, one symptomatic of carpal tunnel syndrome (CTS), who were employed in clerical positions and perform daily keyboarding tasks for most of their workday. Data collection consisted of baseline and follow-up measurements at 6 weeks, including: 1) screening for symptoms based on the Carpal Tunnel Function Disability Form, 2) evaluation using standard physical therapy examination and assessment techniques, including modified Semmes- Weinstein monofilament testing, 3) a typing productivity test, and 4) Doppler ultrasound examination to quantify vascular flow at the wrist. Results revealed that both subjects demonstrated an overall increase in both radial and ulnar blood flow velocity with no decrement in typing productivity. The symptomatic subject also demonstrated an overall improvement of 10 wpm in the typing tests, a decrease in her disability score and symptom severity, and improvement in function. Results suggest that use of CPM as a non-intrusive ergonomic intervention may be used to treat, as well as prevent, carpal tunnel-like symptoms in those who keyboard.

Carpal Tunnel Syndrome↗
PubMed2001

Prolonged alpha-adrenergic stimulation causes changes in leukocyte distribution and lymphocyte apoptosis in the rat.

We have previously shown in the rat model that acutely or chronically increased peripheral catecholamines lead to suppression of lymphocyte responsiveness via alpha(2)-adrenoceptor activation. Here we investigated the effects of alpha-adrenergic treatment on total leukocyte numbers and proportions of leukocyte subsets in peripheral blood and lymphoid tissues. It was found that a 12-h treatment with subcutaneously implanted tablets, one containing norepinephrine (NE) and one propranolol, leads to an increase in total blood leukocyte counts, due to a pronounced increase in granulocytes. In contrast, the numbers of all classes of lymphocytes other than NK cells were decreased. This decrease in blood lymphocytes is apparently not due to redistribution, since in the thymus, spleen, mesenteric and peripheral lymph nodes, the total numbers of lymphocytes were decreased as well, without any changes in subpopulations. Analogous results were obtained with rats adrenalectomized before the catecholamine treatment. Animals that received the alpha-adrenergic treatment displayed significantly more apoptotic cells in the lymphoid organs, as determined by the TUNEL technique. In the spleen, the enhanced rate of apoptosis was confined to the white pulp; red pulp areas exhibited significantly fewer apoptotic cells. Thus, an increased alpha-adrenergic tone in rats led to a general loss of lymphocytes due to lymphocyte directed apoptosis that was independent of glucocorticoids.

Adrenal Medulla↗
PubMed2000

In vivo immunomodulation by peripheral adrenergic and cholinergic agonists/antagonists in rat and mouse models.

Our work is devoted to defining relationships between the immune system and the adrenergic and cholinergic systems in vivo. In the rat model, we have shown that the cells of different immune compartments express the genes of a defined set of adrenergic/cholinergic receptors, and it was shown that lymphocytes are a site of non-neuronal production of norepinephrine and acetylcholine. Furthermore, using implantable slow-release tablets containing adrenergic or cholinergic agonists/antagonists, distinct and partly opposite effects were observed on peripheral immune functions. Concerning sympathetic immunoregulation, our data--in contrast to those of other studies--suggest that an enhanced adrenergic tonus leads to immunosuppression primarily via alpha 2-receptor-mediated mechanisms. Beta-blockade strongly enhances this effect, most likely by inhibition of pineal melatonin synthesis. In recent experiments on the kinetics it was found that the continuous alpha-adrenergic treatment entails a strong suppression of cellular responsiveness during the first few hours, which is increasingly followed by a general loss of lymphocytes in blood and lymphoid organs most likely due to enhanced apoptosis. More recently, we have extended our studies to the mouse model. First data obtained with RNAse protection assays suggest a biphasic effect on the gene expression of several cytokines in spleen cells due to adrenergic in vivo treatment.

Animals↗
PubMed1999

An expert experiment--medico-legal expert testimony.

For the past eight years, Radiology Associates of Albuquerque has provided physician expert testimony to plaintiff and defense attorneys. Initially, the business was confined to radiology consultation only. The division has expanded; it now includes more than 35 specialties and a national client base. This article will include a history of the division's growth and lessons learned as well as a look at the future of expert testimony in light of increasing emphasis on standards of care. Medical marketing in the present as well as in the future will also be addressed.

Expert Testimony↗
PubMed1996

Cold swim stress leads to enhanced splenocyte responsiveness to concanavalin A, decreased serum testosterone, and increased serum corticosterone, glucose, and protein.

This study extends previous observations of the conditions under which enhancement of lymphocyte activity occurs following cold swim stress and presents a possible explanation for the enhancement observed. Eight- to twelve-week old male Sprague-Dawley rats swam for 10 minutes daily for one, three, or five days in cold water at 15 degrees C and were killed 0, 30, or 240 minutes following the last swim. Apparatus control animals were placed into an empty swim tank for 10 minutes and then returned to their home cages. Home cage control animals were not manipulated experimentally at all. Splenocyte but not thymocyte responses to concanavalim A were significantly enhanced after one, three, and five days of stress. This enhancement was seen after 0, 30, and 240 minutes of recovery and also in the apparatus controls! The number of splenocytes did not change significantly, but thymocyte number declined following the swims. The blood displayed no changes in leukocyte percents. Serum corticosterone levels were significantly higher and serum testosterone levels were significantly lower after one, three, and five days of stress. The drop in testosterone levels may have released the lymphocytes from inhibition by this hormone, resulting in increased responsiveness. There were significant elevations in levels of blood glucose and protein following one, three, and five days of stress sessions, correlated with the increases in serum corticosterone.

Animals↗
PubMed1993

Characterization and mechanisms of thymic atrophy in protein-malnourished mice: role of corticosterone.

The purpose of this project was to characterize changes in murine T lymphocyte subpopulations during thymic atrophy induced by protein malnutrition and to determine the role of elevated serum corticosterone in this process. A suitable animal model was generated by placing mice on protein-sufficient (PS) and protein-deficient (PD) diets for 6 weeks. Body weight was monitored to determine the establishment and maintenance of malnutrition. Results obtained using PD mice indicated a direct correlation between serum corticosterone levels and thymic atrophy. Furthermore, results of the experiments using mice implanted with corticosterone-impregnated pellets indicated that corticosterone alone, at the levels observed in PD mice, induced thymic atrophy in normal mice. These results demonstrate that the thymic atrophy induced by protein malnutrition is primarily due to elevated serum corticosterone. As indicated by flow cytometric analysis, the number of cells in all thymocyte subpopulations decreased as protein malnutrition continued, possibly reflecting depletion of immature CD4-/CD8- and CD4+/CD8+ cells, ultimately resulting in loss of mature CD4+ and CD8+ cells. TCR expression by PD thymocytes, especially those with high levels of CD3, increased during the dietary period. Mice implanted with corticosterone pellets experienced severe losses of CD4+/CD8+ cells, resulting in thymocyte subpopulation and CD3 profiles more similar to those of hydrocortisone-injected mice than those of PD mice. Therefore, whereas thymic atrophy in protein-malnourished mice seems to be caused by elevated serum corticosterone, it appears that additional factors further modulate thymocyte proliferation, differentiation, and/or death in this system.

Animals↗
PubMed1993

The effects of detraining on power athletes.

We investigated the effects of 14 d of resistive exercise detraining on 12 power athletes. In comparing performances pre- to post-detraining, there were no significant (P > 0.05) changes in free weight bench press (-1.7%), parallel squat (-0.9%), isometric (-7%) and isokinetic concentric knee extension force (-2.3%), and vertical jumping (1.2%). In contrast, isokinetic eccentric knee extension force decreased in every subject (-12%, P < 0.05). Post-detraining, the changes in surface EMG activity of the vastus lateralis during isometric, and isokinetic eccentric and concentric knee extension were -8.4%, -10.1%, and -12.7%, respectively (all P > 0.05). No significant changes occurred in knee flexion forces or EMGs (P > 0.05). Percentages of muscle fiber types and the Type I fiber area remained unchanged, but Type II fiber area decreased significantly by -6.4% (P < 0.05). Levels of plasma growth hormone (58.3%), testosterone (19.2%), and the testosterone to cortisol ratio (67.6%) increased, whereas plasma cortisol (-21.5%) and creatine kinase enzyme levels (-82.3%) decreased (all P < 0.05). Short-term resistive exercise detraining may thus specifically affect eccentric strength or the size of the Type II muscle fibers, leaving other aspects of neuromuscular performance uninfluenced. Changes in the hormonal milieu during detraining may be conducive to an enhanced anabolic process, but such changes may not materialize at the tissue level in the absence of the overload training stimulus.

Adult↗
PubMed1991

Pseudorabies virus-induced suppression of major histocompatibility complex class I antigen expression.

The ability of pseudorabies virus (PrV) to down-modulate expression of major histocompatibility complex class I antigens in murine and porcine cells was investigated. When quantified by flow cytometry, surface expression of class I Kk and Dk antigens on PrV-infected cells decreased by 60% or more. Down-modulation was associated with a decrease in total cellular class I antigens, indicating regulation at the transcriptional or posttranscriptional level. PrV did not suppress expression of transferrin receptor, suggesting a selective regulatory mechanism.

Animals↗
PubMed1991

Enhancement by restraint stress of natural killer cell activity and splenocyte responsiveness to concanavalin A in Fischer 344 rats.

Stress usually has a depressing effect on immune function. However, we observed apparent immune enhancement following restraint stress. Fischer 344 rats were restrained in snug--fitting wire mesh tubes for 14 hr/day during the light portion of a daily 14:10 hr light/dark cycle for 0, 11, 22, or 33 days. Animals were sacrificed immediately after the last restraint session, and trunk blood and spleens were collected. Blood neutrophil percent was significantly higher after 11 or 22 days of restraint than in controls, as expected, and returned to baseline at 33 days. However, natural killer activity of spleen cells against Yac-1 targets, measured by a lactate dehydrogenase (LDH) release assay, was higher than controls after all periods of restraint, and especially after 11 days. Responses to concanavalin A by spleen cells from restrained rats were also higher than controls after all periods of restraint.

Animals↗
PubMed1989

Effects of corticosterone on responses of murine splenic B and T cells to phytohemagglutinin, concanavalin A, and lipopolysaccharide.

Spleen cells of C57BL/6 mice injected with corticosterone were compared with cells from mice injected with saline in their ability to respond to the mitogens PHA, Con A, and LPS. Both unseparated cells and cells separated into T-enriched and B-enriched fractions were studied. After either seven daily injections or four injections every other day of up to 100 mumoles hormone/kg body weight, the ability of both T and B cells to respond to mitogens was affected, the unseparated cells being more affected than the separated cells. In the whole spleen preparations, corticosterone seemed to inhibit the B cells more than the T cells, whereas when the cells were separated into T and B fractions, only the response of the cells in the T fraction was significantly reduced by the hormone. This suggests that this hormone may have a greater effect on the responsiveness of T cells than on B cells, whereas it reduces B cell number more than T cell number.

Animals↗
PubMed1988

Effects of glucocorticoid and antiglucocorticoid hormones on leukocyte numbers and function.

Hormones were administered to mice in seven daily intraperitoneal injections of saline suspensions. Progesterone and cortexolone, which often fail to act as antiglucocorticoids in vivo, were found to have antiglucocorticoid effects on the immune system under these conditions. The effects seen were increases in numbers of lymphocytes, monocytes, neutrophils and total leukocytes in the blood, increases in the number of peritoneal exudate cells and splenic plaque-forming cells, and increased splenocyte responses to the mitogen phytohemagglutinin. Deoxycorticosterone, sometimes also considered to be an antiglucocorticoid, acted only as a glucocorticoid here. Both deoxycorticosterone and the glucocorticoid corticosterone had effects opposite to those produced by progesterone and cortexolone on these parameters.

Animals↗
PubMed1986

In the murine syngeneic mixed lymphocyte reaction, one T cell subset replicates in the presence of B cells or macrophages and replication is inhibited by simultaneous presence of both stimulator cells.

The murine T-non-T cell syngeneic mixed lymphocyte reaction has been examined to determine whether B cells and macrophages stimulate the same or different subpopulations of T cells. By using experiments in which replicating T cells were suicided, we found that the two different stimulators caused replication of what appears to be the same subset(s) of T cells. Since B cells and macrophages carry the same stimulating antigens (class II plus mls or others), one would expect them to stimulate the same T cell subpopulations were it not that they have been reported to stimulate two different subpopulations in humans. When B cells and macrophages were simultaneously used as stimulators, diminished T cell replication occurred. We have found the reduced response is not attributable to exhaustion of culture nutrients or to displacement of the response peak. Other possibilities to account for this marked reduction have been discussed from the viewpoint of suppression emanating from macrophages and/or T cells.

Animals↗
PubMed1986

Rejection of reovirus-treated L1210 leukemia cells by mice.

L1210 leukemia cells were treated in vitro with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and reovirus to determine their interactive effects on rejection of these tumor cells by mice. The cells were treated with BCNU at concentrations of 0, 3, or 10 microM, incubated for 48 h, then treated with reovirus at a multiplicity of infection of 0, 10, 30, or 100 for 2, 6, or 12 h. The survival of mice injected with cells treated with any amount of reovirus, regardless of BCNU treatment, was greater than that of mice injected with untreated cells. Exposure of the cells to reovirus for 6 or 12 h increased the survival of mice injected with these cells as compared with that of mice injected with cells exposed to reovirus for 2 h. Of the survivors, 76% were resistant to subsequent challenge with untreated L1210 cells. These results suggest that activities associated with reovirus replication may cause modifications of L1210 cells that enable them to induce an immune response, thus facilitating their rejection. A lack of correlation between differences in DNA synthesis (measured by 3H-thymidine uptake) by treated cells and the ability of those cells to kill recipient mice indicates that rejection of cells treated with reovirus or BCNU is not due to a decrease in their ability to proliferate or, presumably, to generate lethal tumors. The survival of mice injected with treated L1210 cell preparations containing as few as 2.9% reovirus-infected cells was enhanced to the same degree as that of mice injected with those containing as many as 14.6% infected cells, indicating that modification of only a minor component of the tumor cell population is sufficient to alter the ability of the cells to generate a lethal tumor.

Animals↗
PubMed1986

Cytotoxic and migration inhibitory effects of bisphosphonates on macrophages.

Two in vitro model systems were developed to facilitate investigation of the mechanisms by which bisphosphonates block bone resorption. These systems assess the cytotoxic and the migration inhibitory activities of bisphosphonates using mouse peritoneal macrophages as osteoclast surrogates. Several bisphosphonates, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP), dichloromethylene bisphosphonate (Cl2MBP), 1-hydroxyethylidene-1,1-bisphosphonate (HEBP), 1-hydroxybutylidene-1,1-bisphosphonate (HBBP), 1-hydroxyhexylidene-1,1-bisphosphonate (HHBP), and 1-hydroxyoctylidene-1,1-bisphosphonate (HOBP), possess the same relative activities in these systems as they do in bone resorption systems. Calcium ion replacement studies using these systems demonstrated that bisphosphonates do not derive all their activity from sequestration of calcium ions from cells by chelation. Whereas calcium ion replacement abrogated the activity of EDTA, a nonbisphosphonate calcium chelator active in both systems, it failed to abrogate either the cytotoxic or the migration inhibitory effects of the bisphosphonates tested. Calcium ion replacement increased the migration inhibitory activity of all the bisphosphonates tested. Further, calcium ion replacement increased the cytotoxicity of HHBP and HOBP; however, it decreased the cytotoxicity of HEBP, HBBP, AHPrBP, and Cl2MBP.

Animals↗
PubMed1983

Impairment of macrophage migration inhibitory factor synthesis and macrophage migration in protein-malnourished mice.

Weanling CD2F1 mice were fed isocaloric diets that were protein sufficient (PS; containing 27% casein) or protein deficient (PD; containing 8% casein). Weight measurements demonstrated that the growth of PD mice was significantly impaired, thus indicating that the PD diet induced protein malnutrition. The cellular immune responsiveness of these mice was assessed from Day 21 to Day 49 of the diet using, as indicators, in vitro production of migration inhibitory factor (MIF) by splenic lymphocytes and MIF responsiveness of peritoneal macrophages. PD lymphocytes, when stimulated with the polyclonal activator concanavalin A, produced significantly less MIF than did PS lymphocytes. The amount of MIF produced by PD lymphocytes, however, increased throughout the study, possibly indicating delayed maturation of MIF synthetic capacity in PD mice. Normal CD2F1 mouse macrophages were used for these assays. MIF responsiveness of PD and PS macrophages was not significantly different when assayed using MIF produced by normal CD2F1 mouse lymphocytes. As compared to that of PS macrophages, the migratory ability of PD macrophages decreased progressively throughout the study. This impaired migratory ability did not interfere with MIF responsiveness of PD macrophages.

Animals↗
PubMed1980

Protective cellular antigen of Clostridium chauvoei.

Cellular antigens of Clostridium chauvoei, strain IRP-128, were demonstrated to be important in induction of immunity against this bacterium in guinea pigs. At least one major component of the cellular antigen complex was heat-labile. Acid extraction of the bacterial cells, followed by selective purification for flagella, led to the preparation of an acid extract antigen that possessed a high degree of immunogenicity. The acid extract antigen contained flagellar components and was resolved into two major and approximately five minor protein components by polyacrylamide-gel electrophoresis.

Animals↗