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M R Powell

Publications and source records attributed to M R Powell.

At least 55 records · Page 3Linked to original sources
PubMed1991

Carbohydrate epitopes are responsible for antibody cross-reactivity in Trypanosoma cruzi-infected mice.

Anti-Trypanosoma cruzi antibodies can be eluted from western blots of T. cruzi antigens and thereby are fractionated on the basis of the electrophoretic mobility of the antigens to which they bind. Antibodies fractionated by these methods can bind antigens with electrophoretic mobility different from those antigens from which they are eluted. Such antibodies thus are considered cross-reactive. Studies in which the target antigens are reacted with sodium periodate to destroy carbohydrate epitopes prior to exposure to the eluted antibodies revealed that antibodies are produced that bind to both carbohydrate and noncarbohydrate epitopes on western blots, but that most of the cross-reactive antibodies are directed toward carbohydrate moieties.

Animals↗
PubMed1990

Analysis of antibody cross-reactivity in experimental American trypanosomiasis.

Susceptible C3H/He mice were immunized with the avirulent Corpus Christi strain of Trypanosoma cruzi and subsequently infected with virulent Brazil stain organisms. Seventy days after infection sera were isolated and analyzed on western blots of electrophoretically separated T. cruzi antigens prepared from culture-form parasites (primarily epimastigotes). More than 25 bands were identified. The antibodies were fractionated by elution from various regions of western blots corresponding to average molecular weights of approximately greater than 130, 77, 70, 60, 48, or 38 kDa. Each of these antibody preparations was then incubated with strips of nitrocellulose containing all of the electrophoretically separated T. cruzi, and cross-reactivity was determined. Antibodies isolated from the 130-, 77-, and 70-kDa regions all cross-reacted with each other. Antibodies eluted from the 60-kDa region bound antigens in the 60-, 70-, and the 77-kDa regions. More importantly, antibodies eluted from every region bound antigens in the 70-kDa region. Conversely, antibodies eluted from this region bound to antigens in all of the other regions. These data indicate the presence of (a) common antigenic epitope(s) in T. cruzi infections in these mice that is predominantly found in the 70-kDa antigen-antibody complex on western blots.

Animals↗
PubMed1987

Low-level, magnetic-field-induced growth modification of Bacillus subtilis.

Experimental studies showed an increase in the growth of Bacillus subtilis mutant strain FJ7 above controls by exposing the bacterial culture to 800-Hz or 1-KHz magnetic fields with a 2-s-on/2-s-off period. The magnetic field strength was between 0.8 and 2.5 mT. Light microscopy and scanning electron microscopy demonstrated the morphology of controls to grow in a macrofiber of right-handed helix formation. In contrast, the field-exposed group showed little to no cohesion; the cells appeared to be homogeneously distributed throughout the sample. These results suggest that growth patterns of Bacillus subtilis can be altered as a result of magnetic-field-induced effects.

Bacillus subtilis↗
PubMed1987

Anti-idiotypic T lymphocyte responsiveness in murine Schistosomiasis mansoni.

Pooled sera from CBA/J mice infected for greater than or equal to 16 weeks with the blood fluke Schistosoma mansoni were immunoaffinity purified using soluble schistosome egg antigens (SEA) coupled to Sepharose 4B. The bound and then eluted fraction was shown to contain only immunoglobulins and to have anti-SEA activity. These anti-SEA antibodies stimulated proliferation of lymph node cells from mice infected with S. mansoni for 8, 12, or greater than or equal to 16 weeks but not from uninfected mice. The cells stimulated by anti-SEA antibodies were nylon wool adherent, Thy-1.2+, L3T4+, Lyt-2-lymphocytes. Immunoglobulins without anti-SEA activity isolated from the sera of syngeneic uninfected mice were not stimulatory for cells from normal or infected animals. Thus the responding T cells appear to be stimulated by the idiotypes expressed on the syngenic anti-SEA antibodies. These data present evidence for anti-idiotypic cellular reactions in murine schistosomiasis that could play important immunoregulatory roles in this disease.

Animals↗
PubMed1987

Increased vertebral bone mineral in response to reduced exercise in amenorrheic runners.

Seven female runners found to have exercise-induced amenorrhea and decreased bone mineral were reevaluated after 15 months. During the 15-month period, four runners took supplemental calcium and reduced their weekly running distance by 43%, resulting in an average 5% increase in body weight, increased estradiol levels and eumenorrhea. Bone mineral content increased from 1.003+/-0.097 to 1.070+/-0.089 grams per cm.(2) Three runners continued to have amenorrhea, with no change in running distance or body weight. Estradiol levels remained abnormally low and there was no significant change in the bone mineral content, although all three took supplemental calcium. We found that early osteopenia associated with exercise-induced menstrual dysfunction improved when runners reduced their running distance, gained weight and became eumenorrheic.

Adult↗
PubMed1985

Demonstration of splenic auto-anti-idiotypic plaque-forming cells in mice infected with Schistosoma mansoni.

Mice exposed to 35 cercariae of the human helminth Schistosoma mansoni develop chronic (greater than 16wk) infections characterized by immunoregulation of their cell-mediated granulomatous responses to schistosome eggs. Evidence was sought regarding the possible development of anti-idiotypic responses against the responses to soluble egg antigens (SEA). Sera were collected from CBA/J mice with chronic S. mansoni infections. Multiclonal idiotypic, anti-SEA antibody (id) was prepared from these pooled sera by affinity chromatography on an SEA immunoadsorbent column. Analysis of the id preparations by polyacrylamide gel electrophoresis demonstrated that this material contained only immunoglobulin heavy and light chains. A modified reverse plaque-forming cell (PFC) assay was developed to quantify anti-idiotypic (anti-id) PFC in spleen cell preparations from infected and age-matched control CBA/J mice. Expression of anti-id PFC began 2 to 3 wk after onset of egg production and continued throughout the course of infection. Positive selection of anti-id-reactive spleen cells by panning cell preparations from chronic mice on id-coated plates resulted in an enrichment of anti-id PFC in the id-adherent population. Conversely, the number of PFC reactive with SEA (id-producing PFC) was lowered by panning on id-coated plates. These data demonstrate the occurrence of anti-id responses during schistosomiasis mansoni. It is possible that such an immunoregulatory mechanism could play an important role in how an animal modulates the granulomatous response that leads to the formation of pathologic lesions and in the maintenance of this chronic infection.

Animals↗
PubMed1985

Fetal and maternal bubbles detected noninvasively in sheep and goats following hyperbaric decompression.

Pregnant sheep and goats were compressed with air to an equivalent depth of 49 msw (160 fsw) for bottom times ranging from 5 to 15 min. Maternal (precordial) and fetal (umbilical artery) circulation were monitored transcutaneously with a Doppler ultrasound flowmeter to determine the presence of decompression gas bubbles. It was found that the number of bubbles detected precordially in the maternal circulation exceeded the number detected in the fetal umbilical artery for any given bottom line. Additionally, bubbles were found in the fetal circulation even when the mother did not display signs of decompression sickness. Thus, avoidance of symptoms of pain-only decompression sickness in the mother is not sufficient to preclude gas phase formation in the fetus.

Age Factors↗
PubMed1984

Schistosoma mansoni egg granuloma size reduction in challenged baboons after vaccination with irradiated cryopreserved schistosomula.

Young male baboons born in captivity were immunized with an attenuated, cryopreserved schistosomular vaccine derived from gamma-irradiated (50 krad) cercariae of the Puerto Rican strain of Schistosoma mansoni. Protection against a heterologous Kenyan strain of S. mansoni, after percutaneous infection, was assessed. Partial protection (33-53% reduction in worm burden) was obtained in three of six vaccinated-challenged baboons, an unremarkable result. Of greater interest was the fact that all six unvaccinated-challenged control baboons, but only one of the six vaccinated-challenged baboons, had macroscopic egg granulomas on their liver surfaces. This difference in granuloma size was substantiated by measuring hepatic and colonic granulomas. The mean (+/- SEM) hepatic and colonic granuloma diameters for the six unvaccinated baboons were 406 +/- 38 micron and 313 +/- 27 micron, respectively, and for the five "typical" vaccinated-challenged baboons the mean diameters were 283 +/- 27 micron and 202 +/- 23 micron, respectively. Both hepatic and colonic granulomas were significantly smaller in the five typical vaccinated-challenged baboons. Not only did the exceptional vaccinated-challenged baboon have very large hepatic and colonic granulomas, but also it was the only one of its group whose mesenteric lymph node cells were not suppressed in their in vitro proliferative response to a schistosome antigen. These results strongly suggest that granuloma size reduction in the majority of the vaccinated baboons was the result of immunoregulation--i.e., the small postvaccination granulomas were "modulated." Despite their small size, hepatic granulomas in the typical vaccinated baboons were apparently as effective in sequestering egg toxins and preventing hepatocyte damage as the larger granulomas of the control baboons. Smaller, less obstructive granulomas are thought to be more beneficial to the host than large, vigorous granulomas, with respect to lessening chronic disease. The present results give encouragement that a vaccine to ameliorate disease in human schistosomiasis is possible. This effect should add to the attractiveness of partial protection against challenge infections conferred by attenuated larval vaccines, as reported by others, to yield a dually beneficial vaccine for human use.

Animals↗
PubMed1983

Gas phase formation and Doppler monitoring during decompression with elevated oxygen.

Subjects in 150 man-dives were precordially monitored with a 5-MHz Doppler ultrasound bubble detector. These measurements were made during a series of dives conducted to test decompression tables that utilize changes of breathing mixtures and a time-average PIO2 of 1.9 b during the entire decompression period. Precordially detected bubbles at depth were predictive for limb pain in divers approximately 50% of the time; however, 70% of the divers encountered bends problems in the absence of precordially detectable bubbles. Thus, while the presence of venous return bubbles can be associated with a risk factor for bends, the Doppler method appears to lack the specificity needed for personal dive monitoring. During the oxygen-breathing portions of the decompression individual bubbles could not be detected precordially. The amplitude of the Doppler-detected pulmonary artery flow sound increased, however, and possibly indicated the presence of numerous microbubbles.

Decompression↗
PubMed1982

Micro-system for the primary immunization of baboon (Papio cynocephalus) peripheral blood mononuclear cells with sheep erythrocytes in vitro.

A micro-culture system for the stimulation of baboon peripheral blood mononuclear cells (PBMC) with sheep erythrocytes (SRBC) in vitro was established. PBMC cultures in 96-well microtiter plates were maintained in 300 microliter of culture medium containing a murine mixed lymphocyte reaction (MLR) supernatant and SRBC. Cultures of 7.5 x 10(5) PBMC and 6 x 10(6) SRBC resulted in the highest anti-SRBC plaque-forming cell (PFC) response. It was also determined that the presence of 50 microliter of murine MLR supernatant was required for optimal PFC generation and that the cultures required supplementation with nutrient cocktail 3 days post-immunization. Although PFC were detectable on days 4-8, the maximum expression of PFC occurred on day 7.

Animals↗
PubMed1982

Schistosomiasis mansoni in baboons. VI. Plastic-adherent-cell suppression of the primary in vitro antibody response of peripheral blood mononuclear cells to a heterologous antigen (SRBC) during chronic infection.

Peripheral blood mononuclear cells (PBMC) from five of six baboons (Papio cynocephalus) with chronic schistosomiasis mansoni showed a marked reduction in the ability to generate anti-sheep erythrocyte (SRBC) plaque-forming cells (PFC) after primary in vitro immunization as compared to the PFC responses of PBMC from normal (non-infected) baboons. Removal of the plastic-adherent (PLAD) cells from the PBMC of these animals results in a population of cells capable of responding to in vitro immunization with SRBC at a level equal to or higher than their normal counterparts. Reconstitution of plastic-non-adherent cells with PLAD cells re-establishes suppression. In contrast, the single apparently non-suppressed infected baboon showed reduced responses after PLAD cell removal, but, upon reconstitution with PLAD cells, responses were higher than those obtained before cell separation. No evidence of PLAD suppressor cells in normal animals was found, and indeed the data suggest that PBMC from normal animals may require a PLAD accessory cell for full responsiveness.

Animals↗
PubMed1980

Measurement of cytolytic antibody in experimental Chagas' disease using a terminal radiolabelling procedure.

The onset and development of anti-Trypanosoma cruzi cytolytic antibody during the course of infection were examined in two strains of mice that differ in their susceptibility to T. cruzi. The relative amounts of cytolytic antibody in the sera of mice were determined by a terminal radiolabeling procedure that measures the amount of 3H-thymidine incorporatedinto culture-form parasites that survive treatment with antibody and complement. The results showed that low levels of anti-T. cruzi cytolytic antibody developed during the course of infection in mice, and that there was no apparent difference in cytolytic antibody responses during the acute phase of infection in relatively resistant C57BL/6 mice and highly susceptible C3H(He)mice.

Animals↗
PubMed1979

An evaluation of salivary scintigraphy in Sjögren's syndrome.

Sequential salivary scintigraphy, labial salivary gland biopsy, and measurement of stimulated parotid flow rate were performed in 50 patients suspected of having Sjögren's syndrome. The value of these tests in the diagnosis of this disease was compared. Salivary scintigraphy and labial salivary gland biopsy can be used together to diagnose the oral component of Sjögren's syndrome. Abnormal salivary scintigraphy correlated with both of the other tests and may be considered optional in the diagnostic evaluation.

Female↗
PubMed1976

Measurement of blood flow in skin with an intact vascular pedicle.

An experimental model was devised to confirm directly the validity of total skin blood flow measurement, as postulated by Sejrsen. A section of skin in the groin of the rat was prepared, which contained an intact artery and vein. Both of these were direct branches of the femoral vessels. When 133Xe was injected intradermally in saline solution, it was demonstrated that a sham isolated vascular pedicle cleared the isotope, and that the clearance was biexpoential, suggesting two compartments. When the vascualr pedicle was ligated, thereby removing direct blood flow to the piece of skin, the 133Xe clearance curve was monexponential. It is concluded that the rapid portion of the biexponential clearance curve, as analyzed by Sejrsen, does represent the dermal vascular components of isotope clearance, and that measurement of cutaneous blood flow by this method is a valid and useful technique. Results using this technique to follow rejection in a new skin transplant model are presented.

Animals↗