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Biomedical subjects

D L Reynolds

Publications and source records attributed to D L Reynolds.

65 records · Page 4Linked to original sources
PubMedDate not supplied

Analytical methods for determining ascorbic acid in biological samples, food products, and pharmaceuticals.

Over the last decade, numerous publications have appeared describing analyses for ascorbic acid in food products, pharmaceuticals, and biological samples. This review focuses on the chemistry associated with many of these procedures. The papers discussed have historical importance, are important to understanding the method, or have significantly advanced ascorbic acid analysis. The review has 4 major sections: spectroscopic, electrochemical, enzymatic, and chromatographic methods of analysis.

Animals↗
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Astrovirus infection in hatchling turkeys: histologic, morphometric, and ultrastructural findings.

In three separate experiments, 2- or 5-day-old commercial turkey poults were inoculated orally with astrovirus and examined for clinical signs and for gross and microscopic lesions over a period of 14 days. By day 2 postinoculation (PI), inoculated poults had developed diarrhea, generalized loss of intestinal tone, and dilated ceca that contained light-yellow fluid feces and gas; these changes persisted through day 10 PI. Mild crypt hyperplasia was the only change discernible by light microscopy, and it was first noted in the proximal jejunum on day 1 PI, in the distal jejunum and ileum on day 3 PI, and in the duodenum on day 5 PI. A significant (P < 0.05) increase in crypt depth and area was documented by image analysis on day 3 PI. Ultrastructural evaluation revealed intracytoplasmic aggregates of astrovirus in enterocytes on the sides and base of villi in the ileum and distal jejunum on day 3 PI. Based on the findings, it was concluded that astrovirus caused lesions and replicated in both upper and lower segments of the small intestine in turkey poults.

Animals↗
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Astrovirus infection in hatchling turkeys: alterations in intestinal maltase activity.

Two experiments were conducted to determine intestinal disaccharidase activity in 1-day-old commercial turkey poults inoculated with astrovirus. Small intestinal samples were collected on days 0.5, 1, 3, and 7 postinoculation (PI) in Expt. 1 and on days 7, 10, and 14 PI in Expt. 2 and evaluated for specific maltase activity (SMA). Astrovirus infection was verified on day 7 PI by immune electron microscopy of intestinal contents. Inoculated poults developed diarrhea and a transient, significant decrease in intestinal SMA. SMA was significantly (P < 0.05) lower in astrovirus-inoculated poults than in control poults throughout the entire small intestine from day 3 through day 7 PI. However, SMA had returned to normal in inoculated poults by day 10 PI and was significantly higher than control values (P < 0.05) in all sections of the small intestine, except in the proximal jejunum, by day 14 PI. Decreased SMA caused by astrovirus infection resulted in disaccharide maldigestion, malabsorption, and subsequent osmotic diarrhea. As astrovirus was cleared from the intestinal tract, SMA was restored and diarrhea was resolved.

Animals↗
PubMedDate not supplied

Mitogenic responses of the head-associated lymphoid tissues of the chicken.

A blastogenesis microassay employing 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) was adapted to measure blastogenic responses of lymphocytes from the chicken's head-associated lymphoid tissues (i.e., the harderian gland and conjunctiva-associated lymphoid tissue) to T- and B-cell mitogens. Lymphocytes isolated from peripheral blood, spleen, and the harderian gland had highly significant (P < 0.01) responses to T- and B-cell mitogens compared with control lymphocytes cultured without mitogens. Cultured lymphocytes obtained from the harderian gland had highly significant mitogenic responses to the T-cell mitogen concanavalin A (25 to 100 micrograms/ml) and to the B-cell mitogen Salmonella typhimurium lipopolysaccharide (1.25 to 5.0 micrograms/ml) compared with the control lymphocytes. Mitogenic responses of cultured lymphocytes obtained from the conjunctiva-associated lymphoid tissue could not be measured within the given parameters of the blastogenesis microassay. This was primarily due to the low yield of lymphocytes, which proved to be a limiting factor. The ability of the MTT blastogenesis microassay to detect blastogenic responses of the harderian gland to mitogens may be indicative of its usefulness for measuring cell-mediated immunity responses to other antigens.

Animals↗
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Characterization of a group D rotavirus.

A rotavirus isolated from the intestinal contents of commercial ring-neck pheasant chicks was determined to be a group D rotavirus based on its RNA electropherotype and its serologic relatedness to known turkey group A and D rotaviruses using immune electron microscopy and agar-gel immunodiffusion assays. Further characterization revealed a buoyant density in cesium chloride of 1.347 g/cm3 for double-shelled particles and 1.365 g/cm3 for single-shelled particles. The average size for the pheasant-origin group D rotavirus was determined to be 80 nm for double-shelled particles and 70 nm for single-shelled particles. In contrast, the average size for a turkey group A rotavirus isolate was determined to be 73 nm for double-shelled particles and 60 nm for single-shelled particles. There was no evidence of viral replication by the pheasant-origin group D rotavirus (either cytopathic effect or increase in numbers of viral particles) after six passages in MA104 cells. The hemagglutinating activity of the pheasant origin group D rotavirus was compared with that of a turkey origin group A rotavirus. Differences and similarities were noted depending upon the species of erythrocytes employed and the temperature of incubation.

Animals↗
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Primary cell culture of turkey intestinal epithelial cells.

Primary cell culture has been widely used in various types of studies and proven useful for the isolation and identification of avian pathogens. Difficulties in growing intestinal epithelial cells in vitro have limited their use for such studies. In the present study, a co-culture system was developed for the primary culture of intestinal epithelial cells. A monolayer obtained from 14-to- 16-day-old turkey embryo intestinal fibroblasts was used as a feeder layer. Feeder layers from turkey embryo fibroblasts and from a continuous cell line (mouse 3T3 fibroblasts) were also employed but were not as successful. The intestinal epithelial cells were isolated by dissociation from the intestinal tracts of 1-day-old turkey poults and grown on the feeder layers. Growth and maintenance media were supplemented with various components, including fetal calf serum, chicken serum, hormones, and other growth factors. The epithelial cells grown on feeder layers from the intestinal fibroblasts allowed the intestinal epithelial cells to be maintained in vitro for periods of 7 to 10 days. This technique may prove useful for various applications, including isolation of enteropathogens, and for basic studies of the intestinal tract concerning such subjects as physiology, immunology, and toxicology.

Animals↗
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B cells and T-lymphocyte subsets of the head-associated lymphoid tissues of the chicken.

The head-associated lymphoid tissues of the chicken, composed of the harderian gland and the conjunctiva-associated lymphoid tissue (CALT), were studied to determine whether changes occurred in lymphocyte subpopulations as chickens age from 1 week to 8 weeks. The B cells and subpopulations of T-lymphocytes of the head-associated lymphoid tissues were identified using in situ immunohistochemical staining. Monoclonal antibodies specific for various lymphocyte surface antigens were used. The concentration of T-lymphocytes, particularly CD3+ and CD4+ cells, within the harderian gland increased with age, whereas the concentration of B cells remained the same. B-lymphocytes were observed within the germinal centers of the CALT of 4-week-old birds. The T-lymphocytes within the CALT surrounded the B-cell-rich germinal centers. CD3+ T-lymphocytes were the predominant cell population in all age groups examined. Increasing concentrations of CD3+, CD4+, and CD8+ T-lymphocytes were observed within the CALT as chicks developed from 1 week to 4 weeks of age. Finally, no changes were observed in lymphocyte populations within the CALT as chicks developed from 4 weeks to 8 weeks of age.

Aging↗
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Stunting syndrome in turkey poults: isolation and identification of the etiologic agent.

Stunting syndrome (SS) is an enteric disease of turkey poults that causes high morbidity including reduced growth, impaired feed efficiency, and diarrhea. The etiologic agent of this disease has not been previously reported. The objectives of the present study were to identify, isolate, and purify the etiologic agent of SS. Day-old poults were orally inoculated with a SS-inducing inoculum. The intestinal epithelial cells (IECs) were isolated on the fourth day postinoculation. The IECs were lysed and filtered through 0.2-, 0.1-, and 0.02-micron filters. The cell lysate filtrate (0.1 micron) was subjected to density gradient ultracentrifugation. Intact IECs, filtrates from IECs (0.2, 0.1, and 0.02 micron ), and IEC lysate fractions from gradients (FRG) were used as inocula to infect day-old turkey poults. The weight gain, jejunal maltase activity, and gross intestinal lesions were used as the parameters of evaluation. Weight gain and maltase activity were reduced (P = 0.001) by the isolated IECs, 0.2 and 0.1 micron filtrates, and FRG when compared with corresponding controls. IEC lysate filtrate (0.1 micron) and FRG were examined under transmission electron microscope (EM). Enveloped, pleomorphic particles varying in size from 60 to 95 nm were observed and termed stunting syndrome agent (SSA). Primary cultures of turkey IECs were used to further isolate and propagate the SSA. Following the fifth passage in the turkey IECs, the cell lysate induced SS in day-old poults. SSA particles were observed under EM after the fifth passage. The results of this study provide evidence that a viral agent has been isolated and identified from IECs of SS-infected poults and is the etiologic agent of SS.

Animals↗
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Syphilis in an urban community.

Recent reports of changes in the epidemiology of syphilis prompted a review of syphilis in our urban community. All records of positive syphilis serology reported to the City of Scarborough Health Department between 1990-94 were reviewed for key epidemiological variables. While infectious stages of syphilis were reported more often among young adults, incidence for all stages increased among successive age groups, with a male/female ratio of 1.0. One in five cases were identified during immigration screening, with a disproportionate number of cases immigrating from the Caribbean, Africa and Subcontinental India. Overall, the incidence of syphilis decreased during the study. However, a correlation of 0.95 was found between the provincial incidence of syphilis and number of tests ordered. The observed decrease in syphilis, therefore, may represent a decrease in detection owing to lack of testing.

Adolescent↗
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The in vitro propagation of stunting syndrome agent.

Stunting syndrome (SS) is a viral enteric disease of turkey poults. The etiologic agent (stunting syndrome agent [SSA]) of this disease has been reported recently. The objective of this study was to develop a method for in vitro propagation of SSA. Primary cells, various continuous cell lines, and embryonated eggs were evaluated. Turkey embryos that were inoculated via the amniotic cavity at 24-25 days of incubation were susceptible to SSA infection. The jejunal maltase activity of SSA-inoculated turkey embryos was significantly (P < or = 0.001) lower than that of control embryos. D-xylose absorption was also altered in SSA-infected turkey embryos. The extent of reduction of D-xylose absorption and maltase activity in the infected embryos was nearly identical to that observed when day-old poults were infected with SSA. The intestines from the infected turkey embryos were pale, thin walled, and distended with fluid. Electron microscopic examination of the intestinal fluid and epithelial cell lysate of infected embryos revealed pleomorphic membraned SSA viral particles. SSA that had been serially passaged in turkey embryos retained its ability to induce SS in day-old poults. All the primary and continuous cells that were evaluated did not support the replication of SSA on the basis of cytopathic effects, electron microscopy, and turkey embryo inoculation. Inoculation of chicken embryos by various routes failed to support SSA. All routes of inoculation, other than the amniotic route at 24-25 days, failed to support SSA in turkey embryos. The results of the this study indicate that the SSA was successfully propagated in turkey embryos that exhibited alterations in embryo intestinal absorption and digestive enzyme activity similar to poults with SS. Successful propagation of SSA in turkey embryos should prove beneficial for future studies including characterization of SSA, prevention and control strategies, and enteric disease modeling.

Animals↗