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Biomedical subjects

A L Allen

Publications and source records attributed to A L Allen.

At least 37 records · Page 2Linked to original sources
PubMed1996

A case-control study of the congenital hypothyroidism and dysmaturity syndrome of foals.

A case-control study was conducted to identify risk factors for the congenital hypothyroidism and dysmaturity syndrome of foals. A questionnaire was used during personal interviews of foal owners and farm managers to collect information on animal signalment, farm environment, and mare management. Information on 39 foals with the congenital hypothyroidism and dysmaturity syndrome were compared with 39 control foals. Foals with the syndrome had a significantly (P < 0.0001) longer gestation (357.6 d) than control foals (338.9 d). Pregnant mares that were fed greenfeed, did not receive any supplemental mineral, left their "home farm" during gestation, or grazed irrigated pasture had 13.1 (P = 0.0068), 5.6 (P = 0.0472), 4.3 (P = 0.0076), and approximately 15.3 (P = 0.0245), respectively, greater odds of producing an affected foal than mares not experiencing these events. Greenfeed often contains high levels of nitrate (NO3-), which is known to impair thyroid gland function. In light of this, forage samples from participating farms were analyzed for nitrate levels. The odds of one or more congenitally hypothyroid and dysmature foals being born on a farm feeding forage with at least a trace of nitrate was 8.0 times greater (P = 0.0873) than the odds of the disease occurring on a farm that fed forage free of nitrate. Further, the odds of a mare producing an affected foal when fed forage containing at least a trace of nitrate were 5.9 times greater (P = 0.0007) than those of a mare fed nitrate free forage. This study suggests that congenital hypothyroidism and dysmaturity syndrome in foals may be the result of diets that contain nitrate or that are low in iodine being fed to pregnant mares.

Animal Feed↗
PubMed1994

Use of the supraperiosteal envelope in soft tissue grafting for root coverage. I. Rationale and technique.

Recent advances in graft procurement and suturing encourage a reassessment of the "envelope" technique in soft tissue grafting for root coverage. Use of the supraperiosteal envelope permits conservation of existing gingiva, minimal surgical trauma to the recipient area, and firm fixation of the connective tissue graft over single and multiple adjacent areas of recession. The intimate coaptation of the bilaminar soft tissue complex thus achieved may facilitate graft survival and postoperative blending of soft tissues.

Connective Tissue↗
PubMed1994

Hyperplasia of the thyroid gland and concurrent musculoskeletal deformities in western Canadian foals: reexamination of a previously described syndrome.

A syndrome of neonatal foals characterized by hyperplasia of the thyroid gland and concurrent musculoskeletal deformities (TH-MSD) has been described in western Canada and may be increasing in incidence. In an attempt to improve recognition and understanding of this syndrome, 2946 records of equine abortuses, stillborns, and dead neonatal foals were examined to determine the laboratory involved, the year and month of submission, the breed and sex of the fetus or foal, the type of perinatal loss, the length of gestation, and whether or not the submission had evidence of a lesion of the thyroid gland, the musculoskeletal system, or other abnormal clinical or postmortem findings. One hundred and fifty-four (5.2%) records indicated the presence of an abnormal thyroid gland. Of these, 79 (2.7%) had additional lesions consistent with the TH-MSD syndrome described in the 1980s, while 75 (2.5%) were without these additional lesions. Comparisons among these two groups and a third group of fetuses and foals without lesions of the thyroids glands are described. The results confirm that the TH-MSD syndrome is a specific and unique disease with no breed or sex predilection. It is argued that there may be an "exposure-related" cause, and based on a review of similar disease syndromes of the horse, it is suggested that an examination of the feed is indicated in outbreaks of the TH-MSD syndrome.

Abortion, Veterinary↗
PubMed1985

Antigenic variation in clones of Trypanosoma brucei grown in immune-deficient mice.

We have produced monoclonal antibodies against six variant surface glycoproteins from early variant antigen types (VATs) of the IsTaR 1 serodeme of Trypanosoma brucei brucei. We have used these in fixed cell immunofluorescence assays to follow the VAT composition of populations of each early VAT when passaged through irradiated mice. The IsTat 1.A and 1.7a populations were stable for more than 30 days (approximately 150 generations), but 1.1a, 1.3a, 1.5a, and 1.11a all changed to 1.A within this time. The time and rate of this antigenic switch were characteristic for each VAT. Growth rates of the VATs were determined when they were both grown separately and grown with 1.A. It appeared that the order of growth rates was 1.7a greater than 1.A = 1.1a greater than 1.11a greater than 1.5a greater than 1.3a. We have generated theoretical curves for the replacement of one VAT by another based on differences in their growth rates and the rate at which one VAT switches to another (switch frequency). These curves closely match those derived experimentally. We postulate that the differences in growth rates between VATs and the different switch frequencies for VATs may be sufficient to generate the loosely defined sequence of VATs seen in chronic infections.

Animals↗
PubMed1983

Effect of toxaphene exposure on immune responses in mice.

Toxaphene was fed to female weanling Swiss-Webster mice at dosages of 10, 100, and 200 ppm for 8 wk. Immunologic assays revealed depressed IgG antibody formation in those animals receiving 100 and 200 ppm toxaphene, as compared to controls. Cell-mediated immune responses were not affected in the toxaphene-exposed mice. In another experiment, mature female mice fed the same amounts of toxaphene were mated 3 wk after feeding began and were maintained on the diets until 3 wk after parturition, at which time the pups were weaned onto the control ration. Assays performed on the offspring 8 wk after their birth revealed suppressed antibody formation in the 100-ppm-toxaphene group and enhanced antibody formation in the 200-ppm group. The cell-mediated immune response was suppressed in the offspring from the 100-ppm group, while no change from the controls occurred in the other groups. Phagocytic ability of macrophages was significantly reduced in all toxaphene-treated groups, but to a greater extent in the offspring of the mice that consumed 100 ppm toxaphene.

Animals↗
PubMed1978

Periodontosis: a case report with scanning electron microscopic observations.

A tooth and associated periodontal tissues from a patient with the diagnosis of periodontosis was subjected to scanning electron microscopic evaluation after reflection of the soft tissue portion of the lingual defect. The cemental surface of the apical portion of the lesion was found to be populated by markedly similar rod-shaped organisms. The microorganisms were observed to be continuously present in a coronal-apical direction as the transition from cementum to the attached soft tissues at the base of the defect were examined. These findings provide additional evidence that the lesion of periodontosis is characterized by a rather distinct microbial population of rod-shaped organisms located predominately at the base of the defect.

Adult↗
PubMed1978

The incidence of transient bacteremia during periodontal dressing change.

Twenty patients undergoing treatment for periodontal disease and not receiving antibiotics, volunteered to donate blood for culture studies to determine the incidence of transient bateremia during the dressing change and suture removal 1 week after periodontal surgery. Each patient contributed 20 ml of blood prior to the dressing change and an additional 20 ml during suture removal. The samples were cultured both aerobically and anaerobically. Bacteria were demonstrated in five out of 20 postoperative cultures (25%). This incidence approached statistical significance at the 0.05 level using Chi-square analysis with a Yates correction. All species were identified as belonging to the genus streptococcus. None of the blood specimens obtained prior to dressing change exhibited bacterial growth. Although the incidence of bacteremia in this study was not statistically significant at the 0.05 level, it may be clinically significant that five out of 20 patients demonstrated transient bacteremia. Commercial materials and equipment are identified in this report to specify the investigative procedures. Such identification does not imply recommendation or endorsement or that the materials and equipment are necessarily the best available for the purpose. Furthermore, the opinions expressed herein are those of the author and are not to be construed as those of the Army Medical Department.

Bacteria↗