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Biomedical subjects

D R Morgan

Publications and source records attributed to D R Morgan.

At least 91 records · Page 5Linked to original sources
PubMed1985

The effects of mild hypoxia on a logical reasoning task.

In an attempt to replicate the findings of Crow and Kelman (1969) and Denison et al. (1966), which suggest that the performance of novel tasks can be impaired at altitudes below 3,050 m, 150 subjects were divided into five independent groups and their performance tested on a logical reasoning task. One group was tested at ground level in a lecture room; the remaining groups were tested in a decompression chamber, one at 305 m, one at 2,440 m, one at 3,050 m and one at 3,660 m. Significant differences were identified between the 'lecture room' and 'chamber' groups in both speed of work and error rate (p less than 0.05); this finding is interpreted as the effect of apprehension on the naive subjects. A significant difference was found between the group tested at 3660 m and the remaining groups for error rate (p less than 0.05); this finding is interpreted as the effect of apprehension on the naive subjects. A significant difference was found between the group tested at 3660 m and the remaining groups for error rate (p less than 0.05) but not for speed of work. However, no effect of altitude on the way in which the task was learned could be demonstrated.

Altitude↗
PubMed1984

Cytotoxicity of leukocytes from normal and Shigella-susceptible (opium-treated) guinea pigs against virulent Shigella sonnei.

Intraepithelial lymphocytes were collected from the ileum of adult Hartley strain guinea pigs and used as effector cells in a 60-min bactericidal assay with virulent Shigella sonnei as target cells. Natural killer cytotoxicity (NKC) and antibody-dependent cellular cytotoxicity (ADCC) were measured and correlated with the resistance of the animals to infection by S. sonnei. Normal guinea pig intraepithelial lymphocytes exhibited mean NKC and ADCC values of 22.8 +/- 5.0 and 34.1 +/- 13.6, respectively. These animals were resistant to oral challenge with virulent S. sonnei. Intraepithelial lymphocytes from guinea pigs which were fasted for 4 days demonstrated NKC and ADCC values similar to those of normal animals (31.0 +/- 8.1 and 41.7 +/- 6.7, respectively). These animals also were resistant to oral challenge. Intraepithelial lymphocytes from guinea pigs which were given 1 ml of deodorized tincture of opium 2 h before cell collection demonstrated deficient NKC (4.7 +/- 4.2) and ADCC (5.3 +/- 4.9) values but remained resistant to infection by S. sonnei. When guinea pigs were fasted for 4 days and given opium, deficient NKC (2.0 +/- 2.0) and ADCC (1.3 +/- 1.3) values were demonstrated; this group of animals was susceptible to infection by S. sonnei (P less than 0.04). These experiments demonstrated that opium treatment depresses one form of gut immunity. When combined with starvation, opium treatment may increase susceptibility to infection by shigellae by modulation of immunity in addition to the effects on gut motility and bacterial flora.

Animals↗
PubMed1984

Cytotoxicity of human peripheral blood and colostral leukocytes against Shigella species.

We examined the ability of human peripheral blood leukocytes to kill strains of Shigella sonnei and Shigella flexneri by using a modified bactericidal assay. Antibody-dependent cellular cytotoxicity (ADCC) was demonstrated in the presence of specific rabbit immune serum directed against S. sonnei. With peripheral blood leukocytes from adults, ADCC was found only in the mononuclear cell and purified lymphocyte populations. Monocyte-macrophages and polymorphonuclear leukocytes were unable to demonstrate ADCC. Lymphocyte ADCC, which was not affected by the addition of phenylbutazone (an inhibitor of phagocytosis), was mediated by a non-T, Fc receptor-positive, HNK-1- cell. ADCC (using antiserum directed against virulent S. sonnei) was demonstrated against virulent S. sonnei but not against virulent S. sonnei or virulent S. flexneri. In contrast to leukocytes from adults, both mononuclear and polymorphonuclear cells from neonatal cord blood and from a patient with chronic granulomatous disease mediated anti-Shigella ADCC. Breast milk leukocytes (BMLs) collected 1 to 3 days postpartum were used as effector cells against virulent S. sonnei. The entire BML population, BMLs which did not adhere to plastic and BMLs which passed through nylon wool columns mediated both natural killer cytotoxicity and ADCC. In paired experiments, natural killer cytotoxicity and ADCC were significantly lower (30 to 45% inhibition) but not ablated, when phenylbutazone was added to BMLs and nylon wool-purified BMLs (P less than 0.05). These experiments suggest that colostral leukocytes mediated both extracellular and intracellular bacteriolysis in the presence and absence of specific antiserum. These mechanisms may be active in vivo in protection against shigellosis.

Age Factors↗
PubMed1984

Single-slit digital radiography: some practical considerations.

Clinical evaluation of an experimental digital chest unit using a solid-state linear detector array has provided information regarding the postpatient photon flux required for clinically acceptable images. Results from computer simulation show that energy subtraction imaging of the chest by the method of x-ray-tube voltage switching will be unsuccessful unless it can be demonstrated clinically that a much lower number of photons per pixel is acceptable in energy subtracted images. In addition, x-ray-tube loading limitations preclude imaging of the abdominal and pelvic regions with this technology.

Analog-Digital Conversion↗
PubMed1983

Definitive nonsurgical therapy of epithelial malignancies of the anal canal. A report of 12 cases.

Twelve patients with epidermoid carcinoma of the anal region ranging in age from 40-89 years were treated with combined chemotherapy (CT) and radiotherapy (RT) in lieu of abdominal-perineal resection. Ten patients received no prior treatment and two patients were treated for local recurrence following limited surgical excision. Two courses of 5-FU infusion and mitomycin C were given 3-4 weeks apart simultaneously with whole pelvis RT to 3000-4140 rad. One patient received an additional tumor volume dose of 3094 rad by interstitial Iridium implant and one patient received an orthovoltage boost of 1000 rad to the anal ring. All patients completed treatment. Complete regression of the anal mass occurred in all patients. Biopsies of the anal region performed after completion of therapy revealed no evidence of residual cancer. Ten of the 12 patients are alive without evidence of disease 4-24 months (median, 14 months) after completion of treatment. Two patients have died seven months after treatment of unrelated causes and were tumor-free at autopsy. All patients developed proctitis, diarrhea, and moist perineal desquamation which resolved by four weeks posttreatment. Based on their experience and that of others recently reported, the authors conclude that the described CT-RT protocol offers a definitive alternative to surgery of epidermoid cancer of the anal region.

Adult↗
PubMed1983

Antimicrobial resistance of gram-negative bacteria isolated from foods in Mexico.

When trimethoprim-sulfamethoxazole was given to US travelers in Mexico to prevent diarrheal illness, high-level resistance to the drug emerged [2], although in previous studies such resistance had not been observed among enteric flora following administration of trimethoprim-sulfamethoxazole as prophylaxis against urinary tract infection [3]. Since food has been shown to be an important vehicle of transmission of travelers' diarrhea, food samples were examined for the presence of drug-resistant bacteria to explain the acquisition of high-level resistance among enteric flora of individuals taking antibiotics as prophylaxis against traveler's diarrhea. Of 34 strains of ETEC isolated from US students in Guadalajara, Mexico, who had acute gastroenteritis, one was resistant to trimethoprim and one was resistant to trimethoprim-sulfamethoxazole. Eight of the ETEC strains tested demonstrated multiple drug resistance. Twenty-two of 149 isolates from food produced enterotoxin. Only one isolate, which was nontoxigenic, was resistant to trimethoprim, and no coliforms were resistant to trimethoprim-sulfamethoxazole; however, 16 isolates demonstrated multiple drug resistance. Of 235 gram-negative organisms recovered from frozen food samples grown on antibiotic-containing media and tested for enterotoxin production, no isolates were enterotoxigenic. Thirty-four isolates were resistant to trimethoprim, 15 were resistant to trimethoprim-sulfamethoxazole, and 33 demonstrated multiple resistance. Multiple drug resistance was demonstrated among gram-negative organisms isolated from patients' stools and foods in Mexico.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1983

Incidence of bacterial enteropathogens in foods from Mexico.

We examined food consumption patterns of U.S. students temporarily living in Guadalajara, Mexico. Consumption of foods prepared in Mexican homes was associated with an increased risk of acquisition of diarrhea. Foods from commercial sources and private Mexican homes in Guadalajara were subsequently examined for contamination with coliforms, fecal coliforms, and bacterial enteropathogens. For comparison, selected restaurant foods were obtained in Houston, Tex. Food obtained from Mexican homes showed generally higher counts of coliforms and fecal coliforms than those obtained from commercial sources in Mexico and Houston. The foods in Mexico, both from homes and commercial sources, commonly contained Escherichia coli and occasionally enterotoxigenic E. coli. Foods in Houston were not contaminated with E. coli or enterotoxigenic E. coli. Salmonella (17 isolates), Shigella (4 isolates), and Aeromonas hydrophila (1 isolate) were found only in the foods obtained from Mexican homes. Enterotoxigenic non-E. coli Enterobacteriaceae was recovered with approximately equal frequency from all food sources.

Diarrhea↗
PubMed1983

Comparison of methods to detect Escherichia coli heat-labile enterotoxin in stool and cell-free culture supernatants.

We compared the standard Y-1 adrenal cell (YAC) assay for heat-labile enterotoxin (LT) with newer rapid and economical immunological methods of detection. Stool samples were collected from 164 acutely ill American students in Guadalajara, Mexico. Supernatants were prepared from each stool. Stools were cultured for Escherichia coli by standard techniques. Individual E. coli-like colonies were examined for LT production by the Biken assay. Culture supernatants and stool supernatants were assayed for the presence of LT by the YAC assay, counterimmunoelectrophoresis, and enzyme-linked immunosorbent assay (ELISA). Standard YAC assays of culture supernatants revealed that 40 of the 164 specimens (24%) were LT positive. Counterimmunoelectrophoresis detected 60% and ELISA detected 65% of the 40 known positives when culture supernatants were used. The Biken assay detected 35% of the 40 known positives. With stool supernatants, the YAC assay detected only 18% of the known positives, counterimmunoelectrophoresis detected 60%, and ELISA detected 90%. In addition, ELISA detected 13 LT-positive stool supernatants not detected by the YAC assay of culture supernatants. The ELISA in which stool supernatants are used may be a useful method to detect LT.

Acute Disease↗
PubMed1975

Cultures of pig macrophages.

Freshly collected blood from pigs was defibrinated with glass beads. The white cells were collected on a Ficoll-Hypaque mixture and grown in RPMI 1640 medium containing 20 per cent fetal calf serum. Monocytes adhered to the plastic or glass flasks and the erythrocytes and lymphocytes remained in suspension. The adherent cells assumed the appearance of macrophages and the mean cell size at eight days was 40 mum. Phagocytosis was demonstrated and, in the first few days, incorporation of tritiated thymidine occurred. Cells remained viable in culture for more than eight weeks. Histo-chemical studies and the appearance of the cells under the electron microscope are described.

Animals↗