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Biomedical subjects

G L Cockerell

Publications and source records attributed to G L Cockerell.

At least 37 records · Page 2Linked to original sources
PubMed1990

Alteration in intestinal morphologic features associated with extensive large-colon resection in horses.

Light microscopy, morphometry, and scanning electron microscopy were used to examine the mucosal morphologic features of 7 intestinal specimens (3 from the small intestine; 4 from the large intestine) from each of 8 horses 1 year after sham operation (group 1; n = 3) or extensive large-colon resection (group 2; n = 5). Qualitative light microscopic examination did not reveal differences between groups, but morphometry revealed significantly (P less than 0.05) greater intercrypt area and distance in horses with colon resection and this was most pronounced in the cecum and remaining right ventral and dorsal colon. Crypt area and depth were similar for horses with colon resection and sham operation (P greater than 0.05). Qualitative evaluation of the scanning electron micrographs revealed more prominent crypt orifices in the large intestine of horses with colon resection. The larger intercrypt distance in the colon of horses with resection was not an obvious feature of the qualitative evaluation of the surface with scanning electron microscopy. Small intestinal morphologic features were variable and significant differences were not detected between horses with sham operation and colon resection. Horses adapted to extensive large-colon resection within 1 year by increasing the absorptive (intercrypt) surface area of the remaining large intestine.

Animals↗
PubMed1989

Correlative morphometry and morphology of normal equine intestinal mucosa and comparison after adaptation to extensive large colon resection.

Light microscopy, morphometry and scanning electron microscopy (SEM) were used to examine the mucosal morphology of seven intestinal specimens (three from the small intestine and four from the large intestine) from two horses not subjected to surgery and three horses one year after sham-operation for colon resection. Qualitative and quantitative evaluation revealed similar morphology for all horses except that the unoperated horses had significantly (P < 0.05) fewer goblet cells in the crypts of the large intestine. In the small intestine, SEM demonstrated that villus shape varied and ranged from coned to broad and flat. In the large intestine, SEM of the right ventral and dorsal colon revealed more prominent crypt openings than in the caecum. The small colon contained the most prominent crypt openings with the least variation among horses. In the small intestine, light microscopy and morphometry revealed a greater number of goblet cells and a decreased width to the enterocytes in an aboral direction from the cranial jejunum to the ileum. In the large intestine, the crypt area and crypt depth increased significantly and the intercrypt area decreased significantly in an aboral direction from the caecum to the small colon (P < 0.05). In comparison to the normal morphology, horses one year after extensive large colon resection had significantly greater intercrypt area in the caecum and remaining large colon.

Adaptation, Physiological↗
PubMed1988

The correlation between the direct and indirect detection of bovine leukemia virus infection in cattle.

Ninety-three cattle from a herd naturally infected with bovine leukemia virus (BLV) were tested for the presence of BLV infection by two indirect indicators, anti-BLV antibodies and lymphocytosis, and two direct indicators, BLV provirus and BLV gp51 antigen expression in peripheral blood mononuclear cells (PBMC). Forty-eight percent (45/93) of the cattle were seropositive, and of these, 53% (24/45) were provirus-positive. Freshly isolated PBMC were negative for gp51 antigen expression, but 11 cattle were positive following short-term culture of their PBMC; 10 of these were seropositive/provirus-positive cattle, and one was a seropositive/provirus-negative cow. Lymphocytosis was present in eight cattle, all of which were seropositive/provirus-positive/gp51-positive. Four cattle were provirus-positive, but negative for all other indicators of BLV infection; a second blood sample was collected from three of these cattle at a later date, at which time two of the three had seroconverted. These results suggest that depending on the stage of the infection, the pathogenesis of BLV in cattle may involve fundamental differences in the host-viral relationship, including the number of cells infected or the number of copies of integrated provirus per cell, regulation of expression of viral antigens, induction of the anti-viral immune response, and the polyclonal or monoclonal proliferation of lymphocytes.

Animals↗
PubMed1987

Development of leukemia and lymphosarcoma induced by bovine leukemia virus in sheep: a hematopathological study.

The hematological and neoplastic disorders induced in sheep by experimental bovine leukemia virus (BLV) infection are described. Seventeen of 19 BLV-inoculated sheep developed a marked increase in peripheral blood lymphocytes by 36 months after the intraperitoneal injection of peripheral blood lymphocytes from a BLV-infected cow. This increase correlated with an increase in the number of circulating B lymphocytes as demonstrated by the presence of surface immunoglobulins (SIg) and a high cell proliferative response to lipopolysaccharide and was considered to be a persistent B cell lymphocytosis. Lymphosarcoma developed in five BLV-infected sheep between 19 and 38 months postinoculation and was preceded in four out of five of these cases by an elevation in peripheral blood lymphocytes which began 4 to 26 months before death due to lymphosarcoma. The majority of tumor cells in all lymphosarcoma cases were of the centroblastic type, and in two cases in which the presence of SIg was assayed, the majority of tumor cells were SIg-positive. Thus, BLV-induced lymphosarcoma in sheep seems to be a B lymphocyte-derived tumor.

Animals↗
PubMed1986

Immunocompetence of sheep experimentally infected with bovine leukemia virus.

The humoral and cellular immunological reactivity of sheep were studied throughout the first 32 weeks following experimental infection with bovine leukemia virus (BLV). Seroconversion of BLV-inoculated sheep occurred within 4 weeks, but infection was not transmitted to contact control sheep. Despite the persistence of the viral infection, no differences were demonstrated in leukograms, serum IgG concentrations, humoral response to immunization with an irrelevant antigen (rabbit red blood cells), phytomitogen (Concanavalin A and Pokeweek mitogen)-induced lymphocyte blastogenesis, or chemical (1-chloro, 2-4 dinitrobenzene) skin contact hypersensitivity, between BLV-infected and uninfected contact control sheep. These results demonstrate the absence of a nonspecific immunosuppressive effect of BLV and further negate the influence of a generalized immunological deficit on the development of clinical disease in BLV-infected animals.

Animals↗
PubMed1984

Effect of BCG immunotherapy on N-nitroso-N-methylurea-induced carcinogenesis of guinea pig colon.

A total of 480 guinea pigs each received twice weekly intrarectal instillations of 1 mg N-nitroso-N-methylurea (NMU) during 14-35 weeks (total dose NMU, 28-70 mg) to induce colon neoplasms. At 24, 28, or 35 weeks after the start of NMU instillation, the distal colon was exposed by a ventral laparotomy and suspected neoplastic lesions were treated by one of four methods: A, intratumoral instillation of an emulsion of killed BCG cell walls attached to oil droplets; B, intratumoral instillation of a control emulsion of killed BCG cell walls in an aqueous phase rather than lipid phase; C, surgical excision of the colon lesion with formation of a ventral diverting colostomy; or D, sham operation (no treatment). All guinea pigs were allowed to recover from surgery and were then observed for a period of 1 year for the study of the effects of these treatments on NMU-induced colon neoplasms. Colon neoplasms were produced in 76% of all sham-operated control guinea pigs, and the frequency of such neoplasms was dependent on the total dose of NMU. Most neoplasms were adenocarcinomas with invasion of the bowel wall but only approximately 5% of them metastasized. Treatment with BCG failed to alter the course of NMU-induced colon carcinogenesis, as determined by the frequency of colon neoplasia, the number, the gross, or microscopic characteristics of colon neoplasms, or the rate of survival.

Animals↗
PubMed1983

Role of suppressor cells in feline leukemia virus-associated immunosuppression.

Protein from detergent-disrupted feline leukemia virus was found to suppress lymphocyte blastogenic responsiveness of peripheral blood mononuclear cells from normal cats. When suppressive doses of this protein were substituted for mitogen in the preactivation step of the concanavalin A-induced suppressor cell assay, significant suppression was observed in five of eleven cats tested. These results suggest that feline leukemia virus-associated immunosuppression may be mediated by a virus-induced suppressor cell.

Animals↗
PubMed1982

Generation of concanavalin A-induced suppressor cells in the cat.

Preactivation of feline peripheral blood mononuclear cells with mitogenic doses of concanavalin A resulted in suppression of proliferation when these cells were cocultured with untreated autologous cells. The degree of suppression was directly proportional to the preactivation time and ratio of preactivated to untreated cells. The generation, but not the activity, of the suppressor cells was dependent on DNA and protein synthesis. Pokeweed mitogen and phytohemagglutinin were also shown to be capable of inducing suppressor cell activity. Suppression was also observed in allogeneic cocultures. Supernatants from concanavalin A-preactivated cell cultures did not suppress proliferation of untreated cells.

Animals↗
PubMed1982

Effect of bacille Calmette-Guerin immunotherapy on feline sarcoma virus-induced neoplasms in the cat.

Kittens infected experimentally with feline sarcoma virus (FeSV) were inoculated with emulsions of bacille Calmette-Guerin (BCG) cell wall preparations to determine the effect of BCG immunotherapy on FeSV-induced sarcoma-genesis. The BCG preparations or emulsificant control preparations were administered (i) subcutaneously at the same time and site as was the FeSV inoculation, (ii) at the same site but 1 week after FeSV inoculation, or (iii) with a mixture of viable autochthonous neoplastic cells approximately 35 days after FeSV inoculation. There was no difference in the percentage of kittens that developed neoplasms, the prepatent period for neoplastic development, the percentage of kittens with neoplastic regression, or the survival rate among groups given BCG, emulsificant control, or FeSV alone. Significantly (P less than 0.05) greater dissemination of neoplasms was seen in groups given BCG or emulsificant control preparations, compared with dissemination in groups given FeSV alone.

Animals↗
PubMed1981

Design and testing of a biocontainment system for chemical carcinogens.

A biocontainment facility was built for studies in which the chemical carcinogen N-methyl-N-nitrosourea (MNU) was instilled intrarectally in guinea pigs. The system operated by constant flow of uncontaminated air into carcinogen-contaminated animal isolation chambers and filtration through a high-efficiency particulate air (HEPA) filter prior to release into the environment. The facility was tested for efficiency of carcinogen containment by substituting for the MNU a similar concentration of a fluorescent tracer, sodium fluorescein, under standard operating procedures for carcinogen administration to guinea pigs. Wipe samples from the floor, isolation chambers, animal handlers and clothing, and intake and exhaust air samples were analyzed for fluorescein before and after intrarectal instillation of the tracer. The recovery of very low concentrations of total and respirable suspended fluorescein from sampling points within the facility and the absence of detectable fluorescein in the air downstream from the HEPA filter indicated that the facility provided adequate protection against contamination of personnel or the environment.

Animals↗
PubMed1981

Establishment and biological properties of a guinea pig colonic adenocarcinoma cell line induced by N-methyl-N-nitrosourea.

A colonic adenocarcinoma cell line, designated GPC-16, was established in culture from tissue removed from an outbred guinea pig which received 56 mg of N-methyl-N-nitrosourea intrarectally over a 28-week period. the GPC-16 has been maintained for more than 30 in vitro passages and was tumorigenic in both the autochthonous host and nude mice. The cells were aneuploid with a wide range in chromosome number (54 to 172) in a bimodal distribution. The cells grew in vitro as a tight monolayer and demonstrated numerous desmosomes by electron microscopy. In vitro-passaged cells had a doubling time of 36 hr and a 5.1% plating efficiency in agar.

Adenocarcinoma↗
PubMed1980

Endoscopic detection of experimentally induced colonic neoplasms in guinea pigs (Cavia porcellus).

Colonoscopic examination was performed daily on 18 normal guinea pigs for 7 weeks and on 27 guinea pigs after 24-35 weeks of biweekly intrarectal instillation of the chemical carcinogen methylnitrosourea. Four normal guinea pigs died during the first 2 weeks of the study, two from colonic perforations and two from cecal bloating due to excessive air insufflation. The other 14 normal animals remained clinically healthy and had no gross abnormalities at the end of the 7-week study. Colonic tumors were detected by colonoscopy in five of seven treated guinea pigs that had grossly visible nodular tumors on the mucosal surface of surgically resected colonic tissue. In another treated guinea pig, a tumor was detected by colonoscopy which was not confirmed grossly. In an additional two treated guinea pigs, tumors were visualized by colonoscopy which could not be demonstrated in surgically resected tissue because of their inaccessible location within the pelvic canal. At necropsy, these latter two guinea pigs had nodular, mucosal growths in the pelvic portion of the colon as indicated by colonoscopy. Microscopically, an additional 13 cases of colonic neoplasms were identified in the resected colonic tissue without gross or colonoscopic evidence of intralumenal nodular growth.

Animals↗
PubMed1979

Necessity for end colostomy with transection of the descending colon in guinea pigs.

Surgical procedures for resection and transection of the descending colon in the guinea pig were studied. Wedge resection with removal of less than 1 cm diameter of tissue resulted in an 80% (8 of 10 guinea pigs) survival rate. Colonic transection with restorative anastomosis, either end-to-end or side-to-side, resulted in a 94% (35 of 37 guinea pigs) death rate due to colonic impaction proximal to the site of anastomosis. A modified procedure for ventral end colostomy resulted in a 79% (19 of 24 guinea pigs) survival rate. These results indicated that caution should be taken in surgical manipulations intended to treat or study diseases of the colon in the guinea pig.

Animals↗
PubMed1979

Increased spontaneous erythrocyte rosette formation of feline lymphocytes preincubated at 37 degrees C.

Preincubation of feline peripheral blood lymphocytes (PBL) in complete medium at 37 degrees C for up to 24 h resulted in as much as a 5.5-fold increase in the per cent of T cells detectable by spontaneous E rosette formation with guinea pig erythrocytes, as compared to non-preincubated PBL. Under these same conditions, the percent of B cells, detected by EAC rosette formation, remained unchanged. Preincubation with either thymosin or levamisole caused no increase in E rosettes other than that seen with complete medium alone. The preincubation-associated increase in E rosettes was temperature dependent, independent of the source of serum in the preincubation medium, not influenced by the lymphocyte isolation procedure, and not observed when feline thymocytes were tested in place of PBL. No increase in functional activity, assayed by phytomitogen-induced lymphocyte blastogenesis, was observed in preincubated as compared to non-preincubated PBL. These results suggested either a non-specific unmasking, or the differentiation and acquisition, of E receptors by feline PBL during the preincubation procedure.

Animals↗
PubMed1979

A light and electron microscopic study of a normal adrenal medulla and a pheochromocytoma from a horse.

The outer medullary (juxtacortical) zone of a normal equine adrenal gland had columnar chromaffin-positive cells arranged with their long axes perpendicular to fine vascular channels. The deeper medullary regions were composed of smaller irregularly round to polygonal chromaffin positive cells in small packets. Both cell types contained two types of membrane-bound cytoplasmic secretory granules. Osmiophilic granules with a homogeneous core, crenated membrane and narrow submembranous halo predominated in the columnar juxtacortical cells. The rounder, central medullary cells contained predominantly electron dense granules with a wide irregular electron lucent space between an eccentric core and the granule membrane. In contrast, irrespective of cell type or zone, cells from a pheochromocytoma contained only one type of granule similar to that described for the juxtacortical region of the normal equine adrenal medulla. The tumor cells could be classified into three subtypes based on density of granule packing but the granules were morphologically similar in all tumor cells.

Adrenal Gland Neoplasms↗