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Biomedical subjects

D A Crouse

Publications and source records attributed to D A Crouse.

At least 19 recordsLinked to original sources
PubMed1995

Epithelial cell proliferation and biodistribution of radiolabeled urogastrone in the gastrointestinal mucosa of young and old mice.

We have evaluated epithelial cell proliferation and biodistribution of radiolabeled recombinant human urogastrone/epidermal growth factor (125I rhUG/EGF) in the gastrointestinal mucosa of young (2+ months) and old (30+ months) mice. Animals were injected intraperitoneally with the metaphase arrest agent vincristine sulfate and intravenously with 125I rhUG/EGF. Animals were killed after two hours. Crypt cell production rate and uptake of radiolabeled urogastrone were measured in the same intestinal tissues. The results demonstrated that older animals had significantly greater crypt cell production rate as compared to young. However, the uptake of 125I rhUG/EGF was not significantly different (except in duodenum, where the uptake of 125I rhUG/EGF was significantly greater in young compared to old animals) between young and old animals. This suggests that increased epithelial cell proliferation in the aging animals is not associated with increased uptake of 125I rhUG/EGF. Thus epidermal growth factor/urogastrone may not be a primary factor for the intestinal kinetic differences which exist between young and old animals.

Aging↗
PubMed1992

Significance of detection of occult non-Hodgkin's lymphoma in histologically uninvolved bone marrow by a culture technique.

Prolonged disease-free survival of patients with recurrent or resistant non-Hodgkin's lymphoma (NHL) has been achieved with high-dose therapy followed by autologous bone marrow transplantation (ABMT). A concern with the use of ABMT is that the marrow that is reinfused may contain undetected NHL cells with the potential to reestablish metastatic disease in the recipient. Using a culture technique that is sensitive for detecting occult lymphoma cells in BM, we analyzed histologically normal marrow harvests from 59 consecutive patients with intermediate- or high-grade NHL who were candidates for high-dose therapy and ABMT. The culture results indicated that 22 of the patients had occult lymphoma in their marrow. Forty-three patients underwent high-dose therapy followed by ABMT. Twenty-four achieved a complete clinical remission. Those with occult lymphoma in their harvests (11 patients) continued to relapse for up to 3 years, whereas no relapses were observed beyond 8 months in 13 patients receiving marrow that did not contain detectable lymphoma cells using the culture technique. The relapses in the patients who achieved a complete remission occurred at sites of prior bulky disease rather than at new sites, suggesting that the ability to detect occult lymphoma cells in marrow is a marker of biologic aggressiveness and/or resistance to therapy, or that the reinfused cells could only grow in previously involved sites. The detection of lymphoma cells in marrow used for ABMT is an important adverse prognostic factor, and appears to be independent of other clinical predictors of outcome such as sensitivity or resistance of disease to prior chemotherapy.

Adolescent↗
PubMed1992

Quantitation of metastatic tumor burden from human colon tumor xenografts using radiolabelled monoclonal antibody 17-A fragments.

In realistic models of human tumor xenograft metastasis, the metastatic foci arise in perivascular sites and rarely grow to sizes which are easily quantifiable by visual inspection. As an alternative approach, we have used monoclonal antibody (MAb) 17-1A F(ab')2 fragments labelled with radioiodine (125I) to study the differential accumulation of label in xenografts and metastatic tumor sites as well as in noninvolved tissues of NIH Swiss nude mice receiving HT-29 human colon tumor cells. Images of the whole-body distribution and sites of localization were determined using a pinhole-collimated Angergamma camera. Radioactivity was determined in tissue samples using a well scintillation system, and pharmacokinetics were assessed during the initial 72 h after injection of antibody fragments. The half-life of 125I-F(ab')2 fragments in the blood, 8.6 h, was similar in nontumor-bearing control and tumor-bearing mice. The half-life in subcutaneous tumor xenografts was 30.1 h. The tumor xenograft to tissue activity ratios per unit weight (radiolocalization indices) at 72 h were: blood 90, lung 65, pancreas 50, muscle 35, spleen 20, liver and mesenteric lymph node 10. All subcutaneous xenografts were successfully imaged, and images of 5 of 9 mice (55%) appeared to demonstrate the presence of metastatic tumor by differential and focal accumulation of MAb fragments after 48 or 72 h in the lung (2 cases) or abdominal cavity (3 cases). Necropsy and subsequent histological and biodistribution studies confirmed the presence of metastatic tumor in these sites and identified tumor in several additional sites. The smallest volume of metastatic tissue in liver or lung determined at necropsy which appeared to have been detected by imaging was about 20 mm3. Generally, for mice with metastatic tumors, the radioactivity per unit weight of metastatic tumor-bearing organs compared to tumor-free organs was 2- to 7-fold greater. The results indicate that a radiolocalization index of > or = 2 is generally necessary for metastatic tumor detection by imaging although this is influenced by the extent of anatomical location of the tumor. It was possible to predict the tissue distribution of the fragments from the planar image for the amounts of radioactivity (approximately 1 mCi/kg body weight) employed in this study. These results demonstrate the utility of this approach to quantitate the metastatic burden arising from human colon tumor xenografts in this experimental model.

Animals↗
PubMed1991

Epithelial cell proliferation and uptake of radiolabeled urogastrone in the intestinal tissues following abdominal irradiation in the mouse.

We have evaluated the rate of crypt cell production and uptake of radiolabeled recombinant human urogastrone (125I-rhUG) in the intestinal tissues of the mouse at 3, 5, 7, 9, and 12 days following irradiation of the abdomen with 9 Gy. At autopsy, the animals were injected intraperitoneally with 1 microgram/g body weight of the metaphase arrest agent, vincristine sulfate, and 25 muCi of 125I-rhUG (specific activity 1.7 muCi/micrograms) to quantify the rate of crypt cell production and uptake of radiolabeled urogastrone, respectively. The results indicated that the rate of crypt cell production was increased significantly in the irradiated animals compared to the unirradiated animals and showed a peak on the 3rd and 5th postirradiation days in small intestine and colon, respectively. The uptake of 125I-rhUG was increased significantly on the 3rd postirradiation day in the intestinal tissues but showed a bimodal pattern with peaks on the 3rd and 9th postirradiation days. These results suggest that there may be a close association between epithelial cell proliferation and uptake of 125I-rhUG, particularly in the early part of recovery of intestinal mucosa following irradiation. However, these data do not discriminate whether the increased uptake of 125I-rhUG is the cause or the effect of proliferation induced by an irradiation stimulus. Further analysis also revealed that there was no relationship between crypt depth and 125I-rhUG uptake. However, crypt depth was inversely correlated with villus height in the proximal small intestine but not in the ileum. Villus height was correlated inversely with 125I-rhUG uptake in the ileum and jejunum but not the duodenum. The rate of crypt cell production was strongly correlated with crypt depth throughout the intestine and inversely correlated with villus height. This suggests that villus-to-crypt inhibitory feedback may be a primary regulator of cellular proliferation in the crypts and the association of 125I-rhUG uptake with proliferation indirectly reflects this interaction.

Animals↗
PubMed1989

Characteristics of submucosal lymphoid tissue located in the proximal colon of the rat.

In this study we have examined the morphology and steroid sensitivity of proximal colonic lymphoid tissue in the Fisher 344 rat. A time course study was conducted in which groups of animals were injected subcutaneously with hydrocortisone sodium succinate (125 mg/kg body weight) and killed on Days 0-4. Thymus, jejunal and ileal Peyer's patches and proximal colonic lymphoid tissue were excised, weighed and processed for histological analysis. The results showed that the maximum cytoreductive effects of the hydrocortisone were evident on Day 2. Thymus and proximal colonic lymphoid tissue weight decreased to 5 and 18% of the control values respectively, before returning towards control values over the next two days. In contrast, jejunal and ileal Peyer's patch weights were unaltered. A dose response experiment was conducted using the same endpoints. Rats were injected subcutaneously with hydrocortisone at 60, 120, 200 and 300 mg/kg body weight and killed on Day 2. The results of this experiment showed that the proximal colonic lymphoid tissue, like thymus, responded with a dose-dependent loss of tissue weight. The spleen and Peyer's patches showed only a slight weight decrease compared to the control. These data showed that the response of proximal colonic lymphoid tissue to steroids was more similar to that of thymus, a primary lymphoid tissue, than to other secondary lymphoid tissues. Finally, grafts of fetal proximal colon under the kidney capsule of syngeneic adults supported the development of this lymphoid aggregate in the absence of luminal antigenic stimulation. These results suggest that the development and functional contribution of proximal colonic lymphoid tissue to the immune system warrants a more detailed examination.

Animals↗
PubMed1989

Apparent synergism between radiation and the carcinogen 1,2-dimethylhydrazine in the induction of colonic tumors in rats.

We have evaluated the interaction of radiation and 1,2-dimethylhydrazine (DMH) with respect to colon carcinogenesis in the Fischer 344 rat and have demonstrated the utility of this model for future more detailed mechanistic studies. In initial experiments, single doses of abdomen-only radiation (9 Gy) or DMH (150 mg/kg) were employed alone or in combination. Radiation was administered 3.5 days prior to the DMH. At 8 months post-treatment, the incidence of DMH-induced colon tumors was doubled by prior radiation exposure. When the protocol was repeated employing a DMH dose of 135 mg/kg with a 6-month observation period, the incidence of tumors induced by DMH alone was reduced, but the combination of radiation plus DMH still resulted in an augmentation of tumor incidence. When the protocol of radiation plus DMH was repeated three times at monthly intervals, a 15-fold increase in tumor incidence (from 5 to 74%) was observed at 6 months post-treatment. This finding demonstrates an apparent synergy between the radiation and the chemical carcinogen. Throughout these studies, the appearance of carcinomas was associated with preexisting colonic lymphoid nodules. The reproducibility of tumor induction as well as range of tumor incidence generated by variations in this system may be adequately sensitive to examine the combination of much lower doses of radiation and/or chemical carcinogen. The relationship between existing lymphoid aggregates which alter local epithelial cell kinetics and which are associated with fenestrations in the basement membrane, and the development of colon cancer in congruent sites may assist in defining dose-response curves for combined agents as well as providing a system for evaluating the mechanisms underlying their interactions.

Adenoma↗
PubMed1988

Intestinal glucose uptake is increased in aged mice.

Carbohydrate metabolism is impaired in the aged. Whether this is related to impaired glucose uptake or to other factors remains unclear. We measured changes in proliferative activity, glucose uptake, and disaccharidase activity in the intestinal mucosa of mice aged 2, 12, 24, and 30+ months to evaluate glucose absorption and its relationship to intestinal structure and proliferative activity. In vitro glucose uptake was increased significantly in the 30+ month-old mice compared to the younger animals. Similarly, crypt cell production rate and thymidine uptake were also increased. However, there were no significant changes in intestinal weight and length and villus height and crypt depth. These findings suggest that altered carbohydrate absorption in the aged is related to factors other than diminished mucosal glucose uptake. Whether this increased function is related to structural changes in the gut remains unclear.

Aging↗
PubMed1987

Stem and stromal cell reconstitution of lethally irradiated mice following transplantation of hematopoietic tissue from donors of various ages.

If the limited life span of hematopoietic tissues in vitro is due to a finite proliferative capacity of individual stem cells, one might expect tissues of young donors to possess a greater proliferative capacity and to contain a larger population of primitive stem cells than those of older donors. To test this hypothesis, we used 12- and 8-day spleen colony formation (CFU-s) to assay more and less primitive stem cell subpopulations of three murine hematopoietic tissues: fetal liver (FL) and weanling (WBM) and adult (ABM) bone marrow. Subsequently, the same assays and a stromal cell assay were performed on the bone marrow from groups of lethally irradiated mice reconstituted with these tissues. Comparison of the CFU-s content of the donor tissues revealed that FL contained a significantly greater proportion of primitive stem cells as evidenced by a (Day 12):(Day 8) CFU-s ratio of 3.0 +/- 1.0 as compared to 0.9 +/- 0.1 for WBM and ABM. In addition, at 21 weeks post-transplantation the CFU-s/femur values of the FL reconstituted group were significantly greater than those of the ABM and WBM reconstituted groups. These results suggest that fetal hematopoietic tissue contains a greater proportion of primitive stem cells and has a greater proliferative potential than hematopoietic tissue from older donors. No differences were seen in stromal cell reconstitution of the three experimental groups. In all cases, assayable fibroblast colony forming cells (CFU-f) remained at 20-40% of control values, even at 21 weeks postreconstitution.

Aging↗
PubMed1987

Ontogeny and regulation of the immune system.

Classic studies in embryology and contemporary research in immunology and molecular biology have disclosed the carefully orchestrated events leading to development of the immune system and immunoregulation that ultimately provide immunohomeostasis. During ontogeny, the pluripotential stem cell emerges and differentiates into all hematopoietic lineages, including three major immunologically relevant components: T-cell differentiation occurs within the thymus; B cells appear within fetal liver, adult bone marrow, and possibly other abdominal sites; and concurrently, the monocyte-macrophage system develops. Under the influence of an array of cytokines and cellular interactions, immune regulation is established. T and B lymphocytes elaborate genetically encoded messages that acquire specificity via transposable genetic elements. Receptors and cytokines provide immune recognition, communication, regulation, and memory for antigens. Inherited and acquired defects in ontogeny and immune regulation are the basis for immunodeficiency disorders.

Animals↗
PubMed1985

Thymic non-lymphoid cells.

In formulating this summary of our simon-pure knowledge of the structure/function relationships in the thymus, we decided that the time may have come to introduce a suitable dose of cynicism to balance the sometimes hopeless optimism of the past. Are the non-lymphoid cells of the thymus necessary for thymic function? Probably, but not to the extent or uniqueness that some authors including ourselves have previously claimed; T cells can probably differentiate in other tissues but may acquire their preference for MHC class II in the thymus. Mouse thymic lymphoid cell traffic and surface phenotype has recently been summarized pictorally by Scollay and Shortman [95]. Briefly stated, within the thymus, cells are hatched, matched and then dispatched. Minimally, the non-lymphoid cells act either as scenically varied obstacles along the way, nurseries for newborn T cells, or as tombstones for life's disenfranchized, effete and autoaggressive thymocytes. Hassall's corpuscles are morphological structures unique to the thymus, which are most useful to medical students for identification of this tissue. Their function remains one of life's great mysteries. Morphologically, they are suitable companions to the more recently described strange multicellular complexes of lymphocytes and epithelial cells which might be functionally important. The thymus of the much studied inbred, environmentally mollycoddled, laboratory mouse has been often and majestically described. It is probably typical for that of man and most mammals. It may, however, be unrepresentative of the thymus of stressed and parasitized wild animals. Diseases of the thymus generally can be categorized as not having enough thymus, having a neoplastic thymus or having a thymus which does not work properly. The bottom line in our knowledge of thymic nonlymphoid cells is that if you are born without them, you get sick and die; unless, of course, you are a nude mouse in Omaha, in which case you just freeze to death.

Animals↗
PubMed1985

Thymic epithelium. I. Lymphoid-free organ cultures grafted in syngeneic intact mice.

Low temperature organ culture of 14 day gestational age mouse thymic lobes leads to the development of a lymphoid-free epithelial matrix. Morphologically, these explants exhibit two distinct epithelial components, which may be indicative of the dual embryologic origin (ectodermal/endodermal) of the thymic epithelium. When such explants are grafted into syngeneic intact recipients, the compound matrix is repopulated by lymphohematopoietic precursors that give rise to an intragraft lymphocyte population. The graft shows additional morphologic development parallel to normal thymus ontogeny. Studies in congenic mice when using the TIa alloantigen as a marker of derivation demonstrate the host origin of these lymphocytes. Cytotoxic assays for the presence of cell surface Thy-1.2, TIa, Lyt-1.2, and Lyt-2.2 reveal that graft lymphocytes express a phenotypic profile and developmental progression that is typical of normal thymocytes. Furthermore, mitogen and mixed leukocyte culture assays show that intragraft lymphopoiesis leads to the generation of a mature population. In addition to the lymphocytes, host-derived Ia+ adherent cells can also be isolated from these thymic epithelial grafts. We conclude that low temperature organ culture-derived thymic epithelium appears to retain those properties of the thymic microenvironment that permit lymphohematopoietic colonization and support thymocyte differentiation.

Animals↗
PubMed1984

A decrease in thymus-mediated immune responses as a result of treatment of neonatal rats with glutamate.

We investigated whether administration of monosodium 1-glutamate (MSG) to neonatal rats would disrupt immune responses in intact and orchidectomized adult male rats. Neonatal male rats were treated with saline or MSG which causes severe endocrine abnormalities. Half of each group of animals were orchidectomized as adults and killed one week later along with intact rats. MSG treatment resulted in suppressed serum LH levels in intact rats. Thymus weight and spleen cellularity in intact animals were not affected by MSG treatment, but thymus weight increased within one week after orchidectomy in both saline- and MSG-treated groups. In intact rats, lymphocyte stimulation by the T cell specific mitogens (concanavalin A or phytohemagglutinin) or the B cell specific mitogen (lipopolysaccharide) was unaffected by prior treatment with MSG. However, MSG treatment blocked the decrease attributable to orchidectomy in concanavalin A and phytohemagglutinin stimulation of lymphocyte blastogenesis. The results suggest that administration of MSG to neonatal male rats can alter some immune responses in the adult animal.

Animals↗
PubMed1984

Segregation and characterization of lymphohematopoietic stromal elements.

In the mouse, long-term maintenance of multipotent hematopoietic stem cells in vitro currently requires the establishment of an appropriate adherent layer. When established employing culture medium supplemented with 20% horse serum and 10(-6) M hydrocortisone, the initial adherent layer contains primitive stem cells that are the major contributor of multipotent stem cells (CFUs) assayed subsequently in the supernatant regardless of the addition of fresh bone marrow cells. In contrast, when the adherent layer is established employing 25% fetal calf serum without hydrocortisone, few if any stem cells survive in the adherent layer. Such cultures are dependent upon a recharge with fresh bone marrow as a source of CFUs. A comparison of the latter stem cell-depleted system with the former intact system permits an evaluation of the relative contributions of the adherent layer and stem cells to the long-term maintenance of hematopoiesis in vitro. Studies of the effects of irradiation of the donor animal for the adherent layer and using the intact system demonstrated a reduction in the supernatant CFUs production that was dose- and time-related and evident at doses of 100 and 500 rads. If the adherent layer itself was irradiated immediately before refeeding, a reduction in supernatant CFUs was evident at a dose of 5 rads. These effects, both in vivo and in vitro, cannot be explained solely on the basis of cell killing. Rather, we propose that such doses inactivate, render impotent, or reduce the self-renewal capacity of stem cells that occupy a limited number of "niches" in the adherent layer. Although they are not killed, these impotent stem cells occupy stem cell niches but do not provide an effective contribution of CFUs to the supernatant cells. The adherent layer consists primarily of fibroblasts with significant numbers of macrophages and endothelial cells. The cellular composition of the adherent layer differs between the intact and stem cell-depleted systems in that the latter has a relatively larger proportion of endothelial cells. The composition of the adherent layer influences the type of differentiated cells in the supernatant. The stem cell-depleted adherent layer cultures had a greater proportion of granulocytes among the supernatant cells than macrophages that eventually predominate in the intact system. We have cloned stromal cells from the intact cultures and obtained several stromal cell lines by spontaneous transformation. One of these stromal cell lines (MC1) transfers at least a partial hematopoietic "microenvironment" (granulocytes, macrophages, erythroid cells) to ectopic sites on transplantation to syngeneic recipients.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗