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Biomedical subjects

C W Hewitt

Publications and source records attributed to C W Hewitt.

At least 73 records · Page 4Linked to original sources
PubMed1988

Lymphocyte chimerism in a full allogeneic composite tissue (rat-limb) allograft model prolonged with cyclosporine.

LEW recipients of ACI vascularized hind limb allografts were analyzed for lymphoid chimerism by a complement-dependent cytotoxicity assay using antisera produced across this strain combination. In assessing the technique, two LEW recipients of sublethal irradiation (400 rad), ACI bone-marrow allografts, and CsA exhibited mixed lymphoid chimerism 23 days posttransplant. Short-term CsA-treated CTA recipients that were assayed at various times following transplantation and underwent subacute rejection did not demonstrate any significant mixed lymphoid chimerism. Long-term CsA-treated CTA recipients that were assayed at various times prior to 100 days posttransplant also did not demonstrate any significant mixed lymphoid chimerism. However, following extensive CTA survival (greater than 100 days) significant mixed donor-host lymphocyte chimerism became evident in the peripheral blood, and in one recipient a large quantity of donor bone marrow remained viable in the ACI limb allograft at necropsy (greater than 200 days posttransplant). The development of donor-host lymphocyte chimerism and a wasting syndrome that followed long-term CTA survival was suggestive of GVHD.

Animals↗
PubMed1987

Two-dimensional immunoelectrophoretic analysis of urinary ultraconcentrates: antigenic differences between bladder cancer positive patients, normal individuals, and patients with urinary tract infections.

Urine ultraconcentrates (100-fold) from bladder cancer patients, patients suffering from urinary tract infection, and normal individuals were analyzed using polyacrylamide gel electrophoresis (PAGE) and two-dimensional immunoelectrophoresis. A combined sample of normal urine was resolved into 1 to 3 protein bands by PAGE, whereas a single concentrated bladder cancer urine was resolved into 10-12 protein bands. Yet, this same concentrated urine sample was resolved into 17-20 antigen peaks by two-dimensional immunoelectrophoresis (2DIEP) against antihuman serum. A significant (P less than 0.05) increase was observed in the relative antigen concentration when comparing 2DIEP profiles of bladder cancer urines to normal controls. A significant increase in the relative antigen concentration and the number of antigen peaks was also found when comparing immunoelectrophoretic patterns obtained from ultraconcentrated urine specimens of bladder cancer positive urine and normal controls using a rabbit antibladder cancer urine antisera (P less than 0.002 and P less than 0.02, respectively). In addition, significant (P less than 0.02) antigenic differences were found when comparing concentrated urine samples from bladder cancer positive individuals to those with urinary tract infection. The bladder cancer group demonstrated 8/9 positive results for relative antigen concentrations greater than 3.0. Fifteen of 16 normal or urinary tract infected individuals combined had relative antigen concentrations less than 3.0. These differences were highly significant (P less than 0.001). No differences were found between concentrated bladder cancer and normal urine specimens tested against rabbit antinormal urine antisera.

Antigens↗
PubMed1987

Decreased reactivity of allosera against target lymphocytes obtained following thermal injury or long-term cyclosporine treatment.

We speculated that two diverse causes of potent cell-mediated immune suppression, cyclosporine (CsA) and thermal trauma, may demonstrate some similar actions, and thus tested whether either could alter antisera reactivity against allogeneic target lymphocytes. Target splenocytes from 40% body surface area full-thickness burned Brown-Norway (BN) rats demonstrated significant (P = 0.004) decreased reactivity (agglutination) with antisera produced across a full allogeneic barrier (RT1 major histocompatibility complex (MHC) and non-MHC) compared to control splenocytes. Depression of allogeneic splenic target cell reactivity against Lewis (LEW)-anti-BN allosera was similarly observed using lymphocytes from long-term CsA-treated rats (P = 0.004). The decreased reactivity induced by burn trauma was transferable to pooled normal splenocytes or blood lymphocytes by preincubation with burn plasma (P less than 0.001), and was confirmed by a cellular enzyme-linked immunosorbent assay (CELISA) (P = 0.003). In summary, a similarity consisting of decreased antibody reactivity against lymphocytes from either burned or long-term CsA-treated animals was demonstrated. These results suggested that lymphocyte cell surface allogeneic determinants and their expression and/or availability were altered by either regimen.

Animals↗
PubMed1987

Angiotensin II infusion increases thoracic duct lymph flow in chronically catheterized sheep.

Both pregnancy and estrogen administration are associated with a decrease in the systemic vasculature pressor response to angiotensin II infusion; however, the lymphatic vessel system response is not clear. In the present study we infused angiotensin II to nine nonpregnant splenectomized ewes with 0.1, 10, or 1,000 ng X kg-1 X min-1 for a 5-min period at each dose. At the lowest dose the mean arterial pressure increased from 10 to 20% over base line. At the highest dose, the left thoracic duct flow rate peaked at 361% 10 min after the infusion was started, whereas arterial pressure peaked at 183% of the control value. Peak lymph flow occurred 4-6 min after the maximal increase in mean systemic arterial pressure. Neither hematocrit nor venous pressure were altered at any of the doses administered. This suggests that the interstitial fluid space pressure remained unchanged and that the increase in lymph flow was not secondary to fluid transfer from the intravascular system. We postulate, therefore, that the effect of angiotensin II in the increase of lymph flow rate is by direct action on the lymphatic vessels themselves.

Angiotensin II↗
PubMed1987

Extensive prolongation of rat renal allograft survival following donor or nonspecific transfusions and concomitant immunosuppressant.

We report here a marked beneficial effect upon rat renal allograft survival transplanted across a strong histocompatibility barrier (BN----LEW) by pretransplant concomitant donor-strain blood transfusion (DST) and CsA treatment. Comparisons between recipient groups treated with pretransplant nonspecific blood (NST) and concomitant cyclosporine (CsA) or azathioprine (Aza) administration were also made. LEW recipients receiving only a BN renal allograft survived for a geometric average time of 8.9 days. Recipients receiving 1 ml of donor blood at weekly intervals, each week for three weeks prior to transplantation, demonstrated a geometric mean survival time (GMST) of 40.5 days. Recipients receiving this same regimen and concurrent CsA cover (5 mg/kg/day) starting 7 days prior to the first transfusion with discontinuation 5 days prior to transplantation showed extensive prolongation (greater than 100 days). Recipients treated with only CsA cover survived for a GMST of 34.4 days. LEW recipients receiving 1 ml of nonspecific blood at weekly intervals (DA, BUF, WKY, respectively) each week for 3 weeks prior to transplantation were prolonged to 27.7 days. Recipients treated with this same regimen while under CsA cover also demonstrated extended prolongation (greater than 100 days). Recipients receiving multiple donor blood transfusions under Aza (2 mg/kg/day) cover demonstrated lesser prolongation (22.8 days). Recipients receiving the multiple nonspecific blood protocol under Aza cover showed similar prolongation (38.6 days). Recipients treated only with Aza did not show prolonged survival (9.3 days). These differences in survival were considered significant among the 9 transplant groups as determined by ANOVA (P less than 0.001). The majority of recipient groups showed relatively poor renal function over their life spans, independent of whether prolongation occurred. Yet, renal function in the NST or particularly the DST groups covered by pretransplant CsA, demonstrated the best renal function in our laboratory over many years of investigations using the BN----LEW combination. In conclusion, there was a dramatic synergistic beneficial effect of prior multiple DST or NST specific to CsA, as opposed to another immunopharmacologic agent, Aza.

Animals↗
PubMed1986

Evaluation of the rat renal allograft model in comparison to man: a physiological perspective.

Fabre has previously questioned the rat kidney allograft model from an immunologic perspective and raised some important considerations. The present study addresses further the fidelity of the rat renal allograft model from a physiologic rather than immunologic perspective. We reviewed several rat renal allograft studies from several laboratories, including our own, that followed BUN or urea levels during renal failure. Also examined were several studies from the literature concerning patient survival and uremia. The percentage of patient and rat survival was plotted against maximal BUNs attained. The frequency of survival was significantly (p less than 0.05) increased in the rats by comparison to the patient population over a range of median BUNmax values. Additional human data that were utilized for analysis included a group of 16 patients who experienced renal failure and subsequently chose not to undergo dialysis. Comparing the mean BUN at death in rats from our laboratory to this patient population, we found that there was a significant difference (p less than 0.001, 292 +/- 142 mg./dl. versus 127 +/- 51 mg./dl., respectively). When all of the rat data was combined, including results from the literature, and compared to the patients, a significant (p less than 0.001) increase in BUN at death was confirmed (204 +/- 95 versus 127 +/- 51, respectively). We also found that 82% of the rats that died with uremia possessed BUNs greater than 200 mg./dl. at some time during their course. In contrast, only one of the 16 patients (6%) that died with uremia demonstrated BUN levels as great as this. Although the rats frequently (13%) went on to indefinite survival after experiencing high levels of uremia, the vast majority did not. We conclude that the rats exhibit superior ability to tolerate high concentrations of urea in comparison to man. However, as a group, they demonstrated little ability to sustain their uremic condition for prolonged periods. This latter consideration is of utmost importance, since most renal transplant studies base their conclusions on length of animal survival following organ allograft failure due to rejection. We feel this is a salient feature of the rat renal allograft model.

Animals↗
PubMed1986

Prolonged viability of human skin xenografts in rats by cyclosporine.

The immunosuppressant cyclosporine (CSA) has shown usefulness in both animal and human transplantation. The present study investigated the effect of CSA in human to rat skin xenografts. Recipient rats received either a fresh split-thickness (0.020 in.) or full-thickness graft obtained from plastic surgery, or frozen cadaver skin. The graft bed of recipient Lewis rats was prepared by full-thickness excision. Animals were maintained on CSA 25 mg/kg/day X 50 days, followed by 12.5 mg/kg 2 X/week. Control animals received an equivalent volume of vehicle. All animals receiving split-thickness grafts and treated with CSA maintained their grafts significantly longer (up to 255 days) than controls. The 2 CSA-treated full-thickness grafts and the 10 vehicle-treated controls showed clinical and microscopic signs of rejection at a mean of 6.4 days. Histologic examination of successful grafts showed areas of viable epidermis with a negligible inflammatory infiltrate. There was some loss of normal polarity and occasional apoptotic pigmented basal cells. The dermis revealed moderate fibrosis, probably secondary to the surgical procedure. Graft viability was confirmed by autoradiography. Immunohistochemical staining for S-100 protein revealed morphologic alteration of suprabasilar dendritic (Langerhans-indeterminate) cells, as well as their existence in xenografts at 12 weeks posttransplantation. Toxicities reflected by weight loss and blood chemistries were felt to be dose-dependent. This in vivo model may provide a means for testing percutaneous drug penetration and pharmacokinetics in human skin, and for observing the immune component of explanted cutaneous neoplasms and dermatoses.

Animals↗
PubMed1986

Composite tissue (limb) allografts in rats. III. Development of donor-host lymphoid chimeras in long-term survivors.

Eight LEW rat recipients possessing long-term-surviving (206-701 days) LBN vascularized hind limb allografts (CTAs) were tested for donor-host lymphoid chimerism. The recipients received various cyclosporine (CsA) treatment protocols in order to induce indefinite CTA acceptance. Histological examination of long-term-surviving CTAs demonstrated normal-appearing bone marrow in the donor limb. Lymphocytes isolated from host hemopoietic tissues (peripheral blood and/or spleen) by ficoll-hypaque density gradient centrifugation were tested against LEW-anti-BN antisera. Comparisons were made to standard curves employing various known concentrations of LBN and LEW cell combinations. The level of lymphocyte agglutination (dependent variable) showed a significant (P less than 0.025-0.005) linear relationship to the concentration of LBN donor cells (independent variable) present. Lymphocyte suspensions isolated from long-term CTA host peripheral blood and/or spleen showed a mean of 19.7% (+/- 9.7-95% confidence interval) donor LBN mononuclear cells present. Thus, it appeared that lymphoid cells originated from, and/or were released from LBN donor bone marrow into the circulation, resulting in chimeric repopulation of hemopoietic tissues. The presence of donor immunocytes in these limb allograft recipients may have been beneficial, and thus could have helped contribute to the long-term CTA survival observed.

Animals↗