PubMed Health⌕ Search

Biomedical subjects

R Ramsamooj

Publications and source records attributed to R Ramsamooj.

13 recordsLinked to original sources
PubMed1998

A novel in vitro model for xenorejection and immune mechanisms using bioengineered living skin equivalents.

We hypothesized that an in vitro bioengineered skin (LSE) could be used for the study of xenogeneic inflammatory or immunosuppressive mechanisms. Murine fibroblasts (10(4)/mL) were mixed with type 1 rat-tail collagen to form a matrix (approximately 5 days) on which human keratinocytes (NHEK, 10(5)/75 microL) were seeded. The xeno-LSE was used as a rejection target organ in vitro. Rejection was achieved by the addition of human lymphocytes (10(6)/75 microL). At various intervals of growth, control LSEs without lymphocytes (CON) and rejecting LSEs with immunocytes (REJ) were analyzed. Slides were stained with hematoxylin & eosin and examined under light microscopy. REJ xenocomposite LSEs showed classic histologic signs of rejection. There was separation of the D-E junction with the presence of dyskeratotic and necrotic cells with a concomitant inflammatory infiltrate. The CON LSEs showed essentially normal dermis (collagen fibroblast matrix) and keratinocytes. A significant finding was the separation of the D-E junction in the absence of an inflammatory infiltrate. Previous studies have shown that human keratinocytes can be grown with human fibroblasts that are histologically similar to natural human skin. This discohesive nature of the murine fibroblasts and human keratinocytes may represent an important intercellular interaction associated with xeno-cellular interactions and is worthy of further study. Furthermore, the ability to grow xeno-composite tissues has profound implications in the face of organ donor shortages. They may represent an eventual in vitro replacement of skin and even solid organs.

Adult↗
PubMed1997

Sclerosing epithelioid fibrosarcoma: short T2 on MR imaging.

A case of sclerosing epithelioid fibrosarcoma and its appearance on MRI is presented. The tumor showed a zonal architecture on MRI with a large central core of very low signal intensity and a peripheral rim of intermediate to high signal intensity on T1- and T2-weighted spin echo pulse sequences. The core showed decreased cellularity with dense collagen deposition on histologic examination, and the peripheral zone increased cellularity with increased nuclear atypia. The presence of a prominent region of very low signal intensity on T1- and T2- weighted images can be seen with neural tumors, giant cell tumor of the tendon sheath, aggressive fibromatosis, and, in rare instances, with soft tissue sarcomas rich in collagen.

Adult↗
PubMed1997

Donor treatment with the lazeroid U74389G reduces ischemia-reperfusion injury in a rat lung transplant model.

BACKGROUND: Antioxidant treatment with lazeroids has proven beneficial for the amelioration of reperfusion injury in experimental lung transplantation. This study compares the effect of donor versus recipient treatment on immediate postoperative graft function. METHODS: A model of acute double-lung transplantation in rats was used to assess graft function. Transplanted controls after 2 (group I) and 16 hours of ischemia (group II) were compared to a recipient (group III; 16-hour ischemia) and a donor treatment group (group IV; 16-hour ischemia) using the lazeroid U74389G (6 mg/kg). Serial assessment of alveolar-arterial oxygen difference, dynamic lung compliance, airway and pulmonary vascular resistance was obtained during a 2-hour reperfusion period. Final analysis included survival, weight gain, and histologic examination. RESULTS: Graft function was significantly better after 2 hours of ischemia than in any of the three 16-hour ischemia groups (II, III, IV). After 16 hours of ischemia, donor treatment provided superior graft function with respect to dynamic lung compliance, airway resistance, and alveolar-arterial oxygen difference when compared with groups II and III. The pulmonary vascular resistance was significantly higher in group III when compared with groups II and IV. Graft weight increase reflecting edema was highest in groups III (104%) and II (98%). CONCLUSIONS: After prolonged ischemia only donor treatment with the lazeroid U74389G was able to significantly reduce ischemia-reperfusion-related graft dysfunction.

Airway Resistance↗
PubMed1997

Exogenous surfactant treatment before and after sixteen hours of ischemia in experimental lung transplantation.

OBJECTIVE: A syngeneic, acute, double lung transplant model in the rat was used to determine the impact of exogenous surfactant treatment on graft function after prolonged cold storage. METHODS: The donor grafts were flush perfused, preserved for 16 hours, and then reperfused for 120 minutes. Untreated lungs served as controls (group I). In group II the recipient received a 200 mg/kg dose of surfactant (CuroSurf) before reperfusion. In groups III and IV, surfactant was administered before perfusion and harvesting (III, 20 mg/kg; IV, 200 mg/kg). Serial measurements of graft pulmonary vascular resistance, alveolar-arterial oxygen difference, and compliance were obtained. Final graft assessment included weight gain and histologic study. RESULTS: Repeated-measures analysis of variance showed significant improvement of graft performance in respect to compliance, alveolar-arterial oxygen difference, and pulmonary vascular resistance in donor surfactant treatment group IV (200 mg/kg) in comparison with recipient treatment (group II) and untreated controls (group I). Reducing the donor surfactant supplementation from 200 mg/kg to 20 mg/kg (group III) improved oxygenation and lung compliance as compared with untreated controls. Grafts in groups I and II had significantly more weight gain after 2 hours of reperfusion. Recipient treatment resulted in significantly more pulmonary hemorrhage in histologic sections. CONCLUSION: Donor treatment with exogenous surfactant is advantageous for preservation of graft function after extended ischemia. Positive effects may be seen with as little as 20 mg/kg of exogenous surfactant given before donor organ perfusion.

Airway Resistance↗
PubMed1996

Donor pretreatment with intravenous prostacyclin versus inhaled nitric oxide in experimental lung transplantation.

The pulmonary vasodilatory effects of prostacyclin (PGI2) were compared with inhaled nitric oxide (NO) for donor treatment in an acute double lung transplantation model in the rat. The PGI2 group (n=10) received 35 microg/kg PGI2 both intravenously and into the flush solution. The NO group (n=10) was ventilated before and during perfusion with nitric oxide for an expiratory NO concentration of 20 ppm. Both groups were compared with untreated controls (n=10). Following cold ischemia of 16 hr the donor lungs were implanted in syngeneic recipients via specially designed stents to the left pulmonary artery and vein. Separate graft ventilation permitted determination of compliance and resistance. During 120 min of reperfusion serial measurements of graft pulmonary vascular resistance (PVR) and alveolar arterial oxygen difference (AAD02) were obtained. Final graft assessment included weight gain and histological analysis. Data are listed as mean+/-SE. The type of donor pretreatment had a definite and negative impact on survival (NO: 106+/-6, controls: 116+/-4, PGI2: 120+/-0 min; P<0.02) and overall graft function. During reperfusion the compliance was significantly reduced in NO (23+/-4) in comparison with controls (34+/-3) and PGI2 (50+/-4 ml/cmH2O; P<0.01). The PVR was 785+/-238 in NO, 240+/-60 in controls and 181+/-71 mmHg/ml/min in PGI2 (P<0.02). The AaD02 was compromised in NO (486+/-44) compared with controls (396+/-53) and PGI2 (108+/-34 mmHg; P<0.02). The weight increase at the end of reperfusion amounted to 101+/-17% in NO, 98+/-13% in controls, and 69+/-7% in PGI2 (P<0.05). Histological analysis showed significantly more interstitial edema in the NO group. In conclusion, PGI2 administration significantly improves global lung function while the inhalation of nitric oxide before and during donor perfusion has a detrimental effect on the quality of graft preservation.

Administration, Inhalation↗
PubMed1996

The importance of static lung inflation during organ storage: the impact of varying ischemic intervals in a double lung rat transplantation model.

To determine the importance of static lung inflation during storage, graft performance was evaluated at different levels of intratracheal pressure and varying ischemic intervals. Lewis rat lungs were perfused with low-potassium Euro-Collins and stored for 4 or 8 hr either in atelectasis (4 hr: group I; 8 hr: group IV, respectively) or 13 (group II; V) or 26 cmH2O of airway pressure (groups III, VI). Following implantation continuous measurement of alveolar-arterial oxygen difference (AaDO2*) and pulmonary vascular resistance (PVR) were performed. Separate ventilation allowed assessment of mechanical lung function of the graft. At the end of reperfusion (120 min) weight gain, histology, and phospholipid and protein content in the pulmonary lavage were compared between the groups. Despite significant differences in survival at 4 hr of ischemia graft function did not differ in groups I to III. In contrast, static inflation had a significant impact after 8 hr of ischemia. Lungs stored in atelectasis (group IV) could not be reperfused and failed immediately. Survival in group V was 83+/-11 versus 107+/-7 min in group VI (P<0.05). Compliance at 80 min was 27+/-3 in group V and 52+/-6 ml/cmH2O in group VI (P<0.02). Corresponding values for PVR were 232+/-92 and 112+/-16 mmHg/ml/min, respectively (P<0.05). Less inflation and longer ischemia resulted in a reduction of the large to small phospholipid aggregate ratio and deterioration of surfactant function in the bubble surfactometer. In conclusion, while the amount of static lung inflation may not be critical following short ischemia, the performance of the graft improves significantly with full inflation (26 cmH2O) following extended ischemia (8 hr).

Animals↗
PubMed1996

Graft-versus-host disease in limb transplantation: digital image analysis of bone marrow and TGF-beta expression in situ using a novel 3-D microscope.

A subpopulation of parental to hybrid VBMT recipients developed characteristic clinical and histopathologic manifestations of GVHD. These changes are similar to those seen in human GVHD secondary to bone marrow transplantation. Human GVHD also manifests itself in an acute and chronic manner. Only a minority (30% to 40%) of animals developed lethal GVHD in our model. Those animals developing GVHD had a significantly (P < .0001) higher expression of TGF-beta in situ compared to the tolerant subpopulation. The differential expression of TGF-beta may represent an important mechanism of immune dysregulation associated with GVHD in CTA recipients.

Animals↗
PubMed1992

A rapid and sensitive cellular enzyme-linked immunoabsorbent assay (CELISA) for the detection and quantitation of antibodies against cell surface determinants. I. A comparison of cell fixation and storage techniques.

A solid phase cellular ELISA was designed and evaluated for the detection of antibodies specific for cell surface determinants. It was hypothesized that certain fixation and freezing procedures would result in stabilization of cell structures for prevention of antigen diffusion and extraction during washing procedures. This would assure assay accuracy and convenient sample management. It was hypothesized that fixation with certain reagents prior to analysis would not alter antigenicity of antibody targeted epitopes. In order to improve the preservation of the cells following cell binding to the solid phase matrix while still retaining antigenicity and morphology, a series of fixatives and storage procedures were screened to determine which were best suited for CELISA. Methanol, washing buffer (WB), Hanks' balanced salt solution (HBSS), and 0.5% formalin in HBSS were examined by comparing their relative cell binding capacity and the subsequent cell morphology. In consideration of all variables, fixation in 0.5% formalin provided the best maintenance of cell antigenicity, morphology, binding, and was associated with consistent results. Cells used immediately after fixation and fixed cells used after storage at -80 degrees C for up to 12 months were compared to determine if long term storage affected antigenicity. Since frozen cells and fresh cells demonstrated statistically identical positive to negative ratios and consistency of antibody binding, it was determined that long term frozen storage of formalin-fixed cells did not adversely affect antibody binding capacity to cell surface determinants.

Animals↗
PubMed1991

Mechanisms of prior blood transfusion-cyclosporine-induced tolerance: a potential role for immune-cellular chimerism.

Skin allografts were not enhanced by prior conditioning of blood and CyA (5 or 10 mg/kg/d). However, when BM-CyA pretreatment was used, SA survival was significantly prolonged (CyA, 5 or 10 mg/kg/d). In examining differences between the BT-CyA and BM-CyA protocols, equivocal levels of donor microchimerism (1.5%) were found in the spleens of BT-CyA conditioned recipients at the time of transplantation (day 0). In contrast, highly significant levels of splenic donor chimerism (17.2%) developed at day 0 for the BM-CyA pretransplant recipients. Skin-allograft prolongation under the BM-CyA protocol implied that the effect may be linked to the existence of a donor-specific stem-cell population in the recipient animal.

Animals↗
PubMed1991

Vascularized bone marrow transplantation (VBMT): induction of stable mixed T-cell chimerism and transplantation tolerance in unmodified recipients.

In this preliminary report, our model of VBMT across a semiallogeneic barrier consistently brings about antigen-specific host tolerance with absence of GVHD in the majority of recipients. No immunologic or radiologic intervention was utilized. These results emphasized a potentially important mechanism for low-level stable mixed lymphoid chimerism (SMLC) in tolerance induction, independent of immune suppressive effects due to irradiation or immunopharmacologic intervention.

Animals↗
PubMed1990

Development of stable mixed T cell chimerism and transplantation tolerance without immune modulation in recipients of vascularized bone marrow allografts.

A consistent majority (62.5%) of immunologically unmodified rat recipients transplanted with vascularized hind-limb bone marrow allografts across a semiallogeneic transplant barrier developed tolerance with absence of graft-versus-host disease. A minority of recipients (37.5%) demonstrated lethal GVHD. Transplantation tolerance in the majority was associated with the induction of stable low-level mixed T cell chimerism, including donor CD5+, CD4+, and CD8+ lymphocytes. Chimeras were specifically immune nonresponsive to host alloantigenic determinants. These results emphasized a potentially important mechanism for low-level stable mixed lymphoid chimerism (SMLC) in tolerance induction, independent of immune suppressive effects due to irradiation or immunopharmacologic intervention. These vascularized bone marrow transplantation (VBMT) results may establish the experimental foundation for a novel approach to stem cell transfer and bone marrow transplantation.

Animals↗
PubMedDate not supplied

Use of regression analysis and flow cytometry for determining levels of mixed semiallogeneic immune chimerism.

It has been shown that tolerance or specific immunologic nonresponsiveness in various lymphohemopoietic transplant models can be associated with the development of mixed lymphoid chimerism. As a specific example, composite tissue (limb) allografts were studied as a model for vascularized bone marrow transplantation (VBMT) and it was demonstrated that development of stable cellular immune chimerism is associated with long-term allograft survival. Recently, studies were initiated using a new parental to hybrid VBMT model, but the detection of donor cells is complicated, due to the fact that they share one parental allotypic determinant. Therefore, regression analysis with a flow cytometric immunofluorescent staining assay was evaluated for the assessment of cellular lymphoid chimerism in donor parental to hybrid (P-->F1) lymphohemopoietic transplant models. Standard curves consisting of known mixed populations of parental donor (Lewis, LEW) and hybrid host F1 (Lew x BN, LBN) lymphocytes were established. Standard curves were analyzed by linear regression statistics and excellent coefficients of determination (r > .881) were obtained for all standard curves. A highly statistically significant (p < .016) linear relationship between level of donor cell chimerism (independent variable) and percent stained (dependent variable) was determined. The technique was then evaluated using the parental to hybrid VBMT model. Levels of donor LEW lymphoid chimerism in all VBMT LBN recipients were successfully assessed by regression analysis and inverse prediction using distinct recipient allodeterminant markers. In conclusion, this technique was proven to be reliable and accurate for the detection of of chimerism in parental to F1 lymphohemopoietic allograft models.

Animals↗