Rejection Phenomenon Research Articles

Characterization of phospholipid reverse micelles in relation to membrane processing of vegetable oils

Studies were conducted to determine the critical micelle concentration (CMC) of phospholipids in vegetable oils and the size of reverse micelles to understand their rejection phenomenon in the membrane process. The CMC values of phosphatidylcholine (PC) in triolein and phospholipids in crude soybean oil were determined to be 440 and 1020 mg/kg, respectively, by using TCNQ (7,7,8,8-tetracyano-quinodimethane) solubilization technique. The surface tension measurements of these samples gave similar values of CMC. From small-angle X-ray scattering (SAXS) analysis, the size of the PC micelles was determined to be in the range of 3.56 to 4.70 nm. The characterization of reverse micelles formed in the oil system was found useful in enhancing the understanding of the possible rejection phenomenon of phospholipids by non-porous polymeric composite membranes used in our earlier studies on vegetable oils and in suggesting suitable types of membranes for the same.

Characterization of phospholipid reverse micelles in relation to membrane processing of vegetable oils

Studies were conducted to determine the critical micelle concentration (CMC) of phospholipids in vegetable oils and the size of reverse micelles to understand their rejection phenomenon in the membrane process. The CMC values of phosphatidylcholine (PC) in triolein and phospholipids in crude soybean oil were determined to be 440 and 1020 mg/kg, respectively, by using TCNQ (7,7,8,8-tetracyano-quinodimethane) solubilization technique. The surface tension measurements of these samples gave similar values of CMC. From small-angle X-ray scattering (SAXS) analysis, the size of the PC micelles was determined to be in the range of 3.56 to 4.70 nm. The characterization of reverse micelles formed in the oil system was found useful in enhancing the understanding of the possible rejection phenomenon of phospholipids by non-porous polymeric composite membranes used in our earlier studies on vegetable oils and in suggesting suitable types of membranes for the same.

Processo modificado de reprodução e amplificação de imagem para mensuração de área por planimetria: Aplicação em feridas planas produzidas em cães, tratadas por curativos oclusivos de pele de rã

Analise digital de imagem e planimetria sao importantes instrumentos de avaliacao de areas de feridas planas submetidas a tratamento local. No processo proposto, os perimetros das areas das feridas foram obtidos in loco por decalque sobre folha transparente e reproduzidos com ampliacao por copiadora a laser, prescindindo-se do uso de fotografia e revelacao. As areas de contracao e granulacao foram medidas utilizando-se um planimetro. As areas de epitelizacao foram determinadas por diferenca entre as referidas areas. Os dados de areas foram transformados em percentuais acumulados de Contracao da Ferida (PCF), Epitelizacao da Ferida (PEF) e Cicatrizacao da Ferida (PCiF). Tal processo foi aplicado em feridas planas quadradas (400 mm²) produzidas nas regioes toracodorsal direita e esquerda de caes. Dezessete lesoes da regiao toracodorsal direita foram tratadas com peles de Rana catesbeiana, previamente preservadas por hipotermia (Grupo Teste). As 17 lesoes da regiao toracodorsal esquerda foram tratadas com gaze umedecida (Grupo Controle). Os dados de PCF, PEF e PCiF foram avaliados no 7o, 14o, 21o e 28o DPO. Estudos macro e microscopicos revelaram destruicao da pele, sugerindo fenomeno de rejeicao. Conclui-se que: 1. O processo de reproducao e ampliacao de imagem permitiu economizar custos. O erro de leitura do planimetro foi de ± 0,5%; 2. Os PCF, PEF e PCiF nao apresentaram diferencas significativas entre os Grupos. Esta equivalencia foi atribuida a destruicao da pele de ra, sugestiva de rejeicao.

Role of Rantes in Experimental Cardiac Allograft Rejection

The host response to alloantigen results in upregulation of Class II MHC antigens and associated cytokine production (especially IL-2 and interferon-gamma (IFN-γ)) as well as lymphocytic infiltration and cellular activation which leads to graft damage/destruction. RANTES (Regulated upon Activation, Normal T-cell Expressed and presumably Secreted) is a member of the β subfamily (CC) of chemokines and has been shown to function as a lymphocyte chemoattractant. We now describe the requirement for RANTES in cardiac heterotopic allograft (brown Norway into Lewis rats) rejection in rats. By Northern blot analysis, mRNA could be detected in allografts at 6 and 8 days post-transplantation but not in isogenic (Lewis) grafts. RANTES protein could be demonstrated by Western blot analysis in homogenates from allografts at day 8 but not at day 0 and could not be identified in isogenic cardiac transplants. By immunostaining, RANTES protein was present in mononuclear cells of allografts at day 6 but was absent in the isogenic transplants. When rats were treated with anti-RANTES serum, there was a significant delay in rejection time (cessation of beating) of the allografts. These data demonstrate that expression of RANTES in rat cardiac allografts is linked to the rejection phenomenon.

NARROWBAND NOISE ATTENUATION CHARACTERISTICS OF IN-DUCT ACOUSTIC SCREENS

Noise attenuation characteristics of acoustic screens installed in a straight section of a rectangular duct is studied. It was observed that sound path asymmetry—which arises when an acoustic screen is installed so as to divide the original duct into two asymmetric channels and recombine—gives rise to large narrowband sound attenuation. At first glance, the observed phenomenon looked like it could be explained in terms of the noise cancellation mechanism in Herschel–Quinke tubes, which can be described mathematically by a plane wave model. However, extensive experimental and numerical analyses by the present authors suggested that the narrowband noise attenuation due to sound path asymmetry involves significant higher order mode contributions, hence cannot be described in terms of the plane wave model. Hence, an analytical model that can accurately describe the noise rejection phenomenon was developed. It was found that the higher modes although non-propagating are absolutely necessary to describe the narrowband noise attenuation phenomenon due to sound path asymmetry, which would not have been predicted by a plane wave model.

The protective effects of meniscal transplantation on cartilage. An experimental study in sheep.

Meniscal loss may result in arthritis. The aim of this study was to establish a simple operative method for meniscal transplantation in a large-animal model and to determine whether meniscal transplantation provides protection of the articular surfaces, whether meniscal allografts have the same protective effect as meniscal autogenous grafts, and whether there is any rejection phenomenon associated with meniscal allografts. Twenty-eight sheep were divided into four study groups, which were treated with (1) a sham operation (four sheep), (2) a meniscectomy (eight sheep), (3) a meniscal autogenous graft (eight sheep), or (4) a meniscal allograft (eight sheep). The meniscal transplant was secured with three suture anchors to the tibia. At four months after the operation, macroscopic and microscopic evaluations of the articular cartilage and the menisci of the sheep knees were performed in a blinded fashion. The group treated with the sham operation had no cartilage damage and had normal meniscal tissue. The meniscectomies resulted in significant macroscopic and microscopic damage to the articular cartilage in the medial compartment. The mean score (and standard error of the mean) for macroscopic damage to the cartilage in the group treated with the meniscectomy was 6.5+/-0.8 points compared with 3.9+/-0.7 points in the group treated with the autogenous graft and 4.3+/-0.6 points in the group treated with the allograft (p<0.05). The size of the area of damaged articular cartilage was reduced by approximately 50 percent in both groups treated with a meniscal transplant compared with the group treated with the meniscectomy (p<0.05). There were no significant differences between the group treated with the autogenous graft and that treated with the allograft. The histological appearance of the meniscal autogenous grafts was within normal limits. Interestingly, all of the allografts had evidence of fibrinoid degeneration with areas of hypocellularity and cloning of chondroid cells. These results suggest that meniscal transplantation provides noticeable although not complete protection against damage to the articular cartilage after a meniscectomy. The meniscal allografts were just as effective in providing this protection as were the meniscal autogenous grafts.

Cytokine gene expression following neural grafts.

A reverse-transcription polymerase chain reaction study of molecular events following solid neural tissue xenogeneic and syngeneic grafts into the mouse caudate nucleus was made between 1 day and 30 days post-grafting. Constitutive expression of interleukin (IL)-1 and transforming growth factor (TGF)-beta1 mRNAs was detected. The sham operation produced minimal cytokine upregulation, indicating that surgical trauma caused minimal damage. A similar picture was seen with syngeneic grafts, which showed good graft survival. Xenografts, however, were rejected within 30 days and cytokine mRNAs for IL-2, IL-2R, IL-4, IL-10 and interferon (IFN)-gamma were detected from 7 days post-graft, correlating with histological identification of a leukocytic infiltrate. This method provides a quick, comparative screen for detecting cytokine mRNA profiles in neural grafts and may assist the diagnosis of early rejection phenomena. As such, it is a potential analytical tool for strategies aimed at depleting/blocking the activity of different cell types and/or cytokines in future neural transplant therapy.

Les odeurs de la ville

Experience and cultural influences stand out as what most likely determines the appraisal or rejection phenomenon linked to odours. In participating to a psychosensory experiences of the urban environment, odours determine one's feelings. That is the reason why odours and their representations are likely to become the characteristics of a situation, of a place, and of each and everybody' sindividual expérience in city life. Our aim here, was to understant how olfactive representations express themselves and how they link together in the city of Paris Through our observations, we were able to notice the existence of a consensus for the classification of odours which we reckon we can impute to a common sociocultural knowledge, fruthennore, it turns out that the level of emotional attachment to the city of Paris influences the structure of olfactive representations itself, lastly, the influence of situationnal, contextual or environmental factors seems to determine the interpretation of the olfactive message to a certain extent. Thus partly accounting for interpersonal differences. Odours and their representations therefore noticeably participate to the elaboration of the image of the city of Paris, to influence on our behaviour in some cases. Olfactive representations seem to come whitin the framework of a complex system, where they become in turn either subject or object of influence in the perception and the evaluation processes of environment.

Thalidomide prolongs experimental autoimmune neuritis in Lewis rats.

Thalidomide is reported to have immunomodulatory and anti-inflammatory effects, which have led to its use in the treatment of a number of immune-mediated disorders, including leprosy, discoid lupus and Behcet's disease, and to prevent immunological rejection phenomena following skin and bone marrow grafts. Experimental autoimmune neuritis (EAN) is a CD4+ T-cell-mediated demyelinating autoimmune disease, which represents an animal model for the study of the immunopathogenesis and immunotherapy of Guillain-Barré syndrome (GBS) in humans. We examined the effect of thalidomide in Lewis rats with EAN, which was induced by immunization with bovine peripheral nerve myelin (BPM) and complete Freund's adjuvant (CFA). Thalidomide prolonged clinical EAN when given at a dose of 200 mg/kg/day by gavage. This clinical effect was associated with increased numbers of inflammatory cells in sciatic nerve sections and elevated numbers of interferon-gamma (IFN-gamma) mRNA-expressing cells among lymph node mononuclear cells from thalidomide-treated EAN rats on day 17 postimmunization, i.e. at the peak of clinical EAN. The finding that thalidomide prolongs clinical EAN is in agreement with the clinical polyneuropathy reported in patients receiving treatment with thalidomide and limits its clinical usefulness.

Microcirculatory hemodynamics during the acute phase of free vascularized muscle allograft rejection.

This study investigated the microcirculatory pattern during acute rejection of a vascularized free muscle graft. Using a new rat cremaster muscle free flap model, isograft transplantation was done between genetically identical Lewis rats (N = 23) and allograft transplantation across a major histocompatibility barrier (Lewis Brown Norway [RT-11 + n] to Lewis [RT-11] rats; N = 24). At days 1, 3, 5, and 7 posttransplantation, microcirculatory measurements were taken of vessel diameter, red blood cell velocity, endothelial edema index, leukocytic-endothelial interaction (rolling, adhering, and transmigrating leukocytes), and capillary perfusion. In the allografts at 5 days the lumen obstruction was 27% greater (p < 0.05) than onset. The number of perfused capillaries decreased by 36% compared with isografts at day 5 (p < 0.05). The number of adhering leukocytes increased significantly in allografts both at day 1 (71%; p < 0.05) and at day 3 (77%; p < 0.05). At day 3, transmigrating leukocytes rose significantly (p < 0.05). Allograft histology showed myocytic destruction and lymphocytic infiltration at day 5. Our results suggest that the microcirculatory signs of acute muscle allograft rejection occurred 24 hours after transplantation, and preceded histological signs of rejection. The critical time for microvascular survival of muscle allografts was 3 days. This procedure allows us to distinguish events related to transplantation trauma from rejection phenomena.

Bias phenomenon and compensation for PDA/JPDA algorithms

Probabilistic Data Association (PDA) and Joint PDA (JPDA) algorithms are approaches for target tracking which have received considerable attention. It has been observed for some years that they both yield biased tracks in a multitarget environment. However, most work assumes no false alarms and the rejection phenomenon of the JPDA algorithm has not been reported. In this paper, the general procedure of multitarget tracking and the PDA/JPDA algorithms are first described. Their bias phenomenon is simulated and investigated. It is observed that (1) the JPDA algorithm has less bias than the PDA algorithm in a clean environment. Both of them yield coalescence (2) the JPDA algorithm has coalescence and rejection bias phenomenon while the PDA algorithm has only coalescence phenomenon in a clutter environment. Bias compensated algorithms are then presented using the polynomial regression method. Simulations are carried out to select the order of polynomial regression. Monte Carlo simulations also demonstrate the effectiveness of the compensated PDA/JPDA algorithms.

Intrastriatal Grafts From Multiple Donors Do Not Result in a Proportional Increase in Survival of Dopamine Neurons in Nonhuman Primates

We examined the potential for “double grafts,” i.e., grafts from two donors in each recipient, to enhance the total number of ventral mesencephalic dopamine neurons that survive grafting in adult African green monkeys. Because dopamine cell survival in grafts represents a small percentage of the total number of neurons grafted, several human clinical trials recently have employed grafts of tissue from multiple donors (e.g., from two to eight embryos per host recipient) in attempts to increase the total number of dopamine neurons that survive in grafts. Presumably, this is intended to elevate dopamine levels by providing more dopamine neurons to the damaged brain to alleviate the symptoms of parkinsonism. While well-developed grafts with several thousand dopamine neurons were found in most recipient animals, we observed a reduced total number of tyrosine hydroxylase positive neurons in the grafts in spite of the presence of some double grafts that were larger than normal. The overall growth of the grafts was impressive; some grafts were so large that they spanned the full dorsoventral extent of the caudate nucleus, probably reflecting the fact that twice as much tissue was implanted in each drop site in comparison to our standard protocol. However, some animals revealed atypical patterns of neurite outgrowth that appeared limited to the grafted tissue, and at least one monkey revealed “amorphous” grafts generally lacking in cellular structure, which suggests a possible rejection phenomenon. These findings raise questions about the use of multiple donors and suggest that the likelihood of rejection and/or cell death may be enhanced, which is of potential importance in the designof grafting strategies for clinical applications.

Intrastriatal grafts from multiple donors do not result in a proportional increase in survival of dopamine neurons in nonhuman primates.

We examined the potential for "double grafts," i.e., grafts from two donors in each recipient, to enhance the total number of ventral mesencephalic dopamine neurons that survive grafting in adult African green monkeys. Because dopamine cell survival in grafts represents a small percentage of the total number of neurons grafted, several human clinical trials recently have employed grafts of tissue from multiple donors (e.g., from two to eight embryos per host recipient) in attempts to increase the total number of dopamine neurons that survive in grafts. Presumably, this is intended to elevate dopamine levels by providing more dopamine neurons to the damaged brain to alleviate the symptoms of parkinsonism. While well-developed grafts with several thousand dopamine neurons were found in most recipient animals, we observed a reduced total number of tyrosine hydroxylase positive neurons in the grafts in spite of the presence of some double grafts that were larger than normal. The overall growth of the grafts was impressive; some grafts were so large that they spanned the full dorsoventral extent of the caudate nucleus, probably reflecting the fact that twice as much tissue was implanted in each drop site in comparison to our standard protocol. However, some animals revealed atypical patterns of neurite outgrowth that appeared limited to the grafted tissue, and at least one monkey revealed "amorphous" grafts generally lacking in cellular structure, which suggests a possible rejection phenomenon. These findings raise questions about the use of multiple donors and suggest that the likelihood of rejection and/or cell death may be enhanced, which is of potential importance in the design of grafting strategies for clinical applications.

Genetic susceptibility to hypertension-induced renal damage in the rat. Evidence based on kidney-specific genome transfer.

To test the hypothesis that genetic factors can determine susceptibility to hypertension-induced renal damage, we derived an experimental animal model in which two genetically different yet histocompatible kidneys are chronically and simultaneously exposed to the same blood pressure profile and metabolic environment within the same host. Kidneys from normotensive Brown Norway rats were transplanted into unilaterally nephrectomized spontaneously hypertensive rats (SHR-RT1.N strain) that harbor the major histocompatibility complex of the Brown Norway strain. 25 d after the induction of severe hypertension with deoxycorticosterone acetate and salt, proteinuria, impaired glomerular filtration rate, and extensive vascular and glomerular injury were observed in the Brown Norway donor kidneys, but not in the SHR-RT1.N kidneys. Control experiments demonstrated that the strain differences in kidney damage could not be attributed to effects of transplantation-induced renal injury, immunologic rejection phenomena, or preexisting strain differences in blood pressure. These studies (a) demonstrate that the kidney of the normotensive Brown Norway rat is inherently much more susceptible to hypertension-induced damage than is the kidney of the spontaneously hypertensive rat, and (b) establish the feasibility of using organ-specific genome transplants to map genes expressed in the kidney that determine susceptibility to hypertension-induced renal injury in the rat.

Transplantation of small bowel alone or with the liver in pigs: Use of peripheral blood lymphocytes in monitoring rejection

The small bowel is an organ with a large lymphoid component. In addition to the organized structures of the Peyer's patches and mesenteric lymph nodes, the lamina propria also contains a vast mass of mobile lymphocytes. The transplantation of the small bowel has thus been associated with significant rejection phenomena and the possibility of graft-versus-host disease (GVHD) in the recipient, despite the immunosuppressive treatment. In a swine model, we have compared by mixed lymphocyte reaction (MLR) the immunological events occurring during orthotopic liver-small bowel transplantation (OLSBTx) and small bowel transplantation alone (SBTx) to evaluate a possible immunological advantage of combined liver-small bowel transplantation in order to prevent intestinal rejection.

Phenytoin and cyclosporine A specifically regulate macrophage phenotype and expression of platelet-derived growth factor and interleukin-1 in vitro and in vivo: possible molecular mechanism of drug-induced gingival hyperplasia.

Phenytoin (pht) is an anticonvulsant drug commonly used for the prevention of seizures. A common side effect of PHT therapy is gingival hyperplasia, occasionally so severe that it requires surgical intervention. Cyclosporine A (CSA) is a drug widely used for the control of rejection phenomena following solid organ and bone marrow transplantation. A frequent side effect of CSA administration is gingival overgrowth. As yet, the molecular mechanisms of drug-induced gingival hyperplasia are unknown although it has been postulated that certain drugs increase fibroblastic activity through alterations in levels of various growth factors and cytokines. The purpose of this study was to: 1) evaluate monocyte/macrophage platelet-derived growth factor (PDGF) and interleukin (IL)-1 beta production in vitro after exposure to CSA; 2) determine the levels of PDGF-B and IL-1 beta gene expression in minimally inflamed gingival tissues of control patients and PHT-treated patients exhibiting gingival overgrowth as well as patients with severe gingival inflammation; and 3) combine characterization of macrophage phenotype with clinical presentation and expression of PDGF-B and IL-1 beta in gingival tissues from the control and PHT-treated patients. For the in vitro studies, commercial ELISA kits were used to measure PDGF-A/PDGF-B and IL-1 beta levels in conditioned media from rat and human monocyte/macrophage cell cultures. CSA caused a significant elevation of PDGF but did not cause any changes in IL-1 beta levels. For the in vivo studies, quantitative competitive reverse transcription polymerase chain reaction (QC-RTPCR) techniques were utilized to measure PDGF-B and IL-1 beta mRNA levels in experimental groups. PHT-treated patients exhibiting gingival overgrowth demonstrated a significant increase in PDGF-B mRNA compared with minimally inflamed controls. Patients with severe gingival inflammation also demonstrated a significant increase in PDGF-B mRNA however, PHT-induced PDGF-B upregulation is approximately 6 times larger than PDGF-B upregulation produced by inflammation alone. PHT-treated patients exhibiting gingival overgrowth demonstrated no significant increase in IL-1 beta mRNA; however, IL-1 beta mRNA levels in the severely inflamed gingival samples demonstrated a significant increase. Additionally, for the clinical samples, macrophage phenotype was characterized immunohistochemically in adjacent sections using specific monoclonal antibodies for inflammatory and reparative/proliferative phenotypes. There were no significant differences in the numbers of either macrophage phenotype in minimally inflamed gingival tissues; however, in the severely inflamed tissue, there was a significant increase in the inflammatory macrophage phenotype and in the hyperplastic gingival tissue, there was a significant increase in the reparative/proliferative macrophage phenotype. The results of this investigation indicate that the clinical presentation of inflamed and hyperplastic gingival tissues is associated with specific macrophages phenotypes which express the pro-inflammatory cytokine IL-1 beta in inflamed tissues or the essential polypeptide growth factor PDGF-B in PHT-induced hyperplastic tissues.

Allograft Meniscus Transplantation

At this time, meniscal allograft transplantation remains an investigational procedure with very limited indications. To date, no work has shown that the transplanted meniscus is capable of protecting and, preserving the hyaline cartilage of the knee joint. The technical aspects of the procedure have been established and are reproducible. Furthermore, it is apparent that a systemic rejection phenomenon does not seem to occur, and the transplanted meniscus is capable of healing. MR imaging appears to be the best method of assessing postoperative position of the transplanted meniscus in the knee. If the transplanted meniscus cannot be maintained in an anatomic position during weight bearing, it is unlikely to have any functional role. Questions remain with regard to the best way to preserve and sterilize the meniscus and whether the transplanted allograft meniscus is capable of assuming the multifaceted role of the normal meniscus in the knee. As more work is conducted, these questions will be answered, and a better understanding of the efficacy of this novel technique will be achieved.

Fertilization and rejection of spermatozoids by egg cells in artificially pollinated ovules ofEncephalartos (Zamiaceae)

The structure and behaviour of free female, male and proembryonal nuclei ofEncephalartos villosus Lem. were studied during a light-microscopical investigation of serially sectioned archegonia in successfully pollinated ovules. Before spermatozoids were released from the pollen tubes into the archegonial chamber, the ventral canal nucleus had disintegrated in the neck region of the egg cell among minute, amoeboid bodies with PAS-positive granules. In archegonia containing multiple spermatozoids, the egg nucleus was unobtrusive and syngamy followed by proembryo formation regularly resulted. The egg cell usually reacted violently in archegonia penetrated by a single spermatozoid. These reactions were regarded as rejection phenomena and considered as indicators that the egg cell can differentiate between compatible and incompatible male gametes.

Information Versus Meaning

The cultural analysis that informs Marten's "Visibility and Vulnerability" article can neither be simply expanded by adding more variables nor simply assimilated to a framework that neglects meaning. The focus of the cultural analysis advocated here is the delineation of meanings used by cultural participants to shape and evaluate their own and their peers' actions. Such an analysis emphasizes emic categories as openings to understanding rejection phenomena. Knowing about more variables will not necessarily further understanding of the meaning of rejection to early adolescents.

Autogenous replacement of the meniscus cartilage: analysis of results and mechanisms of failure.

Autogenous replantation of meniscal cartilage (resection of 80% of the meniscus cartilage followed by immediate replantation) was performed in 14 dogs as a control arm of a meniscal replacement study. The purpose was to assess the ability of the excised tissue to heal to the intact rim and function as a meniscus cartilage. This procedure is an idealized model of allografting meniscus cartilage in that the tissue is fresh, autogenous, and perfectly sized. If this procedure did not succeed, it seemed likely to the authors that allografting meniscal cartilage would have diminished chances for success. Evaluation of these replant failures led us to speculate that the causes and mechanisms might include slow or incomplete revascularization, inadequate mechanical fixation or stabilization, and, perhaps, some type of rejection phenomenon not examined or confirmed in the present study. We believe these mechanisms will be particularly deleterious for allografted meniscal cartilages and recommend further extensive evaluation of meniscal allografts before wide clinical use.