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Biomedical subjects

D Pham

Publications and source records attributed to D Pham.

33 records · Page 2Linked to original sources
PubMed1994

Functional comparison between HTLV-I envelopes originating from TSP/HAM or ATL cell lines.

The human T-cell leukemia type I (HTLV-I) virus is associated with two different diseases, adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM). We have compared the viral envelopes originating from TSP/HAM and ATL patients, using the capacity of infected cells to form syncytia with receptor-expressing cells. We show that like the ATL cell lines, the TSP/HAM ones can form syncytia with a large panel of human target cells, including a variety of hematopoietic cell lines, as well as cell lines of neuroectodermal origin. None of the target cell lines tested was able to discriminate between TSP/HAM- and ATL-infected cell lines. When infected cells of TSP/HAM origin are cocultivated with cells of ATL origins, syncytia are never observed. This interference phenomenon suggests that the viruses expressed by the different cell lines utilize the same receptor.

Blotting, Western↗
PubMed1993

Composite kidney-islet transplantation prevents recurrent autoimmune beta-cell destruction.

BACKGROUND: Clinically successful islet transplantation has been rare despite adequate isolation techniques. Reenactment of the original autoimmune beta-cell destruction may contribute to the poor results. Distinguishing autoimmune effects from rejection can be accomplished with isogeneic transplants exchanged between diabetes-prone (BB-DP) and diabetes-resistant (BB-DR) rats. These experiments determine the relative sensitivity of islet, whole pancreas, and composite kidney-islet transplants to recurrent autoimmunity. METHODS: Acutely diabetic (BB-Ac) BB rats served as recipients of vascularized pancreas, intraportal (IPo) or renal capsular (KC) islet transplants, or vascularized composite kidney-islet grafts from BB-DR or BB-DP donors. Graft function was assessed by daily blood glucose level, and the outcome was confirmed on histologic examination. Cyclosporine 5 mg/kg/day intramuscularly was administered to assess its effect on recurrent beta-cell injury. RESULTS: BB-DP pancreases developed recurrent autoimmunity in 55% of cases; cyclosporine afforded complete protection if maintained. Diabetes resistance was transplanted with 23 of 23 BB-DR pancreas grafts; however, islet isolation led to a loss of diabetes resistance for islet grafts to the KC and IPo. Cyclosporine protected KC but not IPo islets. Composite BB-DR kidney-islet transplants functioned indefinitely in all cases. CONCLUSIONS: Transplanted islets initially survive by passive diffusion but are ultimately revascularized by capillary ingrowth. The finding that composite kidney-islet transplants function indefinitely suggests that the revascularizing endothelium may play a role in resistance or susceptibility to autoimmune beta-cell destruction.

Animals↗
PubMed1992

Human T-cell leukemia virus type I envelope protein maturation process: requirements for syncytium formation.

The human T-cell leukemia virus type I (HTLV-I) envelope protein is synthesized as a gp61 precursor product cleaved into two mature proteins, a gp45 exterior protein and a gp20 anchoring the envelope at the cell membrane. Using N-glycosylation inhibitors and site-directed mutagenesis of the potential glycosylation sites, we have studied the HTLV-I envelope intracellular maturation requirements for syncytium formation. We show here that experimental conditions resulting in the absence of precursor cleavage (tunicamycin, monensin treatments, and use of inhibitors of the reticulum steps of the N glycosylations) also result in no cell surface expression of envelope protein. The lack of syncytium formation observed in these cases is thus explained by incorrect intracellular transport. When the precursor is cleaved in the Golgi stack (no treatment or treatment with inhibitors of the Golgi steps of the N glycosylations), it is transported to the cell surface in all the cases examined. Syncytium formation is markedly reduced, however, when Golgi glycosylations are incorrect, which shows that the sugar moieties are involved in the envelope functions. Site-directed mutagenesis demonstrates that each of the five potential glycosylation sites is actually glycosylated. Glycosylation of sites 1 and 5 is required for normal maturation, whereas that of sites 2, 3, and 4 is dispensable. Glycosylation of each site, however, is required for normal syncytium formation. Altogether, the restraints exerted by the cell for the HTLV-I envelope to be transported and functional are very high, which might play a role in the observed conservation of the envelope amino acid sequence between various strains.

1-Deoxynojirimycin↗
PubMed1992

Transient migratory osteoporosis: a variant of reflex sympathetic dystrophy? Report of 3 cases and literature review.

Three cases of transient migratory osteoporosis treated with sympathetic blocks are described. Review of the literature in conjunction with the presentation and treatment of these 3 cases led to the formulation of a hypothesis of a common mechanism (mediated through the sympathetic nervous system) responsible for the profound osteoporosis and pain of reflex sympathetic dystrophy and transient migratory osteoporosis. Arguments are presented supporting transient migratory osteoporosis as a variant of the classical reflex sympathetic dystrophy.

Adolescent↗
PubMed1989

Suppressor effects and cyclic AMP accumulation by the CD29 molecule of CD4+ lymphocytes.

Integrins are a superfamily of related molecules whose function, where known, is to mediate adhesion. The so-called very-late-activation antigen (VLA) family includes at least five distinct heterodimers, each composed of a unique alpha-subunit non-covalently associated with a common beta-subunit. Several members of the family have been shown to bind extracellular matrix proteins, but the function of VLA-4 is so far unknown. VLA-4 is the only member of the family detected on thymocytes and resting T cells. We show here that an antibody which recognizes the beta-subunit of VLA-4 (CD29) on T cells can inhibit CD4+ cell proliferation triggered by CD2 or CD3, and that binding of this antibody to activated T cells leads to an increase in cyclic AMP levels which is comparable to that elicited by forskolin. These negative signalling effects are unique to this antibody: other CD29 antibodies do not affect the growth of activated CD4 cells but enhance the proliferation of whole T cell populations and abrogate the suppressive effects of mitomycin-treated CD8 cells on CD4-cell growth. Taken together, our results indicate that VLA-4 functions in cell-cell interactions and that it is the target for the suppressive effects of CD8 cells on CD4 cells.

Antigens, Differentiation↗
PubMed1989

The biochemical characterization of E2, a T cell surface molecule involved in rosettes.

We have previously identified a molecule on the T cell surface, which, in addition to CD2 is involved in the rosette phenomenon. This is a 32-kDa single polypeptide chain which we have termed E2. The studies reported here show striking patterns on the glycosylation status of E2. It is a heavily sialylated and glycosylated molecule, the sugar moieties accounting for almost half of its relative molecular mass (Mr). It carries no N-linked sugar residues, only O-linked oligosaccharides. Despite heavy glycosylation, the molecule appears to behave homogeneously on gel electrophoresis, both in terms of Mr and pI. Neuraminidase treatment of E2 lowered its Mr to 28 kDa; this was further decreased to 18 kDa after removal of O-linked sugar residues by treatment with O-glycanase. An identical reduction in size was observed after treatment with trifluoromethane sulfonic acid, showing that the molecule carries no detectable N-linked sugar residues. Moreover, endoglycosidase F and endoglycosidase H treatment of either the immunoprecipitates from 125I surface-labeled thymocytes, or of a purified preparation of E2, did not reduce the Mr of E2, nor did tunicamycin treatment of T cells. Two-dimensional gel electrophoresis revealed two discrete spots of acidic pI (4.4 and 4.6) that were still seen after neuraminidase treatment, though they had moderately shifted. Pulse-chase experiments revealed a single 28-kDa precursor form that could have been the unsialylated molecule. Finally, sequencing 14 amino acid residues of the N-terminal side revealed no homology with known proteins. Since the sugar moieties of adhesion protein could play an important role, the results obtained in this study will prove valuable to our understanding of the role exerted by the E2 molecule.

Amino Acid Sequence↗
PubMed1988

A T cell surface molecule different from CD2 is involved in spontaneous rosette formation with erythrocytes.

Increasing evidence indicates that rosettes which spontaneously from between human T cells and E might be of physiologic relevance. We show here that another T cell-surface molecule than CD2 is involved in rosette formation. Four mAb have been obtained reacting with human T cells that block rosettes with E from many species, including autologous cells. They react with a molecule, we termed E2, which is actively synthetized by T and monocytic cells. Immunoprecipitation revealed a major 32-kDa band. Immunoblots revealed a major 32-kDa band and a minor 20-kDa band. This molecule was detected on all T cells tested--and present at high densities on corticothymocytes, but at low densities on medullary thymocytes. It was also found on monocytes but not on B cells. However B-CLL cells did carry this molecule. E2 molecules were also detected on nonhematologic cells. Together with the recent evidence that 3 molecules from the erythrocyte surface are also involved for rosettes, intricate molecular interactions would account for adhesion of T cells to autologous E and possibly autologous nucleated cells.

Antibodies, Monoclonal↗
PubMed1982

Phenomenon of human T cells rosetting with sheep erythrocytes analyzed with monoclonal antibodies. "Modulation" of a partially hidden epitope determining the conditions of interaction between T cells and erythrocytes.

Anti-D66 is a monoclonal antibody able to inhibit E-rosette formation of T cells both at 4 degrees C and at 37 degree C but that does not inhibit T cell rosette formation with neuraminidase or 2-amino-ethylisothiouronium bromide (AET)-pretreated E. As demonstrated by capping experiments, it defines an epitope, D66, that is directly involved in E-rosette formation. D66 is distinct from the epitope defined by 9.6 because 9.6, a previously defined "pan-T" monoclonal antibody, inhibits E(AET) rosette formation and because no cross-blocking occurred between both antibodies fixation. However, 9.6 and D66 are carried by the same molecule, as demonstrated by sequential immunoprecipitation assays performed on two different T cell lines. On the thymocyte surface, also, 9.6 and D66 are most probably carried by the same molecule, as indicated by cocapping and colysostripping experiments. D66 is present at higher densities on thymocytes and activated T cells than on peripheral blood T cells. Investigation of numerous T cell populations, both normal and malignant, showed a straightforward correlation between elevated D66 density and ability to form 37 degrees C stable E-rosettes. Neuraminidase treatment of thymocytes and peripheral blood lymphocytes forming E-rosettes unmasked a large fraction of D66 not readily accessible on their surface. These hidden D66 epitopes appear to be responsible for a surprising observation: the ability of anti-D66 to inhibit E-rosette formation could be totally reversed by fixation on anti-D66 of an antibody to mouse immunoglobulin or an Fab fragment anti-mouse immunoglobulin. This would induce microdisplacement with emergence of hidden D66, as documented by fluorometric studies. Finally, malignant T cells with a differentiative status of mature T cells, but forming no (or low numbers of) E-rosettes, could be induced both to display D66 and to form E-rosettes by neuraminidase treatment.

Animals↗
PubMed1980

An antigen shared by a human T cell subset and B cell chronic lymphocytic leukemic cells. Distribution on normal and malignant lymphoid cells.

We obtained a monoclonal antibody, A50, after immunizing Biozzi's high responder strain of mice with T cell chronic lymphocytic leukemia (T-CLL) cells. A50 recognized an antigen present on the surface of B cell chronic lymphocytic leukemia cells from many patients and from cells of T lineage from any subject we tested. We could not find this antigen either on the surface of normal B cell or on other non-T cell malignancies. On T cells, this antigen was present on a subpopulation of thymus cells, and on most peripheral T cells. The antigen was present on the surface of cells from T-CLL, Sézary's disease, and a subset o T cell lymphoma. The antigen seemed to belong to a complex set of antigenic determinants that we had defined with rabbit antisera.

Animals↗
PubMed1980

Electrohydraulic ureterolithotripsy. An experimental study.

Electrohydraulic lithotripsy was performed on ureteral calculi of various sizes and composition in 10 female mongrel dogs. Stones were successfully disintegrated in eight dogs with an overall 80 per cent success rate. Short- and long-term effects of the procedure on the ureter and the kidney are discussed.

Animals↗
PubMedDate not supplied

A novel procedure for daily measurements of hemodynamical, hematological, and biochemical parameters in conscious unrestrained rats.

Accurate and chronic measurements of various parameters in conscious animals are fundamental for depicting pathological chronic conditions and their etiology in many experimental models, but they are often difficult to achieve. The aim of the present work was to develop and describe step-by-step a reproducible surgical procedure and daily manipulations for continuous, chronic use of conscious rats as models towards a better understanding of various cardiovascular and renal diseases and the testing of novel pharmacological drugs. The complete apparatus involved the use of a series of specialized devices (harness, rotating swivel, revolving arm) supporting a flexible, permanently implanted vascular catheter into the left femoral artery up to the abdominal aorta connected to a miniaturized individual peristaltic pump for delivering fluid at a constant rate. Such a set-up also enabled easy, quick, and reproducible daily blood sampling for the evaluation of more than 20 parameters, including the monitoring of heart rate (HR) and blood pressure in freely moving conscious rats. The overall success and survival rate reached 98% over 14 days and could be extended further. This model represents a much needed and valuable advance in surgical research techniques to evaluate the hemodynamic, hematological, biochemical, pharmacokinetic, and toxicological profile of any new drugs over time in conscious animal models such as rats. What makes this procedure satisfactory is the long-term reliable arterial access and reproducibility of the methodological approach for accurate and continuous measurements, minimizing the stress or invasiveness associated with the use of currently employed systems.

Animals↗
PubMedDate not supplied

[Safety assessment of a Brazilian company based on analysis of work accidents by the causal tree method].

We present here the results of a study of 21 work-related accidents that occurred in a Brazilian manufacturing company. The aim was to assess the safety level of the company to improve its work accident prevention policy. In the last 6 months of 1992 and 1993, all accidents resulting in 15 days' absence from work, reported for social security purposes, were analyzed using the INRS causal tree method (ADC) and a questionnaire completed on site. Potential risk factors for accidents were identified based on the specific factors highlighted by the ADC. More universal trees were also compiled for the safety assessment. Three hundred and thirty specific accident factors were recorded (mean of 15.71 per accident). This is consistent with there being multiple causes of accidents rather than the assertion of Brazilian business safety departments that accidents are due to "dangerous" or "unsafe" behavior. Introducing the idea of culpability into accidents prevents the implementation of an appropriate information feedback process, essential for effective prevention. However, the large number of accidents related to "material" (78%) and "environment" (70%) indicates that working conditions are poor. This shows that the technical risks, mostly due to unsafe machinery and equipment are not being dealt with. Seventy-five potential accident factors were identified. Of these, 35% were "organizational", a high proportion for the company studied. Improvisation occurs at all levels, particularly at the organizational level. This is thus a major determinant for entire series of, if not most, accident situations. The poor condition of equipment also plays a major role in accidents. The effects of poor equipment on safety exacerbate the organizational shortcomings. The company's safety intervention policy should improve the management of human resources (rules designating particular workers for particular workstations; instructions for the safe operation of machines and equipment; training of operators, etc.) and introduce programs to detect risks and to improve the safety of machines and equipment. We also recommend the establishment of a program to follow the results of any preventive measures adopted.

Accidents, Occupational↗