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Biomedical subjects

M Contreras

Publications and source records attributed to M Contreras.

At least 217 records · Page 12Linked to original sources
PubMed1987

Polytetrafluoroethylene microprosthesis in the arterial system of the rat.

The experimental behavior of a 1-mm internal diameter (i.d.) polytetrafluoroethylene (PTFE) microprosthesis, as a substitute for an abdominal aortic segment in the rat, was reviewed. Fifty Wistar rats were divided into four groups: Group I--12 rats with autotransplant of an abdominal aortic segment (AAS); Group II--12 rats with allotransplant of an AAS obtained from Long-Evans rats; Group III--12 rats with xenotransplant of an AAS taken from rabbit femoral arteries; and Group IV--14 rats with substitution of an AAS by a 1-mm i.d. PTFE microprosthesis. The rats were sacrificed at different time intervals ranging from five to 360 days, with previous aortography. In Group I, there was a 100 percent patency at a mean of 152.41 days; in Group II, a 91.6 percent patency at a mean of 100.08 days; in Group III, an 83.3 percent patency with a 75 percent aneurysmal dilation at a mean of 107.58 days; in Group IV, a 71.42 percent patency with two anastomotic aneurysms at a mean of 105 days (P less than 0.05, chi square) between Groups I and IV, autotransplant vs. PTFE). The 1-mm PTFE microprosthesis placed in the arterial system of the rat proved to be a reliable alternative for microvascular substitution.

Animals↗
PubMed1987

Polytetrafluoroethylene microprosthesis in the venous system of the rat.

In this study, a 2 mm internal diameter (i.d.) polytetrafluoroethylene (PTFE) microprosthesis was used in the venous system of the rat, to determine whether or not it could serve as an acceptable microvenous substitute. Forty Long-Evans rats were divided into four groups: Group 1-10 rats with autotransplant of an inferior vena cava segment; Group 2-10 rats with a segment substitution of the inferior vena cava by a 2 mm i.d. PFTE microprosthesis; Group 3-10 rats with a laterolateral portacaval shunt; and Group 4-10 rats with a portacaval shunt and interposition of a 2 mm i.d. PTFE microprosthesis (new model). The rats were sacrificed at different time intervals up to 100 days, with cavography (femoral access) in Groups 1 and 2 and spleenoportography (direct puncture of the spleen) in Groups 3 and 4, before sacrifice. In Group 1, a 100 percent patency was observed at a mean of 49 days; in Group 2, a 70 percent patency with a 30 percent stenosis at a mean of 39.4 days (p less than 0.05); in Group 3, a 100 percent patency at a mean of 42.5 days; and in Group 4, a 30 percent patency at a mean of 38.4 days (p less than 0.01). Results showed that the 2 mm i.d. PTFE microprosthesis placed in the venous system of the rat is not an efficacious procedure, and that the search for better microvenous substitutes should focus on those of biologic origin.

Animals↗
PubMed1987

Heterogeneity of IgG1 monoclonal anti-Rh(D): an investigation using ADCC and macrophage binding assays.

Three monoclonal IgG1 anti-Rh(D), UCH D4, ARC 7D5 and UKTS FC3, produced by Epstein-Barr virus transformed cells from Rh(D)-sensitized individuals, were compared with polyclonal single donor anti-D sera and therapeutic immunoglobulin preparations in antibody dependent cellular cytotoxicity (ADCC) and macrophage binding tests. When assayed at equal anti-D concentrations monoclonal antibodies varied considerably in their ADCC and macrophage binding activities: only UKTS FC3 showed significant activity in both assays, but these were substantially lower than those of the polyclonal anti-D sera and immunoglobulins. When examined in different combinations the monoclonal antibodies showed little synergism in mediating red cell destruction by the effector cells. Factors which might contribute to the diverse ADCC and macrophage binding activities of the monoclonal anti-Ds of the same IgG subclass are discussed.

Antibodies, Monoclonal↗
PubMed1987

The effect of naturally occurring Rh antibodies on the survival of serologically incompatible red cells.

Investigations on six males with naturally occurring Rh antibodies are described. In two subjects in whom the antibody (one anti-E and one anti-D) could be detected only by a two-stage papain technique, the survival of incompatible red cells was normal. In the remaining four subjects, the antibodies (two anti-E and two anti-D) could be detected by the indirect antiglobulin test and, in these, incompatible red cells were destroyed at an accelerated rate; in two of the subjects, 75-99% of the cells were cleared within 24 h; in the other two, 50% of the cells were cleared within 24 h and the remaining cells were cleared far more slowly. All six antibodies were mainly or wholly IgG; a clear-cut immune response was observed in only one case.

Coombs Test↗
PubMed1987

Swa: a subdivision.

For some time, anomalous serological reactions have been observed when the same anti-Swa sera are tested against red cells from different individuals reported as Sw(a+). A comparative collaborative study using the same collection of Sw(a+) cells and anti-Swa sera was undertaken by 4 reference laboratories, and it was found that Swa represents a heterogeneous group of antigens that can be subdivided into two categories. Both categories, Sw(a+) 700:41 and Sw(a+) 700:-41, were shown to be inherited.

Blood Group Antigens↗
PubMed1987

Serum alanine aminotransferase (ALT) and gamma-glutamyltransferase (gamma-GT) activities in north London blood donors.

Serum alanine aminotransferase (ALT) and gamma-glutamyltransferase (gamma-GT) activities were measured in over 2000 north London blood donors. The results were compared with those from the United States. The percentage of the total donor population with ALT activities above 40 IU/l in 1986 was greater than that found in our earlier studies in 1973 and 1982 (4.6% compared with 2.8% and 3.1%, respectively). There was a noticeable difference in the ALT distribution between male and female donors: mean +2.25 SD for male donors was 55.3 IU/l, while that for female donors was 30.8 IU/l at 37 degrees C. In stability studies the optimal temperature for short term storage (10 days) was 4 degrees C (6.4% loss of activity after 10 days). Surprisingly, storage at lower temperatures (-35 degrees C and -80 degrees C) resulted in greater loss of activity.

Adolescent↗
PubMed1987

Reversal of sleep-induced hypoventilation and chronic respiratory failure by nocturnal negative pressure ventilation in patients with restrictive ventilatory impairment.

The efficacy of negative pressure ventilation (NPV) in alleviating sleep-induced reductions in alveolar ventilation and in producing long-term clinical benefits was studied in 5 patients (54 +/- 8 yr of age; mean +/- SD) with chronic respiratory failure secondary to restrictive ventilatory impairment (VC, 40 +/- 14% predicted; TLC, 72 +/- 18% predicted; FEV1/FVC, 89 +/- 15%). In control sleep studies, arterial O2 saturation decreased from 81 +/- 6% during wakefulness to 79 +/- 1% during non-REM sleep and to 67 +/- 3% during REM sleep, and transcutaneous PCO2 increased from 80 +/- 16 mm Hg during wakefulness and non-REM sleep to 87 +/- 16 mm Hg during REM sleep. Nocturnal NPV in a cuirass ventilator improved baseline ventilation during wakefulness and prevented deterioration of alveolar ventilation during sleep. Upper airway obstruction during sleep induced by NPV was successfully managed with either a tricyclic medication or nasal CPAP. After 8 wk of nocturnal NPV, all patients felt considerably better. Daytime resting arterial PCO2 decreased from 56 +/- 2 to 46 +/- 3 mm Hg (p less than 0.05) and PO2 increased from 51 +/- 9 to 70 +/- 10 mm Hg (NS). Four patients have continued NPV at home on a regular basis and have returned to full-time employment. We conclude that nocturnal NPV is an effective method of preventing sleep-induced reductions in alveolar ventilation and a practical method of long-term management of patients with nonobstructive chronic respiratory failure.

Carbon Dioxide↗
PubMed1987

Assisting ventilation in respiratory failure by negative pressure ventilation and by rocking bed.

The present study was undertaken to evaluate the effectiveness of acute ventilation by rocking bed (RB) and by negative-pressure ventilator (NPV) on arterial oxygenation and carbon dioxide tension in seven patients in whom respiratory failure (PaCO2 [+/- SD], 64 +/- 4 mm Hg; PaO2, 54 +/- 10 mm Hg) was consequent on nonobstructive ventilatory impairment. The increase in SaO2 (percent above baseline, 5 percent RB and 6 percent NPV) was similar for both methods, but a greater fall in PCO2 (percentage change in PCO2, 3 percent RB; 15 percent NPV; p less than 0.05) was observed during NPV. Diaphragmatic and accessory muscle electrical activity was markedly reduced during NPV but remained unchanged or increased on RB. Asynchronous breathing was frequently observed with RB but only rarely with NPV. These preliminary results suggest that effective mechanical ventilatory support could be achieved with either RB or NPV. However, their long-term effects as compared with those of positive-pressure ventilation remain to be explored.

Beds↗
PubMed1986

Trypanosoma cruzi and American Leishmania spp: immunocytochemical localization of a laminin-like protein in the plasma membrane.

Patients with Chagas' disease or different clinical forms of American cutaneous leishmaniasis have high antilaminin antibody levels. An immunogold technique employing a specific antilaminin antibody was used in the present study to determine the presence, and define the ultrastructural localization, of laminin-like molecule(s) in American Leishmania spp. and Trypanosoma cruzi. Laminin was found located specifically in T. cruzi trypomastigotes on the external surface of the plasma membrane, close to the sites where the flagellar veil attaches to the plasma membrane. Laminin immunoreactivity was rapidly lost when trypomastigotes were cultured in liquid medium and no reactivity was found in fresh epimastigotes. Promastigotes and amastigotes of American Leishmania spp. also showed a specific localization of laminin immunoreactivity, this being limited to the lips of the flagellar pocket and to the parasitic side exactly opposite to the flagellar exit. These results confirm the presence of a laminin-like molecule(s) in both trypanosomatids, the specific localization suggesting a presently unknown function for this protein.

Animals↗