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Biomedical subjects

J M Alvarez

Publications and source records attributed to J M Alvarez.

At least 19 recordsLinked to original sources
PubMed2004

Follow-up of Australian aboriginal patients following open-heart surgery in Western Australia.

BACKGROUND: To date there has been only one published report pertaining to the outcomes following open-heart surgery in Australian aboriginal patients. METHODS: The records of 57 consecutive aboriginal patients who underwent open-heart surgery at our institution over a 6-year period were retrospectively reviewed. Attempts were made to contact the patient by telephone, by letter, through their listed next of kin, general practitioners, community nurse or through the aboriginal liaison officer. RESULTS: There were 38 males and 19 females. Forty-five patients had coronary artery bypass grafting, 10 had isolated valve procedures while 2 had a combined operation. Mechanical prostheses were used for all valve replacements. There was a high incidence of diabetes, hypertension, hypercholesterolemia and smoking. There was one hospital death. Follow-up ranged from 6 months to 6 years with a mean of 3.09 years. Forty-four of the 56 (78.6%) hospital survivors were contactable while 21.4% were not contactable. There were two late deaths. Of the coronary patients who could be contacted, only 79% were taking Aspirin and a similar number Statin. 23% patients had recurrence of angina. There were five episodes of anticoagulation related complications in three patients. Only 44% of the patients were conversant with anticoagulation. CONCLUSIONS: The follow-up of the aboriginal patients was disappointing. The compliance with the medications was sub-optimal. There was a high incidence of recurrence of angina and anticoagulation related complications. The results raise concern about the use of mechanical prosthesis in these patients.

Journal Article↗
PubMed2003

Identification of quantitative trait loci involved in fruit quality traits in melon (Cucumis melo L.).

Two populations [an F(2) and a set of 77 double haploid lines (DHLs)] developed from a cross between a 'Piel de Sapo' cultivar (PS) and the exotic Korean accession PI 161375 were used to detect QTLs involved in melon fruit quality traits: earliness (EA), fruit shape (FS), fruit weight (FW) and sugar content (SSC); and loci involved in the colour traits: external colour (ECOL) and flesh colour (FC). High variation was found, showing transgressive segregations for all traits. The highest correlation among experiments was observed for FS and the lowest for FW and SSC. Correlations among traits within experiments were, in general, not significant. QTL analysis, performed by Composite Interval Mapping, allowed the detection of nine QTLs for EA, eight for FS, six for FW and five for SSC. Major QTLs ( R(2)>25%) were detected for all traits. QTLs for different traits were no clearly co-localised, suggesting low pleiotropic effects at QTLs. Sixty-one per cent of them were detected in two or more experiments. QTLs for FS were detected in more trials than QTLs for FW and SSC, confirming that FS is under highly hereditable polygenic control. ECOL segregated as yellow:green in both experimental populations. The genetic control of ECOL was found to be complex, probably involving more than two loci with epistatic interactions. One of these loci was mapped on linkage group 9, but the other loci could not be clearly resolved. FC segregated as white:green:orange. The locus responsible for the green FC was mapped on linkage group 1, and it was proposed to correspond to the previously described locus gf. The genetic control of orange FC was complex: two loci in linkage groups 2 and 12 were associated with orange flesh, but larger population sizes would be necessary to elucidate completely the genetic control of orange flesh in this cross. Exotic alleles from PI161375 showed beneficial effects on EA, FW and SSC, indicating the usefulness of PI 161375 as a new source of genetic variability to improve European and American cultivars.

Chromosome Mapping↗
PubMed2002

Zinc transformations in acidic soil and zinc efficiency on maize by adding six organic zinc complexes.

Experiments under laboratory and greenhouse conditions were conducted to study the response of maize (Zea mays L.) to Zn fertilizer applications (Zn-phenolate, Zn-EDDHA, Zn-EDTA, Zn-lignosulfonate, Zn-polyflavonoid, and Zn-heptagluconate) in an Aquic Haploxeralf soil. The application of Zn complexes significantly increased Zn uptake by the plant compared with that in the control soil. The highest enhancements were obtained in soil treated with Zn-EDTA, Zn-lignosulfonate, and Zn-EDDHA. The highest percentages of Zn taken up by the plants occurred when 20 mg x kg(-1) Zn was applied as Zn-EDTA fertilizer and 10 mg x kg(-1) as Zn-lignosulfonate fertilizer. In the greenhouse experiment, Zn speciation in soil after harvesting showed that almost all Zn was found in the residual fraction followed by metal in the water-soluble plus exchangeable fraction and metal bound to organic matter. The most effective fertilizers maintaining Zn in the most labile fractions were Zn-phenolate, Zn-EDTA, and Zn-lignosulfonate. Conversely, in the incubation experiment, only a small percentage of Zn was found in the water-soluble plus exchangeable fraction and no differences in the Zn distribution were observed between the different fertilizer treatments. The micronutrient content in maize was positively correlated with the water-soluble plus exchangeable Zn as well as with the available Zn determined by the diethylenetriaminepentaacetic acid and Mehlich-3 methods, in the greenhouse experiment. Results of this study showed that the incubation experiment in acidic soil is not a suitable tool to establish the different effectiveness of Zn chelates in plants.

Chelating Agents↗
PubMed2002

Influence of the polyclonal activation induced by Plasmodium chabaudi on ongoing OVA-specific B- and T-cell responses.

Infection by Plasmodium chabaudi results in polyclonal activation, massive proliferation and differentiation of lymphocytes with parasite-unrelated specificities. To verify if polyclonal activation includes experienced B and T lymphocytes and if it modifies pre-established cytokine and Ig-isotype patterns, mice were immunized with ovalbumin (OVA) in alum, a condition that favours T helper 2/immunoglobulin G1 (Th2/IgG1) responses, and infected with P. chabaudi 7 or 80 days later. Polyclonal activation markedly increased the number of anti-OVA Ig-secreting cells in the spleen, an effect more patent in mice infected 7 days after OVA immunization, but also evident in mice infected after 80 days. The Ig-isotype profile predefined by immunization was not qualitatively modified by polyclonal activation. Thus, although P. chabaudi infection preferentially induces IgG2a, the expanded anti-OVA response is dominated by IgG1. Polyclonal expansion of the anti-OVA response did not yield an enlarged memory B-cell pool that could be recalled months later by OVA boosting. Moreover, polyclonal activation of anti-OVA IgG1-secreting cells did not increase this antibody in serum, a probable consequence of the high Ig turnover observed during infection. When OVA-specific T-cell cytokines were evaluated, we observed an increase of both interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) in mice infected 7 days after immunization, whereas in those infected after 80 days, only IL-4 was augmented. These results suggest that polyclonal activation expands experienced B- and T-cell compartments, preserving their antibody and cytokine patterns.

Animals↗
PubMed2001

Solubilization of rapamycin.

The solubilization of rapamycin, a poorly water soluble investigational immunosuppressive drug, by facilitated hydrotropy is presented. Partially water-miscible aromatic solutes (such as benzyl alcohol, benzoate, or benzoic acid) can be solubilized by water-miscible cosolvents, such as ethanol and propylene glycol. Once solubilized, the partially miscible aromatic solute becomes a solubilizing agent. This technique yielded a dramatic (>1000-fold) increase in the aqueous solubility of rapamycin.

Anti-Bacterial Agents↗
PubMed2001

Influence of thermal treatment on sequential extraction and leaching behaviour of trace metals in a contaminated sewage sludge.

The losses of weight and organic matter of a sludge caused by thermal treatments at 180 degrees C, 300 degrees C and 400 degrees C were determined in order to assess how the possibilities of sludge use were influenced. The sludge heated at 180 degrees C lost small amounts of weight and organic matter (9.8%) but the losses from the two other treatments were large enough (92.2% and 99.9% in organic matter) to preclude the use of the sludges as organic amendments. The concentration and potential lability and leachability of Cr, Cu, Fe, Mn, Ni, Pb and Zn in the native sludge and in the thermal-treated sludge samples were studied by means of a five-step chemical fractionation method and a column experiment. As a consequence of heating, the trace metals were more strongly fixed in the treated sludges, as could be seen by the decrease with temperature of the ratio between the sum of the first two sequential-extracted fractions and the residual fraction. The leaching results showed that, for the native sludge, the quantities of studied metals leached were larger than for the sludge heated to 180 degrees C. The order of leachability of metals was the same in both cases, and the same equation could be used to calculate the quantities of metals leached. The amounts of metals leached correlated significantly with the first extracted fraction (exchangeable metals) and an equation could be used to calculate the quantities leached, as a function of that fraction.

Hot Temperature↗
PubMed2001

Controlled release of manganese into water from coated experimental fertilizers: laboratory characterization.

The release of manganese into water from controlled-release formulations containing manganese EDTA or manganese lignosulfonate was studied. These fertilizers were obtained in the laboratory by adhering the source of manganese over urea pellets and by adding a coating. The materials used as adhesives and coatings were mixtures of rosins plus tricalcium phosphate. With regard to the chemical composition, these formulations conformed to national and international standards for commercial fertilizers. The rate of release of manganese was a function of both the source of manganese used and the coating thickness. Under the same conditions the release of manganese was greater for formulations with manganese EDTA than with manganese lignosulfonate. To predict the kinetic behaviors of the two series of formulations, mathematical equations were established. The manganese source plus rosin coatings improved the handling and storage characteristics of the commercial urea pellets. The study of the rosin coatings using scanning electron microscopy showed that they were compact and homogeneous.

Edetic Acid↗
PubMed2001

Mobility and leachability of zinc in two soils treated with six organic zinc complexes.

A study of soil columns was conducted to evaluate Zn movement potential in two reconstructed soil profiles. Zn-phenolate, Zn-EDDHA, Zn-EDTA, Zn-lignosulfonate, Zn-polyflavonoid, and Zn-heptagluconate were applied in the upper zone of the column. The different physicochemical properties of the two soils and the micronutrient source may influence Zn leaching, the distribution of Zn among soil fractions, and the Zn available to the plant in the depth of the layers. In Aquic Haploxeralf soil, the application of six fertilizers produced little migration and very small leaching of Zn in the soil profiles. In Calcic Haploxeralf soil, Zn-EDTA migrated and was distributed throughout the soil columns. This Zn chelate produces a loss of Zn by leaching, which was 36% of the added Zn. In the latter soil, Zn leached very little with the other five fertilizer treatments. The same as for these organic Zn complexes, the retention of added Zn indicated the potential of metal accumulation in the A(p) horizons of the two soil profiles. A large portion of applied Zn was available to plants [diethylenetriaminepentaacetic acid (DTPA) and Mehlich-3 extractable Zn] in the depths reached by the different commercial formulations. The relationship between the two methods was highly significant (Mehlich-3-Zn = 1.25 + 1.13 DTPA-Zn, R(2) = 99.19%). When Zn was added as Zn-EDTA, the amounts of the most labile fractions (water-soluble plus exchangeable and organically complexed Zn) increased throughout the entire profile column in comparison with the control columns, although in the B(t) horizon of the Aquic Haploxeralf soil they increased only slightly.

Adsorption↗
PubMed2001

Most parasite-specific CD8+ cells in Trypanosoma cruzi-infected chronic mice are down-regulated for T-cell receptor-alphabeta and CD8 molecules.

The present study shows that CD8+ T lymphocytes expressing low levels of T-cell receptor (TCR)alphabeta, CD8 and CD3 accumulate in the spleen, blood, peritoneum and liver, but not in the lymph nodes of mice chronically infected with Trypanosoma cruzi. Analysis of spleen lymphocytes reveals that most CD8LOW TCRLOW T cells have an experienced phenotype (CD44HIGH CD62LLOW and CD45RA,B,CLOW). These cells have small size, lack activation markers such as CD69, CD25 and CD11b (Mac-1), and do not spontaneously secrete cytokines, suggesting they are at the resting state. When stimulated in vitro with T. cruzi-infected macrophages, TCRLOW CD8LOW T cells behave as parasite-specific memory cells, readily responding with interferon-gamma (IFN-gamma) production. Indeed, among parasite-activated CD8+ lymphocytes, IFN-gamma production was mostly due to TCRLOW CD8LOW cells. Upon in vitro stimulation with anti-CD3/CD28 monoclonal antibodies, down-regulated cells produce IFN-gamma and tumour necrosis factor-alpha, but not interleukin IL-10 or IL-4. Our results indicate that despite parasite persistence, most T. cruzi-specific experienced CD8+ cells are resting. Nevertheless, when encountering infected macrophages these cells differentiate to Tc1 effectors.

Animals↗
PubMed2001

Susceptibility of the different developmental stages of the asexual (schizogonic) erythrocyte cycle of Plasmodium chabaudi chabaudi to hyperimmune serum, immunoglobulin (Ig)G1, IgG2a and F(ab')2 fragments.

The mechanisms by which antibodies interfere with Plasmodium growth are still under debate. Characterizing the asexual erythrocyte stages susceptible to antibodies from hyperimmune individuals is therefore a relevant contribution to vaccine research. In this study, using a virulent and synchronous murine malaria parasite, Plasmodium chabaudi chabaudi AJ, we have shown that trophozoites and circulating schizonts are not the main targets for antibodies from hyperimmune serum. In drug-cured mice challenged with a high inoculum of ring-infected erythrocytes, parasitemias do not decline until the moment of erythrocyte rupture, suggesting that effector mechanisms operate immediately prior to reinvasion. Confirming these findings, treatment of primary-infected mice with hyperimmune serum inhibited the generation of new ring forms, but did not alter the numbers of schizont-infected erythrocytes, despite the fact that these cells were recognized by immunoglobulin (Ig)G antibodies. When these mice were treated with IgG1 or IgG2a purified from hyperimmune serum, both subclasses limited reinvasion, but IgG2a showed a stronger protective activity. The fact that Fc digestion decreases but does not abrogate protection suggests that both Fc-dependent and independent mechanisms participate in this process. Treatment with cobra venom factor did not interfere with the antibody-mediated protection, ruling out the participation of the complement system in both lysis and phagocytosis of merozoites or infected erythrocytes. Therefore, in mice suffering from P. c. chabaudi AJ malaria, merozoite neutralization seems to be a major mechanism of protection conferred by hyperimmune serum antibodies. However, FcgammaR-mediated interactions, or other mechanisms not yet defined, may also contribute to inhibit erythrocyte reinvasion.

Animals↗
PubMed2001

Cardiac angiosarcoma: too little known, too late treatment or just too bad a tumour?

Cardiac angiosarcoma is a rare tumour. Current imaging techniques (magnetic resonance imaging, MRI; computed axial tomography, CAT; 2-D echocardiography), although useful in delineating the extent of tumour involvement, do not correlate well with intraoperative findings of resectability. We report a case were palliative surgical resection was technically possible, contrary to expectations from CAT and MRI findings. However, the patient was clinically in extremis, with advanced ventricular dysfunction, and died. Despite the short-term risk involved in surgery, if palliative resection is possible, a multidisciplinary approach with adjuvant chemotherapy and radiation can result in mid-term survival.

Journal Article↗
PubMed2001

Low-dose postoperative aprotinin reduces mediastinal drainage and blood product use in patients undergoing primary coronary artery bypass grafting who are taking aspirin: a prospective, randomized, double-blind, placebo-controlled trial.

BACKGROUND: Although low-dose aprotinin administered after cardiopulmonary bypass has been reported to reduce mediastinal blood loss and blood product requirements in patients not taking aspirin, it is unknown whether low-dose postoperative aprotinin has any beneficial effects in patients undergoing coronary artery bypass operations who are at high risk of excessive postoperative bleeding and increased transfusion requirements because of aspirin use until just before the operation. METHODS: Fifty-five patients undergoing primary coronary artery operations with cardiopulmonary bypass who continued taking aspirin (150 mg/d) until the day before the operation were enrolled in a prospective, randomized, double-blind trial to receive a single dose of either placebo (n = 29) or 2 x 10(6) kallikrein inhibiting units of aprotinin (n = 26) at the time of sternal skin closure. RESULTS: Patients in the aprotinin group had a lower rate (28 +/- 18 vs 43 +/- 21 mL/h [mean +/- standard deviation], P <.005) and total volume of mediastinal drainage (955 +/- 615 vs 1570 +/- 955 mL, P <.007), as well as a shorter duration of mediastinal drain tube insertion (24.4 +/- 13.8 vs 31.3 +/- 16.5 hours, P <.05). In addition, a smaller proportion of patients receiving aprotinin required a blood product (31% vs 62%, P =.03), resulting in a reduction in the use of packed cells by 47% (P =.05), platelets by 77% (P =.01), fresh frozen plasma by 88% (P =.03), and total blood products by 68% (P =.01) in this group. CONCLUSIONS: These results suggest that postoperative administration of low-dose aprotinin in patients taking aspirin until just before primary coronary artery operations with cardiopulmonary bypass not only reduces the rate and total amount of postoperative mediastinal blood loss but also lowers postoperative blood product use.

Aged↗
PubMed2000

Prophylactic intravenous mannitol and normal saline in patients with poor renal function prior to cardiac surgery: time for a multicentre trial?

BACKGROUND: Postoperative acute renal failure requiring dialysis has a poor prognosis, which has remained unaltered for 50 years. Therefore, in cardiac surgical patients at increased risk of postoperative oliguric acute renal failure (preoperative serum creatinine >0.13 mmol/L), we assessed the use of prophylactic intravenous (i.v) 20% mannitol and normal saline therapy in addition to traditional methods of therapeutic renal support. METHODS: Seventy-five patients with a mean preoperative serum creatinine of 0.192 mmol/L received i.v. 20% mannitol and normal saline pre-, intra- and postoperatively. This treatment was continued postoperatively until serum creatinine returned to baseline. RESULTS: No patient required dialysis, no patient died, developed a myocardial infarction nor a stroke in the first 30 days post-surgery. Serum creatinine and urea increased to a mean peak on day 3 of 0.233 +/- 94 and 24.6 +/- 13 mmol/L, respectively. However, all patients maintained a high urine output (>2 L/day) and no patient required haemodialysis. CONCLUSION: Therapy with i.v. 20% mannitol and normal saline appears safe and effective in maintaining a diuresis and may avoid the need for dialysis. A randomised controlled trial of this treatment in patients at increased risk of postoperative acute renal failure is warranted.

Journal Article↗