Biomedical subjects

M A Duran

Publications and source records attributed to M A Duran.

6 recordsLinked to original sources

PubMed1999

Long-term storage at -80 degrees C of hematopoietic progenitor cells with 5-percent dimethyl sulfoxide as the sole cryoprotectant.

BACKGROUND: Hematopoietic progenitor cells (HPCs) can be cryopreserved and stored below -120 degrees C in liquid nitrogen or at -80 degrees C in mechanical freezers. STUDY DESIGN AND METHODS: The feasibility of long-term storage of HPCs at -80 degrees C was investigated. The studies included a comparison of 5- and 10-percent dimethyl sulfoxide (DMSO) as cryoprotectant at various lengths of storage time. Mononuclear cell (MNC) recovery and viability and colony-forming unit-granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-E) recovery assays were performed. The peripheral blood HPCs of 24 consecutive patients included in the program of autologous transplantation were studied. RESULTS: The MNC viability decreased progressively with the length of time from cryopreservation, reaching 32 percent after 31 months of storage. The recovery rates of CFU-GM and BFU-E also decreased progressively with the duration of frozen storage, to 50 and 43.5 percent, respectively, after 12 months and to 0 percent (both) after 24 months. At 6 months of storage, MNC viability was 80 percent, and CFU-GM and BFU-E recovery was 63.5 and 80.5 percent, respectively. There were no differences between MNCs cryopreserved with 5- or 10-percent DMSO in terms of cell viability. There were no differences between CFU-GM recovery or BFU-E recovery from HPCs cryopreserved in 5- or 10-percent DMSO. Patients given HPCs stored in these conditions for periods ranging between 123 and 202 days showed a complete and rapid hematologic recovery. CONCLUSION: HPCs can be cryopreserved at -80 degrees C with 5-percent DMSO and stored at -80 degrees C no longer than 6 months. A 5-percent DMSO concentration is comparable to a with 10-percent concentration in terms of recovery and MNC viability.

Adolescent↗

PubMed1991

Irreversible renal failure associated with triamterene.

A 66-year-old man was admitted with acute oliguric renal failure. The patient was known to have chronic heart failure (ejection fraction 13%) and his medication included furosemide, digoxin and triamterene. Physical examination was unremarkable, and blood pressure was 170/80 mm Hg. Serum creatinine was 1,173 mumol/l. Renal ultrasound, CT scan and angiogram were normal. Despite correction of potential reversible factors and discontinuation of triamterene, renal function did not improve. Renal biopsy showed tubular obstruction with deposition of birefringent crystals and interstitial lymphocytic infiltration; the crystals emitted a blue autofluorescence at 425 nm, typical of triamterene. Renal tissue contained large amounts of triamterene (6.44 mg/g kidney at the initial biopsy and 400 micrograms/g kidney 5 months later). Triamterene has been previously reported to cause acute reversible renal failure, but to our knowledge, this is the first case of irreversible renal failure due to intratubular obstruction by triamterene crystal deposition.

Acute Kidney Injury↗

PubMed1990

Renal epithelial amino acid concentrations in mercury-induced and postischemic acute renal failure.

The concentration of 18 alpha-amino acids (AAs) in plasma and renal cortical cell water were measured 3 or 24 hr after 1 hr of unilateral renal artery clamping or 24 or 48 hr after 15 mg/kg body weight HgCl2 injection sc as a test of epithelial integrity. Cellular glycine (Gly), hydroxyproline (Hpr), ornithine (Orn), phenylalanine (Phe), serine (Ser), and tryptophan (Trp) concentrations were depressed 24 hr after HgCl2 (p less than 0.05), but the remaining 12 AAs were not distinguishable from control despite the presence of severe renal failure. ARginine (Arg), glutamic acid (Glu), and valine (Val) also were decreased (P less than 0.05) 24 hr later, but concentrations of half of all measured AAs were still normal. Cellular alanine (Ala), Arg, Glu, Gly, Phe, and Ser concentrations were decreased 3 hr after ischemia, p less than 0.05, but 12 AAs were unchanged and only Arg, Phe, Ser, and threonine (Thr) were reduced 24 hr after ischemia was reversed. Concentrations of even the most affected AAs remained notably higher than in plasma in both forms of acute renal failure (ARF). Total loss of AAs from a small proportion of tubular cells would be hidden by essentially normal concentrations in the rest, and such losses may well have occurred. Unless cellular AAs in ARF are almost completely bound, however, the well-maintained cell:plasma AA concentration ratios indicate that cellular energetics were adequate for AA uptake and that epithelial permeability to AAs in the vast majority of cells was not greatly disturbed. Such findings suggest that most of the epithelium, although seriously damaged, had remained viable.

Acute Kidney Injury↗

PubMed1981

Studies on the mechanism whereby acidemia stimulates collecting duct hydrogen ion secretion in vivo.

The purpose of these studies was to elucidate the mechanism whereby collecting duct hydrogen ion secretion was augmented by acidemia. The urine minus blood PCO2 difference in alkaline urine (U-B PCO2) was used to evaluate this parameter. In dogs with a normal ECF volume, the U-B PCO2 factored was high, and there was no significant relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentrations unless amiloride, an agent that abolishes the transtubular potential difference, was present. In this latter case, the U-B PCO2 was a linear function of the urine bicarbonate concentration, and the U-B PCO2 factored for the urine bicarbonate concentration was directly proportional to the blood hydrogen ion concentration. To extend the pH range considerably, we used lysine to induce bicarbonaturia in dogs with an expanded ECF volume. Amiloride now caused only a small decrease in the U-B PCO2 at any urine bicarbonate concentration, and furthermore, it did not influence the linear relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentration. These results suggests that acidemia stimulates collecting duct hydrogen ion secretion by a mechanism that appears to be independent of the amiloride-sensitive component of the U-B PCO2. We speculate that the mechanism might involve an increased intracellular hydrogen ion concentration during acidemia.

Amiloride↗

PubMed1981

Maintenance of glomerulotubular balance for bicarbonate during carbonic anhydrase inhibition in the dog.

Studies were performed to examine the possible effects of carbonic anhydrase (CA) inhibition on the glomerulotubular balance for bicarbonate in anesthetized dogs. Maximal CA inhibition was achieved by acetazolamide infusion and glomerular filtration rate (GFR) was reduced in a stepwise fashion by progressive clamping of the left renal artery. A close relationship (R equals 0.973) was maintained between the amount of filtered and reabsorbed bicarbonate in normal dogs with CA inhibition. A similar relationship was observed between GFR and bicarbonate reabsorption during CA inhibition in normal dogs (R equals 0.957) as well as in sodium bicarbonate loaded dogs (R equals 0.867). In these two groups, GFR in the clamped kidney was reduced to values ranging respectively from 99 to 5% and from 96 to 3%. Distal tubular blockade with ethacrynic acid and chlorothiazide, performed in normal dogs and in sodium bicarbonate loaded dogs, did not abolish glomerulotubular balance for bicarbonate during CA inhibition. This study demonstrates that the glomerulotubular balance for bicarbonate is maintained during CA inhibition whether or not distal tubular blockade is superimposed. A proportionate decrease in both fractions of bicarbonate reabsorption, either CA dependent or not mediated by CA, or an adaptive increase in the fraction of bicarbonate reabsorption not mediated by CA can explain the maintenance of glomerulotubular balance for bicarbonate.

Acetazolamide↗

PubMedDate not supplied

Comprehensive community initiatives: principles, practice, and lessons learned.

Comprehensive community initiatives strive to improve the lives of children and families in neighborhoods characterized by extreme and concentrated poverty. The initiatives used multifaceted approaches to strengthen communities and improve the provision of social and other services to children and families. Early examples include the settlement houses at the beginning of the twentieth century, the neighborhood programs of the 1930s, and the war on poverty efforts of the 1960s. Using specific examples, this article describes key features of current comprehensive community initiatives, the limitations of efforts to evaluate them, and factors contributing to their success or failure.

Child↗