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Biomedical subjects

M Martinez-Maldonado

Publications and source records attributed to M Martinez-Maldonado.

At least 19 recordsLinked to original sources
PubMed1991

Hypertension in Hispanics, Asians and Pacific-Islanders, and Native Americans.

There is a paucity of information about hypertension and its risk factors, prevalence, morbidity, and mortality in many racial minorities in the United States. Most of the population groups discussed in this section are composed of several subgroups that differ culturally, socioeconomically, educationally, and ethnically. This fact, however, does not lessen the need for more information about the extent of hypertension and risk factors in these groups. Moreover, a bonus from expanded research in these areas will be new information useful to the general population.

Asian↗
PubMed1991

Pathophysiology of renovascular hypertension.

Renovascular hypertension has its experimental counterpart in the two-kidney, one clip model (Goldblatt hypertension). From the study of this model, a general pathophysiological scheme has evolved suggesting that temporal stages in the development and maintenance of hypertension are regulated by complicated hormonal and neural interrelations. The central roles played by the renin-angiotensin system and the renal nerves is discussed as they relate to other hormones. In addition, the possible contribution of converting enzyme inhibitors to understanding the pathophysiology of this condition is discussed.

Adult↗
PubMed1990

Acute renal failure due to urinary tract obstruction.

Urinary tract obstruction is a frequent cause of acute renal failure that is potentially life threatening but reversible, if it is promptly recognized and corrected. The level of urinary tract obstruction is variable, dependent on the underlying disease, and may range from the loop of Henle to the urethral meatus. Clinical manifestations are most commonly due to renal failure, but the history and physical examination can aid in determining the localization and cause of the obstruction. Laboratory findings may suggest urinary tract obstruction as the etiology for acute renal failure. Radiologic procedures, most prominently ultrasonography, can establish the diagnosis. Treatment is variable, but patient management may need to be altered during the postobstructive phase of urinary tract obstruction owing to physiologic response to reestablishment of urine flow.

Acute Kidney Injury↗
PubMed1990

Cellular and molecular aspects of the renal effects of diuretic agents.

In the past few years, increased knowledge of the nature of transport proteins and their molecular regulation in the translocation of ions across kidney membranes has emerged. We are beginning to better understand the characteristics of the interaction of diuretics with these transport proteins. It is likely that this knowledge will permit further insight into nephron function regulation.

Animals↗
PubMed1990

Renal and hemodynamic effects of atrial natriuretic peptide in patients with cirrhosis.

The effects of anaritide, a 25-amino-acid synthetic analogue of ANP, were evaluated in 28 patients with cirrhosis complicated by ascites and/or edema. Each patient received two doses of the agent, as well as an infusion of placebo. Six different doses were tested ranging from 0.015-0.300 microgram/kg/min. The infusions lasted for 2 hours and were flanked by both baseline and recovery periods. There was a significant effect of placebo on urinary sodium and chloride excretion rates but no effect on urine flow rate. In response to anaritide, the urine flow rate increased at 0.03, 0.06, 0.075, and 0.100 microgram/kg/min. The sodium and chloride excretion rates increased at all doses except the highest dose. There was no definite effect of anaritide on urinary potassium, calcium, and phosphate excretion rates. There was also no significant effect on creatinine clearance. The mean arterial pressure decreased in response to the 0.060, 0.075, and 0.100 microgram/kg/min doses. In addition, five of the patients receiving the highest dose (0.300 microgram/kg/min) had decreases in their systolic pressures to 90 mm Hg or less. In conclusion, anaritide is natriuretic and diuretic in patients with cirrhosis complicated by ascites and/or edema. Its effect, however, on arterial pressure may limit its therapeutic potential in this patient population.

Atrial Natriuretic Factor↗
PubMed1990

Deoxycorticosterone hypertension in the intact weanling rat without salt loading.

Deoxycorticosterone (DOC) hypertension in the rat is generally induced in rats at an age of approximately 3 months. Both uninephrectomy and a high sodium diet are necessary, however, to induce DOC hypertension. Considering the inability of the developing kidney to adequately excrete a sodium load, we studied the possibility that DOC alone might induce hypertension when treatment is initiated in rats at the age of 21 days. The contribution of volume expansion as a factor mediating the pressor response to DOC was assessed in rats given a high sodium diet instead of DOC. Systolic blood pressure increased in DOC-treated rats within 3 weeks. Although systolic blood pressure also increased in rats on a high sodium diet, the increase was transient and of a lesser magnitude than that observed in DOC-treated rats. The rise in blood pressure in both groups of rats was associated with suppression of plasma renin activity and aldosterone concentration. Furthermore, extracellular fluid volume was similarly increased in DOC-treated rats and rats given a high sodium diet. Consistent with these data, DOC-treated rats showed an exaggerated natriuretic response to acute saline loading as compared with a vehicle-treated control group. Discontinuation of DOC treatment after 5 weeks led to normalization of all variables studied including blood pressure. Yet, when DOC was continued for 8 weeks, stopping treatment did not lower blood pressure despite normalization of the renin-angiotensin-aldosterone system and the natriuretic response to saline loading. In contrast, discontinuation of the high sodium diet after 8 weeks normalized blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Electron spin resonance of calmodulin-vanadyl complexes.

X-band (9.2 GHz) electron spin resonance spectroscopy was used to investigate the binding of vanadyl to calmodulin. Solution spectra, obtained at ambient temperature with various VO2+:calmodulin molar ratios, suggested a binding stoichioimetry of 4 mol of VO2+/mol of protein and the possibility of two classes of binding sites. The latter was confirmed by using frozen solutions of calmodulin-VO2+ complexes that gave splitting of the spectral bands corresponding to the parallel components, which was particularly pronounced with the three high-field peaks. Competition of Ca2+ for the VO2+ binding sites was investigated, and the results indicated that two of the VO2+ sites corresponded to two of the Ca2+ sites; the other two VO2+ binding sites may have a higher affinity for VO2+ than for Ca2+ or they may correspond to Ca2+-independent sites. These results demonstrate that electron spin resonance spectroscopy can be used advantageously to probe subtle differences in the microenvironments of metal-binding sites in calmodulin.

Binding Sites↗
PubMed1979

Changes in calcium excretion after prolonged metolazone therapy in recurrent stone formers.

The handling of an acute oral calcium load in 22 men with recurrent calcium stone disease was studied before and after diuretic therapy. As a group, the patients had marginal hypercalciuria (150 mg calcium per gram of creatinine in a 24-hr urine collection). Metolazone, a diuretic with an action in the cortical thick ascending limb of Henle's loop, was given in oral daily doses of 5.0 mg for periods of 9 to 34 mo. An oral calcium load induced a rapid rise in urine calcium exeretion, which was blunted markedly by metolazone. Further analysis of the subjects revealed that one group (11 subjects) had higher baseline 24-hr calcium excretion levels and higher parathyroid hormone (PTH) than the others. The effect of metolazone in reducing the calciuric response was significant only in this group. Thus, while long-term treatment with metolazone inhibited the rise in urinary calcium excretion elicited by an oral calcium load, the effect was significant only in patients who had high baseline urinary calcium and PTH values. The reduction in calcium excretion in response to an acute calcium challenge may explain in part the beneficial effects of cortical diluting segment diuretics in recurrent stone formers.

Calcium↗
PubMed1979

Some characteristics of recurrent calcium stone formers in Puerto Rico.

We have studied 83 patients with recurrent calcium stone formation in an attempt to determine an approximate incidence of metabolic disturbances associated with stone disease. Male veterans (n = 42), male non-veterans (n = 13), and women (n = 28) composed the group. We divided the groups in such fashion because they represented generally two distinct socioeconomic groups. Primary hyperparathyroidism was present in 19 per cent of the subjects; a marked predominance of women (15/16) was noted. Hypercalciuria of renal or intestinal origin was present in 23 per cent of the group. Of interest was a group of male veterans (17/83) in whom normocalciuria, normocalcemia, and normal serum phosphate were associated with high values of immunoreactive parathyroid hormone. These subjects had low urine phosphate. This set of findings indicates that these patients may be a new subgroup of stone-forming patients. Metabolic abnormalities could not be detected in 38 per cent of the patients. Classification of stone subjects is essential for rational management.

Adult↗
PubMed1979

Granulocyte adherence in uremia and hemodialysis.

To evaluate granulocyte function in uremia and hemodialysis we studied granulocyte adherence, an important step in chemotaxis. Our studies demonstrate that patients with severe impairment in renal function had normal granulocyte adherence (72.1 +/- 21 vs. 72.9 +/- 14% controls) while patients with end stage renal disease undergoing hemodialysis (45 +/- 30%) had significant impairment (p less than 0.001). Adherence worsened during dialysis (p less than 0.001) but returned towards the abnormal baseline values at the end of the procedure. There was a significant correlation between adherence and potassium (r=0.77; p less than 0.05) and adherence and sodium-potassium ratio (r=-0.78; p less than 0.05) before and after dialysis. Other factors such as changes in creatinine, urea nitrogen, osmolality, calcium, phosphorus or (H+) did not correlate with adherence. It is concluded that the abnormality in adherence is not the result of the basic disease process but a consequence of dialysis.

Adult↗
PubMed1978

Free water clearance curves during saline, mannitol, glucose and urea diuresis in the rat.

1. Free water clearances were measured during infusion of hypotonic saline, glucose, urea, and mannitol in Brattleboro rats. For each solute the free water clearances were plotted using either V or (C(H2O) + C(Na)) as the distal tubular delivery term.2. In all cases the use of (C(H2O) + C(Na)) as distal delivery term yielded a steeper relationship than when V was used. There were no significant differences in the C(H2O) to V relationship when saline, glucose and mannitol was the solute infused. Urea, however, resulted in a curve with a slope significantly less than that for the other solutes.3. When C(H2O) was plotted against (C(H2O) + C(Na)) there was still no significant difference between the slopes of the curves during saline or mannitol infusion. Use of this delivery term, however, resulted in a slope during glucose infusion which was significantly greater than that during saline or mannitol infusion. The slope for urea infusion remained lower than that for any other solute.4. Regardless of the delivery term used, there was no significant difference in the slopes of the curves for awake Wistar and awake Brattleboro rats during mannitol infusion. This indicates that the awake rat is a suitable model for free water clearance studies.5. The results indicate that NaCl and mannitol are both adequate for free water clearance and that (C(H2O) + C(Na)) is a better index of distal delivery than V.

Animals↗