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M Nieves

Publications and source records attributed to M Nieves.

13 recordsLinked to original sources
PubMed2004

Interstock-induced mechanism of increased growth and salt resistance of orange (Citrus sinensis) trees.

Interstocks improve the growth and salt resistance of lemon (Citrus limon (L.) Burm. f.) trees, but their effects on orange (Citrus sinensis (L.) Osbeck) trees are unknown. We grew 'Cleopatra' mandarin (CM) seedlings, budded trees of 'Salustiano' orange (SAO) on CM, 'Valencia Late' orange (VLO) on CM (VLO/CM), and interstock trees VLO/SAO/CM in pots of sand watered with nutrient solution containing 5 (control) or 50 mM NaCl for 12 weeks. Plants were harvested on six successive occasions and the time trends in relative growth rate (RGR) and its components were estimated by fitting a Richards function regression to the harvest data. At low and high salinities, the VLO/SAO/CM combination had higher mean RGR than VLO/CM. Under control conditions, the increase in RGR caused by the interstock was the result of an increase in leaf mass fraction (LMF; leaf dry mass/plant dry mass ratio). Increases in net assimilation rate on a leaf mass basis (NARm) and LMF contributed equally to the increase in RGR in saline conditions, their growth response coefficients being 0.52 and 0.48, respectively. The structural modifications, specific leaf area (SLA) and leaf area ratio (LAR; leaf area:plant dry mass ratio), had a slight influence on the reduction in RGR by salinity. However, NARm had a large influence on RGR, except in CM. The interstock-induced mechanism increased biomass allocation to the assimilatory organs and, under saline conditions, increased Cl- and Na+ allocations to roots. Thus, the flux of ions to the leaves was either delayed or reduced or both. The dilution of imported ions by foliar growth reduced ion concentrations in leaves, resulting in higher NARm, which together with higher LMF, increased RGR.

Citrus sinensis↗
PubMed2003

Improvement in growth and salt resistance of lemon (Citrus limon) trees by an interstock-induced mechanism.

Interstocks can reduce toxic ion accumulations in leaves of budded citrus trees, but the mechanism is not understood. We grew sour orange (Citrus aurantium L.; SO) seedlings, budded trees of 'Salustiano' orange (Citrus sinensis L. Osbeck; SAO) on SO, 'Verna' lemon (Citrus limon L. Burm. f; VL/SO) and interstock trees (VL/SAO/SO) in pots of sand watered with nutrient solution containing 5 (control) or 50 mM NaCl (saline treatment) for 12 weeks. Plants were harvested in six successive harvests and time trends in relative growth rate (RGR) and its components were estimated by fitting a Richards function regression to the harvest data. The VL/SAO/SO trees in saline conditions had higher mean RGR than VL/SO trees in control conditions. Increases in both net assimilation rate on a leaf mass basis (NARw) and leaf mass fraction (LMF) contributed equally to a twofold increase in RGR of VL/SAO/SO trees in saline conditions. In control conditions, the increase in RGR caused by the interstock had growth response coefficients of GRC(NARw) = 0.20 and GRC(LMF) = 0.80. Structural modifications-specific leaf area, leaf area ratio and LMF-had a slight influence on the salt-induced changes in RGR, whereas NARw had a large influence. Salinity decreased root mass fraction (RMF) and increased stem mass fraction (SMF). In contrast, the interstock decreased SMF and increased LMF and RMF. The VL/SAO/SO trees had the highest RMF and proportionally higher Cl- and Na+ allocations in roots than the other plant types. In saline conditions, reductions in leaf ion transport rate and dilution of imported ions by foliar growth nearly halved ion accumulations in leaves of VL/SAO/SO trees.

Agriculture↗
PubMed2001

Nitrogen budget in Scenedesmus obliquus cultures with artificial wastewater.

Semicontinuous cultures of Scenedesmus obliquus in artificial wastewater, recycled into proteins about 33% and 25% of the dissolved nitrogen missing from the medium 24 h after harvesting 50% and 70% of the culture, and replacing the volume harvested with fresh medium. The residual dissolved nitrogen concentrations were 25% and 43% of the initial, respectively, with an imbalance in the mass budget close to 17 and 20 mg N l(-1) d-1. Most or all the nitrogen missing was found in an ammonia trap located at the air vent of the closed cultures, showing that an important role of microalgae in wastewater treatment is that of favouring NH3 stripping due to the photosynthesis-induced pH increases.

Ammonia↗
PubMedDate not supplied

[Gastroduodenitis and Helicobacter pylori in uremic patients].

We studied 26 patients (p) with end stage renal failure (RF) and 26 healthy volunteers (HV) to investigate the prevalence of Helicobacter pylori (Hp) and its relation with chronic gastritis (CG) and chronic duodenitis (CD). We analyzed 312 gastric and duodenal mucosal biopsies stained with H & E and Giemsa. Categorical data were assessed by the X2 and Fisher's exact test. Probability values of p < 0.05 were considered significant. Endoscopic lesions correlated with histological gastritis and duodenitis and Hp was positive in antrum of 6/8p (75%) (p < 0.05). The prevalence of Hp was 54.5% (15/26p) in RF and 47.2% (12/26s) in HV. Hp was found more frequently in pathological mucosa (p < 005.). CG of the antrum and CD were more commonly in RF (88.5% vs 69.5% and 42.3% vs 23.1% respectively). HP was more frequently located in the antrum than in body and duodenum in both groups (p < 0.05). Chronic gastritis of the body was more frequently in HV (p < 0.05). Active chronic antral gastritis and superficial gastritis were more frequently associated to Hp. Hp was associated to chronic inflammatory gastroduodenal diseases in both groups and may be a cofactor in its pathogenesis. We recommended Hp treatment before renal transplantation.

Adolescent↗
PubMedDate not supplied

[Heterotopic pancreas].

Heterotopic pancreas is a rare entity, usually asymptomatic, and found incidentally during laparotomy, when symptomatic it is for some complication, gastric obstruction, gastrointestinal hemorrhage, Meckel's diverticulum, obstructive jaundice. We report four patients, with this diagnostic and make a bibliographic review of this entity.

Adolescent↗
PubMedDate not supplied

[Oral cholecystosonography. A method to establish the diagnosis of minute cholesterol calculi].

We have studied five patients with clinical symptoms and/or ultrasonography with sludge-like irregularities, but not conclusive for gallstones. The layering of bile and floating of cholesterol gallstones induced manly by administration of oral cholecystographic contrast, has been well demonstrated since 1933. These 5 patients were given doses of iopanoic acid. The day after we performed other ultrasonography--oral cholecystosonography method. With this second cholecystosonography was demonstrated inside the gallbladder en layer or a line of hyperechogenic little floating spots of cholesterol gallstones.

Adult↗
PubMedDate not supplied

[Ultrasonography as diagnostic method in abdominal trauma and wounds].

Abdominal trauma is a public health problem. Early diagnosis of this lesion is directly related to the survival of these patients. Ultrasonography is a good method for the study of the traumatized patient. Abdominal ultrasonography was performed in 35 patients seen at the Central Military Hospital of Caracas during the years 1987-1988. Free liquid in the abdominal cavity and parenchymatous hematomas were the most frequent findings followed by retroperitoneal hematomas. Abdominal ultrasonography performed by trained and experienced personnel can be of great help in the management of patients with abdominal trauma. Correlation between ultrasonography, surgical findings and the clinical follow up was 100%. We recommended this method for the initial evaluation of these patients.

Abdominal Injuries↗
PubMedDate not supplied

[Gastric schwannoma. Report of a case].

Gastric schwannoma is a rare and benign neurogenic tumor. Diagnosis of this entity is uncertain previous to surgery, being this tumor localized in the sub-mucosa. Final diagnosis is achieved by surgical removal and histological examination.

Humans↗
PubMedDate not supplied

Hypercholesterolemia in children.

Coronary heart disease is the leading cause of death in Puerto Rico. Enough evidence exists to believe that coronary heart disease begins during the pediatric age. There has been and increased interest in recent years about the rationale for detection and treatment of hypercholesterolemia in children. Blood samples of 506 patients ages 3 to 17 were analyzed for plasma cholesterol level using the method RA-1000 Technicon. Measurement of cholesterol, blood pressure and Quetelex index were obtained during the sampling. Family history, and past history were also determined to compare the relationship between positive family history for coronary heart disease and cholesterol value. Based on these samples we concluded that 30% of the sampled population had high cholesterol values for age.

Adolescent↗
PubMedDate not supplied

[Esophageal varices sclerosis in portal hypertension caused by portal thrombosis secondary to protein C deficiency].

Portal thrombosis is a rare entity classified as idiopathic in 50% of the cases, being protein C deficiency a known cause. We present two cases complicated with portal hypertension diagnosed through sonography and protein C determined though laboratory technics. Complicating esophageal varices sclerosed and follow up at seven months and ten years respectively, satisfactory clinical evolution observed.

Adult↗