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Cristina Cruz

Publications and source records attributed to Cristina Cruz.

7 recordsLinked to original sources
PubMed2006

Enzymatic evidence for the key role of arginine in nitrogen translocation by arbuscular mycorrhizal fungi.

Key enzymes of the urea cycle and (15)N-labeling patterns of arginine (Arg) were measured to elucidate the involvement of Arg in nitrogen translocation by arbuscular mycorrhizal (AM) fungi. Mycorrhiza was established between transformed carrot (Daucus carota) roots and Glomus intraradices in two-compartment petri dishes and three ammonium levels were supplied to the compartment containing the extraradical mycelium (ERM), but no roots. Time courses of specific enzyme activity were obtained for glutamine synthetase, argininosuccinate synthetase, arginase, and urease in the ERM and AM roots. (15)NH(4)(+) was used to follow the dynamics of nitrogen incorporation into and turnover of Arg. Both the absence of external nitrogen and the presence of L-norvaline, an inhibitor of Arg synthesis, prevented the synthesis of Arg in the ERM and resulted in decreased activity of arginase and urease in the AM root. The catabolic activity of the urea cycle in the roots therefore depends on Arg translocation from the ERM. (15)N labeling of Arg in the ERM was very fast and analysis of its time course and isotopomer pattern allowed estimation of the translocation rate of Arg along the mycelium as 0.13 microg Arg mg(-1) fresh weight h(-1). The results highlight the synchronization of the spatially separated reactions involved in the anabolic and catabolic arms of the urea cycle. This synchronization is a prerequisite for Arg to be a key component in nitrogen translocation in the AM mycelium.

Arginine↗
PubMed2005

Tetralogy of Fallot: prognostic factors after surgical repair.

INTRODUCTION AND OBJECTIVE: Corrective surgery for tetralogy of Fallot (TF) has led to excellent survival. However; several years after surgery, the majority of patients have right ventricular (RV) dilatation, and 10% will need reoperation of the RV outflow tract due to limited exercise capacity, ventricular arrhythmias or symptoms of heart failure (HF). Our aim was to identify predictive factors of adverse outcome: moderate to severe RV dilatation, HF, reoperation of the RV outflow tract and cardiac death. METHODS: Eighty-eight adult patients with TF were operated between January 1977 and July 2001; 22 were lost to follow-up and 66 were followed for 18 +/- 6 years. We analyzed clinical, electrocardiographic and echocardiographic variables. RV dilatation was considered to exist if the inlet measurement at end-diastole in 4-chamber apical view was more than 35 mm, being classified as moderate when > or = 50 and < 60 mm and severe when > or = 60 mm. RESULTS: Of the 66 patients, 25 (37.9%) had undergone previous palliative shunt (PS) at the age of 4 +/- 5 years. Mean age at surgical correction was 10 +/- 8 years (range: < 1 to 38 years; median: 6.5 years). Transannular patching was used in 65% of patients, patch closure of a right ventriculotomy in 91%, and in 53% of patients a pulmonary commissurotomy was performed. At the end of follow-up, 3 patients were in NYHA class III-IV and one patient was successfully reoperated with implantation of a biological pulmonary valve. Prevalence of RV dilatation was 97% (57/59), being moderate to severe in 69% (36/52). In patients with moderate to severe RV dilatation we found previous PS (18.8 vs. 50.0%; p = 0.03), transannular patching (37.5 vs. 75.0%; p 0.01) and wide QRS (160 ms) (6.7 vs. 45.7%, p = 0.01) to be more frequent. These patients reported more palpitations (0 vs. 22.2%; p 0.05), but there were no differences in arrhythmic events (18.8 vs. 33.3%; p = 0.28); maximal heart rate on exercise was lower (86.2 +/- 10.9 vs. 79.9 +/- 8.6; p = 0.04), but exercise time and functional capacity were similar between the groups. Follow-up time and use of RV patching were similar. Transannular patching was associated with previous PS at an older age (0.9 +/- 0.7 vs. 4.9 +/- 5.7 years; p = 0.01), a higher grade of pulmonary regurgitation (III-IV) (22.7 vs. 57.5%; p = 0.01), wide QRS (160 ms) (9.5 vs. 41.0%, p = 0.01), and greater RV dilatation. No mortality was reported. CONCLUSION: Transannular patching and performance of previous PS were predictive factors of severe RV dilatation, and pulmonary regurgitation seems to be its physiological mechanism. Despite this, long-term prognosis is favorable and patients have good functional capacity.

Adolescent↗
PubMed2003

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity.

The aim of this research was to investigate the effect of arbuscular mycorrhizal (AM) colonisation on root morphology and nitrogen uptake capacity of carob (Ceratonia siliquaL.) under high and low nutrient conditions. The experimental design was a factorial arrangement of presence/absence of mycorrhizal fungus inoculation (Glomus intraradices) and high/low nutrient status. Percent AM colonisation, nitrate and ammonium uptake capacity, and nitrogen and phosphorus contents were determined in 3-month-old seedlings. Grayscale and colour images were used to study root morphology and topology, and to assess the relation between root pigmentation and physiological activities. AM colonisation lead to a higher allocation of biomass to white and yellow parts of the root. Inorganic nitrogen uptake capacity per unit root length and nitrogen content were greatest in AM colonised plants grown under low nutrient conditions. A better match was found between plant nitrogen content and biomass accumulation, than between plant phosphorus content and biomass accumulation. It is suggested that the increase in nutrient uptake capacity of AM colonised roots is dependent both on changes in root morphology and physiological uptake potential. This study contributes to an understanding of the role of AM fungi and root morphology in plant nutrient uptake and shows that AM colonisation improves the nitrogen nutrition of plants, mainly when growing at low levels of nutrients.

Fabaceae↗
PubMed2003

Interaction between HERC1 and M2-type pyruvate kinase.

HERC proteins are characterized by having one or more RCC1-like domains as well as a C-terminal HECT domain in their amino acid sequences. This has led researchers to suggest that they may act as both guanine nucleotide exchange factors and E3 ubiquitin ligases. Here we describe a physical interaction between the HECT domain of HERC1, a giant protein involved in intracellular membrane traffic, and the M2 isoform of glycolytic enzyme pyruvate kinase (M2-PK). Partial colocalization of endogenous proteins was observed by immunofluorescence studies. This interaction neither induced M2-PK ubiquitination nor affected its enzymatic activity. The putative significance of the association is discussed.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Nitrogen use efficiency by a slow-growing species as affected by CO2 levels, root temperature, N source and availability.

This study examines the importance of N source and concentration on plant response to distinct CO2 concentrations and root temperatures. The experimental design of this work was a factorial combination of: CO2 concentration, nitrogen concentration, nitrogen source and root temperature. Carob (Ceratonia siliqua L.) was assessed as a potential model of a slow growing Mediterranean species. The results showed that: 1) biomass increment under high CO2 varied between 13 and 100% in relation to plants grown under the same conditions but at ambient CO2 concentrations, depending on the root temperature and nitrogen source; 2) nitrate-fed plants attained a larger increase in biomass production compared to ammonium-fed ones. This performance seems to be linked to the co-ordinated regulation of the activities of glutamine synthetase and sucrose phosphate synthase. The variations in the magnitude and nature of growth responses to elevated CO2 observed resulted in substantial changes in the chemical composition of the plant material and consequently in plant nitrogen use efficiency. Although performed with seedlings and under controlled conditions, this work emphasizes the importance of the nitrogen source used by the plants, a factor rarely taken into consideration when forecasting plant responses to global changes. Particularly, the results presented here, highlight the potential for uncoupling biomass accumulation from increment of air CO2 concentration and show that more than nitrogen availability N source may offset positive plant growth responses under elevated CO2 and root temperature.

Biomass↗
PubMed2002

Development of Spinitectus inermis (Nematoda: Cystidicolidae), a parasite of eel, Anguilla anguilla, in Europe.

The development of the nematode Spinitectus inermis (Zeder, 1800), a parasite of the stomach of eels, Anguilla anguilla (L.) in Europe, was experimentally studied. Mayfly nymphs Caenis macrura, Ecdyonurus dispar, Heptagenia sulphurea, Potamanthus luteus and Seratella ignita from Portugal and the Czech Republic were found to serve as experimental intermediate hosts. After ingestion of the nematode eggs by the mayfly nymphs, the toothed first-stage larvae were released and penetrated into the body cavity of the intermediate host. There they moulted twice (on day 4 and 6 post infection [p.i.] at water temperatures of 20-25 degrees C), attaining the third infective stage. The definitive host, A. anguilla, undoubtedly acquires infection by feeding on mayfly nymphs harbouring infective-stage larvae. In an experimentally infected eel, the fourth-stage larva undergoing the third moult was observed 28 days p.i. at water temperature of 20 degrees C. The larval stages, including moulting forms, are described and illustrated. The prepatent period of S. inermis is estimated to be about two months.

Anguilla↗