RESUMEN
We monitored seasonal variations in net primary production (NPP), estimated by allometric equations from organ dimensions, gross primary production (GPP), estimated by the eddy covariance method, autotrophic respiration (R(a)), estimated by a model, and fruit production in a coconut (Cocos nucifera L.) plantation located in the sub-tropical South Pacific archipelago of Vanuatu. Net primary production of the vegetative compartments of the trees accumulated steadily throughout the year. Fruits accounted for 46% of tree NPP and showed large seasonal variations. On an annual basis, the sum of estimated NPP (16.1 Mg C ha(-1) year(-1)) and R(a) (24.0 Mg C ha(-1) year(-1)) for the ecosystem (coconut trees and herbaceous understory) closely matched GPP (39.0 Mg C ha(-1) year(-1)), suggesting adequate cross-validation of annual C budget methods. However, seasonal variations in NPP + R(a) were smaller than the seasonal variations in GPP, and maximum tree NPP occurred 6 months after the midsummer peak in GPP and solar radiation. We propose that this discrepancy reflects seasonal variation in the allocation of dry mass to carbon reserves and new plant tissue, thus affecting the allometric relationships used for estimating NPP.
Asunto(s)
Cocos/fisiología , Frutas/crecimiento & desarrollo , Estaciones del Año , Agricultura , Biomasa , Carbono/metabolismo , Ecosistema , Fotosíntesis/fisiología , Clima TropicalRESUMEN
Beta-2 microglobulin (beta 2 M) is a low molecular weight protein filtered by the renal glomerulus, then reabsorbed and metabolized at the proximal tubule. Its blood concentration is a good renal index, as it is independent from muscle mass and diet contrary to creatinine. We assayed serum beta 2 M in 190 cases of diabetes mellitus divided into 71 non-insulin-dependent and 119 insulin-dependent forms. We found no significant difference between both groups. Serum beta 2 M was not correlated with Hb A 1 C. Conversely, a highly significant positive correlation between beta 2 M and serum creatinine and a negative correlation between beta 2 M and creatinine clearance were demonstrated. Furthermore, patients with borderline serum creatinine and those with normal renal function show very significant differences in mean serum beta 2 M concentrations, thus making combined assay of both parameters advisable. On the other hand, we were unable to evaluate modifications in beta 2 M according to other complications of diabetes mellitus as vascular and neurologic involvement are very often associated with renal dysfunction.
Asunto(s)
Diabetes Mellitus Tipo 1/sangre , Diabetes Mellitus Tipo 2/sangre , Microglobulina beta-2/análisis , Diabetes Mellitus Tipo 1/fisiopatología , Diabetes Mellitus Tipo 2/fisiopatología , Femenino , Humanos , Riñón/fisiopatología , Masculino , Persona de Mediana EdadRESUMEN
Insulin secretion was investigated in 65 insulin-dependent diabetic patients by determining C peptide levels before and after stimulation with either an 800 calories test meal or an injection of glucagon or arginine i.v. Most patients had very low basal C peptide levels and response to all stimulation tests was poor as compared to controls. In normal subjects, response to glucagon or arginine stimulation appeared to be slightly stronger than response to test meal stimulation. There was apparently no correlation between diabetes control, as assessed by haemoglobin A1c values, and C peptide levels before and after stimulation. On the other hand, C peptide levels were inversely proportional to the duration of diabetes. Finally, C peptide levels after test meal stimulation were found to correlate with the doses of insulin administered.