RESUMO
The nonlinear index of refraction (n_{2}) and the two-photon absorption coefficient (ß) of water-based ferrofluids made of magnetite nanocrystals of different sizes and with different coatings have been measured through the Z-scan technique, with ultrashort (femtoseconds) laser pulses. Their third-order susceptibility is calculated from the values of n_{2} and ß. The influence of different particles' coatings and sizes on these nonlinear optical properties are investigated. The values of n_{2} and ß depend more significantly on the nanoparticles' size than on the particular coating. We observe a decrease of ß as the nanoparticles' diameters decrease, although the optical gap is found to be the same for all samples. The results are interpreted considering modifications in the electronic orbital shape due to the particles' nanosize effect.
RESUMO
The neonatal and postpartum periods are characterized by alterations in pituitary GH secretion. We have investigated the proportion of circulating non-22kDa GH isoforms in newborns, in women within the early postpartum phase (just after the disappearance of placental GH from the maternal circulation) and in women during late postpartum (during the somatotroph recovery phase). We studied 10 newborns (7 males; 3 females; median postnatal age, 45h), who had been admitted because of polycythaemia, 10 women in the early postpartum phase (median, 48h after delivery; range, 42-54h), 18 women in the late postpartum phase (median, 10 weeks after delivery; range, 3-25 weeks) and 9 healthy non-pregnant women. The proportion of non-22kDa GH isoforms was determined by the 22kDa GH exclusion assay, which is based on immunomagnetic extraction of 22kDa GH from serum, and quantitation of non-22kDa GH isoforms using a polyclonal GH assay. In newborns, non-22kDa GH isoforms were measured in two arterial blood samples obtained with a 5-6h interval. In the other groups, serum samples were obtained 40min after an i.v. bolus administration of the GH secretagogue, GH releasing peptide-1 (GHRP-1). In newborns, the median proportion of non-22kDa GH isoforms was 10% (range, 7. 2-19.4%) and the values were similar in samples collected at different times. In early postpartum women, total GH levels after GHRP-1 were lower and the proportion of non-22kDa GH isoforms was higher compared with the values in non-pregnant and late-postpartum women. In late postpartum, there was a partial recovery of GH response to GHRP-1, as shown by an increment in total GH levels, which was associated with a decrease in the fraction of non-22kDa GH isoforms. In conclusion, we found that (i) the proportion of non-22kDa GH isoforms in the newborn is comparable to that in the adult (non-pregnant women), (ii) in early postpartum, the non-22kDa fraction is high within the small pool of readily releasable GH, (iii) in late postpartum, recovery of pituitary GH responsiveness is associated with a relative decrease in the release of non-22kDa GH isoforms.
Assuntos
Hormônio do Crescimento Humano/sangue , Recém-Nascido/sangue , Período Pós-Parto/sangue , Adulto , Feminino , Humanos , Masculino , Isoformas de Proteínas/sangue , Fatores de TempoRESUMO
OBJECTIVE: To determine whether some patients with idiopathic short stature have partial resistance to growth hormone (GH). Patients with idiopathic short stature have decreased serum levels of the GH receptor-related GH-binding protein (GHBP), and low GHBP levels are associated with complete GH insensitivity (Laron) syndrome. We hypothesized that patients with idiopathic short stature and low GHBP levels may also have a degree of GH insensitivity. DESIGN: Retrospective analysis of patients in a multicenter study. SETTING: Ninety-six National Cooperative Growth Study centers in the United States and Canada. SUBJECTS: Five hundred eleven patients with idiopathic short stature who were treated with GH. All patients had a baseline height standard deviation score of less than -2 and a maximum stimulated GH level greater than 10 micrograms/L. Of these, 101 (20%) had a baseline GHBP standard deviation score of -2 or less. RESULTS: The patients with low GHBP levels, in comparison with those with normal GHBP levels, had a lower mean extracted standard deviation score for insulin-like growth factor I (-3.3 +/- 1.1 vs -2.5 +/- 1.4; p < 0.0001) but mean 12-hour GH values (2.8 +/- 1.1 vs 2.3 +/- 1.1 micrograms/L; p <0.0001). The differences between groups were statistically significant after control for age and weight-for-height standard deviation score. Among prepubertal patients, there was no significant difference between the low and normal GHBP groups in mean pretreatment or first-year growth rate (p = 0.74, 0.61 respectively) with comparable doses of GH. CONCLUSIONS: Patients with idiopathic short stature and low GHBP levels, compared with those with normal GHBP levels, had significantly lower standardized levels of insulin-like growth factor I, and higher mean 12-hour GH levels, which suggest partial GH insensitivity. There was no significant correlation of GHBP levels with the growth response to exogenous GH.
Assuntos
Proteínas de Transporte/sangue , Transtornos do Crescimento/tratamento farmacológico , Hormônio do Crescimento/uso terapêutico , Estatura/efeitos dos fármacos , Estudos de Casos e Controles , Criança , Feminino , Transtornos do Crescimento/sangue , Hormônio do Crescimento/sangue , Hormônio do Crescimento/deficiência , Humanos , Fator de Crescimento Insulin-Like I/análise , Modelos Lineares , Masculino , Valores de Referência , Estudos RetrospectivosRESUMO
Recently, an isolated population of apparent GH-receptor deficient (GHRD) patients has been identified in the Loja province of southern Ecuador. These individuals presented many of the physical and biochemical phenotypes characteristic of Laron-Syndrome and are believed to have a defect in the GH-receptor gene. In this study, we have compared the biochemical phenotypes between the affected individuals and their parents, considered to be obligate heterozygotes for the disorder. Serum GH, insulin-like growth factor I and II (IGF-I and IGF-II) levels were measured by RIA Insulin-like growth factor binding proteins. (IGFBPs) were measured by Western ligand blotting (WLB) of serum samples, following separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and relative quantitation of serum IGFBPs was performed with a scanning laser densitometer. Serum GH-binding protein (GHBP) levels were measured with a ligand-mediated immunofunctional assay using a monoclonal antibody raised against the GHBP. These values were then compared to values obtained from normal, sex-matched adult Ecuadorian controls, to determine if the above parameters were abnormal in the heterozygotes. The serum IGF-I levels of the GHRD patients were less than 13% of control values for adults and 2% for children. However, the IGF-I levels of both the mothers and fathers were not significantly different from that of the control population. The serum IGF-II levels of the GHRD patients were approximately 20% of control values for adults and 12% for the children. The IGF-II levels of the mothers were reduced, but were not significantly different from that of the control population. However, IGF-II levels of the fathers were significantly lower than those of controls (64% of control male levels). WLB analysis of serum IGFBP levels of the affected subjects demonstrated increased IGFBP-2 and decreased IGFBP-3, suggesting an inverse relationship between these IGFBPs. The GHRD patients who had the lowest serum IGFBP-3 levels (as measured by WLB) demonstrated a serum protease activity that could proteolyze 125I-IGFBP-3. GHRD patients who had higher serum IGFBP-3 levels lacked this serum protease activity. There were no differences in the serum IGFBP profiles of the mothers or the fathers for either IGFBP-2 or IGFBP-3, and serum from both groups lacked the ability to significantly proteolyze 125I-IGFBP-3. While GHRD patients had very low levels of serum GHBP, some patients did have measurable GHBP levels.(ABSTRACT TRUNCATED AT 400 WORDS)