Effects of Freeze-Thaw Cycles and Assessment of Short-Term Storage Stability on Serum Iron, Ferritin, and Transferrin.

BACKGROUND: Most errors in the laboratory occur due to processes related to the pre-analytical phase. The purpose of this study was to investigate the effects of multiple freeze-thaw cycles on serum iron, transferrin, and ferritin, as well as the impact of short-term storage on the stability of these analytes. METHODS: Serum samples from ten volunteers were submitted to three consecutive freeze-thaw cycles at -20°C and -80°C. Serum aliquots were also kept at 4°C, -20°C, and -80°C for 28 days. Iron, ferritin, and transferrin were measured after 1, 7, 14, 21, or 28 days of storage. RESULTS: Serum ferritin and transferrin showed variations from -2.6 to 2.6% and -1.7 to 2.4%, respectively, in their concentrations during the three freeze-thaw cycles of -20°C and -80°C. However, the variations were statistically significant only at -20°C. No significant changes were found for iron at both temperatures. The storage at temperatures of 4°C, -20°C, and -80°C for up to 4 weeks significantly affected the serum concentrations of iron, ferritin, and transferrin (p < 0.01 for all). CONCLUSIONS: Serum iron, ferritin, and transferrin were affected by the storage of samples at temperatures of 4°C, -20°C and -80°C for up to 4 weeks, and the freeze-thaw cycles at -20°C influenced the measurement of serum ferritin and transferrin.

Efeito da suplementação de colecalciferol nos RNA mensageiros urinários associados ao podócito em pacientes com doença renal crônica / Effect of cholecalciferol supplementation on urine podocyte-associated messenger RNAs in patients with chronic kidney disease

RESUMO Introdução: A vitamina D reduz a albuminúria em pacientes com doença renal crônica (DRC), mas o seu efeito sobre os podócitos glomerulares ainda não é claro. Objetivos: Avaliar se a suplementação de colecalciferol reduz os RNAm urinários associados ao podócito em pacientes com DRC. Métodos: Vinte e sete pacientes com DRC estágios 2 a 4 e níveis sub-ótimos de 25-hidroxi-vitamina D [25(OH)D] sérica foram tratados com colecalciferol por seis meses. Foram medidos antes e após a intervenção a 25(OH)D sérica e o RNAm urinário da nefrina, podocina, podocalixina, receptor transitório potencial do canal de cátions, subfamília C, membro 6 (TRPC6), fator A de crescimento do endotélio vascular (VEGF-A) e fator de crescimento transformador beta (TGF-β1). Resultados: A TFGe reduziu em média 4,71 mL/min/1,73 m2 (p = 0,010 vs. basal), sendo 28 ± 16 mL/min/1,73 m2 aos seis meses. Os RNAm dos produtos do podócito na urina não tiveram alteração significativa após o tratamento. Entretanto, pacientes que atingiram níveis de 25(OH)D ≥ 20 ng/mL aos 6 meses tiveram tendência de redução do RNAm da nefrina e da podocina na urina; nos pacientes em que a 25(OH)D permaneceu < 20 ng/mL houve aumento significativo da podocalixina, e tendência de maior expressão do RNAm da nefrina e da podocina. Conclusão: A reposição de colecalciferol por seis meses não teve efeito sobre os RNAm associados ao podócito nestes pacientes com DRC avançada. O efeito protetor da vitamina D ou seus análogos sobre o podócito glomerular deve ser investigado em estágios mais precoces da DRC e com maior tempo de tratamento.

ABSTRACT Introduction: Vitamin D reduces albuminuria in patients with chronic kidney disease (CKD) but its effects on glomerular podocytes are not entirely understood. Objective: To evaluate if cholecalciferol supplementation reduces the levels of podocyte-associated urine mRNAs in patients with CKD. Methods: A total of 27 patients with stages 2 to 4 CKD and suboptimal serum vitamin D [25(OH)D] levels were treated with cholecalciferol for 6 months. Serum 25(OH)D level, estimated glomerular filtration rate (eGFR), proteinuria, and urine mRNA of nephrin, podocin, podocalyxin, transient receptor potential cation channel 6, vascular endothelial growth factor A, and transforming growth factor beta were assessed before and after intervention. Results: eGFR declined at an average rate of -4.71 mL/min/1.73 m2 (p = 0.010 vs. baseline), being 28 ± 16 mL/min/1.73 m2 at six months. No changes in proteinuria or mineral and bone metabolism parameters were observed after cholecalciferol supplementation. Urinary podocyte-associated mRNAs did not change significantly after treatment. However, patients who achieved 25(OH)D level > 20 ng/mL at six months showed a trend of reduction of urinary nephrin and podocin mRNA levels; in patients with 25(OH)D that remained < 20 ng/mL there was a significant increase in urinary podocalyxin, and a trend of higher expression of urinary nephrin and podocin mRNA. Conclusion: Six months of cholecalciferol supplementation had no effect on urine podocyte-associated mRNA profile of patients with advanced CKD. The protective effect of vitamin D or its analogues on the glomerular podocyte should be investigated in early stages of CKD with a longer treatment period.

Fitoconstituintes isolados da fração em diclorometano das folhas de Vernonia tweediana Baker / Phytoconstituents isolated from dichloromethane fraction of Vernonia tweediana Baker leaves

Fracionamento cromatográfico da fração em diclorometano obtida do extrato etanólico das folhas de Vernonia tweediana Baker (Asteraceae) conduziu ao isolamento de α-amirina, β-amirina, lupeol, β-sitosterol, estigmasterol e espinasterol. As estruturas foram identificadas através de técnicas espectroscópicas usuais, além da comparação com dados relatados na literatura. Os compostos isolados são relatados pela primeira vez para a espécie V. tweediana.

Fractionation of the dichloromethane -soluble fraction from the ethanol extract of the leaves of Vernonia tweediana (Asteraceae) led to the isolation of α-amyrin, β-amyrin, lupeol, β-sitosterol, stigmasterol and spinasterol. The structures of the isolates were elucidated by spectroscopic analysis and comparison with literature data. The isolated compounds are reported for the first time to the species V. tweediana.