Mössbauer Study on the Conversion of Different Iron-Based Catalysts Used in Carbon Nanotube Synthesis.

The phase composition and comparison of iron-based catalysts used for the synthesis of carbon nanotubes were investigated. This work reflects typical catalyst conditions and their evolution during the growth of carbon nanotubes. The preparation of carbon nanotubes was carried out by chemical vapour deposition at temperatures between 800 and 1100 °C. Ferrocene or zero-valent iron nanoparticles were used as "catalysts", and toluene, ferrocene and the ferrocene-toluene solution played the role of carbon precursors, respectively. The phase composition of the prepared product was studied by Mössbauer spectroscopy and X-ray powder diffraction. Mössbauer analysis was particularly useful for samples with a low content of the nanoparticle form of the catalyst. The composition of the prepared samples differed depending on the synthesis temperature, catalyst and precursor. Phase analysis revealed the presence of α-Fe and Fe3C in all samples. In addition, γ-Fe and iron oxides were identified under certain conditions. Scanning and transmission electron microscopy confirmed the carbon nanotube/nanofibre-like morphology and the presence of iron species.

Sequence recombination in exon 1 of the TSPY gene in men with impaired fertility.

AIM: The aim of this study was to evaluate TSPY (testis specific protein on the Y chromosome) gene and 5'UTR (UnTranslated Region) polymorphisms in men with impaired fertility compared to fertile controls. METHODS: We analyzed 72 infertile men and 31 fertile controls usingconventional sequencing analysis to find crucial SNPs (single nucleotide polymorphism) and other changes. RESULTS: The most remarkable changes were found in the 1(st) exon only. In one half of the both infertile men and fertile controls, the most frequent finding was 26 SNPs with a similar pattern. In the other half we found highly relevant changes, generating a stop codon in the first third of exon 1. Early termination cut down the protein by 78.5%. This kind of change was not found in the fertile controls. No correlation was found between the spermiogram and the changes leading to the stop codon. The distribution of men with deletions, insertion and higher gene copy number was not statistically different. CONCLUSION: The changes found in exon 1 in infertile men could fundamentally affect the process of spermatogenesis. These findings could significantly enhance our understanding of the molecular-genetic causes of male infertility.

TSPY gene copy number as a potential new risk factor for male infertility.

The human TSPY (testis-specific protein, Y-linked) gene family (30-60 copies) is situated in the MSY (male-specific) region of the Y chromosome. Testis-specific expression indicates that the gene plays a role in spermatogenesis. Refined quantitative fluorescence PCR (polymerase chain reaction) was applied to evaluate the relative number of TSPY copies compared with AMELY/X (amelogenin gene, Y-linked) genes in 84 stratified infertile men and in 40 controls. A significantly higher number of TSPY copies was found in infertile men compared with the controls (P = 0.002). The diagnostic discrimination potential of the relative number of TSPY copies was evaluated by receiver operating characteristic curve analysis. TSPY/AMELY was unambiguously found to be powerful in the diagnostic separation of both the control samples and the infertile men, reaching a good level of specificity (0.642) and sensitivity (0.732) at a cut-off point of 0.46. The findings were supported by independently repeated studies of randomly selected positive samples and controls. Evaluation of the TSPY copy number offers a completely new diagnostic approach in relation to the genetic cause of male infertility. The possible effect of the copy number of TSPY genes on spermatogenesis may explain indiscrete pathological alterations of spermatid quality and quantity.