Quantitative profiling of SiGe/Si superlattices by time-of-flight secondary ion mass spectrometry: the advantages of the extended Full Spectrum protocol.

The abundance of work on SiGe-based devices demonstrates the importance of the compositional characterization of such materials. However, Secondary Ion Mass Spectrometry (SIMS) characterization of SiGe layers often suffers from matrix effects due to the non-linear variation of ionization yields with Ge content. Several solutions have been proposed in order to overcome this problem, each having its own limitations such as a restricted germanium concentration range, or a weak sensitivity to dopants or impurities. Here, we studied the improvements brought by an alternative protocol: the extended Full Spectrum protocol, which states proportionality between the composition of the secondary ion beam and that of the actual material. Previous studies on this protocol showed that it was extremely precise and reproducible for Ge quantification in a permanent regime, because of minimized matrix effects. In this study we thus investigated its accuracy for the simultaneous quantitative depth profiling of both matrix elements (Si, Ge) and impurities (B, C or P) in strained SiGe/Si superlattices by comparing results with those from more classic protocols. The profiles provided by the extended Full Spectrum protocol were found to be accurate, and to exhibit better properties than classic protocols in terms of signal/noise ratio and signal stability, along with a slight enhancement in depth resolution.

Internal carotid artery stenosis: comparison of duplex scan and magnetic resonance angiography with digital subtraction angiography.

OBJECTIVE: We compare duplex scan (DS) and magnetic resonance angiography (MRA) with digital angiography (DGA) in respect to accuracy in measuring internal carotid artery (IC) stenosis in symptomatic patients. METHOD: Ten symptomatic patients with IC stenosis greater than 70% previously diagnosed by DS were submitted to another DS and to both MRA and DGA. Both ICs from each patient (total 20 ICs) were evaluated by physicians blinded for the results of other tests. DS and MRA were compared with DGA, using the intraclass correlation coefficient (r) and its 95% confidence interval (95% ci). For each diagnostic test, the study group (20 Ics) was also divided in surgical patients (IC stenosis between 70 and 99%) and non surgical patients, using kappa concordance coefficient (k) to compare the results. RESULTS: Main comparisons are: DS and DGA, r = 0.71 (0.4 - 0.87); MRA and DGA, r = 0.61 (0.25 - 0.82). After division into surgical vs. non-surgical groups, k = 0.857 (p < 0.0001) between DS and DGA; and k = 0.545 (p = 0.003) between MRA and DGA. Most DS and MRA errors occurred in IC sub-occlusions. CONCLUSION: The results suggest that when they are used together, DS and non-contrast MRA may substitute DGA in the evaluation of patients for IC stenosis surgery, except when there is discordance between their results or when the methods show sub-occlusive stenosis.

Comparison between the NASCET method and subjective visual impression in the evaluation of internal carotid artery stenosis.

OBJECTIVE: To evaluate the accuracy of subjective visual impression (SVI) of an experienced neuro-radiologist in the measurement of the degree of internal carotid artery (IC) stenosis evaluated by digital angiography (DGA). METHOD: Ten symptomatic patients with internal carotid stenosis greater than 70% in a previous duplex scan were submitted to DGA. The degree of stenosis in both sides (symptomatic and asymptomatic) were evaluated by the same neuro-radiologist who gave his SVI and applied the NASCET method immediately after. Both methods were compared using the intraclass correlation coefficient (r) and its 95% confidence interval (95% ci). For each method, the sample (20 ICs) was also divided in surgical (stenosis between 70 and 99%) and non surgical ICs, using kappa concordance coefficient (k) to compare the results. RESULTS: The results comparing the 20 values obtained by each method are: r = 0.90 (95% ci: 0.77-0.96). Dividing the sample in surgical and non surgical ICs, k = 0.857, p < 0.0001; sensitivity = 100% (39.6%-100%); specificity = 93.8% (67.7%-99.7%); positive predictive value = 80% (29.9%-98.9%); negative predictive value = 100% (74,7%-100%). CONCLUSION: The SVI may be used by at least some experienced neuroradiologists as a preliminary tool to evaluate the degree of IC stenosis with DGA, but a standardised and well established method should be routinely performed.

Transferrin is an early marker of hepatic differentiation, and its expression correlates with the postnatal development of oligodendrocytes in mice.

Transferrin (Tf), the iron transport protein, is essential for the growth and differentiation of cells. Therefore, it provides an excellent model to analyze the regulatory mechanisms controlling the expression of a eukaryotic gene in different cell types and during fetal and adult life. In this study, the tissue-specific and developmental regulation of the Tf gene in vivo were analyzed. Human Tf mRNA was detected mainly in fetal and adult liver. A weaker expression was observed in adult and fetal brain and in fetal spleen. By in situ hybridization the presence of mouse Tf mRNA was detected in the hepatic primordia. This is the first observation pointing out Tf as an early marker of hepatic differentiation, prior to the formation of the liver. Thus, TF may be an important tool to follow the hepatic specification of the gut endoderm. Mouse Tf mRNA was also detected in the liver bud and subsequently in the liver throughout fetal life, and in newborn and adult animals. No expression of the Tf gene was observed in the mouse fetal central nervous system (CNS). In contrast, Tf mRNA was detected from the 5th day after birth in the derivatives of the caudal part of the neural tube and subsequently in the derivatives of the rhomboencephalon and that of the prosencephalon. These results indicate that Tf gene expression correlates with the postnatal development of oligodendrocytes in the mouse CNS. To test whether the control elements of the human gene previously found in ex vivo experiments were also active in vivo during fetal and adult life, we fused the -4000/+395' flanking region of the human gene to the coding region of the lacZ gene and generated transgenic mice. The expression of the reporter gene during development was analyzed.

[Causes of unjustified hospital stay following cerebral infarction]. / Tempo de internação por infarto cerebral. Permanência hospitalar não justificada.

The frequency and causes of prolonged length of stay (LOS) in patients with acute ischemic stroke were studied in 20 patients admitted to a university hospital participating in the International Stroke Trial (IST). The protocol for prolonged LOS study designed by R. S. Goldman et al. (1996) was reproduced. Mean (+/- SD) LOS was 13.1 +/- 11.5 days (median = 10 days). Prolonged LOS occurred in 12 (60%) patients. In these 12 patients, a total of 83 (62%) of 134 days were found to be unnecessary (6.9 +/- 4.6). Most of these patients remained hospitalized while awaiting for routinely performed tests, such as 2D echocardiogram or carotid Doppler. LOS was not influenced by patient characteristics (age or gender) or specific location in the hospital (emergency room or other). In conclusion, LOS and hospitalization costs can be markedly reduced in this hospital by rational use of already available diagnostic tests.

[Acute disseminated encephalomyelitis and meningococcal A and C vaccine: case report]. / Encefalomielite disseminada aguda e vacinação antimeningocócica A e C. Relato de caso.

A 25-year-old women developed acute disseminated post-vaccinal encephalomyelitis (ADEM) following vaccination with A plus C meningococcal vaccine (Pasteur-Merieux). Fast disappearance of symptoms and gradual resolution of MRI demyelinating lesions occurred after steroid treatment with high doses of intravenous methylprednisolone. To our knowledge, ADEM has not been previously described in association with meningococcal vaccine. Although most cases of ADEM occur following viral infections and vaccination, the syndrome has previously been related to leptospirosis and Mycoplasma pneumoniae infections. This suggests that it may also be related to exposure to polysaccharide-protein vaccines such as the Group A plus Group C meningococcal vaccine.

Development of a two-site immunoassay of recombinant urate oxidase (SR 29142) and its use for determination of pharmacokinetic parameters in rats and baboons.

Two monoclonal antibodies (Mabs), 12C7 and 11G11, both directed against recombinant urate oxidase (SR 29142), were selected for their epitope specificity to develop a two-site immunoassay of urate oxidase in plasma. A quantitative recovery of urate oxidase in plasma was obtained at all the concentrations tested, and the limit of quantification was found to be 0.5 ng/mL. Intra-and interassay coefficients of variation ranged from 1.2 to 6.7% and from 3.5 to 10.8%, respectively. The specificity of the two antibodies was studied in Western-blot experiments. This assay was used successfully to determine urate oxidase pharmacokinetic parameters after intravenous injection in rats and baboons. In these two species, urate oxidase pharmacokinetics was characterized by a low clearance and a low volume of distribution without gender difference.

Cell type-specific expression of the human transferrin gene. Role of promoter, negative, and enhancer elements.

Transferrin (Tf), the iron transport protein of vertebrate serum, is mainly synthesized in the liver. cis-Acting DNA elements required for liver-specific expression of the human Tf gene were identified by transient and stable expression assays in human hepatoma (HepG2 and Hep3B) and epithelial carcinoma (HeLa) cell lines. Deletion analysis of the 5' DNA sequences of the gene have defined four functionally different regions: (a) A cell type-specific promoter located between positions -125 and -45 which interacts with two nuclear factors and is sufficient for liver-specific expression. (b) A distal promoter region from -620 to -125 base pairs containing positive and negative cis-acting elements which regulate the promoter activity. (c) A negative-acting region between -1.0 and -0.6 kilobase pairs which down-regulates transcription from the Tf promoter. (d) An enhancer located between -4.0 and -3.3 kilobase pairs which is more active in hepatoma than in HeLa cells. Thus, Tf gene expression is modulated by a combination of multiple positive and negative cis-acting elements. The expression results are discussed with respect to our previous description of the trans-acting factors interacting with the proximal and distal promoter regions.

Complete structure of the human transferrin gene. Comparison with analogous chicken gene and human pseudogene.

The complete structure of the human transferrin gene is presented. This gene has a total size of about 33.5 kb and is organized in 17 exons separated by 16 introns. The chicken ovotransferrin gene has a size of 10.5 kb and is also organized in 17 exons and 16 introns. The analysis of the structure of the two genes confirm, at the gene level, that transferrins originated by a gene duplication phenomenon. Finally, the existence of a new member of the transferrin family, a human transferrin non-processed pseudogene is demonstrated.

Structure of the metJBLF cluster in Escherichia coli K12. Sequence of the metB structural gene and of the 5'- and 3'-flanking regions of the metBL operon.

The total nucleotide sequence (1,158 nucleotides) of the metB gene of Escherichia coli coding for cystathionine gamma-synthase (386 amino acid residues, Mr = 41,503/chain) is presented. The nucleotide sequences of the flanking regions of the metB and metL genes are also presented. Analysis of these sequences and identification of a promoter region upstream from the metB gene confirms that metB and metL form an operon. The transcription direction is from metB to metL; the start site of the gene transcription has been determined. There is no structural evidence of a classical attenuation mechanism in the regulation of this operon coding for enzymes implicated in an amino acid biosynthetic pathway. Finally, the overall organization of the metJBLF gene cluster is discussed.

Construction and physical mapping of plasmids containing the metJBLF gene cluster of E. coli K12.

In vitro recombination techniques were used to clone the E. coli metJBLF gene cluster in a plasmid vector. Several chimeric plasmids were obtained, analyzed by restriction mapping and characterized genetically. The combined results establish that the met gene cluster is contained on an approximately 5.6 kilobase segment of bacterial DNA with metL between metB and metF. The origin of metL was localized precisely by its DNA sequence and its transcription direction was established.

The immune response of CBA mice to OSRA, a peripheral protein from the sheep erythrocyte membrane.

The capacity of a membrane protein from sheep erythrocytes (osmotic shock released antigen: OSRA) to elicit an immune response in CBA mice was investigated. While all OSRA preparations tested are antigenically identical en indistinguishable with respect to physicochemical characteristics, they are not equally efficient in stimulating immunocompetent lymphocytes for antibody production upon a primary immunization (immunogenic versus antigenic OSRA). Both antibody-forming and (T and B) memory cells are generated in mice primed with immunogenic OSRA. Evidence is presented that the failure of antigenic OSRA to induce a primary response to SRBC determinants is related to its inability to stimulate unprimed T-cells. OSRA appears to be a major antigenic determinant of the sheep erythrocyte membrane since it specifically inhibits up to 60% of an anti-SRBC response.

Purification and characterization of a peripheral protein from the sheep erythrocyte membrane.

A peripheral protein of the sheep red blood cell membrane has been purified to homogeneity. This protein is completely released from the membrane by osmotic shock. Its amino acid composition, molecular weight and subunit structure have been determined. Antibodies against this protein have been obtained in rabbits.