Tat protein of human immunodeficiency virus type 1 subtype C strains is a defective chemokine

Human immunodeficiency virus type 1 (HIV-1)-associated dementia (HAD) is correlated with increased monocyte migration to the brain, and the incidence of HAD among otherwise asymptomatic subjects appears to be lower in India than in the United States and Europe (1 to 2% versus 15 to 30%). Because of the genetic differences between HIV-1 strains circulating in these regions, we sought to identify viral determinants associated with this difference. We targeted Tat protein for these studies in view of its association with monocyte chemotactic function. Analyses of Tat sequences representing nine subtypes revealed that at least six amino acid residues are differentially conserved in subtype C Tat (C-Tat). Of these, cysteine (at position 31) was highly (>99%) conserved in non-subtype C viruses and more than 90% of subtype C viruses encoded a serine. We hypothesized a compromised chemotactic function of C-Tat due to the disruption of CC motif and tested it with the wild type C-Tat (CS) and its two isogenic variants (CC and SC) derived by site-directed mutagenesis. We found that the CS natural variant was defective for monocyte chemotactic activity without a loss in the transactivation property. While the CC mutant is functionally competent for both the functions, in contrast, the SC mutant was defective in both. Therefore, the loss of the C-Tat chemotactic property may underlie the reduced incidence of HAD; although not presenting conclusive evidence, this study provides the first evidence for a potential epidemiologic phenomenon associated with biological differences in the subtype C viruses.     

Structural analysis of engineered Bb fragment of complement factor B: insights into the activation mechanism of the alternative pathway C3-convertase

The C-terminal fragment, Bb, of factor B combines with C3b to form the pivotal C3-convertase, C3bBb, of alternative complement pathway. Bb consists of a von Willebrand factor type A (vWFA) domain that is structurally similar to the I domains of integrins and a serine protease (SP) domain that is in inactive conformation. The structure of the C3bBb complex would be important in deciphering the activation mechanism of the SP domain. However, C3bBb is labile and not amenable to X-ray diffraction studies. We engineered a disulfide bond in the vWFA domain of Bb homologous to that shown to lock I domains in active conformation. The crystal structures of Bb(C428-C435) and its inhibitor complexes reveal that the adoption of the "active" conformation by the vWFA domain is not sufficient to activate the C3-convertase catalytic apparatus and also provide insights into the possible mode of C3-convertase activation.     

Cytologic characterization of postiodization residual goiter in schoolchildren by fine needle biopsy

OBJECTIVE: To determine the relevance and utility of fine needle biopsy (FNB) for providing a tissue-level diagnosis during a community-based survey of postiodization residual goiter in schoolchildren in India. STUDY DESIGN: A total of 14,762 schoolchildren (56.0% girls and 44.0% boys), aged 6-18 years, with a countrywide representation, were clinically screened for the presence of goiter. FNB was performed under field conditions by means of a nonaspiration technique from both lobes of goitrous glands. The cytologic diagnosis and findings were correlated with age, sex, goiter grade and biochemical parameters of serum T4, TSH, thyroid microsomal (TMA) and thyroglobulin (TGA) antibodies. RESULTS: The overall prevalence of goiter was 23.0%, with a greater frequency in girls (27.1%) than boys (17.8%). FNB was successful in 75.6% of subjects without any significant complications. The cytologic diagnoses in 1,312 successful cases were colloid goiter (92.8%), Hashimoto's thyroiditis (4.6%), focal lymphocytic thyroiditis (1.7%) and hyperplastic goiter (0.9%). Autoimmune thyroiditis (AIT), which accounted for only 6.3% cases, showed a strikingly different age-specific prevalence between girls and boys. Serologic markers of TMA and TGA at various titers were observed to lack requisite sensitivity and specificity for establishing an accurate diagnosis of AIT. CONCLUSION: The nonaspiration technique of FNB is capable of yielding valuable diagnostic information during an epidemiologic survey of goiter. The technique can be easily performed under field conditions on children without significant complications. FNB is preferable to serologic markers for accurate diagnosis of AIT. A relatively low frequency of AIT, as observed in the present study, raises the possibility of a significant role of environmental goitrogens as the underlying pathogenetic factor in postiodization residual goiter in Indian schoolchildren.     

A comparative study on the interaction of acridine and synthetic bis-acridine with G-quadruplex structure

DNA from the telomeres contains a stretch of simple tandemly repeated sequences in which clusters of G residues alternate with clusters of T/A sequences along one DNA strand. Model telomeric G-clusters form four-stranded structures in presence of Na(I), K(I) and NH(4)(I) ions. Electrophoretic and spectroscopic studies were made with the telomeric related sequences d(T6G16) or d(G4T2G4T2G4T2G4). It was noticed earlier that G-quadruplex may either be inter-molecular, or intra-molecular, or a mixture of both. CD spectral characteristics of various G-quadruplex DNA suggests that the CD maximum at 293 nm corresponds to that of an intra-molecular G-quadruplex structure or hairpin dimers. Fluorescence titration studies also show that acridine and the bis-acridine are interacting with G-quadruplex DNA and destabilize the K(I)-quadruplex structure more efficiently than the quadruplex formed by NH(4)(I) ion. Among the two drugs studied, acridine is more capable of breaking the G-quadruplex structure than bis-acridine. This result is further confirmed by the CD experiments.     

Validity and reproducibility of arterial pulse wave velocity measurement using new device with oscillometric technique: A pilot study

Background  

Availability of a range of techniques and devices allow measurement of many variables related to the stiffness of large or medium sized arteries. There is good evidence that, pulse wave velocity is a relatively simple measurement and is a good indicator of changes in arterial properties. The pulse wave velocity calculated from pulse wave recording by other methods like doppler or tonometry is tedious, time-consuming and above all their reproducibility depends on the operator skills. It requires intensive resource involvement. For epidemiological studies these methods are not suitable. The aim of our study was to clinically evaluate the validity and reproducibility of a new automatic device for measurement of pulse wave velocity that can be used in such studies.     

Gravity signal transduction in primary roots

AIMS: The molecular mechanisms that correlate with gravity perception and signal transduction in the tip of angiosperm primary roots are discussed. SCOPE: Gravity provides a cue for downward orientation of plant roots, allowing anchorage of the plant and uptake of the water and nutrients needed for growth and development. Root gravitropism involves a succession of physiological steps: gravity perception and signal transduction (mainly mediated by the columella cells of the root cap); signal transmission to the elongation zone; and curvature response. Interesting new insights into gravity perception and signal transduction within the root tip have accumulated recently by use of a wide range of experimental approaches in physiology, biochemistry, genetics, genomics, proteomics and cell biology. The data suggest a network of signal transduction pathways leading to a lateral redistribution of auxin across the root cap and a possible involvement of cytokinin in initial phases of gravicurvature. CONCLUSION: These new discoveries illustrate the complexity of a highly redundant gravity-signalling process in roots, and help to elucidate the global mechanisms that govern auxin transport and morphogenetic regulation in roots.     

Non-enzymatic protein modification by the Maillard reaction reduces the activities of scavenging enzymes in Vigna radiata

The non-enzymatic modification of proteins through the Maillard reaction plays an important role in the loss of seed viability during seed storage. In the present study we examined whether the Maillard reaction reduces the activities of scavenging enzymes in Vigna radiata (mung bean) seeds during storage. Seeds were stored under various conditions for different duration. Maillard products were monitored by measuring protein fluorescence, and the activities of glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) were determined. The accumulation of Maillard products in seed axes increased during storage with increasing moisture content and temperature, and was correlated with the decline in seed vigour. The activities of GR, CAT and APX decreased in proportion to the increase in Maillard products at all the moisture contents and temperatures tested. These enzymatic changes were also correlated with seed vigour. However, the activities of SOD and POX remained unchanged and appeared to be less sensitive to the Maillard reaction.     

Effect of ciprofloxacin on specific immune response in rabbits

Ciprofloxacin (10 mg/kg body weight, iv, twice daily for 4 days) failed to alter specific antibody titres, total immunoglobulin concentration, total serum protein concentration, total leukocyte count, lymphocyte percentage, phagocytic index and skin thickness in DNCB skin sensitivity test against Brucella plain killed antigen in New Zealand White rabbits. It can be concluded that ciprofloxacin at the dose and duration employed did not adversely affect specific immune response in normal rabbits.