Growth stimulation by serum in Entamoeba histolytica is associated with protein tyrosine dephosphorylation

Very little protein tyrosine phosphorylation was observed in growing (exponential-phase) Entamoeba histolytica cells by immunoblotting and quantitative immunofluorescence. After 1 h of serum deprivation, two proteins (42 and 38 kDa in SDS-PAGE) were tyrosine phosphorylated and two more proteins (96 and 63 kDa) also showed tyrosine phosphorylation when examined after 4 h of serum deprivation. Intense enhancements of anti-phosphotyrosine immunofluorescence levels were observed during this period of serum withdrawal. Membrane-associated tyrosine kinase activity reached a peak (3.5-fold increase) 1 h after serum deprivation and decreased thereafter reaching a basal level by 2 h of serum deprivation. Interestingly, tyrosine kinase activities remained unaffected by serum stimulation (2-60 min) of serum-deprived cells. Also, during this period of serum stimulation tyrosine phosphorylated proteins of serum-deprived cells were dephosphorylated. Tyrosine phosphatase activities were suppressed during serum deprivation and on serum addition to serum-deprived cells tyrosine phosphatase activities increased significantly. Our data attest that protein tyrosine phosphorylation was associated with growth inhibition of E. histolytica and serum stimulation of E. histolytica produced tyrosine phosphatase activation and protein tyrosine dephosphorylation.

Capturing the real value in high-tech acquisitions

Eager to stay ahead of fast-changing markets, more and more high-tech companies are going outside for competitive advantage. Last year in the United States alone, there were 5,000 high-tech acquisitions, but many of them yielded disappointing results. The reason, the authors contend, is that most managers have a shortsighted view of strategic acquisitions--they focus on the specific products or market share. That focus might make sense in some industries, where those assets can confer substantial advantages, but in high tech, full-fledged technological capabilities--tied to skilled people--are the key to long-term success. Instead of simply following the "buzz," successful acquires systematically assess their own capability needs. They create product road maps to identify holes in their product line. While the business group determines if it can do the work in-house, the business development office scouts for opportunities to buy it. Once business development locates a candidate, it conducts an expanded due diligence, which goes beyond strategic, financial, and legal checks. Successful acquires are focused on long-term capabilities, so they make sure that the target's products reflect a real expertise. They also look to see if key people would be comfortable in the new environment and if they have incentives to stay on board. The final stage of a successful acquisition focuses on retaining the new people--making sure their transition goes smoothly and their energies stay focused. Acquisitions can cause great uncertainty, and skilled people can always go elsewhere. In short, the authors argue, high-tech acquisitions need a new orientation around people, not products.

Prevalence of hepatitis B infection in the general population: a rural community based study

BACKGROUND

Available seroprevalence studies of hepatitis B in Indian population has limitations. A community based door to door epidemiological study was conducted between December 1997 and January 1988 to look for the dynamics of hepatitis B exposure in a single village of West Bengal.

METHODS

In all, 960 inhabitants out of 1261 (according to 91 census) in a village of Birbhum district in West Bengal were interviewed and their blood were tested by ELISA for HBV exposure. Odds ratio was calculated to estimate the relative risks for each potential factor facilitating virus transmission.

RESULTS

Participation rate in the present study was 76.1%. Over all HBsAg carrier rate was found to be 5.3%. Only 2/51 (3.9%) carriers were HBeAg positive. Injection by glass syringe (odds ratio = 3.01), age < 20 years (odds ratio = 1.41) and male sex (odds ratio = 1.57) were significant risk factor.

CONCLUSION

The results of this rural, predominantly poor, agrarian worker based community data reveals a fairly large reservoir of infection (5.3%). It is mainly built-up early in life. Injection practices need to be safer in addition to HBV vaccination to fight this menace.

Membrane anchoring of calnexin facilitates its interaction with its targets

Calnexin, a chaperone that resides in the endoplasmic reticulum, participates in the quality control function of this compartment. Many glycoproteins in the process of folding associate transiently with this chaperone via interactions involving the recognition of their mono-glucosylated glycans. Some misfolded proteins which are retained in the endoplasmic reticulum exhibit prolonged association with calnexin. We have examined whether the transmembrane and cytoplasmic domains of calnexin influence the association of this chaperone with its targets. Interactions of wild type and truncated calnexin with a glycoprotein that is retained in the endoplasmic reticulum (the lymphocyte tyrosine kinase, Ltk), with membrane IgM heavy chains, and with the MHC class I heavy chain protein were investigated. A soluble calnexin molecule lacking the transmembrane domain and cytoplasmic tail does not associate with any of these proteins. When a heterologous transmembrane domain is fused to the lumenal portion of calnexin, this membrane-bound protein can bind Ltk, IgM heavy chains, and MHC class I heavy chain proteins. These results suggest that calnexin must be membrane-anchored in order to recognize its substrates.

Effects of gonadotropins and prolactin on ovarian activity of a wild avian species, the tree pie Dendrocitta vagabunda

Ovine FSH (40: g per bird daily for 10 days) increased ovarian weight, follicular size, phosphatase activities, and RNA and protein levels in tree pie (Dendrocitta vagabunda), but exogenous ovine LH (40 micrograms per bird daily for 10 days) with the same dose and duration caused depletion of ovarian cholesterol and ascorbic acid concentrations with a rise in sialic acid and glycogen levels of the ovary. In contrast, prolactin (LTH: 5 I.U. per bird daily for 10 days) administration showed reverse biochemical changes to those of FSH. The findings suggest that FSH induces mainly ovarian follicular growth and LH stimulates ovarian steroidogenesis, but LTH is antigonadal in this wild avian species.

Response to low-dose interferon in chronic liver disease due to hepatitis B virus infection

BACKGROUND

Interferon is at present the only effective therapy for chronic hepatitis B virus (HBV) infection. Data regarding its efficacy in India are scant. The present study was undertaken to assess the efficacy of low-dose interferon in chronic liver disease due to HBV infection.

METHODS

Twenty four patients with histologic evidence of chronic hepatitis with or without cirrhosis, and persistent elevation of serum aminotransferases and persistent positivity for HBsAg and HBeAg for more than six months, were included. Fourteen patients were treated with interferon alpha-2b, 3 million units thrice weekly for 16 weeks; ten patients who could not afford the drug were followed up as controls without specific therapy. Patients were examined weekly for the first 4 weeks, followed by two weekly for 12 weeks and then every two months. Blood tests for viral markers and liver biochemistry were done at 0, 4, 8, 12, 16 weeks and then at two-month intervals for at least one year after therapy. Patients who cleared HBeAg were followed up for 2.2 (1-4) years for HBsAg clearance.

RESULTS

HBeAg clearance occurred in 9 patients (64%) in the interferon group, and in one control patient (p < 0.01). HBsAg clearance occurred in only one patient in the treatment group during follow up of mean 2.4 years. No patient in the control group cleared HBsAg. Patients having high ALT level at the beginning of treatment had significantly higher HBeAg clearance rate (7 of 7) than patients with low ALT levels (2 of 7; p < 0.05).

CONCLUSION

Low-dose interferon therapy is effective in attaining HBeAg, but not HBsAg, clearance in chronic HBV infection.

Why relapse occurs in PB leprosy patients after adequate MDT despite they are Mitsuda reactive: lessons form Convit's experiment on bacteria-clearing capacity of lepromin-induced granuloma

It is amazing how after years of scientific research and therapeutic progress many simple and basic questions about protective immunity against Mycobacterium leprae remain unanswered. Although the World Health Organization (WHO) has recommended short-term multidrug therapy (WHO/MDT) for the treatment of paucibacillary (PB) leprosy patients, from time to time several workers from different parts of the globe have reported inadequate clinical responses in a few tuberculoid and indeterminate leprosy patients following adequate WHO/MDT despite the fact that they are Mitsuda responsive. A few borderline tuberculoid patients harbor acid-fast bacilli (AFB) in their nerves for many years even though they become clinically inactive following MDT, a fact which has been ignored by many leprosy field workers. Keeping these patients in mind, we have attempted to investigate the cause of the persistence of AFB in PB cases and have looked into the question of why Mitsuda positivity in tuberculoid and indeterminate leprosy patients, as well as in healthy contacts, is not invariably a guarantee for protectivity against the leprosy bacilli. We have: a) analyzed the histological features of lepromin-induced granulomas, b) studied the bacteria-clearing capacity of the macrophages within such granulomas, and c) studied the in vitro leukocyte migration inhibition factor released by the blood leukocytes of these subjects when M. leprae sonicates have been used as an elicitor. The results of these three tests in the three groups of subjects have been compared and led us to conclude that the bacteria-clearing capacity of the macrophages within lepromin-induced granuloma (positive CCB test) may be taken as an indicator of the capability of elimination of leprosy bacilli and protective immunity against the disease. This important macrophage function is not invariably present in all tuberculoid and indeterminate leprosy patients or in all contacts even though they are Mitsuda responsive and are able to show a positive leukocyte migration inhibition (LMI) test. It is likely but not certain that this deficit of the macrophage is genetically predetermined and persists after completion of short-term WHO/MDT. Thus, after discontinuation of treatment slow-growing, persisting M. leprae multiply within macrophages leading to relapse.

Evaluation and progression analysis of pulmonary tuberculosis from digital chest radiographs

Pulmonary tuberculosis is one of the most common infections in the third world countries. We propose a method for automated evaluation and progression analysis of this disease by processing a sequence of digital chest radiographs. The presence of radiological features characteristic to pulmonary tuberculosis is detected within the regions of interest using suitable image processing and pattern recognition techniques. The detected features are then quantified to evaluate the extent of the disease. The measures are evaluated for a sequence of radiographs of a patient and are normalized with respect to rib size measures. Temporal changes in these normalized measures indicate the progression of the disease during the period in which the sequence of radiographs is obtained. The details of the proposed technique and results of analysis of a number of tuberculous patients are given in the paper.

A recursive algorithm for maximum likelihood-based identification of blur from multiple observations

A maximum likelihood-based method is proposed for blur identification from multiple observations of a scene. When the relations among the blurring functions are known, the estimate of blur obtained using the proposed method is very good. Since direct computation of the likelihood function becomes difficult as the number of images increases, we propose an algorithm to compute the likelihood function recursively.

On the dynamics of synaptic vesicles: effects on the rate of neurotransmitter release

Release of transmitter substances during synaptic communication in a biological process of great importance, and it is worthwhile to ascertain the basic molecular events underlying this process. We present a minimal model of synaptic vesicle (SV) dynamics, with which most of the major experimentally observed features of evoked neurotransmitter release can be reproduced. The effect of different parameters on the time course of evoked release as well as the effect of repetitive stimulation on this model system has been examined.

Robust detection of skew in document images

We describe a robust yet fast algorithm for skew detection in binary document images. The method is based on interline cross-correlation in the scanned image. Instead of finding the correlation for the entire image, it is calculated over small regions selected randomly. The proposed method does not require prior segmentation of the document into text and graphics regions. The maximum median of cross-correlation is used as the criterion to obtain the skew, and a Monte Carlo sampling technique is chosen to determine the number of regions over which the correlations have to be calculated. Experimental results on detecting skews in various types of documents containing different linguistic scripts are presented here.

Changes in thyroid activity during the annual sexual cycle of a wild avian species, the tree pie Dendrocitta vagabunda

Thyroid activity was studied during the annual gonadal cycle in both sexes of the tree pie (Dendrocitta vagabunda). The study was conducted once a month throughout the year by evaluating thyroid weight, epithelial height and peroxidase activity. The values of these parameters moderately increased during the progressive phase, maximally increased during breeding, decreased in the regression phase and decreased further during the non-breeding phase in both sexes of birds. The findings indicate that thyroid activity, probably including thyroxine synthesis, varies annually, being highest during breeding compared to other phases of the gonadal cycle and that, there may be a progonadal relationship of the thyroid gland in both sexes of the tree pie.

Sequences directing C to U editing of the plastid psbL mRNA are located within a 22 nucleotide segment spanning the editing site

In plastids, editing of an ACG codon to an AUG codon creates the translation initiation codon for the psbL and ndhD transcripts in tobacco. To identify the RNA segment required for psbL editing, chimeric kanamycin resistance genes were constructed containing psbL deletion derivatives, and tested in vivo for editing in transgenic plants. We report here that a 22 nucleotide segment is sufficient to direct efficient psbL editing, including 16 nucleotides upstream and five nucleotides downstream of the editing site. Mutation of the A nucleotide to a C upstream of the editing site completely abolished editing, while mutation of the downstream G to a C only reduced the editing efficiency. Out of the 22 nucleotide editing target sequence, the 16 upstream nucleotides were found to compete with the endogenous psbL transcript for a depletable trans-factor. To test whether editing of initiation codons involves a common trans-factor, a chimeric gene containing the ndhD editing site was expressed in tobacco plastids. As for psbL, editing of the ndhD site requires a depletable trans-factor. However, the ndhD trans-factor is distinct from that required for psbL editing. Distinct cissequences and trans-factor requirements for the psbL and ndhD editing sites indicate an individual recognition mechanism for the editing of plastid initiation codons.