Genetic stability in rice micropropagation

An efficient clonal propagation procedure for six rice varieties cultivated in Argentina was developed by using shoot tip cultures, and the genetic stability of the micropropagated plants was verified by isozyme analysis. One week old seedlings obtained on MS medium were sectioned and subcultured on MS medium (0.75% agar) supplemented with different combination and concentrations of cytokinins (BAP and KIN) and auxins (2,4-D and NAA). After four weeks of culture, multiple shoots were obtained. The best response was observed on MS supplemented with BAP 5 mg l(-1). Shoot clumps were multiplied in MS liquid medium containing BAP 5 mg l(-1). Profuse rooting was obtained after transfer to MS medium lacking growth regulators and with sucrose 8% (w/v). Complete plants were successfully transferred to soil and grown to maturity. ADH and EST patterns of micropropagated rice plants showed polymorphisms compared with plants of the original varieties. However, the zymograms of the seed derived progeny of the micropropagated plants were similar to that of the original varieties. These results indicate the maintenance of the genetic stability in the sexual progeny of micropropagated plants.

DataGrid, prototype of a biomedical grid

BACKGROUND

The availability of large amounts of data in heterogeneous formats and the rapid progress in fields such as computer based drug design, medical imaging and medical simulations have lead to a growing demand for large computational power and easy accessibility to heterogeneous data sources.

OBJECTIVES

The goal is to address these needs by deploying computing grids. Grids provide both large scale and distributed storage facilities and an increased computing power. Moreover, Grids are a promising tool to foster the synergy between bioinformatics and computerised medical imaging.

METHODS

A first biomedical grid is being deployed within the framework of the DataGrid IST project (http://www.edg.org). The goal of the project is to provide a novel environment to support globally distributed scientific exploration involving up to multi-Perabyte datasets.

RESULTS AND CONCLUSIONS

The first biomedical applications deployed inside the project demonstrate the relevance of the grid paradigm for genomics and medical image processing. They also highlight the specific requirements of the biomedical community.

Cytoplasm of sea urchin unfertilized eggs contains a nucleosome remodeling activity

After fertilization the sea urchin sperm nucleus transforms into the male pronucleus which later fuses with the female pronucleus re-establishing the diploid genome of the embryo. This process requires remodeling of the sperm chromatin structure including the replacement of the sperm histones by maternally derived cleavage stage histone variants. In recent years, a group of protein complexes that promote chromatin-remodeling in an ATP-dependent manner have been described. To gain understanding into the molecular mechanisms operating during sea urchin male pronuclei formation, we analyzed whether chromatin-remodeling activity was present in unfertilized eggs as well as during early embryogenesis. We report that in the sea urchin Tetrapygus niger, protein extracts from the cytoplasm but not from the nucleus, of unfertilized eggs exhibit ATP-dependent nucleosome remodeling activity. This cytosolic activity was not found at early stages of sea urchin embryogenesis. In addition, by using polyclonal antibodies in Western blot analyses, we found that an ISWI-related protein is primarily localized in the cytoplasm of the sea urchin eggs. Interestingly, SWI2/SNF2-related proteins were not detected neither in the nucleus nor in the cytoplasm of unfertilized eggs. During embryogenesis, as transcriptional activity is increased an ISWI-related protein is found principally in the nuclear fraction. Together, our results indicate that the cytoplasm in sea urchin eggs contains an ATP-dependent chromatin-remodeling activity, which may include ISWI as a catalytic subunit.

Developmentally-regulated interaction of a transcription factor complex containing CDP/cut with the early histone H3 gene promoter of the sea urchin Tetrapygus niger is associated with changes in chromatin structure and gene expression

During sea urchin embryogenesis the early histone genes are temporally expressed to accommodate the high demand for histone proteins during DNA replication at early cleavage stages of development. The early histone genes are transcriptionally active from the 16-cell stage, reaching a peak in expression at the 128-cell stage that gradually decreases until expression is completely inhibited at the late blastula stage. We are studying the gene regulatory mechanisms that control early histone gene expression in sea urchins to understand the interrelationships between chromatin remodeling and transcriptional activation during development. Here, we have investigated chromatin organization and transcription factor interactions by analyzing nuclease hypersensitivity and protein binding in the promoter region of the early histone H3 gene from the sea urchin Tetrapygus niger. We have found a DNase I hypersensitive domain centered at -90 in the early histone H3 gene promoter which is only detected in embryos at the 128-cell stage expressing high levels of early histone H3 mRNA. This hypersensitive site (-110 to -70) encompasses two regulatory elements (TnH3NFH3.1 and TnH3CCAAT). The -94 to -77 region of the histone H3 promoter is recognized by a transcription factor complex in nuclear extracts from 128-cell embryos. Methylation interference analysis and competition studies demonstrated a specific interaction at the CCAAT sequence. Using specific antibodies we find that the homeodomain transcription factor CDP/cut is the DNA-binding component of the complex interacting with the early histone H3 gene promoter in T. niger. Our results provide further evidence for the functional role of CDP/cut in developmental regulation of histone gene expression in phylogenetically diverse eukaryotic species.

A clinic-based molecular epidemiologic study of tuberculosis in Monterrey, Mexico

SETTING

A tuberculosis clinic associated with a university hospital in Monterrey, Mexico, an urban community with high tuberculosis incidence.

OBJECTIVE

To determine the diversity of DNA fingerprint patterns and the extent of drug resistance of Mycobacterium tuberculosis isolates from patients who attended the clinic.

DESIGN

Isolates of M. tuberculosis obtained from 186 patients during the period from 31 January 1996 to 31 March 1998 were tested for susceptibility to isoniazid, rifampicin, ethambutol and streptomycin. Demographic data and the social history of each patient were obtained prospectively by interview. The IS6110 DNA fingerprints were obtained for 166 of the 186 isolates. Secondary typing was carried out on isolates with fewer than six copies of IS6110.

RESULTS

Thirty-two per cent of the tested isolates (60/ 186) were drug-resistant, and 18% (33/186) were multidrug-resistant. Approximately 55% of the resistant isolates (33/60) were attributed to acquired resistance. A total of 106 different IS6110 fingerprint patterns were observed among the 166 fingerprinted isolates. Based on both IS6110 and pTBN12 fingerprinting, 65 (39%) of the 166 isolates were part of 22 DNA fingerprint clusters. Various drug susceptibility patterns were seen in most clusters.

CONCLUSION

Fingerprint clustering indicates extensive recent transmission of tuberculosis in patients attending the clinic. The prevalence of drug-resistant tuberculosis is high.

Characterization of the lactic acid bacteria in ewe's milk and cheese from northwest Argentina

Indigenous lactic acid bacteria in ewe's milk and artisanal cheese were studied in four samples of fresh raw milk and four 1-month-old cheeses from the provinces of northwest Argentina. Mean growth counts on M17, MRS, and MSE agar media did not show significant differences (P < 0.05) in raw milk and cheeses. Isolates of lactic acid bacteria from milk were identified as Enterococcus (48%), lactococci (14%), leuconostocs (8%), and lactobacilli (30%). All lactococci were identified as Lactococcus lactis (subsp. lactis and subsp. cremoris). Lactobacilli were identified as Lactobacillus plantarum (92%) and Lactobacillus acidophilus (8%). Enterococci (59%) and lactobacilli (41%) were isolated from cheeses. L. plantarum (93%), L. acidophilus (5%), and Lactobacillus casei (2%) were most frequently isolated. L. lactis subsp. lactis biovar diacetylactis strains were considered as fast acid producers. L. lactis subsp. cremoris strains were slow acid producers. L. plantarum and L. casei strains identified from the cheeses showed slow acid production. The majority of the lactobacilli and Lactococcus lactis strains utilized citrate and produced diacetyl and acetoin in milk. Enzyme activities (API-ZYM tests) of lactococci were low, but activities of L. plantarum strains were considerably higher. The predominance of L. plantarum in artisanal cheese is probably important in the ripening of these cheeses due to their physiological and biochemical characteristics.

Occludin localization at the tight junction requires the second extracellular loop

Occludin is a transmembrane protein of the tight junction with two extracellular loops. Our previous demonstration that the extracellular loops are adhesive suggested the possibility that they contribute to localizing occludin at the tight junction. To address this question, truncated forms of occludin were generated in which one or both of the extracellular loops were deleted. These constructs were expressed in both occludin-null Rat-1 fibroblasts and in MDCK epithelial cells. The patterns of sensitivity to proteinase K suggested all constructs were present on the plasma membrane and retained the normal topology. In fibroblasts, all truncated forms of occludin colocalized with ZO-1 at regions of cell-cell contact, demonstrating that even in the absence of tight junctions cytoplasmic interactions with ZOs is sufficient to cluster occludin. In MDCK cell monolayers, both full-length and occludin lacking the first extracellular loop colocalized with ZO-1 at the tight junction. In contrast, constructs lacking the second, or both, extracellular loops were absent from tight junctions and were found only on the basolateral cell surface. By freeze-fracture electron microscopic analysis, overexpression of full length occludin induced side-to-side aggregation of fibrils within the junction, while excess occludin on the lateral membrane did not form fibrils. These results suggest that the second extracellular domain is required for stable assembly of occludin in the tight junction and that occludin influences the structural organization of the paracellular barrier.

Interaction of CBF alpha/AML/PEBP2 alpha transcription factors with nucleosomes containing promoter sequences requires flexibility in the translational positioning of the histone octamer and exposure of the CBF alpha site

Chromatin remodeling at eukaryotic gene promoter sequences accompanies transcriptional activation. Both molecular events rely on specific protein-DNA interactions that occur within these promoter sequences. Binding of CBFalpha/AML/PEBP2alpha (core binding factor alpha/acute myelogenous leukemia/polyoma enhancer binding protein 2alpha) proteins is a key event in both tissue-specific and developmentally regulated osteocalcin (OC) promoter activity. To address linkage between chromatin organization and transcription factor binding, we reconstituted segments of the rat OC gene proximal promoter into mononucleosomes and studied binding of CBFalpha proteins. We analyzed binding of bacterially produced Cbfalpha2Alpha and Cbfalpha2B, two splice variants of the human CBFalpha2 gene, and determined the effect of heterodimerization with the Cbfbeta subunit on binding activity. Our results indicate that binding of the truncated Cbfalpha2A protein to naked DNA is independent of Cbfbeta whereas Cbfalpha2A binding to nucleosomal DNA was enhanced by Cbfbeta. In contrast, the Cbfalpha2B interaction with either naked or nucleosomal DNA was strongly dependent on heterodimerization with the Cbfbeta subunit. Additionally, our results demonstrate that both Cbfalpha2A alone and Cbfalpha2B complexed with Cbfbeta can interact with nucleosomal DNA only if there is a degree of flexibility in the positioning of the histone octamer on the DNA fragment and exposure of the CBFalpha site. This situation was achieved with a DNA segment of 182 bp from the rat OC promoter that preferentially positions mononucleosomes upstream of the CBFalpha binding site and leaves this element partially exposed. Taken together, these results suggest that nucleosomal translational positioning is a major determinant of the binding of CBFalpha factors to nucleosomal DNA.

Bioavailability of praziquantel increases with concomitant administration of food

In the present study we found that after a single oral dose of 1,800 mg of praziquantel, following a high-lipid diet and a high-carbohydrate diet, the maximum levels in plasma increased 243 and 515% and the area under the plasma concentration curve from 0 to 8 h increased 180 and 271%, respectively.

Bioequivalence study of paracetamol tablets: in vitro-in vivo correlation

The bioequivalence of three chemically equivalent paracetamol generic Mexican products (500 mg tablets) was evaluated in 12 healthy volunteers using the American innovator product (Tylenol, McNeil, Fort Washington, PA), as the reference. Single oral doses of each product were administered at 1-week intervals using a 4 x 4 Latin square design balanced for the first residual effect. The total amount of paracetamol excreted in urine in 24 hr was taken as a measure of bioavailability. In addition, moment analysis was used to estimate in vitro mean dissolution time (MDT) from dissolution profiles obtained following the USP 23 dissolution test specified for paracetamol tablets and to estimate in vivo mean residence time (MRT) from urinary excretion data. Significant differences in the dissolution performance and in the cumulative amount of paracetamol excreted in urine up to 24 hr were observed when the data were analyzed by analysis of variance (ANOVA) (p < .05). Classical and Westlake 90% confidence limits, as well as the two-sided t test proposed by Schuirmann, and the Anderson-Hauck power analysis supported the final conclusion that only one of the three generic paracetamol products studied can be considered equivalent to the reference product Tylenol. A linear correlation between in vitro MDT and in vivo MRT was found.

[A short praziquantel regimen for the treatment of parenchymatous neurocysticercosis]

OBJECTIVE

Fifteen-day praziquantel therapy for parenchymal neurocysticercosis has been shown to be effective. Plasma and cerebrospinal fluid concentrations of praziquantel peak two hours after administration. Maintenance of high concentrations of the drug for six hours may be an adequate therapy for the disease.

METHODS

Thirty patients with parenchymal neurocysticercosis were treated with three oral doses of praziquantel(25 mg/kg) at two-hour intervals. Intramuscular dexamethasone (10 mg/day) was administered for three days after the praziquantel treatment.

RESULTS

Cysts disappeared in 21 patients and showed a decrease in number of 30 to 60% in seven patients. Two patients remained without change. Considering the total number of cysts, this therapy showed a 70.7% eradication rate. Two patients had seizures, six reported headache, and nausea was frequently reported. Patients under antiepileptic treatment did not have seizures.

CONCLUSION

The cost and duration of treatment with praziquantel were significantly reduced and the inflammation that follow the destruction of the parasite was treated sequentially.

[Factors affecting the trans-endothelial accumulation of atherogenic plasma proteins in artery walls]

Our experiments were done to find out whether there are factors which influence the passage of the two major "risk factor proteins" LDL and fibrinogen, other than their plasma concentrations, from the blood into the arterial walls, where their accumulation is associated with atherogenesis. The results suggest that administration of a remarkable variety of pressor agents over a few days accelerate the uptake of both proteins by arterial walls, and that, in contrast, the process is no faster in rats that have been spontaneously, i.e., genetically, hypertensive for about 3 months. Considering our experimental findings in relation to human atherosclerotic disease, it is interesting that the risk of coronary heart disease and stroke is increased more than additively when both LDL or fibrinogen levels and systolic or diastolic blood pressures are high (18,46). If our work should point to some mechanistic connection between blood pressure and the accumulation of atherogenic plasma proteins in arterial walls, it would provide, at least in principle, an explanation for the epidemiological facts.