Analysis of lactose metabolism in E.coli using reachability analysis of hybrid systems

We propose an abstraction method for medium-scale biomolecular networks, based on hybrid dynamical systems with continuous multi-affine dynamics. This abstraction method follows naturally from the notion of approximating nonlinear rate laws with continuous piecewise linear functions and can be easily automated. An efficient reachability algorithm is possible for the resulting class of hybrid systems. An efficient reachability algorithm is possible for the resulting class of hybrid systems. An approximation for an ordinary differential equation model of the lac operon is constructed, and it is shown that the abstraction passes the same experimental tests as were used to validate the original model. The well studied biological system exhibits bistability and switching behaviour, arising from positive feedback in the expression mechanism of the lac operon. The switching property of the lac system is an example of the major qualitative features that are the building blocks of higher level, more coarse-grained descriptions. The present approach is useful in helping to correctly identify such properties and in connecting them to the underlying molecular dynamical details. Reachability analysis together with the knowledge of the steady-state structure are used to identify ranges of parameter values for which the system maintains the bistable switching property.

Fractionated X-radiation treatment can elicit an inducible-like radioprotective response that is not dependent on the intrinsic cellular X-radiation resistance/sensitivity

Inducible responses are well documented to play a role in the radiation response of cells. However, it is not known whether clinically relevant fractionated X-radiation treatment could elicit an inducible-like radioprotective response and whether there is a direct correlation between the inducible radiation response phenomenon and the intrinsic radiation response of the cell. Therefore, the purpose of this study was to determine whether closely related human colorectal tumor (HCT116) clones treated with fractionated X rays could elicit an inducible-like radiation response to a subsequent acute (i.e. single) X-ray challenge, and whether the magnitude of the inducible-like response correlates with the intrinsic X-ray resistance of the responding clones. After fractionated X irradiation, only the radiosensitive clone showed enhanced clonogenic survival with a subsequent acute X-ray exposure. Cell cycle changes or the selection of subclones with increased intrinsic radiation resistance induced by the fractionated X rays were excluded as the basis of this enhanced tolerance, suggesting the presence of an inducible-like radioprotective response. Using the comet assay, we found similar amounts of intrinsic DNA damage among the clones after acute X irradiation. Our findings demonstrate that fractionated X-ray treatment can elicit an inducible-like radioprotective response and represent the first evidence that this response is independent of the intrinsic radiation resistance/sensitivity of the responding cells.

Endovascular repair of a recurrent aortocaval fistula and anastamotic false aneurysm

Aortocaval fistula (ACF) and false aneurysm are a recognized complication of open abdominal aortic aneurysm (AAA) repair. Untreated they are often fatal. However, open surgical repair of this complication is associated with a high operative mortality and a significant complication rate. Endovascular management using a stent-graft to exclude the false aneurysm and fistula is a technically feasible alternative and confers many advantages over open repair by virtue of its minimally invasive nature. We report the endovascular management of this rare but serious complication of open AAA repair.

Enhancement of ethyl propionate synthesis by poly (AAc-co-HPMA-cl-MBAm)-immobilized Pseudomonas aeruginosa MTCC-4713, exposed to Hg2+ and NH4+ ions

A purified alkaline thermo-tolerant bacterial lipase from Pseudomonas aeruginosa MTCC-4713 was immobilized on a poly (AAc-co-HPMA-cl-MBAm) hydrogel. The hydrogel-bound lipase achieved 93.6% esterification of ethanol and propionic acid (300 mM: 100 mM) into ethyl propionate at temperature 65 degrees C in 3 h in the presence of a molecular sieve (3 angstroms). In contrast, hydrogel-immobilized lipase pre-exposed to 5 mM of HgCl2 orNH4Cl resulted in approximately 97% conversion of reactants in 3 h into ethyl propionate under identical conditions. The salt-exposed hydrogel was relatively more efficient in repetitive esterification than the hydrogel-bound lipase not exposed to any of the cations. Moreover, bound lipase exposed Hg2+ or NH4+ ions showed altered specificity towards p-nitrophenyl esters and was more hydrolytic towards higher C-chain p-nitrophenyl esters (p-nitrophenyl laurate and p-nitrophenyl palmitate with C 12 and C 16 chain) than the immobilized lipase not exposed to any of the salts. The later showed greater specificity towards p-nitrophenyl caprylate (C 8).

Effect of estradiol on expression of cytoskeletal proteins during spermatogenesis in testis of sexually mature rats

Earlier studies had shown that long term treatment with estradiol arrests spermatogenesis in adult male rats, at a dose of 0.1 mg/kg/day. The present study was therefore undertaken to ascertain the causes underlying the reduction in sperm counts by administering estradiol for a short term, at the dose of 0.1 mg/kg/day. Estradiol valerate was injected at a dose of 0.1 mg/kg/day, for a period of 10 days to one group of adult male rats, which were administered saline for 12 days prior to estradiol injection, and sacrificed after 22 days. The control group was administered saline for 22 days. The sera were analyzed for testosterone and FSH levels. One testis of each male was immersion fixed for histology, and for immunohistochemistry of two testicular cytoskeletal proteins, vimentin and vinculin. The contralateral testes were used for analysis of vimentin and vinculin gene expression by reverse transcriptase polymerase chain reaction (RTPCR) and western blotting. Another group exposed to estradiol for 10 days was injected with bromodeoxyuridine (BrdU), at a dose of 100 mg/kg/day, to ascertain the effect on germ cell proliferation, and sacrificed 12 days later, while estradiol treatment was continued till sacrifice. BrdU, at a dose of 100 mg/kg/day was injected i.p. to a group of control rats treated with saline for 10 days, and sacrificed 12 days later. The testes from both groups were immersion fixed for immunohistochemical detection of BrdU. Histology of estradiol treated testis showed predominance of tubules with round spermatids with accumulation of lipid droplets in Sertoli cell cytoplasm and decreased cell height, whereas controls showed elongating spermatids. BrdU immunolocalization in the testis, irrespective of treatment, indicated its incorporation in deoxyribonucleic acid (DNA) suggesting that estradiol sustained germ cell proliferation. Both vimentin and vinculin could be immunolocalized to the testis. The testicular levels of vimentin and vinculin, quantified after western blotting, were unaffected. The testicular expression of vimentin and vinculin seen by RTPCR was also unaffected. The study suggested that estradiol induced reduction in sperm counts was not due to adverse effects on proliferation. The observed predominance of seminiferous tubules showing round spermatids, accumulation of lipid droplets as compared to controls suggested that reduction in elongated spermatids occurred through reduced spermiation and phagocytosis. The study also suggested that reduction in Sertoli cell height after short-term estradiol treatment was not due to reduced expression of vimentin and vinculin, which could be maintained by estradiol. However, reduction in Sertoli cell height could have been due to suppression of FSH and testosterone, implicated in the polymerization of vimentin and organization of vinculin, two cytoskeletal proteins involved in inter-Sertoli or Sertoli-germ cell junctions. The study suggested that disorganization of Sertoli cell cytoskeleton and reduction in the volume of Sertoli cells could be an important factor for reduced efficiency of spermatogenesis after exposure to estrogenic molecules.

Short chain fatty acids influence virulence properties of Salmonella enterica serovar Typhimurium

The present study investigated SCFA exposed Salmonella enterica serovar Typhimurium for its virulence characteristics such as mouse lethality adhesion, surface hydrophobicity, phagocytic uptake, intracellular survival within the murine peritoneal macrophages, induction of acid tolerance response (ATR), and the expression of outer membrane proteins (OMPs). Lethal dose (LD50) for mice was found to be more for SCFA exposed cells as compared to the normal cells. In vitro adherence to murine intestinal epithelial cells as well as surface hydrophobicity of SCFA exposed cells were found to be lower than the normal cells. Though the phagocytic uptake of normal cells and SCFA exposed cells was similar, the SCFA exposed cells exhibited increased intracellular survival as compared to the normal cells, which were completely killed after 4 h. Moreover, SCFA exposed cells also survived exposure to extremely low pH (3.0). Outer membrane proteins extracted from SCFA exposed cells revealed an enhanced expression of proteins (porins) at 4% SCFA concentration. Thus, SCFA exposure may contribute to enhanced virulence of Salmonella enterica serovar Typhimurium by increased intracellular survival, induction of acid tolerance response, and the enhanced expression of outer membrane matrix proteins (porins).

Acalculous biliary tract disorders: the value of fatty meal-cholescintigraphy

BACKGROUND

The management of patients with symptoms consistent with biliary tract disease but without evidence of cholelithiasis is difficult. This study was undertaken to test the value of cholescintigraphy in predicting the success of cholecystectomy in patients with acalculous biliary tract disorders.

MATERIAL AND METHODS

A prospective study was carried out on 73 patients presenting with recurrent upper quadrant pain without documented evidence of gallstones on ultrasound. Fatty meal-cholescintigraphy was performed on all patients and the gallbladder ejection fraction was calculated. Laparoscopic cholecystectomy was performed in patients with ejection fractions of <40%, followed by histopathological analysis and assessment of symptomatic improvement.

RESULTS

There were 43 men and 30 women with a mean age of 33.4 years. Forty-one patients had abnormal ejection fractions. All except one patient had a laparoscopic cholecystectomy. The pathological diagnosis of chronic cholecystitis was made in 33 patients and acute on chronic cholecystitis documented in four patients. Five patients had cholesterolosis and two of these had associated chronic cholecystitis. All except three patients had complete relief of symptoms post-operatively with a mean follow-up of 10 months.

CONCLUSION

Modified cholescintigraphy is a useful test for predicting which patients with acalculous biliary tract disease benefit from a cholecystectomy.

Comparison of the X-Radiation, Drug and Ultraviolet-Radiation Responses of Clones Isolated from a Human Colorectal Tumor Cell Line

We isolated several clones with a wide range of responses to X radiation from an unirradiated human colorectal (HCT 116) tumor cell line. The responses of one of these clones (HCT116-Clone10) and nine other clones to either fractionated or acute (i.e. single, nonfractionated doses) X irradiation in vitro was similar to that of the parental cell line. By contrast, after the same types of treatment, another clone (HCT116-Clone2) manifested a significantly increased survival whereas a third clone (HCT116-CloneK) manifested a significantly decreased survival relative to the parental cell line. This suggested that they were, respectively, a radioresistant and a radiosensitive clone. All three clones (clones 2, 10, K) retained their tumorigenic phenotype and formed tumors in nude mice. G-banding studies demonstrated that they were of human origin and were derived from the same parental cell line. The metaphases of HCT116-Clone2 demonstrated features commonly associated with genomic instability (i.e. mitotic catastrophe including chromosome and chromatid breaks, dicentrics and additional nonclonal markers). Data obtained by quantitative fluorescence in situ hybridization (Q- FISH) analysis failed to demonstrate any apparent correlation between the radiosensitivity and the relative telomere content of these three clones. Interestingly, HCT116-CloneK was the most resistant to several chemotherapeutic drugs (topotecan, camptothecin, etoposide and cisplatin) with diverse mechanisms of action. Also, there were no significant differences in the survivals of the three clones after treatment with UV radiation. Because of the lack of overlap among the relative sensitivities of these clones to X radiation, chemotherapeutic drugs and UV radiation, these clones may be useful models for evaluating the genetic basis of the response of human tumor cells to these treatment agents both in vitro and in vivo.

Drug susceptibility profiles of Mycobacterium tuberculosis isolates at Jaipur

PURPOSE

To find prevalence of drug resistance in Mycobacterium tuberculosis isolated from patients attending SMS Medical College, Jaipur during 1997-99.

METHODS

Sputum samples from 164 patients with pulmonary tuberculosis were processed and cultured on Lowenstein Jensen medium and M. tuberculosis isolates were tested for drug sensitivity.

RESULTS

M. tuberculosis was isolated in 122/164 (74.3%) samples and comprised 97.6% (122/125) of mycobacterial isolates. There were only three isolates of nontuberculous mycobacteria -one each of M. kansasii, M. avium and M. fortutium. Primary drug resistance in M. tuberculosis was estimated to be 3/44 (6.8%) to rifampicin, 6/44 (13.6%) to isoniazid and 2 strains (4.5%) were multi drug resistant i.e. resistant to both rifampicin and isoniazid. Among the isolates from cases with previous history of treatment of varying duration (acquired drug resistance) resistance to rifampicin was estimated to be 28.2% and for isoniazid to be 39.7%. 24.3% strains of these drug resistant isolates were multi drug resistant.

CONCLUSIONS

While this information may not reflect true prevalence of drug resistance in the region this may help in further planning long term surveillance studies to know the trend of drug resistance in this area.

The quality of hospital records of urethral catheterisation

BACKGROUND

This prospective and retrospective study carried out over a period of one month (50 patients) looked at the quality of hospital records of urethral catheterisation with reference to the hospital protocol. The patients were catheterised on general surgical wards as well as in theatre.

RESULTS

The quality of hospital records of this procedure was poor and a number of complications noted.

CONCLUSIONS

Good documentation of urethral catheterisation would result in a better quality of audit and, therefore, identify potential ways of minimising complications. We recommend this by regular audit of hospital records, re-inforcement of protocols and informed consent of this procedure, with particular reference to theatre.

Human bone marrow transplant rejection is associated with telomere cleavage

Telomeres that guard chromosomes are shortened with each cell division because of replication-dependent sequence loss at both termini. The gradual erosion of telomeric length has been directly related to the process of aging in vivo. Recently we have reported, in murine and human cancer cells treated with different apoptogens, cleavage and extrusion of telomeric DNA prior to cell death on one hand and an amplification of telomeric DNA in metastatic epithelial malignancies of different histopathologic origin on the other. This study tested our hypothesis that telomere cleavage is linked to transplant rejection in cancer patients receiving stem cells either from bone marrow (BM) or umbilical cord blood transfusion. Telomere integrity and mitotic catastrophe were studied by cytogenetic and molecular fluorescence in situ hybridization (FISH) techniques in two BM samples taken from a male stem cell transplant recipient diagnosed with aplastic anemia. The first BM sample, which was aspirated 27 days after transplant, was mitotically active. Only one of 50 metaphases showed a chromatid break. Every cell karyotyped was of male origin with 46, XY chromosome constitution. The second BM sample aspirated 52 days after transplant gave no metaphases and most interphase cells appeared dead. FISH preparations of the second BM sample showed cleavage and drastic reduction of telomeric DNA at the time the patient was rejecting the transplant. In contrast, the first BM sample had shown no indication of cleavage of the telomeric DNA, although the percentage of telomeric area was smaller than in the control. The replicative stress imposed on the stem cells engrafted may result in an accelerated aging effect, possibly due to the erosion of telomeric DNA. We, therefore, conclude that BM rejection could be directly associated with the cleavage, clustering, and extrusion of telomeric DNA in the donor cells.