Uracil-DNA glycosylase-deficient yeast exhibit a mitochondrial mutator phenotype

Mutations in mitochondrial DNA (mtDNA) have been reported in cancer and are involved in the pathogenesis of many mitochondrial diseases. Uracil-DNA glycosylase, encoded by the UNG1 gene in Saccharomyces cerevisiae, repairs uracil in DNA formed due to deamination of cytosine. Our study demonstrates that inactivation of the UNG1 gene leads to at least a 3-fold increased frequency of mutations in mtDNA compared with the wild-type. Using a Ung1p-green fluorescent protein (GFP) fusion construct, we demonstrate that yeast yUng1-GFP protein localizes to both mitochondria and the nucleus, indicating that Ung1p must contain both a mitochondrial localization signal (MLS) and a nuclear localization signal. Our study reveals that the first 16 amino acids at the N-terminus contain the yUng1p MLS. Deletion of 16 amino acids resulted in the yUng1p-GFP fusion protein being transported to the nucleus. We also investigated the intracellular localization of human hUng1p-GFP in yeast. Our data indicate that hUng1p-GFP predominantly localizes to the mitochondria. Further analysis identified the N-terminal 16 amino acids as important for localization of hUng1 protein into the mitochondria. Expression of both yeast and human UNG1 cDNA suppressed the frequency of mitochondrial mutation in UNG1-deficient cells. However, expression of yUNG1 in wild-type cells increased the frequency of mutations in mtDNA, suggesting that elevated expression of Ung1p is mutagenic. An increase in the frequency of mitochondrial mutants was also observed when hUNG1 site-directed mutants (Y147C and Y147S) were expressed in mitochondria. Our study suggests that deamination of cytosine is a frequent event in S.cerevisiae mitochondria and both yeast and human Ung1p repairs deaminated cytosine in mitochondria.

Pyridoxine-dependent seizures: a case report and a critical review of the literature

Pyridoxine-dependent seizures are a recognized, although rare, cause of intractable seizures in neonates. Patients with this autosomal recessive disorder have recurrent seizures that are resistant to conventional anticonvulsants but respond dramatically to intravenous administration of pyridoxine. Life-long supplementation with pyridoxine is required to prevent seizure recurrence. In the absence of a biological marker for the disease, clinical diagnosis is often delayed and severe neurological sequelae are common. Herein, we report on the clinical course of a neonate with pyridoxine-dependent seizures. Delayed normalization of the electroencephalogram and a normal developmental outcome (at 15 months of age) on a dose of 10 mg/kg pyridoxine are distinctive features of the present case. We also review recent clinical observations and neurochemical studies that have added to our knowledge of this disorder.

Validation of a modified GTNM classification in peri-junctional oesophago-gastric carcinoma and its use as a prognostic indicator

AIM

A modified GTNM classification (with additional T and N subdivisions) has been used for many years. The aim of this paper was to validate this classification in a group of patients with oesophago-gastric carcinoma and to see if the more detailed information may be useful.

METHOD

The 3-year survival of 139 consecutive patients who survived resection has been related to the individual values of the modified and international classifications.

RESULTS

A step-wise reduction in the survival was found with increasing values of G, T, N and M. The international T3 value yielded a 17.7% survival rate, when subdivided, rates of 37.5%, 17.3% and 3.2% were found. The international N1 value yielded a rate of 12.9% which subdivided into rates of 25.0%, 18.7% and 7.5%.

CONCLUSION

If these results are repeated in a larger and more detailed study, this modified classification may provide added information when discussing prognosis and management.

Prevalence of self-reported symptoms of reproductive tract infections among recently pregnant women in Uttar Pradesh, India

This study examines the prevalence of self-reported reproductive tract infections (RTIs) and treatment seeking among married, recently pregnant women in Uttar Pradesh state, India. Associations between RTI symptom reporting and background characteristics are examined in a population-based sample of 18,506 married women with a pregnancy in the 3 years prior to a 1995 statewide survey. Logistic regression analyses are used to assess the effects of sociodemographic covariates on the probability of reporting an RTI symptom. Nearly one out of four women reports experiencing at least one RTI symptom, with the most common symptoms being abnormal vaginal discharge and pain during urination. Reporting of RTI symptoms significantly increases if the woman's last pregnancy did not end in a live birth or if she has low economic status. Symptom reports also increase with age and decrease with parity. Only one-third of women reporting an RTI symptom sought treatment. The results indicate that survey interviews can be a cost-effective option for measuring the magnitude of RTI symptoms experienced and identifying sociodemographic influences. The findings suggest the need for improved RTI screening procedures and treatment at health facilities in this populous state of northern India.

Antigens of Mycobacterium tuberculosis expressed during preclinical tuberculosis: serological immunodominance of proteins with repetitive amino acid sequences

Four antigens of Mycobacterium tuberculosis that are expressed in vivo after aerosol infection but prior to the development of clinical tuberculosis (TB) in rabbits were identified by immunoscreening of an expression library of M. tuberculosis genomic DNA with sera obtained 5 weeks postinfection. Three of the proteins identified, PirG (Rv3810), polymorphic GC-repetitive sequence (PE-PGRS; Rv3367), and proline-threonine repetitive protein (PTRP) (Rv0538), have multiple tandem repeats of unique amino acid sequences and have characteristics of surface or secreted proteins. The fourth protein, MtrA (Rv3246c), is a response regulator of a putative two-component signal transduction system, mtrA-mtrB, of M. tuberculosis. All four antigens were recognized by pooled sera from TB patients and not from healthy controls, confirming their in vivo expression during active infection in humans. Three of the antigens (PE-PGRS, PTRP, and MtrA) were also recognized by retrospective preclinical TB sera obtained, prior to the clinical manifestation of TB, from human immunodeficiency virus-TB patients, suggesting that they are potential candidates for devising diagnostic tests for active, preclinical TB.

HNPCC mutations in the human DNA mismatch repair gene hMLH1 influence assembly of hMutLalpha and hMLH1-hEXO1 complexes

Hereditary nonpolyposis colorectal cancer (HNPCC) is a common inherited form of neoplasia caused by germline mutations in DNA mismatch repair (MMR) genes. MMR proteins have been reported to associate with several proteins, including the human exonuclease 1 (hEXO1). We report here novel HNPCC-hMLH1 mutant proteins (T117M, Q426X and 1813insA) in Danish HNPCC patients. We demonstrate that these mutant HNPCC-hMLH1 proteins are unable to form complexes with hEXO1 and hPMS2 in vivo. The results indicate that mutations found in HNPCC gene carriers disrupt hMLH1-hEXO1 complex formation and hMutLalpha heterodimer assembly essential for MMR activity.

Inactivation of Saccharomyces cerevisiae OGG1 DNA repair gene leads to an increased frequency of mitochondrial mutants

The OGG1 gene encodes a highly conserved DNA glycosylase that repairs oxidized guanines in DNA. We have investigated the in vivo function of the Ogg1 protein in yeast mitochondria. We demonstrate that inactivation of ogg1 leads to at least a 2-fold increase in production of spontaneous mitochondrial mutants compared with wild-type. Using green fluorescent protein (GFP) we show that a GFP-Ogg1 fusion protein is transported to mitochondria. However, deletion of the first 11 amino acids from the N-terminus abolishes the transport of the GFP-Ogg1 fusion protein into the mitochondria. This analysis indicates that the N-terminus of Ogg1 contains the mitochondrial localization signal. We provide evidence that both yeast and human Ogg1 proteins protect the mitochondrial genome from spontaneous, as well as induced, oxidative damage. Genetic analyses revealed that the combined inactivation of OGG1 and OGG2 [encoding an isoform of the Ogg1 protein, also known as endonuclease three-like glycosylase I (Ntg1)] leads to suppression of spontaneously arising mutations in the mitochondrial genome when compared with the ogg1 single mutant or the wild-type. Together, these studies provide in vivo evidence for the repair of oxidative lesions in the mitochondrial genome by human and yeast Ogg1 proteins. Our study also identifies Ogg2 as a suppressor of oxidative mutagenesis in mitochondria.

Characterization of a two-component system, devR-devS, of Mycobacterium tuberculosis

By subtractive hybridization, we isolated genes, differentially expressed in virulent strain (dev), that are expressed at higher levels in the virulent Mycobacterium tuberculosis H37Rv strain in comparison to its avirulent counterpart, H37Ra, and consequently may be associated with the virulence phenotype of M. tuberculosis. A two-component system, devR-devS, was identified by DNA sequencing of a dev clone. DevR, the predicted gene product of devR, is a response regulator (RR) in the NarL/ UhpA subfamily of two-component systems. The devS gene product displayed homology with histidine protein kinases (HPKs) including UhpB, NarX and NarQ. The devR-devS locus is preceded by gene Rv3134c that encodes a putative alanine-aline- rich protein. This locus was conserved in M. tuberculosis and M. bovis BCG but not in other mycobacteria. A devR -lacZ transcription fusion demonstrated beta-galactosidase activity in M. smegmatis and in M. tuberculosis. The devR and devS genes were cotranscribed and the levels of their transcripts were lower in two isolates of the avirulent H37Ra strain in comparison to the virulent H37Rv strain of M. tuberculosis. The level of DevR protein was also lower in one of the H37Ra strains in comparison to the H37Rv strain. However, in a third isolate of H37Ra, RNA and protein expression was equivalent to that in the H37Rv strain. Electron microscopic immunogold analysis of M. tuberculosis grown in laboratory medium and within human monocytes revealed specific labelling for DevR protein within the bacteria and the phagosomal lumen of infected monocytes. These findings collectively suggest a potential role for devR-devS in the regulation of genetic programmes unique to the tubercle bacillus.

Human homolog of the MutY repair protein (hMYH) physically interacts with proteins involved in long patch DNA base excision repair

The human MutY homolog (hMYH) is a DNA glycosylase involved in the removal of adenines or 2-hydroxyadenines misincorporated with template guanines or 7,8-dihydro-8-oxodeoxyguanines. hMYH is associated in vivo with apurinic/apyrimidinic endonuclease (APE1), proliferating cell nuclear antigen (PCNA), and replication protein A (RPA) in HeLa nuclear extracts as shown by immunoprecipitation and Western blotting. However, binding of hMYH to DNA polymerases beta and delta was not detected. By using constructs containing different portions of hMYH fused to glutathione S-transferase, we have demonstrated that the APE1-binding site is at a region around amino acid residue 300, that the PCNA binding activity is located at the C terminus, and that RPA binds to the N terminus of hMYH. A peptide consisting of residues 505-527 of hMYH that contains a conserved PCNA-binding motif binds PCNA, and subsequent amino acid substitution identified Phe-518 and Phe-519 as essential residues required for PCNA binding. RPA binds to a peptide that consists of residues 6-32 of hMYH and contains a conserved RPA-binding motif. The PCNA- and RPA-binding sites of hMYH are further confirmed by peptide and antibody titration. These results suggest that hMYH repair is a long patch base excision repair pathway.

Quality of underground waters of semi-arid tract and their impact on soil

Fifty eight (58) irrigation water samples were collected from 58 villages of Chirawa Block, Jhunjhunu district. The cations and anions in irrigation waters were found in the order of Na+ > Cl- > CO3(2+) + HCO3 > Ca2+ (+) Mg2+ > SO4(2)- > K+. SAR and RSC of the waters ranged between 2.54 to 17.21 and 0.10 to 6.0 meq/l, respectively. pHc and adj. SAR of the waters ranged between 7.1 to 8.2 and 4.0 to 36.0 respectively. EC of irrigation water has significant positive non-significant correlation with EC of soil and weak positive correlation with pH of soil. Significant positive correlation was found in SAR (0.53) and RSC (0.47) of irrigation water with pH of soil.

The Saccharomyces cerevisiae Sln1p-Ssk1p two-component system mediates response to oxidative stress and in an oxidant-specific fashion

Aerobic organisms experience oxidative stress due to generation of reactive oxygen species during normal aerobic metabolism. In addition, environmental gamma and UV radiation, as well as several chemicals also generate reactive oxygen species, which induce oxidative stress. Thus oxidative stress constitutes a major threat to organisms living in aerobic environments. Oxidative stress induces the expression of several genes in yeast Saccharomyces cerevisiae. However, the primary sensor(s) that trigger the response is unknown. This study demonstrates that primary sensors of osmotic stress, the Sln1p-Ssk1p two-component proteins, are involved in sensing oxidative stress specifically induced by hydrogen peroxide and diamide, but not by other oxidants used in the study. Wild type and sln1-ssk1 mutant were treated with hydrogen peroxide, diamide, menadione, UV, and gamma-radiation. Results show that sln1-ssk1 mutant is only sensitive to hydrogen peroxide and diamide but not to other oxidants. S. cerevisiae contains an additional cell surface osmosensor, Sho1p, that targets the osmotic signal to Hog1p. Data is presented that shows Sho1 and Hog1 proteins are also involved in signaling oxidant-specific cellular damage. Furthermore, it is demonstrated that expression of the mammalian homolog of Hog1p provides protection from oxidative stress induced by hydrogen peroxide. These results suggest that Sln1p-Ssk1p and Sho1p signal transduction pathways participate in oxidative stress response. However, this response to oxidative stress is limited to specific oxidants.

Use of herbal therapies by adults seen in an ambulatory care research setting: an exploratory survey

OBJECTIVE

To identify and characterize patterns of use of herbal products among patients participating in selected research clinics.

DESIGN

Survey of three National Institutes of Health (NIH) ambulatory care research clinics.

SUBJECTS

Convenience sample of 490 adult patients (168 male, 322 female) attending rheumatology, liver, and endocrinology/metabolic research clinics.

RESULTS

Of the patients surveyed, 16.7%: (n = 82) reported using herbs. There were no significant sociodemographic differences between herb and nonherb users. Indications for herb use differed among the disease groups; patients in the endocrine and rheumatology clinics were taking herbs predominantly for "energy" or "wellness"; those attending the liver clinic tended to use herbal therapies as treatment for their disease. Mean and median monthly expenditure for herbal products was $30 and $10, respectively. There was a significant positive correlation between number of herbs used and use of other dietary supplements (p < 0.0001).

CONCLUSIONS

One in six patients in ambulatory clinical research settings may be taking herbal products in addition to prescribed treatment. This figure is lower than in the general population, possibly because the patients may stop using herbs when participating in a research project. Although empirical evidence on the beneficial or adverse effects of herb therapy alone or in combination with drug therapies is limited, clinical researchers should be aware of the potential for confounding clinical trial results.

Assessment of oxidative stress and effect of antioxidant supplementation during radiotherapy in carcinoma of upper digestive tract

Oxidative stress was studied by estimating plasma levels of malondialdehyde (MDA), beta carotene, vitamin E and erythrocytic superoxide dismutase(E-SOD) activity in 50 cases of carcinoma of upper digestive tract which included carcinoma of oral cavity, pharynx and oesophagus. While plasma MDA level was found to be increased (3.5±1.0 nmole/ml), a significant decrease in beta carotene (81.2±14.5mg%), vitamin E (8.5±1.1 mg/L) level and E-SOD activity (657.0±80.6 U/G Hb) were observed in carcinoma of upper digestive tract. Patients were treated with radiotherapy which itself was toxic enough and produced its deleterious effects by generation of reactive oxygen species (ROS). As antioxdiants can detoxify ROS, beneficial effect if any, of antioxidant administration during radiotherapy was studied in two groups of patients, group A (n=5, supplemented with antioxidants) and group B (n=5, without antioxidant supplementation). Plasma MDA level was found to be elevated in both the groups but the increase in group B was significant, compared to pretreatment level. Further, body weight was found to be significantly decreased in group B patients, which was maintained in group A patients. Moreover, group A patients showed significant elevation in beta carotene concentration, thus showing beneficial effect of administration of antioxidants during radiotherapy without disturbing the desirable therapeutic effect of radiotherapy.

Fluorescence polarization for monitoring ribozyme reactions in real time

Fluorescence polarization has been used recently to monitor diverse macromolecular interactions. In this report, the application of fluorescence polarization has been extended to monitor ribozyme reactions in real time. With fluorescently labeled substrate RNAs, group I ribozyme ligation and hammerhead ribozyme cleavage reactions were studied by fluorescence polarization in substrate excess (multiple turnover) conditions. These results also show that fluorescently labeled RNAs remain active substrates for ribozymes. Furthermore, a direct comparison of fluorescence polarization with fluorescence resonance energy transfer showed that both techniques were comparable for monitoring ribozyme reactions.

The human cyclin B1 protein modulates sensitivity of DNA mismatch repair deficient prostate cancer cell lines to alkylating agents

DNA damage caused by alkylating agents results in a G2 checkpoint arrest. DNA mismatch repair (MMR) deficient cells are resistant to killing by alkylating agents and are unable to arrest the cell cycle in G2 phase after alkylation damage. We investigated the response of two MMR-deficient prostate cancer cell lines DU145 and LNCaP to the alkylating agent MNNG. Our studies reveal that DU145 cancer cells are more sensitive to killing by MNNG than LNCaP. Investigation of the underlying reasons for lower resistance revealed that the DU145 cells contain low endogenous levels of cyclin B1. We provide direct evidence that the endogenous level of cyclin B1 modulates the sensitivity of MMR-deficient prostate cancer cells to alkylating agents.

Comparison of in house polymerase chain reaction with conventional techniques for the detection of Mycobacterium tuberculosis DNA in granulomatous lymphadenopathy

AIMS

To evaluate the usefulness of the devR based polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in lymph node aspirates and tissues of lymphadenitis and to compare PCR with conventional diagnostic techniques.

SUBJECTS AND METHODS

Coded specimens of fine needle aspirates and biopsies from 22 patients with tuberculous lymphadenitis, 14 patients with non-tubercular lymphadenitis, and nine patients with granulomatous lymphadenitis were processed and subjected to analysis by PCR, smear microscopy, M tuberculosis culture, histology, and cytology.

RESULTS

Tuberculous lymphadenitis was correctly diagnosed by PCR in 18 patients, by culture in five patients, by histology in 13 patients, and by cytology in seven patients. PCR gave two false positive results in 14 patients with non-tubercular lymphadenitis. The sensitivity of the conventional techniques was significantly higher with biopsies (17 of 22 specimens; 77%) than with fine needle aspirates (nine of 22 specimens; 41%). However, the sensitivity of PCR was not significantly higher with biopsies (68%) in comparison with fine needle aspirates (55%). The sensitivity of either biopsy PCR or fine needle aspirate PCR was not significantly different from that of either histology combined with culture or cytology combined with culture. The overall combined specificity of PCR was 86%. Mycobacterium tuberculosis DNA was detected in six of nine patients with granulomatous lymphadenitis.

CONCLUSION

PCR is the most sensitive single technique available to date for the demonstration of M tuberculosis in specimens derived from patients with a clinical suspicion of tuberculous lymphadenitis. The value of PCR lies in its use as an adjunct test in the diagnosis of tuberculous lymphadenitis, particularly in those patients where conventional methods fail. Because fine needle aspiration is not an invasive procedure, it is the procedure of choice, and PCR should be performed initially on these samples. Excisional biopsy histology and PCR should be recommended only for patients in whom fine needle aspirate PCR is negative or when there is discrepancy with the clinical impression.

Sexual behaviors and reproductive health outcomes: associations with wife abuse in India

CONTEXT

Wife abuse has been associated with a variety of health concerns. Associations between abuse and reproductive health in India are not well known.

OBJECTIVE

To examine relationships between men's reports of wife abuse and reproductive health issues in northern India.

DESIGN

Structured face-to-face interviews were conducted as part of the male reproductive health supplement of the PERFORM System of Indicators Survey, a systematic multistage survey conducted in 1995-1996.

SETTING

The northern state of Uttar Pradesh, one of the least developed states in India.

PARTICIPANTS

A total of 6632 married men aged 15 to 65 years who lived with their wives and completed all survey questions for the study variables reported here.

MAIN MEASURES

Physically and sexually abusive behaviors toward wives, sexual activities outside marriage, sexually transmitted disease (STD) symptoms, contraception use, unplanned pregnancies, and sociodemographic characteristics.

RESULTS

Fifty-four percent of men reported not abusing their wives, while 17% reported physically but not sexually abusing their wives, 22% reported sexual abuse without physical force, and 7% reported sexual abuse with physical force. Abuse was more common among men who had extramarital sex (for sexual abuse using force: odds ratio [OR], 6.22; 95% confidence interval [CI], 3.98-9.72). Similarly, men who had STD symptoms were more likely to abuse their wives (with current symptoms: OR, 2.43; 95% CI, 1.73-3.42). Unplanned pregnancies were significantly more common among wives of abusive men, especially sexually abusive men who used force (OR, 2.62; 95% CI, 1.91-3.60).

CONCLUSIONS

Wife abuse appears to be fairly common in northern India. Our findings that abusive men were more likely to engage in extramarital sex and have STD symptoms suggest that these men may be acquiring STDs from their extramarital relationships, thereby placing their wives at risk for STD acquisition, sometimes via sexual abuse. These abusive sexual behaviors also may result in an elevated rate of unplanned pregnancies.

Mitochondrial DNA determines the cellular response to cancer therapeutic agents

Mutations in the mitochondrial genome leading to mitochondrial dysfunction have been reported in a variety of cancers. However, the potential implication of these findings in the cellular response to cancer therapeutic agents is unclear. To examine the importance of mitochondrial DNA (mitDNA) encoded functions in cancer therapeutic response, we determined the clonogenic survival of HSL2 (Rho+, HeLa subline), and its derivative cell line lacking mitDNA (Rho0) after exposure to different anticancer agents. We found that isogenic Rho0 cells lacking mitDNA were extremely resistant to adriamycin and photodynamic therapy (PDT) induced cell death, whereas the Rho+ cell line was sensitive. However, there was no measurable difference in the responses of these cell lines to either alkylating agent or gamma-radiation. We show that the development of resistance to adriamycin was not due to changes in apoptotic cell death, cell cycle response or to the uptake of adriamycin in isogenic Rho0 cells. We also demonstrate that exposure of HeLa cells to adriamycin leads to mutations in mitDNA. These studies provide direct evidence that mitDNA plays an important role in cellular sensitivity to cancer therapeutic agents.

Outcome in patients with colorectal cancer managed by surgical trainees

BACKGROUND

The surgeon is an important variable that influences outcome following colorectal cancer surgery. Operative training of suitable quality and quantity is essential if intersurgeon variation is to be reduced. The aim of this study was to examine the outcome of colorectal cancer surgery when a high proportion of the operations were performed by trainee surgeons.

METHODS

A prospective 7-year (1989-1996) audit of 306 consecutive colorectal cancers referred to a single general surgeon with a colorectal interest was carried out. The outcome (anastomotic leakage, 30-day mortality rate, local recurrence and cancer-related survival) of operations performed by the consultant was compared with that of his trainees.

RESULTS

Some 245 (92.5 per cent) of 265 patients undergoing laparotomy had a resection. Seventy (28.6 per cent) and 67 (27.3 per cent) of operations were performed by supervised and independent trainees respectively. There was no difference between the consultant, supervised and independent trainees for 30-day mortality rate (6.5, 6 and 4 per cent respectively), clinical anastomotic leakage rate (9, 2 and 5 per cent) and local recurrence rate (2, 3 and 7 per cent). There was no difference between the three groups for adjusted 5-year disease-related survival rates.

CONCLUSION

Properly supervised trainees can resect a high proportion of colorectal cancers without compromising immediate outcome or long-term survival. Presented in part to the annual meeting of the Association of Surgeons of Great Britain and Ireland, Bournemouth, UK, April 1997, and published in abstract form as Br J Surg 1997; 84(Suppl): 56