Optically stimulated luminescence studies in combustion synthesized Al₂O₃:C,Cu,P

A new Al2O3:C,Cu,P phosphor is developed by the combustion synthesis technique which exhibits entirely different OSL properties as compared to that of the commercial alumina. No thermoluminescence (TL) is observed in this phosphor which also differentiates the present phosphor from the commercially available Al2O3:C (Landauer). The phosphor shows good optically stimulated luminescence (OSL) sensitivity for ionizing radiation with a fast OSL decay as compared to the commercial Al2O3:C. The phosphor heated in air followed by heating under the reactive atmosphere exhibits maximum sensitivity amongst several other phosphors. On the basis of area integration method; integrated over initial 3s, the sensitivity of this phosphor is about 67% of that of commercial Al2O3:C.

Na2SiF6:Cu,P: a new OSL phosphor for the radiation dosimetric applications

A new Cu,P-doped, sodium fluorosilicate-based optically stimulated luminescence (OSL) phosphor is developed. This phosphor shows good OSL properties, and the sensitivity is comparable with that of the commercial Al(2)O(3):C (Landauer, Inc.) phosphor. For the luminescence averaged over initial 1 s, blue-stimulated luminescence and green-stimulated luminescence sensitivities were found to be 0.76 and 3.8 times, respectively, of Al(2)O(3):C (Landauer, Inc.) with 28 % of post-irradiation fading in 3 days and nil thereafter. The simple preparation procedure, fast decay, very good sensitivity and moderate fading will make this phosphor suitable for radiation dosimetry, using OSL.

OSL and thermally assisted OSL response in dental enamel for its possible application in retrospective dosimetry

Dental enamel was studied for its thermoluminescence (TL) and optically stimulated luminescence (OSL) defects. The TL studies showed a wide glow curve with multiple peaks. The thermally assisted OSL (TA-OSL) studies showed that the integrated TA-OSL and thus OSL signal increases with readout temperature between 100 and 250 °C, due to the temperature dependence of OSL. The thermally assisted energy E A associated with this increase is found to be 0.21 ± 0.015 eV. On the other hand, the signal intensity decreases with temperature between 260 and 450 °C. This decrease could be due to depletion of OSL active traps or possible thermal quenching. The increase of the OSL signal at increased temperature can be used to enhance the sensitivity of dental enamel for ex vivo measurements in retrospective dosimetry. The emission and excitation spectra of its luminescence centers were studied by photoluminescence and were found to be at 412 and 324 nm, respectively. It was found to possess multiple OSL active traps having closely lying photoionization cross sections characterized by continuous wave OSL and nonlinear OSL methods. The investigated dental enamel samples showed a linear OSL dose response up to 500 Gy. The dose threshold was found to be 100 mGy using a highly sensitive compact OSL reader with blue LED (470 nm) stimulation.

Prevalence of diabetes mellitus in a rural population of Goa, India

BACKGROUND

We aimed to estimate the prevalence of diabetes mellitus and study the associated factors in a rural population in Goa, India.

METHODS

A cross-sectional study was done in the rural area of Mandur, Goa. Participants>20 years of age were selected by systematic random sampling. They were interviewed with the help of a structured, pretested questionnaire. This was followed by clinical examination, anthropometry and relevant laboratory investigations. Diabetes mellitus was defined as per the American Diabetes Association (ADA) criteria. Statistical analysis was done using the SPSS software package (version 14.0).

RESULTS

The prevalence of diabetes mellitus in the study population was 10.3% (130/1266) with a prevalence of 8.4% among men and 12% among women. On bivariate analysis, the prevalence of diabetes mellitus was found to be significantly associated with age, occupation, family income, family history of diabetes, smoking, obesity, hypertension, and high serum cholesterol and triglycerides levels. Multiple logistic regression analysis identified age, family history, hypertension, smoking, total cholesterol and triglyceride as the Independently associated variables for diabetes mellitus.

CONCLUSION

Innovative community outreach programmes are required to create awareness, and for screening and treatment of diabetes mellitus to curb the growing epidemic of diabetes in the population.

Study of needle stick injuries among health care workers at a tertiary care hospital

A cross-sectional study was conducted among health care workers at a tertiary care hospital in Goa to study the problem of needle stick injuries. A structured questionnaire was used to interview the study participants at their work place. Participants were asked to recall needle stick injuries in the preceding 12 months. Factors such as work experience, type of procedure, action taken following injury etc were also studied. Statistical analysis was done with SPSS software. Around 34.8% (200/575) of the Health care workers had experienced a needle stick injury in the last one year. Needle stick injuries were equally distributed across different work experience periods. Hollow bore needles were responsible for 77.5% of needle stick injuries followed by suturing needles (19.2%). As far as use of personal protection was concerned only 58% of the health care workers were wearing gloves at the time of the injury. There is therefore an urgent need at the hospital level to have a uniform needle stick injuries policy covering safe work practices, safe disposal of sharps, procedures in event of needle stick injury, training including pre-employment training, monitoring and evaluation of needle stick injuries and procedures for reporting needle stick injuries.

A prospective study of surgical site infections in a teaching hospital in Goa

INTRODUCTION

Surgical Site Infections contribute significantly to increased health care costs in terms of prolonged hospital stay and lost work days. The problem was largely unexplored in an apex medical institute in Goa.

AIMS AND OBJECTIVES

To estimate the incidence, and study the bacteriology and the factors associated with SSI in the study setting.

SETTINGS AND DESIGN

Prospective study in the surgical wards of an apex medical teaching hospital in Goa.

MATERIALS AND METHODS

Clinico-bacterilogical follow-up of 114 post-operative cases to the development of SSI, as per the CDC criteria (1991). Incidence was expressed as the infection rate per 100 operations. Antibiotic sensitivity testing was done using the disc diffusion method.

STATISTICAL ANALYSIS

Association was tested by applying the Student t-test and the Chi-square test of significance, and the strength of association expressed as the Odd's Ratio.

RESULTS

The overall SSI rate was estimated to be 30.7%; 5.4% for clean, 35.5% for clean-contaminated, and 77.8% for contaminated operations. Seventy-nine per cent of the isolates were gram-negative and almost 64% demonstrated polyantimicrobial resistance.

CONCLUSIONS

The study emphasizes the need for the evidence-based infection control and antibiotic prescription policies in the hospital.

Prevalence of human cysticercosis and taeniasis in rural Goa, India

A cross sectional study among 450 individuals selected by strafified random sampling was carried out in rural Goa to find out the prevalence of cysticercosis and taeniasis, as well as to study the role of various factors associated with this diseases. The study participants were administered a pre-tested structured questionnaire and subsequently blood and stool samples were examined. SPSS software was used to analyze the data statistically. The sero-prevalence of cysterosis was 22.4%, which increased with age. Prevalence of taeniasis was 9.7% by stool examination. Individuals with taeniasis were thrice more likely to have cysticercosis; however no association between sero-positivity for cysterosis and pork consumption as well as religion could be established. The study confirmed a high sero-prevalence of cysticercosis in Goa underscoring the need to general awareness about good cooking habits and sanitation.

Bed utilization indices at a tertiary care hospital in Goa: an eight year trend analysis

A retrospective data analysis of records from medical records department of Goa Medical College Hospital was done to analyse the trends of various bed utilisation indices from 1999 - 2006. Average length of stay, bed occupancy rate, turnover interval and bed turnover ratio were the indices calculated. During the eight year period from 1999 to 2006, the average length of stay for the entire hospital registered a small decline from 6.23 to 5.51 days, the overall bed occupancy rate increased from 72.13% to 83.12% and the bed turnover interval declined from 2.41 days to 1.12 days. The Orthopaedics ward had the highest increase in bed occupancy and also fastest decline in turnover interval in 2006. Bed utilization indices are an objective measure of the efficiency of the hospital management system.

Conceptual framework of a geographical information system for environment--public health surveillance in Goa

This paper proposes a conceptual framework for establishing a multidiscipline Geographical Information System for environment public health surveillance in the state of Goa. Sectors networking for the Geographical Information System encompass Directorate of Health Services including peripheral health setup, Public Works Department, State Pollution Control Board, Irrigation Department, Inspectorate of Factories and Boilers, Town and Control Planning Department, Meteorological Department etc. the applications of which would predict potential outbreaks / epidemics of water borne diseases, malaria, diseases linked to pollution and would support disease control activities. In addition to health applications, the data generated would be used by the respective sectors for their other planning and programming needs.

Sexual risk behaviors and HIV/AIDS awareness among males in a rural community in Goa

To study the heterosexual risk behaviors and to study the level of HIV/ AIDS awareness among males in a rural community in Goa. Survey was cross-sectional and community based. A sample of 300 males aged 15-49 years selected by stratified random sampling. An "UNAIDS protocol for measurement of HIV/STD prevention indicators" was used. SPSS software package was used for statistical analysis. One hundred and ninety eight (66%) males reported ever having sexual intercourse, of these 17% were single. Fifty three (17.7%) males reported intercourse with a non-regular partner in the past 12 months, of these 90.6% had intercourse with strangers, 92.5% had paid for sex and only 43.4% had used a condom for the last sexual encounter with a non-regular partner. Less educated males (<10th class), single and those employed have higher sexual indulgence with non-regular sexual partners. The level of knowledge about HIV/ AIDS was very high in all areas of causation and prevention. Although the awareness about sexual risk behavior was high, condom use was very low resulting in high risk behavior related to HIV/ AIDS and STDs among males. The study highlights the need for more effective behaviour change communication (BCC) strategies in the community as well as innovative methods like village level peer education.

Frequent inactivation of the cyclin-dependent kinase inhibitor p18 by homozygous deletion in multiple myeloma cell lines: ectopic p18 expression inhibits growth and induces apoptosis

Multiple myeloma (MM) is a clonal neoplasm of plasma cells which offers an excellent model to study multistep molecular oncogenesis. In 20-25% of primary tumors and cell lines examined, cyclin D1 is overexpressed due to the translocation t(11;14)(q13;q32). We have characterized cyclin-dependent kinase inhibitor p15 (CDKN2B), p16 (CDKN2A) and p18 (CDKN2C) deletions in cyclin D1-expressing and non-expressing MM cell lines. p18 was found to be frequently deleted (38%); in some cases p18 deletions coexisted with hemizygous p16 deletion. To examine the function of p18 as a putative tumor suppressor in myeloma cells, a zinc-inducible p18 construct was stably transfected into KMS12, a MM cell line with biallelic p18 and monoallelic p16 deletions as well as cyclin D1 overexpression. Ectopic expression of p18 caused 40-45% growth suppression as determined by trypan blue exclusion and MTS assays. p18 induction also resulted in apoptosis, suggesting that inhibition of the cyclin D1/CDK/pRb pathway in these tumor cells could be a crucial step toward the induction of tumor regression via apoptotic cell death. This cell cycle pathway is thus frequently mutated and provides a potentially novel target for gene therapeutic or pharmacologic approaches to human myeloma.

Critical evaluation of a CLIA-waived streptococcal antigen detection test in the emergency department

STUDY OBJECTIVE

We compare the performance of a Clinical Laboratory Improvement Amendments (CLIA)-waived antigen detection test (ADT) analyzed in the emergency department and a CLIA moderately complex ADT performed in the hospital microbiology laboratory.

METHODS

Samples from throat swabs were obtained using a double-headed Culturette II (Becton Dickinson Medical Systems, Sparks, MD) from a consecutive sample of 322 patients 3 years or older who presented to the ED of a university-affiliated pediatric referral hospital with the complaint of sore throat during 1998. One swab was transported to the microbiology laboratory and analyzed using a CLIA moderately complex ADT; negative results were confirmed using sheep blood agar culture. The second swab remained in the ED where a nurse conducted a CLIA-waived ADT. The accepted standard for documentation of group A beta-hemolytic streptococcal (GABHS) infection was either a positive moderately complex ADT or culture result. The time of specimen collection, as well as the time the ED results and microbiology laboratory results were available to treating physicians, were recorded. Main outcome measures were concordance (kappa statistic), sensitivity, and turnaround time (Mann-Whitney U test).

RESULTS

Three hundred twenty-two patients (mean age 7.5 years) had both ADTs performed. One hundred one (31%) patients had documented GABHS in the microbiology laboratory; 83 (82%) had a positive ADT result in the microbiology laboratory, and 18 (18%) had a positive culture result after a negative moderately complex ADT result. In 299 patients or 93% (95% confidence interval [CI] 90.8%, 95.8%) of patients, the waived ADT and the moderately complex ADT results were concordant (kappa 0.82; 95% CI 0.78, 0.86; P <.001). The sensitivity of the waived ADT was 80%; the sensitivity of the moderately complex ADT approximated 82% (difference of 2%; 95%CI -3%, 7%). The median times from swab specimen collection to availability of ADT results were 10 minutes (range 3 to 37 minutes) for the waived ADT and 35 minutes (range 5 to 162 minutes) for the moderately complex ADT (P <.001) with a difference of 25 minutes (95% CI 22.4, 27.6 minutes).

CONCLUSION

In this study, an ED CLIA-waived rapid streptococcal throat test performed as well as its equivalent CLIA-regulated laboratory test. Further, the ED test provided results more rapidly than the laboratory test. Our results also validate previous work that negative rapid throat test results in pediatric patients in the ED should be confirmed by standard throat culture.

Fatal hypermagnesemia in a child treated with megavitamin/megamineral therapy

We report a case of fatal hypermagnesemia resulting from the unsupervised use of high doses of magnesium oxide administered as part of a regimen of megavitamin and megamineral therapy to a child with mental retardation, spastic quadriplegia, and seizures. The treatment regimen was given at the recommendation of a dietician working as a private nutritional consultant without the involvement or notification of the child's pediatrician. Hypermagnesemia is an uncommon but serious side effect of the use of magnesium containing compounds. These compounds are widely used as laxatives and dietary supplements, and serious side effects are uncommon when used in appropriate dosages and with adequate supervision. The use of alternative medical therapies, including megavitamin/megamineral therapy, is widespread. Many patients use alternative medicine or seek care from alternative medicine practitioners without the recommendation or knowledge of their primary physicians. Despite unproved benefit, many alternative therapies may be safe. However, unsupervised use of generally safe treatments can result in serious side effects. This case report serves to illustrate the characteristic pathophysiologic changes of severe hypermagnesemia, an entity rarely seen in pediatric practice, and more importantly, it alerts primary care and subspecialty pediatricians to be aware of and monitor the use of alternative medical therapies in their patients.

Nesidioblastosis with necrotising enterocolitis: an enigma

Necrotising enterocolitis with nesidioblastosis is a rare, lethal coexistence during the newborn period. We report this unusual combination leading to surgery: a partial pancreatectomy and resection with primary anastomosis, and discuss the dilemma of the procedure of choice during therapy.

Asymmetric conjoined twins

Despite recent advances in diagnosis, particularly organ-imaging, and therapeutic options, the management of conjoined twins is still very challenging. We report conjoined twins attached ()end-on" at the lumbo-sacral level and describe the anatomical findings, methods of investigation, and management.

Agenesis of the urinary bladder with cutaneous ectopic ureteric orifice and multiple birth defects

This is to our knowledge the first case in the world literature of a liveborn baby with a tubular colonic duplication, agenesis of the urinary bladder, urethral atresia, and a single pelvic kidney with its ureter opening directly onto the skin in the region of the natal cleft. A brief review of the embryology is included and an attempt is made to explain the embryologic basis for this anomaly.

Sampling and processing of color signals

Digital signal processing tools are used to determine the proper sampling of color spectra and the effect of sampling on the accuracy of derived properties such as CIE tristimulus values and color rendering indexes. It is found that 10 nm sampling is adequate for most applications, but not for more exacting textile and paint matching applications. Special methods are proposed to treat the cases of color signals with delta function components such as fluorescent lights.

Short colon variant

A one day old neonate with a short colon, associated exomphalos minor; bifid scrotum and ileovesical fistula is reported.

Primary repair or colostomy in the management of civilian colonic trauma

BACKGROUND

Management of civilian colonic trauma remains controversial.

AIM

To determine prognostic factors in patients with civilian colonic trauma undergoing different modes of therapy.

METHODS

Sixty-five patients with colonic injuries were retrospectively analyzed.

RESULTS

Right and left colon injuries were present in 30 and 35 cases respectively. Colon-related complications occurred in 27.7%. One death (1.5%) was directly due to colonic injuries. Left sided colon injuries led to a higher incidence of complications and longer duration of hospital stay; a higher number of complications occurred in relation to colostomy than primary closure.

CONCLUSIONS

Primary repair can be done in more cases than is routinely done. The presence of multiple abdominal injuries or shock does not exclude primary repair. The site of injury may affect the outcome, but does not exclude primary repair. Gross fecal contamination, extensive colonic damage and type of feces in affected colon should be considered as indications favoring colostomy.

Fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma, a histological variant of hepatocellular carcinoma, distinct pathological and clinical features and a better prognosis than other types of hepatocellular carcinoma. We report here a patient who was treated on successful surgically.

NAT2, an essential gene encoding methionine N alpha-acetyltransferase in the yeast Saccharomyces cerevisiae

N alpha-Acetylation is catalyzed by N alpha-acetyltransferases, which transfer acetyl groups from acetyl coenzyme A to the N termini of most eukaryotic proteins co-translationally. NAT1 and ARD1 from the yeast Saccharomyces cerevisiae (Mullen, J. R., Kayne, P. S., Moerschell, R. P., Tsunasawa, S., Gribskov, M., Colavito-Shepanski, M., Grunstein, M., Sherman, F., and Sternglanz, R. (1989) EMBO J. 8, 2067-2075) were previously shown to encode the major N alpha-acetyltransferase, which act on certain proteins having serine, glycine, and alanine but not methionine termini (Sherman, F., Moerschell, R. P., Tsunasawa, S., and Sternglanz, R. (1993) in Methods in Protein Sequence Analysis (Imahori, K., and Sakiyama, F., eds) pp. 173-181, Plenum Publishing Corp., New York). We have identified a second gene, NAT2, that may correspond to the N alpha-acetyltransferase acting on a subset of proteins having methionine termini. Crude extracts of a series of heat-sensitive mutants (Ts-) were screened for acetylation of a 24-amino acid synthetic peptide Met-Asn-Asn- in vitro. One mutant, nat2-1, out of 115 strains examined, lacked acetyltransferase activity, and the mutation co-segregated as a single gene with the heat-sensitive phenotype. The nat2-1 mutants were deficient in the ability to acetylate Met-Asn-Asn- and Met-Glu-Arg-peptides but were able to N alpha-acetylate Ser-Glu-Phe- and Ser-Tyr-Ser- peptides in vitro. The NAT2 wild-type gene was cloned by complementation of the nat2-1 mutant, and the DNA sequence revealed an open reading frame of 288 amino acids. Gene disruption demonstrated that NAT2 is an essential gene, and hybridization analysis indicated that it is located on chromosome VII. Furthermore, there was limited, but significant identities between the yeast N alpha-acetyltransferases Nat1, Ard1, Nat2, and Mak3, although no common motifs could be identified. We propose that NAT2 encodes the major N alpha-acetyl-transferase acting on certain proteins with only methionine termini, and that N alpha-acetylation of some of these proteins is essential for viability.

Total hepatic vascular exclusion for major hepatic resection

Use of vascular occlusion techniques during hepatic resection has besides decreasing blood loss improved the feasibility of surgical extirpation of large hepatic tumors. We report successful use of this technique to resect a large hepatoma in the right lobe of the liver. The hemodynamic and biochemical changes in the perioperative period are documented.

Species differences in the formation of benzo(a)pyrene-DNA adducts in rodent and human endometrium

The formation of adducts of benzo(a)pyrene metabolites on DNA was investigated in endometrial tissue from humans, hamsters, mice, and rats. anti-Benzo(a)pyrene-7,8-diol-9,10-epoxide was the predominant adduct identified in all the species studied. The amount of (+)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide bound to DNA from human endometrium was approximately 3 times higher than to DNA from hamster tissue. Among the three animal species examined, the level of this adduct was highest in hamsters and lowest in rats. The high pressure liquid chromatography profiles of adducts formed in endometrium from humans and hamsters were similar, but the specific activity (pmol/mg DNA) of each adduct formed was different. syn-7,8-Dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene adduct was present in humans, hamsters, and rats but was not detected in mouse endometrium. There was an unidentified adduct present only in rat tissue. Rats had the lowest level of total DNA-bound radioactivity and the largest percentage of this total eluted as an uncharacterized radioactive peak that eluted with water (53%). These results demonstrate that endometrial tissues from humans and three rodent species differ with regard to the quantities and proportions of benzo(a)pyrene-DNA adducts formed from benzo(a)pyrene.

Sequences of the E. coli uvrB gene and protein

The UvrB protein is one of the three subunits of the E. coli ABC excinuclease. We have reported the sequences of the other two subunits, the UvrA and UvrC proteins. In this paper the sequence of the UvrB protein is presented. The protein sequence was determined from the DNA sequence of the uvrB gene and was confirmed by sequencing the NH2-terminus of the UvrB protein and analyzing its overall amino acid composition. The coding region of uvrB is 2019 basepairs, specifying a protein of 672 amino acids and Mr of 76,118. The sequence of the UvrB protein shows a moderate level of homology to that of the UvrC protein and to the ATP binding site of the UvrA protein. During purification of UvrB protein a proteolytic product, UvrB, is produced in high quantities. We find that UvrB results from removal of about 40 amino acids from the COOH-terminus of the UvrB protein. The uvrB gene has complex regulatory features. On the 5' side, the coding region is preceded by 3 promoters, a DnaA box and an SOS box. On the 3' side the gene is followed by an REP (Repetitive Extragenic Palindrome) sequence which has been implicated in gene regulation by an unknown mechanism.

Alkali lability and rapid initiation of excision repair following photoaffinity damage by ethidium azide

DNA damage and repair provoked by ethidium azide (EA) photoaffinity labeling in mouse leukemia cells was studied by measuring sedimentation properties of nucleoids in neutral sucrose gradients, and it was found that the strand opening step was faster than that which followed damage of cells by ultraviolet (UV) light. The two insults were compared at levels of damage which gave the same overall rates of repair synthesis in intact cells and which required the same length of time to complete repair, as judged by the restoration of supercoiling of the isolated nucleoids. In the case of UV, single-strand breaks in DNA were detectable at 30 min, maximum at 2 h, and the superhelical properties restored at 21 h. With photoaffinity labeling, single-strand breaks were prominent immediately, even when photolabeling of cells was done on ice, but restoration of DNA supercoiling still required 21 h. Photolabeling of isolated nucleoids or isolated viral DNA with EA failed to introduce DNA strand breaks. However, it was discovered that photoaffinity labeling of DNA with EA resulted in alkali labile sites shown by single strand breaks produced on alkaline sucrose sedimentation or by alkali exposure followed by sedimentation on neutral formamide gradients. These results suggest that the drug attachment sites should be identifiable by the location of such single strand breaks.

Detection of repair of chemical-induced DNA damage in vivo by the nucleoid sedimentation assay

The nucleoid sedimentation assay was used to study chemical-induced DNA repair in vivo. Nucleoid bodies were prepared from liver and lung of mice at various times after i.p. treatment with 1-methyl-1-nitrosourea or 4-nitroquinoline-1-oxide. Both carcinogens induced a dose-dependent loss in negative DNA supercoiling in liver and lung. The rate of DNA repair of 1-methyl-1-nitrosourea was similar in liver and lung whereas 4-nitroquinoline-1-oxide-induced DNA damage was repaired faster in lung than in liver. Results obtained by the nucleoid sedimentation technique corresponded to measurements of DNA repair by unscheduled DNA synthesis. The nucleoid sedimentation assay should be a useful tool to examine in vivo repair of chemical-induced DNA lesions in various tissues of laboratory animals.

DNA damage and repair in epithelial (mucous) cells and crypt cells from isolated colon

Colon epithelium is made up of two general classes of cells, surface cells which are post-mitotic and crypt cells which contain the proliferative population. Their relative vulnerability to environmental damage and ability to perform DNA repair are important issues in colon carcinogenesis. DNA damage and repair was studied by the nucleoid sedimentation method in freshly isolated crypt cells for comparison with previous studies of post-mitotic surface epithelial cells. Suspensions of crypt cells were isolated from preparations of mouse colon by a series of sequential incubations in buffer containing 1.5 mM EDTA. Treatment of crypt cells for 30 min with 1.2 X 10(-6) M methyl methane sulfonate (MMS), photoaffinity labeling with 1 X 10(-6) M ethidium monoazide, lithocholic acid (2.5 X 10(-4) M) treatment for 1 h or X-irradiation at 1500 rads resulted in single-strand breaks in the DNA, which were repaired after 2 h of additional incubation. Interestingly, X-rays at 1000 rads and lithocholic acid (LA) (2.5 X 10(-6) M) after 30 min incubation failed to produce the detectable shift in nucleoid sedimentation characteristic of single-strand breaks, perhaps due to rapid repair by these proliferative cells. UV-irradiation failed to provoke strand incision as was also observed for the superficial post-mitotic cells in the previous studies. These studies showed the feasibility of studying DNA damage and repair processes in these two classes of colon epithelial cells in response to specific carcinogenic insult.

Detection of in vivo DNA repair synthesis in mouse liver and lung induced by treatment with benzo(a)pyrene or 4-nitroquinoline 1-oxide

We examined in vivo DNA repair synthesis in liver and lung of A/HeJ mice treated with benzo(a)pyrene (BP) or 4-nitroquinoline 1-oxide. To differentiate between the removal of carcinogen metabolite:DNA adducts due to cell turnover and DNA repair, we measured unscheduled DNA synthesis (UDS) in the nonreplicating DNA fraction. Mice were exposed to bromodeoxyuridine pellets 1 hr prior to carcinogen treatment. Immediately following carcinogen exposure, mice received 4 hourly i.v. doses of [3H]thymidine. Mice were sacrificed 5 hr post-carcinogen treatment, and DNA was isolated. Purified DNA was then separated into newly replicated and nonreplicated DNA by ultracentrifugation in alkaline CsCl gradients. BP induced UDS in the liver at p.o. doses of 0.3 and 3.0 mg/mouse, whereas we failed to detect UDS in the lung. However, 4-nitroquinoline 1-oxide, another lung carcinogen, induced a definite repair response in the lung but not in the liver. It is not clear why mouse lung cells have the capacity to repair 4-nitroquinoline 1-oxide-induced damage to DNA and not the damage induced by BP, since both of these lung carcinogens form bulky adducts with DNA. These results demonstrate that (a) the in vivo disappearance of BP metabolite:DNA adducts from the lung of the A/HeJ mouse is due to cell turnover, whereas the disappearance of adducts from the liver is due, in part, to DNA repair and (b) induction of in vivo UDS after treatment with two different lung carcinogens is both tissue and carcinogen dependent in this mouse strain.

Persistence of benzo(a)pyrene metabolite:DNA adducts in lung and liver of mice

The persistence of benzo(a)pyrene (BP) metabolite:DNA adducts has been studied in lung and liver of A/HeJ and C57BL/6J mice after a dose of BP (6 mg/mouse) which induces pulmonary adenomas in A/HeJ mice but not in C57BL/6J mice. BP is not a hepatic carcinogen in either strain. Following p.o. administration of [3H]BP, animals were killed at times ranging from 10 hr to 28 days, and BP metabolite:DNA adducts were analyzed by high-pressure liquid chromatography. The major adduct identified in each tissue was the (+)-7 beta-8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene:deoxyguanosine adduct. A 7 beta, 8 alpha-dihydroxy-9 beta,10 beta,epoxy-7,8,9, 10-tetrahydrobenzo(a)pyrene:deoxyguanosine adduct, a (-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene:deoxyguanosine adduct, and an unidentified adduct were also observed. The disappearance of (+)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydro-BP adduct in A/HeJ mice followed first-order kinetics over the time period examined, with a half-life of 18 and 9 days in lung and liver, respectively. The decay of this adduct in C57BL/6J mice was biphasic in both tissues. Our data on cell turnover suggest that there is active removal of adducts in liver, but that normal DNA turnover can account for the partial or possibly total observed disappearance of adducts in lung. These results suggest that the tissue specificity for BP-induced neoplasia in A/HeJ mice may be related to the relative persistence of adducts and high cell turnover rates in lung. In contrast, the results on formation and persistence of adducts and cell turnover do not provide an explanation for the strain difference in susceptibility to BP-induced pulmonary adenomas. It was also shown that the rates of removal of BP metabolite:DNA adducts in A/HeJ mice are not significantly different at a 500-fold lower BP dose.

Production by lithocholic acid of DNA strand breaks in L1210 cells

Bile acids have been reported to promote colon cancer cells in mice treated with different carcinogens. In this study, we investigated the effects of lithocholic acid on the DNA of mouse lymphoblastoma L1210 cells. Incubation of L1210 cells with lithocholic acid (2.5 X 10(-4) M) at 37 degrees for 30 min and for 1 hr resulted in the appearance of single-strand breaks in the DNA. This was demonstrated by sedimentation of nucleoids in neutral sucrose gradients and by alkaline elution. The DNA damage was repaired upon incubation of the cells in fresh medium lacking lithocholic acid. These results suggest that DNA repair efficiency is an important function for the population of cells which are constantly exposed to low concentrations of lithocholic acid. The presence of even a low level of persistent damage could lead to significant biological consequences including mutations and the induction of error-prone repair processes.