Urinary mutagenicity as a biomarker in workers exposed to benzidine: correlation with urinary metabolites and urothelial DNA adducts

Urinary mutagenicity has been used in occupational and epidemiological studies for over two decades as a cost-effective, general biomarker of exposure to genotoxic agents. However, few studies have compared urinary mutagenicity to additional biomarkers determined among low- and high-exposed groups. To address this issue, we evaluated the relationship between urinary mutagenicity and other types of biomarkers in a cross-sectional study involving 15 workers exposed to the urinary bladder carcinogen benzidine (BZ, high exposure), 15 workers exposed to BZ-dyes (low exposure), and 13 unexposed controls in Ahmedabad, India. Urinary organics were extracted by C18/methanol and evaluated for mutagenicity in the presence of S9 in the Salmonella strain YG1024, which is a frameshift strain that overproduces acetyltransferase. The results were compared to biomarker data reported recently from the same urine samples (Rothman et al., Proc. Natl Acad. Sci. USA, 93, 5084- 5089, 1996) that included a metabolite biomarker (the sum of the urinary levels of BZ + N-acetylbenzidine + N,N'-diacetylbenzidine) and a DNA adduct biomarker [a presumptive N-(3'-phosphodeoxyguanosin-8-yl)- N'-acetylbenzidine (C8dG-ABZ) DNA adduct in exfoliated urothelial cells]. The mean +/- SE urinary mutagenicity (revertants/micromol of creatinine) of the low-exposure (BZ-dye) workers was 8.2 +/- 2.4, which was significantly different from the mean of the controls (2.8 +/- 0.7, P = 0.04) as was that of the mean of the high-exposure (BZ) workers (123.2 +/- 26.1, P < 0.0001). Urinary mutagenicity showed strong, positive correlations with urinary metabolites (r = 0.88, P < 0.0001) and the level of the presumptive C8dG-ABZ urothelial DNA adduct (r = 0.59, P = 0.0006). A strong association was found between tobacco use (bidi smoking) and urinary mutagenicity among the controls (r = 0.68, P = 0.01) but not among the exposed workers (r = 0.18, P = 0.11). This study confirms the ability of a biomarker such as urinary mutagenicity to detect low-dose exposures, identify additional genotoxic exposures among the controls, and correlate strongly with urinary metabolites and DNA adducts in the target tissue (urinary bladder epithelia) in humans.      

Protection against induction of mouse skin papillomas with low and high risk of conversion to malignancy by green tea polyphenols

We earlier showed that a polyphenolic fraction isolated from green tea (GTP) affords protection against tumor promotion and tumor progression in SENCAR mouse skin. The present study was designed to further evaluate the protective effect of GTP against the induction and subsequent progression of papillomas to squamous cell carcinomas (SCCs) in experimental protocols where papillomas were developed with a low or high probability of their malignant conversion. Topical application of GTP (6 mg/animal) 30 min prior to that of 12-O-tetradecanoylphorbol-13- acetate (TPA) either once a week for 5 weeks (high risk TPA protocol) or once a week for 20 weeks (low risk TPA protocol) or mezerein (MEZ) twice a week for 20 weeks (high risk MEZ protocol) in 7,12- dimethylbenz[a]anthracene (DMBA)-initiated mouse skin resulted in significant protection against skin tumor promotion in terms of tumor incidence (32-60%), multiplicity (49-63%) and tumor volume/mouse (73- 90%) at the termination of the experiment at 20 weeks. In three separate malignant progression experiments when papilloma yield in DMBA- initiated and TPA or MEZ promoted low and high risk protocols was stabilized at 20 weeks, animals were divided into two subgroups. These animals were either topically treated twice weekly with acetone (0.2 ml/animal, spontaneous malignant conversion group) or with GTP (6 mg/animal in 0.2 ml acetone) for an additional period of 31 weeks. During these treatment regimens, all suspected carcinomas were recorded and each one was verified histopathologically either at the time when tumor-bearing mouse died/moribund or at the termination of the experiment at 51 weeks. GTP resulted in significant protection against the malignant conversion of papillomas to SCC in all the protocols employed. At the termination of the experiment at 51 weeks, these protective effects were evident in terms of mice with carcinomas (35- 41%), carcinomas per mouse (47-55%) and percent malignant conversion of papillomas to carcinomas (47-58%). The kinetics of malignant conversion suggest that a subset of papillomas formed in the early phase of tumor promotion in all the protocols had a higher probability of malignant conversion into SCCs because all the positive control groups (acetone treated) produced nearly the same number of carcinomas (33-38 in a group of 20 animals) at the end of the progression period. In the GTP- treated group of animals the number of carcinomas formed was less (14- 20 in a group of 20 animals), which shows the ability of GTP to protect against the malignant conversion of papillomas of higher probability of malignant conversion to SCCs. The results of this study suggest that irrespective of the risk involved, GTP may be highly useful in affording protection against skin cancer risk.      

HIGH ALTITUDE PULMONARY OEDEMA – AN EXPERIENCE IN EASTERN HIMALAYA

Three hundred and five cases of high altitude pulmonary oedema (HAPO) hospitalised in eastern Himalayan region have been analyzed. Incidence of HAPO was 5.5 per cent. Eighty per cent cases occurred during latter half of the year. Fifty six per cent of cases belonged to the third decade of life. HAPO cases occurred most commonly between the height of 2740 m to 5960 m. Eighty three per cent cases developed symptoms within 72 hours of induction to high altitude and 65.9 per cent suffered from the illness despite complete acclimatization. Breathlessness, headache and cough were the commonest symptoms. Tachycardia and tachypnoea was present in all cases. Twenty five per cent cases showed various ECG abnormalities. Mortality rate was 0.98 per cent.KEYWORDS: Altitude, ECG abnormalities, Cerebral oedema, Pulmonary oedema     

AN EPIDEMIOLOGICAL STUDY OF BLOOD PRESSURE AMONG SCHOOL CHILDREN

Blood pressure was measured in 1170 school children between 5 and 15 years of age. Mean blood pressure was significantly higher in boys than girls in all age groups and a steady increase in blood pressure with age was seen in both the sexes. Mean blood pressure was significantly higher among children with positive family history of cardiovascular morbidity. Children from higher socio-economic strata and overweight children also showed higher blood pressure. Nine (0.77%) children had persistent hypertension. However, the degree of hypertension was mild and all these children were asymptomatic. Baseline investigations failed to detect any underlying pathology or target organ involvement. This study suggests that childhood could be a reasonably profitable time to look for such factors and to selectively screen children belonging to the high risk group for hypertension.KEY WORDS: Hypertension, Blood pressure, Epidemiology     

MANAGEMENT OF KALA AZAR – AN UPDATE

Kala azar continues to be a medical problem in India and with the increase in incidence of HIV Infection it is likely that kala azar will be encountered more frequently and in its atypical forms. To aid diagnosis, several immunological tests are now available and they are more sensitive and specific than the aldehyde test. Like many other diseases today, the treatment of kala azar is hampered by drug resistance. Newer drugs are available and so are new delivery systems. Kala azar develops frequently in the HIV infected person before development of AIDS. The presentation is atypical and leishmanial species other than L. donovani may also be the infecting agents. A combination of sandfly control, detection and treatment of patients and prevention of drug resistance continues to the ideal approach for the control of the disease.KEY WORDS: Kala azar, Leishmaniasis, HIVWHO estimates that more than 200 million people in the world are exposed to leishmanial parasites and more than 500,000 people develop clinical visceral leishmaniasis each year [1]. Major epidemics have occurred in the eastern part of our country and some other parts of the world [2]. Large scale drug failure has been the outstanding feature of the Indian epidemic of 1991, leading to increased morbidity and mortality. Certain clinical manifestations like lymphadenopathy which were not seen in Indian kala azar earlier, have been reported from Bihar and West Bengal [3]. With the increasing incidence of HIV infection, more atypical presentations are being noted [1]. Due to the development of widespread resistance to conventional drugs, several new drugs and other modalities of treatment have been developed and the conventional drugs are being tried in modified dosages with variable success.     

BENIGN COLONIC STRICTURES - A STUDY OF TWENTY CASES

An analysis of twenty cases of benign colonic strictures is presented. Thirteen (65%) had tubercular strictures, 3 (15%) had ulcerative colitis, one each had ischaemic colitis and Crohn''s disease. In 2 cases the cause could not be established. Eleven patients (55%) presented with subacute intestinal obstruction and 7 (35%) with diarrhoea. Specific diagnoses based on histopathology could be made in only 45 per cent of cases. Most of the patients responded to specific medical therapy. Seven patients (35%) required surgical intervention.KEY WORDS: Colonic strictures, Colonoscopy, Colitis, Tuberculosis     

DRUG RESISTANT TUBERCULOSIS — THE EMERGING SCENARIO

During the period April 1992 to September 1994 a total of 2288 patients of pulmonary tuberculosis were treated at our centre. M. tuberculosis could be isolated from the sputa of 1037 patients (45.3%). All the isolates were subjected to indirect susceptibility testing using drug incorporated Lowenstein-Jensen medium slants. A total of 142 (13.7%) patients showed drug resistance. Single drug resistance was observed in 86 (8.3%) patients whereas resistance to two or more drugs was observed in 56 (5.4%) patients. Patients showing initial drug resistance were more in number (83 cases) than those showing acquired drug resistance (59 cases). Resistance to streptomycin was commonest (8.3% of isolates) followed by isoniazid (5.7%) and rifampicin (5.0%). Multiple drug resistance was mostly acquired (71.4% of drug-resistant isolates).KEY WORDS: Antitubercular agents, Drug resistance microbial, Tuberculosis     

Effects of the class III antiarrhythmic drug ambasilide on outward currents in human atrial myocytes

We have studied the inhibitory influence of the class III antiarrhythmic drug ambasilide (LU 47110) on the transient outward current I _to1 and the sustained current T _so following inactivation of I _to1 in human atrial myocytes. The two currents are separated by a mathematical procedure based on the amplitudes and time constants of the biexponential inactivation of the total outward current. The frequency dependence, the recovery from inactivation and the kinetics of activation and inactivation are described. Ambasilide reversibly and concentration dependently inhibited I _to1, I _so and the sodium current I _Na. Concentration required for half maximal inhibition (IC₅₀) for the effects on I _to1 and I _so were 23.3 mol/l and 45.7 mol/l respectively, concentrations shown by others to be effective in terminating and preventing fibrillation in a dog atrial arrhythmia model. Ambasilide not only reduced the amplitude of I _to1 and I _so but also accelerated the time course of inactivation from 14.22 to 6.69 ms and from 202.3 to 87.9 ms respectively. The amplitude of I _to1 showed only a small dependence on stimulation frequency characteristic for human atrial myocytes, whereas I _so was reduced significantly at higher stimulation frequencies. Ambasilide did not change these relationships (0.1–4 Hz) and therefore did not show the reverse use-dependence known from other class III antiarrhythmic agents and which is an important property for a prospective antiarrhythmic drug. The lack of an effect of ambasilide on both steady-state activation and inactivation of I _to1, and the time constant of recovery from inactivation, suggests that ambasilide acts by changing conductance rather than by influencing the gating mechanism. The described characteristics make ambasilide an interesting substance in the group of class III antiarrhythmic drugs.