Diarrhoea-related knowledge and practice of physicians in urban slums of Kolkata, India.

Diarrhoeal management practices are unsatisfactory in India especially in the slum areas. Dearth of information regarding physicians' diarrhoea-related knowledge and practice in India necessitated this cross-sectional study of allopathic practitioners in the slums of Kolkata, to assess the distribution and interrelationship between physicians' characteristics, knowledge and practice regarding diarrhoea. A total of 264 randomly selected consenting practitioners were interviewed using a field-tested questionnaire. Nineteen percent had good overall knowledge, 49% and 80% prescribed antibiotics to diarrhoea and cholera patients, respectively, and 55% advised stool examination for every case. Qualified and Government physicians had better knowledge regarding diarrhoea [MBBS: odds ratio (OR) 5·96, P < 0·001; postgraduates: OR 9·33, P < 0·001; Government physicians: OR 11·49, P < 0·0001] and were less likely to prescribe antibiotics for all diarrhoea cases (MBBS: OR 0·30, P = 0·002; postgraduates: OR 0·20, P < 0·001; Government physicians OR 0·24, P < 0·029). Better knowledge was associated with a lower likelihood of prescribing antibiotics for diarrhoea (OR 0·72, P < 0·001), cholera (OR 0·78, P = 0·027) and investigative procedure (OR 0·85, P = 0·028). In the slums of Kolkata, diarrhoea-related knowledge and practice were poor with the exception of qualified physicians, hence an improvement in the knowledge of pharmacists and unqualified practitioners is necessary for the overall improvement of diarrhoeal management in these slums.

Role of probiotic in preventing acute diarrhoea in children: a community-based, randomized, double-blind placebo-controlled field trial in an urban slum.

Acute diarrhoea remains a major public health challenge in developing countries. We examined the role of a probiotic in the prevention of acute diarrhoea to discover if there was an effect directed towards a specific aetiology. A double-blind, randomized, controlled field trial involving 3758 children aged 1-5 years was conducted in an urban slum community in Kolkata, India. Participants were given either a probiotic drink containing Lactobacillus casei strain Shirota or a nutrient drink daily for 12 weeks. They were followed up for another 12 weeks. The primary outcome of this study was the occurrence of first episodes of diarrhoea. We assessed this during 12 weeks of intake of study agent and also for 12 weeks of follow-up. There were 608 subjects with diarrhoea in the probiotic group and 674 subjects in the nutrient group during the study period of 24 weeks. The level of protective efficacy for the probiotic was 14% (95% confidence interval 4-23, P<0·01 in adjusted model). The reduced occurrence of acute diarrhoea in the probiotic group compared to nutrient group was not associated with any specific aetiology. No adverse event was observed in children of either probiotic or nutrient groups. The study suggests that daily intake of a probiotic drink can play a role in prevention of acute diarrhoea in young children in a community setting of a developing country.

Molecular characterization of antigen B2 subunit in two genotypes of Echinococcus granulosus from Indian bubaline isolates, its stage specific expression and serological evaluation.

Echinococcus granulosus is a parasitic helminth which affects both man and animals. During infection with larval stage of the organism secretory and membrane-bound (S/M) proteins play a meaningful role for evasion of immune system. Antigen B (AgB) is one of them. Present investigation has defined sequence diversity of AgB2 subunit of cattle and buffalo isolates of the organism. A total of 55 isolates were screened by polymerase chain reaction based single stranded conformation polymorphism (PCR-SSCP). Subsequently, six conformers could be detected. Based on predicted amino acid sequences of 90 amino acid residues, three clusters could be deduced. Sequence information of two buffalo isolates was homologous to AgB4 indicating gene switching phenomenon in between closely related isoforms. Numerical value of Tajima's D test proved negative selection pressure. Using artificial neural network (ANN), B cell linear epitope and stretches of agretope were predicted. Three clusters could be defined on the basis of B cell linear epitope. Out of three clusters, two showed more than 50% binding propensity with same MHCII alleles whereas, cluster 3 exhibited binding propensity with other MHCII alleles (DRB1_1501, DRB1_1502). Relative expression of AgB2 was more in active cysts (1.636 ± 0.092) followed by degenerating (0.449 ± 0.037) and calcified (0.255 ± 0.008). This result suggested that relative expression of AgB2 declines with progression of the disease. Using recombinant AgB2 sensitivity, specificity and accuracy of the ELISA test was 96.7, 94.7 and 95.9%, respectively. No cross reactivity was found with common cestode and trematode infected cattle and buffalo because cross reactive antigen was expressed intracellularly. Finally, this was concluded that AgB2 is the suitable immunological marker for detection, diagnosis and progression of the disease.

Influence of relative humidity in Vibrio cholerae infection: a time series model.

BACKGROUND & OBJECTIVES: Spread of cholera in West Bengal is known to be related to its ecosystem which favours Vibrio cholerae. Incidence of cholera has not been correlated with temperature, relative humidity and rainfall, which may act as favourable factors. The aim of this study was to investigate the relational impact of climate changes on cholera. METHODS: Monthly V. cholerae infection data for of the past 13 years (1996-2008), average relative humidity (RH), temperature and rainfall in Kolkata were considered for the time series analysis of Seasonal Auto-Regressive Integrated Moving Average (SARIMA) model to investigate relational impact of climatic association of V. cholerae infection and General Linear Model (GLM) for point estimation. RESULTS: The SARIMA (1,0,0)(0,1,1) model revealed that monthly average RH was consistently linear related to V. cholerae infection during monsoon season as well as temperature and rainfall were non-stationary, AR(1), SMA(1) and SI(1) (P<0.001) were highly significant with seasonal difference. The GLM has identified that consistent (<10%) range of RH (86.78 ± 4.13, CV=5.0, P <0.001) with moderate to highest (>7 cm) rainfall (10.1 ± 5.1, CV=50.1, P <0.001) and wide (>5-10ºC) range of temperature (29.00 ± 1.64, CV=5.6, P <0.001) collectively acted as an ideal climatic condition for V. cholerae infection. Increase of RH to 21 per cent influenced an unusual V. cholerae infection in December 2008 compared to previous years. INTERPRETATION & CONCLUSIONS: V. cholerae infection was associated higher RH (>80%) with 29°C temperature with intermittent average (10 cm) rainfall. This model also identified periodicity and seasonal patterns of cholera in Kolkata. Heavy rainfall indirectly influenced the V. cholerae infection, whereas no correlation was found with high temperature.

Polymorphism and natural selection of antigen B1 of Echinococcus granulosus isolated from different host assemblages in India.

Antigen B (AgB) is an excretory-secretory product of larval stage of Echinococcus granulosus. This antigen is abundantly secreted by larval stage of the worm. AgB is encoded by a multigene family and is suggested to be involved in evasion of host immune system. During the present study a total of 110 animal isolates of E. granulosus has been screened by mutation scan screening. A total of 14 conformers were detected on the basis of single strand banding profile of 129 bp fragment of AgB1 subunit. Analysis of sequence information of 14 conformers could cluster the isolates into two different group viz. buffalo-cattle and sheep-goat cluster. Conceptual amino acid sequence information of two clusters could be differentiated in terms of MHCII binding propensity of agretope and B-cell epitope region. This type of analysis of clustering of animal isolates on the basis of binding propensity towards different MHC antigens and B-cell linear epitope is the example of its own kind. Positive Tajima's D value indicated that, AgB1 is under balancing selection pressure which might be considered as heterogeneous selection pressure exerted by the host.

Relative expression of antigen B coding gene of bubaline isolates of Echinococcus granulosus in fertile and sterile cysts.

This article communicates the relative quantification of five isoforms of antigen B (AgB) of Echinococcus granulosus. Relative expression of the AgB was quantified in active and inactive cysts. Cysts with germinal membrane, clear cyst fluid and protoscoleces showed uniform expression of the five isoforms and were utilized as control. Relative expression of AgB1 was the highest in cysts, where calcification has initiated. AgB2 and AgB4 were expressed more in fertile cysts irrespective of the condition of germinal membrane. The lowest expression of AgB3 was seen in calcified cysts. The relative expression of AgB5 could not be correlated with respect to the condition of the cyst because AgB5 is typically expressed by the adult stage of the parasite.

Relative expression of the 14-3-3 gene in different morphotypes of cysts of Echinococcus granulosus isolated from the Indian buffalo.

The metacestode stage of Echinococcus granulosus is of zoonotic importance. In general, the 14-3-3 protein is involved in multiplication and survival of eukaryotes. Therefore, this communication presents succinct information on relative expression of the 14-3-3 protein in six different morphotypes of cysts of E. granulosus. All isolated E. granulosus belonged to the common sheep strain (G1). Relative expression of the 14-3-3 protein was higher in fertile cysts when compared to sterile cysts. The predicted amino acid sequence of the 14-3-3 protein was closely clustered with zeta-type isoforms 1 and 2 of the 14-3-3 protein. In addition, the present study demonstrates the presence of the 14-3-3 protein which until now had not been detected in the germinal layer. Our findings indicate that the expression of this biomolecule in the germinal layer of sterile organisms may contribute to the development and survival of the parasite in the host. The uniform expression of actin II conclusively proves the survivability of the harvested organisms.

Occurrence, significance & molecular epidemiology of cholera outbreaks in West Bengal.

BACKGROUND & OBJECTIVE: Diarrhoeal disease outbreaks are causes of major public health emergencies in India. We carried out investigation of two cholera outbreaks, for identification, antimicrobial susceptibility testing, phage typing and molecular characterization of isolated Vibrio cholerae O1, and to suggest prevention and control measures. METHODS: A total of 22 rectal swabs and 20 stool samples were collected from the two outbreak sites. The V. cholerae isolates were serotyped and antimicrobial susceptibility determined. Pulsed- field gel electrophoresis (PFGE) was performed to identify the clonality of the V. cholerae strains which elucidated better understanding of the epidemiology of the cholera outbreaks. RESULTS: Both the outbreaks were caused by V. cholerae O1 (one was caused by serotype Ogawa and the other by serotype Inaba). Clinically the cases presented with profuse watery diarrhoea and dehydration. All the tested V. cholerae isolates were sensitive to tetracycline, gentamycin and azithromycin but resistance for ampicillin, co-trimoxazole, nalidixic acid, and furazolidone. PFGE pattern of the isolates from the two outbreaks revealed that they were clonal in origin. Stoppage of the source of water contamination and chlorination of drinking water resulted in terminating the two outbreaks. INTERPRETATION & CONCLUSION: The two diarrhoeal outbreaks were caused by V. cholerae O1 (Inaba/Ogawa). Such outbreaks are frequently seen in cholera endemic areas in many parts of the world. Vaccination is an attractive disease (cholera) prevention strategy although long-term measures like improvement of sanitation and personal hygiene, and provision of safe water supply are important, but require time and are expensive.

Mechanism of lead induced effects on human spermatozoa after occupational exposure.

OBJECTIVES: Occupational lead exposure caused several types of male reproductive impairments in different working populations. In the present study we examined the paint factory workers of active reproductive age and compared the data with the non-occupationally exposed desk job holders taken as control from Bangalore, India. MATERIALS AND METHODS: In the above perspective, sperm cell morphology, morphometery and motile activity were assessed. Routine seminal biochemistry, cell cycle phase analysis of sperm head DNA, estimation of serum reproductive hormones and metal levels in blood and semen were also taken into account. RESULT: Low sperm velocity, ATPase activity, gross and forward progressive motility with high stationary motile spermatozoa revealed lowering of cellular activity after lead exposure (p<0.001), which was supported by high seminal plasma fructose level (p<0.001). Lowering of seminal plasma total protein with concomitant rise in free amino acid level was prevalent as the exposure increased (p<0.001), suggesting disturbance in cellular nutritional support essential for cellular motility. Prolonged liquefaction time, reduced semen volume and viscosity as well as altered seminal plasma protein, fructose and cholesterol level among the workers indicated dysfunction of accessory sex glands viz. prostate and seminal vesicle after occupational lead exposure (p<0.001). Deterioration of sperm count, structural abnormality of spermatozoa and sperm head DNA hyploidy was also associated with high blood and semen lead levels in the paint factory workers (p<0.001) without interfering serum FSH, LH and testosterone level (non-significant at p<0.05). CONCLUSION: Therefore, the present study suggested that at the present exposure level lead might cross blood-testis-barrier and increased its value in semen of the occupationally exposed paint factory workers in Bangalore, India, thereby producing detrimental effects on semen quality and sperm characteristics.

Epidemiological, microbiological & electron microscopic study of a cholera outbreak in a Kolkata slum community.

BACKGROUND & OBJECTIVE: Epidemics of cholera caused by Vibrio cholerae O1 or O139 have been reported from different parts of India. Factors such as unsafe water supply, poor environmental sanitation, indiscriminate defaecation and lack of personal hygiene are mainly responsible for continued transmission of this disease. We report here epidemiological and microbiological findings of a localized outbreak of cholera, which occurred during March and April 2004 in the eastern part of Kolkata city. METHODS: The affected slum area has a population of 4409, predominantly muslims. Patients suffering from acute watery diarrhoea attended the health outposts organized by National Institute of Cholera and Enteric Diseases, Kolkata and International Vaccine Institute, South Korea as part of a routine surveillance programme at the locality as well as the emergency medical camp organized by the Kolkata Municipal Corporation. Stool and water samples were collected and tested for diarrhoeagenic pathogens in the laboratory. Bacteriophages specific for V. cholerae were isolates and studied electron microscopically for morphology. RESULTS: A total of 89 diarrhoea cases were reported giving an attack rate of 2 per cent. V. cholerae O1 biotype ElTor, serotype Ogawa was isolated as a sole pathogen from 15 (15.8%) of 89 stool samples screened. Water samples (2 from tube wells, 3 from municipal taps and 1 from well) showed presence of coliform bacilli with high MPN (Most Probable Number) count. Bacteriophages specific to V. cholerae were isolated from 2 of 6 water samples examined. A leakage was detected in the main pipeline supplying drinking water to that area. INTERPRETATION & CONCLUSION: The outbreak was caused by V. cholerae O1 (Ogawa) biotype ElTor. The presence of phages in the water samples was an additional indicator for V. cholerae contamination in this community. Occurrences of such outbreaks support vaccination against cholera as an alternative strategy.

Periodic deworming with albendazole and its impact on growth status and diarrhoeal incidence among children in an urban slum of India.

This study was undertaken to measure the impact of periodic deworming with albendazole on growth status and incidence of diarrhoea in children aged 2-5 years in an urban setting in India and to assess the feasibility of local health workers implementing the procedures involved. This was a double-blind, placebo-controlled, randomized, community-based intervention trial with 702 children randomly allocated to receive either albendazole or placebo. The two study groups received two doses of albendazole (400 mg) or placebo six months apart. Mean weight increased significantly in the albendazole group compared to the control group at three months, six months and nine months following treatment (P<0.01, P<0.01 and P<0.001 respectively). The albendazole group also experienced fewer episodes of diarrhoea than their control counterparts (relative risk 1.3, 95% CI 1.07-1.53) with a 28% reduction. The health workers administered the correct dosage satisfactorily and there were no adverse effects. Thus, periodic mass deworming with albendazole would seem to be a safe and effective method that could be adopted at the community level or as an integral part of school health services and could be expected to improve growth and reduce the incidence of diarrhoea in children.

Prognostic significance of plasma markers of immune activation, HIV viral load and CD4 T-cell measurements.

OBJECTIVE: To evaluate the prognostic significance for AIDS occurrence of plasma levels of immune activation markers in comparison with and in conjunction with HIV viral load and CD4 T-cell measurements. DESIGN: A retrospective analysis was conducted of three plasma activation markers, the soluble tumor necrosis factor (TNF) receptor II (TNF-RII), neopterin and soluble interleukin-2 receptor levels, and of CD4 T-cell levels and plasma HIV viral load. SUBJECTS: The participants were 659 men taking part in the University of California Los Angeles Multicenter AIDS Cohort Study who were HIV-seropositive but AIDS-free in 1985. MAIN OUTCOME MEASURE: Clinically defined AIDS within 3 years. Failure time statistical regression models for the time to development of AIDS were used to assess prognostic capacity of the parameters alone and in combination. RESULTS: All the markers had prognostic capability. The levels of the three plasma activation markers correlated well with each other (median r = 0.61). They related less well with HIV RNA plasma levels (median r = 0.50) and least well with CD4 cell levels (median r = 0.36). Furthermore, plasma marker levels were shown to be able to stratify patients for prognosis within all the major categories of CD4 T-cell and HIV RNA levels. CONCLUSIONS: Plasma levels of soluble TNF-RII and other soluble markers of immune activation have prognostic capabilities which are different from HIV and CD4 T-cell levels. Combination of a single plasma activation marker measurement (such as soluble TNF-RII) with CD4 T-cell levels improved the prognostic capability of each. A new graphic technique for presenting prognostic capability indicated that plasma soluble TNF-RII and CD4 cell levels are better prognostic factors than HIV plasma level with CD4 cells < 200 x 10(6)/l. Inexpensive tests for one of the plasma activation markers, such as soluble TNF-RII or neopterin, can be useful for evaluations of HIV disease course, especially when expensive equipment, technical expertise and funding required for flow cytometry and for HIV load measurements are not readily available.

Sexual risk factors for cervical cancer among rural Indian women: a case-control study.

BACKGROUND: The association between sexual behaviour and cervical cancer is well established. Despite a high incidence of cervical cancer in India, its role has not been widely investigated in Indian women among whom the rate of sexual promiscuity is known to be very low. A hospital-based case-control study was carried out to investigate the role of sexual risk factors in cervical cancer among rural Indian women. METHODS: A case-control design was used in which a total of 268 subjects, comprising 134 women with invasive cervical cancer as cases and 134 control women were studied. A multiple logistic regression model was used to analyse the data. RESULTS: The risk factors found to be associated with cervical cancer were early age at first coitus, extramarital sex partners of women and the time interval since first exposure. In a multiple logistic regression model, independent effects were observed for early age at first coitus, showing maximum risk in women who reported their first intercourse at < 12 years of age, compared to that of women at > or = 18 years (odds ratio [OR] = 3.5. 95% confidence interval [CI]: 1.1-10.9). Increased risk was also seen for women who had extramarital sex relationships (OR = 5.5, 95% CI: 1.5-19.5). The significant effect of early age at first coitus persisted after adjustment for latency period which also showed its independent risk association with cervical cancer in the multivariate analysis. CONCLUSION: These findings confirm the association between early age at first coitus and cervical cancer in women with a low rate of sexual promiscuity and define the role of these risk factors in cervical carcinogenesis among rural Indian women.

PIP: The association between sex behavior and cervical cancer was investigated among rural Indian women known to have very low levels of promiscuity. 134 women with invasive cervical cancer were matched with 134 controls and analysis performed using a multiple logistic regression model. Risk factors associated with cervical cancer were early age at first coitus, extramarital sex partners of women, and the time interval since first exposure. Independent effects were observed for early age at first coitus, with maximum risk among women who reported their first intercourse at younger than age 12 years compared to that of women at age 18 years or older. Increased risk was also seen for women who had extramarital sex relationships. The significant effect of early age at first coitus persisted after adjustment for a latency period which also showed its independent risk association with cervical cancer in the multivariate analysis.

The significance of enteroaggregative Escherichia coli in the etiology of hospitalized diarrhoea in Calcutta, India and the demonstration of a new honey-combed pattern of aggregative adherence.

Previous studies have identified enteroadherent Escherichia coli that exhibit localized adherence, diffuse adherence and atypical diffuse adherence as diarrhoeagenic agents associated with infantile diarrhoea in Calcutta, India. In this study, a DNA probe specific for enteroaggregative adherence was used to determine the etiological significance of enteroaggregative E. coli in the causation of diarrhoea. From a total of 330 strains of E. coli recovered from 159 cases of acute secretory diarrhoea and 174 cases of invasive diarrhoea, 20 strains hybridized with the probe, whereas of the 25 E. coli strains recovered from 25 healthy controls only 1 strain hybridized with the probe. Of the 21 probe positive strains, 19 adhered to HeLa cells in the typical stacked-brick pattern while 2 strains recovered from 2 cases of secretory diarrhoea adhered to the glass surface in a hitherto undescribed formation which we have termed, based on the appearance, as the honey-comb pattern. The enteroaggregative E. coli strains identified in this study did not produce any conventional enterotoxins and were significantly associated with patients with secretory diarrhoea (10.7%) than with invasive diarrhoea (1.7%). The results of this study indicate that enteroaggregative E. coli play a causal role in acute secretory diarrhoea in this part of the world which lends credence to the involvement of a potent toxin in the pathogenesis of EAggEC mediated infections.

Use of PCR to identify enteroaggregative Escherichia coli as an important cause of acute diarrhoea among children living in Calcutta, India.

The importance of enteroaggregative Escherichia coli (EAggEC) as a possible aetiological agent of acute diarrhoea among children in Calcutta, India, was investigated. Simultaneously the use of a previously described PCR diagnostic system was assessed for its ability to identify EAggEC infection. E. coli strains isolated during a 1-year case-control study from faecal samples of 388 children aged <5 years, with or without diarrhoea, were examined for EAggEC by HeLa cell adherence assay in parallel with a PCR assay with primers generated from an EAggEC DNA probe. A blind comparison was made between the two methods to determine their diagnostic potential. E. coli isolates that adhered to HeLa cells in an aggregative pattern were the sole isolates significantly more often in 254 cases (9%) than in 134 control (2%) children. Age stratification showed that EAggEC were isolated more frequently from children aged <36 months. The EAggEC isolates belonged to several O serogroups and showed multiple drug resistance. Both methods were positive for 26 samples, nine samples were positive by PCR alone and seven samples were positive by culture alone, thus indicating a 78% sensitivity and 97% specificity for the PCR assay. EAggEC is an important aetiological agent of acute diarrhoea among infants in and around Calcutta, and the PCR diagnostic system may be useful to identify such infection in epidemiological studies.

Epidemiological and clinical profiles of acute invasive diarrhoea with special reference to mucoid episodes: a rural community-based longitudinal study.

A study was carried out in 3 villages near Calcutta, India, having a population of 5464, between August 1992 and December 1994. A cohort of rural children below 4 years of age was prospectively observed to determine the clinico-epidemiological aspects of mucoid diarrhoea and examine propensity to invasiveness. Overall, the incidence of diarrhoea was 1.7 episodes/child/year, and that of mucoid and bloody dysentery was 0.8 and 0.2 episodes/child/year, respectively. Children aged 6-11 months had a higher incidence of mucoid diarrhoea (1.3 episodes/child/year) and the peak season occurred in June and July. Multivariate analysis using logistic regression showed that mucoid diarrhoea and bloody dysentery were closely similar in both clinical and laboratory findings, including raised faecal leucocyte count (> 10/high power microscope field [hpf]). However, abdominal pain occurred more frequently in bloody dysentery than in mucoid diarrhoea. Faecal leucocyte count (> 10/hpf) can therefore be used as an indicator for invasiveness of mucoid diarrhoea at the community level.

Retinoic acid-regulated cellular differentiation and mucin gene expression in isolated rabbit tracheal-epithelial cells in culture.

Rabbit tracheal epithelial cells were cultured in a serum-free and hormone-supplemented medium with and without retinoic acid. The cells showed time-dependent mucin gene expression when cultured in the medium with retinoic acid. In the absence of retinoic acid, however, mucin mRNA was barely detectable in the cells. When retinoic acid was added back to the medium, the mucin message was prominent again. Actinomycin D and cycloheximide did not inhibit mucin gene expression. The mucin message was slightly elevated by cAMP agonists. A mucin antisense oligomer inhibited the retinoic acid-induced mucin mRNA expression and secretion, thus offering an alternate approach in the management of mucus hypersecretion in upper airway respiratory diseases such as chronic bronchitis, asthma, and cystic fibrosis.

Deglycosylation of neutral and acidic human colonic mucin.

Human colonic mucin has been isolated from normal colonic mucosa by a phenol-water extraction procedure and purified by Sepharose 2B column chromatography. The mucin was further purified by cesium bromide density gradient centrifugation. Sodium dodecyl sulfate-polyacrylamide gel (5%) electrophoresis of this material showed high-molecular-weight mucin component(s) at the top of the gel. Chemical analyses of this preparation indicated a typical mucin profile of amino acids and carbohydrates. Ion-exchange chromatography resulted in the separation of two major fractions, one being more acidic than the other. Chemical deglycosylation of the purified preparation at 20 degrees C for 3 1/2 showed loss of sialic acid, fucose, galactose, and N-acetylglucosamine, whereas traces of N-acetylgalactosamine were still detected. High-pressure liquid chromatography of the deglycosylated material resulted in the purification of a major peptide, P1, with high levels of threonine, serine, and proline, resembling, in most respects, the profile of native mucin. The molecular weight of the peptide was determined to be approximately 97 kDa and serine was the single NH2 terminus.

In vitro effects of drugs on production of mucins in rabbit tracheal epithelial cells expressing mucin gene: a model system for studying upper airway respiratory diseases.

Rabbit tracheal epithelial cells, cultured on collagen-coated dishes in serum-free and hormone-supplemented medium, were found to incorporate [3H]glucosamine into high-molecular-weight components that were secreted in the medium. The chemical analysis of the secreted products resulted in a profile that resembled that of mucous glycoproteins (mucins). When examined by dot blot analysis, the total RNA isolated from these cells hybridized to an antisense 30-mer oligonucleotide corresponding to a rat intestine mucin peptide sequence, indicating that mucin gene was expressed in these cell lines. Lung and liver tissues of rabbit did not express this gene. Transmission electron microscopy exhibited secretory granules in these cells. The incorporation of [3H]glucosamine into mucins was inhibited by three aryl-N-acetyl-galactosaminides and a chemical carcinogen, N-nitroso-N-ethyl urea, whereas 5-azacytidine enhanced the proliferation of cells as well as the radiolabeling of mucins. Parasympathetic agent (pilocarpine), cholinergic antagonist (atropine), and beta-adrenergic agonist (isoproterenol) alone have little effect on the secretion of mucins. The cholinergic agonist, methacholine, was found to increase the production of mucins and addition of atropine to the medium before methacholine blocked this stimulation. Histamine was found to stimulate mucin production in these cells.

Differentiation of respiratory epithelium: the effects of retinoic acid and carcinogens on the expression of mucociliary vs. squamous phenotype.

Changes in ultrastructural characteristics and mucin gene expression were examined in rat tracheal explants cultured in a synthetic medium +/- retinoic acid (RA), benzo[a]pyrene (B[a]P) and N-methyl-N-nitrosourea (NMNU). In the RA(+) cultures, no changes in either ultrastructural features or mucin gene expression were detected after 48 h incubation. After 96 h incubation, however, the ultrastructural features associated with the squamous phenotype were characteristics of cultures containing the two carcinogens and the mucin gene expression was slightly reduced. Thus, in the presence of retinoic acid, the carcinogen induced changes in cytology to the squamous phenotypes were not matched by a marked loss of mucin gene expression. Explants cultured for 48 h without RA and +/- carcinogens showed none of the cytological changes associated with onset of the squamous phenotype. While mucin mRNA was still detected, it was clearly reduced compared to 48 h cultures in RA(+) medium. However, 48 h later, all explants exhibited pronounced squamous metaplasia and the mucin message decreased to trace levels. Thus, the results of these experiments with B[a]P and NMNU in RA(+) and RA(-) media indicates that at least the early carcinogen induced changes may be distinct from those associated with the retinoid pathway controlling expression of the mucin component of the mucociliary epithelium.