Use of the polymerase chain reaction and fluorescent-antibody methods for detecting viable but nonculturable Shigella dysenteriae type 1 in laboratory microcosms

Epidemiological studies of shigellosis in Bangladesh have demonstrated that surface-water sources can act as foci of infection. Studies of laboratory microcosms have shown that shigellae become nonculturable but remain viable when exposed to environmental samples of water. The present study was carried out to detect viable but nonculturable Shigella dysenteriae 1 from laboratory microcosms by the polymerase chain reaction and the fluorescent-antibody techniques. S. dysenteriae 1 was inoculated into laboratory microcosms consisting of water samples collected from ponds, lakes, rivers, and drains in Bangladesh. The survival of S. dysenteriae in microcosms was assessed by viable counting on MacConkey agar. After 2 to 3 weeks, S. dysenteriae 1 became nonculturable but remained viable. After 6 weeks, this nonculturable but viable S. dysenteriae 1 was detected by both the polymerase chain reaction and the fluorescent-antibody methods. The viable but nonculturable state of S. dysenteriae 1 demonstrated in this study may be important for understanding the epidemiology of shigellosis.

Growth and survival of Shigella flexneri in common Bangladeshi foods under various conditions of time and temperature

Survival and growth of Shigella flexneri were assessed in various foods, including boiled rice, lentil soup, milk, cooked beef, cooked fish, mashed potato, mashed brinjal, and raw cucumber. Growth at 25 and 37 degrees C and survival at 5 degrees C were observed by viable counts on MacConkey agar. The organism grew well in all tested foods and growth increased from 10(5) to 10(8) to 10(10) cells per ml or g within 6 to 18 h after inoculation at 25 and 37 degrees C.

Ca(2+)-induced Ca2+ release in insulin-secreting cells

The sulphydryl reagent thimerosal (50 microM) released Ca2+ from a non-mitochondrial intracellular Ca2+ pool in a dose-dependent manner in permeabilized insulin-secreting RINm5F cells. This release was reversed after addition of the reducing agent dithiothreitol. Ca2+ was released from an Ins(1,4,5)P3-insensitive pool, since release was observed even after depletion of the Ins(1,4,5)P3-sensitive pool by a supramaximal dose of Ins(2,4,5)P3 or thapsigargin. The Ins(1,4,5)P3-sensitive pool remained essentially unaltered by thimerosal. Thimerosal-induced Ca2+ release was potentiated by caffeine. These findings suggest the existence of Ca(2+)-induced Ca2+ release also in insulin-secreting cells.

Distribution of Plesiomonas shigelloides in various components of pond ecosystems in Dhaka, Bangladesh

Plesiomonas shigelloides is considered to be a waterborne agent of human gastroenteritis. An ecological study was carried out in five ponds in Dhaka city over a period of one year to elucidate the distribution and seasonality of this organism in various components of pond ecosystems. Samples were collected from hydrophytes, water, phytoplankton and sediment every 15 days over 12 months and cultured for P. shigelloides. P. shigelloides was isolated from a total of 120 samples including 25 (20.8%), 16 (13.3%), 22 (18.3%) and 35 (29.2%) of hydrophytes, water, phytoplankton and sediment samples, respectively. Distinct seasonal patterns of isolation of P. shigelloides were observed in the four components with two distinct peaks. The highest peaks were observed in hydrophytes and water samples in May and in phytoplankton and sediment in November. P. shigelloides was isolated from all components from all ponds during the study period. These results suggest that P. shigelloides is an autochthonous member in the freshwater pond ecosystems in Dhaka, Bangladesh.

Interaction with the inositol 1,4,5-trisphosphate receptor promotes Ca2+ sequestration in permeabilised insulin-secreting cells

Electropermeabilised insulin-secreting RINm5F cells sequestered Ca2+, resulting in a steady-state level of the ambient free Ca2+ concentration corresponding to 723 +/- 127 nM (mean +/- SEM, n = 10), as monitored by a Ca(2+)-selective minielectrode. Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) promoted a rapid and pronounced release of Ca2+. This Ca2+ was resequestered and a new steady-state Ca2+ level was attained, which was always lower (460 +/- 102 nM, n = 10, P less than 0.001) than the steady-state Ca2+ level maintained before the addition of Ins(1,4,5)P3. Whereas the initial reuptake of Ca2+ subsequent to Ins(1,4,5)P3 stimulation was relatively slow, the later part of reuptake was fast as compared to the reuptake phases of a pulse addition of extraneous Ca2+. In the latter case the uptake of Ca2+ resulted in a steady-state level similar to that found in the absence of Ins(1,4,5)P3. Addition of Ins(1,4,5)P3 under this condition resulted in a further Ca2+ uptake and thus a lower steady-state Ca2+ level. Heparin, which binds to the Ins(1,4,5)P3 receptor, also lowered the steady-state free Ca2+ concentration. In contrast to Ins(1,4,5)P3, inositol 1,3,4,5-tetrakisphosphate was without effect on Ca2+ sequestration. These findings are consistent with the presence of a high-affinity Ins(1,4,5)P3 receptor promoting continuous release of Ca2+ under basal conditions and/or the Ins(1,4,5)P3 receptor being actively involved in Ca2+ sequestration.

Effect of pulsed electromagnetic field on healing of experimental nonunion in rat tibiae

To see the effect of Pulsed Electromagnetic Field (PEMF) on nonunited fracture healing, nonunion was induced in rat tibiae and PEMF was applied on it. Out of five different techniques utilised for inducing nonunion soft tissue interposition was found to be the most suitable and effective method of experimental induction of nonunion. Twenty eight experimental and 15 control rats were finally evaluated for the effect of PEMF applied for up to 8 weeks. After sacrifice of 8 experimental and 4 controls, 6 experimental and 3 controls, again 6 experimental and 3 controls and finally 8 experimental and 5 controls at 2, 4, 6 and 8 weeks respectively of PEMF application no significant difference as to the quality of healing was observed between the experimental and control animals. It was thus concluded that PEMF appeared to have no beneficial effect on the healing of nonunited fractures in experimental set-up.

Multiple reuse of disposable insulin syringes in hospital

In a prospective study disposable insulin syringes were repeatedly used for injecting insulin to 92 insulin-taking diabetic patients admitted in hospital with various illnesses. One separate syringe was used for each patient; the syringes were not washed or boiled and were not kept in spirit or in refrigerator during reuse. Syringes were flushed with air, needle recapped and replaced into their plastic cover. Number of injections made using one syringe was 2 to 120 (mean 31.3, SEM 2.3). For the patients' total insulin - taking period in hospital one disposable syringe per patient was enough in all but six cases. There were 2792 reinjections and incidence of infection of the injection site was zero.

Captopril induces correction of postrenal transplant erythremia

Kidney transplant patients may develop post-transplant erythremia (PTE), and in order to avoid thromboembolism venesection, anticoagulation and native kidney removal have been suggested. We propose captopril as an alternative therapy for PTE. Seven hypertensive PTE patients, aged 42 +/- 10 years with stable renal function, were investigated to exclude primary or secondary polycythemia. All patients manifested true erythrocytosis [red blood cells (RBC) mass greater than 20% of predicted level] with concomitant increases in hematocrit and hemoglobin levels. Captopril was introduced in gradually increasing doses up to 75 mg/day under careful monitoring of blood pressure and renal function. Weekly follow-up was arranged to evaluate drug efficacy. After captopril, a significant reduction with normalization of the RBC mass (42 +/- 4 vs 31 +/- 5 ml/kg: P less than 0.005) was observed. The RBC counts and hematocrit and hemoglobin levels also decreased. One patient had recurrent erythrocytosis after captopril withdrawal. Captopril may be a simple, effective, and non aggressive treatment for postrenal transplant erythremia.

Initiating a crystallographic study of trypanothione reductase

We have obtained well-ordered single crystals of the flavoenzyme trypanothione reductase from Crithidia fasciculata. The crystals are tetragonal rods with unit cell dimensions a = 128.6 A, c = 92.5 A. The diffraction pattern corresponds to a primitive lattice. Laue class 4/m. Diffraction to better than 2.4 A has been recorded at the Daresbury Synchrotron. The accurate elucidation of the three-dimensional structure of this enzyme is required to support the rational design of compounds active against a variety of tropical diseases caused by trypanosomal parasites.

Production and characterization of monoclonal antibodies with therapeutic potential against Shiga toxin

Four monoclonal antibodies (T2D1, T3B1, T7B2 and T4C4) were produced and characterized against Sh. dysenteriae type 1. These monoclonal antibodies (McAbs) were shown to be directed against the same or adjacent determinants on the A-subunit of the Shiga toxin. All the anti-Shiga toxin McAbs are IgG1 (kappa) antibodies and have the capacity to neutralize the cytotoxic and neurotoxic effects of the Shiga toxin: the data strongly suggest that both of the activities, associated with the toxin, are due to the same molecule. In addition, the McAbs were found to be highly protective, at low dose, when administered therapeutically to lethally-treated animals.

[Dose-response pattern of inhaled sulfur dioxide (SO2) in rabbits pretreated with papain or sodium chloride aerosols]

The study was conducted on 29 New-Zealand female rabbits to examine the dose-response pattern of SO2 in inhaled air. A group of 14 animals was exposed to papain-aerosol (P-A) twice a week for 1 h each over 12 weeks in order to increase bronchial reactivity. A group of 9 animals received similar treatment but with saline-aerosol (NaCl-A); this group served for control. The third group of 6 animals remained untreated (K). After 12 weeks of treatment individual animals were anesthetized and the P-A and NaCl-A groups were exposed for 5 min each to different concentrations of SO2 (0.0, 1.0, 2.0, 4.0 and 9.0 mg/m3). The animals of group K were treated similarly but they were exposed 5X to synthetic air; this group served the purpose to follow the anesthesia effect on respiration and cardio-vascular system. The recovery period was 30 min between the exposures. The K-animals showed gradual decrease of lung resistance (R1). In contrast P-A and NaCl-A animals both showed a clear increase in R1 following exposure to SO2, and R1 was considerably higher in P-A than in NaCl-A animals. The maximum change in R1 was caused by exposure to 4.0 mg/m3 SO2 and it was even greater than the response produced by 9.0 mg/m3 SO2 in P-A animals. A similar pattern of response was also observed in NaCl-A animals, but the highest increase in R1 was caused by exposure to 2.0 mg/m3 SO2. From these results it can be concluded that high concentration of SO2 could have a damaging effect on sensory receptors of the tracheobronchial system.

Effect of various biophysicochemical conditions on toxigenicity of Vibrio cholerae 01 during survival with a green alga, Rhizoclonium fontanum, in an artificial aquatic environment

Toxigenic and nontoxigenic strains of Vibrio cholerae 01 occur in the natural aquatic environment. It is not clear whether V. cholerae 01 lose toxigenicity and become nontoxigenic during survival in the aquatic environment as a result of the effect of various biophysicochemical conditions (e.g., sunlight, pH, temperature, competition with other bacteria for nutrients, etc.). Five toxigenic strains were exposed to artificial aquatic environments in the presence of a filamentous green alga. Rhizoclonium fontanum, and recovered after different time intervals (0 and 0.5 h, 3, 6, 9, and 15 days). This experimental system was exposed to sunlight and the V. cholerae 01 were in competition for nutrients with resident bacterial flora from R. fontanum. The toxigenicity of Vibrio cholerae 01 that were recovered at different time intervals was assessed by tissue culture assay using Vero cells. The toxigenicity of recovered strains was compared with that of the parent strains. The results demonstrated that toxigenic V. cholerae 01 are unlikely to lose their toxigenicity in aquatic environments as a result of the effects of various biophysicochemical conditions. These results are consistent with the hypothesis of environmental reservoirs of V. cholerae.

Increased toxin production by Vibrio cholerae O1 during survival with a green alga, Rhizoclonium fontanum, in an artificial aquatic environment

In the aquatic environment, the physiological state of Vibrio cholerae can be affected by various environmental conditions (e.g., sunlight, pH, temperature, competition with other bacteria for nutrients, etc.). The effect of these factors on the toxigenicity of V. cholerae was investigated. Toxin production by 5 toxigenic strains of V. cholerae incubated in laboratory microcosms containing Rhizoclonium fontanum was tested at different time intervals. The microcosms were exposed to sunlight, and the V. cholerae were in competition for nutrients with the resident bacterial flora of R. fontanum. The increase or decrease in toxin production by V. cholerae recovered at different time intervals was measured by ELISA and compared with the parent strains. Results of the study demonstrated an increase in toxin production by V. cholerae O1 during survival with R. fontanum. It is concluded that various environmental conditions in the aquatic environment affect toxin production by V. cholerae.

Survival of toxigenic Vibrio cholerae O1 with a common duckweed, Lemna minor, in artificial aquatic ecosystems

Cholera epidemics occur twice a year in Bangladesh. During epidemics, Vibrio cholerae O1 are isolated from patients, as well as from the surface water, but the bacteria disappear during inter-epidemic periods. Their reservoirs or sites of survival and multiplication during inter-epidemic period are still unknown. The present survival study in the laboratory explored the role of an aquatic plant, Lemna minor (duckweed), as a possible reservoir. L. minor was added to sea-salt solution at pH 8.5, containing V. cholerae. Survival of V. cholerae on L. minor, in water on which L. minor was floating, and in control water (without L. minor) was monitored at regular intervals. Survival of both environmental and clinical strains of V. cholerae was assessed by viable counts on thiosulphate-citrate-bile salt-sucrose agar. It was observed that both strains survived better on L. minor than in water on which L. minor was floating or in control water. It is suggested that plants may serve as an effective environmental reservoir for V. cholerae either through a non-specific association or by interaction with V. cholerae in commensal relationship.

Long-term persistence of toxigenic Vibrio cholerae 01 in the mucilaginous sheath of a blue-green alga, Anabaena variabilis

Cholera epidemics occur twice a year in the endemic area of Bangladesh. Vibrio cholerae 01 can be isolated from the environment only during the epidemics and the question of possible interepidemic environmental reservoirs of V. cholerae remains open. The present laboratory-based studies investigate the role of an aquatic alga, Anabaena variabilis, as a possible reservoir. Persistence of V. cholerae inside the mucilaginous sheath of A. variabilis was observed by phase-contrast and fluorescent microscopy for more than 15 months after inoculation.

[Status of lung function in females of a North Rhine-Westphalia rural and urban-industrial area]

A comparative investigation of the pulmonary function status was carried out in women, aged between 52 and 56 years, from a rural and a municipal industrial area in North Rhine Westphalia. A questionnaire that the subjects had to complete themselves, provided us with information on personal medical history, smoking habits, the nature of domestic heating, and social status (education). The function tests were performed in a mobile pulmonary function laboratory (Jäger, Inc.). The airway resistance (Raw) and the intrathoracic gas volume (ITGV) were measured with the aid of a constant-volume body plethysmograph; a pneumotachographic system was employed to measure the ventilatory pulmonary function. All lung volumes were recalculated in terms of BTPS, and expressed as a percentage of the predicted values. Women from Leverkusen complained somewhat more frequently of hay fever, allergies of all kinds, and non-respiratory disturbances, than did women from Borken. In contrast, respiratory symptoms were indicated equally frequently in both areas. In the case of the Leverkusen group, a mean Raw of 0.323 +/- 0.183 kPa.1-1.s, was obtained, and in the case of the Borken group, a mean Raw of 0.258 +/- 0.182 kPa.1-1.s; this difference is statistically significant (p less than 0.05). On average, the women from Leverkusen also had a significantly higher SRaw (p less than 0.005) and ITGV (p less than 0.05) than did the women from Borken. These results argue in favour of a negative influence of air pollution on the pulmonary function.

Attachment of toxigenic Vibrio cholerae 01 to various freshwater plants and survival with a filamentous green alga, Rhizoclonium fontanum

In Bangladesh, cholera epidemics occur twice a year. V. cholerae 01 are readily isolated from the environment only during epidemics. The interepidemic reservoirs or sites of survival and multiplication of V. cholerae are still unknown. Investigations were carried out with various fresh-water plants as possible reservoirs of V. cholerae in the environment. Attachment to and acute population changes of V. cholerae on various plant surfaces was used as a screening technique to screen a particular plant species for survival studies. Five plant species, Anabaena variabilis, Rhizoclonium fontanum, Cladophora sp., Fontinalis antipyretica and Elodea canadensis were used for attachment experiments. Among these plants, R. fontanum showed the best attachment. On the basis of attachment results, survival experiments were carried out with R. fontanum. At 0.05% salinity toxigenic V. cholerae 01 survive longer in the presence of R. fontanum than in medium without algae.

Production and characterization of monoclonal antibodies with diagnostic potential against Shigella flexneri

Highly specific monoclonal antibodies (McAbs), 1aM3, 2aM1 and 2bM2 were produced and characterized against Sh. flexneri 1a, 2a and 2b respectively. IaM3 is an IgG3 (lambda) type antibody reactive against whole bacteria or the lipopolysaccharide (LPS) only; 2aM1 is an IgG1 (kappa) type antibody which reacts with the polysaccharide component of LPS; 2bM2 is an IgG3 (lambda) type antibody which binds with both the polysaccharide and protein/peptide components of the LPS. The results indicate that specific McAbs with diagnostic potential can be produced using acetone-killed and dried cells as antigen. Ascitic fluid produced in mice using the anti-Sh. flexneri hybridomas was found not to contain higher titres of McAbs against the bacteria. A "nutritionally-deprived" medium was, therefore, constructed which produced greater than five times the concentration of the McAbs than that could be obtained using normal culture fluid.

Animal experimental model for studying respiratory and cardiovascular parameters in unanaesthetized rabbits

The purpose of the study was to examine the reproducibility of measurements of respiratory and cardiovascular functions in unanaesthetized rabbits. Observed coefficient of variations (CV) and hence the reproducibilities of different measurements in the present study were highly comparable to values reported for anaesthetized rabbits. So it could be concluded that anaesthetization is not a prerequisite to study respiratory and cardiovascular function in rabbits.