Biomedical subjects

M K Islam

Publications and source records attributed to M K Islam.

10 recordsLinked to original sources

PubMed2000

Examination of gastrointestinal helminth in livestock grazing in grassland of Bangladesh.

To determine association of grassland with parasitic diseases of livestock in Bangladesh, the 'Tracer' animals (two cow calves and two goats) were released for a month in a grassland used for communal grazing of livestock near school premise in Kanthal, Trishal, Mymensingh, Bangladesh. After slaughtering of the tracer animals, their gastrointestinal tract examination revealed six species of nematode and one cestode. The nematode species were Haemonchus contortus, Trichostrongylus axei, Mecistocirrus digitatus, Oesophagostomum spp., Trichuris spp. and Bunostomum sp. The cestode was one of the genus Moniezia. With this preliminary study, grasslands are thought to be one of the main sources of gastrointestinal parasitic diseases of livestock in Bangladesh.

Animals↗

PubMed1999

The potential for social mobilisation in Bangladesh: the organisation and functioning of two health insurance schemes.

Health insurance schemes are usually assessed according to technical indicators. This approach, however, neglects the dynamic perspective of insurance schemes as an element of people's mobilisation for participation in organising and managing health care delivery and financing. The first part of this paper describes the technical performance and the level of community involvement in management of the two largest health insurance schemes in Bangladesh, both in the rural areas and in the non-government sector. Part two discusses these achievements in light of the schemes' potential role as a mechanism for people's management of health care. A review of documents and key-informant interviews were conducted. Key findings include that (1) subscribers currently are not actively participating in scheme management. However, existing family groups, involved in credit programmes may serve as entry-points for interaction. This is sustained by the 'natural link' between health insurance as a means of spreading the risks of treatment costs and credit programmes as a means of decreasing the relative impact of illness on household income. (2) The schemes' role could be further enhanced, by improving their technical performance and applying health care systems elements with the input of all partners involved. These issues are avoidance of service duplication with other providers; better protection of the poorer households; inclusion of hospital care in the coverage package; simplification of scheme administration by introduction of episode-based co-payments instead of the current itemised ones and concentrating the schemes at the level of community-based services, which may be self-financed and also self-managed by the community, given available sensitisation, training and interaction. A shift to episode-based co-payments would also introduce solidarity among patients and among individuals at higher risk, such as pregnant women and under-fives. Finally, action-research is needed to document the process of increased community involvement.

Bangladesh↗

PubMed1999

Effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae.

The effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae (L3) to rats were investigated. A significantly higher body length was observed in L3 from filter paper culture (597.3 +/- 32.2 microns) than those in fecal (509.9 +/- 35.0 microns) and nutrient broth culture (503.3 +/- 31.0 microns) (P < 0.05). Larval infectivity was assessed by exposing rats to 1,000 L3 from each culture and worms were recovered from the lungs and small intestines. Recovery rate of these worms did not show any significant difference. A significantly greater body length of adults was recorded in those corresponding to the L3 harvested from filter paper (2,777.5 +/- 204.4 microns) and nutrient broth culture (2,732.5 +/- 169.8 microns) than those corresponding to the L3 obtained from fecal culture (2,600.5 +/- 172.4 microns) (P < 0.05). Although worm fecundity and EPG counts differed among culture methods but worm burdens and course of infection did not. These findings suggest that the methods of cultures have a significant effect on the morphological development of the larvae to the L3 stage, but do not influence the infectivity to rats.

Animals↗

PubMed1999

Partial cross-resistance between Strongyloides venezuelensis and Nippostrongylus brasiliensis in rats.

Rats were immunized through an initial infection with 1,000 filariform larvae (L3) of Nippostrongylus brasiliensis and after complete expulsion of worms they were challenged with 1,000 L3 of Strongyloides venezuelensis to investigate whether cross-resistance developed against a heterologous parasite. Nippostrongylus brasiliensis-immunized rats developed a partial cross-resistance against S. venezuelensis migrating larvae (MSL3) in the lungs and adult worms in the small intestine. The population of MSL3 in the lungs were significantly lower (P < 0.05) in immunized rats (22.0 +/- 7.4) compared with controls (105.0 +/- 27.6). The populations of adult worms, egg output and fecundity were initially decreased but from day 14 post-challenge they did not show any significant difference between immunized and control rats. However, the length of worm in immunized rat was revealed as retardation. Peripheral blood eosinophilia was significantly decreased (P < 0.05) on day 7 post-challenge and then gradually increased, which peaked on day 42 post-challenge when most of the worms were expelled. These results suggest that peripheral blood eosinophilia is strongly involved in the worm establishment and expulsion mechanisms.

Animals↗

PubMed1998

Development of an in vitro culture method for harvesting the free-living infective larvae of Strongyloides venezuelensis.

An in vitro culture technique was established for harvesting Strongyloides venezuelensis free-living infective larvae using a nutrient broth medium as a substitute for rat-feces in polyvinyl culture bags (10 x 12 cm). The egg hatch rate (Y) in sterile saline at different incubation temperatures (X) was expressed as the quadratic function, Y = -0.192X2 + 8.673X - 19.550 (r = 0.901). The highest (100%) egghatch rate was observed at 25 degrees C. A significant difference (p < 0.05) in development rate (Y) of free-living infective larvae was observed between different concentrations of nutrient broth (X) which was highest (20.6%) in 0.12% nutrient broth concentrations, incubated at 20 degrees C for 5 days [Y = -864.032X2 + 245.995X - 0.560 (r = 0.875)]. Yields (Y) of infective larvae were observed relatively high when the culture medium was incubated at higher temperatures (X) which peaked at 25 degrees C (20.0%) than at lower temperatures, 15 degrees C (10.9%) and 20 degrees C (18.1%) [Y = -0.189X2 + 8.387X - 72.795 (r = 0.981)]. The period (Y) required for the development of infective larvae decreased with higher incubation temperatures (X) [Y = 0.035X2 - 2.025X + 32.375 (r = 0.995)]. The highest yield (19.2%) of infective larvae was obtained from culture bag inoculated with 15,000 eggs than with below and over 15,000 eggs in 0.12% nutrient broth and incubated at 25 degrees C for 4 days. The newly adapted culture method (from egg to third-stage larva) may be useful as a bio-bar/bioassay system for screening new chemical products, anthelmintics and pesticides, as well as for parasito-immunological studies with Strongyloides species.

Animals↗

PubMed1998

Viability of eggs, filariform larvae and adults of Strongyloides venezuelensis (Nematoda: Strongyloidea) maintained in vitro.

The present study was performed to check the viability of eggs, filariform larvae and adults of Strongyloides venezuelensis exposed to various conditions for an in vitro maintenance. The eggs in the feces remained viable for about 25 days at 4 degrees C and 15 days at room temperature. However, the isolated eggs in sterile saline lost their viability within 24 hr at 4 degrees C. The eggs in morula stage were very sensitive to air drying and rapidly lost their viability (< or = 12 hr). Filariform larvae survived for a maximum period of 45 days in fecal suspension and 28 days in 0.12% nutrient broth in polyvinyl culture bags maintained at 20 degrees C. On the other hand, those isolated from nutrient broth cultures survived for a maximum period of 32 days in tap water and 22 days in sterile saline at 20 degrees C. The mature adult worms obtained from experimentally infected rats survived maximally for 9 days in serum supplemented (10% rat-serum) 0.12% nutrient broth and 4 days in serum free nutrient broth at 37 degrees C while the culture media were changed at an alternate day. The adult female worms deposited fertile eggs in serum supplemented and serum free nutrient broth cultures, however, the hatched larvae (L1) were not able to develop to the filariform stage in the culture media and found to die within 24 hr of maintenance. The present findings on an in vitro maintenance of different stages of S. venezuelensis may provide useful information for biological and biochemical studies with Strongyloides species.

Animals↗

PubMed1995

Effects of scatter generated by beam-modifying absorbers in megavoltage photon beams.

Transmission through a beam-modifying absorber consists of attenuated primary beam and scattered radiation generated by the absorber. The primary component of the transmitted beam is characterized by the narrow beam attenuation coefficient which depends upon the energy of the beam and type of the absorber. In addition to beam energy and absorber material, the scatter component also depends on field size, thickness and shape of the absorber, location of the absorber with respect to the source, and the point of calculation. Based upon Compton first-scatter, a method has been developed to calculate effective broad beam transmission through any arbitrarily shaped absorber with variable thickness for any points on and off the central axis. The method requires predetermined narrow beam attenuation coefficients as a function of thickness. Transmission calculations for various absorbers such as wedges and attenuators were performed for cobalt-60 and 6-MV beams and were compared with measured data. For a cobalt-60 beam, the measured transmission fraction through a 1.33-cm-thick absorber (alloy, consisting of 55% bismuth and 45% lead) for a field size of 24 x 24 cm2 is 17% higher than the calculated value using a narrow beam attenuation coefficient. Also, for the same absorber, measured central axis transmission is as much as 3.6% higher compared to off-axis locations. The measured transmission fraction through a 1.33-cm absorber was found to differ by as much as 13% and 14% for Cobalt-60 and 6 MV, respectively, as the chamber-to-source distance was varied from 70 to 110 cm. The agreement between calculated and measured values is within 0.5% for both energies whereas conventional narrow beam calculations would have yielded errors of 18% and 19%, respectively. Similar agreement was obtained when comparing calculated and measured wedge factors as a function of field size, with the maximum deviation being 0.7%. Measured scattered doses, due to an attenuator covering part of a beam, show a maximum for a thickness of approximately one mean-free path. This is also predicted by calculations with an agreement of 0.3%.

Biophysical Phenomena↗

PubMedDate not supplied

Small-field electron dosimetry for the Philips SL25 linear accelerator.

Electron-beam characteristics of a Philips SL25 linear accelerator have been studied. Central-axis percentage depth doses, cross-beam profiles and beam output factors of 6-, 10-, and 20-MeV beams, selected from the available energy range of 4 to 22 MeV, are reported in this paper. The main thrust of this work is to determine the systematic variation of beam characteristics, especially the output factor, with standard cone sizes and cerrobend beam-shaping cutouts down to a field size of 2 X 2 cm Output factors for the standard cones (open field) are energy dependent in a complex manner, increasing with the cone size for the 6-MeV beam whereas decreasing for 10- and 20-MeV beams. The output factor falls below unity at lower energies (6 and 10 MeV) for fields with at least one side smaller than 6 cm, and stays nearly constant for the 20-MeV beam. Measured output factors of small fields are least squares fitted by a second-order polynomial function. Output factors for small rectangular fields have been derived from the one-dimensional and square-root formulas, and the equivalent-square method. Only the one-dimensional formula predicts the measured output factors of highly elongated fields to within +/- 1% experimental uncertainties. Different cones with the same size electron cutout show a varied dose response, primarily due to variation in scattered electron contamination from the cones.

Electrons↗

PubMedDate not supplied

Energy constancy checking for electron beams using a wedge-shaped solid phantom combined with a beam profile scanner.

An energy constancy checking method is presented which involves a specially designed wedge-shaped solid phantom in combination with a multiple channel ionization chamber array known as the Thebes device. Once the phantom/beam scanner combination is set up, measurements for all electron energies can be made and evaluated without re-entering the treatment room. This is also valid for the readjustment of beam energies which are found to deviate from required settings. The immediate presentation of the measurements is in the form of crossplots which resemble depth dose profiles. The evaluation of the measured data can be performed using a hand-held calculator, but processing of the measured signals through a PC-type computer is advisable. The method is insensitive to usual fluctuations in beam flatness. The sensitivity and reproducibility of the method are more than adequate. The method may also be used in modified form for photon beams.

Electrons↗

PubMedDate not supplied

A simple method of producing depth ionization data for electron energy constancy check.

A simple method has been developed to reproduce depth ionization data of electron beams for energy determination. The method utilizes a simple set of equipment, a combination of a specially designed wedge-shaped polystyrene phantom and a linear array of detectors, to collect the necessary data. The wedge-shaped phantom provides varying depths to various detectors in the array. The ionization readings received from the detectors were corrected for off-axis ratio and plotted against corresponding ray-line depths to produce depth ionization curves. The instrument setup was fast and simple. The relevant data, for a high-energy linear accelerator with multiple electron energies, were collected in minutes. The depths of 80% and 50% ionization determined by this method were found to differ by 2 and 3 mm, respectively, at the most, with those determined by a conventional method.

Biophysical Phenomena↗