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Biomedical subjects

S Hashmi

Publications and source records attributed to S Hashmi.

At least 19 recordsLinked to original sources
PubMed2004

A stone extraction facilitation device to achieve an improved technique for performing LCBDE.

BACKGROUND: Laparoscopic common bile duct exploration (LCBDE) has proved to be a safe, cost-effective way to treat common bile duct (CBD) stones. Despite this, LCBDE has not gained widespread adoption by surgeons. The technique has proved difficult to master, and damage to the fragile choledochoscope by grasping forceps and passage through the port valves has been problematic. Cases involving large, impacted, or multiple stones have required conversion to open exploration of CBD. METHODS: The Multichannel Instrument Guide (MIG) is introduced as a solution for these problems. The MIG is a J-shaped plastic extrusion with three lumens. It is flexible and can be straightened for insertion through a 10-mm port. The MIG facilitates insertion of a flexible 2.8- to 3.2-mm choledochoscope into the CBD. At the same time, additional tools such as balloon or irrigation catheters and lithotripters can be introduced into the CBD. These can be manipulated under video guidance via the choledochoscope. This procedural multitasking allows for a more efficient LCBDE. The authors describe their initial experience using the MIG for 23 patients. RESULTS: Of the 23 patients who underwent LCBDE procedures, 20 had stones in the CBD. Multiple stones were present in 48% of the patients; impacted stones were present in 26% of the patients; and stones larger than 1 cm were present in 26% of the patients. A 95% stone clearance rate was achieved. Difficult cases with large, impacted or multiple stones were resolved using the MIG. Two choledochoscopes were damaged; one during surgery and one during cleaning and storage. CONCLUSIONS: The MIG has demonstrated significant advantages over previously described techniques. The device secures biliary tract access and allows procedural multitasking while protecting the delicate and expensive equipment. Subsequently, a simplified technique algorithm can be followed that may encourage more surgeons to adopt the routine performance of LCBDE.

Adult↗
PubMed2001

Caenorhabditis elegans and the study of gene function in parasites.

The free-living nematode Caenorhabditis elegans is a tractable experimental model system for the study of both vertebrate and invertebrate biology. Its most significant advantages are its simplicity, both in anatomy and in genomic organization, and the elaborate methods that have been developed to attribute function to previously uncharacterized genes. Importantly, > 40% of parasitic nematode genes exhibit high levels of homology to genes within the C. elegans genome. Studying such genes using the C. elegans model should yield new insights into key molecules and their possible implications in parasite survival, leading to the discovery of new drug targets and vaccine candidates.

Animals↗
PubMed2000

Anorectal malformations in female children--10 years experience.

Despite enormous interest in the development of an ideal operative procedure to treat anorectal malformations, the situation is as confusing as it was 30 years ago. The reasons could be inconsistency of the nature of the lesions found in patients along with multi-system associated malformations primarily affecting the prognosis of available procedures. High imperforate anus is a complex anomaly that requires a combination of careful preservation of structures and precise anatomic reconstruction for optimal results. A retrospective study, comprising a consecutive sample of female children with anorectal malformations treated over a period of 10 years, is presented. Of 130 patients, 83% (n = 108) presented later than 3 months of age as they could pass stools through associated fistulae, of which the commonest type was found to be an ano- or recto-vestibular fistula (65%, n = 83). Ninety-four cases (72%) had what are traditionally known as "low" anorectal malformations (perineal fistulae, anteriorly placed anus and anorecto-vestibular fistulae). Ten percent (n = 14) had translevator, and 17% (n = 22) were found to have "high" lesions. Seventeen percent of patients (n = 22) had associated congenital malformations, predominantly in intermediate and high anorectal lesions, 40% of which pertained to the urogenital system. In total, 137 definitive operative procedures were done including Mollard's anterior perineal approach in 81 patients and posterior sagittal anorecto plasty (PSARP) in 38, enabling a comparison to be made of the functional results and complications in the two groups. Out of 24 post-operative complications noted in the series, 17 were found in the group who had Mollard's procedure carried out (including 3 deaths) as compared with 7 in these cases who had PSARP (two-sided P utilizing Fisher's exact test = 0.475).

Anal Canal↗
PubMed1998

Thermal response of Heterorhabditis bacteriophora transformed with the Caenorhabditis elegans hsp70 encoding gene.

A heat-shock response is induced when cells are exposed to temperatures slightly higher than their optimal physiological temperature. This response is based on the synthesis of heat-shock proteins encoded by the heat-shock genes. A correlation between the increased thermotolerance and production of 70-kDa heat-shock protein (hsp70) has been observed in many organisms. We tested this hypothesis by transferring a Caenorhabditis elegans heat-inducible hsp70 A-encoding gene into the entomopathogenic nematodes Heterorhabditis bacteriophora Hp88. Successful transformation of the gene was confirmed by Southern blot hybridization and polymerase chain reaction. Our blot studies showed that the transgenic nematodes contained five to ten copies per genome of the introduced hsp70 A gene. hsp70 mRNA transcripts were detected in both wild-type and transgenic nematodes. Transcripts increased severalfold in transgenic nematodes upon heat shock. Infective juveniles of both transgenic and wild-type nematodes that exposed to a sublethal heat treatment (35 degrees C) for 2 h followed by a normally lethal heat treatment (40 degrees C) for 1 h. More than 90% of transgenic nematodes survived heat treatment, compared to 2% to 3% of the wild-type strain. Our observations establish that overexpression of hsp70 A gene resulted an enhanced thermotolerance in the transgenic nematodes. The transgenic nematodes displayed normal growth and development.

Animals↗
PubMed1996

Automatic image analysis of antibody assays to measles virus.

A system for the automatic analysis of 24-well plates used in antibody assays to measles virus has been designed and developed based on digitising the information on the plate through a CCD camera, displaying the image and then analysing it using image processing methods. The system is being used in the analysis of sera from individuals vaccinated against measles and has been compared with the previous method where the plates were assessed by eye. The results from both methods are very similar although the manual method consisted of counting numbers of plaques (clear areas in the cells of the plate) and the automatic method measured plaque area. The automatic method is much faster than the original method and prevents operator fatigue. It does not deal, at present, with anomalies such as partially filled wells but could be developed to do so by incorporating intelligence into the system.

Antibodies, Viral↗
PubMed1995

Genetic transformation of an entomopathogenic nematode by microinjection.

We report the first successful transformation of an entomopathogenic nematode. Foreign genes were introduced in Heterorhabditis bacteriophora HP88 by microinjection using vectors carrying the Caenorhabditis elegans genes coding for the roller phenotype and 16-kDa heat shock protein (hsp16) gene. A translational fusion made by inserting lacZ in frame into hsp16 was expressed in the body musculature, hypodermis, and pharyngeal muscles. The transcription of the hsp16/lacZ transgenes resulted in the rapid synthesis of detectable levels of beta-galactosidase. This research opens new avenues for genetic modification of entomopathogenic nematodes.

Animals↗
PubMed1995

The notochord and floor plate guide growth cones in the zebrafish spinal cord.

Elimination of the floor plate, a row of distinctive cells at the ventral midline of the spinal cord, dramatically increased the frequency of errors made by specific growth cones in the zebrafish embryo. This demonstrated that the floor plate participated in guiding specific growth cones at the ventral midline of the spinal cord. However, since a significant proportion of these growth cones followed their normal pathway despite the absence of the floor plate, we hypothesized that a second source of cues must exist at or near the ventral midline. We tested whether the notochord, which is located just ventral to the spinal cord, was an additional source of pathfinding cues by eliminating it prior to axonogenesis. Laser ablation of the notochord in wildtype embryos increased errors by spinal growth cones. Likewise, spinal growth cones made errors in no tail mutants that are missing the notochord but not the floor plate. These results demonstrate that the notochord also participates in guiding growth cones at the ventral midline. Furthermore, removal of both the floor plate and notochord resulted in a higher error rate than removal of either one alone. These results suggest that the notochord and floor plate normally act in concert to guide spinal growth cones at the ventral midline.

Animals↗
PubMed1995

Genetic transformation of nematodes using arrays of micromechanical piercing structures.

Foreign genes were expressed in the nematode Heterorhabditis bacteriophora using a new micro-mechanical device to inject DNA-coated microprobe through the nematode cuticle. After introduction of a plasmid in which a Caenorhabditis elegans 16-kDa heat shock promoter was fused to Escherichia coli, a beta-galactosidase gene was expressed in the progeny of the injected worms. The tip of the microprobe penetrated through the nematode cuticle without causing injury to the nematode, and about 8% of the total progeny tested expressed the foreign gene. We describe and validate a new and efficient genetic transformation system for nematodes. The method is quick and easy to use.

Animals↗
PubMed1993

Three-dimensional computer modelling system for the study of biological structures.

A three-dimensional computer modelling system has been developed for use in biology, and is currently running on a Sun3 computer. The data originate as a series of two-dimensional micrographs which are digitised via a TV camera. The two-dimensional images are used to select features of interest and to construct a three-dimensional model. This model can be viewed in vector or solid format, it can be rotated about three orthogonal axes and can be viewed in three dimensions as a stereo pair or an anaglyph. The system has been used in a large number of projects over the past 10-15 years, for example, to examine physiological and nerve structures. The time-consuming part of the process is the selection of features, which involves a high level of biological expertise. Present developments are concerned with reduction of the time spent in feature recognition and involve the introduction of expert systems together with human-computer interaction to deal with problems of identification.

Computer Simulation↗
PubMed1993

Further evidence of icosahedral symmetry in human and simian immunodeficiency virus.

Specimens of HIV and SIV have been examined by electron microscopy, using the techniques of conventional thin sectioning, freeze-substitution, cryosectioning, and cryomicroscopy of frozen hydrated specimens. In addition freeze-drying and critical point drying were used for both shadowed replicas and scanning electron microscopy. Thin sections revealed hexagonal, pentagonal, or near-spherical profiles. Angular particles were seen in shadowed replicas and also by scanning electron microscopy. The images observed were consistent with an icosahedral shape of the virus. It is proposed that mature HIV (SIV) is an icosadeltahedron with flat triangular facets. Size measurements of the specimens showed a wide range of values for conventional embedding, but a narrow range for specimens prepared by low-temperature techniques.

Animals↗
PubMed1991

Generation of pigmented stripes in albino mice by retroviral marking of neural crest melanoblasts.

The pigment cells of the skin are derived from melanoblasts which originate in the neural crest. The dorsoventral migration of melanoblasts has been visualized in pigment stripes seen in aggregation chimeras, and the width of these bands has suggested that the entire pigmentation of the coat is derived from a small number of founder cells. We have generated mosaic mice by marking single melanoblasts in utero to gain information on the clonal history of pigment-forming cells. A retroviral vector carrying the human tyrosinase gene was constructed and microinjected into neurulating albino mouse embryos. Albino mice are devoid of pigmentation due to deficiency of tyrosinase. Thus, transduction of the wild-type gene into the otherwise normal melanoblasts should rescue the mutant phenotype, giving rise to patches of pigmentation, which correspond to the area colonized by the mitotic progeny of a marked clone. Mosaic animals derived from the injected embryos indeed showed pigmented bands with a width strikingly similar to the 'standard' stripes seen in aggregation chimeras. These results are consistent with the notion that the unit width bands seen in aggregation chimeras represent the clonal progeny of a single melanoblast and verify Mintz's (1967) conclusion that a few founder melanoblasts give rise to coat pigmentation. The pigment cells of the eye are of dual origin: the melanocytes in choroid and outer layer of the iris are derived from the neural crest and those in the pigment layer of the retina from the neuroepithelium of the optic cup. Marked clones in both lineages were observed in the eyes of many mosaic animals.

Animals↗