Biomedical subjects
Y Singh
Publications and source records attributed to Y Singh.
Intrauterine intussusception--a cause for ileal atresia.
A case of ileal atresia consequent to intrauterine intussusception is reported. The baby presented with features of neonatal intestinal obstruction but signs of peritonitis were absent. The intussusception was discovered on gross examination of distal atretic ileal segment. The case was managed successfully by resection and end to back anastomosis. This case is reported to highlight intrauterine intussusception as one of the causes of ileal atresia.
Defluoridation of groundwater in Agra city using low cost adsorbents.
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Multiple neurilemmomas of the penis.
A 10-year-old male with multiple small swellings over the shaft of the penis for 2 years was found to have multiple neurilemmomas on histopathologic examination. The case is reported in view of the extreme rarity of the entity.
Repair of a giant omphalocele by a modified technique.
Large omphaloceles that contain centrally herniated liver pose challenges to surgical closure, the most significant being the space limitation of the abdominal cavity. In addition, the "pedicled" nature of the liver on the inferior vena cava creates a predisposition to acute hepatic vascular outflow obstruction as the liver is reduced into the abdominal cavity. In such cases, the alternatives include conservative treatment or staged silo reduction. The worst complication of silastic silo (SS) placement is tension and infection of the fascia with disruption of the suture line. Once infection or premature disruption occurs, closure of the defect is difficult or impossible. This case report details a different management technique for a newborn with a giant omphalocele and presents an interesting variation of the usual SS technique that may be helpful in the management of some cases, especially in an emergency. The thick silk sutures applied in the present case absorbed the tension and the silastic sheet prevented the risks of infection and adhesions.
Anthrax toxin-mediated delivery of cholera toxin-A subunit into the cytosol of mammalian cells.
The protective antigen (PA) component of anthrax toxin mediates delivery of either lethal factor (LF) or oedema factor into the cytosol of mammalian cells. The N-terminal domain of LF(1-254) (amino acids 1-254 of LF) binds to PA and, when fused to heterologous proteins, delivers such proteins into the cytosol. In the present study, we fused the catalytic subunit of cholera toxin (CT-A) with LF(1-254) and showed that the fusion protein LF(1-254)-CT-A retains ADP-ribosylation activity in solution and increased intracellular cAMP levels in J774A.1 macrophage cells when added together with PA. A mutant fusion protein, in which arginine-7 of CT-A was replaced with lysine, did not show ADP-ribosylation activity in solution and failed to increase cAMP levels in macrophage cells. The data show that LF(1-254)-CT-A retains its catalytic activity in solution as well as when translocated into the cytosol of eukaryotic cells via an alternative pathway to the GM(1) receptor used by CT.
Novel fluorophore for labelling of oligonucleotides.
A novel fluorophore viz. 4-dansylamido-1,8-naphthalimido-N-pentanol has been designed, prepared and characterised. The comparative fluorescence has been studied in different solvents, solvent gradient, aqueous solutions of inorganic ions and buffers. This can be used for covalent tagging of oligonucleotides having potential application in Molecular Biology.
Cloning and characterization of secretory tyrosine phosphatases of Mycobacterium tuberculosis.
Two genes with sequence homology to those encoding protein tyrosine phosphatases were cloned from genomic DNA of Mycobacterium tuberculosis H(37)Rv. The calculated molecular masses of these two putative tyrosine phosphatases, designated MPtpA and MPtpB, were 17. 5 and 30 kDa, respectively. MPtpA and MPtpB were expressed as glutathione S-transferase fusion proteins in Escherichia coli. The affinity-purified proteins dephosphorylated the phosphotyrosine residue of myelin basic protein (MBP), but they failed to dephosphorylate serine/threonine residues of MBP. The activity of these phosphatases was inhibited by sodium orthovanadate, a specific inhibitor of tyrosine phosphatases, but not by okadaic acid, an inhibitor of serine/threonine phosphatases. Mutations at the catalytic site motif, cysteine 11 of MPtpA and cysteine 160 of MPtpB, abolished enzyme activity. Southern blot analysis revealed that, while mptpA is present in slow-growing mycobacterial species as well as fast-growing saprophytes, mptpB was restricted to members of the M. tuberculosis complex. These phosphatases were present in both whole-cell lysates and culture filtrates of M. tuberculosis, suggesting that these proteins are secreted into the extracellular medium. Since tyrosine phosphatases are essential for the virulence of several pathogenic bacteria, the restricted distribution of mptpB makes it a good candidate for a virulence gene of M. tuberculosis.
Antifungal activity of bicyclic heterocyclic-1,2-diazole.
A novel series of heterocyclic-1,2 diazole namely N1-iso nicotinoyl-5,5'-dimethyl cyclohexane-4-(sulpha/substituted phenylazo)-1,2-diazoles have been synthesized. The compounds were screened for the anti-fungal properties against building fungi. The fungal species used for this purpose were Aspergillus niger and Pencillium frequentans. It was found that out of a series of 25 compounds, fourteen have shown significant fungicidal properties against both the above species. Minimum inhibition concentration was observed between 100 and 200 ppm for most of the compounds.
Atrial fibrillation: prevalence and management in an acute general medical unit.
BACKGROUND: Atrial fibrillation (AF) is a common comorbid condition in patients admitted to hospital. In managing patients with AF, recent research has highlighted the importance of heart rate control, cardioversion, maintenance of sinus rhythm and anticoagulation for the prevention of thromboembolism. AIM: To determine the prevalence of AF in patients admitted acutely to the general medical service at Auckland Hospital and to assess the adequacy of heart rate control, the number cardioverted and the use of warfarin to prevent thromboembolism. METHODS: Prospective review of all acute admissions to the general medical service over a 12 week period. Information was collected from hospital notes on the patients' present and past medical conditions, admission and discharge cardiac medication and the use of investigations, particularly thyroid function tests and echocardiography. The heart rate on discharge, number cardioverted either during the admission or after discharge and the number given warfarin and aspirin were recorded. RESULTS: One hundred and forty-seven patients (aged 38-96, mean age 76 years and 52% male) were admitted in AF 165 times out of the 1637 admissions over the study period (a prevalence of 10.4%, 95% CI 8.6-11.5%). The main causes of admission were heart failure (23%), pneumonia or sepsis (17%), cerebrovascular accident (CVA) or transient ischaemic attack (TIA) (14%) and ischaemic heart disease (11%). Past medical history included hypertension (46%), ischaemic heart disease (39%), congestive heart failure (58%), valvular heart disease (12%), chronic obstructive airways disease (24%), CVA, TIA or thromboembolic event (24%) and diabetes (17%). Thyroid function tests were performed in 50% of patients and echocardiograms in 38%. Heart rate control at discharge could not be assessed, as this was not recorded prior to any patient's discharge. Seventy-eight per cent of patients were discharged on digoxin but only 29% on drugs that control the heart rate with exercise. Five patients out of 11 considered for cardioversion had a successful cardioversion in hospital and two were later cardioverted as outpatients. Twenty-eight per cent were discharged on warfarin, 33% on aspirin and one patient on both. Fifty-two per cent were considered to have contraindications to warfarin therapy. Prescribing rates for warfarin did not vary according to the patients' clinical risk for thromboembolism. CONCLUSION: AF is a common comorbid condition in the acute general medical ward. Standard investigations were under-utilised. Attention needs to be paid to the recording and control of heart rate at rest and on exercise. Cardioversion is considered infrequently. This patient group had a high risk for thromboembolism and after excluding the large group in whom warfarin was contraindicated, warfarin was still under-utilised.
Oligomerization of anthrax toxin protective antigen and binding of lethal factor during endocytic uptake into mammalian cells.
The protective antigen (PA) protein of anthrax toxin binds to a cellular receptor and is cleaved by cell surface furin to produce a 63-kDa fragment (PA63). The receptor-bound PA63 oligomerizes to a heptamer and acts to translocate the catalytic moieties of the toxin, lethal factor (LF) and edema factor (EF), from endosomes to the cytosol. In this report, we used nondenaturing gel electrophoresis to show that each PA63 subunit in the heptamer can bind one LF molecule. Studies using PA immobilized on a plastic surface showed that monomeric PA63 is also able to bind LF. The internalization of PA and LF by cells was studied with radiolabeled and biotinylated proteins. Uptake was relatively slow, with a half-time of 30 min. The number of moles of LF internalized was nearly equal to the number of moles of PA subunit internalized. The essential role of PA oligomerization in LF translocation was shown with PA protein cleaved at residues 313-314. The oligomers formed by these proteins during uptake into cells were not as stable when subjected to heat and detergent as were those formed by native PA. The results show that the structure of the toxin proteins and the kinetics of proteolytic activation, LF binding, and internalization are balanced in a way that allows each PA63 subunit to internalize an LF molecule. This set of proteins has evolved to achieve highly efficient internalization and membrane translocation of the catalytic components, LF and EF.
Diagnosis of hydatid disease of abdomen and thorax by ultrasound guided fine needle aspiration cytology.
Five cases of hydatid disease of abdomen and thorax were diagnosed by fine needle aspiration cytology (FNAC) under ultrasound guidance. The age of patients ranged from 25-50 years, with a median age of 37 years. Male to female ratio was 2:3. None of the cases were clinically diagnosed as hydatid disease, but ultrasonography raised suspicion in two cases. The location of cyst in four cases was liver and one aspiration was done from lung. Smears from all cases showed features consistent with hydatid disease. None of the patients showed any untoward allergic reaction following FNAC.
Amebic abscess of both liver lobes: simultaneous rupture into pleura and stomach.
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Value of computed tomography in the evaluation of retroperitoneal organ injury in blunt abdominal trauma.
Computed tomography (CT) is widely used in the evaluation of blunt abdominal trauma. One of its purported advantages is in the evaluation of the retroperitoneum. This study was undertaken to determine the utility of CT in diagnosing retroperitoneal organ injury. A retrospective chart review of 466 stable patients with blunt abdominal trauma who received abdominal CT was conducted. Twelve percent of the patients had CT scans showing retroperitoneal organ injury. There were 58 total injuries, with the kidney being the most frequently injured organ. Twenty-four patients required laparotomy, confirming the CT diagnosis in 8 patients (7 renal and 1 pancreatic). Two duodenal injuries were found at laparotomy that had not been seen on CT scan. Fourteen percent of the patients with positive CT scans had a positive laparotomy, and of those, 38% were therapeutic. Five percent of the patients with positive scans had therapeutic laparotomies. These data infer that the utility of CT to define retroperitoneal organ injury is lower than previously suspected.
Tongue papillae in goat: a scanning electron-microscopic study.
The tongue papillae of 6-9-month-old Jamunapari goats were studied by scanning electron-microscopy. The conical-shaped filiform papillae had 3-6 pointed projections and 6-8 secondary papillae at the free tip and the base of the dorsal surfaced of the tongue, respectively. The convex surfaced fungiform papillae were raised above the lingual mucosa. The vallate papilla was characterized by a papillary groove and an annular pad. The large conical papilla had a round base and a blunt tip without any projection. Two types of lenticular papillae could be distinguished. The irregular surface of all types of papillae revealed microplicae in the form of microridges and micropits. The fungiform papilla was studded with microvilli. The taste pores were oriented on the dorso-lateral surface of the vallate papilla.
Expression and purification of the recombinant lethal factor of Bacillus anthracis.
The structural gene for the 90-kDa lethal factor (LF) isolated from Bacillus anthracis was expressed as a fusion protein with six histidine residues in Escherichia coli. Expression of LF in E. coli under the transcriptional regulation of the T5 promoter yielded a soluble cytosolic protein with an apparent molecular mass of 90 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Recombinant LF reacted with anti-LF antibodies. The protein was purified to homogeneity by nickel nitrilotriacetic acid affinity chromatography and gel filtration on a Sephacryl S-200 column followed by anion exchange on a fast-performance liquid chromatograph with a Resource-Q column. The yield of purified LF from this procedure was 1.5 mg/liter. In solution, trypsin cleaved protective antigen bound to native and recombinant LF with comparable affinities. In macrophage lysis assays, native and recombinant LF exhibited identical potencies. The results suggest that large amounts of biologically active LF can be purified by this procedure.
Study of immunization against anthrax with the purified recombinant protective antigen of Bacillus anthracis.
Protective antigen (PA) of anthrax toxin is the major component of human anthrax vaccine. Currently available human vaccines in the United States and Europe consist of alum-precipitated supernatant material from cultures of toxigenic, nonencapsulated strains of Bacillus anthracis. Immunization with these vaccines requires several boosters and occasionally causes local pain and edema. We previously described the biological activity of a nontoxic mutant of PA expressed in Bacillus subtilis. In the present study, we evaluated the efficacy of the purified mutant PA protein alone or in combination with the lethal factor and edema factor components of anthrax toxin to protect against anthrax. Both mutant and native PA preparations elicited high anti-PA titers in Hartley guinea pigs. Mutant PA alone and in combination with lethal factor and edema factor completely protected the guinea pigs from B. anthracis spore challenge. The results suggest that the mutant PA protein may be used to develop an effective recombinant vaccine against anthrax.
Saline enemas--a potential hazard in newborns.
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