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Biomedical subjects

A Lal

Publications and source records attributed to A Lal.

At least 55 records · Page 3Linked to original sources
PubMed1999

Purification, crystallization and preliminary X-ray crystallographic analysis of recombinant murine Golgi mannosidase IA, a class I alpha-mannosidase involved in Asn-linked oligosaccharide maturation.

Golgi mannosidase IA is a class I alpha-mannosidase which catalyzes the conversion of Man9GlcNAc2 or Man8GlcNAc2 oligosaccharide substrates to Man5GlcNAc2 during the maturation of Asn-linked oligosaccharides. The enzyme is a type II membrane protein, and a recombinant form of mannosidase IA from mouse, lacking the transmembrane domain, has been expressed in Pichia pastoris, purified to homogeneity and crystallized by the hanging-drop vapor-diffusion method. The crystals grow as thin rods, with unit-cell dimensions a = 54.9, b = 135.01, c = 69.9 A. The crystals exhibit the symmetry of space group P2221 and diffract to 2.8 A resolution. The asymmetric unit contains one monomer ( approximately 53 kDa) and has a solvent content of 59%.

Animals↗
PubMed1999

Longitudinal cohort study of the epidemiology of malaria infections in an area of intense malaria transmission I. Description of study site, general methodology, and study population.

A large-scale longitudinal cohort project was initiated in western Kenya in June 1992. The primary purpose of the project was to study Plasmodium falciparum malaria in a highly endemic area using a comprehensive and multidisciplinary approach, which included epidemiology, entomology, and immunology. Between June 1992 and July 1994, pregnant women living in 15 rural villages were identified during a monthly census and 1,164 were enrolled. The women were followed-up throughout their pregnancy and they, along with their newborn infants and direct siblings of the infants' less than 15 years of age, were monitored over time. As of May 1995, 1,017 infants had been born to these women. This paper presents the design and general methodology used in this study and describes the initial experience with intense monitoring of a large population over a prolonged period.

Child, Preschool↗
PubMed1999

Longitudinal cohort study of the epidemiology of malaria infections in an area of intense malaria transmission II. Descriptive epidemiology of malaria infection and disease among children.

A large-scale longitudinal cohort project was initiated in western Kenya in June 1992. Between June 1992 and July 1994, 1,848 children less than 15 years of age were monitored prospectively for a mean of 236 days. During this period, 12,035 blood smears were examined for malaria and only 34% were found to be negative. Parasite prevalence (all species) decreased with age (from a high of 83% among children 1-4 years old to 60% among children 10-14 years old). Even more dramatic decreases were noted in the prevalence of high density falciparum infection (from 37% among children 12-23 months old to < 1% among 10-14-year-old children) and in clinical malaria (20% to 0.3% in the same age groups). Children < 1 year of age accounted for 55% of all cases of anemia detected. Anemia was consistently associated with high density infection in children < 10 years of age (20% to 210% increased risk relative to aparasitemic children). These results demonstrate the relationship between high-density malaria infection and two clinical manifestations of malarial illness.

Adolescent↗
PubMed1999

Molecular epidemiology of cryptosporidiosis outbreaks and transmission in British Columbia, Canada.

Isolates from 25 (13 sporadic and 12 outbreak) cryptosporidiosis cases, 24 of which were from British Columbia, Canada, were characterized using nested polymerase chain reaction amplification of the polymorphic internal transcribed spacer 1 locus. Two predominant Cryptosporidium parvum genotypes were found. Twelve (8 sporadic and 4 outbreak) isolates amplified with the cry7/cry21 primer pair and 12 (5 sporadic and 7 outbreak) isolates amplified with the cry7/cryITS1 primer pair. Multi-locus gene analysis using sequence polymorphisms on 3 other loci, i.e., the thrombospondin-related adhesion protein gene, the dihydrofolate reductase gene, and the 18S rRNA gene on 8 (4 outbreak and 4 sporadic) isolates showed non-random association among the human and animal alleles of the 4 different C. parvum gene loci. Associations between these 2 parasite genotypes and different routes of cryptosporidiosis transmission such as zoonotic, anthroponotic, and waterborne transmission were studied using municipal population and agricultural information, as well as detection of C. parvum oocysts in municipal drinking water specimens of the residential communities of sporadic and outbreak cases.

Animals↗
PubMed1998

Renal colic during pregnancy: a case for conservative treatment.

PURPOSE: We defined the merits of early evaluation and conservative treatment of pregnant patients admitted with renal colic. MATERIALS AND METHODS: We retrospectively evaluated 72 pregnancies in 70 patients who were hospitalized with the diagnosis of renal colic between 1984 and 1995. Urinalysis was performed in every case. Ultrasound was the primary diagnostic test in 65 patients. The patients were followed for 2 weeks to 3 months after delivery (mean 21 days). RESULTS: Mean patient age at presentation was 27.4 years. The majority of patients were multiparous (47 of 70) and presented in the third trimester (44 of 70). Microscopic urinalysis was not helpful in identifying stone disease in pregnant patients. The sensitivity of ultrasound for the diagnosis of renal calculi was 95.2%. Watchful conservative nonsurgical treatment resulted in spontaneous passage of stones in 64.3% of cases. Of the 19 pregnancies in which intervention was necessary cystoscopy and Double-J* silicone stent placement were done in 15, and ureteroscopy and stone basketing were done in 4. Two patients, who presented with pyelonephritis and premature ruptured membranes had fetal loss. Long-term antibiotic prophylaxis was maintained in all stented and bacteriuric patients. CONCLUSIONS: Renal colic in pregnant patients can be complicated by pyelonephritis and premature labor, especially if misdiagnosed or inadequately treated. Ultrasound is a safe and sensitive diagnostic test. Approximately two-thirds of renal calculi will pass spontaneously. For those who require intervention, placement of a Double-J stent is a safe and effective option.

Adult↗
PubMed1998

Substrate specificities of recombinant murine Golgi alpha1, 2-mannosidases IA and IB and comparison with endoplasmic reticulum and Golgi processing alpha1,2-mannosidases.

The catalytic domains of murine Golgi alpha1,2-mannosidases IA and IB that are involved in N-glycan processing were expressed as secreted proteins in P.pastoris . Recombinant mannosidases IA and IB both required divalent cations for activity, were inhibited by deoxymannojirimycin and kifunensine, and exhibited similar catalytic constants using Manalpha1,2Manalpha-O-CH3as substrate. Mannosidase IA was purified as a 50 kDa catalytically active soluble fragment and shown to be an inverting glycosidase. Recombinant mannosidases IA and IB were used to cleave Man9GlcNAc and the isomers produced were identified by high performance liquid chromatography and proton-nuclear magnetic resonance spectroscopy. Man9GlcNAc was rapidly cleaved by both enzymes to Man6GlcNAc, followed by a much slower conversion to Man5GlcNAc. The same isomers of Man7GlcNAc and Man6GlcNAc were produced by both enzymes but different isomers of Man8GlcNAc were formed. When Man8GlcNAc (Man8B isomer) was used as substrate, rapid conversion to Man5GlcNAc was observed, and the same oligosaccharide isomer intermediates were formed by both enzymes. These results combined with proton-nuclear magnetic resonance spectroscopy data demonstrate that it is the terminal alpha1, 2-mannose residue missing in the Man8B isomer that is cleaved from Man9GlcNAc at a much slower rate. When rat liver endoplasmic reticulum membrane extracts were incubated with Man9GlcNAc2, Man8GlcNAc2was the major product and Man8B was the major isomer. In contrast, rat liver Golgi membranes rapidly cleaved Man9GlcNAc2to Man6GlcNAc2and more slowly to Man5GlcNAc2. In this case all three isomers of Man8GlcNAc2were formed as intermediates, but a distinctive isomer, Man8A, was predominant. Antiserum to recombinant mannosidase IA immunoprecipitated an enzyme from Golgi extracts with the same specificity as recombinant mannosidase IA. These immunodepleted membranes were enriched in a Man9GlcNAc2to Man8GlcNAc2-cleaving activity forming predominantly the Man8B isomer. These results suggest that mannosidases IA and IB in Golgi membranes prefer the Man8B isomer generated by a complementary mannosidase that removes a single mannose from Man9GlcNAc2.

Animals↗
PubMed1998

Molecular detection of acute lymphoblastic leukaemia in boys with testicular relapse.

AIMS: To determine the role of polymerase chain reaction (PCR) based minimal residual disease (MRD) detection of leukaemia specific DNA in testicular relapse in childhood acute lymphoblastic leukaemia. METHODS: DNA was obtained from archival testicular and bone marrow samples from boys with acute lymphoblastic leukaemia who relapsed in the testes. Overlapping DJH clone specific primers derived from clonal immunoglobulin heavy chain (IgH) gene rearrangement in each case were used to analyse testicular or bone marrow DNA. RESULTS: Histologically normal end of treatment testicular biopsies in the five patients in longterm remission were all MRD negative, but MRD positive in three of six boys with subsequent testicular relapse. Histologically normal bone marrow samples taken at the end of treatment were MRD negative in five of seven cases, but MRD positive in all cases at the time of isolated testicular relapse. Three boys with unilateral testicular relapse underwent unilateral orchidectomy, rather than bilateral testicular irradiation, as part of their treatment. Two of these boys were MRD positive in the histologically uninvolved testes, and both had subsequent relapses either in the testes or the bone marrow, while the MRD negative patient has not had a testicular relapse. CONCLUSIONS: The presence of MRD in testicular tissue can be assayed with a PCR based method to detect clone specific antigen receptor gene rearrangements. In this setting, PCR is more sensitive than conventional testicular histology for predicting clinical outcomes. MRD assays might be useful in the management of boys at the time of isolated testicular relapse, to confirm the presence of unilateral testicular disease.

Bone Marrow↗
PubMed1998

Information contents of drug advertisements: an Indian experience.

OBJECTIVE: To critically analyze the drug information contained in Indian pharmaceutical advertisements. DESIGN: Analysis of pharmaceutical advertisements supplied by drug representatives (DRs) to prescribers from July 1, 1995, to June 30, 1996. SETTING: A university-affiliated urban teaching hospital in India. PARTICIPANTS: 585 pharmaceutical ad pamphlets. MAIN OUTCOME MEASURES: The ads supplied by DRs to physicians in different clinical departments of the hospital were collected. These were distributed to different systems/categories and a special reference to fixed-dose drug combinations was given. The drug information contained in these ads was evaluated by using a checklist, framed by incorporating the World Health Organization ethical guidelines for medicinal drug promotion and some relevant items from other studies. RESULTS: The most frequently occurring ads were for antimicrobial agents. The ads on fixed-dose drug combinations constituted 37.9% of the total. More than 85% of the ads mentioned the generic name, brand name, contents, and pharmaceutical dosage forms, as well as the name and address of the company. The information concerning adverse effects, precautions, contraindications, warnings, major interactions, ingredients known to cause problems, pharmacology, drug overdose, references, drug storage, and cost was present in less than 40% of these ads. CONCLUSIONS: There has been inadequate information in pharmaceutical ads supplied by DRs to the physicians in India. The current scenario could be improved by formulating some definite legislative guidelines for the minimum level of information to be included in pharmaceutical ads and adhering to that legislation.

Advertising↗
PubMed1997

Cloning, expression, purification, and characterization of the murine lysosomal acid alpha-mannosidase.

Catabolism of alpha-linked mannose residues on eukaryotic glycoproteins is accomplished by a broad specificity lysosomal alpha-mannosidase (EC 3.2.1.24). Based on regions of protein sequence conservation between the lysosomal alpha-mannosidase from Dictyostelium discoideum and the murine Golgi glycoprotein processing alpha 1,3/1,6-mannosidase, alpha-mannosidase II, we have cloned a cDNA encoding the murine lysosomal alpha-mannosidase. The longest of the clones was 3.1 kb in length and encoded a polypeptide of 992 amino acids containing a putative NH2-terminal signal sequence and 11 potential N-glycosylation sites. The deduced amino acid sequence was 76.5% identical to the human lysosomal alpha-mannosidase and 38.1% identical to the lysosomal alpha-mannosidase from D. discoideum. Expression of the cDNA in Pichia pastoris resulted in the secretion of an alpha-mannosidase activity into the culture medium. This recombinant expression product was purified and was shown to have enzymatic characteristics highly similar to the enzyme purified from mammalian sources and to the human lysosomal alpha-mannosidase cDNA expressed in Pichia. These characteristics include a similar pH optimum, Km, Vmax, inhibition by swainsonine, and activity toward natural substrates. Northern blots identified a major 3.5 kb RNA transcript in all murine tissues tested. A minor transcript of 5.4 kb was also detected in some murine tissues similar to the alternatively spliced transcripts that have been previously identified in human tissues.

Amino Acid Sequence↗
PubMed1997

Alpha-mannosidase-II deficiency results in dyserythropoiesis and unveils an alternate pathway in oligosaccharide biosynthesis.

Alpha-mannosidase-II (alphaM-II) catalyzes the first committed step in the biosynthesis of complex asparagine-linked (N-linked) oligosaccharides (N-glycans). Genetic deficiency of alphaM-II should abolish complex N-glycan production as reportedly does inhibition of alphaM-II by swainsonine. We find that mice lacking a functional alphaM-II gene develop a dyserythropoietic anemia concurrent with loss of erythrocyte complex N-glycans. Unexpectedly, nonerythroid cell types continued to produce complex N-glycans by an alternate pathway comprising a distinct alpha-mannosidase. These studies reveal cell-type-specific variations in N-linked oligosaccharide biosynthesis and an essential role for alphaM-II in the formation of erythroid complex N-glycans. alphaM-II deficiency elicits a phenotype in mice that correlates with human congenital dyserythropoietic anemia type II.

Alleles↗
PubMed1997

Ultrasonically guided percutaneous drainage of breast abscess.

Percutaneous drainage of abscess under ultrasound guidance is a well established modality. Its use in breast abscess has still not found wide application. The present study on 25 consecutive cases of breast abscess with success rate of 84% is an attempt to recommend routine use of this modality wherever the facilities exist.

Abscess↗
PubMed1996

Cloning, expression, purification, and characterization of the human broad specificity lysosomal acid alpha-mannosidase.

We have cloned and expressed two cDNAs encoding the human lysosomal alpha-mannosidase (EC 3.2.1.24) by RT-PCR of human spleen mRNA. This enzyme is required for the degradation of N-linked carbohydrates during glycoprotein catabolism in eucaryotic cells. The shorter of the two cDNAs (3 kilobases (kb)) was found to encode an open reading frame of 2964 base pairs and, when expressed in Pichia pastoris, was found to encode an enzyme that could cleave high mannose oligosaccharides, oligosaccharides isolated from alpha-mannosidosis fibroblasts, and p-nitrophenyl-alpha-D-mannopyranoside substrates. In addition, the Pichia-expressed enzyme was inhibited by swainsonine, and had a pH optimum, Km, and Vmax characteristic of the enzyme purified previously from human liver. The second, larger RT-PCR product (3.6 kb) was found to contain an insertion and a deletion relative to the 3-kb spleen amplimer and encoded a truncated coding region, indicating that it resulted from alternate transcript splicing. No alpha-mannosidase activity could be detected in Pichia transformants containing this coding region, indicating that it did not encode a functional enzyme. Antiserum raised to the recombinant product of the 3-kb alpha-mannosidase cDNA immunoprecipitated lysosomal alpha-mannosidase activity from human fibroblast extracts. Northern blots identified a 3-kb RNA transcript in all human tissues tested, including alpha-mannosidosis fibroblasts, while minor transcripts of 3.6 kb were also present in several adult tissues. Human chromosome mapping of the mannosidase gene confirmed that the functional gene maps to the MANB locus on chromosome 19. Sequence comparisons were made to previously published human cDNA sequences encoding a putative lysosomal alpha-mannosidase (Nebes, V. L., and Schmidt, M. C. (1994) Biochem. Biophys. Res. Commun. 200, 239-245) and several differences were found relative to the functional lysosomal alpha-mannosidase encoded by the 3-kb spleen cDNA.

Adult↗