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Biomedical subjects

M Rao

Publications and source records attributed to M Rao.

At least 73 records · Page 4Linked to original sources
PubMed1999

Cytotoxic T lymphocytes to Ebola Zaire virus are induced in mice by immunization with liposomes containing lipid A.

An eight amino acid sequence (TELRTFSI) present in the carboxy terminal end (aa 577-584) of membrane-anchored GP, the major structural protein of Ebola virus, was identified as an H-2k-specific murine cytotoxic T cell epitope. Cytotoxic T lymphocytes (CTLs) to this epitope were induced by immunizing B10.BR mice intravenously with either irradiated Ebola virus or with irradiated Ebola virus encapsulated in liposomes containing lipid A. The CTL response induced by irradiated Ebola virus could not be sustained after the second round of in vitro stimulation of immune splenocytes with the peptide, unless the irradiated virus was encapsulated in liposomes containing lipid A. The identification of an Ebola GP-specific CTL epitope and the requirement of liposomal lipid A for CTL memory recall responses could prove to be a promising approach for developing a vaccine against Ebola virus infection.

Animals↗
PubMed1999

Enhanced contractility and decreased beta-adrenergic receptor kinase-1 in mice lacking endogenous norepinephrine and epinephrine.

BACKGROUND: Elevated circulating norepinephrine (NE) has been implicated in causing the profound beta-adrenergic receptor (betaAR) downregulation and receptor uncoupling that are characteristic of end-stage human dilated cardiomyopathy, a process mediated in part by increased levels of beta-adrenergic receptor kinase (betaARK1). To explore whether chronic sustained NE stimulation is a primary stimulus that promotes deterioration in cardiac signaling, we characterized a gene-targeted mouse in which activation of the sympathetic nervous system cannot lead to an elevation in plasma NE and epinephrine. METHODS AND RESULTS: Gene-targeted mice that lack dopamine beta-hydroxylase (dbh-/-), the enzyme needed to convert dopamine to NE, were created by homologous recombination. In vivo contractile response to the beta1AR agonist dobutamine, measured by a high-fidelity left ventricular micromanometer, was enhanced in mice lacking the dbh gene. In unloaded adult myocytes isolated from dbh-/- mice, basal contractility was significantly increased compared with control cells. Furthermore, the increase in betaAR responsiveness and enhanced cellular contractility were associated with a significant reduction in activity and protein level of betaARK1 and increased high-affinity agonist binding without changes in betaAR density or G-protein levels. CONCLUSIONS: Mice that lack the ability to generate NE or epinephrine show increased contractility associated primarily with a decrease in the level of betaARK1 protein and kinase activity. This animal model will be valuable in testing whether NE is required for the pathogenesis of heart failure through mating strategies that cross the dbh-/- mouse into genetically engineered models of heart failure.

Adrenergic beta-Agonists↗
PubMed1999

Extractive cultivation of recombinant Escherichia coli using aqueous two phase systems for production and separation of extracellular xylanase.

Recombinant Escherichia coli (pATBX 1.8) secreting extracellular xylanase was used as a model system to study the application of an aqueous two phase system for extractive cultivation. An increase in the polymer concentrations from 6 to 20% in the polyethylene glycol phosphate aqueous two phase system resulted in an increase in the phase volume ratio with a concomitant decrease in the partition coefficient (K) and recovery of xylanase in the top phase. However, varying phosphate concentrations from 8 to 16% decreased both the phase volume ratio and the partition coefficient of xylanase. The polyethylene glycol (6%) and phosphate (12%) system was found to be optimum for extracellular cultivation of E. coli, where extracellular xylanase was selectively partitioned to the top phase giving a purification ratio of above 1.0. The process was extended to a semicontinuous operating mode at the optimal condition, wherein the top phase containing xylanase was recovered and the surviving cells were recycled together with the new top phase. The maximum recovery of xylanase was obtained after 12 h in the top phase with a twofold increase in the specific activity as compared to the one obtained in the reference fermentation. In the present work, we report for the first time the use of the two phase system for the extractive cultivation of recombinant E. coli (pATBX 1.8) with the purpose of obtaining a simple and inexpensive separation procedure and achieving the maximal extraction of xylanase to one phase.

Bacteriological Techniques↗
PubMed1999

Trafficking of liposomal antigen to the trans-Golgi of murine macrophages requires both liposomal lipid and liposomal protein.

Major histocompatibility complex (MHC) class I molecules found on antigen-presenting cells present peptides derived from cytoplasmic proteins to T cells. In contrast, peptides from exogenous proteins are mostly presented by class II molecules. It has been well established that liposomes can serve as an efficient delivery system for entry of exogenous protein antigens into the MHC class I pathway. Our previous studies utilizing fluorophore-labeled proteins encapsulated in liposomes demonstrated that after phagocytosis of the liposomes by bone marrow-derived macrophages (BMs), the processed peptides were subsequently visualized in the trans-Golgi, while free conalbumin was excluded from the trans-Golgi area. In the present study, we investigated whether liposomal lipids follow the same intracellular route as the liposomal proteins after phagocytosis by BMs. Multilamellar liposomes with different lipid compositions that also contained fluorescent phospholipids (empty liposomes) were incubated with murine BMs. Our results indicate that although empty liposomes were avidly phagocytosed by macrophages, the fluorescent liposomal lipids did not localize to any particular area of the cell but were distributed throughout the cell. In contrast, when a protein was encapsulated in the liposomes, the liposomal lipids were no longer dispersed throughout the cell, but were concentrated and localized in the trans-Golgi area. Furthermore, when the liposomes contained a fluorescent-labeled protein, the fluorescent peptides also localized to the trans-Golgi. These results demonstrate that the combination of both liposomal lipids and liposomal protein is required for Golgi-specific targeting of liposomal antigens. Transport of both liposomal lipids and liposomal proteins to the Golgi complex, a major subcellular organelle in the passage of MHC class I molecules, might explain why antigens encapsulated in liposomes readily induce cytotoxic T lymphocytes.

Animals↗
PubMed1999

Effect of treating obstructive sleep apnea by tonsillectomy and/or adenoidectomy on obesity in children.

BACKGROUND: Obstructive sleep apnea is common in obese children who have enlarged tonsils and adenoids. OBJECTIVE: To determine if treatment of obstructive sleep apnea by tonsillectomy and/or adenoidectomy will result in normalization of an obese child's weight, as it does in underweight children, and as it does with other signs and symptoms. DESIGN: Retrospective cohort study. We recorded weight and height changes after tonsillectomy and/or adenoidectomy and compared changes of the obese and morbidly obese patients with those of the other patients. SETTING: A tertiary care inner-city hospital. PARTICIPANTS: Children (n = 45) who underwent tonsillectomy and/or adenoidectomy for obstructive sleep apnea in 1994-1995; their mean (+/-SD) age was 4.9+/-2.4 years at operation. RESULTS: At the time of surgery, 25 children were of normal weight; 3, underweight; 7, obese; and 10, morbidly obese. Postoperatively, 31 children (69%), including 10 of the 17 who were obese or morbidly obese, had substantial weight gain: the z score +/- SD for weight of the entire group increased from 1.37+/-2.49 to 2+/-2.27 (P<.001). The mean z score +/- SD for height increased from 0.03+/-1.08 to 0.58+/-0.94 (P<.001). The body mass index (BMI or Quetelet index): calculated as weight in kilograms divided by the square of the height in meters increased in 28 patients (62%) (P = .004). CONCLUSION: Treating obstructive sleep apnea by tonsillectomy and/or adenoidectomy is associated with increased gain in height, weight, and body mass index in most children, including the obese and morbidly obese.

Adenoidectomy↗
PubMed1999

A dietary survey in Indian hemodialysis patients.

Malnutrition is a common problem in maintenance hemodialysis (MHD) patients, and compromised intake is an important cause. There is no information available about the nutrient intakes of MHD patients in India. The nutrient intakes of 106 MHD patients were studied cross-sectionally and on follow-up. A 24-hour recall was used on 4 consecutive days. After 2 months on dialysis, the mean energy intake was 29 +/- 6.6 kcal/kg ideal body weight (IBW) and the mean protein intake was.93 +/-.39 g/kg IBW (high biological value [HBV] protein 49% +/- 8.5%). Dietary deficiency of both protein and calories was present in 64.9%. Intake was better on nondialysis days compared with dialysis days, and in women and older patients. On follow-up there was no significant increase in food intake up to 6 months. After that, the total calorie intake increased significantly with a disproportionate drop in high biological value protein consumed and appeared to be derived predominantly from carbohydrate food (mean kcal/kg, 37 +/- 6.9; mean protein g/kg, 0.96 +/- 0.19; ratio of HBV protein to total protein consumed,.42 +/-.09). In summary this study showed suboptimal energy and protein intake in an MHD population. Intakes were further compromised on dialysis days, and with increasing time spent on dialysis, the quality of nutrient intake became poorer.

Adult↗
PubMed1999

Oral, inactivated, whole cell enterotoxigenic Escherichia coli plus cholera toxin B subunit vaccine: results of the initial evaluation in children. PRIDE Study Group.

Two randomized, double-blinded trials assessed the safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli (ETEC) plus cholera toxin B subunit vaccine in Egyptian children. Two doses of vaccine or E. coli K-12 were given 2 weeks apart to 105 6- to 12-year-olds and 97 2- to 5-year-olds. Safety was monitored for 3 days after each dose. Blood was collected before immunization and 7 days after each dose to measure immune responses. Few children reported postdosing symptoms, with no differences in the frequency of symptoms between treatment groups. Most vaccinees had an IgA antibody-secreting cell response against colonization factor antigen I (100%, 6-12 years; 95%, 2-5 years), coli surface antigen 2 (92%, 6-12 years; 83%, 2-5 years), and coli surface antigen 4 (93%, 6-12 years). Vaccination evoked a >/=4-fold rise in antitoxic IgA and IgG titers in 93% and 81% of children, respectively. In conclusion, the oral ETEC vaccine was safe and immunogenic in 2- to 12-year-old children, justifying further evaluation in infants.

Administration, Oral↗
PubMed1999

Epidemiology of enterotoxigenic Escherichia coli diarrhea in a pediatric cohort in a periurban area of lower Egypt.

Enterotoxigenic Escherichia coli (ETEC) are diverse pathogens that express heat-labile (LT) and/or heat-stable (ST) enterotoxins, yet little is known about whether epidemiologic patterns of pediatric ETEC diarrhea vary by the expressed ETEC toxin phenotype. In total, 242 Egyptian children aged <3 years were prospectively followed in 1993-1995. ETEC episodes were detected during twice-weekly home visits, and asymptomatic ETEC excretion was identified from monthly cross-sectional surveys. ETEC episodes were 0.6 per child-year. ST-only ETEC was 2.6 times (P<.001) more common in warmer than cooler months, while LT-only ETEC showed no seasonal variation. Ownership of a household sanitary latrine, but not breast-feeding, was associated with a lower risk of both enterotoxin phenotypes. Coexpression of a colonization factor by LT- or ST-only ETEC strengthened the association with diarrhea. These findings indicate that the epidemiologic patterns of LT-only and ST-only ETEC are not identical and that disease interventions should include improved household sanitation.

Cohort Studies↗
PubMed1999

In vitro and in vivo effects of phenolic antioxidants against cisplatin-induced nephrotoxicity.

We have investigated the effect of phenolic antioxidants on cisplatin-induced cytotoxicity in vero (African Green Monkey Kidney) cells and in rat renal cortical slices in vitro, and on cisplatin-induced nephrotoxicity in rats in vivo. Incubation of cisplatin with vero cells resulted in time- and concentration-dependent cytotoxicity, as characterized by decreased tryphan blue exclusion (TBE) and increased release of lactate dehydrogenase (LDH) into the medium. Cisplatin also caused reduction of glutathione (GSH) in a concentration-dependent manner. In the rat renal cortical slices model, incubation of cisplatin for 120 min caused an increase in malondialdehyde (MDA), a decrease in GSH and inhibited p-aminohippurate (PAH) uptake in a concentration-dependent manner. Among phenolic antioxidants, isoeugenol (IG) was found to be more active against cisplatin-induced cytotoxicity in vero cells as well as in rat renal cortical slices than eugenol (EG) and dehydrozingerone (DZ). However none of the test compounds were able to arrest the reduction of the GSH content induced by cisplatin in either the vero cells or the renal cortical slice model. Administration of cisplatin (3 mg/kg) i.p. to rats resulted in significant reduction of body weight, and elevation of blood urea nitrogen (BUN) and serum creatinine. Treatment with IG 10 mg/kg i.p. 1 h before cisplatin resulted in partial but significant protection against the cisplatin-induced reduction of body weight, and elevation of BUN and serum creatinine, the protection being 34, 46, and 62%, respectively. EG and DZ (10 mg/kg, i.p.) were found to be inactive in vivo. Because IG is a potent free radical scavenger and protects against cisplatin-induced toxicitiy, the present results have many clinical implications in chemotherapy and thus warrants further investigation.

Animals↗
PubMed1999

Molecular and biotechnological aspects of xylanases.

Hemicellulolytic microorganisms play a significant role in nature by recycling hemicellulose, one of the main components of plant polysaccharides. Xylanases (EC 3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. Recently cellulase-free xylanases have received great attention in the development of environmentally friendly technologies in the paper and pulp industry. In microorganisms that produce xylanases low molecular mass fragments of xylan and their positional isomers play a key role in regulating its biosynthesis. Xylanase and cellulase production appear to be regulated separately, although the pleiotropy of mutations, which causes the elimination of both genes, suggests some linkage in the synthesis of the two enzymes. Xylanases are found in a cornucopia of organisms and the genes encoding them have been cloned in homologous and heterologous hosts with the objectives of overproducing the enzyme and altering its properties to suit commercial applications. Sequence analyses of xylanases have revealed distinct catalytic and cellulose binding domains, with a separate non-catalytic domain that has been reported to confer enhanced thermostability in some xylanases. Analyses of three-dimensional structures and the properties of mutants have revealed the involvement of specific tyrosine and tryptophan residues in the substrate binding site and of glutamate and aspartate residues in the catalytic mechanism. Many lines of evidence suggest that xylanases operate via a double displacement mechanism in which the anomeric configuration is retained, although some of the enzymes catalyze single displacement reactions with inversion of configuration. Based on a dendrogram obtained from amino acid sequence similarities the evolutionary relationship between xylanases is assessed. In addition the properties of xylanases from extremophilic organisms have been evaluated in terms of biotechnological applications.

Amino Acid Sequence↗
PubMed1999

Phenotypic diversity of enterotoxigenic Escherichia coli strains from a community-based study of pediatric diarrhea in periurban Egypt.

No past studies of diarrhea in children of the Middle East have examined in detail the phenotypes of enterotoxigenic Escherichia coli (ETEC) strains, which are important pathogens in this setting. During a prospective study conducted from November 1993 to September 1995 with 242 children under 3 years of age with diarrhea living near Alexandria, Egypt, 125 episodes of diarrhea were positive for ETEC. ETEC strains were available for 98 of these episodes, from which 100 ETEC strains were selected and characterized on the basis of enterotoxins, colonization factors (CFs), and O:H serotypes. Of these representative isolates, 57 produced heat-stable toxin (ST) only, 34 produced heat-labile toxin (LT) only, and 9 produced both LT and ST. Twenty-three ETEC strains expressed a CF, with the specific factors being CF antigen IV (CFA/IV; 10 of 23; 43%), CFA/II (5 of 23; 22%), CFA/I (3 of 23; 13%), PCFO166 (3 of 23; 13%), and CS7 (2 of 23; 9%). No ETEC strains appeared to express CFA/III, CS17, or PCFO159. Among the 100 ETEC strains, 47 O groups and 20 H groups were represented, with 59 O:H serotypes. The most common O serogroups were O159 (13 strains) and O43 (10 strains). O148 and O21 were each detected in five individual strains, O7 and O56 were each detected in four individual strains, O73, O20, O86, and O114 were each detected in three individual strains, and O23, O78, O91, O103, O128, and O132 were each detected in two individual strains. The most common H serogroups were H4 (16 strains), 12 of which were of serogroup O159; H2 (9 strains), all of which were O43; H18 (6 strains); H30 (6 strains); and H28 (5 strains); strains of the last three H serogroups were all O148. Cumulatively, our results suggest a high degree of clonal diversity of disease-associated ETEC strains in this region. As a low percentage of these strains expressed a CF, it remains possible that other adhesins for which we either did not assay or that are as yet undiscovered are prevalent in this region. Our findings point out some potential barriers to effective immunization against ETEC diarrhea in this population and emphasize the need to identify additional protective antigens commonly expressed by ETEC for inclusion in future vaccine candidates.

Bacterial Proteins↗
PubMed1999

Early initiation of breastfeeding and the risk of infant diarrhea in rural Egypt.

BACKGROUND: Initiation of breastfeeding shortly after delivery may enhance breastfeeding's protective effect against diarrhea because of the protective properties of human colostrum contained in early breast milk. OBJECTIVE: To evaluate whether initiation of breastfeeding within the first 3 days of life, when breast milk contains colostrum, was associated with a lower rate of diarrhea in rural Egyptian infants during the first 6 months of life. METHODS: Infants initially breastfed (n = 198) were monitored prospectively with twice-weekly home visits to ascertain dietary practices and diarrheal illnesses. RESULTS: The burden of diarrhea during the first 6 months of life in the cohort was high: seven episodes per child-year of follow-up. Only 151 (76%) infants initiated breastfeeding during the first 3 days of life ("early initiation"). Infants in whom breastfeeding was initiated early had a 26% (95% CI: 2%,44%) lower rate of diarrhea than those initiated late. The protective association between early initiation and diarrhea was independent of the pattern of postinitiation dietary practices and was evident throughout the first 6 months of life. CONCLUSIONS: Early initiation of breastfeeding was associated with a marked reduction of the rate of diarrhea throughout the first 6 months of life, possibly because of the salutary effects of human colostrum. These data highlight the need for interventions to encourage early initiation of breastfeeding in less developed settings.

Breast Feeding↗
PubMed1999

Effect of oil of hydnocarpus on wound healing.

Oil of hydnocarpus has been replaced by other chemotherapeutic agents which have a better mycobactericidal effect. However, none of the currently used antileprosy drugs has been reported to have a positive effect in wound healing. Anecdotal reports claim that leprosy patients who have taken capsules containing oil of hydnocarpus orally have shown more rapid wound healing than those not receiving it. In view of these reports, a pilot experimental study was undertaken to determine the effect of the oil of hydnocarpus in wounds experimentally inflicted on male Wistar rats. The wound-healing effect of oil of hydnocarpus was studied with reference to collagenation and the strength of the scar tissue. The drug-treated group showed a significant increase in body weight and strength of scar tissue in the incision model and, also, increased strength of the collagen tissue and hydroxyproline content in the dead space model. The results of this pilot study indicate that the oil of hydnocarpus, which also has antileprotic activity, could be a useful adjunct in the healing of wounds and ulcers in leprosy patients.

Animals↗
PubMed1999

Neutralising antibody responses to two doses of measles vaccine at 5 and 13 months of age in the United Kingdom.

Fifty-three children born in the United Kingdom between April 1993 and July 1994 were given two doses of measles vaccine, at 5 and 13 months of age, and their neutralising antibody reports were studied to assess the feasibility of protecting infants (aged 1 to 11 months) in the event of an outbreak or who were due to travel abroad. Sixteen infants responded at 5 months, an additional 35 responded at 13 months and two did not respond. The responses were inversely related to the levels of maternal antibodies (p < 0.0001). Infants who responded at 5 months also produced higher responses at 13 months than those who did not respond initially (p = 0.0001). No serious side effects were encountered. These data suggest that measles vaccine protects 30% of infants at 5 months and that a second dose at 13 months results in almost universal seroconversion.

Analysis of Variance↗
PubMed1998

Structural and functional role of tryptophan in xylanase from an extremophilic Bacillus: assessment of the active site.

Microenvironment and conformation of the active site of xylanase from an extremophilic Bacillus was deciphered for the first time using fluorescence spectroscopy. NBS modified enzyme showed complete inactivation and the kinetic analysis implicated the presence of an essential tryptophan at the active site of xylanase. Xylan (0.5%) protected the enzyme completely from inactivation with NBS, whereas it afforded 35% protection against the loss of fluorescence, suggesting that not all the tryptophans are involved at the substrate binding site. Quenching studies revealed that acrylamide was more efficient than KI and CsCl as indicated by the higher Stern-Volmer quenching constants (Ksv). The steric factor represented by the percentage accessibility of the tryptophan residues of XylII was higher with the positively charged Cs+ (80) than with the negatively charged I- (10), suggesting that the tryptophan residues are located in a relatively electronegative environment. In the presence of 6 M Gdn HCl the fluorescence shifted to 350 nm with increased accessibility of the fluorophore to the quenchers. The proximity of the essential carboxyl groups with a high pKa value of 6.9 [Chauthaiwale and Rao (1994) Biochim. Biophys. Acta] probably contributes to the electronegative environment of the tryptophan residue. Our results on sequence analysis of the gene encoding for XylII (Accession Number U83602 in the GenBank database) have shown that Trp 61 is highly conserved and may play a role in the structure-function relationship of the enzyme.

Bacillus↗
PubMed1998

Preemptive live-related renal transplantation.

BACKGROUND: Preemptive transplantation (PTX) utilizes transplantation as the primary renal replacement therapy in the absence of any preceding dialysis. In developing countries, PTX may be a cost-effective option, offering additional benefits to conventional transplantation. METHODS: Between 1989 and 1996, 43 patients who underwent live-related PTX were compared with 86 matched controls who underwent transplantation after hemodialysis. Pre- and posttransplant morbidity, and graft and patient survival rates were compared. RESULTS: Median follow-up was 15 months in the preemptive group and 20.5 months in the control group. Controls received more transfusions (4.6+/-2.6 vs. 2.4+/-2.3), had higher hepatitis B surface antigen positivity [12 (14.6%) vs. 1 (2.4%)], and more commonly had hepatic dysfunction [5 (5.8%) vs. nil)] in the pretransplant period compared with the preemptive group. Similarly, at 6 months after transplant, the incidence of hepatitis B surface antigen positivity (13 vs. 2) and hepatic dysfunction (18 vs. 3) were higher in the control group compared with the preemptive group. The 1- and 2-year graft (preemptive: 82.8% and 77.3%; controls: 82% and 78%, respectively) and patient (preemptive: 92% and 89.5%; controls: 91% and 89.5%, respectively) survival rates were similar. CONCLUSION: PTX offers comparable patient and graft survival to conventional transplantation. It eliminates the complications and inconvenience of dialysis. Transfusion requirements, and therefore associated morbidity, are lower. PTX is more cost effective, therefore, it should be a recommended practice in a developing country.

Adolescent↗