Search PubMed⌕ Search

Biomedical subjects

R K Saxena

Publications and source records attributed to R K Saxena.

At least 19 recordsLinked to original sources
PubMed2006

Differential effects of cyclic and static pressure on biochemical and morphological properties of chondrocytes from articular cartilage.

BACKGROUND: Mechanical stresses are known to play important role on articular cartilage functions in vivo and also on cartilage explants and chondrocytes monolayer culture. This study examined the differential effect of cyclic and static pressures on chondrocytes cultured in alginate matrix, which is physiologically closer to the in vivo environment of cells in cartilage. METHODS: Goat knee joint articular cartilage chondrocytes cultured in alginate beads were exposed to 1.2 and 2.4 MPa cyclic and static loadings via a custom-made cam/follower based machine. Biochemical contents (glycosaminoglycan, collagen, DNA) and protease activity of cells were analyzed separately in cellular matrix, further removed matrix and in culture medium. Morphology of chondrocytes was studied under transmission electron microscopy. FINDINGS: Compared with controls (unloaded cells), cyclic loading increased the glycosaminoglycan content of cells at 1.2 and 2.4 MPa in cellular matrix and further removed matrix (P<0.001) whereas it decreased at similar static loads (P<0.001). In alginate matrix, chondrocytes released a metalloprotease, which required Mn(2+) for activity. Both cyclic load levels inhibited its specific activity in cellular matrix but increased it at static loading (P<0.001). The protease specific activity in further removed matrix increased at both cyclic and static loadings (P<0.001). Transmission electron microscopy data showed improved cells ultrastructure and cell-matrix interactions under cyclic load whereas these deteriorated under static loadings. INTERPRETATION: The study suggests that cyclic load has a positive effect on chondrocytes metabolism and morphology whereas static load has a degenerative effect.

Alginates↗
PubMed2006

A cost effective fermentative production of succinic acid from cane molasses and corn steep liquor by Escherichia coli.

AIM: Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. METHODS AND RESULTS: Initially, 0.8 gl(-1) of succinic acid was produced in 60 h in 300-ml medium. On optimization, glucose and peptone were replaced by cane molasses and corn steep liquor. Three hundred ml of this medium was inoculated with 4% (v/v) of seed inoculum, incubated at 39 degrees C for 72 h, resulted in 7.1 gl(-1) of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO2 supply in this medium resulted in 17 gl(-1) of succinic acid in 30 h. CONCLUSIONS: A ninefold increase in succinic acid production was obtained in 500-ml anaerobic bottles with optimized medium having cane molasses and corn steep liquor as against initial medium containing glucose and peptone. However, a subsequent scale up in a 10-l fermentor resulted in a 2.5-fold increase in succinic acid production as against optimized medium used in 500-ml anaerobic bottles. SIGNIFICANCE AND IMPACT OF THE STUDY: Succinic acid production was enhanced in medium consisting of inexpensive carbon and nitrogen sources in a shorter span of time.

Animals↗
PubMed2003

Purification strategies for microbial lipases.

Microbial lipases today occupy a place of prominence among biocatalysts owing to their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. The chemo-, regio- and enantio-specific behaviour of these enzymes has caused tremendous interest among scientists and industrialists. Lipases from a large number of bacterial, fungal and a few plant and animal sources have been purified to homogeneity. This has enabled their successful sequence determination and their three-dimensional structure leading to a better understanding of their unique structure-function relationships during various hydrolytic and synthetic reactions. This article presents a critical review of different strategies which have been employed for the purification of bacterial, yeast and fungal lipases. Since protein purification is normally done in a series of sequential steps involving a combination of different techniques, the effect of sequence of steps and the number of times each step is used is analyzed. This will prove to be of immense help while planning lipase purification. Novel purification technologies now available in this field are also reviewed.

Bacteria↗
PubMed2003

Glomerular diseases in the elderly in India.

Three hundred fifteen (315) elderly (> or = 60 years) patients with clinical renal diseases were evaluated for the evidence of glomerular diseases between November 1998 to June 2002. Glomerular diseases (GN) were observed in 20.6% (65/315) of the elderly patients. The age of the patients (male 56; female 9) ranged between 60-90 (mean 64.17 +/- 3.83) years. The clinical presentation of GN included: nephrotic syndrome 40 (61.5%), acute nephritic syndrome 19 (29.2%), rapidly progressive GN 4 (6.15%) and asymptomatic urinary abnormality 2 (3.0%). Overall, primary and secondary glomerular disease were seen in 47 (72.3%) and 18 (27.6%) elderly patients respectively. Idiopathic membranous nephropathy was the most common GN responsible for nephrotic syndrome in 11 (27.5%) of elderly patients. Diabetic Nephropathy related to type 2 diabetes mellitus was the second common cause 9 (22.5%) of nephrotic syndrome. Amyloidosis was noted in 6 (15%) patients. Nephrotic syndrome was related to leprosy in one patient. Amyloidosis occurred in association with multiple myeloma in 5 and carcinoma colon in 1 patient. Thus, primary and secondary GN were responsible for nephrotic syndrome in 60% and 40% of cases respectively. Endocapillary proliferative GN of post infectious etiology was the most prevalent (82.6%) form of acute GN in our elderly patients. Hypertension occurred in 78.2% of cases and edema in 69.5%. Pulmonary congestion (52.2%) and ARF (73.9%) were the dominant presenting feature of acute GN and 39% of patients required dialytic support. Glomerular crescents were seen in 4 (17.4%) patients with acute glomerulonephritis. Pauci-immune crescentic GN which is the commonest type of acute GN in the elderly in western countries was not observed in this study. Renal biopsy revealed mesangiocapillary GN (1) and mesangioproliferative GN (1) in two patients with asymptomatic urinary abnormalities. Thus, overall spectrum of glomerular disease in the Indian elderly population is similar to that of developed countries except in two ways: (1) post infectious endocapillary proliferative-GN was the commonest type of acute GN (2) rarity or absence of pauci-immune crescentic glomerulonephritis.

Aged↗
PubMed2003

Acute renal failure due to intrinsic renal diseases: review of 1122 cases.

In this study we have analyzed incidence, causes and clinical course of ARF due to primary intrarenal disease other than acute tubular necrosis. Thousand hundred and twenty two cases of ARF of diverse etiology were studied over a period of 16 years; July 1984 to Dec, 1999. Surgical ARF 231 (20.6%) were not included in the present study. Intrinsic renal diseases were responsible for ARF in 891 (79.4%) of cases. The most common intrinsic renal diseases 705 (79.4%) causing ARF were ischemic/toxic acute tubular necrosis, but not included in this study. Acute renal failure was related to acute glomerulonephritis (9.3%), acute interstitial nephritis (7%), and renal cortical necrosis in (4.6%) of cases. Therefore intrinsic renal diseases other than ATN were the causative factor for acute renal failure in 186 (20.8%) patients in our study. Crescentic (51.8%) and endocapillary proliferative glomerulonephritis (34.9%), were the main glomerular diseases responsible for ARF and 75.9% of GN was related to infectious etiology. Fifty three percent of acute interstitial nephritis was drug induced and in 25 (40%) patients it was related to an infectious etiology. Renal cortical necrosis due to HUS was observed in 16 (39%) children and majority (76.47%) of the cases had a diarrhoeal prodrome. Obstetrical complications were the main causes (61%) of cortical necrosis in adults with acute renal failure. Thus, intrinsic renal diseases other than ATN were responsible for ARF in 186 (20.8%) cases. Post-infectious glomerulonephritis, acute interstitial nephritis and renal cortical necrosis (complicating HUS in children and obstetrical complications in adult) are the main causes of acute renal failure in our study. Both acute GN and interstitial nephritis had excellent prognosis, however renal cortical necrosis was associated with a very high mortality.

Acute Disease↗
PubMed2003

Acute renal failure in Plasmodium vivax malaria.

OBJECTIVES: To analyze incidence, clinical feature and outcome of acute renal failure due to Plasmodium vivax malaria. MATERIAL & METHOD: This is retrospective analysis of smear positive Plasmodium vivax patients with acute renal failure between Jan 1995 to Dec 2000. RESULT: Out of 577 cases of ARF, 93 [falciparum 74 (79.61%); vivax 19 (20.4%)] were related to complicated malaria. 3.2% (19/577) patients, 16 males and three females with age range 17-72, mean 43.3 +/- 13.4 years were due to vivax malaria. Thirteen had only vivax and six had mixed falciparum and vivax infection. The presenting features were fever (100%), jaundice (36.8%), hypotension--eight (42%), encephalopathy--11 (57.9%), sepsis--five (26.3%) and DIC--four (21%). The probable contributory factors for ARF were heavy parasitemia--11 (57.9%), hypotension--six (31.5%), hyperbilirubinemia--seven (36.8%), hemolysis--eight (42%) and DIC--four (21%). Oliguria was present in 47.3%, 13 (68.4%) patients required dialysis. Mortality was noted in 15.7% (3/19) patients. CONCLUSIONS: P. vivax malaria can cause ARF, which occurs more commonly in P. falciparum malaria. Renal ischemia is the dominant pathogenic mechanism that results in acute tubular necrosis. The prognosis of ARF in P. vivax malaria is favorable.

Acute Kidney Injury↗
PubMed2002

Design and development of an immunosensor for the detection of malaria in field conditions.

Eradication of malaria in Southeast Asian countries is still a distant goal, due to the absence of a simple, rapid and inexpensive diagnostic technique. Here, an immunosensor for the photometric detection of malaria, the malaria-detecting immunosensor (MDI), is developed to detect Plasmodium falciparum malarial antibodies in human blood. The method uses the principle of laser light-scattering by latex bead agglutinates in media monitored by a light-detecting device. Agglutination is induced by mixing antigen-coated latex beads with serum antibodies. Immunoreactions are measured in terms of the Tyndall effect in the transmitted beam detected by photodiodes. MDI sensitivity and specificity are compared with the results of enzyme-linked immunoabsorbent assay and laser light-scattering immunoassay techniques, which show that it is a good and sensitive monitoring device.

Agglutination Tests↗
PubMed2002

Kinetic constants determination for an alkaline protease from Bacillus mojavensis using response surface methodology.

The kinetic constants for an alkaline protease from Bacillus mojavensis were determined using a central composite circumscribed design (CCCD) where concentration of substrate (casein) and the assay temperature were varied around their center point. The K(m),V(max), K(cat), activation energy (E(a)) and temperature coefficient (q(10)) were determined and the values of these kinetic constants obtained were found comparable to that obtained with conventional methods. The Michaelis-Menten constant (K(m)) for casein decreased with corresponding increase in V(max), as reaction temperature was raised from 45-60 degrees C. The protease exhibited K(m) of 0.0357 mg/ml, 0.0270 mg/ml, 0.0259 mg/ml, and 0.0250 mg/ml at 45, 50, 55, and 60 degrees C, respectively, whereas V(max) values at these temperatures were 74.07, 99.01, 116.28, and 120.48 microg/ml/min, respectively, as determined by response surface methodology. The Arrhenius plot suggested that the enzyme undergoes thermal activation above 45 degrees C until 60-65 degrees C followed by thermal inactivation. Likewise, the energy of activation (E(a)) was more between 45-55 degrees C (9747 cal/mol) compared to E(a) between 50-60 degrees C (4162 cal/mol).

Bacillus↗
PubMed2002

Microwave-assisted rapid characterization of lipase selectivities.

A rapid screening procedure for characterization of lipase selectivities using microwaves was developed. The rate of reaction of various commercial lipases (porcine pancreas, Mucor miehei, Candida rugosa, Pseudomonas cepacia) as well as lipases from laboratory isolates-Bacillus stearothermophilus and Burkholderia cepacia RGP-10 for triolein hydrolysis was 7- to 12-fold higher in a microwave oven as compared to that by pH stat. The esterification of sucrose/methanol and ascorbic acid with different fatty acids was also achieved within 30 s in a microwave using porcine pancreas, B. stearothermophilus SB-1 and B. cepacia RGP-10 lipases. The relative rates and selectivity of the lipases both for hydrolytic and synthesis reactions remains unaltered. However, the rate of reaction was dynamically enhanced when exposed to microwaves. Microwave-assisted enzyme catalysis can become an attractive procedure for rapid characterization of large number of enzyme samples and substrates, which otherwise is a cumbersome and time-consuming exercise.

Animals↗
PubMed2002

Detection of Mycobacterium tuberculosis antigens in urinary proteins of tuberculosis patients.

A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) that can detect up to 0.5 ng of culture filtrate proteins (CFPs) of Mycobacterium tuberculosis strain H37Ra is described. This detection system features several special characteristics: (i) the use of CFPs from the H37Ra strain of Mycobacterium tuberculosis to generate capture and detection antibodies in rabbits and mice, respectively; (ii) affinity purification of CFP-reactive antibodies and selection of the antibody preparations for best performance in the sandwich ELISA system; and (iii) the use of urine-derived protein preparations for antigen detection. The sandwich ELISA could detect up to 0.5 ng of CFPs of the H37Ra strain of Mycobacterium tuberculosis. The assay did not detect antigens of Escherichia coli, Candida albicans or Saccharomyces cerivisiae but efficiently detected CFP preparations from nine different clinical isolates of Mycobacterium tuberculosis. Significant variations, however, were noted in the relative efficacy of the assay to detect CFPs from different clinical isolates of Mycobacterium tuberculosis. The procedure was utilized for detecting tubercular antigens in urine samples from 29 patients with confirmed (sputum-positive) tuberculosis and from 25 healthy controls. Significant levels of antigen could be detected in 22 of the 29 samples tested.

Animals↗
PubMed2002

Kinetics of changes in lymphocyte sub-populations in mouse lungs after intrapulmonary infection with M. bovis (Bacillus Calmette-Guerin) and identity of cells responsible for IFNgamma responses.

Gamma interferon (IFNgamma) plays a key role in host defense against pulmonary mycobacterial infections. A variety of lymphocyte subsets may participate in producing pulmonary IFNgamma responses, but their relative contributions after mycobacterial infection have not been clearly elucidated. To address this question, C57Bl/6 female mice were infected by intrapulmonary instillation of 2.5 x 104 BCG (Mycobacterium bovis Bacillus Calmette-Guerin). Lymphocyte populations in lung interstitium were examined at different time points after the infection. BCG load in lungs peaked between 4 and 6 weeks post-infection and declined to very low levels by the 12th week of infection. Recovery of lung interstitial lymphocytes doubled by 4-6 weeks after infection and declined thereafter. Flow cytometric analysis of the lung-derived lymphocytes revealed that about 5% of the these cells made IFNgamma in control mice, and this baseline IFNgamma production involved T (CD3+NK1.1-), NK (CD3-NK1.1+) and NKT (CD3+NK1.1+) cells. As the BCG lung infection peaked, the total number of CD3+ T cells in the lungs increased threefold at 5-6 weeks post-infection. There was a marked increase (sixfold) in the number of T cells secreting IFNgamma 5-6 weeks post-infection. Some increase was also noted in the NKT cells making IFNgamma, but the numbers of NK cells making IFNgamma in BCG-infected lungs remained unaltered. Our results suggest that whereas NK and NKT cells contribute to baseline IFNgamma secretion in control lungs, expansion in the IFNgamma-producing T-cell population was essentially responsible for the augmented response seen in lungs of BCG-infected mice.

Animals↗
PubMed2002

Physiological and biochemical alterations in Anabaena 7120 under iron stress.

Various physiological and biochemical process like growth, NO3- -uptake, nitrate reductase, glutamine synthetase and ATPases (Mg2+ and Ca2+ dependent) in the cyanobacterium Anabaena 7120 were observed under iron stress. Growth was found to be maximum in 50 microM Fe3+ added cells however, 20 microM Fe3+ (the Fe3+ concentration generally used for routine culturing of cyanobacterial cell in Chu 10 medium) incubation resulted in lower growth. Fe3+ starvation on the other hand showed very poor growth up to 4th day but once the growth started it reached at significant level on 7th day. Higher Fe3+ concentration reflected reduced growth with lethality at 500 microM Fe3+. Chlorophyll a fluorescence under Fe3+ stress reflected almost the similar results as in case of growth. However, the pigment was found to be more sensitive as compared to protein under Fe3+ stress. Similar results have been observed in case of NO3-uptake with only 80% reduction in nutrient uptake in 500 microM Fe3+ incubated cells. Nitrate reductase activity was lower in Fe3+ starved cells as compared to significant enzyme activity in 20 and 50 microM Fe3+ incubated cells. Similar to nitrate reductase, glutamine synthetase also showed maximum level in 50 microM Fe3+ added cells, however, higher Fe3+ concentration (300-500 microM ) resulted in reduced enzymatic activity. Glutamine synthetase activity was less sensitivity as compared to nitrate reductase activity under Fe3+ stress. ATPase (Mg2+ and Ca2+ dependent) always showed higher level with increasing Fe3+ concentration.

Adenosine Triphosphatases↗
PubMed2001

Abrogation of tumor induced Ly49 expression on mouse spleen cells by mitomycin C.

Mouse spleen cells were activated with IL2 for 4 days in the presence or absence of paraformaldehyde fixed YAC (PFY) tumor cells (spleen cell: PFY ratio 100:1). Fresh spleen cells had poor expression of Ly49A but the expression was significantly upregulated by IL2 activation. Addition of PFYs resulted in a further boosting of Ly49A expression. Besides Ly49A, the Ly49C receptors were also upregulated by PFYs. Upregulated Ly49 expression was not restricted to NK cells (NK1.1 positive cells) but was also seen on T cells (TCRbeta positive cells). Time kinetics studies indicated that maximum upregulation of Ly49 in response to PFY cells occurred on day 3 and 4 and the expression declined thereafter. Ly49 expression in response to PFYs was completely blocked if spleen cells were pre-treated with Mitomycin C, an inhibitor of DNA synthesis. These results show that the addition of a small number of paraformaldehyde fixed YAC cells to spleen cell cultures undergoing IL2 activation, resulted in a significant upregulation of Ly49 receptors and this process was dependent upon cell proliferative activity.

Animals↗
PubMed2001

Microwave induced synthesis and antibacterial activity of cephalosporin derivatives using solid support.

Reaction of 7-amino-3-[5'-methyl-1',3',4'-thiadiazol-2'-ylthiomethyl]cephalo-sporanic acid with heterocyclic amines using basic alumina under microwave irradiation (MWI) afforded new cephalosporin analogs in shorter reaction time with improved yield as compared to conventional heating. All the synthesised compounds were tested for their in vitro antibacterial activity, using cefotaxime and cephalothin as reference drugs. All compounds showed significant in vitro antibacterial activity against E. herbicola, P. vulgaries, and Z. mobilis.

Anti-Bacterial Agents↗
PubMed2001

Reduced uptake as a mechanism of zinc tolerance in Oscillatoria anguistissima.

Oscillatoria anguistissima could tolerate 50 ppm ZnSO4 x 7H2O, and a zinc-tolerant strain with maximum tolerance concentration (MTC) of 100 ppm ZnSO4 x 7H2O was obtained by stepwise transfer to higher concentrations. The adaptation was irreversible even after three generations in metal-free medium. In the presence of metal, the tolerant strain grew with a shorter lag period of 4 days as against 6 days in the case of the wild strain. The tolerant strain had higher MTC than that of the wild strain for other metals also, viz., Ni2+, Co2+, Cu2+ and Cd2+. The zinc resistance in the tolerant strain was a result of reduced uptake, since around 42% of the total metal was present on the surface as against only 30% in the wild strain. The calcium-stimulated uptake, as observed in the wild strain, was absent in the tolerant strain. Ultrastructural comparisons revealed no structural change in the tolerant strain on exposure to zinc, whereas in the wild strain a thick extracellular matrix was observed.

Adaptation, Physiological↗
PubMed2001

Microwave assisted solid support synthesis of novel 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazepines as potent antimicrobial agents.

An environmentally benign and economic synthesis of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazepines is described from readily accessible substituted 2-mercapto-1-amino triazoles and substituted chalcones on basic alumina that are accelerated by exposure to microwaves. The reaction time has been brought down from hours to seconds with improved yield as compared to conventional heating. The method reported herein is devoid of the hazards of solution phase reactions. All the synthesised compounds were tested for their in vitro antibacterial and antifungal activity. Some compounds showed significant antimicrobial properties. The best activity was observed with compounds 3a, 3c, 4a and 4d.

Anti-Bacterial Agents↗
PubMed2001

Spectrum of renal diseases in the elderly: single center experience from a developing country.

From November 1998 to March 2000, two hundred patients over the age of 60 years (Elderly) with clinical renal disease were studied. 144 patients were between ages of 60-69 years, 46 between 70-79 years and 10 were above 80 years. The elderly patients (Male 165; Female 35) with renal disease constituted 11% (200/1816) of the total nephrology consultation during the study period. The clinical presentation included chronic renal failure (42.5%); acute renal failure (28%); nephrotic syndrome (14.5%); acute glomerulonephritis (7.5%); renal vascular disease (5%) and renal cystic disease (2.5%). Diabetic nephropathy, obstructive uropathy and hypertensive nephrosclerosis were the major causes of CRF, accounting for 80% of total CRF in the elderly. Chronic glomerulonephritis and chronic pyelonephritis (CPN) were less common and etiology of CRF was uncertain in 5.9% of cases. However, diabetic nephropathy was the commonest (49.4%) cause of chronic renal failure. We did not see a single case of ischemic nephropathy causing CRF in the present study. Prerenal ARF, obstructive uropathy and sepsis were contributing factors for ARF in 82% of the cases. Volume depletion due to gastrointestinal fluid loss and urinary tract obstruction on account of enlarged prostate were the leading causes of ARF in 20 (35.7%) and 8 (14.3%) cases respectively. Sepsis with or without multiorgan failure was the major (46.7%) cause of mortality in patients with ARF and overall mortality was 26.8%. The commonest (31%) cause of nephrotic syndrome was the idiopathic membranous nephropathy. Diabetic nephropathy related to type-2 diabetes mellitus was the second most common (24.1%) cause of nephrotic syndrome. Diffuse endocapillary proliferative GN of post infectious etiology was the commonest (73.3%) type of acute GN in our elderly patients. Renal cystic diseases were noted in 5 (ADPKD 3; Simple cyst-2) patients. Thus, overall spectrum of renal disease in our elderly patients is similar to that of developed nations except in two ways: (i) Endocapillary proliferative GN of post infectious origin was the commonest type of acute GN and (ii) Rarity or absence of ischemic nephropathy and atherosclerotic renal artery occlusive disease.

Aged↗