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Biomedical subjects

R K Sharma

Publications and source records attributed to R K Sharma.

At least 127 records · Page 7Linked to original sources
PubMed2000

Baggasse preservation: a need for a biotechnological approach.

Paper is one of the basic needs of modern life. With the consumption of paper likely to grow to 320 million MT by the year 2001, the the worldwide pulp and paper industry is gradually realizing that there is a shortage of the traditional raw material of cellulosic fiber. Bagasse--a byproduct of the sugar industry, presents a potential source of fiber for the paper industry without further compromising the environmental concern. It is cheap, perennially replenishible, presently does not have an alternative economically attractive value added usage, and has adequate chemical and mechanical properties for paper making. However, for it to be available to the paper industry throughout the year, it needs to be stored and preserved for a period of 6 to 8 months. With inherent problems associated with bagasse morphology, intricacies reflected as a result of its physicochemical characteristics, army of microbial infestants, cost-effective quality expectations of the paper industry, and the ecofriendly approach demanded by the society/pollution control boards/environmentalists, there does not seem to be any viable alternative except to use biotechnology approaches for bagasse preservation. It envisages the preservation of maximally depithed bagasse in the piles/heaps, using one-time fine misting of a preservative formulation comprised of biodegradable and nondegradable chemicals inhibiting the microbial population at selected enzyme levels. Its efficacy is improved by open, dry, windy, and moderate sunlit sites for storage. The method is simple, sustainable, and superior to the prevalent methods that are cost, capital, and energy intensive, non-eco-friendly and have adverse cost:benefit ratios. The biotechnology approach has an inherent scope for further optimization, automation, and economization.

Biotechnology↗
PubMed2000

Etiology, prognosis, and outcome of post-operative acute renal failure.

A Multivariate analysis was done in all patients who developed post operative ARF, during the period 1990-1995 to determine the etiological spectrum and to identify various variables affecting the outcome. Of 140 patients (110 operated at SGPGI and 30 operated outside) 116 underwent elective surgery. The different types of surgery leading to ARF were urosurgery (3.5%), open heart surgery (32.9%), gastrosurgery (16.4%), pancreatic surgery (9.3%), obstetrical surgery (3.6%) and others (2.8%). The incidence of ARF in SGPGI patients was highest in pancreatic surgery group (8.2%) followed by open heart surgery (3%). The different etiological factors responsible for ARF were perioperative hypotension (67.1%), sepsis (63.6%) and exposure to nephrotoxic drugs (29.3%). Sixty-four patients (45.7%) required dialysis. The overall mortality was 45%. The mortality was highest in patients who underwent open heart surgery (89.1%) followed by pancreatic surgery (84.6%). The factors associated with high mortality, other than the type of surgery, were preoperative hypotension (p < 0.05), oliguria (p < 0.01), need for dialysis (p < 0.05) and multiorgan failure (p < 0.001). AM following emergency surgery had poor outcome, though not statistically significant. Perioperative sepsis (p < 0.05) and preoperative use of aminoglycoside (p < 0.05) were significantly higher in patients operated outside SGPGI. This was associated with higher incidence of ARF. Thus we conclude that presence of multiorgan failure, oligoanuria, preoperative hypotension and need far dialysis are poor prognostic markers in ARF following surgery.

Acute Kidney Injury↗
PubMed2000

Acute renal failure associated with liver disease in India: etiology and outcome.

Acute renal failure (ARF) associated with liver disease is a commonly encountered clinical problem of varied etiology and high mortality. We have prospectively analyzed patients with liver disease and ARF to determine the etiology, clinical spectrum, prognosis and factors affecting the outcome. Other than hepatorenal syndrome patients, out of 221 cases, 66 developed ARF secondary to various liver disease like cirrhosis (n = 29, mortality 8, risk factors-older age p < 0.01, grade III/IV encephalopathy p < 0.05), fulminant hepatic failure (n = 25, mortality 15, risk factor-prolonged prothrombin time p < 0.01), and obstructive jaundice (n = 12, mortality 7, risk factor-sepsis p < 0.01). In these three groups the factors leading to ARF were volume depletion (24), gastrointestinal bleed (28), sepsis (34), drugs (27) [aminoglycosides (9) and NSAID (18)] along with hyperbilirubinemia. Various types of ARF with contemporaneous liver injury were malaria (n = 37, mortality 15, risk factors-higher bilirubin p < 0.001, higher creatinine p < 0.05, anuria p < 0.05 and dialysis dependency p < 0.05), sepsis (n = 36, mortality 22, risk factors-age p < 0.001, higher bilirubin p < 0.01, oliguria p < 0.05), hypovolemia with ischemic hepatic injury (n = 14, mortality 5, risk factors-higher creatinine p < 0.05 and SGPT p < 0.01), acute pancreatitis (n = 12, mortality 4, risk factors-higher bilirubin p < 0.001, higher SGPT p < 0.01, dialysis dependency p < 0.05), rifampicin toxicity (n = 10, no mortality), paroxysmal nocturnal hemoglobinuria (n = 3, no mortality), CuSO4 poisoning (n = 3 mortality 2), post abortal (n = 11, mortality 6, risk factors higher creatinine p < 0.05 and SGPT p < 0.01), ARF following delivery including HELLP syndrome (n = 12, mortality 4, risk factors-higher bilirubin p < 0.01 and SGPT p < 0.01), and of uncertain etiology (n= 14 mortality 4). 133 patients (60.2%), required hemodialysis hemodialfiltration or peritoneal dialysis. ARF associated with liver disease is having high mortality (42.5%). Avoidance of dehydration, hypotension, nephrotoxic drugs and sepsis, with promote dialytic support are necessary to reduce mortality and morbidity.

Acute Kidney Injury↗
PubMed2000

Improvement in motion characteristics and acrosome status in cryopreserved human spermatozoa by swim-up processing before freezing.

The purpose of this study was to examine if selecting a sperm population with improved motion characteristics before freezing reduces the deleterious effects of cryopreservation. Semen specimens from 15 normal donors were divided into two equal aliquots. The first aliquot received no treatment (control), and the second was processed by swim-up from a washed sperm preparation to select a sperm population with better motility and motion characteristics (swim-up). Both aliquots were cryopreserved by the liquid nitrogen vapour method. Percentage motility and motion characteristics were evaluated by computer-assisted semen analysis. Acrosome integrity as well as spontaneous and calcium ionophore-induced acrosome reactions before freezing and after thawing were assessed by fluorescein isothiocyanate conjugated peanut agglutinin combined with a supra vital dye (Hoechst-33258). Swim-up processing enabled selection of a sperm population with better motion characteristics, percentage motility and viability before freezing (P < 0.001), but with no difference in percentage of acrosome-intact spermatozoa (P = 0.63). After thawing, the swim-up specimens exhibited faster velocity and progression than untreated specimens (P < 0.001). They also had higher percentages of spermatozoa with intact acrosomes and spermatozoa able to undergo acrosome reaction in response to calcium ionophore (P < 0.05). Selecting a highly motile sperm population before freezing enhances overall post-thaw spermatozoa quality.

Acrosome Reaction↗
PubMed2000

Development of glycine-accumulating neurons in retinal transplants.

Previous studies have shown that the fetal retina not only survives transplantation but also continues to develop and differentiate in the host eye. Several structural and functional proteins have been demonstrated in the transplanted retinas, and the presence of such proteins has been taken as evidence for the capability of retinal transplants to function. Glycine is an important inhibitory neurotransmitter and is found in a large number of the retinal neurons. Uptake of glycine rather than de novo synthesis is the main source of glycine in glycinergic neurons. The present study examined whether glycine-accumulating neurons develop normally in rabbit retina transplants. Embryonic day (E) 15 rabbit retinas were transplanted into the eyes of adult rabbits of the same strain. Transplants were allowed to survive for various times so that the grafts attained the equivalent ages of (donor age + survival time) E 19, 22 and 29 and postnatal days (PN) 2, 5, 9, 12, 19 and 58. On formaldehyde-fixed cryostat sections of these transplants, glycine-accumulating neurons were demonstrated by immunohistochemistry by using an antibody against one of the glycine transporters: GLYT1. Immunoreactivity was first detected 2 days before birth and increased with age until it reached its mature level at PN 19. The immunoreactivity was found in cells belonging to the inner retinal layers, and in plexiform layers of the transplant equivalent to the normal inner and the outer plexiform layers. In places these cells integrated well with similar cells in the host. In the host retina, the immunoreactivity was found in proximal cell layers of the inner nuclear layer, in certain bipolar cells, and in the inner and the outer plexiform layers. The immunoreactivity was preserved even in the degenerated retina overlying the retinal graft. In conclusion, the present study demonstrates that glycine-accumulating neurons develop, integrate and survive in retinal transplants.

Amino Acid Transport Systems, Neutral↗
PubMed2000

Expanding the living related donor pool in renal transplantation: use of marginal donors.

PURPOSE: In a living related transplantation program it is not always possible to find an ideal donor. Sometimes the only available donor in the family has some benign disease or suboptimal renal anatomy or physiology, or is too old to be accepted and defined as a marginal donor. However, with proper screening the donor pool can be increased by accepting these marginal donors and treating the benign diseases which is beneficial to the donor. We evaluate the outcome of grafts from marginal donors. MATERIALS AND METHODS: From July 1988 to August 1997, 581 live related transplantations were performed. Of the donors 52 were older than 60 years and 34 had associated benign renal or nonrenal anomaly or disease. These donors were accepted after thorough questioning and consultation with family members. The recipients of graft from elderly donors were evaluated for the number of rejections, serum creatinine at last followup and graft survival. RESULTS: Of the recipients 52 received grafts from elderly donors with a mean age of 62.6+/-3.7 years. Mean followup was 34.14+/-0.7 months. The 2 and 5-year actuarial graft survival was 96% and 74%, respectively. Creatinine was normal (less than 1.5) in 37% of recipients and 1.5 to 2.5 mg.% in 46%. The rejection rate in postoperative month 1 was 29%. All donors underwent simultaneous surgery to treat the benign disease, and all did well after surgery. CONCLUSIONS: By accepting these marginal donors a 14.6% increase in the living related donor pool was achieved without compromising recipient or donor safety. Otherwise these recipients would have been forced to undergo unrelated transplantation or be maintained on dialysis, which is particularly difficult in a developing country. Donors with associated disease benefited from cure.

Female↗
PubMed2000

Long-term followup of elderly donors in a live related renal transplant program.

PURPOSE: It is a concern that elderly donors may have increased risks in the perioperative period due to age related changes in various organ systems. Nephrosclerosis, atherosclerosis and low glomerular filtration rate may portend a poor graft outcome. We performed a study to determine function and outcome of kidneys from elderly donors. MATERIALS AND METHODS: A retrospective analysis of our live related transplant program from November 1989 to December 1998 revealed that 112 donors were older than 55 years (range 55 to 81). Of the recipients of these kidneys from elderly donors 98 had a followup of more than 2 years (group 1), and they were compared to a cohort of 87 patients whose kidney donors were younger than 45 years (group 2). Allograft function was evaluated by serum creatinine and differential glomerular filtration rate was determined by (99m)technetium diethylenetriamine pentaacetic acid renal scan. All donors were followed regularly. RESULTS: Mean donor age plus or minus standard deviation was 57.4 +/- 4.3 and 31.4 +/- 7.6 years in groups 1 and 2, respectively. Mean followup plus or minus standard deviation was 42.44 +/- 20.46 months in group 1 and 40.04 +/- 27.28 months in group 2. The 1-year graft survival rate was 91.84% and 88. 51%, and the 5-year graft survival rate was 72.72% and 75.13% in groups 1 and 2, respectively. Serum creatinine was 1.5 +/- 0.65 and 1.7 +/- 1.52 mg./dl. in group 1 and 1.4 +/- 0.55 and 1.5 +/- 1.41 mg. /dl. in group 2 at 1 year and last followup, respectively. Glomerular filtration rate was 37.2 +/- 11.2 and 37.3 +/- 10.7 ml. per minute in group 1 and it was 45.3 +/- 8.6 and 47.7 +/- 11.3 ml. per minute in group 2 at 1 year and last followup, respectively. Acute rejection rate was significantly higher in group 1 (42%) compared to group 2 (19%). Both groups were comparable in terms of infectious episodes, antihypertensive requirement and incidence of acute tubular necrosis. There was no added morbidity for elderly compared to younger donors. CONCLUSIONS: In view of acute donor shortage and if properly screened, elderly kidneys can be used without increasing the risk to donor or compromising graft outcome.

Adult↗
PubMed2000

Does serum albumin at start of continuous ambulatory peritoneal dialysis (CAPD) or its drop during CAPD determine patient outcome?

The impact of serum albumin at start of continuous ambulatory peritoneal dialysis (SA1), serum albumin before death (SA2), and change in serum albumin during continuous ambulatory peritoneal dialysis (delta SA) were prospectively studied in 41 continuous ambulatory peritoneal dialysis (CAPD) patients with a follow-up of 19 +/- 11.6 months. For analysis, patients were divided into two groups at each measurement point: SA1 or SA2 > 3.0 g/dL or delta SA < 1.0 g/dL (group I), and SA1 or SA2 < 3.0 g/dL or delta SA > 1.0 g/dL (group II). On log rank test, the mortality rate was significantly higher in group II patients in relation to SA1 (p < or = 0.0001), SA2 (p = 0.0002), and delta SA (p = 0.001). On univariate Cox proportional hazard regression analysis, SA1 (p = 0.0001), SA2 (p = 0.0001), delta SA (p = 0.002), and episodes of peritonitis (p = 0.0001) were significant. On multivariate analysis, SA2 (p = 0.003) was significantly related to patient mortality. SA2 (r = 0.8; p = 0.0001), but not delta SA, was related to SA1. We conclude that SA2 is the best predictor of patient mortality on CAPD. SA2 is strongly related to SA1. Thus protein restriction in the pre-dialysis stage should be advised cautiously to avoid consequent hypoalbuminemia.

Dietary Proteins↗
PubMed2000

Peritoneal equilibration test in Indian patients on continuous ambulatory peritoneal dialysis: does it affect patient outcome?

The variations in peritoneal equilibration test (PET) characteristics in various ethnic groups have been reported. Data are scarce regarding the pattern of membrane characteristics in Indian patients. The factors affecting PET and the PET, in turn, affecting patient outcome are controversial issues. We prospectively analyzed 41 patients to evaluate: (1) the pattern of PET characteristics in Indian patients; (2) the factors affecting the PET; (3) the effect of membrane characteristics on patient outcome. The mean period of follow up was 17.1 +/- 9.3 months. The PET results revealed 21 high transporters (51%), 13 high-average transporters (32%), 6 low-average transporters (15%), and 1 low transporter (2%). The distribution of the various PET categories in patients below the age of 60 years and those 60 years or above was not significant (p = 0.70). The sex distribution (p = 0.94) and prevalence of diabetes (p = 0.62) were not significantly different in various PET categories. On regression analysis, PET values were not affected by the age of patients (beta = 0.80, p = 0.61). Patient survival among high and high-average transporters was significantly less compared with low and low-average transporters (p = 0.01). We conclude that Indian patients on continuous ambulatory peritoneal dialysis (CAPD) have a higher proportion of high and high-average transporters. The pattern of membrane kinetics cannot be explained by differences in patient characteristics and diabetic status. Patients with high PET values have poorer patient survival on CAPD.

Adult↗
PubMed1999

Regions in vertebrate photoreceptor guanylyl cyclase ROS-GC1 involved in Ca(2+)-dependent regulation by guanylyl cyclase-activating protein GCAP-1.

The membrane bound guanylyl cyclase (GC) photoreceptor membrane GC1 (ROS-GCI) of photoreceptor cells synthesizes cGMP, the intracellular transmitter of vertebrate phototransduction. The activity of ROS-GCI is controlled by small Ca(2+)-binding proteins, named GC-activating proteins (GCAPs). We identified and characterized two short regulatory regions (M445-L456 and L503-1522) in the juxtamembrane domain (JMD) of ROS-GC1 by peptide competition and mutagenesis studies. Both regions are critical for the activation of ROS-GCI by GCAP-1.

Amino Acid Sequence↗
PubMed1999

Mutations in the rod outer segment membrane guanylate cyclase in a cone-rod dystrophy cause defects in calcium signaling.

Rod outer segment guanylate cyclase 1 (ROS-GC1) is a member of the subfamily of Ca(2+)-regulated membrane guanylate cyclases; and it is pivotal for vertebrate phototransduction. Two opposing regulatory modes control the activity of ROS-GC1. At nanomolar concentrations of Ca(2+), ROS-GC1 is activated by Ca(2+)-binding proteins named guanylate cyclase activating proteins (GCAPs). However, at micromolar concentrations of Ca(2+), ROS-GC1 is stimulated by S100beta [also named calcium-dependent (CD) GCAP]. This mode is not linked with phototransduction; instead, it is predicted to be involved in retinal synaptic activity. Two point mutations, E786D and R787C, in ROS-GC1 have been connected with cone-rod dystrophy (CORD6), with only one type of point mutation occurring in each family. The present study shows that the E786D mutation has no effect on the basal catalytic activity of ROS-GC1 and on its activation by GCAP1 and S100beta; however, the mutated cyclase becomes more activated by GCAP2. The R787C mutation has three consequences: (1) it causes major damage to the basal cyclase activity, (2) it makes the cyclase 5-fold more sensitive to activation by GCAP1; and 3) converts the cyclase into a form that is less sensitive to activation by GCAP2 and S100beta. Thus, the two CORD6-linked mutations in ROS-GC1, which occur at adjacent positions, result in vastly different biochemical phenotypes, and they are connected with very specific molecular defects in the Ca(2+) switching components of the cyclase. These defects, in turn, are proposed to have a profound effect on both the machinery of phototransduction and the retinal synapse. The study for the first time defines the biochemistry of CORD6 pathology in precise molecular terms.

Animals↗
PubMed1999

A second calcium regulator of rod outer segment membrane guanylate cyclase, ROS-GC1: neurocalcin.

ROS-GC represents a membrane guanylate cyclase subfamily whose distinctive feature is that it transduces diverse intracellularly generated Ca(2+) signals into the production of the second messenger cyclic GMP. An intriguing feature of the first subfamily member, ROS-GC1, is that it is both stimulated and inhibited by these signals. The inhibitory signals are processed by the cyclase activating proteins, GCAPs. The only known stimulatory signal is by the Ca(2+)-dependent guanylate cyclase activating protein, CD-GCAP. There are two GCAPs, 1 and 2, which link the cyclase with phototransduction, and one CD-GCAP, which is predicted to link ROS-GC1 with its retinal synaptic activity. Individual switches for these GCAPs and CD-GCAP have been respectively defined as CRM1, CRM3, and CRM2. This report defines the identity of a new ROS-GC1 regulator: neurocalcin. A surprising feature of the regulator is that it structurally is a GCAP but functionally behaves as a CD-GCAP. Recombinant neurocalcin stimulates ROS-GC1 in a dose-dependent fashion; the stimulation is Ca(2+)-dependent with an EC(50) of 20 microM; and the modulated domain resides at the C-terminal segment, between amino acids 731 and 1054. Previously, the residence of CRM2 has also been defined in this segment of the cyclase. However, the present study shows that the neurocalcin-regulated domain is distinct from CRM2. This is now designated as CRM4. Thus, the signal transduction mechanisms of neurocalcin and CD-GCAP are different, occurring through different modules of ROS-GC1. Neurocalcin signaling of ROS-GC1 is highly specific. It does not influence the activity of its second subfamily member, ROS-GC2, and of the other retinal guanylate cyclase, atrial natriuretic factor-receptor guanylate cyclase. In conclusion, the findings extend the concept of ROS-GC1's sensing diverse Ca(2+) signals, reveal the identity of its unexpected new Ca(2+) regulator, and show that the regulator acts through its specific cyclase domain. This represents an additional transduction mechanism of Ca(2+) signaling via ROS-GC1.

Animals↗
PubMed1999

Activation of retinal guanylyl cyclase-1 by Ca2+-binding proteins involves its dimerization.

Retinal guanylyl cyclase-1 (retGC-1), a key enzyme in phototransduction, is activated by guanylyl cyclase-activating proteins (GCAPs) if [Ca2+] is less than 300 nM. The activation is believed to be essential for the recovery of photoreceptors to the dark state; however, the molecular mechanism of the activation is unknown. Here, we report that dimerization of retGC-1 is involved in its activation by GCAPs. The GC activity and the formation of a 210-kDa cross-linked product of retGC-1 were monitored in bovine rod outer segment homogenates, GCAPs-free bovine rod outer segment membranes and recombinant bovine retGC-1 expressed in COS-7 cells. In addition to recombinant bovine GCAPs, constitutively active mutants of GCAPs that activate retGC-1 in a [Ca2+]-independent manner and bovine brain S100b that activates retGC-1 in the presence of approximately 10 microM [Ca2+] were used to investigate whether these activations take place through a similar mechanism, and whether [Ca2+] is directly involved in the dimerization. We found that a monomeric form of retGC-1 ( approximately 110 kDa) was mainly observed whenever GC activity was at basal or low levels. However, the 210-kDa product was increased whenever the GC activity was stimulated by any Ca2+-binding proteins used. We also found that [Ca2+] did not directly regulate the formation of the 210-kDa product. The 210-kDa product was detected in a purified GC preparation and did not contain GCAPs even when the formation of the 210-kDa product was stimulated by GCAPs. These data strongly suggest that the 210-kDa cross-linked product is a homodimer of retGC-1. We conclude that inactive retGC-1 is predominantly a monomeric form, and that dimerization of retGC-1 may be an essential step for its activation by active forms of GCAPs.

Animals↗
PubMed1999

Genomic organization of human myristoyl-CoA: protein N-myristoyltransferase-1.

Myristoylation is a biochemical modification of proteins in which the lipid myristate becomes covalently bound to various cellular, viral, and oncoproteins catalyzed by a monomeric enzyme myristoyl-CoA:protein N-myristoyltransferase (NMT). This modification is important for the biological activity of several proteins, especially the regulation of several oncoproteins involved in various types of cancers. Complementary DNA encoding human NMT-1 (hNMT-1) has been previously reported; however, the genomic organization of hNMT-1 has not been available. Attempts to amplify genomic fragments corresponding to hNMT-1 cDNA sequence yielded only one fragment. We have searched databases using both the cDNA and sequence of one of the intron sequence and this identified a human BAC clone sequence from chromosome 17. Alignment of hNMT-1 cDNA coding information on human chromosome 17 resulted in the complete structural identity of 23,960 bp of the hNMT-1 gene. The hNMT-1 gene is composed of 11 exons and 10 introns with consensus GT/AG boundaries. Finally, we show that 140 bp from the 5' end of recently reported full-length cDNA of hNMT-1 was not part of this genomic region raising the possibility for posttranscriptional modification in generating larger transcripts likely by trans splicing. Further, the availability of this genomic sequence will assist in unraveling the molecular basis for several observed NMT isoforms.

Acyl Coenzyme A↗