Biomedical subjects
Publications and source records attributed to R K Sharma.
Reconstruction of a resected femoral or tibial condyle using the ipsilateral patella as an autogenous graft is better than conventional resection arthrodesis. Seven cases are reported with a follow up of from 3 to 6 years. Consolidation of the graft and fair stability were obtained. The range of movement was more than 90 degrees in 5 out of the 7 cases.
We conducted a retrospective analysis of infections in 154 children (114 boys, 40 girls) with nephrotic syndrome who satisfied the International Study of Kidney Disease in Children criteria. Their mean age at onset of symptoms was 6.2 years (range 6 months to 16 years) and the mean duration of follow-up was 32 months (range 6-55 months). One or more infectious complications were observed in 59 of the 154 children (38%), with urinary tract infection being the commonest (13.7%), followed by pulmonary tuberculosis (10.4%), peritonitis (9.1%), skin infections (5.2%), upper respiratory infections (5.2%), lower respiratory tract infections (3.9%) and pyomeningitis (0.6%). There were 3 deaths, the mortality in 2 patients being attributable to infections. There was no significant difference between children who developed infection and those who didn't in terms of age of onset, sex, duration of disease, serum creatinine, blood urea nitrogen and 24-h proteinuria. However, the children who developed infectious complications had significantly higher serum cholesterol levels (P < 0.01) and lower serum albumin levels (P < 0.02). The frequency of infections was higher in children who were frequent relapsers, steroid dependent and subsequent non-responders (28/60) compared with infrequent relapsers and initial non-responders (29/94).
PURPOSE: Although the significance of leukocytospermia in semen remains controversial, evidence exists that white blood cells (WBCs) may adversely affect sperm function and act as a potential cofactor in male infertility. Nevertheless, the mechanisms by which leukocytes may alter sperm function in vitro is unknown. Recent investigations suggest that reactive oxygen species (ROS) generated by the polymorphonuclear (PMN) granulocytes could adversely affect sperm function. The objective of this study was to investigate the relationship between the presence of leukocytospermia as determined by the Endtz test and the excessive formation of ROS. METHODS: The WBC concentration and ROS formation in human semen, obtained from men consulting for infertility, were assessed and compared to that of normal donors. ROS was measured by a chemiluminescence assay using luminol and a Berthold luminometer. The WBC concentration was determined with a myeloperoxidase staining technique (Endtz test). Specimens were obtained from 94 subjects (20 donors, 74 patients). RESULTS: Of the 20 donors, 2 were Endtz positive and ROS positive; 18 were Endtz negative with 2 (11%) ROS positive. In the patient group (n = 74), 26 (35%) were ROS positive, and 17 were Endtz positive and found to be ROS positive. Of the 57 Endtz-negative patients, 9 (15%) were ROS positive. The positive Endtz test results correlated strongly with positive ROS formation in patients and donors (P < 0.001). CONCLUSIONS: Our results indicate that the simple, cost-efficient Endtz test could be used as an indicator of excessive ROS formation in semen.
The efficacy of immunotherapy in the prevention of habitual abortion remains controversial. It has been suggested that the benefits are predominantly due to psychological factors. We have evaluated the success of pregnancy outcome following immunotherapy with allogeneic lymphocytes, in relation to the subsequent development of anti-paternal cytotoxic antibodies (APCA). It was observed that in women who developed an APCA titre of > or = 1:16, live births occurred in 16 out of 21 cases (76%), while only two out of seven (28%) women who failed to achieve an APCA titre of > or = 1:16 had successful pregnancies (P < 0.05). In eight women who had an APCA titre of 1:16 on initial screening, and were, therefore, excluded from the trial, successful pregnancy outcome was noted in 62.5% of cases. Although these results are based on a small sample and on an open, non-randomized trial, they show that the efficacy of immunotherapy is related to immune response to allogeneic lymphocytes, and is not simply a placebo effect. Measurement of APCA titre could serve as a marker for immunopotentiation.
Fluticasone propionate aqueous nasal spray (FPANS) contains fluticasone propionate, which is a new topically active glucocorticoid with approximately twice the potency of belcomethasone dipropionate. In this European multicentre study, 143 children with seasonal allergic rhinitis were recruited: 47 received FPANS 100 micrograms once a day (od), 46 received FPANS 200 micrograms od, and 50 patients received placebo od, for 4 weeks. Treatment efficacy was assessed using diary card nasal symptom scores for sneezing, rhinorrhoea, blockage and itching, and eye watering/irritation. Patients receiving FPANS 100 micrograms or FPANS 200 micrograms demonstrated statistically significant improvements in median nasal symptom scores in all the symptoms recorded, when compared with placebo. There were no statistically significant differences between the FPANS 100 micrograms and FPANS 200 micrograms groups in improvement in nasal symptom scores. There was no effect on eye watering/irritation symptoms which could be attributed to either FPANS 100 micrograms or FPANS 200 micrograms when compared with placebo. Use of rescue antihistamine medication was significantly reduced in the FPANS 100 micrograms group when compared with placebo. The adverse events profile was similar in all three treatment groups, and the events reported were generally mild and related to the patients' rhinitis.
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Thirty-one infants and children with acute failure were treated with peritoneal dialysis using a surgically placed Tenckhoff catheter. In 10 patients a peritoneal dialysis cycler was used, and 21 were dialyzed by the manual method. Initially, hourly exchanges were given for 24 to 48 h and, as the patients stabilized, 10 exchanges per day at 1-h intervals were given. The mean stabilization period was 36 +/- 8 h. The predialysis mean serum creatinine was 5.8 +/- 1.8 mg% and the serum creatinine while on daily dialysis was 2.8 +/- 1.1 mg%. Peritoneal dialysis succeeded in controlling metabolic abnormalities and improving fluid balance. All the catheters except one functioned immediately following insertion. Median duration of catheter placement for dialysis was 18 days (range 2 to 90). The incidence of peritonitis was 12.8%, and exit site infection was 6.4%. The infection rate was decreased when a cycler was used compared with the manual method (23.8% vs. 10.0%), though not statistically significant. Two patients developed hypothermia while being dialyzed via the manual method. To conclude, 10 daily peritoneal dialysis exchanges performed at 1-h intervals after initial stabilization using a surgically placed Tenckhoff catheter is an effective and safe mode of dialytic therapy for children with acute renal failure. Complications (infection and hypothermia) are reduced with the use of a cycler.
Intramuscular administration of vitamin K for prophylaxis against hemorrhagic disease of the newborn has the disadvantage of increased cost, pain, anxiety to parents and risk of transmission of infection. Oral route is a better alternative. Oral absorption of vitamin K has been shown to be equally good using special oral preparations. However, this preparation is not available in India. A prospective study was carried out on 51 full term, healthy breastfed newborns to evaluate if the injectable water soluble preparation of vitamin K (menadione sodium bisulphite) could be as effective. Fourteen babies received 1 mg vitamin K intramuscularly, 24 received 2 mg vitamin K orally while 13 controls did not receive vitamin K at birth. PIVKA-II levels were measured in cord blood and at 72-78 hours of age in all babies as a marker of vitamin K deficiency. The overall PIVKA-II prevalence in cord blood was 64.7%. At 72-78 hours, PIVKA-II was present in 50% of babies in IM group, 58.3% of babies in oral group and in 76.9% of babies in 'no vitamin K' group (p > 0.05). The PIVKA-II levels decreased or did not change at 72-78 hours in 91.6% of babies in oral group versus 92.8% of babies in IM group (p > 0.05). On the other hand, PIVKA-II levels increased in 30.7% of babies who did not receive vitamin K as against in 7.8% of babies receiving vitamin K in either form (p < 0.05). Hence, vitamin K prophylaxis is required for all newborns at birth and injectable vitamin K (menadione sodium bisulphite) given orally to term healthy babies is effective in preventing vitamin K deficiency state.
N-Myristoyl-CoA:protein N-myristoyltransferase (NMT) is the enzyme that catalyses the transfer of myristate from myristoyl-CoA to the N-terminal glycine of protein substrates. NMT was highly purified from bovine brain by procedures involving sequential column chromatography on DEAE-Sepharose CL-6B, phosphocellulose, hydroxylapatite, and mono S and mono Q f.p.l.c.. The highly purified NMT (termed NMT.II) possessed high specific activity with peptide substrates derived from the N-terminal sequences of the cAMP-dependent protein kinase and pp60src (29,800 and 47,600 pmol N-myristoylpeptide formed/min/mg, respectively), intermediate activity with a peptide based on the N-terminal sequence of a viral structural protein (microliter) (M2; 17,300 pmol N-myristoylpeptide formed/min/mg) and very low activity with a peptide derived from the N-terminal sequence of myristoylated alanine-rich C-kinase substrate (MARCKS; 1500 pmol myristoylpeptide formed/min/mg). An NMT protein inhibitor (NIP71) isolated from the particulate fraction of bovine brain (King MJ and Sharma RK: Biochem J 291:635-639, 1993) potently inhibited highly purified NMT activity (IC50 23.7 nM). A minor NMT activity (NMT.PU; 30% total NMT activity), which failed to bind to phosphocellulose, was insensitive to NIP71 inhibition. Inhibition of NMT was observed to be via mixed inhibition with respect to both the myristoyl-CoA and peptide substrates with NIP71 having an apparent higher affinity for NMT than the NMT.myristoyl.CoA complex. Inhibition by NIP71 at subsaturating concentrations of myristoyl-CoA and peptide resulted in a sigmoidal pattern of inhibition indicating that bovine brain possesses a potent and delicate on/off switch to control NMT activity.
Calmodulin is phosphorylated by the purified insulin receptor on tyrosine residues with a maximum stoichiometry of 1 mol phosphate/mol of calmodulin. Isolated tryptic phosphopeptides were sequenced by manual Edman degradation and demonstrated that calmodulin is equally phosphorylated on tyrosine 99 and tyrosine 138. Phosphorylated calmodulin has a decreased affinity (K0.5 = 4.2 nM) for the 63-kDa isozyme of cyclic nucleotide phosphodiesterase compared to nonphosphorylated calmodulin (K0.5 = 2.1 nM). The K0.5 for Ca2+ is marginally increased from 2.8 to 3.2 microM in the presence of phosphotyrosyl calmodulin. The effect of the calmodulin antagonist, mastoparan, was investigated to determine whether mastoparan would differentially inhibit calmodulin- or phosphocalmodulin-dependent enzyme activity. The IC50 of mastoparan is fourfold lower for phosphotyrosyl calmodulin compared to nonphosphorylated calmodulin. Phosphorylation of calmodulin may provide a mechanism for the differential regulation of calmodulin-dependent enzymes. These observations further support a potentially important regulatory function of calmodulin phosphorylation in signal transduction.
BACKGROUND: Preactivation is a novel photochemical method for the production of chemotherapeutic compounds that exert their biologic effects independent of light. The compounds that are produced, preactivated merocyanine 540 (pMC540) and merodantoin, are cytotoxic to cultured human breast cancer cells but are only minimally cytotoxic toward normal cells. Their effects against breast cancer have not been studied in vivo. METHODS: Estrogen-stimulated human MCF-7 breast adenocarcinoma cells were grown as solid tumors in athymic carrier mice. Animals bearing defined sizes of subcutaneously transplanted solid breast tumors received injections of pMC540 (250 mg/kg) with or without concurrent treatment with tamoxifen. Growth inhibitory effects of merodantoin (N,N'-dibutyl-2-thio-4,5-imidazolidion) on the breast tumor growth were determined. RESULTS: Direct injection of established tumors with eight doses of pMC540 (250 mg/kg) administered on alternate days resulted in significant tumor regression (P = 0.002). In three of seven animals, palpable tumors could not be detected after this treatment (16 days). Treatment through intramuscular injections (20 doses) with pMC540 (250 mg/kg) also caused a significant suppression of tumor area (P = 0.004; P = 0.0882; P = 0.0903) and a marginally significant suppression of tumor weight and volume, respectively. Combined treatment with tamoxifen and pMC540 (100 mg/kg) caused a 67% suppression of breast tumor growth. Treatment with 20 doses of merodantoin (75 mg/kg) suppressed the growth of breast tumors by 98%. CONCLUSION: To the authors' knowledge, these results show for the first time that photochemically generated novel compounds in pMC540 alone and in combination with tamoxifen are effective in suppressing in vivo growth of xenografted human MCF-7 breast tumors.
In the vertebrate photoreceptor cell, rod outer segment (ROS) is the site of visual signal-transduction process, and a pivotal molecule that regulates this process is cyclic GMP. Cyclic GMP controls the cationic conductance into the ROS, and light causes a decrease in the conductance by activating hydrolysis of the cyclic nucleotide. The identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown. We now report the cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC.
The type C natriuretic peptide (CNP)-activated guanylate cyclase (CNP-RGC) is a single-chain transmembrane-spanning protein, predicted to contain both ligand binding and catalytic activities. Upon binding CNP, CNP-RGC catalyzes the formation of cyclic GMP. We now show that the Glu-332 residue residing in the extracellular region of CNP-RGC plays an important role in signal transduction. Deletion of the CNP-RGC intracellular region resulted in the CNP receptor which lacked cyclase activity; deletion or substitution of Glu-332 with His or Lys resulted in almost total loss of both CNP binding and the CNP-dependent cyclase activity without affecting the basal cyclase activity of the mutant proteins. These observations support the general signal transduction model of the subfamily of natriuretic factor receptor cyclases where it is predicted that ligand binding to the extracellular receptor domain of the protein activates the cytosolic catalytic domain, generating the second-messenger cyclic GMP, and identify an amino acid residue of CNP-RGC that plays an important role in CNP signaling.
Myristoyl-CoA:protein N-myristoyltransferase (NMT) catalyzes the addition of myristate to the amino-terminal glycine residue of a number of eukaryotic proteins. In this report, a simple and rapid purification as well as the properties of this enzyme from bovine spleen is described. Using combination of ammonium sulfate precipitation, chromatography on SP-Sepharose fast flow, phenyl-Sepharose CL-4B, DEAE-Sepharose CL-6B, and Superose 12 (HR/30) gel filtration fast protein liquid chromatography, the enzyme was purified 1475-fold with a high yield. Under native conditions, the enzyme exhibited an apparent molecular mass of 58 kDa, whereas under denaturing conditions the enzyme represented an apparent molecular mass of 50 kDa, suggesting that spleen NMT is a monomeric protein. The NMT activity could be greatly activated to severalfold with the use of Tris-HCl buffer. Kinetic properties indicated that spleen NMT had an apparent low Km for pp60src and myristoylated alanine-rich C kinase substrate as compared with cAMP-dependent protein kinase and the M2 gene segment of reovirus type 3-derived peptides. Bovine spleen NMT was potently inhibited in a concentration-dependent manner by NIP71 (a bovine brain NMT inhibitory protein) with a half-maximal inhibition of 0.816 microgram/ml. Results of this study along with the existing knowledge on NMT indicate that the activity of enzyme resides in a single polypeptide chain of molecular mass between 50 and 68 kDa.
Calmodulin-dependent phosphodiesterase (CaMPDE) is one of the key enzymes involved in the complex interactions which occur between the cyclic-nucleotide and Ca2+ second-messenger systems. Calmodulin-dependent phosphodiesterase exists in different isoenzymic forms, which exhibit distinct molecular and/or catalytic properties. The kinetic properties suggest that the 63 kDa brain isoenzyme is distinct from the brain 60 kDa and heart and lung CaMPDE isoenzymes. The CaMPDE isoenzymes of 60 kDa from brain, heart and lung are regulated by calmodulin, but the affinities for calmodulin are different. At identical concentrations of calmodulin, the bovine heart CaMPDE isoenzyme is stimulated at a much lower Ca2+ concentration than the bovine brain or lung isoenzymes. The bovine lung CaMPDE isoenzyme contains calmodulin as a tightly bound subunit, so that a change in calmodulin concentration had no effect on the [Ca2+]-dependence of activation of this isoenzyme. These observations are consistent with the notion that differential regulation by calmodulin and Ca2+ is an important function of these isoenzymes, which provide fine-tuning mechanisms for calmodulin action.