Biomedical subjects
Publications and source records attributed to R Jayakumar.
Concentration dependent morphological characteristics of a novel dipeptide derivative Lys-Asp-Lauryl.HBr (1) has been presented. Evidence for "onion" like vesicle formation at higher concentration (>8.2 x 10(-3) M) of peptide (1) in aqueous medium was obtained from conductance and 90 degrees light scattering measurements, and cryo-transmission electron microscopic studies.
The tetrapeptide derivative Tyr-Gly-Phe-Ala-OBz (1) forms monolayers as confirmed by compressibility studies carried out at various temperatures. Peptide 1 monolayer exhibits an anomalous structural transition at 40 degrees C as evidenced by pi-A isotherms recorded at different temperatures. The structural transition is also observed in aqueous solution of trifluoroacetate of peptide 1 as evidenced by fluorescence and Raman scattering intensity measurements.
9-O-Acetyl neuraminic acid specific lectin (AchatininH) was isolated from the hemolymph of the land snail Achatina fulica by affinity chromatography on sheep submaxillary mucin (SSM) coupled cyanogen bromide activated Sepharose 4B. The molecular weight of the native protein was 2.42 kDa. UV-Vis absorption, fluorescence and circular dichroism spectroscopic studies on AchatininH revealed the importance of divalent metal ions (Ca2 +, Mg2+ and Mn2+) on lectin conformational change associated with activity of lectins. The binding of these cations changes lambdamax to shorter wavelength in the far UV region (blue shift) and longer wavelength in UV region (red shift), indicating substantial contribution of aromatic side chain in the far UV region on binding with metal ions. The results infer that divalent cations cause conformational changes in lectin which may be responsible for affinity with their carbohydrate moiety.
The results of the present study clearly shows that a correlation exists between nitric oxide (NO) and gamma-aminobutyric acid transaminase (GABAT-T) activity as well as gamma-aminobutyric acid (GABA), glutamic acid and the activity of glutamic acid decarboxylase (GAD). Supporting of this 10 min after the administration of L-Arginine (L-Arg) increased GABA concentration and diminished the activity of GABA-T. There was no change in GAD activity and glutamic acid level. Administration of convulsion inducing agent Picrotoxin (PCT) decreased the NO concentration in the brain and enhanced the activity of GABA-T, and the fact that the NOS inhibitor (N(G)-nitro-L-Arg methyl ester (L-NAME) diminished the activity of NOS and increased the activity of GABA-T provide another support for the involvement of NO on GABA-T activity. The present study clearly showed that high concentrations of NO in the brain suppresses the activity of GABA-T.
The anticonvulsant drug Diazepam (DIA-2 mg/kg b. wt), the nitric oxide (NO) donor L-Arginine (L-Arg-2000 mg/kg b. wt) and the putative nitric oxide synthase (NOS) inhibitor N(G)-Nitro-L-Arginine methyl ester (L-NAME-50 mg/kg b. wt) were used to determine the role of endogenous NO on convulsions induced by picrotoxin (PCT-5 mg/kg b. wt) in rats. Rats given a convulsant dose of PCT (5 mg/kg b. wt) had convulsion and it suppresses the NOS activity and NO concentration in brain regions. The anticonvulsant L-Arg alone significantly increases the NO concentration and NOS activity in brain regions, but not diazepam. Whereas DIA, along with L-Arg, enhances the NO and NOS activity when compared to L-Arg alone. The combination of both OIA and L-Arg completely suppressed the convulsions. L-NAME alone had no effect to produce convulsions but it completely decreased NO concentration and NOS activity and potentiated the PCT convulsions. This was reverted by pre- and post treatment of DIA plus L-Arg indicating, the increased NO concentration and NOS activity in brain regions suppresses convulsions.
The abilities of Bacillus polymyxa and Bacillus thuringiensis to survive on the rice phyllospere were compared; it was found that B. polymyxa colonizes the crop better. This study also showed that B. polymyxa inoculation to rice plants increased the shoot and the root growth of the crop. Efforts were made to introduce the cry1Ac gene of B. thuringiensis subsp. kurstaki into B. polymyxa so that the application of such transgenic B. polymyxa strains would prove to be dually beneficial to rice crops both as a biopesticide and as a biofertilizer. Immunoblot analysis of the recombinant organism containing the cry1Ac gene, strain BP113, indicated efficient expression of this gene in the heterologous host. Bioassays with the first instar larvae of the yellow stem borer of rice (Scirpophaga incertulas) revealed that the protein preparations from BP113 were toxic.
The impact of monocrotophos on protein and carbohydrate metabolism in different tissues of albino rats was investigated. The monocrotophos (0.25 mg/ml) was orally intubated into an experimental group of rats. In another group, the same amount of water was orally intubated (control group) for 29 days. The protein content was increased in liver, serum and spleen of albino rats after treatment with monocrotophos. The protein content decreased in muscle and kidney, and overall the free sugar level decreased in all tissues. The glycogen content increased in muscle, serum and kidney after treatment with monocrotophos, and the glycogen content and reducing sugar level decreased in liver and spleen. The significance of these results is discussed.
A tetrapeptide corresponding to a region of the N-terminal portion of lactotransferrin with hydrophobic alkyl groups at the terminal ends was synthesized and its physicochemical properties as well as its effect on thrombin-stimulated platelet aggregation were examined. The tetrapeptide derivative, in the aggregated state, produced inhibitory effect on platelet aggregation. The concentration dependent activity of the peptide was analyzed in the light of micelle formation, with the micellar aggregate comprising four tetrapeptide units. The unique action of this peptide derivative on the inhibition of platelet aggregation might be useful in the development of potent antithrombotic drugs.
Isoproterenol hydrochloride (ISO), a beta adrenergic agonist, is known to cause ischemic necrosis in rats. Cardiotoxicity of three different doses of ISO were studied using physiological, biochemical and histopathological parameters. The effects of single and double dose of ISO were analysed, which illustrated that single ISO dose was more cardiotoxic than double ISO dose due to ischemic preconditioning. The tetrapeptide derivatives L-lysine-L-arginine-L-aspartic acid-L-serine (tetrapeptide A) and di-tert.butyloxycarbonyl-L-lysine-L-arginine-L-aspartic acid-tert.butyl O-tert.butyl-L-serinate (tetrapeptide B) along with acetylsalicylic acid as positive control were analysed at different time points for their cardioprotective effect. The results demonstrated that optimal protective effects were observed by pretreatment with 5 mg/kg of tetrapeptide B and this was found to be slightly better than that of acetylsalicylic acid. A lesser degree of cardioprotection was noticed when low doses of tetrapeptide B were administered. This study clearly showed that single dose of ISO (50 mg/kg, s.c.) induced myocardial necrosis could be used as a model to assess cardiovascular drugs and in this model, it was demonstrated that the tetrapeptide B could exhibit optimal cardioprotective effect.
PURPOSE: To determine the clinical and radiological features of the patients who were found to have cavum septum pellucidum (CSP) on the cranial computerized tomographic (CT) scans. METHODS: Fifty four consecutive cases of cavum septum pellucidum were detected amongst 1,281 patients who underwent cranial CT scans; their clinical and radiological features were studied. RESULTS: Recurrent seizures and developmental delay were the commonest presenting symptoms seen. Significant neurological deficits were present in 75.9% of these cases. Additional cerebral abnormalities were observed in the CT scan in 76% of cases, the commonest being cortical atrophy, cerebral infarction and hydrocephalus. CONCLUSIONS: There seems to be a strong association between CSP and certain neurological abnormalities in the population studied. Further interpretation of this study would be possible if normal population in this geographical area is screened for CSP using cranial CT scans or magnetic resonance imaging.
A rapid test has been developed based on the technique of latex immunoassay for the detection of Newcastle disease virus from suspected tissue suspensions. The latex particles were sensitised with globulins and were used for antigen detection. Of the 258 samples tested, 165 samples were positive by this kit which was compared for its efficacy with the standard OIE approved haemagglutination (HA) and haemagglutination inhibition (HI) tests. No significant difference (P > 0.05) was observed between the tests. The sensitivity and specificity of the developed test was 94.19% and 87.63% respectively.
Surface active pentapeptide [2(HCOO-). Lys-Ala-Ala-Lys(Z)-Tyr-OCH3] has been synthesized and its micelle formation investigated using conductometric, pH metric, and UV spectroscopic techniques. The double head double tail peptide molecules are shown to interact with water soluble meso-tetrakis (4-sulfonatophenyl)-porphyrin [TPPS]H2 to form characteristic H-type aggregate at low concentrations, as evidenced by UV-Vis and fluorescence spectroscopic techniques. Spectroscopic analysis reveals that the aggregate contains 1:2 porphyrin-peptide combination. The equilibrium constant for the formation of peptide-porphyrin complex has been obtained by using absorption spectral data. The present studies provide new insight into the peptide-porphyrin interaction.
An avidin-biotin dot ELISA test was standardized to detect rabies viral antigens from the brain of rabies-suspected animals. This test was compared with the direct fluorescent antibody test (FAT). The advantages of the avidin-biotin dot ELISA are discussed. The incorporation of avidin-biotin into a conventional ELISA is a step forward in improving the available rabies antigen detection procedures as this technique is more sensitive, highly specific and exploits the great affinity of avidin for biotin. No significant difference was observed between FAT and avidin-biotin dot ELISA.
A modified enzyme linked immunosorbent assay (Dot ELISA) is described for visual detection of rabies antigen in animals. The test materials were dotted onto the nitrocellulose paper and allowed to react with rabies antiserum. The bound antigen--anti-body were reacted with a peroxidase conjugated antirabbit immunoglobulin. Positive reactions were easily visualized as brown dots after enzyme degradation of the substrate. A total of 400 specimens from various geographical locations were tested with the dot ELISA technique, and also with the fluorescent antibody test (FAT), which was used as a reference method. The concordance between the two tests was 95.25%. The dot ELISA may have potential applications as a rapid, simple and economical field test in the diagnosis of rabies.
Ordered aggregates of Val-Leu-Pro-Phe, tetrapeptide 1, have been found in aqueous solutions. Evidence for the formation of aggregates for the above peptide was obtained by conductometric, pH metric, UV and fluorescence spectroscopic techniques. Values of critical micelle concentration (CMC) for the above peptide obtained by these methods are in good agreement with each other. The formation of organized aggregates of the peptide is favoured upon increasing the temperature (viz. the process of aggregation is endothermic). The aggregation number has been determined at different temperatures. Values of delta G0m, delta H0m, delta S0m and delta C0p have also been estimated. Binding studies with the 8-anilinonaphthyl sulfonic acid (ANS) and pyrene indicate that the interior of the aggregate is nonpolar. There are two processes with regard to the change of thermodynamical parameters like delta G0m, delta H0m, delta S0m, delta C0p and aggregation number (N). In the first process (from 5 degrees C to 40 degrees C) the driving force for aggregation seems to be the positive entropy because of water release due to intermolecular association of ionic moieties. The second process (from 40 degrees C and above) is due to intramolecular ionic interaction. The chemical shifts of the amide protons of the peptide have been presented in the light of inter- and intramolecular hydrogen-bond formation, and forces implicated in aggregation for both the first and second processes.
A novel peptide, tert-butyloxycarbonyl-L-arginine-L-proline lauryl ester laurate, synthesised by a solution-phase method, formed micelles in aqueous solutions and was observed to exhibit anticoagulant activity as shown by clotting assays such as the thrombin time (TT) test, the prothrombin time (PT) test and the activated partial thromboplastin time (APTT) test. TT and PT were found to be normal up to a particular concentration of peptide, and above that level they increased with increasing concentration of peptide, while APTT did not exhibit much significance. Conductometric and potentiometric studies showed that the peptide formed a stable micelle, and the anticoagulant activity of this peptide was also compared with a non-arginine-containing peptide (control) known to form micelles. The anticoagulant action in the micellar form could be due to the inhibition of thrombin, as seen from the decrease in amidolytic activity. The inhibitory activity of the peptide was explained in the light of micelle formation.
A dipstick Dot enzyme immuno diagnosis test was standardized to detect rabies viral antigens from brain, of rabies-suspected dogs, cattle, horses, cats and goats. This test was compared with the direct fluorescent antibody test (FAT). When compared to the direct FAT, the dipstick dot ELISA test did not produce non-specific false-positive results and was therefore specific and reliable. The advantages of the dipstick Dot-ELISA are discussed.
Activity of the dipeptidyl hydrolase angiotensin converting enzyme (ACE) has been observed to be altered by treatment with adriamycin (ADR). We used an animal model of ADR nephrotoxicity to study the effects on ACE in serum, urine and tissues on days 5, 10, 15, 20, 25 and 30 after ADR administration. Both glomerular and tubular injury occurred as evidenced by heavy proteinuria, albuminuria and increased urine N-acetyl glucosaminidase (NAG) excretion. Serum ACE was significantly elevated on days 20, 25 and 30. Of great interest was the excretion of ACE in urine of treated rats which ran parallel with the total protein excretion above the barely detectable levels found in controls. ACE activity increased in kidney, adrenal gland and liver on days 15, 20, 25 and 30. Heart and brain ACE levels increased on days 25 and 30. Increased ACE activity in aorta and lungs occurred on days 20, 25 and 30. ACE activity decreased in kidney, aorta, heart and brain on days 5 and 10. These observations strongly suggest a contribution of various tissues to elevate the serum ACE level. Urinary ACE may be of potential use as an index for renal glomerular and tubular damage.