Biomedical subjects
S Narayan
Publications and source records attributed to S Narayan.
Specific binding and growth effects of bombesin-related peptides on mouse colon cancer cells in vitro.
In the present study, we characterized specific binding of bombesin (BBS)/gastrin-releasing peptide (GRP) to mouse colon cancer (MC-26) cells. MC-26 cells were inoculated into male BALB/c mice subdermally, and tumors were harvested from mice 21-28 days postinoculation. Tumor membranes were analyzed for binding to GRP-related peptides, using either 125I-GRP or 125I-tyrosine4-BBS. Under optimal binding assay conditions, BBS displaced specific binding of both 125I-GRP and 125I-tyrosine4-BBS in a dose-dependent manner, and a curvilinear displacement resulted. Specific binding data, analyzed by either a Scatchard or a Lineweaver-Burk plot, demonstrated presence of 2 classes of specific binding sites, arbitrarily named type I and type II sites. Type I sites had a high binding affinity [Kd 0.45 +/- 0.05 nM (SE)] and a relatively low capacity (226 +/- 27 fmol/mg membrane protein), whereas type II sites had a 10-20-fold lower binding affinity and approximately 6-7-fold higher capacity. BBS/GRP binding sites were specific for GRP-related peptides and demonstrated no significant binding affinity for all other unrelated peptides tested. Relative binding affinity of GRP analogues was in the order of GRP (14-27) greater than neuromedin C greater than or equal to BBS greater than or equal to GRP (1-27) greater than neuromedin B (for the later, P greater than 0.05 versus other peptides). Two BBS receptor antagonists, [D-Arg1,D-trp7,9,Leu11]-substance P (spantide) and [Leu13-psi-(CH2NH)Leu14]BBS also inhibited specific binding of 125I-GRP in a dose-dependent manner. Molecular weight of GRP/BBS binding proteins on tumor membranes was determined by cross-linking methods. A major molecular form (greater than 80-90%) (Mr approximately 75,000) and a minor Mr approximately 180,000 band were evident, both under reducing and nonreducing conditions. BBS (0.5-50 nM) demonstrated a significant dose-dependent growth effect on MC-26 cells in vitro, in terms of [3H]thymidine and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide uptake; these studies indicate that the BBS/GRP binding sites on MC-26 cells may serve as functional receptors and mediate the growth effects of BBS on MC-26 cells.
Family characteristics of autistic children: a further report.
The personality features of parents of a group of 21 well-functioning autistic children have been described previously. The main characteristics of these parents were social gaucheness and a tendency towards the single-minded pursuit of special, often intellectual, interests. We now present the agreement between research interviewers and clinician in the diagnosis of these parents as schizoid, together with clinical details of those parents rated by both as having definite schizoid traits. The educational functioning of the siblings of the autistic children compared with that of siblings of a matched control group is also reported.
Bimodal operation of the ryanodine-sensitive transducer calcium channel.
Ryanodine binds to the transducer calcium channel complex that links depolarization of the transverse tubule to calcium release from the terminal cisternae during excitation-contraction coupling of skeletal muscle. Ryanodine exerts a bimodal action on the transducer calcium channel complex depending upon membrane potential and concentration. When the transmembrane potential is at resting level (-90 mV inside cell vs outside), low concentrations of ryanodine 10(-10) M to 10(-8) M favor calcium influx from outside which in turn causes calcium release from the terminal cisternae via calcium operated calcium channels. The leak from the terminal cisternae is insufficient to cause contraction but does cause a large increase in aerobic energy utilization by the Ca-ATPase of the sarcoplasmic reticulum. When the transmembrane potential is made more positive (-40 mV) the transducer channel is opened to the terminal cisternae of sarcoplasmic reticulum and is maintained in an open state by ryanodine allowing calcium efflux from the terminal cisternae to the sarcoplasm. At higher concentrations of ryanodine the transducer-calcium channel becomes open to the terminal cisternae and its store of ionized calcium leaks from the terminal cisternae in sufficient quantities to cause a contracture. The ryanodine-sensitive calcium transducer calcium channel operates in a bimodal manner. At low concentrations less than 10(-4) M the ryanodine-sensitive transducer calcium channel is open to the lumen of the T-tubule and allows calcium to flow in and trigger further calcium release. At higher concentrations the ryanodine-sensitive transducer channel opens to allow a calcium efflux from the terminal cisternae in sufficient quantities to cause contracture.
Changes in lipid profiles of liver microsomes of rats following intratracheal administration of DDT or endosulfan.
The effect of intratracheal administration of DDT (5 mg/100 g body weight) or endosulfan (1 mg/100 g body weight) to rats for three consecutive days, has been studied on liver lipid metabolism. The administration of DDT but not endosulfan significantly increased the liver weight and the microsomal protein contents. Both DDT and endosulfan treatments significantly increased the contents of microsomal phosphatidylcholine (PC), total-free- and esterified cholesterol. The distribution of unsaturated fatty acids of microsomal PC and PE was increased by DDT treatment. The intratracheal administration of DDT caused fatty infiltration of liver which was probably due to increased synthesis of triglycerides (TG). This is supported by the increased incorporation of radioactive palmitate-1-14C into microsomal TG. However, the increased incorporation of palmitate-1-14C into microsomal PC and phosphatidylethanolamine (PE) after the DDT treatment, was due to the increased transacylation reaction supported by the decreased activity of microsomal phospholipase A. The intratracheal administration of endosulfan did not have pronounced effect on liver fatty infiltration, or transacylation reaction in microsomal PC and PE. However, the results have shown that the treatments of DDT or endosulfan increased the PC contents and the incorporation of radioactive [methyl-3H]choline into PC of microsomes, resulting the increased synthesis of PC via CDPcholine pathway. Thus, the intratracheally administered DDT or endosulfan to rats showed that both the insecticides cause manifestations in the biochemistry of microsomal membrane lipids, although the effects of DDT being more pronounced. Therefore, the translocation effects of these insecticides or metabolites from lung to liver is established.
Lung subcellular fractions and surfactant lipid metabolism of rats exposed with DDT or endosulfan intratracheally.
The effect of intratracheally administered DDT (5 mg/100 g body weight) or endosulfan (1 mg/100 g body weight) for three consecutive days has been studied on lipid metabolism of rat lung subcellular fractions. Both the insecticides did not affect the lung weight and the protein contents of microsomes, lamellar bodies and surfactant but significantly increased the phospholipid contents of microsomal and surfactant system. Most of the neutral lipid components of lung subcellular fractions were also increased by DDT or endosulfan treatments, except that of surfactant triglycerides which were decreased by DDT treatment. DDT or endosulfan both increased the incorporation of radioactive [methyl-3H]choline into microsomal phosphatidylcholine (PC) and surfactant dipalmitoylphosphatidylcholine (DPPC) without affecting the incorporation of radioactive [methyl-14C]methionine, showing the increased synthesis of PC via CDPcholine pathway. The results presented in this communication showed that DDT and endosulfan, the two different chloroinsecticides have similar effects on microsomal lipid metabolism but produce different biochemical manifestations on the secretion of surfactant phospholipids.
Profiles of ethanol-induced microsomal alkoxyresorufin (alkoxyphenoxazone) O-dealkylation: comparison with phenobarbital- and Aroclor 1254-induced systems.
The O-dealkylation of various substituted alkoxyphenoxazones by liver microsomes from rats chronically fed ethanol is compared with that from pair-fed controls to determine whether there is any catalytic selectivity which could serve as an indicator for induction of cytochrome P-450j. Microsomes derived from animals pretreated with the better characterized inducers phenobarbital and Aroclor 1254 were also studied as positive controls. The specific activities (units/mg microsomal protein) but not the turnover numbers (units/nmol cytochrome P-450) were significantly increased by ethanol ingestion compared to pair-fed controls for methoxy-, ethoxy-, and pentoxy-resorufin O-dealkylation. Ethanol ingestion produced a significant increase in both specific activity and turnover number for the O-dealkylation of benzyloxy-resorufin. The degrees of induction of alkoxyresorufin-O-dealkylation activity measured for EtOH-induced microsomes range from 1.7 for methoxyresorufin to 4.8 for benzyloxyresorufin and are small in comparison to the values for phenobarbital and Aroclor 1254. This pattern of induction suggests that the minor isoforms induced by phenobarbital may be propagated by chronic ethanol ingestion.
Binding of insulin-like growth factor-I to rat uterus; variations during sensitization and decidualization.
IGF-I receptors have been identified and characterized in a variety of tissues. In this study receptors for IGF-I in the rat uterine tissue were identified and characterized. We have demonstrated IGF-I receptors in crude uterine membranes by binding and cross-linking experiments. IGF-I binding to the rat uterine membranes displayed time, temperature and pH dependance, and optimal binding conditions were achieved by 20 h of incubation at 4 degrees C, at a pH of 7.8. Uterine IGF-I binding sites were specific for binding IGF-I peptide and demonstrated less than 100 x lower affinity for insulin. The binding was reversible and Scatchard analysis indicated presence of a single class of binding sites with an apparent dissociation constant of 1.68 +/- 0.24 nmol/l and Bmax of 0.82 +/- 0.1 pmol/mg protein. During estrogen treatment, sensitization and decidualization there was an overall increase of membrane proteins in the uterus and a relative decrease of IGF-I receptors per unit of protein. When expressed on a per uterus basis, there was a progressive increment in total IGF-I binding in estradiol-treated, sensitized, and decidualized uterus compared with controls. These data indicate a possible role for IGF-I in uterine cell multiplication and further differentiation to decidual cells in response to deciduogenic stimuli.
Differential induction of peroxygenase-dependent microsomal aniline hydroxylase by chronic ethanol ingestion.
The liver microsomal-mediated hydroxylation of aniline, which is selectively induced by chronic (EtOH) ingestion, has been studied as a function of NADPH plus dioxygen (O2)- or hydroperoxide-dependent reactions. Consistent with the well-documented induction of aniline hydroxylase following chronic ethanol -ingestion, the results showed selectivity towards aniline hydroxylase by the NADPH plus O2- and tert-butyl hydroperoxide (t-BuOOH)-dependent reactions with microsomes from EtOH-fed rats. On the other hand, the cumene hydroperoxide (CumOOH)-dependent aniline hydroxylase activity was not discriminated between microsomes from EtOH- and pair-fed rats. In parallel experiments with positive controls, CumOOH did show selectivity for phenobarbital (PB)-induced microsomal aniline hydroxylase compared to chow-fed rats. The Kcat/KM values, which indicate the efficiency of enzyme catalysis, for NADPH plus O2-, t-BuOOH, and CumOOH-dependent aniline hydroxylase from EtOH-fed rats were 102, 37, and 5 and from pair-fed rats were 68, 4, and 4 (nmol p-aminophenol/min/nmol cytochrome P-450)/mM aniline, respectively. The relative Kcat/KM ratio for EtOH-fed to that of pair-fed microsomal aniline hydroxylase from NADPH plus O2-, t-BuOOH-, and CumOOH-dependent reactions were 1.5, 7.4, and 1.2, respectively. The present preliminary studies indicate that the catalytic efficiency of EtOH-induced aniline hydroxylase is significantly greater for the t-BuOOH-dependent reaction.
The presence of a 33-40 KDa gastrin binding protein on human and mouse colon cancer.
Human and mouse colon cancers have specific binding sites for gastrin and demonstrate a trophic response to gastrin. In the present study we used radiolabeled gastrin (2-17), to determine the molecular weight of gastrin binding proteins (receptors) on mouse and human colon cancers, by cross-linking methods. Crude membrane aliquots prepared from the tumors were radiolabeled with [125I]gastrin (2-17) +/- 1000 fold excess of unlabeled gastrin and cross-linked with 1 mM disuccinimidyl suberate. The cross-linked radiolabeled binding protein complexes were solubilized and subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis. The autoradiographs of the gels demonstrated the presence of a predominant band of approximately 33-40 KDa gastrin binding protein, that was specific for gastrin analogs. Our present findings thus indicate that specific gastrin binding proteins/gastrin receptors on colon cancers are primarily present as one band with a molecular mass of approximately 33-40 KDa and are specific for gastrin-like peptides.
Induction of phosphatidylcholine biosynthesis via CDPcholine pathway in lung and liver of rats following intratracheal administration of DDT and endosulfan.
The induction of phosphatidylcholine (PC) biosynthesis via the CDPcholine pathway in lung and liver of rats has been shown following the intratracheal administration of 1,1,1-trichloro-2m2-bis(p-chlorophenyl) ethane (DDT) (5 mg/100 g body weight) and endosulfan (1 mg/100 g body weight) for 3 days. Controls received only the vehicle solution (groundnut oil, 0.1 m1/100 g body weight). The treatment of DDT and endosulfan significantly increased the PC contents and the incorporation of radioactive [methyl-3H]choline into PC of lung and liver microsomes. The incorporation of radioactive [methyl-14C]methionine into microsomal PC of lung and liver was not affected significantly by treatment with either of the insecticides. 1,4,5,6,7-hexachloro-5-norbornene-2,3-dimethano cyclic sulfite (endosulfan) administration significantly increased the activity of choline kinase and phosphocholine cytidylyltransferase (both cytosolic and microsomal) of lung, whereas DDT increased the activity of only latter. In liver, both DDT and endosulfan administration significantly increased the activity of choline kinase and phosphocholine cytidylyltransferase (both cytosolic and microsomal). However, the activity of phosphocholinetransferase was not affected in both lung and liver microsomes of rats treated with these insecticides. The PC precursor pool sizes, choline and phosphorylcholine, of lung and liver tissues were not altered by DDT and endosulfan treatments. The present results suggest that the increased level of PC and incorporation of radioactive [methyl-3H]choline into microsomal PC could be the result of increased activity of choline kinase and phosphocholine cytidylyltransferase of lung and liver of rats following intratracheal administration of DDT and endosulfan.
Myocardial collagen and mechanics after preventing hypertrophy in hypertensive rats.
To determine if a remodeling of the collagen matrix would occur in the absence of hypertrophy and cell necrosis and if such a remodeling could alter active and passive stiffness of the intact myocardium, five rats with genetic hypertension (SHR) were treated (SHRT) with hydralazine for 32 weeks, beginning at four weeks of age, and compared to six age- and sex-matched SHR and seven Wistar-Kyoto genetic control rats (WKY). Left ventricular (LV) weight of SHRT was 17% lower (P less than .001) than that of SHR and 19% higher (P less than .01) than that of WKY. Collagen volume fraction of SHR (13.7 +/- 3.2%) and SHRT (9.9 +/- 1.8%) were greater (P less than .01) than WKY (5.0 +/- 1.9%). Diastolic and systolic stress-strain relations were determined in the isolated heart. A comparison of these relations revealed: 1) a 24% increase in passive stiffness for SHR and SHRT; and 2) a reduced zero-strain intercept (41% to 54%) and slope (36% to 48%) of the developed stress-strain relation for the SHRT. Thus, in SHR, collagen remodeling occurred in the absence of hypertrophy which suggests that the muscular and collagenous compartments of the myocardium are under separate controls. The excess accumulation of collagen in SHR and SHRT leads to abnormal passive stiffness, and the prevention of hypertrophy with hydralazine reduces active stiffness.
Efficacy of oral water soluble vitamin K in neonates.
Effect of oral water soluble synthetic Vitamin K on prothrombin time was evaluated in 120 full term exclusively breast fed babies. Group A (n = 30) received 1 mg vitamin K (menadione sodium disulphite) intramuscularly at birth, Group B (n = 30) received 0.5 mg intramuscularly, Group C (n = 30) 1 mg orally and Group D (n = 30) did not receive any vitamin K. Prothrombin time (PT) was measured in all between 36-72 hours of age. The PT values in the four Groups A, B, C and D were 17.1 +/- 2.68 seconds, 17.2 +/- 4.42 seconds, 17.0 +/- 2.86 seconds, and 33.1 +/- 12.2 seconds, respectively; the control being 17.0 seconds. The differences between Groups A, B and C were insignificant. Group D babies had a significant prolongation of prothrombin time (p less than 0.001) as compared to the other groups. It is concluded that oral water soluble vitamin K at birth is as good as injectable vitamin K. It is a much simpler form of prophylaxis and avoids intramuscular injection.
Alteration of liver microsomal monooxygenases and substrate competition with aniline hydroxylase from rats chronically fed low-fat and high-fat-containing alcohol diets.
Male Sprague-Dawley rats fed ethanol (EtOH) 36% of total calories for four weeks in a liquid diet containing either 34% (HF) or 12% (LF) of calories as fat were studied with respect to induction of microsomal monooxygenases (MFO) and substrate competition with EtOH-inducible aniline hydroxylase. The specific activity and turnover of aniline hydroxylase were induced to similar extents by HF-EtOH and LF-EtOH diets. Whereas, both LF-EtOH and HF-EtOH caused a decrease in the turnover of arylhydrocarbon (benzo[a]pyrene) hydroxylase (AHH) and aldrin epoxidase compared to pair-fed (PF) controls, LF-EtOH but not HF-EtOH increased the turnover of ethoxycoumarin and ethoxyresorufin O-deethylase (ECOD and EROD). The increase in ECOD and EROD and the decrease in AHH by EtOH is contrary to the parallel induction of these activities by 3-methylcholanthrene (3-MC) and Aroclor 1254 (Aroclor). Benzo(a)pyrene (BaP) stimulated aniline hydroxylase in the HF-EtOH and PF systems, whereas with LF diet, stimulation was seen only in the EtOH group. Ethoxycoumarin (EC) inhibited aniline hydroxylase by microsomes from EtOH- and pyrazole-treated rats, whereas it stimulated aniline hydroxylase by control microsomes, suggesting that the EC effects were associated with EtOH-inducible cytochrome P-450. Ethoxyresorufin (ER) inhibited aniline hydroxylase in EtOH and PF groups, thus the differential effects of EC were not nonspecific O-deethylase effects. The effects of EtOH feeding on ECOD, EROD, and AHH (ie, substrates for 3-MC-inducible cytochrome P-450) displayed a greater differential between the experimental and control group with the LF- than with the HF-containing diet. The findings suggest that the alteration of certain MFO activities by chronic EtOH ingestion can be modified by the content of dietary fat. Moreover, the competition dynamics of MFO substrates toward EtOH-inducible aniline hydroxylase are altered by EtOH feeding and, in turn, modified by dietary fat.
Personality characteristics of parents of autistic children: a controlled study.
Parents of 21 autistic children and of 21 children with other handicaps, matched for sex, age, IQ and father's occupation, were interviewed with a schedule known to discriminate between schizoid and non-schizoid people. Ratings were reliable and the interviewers remained "blind". Parents of autistic children, especially fathers, were significantly more often rated as having schizoid traits. They were also more intellectual.
"Thinking aloud" as a strategy to improve clinical decision making.
Although "thinking aloud" has been used as a research method to collect data about nurses' knowledge and cognitive processes, it has not been used widely for instruction. We suggest that thinking aloud can be an effective teaching strategy for staff development. Two techniques are described for incorporating thinking aloud into dialogue among experienced nurses and into mentoring activities between experts and novices. An excerpt from a transcript of one nurse's thinking aloud while making a triage decision is presented to illustrate the types of knowledge and cognitive processes that can be elicited and revealed by using this strategy. Potential educational benefits are identified, along with suggestions for implementing thinking aloud as an instructional method.
Cytotoxicity of inhaled coal fly ash in rats.
The effect of inhalation of coal fly ash for 6 hr daily for 15 days has been studied on the hematology, blood chemistry, and histopathology of lungs and liver of rats up to 4 months from the first day of exposure. Fly ash inhalation significantly reduced WBC, RBC, and hemoglobin contents at earlier periods after exposure but tended to return to normal values at later periods. Fly ash inhalation reduced lymphocytes and increased polymorphonuclears up to 60 days after exposure and after that the alterations were reversible. Blood glucose increased and blood urea and acid phosphatase decreased at early periods after inhalation, but at later periods returned to control group values. Fly ash inhalation profoundly affected the histological structure of lungs and liver at early periods after inhalation. Numerous fly ash-laden macrophages, thickening of alveolar septa, and alveolar dilatation were noted. In the liver, periportal necrosis was also observed. These changes, however, were reversible.