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J Stewart

Publications and source records attributed to J Stewart.

At least 271 records · Page 15Linked to original sources
PubMed1994

Dendritic branching in cortical pyramidal cells in response to ovariectomy in adult female rats: suppression by neonatal exposure to testosterone.

Female Long-Evans rats were treated with oil or testosterone propionate (TP) at birth (postnatal day zero, PN0) and PN1. As adults, animals from each group were ovariectomized or sham operated. Four months later the brains were prepared using a modified Golgi-Cox staining procedure. In neonatally oil-treated females, ovariectomy in adulthood increased the dendritic arbor of layer II/III pyramidal neurons of the parietal cortex; in addition, there were modest increases in apical dendritic spine density. The dendritic arbor of the pyramidal neurons of intact neonatally TP-treated females was greater than that of intact oil-treated females, but in these animals there was no increase in dendritic arbor in response to ovariectomy.

Animals↗
PubMed1994

Effects of neuropeptide analogues on calcium flux and proliferation in lung cancer cell lines.

Small cell lung cancers (SCLC) and some non-small cell lung cancers (NSCLC) have neuroendocrine features which include production of a variety of neuropeptides, cell surface expression of the receptors for these peptides, and autocrine stimulation by the peptides. Previous studies showed that some peptide antagonists and anti-peptide antibodies inhibited the growth of SCLC cell lines which expressed receptors for the specific peptide. We and others showed that the heterogeneity of peptide receptor expression and responsiveness was a major potential obstacle for developing therapeutic uses of peptide antagonists. In this manuscript we evaluated the effects of 11 peptide antagonists (3 bombesin-specific, 2 cholecystokinin-specific, 1 arginine vasopressin (AVP)-specific, and 5 substance P derivatives with broad specificity) on peptide-induced calcium mobilization and growth of SCLC and NSCLC cell lines. For each antagonist, we determined the dose-response effects, specificity of peptide antagonism, and biological stability in serum using Indo-1AM-based flow cytometric assays. We found that the three bombesin antagonists, S30, SC196, and L336,175, varied in potency from 10 nM to 10 microM, varied in serum stability from 6 h to more than 24 h, and had no effect on the calcium response elicited by other peptides. None of these compounds effectively inhibited the growth of SCLC cell lines in [3H]dThd and cell growth assays in vitro. Similarly, the three cholecystokinin and AVP antagonists were highly specific for cholecystokinin and AVP, respectively, had widely varying potency, but had little inhibitory effect on SCLC growth in vitro. In contrast, the five substance P derivatives inhibited the calcium response to bombesin, AVP, bradykinin, and fetal bovine serum. None of these five antagonists were as potent as the six specific antagonists described above, but they were more effective in inhibiting the growth of SCLC cell lines in vitro. These substance P derivatives inhibited the growth of peptide-sensitive SCLC cell lines more efficiently than their inhibition of peptide-insensitive NSCLC or breast cancer cell lines. Relatively high concentrations of these substance P derivatives were required to inhibit in vitro growth, even in the absence of added peptide. It is likely that more potent broad spectrum antagonists, toxins, or radiolabeled stable antagonists will need to be developed for maximal clinical development of this type of anti-growth factor therapy.

Amino Acid Sequence↗
PubMed1994

Estradiol derived from testosterone in prenatal life affects the development of catecholamine systems in the frontal cortex in the male rat.

We reported previously that exposure to testosterone (T), neonatally, slows the time-course of development of catecholaminergic activity in the anterior cortex of rat pups. In the present study we assessed the role of T in prenatal life on this development and explored the role of the estrogen metabolite of T, estradiol, in these actions. Male pups born to dams injected daily with 5 mg/kg, s.c., of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD), or vehicle only, between gestation days 10 and 21 were either gonadectomized (GX) or anesthetized, only, within 6 h of birth. Dopamine, DOPAC, and noradrenaline levels were assessed, using HPLC-EC, in punched samples taken from cingulate (CING), agranular insular (AID), parietal (PAR) and occipital (OC) cortex on postnatal (PN) days 4 and 10. At PN4 there were no effects of treatment on amine levels, although there were higher levels in frontal areas. At PN10, ATD and ATD GX animals had higher levels of dopamine, DOPAC, and noradrenaline in CING and AID than normal males. It would appear that T acts prenatally through its metabolite, estradiol, to modulate the development of catecholamine activity in the frontal cortex in the neonatal period.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Inhibition of nitric oxide synthase does not block the development of sensitization to the behavioral activating effects of amphetamine.

Pretreatment with the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), a competitive blocker of NO production, did not interfere with the development of sensitization to the behavioral activating effects of amphetamine (AMPH). On five pre-exposure sessions, at 3-day intervals, rats were given two i.p. injections, either 50 mg/kg L-NAME 30 min prior to 1.5 mg/kg D-AMPH sulfate, saline and AMPH, L-NAME and saline, or saline only. L-NAME reduced the levels of activity recorded during the pre-exposure session but had no effect on the degree of sensitization shown to a challenge injection of 0.5 mg/kg AMPH given 10 days later. A separate study using in vivo microdialysis showed that pretreatment with L-NAME did not alter AMPH-stimulated dopamine release in nucleus accumbens.

Amino Acid Oxidoreductases↗
PubMed1994

Manifold sequencing: efficient processing of large sets of sequencing reactions.

Automated instruments for DNA sequencing greatly simplify data collection in the Sanger sequencing procedure. By contrast, the so-called front-end problems of preparing sequencing templates, performing sequencing reactions, and loading these on the instruments remain major obstacles to extensive sequencing projects. We describe here the use of a manifold support to prepare and perform sequencing reactions on large sets of templates in parallel, as well as to load the reaction products on a sequencing instrument. In this manner, all reaction steps are performed without pipetting the samples. The strategy is applied to sequencing PCR-amplified clones of the human mitochondrial D-loop and for detection of heterozygous positions in the human major histocompatibility complex class II gene HLA-DQB, amplified from genomic DNA samples. This technique will promote sequencing in a clinical context and could form the basis of more efficient genomic sequencing strategies.

Base Sequence↗
PubMed1994

Cerebral lupus.

Explore the source record for details and available documents.

Adolescent↗
PubMed1994

Catalytic antibody model and mutagenesis implicate arginine in transition-state stabilization.

To probe the mechanism of the catalytic antibody NPN43C9, we have constructed a three-dimensional model of the NPN43C9 variable region using our antibody structural database (ASD), which takes maximal advantage of immunoglobulin sequence and structural information. The ASD contains separately superimposed variable light and variable heavy chains, which reveal not only conserved backbone structure, but also structurally conserved side-chain conformations. The NPN43C9 model revealed that the guanidinium group of light chain Arg L96 was positioned at the bottom of the antigen-binding site and formed a salt bridge with the antigen's phosphonamidate group, which mimics the negatively charged, tetrahedral transition states in the hydrolysis reaction. Thus, the model predicts both binding and catalytic functions for Arg L96, which previously had not been implicated in either. First, Arg L96 should enhance antigen binding by electrostatically complementing the negative charge of the antigen, which is buried upon complex formation. Second, Arg L96 should promote catalysis by electrostatically stabilizing the negatively charged transition states formed during catalysis. These hypotheses were tested experimentally by design and characterization of the R-L96-Q mutant, in which Arg L96 was replaced with Gln by site-directed mutagenesis. As predicted, antigen binding in the R-L96-Q mutant was decreased relative to that in the parent NPN43C9 antibody, but binding of antigen fragments lacking the phosphonamidate group was retained. In addition, the R-L96-Q mutant had no detectable esterase activity. Thus, the computational model and experimental results together suggest a mechanism by which the catalytic antibody NPN43C9 stabilizes high-energy transition states during catalysis.

Amino Acid Sequence↗
PubMed1994

Results of anal or low rectal anastomosis and pouch construction for megarectum and megacolon.

Over a 16-year period 34 patients underwent surgery for idiopathic megarectum or megacolon; 18 had megarectum with or without megasigmoid, one megacolon only and 15 megarectum and total megacolon (nine with a previous colectomy). Ten patients underwent low rectal or anal anastomosis without pouch formation (colodistal proctostomy, eight; coloanal anastomosis, two), eight had colonic pouch-anal anastomosis (J pouch) and 14 had an ileal J pouch after restorative proctocolectomy; one underwent subtotal colectomy with ileorectal anastomosis and one loop ileostomy alone. There was one death, from intestinal obstruction 24 months after operation. Twenty-seven of 32 evaluable patients without a stoma became fully continent following resection and sphincter-saving procedures. Three of 18 had a poor result after resection for megarectum because of recurrent constipation. One of 14 patients became incontinent after restorative proctocolectomy for megacolon and megarectum and in a further four persistent abdominal distension and pain was treated by pouch excision.

Adolescent↗
PubMed1994

Effect of prepubertal ovariectomy on amphetamine-induced locomotor activity in adult female rats.

Adult female rats show greater behavioral activation in response to both acute and repeated injections of amphetamine (AMPH) than adult male rats. The present experiments investigated whether life-long exposure to ovarian hormones in females contributes to their enhanced responsiveness to AMPH as adults and whether this effect depends on exposure to testosterone (T) in the neonatal period. In Experiment 1, female rats were ovariectomized either prior to puberty (EARLY) or in adulthood (ADULT). Locomotor activity in response to either 1.5 mg/kg AMPH or the saline vehicle was measured for 2 hr every third day on five occasions. On the sixth occasion all animals received 0.75 mg/kg AMPH in a test for sensitization. Each animal received either 5.0 micrograms estradiol benzoate (EB) or the oil vehicle (OIL), 30-35 min prior to each session. Experiment 2 was similar except that all animals were treated with T at birth. In Experiment 1, during the repeated treatment period, group EARLY had lower AMPH-induced activity scores than group ADULT, in both OIL and EB conditions. EB-treated rats had higher levels of AMPH-induced activity and showed greater changes in activity over days of testing than OIL-treated rats, regardless of time of ovariectomy. Animals previously exposed to AMPH showed higher levels of activity on the test for sensitization than animals receiving the drug for the first time, but this effect did not vary as a function of hormone condition or time of ovariectomy. Exposure of females to T at birth reduced responsiveness to AMPH and EB in adulthood, and ovariectomy prior to puberty had little effect in these animals.

Age Factors↗
PubMed1994

Exposure to mild stress enhances the reinforcing efficacy of intravenous heroin self-administration in rats.

The effect of a mild footshock on intravenous heroin self-administration was examined in male rats. Animals in the stress condition were exposed to 10 min of intermittent footshock (0.5 mA; 0.5 s on, with a mean off period of 40 s) before each of four daily self-administration sessions. Animals in the control group were not exposed to footshock. Following acquisition of heroin-reinforced behavior (100 micrograms/kg per infusion), during which no group differences emerged, animals were placed on a progressive ratio schedule of reinforcement and were subsequently tested under a decreasing series of doses. Animals exposed to footshock before each drug session had higher rates of lever pressing for heroin and achieved higher final ratios on the progressive ratio schedule than animals in the control group at the higher doses of heroin. Thus, under the conditions of this experiment, exposure to mild intermittent stress appeared to enhance the reinforcing efficacy of heroin. The parameters of footshock used in the present study, and its relation to drug availability may characterize conditions under which stress leads to increased opioid abuse.

Animals↗
PubMed1994

A comparison of lumbar epidural and intravenous fentanyl infusions for post-thoracotomy analgesia.

This double-blind randomised study compared the analgesic efficacy, respiratory effects, side effects, and pharmacokinetic disposition of 24 hr lumbar epidural and intravenous infusions of the same dosage regimen of fentanyl (1.5 micrograms.kg-1 bolus then 1 microgram.kg-1.hr-1 infusion) in 50 patients after thoracotomy. Patients received either epidural fentanyl and intravenous normal saline, or epidural normal saline and intravenous fentanyl, for postoperative analgesia, after a standard low-dose alfentanil and isoflurane general anaesthetic. Visual analogue pain scores were lower in the epidural group (P < 0.05) only at two hours postoperatively, and there was no difference in the amount of supplementary morphine self-administered by patient-controlled analgesic pump. A mainly spinal analgesic effect probably occurred in the first few hours since fentanyl was not detectable in the plasma of patients in the epidural group until two hours after bolus injection; its concentration was less at that time than after intravenous injection (P < 0.05). Thereafter there was no difference in the plasma concentration profiles between the two groups. Seven patients in the epidural group and ten patients in the intravenous group received naloxone for PaCO2 > 50 mmHg, and one patient in the intravenous group had the infusions stopped because of PaCO2 elevation and somnolence. In patients who did not receive naloxone, the epidural route produced better analgesia throughout the study period (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1994

Six differences in the locomotor-activating effects of amphetamine: role of circulating testosterone in adulthood.

The effects of circulating testosterone (T) on sex differences in locomotor activity elicited by both acute and repeated amphetamine (AMPH) administration were evaluated in adult rats. Male and female rats were gonadectomized in adulthood and implanted with Silastic capsules containing either T or cholesterol (CHOL). In the preexposure period, locomotor activity in response to IP injections of either AMPH (1.5 or 1.3 mg/kg) or saline (1.0 ml/kg) was measured for 2 h, every third day on five occasions. In a subsequent test for sensitization, all animals received AMPH (0.75 or 0.65 mg/kg). Results indicate that regardless of the presence of circulating T, females showed higher levels of activity in response to AMPH than males. In male animals, T suppressed AMPH-induced activity on the first day of the preexposure period, but this effect was lost with repeated testing. In female animals, T enhanced AMPH-induced activity during the first hour of testing. The presence of circulating T did not influence the degree of sensitization in either sex as determined by the difference between AMPH preexposed and SAL preexposed animals on the test day for sensitization.

Animals↗
PubMed1994

Influence of smoking on immunological responses to hepatitis B vaccine.

When 115 health-care workers participated in a study that monitored their serological responses to hepatitis B vaccine at regular intervals, it was found that smoking significantly affected their antibody titre responses adversely. The study group was randomly allocated into two comparable groups that received hepatitis B vaccine either in a rapid schedule (vaccination at 0, 1, 2 and 12 months) or a standard schedule-most commonly used worldwide-(vaccination at 0, 1, and 6 months). A significantly higher proportion of smokers, in both schedules, failed to seroconvert and to achieve higher antibody levels at month 3 (p = 0.01) and at month 13 (p = 0.0003). At month 7 a similar pattern was noted in smokers following the standard vaccination schedule (p < or = 0.05), but not in those following the rapid schedule.

Adult↗