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Biomedical subjects

R Stiller

Publications and source records attributed to R Stiller.

13 recordsLinked to original sources
PubMed1991

Conditioned tolerance to the anorectic and corticosterone-elevating effects of nicotine.

We have shown that tolerance to the behavioral effects of nicotine is partially dependent on conditioned environmental cues that predict drug delivery. The present research extends this finding to physiological effects of nicotine by assessing both the appetite-suppressing and adrenocortical-activating effects of nicotine, as measured by plasma corticosterone (CORT). In the first study, male rats on a 22-h food deprivation schedule were injected daily with 0.33 or 0.66 mg/kg (free base) of nicotine bitartrate or saline in a distinctive environment and tested for milk intake. Nicotine initially suppressed milk intake and tolerance developed over 10 days. Changing cues associated with drug administration partially reversed tolerance since injection of nicotine in a new environment reduced milk intake of tolerant animals. Similarly, animals who repeatedly received nicotine in one environment exhibited CORT levels lower than rats injected for the first time, and this tolerance also was partially reversed when administration occurred in the new environment. The second experiment indicated that the increased CORT of Experiment 1 was not a stress response associated with injecting animals in a different environment. These results indicate that tolerance to both behavioral and neuroendocrine effects of nicotine is influenced by conditioning.

Animals↗
PubMed1990

Isolated fetal ascites: prenatal diagnosis and management.

The perinatal outcomes of four patients with isolated fetal ascites were evaluated. The ascites disappeared prior to delivery in 50% of the cases and was resolved shortly after delivery in the remainder. Excellent neonatal outcomes were observed. Thus, isolated fetal ascites may represent a separate condition that significantly differs from the general category of nonimmune hydrops in both perinatal courses and prognoses. The prenatal diagnosis and management of this condition are discussed.

Adult↗
PubMed1989

Environment-specific tolerance to nicotine.

Research has shown that tolerance to the behavioral effects of numerous drugs is mediated by learning. The present study was designed to test whether animals develop tolerance to the antinociceptive effects of nicotine, and whether these effects are also learned. Rats were given dally injections of nicotine in the same environment. After each injection, the latency of tail withdrawal from a hot water bath was measured. This was continued until they were tolerant to the drug: i.e., their response latencies did not differ from animals repeatedly given saline. The role of learning in nicotine tolerance was assessed by changing the environment in which they received nicotine on the day after tolerance was achieved. When the drug environment was changed, the animals recovered the full dose effect of nicotine on tail-flick latencies. These results show that tolerance develops to nicotine's antinociceptive effects, and that this tolerance also may be influenced by learning.

Analgesics↗
PubMed1989

Changing environmental cues reduces tolerance to nicotine-induced anorexia.

Male rats on a 22-h food deprivation schedule were injected daily with a low dose of nicotine and allowed to drink sweetened milk for 10 min in a test cage in the colony room. Nicotine initially suppressed milk intake but complete tolerance developed within 10 days so that the amount of intake did not differ from saline controls. The role of temporal cues was tested on the next day by changing the timing of cues, and omitting others that normally preceded nicotine injection while keeping constant the physical environment within which injection and testing took place and the drug-test interval. Changing the timing of injection significantly suppressed milk intake. These results show that tolerance to the anorectic effects of a low dose of nicotine is partially dependent on the presence and timing of cues associated with tolerance acquisition.

Animals↗
PubMed1988

Increased intrapulmonary retention of radiolabeled neutrophils in early oxygen toxicity.

Sequential lung injuries, such as oxygen toxicity followed by septicemia, are common during the adult respiratory distress syndrome (ARDS). As these forms of vascular injury may be mediated in part by polymorphonuclear leukocytes (PMN), aberrant interactions between PMN and previously injured pulmonary endothelium are of both theoretical interest and clinical importance. The present study was undertaken to test the hypothesis that early oxygen toxicity at a dose that injuries pulmonary endothelium relatively selectively alters intrapulmonary neutrophil kinetics. Unanesthetized rats breathing 1.0 atmospheres oxygen for 36 h showed ultrastructural endothelial damage but no edema, injury, or neutrophilic inflammation by histologic criteria. However, in these oxygen-toxic animals, whereas initial accumulation of radiolabeled PMN in lungs was normal, washout of PMN was abnormal at 120 min after infusion, at which point the pulmonary retention of radiolabeled PMN in the lungs of oxygen-treated animals was significantly higher than in control animals (139% of control, p less than 0.0096). Features of our methodology, including avoidance of osmotic stress and use of paired control animals, appear to have greatly enhanced the sensitivity of radiolabeled neutrophils for detecting a subtle abnormality of neutrophil-endothelial interactions. Our studies in the oxygen toxicity model provide the first demonstration in vivo of abnormal intrapulmonary neutrophil kinetics in early oxygen toxicity prior to the onset of histologic evidence of lung injury or inflammation.

Animals↗
PubMed1987

Sonographic features of the triploid fetus.

The sonographic characteristics of six viable triploid fetuses, with gestational ages ranging from 16 to 33 weeks, are presented. Each pregnancy was associated with decreased amniotic fluid volume, a significant lag in biparietal diameter and femur length, and severe head-to-body disproportion. No placental abnormalities were noted on ultrasound and only one placenta demonstrated hydropic change (15% to 20% of villi) on pathologic examination. Since the nonmolar triploid fetus often presents with unexplained intrauterine growth retardation, identification of its characteristic sonographic features allows for karyotype confirmation and the avoidance of inappropriate obstetric management.

Female↗
PubMed1986

Behavioral effects of a single neuroleptic treatment grow with the passage of time.

The principal finding of this manuscript is that the incidence of catalepsy observed in the rat after a single administration of low, clinically relevant doses of the dopamine receptor antagonists and antipsychotic agents, haloperidol and fluphenazine hydrochloride, grows over time such that one re-exposure to the same compound up to 8 weeks later results in a marked enhancement (i.e. sensitization) of this response. This phenomenon appears to be independent of pharmacokinetic or conditioning factors as well as alterations in dopamine or dihydroxyphenylacetic acid. It suggests that the antidopaminergic influence of acute exposure to a neuroleptic not only persists but continues to sensitize for extraordinary periods of time even after the drug is no longer detectable in the system. Our findings may hold the key to understanding the apparent paradox that although neuroleptics presumably induce their therapeutic actions in disorders such as Tourette syndrome and schizophrenia as well as their parkinsonian effects by blocking dopamine receptors, this antagonism occurs immediately while behavioral changes often require weeks for maximal development.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

The cardiovascular effects of nicotine during stress.

The acute cardiovascular effects of smoking during stress may be greater than those of smoking or stress alone, a finding which could have implications for determining which smokers may be at particular risk for coronary heart disease (CHD). Methodological problems inherent in using tobacco smoking to deliver nicotine (believed responsible for smoking's cardiovascular effects) prevent clear examination of the cardiovascular effects of inhaled nicotine. This study compared the cardiovascular increases due to a video game stress task plus 1.0 mg nicotine with those of stress or nicotine alone using an aerosol method of presenting nicotine in measured doses. Twelve young male smokers each participated in four conditions on 4 separate days: stress + nicotine, stress + placebo (stress alone), rest + nicotine (nicotine alone), and rest + placebo. The effects of stress and nicotine were additive for heart rate but less than additive for systolic and diastolic blood pressure. These results indicate that the combined effects of stress and nicotine may be relevant to understanding the prevalence of CHD among smokers. They also suggest that the effects of each on cardiovascular activity may be different, as the effects are independent for heart rate but overlap for blood pressure.

Adolescent↗
PubMed1986

Targeting imipramine dose in children with depression.

The response to imipramine (IMI) in children with depression has been shown to correlate with total levels of IMI plus its active metabolite desmethylimipramine (DMI). The pharmacokinetics of IMI + DMI in children with depression are examined, and the single-point prediction of steady-state IMI + DMI levels at minimum therapeutic concentrations for prepubertal depression is proposed. With a single, 25 mg oral dose of IMI, a plasma concentration of IMI + DMI 24 hours after dosing correlates (r = 0.92) with steady-state IMI + DMI levels in children with depression receiving 3 mg/kg/day IMI. The targeting of IMI dose in the child population with depression to rapidly achieve a minimum therapeutic concentration is shown to be feasible and reliable within theoretic limits.

Absorption↗
PubMed1985

Oral pemoline kinetics in hyperactive children.

The time course of pemoline in plasma was investigated in seven prepubescent boys with attention-deficit disorders who were hyperactive. Maximum plasma concentrations of 4.3 +/- 1.0 mg/L were reached 2.8 +/- 1.8 hours after a single, 2 mg/kg oral dose of pemoline, followed by a monoexponential decline in plasma concentration over time. Mean t1/2 and total body clearance of pemoline were 8.6 hours and 0.65 ml/min/kg. The 600% interindividual variation in elimination t1/2 and the 300% variation in total body clearance of pemoline may explain the unpredictable nature of its dynamics and associated neurotoxicity in some cases.

Absorption↗
PubMed1982

Relationships among measures of smoking topography.

Interrelationships between puffing, puff duration, puff volume, and heart rate change were assessed in a sample of 63 chronic, high rate smokers. Results showed puff duration and volume were related for males and females, and that heart rate change was related to volume in males and puff duration in females. Puffs were not related to either volume or heart rate change in males or females. These results call into question research on smoking behavior which does not measure volume, and shows that components of puffing may not be used interchangeably, and that neither puffs nor puff duration are accurate predictors of volume of intake.

Adult↗