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Biomedical subjects

F R Snyder

Publications and source records attributed to F R Snyder.

At least 19 recordsLinked to original sources
PubMed1993

Performance, subjective, and physiological effects of nicotine in non-smokers.

Sixteen human volunteers with little or no experience using tobacco participated in one 4.5-h experimental session in which they were administered three doses of nicotine polacrilex gum (0, 2 and 4 mg) in ascending order at 90-min intervals. Physiological, subjective, and cognitive performance measures were assessed before and after each dose. Nicotine produced dose-related increases in heart rate and blood pressure and decreases in skin temperature. Nicotine also increased subjective ratings of dose strength and negative effects and decreased ratings of desire to repeat the same dose. There were dose-related trends toward decreased accuracy and increased response time on 3 of the 4 cognitive tests. These data do not support the hypothesis that nicotine enhances cognitive functioning in non-smokers.

Adult↗
PubMed1993

Racial differences in sexual behaviors related to AIDS in a nineteen-city sample of street-recruited drug injectors. NADR Consortium.

Questionnaire data from almost 12,000 street-recruited drug injectors in 19 cities were analyzed to determine racial differences that may affect transmission of the human immunodeficiency virus (HIV). Self-reported sexual behaviors of drug injectors differ by city-type. White male drug injectors reported less unprotected vaginal sex than black or Latino males in multicultural--black/white/Mexican-origin and biracial cities. Black drug users of both sexes were less likely than white or Latino drug users to report unprotected and sex in multicultural--black/white/Mexican-origin and multicultural--black/white/Puerto Rican cities. The reported percentage of sex acts in which a condom was used was similar for black, white, and Puerto Rican men, and for black and white women, in all city types, but Puerto Rican women reported more condom use than black women. Mexican-origin drug injectors of each gender were least likely to report using condoms in multicultural--black/white/Mexican-origin cities. Black drug injectors are particularly likely to report having sex partners who do not inject drugs, as are Puerto Rican men and as are whites in multicultural--black/white/Mexican-origin cities. High-risk sex without condoms is widely reported among all groups of drug injectors studied: Each racial/gender group in each city-type averaged 15 or more episodes of unprotected vaginal sex per month, and 10% of most subgroups report having anal sex within the past 6 months. At least 45% of subjects in each city-type reported sex with noninjectors of the opposite gender. Without continued and expanded intervention, these data are consistent with HIV spreading to drug injectors, their sexual partners, and their future children, in all racial/ethnic groups.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Travel and ciguatera fish poisoning.

BACKGROUND: Ciguatera fish poisoning is a distinctive clinical syndrome associated with the consumption of contaminated marine fish. It is endemic in many popular travel destinations, including the Caribbean and Pacific Islands, where travelers are at risk. METHODS: Clinical review of 23 patients (60% were travelers) with ciguatera fish poisoning in whom consultation was provided between 1987 and 1990. RESULTS: Seven patients acquired ciguatera fish poisoning during international travel to the following destinations: Bahamas (n = 4), Dominican Republic (n = 1), British Virgin Islands (n = 1), and United States (n = 1). Suspected fish included grouper, red snapper, and amberjack. Two patients required emergency care, and four patients developed chronic symptoms. Severity was associated with chronicity, duration of peak symptoms, and worsening of symptoms with sexual activity. Chronicity was associated with severity, long latency period, and duration of peak symptoms. The three patients with complete resolution were scuba divers. Amitriptyline was the drug most often providing benefit for chronic symptoms. CONCLUSIONS: Ciguatera fish poisoning is a health risk to travelers to endemic regions, and their risk likely equals that of indigenous population groups. Barracuda should never be eaten, and travelers should exercise caution when considering other fish dishes, notably, grouper and red snapper.

Animals↗
PubMed1990

Morphine-induced metabolic changes in human brain. Studies with positron emission tomography and [fluorine 18]fluorodeoxyglucose.

Morphine sulfate effects (30 mg, intramuscularly) on cerebral glucose utilization and subjective self-reports were examined in 12 polydrug abusers by positron emission tomography and [fluorine 18]fluorodeoxyglucose in a double-blind placebo-controlled crossover study. During testing, subjects sat with eyes covered, listening to white noise and "beep" prompts. Morphine significantly reduced glucose utilization by 10% in whole brain and by about 5% to 15% in telencephalic areas and the cerebellar cortex, assuming no contribution of hypercapnia. When the contribution of PaCO2 (45 minutes after morphine was administered) was partialled out, significant morphine-induced reductions persisted in whole brain and six cortical areas. Irrespective of morphine, left-greater-than-right asymmetry occurred in the temporal cortex, and an interaction between hemisphere and drug was noted in the postcentral gyrus. In most cases, effects on glucose utilization were not significantly related to measures of euphoria.

Blood Pressure↗
PubMed1990

The association of hepatitis delta virus and hepatitis B virus in parenteral drug abusers. 1971 to 1972 and 1986 to 1987.

From 1971 to 1972 (N = 105) and 1986 to 1987 (N = 160), parenteral drug abusers seropositive for hepatitis B virus (HBV) markers were screened for antibodies to the hepatitis delta virus (anti-HD). In both time frames anti-HD was independently associated with the hepatitis B surface antigen. It was observed that 31% of those positive for hepatitis B surface antigen from the early sample and 20% of those from the latter sample had detectable anti-HD, as opposed to 10% and 7%, respectively, of those negative for hepatitis B surface antigen. Anti-HD seropositivity was unrelated to gender and ethnicity, and in the 1971 and 1972 nationwide sample, its presence was unrelated to geographic location. The probability of manifesting anti-HD increased with the more HBV markers detected, particularly the number of different HBV antibody markers. We conclude that anti-HD was wide-spread in parenteral drug abusers at least as early as 1971, and that its expression was associated with hepatitis B surface antigen and the intensity of the immune response to HBV as evidenced by the number of different circulating HBV antibodies.

Adolescent↗
PubMed1989

Effects of nicotine administration following 12 h of tobacco deprivation: assessment on computerized performance tasks.

The purpose of this study was to assess the effects of acute nicotine administration, following a 12-h cigarette deprivation period, using a computerized performance assessment battery (PAB). The PAB was comprised of five tasks which were selected to reflect a variety of complex acquired behaviors, sometimes referred to as "cognitive performance". Subjects were six healthy, male, cigarette smokers who practiced on the approximately 15 min PAB until their performance was stable across trials. In the training and baseline phase, subjects were tested following 5-30 min deprivation of cigarettes. Subjects were then tested following 12 h cigarette deprivation; 20 min before these sessions, subjects were given one piece of gum to chew. The gum contained 0, 2, or 4 mg nicotine, and it was chewed for 10 min at a rate of one chew every 2 s. There were two main findings: (1) when placebo (0 mg) gum was given, the time taken to complete the PAB tasks was significantly elevated above values obtained in the baseline condition; (2) compared to placebo, nicotine administration produced a dose-related decrease in the time taken to complete the tasks such that with either 2 or 4 mg, performance time was similar to that which occurred in the baseline cigarette smoking condition. Performance accuracy was not reliably affected by the experimental manipulations. These data indicate that the performance decrements observed in the placebo condition were specific to deprivation of nicotine following 12 h tobacco abstinence and are treatable using nicotine gum as a replacement formulation.

Adult↗
PubMed1989

The tobacco withdrawal syndrome: performance decrements assessed on a computerized test battery.

The effects of tobacco abstinence and resumption of smoking on cognitive performance were studied in seven cigarette smokers. Subjects were trained on a computerized performance assessment battery (PAB) that included five different tests. Baseline data were obtained under conditions of minimally restricted cigarette smoking. This baseline smoking phase ended at 1000 h on the first day of tobacco deprivation and the PAB was then administered at intervals of 1, 4 and 8 h, and once at 1000 h on each of the next 9 days. Upon resumption of smoking (1000 h on day 11), testing was conducted at intervals of 1, 4, 8 and 24 h. The main findings were that tobacco deprivation resulted in significantly increased response latencies on all of the tests and decreased accuracy on two tests. Some performance impairments were observed within 4 h after the start of the smoke deprivation phase. Impairments peaked at 24-48 h and then begun to return toward baseline values; however, some measures remained significantly changed throughout the 10 days of abstinence. Performance decrements that were still evident throughout the deprivation phase were at least partially reversed after 1 h of resumption of smoking; all values returned to baseline levels within 24 h of resumption of smoking.

Adult↗
PubMed1989

Time course of verapamil interaction with morphine effects on physiological parameters in rats.

The effects of subcutaneous doses of morphine and verapamil on respiratory and cardiovascular parameters have been assessed in conscious rats. Verapamil (10 mg kg-1) was injected simultaneously with morphine (16 mg kg-1) or at 10, 30, or 60 min before morphine administration. Morphine induced respiratory depression, as indicated by marked hypercapnia, hypoxia and acidosis, and caused marked tachycardia. Although morphine produced only a minor and inconsistent (but statistically significant, P less than 0.01) reduction of mean arterial blood pressure, morphine potentiated verapamil-induced hypotension. Verapamil suppressed morphine-induced hypercapnia only when injected simultaneously with morphine. Verapamil alone did not affect arterial blood gases or pH, but decreased heart rate and mean arterial blood pressure. Verapamil attenuated and delayed the maximum positive chronotropic effects of morphine at all times tested. Antagonism by verapamil of respiratory depression and tachycardia produced by morphine was unrelated to morphine levels in plasma. Thus, the explanation of verapamil-morphine interactions on respiration and cardiovascular function is not pharmacokinetic.

Animals↗
PubMed1989

The Lexington addicts, 1971-1972: demographic characteristics, drug use patterns, and selected infectious disease experience.

The demographics, drug habits, and medical complications of a cohort of 1,129 addicts treated at Lexington in the period 1971-1972 were studied. These patients, admitted from 41 different states, had a mean period of addiction of 5.4 years. Over one-third of the sample had engaged in pimping or prostitution, and there were no differences by gender in terms of involvement. Eight-eight percent had shared injection equipment, and surprisingly, 78% admitted to some effort at sterilizing their "works." Hepatitis was the most common associated medical condition: 87% had serologic markers of hepatitis B virus (HBV) infection, 60% had evidence of hepatitis A virus (HAV) exposure, and 47% had abnormal liver function parameters. Gynecomastia was evident in 2% of male subjects. Thirteen percent of the sample had a reactive VDRL assay, but 64% of these were biologically false positive. Subtle abnormalities of immune function were also observed; 18% of the patients had recent unexplained weight loss, 6% had lymphadenopathy, 8% had leukopenia, and 2% had lymphocytopenia. We conclude that both HBV and HAV were important infectious disease risks in these addicts, and that many evidenced deficiencies in immune function well before AIDS became a major public health concern.

Adolescent↗
PubMed1988

Geographic distribution of human immunodeficiency virus markers in parenteral drug abusers.

Drug abuse treatment programs in six regions of the United States collaborated in a study aimed at monitoring trends in the seroprevalence of human immunodeficiency virus (HIV) antibodies. The wide disparities in HIV seroprevalence in the face of similarities in drug using behavior have important implications for prevention. In the New York City area (Harlem, Brooklyn), 61 per cent of samples (N = 280) obtained in late 1986 were positive, up from 50 per cent of samples (N = 585) in early 1985. In Baltimore, Maryland, 29 per cent of samples (N = 184) representing 11 programs were positive. In contrast, samples from programs distant from the Northeast corridor had far lower rates: Denver, Colorado 5 per cent (N = 100); San Antonio, Texas 2 per cent (N = 106); Southern California, 1.5 per cent (N = 413); and Tampa, Florida, 0 per cent (N = 102). Contrary to expectations, there was no corresponding difference in reported lifetime needle sharing experiences, which ranged from 70 per cent in New York to 99 per cent in San Antonio. HIV seropositivity was associated only with geographic location and ethnicity; however, because needle sharing is practiced by parenteral drug abusers in areas where seroprevalence is still relatively low, these areas are potentially vulnerable to the same catastrophic spread seen in the Northeast. A window of opportunity exists where prompt, vigorous, and aggressive efforts at prevention could have major impact.

Adult↗
PubMed1988

Nitrite inhalants: patterns of abuse in Baltimore and Washington, D.C.

Nitrite inhalants, as drugs of abuse, have received a new prominence in the literature since their use has been associated with Kaposi's Sarcoma and possibly other manifestations of acquired immunodeficiency syndrome (AIDS). Changes in patterns and prevalence of use have not been investigated since the onset of the AIDS epidemic. We have examined the abuse patterns of nitrite inhalants (poppers) in several different groups. The use of poppers among drug abusers in the Baltimore-Washington, D.C. metropolitan area has remained constant over the past 5 years, with the prevalence of use being approximately 11% for recreational drug users and 22% for heavy abusers. Self-reported use by a homosexual group had decreased over the same time period. Sixty-nine percent of the homosexual sample had experience with nitrities, but only 21% had used them in the 6 months prior to being surveyed. The mean interval since last use was 25 months, and since peak use, 4.1 years. Among substance abusers, nitrites appear to be a drug whose use starts late, with the mean age of first use being 25.6 years compared to 14.6 years for glue, 17.6 years for marijuana, and 18.5 years for heroin. We found both heterosexual and homosexual groups utilize nitrites primarily to "get high," but homosexuals more often use them during overt sexual activity. Experience with amyl nitrite was much more prevalent than that with the butyl derivative in both populations. We conclude that the prevalence of nitrite abuse among drug users has not changed as a result of the AIDS epidemic, but such use appears to have decreased within the homosexual community.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Effects of diltiazem on morphine-induced respiratory decline.

The individual and combined effects of subcutaneous morphine and diltiazem, a calcium channel inhibitor, on arterial blood gases and pH were assessed in conscious Fischer-344 rats. Morphine (4 mg kg-1) produced hypercapnia, hypoxia and slight acidosis, as compared with control values. Diltiazem (10 mg kg-1) alone did not affect these parameters; however, it significantly delayed the onset of the aforementioned effects of morphine.

Animals↗
PubMed1986

Effects of morphine and calcium antagonists on plasma glucose in male rats.

Subcutaneous administration of morphine sulfate (4-16 mg/kg) did not significantly alter the plasma glucose concentration in fasted adult male Fischer-344 rats. All rats treated with calcium channel antagonists, verapamil or diltiazem (10 mg/kg, with or without morphine), showed marked and significant hyperglycemia, persisting at high levels throughout the 2 h experiment.

Animals↗
PubMed1986

Interactions between verapamil and morphine on physiological parameters in rats.

Effects of s.c. doses of morphine and verapamil, alone and in combination, on arterial blood gases and pH, mean blood pressure and heart rate were assessed in partially restrained, awake Fischer-344 rats. As expected, morphine (4-16 mg/kg) produced a dose-dependent respiratory depression, as indicated by hypoxia, hypercapnia and acidosis. Verapamil, a calcium channel antagonist, alone (10 mg/kg) did not affect these parameters; however, it significantly attenuated and delayed the aforementioned effects of morphine. Morphine caused a slight increase in mean blood pressure, which was not dose dependent, whereas verapamil reduced blood pressure dramatically even in the presence of morphine. All groups showed some tachycardia, but rats treated with morphine alone showed the most pronounced increase in heart rate, which was antagonized by verapamil. The authors conclude that the interaction of verapamil with morphine's respiratory depressant effects differs from the previously reported potentiation of morphine's antinociceptive and hypothermic actions.

Analysis of Variance↗
PubMed1982

Effect of order of presentation on simultaneous and sequential Matching Familiar Figures tests.

48 third grade children were administered both the standard, simultaneous version of the Matching Familiar Figures and a sequential presentation version of the same test. Order of administration of the two formats was counterbalanced. Subjects who took the simultaneous version first committed fewer errors on the sequential version than did subjects who took the more difficult sequential version first. This same finding was reported in other research by the authors and suggests that performance on the easier task primes the subject for the later administration of the more difficult task. Implications for teaching problem-solving skills and the cognitive style literature were presented.

Child↗