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Biomedical subjects

J W Spencer

Publications and source records attributed to J W Spencer.

13 recordsLinked to original sources
PubMed1999

Asbestos fiber release from the brake pads of overhead industrial cranes.

The purpose of this evaluation was to determine the actual contribution of airborne asbestos fibers to the work environment from the operation of overhead cranes and hoists that use asbestos composition brake pads. The evaluation was conducted in a working manufacturing facility. Other potential sources of asbestos were accounted for by visual inspection and background air monitoring. An overhead crane assembly comprised of a trolley and two hoists was employed for this study. The crane was operated for two consecutive eight-hour shifts representative of a heavy-duty cycle. Forty-four personal and area air samples were collected during the assessment. Asbestos fibers were analyzed for by phase contrast (NIOSH 7400), and transmission electron (NIOSH 7402) microscopy methods. Eight-hour time-weighted average (TWA) asbestos fiber concentrations ranged from < 0.005 to 0.011 fibers/cc (PCM), and < 0.0026 to < 0.0094 f/cc (TEM). There were no asbestos fibers detected by the TEM method from air samples collected during the operation of the cranes.

Air Pollutants, Occupational↗
PubMed1995

Procaine-induced increases in limbic rCBF correlate positively with increases in occipital and temporal EEG fast activity.

Previous independent EEG and PET studies suggest that administration of intravenous procaine hydrochloride selectively activates limbic brain structures. To further elucidate procaine's effects and explore the relationship between quantitative EEG (qEEG) and regional cerebral blood flow (rCBF), we simultaneously recorded qEEG and sampled rCBF using O-15 water PET in 20 healthy volunteers during single-blind injections of saline (baseline condition) followed by intravenous procaine (1.84 mg/kg). After thorough screening of EEG records, a subgroup of 7 subjects with EEG data relatively free of both muscle and movement artifacts was selected for analysis. Quantitative spectral EEG data from right occipital and temporal leads were then correlated with each subject's PET rCBF values on a pixel by pixel basis, both at baseline and after procaine. The most striking finding was that the increases in occipital and temporal omega activity from baseline to procaine positively correlated with rCBF increases in the amygdala and its efferents (p < .05), in a pattern very similar to the rCBF increases seen after procaine administration. This suggests that omega activity may reflect activation of deeper brain limbic structures. Also, the convergence of EEG and PET data further supports procaine's selective limbic activation.

Adult↗
PubMed1988

A comparison of chorionic villi sampling and amniocentesis: acceptability of procedure and maternal attachment to pregnancy.

Sixty-one women with high-risk pregnancies participated in a clinical trial comparing chorionic villi sampling and amniocentesis. They were assessed initially on five background measures and maternal attachment to the fetus, then were randomly assigned to either chorionic villi sampling or an amniocentesis group. Women were further assessed for maternal attachment three times during pregnancy. During the final assessment, those who were planning future pregnancies were asked which of the two procedures they would prefer. No differences between groups were found on any of the five background measures. All 31 women who considered future pregnancies indicated a preference for chorionic villi sampling, regardless of the procedure they underwent during the study. Women receiving chorionic villi sampling reported significantly greater attachment during the second trimester than did women receiving amniocentesis, who viewed themselves as being less attached than other pregnant women during this period. The findings were interpreted as evidence for attachment suppression among women undergoing amniocentesis.

Amniocentesis↗
PubMed1987

Emotional responses of pregnant women to chorionic villi sampling or amniocentesis.

Seventy-four "high-risk" pregnant women interested in participating in a clinical trial comparing chorionic villi sampling and amniocentesis were initially assessed on five background measures and for anxiety, depression, hostility, and concern about abortion. The 61 women who then agreed to be randomized into the chorionic villi sampling and amniocentesis groups were assessed three additional times between 9 and 22 weeks' gestational age. Physical discomfort experienced during the diagnostic procedure was also assessed. Women in the chorionic villi sampling group underwent a reduction in anxiety up to 10 weeks earlier and reported less procedure-related discomfort than women in the amniocentesis group. The group X time interaction for depression was also significant, with women undergoing chorionic villi sampling reporting an earlier decrease in depression than women undergoing amniocentesis. No differences were found between the two groups in hostility or concern about abortion. Findings were discussed in the context of evidence linking prenatal maternal emotionality to an increased risk of obstetric complications.

Amniocentesis↗
PubMed1978

5-O-Alkylated derivatives of 5-hydroxy-2'-deoxyuridine as potential antiviral agents. Anti-herpes activity of 5-propynyloxy-2'-deoxyuridine.

Alkylation of 5-hydroxyuridine or 5-hydroxy-2'-deoxyuridine with various activated alkylating agents in the presence of 1 equiv of NaOH gave a series of new nucleoside analogues which were evaluated for antiviral activity against vaccinia virus, herpes simplex-1 virus, and vesicular stomatitis virus in both primary rabbit kidney cells and human skin fibroblasts. One of these analogues, 5-propynyloxy-2'-deoxyuridine, was a potent inhibitor of herpes simplex virus. Structure-activity considerations suggest that the anti-herpes activity is dependent on the integrity of the acetylene group since substitution of phenyl, p-nitrophenyl, vinyl, carboxamido, or carboxyl for the triple bond led to diminished antiviral activity.

Antiviral Agents↗
PubMed1976

Brain stimulation in rats exposed to hyperbaric environments.

Six rats were trained to make an operant response to receive brief trains of electrical current to the lateral hypothalamus (self-stimulation). All animals were then randomly exposed to pressures of 4.03, 5.51, 7.06, or 10.1 ATA breathing either compressed air or N2-O2 and 13.1 ATA (N2-O2 only). When the subjects breathed air at pressures of 7.06 and 10.1 ATA, rate of self-stimulation decreased by 32 and 43%, respectively. No differences were observed in rate of response at any pressure when the animals breathed N2-O2 with the partial pressure of oxygen maintained at 0.2 ATA. When an oxygen-nitrogen mixture was breathed at 3 ATA in which the PO2 was similar to compressed air at 10.1 ATA, self-stimulation rate was decreased by 40%; this suggests that PO2 is a critical variable influencing behavior mediated by brain stimulation. Results are discussed in terms of the use of self-stimulation as one tool for better understanding the neuronal mechanisms of behavior as they relate to breathing-gas mixtures at increased pressures.

Analysis of Variance↗
PubMedDate not supplied

Cognitive brain potential alterations in boys exposed to opiates: in utero and lifestyle comparisons.

Several studies have observed that intrauterine exposure to opiates results in emotional and cognitive complications for the child, but genetic and postnatal social-environmental factors may also affect the CNS development of these children. To assess the relative contribution of the in utero and social-environmental (lifestyle) effects of opiate exposure, event-related potentials (ERPs) and performance were studied in three groups of 7- to 12-year-old boys: (1) the in utero/lifestyle group (IU/LS) contained 16 boys who were exposed to opiates (in utero and lived with opiate-abusing mothers, (2) the lifestyle group (LS) included 14 boys who lived with opiate-abusing mothers, and (3) the control group (CON) composed of 13 boys. The cognitive ERP components and task performance were recorded in the Auditory Rare Event Monitoring (AREM) task and the Sternberg Memory task (Sternberg, 1975). On the AREM and Sternberg Memory tasks, P200 component was significantly decreased for the IU/LS and LS groups. On the Sternberg Memory task, percent correct was also significantly impaired in IU/LS and LS groups. The ERP alterations in the boys living with opiate-abusing mothers with and without intrauterine opiate exposure were similar. A dysfunctional social environment may contribute to the cognitive deficits seen in the sons of opiate-abusing mothers.

Arousal↗