Patients' perceptions and responses to procedural pain: results from Thunder Project II

BACKGROUND

Little is known about the painfulness of procedures commonly performed in acute and critical care settings.

OBJECTIVE

To describe pain associated with turning, wound drain removal, tracheal suctioning, femoral catheter removal, placement of a central venous catheter, and nonburn wound dressing change and frequency of use of analgesics during procedures.

METHODS

A comparative, descriptive design was used. Numeric rating scales were used to measure pain intensity and procedural distress; word lists, to measure pain quality.

RESULTS

Data were obtained from 6201 patients: 176 younger than 18 years and 5957 adults. Mean pain intensity scores for turning and tracheal suctioning were 2.80 and 3.00, respectively (scale, 0-5), for 4- to 7-year-olds and 52.0 and 28.1 (scale, 0-100) for 8- to 12-year-olds. For adolescents, mean pain intensity scores for wound dressing change, turning, tracheal suctioning, and wound drain removal were 5 to 7 (scale, 0-10); mean procedural distress scores were 4.83 to 6.00 (scale, 0-10). In adults, mean pain intensity scores for all procedures were 2.65 to 4.93 (scale, 0-10); mean procedural distress scores were 1.89 to 3.47 (scale, 0-10). The most painful and distressing procedures were turning for adults and wound care for adolescents. Procedural pain was often described as sharp, stinging, stabbing, shooting, and awful. Less than 20% of patients received opiates before procedures.

CONCLUSIONS

Procedural pain varies considerably and is procedure specific. Because procedures are performed so often, more individualized attention to preparation for and control of procedural pain is warranted.

Patients' perceptions and responses to procedural pain: results from Thunder Project II

BACKGROUND: Little is known about the painfulness of procedures commonly performed in acute and critical care settings. OBJECTIVE: To describe pain associated with turning, wound drain removal, tracheal suctioning, femoral catheter removal, placement of a central venous catheter, and nonburn wound dressing change and frequency of use of analgesics during procedures. METHODS: A comparative, descriptive design was used. Numeric rating scales were used to measure pain intensity and procedural distress; word lists, to measure pain quality. RESULTS: Data were obtained from 6201 patients: 176 younger than 18 years and 5957 adults. Mean pain intensity scores for turning and tracheal suctioning were 2.80 and 3.00, respectively (scale, 0-5), for 4- to 7-year-olds and 52.0 and 28.1 (scale, 0-100) for 8- to 12-year-olds. For adolescents, mean pain intensity scores for wound dressing change, turning, tracheal suctioning, and wound drain removal were 5 to 7 (scale, 0-10); mean procedural distress scores were 4.83 to 6.00 (scale, 0-10). In adults, mean pain intensity scores for all procedures were 2.65 to 4.93 (scale, 0-10); mean procedural distress scores were 1.89 to 3.47 (scale, 0-10). The most painful and distressing procedures were turning for adults and wound care for adolescents. Procedural pain was often described as sharp, stinging, stabbing, shooting, and awful. Less than 20% of patients received opiates before procedures. CONCLUSIONS: Procedural pain varies considerably and is procedure specific. Because procedures are performed so often, more individualized attention to preparation for and control of procedural pain is warranted.

Immunological identification of the mammalian H3 histamine receptor in the mouse brain

Affinity-purified antibodies raised against the peptide sequence H3 (349-358) receptor specifically recognized two protein species with Mr 62,000 and 93,000 in adult mouse forebrain membranes. Both immunoreactive species were suppressed greatly by preincubation of the antibody with the respective peptide. Immunohistochemical analysis using affinity-purified anti-H3 (349-358) antibodies yielded a high degree of coincidence with ligand-autoradiographical information, with high levels detected in the CA3 and dentate gyrus of the hippocampus, laminae V of the cerebral cortex, the olfactory tubercle, Purkinje cell layer of the cerebellum, substantia nigra, globus pallidus, thalamus and striatum. This study suggests further biochemical evidence for multiple H3 receptor subtypes and the widespread distribution of the H3 receptor in the mammalian brain.

Hemoglobin adducts from acrylonitrile and ethylene oxide in cigarette smokers: effects of glutathione S-transferase T1-null and M1-null genotypes

Acrylonitrile (ACN) is used to manufacture plastics and fibers. It is carcinogenic in rats and is found in cigarette smoke. Ethylene oxide (EO) is a metabolite of ethylene, also found in cigarette smoke, and is carcinogenic in rodents. Both ACN and EO undergo conjugation with glutathione. The objectives of this study were to examine the relationship between cigarette smoking and hemoglobin adducts derived from ACN and EO and to investigate whether null genotypes for glutathione transferase (GSTM1 and GSTT1) alter the internal dose of these agents. The hemoglobin adducts N-(2-cyanoethyl)valine (CEVal), which is formed from ACN, and N-(2-hydroxyethyl)valine (HEVal), which is formed from EO, and GST genotypes were determined in blood samples obtained from 16 nonsmokers and 32 smokers (one to two packs/day). Smoking information was obtained by questionnaire, and plasma cotinine levels were determined by immunoassay. Glutathione transferase null genotypes (GSTM1 and GSTT1) were determined by PCR. Both CEVal and HEVal levels increased with increased cigarette smoking dose (both self-reported and cotinine-based). CEVal and HEVal levels were also correlated. GSTM1 and GSTT1 genotypes had little effect on CEVal concentrations. GSTM1 null genotypes had no significant impact on HEVal. However, HEVal levels were significantly elevated in GSTT1-null individuals when normalized to smoking status or cotinine levels. The ratio of HEVal:CEVal was also elevated in GSTT1-null smokers (1.50 +/- 0.57 versus 0.88 +/- 0.24; P = 0.0002). The lack of a functional GSTT1 is estimated to increase the internal dose of EO derived from cigarette smoke by 50-70%.

Immunohistochemical localization of N-methyl-D-aspartate receptor NR1, NR2A, NR2B and NR2C/D subunits in the adult mammalian cerebellum

The distributions of the N-methyl-D-aspartate (NMDA) receptor NR1, NR2A, NR2B and NR2C/D subunits were mapped in adult mouse cerebellum using subunit-specific antibodies. Immunostaining with anti-NR1 antibodies was prominent in cell bodies and dendritic arbors of Purkinje cells, was light to moderate in cerebellar granule cells, Golgi interneurons and interneurons in the molecular layer. Anti-NR2A subunit-specific antibody staining of mouse cerebellum was moderate in the granule cells, and moderate to dense in Purkinje neurons and Bergmann glia. However, Purkinje neurons were not immunolabelled in adult rat brain. Anti-NR2B subunit-specific immunostaining was prominent in Purkinje cell bodies and dendrites but absent from the granule cell layer. Anti-NR2C/D subunit-specific immunostaining was largely restricted to cerebellar granule cells. These studies reveal that NMDA receptor subunits display distinct but overlapping expression patterns in the adult mammalian cerebellum. Furthermore, we have observed some differences between rats and mice in terms of the NMDA receptor subunits expressed in specific cerebellar cell types.

Cyclic AMP-mediated regulation of GABA(A) receptor subunit expression in mature rat cerebellar granule cells: evidence for transcriptional and translational control

Exposure of rat cerebellar granule cells cultured to maturity in vitro to forskolin, N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (Bt2cAMP), and 3-isobutyl-1-methylxanthine (IBMX) down-regulated GABA(A) receptor alpha6 and beta3 subunits but up-regulated alpha1 and beta2 subunits with respect to vehicle-treated controls. Dideoxyforskolin had no effect on subunit expression. Protein kinase A inhibitors, H-89 and Rp-adenosine 3',5'cyclic monophosphothioate, prevented these effects on alpha1 but not alpha6 subunit expression. Flunitrazepam-sensitive [3H]Ro 15-4513 binding sites were increased by 144 +/- 20% following forskolin treatment. [3H]Ro 15-4513 photoaffinity labelling showed that the GABA(A) receptor alpha1 subunit was the principal locus of the increased flunitrazepam-sensitive [3H]Ro 15-4513 binding. Forskolin decreased flunitrazepam-insensitive [3H]Ro 15-4513 binding sites by 25 +/- 8% and resulted in a 20% decrease in the irreversible incorporation of radioactivity in the alpha6 subunit. Steady-state levels of GABA(A) receptor subunit mRNAs were determined by semiquantitative RT-PCR in forskolin-treated cultures. Forskolin, Bt2cAMP, and IBMX down-regulated GABA(A) receptor alpha6 subunit mRNA expression; alpha1 and beta3 mRNA levels were unaffected, whereas beta2 subunit mRNA was up-regulated. Dideoxyforskolin had no significant effect on alpha1, alpha6, beta2, and beta3 mRNA levels. Thus, in mature cerebellar granule cells, GABA(A) receptor expression can be regulated by intracellular cyclic AMP levels. This occurs at the level of gene transcription and/or translation by mechanisms that are only partially governed by protein kinase A.

XRCC1 polymorphisms: effects on aflatoxin B1-DNA adducts and glycophorin A variant frequency

Hereditary genetic defects in DNA repair lead to increased risk of cancer. Polymorphisms in several DNA repair genes have been identified; however, the impact on repair phenotype has not been elucidated. We explored the relationship between polymorphisms in the DNA repair enzyme, XRCC1 (codons 194, 280, and 399), and genotoxic end points measured in two populations: (a) placental aflatoxin B1 DNA (AFB1-DNA) adducts in a group of Taiwanese maternity subjects (n = 120); and (b) somatic glycophorin A (GPA) variants in erythrocytes from a group of North Carolina smokers and nonsmokers (n = 59). AFB1-DNA adducts were measured by ELISA, and erythrocyte GPA variant frequency (NN and NO) was assessed in MN heterozygotes with a flow cytometric assay. XRCC1 genotypes were identified by PCR-RFLPs. The XRCC1 399Gln allele was significantly associated with higher levels of both AFB1-DNA adducts and GPA NN mutations. Individuals with the 399Gln allele were at risk for detectable adducts (odds ratio, 2.4; 95% confidence interval, 1.1-5.4; P = 0.03). GPA NN variant frequency was significantly higher in 399Gln homozygotes (19.6 x 10(-6)) than in Gln/Arg heterozygotes (11.4 x 10(-6); P < 0.05) or Arg/Arg homozygotes (10.1 x 10(-6); P = 0.01). No significant effects were observed for other XRCC1 polymorphisms. These results suggest that the Arg399Gln amino acid change may alter the phenotype of the XRCC1 protein, resulting in deficient DNA repair.

Peer reviewed: creating multidisciplinary research opportunities

A unifying framework model helps researchers to address the complexities of environmental problems.

Relationship of auditory middle latency response and stem-word completion test as indicators of implicit memory formation during general anesthesia

Anesthesia providers are unable to objectively evaluate the amnesic status of an anesthetized patient. One purpose of the study was to evaluate the anesthetized patient's ability to process auditory information while receiving an inhalational or intravenous anesthetic regimen. The other purpose was to examine the relationship of the Pa latency of the auditory middle latency response (AMLR) with the stem-word completion test as an intraoperative indicator of implicit memory formation during general anesthesia. One hundred one adults were randomly assigned in a single-blinded design to either a midazolam or sevoflurane anesthetic regimen. Midazolam was administered at 0.540 microgram/kg per minute with fentanyl and 50% nitrous oxide. The other anesthetic regimen was 1.4% end-tidal concentration of sevoflurane with fentanyl and 50% nitrous oxide. A list of 10 words was repeated 16 times. AMLRs were recorded intraoperatively. The difference between the midazolam groups borderlined statistical significance (P = .07) in illustrating that one may potentially process auditory information while anesthetized. Dissimilar findings were found between the sevoflurane groups (P = .77). An inverse correlation was demonstrated between the midazolam group and Pa latency of the AMLR (r = -0.40, P = .047). Multiple regression of the midazolam group demonstrated that the employment status (r2 = .297, P = .005) and the Pa latency (r2 = .238, P = .003) were the best predictors of the postoperative stem-word completion test (F = 12.61, P = .001). In contrast, no correlation was noted in the sevoflurane group (r = 0.43, P = .07). Thus, the continued evaluation of the AMLR as an intraoperative indicator of implicit memory formation is warranted. With the establishment of the AMLR as an indicator of implicit memory formation during general anesthesia, anesthesia providers could then address the occurrences of traumatic neurosis in the postoperative surgical patient and strive to avoid the medicolegal concerns that may face the healthcare team.

Decreased expression of GABAA receptor alpha6 and beta3 subunits in stargazer mutant mice: a possible role for brain-derived neurotrophic factor in the regulation of cerebellar GABAA receptor expression?

The cerebellar granule cells of the spontaneous recessive mutant mouse strain, stargazer (stg/stg), fail to express brain-derived neurotrophic factor mRNA. This deficit is exclusive to these neurons and is believed to underlie the motor irregularities displayed by stg/stg, though the molecular basis for their phenotype has still to be resolved. Brain-derived neurotrophic factor has been shown to play a role in the postnatal maturation of cerebellar granule cells. Differentiation of these neurons, postnatally, is characterised by a switch in their GABAA receptor subunit expression profile. Notably, the GABAA receptor alpha6 subunit, which is specific to these neurons, becomes detectable at postnatal days 10-14 (P10-14). To determine whether cerebellar GABAA receptor expression has been compromised in stg/stg mice, the expression levels of GABAA receptor alpha1, alpha6, beta2 and beta3 subunits were compared between stg/stg mice and the appropriate wild-type background strain, C57BL/6J (+/+). By quantitative immunoblotting, it was found that the expression of the alpha6 and beta3 subunits was 23+/-8% and 38+/-12% (mean+/-S.E.M., n=6) of control (+/+) levels, respectively. In contrast, the expression of the alpha1 and beta2 subunits was not significantly different from controls, being 116+/-11% and 87+/-24% (mean+/-S.E.M., n=6) of +/+ levels, respectively. Total specific [3H]Ro15-4513 binding activity detected in cerebellar membranes prepared from stg/stg was not significantly different from +/+ mice. However, the benzodiazepine agonist-insensitive subtype of [3H]Ro15-4513 binding activity, a pharmacological motif of alpha6 subunit-containing GABAA receptors, was lower in stg/stg mice relative to the +/+ strain which correlated with the lowered level of alpha6 subunit expression. Thus, we have identified an abnormality in the GABAA receptor profile of stg/stg mutant mice that might underpin its irregular phenotype.

Rural junior high school students' risk factors for and perceptions of teen-age parenthood

A sample consisting of 689 junior high school rural adolescents was surveyed about their perceptions of being a teen parent and their current sexual behavior. A risk factor analysis also was conducted to determine factors that significantly predict whether adolescents had engaged in sexual intercourse. Results indicate that one in nine adolescents had engaged in sexual intercourse (11%). The risk factor analyses showed that smoking and efficacy expectations of not engaging in sexual intercourse were significant predictors for both genders. For the most part, adolescents responded positively on four constructs: 1) attitudes toward being a teen parent; 2) efficacy expectations of not engaging in sexual intercourse; 3) benefits of being a teen parent; and 4) and barriers to being a teen parent. However, when analyses were conducted for males and females separately, females scored higher on each factor. Overall, results indicate these teens recognized problems that may occur from being a teen parent.

The application of a modified proportional-derivative control algorithm to arterial pressure alarms in anesthesiology

OBJECTIVE

We have developed an arterial pressure alarm system based on a modified proportional-derivative (PD) controller algorithm, and prospectively tested its ability to predict significant hypotensive episodes, defined as systolic arterial pressure < 80 mmHg, in comparison to conventional limit alarms.

METHODS

The alarm algorithm was tuned to detect hypotension using selected invasive arterial pressure traces taken from ten patients who had large intra-operative arterial pressure changes. The algorithm's performance was then tested prospectively in comparison to conventional limit alarms and median filtered limit alarms, set at 85 mmHg and 90 mmHg, for its ability to predict hypotensive episodes in a further 100 patients who required invasive arterial pressure monitoring.

RESULTS

For the PD alarm algorithm, onset times for significant hypotensive episodes were between those of limit alarms set at 85 mmHg and 90 mmHg. Offset times were similar to the 85 mmHg limit alarms. The false positive rate was 34% compared with 45-64% for the other alarms (p < 0.01). Using our definitions, there was one false negative in the PD group, being a 15 second drop in observed arterial pressure, when a non invasive blood pressure cuff was inflated above the arterial line.

CONCLUSIONS

An arterial pressure alarm system design based on a closed loop control algorithm offered improved perform ance over conventional limit alarms and in addition provided a graded output of severity of the hypotension.

PHOTOREFRACTIVE POLYMERS

▪ Abstract  Rapid advances in the field of photorefractive polymers and composites have in the brief time since their inception in 1991 led to the development of high-performance materials with refractive index modulations approaching 0.01, dif-fraction efficiencies close to 100%, and net two-beam coupling gain coefficients exceeding 200 cm−1 in samples typically 100 μm thick. This paper reviews the current state of research, from the most successful synthetic strategies to produce polymeric photorefractive materials, to their emerging uses in applications. Two-beam coupling and four-wave mixing measurement techniques are presented and their importance in the characterization of the photorefractive properties of new materials is explained. The physics of the photorefractive effect in polymers is discussed with emphasis placed on the differences compared with the traditional inorganic photorefractive crystals. In particular, the orientational enhancement mechanism, which is believed to be responsible for the high performance of most of the low-glass-transition-temperature systems, is discussed in detail.

Measurement of the spatial phase shift in high-gain photorefractive materials

The correct determination of the spatial phase shift ø(p) in photorefractive materials is crucial to the proper characterization of novel materials. It is shown that the grating translation techniques commonly used for the measurement of ø(p) need to be reevaluated for high-gain materials. Strong energy and phase coupling leads to nonuniform slanted gratings, which result in an apparent dependence of the phase shift of the beam ratio and the optical polarization. A revised theory is presented, and analytical solutions are obtained for the special case of ø(p)?pi/2 . Numerical solutions for arbitrary ø(p) are in good agreement with measurements in a photorefractive polymer.

Spectrum of somatic mutation at the hypoxanthine phosphoribosyltransferase (hprt) gene of healthy people

Understanding the significance of somatic mutations requires knowledge of the mutations that occur in vivo in healthy people. The molecular characterization of mutations in the hypoxanthine phosphoribosyltransferase (hprt) gene in 217 independent T-lymphocyte mutants from 172 donors, including smoking and non-smoking males and females, reveals a broad spectrum of in vivo somatic mutation occurring in a population of healthy people. Identification of the DNA alteration in individual mutant clones was accomplished using either one or a combination of multiplex polymerase chain reaction analysis of genomic DNA, sequencing of cDNA, and genomic DNA sequencing. The total spectrum consists of 59% (128/217) base substitutions: 126 simple and two tandem CC>TT base substitutions; 39% (85/217) deletion/insertion type mutations: 30 frameshifts, 26 small (3-200 basepairs) and 27 large deletions, and two duplications; and the remaining 2% (4/217) complex mutations involving the deletion of one to 11 basepairs which are replaced by 1 to 10 basepairs. No significant difference was detected between the base substitution spectra for the smokers and the non-smokers. Analysis of the number of mutations occurring at any one base position led to the identification of three hotspots for mutations at basepairs 197, 508 and 617, in the hprt gene coding region. Spontaneous deamination of CpG may be implicated in the creation of basepair 508 as a hotspot since all mutations detected are C>T transitions resulting in the nonsense mutation, TAG. At basepairs 197 and 617 both G>T transversions and G>A transitions were found indicating that at least two mechanisms were involved in creating mutations at these positions. Comparison of the mutation spectra from two populations can provide insight into the origin of the mutations. This study provides an excellent base for comparison of mutation spectra in other human populations.

Bidirectional regulation of GABAA receptor alpha1 and alpha6 subunit expression by a cyclic AMP-mediated signalling mechanism in cerebellar granule cells in primary culture

Forskolin treatment of cerebellar granule cells in culture resulted in bidirectional regulation of the expression of GABAA receptor alpha1 and alpha6 subunits. Thus, forskolin applied at 2 days in vitro (DIV) increased expression of the alpha1 subunit but decreased the expression of the alpha6 subunit. Values with respect to control cultures, both assayed at 9 DIV by immunoblotting, were 310 +/- 48% for alpha1 and 25 +/- 16% for the alpha6 subunit. Similar effects were evoked following chronic treatment with both dibutyryl cyclic AMP and 3-isobutyl-1-methylxanthine. Dideoxyforskolin had no effect on the level of expression of either the alpha1 or the alpha6 GABAA receptor subunits. The changes in subunit expression were accompanied by a 1.7-fold increase in number of total specific [3H]Ro 15-4513 binding sites expressed by intact cerebellar granule cells. This increase in total binding sites was accommodated by a 2.7-fold increase in number of diazepam-sensitive Ro 15-4513 binding sites in accordance with the observed increase in alpha1 subunit expression. The number of diazepam-insensitive subtype of binding sites were not significantly changed. These results suggest that GABAA receptor subtype expression can be differentially regulated by intracellular cyclic AMP concentration.

Developmental regulation of expression of GABAA receptor alpha 1 and alpha 6 subunits in cultured rat cerebellar granule cells

We have studied the postnatal development of GABAA receptor alpha 1 and alpha 6 subunits expressed by primary cultures of cerebellar granule cells originating from 2-day-old (postnatal day 2, P2) and 10-day-old (P10) rat neonates. At these ages, the granule cells are at distinct stages of cerebellar development. In both cases, GABAA receptor alpha 1 and alpha 6 subunit-like immunoreactivities were detected, and displayed temporal expression profiles that were correlated with the maturity of the cerebella from which the cultured granule cells were derived. Using two different specificity anti-alpha 1 subunit-specific antibodies, immunoreactive species with M(r) 53,000 Da and 54,000 Da were detected by immunoblotting. The lower 53,000-Da band co-migrated with the alpha 1 subunit-like immunoreactivity detected in GABAA receptors purified from adult rat forebrain by benzodiazepine affinity chromatography. This 53,000-Da alpha 1 subunit-like immunoreactive species was detected at day 1 in vitro (1 DIV) in P10 cultures and 3-5 DIV in P2 cultures. The GABAA receptor alpha 6 subunit-like immunoreactivity (58,000 Da) was not detected until 5-7 DIV in P10 and 9-11 DIV in P2-derived cultures. The appearance of alpha 6 subunit-like immunoreactivity was paralleled by an up-regulation of alpha 1 subunit expression and a concomitant increase in diazepam-insensitive (DZ-IS) [3H]Ro 15-4513 binding activity, a pharmacological characteristic of alpha 6 and alpha 1 alpha 6-subunit-containing GABAA receptors (Pollard et al. J. Biol. Chem., 270, 21,285-21,290, (1995)). Antagonism of both non-NMDA and NMDA subtypes of ionotropic glutamate receptors did not significantly affect the developmental profile, the level of GABAA receptor alpha 6 subunit or the total DZ-IS or DZ-S [3H]Ro 15-4513 binding activities expressed by these neurons. These results provide further evidence that the expression of specific GABAA receptor subunit genes is subject to differential regulation. Furthermore, developmental expression of the GABAA receptor alpha 6 subunit gene by these neurons is either a preprogrammed event or is initiated by an environmental cue that is received early in granule cell development, and it is not a result of afferent activation of ionotropic glutamate receptors.

Critical care-acquired pneumonia

Nosocomial infections are the second most common hospital-acquired infections. The Centers for Disease Control and Prevention recently published an updated Guidelines for the Prevention of Nosocomial Pneumonia. A summary of these recommendations and general preventive strategies are presented in this article.

Impact of age and environment on somatic mutation at the hprt gene of T lymphocytes in humans

Analysis of two human populations for dependence of somatic mutation on age has revealed both similarities and differences. The studies performed employed peripheral blood lymphocytes and measured the efficiency with which these cells form clones in vitro (cloning efficiency, CE) and the frequency of cells with inactivating mutations of the hypoxanthine phosphoribosyltransferase gene (mutant frequency, MF). The people studied were between 19 and 64 years of age. In one population, composed of 78 never smokers and 140 current smokers from the United States (US), both CE and MF were dependent on age: CE declined with age (p = 0.005); MF increased 0.15 per 10(6) cells per year of age for nonsmokers (p < 0.001) and at 1.3 times that rate for smokers (p = 0.01). In the second population, 80 people of unknown smoking status from Russia, the increase in MF per year was even greater, 2.5 times that of the US nonsmokers (p = 0.001) but the dependence of CE on age was the same as for the US population (p = 0.043). Because the increase of MF of the Russians with age is 2-fold greater than that of the US smokers, the intensity of smoking and/or other environmental exposures, or the susceptibility to these exposures, must account for the difference in age dependent MF increase, not the proportion of Russians that are smokers. Differences in the lymphocyte subpopulations that survived the longer transit from Russia may have contributed to the observed differences in MF. However, overall, the mutant frequency results suggest that the Russians were chronically exposed to higher levels of agents that induce somatic mutation and that, on an age adjusted basis, the Russia population studied is at increased risk for health consequences from accumulated genetic damage.

Quantitative characterization of alpha 6 and alpha 1 alpha 6 subunit-containing native gamma-aminobutyric acidA receptors of adult rat cerebellum demonstrates two alpha subunits per receptor oligomer

gamma-Aminobutyric acidA (GABAA) receptors were purified from adult rat cerebella by anti-alpha 6(1-16 Cys) antibody affinity chromatography. Immunoblots of the alpha 6 subunit-containing receptors showed the copurification of the alpha 1, beta 2/3, gamma 2, delta but not alpha 2 and alpha 3 GABAA receptor polypeptides. Further fractionation of this receptor subpopulation by anti-GABAA receptor subunit alpha 6(1-16 Cys) and anti-alpha 1(413-429) antibody affinity columns in series substantiated the coassociation of the alpha 1 and alpha 6 polypeptides. The percentage of coexistence of the two subunits was determined by quantitative immunoblotting, which found that 41 +/- 12% of alpha 6 subunit immunoreactivity is associated with the alpha 1 subunit. The ratios of the alpha 1:alpha 6 subunits in the double purified receptor preparations was found to be 1:1, thus determining directly for the first time subunit ratios within native GABAA receptors. The benzodiazepine pharmacology of the alpha 1 alpha 6 subunit-containing receptors was shown to be predominantly benzodiazepine-insensitive by quantitative immunoprecipitation assays. These results are the first direct quantitative studies of subunit ratios within a population of native GABAA receptors.

GABAA receptor subtypes expressed in cerebellar granule cells: a developmental study

The developmental properties of primary rat cerebellar granule cells have been characterised with respect to their expression of GABAA receptor subtypes using both an immunological approach and radioligand binding assays. At day 1 in culture, the GABAA receptor alpha 1 subunit was detectable in immunoblots and increased in level up to day 9. The GABAA receptor alpha 6 subunit was not detectable at day 1; however, at days 3-5, a specific M(r) 58,000 anti-alpha 6 1-16 Cys immunoreactive species was present which further increased in level up to 9 days in culture. Similar qualitative results were obtained for the expression of the GABAA receptor alpha 6 subunit in age-matched rat cerebellar membranes. In parallel studies, it was found that although there was an overall increase in [3H]Ro 15-4513 binding sites with days in culture, the relative contributions of diazepam-sensitive and diazepam-insensitive [3H]Ro 15-4513 binding changed. A time-dependent enrichment of the diazepam-insensitive binding site up to a maximum of 74% of total [3H]Ro 15-4513 sites was found. This was concomitant with the appearance of the GABAA receptor alpha 6 subunit. These results are in agreement with the pharmacology described for alpha 6 beta gamma 2 cloned receptors. They suggest a developmentally regulated expression of the GABAA receptor alpha 6 subunit gene at a time that is correlated in vivo with establishment of neuronal connections.

CYP1A1 mRNA levels as a human exposure biomarker: use of quantitative polymerase chain reaction to measure CYP1A1 expression in human peripheral blood lymphocytes

Accurate human risk assessment requires sensitive methods to evaluate dose-response relationships, especially following low level exposures. We have developed a reverse transcriptase polymerase chain reaction (RT-PCR) method to quantitative cytochrome P450-1A1 (CYP1A1) mRNA levels in human blood lymphocytes. Many polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene, and chlorinated PAH such as polychlorinated dibenzodioxins, dibenzofurans and biphenyls induce CYP1A1 expression through activation of an endogenous protein, the Ah receptor. Using a quantitative competitive RT-PCR method that included a synthetic internal standard we determined copy numbers of CYP1A1 mRNA in resting as well as mitogen-stimulated human blood lymphocytes. In mitogen-stimulated human blood lymphocytes assay variation was approximately 10% for measurement of this low expression gene and mRNA levels correlated well with ethoxyresorufin-O-deethylase (EROD) activity. The expression of mRNA was induced 20-fold upon culturing human lymphocytes with 10 nM TCDD. In nonstimulated, uninduced lymphocytes CYP1A1 levels are extremely low (1000 copies mRNA/10(4) cells) and cannot be measured by EROD activity. Studies of CYP1A1 mRNA expression in chemically-exposed populations are in progress.

Factors affecting HPRT mutant frequency in T-lymphocytes of smokers and nonsmokers

The frequency of thioguanine-resistant, hypoxanthine phosphoribosyltransferase-deficient lymphocytes in the peripheral blood of human subjects was used to study the genotoxic effects of smoking. Sixty-two nonsmokers and 58 smokers, aged 19 to 45 years with average ages of 30 and 32 years, respectively, and with no other known exposures, were studied using an in vitro assay of the frequency of mutant lymphocyte clones. Analysis of variance explained 68% of the variation in the mutant frequencies. Mutant frequency was dependent upon lymphocyte cloning efficiency, length of smoking history, age, and interactions between these variables. Four nonsmokers and three smokers had high mutant frequencies that were not explained by these variables. Mutant frequencies were inversely related to lymphocyte cloning efficiencies; the effect was twice as great for smokers as for nonsmokers. The time-dependent effect of smoking dominated, with mutant frequency increasing 10%/year of smoking as compared with an independent 1%/year of age. Smoking had a greater effect on young smokers' lymphocytes. Heterogeneity of mutant frequency among both smokers and nonsmokers and its implications for use of lymphocyte mutation assays as biomarkers are discussed.

Characterization of in vivo somatic mutations at the hypoxanthine phosphoribosyltransferase gene of a human control population

The ability to recognize a change in mutation spectrum after an exposure to a toxic substance and then relate that exposure to health risk depends on the knowledge of mutations that occur in the absence of exposure. Toward this end, we have been studying both the frequency and molecular nature of mutations of the hypoxanthine phosphoribosyltransferase (hprt) gene in peripheral blood lymphocytes as surrogate reporters of genetic damage. We have analyzed mutants, one per donor to ensure independence, from a control population in which the quantitative effects of smoking and age on mutant frequency have been well defined. Analyses of cDNA and genomic DNA by polymerase chain reaction and sequencing have identified the mutations in 63 mutants, 45 from males and 18 from females, of which 34 were smokers and 29 were nonsmokers. Slightly less than half of the mutations were base substitutions; they were predominantly at GC base pairs. Different mutations at the same site indicated that there are features of the hprt polypeptide that affect the mutation spectrum. Two pairs of identical mutations indicated that there may also be hot spots. Mutations not previously reported have been detected, indicating that the mutation spectrum is only partly defined. The remainder of the mutations were deletions or insertions/duplications; deletions ranged from one base pair to complete loss of the locus. Despite a small average increase in mutant frequency for smokers, an increased proportion of base substitutions at AT base pairs in smokers (p = 0.2) hinted at a smoking-associated shift in the mutation spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)