Comparison of P-POSSUM and O-POSSUM in predicting mortality after oesophagogastric resections.

BACKGROUND: P-POSSUM (Physiological and Operative Severity Score for the enumeration of Mortality and morbidity) predicts mortality and morbidity in general surgical patients providing an adjunct to surgical audit. O-POSSUM was designed specifically to predict mortality and morbidity in patients undergoing oesophagogastric surgery. AIM: To compare P-POSSUM and O-POSSUM in predicting surgical mortality in patients undergoing elective oesophagogastric cancer resections. METHODS: Elective oesophagogastric cancer resections in a district general hospital from 1990 to 2002 were scored by P-POSSUM and O-POSSUM methods. Observed mortality rates were compared to predicted mortality rates in six risk groups for each model using the Hosmer-Lemeshow goodness-of-fit test. The power to discriminate between patients who died and those who survived was assessed using the area under the receiver-operator characteristic (ROC) curve. RESULTS: 313 patients underwent oesophagogastric resections. 32 died within 30 days (10.2%). P-POSSUM predicted 36 deaths (chi2 = 15.19, df = 6, p = 0.019, Hosmer-Lemeshow goodness-of-fit test), giving a standardised mortality ratio (SMR) of 0.89. O-POSSUM predicted 49 deaths (chi2 = 16.51, df = 6, p = 0.011), giving an SMR of 0.65. The area under the ROC curve was 0.68 (95% confidence interval 0.59 to 0.76) for P-POSSUM and 0.61 (95% confidence interval 0.50 to 0.72) for O-POSSUM. CONCLUSION: Neither model accurately predicted the risk of postoperative death. P-POSSUM provided a better fit to observed results than O-POSSUM, which overpredicted total mortality. P-POSSUM also had superior discriminatory power.

Molecular analysis of polymerase gamma gene and mitochondrial polymorphism in fertile and subfertile men.

CAG trinucleotide repeat length in the nuclear polymerase gamma gene (POLgamma) has been shown to be associated with men with reduced fertility. The present study investigated the frequency of CAG repeat length genotypes and three exonuclease motifs of the POLgamma in relation to the frequency of mitochondrial nucleotide substitutions. DNA from semen samples of 93 normozoospermic men and 192 non-normozoospermic men was isolated and the specific regions of the genes were amplified by polymerase chain reactions (PCR) and sequenced to identify mutations. The genotypic frequencies of pooled POLgamma CAG repeat lengths, =10/ not equal 10 heterozygotes and not equal 10/ not equal 10 homozygotes, were significantly different between normozoospermic and non-normozoospermic men (p < 0.05), with non-normozoospermic men having a slightly higher frequency of the =10/=10 genotypes. The allelic frequency for =10 is 0.79 and not equal10 is 0.21 for normozoospermic men and 0.85 and 0.15, respectively, for non-normozoospermic men (p < 0.025). There was no mutation detected in the exonuclease motifs in all the samples tested. Eighty normozoospermic and 124 non-normozoospermic semen samples were analysed for nucleotide substitutions in mitochondrial genes by PCR and sequencing. Heteroplasmic mutations were found in one azoospermic man, four asthenozoospermic men and two normozoospermic men. Only one asthenozoospermic man was heterozygous for the POLgamma genotype. Of the 17 men with non-synonymous nucleotide substitutions, 14 were homozygous for the POLgamma genotype. Non-normozoospermic men had twice as many nucleotide substitutions than normozoospermic men. However, there were no significant differences in the frequencies of nucleotide substitution and POLgamma genotypes in the two groups of men.

Base administration or fluid bolus for preventing morbidity and mortality in preterm infants with metabolic acidosis.

BACKGROUND: Metabolic acidosis in the early newborn period is associated with adverse outcomes in preterm infants. The most commonly used strategies to correct metabolic acidosis are intravascular infusion of base, for example sodium bicarbonate, and intravascular infusion of a fluid bolus, usually a crystalloid or colloid solution. OBJECTIVES: To evaluate the available evidence from randomised controlled trials that either infusion of base, or of a fluid bolus, reduces mortality and adverse neurodevelopmental outcomes in preterm infants with metabolic acidosis. SEARCH STRATEGY: We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2005), MEDLINE (1966 - January 2005), EMBASE (1980 - January 2005), CINAHL (1982 - January 2005). SELECTION CRITERIA: Randomised or quasi-randomised controlled trials that evaluated the following treatments for preterm infants with metabolic acidosis:1. Infusion of base versus no treatment.2. Infusion of fluid bolus versus no treatment.3. Infusion of base versus fluid bolus. DATA COLLECTION AND ANALYSIS: We extracted the data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two authors, and synthesis of data using relative risk and risk difference. MAIN RESULTS: We found two small randomised controlled trails that fulfilled the eligibility criteria (Corbet 1977; Dixon 1999). Corbet 1977 compared treating infants with sodium bicarbonate infusion (N = 30) versus no treatment (N = 32) and did not find evidence of an effect on mortality [Relative risk 1.39 (95% confidence interval 0.72 to 2.67), risk difference 0.12 (95% confidence interval -0.12 to 0.36)], or in the incidence of intra/peri-ventricular haemorrhage [Relative risk 1.24 (95% confidence interval 0.47 to 3.28), risk difference 0.05 (95% confidence interval -0.16 to 0.25)]. Dixon 1999 compared treatment with sodium bicarbonate (N = 16) versus fluid bolus (N = 20). The primary outcome assessed was arterial blood pH/base excess two hours after the intervention. Other clinical outcomes were not reported. Neither trial assessed longer term neurodevelopmental outcomes. AUTHORS' CONCLUSIONS: There is insufficient evidence from randomised controlled trials to determine whether infusion of base or fluid bolus reduces morbidity and mortality in preterm infants with metabolic acidosis. Further large randomised trials are needed.

The neorule: a new instrument to measure linear growth in preterm infants.

OBJECTIVES: To compare measurements of crown-heel length (CHL) made with the neorule with CHL measurements made with a stadiometer in term infants. To examine safety and reproducibility of CHL measurements in infants < 32 weeks gestational age (GA) using the neorule. METHODS: Three measurements of CHL were made by three teams during the first 2 days of life in healthy term infants. One team used the stadiometer and two the neorule. Two different teams made three measurements of CHL on four occasions at two week intervals in infants less than 32 weeks GA. Infants were continuously monitored, and any adverse event was recorded. RESULTS: Fifty term infants were studied, median (range) birth weight 3440 (2020-5010) g. The mean (SD, 95% confidence interval) difference between values obtained with the stadiometer and neorule was 0.08 (6.22, -1.69 to +1.85) mm and between the two neorule teams was 0.8 (4.48, -0.47 to +2.08) mm. Twenty preterm infants were studied, GA median (range) 29 (25(+0)-31(+6)) weeks, median (range) CHL 397 (339-475) mm. There were no adverse events. The difference (SD, 95%CI) between teams in the mean CHL measurement was 0.18 (4.79, -1.02 to +1.38) mm, with interobserver limit of agreement -9.2 to +9.6 mm and coefficient of variation 1.2%. There were no significant differences between measurements made by single observers; the F ratio was 0.449 (df = 61, p = 0.6). CONCLUSION: The neorule is a safe and accurate way to measure CHL in newborn infants.

Characterization of vehicular brake service personnel exposure to airborne asbestos and particulate.

Evaluation of fibers and total particulate generated during the servicing of drum brakes on motor vehicles as well as during the resurfacing (arcing) of brake shoes was conducted. Conditions for the studies were based on review of contemporary (approximately 1950-1980) working practices in the industry. This work was conducted in two parts. Phase 1 estimated the release of asbestos fibers and total particulate during brake inspection and replacement of light-duty vehicle rear drum brakes at an auto/truck repair facility. Two distinct work practices were evaluated: One rear wheel from each vehicle was serviced using compressed air to remove dust while the second rear wheel was serviced without compressed air. Area and personal monitoring of fiber levels demonstrated counts (without compressed air) that ranged from 0.05 to 0.2 f/cc. Fiber counts when using compressed air averaged from 0.05 to 0.9 f/cc. Results from real-time aerosol monitoring indicated elevated dust levels for about 15 minutes after blow out. With shop doors open, dust levels increased to 5.0 mg/m3 at blow out and returned to 0.08 mg/m3 within two minutes. When the shop doors were closed, the dust levels reached 13.5 mg/m3 at blow out and decreased to 1.68 mg/m3 within one minute and to background within 14 minutes. The Phase 2 series evaluated the release of fibers and other particulate from are grinding. For operations conducted under conditions simulating a workplace, a mean of 0.19 f/cc +/- 0.16 was determined. Dust levels averaged 0.25 mg/m3 +/- 0.05. Brake service monitoring in these tests demonstrates that asbestos fiber concentrations, considered on a time weighted average basis, should not exceed currently acceptable workplace standards whether or not the worker uses compressed air, nor during the arc grinding process when arcing is conducted in accord with the design of the equipment.

Morphological characteristics of asbestos fibers released during grinding and drilling of friction products.

There has been considerable interest during the past 30 years regarding the potential for exposure to asbestos fibers generated during asbestos-containing automobile and light-duty truck brake replacement and repair operations. Less attention has been directed to asbestos fiber exposures resulting from servicing of brakes on heavy-duty trucks and other machinery. Potential for the generation of respirable fibers as a result of using a rotary bench grinder and the drilling of asbestos-containing friction pads was investigated to assess the characteristics of the fibers generated from these procedures. The data from the grinding process revealed that this material was either resin matrix or fibers bound to the resin matrix. Fibers generated from the drilling procedure revealed morphology consistent with chrysotile asbestos. In each case, nonfibrous materials remained bound to the fibers released from these processes. These fibers had resin deposits attached. This investigation offers evidence that drilling and grinding of brake pads generates fibers that, for the most part, remain bound to the underlying matrix, suggesting that grinding and drilling may not pose an important source of exposure to respirable asbestos fibers.

Conversational responsiveness in specific language impairment: evidence of disproportionate pragmatic difficulties in a subset of children.

Eighteen children with specific language impairment (SLI), from 6 to 8 years of age, were compared with 9 control children matched on age and nonverbal ability (CA controls) and with 9 younger control children of comparable language level (LA controls). Half of the SLI group were rated on a teacher checklist as having pragmatic difficulties: these were referred to as the pragmatic language impairment (PLI) group; the remainder were the typical (SLI-T) group. Children's responses to adult soliciting utterances were compared. All children usually responded to conversational solicitations, but children in the PLI group were more likely than control children to give no response, and they also made very little use of nonverbal responses, such as nodding. Nonverbal responding was closely related to the quality of children's responses. Children who failed to use nonverbal responses also had a relatively high level of pragmatically inappropriate responses that were not readily accounted for in terms of limited grammar or vocabulary. This study lends support to the notion that there is a subset of the language-impaired population who have broader communicative impairments, extending beyond basic difficulties in mastering language form, reflecting difficulty in responding to and expressing communicative intents. The analytic methods developed for this project have promise for the study of pragmatic difficulties in other clinical groups.

A patent ductus arteriosus is associated with reduced middle cerebral artery blood flow velocity.

UNLABELLED: The study objective was to determine the effect of a patent ductus arteriosus (PDA) on cerebral blood flow velocity in ventilated, very low birth weight neonates, in the first 5 days of life. Sonography of the right middle cerebral artery and ductus arteriosus was performed using a colour Doppler technique. Statistical analysis was by stepwise regression. Thirty-one neonates without and 43 with a PDA, mean (SD) birth weight 1004 g +/- 192 and 1071 g +/- 227 respectively, were studied. The end diastolic and mean velocities were reduced (P = 0.008 and P = 0.129) and the resistive index was increased (P = 0.047) by a PDA. pH was inversely related to end diastolic and mean velocities (P = 0.015 and P = 0.003), suggesting that low pH may increase cerebral artery blood flow velocity. CONCLUSION: A patent ductus arteriosus reduces middle cerebral artery blood flow velocity in very low birth weight neonates.

Does endothelin-1 reduce superior mesenteric artery blood flow velocity in preterm neonates?

AIM: To compare plasma endothelin-1 (ET-1) concentrations in preterm neonates from pre-eclamptic and normal mothers; and to evaluate whether ET-1 has a role in altered arterial blood flow velocity. METHODS: Umbilical arterial blood and neonatal arterial blood were sampled on days 1 and 3 for gas analysis and measurement of plasma ET-1. Doppler ultrasonography of the middle cerebral, renal, and superior mesenteric arteries (SMA) was performed. RESULTS: Neonates in the pre-eclampsia (n = 18) and control (n = 18) groups had mean (SD) gestational ages of 31.1 (2.5) weeks and 30.4 (2.1) weeks; their birth-weights were 1432 (SD 676) g and 1692 (SD 500) g, respectively. In the pre-eclampsia group mean umbilical arterial PO2 was lower--1.88 (0.75) kPa compared with 3.27 (1.41) kPa (p < 0.01)--and mean plasma ET-1 concentration was higher in the umbilical artery--40.6 (SD 15.0) compared with 30.5 (SD 13.8) pg/ml (p = 0.04) and day 1 blood--54.9 (35.0) pg/ml compared with 33.6 (14.6) pg/ml (p = 0.03). Middle cerebral artery peak systolic velocity was higher and SMA time averaged, peak systolic, and mean peak velocities were lower in the pre-eclampsia group. SMA time averaged velocity was inversely related to plasma ET-1 concentration. CONCLUSION: The association between increased production of ET-1 and reduction in SMA time averaged velocity suggests a possible mechanism for hypoperfusion of the intestinal wall in neonates.

Superior mesenteric artery and renal artery blood flow velocity measurements in neonates: technique and interobserver reliability.

The objective of this study was to establish the interobserver reliability for superior mesenteric artery (SMA) and renal artery (RA) Doppler blood flow velocity (BFV) measurements in neonates. Forty-two clinically stable infants were enrolled, mean (SD) gestational age 33 (2) weeks, birthweight 2.00 (0.54) kg, postnatal age 10 (11) days. Doppler recordings were made by two trained observers. The SMA and RA were studied with a 5.0-MHz phased array transducer. The optimal spectral trace from each artery containing a minimum of five consecutive waveforms was analysed. The peak systolic velocity (PS), end diastolic velocity (ED) and mean peak velocity (MV) were measured and the time-averaged mean velocity (TAV) and waveform indices were calculated. Using the intraclass correlation coefficient (ICC) the estimates of interobserver reliability for different measurements varied from 0.40 to 0.83. Substantial agreement was obtained between observers in the TAV, PS, ED and MV; the ICC varied from 0.72 to 0.83 demonstrating that Doppler BFV measurements of the SMA and RA are reliable in neonates.

Adenosine diphosphate glucose pyrophosphorylase genes in wheat: differential expression and gene mapping.

A full-length cDNA clone representing the large (shrunken-2) subunit of ADP-glucose pyrophosphorylase (AGP; EC 2.7.7.27) has been isolated from a cDNA library prepared from developing grain of hexaploid wheat (Triticum aestivum L., cv. Chinese Spring). The 2084-bp cDNA insert contains an open reading frame of 1566 nucleotides and primer-extension analysis indicated that the 5' end is 10 nucleotides shorter than the mRNA. The deduced protein contains 522 amino acids (57.8 kDa) and includes a putative transit peptide of 62 amino acids (6.5 kDa). The similarity of the deduced protein to the small subunit of AGP and to other AGP genes from plants and microorganisms is discussed. Northern hybridisation shows that the Agp1 genes (encoding the small subunit in the wheat endosperm) and the Agp2 genes (encoding the large subunit in the wheat endosperm) are differentially expressed in the wheat grain. Transcripts from both gene sets accumulate to high levels in the endosperm during grain development with the majority of the expression in the endopsperm rather than the embryo and pericarp layers. Although enzyme activity is detected in developing grains prior to 10 d post anthesis, only the Agp1 genes are active at this time (the Agp2 genes are not expressed until 10 d post anthesis). The possibility that the enzyme expressed during early grain development is a homotetramer of small subunits is discussed. The Agp1 and Agp2 genes are arranged as triplicate sets of single-copy homoeoloci in wheat. The Agp2 genes are located on the long arms of chromosomes 1A, 1B and 1D, about 80 cM from the centromere. The Agp1 genes have been mapped to a position just distal to the centromere on the long arms of chromosomes 7A, 7B and 7D.

Why and when do some language-impaired children seem talkative? A study of initiation in conversations of children with semantic-pragmatic disorder.

Six language-impaired children fitting the clinical picture of semantic-pragmatic disorder (mean age 11 years) engaged in conversations with adults in four situations varying in terms of familiarity of the interlocutor (familiar or unfamiliar) and type of setting (interview or toy exploration). These children did not produce more utterances or longer utterances than normally developing children of similar age or ability, but they were more likely to produce utterances that served the conversational function of initiating, rather than responding or acknowledging. This tendency was most pronounced in the toy setting. There was a nonsignificant trend for control children to initiate more with a familiar than with an unfamiliar adult, but no such tendency in the semantic-pragmatic group. A high rate of initiations in children with semantic-pragmatic disorder cannot be regarded as an unusual behavior provoked by the demands of the interview setting, as it is even more apparent during toy exploration, where the child is under less pressure to respond to adult questions.

Toxicokinetics of inhaled bromotrifluoromethane (Halon 1301) in human subjects.

Bromotrifluoromethane (CBrF3), commonly known as Halon 1301, is used as a fire extinguishant in the Space Shuttle. Several scenarios, such as a fire or a faulty alarm, could lead to its discharge resulting in a Halon 1301 concentration of up to 1% in the spacecraft cabin atmosphere. To examine the effects of Halon 1301 on mental performance and physiologic function, the National Aeronautics and Space Administration sponsored a human inhalation study. Four pairs of adult male subjects were each exposed in a double-blind fashion for 24 hr to 1% (10,000 ppm or 60,875 mg/m3) Halon 1301 and to air in two separate exposures approximately 1 week apart. Mental performance and physiologic function were assessed and the results are reported in a companion paper (D. S. Calkins, J. J. Degioanni, M. N. Tan, J. R. Davis, and D. L. Pierson. Fundam. Appl. Toxicol. 20, in press). Blood and breath samples from the exposed subjects were also collected to provide dosimetric and toxicokinetic information, which is presented here. Blood Halon 1301 levels increased rapidly and approached a steady state within 2 hr of beginning the exposure; the steady-state concentration was approximately 3-4.5 micrograms/ml. Breath samples collected during exposures closely reflected chamber concentrations. Analysis of postexposure blood samples revealed that Halon 1301 was eliminated biphasically with an average t1/2 alpha and t1/2 beta of 4.5 min (range 2.5-8.1 min) and 200 min (range 131-347 min), respectively. Halon 1301 concentrations in fat and soft tissues were also estimated. Subsequently, the end-tidal breath/blood/tissue/fat partition coefficients were calculated to be 17/1/0.5/33.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic peptide in the diagnosis of patent ductus arteriosus.

The aim of this study was to measure plasma atrial natriuretic peptide in preterm infants with a patent ductus arteriosus before and after closure with indomethacin. Atrial natriuretic peptide was measured in 28 preterm infants with clinical and echocardiographic evidence of a patent ductus arteriosus and in eight preterm infants who did not develop clinical evidence of a patent ductus arteriosus. Plasma concentration of atrial natriuretic peptide was measured by radioimmunoassay. In 18 infants the patent ductus arteriosus closed after one course of indomethacin; atrial natriuretic peptide levels decreased from median 1240 pg/ml (range 201-5483 pg/ml) to 266 pg/ml (range 62-1108 pg/ml). In four infants the patent ductus arteriosus closed after two courses of indomethacin and two infants had surgical ligation after indomethacin treatment failed. The patent ductus arteriosus closed spontaneously in four infants (atrial natriuretic peptide median level 152 pg/ml, range 61-495 pg/ml). In the eight infants without patent ductus arteriosus, atrial natriuretic peptide level was median 224 pg/ml (range 38-876 pg/ml). Measurement of plasma atrial natriuretic peptide concentration has a role in predicting when indomethacin treatment is indicated.

A method for direct measurement of systemic uptake and elimination of volatile organics in small animals.

A method was developed which was suitable for toxicokinetic studies requiring direct, repetitive sampling of blood and breath during exposures of small animals to volatile chemicals. Anesthetized male Sprague-Dawley rats were tracheostomized, and a specially fabricated one-way breathing valve was inserted directly into the trachea, in order that the inhaled and exhaled breath streams could be separated and independently sampled. The desired concentration of 1,1,1-trichloroethane was generated in a gas sampling bag, which was connected to the inlet side of the valve for inhalation exposures. Rats dosed with 1,1,1-trichloroethane by gavage inhaled ambient air through the valve. A pneumotachograph was positioned in the influent air stream to measure respiration. Respiratory rate, minute volume, and core temperature were continuously recorded on a physiograph. Samples of inspired and expired air were periodically collected from sampling ports immediately adjacent to the breathing valve and were analyzed for their 1,1,1-trichloroethane content by gas chromatography. Using this system, it was possible to determine percentage systemic uptake at any given time and to monitor cumulative uptake (i.e., total dose received) over the course of inhalation exposures. Alveolar concentrations were calculated by taking into account the respiratory indexes and dead space volume. A femoral vein was cannulated, so that concentrations of the chemical in the blood and breath could be measured concurrently. Data from rats dosed orally and by inhalation with 1,1,1-trichloroethane are presented to illustrate the applicability of the method in kinetics studies of volatile chemicals.

Community exposure to hazardous waste disposal sites: assessing reporting bias.

A household health survey of residents living near two hazardous waste disposal sites in Calcasieu Parish, Louisiana was conducted in 1981-1982 as part of a comprehensive study of the effects of those sites on the environment and on the health of nearby residents. An unexposed community was included in the health survey for comparison. Due to media coverage and public concern about the sites, two potential indices of reporting bias, hypochondriasis and respondent's opinion about the environmental effects of waste sites, were included in the survey. Because air and water quality data showed little evidence that hazardous concentrations of chemicals were being released from the sites, questions were raised about the interpretation of the health survey data. The data were analyzed, therefore, for the association between symptom reports and the potential indices of reporting bias. Hypochondriasis scores were associated with symptom reports regardless of location of residence while an individual's opinion showed a different pattern by area of residence. Respondents living near one of the waste disposal sites who answered "yes" to the opinion question were 2-3 times more likely to report some types of symptoms than residents of the comparison community. In contrast, there was little difference in symptom reports between the exposed and comparison communities for those answering "no" to the opinion question. The usefulness of self-reported symptom data in studies of communities near hazardous waste disposal sites is discussed, and attention is called to the need to develop measures sensitive to reporting bias in epidemiologic studies.

Comparison of blood and brain toluene concentrations and circulating triglyceride levels resulting from acute and repeated exposures in rats.

Male Sprague-Dawley rats were exposed by inhalation to 2500 ppm toluene three hours per day, five days per week for three weeks. Blood and brain toluene concentration and circulating triglyceride levels were measured after one day, one week, two weeks and three weeks exposure. A consistent reduction in mean body weight gain was found in the toluene-exposed rats compared to controls as early as three days following initiation of exposure. During the second and third exposure week, the toluene-exposed rats exhibited marked salivation during the exposure periods. A dramatic decrease in brain and blood toluene levels occurred between the second and third exposure weeks. Also, an inverse relationship between circulating triglyceride levels and blood and brain toluene concentrations was found in the exposed rats. Plausible mechanisms for tolerance development and the inverse relationship to circulating triglycerides are offered including induction of hepatic mixed function oxidase activity and alterations in brain biomembrane lipid composition.

Temporal patterns of reported single-vehicle car and truck accidents in Texas, U.S.A. during 1980-1983.

Reported single car and truck accidents due specifically to driver 'fatigue' for the 4-year span of 1980-1983 were analyzed for 24-hr, 7-d and 1-yr patterns. Three types of data were examined: (1) accidents in rural Texas, (2) accidents only in San Antonio, the fourth largest city in Texas and (3) accident ratio (number of accidents per time interval divided by traffic volume for the interval) in this city. A statistically significant seasonal variation of relatively low amplitude with peaks in May and July was detected only for accidents in rural areas. High-amplitude periodicities of 7 d were evident in all the data sets, with a peak on the weekend. A very prominent 24-hr pattern was detected as well, with the acrophase determined by single cosinor around 0300. A slight secondary peak in accidents, around 1500, was evident in the data from the rural areas. This secondary peak represented a 12-hr rhythm in addition to the 24-hr. Overall, features of the temporal patterns in accidents over 24 hr and over the year in urban and rural areas differed only slightly. Accident ratios yielded results similar to accident frequencies. However, with regard to the rural data, the shape of the 24-hr temporal pattern varied with driver age; older drivers exhibited a flatter curve with a more pronounced afternoon rather than early morning (around 0300) peak.

Low-back pain in industry. An old problem revisited.

Low-back pain is a major occupational health problem. Risk factors predisposing to the development of low-back pain are discussed. These include individual risk factors such as age, sex, anthropometry, musculoskeletal abnormalities, muscle strength and physical fitness, psychological factors, and previous attacks of low-back pain and workplace factors such as heavy work, lifting, bending, and slipping. Various programs for prevention are evaluated. These include selection of workers, education and training regarding lifting methods, design of lifting jobs, and fitness training. Limitations of the various studies of these programs are discussed. Preemployment strength testing and ergonomic job design together appear to offer the greatest promise.

The uptake and disposition of 1,1-dichloroethylene in rats during inhalation exposure.

The uptake, disposition, and respiratory elimination of 1,1-dichloroethylene (1,1-DCE) during inhalation exposure were evaluated to gain insight into the pharmacodynamics of the halocarbon. Anesthetized male Sprague-Dawley rats inhaled 25, 75, 150, or 300 ppm 1,1-DCE for 3 hr from an aluminized Mylar bag through a miniaturized one-way breathing valve inserted into the trachea. Periodic air samples were taken immediately adjacent to the valve from the separate inhaled air and exhaled breath streams concurrently with blood samples from a cannulated femoral vein and analyzed for 1,1-DCE content by gas chromatography. 1,1-DCE was absorbed very rapidly, in that substantial levels were present in the venous blood at the first sampling time (i.e., 2 min). Percentage systemic uptake decreased over time after initiation of exposure until equilibrium was established. Percentage uptake after reaching equilibrium varied inversely with the exposure concentration. 1,1-DCE venous whole-blood levels in animals exposed to 25, 75, and 150 ppm 1,1-DCE increased rapidly to near steady state within approximately 45 min, as did concentrations of 1,1-DCE in the exhaled breath and alveolar air. Calculation of the amount of 1,1-DCE taken up by the body over the course of the 3-hr exposures revealed that cumulative uptake of the inhaled chemical was statistically linear for the 25-, 75-, and 150-ppm exposures. Accumulation plots for 300-ppm exposed animals, however, were best fitted to a cubic curve form. Although trends toward the establishment of equilibrium were initially seen in the 300-ppm exposed animals, levels of 1,1-DCE in the blood and breath rose progressively during the latter hour of the 3-hr exposure period. Thus, despite increased exhalation of 1,1-DCE, these animals could not prevent systemic accumulation of the chemical.