Two-dimensional gel electrophoresis analysis of endovacuolar organelles

Cells perform their multiple functions with the aid of a series of distinct membrane organelles. In the last years, many of these compartments have been isolated, purified, and extensively studied. The major roles of each organelle in the cell are well understood. However, most of the molecular basis by which they perform their functions is poorly known. The recent identification and study of a handful of proteins associated with endovacuolar compartments has had a major impact on the understanding of the molecular details of organelle functions even though two-dimensional (2-D) gel analysis indicates that hundreds of proteins are typically associated with a complex organelle. This shows that many details and surprises are still to come for cell biologists. In the present study, we have analyzed and compared different organelles of the endocytic and phagocytic apparatus using 2-D gel electrophoresis.

Alterations of thiamine phosphorylation and of thiamine-dependent enzymes in Alzheimer's disease

There is a growing body of evidence to suggest that thiamine neurochemistry is disrupted in Alzheimer's Disease (AD). Studies in autopsied brain tissue from neuropathologically proven AD patients reveal significantly reduced activities of the thiamine phosphate dephosphorylating enzymes thiamine diphosphatase (TDPase) and thiamine monophosphatase (TMPase) as well as the thiamine diphosphate-dependent enzymes, pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase (alpha KGDH) and transketolase. Reductions in enzyme activities are present both in affected areas of AD brain as well as in relatively well conserved tissue. Decreased TDP concentrations and concomitantly increased TMP in autopsied brain tissue from AD patients and in CSF from patients with Dementia of the Alzheimer Type suggests that CNS thiamine phosphorylation-dephosphorylation mechanisms are disrupted in AD. alpha KGDH is a rate-limiting enzyme for cerebral glucose utilization and decreases in its activity are associated with lactic acidosis, cerebral energy failure and neuronal cell loss. Deficiencies of TDP-related metabolic processes could therefore participate in neuronal cell death mechanisms in AD.

Video-assisted thoracoscopic surgery for the treatment of congenital cardiac defects in the pediatric population

Recent technologic advances have contributed to a renewed interest in thoracoscopic surgery. In our institution, thoracoscopy through video-assisted technology has been successfully applied to congenital heart surgery. We reviewed the charts of 45 consecutive patients (ASA physical status 11-IV) who underwent video-assisted thoracoscopic surgery (VATS) for various congenital heart defects. The mean age of the patients was 2.65 yr and the mean weight was 11.78 kg. The surgical procedures included patent ductus arteriosus interruption (n = 28) and vascular ring division (n = 8), and 9 patients had miscellaneous procedures. The most commonly used anesthetic regimen consisted of isoflurane, pancuronium, fentanyl, air, and oxygen. Seven patients were managed with one-lung ventilation, the remainder by two-lung ventilation with surgical lung retraction. Intraoperative desaturation occurred in 12 patients (26.7%) but resolved quickly with brief reexpansion of the lungs. Postoperative complications included: pleural effusions (n = 3), chylothorax (n = 2), right upper lobe atelectasis (n = 1), small pneumothorax (n = 1), and vocal cord paralysis (n = 1). Seven patients (15.5%) required conversion to a thoracotomy for insufficient exposure (n = 4) or due to concern over bleeding (n = 3). This experience with VATS in pediatric patients with congenital heart disease may provide a database for comparison with others who work with the VATS technique.

Loss of [3H]kainate and of NMDA-displaceable [3H]glutamate binding sites in brain in thiamine deficiency: results of a quantitative autoradiographic study

Previous studies suggest that alterations of brain glutamate synthesis and release occur in experimental thiamine deficiency. In order to assess the integrity of post-synaptic glutamatergic receptors in thiamine deficiency, binding sites for [3H]glutamate (displaced by NMDA), [3H]-kainate, and [3H]quisqualate (AMPA sites) were evaluated using Quantitative Receptor Autoradiography in rat brain following 14 days of treatment with the central thiamine antagonist pyrithiamine. Compared to pair-fed controls, brains of symptomatic thiamine-deficient animals contained significantly fewer NMDA-displaceable binding sites in cerebral cortex, medial septum and hippocampus. It has been suggested that NMDA-receptor mediated glutamate excitotoxicity plays a role in the pathogenesis of neuronal loss in thiamine deficiency. If such is the case, the selective loss of NMDA binding sites in cerebral cortex and hippocampus offers a possible explanation for the relative nonvulnerability of these brain regions to pyrithiamine-induced thiamine deficiency. [3H]quisqualate (AMPA) binding sites were unchanged in all brain regions of pyrithiamine-treated rats whereas [3H]kainate sites were significantly reduced in density in medial and lateral thalamus. The decline in these binding sites may be due to neuronal loss in pyrithiamine-induced thiamine deficiency. Alterations of glutamatergic synaptic function involving both NMDA and kainate receptor subclasses could contribute to the pathogenesis of neurological dysfunction in Wernicke's Encephalopathy in humans.

Reduced activities of thiamine-dependent enzymes in brains of alcoholics in the absence of Wernicke's encephalopathy

The relative roles of alcohol per se, thiamine deficiency, and liver disease in the pathogenesis of alcohol-related brain damage have not been fully elucidated. In particular, the extent to which alterations of brain thiamine metabolism contribute to cognitive dysfunction in alcoholism in the absence of Wernicke's encephalopathy has not been established. In the present study, thiamine diphosphate-dependent enzymes were measured using standard spectrophotometric techniques in homogenates of brain tissue obtained at autopsy from eight alcoholic patients, all of whom died in hepatic coma without clinical or neuropathological evidence of Wernicke's encephalopathy and six nonalcoholic, age-matched controls, matched for autopsy delay time and free, at the time of death, from gross malnutrition or other neurological or psychiatric disorders. Transketolase activities were reduced in cerebellum (by 35%, p < 0.01), thalamus (by 35%, p < 0.01), frontal cortex (by 22%, p < 0.01), temporal cortex (by 20%, p < 0.01), and prefrontal cortex (by 19%, p < 0.01). Activities of the pyruvate dehydrogenase complex were selectively reduced in prefrontal cortex by 25% (p < 0.01). Activities of alpha-ketoglutarate dehydrogenase were within normal limits in all brain regions of alcoholic patients. The generalized reductions of transketolase activity undoubtedly result from thiamine deficiency. Previous studies suggest that the presence of liver disease may exacerbate thiamine deficiency in alcoholics. A sustained loss of transketolase activity in brain could result in disruption of pentose shunt activity and concomitant reductions in reducing equivalents and lipid metabolism within the cell. The selective loss of pyruvate dehydrogenase activity in prefrontal cortex of alcoholic cirrhotics could relate to the phenomenon of hepatic coma.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidural blood patch in a seven-year-old child

We present an unusual case of postoperative headache in a child after an epidural block. A seven-year-old girl (ASA 1) was scheduled to undergo a urological procedure under general anaesthesia combined with an epidural technique for intra- and postoperative analgesia. Although there was no evidence of dural puncture when the block was performed, the patient developed a headache postoperatively. The headache, which was accompanied by neck pain, appeared in the sitting or standing position and was relieved by decubitus. According to the mother, her child had never complained of those symptoms in the past. After independent evaluation by an anaesthetist and a neurologist, a postdural puncture headache (PDPH) was considered the most likely diagnosis. As oral analgesics failed to provide relief, and epidural blood patch (EBP) using 10 ml autologous blood was performed under light sedation. This was followed by resolution of the symptoms. Epidural injections of opioids and local anaesthetics are becoming increasingly popular for pain management in children. This implies that there may be an increasing number of unintentional dural punctures that may result in more PDPHs in children. Epidural blood patches are effective in treating PDPHs in adults but their use has been reported very rarely in children. Resolution of the patient's symptoms following EBP supported the diagnosis while illustrating that EBP can be useful in the treatment of PDPH in children.

Detection of residual flow by transesophageal echocardiography during video-assisted thoracoscopic patent ductus arteriosus interruption

The purpose of this study is to examine prospectively the efficacy of intraoperative transesophageal echocardiography (TEE) monitoring in reducing the incidence of residual ductal flow during video-assisted thoracoscopic (VATS) patent ductus arteriosus (PDA) interruption. Thirty consecutive patients undergoing PDA interruption via the VATS procedure were monitored with an appropriately sized Hewlett-Packard color-Doppler TEE probe. All examinations were performed by the same individual and interpreted with a cardiologist. Real time TEE monitoring was used, but the results were not disclosed to the surgeon until he was prepared to close the wound. The mean age was 2.4 yr and the average weight 11.2 kg. Two patients had residual flow after placement of the vascular clip. One patient had residual flow detected intraoperatively after placement of the vascular clip and residual flow was quickly abolished by the placement of a second clip, thus avoiding a reintervention. A follow-up transthoracic echocardiography was performed on 18 patients 1 mo postoperatively. Three patients presented residual ductal flow. This study using a novel application of TEE, demonstrates that TEE monitoring during PDA interruption may improve the surgical result, thus avoiding reintervention and the complications associated with residual ductal flow. However, late recurrence due to recanalization may occur and may not be detected by intraoperative TEE monitoring.

Effects of propofol or isoflurane anesthesia on cardiac conduction in children undergoing radiofrequency catheter ablation for tachydysrhythmias

BACKGROUND

To determine suitability for ablation procedures in children, two commonly used anesthetic agents were studied: propofol and isoflurane.

METHODS

Twenty patients presenting for a radiofrequency catheter ablation procedure were included and randomly assigned to two groups. A baseline electrophysiology study was performed during anesthesia with thiopental, alfentanil, nitrous oxide, and pancuronium in all patients. At the completion of the baseline electrophysiology study (EPS), 0.8-1.2% isoflurane was administered to patients in group 1 and 2 mg/kg propofol bolus plus an infusion of 150 micrograms.kg-1.min-1 was administered to patients in group 2. Nitrous oxide and pancuronium were used throughout the procedure. After 30 min of equilibration, both groups underwent a repeat EPS. The following parameters were measured during the EPS: cycle length, atrial-His interval, His-ventricle interval, corrected sinus node recovery time, AV node effective refractory period, and atrial effective refractory period. Using paired t tests, the electrophysiologic parameters described above measured during propofol or isoflurane anesthesia were compared to those measured during baseline anesthesia. Statistical significance was accepted as P < 0.05.

RESULTS

There was no statistically significant difference in the results obtained during baseline anesthesia when compared with those measured during propofol or isoflurane anesthesia.

CONCLUSIONS

Neither propofol nor isoflurane anesthesia alter sinoatrial or atrioventricular node function in pediatric patients undergoing radiofrequency catheter ablation, compared to values obtained during baseline anesthesia with alfentanil and midazolam.

Paediatric cardiac catheterization: innovations

In recent years interventional procedures have been introduced to the field of paediatric cardiac catheterization. These procedures continue to develop in complexity and increasingly are being applied to patients with reduced cardiovascular reserve, as an alternative to cardiac surgery or when cardiac surgery with cardiopulmonary bypass is contraindicated. More frequently anaesthetists are being called upon to provide support in sedating, anaesthetizing or/and resuscitating these patients. The purpose of this review is to give a comprehensive update of the interventional procedures and to review the anaesthetic management techniques as they apply to the catheterization laboratory. We will discuss possible complications and management strategies from our own experience and the experience of others. We have observed that as more complicated procedures are performed the anaesthetist plays a pivotal role in the management of the patient from arrival to departure from the cardiac catheterization laboratory, and in preventing mortality and major morbidity. Although the economic consequences of interventional cardiological techniques remain unclear, the field continues to expand and more complex procedures are continually being introduced.

Transoesophageal echocardiography detects residual ductal flow during video-assisted thoracoscopic patent ductus arteriosus interruption

This report describes transoesophageal echocardiographic (TEE) monitoring in a one-year-old boy undergoing patent ductus arteriosus (PDA) interruption. After application of a first vascular clip, echocardiographic monitoring detected incomplete interruption of ductal flow, prompting the surgeon to add a second clip to the ductus. The procedure was performed via a new surgical technique: video-assisted thoracoscopic surgery (VATS). This innovative approach offers many advantages to patient care including reduced postoperative pain and better preservation of pulmonary function. We conclude that the use of TEE monitoring during PDA interruption via the VATS procedure may improve the surgical result, and eliminate reintervention and the complications associated with residual ductal flow.

Flumazenil in cirrhotic patients in hepatic coma: a randomized double-blind placebo-controlled crossover trial

Previous reports have suggested that "endogenous" benzodiazepines could contribute to neural inhibition in hepatic encephalopathy. RO 15-1788 (flumazenil), a specific antagonist of brain benzodiazepine receptors, could thus reverse the neurological symptoms of hepatic encephalopathy. To test this possibility, we conducted a double-blind, placebo-controlled crossover trial of the efficacy of flumazenil in cirrhotic patients in hepatic coma. Seventy-seven cirrhotic patients in hepatic coma were evaluated. Fifty-six were excluded from the trial because of multiorgan failure or because coma was precipitated by prior use of benzodiazepines, and 21 patients were randomly assigned to the flumazenil group (11 patients) or the placebo group (10 patients). Treatment was administered intravenously as a 20-ml solution (placebo or 2 mg flumazenil); seven patients were crossed over. Clinical status was assessed blindly by two observers, using a modified Glasgow scale, every 15 min for 6 hr. Electroencephalogram tracings obtained before and after drug administration were evaluated blindly by two independent observers. Serum concentrations of benzodiazepines before treatment were measured by means of a fluorescence polarization immunoassay. Improvement in neurological symptoms was observed in six patients treated with flumazenil, whereas none in the placebo group showed improvement (p < 0.05; Fisher's exact test). Improvements in electroencephalogram tracings were demonstrated in four patients treated with flumazenil, compared with two patients in the placebo group (p = NS). Benzodiazepines were found in the serum of four patients treated with flumazenil (two responders and two nonresponders); all of these patients had received pharmaceutical benzodiazepines 4 to 6 days before the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Axillary plexus block using a peripheral nerve stimulator: single or multiple injections

This prospective, randomized, double-blind study was undertaken to evaluate the success rates of axillary brachial plexus block performed with the help of a peripheral nerve stimulator when either one, two or four of the major nerves of the brachial plexus were located. Seventy-five patients undergoing upper limb surgery were randomly allocated to one of the following five groups according to the nerve and number of nerves to be located; G-1: musculo-cutaneous, radial, median and ulnar nerves; G-2: musculo-cutaneous plus one of the other three nerves; G-3: radial nerve; G-4: median nerve; G-5: ulnar nerve. The sensory block was evaluated before surgery and cutaneous anaesthesia was considered to be present when the needles of a Wartenberg Pinwheel were no longer felt in all the dermatomes of the nerves implicated in the surgical site. Otherwise, the block was considered to need completion before surgery. Only one out of the 15 patients in G-1 and G-2 needed completion of their block before surgery whereas seven out of 15 for G-3 and eight out of 15 for G-4 and G-5 needed completion of their block (P less than 0.01). We conclude that when performing an axillary block with the help of a peripheral nerve stimulator, stimulation of the musculo-cutaneous nerve and one other nerve or stimulation of all four major nerves of the brachial plexus gives a higher success rate than stimulation of only one nerve, whether the stimulated nerve is the median, radial or ulnar.

Effect of portacaval anastomosis on electrically stimulated release of glutamate from rat hippocampal slices

To evaluate the effects of chronic liver failure on release of the excitatory transmitter glutamate, electrically stimulated Ca2(+)-dependent and Ca2(+)-independent release of glutamate in the absence or presence of NH4+ was studied in superfused slices of hippocampus from portacaval-shunted or sham-operated rats 4 weeks after surgery. Spontaneous and stimulation-evoked release of glutamate was higher in shunted rats in the presence of normal or low Ca2+ concentrations, and this release was depressed by 5 mM ammonium chloride. These findings suggest that portacaval shunting results in increased levels of extracellular glutamate in brain, probably due to a decreased reuptake of glutamate into perineuronal astrocytes, shown in previous studies to undergo neuropathological changes following portacaval shunting. Changes in the inactivation of transmitter glutamate could be responsible, at least in part, for the neurological dysfunction resulting from sustained hyperammonemia and portal-systemic shunting resulting from chronic liver failure.

Airborne microbial contents in two types of swine confinement buildings in Quebec

Airborne microorganisms were isolated with a sampler in two types of swine confinement buildings (farrowing units and fattening units). Respirable (particles less than 5 microns) and total dust fractions were obtained. Samplings were repeated every 2 weeks for a total of 6 samplings per unit between January and April. The predominant microorganisms isolated were bacteria (up to 1.25 x 10(6) CFU/m3) with an important fraction in the respirable size range (up to 0.5 x 10(6) CFU/m3). Only small quantities of gram-negative bacteria, yeasts, and molds were found. Identification of the colonies isolated revealed a great diversity of microorganisms present in the air of the different buildings. Enterobacter agglomerans, Moraxella, Acinetobacter calcoaceticus, and Pseudomonas were the most frequently identified bacteria. Scopulariopsis, Aspergillus, Penicillium, and Candida were the most numerous fungi. Faenia rectivirgula, the causative agent of farmer's lung, was not a major contaminant. The results show some differences in airborne microbial contamination between farrowing and fattening units; the distinction, however, is not clear-cut and was observed only for the total bacteria. The level of airborne microbial contamination in swine units does not significantly vary as a function of the outside temperature. Some species of bacteria and fungi isolated in this study are known to induce extrinsic allergic alveolitis. Other fungi are known to be potentially pathogenic for man. The air of swine confinement buildings is highly contaminated with bacteria, yeasts, and molds at a level up to 1200 time higher than so-called "normal air."

Increased densities of peripheral-type benzodiazepine receptors in brain autopsy samples from cirrhotic patients with hepatic encephalopathy

Peripheral-type benzodiazepine receptors were evaluated using the specific ligand [3H]-PK 11195 in brain homogenates from nine cirrhotic patients who died in hepatic coma and from an equal number of age-matched control subjects. Histopathological studies showed evidence of severe Alzheimer type II astrocytosis in the brains of all cirrhotic patients. Saturation-binding assays revealed a single saturable binding site for [3H]-PK 11195 in brain, with affinities in the 2- to 3-nmol/L range. Diazepam was found to be a relatively potent inhibitor of 3H-PK 11195 binding (IC50 = 253 nmol/L), whereas the central benzodiazepine antagonist Ro 15-1788 displaced 3H-PK 11195 binding with low affinity (IC50 greater than 40 mumols/L). Densities of [3H]-PK 11195 binding sites were found to be increased by 48% (p less than 0.01) and 25% (p less than 0.05) in frontal cortex and caudate nuclei, respectively, from cirrhotic patients. Densities of [3H]-PK 11195 binding sites in frontal cortex from two nonencephalopathic cirrhotic patients were not significantly different from control values. No concomitant changes of affinities of these binding sites were observed. Because it has been suggested that peripheral-type benzodiazepine receptors may be localized on mitochondrial membranes and may therefore be involved in cerebral oxidative metabolism, the alterations observed in this study could be of pathophysiological significance in hepatic encephalopathy.

Neurochemical and electrophysiological studies on the inhibitory effect of ammonium ions on synaptic transmission in slices of rat hippocampus: evidence for a postsynaptic action

To elucidate the mechanisms involved in the inhibition of synaptic transmission by ammonium ions, the effects of NH4Cl on glutamate release and on synaptic transmission from Schaffer collaterals to CA1 pyramidal cells were measured in fully submerged slices of rat hippocampus. The large, Ca(2+)-dependent release of glutamate evoked by electrical-field stimulation or by 56 mM K+ was not reduced by 5 mM NH4Cl. In contrast, 5 mM NH4Cl decreased the smaller, field stimulation-induced release of glutamate observed in the presence of low concentrations of Ca2+ (0.1 mM), as well as the spontaneous release of glutamate both in normal and low Ca2+. Unlike the Ca(2+)-dependent release of glutamate, synaptic transmission was reversibly depressed even by 1 mM NH4 Cl. Firing of CA1 pyramidal cells evoked by iontophoretically applied glutamate was significantly inhibited by 2 or 5 mM NH4Cl. This depression was increased in the presence of 25 microM bicuculline. Results suggest that ammonium ions do not depress the Ca(2+)-dependent release of glutamate originating from synaptic vesicles, which is involved in synaptic transmission. Rather, ammonium ions inhibit synaptic transmission by a postsynaptic action, a conclusion strengthened by the inhibitory effect of NH4Cl on glutamate-induced firing. However, NH4Cl may inhibit the formation of cytoplasmic glutamate, the source of spontaneous and Ca(2+)-independent release.

Pharmacokinetics of benzodiazepine antagonist Ro 15-1788 in cirrhotic patients with moderate or severe liver dysfunction

Ro 15-1788, a benzodiazepine antagonist, has been advocated as a new treatment for hepatic encephalopathy. This drug is extensively metabolized by the liver in normal subjects. In the present study, we examined Ro 15-1788 disposition in eight healthy controls (Group I), eight cirrhotic patients with moderately impaired liver function (Pugh score less than 10, Group II) and eight patients with severe liver dysfunction (Pugh score greater than 10, Group III). The subjects of each group were age and sex matched. After an intravenous infusion of 2 mg Ro 15-1788 over 5 min, blood samples were taken at fixed intervals up to 7 hr after the infusion. Plasma levels of the drug were determined by capillary gas chromatography. In controls, Ro 15-1788 had a high plasma clearance [16.3 +/- 2.6 ml per min per kg (mean +/- S.D.)], a short half-life (45.7 +/- 8.5 min), a large volume of distribution (0.62 +/- 0.09 liter per kg) and a low plasma protein binding (45 +/- 6%). Plasma clearance was reduced markedly in both groups of cirrhotic patients (-57 and -74%, respectively); the volume of distribution was unchanged in Group II and moderately increased in Group III (+37%). The elimination half-life was markedly prolonged in Groups II and III (+66 and +210%, respectively). Plasma clearance and Pugh score were highly correlated in cirrhotic patients (r = 0.830, p less than 0.001). The plasma protein binding of Ro 15-1788 was lower in cirrhotics, resulting in a significant increase in the free fraction of the drug (+16% in Group II; +44% in Group III).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in lectin binding of lumbar dorsal root ganglia neurons and peripheral axons after sciatic and spinal nerve injury in the rat

The effects of chronic lesions of rat lumbar spinal or sciatic nerves on the binding of Glycine max (soybean) agglutinin to galacto-conjugates, in small- and medium-size primary sensory neurons of the L4 and L5 dorsal root ganglia, were examined over a 580-day period. Spinal nerve section resulted in a marked decrease in the population of stained neurons within 7 days. However, despite some retrograde morphological changes triggered by axonal injury, the proportion of stained nerve cells was normalized 180 days postoperatively. This temporary decrease in perikaryal lectin reactivity was initially associated with a marked accumulation of stained material in the nerve, proximal and distal to the site of section, with similar accumulations also being noticeable at each level of injury in sciatic nerves subjected to double ligature. This may reflect the presence of glycocompounds linked to the autolysis of nerve fibers during the phase of retrograde dying-back and Wallerian degeneration. At later stages, stained deposits could be seen scattered along central and peripheral axonal processes of the dorsal root ganglion neurons in the vicinity of the cell body. They may indicate a disturbance in the peripheral turnover of glycoproteins in chronically-transected nerves, with piling up of neuronal products. Sciatic nerve injury caused similar but less severe effects which, except for the L4 ganglion cells, were rapidly reversible.

Congenital defects and work in pregnancy

The risk of congenital defect was examined in 47,913 pregnancies of women employed for 15 hours a week or more at time of conception. The rate of defects of all types per 1000 births in this series was 25.0; 1.8 from defects classified as chromosomal (group A), 10.8 as developmental (group B), and 12.5 as musculoskeletal (group C). Some evidence of an excess in the risk ratio (p less than 0.05) was found in the services sector and in four occupations--agriculture and horticulture (2.61), telephone and postal clerks (1.74), a miscellaneous group of service jobs (1.68), and receptionists and information clerks (1.47); excesses of lower statistical significance (p less than 0.1) were found in those engaged in plastics and rubber manufacture (2.02) and in child minders (1.84). There were two cases of tracheo-oesophageal fistula--a rare defect--among eight defects (1.32 expected) in agriculture and horticulture. Overall, the distribution of risk ratios in the 60 occupations examined was not significantly heterogeneous. Analysis of chemical exposure profiles for each occupational group showed no evidence of any increased risk, perhaps due to lack of sensitivity and discrimination in this method of exposure estimation. In 152 pregnancies of doctors and nurses who had administered antineoplastic drugs in the first month eight defects, miscellaneous in type, were observed compared with 4.05 expected (p = 0.05). Special study of musculoskeletal defects and work demands showed some evidence of an association with a long working week (greater than or equal to 46 hours) but no other ergonomic factor. With these few exceptions the survey failed to identify appreciable risk of congenital defect related to occupation.