The hydrolysis of epoxides catalyzed by inorganic ammonium salts in water: kinetic evidence for hydrogen bond catalysis

Naturally-occurring inorganic ammonium ions have been recently reported as efficient catalysts for some organic reactions in water, which contributes to the understanding of the chemistry in some natural environments (soils, seawater, atmospheric aerosols, …) and biological systems, and is also potentially interesting for green chemistry as many of their salts are cheap and non-toxic. In this work, the effect of NH₄⁺ ions on the hydrolysis of small epoxides in water was studied kinetically. The presence of NH₄⁺ increased the hydrolysis rate by a factor of 6 to 25 compared to pure water and these catalytic effects were shown not to result from other ions, counter-ions or from acid or base catalysis, general or specific. The small amounts of amino alcohols produced in the reactions were identified as the actual catalysts by obtaining a strong acceleration of the reactions when adding these compounds directly to the epoxides in water. Replacing the amino alcohols by other strong hydrogen-bond donors, such as trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) gave the same results, demonstrating that the kinetics of these reactions was driven by hydrogen-bond catalysis. Because of the presence of many hydrogen-bond donors in natural environments (for instance amines and hydroxy-containing compounds), hydrogen-bond catalysis is likely to contribute to many reaction rates in these environments.

Hydrocarbon removal from bilgewater by a combination of air-stripping and photocatalysis

In order to prevent hydrocarbon discharge at sea from the bilge of ships, the International Maritime Organization (IMO) enacted the MARPOL 73/78 convention in which effluents are now limited to those with maximum oil content of 15 ppmv. Thus, photocatalysis and air-stripping were combined for the hydrocarbon removal from a real oily bilgewater sample and an original monitoring of both aqueous and gaseous phases was performed by GC/MS to better understand the process. Our results show that the hydrocarbon oil index [HC] can be reduced to its maximum permissible value of 15 ppmv (MARPOL) in only 8.5h when photocatalysis and air-stripping are used together in a synergistic way, as against 17 h when photocatalysis is used alone. However, this air-assisted photocatalytic process emits a large quantity of volatile organic compounds (VOC) and, within the first four hours, ca. 10% of the hydrocarbon removal in the aqueous phase is actually just transferred into the gaseous one. Finally, we highlight that the n-alkanes with a number of carbon atoms higher than 15 (N(C)>15) are those which most decrease the rate of [HC] removal.

Activin type II receptors in embryonic dorsal root ganglion neurons of the chicken

Activin induces neuropeptide expression in chicken ciliary ganglion neurons. To determine if activin might also influence neuropeptide expression in developing sensory neurons, we examined whether type II activin receptors are expressed during embryonic development of the chicken dorsal root ganglia (DRG), and also examined the effects of activin on neuropeptide expression in cultured DRG neurons. Using reverse transcription polymerase chain reaction (rtPCR), we detected mRNAs for both the activin receptors type IIA (ActRIIA) and type IIB (ActRIIB) in DRG from embryonic day 7 through posthatch day 1. With in situ hybridization, we found that morphologically identifiable neurons express mRNAs for both ActRIIA and ActRIIB. With developmental age, a subset of neurons that hybridizes more intensely with riboprobes to these receptor mRNAs becomes evident. A similar pattern of expression is observed with immunocytochemical staining using antisera against activin type II receptors. To examine whether embryonic DRG cells respond to activin we treated dissociated cultures of DRG with activin A and assessed the expression of vasoactive intestinal peptide (VIP) and calcitonin gene related peptide (CGRP) mRNAs using semiquantitative rtPCR. Activin treatment results in an increase in VIP mRNA, but does not affect CGRP mRNA levels. These observations indicate that neurons in the embryonic chicken DRG can respond to activin and suggest that activin has the potential to play a role in the development and function of DRG sensory neurons.

Agreement between clinical examination and quantitative tests of neurologic function among 384 subjects

BACKGROUND

Quantitative neurological tests are often cheaper and easier than clinical examinations, and provide continuous data which may discriminate between exposed and nonexposed groups with more sensitivity than dichotomous (normal/abnormal) examination data.

METHODS

We compare clinical examinations and analogous quantitative tests for arm tremor, postural sway, and vibrotactile sensitivity (finger and toe), for 384 subjects.

RESULTS

The "abnormal" clinical outcomes studied were relatively common (range, 3-36%), and did not result in impairment of daily activity for affected subjects. All the quantitative tests were reasonably good predictors of the corresponding clinical outcome. The most predictive test was for toe vibrotactile sensitivity. The probability of an abnormal clinical result for those in the worst quartile for the toe test was 0.63, compared with 0.36 for all subjects.

CONCLUSIONS

Our results suggest that certain quantitative tests might be used in epidemiologic studies instead of a physical examination.

Optic disk edema associated with peripapillary serous retinal detachment: an early sign of systemic Bartonella henselae infection

PURPOSE

To describe optic disk edema associated with peripapillary serous retinal detachment as an early sign of systemic Bartonella henselae infection.

METHODS

Multicentered, retrospective case series.

RESULTS

Five women and two men presented with optic disk edema producing peripapillary serous retinal detachment. Each patient had a markedly elevated serum anti-B. henselae antibody titer. Patient age ranged from 11 to 44 years, with a mean and median of 26.6 and 28 years, respectively. The time from the onset of systemic symptoms to the onset of visual symptoms varied from 3 days to 1 month. The peripapillary serous retinal detachment resolved within 1 to 3 weeks in each case, producing a macular star in four of seven patients. Initial vision was 20/200 or worse in five of seven patients and improved in four of these five patients to 20/30 or better.

CONCLUSIONS

Systemic B. henselae infection should be considered in patients who develop optic disk edema associated with a peripapillary serous retinal detachment, even in the absence of classic neuroretinitis with a macular star.

Musculoskeletal Disorders: Work-related Risk Factors and Prevention

Work-related musculoskeletal disorders cause chronic pain and functional impairment, impose heavy costs on society, and reduce productivity. In this position paper from the Scientific Committee for Musculoskeletal Disorders of the ICOH, the most important risk factors at work are described. Work-related musculoskeletal disorders have high incidences and prevalences among workers who are exposed to manual handling, repetitive and static work, vibrations, and poor psychological and social conditions. The application of ergonomic principles in the workplace is the best method for prevention. International organizations should develop standards, common classifications, and terminologies. Surveillance systems should be further developed nationally and in workplaces, and more effort should be directed to information dissemination, education, and training.

Shift work, shift change, and risk of death from heart disease at work

Some epidemiologic studies suggest workers who rotate shift are at increased risk of cardiovascular disease, but no studies have studied the effect of shift workers who do not rotate. To determine whether current shift or recent change in shift was a risk factor for ischemic heart disease, we conducted a nested case-control study of heart disease death at work within a cohort of 21,000 men working at four heavy equipment plants. We identified 163 men who died of ischemic heart disease at work or within 1 week of working, and compared them 781 controls who were working at the same age but did not die. Plant personnel records were used to determine duration of time on current shift. At the time of case death, 72% of study subjects were working on first shift, 22% on second, and 6% on third. The average time on shift without change was 9 years. There was little evidence of any difference in heart disease risk by current shift. There was some indication that recent change from afternoon or night shift to day shift had a protective effect initially, which decreased over time. On the other hand, no corresponding negative effect was found for a change from first to second/third shift, regardless of when the change took place. Our analyses were limited by the small number of workers on the third shift. We consider our analysis to be exploratory, and encourage more research on this topic in other working populations.

Job task and psychosocial risk factors for work-related musculoskeletal disorders among newspaper employees

OBJECTIVES

A cross-sectional study was conducted to assess the association of upper extremity musculoskeletal disorders and work-related factors among employees using video display terminals at a large metropolitan newspaper.

METHODS

The study included 1050 randomly selected workers from four departments. The workers were asked to complete questionnaires on symptoms, job tasks, and psychosocial and work organization conditions. Musculoskeletal disorders of the upper extremities were defined by frequency, duration, and intensity of symptoms not attributable to acute injury. Data were analyzed with the use of logistic regression.

RESULTS

A total of 973 workers completed the survey. The one-year period prevalence rate for any musculoskeletal disorder of the upper extremities was 41%. Neck symptoms (26%) were the most frequently reported, followed by hand or wrist (22%), shoulder (17%), and elbow (10%) symptoms. Greater time working at the video display station was associated with increased hand or wrist symptoms in a dose-response relationship. In addition, variables corresponding to increased work-load demands (eg, increased time working under deadline and increased job pressure) were associated with increased neck, shoulder, and hand or wrist disorders. Women were more likely to report symptoms in several areas, but this finding may reflect the concentration of women in jobs involving more risk factors.

CONCLUSIONS

The results suggest a high prevalence of musculoskeletal disorders of the upper extremities among newspaper employees, and they provide additional evidence that increased work load, time pressure, and greater hours of computer use are related to the occurrence of work-related musculoskeletal disorders among these workers, particularly for disorders in the hand or wrist area.

The private funding of public research. New directions in the administration of occupational and environmental health research

Dr. Cullen: The experience with the new research models, starting with the prototypic experience of the rubber industry studies of the 1970s and expanding to diverse sectors of American industry in the 1980s, has yielded some important lessons for the future. In closing this symposium I shall try to summarize these briefly. Certain strengths of the evolving process seem common to each of the models. Alone and collectively, the new research arrangements have quite apparently served to increase substantially the pool of funds available to the academic sector for the study of occupational health and safety problems. As a consequence, a larger pool of investigators has participated in the research process, greatly strengthening the future academic capability and experience of our fragilely supported teaching centers. Combined with the involvement of the academic centers in the review process, there has been an undeniable broadening and deepening of the nation's research output and long-term capability in occupational health. On the side of the private sector, the new relationships have led to marked progress in the knowledge base about health and safety problems, with a heavily directed focus on those of greatest relevance to the industries involved. The credibility of the knowledge acquired has been enhanced, an important achievement in a society in which perception of truth is often as important as the truth itself! Because of the requirements of the process for broad involvement by the organizations which undertake these activities, health and safety have achieved far greater visibility and attention by corporate and union leaders who may have previously had no involvement in issues of health and safety.(ABSTRACT TRUNCATED AT 250 WORDS)

The prevalence of back pain, hand discomfort, and dermatitis in the US working population

OBJECTIVES

The purpose of the study was to provide the health care and public health communities with national prevalence estimates of selected conditions in the US working population.

METHODS

National prevalence estimates of self-reported conditions among working people were calculated from data collected for the 1988 Occupational Health Supplement to the National Health Interview Survey.

RESULTS

The highest prevalence estimates were found among occupational groups. For example, the prevalence of back pain due to an injury at work among truck drivers was 6.7%; back pain due to repeated activities at work among mechanics and repairers of heavy equipment and machinery was 10.5%; hand discomfort among operators of machines that process metal, plastic, stone, and glass was 23.5%; and dermatitis due to contact with substances at work among physicians, dentists, nurses, pharmacists, and dietitians was 5.6%.

CONCLUSIONS

A substantial proportion of these conditions among occupational groups with the highest prevalence estimates are occupational in origin. These prevalence estimates identify occupations in which efforts are needed to prevent these conditions.

An evaluation of auricular prosthesis using osseointegrated implants

The purpose of this evaluation is to compare whether retention of auricular prostheses, through utilization of osseointegrated implants rather than by adhesive, provides any improvement in patient acceptance and prosthesis longevity. Forty-seven out of a total of 49 patients having facial prostheses, retained by means of Brånemark fixtures, were surveyed. Ease of retention was noted in 91% of the patients. Satisfaction with the shape of the prosthesis, colour and ease of positioning was 100, 85 and 98% respectively. None of the patients experienced skin irritation under the prosthesis and 94% of them wore their prosthesis daily. Of the 13 patients with previous prosthesis experience, 92% stated improved retention and all of them found ease of positioning and wearing comfort had improved. Durability was better in 62%, unchanged in 23% and worse in 15% of these 13 patients.

Acute behavioural comparisons of toluene and ethanol in human subjects

A comparison of toluene and ethanol (EtOH) induced changes in central nervous system (CNS) function and symptoms were evaluated in two studies, and when possible the effects of toluene were expressed in EtOH equivalent units. The toluene concentrations were 0, 75, and 150 ppm, bracketing the American Conference of Governmental Industrial Hygienists threshold limit value (ACGIH TLV) of 100 ppm. The socially relevant EtOH doses were 0.00, 0.33, and 0.66 g EtOH/kg body weight, equivalent to two and four 3.5% 12 ounce beers. Forty two paid college students were used in each study. In the first study, subjects were exposed to toluene and an odour masking agent menthol (0.078 ppm) for seven hours over three days. In the second study EtOH or a placebo was administered at 1530 across three days also in the presence of menthol. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory), perception (pattern recognition), psychomotor skill (simple reaction time, continuous performance, symbol-digit, hand-eye coordination, finger tapping, and critical tracking), manual dexterity (one hole), mood (profile on mood scales (POMS), fatigue (fatigue checklist), and verbal ability were evaluated at 0800, 1200, and 1600. Voluntary symptoms and observations of sleep were collected daily. A 3 x 3 latin square design evaluated solvent effects simultaneously controlling for learning and dose sequence. An analysis of variance and test for trend were performed on am-pm differences reflecting an eight hour workday and on pm scores for each solvent, in which subjects were their own control Intersubject variation in absorbance was monitored in breath. A 5 to 10% decrement was considered meaningful if consistent with a linear trend at p less than 0.05. At 150 ppm toluene, losses in performance were 6.0% for digit span, 12.1% for pattern recognition (latency), 5% for pattern memory (number correct), 6.5% for one hole, and 3% for critical tracking. The number of headaches and eye irritation also increased in a dose-response manner. The greatest effect was found for an increasing number of observations of sleep. A range of 2 to 7% decrements suggest the ACGIH TLV of 100 ppm toluene may be a good estimate of the biological threshold supporting a re-evaluation of the TLV. At 0.66 g EtOH/kg body weight symptoms and performance decrements were 6.6% for digit span, 9.2% for pattern recognition, 4.0% for continuous performance, 7.9% for symbol-digit, 16.5% for finger tapping, 6.2% for critical tracking, and 5.2% for the one hole test. The EtOH equivalents at 150 ppm toluene for digit span (0.56g EtOH/kg/body weight), the latency for pattern recognition (0.66 g EtOH kg body weight), and the one hole element "move" (0.37 g EtOH kg body weight) show that the first two measures would be affected at or above the 50 mg% blood alcohol concentration. This concentration is recognised as the lowest alcohol concentration associated with increased numbers of automobile accidents. The results suggest that EtOH may be a useful acute standard to compare the effects of various industrial solvents and support investigating an association between exposure to solvents and increased risk to safety in industry.

Guidelines for medical screening in the workplace

This chapter deals with general principles of conducting medical examinations to detect adverse health effects of workplace exposures and thereby prevent occupational disease or slow its progression. Much of the discussion is most relevant to screening for effects of chemical hazards, but many of the principles presented apply to physical and biological hazards as well. Procedural and administrative aspects of workplace medical examinations that are not "exposure specific" and are applicable to all medical programs are reviewed.

Acute neurobehavioural effects of toluene

An acute inhalation chamber study of 42 college students was performed to investigate the relation between exposure to 0, 75, and 150 ppm of toluene and changes in central nervous system function and symptoms. Paid subjects were exposed for seven hours over three days. Verbal and visual short term memory (Sternberg, digit span, Benton, pattern memory); perception (pattern recognition); psychomotor skill (simple reaction time, continuous performance, digit symbol, hand-eye coordination, finger tapping, and critical tracking); manual dexterity (one hole); mood (profile of mood scales (POMS]; fatigue (fatigue checklist); and verbal ability were evaluated at 0800, 1200, and 1600 hours. Voluntary symptoms and observations of sleep were collected daily. An analysis of variance and test for trend was performed on the difference and score for each concentration reflecting an eight hour workday where each subject was their own control. A 3 x 3 Latin square study design evaluated toluene effects simultaneously, controlling for learning across the three days and the solvent order. Intersubject variation in solvent uptake was monitored in breath and urine. A 5-10% decrement in performance was considered significant if it was consistent with a linear trend at p less than 0.05. Adverse performance at 150 ppm toluene was found at 6.0% for digit span, 12.1% for pattern recognition (latency), 5.0% for pattern memory (number correct), 6.5% for one hole, and 3.0% for critical tracking. The number of headaches and eye irritation also increased in a dose response manner. The greatest effect was found for an increasing number of observations of sleep. Overall, no clear pattern of neurobehavioural effects was found consistent with the type 1 central nervous system as classified by the World Health Organisation. Subtle acute effects, however, were found just below and above the ACGIH TLV of 100 ppm toluene, supporting the position that the guideline be lowered since the biological threshold of behavioural effects may be comparable with the TLV.

The hollow denture: an alternative treatment for atrophic maxillae

This technique is an adaptation of the double-flask technique that is well-known for the fabrication of the hollow bulb portion of a maxillary obturator. It can be used only for patients with both an atrophic maxillary alveolar ridge and a greater than usual interocclusal distance. Anything less will not permit fabrication of a hollow denture.

Radiation carrier for treatment of nasopharyngeal carcinomas

A technique for intracavitary radiation therapy of nasopharyngeal carcinomas has been presented. This technique includes a direct impression technique of the nasopharynx and fabrication of a silicone carrier to house the radioactive source.

Nasal videoendoscopy in prosthetic management of palatopharyngeal dysfunction

Application of nasal videoendoscopic procedures simplifies and objectifies design of an obturator prosthesis. Although oral videoendoscopic techniques are also valuable, the nasal perspective provides valuable information not visible from the oral perspective. Because the primary function of the obturator prosthesis is to eliminate hypernasal speech and perceived nasal emission of air associated with palatopharyngeal insufficiency, nasal videoendoscopy should be considered to verify proper soft tissue-obturator contact during speech.

Hand-wrist disorders among investment casting plant workers

A survey of the prevalence of chronic soft tissue disorders of the hand and wrist was conducted 3 years after an initial survey of workers in a midwestern investment casting plant. The second survey of 136 (90%) of the original participants disclosed that (1) approximately 25% had different jobs in 1986, (2) 35% of those who had different jobs in 1986 reported transfers because of disorders, and (3) of those workers with the same job during both surveys, 11% reported temporary job changes due to disorders in the preceding 3 years. Workers with hand-wrist disorders in high-force and high-repetitive jobs tended to transfer out of these jobs more frequently than those in low-force-low-repetitive jobs. We failed to detect a relationship between ergonomic changes and change in prevalence of chronic hand-wrist disorders. This may be because the changes did not substantially alter the force and repetitiveness characteristics of the jobs.

Total rhinoplasty or prosthesis?

This article outlines the basic anatomy of the nose as it relates to a pleasing facial appearance and discusses the problems involved in the reconstruction and rehabilitation of the patient sustaining total rhinectomy.

Mechanism of active chloride secretion by shark rectal gland: role of Na-K-ATPase in chloride transport

The isolated rectal gland of Squalus acanthias was stimulated to secrete chloride against an electrical and a chemical gradient when perfused in vitro by theophylline and/or dibutyryl cyclic AMP. Chloride secretion was depressed by ouabain which inhibits Na-K-ATPase. Thiocyanate and furosemide also inhibited chloride secretion but ethoxzolamide, a carbonic anhydrase inhibitor, did not. Chloride transport was highly dependent on sodium concentration in the perfusate. The intracellular concentration of chloride averaged 70-80 meq/liter in intact glands, exceeding the level expected at electrochemical equilibrium and suggesting active transport of chloride into the cell. These features suggest a tentative hypothesis for chloride secretion by the rectal gland in which the uphill transport of chloride into the cytoplasm is coupled through a membrane carrier to the downhill movement of sodium along its electrochemical gradient. The latter is maintained by the Na-K-ATPase pump while chloride is extruded into the duct by electrical forces.

Foreign body-type reaction following crown cementation

1. Hazards of the indirect impression techniques for crown fabrication are discussed. 2. A foreign body reaction caused by retained cotton fibers is substantiated. 3. Since the gingival retraction cord is a possible and likely source, placing the cord and choice of instruments is important.