Effectiveness of rest pauses and cooling in alleviation of heat stress during simulated fire-fighting activity.

This study examined whether cooling a fire-fighter with a high velocity fan, during 10 min rest pauses between, and following, 10 min work periods, decreases heat stress during repetitive fire-fighting activity. Twelve professional fire-fighters (mean age 31.8 +/- 6.7 years) completed two, 40 min work/recovery trials in an environmental chamber at 40 degrees C and 70% relative humidity (RH). One trial was termed an enhanced recovery (ER) trial and the other was termed a normal recovery (NR) trial. In both conditions subjects wore full protective clothing and breathing apparatus during the work. In the ER trial a subject removed his protective coat and sat in front of a fan during each recovery period. In the NR trial a subject merely unbuckled his coat and was not cooled by a fan during either recovery period. The group mean metabolic cost (VO2), and the exercise and recovery heart rates were significantly lower (p < or = 0.05) during the ER trial than in the NR condition. Group mean rectal temperature increased by 1.5 degrees C in the NR trial but by only 0.8 degree C during the ER trial. The latter group's more effective cooling indicates the potential of fan cooling to reduce physiological strain and decrease the risk of heat exhaustion during repetitive fire-fighting activity. The results suggest that a fire-fighter's short 10 min exposure to heavy work in a hot environment of 40 degrees C and 70% RH produces minimal heat stress in a healthy fire-fighter. However, a period of fire-fighting exposure greater than 10 min without adequate rest and cooling may lead to a significant accumulation of heat stress and fatigue during further fire-fighting activity, irrespective of physical prowess.

Training theory and taper: validation in triathlon athletes.

This paper defines a training theory with which to predict the effectiveness of various formats of taper in optimizing physical performance from a standardized period of training and taper. Four different taper profiles: step reduction vs exponential (exp) decay and fast vs slow exp decay tapers, were simulated in a systems model to predict performance p(t) resulting from a standard square-wave quantity of training for 28 days. The relative effectiveness of each of the profiles in producing optimal physical improvement above pre-taper criterion physical test standards (running and cycle ergometry) was determined. Simulation showed that an exp taper was better than a step-reduction taper, and a fast exp decay taper was superior to a slow exp decay taper. The results of the simulation were tested experimentally in field trials to assess the correspondence between simulation and real-training criterion physical tests in triathlon athletes. The results showed that the exp taper (tau = 5 days) group made a significantly greater improvement above a pre-taper standard (P < or = 0.05) than the step-reduction taper group in cycle ergometry, and was better, but not significantly so, in a 5-km run. A fast exp taper group B (tau = 4 days) performed significantly better (P < or = 0.05) in maximal, cycle ergometry above a pre-taper training standard than a slow exp taper group A (tau = 8 days) and was improved more, but not significantly so, than group A in a 5-km criterion run. The mean improvement on both physical tests by exp decay taper groups all increased significantly (P < or = 0.05) above their pre-taper training standard. Maximum oxygen uptake increased significantly in a group of eight remaining athletes during 2 weeks of final taper after three athletes left early for final preparations at the race site.

Modelling the effect of taper on performance, maximal oxygen uptake, and the anaerobic threshold in endurance triathletes.

The purpose of this study was to determine the nature of taper required to optimize performance in Ironman triathletes. Eleven triathletes (26 +/- 4 yrs, 77.0 +/- 6.5 kg) took part in 3 months of training interspersed with two taper periods, one of 10 days (Taper 1) and another six weeks later for 13 days (Taper 2). Reducing training volume by 50% in an exponential fashion (tau < or = 5 days) in one group of triathletes during Taper 1 resulted in a 46 second (4%) improvement in their 5 km criterion run time and a 23 W (5%) increase in maximal ramp power output above the same measurement at the beginning of taper. A 30% step reduction in training volume in the second group did not result in any significant improvement in physical performance on the same measures. Training volume was reduced exponentially from the end of training in both a high volume group (tau > or = 8 days) and a low volume group (tau < or = 4 days) during Taper 2. Criterion run time improved significantly by 74 seconds (6%) and 28 seconds (2%) in the high and low volume groups respectively, while maximal ramp power increased significantly by 34 W (8%) only in the low volume taper group. Maximal oxygen uptake increased progressively from 62.9 +/- 5.8 ml.kg-1.min-1 two weeks prior to taper, to a significantly higher level 68.9 +/- 4.2 ml.kg-1.min-1 during the final week of Taper 2 (p < or = 0.5). The anaerobic threshold determined by a non-invasive method was also observed to increase from 70.9% to 74.9% of a subject's maximal oxygen uptake during Taper 2. These results demonstrate that proper placement of training volume during taper is a key factor in optimizing performance for a specific competition and a high volume of training in the immediate days preceding an event may be detrimental to physical performance.

Musculoskeletal problems in VDT work: a review.

This paper discusses the possible causes of musculoskeletal pain in VDT workers and outlines strategies to minimize it. The paper reviews workstation, chair, and keyboard design, and makes recommendations to improve user comfort. Also discussed is worker selection, training, posture, conditioning, and rest breaks. Short term musculoskeletal discomfort is experienced by many VDT operators in the telecommunications industry and chronic disability may result in the long term. It is important that the ergonomist and office manager work together to improve the working conditions in this important occupational area.

Intradermal hepatitis B vaccination in a 300-bed primary care hospital: experience with a recombinant vaccine in a four-dose schedule.

BACKGROUND: All hepatitis B vaccination programs, regardless of route, must address such factors as primary response rate, additional booster injections for primary nonresponders, antibody persistence, the need for and timing of additional booster injections for primary responders, overall costs, and medical efficacy. A voluntary intradermal hepatitis B vaccination program with postvaccination testing was implemented in a 300-bed primary care hospital with a recombinant vaccine packaged in a concentration of 20 micrograms/ml (Engerix B; SmithKline and French Laboratories, Philadelphia, Pa.). METHODS: After informed consent was obtained, 460 employees were vaccinated intradermally over the deltoid muscle by a single employee health nurse at months 0 (initial), 1, 2, and 6, followed by testing for serologic response 1 to 2 months after the final dose. RESULTS: Of 411 employees who completed the entire protocol, 90.5% had seroconversion, as determined by enzyme immunoassay. Twelve of 29 primary nonresponders (41%) had seroconversion after an additional (fifth) intradermal booster injection. Of the primary responders, 84.5% remained seropositive when tested 18 months after the initial vaccination injection. These results are comparable to those of intramuscular vaccination and to the original studies of intradermal vaccination with plasma-derived vaccines that had shown excellent immunogenicity. CONCLUSIONS: Intradermal and intramuscular hepatitis B vaccination programs must be implemented in somewhat different ways, but both can provide excellent protection against hepatitis B viral infection. Even allowing for the additional expense of postvaccination testing and more frequent booster injections, intradermal vaccination greatly reduces the overall costs of hepatitis B vaccination and may therefore increase compliance in many different settings.

Immunodetection of recombinant proteins based on antibodies directed against a metal binding peptide engineered for purification by immobilized metal affinity chromatography.

Recently we reported (Evans, D.B., Tarpley W.G. and Sharma, S.K. (1991) Expression and characterization of chimeric rDNA proteins engineered for purification and cleavage. Protein Expr. Purif. 2, 205-213) a genetically engineered metal binding peptide (mbp) for the purification of recombinant proteins by immobilized metal affinity chromatography (IMAC). Therefore, we have been interested in developing mbp-based immunodetection methods for these engineered proteins. To this end, the following linker peptide containing the mbp (His-Asp-His-Asp-His) was designed, synthesized and conjugated to porcine thyroglobulin: Ac-Cys-Gly-Glu-Glu-His-Asp-His-Asp-His-Pro-Phe-His-Leu. Rabbits immunized with this conjugate developed antibodies that cross-react with peptides containing the mbp sequence. A number of chimeric recombinant proteins, expressed in E. coli, with and without the mbp portion (His-Asp-His-Asp-His) of the fusion peptide (His-Asp-His-Asp-His-Pro-Phe-His-Leu) were analyzed by ELISA and immunoblotting. Results from these studies show that the anti-mbp antibodies detect chimeric proteins containing the mbp, while chimeric proteins lacking this pentapeptide were negative in both immunodetection techniques. The usefulness of this approach has also been demonstrated in following IMAC purification and enzymatic cleavage of the mbp. These immunodetection techniques utilizing anti-mbp antibodies should be applicable to other proteins engineered to contain the mbp for IMAC purification.

Perfluoro-octane in the treatment of giant retinal tears with proliferative vitreoretinopathy.

Giant retinal tears complicated by proliferative vitreoretinopathy (PVR) pose one of the more complex problems in vitreoretinal surgery. The authors developed a technique using perfluoro-octane, a temporary vitreous substitute that is heavier than water, combined with vitrectomy, scleral buckling, fluid-gas exchange, and direct manipulation of the retina to treat these cases. Ten eyes with giant retinal tears and grade D-1 PVR or worse were treated. In all eyes, the retina was successfully reattached at the end of surgery. Nine of the ten retinas remained attached after 6 months of follow-up. Five eyes required a total of six reoperations for epiretinal membrane formation without retinal detachment. The one eye in which the retina did not remain reattached developed severe recurrent PVR and iris neovascularization. Visual acuity improved in 8 of 10 eyes. Final visual acuity was 20/400 or better in 8 of 10 eyes, and 20/80 or better in 4 eyes.

Iatrogenic retinal breaks complicating pars plana vitrectomy.

To determine the current incidence and outcome of iatrogenic retinal breaks occurring during pars plana vitrectomy, the authors reviewed 404 consecutive operations done on eyes without preexisting retinal breaks. Thirteen eyes had 14 iatrogenic peripheral retinal breaks. Three other eyes had both peripheral breaks and posterior breaks. Twenty-five eyes had 43 posterior breaks. The incidence of peripheral breaks was 4% and of posterior breaks was 6%. Patients with proliferative diabetic retinopathy had a higher incidence of iatrogenic retinal breaks than those with other diagnoses. Peripheral breaks occurred most commonly just posterior to the site of insertion of the vitrectomy probe. Although six eyes required reoperation, 33 of 38 eyes had a successful anatomic outcome.

Familial hemifacial spasm.

Three male patients in successive generations of the same family developed acquired left-sided hemifacial spasm. Magnetic resonance imaging of the proband demonstrated a pontine vertebral artery anomaly near the root of the affected facial nerve. This family and a similar family that was recently presented illustrate several interesting features: (1) hemifacial spasm, from whatever cause, may be autosomal dominant; (2) the spasms involve the same side of the face in affected individuals within an affected family; and (3) the age of onset in familial cases may be younger than in nonfamilial cases.

Acute hydrops in pellucid marginal corneal degeneration.

Three patients had pellucid marginal corneal degeneration complicated by corneal edema. The corneal edema appeared to be a result of a break or detachment of Descemet's membrane as a result of increasing corneal ectasia. The disruption in Descemet's membrane began just above the inferior, crescent-shaped area of stromal thinning. Therapeutic modalities initially included hypertonic solution to determine whether corneal edema would resolve spontaneously, apparently by endothelial migration with healing over the break in Descemet's membrane. One patient required thermokeratoplasty and another penetrating keratoplasty for persistent stromal edema. Acute hydrops can occur with pellucid marginal corneal degeneration by a pathogenesis similar to other noninflammatory corneal thinning disorders such as keratoconus.

Construction of a tissue plasminogen activator gene having unique restriction sites to facilitate domain manipulation: a model for the analysis of multi-domain proteins.

We have designed and constructed a DNA sequence encoding human tissue plasminogen activator (tPA) with convenient restriction sites that flank each of the domains of the heavy chain. To accomplish this, the first 1095 bases of the gene coding for the mature protein were synthesized with unique restriction sites engineered into the interdomainal regions. This synthetic construction was then ligated to a cDNA fragment of the tPA gene that encoded the active site, thus generating a full-length tPA gene. The gene products produced by Chinese hamster ovary (CHO) cells transfected with either the tPA cassette gene or the tPA cDNA gene were then compared with the tPA produced by Bowes melanoma cells to determine whether or not synthetic interdomainal amino acid changes had an effect on the biochemical characteristics of the molecule. Specifically, molecular weight, specific activity, enhancement by fibrinogen fragments and kinetic constants were analysed. None of the properties examined were significantly different from those of the native melanoma tPA. Therefore, the cassette gene described herein should provide considerable versatility and precision in the construction of tPA mutants by facilitating the manipulation of the finger, growth factor and kringle domains, and likewise should be useful in assessing the function of these domains within the tPA molecule. We present this cassette gene system as a model for the analysis of protein domain function applicable to other multi-domain proteins.

Postanesthetic temporomandibular joint dysfunction.

Internal derangements, myofascial pain dysfunction, and chronic dislocation of the temporomandibular joint (TMJ) are three common sequelae resulting from mandibular trauma. Etiologic factors include prolonged dental and otolaryngologic procedures, and intraoperative use of the laryngoscope and bronchoscope. Three cases are reported to document postanesthetic TMJ dysfunction arising from normal preoperative joints. Four types of TMJ dysfunction are discussed: anterior meniscus dislocation with reduction, anterior meniscus dislocation without reduction, dislocation/subluxation of the mandibular condyle, and myofascial pain dysfunction syndrome. Preoperative screening of mandibular function is recommended in identifying patients as either normal or having potential TMJ dysfunction. Failure to recognize postoperative TMJ dysfunction can lead to long-term symptoms that are difficult to alleviate. Litigation is a common sequel in these cases.