Landmarks in burn prevention

The objective of this paper is to highlight landmarks in burn prevention. Novel strategies in the areas of law and regulation, environmental and consumer product design, and educational programs are identified and discussed. Notwithstanding marked reductions in burn morbidity and mortality, especially in economically developed countries, burn injuries remain an important public health concern throughout the world. More, and more effective, burn prevention programs coupled with renewed efforts to reduce the social and environmental correlates of burn injuries (poverty, overcrowding, family stress, and educational deficits) are needed to further reduce burn incidence and its long-term sequelae.

Study of stabilizing CaF2:Dy ultraviolet sensitivity by double annealing treatment

The intrinsic thermoluminescent response to ultraviolet radiation of CaF2:Dy phosphor is enhanced by pre-irradiation high-temperature annealing treatment. The thermoluminescent response is stabilized by adding a medium temperature annealing treatment after the previous annealing. The experimental results show that the annealing treatment of 1 h 850 degrees C high-temperature annealing followed by 1 h 350 degrees C medium-temperature annealing is the optimum treatment to have high thermoluminescent response and good stability. The results also show that (1) the thermoluminescent response to 253.7 nm ultraviolet radiation is increased and stabilized, (2) the thermoluminescent sensitivity and glow curve distribution to 235.7 nm ultraviolet radiation are retained, and (3) the thermoluminescent response to 253.7 nm ultraviolet is linear from 3 to 1 x 10(3) Jm(-2), but there is no linear response with respect to 365 nm ultraviolet.

Symptomatic ossification of the posterior longitudinal ligament of the lumbar spine. Case report

The authors report a case of focal ossification of the posterior longitudinal ligament (OPLL) behind the L-3 vertebral body. This is relatively rare among previously reported cases in the literature. Magnetic resonance (MR) imaging revealed that the ossifying portion of the PLL was impinging on the left L-3 nerve root. Contrast enhancing hypertrophic PLL was also demonstrated around the ossification and along the lumbosacral PLL. Via a laminectomy and wide excision of the PLL the lesion was removed. Pathological examination revealed a nodule composed of fibrous cartilage, lamina bone, and mature fat marrow. Enchondral ossification could be identified under a microscope. The authors believe that preoperative MR imaging evaluation is important for the detection of the relationship between an OPLL and the neural structure. Excision of the symptomatic OPLL should be performed when needed to obtain adequate nerve root decompression.

The crystal structure of the DNase domain of colicin E7 in complex with its inhibitor Im7 protein

BACKGROUND

Colicin E7 (ColE7) is one of the bacterial toxins classified as a DNase-type E-group colicin. The cytotoxic activity of a colicin in a colicin-producing cell can be counteracted by binding of the colicin to a highly specific immunity protein. This biological event is a good model system for the investigation of protein recognition.

RESULTS

The crystal structure of a one-to-one complex between the DNase domain of colicin E7 and its cognate immunity protein Im7 has been determined at 2.3 A resolution. Im7 in the complex is a varied four-helix bundle that is identical to the structure previously determined for uncomplexed Im7. The structure of the DNase domain of ColE7 displays a novel alpha/beta fold and contains a Zn2+ ion bound to three histidine residues and one water molecule in a distorted tetrahedron geometry. Im7 has a V-shaped structure, extending two arms to clamp the DNase domain of ColE7. One arm (alpha1(*)-loop12-alpha2(*); where * represents helices in Im7) is located in the region that displays the greatest sequence variation among members of the immunity proteins in the same subfamily. This arm mainly uses acidic sidechains to interact with the basic sidechains in the DNase domain of ColE7. The other arm (loop 23-alpha3(*)-loop 34) is more conserved and it interacts not only with the sidechain but also with the mainchain atoms of the DNase domain of ColE7.

CONCLUSIONS

The protein interfaces between the DNase domain of ColE7 and Im7 are charge-complementary and charge interactions contribute significantly to the tight and specific binding between the two proteins. The more variable arm in Im7 dominates the binding specificity of the immunity protein to its cognate colicin. Biological and structural data suggest that the DNase active site for ColE7 is probably near the metal-binding site.

Preliminary study of dose equivalent evaluation for residents in radioactivity contaminated rebar buildings

It has recently been found that several resident and office buildings in Taiwan were constructed with 60Co-contaminated reinforcing steel bar (rebar). Both governmental officials and the residents of such buildings have been concerned about this finding. In order to respond to the situation, the government has adopted a number of remedial measures, including full-scale radiation survey, dose evaluation and physical examinations of residents. This article presents three methods for evaluating the dose equivalents of the residents living in the contaminated rebar buildings by means of gamma-ray survey, necklace-type thermoluminescence dosimeters (TLDs) and the human lymphocyte chromosome aberration analyses. The results reveal that the dose evaluation by gamma-ray survey is rather conservative. Generally for the residents whose annual dose equivalents are greater than 5 mSv (0.5 rem) by gamma-ray survey, the dose equivalents from necklace-type TLDs are only within the range of 20 to 50% of the evaluated values mentioned above. For chromosome analyses, at least 500 lymphocyte cells were scored and analyzed for each resident. Most of the chromosome analysis data show that the dose equivalents received by residents are lower than the detection limit of the method (100 mSv) and quite different from the estimated dose obtained from either gamma-ray survey or necklace-type TLD measurements.

Change of thermal stability of colicin E7 triggered by acidic pH suggests the existence of unfolded intermediate during the membrane-translocation phase

Purified colicin E7 was analyzed by CD spectrum and gel filtration chromatography in a mimicking membrane-translocation phase. It was found that the CD spectra of colicin E7 at pH 7 and pH 2.5 were similar. Although the melting temperature of the protein shifted from 54.5 degrees C to 34 degrees C at low pH, the thermal denaturation curves of colicin E7 at different pH conditions still fit a two-state model. These experimental results imply that a minor structural change, triggered by acidic pH, for instance, may reduce the energy required for protein melting. In contrast to the minor change in secondary structure at different pH conditions, we observed that, in vitro, all monomeric colicin E7s converted into multimer-like conformations after recovering from the partial unfolding process. This multimeric form of colicin can only be dissociated by formamide and guanidine hydrochloride, indicating that this protein complex is indeed formed by aggregation of the monomeric colicins. Most interestingly, the aggregated colicins still perform in vivo bacteriocidal activity. We suggest that in a partial unfolding state the colicin is prepared for binding to the specific targets for translocation through the membrane. However, in the absence of specific targets in vitro these unfold intermediates may therefore aggregate into the multimeric form of colicins.

Dose reconstruction for residents living in 60Co-contaminated rebar buildings

The first 60Co-contaminated rebar building was discovered in Taipei city in 1992. As of 18 July 1997, 144 buildings with 1,327 housing units were confirmed to contain 60Co-contaminated rebars. All these reinforced concrete buildings were constructed between 1982 and 1984. Thousands of residents have been exposed to ionizing radiation of various degrees. Preliminary assessments by the Atomic Energy Council showed that the accumulated maximal doses ranged from a few mSv to several Sv. The purpose of this work was to reconstruct more reliable individual doses for epidemiologic and medical uses. This reconstruction provided the best estimated doses as well as conceivable upper and lower bounds. The variation of residential day-life activities by individual members in a family was considered according to their sex, age, profession, etc. Intensive data on exposure rates were collected using thermoluminescent dosimeters positioned at 1 m height and 1 m x 1 m intersections with additional measurements at special locations such as bed, sofa, dining table, etc. Thermoluminescent dosimeter measurements were performed in all 24 residences studied in this work. This showed that the Atomic Energy Council maximal doses were 2-6 times higher than the present best estimated doses. Among all family members, elders and housewives received the highest doses; children received the lowest doses. The difference in doses among all family members belonging to different cohort categories is within a factor of two.

Experimental study of steady and pulsatile flows in cerebral aneurysm model of various sizes at branching site

Pulsatile and steady flow fields in cerebrovascular aneurysm models of various sizes are presented in terms of laser-Doppler velocimetry measurements and flow visualization. The bifurcation angle was 140 deg and volume flow rate ratio between the branches was 3:1. The mean, peak, and minimal Reynolds numbers based on the bulk average velocity and diameter of the parent vessel were 600, 800, and 280, respectively. It is found that among the tested sizes there exists a middle range of aneurysm sizes, above and below which the forced-vortex inside the aneurysmal model is weaker and lacking, respectively, whereas in the middle range of the tested sizes the forced vortex is stronger and the fluctuation level is higher near the dome. The present results also identify the major fluid dynamic factors of the aneurysmal promotion or rupture for the medium and larger aneurysms, respectively. Furthermore, the maximum fluctuation intensity is found to increase with aneurysm size. The locations of the maximum fluctuation intensity are found to occur in the bifurcation area or at the neck instead of intra-aneurysm.

Site-directed mutagenesis of the aspartokinase gene lysC and its characterization in Brevibacterium flavum

Using overlap extension polymerase chain reaction (PCR), five transformants of Escherichia coli containing site-directed mutagenized lysC beta gene were generated and analysed. Exchange of C to A and C to T at nucleotide 1118 of the mutated lysC beta gene causes a substitution of serine301 in the wild-type enzyme for tyrosine301 and phenylalanine301 in the mutant enzymes, respectively. Enzyme assays showed that Brevibacterium flavum cells harbouring pSUMN18 with mutated lysC beta genes exhibited 16-20 fold lower specific activities of aspartokinase as compared to that of host containing wild-type lysC gene. The mutation introduced into lysC beta of B. flavum CCRC 18271 resulted in partial feedback-resistant aspartokinase activity.

[Methicillin-resistant Staphylococcus aureus: an alarming problem in Chang Gung Memorial Hospital]

Strains of methicillin-resistant Staphylococcus aureus (MRSA) have become increasingly common in the United States and in many other countries since 1975. The prevalence of MRSA colonization and infection has increased in acute-care and chronic-care facilities, outpatient clinics, and in the community. We reviewed the sensitivity test of antibiotics in Chang Gung Memorial Hospital system, and revealed a steady decrease in sensitivity to Cephalothin, Oxacillin and Clindamycin during the past 10 years. It is still sensitive to Vancomycin. However, the amount of Vancomycin prescribed in the hospital system has increased three-folds during the recent 4 years. The purpose of this article is to review the MRSA in this hospital and to describe measures used to control MRSA transmission.

The cloning and nucleotide sequence of a Corynebacterium glutamicum 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase gene

The aro gene of Corynebacterium glutamicum CCRC 18310 encoding 3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP) synthase was isolated by complementation of a DAHP synthase-deficient mutant of Escherichia coli AB3257. The specific activity of DAHP synthase was increased four-fold in a C. glutamicum strain harboring the cloned aro gene. The complete nucleotide sequence of the aro gene and its 5' and 3' flanking regions has been determined. The sequence contained an open reading frame of 368 codons, from which a protein with a molecular mass of 39,340 Da could be predicted. The deduced amino acid sequence shows high identity with the aro gene products of E. coli and Salmonella typhimurium.

Gallbladder mucosal blood flow increases during early cholesterol gallstone formation

Gallbladder absorption increases during early cholesterol gallstone formation and is influenced by the intraluminal presence of lithogenic bile. The effect of lithogenic bile on gallbladder mucosal blood flow is unknown. The current study tested the hypothesis that the presence of lithogenic gallbladder and hepatic bile enhances gallbladder mucosal blood flow in cholesterol-fed (0.4%) prairie dogs, as determined by hydrogen gas clearance. Gallbladder mucosal blood flow in control animals was 35.57 +/- 3.9 mL.min-1.100 g-1. In contrast, basal gallbladder mucosal blood flow in cholesterol-fed animals was significantly (P less than 0.01) increased to 64.94 +/- 8.7 mL.min-1.100 g-1. In crossover studies, the addition of lithogenic gallbladder bile to control animals (n = 6) resulted in a significant (P less than 0.025) 26% increase in gallbladder mucosal blood flow, whereas the addition of nonlithogenic gallbladder bile into gallbladders of cholesterol-fed prairie dogs resulted in a significant (P less than 0.025) 58% decrease in gallbladder mucosal blood flow. Similarly, hepatic bile crossover studies showed that the addition of lithogenic hepatic bile to control gallbladders significantly increased (P less than 0.025) gallbladder blood flow by 30%, whereas instillation of nonlithogenic hepatic bile in gallbladders of cholesterol-fed animals significantly (P less than 0.025) decreased gallbladder mucosal blood flow by 29%. These results suggest that alterations in gallbladder mucosal blood flow, influenced by the presence and absence of lithogenic bile, may play a role in cholesterol gallstone formation.

Macromolecule synthesis in temperature-sensitive mutants of methanol-utilizing Hansenula polymorpha

Temperature sensitive (ts) mutants of methanol-utilizing Hansenula polymorpha NTU-AM-P5 were isolated by UV irradiation, EMS and/or NTG treatment. They grow normally at permissive temperature (PT) 38 degrees C, but can not grow at restrictive temperature (RT) 46 degrees C. From chemical composition analysis, it was found that ts mutants NTU-AM-L2 and NTU-AM-L3 had higher RNA content than the others; while ts mutant NTU-AM-E19 had the highest protein content among the isolated strains. Leucinyl-tRNA synthetases activity was the highest among the twenty aminoacyl-tRNA synthetases in both wild type and their ts mutants. When the cells were shifted from PT to RT for 12 h, total aminoacyl-tRNA synthetase activity decreased in all tested strains. Leucinyl-tRNA synthetase of ts mutant NTU-AM-E10 decreased 91.23%. At RT, it was found that ts mutants NTU-AM-E10 and NTU-AM-E20 were defective in DNA synthesis; ts mutants NTU-AM-E15, NTU-AM-E20, NTU-AM-N37 and NTU-AM-m5 were defective in RNA synthesis; ts mutants NTU-AM-E10, NTU-AM-E20 and NTU-AM-m5 were somewhat defective in protein synthesis; while ts mutants NTU-AM-L2 and NTU-AM-L3 did not belong to any one of the above classifications.

Purification and characterization of a benzodiazepine-like substance from mammalian brain

An endogenous brain ligand which competes with [3H]-flunitrazepam for the binding to benzodiazepine receptor has been isolated and purified to homogeneity. The purification procedures involve the extraction of the endogenous ligand by homogenizing the brain tissue in water containing various protease inhibitors followed by filtration through a PM 10 membrane (exclusion limit: 10,000-dalton), column chromatographies on Sephadex G-50, Bio-Rad P2 and a series of C18 reverse phase HPLC columns. The purified endogenous ligand was eluted as a single and symmetrical peak monitored at either 220 or 280 nm. Furthermore, the ligand activity coincided with the absorption peak. The purified endogenous ligand is thermostable, insensitive to various peptidases and proteolytic enzymes, resistant to DNAse, RNAse, and carbohydrate enzyme e.g. neuraminidase (EC 3.2.1.18) and acid treatment. It has a major absorption peak at 220 nm and a minor one at 313 nm. The endogenous ligand appears to be quite specific since it only inhibits the binding of ligand to the central type benzodiazepine receptor but not to other receptors, e.g. peripheral type benzodiazepine receptor, alpha 1-adrenoceptor, alpha 2-adrenoceptor, beta-adrenoceptor and muscarinic cholinergic receptor. Furthermore, the inhibition of the receptor binding by the endogenous ligand is enhanced by GABA suggesting that the endogenous ligand is a benzodiazepine receptor agonist. The structure of the endogenous ligand is unknown.

Isolation and characterization of temperature-sensitive mutants of Hansenula

For investigation of the feasibility of obtaining yeast strains with high protein and low nucleic acid content or high nucleic acid and low protein content for industrial production of single cell protein or nucleotide, the methanol-utilizing Hansenula polymorpha NTU-AM-P5 was chosen for isolation of temperature-sensitive mutants. Approximately 70 temperature-sensitive (ts) mutants were obtained. All of the ts mutants increased in cell size and aggregated when they were cultivated at permissive temperature and shifted to restrictive temperature in the late log phase or in the stationary phase. 86.1% of ts mutants had a lower growth rate than that of their wild-type. Only ts mutants, NTU-AM-L2, NTU-AM-E10, NTU-AM-E19, NTU-AM-E25 and NTU-AM-E30 had same or slightly higher than that of their wild-type strain. Cycloheximide at 1 mg/ml inhibited the growth of ts mutant NTU-AM-E19, but inhibited one-third of the other ts mutants, and their wild-type strain. Rifampicin at 0.1 mg/ml had an inhibitory activity on wild-type strain but not on ts mutant NTU-AM-E1. ts mutants NTU-AM-L2 and NTU-AM-E19 converted methanol to cell mass more efficiently than others. The ts mutants divided into two groups. One included absolute ts mutants, such as NTU-AM-E15 and NTU-AM-E20, which did not grow even in enriched media at restrictive temperature; the other group, such as NTU-AM-L2, NTU-AM-L3, NTU-AM-E10, NTU-AM-E19, NTU-AM-N37 and NTU-AM-m5, was auxotrophic ts mutants, which grew slightly in enriched media at restrictive temperature.

Dissolution rates of corticoid solutions dispersed on silicas

Two nonporous and three porous amorphous silicas were used as dispersion media to convert corticoid solutions into free-flowing powders. The corticoids (prednisone, prednisolone, and hydrocortisone) were dissolved in N,N-dimethylacetamide-polyethylene glycol 400 (7:3 v/v) and their 10% (w/v) solutions were mixed with the silicas (1:3 v/w). Dissolution rates of the corticoids from such powdered solutions were more rapid than their micronized powders in various aqueous media.