A study of evaporation and friction on hydrated forearm skin

When skin is occluded by continuous wearing of incontinence pads, it becomes over-hydrated, making the skin more susceptible to mechanical damage and bacterial attack than normal skin. This project focused on understanding the impact of skin occlusion on (i) the hydration of the stratum comeum (SC) - the outermost layer of the skin, and (ii) friction between the skin and nonwoven materials. A methodology for measuring the excess water in over-hydrated skin using evaporimetry was developed, validated and used to compare the performances of five commonly used evaporimetry devices, and to investigate their strengths and limitations. All measurements were made on the volar forearm skin of one young female subject. Good reproducibility was found for each of the five devices, but some significant differences were found between measurements made with different devices. Some possible causes for these discrepancies were investigated with partial success: correction factors obtained from various calibration procedures were applied and reduced differences to some extent, but significant difference still remained. It was concluded that the methodology developed could be used with confidence to compare readings made with the same device, but it would be unwise to trust the absolute values obtained until the reasons for differences between devices have been more fully explained. A new approach for measuring the water distribution within the SC - Opto-Thermal Transient Emission Radiometry (OTTER) - was adopted in this work and a methodology was developed for measuring the saturation profile within over-hydrated SC. The relationship between the SC saturation at the surface (measured using OTTER) and the water vapour flux from over-hydrated SC (measured using evaporimetry) was investigated using the volar forearms of three young female subjects. As expected, strong correlation was found during desorption, with a dog-leg in the plot at about 36% saturation from two subjects, which was consistent with the transition between loosely and tightly bound water reported by Berardesca (1997). Two methods for measuring friction between nonwoven materials and the over-hydrated or normal skin were developed and validated, on the volar forearms of five young female subjects. Coefficients of friction were measured with the two methods and compared. Good reproducibility and remarkably good agreement was found between the two methods, even though one of the methods (curved friction) assumed the arm to be a rigid cylinder and the nonwoven material to be inextensible. Additional theoretical work (by Cottenden (2007)) and experimental work (by Karavokiros (2007)) was conducted to explain and extend the findings. The theoretical analysis showed that the equation describing friction around a cylinder is valid for any convex prism, and the experimental work supported the solution very well. It was concluded that the curved method developed was simple to run and produced results with good reproducibility

Purification and characterization of a major secretory cellobiase, Cba2, from Cellulomonas biazotea

A novel cellobiase (Cba2) was purified from the culture supernatant of Cellulomonas biazotea and characterized. Cba2 appeared to be a major secretory cellobiase in C. biazotea as its enzymatic activity was estimated to represent over 40\% of the total extracellular beta -glucosidase activity. The enzyme was purified over 260-fold subsequent to ammonium sulfate precipitation, gel-filtration chromatography, anion-exchange chromatography, and reversed-phase high-performance liquid chromatography. Cba2 was shown by SDS-PAGE to have a large molecular mass of 109 kDa, which makes it one of the largest secretory cellobiases characterized. Its homogeneity was confirmed by N-terminal amino acid sequencing. The Km and Vma values were 0.025 mM and 0.0048 mM min(-1), respectively, for the Cba2 hydrolysis of p-nitrophenyl-beta -D-glucopyranoside, and 0.73 mM and 0.00033 mM min(-1), respectively, for the hydrolysis of cellobiose (at 37 degreesC and pH 7.0). The purified enzyme has a pH optimum of 4.8 and the optimum temperature for activity is 70 degreesC. In view of the secretory nature of Cba2 and the fact that it is a major component of secretory cellobiases of C. biazotea, it is potentially important in the enzymatic degradation of cellulose, and its availability as a recombinant protein may facilitate the studies of its biotechnological. applications. (C) 2001 Academic Press

Kinetics modeling of inhibition and utilization of mixed volatile fatty acids in the formation of polyhydroxyalkanoates by Ralstonia eutropha

Acetic, propionic and butyric acids are the major fermentation acids produced on acidogenesis of organic wastes such as food scraps. They can be utilized by Ralstonia eutropha as sole carbon sources for cell growth and polyhydroxyalkanoate (PHA) synthesis. The acids, however, are inhibitory and toxic to the bacterium depending on the medium pH and the total acid concentration. The inhibition and utilization kinetics of the total acids and individual acids in mixed acid media were investigated in flask batch cultures, and simulated by modified Michaelis-Menten models based on variable cell activity. Cell activity, a function of the total acid concentration, is defined as the active fraction of the measurable residual biomass (RBM) under specific culture conditions, which might be as low as 20\% at high acid concentrations. The overall production rate of PHA is contributed from the utilization rates of individual acids as well as the interaction of two acids such as acetate and propionate, depending on the predominant acids in the medium. R. eutropha preferred propionic acid for cell mass synthesis and butyric acid for polymer synthesis, the latter giving the highest polymer yield (0.39 g/g) among the three acids. In mixtures of predominant acetic and butyric acids, a high PHA formation rate (60 mg/g RBM per h) was achieved, compared with the relatively low PHA formation rate (35 mg/g RBM per h) in the mixtures of predominant acetic and propionic acids. Acetic acid in acid mixtures reduced the metabolism of propionic acid, which resulted in a high rate ratio (up to 0.8) of hydroxyvalerate (HV) formation to the overall PHA formation. (C) 2002 Elsevier Science Ltd. All rights reserved

Orthodontic treatment of anterior open bite

Objective. To review the currently available treatment options of anterior open bite. Methods. Search all major dental journals and literature on treatment and management of anterior open bite. Medline search (1960-2006). Literature and data on treatment and management of anterior open bite with keywords 'open bite', 'anterior open bite', 'orthodontic treatment', 'long face', 'vertical dentoalveolar problem' and 'vertical skeletal problem'. Results. Over 50 articles were found and relevant information and data were reviewed by the authors. It was found that the multifactorial nature of anterior open bite makes its management difficult and various treatment modalities are being used. Clinicians must be able to diagnose the problem and choose the best treatment. Conclusion. Successful treatment of anterior open bite greatly relies on both diagnosis and therapeutics. Although there are many different treatment modalities available, stability after treatment is still a critical issue as evidence on long term stability of various treatment options is lacking. Thus, clinicians should pay more attention during retention phase and long-term studies on post-treatment changes and stability should be encouraged. © 2007 BSPD, IAPD and Blackwell Publishing Ltd.link_to_subscribed_fulltex

Identification of O-antigen polymerase transcription and translation start signals and visualization of the protein in Salmonella enterica serovar Typhimurium

The wzy/rfe gene, encoding the O-antigen polymerase, of Salmonella enterica serovar Typhimurium has been previously cloned and sequenced. In the present work, the wry transcriptional startpoint was initially identified by primer extension. Next, wzy promoter strength in Escherichia coli K-12 was measured, and was found to be greater than that of the induced lac promoter. To define the Wzy translational startpoint, DNA including the wry promoter and the putative first five residues of the Wzy protein was fused to the N-terminus of glutathione-S-transferase, and the fusion protein purified by affinity chromatography. N-terminal amino acid sequencing yielded the Wzy translational startpoint. Next, the Wzy protein was C-terminally tagged with the FLAG peptide, and immunoblotting of an S. typhimurium strain expressing a low-copy wzy-FLAG gene (five copies per cell) localized the intact Wzy protein in the cytoplasmic membrane of S. typhimurium cells. The Wzy protein was not well-expressed from a multi-copy wzy-FLAG + plasmid in S. typhimurium, or in E. coli K-12.link_to_subscribed_fulltex

Construction of an efficient Bacillus subtilis system for extracellular production of heterologous proteins

An efficient expression/secretion vector, designated pM2Veg, was constructed for extracellular production of heterologous proteins in Bacillus subtilis. To construct pM2Veg, a synthetic Cassette, the Veg cassette carrying: (1) the strong vegetative vegI promoter from B. subtilis, (2) the Escherichia coli lac operator, (3) the B. subtilis consensus ribosome-binding site, (4) the Staphylococcal protein A leader sequence, (5) a cloning region for insertion of foreign genes, (6) translational stop codons in all three reading frames, and (7) the gnt transcriptional terminator, was cloned into a derivative of the stable pRB373 B. subtilis/E. coli shuttle plasmid, the pM2 vector. The application of pM2Veg to effect secretory production of heterologous proteins was illustrated using two widely different proteins: the endoglucanase (Eng) encoded by the cenA gene of Cellulomonas fimi and human epidermal growth factor (hEGF). Levels of Eng and hEGF measured in culture supernatant samples of B. subtilis transformants harboring recombinant constructs formed between pM2Veg and the cenA and hEGF genes were 8.3 U ml(-1) and 7.0 mg 1(-1), respectively. The Eng activity is more than four times higher than the yield from the best cenA recombinant construct previously reported, and the hEGF data represents the first successful expression of the factor in B. subtilis. (C) 1998 Elsevier Science B.V. All rights reserved

Identification of O-antigen polymerase transcription and translation start signals and visualization of the protein in Salmonella enterica serovar Typhimurium

The wzy/rfc gene, encoding the O-antigen polymerase, of Salmonella enterica serovar Typhimurium has been previously cloned and sequenced. In the present work, the wry transcriptional startpoint was initially identified by primer extension. Next, wry promoter strength in Escherichia coli K-12 was measured, and was found to be greater than that of the induced lac promoter. To define the Wzy translational startpoint, DNA including the wry promoter and the putative first five residues of the Wzy protein was fused to the N-terminus of glutathione-S-transferase, a nd the fusion protein purified by affinity chromatography. N-terminal amino acid sequencing yielded the Wzy translational startpoint. Next, the Wzy protein was C-terminally tagged with the FLAG peptide, and immunoblotting of an S. typhimurium strain expressing a low-copy wry-FLAG gene (five copies per cell) localized the intact Wzy protein in the cytoplasmic membrane of S. typhimurium cells. The Wzy protein was not well-expressed from a multi-copy wzy-FLAG(+) plasmid in S. typhimurium, or in E. coli K-12

Development and experimental validation of a mathematical model for friction between fabrics and a volar forearm phantom.

An analytical mathematical model for friction between a fabric strip and the volar forearm has been developed and validated experimentally. The model generalizes the common assumption of a cylindrical arm to any convex prism, and makes predictions for pressure and tension based on Amontons' law. This includes a relationship between the coefficient of static friction (mu) and forces on either end of a fabric strip in contact with part of the surface of the arm and perpendicular to its axis. Coefficients of friction were determined from experiments between arm phantoms of circular and elliptical cross-section (made from Plaster of Paris covered in Neoprene) and a nonwoven fabric. As predicted by the model, all values of mu calculated from experimental results agreed within +/- 8 per cent, and showed very little systematic variation with the deadweight, geometry, or arc of contact used. With an appropriate choice of coordinates the relationship predicted by this model for forces on either end of a fabric strip reduces to the prediction from the common model for circular arms. This helps to explain the surprisingly accurate values of mu obtained by applying the cylindrical model to experimental data on real arms

Extracellular expression of human epidermal growth factor encoded by an Escherichia coli K-12 plasmid stabilized by the ytl2-incR system of Salmonella typhimurium

A plasmid stabilization system, active in high copy-number plasmids, was cloned from the large resident plasmid, pSLT, of Salmonella typhimurium, The ytl2 gene, together with a 249-bp region (termed incR) downstream of the gene, imparted > 10(4)-fold stability to a pBR322-based plasmid, The ytl2-incR region was then used to stabilize a recombinant plasmid carrying the human epidermal growth factor gene (with the Escherichia coli K-12 ompA signal sequence), behind the lacUV5 promoter, In shake flask tests to optimize expression of human epidermal growth factor, loss of recombinant plasmid was <1\% when growth (both before and after induction with isopropyl-beta-D-galactopyranoside) took place even in the absence of antibiotic selection, and the specific activity of secreted human epidermal growth factor was ca 20 mu g per 10(8) cells at harvest, compared to a figure of ca 3 mu g per 10(8) cells when a comparable plasmid, but devoid of the ytl2-incR region, was employed, as outgrowth of plasmid-free cells after induction severely compromised the specific activity of the secreted product

Enhanced plasmid stability and production of hEGF by immobilized recombinant E-coli JM101

Recombinant Escherichia coli JM101 was immobilized with porous polyurethane foam (PUF) particle as supporter matrix for human epidermal growth factor (hEGF) production. Flask culture showed that cell immobilization in PUF can improve cell growth and hEGF expression. A bubble column and a three-phase fluidized bed bioreactor by self-design was further applied to produce hEGF, respectively. The results demonstrated that PUF is a feasible immobilized supporter material with good biocompatibility. Immobilization could also decrease the probability for segregational plasmid loss and overgrowth of plasmid-free cells. Cell density, plasmid stability and hEGF productivity were higher than those without the foam matrix, respectively. hEGF productivity was enhanced from 8.73 mg/l It of free-culture to 11.4 mg/l h of immobilized cultivation. (c) 2006 Published by Elsevier B.V