Analysis of tissue responses to fin tagging in Australian carcharhinids

Tissue responses to the application of Rototags and Jumbo Rototags in the first dorsal fin of Carcharhinus melanopterus, C. obscurus and C. plumbeus were examined. The acute response included tissue tearing and haemorrhage and was present by 5 days post-tagging. The intermediate response had begun by 20 days post-tagging and continued beyond 207 days. This response involved decreased red blood cell activity as the inflammatory response commenced. The chronic response had begun by 301 days and was complete by 553 days with a layer of fibrous connective tissue walling off the tag. External damage to the fin was caused by continued abrasion by the tag. Repair scales were observed at 242 days using scanning electron microscopy and were confirmed histologically in 61- and 553-day samples. Repair scales were not seen in areas of continuous abrasion. No infection was observed in tissues surrounding the wound. Disruption of the fin surface was observed due to abrasion by the tag, but did not appear to cause a severe tissue reaction. The tissue responses observed were consistent with a normal, but relatively slow, healing in the vicinity of the tag wound. Use of Rototags or Jumbo Rototags appears to be an efficient way of marking elasmobranchs with minimal damage to the shark. (C) 1998 The Fisheries Society of the British Isles.

A computational analysis of substrate binding strength by phosphorylase kinase and protein kinase A

Protein kinases exhibit various degrees of substrate specificity. The large number of different protein kinases in the eukaryotic proteomes makes it impractical to determine the specificity of each enzyme experimentally. To test if it were possible to discriminate potential substrates from non-substrates by simple computational techniques, we analysed the binding enthalpies of modelled enzyme-substrate complexes and attempted to correlate it with experimental enzyme kinetics measurements. The crystal structures of phosphorylase kinase and cAMP-dependent protein kinase were used to generate models of the enzyme with a series of known peptide substrates and non-substrates, and the approximate enthalpy of binding assessed following energy minimization. We show that the computed enthalpies do not correlate closely with kinetic measurements, but the method can distinguish good substrates from weak substrates and non-substrates. Copyright (C) 2002 John Wiley Sons, Ltd.

[beta]-Hydroxy-F128b-Methylbutyrate (HMB) Supplementation and the Promotion of Muscle Growth and Strength

[beta]-Hydroxy [beta]-methylbutyrate (HMB), a metabolite of the essential amino acid leucine, is one of the latest dietary supplements promoted to enhance gains in strength and lean body mass associated with resistance training. Unlike anabolic hormones that induce muscle hypertrophy by increasing muscle protein synthesis, HMB is claimed to influence strength and lean body mass by acting as an anticatabolic agent, minimising protein breakdown and damage to cells that may occur with intense exercise. Research on HMB has recently tested this hypothesis, under the assumption that it may be the active compound associated with the anticatabolic effects of leucine and its metabolites. While much of the available literature is preliminary in nature and not without methodological concern, there is support for the claims made regarding HMB supplementation, at least in young, previously untrained individuals. A mechanism by which this may occur is unknown, but research undertaken to date suggests there may be a reduction in skeletal muscle damage, although this has not been assessed directly. The response of resistance trained and older individuals to HMB administration is less clear. While the results of research conducted to date appear encouraging, caution must be taken when interpreting outcomes as most manuscripts are presented in abstract form only, not having to withstand the rigors of peer review. Of the literature reviewed relating to HMB administration during resistance training, only 2 papers are full manuscripts appearing in peer reviewed journals. The remaining 8 papers are published as abstracts only, making it difficult to critically review the research. There is clearly a need for more tightly controlled, longer duration studies to verify if HMB enhances strength and muscular hypertrophy development associated with resistance training across a range of groups, including resistance trained individuals.

Effect of ionic strength and clay mineralogy on Na-Ca exchange and the SAR-ESP relationship

The relationship between sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) for all soils has traditionally been assumed to be similar to that developed by the United States Salinity Laboratory (USSL) in 1954. However, under certain conditions, this relationship has been shown not to be constant, but to vary with both ionic strength and clay mineralogy. We conducted a detailed experiment to determine the effect of ionic strength on the Na+-Ca2+ exchange of four clay minerals (kaolinite, illite, pyrophyllite, and montmorillonite), with results related to the diffuse double-layer (DDL) model. Clays in which external exchange sites dominated (kaolinite and pyrophyllite) tended to show an overall preference for Na+, with the magnitude of this preference increasing with decreasing ESP. For these external surfaces, increases in ionic strength were found to increase preference for Na+. Although illite (2:1 non-expanding mineral) was expected to be dominated by external surfaces, this clay displayed an overall preference for Ca2+, possibly indicating the opening of quasicrystals and the formation of internal exchange surfaces. For the expanding 2:1 clay, montmorillonite, Na+-Ca2+ exchange varied due to the formation of quasicrystals (and internal exchange surfaces) from individual clay platelets. At small ionic strength and large ESP, the clay platelets dispersed and were dominated by external exchange surfaces (displaying preference for Na+). However, as ionic strength increased and ESP decreased, quasicrystals (and internal exchange surfaces) formed, and preference for Ca2+ increased. Therefore, the relationship between SAR and ESP is not constant and should be determined directly for the soil of interest.

Two-body and three-body abrasion: A critical discussion

It is argued that the common classification of abrasive wear into 'two-body abrasion' and 'three-body abrasion' is seriously flawed. No definitions have been agreed upon for these terms, and indeed there are two quite different interpretations, the implications of which are mutually inconsistent. In the dominant interpretation, the primary thrust of the two-body/three-body concept is to describe whether the abrasive particles are constrained (two-body) or free to roll (three-body). In this view, two-body abrasion is generally much more severe than three-body. The alternative interpretation emphasises the presence (three-body) or absence (two-body) of a rigid counterface backing the abrasive. In this view, three-body abrasion is equated to high-stress (or grinding) abrasion and is generally more severe than two-body (low-stress) abrasion. This paper recommends that the 'two-body/three-body' terminology be abandoned, to be replaced by an alternative classification scheme based directly upon the manifest severity of wear. (C) 1998 Elsevier Science S.A.

An "openable," high-strength gradient set for orthopedic MRI

A novel three-axis gradient set and RF resonator for orthopedic MRT has been designed and constructed. The set is openable and may be wrapped around injured joints. The design methodology used was the minimization of magnetic field spherical harmonics by simulated annealing. Splitting of the longitudinal coil presents the major design challenge to a fully openable gradient set and in order to efficiently design such coils, we have developed a new fast algorithm for determining the magnetic field spherical harmonics generated by an are of multiturn wire. The algorithm allows a realistic impression of the effect of split longitudinal designs. A prototype set was constructed based on the new designs and tested in a 2-T clinical research system. The set generated 12 mT/m/A with a linear region of 12 cm and a switching time of 100 mu s, conforming closely with theoretical predictions. Preliminary images from the set are presented. (C) 1999 Academic Press.

Synthesis of silica films at the air/water interface: Effect of template chain length and ionic strength

We have grown surfactant-templated silicate films at the air-water interface using n-alkyltrimethylammonium bromide and chloride in an acid synthesis with tetraethyl orthosilicate as the silicate source. The films have been grown with and without added salt (sodium chloride, sodium bromide) and with n-alkyl chain lengths from 12 to 18, the growth process being monitored by X-ray reflectometry. Glassy, hexagonal, and lamellar structures have been produced in ways that are predictable from the pure surfactant-water phase diagrams. The synthesis appears to proceed initially through an induction period characterized by the accumulation of silica-coated spherical micelles near the surface. All syntheses, except those involving C(12)TACl, show a sudden transformation of the spherical micellar phase to a hexagonal phase. This occurs when the gradually increasing ionic strength and/or changing ethanol concentration is sufficient to change the position of boundaries within the phase diagram. A possible mechanism for this to occur may be to induce a sphere to rod transition in the micellar structure. This transformation, as predicted from the surfactant-water phase diagram, can be induced by addition of salts and is slower for chloride than bromide counteranions. The hexagonal materials change in cell dimension as the chain length is changed in a way consistent with theoretical model predictions. All the materials have sufficiently flexible silica frameworks that phase interconversion is observed both from glassy to hexagonal and from hexagonal, to lamellar and vice versa in those surfactant systems where multiple phases are found to exist.

Race and sex effects on the association between muscle strength, soft tissue, and bone mineral density in healthy elders: The Health, Aging, and Body Composition Study

Two factors generally reported to influence bone density are body composition and muscle strength. However, it is unclear if these relationships are consistent across race and sex, especially in older persons. If differences do exist by race and/or sex, then strategies to maintain bone mass or minimize bone loss in older adults may need to be modified accordingly. Therefore, we examined the independent effects of bone mineral-free lean mass (LM), fat mass (FM), and muscle strength on regional and whole body bone mineral density (BMD) in a cohort of 2619 well-functioning older adults participating in the Health, Aging, and Body Composition (Health ABC) Study with complete measures. Participants included 738 white women, 599 black women, 827 white men, and 455 black men aged 70-79 years. BMD (g/cm(2)) of the femoral neck, whole body, upper and lower limb, and whole body and upper limb bone mineral-free LM and FM was assessed by dual-energy X-ray absorptiometry (DXA). Handgrip strength and knee extensor torque were determined by dynamometry. In analyses stratified by race and sex and adjusted for a number of confounders, LM was a significant (p < 0.001) determinant of BMD, except in white women for the lower limb and whole body. In women, FM also was an independent contributor to BMD at the femoral neck, and both PM and muscle strength contributed to limb BMD. The following were the respective Beta-weights (regression coefficients for standardized data, Std beta) and percent difference in BMD per unit (7.5 kg) LM: femoral neck, 0.202-0.386 and 4.7-6.9 %; lower limb,.0.209-0.357 and 2.9-3.5%; whole body, 0.239-0.484 and 3.0-4.7 %; and upper limb (unit = 0.5 kg), 0.231-0.407 and 3.1-3.4%. Adjusting for bone size (bone mineral apparent density [BMAD]) or body size BMD/height) diminished the importance of LM, and the contributory effect of FM became more pronounced. These results indicate that LM and FM were associated with bone mineral depending on the bone site and bone index used. Where differences did occur, they were primarily by sex not race. To preserve BMD, maintaining or increasing LM in the elderly would appear to be an appropriate strategy, regardless of race or sex.

Relationship of interleukin-6 and tumor necrosis factor-alpha with muscle mass and muscle strength in elderly men and women: The health ABC study

Background. A decline in muscle mass and muscle strength characterizes normal aging. As clinical and animal studies show it relationship between higher cytokine levels and low muscle mass, the aim of this study was to investigate whether markers, of inflammation are associated with muscle mass and strength in well-functioning elderly persons. Methods. We Used baseline data (1997-1998) of the Health, Aging, and Body Composition (Health ABC) Study on 3075 black and white men and women aged 70-79 years. Midthigh muscle cross-sectional area (computed tomography), appendicular muscle mass (dual-energy x-ray ab absorptiometry). isokinetic knee extensor strength (KinCom). and isometric inip strength were measured. plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were assessed by enzyme-linked immunosorbent assay (ELISA). Results. Higher cytokine levels were generally associated with lower muscle mass and lower muscle strength. The most consistent relationship across the gender and race groups was observed for IL-6 and grip strength: per SD increase in IL-6, grip strength was 1.1 to 2.4 kg lower (p < .05) after adjustment for age, clinic Site. health status, medications, physical activity. smoking. height. and body fat. Ail overall measure of elevated cytokine level was created by combining the levels of IL-6 and TNF-alpha. With the exception of white men, elderly persons having high levels of IL-6 (> 1.80 pg/ml) as well as high levels of TNF-alpha (> 3.20 pg/ml) had a smaller muscle area, less appendicular mass. a lower knee extensor strength. and a lower grip strength compared to those with low levels of both cytokines. Conclusions. Higher plasma concentrations of IL-6 and TNF-alpha are associated with lower muscle mass and lower muscle strength in well-functioning older men and women. Higher cytokine levels. as often observed in healthy older persons. may contribute to the loss Of muscle mass and strength that accompanies aging.

ERP 'old/new' effects: memory strength and decisional factor(s)

Event-related potentials (ERPs) were recorded while subjects made old/new recognition judgments on new unstudied words and old words which had been presented at study either once ('weak') or three times ('strong'). The probability of an 'old' response was significantly higher for strong than weak words and significantly higher for weak than new words. Comparisons were made initially between ERPs to new, weak and strong words, and subsequently between ERPs associated with six strength-by-response conditions. The N400 component was found to be modulated by memory trace strength in a graded manner. Its amplitude was most negative in new word ERPs and most positive in strong word ERPs. This 'N400 strength effect' was largest at the left parietal electrode (in ear-referenced ERPs). The amplitude of the late positive complex (LPC) effect was sensitive to decision accuracy (and perhaps confidence). Its amplitude was larger in ERPs evoked by words attracting correct versus incorrect recognition decisions. The LPC effect had a left > right, centro-parietal scalp topography (in ear-referenced ERPs). Hence, whereas, the majority of previous ERP studies of episodic recognition have interpreted results from the perspective of dual-process models, we provide alternative interpretations of N400 and LPC old/new effects in terms of memory strength and decisional factor(s). (C) 2002 Elsevier Science Ltd. All rights reserved.

Micromorphological study of slumping in a hardsetting seedbed under various wetting conditions

Slumping of hardsetting seedbeds upon wetting has not been extensively studied despite the likelihood that it determines the physical properties after drying. Slumping results from processes similar to those involved in crusting except that overburden pressure can dominate rather than rainfall kinetic energy. Only a few studies have dealt with the morphological description of slumping. To simulate different climatic and management conditions, repacked seedbeds of a hardsetting sandy-loam soil were subjected to a range of wetting conditions, e.g. capillary rise, immersion, and rainfall simulation. Slumping processes were characterized using qualitative and quantitative micromorphological observations of polished blocks and thin sections from resin-impregnated samples. A morphogenetical framework was proposed to help description of the complex associations of processes which can lead to structural collapse (crusting and slumping) on wetting. Three main stages were considered, i.e. aggregate disruption or abrasion, relocation of the released material, and compaction. In the hardsetting material studied here, structural collapse under slow wetting occurred at the bottom of cores due to aggregate coalescence under overburden pressure. Coalescence required aggregate cohesion being reduced by microcracking; therefore, it differed from the coalescence previously described in unstable silty loam soils where microcracking was not necessary for aggregates to coalesce. Macroporosity decreased most strongly under fast wetting due to physical dispersion and aggregate breakdown. Under simulated rainfall, compaction by raindrops could not be distinguish from aggregate breakdown. The role of overburden pressure and of rainfall kinetic energy remains to be stated; new data are required including measurement of total porosity in the initial, wet, and dry states. (C) 2003 Elsevier B.V. All rights reserved.

Molecular motion in miscible polymer blends .1. Motion in blends of PEO and PVPh studied by solid-state C-13 T-1 rho measurements

Changes in molecular motion in blends of PEO-PVPh have been studied using measurements of C-13 T-1 rho relaxation times. C-13 T-1 rho relaxation has been confirmed as arising from spin-lattice interactions by observation of the variation in T-1 rho with rf field strength and temperature. In the pure homopolymers a minimum in T-1 rho is observed at ca. 50 K above the glass transition temperatures detected by DSC. After blending, the temperature of the minimum in T-1 rho for PEO increased, while that for PVPh decreased, however, the minima, which correspond to the temperatures where the average correlation times for reorientation are close to 3.1 mu s, are separated by 45 K (in a 45% PEO-PVPh blend). These phenomena are explained in terms of the local nature of T-1 rho measurements. The motions of the individual homopolymer chains are only partially coupled in the blend. A short T-1 rho has been observed for protonated aromatic carbons, and assigned to phenyl rings undergoing large-angle oscillatory motion, The effects of blending, and temperature, on the proportion of rings undergoing oscillatory motion are analyzed.

Studies of solute self-association by sedimentation equilibrium: allowance for effects of thermodynamic non-ideality beyond the consequences of nearest-neighbor interactions

A sedimentation equilibrium study of a-chymotrypsin self-association in acetate-chloride buffer, pH 4.1 I 0.05, has been used to illustrate determination of a dimerization constant under conditions where thermodynamic non-ideality is manifested beyond the consequences of nearest-neighbor interactions. Because the expressions for the experimentally determinable interaction parameters comprise a mixture of equilibrium constant and excluded volume terms, the assignment of reasonable magnitudes to the relevant virial coefficients describing non-associative cluster formation is essential for the evaluation of a reliable estimate of the dimerization constant. Determination of these excluded volume parameters by numerical integration over the potential-of-mean-force is shown to be preferable to their calculation by approximate analytical solutions of the integral for this relatively small enzyme monomer with high net charge (+ 10) under conditions of low ionic strength (0.05 M). (C) 2001 Elsevier Science B.V. All rights reserved.

beta-hydroxy-beta-methylbutyrate (HMB) supplementation does not affect changes in strength or body composition during resistance training in trained men

This investigation evaluated the effects of oral beta -Hydroxy-beta -Methylbutyrate (HMB) supplementation on training responses in resistance-trained male athletes who were randomly administered HMB in standard encapsulation (SH), HMB in time release capsule (TRH), or placebo (P) in a double-blind fashion. Subjects ingested 3 g (.) day(-1) of HMB; or placebo for 6 weeks. Tests were conducted pre-supplementation and following 3 and 6 weeks of supplementation. The testing battery assessed body mass, body composition (using dual energy x-ray absorptiometry), and 3-repetition maximum isoinertial strength, plus biochemical parameters, including markers of muscle damage and muscle protein turnover. While the training and dietary intervention of the investigation resulted in significant strength gains (p < .001) and an increase in total lean mass (p =.01), HMB administration had no influence on these variables. Likewise, biochemical markers of muscle protein turnover and muscle damage were also unaffected by HMB supplementation. The data indicate that 6 weeks of HMB supplementation in either SH or TRH form does not influence changes in strength and body composition in response to resistance training in strength-trained athletes.

Effects of suppressed bone turnover by bisphosphonates on microdamage accumulation and biomechanical properties in clinically relevant skeletal sites in beagles

We recently demonstrated that suppression of bone remodeling allows microdamage to accumulate, leading to reduced bone toughness in the rib cortex of dogs. This study evaluates the effects of reduced bone turnover produced by bisphosphonates on microdamage accumulation and biomechanical properties at clinically relevant skeletal sites in the same dogs. Thirty-six female beagles, 1-2 years old, were divided into three groups. The control group was treated daily for 12 months with saline vehicle (CNT), The remaining two groups were treated daily with risedronate at a dose of 0.5 mg/kg per day (RIS), or alendronate at 1.0 mg/kg per day (ALN) orally, The doses of these bisphosphonates were six times the clinical doses approved for treatment of osteoporosis in humans. After killing, the L-1 vertebra was scanned by dual-energy X-ray absorptiometry (DXA), and the L-2 vertebra and right ilium were assigned to histomorphometry, The L-3 vertebra, left ilium, Th-2 spinous process, and right femoral neck were used for microdamage analysis. The L-4 vertebra and Th-1 spinous process were mechanically tested to failure in compression and shear, respectively. One year treatment with risedronate or alendronate significantly suppressed trabecular remodeling in vertebrae (RIS 90%, ALN 95%) and ilium (RIS 76%, ALN 90%) without impairment of mineralization, and significantly increased microdamage accumulation in all skeletal sites measured. Trabecular bone volume and vertebral strength increased significantly following 12 month treatment. However, normalized toughness of the L-4 vertebra was reduced by 21% in both RIS (p = 0.06) and ALN (p = 0.05) groups. When the two bisphosphonate groups were pooled in a post hoc fashion for analysis, this reduction in toughness reached statistical significance (p = 0.02), This study demonstrates that suppression of trabecular bone turnover by high doses of bisphosphonates is associated with increased vertebral strength, even though there is significant microdamage accumulation and a reduction in the intrinsic energy absorption capacity of trabecular bone. (C) 2001 by Elsevier Science Inc. All rights reserved.