Creep behaviour and dislocation substructure evolution in the KBr-Kl system

Creep behaviour and dislocation substructure as a function of strain was investigated for two solid solution alloys and the pure components in the KBr-Kl system. The creep characteristics for the KBr-Kl alloys are in good agreement with creep behaviour observed in other ionic and class I metallic solid solution alloys, where the creep rate is controlled by a viscous dislocation glide process. The creep resistance of the KBr-KI alloys is higher than that for the pure components at the same value of homologous temperature. The dislocation substructure of the KBr-Kl alloys and pure components at large strains consists of well defined subgrains. Subgrain formation is shifted to larger strains in the alloys compared to the pure components as a result of solute drag forces on dislocations during glide.     

Prophylactic activity of tetracycline against Brugia pahangi infection in jirds (Meriones unguiculatus)

The ability of oral tetracycline to inhibit the development of third-stage infective larvae (L3) of Brugia pahangi to adult worms in jirds was studied using 2 experimental protocols. Jirds treated with 1.4% tetracycline in drinking water for a period beginning 30 days before inoculation of L3 until 30 days post-inoculation (DPI) had 97% reduction in adult worm recovery compared to untreated controls. Jirds that received 1.2% tetracycline in drinking water beginning 1 day before until either 12 or 26 DPI had adult worm recoveries of 11% and < 1%, respectively. Untreated jirds and those given tetracycline beginning at or later than 13 DPI had similar adult worm recovery (27-29%). Prepatent periods were prolonged, and circulating microfilariae were reduced in jirds given tetracycline from 27 to 54 DPI compared to controls. These data indicate that tetracycline administered to jirds in drinking water inhibits B. pahangi development from L3 to adult worms and suggest that this effect occurs during early larval development. Tetracycline administered to infected jirds prior to and continuing through the onset of patency can also affect development of microfilaremia.     

Emergency medicine and the development of the Food and Drug Administration''s final rule on informed consent and waiver of informed consent in emergency research circumstances

The quality of dental unit water is of considerable importance since patients and dental staff are regularly exposed to water and aerosols generated from the dental unit. The unique feature of dental chair water lines is the capacity for rapid development of a biofilm on the dental water supply lines combined with the generation of potentially contaminated aerosols. The biofilm, which is derived from bacteria in the incoming water and is intrinsically resistant to most biocides, then becomes the primary reservoir for continued contamination of the system. Dental water may become heavily contaminated with opportunistic respiratory pathogens such as Legionella and Mycobacterium spp. The significance of such exposure to patients and the dental team is discussed. There is at the present time, no evidence of a widespread public health problem from exposure to dental unit water. Nevertheless, the goal of infection control is to minimise the risk from exposure to potential pathogens and to create a safe working environment in which to treat patients. This paper evaluates the range of currently available infection control methods and prevention strategies which are designed to reduce the impact of the biofilm on dental water contamination, and are suitable for use in general practice. Bacterial load in dental unit water can be kept at or below recommended guidelines for drinking water (less than 200 colony forming units/ml) using a combination of readily available measures and strict adherence to maintenance protocols. Sterile water should be employed for all surgical treatments.     

Correlation of increased expression of intercellular adhesion molecule-1, but not high levels of tumor necrosis factor-alpha, with lethality of Plasmodium yoelii 17XL, a rodent model of cerebral malaria

Thirty-nine infants, previously examined as neonates, were re-examined at 1 year of age with continuous wide-band noise acoustic rhinometry using a specific probe optimized for infants, to determine the dimensional growth and maturation of nasal airway geometry in otherwise healthy infants. During the first year of life, the acoustically determined dimensions of the nasal airways increased significantly. The total minimal cross-sectional area increased by 67% (0.21 cm2-->0.35 cm2), the volume of the anterior 4 cm of the nasal airway by 36% (1.80 cm3-->2.44 cm3) and the distance to the minimum cross-sectional area by 19% (0.78 cm-->0.93 cm). The rhinometric values of male infants were significantly larger than those of females. However, after adjusting for the significantly larger anthropometric values of males, the difference disappeared, indicating that it was mainly due to body size and not directly to gender. A highly significant correlation (r=0.44, p < 0.006) was observed between the minimum cross-sectional area and head circumference, which anatomically are the most closely related rhinometric and anthropometric values. Furthermore, when differentiating between infants with or without signs of nasal congestion during the fortnight preceding the rhinometric evaluation, a reduction in the total volume of the anterior 4 cm (17% p <0.02) and minimum cross-sectional area (12%, ns) was observed after adjustment. We conclude that the optimized acoustic rhinometric probe is a useful investigative modality, permitting studies of upper airway physiology of healthy and diseased infants.     

Characterization of the transthyretin acid denaturation pathways by analytical ultracentrifugation: implications for wild-type, V30M, and L55P amyloid fibril formation

Analytical ultracentrifugation methods were utilized to further characterize the acid denaturation pathways of wild-type, V30M, and L55P transthyretin (TTR) that generate intermediates leading to amyloid fibril formation and possibly the diseases senile systemic amyloidosis and familial amyloid polyneuropathy. Equilibrium and velocity methods were employed herein to characterize the TTR quaternary structural requirements for amyloid fibril formation. From neutral to slightly acidic conditions (pH 7.5-5.1), wild-type transthyretin (0.2-0.3 mg/mL, 100 mM KCl, 37 degrees C) exists as a tetramer and is incapable of fibril formation. Under more acidic conditions (pH 5 to 3.9), tetrameric wild-type TTR slowly dissociates to a monomer having an alternatively folded tertiary structure(s) that self-assembles at physiological concentration (0.2 mg/mL) into a ladder of quaternary structural intermediates of increasing molecular weight. These intermediates appear to be on the pathway of amyloid fibril formation, since they ultimately disappear when amyloid fibrils are observed. The V30M and L55P TTR variants exhibit similar acid denaturation pathways, with the exception that dissociation of the tetramer to the monomeric amyloidogenic intermediate occurs at a higher pH and to a much greater extent, allowing the quaternary structural intermediates to be readily observed by velocity methods. Partial denaturation and assembly of the monomeric amyloidogenic intermediate(s) occur at pH 5.4 for V30M and L55P TTR over a 72 h period, during which wild-type TTR maintains its normal tetrameric three-dimensional structure. Interestingly, the L55P and V30M familial amyloid polyneuropathy (FAP) associated variants form amyloid protofilaments at pH 7.5 (37 degrees C) after several weeks of incubation, suggesting that the activation barriers for TTR tetramer dissociation to the monomeric amyloidogenic intermediate are much lower for the FAP variants relative to wild-type TTR, which does not form amyloid or amyloid protofilaments under these conditions. This study establishes the key role of the monomeric amyloidogenic intermediate and its self-assembly into a ladder of quaternary structural intermediates for the formation of wild-type, V30M, and L55P transthyretin amyloid fibrils.     

Diaphragmatic and cardiac motion during suspended breathing: preliminary experience and implications for breath-hold MR imaging

PURPOSE: To investigate and quantify motion of the diaphragm and heart during suspended breathing at end inspiration and end expiration. MATERIALS AND METHODS: In 10 healthy adult volunteers, line scanning was performed to monitor the position of the diaphragm during a breath hold at end inspiration and end expiration, with a spatial and temporal resolution of 0.25 mm and 200 msec, respectively. Electrocardiographically gated, turbo fast low-angle shot (FLASH) magnetic resonance (MR) imaging was performed to monitor movement of the diaphragm and heart. RESULTS: During a breath hold, the diaphragm moved upward. At end expiration, the velocity of the diaphragm during suspended breathing was constant (mean, 0.15 mm/sec). At end inspiration, motion of the diaphragm during suspended breathing was more complex (range, 0.1-7.9 mm/sec). During a 20-second breath hold, mean displacement of the diaphragm was 25% of that during normal breathing. FLASH MR imaging revealed variations in the position of the heart during a breath hold. During suspended respiration, the heart did not return to the same position on consecutive heartbeats and, consequently, the margins of the heart typically moved inward. CONCLUSION: Breath holding does not eliminate motion of the diaphragm. Changes in the motion of the diaphragm and transthoracic pressure during a breath hold result in complex movement of the heart and may cause blurring during breath-hold MR imaging.     

Structure of the spiroketal-macrolide ossamycin

The effect of grafting mastoid cavities with small Davis cutaneous pinch grafts was assessed in 15 patients. Following revision of the cavity and Davis pinch grafting the resultant cavity was completely dry in 13 patients (87%) over a period ranging from 1 to 30 months with a mean of 7.3 months, with five becoming dry within 1 month. Patient satisfaction with respect to reduction in discharge and smell was excellent (87%). We believe that the Davis graft technique has a beneficial role in persistent post-mastoidectomy otorrhoea especially when previous standard revision techniques have failed.     

The persistence of fatigue in chronic fatigue syndrome and multiple sclerosis: development of a model

Muscle wasting and weakness are common features of patients with critical illnesses, and may impair their recovery. This study examines whether cytoskeletal and contractile proteins are damaged, and which proteolytic mechanisms might be involved, in the muscle fibre atrophy or necrosis associated with the acute myopathy of critically ill patients. Ninety-eight muscle biopsies were obtained by the conchotome method from 57 critically ill patients and examined morphometrically and by immunohistochemical labelling. Sequential biopsies showed a mean reduction in fibre cross-sectional areas of 3-4% per day. More intense immunolabelling for desmin was seen in the smaller fibres of 52% of the biopsies, while immunolabelling for dystrophin, actin and myosin heavy chains was maintained. Myosin ATPase activity was weak in the smaller fibres in some biopsies, and electron microscopy showed the loss of myosin filaments in atrophic fibres. These changes suggest that loss of the filamentous structure of myosin, without degradation of the immunolabelled epitopes, leads to the collapse of the intermyofibrillar desmin network. Fibres with abnormal desmin labelling showed increased cathepsin B, lysozyme and ubiquitin immunolabelling. Nine cases showed increased immunolabelling for heat shock protein 72. The changes in desmin immunolabelling were more prevalent in patients with higher APACHE II scores on admission, but were not related to other clinical features. The results indicate that fibre atrophy is associated with myosin filament depolymerization and the presence of several proteolytic enzymes. In our study, these changes occurred in patients who were critically ill but who did not receive large doses of steroids or neuromuscular blocking agents.