Physical mechanisms for chemotactic pattern formation by bacteria

This paper formulates a theory for chemotactic pattern formation by the bacteria Escherichia coli in the presence of excreted attractant. In a chemotactically neutral background, through chemoattractant signaling, the bacteria organize into swarm rings and aggregates. The analysis invokes only those physical processes that are both justifiable by known biochemistry and necessary and sufficient for swarm ring migration and aggregate formation. Swarm rings migrate in the absence of an external chemoattractant gradient. The ring motion is caused by the depletion of a substrate that is necessary to produce attractant. Several scaling laws are proposed and are demonstrated to be consistent with experimental data. Aggregate formation corresponds to finite time singularities in which the bacterial density diverges at a point. Instabilities of swarm rings leading to aggregate formation occur via a mechanism similar to aggregate formation itself: when the mass density of the swarm ring exceeds a threshold, the ring collapses cylindrically and then destabilizes into aggregates. This sequence of events is demonstrated both in the theoretical model and in the experiments.     

Doppler grid surface scanning applications for pulmonary subsurface parenchymal perfusion assessment

Subsurface perfusion to lung parenchyma underlying the pleura is difficult to assess in live ventilated animals. The purpose of this study was to assess applicability of a newly developed laser Doppler grid scanning imaging technology that measures perfusion of pleural subsurface lung regions in intact normal and abnormal animal lungs. Eighty-six Doppler grid perfusion measurements were performed in five New Zealand White Rabbits (3-5 kg); four with unilateral bullous lung disease, one normal control. Left upper lobe lung surface was exposed to 10 1-sec spot Nd:YAG exposures (70 W/cm2). One week following laser exposure, all rabbits underwent sequential bilateral open thoracotomy. Unaffected left lower lobes in these animals and all four lobes of a previously untreated rabbit were used as controls. Pleural subsurface perfusion measurements were recorded over a contiguous 900-pixel square surface grid using quantitative noncontact laser Doppler imaging during open thoracotomy procedures. Scans were obtained in a normal volume ventilation mode, at 30 cm of inspiratory hold airway pressure, and postinflation. A perfusion-pressure response curve was obtained in normal lung at 10-, 20-, and 30-cm static airway pressure. Post mortem measurements were used as 0 flow controls. Normal lung tissue was found to have relatively high pleural subsurface perfusion (1362 +/- 328 corrected units on a scale of 0-4095). Areas of atelectasis had decreased perfusion (659 +/- 512 U., 48.4 +/- 12.5% compared to normal lung, p < 0.02), but returned to normal levels after inflation of the lung (1253 +/- 363 U., p = 0.21 compared to normal). Pleural subsurface perfusion decreased uniformly and progressively as lung inflation pressure increased (p < 0.0001). Perfusion increased immediately to supranormal values following release of high inspiratory inflation pressure holds (1603 +/- 626 U., 117 +/- 18% compared to normal lung, p = 0.03). Bullae had markedly decreased perfusion (541 +/- 68 U.) that was not further reduced by increased inflation pressures. Noncontact laser Doppler grid perfusion imaging appears to provide a new tool for measuring pleural subsurface perfusion over a large area of lung surface in clinical experimental settings. Results are rapid, reproducible, and consistent. Sampling errors inherent in current point sampling Doppler flow techniques are reduced by the multiple contiguous measurements. We have used this technique to demonstrate inspiratory pressure-related reduction in pleural subsurface perfusion in normal lung, reversible decreased perfusion in atelectatic regions, and reduced perfusion in bullous and laser-treated lung regions.     

Decomposition of nitric oxide and its reduction by CO over superconducting and related cuprate catalysts

Catalytic activities of five non-conducting and three superconducting cuprates were measured for the decomposition of NO and the reduction of NO by CO. The concentration of the reactants and the space velocities approximate the conditions of automotive catalysts. In contrast to earlier results, obtained at 20 to 30 times higher partial pressures of NO and 20 to 100 times lower space velocities, none of the catalysts, including five perovskite-like cuprates, showed significant activity for the decomposition of NO at reaction temperatures up to 700 °C. All catalysts were fairly active for the reduction of NO. At temperatures above about 400 °C on the perovskite-like cuprates YBa₂Cu₃O_7-x and Ba₂CuO_3.5-x , the rates for NO reduction were higher than on CuO. All catalysts lost activity for NO reduction in the presence of oxygen (oxidizing conditions).     

Lipid binding properties of a factor necessary for linoleic acid desaturation

Suspension and centrifugation of crude microsomes of rat liver in low ionic strength solution separated a soluble protein fraction that is necessary for the full activity of the linoleic acid desaturase. The fraction partially purified through Sephadex G-150 still retains lipids which are mainly constituted by phosphatidylcholine. Linoleic acid predominates in the fatty acid composition. By NaCl gradient centrifugation and electrophoresis in gelatinized cellulose acetate, the factor behaves like a lipoprotein. The factor binds linoleic acid and linolyl-CoA that are desaturated to γ-linolenic acid when incubated with washed microsomes. Albumin does not replace the factor.     

Older workers in the construction industry: results of a routine health examination and a five year follow up

OBJECTIVE: To describe the health status of older construction workers and the occurrence of early retirement due to disability or of mortality within a five year follow up. METHODS: Firstly, a cross sectional study was performed among 4958 employees in the German construction industry, aged 40-64 years, who underwent standardised routine occupational health examinations in 1986-8. The study population included plumbers, carpenters, painters/varnishers, plasterers, unskilled workers, and white collar workers (control group). Job specific prevalence and age adjusted relative prevalence were calculated for hearing loss, abnormal findings at lung auscultation, reduced forced expiratory volume, increased diastolic blood pressure, abnormalities in the electrocardiogram, increased body mass index, hypercholesterolaemia, increased liver enzymes, abnormal findings in an examination of the musculoskeletal system, and abnormalities of the skin. Secondly, follow up for disability and all cause mortality was ascertained between 1992 and 1994 (mean follow up period = 4.5 y). Job specific crude rates were calculated for the occurrence of early retirement due to disability and for all cause mortality. With Cox's proportional hazards model, job specific relative risks, adjusted for age, nationality, and smoking were obtained. RESULTS: Compared with the white collar workers, a higher prevalence of hearing deficiencies, signs of obstructive lung diseases, increased body mass index, and musculoskeletal abnormalities were found among the construction workers at the baseline exam. During the follow up period, 141 men died and 341 men left the labour market due to disability. Compared with white collar workers, the construction workers showed a 3.5 to 8.4-fold increased rate of disability (P < 0.05 for all occupational groups) and a 1.2 to 2.1-fold increased all cause mortality (NS). CONCLUSIONS: This study shows the need and possibilities for further health promotion in workers employed in the construction industry, targeting both work related conditions and personal lifestyle factors. Rehabilitation measures should be enforced to limit the rate of disability among construction workers.     

The rise and fall of atrial natriuretic peptide for acute renal failure

Varices in unusual sites constitute a minor but significant cause of gastrointestinal bleeding in patients with liver disease. We report a case of varices across the anastomotic line between the jejunum and gallbladder after cholecystojejunostomy. Although such varices have been demonstrated by angiography, to our knowledge they have never been demonstrated by small bowel enema (enteroclysis). We report a case and describe the findings on enteroclysis.     

CO2 and Nd:YAG laser-induced pulmonary parenchymal lung injury in a rabbit model

Laser exposure of the pulmonary parenchyma during treatment of emphysema and other clinical indications causes acute lung injury. Animal investigations are needed to understand and control laser-induced lung injury. We hypothesized that lung injury is deeper from Nd:YAG laser exposures than CO2 exposures because of deeper penetration of Nd:YAG wavelength light. We compared the temporal evolution of histologic injury in rabbits resulting from continuous mode shallow CO2 and Nd:YAG laser pulmonary parenchymal exposures applied in rabbits. Forty-six New Zealand white (NZW) rabbits underwent treatment with CO2 laser (n=18), Nd:YAG laser (n=18), or sham thoracotomy control (n=10) to the visceral pleural surface using 1 min of exposure (5 watts, defocused to 70 W/cm2 power density for both lasers). Animals were killed at 0, 4, 7, 21, and 49 d after exposure. Lung injury, similar to that seen clinically in humans, developed in all laser-treated animals. Injury progressed from ischemia and vascular congestion, to edema and necrosis, followed by pleural and parenchymal fibrosis. The acute injury was qualitatively distinct and slightly deeper in CO2 than Nd:YAG-treated animals (p<0.02) despite the shallower depth of penetration of the CO2 laser. These findings may imply that higher absorption coefficient for CO2 laser energy results in greater focal temperatures and injury in the areas of direct exposure, and suggest that Nd:YAG laser exposure at these settings may cause shallower injury than CO2 lasers in humans undergoing clinical treatment.     

Adoptive immunotherapy for Epstein-Barr virus-related lymphoma

Epstein-Barr virus (EBV) causes opportunistic B cell lymphomas in patients whose cellular immunity is compromised. We have been investigating whether infusions of donor-derived, EBV-specific cytotoxic T cells can prevent and/or treat EBV-related lymphoproliferative disease in children receiving T cell-depleted bone marrow from HLA-matched, unrelated or HLA-mismatched, related donors. In this review, we discuss the rationale for this therapeutic approach, describe our experiences with the regimen thus far, and consider some future directions in immunotherapy.