Physiology of aging related to outcome in the adult respiratory distress syndrome

Thirty-nine patients with adult respiratory distress syndrome (ARDS) were enrolled in a study to identify potential age-related changes in organ system function that may help explain the apparent association between age and poor outcome in these patients. Criteria for enrollment included an arterial PO2-to-inspired O2 concentration ratio less than or equal to 200 in a clinical setting consistent with ARDS. Patients were excluded if they were less than 18 yr old, had clinical manifestations of congestive heart failure, were seropositive for the human immunodeficiency virus, or had stage II metastatic lung cancer. Patients were divided into two groups: those less than 60 yr old (mean 42 +/- 3 yr, n = 17) and those greater than or equal to 60 yr old (73 +/- 2 yr, n = 16). A group of six patients was analyzed as a separate subset based on a body temperature less than or equal to 97.5 degrees F at enrollment (hypothermic patients, 73 +/- 4 yr old). Sepsis was present in 67% of the nonhypothermic patients and in all the hypothermic patients. Mortality rates were 12% in the patients less than 60 yr and 69% in the nonhypothermic patients greater than or equal to 60 yr. All the hypothermic patients died. Sequential data obtained over 6 days were compared within and between groups. The following results were obtained. 1) The ratio of arterial PO2 to inspired O2 fraction was greater and the positive end-expiratory pressure used was significantly less in the patients greater than or equal to 60 yr old compared with the younger group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regional Reductions of Transketolase in Thiamine-Deficient Rat Brain

Abstract: Thiamine deficiency impairs oxidative metabolism and causes metabolic encephalopathy. An early reduction in transketolase (TK) activity may be an important pathogenic event. To assess the role of TK, we have delineated the regional/cellular distribution of TK protein and mRNA in adult rat brain in pyrithiamine-induced thiamine deficiency. TK activity declined in both vulnerable and spared regions. Immunoblots showed a parallel reduction of TK protein. With a few exceptions, immunocytochemistry indicated an overall decline of TK immunoreactivity and the decrease was not specific to vulnerable areas. In contrast to the pronounced, general decline of TK protein, in situ hybridization revealed a regional decrease of 0–25% of TK mRNA in thiamine deficiency. Northern blots indicated a similar level of TK mRNA in whole brain in thiamine deficiency. These results show that the decline of TK activity results from a proportional decrease of TK protein, and the deficiency may be due to an instability of TK protein or an inhibition of TK mRNA translation. The lack of correlation of the distribution, and the absence of specific alteration, of TK in affected regions suggest that the reduced TK may not be linked directly to selective vulnerability in thiamine deficiency.     

A study on the in vivo digestibility of retrograded starch

The digestibility of different forms of starch was examined in an ileostomy model. Six otherwise healthy ileostomists were fed a controlled polysaccharide-free diet for four days, on three of which a test starch was added at breakfast. 50 g starch was fed as either whole or homogenized chick peas or as a retrograded starch gel. A readily digestible wheat starch biscuit was used as a control. Ileostomy effluent was collected every 2 hours over a 16 hour period and a final collection made at 24 hours after the test meal. The monosaccharide composition and glycosyl linkages of the residual carbohydrate in the 2 hour peak period following the test meal was determined. Following consumption of the starch gel, poly- and oligo-saccharides from mucin and starch were identified in the effluent. At the peak of effluent production following the test meal, the average ratio of starch polysaccharide to mucin was 1:0.4. Of the 50 g of starch consumed, 7% of the starch escaped digestion in this fraction. Following consumption of cooked, cooled chick peas, which were fed whole or homogenized, polysaccharides deriving from starch, mucin and the cell wall were detected in the effluent. It was estimated from comparison of the composition of the food and effluent that 14% and 16% of the ingested starch in the form of homogenized and whole chick peas had escaped digestion in the small intestine. Linkage analysis showed the chemical structure of the starch escaping digestion after feeding the whole and homogenized chick peas was similar to that obtained after feeding the starch gel.     

Line-scanning microphotolysis for diffraction-limited measurements of lateral diffusion.

Fluorescence microphotolysis was combined with confocal laser-scanning microscopy to yield a method, herein referred to as line-scanning microphotolysis (LINESCAMP), for the measurement of molecular transport at a lateral resolution of approximately 0.34 microns and a temporal resolution of approximately 0.5 ms. A confocal microscope was operated in the line scan mode, while the laser beam power could be switched during scanning between low monitoring and high photolysing levels in less then a microsecond. The number and location of line segments to be photolysed could be freely determined. The length of the photolysed segments could be also chosen and was only limited by diffraction. Together with instrumentation a new, completely general, theoretical framework for the evaluation of diffusion measurements was developed. Based on the numerical simulation of diffusion processes employing a modified Crank-Nicholson scheme, the theory could be applied to any photobleaching geometry and profile as the initial condition and took into account the convolution with the microscope point spread function. With small diffraction-limited areas, the method yielded accurate values for diffusion coefficients in the range between approximately 10(-4) and 1 micron2 s-1. A first application of the method to the diffusion of a fluorescently labeled tracer inside the cell nucleus showed the potential of the method for the study of complex biological systems.     

Subject: foraging

Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressBehavior: Foraging

Subject: foraging     

Kanamycin resistance as a selectable marker for plastid transformation in tobacco

We report on a novel chimeric gene that confers kanamycin resistance on tobacco plastids. The kan gene from the bacterial transposon Tn5, encoding neomycin phosphotransferase (NPTII), was placed under control of plastid expression signals and cloned between rbcL and ORF512 plastid gene sequences to target the insertion of the chimeric gene into the plastid genome. Transforming plasmid pTNH32 DNA was introduced into tobacco leaves by the biolistic procedure, and plastid transformants were selected by their resistance to 50 g/ml of kanamycin monosulfate. The regenerated plants uniformly transmitted the transplastome to the maternal progeny. Resistant clones resulting from incorporation of the chimeric gene into the nuclear genome were also obtained. However, most of these could be eliminated by screening for resistance to high levels of kanamycin (500 g/ml). Incorporation of kan into the plastid genome led to its amplification to a high copy number, about 10000 per leaf cell, and accumulation of NPTII to about 1% of total cellular protein.     

Fine root growth and demographic responses to nutrient patches in four old-field plant species

Proliferation of roots in a nutrient patch can occur either as a result of an increase in root length (morphological response) or by a change in root birth or death rates (demographic responses). In this study we attempted to distinguish between these two mechanisms of response to nutrient patches and to compare the responses of four old-field plant species (two annuals, two perennials). For all four species combined, there were significant increases in root numbers and root length in fertilized patches. Root proliferation in fertilized patches was largely due to increased birth (=branching) rates of new roots. However, there was also a significant increase in root death rates in the fertilized patches which reduced the magnitude of the increase in net root numbers. Plots for individual species suggested they differed in the magnitude and timing of root proliferation in fertilized patches due to differences in root birth and death rates. However, because of the limited sample size in this study, there was only a marginally significant difference among species in root birth rates, and no difference in death rates. Further studies are currently underway to better quantify species differences in the demographic mechanism, as well as magnitude, of response to nutrient patches and if this would affect the ability to exploit small-scale heterogeneity in soil resources.