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)     

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.     

Dynamics of proteins in different solvent systems: analysis of essential motion in lipases.

We have investigated the effect of different solvents on the dynamics of Rhizomucor miehei lipase. Molecular dynamics simulations were performed in water, methyl hexanoate, and cyclohexane. Analysis of the 400-ps trajectories showed that the solvent has a pronounced effect on the geometrical properties of the protein. The radius of gyration and total accessibility surface decrease in organic solvents, whereas the number of hydrogen bonds increases. The essential motions of the protein in different solvents can be described in a low-dimensional "essential subspace," and the dynamic behavior in this subspace correlates with the polarity of the solvent. Methyl hexanoate, which is a substrate for R. miehei lipase, significantly increases the fluctuations in the active-site loop. During the simulation, a methyl hexanoate entered the active-site groove. This observation provides insight into the possible docking mechanism of the substrate.     

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome): six unique arylsulfatase B gene alleles causing variable disease phenotypes.

Mucopolysaccharidosis type VI, or Maroteaux-Lamy syndrome, is a lysosomal storage disorder caused by a deficiency of the enzyme arylsulfatase B (ASB), also known as N-acetylgalactosamine-4-sulfatase. Multiple clinical phenotypes of this autosomal recessively inherited disease have been described. Recent isolation and characterization of the human ASB gene facilitated the analysis of molecular defects underlying the different phenotypes. Conditions for PCR amplification of the entire open reading frame from genomic DNA and for subsequent direct automated DNA sequencing of the resulting DNA fragments were established. Besides two polymorphisms described elsewhere that cause methionine-for-valine substitutions in the arylsulfatase B gene, six new mutations in six patients were detected: four point mutations resulting in amino acid substitutions, a 1-bp deletion, and a 1-bp insertion. The point mutations were two G-to-A and two T-to-C transitions. The G-to-A transitions cause an arginine-for-glycine substitution at residue 144 in a homoallelic patient with a severe disease phenotype and a tyrosine-for-cysteine substitution at residue 521 in a potentially heteroallelic patient with the severe form of the disease. The T-to-C transitions cause an arginine-for-cysteine substitution at amino acid residue 192 in a homoallelic patient with mild symptoms and a proline-for-leucine substitution at amino acid 321 in a homoallelic patient with the intermediate form. The insertion between nucleotides T1284 and G1285 resulted in a loss of the 100 C-terminal amino acids of the wild-type protein and in the deletion of nucleotide C1577 in a 39-amino-acid C-terminal extension of the ASB polypeptide. Both mutations were detected in homoallelic patients with the severe form of the disease. Expression of mutant cDNAs encoding the four amino acid substitutions and the deletion resulted in severe reduction of both ASB protein levels and arylsulfatase enzyme activity in comparison with a wild-type control. The six mutations described in the present study were unique among 25 unrelated mucopolysaccharidosis VI patients, suggesting a broad molecular heterogeneity of the Maroteaux-Lamy syndrome.     

Subject: foraging

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

Subject: foraging     

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.     

Purification and Characterization of an l-Aminopeptidase from Pseudomonas putida ATCC 12633

An l-aminopeptidase of Pseudomonas putida, used in an industrial process for the hydrolysis of d,l-amino acid amide racemates, was purified to homogeneity. The highly l-enantioselective enzyme resembled thiol reagent-sensitive alkaline serine proteinases and was strongly activated by divalent cations. It possessed a high substrate specificity for dipeptides and alpha-H amino acid amides, e.g., l-phenylglycine amide.     

Ultrastructure and Cytochemistry of Periostracum and Mantle Edge of Biomphalaria glabrata (Gastropoda,Basommatophora)

Abstract Three layers of different electron density can be distinguished in the periostracum. Periostracal units of up to 900 nm length are merged into the outer fibrous layer and binding of gold-labelled lectin-WGA indicates the presence of chitin because it is labile to chitinase treatment. The periostracum is formed by the epithelia of the groove and the belt at the mantle edge. The distal and basal epithelium of the groove consists mainly of type A cells with an extended Golgi apparatus and apical vesicles. The presence of peroxidase and phenol oxidase indicates a function in tanning of the periostracum. In the proximal epithelium of the groove, type B cells with protruding apices add more material for periostracum formation. Type C cells secrete single periostracal units which are formed within single vesicles or larger vacuoles. Type D cells secrete electron-dense vesicles which also contain WGA-positive material. The distal cells of the belt are characterized by predominating strands of the rER while subapical vacuoles, to some of which WGA binds, dominate in the cells of the central part. In the belt, phenol oxidase and peroxidase can be localized in cisternae of the rER and the Golgi apparatus. Numerous control incubations indicate that, indeed, two different enzymes are localized.     

The maintenance of genetic diversity under host–parasite coevolution in finite,structured populations

As a corollary to the Red Queen hypothesis, host–parasite coevolution has been hypothesized to maintain genetic variation in both species. Recent theoretical work, however, suggests that reciprocal natural selection alone is insufficient to maintain variation at individual loci. As highlighted by our brief review of the theoretical literature, models of host–parasite coevolution often vary along multiple axes (e.g. inclusion of ecological feedbacks or abiotic selection mosaics), complicating a comprehensive understanding of the effects of interacting evolutionary processes on diversity. Here we develop a series of comparable models to explore the effect of interactions between spatial structures and antagonistic coevolution on genetic diversity. Using a matching alleles model in finite populations connected by migration, we find that, in contrast to panmictic populations, coevolution in a spatially structured environment can maintain genetic variation relative to neutral expectations with migration alone. These results demonstrate that geographic structure is essential for understanding the effect of coevolution on biological diversity.