Frequency-Dependent Selection at the PGM-1 Locus of DROSOPHILA PSEUDOOBSCURA

Frequency-dependent fitness was studied at the Pgm-1 locus of Drosophila pseudoobscura with respect to two fitness components: rate of development and larva-to-adult survival. The Pgm-1 locus is very polymorphic with only two alleles, Pgm-1¹⁰⁰ and Pgm-1¹⁰⁴, occurring at high frequencies. For each of these two alleles, 20 homozygous strains were obtained from a sample of 1,140 wild-inseminated females. First-instar larvae of the two genotypes were combined in a set of eight different frequencies: 0.0, 0.10, 0.25, 0.40, 0.60, 0.75, 0.90, and 1.0. Frequency-dependent fitness effects were observed for the two survival-related fitness components examined: larvae of the less common genotype develop faster and have a higher probability of survival than larvae of the more common genotype. The rate of survival at intermediate genotypic frequencies is similar to that in pure cultures. If selection acted solely as frequency-dependent effects on survival-related components of fitness, the equilibrium frequency of the Pgm-1¹⁰⁰ allele would be 0.615 for a two-genotype system, which fits an observed frequency range for this allele in nature between 0.55 and 0.71. Experimentally created linkage disequilibrium was excluded from the experiment by using a large number of independent strains. It is nevertheless possible that the frequency-dependent selection may not affect the Pgm-1 locus per se, but may reflect a linkage disequilibrium present in the natural population. Even if this were the case, the frequency-dependent selection could affect the frequency of the Pgm-1 alleles in nature.     

The fine structure of a tri-lamellar body in various species ofAnabaena

Summary A tri-lamellar body has been observed either near or adjacent to the crosswalls in 16 out of 20 different isolates ofAnabaena examined in thin sections. These bodies appear to consist of three discoid lamellae approximately 0.3 m in diameter. The outer lamella (closest to the plasma membrane) is separated from the middle lamella by a 12 nm space and is about 8 nm in thickness. The middle and inner lamellae, spaced about 8 nm apart, are approximately 8 nm in thickness. Electron dense granules, interpreted to be -granules, are associated with the inner lamella. In different species, osmiophilic lines 3 nm wide were observed. The osmiophilic lines run at right angles to the lamellae, either between the outer and middle lamellae, between the middle and inner lamellae or between all three lamellae. In some species, osmiophilic lines are absent. Up to six tri-lamellar bodies have been observed in median longitudinal sections. Pores 20 nm in diameter and 60 nm apart were observed in layer 2 of the cell wall of all the species ofAnabaena examined. All species which had tri-lamellar bodies also had wall pores closely associated with the bodies. Wall pores were also observed in four species lacking tri-lamellar bodies. The possible role of these structures is discussed.     

The fine structure of a microplate-microtubule array,microfilaments and polyhedral body associated microtubules in several species of Anabaena

A microplate-microtubule array was observed in Anabaena sp. (B-378). This structure consists of an arched plate, about 8 nm thick, and various microtubules, 12 nm in diameter and 50 nm long, arranged in rows. The microtubules project at right angles from one side of the plate into the cytoplasm or towards the plasma membrane. Up to twelve microplate-microtubule arrays were observed in a single section of a cell.Microfilaments, about 2.8 nm in diameter and of undetermined length, were observed in four isolates of Anabaena. The microfilaments were always found in bundles, which varied in size, up to 0.63 m across and 0.91 long.Microtubules, 10 nm in diameter and about 150 nm in length, were observed associated with one facet of polyhedral bodies in 8 out of 20 isolates of Anabaena. The microtubules occurred in groups of up to 20 or more, and were always oriented with the long axis parallel to a facet of a polyhedral body. In cross section, the microtubules had an electron transparent lumen 5 nm wide and a wall 2.5 nm thick.These structures are compared to previously deseribed microtubules and microfilaments.     

Fitness of Allozyme Variants in DROSOPHILA PSEUDOOBSCURA. I. Selection at the PGM-1 and ME-2 Loci

We have studied in Drosophila pseudoobscura the effect of allozyme variation on seven fitness components: female fecundity, egg hatchability, egg-to-adult survival under near-optimal and under competitive conditions, rate of development under near-optimal and under competitive conditions, and mating capacity of males. Three genotypes at each of two loci, Pgm-1 and Me-2, have been studied in various combinations. These two loci are highly polymorphic in natural populations of D. pseudoobscura. Statistically significant differences involving one or more genotypes exist for all components of fitness. No single genotype is best for all fitness components; rather the relative fitnesses of genotypes are reversed when different parameters are considered, or when they are studied in different environmental conditions. Also, the average egg-to-adult survival and rate of development are better when different genotypes are reared together than when they occur in pure culture. Four different modes of selection have been uncovered by our experiments. These forms of selection may account for the persistence of the two allozyme polymorphisms in nature, and for previously observed seasonal fluctuations of the allelic frequencies in natural populations.     

Hemorrhage induces an increase in serum TNF which is not associated with elevated levels of endotoxin

Although tumor necrosis factor (TNF) and interleukin 6 (IL 6) are purported to be important mediators of inflammatory responses following trauma, it is not known if the serum levels of these cytokines are altered by simple hemorrhage. The objective of this study therefore was to determine whether or not: 1) there is any elevation of TNF or IL 6, and 2) if endotoxin, an important upregulator of these cytokines, is also increased following hemorrhage. To study this, C3H/HeN mice were bled to, and maintained at a mean blood pressure of 35 mmHg for 60 min, and then resuscitated with their own shed blood and adequate fluid. Mice were sacrificed at 30 min into hemorrhage and at 2, 4 or 24 hr post-hemorrhage to obtain serum samples. IL 6 and TNF levels were measured using cytokine dependent cellular assays. Using a quantitative Limulus amebocyte lysate assay, endotoxin levels were determined. TNF levels were significantly elevated at 30 min into hemorrhage, remaining so at 2 hr after resuscitation, but absent by 4 hr. Although there was a trend toward elevated IL 6 levels at 2 hr following hemorrhage, which was sustained up to 24 hr, the values were not significantly different from sham controls. When compared to controls, no marked increase in endotoxin was seen at any time point during or following hemorrhage. These results indicate that hemorrhage, in the absence of significant tissue trauma, causes enhanced TNF release which is not the result of increased endotoxin.     

Ubiquitin conjugation triggers misfolded protein sequestration into quality control foci when Hsp70 chaperone levels are limiting

Ubiquitin accumulation in amyloid plaques is a pathological marker observed in the vast majority of neurodegenerative diseases, yet ubiquitin function in these inclusions is controversial. It has been suggested that ubiquitylated proteins are directed to inclusion bodies under stress conditions, when both chaperone-mediated refolding and proteasomal degradation are compromised or overwhelmed. Alternatively, ubiquitin and chaperones may be recruited to preformed inclusions to promote their elimination. We address this issue using a yeast model system, based on expression of several mildly misfolded degradation substrates in cells with altered chaperone content. We find that the heat shock protein 70 (Hsp70) chaperone pair Ssa1/Ssa2 and the Hsp40 cochaperone Sis1 are essential for degradation. Substrate ubiquitylation is strictly dependent on Sis1, whereas Ssa1 and Ssa2 are dispensable. Remarkably, in Ssa1/Ssa2-depleted cells, ubiquitylated substrates are sequestered into detergent-insoluble, Hsp42-positive inclusion bodies. Unexpectedly, sequestration is abolished by preventing substrate ubiquitylation. We conclude that Hsp40 is required for the targeting of misfolded proteins to the ubiquitylation machinery, whereas the decision to degrade or sequester ubiquitylated proteins is mediated by the Hsp70s. Accordingly, diminished Hsp70 levels, as observed in aging or certain pathological conditions, might be sufficient to trigger ubiquitin-dependent sequestration of partially misfolded proteins into inclusion bodies.     

Diagnosis and management of hypertension: around-the-clock ambulatory blood pressure monitoring is substantially more effective and less costly than daytime office blood pressure measurements

ABSTRACT

The cost-effectiveness of ambulatory blood pressure (BP) monitoring (ABPM) versus traditional office BP measurement (OBPM) for the diagnosis and management of hypertension has been evaluated only by few studies and based solely on the reduction of medical care expenses through avoiding treatment of isolated-office hypertension. Data from the 21963 participants in the Hygia Project, a multicenter outcomes study that incorporates into routine primary care periodic, at least yearly, 48 h ABPM evaluation, were utilized to assess the cost-effectiveness – relative to vascular pathology expenditures countrywide in Spain – of ABPM versus OBPM. The actual reported Spanish healthcare expenditure for vascular pathology in 2015 – aggregate costs of medical examinations, outpatient and inpatient care, therapeutic interventions, plus non-healthcare services (productivity losses due to morbidity/mortality and informal family/friends-provided care) – was used to compare yearly costs when diagnostic and treatment decisions for hypertension are based on the OBPM versus the ABPM-model. Our economic analysis is based on the more realistic and feasible approach of restricting ABPM solely to high-risk individuals of age ≥60 years and/or with diabetes, chronic kidney disease, and/or previous cardiovascular event, who in the Hygia Project accounted for >90% of all documented events. The projected net benefit countrywide in favor of the proposed ABPM-model is ~5294M€/year, i.e., 360.33€/year (95%CI [347.52–374.85]) per ABPM-evaluated person. This highly conservative economic analysis indicates ABPM is a much more cost-effective strategy than repeated OBPM not only for accurate diagnosis and management of true hypertension but marked reduction of expenditures on elevated BP-associated vascular pathology.     

Formation of S-(carboxymethyl)-cysteine in rat liver mitochondrial proteins: effects of caloric and methionine restriction

Maillard reaction contributes to the chemical modification and cross-linking of proteins. This process plays a significant role in the aging process and determination of animal longevity. Oxidative conditions promote the Maillard reaction. Mitochondria are the primary site of oxidants due to the reactive molecular species production. Mitochondrial proteome cysteine residues are targets of oxidative attack due to their specific chemistry and localization. Their chemical, non-enzymatic modification leads to dysfunctional proteins, which entail cellular senescence and organismal aging. Previous studies have consistently shown that caloric and methionine restrictions, nutritional interventions that increase longevity, decrease the rate of mitochondrial oxidant production and the physiological steady-state levels of markers of oxidative damage to macromolecules. In this scenario, we have detected S-(carboxymethyl)-cysteine (CMC) as a new irreversible chemical modification in mitochondrial proteins. CMC content in mitochondrial proteins significantly correlated with that of the lysine-derived analog N ^ε-(carboxymethyl)-lysine. The concentration of CMC is, however, one order of magnitude lower compared with CML likely due in part to the lower content of cysteine with respect to lysine of the mitochondrial proteome. CMC concentrations decreases in liver mitochondrial proteins of rats subjected to 8.5 and 25 % caloric restriction, as well as in 40 and 80 % methionine restriction. This is associated with a concomitant and significant increase in the protein content of sulfhydryl groups. Data presented here evidence that CMC, a marker of Cys-AGE formation, could be candidate as a biomarker of mitochondrial damage during aging.