Ultrastructure of Porocephalus crotali (Pentastomida) cuticle with phylogenetic implications.

The cuticle of P. crotali is pro-arthropodan, composed of an epi-, exo-, and endocuticle. The exo- and endocuticles are separated by a 600-A intermediate cuticular zone. The epicuticle is homogeneous and varies from 100 to 350 A in thickness. The exocuticle varies from 2 to eight mu in thickness and is divided into superficial and deep exocuticular zones. The endocuticle is lamellate and varies from 8 to 30 mu in thickness. Lamellae result from ordered parabolic orientations of 40-A chitin fibrils. Underlying cells lack a basement membrane. Subcuticular muscle cells insert tonofibrils directly into the adjacent endocuticle. No apodemes or apophyses occur.     

Amino acids of barley plants in relation to nitrate,urea or ammonium nutrition

Summary When barley seedlings were transplanted into media containing either nitrate, ammonium, or urea their protein and free glutamate content increased during the first few hours. Following the commencement of active growth both the ammonium and urea assimilating plants showed greater increase in free aspartate and organic nitrogen content than the nitrate assimilating plants. Form of nitrogen had no effect on protein concentration and composition, and was of little importance as a source of differences in the total amino acid composition of the plant. re]19740503     

Gap junction remodeling and altered connexin43 expression in the failing human heart

Gap junctions (GJ) are important determinants of cardiac conduction and the evidence has recently emerged that altered distribution of these junctions and changes in the expression of their constituent connexins (Cx) may lead to abnormal coupling between cardiomyocytes and likely contribute to arrhythmogenesis. However, it is largely unknown whether changes in the expression and distribution of the major cardiac GJ protein, Cx43, is a general feature of diverse chronic myocardial diseases or is confined to some particular pathophysiological settings. In the present study, we therefore set out to investigate qualitatively and quantitatively the distribution and expression of Cx43 in normal human myocardium and in patients with dilated (DCM), ischemic (ICM), and inflammatory cardiomyopathies (MYO). Left ventricular tissue samples were obtained at the time of cardiac transplantation and investigated with immunoconfocal and electron microscopy. As compared with the control group, Cx43 labeling in myocytes bordering regions of healed myocardial infarction (ICM), small areas of replacement fibrosis (DCM) and myocardial inflammation (MYO) was found to be highly disrupted instead of being confined to the intercalated discs. In all groups, myocardium distant from these regions showed an apparently normal Cx43 distribution at the intercalated discs. Quantitative immunoconfocal analyis of Cx43 in the latter myocytes revealed that the Cx43 area per myocyte area or per myocyte volume is significantly decreased by respectively 30 and 55% in DCM, 23 and 48% in ICM, and by 21 and 40% in MYO as compared with normal human myocardium. In conclusion, focal disorganization of GJ distribution and down-regulation of Cx43 are typical features of myocardial remodeling that may play an important role in the development of an arrhythmogenic substrate in human cardiomyopathies.     

The age of fine-root carbon in three forests of the eastern United States measured by radiocarbon

Using a new approach involving one-time measurements of radiocarbon (¹⁴C) in fine (<2 mm diameter) root tissues we have directly measured the mean age of fine-root carbon. We find that the carbon making up the standing stock of fine roots in deciduous and coniferous forests of the eastern United States has a mean age of 3-18 years for live fine roots, 10-18 years for dead fine roots, and 3-18 years for mixed live+dead fine roots. These ¹⁴C-derived mean ages represent the time C was stored in the plant before being allocated for root growth, plus the average lifespan (for live roots), plus the average time for the root to decompose (for dead roots and mixtures). Comparison of the ¹⁴C content of roots known to have grown within 1 year with the ¹⁴C of atmospheric CO₂ for the same period shows that root tissues are derived from recently fixed carbon, and the storage time prior to allocation is <2 years and likely <1 year. Fine-root mean ages tend to increase with depth in the soil. Live roots in the organic horizons are made of C fixed 3-8 years ago compared with 11-18 years in the mineral B horizons. The mean age of C in roots increases with root diameter and also is related to branching order. Our results differ dramatically from previous estimates of fine-root mean ages made using mass balance approaches and root-viewing cameras, which generally report life spans (mean ages for live roots) of a few months to 1-2 years. Each method for estimating fine-root dynamics, including this new radiocarbon method, has biases. Root-viewing approaches tend to emphasize more rapidly cycling roots, while radiocarbon ages tend to reflect those components that persist longest in the soil. Our ¹⁴C-derived estimates of long mean ages can be reconciled with faster estimates only if fine-root populations have varying rates of root mortality and decomposition. Our results indicate that a standard definition of fine roots, as those with diameters of <2 mm, is inadequate to determine the most dynamic portion of the root population. Recognition of the variability in fine-root dynamics is necessary to obtain better estimates of belowground C inputs.     

Fast estimation of ATP/ADP ratio as a special step in pharmacological and toxicological studies using the cell-free translation systems

We have developed a simple and effective reversed-phase HPLC procedure for rapid estimation of the ATP/ADP ratio in a cell-free translation system containing creatine kinase. Analysis of the acetone-extractable pool derived from a reticulocyte lysate cell-free system was carried out by automatic chromatography on S5CN-ODS stationary phase using a linear 10-65% pyridine elution gradient formed on the basis of methanol/water (9:1, v/v) mobile phase. This method was used to detect and characterize the inhibition of translation induced by considerable suppression of ATP resynthesis in vitro. It was shown that methyl mercury, unlike cycloheximide, pactamycin, CCl4 and barbituric acid, exerts inhibitory effect on the ATP regeneration in a cell-free translation system.