Statistical recognition of late Cretaceous cyclic sedimentation by means of calcareous nannofossil population studies

The relative abundance of calcareous nannofossil taxa in a sequence of samples collected from a continuous Upper Maastrichtian section in Alabama has been analyzed using statistical techniques. Results indicate that an increase of arbitrarily chosen long-ranging forms can be represented by a slowly fluctuating secular trend with a superimposed cyclical component. Provided that a number of reasonable assumptions are made, the dominant frequencies of the periodic component are within the order of magnitude of the accepted frequency of the Perihelion cycle or “Milenkovitch astronomical insolation curves” (Milenkovitch, 1938).     

Alveolar epithelial integrity in athletes with exercise-induced hypoxemia.

The effect of incremental exercise to exhaustion on the change in pulmonary clearance rate (k) of aerosolized (99m)Tc-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) and the relationship between k and arterial PO(2) (Pa(O(2))) during heavy work were investigated. Ten male cyclists (age = 25 +/- 2 yr, height = 180.9 +/- 4.0 cm, mass = 80.1 +/- 9.5 kg, maximal O(2) uptake = 5. 25 +/- 0.35 l/min, mean +/- SD) completed a pulmonary clearance test shortly (39 +/- 8 min) after a maximal O(2) uptake test. Resting pulmonary clearance was completed >/=24 h before or after the exercise test. Arterial blood was sampled at rest and at 1-min intervals during exercise. Minimum Pa(O(2)) values and maximum alveolar-arterial PO(2) difference ranged from 73 to 92 Torr and from 30 to 55 Torr, respectively. No significant difference between resting k and postexercise k for the total lung (0.55 +/- 0.20 vs. 0. 57 +/- 0.17 %/min, P > 0.05) was observed. Pearson product-moment correlation indicated no significant linear relationship between change in k for the total lung and minimum Pa(O(2)) (r = -0.26, P > 0.05). These results indicate that, averaged over subjects, pulmonary clearance of (99m)Tc-DTPA after incremental maximal exercise to exhaustion in highly trained male cyclists is unchanged, although the sampling time may have eliminated a transient effect. Lack of a linear relationship between k and minimum Pa(O(2)) during exercise suggests that exercise-induced hypoxemia occurs despite maintenance of alveolar epithelial integrity.     

Effect of self-association on the structural organization of partially folded proteins: inactivated actin

The propensity to associate or aggregate is one of the characteristic properties of many nonnative proteins. The aggregation of proteins is responsible for a number of human diseases and is a significant problem in biotechnology. Despite this, little is currently known about the effect of self-association on the structural properties and conformational stability of partially folded protein molecules. G-actin is shown to form equilibrium unfolding intermediate in the vicinity of 1.5 M guanidinium chloride (GdmCl). Refolding from the GdmCl unfolded state is terminated at the stage of formation of the same intermediate state. An analogous form, known as inactivated actin, can be obtained by heat treatment, or at moderate urea concentration, or by the release of Ca(2+). In all cases actin forms specific associates comprising partially folded protein molecules. The structural properties and conformational stability of inactivated actin were studied over a wide range of protein concentrations, and it was established that the process of self-association is rather specific. We have also shown that inactivated actin, being denatured, is characterized by a relatively rigid microenvironment of aromatic residues and exhibits a considerable limitation in the internal mobility of tryptophans. This means that specific self-association can play an important structure-forming role for the partially folded protein molecules.     

The Role of Polygalacturonase (PG) in the Ripening of Apple Fruits

Polygalacturonase (PG) activity and changes in respiratory intensity of apple fruits were investigated. The respiratory rate was decreased to a preclimacteric minimum from 30 Aug. to 20 Sept., Then increased to a climacteric peak (20–30 Sept.) and again drop down gradually with approaching the senescence stage. The PG activity was undetectable in a developing fruit until the onset climacteric phase. It rose rapidly after harvest, and reaching its highest level on 27 Oct. Just a month after the climacteric peak. The PG activity fell gradually. The amount of the fractions of pectic acid in fruits changed with the modifications of PG activity. With the ripening of fruits, the content of alcohol-soluble small molecules of pectic acids was increased from 12 to 13 5 mg/100 g of tissue, while the amount of alcohol- insoluble large molecules of pectic acids reduced from 530 to 280/100 g of tissue. PG activity would indicate the destruction of cell walls and the separation of cells. The onset of softening of fruits occurred 20 days after the rise of PG activity. It is supposed that the process of softening is directly controlled by PG activity.     

ST-segment elevation associated with allergic reaction to echocardiographic contrast agent administration

We report a case of an allergic reaction after the administration of an echocardiographic contrast agent which resulted in ST-segment elevation. Hypersensitivity and allergic reactions are known causes of acute cardiovascular events. However, only limited reports are available which suggest the exact mechanism of the occurrence of angina or myocardial infarction during severe allergic reactions. In our case, through invasive imaging (coronary angiography and IVUS) we have shown for the first time a transient coronary spasm in the absence of intra-coronary thrombus and only minimal neointimal hyperplasia.     

SUMOylation and PARylation cooperate to recruit and stabilize SLX4 at DNA damage sites

SUMOylation plays important roles in the DNA damage response. However, whether it is important for interstrand crosslink repair remains unknown. We report that the SLX4 nuclease scaffold protein is regulated by SUMOylation. We have identified three SUMO interaction motifs (SIMs) in SLX4, mutating all of which abrogated the binding of SLX4 to SUMO-2 and covalent SLX4 SUMOylation. An SLX4 mutant lacking functional SIMs is not recruited to PML nuclear bodies nor stabilized at laser-induced DNA damage sites. Additionally, we elucidated a novel role for PARylation in the recruitment of SLX4 to sites of DNA damage. Combined, our results uncover how SLX4 is regulated by post-translational modifications.     

Reproductive failure: a new paradigm for extinction

Extinction was recognized as a scientific fact 200 years ago, although no adequate paradigm has emerged to explain the process. Prevailing theory has focused on ‘cause(s)’ of extinction but has neglected ‘effect’ and ‘mechanism’. These omissions preclude the formulation of a functional paradigm necessary for remedial action in response to the impending anthropogenic mediated, worldwide extinction crisis. The new paradigm is defined as the multi‐generational, attritional loss of reproductive fitness. Stabilizing selection continuously adapts species to specific ecosystems, which often results in highly evolved species prone to extinction when environments shift. Some species survive by tracking the declining palaeoclimates in which they presumably evolved, often becoming relicts prior to extinction. Compelling new evidence shows that even mass extinctions are largely a result of environmental change leading to widespread, attritional reproductive decline, rather than a result of instantaneous global catastrophes.