Temperature acclimation and oxygen-binding properties of blood and multiple haemoglobins of rainbow trout.

Acclimation of rainbow trout to 5, 15 and 22 degrees C for periods exceeding 4 months had no significant effect on the oxygen affinity of whole blood or on the concentration of ATP, which is the main organic phosphate in red cells. Slight differences were, however, found in the oxygenation properties of the haemolysates, which correlate with changes in the relative concentration of the multiple haemoglobins. The oxygen-binding properties of the main haemoglobin components account for the observed differences in the haemolysates. The possible thermoacclimatory significance of changes in haemoglobin multiplicity and co-factor concentrations is discussed.     

Steady state and exchange kinetics of pyruvate, phosphate dikinase from Propionibacterium shermanii.

Evidence is presented based on requirements for exchange in the partial reactions, initial velocity and exchange kinetics and product inhibition, that the pyruvate, phosphate dikinase reaction of propionibacteria occurs by a nonclassical Tri Uni Uni Ping Pong mechanism. The mechanism involves a pyrophosphoryl enzyme, a phosphoryl enzyme, and the free enzyme, and three functionally distinct and independent substrate sites. On the first site, there is pyrophosphorylation of the enzyme by ATP with subsequent release of AMP. The pyrophosphoryl moiety then reacts at the second site with Pi yielding the product PPi and the phosphoryl from of the enzyme. At the third site pyruvate is phosphorylated yielding P-enolpyruvate and the free enzyme. The three catalytic sites are proposed to be linked by a histidyl residue which functions as a pyrophosphoyrl- and phosphoryl-carrier between the three sites. This proposal is based on the following observations. (A) The patterns of the double reciprocal plots of the initial velocities were all parallel; (b) product inhibition between each pair of substrates and products of the three partial reactions were competitive, i.e. ATP against AMP, Pi against PPi, and pyruvate against P-enolpyruvate; (c) the other product inhibitions, with one exception, were noncompetitive as required by the nonclassical ping-pong mechanism; (d) ATP or P-enolpyruvate was required for the Pi in equilibrium PPi exchange reaction which is in accord with the participation of a pyrosphosphoryl or phosphoryl form of the enzyme in this exchange; (e) the ATP in equilibrium AMP exchange and pyruvate in equilibrium P-enolpyruvate exchange did not require additional substrates. In addition, the inhibition and participation in the exchange reactions of the alpha,beta and beta,gamma-methylene analogues of ATP and of the methylene analogue of inorganic pyrophosphate were investigated and the results were in accord with the proposed mechanism. The combined evidence provides a well documented example of a three site nonclassical Tri Uni Uni Ping Pong mechanism.     

Relationship between the chromatoid body and the acrosomal system in early spermatids of Myxine glutinosa L.

Summary A transient close relationship between the chromatoid body and the developing acrosome is demonstrated in early spermatids of Myxine glutinosa.This work was supported by the Norwegian Research Council for Science and Humanities (NAVF, Grant Nr. D 61.44) and the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, Projekt 2183     

Cell surface charge and regulation of cell division of 3T3 cells and transformed derivatives.

The cell surface charge of 3T3, 3T6, SV40-3T3 cells and trypsin-, neuraminidase- and serumtreated preparations of these has been characterized by microcell electrophoresis. At 25 °C, density-inhibited 3T3 cells show a decrease in electrophoretic mobility when treated with various stimuli of cell division. This effect is not observed at 25 °C for transformed derivatives. The surface charge configuration of various cell preparations exhibits a thermal transition which is located within a temperature range characteristic of each preparation. These and other results from cell electrophoresis, taken together with those obtained in agglutination studies by other authors, are considered evidence for the occurrence in the plasma membrane of these cells of a twodimensional phase separation. The temperature range of this phase separation is shifted on treating the cells by growth stimuli. This effect might be an indication of a basic trigger mechanism in the cell cycle.     

The application of biomechanical motion analysis to aspects of green monkey (Cercopithecus a. sabaeus) locomotion

A cinematographic method of biomechanical motion analysis is presented which permits the determination of body segment forces and joint moments of force, and thereby dominant muscle action. An analysis of the horizontal leap of Cercopithecus is used as an example of the utility of this approach in the area of functional morphology. Kinematic and kinetic data are presented and discussed in terms of the biomechanical requirements of this form of locomotion. The importance of a consideration of inertial as well as gravitational forces in an analysis of positional behavior involving body motion is stressed.     

Sensitivity of the S1 neuronal calcium network to insulin and Bay‐K 8644 in vivo: Relationship to gait,motivation, and aging processes

Neuronal hippocampal Ca²⁺ dysregulation is a critical component of cognitive decline in brain aging and Alzheimer''s disease and is suggested to impact communication and excitability through the activation of a larger after hyperpolarization. However, few studies have tested for the presence of Ca²⁺ dysregulation in vivo, how it manifests, and whether it impacts network function across hundreds of neurons. Here, we tested for neuronal Ca²⁺ network dysregulation in vivo in the primary somatosensory cortex (S1) of anesthetized young and aged male Fisher 344 rats using single‐cell resolution techniques. Because S1 is involved in sensory discrimination and proprioception, we tested for alterations in ambulatory performance in the aged animal and investigated two potential pathways underlying these central aging‐ and Ca²⁺‐dependent changes. Compared to young, aged animals displayed increased overall activity and connectivity of the network as well as decreased ambulatory speed. In aged animals, intranasal insulin (INI) increased network synchronicity and ambulatory speed. Importantly, in young animals, delivery of the L‐type voltage‐gated Ca²⁺ channel modifier Bay‐K 8644 altered network properties, replicating some of the changes seen in the older animal. These results suggest that hippocampal Ca²⁺ dysregulation may be generalizable to other areas, such as S1, and might engage modalities that are associated with locomotor stability and motivation to ambulate. Further, given the safety profile of INI in the clinic and the evidence presented here showing that this central dysregulation is sensitive to insulin, we suggest that these processes can be targeted to potentially increase motivation and coordination while also reducing fall frequency with age.     

Reversible bacteriophage resistance by shedding the bacterial cell wall

Phages are highly abundant in the environment and pose a major threat for bacteria. Therefore, bacteria have evolved sophisticated defence systems to withstand phage attacks. Here, we describe a previously unknown mechanism by which mono- and diderm bacteria survive infection with diverse lytic phages. Phage exposure leads to a rapid and near-complete conversion of walled cells to a cell-wall-deficient state, which remains viable in osmoprotective conditions and can revert to the walled state. While shedding the cell wall dramatically reduces the number of progeny phages produced by the host, it does not always preclude phage infection. Altogether, these results show that the formation of cell-wall-deficient cells prevents complete eradication of the bacterial population and suggest that cell wall deficiency may potentially limit the efficacy of phage therapy, especially in highly osmotic environments or when used together with antibiotics that target the cell wall.