Rescue of developmental lens abnormalities in chimaeras of noncataractous and congenital cataractous mice

In the study of the lens of a congenital cataractous mouse mutant (CAT), it has been shown that a loss of growth regulation at the cellular level causes gross lens abnormalities. The phenotypic characteristics of the cataractous mouse lens are similar to those seen in human congenital cataract and thus serves as a model system for medical research. In this present investigation, we have demonstrated that the abnormalities of the congenital cataractous lens can be rescued by forming chimaeras between DBA/2 (a noncataractous strain of mouse) and the CAT mutant. This report describes the histological, cellular and biochemical analysis of the resultant chimaeric eyes, and discusses possible mechanisms by which these results were achieved.     

Hydrolysis of N3-methyl-2'-deoxycytidine: model compound for reactivity of protonated cytosine residues in DNA

Protonation of cytosine residues at physiological pH may occur in DNA as a consequence of both alkylation and aberrant base-pair formation. When cytosine derivatives are protonated, they undergo hydrolysis reactions at elevated rates and can either deaminate to form the corresponding uracil derivatives or depyrimidinate generating abasic sites. The kinetic parameters for reaction of protonated cytosine are derived by studying the hydrolysis of N3-methyl-2'-deoxycytidine (m3dC), a cytosine analogue which is predominantly protonated at physiological pH. Both deamination and depyrimidimation reaction rates are shown to be linearly dependent upon the fraction of protonated molecules. We present here thermodynamic parameters which allow determination of hydrolysis rates of m3dC as functions of pH and temperature. Protonation of cytosine residues in DNA, as induced by aberrant base-pair formation or base modification, may accelerate the rate of both deamination and depyrimidation up to several thousand-fold under physiological conditions.     

Comparison of the catalytic and structural properties of Ca2+-ATPase in longitudinal tubules and terminal cisternae of the sarcoplasmic reticulum

The catalytic behavior and structural features of Ca2+-ATPase in the vesicles of longitudinal tubules and terminal cisternae of the sarcoplasmic reticulum isolated from rabbit skeletal muscles was analysed. pH measurements have shown under optimal conditions Ca2+-ATPase has similar catalytic behavior both in the fractions of longitudinal tubules and terminal cisternae. Under non-optimal conditions, the behavior similarity was not observed. The specific activity of the ATPase enzyme under optimal conditions was shown to be much higher in the fraction of longitudinal tubules than in the fraction of terminal cisternae. Caffeine added to both fractions had no effect on the catalytic behavior of Ca2+-ATPase. As judged from fluorescence analysis, the structure of Ca2+-ATPase of longitudinal tubules differs from that structure of terminal cisternae. In sarcoplasmic reticulum membrane, at least half of the tryptophan residues of Ca2+-ATPase was shown to be buried in the lipid bilayer. Our findings suggest that in terminal cisternae some of the Ca2+-ATPase molecules exist as an oligomeric protein and do not participate in ATP hydrolysis (named "silent" Ca2+-ATPase).     

Calculation of the stability of mini-duplexes of DNA in an electrolyte solution using a molecular mechanics method in approximating a statistical model of the environment

Approximation of the statistical model of environment (SME) to estimate the energy of the macromolecule in electrolyte solution has been developed and used for calculating the conformational energy of nucleic acids by means of the molecular mechanics method. Calculation of base pairs opening delta Hcalop enthalpies and enthalpies of DNA miniduplexes dissociation delta Hcaldis were performed for 10 types of diduplexes. The approximation SME enable to perform calculations of the absolute base-dependent values of delta Hcalop which coincide in the range of 1 kcal/mol with the experimental base-dependent values of the helix-coil transition enthalpies. Values of dissociation enthalpies delta Hcalop greater than delta Hcaldis for all miniduplexes, the difference of delta Hcalop--delta Hcaldis determine the base-dependent energy of the helix-coil boundary. The values of activation barriers for the strands dissociation delta H d not equal to congruent to 8 kcal/mol and association delta H not equal to as congruent to 4 kcal/mol were obtained for GG/CC and AA/TT duplexes. It is concluded that the approximation SME enables to increase substantially the accuracy of the calculations of the macromolecule conformational rearrangement enthalpies in the electrolytes solution.     

Histochemical reaction to biogenic amines of the nervous system of the larval and mature cestode Microsomacanthus microskrjabini

Histochemical reaction with glyoxylic acid has revealed a specific fluorescence caused by the presence of indolamine (apparently serotonin) in the nervous system of larva and mature cestode. Fluorescence manifests itself in neurons and nerve fibres of the central ganglion and its commissure, in nerve cells of the proboscis, in longitudinal trunks and transverse commissures, and in the nerve elements connected with genital system.     

Physiological integration in Cassia fasciculata Michx.: inflorescence removal and defoliation experiments

Summary In the annual herb Cassia fasciculata virtually every leaf subtends an axillary inflorescence. We examined the degree to which these leaf-inflorescence units (reproductive nodes) were physiologically independent of each other in the production of flowers, fruits, and seeds. Removal of up to 4 of every 5 inflorescences resulted in substantial increases in fruit and seed production by remaining, intact reproductive nodes. These increases nearly compensated for and manipulated reproductive nodes were associated with different vascular strands. When 2 of every 3 leaves were removed, fruit and seed production were reduced at both intact and defoliated reproductive nodes. Taken together, these results suggest that neighboring reproductive nodes in C. fasciculata are not physiologically independent of one another, and that competition among fruits and seeds for parental resources occurs over several reproductive nodes.Scientific contribution no. 1595 from the New Hampshire Agricultural Experiment Station     

Two isozymes of dihydroxyacetone phosphate reductase in dunaliella

Two isoforms of dihydroxyacetone phosphate reductase were present in Dunaliella tertiolecta. The major form was located in the chloroplast and the minor form in the cytosol. The chloroplastic reductase eluted first from a DEAE cellulose column followed immediately by the cytosolic form. Both forms were unstable and cold labile. Addition of 5 millimolar dithiothreitol helped to stabilize the enzymes. The cytosolic isoform of DHAP reductase was detected only if the cells were in an active log phase of growth. Then its activity was 20 to 30% of the total reductase activity. When cell cultures entered late log phase of growth the activity of the cytosolic form of the enzyme disappeared, but the chloroplastic form remained. The cytosolic DHAP reductase from Dunaliella has some properties similar to the cytosolic isoform from spinach leaves. Detergents inhibited both enzymes. However, neither form of the algal dihydroxyacetone phosphate reductase was stimulated by fructose 2,6-bisphosphate. In Dunaliella the properties of the chloroplastic form were those expected for glycerol production for osmoregulation, whereas the cytosolic form, like the reductases in leaves, is more likely involved in glycerol phosphate formation for lipid synthesis.     

The dosage thresholds for disordered physical work capacity in mice and rats following irradiation

Physical efficiency of mice and rats at early times following irradiation with doses of 35 to 200 Gy was estimated by the muscle endurance and motor coordination indices. A threshold nature of the effects was exhibited at high doses. For instance, as large as 40 Gy was the dose threshold at which stability in the accomplishment of the known operations was impaired; at 70-100 Gy, the accomplishment decreased down to 50% of the initial level, by the 2nd hour after irradiation, with the subsequent partial restoration; 200 Gy was the threshold dose at which the disturbances were irreversible. These values were also similar to those of the threshold doses at which clinical picture of the affection was changed.