Synthesis of LDH-1 during mamalian oogenesis and early development.

Nuclear multiplication stage embryos were punctured in either the anterior, midlateral, or posterior regions. Both embryos and adults were examined for defects, and the defects were correlated with whether there had been any leakage of cytoplasmic material from the egg at the time of puncturing. Embryonic defects were found, correlated to the site of damage, in all three regions. A number of embryos was followed through development and it was found that 15.1% of the embryos which leaked cytoplasm hatched into larvae, compared to 82.3% of those which did not leak any cytoplasm. Morphological defects arising as a result of lateral puncture only were observed in adults. Many sterile adults were obtained from eggs in which the posterior region had been punctured. The results show that nuclear multiplication embryos are well able to tolerate the disturbance of the cortical cytoplasm created by puncture, but only rarely are they able to compensate for the actual loss of material by regulation. The results were similar to those observed after puncturing Drosophila embryos at the cellular blastoderm stage.     

Viral transformation of rat myoblasts: effects on fusion and surface properties.

Lines of rat myoblasts infected by avian sarcoma viruses have been isolated, cloned, and used to study the effects of viral transformation on myogenic differentiation and the surface changes associated with differentiation. The lines transformed by sarcoma viruses failed to fuse into myotubes and did not show the increase in myosin synthesis normally associated with fusion. The parental nontransformed line showed, subsequent to fusion, a surface alteration detectable by external labeling methods. This alteration, an increase in the level of an external protein of MW > 200 × 10³, is similar to that observed in fibroblasts arrested in the G₁ phase of the cell cycle. This protein was absent or greatly reduced on the surfaces of the myoblast lines that had been transformed by sarcoma viruses. Therefore, viral transformation causes loss of several properties normally associated with arrest of myoblasts in G₁.     

Cation transport in Escherichia coli. VIII. Potassium transport mutants

Analysis of K transport mutants indicates the existence of four separate K uptake systems in Escherichia coli K-12. A high affinity system called Kdp has a Km of 2 muM, and Vmax at 37 degrees C of 150 mumol/g min. This system is repressed by growth in high concentrations of K. Two constitutive systems, TrkA and TrkD, have Km's of 1.5 and 0.5 mM and Vmax's of 550 and 40 at 37 and 30 degrees C, respectively. Mutants lacking all three of these saturable systems take up K slowly by a process, called TrkF, whose rate of transport is linearly dependent on K concentration up to 105 mM. On the whole, each of these systems appears to function as an independent path for K uptake since the kinetics of uptake when two are present is the sum of each operating alone. This is not true for strains having both the TrkD and Kdp systems, where presence of the latter results in K uptake which saturates at a K concentration well below 0.1 mM. This result indicates some interaction between these systems so that uptake now has the affinity characteristic of the Kdp system. All transport systems are able to extrude Na during K uptake. The measurements of cell Na suggest that growing cells of E. coli have very low concentrations of Na, considerably lower than indicated by earlier studies.     

Comparison of water immersion and saline infusion as a means of inducing volume expansion in man.

Although previous studies have demonstrated that water immersion to the neck (NI) results in both central hypervolemia and a significant natriuresis, it is unclear whether the magnitude of the "volume stimulus" of NI is comparable to that induced by the extracellular fluid volume expansion (ECVE) induced by acute saline administration. The present study was undertaken therefore to compare the natriuresis induced by these two different stimuli. All subjects were studied on four occasions while in balance on a diet containing 150 meq of sodium and 80 meq of potassium daily: seated control; seated immersion; and saline administration in both the seated and recumbent posture. The increment in UNaV during NI was indistinguishable from that of seated saline. Similarly, the kaliuretic response during NI was similar to that induced by seated saline infusion. In contrast, supine saline infusion resulted in a greater increment in UNaV than either NI or seated saline. The present data indicate that the "volume stimulus" of immersion is identical with that of standard saline-induced ECVE in normal seated subjects. Furthermore, the ability of NI to induce a natriuresis without a concomitant increase in total blood volume and with a decrease in body weight, rather than the increase which attends saline infusion, suggests that NI may be a preferred investigative tool for assessing the effects of ECVE in man.     

Uptake and fate of IAA in apple callus tissues: metabolism of IAA-2-14C

Young and old apple callus tissues were incubated in light ordarkness with IAA-2-¹⁴C. A large portion of the IAA disappearedfrom the medium with both young and old calluses. Whereas withold calluses the loss was mainly due to IAA destruction, youngcalluses accumulated IAA to a level which exceeded the externalconcentration and, in addition, seemed to protect it from breakdown.After 24 hr the level of IAA-2-¹⁴C in the medium dropped to50% with old calluses both in the dark and light, and with youngcalluses to 20% in the light and 50% in the dark. Chromatographyand scanning of the media and calluses showed that IAA was convertedinto two compounds (comp. A and comp. B). The amounts and proportionsof these metabolites in the medium and tissue were dependenton the different treatments and callus age. The breakdown ofIAA by old tissue gave rise to a higher level of comp. B bothin the tissue and medium, particularly after 6 hr of incubation.In the medium of young tissues the level of comp. A was higherthan comp. B while equal amounts of the two compounds were detectedin the tissue, itself. The origin of the IAA products in thetissue was probably endogenous and not via absorption from themedium. The IAA metabolism of apple callus tissues seems toproceed via the oxindole pathway and it is proposed that compoundsA and B are 3-hydroxymethyloxindole and 3-methylene oxindole,respectively. ¹ Contribution from the Agricultural Research Origanization,The Volcani Center, Bet Dagan, Israel. 1973 Series No. 275-E. (Received May 30, 1974; )     

The influence of electric fields red blood cells.

The effect of electric fields as related to red blood cell sizing techniques, hemolysis, mobility, and general behavior is examined. A review is made of the varying theories concerning these effects. In addition, the physical ramifications of electric field experimentation is viewed. Criticisms are made with regard to technique and lack of consideration for certain experimental variables.