Pattern formation in the egg of the leafhopper Euscelis plebejus Fall. (Homoptera): Developmental capacities of fragments isolated from the polar egg regions

The egg of the leafhopper Euscelis plebejus has been separated into three fragments [for nomenclature, see Sander, K. (1976). Advan. Insect Physiol.12, 125–238] by two constrictions in order to exclude the middle egg part from possible terminal influences on pattern specification. Middle fragments of freshly laid eggs (two pronuclei or one nucleus) differentiate middle segments of the embryonic pattern. The segment composition of those partial patterns varies with the position of the two constrictions. Eggs subdivided at later stages of development produce similar partial patterns in the middle fragment, but with more segments. The mode of segment expression in single and double fragmented eggs is compatible with the assumption that the metameric pattern is differentiated by a sequence of short-range inductions rather than by an extensive gradient field.     

H-Y antigen expression in a case of mixed gonadal dysgenesis

Summary H-Y antigen expression was studied on leukocytes and gonad-derived fibroblasts from a patient affected by mixed gonadal dysgenesis. Blood leukocytes and fibroblasts derived from the testis were typed H-Y positive, but the fibroblasts derived from the streak gonad were H-Y negative. Although the patient's karyotype was a mosaic, 45,XO/46,X+mar, as detected in-peripheral blood cells and testis-derived fibroblasts, all the fibroblasts derived from the streak gonad were 45,XO. These data suggests that the marker chromosome was in fact a Y-derived chromosome. Moreover, they showed that, at the gonadal level, a minority of H-Y positive 46,X+mar cells were able to organize a testis. Nevertheless, a large number of XO cells probably did not receive the testicular forming influence of the H-Y antigen and of the other masculinizing factors.     

Effect of methionine sulfoximine on methylation of guanine residues in astroglial transfer ribonucleic acids

Culture-grown astrocytes derived from 3-day-old rat brain were incubated in the presence of [³H]guanosine and of the convulsant agentl-methionine-dl-sulfoximine (MSO). The resulting [³H]tRNA was purified from control and MSO-exposed cells at several time points during the incubation and was hydrolyzed to [³H]guanine and four [³H]methyl guanines which were separated by high pressure liquid chromatography. Three of the four [³H]methyl guanines were more highly labeled in the [³H]tRNA of the MSO-exposed cells, relative to that of the control cells throughout the entire incubation period. The findings extend to cultured astrocytes, the stimulatory effect of MSO on the methylation of neural tRNA guanines, previouly observed both in vitro using [¹⁴C]S-adenosyl-l-methionine and in vivo using [methyl ³-H]l-methionine.     

Neocarzinostatin chromophore: Presence of a cyclic carbonate subunit and its modification in the structure of other biologically active forms

On the basis of spectroscopic evidence, opening of a five-membered cyclic carbonate ring (1,3-dioxolan-2-one) in the C₁₅-subunit of the previously determined partial structure $\text{1}$ (Fig. 1) of the major neocarzinostatin chromophore (NCS-Chrom $\text{A}$), is proposed to account for its base-catalyzed methanolysis to NCS-Chrom $\text{C}$. NCS-Chrom $\text{B}$, apparently an authentic natural product present as a minor component in all preparations of NCS studied, was found to be formally equivalent to the hydrolysis/decarboxylation product of the cyclic carbonate functionality in NCS-Chrom $\text{A}$. The mercaptan-dependent DNA strand-scission activity, equivalent for NCS-Chrom $\text{A}$, $\text{B}$ and $\text{C}$, is independent of the integrity of the cyclic carbonate ring system and implicates a secondary site in the C₁₅-substructure for mercaptan activation.     

A comparison of the influence of potassium and ammonium ions on the phosphofructokinases from rabbit muscle and rat erythrocytes.

Phosphofructokinases from rat erythrocytes and rabbit muscle have been compared in their kinetic behavior with respect to monovalent cation activation and ATP inhibition. Both ammonium and potassium ions affect the muscle enzyme in a two-fold manner: they act both as activators and effectors. On the other hand only ammonium exerts the two-fold effects on the erythrocyte enzyme, while the potassium ions activate without affecting cooperativity. The lower ATP inhibition of muscle phosphofructokinase may be partially explained by the action of potassium ions on the cooperative behavior of the enzyme. The differences between the phosphofructokinases from erythrocytes and muscle in the potassium type-II activation and ATP inhibition represent an organ specifity. Furthermore, the inhibition constants for 2, 3-bisphosphoglycerate differ by 10-fold between the two enzymes.     

The effect of methionine on the uptake,distribution, and binding of the convulsant methionine sulfoximine in the rat

The effect of methionine on the uptake, distribution, and binding of the convulsant methionine sulfoximine (MSO) in 7 rat brain regions, the spinal cord, the liver, and the kidney was investigated. The administration of methionine decreased the uptake of MSO in all brain regions. The uptake of MSO by and its distribution in the nervous tissue was uniform and failed to result in any preferential accumulation of the drug. Methionine decreased the amount of MSO bound to cerebral structures and to the spinal cord. MSO bound to the spinal cord was less susceptible to release by Triton X-100 than was brain-bound MSO.     

In vitro cleavage of double- and single-stranded DNA by plasmid RSF1010-encoded mobilization proteins.

We have used purified RSF1010 mobilization proteins to reproduce in vitro a strand-specific nicking at the plasmid origin of transfer, oriT. In the presence of Mg2+, the proteins MobA (78-kDa form of RSF1010 DNA primase), MobB, and MobC and supercoiled or linear duplex oriT DNA form large amounts of a cleavage complex, which is characterized by its sensitivity to protein-denaturant treatment. Upon addition of SDS to such a complex, a single strand break is generated in the DNA, and MobA is found linked to the 5' nick terminus, presumably covalently. The double-strand nicking activity of MobA requires, in addition to Mg2+, the presence of MobC and is stimulated by the presence of MobB. The nick site has been shown by DNA sequencing to lie at the position cleaved in vivo during transfer, between nucleotides 3138/3139 in the r strand of RSF1010. We have found that MobA will also cleave DNA at sites other than oriT if the DNA is present in single-stranded form. Breakage in this case occurs in the absence of denaturing conditions, and after prolonged incubation, reclosure can be demonstrated.     

Recanalization of occlusion of the peripheral segment of the femoral artery by the Kensey method]

The aim of the presented study was to analyse the surgical technique and results of recanalization of the peripheral segment of iliac artery with Kensey's technique. Altogether 16 patients were operated. Arterial patency was observed in 14 patients immediately after surgery. This number decreased to 11 after a 3-month follow-up. Complications in the form of perforation of the arterial wall, hemorrhage at the site of puncture and thrombotic lesions in the reconstructed arterial channel were seen in 4 cases. Authors' own experience suggests that Kensey's technique together with laser surgery are the treatment of choice in case of iliac arterial occlusion in patients, in whom classic surgery is contraindicated.     

Lactate efflux-induced electrical potential in membrane vesicles of Streptococcus cremoris.

We developed a procedure for isolating membrane vesicles from the homolactic fermentative bacterium Streptococcus cremoris. The membrane vesicles were shown to have a right-side-out orientation by freeze-etch electron microscopy and to be free of cytoplasmic constituents. The membrane vesicles retained their functional properties and accumulated the amino acids L-leucine, L-histidine, and L-alanine in response to a valinomycin-induced potassium diffusion gradient. Studies with these membrane vesicles strongly supported the possibility that there was a proton motive force-generating mechanism by end product efflux (Michels et al., FEMS Lett. 5:357-364, 1979). Lactate efflux from membrane vesicles which were loaded with L-lactate and diluted in a lactate-free medium led to the generation of an electrical potential across the membrane. The results indicate that lactate efflux is an electrogenic process by which L-lactate is translocated with more than one proton.