Inactivation of Nitrate Reductase of the Yeast, Rhodotorula glutinis

Nitrate reductase (NR) from the yeast, Rhodotorula glutinis var. salinaria was composed of two enzymatic components, diaphorase and terminal nitrate reducing moieties. The enzyme used NADPH as electron donor and FAD as cofactor. The synthesis of nitrate reductase was promoted specifically by nitrate and repressed by ammonium and amino acids. Nitrate reductase from this yeast had an inactive as well as an active form. Inactive enzyme was reactivated by oxidation with ferricyanide in vitro. Hydroxylamine promoted the formation of inactive enzyme in vivo. Ammonium could neither promote the inactivation nor reduce the total level of nitrate reductase activity. Nitrate could protect nitrate reductase from inactivation caused by nitrogen starvation or hydroxylamine.     

MITOTIC ACTIVITY AND CELL PROLIFERATION IN PRIMARY INDUCTION OF NEWT EMBRYO

Mitotic activity and cell proliferation of newt ( Triturus pyrrhogaster ) embryo were examined with special reference to primary induction.
Mitotic activity of gastrula ectoderm gradually decreases during gastrulation. The ectoderm, which is isolated from mid-gastrula (stage 12b) and cultured in vitro , also shows gradual decrease in mitotic activity during cultivation and the mitotic activity steeply decreases after 48 hr.
The ectoderm cultured with heterologous inductor (GPL-extract) shows a temporal suppression in mitotic activity. The ectoderm of the whole gastrula also shows a regional suppression where it is in contact with the chorda-mesoderm.
The number of the ectodermal cells increases about 2 times after 24 hr culture and to more than 3 times after 48 hr culture. Accordingly it is certain that the majority of the ectodermal cells divides at least one time in the course of 48 hr.
Histological examination of the ectoderm cultured together with the inductor reveals that differentiation of undifferentiated ectoderm to neural tissues is accomplished at least within 48 hr after cultivation with the inductor.
The present examination shows the possibility that the mitotic activity of the ectoderm may be temporarily suppressed by the inductor and that it then decreases along with neural cell differentiation after recovery of the activity.
The results also suggest that the determination of undifferentiated ectoderm to neural tissues occurs before the second cell division after the contact with the inductor and the events occurring during the first cell cycle after activating by the inducing stimulus are critical for the primary induction.     

Effects of Some Inhibitors of Nucleic Acid and Protein Synthesis on the Development of Amine Oxidase in Germinating Pea Cotyledons

The germination of pea seed was accompanied by a rapid increase of amine oxidase (E.C. 1.4.3.6.) in the cotyledon and over half the increase was ascribable to the presence of axial tissue. The presence of actinomycin D, 6-methylpurine and cycloheximide in the early period of soaking inhibited markedly the increase in amine oxidase activity. However, actinomycin D and cycloheximide had little effect on the enzyme development when added after one day and 2 days of germination respectively. The amine oxidase development was also inhibited by dl -p-fluorophenylalanine, 5-methyltryptophan, chloramphenicol and phenylthiourea.     

Mesodermalizing Factors in Fetal Calf Serum

The inducing activities of fetal calf serum (FCS) and fetal calf serum heated for a short time (HFCS) were tested with early gastrula presumptive ectoderm of the newt, Cynops pyrrhogaster as a reactor. Inducing activity was measured by sitting-drop culture of pieces of ectoderm before and after treatment with Ca, Mg-free solution (CMF) in culture medium contained FCS or HFCS (10–50%) as inductor. Results showed that FCS did not induce mesodermalization of ectoderm, before or after treatment with CMF, and that HFCS induced mesodermalization only of ectoderm treated with CMF. The treated ectoderm cells differentiated into mesoderm cells such as muscle and notochord. The induction increased with increase in the duration of CMF treatment and with the concentration of HFCS in the medium. This indicates that FCS changes into mesodermalizing material when heated for a short time and that mesodermal induction by HFCS depends on some effect of CMF on presumptive ectoderm. Since CMF was found to be a neuralizing factor, activation of presumptive ectoderm with a neuralizing factor is probably a prerequisite for mesodermal induction with HFCS.     

NEURAL COMPETENCE AND CELL LINEAGE OF GASTRULA ECTODERM OF NEWT EMBRYO

The change in the capacity to form neural structures was quantitatively analyzed in both intact and isolated ectoderms of Cynops pyrrhogaster gastrula. The frequency of explants with induced neural structures abruptly decreases between stage 12c and stage 13b in intact ectoderm, and between 12 hr and 18 hr preculture in isolated ectoderm. The quantitative analysis also made clear that the size of the cell population of induced neural structures was gradually reduced with the aging of the ectoderm. The authors simultaneously examined the cell proliferation of early gastrula ectoderm and confirmed that all ectodermal cells divided at least once within 18 hr at 23°C, after which the neural competence of the ectoderm completely disappeared.
The relationships between neural competence and cell lineage (cell generation) of the ectoderm are discussed in the light of these findings.     

PURIFICATION AND PROPERTIES OF THE PROTHORACICOTROPIC HORMONE OF THE SILKWORM, BOMBYX MORI

A simple and highly reproducible procedure for partial purification of prothoracicotropic hormone (PTTH) was established starting with 96,000 male adult Bombyx heads. Approximately 28,500-fold purification of PTTH was accomplished with a yield of about 50% and 6 ng of the most purified preparation ("highly purified PTTH") caused adult development in a brainless Samia pupa. The peptidal nature of PTTH was reconfirmed through the effects of various enzymatic and chemical treatments on the biological activity of "highly purified PTTH". Gel-filtration indicated the molecular weight of PTTH to be 4,400.     

The metatibial extensor and flexor tendons in Coleoptera

The metatibiae of genera in several families of Coleoptera with enlarged metafemora are examined, including Chrysomelidae (Alticinae, Galerucinae, Sagrinae), Bruchidae (Pachymerinae, Rhae-binae, Eubaptinae, Bruchinae), Scirtidae and Oedemeridae. There is an evident pattern concerning the relative size of the tibial extensor and flexor tendons that is dependent on the type of hind leg movement of a specific beetle group. Beetle groups that jump (e.g. Alticinae, Scirtidae) always have a greatly enlarged metatibial extensor tendon and associated musculature. However, other groups with swollen metafemora that do not jump have enlarged metatibial flexor tendons with the associated musculature for holding/grasping onto the vegetation (Sagrinae, Bruchidae) or onto the female during copulation (male Oedemera). This indicates a strong functional relationship between Sagrinae and Bruchidae, both with large flexor tendons, and between the Alticinae and Galerucinae, with relatively large extensor tendons; these two cases may also have phylogenetic meaning. This pattern of the metatibial extensor and flexor tendon size related to function is presumably true for at least all other Coleoptera.     

Comparative morphology of the tibial flexor and extensor tendons in insects

Abstract. The relative size, orientation, and degrees of sclerotization of the tibial flexor and extensor tendons are compared in nineteen orders of insects. The sclerotized, independently movable tibial flexor sclerite, known previously only from Alticinae and Carabidae (Coleoptera), is found in some other Coleoptera, Megaloptera, Neuroptera, Hymenoptera and Heteroptera. The Heteroptera also have another small sclerite at the base of the tibial extensor tendon. The tibial flexor sclerite is presumed to provide additional strength and leverage to the flexion of the tibia in certain insect groups; it may also provide protection for the ventral side of the femoro-tibial joint of the leg.