Protein kinase from Mucor rouxii

Summary Cyclic AMP binding to Mucor rouxii protein kinase holoenzyme and free regulatory subunit was measured by the classical membrane filtration technique and by equilibrium dialysis. The results obtained demonstrate that the filtration method can be used without loss of any cyclic AMP binding site. Both methods unambiguously demonstrate that the number of molecules of cyclic AMP bound to the holoenzyme are half of those bound to the regulatory subunit. This result suggests that unshielding of new cyclic AMP binding sites occurs upon dissociation of the ternary complex holoenzyme-cyclic AMP.     

A NEW GENUS OF PROTOSTELIDS SHOWING AFFINITIES WITH CERATIOMYXA

A new genus and species of the Protosteliida (Mycetozoa), Ceratiomyxella tahitiensis, was isolated from dead plant material—var. tahitiensis from Tahiti and var. neotropicalis from Brazil and Colombia. The sporocarps have deciduous spores borne singly on slender hollow stalks; zoocysts with anteriorly flagellate planonts are produced. The trophic stage is comprised of uninucleate to plurinucleate amoeboid cells and reticulate plasmodia; the uninucleate cells become flagellate in water. The prespore cells and spores are plurinucleate. Sexuality has not been demonstrated. Var. tahitiensis has globose spores and produces its zoocysts just after spore germination, whereas var. neotropicalis has subglobose spores and forms zoocysts later in the life cycle. The species is thought to show phylogenetic relationships with Ceratiomyxa, which was recently transferred to the Protosteliida by Olive.     

MONOGRAPH OF THE GENUS PROTOSTELIUM

Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatura, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included.     

An electron microscopical study of developing sympathetic neurons in man

Summary An electron microscopic study has been made of the sympathetic ganglia of a 15 and a 17 week old male human fetus. The fetal sympathetic neurons were densely packed in a scanty connective tissue matrix which also contained blood vessels. The fetal sympathetic neurons had a large, electron-light nucleus with one or two nucleoli, and was of a somewhat mottled appearance due to irregularly dispersed aggregates of fine and coarse granules. The perikaryon usually formed a thin envelope around the nucleus and contained, except for large pigment granules, all intracytoplasmic structures which were also found in mature sympathetic neurons. Adjacent sympathetic cells were either in immediate contact, or slightly separated by a wedge of electron-light satellite expansions, or lined by primitive axons. The satellite cells were in the early state of development. Electron-dense axons either stood side by side with, or were slightly engulfed by light Schwann cell expansions and formed distinct bundles surrounded by a common basement membrane. There was practically no trace of myelin formation or Schwann cell wrapping characteristic for unmyelinated fibers as seen in the adult.This investigation was supported (in whole) by United States Public Health Service Grant NB-01879-05, Institute for Nervous Diseases and Blindness.Grateful acknowledgment is made to Professor Dr. John Lind who madea vailable the fetal material through the Laboratory of Prenatal Growth and Development, Karolinska Institutet, Stockholm, Sweden.The authors wish to thank Docent Dr. Gunnar Bloom who provided the facilities necessary to prepare the fetal material for electron microscopical examination, in his laboratory for Cell Research, Karolinska Institutet, Stockholm, Sweden.     

Response to osmotic medium and fusicoccin by seeds of radish (Raphanus sativus) in the early phase of germination

The effect of increasing osmotic values of the medium (mannitol) on the growth and the response mechanisms of seeds of radish ( Raphanus sativus L., cv. Ton do Rosso Quarantino) during the early phase of germination was investigated in the presence or absence of fusicoccin (FC). Decreasing the water potential in the medium inhibited the growth and the evolution of protein synthesis and enhanced H⁺ extrusion, net uptake of K⁺ and malic acid synthesis. FC, which stimulates these latter functions, counteracted the inhibitory effect of the decreasing water potential of the medium on growth and protein synthesis. Neither in the absence nor in the presence of FC did decreasing water potential of the medium enhance the synthesis of soluble sugars and amino acids to support the osmotic pressure of the seeds. The osmotic and water potentials of the seeds increased during germination. FC made the increase more rapid, while mannitol kept both potentials low. The pressure potentials of the seeds also decreased with time, and both FC and mannitol enhanced this change. If the seeds were without turgor, the development of protein synthesis was blocked. The seeds counteract the effect of decreasing water potentials in the medium by: a) enhancing H⁺ extrusion (and, as a consequence, wall loosening and transport mechanisms) and the synthesis of malic acid as apparent in the presence of FC; b) regulating the osmotic potentials of the cells (with a lower dilution of the osmotic compounds present in the seeds due to the diminished uptake of water); c) controlling the growth through the effects of a) and b) on the pressure potentials (internal hydrostatic pressure) of the seeds and on protein synthesis.     

Consequences of the iron-dependent formation of ferredoxin and flavodoxin on photosynthesis and nitrogen fixation on Anabaena strains

Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply.Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same K_m values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.     

Substance P affects the GABAergic system in the hypothalamo-pituitary axis

In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K⁺-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA.     

CORRELATED BIOCHEMICAL AND ULTRASTRUCTURAL CHANGES IN NITROGEN-STARVED EUGLENA GRACILIS1

Growth of Euglena gracilis Z Pringsheim under photoheterotrophic conditions in a nitrogen-deprived medium resulted in progressive loss of chloroplastic material until total bleaching of the cells occurred. Biochemical analysis and ultrastructural observation of the first stages of the starvation process demonstrated an early lag phase (from 0 to 9 h) in which cells increased in size, followed by a period of cell division, apparently supported by the mobilization of some chloroplastic proteins such as the photosynthetic CO₂-fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. The degradation of the enzyme started after 9 h of starvation and was preceded by a transient concentration of this protein in pyrenoidal structures. Protein nitrogen and photosynthetic pigments as well as number of chloroplasts per cell decreased during proliferation through mere distribution among daughter cells. However, after 24 h, when cell division had almost ceased, there was a slow but steady decline of photosynthetic pigments. This was paralleled by observable ultrastructural changes including progressive loss of chloroplast structure and accumulation of paramylon granules and lipid globules in the cytoplasm. These findings reinforce the role of chloroplastic materials as a nitrogen source during starvation of E. gracilis in a carbon-rich medium. The excess of ribulose-1,5-bisphosphate carboxylase/oxygenase acts as a first reservoir that, once exhausted, is superseded by the generalized disassembly of the photosynthetic structures, if the adverse environment persists more than 24 h.