Resonance electroconformational coupling: A proposed mechanism for energy and signal transductions by membrane proteins

Recent experiments show that membrane ATPases are capable of absorbing free energy from an applied oscillating electric field and converting it to chemical bond energy of ATP or chemical potential energy of concentration gradients. Presumably these enzymes would also respond to endogenous transmembrane electric fields of similar intensity and waveform. A mechanism is proposed in which energy coupling is achieved via Coulombic interaction of an electric field and the conformational equilibria of an ATPase. Analysis indicates that only an oscillating or fluctuating electric field can be used by an enzyme to drive a chemical reaction away from equilibrium.In vivo, the stationary transmembrane potential of a cell must be modulated to become locally oscillatory if it is to derive energy and signal transduction processes.     

Evidence for a Sertoli cell, FSH-suppressible inhibiting factor(s) of testicular steroidogenic activity

By using a model of immature porcine Leydig and Sertoli cells cultured in serum free defined medium, we evidenced a paracrine control of Leydig cell steroidogenic activity by Sertoli cells via a secreted inhibiting protein(s). This protein(s), partially purified using gel filtration (M.W. 20,000-30,000) suppresses the steroidogenic responsiveness to LH/hCG by decreasing the specific LH/hCG binding (52% decrease) and hormone steroid biosynthesis (73% decrease) at a level(s) located between cAMP production and pregnenolone formation. The suppression of this inhibitor(s) by FSH, in a dose dependent manner, is one mechanism by which FSH "sensitizes" Leydig cell response to LH/hCG stimulation.     

The six genes of the Rubisco small subunit multigene family from Mesembryanthemum crystallinum,a facultative CAM plant

The nucleotide sequences of the entire gene family, comprising six genes, that encodes the Rubisco small subunit (rbcS) multigene family in Mesembryanthemum crystallinum (common ice plant), were determined. Five of the genes are arranged in a tandem array spanning 20 kb, while the sixth gene is not closely linked to this array. The mature small subunit coding regions are highly conserved and encode four distinct polypeptides of equal lengths with up to five amino acid differences distinguishing individual genes. The transit peptide coding regions are more divergent in both amino acid sequence and length, encoding five distinct peptide sequences that range from 55 to 61 amino acids in length. Each of the genes has two introns located at conserved sites within the mature peptide-coding regions. The first introns are diverse in sequence and length ranging from 122 by to 1092 bp. Five of the six second introns are highly conserved in sequence and length. Two genes, rbcS-4 and rbcS-5, are identical at the nucleotide level starting from 121 by upstream of the ATG initiation codon to 9 by downstream of the stop codon including the sequences of both introns, indicating recent gene duplication and/or gene conversion. Functionally important regulatory elements identified in rbcS promoters of other species are absent from the upstream regions of all but one of the ice plant rbcS genes. Relative expression levels were determined for the rbcS genes and indicate that they are differentially expressed in leaves.     

Expression of the cold-induced wheat gene Wcs120 and its homologs in related species and interspecific combinations.

Low-temperature response was measured at the whole plant and at the molecular level in wheat-rye amphiploids and in other interspecific combinations. Cold tolerance of interspecifics whose parents diverged widely in hardiness levels resembled the less hardy higher ploidy level wheat parent. Expression of the low-temperature induced Wcs120 gene of wheat (Triticum aestivum L. em. Thell.) has been associated with freezing tolerance and was used here to study mRNA and protein accumulation in interspecific and parental lines during cold acclimation. Northern and Western analyses showed that homologous mRNAs and proteins were present in all the related species used in the experiments. Cold-tolerant rye (Secale cereale L.) produced a strong mRNA signal that was sustained throughout the entire 49-day cold-acclimation period. The wheats produced a mRNA signal that had diminished after 49 days of low-temperature exposure. The wheat-rye triticales did not exhibit the independent accumulation kinetics of the cold-tolerant rye parent but, rather, more closely resembled the wheat parent in that the mRNA signal was greatly diminished after 49 days of low-temperature exposure. The influence of the rye genome was manifest in slightly greater mRNA and protein accumulation in earlier stages of acclimation. Protein accumulations in the triticales were also maintained to a somewhat greater extent than found in the wheats at the end of the 49-day acclimation period. Protein accumulations in the wheat-crested wheatgrass (Agropyron cristatum L. Gaertner) interspecific resembled that of the wheat parent. The influence of the higher ploidy level wheats of the expression of homologous gene families from wheat-related hardy diploids in interspecific combinations may in part explain the poor cold tolerance observed.     

Iron mobilization from ferritin by chelating agents

The release of iron from horse spleen ferritin by the chelating agents desferrioxamine B, rhodotorulic acid, 2,3-dihydroxybenzoate, 2,2′-bipyridyl and pyridine-2-aldehyde-2-pyridyl hydrazone (Paphy) has been studied in vitro. Ferritin prepared by classical procedures involving thermal denaturation releases its iron less effectively than ferritin isolated by a modified procedure that avoids this step. Desferrioxamine B and rhodotorulic acid are the most effective in releasing iron from both preparations of ferritin. When FMN is added, iron release by desferrioxamine B, rhodotorulic acid, and 2,3-dihydroxybenzoate was effectively blocked, whereas both bipyridyl and Paphy showed a marked simulation. A substantial increase in iron release was also observed for bipyridyl and Paphy with ascorbate; a less important increase was noted for rhodotorulic acid. EDTA exerted a marked inhibition of iron release from ferritin with rhodotorulic acid, 2,3-dihydroxybenzoate, bipyridyl, and Paphy. The effects of citrate and oxalate on iron release by the chelators was small. The effect of the concentration of flavin on iron release from ferritin by bipyridyl and desferrioxamine B have been studied. Desferrioxamine is unable to mobilize FeII from ferritin following reduction by reduced FMN, whereas bipyridyl can rapidly complex the ferrous iron. The results are discussed in the context of our current concepts of storage iron mobilization in the treatment of iron overload.     

Variations in litter size and reproductive effort within and between some populations of Lacerta vivipara

We studied the relationships between litter size, litter weight, newborn weight, relative clutch mass and the female snout-vent length in some Lacerta vivipara populations over a period of three years.
Litter size and litter weight were positively correlated with female snout-vent length in all the populations for all the years, as in most other lizard species. Relative clutch mass generally increased with female size, though correlations appear not to be very tight.
Considering the two best studied populations suggests that montane females invest less in reproduction than lowland ones.
The main reproductive traits of the species appeared highly variable between as well as within the different populations hitherto studied.
We argue that current theory about lizard reproductive strategy requires, first to work out a good estimate of reproductive effort, and second to get more information about the relations between the species and their environmental, biotic and abiotic conditions.     

A study of factors affecting anther culture of cauliflower (Brassica oleracea var. botrytis)

Experiments on three autumn-heading cauliflower genotypes (2 hybrids and a genotype selected from a population) were conducted to study different factors affecting anther culture. Culture conditions of the donor plants proved to be important: the best results were obtained during spring in a greenhouse where the temperature was maintained between 10 and 20°C. Overall winter and spring seemed more suitable than summer and early autumn for culture establishment. The optimal bud development stage depended on the genotype: for the hybrid 702, the greatest number of embryos for 100 plated anthers was obtained at the uninucleate pollen stage of the microspores; for V23.2 and 703, the optimal stage of the buds corresponded to the first mitotic division. Sucrose proved to be the best carbon supply for embryogenesis with an optimal concentration of 140 g l^-1. The addition of a cytokinin (BAP) in the medium led to lower embryo production, and this negative effect increased when the hormone concentration in the medium increased. The use of liquid medium and a dark incubation period immediately after the high temperature treatment were favourable for embryogenesis.     

The role of acetylcholine receptor antibodies in myasthenia gravis.

Myasthenia gravis is an autoimmune disease of man characterized by remitting and relapsing muscle fatigability. Although the etiology and pathogenesis are incompletely understood, the presence of circulating antibodies directed against the nicotinic acetylcholine (ACh) receptor in 80--90% of patients with myasthenia gravis and the identification of immune complexes at their neuromuscular junction have helped explain the altered neuromuscular transmission. The ACh receptor antibodies do not block access of ACh to the receptor, but do decrease the number of receptors by accelerating their degradation both in rat myotube cultures and in vivo models. In vitro these antibodies play a major role in myasthenia gravis. However, correlations of antibody titers with the clinical state following thymectomy or in neonatal myasthenia suggest that host factors may be equally important in determining whether the ACh receptor antibodies will result in clinical myasthenia.     

On the state of carotenoids bound to reaction centers of photosynthetic bacteria: A resonance raman study

The carotenoids bound to reaction centers of wild, Ga and GlC strains of Rhodopseudomonas spheroides, of Rhodospirillum rubrum, strain S1 and of Rhodopseudomonas viridis, yield very similar, but unusual resonance Raman spectra. Through a comparison with resonance Raman spectra of 15,15′-cis-β-carotene, these carotenoids are shown to assume cis conformations, while the corresponding chromatophores contain all-trans forms only. These cis conformations likely are identical for all the carotenoids studied. They remain unaffected by variations of temperature from 20 to 300 K as well as by the redox state of $\text{P-870}$. They are unstable, being rapidly isomerised towards the all-trans forms when extracted from the reaction centers. The possible nature of these conformers is discussed on the basis of their electronic and vibrational spectra.