Voltage dependence of Na-Ca exchanger conformational currents.

Properties of a transient current (Icont) believed to reflect a conformational change of the Na-Ca exchanger molecules after Ca2+ binding were investigated. Intracellular Ca2+ concentration jumps in isolated cardiac myocytes were generated with flash photolysis of caged Ca2+ dimethoxynitrophenamine, and membrane currents were simultaneously measured using the whole-cell variant of the patch-clamp technique. A previously unresolved shallow voltage dependence of Icont was revealed after developing an experimental protocol designed to compensate for the photoconsumption of the caged compound. This voltage dependence can be interpreted to reflect the distribution of Na-Ca exchanger conformational states with the Ca2+ binding site exposed to the inside of the cell immediately before the flash. Analysis performed by fitting a Boltzmann distribution to the observed data suggests that under control conditions most exchanger molecules reside in states with the Ca2+ binding site facing the outside of the cell. Dialysis of the cytosol with 3',4'-dichlorobenzamil, an organic inhibitor of the Na-Ca exchange, increased the magnitude of Icont and changed the voltage dependence, consistent with a parallel shift of the charge/voltage curve. This shift may result from intracellular DCB interfering with an Na(+)-binding or Na(+)-translocating step. These observations are consistent with Icont arising from a charge movement mediated by the Na-Ca exchanger molecules after binding of Ca2+.     

Autofluorescence imaging for recurrence detection in skin cancer postoperative scars

This clinical study is a first attempt to use autofluorescence for recurrence diagnosis of skin cancer in postoperative scars. The proposed diagnostic parameter is based on a reduction in scar autofluorescence, evaluated in the green spectral channel. The validity of the method has been tested on 110 postoperative scars from 56 patients suspected of non‐melanoma skin cancer, with eight patients (13 scars) available for the repeated examination. The recurrence diagnosis within a scar has been made after two subsequent autofluorescence check‐ups, representing the temporal difference between the scar autofluorescence amplitudes as a vector. The recognition of recurrence has been discussed to represent the significant deviations from the value of vector angle θ. This new autofluorescence‐based method can be easily integrated into the postoperative monitoring of surgical scars and can help diagnose the recurrence of skin cancer from the early stage of scar development.     

Concentration gradients of free sterols,steryl esters and lipid phosphorus in the trunkwood of Scot's pine (Pinus sylvestris L.)

The amounts of free sterols, steryl esters and lipid phosphorus were determined in the sapwood and heartwood of mature, and in the outer and inner sapwood of young Pinus sylvestris trees. In the mature trees (up to 70 years old) the heartwood contains significantly higher amounts of free sterols than the sapwood. No radial gradient can be demonstrated in the amounts of steryl esters. Lipids extracted from the sapwood contain higher amounts of phosphorus than those from the heartwood. Stems of young Pinus sylvestris trees (up to 13 years old) show in the inner sapwood higher amounts of both free sterols and steryl esters than the peripheral younger wood zone. The inner sapwood of the young stems shows slightly higher amounts of lipid phosphorus than the outer sapwood. The results indicate that Pinus sylvestris accumulates both free sterols and steryl esters in the stems at a very early stage of the life cycle. Sterol accumulation in the innermost parts of the stems seems not to depend on heartwood formation.     

Perinatal anti-androgen treatment and genotype affect the mesotelencephalic dopamine system and behavior in mice

Sex and strain differences in tyrosine hydroxylase activity (TH) of brain dopamine systems have been reported for mice. To investigate if there might be a causal relationship between perinatal androgen secretion and regional mesotelencephalic TH activity, BALB/cJ and C57BL/6ByJ male mice were treated perinatally with cyproterone, a steroidal anti-androgen (or vehicle), and orchiectomized at 1 month of age. Two-way analysis of variance indicated significant treatment and strain effects in the mesencephalon and tuber olfactorium: perinatal cyproterone treatment lowered TH activity, and BALB/cJ had higher regional TH activities than those of C57BL/6ByJ. The most prominent behavioral effects of cyproterone treatment were found in the expression of scratching, which was considerably increased in both strains. Possible implications of these results are discussed.     

Heterologous hybridization of Azospirillum DNA to Rhizobium nod and fix genes

Abstract Probes containing the nod and hsn regions of Rhizobium meliloti and the fixABC genes of Rhizobium japonicum were used to perform hybridization experiments with endonuclease-restricted DNA from Azospirillum brasilense strains and 2 Azospirillum lipoferum strains. Homology to nod, hsn and fixA was found in the 4 Azospirillum strains.     

An RP4-prime containing a 285 kb fragment of rhizobium meliloti pSym megaplasmid: Structural characterization and utilization for genetic studies of symbiotic functions controlled by pSym

Summary We integrated the RP4 plasmid into a selected region of the pSym megaplasmid of Rhizobium meliloti 2011 by homologous recombination between pSym and a cloned fragment of pSym present in the RP4. This cointegrate was used to mobilize into Escherichia coli a Tn5 transposon located on pSym in the vicinity of the site of integration of the RP4. By this technique we obtained a series of RP4-primes that contained large fragments of the pSym megaplasmid and that were most probably generated by IS8 promoted deletions in the RP4-pSym cointegrate. One of them, pGMI42, which carries nitrogenase genes nifD and H as well as nodulation genes, was used for mutagenesis of the corresponding region of pSym after insertion of the Mu prophage into the tet gene. When various (pGMI-42:: Mu)::Tn7 were introduced into R. meliloti 2011 by conjugation, homologous recombination allowed insertion of Tn7 into pSym whereas the pGMI42::Mu was lost due to the suicide effect of Mu. In this way we obtained several symbiotic mutants deficient in either nodulation (Nod^-) or nitrogen fixation (Fix^-) in association with the host plant Medicago sativa.This paper is affectionately dedicated to the memory of Jean-Simon Julliot who initiated and inspired this work and who was killed by an avalanche on February 21, 1982     

Occurrence of ethanol in pea plants in the course of growth under normal and anaerobic conditions

1. At a so-called natural anaerobiosis during the first 48 hours of germination the concentration of ethanol in pea tissues increases (according to the cultivation conditions) up to 40 μmol per gram fresh weight.
2. In a nitrogen atmosphere the content of ethanol in pea seedlings increases as well, and after a 90 hour incubation in N₂ it can reach even 100 μmol ethanol per gram fresh weight. In older plants the content increases the most markedly in cotyledons, but considerable amounts were revealed also in stems and roots. Its increase in vegetative organs of plants cultivated both in light and darkness is more or less identical. Ethylalcohol can be formed by the vegetative organs themselves, as proved by the increase of this metabolite in plants deprived of reserve organs; in addition, however, it is evidently transported into them from reserve parts. Ethanol formed under anaerobiosis is catabolyzed after transferring plants to the air.

     

MHC class II invariant chains in antigen processing and presentation

Most protein antigens cannot elicit a T-cell response unless they are processed to peptides, which are then presented to T lymphocytes by surface MHC class II molecules. Recent evidence supports an essential role of the invariant chain associated with class II MHC polypeptides in antigen processing.