T-DNA length variability in mannopine hairy root: more than 50 kilobasepairs of pRi T-DNA can integrate in plant cells

Independent carrot (Daucus carota) hairy root lines were established by inoculation of discs taken from the same carrot with Agrobacterium rhizogenes 8196 and A. tumefaciens C58C1(pRi8196) carrying pRi8196. Several lines were compared with respect to T-DNA length. One of them was found to have integrated sequences covering more than 50 kbp of the Ri plasmid     

Transport of proteins into yeast mitochondria

The amino-terminal sequences of several imported mitochondrial precursor proteins have been shown to contain all the information required for transport to and sorting within mitochondria. Proteins transported into the matrix contain a matrix-targeting sequence. Proteins destined for other submitochondrial compartments contain, in addition, an intramitochondrial sorting sequence. The sorting sequence in the cytochrome c1 presequence is a stop-transport sequence for the inner mitochondrial membrane. Proteins containing cleavable presequences can reach the intermembrane space by either of two pathways: (1) Part of the presequence is transported into the matrix; the attached protein, however, is transported across the outer but not the inner membrane (eg, the cytochrome c1 presequence). (2) The precursor is first transported into the matrix; part of the presequence is then removed, and the protein is reexported across the inner membrane (eg, the precursor of the iron-sulphur protein of the cytochrome bc1 complex). Matrix-targeting sequences lack primary amino acid sequence homology, but they share structural characteristics. Many DNA sequences in a genome can potentially encode a matrix-targeting sequence. These sequences become active if positioned upstream of a protein coding sequence. Artificial matrix-targeting sequences include synthetic presequences consisting of only a few different amino acids, a known amphiphilic helix found inside a cytosolic protein, and the presequence of an imported chloroplast protein. Transport of proteins across mitochrondrial membranes requires a membrane potential, ATP, and a 45-kd protein of the mitochondrial outer membrane. The ATP requirement for import is correlated with a stable structure in the imported precursor molecule. We suggest that transmembrane transport of a stably folded precursor requires an ATP-dependent unfolding of the precursor protein.     

Inhibition of endocytosis from coated pits by acidification of the cytosol

Binding and endocytosis of the ligands transferrin, epidermal growth factor (EGF), and ricin were measured in a number of different cell lines after treatment of cells with compounds that react with SH-groups and under conditions where the cytosolic pH was lowered. N-ethylmalemide and diamide irreversibly inhibited endocytosis of all ligands tested, whereas low pH in the cytosol strongly inhibited endocytosis of transferrin and EGF. Data obtained by electron microscopy indicated that the formation of coated vesicles from coated pits is inhibited in acidified cells. Entry of ricin was much less affected, and ricin endocytosed under these conditions was able to intoxicate the cells. At low pH in the cytosol there was a calcium-dependent increase in the number of transferrin receptors at the cell surface. The increase was even larger in the presence of the calcium ionophore A23187, whereas it was completely blocked by the calmodulin antagonists trifluoperazine and W7. The results show that endocytosis from coated pits can be inhibited in a reversible way by acidification of the cytosol and they suggest that a second pathway of endocytosis exists, possibly involving formation of vesicles from uncoated areas of the membrane.     

Alzheimer's disease: study of the distribution of tau proteins constituting helical filament pairs in human central nervous tissue

Tau proteins are the major components of Paired Helical Filaments (PHF) of Alzheimer's disease. Using the immunoblot technique and an antiserum against PHF, we have studied the distribution of Tau proteins in the different areas of normal human brains and Alzheimer brains. Tau proteins were clearly present in cortical grey matter but were difficult to detect in the white matter. In Alzheimer brains, we observed two differences: first, there is an important background due to the partial dissociation of the lesions containing Tau aggregates. Second, the profile of Tau proteins is modified, due to abnormal phosphorylation. Thus, Tau proteins are found in large amounts in the grey matter of the cortical areas and are not exclusively distributed in the axonal domain. The normal cortical distribution of Tau in the human brain correlates well with the distribution of histological lesions that contain PHF (neurofibrillary tangles and neuritic plaques) in the Alzheimer cortex.     

The effects of intraventricular carbachol injections on the free-running activity rhythm of the hamster

The effects of light on the circadian pacemaker in the suprachiasmatic nucleus (SCN) are mediated by the retinohypothalamic tract (RHT) and by the retinogeniculosuprachiasmatic tract (RGST). The neurotransmitter of the RGST is neuropeptide Y. The RHT may contain glutamate and aspartate. Recent evidence indicates that acetylcholine could also be involved in phase shifting by light. We determined that intraventricular injections with an acetylcholine agonist, carbachol, induces phase advances during the subjective day and phase delays during the early subjective night. No differences were observed between phase shifts induced in constant darkness and those induced in continuous light. A dose-response curve for carbachol was described at circadian time 6 (CT6). Injections at CT14 with various dosages of carbachol indicated the same dose dependency for this circadian time. Finally, carbachol injections in split animals resulted in similar responses of the two components of the split activity rhythm.     

Existence and function of a receptor for immunoglobulin A on human eosinophils

The existence of receptors for immunoglobulin A on human eosinophils is demonstrated by flow cytofluorometry. Between 5 and 60% of eosinophils purified from peripheral blood of hypereosinophilic patients are able to bind monomeric serum IgA. The addition of antihuman IgA antibodies to surface IgA-bearing eosinophils induces the exocytosis of peroxidase contained in the granules suggesting a cell activation due to IgA receptors. The inhibition of antiparasitic cytotoxicity by eosinophils preincubated with IgA under a polymeric form only, indicates the low affinity of IgA receptors as well as their participation in the effector function of eosinophils.     

Death and brain death: a new formulation for Canadian medicine. Canadian Congress Committee on Brain Death.

Between June 1984 and December 1986, 35 patients with acute myocardial infarction received streptokinase intravenously within 3 hours after the beginning of chest pain and underwent percutaneous transluminal coronary angioplasty (PTCA) either immediately (in 2 cases) or 1 to 19 (mean 4.4) days later (in 33). The rate of successful PTCA was 89%. Reocclusion occurred in one patient. The mean percentage of stenosis decreased from 86% to 11%. The mean trans-stenotic gradient was reduced from 41 to 11 mm Hg. The results suggest that in patients whose condition is stable, PTCA performed a few days after thrombolysis is a valuable alternative to more aggressive treatment with immediate PTCA.     

The limited photochemical activity of solid aggregated forms of bovine rhodopsin

The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin.