Photoreactions of human lens monomeric crystallins

Human lens beta s- and gamma A-crystallins exhibit very similar tryptophan fluorescence emission maxima (329 nm). gamma A isolated from infant human lenses is photo-oxidized by 300 nm irradiation and forms water-insoluble aggregates; beta s or gamma A from young human lenses form a small amount of water-soluble crosslinked species. At least part of the mechanism of photodamage by 300 nm irradiation is photogeneration of the oxidant H2O2 via the generation of O2- radical, this reaction occurs via photosensitization by the tryptophan photo-oxidation product N-formylkynurenine (N-FK) or related species. These results indicate that even though the tryptophan residues of beta s- and gamma A-crystallins are in hydrophobic (buried) microenvironments as compared to those of the alpha- and beta-crystallins, the photogeneration of N-FK is sufficient to produce O2- and H2O2.     

Bcl-2 phosphorylation is required for inhibition of oxidative stress-induced lysosomal leak and ensuing apoptosis.

B-cell leukemia/lymphoma 2 (Bcl-2) blocks oxidant-induced apoptosis at least partly by stabilizing lysosomes. Here we report that phosphorylation of Bcl-2 may be required for these protective effects. J774 cells overexpressing wild-type Bcl-2 resist oxidant-induced lysosomal leak as well as apoptosis, and this protection is amplified by pretreatment with phorbol 12-myristate 13-acetate (which promotes protein kinase C (PKC)-dependent phosphorylation of Bcl-2). In contrast, cells overexpressing the Bcl-2 mutant S70A (which cannot be phosphorylated) are not protected in either circumstance. Transfection with Bcl-2(S70E), a constitutively active Bcl-2 mutant which does not require phosphorylation, is protective independent of PKC activation. In contrast, C(2)-ceramide, a putative protein phosphatase 2A activator, abolishes the protective effects of wild-type Bcl-2 overexpression but does not diminish protection afforded by Bcl-2(S70E). Additional results suggest that, perhaps as a consequence of lysosomal stabilization, Bcl-2 may prevent activation of phospholipase A2, an event potentially important in the ultimate initiation of apoptosis.     

Microvascular pressures measured by micropuncture in isolated perfused lamb lungs

To investigate the influence of vasomotor tone and vessel compliance on pulmonary segmental vascular resistance, we determined the longitudinal distribution of vascular pressures in 15 isolated blood perfused lungs of newborn lambs. We measured pulmonary arterial and left atrial pressures and by micropuncture the pressures in 20- to 80-micron-diam subpleural arterioles and venules, both before and after paralyzing the vasculature with papaverine hydrochloride. In five lungs we also determined the microvascular pressure profile during reverse perfusion. In lungs with baseline vasomotor tone, approximately 32% of the total pressure drop was in arteries, approximately 32% in microvessels, and approximately 36% in veins. With elimination of vasomotor tone, arterial and venous resistances decreased to one-fifth and one-half of base-line values, respectively, indicating that vasomotor tone contributed mainly toward arterial resistance. During reverse perfusion, the pressure drop in veins was similar to that in arteries during forward perfusion, suggesting that the compliance of arteries and veins is comparable. We conclude that vascular tone and compliance are important factors that determine the distribution of segmental vascular resistance in lungs of the newborn.     

The signal sequence suffices to direct export of outer membrane protein OmpA of Escherichia coli K-12.

We studied whether information required for export is present within the mature form of the Escherichia coli 325-residue outer membrane protein OmpA. We had previously analyzed overlapping internal deletions in the ompA gene, and the results allowed us to conclude that if such information exists it must be present repeatedly within the membrane part of the protein encompassing amino acid residues 1 to 177 (R. Freudl, H. Schwarz, M. Klose, N. R. Movva, and U. Henning, EMBO J. 4:3593-3598, 1985). A deletion which removed the codons for amino acid residues 1 to 229 of the OmpA protein was constructed. In this construct the signal sequence was fused to the periplasmic part of the protein. The resulting protein, designated Pro-OmpA delta 1-229, was processed, and the mature 95-residue protein accumulated in the periplasm. Hence, information required for export does not exist within the OmpA protein.     

A nuclear yeast gene (GCY) encodes a polypeptide with high homology to a vertebrate eye lens protein

We describe here the nuclear gene for a yeast protein showing unexpectedly high homology with mammalian aldo/keto reductases as well as with p-crystallin, one of the prominent proteins of the frog eye lens. Although it could be proven that the gene occurs as a single copy in the haploid yeast genome, replacement of the intact by a disrupted, nonfunctional allele led to no obvious phenotype, indicating that the gene is dispensable. The gene was assigned to chromosome XV. It is transcribed in vivo into an mRNA of about 1300 bases with a coding capacity for a protein of 312 amino acids (estimated Mr 35,000).     

Effects of 6-hydroxydopamine and 5-hydroxydopamine onlthe teleost melanophores innervation

Intraperitoneal injections of 6-OH-dopamine (80 mg kg^−l) promote, in toad fish, killifish, lsummer and winter flounders, a darkening of their colour and loss of capacity to adapt tolthe colour of the background. This condition persisted for three weeks after which thelanimals gradually returned to normal. The study of the skin of 6-hydroxydopamineltreated killifish showed degenerative lesions in the fine nerves and synapses of its melanophores, 124 h after the administration of the drug. These lesions progressed and 4 days later, lno synaptic structures could be detected in these cells. This condition persisted up to thel20th day. These results suggest that melanophores have a single monoaminergic innervaion.