The roles of c-type cytochromes in algal photosynthesis. Extraction from algae of a cytochrome similar to higher plant cytochrome f.

A membrane-bound cytochrome resembling higher plant cytochrome f in many respects has been extracted from the algae Chlamydomonas. Euglena and Anacystis, and partially purified. The spectra of the cytochromes from Chlamydomonas and Euglena are virtually identical to that of parsley cytochrome f, with alpha-band maxima near 554 nm, very asymmetrical beta-bands, and gamma-band maxima at 421 nm. The cytochrome from Anacystis had alpha and gamma-bands both shifted to slightly longer wavelengths. The redox potential of the cytochrome from Chlamydomonas was determined as +350 mV, and its minimum molecular weight in sodium dodecyl sulphate as 31 000. The cytochrome from Euglena showed a rate of reaction with higher plant plastocyanin at least 100 times that of the soluble Euglena cytochrome c-552, and was unaffected by Euglena cytochrome c-552 antiserum. A very fast rate of electron transfer occurred between this cytochrome purified from Euglena and cytochrome c-552. The roles of the membrane-bound and soluble c-type cytochromes in algal photosynthesis are discussed, and it is recommended that the name cytochrome f should be reserved for the membrane-bound cytochrome (to emphasize its affinity with higher plant cytochrome f), while the soluble one should be named by its alpha-band (c-552, c-553, etc.) to make clear its distinctness from higher plant cytochrome f and homology with mitochondrial cytochrome c.     

Retrospective evaluation of gynecologic cytodiagnosis. II. Interlaboratory reproducibility as shown in rescreening large consecutive samples of reported cases

Two laboratories exchanged and rescreened a large sample of cases with cervicovaginal smears they had consecutively accessioned to examine the reproducibility of gynecologic cytodiagnosis under optimum conditions. At least a "working agreement" (diagnoses within +/- 1 category on a ten-category scale) was achieved in diagnoses of normal, benign reaction and squamous abnormality (from minimal dysplasia though invasive cancer) in 18,859 cases (96.8%), of endometrial abnormality in 21 cases (42%) and of "unsatisfactory" in 99 cases (20.7%). Larger differences occurred in greater than or equal to 30% of cases except in the categories of "normal" and "benign reaction," reaching a maximum of 82% for moderate dysplasia. Reexamining 382 cases decreased disagreement by category to the 20% to 65% range only in the five categories of dysplasia plus carcinoma in situ. Agreement was not predicated on the presence of endocervical cells or squamous metaplasia; the basis for "unsatisfactory" calls was not uniform. Comparison of the laboratories' diagnoses with referee diagnoses or, on 178 cases, with tissue diagnoses also demonstrated differences in diagnostic criteria.     

Effects of phorbol esters on endothelial cell microfilaments: Laser scanning confocal microscopy and quantitative morphometry of dose dependent changes

Phorbol esters are known to alter microfilaments but it is not clear if the changes correspond to modulation of the phosphoinositide turnover/protein kinase C system. The novel technique of laser scanning confocal epifluorescence was used to study fiber orientation in phorbol ester treated cells. We treated endothelial cells with control agents and agents known to stimulate protein kinase C: 4 alpha-phorbol, phorbol 12-myristate 13-acetate (PMA), phorbol dibutyrate (PDB), or lipopolysaccharide. After incubation with the test agents, the endothelial cell microfilaments were stained with rhodamine pholloidin and viewed by conventional epifluorescence and by laser scanning confocal epifluorescence microscopy. The images obtained by the confocal microscopy corresponded to a thin optical section through the cells, 300 nm or more in thickness. The microfilaments extended predominantly in the plane of focus. After exposure of the cells to phorbol esters, the stress fibers became more nearly parallel in arrangement or were shortened, but remained in the plane of focus. The modification of microfilaments in response to phorbol esters was quantitated by a single blind analysis. In order to compare the morphological changes with a biochemical action of the phorbol esters, we measured phosphoinositide turnover. The dose-dependence of morphological changes was compared and contrasted to the dose-dependent effect of phorbol esters on bradykinin-stimulated phosphoinositide turnover. PMA had about the same EC50 (1-5 nM) for both biochemical and morphological processes. PDB was less potent in inducing the disruption of microfilament structure than in inhibiting phosphoinositide turnover. Lipopolysaccharide was ineffective in inducing a morphological change under these conditions. A simple activation of protein kinase C is insufficient to explain the dose-dependent effects of phorbol esters. Thus a morphometric analysis can help distinguish the potency of cytoskeleton modulators.     

Pain, paradox, and value

The author argues that "as soon as one begins to study the understanding and management of pain in science, human medicine, and veterinary medicine, one begins to encounter a variety of apparent paradoxes." He contends that these paradoxes, ten of which he identifies and discusses in this essay, are based on flawed philosophical and valuational assumptions underlying science and medicine. Rollins concludes that, as social morality increasingly has an impact on science, a new ideology will evolve that is more receptive to the moral universe and more capable of a "coherent vision of pain, one which acknowledges that the medical notion of adequacy of anaesthesia is as much a moral as a scientific one."     

Amplification by glycine of the effect of the GABA transport inhibitor THPO on synaptosomal GABA level

Mice were injected intramuscularly (2 mmol/kg) with the glia-selective GABA uptake inhibitor 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol (THPO) 60 min prior to sacrifice, or with glycine (10 mmol/kg) 45 min before death, or with a combination of both. After decapitation of the animals, the brains were removed and synaptosomes prepared and analyzed for content of GABA, taurine, glutamine, serine, glutamate and aspartate. While no differences as compared with control animals were found for aspartate, serine and glutamine, synaptosomal GABA levels were increased significantly after injections with either THPO or glycine. The individual effects of THPO and glycine were found to be additive. Taurine levels were decreased to a similar extent in animals which had received either THPO alone or THPO in conjunction with glycine. Treatment with THPO and glycine in combination led to a decrease in the synaptosomal glutamate content. The findings are consistent with the previously observed synergistic anticonvulsant actions of THPO and glycine being mediated via the GABA neurotransmitter system.     

Intercalation of anthracyclines into living cell DNA analyzed by flow cytometry.

Anthracyclines (ANT) are used in the treatment of leukemia and other cancers. These drugs have been shown to intercalate between the strands of DNA. In the present study, we show that the amount of ANT intercalated into DNA can be determined by measuring the fluorescence resonance energy transfer (FRET) between Hoechst 33342 (H33342) and ANT bound to DNA. The transfer efficiency was found to depend on the amount of disposable ANT but was independent of the amount of H33342 bound to DNA over a wide range of H33342 concentrations. The method was adapted for flow cytometric measurement of FRET in whole living cells and was used to evaluate the degree of intercalation of daunorubicin (DAU) and idarubicine (IDA) into DAU-sensitive and DAU-resistant leukemic cell lines. ANT intercalation into DNA was affected by factors which modify the intracytoplasmic concentration of ANT, and it was shown that the action of ANT and the resistance to ANT could not be attributed solely to the intercalative effect of the drugs. The method has advantages over previously described methods and represents a useful complementary tool in studies on the mode of action of ANT and the mechanisms of chemoresistance.     

Structure and evolution of insulins: implications for receptor binding.

Insulin is a member of a family of hormones, growth factors and neuropeptides which are found in both vertebrates and invertebrates. A common 'insulin fold' is probably adopted by all family members. Although the specificities of receptor binding are different, there is a possibility of co-evolution of polypeptides and their receptors.     

Prohibitin, an evolutionarily conserved intracellular protein that blocks DNA synthesis in normal fibroblasts and HeLa cells.

Genes that act inside the cell to negatively regulate proliferation are of great interest because of their implications for such processes as development and cancer, but these genes have been difficult to clone. This report details the cloning and analysis of cDNA for prohibitin, a novel mammalian antiproliferative protein. Microinjection of synthetic prohibitin mRNA blocks entry into S phase in both normal fibroblasts and HeLa cells. Microinjection of an antisense oligonucleotide stimulates entry into S phase. By sequence comparison, the prohibitin gene appears to be the mammalian analog of Cc, a Drosophila gene that is vital for normal development.     

A restriction-fragment-length difference detected by the anonymous probe DXS199 exhibits non-Mendelian inheritance.

Anonymous DNA probes were isolated from an X chromosome-enriched flow-sorted library. One of these probes, DXS199, identified a restriction-fragment difference that failed to show Mendelian segregation. All normal females were found to have two AvaII fragments of 6.5 kb and 6.0 kb, whereas all normal males had only the 6.5-kb fragment. DNA from a 49,XXXXY male was found to have both 6.0- and 6.5-kb AvaII fragments, in the same 3:1 ratio as seen in the inactive:active number of X chromosomes. This variant, which reflects a structural difference between active and inactive X chromosomes, is likely to be due to a methylation site on the active X chromosome.