Evidence for a two pigment visual system in the fiddler crab, Uca thayeri

Intraocular recordings were made from the eyestalks of dark-adapted fiddler crabs (Uca thayeri) during presentation of monochromatic light flashes of different wavelengths and intensities. Two types of signals were recorded in different experiments: slow potentials (electroretinogram) and fast potentials (spikes). The latter were also recorded in the presence of a continuous green or red adapting light. The resulting visual spectral-sensitivity curves, when fitted to rhodopsin-based visual pigment absorption spectra (from Dartnall nomograms), indicated the presence of two visual pigments, one with an absorption maximum near 430 nm, and the other with a peak absorption between 500 nm and 540 nm. The data also provided evidence for some differential bleaching of the pigments in the presence of a colored adapting light, but most of the adaptation effect was probably due to changes in screening pigment and neural desensitization or inhibition. These two observations suggest that an adequate substrate for color vision may exist in this and other species of fiddler crabs. The electroretinogram and spike-recording methods produced similar visual-sensitivity data, suggesting that latter technique, a much more efficient way of collecting data that is physiologically relevant, may be the method of choice for determining spectral sensitivity in crustaceans.     

6-Amino-chrysene, a potent inhibitor of transferase activity in single living RTG2 cells

Previous reports on the inhibitory effect of 6-amino-chrysene (6AC) on benzo(a)pyrene (BP) metabolism using single living cells have suggested that aryl hydrocarbon hydroxylase (AHH) is not the only pathway for 6AC metabolism. We present here results demonstrating that direct glucuronidation may constitute an alternative pathway for 6AC elimination. First, we describe the conjugate of 6AC to UDP-glucuronic acid (UDPGA) in solution. We performed competition experiments between 6AC and monohydroxy BP, which are known to be good substrates for glucuronic transferase (GT), in RTG2 cells, using microspectrofluorimetry. Because of intracellular accumulation of fluorescent metabolites during BP metabolism, RTG2 cells can be used as a tool for simultaneous study of AHH and GT activities. When RTG2 cells have been simultaneously treated with BP and 6AC, GT appeared to be a more specific target for 6AC than AHH in these cells. Therefore, 6AC can be expected to act as a more specific inhibitor for GT than for AHH activity.     

Operative Colonoscopy

In 12 patients with radiologically-proved lesions of the colon total retrograde fibreoptic colonoscopy was performed on the unopened bowel at laparotomy. Additional polyps were found in five patients, and in four of these the polyp was not readily palpable through the bowel wall. This procedure is indicated whenever there are reasonable grounds for suspecting the presence of multiple polypi.     

The effect of atebrine and an acridine analog (BCMA) on the coenzyme fluorescence spectra of cultured melanoma and Ehrlich ascites (EL2) cells.

Coenzyme fluorescence spectra of single living cells are due to free pyridine nucleotides (folded configuration), bound pyridine nucleotides (unfolded configuration) and a third component, possibly a mixture or flavins. Such spectra can be used to recognize possible differences in coenzyme composition between cell lines or changes of metabolic pathways due to chemicals acting at levels below or above cytotoxicity, by high resolution spectrofluorometry. A study of spectra recorded from cultured Ehrlich ascites (EL2), and Harding Passey melanoma cells (HPM-67 and HPM-73 line) grown under comparable conditions, shows that free NAD(P)H predominates in HPM-67 and EL2, while this coenzyme is bound in HPM-73. The free/bound ratio may be profoundly modifed by chemicals, e.g. in the HPM-73 increase of free and decrease of bound NAD(P)H occurred upon treatment with 10(-6) oligomycin. When atebrine at levels (10(-6) M) below cytotoxicity was added, there was a decrease of the free NAD(P)H spectrum possibly through energy transfer from NAD(P)H to atebrine. Consideration of long range energy transfer i.e., excitation of atebrine by fluorescence of NAD(P)H vs. short range transfer of excitation energy from free NAD(P)H to atebrine, favors the latter mechanism. A transient (reversible) increase in atebrine fluorescence is seen following intracellular microinjection of substrate (e.g. glucose-6-P) leading to an increase in free NAD(P)H. At cytotoxic levels of atebrine (e.g 2 x 10(-5) M) an irreversible increase of atebrine fluorescence is seen. The microspectrofluorometric technique appears therefore well suited to study physiological processes at the level of intracellular coenzymes, as well as possible processes of intermolecular energy transfer in the microenvironment.     

Two-dimensional immunoelectrophoresis of spontaneous dissociation of low density lipoproteins]

Plasma-lipoproteins isolated between d 1.020 and d 1.055 g/ml were partially delipidated with ethyl ether at 4 degrees C. This treatment induces a transformation of the lipoproteins which is evolutive during several days. Bidimensional immunoelectrophoresis reveals the lipoproteins dissociation and the appearance of 4 immunologically different fractions. The time dependent formation of these subunits is slowed down by EDTA and less efficiently by antioxydants. Once started, the dissociation can be accelerated by heating at 37 degrees C or by UV exposition. Another lipopeptide is more easily revealed by anti VLDL antiserum. It can be shown in the native and in the partially or completely delipidated LDL. Its presence does not depend on lipoprotein dissociation.