Enzymatic digestive activity in Mytilus chilensis (Hupé 1854) in response to food regimes and past feeding history

Digestive enzyme activities (amylase, cellulase, laminarinase and protease) were analysed in mussels (Mytilus chilensis) from intertidal and subtidal habitats in Yaldad Bay, Chiloé, Chile. In order to analyse the effects of the past-feeding history (origin) and new nutritional conditions (habitat) on these enzymatic activities, a cross-over transplant was carried out and the analysis performed after a 7-day acclimation period. Crystalline styles showed higher carbohydrase and lower protease activities than digestive glands, with the highest differences recorded for subtidal mussels. Cellulase is the enzyme with the highest activity in both the digestive gland and crystalline style in all the experimental conditions. Intertidal mussels transplanted to a subtidal habitat showed enzyme resources significantly higher than in their original habitat. In the inverse case, mussels transferred from an original subtidal habitat to an intertidal one, a significant decrease in carbohydrase and protease activities was observed. The "past feeding history' is involved in the specific and total carbohydrase and protease activities, with a highly significant effect on amylase and cellulase activities in both the crystalline style and the digestive gland. Laminarinase activity can be interpreted considering the habitat (trophic regime), either individually or interacting with mussels' origin, in relation with the feeding periods. The results establish that in M. chilensis, an investment in enzyme resources is one of the mechanisms employed to optimise the acclimated response in terms of energy gains when variations in the food regime occur.

The enhancement of glucose uptake caused by the collapse of gap junction communication is due to an increase in astrocyte proliferation

We have previously shown that several gap junction uncouplers increase the uptake of glucose in astrocytes. The aim of the present work was to study whether the increase in glucose uptake was a consequence of the inhibition of gap junction communication and the purpose of this effect. Our results show that alpha-glycyrrhetinic acid and endothelin-1 increase the uptake of glucose in highly, but not in poorly, coupled astrocytes. This effect depended on connexin 43 levels and was abolished when the inhibition of gap junction communication was prevented by tolbutamide or ouabain. The inhibition of gap junctions increased the rate of glucose incorporation into DNA and RNA, which was inhibited by treatment with dehydroepiandrosterone, an inhibitor of glucose-6-phosphate dehydrogenase, the regulatory enzyme of the pentose phosphate pathway. The inhibition of gap junctions significantly increased astrocyte proliferation, which was counteracted by tolbutamide. These effects were not observed in poorly coupled astrocytes expressing low levels of connexin 43. The increase in astrocyte proliferation caused by gap junction inhibition was prevented when either glucose uptake or the pentose phosphate pathway were inhibited. We conclude that the inhibition of gap junction communication induces astrocyte proliferation, resulting in an enhancement of glucose uptake and its utilization through the pentose phosphate pathway to provide ribose-5-phosphate for the synthesis of nucleic acids.

Non-neuronal cells involved in the degeneration and regeneration of the fish retina

In the present work we show that during the degenerative process occurring after the cryo-elimination of the tench peripheral growing zone many non-neuronal cell types in addition to the resident microglial cells, appear within the affected areas. Some of them are normally found in the retina, such as the retinal pigmented epithelium cells and others originate from extra-retinal tissues. We identified these as granular leukocytes and macrophages. The microglial cells and macrophages, those resident in the sub-retinal space, and the invasive ones, act as phagocytes. The analysis of the injured retina following lesion shows that the invasive macrophages, arising from the scleral extra-retinal tissues, penetrate the neural retina, and migrate from the scleral to the vitreal portion. In contrast those coming from the vitreal extra-retinal tissues migrate in the opposite direction. Moreover, the retinal pigmented epithelium cells present remarkable modifications in their morphology and distribution and enter the neural retina, where they disrupt the surrounding tissue. We have also observed that this cryo-lesion causes an inflammation mediated by a type of granular leukocyte, denominated heterophils which penetrate the neural retina and probably come from the blood supply. Our results suggest that, during the first days after the lesion, the participation of diverse non-neuronal cells removing cell debris from the damaged zone should create a favourable environment allowing the regeneration of the neural retina.

A comparative study of protein kinase C-like immunoreactive cells in the retina

The present study is a morphological and quantitative analysis of protein kinase C-like immunoreactive (PKC-L ir) bipolar cells in the retinas of five different vertebrate species (chicken, tench, zebrafish, goldfish and rat). The morphology of PKC-L-ir bipolar cell axon terminals in fish differs significantly from those of chicken and rat retinas. Fish have bulky terminals whereas chicken and rat have their terminals in the form of small knob-shaped branches. In tench and goldfish, PKC-L-ir bipolar cells gradually decrease in size from the medial (i.e., in tench: mean +/- SD soma area of 30.09 +/- 5.98 microm2) to the peripheral (i.e., in tench: 19.93 +/- 1.73 microm2) retinal regions. This is not observed in chicken, rat or zebrafish where there is more homogeneity in s oma and axon terminal sizes between different retinal regions. Except in chicken, cell density increases from the central (i.e., in tench: mean +/- SD 1795.88 +/- 242.35 cells/mm2) to the peripheral (i.e., in tench: 4295.41 +/- 279.23 cells/mm2) retina. This study provides data that show relevant differences in the PKC-L-ir bipolar morphology and density among birds, fish and mammals. Moreover, these structural variations could mean not only differences in the cellular physiology, but also in the patterns of development and maintenance of the retina in each species.

Growing and regenerating axons in the visual system of teleosts are recognized with the antibody RT97

We have analyzed the immunolabeling with the antibody RT97, a good marker for ganglion cell axons in several species, in the normal and regenerating visual pathways of teleosts. We have demonstrated that RT97 antibody recognizes several proteins in the tench visual system tissues (105, 115, 160, 200, 325 and 335 kDa approximately). By using immunoprecipitation and Western blot we have found that after crushing the optic nerve the immunoreactivity to anti RT97 increased markedly in the optic nerve. In immunohistochemical analysis we also found a different pattern of labeling in normal and regenerating visual pathways. In normal tench RT97 is a good marker for the horizontal cells in the retina, for growing ganglion cell axons which run along the optic nerve from the retina to the optic tectum and of the axon terminals in the stratum opticum and stratum fibrosum and griseum superficiale in the optic tectum. After optic nerve crush, no immunohistochemistry modifications were observed in the retina. However, in accordance with Western blot experiments, in the optic nerve intensely stained groups of regenerating axons appeared progressively throughout the optic nerve as far as the optic tectum. We conclude that the antibody RT97 is an excellent marker of growing and regenerating axons of the optic nerve of fish.

The mismatch repair gene hMSH2 is mutated in the prostate cancer cell line LNCaP

PURPOSE

Mismatch repair genes are responsible for the coordinated correction of misincorporated nucleotides formed during DNA replication. Inactivating and inherited mutations in the prototypic mismatch repair gene hMSH2 have been described in a cancer predisposition syndrome known as hereditary nonpolyposis colon cancer. Patients with hereditary nonpolyposis colon cancer are at increased risk for colon cancer and extracolonic cancers such as upper tract transitional cell carcinoma but not prostate cancer. We investigated expression of hMSH2 in prostate cancer cell lines using genetic and molecular analysis.

MATERIALS AND METHODS

We used the 3 well described prostate cancer cell lines, DU145, LNCaP and PC3. Western blot analysis with monoclonal antibody to hMSH2 was used to assess expression. Southern blot and polymerase chain reaction of genomic DNA were used to identify genetic alterations in the hMSH2 gene. Single cell cloning, dinucleotide repeats and BAT-26 were used to assess the cell lines for microsatellite instability.

RESULTS

The prostate cancer cell line LNCaP did not express hMSH2 and was found to have a homozygous deletion of hMSH2 exons 9 to 16, resulting in truncation of the protein. While microsatellite analysis did not reveal alterations at the BAT-26 locus, single cell cloning produced several LNCaP subclones with alteration at 1 dinucleotide repeat.

CONCLUSIONS

The well described prostate cancer cell line LNCaP has a mutation in the hMSH2 gene, resulting in loss of expression and possible evidence of microsatellite instability. To our knowledge our finding is the first demonstration of a genetic alteration in hMSH2 in a prostate cancer cell line.

IgA nephropathy in psoriasis

IgA nephropathy (IGAN) was first described by Berger and Hinglais in 1968. It is now the most common glomerular disease worldwide. IGAN has been associated with several diseases. Its association with psoriasis has been rarely described. We report a case of IGAN with crescentic changes, associated with psoriasis vulgaris. We review the literature on the association of IGAN with psoriasis and discuss the likely pathogenetic linkage.

Effect of protein kinase A activity on the association of ADP-ribosylation factor 1 to golgi membranes

The small GTP-binding protein ADP-ribosylation factor 1 (ARF1) is an essential component of the molecular machinery that catalyzes the formation of membrane-bound transport intermediates. By using an in vitro assay that reproduces recruitment of cytosolic proteins onto purified, high salt-washed Golgi membranes, we have analyzed the role of cAMP-dependent protein kinase A (PKA) on ARF1 incorporation. Addition to this assay of either pure catalytic subunits of PKA (C-PKA) or cAMP increased ARF1 binding. By contrast, ARF1 association was inhibited following C-PKA inactivation with either PKA inhibitory peptide or RIIalpha as well as after cytosol depletion of C-PKA. C-PKA also stimulated recruitment and activation of a recombinant form of human ARF1 in the absence of additional cytosolic components. The binding step could be dissociated from the activation reaction and found to be independent of guanine nucleotides and saturable. This step was stimulated by C-PKA in an ATP-dependent manner. Dephosphorylated Golgi membranes exhibited a decreased ability to recruit ARF1, and this effect was reverted by addition of C-PKA. Following an increase in the intracellular level of cAMP, ARF proteins redistributed from cytosol to the perinuclear Golgi region of intact cells. Collectively, the results show that PKA exerts a key regulatory role in the recruitment of ARF1 onto Golgi membranes. In contrast, PKA modulators did not affect recruitment of beta-COP onto Golgi membranes containing prebound ARF1.

Efficacy of fenfluramine and dexfenfluramine in the treatment of obesity: a meta-analysis

A meta-analysis was conducted to estimate the difference of weight loss among patients treated with placebo and with fenfluramine or dexfenfluramine after 1, 2, 3, 6, and 12 months of treatment. Placebo-controlled, double-blind, randomized clinical trials, whose results were presented as weight loss by the placebo group and the drug-treated patient group, were selected for the analysis. For the pooled estimations, the method of the weighted means by the inverse of the variance was used. The association between the difference of means and several predictive variables was studied by means of weighted linear regression. Patients treated with fenfluramine or dexfenfluramine achieved a higher weight loss than those receiving placebo in all the periods studied. The greatest efficacy was observed after 3 months of treatment. Beyond this time, there is a decline in the effectiveness. Based on the efficacy data, treatments longer than 3 months would not be justified.

Distribution of the calcium-binding proteins parvalbumin, calbindin D-28k and calretinin in the retina of two teleosts

Using monoclonal antibodies against parvalbumin (PV) and calbindin (CB), and a polyclonal antiserum against calretinin (CR), the expression patterns of these proteins in the retina of the tench and rainbow trout were studied at light microscopic level in in toto preparations and radial sections. Parvalbumin was present in subpopulations of small amacrine cells in both species, but these cells were more abundant and had a clear centre-periphery gradient distribution in the tench. Using the McAB 300 monoclonal antibody against CB, glial cells such as Müller cells, astrocytes in the nerve fibre layer, and sparse large cells close to the entrance of the optic nerve were observed in both species. Moreover, this antibody strongly labelled H1 horizontal cells and their thick axon terminals in the tench retina, whereas only a small population of amacrine cells was stained in the trout. Calretinin was expressed in different types of ganglion cells and numerous neurones located in the inner plexiform layer in both species, but was more abundant and more strongly stained in the trout retina, where some bipolar cells were easily distinguishable. A comparison to current results in other vertebrate species is offered.

Effect of nicorandil upon different guinea-pig and rat isolated organ preparations in vitro

A study of the effect of nicorandil (N-2-(hydroxyethyl)nicotinamide nitrate, CAS 65141-46-0), a potassium channel and guanylatecyclase activator, upon preparations of rat was deferens and uterus, and guinea pig ileum was performed. Nicorandil does not modify rat isolated was deferens responses to noradrenaline (norepinephrine) and potassium. The drug exerts a non-competitive antagonist effect upon rat isolated uterus response to serotonin, histamine, oxytocin, and, at high concentrations, inhibits guinea-pig isolated ileum responses to acetylcholine, histamine, 4-aminopyridine and potassium.

ATP-sensitive potassium channel regulates astrocytic gap junction permeability by a Ca2+-independent mechanism

Using the scrape-loading technique in cultured astrocytes, we show that sulfonylureas such as tolbutamide and glybenzcyclamide, which inhibit the ATP-sensitive K+ channel, prevent the inhibition of gap junction permeability caused by several structurally unrelated uncouplers such as oleic acid, arachidonic acid, endothelin-1, octanol, and alpha-glycyrrhetinic acid. When the intracellular level of Ca2+ was diminished, all the uncouplers tested were still able to inhibit gap junction communication, indicating that their inhibitory effect was not mediated by Ca2+. In addition, tolbutamide and glybenzcyclamide prevented the inhibitory effect of these uncouplers in Ca(2+)-depleted astrocytes, suggesting that the inhibition of the ATP-sensitive K+ channel increases gap junction permeability through a Ca(2+)-independent mechanism. The activation of the ATP-sensitive K+ channel caused by potassium channel openers such as diazoxide and pinacidil led to the inhibition of gap junction communication and overcame the effect of sulfonylureas. These results suggest that the ATP-sensitive K+ channel regulates gap junctional permeability.

Protein kinase C-like immunoreactive cells in embryo and adult chicken retinas

Morphological evidence of a temporal parallelism between the appearance of the alpha isoform of protein kinase C (PKC) and some processes such as synaptogenesis in the plexiform layers of the chicken retina is offered. Immunostaining experiments were performed throughout embryonic, young and adult chicken life. The results help to understand the development of rod bipolar cells.

Trimeric G proteins modulate the dynamic interaction of PKAII with the Golgi complex

The Golgi complex represents a major subcellular location of protein kinase A (PKA) concentration in mammalian cells where it has been previously shown to be involved in vesicle-mediated protein transport processes. We have studied the factors that influence the interaction of PKA typeII subunits with the Golgi complex. In addition to the cytosol, both the catalytic (Calpha) and regulatory (RIIalpha) subunits of PKAII were detected at both sides of the Golgi stack, particularly in elements of the cis- and trans-Golgi networks. PKAII subunits, in contrast, were practically absent from the middle Golgi cisternae. Cell treatment with either brefeldin A, AlF(4-) or at low temperature induced PKAII dissociation from the Golgi complex and redistribution to the cytosol. This suggested the existence of a cycle of association/dissociation of PKAII holoenzyme to the Golgi. The interaction of purified RIIalpha with Golgi membranes was studied in vitro and found not to be affected by brefeldin A while it was sensitive to modulators of heterotrimeric G proteins such as AlF(4-), GTPgammaS, beta(gamma) subunits and mastoparan. RII(alphaa) binding was stimulated by recombinant, myristoylated Galpha(i3) subunit and inhibited by cAMP. Pretreatment of Golgi membranes with bacterial toxins known to catalyze ADP-ribosylation of selected Galpha subunits also modified RIIalpha binding. Taken together the data support a regulatory role for Golgi-associated Galpha proteins in PKAII recruitment from the cytosol.

Effect of venlafaxine hydrochloride in different preparations of isolated guinea-pig and rat organ tissues

A study was undertaken to know better the effects of venlafaxine hydrochloride on the responses of isolated rat vas deferens to noradrenaline and dopamine, those of isolated rat uterus to serotonin and histamine, and those of isolated guinea-pig ileum to acetylcholine and histamine. Venlafaxine hydrochloride increased the response of rat vas deferens to noradrenaline but not to dopamine. Venlafaxine did not alter the response of rat isolated uterus to serotonin. In rat uterus, venlafaxine did not modify the response to histamine but was able to increase it in guinea-pig ileum. An anticholinergic effect was observed with the lowest concentration tested. Although venlafaxine is a selective serotonine reuptake inhibitor in the central nervous system, serotonin uptake was not seen in the rat uterus. The anticholinergic effects observed in the present study might be consistent with some of the side-effects associated with venlafaxine.

Enzyme histochemical identification of microglial cells in the retina of a fish (Tinca tinca)

Histochemistry for nucleoside diphosphatase was used to study the microglial cells in the adult tench retina. An abundant population of microglial cells was located in the vascular membrane, nerve fibre layer, inner and outer plexiform layers and scattered cells were observed in the inner nuclear layer. Rounded and amoeboid cells could be seen close to the vessel in the vascular membrane, bipolar cells in the nerve fibre layer and ramified cells in the rest of the layers. Several microglial forms could correspond to developing cells. The pattern of distribution was similar to that described in other vertebrates, but with several differences, such as the presence of microglial cells in the vascular membrane and inner nuclear layer and the overlap of processes in the plexiform layers.

Response of microglial cells after a cryolesion in the peripheral proliferative retina of tench

We studied the glial response after inducing a lesion in the zone of the peripheral retina of tench, where there is proliferative neuroepithelium. In the retina and optic nerve, the microglial response was analysed with tomato lectin and the macroglial response with antibodies against GFAP and S-100. In lesioned retinas, there was a temporal-spatial distribution pattern of microglia. One day after lesion, primitive ramified cells appeared in the nerve fibre layer. These cells appeared progressively from the vitreal to the scleral layers until day 7 when cells appeared in all layers, with the exception of the outer plexiform layer. From this point, labelling decreased. In the optic nerve, 3 days after lesion, an increase in the number of microglial cells was observed, first in the nerve folds and from day 15 in specific areas of the optic nerve. In the central retina, in the optic nerve head and within the optic nerve itself, the appearance of microglial cells, after the lesion, near the blood vessels, could indicate a vascular origin of microglia, as has been proposed by many authors. However, we cannot discount the idea that some of the reactive microglial cells arise by proliferation of the microglia existing in the normal state. Using GFAP and S-100 antibodies, no important changes in the retina were observed, however in the optic nerve there was response to the lesion. Thus, the macroglial cells appeared to be involved in reorganisation of the optic nerve axons after lesion.

The mer operon of the acidophilic bacterium Thiobacillus T3.2 diverges from its Thiobacillus ferrooxidans counterpart

The chromosomal mercury resistance (mer) region of the acidophilic bacterium Thiobacillus T3.2 was cloned, characterized, and compared to reported homologous sequences. The Thiobacillus T3.2 mer resistance system is organized as an operon that transcribes into a polycistronic mRNA encoding the Hg2+ ion transport MerT and MerP proteins and the mercuric reductase MerA. In contrast to the Thiobacillus ferrooxidans mer determinant, no merC gene was detected. Transcription of structural genes is regulated by the product of the regulatory merR gene. On the basis of sequence data and expression experiments in E. coli, both merTPA and merR transcription units could be located close to each other and in different strands, with their promoters (PTPA and PR, respectively) overlapping the putative MerR binding site in the intergenic operator/promoter (O/P) region. Amino acid sequences of mer gene products were compared to their homologs. Some sequence features, such as the number and position of cysteine residues, are unique for the Mer proteins of this bacterium. Similarities (-10 and -35 boxes are 19bp apart in both PR and PTPA promoters) and differences (inverted repeats in the Thiobacillus T3.2 MerR-binding site are 2bp shorter than in Thiobacillus ferrooxidans) exist between the O/P intergenic regions of both Thiobacilli. In vivo experiments showed inducible expression of mercury resistance in E. coli cells transformed with the entire Thiobacillus T3.2 mer genetic determinant (structural plus regulatory genes), and little or no expression in clones containing only the structural merT, merP, and merA genes.

Effect of hemodialysis and antiretroviral therapy on plasma viral load in HIV-1 infected hemodialysis patients

BACKGROUND

Plasma viral load has become an important test in predicting the progress of HIV-1 infected patients. The higher the viral load the faster is the progression to AIDS. As HIV-1 infected hemodialysis (HD) patients have higher mortality and morbidity than HIV-1 infected non-dialysis patients, and as all the blood tests in the HD patients are drawn during HD, we measured the effect of HD and antiretroviral therapy on viral load in HIV-1 infected HD patients.

PATIENTS AND METHODS

We measured plasma viral load pre-dialysis and post-dialysis in 10 HIV-1 infected HD patients. The viral load was measured using an in vitro quantitative nucleic acid amplification test. We also compared viral load in 8 HIV-1 infected HD patients on one antiretroviral drug with 8 HIV-1 patients on two (6) or three (2) antiretroviral drugs.

RESULTS

There was a small reduction in plasma viral load postdialysis in all HIV-1 infected HD patients (45% +/- 5.4, 0.3 log +/- 0.05, p < 0.0004). However, HIV-1 RNA could not be detected in the ultrafiltrate. The patients who were on two or three antiretroviral drugs had lower viral load (8915 +/- 3702 vs. 351440 +/- 101237, p < 0.004) and higher CD4 count (355 +/- 81 vs 82 +/- 39, p < 0.009) than patients on only one antiretroviral drug.

CONCLUSION

We conclude that there is a small reduction in plasma viral load in HIV-1 infected hemodialysis patients post-dialysis. As no viral RNA could be detected in the ultrafiltrate, the reduction could be due to nonspecific adsorption of the viral RNA to the dialysis membrane. HIV-1 infected hemodialysis patients who are on two or three antiretroviral drugs had significantly lower viral load and higher CD4 count than patients on only single antiretroviral drug. Therefore a single antiretroviral drug should not be used in treating HIV-1 infected HD patients.