Insulin induces the correlation between renal blood flow and glomerular filtration rate in diabetes: implications for mechanisms causing hyperfiltration

Glomerular filtration rate (GFR) and renal blood flow (RBF) are normally kept constant via renal autoregulation. However, early diabetes results in increased GFR and the potential mechanisms are debated. Tubuloglomerular feedback (TGF) inactivation, with concomitantly increased RBF, is proposed but challenged by the finding of glomerular hyperfiltration in diabetic adenosine A(1) receptor-deficient mice, which lack TGF. Furthermore, we consistently find elevated GFR in diabetes with only minor changes in RBF. This may relate to the use of a lower streptozotocin dose, which produces a degree of hyperglycemia, which is manageable without supplemental suboptimal insulin administration, as has been used by other investigators. Therefore, we examined the relationship between RBF and GFR in diabetic rats with (diabetes + insulin) and without suboptimal insulin administration (untreated diabetes). As insulin can affect nitric oxide (NO) release, the role of NO was also investigated. GFR, RBF, and glomerular filtration pressures were measured. Dynamic RBF autoregulation was examined by transfer function analysis between arterial pressure and RBF. Both diabetic groups had increased GFR (+60-67%) and RBF (+20-23%) compared with controls. However, only the diabetes + insulin group displayed a correlation between GFR and RBF (R(2) = 0.81, P < 0.0001). Net filtration pressure was increased in untreated diabetes compared with both other groups. The difference between untreated and insulin-treated diabetic rats disappeared after administering N(ω)-nitro-l-arginine methyl ester to inhibit NO synthase and subsequent NO release. In conclusion, mechanisms causing diabetes-induced glomerular hyperfiltration are animal model-dependent. Supplemental insulin administration results in a RBF-dependent mechanism, whereas elevated GFR in untreated diabetes is mediated primarily by a tubular event. Insulin-induced NO release partially contributes to these differences.     

Oxidative metabolism of dopamine: a colour reaction from human midbrain analysed by mass spectrometry

In order to identify the protein responsible for a dopamine peroxidizing activity, previously described in human normal and parkinsonian substantia nigra by our group, we developed non-denaturing polyacrylamide gel electrophoresis conditions, mimicking the characteristic colour in vitro reaction, resulting from cyclic oxidation of dopamine (DA). After separating protein mixtures from human normal midbrain homogenates on two sets of identical native gels, one gel set was subjected to specific activity staining by using DA and hydrogen peroxide. An activity red/orange band appeared in midbrain tissue lanes, similarly to the lane where commercial horseradish peroxidase (HRP) was present as control of peroxidative activity. The second set of gels, stained with Coomassie Blue, showed other, not enzymatically active protein bands. Mass spectrometry analysis of the bands containing the activity and the corresponding Coomassie Blue bands revealed the presence of proteins that may play a role in neurodegenerative disease, highlighting a possible functional link among dopamine/dopaminochrome redox cycle and protein metabolism.     

Science in drug control: the alkaloid content of afghan opium

Opium samples from Afghanistan were analyzed by HPLC for their content of morphine and three further alkaloids (codeine, thebaine, and papaverine). To our knowledge, this is the largest set of authentic opium samples analyzed in one study until now. The purpose was to assess possible correlations between samples and selected external factors, such as region of origin within Afghanistan, year of harvest, or intra-batch variation. In the investigated samples, a trend towards higher morphine concentrations in opium from the North-Eastern parts of Afghanistan was observed in the period from 2003 to 2005. More than 75% of the samples contained above 10% of morphine, the overall average was 14.4%.     

HIV-1 with multiple CCR5/CXCR4 chimeric receptor use is predictive of immunological failure in infected children

Background

HIV-1 R5 viruses are characterized by a large phenotypic variation, that is reflected by the mode of coreceptor use. The ability of R5 HIV-1 to infect target cells expressing chimeric receptors between CCR5 and CXCR4 (R5^broad viruses), was shown to correlate with disease stage in HIV-1 infected adults. Here, we ask the question whether phenotypic variation of R5 viruses could play a role also in mother-to-child transmission (MTCT) of HIV-1 and pediatric disease progression.

Methodology/Principal Findings

Viral isolates obtained from a total of 59 HIV-1 seropositive women (24 transmitting and 35 non transmitting) and 28 infected newborn children, were used to infect U87.CD4 cells expressing wild type or six different CCR5/CXCR4 chimeric receptors. HIV-1 isolates obtained from newborn infants had predominantly R5^narrow phenotype (n = 20), but R5^broad and R5X4 viruses were also found in seven and one case, respectively. The presence of R5^broad and R5X4 phenotypes correlated significantly with a severe decline of the CD4+ T cells (CDC stage 3) or death within 2 years of age. Forty-three percent of the maternal R5 isolates displayed an R5^broad phenotype, however, the presence of the R5^broad virus was not predictive for MTCT of HIV-1. Of interest, while only 1 of 5 mothers with an R5X4 virus transmitted the dualtropic virus, 5 of 6 mothers carrying R5^broad viruses transmitted viruses with a similar broad chimeric coreceptor usage. Thus, the maternal R5^broad phenotype was largely preserved during transmission and could be predictive of the phenotype of the newborn''s viral variant.

Conclusions/Significance

Our results show that R5^broad viruses are not hampered in transmission. When transmitted, immunological failure occurs earlier than in children infected with HIV-1 of R5^narrow phenotype. We believe that this finding is of utmost relevance for therapeutic interventions in pediatric HIV-1 infection.     

Impaired cognitive performance in neuronal nitric oxide synthase knockout mice is associated with hippocampal protein derangements

Nitric oxide is implicated in modulation of memory and pharmacological as well as genetic inhibition of neuronal nitric oxide synthase (nNOS) leads to impaired cognitive function. We therefore decided to study learning and memory functions and cognitive flexibility in the Morris water maze (MWM) in 1-month-old male mice lacking nNOS (nNOS KO). Hippocampal protein profiling was carried out to possibly link protein derangement to impaired cognitive function. Two-dimensional gel electrophoresis with in-gel digestion of spots and subsequent MALDI-TOF identification of proteins and quantification of proteins using specific software was applied. In the memory as well as in the relearning task of the MWM, most of the nNOS KO failed to find the submerged platform within a given time. Proteomic evaluation of hippocampus, the main anatomical structure computing cognitive functions, revealed aberrant expression of a synaptosomal associated protein of the exocytotic machinery (NSF), glycolytic enzymes, chaperones 78 kDa glucose-regulated protein, T-complex protein 1; the signaling structure guanine nucleotide-binding protein G(I)/G(S)/G(T) and heterogeneous nuclear ribonucleoprotein H of the splicing machinery. We conclude that nNOS knockout mice show impaired spatial performance in the MWM, a finding that may be either linked to direct effects of nNOS/NO and/or to specific hippocampal protein derangements.     

Reproductive sharing among queens in the ant Formica fusca

Reproductive sharing among cobreeders, in which reproductiveshares may vary from equal contribution (low reproductive skew)to reproductive dominance by one individual (high reproductiveskew), is a fundamental feature of animal societies. Recenttheoretical work, the reproductive skew models, has focusedon factors affecting the degree to which reproduction is skewedwithin a society. We used the parameters provided by skew modelsas a guideline to study determinants of reproductive sharingin polygyne ants. As a model system we used two-queen laboratorycolonies of the ant Formica fusca in which the reproductiveshares of each queen was assessed from offspring by using allozymesand DNA microsatellites. We tested how the different variablesincluded in reproductive skew models (queen-queen relatedness,potential fighting ability, productivity, and worker relatednessreflected by queen number in the colony of origin) affect reproductivesharing among queens. The results showed that the relatednessamong queens explained 26% of the variation in reproductiveskew. The size difference between queens (reflecting potentialfighting ability), colony productivity, and worker relatednessdid not have an effect on reproductive partitioning among cobreeders.To our knowledge, this is the first study to test for the effectsof various determinants of skew in an experimental setting.     

Lep d 2 polymorphisms in wild and cultured Lepidoglyphus destructor mites.

We have previously cloned, expressed and characterized two variants of the major allergen Lep d 2 from cultured Lepidoglyphus destructor mites. These variants, Lep d 2.0101 and Lep d 2.0201, differ at 13 amino acid positions. In this study we investigated Lep d 2 sequence diversity between wild and cultured mites. PCR, Southern blot and DNA sequence analysis revealed the presence of two different Lep d 2 genes, one with and one without an intron. In addition, two new variants of Lep d 2, Lep d 2.0102 and Lep d 2.0202, were found at different frequencies in wild and cultured mites. When we expressed the Lep d 2 variants and compared their IgE binding properties by ELISA inhibition, we found that Lep d 2.0102 was a more potent inhibitor than Lep d 2.0101, and to a lesser extent Lep d 2.0202 was more potent than Lep d 2.0201. Long-term cultures of peripheral blood mononuclear cells were used to assess the ability of the expressed Lep d 2 variants to induce cytokine release. Although cells from different individuals released different amounts of interferon-gamma and interleukin-5, no consistent cytokine release pattern could be linked to any specific Lep d 2 variant. In conclusion, we show that both cultured and wild Lepidoglyphus destructor mites contain the same pattern of polymorphism. Furthermore, this Lep d 2 sequence diversity seems not to have any significant impact on the allergens IgE binding or its ability to induce T cell cytokine release.     

Biosynthesis of collagen

During the biosynthesis and assembly of collagen structures, disulfide links can serve several functions. During biosynthesis they successively stabilize intra-peptide folding and associations of three chains into one molecule. Studies on the refolding and reassociation of reduced and denatured carboxyl propeptides of procollagen I showed that successive interactions of folding and assembly are successively weaker. Disulfide bridges were reestablished within correctly refolded carboxyl propeptides. Rearrangements of disulfide bridges may occur during the processing of type V procollagen molecules as these collagens become incorporated into extracellular matrix. The basement membrane procollagen IV molecules become disulfide linked at each end into networks, and there are indications that further rearrangements of disulfide links may allow additional modulation.     

Salinity Induced Regime Shift in Shallow Brackish Lagoons

In brackish lagoons, Daphnia is replaced by calanoid copepods (Eurytemora affinis, Acartia spp.) and rotifers when a certain threshold (depending on, for instance, fish density) is reached. We hypothesize that loss of Daphnia induces a regime shift from clear to turbid at high nutrient concentrations. We conducted a factorial designed enclosure experiment with contrasting salinities (0–16‰), low fish predation (one three-spined stickleback, Gasterosteus aculeatus, m⁻²) and three levels of nutrient loading in a shallow brackish lagoon. A change point analysis suggests a strong regime shift from a clear to a turbid state at 6–8‰ salinity at low and high loading, but not for the control. From the low to the high salt regime, chlorophyll a (Chla), Chla:total phosphorus (TP) and Chla:total nitrogen (TN) ratios shifted highly significantly for all nutrient treatments, and the bacterioplankton production followed the changes in Chla. These changes occurred parallel with a shift from cladoceran and cyclopoid copepod to rotifer dominance. Monitoring data from 60 Danish brackish lagoons show increasing Chla with increasing TP and TN as well as interactive effects of TN and salinity, peaking at intermediate salinity. A relatively weak effect of salinity at low nutrient concentrations and the stronger effect at intermediate high salinity are in accordance with the experimental results. However, these data suggest a lower salinity threshold than in the experiment, which may be explained by a higher fish density. Our results have implications for the management of coastal lagoons both at present and in a future (predicted) warmer climate: (1) improved water quality can be obtained by reducing the nutrient loading or enhancing the freshwater input to a level triggering a shift to Daphnia dominance (typically <2‰), (2) fish manipulation is probably not a useful tool for brackish lagoons, unless the salinity is below the threshold for a potential shift to a clear Daphnia dominated state, and (3) more abrupt changes will expectedly occur in low-saline coastal lagoons at increasing salinity during summer in a future warmer climate.     

Beitrag zur entwicklungsgeschichte von Alcippe Lampas Hancock

Ohne ZusammenfassungDissertation der Philosophischen Fakultät der Universität Kiel.