The diet of two species of Isoperla (Plecoptera: Perlodidae) in relation to season,site, and sympatry

The seasonal change in gut contents of nymphs of Isoperla grammatica and I. difformis from six streams in southern Sweden was analysed. Both species had ingested a variety of benthic prey and vegetable matter, predominantly diatoms. Some seasonality was evident with high percentages of diatoms in spring in I. grammatica, and in autumn in I. difformis. The scope of food was larger in the latter species which contained about equal proportions of vegetable matter, chironomids, mayfly, stonefly, and black fly larvae. In I. grammatica plant matter and chironomids dominated strongly, comprising > 50% of the gut contents on an annual basis, > 90 % in spring. While small nymphs of I. difformis contained a low proportion of animal matter, only gradually increasing with size, the nymphs of I. grammatica were carnivorous from very early instars. Both species switched to a temporarily strong utilization of algae in spring. This differed among sites, and appeared to reflect differences in insolation and thus the availability of algae. There was a significant negative relationship between the mean densities of Isoperla nymphs and the proportion of animal material found in the guts of I. grammatica (R ² = 0.86). Considering the density of I. grammatica alone, the relationship was weaker (R ² = 0.56). A positive correlation between predator and prey size was observed. With chironomid prey the size range increased with predator size. With simuliid prey, however, prey size increased with predator size in such a way that it suggests selection rather than just an expanding prey size range. Correlations were stronger and regression coefficients significantly higher for I. grammatica than for I. difformis. We suggest that I. grammatica, which ingests a much wider size range of prey might choose prey of optimal sizes more readily than the more synchronously developing I. difformis. Although the life cycles of the two species are staggered, overlap in size distribution indicates that competition for food could be important in spring. However, observed differences in diet should facilitate coexistence. Gut content differences might in turn be accomplished through microhabitat segregation.     

Noradrenaline nerve terminals in the hippocampal region of the rat and the guinea pig

Summary The hippocampal region of the rat has been studied with the histochemical fluorescence method for demonstration of catecholamines and 5-hydroxytryptamine. Noradrenalin nerve terminals of characteristic appearance were observed throughout the region, but the density of the terminals in the various areas differed considerably. The highest amount of terminals were seen in the hilus of the area dentata of the rat. Otherwise, noradrenalin nerve terminals constitute a small percentage of the afferents to the hippocampal region. Noticeable differences existed between rat and guinea-pig. In both species there was a conspicuous lack of stratification and delineation of areas as compared with the pictures seen with most other methods, which have revealed precise architectonic patterns.Supported by a Research Grant (12X-715-02) from the Swedish Medical Research council and by a Grant from Stiftelsen M. Bergwalls Minne.     

Bovine Carbonyl Lactoperoxidase Structure at 2.0? Resolution and Infrared Spectra as a Function of pH

Lactoperoxidase (LPO) is a hemeprotein catalyzing the oxidation of thiocyanate and I^? into antimicrobials and small aromatic organics after being itself oxidized by H₂O₂. LPO is excreted by the lungs, mammary glands, found in saliva and tears and protects mammals against bacterial, fungal and viral invasion. The Fe(II) form binds CO which inactivates LPO like many other hemeproteins. We present the 3-dimensional structure of CO?CLPO at 2.0? resolution and infrared (IR) spectra of the iron-bound CO stretch from pH?3 to 8.8?at 1 cm^?1 resolution. The observed Fe?CC?CO bond angle of 132° is more acute than the electronically related Fe(III), CN?CLPO with a Fe?CC?CN angle of 161°. The orientations of the two ligands are different with the oxygen of CO pointing towards the imidazole of distal His109 while the nitrogen of CN points away, the Fe(II) moves towards His109 while the Fe(III) moves away; both movements are consistent with a hydrogen bond between the distal His109 and CO, but not to the nitrogen of CN?CLPO. The IR spectra of CO?CLPO exhibit two major CO absorbances with pH dependent relative intensities. Both crystallographic and IR data suggest proton donation to the CO oxygen by His109 with a pK ?? 4; close to the pH of greatest enzyme turnover. The IR absorbance maxima are consistent with a first order correlation between frequency and Fe(III)/Fe(II) reduction potential at pH?7; both band widths at half-height correlate with electron density donation from Fe(II) to CO as gauged by the reduction potential.     

Trans-Atlantic genetic uniformity in the rare snowbed sedge <Emphasis Type="Italic">Carex rufina</Emphasis>

The red-listed, amphi-Atlantic sedge Carex rufina is highly specialized to certain alpine snowbeds, and threatened by current changes in snow cover duration and moisture conditions. Here we address its range-wide genetic diversity, history, and conservation using amplified fragment length polymorphisms (AFLPs). Despite extensive primer testing, we detected very low overall diversity (4.1% polymorphic markers). Only a single AFLP phenotype was found throughout Norway and across the Atlantic to Iceland and Greenland, while another was found in Canada, suggesting glacial survival in one East and one West Atlantic refugium. East Atlantic C. rufina has probably been heavily bottlenecked in a small refugium, possibly situated within the maximum limits of the ice sheets. Its lack of diversity is likely maintained through local clonal growth causing longevity of genotypes. Habitat availability appears as the main limiting factor for C. rufina, and its currently occupied habitats need to be preserved to ensure its long-time survival.     

The 5' flank of mouse H19 in an unusual chromatin conformation unidirectionally blocks enhancer-promoter communication

BACKGROUND: During mouse prenatal development, the neighbouring insulin-like growth factor II (Igf2) and H19 loci are expressed monoallelically from the paternal and maternal alleles, respectively. Identical spatiotemporal expression patterns and enhancer deletion experiments show that the Igf2 and H19 genes share a common set of enhancers. Deletion of a differentially methylated region in the 5' flank of the H19 gene partially relieves the repression of the maternal Igf2 and paternal H19 alleles in the soma. The mechanisms underlying the function of the 5' flank of the H19 gene are, however, unknown. RESULTS: Chromatin analysis showed that the 5' flank of the mouse H19 gene contains maternal-specific, multiple nuclease hypersensitive sites that map to linker regions between positioned nucleosomes. These features could be recapitulated in an episomal-based H19 minigene, which was propagated in human somatic cells. Although the 5' flank of the H19 promoter has no intrinsic silencer activity under these conditions, it unidirectionally extinguished promoter-enhancer communications in a position-dependent manner, without directly affecting the enhancer function. CONCLUSIONS: The unmethylated 5' flank of the H19 gene adopts an unusual and maternal-specific chromatin conformation in somatic cells and regulates enhancer-promoter communications, thereby providing an explanation for its role in manifesting the repressed state of the maternally inherited Igf2 allele.     

The formation of ES of cytochrome-c peroxidase: a comparison with lactoperoxidase and horseradish peroxidase

The activation energy for the formation of the first red compound, ES, for cytochrome-c peroxidase (ferrocytochrome-c: hydrogen-peroxide oxidoreductase, EC 1.11.1.5) by i-propyl hydroperoxide and the rate constants for the formation of ES with various hydroperoxides have been determined. Multivariate data analysis by the partial least-squares model in latent variables has been used to compare the rate constants with the corresponding rate constants for the formation of compound I from lactoperoxidase and two isoenzymes of horseradish peroxidase. The results show that the rate of formation of ES from cytochrome-c peroxidase is highly correlated with the pKa of the hydroperoxides. The activation energy for the formation of ES with i-propyl hydroperoxide is close to the corresponding value for hydrogen peroxide.     

Long-term survival from adenocarcinoma of the esophagus after transthoracic and transhiatal esophagectomy

ABSTRACT: BACKGROUND: The effects of transthoracic or transhiatal esophagectomy on the long-term survival of patients who had adenocarcinoma of the esophagus were compared, as were factors applicable in preoperative stratification of patient treatment. METHODS: A cohort of 147 consecutive patients with adenocarcinoma of the esophagus was evaluated for esophagectomy between 1984 and 2000. The patients were followed prospectively and observed survival rates of patients with a transthoracic or transhiatal approach to esophagectomy were compared by standardized mortality ratio (SMR) and relative mortality ratio (RMR) using the expected survival of a matched Norwegian population. RESULTS: A R0 resection was performed by transthoracic (n = 33) or a transhiatal (n = 55) esophagectomy in 88 (60%) patients with a median age of 61 (range: 35-77) and 70 (42-88) years, respectively (P <0.001). Tumor stages and other possible risk factors were similar in the two groups. Transthoracic or transhiatal esophagectomy resulted in a median survival time of 20.5 (95% confidence interval (CI): 10.4-57.6) and 16.4 (10.6-28.7) months, respectively. The respective survival rates were 31.2% and 27.8% by 5 years, and 21.3% and 16.6% by 10 years with an overall RMR of 1.14 (P = 0.63). Median survival time in the absence or presence of lymph node metastases was 74.0 (95% CI: 17.5-166.4) and 10.7 (7.9- 14.9) months. The corresponding survival rates by 10 years with non-involved or involved nodes were 48.9% and 3.8% respectively (RMR 2.22, P = 0.007). Patients with a pT1-tumor were few and the survival rate was not very different from that of the general population (SMR = 1.7, 95% CI: 0.7-4.1). The median survival time of patients with a pT2-tumor was 30.4 (95% CI: 9.0-142) months and with a pT3-tumor 14 (9.2-16.4) months. The survival rates by 10 years among patients with a pT1 tumor were 57.0% (95% CI: 14.9-78.9), pT2 33.3% (11.8-52.2), and pT3 7.1% (1.9-15.5). The relative mortality for T3 stages compared to T1 stages was statistically significant (RMR = 3.22, P = 0.024). CONCLUSION: Transthoracic and transhiatal esophagectomy are both effective approaches for treatment of adenocarcinoma of the esophagus and survival of more than 10 years can be expected without adjuvant chemotherapy. However, increasing depth of tumor invasion and lymph node metastases reduce life expectancy.     

Dopamine D2 and 5-hydroxytryptamine 5-HT(₂A) receptors assemble into functionally interacting heteromers

In view of the co-distribution of dopamine D_2LR and 5-hydroxytryptamine 5-HT_2A receptors (D_2LR and 5-HT_2AR, respectively) within inter alia regions of the dorsal and ventral striatum and their role as a target of antipsychotic drugs; in this study we assessed the potential existence of D_2LR-5-HT_2AR heteromers in living cells and the functional consequences of this interaction. Thus, by means of a proximity-based bioluminescence resonance energy transfer (BRET) approach we demonstrated that the D_2LR and the 5-HT_2AR form stable and specific heteromers when expressed in HEK293T mammalian cells. Furthermore, when the D_2LR-5-HT_2AR heteromeric signaling was analyzed we found that the 5-HT_2AR-mediated phospholipase C (PLC) activation was synergistically enhanced by the concomitant activation of the D_2LR as shown in a NFAT-luciferase reporter gene assay and a specific and significant rise of the intracellular calcium levels were observed when both receptors were simultaneously activated. Conversely, when the D_2LR-mediated adenylyl cyclase (AC) inhibition was assayed we showed that costimulation of D_2LR and 5-HT_2AR within the heteromer led to inhibition of the D_2LR functioning, thus suggesting the existence of a 5-HT_2AR-mediated D_2LR trans-inhibition phenomenon. Finally, a bioinformatics study reveals that the triplet amino acid homologies LLT (Leu-Leu-Thr) and AIS (Ala-Ile-Ser) in TM1 and TM3, respectively of the D₂R-5-HT_2AR may be involved in the receptor interface. Overall, the presence of the D_2LR-5-HT_2AR heteromer in discrete brain regions is postulated based on the existence of D_2LR-5-HT_2A receptor-receptor interactions in living cells and their codistribution inter alia in striatal regions. Possible novel therapeutic strategies for treatment of schizophrenia should be explored by targeting this heteromer.     

Perinatal essential fatty acid deficiency influences body weight and bone parameters in adult male rats

Electropermeabilization designates the use of electric pulses to overcome the barrier of the cell membrane. This physical method is used to transfer anticancer drugs or genes into living cells. Its mechanism remains to be elucidated. A position-dependent modulation of the membrane potential difference is induced, leading to a transient and reversible local membrane alteration. Electropermeabilization allows a fast exchange of small hydrophilic molecules across the membrane. It occurs at the positions of the cell facing the two electrodes on an asymmetrical way. In the case of DNA transfer, a complex process is present, involving a key step of electrophoretically driven association of DNA only with the destabilized membrane facing the cathode. We report here at the membrane level, by using fluorescence microscopy, the visualization of the effect of the polarity and the orientation of electric pulses on membrane permeabilization and gene transfer. Membrane permeabilization depends on electric field orientation. Moreover, at a given electric field orientation, it becomes symmetrical for pulses of reversed polarities. The area of cell membrane where DNA interacts is increased by applying electric pulses with different orientations and polarities, leading to an increase in gene expression. Interestingly, under reversed polarity conditions, part of the DNA associated with the membrane can be removed, showing some evidence for two states of DNA in interaction with the membrane: DNA reversibly associated and DNA irreversibly inserted.