Elaborations of the basal surface of the cells of the Malpighian tubules of an insect

Electrical measurements of membrane potential and resistance using intracellular microelectrodes showed that the fluid-secreting parts of the Malpighian tubules of Rhodnius have superficial regions different in electrical properties from the main body of the cell. The membrane potential in these superficial regions was smaller by 30-40 mV, but showed a standard depolarization on changing the potassium concentration of the bathing medium. The response to changes in the external chloride concentration also differed in the two regions, a finding that was reinforced by different responses to the drug, furosemide. Electron microscopy of the basal regions of the cells revealed many long cellular projections that run parallel to the cell surface and interdigitate with similar projections from neighbouring cells. The degree of interdigitation was examined by marking individual cells with alcian blue or by horseradish peroxidase injection. A survey of the published micrographs of insect Malpighian tubules shows that most have similar projections on their basal surfaces and not the simple basal infoldings previously supposed.     

Decomposition of cellulose,soil organic matter and plant litter in a temperate grassland soil

The formation of mor humus in an experimental grassland plot, which has been acidified by long-term fertiliser treatment, has been studied by comparing the rates of cellulose, soil organic matter and plant litter decay with those in an adjacent plot with near-neutral pH and mull humus. The decomposition of cellulose filter paper in litter bags of 5 mm, 1-mm and 45-μm mesh size buried at 3 to 4 cm depth the plots was followed by measuring the weight loss and changes in glucose content over a 6 month period. Soil pH was either 5.3 or 4.3. Decomposition of native soil organic matter and plant litter in soil from the same plots were followed using CO₂ evolution in laboratory microcosms. Cellulose weight loss at pH 5.3 was greatest from the 5-mm mesh bags and least from the 45-um mesh bags. At pH 4.3 there was little weight loss from bags and no significant differences in weight loss between bags with different sized mesh. There was, however, a reduction in the glucose content of the hydrolysed and derivatised filter paper with time. The decomposition rate of native soil organic matter in the low pH soil was increased to that observed in the less acid soil when the pH of the former was increased from 4.3 to 5.3. The increase in decomposition rate of added plant litter in the more acid soil as a result of CA(OH)₂ addition was only 60% of that observed in the soil with pH 5.3. These data support the hypothesis that the absence of soil animals and the restricted microbial decomposition in the acidic soil was responsible for mor humus formation.     

Salicylic acid-independent plant defence pathways

Salicylic acid is an important signalling molecule involved in both locally and systemically induced disease resistance responses. Recent advances in our understanding of plant defence signalling have revealed that plants employ a network of signal transduction pathways, some of which are independent of salicylic acid. Evidence is emerging that jasmonic acid and ethylene play key roles in these salicylic acid-independent pathways. Cross-talk between the salicylic acid-dependent and the salicylic acid-independent pathways provides great regulatory potential for activating multiple resistance mechanisms in varying combinations.     

Androgen receptor status predicts response to chemotherapy, not risk of breast cancer in Indian women

Voltage gated potassium channels have been extensively studied in relation to cancer. In this review, we will focus on the role of two potassium channels, Ether à-go-go (Eag), Human ether à-go-go related gene (HERG), in cancer and their potential therapeutic utility in the treatment of cancer. Eag and HERG are expressed in cancers of various organs and have been implicated in cell cycle progression and proliferation of cancer cells. Inhibition of these channels has been shown to reduce proliferation both in vitro and vivo studies identifying potassium channel modulators as putative inhibitors of tumour progression. Eag channels in view of their restricted expression in normal tissue may emerge as novel tumour biomarkers.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

<Emphasis Type="Italic">Arabidopsis</Emphasis> ETO1 specifically interacts with and negatively regulates type 2 1-aminocyclopropane-1-carboxylate synthases

Background  

In Arabidopsis, ETO1 (ETHYLENE-OVERPRODUCER1) is a negative regulator of ethylene evolution by interacting with AtACS5, an isoform of the rate-limiting enzyme, 1-aminocyclopropane-1-carboxylate synthases (ACC synthase or ACS), in ethylene biosynthetic pathway. ETO1 directly inhibits the enzymatic activity of AtACS5. In addition, a specific interaction between ETO1 and AtCUL3, a constituent of a new type of E3 ubiquitin ligase complex, suggests the molecular mechanism in promoting AtACS5 degradation by the proteasome-dependent pathway. Because orthologous sequences to ETO1 are found in many plant species including tomato, we transformed tomato with Arabidopsis ETO1 to evaluate its ability to suppress ethylene production in tomato fruits.     

Protein expression profiling of the drosophila fragile X mutant brain reveals up-regulation of monoamine synthesis

Fragile X syndrome is the most common form of inherited mental retardation, associated with both cognitive and behavioral anomalies. The disease is caused by silencing of the fragile X mental retardation 1 (fmr1) gene, which encodes the mRNA-binding, translational regulator FMRP. Previously we established a disease model through mutation of Drosophila fmr1 (dfmr1) and showed that loss of dFMRP causes defects in neuronal structure, function, and behavioral output similar to the human disease state. To uncover molecular targets of dFMRP in the brain, we use here a proteomic approach involving two-dimensional difference gel electrophoresis analyses followed by mass spectrometry identification of proteins with significantly altered expression in dfmr1 null mutants. We then focus on two misregulated enzymes, phenylalanine hydroxylase (Henna) and GTP cyclohydrolase (Punch), both of which mediate in concert the synthetic pathways of two key monoamine neuromodulators, dopamine and serotonin. Brain enzymatic assays show a nearly 2-fold elevation of Punch activity in dfmr1 null mutants. Consistently brain neurochemical assays show that both dopamine and serotonin are significantly increased in dfmr1 null mutants. At a cellular level, dfmr1 null mutant neurons display a highly significant elevation of the dense core vesicles that package these monoamine neuromodulators for secretion. Taken together, these data indicate that dFMRP normally down-regulates the monoamine pathway, which is consequently up-regulated in the mutant condition. Elevated brain levels of dopamine and serotonin provide a plausible mechanistic explanation for aspects of cognitive and behavioral deficits in human patients.     

Prior exposure to indole-3-carbinol decreases the incidence of specific cyclophosphamide-induced developmental defects in mice

BACKGROUND: Indole-3-carbinol (I3C) is a product of the hydrolysis of glucobrassicin that is found in cruciferous vegetables. I3C can intervene in toxic processes that are mediated by oxidative mechanisms because it possesses the chemical and pharmacokinetic properties necessary to provide a free radical trap. Cyclophosphamide (CP) is a bifunctional alkylating agent known to produce DNA damage and to cause developmental toxicity, including malformations, in laboratory animals. METHODS: Pregnant CD-1 mice were given a 100 mg/kg dose of I3C 24 or 48 hr before administration of 20 mg/kg CP on gestation day 10 (GD 10). Controls were given the vehicle (DMSO), I3C, or CP. This regimen was carried out to determine if I3C could protect against the developmental toxicity of alkylating agents, such as CP. Dams were sacrificed on GD 17 and their litters were examined for adverse effects. RESULTS: Treatment with I3C 48 hr before CP administration was associated with decreased fetal limb and tail malformations. Limb malformation incidences were reduced from 42% litters affected in the CP control to 16% in the I3C/CP 48-hr treatment group, and tail malformations were reduced from 45% in the CP control to 16% in the I3C/CP 48-hr treatment group, indicating a protective effect of prior exposure to I3C. I3C given 24 hr before CP had no significant protective effect, while having an apparently adverse consequence with regard to the incidence of talipes. CONCLUSIONS: Exposure of a developing mammal to indole-3-carbinol before exposure to cyclophosphamide during organogenesis can influence the teratogenicity of cyclophosphamide.     

Solvent isotope effects on alpha-glucosidase

The solvent kinetic isotope effects (SKIE) on the yeast alpha-glucosidase-catalyzed hydrolysis of p-nitrophenyl and methyl-d-glucopyranoside were measured at 25 degrees C. With p-nitrophenyl-D-glucopyranoside (pNPG), the dependence of k(cat)/K(m) on pH (pD) revealed an unusually large (for glycohydrolases) solvent isotope effect on the pL-independent second-order rate constant, (DOD)(k(cat)/K(m)), of 1.9 (+/-0.3). The two pK(a)s characterizing the pH profile were increased in D(2)O. The shift in pK(a2) of 0.6 units is typical of acids of comparable acidity (pK(a)=6.5), but the increase in pK(a1) (=5.7) of 0.1 unit in going from H(2)O to D(2)O is unusually small. The initial velocities show substrate inhibition (K(is)/K(m) approximately 200) with a small solvent isotope effect on the inhibition constant [(DOD)K(is)=1.1 (+/-0.2)]. The solvent equilibrium isotope effects on the K(is) for the competitive inhibitors D-glucose and alpha-methyl D-glucoside are somewhat higher [(DOD)K(i)=1.5 (+/-0.1)]. Methyl glucoside is much less reactive than pNPG, with k(cat) 230 times lower and k(cat)/K(m) 5 x 10(4) times lower. The solvent isotope effect on k(cat) for this substrate [=1.11 (+/-0. 02)] is lower than that for pNPG [=1.67 (+/-0.07)], consistent with more extensive proton transfer in the transition state for the deglucosylation step than for the glucosylation step.