Glucocorticoid regulation of phenylethanolamine N-methyltransferase in vivo.

In vivo, supraphysiological doses of glucocorticoids are required to restore adrenal medullary phenylethanolamine N-methyltransferase (PNMT, E.C. 2.1.1.28) activity after hypophysectomy. However, in vitro, phenylethanolamine N-methyltransferase gene expression appears normally glucocorticoid-responsive. To explore this paradox, rats were given dexamethasone or the type II-specific glucocorticoid RU28362 (1-1000 micrograms/day), and adrenal phenylethanolamine N-methyltransferase activity and mRNA levels were determined. At low doses (1-30 micrograms/day), neither steroid altered mRNA whereas at higher doses (100-1000 micrograms/day), mRNA rose 10- to 20-fold, with dexamethasone approximately 3 times as potent as RU28362. In contrast, enzyme activity fell with low doses of either steroid, consistent with suppression of ACTH and endogenous steroidogenesis. At higher doses of RU28362, enzyme activity remained low and unchanged despite increased mRNA expression, whereas higher doses of dexamethasone progressively restored the enzyme to normal. These findings suggest 1) that glucocorticoid regulation of phenylethanolamine N-methyltransferase activity occurs largely independent of gene expression; 2) that glucocorticoid effects on enzyme activity are primarily indirect, probably through cosubstrate regulation and/or enzyme stabilization; and 3) that these effects are not mediated via a classical (type II) glucocorticoid receptor mechanism, given the high doses of dexamethasone and corticosterone required and the inability of RU28362 to mimic the effects of these less selective steroids.     

The effect of rigid fixation on growth of the neurocranium

The effects on skull growth of plating the coronal suture and frontal bone were studied in New Zealand White rabbits. Three-dimensional coordinate landmarks were digitized and analyzed to determine the differences in form between operated and unoperated animals using Euclidian distance matrix analysis. This method compares sets of interlandmark distances in three dimensions and was used to demonstrate changes induced by plating. We interpret these changes in morphology to be the result of differences in growth between the operated and unoperated groups. Periosteal elevation alone (n = 6) resulted in a minimal local growth increase. Coronal suture plating (n = 8) resulted in local growth restriction with contralateral and adjacent size increases. Frontal bone plating (n = 6) without crossing a suture line also resulted in local growth restriction and adjacent bone size increases. The timing of intervention in relation to the completion of bone growth may explain the magnitude of clinically apparent effects. Changes in bones adjacent to those directly manipulated may be an attempt to maintain a normal skull volume.     

Immunocytochemical Localization of Glutamine Synthetase in Organs of Phaseolus vulgaris L

Glutamine synthetase was localized in nodules, roots, stems, and leaves of red kidney bean (Phaseolus vulgaris L.) by immunocytochemistry. Affinity purified antibodies reactive with glutamine synthetase were prepared using purified nodule-enhanced glutamine synthetase. Immunogold labeling was observed in the cell cytoplasm in each plant organ. In nodules, the labeling was more intense in the infected cells than in the uninfected cells. No labeling was observed in nodule bacteroids, peribacteroid spaces, or in peribacteroid membranes, while previous reports of glutamine synthetase immunolabeling of legume nodules showed labeling in the bacteroid fraction. Significant labeling was observed in nodule proplastids which contained starch granules. Substantial labeling was also observed in leaf chloroplasts. No labeling was observed in other organelles including mitochondria, peroxisomes, and endoplasmic reticulum. Preimmune IgGs did not bind to any structure in the tissues examined.     

Antiport mediated rounding and endocytosis are enhanced by sulphate

Rapid cell detachment concomitant with the flat-to-round (FTR) change that is mediated by an upshifted Na+/H+ antiporter via HCO3(-)-dependent H+ pumping, is significantly enhanced by the addition of Na2SO4 (FTR + SO4): (1) a faster and greater reduction in cell surface area and perimeter, and (2) a higher level of macromolecular internalization which is also amiloride sensitive. At a fixed 1 mg/ml extracellular FITC-dextran (FDx) concentration, the intracellular FDx load is similar irrespective of the particle size, in the range from 4400 to 2 million mol.wt which is a 455-fold diversity. This is inconsistent with entry via limited sized portals which would discriminate against the larger molecular weight species, such as the 2 million mol.wt species that measures up to 5 microns in width. Two million mol.wt FDx loads linearly in direct proportion to the extracellular FDx concentration, simulating simple diffusion. Large-channel endocytosis is considered to be a characteristic of specialized cell types such as phagocytes and macrophages. However, the antiporter mediated endocytosis (AME) shown here is demonstrated in two different cell types which are not known for their endocytic prowess, viz. epitheloid human Chang liver cells (ATCC CCL 13) and human lung fibroblasts (ATCC CCL 202). The rounded cells with internalized FDx start reverting back to their flat and protracted form upon flooding with warm growth medium, a round-to-flat (RTF) change. However the cell surface reversion is not associated with efflux of FDx which are sorted out into 'granular patches', the later stage endosomes without membrane outlines in AME. FDx-loaded cells grow as well as trypsinized cells without FDx loaing and they maintain a significant FDx load even after nearly 4 cell divisions. Toad sperms internalized into Chang cells via antiporter activation are also sorted into granular patches. AME provides (a) distinctive access to large particles, simulating small ion influx, and (b) an alternate membrane recycling capability where granular patches are instrumental in sorting. It appears to be not a simple endocytosis-exocytosis pathway.     

Effect of N-alkyl substituents on the DNA binding properties of meso-tetrakis (4-N-alkylpyridinium-4-yl)porphyrins and their nickel derivatives

Resonance Raman, NMR, and visible spectroscopies, as well as viscosity and equilibrium dialysis studies were used to assess the effect of the N-alkyl substituent of meso-tetrakis(4-N-alkylpyridinium-4-yl)porphyrin cations on DNA binding. The DNAs studied include the native DNA, calf thymus DNA (CT DNA), the synthetic polynucleotides [poly(dGdC)]2 and [poly(dAdT)]2, and the oligonucleotide d(TATACGTATA)2. Both the porphyrins and the metalloporphyrins containing Ni(II) were examined with the N-alkyl = propyl (TPrpyP(4) and NiTPrpyP(4)) and 2-hydroxyethyl (TEtOHpyP(4) and NiTEtOHpyP(4)). The results were compared to those from the parent porphyrins with the N-methyl substituent (TMpyP(4) and NiTMpyP(4)). For almost all the comparisons made, the new porphyrin cations gave results very similar to those for the TMpyP(4) species. The resonance Raman study indicated that for the three DNA polymers all the Ni species were in the four-coordinate form when bound to all three polymers. It is suggested that both TPrpyP(4) and TEtOHpyP(4) bind to GC regions of DNA in the same intercalative manner as TMpyP(4) with the N-alkyl substituent extended into the solvent. For AT regions of DNA, the binding of TPrpyP(4) and TEtOHpyP(4) is nonintercalative, as found previously for TMpyP(4). The NiPrpy(4) and NiTEtOHpyP(4) cations bind to these polymers in a similar manner to the apo-porphyrins. The similar Raman spectral changes for the three Ni porphyrins upon addition of [poly(dAdT)]2 suggest that partial intercalation is not occurring because models indicate that it would be difficult to accommodate the bulkier N-alkyl substituents.     

The role of the pro-sequence in the processing and secretion of the thermolysin-like neutral protease from Bacillus cereus

The Bacillus cereus cnp gene coding for the thermolysin-like neutral protease (TNP) has been cloned, sequenced, and expressed in Bacillus subtilis. The protease is first produced as a pre-pro-protein (M(r) = 61,000); the pro-peptide is approximately two-thirds of the size of the mature protein. The pro-sequence has been compared with those of six other TNPs, and significant homologies have been found. Additionally, the TNP pro-sequences are shown to be homologous to the pro-sequence of Pseudomonas aeruginosa elastase. A mutant has been constructed from cnp, in which 23 amino acids upstream from the pro-protein processing site have been deleted. This region has no homologous analogue in any of the other TNP pro-sequences. The deletion results in a delay of six to eight hours in detection of active protease in the growth medium, as well as a 75% decrease in maximum protease production. N-terminal analysis of the mutant mature protein demonstrates that the processing site is unaltered by the pro-sequence deletion. The deletion must, therefore, modulate the kinetics of processing and/or secretion of the pro-protein.     

Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

一种复合神经元网络结构的并行动力学及快速学习算法

提出两种功能互相不同的神经细胞组成的复合神经元网络(CNN)模型;导出一种特殊结构的CNN的并行动力学;而且证明了它的稳定性。在这些结果基础上,得到快速的假逆矩阵学习算法。计算机仿真试验证实学习算法与动力学稳定性的正确性,并表现出良好的容错性能与存储容量。