Hormonal regulation of an islet-specific enhancer in the pancreatic homeobox gene STF-1

The homeobox protein STF-1 appears to function as a master control switch for expression of the pancreatic program during development. Here we characterize a composite enhancer which directs STF-1 expression to pancreatic islet cells via two functional elements that recognize the nuclear factors HNF-3beta and BETA-2. In keeping with their inhibitory effects on islet cell maturation, glucocorticoids were found to repress STF-1 gene expression by interfering with HNF-3beta activity on the islet-specific enhancer. Overexpression of HNF-3beta suppressed glucocorticoid receptor-mediated inhibition of the STF-1 gene, and our results suggest that the expansion of pancreatic islet precursor cells during development may be restricted by hormonal cues which regulate STF-1 gene expression.     

Constrained multi-item inventory systeṁs an implicit approach

This paper examines the N-item deterministic inventory model subject to a single linear constraint. Functional relationships between the Lagrangian multipliers and shifts occurring simultaneously in multiple system parameters are identified and used to establish effective initial bounds on the optimal multiplier, Φ^*, in closed form. A recursive process which rapidly converges to Φ^* is also presented. Finally, a comparative analysis highlighting the efficiency of the proposed process in relation to existing algorithms is exhibited.     

The pyrophosphate-dependent phosphofructokinase of the protist, Trichomonas vaginalis, and the evolutionary relationships of protist phosphofructokinases

Apoptosis is essential for the precise regulation of cellular homeostasis and development. The role in vivo of Apaf1, a mammalian homolog of C. elegans CED-4, was investigated in gene-targeted Apaf1-/- mice. Apaf1-deficient mice exhibited reduced apoptosis in the brain and striking craniofacial abnormalities with hyperproliferation of neuronal cells. Apaf1-deficient cells were resistant to a variety of apoptotic stimuli, and the processing of Caspases 2, 3, and 8 was impaired. However, both Apaf1-/- thymocytes and activated T lymphocytes were sensitive to Fas-induced killing, showing that Fas-mediated apoptosis in these cells is independent of Apaf1. These data indicate that Apaf1 plays a central role in the common events of mitochondria-dependent apoptosis in most death pathways and that this role is critical for normal development.     

应用GT-Styrene~苯乙烯回收技术对裂解汽油的改质分析

通过采用GT-Styrene苯乙烯回收技术对传统的裂解汽油处理工艺进行改进,汽油的产品性能可以得到有效的改善,并回收有价值的苯乙烯产品和得到高质量的混合二甲苯产品。     

NR2A subunit expression shortens NMDA receptor synaptic currents in developing neocortex

NMDA receptors play important roles in learning and memory and in sculpting neural connections during development. After the period of peak cortical plasticity, NMDA receptor-mediated EPSCs (NMDAR EPSCs) decrease in duration. A likely mechanism for this change in NMDA receptor properties is the molecular alteration of NMDA receptor structure by regulation of NMDA receptor subunit gene expression. The four modulatory NMDAR2A-D (NR2A-D) NMDA receptor subunits are known to alter NMDA receptor properties, and the expression of these subunits is regulated developmentally. It is unclear, however, how the four NR2 subunits are expressed in individual neurons and which NR2 subunits are important to the regulation of NMDA receptor properties during development in vivo. Analysis of NR2 subunit gene expression in single characterized neurons of postnatal neocortex revealed that cells expressing NR2A subunit mRNA had faster NMDAR EPSCs than cells not expressing this subunit, regardless of postnatal age. Expression of NR2A subunit mRNA in cortical neurons at even low levels seemed sufficient to alter the NMDA receptor time course. The proportion of cells expressing NR2A and displaying fast NMDAR EPSCs increased developmentally, thus providing a molecular basis for the developmental change in mean NMDAR EPSC duration.     

Liposome-mediated therapy of intracranial brain tumors in a rat model

PURPOSE: Malignant brain tumors represent a serious therapeutic challenge, and survival often is low. We investigated the delivery of doxorubicin (DXR) to rat brain tumors in situ via liposomes, to test the hypothesis that intact liposomes undergo deposition in intracranial tumor through a compromised blood-tumor vasculature. Both therapeutic effect and intra-tumor drug carrier distribution were evaluated to identify variables in carrier-mediated delivery having impact on therapy. METHODS: The rat 9L gliosarcoma tumor was implanted orthotopically in Fischer 344 rats in the caudate-putamen region. The tumor-bearing rats were treated with DXR, either free or encapsulated in long-circulating, sterically-stabilized liposomes. Anti-tumor efficacy was assessed by survival time. In parallel, liposomes labeled with a fluorescent phospholipid analog were injected into tumor-bearing rats. At predetermined intervals, the brains were perfused with fixative, sectioned, and imaged with laser scanning confocal microscope (LSCM) to investigate the integrity of the tumor vascular bed and the intratumor deposition of liposomes. RESULTS: Free DXR given in 3 weekly iv injections was ineffective in increasing the life span of tumor-bearing rats at cumulative doses < or = 17 mg/kg, and at the highest dose (17 mg/kg) decreased survival slightly, compared to saline-treated controls. In contrast, DXR encapsulated in long-circulating liposomes mediated significant increases in life span at 17 mg/kg. Rats showed a 29% percent increase in median survival, respectively, compared to saline-control animals. The delay of treatment after tumor implantation was a major determinant of therapeutic effect. Fluorescent liposomes were deposited preferentially in tumor rather than normal brain, and were distributed non-uniformly, in close proximity to tumor blood vessels. CONCLUSIONS: Liposomes can be used to enhance delivery of drugs to brain tumors and increase therapeutic effect. The therapeutic effect may arise from release of drug from liposomes extravasated in discrete regions of the tumor vasculature and the extravascular space.     

Evaluation of levels and methods of zinc application to rice in sodic soils

Field experiments were conducted in zinc-deficient sodic soil to study the effect of levels and methods of zinc fertilization on yield, concentration and uptake of zinc by rice. Zinc was incorporated in the soil at the rate of 0, 5.6, 11.2 and 22.4 kg Zn per ha as zinc sulfate; sprayed on the plants at 1% and 2% zinc sulfate solution; and roots of rice seedlings were dipped in 2% and 4% ZnO suspensions in water. Grain yield, zinc content and its uptake increased in all the experiments up to 22.4 kg Zn per ha. Soil applied zinc was significantly correlated with yield of rice (r = 0.80^**) and zinc uptake (r = 0.89^**). Zinc content in 45-day old plants gave a significantly higher correlation with grain yield (r = 0.84^**) than the zinc content of rice straw and grain at maturity. Roots of rice seedlings dipped in 2% or 4% zinc oxide suspension in water were not only comparable with soil application of Zn at 5.6 and 11.2 kg Zn per ha, but also proved to be more economical for sodic soils showing moderate zinc deficiency.     

Methods and rates of application of Mn and its critical levels for wheat following rice on coarse textured soils

Two field experiments were conducted on Mn-deficient soils to evaluate the efficiency of rates, methods and time of MnSO₄.H₂ O application for wheat. Manganese sulphate was broadcast and mixed in soils at the rate of 5 to 50kg Mn ha^–1 before seeding and 10 to 40 kg Mn ha^–1 as top dress at 28 days — just before first irrigation. Three sprays of 1% MnSO₄·H₂O unneutralised solutions were applied, the first at 26 days — 2 days before first irrigation and the others afterward at weekly intervals. Both the methods caused a significant and marked increase in grain yield. Three foliar sprays were as effective as soil applications of 20 to 40 Kg Mn ha^–1 before seeding. The difference in grain yield resulting from soil applications of Mn before seeding and applications at the first irrigation was not significant. The DTPA-Mn status of 20 fields, selected on the basis of varying degree of Mn deficiency, was related to grain yield (r = 0.77^**). Also grain yield of all the experiments had a significant correlation with Mn content of grain (r = 0.55^** to 0.82^**) and straw (r = 0.77^** to 0.82^**). The critical limits calculated by statistical method were 1.25, 2.18 and 3.5 mg Mn kg^–1 soil for severe deficiency, deficiency and latent deficiency respectively for wheat.