Signal transduction pathways and their relevance in human astrocytomas

Aberrations in a number of signal transduction pathways have been identified as playing a key role in the molecular pathogenesis of astrocytomas and their progression to high grade glioblastoma multiforme (GBM). GBMs are characterized by overexpression of the Platelet Derived Growth Factor Receptors (PDGFR) and their ligands (PDGF), as well as the Epidermal Growth Factor Receptor (EGF-R). These receptors activate the Ras pathway, a key cellular signal transduction pathway, culminating in the activation of a wide range of Ras-dependent cellular events. GBMs have also been found to either overexpression or lose expression of various Protein Kinase C (PKC) isoforms. Major strides are being made in developing pharmacological agents which specifically inhibit these growth factor receptors and intracellular signal transduction pathways. Elucidating the role of these pathways in GBMs is thus of major clinical importance, as these novel molecularly-targeted agents may prove of use in the clinical management of GBMs in the future.     

Some characteristics of ridge-trough waveguide

A single-ridged waveguide with a symmetrical longitudinal trough below the ridge, designated as a ridge-trough waveguide (RTW) has been recently proposed as a wafer probe. The authors have theoretically calculated the cutoff, bandwidth, and impedance characteristics of this modified single-ridged waveguide in two different configurations using the Ritz-Galerkin technique and different domain decompositions. The results indicate that a RTW can be a low impedance broad-band structure     

Fast track thrombolysis in acute myocardial infarction: a quality improvement project

To understand the clinical efficacy of traditional anti-rheumatic herbal medicines on acute and severe arthritis or immune diseases, four herbal formulas and one herb were tested in vitro to determine their effects on prostaglandin E2 (PGE2) and interleukin 2 (IL2). Peripheral blood mononuclear cells from healthy subjects were incubated with different concentrations of four herbal formulas including Shaur Yau Gan Tsao Tang (SYGTT), Shang Jong Shiah Tong Yong Tong Feng Wan (SJSTY), Shu Jin Lih An Saan (SJLAS), Ma Shing Yih Gan Tang (MSYGT) and one herb, Tripterygium wilfordii (T2) with and without mitogen stimulation. PGE2 and IL2 from culture supernatant were measured by enzyme immunoassay. The results showed that SYGTT, SJSTY, SJLAS at concentration of 100 microg and MSYGT at 500 microg/ml can significantly inhibit PGE2 release (P < 0.05) from mononuclear cells. However, T2 at 2 microg/ml expressed the same response. For the inhibition of IL2, the concentration of SYGTT, SJSTY and SJLAS must exceed 100 symbol microg/ml. MSYGT failed to inhibit IL2 at even concentrations of 500 microg/ml but T2 at a very low concentration (0.6 microg/ml) could strongly inhibit it. The findings suggest that the majority of traditional anti-rheumatic herbal formulas or herbs, except for T2, should not be used to treat acute and critical arthritis or immune diseases.     

Industrial fires and explosions due to electrostatic ignition

Static electricity is a frequent source of fires and explosions in industry. A variety of operations may generate static electricity leading to such fires and explosions. This requires adequate preventive and protective measures against this hazard. The present paper describes the theory and mechanism of electrostatic sparking, parameters needed to assess the respective hazard in a plant, safety measures to combat electrostatic problems, common operations where such problems exist and measures to eliminate or mitigate these problems.     

Impedance, attenuation and power-handling characteristics of doubleL-septa waveguides

Rectangular waveguides with two L-shaped septa attached to the broad walls in antipodal configuration have been shown theoretically by the authors (see ibid. vol.40, no.4, p.777-781, 1992) to be an improved variant of the double T-septa guide having larger cut-off wavelength and broader bandwidth of the dominant TE mode. Numerical data on the attenuation, impedance, and power handling capability of this new type of broadband guide are presented as additional design information     

Supporting real-time and multimedia applications on the Mercuritestbed

This paper describes the distributed system, network and software architecture, the application development environment, the performance, and the early lessons learned on the ATM LAN testbed Mercuri established at the Honeywell Technology Center, to develop distributed multimedia technologies for real-time control applications. We have developed a client-server-based software architecture on Sun Sparcstation-2s connected by a Fore Systems' ASX-100 ATM switch, with video processing handled by Parallax's X Video cards. The architecture enables network-transparent applications and provides simple primitives for multimedia capture, display, transmission, storage, and retrieval. A real-time multimedia-in-the-loop control application was developed as the vehicle for testing the capabilities and performance of the network. Our test measurements focus on the end-user-level performance metrics such as message throughput and round-trip delay as well as video-frame jitter under no-load and load conditions. Our results show that the maximum burst throughput that can be supported at the user level is 48 Mb/s using AAL 5, while round-trip delays for 4-kbyte messages are about 3 ms. Our experience reveals a number of performance bottlenecks and open issues in using commercial ATM switches for practical applications. Our conclusions are outlined     

Environmentally Inert Nano-Crystalline Materials

A novel process to generate environmentally-inert nano-crystalline materials is discussed here. In this process, nano-crystals of different metals such as Ni, Cu, Al, Ti etc. can be produced in a single processing step with each crystal protected by several carbon ((graphite) layers. The technology is an adaptation of the arc technique utilized to produce carbon nano-crystals (Fullerenes) and can be controlled to produce nano-crystals with a variety of coatings including graphite. These nano-crystals are in the 10-50 nm diameter range (typically 30 nm) and of uniform size distribution. These nano-crystals were chemically stable in air and inert to various acids. Further, initial (unoptimized) experiments demonstrated the feasibility of consolidating these coated nano-particles using conventional processing approaches. Novel applications of these nano-crystals such as in the magnetic recording industry are also discussed here.     

Ras activation in astrocytomas and neurofibromas

Oncogenic mutations resulting in activated Ras Guanosine Triphosphate (GTP) are prevalent in 30% of all human cancers, but not primary nervous system tumors. Several growth factors/receptors are implicated in the pathogenesis of malignant astrocytomas including epidermal growth factor (EGFR) and platelet derived growth factor (PDGF-R) receptors, plus the highly potent and specific angiogenic vascular endothelial growth factor (VEGF). A significant proportion of these tumors also express a truncated EGFR, which is constitutively activated. Our work demonstrates that the mitogenic signals from both the normal PDGF-R and EGFR and the truncated EGFR activate Ras. Inhibition of Ras by genetic or pharmacological strategies leads to decreased astrocytoma tumorgenic growth in vitro and decreased expression of VEGF. This suggests that these agents may be potentially important as novel anti-proliferative and anti-angiogenic therapies for human malignant astrocytomas. In contrast to astrocytomas, where increased levels of activated Ras GTP results from transmitted signals from activated growth factor receptors, the loss of neurofibromin is postulated to lead to functional up-regulation of the Ras pathway in neurofibromatosis-1(NF-1). We have demonstrated that NF-1 neurofibromas and neurogenic sarcomas, compared to non-NF-1 Schwannomas, have markedly elevated levels of activated Ras GTP. Increased Ras GTP was associated with increased tumor vascularity in the NF-1 neurogenic sarcomas, perhaps related to increased VEGF secretion. The role of Ras inhibitors as potential therapy in this tumor is also under study.     

Increased expression of a hemimethylated oriC binding protein, SeqA, in an aphA mutant

In Escherichia coli, the origin of DNA replication, oriC, becomes transiently hemimethylated at the GATC sequences immediately after initiation of replication and this hemimethylated state is prolonged because of its sequestration by a fraction of outer membrane. This sequestration is dependent on a hemimethylated oriC binding protein such as SeqA. We previously isolated a clone of phage lambda gt11 called hobH, producing a LacZ fusion protein which recognizes hemimethylated oriC DNA. Very recently, Thaller et al. (FEMS Microbiol. Lett. 146 (1997) 191-198) found that the same DNA segment encodes a non-specific acid phosphatase, and named the gene aphA. We show here that the interruption of the aphA reading frame by kanamycin resistance gene insertion, abolishes acid phosphatase (NAP) activity. Interestingly, in the membrane of the null mutant, the amount of SeqA protein is about six times higher than that in the parental strain, suggesting the existence of a regulatory mechanism between SeqA and NAP expression.