The control of hyperglycemia in alloxan treated diabetic mice through the stimulation of hepatic insulin synthesis due to the production of nitric oxide

OBJECTIVE

The hepatocytes from the adult mice when stimulated by glucose had been reported to synthesize and secrete insulin. The feasibility of controlling hyperglycemia in alloxan induced diabetic mice through hepatic synthesis of insulin was studied.

MATERIALS AND METHODS

Insulin synthesis was determined by in vitro translation of mRNA and by immunohistochemistry of the hepatocytes and assayed by enzyme linked immunosorbent assay (ELISA). Dermcidin isoform 2 (dermcidin) was measured by ELISA. Nitric oxide was measured by methemoglobin method. Insulin synthesis was quantitated by immunoblot technique and the expression of proinsulin genes I and II in the hepatocytes was quantitated by cDNA synthesis.

RESULTS

It was found that in contrast to normal hepatocytes, the hepatocytes from the diabetic mice showed impaired insulin synthesis in the presence of glucose that was related to the inhibition of nitric oxide synthesis through the synthesis of dermcidin, a potent competitive inhibitor of nitric oxide synthase. The increase of systemic NO synthesis either by oral use of 0.7 mM acetyl salicylic acid (aspirin) or by dermal application of 0.28 mmol sodium nitroprusside in saline soaked in cotton pad was found to decrease blood glucose level from 600 mg/dL to 120 mg/dL with concomitant increase of plasma insulin level from 5 µunits/dL to 38 µunits/dL. And subsequently normalized dermcidin level from 80 nM to 4.5 nM within 24 h (p<0.001; n=10).

CONCLUSION

Our studies suggested the possibility of controlling hyperglycemia in alloxan induced diabetic mice by the stimulation of the hepatic insulin synthesis through the systemic stimulation of NO production in the hepatocytes.

Two functionally distinctive phosphopantetheinyl transferases from amoeba Dictyostelium discoideum

The life cycle of Dictyostelium discoideum is proposed to be regulated by expression of small metabolites. Genome sequencing studies have revealed a remarkable array of genes homologous to polyketide synthases (PKSs) that are known to synthesize secondary metabolites in bacteria and fungi. A crucial step in functional activation of PKSs involves their post-translational modification catalyzed by phosphopantetheinyl transferases (PPTases). PPTases have been recently characterized from several bacteria; however, their relevance in complex life cycle of protozoa remains largely unexplored. Here we have identified and characterized two phosphopantetheinyl transferases from D. discoideum that exhibit distinct functional specificity. DiAcpS specifically modifies a stand-alone acyl carrier protein (ACP) that possesses a mitochondrial import signal. DiSfp in contrast is specific to Type I multifunctional PKS/fatty acid synthase proteins and cannot modify the stand-alone ACP. The mRNA of two PPTases can be detected during the vegetative as well as starvation-induced developmental pathway and the disruption of either of these genes results in non-viable amoebae. Our studies show that both PPTases play an important role in Dictyostelium biology and provide insight into the importance of PPTases in lower eukaryotes.

Observation of noise phase locking in a single-frequency VECSEL

We present an experimental observation of phase locking effects in the intensity noise spectrum of a semiconductor laser. These noise correlations are created in the medium by coherent carrier-population oscillations induced by the beatnote between the lasing and non-lasing modes of the laser. This phase locking leads to a modification of the intensity noise profile at around the cavity free-spectral-range value. The noise correlations are evidenced by varying the relative phase shift between the laser mode and the non-lasing adjacent side modes.

Phosphatidylinositol transfer proteins: negotiating the regulatory interface between lipid metabolism and lipid signaling in diverse cellular processes

Phosphoinositides represent only a small percentage of the total cellular lipid pool. Yet, these molecules play crucial roles in diverse intracellular processes such as signal transduction at membrane-cytosol interface, regulation of membrane trafficking, cytoskeleton organization, nuclear events, and the permeability and transport functions of the membrane. A central principle in such lipid-mediated signaling is the appropriate coordination of these events. Such an intricate coordination demands fine spatial and temporal control of lipid metabolism and organization, and consistent mechanisms for specifically coupling these parameters to dedicated physiological processes. In that regard, recent studies have identified Sec14-like phosphatidylcholine transfer protein (PITPs) as "coincidence detectors," which spatially and temporally link the diverse aspects of the cellular lipid metabolome with phosphoinositide signaling. The integral role of PITPs in eukaryotic signal transduction design is amply demonstrated by the mammalian diseases associated with the derangements in the function of these proteins, to stress response and developmental regulation in plants, to fungal dimorphism and pathogenicity, to membrane trafficking in yeast, and higher eukaryotes. This review updates the recent advances made in the understanding of how these proteins, specifically PITPs of the Sec14-protein superfamily, operate at the molecular level and further describes how this knowledge has advanced our perception on the diverse biological functions of PITPs.

Photon lifetime in a cavity containing a slow-light medium

We investigate experimentally the lifetime of the photons in a cavity containing a medium exhibiting strong positive dispersion. This intracavity positive dispersion is provided by a metastable helium gas at room temperature in the electromagnetically induced transparency regime, in which light propagates at a group velocity of the order of 10⁴ m·s⁻¹. The results definitely prove that the lifetime of the cavity photons is governed by the group velocity of light in the cavity and not its phase velocity.

Emergency presentations of Parkinson's disease: early recognition and treatment are crucial for optimum outcome

Parkinson's disease (PD) is a debilitating condition associated with significant morbidity and mortality. Pathophysiologically the illness is due to a disruption of dopamine production in the basal ganglia and leads to a wide array of symptoms. These symptoms are not restricted to the nervous system; thus, the illness often presents acutely to a wide range of specialties, many of which may have limited experience in the condition. Patients often become unwell with illnesses unrelated to their PD. However, these conditions frequently lead to a deterioration in PD control. In addition, there exist certain acute complications of PD which are often difficult to recognise and carry significant mortality. Discussing the acute presentations of the illness under the umbrella of PD is important as it enables clinicians to focus upon the specific concerns involved in managing patients with the illness. A number of conditions are extremely common in PD and include falls, orthostatic hypotension, swallowing difficulties, psychosis, and hyperkinetic movement disorders. Optimal treatment of these conditions requires the consideration of issues specific to PD. Lesser recognised acute presentations of PD include the serotonin syndrome and neuroleptic malignant-like syndrome. While encountered less commonly, these conditions have been well described in the literature and untreated may prove fatal. They require urgent management, with their importance being further highlighted by the fact they may often mimic other illnesses, making diagnosis difficult. Therapeutic interventions aimed at treating PD and preventing its complications are evolving rapidly.

Optimization of the Sistrom Culture Medium for Large-Scale Batch Cultivation of Rhodospirillum rubrum under Semiaerobic Conditions with Maximal Yield of Photosynthetic Membranes

The defined medium A of W. R. Sistrom (W. R. Sistrom, J. Gen. Microbiol. 22:77-85, 1960) has been modified to allow the growth of Rhodospirillum rubrum in large-scale batch cultures under dark, semiaerobic conditions. The simultaneous use of two substrates, NH(4)-succinate (46 mM) and fructose (0.3%), which are utilized in aerobic and fermentative metabolism, respectively, leads to very high cell densities with a maximal yield of photosynthetic membranes.

Fractional order phase shaper design with Bode's integral for iso-damped control system

The phase curve of an open loop system is flat in nature if the derivative of its phase with respect to frequency is zero. With a flat-phase curve, the corresponding closed loop system exhibits an iso-damped property i.e. maintains constant overshoot with the change of gain. This implies enhanced parametric robustness e.g. to variation in system gain. In the recent past, fractional order (FO) phase shapers have been proposed by contemporary researchers to achieve enhanced parametric robustness. In this paper, a simple methodology is proposed to design an appropriate FO phase shaper to achieve phase flattening in a control loop, comprising a plant controlled by a classical Proportional Integral Derivative (PID) controller. The methodology is demonstrated with MATLAB simulation of representative plants and accompanying PID controllers.

Measurement of the coupling constant in a two-frequency VECSEL

We measure the coupling constant between the two perpendicularly polarized eigenstates of a two-frequency Vertical External Cavity Surface Emitting Laser (VECSEL). This measurement is performed for different values of the transverse spatial separation between the two perpendicularly polarized modes. The consequences of these measurements on the two-frequency operation of such class-A semiconductor lasers are discussed.

Differential Signaling by ErbB Receptor (HER) Dimers: Implications for Response to Anti-HER2 Therapies in Breast Cancer

The ErbB family of receptor tyrosine kinases comprises of EGFR, HER2, HER3 and HER4. Ligand binding induces receptor homo- and heterodimerization and activation of downstream signaling. No ligand(s) have been identified for HER2. Recruitment of HER2 to ligand-activated co-receptors potentiates signaling by HER2-containing heterodimers. To identify differential signaling induced by HER2/HER3 and HER2/EGFR heterodimers and HER2 homodimers, we developed a cell system where HER2 dimerization can be conditionally regulated. A retroviral vector encoding HA-tagged full-length human HER2 fused to ligand-binding domain of FK506 binding protein (FKBP) in the C-terminus was stably transduced into MCF10A mammary epithelial cells. Treatment of MCF10A-HER2-FKBP-HA cells with the intracellular dimerizer AP1510 resulted in homodimerization and tyrosine phosphorylation of the HER2 chimera. The EGFR ligands EGF and TGFα and the HER3 ligand heregulin induced HER2/EGFR and HER2/HER3 heterodimers. Microarray analysis with RNA isolated from vehicle, AP1510, TGFα and heregulin treated cells identified unique transcriptional activities associated with HER2/HER2, HER2/HER3 and HER2/EGFR induced signaling. Ingenuity Pathway analysis of the microarray data showed that HER2 homodimers had the most significant effect on the “G2/M DNA damage checkpoint regulation pathway” whereas HER2/EGFR dimers had the most pronounced effect on the “pyrimidine metabolism pathway”. Active HER2/HER3 dimers affected the NF-κB signaling pathway the most.To determine if differential signaling by ErbB dimers have any implications for the response to anti-HER2 therapies, we treated MCF10A-HER2-FKBP-HA cells with AP1510, TGFα or heregulin in the presence or absence of trastuzumab, pertuzumab or lapatinib. In 3D Matrigel, AP1510-treated cells formed invasive acini while untreated cells failed to grow. EGF and TGFα and heregulin also stimulated acini growth in 3D. The anti-HER2 antibody trastuzumab completely inhibited AP1510-stimulated but not EGF, TGFα, or heregulin-stimulated growth. Lapatinib, a dual inhibitor of the HER2 and EGFR tyrosine kinases, blocked EGF, heregulin, and AP1510-induced growth. Pertuzumab, an antibody that blocks ligand-induced HER2 heterodimerization, inhibited heregulin-induced but not AP1510-induced growth. Reverse Phase Protein Array performed with lysates from cells treated with AP1510, TGFα or heregulin indicated that AP1510 failed to activate S473 p-AKT. This is a key enzyme in the PI3K pathway, which has been associated with resistance to HER2 inhbitors. Western blot analyses showed that AP1510 induced p-ERK whereas TGFα and Heregulin activated p-AKT. Binding assays with 125I-labeled trastuzumab indicated that treatment with AP1510 enhanced binding of trastuzumab compared to untreated cells. This result suggests that HER2 homodimers present a conformation to which trastuzumab binds better. Taken together, these data suggest that 1) because of their inability to activate Akt, cells dependent on HER2-containing homodimers are less able to bypass trastuzumab action; and 2) high levels of HER2 homodimers in breast cancers with HER2 gene amplification may represent a biomarker predictive of response to trastuzumab.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 705.

Observation of electromagnetically induced transparency and slow light in the dark state--bright state basis

The quantum coherence phenomenon of electromagnetically induced transparency (EIT) is observed in a three-level system composed of an excited state and two coherent superpositions of the two ground-state levels. This peculiar ground state basis is composed of the so-called bright and dark states of the same atomic system in a standard coherent population trapping configuration. The characteristics of EIT, namely, width of the transmission window and reduced group velocity of light, in this unusual basis, are theoretically and experimentally investigated and are shown to be essentially identical to those of standard EIT in the same system.

Multi-loop networked process control: a synchronized approach

Modern day process control uses digital controllers which are based on the principle of distributed rather than centralized control. Distributing controllers, sensors and actuators across a plant entails considerable wiring which can be reduced substantially by integrating the components of a control loop over a network. The other advantages include greater flexibility and higher reliability with lower hardware redundancy. The controllers and sensors are on a network and can take over the function of a failed component automatically, without the need of manual reconfiguration, thus eliminating the need of having a redundant component for each and every component. Though elaborate techniques have been developed for Single Input Single Output (SISO) systems, the major challenge lies in extending these ideas to control a practical process plant where de-centralized control is actually achieved through control of individual SISO control loops derived through de-coupling of the original system. Multiple loops increase network load and hence the sampling times associated with the control loops and makes synchronization difficult. This paper presents a methodology by which network based process control can be applied to practical process plants, with a simple direct synchronization mechanism.

Investigations and control measures following a case of inhalation anthrax in East London in a drum maker and drummer, October 2008

The patient is believed to have acquired the infection from making animal hide drums. Environmental investigations identified one drum and two pieces of animal skins contaminated with anthrax spores.