Network modeling of signal transduction: establishing the global view

Embryonic development and adult tissue homeostasis are controlled through activation of intracellular signal transduction pathways by extracellular growth factors. In the past, signal transduction has largely been regarded as a linear process. However, more recent data from large-scale and high-throughput experiments indicate that there is extensive cross-talk between individual signaling cascades leading to the notion of a signaling network. The behavior of such complex networks cannot be predicted by simple intuitive approaches but requires sophisticated models and computational simulations. The purpose of such models is to generate experimentally testable hypotheses and to find explanations for unexpected experimental results. Here, we discuss the need for, and the future impact of, mathematical models for exploring signal transduction in different biological contexts such as for example development.     

Intracellular depletion of insulin by oleate is due to an inhibited synthesis and not to an increased secretion

In the polyclonal rat pancreatic beta-cell line INS-1, immunoreactive insulin (IRI, insulin and its precursors) and C-peptide (surrogate marker for mature insulin) were quantified after a 1-h incubation at 16.7 mM glucose with or without oleate. Oleate caused a 20% decrease (P 相似文献   

The nature of driving forces for passive water transport through arthropod cuticle

1. 1.|We demonstrate using thermodynamic arguments that water loss through arthropod epicuticle is well described by a linear law relating water flux to transmembrane vapour pressure drop.

2. 2.|The relationship applies equally to systems where the liquid or vapour exist on either side of a membrane.

3. 3.|An earlier claim by some workers that water diffusion through arthropod epicuticle is proportional to chemical potential drop across the membrane is found to be theoretically unjustified.

4. 4.|Recent measurements with Periplaneta cuticle support the prediction that flux at a given temperature is proportional to the difference in vapour pressure.

Importance of the nef gene for maintenance of high virus loads and for development of AIDS

When rhesus monkeys were infected with a form of cloned SIVmac239 having a premature stop signal at the 93rd codon of nef, revertants with a coding codon at this position quickly and universally came to predominate in the infected animals. This suggests that there are strong selective forces for open functional forms of nef in vivo. Although deletion of nef sequences had no detectable effect on virus replication in cultured cells, deletion of nef sequences dramatically altered the properties of virus in infected rhesus monkeys. Our results indicate that nef is required for maintaining high virus loads during the course of persistent infection in vivo and for full pathologic potential. Thus, nef should become a target for antiviral drug development. Furthermore, the properties of virus with a deletion in nef suggest a means for making live-attenuated strains of virus for experimental vaccine testing.     

The influence of UV radiation on number and ultrastructure of the endosymbiotic dinoflagellates in the sea anemoneCereus pedunculatus (Anthozoa: Actiniaria)

The sea anemoneCereus pedunculatus was artificially UV-irradiated to test the effect of UV-light on the number of endosymbiotic dinoflagellates in its gastrodermis and on their ultrastructure. Anemones were kept in the laboratory in a light: dark cycle (LD 12∶12; 13 W m⁻²) at 18 °C and briefly (2, 5 and 9 d) exposed to UV radiation at quasisolar intensities, 0.5 or 1 W m⁻². Their tentacles were then examined in the electron microscope for qualitative and quantitative changes in the zooxanthellae. There was an intensity-dependent decrease in the number of symbionts, which in some cases were lost altogether (bleaching). Irradiated anemones contained a larger proportion of symbionts with ultrastructural abnormalities, namely diminished starch, some mitochondria with altered matrix and, in particular, characteristic changes in the chloroplasts; instead of being densely stacked, the thylakoids were spread apart and swollen at the ends of their membranes to form vesicle-like structures. Relatively large vesicles also appeared in the cytoplasm. The resulting enlargement of the whole dinoflagellate cell was documented morphometrically. Another intensity-dependent effect was a significant decrease in mitosis rate, established by counting dividing symbiont cells in TEM micrographs. *** DIRECT SUPPORT *** A03B6037 00006     

A Novel Educational Strategy Targeting Health Care Workers in Underserved Communities in Central America to Integrate HIV into Primary Medical Care

Background

Current educational strategies to integrate HIV care into primary medical care in Central America have traditionally targeted managers or higher-level officials, rather than local health care workers (HCWs). We developed a complementary online and on-site interactive training program to reach local HCWs at the primary care level in underserved communities.

Methods

The training program targeted physicians, nurses, and community HCWs with limited access to traditional onsite training in Panama, Nicaragua, Dominican Republic, and Guatemala. The curriculum focused on principles of HIV care and health systems using a tutor-supported blended educational approach of an 8-week online component, a weeklong on-site problem-solving workshop, and individualized project-based interventions.

Results

Of 258 initially active participants, 225 (225/258 = 87.2%) successfully completed the online component and the top 200 were invited to the on-site workshop. Of those, 170 (170/200 = 85%) attended the on-site workshop. In total, 142 completed all three components, including the project phase. Quantitative and qualitative evaluation instruments included knowledge assessments, reflexive essays, and acceptability surveys. The mean pre and post-essay scores demonstrating understanding of social determinants, health system organization, and integration of HIV services were 70% and 87.5%, respectively, with an increase in knowledge of 17.2% (p<0.001). The mean pre- and post-test scores evaluating clinical knowledge were 70.9% and 90.3%, respectively, with an increase in knowledge of 19.4% (p<0.001). A survey of Likert scale and open-ended questions demonstrated overwhelming participant satisfaction with course content, structure, and effectiveness in improving their HIV-related knowledge and skills.

Conclusion

This innovative curriculum utilized technology to target HCWs with limited access to educational resources. Participants benefited from technical skills acquired through the process, and could continue working within their underserved communities while participating in the online component and then implement interventions that successfully converted theoretical knowledge to action to improve integration of HIV care into primary care.     

Distribution of P2X<Subscript>3</Subscript> receptor immunoreactivity in myenteric ganglia of the mouse esophagus

Intraganglionic laminar endings (IGLEs) represent the major vagal afferent terminals throughout the gut. Electrophysiological experiments revealed a modulatory role of ATP in the IGLE-mechanotransduction process and the P2X₂-receptor has been described in IGLEs of mouse, rat and guinea pig. Another purinoceptor, the P2X₃-receptor, was found in IGLEs of the rat esophagus. These findings prompted us to investigate occurrence and distribution of the P2X₃-receptor in the mouse esophagus. Using multichannel immunofluorescence and confocal microscopy, P2X₃-immunoreactivity (-iry) was found colocalized with the vesicular glutamate transporter 2 (VGLUT2), a specific marker for IGLEs, on average in three-fourths of esophageal IGLEs. The distribution of P2X₃ immunoreactive (-ir) IGLEs was similar to that of P2X₂-iry and showed increasing numbers towards the abdominal esophagus. P2X₃/P2X₂-colocalization within IGLEs suggested the occurrence of heteromeric P2X_2/3 receptors. In contrast to the rat, where only a few P2X₃-ir perikarya were described, P2X₃ stained perikarya in ~80% of myenteric ganglia in the mouse. Detailed analysis revealed P2X₃-iry in subpopulations of nitrergic (nNOS) and cholinergic (ChAT) myenteric neurons and ganglionic neuropil of the mouse esophagus. We conclude that ATP might act as a neuromodulator in IGLEs via a (P2X₂)-P2X₃ receptor-mediated pathway especially in the abdominal portion of the mouse esophagus.     

Characterization of infectious molecular clones of simian immunodeficiency virus (SIVmac) and human immunodeficiency virus type 2: persistent infection of rhesus monkeys with molecularly cloned SIVmac.

Infection of macaque monkeys with simian immunodeficiency virus (SIV) is probably the best animal model currently available for studying acquired immunodeficiency syndrome. In this report, we describe three infectious molecular clones of SIVmac and one of human immunodeficiency virus type 2 (HIV-2) and their use in the study of cell and species specificity, animal infection, and the relationship of gene sequence to function. Replication of the cloned viruses in different cell lines varied dramatically. Some human CD4+ cell lines (HUT 78 and MT-4) supported the replication of SIVmac and HIV-2, while others (CEM and Jurkat-T) supported the replication of HIV-2 but not SIVmac. Growth of cloned virus in macaque lymphocytes in vitro was predictive of macaque infection in vivo. Macaque lymphocytes supported the replication of SIVmac239 and SIVmac251 but not SIVmac142 or HIV-2ROD. Using virus recovery and antibody response as criteria for infection, macaques that received cloned SIVmac251 and SIVmac239 became infected, while macaques receiving cloned SIVmac142 and HIV-2ROD did not become infected. Nucleotide sequences from the envelope region of all four cloned viruses demonstrated that there is considerable flexibility in the location of the translational termination (stop) signal. These infectious molecular clones will be very useful for future studies directed at the molecular basis for persistence, pathogenicity, tropism, and cell and species specificity.     

Construction, expression, and analysis of recombinant HIV gp41 constructs containing a novel cellular binding domain

The gp41 polypeptide of human immunodeficiency virus (HIV) contains an immunosuppressive domain, an epitope which elicits specific cytolytic T cell responses to HIV, and a complement Clq interactive domain. In addition, a synthetic peptide called CS3, derived from gp41 (amino acids 576-593 of gp160) and contiguous with the major immunodominant domain, binds to cellular proteins and may be important in HIV entry/fusion. In order to further investigate the role of the CS3 region of gp41 in cellular binding and to investigate other properties of gp41, sufficient quantities of this polypeptide must be readily available. We have therefore cloned the region of the HIV genome between nucleotides 7891 and 8188 (corresponding to amino acids 541-639 of gp160) into a series of procaryotic expression vectors. The resulting clones express a recombinant polypeptide of gp41 (r41). Two of these recombinants, pMAL-cRl/r41 and pGEMEX-2/r41, expressed the highest and most consistent levels of r41 as judged by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. With the pMAL-cRl/r41 construct, r41 was expressed as a fusion to the maltose-binding protein (MBP) and, following purification by affinity chromatography, was cleaved from MBP by factor Xa protease digestion. MBP/r41 may be useful for studies of a reported gp41 cellular binding domain and may facilitate studies involving other functions ascribed to this region of gp41. (c) 1993 John Wiley & Sons, Inc.