Deficiency of kinase suppressor of Ras1 prevents oncogenic ras signaling in mice

In Drosophila and Caenorhabditis elegans, kinase suppressor of ras (KSR) positively modulates Ras/Raf-mitogen-activated protein kinase (MAPK) signaling. The precise signaling mechanism of mammalian KSR1 and its role in Ras-mediated transformation, however, remain uncertain. To gain insight into KSR1 function in vivo, we generated mice homozygous null for KSR1. ksr1-/- mice are viable and without major developmental defects. However, an unusual disorganized hair follicle phenotype manifest in epidermal growth factor receptor knockout mice is recapitulated in ksr1-/- mice, providing genetic support for the notion that epidermal growth factor receptor, Ras, and KSR1 are on the same signaling pathway in mammals. Furthermore, ksr1-/- mice allow for the definition of KSR1-dependent and -independent mechanisms of c-Raf-1 activation. In embryonic fibroblasts, epidermal growth factor and 12-O-tetradecanoylphorbol-13-acetate activated the MAPK cascade to a similar extent, yet only c-Raf-1 activation by epidermal growth factor depended on KSR1. Moreover, whereas the genesis of polyomavirus middle T antigen (MT)-driven mammary cancer appears independent of KSR1, KSR1 is obligate for v-Ha-ras-mediated skin tumor formation. The growth of MT-driven mammary tumor was moderately slowed in ksr1-/- mice, however, consistent with a decreased rate of proliferation of ksr1-/- cells (T cells and embryonic fibroblasts). Nonetheless, all ksr1-/- animals succumbed to mammary cancer. In contrast, papilloma formation in Tg.AC mice, resulting from skin-specific v-Ha-ras expression, was completely abrogated in the ksr1-/- background. Hence, MT-driven mammary tumor genesis, which is signaled through src and phosphatidylinositol 3'-kinase, appears KSR1 independent, whereas v-Ha-ras-mediated skin cancer, signaled through the Raf-1/MAPK cascade, requires KSR1. These results suggest KSR1 may represent a therapeutic target for Ras/MAPK signaling of human tumorigenesis.     

Biting behavior and seasonal variation in the abundance of Anopheles minimus species A and C in Thailand

We measured the seasonal abundance and bloodfeeding behavior of species A and C of the mosquito Anopheles minimus Theobald 1901 in an endemic malarious area of western Thailand. An. minimus s.l. is a major vector of human malarial and filarial parasites in Southeast Asia. Mosquitos were collected once a month for one year using four collection methods: human-baiting indoors, human-baiting outdoors, human-baiting in the forest, and cow-baiting. We found that both species A and C tend to feed from cows rather than humans; we did not find any preference for indoor, outdoor or forest-biting in either species. Both species had a peak biting density in October/November, at the end of the rainy season, and species C showed a second, smaller peak at the end of the cool season. These findings are discussed in relation to previous reports of the behavior of An. minimus s.l., particularly in light of suggestions that An. minimus s.l. has changed its feeding behavior in response to DDT spraying.     

IL-4 induces characteristic Th2 responses even in the combined absence of IL-5, IL-9, and IL-13

Functional redundancy is highly prevalent among the Th2 interleukins (IL)-4, IL-5, IL-9, and IL-13. To define the critical functions of these cytokines, we have generated a novel panel of compound Th2 cytokine-deficient mice (from single to quadruple cytokine knockouts). We find that these Th2 cytokines are not essential for fetal survival even during allogeneic pregnancy. Using intestinal parasite infection and a pulmonary granuloma model, we demonstrate cryptic roles for IL-4, IL-5, IL-9, and IL-13 in these responses. Significantly, although IL-5, IL-9, and IL-13 add to the speed and magnitude of the response, a threshold is reached at which IL-4 alone can activate all Th2 effector functions. These mice reveal distinct spatial, temporal, and hierarchical cytokine requirements in immune function.     

A simple model accounts for the response of disparity-tuned V1 neurons to anticorrelated images

Disparity-tuned cells in primary visual cortex (VI) are thought to play a significant role in the processing of stereoscopic depth. The disparity-specific responses of these neurons have been previously described by an energy model based on local, feedforward interactions. This model fails to predict the response to binocularly anticorrelated stimuli, in which images presented to left and right eyes have opposite contrasts. The original energy model predicts that anticorrelation should invert the disparity tuning curve (phase difference pi), with no change in the amplitude of the response. Experimentally, the amplitude tends to be reduced with anticorrelated stimuli and a spread of phase differences is observed, although phase differences near pi are the most common. These experimental observations could potentially reflect a modulation of the V1 signals by feedback from higher visual areas (because anticorrelated stimuli create a weaker or nonexistent stereoscopic depth sensation). This hypothesis could explain the effects on amplitude, but the spread of phase differences is harder to understand. Here, we demonstrate that changes in both amplitude and phase can be explained by a straightforward modification of the energy model that involves only local processing. Input from each eye is passed through a monocular simple cell, incorporating a threshold, before being combined at a binocular simple cell that feeds into the energy computation. Since this local feedforward model can explain the responses of complex cells to both correlated and anticorrelated stimuli, there is no need to invoke any influence of global stereoscopic matching.     

Massive mycobacterial choroiditis during highly active antiretroviral therapy: another immune-recovery uveitis?

PURPOSE: To describe the ocular presentation of disseminated mycobacterial disease occurring during immune-recovery in a patient with acquired immune deficiency syndrome (AIDS). STUDY DESIGN: Case report and literature review. PARTICIPANTS: A 41-year-old AIDS patient with a prior diagnosis of cytomegalovirus retinitis. METHODS: The patient developed progressive, bilateral multifocal choroiditis with panuveitis 2 months after beginning and responding to highly active antiretroviral therapy. His left eye became blind and painful and was enucleated. Pathologic examination revealed massive choroiditis with well-formed, discrete granulomas and multiple intracellular and extracellular acid-fast organisms within the choroidal granulomas. Culture and polymerase chain reaction of vitreous specimens revealed Mycobacterium avium complex (MAC). RESULTS: Empiric, and later sensitivity-guided, local and systemic antibiotic therapy was used to treat the remaining right eye, but it continued to deteriorate. Despite medical therapy, three vitrectomies and repeated intravitreal injections of amikacin, a total retinal detachment ensued. One week after the third vitrectomy, the patient died from mesenteric artery thrombosis in the setting of disseminated mycobacterial disease. CONCLUSIONS: This is the first report of ocular inflammation as the presenting finding in the recently recognized syndrome of immune-recovery MAC disease. Pathogenesis of this entity is related to an enhanced immune response to a prior, subclinical, disseminated infection. The formation of discrete granulomas, normally absent in MAC infections in AIDS, reflects this mechanism.     

Design, synthesis and evaluation of human telomerase inhibitors based upon a tetracyclic structural motif

There is currently significant interest in the development of inhibitors of human telomerase for the treatment of cancer. We describe here the design and synthesis of a new class of mono-substituted small-molecule inhibitors of human telomerase based upon a tetracyclic structural motif. In contrast to the structurally related molecule 9-hydroxyellipticine, recently shown to inhibit telomerase activity in cell cultures but found to be inactive in a cell-free system, we demonstrate direct inhibition of the telomerase enzyme by the tetracyclic compounds in a modified cell-free TRAP assay. The most potent compounds exhibit activity in the low micromolar range and are thus comparable with some of the more active small-molecule telomerase inhibitors based on planar aromatic chromophores, previously described by ourselves and others. These compounds may represent useful leads for the development of more potent inhibitors of human telomerase.     

Bilateral adrenal non-Hodgkin's lymphoma with adrenal insufficiency

A 74 year old women presented with lethargy and weight loss and was found to have profound adrenal insufficiency and bilateral adrenal mass lesions. Histological examination revealed non-Hodgkin's lymphoma. There was no evidence of lymphoma outside the adrenal glands. Isolated bilateral adrenal masses may rarely be due to primary adrenal non-Hodgkin's lymphoma, which is often associated with adrenal insufficiency.     

Identification of differentially expressed genes in shrimp (<Emphasis Type="Italic">Penaeus stylirostris</Emphasis>) infected with <Emphasis Type="Italic">White spot syndrome virus</Emphasis> by cDNA microarrays

Summary. White spot syndrome virus (WSSV) is currently the most important viral pathogen infecting penaeid shrimp worldwide. Although considerable progress has been made in characterizing the WSSV genome and developing detection methods, information pertaining to host genes involved in WSSV pathogenesis is limited. We examined the potential of cDNA microarray analysis to study gene expression in WSSV-infected shrimp. Shrimp cDNAs were printed as low-density arrays on glass slides and were hybridized with Cy3/Cy5 labeled probes derived from RNA isolated from healthy and WSSV-infected shrimp. Genes that code for proteins that are relevant to crustacean immunity, structural proteins, as well as proteins of unknown function were among those whose mRNA expression was altered upon WSSV infection. To validate the microarray data, the temporal expression of three differentially expressed genes, an immune gene (C-type lectin-1), a structural gene (40S ribosomal protein), and a gene involved in lipid metabolism (fatty acid binding protein) was measured in healthy and WSSV-infected shrimp by real-time RT-PCR. The data suggest that WSSV infection alters the expression of a wide array of cellular genes, and provides a framework for further studies aimed at identifying genes whose function may provide insight into the mechanism of WSSV infection in shrimp.