Antipredator benefits of group living in colonial web-building spiders: the ‘early warning’ effect

The Mexican colonial web-building spider Metepeira incrassata is frequently attacked by predatory wasps from a number of families. Previous studies have shown that wasps often attack more than one spider during a ‘run’ on a colony, but capture success declines as colony size increases, and that spiders in the central core of the colony have lower risk (Rayor & Uetz 1990, Behavioral Ecology and Sociobiology, 27, 77-85; Uetz & Hieber 1994, Behavioral Ecology, 5, 326-333). We used data from direct observation of attacks and field experiments to test the hypothesis that colonial web-building spiders benefit from ‘early warning’ of predator approach through vibrations in the colony web. Analysis of 135 naturally occurring wasp attack ‘runs’ (attacks on 454 spiders) showed that the per-attack run and per-spider capture success of wasps decreased significantly with increased spider colony size. Spider defensive and evasive behaviours observed in a subset of these attacks varied with the attack sequence. Evasive responses by spiders were more frequent later in the attack, suggesting advance warning of predator approach. Experiments using a predator-simulating vibration source demonstrated that mean reaction distance of spiders increased with increasing colony size. Adult female spiders in core positions reacted at greater distances than those on the periphery, but immature spiders, whose capture risk is lower, showed no difference. Behaviour of spiders during simulated attacks was similar to observed encounters with wasps: evasive responses were more frequent and response latency was shorter in spiders attacked later in the sequence, and in many cases, spiders took evasive action prior to any contact with the stimulus. Additional experiments testing isolated cues (web contact, airborne vibration, web-borne vibration) suggest spiders respond to web-borne vibrations generated by predators and evasive behaviours of other spiders. Together, these results support the ‘early warning’ hypothesis of antipredator benefits for colonial web-building spiders.     

Transforming growth factor beta (TGFbeta ) signaling via differential activation of activin receptor-like kinases 2 and 5 during cardiac development. Role in regulating parasympathetic responsiveness

Little is known regarding factors that induce parasympathetic responsiveness during cardiac development. We demonstrated previously that in atrial cells cultured from chicks 14 days in ovo, transforming growth factor beta (TGFbeta) decreased parasympathetic inhibition of beat rate by the muscarinic agonist, carbamylcholine, by 5-fold and decreased expression of Galpha(i2). Here in atrial cells 5 days in ovo, TGFbeta increased carbamylcholine inhibition of beat rate 2.5-fold and increased expression of Galpha(i2). TGFbeta also stimulated Galpha(i2) mRNA expression and promoter activity at day 5 while inhibiting them at day 14 in ovo. Over the same time course expression of type I TGFbeta receptors, chick activin receptor-like kinase 2 and 5 increased with a 2.3-fold higher increase in activin receptor-like kinase 2. Constitutively active activin receptor-like kinase 2 inhibited Galpha(i2) promoter activity, whereas constitutively active activin receptor-like kinase 5 stimulated Galpha(i2) promoter activity independent of embryonic age. In 5-day atrial cells, TGFbeta stimulated the p3TP-lux reporter, which is downstream of activin receptor-like kinase 5 and had no effect on the activity of the pVent reporter, which is downstream of activin receptor-like kinase 2. In 14-day cells, TGFbeta stimulated both pVent and p3TP-lux. Thus TGFbeta exerts opposing effects on parasympathetic response and Galpha(i2) expression by activating different type I TGFbeta receptors at distinct stages during cardiac development.     

Fibroblast growth factor 18 influences proximal programming during lung morphogenesis

The structure and functions of the airways of the lung change dramatically along their lengths. Large-diameter conducting airways are supported by cartilaginous rings and smooth muscle tissue and are lined by ciliated and secretory epithelial cells that are involved in mucociliary clearance. Smaller peripheral airways formed during branching morphogenesis are lined by cuboidal and squamous cells that facilitate gas exchange to a network of fine capillaries. The factors that mediate formation of these changing cell types and structures along the length of the airways are unknown. We report here that conditional expression of fibroblast growth factor (FGF)-18 in epithelial cells of the developing lung caused the airway to adopt structural features of proximal airways. Peripheral lung tubules were markedly diminished in numbers, whereas the size and extent of conducting airways were increased. Abnormal smooth muscle and cartilage were found in the walls of expanded distal airways, which were accompanied by atypically large pulmonary blood vessels. Expression of proteins normally expressed in peripheral lung tubules, including SP-B and pro-SP-C, was inhibited. FGF-18 mRNA was detected in normal mouse lung in stromal cells surrounding proximal airway cartilage and in peripheral lung mesenchyme. Effects were unique to FGF-18 because expression of other members of the FGF family had different consequences. These data show that FGF-18 is capable of enhancing proximal and inhibiting peripheral programs during lung morphogenesis.     

Selective expression of Narp,a secreted neuronal pentraxin,in orexin neurons

Recent studies have provided compelling evidence demonstrating that orexin (also known as hypocretin) neurons play a central role in the pathophysiology of narcolepsy. However, targeted deletion of orexin does not fully mimic the functional deficits induced by selective ablation of these neurons; implying that other secreted signaling molecules expressed in these neurons mediate key aspects of their function. In this study, we demonstrate that orexin neurons display robust expression of neuronal activity-regulated pentraxin (Narp), a secreted neuronal pentraxin, implicated in regulating clustering of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors. Furthermore, we have found that hypothalamic melanin-concentrating hormone (MCH) neurons, which form a peptidergic pathway thought to oppose the effects of the orexin system, express another neuronal pentraxin, NP1. Thus, these findings suggest that these pathways utilize neuronal pentraxins, in addition to neuropeptides, as synaptic signaling molecules.     

Activation of cytomegalovirus in pig-to-primate organ xenotransplantation

Xenotransplantation of porcine organs carries the risk of reactivation of latent virus in donor and recipient tissues as well as transmission of viruses between species. We have investigated the activation of baboon cytomegalovirus (BCMV) and porcine CMV (PCMV) in a pig-to-primate model of xenotransplantation. Tissues originating from a series of six swine-to-baboon composite thymokidney xenotransplants were investigated. Four immunosuppressed baboons died (survival range, 7 to 27 days) with the graft in situ. Increases in BCMV DNA copy numbers occurred in three (75%) of these baboons and was thought to be responsible for pneumonitis and the death of one animal. In two baboons, disseminated intravascular coagulation was successfully treated by graftectomy and discontinuation of immunosuppression. PCMV was upregulated in five of six xenografts (83%). PCMV infection was associated with ureteric necrosis in one xenograft. Although significantly increased in native tissues, low levels of BCMV and PCMV were also detected in tissues other than that of the native viral host species. The cross-species presence of CMV did not appear to cause clinical or histological signs of invasive disease. Thus, viral infections with clinical disease were restricted to tissues of the native species of each virus. Intensive immune suppression currently required for xenotransplantation results in a significant risk of reactivation of latent infections by BCMV and PCMV. It is not yet known whether viral DNA detected across species lines represents cellular microchimerism, ongoing viral infection, or uptake of free virus. The observation of graft injury by PCMV demonstrates that CMV will be an important pathogen in immunosuppressed xenograft recipients. Strategies must be developed to exclude CMV from porcine organ donors.     

Retrieval of human cytomegalovirus glycoprotein B from cell surface is not required for virus envelopment in astrocytoma cells

Human cytomegalovirus (HCMV) is a prototypic member of the betaherpesvirus family. The HCMV virion is composed of a large DNA genome encapsidated within a nucleocapsid, which is wrapped within an inner proteinaceous tegument and an outer lipid envelope containing viral glycoproteins. Although genome encapsidation clearly occurs in the nucleus, the subsequent steps in the virion assembly process are unclear. HCMV glycoprotein B (gB) is a major component of the virion envelope that plays a critical role in virus entry and is essential for the production of infectious virus progeny. The aim of our present study was to identify the secretory compartment to which HCMV gB was localized and to investigate the role of endocytosis in mediating gB localization and HCMV biogenesis. We show that HCMV gB is localized to the trans-Golgi network (TGN) in HCMV-infected cells and that gB contains all of the trafficking information necessary for TGN localization. Endocytosis of gB was shown to play a role in mediating TGN localization of gB and in targeting of the protein to the site of virus envelopment. However, inhibition of endocytosis with a dominant-negative dynamin I molecule did not affect the production of infectious virus. These observations indicate that, although endocytosis is involved in the trafficking of gB to the site of glycoprotein accumulation in the TGN, endocytosis of gB is not required for the production of infectious HCMV.     

Laparoscopic radical nephrectomy: morcellate or leave intact? Definitely morcellate!

Eleven years after the first laparoscopic radical nephrectomy (LRN), which was performed with morcellation, the best approach to the procedure remains controversial. Concerns include tumor seeding, recurrence, accuracy of staging, histopathological diagnosis, and longer surgery time. Enclosing the kidney in an impermeable sac prior to morcellation helps prevent seeding. Pathological review of morcellated LRN specimens has been shown to be as accurate as that of intact specimens. Ten-year survival data for LRN with morcellation are not available yet, but 5-year rates are as good as those for open nephrectomy. The utility of morcellation in LRN is supported by the results of clinical practice.     

Flow Patterns Around the Carapaces of Rigid-bodied, Multi-propulsor Boxfishes (Teleostei: Ostraciidae)

Boxfishes (Teleostei: Ostraciidae) are rigid-body, multi-propulsorswimmers that exhibit unusually small amplitude recoil movementsduring rectilinear locomotion. Mechanisms producing the smoothswimming trajectories of these fishes are unknown, however.Therefore, we have studied the roles the bony carapaces of thesefishes play in generating this dynamic stability. Features ofthe carapaces of four morphologically distinct species of boxfisheswere measured, and anatomically-exact stereolithographic modelsof the boxfishes were constructed. Flow patterns around eachmodel were investigated using three methods: 1) digital particleimage velocimetry (DPIV), 2) pressure distribution measurements,and 3) force balance measurements. Significant differences inboth cross-sectional and longitudinal carapace morphology weredetected among the four species. However, results from the threeinterrelated approaches indicate that flow patterns around thevarious carapaces are remarkably similar. DPIV results revealedthat the keels of all boxfishes generate strong longitudinalvortices that vary in strength and position with angle of attack.In areas where attached, concentrated vorticity was detectedusing DPIV, low pressure also was detected at the carapace surfaceusing pressure sensors. Predictions of the effects of both observedvortical flow patterns and pressure distributions on the carapacewere consistent with actual forces and moments measured usingthe force balance. Most notably, the three complementary experimentalapproaches consistently indicate that the ventral keels of allboxfishes, and in some species the dorsal keels as well, effectivelygenerate self-correcting forces for pitching motions—acharacteristic that is advantageous for the highly variablevelocity fields in which these fishes reside.     

Quantitative flow visualization: toward a comprehensive flow diagnostic tool

Quantitative flow visualization has many roots and has takenseveral approaches. The advent of digital image processing hasmade it possible to practically extract useful information fromevery kind of flow image. In a direct approach, the image intensityor color (wavelength or frequency) can be used as an indicationof concentration, density and temperature fields or gradientsof these scalar fields in the flow (Merzkirch, 1987). For whole-fieldvelocity measurement, the method of choice by experimental fluidmechanicians has been the technique of Particle Image Velocimetry(DPIV). This paper presents a novel approach to extend the DPIVtechnique from a planar method to a full three-dimensional volumemapping technique useful in both engineering and biologicalapplications.