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At least 865 records · Page 48Linked to original sources
PubMed2005

Characterization of a novel class II bHLH transcription factor from the black widow spider, Latrodectus hesperus, with silk-gland restricted patterns of expression.

Members of the basic helix-loop-helix (bHLH) family are required for a number of different developmental pathways, including lymphopoiesis, myogenesis, neurogenesis, and sex determination. Screening a cDNA library prepared from silk-producing glands of the black widow spider, we have identified a new bHLH transcription factor named SGSF. Within the bHLH region, SGSF showed considerable conservation with other HLH proteins, including Drosophila melanogaster achaete and scute, as well as three HLH proteins identified by gene prediction programs. The expression pattern of SGSF was restricted to a subset of silk-producing glands, which include the tubuliform and major ampullate glands. SGSF was capable of binding an E-box element as a heterodimer with the E protein, E47, but was unable to bind this motif as a homodimer. SGSF was demonstrated to be a nuclear transcription factor capable of attenuating the transactivation of E47 homodimers in mammalian cells. SGSF represents the first example of a silk gland-restricted bHLH protein, and its expression pattern suggests that SGSF plays a role in regulating differentiation of cells in the spider that control silk gland formation or egg case silk gene expression.

Amino Acid Sequence↗
PubMed1984

Spider bite hemolytic anemia: positive Coombs' test, erythrophagocytosis, and leukoerythroblastic smear.

The full hematologic profile of spider bite hemolytic anemia has not been documented in the literature. The two patients had brisk intravascular hemolysis with direct Coombs' tests positive for complement and with peripheral blood smears showing spherocytosis, erythrophagocytosis, and leukoerythroblastosis. The author's experience, along with that in the literature reviewed herein, suggests that the hemolytic anemia that can follow the bite of the brown recluse spider could be confused with autoimmune hemolytic anemia.

Adult↗
PubMed2005

Unique molecular architecture of egg case silk protein in a spider, Nephila clavata.

We describe a unique silk protein secreted from the cylindrical silk glands of the spider Nephila clavata. This silk is primarily composed of three proteins, whose transcripts of approximately 16.0, 14.5 and 13.0 kb are homologous to one another in two termini and repetitive units, as determined on Northern blotting. Its overall organization shows that it is similar to other characterized silk proteins, including in the mainly central repetitive region as well as the non-repetitive N-terminal (166 residues) and C-terminal (176 residues) parts. However, up to 90% of the protein consists of highly ordered repetitive structures that are not found in other silks. The repetitive region mainly consists of several types of complexes and remarkably conserved polypeptide repeats. The assembled repeat units (A1B1) contain a high proportion of Ala (30.41%), Ser (25.15%), and residues with hydrophobic side chains (22.22% for Gly, Leu, Ile, Val and Phe combined). The presence of Ser-rich and GVGAGASA motifs suggests the formation of a beta-sheet. The repetitive region is characterized by alternating arrays of hydrophobic and hydrophilic blocks. The results suggested that this egg case silk is an exceptional protein when compared with previously investigated spider silks.

Amino Acid Motifs↗
PubMedDate not supplied

Genome sizes of spiders.

Spiders represent a diverse and familiar group of animals, but to date no information has been made available regarding their genome sizes. Arachnids in general have been almost entirely overlooked, and are currently represented by a single tick in the animal genome size data set. The present study provides new genome size estimates for 115 species of spiders from 19 families (all from the infraorder Araneomorphae), thereby adding considerably to the coverage of these arthropods. No clear-cut patterns of variation were detectable even with this relatively large data set, but some interesting avenues for future research have been illuminated by this preliminary survey.

Animals↗
PubMed1988

The brown recluse spider bite.

A review of the literature confirms that the brown recluse spider bite is a common and sometimes serious clinical entity. Local and systemic manifestations are extremely variable, thus complicating management of the bite. Pathophysiological studies in laboratory animals yield conflicting results and therapeutic recommendations because of technical and species-specific differences. Standard therapies include aggressive, early debridement as well as systemic and intralesional corticosteroids; however, well-controlled clinical studies to establish their efficacy have not been performed. Variable and unpredictable patient responses to the spider bite necessitate a conservative yet vigilant position in managing these bites.

Humans↗
PubMed1985

Brown recluse spider bites. A comparison of early surgical excision versus dapsone and delayed surgical excision.

In a prospective study, 31 patients with brown recluse spider bites were treated by either immediate surgical excision or with the leukocyte inhibitor, dapsone, followed by delayed surgical excision. Patients were matched for age, gender, and lesion size and were excluded if the typical history and physical findings were not present. In patients treated with immediate surgical excision (N = 14), delayed wound healing (N = 5) and objectional scarring (N = 7) were common complications. However, pretreatment treatment with dapsone reduced the incidence of wound complications (N = 1) and objectional scarring (N = 1) (p less than 0.05), while reducing the need for surgical excision (N = 1). There were no severe drug reactions due to dapsone, although one patient had persistent G.I. upset. Pretreatment with dapsone not only reduced surgical complications but also improved the outcome of patients bitten by the brown recluse spider.

Adolescent↗
PubMed1993

Transmitter release and presynaptic Ca2+ currents blocked by the spider toxin omega-Aga-IVA.

Mammalian neuromuscular transmission is resistant to L and N type calcium channel blockers but very sensitive to a low molecular weight funnel web spider venom toxin, FTX, which selectively blocks P type calcium channels. To further characterize the calcium channels involved in neuromuscular transmission we studied the effect of omega Agatoxin (omega-Aga-IVA) a polypeptide P type channel blocker from the same spider venom. We show that omega-Aga-IVA is a potent and irreversible inhibitor of the presynaptic Ca2+ currents and of acetylcholine release induced by electrical stimulation or by K+ depolarization. This provides further evidences that transmitter release at the mammalian neuromuscular junction is mediated by P type Ca2+ channels.

Acetylcholine↗
PubMed1996

Treatment of snake, insect, scorpion, and spider bites in the pediatric emergency department.

Most people seem to have a visceral fear of snakes, spiders, scorpions, and insects out of proportion to the actual danger they pose. The vast majority of bites and stings cause little more than local pain and never require medical attention. Nevertheless, physicians who work in the emergency department must be prepared to treat the few patients who present with anaphylactic reactions to Hymenoptera stings, as well as to recognize and treat those rare individuals who receive severe envenomation from poisonous snakes, spiders, or scorpions.

Anaphylaxis↗
PubMed2000

Precise, highly female-biased sex ratios in a social spider.

It has been recognized for some time that the risk of producing maleless clutches should select for a lower than binomial variance in the sex ratio of organisms with female-biased sex ratios, small clutches and breeding groups containing the clutch of a single female. However, to date, precise sex ratios have only been reported for organisms with haplodiploid sex determination, a system which allows direct control of the sex of individual offspring. In contrast, under heterogametic sex determination chance is expected to play a crucial role in determining the sex composition of any one family, in particular when males are the heterogametic sex. Here, we present evidence of precise or underdispersed primary sex ratios in the Neotropical social spider Anelosimus domingo Levi. We show that this diplodiploid species with male heterogamety has not only beaten the odds of meiosis by producing mostly daughters, but has also attained relative precision in the proportion of sons and daughters produced in any one clutch. The latter finding suggests the existence of mechanisms that allow sorting of the two types of sperm in this spider species.

Animals↗
PubMed2001

The effect of spinning conditions on the mechanics of a spider's dragline silk.

We studied the mechanical properties of dragline threads of the edible golden silk spider Nephila edulis that are produced under spinning speeds ranging from 0.1 to 400 mm s(-1) and temperatures ranging from 5 to 40 degrees C. These conditions affected the silk in all of the mechanical traits we tested (strain at breaking, breaking energy, initial Young's modulus and point of yielding). We argue that both trade-offs (between mechanical properties) and constraints (in the manufacturing process) have a large role in defining spider silk fibres.

Animals↗
PubMed2003

Low propensity for aerial dispersal in specialist spiders from fragmented landscapes.

Aerial dispersal by ballooning is a passive flight, by which wind drag generates an upward lift on a silk thread. It is likely to reflect an aerial lottery, in which the absence of flight direction control is a serious cost for long-distance dispersal in a fragmented landscape. For species occurring in one patchily distributed habitat type, dispersal should evolve in a different way from morphological traits, directly linked to active dispersal. Therefore, we expect that if the risk of landing in an unsuitable habitat is lower than the probability of reaching a suitable habitat, selection should benefit a well-developed ballooning behaviour. We investigated interspecific variation in the ballooning-initiating tiptoe behaviour as it is linked to spider dispersal performance. Our results indeed indicate that ballooning performance is negatively related to habitat specialization in spiders from patchy grey dunes, so habitat specialists are characterized by poorly developed dispersal behaviour. These findings are concordant with recent insights that dispersal is selected as risk spreading in generalists, while it is selected against in specialist species.

Animals↗
PubMed1993

Moult-related changes in ampullate silk gland morphology and usage in the araneid spider Araneus cavaticus.

Major ampullate (MaA) and minor ampullate (MiA) silk glands of juvenile Araneus cavaticus (third to penultimate instars) were examined by dissection at various times relative to ecdysis. Several days before ecdysis the larger pairs of MaA and MiA glands become non-functional and remain so until ecdysis. Nevertheless, proecdysial spiders are able to draw ampullate fibres due to the presence of smaller pairs of MaA and MiA glands which are functional at this time. Indeed, it appears that these smaller ampullate glands are intended for use only during proecdysis. Thus, larger MaA and MiA glands and smaller MaA and MiA glands are typically not used concurrently (a brief transitional period is an exception). The smaller ampullate glands functioning in one juvenile stadium regress in the following stadium and become (what have previously been referred to as) accessory MaA and MiA glands. These nonfunctional accessory ampullate glands do not re-develop into functional smaller ampullate glands until the following stadium. Thus, a given pair of smaller MaA or MiA glands is only functional in every other juvenile stadium. However, because there are two sets of smaller/accessory MaA and MiA glands which function alternately, the spider is able to produce ampullate fibres during the proecdysial portion of each stadium. A new terminology for the larger, smaller and accessory ampullate glands is proposed which emphasizes the kinship between the two sets of smaller/accessory ampullate glands.

Animals↗
PubMed2005

Hierarchical chain model of spider capture silk elasticity.

Spider capture silk is a biomaterial with both high strength and high elasticity, but the structural design principle underlying these remarkable properties is still unknown. It was revealed recently by atomic force microscopy that an exponential force-extension relationship holds both for capture silk mesostructures and for intact capture silk fibers [N. Becker et al., Nat. Mater. 2, 278 (2003)]]. In this Letter a simple hierarchical chain model was proposed to understand and reproduce this striking observation. In the hierarchical chain model, a polymer is composed of many structural motifs which organize into structural modules and supramodules in a hierarchical manner. Each module in this hierarchy has its own characteristic force. The repetitive patterns in the amino-acid sequence of the major flagelliform protein of spider capture silk is in support of this model.

Animals↗
PubMed2003

Do female spiders select heavier males for the genes for behavioral aggressiveness they offer their offspring?

We explore the hypothesis that females choose to mate with heavier males for the genes for behavioral aggressiveness they offer their offspring in the desert spider, Agelenopsis aperta. Behavioral aggressiveness is important to competition for limited resources in the field and is thus correlated with the mass spiders achieve. We established four crosses based on the body mass relationships of parents subjected to selection in their natural environment (female mass/male mass: HI/HI, HI/LO, LO/HI, and LO/LO) and reared the F1 offspring in a noncompetitive laboratory environment. Offspring size and mass at maturity were measured, life history parameters recorded, and behavioral aggressiveness scored in a series of tests. Significant familial effects were detected in all of these measures, but pertinent cross effects were observed only in the assays measuring behavioral aggressiveness. The results were summarized in terms of the fitness costs to HI females of mating with LO males (fewer female offspring of the more aggressive phenotypes) and the benefits to LO females of mating with HI males (fewer fearful offspring of both sexes).

Aggression↗
PubMed2003

Resistance of spiders to Cretaceous-Tertiary extinction events.

Throughout Earth history a small number of global catastrophic events leading to biotic crises have caused mass extinctions. Here, using a technique that combines taxonomic and numerical data, we consider the effects of the Cenomanian-Turonian and Cretaceous-Tertiary mass extinctions on the terrestrial spider fauna in the light of new fossil data. We provide the first evidence that spiders suffered no decline at the family level during these mass extinction events. On the contrary, we show that they increased in relative numbers through the Cretaceous and beyond the Cretaceous-Tertiary extinction event.

Animals↗
PubMed2005

Inhibitory glutamate receptors in spider peripheral mechanosensory neurons.

Most mechanosensory neurons are inhibited by GABAergic efferent neurons. This inhibition is often presynaptic and mediated by ionotropic GABA receptors at the axon terminals. GABA receptor activation opens Cl- channels, leading to membrane depolarization and an increase in membrane conductance. In many invertebrate preparations, efferent neurons that innervate mechanosensory afferents contain glutamate in addition to GABA, suggesting that the sensory neurons are also modulated by glutamate. However, the effects of glutamate on these neurons are not well understood. Peripheral parts of the spider (Cupiennius salei) mechanosensory neurons are surrounded by efferent fibers immunoreactive to antibodies against GABA and glutamate. GABA and its analogue muscimol were shown to effectively inhibit spider mechanosensory neurons innervating lyriform slit sensilla VS-3 that detects cuticular strains in the leg. Here, we show that glutamate also inhibits the VS-3 neurons, but its effects are different from those of GABA or muscimol, suggesting that it acts on a different group of receptors. GABA and muscimol always depolarized these neurons and the inhibitory effect was strongly correlated with the amount of depolarization. In contrast, glutamate inhibited the VS-3 neurons even when it did not depolarize them. In addition, while glutamate inhibited both the axonal action potentials elicited with electrical stimulation and dendritic action potentials produced by mechanical stimulation, muscimol only inhibited the axonal action potentials. Therefore, the inhibitory glutamate receptors in the VS-3 neurons are distinct from and differently distributed than the GABA receptors, providing a subtle control of the neurons' sensitivity in varying behavioural situations.

Animals↗
PubMed2000

The function significance of silk decorations of orb-web spiders: a critical review of the empirical evidence.

A number of taxonomically diverse species of araneoid spiders adorn their orb-webs with conspicuous silk structures, called decorations or stabilimenta. The function of these decorations remains controversial and several explanations have been suggested. These include: (1) stabilising and strengthening the web; (2) hiding and concealing the spider from predators; (3) preventing web damage by larger animals, such as birds; (4) increasing foraging success; or (5) providing a sunshield. Additionally, they may have no specific function and are a consequence of stress or silk regulation. This review evaluates the strength of these explanations based on the evidence. The foraging function has received most supporting evidence, derived from both correlative field studies and experimental manipulations. This contrasts with the evidence provided for other functional explanations, which have not been tested as extensively. A phylogenetic analysis of the different decoration patterns suggests that the different types of decorations are as evolutionary labile as the decorations themselves: the analysis shows little homology and numerous convergences and independent gains. Therefore, it is possible that different types of decorations have different functions, and this can only be resolved by improved species phylogenies, and a combination of experimental and ultimately comparative analyses.

Animals↗
PubMed2007

Loxosceles spider venom induces the release of thrombomodulin and endothelial protein C receptor: implications for the pathogenesis of intravascular coagulation as observed in loxoscelism.

BACKGROUND: The venom of the spider Loxosceles can cause both local and systemic effects including disseminated intravascular coagulation. AIM: The aim of this study was to investigate the effects of the venom of Loxosceles intermedia (L. intermedia) and the purified Sphingomyelinase D (SMaseD) toxin upon the Protein C (PC) natural anticoagulant pathway. RESULTS: Both the venom and e purified SMaseD reduced the cell surface expression of thrombomodulin (TM) and Endothelial PC Receptor on endothelial cells in culture. The reduction of cell surface expression was caused by cleavage from the cell surface mediated by activation of an endogenous metalloproteinase. Reduction of TM and Endothelial PC Receptor on the surface of these cells resulted in an impaired ability of the cells to assist in the thrombin-induced activation of PC. CONCLUSION: This novel observation gives further insight into the mechanisms of the pathology induced by venom from Loxosceles spiders and may aid the development of a suitable therapy.

Animals↗