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PubMed2006

Surface extraction and thickness measurement of the articular cartilage from MR images using directional gradient vector flow snakes.

The accuracy of the surface extraction of magnetic resonance images of highly congruent joints with thin articular cartilage layers has a significant effect on the percentage errors and reproducibility of quantitative measurements (e.g., thickness and volume) of the articular cartilage. Traditional techniques such as gradient-based edge detection are not suitable for the extraction of these surfaces. This paper studies the extraction of articular cartilage surfaces using snakes, and a gradient vector flow (GVF)-based external force is proposed for this application. In order to make the GVF snake more stable and converge to the correct surfaces, directional gradient is used to produce the gradient vector flow. Experimental results show that the directional GVF snake is more robust than the traditional GVF snake for this application. Based on the newly developed snake model, an articular cartilage surface extraction algorithm is developed. Thickness is computed based on the surfaces extracted using the proposed algorithm. In order to make the thickness measurement more reproducible, a new thickness computation approach, which is called T-norm, is introduced. Experimental results show that the thickness measurement obtained by the new thickness computation approach has better reproducibility than that obtained by the existing thickness computation approaches.

Algorithms↗
PubMed2006

A faster converging snake algorithm to locate object boundaries.

A different contour search algorithm is presented in this paper that provides a faster convergence to the object contours than both the greedy snake algorithm (GSA) and the fast greedy snake (FGSA) algorithm. This new algorithm performs the search in an alternate skipping way between the even and odd nodes (snaxels) of a snake with different step sizes such that the snake moves to a likely local minimum in a twisting way. The alternative step sizes are adjusted so that the snake is less likely to be trapped at a pseudo-local minimum. The iteration process is based on a coarse-to-fine approach to improve the convergence. The proposed algorithm is compared with the FGSA algorithm that employs two alternating search patterns without altering the search step size. The algorithm is also applied in conjunction with the subband decomposition to extract face profiles in a hierarchical way.

Algorithms↗
PubMed1997

Bov-B long interspersed repeated DNA (LINE) sequences are present in Vipera ammodytes phospholipase A2 genes and in genomes of Viperidae snakes.

Ammodytin L is a myotoxic Ser49 phospholipase A2 (PLA2) homologue, which is tissue-specifically expressed in the venom glands of Vipera ammodytes. The complete DNA sequence of the gene and its 5' and 3' flanking regions has been determined. The gene consists of five exons separated by four introns. Comparative analysis of the ammodytin L and ammodytoxin C genes shows that all intron and flanking sequences are considerably more conserved (93-97%) than the mature protein-coding exons. The pattern of nucleotide substitutions in protein-coding exons is not random but occurs preferentially on the first and the second positions of codons, which suggests positive Darwinian evolution for a new function. An Ruminantia specific ART-2 retroposon, recently recognised as a 5'-truncated Bov-B long interspersed repeated DNA (LINE) sequence, was identified in the fourth intron of both genes. This result suggests that ammodytin L and ammodytoxin C genes are derived by duplication of a common ancestral gene. The phylogenetic distribution of Bov-B LINE among vertebrate classes shows that, besides the Ruminantia, it is limited to Viperidae snakes (Vipera ammodytes, Vipera palaestinae, Echis coloratus, Bothrops alternatus, Trimeresurus flavoviridis and Trimeresurus gramineus). The copy number of the 3' end of Bov-B LINE in the Vipera ammodytes genome is between 62,000 and 75,000. The absence of Bov-B LINE at orthologous positions in other snake PLA2 genes indicates that its retrotransposition in the V. ammodytes PLA2 gene locus has occurred quite recently, about 5 My ago. The amplification of Bov-B LINEs in snakes may have occurred before the divergence of the Viperinae and Crotalinae subfamilies. Due to its wide distribution in Viperidae snakes it may be a valuable phylogenetic marker. The neighbor-joining phylogenetic tree shows two clusters of truncated Bov-B LINE, a Bovidae and a snake cluster, indicating an early horizontal transfer of this transposable element.

Animals↗
PubMed1985

An investigation, in vitro, of the actions of three Western Australian snakes on the blood coagulation of the dog, cat, horse and wallaby.

Venoms of the tiger snake and brown snake were procoagulant, in vitro, when tested with cat, dog, horse and wallaby plasma. In the absence of calcium and phospholipid the coagulant activity of tiger snake venom was minimal. In contrast, brown snake venom alone had marked procoagulant activity. This activity, however, was enhanced by the presence of calcium and phospholipid. Death adder venom exerted an anticoagulant effect. Apparent species' differences in susceptibility to the coagulant venoms were noted. However, the probable explanation of these differences was attributed to variation in the control values of the special studies rather than to a difference in the postulated actions of the venoms on prothrombin. A possible role for clotting studies in suspected snake bite in veterinary practice is suggested.

Animals↗
PubMed2003

Dynamical properties of the slithering-snake algorithm: a numerical test of the activated-reptation hypothesis.

Correlations in the motion of reptating polymers in a melt are investigated by means of Monte Carlo simulations of the three-dimensional slithering-snake version of the bond-fluctuation model. Surprisingly, the slithering-snake dynamics becomes inconsistent with classical reptation predictions at high chain overlap (created either by chain length N or by the volume fraction phi of occupied lattice sites), where the relaxation times increase much faster than expected. This is due to the anomalous curvilinear diffusion in a finite time window whose upper bound tau+(N) is set by the density of chain ends phi/N. Density fluctuations created by passing chain ends allow a reference polymer to break out of the local cage of immobile obstacles created by neighboring chains. The dynamics of dense solutions of "snakes" at t<<tau+ is identical to that of a benchmark system where all chains but one are frozen. We demonstrate that the subdiffusive dynamical regime is caused by the slow creeping of a chain out of its correlation hole. Our results are in good qualitative agreement with the activated-reptation scheme proposed recently by Semenov and Rubinstein (Eur. Phys. J. B, 1 (1998) 87). Additionally, we briefly comment on the relevance of local relaxation pathways within a slithering-snake scheme. Our preliminary results suggest that a judicious choice of the ratio of local to slithering-snake moves is crucial to equilibrate a melt of long chains efficiently.

Journal Article↗
PubMed1995

Intracellular pH in snake renal proximal tubules.

Intracellular pH (pHi) was studied in isolated proximal renal tubules of garter snakes (Thamnophis spp.) with oil-filled lumens under control conditions [N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered medium with pH 7.4 at 25 degrees C] and in response to NH4Cl pulse. pHi was measured with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF). Control resting pHi (7.1) and acidification in response to NH4Cl pulse (minimum pHi, 6.6) were essentially the same in snake tubules with oil-filled lumens or perfused lumens and in rabbit S2 proximal tubules with oil-filled lumens. Rate of recovery of pHi (dpHi/dt) from acid to resting level in snake tubules (2.5 x 10(-3) pH U/s was about one-third of that in rabbit tubules. Resting pHi and dpHi/dt from acid to resting level were Na+ dependent in the distal portion but not the proximal portion of snake proximal tubules. However, dpHi/dt was not influenced by amiloride or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid in snake proximal tubules, suggesting that the effect of Na+ on dpHi/dt and resting pHi may involve membrane potential. This study also indicates that oil-filled lumens do not interfere with measurements of resting pHi and do permit evaluation of pHi regulation at the basolateral membrane without complications from transport at the luminal membrane.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1997

Control of venom production and secretion by sympathetic outflow in the snake Bothrops jararaca.

Many studies have examined the morphological and biochemical changes in the secretory epithelium of snake venom glands after a bite or milking. However, the mechanisms of venom production and secretion are not yet well understood. The present study was undertaken to evaluate the role of the sympathetic nervous system in the control of venom production and secretion. Venom glands were obtained from Bothrops jararaca (Viperidae) snakes, either unmilked previously or milked 4, 7 or 15 days before they were killed. Levels of tyrosine-hydroxylase-like immunoreactivity were higher in venom glands collected 4 days after milking, coinciding with the maximal synthetic activity of the secretory cells. The only catecholamine detected by high-performance liquid chromatography was noradrenaline, indicating the presence of noradrenergic fibres in these glands. In reserpine-treated milked snakes, no venom could be collected, and electron microscopic analysis showed narrow rough endoplasmic reticulum cisternae, instead of wide cisternae, and less well-developed Golgi apparatus compared with milked untreated snakes, indicating impairment of protein synthesis and secretion. The administration of isoprenaline or phenylephrine (beta- and alpha-adrenoceptor agonists, respectively) to reserpine-treated milked snakes promoted the widening of the rough endoplasmic reticulum and restored venom production, but only phenylephrine restored the development of the Golgi apparatus and the formation of many secretory vesicles. These results provide the first evidence that the sympathetic nervous system plays an important role in venom production and secretion in the venom glands of Bothrops jararaca. Understanding the importance of noradrenergic stimulation in venom production may provide new insights for research into the treatment of snakebites.

Animals↗
PubMed1998

Kinematics, muscular activity and propulsion in gopher snakes

Previous studies have addressed the physical principles and muscular activity patterns underlying terrestrial lateral undulation in snakes, but not the mechanism by which muscular activity produces curvature and propulsion. In this study, we used synchronized electromyography and videography to examine the muscular basis and propulsive mechanism of terrestrial lateral undulation in gopher snakes Pituophis melanoleucus affinis. Specifically, we used patch electrodes to record from the semispinalis, longissimus dorsi and iliocostalis muscles in snakes pushing against one or more pegs. Axial bends propagate posteriorly along the body and contact the pegs at or immediately posterior to an inflection of curvature, which then reverses anterior to the peg. The vertebral column bends broadly around a peg, whereas the body wall bends sharply and asymmetrically around the anterior surface of the peg. The epaxial muscles are always active contralateral to the point of contact with a peg; they are activated slightly before or at the point of maximal convexity and deactivated variably between the inflection point and the point of maximal concavity. This pattern is consistent with muscular shortening and the production of axial bends, although variability in the pattern indicates that other muscles may affect the mechanics of the epaxial muscles. The kinematic and motor patterns in snakes crawling against experimentally increased drag indicated that forces are produced largely by muscles that are active in the axial bend around each peg, rather than by distant muscles from which the forces might be transmitted by connective tissues. At each point of force exertion, the propulsive mechanism of terrestrial lateral undulation may be modeled as a type of cam-follower, in which continuous bending of the trunk around the peg produces translation of the snake.

Journal Article↗
PubMed2000

The mechanics of swallowing and the muscular control of diverse behaviours in gopher snakes.

Snakes are excellent subjects for studying functional versatility and potential constraints because their movements are constrained to vertebral bending and twisting. In many snakes, swallowing is a kind of inside-out locomotion. During swallowing, vertebral bends push food from the jaws along a substantial length of the body to the stomach. In gopher snakes (Pituophis melanoleucus) and king snakes (Lampropeltis getula), swallowing often begins with lateral bending of the head and neck as the jaws advance unilaterally over the prey. Axial movement then shifts to accordion-like, concertina bending as the prey enters the oesophagus. Once the prey is completely engulfed, concertina bending shifts to undulatory bending that pushes the prey to the stomach. The shift from concertina to undulatory bending reflects a shift from pulling the prey into the throat (or advancing the mouth over the prey) to pushing it along the oesophagus towards the stomach. Undulatory kinematics and muscular activity patterns are similar in swallowing and undulatory locomotion. However, the distinct mechanical demands of internal versus external force exertion result in different duty factors of muscle activity. Feeding and locomotor movements are thus integral functions of the snake axial system.

Animals↗
PubMed1991

[Effect of cepharanthin on the lethality and cardiovascular disorder by Mamushi, Agkistrodon halys blomhoffi, snake venom].

Effects of Cephranthin on the lethality to mice and the cardiovascular disorder in rat induced by Mamushi (Agkistrodon halys blomhoffi) snake venom were studied. The LD50 of Mamushi snake venom was 1.22 mg/kg in mice by i.p. administration. Cepharanthin activated slightly the lethal activity when it was administered just after injection of the venom. However, this drug was effective against the venom at 4 to 5 times the lethal dose, if it was administered at the optimal interval. Mamushi snake venom and Cepharanthin showed a lethality and dose relationship that were clearly prolonged by Cepharanthin. In rat, Mamushi snake venom administered intraperitoneally produced an irreversible decrease of blood pressure accompanied by capillary hemorrhage. Moreover, it suppressed the heart rate. On the electrocardiogram, prolongation of ventricular contraction, extension of the relative refractory period and reduction of diastole were induced by the venom. These observations show that the venom suppresses cardiac functions inotropically and chronotropically. Cepharanthin shortened the refractory period and prolonged the diastole, indicating that it activated cardiac function. It was able to produce recovery from several cardiac disorders induced by Mamushi snake venom, for example, increase of blood pressure with inhibition of capillary hemorrage, release of heart rate suppression, partial recovery of the amplitudes of P and R waves, and shortening of extensive relative refractory period. These cardiac recoveries by Cepharanthin will be reflected in the suppression of lethality.

Alkaloids↗
PubMed1998

Amelogenin protein in tooth germs of the snake Elaphe quadrivirgata, immunohistochemistry, cloning and cDNA sequence.

In the snake, Elaphe quadrivirgata, the occurrence of amelogenin was immunohistochemically demonstrated in the enamel of developing tooth germs. Teeth of the snake are covered with a thin true enamel layer about 1-2 microns in thickness. Light and electron microscopic immunohistochemistry indicated an intense amelogenin immunoreactivity occurring in the enamel layer during the secretory stage of tooth development. Cloning and cDNA sequence of snake amelogenin was performed by RT-PCR. The amino acid sequence of the snake amelogenin cDNA--in its portion corresponding to the area from exon 5 to exon 7 of human X189 amelogenin gene--showed 45% homology with humans. Regions of both the N-terminus and C-terminus were well conserved. Furthermore, the positions of prolin in the amino acid alignment of the snake amelogenin corresponded well with those of human amelogenin. It is suggested that prolin is an essential constituent of amelogenin and therefore its positions in the molecule have been conserved after the evolutionary divergence of reptiles and mammals. This study using reptiles is the first detection of specific amelogenin immunoreactivity by high resolutional immunoelectron microscopy and the first cloning of amelogenin cDNA in a non-mammalian animal.

Amelogenin↗
PubMed1999

Identification of relative protein bands in polyacrylamide gel electrophoresis (PAGE) using a multi-resolution snake algorithm.

In polyacrylamide gel electrophoresis (PAGE) image analysis, it is important to determine the percentage of the protein of interest of a protein mixture. This study presents reliable computer software to determine this percentage. The region of interest containing the protein band is detected using the snake algorithm. The iterative snake algorithm is implemented in a multi-resolutional framework. The snake is initialized on a low-resolution image. Then, the final position of the snake at the low resolution is used as the initial position in the higher-resolution image. Finally, the area of the protein is estimated as the area enclosed by the final position of the snake.

Algorithms↗
PubMed2002

Effects of chronic dietary exposure to trace elements on banded water snakes (Nerodia fasciata).

Little currently is known about the accumulation or effects of contaminants on reptiles. To date, most studies examining reptile exposure to trace elements report tissue burdens of field-captured animals, but seldom provide insight into the dose, duration, or mode of exposure involved. For two years, we fed juvenile banded water snakes (Nerodia fasciata) prey items collected from a coal ash-contaminated site that contained elevated levels of As, Cd, Cu, Se, Sr, and V. With the exception of Cu, snakes accumulated significant concentrations of elements, usually in a dose-dependent manner. Accumulation varied significantly among liver, kidney, and gonads, and in most cases between sexes. Selenium accumulation was most notable, greatly exceeding established toxicity thresholds for other vertebrates. Despite the high concentrations of pollutants accumulated, snakes exposed to the contaminated diet survived through the study and exhibited normal food consumption, growth, condition factor, overwinter survival and mass loss, metabolic rate, and gonadosomatic index. The results of this study confirm that diet can be a significant route of exposure to trace elements in snakes and indicate that further studies on snakes are warranted to better understand their responses to contaminants.

Administration, Oral↗
PubMed2004

The male red-sided garter snake (Thamnophis sirtalis parietalis): reproductive pattern and behavior.

Among the small group of species (e.g., some temperate zone turtles, snakes, and bats) that exhibit a dissociated reproductive pattern, the red-sided garter snake (Thamnophis sirtalis parietalis) is probably the most well studied. For these species, courtship and mating occur immediately upon emergence from winter dormancy; the gonads remain essentially inactive. Male red-sided garter snakes are a particularly informative animal model for examining the role of neuroendocrine factors associated with reproductive physiology and behavior because unlike species that exhibit an associated reproductive pattern, in which sex steroids initiate and control sexual behavior, reproductive behavior in the male garter snake appears to be independent of circulating sex hormone control. In fact, the only factor associated with the initiation of courtship behavior and mating in the male garter snake is an extended period of low temperature dormancy followed by exposure to warm temperatures. Yet the presence of sex steroid-concentrating neurons within the pathways regulating courtship and mating suggests that sex hormones may be involved in the activation of sexual behavior. Although circulating androgens are elevated upon emergence from hibernation, the initiation of courtship behavior and mating appears to be independent of direct androgen control. Thus steroid hormones may have indirect effects on mating behavior in animals that display "dissociated" reproductive behaviors.

Animal Husbandry↗
PubMed2005

[Correlation of antitumor effect of recombinant sea snake basic phospholipase A2 to its enzymatic activity].

BACKGROUND & OBJECTIVE: Snake venom phospolipase A2 (PLA(2)), a large family of homologous (14 ku) soluble proteins, exerts diverse pharmacologic activities as well as enzymatic activities. So far, the structure and function of terrestrial snake PLA(2), especially the relationship of its enzymatic and pharmacologic activities have been studied extensively, but the investigation of sea snake PLA(2) are limited. This study was to investigate the in vitro and in vivo antitumor effects of recombinant sea snake basic PLA(2) (rSSBPLA(2)) and its mutants rN48 and rK4 from sea snake Lapemis hardwickii venom, and to explore the influence of 2 residues related with the enzymatic activity on the antitumor effects. METHODS: Site-directed mutagenesis of the 2 conserved residues related with enzymatic activity (His48 mutated to Asn and Asp49 mutated to Lys) was performed. The inhibitory effects of rSSBPLA(2), rN48 and rK49 on proliferation of human myeloid leukemia cell line HL-60, human neuroblastoma cell line SK-N-SH, human gastric cancer cell line MGC-803, and human liver cancer cell line HepG2 were assessed by MTT assay. Their antitumor effects on sarcoma cell line S180 xenograft and EAC ascites cancer model in mice were detected. RESULTS: The relative enzymatic activities of rN48 and rK49 were 0 and 5% of that of rSSBPLA(2). The 50% inhibitory concentration (IC(50)) of rSSBPLA(2) for HL60, SK-N-SH, and MGC-803 cells were (45.28+/-0.09) microg/ml, (57.07+/-0.12) microg/ml, and (69.34+/-0.35) microg/ml, respectively, but it had no inhibitory effect on proliferation of HepG2 cells. rSSBPLA(2) obviously inhibited growth of S180 xenograft in miceû the inhibitory rates were 50.8%, 43.2%, 38.2%, and 55.5%, respectively, under the dose of 2 mg/kg (qd x 10), 2 mg/kg (q2d x 5), 4 mg/kg (qd x 1) and 4 mg/kg (q5d x 2). The inhibitory rate of EAC model was 33.5% under the dose of 4 mg/kg (q5d x 2). The inhibitory rates were significantly higher in test groups than in control groups (P<0.01). rN48 and rK49 had no inhibitory effect on proliferation of the 4 tumor cell lines and on growth of the xenograft tumors. CONCLUSION: The antitumor effect of rSSBPLA(2) may be closely related with its enzymatic activity.

Animals↗
PubMed1996

Enzymatic activities of some snake venoms from families Elapidae and Viperidae.

Alkaline phosphomonoesterase, phosphodiesterase, L-amino acid oxidase, hyaluronidase, 5'-nucleotidase, arginine ester hydrolase, phospholipase A2 and proteinase activities were determined in eight snake venoms, including three from sea snake, of families Elapidae and Viperidae from Pakistan. The species includes three sea snakes Hydrophis cyanocinctus, Enhydrina schsitosa, Microcephalophis gracilis gracilis and two land snakes Naja naja naja, Bungarus caeruleus of family Elapidae while three land snakes Vipera russelli russelli, Echis carinatus and Eristocophis macmahoni of family Viperidae. The venoms of family Elapidae are characterized by low levels to traces of proteinase, L-amino acid oxidase and arginine ester hydrolase activities with the exception of Naja naja naja and a moderate to high levels of phospholipase A2 activities. The venoms of family Viperidae, on the other hand, are characterized by the presence of moderate to high levels of 5'-nucleotidase, proteinase, phosphodiesterase and phosphomonoesterase activities.

Journal Article↗
PubMed1994

Experimental infection of elaphid snakes with Cryptosporidium serpentis (Apicomplexa: Cryptosporidiidae).

The shedding pattern of fecal Cryptosporidium serpentis oocysts, histopathologic changes in the gastric region, and the effect of spiramycin treatment were investigated in 6 experimentally infected, captive black rat (Elaphe obsoleta obsoleta), 4 yellow rat (Elaphe obsoleta quadrivittata), and 2 corn snakes (Elaphe guttata guttata). Feces were monitored for up to 2 years postinfection (PI). No significant (P > 0.07) differences were observed between expected and observed numbers of PI oocyst-positive feces. Two of 5 control animals acquired natural infections of C. serpentis over the period of study. No morphological differences were observed between oocysts from experimental and natural infections. Clinical signs included postprandial regurgitation in 5 of 13 (38%) snakes, not coinciding with the shedding of fecal oocysts. Midbody swelling and self-cure were not observed. Spiramycin treatment of 4 of 12 experimentally infected animals resulted in negative fecal examinations in 2 snakes and reduced the percentage of oocyst-positive feces in 2 other snakes from 75.5% to 24.5% and from 83.9% to 33.6%. Biopsies and necropsies revealed stages of Cryptosporidium in the gastric mucosa of all spiramycin-treated animals. The gastric mucosa was thickened and edematous, with focal necrosis, mucosal petechiae, and brush hemorrhages. Fibroplasia of lamina propria associated with chronic mucosal inflammation were common. Examination of direct fecal smears was found not to be a reliable technique for diagnosis of cryptosporidial infections in snakes.

Analysis of Variance↗
PubMed1993

Induction of apoptosis by hemorrhagic snake venom in vascular endothelial cells.

Vascular degeneration appears to play crucial roles in producing many vascular malfunctions (1-3). In order to identify specific inducers of programmed death in vascular endothelial cells (VEC), examinations were made of the effects of substances that are known to affect the vascular system by using VEC in culture (4,5). We found that hemorrhagic snake venoms induced apoptotic cell death or programmed cell death of VEC. By contrast, neurotoxic snake venoms did not induce programmed cell death but caused necrosis at much higher doses of the venoms. No effect of hemorrhagic venom was observed with many types of cultured cells other than VEC. Thus, hemorrhagic snake venom appears to be a useful tool for studies of the molecular mechanisms of vascular apoptosis. The results also suggest a possible mechanism of action of hemorrhagic snake venom on the vascular system.

Animals↗