Influence of stent-induced vessel deformation on hemodynamic feature of bloodstream inside ICA aneurysms

One of the effective treatment options for intracranial aneurysms is stent-assisted coiling. Though, previous works have demonstrated that stent usage would result in the deformation of the local vasculature. The effect of simple stent on the blood hemodynamics is still uncertain. In this work, hemodynamic features of the blood stream on four different ICA aneurysm with/without interventional are investigated. To estimate the relative impacts of vessel deformation, four distinctive ICA aneurysm is simulated by the one-way FSI technique. Four hemodynamic factors of aneurysm blood velocity, wall pressure and WSS are compared in the peak systolic stage to disclose the impact of defamation by the stent in two conditions. The stent usage would decrease almost all of the mentioned parameters, except for OSI. Stenting reduces neck inflow rate, while the effect of interventional was not consistent among the aneurysms. The deformation of an aneurysm has a strong influence on the hemodynamics of an aneurysm. This outcome is ignored by most of the preceding investigations, which focused on the pre-interventional state for studying the relationship between hemodynamics and stents. Present results show that the application of stent without coiling would improve most hemodynamic factors, especially when the deformation of the aneurysm is high enough.

     

Newtonian and non-Newtonian blood flow in coiled cerebral aneurysms

Endovascular coiling aims to isolate the aneurysm from blood circulation by altering hemodynamics inside the aneurysm and triggering blood coagulation. Computational fluid dynamics (CFD) techniques have the potential to predict the post-operative hemodynamics and to investigate the complex interaction between blood flow and coils. The purpose of this work is to study the influence of blood viscosity on hemodynamics in coiled aneurysms. Three image-based aneurysm models were used. Each case was virtually coiled with a packing density of around 30%. CFD simulations were performed in coiled and untreated aneurysm geometries using a Newtonian and a Non-Newtonian fluid models. Newtonian fluid slightly overestimates the intra-aneurysmal velocity inside the aneurysm before and after coiling. There were numerical differences between fluid models on velocity magnitudes in coiled simulations. Moreover, the non-Newtonian fluid model produces high viscosity (>0.007$>0.007$ [Pa s]) at aneurysm fundus after coiling. Nonetheless, these local differences and high-viscous regions were not sufficient to alter the main flow patterns and velocity magnitudes before and after coiling. To evaluate the influence of coiling on intra-aneurysmal hemodynamics, the assumption of a Newtonian fluid can be used.     

Quantitative Evaluation of Performance in Interventional Neuroradiology: An Integrated Curriculum Featuring Theoretical and Practical Challenges

Purpose

We sought to develop a standardized curriculum capable of assessing key competencies in Interventional Neuroradiology by the use of models and simulators in an objective, quantitative, and efficient way. In this evaluation we analyzed the associations between the practical experience, theoretical knowledge, and the skills lab performance of interventionalists.

Materials and Methods

We evaluated the endovascular skills of 26 participants of the Advanced Course in Endovascular Interventional Neuroradiology of the European Society of Neuroradiology with a set of three tasks (aneurysm coiling and thrombectomy in a virtual simulator and placement of an intra-aneurysmal flow disruptor in a flow model). Practical experience was assessed by a survey. Participants completed a written and oral examination to evaluate theoretical knowledge. Bivariate and multivariate analyses were performed.

Results

In multivariate analysis knowledge of materials and techniques in Interventional Neuroradiology was moderately associated with skills in aneurysm coiling and thrombectomy. Experience in mechanical thrombectomy was moderately associated with thrombectomy skills, while age was negatively associated with thrombectomy skills. We found no significant association between age, sex, or work experience and skills in aneurysm coiling.

Conclusion

Our study gives an example of how an integrated curriculum for reasonable and cost-effective assessment of key competences of an interventional neuroradiologist could look. In addition to traditional assessment of theoretical knowledge practical skills are measured by the use of endovascular simulators yielding objective, quantitative, and constructive data for the evaluation of the current performance status of participants as well as the evolution of their technical competency over time.     

In vitro evaluation of flow divertors in an elastase-induced saccular aneurysm model in rabbit

Endovascular coiling is an acceptable treatment of intracranial aneurysms, yet long term follow-ups suggest that endovascular coiling fails to achieve complete aneurysm occlusions particularly in wide-neck and giant aneurysms. Placing of a stentlike device across the aneurysm neck may be sufficient to occlude the aneurysm by promoting intra-aneurysmal thrombosis; however, conclusive evidence of its efficacy is still lacking. In this study, we investigate in vitro the efficacy of custom designed flow divertors that will be subsequently implanted in a large cohort of animals. The aim of this study is to provide a detailed database against which in vivo results can be analyzed. Six custom designed flow divertors were fabricated and tested in vitro. The design matrix included three different porosities (75%, 70%, and 65%). For each porosity, there were two divertors with one having a nominal pore density double than that of the other. To quantify efficacy, the divertors were implanted in a compliant elastomeric model of an elastase-induced aneurysm model in rabbit and intra-aneurysmal flow changes were evaluated by particle image velocimetry (PIV). PIV results indicate a marked reduction in intra-aneurysmal flow activity after divertor implantation in the innominate artery across the aneurysm neck. The mean hydrodynamic circulation after divertor implantation was reduced to 14% or less of the mean circulation in the control and the mean intra-aneurysmal kinetic energy was reduced to 29% or less of its value in the control. The intra-aneurysmal wall shear rate in this model is low and implantation of the flow divertor did not change the wall shear rate magnitude appreciably. This in vitro experiment evaluates the characteristics of local flow phenomena such as hydrodynamic circulation, kinetic energy, wall shear rate, perforator flow, and changes of these parameters as a result of implantation of stentlike flow divertors in an elastomeric replica of elastase-induced saccular aneurysm model in rabbit. These initial findings offer a database for evaluation of in vivo implantations of such devices in the animal model and help in further development of cerebral aneurysm bypass devices.     

Coiling dimorphism within a genetic type of the planktonic foraminifer Globorotalia truncatulinoides

The coiling direction—sinistral (left-coiled) or dextral (right-coiled)—of planktonic foraminiferal shells is a classical proxy used to assess past environmental changes and to understand their evolutionary patterns. Globorotalia truncatulinoides is composed of five different genetic types (I to V), each with a specific biogeographic distribution. So far, type II is the only type within which both coiling types have been frequently found. Here we examine the coiling direction as a dimorphic variation in a single genetic type, and show that the two forms with different coiling directions differ in ecology. The studied 140 left- and 137 right-coiled specimens from eight depth layers at four stations in the Sargasso Sea all belonged to Type II, based on the phylogenetic analyses of the ITS (internal transcribed spacer) region of ribosomal DNA. The distributions of left- and right-coiled Type II (Type II-L and II-R) differed strongly: Type II-L dominated between 400 and 200 m depth in the central water mass, whereas Type II-R was common in the top 200 m of the subtropical gyre. The left- and right-coiled forms are thus associated with different water masses. However, the vertical distribution along a temperature gradient indicates that their coiling direction is not determined by temperature, and might have some genetic basis. Our molecular phylogenetic analyses showed that the two forms probably share the same gene pool through their dispersals between different water masses. Moreover, the lineage of G. truncatulinoides is young (< 3 Ma), which might not be long enough to evolve into two lineages with opposite coiling direction. We discuss the practical and theoretical usefulness of a simple genetic model for coil dimorphism, in order to build testable hypotheses regarding the evolutionary history of planktonic foraminifera at the population level.     

介入栓塞治疗内脏动脉瘤的临床研究

目的:探讨介入血管腔内栓塞治疗内脏动脉瘤的方法、疗效及安全性。方法:选择内脏动脉瘤患者23例,包括脾动脉瘤13例,肝动脉瘤2例,胃十二指肠动脉瘤3例,肠系膜上动脉瘤4例,肾动脉瘤1例。其中,9例行远近端动脉栓塞术,4例采用支架辅助弹簧圈瘤体内填塞,3例采用弹簧圈瘤体内填塞加瘤体内注胶栓塞术,4例行弹簧圈瘤体内栓塞术,2例行分支动脉颗粒栓塞术,1例行单纯注胶栓塞术。术后1月、3月、6月行超声、CTA或血管造影复查,以后每年复查一次。结果:本组均成功行介入血管腔内栓塞治疗内脏动脉瘤,栓塞治疗后造影示动脉瘤体和/或载瘤动脉闭塞,动脉瘤体内无明显对比剂显影,脾动脉瘤栓塞患者有3例出现发热,脾区疼痛等脾梗塞症状,未见栓塞术相关严重并发症发生。4例消化道出血患者出血均停止。术后随访3~48个月,未见动脉瘤破裂出血、动脉瘤复发或增大,支架置入者,支架内及分支动脉血流均保持通畅。结论:介入血管腔内栓塞是一种治疗内脏动脉瘤的简便、微创、安全有效的方法。     

A novel strategy for combination of clofarabine and pictilisib is synergistic in gastric cancer

Gastric cancer (GC) is frequently characterized by resistance to standard chemotherapeutic regimens and poor clinical outcomes. We aimed to identify a novel therapeutic approach using drug sensitivity testing (DST) and our computational SynerySeq pipeline. DST of GC cell lines was performed with a library of 215 Federal Drug Administration (FDA) approved compounds and identified clofarabine as a potential therapeutic agent. RNA-sequencing (RNAseq) of clofarabine treated GC cells was analyzed according to our SynergySeq pipeline and identified pictilisib as a potential synergistic agent. Clonogenic survival and Annexin V assays demonstrated increased cell death with clofarabine and pictilisib combination treatment (P<0.01). The combination induced double strand breaks (DSB) as indicated by phosphorylated H2A histone family member X (γH2AX) immunofluorescence and western blot analysis (P<0.01). Pictilisib treatment inhibited the protein kinase B (AKT) cell survival pathway and promoted a pro-apoptotic phenotype as evidenced by quantitative real time polymerase chain reaction (qRT-PCR) analysis of the B-cell lymphoma 2 (BCL2) protein family members (P<0.01). Patient derived xenograft (PDX) data confirmed that the combination is more effective in abrogating tumor growth with prolonged survival than single-agent treatment (P<0.01). The novel combination of clofarabine and pictilisib in GC promotes DNA damage and inhibits key cell survival pathways to induce cell death beyond single-agent treatment.     

Finite element modeling of embolic coil deployment: Multifactor characterization of treatment effects on cerebral aneurysm hemodynamics

Endovascular coiling is the most common treatment for cerebral aneurysms. During the treatment, a sequence of embolic coils with different stiffness, shapes, sizes, and lengths is deployed to fill the aneurysmal sac. Although coil packing density has been clinically correlated with treatment success, many studies have also reported success at low packing densities, as well as recurrence at high packing densities. Such reports indicate that other factors may influence treatment success. In this study, we used a novel finite element approach and computational fluid dynamics (CFD) to investigate the effects of packing density, coil shape, aneurysmal neck size, and parent vessel flow rate on aneurysmal hemodynamics. The study examines a testbed of 80 unique CFD simulations of post-treatment flows in idealized basilar tip aneurysm models. Simulated coil deployments were validated against in vitro and in vivo deployments. Among the investigated factors, packing density had the largest effect on intra-aneurysmal velocities. However, multifactor analysis of variance showed that coil shape can also have considerable effects, depending on packing density and neck size. Further, linear regression analysis showed an inverse relationship between mean void diameter in the aneurysm and mean intra-aneurysmal velocities, which underscores the importance of coil distribution and thus coil shape. Our study suggests that while packing density plays a key role in determining post-treatment hemodynamics, other factors such as coil shape, aneurysmal geometry, and parent vessel flow may also be very important.     

Physiological Studies on Pea Tendrils: VII. Evaluation of a Technique for the Asymmetrical Application of Ethylene

A technique has been devised for the asymmetrical application of ethylene to specific surfaces of plant tissue. 2-Chloroethylphosphonic acid (CEPA) was dissolved in a phosphate buffer (pH 6.5) containing Tween-20 or dimethylsulfoxide as adjuvant. Ethylene evolution from tendrils of Pisum sativum cv. Alaska was greater during coiling than when they were at rest; and via topical application to the ventral surface, CEPA was able to stimulate contact coiling. Within 1 day of application of CEPA, the tendrils showed symptoms of senescence. It is concluded that ethylene participates in the control of contact coiling stimulated by touch, and it is suggested that this control may be exerted via permeability changes in the membranes of the motor cells.     

Correlation Between the Rupture Risk and 3D Geometric Parameters of Saccular Intracranial Aneurysms

The purpose of this study is to evaluate the association of the location and geometric parameters of intracranial aneurysm with the risk of rupture. A retrospective study consisted of 284 patients diagnosed with saccular intracranial aneurysm between January 2009 and May 2013 at Wuxi Third People’s Hospital was conducted. 3D digital subtraction angiography images from all patients (240 ruptured, 44 unruptured) were obtained and analyzed. The location of the aneurysms and the 3D geometric parameters including the aneurysm depth, the neck size, diameter of the parent artery, aneurysm angle, aspect radio, size ratio, and the neck-to-parent-artery ratio (NPR) were compared between ruptured and unruptured groups. Results: In ruptured group, anterior communicating artery, posterior communicating artery (PCoA), and the bifurcation of internal carotid artery (ICA) were the top three locations for aneurysm occurrence, accounting for 40.00, 30.42, and 12.08 % respectively. While in the unruptured group, top three locations were PCoA (36.36 %), posterior cerebral circulation (18.18 %), and the bifurcation of the ICA (15.91 %). Distribution of aneurysm location is significantly different (p < 0.05) between ruptured and unruptured aneurysms. For the 3D geometric parameters characterizing aneurysm, aneurysm depth (p < 0.05), parent artery diameter (p < 0.05), aneurysm angle (p < 0.01), aspect ratio (p < 0.01), and size ratio (p < 0.01) all showed a significant difference between ruptured and unruptured group. No difference was found in the neck size and the NPR ratio between the two groups. 3D geometric parameters such as aneurysm depth, parent artery diameter, aneurysm angle, aspect ratio, and size ratio can be helpful in evaluating the rupture risk of saccular intracranial aneurysm for a better prevention and prognosis.     

The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis

Wharton D.A.1981. The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis. International Journal for Parasitology11: 353–357. Infective larvae of Trichostrongylus colubriformis coil during the evaporation of water films. Decreasing the depth of the liquid film does not initiate coiling but enclosure in capillary tubes of similar diameter to the track width of actively swimming or crawling larvae results in a marked stimulation of coiling behaviour. It is suggested that larvae coil in response to the progressive restriction of lateral movement in an evaporating water film. The behavioural flexibility of the infective larvae of T. colubriformis maximizes both their survival and their chances of infection.     

Potato coiled sprout in relation to seed tuber storage treatment and to infection by Verticillium nubilum Pethybr

Inoculation of seed potato tubes with Verticillium nubilum produced infection on the underground stem bases to subsequent growth in the form of brown lesions, often accompanied by longitudinal or transverse cracking. Some inoculation tests provided further evidence of a causal relationship between infection with V. nubilum and coiled sprout, but it was not possible to define the conditions in which the fungus gave rise to coiling. Seed tubers sprouted in light before planting produced more coiling than unsprouted or desprouted tubers. Sprouting had this effect whether V. numbilum was present or not and coiling induced by sprouting and that induced by V. nubilum occurred independently. The increased coiling of stem bases from sprouted tubers was often accompanied by fasciation, whereas this symptom was not usually associated with the coiling from unsprouted or desprouted seed tubers inoculated with the fungus. Brown lesions associated with V. nubilum were readily distinguishable from those of Rhizoctonia solani but not from those caused by Oospora pustulans. Neither of these fungi was found to cause coiling. Different varieties of potatoes showed differences in the incidence of coiling in response to sprouting treatment. There was no apparent differences in varietal response to infection by V. nubilum.     

Intestinal morphology in oily bitterlings (Cyprinidae: Acheilognathinae)

We evaluated inter- and intraspecific variations of the intestinal coiling patterns and intestinal length of the oily bitterlings, Tanakia limbata, Tanakia koreensis, Tanakia somjinensis, and Tanakia signifer. All the oily bitterling species shared a unique intestinal coiling pattern, expressed as an oval shaped loop. The ratio of the intestinal length to standard length varied among species, viz., both T. koreensis and T. signifer have significantly longer intestines than T. limbata and T. somjinensis. The intestinal length may be a useful diagnostic character between two sibling species, T. koreensis and T. somjinensis, although we observed intraspecific variation in the intestinal length of T. limbata and T. koreensis among collection sites.     

栓塞治疗颅内动脉瘤的并发症及处理方法分析

目的:分析栓塞治疗颅内动脉瘤过程中并发症的发生原因及处理方法。方法:回顾性分析微弹簧圈栓塞治疗的97例颅内动脉瘤患者的临床资料,包括性别、年龄、Hunt-Hess分级,对住院患者进行术前整体状况评估。影像学检查主要记录动脉瘤的位置、瘤体长度和瘤颈宽度,测量其长宽比例。血管内介入手术治疗观察各种介入治疗方法以及相关并发症。结果:本组97例颅内动脉瘤患者中,男44例、女53例,男性平均年龄51.3岁,女性平均年龄46.7岁,男女共同平均年龄48.7岁。颈内动脉-后交通支及其附近动脉瘤51个,前交通动脉和大脑前动脉29个,大脑中动脉11个,椎-基底动脉系统6个,所用到的栓塞材料包括各种弹簧圈、颅内支架、不可脱球囊等。97例中15例出现并发症(15.5%),动脉瘤破裂出血4例,术中发生血管痉挛3例,血栓形成或血栓性栓塞5例,3例死亡。结论:栓塞治疗颅内动脉瘤过程中最主要并发症包括动脉瘤破裂、栓塞和血栓形成、血管痉挛等,术前评估、术中谨慎操作以及正确及时的处理能够降低栓塞治疗颅内动脉瘤的并发症。     

Relapsing polychondritis associated with bilateral stapes footplate fixation: a case report

Introduction

Two types of gliomatosis cerebri exist: Type I and Type II. We report the results of a histological and genetic study of two cases of gliomatosis cerebri Type II, correlating these results with therapy and prognosis.

Case presentation

Two patients, a 52-year-old man (Patient 1) and a 76-year-old man (Patient 2) with gliomatosis cerebri II were admitted to our institution; they underwent surgical treatment and received radiotherapy and chemotherapy. At the 24-month follow-up, Patient 1 was still alive, while Patient 2 had died. The poor prognosis of Patient 2 was underlined by molecular analysis which showed that the angiogenesis related genes VCAM1 and VEGF were overexpressed, reflecting the high degree of neovascularization.

Conclusion

Genes involved in drug resistance and metallothioneins were highly expressed in Patient 2 and this, associated with unmethylated O6-methylguanine methyltransferase, can explain the lack of response to chemotherapy.     

Trimethoprim-sulfamethoxazole compared with sulfamethoxazole in urinary tract infection

Thirty-nine subjects with active non-obstructive urinary tract infection due to common pathogens were treated in a randomized fashion either with sulfamethoxazole alone (22 patients) or a combination of trimethoprim-sulfamethoxazole (17 patients) during four consecutive weeks in the course of a controlled study. The combination trimethoprim-sulfamethoxazole appeared more effective than sulfamethoxazole alone in eradicating infection. Complete disappearance of urinary tract infection was obtained in 82% of subjects treated with the combination versus 59% in those treated with sulfamethoxazole alone. Recurrence of infection averaged 43% in the group treated with the combination and 54% in those treated with sulfamethoxazole alone. The mean time interval between successful response and recurrence of infection was 17 weeks for the combination and 20 weeks for sulfamethoxazole alone. When the comparison of the results between sulfamethoxazole alone and the combination trimethoprim-sulfamethoxazole is restricted to the subjects with E. coli infection (69% of all cases), no important difference between the two groups can be demonstrated. A skin rash which sometimes disappeared spontaneously despite continued medication was the only side effect noted with the trimethoprim-sulfamethoxazole combination.     

Sea-surface temperature for left-coiling Neogloboquadrina populations inhabiting the westernmost Mediterranean in the middle Pleistocene and the Pleistocene-Pliocene transition

Using the modern analog methodology applied to planktonic foraminifers, we analyze the relation between the frequency of the coiling type in Neogloboquadrina populations and the sea-surface temperatures (SST) during the middle Pleistocene and the Pleistocene-Pliocene transition in the Alboran Sea (westernmost Mediterranean), close to the Atlantic connection. The results reveal that the present-day positive correlation between the two variables (r = 0.649) is maintained even with a higher coefficient (r = 0.783) in the middle Pleistocene but falls slightly (r = 0.517) in the Pleistocene-Pliocene transition due mainly to a dispersal of the temperatures for the samples bearing predominantly left-coiling Neogloboquadrina. The temperature used as a reference for the coiling change resulted 5-6 °C above its North Atlantic present-day reciprocal, but these thermal differences could be caused by: i) a slight overestimate (1–2 °C) due to the lumping of all neogloboquadrinids into a single variable when SST are estimated; ii) only the warmer range of temperatures for the left-coiling populations would be represented in the samples; and iii) a remarkable warming inside the westernmost Mediterranean during the summer stage mixing cold and warm assemblages in bottom sediments. In addition, these results in combination with those derived from the isotopic analyses (δ¹⁸O) in G. bulloides tests, suggest that during the Pliocene-Pleistocene transition two different populations of left-coiling Neogloboquadrina could have existed with different environmental requirements: one, derived from late Miocene-Pliocene (i.e., left-coiling N. acostaensis group), and another being the ancestor of the modern N. pachyderma (left-coiling). Similarity analyses were achieved in order to locate the position of the core-tops with the assemblages most analogous to those of the fossil samples containing left-coiling Neogloboquadrina. The results reinforce the idea that the presence of these forms in the Mediterranean during the intervals studied would be related mainly to the input of cold waters from the North Atlantic during glacial stages, although it could be secondarily favored by the establishment of upwelling conditions, as in the present-day North Alboran waters.     

Influence of stent configuration on cerebral aneurysm fluid dynamics

Embolic coiling is the most popular endovascular treatment available for cerebral aneurysms. Nevertheless, the embolic coiling of wide-neck aneurysms is challenging and, in many cases, ineffective. Use of highly porous stents to support coiling of wide-neck aneurysms has become a common procedure in recent years. Several studies have also demonstrated that high porosity stents alone can significantly alter aneurysmal hemodynamics, but differences among different stent configurations have not been fully characterized. As a result, it is usually unclear which stent configuration is optimal for treatment. In this paper, we present a flow study that elucidates the influence of stent configuration on cerebral aneurysm fluid dynamics in an idealized wide-neck basilar tip aneurysm model. Aneurysmal fluid dynamics for three different stent configurations (half-Y, Y and, cross-bar) were first quantified using particle image velocimetry and then compared. Computational fluid dynamics (CFD) simulations were also conducted for selected stent configurations to facilitate validation and provide more detailed characterizations of the fluid dynamics promoted by different stent configurations. In vitro results showed that the Y stent configuration reduced cross-neck flow most significantly, while the cross-bar configuration reduced velocity magnitudes within the aneurysmal sac most significantly. The half-Y configuration led to increased velocity magnitudes within the aneurysmal sac at high parent-vessel flow rates. Experimental results were in strong agreement with CFD simulations. Simulated results indicated that differences in fluid dynamic performance among the different stent configurations can be attributed primarily to protruding struts within the bifurcation region.     

Morphological investigations of Miliolidae (Foraminifera) from the Upper Permian of the Southern Alps,based on thin sections and stereoscopic X-ray microradiographs

Shallow marine deposits of the Upper Permian and lowermost Triassic in the Southern Alps between Val Adige (Southern Tyrol, northern Italy) in the west and the Karawanken Mountains (northern Yugoslavia) in the east contain abundant miliolid foraminifera of the genusHemigordius Schubert, 1908. These two-chambered Miliolacea show a great diversity of morphotypes due to numerous combinations in the mode of coiling, the shape of the umbonal thickening, the degree of involution, and the dimensions of the test. The spectrum of internal structures ofHemigordius observed in thin-sections is schematized and illustrated in a diagram. Of special interest are irregularly coiled specimens whose complicated mode of coiling is analysed with help of stereomicroradiographs. According to the number of spiral planes, their angles in between and the number of volutions a streptospiral and a glomospiroid type are distinguished. While the streptospiral mode is characterized by a ± regular coiling plan, the glomospiroid type does not show any rules in the succession of the spiral planes and angles. p [Three-dimensional illustrations eludicate the streptospiral and glomospiroid coiling plan of the genusHemigordius. The new developed X-ray microradiographic technique used in our investigation is described in some details.     

Physiological Studies on Pea Tendrils: VI. The Characteristics of Sensory Perception and Transduction

Tendrils may be said to possess a sense of touch, and the direction and amplitude of the coiling response can be used to define the characteristics of this sense. These characteristics are, first, that the tendril will coil only in response to ventral mechanical stimulation, that this coiling can be inhibited by subsequent dorsally presented stimulation, and that dorsal stimulation alone causes no coiling. This phenomenon seems to be due to some asymmetry in the response system. Second, the nature of the response is always determined by the location (i.e., dorsal or ventral) of the last stimulation the tendril experienced. Third, the ability of dorsally presented stimulation to reverse ventrally stimulated coiling is gradually lost. Complete escape from reversibility is attained if the interval between ventral and dorsal stimulation reaches 9 minutes. Fourth, the magnitude of response is determined by both the number and the frequency of the stimuli. Both ventrally stimulated coiling and dorsally stimulated inhibition of coiling can be temporarily stopped by a 9-minute cold break at 10 C, given immediately after stimulation. As soon as the tendrils are restored to room temperature, they proceed to respond to the stimulus.