Two Sri Lankan cases of identified sea snake bites, without envenoming.

Sea snakes are among the most venomous creatures encountered around coasts and reefs, in estuaries, rivers and at sea. Their venoms are more toxic than those of land snakes. However, they are rarely aggressive or menacing. Bites have become unusual with the advent of modern fishing methods but the two encounters we report, in the Indian Ocean off the shores of Sri Lanka, emphasise that sea snake bites may not result in envenoming.     

Finger opening in an overarm throw is not triggered by proprioceptive feedback from elbow extension or wrist flexion

 Accuracy in an overarm throw requires great precision in the timing of finger opening. We tested the hypothesis that finger opening in an overarm throw is triggered by proprioceptive feedback from elbow extension or wrist flexion. The hypothesis was tested in two ways: first, by unexpectedly perturbing elbow extension or slowing wrist flexion and determining whether changes occurred in finger opening, and second, by measuring the latency from the start of these joint rotations to the start of finger opening. Subjects threw balls fast and accurately from a sitting or standing position while joint rotations were recorded with the search-coil technique. Elbow extension was unexpectedly blocked near the start of forward motion of the hand by a rope attached to the wrist that passed through a catch mechanism located behind the subject. In spite of a slowing or complete block of elbow extension, and in some cases a replacement of elbow extension by elbow flexion, finger opening always occurred and at the same latency as for normal throws. Wrist flexion was slowed in seven of eight subjects when subjects changed from throwing with a light ball (14 g, 70 mm diam.) to a heavy ball (210 g, 65 mm diam.). For the first throw with the heavy ball, this slowing was neither fully anticipated by the subject nor compensated for by the changed proprioceptive feedback associated with the slowing. Consequently, the timing of finger opening was unchanged and (to the surprise of the thrower) the ball went high. Furthermore, in unperturbed throws with tennis balls, the latency from onset of wrist flexion or elbow extension to onset of finger opening was too short for either to have triggered finger opening (across subjects means were 4 ms for wrist flexion and 21 ms for elbow extension). In additional analysis, no relation was found between the time of onset of earlier occurring rotations at the shoulder and the time of onset of finger opening. We concluded that, although a role for all proprioceptive feedback in triggering finger opening cannot be disproved by these experiments, it can be ruled out for feedback arising from elbow extension and wrist flexion, and it seems unlikely for feedback arising from events occurring very early in the throw. The more likely possibility is that finger opening in an overarm throw is triggered by a central command based on an internal model of hand trajectory. Received: 6 July 1998 / Accepted: 16 October 1998     

A synthetic leaflet heart valve with improved opening characteristics

A new geometry for the design of polyurethane leaflet heart valves has been investigated. The geometry termed the ‘alpharabola’ has a radius of curvature that increases from the centre of the leaflet at the free edge towards the base of the valve and perimeter of the leaflet. The hydrodynamic function and leaflet opening characteristics of the new valve design have been compared to a valve with a spherical leaflet geometry using the same material. The pressure and flow required to open alpharabola leaflets in steady flow tests was markedly lower than for spherical leaflets. Under pulsatile flow conditions with the valve leaflets fully open, the pressure drop across the alpharabola and spherical leaflets was similar, but much lower than in a porcine bioprosthesis. High speed photography showed that the alpharabola leaflets opened in less than 30 ms with the leaflet opening initiating in the base of the leaflet where the radius of curvature was larger. The synthetic leaflet valve has demonstrated short term durability in accelerated fatigue tests to 100 million cycles.     

Predicting Skull Loading: Applying Multibody Dynamics Analysis to a Macaque Skull

Evaluating stress and strain fields in anatomical structures is a way to test hypotheses that relate specific features of facial and skeletal morphology to mechanical loading. Engineering techniques such as finite element analysis are now commonly used to calculate stress and strain fields, but if we are to fully accept these methods we must be confident that the applied loading regimens are reasonable. Multibody dynamics analysis (MDA) is a relatively new three dimensional computer modeling technique that can be used to apply varying muscle forces to predict joint and bite forces during static and dynamic motions. The method ensures that equilibrium of the structure is maintained at all times, even for complex statically indeterminate problems, eliminating nonphysiological constraint conditions often seen with other approaches. This study describes the novel use of MDA to investigate the influence of different muscle representations on a macaque skull model (Macaca fascicularis), where muscle groups were represented by either a single, multiple, or wrapped muscle fibers. The impact of varying muscle representation on stress fields was assessed through additional finite element simulations. The MDA models highlighted that muscle forces varied with gape and that forces within individual muscle groups also varied; for example, the anterior strands of the superficial masseter were loaded to a greater extent than the posterior strands. The direction of the muscle force was altered when temporalis muscle wrapping was modeled, and was coupled with compressive contact forces applied to the frontal, parietal and temporal bones of the cranium during biting. Anat Rec, 291:491–501, 2008. © 2008 Wiley‐Liss, Inc.     

Diblock Copolymers Based on 1,4‐Dioxan‐2‐one and ε‐Caprolactone: Characterization and Thermal Properties

Summary: Various poly(ε‐caprolactone‐block‐1,4‐dioxan‐2‐one) (P(CL‐block‐PDX)) block copolymers were prepared according to the living/controlled ring‐opening polymerization (ROP) of 1,4‐dioxan‐2‐one (PDX) as initiated by in situ generated ω‐aluminium alkoxides poly(ε‐caprolactone) (PCL) chains in toluene at 25 °C. 1 ¹H NMR, PCS and TEM measurements have attested for the formation of colloids attributed to a growing PPDX core surrounded by a solvating PCL shell during the polymerization of PDX promoted by ω‐Al alkoxide PCL chains in toluene. The thermal behavior of the P(CL‐block‐PDX) copolymers was studied by DSC; showing two distinct melting temperatures (as well as two glass transition temperatures) similar to those of the respective homopolyesters. Finally, the thermal degradation of the P(CL‐block‐PDX) block copolymers was investigated by TGA simultaneously coupled to a FT‐IR spectrometer and a mass spectrometer for evolved gas analysis (EGA). The degradation occurred in two consecutive steps involving a first unzipping depolymerization of the PPDX blocks followed by the degradation of the PCL blocks via both ester pyrolysis and unzipping reactions.

TEM observation of P(CL‐block‐PDX) block copolyesters ( = 11 600 and = 22 100) as formed by vaporization starting from a diluted suspension in toluene/TCE mixture solvent (50/50 v/v).     

Primary Amine‐Initiated Polymerizations of Alanine‐NCA and Sarcosine‐NCA

Summary: Sarcosine‐N‐carboxyanhydride (Sar‐NCA), L ‐alanine‐NCA and D,L ‐alanine‐NCA were polymerized with benzylamine as initiator in three different solvents: dichloromethane (CH₂Cl₂), 1,4‐dioxane and dimethylformamide (DMF). The isolated polyaminoacids were characterized by ¹H NMR spectroscopy and MALDI‐TOF mass spectrometry. High conversions and degrees of polymerization s close to the monomer‐initiator (M/I) ratios were found for all polypeptides. For polysarcosine which was soluble under the given reaction conditions a narrow monomodal frequency distribution was found. In contrast, a broad frequency distribution was observed, when L ‐alanine NCA was polymerized in dioxane and DMF. These results were attributed to a partial precipitation of oligopeptides in the β‐sheet structure, which reduces the reactivity of endgroups for steric reasons. The polymerizations of D,L ‐alanine‐NCA showed features in between the extremes of Sar‐NCA and L ‐Ala‐NCA.

Schematic illustration of the secondary structures formed in a primary amine initiated polymerization of L ‐Ala‐NCA.     

腹腔镜胆囊切除术时中转开腹的临床分析

目的 :探讨腹腔镜胆囊切除术 (LC)时中转开腹手术的原因。方法 :回顾性分析本院 2 10例中 8例中转开腹的临床资料。结果 :LC中转开腹手术的发生率为 3 8%。主要原因是有急性胆囊炎病史 ,近期有急性发作史。B超提示胆囊壁粗糙 ,壁厚大于 0 5cm。术中Colat三角粘连重 ,难以辨认胆囊管。结论 :胆囊病变如有急性胆囊炎发作史 ,近期有急性发作史 ,B超提示胆囊壁厚大于 0 5cm时 ,选择LC应慎重     

Ba2+ differentially inhibits the Rb+ efflux promoting and the vasorelaxant effects of levcromakalim and minoxidil sulfate in rat isolated aorta

The K⁺ channel openers activate ATP-sensitive K⁺ channels (K_ATP) in vascular smooth muscle and induce relaxation. In this study, the relationship between these two effects was examined in rings of rat aorta using levcromakalim and minoxidil sulfate as the openers and Ba²⁺ as the K⁺ channel blocker; K⁺ channel opening was assessed by determining the rate constant of ⁸⁶Rb⁺ efflux from the preparation.Ba²⁺ inhibited the ⁸⁶Rb⁺ efflux stimulated by levcromakalim in a noncompetitive manner with an IC₅₀ value of 29 M and a Hill-coefficient of 1.2. At concentrations > 300 M, Ba²⁺ increased the tension of rat aortic rings concentration-dependently. Levcromakalim relaxed contractions to Ba²⁺ (0.5 and 1 mM) with potencies similar to those determined against KCl (25 mM) or noradrenaline as spasmogens (EC₅₀ values 15–40 nM). The vasorelaxant effect against Ba²⁺ was inhibited by the K_ATP channel blockers, glibenclamide and tedisamil, and abolished in depolarizing medium (55 mM KCl). At 3 mM Ba²⁺, levcromakalim was still able to transiently induce complete relaxation; however, within 1 h oscillations in tension developed, leading to a stable level of only 15% relaxation. A similar level of relaxation was achieved against 10 mM Ba²⁺ whereas the combination of 0.5 mM Ba²⁺ and 3 M tedisamil blocked the relaxant effect of levcromakalim completely. With minoxidil sulfate as the K_ATP channel opener the results of the ⁸⁶Rb⁺ efflux and tension experiments were similar to those obtained with levcromakalim.It is concluded that Ba²⁺ is more potent in inhibiting the K⁺ channel opening than the vasorelaxant effects of the openers. On the basis of the ⁸⁶Rb⁺ efflux experiments it is estimated that at least 97% of the channels opened by the activators can be blocked without major effects on vasorelaxation suggesting a dissociation between the two effects. However, if the block is pushed to extremes ( 99.95%) the vasorelaxant effect of the openers is also abolished suggesting a link between both effects. This paradoxon remains to be solved.     

The Use of Intracerebral Microdialysis to Determine Changes in Blood-Brain Barrier Transport Characteristics

The aim of this study was to determine whether changes in the transport of drugs into the brain could be determined by in vivo intracerebral microdialysis. Atenolol was used as a model drug to determine blood-brain barrier (BBB) transport characteristics. In rats, unilateral opening of the blood-brain barrier was achieved by infusion of hyperosmolar mannitol (25%, w/v) into the left internal carotid artery. BBB transport, expressed as the ratio of the area under the curve (AUC) of atenolol in brain extracellular fluid over plasma, was three times higher for the mannitol treated hemisphere as compared with the contralateral brain or after infusion of saline, being (mean ± SEM) 0.094 ± 0.024 (n = 16), 0.029 ± 0.007 (n = 12) and 0.030 ± 0.009 (n = 12) respectively. Further evaluation of the data indicated that for experiments performed in the morning the mannitol infusion had little effect on the extent of transport of atenolol into the brain, while in the afternoon BBB transport was about 10-fold higher than in the contralateral and saline group. The mean afternoon ratios ± SEM were 0.155 ± 0.038 (n = 8), 0.012 ± 0.003 (n = 6) and 0.018 ± 0.006 (n = 6) respectively. It is concluded that intracerebral microdialysis is capable of revealing changes in BBB transport and regional and time-dependent differences in drug levels can be demonstrated with the use of this technique.     

Integration in trigeminal premotor interneurones in the cat

Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3 microA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsi- and nineteen (n = 19) from the contralateral digastric subnucleus. One neurone out of four tested was antidromically activated from both stimulation sites suggesting a bifurcated axon. The identified premotor neurones had a unique convergence profile of oral and perioral primary afferents. Latency calculations indicated that at least 55% of these interneurones were monosynaptically activated by low stimulus strength applied to the inferior alveolar (minimum = 1.0 T) and/or the lingual nerve (minimum = 1.0 T). The thresholds for evoking the neuronal discharges coincided statistically with those required to evoke a jaw opening reflex response by stimulation of the same nerves. It is suggested that the specific group of NVspo-gamma interneurones under different contexts mediates the disynaptic reflex and participates in the centrally and reflexly evoked "patterning" adjustments of the digastric jaw opening motoneurones during ongoing jaw movements. A companion paper reports the convergence of descending cortical, tectal and ascending cervical inputs, as well as of oro-facial and neck primary afferent inputs onto an unselected population of interneurones in the NVspo-gamma (Westberg and Olsson 1991).