Biology and functional morphology of a new species of endolithic Bryopa (Bivalvia: Anomalodesmata: Clavagelloidea) from Japan and a comparison with fossil species of Stirpulina and other Clavagellidae

Abstract. A new species of Clavagellidae, Bryopa aligamenta, from Okinawa, Japan, is described. The species is endolithic in living corals, with the left valve cemented to the crypt wall, as in all clavagellids. The free right valve exhibits an unusual growth pattern, with commarginal lines seemingly arising from the posterior valve margin and extending towards the anterior. This results from: (i) progressive anterior erosion of the umbones, probably as a consequence of the boring process; (ii) the apparent migration posteriorly, as the umbones are eroded, of the dorso‐ventral growth axis of the shell; and (iii) enhanced posterior inter‐commarginal growth. Unlike other clavagellid genera and species, however, there is no discernible primary ligament, at least in the adult. It is possible, however, that if a juvenile ligament were present (as in B. lata), it too would be lost as a consequence of antero‐dorsal erosion during boring. To retain valve alignment in the absence of a primary ligament, and possibly upon reaching an adult size, the mantle lays down alternating layers of calcium carbonate and proteinaceous periostracum onto the interior surface of the shell to thicken it, most noticeably marginally and, especially, posteriorly. The two valves are united dorsally, therefore, by thin layers of periostracum that probably exert a minimal opening force. B. aligamenta is, however, further characterised by large adductor, pallial, and siphonal retractor muscles so that the entire animal is encased tightly within an internally strengthened shell within a crypt. Movement must be minimal, blood being pumped into pallial haemocoels to push open the valves and extend the siphons. Despite a suggestion to the contrary, Bryopa is retained in the Clavagellidae, its unusual growth processes resulting from an endolithic life style within living corals. The fossil clavagellid Stirpulina bacillus, from the Pliocene/Pleistocene of Palermo, Sicily, Italy, was, unlike Bryopa aligamenta and other clavagellids, endobenthic, with a long adventitious tube and anterior watering pot superficially similar to species of Penicillidae, another family of the Clavagelloidea. Furthermore, as in all clavagellids only the left valve is fused into the fabric of the tube, the right being free within it. In all penicillids, both valves are fused into the fabric of their tubes. The watering pots of the fossil S. coronata, S. vicentina, and S. bacillus, moreover, are formed in a different manner to that of penicillids, by progressive encasement of the right valve inside the tube. In penicillids, the tube is secreted in a single event from the general mantle surface and the incorporation of both valves into its fabric. The constituent genera of the Clavagellidae thus constitute an example of parallel evolution with members of the Penicillidae.     

Morphological and structural adaptations to soft substrates in the Early Jurassic monomyarians Lithiotis and Cochlearites

Lithiotis problematica and Cochlearites loppianus are sessile monomyarian bivalves known from the Early Jurassic of the Tethyan region, where they are found standing vertically in the calcareous mud of lagoonal fades. Their shells are characterized by a long cardinal area, ventrally displaced body space, thick attached valve, and a thin, flat free valve of equal length. A functional ligament is present only in juvenile stages of Cochlearites. To grow straight, the ventral end of the shell had to gape, so in both species it was probably the elasticity of the thin free valve that caused the shell to open. In the adult stage the shell grew only towards the venter with an apparently constant growth rate, while the soft body size remained unchanged. The outer shell is composed of a compact aragonitic layer, while the inner part is filled with loose chalky deposits which are thought to have functioned as supporting the soft body and lifting it upwards. These and other morphologic and structural features, as well as the growth pattern, can be explained as an adaptation of a sessile animal to soft muddy bottoms and rapid sedimentation. Some elongated Crassostrea living in similar environments show remarkable morphologic and structural convergence with Lithiotis and Cochlearites.     

NEW TUBE-BEARING ANTILLOCAPRINID RUDIST BIVALVES FROM THE MAASTRICHTIAN OF JAMAICA

Abstract:  Two genera of tube-bearing antillocaprinid rudist bivalves from the Maastrichtian of Jamaica are recognised: Titanosarcolites Trechmann and Parasarcolites gen. nov. Titanosarcolites is recumbent, broadly equivalve and coils parallel to the myocardinal line, with tubes on the anteriodorsal, anterior, and anterioventral regions of the inner layer; there are two teeth and two teeth-like myophores in the left valve. Sockets for teeth have conical tabulae, those for myophores are filled with normal shell structure. A ligamental cavity is lacking. Parasarcolites is recumbent, with equal, subequal or moderately inequal valves, and the plane of coiling is at an angle of 34–63 degrees to the mediocardinal line. It has tubes in the dorsal and anterior-dorsal regions, and a myocardinal structure with blade like myophores, with the posterior tooth and socket strongly flattened. The position of the ligament is indicated by a comma-shaped cavity situated dorsalwards of the posterior tooth. Additional toothlets are present in the left valve. All sockets are filled with canal-bearing shell-structure. Five new species of Parasarcolites are described from the Upper Maastrichtian of Jamaica: Parasarcolites atkinsoni , P. baileyi , P. greeni , P. monotubularis and P. quadratus .     

Modeling leaflet correction techniques in aortic valve repair: A finite element study

In aortic valve sparing surgery, cusp prolapse is a common cause of residual aortic insufficiency. To correct cusp pathology, native leaflets of the valve frequently require adjustment which can be performed using a variety of described correction techniques, such as central or commissural plication, or resuspension of the leaflet free margin. The practical question then arises of determining which surgical technique provides the best valve performance with the most physiologic coaptation. To answer this question, we created a new finite element model with the ability to simulate physiologic function in normal valves, and aortic insufficiency due to leaflet prolapse in asymmetric, diseased or sub-optimally repaired valves. The existing leaflet correction techniques were simulated in a controlled situation, and the performance of the repaired valve was quantified in terms of maximum leaflets stress, valve orifice area, valve opening and closing characteristics as well as total coaptation area in diastole. On the one hand, the existing leaflet correction techniques were shown not to adversely affect the dynamic properties of the repaired valves. On the other hand, leaflet resuspension appeared as the best technique compared to central or commissural leaflet plication. It was the only method able to achieve symmetric competence and fix an individual leaflet prolapse while simultaneously restoring normal values for mechanical stress, valve orifice area and coaptation area.     

PUNCTICULATA VERSIFORMIS SP. NOV. AND CYCLOTELLA KATHMANDUENSIS SP. NOV. (BACILLARIOPHYTA), NEW FOSSIL SPECIES FROM MIDDLE PLEISTOCENE LACUSTRINE SEDIMENTS,KATHMANDU, NEPAL HIMALAYA1

New fossil species, Puncticulata versiformis sp. nov. and Cyclotella kathmanduensis sp. nov., are described from lacustrine sediments in the Kathmandu Basin on the southern slope of the Nepal Himalaya. They were dominant in the Middle Pleistocene. Both LM and SEM observations reveal their unique morphological features. Puncticulata versiformis is characterized by (1) various valve outlines (circular, elliptical, or oval), (2) a tangentially undulate central area, (3) a complex alveolar structure composed of three kinds of costae (thick costae, thin costae, and thin and short costae), (4) well‐developed spines (Y‐shaped and tapering) located on one side of the valve face/mantle area junction, and (5) a valvocopula with an extremely undulate margin. The species‐specific feature of C. kathmanduensis is the presence of two kinds of alveolate zones in a single valve: type‐1 zone composed only of normal costae, and type‐2 zone composed of both normal costae and recessed costae bearing fultoportulae. Changes in valve ornamentation occur in these two species from initial valves to vegetative valves. In P. versiformis, the arrangement of areolae with internal domed cribra and fultoportulae in the central area changes from radial rows in the initial valve to groups in the vegetative valve. In the initial valve of C. kathmanduensis, the type‐1 alveolate zone is generally absent.     

Comparative study of the amount of backflow produced by four types of aortic valve prostheses

To determine the extent of backflow encountered with currently used prosthetic valves, four types of aortic valves with comparable orifice diameters were tested in a pulse duplicating system. These were a Hancock porcine valve, a Lillehei-Kaster pivoting disk valve, a St. Jude bileaflet valve and a Bj?rk-Shiley tilting disk valve. Mean aortic pressure was sequentially increased from 83 to 147 mmHg, keeping the pump rate essentially constant (69-73 strokes/min). The porcine valve produced the least amount of total backflow (backflow due to closure plus leakage backflow) (1.6 to 2.4 mL/stroke). Among the mechanical valves the Bj?rk-Shiley valve showed the least amount of total backflow (5.0 to 6.0 mL/stroke). At a mean aortic pressure of 100 mmHg and a low cardiac output of 2 L/min, the total backflow with the porcine valve was only 6 percent of forward flow; whereas it was 19 percent with the Lillehei-Kaster valve, 22 percent with the St. Jude valve and 18 percent with the Bj?rk-Shiley valve. Leakage backflow at a given level of mean aortic pressure was, as expected, directly related to the annular clearance area. It is concluded that the Hancock valve showed the least amount of backward flow, which would be particularly beneficial in low output states. In the presence of normal hemodynamics, the amount of backflow with the three mechanical valves appeared to be well below the level of backflow considered to be clinically significant.     

Ionescu-Shiley pericardial xenograft valve: Hemodynamic evaluation and early clinical follow-up of 326 patients

Dissatisfaction with the hemodynamic characteristics of available porcine valves prompted a clinical trial of the Ionescu-Shiley percardial xenograft (ISPX) valve. Three hundred fifty-six ISPX valves were implanted consecutively in 326 patients. Operative mortality was 2.6% (2/75) for aortic valve replacement alone and 7.7% (12/155) for aortic valve replacements that included reoperations and combined procedures such as mitral commissurotomy, annuloplasty, and coronary artery bypass. Operative mortality for all patients who underwent mitral valve replacement was 9.5% (14/147). The mean peak systolic gradient pressure in the aortic position was 5.4 mm Hg overall and 4.27 mm Hg with the size 19 mm valve. There were no embolic episodes in patients who received the ISPX valve in the aortic position. The available data indicate that the rate of peripheral embolism with the ISPX valve compares favorably with that of porcine valves. Considering its hemodynamic advantage, if the longterm durability of the full-orifice Ionescu-Shiley pericardial xenograft valve continues to be confirmed by follow-up studies, it is our opinion that it is the biologic valve of choice.     

Vascular-nervous relationships in the valves of the heart]

Method of silver nitrate impregnation was used in order to study 50 preparations of not-changed atrioventricular valves of the heart of domestic bulls and 30 preparations of the same valves of adult humans. It has been shown that in heart valves there are certain relationships between striated muscle fibres, blood vessels and nerve elements. The nerve structures of the valves are represented by nerve bundles of different thickness. In their composition there are comparatively thin non-myelinated and thicker myelinated fibres. Towards the free edge of cusps the nerve bundles become thinner and the nerve trunks give off separate thin nerve fibres disposed along the vessels of a capillary type and in some places getting around them. In certain portions of cusps the nerve bundles, some of which have zigzag sinuosity, cross blood vessels in different directions. In man the major mass of blood vessels and nerve elements are disposed near the base of the valve cusps, accompanying the muscle fibre bundles penetrating from the base side. In the bull heart valves an amount of blood vessels and nerve elements is found in considerable portions of the cusps not connected with muscle fibres.     

Comparison of first and second heart sounds after mechanical heart valve replacement

In this article, the spectral features of first heart sounds (S1) and second heart sounds (S2), which comprise the mechanical heart valve sounds obtained after aortic valve replacement (AVR) and mitral valve replacement (MVR), are compared to find out the effect of mechanical heart valve replacement and recording area on S1 and S2. For this aim, the Welch method and the autoregressive (AR) method are applied on the S1 and S2 taken from 66 recordings of 8 patients with AVR and 98 recordings from 11 patients with MVR, thereby yielding power spectrum of the heart sounds. Three features relating to frequency of heart sounds and three features relating to energy of heart sounds are obtained. Results show that in comparison to natural heart valves, mechanical heart valves contain higher frequency components and energy, and energy and frequency components do not show common behaviour for either AVR or MVR depending on the recording areas. Aside from the frequency content and energy of the sound generated by mechanical heart valves being affected by the structure of the lungs–thorax and the recording areas, the pressure across the valve incurred during AVR or MVR is a significant factor in determining the frequency and energy levels of the valve sound produced. Though studies on native heart sounds as a non-invasive diagnostic method has been done for many years, it is observed that studies on mechanical heart valves sounds are limited. The results of this paper will contribute to other studies on using a non-invasive method for assessing the mechanical heart valve sounds.     

Aurikirkbya wordensis (hamilton): ein vermutlich filtrierender palaeocopider ostracode

The valves ofAurikirkbya wordensis (Hamilton, 1942) from the Upper Permian, Word Formation of W Texas (USA), show a crenulated contact groove in the larger valve and smooth contact list in the smaller one. The right valve is usually the larger but occasionally inversion of valves take place. The contact elements of the free margin of valves are discussed in terms of functional morphology. In addition, the muscle-scar areas and the carapace outline have also been regarded. Based on the new discoveries, it is suggested thatA. wordensis was a nectobenthonic filter-feeder. The evidence from the valve interiors is not consistent with a platycopine position for the kirkbyacean taxa.

     

Effect of systolic flow rate on the prediction of effective prosthetic valve orifice area

The Gorlin equation for the hemodynamic assessment of valve area is commonly used in cardiac catheterization laboratories. A study was performed to test the prediction capabilities of the Gorlin formula as well as the Aaslid and Gabbay formula for the effective orifice area of prosthetic heart valves. Pressure gradient, flow, and valve opening area measurements were performed on four 27 mm valve prostheses (two mechanical bileaflet designs, St. Jude and Edwards-Duromedics, an Edwards pericardial tissue valve, and a trileaflet polyurethane valve) each mounted in the aortic position of an in vitro pulse duplicator. With the known valve orifice area, a different discharge coefficient was computed for each of the four valves and three orifice area formulas. After some theoretical considerations, it was proposed that the discharge coefficient would be a function of the flow rate through the valve. All discharge coefficients were observed to increase with increasing systolic flow rate. An empirical relationship of discharge coefficient as a linear function of systolic flow rate was determined through a regression analysis, with a different relationship for each valve and each orifice area formula. Using this relationship in the orifice area formulas improved the accuracy of the prediction of the effective orifice area with all three formulas performing equally well.     

Probing the effect of morphology on lymphatic valve dynamic function

The lymphatic system is vital to the circulatory and immune systems, performing a range of important functions such as transport of interstitial fluid, fatty acid, and immune cells. Lymphatic vessels are composed of contractile walls and lymphatic valves, allowing them to pump lymph against adverse pressure gradients and to prevent backflow. Despite the importance of the lymphatic system, the contribution of mechanical and geometric changes of lymphatic valves and vessels in pathologies of lymphatic dysfunction, such as lymphedema, is not well understood. We develop a fully coupled fluid–solid, three-dimensional computational model to interrogate the various parameters thought to influence valve behavior and the consequences of these changes to overall lymphatic function. A lattice Boltzmann model is used to simulate the lymph, while a lattice spring model is used to model the mechanics of lymphatic valves. Lymphatic valve functions such as enabling lymph flow and preventing backflow under varied lymphatic valve geometries and mechanical properties are investigated to provide an understanding of the function of lymphatic vessels and valves. The simulations indicate that lymphatic valve function is optimized when valves are of low aspect ratio and bending stiffness, so long as these parameters are maintained at high enough values to allow for proper valve closing. This suggests that valve stiffening could have a profound effect on overall lymphatic pumping performance. Furthermore, dynamic valve simulations showed that this model captures the delayed response of lymphatic valves to dynamic flow conditions, which is an essential feature of valve operation. Thus, our model enhances our understanding of how lymphatic pathologies, specifically those exhibiting abnormal valve morphologies such as has been suggested to occur in cases of primary lymphedema, can lead to lymphatic dysfunctions.     

Numerical simulation of steady turbulent flow through trileaflet aortic heart valves—II. Results on five models

Turbulent flow simulations are run for five aortic trileaflet valve geometries, ranging from a valve leaflet orifice area of 1.1 cm² (Model A1—very stenotic) to 5.0 cm² (Model A5—natural valve). The simulated data compares well with experimental measurements made downstream of various aortic trileaflet valves by Woo (PhD Thesis, 1984). The location and approximate width and length of recirculation regions are correctly predicted. The less stenotic valve models reattach at the end of the aortic sinus region, 1.1 diameters downstream of the valve. The central jet exiting the less stenotic valve models is not significantly different from fully developed flow, and therefore recovers very quickly downstream of the reattachment point. The more stenotic valves disturb the flow to a greater degree, generating recirculation regions large enough to escape the sinuses and reattach further downstream. Peak turbulent shear stress values downstream of the aortic valve models which approximated prosthetic valves are 125 and 300 N m⁻², very near experimental observations of 150 to 350 N m⁻². The predicted Reynolds stress profiles also present the correct shape, a double peak profile, with the location of the peak occuring at the location of maximum velocity gradient, which occurs near the recirculation region. The pressure drop across model A2 (leaflet orifice area 1.6 cm²) is 20 mmHg at 1.6 diameters downstream. This compares well with values ranging from 19.5 to 26.2 mmHg for valves of similar orifice areas. The pressure drop decreases with decreasing valve stenosis, to a negligible value across the least stenotic valve model. Based on the good agreement between experimental measurements of velocity, shear stress and pressure drop, compared to the simulated data, the model has the potential to be a valuable tool in the analysis of heart valve designs.     

PERIZONIUM AND INITIAL VALVE FORMATION IN THE DIATOM NAVICULA CUSPIDATA (BACILLARIOPHYCEAE)1

This paper describes the perizonium and initial valve formation in Navicula cuspidata Kütz., based on light microscope (LM) and scanning electron microscope (SEM) observations. The perizonium consists of concentric over-lapping bands, laid down sequentially at the tips of the expanding biconical auxospore during its elongation. The central perizonial band has fimbriate edges and is considerably more rigid than the more distal bands. During auxospore elongation and the band secretion, the chloroplasts continuously oscillate between the two ends of the cell; this oscillation ceases once the elongation is complete. The initial valves, formed within the perizonium, are molded into the basically biconical shape of the perizonium except for a central flattening of each valve face. In contrast to the raphes in gametangial and vegetative valves which are surrounded by a smooth axial area, the raphes in initial valves lie within a raised ridge running along the apical axis of the valve. The regular pattern of apically oriented ridges on the outer surface of vegetative valves is also lacking on initial valves. Comparison of pore–pore spacing within striae of gametangial valves, initial values and post-initial valves (first division and vegetative cells) reveals that the pore–pore distance within striae is conserved at all sexual stages. However, the distance between striae is considerably larger in initial valves than in gametangial and post-initial valves. Vegetative interstriae spacing as well as the planar morphology of the valve face is regained at the first division of the initial cell. This suggests that the spacing between striae is dependent on the sexual stage of the cell during valve formation (i.e. not directly dependent on the cell size) and can be altered independently of the pore–pore spacing.     

Fluid dynamic models as a guide to determine prosthetic heart valve diameter

The diameter of prosthetic heart valves is usually chosen according to the anatomic annulus size as determined during open-heart surgery. Therefore, this approach does not take into account the dimensional changes induced by heart pathology and surgical procedures. In addition, current practice fails to consider the variations of heart dimensions due to hemodynamic improvement following valve replacement. Here we suggest a method to determine the appropriate prosthesis diameter according to the hemodynamic features of the patient, to its kind of activity, and to the type of prosthesis. Assuming that the pressure drop across a valve can be calculated as delta p = apv 2/2, and considering the variation of blood flow with time and its change induced by frequency, it is possible to obtain the relationship between pressure drop and prosthetic valve diameter. The results obtained with this analytical method have been plotted on diagrams which allow the graphical determination of the proper valve diameter.     

A calcified polymeric valve for valve-in-valve applications

The prevalence of aortic valve stenosis (AS) is increasing in the aging society. More recently, novel treatments and devices for AS, especially transcatheter aortic valve replacement (TAVR) have significantly changed the therapeutic approach to this disease. Research and development related to TAVR require testing these devices in the calcified heart valves that closely mimic a native calcific valve. However, no animal model of AS has yet been available. Alternatively, animals with normal aortic valve that are currently used for TAVR experiments do not closely replicate the aortic valve pathology required for proper testing of these devices. To solve this limitation, for the first time, we developed a novel polymeric valve whose leaflets possess calcium hydroxyapatite inclusions immersed in them. This study reports the characteristics and feasibility of these valves. Two types of the polymeric valve, i.e., moderate and severe calcified AS models were developed and tested by deploying a transcatheter valve in those and measuring the related hemodynamics. The valves were tested in a heart flow simulator, and were studied using echocardiography. Our results showed high echogenicity of the polymeric valve, that was correlated to the severity of the calcification. Aortic valve area of the polymeric valves was measured, and the severity of stenosis was defined according to the clinical guidelines. Accordingly, we showed that these novel polymeric valves closely mimic AS, and can be a desired cost-saving solution for testing the performance of the transcatheter aortic valve systems in vitro.     

Variations in atrioventricular valve innervation in four species of mammals

In this series of studies, the innervation patterns of whole-mount preparations of bicuspid and tricuspid valves were studied by light microscopy in the mouse, rat, guinea pig, and opossum. The acetylcholinesterase-positive networks of nerve fibers showed many similarities in the basic patterns of valve innervation in all of the species studied, but several interspecies variations were observed. The basal zone of the valve adjacent to the fibromuscular atrioventricular ring displayed the most dense plexus of nerves, with acetylcholinesterase-positive fibers being seen across the width of the valve. In the intermediate zone of the valve, less dense plexuses of nerve fibers were found; and these were more numerous in the cuspal areas and less numerous in the intervening commissural areas. In the distal portions of the valve, nerve networks arborized extensively, with some of their nerve fibers extending toward the chordae tendineae and the free edges of the valve cusps. Only in the guinea pig and opossum did these fibers reach the free margin of the valve cusp, where they either ended directly as free nerve endings or lay parallel to the free edge of the cusp, often running between adjacent chordae tendineae. Although the patterns of innervation were similar in both bicuspid and tricuspid valves, the innervation density of the bicuspid valve was greater than that of the tricuspid valve for each species examined. A distinguishing feature of guinea pig and opossum tricuspid valves was that their chordae tendineae were relatively more prominent and more densely innervated than the bicuspid chordae tendineae. Free nerve endings with no light microscopic evidence of specialization were present throughout the bicuspid and tricuspid valves of all species studied. Some nerve endings in the opossum showed evidence of specialization, with brush-like arborizations leading to presumed free terminals seen chiefly in the distal zone of the valve cusps. Although some general tendencies were apparent, we have demonstrated that interspecies heterogeneity exists in the terminal networks of the atrioventricular valves of mouse, rat, guinea pig, and opossum.     

Macromolecular transport in heart valves. I. Studies of rat valves with horseradish peroxidase

The present study aims to experimentally elucidate subtle structural features of the rat valve leaflet and the related nature of macromolecular transport across its endothelium and in its subendothelial space, information necessary to construct a rational theoretical model that can explain observation. After intravenous injection of horseradish peroxidase (HRP), we perfusion-fixed the aortic valve of normal Sprague-Dawley rats and found under light microscopy that HRP leaked through the leaflet's endothelium at very few localized brown spots, rather than uniformly. These spots grew nearly as rapidly with HRP circulation time before euthanasia as aortic spots, particularly when the time axis only included the time the valve was closed. These results suggest that macromolecular transport in heart valves depends not only on the direction normal to, but also parallel to, the endothelial surface and that convection, as well as molecular diffusion, plays an important role in macromolecular transport in heart valves. Transmission electron microscopy of traverse leaflet sections after 4-min HRP circulation showed a very thin ( approximately 150 nm), sparse layer immediately beneath the endothelium where the HRP concentration was much higher than that in the matrix below it. Nievelstein-Post et al.'s (Nievelstein-Post P, Mottino G, Fogelman A, Frank J. Arterioscler Thromb 14: 1151-1161, 1994) ultrarapid freezing/rotary shadow etching of the normal rabbit valve's subendothelial space supports the existence of this very thin, very sparse "valvular subendothelial intima," in analogy to the vascular subendothelial intima.     

Polymer actuator valves toward controlled drug delivery application

A novel controlled drug delivery system in which drug release is achieved by electrochemically actuating an array of polymeric valves on a set of drug reservoirs has been developed. The valves are bilayer structures, made in shape of a flap hinged on one side to a valve seat, consisting of thin films of evaporated gold and electrochemically deposited polypyrrole (PPy). Drugs (dry or wet) were pre-stored in an array of these reservoirs and their release is accomplished by bending the bilayer flaps away from the substrate with a small applied bias. In vitro color dye release experiment has been conducted. Seventy-five percent less energy consumption was achieved with this bilayer polymer valve design to open a same size reservoir compared to metal-corrosion based valves. Complex release patterns such as multiple drug pulsatile release and continuous linear release have been successfully implemented through flexible control of valve actuation sequence. These valves can be actuated under closed-loop-control of sensors responding to a specific biological or environmental stimulus, leading to potential applications in advanced responsive drug delivery systems.