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Cytofluorometric quantitation of 5-hydroxytryptamine and heparin in individual mast cell granules.

Cytofluorometric quantitation of 5-hydroxytryptamine (5-HT) and heparin in individual mast cell granules is described. The technique is based on micromanipulation of intact mast cells reacted with formaldehyde or stained with Berberine sulfate and the use of a cytofluorometer equipped with a sensitive peak detecting device. The quantities of 5-HT and heparin contained in mast cell granules which are of the order of 10(-16) and 10(-13) g, respectively were expressed as relative fluorescence guanta. The results of measurements on representative samples of mast cell granules indicate that all granules contain heparin as well as 5-HT, and that there are large variations in both 5-HT and heparin content within the granule populations of individual cells. A dose dependent increase in 5-HT content in both cells and individual mast cell granules occurred 24 hr after the injection of 10--50 mg L-5-hydroxytryptophan/kg intraperitoneally. There was no evidence for an increase in the heparin content of granules or cells, indicating that a new synthesis of granular macromolecules is not required for the 5-HT uptake. The results further suggest that 5-HT may be stored initially in a cytoplasmic extragranular pool and then taken up in the mast cell granules.

5-Hydroxytryptophan↗

Cerebral blood flow and tissue oxygen saturation in immediate and progressive ischemia in rat brain.

The aim of the present study was to investigate whether immediate ischemia is more harmful to the brain than progressive ischemia. To do so, we examined the correlation between the degree and the process of ischemia using hypobaric hypotension technique, which was used to reduce systemic blood pressure acutely or progressively below the lower threshold of CBF regulation, in rat brain. In Wistar rats (n = 21), global ischemia using bilateral carotid arteries occlusion coupled with hypobaric hypotension was induced by lowering mean arterial blood pressure (MABP) progressively to 55, 45 and 35 mmHg or immediately to 35 mm Hg. Local cerebral blood flow (ICBF) by laser Doppler (LD) flowmetry and tissue hemoglobin oxygen saturation (HbSO2) by a microspectrophotometric method were measured at 25 corresponding locations using a 'scanning' technique which employs a computer-controlled micromanipulator. Regional CBF (rCBF) and rHbSO2 were determined by calculation of the median value from the 25 ICBF and IHbSO2 data. In the 'progressive' group, rCBF and rHbSO2 decreased gradually and reached 12.2 +/- 15.8 LD-units and 44.9% +/- 13.4% at 35 mm Hg of MABP, respectively. In the 'immediate' group, both parameters dropped suddenly to 7.86 +/- 10.6 LD-units (p < 0.01 vs. CBF of the progressive group) and 22.5% +/- 15.5% (p < 0.001 vs. tissue HbSO2 of the progressive group) from the control at 35 mmHg. These data suggested that cerebral ischemia is better tolerated if it is induced gradually. CBF recorded by LD-scanning technique and HbSO2 value by microspectrophotometric method correlated well in the ischemic condition, indicating that HbSO2 can be preserved if CBF is decreased gradually.

Animals↗

Tumor cell dissemination in follicular lymphoma.

The derivation of follicular lymphomas (FLs) from germinal centers is not only supported by their morphologic appearance with a nodular growth pattern and a germinal center-like cellular composition, but also by the presence of ongoing somatic hypermutation (a germinal center B cell-specific process) during their clonal expansion. The intraclonal sequence diversity of the tumor cells and their follicular growth pattern allows one to analyze lymphoma cell dissemination and the way the tumor "metastasizes" to distinct follicles. In the present study, we analyzed individual follicles of 3 FLs by micromanipulation of single cells from individual lymphoma follicles and amplification of immunoglobulin V region genes. Genealogical trees for the V(H) and the V(L) gene rearrangements were constructed to analyze the clonal relationship among individual cells of 3 distinct follicles of each case. In all 3 cases there is evidence that distinct tumor follicles are founded by many tumor cells, suggesting that there is extensive migration of the tumor cells among follicles. The observation that the tumor cells of FLs retain their follicular growth patterns despite this cellular migration supports the idea that they depend on the follicular microenvironment for their clonal expansion.

Cell Movement↗

Electron microscope radioautographic evidence of in vivo androgen-binding protein internalization in the rat epididymis principal cells.

The androgen-binding protein (ABP) has been purified from rat testes with a yield of 14% using four steps of HPLC and was subsequently iodinated to a specific activity of 0.1 mCi/mg protein. Using a micromanipulator, [125I] iodo-ABP-dihydrotestosterone was injected intraluminally into the proximal caput of the rat epididymis. Epididymides were sampled from 3 to 120 min after the injection of the tracer and processed for transmission electron microscopy autoradiography. Our results showed the accumulation of detectable radioactive sources in the apical cytoplasm of only one of the epithelial cell type lining the ductus, the principal cells. In the interval from 3 to 120 min, the iodinated ABP was mainly present in the supranuclear region and was especially concentrated over coated structures, endosomes, multivesicular bodies, and over the Golgi apparatus. The same pattern was obtained using [3H]dihydrotestosterone-ABP complex instead of iodinated ABP. In addition, there was a negative correlation between the log time and the distribution of the silver grains in the luminal border and in the compartment of the apical vesicles. On the contrary, there was a positive correlation between the log time and the distribution of the silver grains in the Golgi apparatus. These results provide, for the first time, direct histological evidence of the in vivo ABP internalization by the principal cells. Since horseradish peroxidase, a fluid-phase endocytosis marker, when injected under the same conditions was internalized in both apical and principal cells, since labeled radioactive ABP appeared to be bound to the membrane of the endocytic apparatus rather than to its content, and since this binding and uptake could be prevented in the presence of an excess of unlabeled ABP, it is concluded that the internalization of ABP could not be a nonspecific fluid-phase endocytosis but should be dependent on its interaction with the apical plasma membrane of the principal cell. It still remains to be determined if these mechanisms involve the binding of ABP to a specific membrane receptor.

Androgen-Binding Protein↗

Clinical review 100: Evaluation and treatment of the infertile couple.

Infertility by itself does not threaten physical health but has a strong impact on the psychological and social well-being of couples. In the last two decades, progress in caring for the infertile couple, in particular progress in the field of assisted reproduction and micromanipulation, has provided significant hope for many couples for whom hope could not have been offered in the past. This is especially true for bilateral tubal disease and for male factor infertility, as nearly all couples with male factor infertility can now undergo either one (or more) IVF or ICSI attempt(s). For couples with other causes of infertility, however, the differences in pregnancy rates often do not reach statistical significance. We must also remember that the total cost incurred for successful delivery for couples with a better chance of successful IVF (i.e. those with tubal disease) increases from approximately $55,000 in American dollars for the first cycle to $73,000 by the sixth cycle. Because of these high costs, many insurers in the United States and many public health systems in Europe do not cover or only partially cover these procedures. Consequently, the availability of IVF and related therapies frequently depends on the couple's ability to pay. Therefore, after having established the correct diagnosis, appropriate treatment should be counseled to the infertile couple keeping in mind the following points: 1) in subfertile couples expectant management should be reasonably counselled if the age of the woman is less than 30 yr and the duration of infertility is less than 36 months, even if oligozoospermia is present; 2) superovulation and timed intercourse seems also to be a reasonable approach in couples with anovulatory, mild/moderate endometriosis, and unexplained infertility; 3) in unexplained infertility, ovarian stimulation (with clomiphene or gonadotropin) and IUI seem to offer some advantage over ovarian stimulation and timed intercourse; 4) IVF can be a firstline approach in tubal sterility and when IUI or IPI cannot be performed because the number of motile sperm is insufficient, but is usually also the final treatment attempt when other methods have failed. The outcome of IVF is negatively influenced mainly by the woman's age; however, the number of deliveries is also generally lower in couples with male factor; 5) ICSI is a further option, which should be limited to couples: a) with very poor semen parameters; b) previous failed fertilization; c) presence of obstructive or nonobstructive azoospermia in which ICSI is combined with sperm extraction from the epididymis or the testis; 6) international register studies demonstrate that the risk of malformation after conventional IVF is not increased; 7) some reports suggest that incidence of congenital major and minor malformations is not increased in children born after ICSI. However, the rate of sex chromosome anomalies in ICSI fetuses has been reported to be approximately 1% in 585 prenatal diagnoses, a frequency increased by a factor of 4 if compared with naturally conceived live-born babies. ICSI bypasses the physiological selection of spermatozoa that occurs at the level of the testis and epididymis, and in the female reproductive tract as well as at the sperm-oocyte interface. As genetic abnormalities are present in a significant percentage of infertile males with impaired spermatogenesis, karyotyping and analysis of the Y chromosome for microdeletions should be carried out in all potential ICSI fathers. Screening for cystic fibrosis gene mutations should also be performed in azoospermia caused by congenital absence of the vas deferens and seminal vesicles. Appropriate genetic counseling should be made available to all ICSI couples whenever a gene or chromosomal anomaly has been identified. With most ARTs the average delivery rate per cycle is approximately 15% and the cumulative delivery rate after several cycles is about 50%. (ABSTRACT TRUNCATED)

Endocrinology↗

Prenatal diagnosis of Duchenne muscular dystrophy using a single fetal nucleated erythrocyte in maternal blood.

We developed a method that allows prenatal diagnosis of Duchenne muscular dystrophy using a single nucleated erythrocyte (NRBC) isolated from maternal blood. Maternal blood was obtained at 8 to 20 weeks of gestation. NRBCs were separated with Percoll using a discontinuous density gradient method and then collected by micromanipulator under microscopic observation. The entire genome of a single cell was amplified by primer extension preamplification (PEP). Sex was determined from a small aliquot of the PEP reaction. After an NRBC was determined to be male and confirmed to be of fetal origin, dystrophin exons 4, 8, 12, 45, 48, 50, and 51 were determined from the same PEP reaction. This diagnostic method using maternal blood is safer than amniocentesis or cordocentesis and can be applied to other X-linked diseases.

Base Sequence↗

A micrometric multiple electrode array for the exploration of gasserian and retrogasserian trigeminal fibers: preliminary report. Technical note.

The determination of the target for percutaneous thermocoagulation of the trigeminal rootlets has been generally based on the analysis of subjective clinical verbal and motor responses as assessed by freehand displacement of an electrode active at its straight or curved distal tip. In a previous report, we demonstrated that sensory and motor trigeminal evoked potentials are of practical value when attempting to localize the position of trigeminal electrodes. This report describes the technical features of a multiple electrode array designed to provide simultaneous access to various segments along a chosen trigeminal division or divisions, correlating at each segment clinical and electrophysiological data with radiological landmarks in the individual patient. The system consists of an outer needle with four windows at a distance of 15 mm from the tip. A multiple electrode array occludes the windows with four isolated caps for stimulation and recording. After correlating clinical verbal and motor responses with sensory and motor evoked potentials at each window and inter se, a target window is selected. A thermocouple fitted with a micromanipulator allows the accurate placement of the center of the active tip at the center of the chosen window. Preliminary data from 25 patients indicate that the technique provides a reliable sequential analysis of clinical, electrophysiological, and radiological data along the explored tract.

Aged↗

Cranial paraxial mesoderm: regionalisation of cell fate and impact on craniofacial development in mouse embryos.

A combination of micromanipulative cell grafting and fluorescent cell labelling techniques were used to examine the developmental fate of the cranial paraxial mesoderm of the 8.5-day early-somite-stage mouse embryo. Mesodermal cells isolated from seven regions of the cranial mesoderm, identified on the basis of their topographical association with specific brain segments were assessed for their contribution to craniofacial morphogenesis during 48 hours of in vitro development. The results demonstrate extensive cell mixing between adjacent but not alternate groups of mesodermal cells and a strict cranial-to-caudal distribution of the paraxial mesoderm to craniofacial structures. A two-segment periodicity similar to the origins of the branchial motor neurons and the distribution of the rhombencephalic neural crest cells was observed as the paraxial mesoderm migrates during formation of the first three branchial arches. The paraxial mesoderm colonises the mesenchymal core of the branchial arches, consistent with the location of the muscle plates. A dorsoventral regionalisation of cell fate similar to that of the somitic mesoderm is also found. This suggests evolution has conserved the fate of the murine cranial paraxial mesoderm as a multiprogenitor population which displays a predominantly myogenic fate. Heterotopic transplantation of cells to different regions of the cranial mesoderm revealed no discernible restriction in cell potency in the craniocaudal axis, reflecting considerable plasticity in the developmental fate of the cranial mesoderm at least at the time of experimentation. The distribution of the different groups of cranial mesoderm matches closely with that of the cranial neural crest cells suggesting the two cell populations may share a common segmental origin and similar destination.

Animals↗

Cranial paraxial mesoderm and neural crest cells of the mouse embryo: co-distribution in the craniofacial mesenchyme but distinct segregation in branchial arches.

The spatial distribution of the cranial paraxial mesoderm and the neural crest cells during craniofacial morphogenesis of the mouse embryo was studied by micromanipulative cell grafting and cell labelling. Results of this study show that the paraxial mesoderm and neural crest cells arising at the same segmental position share common destinations. Mesodermal cells from somitomeres I, III, IV and VI were distributed to the same craniofacial tissues as neural crest cells of the forebrain, the caudal midbrain, and the rostral, middle and caudal hindbrains found respectively next to these mesodermal segments. This finding suggests that a basic meristic pattern is established globally in the neural plate ectoderm and paraxial mesoderm during early mouse development. Cells from these two sources mixed extensively in the peri-ocular, facial, periotic and cervical mesenchyme. However, within the branchial arches a distinct segregation of these two cell populations was discovered. Neural crest cells colonised the periphery of the branchial arches and enveloped the somitomere-derived core tissues on the rostral, lateral and caudal sides of the arch. Such segregation of cell populations in the first three branchial arches is apparent at least until the 10.5-day hindlimb bud stage and could be important for the patterning of the skeletal and myogenic derivatives of the arches.

Animals↗

Morphogenetic pattern formation during ascidian notochord formation is regulative and highly robust.

The ascidian notochord forms through simultaneous invagination and convergent extension of a monolayer epithelial plate. Here we combine micromanipulation with time lapse and confocal microscopy to examine how notochord-intrinsic morphogenetic behaviors and interactions with surrounding tissues, determine these global patterns of movement. We show that notochord rudiments isolated at the 64-cell stage divide and become motile with normal timing; but, in the absence of interactions with non-notochordal tissues, they neither invaginate nor converge and extend. We find that notochord formation is robust in the sense that no particular neighboring tissue is required for notochord formation. Basal contact with either neural plate or anterior endoderm/lateral mesenchyme or posterior mesoderm are each alone sufficient to ensure that the notochord plate forms and extends a cylindrical rod. Surprisingly, the axis of convergent extension depends on the specific tissues that contact the notochord, as do other patterns of cell shape change, movement and tissue deformation that accompany notochord formation. We characterize one case in detail, namely, embryos lacking neural plates, in which a normal notochord forms but by an entirely different trajectory. Our results show ascidian notochord formation to be regulative in a fashion and to a degree never before appreciated. They suggest this regulative behavior depends on a complex interplay between morphogenetic tendencies intrinsic to the notochord plate and instructive and permissive interactions with surrounding tissues. We discuss mechanisms that could account for these data and what they imply about notochord morphogenesis and its evolution within the chordate phylum.

Animals↗

Phagosomal oxidative activity during beta2 integrin (CR3)-mediated phagocytosis by neutrophils is triggered by a non-restricted Ca2+ signal: Ca2+ controls time not space.

The temporal and spatial relationship between particle binding to the neutrophil by beta2 integrin (CR3), the Ca2+ elevation and subsequent oxidase activation has been unclear. This is because of the difficulty in studying the time course of individual phagocytic events in individual neutrophils. Here, we have used a micromanipulation technique to present C3bi-opsonised zymosan particles to the neutrophil under observation. In this way, the moment of particle contact, pseudopod formation and internalisation has been established and cytosolic free Ca2+ and oxidation of dichlorodihydrofluorescein (DCDHF)-labelled particles determined simultaneously. Using this approach, we have found that the Ca2+ signal, which is triggered by CR3-mediated phagocytosis, can be resolved into two temporally separated components. The first Ca2+ signal occurs during beta2 integrin engagement as the phagocytic cup forms but does not trigger oxidation of the particle. The second global Ca2+ signal, which is triggered about the time of phagosomal closure, causes an abrupt activation of the oxidase. This second Ca2+ signal was not restricted to the region of the phagosome yet only triggered the oxidase activation locally in the phagosome, with no evidence of activation at other sites in the neutrophil. This points to a dual control of oxidase activation, with Ca2+ controlling the timing of oxidase activation but slower and more localised molecular events, perhaps involving oxidase assembly and phosphatidylinositol 3-phosphate generation, determining the site of oxidase activation.

Anticoagulants↗

Force contribution of the LFA-1/ICAM-1 complex to T cell adhesion.

Little is known in quantitative terms about forces between cells generated during adhesion and recognition, or about the contribution of any one set of molecular associations to the development of these forces. To determine the forces involved in adhesion dependent on lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1), we have measured the junctional avidity between single cell pairs consisting of a cloned T cell that expresses LFA-1 and a fibroblast cell that expresses MHC class II molecules and ICAM-1 after transfection. Micromanipulation was used to induce conjugation of cell pairs and to determine the force required to separate the conjugate. T cell adhesion to three related fibroblast cell lines was compared: the parent line that does not express ICAM-1 or other LFA-1 counter-receptors, and two transfectants that have high and moderate levels of surface ICAM-1 expression. The force needed to separate the conjugates varied with the fibroblast ICAM-1 expression levels. The T cell adhesion to ICAM-1-expressing fibroblasts was strong, and the critical separation stresses measured for the three cell lines were 1.4 x 10(3) dyn/cm2 (1 dyn=10(-5) N) for the ICAM-1-negative fibroblast, 4.98 x 10(3) dyn/cm2 for the fibroblast with a moderate level of ICAM-1 expression, and 6.25 x 10(3) dyn/cm2 for the fibroblast line with the highest ICAM-1 expression. The dependence of adhesion strength on the LFA-1/ICAM-1 complex was confirmed by the use of blocking antibodies, which showed the contribution from the interaction of CD4/MHC class II to be negligible.

Animals↗

A casein kinase I isoform is required for proper cell cycle progression in the fertilized mouse oocyte.

Casein kinase I is a family of serine/threonine protein kinases common to all eukaryotes. In yeast, casein kinase I homologues have been linked to the regulation of growth, DNA repair and cell division. In addition, their subcellular localization to membraneous structures and the nucleus is essential for function. In higher eukaryotes, there exist seven genetically distinct isoforms: (alpha), ss, (gamma)1, (gamma)2, (gamma)3, (delta) and (epsilon). Casein kinase I(alpha) exhibits a cell cycle-dependent subcellular localization including an association with cytosolic vesicular structures and the nucleus during interphase, and the spindle during mitosis. casein kinase I has also been shown to modulate critical regulators of growth and DNA synthesis/repair in mammalian cells such as SV40 large T antigen and p53. These results suggest that casein kinase I may be involved in processes similar to those ascribed to the yeast casein kinase I homologues. To define a role for casein kinase I(alpha) in cell cycle regulation, the mouse oocyte was utilized because of its well-defined cell cycle and ease of micromanipulation. Immunofluorescence studies from meiosis I of maturation to the first zygotic cleavage demonstrated that the kinase was associated with structures similar to those previously reported. Microinjection of casein kinase I(alpha) antibodies at metaphase II-arrest and G2 phase, had no effect on the completion of second meiosis or first division. However, microinjection of these antibodies during the early pronucleate phase prior to S-phase onset blocked uptake of the kinase into pronuclei and interfered with proper and timely cell cycle progression to first cleavage. These results suggest that the kinase regulates the progression from interphase to mitosis during the first cell cycle.

Animals↗

Tension on chromosomes increases the number of kinetochore microtubules but only within limits.

When chromosomes attach properly to a mitotic spindle, their kinetochores generate force in opposite directions, creating tension. Tension is presumed to increase kinetochore microtubule number, but there has been no direct evidence this is true. We micromanipulated grasshopper spermatocyte chromosomes to test this assumption and found that tension does indeed affect the number of kinetochore microtubules. Releasing tension at kinetochores causes a drop to less than half the original number of kinetochore microtubules. Restoring tension onto these depleted kinetochores restores the microtubules to their original number. However, the effects of tension are limited. Prometaphase kinetochores, when under normal tension from mitotic forces, have about half as many microtubules as they will in late metaphase. We imposed a tension force of 6 x 10(-5) dynes, three times the normal tension, on prometaphase kinetochores. The elevated tension did not drive kinetochore microtubule number above normal prometaphase values. Tension probably increases the number of kinetochore microtubules by slowing their turnover rate. The limited effect of tension at prometaphase kinetochores suggests that they have fewer microtubule binding sites than at late metaphase. The relatively few sites available in prometaphase may be the decisive sites whose binding of microtubules regulates the dynamics of transient kinetochore constituents, including checkpoint components.

Animals↗

Checkpoint signals in grasshopper meiosis are sensitive to microtubule attachment, but tension is still essential.

The spindle checkpoint detects errors in kinetochore attachment to microtubules and delays anaphase if attachment is improper. The checkpoint is activated by attachment-sensitive components including Mad2 and certain phosphorylated proteins detected by the 3F3/2 antibody. We have studied Mad2 and 3F3/2 immunofluorescence in grasshopper spermatocytes. As in other cells, unattached kinetochores are loaded with Mad2 and are highly phosphorylated, whereas after proper attachment, Mad2 is lost and kinetochores are dephosphorylated. What is it about proper attachment that produces these changes--is it microtubule attachment itself or is it the tension from mitotic forces that follows proper attachment? Using micromanipulation, we created an intermediate state, weak attachment, that provides an answer. Weakly attached kinetochores are not under tension and have few kinetochore microtubules. Despite the absence of tension, many weakly attached kinetochores lose their Mad2 and become dephosphorylated. Therefore we conclude that microtubule attachment determines both Mad2 binding and phosphorylation. Nevertheless, tension plays an absolutely essential role. Tension elevates the number of kinetochore microtubules to the level necessary for the complete loss of Mad2 and dephosphorylation from all kinetochores. This gives a reliable 'all clear' signal to the checkpoint, allowing the cell to progress to anaphase.

Animals↗

Mussel MAP, a major gonad-duct esterase-like protein, is released into sea water as a dual constituent of the seminal fluid and the spermatozoon.

Our interest in the comparative analysis of male reproductive-tract esterases in different animal groups has led us to undertake a detailed study of the Mytilus galloprovincialis male-associated polypeptide (MAP) throughout the mussel gonad-duct tract and at spawning. The results of this work indicate that MAP is a major protein in M. galloprovincialis semen, with dual presence in both sperm cells and cell-free seminal fluid. Shortly after spawning, the released sperm mass is subdivided in diffused cloudy-like and thread-shaped 'clots', in which a soluble-phase MAP may persist as long as the clots keep their compact form. Additional experiments involving the incubation of spawned spermatozoa at increasing Triton X-100 concentrations demonstrated that MAP is also strongly associated with sperm cells. These results were further validated by immunofluorescent staining, which revealed that MAP is localized in the mid-piece region of spawned spermatozoa. This unexpected finding raises the possibility that MAP may play a role in sperm fertility in bivalves. Using whole-mount histology and micromanipulation techniques, we studied the structural patterning of the mantle gonad-duct network and assessed the sampling of luminal contents from the ducts. Of particular interest is the observation that MAP content in the luminal fluid increases from the lumen of the spermatogenic tubules to that of the collecting gonad ducts, where MAP is detected at a very high concentration. These high levels may lead to a significant presence of MAP in semen and consequently to a prolonged survival of sperm spawned at sea. In addition, data related to the potential structural similarity between mussel MAP and esterase S of the Drosophila virilis ejaculatory bulb are presented and discussed. Finally, we show that the 64kDa protein of human semen reveals positive cross-reactivity with antibodies directed against Mytilus MAP and Drosophila esterase S. Taken together, the results reveal mussel MAP as the only esterase-like protein described so far whose distribution in the gonad and semen can be specifically associated with maturation, transport, emission and survival of spermatozoa outside.

Amino Acid Sequence↗

Requirement of the fixed end for spontaneous beating in flagella.

It is well known that any part of a flagellum has the ability to bend. However, it is not clearly understood how flagella generate successive bending waves spontaneously. Some micromanipulation experiments have suggested that the base of the flagellum is required. By contrast, spontaneous bending waves could be generated in computer simulation work if the microtubules were tied together at one end. We hypothesized that the basal structure of flagella can only act as a tied end when the outer doublet microtubules are tightly bound together so as not to slide. We developed a new technique for introducing local inhibition at any position on the demembranated and reactivated flagellum. The flagellum maintained spontaneous beating when the local inhibition was introduced at any position on it. In addition, spontaneous beating occurred without the basal body when an artificial fixed region was introduced to the flagellum. We conclude that the axoneme, a bundle of microtubules, requires the fixed end for spontaneous beating.

2-Naphthylamine↗

Specific behavioural responses triggered by identified mechanosensory receptor cells in the apical field of the giant rotifer Asplanchna sieboldi.

The giant rotifer Asplanchna sieboldi swims by the propulsive effect of thousands of cilia arrayed in clusters around the apical field, which has several mechanosensory structures (sensilla) located at defined positions. Males and females differ in both their patterns of behaviour and their sensory receptor equipment. Unstimulated males swim straight with occasional spontaneous changes in direction until they hit an obstacle with their apical field. Depending on the direction and the strength of the mechanical interference, the animals show different behavioural responses. To analyse the effect of excitation of the apical mechanosensitive sensilla on these responses, males were held on microcapillaries, and the sensitivity of individual sensilla was assayed using micromanipulator-mediated mechanical stimulation. Stimulation of each of the four different types of sensillum triggered a specific and well-defined initial behavioural response. Individual animals behaved identically with respect to the receptor specificity of the responses. The behaviour of free-swimming males upon contact with obstacles or females is discussed on the basis of these results.

Animals↗