ZYP1-mediated recruitment of PCH2 to the synaptonemal complex remodels the chromosome axis leading to crossover restriction

Chromosome axis-associated HORMA domain proteins (HORMADs), e.g. ASY1 in Arabidopsis, are crucial for meiotic recombination. ASY1, as other HORMADs, is assembled on the axis at early meiosis and depleted when homologous chromosomes synapse. Puzzlingly, both processes are catalyzed by AAA+ ATPase PCH2 together with its cofactor COMET. Here, we show that the ASY1 remodeling complex is temporally and spatially differently assembled. While PCH2 and COMET appear to directly interact in the cytoplasm in early meiosis, PCH2 is recruited by the transverse filament protein ZYP1 and brought to the ASY1-bound COMET assuring the timely removal of ASY1 during chromosome synapsis. Since we found that the PCH2 homolog TRIP13 also binds to the ZYP1 homolog SYCP1 in mouse, we postulate that this mechanism is conserved among eukaryotes. Deleting the PCH2 binding site of ZYP1 led to a failure of ASY1 removal. Interestingly, the placement of one obligatory crossover per homologous chromosome pair, compromised by ZYP1 depletion, is largely restored in this separation-of-function zyp1 allele suggesting that crossover assurance is promoted by synapsis. In contrast, this zyp1 allele, similar to the zyp1 null mutant, showed elevated type I crossover numbers indicating that PCH2-mediated eviction of ASY1 from the axis restricts crossover formation.

Non-cell-autonomous regulation of petal initiation in Arabidopsis thaliana

In many flowering plants, petals initiate in alternate positions from first whorl sepals, suggesting possible signaling between sepal boundaries and petal initiation sites. PETAL LOSS (PTL) and RABBIT EARS (RBE) regulate petal initiation in Arabidopsis thaliana and their transcripts are expressed in sepal boundary and petal initiation sites, respectively, suggesting that PTL acts in a non-cell-autonomous manner. Here, we determined that cells expressing PTL and RBE fusion proteins did not overlap but were adjacent, confirming the non-cell-autonomous function of PTL. Genetic ablation of intersepal cells by expressing the diphtheria toxin-A chain gene driven by the PTL promoter resulted in flowers lacking petals, suggesting these cells are required for petal initiation. Transcriptome analysis combined with a PTL induction system revealed 42 genes that were upregulated under PTL activation, including UNUSUAL FLORAL ORGANS (UFO), which likely plays an important role in petal initiation. These findings suggest a molecular mechanism in which PTL indirectly regulates petal initiation and UFO mediates positional signaling between the sepal boundary and petal initiation sites.

Caught in the Act: Live-Cell Imaging of Plant Meiosis

Live-cell imaging is a powerful method to obtain insights into cellular processes, particularly with respect to their dynamics. This is especially true for meiosis, where chromosomes and other cellular components such as the cytoskeleton follow an elaborate choreography over a relatively short period of time. Making these dynamics visible expands understanding of the regulation of meiosis and its underlying molecular forces. However, the analysis of meiosis by live-cell imaging is challenging; specifically in plants, a temporally resolved understanding of chromosome segregation and recombination events is lacking. Recent advances in live-cell imaging now allow the analysis of meiotic events in plants in real time. These new microscopy methods rely on the generation of reporter lines for meiotic regulators and on the establishment of ex vivo culture and imaging conditions, which stabilize the specimen and keep it alive for several hours or even days. In this review, we combine an overview of the technical aspects of live-cell imaging in plants with a summary of outstanding questions that can now be addressed to promote live-cell imaging in Arabidopsis and other plant species and stimulate ideas on the topics that can be addressed in the context of plant meiotic recombination.

CDKD-dependent activation of CDKA;1 controls microtubule dynamics and cytokinesis during meiosis

Precise control of cytoskeleton dynamics and its tight coordination with chromosomal events are key to cell division. This is exemplified by formation of the spindle and execution of cytokinesis after nuclear division. Here, we reveal that the central cell cycle regulator CYCLIN DEPENDENT KINASE A;1 (CDKA;1), the Arabidopsis homologue of Cdk1 and Cdk2, partially in conjunction with CYCLIN B3;1 (CYCB3;1), is a key regulator of the microtubule cytoskeleton in meiosis. For full CDKA;1 activity, the function of three redundantly acting CDK-activating kinases (CAKs), CDKD;1, CDKD;2, and CDKD;3, is necessary. Progressive loss of these genes in combination with a weak loss-of-function mutant in CDKA;1 allowed a fine-grained dissection of the requirement of cell-cycle kinase activity for meiosis. Notably, a moderate reduction of CDKA;1 activity converts the simultaneous cytokinesis in Arabidopsis, i.e., one cytokinesis separating all four meiotic products concurrently into two successive cytokineses with cell wall formation after the first and second meiotic division, as found in many monocotyledonous species.

Functional Analysis of the Plant Chromosomal Passenger Complex

The Aurora B kinase, encoded by the AURORA 3 (AUR3) gene in Arabidopsis (Arabidopsis thaliana), is a key regulator of cell division in all eukaryotes. Aurora B has at least two central functions during cell division; it is essential for the correct, i.e. balanced, segregation of chromosomes in mitosis and meiosis by controlling kinetochore function, and it acts at the division plane, where it is necessary to complete cytokinesis. To accomplish these two spatially distinct functions, Aurora B in animals is guided to its sites of action by Borealin, inner centromere protein (INCENP), and Survivin, which, together with Aurora B, form the chromosome passenger complex (CPC). However, besides Aurora homologs, only a candidate gene with restricted homology to INCENP has been described in Arabidopsis, raising the question of whether a full complement of the CPC exists in plants and how Aurora homologs are targeted subcellularly. Here, we have identified and functionally characterized a Borealin homolog, BOREALIN RELATED (BORR), in Arabidopsis. Together with detailed localization studies including the putative Arabidopsis INCENP homolog, these results support the existence of a CPC in plants.

A Practical Guide to Live-Cell Imaging of Meiosis in Arabidopsis

Plants are powerful model systems to study meiosis. Our knowledge about the cytology of plant meiosis is mainly based on the analysis of fixed material. Although highly informative, this approach is limited in understanding the dynamics of meiosis. Here, we present a step-by-step instruction for a newly developed method to follow meiosis in male meiocytes of Arabidopsis in real time by confocal laser scanning microscopy. We envision that this method can be easily translated to other plant species and especially crops (e.g., Brassica, maize, and potato).

The Arabidopsis Cdk1/Cdk2 homolog CDKA;1 controls chromosome axis assembly during plant meiosis

Meiosis is key to sexual reproduction and genetic diversity. Here, we show that the Arabidopsis cyclin-dependent kinase Cdk1/Cdk2 homolog CDKA;1 is an important regulator of meiosis needed for several aspects of meiosis such as chromosome synapsis. We identify the chromosome axis protein ASYNAPTIC 1 (ASY1), the Arabidopsis homolog of Hop1 (homolog pairing 1), essential for synaptonemal complex formation, as a target of CDKA;1. The phosphorylation of ASY1 is required for its recruitment to the chromosome axis via ASYNAPTIC 3 (ASY3), the Arabidopsis reductional division 1 (Red1) homolog, counteracting the disassembly activity of the AAA⁺ ATPase PACHYTENE CHECKPOINT 2 (PCH2). Furthermore, we have identified the closure motif in ASY1, typical for HORMA domain proteins, and provide evidence that the phosphorylation of ASY1 regulates the putative self-polymerization of ASY1 along the chromosome axis. Hence, the phosphorylation of ASY1 by CDKA;1 appears to be a two-pronged mechanism to initiate chromosome axis formation in meiosis.

SWITCH 1/DYAD is a WINGS APART-LIKE antagonist that maintains sister chromatid cohesion in meiosis

Mitosis and meiosis both rely on cohesin, which embraces the sister chromatids and plays a crucial role for the faithful distribution of chromosomes to daughter cells. Prior to the cleavage by Separase at anaphase onset, cohesin is largely removed from chromosomes by the non-proteolytic action of WINGS APART-LIKE (WAPL), a mechanism referred to as the prophase pathway. To prevent the premature loss of sister chromatid cohesion, WAPL is inhibited in early mitosis by Sororin. However, Sororin homologs have only been found to function as WAPL inhibitors during mitosis in vertebrates and Drosophila. Here we show that SWITCH 1/DYAD defines a WAPL antagonist that acts in meiosis of Arabidopsis. Crucially, SWI1 becomes dispensable for sister chromatid cohesion in the absence of WAPL. Despite the lack of any sequence similarities, we found that SWI1 is regulated and functions in a similar manner as Sororin hence likely representing a case of convergent molecular evolution across the eukaryotic kingdom.

Dynamic F-actin movement is essential for fertilization in Arabidopsis thaliana

In animals, microtubules and centrosomes direct the migration of gamete pronuclei for fertilization. By contrast, flowering plants have lost essential components of the centrosome, raising the question of how flowering plants control gamete nuclei migration during fertilization. Here, we use Arabidopsis thaliana to document a novel mechanism that regulates F-actin dynamics in the female gametes and is essential for fertilization. Live imaging shows that F-actin structures assist the male nucleus during its migration towards the female nucleus. We identify a female gamete-specific Rho-GTPase that regulates F-actin dynamics and further show that actin-myosin interactions are also involved in male gamete nucleus migration. Genetic analyses and imaging indicate that microtubules are dispensable for migration and fusion of male and female gamete nuclei. The innovation of a novel actin-based mechanism of fertilization during plant evolution might account for the complete loss of the centrosome in flowering plants.

Live imaging of calcium spikes during double fertilization in Arabidopsis

Ca²⁺ waves and oscillation are key signalling elements during the fertilization process of animals, and are involved, for example, in egg activation. In the unique double fertilization process in flowering plants, both the egg cell and the neighbouring central cell fuse with a sperm cell each. Here we succeeded in imaging cytosolic Ca²⁺ in these two cells, and in the two synergid cells that accompany the gametes during semi-in vivo double fertilization. Following pollen tube discharge and plasmogamy, the egg and central cells displayed transient Ca²⁺ spikes, but not oscillations. Only the events in the egg cell correlated with the plasmogamy. In contrast, the synergid cells displayed Ca²⁺ oscillations on pollen tube arrival. The two synergid cells showed distinct Ca²⁺ dynamics depending on their respective roles in tube reception. These Ca²⁺ dynamics in the female gametophyte seem to represent highly specific signatures that coordinate successful double fertilization in the flowering plants.

Intracellular calcium waves are key signalling elements during the fertilization process of animals, involved in egg activation. Here the authors image calcium oscillations during the fertilization process in flowering plants, revealing specific signatures involved in the success of this process.

Septins promote dendrite and axon development by negatively regulating microtubule stability via HDAC6-mediated deacetylation

Neurite growth requires two guanine nucleotide-binding protein polymers of tubulins and septins. However, whether and how those cytoskeletal systems are coordinated was unknown. Here we show that the acute knockdown or knockout of the pivotal septin subunit SEPT7 from cerebrocortical neurons impairs their interhemispheric and cerebrospinal axon projections and dendritogenesis in perinatal mice, when the microtubules are severely hyperacetylated. The resulting hyperstabilization and growth retardation of microtubules are demonstrated in vitro. The phenotypic similarity between SEPT7 depletion and the pharmacological inhibition of α-tubulin deacetylase HDAC6 reveals that HDAC6 requires SEPT7 not for its enzymatic activity, but to associate with acetylated α-tubulin. These and other findings indicate that septins provide a physical scaffold for HDAC6 to achieve efficient microtubule deacetylation, thereby negatively regulating microtubule stability to an optimal level for neuritogenesis. Our findings shed light on the mechanisms underlying the HDAC6-mediated coupling of the two ubiquitous cytoskeletal systems during neural development.

Septins are a family of heteropolymerizing GTP/GDP-binding proteins and are implicated in neuritogenesis in nematodes. Ageta-Ishihara et al. show that septins also facilitate this process in the developing mouse brain as scaffolds that coordinate HDAC6-mediated deacetylation of microtubules.

An EAR-Dependent Regulatory Module Promotes Male Germ Cell Division and Sperm Fertility in Arabidopsis

The production of the sperm cells in angiosperms requires coordination of cell division and cell differentiation. In Arabidopsis thaliana, the germline-specific MYB protein DUO1 integrates these processes, but the regulatory hierarchy in which DUO1 functions is unknown. Here, we identify an essential role for two germline-specific DUO1 target genes, DAZ1 and DAZ2, which encode EAR motif-containing C₂H₂-type zinc finger proteins. We show that DAZ1/DAZ2 are required for germ cell division and for the proper accumulation of mitotic cyclins. Importantly, DAZ1/DAZ2 are sufficient to promote G2- to M-phase transition and germ cell division in the absence of DUO1. DAZ1/DAZ2 are also required for DUO1-dependent cell differentiation and are essential for gamete fusion at fertilization. We demonstrate that the two EAR motifs in DAZ1/DAZ2 mediate their function in the male germline and are required for transcriptional repression and for physical interaction with the corepressor TOPLESS. Our findings uncover an essential module in a regulatory hierarchy that drives mitotic transition in male germ cells and implicates gene repression pathways in sperm cell formation and fertility.

Ca2+-activated reactive oxygen species production by Arabidopsis RbohH and RbohJ is essential for proper pollen tube tip growth

In flowering plants, pollen germinates on the stigma and pollen tubes grow through the style to fertilize the ovules. Enzymatic production of reactive oxygen species (ROS) has been suggested to be involved in pollen tube tip growth. Here, we characterized the function and regulation of the NADPH oxidases RbohH and RbohJ (Respiratory burst oxidase homolog H and J) in pollen tubes in Arabidopsis thaliana. In the rbohH and rbohJ single mutants, pollen tube tip growth was comparable to that of the wild type; however, tip growth was severely impaired in the double mutant. In vivo imaging showed that ROS accumulation in the pollen tube was impaired in the double mutant. Both RbohH and RbohJ, which contain Ca(2+) binding EF-hand motifs, possessed Ca(2+)-induced ROS-producing activity and localized at the plasma membrane of the pollen tube tip. Point mutations in the EF-hand motifs impaired Ca(2+)-induced ROS production and complementation of the double mutant phenotype. We also showed that a protein phosphatase inhibitor enhanced the Ca(2+)-induced ROS-producing activity of RbohH and RbohJ, suggesting their synergistic activation by protein phosphorylation and Ca(2+). Our results suggest that ROS production by RbohH and RbohJ is essential for proper pollen tube tip growth, and furthermore, that Ca(2+)-induced ROS positive feedback regulation is conserved in the polarized cell growth to shape the long tubular cell.

Spatial distribution of the RABBIT EARS protein and effects of its ectopic expression in Arabidopsis thaliana flowers

In many flowering plants, flowers consist of two peripheral organs, sepals and petals, occurring in outer two whorls, and two inner reproductive organs, stamens and carpels. These organs are arranged in a concentric pattern in a floral meristem, and the organ identity is established by the combined action of floral homeotic genes expressed along the whorls. Floral organ primordia arise at fixed positions in the floral meristem within each whorl. The RABBIT EARS (RBE) gene is transcribed in the petal precursor cells and primordia, and regulates petal initiation and early growth in Arabidopsis thaliana. We investigated the spatial and temporal expression pattern of a RBE protein fused to the green fluorescent protein (GFP). Expression of the GFP:RBE fusion gene under the RBE cis-regulatory genomic fragment rescues the rbe petal defects, indicating that the fusion protein is functional. The GFP signal is located to the cells where RBE is transcribed, suggesting that RBE function is cell-autonomous. Ectopic expression of GFP:RBE under the APETALA1 promoter causes the homeotic conversion of floral organs, resulting in sterile flowers. In these plants, the class B homeotic genes APETALA3 and PISTILLATA are down-regulated, suggesting that the restriction of the RBE expression to the petal precursor cells is crucial for flower development.

The simplest integrated multicellular organism unveiled

Volvocine green algae represent the "evolutionary time machine" model lineage for studying multicellularity, because they encompass the whole range of evolutionary transition of multicellularity from unicellular Chlamydomonas to >500-celled Volvox. Multicellular volvocalean species including Gonium pectorale and Volvox carteri generally have several common morphological features to survive as integrated multicellular organisms such as "rotational asymmetry of cells" so that the cells become components of the individual and "cytoplasmic bridges between protoplasts in developing embryos" to maintain the species-specific form of the multicellular individual before secretion of new extracellular matrix (ECM). However, these morphological features have not been studied in the four-celled colonial volvocine species Tetrabaena socialis that is positioned in the most basal lineage within the colonial or multicellular volvocine greens. Here we established synchronous cultures of T. socialis and carried out immunofluorescence microscopic and ultrastructural observations to elucidate these two morphological attributes. Based on immunofluorescence microscopy, four cells of the mature T. socialis colony were identical in morphology but had rotational asymmetry in arrangement of microtubular rootlets and separation of basal bodies like G. pectorale and V. carteri. Ultrastructural observations clearly confirmed the presence of cytoplasmic bridges between protoplasts in developing embryos of T. socialis even after the formation of new flagella in each daughter protoplast within the parental ECM. Therefore, these two morphological attributes might have evolved in the common four-celled ancestor of the colonial volvocine algae and contributed to the further increase in cell number and complexity of the multicellular individuals of this model lineage. T. socialis is one of the simplest integrated multicellular organisms in which four identical cells constitute the individual.

Double fertilization on the move

Double fertilization is a flowering plant mechanism whereby two immotile sperm cells fertilize two different female gametes. One of the two sperm cells fertilizes the egg cell to produce the embryo and the other fertilizes the central cell to produce the endosperm. Despite the biological and agricultural significance of double fertilization, the mechanism remains largely unknown owing to difficulties associated with the embedded structure of female gametes in the maternal tissue. However, molecular genetic approaches combined with novel live-cell imaging techniques have begun to clarify the actual behavior of the sperm cells, which is different from that described by previous hypotheses. In this review article, we discuss the mechanism of double fertilization based on the dynamics of the two sperm cells in Arabidopsis.

Sperm entry is sufficient to trigger division of the central cell but the paternal genome is required for endosperm development in Arabidopsis

Fertilization in flowering plants involves two sperm cells and two female gametes, the egg cell and the central cell, progenitors of the embryo and the endosperm, respectively. The mechanisms triggering zygotic development are unknown and whether both parental genomes are required for zygotic development is unclear. In Arabidopsis, previous studies reported that loss-of-function mutations in CYCLIN DEPENDENT KINASE A1 (CDKA;1) impedes cell cycle progression in the pollen leading to the production of a single sperm cell. Here, we report that a significant proportion of single cdka;1 pollen delivers two sperm cells, leading to a new assessment of the cdka;1 phenotype. We performed fertilization of wild-type ovules with cdka;1 mutant sperm cells and monitored in vivo the fusion of the male and female nuclei using fluorescent markers. When a single cdka;1 sperm was delivered, either female gamete could be fertilized leading to similar proportions of seeds containing either a single endosperm or a single embryo. When two cdka;1 sperm cells were released, they fused to each female gamete. Embryogenesis was initiated but the fusion between the nuclei of the sperm cell and the central cell failed. The failure of karyogamy in the central cell prevented incorporation of the paternal genome, impaired endosperm development and caused seed abortion. Our results thus support that the paternal genome plays an essential role during early seed development. However, sperm entry was sufficient to trigger central cell mitotic division, suggesting the existence of signaling events associated with sperm cell fusion with female gametes.

Double fertilization - caught in the act

In flowering plants, fertilization is unique because it involves two pairs of male and female gametes, a process known as double fertilization. Here, we provide an overview of the field and a detailed review of the outstanding recent advances, including in vivo imaging of double fertilization and the identification of a signaling pathway controlling the release of the male gametes and of a protein involved in gamete membrane fusion. These recent results are stepping stones for further research; our knowledge of double fertilization is expanding as newly discovered molecular pathways are explored and new mutants are characterized. Controlling plant fertilization is essential for seed production, and molecular understanding of double fertilization will provide the tools to improve crops and breeding programs.

Distinct dynamics of HISTONE3 variants between the two fertilization products in plants

Sexual reproduction involves epigenetic reprogramming comprising DNA methylation and histone modifications. In addition, dynamics of HISTONE3 (H3) variant H3.3 upon fertilization are conserved in animals, suggesting an essential role. In contrast to H3, H3.3 marks actively transcribed regions of the genome and can be deposited in a replication-independent manner. Although H3 variants are conserved in plants, their dynamics during fertilization have remained unexplored. We overcame technical limitations to live imaging of the fertilization process in Arabidopsis thaliana and studied dynamics of the male-gamete-specific H3.3 and the centromeric Histone Three Related 12 (HTR12). The double-fertilization process in plants produces the zygote and the embryo-nourishing endosperm. We show that the zygote is characterized by replication-independent removal of paternal H3.3 and homogeneous incorporation of parental chromatin complements. In the endosperm, the paternal H3.3 is passively diluted by replication while the paternal chromatin remains segregated apart from the maternal chromatin (gonomery). Hence epigenetic regulations distinguish the two products of fertilization in plants. H3.3-replication-independent dynamics and gonomery also mark the first zygotic divisions in animal species. We thus propose the convergent selection of parental epigenetic imbalance involving H3 variants in sexually reproducing organisms.

Quiet MRI with novel acoustic noise reduction

Fast scan techniques, which are used to reduce scanning times, have raised scanning noise levels in magnetic resonance imaging (MRI) systems, resulting in greater patient discomfort and stress. It is well known that this noise is caused by vibration of the gradient coil due to the Lorentz forces generated by the current in the gradient coil, which is placed in a static magnetic field. We have confirmed that MRI noise can be substantially reduced by sealing the gradient coil in a vacuum chamber to block airborne vibration propagation, by supporting the gradient coil independently to block solid vibration propagation and by decreasing the eddy currents induced in RF coils, the RF shield and the static-field-magnet cryostat. Based on these findings, we have developed a silent MRI system in which scanning noise is markedly reduced under a wide range of scanning conditions.

Massive subchorionic hematoma (Breus' mole) complicated by intrauterine growth retardation

We present here a case of massive subchorionic hematoma complicated by intrauterine growth retardation and oligohydramnios diagnosed at 22 weeks' gestation. The patient was managed with the following medications: (1) tocolysis with ritodrine infusion, (2) 10%maltose infusion therapy (1500mL/day), (3) antibiotic infusion (cefotaxim sodium, 2 g/dayx7) and (4) kampo therapy with Sairei-to until delivery. At 33 weeks and 0 days' gestation, a female baby weighing 1,342 g was delivered without complication by caesarean section. During surgery, an escape of about 500~600 g of dark brown blood with no clots was noted from the subchorionic space of the placenta. Examination of the placenta showed a large fibrosis with well-defined margins on the fetal surface.

Mechanical contraction property of the levator veli palatini muscle

Twenty adult dogs anesthetized with sodium pentobarbital were used as experimental animals in an analysis of the mechanical contraction properties of the levator veli palatini muscle. The following results were obtained: the contraction time and half relaxation time of maximal isometric twitch of the muscle were revealed to be 43 msec and 33 msec, respectively; a summation curve was obtained with stimulation at 15 Hz and maximal tetanic tension was at 70 Hz. The average of the tetanic tension ratio was found to be 5.7. The maximum rate of tension rise was observed at 150 Hz, and the value was twice the rate of the twitch contraction. The duration time of the active state plateau showed values of 3.9 to 4.5 msec. The contraction time of the levator veli palatini muscle closely resembles that of the intrinsic laryngeal and the orbicularis oris muscle.

[Radial flap: a valuable fasciocutaneous flap for intra-oral reconstruction]

The radial forearm flap, or the forearm flap, is called "Chinese flap" for its development of the chinese doctors, and is originally designed for the correction to the post-burn contraction of the face and neck. The radial forearm flap is one of the fasciocutaneous flap, supplied by the radial artery, and transferred as a single-stage reconstruction micro-surgically. In oral and maxillofacial region, the deltopectral flap (D-P flap) and the pectralis major myocutaneous flap (P-M-M-C flap) are mainly used for the reconstruction. These flaps, however, are sometimes too bulky and limited to transfer, and more require two-stage operations. On the other hand, as the forearm flap being thin and pliable, some doctors use this flap micro-surgically at single-stage free flap reconstruction. Before two years, we have begun to transfer the radial forearm flap for the intra-oral reconstruction. The operation method is as follows. Design and Elevation of the Radial Forearm Flap 1. Using the ultrasonic doppler flow meter, the radial artery and the subcutaneous forearm veins are marked on the skin. 2. The flap is designed 20% larger according to the pattern to be reconstructed, with the distal section of the radial artery as an axis on the forearm and the median vein of forearm inclusively. 3. Before the operation, Allen test must be performed in order to determine whether the hand will survive without a radial arterial in-put. 4. The operation is performed with a arm tourniquet. The margin of the flap are incised down to the deep fascia, isolating and preserving the proximal subcutaneous veins as required.(ABSTRACT TRUNCATED AT 250 WORDS)

Coordination of the levator veli palatini and intrinsic laryngeal muscles: an evoked electromyographic study in the dog

Fourteen dogs anesthetized with sodium pentobarbital were used as experimental animals in an electromyographic study of the functional relationships among the levator veli palatini and the intrinsic laryngeal muscles. The following results were obtained: A single pulse stimulation to the afferent fibers of the pharyngeal branches of the glossopharyngeal nerve evoked ipsilateral reflexes from the levator veli palatini and laryngeal adductor muscles. The laryngeal abductor muscle, however, did not respond to this stimulation. A repetitive pulse stimulation (3-5 Hz) to the afferent fibers of the pharyngeal branches of the glossopharyngeal nerve decreased the level of amplitude of the respiratory discharge from the laryngeal abductor muscle. The reflex discharges in the levator veli palatini muscle were decreased when the respiratory discharges in the laryngeal abductor muscle were enhanced. The present study indicates that there are relationships between the palatal and glottal movements and that the coordinate actions in these regions are influenced by two types of relationships among the palatal and laryngeal muscles. One is the relationship between the levator veli palatini and laryngeal adductor muscles, and the other is that between the levator veli palatini and laryngeal abductor muscle.

Herpes zoster of the maxillary branch of the trigeminus nerve. Virological and serological studies

A 70-year-old male had erythematous and vesiculous lesions in the area of the right maxillary branch of the trigeminus nerve and was clinically diagnosed as having herpes zoster; virological and serological investigations of this case were carried out. Consequently, an electron microscopic observation revealed a great number of virus particles of herpes type in the vesiculous lesion and in baby hamster kidney BHK21/WI-21 cells, cultured after inoculating the fluid from the vesicle formed on the patient's upper lip or from serum harvested during the viremia. When BHK21/WI-21 cells infected with this virus were tested for antigenicity by an indirect immunofluorescent staining technique, they showed a positive staining to antivaricella-zoster virus. When serum of this patient was assayed fof the antibody level against varicella-zoster virus by the complement fixation test at various time intervals during the therapeutic period, this antibody titer on recovery period showed a threefold increase in comparison to that at onset. From these findings, this infectious disease was precisely diagnosed as herpes zoster.

The course of facial nerve innervation for the levator veli palatini muscle

The present study was designed to determine the motor nerve pathway of the facial nerve to the levator veli palatini muscle. The experiments were carried out on 10 anesthetized rhesus monkeys. Recorded and analyzed were evoked EMG responses of the levator veli palatini and the orbicularis oris muscles by electrical stimulation to both the facial nerve and its branch within the cranium. Muscle action potentials (M-waves) from the two muscles could be recognized on stimulating the facial nerve at the petrosal area of the temporal bone. On stimulating the greater petrosal nerve, M-waves from the levator muscle could be elicited. By cutting off the greater petrosal nerve at the middle cranial fossa, M-waves from the levator muscle completely disappeared on stimulating the facial nerve at the petrosal area. Results indicated that the course of the facial nerve for the levator veli palatini muscle is through the greater petrosal nerve.