Neuromast morphology and lateral line trunk canal ontogeny in two species of cichlids: an SEM study

A study of neuromast ontogeny and lateral line canal formation in Oreochromis aureus and Cichlasoma nigrofasciatum reveals the existence of two classes of neuromasts: those that arise just before hatching (presumptive canal neuromasts, dorsal superficial neuromasts, gap neuromasts, and caudal fin neuromasts) and pairs of neuromasts that arise on each lateral line scale lateral to each canal segment at the same time as canal formation. In the anterior trunk canal segment, each presumptive canal neuromast is accompanied by a dorsoventrally oriented superficial neuromast forming an orthogonal neuromast pair. It is suggested that each of these dorsoventrally oriented superficial neuromasts is homologous to the transverse superficial neuromast row described by Münz (Zoomorphology 93:73-86, '79) in other cichlids. It is further suggested that the longitudinal lines described by Münz (Zoomorphology 93:73-86, '79) are derived from the pair of superficial neuromasts that arise during canal formation. Distinct changes in neuromast topography are documented. Neuromast formation, scale formation, and lateral line canal formation are three distinct and sequential processes. The distribution of neuromasts is correlated with myomere configuration; there is always one presumptive canal neuromast on each myomere. A single scale forms beneath each presumptive canal neuromast. Canal segment formation is initiated with the enclosure of each presumptive canal neuromast by an epithelial bridge which later ossifies. The distinction of these three processes raises questions as to the causal relationships among them.     

峨眉凤丫蕨配子体发育及卵发生的研究

用显微观察及透射电镜技术对峨眉凤丫蕨的配子体发育及卵发生过程进行了观察研究,以探讨其卵发生细胞学机制及蕨类植物演化关系。结果表明:(1)峨眉凤丫蕨孢子接种7～9d萌发,经丝状体和片状体阶段发育为心形原叶体,成熟原叶体雌雄同株,在原叶体基部产生精子器,在原叶体生长点下方产生颈卵器。(2)卵发生研究表明,峨眉凤丫蕨颈卵器产生于生长点下方的表面细胞,该细胞经2次分裂形成3层细胞,中间者为初生细胞,它经2次不等分裂产生卵细胞、腹沟细胞和颈沟细胞;新产生的卵与腹沟细胞间连接紧密,有发达的胞间连丝,随着发育,卵细胞与腹沟细胞之间产生分离腔,而腹沟细胞与卵细胞始终通过孔区相连;发育中期,卵核形成大量核外突;发育后期,在卵细胞外侧形成卵膜,孔区演变为受精孔,核外突数量减少。     

Tsukushi is essential for the formation of the posterior semicircular canal that detects gait performance

Tsukushi is a small, leucine-rich repeat proteoglycan that interacts with and regulates essential cellular signaling cascades in the chick retina and murine subventricular zone, hippocampus, dermal hair follicles, and the cochlea. However, its function in the vestibules of the inner ear remains unknown. Here, we investigated the function of Tsukushi in the vestibules and found that Tsukushi deficiency in mice resulted in defects in posterior semicircular canal formation in the vestibules, but did not lead to vestibular hair cell loss. Furthermore, Tsukushi accumulated in the non-prosensory and prosensory regions during the embryonic and postnatal developmental stages. The downregulation of Tsukushi altered the expression of key genes driving vestibule differentiation in the non-prosensory regions. Our results indicate that Tsukushi interacts with Wnt2b, bone morphogenetic protein 4, fibroblast growth factor 10, and netrin 1, thereby controlling semicircular canal formation. Therefore, Tsukushi may be an essential component of the molecular pathways regulating vestibular development.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12079-021-00627-1.     

阔叶鳞盖蕨配子体发育及卵发生的研究

采用显微镜和透射电镜对阔叶鳞盖蕨(Microlepia platyphylla)的配子体发育和卵发生过程进行了观察,以阐明其卵发生的细胞学机制,探讨其演化地位。阔叶鳞盖蕨孢子褐色,四面体形,具三裂缝,接种5~10d后孢子萌发,经丝状体和片状体阶段发育为心形原叶体,原叶体发育是铁线蕨型,通常为雌雄异株,精子器产生于不规则配子体的表面,颈卵器产生于心形原叶体生长点的下方,性器官是薄囊蕨型。卵发生研究表明,阔叶鳞盖蕨颈卵器产生于生长点下方表面细胞,经两次分裂形成了顶细胞、初生细胞和基细胞。其中初生细胞再经两次不等分裂产生卵细胞、腹沟细胞和颈沟细胞,此3个细胞通过胞间连丝紧密相连,随发育,腹沟细胞与卵细胞间形成了分离腔,但在孔区处始终通过胞间连丝相连,成熟卵细胞上形成了卵膜和受精孔,卵核表面产生了核外突,通过比较表明阔叶鳞盖蕨卵发生与蕨（Pteridium aquilinum）卵发生相似。     

Development of the supraorbital and mandibular lateral line canals in the cichlid,Archocentrus nigrofasciatus

The development of two of the cranial lateral line canals is described in the cichlid, Archocentrus nigrofasciatus. Four stages of canal morphogenesis are defined based on histological analysis of the supraorbital and mandibular canals. "Canal enclosure" and "canal ossification" are defined as two discrete stages in lateral line canal development, which differ in duration, an observation that has interesting implications for the ontogeny of lateral line function. Canal diameter in the vicinity of individual neuromasts begins to increase before ossification of the canal roof in each canal segment; this increase in canal diameter is accompanied by an increase in canal neuromast size. The mandibular canal generally develops later than the supraorbital canal in this species, but in both of these canals development of the different canal segments contained within a single dermal bone is asynchronous. These observations suggest that a dynamic process requiring integration and interaction among different tissues, in both space and time, underlies the development of the cranial lateral line canal system. The supraorbital and mandibular canals appear to demonstrate a "one-component" pattern of development in Archocentrus nigrofasciatus, where the walls of each canal segment grow up from the underlying dermal bone and then fuse to form the bony canal roof. This is contrary to numerous published reports that describe a "two-component" pattern of development in teleosts where the bony canal ossifies separately and then fuses with an underlying dermal bone. A survey of the literature in which lateral line canal development is described using histological analysis suggests that the occurrence of two different patterns of canal morphogenesis ("one-component" and "two-component") may be due to phylogenetic variation in the pattern of the development of the lateral line canals.     

Development of the inner ear of the brown trout (Salmo trutta fario): I. Gross morphology and sensory cell proliferation

The gross development of the trout inner ear between embryonic and juvenile stages was studied by light microscopy. The otocyst has already formed in 3–4 mm embryos. The semicircular canals begin to separate from the utriculo-saccular cavity in 6 mm embryos, the anterior canal first, then the posterior and the horizontal canal later. The formation of the saccular cavity begins in 7 mm embryos, whereas that of the lagena occurs in 18 mm fry. The first macular primordia appear before the separation of cavities. The anterior and horizontal crests arise from the primordium of the utricular macula, and the posterior crest, macula lagena, and macula neglecta arise from that of the saccular macula. The macula lagena and macula neglecta appear later. The sensory areas of the labyrinth and the number of receptor cells grow continuously between the embryonic and juvenile stages. © 1993 Wiley-Liss, Inc.     

The development of semicircular canals in the inner ear: role of FGFs in sensory cristae

In the vertebrate inner ear, the ability to detect angular head movements lies in the three semicircular canals and their sensory tissues, the cristae. The molecular mechanisms underlying the formation of the three canals are largely unknown. Malformations of this vestibular apparatus found in zebrafish and mice usually involve both canals and cristae. Although there are examples of mutants with only defective canals, few mutants have normal canals without some prior sensory tissue specification, suggesting that the sensory tissues, cristae, might induce the formation of their non-sensory components, the semicircular canals. We fate-mapped the vertical canal pouch in chicken that gives rise to the anterior and posterior canals, using a fluorescent, lipophilic dye (DiI), and identified a canal genesis zone adjacent to each prospective crista that corresponds to the Bone morphogenetic protein 2 (Bmp2)-positive domain in the canal pouch. Using retroviruses or beads to increase Fibroblast Growth Factors (FGFs) for gain-of-function and beads soaked with the FGF inhibitor SU5402 for loss-of-function experiments, we show that FGFs in the crista promote canal development by upregulating Bmp2. We postulate that FGFs in the cristae induce a canal genesis zone by inducing/upregulating Bmp2 expression. Ectopic FGF treatments convert some of the cells in the canal pouch from the prospective common crus to a canal-like fate. Thus, we provide the first molecular evidence whereby sensory organs direct the development of the associated non-sensory components, the semicircular canals, in vertebrate inner ears.     

Formation of actin filament bundles in the ring canals of developing Drosophila follicles

Growing the intracellular bridges that connect nurse cells with each o ther and to the developing oocyte is vital for egg development. These ring canals increase from 0.5 microns in diameter at stage 2 to 10 microns in diameter at stage 11. Thin sections cut horizontally as you would cut a bagel, show that there is a layer of circumferentially oriented actin filaments attached to the plasma membrane at the periphery of each canal. By decoration with subfragment 1 of myosin we find actin filaments of mixed polarities in the ring such as found in the "contractile ring" formed during cytokinesis. In vertical sections through the canal the actin filaments appear as dense dots. At stage 2 there are 82 actin filaments in the ring, by stage 6 there are 717 and by stage 10 there are 726. Taking into account the diameter, this indicates that there is 170 microns of actin filaments/canal at stage 2 (pi x 0.5 microns x 82), 14,000 microns at stage 9 and approximately 23,000 microns at stage 11 or one inch of actin filament! The density of actin filaments remains unchanged throughout development. What is particularly striking is that by stages 4-5, the ring of actin filaments has achieved its maximum thickness, even though the diameter has not yet increased significantly. Thereafter, the diameter increases. Throughout development, stages 2-11, the canal length also increases. Although the density (number of actin filaments/micron2) through a canal remains constant from stage 5 on, the actin filaments appear as a net of interconnected bundles. Further information on this net of bundles comes from studying mutant animals that lack kelch, a protein located in the ring canal that has homology to the actin binding protein, scruin. In this mutant, the actin filaments form normally but individual bundles that comprise the fibers of the net are not bound tightly together. Some bundles enter into the ring canal lumen but do not completely occlude the lumen. all these observations lay the groundwork for our understanding of how a noncontractile ring increases in thickness, diameter, and length during development.     

川硬皮肿腿蜂的胚胎发育

在 2 6℃恒温和 70 %相对湿度条件下 ,川硬皮肿腿蜂胚胎发育全历期为 60～ 70h。卵黄少 ,原足期 (protopod)孵化。根据其胚胎形态变化特征可分 4个发育阶段 :早期发育阶段 ,卵产后 1～ 1 2h,包括卵割期、胚盘期和胚带期 ;胚胎伸长及器官发育阶段 ,卵后 1 2～ 5 0h,包括胚带分节、原头原躯分化、胚带再伸长、消化道和口器形成 ;胚胎背合阶段 ,卵产后 5 0～ 60h和胚胎成熟阶段 ,卵产后 60～ 70h。     

Effect of a juvenoid on embryonic development of Earias fabia (Stoll) (Lepidoptera: Noctuidae)

Eggs of Earias fabia were treated with three different quantities of a juvenoid, 6–7 epoxy-3-ethyl-1-(p-ethyl phenoxy)-7 methylnonane at 5 distinct stages. These were: (a) before blastoderm formation; (b) before gastrulation; (c) before segmentation; (d) before blastokinesis; and (e) just after blastokinesis. The effect on embryonic development was studied. If sufficient hormone is administered early enough, development may be arrested at stages as early as blastoderm formation. With moderate and smaller doses, developmental arrest mostly occurred at certain well-defined stages, such as germ-band formation; before blastokinesis; post blastokinesis; when the embryo assumes its larval form; at the time of chitin formation and during embryonic moulting. Observations also bring in focus the importance of the quantity of hormone and its relationship to the speed of its action. Toxic action is apparent when eggs are treated with relatively larger quantities of the compound: application of juvenoid to younger stages causes fewer deaths.     

Perivascular cells in cartilage canals of the developing mouse epiphysis

Morphological variability among perivascular cells adjacent to cartilage matrix during the elongation of canals through both uncalcified and calcified matrix has not been reported. Cartilage canals were located in distal femoral epiphyses of 5- to 7-day-old mice and identified as vascular channels arising from perichondrial surfaces along the condyles and intercondylar fossae. Three stages of canal development were identified based on the length of canals and on characteristics of chondrocytes and matrix surrounding the canals. Superficial canals terminated in uncalcified matrix of resting cartilage; intermediate canals terminated in matrix containing hypertrophic chondrocytes; deep canals terminated in calcified matrix. The ultrastructural morphology of perivascular cells in contact with the matrix varied in the three stages. Cells resembling fibroblasts and vacuolated macrophages were present adjacent to the uncalcified matrix in superficial canals. At the tips of intermediate canals, cells resembling fibroblasts were larger, contained numerous lysosomes and phagolysosomes, and were in intimate contact with the matrix. At the tips of deep canals, chondroclasts with ruffled borders and clear zones contacted the calcified matrix. The results indicate that 1) mouse epiphyses provide a suitable model for studying cartilage-canal perivascular cells, 2) calcification of cartilage matrix occurs along the course of the canal, and 3) the morphology of perivascular cells in contact with the matrix may be determined, in part, by matrix calcification.     

Development of excretory organs in <Emphasis Type="Italic">Phoronopsis harmeri</Emphasis> (Phoronida): From protonephridium to nephromixium

Larval protonephridia appear as paired ectodermal invaginations on the posterior body end of the larva (actinotrocha), at early stages of its development. The protonephridium of the early actinotrocha has a straight canal and one group of solenocytes distally. The protonephridium of the late actinotrocha has a U-shaped canal and two (upper and lower) groups of solenocytes. After metamorphosis, solenocytes degenerate and the canal is connected with metacoel. The metanephridial funnel is formed from the upper metacoelomic wall epithelium and the lateral mesentery. The definitive nephridium consists of two parts: the ectodermal canal (derived from the protonephridial canal) and the mesodermal funnel, a derivative of the coelomic epithelium. Thus, the phoronid excretory organ is a nephromixium. Consecutive stages of the evolution of nephridia in phoronids are discussed.     

Left-right positioning of the adult rudiment in sea urchin larvae is directed by the right side.

Indirect-developing sea urchins eventually form an adult rudiment on the left side through differential left-right development in the late larval stages. Components of the adult rudiment, such as the hydropore canal, the hydrocoel and the primary vestibule, all develop on the left side alone, and are the initial morphological traits that exhibit left-right differences. Although it has previously been shown that partial embryos dissected in cleavage stages correctly determine the normal left-right placement of the adult rudiment, the timing and the mechanism that determine left-right polarity during normal development remain unknown. In order to determine these, we have carried out a series of regional operations in two indirect-developing sea urchin species. We excised all or a part of tissue on the left or right side of the embryos during the early gastrula stage and the two-armed pluteus stage, and examined the left-right position of the adult rudiment, and of its components. Excisions of tissues on the left side of the embryos, regardless of stage, resulted in formation of a left adult rudiment, as in normal development. By contrast, excisions on the right side of the embryos resulted in three different types of impairment in the left-right placement of the adult rudiment in a stage-dependent manner. Generally, when the adult rudiment was definitively formed only on the right side of the larvae, no trace of basic development of the components of the adult rudiment was found on the left side, indicating that a right adult rudiment results from reversal of the initial left-right polarity but not from a later inhibitory effect on the development of an adult rudiment. Thus, we suggest that determination of the left-right placement of the adult rudiment depends on a process, which is directed by the right side, of polarity establishment during the gastrula and the prism stages; however, but commitment of the cell fate to initiate formation of the adult rudiment occurs later than the two-armed pluteus stage.     

水蕨颈卵器的形成与发育

主要运用电子透射显微镜技术对水蕨(Ceratopteris thalictroides(L.)Brongn)颈卵器形成与发育进行了研究。结果表明:水蕨颈卵器是由原叶体分生组织内颈卵器原始细胞形成的。该原始细胞经2次分裂形成3层细胞,上下两层发育成颈卵器颈部与底部的壁细胞,中层为初生细胞。初生细胞是颈卵器内雌配子发生的第一个细胞,该细胞经2次不等分裂形成1个卵细胞,1个腹沟细胞、1个双核的颈沟细胞。本研究首次阐明了水蕨颈卵器内细胞的发育顺序和特征。     

水蕨颈卵器的形成与发育

主要运用电子透射显微镜技术对水蕨（Ceratopteris thalictroides（L．）Brongn）颈卵器形成与发育进行了研究。结果表明：水蕨颈卵器是由原叶体分生组织内颈卵器原始细胞形成的。该原始细胞经2次分裂形成3层细胞,上下两层发育成颈卵器颈部与底部的壁细胞,中层为初生细胞。初生细胞是颈卵器内雌配子发生的第一个细胞,该细胞经2次不等分裂形成1个卵细胞,1个腹沟细胞、1个双核的颈沟细胞。本研究首次阐明了水蕨颈卵器内细胞的发育顺序和特征。     

Characterization of the DNA in DROSOPHILA MELANOGASTER

DNA has been quantitatively extracted from Drosophila melanogaster at various stages of embryonic development and analyzed by isopycnic centrifugation in CsCl and by fractionation on methylated albumin columns. The DNA is composed of three main classes of DNA, as defined by their buoyant density, rho, in CsCl: a bulk DNA, rho = 1.699 g cm(-3), and two satellite DNAs, rho = 1.685 g cm(-3) and rho = 1.669 g cm(-3). These three types of DNA persist throughout the development of the insect. In the unfertilized egg, 80% of the total DNA consists of the satellite DNAs; this amount decreases to 18% during the first three hours after fertilization and then remains constant through embryogenesis. There is a concomitant increase of the satellite DNA's with the bulk DNA after blastoderm formation.     

The eggshell of the almond wasp Eurytoma amygdali (Hymenoptera, Eurytomidae) - 2. The micropylar appendage

Micropylar apparatuses in insects are specialized regions of the eggshell through which sperm enters the oocyte. This work is an ultrastructural study and deals with the structure and morphogenesis of the micropylar appendage in the hymenopteran Eurytoma amygdali. The micropylar appendage is a 130 mum long cylindrical protrusion located at the posterior pole of the egg, unlike other insects i.e. Diptera. in which the micropylar apparatus is located at the anterior pole. In mature eggs there is a 0.4 mum wide pore (micropyle) at the tip of the appendage leading to a 6 mum wide micropylar canal. The canal contains an electron-lucent substance, it travels along the whole appendage and finally reaches the vitelline membrane of the oocyte. The vitelline membrane is covered by a wax layer and an electron-lucent layer, whereas the chorion surrounding the canal consists of a granular layer (fine and rough) and a columnar layer. The morphogenesis of the appendage starts in immature follicles: four central cells located at the posterior tip of the oocyte near the vitelline membrane, differing morphologically from the adjacent follicle cells. These central cells degenerate during early chorionic stages, thus assisting in the formation of the micropylar canal. The adjacent, peripherally located cells secrete the electron-lucent substance which fills the canal and at the same time, the fine granular layer is formed starting from the base towards the tip of the appendage. The secretion persists at late chorionic stages and results in the formation of the chorion around the micropylar canal. The extremely long (compared to other insects) micropylar appendage seems to facilitate the egg passage through the very thin and long ovipositor. The structure and morphogenesis of this appendage differs significantly from the micropylar apparatuses studied so far in other insects i.e. Diptera, and may reflect adaptational and evolutionary relationships.     

Pathogenesis of nitrofen-induced congenital diaphragmatic hernia in fetal rats

Allan, Douglas W., and John J. Greer. Pathogenesis ofnitrofen-induced congenital diaphragmatic hernia in fetal rats. J. Appl. Physiol. 83(2): 338-347, 1997.Congenital diaphragmatic hernia (CDH) is a developmental anomalycharacterized by the malformation of the diaphragm and impaired lungdevelopment. In the present study, we tested several hypothesesregarding the pathogenesis of CDH, including those suggesting that theprimary defect is due to abnormal 1)lung development, 2) phrenic nerveformation, 3) developmentalprocesses underlying diaphragmatic myotube formation, 4) pleuroperitoneal canal closure,or 5) formation of the primordial diaphragm within the pleuroperitoneal fold. The2,4-dichloro-phenyl-p-nitrophenyl ether (nitrofen)-induced CDH rat model was used for thisstudy. The following parameters were compared between normal andherniated fetal rats at various stages of development:1) weight, protein, and DNA contentof lungs; 2) phrenic nerve diameter,axonal number, and motoneuron distribution;3) formation of the phrenic nerve intramuscular branching pattern and diaphragmatic myotube formation; and 4) formation of the precursor ofthe diaphragmatic musculature, the pleuroperitoneal fold. Wedemonstrated that previously proposed theories regarding the primaryrole of the lung, phrenic nerve, myotube formation, and the closure ofpleuroperitoneal canal in the pathogenesis of CDH are incorrect.Rather, the primary defect associated with CDH, at least in thenitrofen rat model, occurs at the earliest stage of diaphragmdevelopment, the formation of the pleuroperitoneal fold.

     

Ectopic noggin blocks sensory and nonsensory organ morphogenesis in the chicken inner ear

Bone morphogenetic protein 4 (Bmp4) is expressed during multiple stages of development of the chicken inner ear. At the otocyst stage, Bmp4 is expressed in each presumptive sensory organ, as well as in the mesenchymal cells surrounding the region of the otocyst that is destined to form the semicircular canals. After the formation of the gross anatomy of the inner ear, Bmp4 expression persists in some sensory organs and restricted domains of the semicircular canals. To address the role of this gene in inner ear development, we blocked BMP4 function(s) by delivering one of its antagonists, Noggin, to the developing inner ear in ovo. Exogenous Noggin was delivered to the developing otocyst by using a replication-competent avian retrovirus encoding the Noggin cDNA (RCAS-N) or implanting beads coated with Noggin protein. Noggin treatment resulted in a variety of phenotypes involving both sensory and nonsensory components of the inner ear. Among the nonsensory structures, the semicircular canals were the most sensitive and the endolymphatic duct and sac most resistant to exogenous Noggin. Noggin affected the proliferation of the primordial canal outpouch, as well as the continual outgrowth of the canal after its formation. In addition, Noggin affected the structural patterning of the cristae, possibly via a decrease of Msx1 and p75NGFR expression. These results suggest that BMP4 and possibly other BMPs are required for multiple phases of inner ear development.     

Spontaneous activity of hippocampal neurons and stimulation rhythm acquisition in young rabbits during learning: age features

Ontogenetic mechanisms of memory formation were studied using an experimental model of conditioned reflex to time, i.e., trace acquisition of a stimulation rhythm by hippocampal CA1 neurons of young (1-4 weeks old) and adult rabbits (5-6 months old). It was found that age-related development of learning ability includes several stages: complete absence of memory traces (6-7 days old), rapid acquisition without consolidation (8-14 days old), and formation of perfect memory (25-30 days old). Both specific and nonspecific changes in spontaneous activity of neurons were observed. Changes in the rate of discharges related to rhythmic stimulation were accompanied by changes in spontaneous activity. With the development of an animal, spike activity increased in parallel with improving of the functional properties of neurons, their structural organization, formation of the afferent contacts in the hippocampus completed after a period of three weeks from birth, and formation of metabolic processes, modulatory systems, and traffic function of hippocampal neurons. A capability for plastic reorganization is of great importance for adaptation mechanisms and conditioned behavior of a developing animal in accordance with structural maturation and development of the functional regulation of neuronal reactivity in the hippocampus.