Ultrastructural Study of the Outer Cortex, Deep Cortex and Medulla of Mesenteric Lymph Node in Adult Goats

Background: A mesenteric lymph node in the sub pyloric region which is the longest among all mesenteric lymph nodes in adult goats was identified for study under the scanning electron microscope. Methods: The outer cortical, deep cortical and medullary parenchyma of the collected lymph nodes was thoroughly screened under VEGA3 TESCAN. The outer cortical parenchyma revealed T lymphocytes, B lymphocytes, Sinus Lining Cells (SLC) and Sinus Reticular Cells (SRC) at a magnification of 9600x. The deep cortical parenchyma revealed Reticular cells, T lymphocytes and Interdigitating cells (IDC) at 8000x magnification.Result: The medullary parenchyma revealed T lymphocytes, B lymphocytes, Sinus Lining Cells (SLC), Fibrous Reticular Cells (FRC) and medullary sinuses at a magnification of 8500x. Plasma cells and lymphocytes also remained in the sinus. The morphology and relations of the cells observed were recorded.

Selective expression of claudin-5 in thymic endothelial cells regulates the blood–thymus barrier and T-cell export

T-cell development depends on the thymic microenvironment, in which endothelial cells (ECs) play a vital role. Interestingly, vascular permeability of the thymic cortex is lower than in other organs, suggesting the existence of a blood–thymus barrier (BTB). On the other hand, blood-borne molecules and dendritic cells bearing self-antigens are accessible to the medulla, facilitating central tolerance induction, and continuous T-precursor immigration and mature thymocyte egress occur through the vessels at the cortico-medullary junction (CMJ). We found that claudin-5 (Cld5), a membrane protein of tight junctions, was expressed in essentially all ECs of the cortical vasculatures, whereas approximately half of the ECs of the medulla and CMJ lacked Cld5 expression. An intravenously (i.v.) injected biotin tracer hardly penetrated cortical Cld5+ vessels, but it leaked into the medullary parenchyma through Cld5– vessels. Cld5 expression in an EC cell line caused a remarkable increase in trans-endothelial resistance in vitro, and the biotin tracer leaked from the cortical vasculatures in Cldn5–/– mice. Furthermore, i.v.-injected sphingosine-1 phosphate distributed selectively into the medulla through the Cld5– vessels, probably ensuring the egress of CD3high mature thymocytes from Cld5– vessels at the CMJ. These results suggest that distinct Cld5 expression profiles in the cortex and medulla may control the BTB and the T-cell gateway to blood circulation, respectively.

Functional ultrastructure of eggs and cellular organization of hexacanths of the cyclophyllidean cestode Thysanotaenia congolensis: a phylogenetic implication of obtained results

SUMMARYThe functional ultrastructure of eggs and cellular organization of hexacanths from gravid proglottids of Thysanotaenia congolensis, from black rats from Cape Verde, were examined by transmission electron microscopy. Mature eggs with fully formed hexacanths are grouped within parenchymatous capsules of gravid proglottids. Oncospheral envelopes surrounding mature hexacanths are reduced to a very thin membranous embryophore as their protective function is taken over by the parenchymatous capsules originating from the medullary parenchyma of immature proglottids and composed of three layers. Six major cell types are present: a bi-nucleate medullary centre; a six-nucleate U-shaped penetration gland; a second type of penetration gland; two neurosecretory-type nerve cells; about 30 somatic cells; and about 12 germinative cells. Present results on the functional ultrastructure of eggs and cellular organization of hexacanths support the phylogenetic distinction between T. congolensis and cestodes of the subfamily Anoplocephalinae.

Morphoanatomy of Schultesia pachyphylla (Gentianaceae): a discordant pattern in the genus

Schultesia Mart. comprises 21 closely related taxa. The revision of the genus showed that Schultesia pachyphylla Griseb. and Xestaea lisianthoides Griseb. are different from other species. The aim of this study was to describe the morphoanatomy of S. pachyphylla, comparing it with other Schultesia species and X. lisianthoides, and to provide data on their geographical distribution and habitat. Morphological and anatomical data were subjected to multivariate analysis. Schultesia pachyphylla is endemic to the state of Bahia, Brazil, and is separated from the other species by having 5-merous flowers, 5-winged calyx, wings between the calyx lobes, loss of interveinal tissue on sepals during fruit maturation, dark red colored immature calyces, capsules opening from base to apex, 3-anaporate pollen grains, and epidermal papillae evident in the field. Schultesia pachyphylla has amphistomatic leaves with anisocytic stomata, uniseriate epidermis, dorsiventral mesophyll, and bicollateral vascular bundles. The stem has small wings, cortical and medullary parenchyma, and internal phloem. Foliar colleters and nectaries on leaves and stem were observed. We believe that morphological and anatomical data could support the creation of a monotypic genus or the relocation of this species into another genus. Phylogenetic analyses are in progress to define the species’ positioning.

Post-embryonic development and ultrastructural characteristics of the polycephalic larva of Taenia parva Baer, 1926 (Cyclophyllidea, Taeniidae)

Post-embryonic development and fully-formed polycephalic larvae of Taenia parva Baer, 1926 were examined by light (LM) and transmission electron microscopy (TEM). Three developmental stages were recognised: (1) an early stage of exogenous budding at the surface of the central vesicle; (2) a stage of polycephalic cyst development accompanied by segmentation of the growing larval strobile and an obvious decrease in the size of the central vesicle; (3) fully-formed larval strobile and invaginated scoleces. In fully-developed encysted polycephalic larvae, there are usually 14–24 segmented larval strobilae, each terminating with an invaginated scolex; larval strobilae arise from a common central vesicle and remain attached posterior to it during the entire development. The number of segments varies between 109 and 120 per larval strobila. The polycephalic larvae examined closely resemble the strobilocercus type of taeniid larvae. The structure of developing and fully-formed larvae was examined by TEM. The tegument, scolex, subtegumental musculature of the strobilar segments, protonephridial system, calcareous corpuscles and medullary parenchyma of larvae exhibit general similarity with the same structures in adults at both LM and TEM levels. The morphogenesis of the larva of T. parva is compared with that of the polycephalic larvae of other Taenia spp. (T. krepkogorski, T. twitchelli and T. endothoracica) and with other asexually-multiplying cestode larvae (mesocestoidids, hymenolepidids and dilepidids).

The gull-tapeworm, Diphyllobothrium dendriticum and neuropeptide F: an immunocytochemical study

Neuropeptide F (Moniezia expansa) immunoreactivity (NPF-IR) has been detected in the nervous system of plerocercoid and adult stages of the gull-tapeworm Diphyllobothrium dendriticum, using immunocytochemical methodology. The application of the antiserum for this authentic flatworm neuropeptide to whole-mounts and frozen sections of the worm has resulted in new information about its neuroanatomy. Thus, at regular intervals, transverse nerves extend from the main nerve cords laterally, joining the longitudinal lateral minor cords in the cortical parenchyma. In the adult worm, the transverse nerves are located at the posterior border of each proglottis. The medullary parenchyma lacks NPF-IR. The NPF-immunoreactive cell bodies are bi- to multipolar and preferentially located in the peripheral nervous system, in close association with the holdfast musculature of the scolex and the extensive body musculature. NPF-IR was observed in the innervation to the muscular ducts of the reproductive system. The pattern of NPF-IR was compared with that recorded for RFamide- and 5-HT-IR and double-immunostaining has revealed separate populations of serotoninergic and peptidergic neurones.

Comparative histology of the scolex and neck region of Glaridacris laruei (Lamont, 1921) Hunter, 1927 and Glaridacris catostomi Cooper, 1920 (Cestoidea: Caryophyllidea)

The histology of the scolex and neck region was examined in adults of the caryophyllidean tapeworms Glaridacris laruei and Glaridacris catostomi, parasites of the white sucker, Catostomus commersoni (Lacépède). Several distinct cell types were identified in the parenchyma including tegumental cells, flame cells, longitudinal muscle cells (myoblasts), transverse and dorsoventral muscle cells, parenchyma cells, epithelioid cells, and cells associated with the calcareous corpuscles. The proliferative zone of germinative cells reported for strobilate tapeworms was not found in these species. Faserzellen, or neck cells, which consisted of a deeply staining mass of cells, were found in the medullary parenchyma of the neck. Histochemical tests revealed that the cytoplasm of the Faserzellen was rich in RNA and protein, but alkaline and acid phosphatase activity were not detected. The arrangement of musculature in the scolex was examined; muscles associated with the attachment organs of G. laruei appear more developed compared with those of G. catostomi. Measurements of the various cells and their characteristic staining properties are presented in tabular form.

Posttraumatic syringomyelia

✓ The ninth case of posttraumatic syringomyelia with postmortem confirmation is presented. Onset of symptoms occurred 19 years after the original trauma. A review of the literature with a discussion of postulated mechanisms of syrinx distention follows. The present case differs from previously reported postmortem cases in that there was communication through the medullary parenchyma with the fourth ventricle.

Histochemical studies on Raillietina (Raillietina) johri (Cestoda: Davaineidae). II. Nucleoside diphosphatase and thiamine pyrophosphatase

ABSTRACTThiamine pyrophosphatase and nucleoside diphosphatase have been studied histochemically in Raillietina (Raillietina) johri. Thiamine pyrophosphatase activity has been observed in the tegument, subtegumental muscle, subtegumental cells, medullary parenchyma, excretory canal and various reproductive structures like testes, ovary, vas deferens, spermatozoa and vitellaria. Eggs exhibit moderate enzyme activity. Various nucleoside diphosphates have been found to be hydrolyzed by thiamine pyrophosphatase. CaC12, MgC12 and MnC12 each activated the enzyme at a final concentration of 6 mM whereas cysteine, reduced glutathione and PCMB inhibited the enzyme activity at a final concentration of 10 mM, 10 mM and 20mM, respectively. KCN and NaF had no effect on the enzyme staining at concentration as high as 50 mM and 30 mM, respectively. Possible roles of the enzyme in the parasite have been discussed.

Experimental investigations of the shoot apex of Dryopteris aristata Druce

A method whereby the apical meristem of the fern Dryopteris aristata Druce can be partially isolated from the adjacent lateral organs and tissues is described. This procedure has been adopted as a means of investigating growth and morphogenesis at the shoot apex. The technique involves the severance of the incipient vascular tissue which originates immediately below the apical meristem; the isolated meristem is thus seated on a plug of growing medullary parenchyma. Leaf primordia can be similarly isolated. Meristems treated in this way are capable of growth. They develop into short vasculated shoots bearing leaves. The nutrients sustaining this growth must reach the apical meristem from below by diffusing through medullary parenchyma at the base of the isolated terminal region. Above the parenchymatous region a solenostelic vascular system is present in the new axis; this is in marked contrast to the dictyostelic configuration of the parental shoot below. On the further growth of the isolated meristem leaves are produced and the stele becomes dictyostelic. The new leaves, of which as many as fourteen have been observed after 11 weeks’ growth, show the normal phyllotactic arrangement, and this is continuous with that of the main shoot below. The procedure adopted has the effect of removing the physiological dominance of the apical meristem relative to the main shoot; thus numerous large buds develop on the lateral segments of the parental shoot but none on the isolated terminal region. The growth of isolated leaf primordia is very limited. The vascular system develops as a solenostele, foliar gaps are not formed in the region of confluence with the shoot stele, axillary buds are developed, and the leaf apex becomes directed outwards. These several features are in marked contrast to the normal development. The isolated lateral segments are also capable of further growth. The experimental procedure adopted involves the severance of the vascular tissues at various levels. An account is given of new and hitherto unrecorded morphological developments observed in these segments. Interesting features include the formation of large solenostelic buds, the solenostelic development of isolated meristeles, medullation of meristeles and the induction of a polycyclic stelar condition, in one instance by a process of cambium-like activity. These are all in marked contrast to the normal development of the intact shoot. The data which have been obtained are discussed with special reference to the path of translocation of nutrients to the terminal meristem and to leaf primordia, morphogenetic processes at the shoot apex, the factors influencing the differentiation of the vascular system, and theories of shoot formation and constitution. The results of these experiments give no support to phytonic theories but emphasize the difference in potentiality for development between shoot and leaf primordia. In this connexion the factors which determine the shape and system of segmentation of the apical initials of shoot and leaf are seen to require further investigation. The hypotheses that lateral buds are inhibited by substances proceeding from the apical meristem, that the initial differentiation of vascular tissue can be attributed to the basipetal diffusion of a substance or substances from the actively growing apical meristem, and that under conditions of tensile stress incipient vascular tissue undergoes a parenchymatous development, are supported by the data of these experiments. The observations afford a clear indication of the diversity of the morphogenetic activity in the growing region. Nutritional, mechanical and other factors are seen to be important in influencing the distribution of tissues during development. The view entertained by comparative morphologists that the vascular system in ferns is of a highly conservative nature and therefore of great value in phyletic studies is to some extent opposed by the data of these experiments. But notwithstanding the several unusual vascular configurations produced as a result of the experimental treatment, there is eventually a return to the typical vascular arrangements of the normal shoot. There is thus a need for harmonizing the data of the causal and phyletic aspects. The more thoroughly the operation of morphogenetic factors extrinsic to the specific hereditary substance is understood, the more critical will be the selection of criteria of comparison for phyletic purposes.