Cells capable of uptake of horseradish peroxidase in some circumventricular organs of the cat and rat

Summary The structure of mesenchymal cells distributed in some of the hypendymal organs of the circumventricular system in the cat and rat was demonstrated after intravenous injection of high doses of horseradish peroxidase. These cellular elements were observed in the vicinity of blood vessels of the organon vasculosum laminae terminalis, subfornical organ and area postrema. Electron-microscopically, these cells located between the basal laminae of the brain parenchyma and the blood capillaries show long cellular processes encircling fenestrated capillaries. Light and electron-microscopic examination revealed that this cell type is identical with the horseradish peroxidase-uptake cells, previously reported in the vicinity of the hypophysial portal system. Such phagocytic cells may be considered as a cellular component intervening between the brain parenchyma and the blood stream, playing a role in selective barrier functions in the above-mentioned circumventricular organs where a blood-brain barrier in the classical sense of the definition is lacking.This work was supported by grant No. 437002 from the Ministry of Education, Science and Culture, Japan     

The coxal glands of geophilomorpha (chilopoda): Organs of osmoregulation

Summary The organs terminating at the coxal pores of the tug-legs of Geophilomorpha are not repugnatorial glands, but possess typical transport epithelia with deep apical and basal infoldings of the cell membranes, between which numerous large mitochondria are located. Many transport vesicles are found in the basal region but fewer in the apical cytoplasm. The apex is characterized by bundles of longitudinally oriented microtubules, sparse endoplasmic reticulum and free ribosomes. Single neurosecretory axons with synaptoid areas are scattered among the cells. It is suggested that the coxal organs have a diuretic function in moist habitats and an antidiuretic effect in arid environments. The switch-over is evidently controlled by a neuroendocrine mechanism.     

On the phylogenetic significance of sagittocysts and copulatory organs in acoel turbellarians

Viewed by SEM and TEM, sagittocysts of Convoluta bifoveolata Mamkaev, 1971, and needles of C. sagittifera Ivanov, 1952, have the same structure. Both are capsule-form extrusomes containing a protrusible needle. Only seven similar species of convolutimorph acoels symbiotic with green algae and C. sagittifera, without algae, possess extrusomes of this peculiar and complicated type. The sagittocyst is a clear synapomorphy of all these species. A sacciform ciliated antrum lacking a seminal vesicle is also characteristic of these species and also of three Japanese species of green (algae-symbiotic) convolutimorph acoels lacking sagittocysts. We suggest schemes of the possible evolution of male and female copulatory organs to provide a basis for better using such organs as phylogenetic characters. We regard the formation of a ciliated sacciform antrum as an independent evolutionary trend. This conclusion forms the basis for establishing the separate family Sagittiferidae. Species of this family seem to have originated in the West Pacific.     

Salinity tolerance and morphology of the osmoregulation organs in Cladocera with special reference to Cladocera from the Aral sea

The hyperosmotic regulation of adult Cladocera is determined mainly by the amount of salts consumed with the food and by reabsorption of salts in cells of the nuchal (neck) organ. The hypoosmotic regulation both in adults and embryos is determined mainly by excretion of salts in special epipodite cells or in cells of the nuchal (neck) organ. The salinity of the Aral sea for the last 30 years increased from 8–10 to 26–28, which led to changes in the Cladocera fauna. At present only 4 species of Cladocera inhabit the Aral sea instead of 14 species that were previously found. These changes are in agreement with osmoregulation capacities of Cladocera. Note added in proof. Since this paper was accepted for publication, all Cladocera have disappeared from the Aral Sea. This happened when salinity reached 30–32. This disappearance was predicted by and agrees with earlier laboratory experiments with Aral Sea Cladocera (Aladin, 1982b).     

Peculiarities of sexual reproduction inFagus crenata forests in relation to annual production of reproductive organs

Annual production rates of reproductive organs inFagus crenata forests in the lower area of the species' range were studied using 10 litter traps in 1980–1986. The production rates of dispersed pollen were estimated by multiplying the number of fallen male inflorescences per ha per year by the mean amount of pollen per inflorescence before anthesis. Large annual fluctuations in the production rates of male and female inflorescences were recognized, whereas their annual trends were synchronized with each other. Pollen production rates were within the range 1.0–6900 (mean: 1630)×10⁹ha⁻¹ yr⁻¹, the maximum/minimum ratio attaining 7000.F. crenata was the lowest producer of pollen among seven tree species studied: the number of pollen grains equivalent to a single ovule was in the range 6.0–14×10⁴. Furthermore, the mean dry weight of a single pollen grain (3.77×10⁻⁵mg) was higher than for wind-pollinated species. Three factors seemed to cause the low seed fertility ofF. crenata. The dry-matter production rate in the best seed year reached 3252 kg ha⁻¹ yr⁻¹, of which pollen accounted for 259 kg ha⁻¹ yr⁻¹. Unproductive years with less than 10% of the maximum production occurred four times in a 7-yr period. In such years there were fewer male and female inflorescences, and more fruit dropped as a result of insect damage. Lower nut dissemination would play an important role in suppressing any increase in nut predators, and fewer flowers would be produced to avoid wastage of photosynthates in a cool-temperate climate.     

Localization of immunoreactive prolactin in ependyma and circumventricular organs of rat brain

Summary Immunoreactive prolactin (IMP) has been localized in the male rat brain using the soluble peroxidase-anti-peroxidase (PAP) technique. In normal untreated animals, reaction product was seen in choroid plexus (CP) and in ependymal cells of the ventricular lining with heaviest concentrations of positively staining cells in the 3rd ventricle near the subcommisural organ (SCO), in the lateral ventricles near the subfornical organ (SFO), and in the 4th ventricle near the area postrema (AP). IMP was also present in numerous ependymal cells resembling tanycytes in the cerebral aqueduct, central canal of the spinal cord at the level of the AP, the organum vasculosum of the lamina terminalis (OVLT) and the floor of the infundibular recess. Immunoreactive cells resembling neurons were localized within the substance of the AP, SCO, and OVLT. IMP was also present in fibers of the zona externa of the median eminence and infundibular stalk; a few cells of the pars tuberalis contained reaction product. Hypophysectomized rats and bromocriptine-treated rats exhibited a similar staining pattern except that bromocriptine treatment eliminated IMP from most CP cells. Hypophysectomy, bromocriptine or estrogen treatment enhanced staining for IMP in cells of the pars tuberalis; estrogen treatment or hypophysectomy produced an increase in the number and distribution of immunoreactive cells as well as increased density of reaction product in cells of the medial habenular nucleus. The functional relevance of prolactin in these locations in the brain, the possible routes of transport of prolactin from the pituitary gland to the central nervous system, and the strong suggestion of extra-pituitary sites of synthesis of a prolactin-like hormone are discussed.     

Uptake of Exogenous Glutamate and Aspartate by Circumventricular Organs but Not Other Regions of Brain

Abstract: Glutamate (Glu) and aspartate (Asp) concentrations in blood and selected regions of brain were measured at sequential intervals over a 3-h period following subcutaneous administration of Glu, Asp, or Glu plus Asp (2 mg/g body wt) to 4-day-old mouse or rat pups. Marked serum elevations of the administered amino acids (peak values exceeding 200 times control levels) were detected within 1 h. In circumventricular organ (CVO) regions of brain, which are thought to have no blood-brain barriers, a sharp and steady increase in tissue concentrations of the administered amino acids (peak values 4–10 times higher than control levels) occurred during a 15–120 min interval, whereas no appreciable increases were detected in other brain regions. When 2 mg/g Glu plus 2 mg/g Asp were administered, CVO tissue concentrations of each amino acid rose to approximately the same level obtained when the individual amino acids were given. It is concluded that blood-brain barriers preventing net entry of Glu or Asp into brain proper are relatively well established by the 4th postnatal day in rodents, but that CVO brain regions lack such barriers; selective access of blood-borne Glu or Asp to CVO neurons explains why these neurons are selectively destroyed by systemic administration of these neurotoxic amino acids.     

Larval adhesive organs and metamorphosis in ascidians

Summary The cup-shaped adhesive papillae of Distaplia occidentalis evert at the onset of metamorphosis and each transforms into a hyperboloidal configuration. The rate of transformation is a function of temperature. At 14° C complete eversion takes about 30 seconds. Myoepithelial cells that extend from the rim to the base on the cup contract. Simultaneously the central part of the papilla advances 60–70 m. During the last phases of eversion, collocytes (cells that secrete adhesives) on the inner wall of the cup and on the sides of the axial protrusion flow outward and form a collar-like structure.The myoepithelial cells contain arrays of thick and thin filaments. These become compacted during contraction. The surfaces of these cells become extensively folded as they shorten to about 1/3 of rest length. According to the proposed model the myoepithelial cells are the driving force in papillary eversion.Immediately after eversion is completed the papillae begin to retract. Eversion of the papillae is not inhibited by cytochalasin B, but the process of retraction is reversibly inhibited.Some histological characteristics of five types of everting papillae in four families of ascidians are compared.     

Theileria parva: Effects of irradiation on a culture of parasitized bovine lymphoid cells

Aliquots of a culture of Theileria parva-infected bovine lymphoid cells were irradiated at 0, 300, 600, 900, and 1200 rads. The short-term effects of irradiation were evaluated on examination of Giemsa-stained smears and on autoradiography of cells labeled with [³H]thymidine. Irradiation inhibited cell division but parasite division did not appear to be inhibited and macroschizont nuclear particles increased in number, frequently to several hundred per schizont. There was no evidence of an increased percentage switch from macro- to microschizont. Apparently viable cells were still present in all cultures 4 days after irradiation.     

Tracing the toxic ions of an endodontic tricalcium silicate-based sealer in local tissues and body organs

BackgroundThis study aimed to track the toxic ions released by MTA Fillapex, BioRoot RCS, and an experimental tricalcium silicate-based sealer (CEO) into local and distant tissues as well as to investigate their potential adverse effects. In addition, the chemical constituents of the sealers were also evaluated. The main components of the dry powders, pastes, and mixed sealers were characterized.Material and methodsDry powder and sealer discs were each set for 72 h and their main components were characterized by energy dispersive X-ray spectroscopy. Polyethylene tubes filled with sealers were used to measure silicon and calcium ions. Polyethylene tubes filled with sealers or empty tubes were implanted into the dorsal connective tissue of Wistar rats. On days 7, 15, 30, and 45, the animals were euthanized and their brains, livers, kidneys, and subcutaneous tissues were removed and processed to determine the concentrations of chromium, cobalt, copper, lead, iron, magnesium and nickel using an inductively coupled plasma optical emission spectrometer.ResultsThe main compounds in all sealers were carbon, oxygen, silicon, and calcium. MTA Fillapex release more Si while highest levels of Si were found in presence of BioRoot. The release of Si and Ca ions promoted by MTA Fillapex raise by time. No traces of cobalt, chromium, or magnesium were detected in any tissue. Irrespective of the sealer, no traces of copper and lead were found in the subcutaneous tissue; however, they were observed in the organs. The highest concentration of iron was identified in the liver. All sealers exhibited similar nickel traces in the brain, kidney, and liver except for MTA Fillapex, which demonstrated levels higher than CEO in the subcutaneous tissue on day 7. Tracing nickel ions over time revealed that lowest concentrations were found in subcutaneous tissue.ConclusionTaken together, our data demonstrate that CEOs have chemical compositions similar to those of other commercial sealers. Furthermore, none of them exhibited a threat to systemic health. Moreover, the minimal amounts of iron and nickel detected were not related to the sealers.