Mitochondriogenesis in nerve fibers of the infrared receptor membrane of pit vipers

Summary The myelinated nerve fibers that innervate the infrared receptor membrane of pit vipers were studied under the electronmicroseope. Along the course of the fiber, toward the nerve terminal, segments of the axon with an increasing concentration of mitochondria were found, and a special region was recognized where an active process of mitochondriogenesis seems to occur. In these regions the axon has varying amounts of mitochondria, is devoid of neuroprotofibrils, and the axoplasmic matrix is dense and contains numerous membranes, some of which can be traced as infoldings of the axolemma.The images observed have led to postulate tentatively a mechanism of mitochondrial formation, which would start with the infolding of the axolemma, would continue with the curving of two parallel membranes around a denser portion of axoplasmic matrix, the development of inner crests and the final closing of the membrane. In this mechanism both the axon membrane and the axoplasmic matrix would be involved.The possible electrochemical properties of mitochondrial membranes deriving from an excitable membrane are discussed in relation to the special receptive properties of these nerve fibers.This paper was supported by a grant of the Office of Scientific Research of the U.S. Air Force given to the Instituto de Anatomía General y Embriología, Facultad de Ciencias Médicas, Universidad de Buenos Aires, Argentina.Postdoctoral fellow of the Instituto Nacional de Microbiología, Buenos Aires, Argentina.     

Phytomicrofauna of pampasic lotic environments (Argentina)

During 1985–1986, twelve rivers and streams belonging to the Delta Sub-basin (Río de la Plata estuary Basin, Argentina) were sampled for microfauna associated with fifteen species of aquatic macrophytes. A total of 171 species were determined. Ciliates and rotifers were most abundant. Dissimilarities in the colonization of the macrophytes were demonstrated. Water level and current influenced the periphyton community and contributed to the differences observed.Scientific Contribution N 398 of the Instituto de Limnología Dr. Raúl A. Ringuelet. This work was supported by the Comisión de Investigaciones Cientificas de la Provincia de Buenos Aires (Sub. 2109-1449/85).     

Fine Structure of Subepithelial “Free” and Corpuscular Trigeminal Nerve Endings in Anterior Hard Palate of the Rat

Axonally transported protein labeled many trigeminal nerve endings in subepithelial regions of the anterior hard palate of the rat. Sensory endings were most numerous in the lamina propria near the tips of the palatal rugae where large connective tissue and epithelial papillae interdigitated. Two kinds of sensory ending were found there: “free” endings, and a variety of corpuscular endings. The “free” sensory endings consisted of bundles of unmyelinated axons separated from the connective tissue by relatively unspecialized Schwann cells covering part or all of their surface and a completely continuous basal lamina; they were commonly found running parallel to the epithelium or near corpuscular endings. The corpuscular sensory endings all had a specialized nerve form, specialized Schwann cells, and axonal fingers projecting into the corpuscular basal lamina or connective tissue. There were at least four distinct types of corpuscular ending: Ruffini-like endings were found among dense collagen bundles, and they had a flattened nerve ending with a flattened Schwann lamella on either side. Meissner endings had an ordered stack of flattened nerve terminals with flattened Schwann cells and much basal lamina within and around the corpuscle. Simple corpuscles were single nerve endings surrounded by several layers of concentric lamellar Schwann processes. Glomerular endings were found in lamina propria papillae or encircling epithelial papillae; they were a tangle of varied neural forms each of which had apposed flattened Schwann cells, and a layer of basal lamina of varied thickness. Fibroblasts often formed incomplete partitions around Meissner and simple corpuscles.

The axoplasm of all kinds of subepithelial sensory endings contained numerous mitochondria and vesicles, as well as occasional multivesicular bodies and lysosomes; the axoplasm of all endings was pale with few microtubules and neurofilaments. The specialized lamellar Schwann cells had much pinocytotic activity. Four kinds of junctions were found between the corpuscular sensory endings and the lamellar Schwann cells: (1) symmetric densities that resemble desmosomes; (2) asymmetric densities with either the neuronal or glial membrane more dense; (3) neural membrane densities adjacent to Schwann parallel inner and outer membrane densities; and (4) sites of apparent Schwann endocytosis associated with neural blebs. The “free” sensory endings only made occasional desmosome-like junctions with their Schwann cells.

These observations are discussed in relation to possible mechanosensory transduction mechanisms, with particular attention to axoplasmic structure, axonal fingers, and neural and nonneural cell associations.     

Dissolved organic matter in Chascomús Pond (Argentina). Influence of calcium carbonate on humic acid concentration

Water chemistry of the Chascomús Pond (Province of Buenos Aires, Argentina) was studied during a year characterized by low precipitation. Supersaturation of calcium carbonate up to a calcite saturation index of about 20 in spring and summer was observed, together with a diminution of the concentration of dissolved organic matter, in particular humic substances (HS). These results suggested an adsorption between organic matter and calcium carbonate which should influence the growth of calcium carbonate crystals. A preferential removal of higher molecular weight HS was observed by gel permeation chromatography experiments.Contribution N° 524, Instituto de Limnología Dr Raúl A. Ringuelet.     

Transitional epithelium of urinary tract in normal and dehydrated rats

Summary This report is a light microscopic histochemical and fine structural study of transitional epithelium of the urinary tract of normal and dehydrated rats. Four types of cells were recognized: basal, intermediate, squamous or luminal and bundle cells. The transitional epithelium of normal rat ureter and bladder shows distinct cytoplasmic staining of the squamous cells layer by PAS. The luminal free border stains more intensely with PAS. With the electron microscope, abundant cytoplasmic tonofilaments, free ribosomes and the characteristic thick-walled fusiform and round vesicles are observed, which were in greater number in the squamous cells. Lysosomes are identified with PAS, and Toluidine Blue 0, by their content of acid phosphatase and non-specific carboxylic esterase, and by their ultrastructural appearance. The bundle cell (Hicks, 1965) is characterized by histochemical technics. These cells form about 2.5% of the total cell population of normal transitional epithelium. The bundle cell contains basophilic metachromatic granules, which indicates the presence of a weakly acid mucosubstance. It is suggested that bundle cell granules are released in the intercellular spaces of transitional epithelium and that the mucosubstance may regulate flow of ions and metabolites in the epithelial intercellular channels.Several ultrastructural changes occur in the transitional epithelium of dehydrated rats: marked increase in number of thick-walled vesicles, development of polysomes, relative increase of cytoplasmic filaments and greater number of enlarged lysosomes. Bundle cells decrease in number. These ultrastructural changes promptly regressed by allowing the animal to drink water.It is suggested that the rate of formation of the characteristic vesicles of transitional epithelium, a function of membrane synthesis, may be under the control of the antidiuretic hormone.This investigation was supported in part by the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina, through a travel grant to Dr. Monis, who would like to thank Dr. E. de Robertis for the use of the electron microscope facilities of the Instituto de Anatomía General y Embriología, Facultad de Medicina, Universidad de Buenos Aires.     

Estudio y clasificacion de 156 cepas del genero „Candida“ Berkhout, 1923. — Consideraciones sobre candidomicosis, (Moniliasis)

Summary The authors have made an study and an specific classification of 156 yeast-like forms of fungus beloning to the genusCandida isolated in their majority from differents products of the human body.They verify also the high percentage of parasitism with is found theCandida albicans and the roll this specimen has as an aetiological agent in certain vulvo-vaginitis, bronchomycosis, onychomycosis and perionychomycosis, moist mycosis of interdigital spaces, inguinocrural, perianal, axillary and others cutaneous folds.With the name of Candidomycosis are designed the pathological process produced by fungus beloning to the GenusCandida.

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Trabajo presentado a la 4a. Jornada Clínica de Verano en el Hospital Viña del Mar los días 25-26-27-28 de Enero de 1950. (Viña del Mar;Chile).

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Profesor Adjunto de Parasitología de la Facultad de Medicina de Buenos Aires. — Jéfe del Laboratorio del Instituto de Clínica Quirürgica.

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Médico Jefe del Laboratorio de Micología y Tuberculosis del Instituto de Microbiología e Inmunología del ProfesorHugo Vaccaro de la Universidad do Chile.-Becado durante el año 1949 en Argentina por la Comisión Nacional de Cultura, para realizer estudios de Micología con el Prof. Dr. Flavio L. Niño.

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Ayudante del Laboratorio del Instituto de Clínica Quirúrgica.     

Eremothecium ashbyii: revision y actualizacion de conceptos sobre la especie

Summary A general review of knowledge complemented with personal observations ofEremothecium ashbyii, a high level fungus producer of riboflavin (vitamin B₂), is made.Following a short history of the species, all the macro- and microscopic aspects of the cultures are investigated: hyphae, nuclei protoplasmatic inclusions, formation of sporangia (ascus) and spores germination of spores and appearance of riboflavin in the mycelial filaments. Bulbar forms, not previously reported in the literature, are described in this species for the first time. Finally, in view of the unusual morphology of the fungus, its systematic placing and phylogenetic relations are discussed.

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Trabajo realizado en el Instituto de Industrias Bioquímico Farmacéuticas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires.     

Coupled saccharification and fermentation of pre-treated Eucalyptus wood: a simple kinetic model

Coupled saccharification and fermentation of Eucalyptus globulus wood, pre-treated by acid hydrolysis and sodium hypochlorite, was carried out in two column reactors: one for enzymatic hydrolysis of the substrate at 50°C and the other for fermentation of sugars with calcium alginate-immobilized Saccharomyces cerevisiae at 30°C. A buffered solution containing cellulases at pH 4.8 was recycled through both reactors. The maximum yields were about 0.26 g ethanol per g of substrate. The results were reproduced reasonably well using a simple kinetic model consisting of two successive pseudo-first-order reactions.C. Albornoz and D. M. Ferrari are with the Centro de Investigaciones Tecnológicas (CIT), Administración Nacional de Combustibles, Alcohol y Portland (ANCAP), Pando, Canelones, C.P. 91000, Uruguay. S. Blanco and G. Ellenrieder are with Instituto de Investigaciones para la Industria Química (INIQUI), Universidad Nacional de Salta (UNSa), Buenos Aires 177, 4400 Salta, Argentina.     

Contribution à l'etude des thecamoebiens de la Province de Buenos Aires

Résumé La faune des Thécamoebiens fut étudiée dans deux étangs (La Brava et De los Padres) situe dans la Province de Buenos Aires (Argentina). Le nombre d'espèces trouvé en tout a été de 14, quelques-unes desquelles représentées par de différentes formae. Une nouvelle forma Centropyxis compressa (Cushman), forma brava n.f. a été trouvée et décrite, et une espèce de Pontigulasia a été proposée en nomenclatura aperta.

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Summary The Thecamoebiens of two lakes (La Brava and de los Padres) located in the Province of Buenos Aires (Argentina) were studied. The total number of species found is 14, several of them are represented by various formae. A new forma was found and described, namely Centropyxis compressa (Cushman), forma brava n.f. and one species of Pontigulasia was put in nomenclatura aperta.

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Departamento de Ciencias Biologicas, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires     

Activité cholinestérasique des corpuscules sensoriels cutanés de Herbst et de Grandry

Résumé L'activité cholinestérasique (ChE) a été étudiée dans les corpuscules de Herbst et de Grandry du bec de canard par la méthode de Karnovsky. Le BW 284 C 51, l'iso-OMPA et l'ésérine ont été utilisés comme inhibiteurs. Une activité cholinestérasique non spécifique (nsChE) a été identifiée dans les corpuscules. Elle est présente dès le début de leur différenciation.Corpuscule de Herbst: l'activité nsChE est localisée dans les cellules du bulbe interne (citernes périnucléaires, reticulum endoplasmique granulaire, vésicules associées à l'apppareil de Golgi) et à la surface de la membrane plaamique des cellules du bulbe interne et de la terminaison nerveuse.Corpuscule de Grandry: l'activité nsChE est localisée dans les cellules satellites (citernes périnucléaires, reticulum endoplasmique granulaire) et à la surface de la membrane plasmique des cellules satellites, des cellules de Grandry et de la terminaison nerveuse.Une forte activité nsChE a été mise en évidence dans certaines zones de contact entre les cellules dites sensorielles (cellules du bulbe interne et de Grandry) et les terminaisons nerveuses. Une réaction positive a été observée au niveau des mitochondries des cellules satellites et de la terminaison nerveuse du corpuscule de Grandry, et dans des vésicules du réticulum endoplasmique lisse des terminaisons nerveuses.Aucune activité ChE n'a été détectée dans les cellules capsulaires, les cellules de l'espace interne, les cellules de Grandry, et dans les vésicules synaptiques.Ces résultats ont été discutés en relation avec ce que l'on sait sur l'activité ChE des autres types de corpuseules sensoriels. La signification fonctionnelle de cette activité ChE et le problème de l'origine des différentes catégorics cellulaires qui constituent les corpuscules de Herbst et de Grandry ont été envisagés.

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Cholinesterase activity in the Herbst and Grandry cutaneous sensory corpusclesHistochemical study at the light and electron microscope

Summary Cholinesterase activity (ChE) was localized in the Herbst and Grandry cutaneous sensory corpuscle of the duck beak with Karnovsky's method. Controls with BW 284 C 51, iso-OMPA and eserine were carried out. A non-specific cholinesterase activity (nsChE) was identified in the corpuscles. This enzyme activity is present from the beginning of their differenciation.Herbst corpuscle: nsChE activity was localized in the inner bulb cells (perinuclear cisterna, granular endoplasmic reticulum, vesicles associated with the Golgi complex) and along the plasma membrane of inner bulb cells and nerve ending.Grandry corpuscle: nsChE activity was localized in the satellite cells (perinuclear cisterna, granular endoplasmic reticulum) and along the plasma membrane of satellite cells, Grandry cells, and nerve ending.A high nsChE activity was evident in certain zones of contact between the so-called sensory cells (inner bulb and Grandry cells) and the nerve endings. A positive reaction was seen in mitochondria of satellite cells and nerve ending for the Grandry corpuscle, and in smooth endoplasmic vesicles of the nerve endings.No ChE activity was detected in capsular cells, inner space cells, Grandry cells and in synaptic vesicles.These results are discussed in relation with what is known about ChE activity of other sensory corpuscles. The functional significance of this ChE activity and the problem of the origin of the different cells of Herbst and Grandry corpuscles have been considered.

     

Phylogeny of the tribe Colletieae (Rhamnaceae) – a sensitivity analysis of the plastid region trnL-trnF combined with morphology

The phylogenetic relationships within the tribe Colletieae (Rhamnaceae) were examined combining data from a previous morphological analysis with data from the trnL intron and trnL-F spacer. Previous studies have failed to confirm monophyly of the genus Discaria, the only genus of the tribe with an amphiantarctic distribution. The data set was analyzed using direct optimization as implemented in the computer program POY. Direct optimization searches for multiple optimal sequence alignments and is therefore well suited for analyzing DNA sequences including ambiguous alignable regions as found in the present study. Eight different costs were used for treating the indel information. Indels were treated as single events, equal to a fifth character state, or strings of gaps were treated as single events using different costs for opening a gap and extending the gap. The optimal cost set was selected by use of both character-based and topological congruence measures. Both congruence measures agreed upon a single optimal cost set. The resulting tree generally agrees with the current taxonomic treatment of the tribe Colletieae that recognizes six genera out of which three are monotypic. However, monophyly of Discaria was not supported and the results strongly suggest segregating D. nana and D. trinervis, and re-establishing the genus Ochetophila.We are grateful to the curator of the Herbario Gaspar Xuárez, Universidad de Buenos Aires (BAA), and to the curators of the Botanic Garden of the University of Copenhagen, Botanischer Garten und Botanisches Museum Berlin-Dahlem, Jardín Botánico Lucien Hauman (Facultad de Agronomía de la Universidad de Buenos Aires), Rancho Santa Ana Botanic Garden, and Royal Botanic Gardens, Melbourne, for permission to use material from their collections. María Elena Arce, María Martha Bianchi, Eugenia Chaia, and Neville Walsh kindly provided freshly collected material. We also thank Pablo A. Goloboff, Niels Klazenga, Pauline Y. Ladiges, Martín Ramírez, Ole Seberg, Llywela Williams, and two anonymous reviewers for critically reading earlier drafts of this paper. This work was supported in part by grants TG 028 (Universidad de Buenos Aires) and PIP 4027/96 (CONICET) to D. Medan. The University of Copenhagen supported Lone Aagesen (Ph.D. grant). Jürgen Kellermann received a Ph.D.-scholarship from the University of Melbourne.     

Occurrence of killer yeasts in Argentine wineries

Fifty-six wine must samples, from wineries in various regions of Argentina, were examined at different fermentation stages for the presence of killer yeast strains. The distribution of isolated killer strains was markedly different from one region to another.The authors are with the Instituto de Biotecnología, Facultad de Ingeniería, Universidad Nacional de San Juan, Av. Lib, Gral. San Martín 1109, Oeste 5400, San Juan, Argentina;     

Histology and ultrastructure of the neural lobe of the lizard,Klauberina riversiana

Summary The pars nervosa of Klauberina riversiana belongs to a primitive tetrapod type which is characterized by the deep penetration of the infundibular recess, a thin-walled structure, and the virtual absence of pituicytes. The differential response of this gland to aldehyde fuchsin and periodic acid Schiff suggests the presence of two types of neurosecretory nerve endings. Ultrastructurally four kinds of nerve endings are distinguishable. Type I, probably a cholinergic nerve ending, contains only small clear vesicles ca. 400 Å in diameter. The relative abundance of cholinergic nerve endings in this pars nervosa may be related to the necessity of transporting hormone through the ependymal cell. Type II, containing granulated vesicles about 1,000 Å in diameter and probably aminergic, is very rare. The two remaining types apparently secrete neurohypophysial hormones. They are Type III, containing dense granules ca. 1,500 Å in diameter and Type IV containing pale granules ca. 1,500 Å in diameter. Evidence is reviewed which suggests that Type III nerve endings may secrete arginine vasotocin while Type IV endings may secrete (an)other hormone(s).All these axons end only on the ependymal cells, the vascular processes of which form a continuous cuff over the basement membranes of the blood vessels. Hence the ependymal cells link the cerebrospinal fluid, the nerve endings and the blood vessels. Particles resolvable with the electron microscope are traced through a possible transport pathway from the granules, through the ependymal cells to the basement membrane. It is suggested that pituicytes replace ependymal cells and assume their transport functions in animals with massive neural lobes containing large numbers of nerve endings and blood vessels.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.This investigation was supported in part by a Public Health Service fellowship 1 FZ HD 32,949-01 REP from the national Institute of Child Health and Human Development.The authors wish to thank Professor H. Heller for his constant interest and constructive criticism.     

Ultrastructure of the neurohaemal region of the toad median eminence

Summary According to the internal structure and size of the granules, six types of nerve endings can be distinguished in the toad median eminence: 1. Endings containing mostly dense granules of 600 Å in diameter; 2. Endings containing dense granules of about 800 Å in diameter; 3. Endings which contain dense granules 1,000–2,000 Å in diameter, with the peak at 1,200–1,400 Å; 4. Endings containing granules with a characteristic structure, which differentiate them from the other three types; 5. Scarce endings containing granules 2,000 to 3,800 Å in diameter; and 6. Endings containing only vesicles 400–500 Å in diameter. Types 3 and 4 endings are mainly found in the outer pericapillary zone, and are probably responsible for the strong Gomori-positive reaction observed in this zone. The other four types of endings occur mainly in the inner pericapillary zone, and appear to be Gomori-negative.The probable origins of the different types of endings, and their possible relations with the different releasing factors is discussed.The subendothelial basement membrane has numerous long processes which form a complicated network in contact with all the nerve endings, some nerve fibres and glial cells.Two types of glial cells are described. Pinocytotic vesicles are frequently seen at the points where these cells contact the basement membrane. All the ultrastructural features suggest that these cells are carrying out transport functions.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.The author is very grateful to Professor H. Heller for his continued encouragement and criticism and to Mr. J. Lane and Mr. P. Heap for their valuable help.     

Plant communities and phytogeographical position of a large depression in the Great Chaco,Argentina

A survey is presented of the vegetation of the central region of the Santafesinian Chaco (Argentina), a scarcely populated flat area of 20 000 km², with seasonal flooding. Soils have a strong halo-hydromorphic character and vegetation is basically halophilous. Trees are scarce and most communities are savannas, grasslands or swampy vegetation. Twenty-three communities are described, some of them with several variants. The most widespread communities areSpartina argentinensis grasslands,Elyonurus muticus savannas and a complex of hygrophilous communities. The most important communities are distributed in relation to a topographical gradient, and their structure is shaped by recurrent flooding and fire disturbance. Most of the area is virgin land with very little human interference. The phytogeographical position of the area is discussed. Nomenclature: Burkart, A. 1969, 1974, 1979. Flora ilustrada de Entre Rios, INTA, Buenos Aires, and Cabrera, 1963, 1965a, b, 1967, 1968, 1970. Flora de la Provincia de Buenos Aires, INTA, Buenos Aires.     

Filiform papillae as a sensory apparatus in the tongue: An immunohistochemical study of nervous elements by use of neurofilamcnt protein (NFP) and S-100 protein antibodies

Summary Nervous elements supplying the filiform papillae of the tongue of cattle and rats were investigated using immunohistochemistry against neurofilament protein (NFP) and glia-specific S-100 protein. The rod-shaped bovine filiform papillae were heavily keratinized along their entire length and lacked the connective tissue core that occurs in other mammals. Instead, the core was located posterior to the filiform papilla. The base of the bovine filiform papillae was invaded vertically by laminar connective tissue papillae. The core contained a large number of NFP-positive nerve fibers, most of them terminating as free endings in its anterior margin. NFP-positive nerves gathered around the anterior ridge of the epithelium at the base of the core and occasionally penetrated into the epithelium. The laminar connective tissue papillae at the base of the filiform papilla also contained NFP-positive nerve fibers. The core contained S-100-immunoreactive lamellated corpuscles, which were identified as simple corpuscles in electron micrographs. The structure and innervation of the bovine filiform papilla suggest that they represent a specialized sensory apparatus. The pyramidal filiform papillae of the rat were smaller, each containing a simple connective tissue core. Few NFP-positive nerve fibers from the nerve plexus entered the core. Filiform papillae are thus less specialized in rats than in cattle.     

Ependymal specializations

Summary The primary plexus of the toad hypothalamic-adenohypophysial portal system has two types of loops. The short loops are localized in the external region of the median eminence and surrounded by nerve endings and glial cells. The long loops approach the ependymal lining of the median eminence. The ascending and descending branches of these loops are surrounded by nerve and ependymal endings and glial cells. The actual subependymal portion of the long loops is virtually in contact with ependymal processes only, which form a cuff interposed between this portion of the long loops and the fibres of the hypothalamic-neurohypophysial tract. Many of the vascular endings of the ependymal processes have electron dense granules whose diameter ranges between 700 and 1400 Å. The ultrastructure of the ependymal cells suggests that these granules are transport material and not secretory material.This anatomical arrangement linking the ependyma of the median eminence and the long loops of the primary plexus of the hypothalamic-adenohypophysial portal system makes the possibility of an interrelationship between the cerebrospinal fluid and the portal blood very considerable.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina. The author takes great pleasure in thanking Prof. H. Heller for his constant interest and criticism.     

Yearly reproductive activity of Limnoperna fortunei (Bivalvia) as inferred from the occurrence of its larvae in the plankton of the lower Paraná river and the Río de la Plata estuary (Argentina)

Densities of planktonic larvae of the Asian freshwater invasive pest bivalve Limnoperna fortunei (Dunker) were monitored weekly between 19 September 1997 and 22 January 1999 at two sites: the Paraná de las Palmas river, ca. 130 km north of Buenos Aires (33°57.5 S, 59°12.5 W), and a coastal station on the Río de la Plata estuary, in Buenos Aires (34°33.5 S, 58°24.5 W). Very variable but generally high (up to 25000–35000 ind. m^–3) concentrations were recorded at both sites in September 1997-April 1998, and again in August 1998–January 1999, suggesting continuous reproduction during these months. In May through July 1998 larval densities were generally below 100-200 ind. m^–3. The threshold temperature level associated with the onset and termination of reproduction was ca. 16–17 °C. With the exception of August-September 1998, when Río de la Plata temperatures were below 16.7 °C and larval concentrations less than 1000 ind. m^–3, whereas those of the Paraná were above 16.7 °C, with 1300–13000 larvae m^–3, coupling between the two sites investigated was generally good. Since its invasion in Argentina around 1990, L. fortunei has rapidly become a major nuisance for industrial and power plants located along the lower Paraná and Río de la Plata. The fact that the mollusc produces larvae during 9 months per year greatly hinders its control.     

Structure of the sensory innervation of the anal canal in the pig. A light- and electron-microscopical study

The sensory innervation of the anal canal of the pig was investigated by light and electron microscopy. The distribution of the different types of sensory nerve endings correlates with the histology of different zones: (1) After the rectal mucosa there was a zone lined with nonkeratinized stratified squamous epithelium. (2) A middle zone was lined with keratinized stratified squamous epithelium. Here the dermis already showed a papillary and reticular layer. (3) The last zone showed hairy skin with a high hair density. The following nerve endings were found: Free nerve endings reached the stratum superficiale in nonkeratinized squamous epithelium and the stratum granulosum in the keratinized squamous epithelium. Dermal free nerve endings were found in all zones near the epithelium and two different types were identified as those derived from C-fibers and those from A-delta-fibers. Merkel nerve endings showed different features depending on their location. Few Merkel-like cells were found in the epithelium of the anal crypts. Typical Merkel Tastscheiben were located at the base of epithelial ridges or pegs in zones 2 and 3. The number of Merkel cells varied up to 200. The myelinated afferent fiber supplied 10-15 Merkel cells. Merkel cells were also found regularly in the outermost layer of the external rooth sheath of hair follicles at about the same level as perifollicular nerve endings. Lamellated corpuscles were found in the dermis of all zones except the cranial part of zone 1, where the anal crypts are located. Generally they consisted of a central nerve terminal which may be branched. Each terminal was surrounded by an inner core of concentrically arranged lamellae of the terminal Schwann cell and one or several inner cores were included in a capsule of perineural cells. The size of the corpuscle, the regularity of the inner core and the number of capsular layers depended on the location of the corpuscle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histology and ultrastructure of the neurohypophysis of the south american lungfish,Lepidosiren paradoxa

Summary The neurohypophysis of the South American lungfish Lepidosiren paradoxa has been studied with light and electron microscopy, including the Falck-Hillarp technique for catecholamines. The pars nervosa hypophyseos is a well-marked, dorsally located subdivision of the pituitary gland composed of lobes or follicles, each one constituted of a central core of ependymal cells, a subependymal hilar region made up of nerve fibers and a peripheric palisade zone of nerve endings which contact capillary vessels. Four types of neurosecretory axons can be distinguished under the electron microscope. Type I, the most common, contains spherical elementary granules of high electron density, 1500–1800 Å in diameter. The scarce type II axons contain irregularly-shaped elementary granules. Type III contains only small clear vesicles, 400–600 Å in diameter. Type IV, mostly present in regions of the gland contacting the pars intermedia, contain large granulated vesicles, 900–1000 Å in diameter. The Falck-Hillarp technique revealed axons with a positive reaction for catecholamines at sites corresponding approximately to the location of type IV of the electron microscope.Ependymal cells are of large size, linking the cerebrospinal fluid, the nerve endings and the blood vessels. A conspicuous membrane-bound, spherical dense material, 1400–2000 Å in diameter, is observed in both the apical and vascular processes of these cells. The ependymal processes which traverse the hilar and palisade regions contain structures resembling degenerated neurosecretory axons. These results are discussed in relation with the currently available information on the comparative anatomy of the pars nervosa. The possible functional significance of ependymal cells and of each type of axon are also discussed.This study was aided by the following grants: NIH NS 06953 to Prof. De Robertis, Consejo Nacional de Investigaciones Científicas y Técnicas to Prof. Zambrano, Comisión de Investigaciones Científicas de la Provincia de Buenos Aires and Comisión de Investigaciones Cientificas de la Universidad Nacional de la Plata: to Prof. Iturriza.The authors are indebted to Prof. De Robertis for his generosity in granting us his laboratory facilities, and to Dr. F. J. J. Risso and Mr. A. Fernández (Resistencia, Chaco) who provided the specimens used in this study. The able microtechnical assistance of Miss L. Riboldazzi and Mrs. R. Raña and the photographic work of Mr. A. Saenz are much appreciated.Members of the Scientific Career, Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.