Hypothalamic control of the pars intermedia in Xenopus laevis tadpoles

Summary In Xenopus laevis tadpoles the relation between a paired nucleus of bio-amine producing neurons in the caudal hypothalamus and the pars intermedia of the hypophysis was studied.Treatment of the animals (stage 49 to 50 of Nieuwkoop and Faber's normal table) with reserpine caused aggregation of the skin melanophores within one hour, followed by redispersion five to six hours after the beginning of the experiment. This was at exactly the same time as the bio-amines in the caudal hypothalamus disappeared. However, the drug was ineffective if the nuclei had been removed. This indicates that reserpine acts via these nuclei and does not influence the skin melanophores directly.It was concluded that the initial aggregation of the melanophores may be the result of a reduced extrusion of MSH from the pars intermedia, caused by an increased output of a MIF by the bio-amine producing nuclei. The redispersion was explained by assuming that the bio-amines were depleted and the nuclei stopped with the extrusion of the MIF. This does not mean that the production of a MIF is the only function of the paired bio-amine producing nucleus in the caudal hypothalamus.The author thanks Prof. Dr. P. G. W. J. van Oordt for his helpful comments and criticism. Mr. J. H. I. J. M. ten Berge and Mr. E. W. A. Kamperdijk provided great assistance during the course of the experiments. Mr. H. van Kooten made the diagram and the photograph.     

The taxonomic status ofToxoplasma gondii

Summary The taxonomic status ofToxoplasma gondii is reviewed. Two electron photographs are figured, in which up to now non described structures are visible: 1. at the anterior end a conus, which is not identical with the conoid ofGustafson, Agar andCramer; 2. the invagination of this conoid into the anterior pole (conus). Arguments are mentioned speaking for the possibility of a relationship ofToxoplasma with theGregarines. So long as no more arguments are put forward, it deserves recommendation to classifyToxoplasma with unclassifiedSporozoa.     

Some aspects of the fine structure of the statocysts of the molluscsPecten andPterotrachea

Summary The statocyst ofPecten is composed of hair cells and supporting cells. The hair cells bear kinocilia and microvilli at their distal ends and the supporting cells bear microvilli. The cilia have a 9+2 internal filament content, and arise from basal bodies that have roots, basal feet and microtubular connections. Two different ciliary arrangements are described, one with a small number of cilia arranged in a ring, and another with many more cilia arranged in rows. Below the hair cells are probable synapses. A ciliated duct connects to the lumen of the static sac and passes through the centre of the static nerve. The hair cells in the statocyst ofPterotrachea bear kinocilia and microvilli. The possible importance of cilia and microvilli in the transduction process is discussed.We would like to thank ProfessorJ. Z. Young for bringing specimens ofPterotrachea from Naples and also the staff of the Stazione Zoologica for the provision of specimens, Dr.M. Land for providing specimens ofPecten, the Science Research Council (U.K.) for providing the electron microscope used in much of the study and also for a grant to one of us (V.C.B.), and Mrs.J. Parkers and Mr.R. Moss and Mrs.J. Hamilton for much photographic and technical assistance.     

Effects of fumarate,l-malate,and anAspergillus oryzae fermentation extract ond-lactate Utilization by the ruminal bacteriumSelenomonas ruminantium

Growth ofSelenomonas ruminantium HD4 in medium that contained 21mm d-lactate was stimulated to varying degrees by 10mm l-malate, 10mm fumarate, and 2% (v/v)Aspergillus oryzae fermentation extract (Amaferm). Amaferm treatment caused the greatest growth stimulation. Initial uptake rates (30s) and long-term uptake rates (30 min) ofd-lactate by whole cells ofS. ruminantium were increased in the presence of 10mm l-malate. Amaferm (25 l/ml) also stimulated long-term uptake rates ofd-lactate, whereas fumarate had no effect. Initial uptake ofd-lactate was depressed in the presence of fumarate or Amaferm. When eitherl-malate, fumarate, or Amaferm was included in thed-lactate growth medium, a homosuccinate fermentation resulted and an inverse relationship was observed between growth (protein synthesis) and succinate production. Recent research demonstrated that Amaferm containsl-malate, and this dicarboxylic acid may be involved in stimulatingd-lactate utilization byS. ruminantium.     

Skeletal anatomy of the Late Cretaceous shark,Squalicorax (Neoselachii: Anacoracidae)

The paleobiology of the Cretaceous neoselachian shark,Squalicorax, has largely been based on isolated teeth. We examined partial and nearly complete skeletons of three species ofSqualicorax, S. falcatus (Aoassiz),S. kaupi (Agassiz), andS. pristodontus (Agassiz), that were collected from the U.S.A. These specimens suggest that the total body length (TL) ofS. falcatus typically measured 1.8–2.0 m, and probably did not exceed 3 m. Moderatesized individuals ofS. kaupi andS. pristodontus perhaps measured about 3 m TL. AlthoughS. pristodontus was the largest form among the three species examined, this taxon possessed a set of large jaws (with large but fewer teeth) relative to its body size compared toS. falcatus orS. kaupi. This suggests that tooth size is not an accurate indicator of the TL if one compares oneSqualicorax species to another. Neurocranial features suggest that the vision ofSqualicorax was not as acute as that of a contemporaneous macrophagous lamniform shark,Cretoxyrhina mantelli (Agassiz) , but olfaction ofSqualicorax may have been better thanC. mantelli. The morphology of placoid scales suggests thatSqualicorax was capable of fast swimming. New skeletal data support the view that the feeding dynamics ofSqualicorax was similar to the modern tiger shark (Galeocerdo Müller & Henle). The present data do not allow for exact ordinal placement, but, contrary to some previous interpretations,Squalicorax can be excluded from the Hexanchiformes and Orectolobiformes. The taxon should more appropriately be placed within the Lamniformes or Carcharhiniformes.      

Fine structure of mycota 12. Karyochorisis — somatic nuclear division — in Cordyceps militaris

Summary The literature on somatic nuclear division in the fungi consistently suggests that, with but one present exception, the process is non-mitotic. The correlation of previous electron microscopic studies of yeasts with the present study of Cordyceps militaris supports this interpretation and provides a possible mechanism, identified as karyochorisis (nuclear sundrance). During karyochorisis there are two successive invaginations of the inner and outer elements of the perinuclear cisterna. The invagination of the inner nuclear membrane divides the nucleoplasm into two or more subunits described by the new term karyome. The subsequent invagination of the outer nuclear membrane separates the karyomes into daughter nuclei. It is suggested that, in contrast to continued sterile efforts to prove that mitosis is the general mode of fungal somatic nuclear division, the hypothesis of karyochorisis raises new questions that offer new areas for future research. Four that are put forth are 1. the possibility of a correlation between nuclear size and the mode of division; 2. the nature of the mechanism of chromosome replication and separation; 3. the cause of nuclear elongation and the possibility that its initiation depends on a critical RNA volume; and 4. the possibility that colchicine produces polyploidy by blocking the invaginations of the nuclear envelope. In a concluding section the suggestion is made that the proposed hypothetical mode of fungal nuclear division, karyochorisis, may represent only a special example of a general phenomenon of division of double membrane organelles in primitive cells.It is a pleasure to acknowledge the technical assistance of Mrs. Barbara Raymond, Messrs. Lloyd Thibodeau and Philip Spencer of our Laboratory and to thank Professor R. Emerson and Mr. Robert Berman of the Botany Department for making available material of Blastocladiella.This investigation was supported by Postdoctoral Fellowships 9197-C2 and 2F2 AI 9197-04 from the United States National Institute of Allergy and Infectious Diseases, Dr. James H. McAlear, sponsor; and partly by grant AI-05514-01 from the same Institute.     

The ultrastructure of the test of the tadpole larva ofCiona intestinalis

Summary The test of the tadpole larva ofCiona intestinalis consists of an amorphous background substance in which are long 4–7 nm fibrils. There is a narrow outer dense region of the test where both the background material and the test fibrils are more concentrated and orientated. Fibrils of similar dimensions are found in the epithelial cells below the test, and also in cells associated with the outside surface of the test. No such fibrils are found in the cells located within the test substance. There are some regions where the external cell membrane of the epithelial cells is indistinct and in these regions the fibrils of the test are continuous with the fibrils within the epithelial cells. No large or small vesicles opening from the epithelial cells into the test have been seen.This evidence has been interpreted as support for the tunicization theory of test formation. It is suggested that the cells within the test are the source of the polyphenols that are necessary for quinone tanning that gives rigidity to the test.The fibril-containing cells outside the test probably add fibres to the cuticular region of the test.I wish to thank ProfessorJ. Z. Young, F.R.S. for much advice and encouragment, also Dr.R. Bellairs for the use of electron microscope facilities and Mr.R. Moss and Mrs.J. Hamilton for skillful technical assistance.     

The fine structural localization of acid phosphatase in the gut epithelial cells of the slug,Avion ater (L.)

Summary Acid phosphatase, generally thought of as a lysosomal enzyme and indeed widely employed as a lysosomal marker, has been found associated with the Golgi complex of all cell types from the crop, intestine and digestive gland ofArion ater. Reaction product was also detected within the multivesicular bodies and cytoplasm of columnar cells from the crop and the multivesicular bodies of mucous cells from the intestine. A vacuolar localization was obtained in the digestive cells of the intestine and digestive gland. Secretory protein granules in the calcium cells of the same gland and apical vacuoles in the so-called thin cells also showed a positive reaction.This work was undertaken as part of a slug research project under the direction and co-ordination of Dr. D. K.Roach, supported by A.R.C. Assistance was given by Mr. T. R.Mainwaring in the preparation of tissue for electron microscopy.I would like to thank Professor J.Brough and Professor D.Bellamy for providing facilities and encouragement.     

Evidence for the association of homologous chromosomes during premeiotic stages inImpatiens andSalvia

Chromocenters in the last premeiotic interphase nuclei ofImpatiens balsamina (2n=14) andSalvia nemorosa (2n=14) were found to be associated in groups of two's, some times so closely that only the haploid number was seen. InImpatiens balsamina, the chromosomes during the mitotic prophase in sporogenous cells and the chromocenters in the root tip cells were observed to be homologously aligned. It is concluded on the basis of their morphology that the homologous chromocenters remain associated in pairs at least during the last premeiotic interphase and loosely aligned in other tissues of the plants studied.This work was supported by a German Academic Exchange Service (DAAD) Scholarship awarded toK. P. S. Chauhan, who is thankful to Prof. Dr.E. Knapp for kindly providing the necessary facilities to carry out this work at his Institut.     

On the occurrence of twisted fibrillar structures in the cytoplasm of the red algaAlsidium helminthochorton (La Tourette) Kütz., ultrastructural and cytochemical observations

Summary The cytoplasm ofAlsidium cells contains unusual structures showing various fibrillar arrangements, either stacked rows of arcs or parallel fibrils in longitudinal view alternating with fibrils in cross-section. These regions, located exclusively in the cytoplasmic matrix, are highly proteinaceous and do not seem to be complexed with polysaccharides. Tilting observations under the electron microscope show that the appearance of arcs is an illusion and that the pattern fits the explanation given byBouligand and collaborators for various twisted biological structures.     

The comparison of four strains of Coccidioides immitis with diverse histories

Summary By the criterion of lethality in mice, a strain ofCoccidioides immitis recently isolated from a most devastating form of human coccidioidomycosis was of no greater virulence than another isolated from a much less severe case or even one cultured from soil fifteen years ago and which presumably had caused seven self-limited, benign cases of primary coccidioidomycosis. There was no enhancement of virulence to mice by twelve passages of a relatively avirulent strain which had been recovered twenty-one years ago from a fatal human case.This work was supported in part by a contract between the University of Calif., Department of Bacteriology and the Office of Naval Research and part under the sponsorship of the Commission on Acute Respiratory Diseases of the Armed Forces Epidemiological Board and was supported by the Office of the Surgeon General, Department of the Army.The opinions contained in this report are not to be construed as reflecting the views of the Navy Department or the Naval Service at large (Article 1252, U.S. Navy Regulations, 1948).The authors gratefully acknowledge the photographic service of Mr.William F. Hetrick and the technical services of Mr.Robert J. Berman.     

Ultrastructural study of the regressing prothoracic glands of blattarian insects

Summary The prothoracic glands, source of the molting hormone ecdysone, regress within a few days after the final molt, a process which was analyzed with electron microscopic methods in the cockroaches Leucophaea and Blaberus. This strictly timed event is accompanied by drastic alterations in cellular fine structure. Early signs of breakdown appear in groups of nuclei whose substance becomes segregated into patches of contrasting electron density characteristic of pyknosis.The most conspicuous change in the cytoplasm of parenchymal cells concerns the appearance of large, heterogeneous inclusion bodies in which various cellular elements become segregated. These compartments seem to represent autophagic vacuoles within which the gradual degradation of much of their contents takes place, presumably under the influence of lysosomal enzymes. Undigested swirls of membranous character may remain sequestered within these packets for some time.At advanced stages of cellular atrophy, plasma membranes and nuclear envelopes have gradually disappeared, and masses of protoplasm undergoing autolysis become invaded by a greater number of hemocytes than are present in nymphal glands. These phagocytic elements appear to engulf debris of parenchymal cells as well as some degenerating connective tissue elements. After the completion of the regressive process, the axial band of musculature characteristic of the nymphal gland persists on its own. Whether or not some parenchymal cells (or possibly their precursors) capable of reactivation persist in the proximity of this muscle is unknown.The resorption of the prothoracic gland in the newly emerged insect is the result of physiological autolysis and seems to be aided by the activity of phagocytic hemocytes.Dedicated to Professor W. Bargmann on his 60th birthday in friendship and admiration.This study was supported by Research Grants AM-03984, NB-02145 and NB-05219 from the U.S.P.H.S.I wish to express my thanks to Mrs. S. Wurzelmann, Mrs. C. Jones, Mrs. C. Grubman, and Mr. S. Brown for their excellent technical assistance.     

Phage typing ofSalmonella Typhi in the Netherlands

Summary A survey has been given of the results of phage typing of strains ofS. typhi found in Holland. It has been shown, that type A includes a different group of strains in systems drawn up with different Vi phages. An auxiliary system — to be used besides the system ofCraigie andYen — and a few new types, have been described.     

The role of the thyroid in the development of Mauthner's neuron

Summary Although the normal postmetamorphic atrophy of the giant neurons of Mauthner in anuran amphibians has been attributed to the direct or indirect action of thyroid hormone, the administration of exogenous thyroxin to Rana pipiens larvae appears to facilitate growth of the neuron rather than inhibit it. In the present investigation, Rana pipiens embryos were surgically thyroidectomized. In the absence of the thyroid, metamorphosis never occurred, and hind limb development was arrested at larval stages VI–VIII. However, these animals continued their growth and often exceed their controls in overall size. Mauthner cells of thyroidectomized larvae have nuclei of significantly smaller size than their controls. The observations are consonant with the view that thyroid hormones play an important positive role in the growth and maintenance of Mauthner's cell. It is further indicated that the growth of Mauthner's neuron is more dependent upon the titer of thyroid hormone in the blood than it is upon age, brain size, tail motor influences, or the state of the lateral line system.Dedicated to Professor Berta Scharrer on her 60th birthday. This study was supported by Grants NB-04555, IGS-98 and 5 T 1-GM-102 from the U.S.P.H.S.I am pleased to acknowledge the excellent technical assistance of Mrs. Celia Grubman.     

Development of the zoosporangia ofSynchytrium endobioticum,the causal agent of potato wart disease

Summary An ultrastructural study of zoosporangium development ofSynchytrium, endobioticum (Schilb.) Perc. is presented. Emphasis is placed on the location of the parasitic fungal thallus in the potato host cell, on the specific location of organelles in relation to the developing zoosporangial wall, and on the host cell reaction to the fungal infection. The cytoplasmic organization of the individual sporangia after division of the zoosporangium into a sorus of sporangia is characterized by numerous similarly sized nuclei, well developed dictyosomes, and the presence of many lipid bodies of variable size. Cytoplasmic microtubules are observed to flare out from the functional kinetosome both before and after zoospore cleavage.The ultrastructural details of zoosporangium development are used to revaluate the life cycle ofS. endobioticum as described from light microscopic observations made early in the century (Curtis 1921;Köhler 1923, 1932;Percival 1910).     

Transport of basic amino acids and regulation of aspartate kinase activity in thialysine andL-canavanine resistant strains ofSerratia marcescens

Growth ofSerratia marcescens was not inhibited by high concentrations ofL-lysine and its structural analogues,L-canavanine and S-(2-aminoethyl)-L-cysteine (thialysine). This insensitivity was not caused by deficient transport of basic amino acids, unlike in mutant strains ofEscherichia coli having the same properties. The tested strains showed a lack of regulation at the aspartate kinase level towardL-lysine and thialysine. The data indicate great intraspecific variability for aspartate kinase regulation inS. marcescens.     

Ultrastructural localization ofl -fucose residues in nuclei of root primordia of the green peaPisum sativum

Summary Sugars have been demonstrated in animal cell nuclei, but only a few studies have mentioned their presence in plant cell nuclei. In this studyl-fucose residues were localized at the ultrastructural level, usingUlex europeaus agglutinin I lectin, during the early stages of germination ofPisum sativum and in mature root tip cells. This sugar was present after 1 h of germination, and its concentration was found to vary during 3 to 6 h imbition; after 72 h of imbition its concentration had more than doubled. Furthermore, labelling was particularly abundant in the nucleolus, nucleolus-associated bodies and dense nuclear bodies. The possibility that some of thel-fucose residues are associated with proteins is discussed.     

Neoschumannia (includingSwynnertonia), a primitive genus of theAsclepiadaceae-Stapelieae

A comparison of the West AfricanNeoschumannia Schltr. and the East AfricanSwynnertonia S. Moore reveals that the two monotypic genera must be united.Swynnertonia is sunk into synonymy ofNeoschumannia and the new combinationNeoschumannia cardinea (S. Moore)Meve is made for the East African species.Neoschumannia is shown to belong to the tribeStapelieae. The taxon exhibits a very unusual character combination: the growth form of a woody liana is combined with a tripartite corona unique within theAsclepiadaceae. The morphology of the corona suggests a position ofNeoschumannia close to the base of theStapelieae —Ceropegiinae alliance.     

Morphological and cytological investigations ofUlothrix zonata and taxonomy of the related species

The present communication deals with the observations made on the morphology, reproduction and cytology ofUlothrix zonata (Weber & Mohr)Kütz. in culture. The alga displays a remarkable phenotypic plasticity in nature as well as in culture. The present study provides additional evidence of karyology in support ofLokhorst andVroman's treatment ofU. zonata which merges a number of earlier described species in it. The cytological details and chromosome number (n = 10) determined for the Indian isolates ofU. zonata agree with those ofSarma for the British material.NBRI Research Publication No. 63 (N.S.)     

Zur elektronenmikroskopischen Untersuchung der juxtaglomerulären Spezialeinrichtungen der Niere

Summary After a general view of the constituents of the juxtaglomerular apparatus of the kidney, the authors are presently publishing on this subject some of their preliminary findings which have been obtained with the aid of the electron microscope:The cells of the macula densa are distinguished from the other cells of the distal convoluted tubule by a lesser development of the infolded basal plasma membranes as well as that of the chondriome which is generally found in a circumand supranuclear position.The cells of Goormaghtigh are in a close topographical relationship with the macula densa, although separated from it by a basement membrane; they are integrated in a complex system of basement membranes.The epithelioid cells of the afferent arteriole contain, in addition to ribosomes and ergastoplasmic structures, vesicles of which the size and the contrast of the content are different. paraportal cells of Becher have not as yet been positively identified with the electron microscope.The intertubular space is poor in cells; the various interstitial cells, often rich in ergastoplasm, are yet to be studied in detail.

---

---

Mit Unterstützung durch die Fritz Hoffmann-La Roche-Stiftung zur Förderung wissenschaftlicher Arbeitsgemeinschaften in der Schweiz.