The influence of sulfhydryl on the formation of aberrant disorganized overgrowths in the regenerating right chela of the hermit crab (Pagurus Longicarpus)

Conclusions Sulfhydryl accelerates and sulfoxide retards the growth, differentiation, and expression of trend to organization of aberrant disorganized overgrowths emerging from tear lesions arising from injury to the regenerating chelae of the Hermit crab.Sulfhydryl is specifically responsible for the formation of certain typical emergent disorganized growths from the distal end of the Hermit crab chela.The material for this study was collected at the Marine Experimental Station of The Research Institute of the Lankenau Hospital at North Truro, Massachusetts, under grants from Mr.August Bein of Philadelphia, and the Capt. L. D.Baker Estate of Boston and Wellfleet.     

The effect of radium on growth and development in eggs of Crepidula and Pagurus

Summary Radiant energy from radium in weak and non-destructive amounts slows down the size growth ofCrepidula eggs and markedly retards their course of differentiation and that ofPagurus embryos. Since this can be traced to destruction of sulfhydryl, again evidence is adduced of the relationship between this chemical group, cell multiplication, and differential development.Research Fellows of The Ladies Aid Society of The Lankenau Hospital.This study was made at the Marine Experimental Station of The Research Institute of The Lankenau Hospital, North Truro, Massachusetts, under grants from Mr.August Bein of Philadelphia, and the Capt. L. D.Baker Estate of Boston and Wellfleet.     

Nerve supply and distribution of cholinesterase activity in the external nose of the mole

Summary Nerve supply and the distribution of cholinesterase activity were studied in the skin of the external nose of seven moles using a simplified Bielschowsky-Gross silver method and Koelle's histochemical technique.The sensory units of the mole's nose or the organs of Eimer are surrounded by blood sinuses which facilitate their movements during mechanical stimulation. All nerve fibres of the plexus deep to the basal cell layer of Eimer's organ ultimately become intra-epidermal endings. Contrary to the findings of earlier investigators, Merkel's discs, Pacinian corpuscles and Ruffini corpuscles have not been observed at the base of Eimer's organ. In the superficial layer of the plexus, the Schwann sheath cells increase in number, undergo modification and give a positive cholinesterase reaction.It is suggested that the organ of Eimer, the specialised nerve plexus deep to it and the surrounding blood sinus together constitute the touch receptor on a similar principle of transmission by leverage as in the tactile hair or the intermediate ridge of the papillary ridge.The role of the intra-epidermal nerve endings of the mole's nose as tactile receptors is disputed. A suggestion is made that tnese nerves may constitute pain and temperature receptors and that several modalities of sensation may be carried to the brain along one and the same medullated axon.We gratefully acknowledge the technical assistance of Miss Jill Hocknell. Our thanks are also due to Mr. C. J. Duncan and the staff of the Photography Department for their aid with the photographic work. We are particularly grateful to Mr. D. Burgess of the Ministry of Agriculture and Fisheries for kindly supplying us with live moles. One of the authors (N.C.) acknowledges an equipment grant from the Royal Society.     

On the invagination of the gastrula

Conclusions An experimental study of the problem of gastrulation has yielded evidence which shows that the present prevailing theories are inadequate to account for the facts.Especial attention has been given to the theory ofAssheton, according to which the geometrical relation of nuclei to the cells in the blastula is of fundamental importance to invagination. It was found that an excess of calcium added to the sea water in which the cultures ofS. purpuratus were raised caused a displacement of the nuclei to the inside so that they appeared at the edge of the blastocoele. Lithium larvae on the other hand showed the nuclei disposed toward the periphery in the cells of the blastulae. Since, however, nuclear position did not uniformly correspond to invagination or evagination as the case happened to be, the view that the position of the nuclei determines invagination had to be given up.A modification ofAssheton's view is suggested, namely, that invagination is caused by cell bridges asymmetrically placed. The eccentric attraction between the cells at the vegetal pole therefore presumably depends upon physical structures and not, asAssheton supposed, upon an attraction between the nuclei.I am glad to express my thanks to MissWinnefred Bradway and Mr. S. H.Whong for their assistance in preparing sections and making sketches, and to Mr.Henry Hill of the Yaquina Head Light House for his kindness and hospitality which made part of the work possible.Aided by a grant from the research fund of the University of Oregon.     

Studies of the effects of aminopterin on the crypts of Lieberkühn in rats

Summary Studies have been made on the effects of an intramuscular injection of aminopterin on the crypts of Lieberkühn in rats. A decrease in the mitotic counts was accompanied by a rapid increase in the number of abnormal cells present in the epithelium of the crypt. Three hours after administration of the aminopterin, an almost complete absence of true metaphase chromosoms was found. By 24 hours, a partial return towards normal mitotic activity was observed but the number of abnormal cells present was still very high. It is suggested that the mitotic changes are in keeping with the conclusion of Grampa and Dustin (1952) of an arrest at interphase but that a secondary arrest at metaphase cannot be excluded.A morphological feature of some of the abnormal cells was the presence of a Feulgen positive granule in the cytoplasm, which by electron microscopy was also shown to contain many cytoplasmic constituents. It is suggested that material is lost from the nucleus and incorporated into a granule in the cytoplasm. A possible explanation of the purpose and function of the granule, as a means of disposing of unwanted or aberrant material, is put forward. Acknowledgements. I am grateful to Professor R. J. Brocklehurst for his continued interest and support of this work, and to the Stage II, B. Sc. students (1964) who counted the cells in many of the specimens as a laboratory exercise. My thanks are also due to Mr. J. Clements for technical assistance.     

Development of the acrosomic system of the spermatozoon in the Norwegian lemming (Lemmus lemmus)

Summary An electronmicroscopic study on the development of the acrosome system of the spermatozoon in the Norwegian lemming (Lemmus lemmus) has been performed. The proacrosomal granules were found to be few and to consist of a dense center and a less dense periphery, and the acrosomal vesicle to contain stainable material of the same structure but of lower density than that of the acrosomal granule. Like in the guinea pig, two zones of different density exist throughout acrosome development and are visible also in mature spermatozoa. A large osmiophilic formation consisting of saccular, tubular, and lamellar structures, was found between the apex of the condensed nucleus and the acrosome and was identified as perforatorium.We are greatly thankful to Dr. Antti Telkkä, and Mr. Mauri Nyholm, M. Sc. for expert advise in electronmicroscopy and Mr. P. Lehtimäki for photographic help. For the supply of the lemmings we are indebted to Prof. K. Lagerspetz, and Mr. O. Hissa, M. Sc. This work is related to a series of studies on the biology of the Norwegian lemming (for previous works see Asp et al.).     

On the alleged presence of non-argyrophile argentaffin cells in the human gastro-intestinal tract

Summary The relationship between the argentaffin and argyrophile cells of the human gastrointestinal tract has been studied, in foetal and adult material, by a technique involving the staining of sections first by an argentaffin method (Gomori-hexamine silver, Schmorl, Diazonium) and subsequently by an argyrophile method (Bodian). A comparison of the cells staining by the two methods shows that all argentaffin cells of the human gastrointestinal tract are also argyrophile and that there is no evidence to support the claim of Hellweg (1952) and of HamPerl (1952) regarding the presence of non-argyrophile argentaffin cells.W. H. O. fellow from the Department of Anatomy, Medical College, Rohtak, India. — I am very grateful to Professor J. D. Boyd and to the World Health Organisation for having made it possible for me to carry out this research at the Anatomy School, Cambridge. I am indebted to Dr. G. A. Gresham and his staff for their very willing cooperation in providing material from surgical resections. My thanks are also due to Mr. J. F. Crane for the photographs and to Mr. J. W. Cash and Mr. R. Smith for helpful discussions on staining techniques.     

A possible correlation between ultrastructure and function in the thin descending and ascending limbs of the loop of Henle of rabbit kidney

Summary An ultrastructural study of the thin loops of Henle has been made in the renal papilla of the rabbit. Animals in different states of water balance were used but no morphological difference was observed in the loops obtained from animals in different experimental groupings. The cytoplasm of the squamous cells lining the limbs was characterised by a paucity of organelles. Descending and ascending limbs were distinguishable. A distinct morphological difference was seen in the junctional regions of cell processes of the descending and ascending thin limbs of the loop. The ascending limb processes were joined by continuous tight junctions whereas the descending limb junctional regions invariably showed a space of at least 70 Å between adjacent processes. It is suggested that there may be a correlation between the structure of these junctional regions and the different permeability characteristics of the two limbs. The thin ascending limb must, on physiological evidence, be relatively impermeable with reference to the thin descending limb.The author wishes to thank Professor F. R. Johnson for his advice and assistance, and Mr. R. F. Birchenough, Mr. P. L. Hyam and Mr. J. Manston for valuable technical assistance.     

Fine structure of the Paraventricular organ of Xenopus laevis tadpoles

Summary The ultrastructure of the Paraventricular organ in the hypothalamus of Xenopus laevis tadpoles is described. It appeares that the Paraventricular organ of this anuran species is homologous with the Organon vasculosum hypothalami or the Paraventricular organ of other vertebrates.The Paraventricular organ of Xenopus laevis is characterized by an ependymal lining with only few cilia and by two types of nerve cells. Both types of nerve cells have ventricular processes, protruding into the lumen of the third ventricle and forming a network. The protrusions bear cilia of the 8+1 pattern. It has been possible to distinguish both types of nerve cells on account of their dense-core vesicles. A secretory function of both cell types is suggested.In a region close to the Paraventricular organ, another granulated type of nerve cell has been observed. A relationship between these cells and the preoptic nucleus is discussed.The author thanks Prof. Dr. P. G. W. J. van Oordt for his helpful comments and criticism, Mr. H. van Kooten for photographic assistance and Mr. F. Dijk for technical assistance.     

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.     

Fine structure of cilia in rat cerebral cortex

Summary Cilia have been demonstrated on granular neurons and astroglial cells in the fascia dentata, a part of the hippocampal region, in the rat. Every granular cell seems to possess one cilium, which shows an 8+1 pattern in the greater part of its length. This 8+1 pattern is shown to result from the displacement of one peripheral doublet of a 9+0 cilium into the middle of the cilium. The neuronal cilia have a two-centriole basal organization, and fine rootlets radiate from the basal body proper into the cytoplasm. The possible function and significance of these cilia are discussed on the basis of earlier literature.This study was supported in part by Grant NB 02215 of The National Institute of Neurological Diseases and Blindness, U.S. Public Health Service, in part by The Norwegian Research Council for Science and the Humanities. This aid is gratefully acknowledged. I am greatly indebted to Dr. Th. Blackstad for encouragement and advice during this study, to Mrs. J. L. Vaaland, Mr. B. V. Johansen and Mr. E. Risnes for technical assistance, and to Dr. B. Afzelius for valuable discussions.     

Evolution of aromatic biosynthesis and fine-tuned phylogenetic positioning of Azomonas,Azotobacter and rRNA group I pseudomonads

The evolutionary history of biochemical pathways can be determined in microbial groupings for which phylogenetic trees have been established. This has been demonstrated best in Superfamily B, an assemblage of rRNA homology groups containing lineages that lead to genera such as Escherichia and other enteric microbes, Pseudomonas (Group I), Xanthomonas, Oceanospirillum, and Acinetobacter. The rRNA homology group that defines Group I pseudomonads also includes Azomonas and Azotobacter, but particular dendrogram points of evolutionary divergence for these genera within Superfamily B have not been established. Phylogenetic relationships at such intergeneric levels can be deduced by analysis of aromaticpathway enzyme arrangement and regulation in selected groupings where dynamic evolutionary changes have occurred. A case in point is illustrated by Axomonas insignis, Azotobacter paspali, and Azotobacter vinelandii — a grouping that appears to be homogeneous with respect to the evolutionary state of the aromatic pathway. The conclusion that this phylogenetic cluster diverges from an ancestor common to pseudomonad subgroup Ia (rather than to subgroup Ib) is based upon the absence of chorismate mutase-F and arogenate dehydratase, enzymes making up a twostep pathway of phenylalanine biosynthesis that is absent in subgroup Ia, but present in subgroup Ib. Of further interest, Azomonas insignis and Azotobacter sp. were found to comprise a distinctive and recently evolved sublineage, differing from subgroup Ia species in their loss of a regulatory isozyme of 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (ADHP synthase-trp) that is subject to feedback inhibition by l-tryptophan. DAHP synthase-trp is an ancient character state of Superfamily B that has been retained during the evolutionary history of most members of this Superfamily.Abbreviation DAHP 3-Deoxy-d-arabino-heptulosonate 7-phosphate     

Further evidence for the proposed way of spermatogonial stem cell renewal in the rat and the mouse

Summary By means of ³H-thymidine and autoradiography it could be established that in rats and mice the A₁, A₂ and A₃ spermatogonia do not give rise to a significant number of stem cells.The number of A₀ spermatogonia was found to be circa 20% of the number of A₀+A₁ spermatogonia in the rat and circa 10% in the mouse.The author wishes to thank Prof. Dr. M. T. Jansen and Dr. M. F. Kramer for helpful discussions and Mr. J. G. van Essen for technical assistance.     

Synaptic organization in the lateral geniculate nucleus of the monkey

Summary The synaptic organization in the lateral geniculate nucleus of the monkey has been studied by electron microscopy.The axon terminals in the lateral geniculate nucleus can be identified by the synaptic vesicles that they contain and by the specialized contacts that they make with adjacent neural processes. Two types of axon terminal have been recognized. The first type is relatively large (from 3–20 ) and contains relatively pale mitochondria, a great many vesicles and, in normal material, a small bundle of neurofilaments. These terminals have been called LP terminals. The second type is smaller (1–3 ), contains darker mitochondria, synaptic vesicles, and no neurofilaments. These have been called SD terminals.Both types of terminal make specialized axo-somatic and axo-dendritic synaptic contacts, but the axo-somatic contacts are relatively rare. In addition the LP terminals frequently make specialized contacts with the SD terminals, that is, axo-axonal contacts, and at these contacts the asymmetry of the membranes is such that the LP terminal must be regarded as pre-synaptic to the SD terminal.The majority of the synaptic contacts are identical to those that have been described previously (Gray, 1959 and 1963a) but, in addition, a new type of contact has been found. This is characterized by neurofilaments that lie close to the post-synaptic membrane, and by an irregular post-synaptic thickening. Such filamentous contacts have been found only where an LP terminal contacts a dendrite or a soma.The degeneration that follows removal of one eye demonstrates that the LP terminals are terminals of optic nerve fibres. The origin of the SD terminals is not known.The glial cells often form thin lamellae around the neural processes and tend to isolate synaptic complexes. These lamellae occasionally show a complex concentric organization similar to that of myelin.It is a pleasure to thank Prof. J. Z. Young for advice and encouragement and Dr. E. G. Gray for the considerable help he has given us. Dr. J. L. de C. Downer gave us much help with the care of the animals and with the operations. We also wish to thank Mr. K. Watkins for technical assistance and Mr. S. Waterman for the photography.     

Argyrophile and argentaffin reactions in individual granules of enterochromaffin cells of the guinea pig

Summary Successive staining of cells of the enterochromaffin system of the guinea pig by an argentaffin and an argyrophile method shows that, as in man and rabbit, they can be divided into (a) those in which all granules are apparently argentaffin, (b) those in which all granules are argyrophile but none are argentaffin, and (c) those in which some granules are argentaffin (as well as argyrophile) while others are purely argyrophile. The presence of the third type makes it evident that no hard and fast line of distinction can be drawn between the so called argentaffin and argyrophile cells.I am grateful to Mr. Mohan Lal Sharma for help with the photographs and to Mr. Anand Parkash for technical assistance.     

Argyrophile and argentaffin reactions in individual granules of enterochromaffin cells of reserpine treated guinea pigs

Summary The individual granules of enterochromaffin cells of normal and reserpine treated guinea pigs have been studied by staining slides of the duodenum first by an argentaffin method and subsequently by an argyrophile method. Some argentaffin cells can be shown to contain not only argentaffin granules, but also granules that are purely argyrophile. The relative number of such argentaffin cells is greatly increased following administration of reserpine, as depletion of their 5-hydroxytryptamine content converts argentaffin granules into purely argyrophile ones. On the basis of this finding it is confirmed that the argyrophile granule is merely an argentaffin granule depleted of its 5-HT content, and that the argyrophile (nonargentaffin) and the argentaffin cells represent different phases of a secretory cycle.This investigation was supported by a grant from the Indian Council of Medical Research. I am grateful to Ms. Ciba of India Ltd. for making available reserpine (Serpasil) and solvent for reserpine. It is a pleasure to thank Mr. Anand Parkash for technical assistance and Mr. M. L. Sharma for the photographs.     

On the glycocalyx,the external coat of the plasma membrane,of some secretory cells

Summary The free surface of epithelial cells of secretory organs (human placenta, lactating mammary gland of the rat, choroid plexus of man and rat) and of the accessory organs of the genital tract of the male rat is characterized by a plasmalemmal differentiation named glycocalyx or surface mucous coat. This structure is built up by filamentous or globular substructures.Two main ultrastructural types of the glyeocalyx were observed: 1) The filamentous type such as in the rat epididymis, which resembles the cat intestinal glyeocalyx (Ito, 1965) and that one of human transitional epithelium (Monis and Zambrano, 1968), and 2) The globular type, as observed in the lumen of the lactating mammary gland of the rat.Sialic acid was demonstrated histochemically in the luminal glyeocalyx of all organs studied. In addition, the glyeocalyx of acinar cells of the lactating mammary gland contains sulfate and phosphate groups which were identified by histochemical technics, using enzymatic digestion procedures, suggesting the chemical heterogeneity of this glyeocalyx.Present investigations follow the working hypothesis that the complex carbohydrates of glycocalyces become part of the product of activity of secreting cells.We thank Mr. Luis Iwakawa, Miss Silvia Falcón, Miss Elsa M. Orgnero for technical help, Miss Graciela Aliaga for secretarial assistance. Photography by Mr. H. Magnani. Dr. Hugo F. Carrer cooperated in the initial stages of this investigation.The authors acknowledge the use of the electron microscope of the Department of Pathology, Córdoba University Medical School, for which they thank Prof. E. Mosquera and Dr. E. Hliba. Dr. Hliba photographed picture number 4.     

Ultrastructure of the human submaxillary gland

Summary Myoepithelial cells in the human submaxillary gland are stellate in form, with long, tapering processes. They are interposed between the base of the secretory cells and the basement membrane, and are bound to the secretory cells by desmosomes. Their cytoplasm contains numerous myofilaments measuring approximately 40 Å in diameter, which frequently aggregate to form structures similar to the dark bodies seen in smooth muscle cells. The myofilaments are anchored to the plasma membrane by attachment devices. The myoepithelial cells are often accompanied by cells which have a similar shape, but possess an extremely electron-lucent cytoplasm that contains almost no organelles or inclusions. Electron microscopical observations indicate that these cells, termed clear cells, are transformed directly into myoepithelium, since all morphological intergrades between the two cell types have been recognized.This work was supported in part by a grant from the Henry Spenadel Trust. The technical assistance of Mr. Roy R. Keppie and Mrs. Mona Brandreth is gratefully acknowledged.     

Studies by negative staining on the structure of collagen fibrils in normal and lathyritic rats

Summary Electron microscope studies on collagen from rat-tail tendon using the negative staining technique indicate the presence of fine filaments 15–30 Å in diameter within the fibres. The banding of the fibrils was only slightly affected by aminoacetylnitrile bisulphate, but an increased amount of fine fibrous material was present in preparations from experimental animals. It is suggested that this material represents a soluble form of collagen which is known to predominate after administration of the drug. Despite the fact that this would be a chemically abnormal collagen, its structure by electron microscopy corresponds remarkably well with the form suggested from X-ray diffraction and physico-chemical studies on normal soluble collagen.The author would like to thank Mr. J. Clements for technical assistance and Mr. R. Thomas (Dental School, Bristol) for discussion on the effects of aminoacetylnitriles in rats.     

An electron microscopical study of the ventral nerve cord of the leech

Summary Three types of fibrillar structure can be seen with the electron microscope in nerve cells of the vental nerve cord of the leech: the neurofibrillar bundles, the tubules and the tonofibrils. In neuroglial cells only the tonofibrils are present. The three types are structurally distinct, and, contrary to past suggestions, there is no evidence that neurofibrillar bundles may consist of tightly packed or badly fixed tubules.In vertebrates the electron microscope reveals bundles of discrete neurofilaments that form the basis for the argyrophilic neurofibrillae seen by light microscopy. Each neurofilamentous unit appears as a dot in cross section. In contrast, in the leech, the electron microscope shows compact fibrillar bundles that clearly correspond to the neurofibrils described by light microscopists. These bundles are made up of closely packed units rather than discrete filaments and where the units occur singly they are seen to have an angular or stellate outline in cross section. To make this distinction clear these have been termed neurofibrillar bundles rather than neurofilaments.Attachment plaques occur in both neurons and neuroglia. These plaques have tonofibrils attached, and the glial tonofibrils are far more numerous than the neuronal tonofibrils. The glial fibrils are identical with the tonofibrils in the glial cells.The attachment plaques are invariably related to an extracellular space that contains material identical with the basement membrane. This material is continuous, by a complex system of channels and diverticulae, with the outer basement membrane in the neuron packets, but forms isolated patches in the other parts of the nervous system.We are grateful to Prof. J. Z. Young, F. R. S., for his encouragement to Mrs. Astafiev for the drawings, to Miss B. Shirra and Mr. K. Watkins for technical assistance and to Mr. S. Waterman for photography.