Scanning electron microscopic studies of cilia

Summary A simple method for the preparation of ciliated epithelia for study with the scanning electron microscope is described. Ciliary groups are well preserved and it is possible to discern individual cilia and work out their numbers and orientation. Following scanning electron microscopical study some of the material was prepared for transmission electron microscopy and the ultrastructure of the tissue was found to be surprisingly well preserved. The tracheal epithelium of the rabbit, the olfactory epithelia of the goldfish and the rabbit, and the sensory epithelia in the statocyst of a cephalopod mollusc were examined with the scanning electron microscope to demonstrate the possibilities of the method. Acknowledgements. We would like to thank Professor J. Z. Young for his continued interest and support. The scanning electron microscope was purchased with a grant provided by the Science Research Council to Dr. Boyde, Mr. R. Willis helped in the initial stages of the study, Mr. G. Savage provided help with the goldfish material, Mr. S. Waterman provided much photographic assistance, and Mrs. N. Finney the secretarial assistance.     

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.     

Effect of polyamines and L-ornithine on the development of proembryogenic masses of Cryptomeria japonica

We examined the effects of polyamines, namely, putrescine, spermidine and spermine, and of amino acids, such as l-arginine and l-ornithine, as part of our efforts to identify factors that stimulate the development of proembryogenic masses (PEMs) of Cryptomeria japonica. We maintained two distinct types of PEM designated PEMs A, which consisted of normal embryogenic cells as single embryos with elongated suspensor cells, and PEMs B, which consisted of abnormal embryogenic cells with coalesced embryos on modified Campbell and Durzan medium (mCD) supplemented with individual polyamines at 0–100 μM or amino acids at 0–16.4 mM. All additives had a stimulatory/suppressive effect. Microscopy and image-processing techniques revealed that the regions of authentic embryos of PEMs that were treated with l-ornithine were remarkably enlarged and that the suspensor cells had elongated in the same direction. When all PEMs A were transferred to maturation medium (mCD that contained abscisic acid and maltose at various concentrations), only PEMs that had been treated with l-ornithine matured into somatic embryos and were able to germinate on hormone-free mCD. Our results indicate that l-ornithine is an important stimulator of the development of PEMs to the pre-filamentous stage in C. japonica.     

Electron microscope studies on the structure of collagen fibrils by negative staining

Summary Electron microscope studies on collagen from rat-tail tendon using a negative staining technique have indicated the presence of filaments 15–20 Å in diameter within the fibres. These filaments are thought to correspond to the collagen macromolecule.We would like to thank Prof. R. A. McCance for supplying the specimens of fowl tendon used in this investigation, and Dr. F. H. C. Crick, Dr. S. Fitton-Jackson and Dr. T. Gillman for a number of valuable discussions. One of us (W. J. T.) wishes to thank the Medical Research Council for financial support during this work.     

The integument of the Queensland fruit fly,Ddacus tryoni (Frogg.)

Summary During the pupal stage of Dacus tryoni, the hypodermis of the larva is replaced by an imaginal generation of smaller cells. The hypodermal cells of the tergal glands on the fifth abdominal segment of the adult were examined with the electron microscope; they contain slender, membrane-limited bundles of hollow wax filaments that traverse the cuticle in branched pore canals. Outside the glandular areas, the pore canals are narrower. The cuticle of the adult undergoes its greatest increase in thickness soon after emergence; it becomes sclerotized gradually. No epicuticle was detected with either the light or electron microscopes.Early in adult development, bristles are formed over the general surface of the terga. Most of these are innervated by single, bipolar nerve cells, and have more or less enlarged trichogen cells that appear to secrete wax through pore-plates in the cuticle. The bristles in different regions of the abdomen range in function from pure sensory receptors to pure secretors. The sensory bristles on the tergal glands were examined with the electron microscope.For assistance with the electron microscopy, I thank Mr. Tony Webber and Miss Ann Miller of the Electron Microscopy Unit at Sydney University. — Supported by a C.S.I.R.O. Junior Post-Graduate Studentship.     

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.     

The development of the hypophysial portal system in the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The development of the hypophysial portal system has been studied in 35 embryos and 45 nestlings of the White-crowned Sparrow. The primordium of the hypophysis is vascularized by the infundibular (primary) capillary plexus, supplied by the right and left infundibular arteries, which, in the embryo, are constant branches of the right and left internal carotid arteries.The cellular proliferation and differentiation of the pars distalis into rostral and caudal lobes is accompanied by a penetration of portal vessels from the infundibular (primary) capillary plexus into these lobes beginning on the fifth day of incubation. The cellular proliferation of the rostral lobe of the pars distalis and development of the rostral group of the portal vessels precedes that of the caudal lobe of the pars distalis and the development of the caudal group of the portal vessels.The periglandular vessels, which originate in younger embryos from the infundibular (primary) capillary plexus, apparently become a part of the portal vessels.The portal vessels are the sole blood supply to the developing pars distalis of the White-crowned Sparrow; there is no evidence of a direct arterial supply at anytime during embryonic development. The neural-lobe artery appears at the end of incubation as a secondary branch of the right and left infundibular arteries. The rostral and caudal groups of the portal vessels are well-developed at the end of incubation (17–29 mm CRL) when aldehyde-fuchsin positive neurosecretory material first appears in the supraoptic and paraventricular nuclei, in the median eminence and in the neural lobe.The differentiation of the median eminence into rostral and caudal divisions begins at the end of the nestling period although its adult form is not achieved until later. The formation of the portal zone begins at the end of incubation (17–29 mm CRL) and is completed by the time of fledging.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.The investigations reported herein were supported by a research grant (HE 07240 NEUA) from the National Institutes of Health to Professor Vitums, by funds for biological and medical research made available by State of Washington Initiative Measure No 171 to Professor Vitums, by a research grant from the Deutsche Forschungsgemeinschaft to Professor Oksche, by aresearch grant (NB 01353) from the National Institutes of Health to Professor Farner, and by a Research Career Development Award from the National Institute of Arthritis and Metabolic Diseases (5 K 3 AM-18,370) to Professor King. We are grateful to Professor Bargmann for his generosity in making available the facilities of the Anatomisches Institut Kiel for this investigation. We wish to thank Frau Karin Graap and Mrs. Dianne Reno for technical assistance and Miss Janice Austin for the preparation of the drawings.     

Increased frequency of dividing microspores and improved maintenance of multicellular microspores of Coffea arabica in medium with coconut milk

The number of dividing microspores of Coffea arabica L. cv. Catuai and Catimor could be drastically increased in microspore media containing 16% (w/v) coconut milk, allowing cell divisions to continue in the microspore and multicellular microspores to survive until day 60. After a cold treatment, the microspores were mechanically isolated prior to cultivation in Murashige and Skoog medium supplemented with sucrose and maltose and (mg l^-1) 2,4-d: 2, BAP: 1 or a combination of kinetin: .5, 2,4-d: .5 and NAA: .5 as stationary suspension at a density of 1,200/ml. The crucial stage during microsporogenesis suitable for in vitro androgenesis proved to be mid uninucleate till early binucleate in flowerbuds with the size of 13–15 mm two to three days before anthesis. The initial steps of androgenesis were determined.Abbreviations BAP 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxy-acetic acid - NAA 1-naphthaleneacetic acid     

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.     

Characterization of the exogenous interleukin-2 requirements for the generation of enhanced antitumor cytotoxicity by thymocytes from low-dose melphalan-treated MOPC-315 tumor bearers

We have shown previously that thymocytes from MOPC-315-tumor-bearing mice treated with low-dose melphalan (l-phenylalanine mustard) (l-PAM TuB mice) are superior to thymocytes from untreated MOPC-315-tumor-bearing mice or thymocytes from untreated normal mice or normal mice treated with low-dose melphalan in their ability to generate an antitumor cytotoxic response following 5-day in vitro stimulation with MOPC-315 tumor cells in the presence of a low concentration of recombinant interleukin-2 (rIL-2) [Mokyr MB, Bartik MM, Ahn M-C (1989) Cancer Res 49; 870]. Here we characterize the rIL-2 requirements for the generation of enhanced antitumor cytotoxicity byl-PAM TuB thymocytes relative to normal thymocytes upon in vitro stimulation with MOPC-315 tumor cells. Specifically, we show that delaying the addition of a low concentration of rIL-2 to 5-day in vitro stimulation cultures of thymocytes resulted in a progressive decline in the generation of antitumor cytotoxicity by both normal andl-PAM TuB thymocytes. However, even when rIL-2 was added on day 2 after culture initiation, thymocytes froml-PAM TuB mice generated a more potent antitumor cytotoxicity than did thymocytes from normal mice. In addition, when rIL-2 was added at the time of culture initiation, replacement of the conditioned medium with fresh medium lacking rIL-2 on day 3 of the 5-day in vitro stimulation culture period eliminated the ability of normal thymocytes, and reduced (but did not eliminate) the ability ofl-PAM TuB thymocytes, to generate a significant level of antitumor cytotoxicity. A low concentration of fresh rIL-2 was sufficient to restore completely the generation of antitumor cytotoxicity by normal orl-PAM TuB thymocytes when added to the stimulation cultures immediately after the removal of the rIL-2-containing conditioned medium. The same low concentration of rIL-2 was also sufficient for restoring the generation of antitumor cytotoxicity by cultures ofl-PAM TuB thymocytes, but not normal thymocytes, from which the rIL-2-containing medium was removed 1 day earlier. At the same time, conditioned medium from stimulation cultures ofl-PAM TuB thymocytes was not superior to conditioned medium from stimulation cultures of normal thymocytes in supporting the generation of antitumor cytotoxicity by either normal orl-PAM TuB thymocytes. Thus, the enhanced lytic activity generated byl-PAM TuB thymocytes, relative to normal thymocytes, upon stimulation with MOPC-315 tumor cells and a low concentration of rIL-2, does not appear to be the result of enhanced production of helper-like factors byl-PAM TuB thymocytes.Supported by research grant CA-35 761 from the National Cancer InstituteIn partial fulfillment of the requirements for the Doctor of Philosophy degreeSupported by Career Development Award CA-01350 from the National Cancer Institute     

Rapid and high frequency shoot regeneration from hypocotyl protoplasts of Brassica nigra

Protoplasts, isolated from etiolated hypocotyls of seven day old seedlings of Brassica nigra, were cultured in Kao's liquid medium containing 7.2% glucose, 2,4-d (1 mg 1^-1), NAA (0.1 mg 1^-1) and zeatin riboside (0.5 mg 1^-1). After initial incubation for 3 days in dark at 25±1°C, cultures were transferred to a photoperiod cycle of 16/8 h and diluted on seventh and tenth day with MS medium containing 3.4% sucrose, 2,4-d (0.1 mg 1^-1) and BAP (1 mg 1^-1). About 62% of the cells divided at least once and 46% of them reached 8–16 cell stage in one week. The dividing cell clusters could be plated on agarose medium on the fifteenth day to obtain proliferating minicalli with a plating efficiency of 1.8%. 56.8% of minicalli, regenerated shoots on a regeneration medium containing 2 IP and IAA at 1 and 0.2 mg 1^-1 respectively. The in vitro produced shoots were rooted in MS medium containing 1 mg 1^-1 IBA and established in soil without difficulty. The time taken for protoplasts to develop into plants varied from 9 to 10 weeks.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine - 2 IP 2-isopentenyladenine - IAA indole-3-acetic acid - IBA indole-3-butyric acid - NAA -naphthaleneacetic acid - Kn kinetin     

Synthesis of serum thymic factor (FTS) and two analogs

Serum thymic factor (FTS) and [Gln¹]-FTS were synthesized by fragment condensation using the azide procedure. [d-Ala⁶]-FTS was prepared by stepwise amino acid condensation in combination with fragment condensation on solid-phase resin. Synthetic FTS and [Gln¹]-FTS both enhanced the delayed-type hypersensitivity (DTH) level to sheep red blood cells (SRBC) in mice at a dose of 0.1 ng/mouse per day, while a dose of 1.0 ng/mouse per day of [d-Ala⁶]-FTS was needed for the enhancement reaction.     

Twenty-four-hour rhythm in the mitotic activity and in the water and dry matter content of regenerating liver

Summary A twenty-four hour rhythm is described in the variations of mitotic activity, dry weight, and water content of the regenerating liver of mice hepatectomized about noon. These variables have their maximal value at the onset of the rest periods in the morning and their minimal values at the initiation of the body activity periods in the evening. The rhythm is well defined on the second day and is repeated on the third day on a higher level.We acknowledge the assistance of Mrs. R. Cavoura in performing the hepatectomies and that of Mrs. M. A. V. Albornoz in making the histologic slides.The present work was carried out with the help of grants from the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and Liga Mendocina de Lucha contra el Cáncer.     

Membrane formation and membrane contacts during the development of the sea urchin embryo

Summary Sea urchin embryos, 8-cell stage to pluteus stage, fixed in osmium tetroxide and embedded in Epon 812 were observed by electron microscopy. At no point in the development were syncytial junctions between the embryonic cells found. During the cleavage stages the membrane contact was closer than in later stages. In early blastula stages intercellular clefts appeared which in the gastrula stage demarcate every cell. At the same time a ringshaped desmosome structure develops at the outer cell surface. In the pluteus stage a closer cell contact is re-established. With proceeding embryogenesis endoplasmic membranes will attach to the cell membrane. These membrane structures may even be of nuclear origin. Gradually, long protrusions, vesicles and lamellae begin to be formed from the nuclear membrane. The commencement of this nuclear activity coincides in time with the formation of nucleoli. At cell division the new cell membrane seemed to arise partly independently of the cleavage furrow from a system of cytoplasmic vesicles.The investigation was facilitated by grants from the Nordic Insulin Foundation.I am indebted to Dr. Torsten Olsson and Miss Brita Nilsson for procuring the material and to Mrs. Mariann Carleson for technical aid.     

The cell types in the endocrine pancreas of the human fetus

Summary Morphological and histochemical studies of the developing human islet cells are facilitated by the characteristic localization of the different islet cell types from about the third intrauterine month. By combining light microscopical analyses of silver impregnated and granule stained pancreatic sections with electron microscopy of osmium fixed material, the following four types of islet cells could be identified: (1) A₁ cells containing faint globular granules. These granules could be visualized only with the electron microscope. (2) A₂ cells containing electron-dense globular granules. It is uncertain whether the observation of a light and a dark variety of the A₂ cells reflects different stages of maturation or signifies cells with different secretion products. (3) B cells with irregular granules, which were often accumulated at the capillary pole of the cells. (4) Agranular islet cells. Mixed forms of A cells containing both faint and dense granules were also encountered. The difficulties in evaluating in the light microscope what may be called D cells in the human fetal islets were obvious from the observation of more cells stained with light-green than A₁ cells. Except for acid phosphatases, the histochemical tests for different phosphatases and esterases revealed rather weak or negative reactions in the islet cells. The development of phosphatase and esterase activities in the islets seemed far from complete, when morphologically differentiated islet cells could be recognized.Supported by the United States Public Health Service [grants RF-83(01) and TW-83(02)] and the Swedish Medical Research Council. The authors are indebted to Professor Carl Gemzell and Dr. Ulf Elvkull at the Department of Obstetrics and Gynecology, University Hospital, Uppsala, for the generous supply of the fetal pancreatic material.     

The integument of the Queensland fruit fly,Dacus tryoni (Frogg.)

Summary Testes of the Japanese freshwater turtle Clemmys japonica Temmnick et Schlegel were fixed in 3% potassium permanganate buffered to pH 7.2 with Veronal-acetate buffer, and thin sections of the tissue, embedded in epoxy Epon resin, were studied under the electron or light microscope.At the early stage of differentiation of the spermatid, the cytoplasm contains a few mitochondria provided with cristae which are oriented transversely or longitudinally. As the differentiation of spermatids proceeds, the mitochondrion has been modified into a cupshaped body with a wall consisting of several concentric layers. Such body has been referred to the mitochondrial lamellar body. The formation of such a body is mainly attributed to the mitochondrial cristae, and subsequently to the membrane system of the endoplasmic reticulum. In a more advanced stage of differentiation, the mitochondrial lamellar bodies appear wrapped around a bundle of tail filaments, and seem to present a very wide surface available for the localization of organized enzyme systems to facilitate the motion of spermatozoa.Prior to the formation of the mitochondrial lamellar bodies, the Golgi apparatus has been reorganized into a peculiar body with a floral appearance, consisting of numerous tubular elements, and revealing to be positive in PAS-reaction. The body has been designated as the tubular body which has never been demonstrated in any spermatogenic cells through animal kingdom.One to three tubules oval in cross section, approximately 430 × 700 Å in diameter, have been found in the nucleoplasm along the longitudinal axis of a greatly elongated, cone-shaped nucleus of the spermatid. The tubules open on the apex surface of the nucleus, but they are not encountered in the acrosome. A possible physiological significance of the tubules has been discussed in view of the function of the acrosomal tubules in the decapod and other species spermatozoa as well as on the basis of the metabolism of nucleus.This study was supported by Grant GM-8327 from the United States Public Health Service.We wish to express our gratitude to Dr. B. A. Afzelius, Wenner-Gren Institute, University of Stockholm, for his valuable suggestion to the present work.     

Lymphocyte subsets and T(h)1/T(h)2 immune responses in patients with adenocarcinoma of the oesophagus or oesophagogastric junction: relation to pTNM stage and clinical outcome

Introduction Recent studies have indicated that the cytokines produced by CD4⁺ T helper type 1 (T_h1) and type 2 (T_h2) cells are critically important in antitumour immunity and perhaps clinical outcome. From this perspective, we investigated the immunocompetence of patients with previously untreated cancer of the oesophagus or oesophagogastric junction (OGJ) in relation to stage of disease and postoperative survival.Methods Blood samples were taken prior to surgery from 32 patients with adenocarcinoma of the oesophagus or OGJ. Ten healthy volunteers served as normal controls. T-cell and monocyte subpopulations were determined using flow cytometry. Monocyte as well as T_h1- and T_h2-lymphocyte cytokine levels were assessed in stimulated whole blood cultures.Results Absolute T-cell and monocyte (subset) counts as well as monocyte cytokine levels were similar among patients and controls. Production of T_h1-type cytokines was higher in patients than in controls (IFN-, p=0.01; IL-2, p=0.05), whereas T_h2-type cytokine levels were comparable (IL-4, p=0.5; IL-13, p=0.3). T-cell CD4⁺/CD8⁺ ratios decreased as pTNM stage worsened (stage I/II vs stage III/IV, p=0.009). Of all measured immunological parameters, only IL-2 production significantly affected both overall survival (p=0.015) and disease-free survival (p=0.0062). High IL-2 levels corresponded with a favourable prognosis.Conclusions Patients awaiting surgery for adenocarcinoma of the oesophagus or oesophagogastric junction demonstrated a shift in the T_h1/T_h2 balance—in favour of T_h1—compared with healthy volunteers. The ability of T cells to produce IL-2 was related to survival indicating a crucial role of T_h1-type cells in antitumour immunosurveillance.     

Fermentation of seaweed sugars by Lactobacillus species and the potential of seaweed as a biomass feedstock

It is known that seaweeds differ greatly from land plants in their sugar composition. The current research on the L-lactic acid fermentation process focuses on land plant sugars as a carbon source, with the potential of seaweed sugars being largely ignored. This study examined the feasibility of seaweed biomass as a possible carbon source for the production of l-lactic acid, by comparing the fermentation of seaweed sugars (d-galactose, d-mannitol, l-rhamnose, d-glucuronic acid, and l-fucose) and land plant sugars (d-glucose, d-xylose, d-mannose, and l-arabinose). The experiments were repeated with 2 sugar acids (d-gluconic acid, d-glucaric acid) in order to investigate the effect of the degree of reduction of carbon source on the fermentation yield. This research also examined the effect of bacterial strain on the characteristics of fermentation reactions, by conducting l-lactic acid fermentation with 7 different Lactobacillus species. Taking into account the sugar composition of seaweed and the levels of lactic acid production from each pure sugar, it was possible to predict the lactic acid production yield of various seaweeds and land plants. From comparative analysis of the predicted lactic acid production yield, it was found that seaweeds are already comparable to lignocellulosics at the current stage of technology. If new technologies for the utilization of non-fermentable seaweed sugars are developed, seaweeds show promise as an even more useful biomass feedstock than lignocellulosics.     

Electron microscope observations of some peripheral synapses in the sensory pathway of the sucker of Octopus vulgaris

Summary A synaptic axo-dendritic linkage is described between primary receptors lying in the epithelia of the sucker of Octopus and encapsulated nerve cells found near the rim of the sucker in the subepithelial connective tissue. These synapses are postulated to perform a drastic reduction of inputs between the primary receptors of the order of more than ten thousand and the subjacent encapsulated nerve cells of the order of some hundreds. The morphology of these cells as well as that of the synaptic structures are described from electron microscope studies. Aknowledgement. This work was done at University College London, while I was in receipt of a Medical Research Council grant.I am deeply indebted to Prof. J. Z. Young F. R. S. for support and criticism, and to Dr. E. G. Gray for advice and discussion. My thanks are due to Mr. A. Aldrich for the photographs.     

Some aspects of the fine structure of the reticulo-endothelial system; the cells which clear colloids from the blood stream

Summary The macrophages in various sites in the mouse have been examined with the electron microscope in normal animals, and in animals which had recently received intravenous colloids. There was a general structural similarity at all sites. The most obvious common feature was the presence of small granules which stain with toluidine blue. These were of two types. One, the smaller had a finely granular substructure and may represent the primary lysosome; the other, the larger was heterogeneous, contains banded probably fibrillar material with a repeating pattern of 35–50 A, and may represent the residual body.Colloids given intravenously were cleared by phagocytosis by endothelial cells and endothelial macrophages, by leakage through patent intercellular junctions, and by phagocytosis by paravascular macrophages. Such clearance is commonly held to be a measure of reticulo-endothelial function. This measure is therefore clearly dependent on several cellular factors.I am grateful to Prof. R. Barer for his advice and criticism, to Dr. G.A. Meek for guidance on electron microscopy, and to Mrs. B. Romans and Miss M. Tune for technical and photographic assistance.This work was supported by grants from the M.R.C. and the University of Sheffield Tuberculosis Research Fund and by a grant to the Department from Unilever Ltd.