Electron microscopy of degeneration in the lateral olfactory tract and plexiform layer of the prepyriform cortex of the rat

Summary The synaptic organization of the plexiform layer of the prepyriform cortex in the rat has been studied with the electron microscope both in the normal and after ipsilateral olfactory bulb removal. Survival times ranged from six hours to three months.In normal preparations synaptic contacts occur mainly on dendritic branches, spines or lateral projections. Gray's Type I contacts are most frequent and Type II contacts usually contain flattened vesicles after formalin fixation.Degeneration of the presynaptic bags begins within 24 hours after the lesion and some degenerated bags are still seen after three months survival. During this time degenerated bags are apparently removed by astroglia but the spine tips appear to be unaffected by the phagocytosis. Glia or other processes may come to occupy the denervated sites. The evidence for possible reestablishment of new contacts is considered.The severed axons show a characteristic mode of degeneration and at three months some appear to be phagocytosed by oligodendroglia which also contain lamellated inclusion bodies.This study represents a part of a thesis accepted in fulfillment of requirements for the degree of Doctor of Philosophy at the University of London (England), June 1966.This investigation was supported in part by a U.S. Public Health Service Fellowship NB 20-844 from the N.I.N.D.S. while the author was a postdoctoral fellow at the Anatomy Department, University College, London, England, and by grants NB 02896 and NB 04053 from the N.I.N.D.S. The author gratefully acknowledges this support and would also like to thank Professors J. Z. Young and E. G. Gray for encouragement and advice throughout the course of this study.     

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.     

Ultrastructural localization of some phosphatases in the prothoracic gland of the insect Leucophaea Maderae

Summary The cytochemical localization of acid phosphatase and thiamine pyrophosphatase activity was studied by light and electron microscopy in prothoracic gland cells of the cockroach Leucophaea moderae. Nymphal and young adult animals were used.Prominent sites of acid phosphatase activity included large membrane-bounded dense bodies or lysosomes, and certain cisternae of the Golgi apparatus. The results suggest a possible difference in the enzymatic activity toward glycerophosphate and aromatic phosphates as substrates.Thiamine pyrophosphatase activity was localized in elements of the Golgi apparatus and endoplasmic reticulum, and in lysosome-like dense bodies. This latter activity was abolished by sodium fluoride treatment, whereas the phosphatase activity in the Golgi apparatus and endoplasmic reticulum is unaffected by such inhibition.The cytochemical results confirm through direct evidence the suggestions of Scharrer (1964), that the large dense bodies present in the prothoracic gland cells are lysosomes, and that their activity may be related to stages in the life history of the glands. Furthermore, the lysosomes or their derivative structures may play an essential role in the autolysis of the prothoracic glands toward the end of their active period.The enzymatic activity of the endoplasmic reticulum may indicate the involvement of this organelle in the metabolism of steroid-like precursor materials necessary for the synthesis of ecdysone.This study was supported by U.S.P.H.S. grants 5 T1-MH-6418 and NB-05219, and grant RO 1-AM-3984 to Dr. Berta Scharrer. I would like to express my appreciation to Dr. Scharrer for her encouragement and assistance during this study. I also wish to thank Mrs. Sarah Wurzelmann for her competent technical aid.     

Investigations into the structure and fixation properties of cytoplasmic lamellae in the hamster oocyte

Summary Lamellar structures have been revealed in the cytoplasm of rapidly growing hamster oocytes by glutaraldehyde fixation and by fixation in 30% ethanol followed by osmication. The structures are not preserved after osmium tetroxide either used alone or followed by glutaraldehyde; nor are they preserved by absolute ethanol, formaldehyde, glyceraldehyde, glyoxal, 2-hydroxy-adipaldehyde or potassium permanganate. Immersion in 30% ethanol followed by extraction in distilled water and fixation in glutaraldehyde and osmium tetroxide exposes the lattice-like skeletal structure of the lamellae. The lamellae are present but slightly altered after short digestion in pepsin. Longer digestion results in complete dissolution of the structures.Supported by U.S.P.H.S. Post-doctoral Fellowship 5 F2 HD-25, 190–02.I wish to thank Prof. R. E. Coupland for his continued interest in this work and for his helpful criticisms.     

Changes in the fine structure of the human testicular interstitial cells after treatment with human gonadotrophins

Summary Study of the fine structure of the human interstitial cells after prolonged stimulation with human gonadotrophin reveals a striking increase in the quantity of the agranular endoplasmic reticulum. This is accompanied by an increase in the number of mitochondria which exhibit more extensive cristae, collections of intramitochondrial lipid and aggregations of electron-dense granular deposits. A rise is also evident in the number of lipofuscin pigment deposits and granular membrane-bounded bodies, both of which exhibit acid phosphatase activity. These changes after gonadotrophic stimulation are discussed in relation to steroid biosynthesis.In the pretreatment biopsies of these patients aged between 25–35 years, some interstitial cells contain intranuclear crystals which exhibit a hexagonal structure. The relationship of these intranuclear crystals to the cytoplasmic crystals of Reinke is discussed.The author is indebted to Dr. J. W. Johnstone and Dr. A. Long for the human material used in this study. Thanks are also due to Dr. H. P. Taft for helpful suggestions in the management of these patients, to Professor B. Hudson for the estimations of plasma testosterone and to Dr. J. B. Brown for the supply of human pituitary gonadotrophin and the estimations of urinary oestrogens. The technical help of Mr. T. Mezciems and the photographic assistance of Mr. J. S. Simmons F. R. P. S. and Miss S. Flett is gratefully acknowledged.     

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.     

Thyroidal radioiodine uptake and thyrotropic potency of the pituitary in a freshwater catfish,Mystus vittatus (Bloch), in response to L-thyroxin,antithyroid drugs,and heavy doses of 131I

Summary Experiments were conducted to ascertain the thyroidal ¹³¹I uptake and thyrotropic potency of the pituitary gland in a freshwater catfish, in response to L-thyroxine, antithyroid drugs and heavy doses of radioiodine. L-thyroxine treatments slightly lowered thyroidal radioiodine uptake, and there was at least a trend of lowered TSH content in the pituitaries of these animals. Administration of antithyroid drugs (propylthiouracil, thiourea, KSCN) caused a significant decrease in radioiodine uptake and a highly significant increase in TSH content of the pituitary. Heavy doses of I¹³¹ almost completely blocked thyroidal iodine uptake but they were as effective as antithyroid drugs in elevating TSH content of the pituitary.I am greatly indebted to Dr. G. E. Pickford, Yale University, U.S.A. for her helpful suggestions; to Dr. A. G. Sathyanesan, Banaras Hindu University, India, for encouragements; to Professor S. P. Ray-Chaudhuri, Banaras Hindu University, India, for providing laboratory facilities. I am also grateful to Baxtor Laboratories Inc., Morton Grove, Illinois, U.S.A. for the gift of Crystalline L-thyroxine which was made available through the courtesy of Professor Paul Starr and Dr. Thomas Garrett.     

The presence of two serine racemases in Streptomyces garyphalus,a d-cycloserine producer

Two serine racemases (I and II) were isolated from Streptomyces garyphalus. Serine racemase I (molecular weight 93,000) was purified to a single band in an analytical electrofocusing system. Serine racemase II (molecular weight 73,000) was partially purified. Both enzymes used pyridoxal-5-phosphate as cofactor. Besides serine the enzymes utilized alanine as substrate but no other amino acid tested. The K _m values of l-alanine and l-serine for enzyme I were 111 mM and 35 mM respectively. Enzyme I was not inhibited by d-cycloserine but by hydroxylamine. Both substances inhibited enzyme II. The serine racemases may be involved in the biosynthesis of d-cycloserine in S. garyphalus.     

The fine structure of photoreceptors in a marine flatworm

Summary The ocelli or eyes of the marine polyclad turbellarian Notoplana acticola are clustered on the paired dorsal nuchal tentacles and in two longitudinal bands lateral to the cerebral ganglion. The ocelli, studied by electron microscopy, were characterized as rhabdomeric and non-ciliary in origin. There are 60 to 80 ocelli per animal each enclosed in a fibrous capsule to which muscle fibers may attach. An ocellus consists of a pigmented eyecup into which 30 to 50 photoreceptor cells send dendritic processes through interruptions in or among pigment cell projections across the eyecup opening. The dendritic processes terminate in numerous long intertwined microvilli which fill the eyecup. The nucleated cell body of each photoreceptor cell lies outside the eyecup and projects an axonal process to the cerebral mass. Within the dendritic processes are observed mitochondria, ribosomes, neurotubules, multivesicular bodies, vesicles and vacuoles. The cell body contains smaller mitochondria, endoplasmic reticulum, ribosomes, vesicles and prominent Golgi complexes.After dark adaptation, there are some structural alterations in terms of swelling of microvilli, increased numbers of vacuoles associated with the microvilli and dendritic processes, and changes in the pigment cell projections.This work was supported by Grant No. GM 10292 from the U.S. Public Health Service to Professor Richard M. Eakin, Department of Zoology at the University of California, Berkeley, U.S.A., where this investigation was conducted during the author's sabbatical leave of absence from the University of Illinois, and by Grant No. 1 SO 1 FR 5369 from the U.S. Public Health Service to the University of Illinois at the Medical Center.I express appreciation to Professor Eakin for interesting discussions and generous hospitality to me as a guest in his laboratory, and to the John Simon Guggenheim Memorial Foundation for the Fellowship which I held during 1964–65. I thank Dr. John P. Marbarger, Director of the Aeromedical Laboratory for the electron microscope facilities used at the University of Illinois.     

Changes in retinal fine structure induced in the crab Libinia by light and dark adaptation

Summary The cytological influence of light and dark adaptation (LA and DA) on the retinular cells of the spider crab Libinia emarginata has been studied by light and electron microscopy in four adaptive states: 17 hours darkness, 5 hours darkness, 5 hours diffuse light and 17 hours diffuse light. The rhabdom's fine structure is typical of decapods but its dual overall form and position mingle certain features of both apposition and superposition compound eye types. Distal and proximal retinal pigments both showed adaptive migration, but the distal pigment cells moved over a restricted range, and DA separated the retinular cell pigment granules into two groups, perinuclear and basilar.In the rhabdom no changes in its position, dimensions or microvillus fine structure were observed with LA or DA. But at the base of the rhabdom microvilli the rate of pinocytosis was strongly affected by the eye's adaptive state, being lowest after 17 hours DA and greatest after 17 hours LA; the wall of the 0.1 microvesicles so formed, looked like the membrane of the rhabdom microvillus and they were the same size as the vesicles in multivesicular bodies and in vesicular lamellar bodies.Three categories of complex cytoplasmic particles about 1 in diameter (multivesicular bodies, vesicular lamellar bodies and purely lamellar bodies) were all increased in number by decreased DA and by increased LA; similar quantitative effects occurred in the endoplasmic reticulum and in the ribosomes.The pinocytotic vesicles and the complex cytoplasmic bodies may represent part of an intracellular system to dispose of rhabdom metabolites whose production was initiated or increased by light absorption.Cytoplasmic and perirhabdomal vacuoles mainly distal in location, were also affected by light, but inversely; their maximal extent occurred after 17 hours DA; less DA or any LA significantly decreased their presence and aggregation.The data reported are of interest not only because they correlate retinal fine structure with the metabolism of vision but also because they provide a new and specific tool for distinguishing active from inactive neurosensory cells in the optic pathway.This research was initiated with the aid of U.S. Public Health Service Grant NB-03076 and has been continued with the support of U.S. Air Force Grant AFOSR-1064. The authors wish to thank Dr. Joseph G. Gall and Dr. William R. Adams for generously sharing their electron microscopic facilities; they are also grateful to Mrs. Mabelita Campbell for her collaboration on the light microscopy.     

Electron microscopic observations of lung alveolar epithelial cells of normal young mice,with special reference to formation and secretion of osmiophilic lamellar bodies

Summary Using the electron microscopy and electron microscopic histochemistry the authors studied the lung alveolar epithelial cell of normal young mice.Type II cell of the alveolar epithelium has characteristically numerous osmiophilic lamellar bodies. The lamellar boies are formed in the cytoplasmic vesicle, and never originate from the mitochondrion. These bodies have abundant acid phosphatase activity in their limiting membrane therefore it is considered to be lysosomal origin, but the mitochondria have no such enzyme activity.The body which is newly formed in the cytoplasmic vesicle grows up to the large lamellar body as a result of an accumulation of the fibrous dense substance, migrates to the free margin of the type II cell of alveolar epithelium, and then is discharged into the alveolar lumen as a merocrine type secretion.Acknowledgement is given to Professor Dr. Y. Sano and Professor Dr. H. Fujita, Department of Anatomy, and Assistant Professor Dr. S. Fujita, Department of Pathology, for their kind advice and criticism.     

Ultrastructure of juvenile hormone-induced degenerating flight muscles in a bark beetle,Ips paraconfusus

Summary Topical application of 5 g of a juvenile hormone analogue (JHA), ZR-615, to female callow adults of Ips paraconfusus induced degeneration of the dorsoventral flight muscles. Within 24h after JHA-treatment the diameter of the myofibrils was reduced to almost half due to the lysis of the peripheral myofilaments. Mitochondria showed conspicuous degenerative changes like swelling, dissolution of the matrix or presence in the matrix of dense filamentous material or myelin-like figures. Degeneration of the mitochondria seemed to take place inside isolation membranes derived from sarcoplasmic reticulum. A number of granular osmiophilic bodies appeared in the sarcoplasm. Three days after JHA-treatment the muscles were very thin and sheath-like. Most of the mitochondria had already degenerated. The dense sarcoplasm contained numerous crystalline bodies. The granular dense bodies were also more frequent. The myofibrils were comprised of only occasional small bundles of myofilaments. The tubules of the T system enclosed an amorphous material. The nuclei and the tracheal system remained intact but they were crowded due to the decreased volume of the muscle. In some specimens degeneration of the myofibrils and mitochondria was completed by the third day. No sign of degeneration was observed in the flight muscles of acetone treated control insects.Supported by the National Research Council of Canada grant A4669.We thank Dr. G.B. Staal, Zoecon Corp., Palo Alto, California, for the generous gift of ZR 615, and Messrs A. Syed and M. Horta for rearing the insects     

Mastophorus muris (Nematoda: Spirurina): Ultrastructure of somatic muscle development

Hamada G. S. and Wertheim G. 1978. Mastophorus muris (Nematoda: Spirurina): ultrastructure of somatic muscle development. International Journal for Parasitology8; 405–414. The ultrastructure of the somatic muscle cells of the adult and six developmental stages of Mastophorus were studied. In all stages the cells consisted of a contractile region containing myofibrils separated by dense bands and a noncontractile region with nuclei, mitochondria, glycogen, lipid droplets and vesicles. Two sizes of myofilaments were present. The dense band contained T tubules and sarcoplasmic reticulum, and, in more advanced stages, support filaments, glycogen and dense bodies. The contractile region of the adult muscle cell consisted of several hundred irregularly shaped myofibrils arranged in a random pattern. This pattern of myofibrils was defined as irregular-coelomyarian. The third stage larva had a shallow-coelomyarian myofibril configuration, which changed to coelomyarian in the late third stage through the addition of new myofibrils at the apical contractile border. In the fourth stage larvae, the subdivision of existing myofibrils changed the pattern to irregular-coelomyarian.     

Investigations on the hypothalamo-neurohypophysial neurosecretory system of the grass frog (Rana pipiens) after transection of the proximal neurohypophysis

Summary With the onset of degeneration of the neurosecretory nerve fibers following transection of the proximal neurohypophysis, the pituicytes phagocytize these nerve fibers. Concomitant with a considerable increase in the size of the pituicytes, which reaches a peak between 8 and 10 days after the transection, the following sequence of events can be observed: reduction of the amount of intergranular axoplasm, increase in the size of some granules, partial or total loss of the electron density of the neurosecretory granules, loss of granule membranes, fusion of some granules, polymorphous axonal content in digestion vacuoles, formation of multilamellate bodies, digestion vacuoles with moderately electron dense peripheral material, empty digestion vacuoles. At about 12 days after the transection many vacuoles appear which subsequently disappear as the pituicytes shrink. Free neurosecretory granules resulting from the disappearance of the axolemma remain intact in the intercellular and perivascular connective tissue spaces and are eventually phagocytized by pituicytes and pericytes.Phagocytosis is considered to be a basic function of pituicytes. The problems related to this function as well as the possible implications for the interpretation of Herring bodies are discussed.This investigation was supported by Grant No. NB-06641 of the National Institute of Neurological Diseases and Blindness. The technical assistance of Mrs. Mildred Floyd and Christa Cooper is gratefully acknowledged.Dedicated to Prof. Dr. H. Grau on the occasion of his 70th birthday.     

The effect of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretion in the rat

Summary The present investigation was undertaken to study the effects of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretory system in rats.The drugs were injected intraperitoneally and into the lateral brain ventricle. The water diuresis was measured (I group). The animals were killed 45 min after intraperitoneal and 20 min after intraventricular administration of the drugs for the histological observations on the neurosecretory system and the histochemical studies of catecholamines in this area (II group).The antidiuretic effect of adrenaline and acetylcholine was established. The antidiuresis was more remarkable following intraventricular treatment.There was no direct relationship between the amount of neurosecretory substance and ADH activity in the posterior pituitary in the short term experiment after intraperitoneal administration of these drugs.The rapid release of ADH from the posterior pituitary was accompanied with a remarkable output of neurosecretory substance from the neurosecretory cell bodies into the axons and these effects were considerable after intraventricular introduction of the drugs. Some neurosecretory cells in the state of the initial hyperfunction were observed. In the posterior pituitary the initial mobilisation of the neurosecretory material from the neurosecretory terminals following intraventricular introduction of the drugs was observed.The supraoptic nucleus seems to be more sensitive to acetylcholine and the paraventricular nucleus to adrenaline treatment.The significant vasodilatation in the posterior pituitary and in the area of the supraoptic nucleus following intraventricular acetylcholine introduction was established.According to the data described it is possible to expect the existence of control of the hypothalamic neurosecretory activity by means of adrenergic and cholinergic structures.I am very obliged to Prof. W. Bargmann for his stimulating interest in this Study. I am grateful to Dr. G. Leontieva and Dr. V. Govyrin for the possibility to use the fluorescence catecholamine method, to Dr. E. Zeimal and Prof. M. Michelson for using the method for intraventricular injections.     

Cytogenetic studies following high dosage paternal irradiation in the mealy bug,Planococcus citri

Summary In the mealy bug, Planococcus citri, following high dosage paternal irradiation (60,000–120,000 rep), the survivors are mostly female (about 30–40% of the unirradiated control value) whereas very few males survive (about 5% of control value). After lower doses of paternal irradiation (P. I.), however, few or no females survive while the normal number of males (never less than the control value) survive.The females developing after high dosage P. I. are gynogenetic and are triploid or diploid or 3N/2N or 2N/N mosaics (Chandra 1963).The cytology of X₁ embryos following 90,000 rep is described in this report, in comparison with data from embryos following lower doses (8,000 r) of P. I. and unirradiated controls, to illustrate the chromosomal mechanisms leading to the production of gynogenetic females and the probable reasons for lethality of X₁ males after heavy P. I.It has been shown that triploid females stem from a fusion nucleus of the first and second polar bodies. This triploid polar nucleus, which normally participates in the formation of a polyploid sector in the young embryo, undertakes a successful embryogeny in many embryos when the zygote nucleus is unable to do so because of the heavily damaged paternal complement of chromosomes. Since the chromosomes are characterized by holokinetic activity, the irradiated paternal set manages to divide with the maternal complement but did not always segregate as successfully. Restitution divisions of the zygotic nuclei result in haploid, hyperhaploid, diploid and polyploid nuclei. Most of the diploid gynogenetic females probably originate from diploid nuclei of zygotic origin although it is possible that a few diploid females and the 2N/N mosaic females develop from polar bodies.From a dissertation submitted to the University of California, in partial satisfaction of the requirements for the degree of Doctor of Philosophy.Supported in part by a National Science Foundation Grant (No. G-9772) to Professor Spencer W. Brown.N. I. H. Predoctoral Trainee in Genetics 1961–1962.     

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).     

The fine structure of muscle in a marine turbellarian

Summary The fine structure of the myofibers of Notoplana acticola as studied by electron microscopy indicates that they are composed of thick myofilaments about 200 Å wide with tapering ends and thin myofilaments about 50 Å wide, arranged alongside each other parallel to the long axis of the cell. There is no orderly transverse arrangement of filaments; instead they appear staggered in the fiber. In cross sections 6 to 10 thin filaments form an orbit around one thick filament with possible cross-linkage between the two types of filaments.Dense bodies are associated with the sarcolemma and with the sarcoplasmic reticulum, and appear to serve as attachments for the thin filaments. Dense bodies are compared to elements forming a fragmented Z-disc.Mitochondria, situated in the periphery or the center of fibers, are associated with granules interpreted as glycogen.The sarcoplasmic reticulum consists of: sacs or cisternae in close proximity to the sarcolemma, longitudinal tubular elements between and parallel to the myofilaments, and a tubular network around the filaments. There is no well-defined sarcolemmal-derived transverse tubule system as described in striated muscles. It is hypothesized that in these muscles, the functional equivalent of the T system may be the area of sarcolemma in contact with the cisternae of the sarcoplasmic reticulum.This work was supported by Grant No. GM 10292 from the U. S. Public Health Service to Professor Richard M. Eakin, Department of Zoology at the University of California, Berkeley, USA, where this investigation was conducted during the author's sabbatical leave of absence from the University of Illinois.I wish to thank Professor Eakin for valuable discussions and for his kind hospitality in extending the facilities of his laboratory and the use of the electron microscope to me, and the John Simon Guggenheim Memorial Foundation for the Fellowship which I held during 1964–65.     

Seasonal and annual variations in biological regime of lakes in an ultracontinental climate (Trans-Baikal Region of U.S.S.R)

Summary The lakes are covered 7 months with ice, but under the transparent ice (up to 180 cm thickness) a rich vegetation of phytoplankton, phytomicrobenthos and macrophyta develop and activate the bacterial and animal population. Winter production of the phytoplankton reaches 36 g/m² C and that of the phytomicrobenthos 70 g/m² C.The water levels of the lakes show fluctuations with an amplitude of 2–4 m, affecting the whole trophic system inclusive species composition, proportion and abundance of individual aquatic organisms as well as related abiotic conditions.Co-authors: E. I. Bondereva, T. N. Morozova, (primary production), A. A. Topolov, K. A. Shishkina (microbiology), V. P. Gorlachov (zooplankton), I. M. Shapovalova (zoobenthos), N. M. Pronin (fish and their parasites), V. N. Kuzmich (nutrition of fish).Co-authors: E. I. Bondereva, T. N. Morozova, (primary production), A. A. Topolov, K. A. Shishkina (microbiology), V. P. Gorlachov (zooplankton), I. M. Shapovalova (zoobenthos), N. M. Pronin (fish and their parasites), V. N. Kuzmich (nutrition of fish).     

Degradation of polycyclic aromatic hydrocarbons by an immobilized mixed bacterial culture

The mixed bacterial culture MK1 was capable of degrading a wide spectrum of aromatic compounds both as free and as immobilized cells. By offering anthracene oil or a defined mixture of phenol, naphthalene, phenanthrene, anthracene and pyrene (in concentrations of 0.1–0.2 mm, respectively) as sources of carbon and energy, a specific degradation pattern correlating with the condensation degree was observed. Regarding the defined mixture of aromatic hydrocarbons, complete metabolism was reached for phenol (0.1 mm) after 1 day, for naphthalene (0.1 mm) after 2 days and for phenanthrene (0.1 mm) after 15 days of cultivation. The conversion of anthracene (0.1 mm) and pyrene (0.1 mm) resulted in minimal residual concentrations, analogous to fluoranthene and pyrene of the anthracene oil (0.1%). Maximal total degradation for the tricyclic compounds dibenzofurane, fluorene, dibenzothiophene, phenanthrene and anthracene of the anthracene oil (0.1%) occurred after 5 days. In general, a significant metabolisation of the tetracyclic aromatic hydrocarbons fluoranthene and pyrene was observed after the degradation of phenol, naphthalene and most of the tricyclic compounds. Doubling the start concentrations of the polycyclic aromatic hydrocarbons effected higher degradation rates. Cell growth occurred simultaneously with the conversion of phenol, naphthalene and the tricyclic compounds. The immobilized cells showed stable growth and, compared to freely suspended cells, the same degradation sequence as well as an equivalent degradation potential — even in a model soil system. Correspondence to: I. Wiesel