A revised description of Haplosporidium armoricanum, parasite of Ostrea edulis L. from Galicia, northwestern Spain, with special reference to the spore-wall filaments

Haplosporidian spores from Ostrea edulis, previously described as Minchinia armoricana, were reexamined by light and electron microscopy. These spores were either free among host cells or enclosed in sporocysts. They contained two long epispore cytoplasm extensions (ECE), each possessing cytoskeletal structures corresponding to the filaments. After lysis and degradation of the ECE, these extensions disappeared and the spores became devoid of membrane-bound extensions. However, 2 long filaments (approximately 130 microm long) persisted that were closely attached, in opposition to the spore wall, by a bundle of 9-13 fibers each. Thus, we propose a revised description of M. armoricana (= H. armoricana) to confirm its placement in the genus Haplosporidium as H. armoricanum.

A novel class of eukaryotic zinc-binding proteins is required for disease resistance signaling in barley and development in C. elegans

Barley Rar1 is a convergence point in the signaling of resistance to powdery mildew, triggered by multiple race-specific resistance (R) genes. Rar1 is shown to function upstream of H2O2 accumulation in attacked host cells, which precedes localized host cell death. We isolated Rar1 by map-based cloning. The sequence of the deduced 25.5 kDa protein reveals two copies of a 60-amino acid domain, CHORD, conserved in tandem organization in protozoa, plants, and metazoa. CHORD defines a novel eukaryotic Zn2+-binding domain. Silencing of the C. elegans CHORD-containing gene, chp, results in semisterility and embryo lethality, suggesting an essential function of the wild-type gene in nematode development. Our findings indicate that plant R genes have recruited a fundamental cellular control element for signaling of disease resistance and cell death.

Nail changes secondary to docetaxel (Taxotere)

Docetaxel is a new taxoid antineoplastic drug widely used for advanced breast cancer. Skin and nail toxicity are one of the more frequent nonhematologic adverse reactions. Besides dark pigmentations and Beau's lines, subungual hemorrhage, orange discoloration, acute painful paronychia, onycholysis, subungual hyperkeratosis and transverse loss of the nail plate are described. The type of nail alteration is related with the number of cycles administered and there are no efficacious preventive measures to avoid its development. Clinicians should recognize the clinical picture of these adverse nail reactions because docetaxel is used for several neoplastic disorders.

Enzymes Involved in Defense Functions of Hemocytes of Mussel Mytilus galloprovincialis

Mytilus galloprovincialis hemocytes contain phosphatases, esterases, proteases, and glucosidases as revealed by a semiquantitative colorimetric method. The activity levels of some enzymes changed throughout the months of the experiment without a seasonal pattern. No differences in the enzyme levels were found between the two groups of mussels of different age (cultivated 11 and 19 months on ropes hung from the same raft). Light microscopy study of hemocyte enzymes showed that hyalinocytes and granulocytes had reaction of acid phosphatase, beta-glucuronidase, alpha-naphthyl butyrate esterase, naphthol AS-D chloroacetate esterase, and alpha-naphthyl acetate esterase. Phenoloxidase and peroxidase activities were also detected in monolayers of hemocytes. Ultrastructural study revealed that the granules of hemocytes contained acid phosphatase, beta-glucuronidase, nonspecific esterases, peroxidase, and NADH oxidase. Products of beta-glucuronidase and peroxidase reaction were also localized in the plasma membrane. Lysozyme activity level was higher in hemocytes than in serum. Comparison between the two groups of different age showed a higher activity level of lysozyme in younger mussels.

Morphological characterization of the hemocytes of the clam, Ruditapes decussatus (Mollusca: Bivalvia)

Hemocytes play an important role in internal defence in molluscs. The morphology of hemolymph cells was studied for the first time in Ruditapes decussatus. Two main types of hemocytes (hyalinocytes and granulocytes) exist in R. decussatus. Three types of granulocytes were identified by light microscopy, in accordance with the presence of basophilic or acidophilic granules or a mixture of both in the cytoplasm. The existence of hyalinocytes and granulocytes was confirmed by electron microscopy. Some monoclonal antibodies (MABs) raised against hemocytes of Crassostrea gigas showed cross-reactivity with the total population of hemocytes of R. decussatus; however, none of the MABs raised against hemocytes of Mytilus edulis showed cross-reactivity. The MABs assayed did not allow us to distinguish hemocyte subpopulations.

Light and electron microscopic study of a myxosporean, Tetrauronema desaequalis n. sp. (fam. Tetrauronematidae), from an Amazonian fish

Tetrauronema desaequalis n. sp. described from the bases of the ventral fins of the teleost Hoplias malabaricus Boch, 1794, was collected in an estuarine region of the Amazon river near Belem, Brazil. This myxosporean produces large cysts (1-2 mm in diameter) that represent plasmodia containing all life cycle stages, including spores. Spores averaged 22.5 microns in total length and possess 2 pairs of posterolateral unequal projections extending from beside the sutural ridges near the terminus of the shell valves. The spore body was ellipsoidal and laterally compressed. Spore bodies measured 13.6 microns in length, 6.5 microns in width, and 3.7 microns in thickness. The 4 projections averaged 13.0, 12.2, 7.2, and 5.1 microns in length. The ellipsoidal polar capsules (7.0 x 2.6 microns) possessed a polar filament with 9-11 turns.

Henneguya malabarica sp. nov. (Myxozoa, Myxobolidae) in the Amazonian fish Hoplias malabaricus

Henneguya malabarica sp. nov. is described from the Amazonian teleost fish Hoplias malabaricus Boch, 1794, collected from the estuarine region of the Amazon river near Belém, Brazil. Plasmodia were represented by several vegetative nuclei, generative cells, and sporogony stages contained in cyst-like plasmodia. The spore body was ellipsoidal (12.6 microns in length and 4.8 x 3.6 microns in width) and each valve presented a tapering tail (17.1 microns in length). Thin valves surrounded the binucleate sporoplasm cell and two spherical polar capsules (3.7 x 1.8 microns) that contain five to six coils of the polar filament. The spore had an iodinophilous vacuole. The basal portion of the spore body of immature and mature spores and the whole surface of the tails were surrounded by a close homogeneous sheath. The prevalence of infection was 6.7% in the fish examined. The spores differed from those of previously described species of Henneguya in their shape, size, spore, and arrangement of the polar-filament coil. The taxonomic affinities of this parasite to other species are discussed.

Henneguya adherens n. sp. (Myxozoa, Myxosporea), parasite of the Amazonian fish, Acestrorhynchus falcatus

A new species of myxosporean from the gill filaments of the freshwater teleost fish, Acestrohynchus falcatus collected in the Amazon river is described from light and transmission electron microscope observations. The mature spores (total length 32.3 [30.7-35.1] micron) and all developmental stages were found in the same sporogonic plasmodium. The ellipsoidal spore body consists of 2 unequal shell valves adhering together along the suture lines. Each valve, tapering as a caudal projection, forms a long tail (length 20.5 [18.0-21.7] micron). The tail was surrounded by a homogeneous sheath on its length. The polar capsules measuring 3.1 x 1.2 micron contain 3-4 coils of the polar filament. All surfaces of the immature and mature spores were surrounded by a closely adherent homogenous structural sheath, mainly thicker around the tails. The taxonomic affinities of this parasite to other species are discussed.

Histochemical Studies of Jelly Coat of Marthasterias glacialis (Echinodermata, Asteroidea) Oocytes

Histochemical studies revealed the presence of two major polysaccharides in the oocyte jelly coat (JC) of Marthasterias glacialis: a fibrillar component that contains carboxylic and sulfated groups and a loose component composed of neutral or weakly acidic polysaccharides. When isolated JC was submitted to cellulose acetate electrophoresis (CAE) and then stained with alcian blue, three bands appeared, of which one remained at the origin and two migrated toward the anode. Glycosaminoglycan-like molecules isolated from JC were separated by CAE into three main moving bands, two that present an Rf similar to that of the intermediary moving band of total JC and one that has an Rf similar to that of the faster moving band of total JC. These bands also have critical electrolyte points similar to those of total JC. Chondroitinase ABC mainly attacked the faster moving band, whereas protease and hyaluronidase seemed to digest all bands. These results and the Rfs of isolated and standard glycosaminoglycans after mono- and bidimensional CAE suggest that the glycosaminoglycan-like molecules bear some resemblance to chondroitan sulfate, heparan sulfate, and hyaluronic acid.

Ultrastructural Histochemistry of Marthasterias glacialis (Echinodermata, Asteroidea) Gametes Before and After Fertilization

The gametes of the starfish Marthasterias glacialis were studied, both before and after fertilization, using several histochemical methods at the ultrastructural level. Results showed that the oocyte jelly coat (JC) could be morphologically differentiated into a fibrillar network of acidic polysaccharides, probably containing glycosaminoglycans (GAGs), and a loose component made of neutral polysaccharides that occupies the interstices of the former. Results also suggested that it is the fibrillar component of the JC to which the spermatozoon attaches and reacts. Staining of the acrosomal vesicle contents confirmed that the peripheral dense component attaches the spermatozoon to the JC, whereas the central and apical electron-lucent component coats the acrosomal process as it extends through the oocyte investments. The acrosomal process membrane was also shown to be negatively charged. Staining of cortical vesicles confirmed their tripartite compartmentalization: the spiral lamellae fused with the fertilization envelope (FE), transferring its staining to the inner layer of the FE, whereas the matrix could be subdivided into two components--a fibrillar mesh of acidic polysaccharides that fused with the FE and some amorphous aggregates that seem to become dispersed in the perivitelline space.

Ultrastructural and cytochemical identification of peroxisomes in the ciliate Ichthyophthirius multifiliis

The peroxisomes of the parasitic ciliate Ichthyophthirius multifiliis were studied, using ultrastructural and cytochemical techniques. In this ciliate most peroxisomes possess a circular or oval section less than 0.6 micron in diameter. However, some dumbbell-shaped and elongated peroxisomes could also be observed. These organelles were frequently associated with the mitochondria and were more abundant in the cell cortex than in the center of the ciliate. Small vesicles and dense nucleoids were usually present in the ultrathin sections of these peroxisomes. Peroxisomal vesicles and tubular structures were selectively impregnated with osmium tetroxide. Catalase was detected by cytochemical techniques in I. multifiliis peroxisomes.

Processing of food vacuoles in the parasitic ciliate Ichthyophthirius multifiliis after exit from the host

The digestive cycle of the fish parasite Ichthyophthirius multifiliis (Ciliophora) can be divided into three main stages. During stage A the vacuoles are not yet condensed. This stage can be subdivided into an early phase in which food vacuoles contain almost intact fish cells and a later phase in which dense material accumulates at the periphery of the vacuoles. At stage B, food vacuoles attain a very high density, and at stage C the vacuole expands when the membrane pulls away from a condensed mass of substances in digestion. After its exit from the host the parasite encysts and divides, but new food vacuoles are not formed during this phase of the life cycle. Type A vacuoles are the first to disappear after exit from the host. The percentage of type B vacuoles increases during the first few hours of free life, decreasing later when the percentage of type C vacuoles starts to increase. At the end of the division phase, type C vacuoles are the most common. Food-vacuole egestion was observed only 20 h after exit from the host. At the theront stage, food vacuoles were not evident, but small vacuoles with acid phosphatase activity were observed.

Presence of a trypsin-like protease in starfish sperm acrosome

Marthasterias glacialis sperm cells were treated with ionophore A23187, centrifuged, and the supernatants were assayed for esterase activity. With N-benzoyl-L-arginine ethyl ester-HCl (BAEE) as substrate, a net activity was determined which was not detectable when N-acetyl-L-tyrosine ethyl ester (ATEE) was used. The BAEE trypsin-like activity was inhibited by soybean trypsin inhibitor (SBTI), N-alpha-p-tosyl-L-lysine chloromethyl ketone-HCl (TLCK), and phenyl methyl sulfonyl fluoride (PMSF), but not by L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK). The presence of proteolytic activity in acrosomal exudates was further demonstrated by gelatin-sodium dodecyl sulfate-polyacrylamide gel electrophoretic zymography (gelatin-SDS-PAGE). The presence of several bands of low proteolytic activity and of one band of high proteolytic activity, which also has the lower molecular weight, together with the fact that all are inhibited by benzamidine, suggests the existence of a trypsin-like proteinase system. The effect of the acrosomal exudate on the oocyte jelly coat was investigated by SDS-PAGE analysis. All jelly proteins appeared to be digested by the acrosomal enzymes. Furthermore, if SBTI is added shortly after insemination, the sperm fail to fertilize the oocytes. These results indicate that the starfish sperm acrosomal vesicle contains a trypsin-like protease which may be involved in sperm penetration through the oocyte jelly coat.

Silver staining of the postacrosomal sheath during human spermiogenesis

Applying the silver staining technique, it could be shown that in the early phase of spermiogenesis a layer of argyrophilic material accumulated at the base of the acrosomal vesicle and at the outer side of the nuclear envelope opposite that region, and, later, at the inner side of the plasma membrane near the base of the acrosomal vesicle. During further development of the postacrosomal region of the spermatozoon head, the argyrophilic material associated with the plasmalemma grew caudally to form the postacrosomal dense lamina, while the argyrophilic material associated with the nuclear envelope, staying the same size, shifted to the caudal end of the postacrosomal dense lamina to form the post-nuclear band.

Extracellular giant rickettsiae associated with bacteria in the gill of Crassostrea gigas (Mollusca, Bivalvia)

Extracellular giant rickettsiae closely associated with bacteria with a Gram-negative type wall are reported among the basal insertions of the cilia of the gill epithelium of the oyster Crassostrea gigas (Mollusca, Bivalvia) from the north of Spain. These rickettsiae are extremely pleomorphic cells with a maximum 9 microns length. The internal elements are ribosome-like particles and DNA strands are distributed in some light areas. Some rickettsial cells show one to two vacuole-like dense inclusions formed by curved concentric bands approximately 4 nm thick separated by an approximately 5-nm light space (myelin-like bodies). Numerous bacteria are closely associated with the rickettsiae in the surrounding zone. The cytopathic effects of this association seemed to give rise to the epithelial lysis and concomitant disappearance of the apical microvilli and cilia and the consequent destruction and disintegration of the gill epithelial cells, where these rickettsiae live in close proximity. This is believed to be the first description of extracellular giant pathogenic rickettsiae of these oyster species.

Fine structure of zoosporulation in Perkinsus atlanticus (Apicomplexa: Perkinsea)

Light and transmission electron microscopy were used to study different stages of Perkinsus atlanticus (Apicomplexa) during induced zoosporulation, with fluid thioglycollate medium and seawater. Cytokinesis and nucleokinesis of different developmental stages were studied every 12 h during the incubation period of 72 h, at which time the zoospores became free. Uninucleated and flagellated zoospores present the apical complex formed by conoid, polar ring, micronemes, rhoptries and subpellicular microtubules observed at different sections. Ultrastructural details were compared with the other two species of the genus Perkinsus.

Enzyme cytochemistry of the alveolar sacs and golgian-like cisternae in the ciliate Ichthyophthirius multifiliis

In the cell cortex of the parasitic ciliate Ichthyophthirius multifiliis different kinds of cisternae were observed: the alveolar sacs, thick membrane cisternae and the endoplasmic reticulum. The thick membrane cisternae possess coated dilated rims and sometimes could be observed close to the endoplasmic reticulum. Using cytochemical techniques acid phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase activities were detected in the thick membrane cisternae and in the alveolar sacs of trophozoites. In the endoplasmic reticulum acid phosphatase activity was not detected and only very small amounts of thiamine pyrophosphatase and nucleoside diphosphatase reaction product were observed. After exit from the host, a reduction in acid phosphatase activity was evident in the alveolar sacs. At theront stage acid phosphatase activity is absent from these structures. However, high thiamine pyrophosphatase and nucleoside diphosphatase activities remain in the alveolar sacs during the whole life cycle. On the other hand, acid phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase activities were detected in thick membrane cisternae of theronts. Based on the morphological aspects and enzymatic content the thick membrane cisternae of the cell cortex are designated as golgian-like cisternae. The cytochemical results point out a relationship between the alveolar sacs and the Golgi complex.

Ultrastructural and cytochemical study of spermatogenesis in Scrobicularia plana (Mollusca, Bivalvia)

The ultrastructure of the mature spermatozoa and spermatogenesis of the bivalve Scrobicularia plana are described. Support cells extend from the basal lamina to the lumen of the testis and are laterally connected to the germinal epithelium. Germ cells present intercellular bridges and flagella since the spermatogonial stage. While spermatogonia and spermatocytes appear connected to support cells by desmosome-like junctions, elongated spermatids are held at the acrosomal region by support cell finger-like processes. During spermiogenesis, the acrosomal vesicle differentiates from a golgian saccule and then migrates to the nuclear apex. A microtubular manchette arising from centrioles surrounds the acrosomal vesicle, the nucleus, and the mitochondria at the time these three organelles start their elongation, disappearing after that. The mature spermatozoon of S. plana lacks a distinct midpiece because the mitochondria extend from the region of the pericentriolar complex along the nucleus anteriorly for approximately 1.4 microns. The features of this bivalve type of modified spermatozoon are compared with those of other animal groups having similar modifications.

Fine structure of Perkinsus atlanticus n. sp. (Apicomplexa, Perkinsea) parasite of the clam Ruditapes decussatus from Portugal

A new apicomplexan species, Perkinsus atlanticus, is described from gill filaments of the clam Ruditapes decussatus (Bivalvia) from Portugal, where it causes great mortality. The zoospores differ from those of other species of Perkinsus in size and shape, dimensions, insertion of the 2 flagella, and in the identity of the host. On the other hand, the life cycle stages showed some ultrastructural differences compared with Perkinsus marinus, the only species previously studied in detail. When the clams were parasitized heavily, ultrastructurally similar life cycle stages were found in foot and mantle tissues.

Starfish sperm-oocyte jelly binding triggers functional changes in cortical granules. A study using acid phosphatase and ruthenium red ultrastructural histochemistry

Starfish oocytes were examined before fertilization, immediately after insemination, and during the cortical reaction by means of acid phosphatase and ruthenium red ultrastructural histochemistry. Oocyte cortical granules are composed of a lamellar body and a surrounding matrix which is subdivided into dense and light portions. In unfertilized oocytes cortical granules are not stained by ruthenium red but show a weak acid phosphatase activity in the light portion of the granule matrix. Immediately after the adhesion of the spermatozoon to the oocyte jelly coat, the light matrix portion of cortical granules appears stained by ruthenium red and shows a strong acid phosphatase activity. During the cortical reaction, cortical granules are released into the perivitelline space and the lamellar body, surrounded by the stained matrix, fuses with the fertilization envelope. Our data suggest that membrane permeability changes and enzyme activation occur in the egg when the spermatozoon binds to the oocyte jelly coat.

Some ultrastructural data on the spore development in a Henneguya sp. parasite of the gill of a Brazilian fish

A myxosporean Henneguya sp. was found in the gill filaments of a freshwater fish, Hoplosternum littorale, from the lower Amazon river near Belém, Brazil. Plasmodia were represented by numerous vegetative nuclei, generative cells and sporogony stages. The spore body was ellipsoidal and each valve presented a tapering tail approximately 45.2 microns in length. The spores differed from those of previously described species in their shape and size. The developmental stages are described and discussed. This histozoic species is reported to be pathogenic, inducing great mortality in the host.

Presence of ATPase and alkaline phosphatase activities in the starfish sperm acrosome

ATPase activity was cytochemically detected in the peripheral acrosomal component of ionophore-reacted sperm, while alkaline phosphatase activity was demonstrated in the upper and central components of the acrosome and, at fertilization, at the site of sperm-oocyte binding. Supernatants of ionophore treated sperm suspensions were assayed for ATPase, alkaline and acid phosphatase activities. Results suggest that alkaline phosphatase may be involved both in the acrosomal reaction and oocyte jelly lysis but the function of the acrosomal ATPase remains unknown.

Presence of argyrophilic cytoplasmic and nuclear proteins in the spermatic cells of Nucella lapillus (Gastropoda, Prosobranchia)

The technique for ultrastructural localization of argyrophilic proteins was modified and NOR-Silver staining methods were applied to the study of the distribution of these proteins in the spermatic cells of Nucella lapillus (Gastropoda, Prosobranchia). Two types of selective silver deposits were found during the different phases of spermiogenesis and in mature spermatozoa. Argyrophilic nuclear, nucleolar and cytoplasmic proteins were simultaneously detected by improvement of a modified one-step silver technique.

Ultrastructural and cytochemical observations of the spherites in a parasite trematoda larva

Concentric laminated concretions, termed 'spherites', were found in the parenchymal cells and in the lumen of the collecting vessels of the trematode Meigymnophallus minutus, parasite of a lamellibranch mollusc. In the initial stage, the spherites are surrounded by a membrane and located in close proximity to the endoplasmic reticulum and Golgi complexes, increasing in size with age and by deposit of concentric layers. Later, they migrate and are released into the lumen of the collecting vessels. These structures contain high concentrations of calcium and phosphorus. The organic matrix is mainly composed of protein, lipids, acid phosphatase and glycoproteins as demonstrated by several cytochemical staining methods. It is possible that these calcareous concretions play an important role in the excretory system of the adult trematode, the life cycle of which takes place within the mantle of the host mollusc.

Ultrastructure of a microsporidian hyperparasite, Unikaryon legeri (Microsporida), of trematode larvae

Unikaryon legeri (Dollfus, 1912) Canning and Nicholas, 1974, has been reexamined by electron microscopy from material collected in Portugal. It parasitises metacercariae of Meigymnophallus sp. in Cardium edule. A sporophorous vesicle forms around the sporonts, arising as a blister that separates from the electron-dense surface coat of the sporont. Sporogony is disporoblastic, giving rise to 2 spores that are retained in pairs within the sporophorous vesicle. Unikaryon piriformis, which is the type species of the genus and is also hyperparasitic in platyhelminth larvae, has not been examined by electron microscopy, and it is not known whether this species also produces sporophorous vesicles. If it does, then all that will be required is a simple addition of this character to the definition; if not, U. legeri will have to be transferred to a new genus and reclassified with other disporoblastic genera that sporulate in sporophorous vesicles.

Prognosis in colorectal carcinoma. A reassessment of the pathologist's role

The prognostic significance of some pathologic features was evaluated in a series of 177 patients with colorectal carcinoma consecutively treated by curative resection in a department of Surgery from 1960 to 1981. There were 90 men and 87 women with a mean age of 59.2 +/- 12.8 and a range from 23 to 88 years. Current follow-up information was obtained in 92.7% of the patients. Pathologic staging as classified according to a modification of Dukes' original scheme was found to be the most important prognostic factor. Evaluation of lymphatic and venous invasion, histologic differentiation, and site of tumors also provided valuable prognostic information. Size, configuration, mucin-producing ability and the morphologic evaluation of the so-called "host immunologic response" were found to be irrelevant for the prognosis when the influence of the other indices was controlled.

Evidence for the generation of specific T suppressor lymphocytes by Streptococcus intermedius

Crude extracellular products of the Streptococcus intermedius "CEP-Si" were able to strongly decrease the in vitro proliferation of stimulated human peripheral blood mononuclear cells (HPBMC) when evaluated by (3H)-thymidine and (3H)-leucine uptake. On the other hand, CEP-Si only slightly decreased this proliferation when HPBMC were either not stimulated or cultured in poor conditions or immature cells, i.e. thymocytes were used as target instead. Also in vivo CEP-Si was ineffective when target cells were not highly reactive. Both in vivo and in vitro, the effect of CEP-Si was proportional to the time of contact with the target cells. The dynamics of the effects of CEP-Si suggest the generation of "something" ("suppressor cells") which cause an abrupt drop in the values of (3H)-thymidine uptake rather than a progressive decrease of the values, which could indicate a loss effector or helper cells. On the other hand, CEP-Si suppressed the in vitro primary immunization of human HPBMC against SRBC and, furthermore, human HPBMC incubated with CEP-Si were able to suppress the primary immune response against SRBC of, CEP-Si untreated, HPBMC. In some instances of insufficient time of contact of CEP-Si with the target cells, an enhancement of the immune response was observed both in vivo and in vitro. Moreover, the histological pattern of the spleens of C57 BL/6 mice injected with semipurified products of CEP-Si were consistent with an adjuvant-like effect. Finally, the target HPBMC for the semipurified products of CEP-Si acquired the ultrastructural and antigenic characteristics of suppressor T lymphocytes.

Intranuclear membranous inclusions in oocytes of a viviparous teleost (Xiphophorus helleri)

Intranuclear inclusions were observed in oocytes of Xiphophorus helleri during prophase I. In osmium-fixed leptotene nuclei, the inclusions were made up of groups of membrane-limited vesicles or tubules with pale contents, situated near the inner nuclear membrane with which some of them exhibited apparent continuities. In zygotene nuclei, larger vesicles also appeared bounded by two or three membranes and containing tubules apparently invaginated from their walls. In pachytene-dictyate nuclei most vesicular bodies had a wall formed by stratified membranes, or were entirely made up of membranous whorls. In glutaraldehyde-osmium fixed material some of these myeline-like bodies showed a peculiar arrangement, consisting of concentric bands each containing thick inner dense lamellae 2-0-3-0 nm thick and a 5-0 nm outer lamella. It is suggested that these inclusion bodies arise from the inner nuclear membrane of oocytes when cells start to grow intensely during prophase I. The bodies seem to become more complex at late prophase, probably by association of individual vesicles and the occurrence of multiple membrane invaginations, which may be related to active metabolic phenomena taking place at this stage in oocytes.