Cytochemical localization of catalase activity in methanol-grown Hansenula polymorpha

The localization of peroxidase activity in methanol-grown cells of the yeast Hansenula polymorphia has been studied by a method based on cytochemical staining with diaminobenzidine (DAB). The oxidation product of DAB occurred in microbodies, which characteristically develop growth on or methanol, and in the intracristate space of the mitochondria. The staining of microbodies was H2O2 dependent, appeared to be optimal at pH 10.5, diminished below pH 10 and was inhibited by 20 mM 3-amino 1,2,4 triazole (AT). In contrast to these observations, the reaction in the mitochondria was not H2O2 dependent and not notably affected by differences in pH in the range of 8.5 to 10.5. Microbodies and mitochondria were also stained when H2O2 was replaced by methanol. Appropriate control experiments indicated that in this case methanol oxidase generated the H2O2 for the peroxidative conversion of DAB by catalase. These results suggest that catalase is located in the microbodies of methanol-grown yeasts. A model for a possible physiological function of the microbodies during growth on methanol is put forward.

Conjugation in the yeast Saccharomycopsis capsularis Schiönning

Cells of the yeast Saccharomycopsis capsularis fused in pairs after disolving of part of the cross wall between them near the lateral wall. After nuclear migrations through the opening, the cross wall was closed again and the cells at both sides became asci. The wall of the ascospores developed from a prospore wall. Between the two unit membranes a very thin dark layer broadened to the dark layer of the wall and after that, the light inner layer developed. Immature spores in the strain studied had a ledge which disappeared during maturation.

Electron microscopy of ascus formation in the yeast debaryomyces hansenii

Ascus formation in Debaryomyces hansenii includes fusion of two cells, usually mother and daughter while still attached to each other, through short protuberances developed from the cross wall between them. Nuclear fusion takes place in the channel connecting the two cells; meiosis apparently occurs in the mother cell. Generally, only one lobe of the meiotic nucleus is surrounded by a prospore wall and it becomes the nucleus of a spore with a warty wall. The rest of the nucleus disappears. The spores germinate by swelling in the ascus and forming one or more buds.

On the localisation of d-tubocurarine in rat liver lysosomes in vivo by electron microscopy and subcellular fractionation

After i.v. injection in the rat, d-tubocurarine is taken up and concentrated by the liver. A method is developed for the visualisation of d-tubocurarine inside the liver cell by electron microscopy. Glutaraldehyde fixed liver blocks were immersed in an ammonium molybdate solution; d-tubocurarine was precipitated at sites of high concentration by molybdate, to form an insoluble d-tubocurarine-molybdate complex. This precipitate was found predominantly at the surface of lysosome-like particles, but also inside these organelles. In subcellular fractionation experiments, d-tubocurarine was found with a high relative specific "activity" in the lysosomal fraction, lending support to a lysosomal localisation of d-tubocurarine.

Microbodies in methanol-assimilating yeasts

Cells of 3 yeast species capable of assimilating methanol have been examined by electron microscopy. When grown on methanol as the sole source of carbon and energy they contained many microbodies. Cells grown on glucose or ethanol either did not contain such bodies at all, or only to a limited extent.

The Effect of Prolactin on the Number of Membrane-Associated Particles in Kidney Cells of the Euryhaline Teleost Gasterosteus Aculeatus during Transfer from Seawater to Freshwater: A Freeze-Etch Study

The membranes of kidney cells of 3-spined sticklebacks were examined in freeze-etch replicas. The numbers of particles adhering to surfaces and fracture faces of the outer cell membranes and the membranes of the basal labyrinth were determined. The latter membranes probably are the main location of ion-transporting enzyme complexes.

The total number of particles per cell in freshwater fish exceeds that of seawater fish by about 50 % for the outer cell membrane, and by almost 200 % for the membranes of the basal labyrinth.

After transfer of seawater fish to freshwater, particle numbers increase and their densities approximate freshwater values after 20 h. This rise in particle numbers coincides with the increase of ion-transporting activity of the cells known to take place after transfer to freshwater.

The rate of increase of particle densities is enhanced after injection of ovine prolactin. This hormone is known to stimulate Na+/K+-ATPase activity of the basal labyrinth of teleost kidney cells.

The results indicate that the particles represent enzyme complexes. The number of particles is probably under hormonal control. The increase in particle densities after transfer to freshwater is accompanied by a rise in the number of nuclear pores, which is noticeable by 10 h.

No changes were observed in the density of the particles adhering to the fracture faces of gap junctions.

Spores and septa in the genus Dipodascus

Electron microscopy of the septa in hyphae of Dipodascus species showed a narrow, central pore in D. uninucleatus and plasmodesmata in D. aggregatus, Ascospores in D. uninucleatus are small, oval, or reniform; in D. aggregatus they are much bigger with a wall which is first narrow and later expands considerably. The description of the spores of the type species, D. albidus, of which no strains were available for examination, agrees with that of D. aggregatus. Apart from the features mentioned above, D. uninucleatus differs from D. albidus and D. aggregatus in other important characteristics, such as the method of gametangia formation and the structure of the cell wall.

The Membranes of the Basal Labyrinth in Kidney Cells of the Stickleback, Gasterosteus Aculeatus, Studied in Ultrathin Sections and Freeze-Etch Replicas

The structure of the basal labyrinth in kidney cells of freshwater sticklebacks was studied in ultrathin sections (after fixation with permanganate, osmium tetroxide, and combinations of glutaraldehyde with osmium tetroxide) and in freeze-etch replicas (after pretreatment with glutaraldehyde and/or glycerol, or without pretreatment). The structure of the basal labyrinth in sticklebacks, and probably in other teleost species, differs essentially from the type of labyrinth found in kidney cells of mammals like the rat. In the latter animals, the space enclosed by the membranes of the labyrinth is intercellular. In the stickleback the labyrinth consists of an intracellular system of branched membranes lining narrow saccular spaces. These spaces communicate with the exterior of the cells by means of small pores, located in the lateral and basal parts of the outer cell membranes.

All chemical fixation procedures used introduced specific structural artifacts. It is concluded that the structure of the basal labyrinth is relatively well preserved after fixation with potassium permanganate, with a mixture of glutaraldehyde and osmium tetroxide, or with osmium tetroxide when applied for 10 min only. The unit-membrane structure was, however, absent after all procedures involving osmium tetroxide.

In freeze-etch replicas determinations were made of the numbers of small particles covering the surfaces and fracture faces of the membranes of the basal labyrinth and of the outer cell membranes. The numbers per unit area of surface proved to be markedly constant and specific for each of the four faces of both types of membranes. Specific differences were found between the particle densities of the outer cell membranes and the membranes of the basal labyrinth. This finding points to functional differences between these types of membranes.

Particle densities were not influenced by pre-incubation with glycerol. After fixation with glutaraldehyde, the particles adhering to the outer and inner surfaces had decreased in number.

It is concluded from this study that membrane structure, as revealed in thin sections as well as in freeze-etch replicas, is consistent with Singer's ‘fluid lipid-crystal protein’ model.

New procedure for the isolation of membrane vesicles of Bacillus subtilis and an electron microscopy study of their ultrastructure

A rapid procedure for the isolation of membrane vesicles of Bacillus subtilis is described that minimizes the action of proteolytic enzymes, excreted by this organism, on the membrane proteins. The membrane vesicles obtained have, in addition to a low endogenous respiration rate, a low endogenous activity for transport of amino acids and carboxylic acids. In the presence of the electron donor, ascorbate-phenazine methosulfate, the transport activities for these compounds were comparable to the activities of intact cells. In addition, these activities were retained for a prolonged period of time. Electron microscopy examination of thin sections of the vesicles showed that the preparation consisted almost exclusively of membrane vesicles which were not contaminated with other cell components. The membrane vesicles, which are six to seven times smaller in diameter than protoplasts, often enclosed smaller vesicles. Freeze-etching of intact cells, protoplasts, and membrane vesicles showed that the orientation of the membrane of the vesicles was identical to the orientation of the plasma membrane in intact cells and protoplasts. This also held for the majority of the membranes of the enclosed vesicles, only 15% having the opposite orientation.

Electron microscopy of some special cell contracts in yeasts

Anastomosis in Endomycopsis javanensis and some other filamentous yeasts was brought about by contact of a denticle from one cell with the wall of another cell, resulting in the disappearance of the outer layer and the thickening of the inner layer of the cell wall of the contacted cell. Another form of contact between cells was the penetration of one cell by a denticle on another cell which had grown out to a stalk; this occurred between cells of E. javanensis and between cells of this species and other yeast species.

Some features of vegetative and sexual reproduction in Endomyces species

Vegetative reproduction and, as far as possible, sexual reproduction have been studied by light and electron microscopy in six Endomyces species. In most of these species multiple scars were observed on the arthrospores as a result of repeated germination from the same site. Plasmodesmata in the septa of Endomyces decipiens, E. reessii, and E. geotrichum were arranged at random, while those of E. magnusii, E. ovetensis, and E. tetrasperma appeared in a circle. For all species, except E. decipiens, gametangiogamy preceding ascus formation has been described. Mature ascospores in E. ovetensis and E. tetrasperma have a wide, regular, smooth wall and are dehisced. Ascospores of E. reessii and E. geotrichum are not liberated from the ascus and have a lobed, punctate wall. In E. geotrichum the lobes are arranged in such a way that a groove runs around the spore.