Richard A. Ellis

Electron microscope study of mitosis in Physarum polycephalum.

Mitosis in the slime mold Physarum polycephalum occurs within the nuclear membrane. The nucleolus breaks down into fragments which, until late in anaphase, remain identifiable by groups of electron dense granules. The mitotic spindle is formed within the nuclear membrane, and it first appears as a small plaque of fibrous material at a short distance from the surface of the disintegrating nucleolus. No centriole was found. When the daughter plates move toward the poles at anaphase, fragments of spindle fibers and clumps of amorphous material of unknown (nucleolar ?) origin are left in the middle of the interzone. The parts of the nuclear membrane around the interzone between the daughter plates and toward the poles disappear at late anaphase, and the remainder is probably reutilized in the formation of a new nuclear envelope. The nucleolus is formed by coalescence of material which first appears dispersed among the telophase chromosomes.

THE EFFECT OF A SALT WATER REGIMEN ON THE DEVELOPMENT OF THE SALT GLANDS OF DOMESTIC DUCKLINGS.

Abstract Commencing on the fourth day after hatching and continuing for 2 weeks, 84 experimental ducklings were given drinking water containing 1 or 1.2% sodium chloride for 12 hours daily and fresh tap water for the remainder of each day; 39 control birds drank only tap water. During the third day of the experiment, salt gland effluent, high in sodium content, appeared at the external nares of the ducklings. After 5 days of the salt water treatment the salt glands of experimental birds weighed significantly more than those of the control birds, while the body weights of the experimental ducklings increased more slowly than those of the controls. The salt water regimen evoked a rapid increase in the size of the secretory cells, an apparent increase in the number of secretory cells, an elongation of the secretory tubules, and an increase in the size of the secretory lobules, with concomitant dilution of the connective tissue. Histochemical differences between the salt glands of experimental and control birds, evident by the end of the third day, were intensified during the remainder of the experiment. In addition to their rich complement of phospholipid, the large secretory cells in the salt glands of the experimental birds contained abundant succinic dehydrogenase and cytochrome oxidase activity. Smaller but similar cells in the glands of control birds of the same age bore little phospholipid and were only slightly reactive for these enzymes. In addition, the secretory cells of the experimental birds gave moderate reactions for nonspecific esterase, monoamine oxidase, and acid phosphatase. The onset of the secretory competence of the salt gland coincided with the appearance of abundant phospholipid and strong oxidative enzyme activity in the secretory cells. In the secretory lobules of both experimental and control birds, two distinct cell types could be distinguished by their enzyme content. The principal secretory cells were acidophilic; they contained no alkaline phosphatase, but abounded in succinic dehydrogenase and cytochrome oxidase. The terminal or peripheral cells at the blind ends of the secretory tubules were basophilic; they reacted for alkaline phosphatase, but contained little succinic dehydrogenase or cytochrome oxidase. The position, as well as the relatively undifferentiated state of the peripheral cells, suggests that they have a generative function. The pattern of innervation, revealed by the cholinesterase technique, was more elaborate in the salt glands of experimental birds than in the controls. This observation, when correlated with available physiological data, suggested that the salt water regimen might not directly influence the growth and differentiation of the salt gland but that the effect might be mediated by the nervous system.

The effect of salt regimens on the development of (Na+K+)-dependent ATPase activity during the growth of salt glands of ducklings.

1. 1. A Mg2+-activated, ouabain-sensitive (Na+-K+)-ATPase and a ouabain-insensitive Mg2+-ATPase were characterized in salt gland homogenates of the domestic duck. 2. 2. 3 days after hatching, experimental birds were given 1% aqueous NaCl to drink for 12 h and fresh water for the remainder of each day. Control ducklings were maintained exclusively on fresh tap water. In homogenates of salt glands from experimental birds the specific activity of ATPase reached maximal levels in 9 days. (Na+-K+)-ATPase increased by a factor 4.1 and Mg2+-ATPase increased by a factor of 1.8. There was no increase in ATPase activity in homogenates from control birds. 3. 3. Homogenates of glands from birds drinking only fresh water, after being maintained on the salt-water regimen for 22 days, exhibited a logarithmic decrease in (Na+-K+)-ATPase activity and in 9 days reached the level of activity recorded for control birds maintained only on fresh water. The Mg2+-ATPase activity decreased rather slowly for the first 5 days on fresh water, and then dropped rapidly during the last 4 days of the experiment. 4. 4. The increase in ATPase levels in the salt glands of birds on the salt-water regimen is not cation-specific: both KCl and MgCl2 regimens are capable of increasing this level, although neither is as effective as NaCl. 5. 5. Differential rates of increase and decrease of (Na+-K+)-ATPase and Mg2+-ATPase activity resulting from various salt diets suggest that these activities may not be a consequence of bimodal functioning of the same enzyme.

Cytodifferentiation of the crayfish spermatozoon: acrosome formation, transformation of mitochondria and development of microtubules

SummaryDuring spermiogenesis in the crayfish, the acrosome, mitochondrial derivatives and the centrioles are retained within the admixed nucleoplasm and cytoplasm (spermioplasm). Fused nuclear and plasma membranes form the tegument that invests the spermioplasm. A well-defined system of small tubules that originate during spermiogenesis from densities surrounding the centrioles also defines the axes of the nuclear processes in the mature spermatozoon. These tubules are larger in diameter than the microtubules in adjacent interstitial cells and their development coincides with the formation and extension of the nuclear processes. The small tubules seem related to the changes in the cell accompanying nucleoplasmic streaming and to the growth and stabilization of form of the elongate, assymmetric nuclear processes.The mitochondria of spermatocytes are transformed into membranous lamellae that lie in the spermioplasm of the mature spermatozoon, and may by oxidative phosphorylation or some alternative pathway provide energy for metabolic activity and motility.The apical cap of the mature acrosome of the crayfish spermatozoon is enveloped by a sheath of PAS-positive material. The acrosomal process is attached to a dense crescent-shaped acrosome embedded in the spermioplasm. A fine granular substance at the base of the acrosome gives rise to beaded filaments that radiate into the central acrosomal concavity.

Intercellular Channels in the Salt Secreting Glands of Marine Turtles

Long, pleomorphic microvilli project from the walls of adjacent secretory cells in the lacrymal glands of sea turtles, and a substance identified histochemically as a mucopolysaccharide fills the intercellular channels. These features are not characteristic of the principal secretory cells in the salt glands of marine birds.

HISTOLOGY AND CYTOCHEMISTRY OF HUMAN SKIN. XV. SITES OF PHOSPHORYLASE AND AMYLO-1,6-GLUCOSIDASE ACTIVITY

The localization of phosphorylase and amylo-1,6-glucosidase activity has been studied in surgical specimens of human skin from the palm, sole, axilla, external auditory meatus, and other representative regions of the body. With few exceptions these enzymes are found in cells which are known to contain glycogen normally. The epidermis shows some variability, but amylo-1,6-glucosidase is generally present in the stratum spinosum, while phosphorylase is found in both the stratum basale and the stratum spinosum. The relative amounts of the enzymes vary with the thickness of the epidermis and with the age of the donor. Growing hair follicles have abundant phosporylase and amylo-1,6-glucosidase in their outer root sheaths, while resting ones contain only phosphorylase. A short portion of the epidermal duct of the eccrine sweat glands has no enzymatic activity, but the remainder of the duct and the secretory portion of the gland is richer in phosphorylase than any other structure of the skin. The apocrine sweat glands have neither enzyme in their secretory coils, but the duct of these glands is rich in phosphorylase. Time sebaceous glands contain both enzymes, but phosphorylase is more concentrated in the peripheral cells of the gland. Neither the centers of the glands nor the sebum contain either enzyme.

VASCULAR PATTERNS ASSOCIATED WITH CATAGEN HAIR FOLLICLES IN THE HUMAN SCALP

The growing (anagen) hair follicle is richly supplied with blood vessels. In addition to the capillary loops within the mesodermal papilla, a plexus of vessels is embedded in the connective tissue sheath surrounding the lower third of the follicle and an upper plexus encircles the pilosebaceous cana1.l In the quiescent (telogen) follicle the dermal papilla contains no capillaries and the lower plexus forms a loose bundle of vessels a t the base of the club hair, while the upper plexus is unaltered.lV2 The transitional changes that occur during ~ a t a g e n , ~ the period between anagen and telogen, are not fully known. The present study describes some of the more obvious features of catagen with particular emphasis on the follicular blood vessels. These observations indicate that the degeneration of the blood vessels in the dermal papilla during catagen is a secondary effect and not the primary cause for cessation of hair growth. Changes in the connective tissue sheath, the glassy membrane, and the external root sheath appear first.

A comparative study of microtubules in some vertebrate and invertebrate cells

SummaryAn electron microscope study of a variety of invertebrate and vertebrate cell types has supported the postulate that the microtubule is a universal cellular organelle. Microtubules of similar dimensions have been observed in the flagellum and beneath the plasma membrane of Trypanosoma lewisi, in the flagellum, manchette and mitotic spindle of the earthworm (Lumbricus terrestris) spermatid; and in fibroblasts, proximal convoluted and collecting tubule cells of the hypertrophying rat kidney. The specific occurrence and organization of the microtubules in cells undergoing morphological and developmental changes have suggested that these organelles are contractile and that they effectively contribute to the maintenance of cellular form. The possibility that microtubules may function as an intracellular transport system is also suggested.

The effect of salinity acclimation on the ultrastructure of the gills of Gammarus oceanicus (Segerstråle, 1947) (Crustacea: Amphipoda).

SummaryAcclimation to low salinity induces changes in the ultrastructure of the gill cells of the marine euryhaline amphipod, Gammarus oceanicus. The gills are composed of a single cell type. In 100% artificial sea water, these cells contain moderate numbers of mitochondria which are randomly distributed in the cytoplasm. The plasma membrane is extensively invaginated at the apical, lateral, and basal surfaces. Acclimation to 20% artificial sea water induces a further invagination at the apical cell membrane to form an elaborate apical labyrinth. The extracellular spaces between the folds in the basal cell membrane dilate to 1500 Å or more. Mitochondria are more abundant and in many cells they undergo a change in conformation. The mitochondria are crowded into thin leaflets of cytoplasm between the dilated basal invaginations or into the narrow space between apical and basal cell membranes. Consequently, they lie in close contact with the plasma membrane over much of their surface.

Acrosome morphogenesis in Lumbricus terrestris

SummaryAcrosome morphogenesis commences in the juxtanuclear cytoplasm at the posterior end of spermatids of Lumbricus terrestris. A dense rod-shaped structure and the Golgi apparatus together participate first in forming an acrosome vesicle that contains the acrosome granule, and somewhat later shape the conical base of the acrosome in the cytoplasm beneath the vesicle. Cytoplasmic flow may account for the migration of the immature acrosome to the apical surface of the nucleus of the spermatid. Manchette microtubules play a key role in the final modelling of the acrosome. Sheathed by the manchette the acrosome elongates to 3–4 times its pre-attachment length. The conical base of the acrosome then extends anteriorly to enclose the acrosome vesicle. A dense rod emerging from the rod-shaped granule occupies an indentation of the base of the acrosome vesicle. The mature acrosome of Lumbricus is an extremely complex structure about 5–7 microns long and is bounded by the plasmalemma of the spermatozoon.