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The ejaculatory duct of adult male locusts is surrounded by a thick layer of collagenous tissue. It starts to develop during the second instar when a group of cells come to lie adjacent to the basal regions of the epidermal cells which form the duct. From the fourth instar onwards, connective tissue is present between these cells. The matrix contains many collagen fibrils, some of which are very large and of irregular cross section. The banding periodicity is about 625 A. The cells differentiate into typical fibroblasts with highly dilated rough endoplasmic reticulum and small Golgi complexes. In the sexually mature adult, the cells are smaller and appear less active.

Blood vessels in Nereis japonica were studied by electron microscopy. It was found that blood vessels regardless of location were similar in the basic organization of the basal lamina and the usual presence of collagen fibrils on the vessel wall. Differences arise, depending on whether the outside of the basal lamina is covered by peritoneal cells, by gut epithelium, or by epidermis. These relate to the location of the vessels in mesenteries, gut or epidermis, but do not reflect basic structural differences in the vessels themselves. Furthermore, it was concluded that true endothelial cells do not exist in the circulatory system of Nereis japonica and that, in this respect, the system is essentially different from that of vertebrates, in which endothelial cells line the vessels of a closed circulatory system. These considerations lead to the further conclusion that the vascular lumen in Nereis is essentially interstitial space and that the system, which has been known as a typical "closed" circulatory system in annelids, is actually an open circulatory system. Peritoneal cells covering the walls of internal vessels show various degrees of muscular differentiation and those possessing myofilaments may be called "myomesothelial cells.", (Copyright © 1974 Wiley-Liss, Inc.)

Allografts of skin were observed in Chelydra serpentina. The response to these grafts was modified by a previous transplantation of a limb bud at an early embryonic stage. When the same donor was used for all transplants, the first skin graft was accepted by the host. A second skin graft, however, was rejected at about the rate of a simple first set allograft of skin. The animals were conditioned by the embryonic limb graft; this embryonic graft can be undergoing rejection at the same time a first set skin graft from the same donor was being accepted. The tolerance induced by the embryonic graft was sepcific for its donor., (Copyright © 1974 Wiley-Liss, Inc.)

Well orientated two-dimensional rosettes were produced in stationary cultures of dissociated neural retinal cells of 5 1/2-day-old chick embryos. Observations by electron microscopy were made on aggregates at the different steps in the process leading to rosette formation. Though all of the dissociated neural retinal cells showed a clear morphological polarity, primary cell-to-cell adhesion occurred at random with respect to the cellular polarity. A special junction of the zonula adhaerens type was found at the contact area between the "mitochondria-containing portions" or their neighboring regions of both adjoining cells. During stationary culturing, the contact area between the cells gradually increased. Where the "mitochondria-containing portions" of adjoining cells were brought into contact with each other, junctions of zonula adhaerens type were formed between them. In this way, a radial arrangement of all the cells within an aggregate was established, leading to the formation of the fundamental structures of rosettes.

Allografts of embryonic limb buds were grafted orthotopically on embryos of Chelydra serpentina. Donors were from a different geographic area, the same geographic area, or siblings. The initial indication of rejection was excessive sloughing of epidermis. This was followed by loss of muscle, claws and bone. Early histological changes involved an infiltration of mononuclear or rejection cells primarily associated with small blood vessels of the connective tissue. Subsequently, muscle and bone were lost and they were replaced by connective tissue. Epidermis and nerves persisted. The skeletal cartilages were isolated from immunological activity. Although the incidence of rejection was essentially the same in sibling and non-sibling combinations, the initial external signs of rejection occurred earliest when donor and host were from different geographic areas but not later than two years after hatching. The first signs of rejection in sibling allografts occurred not later than three years after hatching. Animals that survived these periods without rejection did not show subsequent rejection., (Copyright © 1974 Wiley-Liss, Inc.)

The ultrastructure of the phyllobranchiate type gill of the shrimp, Caridina japonica, was studied. The most characteristic feature of the open circulatory system of Cardina is the vascular lumen of the gill capillaries which is considered to be the interstitial space. The following observations substantiate this view: (1) a thin fibrous layer forms the innermost structure of the walls of gill capillaries and is in direct contact with the blood stream; (2) filaments in the fibrous layer are assumed to correspond to the reticular fibers in the interstitial space of the alveolar wall of mammals; (3) the absence of the endothelium as well as the endothelial basal lamina which are the essential structural components of the closed circulatory system in vertebrates. The gill epithelium contains intermediate, septate and tight junctions. The first two form a junctional complex near the apical cell border and may function as a permeability barrier by occluding the intercellular space as well as functioning in electrical coupling and cellular adhesion. The tight junction is spot-like and may serve no role in the function of the permeability barrier., (Copyright © 1974 Wiley-Liss, Inc.)

Specimens, representative of each of the major taxa of mosquitoes, were fixed in copula and the external genitalia examined by scanning electron microscopy. The periphery of the basin-like everted aedeagus of Aedus aegypti precisely matches that of the everted atrial membrane of the female. These structures are appressed during coitus and sealed by pressure of the paraprocts, aedeagal pouch and proctiger. When everted, the aedeagus of male Culex pipiens reveals a ridged dome that surrounds the genital opening. This dome seals itself laterally into a gutter formed by pad-like extensions of the female's genital lips and is sealed dorsally by pressure of the aedeagal apodeme. The aedeagus of another culicine species, Wyeomyia smithii, bears the gonopore at the apex of a spined tube. This tube is inserted between the female's genital lips and is sealed within the genital atrium. The aedeagus of the toxorhynchitine species Toxorhynchitis brevipalpus is immobile and is inserted deep within the genital atrium of the female where it is sealed by pressure of the atrial walls. Males of each of these mosquitoes deliver a mixture of semen and sperm to the copulatory bursa of the female. After withdrawal of the aedeagus, sperm is transferred to the spermathecae. In contrast, sperm of Anopheles quadrimaculatus are delivered directly to the spermathecal duct. The tube-like aedeagus is positioned by its leaflets during sperm transfer and is driven deep into the atrium, where a mixture of semen and sperm is ejaculated. The significance of mechanical barriers to mating between species is discussed., (Copyright © 1974 Wiley-Liss, Inc.)

Laboratory-reared outgrowths of the freshwater sponge Corvomeyenia carolinensis Harrison were examined using histological and histochemical techniques, supplemented by phase contrast observations of cellular behavior. The tissue and cellular components of the spongillid outgrowth region were defined in terms of function and morphogenic state. Archeocytes differ considderably, in both histochemical and morphological characteristics, from other cell types of the adult sponge, being histochemically similar to stem cells reported from a variety of developmental series. Archeocytes exhibit cytological characteristics of unspecialized cells capable of high levels of synthetic activity while other cell types of C. carolinensis, for the most part, can be characterized as fully differentiated cells displaying more restricted synthetic capabilities but often accumulating neutral mucoproteins. The presence of aggregates of amebocytes, not identifiable as archeocytes and possibly engaged in gemmule formation, is discussed in terms of current concepts of gemmulation and cellular developmental capabilities in sponges., (Copyright © 1974 Wiley-Liss, Inc.)

In vertebrates from Amphibia to Man there are striking similarities between thoracic and pelvic limbs, between hands and feet, between fingers and toes. Most standard textbooks of Human Anatomy describe the foot by pointing to similar features in the hand: the extensor apparatus of the toes, for instance, is usually dispatched in a few words as being the same as in the fingers, the axis of attachment of the interossei presenting the only difference. One concept, however, has evolved in reverse, starting in the foot, namely the arch., (Copyright © 1974 Australian Physiotherapy Association. Published by . All rights reserved.)

1. The fluorescent antibody method was used to study the first appearance of delta-crystallin in the lens rudiment of the chicken embryo, in relation to the cell cycle. At the beginning of lens invagination a few cells, with their nuclei in a basal position, displayed fluorescence. The percentage of cells with a positive reaction increased steadily, but it was not until invagination was well underway, about 3 hours after its start, that fluorescence was seen in dividing cells. It was concluded that in this system cell replication and synthesis of specific protein are not mutually exclusive. 2. Because the number of hours passing by before the appearance of fluorescent mitoses was about equal to the previously calculated duration of the G-2 phase of the cell cycle it follows that crystallin production becomes detectable in the late S- or early G-2 phase. Observations on the cellular shape, which is a function of cell cycle phase, at the time that cells first reacted with the fluorescent antibodies agree with this interpretation. 3. The suggestion is made that the inductive influence of the optic cup on the lens primordium may primarily be exerted during the DNA synthetic phase of the presumptive lens cells.

This study of the testicular capsule of rat, dog, cat and human has confirmed the presence of three layers, viz., the tunica vaginalis, the tunica albuginea proper and an innermost tunica vasculosa. Smooth muscle cells are present in the tunica albuginea of all four species and are more prominent at the posterior pole of the testis where the capsule merges with the mediastinum testis. In the rat and the dog, a few striated muscle fibers also are present. While the tunica albuginea is to be considered as a dense connective tissue, the arrangement of the collagen bundles and the presence of a relatively high content of elastic fibers probably permits changes in size of the testis following spontaneous contractions of the muscle elements, which are known to occur. The role of the testicular capsule in sperm transport is discussed in relation to other factors, the spontaneous contractions of the capsule presumably having a "pumping" action and aiding the movement of non-motile spermatozoa from the testis to the epididymis. The presence of striated muscle fibers in two species is of interest and, while these may function in a similar manner to the smooth muscle, they may represent simply an unusual differentiation of embryonic myoblasts., (Copyright © 1974 Wiley-Liss, Inc.)

Young seedlings of the tumor-prone amphiploid Nicotiana suaveolens X N. langsdorffii were grown aseptically on nutrient medium in a controlled environment chamber. At regular intervals after the seeds had been sown, the incidence of tumor formation was scored and plants were harvested. Indole-3-acetic acid was extracted, purified, and assayed spectrofluorometrically. A close correlation in time between onset of tumor formation and decline in endogenous level of indole-3-acetic acid was demonstrated.

1. Dissociated neural retinal cells of 7-day-old chick embryos were reaggregated under rotation culture and the relation between the several kinetic changes in reaggregation and further histogenesis occurring in the reaggregates was analysed. 2. Aggregates formed by 72 hours' culturing consisted of many rosettes, each of which contained a receptor lumen in its center, and the ganglion lumen with many ganglionic cells. 3. Cell sorting occurred within a rosette, but not within an aggregate. 4. Retinal cells labeled with 3 H-thymidine and unlabeled cells were allowed to reaggregate separately. By mixing such labeled and unlabeled aggregates formed in the early phase of reaggregation, further fusion of aggregates was achieved. Through these experiments, the following facts were revealed. 4a. In 2 to 3 hours of culturing, primary aggregates of 35 to 70 μ diameter were formed. 4b. All cells within these primary aggregates were well oriented, and the orientation of cells persisted through the further process of fusion of aggregates. 4c. By the fusion of more than 10 primary aggregates, the H unit which contained a full set of structures of the reconstructed neural retina was formed. 4d. The final aggregate was formed by the fusion of aggregates of H units. The ganglion lumen was formed between the two cell groups of H units. 5. When a primary aggregate consisting of about 20 cells was transferred into stationary culture, a single rosette was formed in it. 6. On the basis of these results, the mechanism of the reconstruction of the histological architecture from dissociated retinal cells is discussed.

Lymph flow and the composition of lymph lipids from the hepatic and thoracic ducts of rabbits with cirrhosis of the liver (induced by 46-51 intramuscular injections of a mixture of carbon tetrachloride and olive oil at 4-day intervals) have been compared with those of control animals injected with olive oil only. In cirrhotic animals, the concentration of lymph lipids was not greatly altered, but lymph flow, and consequently the hourly transport of lipids by lymph were greatly increased; the increase in transport of cholesteryl esters, free cholesterol, and phospholipids by way of the thoracic and hepatic duct lymph was particularly striking. The concentration of these lipid fractions in serum from the cirrhotic rabbits was also increased. The differences normally observed between lipid fatty acid compositions of serum and lymph disappeared in cirrhotic animals; this is interpreted as due to increased hepatic permeability to lipoproteins.

Lobster and squid giant nerve fibers respond differently when subjected to osmotic challenges. The axons proper, as distinct from the total (fiber) complex formed by the axon and connective sheath, both behave as "fast" osmometers for changes in the concentration of NaCl, but the maximum degree of swelling in hyposmotic media is by about 60% in lobster and only by 20% in squid. The relative volume intercepts of the van't Hoff relation are about 0.2 for lobster and 0.4 for squid. The sheaths of both axons undergo only small, apparently passive changes in volume. Lobster axons are permeable to Cl, but squid axons are impermeable to this anion. Lobster axons are also permeable to glycerol. The implications of the data as to the nature of volume regulation of cells are discussed.

The attachment to the surface of the ameba (Chaos chaos L. (Pelomyxa carolinensis, Wilson)) of two proteins, ribonuclease and ferritin, and two colloidal suspensions, thorium dioxide and gold, was studied in the electron microscope. The initial step in the pinocytosis of ferritin and thorium dioxide particles by amebas is shown to be the attachment of these substances to the "hairlike" extensions of the plasmalemma. Ribonuclease caused alterations in the structure of the plasmalemma, but on account of its relative lack of density, it could not be definitely localized. Colloidal gold did not appear to be active with respect to pinocytosis in amebas. Since molecules in solution and particles in suspension are taken up by the same mechanism, the first step of which is their attachment to the cell surface, it is suggested that a single mechanism underlies phagocytosis, pinocytosis, ropheocytosis, cytopempsis, and potocytosis.

Light and electron microscope studies indicate that the old ependyma just proximal to the plane of amputation in early lizard tail regenerates shows a sequence of morphological changes which suggests that it as well as the new ependyma growing into the regenerate may play an active role in the initiation and maintenance of early tail regeneration. The old ependyma close to the plane of amputation undergoes hypertrophy and/or hyperplasia causing a partial closure of the central canal and pseudostratification. Its nuclei shift from an original apical position to a basal one. The ependymal processes become more prominent and extend to the pia, a condition not found more rostrally. There is also a significant increase in the amount of Golgi substance and a moderate increase in the rough endoplasmic reticulum. These observations lead to the thought that these cellular changes may be an expression of enhanced secretion and other activities in the old and new ependyma just proximal or distal to the plane of amputation., (Copyright © 1973 Wiley-Liss, Inc.)