The physical basis for communication between animal cells is thought largely to depend on the presence of gap junctions which are wide-spread among various vertebrate and invertebrate tissues (14,20). Studies on cultured cell lines have indicated that, in addition to mediating electrical impulse propagation between neighboring cells (electrotonic coupling), gap junctions mediate certain metabolic aspects of cellular function by permitting the transcellular passage of "informational" cytoplasmic molecules between physically conjoined cells (metabolic cooperation) (10,15,23). Moreover, the morphological demonstration that gap junctions conjoin different cell types within tissues such as the vertebrate retina (19), an arachnid midgut (16), and the mammalian kidney (18) establishes a precedent for gap junction-mediated cooperation between distinct cell types in other tissues.Recent physiological findings (3, 13) suggest that metabolic cooperativity between folliculargranulosa cells and oocytes within developing mammalian ovarian follicles may importantly regulate both the meiotic maturation of the egg and the transformation of the follicular epithelium into the corpus luteum. As an extension of our studies into the nature of coordinative cellular interactions in the ovarian follicle (2), we report here that gap junctions conjoin oocytes to companion follicular cells. MATERIALS AND METHODS Thin Section and Tracer AnalysisOvaries from adult cycling female mice, rats, and rhesus monkeys (Macaca mulatta), from 1-and 5-6-day old rats and from estrous rabbits were fixed for freezefracture studies by immersion for 20 rain at room temperature in 0.1 M cacodylate buffer (pH 7.4) containing 2% paraformaldehyde, 3% glutaraldehyde, and 5% sucrose. Thin-section and tracer samples were fixed for a total of 60 rain. Final fixation in all cases was carried out on individual follicles which had been dissected free from surrounding stromal tissue (with the exception of the 5-6-day-old rat ovaries) and cut into l-ram cubes. Better fixation of rabbit follicles from animals in estrous was achieved by omitting the paraformaldehyde from the primary fixative,. Ionic lanthanum was used as an extracellular tracer as previously described (2). After several washes in buffer, the tissues were postfixed in 1% OsO4 in 0.1 M cacodylate buffer at room temperature for 1 h, washed, dehydrated in a graded series of ethanol, and embedded in a mixture of Epon-Araldite (5). Thin sections were cut on a diamond knife, collected on 300-mesh copper grids, and examined in either a Philips 200 or 300 electron microscope, both unstained and after staining with uranyl acetate (25) and lead (21). Freeze-Fracture AnalysisAfter primary fixation for 20 min, cubes of tissue were washed thoroughly, equilibrated for 90 rain in 20% glycerol in 0.1 M cacodylate buffer, frozen on paper disks in liquid Freon 22, and stored in liquid nitrogen. A

A total of 44 patients with renal cell carcinoma and vena caval tumor thrombus underwent surgical resection. Of these patients 27 had primary tumor confined within Gerota's fascia, negative lymph nodes and no distant metastases (stage T3cN0M0). Patients who underwent extraction of a mobile tumor thrombus from the vena cava had a 69% 5-year survival rate (median 9.9 years) but patients with tumor thrombus directly invading the vena cava had a 26% 5-year survival rate (median 1.2 years), which improved to 57% (median 5.3 years) if the involved vena caval side wall was resected successfully. Of these patients 17 had renal cell carcinoma with vena caval thrombus as well as extrafascial extension, regional lymphadenopathy or distant metastases, and the 5-year survival rate was less than 18% in all groups (median survival less than 0.9 years). Prognosis was determined by the pathological stage of the renal cell carcinoma and by the presence or absence of vena caval side wall invasion but not by the level of tumor thrombus extension. Patients with incomplete resection of localized renal cell carcinoma with tumor thrombus do not survive any longer than those with extensive cancer, positive lymph nodes or distant metastases. However, when partial venacavectomy establishes negative surgical margins then survival markedly improves.

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Fertilization events following coalescence of the gamete plasma membranes and culminating in the formation of the zygote nucleus were investigated by light and electron microscopy in the sea urchin, Arbacia punctulata. Shortly after the spermatozoon passes through the fertilization cone, it rotates approximately 180 ° and comes to rest lateral to its point of entrance. Concomitantly, the nonperforated nuclear envelope of the sperm nucleus undergoes degeneration followed by dispersal of the sperm chromatin and development of the pronuclear envelope. During this reorganization of the sperm nucleus, the sperm aster is formed. The latter is composed of ooplasmic lamellar structures and fasciles of microtubules. The male pronucleus, sperm mitochondrion, and flagellum accompany the sperm aster during its migration. As the pronuclei encounter one another, the surface of the female pronucleus proximal to the advancing male pronucleus becomes highly convoluted. Subsequently, the formation of the zygote nucleus commences with the fusion of the outer and the inner membranes of the pronuclear envelopes, thereby producing a small internuclear bridge and one continuous, perforated zygote nuclear envelope.

This paper presents morphological evidence on the origin of cortical granules in the oocytes of Arbacia punctulata and other echinoderms. During oocyte differentiation, those Golgi complexes associated with the production of cortical granules are composed of numerous saccules with companion vesicles.

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Membrane topography and organization of cortical cytoskeletal elements and organeUes during early embryogenesis of the mouse have been studied by transmission and scanning electron microscopy with improved cellular preservation. At the four-and early eight-cell stages, blastomeres are round, and scanning electron microscopy shows a uniform distribution of microvilli over the cell surface. At the onset of morphogenesis, a reorganization of the blastomere surface is observed in which microvilli become restricted to an apical region and the basal zone of intercellular contact. As the blastomeres spread on each other during compaction, many microvilli remain in the basal region of imminent cell-cell contact, but few are present where the cells have completed spreading on each other. Microvilli on the surface of these embryos contain linear arrays of microfilaments with lateral cross bridges.Microtubules and mitochondria become localized beneath the apposed cell membranes during compaction. Arrays of cortical microtubules are aligned parallel to regions of apposed membranes. During cytokinesis, microtubules become redistributed in the region of the mitotic spindle, arid fewer microvilli are present on most of the cell surface. The cell surface and cortical changes initiated during compaction are the first manifestations of cell polarity in embryogenesis. These and previous findings are interpreted as evidence that cell surface changes associated with trophoblast development appear as early as the eight-cell stage. Our observations suggest that morphogenesis involves the activation of a developmental program which coordinately controls cortical cytoplasmic and cell surface organization.During the development of the preimplantation mouse blastocyst, a major period of membrane differentiation takes place at approx, the eight-cell stage. At this time, changes occur in membrane transport systems (4, 16), surface glycoproteins (33), surface antigens (2, 30, 50), and intercellular junctions (12).At the two-and four-cell stages, cell shape changes are limited to blastomere cleavage, whereas at the eight-cell stage morphogenetic al-THE JOURNAL OF CELL BIOLOt;V 9 VOLUME 74, 1977 9 pages 153-167 153 on