434 Abstracts of The Israel Society ol'Electron Microscopy

which are less abundant, or masked, in the non-transformed cells.

Supported by N.C.R.D. Israel and D.K.F.Z. Heidelberg, FRG, B.S.F., Jerusalem, Xsrael and I.C.R.F.

ULTRASTRUCTURE OF VASOPRESSINERGIC AXO- SPINOUS SYNAPSES IN THE HYPOTHALAMIC SUP~CHIASMATICNUCLEUS

Mona Castel and Nurit Harari

Department of Experimental Zoology, Hebrew University of Jerusalem, Israel

At several different locations within the central nezvous system, the import- ance of dendritic spines as post-synaptic sites has been realized, both structur- ally and theoretically. Spines serve to extend available receptor-rich membrane into fortuitous sites within the crowded neurcpil, while their narrow stalks at- tenuate electrical conductance, thereby varying the strength of afferent stimuli destined for the parent neurone. Since spines are capable of subtle changes in shape, they may serve to "finely tune" the incoming stimuli that they conduct.

Within the mouse suprachiasmatic nuc- leus we have demonstrated immunocyto- chemically that many vasopressinergic synaptic terminals impinge on spines, both dendritic and somatic. Serial thin sections were studied; primary antibodies were either pelyclonal anti-vasopressin or monoclonal anti-vasopressin-neuophysin; immunoc~hochemistry was either pre-embed- ding immun(~-peroxidase or post-embedding immuno-gold. The axo-spinous synapses observed were unusual, since the vaso- pressin-immunoreactive terminals almost completely enveloped their associated spines, so that presynaptic profiles were seen to be deeply invaginated by post- synaptic elemen£s. The synaptic contact region was extensive. Somatic spines were as abundant as dendritic spines, an unusual ratio compared to other brain locations where the dendritic variety predominated conspicuously.

The suprachiasmatic nucleus is regard- ed as the biological clock of the brain, ~et its unique functional mechanism is not yet understood, nor has its intricate and variegated neuronal circuitry been unravelled. It will be interesting to learn the significance of its nume£ous axo-spinous configurations.

(Research supported by the USA-Israel Binational Science Fd. Grant 84/00268.)

QUANTITATIVE ANALYSIS OF GRANULE FORMATION IN MOUSE PANCREATIC ACINAR CELLS

Ilan Hamme~,Sylvia Lew* ** and Stephen J. Galli***with the technical assistance of DinaAmi'cha9 and Tora Eldar*

*Department of Pathology, The Sackler School of Medicine, Tel-Aviv Univer- sity, Ramat-Aviv, Tel Aviv 69978; **and Institute of Pathology, Meir Hospital, Kfar-Saba 44281, ***Dept. of Pathology, Beth Israel Hospit~1 and Harvard Medical School, Boston, Massachusetts 02215, USA

We used a computer-assisted morpho- metric approach to analyze the process of mature granule formation in mouse pancreatic acinar cells. In "resting" pancrsatic acinar cells, of mice fasted overnight, the volume of Golgi Complex and mature granules were 58.1 ± 8.0 ~m 3 and 404 ± 50 um 3 respectively. Stimu- lation with pilocarpine resulted in a 95% diminution of mature granule con- tent (one hour after injection) and a significant increase in the Golgi Complex volume (151 ± 20 ~m 3, 17 hours after injection). Analysis of the size distri- bution of individual progranule indicated that the predominant change after pilo- carpine stimulation was a marked increase in the proportion of the smallest pro- granules. Mean granule size was linear- ly increased during the first 17 hours afher injection. The exhrapolation of the linear curve to injection time (t O ) indicated a volume equal to the inter- modal spacing and the first mode of the mature granule periodic granule equiva- lent volume size distribution. These data are consistent with the hypothesis that the mature granules of pancreatic acinar cells are enlarged by a progress- ive fusion of granules composed of quantal units of narrowly defined volume.

MURINE LYMPHOKINE-ACTIVATED KILLER (LAK) CELLS AND GRANULAR METRIAL GLAND CELLS: TEM AND SEM STUDIES

R. Coleman, S. Davidson*,M. Amira*, C. Khouri* and H. Ginsburg*

Division of Morphological Sciences and *Department of Immunology; Faculty of Medicine and Rappaport Family Institute, Technion-Israel Institute of Technology, Haifa 31096

Abstracts of ~ e Israel Society of Eiectro~ Microscopy 435

Lymphocytes from lymph nodes of nude mice plated on mouse embryonic fibroblast monolayers together with Interleukin-2 selectively develop into colonies of LAK cells. These cells are an active blast type of large granular lymphocytes char- acterized by prominent granules and glycogen. During colony expansion the LAK cells kill the fibroblasts of the mcnolayer resulting in cytopathic plaques. When plated on mesenchymal monolayers prepared from 16- to 18-day- old whole embryos, the LAK cells are triggered to synthesize and secrete a flowing mucoid mass. This secretory process has been followed by means of histochemical staining, transmission and scanning electron microscopy. The area of secretion is marked by surface budding and an extracellular accumulation of numerous small membrane-limited vesi- cles. We have recently been examining the metrial gland of mice during preg- nancy. The metrial gland possesses ac- cumulations of large granular metrial gland cells (GMG), which show ultra- structural characteristics identical to those found in our LAK cells developed in vitro. In view of their common ap- pearance we conclude that the LAK cells and GMG cells belong to a single cell type. The function of the granular metrial gland cells is still not known, but we believe that they may play an important role in immune responses of the uterine area and may help prevent the spread of infection during pregnancy.

SCANNING ELECTRON MICROSCOPIC OBSERVA- TIONS ON INTIMAL GROWTH IN BIODEGRADABLE- MATERIAL -IMPREGNATED KNITTED DACRON, AND IN WOVEN DACRON EXTRACARDIAL CONDUITS

Yori Appelbaum, Daniel Cohn*, Hani Younes*, Raffael Udassin, Ezra Rahamim** and Gideon Uretzky

Lunenfeld Cardiac Surgery Research Center, Hadassah Univer~ty Hospital, Jerusalem; *Casali Institute of Applied Chemistrg, Hebrew University, Jerusalem; **Electron Microscopy Unit, Hebrew University, Jerusalem

Porcine valved external conduits and aortic homografts have been utilized to establish continuity between the right ventricle and the pulmonary artery in the repair of many complex congenital cardiac lesions. Despite its popularity, the preferential use of Dacron conduits

has been challenged by clinical and experimental reports which demonstrate fibrous peels obstruction with time in both th? valve and the graft levels. This obstruction was associated with the lack of fibrous anchoring of the neointima to the conduit wall, and re- sulted in late stenosis of the conduit. The use of the highly porous knitted Dacron graft rather than the woven Dacron type might improve the intimal anchorage to Dacron. This can be achieved after preimpregnation of the Dacron with biodegradable material such as Polylactic Acid.

The aim of our study was to investi- gate this assumption. Fifteen mongrel dogs divided into two groups underwent implantation of right ventricle to pul- monary extracardiac conduit: eight dogs were implanted with untreated woven Dacron grafts (control group), while seven dogs were implanted with poly- ethylene oxide/polylactic acid copolymer-impregnated knitted Dacron grafts (experimental group). Following the one-year study, physiological and hemodynamic measurements showed no sig- nificant difference between the two groups. Upon opening the grafts, how- ever, the knitted Dacron showed a high- er patency than the woven Dacron. The knitted luminal surface was fhrombus- free, while focal luminal thrombi partly occluding the lumen were found in most of the woven type grafts, as well as intimal elevation by subintimal thrombi. Scanning electron microscopy revealed a confluent appearance which may consist of endothelial cells in both groups. Nevertheless, the substantial subendo- thelial layer protruded between fiber bundles and single fibers, enveloped each fiber separately and joined the outer tissue to build one solid struc- ture with the knitted Dacron. The woven grafts showed detachment of the subendo- theliai layer from the Dacron, poor protrusion between fibers and separation of the outer tissue. These findings indicate that the use of biodegradable- material-impregnated knitted Dacron might increase graft patency and lifetime.

LOW-DOSE ELECTRON MICROSCOPY OF FROZEN ~IYDRATED BIOLOGICAL SPECIMENS

S. Trachtenberg

Department of Membrane and ultra- structure Research, The Hebrew