Cellular Lining Research Articles

Isolated rat brain capillarie spossess intact, structurally complex, interendothelial tight junctions; freeze-fracture verification of tight junction integrity

Populations of isolated brai capillaries have been proposed as useful models for in vitro studies of the blood-brain barrier. Preliminary investigations of barrier properties using such preparations of brain microvessels have suggested that the tight interendothelial junctions (zonulae occludentes) are intact and retain the impermeability to the protein tracer horseradish peroxidase, exhibited by them in vivo. The endothelial junctions of isolated capillaries are therefore assumed to be functionally ‘tight’ in vitro. In order to determine the precise structural organization of these occluding junctions, including an estimate of their tightness (complexity), and to demonstrate a method for simple but precise assessment of junctional integrity, pellets of isolated rat brain capillaries were freeze-fractured and then replicated with platinum and carbon. The freeze-fracture images of interendothelial zonulae occludentes revealed complex arrays of intramembrane ridges and grooves characteristics of tight junctions. Longitudinal fractures of the cellular lining of capillaries exposed vast expanses of interendothelial plasma membrane interfaces and the junctional complexes situated between the cells. From such arrays, the elaborate and complex architecture of the zonulae occludentes could bre readily appreciated. Situated on the PF fracture faces are 6–8 parallel ridges which display a high degree of anastomosing between adjacent strands. The EF facture face contains grooves complementary to the PF face ridges. The zonulae occludentes of these capillary endothelial cells are similar in complexity to those reported in the literature for reptilian brain capillaries and therefore can be presumed ‘very tight’. This study demonstrate that freeze-fracture of pellets of brain capillaries alleviates problems inherent in whole tissue preparations and, in addition, demonstrates the usefulness of freeze-fracture as a tool to monitor junction structure during in vitro investigation of the blood-brain barrier.

Patency and neo-intima development in 10 cm-long microvascular polyurethane prostheses implanted into the rat aorta.

Microvascular fibrous polyurethane prostheses (inner diameter 1.5 mm, length 10 cm) were implanted in the abdominal aorta of rats. The prostheses were fixed in a loop. All rats (n = 37) were reoperated 6 weeks after implantation to verify the patency of the prostheses. Eight prostheses were obliterated from various causes. The remaining 29 prostheses were found to be patent 3 months after implantation, which gives a patency rate of 79%. Six weeks and 3 months after implantation 7 and 4 rats, respectively, with patent prostheses were sacrificed. The remaining 18 rats of this study are still alive, more than 4 months after implantation, and will be included in long-term observation studies. The prostheses were examined using both light and scanning electron microscopy. The patent prostheses exhibited macroscopically a clear and transparent inner surface. No obliterative processes could be found either macroscopically or microscopically. Neo-intima ingrowth had advanced +/- 10 mm into the prostheses over the anastomotic line from both ends 3 months after implantation, and was continued by a single endothelium layer for several centimeters. An acellular, stable fibrin film was found inbetween the cellular lining. The neo-intima was anchored at the prosthesis by cellular protrusions extending between the polyurethane fibers. Though 10 cm long prostheses were implanted under unfavorable hemodynamic conditions, a patency rate of 79% was achieved, both 6 weeks and 3 months after implantation. This patency rate could have been higher if evident technical failures had been avoided.(ABSTRACT TRUNCATED AT 250 WORDS)

One millimetre polytetrafluoroethylene (Gore-Tex) as a microvascular prosthesis: technique and early patency.

We have described a technique for grafting 1 mm internal diameter polytetrafluoroethylene (Gore-Tex) to the rat femoral artery. By spatulating the ends of the recipient artery and completing the proximal anastomosis before commencing the distal one, gentle and accurate suture placement is assured. At a mean of 40 days postoperatively (range 35-42 days) 16 of 20 Gore-Tex grafts (80%) were patent compared with 17 of 20 autogenous femoral vein grafts (85%). Examination of the prosthetic grafts by light microscopy and scanning electron microscopy showed incomplete development of a cellular lining and some areas of neo-intimal hyperplasia. One millimetre Gore-Tex provides excellent early patency as a microvascular graft in this experimental setting but long term patency is still undetermined.

Pathogenesis of the so-called cystic adventitial degeneration of peripheral blood vessels.

Eleven cases of cystic adventitial degeneration of peripheral blood vessels were examined by light and (in three instances) by electron microscopy. Eight cases were in arteries, three were detected in veins. In six cases a cellular lining of the cysts was observed. Ultrastructurally the lining cells resembled synovial mesothelial cells. In three cases a pedicle connection was detected between the adventitial cysts and an adjacent joint. In one case such a pedicle could be followed to its junction with the knee joint capsule and was also lined by synovial mesothelium. These findings indicate that the so-called cystic adventitial degeneration is not a primary dysplasia of the blood vessel wall but originates from ectopic tissue of a joint capsule or bursa.

Malaria parasites--discovery of the early liver form.

Infections of mammalian malaria parasites start when sporozoites from an infected anopheline mosquito are injected into the bloodstream of the host. The sporozoites enter the hepatocytes and become transformed into exoerythrocytic schizonts. Since the discovery of the primate parasite Plasmodium cynomolgi in monkey hepatocytes and the rodent parasite Plasmodium berghei in hamster hepatocytes, the ultrastructure of these stages has been extensively studied both in primate and rodent plasmodia. These observations relate only to the development of the exoerythrocytic schizont 25 h after sporozoite injection until the final maturation (of P. berghei) 50 h post-inoculation. Recently, we have studied the route of entry of sporozoites across the cellular lining of liver sinusoids and invasion of the liver parenchymal cells by using transmission electron microscopy. The results of these studies in combination with other physiological experiments strongly suggested that the sporozoite was initially harboured by the Kupffer cell, from which the parasite escaped into the neighbouring hepatocyte. The migration of sporozoites from liver sinusoids to hepatocytes can be achieved within a few minutes. We present here the first ultrastructural observations on the natural transformation of intrahepatocytic sporozoites into exoerythrocytic forms in vivo, using the rodent malaria parasite P. berghei in a laboratory host, the Brown Norway rat. These observations complete the search for the final link in the life cycle of malaria parasites.

Histology and Biology of the Larval Stages of Leucochloridium Carus, 1835 (Trematoda, Digenea) as Revealed by Light and Electron Microscopy

Ultrastructural studies of the metacercarial cyst and the coloured broodsacs of Leucochloridium variae and L. holostomum recovered from succineid pulmonates are presented. The metacercarial cyst wall is composed of three layers, designated outer (more or less lamellated with electron dense granules), middle and inner layer (both fibrous mucoid). A description of the cyst layers is given. Cyst development and functional biology of the metacercaria are briefly commented upon. Electron micrographs of the anucleate distal cytoplasm of the broodsac tegument show that the whole surface is provided with microvilli embedded within a tegumental surface coat, and rests on a prominent distal layer of interstitial material. The brood chamber in contrast is provided with a nucleated cellular lining, but rests similarly on a prominent layer of granular-fibrous interstitial material. The tegument and the epithelial lining are described. The perinuclear parts of the tegument and pigment cells were located inside the outer circular and the inner longitudinal muscle bundles. Multinucleated pigment cells were found and the pigment types that were observed are described. One of the geometrically organized membranous structures observed is suggested to have a photoreceptive function. Problems concerning sporocyst metabolism and biology are discussed.

Evaluation of microvascular prosthesis of microporous polytetrafluorethylene

The present study assesses the patency and tissue response to a microvascular graft of expanded polytetrafluorethylene (PTFE) of internal diameter 1 mm, used to bridge a surgical gap in the abdominal aorta of 18 Sprague-Dawley rats. No anticoagulants were given. The prostheses were excised at autopsy at intervals from 3 days to 3 months postsurgery. Seventy-eight percent of the prostheses remained patent, some up to 3 months. Histological evidence of a functional prosthesis was recognized in the presence of a constant adventitial capsule to the prosthesis, without evidence of obstructing luminal material. Some cellular infiltration of the wall occurred, but the neointimal cellular lining of the prosthesis was minimal, suggesting that the fibrilar length allowed the wall to be sealed without decreasing the patency rate.

Tegument and apical end organ fine structure in the metacestode and adult Proteocephalus ambloplitis

The tegument of plerocercoid and adult P. ambloplitis was examined. Differences in tegument structure existed between these two stages. Plerocercoids of P. ambloplitis lacked extensive vacuolization and unicellular gland cells characteristic of adult tegument. Plerocercoid microtriches were short and conoid; adult microtriches were lenticular with an extended, whip-like shaft. An inclusion, not previously reported from proteocephalid cestodes, is described. Adult tegument had ducts, originating from underlying unicellular glands, extending through the distal cytoplasm and opening to the exterior between microtriches. The apical end organ cavity of P. ambloplitis contained numerous labyrinth-like spherical bodies. These structures appeared to be synthesized and secreted into the end organ by a thin cellular lining of the end organ. This lining was composed of discrete, filamentous cells believed to be modified subtegumental cell bodies. Spherical structures identical to those observed within the end organ cavity occurred within this cellular lining. The spherical bodies may be associated with enzymes necessary for tissue migration by the metacestode.

Lining cell and intimal smooth muscle cell response and Evans blue staining in abdominal aorta of young swine after denudation by balloon catheter

Young male Yorkshire swine underwent denudation of the abdominal aorta by transfemoral intraarterial ballooning followed by the intravenous injection of Evans blue dye at intervals up to 28 days after ballooning. A small number of swine were also sacrificed 30 min after ballooning. Approximately half the swine were fed a hypercholesterolemic diet, while the others received a mash diet. Quantitation by light microscopy showed that ballooning had removed 99% of the endothelial cells and approximately 50% of the native intimal smooth muscle cells. Three hours after ballooning, the entire luminal surface of the abdominal aorta was stained with Evans blue. By 3 days, a continuous cellular lining had been reformed over at least one-fifth of the denuded surface and the area stained with Evans blue had sharply decreased. The number of intimal smooth muscle cells had returned to nearly normal values, and continued to increase steadily from that day onward. By 8 days, the continuous lining cells had further increased in number and most could be identified as endothelial cells by electron microscopy. Proliferation of the intimal smooth muscle cells and endothelial cells appeared independent, and not influenced by each other. From 8 to 28 days, the percentage of reendothelialized aortic surface increased and Evans blue staining decreased so that by 28 days, values for both were close to those in nonballooned controls. The rate of return of endothelial cells with consequent decrease in Evans blue staining did not appear to be influenced by the hypercholesterolemic diet in any consistent manner. However, at Day 28, the number of intimal smooth muscle cells was approximately four times greater in the hypercholesterolemic group than in the mash-fed and ballooned group. Thirty minutes postballooning, layers of platelets covering most of the surface were adherent to the denuded abdominal aorta. By 3 hr, they were found only as scattered clumps and became even scarcer at later times. If adherent platelets were a factor in the intimal smooth muscle cell proliferation, they appear to have been operative only in the immediate postballooing period.

The surface ultrastructure of ganglia.

The surface ultrastructure of ganglia has been studied using the scanning electron microscope. This study showed that the ganglion wall consists of multidirectional strata of collagen fibres and has no cellular lining. The wall has a sponge-like appearance and does not appear degenerate or necrotic. Comparison with synovial membrane and adventitious bursa confirmed that these are distinct structures which have a cellular lining. Ganglia probably arise from the multifunctional mesenchymal cells which are found within their walls. The ganglion fluid may also originate from these cells.

Bacteremic infectability: A function of vascular graft material and design

Ninety female mongrel dogs had their infrarenal adbominal aortas alternately replaced with ultralightweight Dacron, expanded Teflon, or external velour Dacron grafts. The grafts were left in place for either 3 or 6 months, challenged with an intravenous infusion of Staphylococcus aureus, and then retrieved. 1. 1.|Gross examination showed that the external velour grafts were most frequently lined at 3 months. At 6 months the velour and Teflon grafts were lined significantly more frequently than the ultralightweight graft. 2. 2.|Microscopic examination reveals that the velour grafts are cellularly healed more frequently at 3 months than the other two grafts. At 6 months the velour and Teflon grafts were more frequently healed than the ultralightweight Dacron; however the cellular lining of the teflon grafts was very thin compared to that of the velour and ultralightweight grafts. 3. 3.|The infection rates at 3 months were: velour, 50%; Teflon, 50%; and ultralightweight, 80%. At 6 months the rates were: velour, 20%; Teflon, 40%; and ultralightweight, 60%. We conclude that the velour graft is most resistant to infection of bacteremic origin because of its tendency to heal more quickly and completely.

External velour dacron grafts in renal artery reconstruction

Aortorenal interposition grafts were performed in dogs using a new external velour knitted Dacron graft. Encapsulation and endothelialization of these grafts occurs as early as two weeks postoperatively. Complete healing is seen by six weeks, and the cellular lining of these grafts appears to be continuous with, and histologically similar to, the endothelium of contiguous arteries. The healed nonthrombogenic characteristics of this graft material represents a considerable improvement over graft materials of conventional design.

Pressure Gradient Changes On The Trabecular Meshwork of Monkeys

The cellular lining of the inner wall of Schlemm's canal was anatomically different at different pressure levels. When the anterior chamber pressure rose above that of the canal, there was a marked increase in the number and size of the vacuoles present. At the same time the canal became smaller. When Schlemm's canal pressure exceeded that of the anterior chamber, the vacuoles decreased in size and number, and the canal enlarged. These findings were independent of postmortem artifacts.

Subcellular distribution of carbohydrates in transitional epithelium of urinary system

Hexoses, hexosamines, methyl pentoses and sialic acids were assayed in sheep transitional epithelium of urinary tract, kidney and liver and their subcellular fractions. High carbohydrate content, especially of sialic acids, was noted in homogenates of transitional epithelium, the cellular lining of urinary tract. Sialic acids and methyl pentoses were mostly present in the lysosomal, microsomal and soluble fractions. Highest values for neutral carbohydrates was noted in the microsomal and soluble fractions. Hexosamines were uniformely distributed in all cell fractions.

Route of retrograde flow in the exocrine pancreas during ductal hypertension.

Retrograde infusions of ferritin into the canine pancreatic duct revealed accumulation of ferritin in a previously described periacinar space. Access to this space appeared to occur through minute disruptions of the cellular lining at the ductoacinar junction. Particulate material observed between acinar cells apparently extended from accumulations at the base of the cells. The periacinar space is bounded by the cell plasma membrane and the basal lamina of the acinar unit. The basal lamina appeared to permit diffusion of contents of the space into the interstitium where absorption occurred. In some cases following injection, disruption of the plasma membrane occurred, and zymogen granules were observed to mix with the infused fluid at the base of the cell. With more prolonged infusions at low pressures dilation of the ducts occurred along with focal intracellular areas of spheroid degeneration.

37. Alveolar and capillary permeability in the lung of the fetal lamb

Radioisotope-labeled, metabolically inactive molecules of varying radii (2-13 A) were used as probes to investigate the permeability properties of the internal cellular lining of the lung in exteriorized fetal lambs (mean gestational age of the two groups: 127 and 140 days). By placing the isotopes in the blood or lung liquid compartments and serially collecting samples of blood, lung liquid, and lung lymph, information was obtained about the separate capillary and alveolar components of the barrier. The results show that for both parts of the barrier the permeability constants for water-soluble/fat-insoluble molecules increase with diminution in size, and that the alveolar component is much less permeable than the capillary component (e.g., 1,000 fold difference for sucrose). Preliminary studies suggest that thte same size dependence holds for fat-soluble molecules, and that for a given size, permeability constants increase with fat solubility. There was no difference between the mature and immature fetuses.

The rotifer jaw: A scanning and transmission electron microscope study: II. The trophi of Asplanchna sieboldi

Trophi of the monogonont rotifer Asplanchna is a hollow structure coated internally by a cellular lining. This lining is continuous (through openings in the trophi) with cells which invest the external, more basal, aspects of the jaw. These highly filamentous lining cells are the sites of contact for muscle fibers which control jaw movement. Desmosomes and hemidesmosomes are responsible for the attachment of muscles to lining cells and lining cells to jaw, respectively. Both transmission and scanning electron microscopy confirm that the various components of the trophi are fused together and lack joint-like connections.

Vitreous Effect on Collagen : I. An Electron Microscope Study of the Sclera in Retinal Detachment and Phthisis Bulbi

Previous reports from this laboratory have described the degenerative effect of aqueous and vitreous on exposed collagen and nerve fibers as observed in histologie sections under light microscopy. Because of the great importance of this phenomenon further studies were undertaken utilizing the electron microscope and histochemical techniques. This report deals with the ultrascopic appearance of two of the most common manifestations of this type of de­ generation—the scierai changes in retinal detachment and atrophy of the globe or phthisis bulbi. The findings of this study confirm the na­ ture of the changes as they were described in earlier communications and further de­ lineate the change process. To summarize briefly the main theses of the previous reports : Vitreous and aqueous both have a de­ structive effect on collagen and nerve fibers when they are not protected by the normally present cellular lining, or basement mem­ brane. The degenerative effect of vitreous on collagen can be demonstrated in equatorial staphyloma and in the scierai changes in simple retinal detachment and phthisis bulbi. The same phenomenon is seen in the physi­ ologic perivascular change of the optic disc in normal rabbits' eyes, and can be produced by the implantation of pieces of sclera into the anterior chamber and vitreous chamber of rabbit eyes. A common manifestation of the effect of vitreous on nerve fibers is found in cystoid degeneration of the retina. In these cases

Epidermoid cyst of the spleen; report of a case.

The first reported case of epidermoid cyst of the spleen appeared in 1929. 19 This represents only one variety of Fowler's classification of 265 recorded cases (to May, 1952) of splenic cysts. 6 Fowler's pathogenic classification of nonparasitic benign cysts follows: I. Primary with cellular lining; component endothelium 1. Congenital 2. Traumatic 3. Inflammatory ( a ) Infoliation cysts ( b ) Dilatation cysts: lymphangiectatic, polycystic disease 4. Neoplastic cysts (also congenital) ( a ) Epidermoid ( b ) Dermoid } noncomponent, epithelium ( c ) Lymphangioma ( d ) Benign, cavernous, and capillary hemangioma II. Secondary; no cellular lining 1. Traumatic (blood and serous types) 2. Degenerative (liquefaction) 3. Inflammatory (necrosis, tuberculosis) Report of Case A woman aged 33, secundipara, secundigravida, first became aware of soreness in her left rib cage on washing windows, in February, 1950. She was examined at that time, and it was thought that an enlarged spleen was palpable. A K. U. B. film was obtained, which demonstrated

Recurrent myxomatous cyst of the skin.

MYXOMATOUS lesions are generally accepted as being either true neoplasms or foci of mucinous degeneration. Those involving the skin are localized in a zone of dermis or subcutaneous tissue, and they usually present cystic centers with no definite cellular lining. The wall, which is indefinite in outline and is made up of collagen fibers, usually sends thin, irregular trabeculae toward the center of the cyst, producing a lace-like pattern in which mucoid material is seen. The material is probably hyaluronic acid. Although the lesions are innocuous in appearance, both grossly and microscopically, recurrence may take place repeatedly, even after complete excision of the affected area. Malignant transformation, however, has not been reported. Recurrence of the lesion usually follows excision, drainage, curettage, carbon-dioxide-snow treatment, or cauterization, but Jacox and Freedman 1 noted that the tumors completely disappeared after low voltage roentgen therapy of 1,500 to 1,600 r. Patients who have pricked