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Biomedical subjects

L Weiss

Publications and source records attributed to L Weiss.

At least 451 records · Page 25Linked to original sources
PubMed1981

Periarterial macrophage sheaths (ellipsoids) in cat spleen--an electron microscope study.

Periarterial macrophage sheaths (PAMS), a term we introduce to replace "ellipsoids," surround arterial capillaries in the red pulp of the spleen and are major sites for clearance of blood-borne particles. PAMS and their arterial capillaries in cat spleens in various states of congestion and contraction were studied by transmission electron microscopy. Thorotrast, a colloidal suspension of thorium dioxide, was injected to label macrophages. A PAMS consisted of a fine meshwork of reticular cells and reticular fibers which held macrophages and formed a cylindrical sheath around an arterial capillary lying in its longitudinal axis. Some PAMS were spongy due to loosening of cell associations by plasma infiltration; others were tightly compressed. Blood cells were both free in the interstices of the PAMS and attached to macrophages. Reticular cells formed a closely applied but incomplete layer adventitial to the arterial capillary and extended branches which contributed to the meshwork. Small villous processes on the major branches of reticular cells approached each other, sometimes forming intercellular junctions, and fit into complementary indentations in the surfaces of macrophages and endothelial cells. Thin filaments within reticular cells filled the villous processes and formed a border beneath the plasmalemma; intermediate filaments ran through the centers of the branches. Reticular fibers lay between reticular cells. Basement membrane fabricated of the same material as reticular fibers lay between the endothelium and reticular cells. Macrophages contained Thorotrast and abundant debris of phagocytized cells and were joined by extensive interdigitation of micropseudopodia. Endothelial cells were long rods which lay parallel and were joined along their bases by interdigitating lateral processes. Intercellular junctions were present at some points, but at others lateral processes were everted to form open interendothelial slits through which blood cells could pass. Endothelial cells possessed great numbers of randomly oriented intermediate filaments and small patches of thin filaments scattered along the basal plasmalemma and in lateral processes. Thin filaments may function to attach cells to one another and to the basement membrane and may assist in closing interendothelial slits. We believe that the endothelium responds to changes in arterial blood pressure and blood flow. It stretches to allow dilatation and recoils, probably due to the intermediate filaments, squeezing blood cells through interendothelial slits.

Animals↗
PubMed1981

Vascular pathways in nonsinusal red pulp--an electron microscope study of the cat spleen.

The red pulp of the cat spleen, including terminal segments of arterial capillaries, pulp venules, and the reticular meshwork, was studied by transmission electron microscopy. Splenic congestion and contraction were produced by barbiturate anesthetic and norepinephrine. Terminal segments of arterial capillaries were ampullary and flared. Blood escaped into surrounding pulp spaces through interendothelial gaps. Pulp venules originated as open-ended vessels in the reticular meshwork near trabeculae and drained into trabecular veins. Venule walls were thin and composed of squamous endothelial cells, a continuous basement membrane, and reticular cells. Venules in congested spleens had many mural apertures, but venules in contracted spleens had few. The interstices of the reticular meshwork in congested spleens contained large amounts of blood, which often was concentrated, many macrophages, lymphocytes, and plasma cells. Fewer blood cells and scant plasma were present in contracted spleens. The vascular arrangements are anatomically open. Blood takes pathways through the reticular meshwork from arterial terminations to pulp venules. Some pathways through the reticular meshwork probably function as closed vascular channels conveying rapidly flowing blood. Other pathways are functionally open and probably contain slowly moving blood that constitutes a reservoir of red cells. Macrophages formed associations with mature red cells and with reticulocytes. Mature red cells were attached to macrophages in a manner indicating erythrophagocytosis. Reticulocyte attachment had a different appearance and likely resulted in reticulocyte sequestration. Platelets bore pseudopodia which would impede their passage through irregular and cell-filled pulp spaces. The change in platelet shape probably is responsible for the formation of the splenic pool of platelets.

Animals↗
PubMed1981

Species variation in the structure and function of the marginal zone--an electron microscope study of cat spleen.

The marginal zone in the cat spleen consisted of a characteristic mixture of lymphocytes and other blood cells located mainly between the several layers of circumferential reticulum around white pulp. A region of fine-meshed reticulum between white pulp and red pulp, as present in some species, was absent from the cat spleen. Arterial capillaries to the marginal zone were few. Some were continuations of white pulp capillaries, whereas others were red pulp capillaries that likely were continuations of axial capillaries of periarterial macrophage sheaths (PAMS) (ellipsoids). Blood cells deposited in the marginal zone could reach red pulp by passing through the numerous openings in each layer of circumferential reticulum. Lymphocytes appeared to migrate across the marginal zone both toward and away from white pulp. Macrophages lying on the circumferential reticulum of the marginal zone phagocytized cells but did not ingest Thorotrast, although it coated their surfaces. Because of the scarcity of arterial endings and the lack of a macrophage-charged reticular meshwork, the marginal zone in cat spleen is not a major site of blood clearance and phagocytosis. These functions are better served in PAMS and red pulp.

Animals↗
PubMed1981

Electron microscopy of the red pulp of the dog spleen including vascular arrangements, periarterial macrophage sheaths (ellipsoids), and the contractile, innervated reticular meshwork.

The vascular and stromal arrangements of the red pulp in congested and contracted dog spleens were studied by transmission electron microscopy. Each dog had been injected intravenously with Thorotrast to label actively endocytizing cells. Only macrophages ingested Thorotrast. The proximal portion of each arterial capillary was surrounded by a "periarterial macrophage sheath" (PAMS), a term we introduce to replace the term "ellipsoid". PAMS were composed of a fine meshwork of reticular cells and reticular fibers which held tightly-packed macrophages and interspersed blood cells. These macrophages, as well as those in the reticular meshwork of red pulp, contained Thorotrast, cell debris, and deposits of hemosiderin. The arterial capillary at the center of each PAMS was formed by parallel, rod-shaped endothelial cells and discontinuous layers of basement membrane and reticular-cell cytoplasm. PAMS were tapered at their distal ends; the terminal portion of the arterial capillary continued beyond the PAMS to end in the reticular meshwork of red pulp. Endothelial cells in the terminal arterial capillaries were separated by gaps through which blood cells passed into the spaces of the reticular meshwork of red pulp. The reticular meshwork was formed by reticular cells which appeared to be specialized for contraction. These cells were filled with thin filaments and possessed plasmalemmal dense bodies as found in smooth muscle cells. Furthermore, the reticular meshwork was innervated by unmyelinated adrenergic axons which probably were derived from nerves that followed arterioles. Axons were enclosed in surface invaginations of cells which were similar to reticular cells in shape and cytologic detail and which we called "axon-bearing reticular cells". Axon-bearing reticular cells were inserted between the branches of the reticular cells that formed the meshwork. Venous sinuses formed an anastomosing system of vessels draining into pulp veins which then joined trabecular veins. Sinuses were formed by parallel, rod-shaped endothelial cells encircled by strands of basement membrane and reticular-cell branches. Endothelial cells lay closely side by side except where interendothelial slits were opened by blood cells passing into the lumen or by pseudopodia of macrophages which lay outside the sinus. Cell traffic across the sinus wall was greatest in areas where blood cells were mixed with plasma. Congested spleens stored concentrated red cells in both sinuses and the reticular meshwork; contracted spleens were emptied of blood. The reticular meshwork may contract to assist trabecular and capsular smooth muscle in expelling stored red cells and effecting hemoconcentration.

Animals↗
PubMed1981

Prenatal diagnosis of Maroteaux-Lamy syndrome.

Maroteaux-Lamy syndrome exhibits deficient activity of the enzyme arylsulfatase-B in cultured skin fibroblasts. Prenatal diagnosis was successfully attempted in two pregnancies of a consanguineous Chaldean couple whose first child is affected with Maroteaux-Lamy syndrome. In both instances, deficient arylsulfatase-B activity was observed in amniotic fluid cell cultures, and the diagnosis was confirmed by 35S-sulfate studies and postmortem enzymology and electron microscopy. The prenatal diagnosis of Maroteaux-Lamy syndrome remains problematic. Residual activity of arylsulfatase-B in the affected homozygote can make interpretation difficult, and the behavior of many lysosomal enzymes varies greatly in response to tissue culture conditions and enzyme extraction processes.

Adult↗
PubMed1981

Malformation syndrome of duplication 12q24.1 leads to qter.

While duplication and deletion of the short arm of chromosome 12 cause well-recognized syndromes, duplication of the long arm chromosome 12 is rarely observe. We are reporting a duplication of chromosome 12 distal to band q24.1 in a five-month-old child. His chromosome constitution is 46,XY,-4+der(4),t(4:12)(p16;q24.1)mat. The balanced translocation is also carried by his maternal grandmother and two of the mother's brothers. The malformation syndrome consisted of unusual facial appearance and anomalies of the musculoskeletal, cardiovascular, genitourinary, and central nervous systems. Four previously reported patients had similar break points on chromosome 12 with similar malformations; therefore, phenotype-karyotype correlation suggests a definitive malformation syndrome associated with duplication of chromosome region 12q24.1 leads to qter.

Abnormalities, Multiple↗
PubMed1981

Metastasis and the reticuloendothelial system. II. Effect of triamcinolone acetonide on organ retention of malignant cells in endotoxin-treated mice.

The lung retention patterns of B16 melanoma cells were determined after intravenous injection of [125i]dUrd-labelled tumor cells into B16 melanoma-bearing mice. Experiments were performed to assess the effects of a synthetic glucocorticoid, triamcinolone acetonide, on the retention of B16 melanoma cell arrested in the lungs of mice with endotoxin-induced reticuloendothelial system hyperfunction. Lung clearance of malignant cells was greatly accelerated in mice treated with endotoxin alone but was markedly inhibited in mice with only triamcinolone acetonide. In mice treated with both endotoxin and subsequently triamcinolone acetonide after tumor-cell arrest processes had occurred, the endotoxin-induced increase in clearance was nullified. These results are discussed in terms of the mutually antagonistic activity of both pharmacologic agents upon the reticuloendothelial system and the role of the latter in regulating organ retention of disseminated malignant cells.

Animals↗
PubMed1981

Electrokinetic determinations of enzymatic susceptibilities of cell surface-associated RNA.

Earlier investigations suggested, using electrokinetic evidence, that RNA is present at the surfaces of some types of cultured and freshly isolated cells. In this report, further investigations of the nature of cell surface RNA of cultured Ehrlich ascites (EAT) cells are reported. These experiments were carried out by determining the changes in electrophoretic mobility of EAT cells after treatment with several highly purified nucleases, neuraminidase, and hyaluronidase. The results suggested that cell surface RNA is located at surface sites separate from those susceptible to neuraminidase and hyaluronidase, that alpha and omega termini of RNA are absent from the electrokinetic surface, and that the RNA present at the cell surface might exist predominantly in a double-stranded form. A model is proposed in which cell surface RNA strand termini are buried out of the electrokinetic surface, but where RNA extends from these buried termini into the electrokinetic surface in loops.

Animals↗
PubMed1981

Multiple active X chromosomes in myelofibrosis with myeloid metaplasia.

A woman with myelofibrosis and myeloid metaplasia had a karyotype of 47,X,del(X)(q22),+del(X)(q22) in unstimulated peripheral blood and bone marrow aspirate cultures. The normal X chromosome was late replicating, and the two deleted X chromosomes always replicated early and synchronously. The karyotype from phytohemagglutin-stimulated peripheral blood cultures was uniformly 46,XX. Structurally abnormal X chromosomes are exceedingly rare in myeloproliferative disease. The abnormal karyotype very likely reflects monoclonal proliferation of an abnormal myeloid cell line. The X chromosome inactivation process, which acts upon embryonic somatic cells of all mammals, apparently does not react to postembryonic nondisjunction of the active X chromosome.

Bone Marrow↗
PubMed1981

Analysis of aprotinin-induced enhancement of metastasis of Lewis lung tumors in mice.

The antiproteinase, aprotinin, has been reported by some workers to inhibit the growth and development of a number of different types of primary cancers in animals; however, its effects on metastasis particularly need clarification. As proteolytic enzymes are thought to be involved in some steps of metastasis, we have investigated the effects of aprotinin on the spontaneous metastasis of Lewis lung (LL) tumors in mice together with its effects on the detachment of cells from primary LL cancers, the development of lung tumors from i.v. injections of LL cells, LL cell adhesion in vitro, and LL cell retention in the lungs. The results suggest that the metastasis-enhancing effect of aprotinin is due partly to promotion of the retention of circulating cancer cells at the vascular endothelium. As these effects could well occur with cancers in general, we conclude that antiproteinases may do more harm than good if used in cancer therapy.

Animals↗
PubMed1981

Colon epithelium. IV. Human colon carcinogenesis. Changes in human colon mucosa adjacent to and remote from carcinomas of the colon.

To verify the popular belief that the mucosa of the colon remote from a carcinoma is normal, in a retrospective study colon mucosae from 30 patients were studied; 15 patients had colon carcinoma and the other 15 patients without any obvious tumor in their colons served as controls. All the patients having colon carcinoma showed definite abnormalities in the mucosa remote from the tumor. None of the 15 control patients showed such morphologic changes in the mucosal sections sampled at random. The mucous changes observed were: dilatation and distortion of the crypts with flattening of the lining cells, overcrowding of crypts with mucous cells and basophilic cells, lining of the crypt with eosinophilic surface epithelial cells, and focal cellular stratification in the crypts. These abnormalities were also consistently observed in the transitional mucosa adjacent to the tumor in all of the 15 patients with colon cancer. Histochemical studies for the detection of epithelial acidic mucosubstances showed that sialomucin predominated in the colon mucosa harboring a carcinoma irrespective of the location of the tumor, whereas colon mucosa from otherwise normal individuals and patients with noncarcinomatous diseases showed a predominance of sulfomucin. Therefore, mucosa of the colon harboring a carcinoma was conclusively demonstrated to be morphologically and histochemically abnormal. The significance of these abnormalities and their possible role in the de novo histogenesis of colon carcinoma are discussed.

Adenocarcinoma↗
PubMed1981

Ultrastructural, cell membrane, and cytogenetic characteristics of B-cell leukemia, a murine model of chronic lymphocytic leukemia.

A murine model of a spontaneous, transplantable BALB/c B-cell leukemia (BCL1) is described. Extreme leukemia and splenomegaly develop in H-2d-compatible recipients of tumor cells. Tumor cells are medium to large lymphocytes that can be transformed into plasmacytoid cells following in vitro stimulation with lipopolysaccharide. Karyotypic analysis of transformed tumor cells reveals 36 chromosomes with several monosomies and 7 markers chromosomes. The ultrastructure of the tumor cells was studied using transmission and scanning electron microscopy. Although the appearance of tumor cells seems normal by morphological criteria, an impaired capping ability was documented using the fluorescein-conjugated concanavalin A-binding test. Impaired capping ability was documented before leukemia was overt as early as 1 to 3 days following inoculation of tumor cells. The B-cell leukemia (BCL1) provides a useful murine model for the study of various aspects of human bone marrow-derived malignant disorders.

Animals↗
PubMed1981

Metastatic patterns and target organ arterial blood flow.

The frequency of metastatic involvement of eight 'target' organs from primary adenocarcinomas of the rectum and squamous cell carcinomas of the esophagus correlates significantly with target organ arterial blood flow (ml/min/g) when the primary cancers were in the upper third of the rectum or lower third of the esophagus, where the initial main venous drainage was into the portal system. When the primary cancers were located in other regions of these two organs where the initial main venous drainage was into the systemic venous system, this correlation was not seen. The results confirm that the 'hemodynamic' or 'mechanical' theory holds for two types of primary cancers in specific anatomic locations. In addition, they support the hypothesis that as yet unspecified interactions of cancer cells with the portal system, when this represents the initial main route for venous drainage, produce conformation with the 'hemodynamic' theory.

Adenocarcinoma↗
PubMed1981

[Metabolic and circulatory aspects of hypothermic perfusion of human kidney cancers].

In this study a report is made on the hypothermal perfusion of 15 renal tumours. Protein synthesis by incorporation of 14C leucine, lipide synthesis by conversion of 14C mevalonic acid and the activity of the sodium-potassium pump by incubation of sections of tissue were used as parameters of the vitality of the tissue. Circulation was studied before and after perfusion by means of angiography and the microsphere technique. After 6 days of perfusion the tumour tissue is found to be less vital in comparison with the renal cortex.

Cold Temperature↗