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Biomedical subjects

L Weiss

Publications and source records attributed to L Weiss.

At least 541 records · Page 30Linked to original sources
PubMed1976

Ultrastructural observations of cytoplasmic inclusions in Tay-Sachs lymphocytes.

Our preliminary study on the circulating leukocytes from two children with Tay-Sachs disease and six heterozygotes from four different families is reported at the levels of both light and transmission electron microscopy. Ultrastructural investigation revealed two types of cytoplasmic inclusions in the lymphocytes of the Tay-Sachs homozygotes. The heterozygotes demonstrated only one of the inclusion forms within the cytoplasm of their circulating lymphocytes. These fine structural observations have not been described previously in Tay-Sachs disease and they may suggest new functional implications for the involvement of the lymphocyte in this storage disorder.

Female↗
PubMed1976

[Experience with the glucose-dehydrogenase-UV-method for the determination of blood glucose (author's transl)].

A method for glucose determination using glucose-dehydrogenase is described. Our experience with this method is based on 70 000 determinations of blood glucose within six months. Linearity over a wide range, accuracy and specificity highly recommend this method. No interference was noticed by substances physiologically occuring in blood. The glucose-dehydrogenase-method correlated well with the hexokinase glucose-6-phosphatedehydrogenase method for the determination of blood glucose.

Alcohol Oxidoreductases↗
PubMed1976

The physicochemical properties of hair in the BIDS syndrome.

The physicochemical properties of hair from a new recessive syndrome associated with brittle hair, intellectual impairment, decreased fertility, and short stature have been studied. Electrophoresis of the SCM-structural proteins showed that the alpha polypeptides appeared normal, but the matrix component was markedly reduced. This was confirmed by finding a normal alpha X-ray diffraction pattern but a reduced 1/2 cystine content of hair and an abnormal stress-strain curve. Electron-microscopic studies revealed extreme disorganization of the filaments which most likely resulted from the absence of normal cross-linking. Nails, which contain structural proteins similar to hair, also showed the abnormality. Since the matrix component seen by electrophoresis consists of more than one component the defect cannot be explained as a single structural gene abnormality.

Amino Acids↗
PubMed1975

Some electrical properties of the peripheries of murine 3T3 cells with respect to viral transformation and reversion.

Mouse 3T3, Simian virus 40 transformed 3T3 cells (SV3T3) and two SV3T3 lines showing reversion of their transformed phenotype (Rev 3 and Rev 5) have been studied with respect to electrophoretic mobilities and colloidal iron hydroxide (CIH) binding density visible by electron microscopy, before and after incubation with neuraminidase or ribonuclease. The results show that, in general, the marked changes in both sets of surface parameters associated with transformation are largely reversed in the Rev 5 revertant, and only partially reversed in the Rev 3 line. It was also observed that, in common with Ehrlich ascites tumor (EAT) cells examined previously, the densities of CIH-particles bound over the microvilli of all the cell types was 1.5 to 2.7 times higher than those bound to the spaces between them. In contrast to the EAT cells, the higher density of CIH particles bound over the microvilli was not due to neuraminidase-sensitive binding sites.

Animals↗
PubMed1975

Ontogeny of human fetal lymph nodes.

Developing lymph nodes from 30 human embryos and fetuses with crown-rump lengths (CRL) of 18 mm (5.6 wk) to 245 mm (26 wk) were examined by light microscopy. The nodes were embedded in araldite, and the sections examined were approximately 1 mu in thickness. The development of nodes was divided into three stages: 1. the lymphatic plexus and connective tissue invagination (30 mm to 67 mm CRL); 2. the early fetal lymph node (43 mm to ,5 mm CRL); and 3. the late fetal lymph node (CRL greater than 75 mm). The lymphatic plexus was formed by connective tissue invaginations and bridges which divided a lymph sac into a meshwork of channels and spaces. Connective tissue invaginations were endothelially-lined and were surrounded by lymphatic space. Reticular cells, macrophages, and blood vessels were found in these invaginations. Early fetal lymph nodes were formed from invaginations when the cellular density and lymphocyte content increased. The lymphatic space surrounding the early node was the developing subcapsular sinus. With further development the early node became packed with lymphocytes, increasing the cellular density and size of the node. The connective tissue surrounding the subcapsular sinus condensed to form the capsule. Afferent lymphatic vessels pierced the capsule. Capillaries, veins, postcapillary venules, and occasional arteries were found in early and late nodes.

Blood Vessels↗
PubMed1975

Light and electron microscopic studies of postcapillary venules in developing human fetal lymph nodes.

Developing lymph nodes from 30 human fetuses with crownrump lengths (CRL) of 38 mm (8.7 wk) to 245 mm (26 wk) were studied by light and electron microscopy. Blood vessels that appear to be postcapillary venules (PCV) are present in nodes of 47 mm CRL and older fetuses. These venules first appear in nodes whehn the nodal population of lymphocytes is sparse. In these early nodes PCV are distributed randomly and consist of a low endothelium, underlying basal lamina and incomplete pericyte sheath. Early nodal PCV are distinguised from other nodal blood vessels by the presence of lymphocyte diapedesis and several luminal lymphocytes. In the late stages of nodal development PCV are the more common non-capillary blood vessel and appear in the parenchyma near the periphery of the node. Late nodal PCV are generally characterized by a cuboidal endothelium that is rich in Golgi apparatus, lysosomes and Weibel-Palade bodies. The lumen and wall of late nodal PCV contain lymphocytes. The relationship between the development of the parenchyma of fetal nodes and the appearance and activity of PCV, the passage of lymphocytes through the PCV wall and the fine structure of developing PCV are described. It is suggested that the lymphocytes that first appear in developing nodes, and the majority of the lymphocytes found in late nodes, migrate to the node via the blood vascular system and enter the nodal parenchyma by passing across PCV endothelium.

Abortion, Spontaneous↗
PubMed1975

The binding of cationized ferritin at the surfaces of ehrlich ascites tumor cells: the effect of pH and glutaraldehyde fixation.

The densities of cationized ferritin (CF) particles binding to the surfaces of cultured Ehrlich ascites tumor cells were determined at pH 7.4, where the ferritin stain was applied either prior to or following glutaraldehyde fixation. The densities were also determined with CF adjusted to pH 1.9 and applied after fixation. For all fixed samples there was a higher density of particles bound to microvilli than to the spaces between them. Treatment with neuraminidase removed more particles from microvilli than from the inter-microvillus spaces, but did not reduce the levels of binding to the same value. When cationized ferritin is applied prior to fixation, an aggregation of the CF particles at the cell surface was observed, with the internalization of some clusters. This effect was independent of neuraminidase treatment.

Aldehydes↗
PubMed1975

Re-evaluation of Sepharose-insulin as a tool for the study of insulin action.

The biological activity of Sepharose-insulin in different assays in vitro, e.g., stimulation of glucose oxidation, lipogenesis, and antilipolysis and activation of pyruvate dehydrogenase (EC 1.2.4.1) activity, has been investigated. According to amino acid analysis, between 270 and 330 mug (6.9-8.2 U) of insulin were coupled per ml of packed beads. Related to the total insulin content, 0.2-0.7% of the insulin was biologically active. Comparable biological activity was observed with isolated fat cells and fat pad pieces. After incubation with tissue or cells, Sepharose-insulin particles were separated by centrifugation from the medium. The clear supernatant was assayed for biologically and immunologically reactive insulin and contained soluble insulin activity. A quantitative evaluation of the soluble biological and immunological insulin activity in the supernatant accounted for the total insulin activity of Sepharose-insulin.

Adipose Tissue↗
PubMed1975

Growth of mammalian cells on substrates coated with cellular microexudates. I. Effect on cell growth at low population densities.

Mammalian and avian cells cultured on glass or plastic substrates produce microexudates of cellular macromolecules which remain bound to the substrate when the cells are detached. The gross macromolecular composition of microexudates from a range of diploid, heteroploid, and virus-transformed cells was determined with cells labeled with radioisotopes. Significant differences in the amounts of cellular glycoproteins, proteins, and RNA present in microexudates were found between different cell types and between cells of the same type at different stages of growth. Inoculation of cells onto substrates "coated" with microexudates altered their growth behavior. Microexudates from exponentially growing subconfluent homotypic and heterotypic cell populations enhanced the growth of mouse and chick embryo cells seeded at very low densities, but similar microexudates had no effect on the proliferation of cells seeded at higher densities. The enhanced growth of low-density cell populations seeded on microexudates was compared with the growth enhancement produced by feeder cell layers and conditioned medium.

Animals↗
PubMed1975

Arterial pressure, cardiac output and systemic resistance before and after pithing in normotensive and spontaneously hypertensive rats.

After complete cardiovascular denervation mean arterial pressure (MAP) falls to almost equally low levels in spontaneously hypertensive rats (SHR) and normotensive control rats (NCR). This has earlier been suggested to indicate a dominance of neurogenic mechanisms in established SHR hypertension. -- In the present study, total peripheral resistance (TPR) remains, however, some 35 per cent higher in adult SHR than in NCR after pithing while cardiac output (CO), and stroke volume, is 35 per cent lower in SHR. These opposite differences in TPR and CO after denervation, resulting in equal MAP levels in SHR and NCR, seem rather to be a consequence of the rapidly established structural adaptation that affects all SHR high-pressure cardiovascular sections. Thus, the SHR precapillary resistance vessels display thickened walls and luminal narrowing, which keeps TPR higher than in NCR even during maximal vasodilatation. Due to hypertrophy, the SHR left ventricle exhibits a reduced myocardial stretch for a given filling pressure and stroke volume is consequently reduced more than in NCR after complete denervation. -- Paradoxically, therefore, rather than reflecting any dominance of neurogenic mechanisms in established SHR hypertension the MAP equalization in SHR and NCR after cardiovascular denervation emphasizes the hemodynamic importance of cardiovascular structural changes present in hypertension.

Animals↗
PubMed1975

The development of vertebral bone marrow of human fetuses.

The development of the bone marrow of the thoracic vertebrae in seven human fetuses ranging from 95 to 150 mm in crown-rump length (CRL) was studied using light and electron microscopy. In the 95-mm CRL, hypertrophy of the chondrocytes occurred in the central region of the vertebrae, and blood vessels penetrated there from dorsal and ventral sides of the vertebral body. The primary marrow was represented by liberated cartilage lacunnae, occupied by the thin-walled blood vessels and a few mesenchymal cells and mononuclear cells containing granules or vacuoles (GMC). In the 99-mm CRL, chondroclasts were active in removing the cartilage near the central region of the vertebrae. Consequently, a large cavity was formed and occupied by a dilated sinus. GMC were numerous. Osteoblasts and osteocytes were increased in number. Reticular cells with long processes containing large amounts of glycogen began to appear in the extravascular space and formed the loosely arranged cellular meshwork of the hematopoietic compartment. Bundles of collagen fibrils were scattered in the meshwork. Hematopoietic cells were recognizable only in the 105-mm-CRL fetus and increased in number in the 120-mm-CRL fetus. The sinus endothelium was very thin and continuous without apertures except where blood cells crossed the wall. The developing blood cells lying against the outside of the sinus endothelium indented it. At points, collagen fibrils attached to the outside of endothelial cells and appeared to function as the anchoring filaments of lymphatics. The physiologic implications of the association of stromal cells, vascular sinuses, and hematopoietic cells are discussed in relationship to the microhematopoietic environment of the bone marrow.

Bone Marrow↗
PubMed1975

Effects of migration inhibiting factor(s) on the in vitro detachment of macrophages.

Supernatants from spleen cells, derived from mice injected with BCG and cultured with PPD, specificially inhibited the migration of normal mouse peritoneal macrophages when compared with control supernatants. Migration inhibitory supernatants were also shown to decrease the detachment of adherent macrophages in a novel test system. Both macrophage migration and detachment inhibitory activities were abrogated by neuraminidase and chymotrypsin treatment of supernatants but were thermostable, suggesting that the detachment test is a sensitive index of MIF activity.

Animals↗
PubMed1975

Bone marrow sinus cell packing: a determinant of cell release.

Ultrastructural studies of erythropoietin effects on the bone marrow of control and hypertransfused (65 hct) mice revealed a decrease in adventitial cell cover of the sinus apertures in erythropoietin-treated animals. A more striking finding, however, was the marked inhibition of erythropoietin-induced reticulocytosis by hypertransfusion itself. Hypertransfusion of the erythropoietin-treated animals appeared to decrease the reticulocyte response by inhibiting reticulocyte response by marrow cords in addition to inhibiting erythroid proliferation. This inhibition of reticulocyte response was associated with clustering of reticulocytes around the marrow sinuses which were packed with red cells. Acute lowering of the hematocrit of erythropoietin-treated, hypertransfused animals to normal at the time of maximal reticulocyte response in control animals resulted in more than a twofold increase in reticulocytosis with 2 hr. It is suggested that (1) elevated levels of erythropoietin are associated with a diminution of the normal marrow-peripheral blood barrier, thereby contributing to the premature release of marrow elements and (2) the hematocrit is an important determinant of cell release from the marrow into the peripheral circulation.

Animals↗
PubMed1975

Ultrastructural changes of endothelium associated with thrombocytopenia.

In a study of the relationship between thrombocytopenia and increased vascular fragility, changes in the endothelium of capillaries and postcapillary venules of the tongue were examined by electron microscopy. Adult male albino rabbits (4 kg) were maintained thrombocytopenic (platelets less than 20,000/cu mm) up to 24 hr by one to three injections of guinea pig antirabbit platelet serum. Within 6 hr the normal projections and folds of the lumenal surface of the endothelial surface were largely effaced. In addition, the endothelium became thinner. In places, pores and membranous diaphragms were observed. Endothelial junctions appeared normal. Identical findings were observed if rabbits were made thrombocytopenic by administration of intraperitoneal busulfan. Intravenously administered Thorotrast was observed in endothelial cells and in the extravascular spaces within 3 min after injection into thrombocytopenic animals, while it was seen only intravascularly in control rabbits. With the spontaneous restoration of circulating platelets, the endothelium reverted to normal.

Animals↗