Isolation and enrichment of two sublobular compartment-specific endothelial cell subpopulations from liver sinusoids

Similar to the well-recognized phenotypical heterogeneity of hepatocytes, in situ sublobular variations have recently been detected in the cell structure, fenestration patterns, filtrating efficiency, surface glycosylation, scavenger function and pathological responses of the sinusoidal lining endothelium. However, unlike other liver cell populations, until now no endothelial cell subpopulations had been isolated or defined with clarity, much less with sublobular/acinar zone-related differential properties. On the basis of our previous studies showing that periportal segments of mouse liver sinusoids express a significantly higher number of wheat germ agglutinin-binding sites than do perivenous ones, we used this differential feature for in vitro labeling of the specific sublobular derivation of isolated sinusoidal lining endothelial cells to correlate their original lobular position with other features determined on flow cytometry, centrifugal elutriation, discontinuous arabinogalactan density gradients and electron microscopy. Our results revealed additional heterogeneous properties whose association with high or low wheat germ agglutinin-binding capacity made it possible to define in vitro two dominant endothelial cell subpopulations that appear similar to the differential features in the periportal and perivenous sinusoidal segments. Type 1 endothelial cells had low forward angle light scatter and high integrated side scatter, low cytoplasmic porosity index (12% +/- 5%) and high wheat germ agglutinin-binding efficiency (160 +/- 35 fluorescence intensity units/cell size); these findings are similar to what was observed in situ in the periportal sinusoidal endothelium. On the other hand, type 2 endothelial cells, with high forward angle light scatter and low integrated side scatter, had a high cytoplasmic porosity index (25% +/- 8%) and low wheat germ agglutinin-binding efficiency (60 +/- 15 fluorescence intensity units/cell size), findings similar to in situ observations of the perivenous sinusoidal lining endothelium. Moreover, these physical and morphological differences entail different cell sedimentation behaviors: type 1 endothelial cell sedimented at high centrifugal elutriation counterflow rates (23 to 37 ml/min) and high arabinogalactan density gradient levels (10% to 15%), whereas type 2 endothelial cell sedimented at low counterflow rates (18 to 23 ml/min) and low density levels (6% to 10%). The combination of these separation procedures made it possible to isolate a 90%-enriched type 1 endothelial cell population in the 12% to 15% interphase of the 23 and 37 ml/min elutriation flow rates and a 75%-enriched type 2 endothelial cell population in the 6% to 10% interphase of the 18 and 23 ml/min flow rates.

Differences in the lectin-binding patterns of the periportal and perivenous endothelial domains in the liver sinusoids

We have studied the distribution patterns of carbohydrate terminals on the endothelial surface of the mouse liver microvasculature. For this purpose, a wide battery of FITC lectins specific to glucose, mannose, galactose, fucose, N-acetyl-neuraminic acid, N-acetyl-galactosamine and N-acetyl-glucosamine residues were incubated on liver cryostat sections or intraportally perfused under physiological conditions. All the resulting hepatic sections were examined under fluorescent microscopy and confocal laser scanning microscopy. With the exception of N-acetyl-galactosamine- and fucose-binding lectins, all the perfused lectins specifically bound to the microvascular wall as confirmed by blocking methods using their corresponding sugars. A wide range of binding was, however, observed among the lectins, and the latter were classified into four groups according to their affinities for the different segments of the hepatic microvasculature: (a) equal affinity for all segments (concanavalin A); (b) different affinities depending on acinar zone (wheat germ agglutinin, Ricinus communis toxin, phytohemagglutinin E, Erythrina cristagalli agglutinin and Pisum sativum agglutinin); (c) preferential binding to the sinusoidal network (Lathyrus odoratus, phytohemagglutinin); and (d) lectins that fail to bind to the hepatic microvasculature (N-acetyl-galactosamine- and fucose-binding lectins). Sinusoidal segment walls in acinar zone 1 expressed a higher concentration of certain lectin-binding carbohydrate residues (N-acetyl-neuraminic acid, N-acetyl-galactosamine, galactose, mannose and glucose) than in acinar zone 3. The labeling patterns obtained through the incubation of liver sections or through in vivo perfusion with the different lectins did not always coincide. Only concanavalin A, wheat germ agglutinin and phytohemagglutinin E lectins proved to be concordant (i.e., they produced identical labeling patterns in both procedures).(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleotide sequence of the glnA-glnL intercistronic region of Escherichia coli

The nucleotide (nt) sequence of a 682-bp fragment containing the 3' end of the glnA gene, the region between the glnA and glnL genes, and the 5' end of the glnL gene from Escherichia coli was determined. This segment contains the region coding for the last 107 amino acids (aa) of glutamine synthetase, including the adenylylation site of this enzyme. The analysis of this sequence revealed two REP sequences, a Rho-independent terminator, the putative glnL promoter and the possible binding site for the glnG product, NRI.

cis-Dominant, glutamine synthetase constitutive mutations of Escherichia coli independent of activation by the glnG and glnF products

Mutants resistant to 80 microM L-methionine-DL-sulfoximine (MS) were isolated on glucose-minimal 15 mM NH4+ medium plates from Escherichia coli cells which were hypersensitive to this concentration of the analogue by virtue of their harboring glnG mutations. MS-resistant mutants derived from strain MX902 carried, in addition to its glnG74 ::Tn5 allele, mutations tightly linked to glnA, as shown by P1-mediated transduction experiments. One particular allele, gln-76, which suppressed the MS-sensitivity conferred by glnG74 ::Tn5 but not its Ntr- phenotype (inability to transport and utilize compounds such as arginine or proline as the only nitrogen sources), was shown to allow constitutive expression of glutamine synthetase in the absence not only of a functional glnG product but also of a functional glnF product. This behavior was found to be cis-dominant in complementation experiments with F'14 merogenotes . In an otherwise wild-type genetic background as in MX929 (gln-76 glnA+ glnL+ glnG+ glnF +), however, normal activation, mediated by the glnG and glnF products was preferred over that mediated by gln-76.

Cloning and physical mapping of the glnA gene of Escherichia coli K-12

We have isolated part of the glnA region of Escherichia coli K-12 as a 6.4 Md DNA fragment on the ColE1 hybrid plasmid pACR1. DNA fragments from pACR1 obtained by cleavage with certain restriction endonucleases were subcloned into the pBR322 cloning vehicle. Recognition sites for the endonucleases BamHI, SmaI, BglII, and EcoRI were localized inside the glnA gene sequence. De novo synthesized polypeptides, employing minicells that carried some of these plasmids, allowed us to determine the direction of transcription of the glnA gene relative to an adjoining gene that codes for a 65 000 dalton protein.

[Comparative study of six methods for lymphocyte isolation from several mammalian sources and determination of their carbohydrate composition (author's transl)]

The present paper deals with a comparative study on six methods for isolation of peripheral blood lymphocytes from various mammalian sources: Bos taurus L. (adult cow), Equus caballus L. (adult horse), Equus asinus L. (adult and young donkeys) and Sus scropha L. (adult pig). The following systems were used: a) Filtration through sand columns (a modification of Blaszczyszyn's method); b) Sodium metrizoate and "Ficoll 400" c) "Lymphoprep"; d) "Urovison" and dextran T150 (a modification of GILI et al.'s method); e) "Urografin" and dextran T150; f) "Ficoll-Paque". The final preparation of lymphocytes obtained by "Urovison" and dextran T150 (d = 1.081) procedure was free from platelets and erythrocytes; lymphocytes degree of purity was found to be 98%. The sialic acids, hexoses and hexosamines contents were determined.

Isolation and chemical composition of the leucocytes from donkey, horse, mule and pig

1. Leucocytes from the blood of adult and young donkeys (Equus asinus L.), adult horses (Equus caballus L.), adult mules (Equus asinus x Equus caballus) and adult pigs (Sus scrofa L.) were obtained in a high degree of purity (99.9%) using Na2-EDTA-dextrans mixtures. 2. Sialic acids were released, purified, identified and determined from both non-delipided and delipided leucocytes. 3. N-glycolylneuraminic was the predominant sialic acid. N-acetylneuraminic acid and N,O-diacetyl-neuraminic acid were also found in all materials. Except in pig, other unidentified sialic acid(s) were also detected. 4. The concentration of total sialic acids (microgram/mg protein) is different according to the species, and in donkey species according to the age. 5. Galactose, glucose, mannose, fucose and (in a less amount) ribose were determined. Their total content is about 2-3-fold that of hexosamines. 6. There is a higher cholesterol content in adult donkey leucocytes than in those of young ones. 7. Total lipids, cholesterol or phospholipid contents are similar among the leucocytes of the above-mentioned species. 8. The similarities are marked in the electrophoresis patterns of proteins and glycoproteins for the donkey, mule and horse samples. 9. The molecular weights for leucocytes proteins were estimated as ranging between 230,000 and 20,000; and for the main protein bands, between 120,000 and 22,000.

Comparative study on the activity, pH optimum and thermal stability of some glycosidases and acid phosphatase from pig and mule leukocytes

1. alpha-D-mannosidase, beta-D-galactosidase, alpha-L-fucosidase, beta-N-acetylgalactosaminidase, alpha-D-glucosidase and acid phosphatase activities were studied in circulating blood leukocytes from Sus scropha var. domestica L. (pig) and Equus asinus x caballus (mule) by spectrophotometric procedures using p-nitrophenyl derivatives as substrates and three different buffer solutions. 2. The highest specific activity corresponds to acid phosphatase. The specific activities of the glycosidases, all relatively close together in all cases, were low in comparison with that of phosphatase. 3. Generally, each of the above-mentioned enzymes shows one common peak for the pH optimum between 3.5 and 6.0, except alpha-D-glucosidase, which shows two peaks. 4. The pH optima values are generally similar in three buffer solutions employed. 5. Specific activities of the studied enzymes show a parallelism in leukocytes from both pig and mule. Also, this parallelism is observed in their pH optima values. 6. Thermal stability of alpha-D-mannosidase is high whereas that of acid phosphatase is low, in both materials. For other enzymes, differences in the thermal stability was observed according to their source.