A testis antigen related to the brain D2 adhesion protein

The localization of an antigen immunochemically crossreactive with the rat brain interneuronal adhesion molecule, D2-protein, has in testis been demonstrated by immunoelectrophoresis and immunocytochemistry. This D2-like antigen is localized to spermatids and residual bodies in testis, but it is absent both from spermatogonia and mature spermatozoa and from Sertoli cells. By immunoperoxidase electronmicroscopy D2-like antigen was observed in the head region posterior to the acrosomal membrane of late spermatids. In the nervous system D2-protein is involved in interneuronal adhesion. It is suggested that D2-like antigen in testis may be involved in a similar adhesion between late spermatids and Sertoli cells during spermiation.     

Barrier properties of glycophorin-phospholipid systems prepared by different methods

Glycophorin was incorporated into large unilamellar dioleoylphosphatidylcholine vesicles by either a detergent dialysis method using octylglucoside or a method avoiding the use of detergents. The vesicles were characterized and the permeability properties and transbilayer movement of lipids in both vesicles were investigated as a function of the protein concentration and were compared to protein-free vesicles. An insight in the permeability properties of the vesicles was obtained by monitoring the ratio potassium (permeant): dextran (impermeant) trap immediately after separation of the vesicles from the external medium. Glycophorin incorporated without the use of detergents in 1:300 protein:lipid molar ratio induces a high potassium permeability for the majority of the vesicles as judged from the low potassium trap (K⁺:dextran trap = 0.21). In contrast, the vesicles in which glycophorin is incorporated via the octylglucoside method (1:500 protein:lipid molar ratio) are much less permeable to potassium (K⁺:dextran trap = 0.67 and $\text{t}\text{1}\text{2}$ of potassium efflux at 22°C is 7.5 h.). The relationship between protein-induced bilayer permeability and lipid transbilayer movement in both vesicle preparations is discussed. Addition of wheat-germ agglutinin to glycophorin-containing vesicles comprised of dioleoylphosphatidylcholine and total erythrocyte lipids caused no or just a small effect (less than 20% release of potassium) on the potassium permeability of these vesicles. Also, addition of lectin to dioleoylphosphatidylethanolamine-glycophorin bilayer vesicles in a 25:1 lipid:glycophorin molar ratio had no effect on the permeability characteristics of the vesicles. In contrast, addition of wheat-germ agglutinin to bilayer vesicles made of dioleoylphosphatidylethanolamine and glycophorin in a 200:1 molar ratio resulted in a release of 74% of the enclosed potassium by triggering a bilayer to hexagonal (H_II) phase transition. The role of protein aggregation and the formation of defects in the lipid bilayer on membrane permeability and lipid transbilayer movement is discussed.     

Complex formation of zinc,cadmium, and mercury with penicillamine

The complex formation of zinc, cadmium, and mercury with D-penicillamine has been studied by pH titrations, using computer evaluation of the most likely complexes, which were found to be of the general formulas ML, MH₂L₂, MHL₂-, ML₂^2?, and ML₃^4?. The formation constants of the complexes were determined at 25 0°C in 0.1 M KNO₃. The magnitude of the respective constants cannot, by itself, account for the lack of effect of penicillamine treatment for mercury and cadmium poisoning.     

A tetranectin-related protein is produced and deposited in extracellular matrix by human embryonal fibroblasts

Tetranectin is a tetrameric human plasma protein that binds to plasminogen kringle 4. Its amino acid sequence is homologous with the C-terminal parts of asialoglycoprotein receptors and proteoglycan core proteins. In the present study, we have demonstrated that the human embryonal fibroblast cell line WI-38 produce a tetranectin-related molecule, which might, by several criteria, be similar to tetranectin from plasma. These criteria include immunoblotting analysis of conditioned cell medium revealing a protein band with Mr 17,000, indistinguishable from the Mr of plasma tetranectin. A preparation obtained by purification of conditioned medium by affinity chromatography on an anti-(plasma tetranectin) IgG column also contained the Mr 17,000 protein. This protein (partly purified from the conditioned medium) was shown by crossed immunoelectrophoresis to bind to heparin, CaCl2 and plasminogen kringle 4, as previously described for tetranectin in plasma. Importantly, this tetranectin-related protein is not only present in conditioned culture medium, but the Mr 17,000 protein reacting with anti-(plasma tetranectin) IgG was also present in the extracellular material, remaining after removal of WI-38 cells from the culture dishes, as demonstrated by immunoblotting analysis and immunocytochemical staining. We conclude that WI-38 cells produce a tetranectin-related protein and secrete it into the extracellular matrix.     

Presynaptic regulation of cardiac sympathetic function in hypoxic guinea pigs

In the normal heart, presynaptic cholinergic muscarinic and alpha 2-adrenergic mechanisms modify the fractional rate constant for norepinephrine (NE) synthesis (kNE), an index of sympathetic neural function. To evaluate presynaptic regulation of kNE, conscious guinea pigs subjected to normoxia and then hypoxia (n = 7-8 in each group) were pretreated with 1) vehicle; 2) a cholinergic muscarinic antagonist, methyl atropine; 3) an alpha 2-antagonist, yohimbine; or 4) a combination of the two. An increase of kNE was determined from incorporation of radiolabeled tyrosine into NE in a control period (arterial PO2 130 +/- 1.7 Torr, PCO2 36 +/- 0.5 Torr) and during a hypoxic state (PO2 49.6 +/- 1.0 Torr, PCO2 36 +/- 0.5 Torr). Hypoxia activated kNE in the atrioventricular node and right ventricular moderator band in vehicle-treated animals (P less than 0.05). Sympathetic activation was more general, however, because alpha 2-presynaptic influence acted to limit kNE in all tissues tested (P less than 0.05) except muscle, spleen, and posterior left ventricle. Cholinergic muscarinic presynaptic restraint on kNE was detected during hypoxia only in the left atrial appendage and lung (P less than 0.05). These data indicate that hypoxia increases kNE in the heart, but restraint by cholinergic muscarinic and alpha 2-adrenergic presynaptic mechanisms limits increases in neurotransmitter synthesis and noradrenergic activation regionally.     

Cell cycle-specific expression and nuclear binding of DNA polymerase alpha.

The expression and distribution of DNA polymerase alpha was measured by cytometry and confocal laser scanning microscopy. Expression was proportional to DNA content in proliferating cells, while only S-phase cells retained DNA polymerase alpha after detergent extraction. Nuclear DNA polymerase alpha binding may be one of the key events of S-phase entry.     

Metastatic behavior of human melanoma cell lines in nude mice correlates with urokinase-type plasminogen activator, its type-1 inhibitor, and urokinase-mediated matrix degradation

Five out of six human melanoma cell lines tested were able to degrade in vitro a smooth muscle cell extracellular matrix in a plasmin-dependent way. In three of these five cell lines, this process was mediated by tissue-type plasminogen activator (t-PA) and in the other two cell lines by urokinase-type plasminogen activator (u-PA). All melanoma cell lines produced t-PA mRNA and protein, whereas only the two cell lines showing u-PA-mediated matrix degradation produced u-PA mRNA and protein. These latter cell lines also produced plasminogen activator inhibitor type-1 (PAI-1) and type-2 (PAI-2) mRNA and protein. u-PA receptor (u-PA-R) mRNA and binding of radiolabeled u-PA was found in all melanoma cell lines. The metastatic capacity of these cell lines was studied in nude mice. All cell lines were able to develop primary tumors at the subcutaneous inoculation site. The production of plasminogen activators, their inhibitors and urokinase receptor by subcutaneous tumors corresponded with the production by the parental cell lines in vitro. The two u-PA and PAI-1 producing cell lines showed the highest frequency to form spontaneous lung metastases after subcutaneous inoculation, whereas five of the six cell lines formed lung colonies after intravenous inoculation. In conclusion, u-PA mediated matrix degradation in vitro and production of u-PA and PAI-1 by human melanoma cell lines correlated with their ability to form spontaneous lung metastasis in nude mice. No correlation was found with the ability to form lung colonies after intravenous injection. These findings suggest a role for u-PA and PAI-1 in a relatively early stage of melanoma metastasis.