Assignment of congenital cataract Volkmann type (CCV) to chromosome 1p36

Congenital cataract, type Volkmann (McKusick no 115665, gene symbol CCV) is an autosomal dominant eye disease. The disease is characterized by a progressive, central and zonular cataract, with opacities both in the embryonic, fetal and juvenile nucleus and around the anterior and posterior Y-suture. We examined blood samples from 91 members of a Danish pedigree comprising 426 members, by using highly informative short tandem repeat polymorphisms and found the closest linkage of the disease gene (CCV) to a (CA) _n dinucleotide repeat polymorphism at locus D1S243 (Zmax = 14.04 at _M = 0.025 _F = 0.000), at a penetrance of 0.90. Using two additional chromosome 1 markers, we were able to map the CCV gene in the sequence 1pter-(CCV, D1S243)-D1S468-D1S214. The (enolase 1) gene has been mapped to this area; however, a mutation described in this gene did not give eye disease.     

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.     

Intracellular ATP mimics GTP-gamma-S in generating Ca2+ oscillations in pancreatic beta-cells

Intracellular free calcium ([Ca2+]i) was measured in individual pancreatic beta-cells from mice using dual emission microfluorometry and the indicator Indo-1 applied by a patch clamp pipette. GTP-gamma-S (100 microM) injected together with 0.3 or 3 mM ATP evoked repetitive [Ca2+]i transients with a frequency of about 1 per min in beta-cells kept at a membrane potential of -70 mV. The oscillatory pattern was unaffected by the Ca2+ channel blocker verapamil (50 microM). When omitting GTP-gamma-S from the pipette medium it became evident that 3 mM ATP alone can induce oscillations. The results provide additional evidence for an important role of ATP in the ionic control of insulin release, indicating that such regulation may also involve activation of G-proteins.     

Urokinase binds to a plasminogen activator inhibitor type-2-like molecule in placental microvillous membranes

Placental microvillous membranes exhibited saturable binding of urokinase-type plasminogen activator with plateau achieved by 30 min at 4 degrees C and 10 min at 37 degrees C. The binding was essentially irreversible. The capacity was about 8 pmol urokinase per mg membrane protein. Half-maximal displacement of 125I-labelled urokinase was achieved with about 1.0 nM unlabelled urokinase when using 75 micrograms membrane protein/ml. 125I-labelled urokinase did not bind when treated with diisopropylfluorophosphate to block the catalytic activity. Single-chain urokinase (prourokinase), devoid of catalytic activity, did not bind. Catalytically active tissue-type plasminogen activator did compete with 125I-labelled urokinase for binding although less efficiently than urokinase. Binding activity remained in the 100,000 x g pellet after treatment of the membranes with 3 M KCl, alkaline stripping at pH 12 or extraction by the detergent Triton X-100. The binding was essentially blocked by antibodies against plasminogen activator inhibitor-type-2 (PAI-2). Sodium dodecyl sulfate polyacrylamide gel electrophoresis of solubilized membranes with bound 125I-labelled urokinase showed that the urokinase-PAI-2 complexes largely migrated in fractions corresponding to a very large Mr although no clearly defined peaks were observed. It is suggested that PAI-2 occurs in a form anchored to syncytiotrophoblast microvilli, possibly to the cytoskeleton.     

Chelating agents and rat liver mitochondria

The chelating agents (EGTA and EDTA) and inorganic phosphate (Pi) are the most variable components of experiments involving isolated liver mitochondria. In the absence of EGTA or EDTA, swelling induced by Pi leads to rapid loss of endogenous adenine nucleotides to adenosine. Chelating agents prevent swelling and loss of adenine nucleotides. Concentrations below about 0.1 mM are ineffective. The protective effects depend on the continuous presence of the chelating agent; they are lost on washing EGTA-containing suspensions with chelating-agent-free medium. We question the accepted view that chelating agents stabilize mitochondria by binding Ca2+ to prevent activation of phospholipase.