Protease-nexin: A cellular component that links thrombin and plasminogen activator and mediates their binding to cells

This report identifies a component of normal human fibroblasts that forms a covalent linkage with thrombin and urokinase (urinary plasminogen activator) and mediates most of the specific cellular binding of these proteases. This component, here named protease-nexin (PN), is both associated with the cell surface and released into the culture medium. In several ways PN resembles antithrombin III (AT3), a prominent inhibitor of thrombin in serum: PN links thrombin, probably via an ester bond; PN does not link thrombin blocked at its catalytic site serine; PN has a high-affinity heparin-binding site; and heparin greatly accelerates the rate of linkage between soluble PN and thrombin. Despite these similarities, PN and AT3 are distinct; they differ in size and are not immunologically cross-reactive. Whereas AT3 regulates the proteolytic activity of thrombin in serum, PN may regulate the activity of serine proteases at and near the cell surface.     

Phosphatidylinositol distribution and translocation in sonicated vesicles. A study with exchange protein and phospholipase C

The distribution of phosphatidylinositol and phosphatidylcholine in sonicated phospholipid vesicles (phosphatidylcholine: diphosphatidylglycerol: phosphatidylinositol, 90:5:5 mol%) has been determined by the use of exchange protein from beef heart and phosphatidylinositol-specific phospholipase C from Staphylococcus aureus. Approximately 70% of the phosphatidylinositol in the sonicated vesicles was accessible to the exchange protein and 70–75% was accessible to the phospholipase C. A similar proportion (65%) of the phosphatidylcholine was accessible to the exchange protein suggesting that phosphatidylinositol was not preferentially located in either surface of the phospholipid bilayer. The rate of translocation of both phospholipids was very slow but the rate for phosphatidylcholine ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 4–7}\text{days}$) appeared to be greater than that for phosphatidylinositol ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 8–60}\text{days}$). Production of asymmetric vesicles by removing phosphatidylinositol from the outer surface with either exchange protein or phospholipase C did not induce rapid phospholipid translocation.     

The Fcu controlling-element system in maize

Summary The relationship between the Fcu controlling-element system and the spotted-dilute R system was investigated. The Fcu controlling-element system consists of the receptor element allele r-cu and the regulatory element Fcu. The equivalent components of the spotted-dilute R system are respectively R-r#2 (or R-r#2 Dil) and Spf. The R-r#2 allele of the latter system was shown to be responsive (mutable) to Fcu, provided that it has had an uninterrupted association with Dil or Dpf as evidenced by the color variegation of the aleurone tissue. The reverse test, in which the r-cu allele of the Fcu controlling element system was tested for its response to Spf, proved negative. This was surprising in view of the relationship and specificity between systems. The possibility was considered that maize controlling elements may have different sizes as is known for bacterial insertion sequences. —The variable dilute pigmenting capacity of the r-cu allele also was studied. A given level of r-cu-induced pigmentation, despite the wide range in pigmentation expression, was found to be generally non-heritable, as based on a test of correspondence between parent and progeny.Journal Paper No. J-9204 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1884Now with Funk's Seeds, Casalmorano (Cremona), Italy     

Fitting multiple trajectories simultaneously to a model of inducible enzyme synthesis

The iterative scheme described by Milstein [6] is used to estimate the rate constants of a model describing an inducible enzyme system. The model was formulated by Heinmets [5], and was mathematically analyzed by Roth and Roth [9] using Bellman's quasilinearization technique. The method used in this article makes use of multiple trajectories of the system to obtain a set of parameters which fit the data of all trajectories simultaneously. A comparison of the numerical results is presented. The data used in the calculations were generated in a similar way to that of Roth and Roth. However, we introduce into each datum 5% noise from a random number generator uniformly distributed [0,1].     

Differential scanning calorimetry of milk fat globule membranes

Differential scanning calorimetry was employed as an aid in examining the structure of the bovine milk fat globule membrane. At least six major endotherms are observed between 10 and 90°C, corresponding to order-disorder transitions of discrete structural domains of the membrane. These endothermic transitions occur at 16, 28, 43, 58, 68, and 75°C. The transitions occurring between 10 and 50°C were reversible, suggesting the involvement of lipid. However, the high temperature transitions were irreversible. The calorimetric C transition, centered at 43°C, was shown to involve neutral lipid, since the endotherm was reversible, insensitive to proteolysis, and similar to the endotherm of the isolated neutral lipid fraction of the milk fat globule membrane. The glycolipid and phospholipid fractions of the milk fat globule membrane yielded endotherms outside of the temperature range of the C transition. Another endotherm, the D transition (58°C), was found to involve the denaturation of the major membrane coat protein, butyrophilin (band 12). Evidence for this assignment included the following observations: (i) the nearly selective proteolysis of butyrophilin resulted in the complete removal of the D transition, (ii) the butyrophilin-enriched, Triton X-100-insoluble pellet of milk fat globule membrane yielded a relatively normal D transition, and (iii) the irreversible, disulfide-stabilized aggregation of butyrophilin occurred in the membrane solely at the temperature of the D transition. Furthermore, no other prominent milk fat globule membrane polypeptide formed these non-native disulfide crossbridges during the D transition. The sources of the other major endotherms of the milk fat globule membrane have not yet been assigned.     

β-Carotene, vitamin C and vitamin E content of the marine microalga Dunaliella tertiolecta cultured with different nitrogen sources

Variations in the β-carotene, vitamin C and vitamin E content of D. tertiolecta have been shown to result from the nitrogen source used in the culture medium. Differences of 101%, 38% and 69% have been found in β-carotene, ascorbic acid and tocopherol content in mg/g of dry matter, respectively, and differences of 147%, 63% and 37% occurred in β-carotene, vitamin C and E concentrations in mg/litre of culture, respectively. Considering the β-carotene, vitamin C and vitamin E content in mg/g of chlorophyll a, maximum variations occurred in β-carotene content, with differences of 145% among the different nitrogen sources. Maximum β-carotene and vitamin C values were found in urea cultures, whereas urea cultures showed the minimum values for vitamin E.     

Heteronarce rierai,a new narkid ray from Mozambique,western Indian ocean

Heteronarce rierai sp. nov. is described on the basis of six specimens, one male and five females, caught in the waters off Mozambique (western Indian Ocean). Total lengths range from 257 to 296 mm. The new species is distinguished from the three other species of the genusHeteronarce by its narrower disc width (29.6% of TL in male, and 33.0 to 39.2% of TL in females), shorter disc length (32.7% of TL in male, and 34.4 to 40.6% of TL in females), and its longer interdorsal distance (10.1 to 11.7% of TL).