Responsiveness of the lamb ductus arteriosus to prostaglandins and their metabolites

The relative potencies of the prostaglandins A₁, A₂, E₁, E₂, F_2α and their 15-keto-, 15-keto-13,14-dihydro-, and 13,14-dihydro-metabolites were investigated on isolated lamb ductus arteriosus preparations contracted by exposure to elevated PO₂. All the prostaglandins (except PGF_2α and its 15-keto-metabolites) relaxed the tissue. However, only PGE₁, E₂, and their 13,14-dihydro-metabolites, were effective at concentrations below 10⁻⁸ M. Therefore, events that alter metabolism of circulating PGs in the perinatal period may have significant effects on the relative patency or closure of the ductus arteriosus.     

Identification of the C. coli dnaK (groPC756) gene product.

Summary The E. coli dnaK (groPC756) gene product is essential for bacteriophage DNA replication. Bacterial DNA segments carrying this gene have been cloned onto a bacteriophage vector. The product of the dnaK gene has been identified on SDS polyacrylamide gels after infection of UV-irradiated E. coli cells. The dnaK gene codes for a polypeptide with an apparent molecular weight of 93,000-Mr. Transducing phages carrying amber mutations in the dnaK gene fail to induce the synthesis of the 93,000-Mr polypeptide chain upon infection of sup ⁺ bacteria, but do so upon infection of supF bacteria. E. coli carrying the dnaK756 mutation are, in addition, temperature sensitive for growth at 43° C. It is shown that the dnaK756 mutation results in an overproduction of the dnaK gene product at that temperature.     

A new sensitive radial diffusion method for microdetermination of α-amylase

A sensitive agarose diffusion method for the determination of α-amylase has been developed, using Reactone Red 2 B-amylopectin as the substrate. The logarithm of enzyme activity is linearly correlated with the diameters of the diffusion zones over a very extended range from 1 mU/ml to at least 1100 U/ml. The α-amylase activity in biological samples may be determined without dilution or pretreatment, and the test can be performed at any desired temperature between 4 and 45°C. The clear radial diffusion zones may be fixed, further enhancing the contrast to the bright red surrounding.     

Production of human plasminogen activators by cell culture

Plasminogen activators are a group of enzymes which play a crucial role in the breakdown of blood clots. The plasminogen activators currently used in medicine to remove clots from veins and arteries suffer from several disadvantages, but new cell culture techniques or cloned genes could make available safer and cheaper enzymes.     

WOMEN IN NINETEENTH CENTURY AMERICAN BOTANY; A GENERALLY UNRECOGNIZED CONSTITUENCY

Botany was thought to be a suitable study for young women in schools and an amateur avocation in the Nineteenth Century. A surprisingly large number of American women identified themselves as being seriously interested in botany. For example, in the first published directory of American botanists in 1873, 13 percent of the 599 names are women's and that increased to 16 percent of the 982 names in 1878. In this paper, 1,185 women have been identified as a sample of those actively interested in botany during the century. Less than 2% of them were active before 1870, and most of them, 67%, resided in New England and the Middle Atlantic States. Almost three quarters of them were unmarried, and only 10% had higher educational degrees although 15% had some identifiable profession. Some particular individuals are noted for their contributions to science, their activity as plant collectors, and their support of botanical societies. Though few American women became professional botanists in the Nineteenth Century, they constitute an important overlooked constituency for the developing profession of botany.     

Protective effects of soluble CR1 in complement- and neutrophil-mediated tissue injury.

Complement activation is an important step for triggering of acute inflammatory reactions. Soluble human recombinant complement receptor type 1 (sCR1) blocks complement activation by both classical and alternative pathways. In addition to glycogen-induced peritonitis, three models of complement-dependent acute inflammatory injury have been used to assess the protective effects of sCR1: lung and dermal injury after intraalveolar or intradermal deposition of IgG immune complexes; acute lung injury resulting from intravascular activation of complement after the i.v. injection of cobra venom factor; and acute skin and lung injury (at 4 h) after thermal trauma involving 25 to 30% total body surface area. Vascular injury was quantified by increases in vascular permeability, hemorrhage, neutrophil infiltration, and, as indicated, tissue water content. Intravenous infusion of sCR1 reduced lung and dermal vascular injury in all models studied. In glycogen-induced peritoneal exudates sCR1-reduced neutrophil accumulation by 79%. In animals undergoing IgG immune complex-induced alveolitis, sCR1 treatment reduced vascular permeability and hemorrhage by 72 and 71%, respectively, and tissue accumulation of neutrophils was reduced by 68%. After cobra venom factor injection, sCR1 reduced increases in lung vascular permeability by 67%, hemorrhage by 73%, and lung myeloperoxidase content by 55%. Four hours after thermal injury of skin, sCR1-treated animals demonstrated significant protection against lung injury; increases in vascular permeability and hemorrhage were reduced by 45 and 46%, respectively, and myeloperoxidase content was lowered by 39%. In thermal injury of the skin, sCR1 injection reduced dermal vascular permeability by 25% at 1 h (p = NS) and 44% at 4 h. Water content in skin biopsies was also decreased. There was a dose-response relationship between the amount of sCR1 infused and the extent of protection in each of the injury models. These data demonstrate that sCR1 offers significant protection against complement-dependent tissue injury in the animal models studied and that the protective effects are related to reduced neutrophil content.     

Alternatively folded states of an immunoglobulin

Well-defined, non-native protein structures of low stability have been increasingly observed as intermediates in protein folding or as equilibrium structures populated under specific solvent conditions. These intermediate structures, frequently referred to as molten globule states, are characterized by the presence of secondary structure, a lack of significant tertiary contacts, increased hydrophobicity and partial specific volume as compared to native structures, and low cooperativity in thermal unfolding. The present study demonstrates that under acidic conditions (pH less than 3) the antibody MAK33 can assume a folded stable conformation. This A-state is characterized by a high degree of secondary structure, increased hydrophobicity, a native-like maximum wavelength of fluorescence emission, and a tendency toward slow aggregation. A prominent feature of this low-pH conformation is the stability against denaturant and thermal unfolding that is manifested in highly cooperative reversible phase transitions indicative of the existence of well-defined tertiary contacts. These thermodynamic results are corroborated by the kinetics of folding from the completely unfolded chain to the alternatively folded state at pH 2. The given data suggest that MAK33 at pH 2 adopts a cooperative structure that differs from the native immunoglobulin fold at pH 7. This alternatively folded state exhibits certain characteristics of the molten globule but differs distinctly from it by its extraordinary structural stability that is characteristic for native protein structures.     

A kinetic study of the competition between renaturation and aggregation during the refolding of denatured-reduced egg white lysozyme

The recovery of proteins following denaturation is optimal at low protein concentrations. The decrease in yield at high concentrations has been explained by the kinetic competition of folding and "wrong aggregation". In the present study, the renaturation-reoxidation of hen and turkey egg white lysozyme was used as a model system to analyze the committed step in aggregate formation. The yield of renatured protein for both enzymes decreased with increasing concentration in the folding process. In addition, the yield decreased with increasing concentrations of the enzyme in the denatured state (i.e., prior to its dilution in the renaturation buffer). The kinetics of renaturation of turkey lysozyme were shown to be very similar to those of hen lysozyme, with a half-time of about 4.5 min at 20 degrees C. The rate of formation of molecular species that lead to formation of aggregates (and therefore fail to renature) was shown to be rapid. Most of the reaction occurred in less than 5 s after the transfer to renaturation buffer, and after 1 min, the reaction was essentially completed. Yet, by observing the effects of the delayed addition of denatured hen lysozyme to refolding turkey lysozyme, it was shown that folding intermediates become resistant to aggregation only much more slowly, with kinetics indistinguishable from those observed for the appearance of native molecules. The interactions leading to the formation of aggregates were nonspecific and do not involve disulfide bonds. These observations are discussed in terms of possible kinetic and structural aspects of the folding pathway.