PHYSICOCHEMICAL PROPERTIES OF THE PROTEOLYTIC ENZYME FROM THE LATEX OF THE MILKWEED,ASCLEPIAS SPECIOSA TORR. SOME COMPARISONS WITH OTHER PROTEASES : III. KINETICS OF THE HEAT INACTIVATION OF PAPAIN,BROMELIN, AND ASCLEPAIN

1. The rates of heat inactivation of papain, bromelin, and asclepain were determined at several different temperatures. Papain was by far the most resistant to heat. 2. The destruction of papain at 75–83° and bromelin at 55–70° followed the course of a first order reaction, except that for longer times of heating, bromelin (at 60–70°) was inactivated more rapidly than the first order equation required. 3. The rate of inactivation of asclepain at 55–70° followed the second order equation. 4. The critical thermal increments of inactivation of papain and bromelin, calculated with the van''t Hoff-Arrhenius equation, were of the same high order that has been found for protein denaturation. The increment for asclepain was somewhat lower.     

NEW SPECIES AND RECORDS OF POLYCHAETA FROM CEYLON

A collection of polychaetes made by the author in December 1961 and April 1962 from a number of places on the coast of Ceylon was examined. Seven new species and one new subspecies are described and sixteen species are recorded new to the fauna of Ceylon. The holotypes and lectotypes have been deposited in the British Museum (Natural History).     

A microtiter plate transglutaminase assay utilizing 5-(biotinamido)pentylamine as substrate.

Transglutaminases belong to an important family of enzymes involved in hemostasis, skin formation, and wound healing. We describe a technique for the measurement of transglutaminase activity using polystyrene microtiter plates coated with N,N'-dimethylcasein. The substrate 5-(biotinamido)pentylamine is covalently incorporated into N,N'-dimethylcasein by transglutaminase in a calcium-dependent reaction. The biotinylated product is detected by streptavidin-alkaline phosphatase and quantitated by measuring the absorbance at 405 nm following the addition of p-nitrophenyl phosphate. The assay is sensitive, specific, and linear at plasma factor XIIIa concentrations between 0.08 and 1.25 micrograms/ml and at purified guinea pig liver transglutaminase concentrations between 0.05 and 0.8 microgram/ml. The intra-assay coefficient of variation is less than 8%. The solid-phase assay was used to quantitate the transglutaminase activity in Escherichia coli extracts expressing recombinant factor XIII A-chains and to analyze factor XIIIa inhibitors. This method will facilitate the analysis of structure-function relationships of the transglutaminases using recombinant DNA methods. Furthermore, screening of natural and synthetic factor XIIIa inhibitors will be expedited by this solid-phase microtiter plate assay.     

Relationship of postprandial motilin, gastrin, and pancreatic polypeptide release to intestinal motility during vagal interruption.

Experiments were performed to determine how postprandial motilin, gastrin, and pancreatic polypeptide plasma concentrations measured during vagal blockade relate to coincident small intestinal motility patterns. Feeding produced a postprandial pattern of intestinal motility coincident with a sustained increase in gastrin and pancreatic polypeptide and a decline in motilin plasma concentrations. Vagal blockade replaced the fed pattern with one similar to migrating motor complex (MMC) activity. Highest motilin plasma concentrations were observed during phase III of this MMC-like activity, as occurs in the fasted state. Vagal blockade reduced but did not abolish the postprandial increase in plasma gastrin and pancreatic polypeptide concentrations. Termination of vagal cooling produced a decline in motilin and an elevation in gastrin and pancreatic polypeptide concentrations, coincident with the return of the fed pattern. In conclusion, during vagal blockade in the fed state (i) motilin, but not gastrin or pancreatic polypeptide plasma concentrations, fluctuate with the MMC-like activity, and any measurement of motilin concentration under these circumstances must be interpreted on the basis of gut motility patterns, and (ii) gastrin and pancreatic polypeptide concentrations are marginally elevated, but these changes are not enough to disrupt the MMC or have any motor effect. Lastly, the fed pattern and the postprandial changes in motilin, gastrin, and pancreatic polypeptide concentrations are in part dependent upon intact vagal pathways.     

The meiotic stage of nondisjunction in trisomy 21: Determination by using DNA polymorphisms

We have studied DNA polymorphisms at loci in the pericentromeric region on the long arm of chromosome 21 in 200 families with trisomy 21, in order to determine the meiotic origin of nondisjunction. Maintenance of heterozygosity for parental markers in the individual with trisomy 21 was interpreted as resulting from a meiosis I error, while reduction to homozygosity was attributed to a meiosis II error. Nondisjunction was paternal in 9 cases and was maternal in 188 cases, as reported earlier. Among the 188 maternal cases, nondisjunction occurred in meiosis I in 128 cases and in meiosis II in 38 cases; in 22 cases the DNA markers used were uninformative. Therefore meiosis I was responsible for 77.1% and meiosis II for 22.9% of maternal nondisjunction. Among the 9 paternal nondisjunction cases the error occurred in meiosis I in 2 cases (22.2%) and in meiosis II in 7 (77.8%) cases. Since there was no significant difference in the distribution of maternal ages between maternal I error versus maternal II error, it is unlikely that an error at a particular of maternal ages between maternal I error versus maternal II error, it is unlikely that an error at a particular meiotic stage contributes significantly to the increasing incidence of Down syndrome with advancing maternal age. Although the DNA polymorphisms used were at loci which map close to the centromere, it is likely that rare errors in meiotic-origin assignments may have occurred because of a small number of crossovers between the markers and the centromere.(ABSTRACT TRUNCATED AT 250 WORDS)     

Repetitive proline-rich proteins in the extracellular matrix of the plant cell

Several classes of hydroxyproline-rich proteins have been found in the cell walls of plants. Monomeric forms of the proteins can be solubilized from the walls, but the majority of the proteins are insolubilized by as yet unidentified crosslinks. The proteins have repeated sequences and are often rich in basic amino acids. The repeat proline-rich region may be serving to generate an elongated rod-like structure while the regularly spaced lysines probably interact with the acidic pectins. Several of the genes coding for these proteins have been isolated, and their expression has been found in some cases to be tissue specific and in others inducible by hormones and various types of stress.