The origin of matrix metalloproteinases and their familial relationships

New computer comparisons of the sequences of mammalian matrix metalloproteinases have established for the first time strong links with bacterial metalloproteinases. We also propose that there are five groups in the family of matrix metalloproteinases, although only three are as yet well-characterized as proteins, and discuss their origin and relationships with other zinc containing proteases.     

Effects of Monovalent and Divalent Cations on 3-(+)[125I]Iododizocilpine Binding to the N-Methyl-d-Aspartate Receptor of Rat Brain Membranes

We have investigated the binding of 3-[125I]iododizocilpine ([125I]iodo-MK-801) to the N-methyl-D-aspartate (NMDA) receptor in well-washed rat brain membranes. [125I]Iododizocipline binding was displaced by the following: dizocilpine greater than thienylphencyclidine greater than phencyclidine greater than ketamine. Binding of [125I]iododizocilpine was enhanced by glutamate, glycine, and spermidine, whose actions could be reversed by CGS-19755, 7-chlorokynurenate, and arcaine, respectively. [125I]Iododizocilpine binding was also enhanced by a number of divalent cations, including Ba2+, Ca2+, Mg2+, Mn2+, and Sr2+, and several monovalent cations, including Na+ and K+. These cations enhanced [125I]iododizocilpine binding by an action at the polyamine site. In addition, the inhibitory effects associated with high concentrations of these cations was markedly reduced compared to those found in previous studies with [3H]dizocilpine. Analysis of the ability of spermidine, Mg2+, and Sr2+ to alter the inhibition of [125I]iododizocilpine by arcaine gave pA2 values of 5.41, 4.47, and 4.93, corresponding to EC50 concentrations of 3.9, 34.7, and 12.0 microM, respectively, suggesting that physiological concentrations of Mg2+ may occupy the polyamine site. These results demonstrate that [125I]iododizocilpine is a useful probe for the NMDA receptor. Moreover, its high specific activity and relative insensitivity to the inhibitory actions of divalent cations should make [125I]iododizocilpine a valuable ligand for the study of NMDA receptors in intact cellular systems.     

Enzymes of amide and ureide biogenesis in developing soybean nodules

Amide and ureide biogenic enzymes were measured in the plant fraction of soybean (Glycine max) nodules during the period 11 to 23 days after inoculation with Rhizobium japonicum (USDA 3I1b142). Enzymes involved in the initial assimilation of ammonia, i.e. glutamine synthetase, glutamate synthase, and aspartate aminotransferase, showed substantial increases in their specific activities over the time course. These increases paralleled the induction of nitrogenase activity in the bacteroid and leghemoglobin synthesis in the plant fraction. The specific activity of asparagine synthetase, however, showed a rapid decline after an initial increase in specific activity. Following the initial increases in the ammonia assimilatory enzymes, there was an increase in the activity of 5-phosphoribosylpyrophosphate amidotransferase, the enzyme which catalyzes the first committed step of de novo purine biosynthesis. This was followed by a dramatic increase in the purine oxidative enzymes, xanthine dehydrogenase and uricase. Smaller increases were observed in the activities of enzymes associated with the supply of metabolites to the purine biosynthetic pathway: phosphoglycerate dehydrogenase, serine hydroxymethylase, and methylene tetrahydrofolate dehydrogenase.     

Validation of a primary production model of the desert shrub Larrea tridentata using soil-moisture augmentation experiments

Summary In previous papers we have described and verified a primary production model of the desert shrub Larrea tridentata. Here we address the validation phase of the evaluation of this model. Two versions of the model which differ in the priority scheme used for allocating carbon to reproductive or vegetative organs were compared on the basis of their usefulness and reliability over a range of soil-moisture conditions. Over an entire growing season when soil-moisture conditions were near normal both versions of the model were adequate predictors of total above-ground vegetative growth and one was an adequate predictor of reproductive growth as well. A more detailed analysis revealed that the versions varied in the range of soil-moisture conditions over which they were adequate and that neither was adequate when soil-moisture had remained high for extended periods. The validation process has revealed some likely areas for model improvement to increase adequacy.     

Polypeptide molecular weights of the (Na+,K+)-ATPase from porcine kidney medulla

The molecular weights of the polypeptide chains from (Na+,K+)-ATPase of porcine kidney medulla have been determined by analytical sedimentation equilibrium. The alpha-subunit molecular weight is 93 900, and the beta subunit is a glycoprotein with a polypeptide molecular weight of 32 300 (41 400 including protein and carbohydrate). Amino acid and carbohydrate compositions are presented together with related properties (i.e., partial specific volumes, extinction coefficients, and hydrophobic/hydrophilic amino acid content).     

Thermoregulatory behavior of the bluespotted sunfish,Enneacanthus Gloriousus

Twenty bluespotted sunfish, Enneacanthus gloriosus, were individually tested for thermoregulatory behavior in an electronic shuttlebox. The first fishes of this genus to be tested for thermoregulatory behavior, these individuals were captured near the northern limit of their zoogeographic range, in northeastern Pennsylvania. The mean final preferendum from pooled data of all 20 fish was 28.5°C; there were no significant differences between day and night.     

Behavioral thermoregulation by Ammocoete larvae of the sea lamprey (Petromyzon marinus) in an electronic shuttlebox

Ammocoete larvae of the sea lamprey Petromyzon marinus, a member of the primitive vertebrate class Agnatha, were tested for thermoregulatory behavior in an electronic shuttlebox (ichthyotron). The final preferendum derived from pooled data for 24 individually tested ammocoetes was characterized by a mean of 13.6 ± 0.17 (s.e.m.)°C, a mode and median of 140°C, and a range of voluntarily occupied temperatures from 10–19°C over a 3-day period.     

The molar ratio of the two major polypeptide components of human high density lipoprotein.

Human high density lipoprotein (HDL) and its subfractions (HDL2 and HDL3) were separated by ultracentrifugation and the molar ratio of the two major polypeptide chains apo-Gln-I and apo-Gln-II was determined by fluorescence tagging of sodium dodecyl sulfate-denatured proteins combined with polyacrylamide disc gel electrophoresis. Using purified apo-Gln-I and apo-Gln-II standards, it was found that holo HDL, holo HDL2, and holo HDL3 from all plasma samples contained a molar ratio of apo-Gln-I to the disulfide-bound dimer of apo-Gln-II of 2:1, that is a 1:1 ratio in terms of each species of polypeptide chain. The method described is useful for making repeated and rapid measurements on microgram quantities of intact lipoproteins.