Demonstration of a receptor on rabbit neutrophils for chemotactic peptides

[³H]formylNorleu-Leu-Phe, a potent leucocyte chemoattractant, binds specifically to a site on rabbit neutrophils with an affinity of 1.5 × 10^?9 M. Other acylated peptide chemoattractants displace this binding at concentrations closely related to those levels required to elicit chemotaxis. The binding fulfills the major criteria for demonstration of specific receptor sites and indicates that a natural bacterial product and synthetic formyl-peptides produce chemotaxis by the same receptor mechanism.     

Antibiotics and peptides with agonist and antagonist chemotactic activity.

It has been found that the polypeptide antibiotics gramicidin S, tyrocidin and bacitracin, containing Leu-Phe or Ile-Phe sequences, are chemoattractants for neutrophils. Related synthetic pentapeptides containing the sequence Leu-Phe have stronger biological activities, provided the N-terminal residue is acylated. The formylated peptide f-L-Phe-D-Leu-L-Phe-D-Leu-L-Phe is a potent agonist (4 × 10^?9 M) whereas the t-butyloxycarbonyl analog is a good antagonist (8 × 10^?7 M).     

Studies on a peptidase acting on a synthetic collagenase substrate Developmental pattern in rat granuloma tissue and distribution of enzyme in the tissues of various animals

The developmental pattern in experimental rat granuloma tissue and the distribution in the tissues of a few animals (monkey, rabbit, guinea pig anrat) of a peptidase acting on a synthetic collagenase substrate, 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg (Pz-peptide) has been studied. Maximum enzyme activity was found in 4-month-old rats and on the fourth day of implantation of the cotton wick. Pz-peptidase appears to have a ubiquitous distribution in animal tissues; the highest enzyme activity was generally found in liver, intestine and kidney of the animals. The total activity in other organs (spleen, heart, lungs and brain) was much less compared to that of liver, intestine or kidney.     

Purification and properties of a peptidase acting on a synthetic substrate for collagenase from monkey kidney.

A peptidase cleaving a synthetic substrate for collagenase, 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg (designated as PZ-peptide) has been purified extensively (about 5200-fold) from a soluble extract of monkey kidney with a view of carrying out studies on its possible physiological role. The purified PZ-peptidase appeared essentially free of collagenase, nonspecific protease and di- and tri-peptidase activities. The properties of the purified PZ-peptidase resemble very much the granuloma enzyme. It is optimally active around pH 7.0. Its apparent Km value for PZ-peptide is 0.72 mM and V is 10.1 mumol/mg protein/min. It is reversibly inhibited by p-hydroxymercuribenzoate and HgCl2, whereas iodoactetamide does not affect the enzyme activity. N-Ethylmaleimide inhibited the enzyme partially (50%). Heavy metals like Cu-2+, Cd-2+, Ag+, Pb-2+, Ni-2+, and Zn-2+ completely inhibited the enzyme activity, while the inhibition by Co-2+ was only partial. Fe-2+ did not exert any effect on the activity. The enzyme activity was completely inhibited by EDTA and was restored almost to the original value by metal ions like Mn-2+, Mg-2+, Ca-2+ and Ba-2+. The approximate molecular weight of the purified enzyme was estimated to be 56 000.     

Histamine release by chemotactic, formyl methionine-containing peptides.

Certain formyl dipeptides and tripeptides containing methionine released histamine from human basophils at concentrations of 10(-4) to 10(-7) M. However, N-formyl amino acids did not release histamine. Tripeptides, in general, were more active than dipeptides. An acyl group was required for histamine release although an N-terminal position for Met was not essential. Histamine release from human basophils by these peptides correlated well with their chemotactic activity for rabbit leukocytes.     

Subsurface chlorophyll maxima in the north-western Bay of Bengal

The depth profiles of phytoplanlkton pigments in the north-westernBay of Bengal are generally characterized by a subsurface chlorophyllmaximum The occurrence of subsurface chlorophyll maxima is discussedin relation to other information on water column propertiesin the study area. The gradual deepening of the subsurface maximumfrom inshore to offshore waters coincides with the deepeningof the thermocline Significant correlation between the depthof the subsurface chlorophyll maximum and depth of thermoclinesuggests that the formation of the subsurface maximum is influencedby the presence of seasonal thermocline. Further the subsurfacechlorophyll maximum is noticed within the depth ranges of ammoniummaximum and intracline, suggesting the regenerated nutrientsmay also extend a more important influence on the subsurfacemaxima. The presence of chlorophyll b and a high ratio of chlorophylla/phaeopigments in the subsurface layers substantiates the formationof the subsurface maximum due to growth of the photosyntheticallyactive phytoplanlkton community