[Mixed "n" type inhibition of alpha-glucosidase activity by glucose in hemolymph of honeybee prenymphs]

Under in vitro inhibition of alpha-glucosidasic activity by glucose in hemolymph of Bee prenymphas, the reaction order (n) (predetermined according to the initial natural glycemia) decreases with increasing inhibitor concentration and the affinity constant between enzyme and substrate undergoes lower variations than in other cases where (n) does not change. The study of inhibited molecular forms suggests the possibility of a gradual negative-cooperativity mechanism concerning a dimeric form of the enzyme.

[Modification of alpha-glucosidases (E.C. 3.2.1.20) activity in honeybee hemolymph during nymphosis]

The main alpha-glucosidase fraction of Honey-Bee hemolymph undergoes an important increase of activity for a short time, at a precise stage of nymphosis (pink-brown eyes), without any changes of the apparent-Michaelis constant, nor corresponding increase of the protein quantity.

Bactericidal activity of the normal, cell-free hemolymph of silkworms (Bombyx mori)

Cell-free hemolymph from silkworm (Bombyx mori) larvae can kill Escherichia coli B/SM. The bactericidal principle can be resolved into at least two factors. One is a lysozyme-like enzyme that can be absorbed on crab shell chitin and on bentonite, and the other (cofactor) is an anionic factor that is of low molecular weight, can pass through the chitin column and a carboxymethyl-cellulose column, and can be eluted from a diethylaminoethyl-cellulose column at mu = 0.15 and pH 7.5. Egg-white lysozyme cannot replace the silkworm lysozyme-like enzyme for restoring the bactericidal activity when it is mixed with the cofactor, although it can enhance the bactericidal activity of the mixture of silkworm enzyme and cofactor. Mg2+ and Ca2+ can inhibit the bactericidal activity.

[Occurrence of an acetylcholinesterase (E.C. 3.1.1.7) in the haemolymph of the mussel Mytilus edulis (author's transl)]

A cholinesterase deriving from the hemolymph of the mussel Mytilus edulis was partially purified by use of gel-permeation and ion-exchange chromatography; the specifity to different substrates or inhibitors indicates clearly the occurrence of a "true" acetylcholinesterase.

Symbiosis and attenuation

Parasitic protozoa and bacteria transmitted by vector insects and ticks resist destruction in the intermediate host, possibly through the possession of antigens similar to those of the host. There is no evidence that symbiotic microorganisms have evolved similar eclipsed antigens. Symbiotes are protected from destruction by the natural lytic agents in the host, because they remain for the most part inside special cells that have lost the ability to recognize the symbiotes as "nonself." Metallic ions may play an important role in attenuation through their effect on cell membranes and on the release of lytic agents. The symbiotes of insects are useful and interesting subjects for studying attenuation.

Properties of cyclic nucleotide phosphodiesterase in the central nervous system of Manduca sexta

The properties of cyclic nucleotide phosphodiesterase were studied in soluble and particulate fractions from the central nervous system of Manduca sexta (Lepidoptera: Sphingidae). It was determined that: (1) The highest levels of phosphodiesterase occur in nervous tissue. (2) The total and specific enzyme activities of larval and adult brains are greater than those of the remaining ganglia. (3) Specific central nervous sy stem phosphodiesterase activities of the adult are lower than those of the larva, but both protein and total phosphodiesterase contents are considerably greater in the adult central nervous system. (4) Mg2+ is not absolutely required for either cyclic AMP-phosphodiesterase or cyclic GMP-phosphodiesterase activity. (5) Phosphodiesterase is inhibited by a variety of physiological and non-physiological compounds, nucleoside triphosphates being particularly effective; Some potent inhibitors of mammalian phosphodiesterase are comparatively ineffective toward Manduca sexta phosphodiesterase. (6) Kinetic analyses of soluble and particulate phosphodiesterase revealed non-linear double-reciprocal plots for the hydrolysis of both cyclic AMP and cyclic GMP, with Michaelis constants of approximately 10 mu M and 20 mu M; (7) The hydrolysis of both cyclic nucleotides appears in part to be the function of a single enzyme or related enzymes in the insect central nervous system. It follows that the intracellular level of one cyclic nucleotide may influence the concentration of the other by inhibiting its DEGRADATION.

Isolation and characterization of acetylcholinesterase and other particulate proteins in the hemolymph of Aplysia californica

Hemolymph of the marine mollusc, Aplysia californica, contains four large particles: acetylcholinesterase, hemocyanin, a hemagglutinin, and a structure tentatively identified as erythrocurorin. We purified the acetylcholinesterase 20-fold by differential centrifugation and filtration through a column of 4% agarose. The freshly isolated esterase complex was found to have a sedimentation coefficient of 69, but the negatively stained enzyme lacked a definite structure in the electron microscope, and appeared as irregular aggregates of a 60 A subunit. The complex was unstable below pH 5 or during storage at 7 degrees. Under these conditions, enzymatic activity remained essentially unchanged. Treatment of the purified enzyme with trichloroacetic acid, organic solvents, and sodium dodecyl sulfate broke the complex down into two major subunits with molecular weights of about 70,000. Exposure of the enzyme to [3H]diisopropylfluorophosphate resulted in the labeling of one of these subunits. Although similar in specificity, the cholinesterase of the blood differed from the enzyme in Aplysia nervous tissue, which is associated with membrane. Treatment with sodium deoxycholate activated the membrane-associated enzyme but inhibited slightly that of the hemolymph; tyrocidine inhibited the hemolymph enzyme but not the enzyme of nervous tissue; and mild digestion with trypsin released the membrane-bound enzyme in an active, soluble form, but inactivated the enzyme of hemolymph. The other particulates of Aplysia hemolymph were partially characterized. Aplysia hemocyanin was similar in structure to other molluscan hemocyanins. When negatively stained, the unit particle appeared to be a disc with a diameter of 280 A and a width of 45 A. These discs were stacked to form long cylindrical arrays. The purified hemocyanin was found to contain 0.26% copper (dry weight). Using differential centrifugation and gel filtration we also obtained a 9-fold purification of Aplysia hemagglutinin. This particle was 120 A in diameter with a dark staining central core of 40 A consisting of 6 subunits. The particle tentatively identified as erythrocurorin appeared as a structure 200 A in diameter consisting of 5 V-shaped subunits.