Emile Van Handel

Estimation of glycogen in small amounts of tissue.

Some physical properties of glycogen have been investigated and applied to micro isolation and assay in biological material containing only a few micrograms of glycogen. Losses of glycogen in the ethanol precipitation step were found to be preventable by the use of a coprecipitant, of which Na2SO4 was the most satisfactory. Evidence for the existence or formation of at least two water-insoluble glycogen complexes in liver was presented. Treatment at 100°C with concentrated KOH for 20 hr rendered all glycogen soluble in water.

Direct microdetermination of sucrose.

Abstract A method is described for direct determination of sucrose. It depends on destruction of reducing sugars with hot alkali, followed by determination of the fructose moiety of sucrose, using cold anthrone.

Microseparation of glycogen, sugars, and lipids.

Abstract A procedure for the separation of glycogen, sugars, and lipids is described for use of milligram amounts of tissue containing at least 10 μg of each of the components. Lipids are extracted with chloroform-methanol; subsequently, sugars are extracted with 66% ethanol while glycogen remains adsorbed on sodium sulfate. Sugar extracted along with lipids is re-extracted with water and added to the sugar fraction.

Sex as Regulator of Triglyceride Metabolism in the Mosquito

The female mosquito, in contrast to the male mosquito or the male and female house fly, synthesizes triglycerides when maintained on glucose; after 7 days, the amount of triglycerides in the female may be 50 times that in the male. Polyunsaturated fatty acids are absent from the newly synthesized triglycerides.

Does ovarian ecdysone stimulate mosquitoes to synthesize vitellogenin

Abstract Physiological amounts of 20-hydroxyecdysone do not initiate vitellogenin synthesis in unfed, non-vitellogenic mosquitoes. Injecting more than 10,000 times the physiological amount induced synthesis, but considerably less than was induced by a blood meal. A dose of 20-hydroxyecdysone which exceeded the physiological level only several hundred times, did not sustain vitellogenin synthesis, when blood-fed mosquitoes were ovariectomized just prior to injection. Transplanting ovaries from vitellogenic to non-vitellogenic females did not initiate synthesis of vitellogenin in the recipient. In vitro, neither 20-hydroxyecdysone nor the ovaries of vitellogenic females were able to induce synthesis of vitellogenin in non-vitellogenic fat bodies. These experiments suggest that ecdysteroid, released by the ovaries, does not initiate ovarian development in mosquitoes.

Medial Neurosecretory Cells as Regulators of Glycogen and Triglyceride Synthesis

In the female mosquito, medial neurosecretory cells restrict synthesis of glycogen from sugar and stimulate triglyceride synthesis. Removal of these cells greatly increases the storage capacity for glycogen at the expense of triglyceride storage.

Suppression of glycogen synthesis in the mosquito by a hormone from the medial neurosecretory cells

Abstract In the female mosquito, removal of medial neurosecretory cells greatly increases the amount of glycogen and greatly diminishes the amount of fat deposited after a single meal of sugar. Implantation of medial neurosecretory cells restricts glycogen synthesis in the operated female to that in the unoperated control but does not restore the interrupted fat synthesis. These experiments indicate that glycogen synthesis is suppressed by a hormone from the medial neurosecretory cells.

Synthesis of ovary-specific proteins in mosquitoes

Synthesis of soluble proteins by the ovary was studied in blood-fed Aedes aegypti and Culex nigripalpus, and in unfed, autogenous Aedes atropalpus. Synthesis of the ovary-specific proteins was compared, in vitro and in vivo, with synthesis of vitellogenin by the fat body. Both types were found to be phosphoproteins. Synthesis of ovary-specific proteins reached a peak, dependent on species, 12–24 h after maximal synthesis of vitellogenin. A. atropalpus synthesized both types of proteins without a blood meal.

Trehalase and maltase in the serum of vertebrates.

Abstract 1. 1. The enzyme trehalase is present in the blood serum of several mammals, including man, and in some turtles. 2. 2. Maltase occurs in the serum of many mammals, birds, reptiles, amphibians and fish. 3. 3. Closely related species show widely different activities. 4. 4. Sucrase was not found in any vertebrate serum.

A specific radioimmunoassay for vitellogenesis in mosquitoes

Abstract Hagedorns assay for vitellogenesis, in which a crude antigen-antibody complex is collected directly on a Millipore membrane, without prior separation of soluble from insoluble proteins, is unspecific. This was proven as follows. Fat bodies of blood-fed mosquitoes ( Aedes aegypti ) were incubated in a medium containing 3 H valine. The medium was analyzed for synthesis of vitellogenin by incubation with serum of normal rabbits (control) or of rabbits which were immunized against mosquito egg protein (antibody). When these mixtures were filtered directly through Millipore membranes (Hagedorns method), the radioactivity in the control was about two-thirds of that in the antibody membrane. However, when the antigen-serum and antigen-antibody complex were centrifuged, the antigen-serum precipitate (control) contained only a very small percentage of the radioactivity present in the antigen-antibody precipitate. Apparently, the medium contained a large amount of soluble, nonvitellogenic protein that binds to the membrane. Analysis of the fat body homogenate showed that a large amount of the newly synthesized vitellogenin was stored intracellularly. Since all published data on vitellogenesis in mosquitoes depend on Hagedorns assay, the validity of current concepts of the control of vitellogenesis in mosquitoes is open to question.