Victor J. Brookes

The induction of yolk protein synthesis in the fat body of an insect, Leucophaea maderae, by an analog of the juvenile hormone☆

Abstract During the time that eggs are developing, the fat body from female Leucophaea maderae synthesizes a protein with characteristics similar to a subunit of the major yolk protein. Synthesis does not occur or is much reduced in fat bodies from males, nymphs, and abdomens amputated from adult females before the onset of egg development. Topical application of an analog of the juvenile hormone initiates the development of eggs in isolated abdomens. Forty hours after hormonal treatment and prior to an obvious change in the eggs, labeled leucine is incorporated into a fraction that can be isolated from the fat body together with added yolk protein. This fraction exhibits the same sedimentation characteristics as the subunit of the yolk protein during density gradient centrifugation.

Solubility and electrophoretic properties of ovarial protein of the cockroach, Leucophaea maderae

During the maturation of the ovaries of Leucophaea maderae, the protein content increases about seventyfold. Approximately 80 per cent of the total protein from the mature ovary is soluble in saline at an ionic strength of 0·4 or greater. Analysis by disk electrophoresis on polyacrylamide gel of saline extracts from ovaries at progressive stages of maturation showed an increase in relative concentration of five bands. These five bands are presumed to be yolk. Most of the increase is identified with one band which is a lipoprotein. Lowering the ionic strength of the saline extracts to 0·2 by dilution with water precipitates protein corresponding to three of the five bands including the major band.

Yolk Protein: Structural Changes during Vitellogenesis in the Cockroach Leucophaea maderae

Most of the yolk protein in the mature egg of Leucophaea maderae consists of one large component, whereas a second smaller protein is present during the early stages of vitellogenesis. The large protein can be converted to the smaller one and to even smaller units by mild alkaline conditions in vitro. After injection of uniformly labeled leucine-C14 into females with developing eggs, the smaller yolk protein becomes labeled first, the label is then transferred to the large protein upon prolonged exposure.

Osmoregulation in an alkaline salt lake insect, Ephydra (Hydropyrus) hians Say (Diptera: Ephydridae) in relation to water chemistry

Larvae of the alkali fly Ephydra hians, from Mono Lake (California), were exposed to osmotic concentrations ranging from distilled water to over 6000 mOsm of either alkaline Mono Lake water, or non-alkaline sea water/sodium chloride solutions. Larvae were capable of both hyper- and hypo-osmotic regulation of haemolymph osmolality (at around 300mOsm) in Mono Lake water, but this ability was less effective in sea water/sodium chloride. In addition, higher mortality rates in sea water/sodium chloride suggest larvae are less tolerant of this chloride-dominated water chemistry. Pm-acclimation of larvae in sea water/sodium chloride did not improve survival in higher concentrations of this solution relative to larvae acclimated to Mono Lake water. At and above 200 g/l total dissolved solids (about 4800 mOsm) of Mono Lake water, larval survival is severely reduced, in association with osmotic dehydration. Sodium and chloride are the major haemolymph osmolytes, comprising about 70% of the total osmotic concentration. The results suggest that this species is alkali-adapted, and that restriction in habitat distribution from non-alkaline chloride waters and salinities above 200 g/l has a physiological basis.

The isolation of a methylcholine containing phospholipid from Phormiaregina larvae

Abstract Although carnitine, β-hydroxy-γ-butyrobetaine, occurs in many animal systems, its function and intermediary metabolism remains obscure (Fraenkel 1957). The results of previous experiments in our laboratory indicated that on a chemically defined diet, carnitine and several related compounds, including γ-butyrobetaine, etc., replaced the choline requirement. (Hodgson, Cheldelin and Newburgh 1956, 1960). Since choline is a major constitent in Phormia regina phospholipids it seemed reasonable to postulate that when larvae are reared on a diet devoid of choline but containing carnitine, a phospholipid in which choline is replaced by carnitine might be observed. This communication reports the formation of a new “lecithin” when blowflies are reared in the presence of carnitine.

Partial purification of a proteolytic enzyme from an insect, Phormia regina☆

Abstract 1. 1. The larva of the blowfly, P. regina, excretes a complex of proteolytic enzymes into the culture medium during its growth period. 2. 2. A partially purified protease has been obtained by (NH4)2SO4 and acid precipitation. With casein as a substrate, maximal activity was obtained in the pH range 7.8–8.3. The activity was unaffected by p-chloromercuribenzoate, iodoacetic acid, Mg++, Mn++ or NaCl. 3. 3. N benzoyl- l -arginine ethyl ester and N benzoyl- l -argininamide were degraded by the purified fraction. 4. 4. The soybean trypsin inhibitor inhibited approximately 85% of the protease activity and 75% of the esterase activity. 5. 5. Crude preparations contained enzymes capable of degrading glycylglycylglycine, leucylglycylglycine, and carbobenzoxyglycyl- l -phenylalanine. Purification resulted in removal of all but this last activity. 6. 6. The insect enzyme resembled trypsin in some of its properties but appears to be more stable and less soluble at an acid pH than the pancreatic enzyme.

Protein synthesis in the fat body of Leucophaea maderae during vitellogenesis

During the early stages of vitellogenesis in Leucophaea, vitellogenin accounted for most if not all of the secreted protein synthesized by the fat body. Synthesis began about 5 days after mating and continued until 24 hr or so before the formation of the ootheca. Ligation resulted in the degeneration of the oocytes, the first evidence of which was seen within 24 hr. Ligation also curtailed the synthesis of vitellogenin at about the same time. Isolated abdomens treated with an analog of juvenile hormone commenced vitellogenesis within 12 to 24 hr and measureable oocyte growth occurred after 5 days. Despite continued synthesis of vitellogenin, the oocytes in isolated abdomens always degenerated.

The phospholipid pattern of Tenebrio molitor larvae

Abstract The phospholipids of Tenebrio molitor larvae have been examined by chromatography on columns of DEAE-cellulose and silicic acid-Hyflo Super Cel. The major constituents consist of choline and ethanolamine phospholipids. Inositol phosphatides represented a relatively small portion of the total phospholipids. Phosphatidyl serine and lysolecithin compounds were not detected. A choline sphingolipid was demonstrated to be present, and only ethanolamine phosphatides were detected in the plasmalogen form. The overall phospholipid pattern was qualitatively similar to other insects.

The maturation of the oöcytes in the isolated abdomen of Leucophaea maderae

Abstract Ovarian development has been induced in abdomens amputated from females of the cockroach, Leucophaea maderae , by implanting corpora allata. Amputation resulted in some sort of deficiency which prevented normal secretion of the corpora allata and growth of the oocytes was much slower than in intact animals. More rapid growth took place when corpora allata were implanted at several intervals. Topical application of an artificial hormone prepared from farnesenic acid also stimulated growth of oocytes which was more uniform than that which took place under the influence of corpora allata.

Hormonal control of reproduction—I. Initiation of oöcyte development in the isolated abdomen of Leucophaea maderae

Abstract Abdomens of female Leucophaea maderae have been isolated and maintained in a viable condition for several months. When acetate-1-C 14 was injected into isolates about one-half of the label was recovered as C 14 O 2 within 12 hr. Glucose-U-C 14 was oxidized much more slowly and nearly 70 per cent of the label was still retained after 5 days. Leucine-U-C 14 was readily incorporated into the protein of the fat body, blood, and immature ovaries. Isolation effectively terminated the development of the ovaries, but when active corpora allata were implanted there was an increase of 10 to 34 per cent in the size of the terminal oocyte. The data suggest that only the corpora allata are necessary for the initiation of ovarian development, but other factors such as hormone titre and nutritional state may influence the rate at which development takes place.