Insect hormones: alpha ecdysone and 20-hydroxyecdysone in bracken fern

The two major molting hormones of insects, alpha ecdysone and 20-hydroxyecdysone, were isolated in crystalline form from dry pinnae of the bracken fern, Pteridium aquilinum (L.) Kuhn. Three unidentified substances with molting hormone activity were also detected. Bracken is the first plant found to contain both of the major insect ecdysones, and it is the first known plant source of alpha ecdysone.     

Ovarian maturation in stable flies: inhibition by 20-hydroxyecdysone

The steroid 20-hydroxyeedysone when given by mouth inhibits ovarian maturation in the stable fly, Stomoxys calcitrans (L.). by preventing lipid synthesis flecessary foir vitellogenlesis in the developing oocyte.     

26-hydroxyecdysone: new insect molting hormone from the egg of the tobacco hornworm

Five kilograms of tobacco hornworm eggs (48 to 64 hours old) afforded 26.5 milligrams of a new crystalline insect molting hormone identified as 26-hydroxyecdysone. The three known insect ecdysones-alpha-ecdysone, 20-hydroxyecdysone, and 20,26-dihydroxyecdysone-were also present but in much smaller quantities. The new hormone is the predominant molting hormone in the hornworm during this stage of embryonic development. These results takent in context with the current knowledge of the chemistry and biochemistry of the molting hormones during postembryonic development in the hornworm indicate quantitative and qualitative differences in the biosynthetic-mnetabolic pathways as well as in the ecdysones in different developmental stages of this insect.     

Puparium formation in flies: contraction to puparium induced by ecdysone

Larvae of the fly Calliphora erythrocephala (Meigen) were deprived surgically of their ring glands at an age prior to the appearance of ecdysone in the blood, and then injected with ecdysone. They contracted into the typical barrel-shaped puparium, before the onset of tanning. This proved that ecdysone controls the puparium contraction as well as tanning.     

Mosquitoes: biting behavior inhibited by ecdysone

Biting in Anopheles freeborni is inhibited during ovarian development. Biting inhibition is triggered by ecdysone, a hormone produced by the ovary during oogenesis. Biting inhibition does not occur in females after the removal of ovaries, but is restored by replacing ovaries or injecting ecdysone. Ecdysone also inhibits biting behavior when it is fed to females. This is the first example of ecdysone controlling a nonmolt-related behavior in insects.     

Binocular unmasking: an analog to binaural unmasking?

A visual analog to binaural unmasking was explored. The observer's task was to detect, under stereoscopic viewing conditions, an apertured sinusoidal grating added to a square patch of visual noise. In the experimental condition, the square patch of noise was presented within a frame such that the right-eye noise was a shifted version of the left-eye noise. Because of the disparity in the noise images, subjects perceived, under stereoscopic viewing conditions, that the noise patch was located behind the frame. When sinusoidal signals were added to this noise patch, the signals were clearly more detectable when the signal disparity was zero than when the signal disparity equaled that of the noise patch, demonstrating the existence of visual unmasking. Hence, under appropriate circumstances, binocular processing, in addition to providing information about depth, can also enhance the detectability of visual patterns.     

Conversion of beta sitosterol to cholesterol blocked in an insect by hypocholesterolemic agents

Two vertebrate hypocholesterolemic agents (triparanol and 22,25-diazacholesterol) block the conversion of beta-sitosterol to cholesterol in the larva of the tobacco hornworm, Manduca sexta (Johannson). A primary site of inhibitory action is the terminal step in this conversion-the reduction of desmosterol (24-dehydrocholesterol) to cholesterol. This is also the site at which these compounds inhibit de novo cholesterol biosynthesis in higher animals. Both agents severely inhibit growth and maturation of the tobacco hornworm.     

Galactose conversion to D-xylulose: an alternate route of galactose metabolism

Galactose dehydrogenase, a soluble enzyme of the mammalian liver, catalyzes the conversion of galactose to galactonic acid. This reaction, together with the subsequent formation of 3-ketogalactonic acid which can be decarboxylated to yield d-xylulose, is a newly discovered pathway for the metabolism of galactosee. This pathway may account for the oxidation of galactose observed in pathients with galactosemia.     

Defensive use by an insect of a plant resin

Larvae of the sawfly Neodiprion sertifer (Hymenoptera: Diprionidae), when disturbed, discharge an oily oral effluent essentially identical chemically to the terpenoid resin of its host plant (Pinus sylvestris). The resin is sequestered by the larva upon feeding, and stored in two compressible diverticular pouches of the foregut. The fluid is effectively deterrent to predators. The defensive use by an insect of a plant resin provides an instance of secondary utilization by a herbivore of the protective chemical weaponry of its host.     

Photoperiodic induction and termination of diapause in an insect: response to changing day lengths

Chrysopa carnea diapaused after experiencing a decrease in day length above the critical photoperiod. Animals experiencing increasing day lengths less than the critical photoperiod did not diapause, and those in diapause began to reproduce. These experiments are the first to demonstrate that insects respond to the direction of change in photoperiods (both increasing and decreasing) which do not encroach on the critical photoperiod.     

Adaptation of an insect cell line (Grace's Antheraea cells) to medium free of insect hemolymph

Cultures of the insect cell line derived by Grace from Antheraea eucalypti Scott [Austrocaligula eucalypti (Scott)] were successfully adapted to medium supplemented with fetal bovine serum, whole-egg ultrafiltrate, and bovine plasma albumin instead of insect hemolymph. Cells, now in their 37th passage, have a population doubling time of 2.5 days; those of unadapted cultures, 4.2 days.     

Ultraviolet video-viewing: the television camera as an insect eve

A television camtiera, like the eyes of some insects, is sensitive to ultraviolet light. When equipped with an appropriate ultraviolet-transmitting lens, such a camera can be used for the direct examtiination of ultraviolet reflectiont patterns (for example, on flowers, butterflies) that are invisible to us, but visible to inisects.     

Reversed development and cellular aging in an insect

Larvae of the beetle Trogoderma glabrum undergo partially reversed development when deprived of food and water. Retrogressive larval ecdyses occur, and the larvae become diminished in size and weight. Given food, the larvae regrow, ecdyze, and regain their previous degree of maturity. Repeated cycles of retrogression and regrowth are possible. Although larval in form and organ differentiation, repeatedly retrogressed insects display a physiological deterioration suggestive of aging. A deterioration of the ability to regrow is accompanied by increasing fat body polyploidy.     

Procollagen: conversion of the precursor to collagen by a neutral protease

An enzymatic activity (procollagen peptidase), capable of converting the biosynthetic precursor procollagen to collagen at neutral pH, has been identified in rat and chick calvarial bone. Limited proteolysis of procollagen with chymotrypsin resulted in a similar transformation. The activity in bone can be demonstrated in vitro despite inhibition of new collagen synthesis by cycloheximide. Preservation of the collagen precursor in preparations extracted with acetic acid results from inhibition of the enzymatic activity at low pH.     

Chemical weathering in central iceland: an analog of pre-silurian weathering

The rate of chemical weathering in central Iceland is two to three times more rapid in areas with plant cover than in barren areas. This relatively small difference in chemical weathering rates suggests that atmospheric CO(2), pressures no greater than five times the present value were needed to sustain present-day rates of chemical weathering before the development of higher land plants in the Silurian.     

Erythropoietin: hypothesis of action tested by analog computer

The action of erythropoietin on the pool of undifferentiated bone marrow cells has been examined with the aid of a model tested with an analog computer. The model is consistent with reported experimental results. The essential aspects of the action are (i) the effect is exerted during the S phase of the cell's cycle; (ii) " effective " erythropoietin is present in the cell only during G(1) and part of S; and, (iii) hormone molecules survive in the cell for only a limited time in effective form and require a certain time to assume this form.     

Phenylmercuric acetate: metabolic conversion by microorganisms

Phenylmercuric acetate, an organomercurial that has been widely used as a fungicide and slimicide, was found to be metabolized quickly by soil and aquatic microorganisms. One of the major metabolic products was identified to be diphenylmercury. In none of the cases has a methylmercury derivative been found among the microbial metabolic products of phenylmercuric acetate.     

Properties of bursicon: an insect protein hormone that controls cuticular tanning

On gel filtration the retention volume of bursicon indicates a molecular weight of about 40,000. On disc electrophoresis bursicon migrates toward the anode and appears at an R(F) (relative to the marker dye) of 0.3 to 0.4. The properties of fractions with bursicon activity in blood, brain, and ganglion of a fly (Sarcophaga bullata), and in blood, ganglion, and corpora cardiaca of a roach (Periplaneta americana) are similar, but not identical. Bursicon in the blood is more heat labile, and the activity in brain and corpora cardiaca shows two peaks in electrophoresis, instead of one as in the other fractions.     

Thermoperiodic control of diapause in an insect: theory of internal coincidence

Females of the parasitic wasp Nasonia vitripennis raised from the egg stage in the total absence of light but subjected to daily temperature cycles (13 degrees to 23 degrees C), are able to distinguish a "short-day" thermoperiod ( 13 hours at 23 degrees C per day) from a "long-day" thermoperiod ( 13 hours at 23 degrees C per day) and produce diapausing or developing progeny accordingly.