Cecropia Silkworm Research Articles

CONTROL OF SYNTHESIS OF RNA AND PROTEIN IN DIAPAUSING AND INJURED CECROPIA PUPAE.

Injury to diapausing pupae of the cecropia silkworm moth stimulates the synthesis of RNA in all pupal tissues and the synthesis of several blood proteins; such injury also induces the precocious synthesis of a protein, termed "injury protein," which normally appears in the blood during adult development. Actinomycin D, injected in concentrations of 2 micrograms per gram of body weight, blocks the injury-stimulated increase in blood protein synthesis and the injury-induced synthesis of injury protein. However, at concentrations of 0.5 micrograms per gram it prevents the induction of injury-protein synthesis but does not prevent the increased synthesis of other blood proteins. These results suggest that low concentrations of actinomycin may inhibit the synthesis of new kinds of messenger RNA but still permit the continued synthesis of messenger RNA's already in production at the time the actinomycin is injected.

Spontaneous Electrical Activity in the Brains of Diapausing Insects

The spontaneous electrical activity in cerebral ganglia of several insect species does not disappear during diapause. Some recordings of electrical activity in pupae of the cecropia silkworm (in which the brain is considered to be electrically "silent" during diapause) suggest that at least some activity is maintained, but possibly it is restricted to certain regions of the brain.

THE MECHANISM OF BLOOD PROTEIN UPTAKE BY INSECT OOCYTES

what was described by Dr. Schjeide (this symposium) and the role of blood proteins in yolk formation by the moth of the Cecropia silkworm. By immunological procedures, it has been possible to show that most, and possibly all proteins present in the blood at the time of yolk formation are also detectable in the yolk (Telfer, 1954). As in the experiments of Knight and Schechtman (1954), even foreign pro? teins which have been injected into the blood are detectable in the yolk (Telfer, 1960). As if in imitation of serum lipo? vitellin in the chicken, a protein which circulates in the blood of female moths is

Metabolic conversions during pupation of the cecropia silkworm. 2. Tests for the operation of the glyoxylate cycle.

Metabolic conversions during pupation of the cecropia silkworm. 2. Tests for the operation of the glyoxylate cycle.

Metabolic conversions during pupation of the cecropia silkworm. 1. Deposition and utilization of nutrient reserves.

Metabolic conversions during pupation of the cecropia silkworm. 1. Deposition and utilization of nutrient reserves.

THE JUVENILE HORMONE. II. ITS ROLE IN THE ENDOCRINE CONTROL OF MOLTING, PUPATION, AND ADULT DEVELOPMENT IN THE CECROPIA SILKWORM

1. By means of a standardized "pupal assay" for juvenile hormone, the endocrine activity of the corpora allata was found to undergo large and systematic changes during the postembryonic development of the Cecropia silkworm.2. In each of the larval instars that were studied, the glands are least active just prior to the larval molt and most active shortly after the molt. Larval molting therefore appears to take place in the presence of a declining titer of juvenile hormone—an endocrine situation which apparently permits the striking changes in morphology and pigmentation which occur in successive larval stages of the Cecropia silkworm.3. The corpora allata show low but definite activity at the time of pupation. If the glands are extirpated so that pupation occurs in the absence of juvenile hormone many larval tissues overleap the pupal stage and undergo precocious adult differentiation. Therefore, the low concentration of juvenile hormone in the mature larva plays a definite role in the endocrine control of pupation.4. The corpora allata are inactive throughout the entire pupal stage. This inactivity persists during the first two-thirds of adult development. During the final week of adult development, the glands recover their endocrine function and are maximally active by the time of emergence of the adult moth.5. The absence of juvenile hormone proves to be an obligatory feature of the initial phase of adult differentiation. If active corpora allata are implanted into a pupa so that adult development is initiated in the presence of juvenile hormone, the pupa develops and molts into a creature which is a mixture of pupa and adult. The higher the titer of juvenile hormone, the more extensive is the preservation of pupal characters.6. Juvenile hormone is effective in blocking adult differentiation only when it is present during the first five days of adult development. Consequently, the target of juvenile hormone appears to be certain early events which are the normal reactions to ecdyson at the outset of adult development. If unopposed by juvenile hormone, these events commit the cells to developmental reactions accompanied by metamorphosis.7. A comprehensive theory is presented for the action of juvenile hormone in the Cecropia silkworm. According to this theory, juvenile hormone modifies the cellular reactions to ecdyson by opposing the de-repression, de-coding or acting-out of fresh genetic information prerequisite for progressive differentiation but not prerequisite for growth in an unchanging state.

The injury metabolism of the Cecropia silkworm—I: Biological amplification of the effects of localized injury

If the integument of a diapausing Cecropia pupa is incised or perforated, the rate of oxygen consumption rapidly increases to levels characteristic of the nondiapausing insect. The Q O 2 persists at this high level for a few days and then, over a period of several weeks, slowly returns to the pre-injury level. The magnitude of the ‘injury metabolism’ is a function of the circumference of the wound; after large injuries, the Q O 2 undergoes a 5- to 10-fold increase. The effects of the localized injury spread in a decremental manner throughout the insect as a whole—apparently by means of an ‘injury factor’ which is released into the blood. The factor seems to be released until the wound is sealed off by a deposit of blood cells. If the latter are prevented from reaching the wound, the injury metabolism is enhanced and greatly prolonged. The hypothetical injury factor causes a speeding up of the heart and a mobilization of blood cells into the circulating haemolymph; it also provokes striking chemical and cytological changes in most other cells. The biochemical and metabolic responses to injury closely resemble the changes induced by the prothoracic gland hormone (ecdyson) at the outset of adult development. Despite this fact, ecdyson is apparently not involved in the injury response. Moreover, the pupa shows no developmental reactions aside from the healing of the wound. This accomplished, the chemical, cytological, and metabolic components of the injury response gradually disappear and the pupa continues to diapause. According to the theory here presented, the fundamental action of the injury factor is to disturb and disrupt the conservative devices of the diapausing cells and, thereby, to enforce a temporary, compensatory, and obligatory increase in the ‘cost of maintenance’.

Some physiological aspects of glutamate-aspartate transmination in insects

1. 1. The quantitative distribution of glutamate-aspartate transminase in several tissues of the roach was demonstrated and the enzymatic activity relative to both protein content and tissue weight is presented. Significant differences between tissues were observed. 2. 2. Centrifugal fractionation of roach muscles showed that transminase activity is mainly localized in the soluble fraction of the sarcoplasm. 3. 3. Glutamate-aspartate transminase activity was followed throughout the life cycle of the housefly. During larval growth the concentration and specific activity of the enzyme increased, then fell during the pupal stage. Enzymic activity rose sharply during adult emergence. Similar quantitative determinations were made using several tissues during adult development of the cecropia silkworm. The only striking increase in transaminase activity during adult development occurred in the thoracic muscles. 4. 4. It is suggested that the U-shaped curve of transamination is related to U-shaped curve for protein synthesis during morphogenesis and that the main site for the interconversion of amino acids during adult development may be the muscles.

THE RESPIRATORY EXCHANGE OF DIAPAUSING PUPAE OF THE CECROPIA SILKWORM IN THE PRESENCE OF CARBON MONOXIDE

1. After due correction for complicating reactions, the rate of total gas uptake of normal diapausing pupae of the Cecropia silkworm in a carbon monoxide-oxygen mixture of 5 to 1 is found to be stimulated approximately 2-fold over the rate in air. 2. Ninety per cent of this extra gas uptake is due to a stimulation of the true respiration of the pupa. 3. The remaining ten per cent is due to the combustion of carbon monoxide to carbon dioxide. 4. The combustion of carbon monoxide is increased slightly when the metabolism of the pupa is enhanced following integumentary injury. 5. There is a slight fixation of carbon-14 in pupae under aerobic conditions presumably as a result of fixation of C14O2 manufactured from C14O by the pupa. 6. There is no detectable fixation of C14O in pupae exposed to this gas under anaerobic conditions. 7. After correction for carbon monoxide-combustion, it is clear that the enhanced oxygen uptake following integumentary injury of diapausing pupae is inhibited by carbon monoxide. 8. This carbon monoxide-inhibition is directly proportional to the enhancement of oxygen uptake following injury.

The effects of diapause, development, and injury on the incorporation of radioactive glycine into the blood proteins of the Cecropia silkworm

Glycine-1- 14C, injected into the haemocoele of diapausing pupae and developing adults of the Cecropia silkworm, is incorporated into the proteins of the blood. The rate of incorporation parallels previously described rates of oxygen consumption (Schneiderman and Williams, 1953) under a variety of conditions. Amino-acid incorporation into blood proteins is thus representative of the endergonic processes occurring in the insect. The incorporation of amino acids can be added to the list of metabolic processes which proceed at depressed rates during diapause, but which accelerate temporarily in response to injury. The pro-thoracic gland hormone, in causing the termination of diapause in Cecropia, evokes metabolic changes which are as yet indistinguishable from those elicited by injury. The accelerated respiration following injury is probably due primarily to a general acceleration of energy-requiring maintenance processes which are normally suppressed during diapause, rather than to energy invested in the morphogenetic work of wound repair.

OXIDATIVE ENZYMES AND THE INJURY METABOLISM OF DIAPAUSING CECROPIA SILKWORMS*

The remarkable control of insect growth by the hormone ecdyson is readily apparent in the events that transform a diapausing Cecropia pupa into a developing adult moth. The pupal diapause, as shown by Williams,' is a state of developmental arrest enforced by the failure of the insect's endocrine system to supply the hormonal stimulus required for growth and development. In essence, what the individual diapausing tissues require is ecdyson, secreted by the prothoracic glands. The latter become inactive after pupation and remain so for many months; but when the prothoracic glands recover their secretory function under neuroendocrine stimulation from the brain, the individual tissues once again begin to grow, and commence a sequence of rnorphogenetic changes that culminates in three weeks' time with the emergence of the adult moth.' One of the principal tasks of present-day insect endocrinology is to seek an understanding of how ecdyson is able to exert its control over the growth process. In molecular terms, one avenue of approach to the problem lies in elucidating the biochemical changes that occur a t the termination of diapause in response to the growth-promoting action of ecdyson. The properties of the diapausing insect itself are likewise of interest for understanding the physiological and biochemical adaptations of cells to life in a state of arrested developmen t. Both these matters were discussed by Williams2s3 about ten years ago in papers that called attention to the suitability of diapausing and developing silkmoths as subjects for examining biochemical mechanisms in insect growth and metamorphosis. At the time of these papers i t was already clear that alterations in oxidative enzymes a t the onset and termination of diapause had an important bearing on the probIems just mentioned. In particular, and of special interest for the present paper, was the evidence that a synthesis of oxidative enzymes within the pupal tissues represented one type of change promoted by ecdyson in favoring growth. This matter has subsequently been explored in detail in a number of publication^.^-* In the present paper I propose to review recent progress in our understanding of respiratory metabolism and respiratory enzymes in relation to the diapause and development of the Cecropia silkworm. After a brief rCsum6 of the metabolic and enzymatic changes during the course of metamorphosis, two principal topics will be considered: (1) the peculiar properties of respiratory metabolism in diapausing tissues and recent changes in our ideas as to their physiological basis; and (2) the close parallel between respiratory changes normally associated with the termination of diapause and those that follow * The work described in this article was supported in part by research grants from the Faculty Research Fund of the Horace H. Rackham School of Graduate Studies, University of Michigan, Ann Arbor, Mich., and by Research Grant RG-6101 from the National Institutes of Health, Public Health Service, Bethesda, Md.

PHYSIOLOGY OF INSECT DIAPAUSE. XI. CYANIDE-SENSITIVITY OF THE HEARTBEAT OF THE CECROPIA SILKWORM, WITH SPECIAL REFERENCE TO THE ANAEROBIC CAPACITY OF THE HEART

1. During the course of metamorphosis the heart of the Cecropia silkworm appears to undergo pronounced shifts in its sensitivity to cyanide.2. In the mature larva the heartbeat is promptly blocked by 10-3 M cyanide; in the adult moth it is even more sensitive and is brought to a standstill by 10-5 M cyanide.3. In the intervening pupal stage the heart is insensitive to acute poisoning by physiological concentrations of cyanide.4. This insensitivity is observed only in experiments of short duration. When the exposure to cyanide is continued for many hours, the pupal heartbeat is blocked by 10-2 or 10-5 M cyanide.5. The paradoxical response of the pupal heart can be accounted for in terms of a pronounced capacity for anaerobic metabolism which is peculiar to this particular stage. The pupal heart can beat for as long as 5½ hours in the complete absence of oxygen. During this same period the heart is insensitive to cyanide.6. While discounting any true insensitivity of the pupal heart to cyanide, the experime...

The cytochrome system of the Cecropia silkworm. II. Spectrophotometric studies of oxidative enzyme systems in the wing epithelium

As shown by spectroscopic studies, the wing epithelium of the Cecropia silkworm is typical of the insect’s non-muscular tissues in undergoing a virtual breakdown of the cytochrome system at the outset of pupal diapause, and a prominent resynthesis of this system when diapause is terminated. Further information on these marked changes has now been provided by spectrophotometric determinations of DPNH oxidase, succinate-cytochrome c reductase, DPNH-cytochrome c reductase, and cytochrome c oxidase activities in particulate preparations from wing homogenates. By the measurement of these activities, the changing concentrations of cytochromes c , b , b 5 and a + a 3 , respectively, have been followed during the course of metamorphosis. In the freshly pupated insect, all the cytochrome components are present in high concentration. However, during the next 24 h the wing loses all but a trace of its cytochrome system; cytochromes b and c decline in concentration by more than 95 % and, by present techniques, thus reach undetectable levels which then persist throughout diapause. Cytochromes b 5 and a + a 3 also decrease prominently, but to a lesser degree, and low concentrations of both components remain detectable in the diapausing wings. Several months later, when the insect’s prothoracic glands function to terminate diapause, cytochromes b and c reappear in detectable concentration. During the subsequent growth and development of the adult moth, b and c , together with a + a 3 and b 5 , once again return to a high level. These findings confirm the results of the earlier, spectroscopic studies, afford a quantitative insight, and provide an explanation for several metabolic peculiarities of the diapausing tissues, particularly their extremely low respiration and the virtual insensitivity of this respiration to cyanide or carbon monoxide. In addition, the present findings strongly support the view that cytochrome synthesis in Cecropia and its relatives is closely linked to the action of the prothoracic gland hormone. According to the present analysis, withdrawal of this endocrine support for growth at the outset of diapause is causally related to the breakdown of the cytochrome system. And when the endocrine organs recover their function to bring about the termination of diapause, resynthesis of the cytochrome system appears to represent at least one type of reaction which intervenes between the primary action of the prothoracic gland hormone and the insect’s developmental response.

The cytochrome system of the Cecropia silkworm. I. Spectroscopic studies of individual tissues

Except in the somatic muscles (which throughout metamorphosis retain a classical cytochrome system in high concentration), the cytochrome system of the Cecropia silkworm is known to undergo marked changes during the course of metamorphosis, especially in relation to the onset and termination of the pupal diapause. These changes have now been studied in individual tissues and organs by the technique of low-temperature spectroscopy. The larval tissues contain a complete cytochrome system including moderate to high concentrations of cytochromes a + a 3 , b , c and b 5 . By contrast, the tissues of the diapausing pupa show a seemingly incomplete cytochrome system in that components b and c are not detectable; cytochromes a + a 3 and b 5 persist in low though still detectable concentration. Consequently, the onset of pupal diapause is accompanied by a generalized decrease in concentration of the several cytochromes, including the virtual disappearance of b and c . Several months later, when the insect’s prothoracic glands function to terminate diapause, cytochromes b and c promptly reappear and, together with a + a 3 and b 5 , then undergo a progressive increase in concentration during adult development. The net result is that the post-diapausing tissues are re-equipped with a normal cytochrome system. In view of the intracellular localization of cytochromes a + a 3 , b and c in mitochondria, and that of b 5 in the endoplasmic reticulum, the results of the present study implicate prominent alterations in these organelles during the course of metamorphosis. And, since the growth and development of the post-diapausing insect are known to require the renewed presence and function of a normal cytochrome system, the resynthesis of this system at the termination of diapause is evidently closely linked to the action of the prothoracic gland hormone.

Histological study of regenerative processes after transsection of the nervi corporis cardiaci in transplanted brains of the cecropia silkworm (Platysamia cecropia L).

Histological study of regenerative processes after transsection of the nervi corporis cardiaci in transplanted brains of the cecropia silkworm (Platysamia cecropia L).

OXYGEN UPTAKE IN INSECTS WITH CYCLIC CO2RELEASE

1. The simultaneous determination of CO2 production and O2 uptake in Hadrocarabus problematicus Hrbst. is described. Both CO2 release and O2 uptake are cyclic, but there is some interburst O2 uptake.2. The diaferometrically recorded O2 uptake is discussed, and compared with the results as obtained with the Warburg technique.3. In diapausing pupae of the cecropia silkworm (Hyalophora cecropia) the continuous O2 uptake forms a larger percentage of the total amount of O2 consumption than in Hadrocarabus. Still there was found an initial maximum of O2 uptake of short duration at every CO2 burst.4. Some experiments on the CO2 dissociation curve of haemolymph of pupae of Sphinx ligustri are mentioned. There is evidence that in haemolymph a CO2-binding principle is present.5. The interaction of O2, haemolymph and CO2, resulting in a certain intertracheal pCO2 controlling spiracle movement, is discussed. Probably the pO2 is only indirectly involved in the triggering of spiracle opening.

An Ecdysial Membrane in the Locust Cuticle

Passonneau and Williams1 have described in the developing cecropia silkworm an ‘ecdysial membrane’ situated between pupal and adult cuticles. Richards2 has studied the fine structure of this membrane, but was unable to demonstrate clearly its nature and origin.

PHYSIOLOGY OF INSECT DIAPAUSE. X. AN ENDOCRINE MECHANISM FOR THE INFLUENCE OF TEMPERATURE ON THE DIAPAUSING PUPA OF THE CECROPIA SILKWORM

1. The termination of the pupal diapause of the Cecropia silkworm is potentiated by preliminary exposure to low temperature and, especially, to temperatures in the range 6 to 15° C.2. This effect is mediated by an endocrine mechanism which centers in the brain, and is specifically concerned with restoring the competency of the brain's neurosecretory cells to synthesize and secrete the brain hormone.3. The time required for the initiation of adult development at 25° C. is thereby reduced from 27 weeks to as little as one day.4. As soon as the brain has recovered its endocrine function, the catalytic effects of low temperature are at an end; the actual secretion of the hormone and the developmental response that follows are then favored by high temperature. In this manner the low temperatures of winter potentiate the initiation of adult development the following spring.5. The effects of low temperature on the inactive, diapausing brain are considered in detail. The action is apparently a direct one on temperature-sensitive reactions within the brain itself. The over-all process of activation shows the kinetics of a threshold reaction but not of an all-or-none reaction.6. These findings are discussed in the light of Van der Kloot's chemical and physiological studies of the brain of Cecropia. Within the substance of the brain the primary change induced by low temperature appears to be the synthesis and accumulation of a cholinergic substrate.

THE CONTROL OF NEUROSECRETION AND DIAPAUSE BY PHYSIOLOGICAL CHANGES IN THE BRAIN OF THE CECROPIA SILKWORM

1. The 26 neurosecretory cells in the brain of the Cecropia silkworm have been shown by Williams to undergo systematic changes in endocrine activity during metamorphosis. At the pupal molt the neurosecretory cells lose endocrine activity. Consequently, growth is checked and the animal enters pupal diapause. Endocrine activity is restored following prolonged exposure to low temperatures. When the brain hormone is released, diapause ends and the development of the adult moth begins.2. The electrical events in the brain as a whole have been studied in relation to these changes in endocrine activity. The larval brain shows abundant "spontaneous" electrical activity. However, on the day before the pupal molt the brain loses spontaneous activity and is no longer excited by direct electrical stimulation. The electrical silence of the brain persists throughout the months of diapause. Electrical activity reappears in the pupal brain a few days before the end of diapause.3. Cholinesterase (ChE) is present in high titer in the larval brain. However, two days before pupation the brain ChE begins a rapid decline, so at pupation ChE is undetectable in the brain. ChE does not reappear in the pupal brain until shortly before the recovery of electrical and endocrine activities. There is no evidence that an inhibitor of ChE is present in the diapausing brain. Evidently, ChE is absent or in low titer and is synthesized just before the onset of adult development.4. During diapause the cholinergic action of brain extracts steadily increases. The increase is slow in the brains of pupae stored at 25° C. and rapid in the brains of pupae stored at 15° or 6° C. Therefore the rate of accumulation of the cholinergic substance parallels the effectiveness of the temperature treatment in restoring the brain to endocrine activity.5. When ChE reappears in the brain, just before the onset of adult development, the titer of cholinergic substance in the brain falls to a low level. The low level is maintained until shortly before adult emergence, when the titer of cholinergic substance increases five-fold.6. Choline acetylase activity remains uniform in brain homogenates from unchilled and chilled pupae.7. The changes in electrical activity, ChE, and cholinergic substance during metamorphosis are peculiar to the brain. The ganglia of the ventral nerve cord retain normal function throughout diapause.8. ChE is synthesized in chilled pupal brains which are cultured at 25° C. in the absence of prothoracic glands. Under the same circumstances unchilled brains are unable to synthesize ChE. Moreover, exposure to the brain and the prothoracic gland hormones fails to promote the synthesis of ChE in unchilled pupal brains.9. ChE and electrical activity remain constant during the metamorphosis of Galleria, a non-diapausing insect. Two additional diapausing species, Telea polyphemus and Samia walkeri showed variations in brain ChE and electrical activity identical to those described in Cecropia.10. The evidence suggests that the pupal diapause of Cecropia results from the failure of the brain as a whole. The diapausing brain is electrically silent, apparently because of the absence of ChE. During diapause there is an accumulation of a cholinergic substance in the brain—an observation which suggests that the reappearance of ChE is elicited by high substrate concentrations. When ChE reappears, the brain becomes electrically active, the neurosecretory cells release brain hormone, and diapause is ended.

MICRO GASOMETRIC DETERMINATION OF DISSOLVED OXYGEN AND NITROGEN

Previous article No AccessJournal ArticlesMICRO GASOMETRIC DETERMINATION OF DISSOLVED OXYGEN AND NITROGENP. F. SCHOLANDER, L. VAN DAM, C. LLOYD CLAFF, and J. W. KANWISHERP. F. SCHOLANDERWoods Hole Oceanographic Institution, Marine Biological Laboratory, Woods Hole, Massachusetts, and Harvard Univ. Medical School, Boston, Massachusetts Search for more articles by this author , L. VAN DAMWoods Hole Oceanographic Institution, Marine Biological Laboratory, Woods Hole, Massachusetts, and Harvard Univ. Medical School, Boston, Massachusetts Search for more articles by this author , C. LLOYD CLAFFWoods Hole Oceanographic Institution, Marine Biological Laboratory, Woods Hole, Massachusetts, and Harvard Univ. Medical School, Boston, Massachusetts Search for more articles by this author , and J. W. KANWISHERWoods Hole Oceanographic Institution, Marine Biological Laboratory, Woods Hole, Massachusetts, and Harvard Univ. Medical School, Boston, Massachusetts Search for more articles by this author Woods Hole Oceanographic Institution, Marine Biological Laboratory, Woods Hole, Massachusetts, and Harvard Univ. Medical School, Boston, MassachusettsPDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Biological Bulletin Volume 109, Number 2October 1955 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.2307/1538732 Views: 38Total views on this site Citations: 4Citations are reported from Crossref © 1955 Marine Biological LaboratoryPDF download Crossref reports the following articles citing this article: John M. Teal , and Francis G. Carey The Metabolism of Marsh Crabs under Conditions of Reduced Oxygen Pressure, Physiological Zoology 40, no.11 (Sep 2015): 83–91.https://doi.org/10.1086/physzool.40.1.30152440JOHN W. KANWISHER TRACHEAL GAS DYNAMICS IN PUPAE OF THE CECROPIA SILKWORM, The Biological Bulletin 130, no.11 (Sep 2016): 96–105.https://doi.org/10.2307/1539956RAGNAR FÄNGE and JONATHAN B. WITTENBERG THE SWIMBLADDER OF THE TOADFISH (OPSANUS TAU L.), The Biological Bulletin 115, no.22 (Sep 2016): 172–179.https://doi.org/10.2307/1539023JOHN KANWISHER FREEZING AND DRYING IN INTERTIDAL ALGAE, The Biological Bulletin 113, no.22 (Sep 2016): 275–285.https://doi.org/10.2307/1539085