Juvenile hormone-induced vitellogenesis in Apterous4, a non-vitellogenic mutant in Drosophila melanogaster

D. melanogaster females homozygous for the ap⁴ mutant synthesize yolk protein and circulate this protein in the haemolymph at concentrations not different from concentrations found in normal females. However, ap⁴ females deposit little or no yolk protein into developing oöcytes. Topical application of a juvenile hormone analogue (JHA), ZR-515, stimulated sequestration of yolk protein by developing oöcytes of ap⁴ females. JHA had no detectable effects on haemolymph concentrations of yolk protein in either normal or ap⁴ females nor on the protein profiles obtained from electrophoresis of haemolymph samples.     

Transfer and fate of male secretions deposited in the spermatophore of females of Acanthoscelides obtectus Say (Coleoptera Bruchidae)

During mating, males of Acanthoscelides obtectus deposit a spermatophore in the female genital tract. Spermatophore structure subsequently undergoes considerable modification, especially the central portion, which becomes vacuolated. Two methods were used to show that certain male secretions could thus pass into female haemolymph. When young males were injected with [¹⁴C]-arginine or [¹⁴C]-histidine, the accessory glands actively incorporated the isotope and the resulting spermatophores were radioactive. After mating, spermatophore radioactivity declined and then appeared in the haemolymph of females and in the oöcytes after a delay. Immunoelectrophoresis also showed that antigens appeared in the haemolymph of females after mating which reacted against male-gland antiserum. This technique, however, did not enable us to detect the presence of male antigens in the oöcytes formed after mating. The fate of some male secretions in the female and their physiological importance in the control of the female reproductive function were analysed in the present work.     

Yolk deposition in Douglas-fir beetle oöcytes: Possible rôle of RNA synthesis in the follicular epithelium

RNA synthesis and morphological changes in the follicular epithelial cells of oöcytes of Douglas-fir beetle, Dendroctonus pseudotsugae were studied during the reproductive phase. Inhibition of synthesis of DNA dependent RNA by actinomycin D injections blocked yolk deposition in the oöcytes as well as oviposition within the normal period. A mixture of radioactively labelled haemolymph and ovarial proteins was deposited as yolk proteins in the oöcytes of normal beetles. Such proteins were not deposited in the oöcytes of females injected with actinomycin D; the blockage of yolk deposition persisted even when such females were treated extraneously with juvenile hormone.     

Gene-controlled incorporation of haemolymph protein into the ovaries of Bombyx mori

The haemolymph protein concentration in Bombyx mori decreases normally by about one-fourth during pharate adult development. In females homozygous for the small egg gene, the concentration of haemolymph protein remained constant throughout the pupal and pharate adult stages. The sm gene does not influence the synthesis of vitellogenic female protein of pupal and pharate adult haemolymph (FP). Normal ovaries transferred to the haemocoele of sm females undergo normal vitellogenesis. In the absence of normal alleles of sm, the ovaries encounter difficulties in the incorporation of FP into their oöcytes from pharate adult haemolymph. These results suggest that an active translocation mechanism is involved in the transfer of haemolymph protein into the ovaries.     

Synthesis and deposition of yolk protein in adult Drosophila melanogaster

Newly eclosed Drosophila melanogaster females contain only previtellogenic stage oöcytes and no immunologically detectable female specific haemolymph protein. During the subsequent 48 hr the concentration of female specific protein in the haemolymph rises to a plateau value of 21 μg/μl; at this time yolk protein represents about one third of the total haemolymph protein in adult females. The first mature (stage 14) oöcytes are observed at 48 hr post eclosion. The female specific haemolymph protein and the major protein from mature oöcytes are electophoretically and immunologically the same or very similar. Injection of alpha amanitin into newly eclosed females inhibits the development of mature oöcytes and the degree of inhibition depends on the age of the female at the time of injection. Phenocopies of non-vitellogenic mutants result when alpha amanitin is injected into newly eclosed females; after 36 hr post eclosion no visible inhibition of vitellogenesis (as observed morphologically at 72 hr post eclosion) can be produced by alpha amanitin.     

Haemolymph vitellogenin,juvenile hormone,and oöcyte growth in the adult cockroach Nauphoeta cinerea during first pre-oviposition period

In the cockroach Nauphoeta cinerea the incorporation of a protein of low solubility into the oöcytes begins at day 5 of its adult life. An immunologically identical protein appears in the haemolymph two days earlier. The concentration of this protein, i.e. ‘vitellogenin’ in the haemolymph increases up to the onset of yolk incorporation into the oöcytes. During ovarian development no correlation could be detected between vitellogenin titre and several other parameters (ovary dry weight, length of the basal oöcytes, haemolymph protein concentration, body weight and age when ovulation occurred). In young females vitellogenin titre depends on the age, i.e. the volume of the corpora allata and hence on the presence and the titre of JH. During the period of egg maturation the total haemolymph protein concentration generally tends to drop while materials not precipitable by trichloracetic acid circulate at higher concentration after ecdysis and before ovulation.Early decapitation prevents vitellogenin synthesis and oöcyte growth, but when JH is applied to decapitated females, the normal vitellogenin titre is re-established, ovarian development, however, cannot be fully resumed. A dose-response curve shows that serial application of the hormone is much more effective than single large doses. Farnesylmethylester, a JH mimic, is about a hundred times less active, but more persistent than JH. Copulation seems to enhance the synthesis and release of endogenous JH, while food and water uptake are necessary to guarantee and optimal ovarian development. JH and high vitellogenin titre never restore ovarian development in females deprived of food and/or water or in those decapitated shortly after ecdysis.     

Juvenile hormone induces ovarian development in diapausing cave-dwelling Drosophila species

Drosophila grisea and macroptera were collected in caves overwintering as adults. The females remained in a state of reproductive diapause which extended until May for macroptera and until July for grisea, whereas the males of both species had mature sperm at all times. Termination of the reproductive diapause under laboratory conditions was accomplished in grisea by exposing them to 14 hr of illumination daily and in macroptera by increasing the temperature to 20°C. Topical application of juvenile hormone (JH) on diapausing grisea caused a prompt termination of diapause and maturation of oöcytes within 10 days. Yolk proteins were found in the haemolymph of diapausing flies but not in their ovaries. In the JH-treated flies, yolk proteins were found in both the haemolymph and the ovaries, suggesting that in this species JH regulates the uptake of yolk proteins.     

Vicilin-derived peptides are transferred from males to females as seminal nuptial gift in the seed-feeding beetle Callosobruchus maculatus

The fate of vicilins ingested by Callosobruchus maculatus and the physiological importance of these proteins in larvae and adults have been recently investigated. Vicilins have been demonstrated to be absorbed through the midgut epithelium, circulate in their trimeric form in the haemolymph and are deposited in the fat body. In fat body cells of both sexes, vicilins are partially hydrolyzed and the fragments are eventually deposited in the eggs. Tracking the fate of FITC-labelled vicilins in adult males revealed that the labelled vicilin fragments were also detected in oöcytes and eggs, when the males copulated with non-labelled females. Based on the results presented here, we propose that following absorption, vicilins accumulate in the fat body, where they are partially degraded. These peptides are retained throughout the development of the males and are eventually sequestered by the gonads and passed to the female gonads during copulation. It is possible that accumulation in the eggs is a defensive strategy against pathogen attack, as these peptides are known to have antimicrobial activity. The contribution of vicilin-derived peptides from seminal fluids may be an investment that helps to increase the offspring survival. This study provides additional insights into the possible contributions of males to female fecundity following copulation in C. maculatus.     

Vitellogenin fluctuations in haemolymph and fat body and dynamics of uptake into oöcytes during the reproductive cycle of Diploptera punctata

Haemolymph and fat body soluble protein titres have been examined during the reproductive cycle of Diploptera punctata, with particular emphasis on the occurrence of vitellogenin and its uptake into the developing oöcytes. Vitellogenin was first detected in the haemolymph of mated females 2 days after adult eclosion at about the same time that vitellin deposition in basal oöcytes began. Peak haemolymph titres of vitellogenin occurred on day 6, correlated with the completion of yolk uptake. Thereafter vitellogenin levels declined and were generally undetectable throughout most of gestation, rising again shortly before parturition in association with the second gonotrophic cycle. Total haemolymph protein levels were not correlated with vitellogenesis.Soluble fat body vitellogenin titres of mated females remained low during the first oöcyte growth period but then rose several-fold at its completion and remained high throughout pregnancy and the second gonotrophic cycle. Total fat body soluble proteins decline after adult eclosion in association with oöcyte growth.Vitellin accumulation in basal oöcytes was related linearly to increase in volume until the onset of chorion formation. Thus no post-vitellogenic growth period was detected.     

Studies of the reproductive physiology of Cimicidae (Hemiptera)—I. Fecundation and egg maturation

Observations were made under controlled conditions to determine the time required for the spermatozoa to reach various points in their migration. Special organs at the base of the ovarioles serve to hold the sperm until eggs are ready for fertilization. In virgin and mated females egg maturation is similar up to an early stage of yolk deposition, at which time eggs of the virgin females are resorbed. Ligation and implantation experiments indicate that the corpus allatum is essential for egg maturation. Its secretion does not become effective until at least 10 hr after feeding and is required for egg maturation to continue. Virgin females may be induced to produce eggs by corpora allata implants. Implants from males and virgin females as well as mated females are effective. External application of farnesol has an effect on egg maturation similar to corpus allatum implantation.     

Endocrine control of vitellogenin synthesis and vitellogenesis in Triatoma protracta.

The corpus allatum (CA) is required for vitellogenesis in the blood-sucking reduviid, Triatoma protracta, as seen by the total lack of yolk deposition in allatectomized females. Normally the CA becomes active within a day after emergence. After a period of activity during which unfed virgins may mature a few eggs, the CA is inhibited via its neural connectives from the brain. The CA is activated by mating, while a blood meal provides an additional stimulus for vitellogenesis. If the ventral nerve cord (VNC) is severed within 48 hr after copulation, the mating stimulus does not get through. However, the pathway of the feeding stimulus does not involve the VNC. The brain does not have any allatotropic or gonadotropic function in this species.A female-specific protein (vitellogenin) was identified by immunoelectrophoresis in the haemolymph of egg-maturing females. This protein is taken up by the oöcytes immunologically unaltered and forms the bulk of the yolk. Allatectomy at emergence prevents the appearance of the vitellogenin, and the topical application of JH_III to allatectomized females led to its synthesis de novo, as shown by the incorporation of labelled precursors into vitellogenin. From its mobility in polyacrylamide gels of different concentrations, the molecular weight of the yolk protein is estimated to be 4.37 × 10⁵ daltons.     

Änderungen im muster der Haemolymphproteine von adulten Königinnen der Hummelart Bombus terrestris

The soluble proteins of haemolymph during the life cycle from adult bumblebee queens (Bombus terrestris) were separated by disk electrophoresis on polyacrylamide gels. Twenty-three fractions stainable with amido black were detected. Every phase of the bee's adult life is characterized by a specific pattern of haemolymph proteins.Newly emerged queens have a low haemolymph protein concentration which increases in the first 5 days to a maximum. The high concentration is probably connected with the synthesis of hibernation reserves. Before the beginning of hibernation the concentration of some protein fractions seems to decrease; the concentration of these fractions is low also after hibernation.During the spring the first oöcytes begin to grow and the activity of corpora allata, hypopharyngeal glands, and wax glands reaches a maximum at the time of starting nests. A large increase in the concentration of haemolymph proteins is correlated with the activity of these glands. This high concentration does not change during the whole egg-laying period; however, the concentration decreases to a minimum in old queens with degenerating ovaries.In the protein pattern of ovary homogenate we detected three fractions with an RF identical to haemolymph fractions. Investigations on queens parasitized with the nematode Sphaerularia bombi confirmed that these fractions are yolk material (vitellogenin) taken up by ovaries. In parasitized queens oöcytes do not grow and the fractions are of a much lower concentration than in nonparasitized queens with maturing eggs. Therefore it appears that the parasite injures primarily the corpora allata known to stimulate the synthesis of yolk protein.     

The scheduling of spawning with the moult cycle in Northern krill (Crustacea: Euphausiacea): a strategy for allocating lipids to reproduction

Summary

Euphausiids moult and grow throughout their life, which implies sharing of resources between growth and reproduction for adult krill. In the Northern krill, Meganyctiphanes norvegica (M. Sars), female krill produce eggs cyclically. Spawning moult cycles alternate with vitellogenic moult cycles for lipid yolk accumulation. Histology shows that lipids are associated with the R cells of the digestive gland in both sexes, with the yolk platelets of mature oocytes and with the fat body cell membranes and blood lacunae in reproducing females. Mature female krill can have a total lipid content twice as high as males, mostly due to accumulation in the ovary, the fat body and the haemolymph. In contrast, in males, as well as in non-reproducing females, the highest percentage of lipids is found in the digestive gland and the haemolymph. In Meganyctiphanes norvegica, the most abundant lipid fractions are polar lipids and triglycerides, the latter being relatively low in reproducing female gonad and fat body. Triglycerides are believed to be a pure energy source and polar lipids are essential for membrane development in embryos. The fatty acid content and composition of the triglyceride and polar lipid fractions in females are different from males, related to both reproductive and dietary processes. Higher levels of polyunsaturated fatty acids (PUFA) in the polar lipid fraction were found in reproductive females. During the non-reproductive season, the converse was found, indicating the specific role PUFA and other fatty acids play in growth and egg production. Adaptive processes linked to reproduction were studied comparatively in three populations of the Northern krill—Clyde Sea (W, Scotland), Kattegat (E, Denmark), Ligurian Sea (Mediterranean)—all differing considerably in climatic and trophic conditions. Such adjustments in lipid synthesis and storage are viewed as reproductive strategies developed by the Northern krill in response to different environmental conditions.     

Hormonal aspects of oögenesis in the flies Phormia regina and Sarcophaga bullata

The corpora allata (CA) and median neurosecretory cells (MNC) of Phormia regina and Sarcophaga bullata become active with increasing age of the fly, on a diet of sugar alone. To prevent or retard oögenesis the CA or MNCs must be removed shortly after emergence, with subsequent protein meals. Topical JH application partially compensates for CA or MNC removal. This shows that the MNC activate the CA, and not vice versa. The trauma of either operation slightly depresses egg development.Injection of ecdysone into both species in the stage of initial yolk deposition causes the primary oöcytes to degenerate. This leads to development of the penultimate oöcytes. Older and younger egg stages are not sensitive to ecdysone. In P. regina the application of JH to females with developing primary oöcytes stimulates yolk deposition in the penultimate oöcytes.     

Quantitative Untersuchungen zum Dotterprotein-Haushalt der Honigbiene (Apis mellifica)

Zusammenfassung Die löslichen Hämolymph-, Ovarund Eiproteine der Honigbiene wurden elektrophoretisch auf Celluloseacetat-Streif en und Polyacrylamid-Gelen aufgetrennt. Die dominierende Hämolymph-Fraktion (60–80%) ist ein Weibchen-spezifisches Protein. Korrespondierende Fraktionen sind im Ovar und in ungefurchten Eiern zu finden. Aufgrund verschiedener Ergebnisse wird es als sehr wahrscheinlich angesehen, daß diese Fraktionen das Dotter-Material (= Vitellogenin) reprentieren. Bei Apis besteht das Vitellogenin nur auseiner Protein-Bande ohne Kohlenhydrat-Komponenten.Der Titer des Dotter-Proteins in der Hämolymphe hängt vom physiologischen Zustand der weiblichen Bienen ah. Bei der Arbeiterin ist nur während der Ammen-Tätigkeit Vitellogenin in der Hämolymphe zu finden, bei der Königin dagegen permanent und zu allen Jahreszeiten. Bemerkenswerterweise ist bei begatteten und eierlegenden Königinnen die Konzentration des Dotter-Materials in der Hämolymphe niedriger als bei unbegatteten und adulten, nicht-eierlegenden.Die Proteinsynthese-Raten wurdenin vivo nach Injektion eines¹⁴C-Aminosäuren-Gemisches bestimmt. Zur Messung der Radioaktivität der einzelnen Pherogramm-Banden wurde ein Methan-Durchflußzähler verwendet. Bei intensiver Legetätigkeit einer Königin liegt die Rate der Vitellogenin-Synthese dreimal höher als die der nicht-weibehen-spezifischen Blutproteine. Ungefähr 85% der vom Fettkörper abgegebenen Proteine sind Dotter-Material. Im Gegensatz zu anderen Insekten synthetisieren auch nicht-eierlegende Königinnen Vitellogenin; in diesem Falle liegt die Syntheserate jedoch nicht höher als die der übrigen Serum-Proteine. Der Verbleib des Dotter-Materials bei solchen Königinnen ist unbekannt. Im Ovar verläuft die Synthese der Euplasma-Proteine ungefähr mit der gleichen Rate wie die der nicht-weibchen-spezifischen Hämolymph-Fraktionen. Im Vergleich mit allen anderen Proteinen tritt die Markierung des Ovar-Dotters verspätet auf. Daraus kann geschlossen werden, daß das Dotter-Material nicht innerhalb des Ovars synthetisiert wird. Dieser Schluß wird außerdem durch den Befund gestützt, daß der Anstieg der spezifischen Aktivität der Dotter-Proteine im Ovar erst zu einem Zeitpunkt erfolgt, in dem in der Hämolymphe keine freien¹⁴C-Aminosäuren mehr verfügbar sind. Auf das Markierungs-Maximum der Dotter-Proteine folgt ein relativ rascher Abfall der spezifischen Aktivität. Aus den Werten kann die Vitellogenese-Dauer eines einzelnen Follikels mit 2 Tagen bestimmt werden. Bis zur Eiablage werden anschließend noch 2 weitere Tage benötigt, in denen die Glykogen-Synthese und Chorion-Bildung ablaufen.

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Quantitative investigations on vitellogenic protein metabolism in the honey bee (Apis mellifica)

Summary The soluble proteins of the haemolymph, ovary and eggs of the honey bee were separated by electrophoresis on cellulose acetate foils and on polyacrylamide gels. The predominant haemolymph fraction (60–80%) is a female-specific protein. Corresponding fractions are found in the ovary and in uncleaved eggs. According to the results, it is highly probable that these fractions represent the yolk material or vitellogenin. InApis, this vitellogenin is represented by only one protein band which carries no carbohydrate components.The haemolymph titre of vitellogenic protein depends on the physiological state of the female bees. In the worker bees, haemolymph yolk proteins are detectable only during the nurse age, whereas in queens they can be found throughout the year. It may be noted that in the mated and egg producing queens the concentration of vitellogenin in the haemolymph is lower than in virgin queens and in adult non-laying queens.The rate ofin vivo protein synthesis was determined by injecting a mixture of¹⁴C-amino acids and measuring the radioactivity in pherogram bands using a methane flow counter. In the actively laying queen the rate of vitellogenin synthesis is 3 times higher than that of the non-sex-specific blood proteins. Approximately 85% of the labeled proteins which are released from the fat body are yolk material. In contrast to other insects, non-laying queens were also found to synthesize vitellogenin; however, the rate did not exceed that of the other serum proteins. The fate of yolk material in such females is unknown. In the ovary, synthesis of the euplasmic proteins occurs at a rate similar to that of the nonspecific haemolyph fractions. The appearance of radioactivity in the ovarian yolk is delayed compared with all other proteins. This indicates that these proteins are labeled byde novo synthesis, whereas the yolk is not built up within the ovary. This conclusion is further supported by the fact that the increase in specific radioactivity of ovarian yolk proteins occurs at a time when free¹⁴C-amino acids are no longer available in the haemolymph. Following the maximum intensity of labelling of yolk proteins the specific activity declines. From the data it can be estimated that the period of vitellogenesis for a single follicle is 2 days; 2 additional days of maturation, during which glycogen synthesis and chorion formation occur, are required before oviposition.

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Herrn H. Fahrenhorst danke ich für Hilfe bei den Bienen-Arbeiten, Frl. B. Höltken und Frl. A. Rath für sorgfältige technische Assistenz, Frl. M. Krink für Zeichenhilfe bei den Abbildungen. Ein Teil der Untersuchungen wurde durch eine Herrn Prof. Dr. K. Bier gewährte Sachmittel-Zuwendung des Landesamtes für Forschung in Nordrhein-Westfalen gefördert     

Dummy Egg Production by Female Cardinalfish to Deceive Cannibalistic Males: Oogenesis without Vitellogenesis

Filial cannibalism occurs in a variety of taxa, especially in fish exhibit paternal care. In the Apogonidae, males mouthbrood a cohesive mass of eggs received from a single female, although the males frequently eat the entire brood. It has been recognized that a primary factor concerning entire brood cannibalism is the brood size produced by females, as the parent eats a small egg mass so long as the reproductive return does not exceed the cost of providing care. In Apogon lineatus, approximately 18% of each brood was occupied by abnormal eggs lacking yolk, which were hydrated without the vitellogenesis phase and eventually ovulated with other normal eggs as a single egg mass. By not providing yolk to some eggs within the brood, A. lineatus females may succeed in producing an apparently large brood, reducing the likelihood of entire brood cannibalism by males.     

Côntrole neuroendocrine des protéines sanguines vitellogenes d'Anacridium aegyptium sain et parasite

The changing patterns of haemolymph proteins were followed in male and female adults of normal and parasitized Anacridium aegyptium during diapause (autumn, winter) or during activity (spring) of their endocrine system without or with electrostimulations of the pars intercerebralis (PI).The haemolymph protein concentration is high in winter and decreases in spring. It is comparatively depleted in locusts infected by the fly Metacemyia calloti. However, the depletion is significant only in ‘castrated’ females.Fifteen protein fractions were resolved by polyacrylamide disk gel electrophoresis in haemolymph of normal and infected locusts during diapause and activity. Some fractions decrease in quantity during activity in males, normal females, and parasitized females with complete ovarian development. One fraction disappears in females with mature eggs and seems correlated with formation of the eggshell. Eight others protein fractions exhibit electrophoretic mobility identical to the 7 protein fractions of homogenates of eggs. There is little doubt that these haemolymph protein fractions are involved in yolk synthesis and are thus ‘vitellogenic’. One of these ‘vitellogenic’ fractions (band 6) is larger in yolk than in blood.Five protein fractions were demonstrated by electrophoresis of homogenates of parasites. Their electrophoretic mobilities are similar to those of 5 of the 8 haemolymph ‘vitellogenic’ fractions of the host. There is little doubt that these 5 haemolymph protein fractions (one of them is the band 6) are involved in the nutritional requirements of the parasite.Electrostimulation of the PI, during diapause and activity, increase the haemolymph protein concentration and chiefly the protein concentration of the blood band 6. Thus, the median neurosecretory cells of the brain (M-NSC) regulate protein synthesis and chiefly the synthesis of ‘vitellogenic’ proteins.In parasitized females, the increase of the haemolymph protein concentration after electrostimulations of the PI is associated with an enhancement of ovarian development. The depletion of the haemolymph protein concentration in ‘castrated’ females is thus involved in the inability of the oöcytes to sequester available proteins from the haemolymph. The haemolymph protein deficiency may be attributed to (1) an impairment of protein synthesis, attendant upon the hypoactivity of the M-NSC, and (2) the nutritional requirements of the parasite.     

Mating affects reproductive investment into eggs,but not the timing of oogenesis in the flesh fly <Emphasis Type="Italic">Sarcophaga crassipalpis</Emphasis>

We examined the effects of mating on reproductive investment and the timing of oogenesis in the flesh fly Sarcophaga crassipalpis by exposing females to males or not. All females exposed to males were mated within a few days and we found that mating affected reproductive investment. Virgin females not exposed to males produced a large clutch of eggs (∼91), but females exposed to males and mated produced 10% more. There was no effect of mating on egg length or mass. There was also no effect of mating on the timing of oogenesis. Females in both treatments provisioned their eggs at the same rate with yolk first becoming visible in the oocytes on day three of adulthood and complete provisioning of eggs occurring by the seventh day of adulthood. We examined the biochemical basis of egg provisioning by identifying the yolk proteins and quantifying their blood titer during the oogenic period in both, females exposed to males and mated and those not exposed to males. There was no difference in the timing of the first appearance, peak titer, or disappearance of yolk proteins in the blood between the two treatments. However, consistent with our observation of greater egg production in mated females, these females contained a greater peak yolk protein titer.     

The presence of a common embryonic blastema for ovarian and testicular parenchymal (follicular,interstitial and tubular) cells in cattle,Bos taurus

Summary The early embryonic gonadal development in the cattle is characterized by the appearance of an alkaline phosphatase positive blastema. Its derivatives in gonads of both sexes, follicular cells in the female and interstitial cells in the male, also show positive alkaline phosphatase reaction. Primordial germ cells are equally alkaline phosphatase positive, but loose this activity when they later transform to oögonia and oöcytes, or to spermatogonia respectively. Using the enzyme activity as label to trace these constituents in the developmental steps of the bovine gonads, the following results were obtained.Differentiation processes leading to the appearance of the sex cords take place in situ within the gonadal blastema which occupies the main central part of the gonadal fold. It is essentially a segregation process of the follicular cell cords or of the interstitial cells and the tubular primordia from the undifferentiated common anlage.The so-called germinal epithelium is not involved in the differentiation of sex cords. Its participation — if any — in the gonadal development is restricted to a very short and rather early period. Secondary sex cords (Pflügers cords) do not occur. In the cattle there is no reason to assume a cortico-medullary antagonism in the sex determined gonadal development.It can be assumed that the follicular cells in the ovary and the interstitial cells in the testis are homologous. This applies possibly also to the tubular cells of the testis. Homology should be admitted also for the rete structures, which remain small and undeveloped in the ovary while in the male they show considerable development.In the ovary the follicular cell cords differentiating within the central blastema match in a junctional zone with the peripheral layer of oögonia. These are taken up by the most peripheral branches of the follicular cell cords, thus transforming to ovigerous cords. During the downward movement within these cords the germ cells transform to oöcytes which for their part proceed through first meiotic prophase and reach the dictyotene stage. The maturation of the germ cells seems to be controlled by the follicular cells and may even temporarily get out of control until an adequate number of follicular cells is found in vicinity of individual oöcytes to form primordial follicles.The alkaline phosphatase reaction reveals the presence of numerous persisting remnants of follicular cell cords in the developing and even adult ovary.It is suggested that the findings in the cattle gonads can be applied also to other mammals, mainly to those with longer gestation periods like man.Contribution No 58-66, Department of Biology, City of Hope Medical Center. This work was supported in part by a grant (CA 05138) from the National Cancer Institute, U.S. Public Health Service. The project was undertaken during a five-month visit to Dr. Ohno's laboratory by the senior author whose expenses were covered by the Deutsche Forschungsgemeinschaft.     

Control of reproduction in female cockroaches with special reference to Nauphoeta cinerea—I. First pre-oviposition period

Prior to the first oviposition, a receptivity centre, perhaps neurosecretory cells in the brain, controls the female's acceptance of courting males. In L. maderae this centre is affected by starvation. A brief exposure to food can induce mating but is inadequate for oöcyte development. Before the first ovulation starvation has no effect on receptivity in N. cinerea.

In N. cinerea mechanical stimulation caused by the firm insertion of the spermatophore in the bursa copulatrix releases stimuli via the nerve cord to the brain which render the female unreceptive and, at the same time, increases the activity of the corpora allata resulting in rapid development of the oöcytes.

The mechanical presence of the oötheca in the uterus also has two principal effects. Like spermatophore insertion, it inhibits mating. But its effect on the corpora allata is inhibitory, rather than stimulatory, and, consequently, the oöcytes remain underveloped for almost the entire gestation period. The effectiveness of inhibitory stimulation from the stretched uterus depends upon the period in the reproductive cycle in which it occurs-i.e. on the physiological state of the female. In N. cinerea uterine stretching inhibits mating and oöcyte development after oviposition or during gestation but is not effective when exerted during the first pre-oviposition period. In P. surinamensis, uterine stretching does not inhibit the corpora allata prior to the first ovulation but does prevent oöcyte development during gestation.

In fed L. maderae and N. cinerea there appears to be a synergistic action of nutrition and mating in controlling the rate of oöcyte development. Mating (mechanical) and feeding (chemical) stimuli are both usually required for activating the corpora allata to their fullest extent so that the oöcytes mature at their maximum rate. There is some indication that mating stimuli in N. cinerea and L. maderae are effective in further stimulating the corpora allata only if the corpora allata have reached a certain level of activity, if activating stimuli have begun to occur in the brain, or if the mating stimulus occurs in combination with nutritional factors. Thus, the corpora allata in starved virgin females of N. cinerea become sufficiently active so that some yolk is deposited in the oöcytes but these oöcytes do not mature; mating is effective in further stimulating the endocrine glands in these starved females and oviposition occurs in about the normal period. In starved virgins of L. maderae the corpora allata are virtually inactive and yolk is not deposited in the oöcytes; mating has no effect on oöcyte development in starved females. D. punctata differs from both the above species in that the corpora allata in the virgin female usually remain inactive whether she feeds or starves. Mating stimuli alone can activate the corpora allata, in fed or starved females, and consequently the oöcytes mature.