@article{holbrook_schal_2004, title={Maternal investment affects offspring phenotypic plasticity in a viviparous cockroach}, volume={101}, ISSN={["1091-6490"]}, DOI={10.1073/pnas.0400209101}, abstractNote={Maternal effects, crossgenerational influences of the mother's phenotype on phenotypic variation in offspring, can profoundly influence the fitness of offspring. In insects especially, social interactions during larval development also can alter life-history traits. To date, however, no experimental design, to our knowledge, has manipulated the prenatal and postnatal environments independently to investigate their interaction. We report here that the degree of maternal nutrient investment in developing embryos of the viviparous cockroachDiploptera punctatainfluences how quickly neonate males become adults and how large they are at adulthood. An offspring's probability of reaching adulthood in fewer than four molts increased with birth weight: the heavier neonates were, consequently, more likely to become smaller adults. Social interaction also affected nymphal development and adult size. Nymphs reared in pairs molted fewer times than solitary nymphs and, thus, became smaller adults. The social effect on developmental trajectory was, however, eliminated by experimentally increasing the level of maternal nutrient investment per offspring, which was accomplished by removing one of the female's paired ovaries (allometric engineering). We conclude that a particular prenatal environment can result in different offspring phenotypes under different postnatal social conditions. By investing more in each offspring, however,D. punctatamothers, because they are viviparous, are able to produce broods with environmentally (socially) independent phenotypes.}, number={15}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Holbrook, GL and Schal, C}, year={2004}, month={Apr}, pages={5595–5597} }
 @article{tillman_holbrook_dallara_schal_wood_blomquist_seybold_1998, title={Endocrine regulation of de novo aggregation pheromone biosynthesis in the pine engraver, Ips pini (Say) (Coleoptera : Scolytidae)}, volume={28}, ISSN={["0965-1748"]}, DOI={10.1016/S0965-1748(97)00117-3}, abstractNote={In vivo and in vitro radiotracer studies were conducted with the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), to elucidate the relationships among feeding on host (Pinus jeffreyi Grev. & Balf.) phloem, juvenile hormone III (JH III) biosynthesis, and de novo aggregation pheromone (ipsdienol) biosynthesis. The in vivo incorporation of [1-14C]acetate into ipsdienol by male I. pini increased with increasing dose of topically-applied JH III, demonstrating the stimulatory role by JH III in de novo pheromone production. In vivo incorporation of (RS)-[2-14C]mevalonolactone into ipsdienol by male I. pini was not affected by increasing JH III dose. However, injection of [14C]mevalonolactone resulted in significantly higher levels of [14C]ipsdienol than those observed in saline-injected controls. This is direct evidence for the mevalonate-based isoprenoid pathway in de novo ipsdienol biosynthesis, and suggests that in this pathway JH III does not influence enzymatically-catalyzed reactions subsequent to the conversion of 3-hydroxy-3-methylglutaryl-coenzyme A to mevalonate. An additional in vivo [14C]acetate study demonstrated that de novo ipsdienol biosynthesis is also stimulated by feeding on host phloem. Lastly, an in vitro radiotracer study utilizing L-[methyl-3H]methionine demonstrated that feeding stimulates JH III biosynthesis by the corpora allata (CA) of male, but not female, I. pini. Analysis by radio-high pressure liquid chromatography revealed that JH III is likely the type of juvenile hormone produced by the male CA. These data support a sequence of events leading to feeding-induced de novo pheromone biosynthesis in male I. pini: (1) feeding on host phloem; (2) feeding-dependent JH III biosynthesis by the CA; and (3) JH III-stimulated de novo ipsdienol biosynthesis.}, number={9}, journal={INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY}, author={Tillman, JA and Holbrook, GL and Dallara, PL and Schal, C and Wood, DL and Blomquist, GJ and Seybold, SJ}, year={1998}, month={Sep}, pages={705–715} }
 @article{holbrook_chiang_lee_lin_schal_1998, title={Juvenile hormone synthesis in relation to corpus allatum development in embryos of the viviparous cockroach Diploptera punctata}, volume={33}, ISSN={["2157-0272"]}, DOI={10.1080/07924259.1998.9652343}, abstractNote={Summary Few studies have addressed endocrinology of the corpora allata (CA) in insect embryos. We now report on development and biosynthetic activity of CA in embryos of a viviparous cockroach, Diploptera punctata. When newly-eclosed adult females of D. punctata were mated, they oviposited and gave birth, respectively, about 8 and 73 days later; thus, gestation and corresponding embryogenesis lasted approximately 65 days. Dorsal closure, which coincides with differentiation of the CA, was concluded when embryos were about 13 days old and had completed 20% of embryogenesis. Reverse phase-high performance liquid chromatography revealed that embryonic CA released predominantly juvenile hormone III (JH) in vitro. Furthermore, an in vitro radiochemical assay showed that between day 28 of embryogenesis (43% of embryonic development completed) and hatch rates of JH synthesis rose, plateaued and then fell. When CA activity was increasing or was high, from day 28 to 54 (83% development), mitosis occurred at low an...}, number={1}, journal={INVERTEBRATE REPRODUCTION & DEVELOPMENT}, author={Holbrook, GL and Chiang, AS and Lee, YJ and Lin, CY and Schal, C}, year={1998}, month={Jan}, pages={69–79} }
 @article{chiang_holbrook_cheng_schal_1998, title={Neural control of cell size in the corpora allata during the reproductive cycle of the cockroach Diploptera punctata (Dictyoptera : Blaberidae)}, volume={33}, ISSN={["0168-8170"]}, DOI={10.1080/07924259.1998.9652339}, abstractNote={Summary Rising and subsequent falling rates of juvenile hormone (JH) synthesis occurred concurrently with synchronous growth and atrophy of CA cells during the ovarian cycle in mated adult females of Diploptera punctata. Ultrastructural observations revealed that growth of CA cells resulted from synchronous proliferation of cellular machinery required for JH synthesis. Cell growth was suppressed in CA of virgin females, in which rates of JH synthesis remained low, but was stimulated by mating or by severance of nerves leading from the brain to the CA. Atrophy of CA cells during declining rates of JH synthesis was due to synchronous autophagy of cellular organelles. While the mechanism initiating autophagy is unclear, it is independent of nervous connections between the CA and brain. We propose that under normal physiological conditions the quantity of JH synthesized by a corpus allatum is determined largely by the total amount of cellular machinery available for JH production. Therefore, the cycle of JH s...}, number={1}, journal={INVERTEBRATE REPRODUCTION & DEVELOPMENT}, author={Chiang, AS and Holbrook, GL and Cheng, HW and Schal, C}, year={1998}, month={Jan}, pages={25–34} }
 @article{holbrook_schal_1998, title={Social influences on nymphal development in the cockroach, Diploptera punctata}, volume={23}, ISSN={["1365-3032"]}, DOI={10.1046/j.1365-3032.1998.232077.x}, abstractNote={Solitary male nymphs of the cockroach Diploptera punctata (Eschscholtz) (Blattaria: Blaberidae) took significantly longer to reach adulthood than males paired with either a male or female nymph or grouped with four other male nymphs since birth. When isolated throughout nymphal development, 15.8% of males passed through 3 stadia before adult eclosion, and the remainder went through 4 stadia. In contrast, 61.3% of paired males became adults in 3 stadia. Males need not, however, be isolated or paired for the entire nymphal period to express isolated or paired patterns of development. About 60% of males paired in just the first stadium or its initial 9 days became adults in 3 stadia, and only 20.4% of males isolated in the first stadium and the first 3 days of the second reached adulthood within 3 stadia. Although the first stadium was a critical period in which social condition determined the course of future development, analyses of covariance showed that isolated males gained less weight than paired ones, not only in the first stadium, but in the second as well. Moreover, the degree of growth of a male in the second stadium, measured as either weight gain or relative growth rate, did not depend on the male’s social condition in the first stadium, because isolated second‐instar males grew less than paired ones, even when both sets of insects had been paired in the first stadium. Female nymphal development, unlike that of males, was not greatly affected by social factors.}, number={2}, journal={PHYSIOLOGICAL ENTOMOLOGY}, author={Holbrook, GL and Schal, C}, year={1998}, month={Jun}, pages={121–130} }
 @article{holbrook_chiang_schal_1997, title={Improved conditions for culture of biosynthetically active cockroach Corpora allata}, volume={33}, DOI={10.1007/s11626-997-0063-9}, abstractNote={Currently, short-term culture of insect corpora allata is most often performed in TC199. We now show that L-15B, a medium widely used in arthropod tissue culture, is superior to TC199 for both short- and long-term culture of cockroach corpora allata. In 3-h and 48-h incubations, juvenile hormone biosynthesis by corpora allata from Diploptera punctata was significantly higher in L-15B than in TC199. In addition, in both media, corpora allata activity was significantly improved by flotation of glands at the medium surface. Characteristics of L-15B responsible for its superiority were examined by comparison of gland activities in several TC199 formulations that had been modified in different ways to be more similar to L-15B. Adjusting the osmotic pressure of TC199 (288 mOsm/l) to near that of L-15B (362 mOsm/l) and D. punctata hemolymph (360 mOsm/l) significantly improved gland activity during the second 12 h of a 36-h incubation. Increasing the concentrations of amino acids, sugars, and organic acids in TC199 to the same levels as in L-15B significantly improved gland activity during both the second and third 12-h intervals of a 36-h incubation. These results suggest that L-15B is superior to TC199 because L-15B is isoosmotic with D. punctata hemolymph and because L-15B, like cockroach hemolymph, contains a high level of organic constituents. It is therefore more appropriate to use L-15B than TC199 for short-term in vitro assays of juvenile hormone biosynthesis and for extended corpora allata culture.}, number={6}, journal={In Vitro Cellular & Developmental Biology. Animal}, author={Holbrook, G. L. and Chiang, A. S. and Schal, C.}, year={1997}, pages={452–458} }
 @article{schal_holbrook_bachmann_sevala_1997, title={Reproductive biology of the German cockroach, Blattella germanica: Juvenile hormone as a pleiotropic master regulator}, volume={35}, ISSN={["0739-4462"]}, DOI={10.1002/(SICI)1520-6327(1997)35:4<405::AID-ARCH5>3.0.CO;2-Q}, abstractNote={Juvenile hormone (JH) exerts major pleiotropic effects on cockroach development and reproduction. The production of JH by the corpora allata (CA) in the adult female German cockroach, Blattella germanica, is dependent upon and modulated by both internal and environmental stimuli. Mating, intake of highquality food, social interactions, and the presence of vitellogenic ovaries facilitate JH synthesis. Conversely, starvation, deficient diets, enforced virginity, isolation, and a pre- or post-vitellogenic ovary cause the CA to produce less JH. Sensory stimulation of the genital vestibulum by the ootheca also inhibits the CA via signals that ascend the ventral nerve cord. All these stimulatory and inhibitory signals are integrated by the brain, and a preponderance of favorable signals results in a graded lifting of brain inhibition, permitting the synthesis and release of JH. The effects of inhibitory signals on JH biosynthesis can be lifted experimentally by severing nervous connections between the brain and the CA. Such an operation accelerates activation of the CA. Besides controlling gonadal maturation in females, JH concurrently regulates the production of sexual signals, including both attractant- and courtship-eliciting pheromones, and the behavioral expression of calling (pheromone release) and sexual receptivity. Although JH is required for the expression of copulatory readiness in female B. germanica, it appears that signals associated with copulation (spermatophore, sperm, accessory secretions) can inhibit this behavioral state even when titers of JH are permissive for receptivity. These observations suggest that JH might regulate sexual receptivity in females indirectly through}, number={4}, journal={ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY}, author={Schal, C and Holbrook, GL and Bachmann, JAS and Sevala, VL}, year={1997}, pages={405–426} }
 @article{holbrook_chiang_schal_1996, title={Allatostatin inhibition and farnesol stimulation of corpus allatum activity in embryos of the viviparous cockroach, Diploptera punctata}, volume={32}, ISSN={["0739-4462"]}, DOI={10.1002/(SICI)1520-6327(1996)32:3/4<341::AID-ARCH7>3.3.CO;2-X}, abstractNote={Juvenile hormone (JH) biosynthesis by corpora allata (CA) from embryos of the cockroach Diploptera punctata was measured at four stages during the latter half of embryogenesis. Individual glands from 32-day-old embryos that had completed 49% of embryonic development synthesized 0.3 pmol JH III h−1. By day 46 (70% development) gland activity rose to 1.1 pmol JH h−1, but on subsequent days JH synthetic rates declined, measuring only 0.8 pmol h−1 on day 56 (86% development) and 0.5 pmol h−1 on day 60 (92% development). Differences in JH biosynthesis by CA from different-aged embryos were more evident when gland activity was corrected for either corpus allatum cell number, which increased progressively from fewer than 200 cells per gland on day 32 to almost 700 cells per gland on day 60, or embryo mass, which increased from 1.6 mg per embryo on day 32 to 10.8 mg per embryo on day 60. JH biosynthetic rates were significantly inhibited in a medium containing 10−8 M Dip-allatostatin 7 which suppressed CA activity by 68, 83, 76, and 51% on days 32, 46, 56, and 60, respectively. In all embryonic stages JH production was significantly stimulated by incubation of glands with 200 μM farnesol, a late precursor in the JH biosynthetic pathway. © 1996 Wiley-Liss, Inc.}, number={3-4}, journal={ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY}, author={Holbrook, GL and Chiang, AS and Schal, C}, year={1996}, pages={341–352} }