Methyl farnesoate and juvenile hormone production in embryos of Diploptera punctata in relation to innervation of corpora allata and their sensitivity to allatostatin

An overview of the orexinergic system in different animal species

Orexin (hypocretin), is a neuropeptide produced by a subset of neurons in the lateral hypothalamus. From the lateral hypothalamus, the orexin-containing neurons project their fibres extensively to other brain structures, and the spinal cord constituting the central orexinergic system. Generally, the term ''orexinergic system'' usually refers to the orexin peptides and their receptors, as well as to the orexin neurons and their projections to different parts of the central nervous system. The extensive networks of orexin axonal fibres and their terminals allow these neuropeptidergic neurons to exert great influence on their target regions. The hypothalamic neurons containing the orexin neuropeptides have been implicated in diverse functions, especially related to the control of a variety of homeostatic functions including feeding behaviour, arousal, wakefulness stability and energy expenditure. The broad range of functions regulated by the orexinergic system has led to its description as ''physiological integrator''. In the last two decades, the orexinergic system has been a topic of great interest to the scientific community with many reports in the public domain. From the documentations, variations exist in the neuroanatomical profile of the orexinergic neuron soma, fibres and their receptors from animal to animal. Hence, this review highlights the distinct variabilities in the morphophysiological aspects of the orexinergic system in the vertebrate animals, mammals and non-mammals, its presence in other brain-related structures, including its involvement in ageing and neurodegenerative diseases. The presence of the neuropeptide in the cerebrospinal fluid and peripheral tissues, as well as its alteration in different animal models and conditions are also reviewed.

Juvenile hormone signaling in short germ-band hemimetabolan embryos

The role of juvenile hormone (JH) in insect embryos is far from understood, especially in short germ-band hemimetabolan species. To shed light on this issue, we depleted the mRNA levels of Krüppel homolog 1, Methoprene-tolerant and JH acid O-methyltransferase, key elements of JH signaling, in embryos of the short germ-band hemimetabolan species Blattella germanica This precluded the formation of the germ-band anlage in a group of embryos. Hatchability was also reduced, which might have been caused by premature upregulation of laccase 2, a promoter of cuticle tanning. In other cases, development was interrupted in mid embryogenesis, involving defects related to dorsal closure and appendage formation. These phenotypes possibly result from the low levels of Broad-complex (BR-C) produced under JH-depleted conditions. This contrasts with holometabolan species, in which JH does not promote BR-C expression, which remains low during embryo development. Possibly, the stimulatory role of JH on BR-C expression and the morphogenetic functions of BR-C in hemimetabolan embryos were lost in holometabolan species. If so, this might have been a key driver for the evolution of holometabolan metamorphosis.

The pleiotropic allatoregulatory neuropeptides and their receptors: A mini-review

Juvenile hormones (JH) are highly pleiotropic insect hormones essential for post-embryonic development. The circulating JH titer in the hemolymph of insects is influenced by enzymatic degradation, binding to JH carrier proteins, uptake and storage in target organs, but evidently also by rates of production at its site of synthesis, the corpora allata (CA). The multiple processes in which JH is involved alongside the critical significance of JH in insect development emphasize the importance for elucidating the control of JH production. Production of JH in CA cells is regulated by different factors: by neurotransmitters, such as dopamine and glutamate, but also by allatoregulatory neuropeptides originating from the brain and axonally transported to the CA where they bind to their G protein-coupled receptors (GPCRs). Different classes of allatoregulatory peptides exist which have other functions aside from acting as influencers of JH production. These pleiotropic neuropeptides regulate different processes in different insect orders. In this mini-review, we will give an overview of allatotropins and allatostatins, and their recently characterized GPCRs with a view to better understand their modes of action and different action sites.

Identification of putative ecdysteroid and juvenile hormone pathway genes in the shrimp Neocaridina denticulata

Although the sesquiterpenoid juvenile hormone (JH) and the steroidal ecdysteroids are of vital importance to the development and reproduction of insects, our understanding of the evolution of these crucial hormonal regulators in other arthropods is limited. To better understand arthropod hormone evolution and regulation, here we describe the hormonal pathway genes (e.g. those involved in hormone biosynthesis, degradation, regulation and signal transduction) of a new decapod model, the shrimp Neocaridina denticulata. The majority of known insect sesquiterpenoid and ecdysteroid pathway genes and their regulators are contained in the N. denticulata genome. In the sesquiterpenoid pathway, these include biosynthetic pathway components: juvenile hormone acid methyltransferase (JHAMT); hormone binding protein: juvenile hormone binding protein (JHBP); and degradation pathway components: juvenile hormone esterase (JHE), juvenile hormone esterase binding protein (JHEBP) and juvenile hormone epoxide hydrolase (JHEH), with the JHBP, JHEBP and JHEH genes being discovered in a crustacean for the first time here. Ecdysteroid biosynthetic pathway genes identified include spook, phantom, disembodied, shadow and CYP18. Potential hormonal regulators and signal transducers such as allatostatins (ASTs), Methoprene-tolerant (Met), Retinoid X receptor (RXR), Ecdysone receptor (EcR), calponin-like protein Chd64, FK509-binding protein (FKBP39), Broad-complex (Br-c), and crustacean hyperglycemic hormone/molt-inhibiting hormone/gonad-inhibiting hormone (CHH/MIH/GIH) genes are all present in the shrimp N. denticulata. To our knowledge, this is the first report of these hormonal pathways and their regulatory genes together in a single decapod, providing a vital resource for further research into development, reproduction, endocrinology and evolution of crustaceans, and arthropods in general.

Diploptera punctata as a model for studying the endocrinology of arthropod reproduction and development

The Pacific beetle cockroach, Diploptera punctata, has proven to be a valuable model insect in the study of the dynamics regulating juvenile hormone (JH) biosynthesis and metabolism, particularly during late nymphal development and reproduction. This stems in part from its unusual mode of reproduction, adenotrophic viviparity, in which females give birth to live young that have been nourished throughout embryonic development by a protein-rich 'milk' secreted by the wall of the brood sac or uterus. In this animal, as in most insects, JH regulates both vitellogenin production and its uptake by developing oocytes. However, JH has an antagonistic effect on embryonic development and following oviposition of the fertilized oocytes into the brood sac, JH production halts, in part through the action of a peptide family, the FGLa allatostatins. JH production remains at a low level throughout pregnancy and is only reinstated at the end of gestation, at which time, the next wave of oocytes begins to develop and enter vitellogenesis. Thus, JH production in this species is precisely regulated, since the appearance of JH at inappropriate times would result in abortion of the embryos. Numerous factors are responsible for the regulation of JH biosynthesis, including peptides, biogenic amines, neurotransmitters, ecdysteroids and second messenger effectors. In this review, we discuss these factors and highlight potentially fruitful areas of future research. Although several of the enzymes of the biosynthetic pathway have been cloned, the precise points of rate limitation remain uncertain. The dissection of the biosynthetic pathway and its control awaits the completion of the genome and transcriptome of this important model insect.

Function, diversity, and application of insect juvenile hormone epoxidases (CYP15)

Juvenile hormones (JHs) represent a family of sesquiterpenoid hormones in insects, and they play a key role in regulating development, metamorphosis, and reproduction. The last two steps of the JH biosynthetic pathway, epoxidation and methyl esterification of farnesoic acid to JH, are insect specific, and thus have long been considered a promising target for biorational insecticides. Recently, the enzymes involved in the last two steps have been molecularly identified: JH acid methyltransferase catalyzes the esterification step and the cytochrome P450 CYP15 enzyme catalyzes the epoxidation step. In this review, we describe the recent progress on the characterization of JH biosynthetic enzymes, with special focus on the function and diversity of the CYP15 family. CYP15 genes have evolved lineage-specific substrate specificity and regulatory mechanisms in insects, which appear to be associated with the lineage-specific acquisition of unique JH structure and function. In addition, the lack of CYP15 genes in crustacean (Daphnia pulex) and arachnid (Tetranychus urticae) species, whose genomes have been fully sequenced, may imply that CYP15 enzymes are an evolutionary innovation in insects to use the epoxide forms of methylated farnesoid molecules as their principal JHs. Molecular identification and characterization of CYP15 genes from broad taxa of insects have paved the way to the design of target-specific, biorational anti-JH agents.

Molting dynamics and juvenile hormone titer profiles in the nymphal stages of a lower termite, Cryptotermes secundus (Kalotermitidae)--signatures of developmental plasticity

Termites are social cockroaches and this sociality is founded on a high plasticity during development. Three molting types (progressive, stationary and regressive molts) are fundamental to achieve plasticity during alate/sexual development, and they make termites a major challenge to any model on endocrine regulation in insect development. As the endocrine signatures underpinning this plasticity are barely understood, we studied the developmental dynamics and their underlying juvenile hormone (JH) titers in a wood-dwelling termite, Cryptotermes secundus, which is characterized by an ancestral life style of living in dead wood and individuals being totipotent in development. The following general pattern elements could be identified during winged sexual development (i) regressive molts were accompanied by longer intermolt periods than other molting types, (ii) JH titers decreased gradually during the developmental transition from larva (immatures without wing buds), to nymph (immatures with wing buds), to winged adult, (iii) in all nymphal stages, the JH titer rose before the next molt and dropped thereafter within the first week, (iv) considerable variation in JH titers occurred in the midphase of the molting cycle of the 2nd and 3rd nymphal instar, inferring that this variation may reflect the underlying endocrine signature of each of the three molting types, (v) the 4th nymphal instar, the shortest of all, seems to be a switch point in development, as nymphs in this stage mainly developed progressively. When comparing these patterns with endocrine signatures seen in cockroaches, the developmental program of Cryptotermes can be interpreted as a co-option and repetitive use of hormonal dynamics of the post dorsal-closure phase of cockroach embryonic development.

Juvenile hormone and allatostatins in the German cockroach embryo

Levels of juvenile hormone III (JH), FGLamide allatostatin peptides (ASTs), ASTs precursor (preproAST) mRNA and methyl farnesoate epoxidase (CYP15A1) mRNA were measured in embryos of the cockroach Blattella germanica. JH starts to rise just after dorsal closure, reaches maximal levels between 60% and 80% of embryogenesis, and decrease subsequently to undetectable levels. ASTs show low levels during the first two thirds of embryogenesis, increase thereafter and maintain high levels until hatching. PreproAST mRNA shows quite high levels during the two days following oviposition, thus behaving as a maternal transcript, the levels then become very low until mid embryogenesis, and increase afterwards, peaking towards the end of embryo development. CYP15A1 transcripts were detected around 25% embryogenesis and the levels tended to increase through embryogenesis, although differences amongst the days studied were not statistically significant. The opposite patterns of JH and AST towards the end of embryo development, along with the detection of AST immunoreactivity in corpora allata from late embryos, suggest that JH decline is caused by the increase of AST. Moreover, the uncorrelated patterns of JH concentration and CYP15A1 mRNA levels suggest that CYP15A1 expression does not modulate JH production.

Neuropeptide receptor transcriptome reveals unidentified neuroendocrine pathways

Neuropeptides are an important class of molecules involved in diverse aspects of metazoan development and homeostasis. Insects are ideal model systems to investigate neuropeptide functions, and the major focus of insect neuropeptide research in the last decade has been on the identification of their receptors. Despite these vigorous efforts, receptors for some key neuropeptides in insect development such as prothoracicotropic hormone, eclosion hormone and allatotropin (AT), remain undefined. In this paper, we report the comprehensive cloning of neuropeptide G protein-coupled receptors from the silkworm, Bombyx mori, and systematic analyses of their expression. Based on the expression patterns of orphan receptors, we identified the long-sought receptor for AT, which is thought to stimulate juvenile hormone biosynthesis in the corpora allata (CA). Surprisingly, however, the AT receptor was not highly expressed in the CA, but instead was predominantly transcribed in the corpora cardiaca (CC), an organ adjacent to the CA. Indeed, by using a reverse-physiological approach, we purified and characterized novel allatoregulatory peptides produced in AT receptor-expressing CC cells, which may indirectly mediate AT activity on the CA. All of the above findings confirm the effectiveness of a systematic analysis of the receptor transcriptome, not only in characterizing orphan receptors, but also in identifying novel players and hidden mechanisms in important biological processes. This work illustrates how using a combinatorial approach employing bioinformatic, molecular, biochemical and physiological methods can help solve recalcitrant problems in neuropeptide research.

Reconstruction of ancestral FGLamide-type insect allatostatins: a novel approach to the study of allatostatin function and evolution

Allatostatins (ASTs) are a class of regulatory neuropeptides, with diverse functions, found in an array of invertebrate phyla. ASTs have complex gene structure, in which individual ASTs are cleaved from a precursor peptide. Little is known about the molecular evolution of AST structure and function, even in extensively studied groups such as cockroaches. This paper presents the application of a novel technique for the analysis of this system, that of ancestral reconstruction, whereby ancestral amino acid sequences are resurrected in the laboratory. We inferred the ancestral sequences of a well-characterized peptide, AST 7, for the insect ancestor, as well as several cockroach ancestors. Peptides were assayed for in vitro inhibition of JH production in Diploptera punctata and Periplaneta americana. Our results surprisingly, indicate a decrease in potency of the ancestral cockroach AST7 peptide in comparison with more ancient ones such as the ancestral insect peptide, as well as more recently evolved cockroach peptides. We propose that this unexpected decrease in peptide potency at the cockroach ancestor may be related to the concurrent increase in peptide copy number in the lineages leading to cockroaches. This model is consistent with current physiological data, and may be linked to the increased role of ASTs in the regulation of reproductive processes in the cockroaches.

Endocrine and reproductive differences and genetic divergence in two populations of the cockroach Diploptera punctata

The viviparous cockroach, Diploptera punctata, has been a valuable model organism for studies of the regulation of reproduction by juvenile hormone (JH) in insects. As a result of its truly viviparous mode of reproduction, precise regulation of JH biosynthesis and reproduction is required for production of offspring, providing a model system for the study of the relationship between JH production and oocyte growth and maturation. Most studies to date have focused on individuals isolated from a Hawaiian population of this species. A new population of this cockroach was found in Nakorn Pathom, Thailand, which demonstrated striking differences in cuticle pigmentation and mating behaviours, suggesting possible physiological differences between the two populations. To better characterize these differences, rates of JH release and oocyte growth were measured during the first gonadotrophic cycle. The Thai population was found to show significantly earlier increases in the rate of JH release, and oocyte development as compared with the Hawaiian population. Breeding experiments to determine the degree of interfertility between the two populations demonstrated greatly reduced fertility in crosses between the two populations. Additionally, levels of genetic divergence between the two populations estimated by sequencing a fragment of the mitochondrial 16S rRNA gene were surprisingly high. The significant differences in physiology and mating behaviours, combined with the reduced interfertility and high levels of sequence divergence, suggest that these two populations of D. punctata are quite distinct, and may even be in the process of speciation. Moreover, these studies have important implications for the study of JH function in the reproductive cycle of insects, as differences in timing of rates of JH biosynthesis may suggest a process of heterochrony in reproduction between the two populations.

RNA interference with the allatoregulating neuropeptide genes from the fall armyworm Spodoptera frugiperda and its effects on the JH titer in the hemolymph

The juvenile hormone (JH) titer was measured by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI). Three JH homologs, the JH I-III were detected in various amounts in larvae, prepupae and virgin adult females of Spodoptera frugiperda. In penultimate larvae, the JH II and III titers were relatively high, but decreased continuously during the 3 days of that stage, whereas JH I was detectable at low amounts only on the first 2 days. At the beginning of the last larval stage almost no JH could be detected but thereafter, a consistent low amount of JH III was present until the prepupal stage. In adult virgins, the JH titer peaked on the 2nd and 6th day after the imaginal molt. The measured hormone titers well agree with general lepidopteran physiology, because in larvae the JH titer should be high to prevent premature metamorphosis, but decrease in last instar larvae before pupation, whereas in adults JH returns to control various aspects of reproduction. JH biosynthesis is thought to be the main factor influencing the JH titer in the hemolymph and there is evidence that neuropeptides either act stimulatory (allatotropins) or inhibitory (allatostatins) on this process. After silencing of either the allatostatin AS-C-type (Spofr/Manse-AS) or the allatotropin AT 2 (Spofr-AT 2) gene the transcript level was reduced in brain and gut of last instar larvae as well as of adult S. frugiperda. This suppression led to an increased JH titer in larvae, suggesting an allatostatic activity of both the peptides in this stage. As a result of the elevated hormone titer, the last larval stage was prolonged. In prepupae, the JH titer was decreased, but the animals pupated and molted normally. In adult female virgin moths the effect on the JH titer was inversely dependent on the age of the moths and varied among the JH homologs, indicating that the peptides act either allatostatic or allatotropic. For both peptides, gene silencing clearly reduced the oviposition rates of adult females.

A Caenorhabditis elegans allatostatin/galanin-like receptor NPR-9 inhibits local search behavior in response to feeding cues

Movement in Caenorhabditis elegans is the result of sensory cues creating stimulatory and inhibitory output from sensory neurons. Four interneurons (AIA, AIB, AIY, and AIZ) are the primary recipients of this information that is further processed en route to motor neurons and muscle contraction. C. elegans has >1,000 G protein-coupled receptors (GPCRs), and their contribution to sensory-based movement is largely undefined. We show that an allatostatin/galanin-like GPCR (NPR-9) is found exclusively in the paired AIB interneuron. AIB interneurons are associated with local search/pivoting behavior. npr-9 mutants display an increased local search/pivoting that impairs their ability to roam and travel long distances on food. With impaired roaming behavior on food npr-9 mutants accumulate more intestinal fat as compared with wild type. Overexpression of NPR-9 resulted in a gain-of-function phenotype that exhibits enhanced forward movement with lost pivoting behavior off food. As such the animal travels a great distance off food, creating arcs to return to food. These findings indicate that NPR-9 has inhibitory effects on the AIB interneuron to regulate foraging behavior, which, in turn, may affect metabolic rate and lipid storage.

Juvenile hormone and methyl farnesoate production in cockroach embryos in relation to dorsal closure and the reproductive modes of different species of cockroaches

Juvenile hormone (JH), produced by the corpora allata (CA), is first detectable after dorsal closure, a conspicuous event in embryogenesis. The present research found that the timing of dorsal closure was consistently at about 45% of the total embryonic development time across most of the oviparous and ovoviviparous cockroach species examined. These included the ovoviviparous cockroaches Blaberus discoidalis, Byrsotria fumigata, Rhyparobia maderae, Nauphoeta cinerea, Phoetalia pallida, Schultesia lampyridiformis, and Panchlora nivea, as well as the oviparous cockroaches Blatta orientalis, Periplaneta americana, Eurycotis floridana, and Supella longipalpa. However, the only known viviparous cockroach Diploptera punctata completed dorsal closure at 20.8% of embryo development time. Methyl farnesoate (MF), the immediate precursor of JH III, is considered a functional molecule in crustaceans; however, in insects its function is still unclear. To understand the role of JH and MF in cockroach embryos, I compared JH and MF biosynthesis and release in several cockroach species of known phylogenetic relationships. Using a radiochemical assay, the present research showed that cockroach embryos representing all three reproductive modes produced and released both JH and MF, as previously shown for B. germanica, N. cinerea, and D. punctata. Members of a pair of embryonic CA from B. discoidalis, B. fumigata, R. maderae, and D. punctata were incubated with and without farnesol. MF accumulated in large amounts only in CA of R. maderae in the presence of farnesol, which indicates that control of the last step of biosynthesis of JH, conversion of MF into JH by MF epoxidase, is probably a rate-limiting step in this species.

Ecdysteroids and juvenile hormones of whiteflies, important insect vectors for plant viruses

Ecdysteroids and juvenile hormones (JHs) regulate many physiological events throughout the insect life cycle, including molting, metamorphosis, ecdysis, diapause, reproduction, and behavior. Fluctuation of whitefly ecdysteroid levels and the identity of the whitefly molting hormone (20-hydroxyecdysone) have only been reported within the last few years. An ecdysteroid commitment peak that is associated with the reprogramming of tissues for a metamorphic molt in many holometabolous and some hemimetabolous insect species was not observed in last nymphal instars of either the sweet potato whitefly, Bemisia tabaci (Biotype B), or the greenhouse whitefly, Trialeurodes vaporariorum. Ecdysteroids reach peak levels 1-2 days prior to the initiation of the nymphal-adult metamorphic molt. Adult eye and wing differentiation which signal the onset of this molt begin earlier in 4th instar T. vaporariorum (Stages 4 and 5, respectively) than in B. tabaci (Stage 6), and the premolt peak is 3-4 times greater in B. tabaci ( approximately 400 fg/microg protein) than in T. vaporariorum ( approximately 120 fg/microg protein). The JH of B. tabaci nymphs and eggs was found to be JH III, supporting the view that JHs I and II are, with rare exception, only present in lepidopteran insects. In B. tabaci eggs, JH levels were approximately 10 times greater on day 2/3 (0.44 fg/egg or 0.54 ng/g) than on day 5 (0.04 fg/egg or 0.054 ng/g) post-oviposition. Approximately, 1.4 fg/2nd-3rd instar nymph (0.36 ng/g) was detected. It is probable that the relatively high level of JH in day 2/3 eggs is associated with the differentiation of various whitefly tissues during embryonic development.

The role of allatostatins in juvenile hormone synthesis in insects and crustaceans

Allatostatins are pleiotropic neuropeptides for which one function in insects is the inhibition of juvenile hormone synthesis. Juvenile hormone, an important regulator of development and reproduction in insects, is produced by the corpora allata. Mandibular organs, the crustacean homologs of insect corpora allata, produce precursors of juvenile hormone with putatively similar functions. Three types of allatostatins in insects have been isolated: FGLamides, W(X)(6)Wamides, and PISCFs. All act rapidly and reversibly; however, although these types occur in all groups of insects studied, they act as inhibitors of juvenile hormone production in only some groups. Only the FGLamide-type peptides have been isolated in crustaceans, in which they may function to stimulate production of hormone by the mandibular glands, as occurs in early cockroach embryos. Much remains to be learned in order to understand the role of allatostatins in the modulation of hormone production.

Characteristic expression patterns of allatostatin-like peptide, FMRFamide-related peptide, orcokinin, tachykinin-related peptide, and SIFamide in the olfactory system of crayfish Procambarus clarkii

The olfactory system plays important roles in various crustacean behaviors. Despite numerous studies on different aspects of the olfactory neural pathway, only the decapod-tachykinin-related peptide (decapod-TRP) has been identified as a neuromodulator in this processing to date. To establish the functions of other related neuropeptides, we initially performed cDNA cloning of FMRFamide-related peptide (FaRP) and allatostatin (AST)-like peptide from the crayfish Procambarus clarkii, followed by in situ hybridization (ISH) analysis of these peptides, along with decapod-TRP, orcokinin, and crustacean-SIFamide. Cloned FaRP cDNA encodes seven copies of C-terminal RN(F/Y)LRFamide-containing peptide, whereas AST-like peptide cDNA comprises 29 copies of AST-like peptide (-YXFGLamide) and three additional putative peptides. ISH analysis of the brain revealed specific expression of crustacean-SIFamide mRNA in most projection neurons (cell cluster 10), and predominant localization of other mRNAs to interneurons. The data suggest that the crustacean-SIFamide neuropeptide is involved in output of the deutocerebrum to the protocerebrum. Double-fluorescence ISH data further disclose that, in cluster 9, orcokinin is coexpressed in decapod-TRP-specific interneurons, whereas AST-like peptide-containing cells do not overlap with orcokinin-expressing cells. On the other hand, FaRP-expressing cells overlap with both orcokinin- and AST-like peptide-specific cells. In cluster 11, where signals for AST-like peptide are absent, a number of interneurons express both decapod-TRP and orcokinin, emphasizing a close relationship between these two factors with regard to olfactory processing, and possibly tactile and/or visual sensory systems. These characteristic expression patterns of neuropeptides support their distinct involvement in the modulation of olfactory processing.

Regulation of methyl farnesoate production by mandibular organs in the crayfish, Procambarus clarkii: a possible role for allatostatins

Decapod crustaceans do not appear to produce juvenile hormone, but rather its immediate precursor, methyl farnesoate (MF). Both MF and its immediate precursor, farnesoic acid (FA) are produced by the mandibular organs (MO) in crustaceans. The MO are homologous to the insect corpora allata (CA), the site of juvenile hormone biosynthesis. However, the FGLamide allatostatin (ASTs) peptides, of which there are about 60 distinct forms reported from crustaceans, have previously been found to have no effect on MO activity in crustaceans. We have identified by immunocytochemistry the presence of FGLamide-like AST immunoreactivity in neurosecretory cells throughout the CNS as well as in neurohaemal structures such as the sinus gland and pericardial organs. The ASTs are likely delivered to the MO hormonally and/or by local neurohaemal release. Using MO from adult males, we have found wide variability between animals in the in vitro rates of MF and FA biosynthesis. Treatment with Dippu-ASTs has a statistically significant stimulatory effect on MF synthesis, but only in MO that are initially producing MF at lower rates. No effect on FA production was observed, suggesting that the FGLamide ASTs exert their effect on the o-methyl transferase, the enzyme responsible for the conversion of FA to MF.