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Biomedical subjects

S W Applebaum

Publications and source records attributed to S W Applebaum.

At least 19 recordsLinked to original sources
PubMed2006

Tomato fruit size, maturity and alpha-tomatine content influence the performance of larvae of potato tuber moth Phthorimaea operculella (Lepidoptera: Gelechiidae).

Various physical and chemical properties of host plants influence insect larval performance and subsequent adult fitness. Tomato plants are relatively new hosts to the potato tuber moth, Phthorimaea operculella (Zeller), with the fruit being its preferred feeding site. However, it is unclear how the biochemical and physical properties of tomato fruits relate to potato tuber moth performance. Significant amounts of alpha-tomatine were detected in maturing green and ripening fruits of cherry (cv. Ceres) and processing (cv. Serio) types of tomatoes whereas none was detected in a fresh market variety (cv. Marglobe), at comparable stages. alpha-Tomatine is negatively and significantly correlated with development rate (head capsule size) of larvae reared in the fruits of the cherry and processing type tomatoes. Generally, survival, growth and development were significantly superior for larvae reared in the ripening fruits of the fresh market cultivar. At this stage, the fruits of this cultivar are also the largest. Based on these results it is concluded that fruit alpha-tomatine content, as well as fruit size and maturity, all affect performance of P. operculella larvae in the fruits of cultivated tomatoes.

Analysis of Variance↗
PubMed2005

Presence and titer of methyl palmitate in the Medfly (Ceratitis capitata) during reproductive maturation.

The relative amounts of methyl palmitate (MP) during the first 10 days post-eclosion were determined in whole-body extracts of adult female Ceratitis capitata by SIM monitoring of the 74 m/z fragment. MP peaks in receptive 3-day-old virgin females coincide with previously reported production of Juvenile Hormone (JH) by the corpus allatum (CA). Mating in the Medfly induces female non-receptivity. Indirect evidence suggests that the mevalonate pathway to sesquiterpene biosynthesis is underdeveloped in newly eclosed females. We propose that the pathway leading to synthesis of JH is markedly diverted in non-receptive virgin females to fatty acid synthesis, and partly so-in non-receptive mated females, leading to production of palmitic acid, presumably methylated thereafter. MP is depressed and remains marginal thereafter for the 7 days examined in the virgin female but goes through an apparent second cycle in the mated female. This contrasts with the consistent increase of allatal biosynthesis of MP of virgin and mated females previously reported and suggests additional control mechanisms in vivo. During the period of reduced receptivity following the first mating a second apparent peak of MP is observed. MP is a metabolic default metabolite of reproductively immature females whose putative role in reproductive physiology remains to be defined.

Animals↗
PubMed2003

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum.

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB(3) and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB(3) biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C(16:0) and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.

Animals↗
PubMed2003

Inhibition of pheromone biosynthesis in Helicoverpa armigera by pheromonostatic peptides.

Male insect accessory glands contain factors that are transferred during mating to the female, some inducing post-mating behavior, including the cessation of pheromone production, non-receptivity and the initiation of oviposition. One such factor is the Drosophila melanogaster sex-peptide (DrmSP). A pheromone suppression peptide, termed HezPSP, was identified in the moth Helicoverpa zea, isolated by HPLC and the active peak sequenced, but the activity of the synthesized peptide has not been reported to date. HezPSP bears no sequence homology to DrmSP. However, both peptides contain a disulfide bridge separated by an equal number, but dissimilar, amino acids. We herein report on the pheromonostatic activity of HezPSP partial peptides in the moth Helicoverpa armigera.

Amino Acid Sequence↗
PubMed2003

Biosynthetic maturation of the corpus allatum of the female adult medfly, Ceratitis capitata, and its putative control.

The major juvenile hormone (JH) homolog synthesized in vitro by the adult female Medfly (Ceratitis capitata) corpus allatum (CA) is JHB(3), with JH-III the minor homolog. Methyl-incorporation in vitro in post-eclosion virgin females is age-dependent. Basal activity occurs during the first four days post-eclosion and increases significantly thereafter, peaking at five days. Biosynthetic maturation of the mated female CA is delayed by one day and reduced considerably. The delayed response may be due to direct cerebral or neural inhibition. Synthetic Drosophila melanogaster sex peptide depresses JH biosynthesis by the Medfly female CA in vitro. Male-derived accessory gland peptides of the Medfly are transferred to the female during mating and a Medfly SP-analog may be responsible for down-regulation of JH synthesis by the CA in mated Medfly females. Mevinolin, an inhibitor of the mevalonate pathway, significantly reduces the biosynthesis of JHB(3), while farnesoic acid, a proximate precursor of JHIII, significantly stimulates the biosynthesis of both JHB(3) and JHIII in vitro.

Aging↗
PubMed2000

Population structure of the pestiferous moth Helicoverpa armigera in the eastern Mediterranean using RAPD analysis.

The genetic structure of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), was studied in the eastern Mediterranean. Moths were sampled in six locations (five in Israel, and one in Turkey) and their genetic relationship was analysed using RAPD-PCR. Three 10-oligonucleotide primers revealed 84 presumptive polymorphic loci that were used to estimate population structure. Results reveal low level of genetic distances among Israeli and Turkish populations. The estimated values of FST and theta for the eastern Mediterranean populations were very low across all populations, indicating a high level of gene flow. Four distinct RAPD-product profile types were defined, and found in all Israeli and Turkish populations. Although no isolation by geographical distance was detected, topographical barriers may play a role in such isolation.

Alleles↗
PubMed1999

Density-dependent physiological phase in insects.

Insects respond to crowding in a variety of ways that are usually exemplified by rapid changes in behavior and culminate in enduring long-term morphological and/or chromatic responses. A common feature of both short-term and long-term effects is that they are graded, dependent not only on density but also on the duration and on phase history of the maternal generation. Because of their exoskeletons, which are persistent for the duration of each instar and endure throughout adult life, overt changes in morphology or coloration are restricted to the molting period and shortly afterward, when cuticular hardening and pigmentation are expressed. Changes in internal organs or metabolism elicited by population density, being independent of integumental constraints, are not restricted to the molting period, but the temporal difference between internal and external responses is not of fundamental significance. Intraspecific responses to the presence of sibling insects are of apparent ecological significance and often involve directional movement and/or migration. They are mediated via the sensory system, involve signal transduction, and elicit downstream biochemical and physiological changes.

Journal Article↗
PubMed1996

Sex-peptide activates juvenile hormone biosynthesis in the Drosophila melanogaster corpus allatum.

Mating elicits two well-defined reactions in sexually matured females of many insects: reduction of receptivity and increased oviposition. These post-mating responses have been shown to be induced by factors synthesized in the reproductive tract of the adult male and transferred in the seminal fluid to the female during copulation. One of these factors, named sex-peptide (SP), has been identified in Drosophila melanogaster. Using an in vitro radiochemical assay, we show that synthetic sex-peptide considerably activates juvenile hormone III-bisepoxide (JHB3) synthesis in corpus allatum (CA) excised from Days 3 and 4 post-eclosion virgin females. Base levels are significantly lower at emergence (Day 0) than on subsequent days, and only weak stimulation is obtained on Day 1, while none is obtained on Day 2, where maximal basal synthesis occurs. The CA of mated females cannot be stimulated further for at least 7 days, but regain responsiveness by Day 10 after mating. Synthesis of JHB3 stimulated by SP in vitro persists for at least 4 h after removal of the peptide. Development of responsiveness of the CA to SP in vitro is compared with development of the post-mating reactions of sex-peptide injected virgin females. Our results suggest that the CA is a direct target for SP in vivo and that sexual maturity is established separately for the two post-mating reactions.

Animals↗
PubMed1995

Pathway and regulation of JHIII-Bisepoxide biosynthesis in adult Drosophila melanogaster corpus allatum.

Adult female Drosophila melanogaster corpus allatum (CA) synthesize JHB3 from endogenous and exogenous precursors in vitro. We present evidence supporting the thesis that biosynthesis proceeds from precursor FA via initial epoxidation and terminal methylation on the basis of the following: (1) Methyl farnesoate is not epoxidized to JHIII or JHB3; (2) Authentic JHIII is not epoxidized to JHB3; and (3) FABE is markedly metabolized to JHB3. Cerebral allatostatic factors act at some stage subsequent to FA and this precursor is not normally rate-limiting. Additionally, neural inhibition from the brain acts at some biosynthetic step prior to FA.

Animals↗
PubMed1994

The kinetics of nutrient incorporation into body tissues of gilthead seabream (Sparus aurata) females and the subsequent effects on egg composition and egg quality.

The interaction between essential dietary components and changes in tissue nutrient reserves, egg quality and egg composition, were studied from 60 d before and during the spawning of Sparus aurata broodstock. Fish were given isonitrogenous (550 g/kg dry weight) and isolipidic (100 g/kg dry weight) diets, based on protein and lipid extracts of squid meal. Diets differed in the levels of n-6 (10-30 mg/g dry weight) and n-3 (0-10 mg/g dry weight) essential fatty acids. The effects of these diets on biochemical and fatty acid composition of body tissues, and the subsequent effects on egg composition and egg viability were measured. Dietary essential fatty acids were mostly incorporated into the liver, ovaries, digestive tract and associated adipose tissues. The lipid composition of these tissues reached an equilibrium with dietary lipid composition within 15 d of feeding on any given diet. Muscle and gill cartilage tissues did not show any significant changes in their biochemical and fatty acid composition, even after 60 d feeding. Egg viability decreased significantly within 10 d of feeding the broodstock with a diet deficient in n-3 highly unsaturated fatty acids (n-3 HUFA). The levels of n-3 HUFA in both polar and neutral fractions of egg lipid were directly correlated with their levels in the broodstock diet. When the total amount of egg n-3 HUFA dropped below 17 mg/g dry weight, egg viability and larvae hatching rate decreased by 53% and 47% respectively. These results suggest that the biochemical composition of organs involved in S. aurata reproduction are highly sensitive to the nutritional value of the diet, which affects egg and larval quality rapidly.

Adipose Tissue↗
PubMed1991

Identification of a diuretic hormone of Locusta migratoria.

We have isolated a peptide from brains and corpora cardiaca of Locusta migratoria which is immunologically related to the diuretic hormone of Manduca sexta. We determined its structure as a 46 amino acid linear peptide with 43-50% identity to the M. sexta hormone. Moreover, we showed that the new peptide functions as a diuretic hormone in L. migratoria, stimulating urine production by Malpighian tubules and elevating levels of cAMP in tubules.

Amino Acid Sequence↗
PubMed1991

Regulation of juvenile hormone synthesis in wild-type and apterous mutant Drosophila.

Juvenile hormone (JH) is a major regulator of insect development and reproduction and its titer is determined largely by central nervous system regulation of JH synthesis by the corpora allata. To establish the basis for a molecular genetic dissection of the neuroendocrine system responsible for modulating JH titer, a radiochemical assay was utilized to examine JH synthesis in vitro by the isolated corpus allatum as well as the regulation of this synthesis by brain extracts of wild-type and apterous mutant Drosophila melanogaster females during reproductive maturation. JH production by glands of wild-type females increases in parallel with the progress of ovarian maturation, the major product of the adult corpus allatum being juvenile hormone 3 bis-epoxide (JHB3). Gland activity appears to be regulated by both the availability of JH precursors and the level of terminal oxidase(s) in the JH biosynthetic pathway. The brain contains an allatostatic factor, that is transmitted to the glands via nervous connections. Allatostatin production in the brain appears to be positively regulated by JHB3. Adult corpora allata from the mutants ap4 and ap56f synthesize very low levels of JH; additionally, brains of ap56f homozygotes lack allatostatic activity.

Animals↗
PubMed1990

Allatostatic regulation of juvenile hormone production in vitro by the ring gland of Drosophila melanogaster.

A factor(s) extracted from the third instar larval brains of the dipteran species Sarcophaga bullata and Drosophila melanogaster causes a dose-dependent reduction of juvenile hormone (JHB3) biosynthesis by isolated ring glands in vitro. In situ, this factor is presumably neuronally transmitted from the brain to ring gland. The allatostatic effect of the brain factor is reversible in vitro and may be overcome partially by the JHB3 precursor farnesoic acid. Agents which act to increase the intracellular levels of cAMP (3-isobutyl-1-methylxanthine (MIX), forskolin, 8-benzoyl cAMP) all caused the reduction of JHB3 synthesis in vitro in a reversible manner. The inhibitory effect of increased levels of cAMP was overcome by the addition of farnesoic acid to the culture medium. The dependence of JHB3 synthesis on extracellular calcium was demonstrated by incubation of ring glands in the presence of the Ca2+ channel blocker lanthanum chloride, and in Ca2(+)-free medium containing EGTA. The inclusion of farnesoic acid abolished the zero Ca2+ effect completely. However, the Ca2+ ionophore A23187 inhibited JHB3 production in medium containing Ca2+, suggesting that elevated intracellular levels of Ca2+ also suppress JHB3 production. This latter inhibition could not be reversed completely by farnesoic acid.

Animals↗
PubMed1990

Photoperiodic diapause in Drosophila melanogaster involves a block to the juvenile hormone regulation of ovarian maturation.

Females of Drosophila melanogaster held under short-day photoperiods at a moderately low temperature (12 degrees) enter a state of ovarian diapause in which yolk deposition in the oocytes is suspended (D. S. Saunders, V. C. Henrich, and L. I. Gilbert, Proc. Natl. Acad. Sci. USA 86, 3748-3752, 1989). An enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies raised against D. melanogaster yolk polypeptides (YPs) showed that diapausing flies synthesize and accumulate YPs in the hemolymph, but very little in the ovary. Nondiapausing females at the same temperature but at long days, and short-day flies in which diapause was broken by an upshift in temperature or topical application of juvenile hormone (JH), showed enhanced titers of YPs in the ovaries, suggesting stimulating uptake. Determinations of juvenile hormone bisepoxide (JHB3) and JH III synthesis in vitro by single excised corpora allata showed that glands from nondiapausing flies or corpora allata from flies in which diapause had been broken synthesized JH at a rate about four times higher than glands from diapausing flies. Corpora allata incubated in medium supplemented with farnesoic acid showed an increase in the rate of JH synthesis, but the increase was relatively greater with corpora allata from nondiapausing flies. Glands from diapausing flies presented the appearance of newly emerged or "immature" glands. Ovarian diapause is terminated at 12 degrees LD 10:14 in 7 days following topical application of either JH III or JHB3 at a concentration of about 0.5 micrograms per fly, diapause termination being expressed by an increased rate of vitellogenesis and by an increase in the number of fully developed eggs per vitellogenic female. It is concluded that the short-day-elicited diapause in D. melanogaster results from a "block" to the JH-stimulated uptake of yolk proteins from the hemolymph, caused by a reduced rate of JH synthesis by the corpus allatum. Photoperiodic regulation of the corpus allatum may be mediated via the brain.

Animals↗
PubMed1989

Developmental regulation of juvenile hormone biosynthesis by the ring gland of Drosophila melanogaster.

The synthesis in vitro of the putative dipteran juvenile hormone (JHB3) by ring glands isolated from third instar Drosophila melanogaster larvae was quantified by a radiochemical assay. The data indicate that JHB3 synthesis is developmentally regulated during the period prior to wandering until after puparium formation. The highest level of basal production occurred during the postfeeding stage, and synthesis declined after pupariation. Similar relative profiles of synthesis were obtained upon the addition of the JHB3 precursor, farnesoic acid, although the absolute levels of production were elevated considerably. Basal JHB3 production by brain-ring gland complexes in vitro was also highest during the postfeeding stage, although the synthetic rates were much lower than displayed by isolated ring glands. Further analysis revealed that methyl farnesoate, a JHB3 precursor, was synthesized by brain-ring gland complexes in significant quantity. A dual mechanism of brain-centered control of JHB3 biosynthesis is proposed.

Animals↗
PubMed1989

Juvenile hormone bisepoxide biosynthesis in vitro by the ring gland of Drosophila melanogaster: a putative juvenile hormone in the higher Diptera.

The in vitro production of juvenile hormone (JH) was investigated by using isolated ring glands from third instar Drosophila melanogaster. A JH-like molecule is secreted that comigrates with a synthetic sample of methyl 6,7;10,11-bisepoxy-3,7,11-trimethyl-(2E)-dodecenoate (JHB3) during TLC, liquid chromatography, and GC analysis. Purified product from farnesoic acid-stimulated ring glands was analyzed by electron impact GC/MS and gave a mass spectrum identical to synthetic JHB3. Additional structure confirmation was obtained following conversion of product from unstimulated biosynthesis to a derivative that comigrated on liquid chromatography with the derivative prepared from synthetic JHB3. Physiological studies revealed that JHB3 is produced solely by the corpus allatum portion of the ring gland in vitro. Isolated ring glands from other cyclorrhaphous dipteran larvae also produce JHB3 almost exclusively in vitro. Corpora allata from mosquito larvae, however, produce only JH III, indicating that JHB3 production may be restricted to the higher Diptera. Topically applied synthetic JHB3 caused developmental responses in newly formed D. melanogaster white puparia similar to those obtained with JH III. The data suggest that JHB3 is a fly juvenile hormone.

Animals↗
PubMed1989

Purification and characterization of trypsins from the digestive tract of Locusta migratoria.

Two trypsin-like enzymes were isolated from the digestive tract of the African migratory locust Locusta migratoria migratorioides. Primary purification was carried out on a DEAE-cellulose column, from which the two trypsins emerged in the anionic fraction. Further purification was achieved by affinity chromatography on a p-aminobenzamidine (PABA)-Sepharose column, which also separated the two trypsins (TLEAff.1. and TLEAff.2.), or by HPLC on an anion exchange column. The purity and homogeneity of the trypsins were demonstrated by electrophoresis of cellulose acetate strips and in polyacrylamide gels, with and without SDS. The molecular weights of TLEAff.1 and TLEAff.2, as determined by SDS-PAGE, were 17,000 and 24,000 respectively. The amino acid compositions of the locust trypsins were similar to those of trypsins from the digestive systems of other insects, which are characterized by the lack or low content of half cystines. The isoelectric points were 3.2 for TLEAff.1 and 3.5 fold for TLEAff.2. Since most of the locust trypsin comprised TLEAff.2, the latter served as the main object of this study. TLEAff.2 was unstable at low pH, differing in this respect from mammalian trypsins. The optimum activity was at pH 8.5-9.0. The Km and kcat, values were similar to those for bovine trypsin. Activation by substrate, a phenomenon in bovine trypsin, was also observed for TLEAff.2. The locust trypsin was full inhibited by the proteinaceous trypsin inhibitors Bowman-Birk (BBI) and Kunitz from soybeans, CI from chickpeas, chicken ovomucoid (COM), and turkey ovomucoid (TOM). It was inactivated by phenylmethylsulfonyl fluoride (PMSF) and tosyl-L-lysine chloromethyl ketone (TLCK), indicating the involvement of serine and histidine in the active site.

Amino Acids↗