Changes in lipid and fatty acid composition of eggs during development of the beet armyworm, Spodoptera exigua

The dry weight of Spodoptera exigua eggs decreased by 15·9 μg/egg or 64% of initial weight during embryogenesis and development of pharate first instar larvae. Lipid depletion accounts for 36% of this total dry weight loss and this occurs at an essentially constant rate throughout development. This marks S. exigua as an exception since most insects utilize lipids more rapidly during later developmental stages. Lipid depletion is due primarily to triglyceride catabolism, although phospholipids also decrease significantly.Fatty acid composition remains stable during development. In triglycerides, 18:1 is most common followed by 16:0 and 18:2; in the phospholipids, the order of abundance is 18:1, 18:2, and 16:0. Egg fatty acids differ from dietary fatty acids: 16:1 comprises 7% of triglyceride fatty acids although it is not present in the larval media; 18:1 predominates in the egg whereas 18:2 is most abundant in the diet.     

A plasmid sequence from Rhizobium leguminosarum 300 contains homology to sequences near the octopine TL-DNA right border

Summary The DNA sequence from a Rhizobium leguminosarum 300 (RL300) plasmid that contains homology to the T_c-DNA of Agrobacterium tumefaciens is described. The RL300 sequence has 78% homology to a 359 bp sequence in the T_c-DNA of pTi15955. The RL300 homology starts approximately 100 bp from the 24 bp border sequence of the T_L-DNA and ends approximately 3 bp from an IS66 homolog in the T_c-DNA. An unusual feature of the RL300 homology is the presence of 81 bp direct repeats with T_c-DNA homology, separated by 201 bp. One end of each direct repeat has a 12 bp palindrome. Four cloned sequences of RL300 with homology to the T DNA region were hybridized to plasmid lysates of RL300 derivatives to determine the source of each plasmid. The sequenced homolog, originally on pRH228, was isolated from pRL7JI; the other 3 homologs were isolated from the transmissable plasmids pRL7JI (pRH235) and pRL8JI (pRH235 and pRH236).     

Microhabitat segregation and physiological differences in co-occurring tiger beetle species,Cicindela oregona and Cicindela tranquebarica

Summary The daily movements of two co-occurring tiger beetle species were monitored in conjunction with changes in microclimate along streams in Northeast Arizona. Cicindela oregona and C. tranquebarica temporarily segregated across areas of beach exhibiting different microclimates. C. oregona progressively moved from the dry upper beach to the wet stream edge as beach temperatures increased and humidity decreased. The actively foraged throughout the day in this moist habitat at air temperatures between 25 and 38°C. C. tranquebarica remained on the dry, upper portions of the beach and shuttled between sun and shade at air temperatures above 35°C. Only when stream edge temperatures exceeded 30°C was tranquebarica found in this subhabitat. Both species exhibited physiological tolerances in the laboratory that were consistent with their microhabitat preferences in the field. Although both species had similar high lethal temperatures (47–48°C) in saturated air, oregona died at lower temperatures (39–43°C) than tranquebarica (46–47°C) under dry (0% RH) conditions. C. oregona was considerably more active than tranquebarica at body temperatures below 30°C and exhibited higher levels of active metabolism between 25 and 40°C. In addition, C. tranquebarica exhibited significantly lower water loss rates than oregona at 30, 35 and 40°C.     

D-isomeric replacements within the 6-9 core sequence of Ac-[Nle4]-alpha-MSH4-11-NH2: a topological model for the solution conformation of alpha-melanotropin

Analogs of Ac-[Nle⁴]-α-MSH_4–11-NH₂ and Ac-[Nle⁴, D -Phe⁷]-α-MSH_4–11-NH₂ were prepared with D -isomeric replacements at the His⁶, Arg⁸, and Trp⁹ residues. The requirement for an indole moiety at position 9 also was evaluated by replacement with L -leucine in both parent fragment analogs. D -isomeric replacements at positions 6 and 8 in either series were detrimental to biological potency in frog (Rana pipiens) and lizard skin (Anolis carolinensis) in vitro melanotropic assays. However, Ac-[Nle⁴, D -Trp⁹]-α-MSH_4–11-NH₂ and Ac-[Nle⁴, D -Phe⁷, D -Trp⁹]-α-MSH_4–11-NH₂ were equipotent and 10 × more potent than Ac-[Nle⁴]-α-MSH_4–11-NH₂, respectively, in the lizard skin bioassay, and 30 and 1900 times more potent in the frog skin bioassay. Ac-[Nle⁴, D -Phe⁷, D -Trp⁹]-α-MSH_4–11-NH₂ was 3 × more potent than α-MSH in the frog skin bioassay. Proton nmr studies in aqueous solution revealed a marked preservation of the backbone conformation of these linear analogs. Chemical-shift variations due to the through-space anisotropic influence of the core aromatic amino acid residues permitted evaluation of side-chain topology. The observed topology was consistent with nonhydrogen-bonded β-like structure (? = ?139°, ψ = +135° for L -amino acids; ? = +139°, ψ = ?135° for D -amino acids) as the predominant solution conformation. The biological and conformational data suggest that high melanotropic potency requires a close spatial arrangement of the His⁶, Phe⁷, and Arg⁸ side chains.     

Cyclic lactam analogues of Ac-[Nle4]alpha-MSH4-11-NH2

Two side-chain cyclic lactam analogues of the 4-11 fragment of alpha-melanocyte-stimulating hormone (alpha-MSH), Ac-[Nle4,D-Orn5,Glu8]alpha-MSH4-11-NH2 and Ac-[Nle4,D-Orn5,D-Phe7,Glu8]alpha-MSH4-11-NH2, were prepared on p-methylbenzhydrylamine resin by using a combination of N alpha-Boc and N alpha-Fmoc synthetic strategies with diphenyl phosphorazidate mediated cyclization. The melanotropin activities of these two analogues were examined and compared relative to those of alpha-MSH, Ac-[Nle4]alpha-MSH4-11-NH2, and Ac-[Nle4,D-Phe7]alpha-MSH4-11-NH2. In the frog (Rana pipiens) skin bioassay, the L-Phe7 17-membered ring cyclic analogue was slightly more potent than the linear Ac-[Nle4]alpha-MSH4-11-NH2 and exhibited prolonged melanotropic bioactivity (greater than or equal to 4 h). In this same assay, the D-Phe7 cyclic analogue was more than 100-fold less potent than the L-Phe cyclic analogue and was 10,000 times less potent than linear Ac-[Nle4,D-Phe7]alpha-MSH4-11-NH2. In the lizard skin (Anolis carolinensis) bioassay, the L-Phe7 cyclic analogue was 100-fold less potent than Ac-[Nle4]alpha-MSH4-11-NH2, while the D-Phe7 cyclic analogue was 10,000-fold less potent than both Ac-[Nle4]alpha-MSH4-11-NH2 and the D-Phe7 linear derivative Ac-[Nle4,D-Phe7]alpha-MSH4-11-NH2. The solution conformation of these two cyclic analogues in dimethyl sulfoxide-d6 was examined by 1D and 2D 500-MHz 1H NMR spectroscopy. Our analysis suggests an H bond stabilized C10 (or C13) turn for the D-Phe7 cyclic structure while the L-Phe7 analogue is more conformationally flexible.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and biological actions of melanin concentrating hormone

A melanin (melanosome) concentrating hormone, MCH, was synthesized and the methodology for its synthesis is detailed. This heptadecapeptide, H-Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val-OH , stimulated melanosome concentration (centripetal aggregation) within melanophores of all species of teleost fishes studied. Melanosome aggregation in response to MCH was not blocked by Dibenamine as was the response to norepinephrine (NE), demonstrating that melanosome aggregating responses to MCH and NE are mediated through separate receptors. Melanosome aggregation in response to MCH was reversed by an equimolar concentration of alpha-melanocyte stimulating hormone (alpha-MSH). In contrast, MCH stimulated melanosome dispersion (centrifugal movement) within melanophores of a frog (Rana pipiens) and a lizard (Anolis carolinensis). Therefore, MCH exhibits both melanosome concentrating and dispersing actions depending upon the species studied.     

Formation of novel central and peripheral connections between molluscan central neurons in organ cultured ganglia

An in vitro organ culture system for buccal ganglia of the adult snail, Helisoma, is described. The system supports: (1) maintenance of characterstic electrophysiological parameters of identified neurons over seven days of culture; (2) choline metabolism including uptake and synthesis over the same duration; (3) sprouting and growth of neurons in response to axotomy; (4) the formation of novel central electrotonic connections between identified neurons as a result of sprouting and growth. These observations on neuronal growth and the formation of connections are similar to those made with in vivo culture. The use of in vitro culture allows precise manipulations not previously possible. When buccal ganglia are cultured in vitro with the cut distal ends of peripheral nerve trunks held closely apposed, axons of neurons 5R and 5L in the nerve trunks are capable of forming electrotonic connections similar to central connections. The capability of these neurons to form electrotonic connections via their peripheral axons implies that special structures (i. e., central neurites) are not required for the formation of connections; and neither are special environments (i. e., the central neurites) required for these connections.