The uptake of organic molecules by the ventral tube of Tomocerus flavescens (Tullberg, 1871) (Insecta: Collembola)

The net influx of water-soluble organic molecules by the ventral tube of Tomocerus flavescens, a soil litter-inhabiting Collembolan, was investigated. The following substances were tested: [¹⁴C]urea, [¹⁴C]glycerol, [¹⁴C]erythritol, [¹⁴C]l-leucine, [¹⁴C]d-glucose, [³H]inulin. The animals were exposed to moist filter paper containing a specific test solution. When they evert their ventral-tube vesicles, they absorb water and solutes through the cuticle and the transport epithelium into the body haemolymph. Contamination by radioactive substances and oral solute uptake was avoided by an experimental device. It is evident that the uptake rates decrease with increasing molecular mass especially in a range of 100–200. Further, the rates correlate with the radius of hydrated molecules and their lipid solubility. Significant differences in urea uptake have been shown for animals less than 10 days in culture (“field” animals) and more than 10 days in culture (“laboratory” animals). Whether changes in cuticle permeability could be affected by abrasion is discussed. There is a high deviation amongst uptake values in all experimental series. It seems probably that, besides individual differences caused by abrasion, the animals differ physiologically, e.g. during the moulting cycle and seasonally. A nutritive function of the ventral tube seems to be unlikely. Calculation reveals that the absorbed glucose provides only 0.013% of the amount the animals need for respiration.     

Mode of entry of insecticides in Triatoma infestans

Penetration of insecticides through the integument of adult and nymph V of Triatoma infestans was examined. Intersegmental membranes and the union between dorsal and ventral cuticle appear to be preferential portals of entry of [¹⁴C]parathion in adult insects. In both possible entry points, cuticle has a higher proportion of endocuticle over exocuticle, in comparison to other areas of the integument. In nymph V the whole integument seems to be the entry point for [¹⁴C]parathion, which correlates with its cuticle being almost completely composed of endocuticle. The percent penetration of [¹⁴C]parathion was almost double in nymph V compared with adult insects. The effect of carriers on [¹⁴C]malathion penetration was that they modified the penetration rate and the mode of entry. Differences in the surface distribution of carriers with and without malathion were established.     

Catechol conjugation with hemolymph proteins and their incorporation into the cuticle of the American cockroach,Periplaneta americana

Newly ecdysed American cockroaches, Periplaneta americana (sixth to last instar) were injected with radioactive dopamine (DA) and hemolymph was collected at 10–60 min post-ecdysis. Size-exclusion chromatography established the presence of at least three proteins that serve as catecholamine carriers. Reinjection of the smaller radiolabeled phenol-bound proteins into newly ecdysed animals results in in vivo aggregation, with the radiolabel bound to large MW proteins (30->200 kDa). In addition, the reinjection of radiolabeled protein of any size resulted in the incorporation of the label into the newly sclerotized cuticle. Hemolymph proteins were synthesized in vivo using [¹⁴C]leucine and subsequently double labeled in vivo with [³H]dopamine. After sclerotization (7 h post-ecdysis) the cuticle was extirpated, hydrolyzed and counted. An identical ratio of ¹⁴C to ³H was found in cuticle extracts as in the double-labeled hemolymph proteins, suggesting that the phenol-bound protein was incorporated in the cuticle unchanged. It appears that the catechol bound to the proteins exists as a β-glucoside.     

Soldier differentiation during embryogenesis of a social aphid, Pseudoregma bambucicola

To understand the developmental process of aphid soldier differentiation, we investigated the morphological characters of normal nymphs, soldier nymphs and developing embryos of Pseudoregma bambucicola. Results of morphometric analyses showed that normal and soldier nymphs formed discrete clusters on the basis of several morphological characters, although a small number of intermediate individuals, termed ‘intercaste nymphs’, were present. In late embryonic stages, normal and soldier embryos were morphologically distinguishable. The earlier the embryonic stage, the smaller the morphological differences between them. In early embryos less than 1000 µm in length, normal and soldier embryos were not morphologically distinguishable, suggesting that the onset of soldier differentiation occurs at an early embryonic stage. Throughout embryonic development, morphological differentiation of the soldier caste proceeded gradually. Notably, several morphological characters of soldiers grew remarkably upon larviposition. Observation of embryonic leg cuticle revealed a characteristic folding structure, indicating that some morphological traits of the soldier are exaggerated upon larviposition through expansion of the folded cuticle. We suggest that morphological differentiation of the soldier caste in P. bambucicola comprises two phases: gradual growth during embryogenesis and rapid growth upon larviposition.     

Expression of the mitochondrial genome in HeLa cells. XXI. Mitochondrial protein synthesis during the cell cycle

Chloramphenicol sensitive [³H]leucine incorporation into protein (due to mitochondrial protein synthesis) in synchronized HeLa cells has been found to continue throughout interphase, its rate per cell approximately doubling from the G₁ to the G₂ phase. This increase in the rate of [³H]leucine incorporation during the cycle does not seem to parallel closely the increase in cell mass. In fact, the observations made on cultures incubated at 34.5 °C, where the G₁ and S phases are better resolved than at 37 °C, indicate that the rate remains constant during the G₁ phase, and starts to accelerate with the onset of nuclear DNA synthesis. Correspondingly, on a per unit mass basis, there appears to be a slight decline in the rate of [³H]leucine incorporation into protein during the G₁ phase, which is compensated by an increase in the early S phase. No significant variations were observed in the mitochondrial leucine pool labeling during the cell cycle; therefore, the observed pattern of [³H]leucine incorporation into protein should reflect fairly accurately the behavior of mitochondrial protein synthesis. Evidence has been obtained indicating a depression in the rate of incorporation of [³H]leucine into protein in mitochondria of mitotic cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the products of mitochondrial protein synthesis has not revealed any differences in the size distribution of the proteins synthesized in the various portions of the cell cycle.     

Increased GABA Release in the Human Brain Cortex as a Potential Pathogenetic Basis of Hyperosmolar Diabetic Coma

Human cerebral cortical slices preincubated with [³H]GABA, [³H]noradrenaline, or 5-[³H]hydroxytryptamine and superfused with Krebs solution or Mg²⁺-free Krebs solution were used to investigate the influence of increased D-glucose concentrations on the release of these [³H]-neurotransmitters evoked by high K⁺ content or NMDA receptor activation, respectively. An increase in level of D-glucose (normal content, 11.1 mM) by 32, 60, and/or 100 mM (a range characteristic for hyperosmolar diabetic coma) increased the [³H]GABA release and inhibited the [³H]noradrenaline release evoked by both methods of stimulation. The K⁺-induced 5-[³H]hydroxytryptamine release was also inhibited by high D-glucose content. Blockade of GABA_B receptors by p-(3-aminopropyl)-p-diethoxymethylphosphinic acid (CGP 35348) attenuated the inhibitory effect of high D-glucose content on the K⁺-evoked release of [³H]noradrenaline and 5-[³H]hydroxy-tryptamine, suggesting that the effect on monoamine release is, at least to a major part, the result of the increased GABA release and, as a consequence, of an increased GABA concentration at inhibitory GABA_B receptors. The membrane-impermeable sorbitol mimicked the increasing effect of D-glucose on [³H]GABA release and its inhibitory effect on 5-[³H]hydroxytryptamine release. However, dimethyl sulfoxide, which is known to permeate rapidly through biological membranes, had no effect at concentrations equiosmolar to D-glucose. It is concluded that a reduction in brain cell volume caused by increased extracellular, compared with cytoplasmic, osmolarity is crucial for the changes in neuronal function observed at high D- glucose and sorbitol content, In view of the fact that GABA is the main inhibitory neurotransmitter in the brain, the increased GABA release may be assumed to contribute to the pathogenesis of hyperosmolar diabetic coma.     

Calcium translocations during the moulting cycle of the semiterrestrial isopod <Emphasis Type="Italic">Ligia hawaiiensis</Emphasis> (Oniscidea,Crustacea)

Terrestrial isopods moult first the posterior and then the anterior half of the body. During the moulting cycle they retain a significant fraction of cuticular calcium partly by storing it in sternal CaCO₃ deposits. We analysed the calcium content in whole Ligia hawaiiensis and the calcium distribution between the posterior, the anterior ventral, and the anterior dorsal cuticle during four stages of the moulting cycle. The results indicate that: (1) overall, about 80% of the calcium is retained and 20% is lost with the exuviae, (2) in premoult 68% of the calcium in the posterior cuticle is resorbed (23% moved to the anterior ventral cuticle, 17% to the anterior dorsal cuticle, and the remaining 28% to internal tissues), (3) after the posterior moult 83% of the calcium in the anterior cuticle is shifted to the posterior cuticle and possibly to internal storage sites, (4) following the anterior moult up to 54% of the calcium in the posterior cuticle is resorbed and used to mineralise the new anterior cuticle. ⁴⁵Ca-uptake experiments suggest that up to 80% of calcium lost with the anterior exuviae may be regained after its ingestion. Whole body calcium of Ligia hawaiiensis is only 0.7 times that of the fully terrestrial isopods. These terrestrial species can retain only 48% of whole body calcium, suggesting that the amount of calcium that can be retained by shifting it between the anterior and posterior integument is limited. We propose that fully terrestrial Oniscidea rely to a larger degree on other calcium sources like internal stores and uptake from the ingested exuviae.     

A precursor of the reserve-protein, phaseolin, is transiently associated with the endoplasmic reticulum of developing Phaseolus vulgaris cotyledons

Developing cotyledons of Phaseolus vulgaris L. were labeled for 30 min with [³H] amino acids, homogenized, and the proteins fractionated on sodium dodecylsulfate (SDS) polyacrylamide gels. Fluorographs of these gels showed that the polypeptides of phaseolin, the major reserve protein of P. vulgaris, were synthesized as precursors which could be distinguished from the polypeptides of mature phaseolin by their slightly lower mobility. When extracts of cotyledons labeled for 45 min with [³H] amino acids were fractionated on isopynic sucrose gradients, radioactive phaseolin banded at the same density (1.14 g cm^-3) as the endoplasmic reticulum (ER)-marker enzyme NADH-cytochrome c reductase. Fractionation in the presence of 3 mM MgCl₂ indicated that the newly-synthesized phaseolin was associated with the rough ER. Pulse-chase experiments showed that phaseolin was transiently associated with the ER, and later accumulated in the protein bodies. Treatment of isolated ER with proteinase K showed that phaseolin polypeptides were degraded only if Triton X-100 was present, indicating that phaseolin was membrane-protected, probably enclosed within the vesicles. ER-associated phaseolin associated to an 18S form at pH 4.5 in the presence of 0.3 M NaCl and 100 mM sodium acetate. The polypeptides of ER-associated phaseolin had a slightly lower mobility on SDS-gels than polypeptides of protein body phaseolin. ER-associated phaseolin had a carbohydrate content of 6.8%, while protein body-derived phaseolin had a carbohydrate content of 6.2%. When cotyledons were labeled simultaneously with [¹⁴C] amino acids and [³H] glucosamine or with [¹⁴C] amino acids and [³H] mannose, the [³H]/[¹⁴C] ratio of ER-derived phaseolin was similar to that of protein body derived phaseolin, indicating that the faster mobility on SDS-gels was not due to the detachment of carbohydrate. Experiments in which the carbohydrate side chains were removed with endoglycosidase H, and the resulting polypeptides subjected to electrophoresis in SDS-gels showed that the differential mobility of the glycopolypeptides of phaseolin resided in their polypeptide chains.     

Protein synthesis by the milk gland and fat body of the tsetse fly,Glossina pallidipes

The patterns of protein synthesis by the milk gland and the fat body of female Glossinapallidipes during the pregnancy cycle were studied by incubation with [³⁵S]methionine both in vivo and in vitro. The pattern of protein synthesis by the milk gland changed with the stage of the larva in the uterus. Very little synthesis occurred in the milk gland until the first instar larva hatched. Then four proteins (13, 16, 24 and 72 kDa) were prominently synthesized. As the larva matured, the synthesis of 19, 38, 40 and 72 kDa proteins increased, whereas that of the 13 and 24 kDa proteins decreased. Just before larviposition, only the 16 and 72 kDa proteins were still being synthesized. The milk gland secreted into the medium primarily the 13, 16, 19 and 72 kDa proteins, all of which were found in the larval gut after a 5 hr pulse of labeled methionine in vivo. During most of the pregnancy cycle protein synthesis in the fat body was low compared to that of the milk gland and only small amounts of several low molecular weight proteins (less than or equal to 16 kDa) were released into the medium. But when a large third instar larva was present in the uterus, the fat body synthesized and secreted a 72 kDa and a 15–17 kDa complex of proteins.     

Cell cycle-related transfer of proteins between the nucleus and cytoplasm of Physarum polycephalum

The proteins of wild-type and polyploid plasmodia of P. polycephalum were prelabelled with [³H]leucine and [¹⁴C]leucine. The two types of plasmodia were then fused for 2 h. Following fusion the nuclei were isolated and the smaller wild-type cell nuclei separated from the larger polyploid cell nuclei. The proteins were isolated from the recipient cell nuclei and the recipient nuclear proteins extracted. Ratios of ³H/¹⁴C in the various nuclear protein fractions show that during fusion differential transfer of labelled preformed proteins from the donor cell into the recipient cell nucleus occurs. The quantity of proteins transferred varies among the different fractions and with the phase of the cell cycle. Isotopic dilution experiments indicate that these differences in protein transfer are, in part, due to a high rate of synthesis and turnover of the nuclear proteins.     

Activation of ribosomal and messenger RNA synthesis in excised Jerusalem artichoke tuber slices

RNA synthesis was studied in Jerusalem artichoke (Helianthus tuberosus L.) tuber slices immediately following excision and during the early period of aging in water. Incorporation of [³H]adenosine into RNA was detected as early as 20 min after excision. Measurement of the specific activities of RNA (cpm/g) and of ATP showed that RNA synthesis proceeded at a constant rate for the first several hours of aging and then increased moderately. [³H]adenosine was incorporated into polysomes throughout the aging period examined. Sucrose gradient fractionation of EDTA-dissociated polysomes showed that during the first 2 h of aging most of this incorporation was not into ribosome subunits but into presumed mRNA. Autoradiographic analysis of [³H]adenosine labelled nuclei showed that this was caused, at least in part, by a delay in the onset of rRNA synthesis synthesized during this time chromatographed as poly(A)-RNA on oligo(dT)-cellulose, indicating that a large part of the mRNA was not polyadenylated.     

The formation of the pupal cuticle by Drosophila imaginal discs in vitro

Mass-isolated imaginal discs of Drosophila melanogaster form a chitin-containing pupal procuticle In vitro. Optimal procuticle deposition occurs when the discs are incubated for 4–6 hr with 0.5–1.0 μg/ml of 20-hydroxyecdysone and then with less than 0.05 μg/ml of 20-hydroxyecdysone. The formation of the chitin-containing procuticle is demonstrated using three independent assays: with fluorescene-conjugated cuticle proteins that bind to chitin; by electron microscopy; by incorporation of [³H]glucosamine into a chitin fraction. Synthesis and deposition of pupal cuticle proteins are also demonstrated. Incorporation of [³H]glucosamine into chitin is sensitive to inhibitors of protein, RNA and chitin synthesis, but has little sensitivity to inhibitors of DNA synthesis, and dolichol-dependent glycosylation.     

Visualization of the NMDA recognition site in rat and mouse spinal cord by [3H]CGS 19755in vitro autoradiography

Summary The possibility to visualize the NMDA recognition site with [³H]CGS 19755in vitro autoradiography was evaluated in rat brain and spinal cord sections and thereafter used to study the distribution of the NMDA recognition site in rat and mouse spinal cord. The [³H]CGS 19755 binding was concentrated to the dorsal horn, in particular to the substantia gelatinosa. Notable binding was also seen in the intermediate area and ventral horn, while some binding was observed in the funiculi. No major differences were seen in [³H]CGS 19755 binding at various levels of the rat or mouse spinal cord, although a more dense binding was seen in the mouse. A similar distribution of the [³H]CGS 19755 specific binding and the NMDA receptor associated ion-channel site, labeled with [³H]TCP, was found in the mouse spinal cord. Taken together, our data indicate that the NMDA recognition site can be visualized in rat and mouse spinal cord byin vitro [³H]CGS 19755 autoradiography.Abbreviations NMDA N-methyl-D-aspartate - CGS 19755 Cis-4-phosphonomethyl-2-piperidine carboxylic acid - D-AP5 D(—)-2-Amino-5-phosphonopentanoic acid - TCP N-(1-2-thienylcyclohexyl)-3,4-piperidine - MK-801 (±)-5-Methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate - AMPA -Amino-3-hydroxy-5-methyl-isoxazolepropionic acid - kainate 2-Carboxy-3-carboxymethyl-4-isopropenyl pyrrolidine - CGP 39653 D,L-(E)-2-amino-4-propyl-5-phosphonopentenoic acid     

Chronic Ethanol Increases the Cannabinoid Receptor Agonist Anandamide and Its Precursor N-Arachidonoylphosphatidylethanolamine in SK - N - SH Cells

Abstract : In an earlier study, we demonstrated that chronic ethanol (EtOH) exposure down-regulated the cannabinoid receptors (CB1) in mouse brain synaptic plasma membrane. In the present study, we investigated the effect of chronic EtOH on the formation of anandamide (AnNH), an endogenous cannabimimetic compound, and its precursor N-arachidonoylphosphatidylethanolamine (N-ArPE) in SK-N-SH cells that were prelabeled with [³H]arachidonic acid. The results indicate that exposure of SK-N-SH cells to EtOH (100 mM) for 72 h significantly increased levels of [³H]AnNH and [³H]N-ArPE (p < 0.05) (1.43-fold for [³H]AnNH and 1.65-fold for [³H]N-ArPE). Exposure of SK-N-SH cells to EtOH (100 mM, 24h) inhibited initially the formation of [³H]AnNH at 24 h, followed by a progressive increase, reaching a statistical significance level at 72 h (p < 0.05). [³H]N-ArPE increased gradually to a statistically significant level after 48 and 72 h (p < 0.05). Incubation with exogenous ethanolamine (7 mM) and EtOH (100 mM, 72 h) did not result in an additive increase in the formation of [³H]AnNH. The formation of [³H]AnNH and [³H]N-ArPE by EtOH was enhanced by the Ca²⁺ ionophore A23187 or by the depolarizing agent veratridine and the K⁺ channel blocker 4-aminopyridine. Further, the EtOH-induced formation of [³H]AnNH and [³H]N-ArPE was inhibited by exogenous AnNH, whereas only [³H]AnNH formation was inhibited by the CB1 receptor antagonist SR141716A and pertussis toxin, suggesting that the CB1 receptor and G_i/o protein mediated the regulation of AnNH levels. The observed increase in the levels of these lipids in SK-N-SH cells may be a mechanism for neuronal adaptation and may serve as a compensatory mechanism to counteract the continuous presence of EtOH. The present observation taken together with our previous results indicate the involvement of the endocannabinoid system in mediating some of the pharmacological actions of EtOH and may constitute part of a common brain pathway mediating reinforcement of drugs of abuse including EtOH.     

Autoradiographic study of protein synthesis in abdominal tissues of Glossina austeni

Protein synthesis at various times during the pregnancy cycle of G. austeni was determined by autoradiographic measurement of the incorporation of H³-leucine and H³-tyrosine into the cells of the fat body, oenocytes, milk gland and epidermis. The rate of utilization of these molecules is such that the labelled pool in the haemolymph is depleted before 0.5 hr after injection. The incorporation of both amino acids into fat body and oenocytes is high at eclosion and just after larviposition, with the incorporation of tyrosine by the oenocytes being much higher than that in the fat body. The same pattern of incorporation is observed in the epidermal cells. Label also appears in the endocuticle during the first 10 days of adult life. Except during the first 4 days following emergence, the incorporation of the two amino acids into the milk gland is very high, with periods of less intense protein synthesis at about the time of larviposition. The milk gland represents a highly efficient secretory system, with a t₅₀ of less than 30 min.     

Effects of Mitochondrial Protein Synthesis Inhibitors on the Incorporation of Isoleucine into Plasmodium falciparum In Vitro1

Plasmodium falciparum was grown in human erythrocytes in vitro and the effect of chloramphenicol, erythromycin, and tetracycline on growth and maturation of the parasites and on their ability to incorporate [³H]isoleucine into protein was observed. Exposure of rings to high concentrations of chloramphenicol had little effect on subsequent maturation of the rings whereas brief (4 h) exposure of trophozoites caused a dose-dependent inhibition of subsequent ring formation. Incorporation of [³H]isoleucine into protein was not affected during at least 6 h of exposure to high concentration of the three drugs examined, but appreciable inhibition was observed after 21 h, with chloramphenicol being the least effective inhibitor. These results suggest that there is a stage-specific effect of inhibition of mitochondrial protein synthesis on subsequent development and that the mitochondria are essential for growth and development even though they lack a functional Krebs cycle.     

A quantitative microdensitometric and autoradiographic study of the effect of 4''-demethyl-epipodophyllotoxin-beta-D-thenylidene glucoside (VM-26) on the cell cycle of cultured fibroblasts

Synopsis The effect of 4-demethyl-epipodophyllotoxin--d-thenylidene glucoside (VM-26), a semi-synthetic derivative of podophyllotoxin, on the cell cycle was studied with chick embryo fibroblasts cultivatedin vitro. DNA, RNA and protein content, as well as NADH-diaphorase activity were determined by quantitative microdensitometry and cytofluorometry. The incorporation of [³H]thymidine and [³H]leucine into DNA and proteins were analysed by autoradiography. These metabolic data correlated with morphological observation showed that VM-26 blocks the cell cycle at different moments of its kinetics depending on both the dose and the time exposure. NADH-diaphorase activity is the first to be affected, then biochemical changes (involving the metabolism of RNA and proteins) and morphological alterations (especially of mitochondria) follow. This suggests that VM-26 may act primarily upon the mechanism of respiration of the cell.Dedicated to Professor G. Conti on the occasion of his 60th birthday.     

Growth patterns,chemical composition and oxygen consumption in early juvenileHyas araneus (Decapoda: Majidae) reared in the laboratory

Early (instar I and II) juveniles of the spider crabHyas araneus were reared under constant conditions (12 °C, 32‰S) in the laboratory, and their growth, biochemical composition, and respiration were studied. Every second day, dry weight (W), ash-free dry weight (AFW), and contents of ash, organic and inorganic carbon (C), nitrogen (N), hydrogen (H), protein, chitin, lipid, and carbohydrates were measured, as well as oxygen consumption. Changes in the absolute amounts of W. AFW, and C, N, and H during the moulting cycle are described with various regression equations as functions of age within a given instar. These patterns of growth differ in part from those that have been observed during previous studies in larval stages of the same and some other decapod species, possibly indicating different growth strategies in larvae and juveniles. There were clear periodic changes in ash (% of W) and inorganic C (as % of total C), with initially very low and then steeply increasing values in postmoult, a maximum in intermoult, and decreasing figures during the premoult phase of each moulting cycle. Similar patterns were observed in the chitin fraction, reaching a maximum of 16% of W (31% of AFW). Ash, inorganic C, and chitin represent the major components of the exoskeleton and hence, changes in their amounts are associated with the formation and loss of cuticle material. Consequently, a high percentage of mineral matter was lost with the exuvia (76% of the late premoult [LPM] ash content, 74% of inorganic C), but relatively small fractions of LPM organic matter (15% of AFW, 11% of organic C, 5–6% of N and H). These cyclic changes in the cuticle caused an inverse pattern of variation in the percentage values (% of W) of AFW, organic C, N, H, and biochemical constituents other than chitin. When these measures of living biomass were related to, exclusively, the organic body fraction (AFM), much less variation was found during individual moulting cycles, with values of about 43–52% in organic C, 9–10% in N, 6–9% H, 31–49% of AFW in protein, 3–10% in lipid, and <1% in carbohydrates. All these constituents showed, on the average, a decreasing tendency during the first two crab instars, whereas N remained fairly constant. It cannot be explained at present, what other elements and biochemical compounds, respectively, might replace these decreasing components of AFW. Decreasing tendencies during juvenile growth were observed also in the organic C/N and in the lipid/protein weight ratios, both indicating that the proportion of lipid decreased at a higher rate than that of protein. Changes were observed also in the composition of inorganic matter, with significantly lower inorganic C in early postmoult (2–4% of ash) than in later stages of the moult cycle (about 9%). This reflected probably an increase in the degree of calcification, i.e. in the calcium carbonate content of the exoskeleton. As a fraction of total C, inorganic C reached maximum values of 17 and 20% in the crab I and II instars, respectively. The energy content of juvenile spider crabs was estimated independently from organic C and biochemical constituents, with a significant correlation between these values. However, the former estimates of energy were, on the average, significantly lower than the latter (slope of the regression ≠1). Since organic C should be a reliable integrator of organic substances, but the sum of protein, lipid, chitin, and carbohydrates amounted to only 60–91% of AFW, it is concluded that the observed discrepancy between these two estimates of energy was caused by energy from biochemical constituents that had not been determined in our analyses. Thus, energy values obtained from these biochemical fractions alone may underestimate the actual amount of organic matter and energy. Respiration per individual in juvenile spider crabs was higher than that in larval stages of the same species (previous studies), but their W-specific values of oxygen consumption (QO₂) were lower than in conspecific larvae (0.6–2μg O₂·[mg W]⁻¹). QO₂ showed a consistent periodic pattern in relation to the moult cycle: maximum values in early postmoult, followed by a rapid decrease, and constant values in the intermoult and premoult phases. This variation is interpreted as an effect mainly of cyclic changes in the amounts of cuticle materials which are metabolically inactive. From growth and respiration values (both expressed in units of organic C), net growth efficiency, K₂, values may be calculated. In contrast to previous findings in larval stages, K₂ showed an increasing trend during growth of the first two juvenile instars ofH. araneus.     

Ornithine decarboxylase activity during neonatal development of the rat ventral prostate

The relationship between ornithine decarboxylase activity and growth has been examined in ventral prostates from rats aged 2–60 weeks. The incorporation of [¹²⁵I]iododeoxyuridine in vitro was used to assess DNA-synthetic activity. During 2–7 weeks post-partum ornithine decarboxylase activity/prostate and the protein content and wet weight increased exponentially. In contrast, the incorporation of [¹²⁵I]iododeoxyuridine/prostate fell during the first 4 weeks. This decline was reversed at about the time when the systemic concentrations of gonadal androgens start to rise. After 10 weeks post-partum the incorporation of [¹²⁵I]iododeoxyuridine/prostate and ornithine decarboxylase activity/prostate levelled off, whereas the DNA and protein content of the prostate contonued to increae at a slow rate.     

The cuticle proteins of Drosophila melanogaster: stage specificity

Five stage-specific cuticles are produced during the development of Drosophila. Urea-soluble proteins were extracted from each developmental stage and compared by gel electrophoresis. Proteins from first and second instar cuticle are identical except for minor differences in two proteins. Each subsequent stage, third instar, pupa, and adult, has a unique set of cuticle proteins. Qualitative changes within stages are seen in proteins from third instar and adult cuticle. Third instar cuticle proteins can be divided into “early” [proteins 2a, 3, 4, 5, 7, and 8] and “late” [proteins 2 and 1] groups. Adult cuticle proteins change in relative amounts during pharate adult development and change mobility at eclosion. The lower abdominal pupal cuticle lacks a protein found in the pupal cuticle covering the head and thorax. Cuticle proteins from each stage are immunologically related. Nonetheless, electrophoretic variants of three larval proteins do not affect any major changes in the electrophoretic mobility of proteins from other stages. We propose that each stage (except first and second instar) has proteins encoded by discrete genes.