The rectal intima of the desert locust was found to possess fixed negative charges, rather than fixed neutral sites. It was suggested that the molecular species responsible for the negative sites might be acidic amino acids. The selective permeability of the intima as estimated from diffusion potentials, for divalent cations was 3a⁺² > Ca⁺² > Sr⁺² > Mg⁺² > Mn⁺², for monovalent cations was NH₄⁺ > Rb⁺ > Cs⁺ > K⁺ > Na⁺ > Li⁺ > TEA⁺ and for monovalent anions was HCO₃⁻ > CN⁻ > F⁻ > NO₃⁻ > CL⁻ > CH₃COO⁻ > Br⁻ > H₂PO₄⁻ > I⁻. Cation affinity for the fixed charged site was found to be in the order of Ca⁺² > Mg⁺⁺ » K⁺ > Na⁺. Similarity of effects of pH and ion concentration on streaming and diffusion potentials indicated that ion movement and water flow might take place through the same route. The intima was found to act as an osmotic compartment such that at high external osmotic pressures, the rate of water flow was reduced due to a shrinkage of the effective pore size in the intima, however the relative permeability of ions did not seem effected by membrane dehydration. Unstirred layers at the membrane-solution interfaces were found to have a minimal effect on diffusion potentials, however half of the value for streaming potentials was found to be due to a diffusion potential caused by an ion concentration difference in opposing unstirred layers. Calcium -45 flux across the intima at pH 5.5 (i.e. possessing fixed charge) was found to be 81 times greater, at a concentration of 10 mM/l CaCl₂, than calcium flux at the same concentration across the uncharged membrane (pH 2.2). The same effect was not significant for rubidium. Conversely, the removal of fixed charge enhanced anion flux. Calcium permeation rate was found to be a function of its dissociation rate from the fixed charge and did not correlate in a simple manner with the membrane binding capacity for calcium. A trans effect on calcium flux was also found in the intima and is believed to be a function of the dissociation rate of calcium from the fixed negative site. It was concluded that electro-osmosis was not the mode of water movement across the rectum, however physiological advantage of electro-osmosis was discussed. Flux experiments possible indicate that the intima might be the rate limiting step for K⁺ reabsorption in a hydrated animal. / Science, Faculty of / Zoology, Department of / Graduate

An in vitro preparation of the rectum of the desert locust Schistocerca gregaria is described and characterized. The rectal epithelium was mounted as a flat sheet separating two well stirred chambers and the trans-membrane potential difference (PD), membrane resistance, and short circuit current (SCC) were monitored. The PD and membrane resistance remained relatively constant for at least six hours at 35 mV (lumen positive) and 6000 Ohms . cm ⁻², respectively. After an initial two hour transient period during which the SCC dropped from 8 uMoles of charge .cm⁻² .hr⁻¹ to 3.5 uMoles. cm⁻² .h⁻¹ an approximate steady-state condition was reached and maintained for at least another four hours. The SCC was consistant with either a net cation transport from the hemolymph to the lumen of the rectum or a net anion transport in the opposite direction. Since Cl⁻ was the only major anion in the bathing media some experiments were carried out to evaluate the contribution of active Cl⁻ transport to the SCC. Substitution of SO4⁻ of NO3⁻ during the third and fourth hours in vitro had no effect on the SCC, although they abolished the initial two hours transient. Similar experiments in which Cl⁻ was substituted by acetate had a complex stimulatory effect on the SCC. Measurements of ³⁶Cl⁻ fluxes under SCC conditions during the same time period demonstrated a mean net flux of 1.52 uMoles of Cl⁻ cm⁻².hr from the rectal lumen to the hemolymph. This value is equivalent to one half the simultaneous SCC. These experiments clearly demonstrate that the rectal epithelium actively transports Cl⁻ in a direction consistent with the observed SCC but that this active transport of Cl⁻ does not contribute to the SCC during the third and fourth hours in vitro. Since rectal Na+ and K+ transport reported by other workers is in the wrong direction to account for the observed SCC, it seems necessary to propose (1) a Cl⁻ exchange pump (probably with HCO3⁻) perhaps located on the luminal membrane to account for the fact that active Cl⁻ transport does not contribute to the SCC and (2) a H+ and/or HCO3⁻ pump to account for the SCC. These proposals are incorporated in a model for organization of ion transport processes in the locust rectum. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

The rectal pad of Schistocerca gregaria consists of a layer of large columnar epithelial cells and a layer of smaller oval-shaped cells. Both layers appear specialized for transport, as judged by the large number of mitochondria and membrane infoldings within the two cell types. The ultrastructure of the columnar epithelium and of the secondary cells is described as it appears under the electron microscope. The ability of the rectum to transport water and salts was tested in vitro. Unlike the in vivo preparation, the rectum in vitro does not transport potassium and chloride and has only a limited ability to transport sodium and water against a gradient. Dinitrophenol (10⁻³M.), iodoacetate (10⁻²M.) and ouabain (10⁻²M.) abolish water and sodium transport. Potassium cyanide (10⁻²M.) and ouabain (10⁻³M.) do not appear to inhibit water or sodium transport. Iodoacetate (10⁻³M.) inhibits sodium transport but does not affect water transport. The in vitro rectum is dependent upon anaerobic respiration. The results are discussed in terms of a scheme presented for in vivo cellular function. (Phillips, 1965). The studies of ultrastructure and transport physiology of the locust rectum do not refute the hypothetical schemes presented in this thesis. / Science, Faculty of / Zoology, Department of / Graduate

The development of a chemically defined artificial diet for Schistocerca gregaria (Forsk.) is described,. The diet that permitted the best growth of S. gregaria was used to determine the amino acid requirements of this animal. Further studies were performed to determine whether amino acids were required as nutrient per se or as phagostimulants. The moist artificial diets initially used in growth trials showed signs of deterioration after 20-days storage at -15°C. This deterioration was evidenced by reduced growth of animals on 20-day-old diets, and by the loss of ascorbic acid from such diets. Freeze-or oven-drying diets increased their storage life and their stability under experimental conditions. Growth trials showed that dried diets were stable for at least 2 months when stored in vacuum desiccators. Little ascorbic acid was degraded in diets kept under experimental conditions (30°C, 55% E.H.) for 2 days, suggesting that such diets could be kept under these conditions for at least 2 days without being replaced. S. gregaria showed poor growth on artificial diets containing either an ad hoc mixture of amino acids or a mixture of amino acids based on analysis of lettuce protein. However, growth of animals was improved by using an amino acid mixture based on analysis of cabbage proteins. Diets could be prepared mere rapidly if the vitamin solutions used in compounding the diets were replaced by vitamins triturated in sucrose. The physical properties of the diet were important, and fine-powder diets caused heavy mortality of S. gregaria hoppers.. Powder diets had to be formed into granules or tablets before they could be utilized by S. gregaria. Although few animals reached the adult stage on artificial diets, the best diet did allow S. gregaria hoppers to develop to the 5th instar (with a mean weight of approximately 550 mg) after 33-days growth. To determine which amino acids were essential for S. gregaria, the growth of animals reared on test-diets lacking an individual amino acid was compared with growth of animals on control diets containing the full complement of amino acids. If the removal of an amino acid had no effect on the growth of animals it was classed as an inessential amino acid; if it had an marked detrimental effect it was classed as an essential amino acid, and if it only had a marginally detrimental effect it was termed a semi-essential amino acid. The results of growth trials indicated that tyrosine, alanine, aspartate, glutamate, cystine, serine and proline were inessential amino acids for S. qreqaria, whereas lysine, phenylalanine, isoleucine, valine, threonine, tryptophan, leucine, histidine, methionine and arginine were essential, and glycine was semi-essential. Although the growth of animals on arginine deficient diets was poor enough to warrant arginine being classed as an essential amino acid, S. qreqaria's requirements for this amino acid did not appear to be as stringent as its requirements for the ether essential amino acids. Ihe semi-essential nature of glycine, and the suprisingly good growth of animals on arginine-deficient diets are discussed in relation to S. qreqaria1s amino-acid metabolism. It is suggested that the poor growth of animals on glycine-deficient diets is a result of glycine not being synthesized rapidly enough to meet S. gregaria’s metabolic requirements, and that the growth of animals on arginine-deficient diets is due to limited synthesis of this amino acid via the ornithine cycle. Feeding trials indicated that the failure of animals to show good growth on diets lacking any of the 10 essential amino acids was due to the reduced feeding activity of animals reared on these diets. Individual removal of any of the other 8 amino acids (i.e. the 7 inessential amino acids and glycine) had no effect on food consumption. The role of amino acids as phagostimulants is discussed in relationship to current theories concerning host-plant selection by phytophagous insects, and it is suggested that food selection is based on a learned-aversion response to the metabolic effects associated with the ingestion of an imbalanced ratio of nutrients. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Previous studies of selective reabsorption in insect excretory system have concentrated almost exclusively on the rectum, while the role of the ileum has been assumed to be minor. The properties and control of solute and fluid transport in two segments of the hindgut, the ileum and rectum, from the desert locust (Schistocerca gregaria) have been studied and compared in vitro using everted sac and flat sheet preparations. Everted sacs of locust ileum transported fluid from the lumen side to hemocoel side over a 5 h period at near constant rates of 3.0 to 3.5 μL-h⁻¹-ileum⁻¹ and tissue volume did not change. Inhibition by azide indicated metabolic dependence of fluid transport. Fluid absorption occurred against osmotic concentration differences of up to 600 mosmol. Fluid transport was stimulated by cAMP, both nervous and glandular lobes of corpus cardiacum (CC), and fifth ventral ganglia (VG) in a dose-dependent manner. All stimulants caused ilea to absorb against larger osmotic concentration differences than unstimulated sacs. The ileal absorbate remained hyperosmotic to the luminal saline under all conditions and stimulants increased absorbate osmolality. Unstimulated fluid transport was supported at 50% of control levels by any one of Na+, K+, or CI⁻. Stimulation of fluid transport by CC or VG was dependent on CI⁻ and maximal stimulation occurred when the Na+:K+ ratio was 1:1. Cyclic AMP, CC and VG all stimulated Na+,K+ and CI⁻ absorption across everted ileal sacs. This is the first direct demonstration that Na+ reabsorption is controlled in insect excretory systems. Stimulation resulted in a decrease in absorbate HCO₃⁻ levels and pH concurrently with an increase in absorbate CI⁻ levels. Stimulation of fluid transport was associated with a 3-fold increase in transepithelial potential (hemocoel negative) suggesting stimulation of electrogenic anion (CI⁻) movement to the hemocoel. Net Na+ absorption occurs largely by electroneutral active transport. NH₄+/Na+ exchange may account for one-third of stimulated net Na+ flux. Extracts from both CC and VG stimulated fluid, K+, and CI⁻ transport across everted rectal sacs, but only a small stimulation of Na+ flux was observed which was an order of magnitude less than that observed for stimulated ilea (0.4 versus 5.1 μequiv-h⁻¹ -cm⁻²). Unlike the rectum, the ileum did not transport proline transepithelially and ileal fluid transport was not stimulated by increasing concentrations of proline in the bathing saline. Rectal fluid transport was stimulated 50% by increasing external proline concentration from 1 to 80 mM. Stimulation of rectal fluid transport by proline also occurred in the absence of Na+, K+, and CI⁻ and occurred against larger osmotic concentration differences. These results are consistent with previous reports of a high capacity transport system for proline in locust rectum. The presence of anion-stimulated ATPase and Na+,K+-ATPase in locust hindgut was also investigated. Anion-stimulated ATPase activities were observed in microsomal fractions of both rectum and ileum. Microsomal fractions from both tissues had enriched specific activities of several plasma membrane marker enzymes and decreased activities of two mitochondrial markers as compared to homogenate enzyme activities. Na+,K+-ATPase activity was 20-fold higher in the rectum than in the ileum, associated with the greater development of the basolateral membrane in the rectum. Overall the results suggest that ion and fluid reabsorption in the locust ileum is much more important in the excretory process than previously supposed. Moreover, this reabsorption was shown to be under neuroendocrine control. / Science, Faculty of / Zoology, Department of / Graduate

Previous studies on the regulation of salt and water reabsorption in the insect excretory system have concentrated on the rectum, while regulation of the ileum has received little attention. Cl⁻ transport is the predominant ion transport process in both the ileum and rectum of the desert locust and drives fluid absorption. The central nervous system (CNS) was surveyed for factors which stimulate Cl⁻-dependent short-circuit current (I[formula omitted]) using in vitro flat sheet preparations of locust ileum as a bioassay. All ganglia extracts tested (except the corpora allata) caused significant increases in ileal I[formula omitted]. Extracts of muscle tissue, used as a control, had no effect on ileal I[formula omitted] indicating that stimulants were not general metabolites present in locust tissue. Crude extracts of the corpus cardiacum (CC) and fifth ventral ganglion (VG5) stimulated ileal I[formula omitted] in a dose-dependent manner and both caused an increase in K⁺ and Na⁺ absorption as previously observed with cAMP. CC and VG5 had no effect on ileal NH₄⁺ secretion but both inhibited ileal H⁺ secretion. Most of the stimulatory effects of CC and VG were largely abolished by treatment with trypsin and chymotrypsin, suggesting that the stimulants were peptides. CC and VG5 factors were apparently separate compounds because they differed in the time courses of ileal I[formula omitted] response, thermal stability, and extraction properties. Reversed-phase high performance liquid chromatography (RP-HPLC) of water extracts of CC identified two distinct factors (fractions D and F) which stimulated ileal I[formula omitted] and a third factor (fraction G) which had little effect on I[formula omitted], but which caused a five-fold increase in ileal fluid transport (J[formula omitted]). None of these fractions increased rectal J[formula omitted]; moreover, fraction D stimulated rectal I[formula omitted] at higher doses. These results provided the first indication that separate stimulants act on locust rectum and ileum. The most potent factor in CC acting on ileal I[formula omitted] was isolated using a four-step purification procedure, utilizing C₈ and phenyl RP-columns for separation. Amino acid analysis of this purified peptide indicated a molecular weight of 7700 daltons and a near complete amino acid sequence (50 out of 65) was determined. The purified factor (S. gregaria ion transport peptide; ScgITP) was assayed on all ileal ion transport processes influenced by crude CC extracts. ScgITP caused quantitatively the same range of effects as crude CC extracts, in that it stimulated Cl⁻, K⁺, and Na⁺ reabsorption and inhibited H⁺ secretion. High doses of ScgITP (5 CC equiv.ml⁻¹) caused the same maximum response on all these systems as crude CC extracts (0.25 CC equiv.ml⁻¹). ScglTP is unlikely to be chloride transport stimulating hormone, previously reported to act on the rectum, because a maximum rectal I[formula omitted] response was not achieved and there was no effect on rectal J[formula omitted], which is Cl⁻-dependent. It appears that ScgITP acts through cAMP as the second messenger to stimulate reabsorptive processes because this cyclic nucleotide mimicked the actions of ScgITP and crude CC extracts. In support of this view, ileal I[formula omitted] was also stimulated to maximum levels by 5mM theophylline and 50μM forskolin. The inhibition of H⁺ secretion by ScgITP must occur through a different intracellular pathway because this action was not mimicked by cAMP. / Science, Faculty of / Zoology, Department of / Graduate

The cellular mechanisms responsible for rectal acidification in the desert locust, Schistocerca gregaria, were investigated in isolated recta mounted as flat sheets in modified Ussing chambers. In the absence of exogenous CO₂, HCO₃⁻, and phosphate, the isolated rectum (under both open- and short-circuit current conditions) was capable of rates of net acid secretion (J[subscript]H+) similar to those observed in vivo, demonstrating the viability of the preparation and suggesting that rectal acidification was due to proton secretion rather than selective movements of HCO₃⁻ or phosphate. The possibility that trace levels of metabolic CO₂ might be generating sufficient HCO₃⁻ to account for the observed rates of rectal acidification (via HCO₃⁻ reabsorption) was assessed by adding exogenous CO₂/HCO₃⁻ to the contraluminal bath. The small increases in J[subscript]H+ observed after addition of 2% or 5% CO₂ were shown to be due to simple hydration of CO₂ which had diffused into the lumen (from the contraluminal bath), rather than changes in rates of HCO₃⁻ reabsorption. Since measurable quantities of luminal HCO₃⁻ did not directly affect the apical acid/base transport mechanism per se, it was concluded that metabolic CO₂ could not generate sufficient HCO₃⁻ in the lumen to account for the rates of rectal acidification observed under nominally CO₂/HCO₃⁻-free conditions and that J[subscript]H+ must be due to a proton secretory rather than bicarbonate reabsorptive mechanism. Microelectrode measurements of intracellular pH (pHi) and apical and basolateral membrane potentials (Va and Vb respectively) indicated that luminal pH was not in equilibrium with either contraluminal pH or pHi and that the mechanism responsible for active luminal acid secretion resided on the apical membrane. Preliminary measurements of bath total ammonia (ie. NH₃ + NH₄+) levels in the previous experiments suggested that the rectum was actively secreting ammonia at significant rates across the apical membrane into the lumen. If the ammonia crossed the apical membrane as NH₃ rather than NH₄+, rates of luminal ammonia secretion (J[subscript]Amm) would have to be added to J[subscript]H+ to obtain corrected values of luminal proton secretion. In the absence of exogenously added ammonia and CO₂, ammonia was preferentially secreted into the lumen under both open- and short-circuit current conditions. J[subscript]Amm was dependent on the presence of luminal amino acids and was relatively unaffected by K[superscript]+ removal or changes in luminal pH from 7.00 to 5.00. Bilateral Na+ substitution or luminal addition of ImM amiloride reduced J[subscript]Amm by 63% and 65% respectively. The data consistently demonstrate that the rectum secretes significant quantities of endogenously produced ammonia preferentially into the lumen as NH₄+ rather than NH₃ via an apical Na[superscript]+/NH₄[superscript]+ exchange mechanism. Clearly, rates of net acid secretion estimated by titratable acidity do not have to include a correction for luminal ammonia secretion. Although J[subscript]H+ was completely unaffected by changes in contraluminal pH, it could be progressively reduced (and eventually abolished) by imposition of either transepithelial pH gradients (lumen acid) or transepithelial electrical gradients (lumen positive). Under short-circuit current conditions, the bulk of J[subscript]H+ was not dependent on Na[superscript]+, K[superscript]+, CI⁻, Mg₂+, or Ca+ and was due to a primary electrogenic proton translocating mechanism located on the apical membrane. A small component (10-16%) of J[subscript]H+ measured under these conditions could be attributed to an apical amiloride-inhibitable Na[superscript]+/H[superscript]+ exchange mechanism. Inhibition of JH+ by anoxia or reduction of luminal pH unmasked a significant proton diffusional pathway on the apical membrane in parallel with the active proton pump. The fact that J[subscript]H+ was significantly inhibited (42%-66%) by contraluminal addition of ImM cAMP and relatively unaffected by changes in contraluminal pCO₂ or pH suggests that net acid secretion in the locust rectum in vivo is modulated by circulating hormonal factors rather than haemolymph pH or pCO₂ per se. / Science, Faculty of / Zoology, Department of / Graduate

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-04-17T12:23:49Z No. of bitstreams: 1 Tiago Martins Ribeiro.pdf: 2146814 bytes, checksum: c04c7e63303157b4345d0985576e1620 (MD5) / Made available in DSpace on 2017-04-17T12:23:49Z (GMT). No. of bitstreams: 1 Tiago Martins Ribeiro.pdf: 2146814 bytes, checksum: c04c7e63303157b4345d0985576e1620 (MD5) Previous issue date: 2017-02-20 / CAPES / Complex optimization problems have been studied over the years by researchers seeking better solutions, these studies have encouraged the development of several algorithms of artificial intelligence, and a part of them are bio-inspired methods, based on the behavior of populations. These algorithms target to develop techniques based on nature in search of solutions to these problems. In this work, was introduced as a purpose, an algorithm based on the behavior of locust swarms, the Locust Swarm Optimizer (LSO). The behavior of the desert locust is introduced highlighting the formation of clouds of attacks caused by a synthesized neurotransmitter monoamine, present on the insect, known as serotonin. Observing this behavior, the LSO was developed. It was compared to other known artificial intelligence techniques through 23 benchmark functions and also tested on an power system economical dispatch problem. From the point of view of the results and the ease of implementation, it can be concluded that the LSO algorithm is very competitive as compared to existing methods / Problemas complexos de otimização vêm sendo estudados ao longo dos anos por pesquisadores que buscam melhores soluções, estes estudos incentivaram o desenvolvimento de vários algoritmos de inteligência artificial, sendo que uma parte deles são métodos bioinspirados, baseados no comportamento de populações. Estes algoritmos têm como objetivo desenvolver técnicas baseadas na natureza em busca de soluções para estes problemas. Neste trabalho um algoritmo baseado no comportamento de enxames de gafanhotos-do-deserto, o Locust Swarm Optimizer (LSO), foi introduzido como objetivo. O comportamento do gafanhoto-do-deserto é apresentado destacando a formação de nuvens de ataques causada por uma monoamina neurotransmissora sintetizada, presente no inseto, conhecido por serotonina. Observando este comportamento, foi desenvolvido o LSO. Ele foi comparado com outras conhecidas técnicas de inteligência artificial através de 23 funções benchmarks e também, testado em um problema de despacho econômico. Do ponto de vista dos resultados e da facilidade de implementação, pode-se concluir que o algoritmo LSO é bastante competitivo comparado aos métodos atuais existentes.