Localization of metals in cells of pterygote insects

ZnT4 provides zinc to zinc-dependent proteins in the trans-Golgi network critical for cell function and Zn export in mammary epithelial cells

Zinc (Zn) transporter 4 (ZnT4) plays a key role in mammary gland Zn metabolism. A mutation in ZnT4 (SLC30A4) that targets the protein for degradation is responsible for the "lethal milk" (lm/lm) mouse phenotype. ZnT4 protein is only detected in the secreting mammary gland, and lm/lm mice have ∼35% less Zn in milk, decreased mammary gland size, and decreased milk secretion. However, the precise contribution of ZnT4 is unknown. We used cultured mouse mammary epithelial cells (HC11) and determined that ZnT4 was localized to the trans-Golgi network (TGN) and cell membrane and transported Zn from the cytoplasm. ZnT4-mediated Zn import into the TGN directly contributed to labile Zn accumulation as ZnT4 overexpression increased FluoZin3 fluorescence. Moreover, ZnT4 provided Zn for metallation of galactosyltransferase, a Zn-dependent protein localized within the TGN that is critical for milk secretion, and carbonic anhydrase VI, a Zn-dependent protein secreted from the TGN into milk. We further noted that ZnT4 relocalized to the cell membrane in response to Zn. Together these studies demonstrated that ZnT4 transports Zn into the TGN, which is critical for key secretory functions of the mammary cell.

The evidence on the degradation processes in the midgut epithelial cells of the larval antlion Euroleon nostras (Geoffroy in Fourcroy, 1785) (Myrmeleontidae, Neuroptera)

We analysed structural differences between midgut epithelial cells of fed instar antlions' larvae Euroleon nostras and starved ones. In starved larvae the presence of autophagolysosome-like structures was observed, which are characteristic structures associated with autophagy. The results presented here provide insight supporting the role of autophagy as a cell survival mechanism for the periods of food deprivation. Additional structural changes in the cytoplasm were seen in the spherites. The ultrastructure and chemical composition of spherites in the midgut epithelial cells of first, second and third instar larvae were observed with light microscopy and transmission electron microscopy (TEM). A detailed characterization of the elemental composition of the spherites was studied using analytical electron microscopy; a combination of energy dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy filtering TEM (EFTEM) was applied. The structure and elemental composition of the spherites changed during the period of larval life. Moreover, changes in chemical composition were found between spherites from fed and starved E. nostras. In fed first instar larvae, the spherites contained an organic matrix, composed of C, N and O. In this matrix, P, Cl, Ca and Fe were detected. In starved first instar larvae, only C, N and P were present. The spherites of fed second instar larvae were rich in organic and inorganic elements and were composed of C, N, O, Na, Mg, P, S, Cl, K, Ca, Mn, Fe and Zn. In starved second instar larvae, the chemical elements N, O, P, Ca and Fe were found. In fed third instar larvae, the spherites contained C, N, O, Na, Mg, P, Cl, K, Ca, Mn, Fe, Co and Zn. In starved third larvae, C, O, Si, Ca, and Fe were detected. Generally, the spherites are exploited in starved larvae. These results suggest that the elemental supply of spherites may provide crucial support for physiological processes during starvation periods amongst E. nostras instar larvae. In some cases in fed second and fed third instar larvae, spherites were seen in the lumen of the midgut. Such spherites could serve as reservoirs for nontoxic waste material that cannot be metabolized.

Distribution of metals in the termite Tumulitermes tumuli (Froggatt): two types of Malpighian tubule concretion host Zn and Ca mutually exclusively

The aim of this study was to determine specific distribution of metals in the termite Tumulitermes tumuli (Froggatt) and identify specific organs within the termite that host elevated metals and therefore play an important role in the regulation and transfer of these back into the environment. Like other insects, termites bio-accumulate essential metals to reinforce cuticular structures and utilize storage detoxification for other metals including Ca, P, Mg and K. Previously, Mn and Zn have been found concentrated in mandible tips and are associated with increased hardness whereas Ca, P, Mg and K are accumulated in Malpighian tubules. Using high resolution Particle Induced X-Ray Emission (PIXE) mapping of whole termites and Scanning Electron Microscope (SEM) Energy Dispersive X-ray (EDX) spot analysis, localised accumulations of metals in the termite T. tumuli were identified. Tumulitermes tumuli was found to have proportionally high Mn concentrations in mandible tips. Malpighian tubules had significant enrichment of Zn (1.6%), Mg (4.9%), P (6.8%), Ca (2.7%) and K (2.4%). Synchrotron scanning X-ray Fluorescence Microprobe (XFM) mapping demonstrated two different concretion types defined by the mutually exclusive presence of Ca and Zn. In-situ SEM EDX realisation of these concretions is problematic due to the excitation volume caused by operating conditions required to detect minor amounts of Zn in the presence of significant amounts of Na. For this reason, previous researchers have not demonstrated this surprising finding.

Insight of EDX analysis and EFTEM: are spherocrystals located in Strombidae digestive gland implied in detoxification of trace metals?

Digestive tubules of Strombidae are composed by three cell types: digestive cells, vacuolated cells, and crypt cells. The last one is characterized by the presence of intracellular granules identified as spherocrystals. Such structures are known to occur in basophilic cells of gastropod digestive gland, where they are supposed to be involved in the regulation of some minerals and in detoxification. In this study, energy-dispersive X-ray analysis (EDX) and energy filtered transmission electron microscopy (EFTEM) were used to determine the elemental content of spherocrystals in two Strombidae, Strombus gigas and Strombus pugilis. In freshly collected individuals of both species, the following elements were detected: Ca, Fe, Mg, P, and Zn. Aluminum and Mn were also detected in S. gigas. Their presence in spherocrystals indicates that, in Strombidae, spherocrystals are involved in the regulation of minerals and essential trace metals. In order to answer the question "are spherocrystals involved in nonessential trace metals scavenging?," artificial cadmium and lead exposure by both waterborne and dietary pathways was applied to S. pugilis. No evidence of cadmium (Cd(NO(3))(2)) or lead (Pb(NO(3))(2)) provided by food was found in spherocrystals. Cadmium provided in water (Cd(NO(3))(2) and CdCl(2)) causes structural modifications of the digestive gland; however, this element was not trapped in spherocrystals. These results suggest that spherocrystals are not involved in detoxification of such nonessential trace metals.

Application of analytical electron microscopic methods to investigate the function of spherites in the midgut of the larval antlion Euroleon nostras (Neuroptera: Myrmeleontidae)

This study presents an application of analytical electron microscopy in biology to investigate the chemical composition of the spherites and to elucidate the importance of these methods in the life sciences. The structure of the spherites in the midgut cells of first, second, and third instar larvae Euroleon nostras was investigated by a combination of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS), and energy filtering TEM (EFTEM). The structure and chemical composition of the spherites changed during the metamorphosis. In first larvae, the spherites are composed of amorphous, flocculent material, containing C, N, and O. In second larvae and third ones, the spherites have concentric layers of alternating electron-dense and electron-lucent material. In second larvae, Si, P, Ca, and Fe are accumulated in the spherite organic matrix, composed of C, N, and O. In the spherites of third larvae, additionally Al was found. Therefore, the spherites are thought to store organic compounds in all three larval stages of E. nostras and additionally inorganic compounds in second and third ones. In first larvae, spherites are present in the midgut cells; in second and third larvae, they are present in the cells of the midgut and in its lumen. It could be suggested that the spherites might be involved in the regulation of the appropriate mineral composition of the internal environment and could serve as the accumulation site of nontoxic waste materials that cannot be metabolized.

Chronic accumulation of cadmium and its effects on antioxidant enzymes and malondialdehyde in Oxya chinensis (Orthoptera: Acridoidea)

The accumulation of cadmium (Cd) and its effects on antioxidant enzyme activities and malondialdehyde (MDA) levels of Chinese rice grasshopper (Oxya chinensis) were evaluated under the laboratory conditions. Our results showed that Cd accumulation in O. chinensis exhibited a concentration-dependent increase in both males and females under Cd pollution. Environmental Cd can lead to the absorption of large quantities of Cd, which induces oxidative damage in insects by altering antioxidant defense enzyme systems. Our results demonstrated that Cd stress caused a significant decrease in glutathione peroxidase (GPx) levels and a significant increase in superoxide (SOD) dismutase and catalase (CAT) activities. In the grasshoppers, the MDA content was also enhanced, with an increase in Cd concentrations and a positive correlation between them; for females from second instar nymphs to the adult stage, R(2) was 0.6467, 0.9136, 0.6516, 0.942 and 0.7182, whereas for males, it was 0.6467, 0.8239, 0.9302, 0.7861, 0.8632, respectively. We also observed differences in the effects of Cd between grasshoppers of different developmental stages and genders, which suggested that the insect's developmental stage and sex should be considered when studying enzyme activity.

Histological and ultrastructural characterization of the alimentary system of solifuges (Arachnida, Solifugae)

Solifuges are voracious and fast predators. Once having captured a prey item, mostly small arthropods or even small vertebrates, they start feeding on their prey by constant chewing movements with their huge chelicerae. At the same time, they squeeze out the soft tissue that passes the anterior lattice-like part of the mouthparts. The digestion of the food takes place in the midgut, which is anatomically highly complex. It consists of the midgut tube from which numerous prosomal and opisthosomal diverticula and tubular lateral branches arise. The dimorphic epithelium of the midgut tube and the diverticula is constituted of digestive and secretory cells. The digestive cells are characterized by an apical tubulus system and contain nutritional vacuoles, lipids, spherites, and glycogen. Secretory cells contain a huge amount of rough endoplasmic reticulum and secretory vacuoles. The lateral branches are ultrastructurally similar to Malpighian tubules and are likely involved in excretion. In contrast to the midgut, the epithelium of the hindgut consists of only one type of cell overlain by a thin cuticle. Digested residuals are stored in the hindgut until defecation.

Structure of the Malpighian tubule cells and annual changes in the structure and chemical composition of their spherites in the cave cricket Troglophilus neglectus Krauss, 1878 (Rhaphidophoridae, Saltatoria)

Periodical changes in the structure of spherites in the Malpighian tubule cells of the cave cricket Troglophilus neglectus were studied to elucidate their role during the cricket's life cycle in natural circumstances. Special interest was given to the dormant overwintering period when we hypothesized that the primary role of spherites is to supply minerals for basic vital processes. The investigation was carried out by light and transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy-loss spectroscopy and energy-filtering TEM. Spherites are present only in the middle Malpighian tubule segment, consisting of Type 1 cells, characterized, among other features, by a round, apically placed nucleus and numerous spherites, and a few Type 2 cells with an elongated nucleus in the centre and sparse spherites. At the beginning of dormancy in November juveniles, minerals are accumulated in spherites and then decline until March. In one-year-old May larvae, spherites are commonly rich in minerals, and from July onwards they are progressively exploited in the adults. Spherite destruction starts with apoptosis in senile October individuals. The findings suggest that the mineral supply of spherites in Malpighian tubules is crucial to supporting vital processes throughout the life cycle of T. neglectus.

Arsenic speciation of terrestrial invertebrates

The distribution and chemical form (speciation) of arsenic in terrestrial food chains determines both the amount of arsenic available to higher organisms, and the toxicity of this metalloid in affected ecosystems. Invertebrates are part of complex terrestrial food webs. This paper provides arsenic concentrations and arsenic speciation profiles for eight orders of terrestrial invertebrates collected at three historical gold mine sites and one background site in Nova Scotia, Canada. Total arsenic concentrations, determined by inductively coupled plasma mass spectrometry (ICP-MS), were dependent upon the classification of invertebrate. Arsenic species were determined by high-performance liquid chromatography (HPLC) ICP-MS and X-ray absorption spectroscopy (XAS). Invertebrates were found by HPLC ICP-MS to contain predominantly arsenite and arsenate in methanol/water extracts, while XAS revealed that most arsenic is bound to sulfur in vivo. Examination of the spatial distribution of arsenic within an ant tissue highlighted the differences between exogenous and endogenous arsenic, as well as the extent to which arsenic is transformed upon ingestion. Similar arsenic speciation patterns for invertebrate groups were observed across sites. Trace amounts of arsenobetaine and arsenocholine were identified in slugs, ants, and spiders.

Ultrastructural alterations in midgut and Malpighian tubules of Boettcherisca peregrina exposure to cadmium and copper

The effects of Cu and Cd at their at their low concentrations (80microg/g diet) on the morphology and ultrastructure of the midgut and Malpighian tubules of Boettcherisca peregrina larvae were observed by light and transmission electron microscopy. After exposure to both metals, the midgut got darker, shorter, and thicker than in control, and many strumae occurred on the surface of the midgut. Similarly, Malpighian tubules got shorter and thinner. Ultrastructural alterations in the midgut included mitochondrial condensation, swelling, and lysis. The rough endoplasmic reticulum (rER) showed dilation and vesiculation. The microvilli were shortened and disorganized. The stored glycogens increased and many mineral spherites appeared along with lipid droplets decreased. Ultrastructural alterations observed in the Malpighian tubules included rER vesiculation and mitochondria swelling with loss of cristae. Shortened and disordered microvilli, increased numbers of large hydropic vacuoles, and mineral spherites were also observed.

Bioavailability of heavy metals and their effects on the midgut cells of a phytopaghous insect inhabiting volcanic environments

Organisms living in volcanic environments are chronically exposed to metals, either as particles or associated with gases, from volcanic emissions, being therefore potential sentinels of the effects derived from such exposure. Concentrations of Ca, Cd, Cu, Mg, Mn, Pb, Rb, and Zn were measured in soil, grass (Lolium perenne), and larvae of Pseudaletia uninpuncta captured in sites exposed and non-exposed to volcanic activity. The midgut epithelial cell morphometry and apoptosis of P. unipuncta larvae were also analyzed. Larvae from the site with volcanic activity showed higher levels of Cu, Mn, Rb and Zn. Metals such as Pb, Cd and Mg levels of P. unipuncta larvae were similar between sites. Apoptosis was higher in cells from digestive epithelium of larvae exposed to volcanic activity. Soils and grass not exposed to volcanic activity showed higher levels for most of the analyzed elements with the exception of Rb. Such result when compared with metal levels of larvae may reveal that bioavailability of elements differs between sites. The higher levels of Cd, Zn and Mg in soils and grass from the site with no volcanic activity are probably related to the severe artificial fertilization in the studied pastures. Such result, when compared with metal levels of larvae, suggest that the bioavailability of metals differs between sites.

Cadmium is deposited in the gut content of larvae of the beetle Tenebrio molitor and involves a Cd-binding protein of the low cysteine type

Binding of cadmium (Cd) to metallothionein (MT) and non-MT proteins with low contents of cysteine has been observed in terrestrial arthropods. We recently isolated a Cd-binding protein with no cysteine that was induced in Cd-exposed larvae of the beetle Tenebrio molitor. In this study we have examined the molecular distribution of Cd within extracts of different tissues and compartments of Cd-exposed T. molitor larvae. A Cd-peak consistent with the low cysteine Cd-binding protein was induced within the gut content where it could be detected after 4-8 days of exposure. Examination of gut wall tissue revealed no increase in Cd-binding capacity, indicating that no accumulation of MTs was taking place in this tissue. Incorporation of Cd in the gut wall tissue stabilized after 8 days of Cd-exposure at a rather low level compared to the other organs. There was a statistical trend towards Cd being incorporated in the gut content in a manner that was disproportionally high compared to the amount of Cd in the gut wall tissue. The possible role of the low cysteine Cd-binding protein in reducing the uptake of Cd in the tissues is discussed.

Assessment of heavy metals concentrations in soil samples from the vicinity of busy roads: influence on Drosophila melanogaster life cycle

An assessment of Cd, Cu, Pb, and Zn in 25 soil samples collected near busy roads in Irbid city, Jordan indicated contamination of these soil samples with different concentrations of 624, 1.243, 242, and 847 microg/g for Pb, Cd, Cu, and Zn, respectively. The survival percentage of Drosophila melanogaster third-instar larvae on synthetic medium containing these concentrations for the first generation shows a significant reduction in their growth and development or metamorphosis for most soil extracts. Moreover, there was a significant reduction in survival growth and development in the second generation. The survival percentages of the second generation at pupa stage was higher than the first generation, whereas at the adult stage, there was a lower survival percentage indicating some effects on metamorphosis caused by concentration of heavy metals on Drosophila melanogaster.

The future of stone research: rummagings in the attic, Randall's plaque, nanobacteria, and lessons from phylogeny

The prevention or cure of stone disease will be achieved only by identifying biochemical, physiological and molecular mechanisms operating before the formation of a calculus. Yet, the gradual increase in the total number of papers devoted to the study of kidney stones that has occurred since the beginning of the 21st century can be attributed almost entirely to papers concerned with the investigation of factors associated with urolithiasis after stones have already formed. The need to prevent stones by discovering how the human body routinely stops their formation in those of us who do not suffer from them is therefore as exigent as ever and a new approach to investigating the causes of stones is urgently needed. In this paper, I develop the view that stone research will best progress by examining and understanding how healthy plants and animals control the formation of biominerals. In addition to structures like bones, teeth, shells and spines, many organisms spanning the entire phylogenetic tree form intra- and extracellular granules which are use as storage depots for calcium and other important ions, which they can reclaim to maintain homeostasis or to satisfy specific needs during periods of high demand, such as shell formation, moulting or skeletal development. These electron-dense granules, which also bear an uncanny resemblance to calcified nanobacteria, are remarkably similar in general structure, size and composition to particles observed in healthy human kidneys and in Randall's plaque. Therefore, it is likely that the granules in human kidneys fulfil analogous functions to those in other organisms-particularly in calcium homeostasis. Their study in a large range of creatures has already provided a deep well of information about their structure, movement, composition, macromolecular content, synthesis and resorption, from which we can draw to quench our thirst for knowledge of basic mechanisms and events involved in the formation of human kidney stones.

Insoluble detoxification of trace metals in a marine copepod Tigriopus brevicornis (Müller) exposed to copper, zinc, nickel, cadmium, silver and mercury

The marine harpacticoid copepods Tigriopus brevicornis were collected along the French Atlantic Coast (Loire Atlantique) and subsequently exposed to different lethal and sublethal concentrations of various metals (copper, zinc, nickel, cadmium, silver and mercury) for varying lengths of time. Ultrastructural investigations of control and experimentally exposed copepods were performed to investigate the intracellular localization of metals using transmission electronic microscopy (TEM). Copepod digestive epithelium cells as well as the cuticular integument were found to be the major metal storage tissues. Different types of metal-containing granules were found in both metal-exposed copepods and the controls: (1) within lysosomes, (2) in intracellular calcospherites and (3) in extracellular tiny granules. The elemental composition of the granules was determined on ultrathin sections by means of energy dispersive X-ray spectroscopy (EDS). The results were interpreted by considering previous data in order to understand how Tigriopus brevicornis copes with the presence of metals in its environment.

Copper homeostasis in Drosophila by complex interplay of import, storage and behavioral avoidance

Copper is an essential but potentially toxic trace element. In Drosophila, the metal-responsive transcription factor (MTF-1) plays a dual role in copper homeostasis: at limiting copper concentrations, it induces the Ctr1B copper importer gene, whereas at high copper concentrations, it mainly induces the metallothionein genes. Here we find that, despite the downregulation of the Ctr1B gene at high copper concentrations, the protein persists on the plasma membrane of intestinal cells for many hours and thereby fills the intracellular copper stores. Drosophila may risk excessive copper accumulation for the potential benefit of overcoming a period of copper scarcity. Indeed, we find that copper-enriched flies donate a vital supply to their offspring, allowing the following generation to thrive on low-copper food. We also describe two additional modes of copper handling: behavioral avoidance of food containing high (>or=0.5 mM) copper levels, as well as the ability of DmATP7, the Drosophila homolog of Wilson/Menkes disease copper exporters, to counteract copper toxicity. Regulated import, storage, export, and avoidance of high-copper food establish an adequate copper homeostasis under variable environmental conditions.

Transcriptome response to heavy metal stress in Drosophila reveals a new zinc transporter that confers resistance to zinc

All organisms are confronted with external variations in trace element abundance. To elucidate the mechanisms that maintain metal homeostasis and protect against heavy metal stress, we have determined the transcriptome responses in Drosophila to sublethal doses of cadmium, zinc, copper, as well as to copper depletion. Furthermore, we analyzed the transcriptome of a metal-responsive transcription factor (MTF-1) null mutant. The gene family encoding metallothioneins, and the ABC transporter CG10505 that encodes a homolog of 'yeast cadmium factor' were induced by all three metals. Zinc and cadmium responses have similar features: genes upregulated by both metals include those for glutathione S-transferases GstD2 and GstD5, and for zinc transporter-like proteins designated ZnT35C and ZnT63C. Several of the metal-induced genes that emerged in our study are regulated by the transcription factor MTF-1. mRNA studies in MTF-1 overexpressing or null mutant flies and in silico search for metal response elements (binding sites for MTF-1) confirmed novel MTF-1 regulated genes such as ferritins, the ABC transporter CG10505 and the zinc transporter ZnT35C. The latter was analyzed in most detail; biochemical and genetic approaches, including targeted mutation, indicate that ZnT35C is involved in cellular and organismal zinc efflux and plays a major role in zinc detoxification.

Social paper wasps as bioindicators: a preliminary research with Polistes dominulus (Hymenoptera Vespidae) as a trace metal accumulator

The wasps of the genus Polistes (paper wasps), have a worldwide distribution and are widespread in human-built areas. Like other social wasps, they are at the top of food chains and are therefore exposed to the dangers of biomagnification, given that the larvae are fed predominantly with prey that consist of herbivorous insects. The larval faeces, larval fecal masses, in the form of a semi-solid ball, are made up of the residues of the diet of the larva, which are emitted and compressed on the floor of the cell during the larval metamorphosis. Larval fecal masses may accumulate lead (up to 36 times with respect to the adult body), therefore they were used as substrate for the analysis. From the analysis of sample nests of Polistes dominulus in various sites of the urban area of Florence, it emerges that the larval fecal masses are an analytical substrate with which it is possible to distinguish zones with differing degrees of lead pollution. The lead concentration measured in the larval fecal masses turns out to be directly correlated with vehicle traffic density, the main lead source in Florence when the survey was carried out. The notable increase in the lead concentration of larval fecal masses from the rural to the urban nest (11.15 times), in contrast with the much more limited level of pupae (4.39 times), seems to indicate the efficiency of the excretion and/or barrier mechanisms. These wasps seem to be a promising species for biomonitoring lead pollution in order to better understand its dynamics in anthropic ecosystems after the progressive diffusion of unleaded gasoline.

A family knockout of all four Drosophila metallothioneins reveals a central role in copper homeostasis and detoxification

Metallothioneins are ubiquitous, small, cysteine-rich proteins with the ability to bind heavy metals. In spite of their biochemical characterization, their in vivo function remains elusive. Here, we report the generation of a metallothionein gene family knockout in Drosophila melanogaster by targeted disruption of all four genes (MtnA to -D). These flies are viable if raised in standard laboratory food. During development, however, they are highly sensitive to copper, cadmium, and (to a lesser extent) zinc load. Metallothionein expression is particularly important for male viability; while copper load during development affects males and females equally, adult males lacking metallothioneins display a severely reduced life span, possibly due to copper-mediated oxidative stress. Using various reporter gene constructs, we find that different metallothioneins are expressed with virtually the same tissue specificity in larvae, notably in the intestinal tract at sites of metal accumulation, including the midgut's "copper cells." The same expression pattern is observed with a synthetic minipromoter consisting only of four tandem metal response elements. From these and other experiments, we conclude that tissue specificity of metallothionein expression is a consequence, rather than a cause, of metal distribution in the organism. The bright orange luminescence of copper accumulated in copper cells of the midgut is severely reduced in the metallothionein gene family knockout, as well as in mutants of metal-responsive transcription factor 1 (MTF-1), the main regulator of metallothionein expression. This indicates that an in vivo metallothionein-copper complex forms the basis of this luminescence. Strikingly, metallothionein mutants show an increased, MTF-1-dependent induction of metallothionein promoters in response to copper, cadmium, silver, zinc, and mercury. We conclude that free metal, but not metallothionein-bound metal, triggers the activation of MTF-1 and that metallothioneins regulate their own expression by a negative feedback loop.

Abnormal lysosomal trafficking and enhanced exosomal export of cisplatin in drug-resistant human ovarian carcinoma cells

Previous work has shown that cisplatin (CDDP) becomes concentrated in lysosomes, and that acquired resistance to CDDP is associated with abnormalities of protein trafficking and secretion. The lysosomal compartment in CDDP-sensitive 2008 human ovarian carcinoma cells was compared with that in CDDP-resistant 2008/C13*5.25 subline using deconvoluting imaging and specific dyes and antibodies. The lysosomal compartment in CDDP-resistant cells was reduced to just 40% of that in the parental CDDP-sensitive cells (P<0.002). This was accompanied by a reduced expression of the lysosome-associated proteins 1 and 2 (LAMP1 and LAMP2) as determined by both microscopy and Western blot analysis. The CDDP-resistant cells released more protein as exosomes and Western blot analysis revealed that these exosomes contained substantially more LAMP1 than those released by the CDDP-sensitive cells. Following loading of the whole cell with CDDP, the exosomes released from 2008/C13*5.25 cells contained 2.6-fold more platinum than those released from sensitive cells. Enhanced exosomal export was accompanied by higher exosomal levels of the putative CDDP export transporters MRP2, ATP7A, and ATP7B. Expression profiling identified significant increases in the expression of several genes whose products function in membrane fusion and vesicle trafficking. This study shows that the lysosomal compartment of human ovarian carcinoma cells selected for stable resistance to CDDP is markedly reduced in size, and that these cells abnormally sort some lysosomal proteins and the putative CDDP transporters into an exosomal pathway that also exports CDDP.

Fine structure of the midgut and Malpighian papillae in Campodea (Monocampa) quilisi Silvestri, 1932 (Hexapoda, Diplura) with special reference to the metal composition and physiological significance of midgut intracellular electron-dense granules

The fine structure of the midgut and the Malpighian papillae in Campodea (Monocampa) quilisi Silvestri, 1932 (Hexapoda, Diplura) specimens was described. We observed the presence of electron-dense granules (EDGs) in the midgut epithelial cells, similar in genesis, structure and aspect to the type A spherocrystals described in the midgut epithelium of Collembola and Diplopoda. Energy-dispersive X-ray microanalysis was used to detect the chemical composition of the granules and to relate it to the concentrations of some potential toxic heavy metals (Pb, Cu, Zn) in soil and litter. Chemical composition of the granules seems strongly influenced by the presence and bioavailability of heavy metals in the external environment. Specimens from a contaminated abandoned mining and smelting area (Colline Metallifere, southern Tuscany) were able to accumulate Fe, Mn, Zn, Pb and Cu in their midgut EDGs. In addition, we observed that C. (M.) quilisi was able to excrete the metal-containing granules into the external medium by the moulting of the intestinal epithelium. This confirms that the process of ionic retention of midgut cells is particularly significant in animals lacking Malpighian tubules.

Function-informed transcriptome analysis of Drosophila renal tubule

Analysis of the transcriptome of the Drosophila melanogaster Malpighian (renal) tubule gives a radically new view of the function of the tubule, emphasising solute transport rather than fluid secretion.

Background

Comprehensive, tissue-specific, microarray analysis is a potent tool for the identification of tightly defined expression patterns that might be missed in whole-organism scans. We applied such an analysis to Drosophila melanogaster Malpighian (renal) tubule, a defined differentiated tissue.

Results

The transcriptome of the D. melanogaster Malpighian tubule is highly reproducible and significantly different from that obtained from whole-organism arrays. More than 200 genes are more than 10-fold enriched and over 1,000 are significantly enriched. Of the top 200 genes, only 18 have previously been named, and only 45% have even estimates of function. In addition, 30 transcription factors, not previously implicated in tubule development, are shown to be enriched in adult tubule, and their expression patterns respect precisely the domains and cell types previously identified by enhancer trapping. Of Drosophila genes with close human disease homologs, 50 are enriched threefold or more, and eight enriched 10-fold or more, in tubule. Intriguingly, several of these diseases have human renal phenotypes, implying close conservation of renal function across 400 million years of divergent evolution.

Conclusions

From those genes that are identifiable, a radically new view of the function of the tubule, emphasizing solute transport rather than fluid secretion, can be obtained. The results illustrate the phenotype gap: historically, the effort expended on a model organism has tended to concentrate on a relatively small set of processes, rather than on the spread of genes in the genome.