The development stages of limnophyes globifer (Lundström) (diptera: chironomidae)

The larva, pupa and adult female of Limnophyes globifer (Lundström) are described for the first time, and the adult male is redescribed from material from a greater geographic range than hitherto. A lectotype is designated for L. globifer and it is suggested that Limnophytes folliculatus Saether is a junior synonym of L. globifer.Entomology Department, British Museum (Natural History)     

Integrin αvβ5 in endothelial cells of rat splenic sinus: an immunohistochemical and ultrastructural study

Localization of integrins β1-8, α1, α2, α3, α5, α6 and αv in sinus endothelial cells of the rat spleen was examined by immunofluorescence microscopy. Labeling for anti-integrin β5 and integrin αv was detected and colocalized in the entire circumference of endothelial cells. Labeling for integrin β5, vinculin and actin filaments demonstrated that they lay close to each other in the basal part of the endothelial cells. Although the other integrin βs, including integrin β1 and integrins α1, α2, α3, α5 and α6 in combination with integrin β1, were localized in leukocytes, slightly large cells, megakaryocytes and/or platelets in the sinus lumen and splenic cords, they were not detected in endothelial cells. Labeling for vitronectin, a component of the extracellular-matrix-binding integrin αvβ5, was strongly stained in the periphery of the wall of sinuses, as was collagen IV and, in addition, was localized in the cytoplasm of endothelial cells. Ultrastructural localization of integrin β5, vitronectin and clathrin was examined by immunogold electron microscopy to elucidate the involvement of integrin αvβ5 in the endocytosis of vitronectin in sinus endothelial cells. Electron microscopy with detergent extraction revealed abundant coated pits and coated vesicles in endothelial cells. Immunogold labeling for vitronectin was present in pits, vesicles and the stacked endoplasmic reticulum. Double-labeling for integrin β5 or integrin αv and clathrin revealed that they were colocalized in some vesicles in close proximity to the apical and lateral plasma membrane of the endothelial cells. The possible functional roles of integrin αvβ5 in endothelial cells of the splenic sinus are discussed.     

Effects of hydroxylamine and N-Methyl-N′-Nitro-N-nitrosoguanidine in Mimulus cardinalis (Scrophulariaceae): Survival curves and dominant mutants

Summary The lethal and mutagenic effects of hydroxylamine (HA) and N-methyl-N-nitro-N-nitrosoguanidine (MNNG) were investigated in the higher plant Mimulus cardinalis. MNNG was found to be more toxic than HA. The shapes of the survival curves obtained at different concentrations of HA and MNNG are interpreted on the basis of decreased biological activity of the solution to increased age of solution. Based on the appearance of chlorophyll-deficient mutants, MNNG is mutagenic in Mimulus. No albinos were detected in HA treated plants. A total of 67 putative mutants were isolated in the mutation spectra of HA and MNNG treated plants. The frequency of mutants induced by HA and MNNG are different. MNNG is mutagenic at 1/10 the concentration of HA in inducing putative mutations in M ₁ plants.A portion of this work will be submitted by the senior author to the Faculty of Miami University in partial fulfillment of the Doctor of Philosophy degree.     

EPR and Mössbauer studies of benzoyl-CoA reductase

Benzoyl-CoA reductase catalyzes the two-electron transfer from a reduced ferredoxin to the aromatic ring of benzoyl-CoA; this reaction is coupled to stoichiometrical ATP hydrolysis. A very low reduction potential (less than -1 V) is required for the first electron transfer to the aromatic ring. In this work the nature of the redox centers of purified benzoyl-CoA reductase from Thauera aromatica was studied by EPR and M?ssbauer spectroscopy. The results obtained indicated the presence of three [4Fe-4S] clusters. Redox titration studies revealed that the reduction potentials of all three clusters were below -500 mV. The previously reported S = 7/2 state of the enzyme during benzoyl-CoA-independent ATPase activity (Boll, M., Albracht, S. J. P., and Fuchs, G. (1997) Eur. J. Biochem. 244, 840-851) was confirmed by M?ssbauer spectroscopy. Inactivation by oxygen was associated with the irreversible conversion of part of the [4Fe-4S] clusters to [3Fe-4S] clusters. Acetylene stimulated the benzoyl-CoA-independent ATPase activity and induced novel EPR signals with g(av) >2. The presence of simple cubane clusters in benzoyl-CoA reductase as the sole redox-active metal centers demonstrates novel aspects of [4Fe-4S] clusters since they adopt the role of elemental sodium or lithium which are used as electron donors in the analogous chemical Birch reduction of aromatic rings.     

Biochemical,immunochemical, and ultrastructural studies of protein storage in poplar(Populus × canadensis ‘robusta’) wood

The seasonal changes in protein content have been followed in the wood of Populus × canadensis Moench robusta, both biochemically and electronmicroscopically at the cellular level. In the storage-parenchyma cells of the twig wood, 4–6 g · mg^–1 DW protein were deposited in the fall, parallel to the yellowing of leaves, and mobilized completely again during the outgrowth of buds in the spring. Environmental impacts on the leaves, e.g. a fungal attack and mechanical injury by a hurricane, were found to affect protein deposition in the wood considerably. Accumulation of protein bodies in the fall and their disappearance from the cells in the spring proceeded parallel to the changes in protein content measured biochemically, proving that these organelles are the main sites of protein storage in the wood parenchyma cells. Using immunogold labelling and an anti-32-kDa poplar storage-protein antibody the protein bodies were shown to be the exclusive sites of storage of a 32-kDa polypeptide. Transient changes in protein content were also observed during fall and winter. Because these changes coincided with changes in protein-body structure and with changes in the population of vesicles and-or tubular membrane cisternae of the cells, an exchange of nitrogen compounds from the storage pool into the structural protein of membranes possibly takes place during these periods. The structural events observed during proteolysis in spring are very similar to those found in seeds. The possible roles of small cytoplasmic vesicles found within protein bodies during proteolysis and of multimembraneous vacuolar compartments during membrane retrieval are discussed.Abbreviations DW dry weight - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis Dedicated to Professor Dr. Dr. Hans Marquardt on the occasion of his 80th birthdayThe valuable technical assistance of Miss Sabine Karg and Miss Astrid Diercks is gratefully acknowledged. This work was supported by the Deutsche Forschungsgemeinschaft.     

Uterine Müllerian adenosarcoma with psammoma bodies: cytologic, histologic and ultrastructural studies of a case

Epithelial cells associated with psammoma bodies and undifferentiated sarcomatous tumor cells were found in peritoneal washings obtained during laparotomy for removal of metastatic lesions from a uterine stromal sarcoma. Histologic studies of the primary and recurrent tumors showed characteristics of Müllerian adenosarcoma. The cytologic, histologic and ultrastructural features are described.     

Assessment of bioburden on human and animal tissues: Part 1—Results of method development and validation studies

Recovered human and animal tissues are used extensively in surgery for wound repair and reconstruction. In preparation for the validation of chemical disinfection and radiation sterilization processes, studies were performed on the development and validation of quantitative bioburden recovery methods for human bone and soft tissue and also for porcine dermis. The use of a swab-based method was not considered due to the known poor efficiency of recovery for this technique. The “exhaustive extraction” and “inoculated product” approaches to validation of a bioburden recovery efficiency factor have inherent strengths and weaknesses; in this study, tissues were inoculated and also subjected to a series of extractions to determine if/when “exhaustion” occurred. Femoral and tibial shaft rings, iliac crest wedges, sections of Achilles tendon, a soft tissue composite sample, and porcine dermis, were inoculated at several sites with Bacillus atrophaeus spores, and then subjected to either shaking by hand, mechanical shaking, or sonication plus mechanical shaking. Each of these methods of agitation were performed in combination with three rinse (extraction) fluids: phosphate buffer (Butterfield’s buffer), phosphate buffer with 0.2% polysorbate 80 (a surfactant), and water with 1% peptone and 1% polysorbate 80 (Fluid D). The highest recovery efficiencies were observed with sonication plus mechanical shaking; of the three extraction media, Fluid D gave the highest first-rinse recovery efficiency (65%) and Butterfield’s buffer gave the lowest (39%). Each of the three recovery methods, however appeared to reach “exhaustion”, a subsequent rinse giving less than 10% of the recovery found in the first rinse. The results demonstrated the importance of performing bioburden method development and validation studies. The method validation strategy described here, using a combination of tissue inoculation and repetitive extraction, showed the superiority of sonication plus mechanical shaking using Fluid D as the rinse medium. In addition, the use of only the exhaustive extraction approach could have resulted in the development of a methodology that consistently underestimated the bioburden present on/in recovered tissue.     

Hominid palaeobiology: Have studies of comparative development come of age?

It is 70 years since Adolf Schultz urged his colleagues to consider how studies of primate growth and development could help them interpret the course of human evolution. This paper considers the evolutionary context of comparative growth studies. It compares and contrasts aspects of the ontogeny of living modern humans and chimpanzees, and considers whether relatively simple models of heterochronic change can account for the modifications which have taken place during the course of human evolutionary history. © 1995 Wiley-Liss, Inc.     

Recent advancement in the discovery and development of COX-2 inhibitors: Insight into biological activities and SAR studies (2008–2019)

Cyclooxygenase-2 is a very important physiological enzyme playing key roles in various biological functions especially in the mechanism of pain and inflammation, among other roles, making it a molecule of high interest to the pharmaceutical community as a target. COX 2 enzyme is induced only during inflammatory processes or cancer and reflects no role in the guarding stomach lining. Thus, selective COX-2 inhibition can significantly reduce the adverse effects including GI tract damage and hepatotoxic effects of traditional NSAIDs like aspirin, ibuprofen, etc. Recent developments on COX-2 inhibitors is primarily focused on improving the selectivity index of the drug towards COX-2 along with enhancing the potency of the drug by modifying the scaffolds of Coxibs currently in the market like Celecoxib, Indomethacin, Oxaprozin, etc. We have reported the progress on new COX-2 inhibitors in the last decade (2008–2019) focussing on five heterocyclic rings- Pyrazole, Indole, Oxazole, Pyridine and Pyrrole. The addition of various moieties to these core rings and their structure-activity relationship along with their molecular modelling data have been explored in the article. This review aims to aid medicinal chemists in the design and discovery of better COX-2 inhibitors constructed on these five heterocyclic pharmacophores.     

Mössbauer and NMR studies of protonated acyl diphosphaferrocenes

The acyl derivatives of 3,3′,4,4′-tetramethyldi- phosphaferrocene (TMDPF) have been examined in strong acids by ⁵⁷Fe Mössbauer, ¹H and ³¹P NMR spectroscopy. As with ferrocenyl ketones, protonation was found to occur at the keto function, the diphosphaferrocenyl ketones having comparable or, in some cases, reduced basicities compared to ferrocenyl ketones. [p ]Trends in the ⁵⁷Fe Mössbauer parameters are not as additive as in ferrocene systems due to steric crowding. The keto derivatives show some unusual deuteriation patterns and these have been compared with those of ferrocenyl ketones. The ¹³C spectra of several derivatives have been reported to illustrate the rather complex stereochemistry found in these derivatives.     

Organisation of the endosperm and endosperm–placenta syncytia in bladderworts (Utricularia, Lentibulariaceae) with emphasis on the microtubule arrangement

Multinucleate cells play an important role in higher plants, especially during reproduction; however, the configurations of their cytoskeletons, which are formed as a result of mitosis without cytokinesis, have mainly been studied in coenocytes. Previous authors have proposed that in spite of their developmental origin (cell fusion or mitosis without cytokinesis), in multinucleate plant cells, radiating microtubules determine the regular spacing of individual nuclei. However, with the exception of specific syncytia induced by parasitic nematodes, there is no information about the microtubular cytoskeleton in plant heterokaryotic syncytia, i.e. when the nuclei of fused cells come from different cell pools. In this paper, we describe the arrangement of microtubules in the endosperm and special endosperm–placenta syncytia in two Utricularia species. These syncytia arise from different progenitor cells, i.e. cells of the maternal sporophytic nutritive tissue and the micropylar endosperm haustorium (both maternal and paternal genetic material). The development of the endosperm in the two species studied was very similar. We describe microtubule configurations in the three functional endosperm domains: the micropylar syncytium, the endosperm proper and the chalazal haustorium. In contrast to plant syncytia that are induced by parasitic nematodes, the syncytia of Utricularia had an extensive microtubular network. Within each syncytium, two giant nuclei, coming from endosperm cells, were surrounded by a three-dimensional cage of microtubules, which formed a huge cytoplasmic domain. At the periphery of the syncytium, where new protoplasts of the nutritive cells join the syncytium, the microtubules formed a network which surrounded small nuclei from nutritive tissue cells and were also distributed through the cytoplasm. Thus, in the Utricularia syncytium, there were different sized cytoplasmic domains, whose architecture depended on the source and size of the nuclei. The endosperm proper was isolated from maternal (ovule) tissues by a cuticle layer, so the syncytium and chalazal haustorium were the only way for nutrients to be transported from the maternal tissue towards the developing embryo.     

Comparative studies of α-lactalbumin and lysozyme: The proteins of kangaroo (Megaleia rufa and Macropus giganteus) and horse (Equus caballus)

Summary As part of a study of the whey proteins of various mammals, a comparison is made of the -lactalbumins and lysozymes of the kangaroo and horse. In the milk of the red kangaroo (Megaleia rufa) there is only one -lactalbumin and it occurs throughout lactation, but no lysozyme has been detected. There are two -lactalbumins in the milk of the grey kangaroo (Macropus giganteus), one, designated -lactalbumin Zone B, is present throughout lactation; the second, designated -lactalbumin Zone A, is present only in late lactation. One lysozyme is also present. The milk of the horse (Equus caballus) contains one -lactalbumin and at least one lysozyme. Partial amino acid sequences are proposed from sequence determination and from analyses of tryptic peptides compared with the known sequences of other -lactalbumins and lysozymes.     

Interaction of aristololactam-β-D-glucoside and daunomycin with poly(A): spectroscopic and calorimetric studies

The binding of two sugar containing antibiotics viz. aristololactam-β-D-glucoside and daunomycin with single and double stranded poly(A) was investigated by spectroscopic and calorimetric studies. The binding affinity of daunomycin to ss poly(A) was of the order of 10⁶ M^− 1 and that to ds poly(A) was of the order of 10⁵ M^− 1. Aristololactam-β-D-glucoside showed a relatively weaker binding with an affinity of the order of 10⁴ M^− 1 with both the conformations of poly(A). Fluorescence studies showed maximum quenching for daunomycin-ss poly(A) complexes. The binding constants calculated from fluorescence spectroscopy were in good agreement with that obtained from UV spectroscopy. Moderate perturbation of circular dichroic spectra of both the conformations of poly(A) in presence of these molecules with concomitant formation of prominent extrinsic CD bands in the 300-450 nm region further revealed the association. Isothermal titration calorimetry results showed an overall entropy driven binding in all the four systems though the entropy change was maximum in daunomycin-ss poly(A) binding. The binding affinity was also maximum for daunomycin-ss poly(A) and varied as daunomycin-ds poly(A)>aristololactam-β-D-glucoside-ds poly(A)>aristololactam-β-D-glucoside-ss poly(A). A 1:1 binding stoichiometry was observed in all the cases, as confirmed by Job plot analysis, indicating the interaction to consist of a single binding mode. Ferrocyanide quenching studies showed good stacking interaction in all cases but was best for daunomycin-ss poly(A) interaction. No self-structure formation was observed in poly(A) with both daunomycin and aristololactam-β-D-glucoside suggesting the hindrance of the sugar moiety for such structural organization.     

Structural,infrared and Mössbauer studies of octahedral cis-dichlorobis(diketonate)tin(IV) complexes having anti-tumour activity

Two complexes, SnCl₂(bzac)₂ [Hbzac = benzoylacetone] and SnCl₂(bzbz)₂ [Hbzbz = dibenzoylmethane], have been prepared and characterised by analytical, infrared and Mössbauer studies. In addition, the X-ray crystal structure of SnCl₂(bzbz)₂ has been determined. The crystals are orthorhombic, space group Pbca with cell parameters a=18.767(9), b=17.611(8), c=16.563(8) Å. A total of 2116 reflections with I/σ(I)⩾3 gave R=3.0%. The tin is coordinated to two cis-chlorine and four oxygen atoms from the dibenzoylmethanato ligands in an approximately octahedral arrangement. The bond distances in the tin coordination sphere are SnCl 2.335(2) and 2.344(2) Å and SnO 2.062(4), 2.074(4), 2.063(4) and 2.063(4) Å and the ClSnCl angle is 95.1(1)°. The results of anti-tumour tests on these complexes are given and attempts are made to correlate the anti-tumour activity of SnCl₂(bzbz)₂ with its structure.     

Models of the bis-histidine-coordinated ferricytochromes: Mössbauer and EPR spectroscopic studies of low-spin iron(III) tetrapyrroles of various electronic ground states and axial ligand orientations

The EPR and magnetic Mössbauer spectra of a series of axial ligand complexes of tetrakis(2,6-dimethoxyphenyl)porphyrinatoiron(III), [(2,6-(OMe)₂)₄TPPFeL₂]⁺, where L=N-methylimidazole, 2-methylimidazole, or 4-(dimethylamino)pyridine, of one axial ligand complex of tetraphenylporphyrin, the bis(4-cyanopyridine) complex [TPPFe(4-CNPy)₂]⁺, and of one axial ligand complex of tetraphenylchlorin, [TPCFe(ImH)₂]⁺, where ImH=imidazole, have been investigated and compared to those of low-spin Fe(III) porphyrinates and ferriheme proteins reported in the literature. On the basis of this and previous complementary spectroscopic investigations, three types of complexes have been identified: those having (d_xy)²(d_xz,d_yz)³ electronic ground states with axial ligands aligned in perpendicular planes (Type I), those having (d_xy)²(d_xz,d_yz)³ electronic ground states with axial ligands aligned in parallel planes (Type II), and those having the novel (d_xz,d_yz)⁴(d_xy)¹ electronic ground state (Type III). A subset of the latter type, with planar axial ligands aligned parallel to each other or strong macrocycle asymmetry that yield rhombic EPR spectra, cannot be created using the porphyrinate ligand. Type I centers are characterized by "large g_max" EPR spectra with g>3.2 and well-resolved, widely spread magnetic Mössbauer spectra having A_zz/g_NN>680 kG, with A_xx negative in sign but much smaller in magnitude than A_zz, while Type II centers have well-resolved rhombic EPR spectra with g_zz=2.4–3.1 and also less-resolved magnetic Mössbauer spectra, and usually have A_zz/g_NN in the range of 440–660 kG (but in certain cases as small as 180 kG) and A_xx again negative in sign but only somewhat smaller (but occasionally larger in magnitude) than A_zz, and Type III centers have axial EPR spectra with g_┴2.6 or smaller and g_║<1.0–1.95, but often not resolved, and less-resolved magnetic Mössbauer spectra having A_zz/g_NN in the range of 270–400 kG, and A_xx again negative in sign but much smaller in magnitude than A_zz. An exception to this rule is [TPPFe(4-CNPy)₂]⁺, which has A_xx/g_NN=–565 kG, A_yy/g_NN=629 kG, and A_zz/g_NN=4 kG. A subset of Type II complexes (Type II) have rhombicities (V/) much greater than 0.67 and A_zz/g_NN ranging from 320 to 170 kG, with A_xx also negative but with the magnitude of A_xx significantly larger than that of A_zz. These classifications are also observed for a variety of ferriheme proteins, and they lead to linear correlations between A_zz and either A_xx, g_zz, or V/ for Types I and II (but not for A_zz versus V/ for Type II). Not enough data are yet available on Type III complexes to determine what, if any, correlations may be observed.Abbreviations CCP cytochrome c peroxidase - 4-CNPy 4-cyanopyridine - cyt cytochrome - EFG electric field gradient - ESEEM electron spin echo envelope modulation - ImH imidazole - Mb myoglobin - MCD magnetic circular dichroism - 2-MeImH 2-methylimidazole - N-MeIm N-methylimidazole - 3NH₂PzH 3-aminopyrazole - 4-NMe₂Py 4-(dimethylamino)pyridine - [2,6-(OMe)₂]₄TPP dianion of tetrakis(meso-2,6-dimethoxyphenyl)porphyrin - OEiBC dianion of octaethylisobacteriochlorin - OEP dianion of octaethylporphyrin - PPIX dianion of protoporphyrin IX - Py pyridine - TMP dianion of meso-tetramesitylporphyrin - TPC dianion of meso-tetraphenylchlorin - TPP dianion of meso-tetraphenylporphyrin - 2,6-XylylNC 2,6-xylyl isocyanide     

Larval development and morphogenesis of the sea spider Pycnogonum litorale (Ström, 1762) and the tagmosis of the body of Pantopoda

Aspects of pantopod ontogeny have been known for a long time, but specific information is available for only a few species. Our account of the postembryonic development of Pycnogonum litorale is based on laboratory-reared individuals and SEM studies. We documented particularly all early developmental stages, with emphasis on morphogenetic changes of head structures and appendages. In P. litorale the protonymphal limbs, the chelicerae and two more uniramous legs, degenerate already during the larval phase; only the third one, the ovigers, reappears in male juveniles. Other Pantopoda vary in this aspect from retention of all three protonymphal appendages to their complete reduction, as in P. litorale. Accordingly, the two post-cheliceral larval appendages are separate legs in front of the walking legs in the adults, the ‘parapalps’ and the ‘ovigers’, but they do not occur in all pantopods. The scarcity of studies of the ontogeny of Pantopoda prevents us from a more conclusive picture, but our data are promising to state that additional such studies will increase the usability of ontogenetic data for a phylogenetic analysis of Pantopoda, the crown group of the Pycnogonida. We also discuss the phylogenetic implications of our data in the light of new information from Hox genes and developmental-biological data on body segmentation and tagmosis of the Chelicerata. These suggest the homology of chelicerae and antenn(ul)ae of other euarthropods. Accepting this, we conclude that the adult pycnogonid/pantopod head, the cephalosoma, corresponds to the euarthropod head and that the protonymph with three appendage-bearing segments may represent an even shorter, possibly phylogenetically older larval type than the euarthropod ‘head larva’ bearing four pairs of appendages. In further consequence, the fourth walking legs of Pycnogonida/Pantopoda should correspond to the first opisthosomal appendages, the chilaria, of euchelicerates. This implies that within Pycnogonida the post-prosomal region became compacted during evolution to a single leg-bearing segment plus a tubular end piece. Accordingly, neither the anterior nor the posterior functional boundaries of the walking-leg region correspond to the original tagma borders.     

Luminescent activity and ultrastructural characterization of photocytes dissociated from the coelenterate Renilla köllikeri

Dissociation and Percoll sedimentation techniques were used to separate and pool the autofluorescent luminescent cells (photocytes) of the pennatulid anthozoan Renilla k?llikeri. Photometric recordings of luminescent activity of photocyte suspensions show that activation of flashing and glowing by KCl depolarization is suppressed in calcium-free sea water and by cobalt but enhanced by trifluoperazine, thus suggesting that luminescence excitation is dependent on extracellular calcium and calmodulin-mediated mechanisms. Of several neuroactive substances tested, adrenaline, dopamine, N-methyl-N-phenylethanolamine, serotonin and the native neuropeptide Antho-RFamide all induced photocyte responses at high concentrations (0.1-1 mM) only, whereas lower concentrations of adrenaline and Antho-RFamide are known to activate or enhance luminescence or muscular contractions in intact Renilla tissues (Anctil et al., 1982; Anctil, 1987). Hence, none of these substances is a likely neurotransmitter candidate for direct photocyte activation. Ultrastructural observations of dissociated photocytes reveal that they are musculo-epithelial cells containing numerous 0.2-mum vesicles resembling previously extracted and light-emitting lumisomes (Anderson and Cormier, 1973). Similar cells were traced ultrastructurally in situ in the endodermal luminescent zones, but not in non-luminescent endoderm.     

Morphological and ultrastructural studies of some acritarchs from the Lower Cambrian Lükati Formation, Estonia

Six acritarch species from the Lükati Formation were studied using a combination of techniques, including transmitted light, scanning electron (SEM) and transmission electron (TEM) microscopy. New details of wall ultrastructure, surface microsculpture and internal morphology of the vesicle and processes significantly add to the previously known morphological features and increase the understanding of the form-genera Archaeodiscina, Globosphaeridium, Comasphaeridium, Skiagia, Tasmanites and Leiosphaeridia. Examination of microfossils using TEM revealed a substantial variation in wall ultrastructure among acritarchs. The diversity includes four structural types of vesicle wall in addition to their single- and multi-layered structure and the variable thickness of the wall. These are: electron-tenuous and fibrous; electron-dense and homogeneous; electron-dense and homogeneous but perforated by radial canals; and composite laminated structure. Morphologically recognised groupings of acritarchs (acanthomorphic, disphaeromorphic, sphaeromorphic) and tasmanitid taxa appear to be characterised by particular features of the wall structure, although the wall structure in itself may not be directly indicative of systematic relationships. Structurally diverse vesicle walls are observed in Tasmanites and Leiosphaeridia, taxa that both have been interpreted, based on other lines of evidence, to be of prasinophycean (green algal) affinities. The distinct wall ultrastructure of the Leiosphaeridia studied is similar to that of extant green algal genera, which provides evidence that some Cambrian leiosphaerids were chlorophycean algae, probably related to the Order Chlorococcales. Previous research and interpretations of the wall ultrastructure are also briefly discussed.     

Heterosis in early seed development: a comparative study of F1 embryo and endosperm tissues 6 days after fertilization

Heterosis specifies the superior performance of heterozygous individuals and although used in plant breeding the underlying molecular mechanisms still remain largely elusive. In this study, we demonstrate the manifestation of heterosis in hybrid maize embryo and endosperm tissue 6 days after fertilization in crosses of several inbred lines. We provide a comparative analysis of heterosis-associated gene expression in these tissues by a combined approach of suppression subtractive hybridization and microarray hybridizations. Non-additive expression pattern indicated a trans-regulatory mechanism to act early after fertilization in hybrid embryo and endosperm although the majority of genes showed mid-parental expression levels in embryo and dosage dependent expression levels in endosperm. The consistent expression pattern within both tissues and both inbred line genotype combinations of genes coding for chromatin related proteins pointed to heterosis-related epigenetic processes. These and genes involved in other biological processes, identified in this study, might provide entry points for the investigation of regulatory networks associated with the specification of heterosis.     

Biosorption of Cd(II) and Pb(II) onto brown seaweed, Lobophora variegata (Lamouroux): kinetic and equilibrium studies

The present work deals with the biosorption performance of raw and chemically modified biomass of the brown seaweed Lobophora variegata for removal of Cd(II) and Pb(II) from aqueous solution. The biosorption capacity was significantly altered by pH of the solution delineating that the higher the pH, the higher the Cd(II) and Pb(II) removal. Kinetic and isotherm experiments were carried out at the optimal pH 5.0. The metal removal rates were conspicuously rapid wherein 90% of the total sorption occurred within 90 min. Biomass treated with CaCl₂ demonstrated the highest potential for the sorption of the metal ions with the maximum uptake capacities i.e. 1.71 and 1.79 mmol g⁻¹ for Cd(II) and Pb(II), respectively. Kinetic data were satisfactorily manifested by a pseudo-second order chemical sorption process. The process mechanism consisting of both surface adsorption and pore diffusion was found to be complex. The sorption data have been analyzed and fitted to sorption isotherm of the Freundlich, Langmuir, and Redlich–Peterson models. The regression coefficient for both Langmuir and Redlich–Peterson isotherms were higher than those secured for Freundlich isotherm implying that the biosorption system is possibly monolayer coverage of the L. variegata surface by the cadmium and lead ions. FT-IR studies revealed that Cd(II) and Pb(II) binding to L. variegata occurred primarily through biomass carboxyl groups accompanied by momentous interactions of the biomass amino and amide groups. In this study, we have observed that L. variegata had maximum biosorption capacity for Cd(II) and Pb(II) reported so far for any marine algae. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.