Computational constraints that may have favoured the lamination of sensory cortex

At the transition from early reptilian ancestors to primordial mammals, the areas of sensory cortex that process topographic modalities acquire the laminar structure of isocortex. A prominent step in lamination is granulation, whereby the formerly unique principal layer of pyramidal cells is split by the insertion of a new layer of excitatory, but intrinsic, granule cells, layer IV. I consider the hypothesis that granulation, and the differentiation between supra- and infra-granular pyramidal layers, may be advantageous to support fine topography in their sensory maps. Fine topography implies a generic distinction between where information, explicitly mapped on the cortical sheet, and what information, represented in a distributed fashion as a distinct firing pattern across neurons. These patterns can be stored on recurrent collaterals in the cortex, and such memory can help substantially in the analysis of current sensory input. The simulation of a simplified network model demonstrates that a non-laminated patch of cortex must compromise between transmitting where information or retrieving what information. The simulation of a modified model including differentiation of a granular layer shows a modest but significant quantitative advantage, expressed as a less severe trade-off between what and where. The further connectivity differentiation between infra-granular and supra-granular pyramidal layers is shown to match the mix of what and where information optimal for their respective target structures.     

Über die Kalkausscheidungen beiMonophyllaea horsfieldii (Gesneriaceae)

The lower surface of the leaf (macrocotyledon) ofM. horsfieldii is heavily calcified. SEM investigations reveal that the cristalline depositions of CaCO₃ (mainly needles, but also clump-like structures) are excreted by the head cells of two-cellular trichomhydathodes. First, a cap-like structure is formed. As the excretion continues, the cap takes on the shape of a hat with wide brim. Thus, the dense layer of CaCO₃ depositions is composed of hat-like structures whose brims at least partially touch. There is no evidence for the excretion of CaCO₃ by cells other than trichomhydathodes.

     

Na,K-ATPase: Isoform structure,function, and expression

An interesting feature of the Na,K-ATPase is the multiplicity of and isoforms. Three isoforms exist for the subunit, 1, 2, and 3, as well for the subunit, 1, 2, and 3. The functional significance of these isoforms is unknown, but they are expressed in a tissue- and developmental-specific manner. For example, all three isoforms of the subunit are present in the brain, while only 1 is present in kidney and lung, and 2 represents the major isoform in skeletal muscle. Therefore, it is possible that each of these isoforms confers different properties on the Na,K-ATPase which allows effective coupling to the physiological process for which it provides energy in the form of an ion gradient. It is also possible that the multiple isoforms are the result of gene triplication and that each isoform exhibits similar enzymatic properties. In this case, the expression of the triplicated genes would be individually regulated to provide the appropriate amount of Na,K-ATPase to the particular tissue and at specific times of development. While differences are observed in such parameters as Na⁺ affinity and sensitivity to cardiac glycosides, it is not known if these properties play a functional role within the cell.Site-directed mutagenesis has identified amino acid residues in the first extracellular region of the subunit as major determinants in the differential sensitivity to cardiac glycosides. Similar studies have failed to identify residues in the second extracellular region involved in cardiac glycoside inhibition. Further analysis of the enzymatic properties of the enzyme, understanding the regulated expression of the genes, and structure-function studies utilizing site-directed mutagenesis should provide new insights into the enzymatic and physiological roles of the various subunit isoforms of the Na,K-ATPase.     

Ultrastructure of the tubule of the aglomerular teleost Nerophis ophidion

Summary The tubules in the aglomerular kidney of Nerophis ophidion are composed of cells showing different types of specializations of their plasma membrane. All cells possess a luminal brush border composed of microvilli, and show presence of vesicles with 100 Å thick unit membranes — some containing electron dense material —, tubular elements, multivesicular bodies, and plasma membrane invaginations in their apical cytoplasm. These features suggest an absorptive function of the cells. The apical portions of the cells are supplied with typical cilia.Some cells have abundant basilar plasma membrane invaginations usually lacking cytoplasmic organelles. Other cells appear to form interdigitating basilar cytoplasmic processes containing mitochondria; still other cells have smooth basilar cell membranes. These findings are discussed with reference to the known secretory function of the tubules and are compared with tubular fine structure in other species. It was concluded that urine formation by tubular secretion may occur in cells with different types of basilar cell membrane specializations.The occurrence of coated vesicles associated with invaginated basilar plasma membranes indicates transport of proteins (from peritubular blood vessels ?) at these sites.The tubule cells have abundant smooth surfaced endoplasmic reticulum and large and numerous active Golgi zones.Supported by grants from Fonden til Videnskabens Fremme and Therese och Johan Anderssons Minne. Part of this study was done at the Zoologica Stazione, Naples.The assistance of Miss Britt-Marie Petterson and Mr. Magnus Norman is gratefully acknowledged.     

Suppression of cytokine production by supernatants from CD8+ lymphocytes activated by mycobacterial fractions: The role of interleukins 4 and 6

Supernatants derived from CD8⁺ lymphocytes treated with mycobacterial components, or the partially purified carbohydrates from these supernatants, increased the production of IL-4 and IL-6 by mononuclear cells. The addition of anti-IL4 or anti-IL6 antibodies to LPS stimulated MN cells incubated with supernatants from CD8⁺ lymphocytes or carbohydrates resulted in the restoration of other cytokine production by these MN cells. Recombinant IL-4 and IL-6 on their own suppressed the production of IL-1, TNF-, IL-2 and IFN- by mononuclear cells. Such suppression could be reversed with antibodies to IL-4 and IL-6. The addition of rIL-4 and rIL-6 did not increase the suppression of cytokine production induced by suppressor supernatants or carbohydrates. Interleukin 4 decreased the production of IL-6 by MN cells; whilst IL-6 suppressed IL-4 production in a dose dependent manner. Both effects could be reversed with the appropriate antisera. Our results suggest that mycobacteria could evade host immunity by inducing the production of IL-4 and IL-6 by host mononuclear cells. These cytokines, in turn, would suppress the production of other cytokines necessary for effective cellular immunity.Abbreviations IL-1 interleukin 1 - IL-2 interleukin 2 - IL-4 interleukin 4 - IL-6 interleukin 6 - IFN- gamma interferon - TNF- tumour necrosis factor alpha - MN cells mononuclear cells - NAL's non-adherent lymphocytes - LPS lipopolysaccharide - PMA phorbol myristate acetate - RIA radioimmunoassay - ELISA enzyme-linked immunosorbent assay - rIL-4 recombinant interlukin-4 - rIL-6 recombinant interleukin-6 - U/ml units per millilitre - g/ml micrograms per millilitre - ng/ml nanograms per millilitre     

Application of percolation theory principles to the analysis of interaction of adenylate cyclase complex proteins in cell membranes

Summary Lateral protein movement in cell membranes takes place in a medium with obstacles. These obstacles are: (a) aggregates of major integral proteins immobilized by submembraneous structures and cytoskeleton, and (b) membrane lipids in the gel phase. Hormonal activation of the adenylate cyclase complex is associated with lateral mobility of the constituent proteins. Modification of the interaction of these proteins due to variation of the fluid lipid fraction in reticulocyte membranes has been studied. A decrease in the percentage of fluid lipids in membranes resulted in the inhibition (up to the full cessation) of the interaction of -adrenoreceptors with regulatory N_s-proteins. The interaction of N_s-proteins with catalytic proteins stopped as well. On the other hand, an increase in the fluid lipid fraction led to a more intensive interaction. These facts do not arise from the functional damage of interacting proteins. Conseqently, hormonal activation of the adenylate cyclase complex depends on the fraction of fluid lipids in the membrane. The data obtained are in conformity with the percolation theory which makes it possible to characterize long-distance protein movement in a medium (fluid lipids) containing obstacles. Thus, interacting proteins prove to diffuse within distances greatly exceeding protein sizes. As a consequence, the intrinsic activity of a -agonist, isoproterenol, varies from 1 to 0 depending on the fluid lipid fraction. Our findings also suggest that in vitro there are no -receptors precoupled with N_s-proteins in rat reticulocyte membranes in the absence of guanine nucleotides.     

Plant regeneration via somatic embryogenesis in Styrian pumpkin: cytological and biochemical investigations

Somatic embryo formation was induced from cotyledon explants of Styrian pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) by using a solid MS medium supplemented with 16.11M NAA and 4.44M BA or 26.85M NAA and 13.32M BA. The callus proliferation was more efficient on medium supplemented with 26.85M NAA and 13.32M BA. In contrast, the embryogenic response was higher on medium with lower concentrations of growth regulators (16.11M NAA and 4.44M BA). The time needed for embryo induction did not depend on medium composition. Embryos in globular stage were transferred to three different maturation media, containing 2.89M GA₃ in combination with 0.54M NAA, 11.42M IAA and growth regulator-free medium. The germination rate was the highest when embryos were cultured on medium with 11.42M IAA. Plantlets grown on this medium achieved maturity suitable for transplantation into soil within 9 to 10weeks. The regenerated plants were successfully transferred into field and developed fertile flowers and set fruits. Biochemical analysis showed significant lower total glutathione levels among in vitro grown plantlets compared to seedlings grown in soil. When the plantlets were transferred into soil, they reached a normal size within a month and the glutathione concentration was comparable to seed-derived plants at the same developmental stage. Transmission electron microscopy was used to investigate possible differences in the ultrastructure of cells from callus cultures, and leaf cells of regenerated and seed-derived plants. Differences in the ultrastructure were found within chloroplasts which contained only single thylakoids, large starch grains and small plastoglobuli in callus cells in comparison to leaf cells, which possessed a well developed thylakoid system, small starch grains and large plastoglobuli.     

A model for light adaptation: Producing Weber's law with bleaching-type kinetics

An adaptation model having two stages is introduced and its mathematical properties are examined. The two stages are the adaptive process (parameter K _b), which has bleaching-type kinetics, and the response function (parameters K _r and n), which incorporates response saturation. In order to study the increment threshold functions generated by the adaptation model the concept of a detector is required. It is demonstrated that without an adaptive process the compression hypothesis, in the form of the difference equation, produces increment threshold functions which saturate and do not obey Weber's law. It is then shown that an adaptive process with bleaching-type kinetics can prevent saturation and produce Weber's law behavior provided that the adaptive strength of the system exceeds the detector sensitivity.     

Effect of lipid supplements on the production and glycosylation of recombinant interferon-γ expressed in CHO cells

The effects of lipids on the glycosylation of recombinant human interferon- expressed in a Chinese Hamster Ovary cell line were investigated in batch culture. Lipids form an essential part of the N-glycosylation pathway, and have been shown to improve cell viability. In control (serum-free) medium the proportion of fully-glycosylated interferon- deteriorated reproducibly with time in batch culture, but the lipoprotein supplement ExCyte was shown to minimise this trend. Partially substituting the bovine serum albumin content of the medium with a fatty-acid free preparation also improved interferon- glycosylation, possibly indicating that oxidised lipids carried on Cohn fraction V albumin may damage the glycosylation process.Abbreviations BSA bovine serum albumin - CHO chinese hamster ovary - DHFR dihydrofolate reductase - FCS foetal calf serum - IFN- human interferon-gamma - q _IFN specific interferon production rate - specific growth rate - 2N doubly-gycosylated - 1N singly-glycosylated - ON non-glycosylated     

Detection and partial characterization of two antigenically distinct β-amylases in developing kernels of wheat

A -amylase (EC 3.2.1.2) was identified in the outer pericarp (P) of developing seeds of wheat (Triticum aestivum L.) and compared with the well known -amylase which is synthesized during seed development in the starchy endosperm (E). The enzyme P already exists in the tissues before anthesis and vanishes at the time when E starts to accumulate. The isoelectric-focusing patterns of P and E are very similar. The relative molecular weight (M_r) of P is slightly higher than that of E (66 and 64.5 kDa, respectively). Both P and E exhibit common epitopes in addition to epitopes specific for each of them. The two enzymes were identified in small amounts in the green tissues of the developing seeds (inner pericarp and testa). No antigenic difference was detected between P and the -amylases of roots and leaves.Abbreviations P pericarp -amylase - E endosperm -amylase - IS1 anti--amylase immune serum - IS2 anti- and anti- amylase immune serum - IS3 anti- amylase immune serum - IEF isoelectric focusing - IgG immunoglobulin G The authors thank Dr. P. Ziegler (Universität Bayreuth, FRG) for stimulating discussion and for useful suggestions during the writing of the text. The authors thank Miss C. Mayer for her skillful technical assistance.     

Microaerophily

Objections to previous definitions of anaerobiosis and micro-aerophily are discussed, and a new definition of micro-aerophily is proposed. A survey of physiological characteristics of the micro-aerophilic bacterium Campylobacter sputorum spp. bubulus is given, and the concept of micro-aerophily is illustrated by the results of a study on the oxygen metabolism and oxygen sensitivity of this bacterium.     

Comparative residual toxicities of pesticides to the predator Agistemus industani (Acari: Stigmaeidae) on citrus in Florida

Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731ml/ha+FC 435-66 petroleum oil at 46.8l/ha, pyridaben 75WP at 469g/ha, ethion 4EC at 7.01l/ha+FC 435-66 petroleum oil at 46.8l/ha, propargite 6.55 EC at 3.51l/ha, chlorfenapyr 2SC at 1.46l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8l/ha, sulphur 80DF at 16.81kg/ha, dicofol 4EC at 7.01l/ha, fenbutatin oxide 50WP at 2.24kg/ha, benomyl 50WP at 2.24kg/ha, benomyl 50WP at 1.68kg/ha+ferbam 76 GF at 5.60kg/ha, ferbam 76GF at 11.21kg/ha, neem oil 90EC at 46.8l/ha, and copper hydroxide DF (40% metallic copper) at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha, fenbuconazole 2F at 280ml/ha+FC 435-66 petroleum oil at 46.8l/ha, FC 435-66 petroleum oil applied alone at 46.8l/ha or 23.4l/ha, and diflubenzuron 25WP at 1.40kg/ha. Pesticides that were non-toxic included: fenbuconazole 2F at 585ml/ha, malathion 57EC at 5.85l/ha, FC 435-66 petroleum oil at 46.8l/ha, carbaryl 80S at 3.36kg/ha, chlorpyrifos 4EC at 4.68l/ha, and formetanate 92SP at 1.12kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.     

Further evidence for abnormal protein kinase C regulation of macromolecule secretion in fibroblasts from cystic fibrosis patients

In comparison to skin fibroblasts from normal subjects, those from patients with cystic fibrosis (CF): (1) bound [20-³H] phorbol 12,13-dibutyrate (PDBu) with a higher affinity (K_d=25.8 vs 12.8 nM respectively) but expressed a similar number of total phorbol ester binding sites (about 2.5 pmol PDBu bound/mg of protein); (2) exhibited a faster and higher response to 4-phorbol 12-myristate 13-acetate (PMA) for the stimulation of [³⁵S]-labelled glycoconjutate release, but were equally sensitive to the synergistic effect of A23187 on this process; and (3) secreted glycoconjugates with similar [³⁵S]-sulfate and [¹⁴C]-leucine to [¹⁴C]-glucosamine labelling ratios. Taken together, these results provide further evidence for abnormal protein kinase C (PKC) regulation of macromolecule secretion in CF disease.Abbreviations BSA Bovine serum albumin - DBcAMP Dibutyryl cyclic AMP - DMEM Dulbecco's modified Eagle's medium - DMSO Dimethylsulfoxide - LDH Lactate dehydrogenase - PBS Phosphate-buffered saline - PDBu 4-phorbol 12,13-dibutyrate - 4-PDD 4-phorbol 12,13-didecanoate - PMA 4-phorbol 12-myristate 13-acetate - TCA Trichloroacetic acid     

Activation of peritoneal macrophages in patients with gynecological malignancies by sizofiran and recombinant interferon-γ

We investigated the influence of the combined use of sizofiran, a-1,3-glucan and a recombinant interferon- (rIFN-) upon biological activities of peritoneal macrophages (M). The number of peritoneal M and the production of cytokines (interleukin-1, interferon- and tumor necrosis factor) was increased by the combined treatment. Fully activated peritoneal M based on the increased number of elongated pseudopods were observed by electromicroscope. Sizofiran seems to assure a sufficient supply of M to kill tumor cells in the peritoneal cavity and co-administered rIFN- seems to directly stimulate the accumulated M in addition to its direct cytotoxicity against tumor cells. This combination therapy may be a step to the prevention of the recurrence of gynecological malignancies including ovarian cancer, after a negative second-look laparotomy.Abbreviations rIFN- recombinant interferon- - IL-1 interleukin-1 - TNF tumor necrosis factor - SLL second look laparotomy     

Unique sequences for two HLA-DRB1 genes expressed on distinct DRw6 haplotypes

We have used restriction fragment length polymorphism (RFLP) analysis and DNA sequencing to characterize two distinct DRB1 alleles expressed on DRw52 and DQw7-associated haplotypes but not readily defined by conventional DR serology. These two haplotypes, designated HLA-D HAG and PEV, react variably with DRw13(w6), DRw14(w6), and the more broad DR 3+6 antisera. Analysis of RFLP revealed that HLA-D HAG and PEV are associated with different DRw52 variants, and that HAG is indistinguishable from DRw18(3) haplotypes. Sequencing of the HAG and PEV DRB1 genes showed each to represent novel alleles. Nevertheless, these sequences show similarities with the other alleles of the DR5, w6, and w8 family. HAG (DRB1*1303) appears to have arisen either from two recombinational events involving at least three DRB1 sequences (DRB1*1101, DRB1*0803, DRB1*0401) or from a single recombinational event together with multiple point mutational events. PEV appears to represent a DRB1*1301-1302/DRB1*1101 recombinant allele, with recombination having occured in the region of bases 175 – 198. The results of this study suggest that the DRw52 family haplotypes is derived from a relatively restricted number of ancestral sequences, with diversity among DRB1 alleles within this family arising through gene conversion or recombination events.     

β-Glucuronidase activity in human T and B lymphocytes and the Tμ and Tγ subpopulations

Summary The -glucuronidase staining characteristics of isolated T cell populations and the T and T enriched fractions derived of them were studied. T lymphocytes were obtained from purified T lymphocytes by ox-IgG rosette sedimentation. The rosette-forming cells in the pellet were referred to as T lymphocytes, whereas the lymphocytes in the interface were referred to as T depleted or T lymphocytes. B cells were studied on rosetted mononuclear cells with either mouse erythrocytes or with Staphylococcus Aureus (Cowan I) bacteria, after a preceeding polyvalent anti-human Ig treatment of the cells. While B cells showed mostly no reactivity, T and T cells were respectively characterised by a dot-like and granular pattern of reactivity. These findings are in agreement with those observed by others after -naphthyl-acetate esterase or acid phosphatase staining. Within the T lymphocyte fraction, the T non-, non lymphocytes seemed to have a granular pattern of reactivity. The same staining pattern was found in non-B, non-T lymphocytes.     

Genetics of Ia-like alloantigens in chickens and linkage withB major histocompatibility complex

Two sets of backcross matings were performed to test for linkage between genes coding for the Ia-like antigens (Ia) and the B erythrocyte antigens (Ea-B) of the chicken. Evidence is presented which indicates that the la antigens are determined by a single codominant locus and that theEa-B and Ia loci are on the same chromosome. Failure to detect a single recombinant between theEa-B and Ia loci out of 208 progeny suggests close linkage of the two genes with a map distance of up to about 2 centimorgans. The Ia genes are thus included in theB major histocompatibility complex of the chicken.     

A novel 2-oxoglutarate-dependent dioxygenase involved in vindoline biosynthesis: characterization,purification and kinetic properties

The enzyme, desacetoxyvindoline 4-hydroxylase, was purified to apparent homogeneity from Catharanthus roseus by ammonium sulfate precipitation and successive chromatography on Sephadex G-100, green 19-agarose, hydroxylapatite, -kg sepharose and Mono Q. The 4-hydroxylase was characterized by its strict specificity for position 4 of desacetoxyvindoline suggesting it to catalyze the second to last step in vindoline biosynthesis. The molecular mass of the native and denatured 4-hydroxylase was 45 kDa and 44.7 kDa, respectively, suggesting that the native enzyme is a monomer. Two-dimensional isoelectric focusing under denaturing conditions resolved the purified 4-hydroxylase into three charge isoforms of pIs 4.6, 4.7 and 4.8. The purified 4-hydroxylase exhibited no requirement for divalent cations, but inactive enzyme was reactivated in a time-dependent manner by incubation with ferrous ions. The enzyme was not inhibited by EDTA or SH-group reagents at concentrations up to 10 mM. The mechanism of action of desacetoxyvindoline 4-hydroxylase was investigated. The results of substrate interaction kinetics and product inhibition studies suggest an Ordered Ter Ter mechanism where -kg is the first substrate to bind followed by the binding of O₂ and desacetoxyvindoline. Their K _m values for -kg, O₂ and desacetoxyvindoline are 45 M, 45 M and 0.03 M, respectively. The first product to be released was deacetylvindoline followed by CO₂ and succinate, respectively.Abbreviations -kg -ketoglutarate or 2-oxoglutarate - NMT N-methyltransferase - SAM S-adenosyl-l-methionine - TLC thin layer chromatography - VBL vinblastine - VCR vincristine     

Partial purification and characterization of a folatebinding protein from human choroid plexus

A folate-binding protein (binder) from human choroid plexus was solubilized with Triton X-100 and partially purified in three steps: (1) affinity chromatography, (2) Sephadex G-200 column chromatography, and (3) polyacrylamide gel electrophoresis. When the partially purified binder was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the binding activity was located in the region of the gel with a molecular weight between 45,000 and 60,000. The specific activity of the binder after the three purification steps was 1.2 g folic acid/mg protein, a 316-fold purification. Binding activity of the partially purified binder decreased below pH 6.0 and above pH 8.0 was unaffected by treatment with ribonuclease or deoxyribonuclease, but was abolished with trypsin, chymotrypsin, or protease (Streptomyces griesus). The binding of folic acid to the human binder was inhibited by folate > H₄-folate > methyl-H₄-folate dihydrofolate pteroic acid methotrexate aminopterin.