Synthesis of oligoguanylates on oligocytidylate templates

Summary Short oligocytidylates can act as templates for the self-condensation of guanosine 5-phosphorimidazolide. In the absence of a catalytic metal ion or in the presence of Pb²⁺ a noticeable template effect is already observed with the dimer and the yield of long oligomers reaches a plateau with a hexamer template. Short templates give oligomers longers than the template length. The products are predominantly 2-5 linked for the Pb²⁺-catalyzed reaction while mixed linkages are observed in the uncatalyzed reaction.In the presence of Zn²⁺, a template effect is first observed with the pentamer and is maximal by the heptamer. The products are predominantly 3-5 linked. Oligomers shorter than or as long as the template are obtained in substantial yield, and longer products in much lower yields.Abbreviations G Guanosine - Gp guanosine 2(3)-phosphate - pG guanosine 5-phosphate - Gp! guanosine cyclic 2,3-phosphate - ImpG guanosine 5-phosphorimidazolide - ImpG^* [8-¹⁴C]-guanosine 5-phosphorimidazolide - pGp 5-phosphoguanosine 2(3)-phosphate - G²pG guanylyl-[2-5]-guanosine - G³pG guanylyl-[3-5]-guanosine - ImpGpG 5-phosphorimidazolide of GpG - (pG)_n (n = 2,3) oligomers of pG - GppG P₁, P₂-diguanosine 5-diphosphate - GppGpG 5-[guanosine 5-pyrophosphate] of GpG - NH₂pG guanosine 5-phosphoramidate - (pG)₄₊ tetramer and higher oligoguanylates with 5 terminal phosphate - oligo(G) oligoguanylate - Cp cytidine 2(3)-phosphate - Cp! cytidine cyclic 2,3-phosphate - (Cp)_n–1 Cp! (n= 2,3,4) oligocytidylates terminated by 5-OH groups and 2,3-cyclic phosphates - oligo(C) oligocytidylate - poly(C) polycytidylic acid - poly(U) polyuridylic acid - poly(C,G) random copolymer of C and G - BAP bacterial alkaline phosphatase (E. coli) - EDTA ethylenediaminetetraacetic acid - R_f chromatographic mobility     

Effects of type beta transforming growth factor in combination with retinoic acid or tumor necrosis factor on proliferation of a human glioblastoma cell line and clonogenic cells from freshly resected human brain tumors

Summary Type beta transforming growth factor (-TGF) is a potent regulator of cell growth and differentiation. The human glioblastoma cell line, T-MGl, was growth inhibited by -TGF under anchorage independent conditions. The antiproliferative effect of -TGF was potentiated to nearly total arrest by low doses of retinoic acid (RA) or tumor necrosis factor (TNF), while epidermal growth factor, platelet-derived growth factor, interleukin-2, and gamma interferon did not have this potentiating effect. The potentiation of the -TGF effect by RA and TNF could not be explained by modulation of the epidermal growth factor receptor, the -TGF receptor, or the TNF receptor. -TGF alone and in combination with RA or TNF were further tested on primary cultures from freshly resected human glioma biopsies (n=13). There was great individual variation in sensitivity to -TGF, RA, or TNF. The astrocytoma and oligodendroglioma cells were inhibited to various degrees by -TGF or TNF, while most of the glioblastomas were not sensitive to these agents. Most of the biopsies were stimulated by RA. RA or TNF did not potentiate the growth inhibitory effect of -TGF on biopsy cells. We therefore think it unlikely that -TGF in combination with RA or TNF will be effective agents in the treatment of gliomas.     

Freeze-fracture studies on the cockroach hemocyte membrane complex: Symmetric and asymmetric membrane particle distributions

Summary Freeze-fracture studies were conducted on the membranes of normal cockroach hemocytes. The plasmalemma is asymmetric with the A fracture face containing 80–100 Å membrane intercalated particles at a concentration of 2500/². The B fracture face contains 120–150 Å particles with a relatively low density (800/²). The nuclear envelope displays an asymmetry with the A fracture face containing 1500 particles/² and the B face containing 300/ ². No significant particle size differences were observed in nuclear envelope fracture faces. Two types of symmetric membranes were also found in these cells. Both A and B fracture faces of the membrane surrounding the numerous cytoplasmic inclusion bodies contain particle sizes and concentrations similar to the B face of the plasmalemma. A second type of symmetry was observed in cells apparently engaged in exocytosis. Vesicles (0.1 D) from this process were completely particle free on both fracture faces. Such particle free vesicles could be found in the cytoplasm, attached to the plasmalemma, or completely separated from the cell.Supported by a Pharmaceutical Manufacturers Association Foundation Fellowship.The author wishes to thank Ms. Annalena K. Charla for assistance in plate preparation, Dr. Julius Schultz and the Papanicolaou Cancer Research Institute for use of the freeze-etch device, and Dr. David Smith for the electron microscope facilities.     

Is haemoglobin Gα Philadelphia linked to α-thalassaemia?

Summary The question, Is Hb G Philadelphia linked to -thalassaemia? was first posed because the abnormal haemoglobin is found in heterozygotes at a concentration greater than 25%, the proportion predicted from a 4 -chain gene model. Globin chain biosynthesis was studied in a West Indian family in which one parent had ⁺ thalassaemia and the other was heterozygous for the G Philadelphia chain gene. The former had a globin chain production ratio / well above 1, while the latter had a ratio significantly less than 1. One child of the marriage had inherited the ⁺ thallassaemia from one parent and the G Philadelphia chain gene from the other and showed the typical picture of /-thalassaemia (/ ratio slightly above normal). It is explained in the discussion that the evidence favours a close linkage of 2 -chain genes.     

Histoenzymatic characterization of sub-types of Type I fibres in fast muscles of rats

Summary The histochemical activities of succinic dehydrogenase (SDH), myofibrillar Adenosine triphosphatase (ATPase) and alpha glycerophosphate dehydrogenase were studied in serial sections of rat vastus lateralis (red) (RVL), gastrocnemius and diaphragm muscles. Three main fibre-types were distinguished. The Type I fibres of RVL and gastrocnemius muscles fell into two distinct groups: one category-Type IA showed very low ATPase activity. The second category of Type IB fibres displayed moderate ATPase reaction. The Type IA fibres were divisible into two sub-groups when tested for SDH reaction. Type IA₁ fibres possessed a homogenous distribution of diformazan·granules throughout the fibre: Type IA₂ fibres displayed characteristic moth-eaten pattern of diformazan localization. The diaphragm muscle did not show either Type IB or Type IA₂ varieties. The great majority of Type I fibres were sub-type IA₁ in the three fast muscles studied. It is also demonstrated here that an inherent heterogeneity exists between Type I fibres of diaphragm and leg muscles in regard to -GPD localization. This histochemical data emphasizes the fact that subdivision of Type I striated muscle fibres of mammalian animals into two sub-types is only approximate and that a further subcategorization is possible.     

The cytology of phytophthora infestans

Summary Phytophthora infestans has three kinds of somatic nuclei: an oval shaped nucleus (approx. 3.1×2.7 ) which stains diffusely except for a crescent shaped Feulgen positive cap which stains intensely; a granular nucleus whose contents are organized into a fairly constant number of stained bodies, and, a deeply staining condensed nucleus. The capped nucleus is thought to be metabolic or resting and the granular nucleus is thought to be dividing as it is most commonly found in hyphal tips. Attenuated forms of all three kinds of nuclei are found.Nuclear division is mitotic and intranuclear. Eight—ten chromosomes are seen at metaphase.Sporangia have a mean of 6.3 nuclei which is constant for age and strain of culture. Sporangia become multinucleate as a result of nuclear migration and not by division in the developing sporangium. Zoospores are usually uninucleate.The nuclear cap is persistent throughout nuclear division when it also divides. It is associated with flagella production and nuclear migration and has some of the properties of a blepharoplast.     

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.     

High D-glucose does not affect binding of α-tocopherol to human erythrocytes

The role of -tocopherol uptake system in human erythrocyte in the uptake of plasma -tocopherol has been suggested. However no information is available on -tocopherol uptake activity of human erythrocytes in the presence of high levels of D-glucose which is known to lead to pathological alterations in different cells including human erythrocytes. Therefore, in order to examine the effect of D-glucose on the binding of -tocopherol to human erythrocytes, the binding characteristics of -tocopherol to these cells were established first. Binding of [3H]-tocopherol to human erythrocytes was both saturable and specific. Scatchard analysis of -tocopherol binding to these cells showed the presence of two independent classes of binding sites with widely different affinities. The high affinity binding sites had a dissociation constant (Kd1) of 90 nM with a binding capacity (n1) of 900 sites per cell, whereas the low affinity binding sites had a dissociation constant (Kd2) of 5.2 M and a binding capacity (n2) of 105,400 sites per cell. Trypsin treatment abolished all the -tocopherol binding activity. Competition for the binding of -tocopherol to human erythrocytes was effective with other homologues of -tocopherol (-tocopherol, -tocopherol and -tocopherol) and their potency was almost equal to -tocopherol itself. The order of preference was -tocopherol > -tocopherol -tocopherol -tocopherol. Incubation of human erythrocytes with various concentrations of D-glucose did not affect -tocopherol uptake activity. Our data demonstrate the presence of an -tocopherol uptake system in human erythrocytes and that the -tocopherol uptake activity is not modulated by the presence of D-glucose.     

Structures of the N-linked sugar chains in the PAS-6 glycoprotein from the bovine milk fat globule membrane

The structures of the N-linked sugar chains in the PAS-6 glycoprotein (PAS-6) from the bovine milk fat globule membrane were determined. The sugar chains were liberated from PAS-6 by hydrazinolysis, and the pyridylaminated sugar chains were separated into a neutral (6N) and two acidic chains (6M and 6D), the acidic sugar chains then being converted to neutral sugar chains (6MN and 6DN). 6N was separated into two neutral fractions (6N13 and 6N5.5), while 6MN and 6DN each gave a single fraction (6MN13 and 6DN13). The structure of 6N5.5, which was the major sugar chain in PAS-6, is proposed to be Man16 (Man13) Man14GlcNAc14GlcNAc-PA; 6N13, 6MN13 and 6DN13 are proposed to be Gal13Gal14GlcNAc12Man16 (Gal13Gal14GlcNAc12Man13) Man14GlcNAc14 (Fuc16)GlcNAc-PA;6M and 6D had 1 or 2 additional NeuAc residues at the non-reducing ends of 6MN13 and 6DN13, respectively. © 1998 Rapid Science Ltd     

Protein kinase C (α, β, γ) in Pacinian corpuscle

Immunocytochemical demonstration of protein kinase C (PKC) subspecies (, , ) was carried out in Pacinian corpuscles of rat hind feet using monoclonal or polyclonal antibodies against each of these subspecies. The inner core cells and lamellae and the Schwann cell cytoplasm of the nerve fiber innervating the corpuscle were strongly positive for PKC -immunoreactivity (IR). In contrast, the axon terminal and the outer core did not display any positive -IR. Very weak PKC -IR was detected in the ultraterminal region of the axon terminal, while the trunk region showed no immunoreactivity. Very faint PKC -IR was found also in the lamellar cells located at the periphery of the inner core and the endoneurial fibroblasts in the intermediate layer. PKC -IR was not detected in any part of the corpuscle. The strong PKC -IR in the inner core and the presence of absence of PKC -, -, and -IR in the axon terminal are discussed from the point of view of the functional aspects of each part.     

Effects of high ambient temperatures on the metabolism of West African dwarf goats. I

Thirty-two West African dwarf goats were exposed to temperature treatments: 20, 25, 30, 35, 35, 35, 30, 25, 20°C each lasting three days.Sixteen goats were kept in individual pens (I), the others in two group pens (G). Heat production (HP) and activity were recorded during 48 hours in each temperature treatment.Mean HP and ME intake were similar for G and I animals, but I animals had lower values than G animals at low chamber temperatures and higher values than G animals at high temperatures. Upper critical temperature was between 25°C and 30°C under an increasing T and between 30 and 35°C under a decreasing T. Adaptation of heat production and ME intake to a change in temperature of 5°C required at least six and possibly more than nine days.Diurnal variation in HP was large, up to 44% between extremes. This was largely due to variation in activity.     

Clonal propagation of mature elite trees of Commiphora wightii

Elite trees of Commiphora wightii (Arnott) Bhandari were selected from the wild on the basis of their content of guggul, an oleoresin. The selected tree was micropropagated through forced axillary branching on Murashige and Skoog's (MS) medium supplemented with benzyladenine (BA) and kinetin. Highest frequency of shoot formation was achieved on MS medium supplemented with 17.8 M BA, 18.6 M kinetin, 100 mg l^-1 glutamine, 10 mg l^-1 thiamine HCL and 0.3% activated charcoal. Seasonal changes affected the shoot proliferating potential of the initial explants in vitro. Transfer of shoots to a medium containing a lower concentration of BA (1.8 M) and kinetin (1.9 M) before rooting markedly stimulated shoot elongation. Shoots could be rooted by treating them with both indoleacetic acid and indolebutryic acid for 24 h in darkness and transferring them to a low-salt basal medium with activated charcoal. After rooting, transfer to a half-strength White's (modified) medium was necessary for further development of the plantlet. Regenerated plantlets were successfully established in soil.Abbreviations AC activated charcoal - BA benzyladenine - IAA indoleacetic acid - IBA indolebutyric acid - 2-iP isopentenyladenine - MS Murashige and Skoog's medium - NAA -naphthaleneacetic acid - PG phloroglucinol     

Existence and uniqueness of a sharp travelling wave in degenerate non-linear diffusion Fisher-KPP equations

In this paper we use a dynamical systems approach to prove the existence of a unique critical value c ^* of the speed c for which the degenerate density-dependent diffusion equation u _ct = [D(u)u _x ] _x + g(u) has: 1. no travelling wave solutions for 0 < c < c ^*, 2. a travelling wave solution u(x, t) = (x - c ^* t) of sharp type satisfying (– ) = 1, () = 0 ^*; '(^*–) = – c ^*/D'(0), '(^*+) = 0 and 3. a continuum of travelling wave solutions of monotone decreasing front type for each c > c ^*. These fronts satisfy the boundary conditions (– ) = 1, '(– ) = (+ ) = '(+ ) = 0. We illustrate our analytical results with some numerical solutions.     

Changes in DNA content and chromosomal size during cell culture and plant regeneration of Scilla siberica: selective chromatin diminution in response to environmental conditions

The chromosomal complement and DNA content of cells of the monocotyledonous plant Scilla siberica were studied at various stages of growth, such as callus outgrowths from bulb tissue (bulb callus), callus grown from single protoplasts prepared from bulb callus (protoplast callus), regenerated plants kept for 2–4 years on agar medium and under constant climatic conditions, and regenerated plants grown first for 2 years on agar and then for 1 year in the garden. During callus culture, several different forms of chromatin loss were observed: (1) chromosome elimination early during cell culture, resulting in cells which were mostly diploid but still had large chromosomes similar to those of the original triploid plants (type 1 cells); from these cells no plants could be regenerated. (2) Dramatic reduction in heterochromatin containing the satellite DNA and, apparently subsequently, also of many other chromatin moieties, resulting in the formation of small chromosomes; frequent polyploidization in these cells, resulting in a variable number of chromosomes per cell (preferentially 30–40, in ca. 70% of the cells; type 2 cells). (3) Appearance of a large number of very small (< 1 m) Feulgenpositive chromatin particles (minute chromosomes; often arranged in metaphase-like arrays, suggesting that they were effectively distributed during mitosis). Such cells could survive and divide under cell culture conditions but did not regenerate plants (type 3 cells). In bulb calli, all three cell types were found whereas in protoplast calli only cells of type 2 and 3 were seen. Type 2 and 3 cells had lost, despite their frequent polyploidization, about 80% of their initial nuclear DNA content and an even higher proportion (>95%) of the satellite sequences. Southern DNA blot analysis revealed that sequences hybridizing with certain protein-coding genes such as that for chalcone synthase were also drastically reduced in copy number whereas the proportion of rDNA was even somewhat increased. In plants regenerated from type 2 cells of protoplast calli, which were aneuploid at near-pentaploidy to hexaploidy, further conspicuous changes in chromosomal and DNA content were not observed, as long as they were kept on agar medium and under constant climatic conditions. However, when such plants were grown in the garden for at least 1 year, the satellite DNA as well as the sequences hybridizing with the chalcone synthase gene were disproportionately increased to 30%–40% of their normal proportion, whereas the total DNA had increased by only approximately 15%. The chromosome numbers remained near-pentaploid to hexaploid as in the cell cultures from which these plants had been regenerated. These phenomena of selective loss and regain of chromatin in response to environmental conditions (cell culture, regenerated plants on agar, regenerated plants grown outdoors) are discussed in relation to other forms of chromatin loss, including developmentally controlled chromatin diminution in certain animals.     

α-and β-Glycosidases in maize roots

Four glycosidases were analyzed in 10 mm apical segments prepared from growing roots (15 mm) of Zea mays L. The pH optima were found to be 5.8 for -glucosidase, 4.4 for -galactosidase, 6.4 for -glucosidase and 6.0 for -galactosidase. The -glucosidase showed 4-fold higher activity than the -galactosidase. The distribution of the -glucosidase activity was signifcantly different from that of the -galactosidase, -glucosidase and -galactosidase.Abbreviations -Glu -glucosidase - -Gal -galactosidase - -Glu -glucosidase - -Gal -galactosidase     

Isoform-Specific Membrane Translocation of Protein Kinase C After Ischemic Preconditioning

Mild cerebral anoxic/ischemic/stress insults promote tolerance and thereby protect the brain from subsequent lethal anoxic/ischemic insults. We examined whether specific activation of PKC , , , or isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKC, , , and . PKC showed a significant translocation to the membrane fraction from 30 min to 4 h and PKC at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKC showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKC was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKC and PKC may be associated with IPC-induced tolerance in the rat hippocampus.     

Multiple shoot-bud formation and plantlet regeneration on Castanea sativa Mill. seeds in culture

Primordial initiation and development of shoot-buds has been accomplished by using shoots derived from chestnut (Castanea sativa Mill) seedlings cultured with added 6-benzylaminopurine (BAP). Germination of chestnut seeds in the presence of BAP (4 – 40 M) stimulated varying numbers of shoot-buds in those areas of the main axis that were favorably altered. When excised single shoots from these treated seeds were subcultured on a fresh medium containing BAP (4 – 40 M) continual shoot production was observed. Bud growth and shoot elongation were stimulated by transferring cultures to a reduced concentration of BAP (2 M) plus indole-3-butyric acid (IBA 0.4 M). Plant regeneration occurred in the presence of IBA (0.8 M) after a preconditioning treatment in which naphthaleneacetic acid (NAA 50 M) and kinetin (k 2 M) were applied to the tissue culture shoots for 7 days in light.     

Probable male heterogamety in the deep-sea fish Bathylagus wesethi (Teleostei: Bathylagidae)

A presumed XY chromosome pair is described fromt estis squashes from the mesopelagic deep-sea fish Bathylagus wesethi, whose 2N chromosome number was determined as 34-XY. Although the metacentric X-chromosome is the largest in the entire compliment, the Y is the smallest and only acrocentric element. The positive heteropycnosis of the sex elements was not easily distinguishable in the nuclei of first meiotic prophase. Tetraploid nuclei were observed in peripheral supporting cells of the testis. Males of at least two other congeners have similar karyotypes.     

Stable isotope and radiocarbon compositions of methane emitted from tropical rice paddies and swamps in Southern Thailand

Stable isotopes (¹³C, D) and radiocarbon weremeasured in methane bubbles emitted from rice paddies and swamps in southernThailand. Methane emitted from the Thai rice paddies was enriched in¹³C (mean ¹³C; –51.5 ±7.1 and–56.5 ± 4.6 for mineral soil and peat soil paddies,respectively)relative to the reported mean value of methane from temperate rice paddies(– 63 ± 5). Large seasonal variation was observed in¹³C(32) in the rice paddies, whereas variationinD was much more smaller (20), indicating that variation in¹³C is due mainly to changes in methane production pathways.Values of ¹³C were lower in swamps (–66.1 ±5.1)than in rice paddies. The calculated contribution of acetate fermentation from¹³C value was greater in rice paddies (mineral soils:62–81%, peat soils: 57–73%) than in swamps (27–42%). Din methane from Thai rice paddies (–324± 7 (n=46)) isrelativelyhigher than those from 14 stations in Japanese rice paddies ranging from–362 ± 5 (Mito: n=2) to –322 ± 8(Okinawa: n=3), due tohigher D in floodwaters. ¹⁴C content in methane produced fromThai rice paddies (127±1 pMC) show higher ¹⁴Cactivity compared with previous work in paddy fields and those from Thai swamps(110±2 pMC).     

Circadian changes in synaptic ribbons and spherules in pinealocytes of the Syrian hamster (Mesocricetus auratus)

Summary In the present study, synaptic ribbons were studied morphologically and quantitatively in hamster pineal gland. The number of ribbons and spherules of hamster pinealocytes was counted over a 24-h period. The 24-h variations in the quantity of synaptic ribbons were found to parallel fluctuations in pineal melatonin concentrations. No significant circadian changes were observed for synaptic spherules, indicating different roles for these two structures.