Microfibrillar Structure, Cortical Microtubule Arrangement and the Effect of Amiprophos-methyl on Microfibril Orientation in the Thallus Cells of the Filamentous Green Alga, Chamaedoris orientalis

Microfibrillar structure, cortical microtubule orientation andthe effect of amiprophos-methyl (APM) on the arrangement ofthe most recently deposited cellulose microfibrils were investigatedin the marine filamentous green alga, Chamaedoris orientalis.The thallus cells of Chamaedoris showed typical tip growth.The orientation of microfibrils in the thick cell wall showedorderly change in longitudinal, transverse and oblique directionsin a polar dependent manner. Microtubules run parallel to thelongitudinally arranged microfibrils in the innermost layerof the wall but they are never parallel to either transverseor obliquely arranged microfibrils. The ordered change in microfibrilorientation is altered by the disruption of the microtubuleswith APM. The walls, deposited in the absence of the microtubules,showed typical helicoidal pattern. However, the original crossedpolylamellate pattern was restored by the removal of APM. Thissuggests that cortical microtubules in this alga do not controlthe direction of microfibril orientation but control the orderedchange of microfibril orientation. Amiprophos-methyl, Chamaedoris orientalis, coenocytic green alga, cortical microtubule, microfibrillar structure, tip growth     

Effect of recombinant human tumor necrosis factor α on the induction of antibody-dependent cellular cytotoxicity in the treatment of established B16 melanoma liver nodules

Summary Incubation of C3H/Hen thymocytes in the presence of recombinant human tumor necrosis factor (TNF) and interleukin-2 (IL-2) augmented the generation of antibody-dependent cellular cytotoxicity (ADCC) when compared to cells cultured in TNF or IL-2 alone. This effect was optimal when 100–200 units/ml IL-2 was used together with 10³–10⁴ units/ml TNF. TNF alone at any concentration could not mediate the induction of ADCC. Similar to the results obtained in vitro, TNF, when given alone, had no effect on the generation of ADCC in vivo. The addition, however, of TNF to IL-2, given at 10 000 and 20 000 but not 40 000 units, enhanced the IL-2-induced ADCC on a per-cell basis. Furthermore, TNF enhanced the total ADCC activity in various organs including the liver, spleen and thymus as a result of an increase in the number of mononuclear cells isolated from these organs. The increase in total ADCC activity was optimal when 110 000–220 000 units (5–10 µg) TNF were employed together with IL-2. The combined treatment with TNF and IL-2 also increased the intracellular benzyloxycarbonyl-l-l-lysinethiobenzyl-ester esterase content in cells isolated from the livers of mice treated with these cytokines. On the basis of these results we treated mice bearing a single B 16 melanoma nodule with TNF and TNF + IL-2 given with or without anti-B 16 monoclonal antibody. We found that TNF administration augmented the anti-tumor effect of specific anti-B 16 antibodies, and the addition of IL-2 further increased this anti-tumor effect. Offprint requests to: S. A. Rosenberg, Surgery Branch, National Cancer Institute, Building 10, Room 2B42, Bethesda, MD 20892 USA     

Gregarina coronata N. Sp. (Apicomplexa: Eugregarinida) Described from Adults of the Southern Corn Rootworm, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae)

ABSTRACT. Gregarina coronata n. sp. (Apicomplexa: Eugregarinida) is described from the adults of the Southern Corn Root Worm, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae). Measurements given are means, in micrometers, taken from mature gamonts in association. Primite: protomerite hemi-ellipsoidal with basal tumidus, length 47.6, width 44.0, with cytoplasmic granule, apical crown apparent; deutomerite elongate ellipsoidal, length 227.9, width 81.3; epimerite absorbed into anterior in gamont, globular in trophozoite. Satellite: protomerite hemi-ellipsoidal, truncated at association interface to appear trapezoidal, length 39.2, width 49.6, with cytoplasmic granule; deutomerite elongate ellipsoidal, length 240.6, width 80.2; epimerite absorbed into anterior in gamont. Association caudofrontal and often precocious, occurring during growth of trophozoites. Gametocysts spherical, 115.3 in diameter, 132.9 with hyaline coat; producing multiple oocyst chains under moist storage in 24–36 h. Oocysts very uniform in shape and size, dorsad: doliform, length 6.4, equatorial width 3.4, polar width 2.9; pleuron: dorso-ventrally flattened, corpus concave with bicondylic termina; corpus height 0.98, width 4.44; terminus height 1.96, width 0.98.     

Immobilization Antigens from Tetrahymena thermophila Are Glycosyl-Phosphatidylinositol-Linked Proteins

We have studied four strains of Tetrahymena thermophila , each of which expresses a different allele of the SerH gene and produces a distinctive surface protein of the immobilization antigen (i-antigen) class. Following exposure of the strains to [³H]ethanolamine or [³H]myristic acid, a protein corresponding in molecular mass to the characteristic i-antigen for that strain became highly labeled, as determined by mobility in sodium dodecylsulfate-polyacrylamide eiectrophoresis gels. Furthermore, antibodies raised to the i-antigens of the T. thermophila strains selectively immunoprecipitated radioactive proteins having molecular mass identical to that of the i-antigen characteristic for that particular strain. The lipid moieties labeled by [³H]myristate were not susceptible to hydrolysis by exogenous phosphatidylinositol-specific phospholipase C from bacteria. However, when protein extraction was carried out in the absence of phospholipase C inhibitors, radioactive fatty acids derived from [³H]myristate were rapidly cleaved from the putative i-antigens. On the basis of available data, it was concluded that T. thermophila i-antigens contain covalently-Iinked glycosyl-phospha-tidylinositol anchors.     

Studies of the ethanol-induced interdigitated gel phase in phosphatidylcholines using the fluorophore 1,6-diphenyl-1,3,5-hexatriene

It is now well established that a number of amphiphilic molecules such as ethanol can induce the formation of the fully interdigitated gel phase in phosphatidylcholines. We have shown earlier that alcohols such as ethanol induce biphasic melting behavior in phosphatidylcholines [Rowe, E. S. (1983) Biochemistry 22, 3299-3305] but not in phosphatidylethanolamines [Rowe, E. S. (1985) Biochim. Biophys. Acta 813, 321-330]. Simon and McIntosh [(1984) Biochim. Biophys. Acta 773, 169-172] showed that the alcohol-induced biphasic melting behavior in phosphatidylcholines is a consequence of acyl chain interdigitation. In the present study we demonstrate the detection of the transition of DPPC and DSPC to the interdigitated phase in the presence of ethanol using the fluorescence properties of the commonly used fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). By correlating fluorescence and X-ray diffraction results, we have demonstrated the use of fluorescence to study the phase transition from the noninterdigitated to the interdigitated phase. Using this method, we have investigated the temperature and ethanol concentration dependence of the induction of the interdigitated phase in DSPC and DPPC and shown that the induction of interdigitation by ethanol is temperature dependent, with higher temperature favoring interdigitation. The temperature-ethanol phase diagrams have been determined for DPPC and DSPC.     

Influence of lead exposure on catecholamine metabolism in discrete rat brain nuclei

1. Using the rat exposed both acutely and chronically to lead as a model of lead neurotoxicity, various parameters of catecholamine metabolism were investigated. 2. The steady-state concentrations of noradrenaline, adrenaline and dopamine together with the activities of tyrosine hydroxylase and phenylethanolamine N-methyl transferase were measured in discrete brain nuclei--periventricular, paraventricular, median eminence, posterior and anterior hypothalamus, caudate putamen and globus pallidus. 3. Lead exposure resulted in significant fall in the activity of the rate-limiting enzyme of catecholamine synthesis, tyrosine hydroxylase which was associated with alterations in concentrations of catecholamines in the median eminence, periventricular nucleus and anterior hypothalamus. 4. No other brain nuclei investigated exhibited any effect of lead on the catecholaminergic nervous system and, therefore, the effect of lead on rat brain can be considered to be regionally specific.     

Effects of lead exposure on rat brain catecholaminergic neurochemistry

1. The effects of lead on catecholaminergic neurotransmission have been investigated. 2. Using the rat as a model, animals were exposed both acutely and chronically to lead. The levels of catecholamines, noradrenaline, adrenaline, and dopamine along with the activities of tyrosine hydroxylase and phenylethanolamine-N-methyl transferase were measured in 5 brain regions--cerebral cortex, brainstem, hippocampus, anterior and posterior hypothalamus. 3. A lead related reduction in the activity of tyrosine hydroxylase was observed in association with alterations in steady-state levels of the catecholamines in the posterior and anterior hypothalamus. 4. Thus, lead exposure, known to result in behavioural changes, is associated with localised neurochemical effects on the hypothalamus.     

Dynamics of a fluorescent calmodulin analog in the mammalian mitotic spindle at metaphase

We have compared the exchange kinetics of fluorescein-labeled calmodulin and tubulin in the spindles of living mitotic cells at metaphase. Cultured mammalian cells in early stages of mitosis were microinjected with labeled calmodulin or tubulin and returned to an incubator to allow equilibration of the fluorescent protein with the endogenous protein pools. Calmodulin becomes concentrated in the mitotic spindle, and treatments with inhibitors of tubulin assembly show that this concentration is dependent on the presence of microtubules. The steady-state exchange rates of both tubulin and calmodulin were measured by an analysis of fluorescence redistribution after photobleaching (FRAP), using cells pre-equilibrated to either 26 +/- 2 degrees C or 36 +/- 2 degrees C. A pulse of laser light focused to a 5-microns diameter column was used to destroy the fluorescence at one pole of a metaphase mitotic spindle. Ratios of fluorescence intensity from the two half-spindles and from the two polar regions were calculated for each image in a post-bleach time series to determine the rates and extents of FRAP. For tubulin, we confirm earlier observations concerning the temperature dependence of the extent of FRAP, but our data do not show a significant temperature dependence for the rate of FRAP. We hypothesize that the reduced extent of tubulin FRAP at the lower temperatures is a result of microtubules that are stable to depolymerization at 26 degrees C and are thus less likely to exchange subunits. Calmodulin's FRAP, however, does not exhibit any of the temperature dependence observed with fluorescent tubulin. At 26 +/- 2 degrees C calmodulin exchanges rapidly with the relatively stable population of microtubules, suggesting that calmodulin is bound, either directly or indirectly, to microtubule walls.     

On the localization of ubiquinone in phosphatidylcholine bilayers

The location of ubiquinone-10 in phospholipid bilayers was analyzed using a variety of physical techniques. Specifically, we examined the hypothesis that ubiquinone localizes at the geometric center of phospholipid bilayers. Light microscopy of dipalmitoylphosphatidylcholine at room temperature in the presence of 0.05–0.5 mol fraction ubiquinone showed two separate phases, one birefringent lamellar phase and one phase that consisted of isotropic liquid droplets. The isotropic phase had a distinct yellow color, characteristic of melted ubiquinone. [¹³C]NMR spectroscopy of phosphatidylcholine liposomes containing added ubiquinone indicated a marked effect on the ¹³C-spin lattice relaxation times of the lipid hydrocarbon chain atoms near the polar head region of the bilayer, but almost no effect on those atoms nearest the center of the bilayer. X-ray diffraction experiments showed that for phosphatidylcholine bilayers, both in the gel and liquid-crystal-line phases, the presence of ubiquinone did not change either the lamellar repeat period or the wide-angle reflections from the lipid hydrocarbon chains. In electron micrographs, the hydrophobic freeze-fracture surfaces of bilayers in the rippled (Pβ′) phase were also unmodified by the presence of ubiquinone. These results indicate that the ubiquinone which does partition into the bilayer is not localized preferentially between the monolayers, and that an appreciable fraction of the ubiquinone forms a separate phase located outside the lipid bilayer.     

The impact of digging on craniodental morphology and integration

The relationship between the form and function of the skull has been the subject of a great deal of research, much of which has concentrated on the impact of feeding on skull shape. However, there are a number of other behaviours that can influence craniodental morphology. Previous work has shown that subterranean rodents that use their incisors to dig (chisel‐tooth digging) have a constrained cranial shape, which is probably driven by a necessity to create high bite forces at wide gapes. Chisel‐tooth‐digging rodents also have an upper incisor root that is displaced further back into the cranium compared with other rodents. This study quantified cranial shape and upper incisors of a phylogenetically diverse sample of rodents to determine if chisel‐tooth‐digging rodents differ in craniodental morphology. The study showed that the crania of chisel‐tooth‐digging rodents shared a similar place in morphospace, but a strong phylogenetic signal within the sample meant that this grouping was nonsignificant. It was also found that the curvature of the upper incisor in chisel‐tooth diggers was significantly larger than in other rodents. Interestingly, most subterranean rodents in the sample (both chisel‐tooth and scratch diggers) had upper incisors that were better able to resist bending than those of terrestrial rodents, presumably due to their similar diets of tough plant materials. Finally, the incisor variables and cranial shape were not found to covary consistently in this sample, highlighting the complex relationship between a species’ evolutionary history and functional morphology.