Crystal-associated matrix components in rat incisor enamel

Summary Sections of glutaraldehyde-OsO₄-fixed, plastic-embedded rat incisor enamel were left untreated, stained, decalcifed (1% formic acid in 10% sodium citrate), or decalcified-stained. The presence of apatite crystals was monitored with electron diffraction. After brief decalcification and staining, apatite crystals and matrix components were visualized in the same field. The ghost was continuous with crystal fragments, and the coat appeared as a dense line next to crystals and ghosts. Position of ghosts and crystals at the ameloblast-enamel junction (AEJ) of the secretion zone suggested that there may be a lag of no more than 1/5 min between the elaboration of ghost and crystal. A major change in enamel morphology occurs between the AEJ and the deep enamel of the secretion zone. The ghost becomes thinner, the coat more pronounced, and the crystal enlarges. There is only little change from the deep secretion to the maturation zone enamel.     

CO2 sensitive receptors on labial palps ofRhodogastria moths (Lepidoptera: Arctiidae): physiology,fine structure and central projection

Summary The tips of the labial palps ofRhodogastria possess a pit housing uniform sensilla (Fig. 1), histologically characterized by wall-pores and receptor cells with lamellated outer dendrites (Fig. 2). The receptor cell axons project to glomeruli in the deutocerebrum (cf. Fig. 3) which are not innervated by antennal receptors. From their histology as well as from their central projection these sense organs are identical with palpal pit organs of other Lepidoptera (Lee et al. 1985; Kent et al. 1986; Lee and Altner 1986).Physiologically, the palp-pit receptors respond uniformly; they are most excitable by stimulation with carbon dioxide (Fig. 6) while they exhibit relatively moderate responses to various odorants (Fig. 4). The responses to CO₂ (Fig. 7) show a steep dose-response characteristic. In ambient atmosphere (i.e., ca. 0.03% CO₂) the cells are in an excited condition already; the seeming spontaneous activity exhibited in air is decreased if the preparation is kept under N₂ or O₂ or CO₂-free air (Figs. 7, 10). There is hardly any adaptation of the responses to continuous or repeated stimulation (Fig. 8). Perhaps CO₂ sensitivity is correlated with sensilla characterized by both wall-pores and lamellated dendrites. Pilot tests indicate that CO₂ perception might be widespread in the Lepidoptera (cf. Fig. 12), but the biological significance remains obscure.     

Synthesis and characterization of lipid-linked mannosyl oligosaccharides in Volvox carteri f. nagariensis

Particulate membrane fractions from Volvox carteri catalyze the transfer of mannose from GDP-mannose to dolichyl diphosphate-[¹⁴C]chitobiose to form lipid-linked oligosaccharides up to a dolichyl diphospnate-chitobiose-(mannose)₅ structure. Mannosylation of the chitobiosyl lipid requires divalent cations and detergents as solubilizing agents. Depending on the nature of the detergent, the oligosaccharide pattern differs markedly: With deoxycholate or the zwitterionic detergent 314 a lipid-linked trisaccharide accumulates. The nonionic Triton X-100, however, gives rise to a spectrum of compounds up to a heptasaccharide. Enzyme digestion of the tri- and pentasaccharide structure, obtained after mild acid hydrolysis of the corresponding [¹⁴C]glycolipids, revealed that the first mannose is bound via a β-glycosidic linkage to the chitobiosyl core, whereas the outer mannose residues are linked as α-mannosides. Our studies indicate that, in agreement with recent findings in other organisms, the innermost α-mannosidic residues are donated directly from GDP-mannose. The structure of oligosaccharides synthesized by Volvox membranes is thus consistent with results from other eucaryotic species, suggesting a common pathway of N-glycosylation of glycoproteins.     

The early effect of sublethal X-irradiation of phagocytic cells in mouse blood and the influence of cystamine as measured by chemiluminescence

The metabolic burst accompanying phagocytosis of granulocytes (PMN) leads to the generation of activated oxygen species such as O-2, H2O2, 1O2 and OH; which give rise to chemiluminescence (CL) in the presence of luminol. Reliable CL-measurements of stimulated PMN can be carried out in freshly drawn mouse blood, when photon counts are related to the number of PMN. Effects of low dose total body X-irradiation were studied using C57B1/6 mice. It was found that 24 and 48 hours after irradiation (0.24-0.95 Gy) CL of whole blood was slightly decreased. If however CL-counts were related to the number of PMN, an enhanced CL per single granulocyte was recorded. The administration of cystamine leads to an immune stimulating effect of unirradiated animals. In animals, who received 0.95 Gy a distinct radioprotective effect of cystamine can be observed.     

Genetic control of murine hemagglutinin formation to H-2.5

When B10.D2 (H-2^d) mice are immunized with lymphoid cells from C57B1/10 (H-2 ^d ) and their antisera tested against B10.A (H-2 ^a ) target cells, only antibodies to H-2.5 are measured. The same is true for immunization of DBA/2 (H-2 ^d ) mice when their antisera are absorbed with B10.D2 cells prior to testing. Irrespective of the dose of immunogen administered, the primary hemagglutinin response of B10.D2 mice is significantly lower than that of DBA/2 mice and (B10.D2 × DBA/2)F₁ hybrids, but the secondary responses are similar. The low responsiveness of B10.D2 mice appears to be determined by a single dominant gene with incomplete penetrance; the gene is not linked to eitherH- 2, Hc, or the immunoglobulin allotype loci. In addition, the H-2.5 hemagglutinin response is susceptible to nongenetic influences. When antisera from B10.D2, devoid of H-2.5 hemagglutinins, were assayed in a complement-mediated cytotoxic test, they contained almost as much anti-H-2.5 activity as did the antisera from DBA/2 mice or (B10.D2 × DBA/2)F₁ hybrids. The possibility is discussed that the locus responsible for the deficient primary hemagglutinin response of B 10.D2 may not be determinant-specific but may affect hemagglutinin responses in general.     

Electron-paramagnetic-resonance studies on cobalt(II) carbonic anhydrase–sulphonamide complexes

Sulphonamide adducts of three Co(II) carbonic anhydrases were investigated by e.p.r. (electron paramagnetic resonance) at helium temperatures. The highly anisotropic 9 GHz spectra exhibited only three distinct features, with g values between 6.3 and 1.5. Such spectra arise from an electronic state with effective spin S'=(1/2), indicating that the high-spin (S=3/2) ground level is split into two spin doublets differing in energy by an amount large compared with the microwave quantum, but small in relation to thermal energies at ambient temperature. This situation would occur in a tetrahedral system suffering a large rhombic distortion. Calculations based on this model accounted for apparent discrepancies in integrated spectral intensities, and yielded magnetic moments in good agreement with independent measurements, especially in the case of certain small Co(II) complexes resembling the enzyme adducts in their e.p.r. signals. Precise sets of g values, reflecting a particular co-ordination geometry, were found to be representative of each enzyme variant and the type of sulphonamide inhibitor, whether benzocyclic or heterocyclic. A series of substituted benzene sulphonamides bound to the same enzyme gave rise to closely similar spectra despite a wide range of pK(i) values. Thus benzocyclic and heterocyclic sulphonamides were evidently held in the active-site cleft in characteristic orientations irrespective of side chains that might considerably influence the total binding strength. Visible absorption spectra of various sulphonamide adducts at room temperature showed a similar pattern of inhibitor dependence to the e.p.r. spectra, suggesting a correspondence between the co-ordination structures in liquid and frozen solution. E.p.r. spectra of the sulphonamide complexes were remarkable not only for their range of g values, but also for their variations in line-width and spin-lattice relaxation behaviour. Addition of glycerol to the medium produced marked enhancement in resolution, owing to the creation of a more homogeneous frozen matrix. The non-uniform spin relaxation was probably a consequence of the large anisotropy in effective g tensor.     

Alkaline phosphatase from pig kidney. Microheterogeneity and the role of neuraminic acid

Several alkaline phosphatases (EC 3.1.3.1) could be obtained from pig kidney brush-border membrane on extraction with butan-1-ol. Three of the multiple forms were separated by DEAE-cellulose chromatography and further purified. They form a regular series with different degrees of glycosylation (mainly owing to N-acetylneuraminic acid), of charge, of molecular weight, of stability to temperature, to pH and to urea, of minimal requirement for Mg²⁺ and of extractability by butan-1-ol. In contrast, the detectable antigenic sites, the inhibition by amino acids and the pH-dependency of K_m and V_max. were identical for these multiple forms. On treatment with neuraminidase, the multiple forms became identical in all their properties. It was therefore concluded that the microheterogeneity of alkaline phosphatase is due to different degrees of glycosylation at polypeptide chains which appear to be otherwise identical.     

Recombination of human erythrocyte apoprotein and lipid. II. Visualization of apoprotein-lipid bilayer complex by freeze-etching

Bilayers of human erythrocyte apoprotein-lipid complexes were made by dipping a mica plate through monolayers of the complex formed at the air-water interface. Stearic acid and erythrocyte lipid alone served as controls. Freeze-fracture images of the complex at high lipid surface pressures (30 dynes/cm) showed particles (average diameter, 109 Å ± 18 Å) similar to those of erythrocyte ghosts (average diameter, 102 Å ± 19 Å). Control surfaces were smooth. We conclude that part or all of the protein molecule penetrated into the lipid bilayer and that erythrocyte apoprotein-lipid complexes yield fracture faces similar to the native erythrocyte membrane.     

The Organically Handicapped Child—How Can the Family Physician Help?

The better his understanding of some of the ways in which an organic deficit might affect normal development of the handicapped child, the more able the family physician will be to offer guidance to the family aimed at preventing the development of secondary problems. He can thus be instrumental in helping a child achieve his maximal potential.First, it is important to take into account how the parents'' emotional and intellectual responses to having a defective child may interfere markedly in normal parent-child relationship. Second, ways in which each deficit will limit a child''s exposure to stimuli must not be over-looked. Third, one must consider how a deficit may indirectly distort the normal learning patterns when parents do not make age appropriate demands. Fourth, it is important to understand how specific interference in the area of language skills may cause further developmental retardation. Fifth, one must be aware of special problems that an organically handicapped child must face in the society outside of the family. Last of all, in an older child, one must consider the need for a full scale evaluation to sort out primary and secondary factors in the picture.     

Ethylene Oxide Gaseous Sterilization: II. Influence of Method of Humidification

The duration of the equilibration period between admission of water vapor and subsequent introduction of gaseous ethylene oxide to an evacuated sterilizer chamber was studied with respect to its effect on the inactivation of spores of Bacillus subtilis var. niger under simulated practical conditions. Introduction of a water-adsorbing cotton barrier between the spores and an incoming gas mixture of water vapor and ethylene oxide caused a marked increase in the observed thermochemical death time of the spore populations. This effect was negated by admission of water vapor one or more minutes prior to introduction of ethylene oxide gas. Increases in temperature and relative humidity of the system promoted passage of water vapor through the cotton barriers and diminished their effect.