A machine for sawing 80-micrometer slices of carious enamel

Design and construction of a machine that cuts 80-microns slices of sound and carious dental enamel and other calcified tissues is described. These slices can be used for quantitative microradiographic studies. Preparation takes minutes. Thickness for a given slice is uniform within 2 microns, mean thickness is within 4 microns of the intended value and roughness is about 0.1 micron. Commercial components have been used where possible. Information is provided to permit purchase of the components of the machine and its construction in the average university workshop.     

Characterization of the Stimulation of Ethylene Production by Galactose in Tomato (Lycopersicon esculentum Mill.) Fruit

We have characterized the stimulation of ethylene production by galactose in tomatoes (Lycopersicon esculentum Mill.). The effect of concentration was studied by infiltrating 0, 4, 40, 100, 200, 400, or 800 micrograms galactose for each gram of fresh fruit weight into mature green `Rutgers' fruit. Both 400 and 800 micrograms per gram fresh weight consistently stimulated a transient increase in ethylene approximately 25 hours after infiltration; the lower concentrations did not. Carbon dioxide evolution of fruit infiltrated with 400 to 800 micrograms per gram fresh weight was greater than that of lower concentrations. The ripening mutants, rin and nor, also showed the transient increase in ethylene and elevated CO₂ evolution by 400 micrograms per gram fresh weight galactose. 1-Aminocyclopropane-1-carboxylic acid (ACC) content and ACC-synthase activity increased concurrently with ethylene production. However, galactose did not stimulate ACC-synthase activity in vitro. The infiltrated galactose in pericarp tissue was rapidly metabolized, decreasing to endogenous levels within 50 hours. Infiltrated galacturonic acid, dulcitol, and mannose stimulated transient increases in ethylene production similar to that of galactose. The following sugars produced no response: sucrose, fructose, glucose, rhamnose, arabinose, xylose, raffinose, lactose, and sorbitol.     

Effect of GA3 on the Cyclic AMP Biosynthesis in Maize Seedling

The effect of GA₃ on the biosynthesis of cAMP was studied toinvestigate the mechanism of gibberellic acid action. The presenceof cAMP in germinating maize seedlings was confirmed. The concentrationgradient of cAMP in maize seedlings inclined from shoot apexto root. The amount of cAMP in maize shoot was increased about3.3 times by exogenous GA₃. These results indicate that thebiosynthesis of cAMP is stimulated by GA₃. (Received June 17, 1986; Accepted January 22, 1987)     

Molecular cloning and differential expression of somatic and testis-specific H2B histone genes during rat spermatogenesis

We have cloned cDNA of a testis-specific histone, TH2B (a variant of H2B), and rat somatic H2B gene to investigate regulation of testis-specific histone genes during rat spermatogenesis. The amino acid sequences deduced from DNA sequences show extensive sequence divergence in the N-terminal third of the two histones. The rest is highly conserved. One cysteine residue was found in TH2B. No cysteine is present in somatic histones except in H3 histone. We investigated the expression of TH2B and H2B genes using the regions of sequence divergence as hybridization probes. The TH2B gene is expressed only in the testis, and the expression of this gene is detected 14 days after birth, reaching a maximum at Day 20. The level of H2B mRNA shows a reciprocal pattern. This contrasting pattern can be explained by the gradually changing proportion of spermatogonia and spermatocytes with testicular maturation. In situ cytohybridization studies show that H2B gene is expressed primarily in proliferating spermatogonia and preleptotene spermatocytes, whereas TH2B gene is expressed exclusively in pachytene spermatocytes which first appear in testis about 14 days after birth. H2B and TH2B genes appear to be ideal markers for the study of proliferation and differentiation events in spermatogenesis and their regulatory mechanisms.     

Recalibration of the Pseudomonas aeruginosa Strain Pao Chromosome Map in Time Units Using High-Frequency-of-Recombination Donors

High-frequency-of-recombination donors of P. aeruginosa strain PAO were generated using a temperature-sensitive, replication mutant of the IncP-1 plasmid R68, loaded with the transposon Tn2521. Fourteen donors so isolated mobilized the chromosome in a polarized manner from a number of different transfer origins. The donors were used to construct a time of entry map of the entire chromosome and this was achieved by determining the time of entry of 32 randomly dispersed markers in crosses using nalidixic acid to interrupt chromosome transfer. Analysis of the time of entry data enabled the recalibration of the chromosome map to 75 min.     

Die Entwicklung der Laut?u?erungen bei der Graugans (Anser anser)

Zusammenfassung Das Lautrepertoire von sechs handaufgezogenen Graugänsen wurde in individuellen Längsschnitten vom Schlüpfen bis zum Alter von 100 Tagen mit sonagraphischer Methode analysiert. Die Einteilung des Repertoires erfolgte nach drei verschiedenen Kriterien: Klang, Sonagramm und Kontext. Im jugendlichen Repertoire ließen sich 4 Rufklassen voneinander trennen. Im Laufe der Jugendentwicklung veränderten sich vor allem die phonetischen Parameter der Rufe, während die syntaktischen weitgehend konstant blieben. Nach einem Anstieg in der ersten Woche fiel die Tonhöhe der Rufe bei allen untersuchten Individuen und Rufklassen gleichmäßig ab. Der Stimmbruch, meßbar an der Zunahme geräuschhafter Komponenten, war ein kontinuierlicher, langfristiger Prozeß. Die Individualität war nicht in einem einzelnen, wohl aber in der Kombination mehrerer Merkmale faßbar. Die Geschlechter waren schon früh an Unterschieden in der Tonhöhe erkennbar. An sonstigen ontogenetischen Veränderungen innerhalb des Untersuchungszeitraumes konnten die Erweiterung des Repertories durch Aufspaltung und Reifung sowie ein möglicher Verlust von Rufklassen beobachtet werden.

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Juvenile development of vocalizations in Greylag Geese (Anser anser)

Summary The juvenile vocal development of six Greylag Geese from hatching up to the age of 100 days was analysed by using sonagraphic methods. The calls were classified by means of the acoustic phenomenon, sonagrams, and context criteria. The juvenile repertoire included four main call types. During ontogeny, changes of call parameters mainly referred to phonetic characteristics, whereas syntactic parameters remained more or less constant. The frequency pitch of calls changed to higher levels during the first week of development while in older goslings this parameter decreased constantly. This held true for each individual and call type. Breaking of the voice, defined as an increment of noisy parts in the vocalizations, is described as a continuous long term process. Structural individuality of calls apparently was not based on one single parameter, but on the combination of several ones. Sex differences were found in the pitch of vocalizations, correlating with different body weights of male and female geese. Additional developmental processes of the vocal repertoire included differentiation, maturation of new call types, and apparent suppression of juvenile ones. The functional organization of the juvenile call system in Greylags is discussed.

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Herrn Dr. Hans Löhrl zum 75. Geburtstag gewidmet     

The nifA gene of Rhizobium meliloti is oxygen regulated.

Experiments using plasmid-borne gene fusions and direct RNA measurements have revealed that expression from the nifA gene is induced in Rhizobium meliloti when the external oxygen concentration is reduced to microaerobic levels. Induction occurs in the absence of alfalfa and in the presence of fixed nitrogen and does not require ntrC. The production of functional nifA gene product (NifA) can be demonstrated by its ability to activate the nitrogenase promoter P1. Aerobic induction of nifA can also occur during nitrogen starvation at low pH, but in this case induction is dependent on ntrC and does not lead to P1 activation. The data indicate that reduced oxygen tension is potentially a major trigger for symbiotic activation of nitrogen fixation in Rhizobium species.     

Regulation of protein kinase C activity by gangliosides

The activity of protein kinase C (Ca2+/phospholipid-dependent enzyme) in the presence of phosphatidylserine and its physiological regulator, diacylglycerol, could be suppressed by a mixture of brain gangliosides. Half-maximal inhibition was observed at 30 microM and was nearly complete at 100 microM. Inhibition was observed at all concentrations of Ca2+ between 10(-8) and 10(-4) M. Inhibition of protein kinase C activity could not be reversed by increasing the concentration of diacylglycerol or the substrate, histone. Inhibition was also observed when myelin basic protein or a synthetic myelin basic protein peptide was used as substrate. Among the individual gangliosides, the rank order of potency was GT1b greater than GD1a = GD1b greater than GM3 = GM1. Our results suggest that gangliosides may regulate the responsiveness of protein kinase C to diacylglycerol.     

Effect of amino acid at the beta 6 position on surface hydrophobicity, stability, solubility, and the kinetics of polymerization of hemoglobin. Comparisons among Hb A (Glu beta 6), Hb C (Lys beta 6), Hb Machida (Gln beta 6), and Hb S (Val beta 6)

Surface hydrophobicity, stability, solubility, and kinetics of polymerization were studied using hemoglobins with four different amino acids at the beta 6 position: Hb A (Glu beta 6), Hb C (Lys beta 6), Hb Machida (Gln beta 6), and Hb S (Val beta 6). The surface hydrophobicity increased in the order of Hb C, Hb A, Hb Machida, and Hb S, coinciding with the hydrophobicity of the amino acid at the beta 6 position. Solubility of the oxy-form of these hemoglobins decreased in relation to increases in their surface hydrophobicity, suggesting that the solubility is controlled by the strength of hydrophobicity of the amino acid at the beta 6 position. The solubility of the oxy-form of these hemoglobins is always higher than that of the deoxy-form. There is a similar linear relationship between the solubility and surface hydrophobicity among deoxyhemoglobins A, C, and Machida. However, the solubility of deoxy-Hb S deviated significantly from the expected value, indicating that the extremely low solubility of deoxy-Hb S is not directly related to the hydrophobicity of the beta 6 valine. Kinetic studies on the polymerization of deoxy-Hb Machida revealed a distinct delay time prior to polymerization. This confirms our previous hypothesis that beta 6 valine is not responsible for the delay time prior to gelation. The kinetics of the polymerization of 1:1 mixtures of sickle and non-sickle hemoglobins were similar to those of pure Hb S, suggesting that only one of the two beta 6 valines is involved in an intermolecular contact. In mixtures of equal amounts of Hb S and Hb A, Hb C, or Hb Machida, half of the asymmetrical AS, SC, and S-Machida hybrid hemoglobins behaved like Hb S during nucleation, while the other half behaved like the non-sickle hemoglobin.