A small-scale saturator for experiments in which a high accuracy in humidity is required

Summary A saturator of small dimensions is described. Moist air with dewpoint temperatures ranging from 2°C to 30°C with a long-term stability of ±0.05°C and a maximum output of 400 1/h can be attained.Special attention is paid to the calibration procedure and to the effect of the reduction of dewpoint temperature of moist air flowing through a tube.     

Population,formal genetics,and linkage relations of the phosphoglycolate phosphatase (PGP)—E.C.3.1.3.18

Summary One hundred and sixty-seven blood donors, 26 families with 72 offspring and 12 motherchild couples were studied for the phosphoglycolate phosphatase polymorphism. In hemolysates, the isozymes are stable for at least five weeks. The distribution of observed phenotypes in the population study did pot diverge from the expected values according to Hardy-Weinberg law. In the family study, the formal genetic model of three alleles—PGP ¹, PGP ² and PGP ³ at one autosomal locus-could be confirmed. Among 33 individuals from a Mongoloid population PGP 1 was observed in 100%. This observation lead us to the conclusion, based also on recent data in Negroid populations (Barker and Hopkinson 1978), that phosphoglycolate phosphatase may be a more recent polymorphism of Caucasoid populations. Linkage studies with the hp locus an chromosome 16 resulted in 19 meiotic divisions of 4 informative families in a lod score peak of 0.23 at =0.25 being inconclusive. The inclusion of the PGP system in paternity testing is also discussed.     

The spatial distribution of currents in the receptor layer of the frog retina

Steady state patterns of currents flowing extracellularly in the receptor layer of the frog retina are used to work out an electrical model of vertebrate rods. The model can be thought of as a linear network consisting of resitances and current sources. The model predicts the axial spread of currents along the outside of the receptors. In addition, it predicts membrane voltages in light and darkness. If the dark-adapted receptors are assumed to have a uniform membrane with a specific resistance of 500 ·cm², a single rod gives rise to an extracellular dark current of about 200 pa.     

Genetic variation in irradiated and control populations of Cnemidophorus tigris (sauria,teiidae) from Mercury,Nevada with a discussion of genetic variability in lizards

Summary Whiptail lizards (Cnemidophoms tigris) were collected from fenced irradiated, fenced control, and unfenced areas near Mercury Nevada. No changes in allele frequencies at 26 allozyme loci could be ascribed to irradiation or fencing. This species is the most polymorphic and heterozygous lizard so far examined. — Heterozygosity estimates derived from electrophoretic studies on 20 additional species of lizards are compared with Cnemidophorus. A general trend seems to emerge. Fossorial lizards have uniformly low levels of heterozygosity (ca. 1 %). Territorial sit and wait predators are intermediate (ca. 5%). Highly vagile apparently nonterritorial lizards are the most heterozygous (ca. 10%). Assuming that this trend does not reflect some of sampling error, two current, non-mutually exclusive hypotheses explain the observed situation: (1) the niche width variation hypothesis predicts, higher variability in populations where individuals are exposed to largescale environmental heterogeneity; and (2) the population size hypothesis predicts that, all other things being equal, vagility would tend to increase the effective population size by reducing inbreeding, which would promote higher levels of genetic variation.     

Effects of CO2, CH4 and N2 on growth and nutrition of rice seedlings

Summary Flooded soils, which accumulate gaseous products of anaerobic fermentation, are often associated with poor rice plant growth. In the present experiment the effects of CO₂, CH₄, N₂, and air on rice seedling growth and nutrition were evaluated. Nutrient culture techniques were used to avoid secondary soil effects normally experienced.Carbon dioxide gas in the root zone of rice reduced seedling growth significantly, whereas CH₄ and N₂ had no significant effect. Methane gave no stimulatory benefits, unlike results reported by some earlier workers. Of three major nutrient elements studied, P uptake was affected more than N or K. Phosphorus uptake was significantly reduced in leaves and sheaths by all three gases, but was significantly increased in roots. This suggests an immobilization mechanism affecting P in roots, and since CO₂, CH₄, and N₂ behaved similarly in contrast to air, a lack of oxygen in the root system is suspected as the causal mechanism rather than toxic effects of gases. Effects on N and K uptake were minimal and insignificant.Contribution from the Department of Agronomy and Range Science, University of California, Davis, California 95616.Contribution from the Department of Agronomy and Range Science, University of California, Davis, California 95616.     

Application of the ‘profiles of relationship’ method to distantly related proteins

Summary An analysis is made of the applicability of the recently published profiles of relationship method for establishing evolutionary relatedness among proteins by using the distantly related proinsulin and neurotoxin protein se-quences as a test object. The method is based on a simultaneous group analysis of both the frequency of acceptance of mutations and their genetic code inter-changeability. Regularities in the patterns of the profiles, which reflect decreased similarity with the passage of time, are established for typical cases of closely related, distantly related and unrelated proteins. This makes it possible to distinguish distantly related from unrelated proteins without extensive statistical randomization procedures. New evidence is stated in favour of a previously suggested definition of interchangeability which does not consider the third base in the codon. The applicability of the profiles of relationship method is examined on the distant relationship between proinsulin and the snake and scorpion neurotoxins which has been established previously by means of conventional approaches.     

A negative influence of manure on calcareous soils

Summary On a soil rich in CaCO₃ in a semiaride climate in Algeria a hard soil layer, impermeable for plant roots, was formed in a depth of 20–40 cm after farmyard manure application and irrigation. To find the reason soil samples of this field were taken and leaching experiments were carried out in the laboratory, with the result that much more Caions and HCO₃-ions were leached out of the soils with farmyard manure application than from the soils without manure. Probably the high amount of CO₂, being liberated by the organic matter, and the irrigation water dissolved the CaCO₃ in the soil, and the formed Ca- and HCO₃-ions followed the movement of water in the soil. Where the Ca(HCO₃)₂ reached soil layers with a less amount of CO₂, CaCO₃ precipitated and formed the hard soil layer. In order to avoid the formation of such calcareous crusts on irrigated, limy soils in a dry climate it is recommended to fertilize rather often small quantities instead of rarely big quantities of farmyard manure.     

Fractionation of plant protoplast types by iso-osmotic density gradient centrifugation

Summary A simple effective technique for the fractionation of protoplast populations is described. Protoplasts are separated by low-speed centrifugation in an iso-osmotic, discontinuous density gradient system on the basis of differences in their buoyant densities. At a constant osmolality of 660±20 mOs/kg H₂O, the gradients provide a density range from 1.017 to 1.069 g/cm³ at 20 °C which corresponds to the buoyant densities of most protoplast types studied. Characteristics of the KMC/S-density gradient system and factors affecting the fractionation were investigated. Protoplasts were isolated from various tissues and cultivars of tobacco, barley, wheat, rye, oat and maize. Their density-dependent distribution profiles in KMC/S-gradients and their average buoyant densities were determined under standardized conditions. Great differences in the buoyant densities were found between protoplasts of different tissues. Mixed populations of two types of protoplasts, differing in buoyant density by about 15–20 mg/cm³, were separated to give highly purified fractions. Factors affecting the buoyant densities of protoplasts have been investigated. Ploidy level and species differences did not significantly affect the fractionation profiles. However, an age-dependent variation in the average buoyant density of tobacco mesophyll protoplasts was observed. Fractionation of tobacco mesophyll protoplasts and their subsequent regeneration to plants demonstrates the practicability and physiological compatibility of the KMC/S-density gradient system under sterile conditions. The morphogenetic potential of protoplasts was not affected by the separation procedure or the gradient components.     

The mutagenicity and DNA-damaging activity of cyclic aliphatic sulfuric acid esters.

The cyclic aliphatic sulfuric acid esters 1,2-ethylene sulfate (ESF), 1,3-propylene sulfate (PSF) and 1,3-butylene sulfate (BSF) have been tested for their mutagenic and DNA-damaging activity. Mutagenicity of the compounds was established with his-auxotrophic indicator strains of Salmonella typhimurium using the in vitro plate test and the host-mediated assay technique with mice as host animals. The DNA-damaging activity was tested in a repair test with Proteus mirabilis mutants defective in DNA repair.In the repair test with a set of P. mirabilis strains (PG713 hcr^?rec^?: PG273 hcr⁺rec⁺) PSF and BSF showed a preferential growth inhibition of the repair-defective strain suggesting DNA-damaging activity of these chemicals. No such activity was found for ESF using the same concentrations of 5 and 15 μmol/plate.All cyclic sulfates revert the tester strain TA1535 of S. typhimurium in vitro indicating their ability to induce base substitutions. Compared with the reference compounds dimethyl sulfate (DMS), diethyl sulfate (DES), 1,3-propane sulfone (PPS) and 1,4-butane sulfone (BTS) the mutagenic activity in the plate test can be described as follows: PPS > PSF > BSF > BTS > ESF > DES > DMS.Dose-response studies in the host-mediated assay with tester strain TA1950 of S. typhimurium as genetic indicator system revealed a linear dosedependency of mutagenic activity. For PPS and PSF the lowest effective dose (LED) has been established as 10 μmol/kg. The LED for BSF and BTS was 50 μmol/kg, DMS and DES were mutagenic in doses of 2500 μmol/kg, while ESF was only weakly mutagenic with a LED of 5000 μmol/kg.The dose-response studies in the host-mediated assay and the results obtained in the in vitro spot test demonstrate similarities in the mutagenic action of the cyclic sulfates PSF and BSF and the respective sulfones, while the stronger alkylating compound ESF was a weak mutagen both in vitro and in vivo.     

Angiotensin-like activity in resistance vessels

Summary Angiotensin II (ANG II) was localized immunocytochemically in kidney and various other organs of the chinese hamster. In the kidney ANG II-like activity was found in the epitheloid cells of the juxtaglomerular apparatus as well as in the media i.e. the smooth muscle cells of arcuate and interlobular arteries and afferent arterioles. ANG II-like activity was also observed in the medial muscle cells of resistance vessels in other organs and tissues such as submandibular gland and brown adipose tissue. The site of synthesis of ANG II needs to be investigated but the data point to the possibility of an intracellular function of ANG II in smooth muscle cells of blood vessels.These studies were supported by the Deutsche Forschungsgemeinschaft within the SFB 90 Cardiovasculäres System