Deterministic Three-Half-Order Kinetic Model for Microbial Degradation of Added Carbon Substrates in Soil

The kinetics of mineralization of carbonaceous substrates has been explained by a deterministic model which is applicable to either growth or nongrowth conditions in soil. The mixed-order nature of the model does not require a priori decisions about reaction order, discontinuity period of lag or stationary phase, or correction for endogenous mineralization rates. The integrated equation is simpler than the integrated form of the Monod equation because of the following: (i) only two, rather than four, interdependent constants have to be determined by nonlinear regression analysis, (ii) substrate or product formation can be expressed explicitly as a function of time, (iii) biomass concentration does not have to be known, and (iv) the required initial estimate for the nonlinear regression analysis can be easily obtained from a linearized form rather than from an interval estimate of a differential equation. ¹⁴CO₂ evolution data from soil have been fitted to the model equation. All data except those from irradiated soil gave better fits by residual sum of squares (RSS) by assuming growth in soil was linear (RSS = 0.71) as opposed to exponential (RSS = 2.87). The underlying reasons for growth (exponential versus linear), no growth, and relative degradation rates of substrates are consistent with the basic mechanisms from which the model is derived.     

Separation and subfractionation of small numbers of cells (approximately 10(6)) by countercurrent distribution in dextran-poly(ethylene glycol) aqueous-phase systems

Separation and subfractionation of cells on the basis of subtle differences in surface properties by partitioning in dextran-poly(ethylene glycol) aqueous phase systems is an established method. We report here that the incorporation of fetal bovine serum into such systems permits countercurrent distribution of small quantities of cells (approximately 10(6]. In the absence of serum such small quantities of cells are lost (probably by adherence) and cannot be recovered after countercurrent distribution.     

Acoustic communication in spring peepers

Summary In the previous study (Wilczynski et al. 1984) we found that neurons in the auditory nerve of female spring peepers (Hyla crucifer) are tuned to frequencies in the male advertisement call, whereas auditory units in male peepers are mismatched in spectral sensitivity to their call. We investigated, in the present report, behavioral consequences of this sexual dimorphism in auditory sensitivity. Call amplitude, rate of call attenuation with environmental transmission, and the amplitude of ambient noise were measured and used to compute the active space of this signal for males and females. The effect of calling height upon active space was considered. Measurements of active space were compared with intermale distances within breeding choruses.Results indicate that active space of the advertisement call for females is as much as 6 times greater than that for males, and varies directly with the height above ground from which males call. Observed maximum intermale distances correspond closely to the active space of the call for this sex. This suggests that males space themselves so that the amplitude of a neighbor's calls approximates their auditory neural threshold to call frequencies. By this proximal mechanism, peepers maximize intermale distance but ensure that they remain within a chorus.Abbreviation dB SPL decibels sound pressure levelre: 20 Pa     

A simple liquid medium for chlamydospore formation in Candida albicans

A new, relatively simple and inexpensive liquid medium was devised to produce all structural forms ofC. albicans. Optimum conditions to induce the yeast cells, germ tubes, pseudohyphae and chlamydospores along with the methods to obtain them are described.Supported in part by Grant CA 20917, National Cancer Institute, National Institutes of Health and ALSAC.     

Molecular and cytological characteristics of nuclear DNA and chromatin for angiosperm systematics: DNA diversification in the evolution of four orchids

The species- and genus-specific DNA content, average base composition of nuclear DNA, presence or absence of satellite DNA, the percentage of heterochromatin and other characteristics of nuclear DNA and nuclear structure allow to deduce the molecular changes which accompanied, or more probably caused, cladogenesis in the orchids studied. It is suggested that saltatory replication (generative amplification) of certain DNA sequenes, diversification of reiterated DNA sequences, and loss of DNA play an important role in the evolution of orchids.—The relationship between changes of genome composition and of nuclear structure and ultrastructure is discussed on the basis of cot curves, heterochromatin staining with Giemsa (C banding), electron microscopy of nuclei, and molecular hybridization in situ.Some aspects of this paper have been presented at the Helsinki Chromosome Conference, August 1977 (Nagl & Capesius 1977).     

Inhibition of protein kinase activity from Trypanosoma cruzi and Trypanosoma gambiense by 3'-deoxyadenosine.

3'-Deoxydadenosine was found to be a potent inhibitor of nucleoside-stimulated protein kinase activity from culture forms of Trypanosoma cruzi and bloodstream forms of Trypanosoma gambiense. The type of inhibition by 3'-deoxyadenosine was competitive with respect to ATP. The inhibition constants for 3'-deoxyadenosine were determined to be 0.11mM and 0.085mM for the enzyme from T. cruzi and T. gambiense, respectively. The apparent Km value for ATP was 0.2mM for both enzymes. 2'-Deoxyadenosine was less effective as inhibitor of the protein kinase activity. The inhibition constants were calculated to be 0.8mM and 0.67mM, respectively.     

Contributions of subterranean termites to the “economy” of Chihuahuan desert ecosystems

Summary We examined the role of subterranean termites in decomposition of cattle dung, various herbaceous plant species and wood in a Chihuahuan desert ecosystem. From July–September, termites removed dung at a rate of 0.63 g day^-1 accounting for a percent mass loss of 19.5–100%. During the autumn subterranean termites consumed more than 50% of the leaves of the shrub Larrea tridentata, the grass Erioneuron pulchellum and annual plant Lepidium lasiocarpum and Baileya multiradiata but used very little of two other annuals Eriastrum diffusum and Eriogonum trichopes. Yucca inflorescence stalks on plots with termites lost 23% of their original mass in 30 months while those on termite free soils lost 11%. Elimination of termites resulted in reduction of fluff grass, Erioneuron pulchellum biomass, thereby affecting the structure of the ecosystem.     

On the population genetics of beta2-glycoprotein I.

Beta2-glycoprotein I typings on 152 healthy Germans and 150 patients with atopic diseases did not show any differences in the serum protein concentrations or in the phenotype and gene frequencies. Compared to these German samples, Philippinos (n = 88) as well as healthy Negroes from South Africa (n = 192) revealed statistically significant lower concentrations of this serum protein. They differ also from the Germans with regard to phenotype and gene frequencies. A most striking result was found in the comparison of healthy and leprous Negroes (n = 250) from South Africa. In these, quite different and statistically significant beta 2-Glycoprotein I concentrations, respectively, phenotype and gene frequencies were seen, which may be due to this disease. The possible reasons for these observations as well as for the observed population differences are discussed.