Thermodynamic approach to biomass distribution in ecological systems

In the derivation of the biomass distribution function for an ecological population critical use is made of an energetic constraint on the maximization of biomass diversity. The nature of this constraint is explored in detail using Kleiber's relation σ(m)=cm ^γ between animal metabolic rate σ(m) and body weightm in conjuction with the Prigogine-Wiame thermodynamic paradigm for specific entropy production in biological stationary states. These two inputs fix the energetic constraint on the maximization of biomass diversity to be the constancy of the mean metabolic rate of the ecosystem. The resulting biomass distribution function is tested against observational data.     

BIOCHEMISTRY OF CEREBRAL TUMOURS: SODIUM, POTASSIUM, CALCIUM, PHOSPHORUS, MAGNESIUM, COPPER AND SULPHUR CONTENTS OF ASTROCYTOMATA, MEDULLOBLASTOMATA AND GLIOBLASTOMATA MULTIFORME

Abstract— Twenty-nine autopsy specimens of intracerebral tumours (nine astrocytomata, ten medulloblastomata and ten glioblastomata multiforme), as well as samples of peritumoral and apparently normal brain tissue, have been studied for Na, K, P, Ca, Mg, Cu, and S contents.
The tumour tissue, irrespective of the histological characteristics, as compared to the 'normal' and perineoplastic tissues, showed higher concentration of Ca, Mg, Cu and S. The peritumoral tissue, regardless of the tumour type, showed a higher concentration of Cu than the 'normal' control brain.
The more malignant glioblatomata and medulloblastomata. The Cu levels did not show a significant diference.     

The effect of reversion and duplication of leaf disks on the accuracy of photosynthesis determination by the dry weight method

Experiments with sunflower and fodder cabbage showed that reversion of the leaf disks lower side upwards (towards the radiation source) decreased the photosynthetic rate by as much as 26% both at full (2. 10⁵ erg. cm^?2. sec.^?1) and half density of irradiation. On placing two disks one on another the photosynthetic rate was decreased in the upper disk in a similar way as it was on reversion even if it were placed in the normal position (upper side upwards). But assimilation in the lower disk was only a fraction (0–40%) of that of the upper disk and in thick leaves was within the limits of the compensation point. The sum of the increase in dry weight in both disks due to photosynthesis exceeds the increment in one normally placed disk only in thin leaves and at high density of radiation. On the basis of the differences found it is advised to discard experimental samples where a quarter of the disks were reversed during exposure. On evaluating samples in which some of the disks were duplicated in error, it is most accurate to deduct the weight of one control disk from the weight obtained. The decrease in photosynthetic rate found in reversed and duplicated disks is evidently due to the simultaneous effect of differences in the supply of CO₂ and radiation energy to the assimilating tissue and apparatus and also to differences in the photosynthetic capacity of different leaf tissues.     

Antimicrobial activity of clove oil dispersed in a concentrated sugar solution

Essential oil of clove, dispersed (0.4%v/v) in a concentrated sugar solution, had a marked germicidal effect against various bacteria and Candida albicans. Staphyloccus aureus (five strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, Clostridium perfringens , and Escherichia coli inoculated at a level of 10⁷ cfu/ml, and C. albicans (inoculum 4.0×10⁵ cfu/ml) were killed (< 99.999%) after 2–7 min in a laboratory broth supplemented with 63% (v/w) of sugar, and containing 0.4% (v/w) of essential oil of clove. Added organic matter (i.e. human or bovine serum) did not impair its antimicrobial activity.
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications.     

Terminal nerve sprouting at the frog neuromuscular junction induced by prolonged tetrodotoxin blockade of nerve conduction

Brain Cell Biology - The effects of a prolonged blockade of nerve conduction by tetrodotoxin on frog motor innervation were studied in the cutaneous pectoris muscle ofRana esculenta. Prolonged...     

Serotypes and antibiotic resistance of Verotoxigenic (VTEC) and Necrotizing (NTEC) Escherichia coli strains isolated from calves with diarrhoea

Serotypes and antibiotic resistance of 51 Verotoxigenic (VTEC) and 33 Necrotizing (NTEC) bovine Escherichia coli strains were determined and compared with those shown by 205 non-VTEC non-NTEC strains isolated from the same batch of calves. E. coli untypable for O-antigen represented 47% of the VTEC, 12% of the NTEC and 8.8% of the non-VTEC non-NTEC. Typable VTEC belonged to serotypes 02:K?, 0103:K-, 0104:K?, 0128:K?, 0153:K- and O157:K-:H7, whereas typable NTEC were of serotypes 08:K87, 015:K14, 015:K-, 054:K?, 076:K-, 078:K(80), 088:K?, 0123:K-, 0139:K- and 0153:K-. Non-VTEC non-NTEC showed a wide variety of serotypes which were generally unrelated to those found in VTEC and NTEC. VTEC were resistant to antibiotics at higher rates than NTEC and non-VTEC non-NTEC, and showed also the highest multidrug-resistant pattern. Our results show that bovine VTEC strains belonged to O-groups usually found in human VTEC causing sporadic diarrhoea, haemorrhagic colitis and/or haemolytic uraemic syndrome, such as 02, 0103, 0104, 0153 and especially 0128 and O157. In contrast, bovine NTEC strains belonged to serotypes different from those previously found in necrotizing E. coli strains of human origin.     

The role of secreted acid hydrolases in the utilization of complex nutrients byTetrahymena

In an attempt to extend our knowledge of the biology of feeding of the ciliateTetrahymena thermophila, this organism was grown axenically on complex organic material. The nutrient substrate was based on autoclaved wheat grains and adjusted to either pH 5.5 or 7.5. In wild type cultures the cells grew and multiplied only under acidic conditions. In cultures of a mutant cell line blocked in the secretion of acid hydrolases the cells did not grow at either pH value. Thus released acid hydrolases may play a key role in the utilization of complex nutrients in combination with uptake of small organic molecules. Mechanisms in the feeding biology ofTetrahymena thermophila andParamecium tetraurelia are compared.