Photosynthetic properties of leaves of a yellow green mutant of wheat compared to its wild type

We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O₂ evolution of the leaf tissue in saturating light and CO₂ was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO₂ assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f cytochrome f - chl chlorophyll - PS II photosystem II - Pn_max maximum photosynthesis - RuBCase Ribulose, 1-5,bisphosphate carboxylase     

Clustering of hypervariable minisatellites in the proterminal regions of human autosomes

Six of the human minisatellites detected by DNA fingerprint probes have been localized by in situ hybridization to human metaphase chromosomes. These hypervariable loci are not dispersed at random in the human genome, but show preferential, though not exclusive, localization to terminal G-bands of human autosomes. Two of the proterminal minisatellites are very closely linked to other variable loci. Sequence analysis of one of these additional minisatellites suggests that the two linked minisatellites arose by independent amplification of different repeat units. The proterminal regions of human autosomes may therefore be rich in minisatellites, analogous to the pseudoautosomal terminal pairing region of human sex chromosomes that is similarly abundant in hypervariable minisatellites.     

Selective isolation of bacteria with dipeptidyl aminopeptidase type I activity from the sheep rumen

Five-hundred-and-six fresh isolates of rumen bacteria were tested for their ability to hydrolyse the synthetic substrate for dipeptidyl aminopeptidase type I, GlyArg-4-methoxy-2-naphthylamide (GlyArg-MNA), using a gel overlay technique. Twelve positive isolates were small Gram-negative rods which resembled Bacteroides ruminicola in their biochemical and morphological properties. SDS-PAGE of whole cell extracts indicated that two were similar to B. ruminicola strain B14, six resembled B. ruminicola strain M384, and four were similar to B. ruminicola GA33. All hydrolysed GlyArg-MNA, Ala2 and Ala5, and showed no activity against Leu-MNA. Ala3 and Ala2, but no Ala4, was produced from Ala5. The different groups had different, distinctive activity profiles. The two remaining positive isolates were Lactobacillus spp. with an exceptionally high Leu-MNA activity. It was concluded that, although different strains may only be distantly related, B. ruminicola forms the most important group of bacteria in the rumen to possess a dipeptidyl aminopeptidase type I activity.     

Multivariate analysis of metastasis risk in laryngeal carcinoma. II. Immune response

The presence of inflammatory reaction, plasma cells, and eosinophils in peritumoral connective tissue and in neoplastic stroma was evaluated with morphometrical method in 181 patients affected by laryngeal carcinoma. A logistic multiple regression model was applied making it with the use of an independent variable represented by the "infiltrating" or "expansive" types of tumor growth, in order to evaluate the probability of nodal metastatsis of each parameter. The results suggest an inverse correlationship between plasma cells and inflammatory infiltration and incidence of nodal metastatsis only in the comparison of the extreme conditions: those with scarce infiltration versus the ones with large infiltration. Inflammatory or plasmacellular infiltration may represent both a defense mechanism against cancer and an aspecific or allergic reaction. The eosinophilic infiltration shows no value in the prevention of nodal involvement.     

In vitro adventitious root induction in Antirrhinum majus L.

A broadly applicable method for the successful induction of root systems in a number of cultivars of A. majus has been determined. This involves a double filter-paper bridge with a liquid medium for root induction and allows the transfer of culture-grown plantlets to a glasshouse environment with minimal disturbance to the plant as a whole. 100% survival of transferred plantlets has been achieved with the inclusion of a few simple precautions upon shoot transfer and during the initial stages of plant establishment in vivo.     

Elastic properties of the hind foot of the Donkey, Equus asinus

The elastic properties of the hind feet of Donkeys, and of tendons removed from the feet, have been investigated by methods similar to those used in a previous study of the forefoot. The elastic strain energy stored in the foot, during a trotting step, is calculated to be approximately the optimum which would minimize the work required of the muscles in this gait.     

The mechanics of scratching in the squirrel (Neosciurus carolinensis)

Film observations of scratching in the squirrel suggested that a mechanism involving storage of elastic strain cncrgy in the tendons of thc lower leg may bc responsible for the movement. A model of the lower limb, based on such a mechanism, is put forward and tested.     

Scanning and transmission electron microscopy evidence of the cytological effect of pyrrolnitrin on ‘Microsporon audouinii’ Gruby CBS 313-54 ‘in vitro’

Scanning and transmission electron microscopy showed that a ceiling quantity (1.56 mcg) of antifungal antibiotic Pyrrolnitrin caused heavy damage to dermathophyteMicrosporon audouinii Gruby CBS 313-54in vitro. Suitable preparation technique made it clear that the changes involved consisted of hyphal collapse on the edge of the culture, with loss of euplasmic organelles identity and cell autolysis. The cell wall, however, was apparently undamaged. These findings fit in with the suggestion that the mode of action of the antibiotic leads to generalised lipoproteic membranes damage. They must, however, be considered as representing the result of the terminal phase of cell distress.