Structural, mechanical and enzymatic study of pectin and cellulose during mango ripening.

Mango is an important crop worldwide, with a postharvest loss that is huge due to its climacteric behaviour. This study evaluated the softening of Tommy Atkins mangos during the ripening process. Ripening index (RPI) shown a decrease from 9.18 ±â€¯0.14 to 4.75 ±â€¯0.47. The enzymatic activity agreed with physicochemical parameters and with the structural and mechanical changes. Three pectin fractions were isolated from the mango cell wall: water soluble (WSP), chelator soluble (CSP) and diluted alkali soluble (DASP) pectin. The Younǵs modulus (E) of the primary cell wall was evaluated, it decreased from 1.69 ±â€¯1.02 to 0.39 ±â€¯0.16 MPa, which could be attributed to the softening of the fruit. A linear fit correlation between E and RPI was found. X-ray and confocal laser scanning microscopy analysis showed the changes occurred in the mango cell wall structure during maturation. Novelties of current study can be helpful in the use of mango wastes to obtain cellulose.

Input of different kinds of soluble pectin to cation binding properties of roots cell walls.

It is widely believed that pectin are responsible for the vast majority of cation binding positions in the root cell walls. To estimate the role of particular kinds of pectin, we studied the cell wall material isolated from the roots of monocots (wheat and rye) and dicots (clover and lupine) before and after removal of different fractions of soluble pectin. Simultaneously PME activity and degree of pectin methylation were determined. From potentiometric titration curves cation exchange capacity, total surface charge and acidic strength of surface functional groups responsible for surface charging were determined. Monocots had smaller cation exchange capacity and lower pectin content than dicots. Removal of pectin induced up to 50% reduction in the cell walls surface charge. Pectin seem to have more acidic character than the other roots components that is seen from an increase in very weakly acidic groups fraction and significant decrease in the average dissociation constant of the cell walls material after pectin removal. Water soluble pectin and non-pectic soluble compounds had the dominant role in surface charging, while chelator and diluted alkali soluble pectin contributed to surface charge only at high pH's.

Umbilical vessels endothelium and vascular reactivity.

In vitro preparations of isolated umbilical vessels are ideal for the study of vasoactive substances. These vessels display vascular reactivity in response to numerous substances, although the mechanism of action of many of these agents is unknown. The present study was undertaken to study the role of the endothelium in the vasoactivity of these preparations, and to examine their cellular integrity. Umbilical artery and vein were studied using conventional isometric techniques, and using high power light microscopy. We found that umbilical vessel rings had no relaxant response to agents believed to release endothelium-derived relaxant factor (EDRF). Mechanical and chemical treatment to remove endothelium did not significantly alter vascular response to known contractile agonists. Cellular morphology is well maintained in ring preparations. Finally, mechanical rubbing of the intima of these rings is more reliable in endothelium removal, as compared to chemical removal with the detergent saponin.

Prevalence of serological groups of Neisseria meningitidis and their susceptibility to 31 antimicrobial agents.

One hundred and forty four strains of Neisseria meningitidis were isolated from pathological specimens and from carriers. The source of material was randomized in Poland. Out of seven existing serological groups of Neisseria meningitidis, no strains belonging to groups D and X were isolated. Serological group B was dominating; strains isolated from patients comprised 68%, while strains from carriers were group B-positive in 52%. Pathological specimens revealed presence of strains belonging to groups A, B and C only. All strains were tested toward susceptibility to 31 antimicrobials (8 penicillins, 5 cephalosporins, 3 tetracyclines, 4 sulphonamides and 11 other drugs). Most effective were: penicillin, carbenicillin, amoxycillin, cephalothin, and sulphonamides. Some sulphonamide-resistant strains, especially belonging to serological group C and to a lesser extent to group B, have been isolated.

Susceptibility of Staphylococcus aureus, Streptococcus pyogenes and Diplococcus pneumoniae to antibiotics. Comparison of patterns in Poland and Federal Republic of Germany.

One hundred and eighty five strains of Gram-positive cocci were tested for susceptibility to 16 antibiotics, including some newer drugs, by agar dilution technique. Of these, 100 strains (50 each isolated in Poland and Germany) were Staphylococcus aureus, 55 Streptococcus pyogenes, and 30 Diplococcus pneumoniae. Previous investigations of streptococci and pneumococci isolated in Poland and Federal Republic of Grmany, revealed no differences in antibiotic-susceptibility patterns in both countries, which was not the case with staphylococci. Present study demonstrates further evidence for existence of differences in antibiotic-sensitivity of staphylococci, depending of their geographical origin, and presents actual state of susceptibility to antibiotics of Streptococcus pyogenes and Diplococcus pneumoniae.

Susceptibility of Streptococcus faecalis to 32 antimicrobial agents. Comparison of patterns in Poland and Federal Republic of Germany.

Two hundred and twenty strains of Streptococcus faecalis (103 isolated in Poland and 117 in Federal Republic of Germany), were tested for antibiotic-susceptibility to 32 antimicrobial agents by agar dilution technique. Most effective in vitro appeared ampicillin, penicillin G, and a combination (1:1) of penicillin and streptomycin. Partly effective were also macrolide antibiotics, trimethoprim + sulfamethoxazole and five tetracyclines. Other antibiotics, including five cephalosporin derivatives, five aminoglycoside antibiotics, two lincomycins, two polymyxins, chloramphenicol and fucidin, appeared practically ineffective in vitro. Effectiveness of antimicrobials in vitro was considered on the basis of standard bioavailability of antimicrobial agents. No differences in antibiotic-susceptibility patterns of any practical significance were found, when strains isolated in Poland and Federal Republic of Germany were compared.

Susceptibility of clinically important gram-negative bacilli to 15 antibiotics. Comparison of patterns in Poland and Federal Republic of Germany.

Three hundred and sixty strains of Gram-negative bacilli (Escherichia coli, Salmonella enteritidis, Enterobacter cloacae, Providencia, indole-positive and indole-negative Proteus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens), were isolated by random in Poland and Germany, and tested by agar dilution method for susceptibility to 15 antimicrobial agents, including six cephalosporin derivatives, colistin, gentamycin and tobramycin, three newer tetracyclines, ampicillin and carbenicillin, and a combination of trimethoprim and sulfamethoxazole. This investigation revealed existence of growing antibiotic-resistance of Gram-negative bacilli to all antimicrobial agents. A detailed analysis of this problem is described and a list of agents effective in vitro is presented. Some evidence has been found concerning possible existence of geographical differences in antibiotic-susceptibility patterns of strains of Gram-negative bacilli, isolated in Poland and Federal Republic of Germany.