Comment on ‘Spectroscopie infra-rouge de quelques fractions d'acides humiques obtenues sur Sephadex’

Summary It is suggested that, in IR spectra of fractions of soil organic matter eluted from Sephadex, absorption bands ascribed to aromatic ethers, epoxide rings and alcoholic or phenolic hydroxyl groups by Bailly¹ are more consistent with a conventional humic material in its carboxylate from and an associated soil clay mineral such as illite. re]19770204     

Plants interact with microbial polysaccharides

Plants are resistant to almost all of the microorganisms with which they come in contact. In response to invasion by a fungus, bacterium, or a virus, many plants produce low molecular weight compounds, phytoalexins, which inhibit the growth of microorganisms. Phytoalexins are produced whether or not the invading microorganism is a pathogen. The production of phytoalexins appears to be a widespread mechanism by which plants attempt to defend themselves against pests. Molecules of microbial origin which trigger phytoalexin accumulation in plants are called elicitors. Structural polysaccharides from the mycelial walls of several fungi elicit phytoalexin accumlation in plants. Approximately 10 ng of the polysaccharide elicits the accumulation in plants of more than sufficient amounts of phytoalexin to stop the growth of microorganisms in vitro. The best characterized elicitors have been demonstrated to be β-1,3-glucans with branches to the 6 position of some of the glucosyl residues. Oligosaccharides, produced by partial acid hydrolysis of the mycelial wall glucans, are exceptionally active elicitors. The smallest oligosaccharide which is still an effective elicitor is composed of about 8 sugar residues. Bacteria also elicit phytoalexin accumulation in plants, but the Rhizobium symbionts of legumes presumably have a mechanism which allows them to avoid either eliciting phytoalexin accumulation or the effects of the phytoalexins if they are accumulated. The lectins of legumes bind to the lipopolysaccharides of their symbiont, but not of their non-symbiont, Rhizobium. It is not known whether the lectin-lipopolysaccharide interaction is involved with the establishment of symbiosis. However, evidence will be presented that suggests that lectins are, in fact, enzymes capable of modifying the structurs of the lipopolysaccharides of their symbiont, but not of their non-symbiont, Rhizobium. It will also be shown that the lipopolysaccharides isolated from different Rhizobium species and from different strains of individual Rhizobium species have different sugar compositions. Thus, the different strains of a single Rhizobium species are as different from one another as the different species of Salmonella and other gram-negative bacteria. This conclusion is substantiated by experiments demonstrating that antibodies to the lipopolysaccharide from a single Rhizobium strain can differentiate that strain from other strains of the same species as well as from other Rhizobium species. The role in symbiosis of the strain-specific O-antigens is unknown.     

SCANNING ELECTRON MICROSCOPE OBSERVATINS ON ZOOSPORANGIAL ABSCISSION IN PHYCOPELTIS EPIPHYTON (CHLOROPHYA)1

Zoosporangial abscissin in asexually reproductive Phycopeltis epiphyon, Millardet, epiphytic on leaces of Osmanhus fragrans Loureiro and Sabal minor (Jacquin) Person, examined with scanning electron micrsscopy is described and compared with the process in related Cephaleuros virescens Kunze. The laeral wall of he zoosporangium-pedicel septum begins to rupure early in he abscission process and is followed by continued learing of the lateral wall and partial spliing of the septum. The zoosporangium remains attached in a hinge-like fashion to the pedicel by a portion of the lateral wall and septum. A centrally located protuberance emerges from wihin the septa of both the zoosporangium and pedicel, and together with a slight bulging of the septa, is involved in the final separation of the zoosporangium. Although there are differences in surface morphlogy of identical in P. the zoosporangia and the location of the exit pores, the process of abscission is identical in P. epiphyton and C. virescens.     

A fermentation process for producing both ethanol and lysine-enriched yeast.

In 18 batch-fermentation experiments, baker's yeast was grown in an enriched mineral medium, containing 10% by weight glucose, at various pH and temperature levels. The pH and temperature are just two representative engineering variables which can be easily varied at negligible cost. The commercial yeast inoculum, 20% by weight or about .16% viable cells, was selected to represent industrial (nonsterile) conditions. Free L-lysine, ethanol, and cell growth were followed in time for each batch run held at a fixed pH and temperature. The maximum free lysine level reached at either 10 1/2 or 24 hr occurred at a pH of 5 and 32 degrees C. At 24 hr, the peak free lysine level, 120 mg/liter, is three times as great as the uncontrolled pH counterpart. In terms of total L-lysine (free plus protein-bound) the peak represents a 25% improvement over the uncontrolled case, based on an average 3.5% lysine level per cell weight. The greatest measured cell level, .9% by weight in the fermentation broth, or a 5 1/2-fold increase over th inoculum, was reached during the 36 degrees C and pH 3 run, while the largest measured ethanol value (3%, or 30% conversion by weight from glucose) was achieved during the 28 degrees C and pH 6 experiment. The optimal lysine run product, however, no less than 15% of the maximum cell and 30% of the maximum ethanol levels.     

Amaurosis fugax and carotid artery disease: indications for angiography.

A prospective study of 80 patients presenting with amaurosis fugax was performed in an attempt to relate clinical features to angiographic findings in the internal carotid artery. Carotid bruit, transient cerebral ischaemic attacks, hypertension, and claudication were associated with a high prevalence of angiographic abnormality. Every patient who showed all these features had an operable lesion, as did 88% of those who had three features. In patients over 50 years of age carotid stenosis and atheromatous ulceration were occasionally found in the absence of bruit and transient cerebral ischaemia, but only one patient aged under 50 had an operable lesion and no associated features. Clinical features were therefore valuable in predicting the outcome of angiography, but it seems prudent to restrict angiography to patients aged over 50, who are most likely to benefit from surgery on the carotid artery.     

Rabbit muscle phosphorylase derivatives with oligosaccharides covalently bound to the glycogen storage site

Linear maltooligosaccharides, e.g., maltoheptaose or terminal 4-O-methylmaltoheptaose, activated by cyanogen bromide, react covalently with rabbit muscle phosphorylases b and a (EC 2.4.1.1). Site-specific modification prevents further binding to glycogen and shifts the phosphorylase a tetramer-dimer equilibrium in favor of the dimer. Use was made of these properties to separate by affinity chromatography and gel filtration phosphorylase a dimers with specifically bound oligosaccharide from unspecifically modified products. The phosphorylase a-maltoheptaose derivative carries one oligosaccharide residue per monomer and can be distinguished from the native enzyme by its electrophoretic mobility in polyacrylamide gels or by affinity electrophoresis. Phosphorylase a preparations with covalently bound maltooligosaccharides are enzymatically active in the presence of a primer and alpha-D-glucopyranose 1-phosphate (glucose-1-P). Methylation of the nonreducing chain terminus of the bound oligosaccharide has no effect on glycogen synthesis. These findings exclude the participation of bound oligosaccharides in chain elongation. Purified covalent phosphorylase a-maltoheptaose complexes are stable dimers. They are no longer activated by glycogen. The properties of covalently modified phosphorylase-oligosaccharides are consistent with and provide direct evidence for the existence of a glycogen storage site in rabbit muscle phosphorylases. Covalent occupation of the storage site renders the affinity of glucose-1-P to phosphorylase a independent of modulation by glycogen, supporting the assumption that the glycogen storage site is involved in interactions with the catalytic site.     

Effect of hydration on the morphology of enzyme powder

We report the first direct images of the hydration of protein powders. Using an environmental scanning electron microscope (ESEM) we have taken a series of micrographs of a region of the enzyme (subtilisin) power whilst hydrating the sample. In addition, the sample has been viewed during exposure to toluene vapors. The ESEM is a remarkable new instrument that will have wide applicability in imaging of biological materials in their native environments.     

Quantitation of Sertoli cell-germ cell desmosome gap junctions in relation to meiotic divisions in the male rat.

Desmosome-gap (D-G) junctions were quantified in relation to germ cell meiosis in the male, specifically to test the hypothesis that the loss of these junctions is related to successful passage of cells through diplotene phase of Meiosis I and the two cytokineses that follow. Such a hypothesis has been proposed as the cause for the resumption of meiosis that occurs prior to ovulation in the female. D-G junctions were quantified in pachytene spermatocytes (stage XII), diplotene spermatocytes (stage XII), secondary spermatocytes (stage XIV) and step 1 spermatids (stage I). These were referred to as the cells of interest as compared with spermatocytes (zygotene spermatocytes, zygotene spermatocytes, pachytene spermatocytes, pachytene spermatocytes) in the same stages, respectively, that served as controls termed control cells. Since gap junctions are not easily recognized in the average sectioned profile of a desmosome-gap junction, only the desmosomal component was quantified. The data were expressed as both numbers and length of junctions per tubule, per cell profile and per unit lineal membrane length to overcome errors inherent in the methodologies utilized. There was no indication that numbers of junctions changed specifically in the cells of interest after passage through diplotene suggesting that these junctions do not have a comparable role in meiotic continuance in the male as proposed for the female. Interestingly, the control cells always showed greater numbers and length of junctions than the cells of interest suggesting that junction may relate more to the period of initiation of meiosis than to its continuance.     

Properties of a genetically reconstructed Prevotella ruminicola endoglucanase.

A pUC19-derived plasmid was constructed that coded for a hybrid cellulase with the Thermomonospora fusca E2 cellulose-binding domain at its C terminus joined to the Prevotella ruminicola 40.5-kDa carboxymethyl cellulase (CMCase). The hybrid enzyme was purified and characterized enzymatically. It bound tightly to cellulose, and its specific activities on carboxymethyl cellulose, amorphous cellulose, and ball-milled cellulose were 1.5, 10, and 8 times that of the 40.5-kDa CMCase, respectively. Furthermore, the modified enzyme gave synergism with an exocellulase in the degradation of filter paper, while the 40.5-kDa CMCase did not.