Fine structure of Lily pollen tubes following various fixation and staining procedures

Summary The cytoplasm of the growth zone at the tip of theLilium pollen tube contains numerous membrane-bound vesicles and an abundance of smooth endoplasmic reticulum. Covering the tip of the tube is a cap of compartmentalized wall material which arises from coalesence of vesicles with each other and with the existing cap.This organization, seen following glutaraldehyde fixation, is altered to varying degrees by different fixation procedures. Neither the cap nor the e. r. are preserved by osmium fixation. Formalin or permanganate preserve the cap but not its compartments. Preservation of the cap by permanganate is concentration-dependent but poor at best. Combined fixation by acrolein and glutaraldehyde results in better preservation of membranous elements than glutaraldehyde alone.Supported by grant RG 8827 from the National Institutes of Health, U. S. A.     

The effect of neuraminidase on genetic variants of alpha anitrypsin.

Sera of Pi types M, F, S, Z, IM, FM, MS, and MZ were incubated with neuraminidase and the reaction products followed by electrophoresis. The alpha1 antitrypsin components showed a series of changes in mobility as sialic residues were removed. Removal of sialic acid was confirmed by chemical assay. Results of studies with two different electrophoretic systems suggested that the Z type alpha1 antitrypsin has less sialic acid than the M, F, and S types. There was no evidence that other genetic variants have a reduced sialic acid content. The two major bands of alpha1 antitrypsin seen in certain electrophoretic systems may reflect a difference of one sialic acid residue. It is proposed that the Z protein lacks a carbohydrate chain with two terminal sialic acid residues. This carbohydrate deficiency results in lack of secretion of type Z alpha1 antitrypsin from the endoplasmic reticulum, perhaps because of binding to sites specific for the incomplete glycoprotein or because of aggregation of the Z asialo protein. A carbohydrate chain could be prevented from attaching to the Z type either because of a conformational change or because of the replacement of a carbohydrate-binding asparagine residue in the Z protein.     

The effect of rigid fixation on growth of the neurocranium

The effects on skull growth of plating the coronal suture and frontal bone were studied in New Zealand White rabbits. Three-dimensional coordinate landmarks were digitized and analyzed to determine the differences in form between operated and unoperated animals using Euclidian distance matrix analysis. This method compares sets of interlandmark distances in three dimensions and was used to demonstrate changes induced by plating. We interpret these changes in morphology to be the result of differences in growth between the operated and unoperated groups. Periosteal elevation alone (n = 6) resulted in a minimal local growth increase. Coronal suture plating (n = 8) resulted in local growth restriction with contralateral and adjacent size increases. Frontal bone plating (n = 6) without crossing a suture line also resulted in local growth restriction and adjacent bone size increases. The timing of intervention in relation to the completion of bone growth may explain the magnitude of clinically apparent effects. Changes in bones adjacent to those directly manipulated may be an attempt to maintain a normal skull volume.     

The effect of neuraminidase treatment of ribosome-free membranes on their ribosomal reattachment ability

Ribosome-free membranes prepared by means of 2M lithium chloride lose 90% of their ability to reattach ribosomes after digestion with neuraminidase for 1 hour. It can be shown that this is not due to proteolytic degradation of the membranes by contaminating proteases presant in neuraminidase preparations. It was found that neuraminidase troatment of rat liver RER results in the release of approximately 50% of the bound ribosomes. Ribosomal reattachment ability can be restored to the neuraminidase-treated membranes by incubation with N-acetylneuraminic acid and nucleotide triphosphates.     

The impact of different fixation procedures on staining of macromolecules in a microtiter system

Summary The effects of formaldehyde, glutaraldehyde, methanol, Clarke's fixative and microwave irradiation on the quantitative staining of proteins (Naphthol Yellow S) and nucleic acids (Ethyl Green—Pyronin) in a cell culture system have been investigated. Overall, glutaraldehyde rapidly yielded the highest and most consistent levels of staining when compared to all other chemical fixatives. Although microwave irradiation was found to be uneven, 4 min exposure to 700W was found to give higher levels of protein staining than those achieveable with glutaraldehyde. Time-dependent processes were observed with all procedures. In addition, dissociations in the trends of protein and nucleic acid staining were observed. It is suggested that these results domonstrate fixation events that have not previously been resolved from the effects of reagent penetration into tissue blocks.     

The effect of water-logging on fixation of nitrogen by soil incubated with straw

Summary When straw was incubated with a calcareous soil under water-logged conditions nitrogen fixation occurred if the gas above the incubation contained oxygen: no detectable fixation occurred if oxygen was excluded. Moist soil failed to fix nitrogen when incubated with straw in either the presence or absence of oxygen.