METHOD FOR COMBINED ULTRASTRUCTURAL AND BIOCHEMICAL ANALYSIS OF NEURAL TISSUE

Something worth dyeing for: molecular tools for the dissection of lipid metabolism in Caenorhabditis elegans

The nematode Caenorhabditis elegans (C. elegans) has during the last decade emerged as an invaluable eukaryotic model organism to understand the metabolic and neuro-endocrine regulation of lipid accumulation. The fundamental pathways of food intake, digestion, metabolism, and signalling are evolutionary conserved between mammals and worms making C. elegans a genetically and metabolically extremely tractable model to decipher new regulatory mechanisms of lipid storage and to understand how nutritional and genetic perturbations can lead to obesity and other metabolic diseases. Besides providing an overview of the most important regulatory mechanisms of lipid accumulation in C. elegans, we also critically assess the current methodologies to monitor lipid storage and content as various methods differ in their applicability, consistency, and simplicity.

Stabilization of pericardial tissue by glutaraldehyde

The effect of glutaraldehyde on pericardial tissue has been studied with special reference to the degree of chemical modification, thermal stability and enhancement of the resistance to proteolytic digestion. The nature of the cross-links depends on time and reagent concentration. At least two populations of lysine and hydroxylysine residues can be distinguished on the basis of their reactivity against the aldehyde. The appearance of these families is not dependent on the structural integrity of the tissue. The time course of the tissue modification is not modified by removing lipids and proteoglycans from the biomaterial. Highest thermal stability is obtained by long-term modification at low reagent concentration.

Mechanism of crosslinking of proteins by glutaraldehyde I: reaction with model compounds

3H-Glycine and 6-aminohexanoic acid were used as model amine compounds and reacted with glutaraldehyde. Based on the spectral characteristics and the molecular weights obtained from the reaction products, it is concluded that glutaraldehyde can modify amines to form an intermediate which absorbs at 300 nm and has a molecular weight of about 200. In the presence of excess glutaraldehyde, this intermediate is quickly converted to a much larger intermediate which absorb strongly at 265 nm. The larger intermediates are finally altered to yield a strong absorption peak at 325 nm with no apparent change in the molecular weight. These results suggest that a process of polymerization is induced by the initial reaction of glutaraldehyde with amines. The glutaraldehyde-polymer amine complex is self-limiting in size and can undergo internal rearrangement to become chemically inert.

The peroxisome (microbody) membrane: effects of detergents and lipid solvents on its ultrastructure and permeability to catalase

The effects of detergents, organic lipid solvents, and several adjuvants used in cell fractionation on the ultrastructure of the peroxisomal (microbody) membrane and its permeability to catalase have been investigated. Chopper sections of glutaraldehyde-fixed liver were incubated in the presence of various agents, followed by cytochemical staining for catalase and processed for electron microscopy. Catalase activity was also determined biochemically in the incubation medium. Marked catalase diffusion was found after treatment with 1% or 0.5% Triton X-100 or deoxycholate, as well as with 50% ethanol or acetone or 20% propanol or t-butanol. In contrast, 1% digitonin and lower concentrations of the above agents, as well as sucrose or glycerine caused selective diffusion of catalase from a limited population of peroxisomes. Treatment with 10% polyvinylpyrrolidone (PVP), which has been used as a protective agent in the isolation of microbodies, did not produce any alteration in the fine structure and cytochemical appearance of peroxisomes. These findings concur with earlier biochemical studies on freshly isolated peroxisomes and demonstrate the susceptibility of microbodies, even in glutaraldehyde-fixed rat liver to the effects of various agents which affect the microbody membrane. A close correlation between the ultrastructural integrity of the microbody membrane and its permeability to catalase has been found. The significance of these observations for the assessment of the permeability characteristics of the microbody membrane is discussed.

Ultrastructure of the oocytes of the Egyptian sping mouse (Acomys cahirinus)

The oocytes of types 2, 3, 4 and 5 follicles from the normal spiny mouse were examined withe the electron microsome. Multiple juxtanuclear Golgi bodies, mitochondria associated with flattened granular endoplasmic reticulum, and large nucleus are the main features of the type 2 follicle oocyte. The numbers of mitochondria and Golgi apparati increase significantly at later stages. Small mitochondrial aggregates lacking "intermitochondrial cement" are seen in the ooplasm of types 3, 4 and 5 follicles. "Lamellar complexes" comprising two to six elongate flattened rough ER cisternae and intercisternal filaments begin to appear in the occyte of the type 3 follicle. The intercisternal filaments may be observed as punctate-, dashed-, and solid-lines in cross sections. In tangential sections the filaments display a paracrystalline structure. In the type 4 follicle oocytes, the "lamellar complex" becomes more extensive; polysomes and ribosomal fibrils are juxtaposed to the "lamellar complexes." Bundles of ribosomal fibrils are abundant in the ooplasm of the type 5 follicle. The origin of ribosomal filaments and the functional significance of "lamellar complexes" are discussed.