Ultrastructural immunocytochemistry of nascent albumin topology: proposed cytosolic folding and membrane transit of the protein

Quantitative analysis of streptococcal exoprotein flow to the host receptor--exact basis for therapy of tumors and Alzheimer's disease

The basis of a bacterial pathogenic process consists in the change of a certain host structure to a completely different one. This is accomplished by binding of a bacterial protein product to the host structure. Streptococcal NAD+-nucleosidase was explored as to its binding to the host receptor represented by beef heart extract. The bacterial product was found to bind to the host structure until the available host structure was fully saturated. The similarity of the above flows of macromolecules with some models of morphogenesis indicates the existence of diseases associated with the flow of a protein to the undesirable site in the organism. In such a case therapy with low-molar-mass substances is wrong in principle.

Immunohistochemical localization of albumin and in situ hybridization of albumin mRNA

Hepatocytes actively involved in albumin synthesis were identified by immunohistochemical method. In sections of perioidate-lysine-2 per cent (w/v) paraformaldehyde fixed normal rat liver, albumin was detected in all hepatocytes. At the ultrastructural level, albumin was localized in the rough endoplasmic reticulum and in Golgi complexes located near the nucleus in only a small subpopulation of hepatocytes, while all other hepatocytes contained albumin only in Golgi complexes located near the bile canaliculi. Stimulation of albumin synthesis by puromycin aminonucleoside-induced nephrosis resulted in an altered intracellular distribution of albumin at the light microscopic level. When examined at the ultrastructural level, albumin was localized in the rough endoplasmic reticulum as well as in Golgi complexes located near the nucleus in nearly all these hepatocytes. Hepatocytes with the potential to synthesize albumin were identified by in situ hybridization of albumin mRNA. In sections of 0.1 per cent (v/v) glutaraldehyde perfusion fixed normal rat liver, albumin mRNA was detected in the cytoplasm of only a few hepatocytes scattered throughout the lobule. Following stimulation of albumin synthesis by the induction of nephrosis, albumin mRNA was detected in the cytoplasm of the hepatocytes. The source of albumin in those hepatocytes which lacked albumin mRNA was identified in analbuminemic rats injected with rat albumin. At 6 h post injection, the light microscopic distribution of albumin in the liver of these animals was virtually indistinguishable from that in normal rat liver. At the ultrastructural level, injected albumin was localized in lysosomes and in Golgi complexes located near the bile canaliculi.

Routine overnight starvation and immunocytochemistry of hepatocyte albumin content

The indirect immunoperoxidase method was used to identify albumin in hepatocytes of rats before and after periods of starvation. All hepatocytes in fed rats contained a relatively large amount of nascent albumin. Overnight fasting reduced the number of hepatocytes with a large amount of albumin to primarily those surrounding terminal hepatic venules. These were estimated to be about 30% of the population. The other cells had only a slight amount of albumin. After 48 h of fasting all hepatocytes contained a low level of albumin.

Advances in ultrastructural postembedment localization of antigens in Epon sections with peroxidase labelled antibodies

Procedures for ultrastructural postembedment immunolocalization of antigens were investigated by use of the indirect peroxidase labelled antibody method. Results were compared with those obtained with the ultrastructural preembedment technique. IgG globulins in IgG synthesizing cells of rat lymph nodes served as model. Formaldehyde fixation, ethanol dehydration and embedment in Epon 812 did not abolish immunoreactivity. Sufficient numbers of antigens remained for subsequent postembedment immunohistology. Antigen binding sites were readily localized in ultrathin sections. For this purpose, polymerized resin had to be partially removed. Sodium methoxide in methanol/benzene mixture rapidly dissolved ultrathin sections. Diluted alcoholic sodium hydroxide enabled reliable resin etching and subsequent immunostaining. Treatment of ultrathin sections with hydrogen peroxide alone, did not permit immunolocalization of IgG. Optimal antigen detection was attained with antibodies isolated by affinity chromatography and purified peroxidase conjugates. IgG was stained in the rough-surfaced endoplasmic reticulum, the perinuclear space and the Golgi apparatus; the subcellular distribution corresponded to that obtained with preembedment immunohistology. In the latter technique, substrate accumulation was more homogenous than in postembedment staining.