Immunohistochemical investigations on the differentiation marker protein E11 in rat calvaria, calvaria cell culture and the osteoblastic cell line ROS 17/2.8

 Until now, many extracellular matrix proteins, e.g. osteopontin and osteonectin, have been used to determine a cell’s osteogenic maturation. The disadvantage in evaluation of these proteins is their relative wide-ranging appearance throughout the osteogenic differentiation process. Thus, the aim of this study was to establish an immunohistochemical setup using E11, a marker that binds selectively to cells of the late osteogenic cell lineage. In addition, the histochemical expression of the bone matrix proteins osteonectin, osteopontin and fibronectin was compared to that of E11 using monoclonal antibodies. For light microscopical detection of osteogenic markers in cultured cells we developed a simple paraffin technique using a fibrin glue as embedding medium. This allows the handling of cultured cells such as a tissue sample and includes the use of stored biological specimens for further immunohistochemical experiments. We used newborn rat calvariae for whole tissue preparations and for isolation and cultivation of bone cells. In addition, we included the rat osteosarcoma cell line ROS 17/2.8 in this study. For the first time, we have localised E11 in osteocytes of rat calvaria preparations at the electron microscopical level. E11 was detected at plasma membranes of osteocytes and their processes, but not at those of osteoblasts. Accompanying experiments with cultured newborn rat calvaria cells and ROS 17/2.8 cells revealed E11 reactivity on a subset of cells. The results obtained confirm the suitability of the differentiation marker E11 as a sensitive instrument for the characterisation of bone cell culture systems. Accepted: 25 August 1998     

First records of <Emphasis Type="Italic">Trichodectes canis</Emphasis> (Insecta: Phthiraptera: Trichodectidae) from Darwin’s fox, <Emphasis Type="Italic">Pseudalopex fulvipes</Emphasis> (Mammalia: Carnivora: Canidae)

The presence of the dog biting louse, Trichodectes canis (De Geer, 1778; Ischnocera: Trichodectidae), is reported for the first time in the critically endangered Pseudalopex fulvipes (Martin, 1837) in Chiloé Island, south Chile.     

Apo B metabolism in the cynomolgus monkey: evidence for post-transcriptional regulation.

Previous studies have shown that hepatic apo B mRNA levels do not increase in animals fed high cholesterol diets, even though plasma apo B concentrations increase markedly. As a result, it has been suggested that the diet-induced increase in plasma apo B levels was due solely to an inhibited clearance of those lipoproteins. The present study was undertaken to test that hypothesis. Hepatic apo B mRNA levels were measured in liver biopsies taken from five male cynomolgus monkeys before and twice after, they began to consume a high cholesterol diet. The diet had no effect on hepatic apo B mRNA levels, even though it caused a 7-fold increase in the plasma apo B levels. However, measurements of the apo B secretion rate in eight separate monkeys (four chow-fed and four cholesterol-fed) by isotope dilution showed that apo B secretion by the liver was increased 4-fold in the cholesterol-fed monkeys. These data, taken together, indicate that apo B secretion is not regulated by the rate at which the apo B gene is transcribed, but at some point further along in the secretion pathway.