Endothelial cell junctions

In the course of a freeze-cleave study on intercellular junctions in the regenerating rat liver, we observed an unusual array of intramembranous particles located in regions of contact between endothelial cells lining the hepatic sinusoids. These arrays were characterized by an accumulation of particles which resembled a zonula occludens in their linear deployment but differed in that the contact regions were composed of individual particles which remained separated from each other by regular particle-free intervals.     

Transport of L-alanine in cultured human fibroblasts: Evidence for two kinetically distinguishable systems

The transport of L-alanine in human diploid fibroblasts was investigated. Transport measurements were performed on subcultures between the third and eighth passages with subconfluent cells growing on glass coverslips. Kinetic analysis of approximate initial rates of transport at substrate concentrations from 0.05 to 10 mmole/liter indicate the presence of two distinguishable systems. The high affinity system has a K_m of 0.24 mmole/liter and a V_max of 6.4 nmole/100 μg protein/2 min. For the low affinity system, the contribution of the high affinity system to the uptake must absolutely be taken into account. The K_m and V_max values, obtained by using a computer program, are a K_m of 15.0 mmole/liter and a V_max of 14.7 nmole/100 μg protein/2 min. For alanine concentrations below 1 mmole/liter, the contribution of the Na⁺-independent uptake is less than 10%, and the kinetic constants of the high affinity system are in the same range if this contribution is taken into account. On the contrary the influence of a diffusion-like process is more significant on the low affinity system whose K_m is about 49 mmole/liter after subtraction of the Na⁺-independent uptake from the experimental velocities. Inhibition studies were performed with NCH₃-alanine. They permitted us first to confirm the existence of system A in cultured human fibroblasts in agreement with two recent works and second to show how this system contributes to L-alanine uptake. This contribution seems very small in low concentrations but it rises as the concentrations increase.     

Consequences of concurrent Ascaridia galli and Escherichia coli infections in chickens

   

Three experiments were carried out to examine the consequences of concurrent infections with Ascaridia galli and Escherichia coli in chickens raised for table egg production. Characteristic pathological lesions including airsacculitis, peritonitis and/or polyserositis were seen in all groups infected with E. coli. Furthermore, a trend for increased mortality rates was observed in groups infected with both organisms which, however, could not be confirmed statistically. The mean worm burden was significantly lower in combined infection groups compared to groups infected only with A. galli. It was also shown that combined infections of E. coli and A. galli had an added significant negative impact on weight gain.