Movements of sodium and potassium into ejaculated boar spermatozoa suspended in seminal plasma and a biological salt solution

Uptake of 22Na and 42K into ejaculated boar spermatozoa was measured in vitro. Cells were suspended either in seminal plasma or in a biological salt solution of essentially the same composition as boar seminal plasma. Samples were incubated at 30 degrees C. Correction was made for extracellular space in the centrifuged sperm pellet. This was determined as 22Na-space, which was less (P less than 0.001) than [14C] carboxyinulin space. Large differences were observed among individual ejaculates. The half-time for potassium uptake into the spermatozoa averaged 11.5 min, which is much faster than that for leukocytes or erythrocytes. When the spermatozoa were suspended in the biological salt solution, the initial rate of 42K uptake was significantly decreased. This may be due to disturbances of the protein components of the sperm membrane. The uptake of 22Na into the spermatozoa was slow. Sodium and potassium transport appeared not to be coupled in the 3/2 ratio which has been reported for erythrocyte membranes. The average concentration of sodium was 108 mM in seminal plasma and 26 mM in the spermatozoa (112 mmol/kg water and 38 mmol/kg water, respectively). The corresponding figures for potassium were 26 mM and 51 mM (27 mmol/kg water and 74 mmol/kg water). The random error for a single determination for the various methods used varied between 2.4 and 13.3% of the mean.     

Properties of refractory materials for primary aluminum production electrolyzers

Results are provided for a study of changes in the properties of barrier materials during laboratory and industrial tests. Some autopsy results are presented for electrolyzers with a different service life. Directions are indicated for improving barrier layer properties in electrolyzers due to the use of new technology and equipment intended for vibration compaction of materials directly in electrolyzer socles. __________ Translated from Novye Ogneupory, No. 3, pp. 96–102, March 2008.     

Trans-splicing ribozymes for targeted gene delivery

Ribozymes are potential tools for genetic manipulation, and various naturally occurring catalytic RNAs have been dissected and used as the basis for the design of new endoribonuclease activities. While such cleaving ribozymes may work well in vitro, they have not proved to be routinely effective in depleting living cells of the chosen target RNA. Recently, trans-splicing ribozymes have been employed to repair mutant mRNAs in vivo. We have designed modified trans-splicing ribozymes with improved biological activity. These allow accurate splicing of a new 3' exon sequence into a chosen site within a target RNA, and in frame fusion of the exon can result in expression of a new gene product. These trans-splicing ribozymes contain catalytic sequences derived from a self-splicing group I intron, which have been adapted to a chosen target mRNA by fusion of a region of extended complementarity to the target RNA and precise alteration of the guide sequences required for substrate recognition. Both modifications are required for improved biological activity of the ribozymes. Whereas cleaving ribozymes must efficiently deplete a chosen mRNA species to be effective in vivo, even inefficient trans-splicing can allow the useful expression of a new gene activity, dependent on the presence of a chosen RNA. We have targeted trans-splicing ribozymes against mRNAs of chloramphenicol acetyltransferase, human immunodeficiency virus, and cucumber mosaic virus, and demonstrated trans-splicing and delivery of a marker gene in Escherichia coli cells. The improved trans-splicing ribozymes may be tailored for virtually any target RNA, and provide a new tool for triggering gene expression in specific cell types.     

A cross-sectional study into the prevalence of root caries in periodontal maintenance patients

BACKGROUND: Epidermal growth factor (EGF) has been shown to increase intestinal absorptive surface area and transport function in normal animals. AIMS: To examine the effect of EGF on absorptive surface area and brush border membrane function in a model of massive small bowel resection. METHODS: New Zealand white rabbits were randomised into two groups: a resected group (60% proximal small bowel resection); and an unmanipulated control group. Distal remnant tissue was examined 10 and 21 days postsurgery. In separate experiments oral EGF (40 g/kg/day) was administered to resected animals from days 3 to 8 and animals were studied on day 10. RESULTS: Ten days postsurgery brush border surface area and total absorptive surface area were significantly increased in remnant tissue while brush border membrane vesicle (BBMV) glucose uptake was significantly decreased compared with controls. By 21 days brush border surface area returned to control levels though BBMV glucose uptake remained depressed. EGF treatment induced a further increase in brush border surface area in remnant intestine but did not alter BBMV glucose uptake. CONCLUSIONS: Surgical resection results in significant elevations in absorptive surface area coupled with a decrease in brush border membrane transport function distal to the site of anastomosis. EGF enhances glucose uptake in remnant intestine via recruitment of additional microvillus membrane into the brush border.