Cellular localization of intrinsic factor in pancreas and stomach of the dog

Summary A cobalamin (vitamin B₁₂)-binding protein has recently been identified in canine pancreatic juice which is biochemically, immunochemically and functionally similar to canine gastric intrinsic factor. However, the cellular sources of both this pancreatic intrinsic factor and gastric intrinsic factor in the dog are not known. Antisera raised against canine gastric intrinsic factor have been used to examine the distribution of intrinsic factors in the canine pancreas and stomach. Immunoreactivity was demonstrated in duct cells but not acinar or endocrine cells in the pancreas, and in fundic peptic and pyloric gastric pit cells in stomach. All immunostaining was abolished by preabsorption of the antisera with purified canine gastric and pancreatic intrinsic factors. A cellular source of pancreatic intrinsic factor has not been previously described, and the demonstration of intrinsic factor-like immunoreactivity in two cell types in the canine stomach contrasts with its localization in a single cell type in the gastric mucosa of other mammalian species. Furthermore, immunoreactivity in pancreatic duct cells was detected at much higher dilutions of antisera than those required for staining of peptic and gastric pit cells. This suggests a higher concentration of antigen, and supports previous evidence that the pancreas is a major source of intrinsic factor in the dog.     

Influence of restricted food intake on brown adipose tissue function in genetically obese mice (genotype, ob/ob)

Measurements were made of cytochrome c oxidase activity and the GDP-binding capacity of mitochondria in brown adipose tissue of genetically obese mice and wild-type siblings, to estimate the thermogenic capacity of the tissue. The binding capacity was decreased in ad libitum fed obese animals compared with wild-type animals. Limited feeding of obese animals to restrict their body weight caused a large increase in the binding capacity of the tissue, which was greater than that in wild-type animals fed either ad limitum or on a limited diet. The decreased binding capacity of brown adipose tissue mitochondria in obese mice appears to be a consequence of ad libitum feeding and therefore not a cause of the obesity. Limit feeding of obese animals also corrected their characteristic hypothermia at low ambient temperature. The large increase in the thermogenic capacity of brown adipose tissue in obese animals, induced by limited feeding, may account for the vital improvement of their thermoregulation. However, close similarities were found between obesity hypothermia and hypothermia induced in wild-type animals by restraint. It is suggested that changes in posture caused by obesity, resulting in increased loss of body heat, may be important in the development of obesity hypothermia. Obese animals fed less than wild-type grained more weight than wild-type animals, indicating that the high thermogenic capacity of their brown adipose tissue did not function to regulate their calorie intake.     

Genetic engineering of coryneform bacteria

The coryneforms are a diverse group of bacteria which includes animal and plant pathogens as well as non-pathogenic bacteria. Although they are of significant economic and health importance, their genetics is poorly understood. The development of genetic engineering techniques for coryneforms and initial gene cloning studies are discussed.     

The effects of mispair and nonpair correction in hybrid DNA on base ratios (G + C content) and total amounts of DNA

Base ratios and total DNA amounts can vary substantially between and within higher taxa and genera, and even within species. Gene conversion is one of several mechanisms that could cause such changes. For base substitutions, disparity in conversion direction is accompanied by an equivalent disparity in base ratio at the heterozygous site. Disparity in the direction of gene conversion at meiosis is common and can be extreme. For transitions (which give purine [R]/pyrimidine [Y] mispairs) and for transversions giving unlike R/R and Y/Y mispairs in hybrid DNA, this disparity could give slow but systematic changes in G + C percentage. For transversions giving like R/R and Y/Y mispairs, it could change AT/TA and CG/GC ratios. From the extent of correction direction disparity, one can deduce properties of repair enzymes, such as the ability (1) to excise preferentially the purine from one mispair and the pyrimidine from the other for two different R/Y mispairs from a single heterozygous site and (2) to excise one base preferentially from unlike R/R or Y/Y mispairs. Frame-shifts usually show strong disparity in conversion direction, with preferential cutting of the nonlooped or the looped-out strand of the nonpair in heterozygous h-DNA. The opposite directions of disparity for frame-shifts and their intragenic suppressors as Ascobolus suggest that repair enzymes have a strong, systematic bias as to which strand is cut. The conversion spectra of mutations induced with different mutagens suggest that the nonlooped strand is preferentially cut, so that base additions generally convert to mutant and deletions generally convert to wild-type forms. Especially in nonfunctional or noncoding DNA, this could cause a general increase in DNA amounts. Conversion disparity, selection, mutation, and other processes interact, affecting rates of change in base ratios and total DNA.      

Heterogeneity of hepatic microsomal UDP-glucuronosyltransferase(s) activities: comparison between human and mammalian species activities

The first comparative profiles of UDP-glucuronosyltransferase(s) (UDPGT) activities obtained under standard conditions in vitro in mammals (man, rat [Wistar and Gunn], mouse, monkey [Papio papio and Cynomolgus], pig, guinea pig, rabbit, dog) are presented for 16 aglycones. A decreasing scale of these activities was obtained from planar to bulky molecules. The scale was identical for each of the mammals studied, including man. Statistical analysis of the results revealed a division of the aglycones into three groups, one being correlated with the molecular form called GT1 the two others with the GT2 form. The profile of activities in the Gunn rat revealed very weak activity towards planar molecules (GT1). These results provide evidence that under standard conditions, human UDPGT activities are comparable to those from other animals.     

Study of the in vitro bioactivation of albendazole in human liver microsomes and hepatoma cell lines

The metabolism of albendazole (ABZ), a benzimidazole anthelminthic, was studied in either microsomal preparations of human liver biopsies or cultured human hepatoma cell lines. Metabolites were analyzed by HPLC. Our data show that microsomes from human biopsies and two human cell lines, HepG2 and Hep3B, oxidize the drug to the sulfoxide very efficiently, whereas the third cell line tested, SK-HEP-1, does not. Both cytochrome P-450 dependent monooxygenases and favin-containing monooxygenases appear to be involved in human ABZ metabolism. Using the cell line displaying the highest ABZ-metabolizing activity, HepG2, the cytotoxic and the inducing effects of the parent drug ABZ and of two primary metabolites, the sulfoxide and the sulfone were studied. These three chemicals provoked a rise in mitotic index resulting from cell division blockage at the prophase or at the metaphase (ABZ metabolites) stage, and ABZ was more cytotoxic than its metabolites. With regard to enzyme-inducing effects, our data clearly demonstrate that the sulfoxide and, to a lesser degree, the sulfone are potent inducers of some drug metabolizing enzymes (i.e., cytochrome P-488 dependent monooxygenases and UDP glucuronyltransferase), whereas ABZ fails to increase and even slightly decreases these enzymatic activities. In conclusion, the HepG2 human hepatoma cell line appears to be suitable for the study of many parameters of metabolism and action of ABZ and other structurally related compounds in humans.Abbreviations ABZ albendazole - B[a]P benzo[a]pyrene - HPLC high-performance liquid chromatography - MC 3-methylcholanthrene - MFO mixed-function oxidase - UDPGT UDP-glucuronyltransferase     

Inclined sedimentation for selective retention of viable hybridomas in a continuous suspension bioreactor.

The continuous separation of nonviable hybridoma cells from viable hybridoma cells by using a narrow rectangular channel that is inclined from the vertical has been investigated experimentally. The effectiveness of the settler in selectively retaining viable hybridomas in the bioreactor while permitting the removal of nonviable hybridomas has been shown to depend on the flow rate through the settler. Intermediate flow rates through the settler have been found to provide the highest removal of nonviable hybridomas relative to viable hybridoma retention. At high dilution rates through the chemostat, over 95% of the viable cells could be partitioned to the bottom of the settler while over 50% of the nonviable cells are removed through the top of the settler. This successful separation is due to the significantly larger size of the viable hybridomas than the nonviable ones. A continuous perfusion experiment was performed in which an external inclined settler was used to retain virtually all of the viable hybridomas in the culture, while selectively removing from the culture approximately 20% of the nonviable cells that entered the settler. A stable viable cell concentration of 1.0 x 10(7) cells/mL was achieved, as was an antibody productivity of over 50 micrograms/(mL.day). These represent 3- and 6-fold increases, respectively, over the values obtained from a chemostat culture without cell retention.