Genetic polymorphism of a bovine t-complex gene (TCP1) linkage to major histocompatibility genes

Southern blot analysis of genomic cattle DNA was carried out using murine cDNA probes representing the Tcp-1 gene of the t complex. Excellent cross-hybridization was obtained, and the probes apparently hybridized to at least two bovine TCP1 genes. Two independent restriction fragment length polymorphisms, each composed of two allelic variants, were detected; the inheritance of the restriction fragment length polymorphisms was confirmed by family data. One of the restriction fragment length polymorphisms, designated TCP1B, was evidently due to a gene duplication and was revealed with any restriction enzyme used. The duplication was found in three different cattle breeds investigated. Family segregation data indicated that TCP1B is linked to major histocompatibility complex genes. The result was consistent with close linkage to the major histocompatibility complex class II DO beta gene, whereas a fairly high recombination frequency was indicated between TCP1B/DO beta and other major histocompatibility complex genes. The result assigns TCP1B to a bovine linkage group previously comprising major histocompatibility complex class I and class II genes and blood group locus M. The similarity between this linkage group and parts of mouse chromosome 17 (t-H-2) and human chromosome 6 (TCP1-HLA) is discussed.     

Inhibitory effect of 11-ketoandrostenedione and androstenedione on spermatogenesis in the three-spined stickleback, Gasterosteus aculeatus L.

Stickleback males were implanted with Silastic capsules filled with 11-ketoandrostenedione or androstenedione at the end of the breeding season. 11-Ketoandrostenedione prevented the natural decline in secondary sexual characters and testes weight. It also completely inhibited the commencement of spermatogenesis, which normally takes place in late summer after having been quiescent during the breeding season. Androstenedione also exerted these effects, but to a lesser degree.     

Enterochromaffin-like cells in the rat stomach: effect of α-fluoromethylhistidine-evoked histamine depletion

Summary In the rat, gastric histamine is stored predominantly in the enterochromaffin-like (ECL) cells, which are located basally in the oxyntic mucosa. The functional significance of histamine in the ECL cells is a matter of speculation. In this study the effect of depletion of histamine on the properties and ultrastructure of the ECL cells was examined. Histamine synthesis was inhibited with -fluoromethylhistidine (3 mg·kg^-1·h^-1) given via osmotic minipumps over a period of 24 h. The treatment reduced the histidine decarboxylase activity (approximately 20% remaining) and histamine concentration (less than 20% remaining) in the oxyntic mucosa, as well as the intensity of histamine- and chromogranin A-immunostaining in the ECL cells, compared to control rats. The cytoplasmic (secretory) granules/vesicles were greatly reduced in number and size following -fluoromethylhistidine administration. The histamine immunostaining of the mast cells, which occurs at the mucosal surface and in the submucosa, appeared unaffected. We conclude that ECL cell histamine accounts for at least 80% of the total oxyntic mucosal histamine in the rat and that it represents a more mobile pool than mast cell histamine. The reduction in the number and size of the ECL cell granules/vesicles following histamine depletion is in accord with the idea that they represent the storage site for histamine.     

Mutation analysis and prenatal diagnosis in a Lesch-Nyhan family showing non-random X-inactivation interfering with carrier detection tests

Summary A nonsense mutation at the CpG-site in the codon for Arg(169) in the gene for hypoxanthine phosphoribosyltransferase (hprt) was identified by genomic polymerase chain reaction (PCR) and DNA sequencing in cultured fibroblasts from two brothers with Lesch Nyhan's syndrome. The recurrence of mutation at this CpG-site in several unrelated Lesch-Nyhan families suggests that deamination of 5-methylcytosine is a possible mechanism for mutagenesis. The level of hprt-mRNA in the fibroblasts of the patients was similar to that in healthy controls, whereas hprt-enzyme activity was not detectable. The mutation in this family was also identified in five female relatives and prenatally in a male fetus. Unexpectedly, results from hair follicle analyses and fibroblast selection studies in 8-azaguanine and 6-thioguanine medium showed a non-carrier phenotype in three of the female heterozygotes, whereas X-inactivation mosaicism was demonstrated in one heterozygote. A possible explanation for the apparent non-random X-inactivation in this family is the co-existence of the hprt mutation with an undefined X-linked lethal mutation. This observation is of practical relevance for carrier detection in other Lesch-Nyhan families.     

The gene for dominant white color in the pig is closely linked to ALB and PDGRFRA on chromosome 8.

White is a widespread coat color among domestic pig breeds and is controlled by an autosomal dominant gene I. The segregation of this gene was analyzed in a reference pedigree for gene mapping developed by crossing the European wild pig and a Large White domestic breed. The gene for dominant white color was shown to be closely linked to the genes for albumin (ALB) and platelet-derived growth factor receptor alpha (PDGFRA) on chromosome 8. An unexpected phenotype with patches of colored and white coat was observed among the F1 and F2 animals. The segregation data indicated that the phenotype was controlled by a third allele, denoted patch (Ip), most likely transmitted by one of the Large White founder animals. It is shown that the ALB, PDGFRA, I linkage group shares homologies with parts of mouse chromosome 5, human chromosome 4, and horse linkage group II, all of which contain dominant genes for white or white spotting. Candidate genes for the dominant white and patch mutations in the pig are proposed on the basis on these linkage homologies and the recent molecular definition of the dominant white spotting (W) and patch (Ph) mutations in the mouse.     

Evolution ofMHC polymorphism: Extensive sharing of polymorphic sequence motifs between human and bovine DRB alleles

The evolution ofMHC polymorphism has been studied by comparing the amino acid and nucleotide sequences of 14 bovine and 32 humanDRB alleles. The comparison revealed an extensive sharing of polymorphic sequence motifs in the two species. Almost identical sets of residues were found at several highly polymorphic amino acid positions in the putative antigen recognition site. Consequently, certain bovine alleles were found to be more similar to certain human alleles than to other bovine alleles. In contrast, the frequencies of silent nucleotide substitutions were found to be much higher in comparisons between species than within species implying that none of the human or bovine DRB alleles originated before the divergence of these distantly related species. The results suggest that the observed similarity inDRB polymorphism is due to convergent evolution and possibly the sharing of short ancestral sequence motifs. However, the relative role of the latter mechanism is difficult to assess due to the biased base composition in the first domain exon of polymorphic class 11 genes. The frequency of silent substitutions betweenDRB alleles was markedly lower in cattle than in man suggesting that theDRB diversity has evolved more rapidly in the former species.     

A simple method for the preparation of paraffin-embedded cell blocks from fine needle aspirates, effusions and brushings

A simple method for the preparation of paraffin-embedded cell blocks from cytologic specimens obtained by fine needle aspiration, by brushing or from effusions is described. The cells are fixed in suspension in 50% ethanol for one hour and pelleted by centrifugation in a 50-mL plastic tube. The fixative is removed, and the pellet is suspended in 3 mL of acetone for dehydration for ten minutes and thereafter repelleted. The acetone is then removed, and the cell pellet is dried at 60 degrees C for one hour. Melted paraffin is added onto the dry warmed cell mass and allowed to solidify at room temperature. A conical paraffin block with the cells in the top is obtained and can be handled as a routine tissue block.     

The influence of animals on phosphorus cycling in lake ecosystems

Aquatic animals directly influence the cycling of phosphorus in lakes through feeding and excretion. Traditionally, animals (zooplankton, benthic invertebrates and fish) have been assigned only minor roles in the process of freshwater phosphorus cycling. They were regarded as consumers without much regulating influence. Today there is growing evidence that animals, predators and herbivores, directly or indirectly can control biomass of primary producers and internal cycling of phosphorus.This paper summarizes different mechanisms of transformation and translocation of phosphorus via different groups of organisms.     

Regulation of receptor-mediated calcium influx across the plasma membrane in a human leukemic T-cell line: evidence of its dependence on an initial calcium mobilization from intracellular stores

It has been repeatedly shown that stimulation of a human leukemic T-cell line, JURKAT, by lectins such as phytohaemagglutinin and anti-T3 antibody (OKT3) leads to an elevation in the concentration of cytosolic free Ca2. This Ca2+ transient results from both an intracellular mobilization and an influx of Ca2+ through specific membrane channels. The objective of this study was to investigate the mechanism by which receptor-mediated influx of Ca2+ is regulated in JURKAT cells, which demonstrably lack 'voltage-dependent calcium channels'. It was found that upon increased loading with quin2 or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate (BAPTA) there was a pronounced decline of both phytohaemagglutinin-stimulated and OKT3-stimulated influx of 45Ca2+. Using 15 microM quin2/AM or 30 microM BAPTA/AM, agonist-stimulated 45Ca2+ influx was almost totally abolished. At these concentrations of both quin2/AM or BAPTA/AM, phytohaemagglutinin and OKT3 could still induce a rise of cytosolic free Ca2+ above 200 nM. In the presence of La3+ (200 microM), which completely inhibited the agonist-induced 45Ca2+ influx, both phytohaemagglutinin and OKT3 were able to raise the concentrations of cytosolic free Ca2+ to well above 200 nM by merely mobilizing Ca2+ from intracellular stores alone. The data suggest that an agonist-induced increase in the concentration of cytosolic free Ca2+, due to mobilization from intracellular stores, could either directly or indirectly, initiate receptor-mediated Ca2+ influx across the plasma membrane in JURKAT cells.