Microsatellite DNA analysis of population structure in Atlantic herring (Clupea harengus), with direct comparison to allozyme and mtDNA RFLP analyses

Previous attempts to test for small-scale stock structuring within Atlantic herring (Clupea harengus L.) with molecular markers have been hampered by uninformative levels of genetic variation. Here we report the first application of microsatellite DNA markers to investigate population subdivision in Atlantic herring from Norwegian waters and the Barents Sea, and also examine microsatellite differentiation between C. harengus and Pacific herring (C. pallasi). Results from four microsatellite loci indicate high, and informative, variation compared to molecular markers used previously: number of alleles per locus=18-41; mean expected heterozygosity within samples=0.90-0.93. Significant genetic differences were detected between almost all samples representing postulated Icelandic summer-spawner, Norwegian spring-spawner and Norwegian fjord stocks, using Fisher's exact test, FST and RST values. Levels of allele frequency differentiation between Atlantic and Pacific herring overlapped the range seen among Atlantic herring samples, indicating that microsatellites are poor indicators of the degree of species differentiation. Comparison with allozyme and mitochondrial DNA restriction fragment length polymorphism (RFLP) datasets from the same samples suggests that microsatellites may detect structuring at a finer scale, but are less informative at larger scales of divergence.

Inhibition of isoniazid-induced hepatotoxicity in rabbits by pretreatment with an amidase inhibitor

Isoniazid (INH), a widely used drug in the prophylaxis and treatment of tuberculosis, is associated with a 1 to 2% risk of severe and potentially fatal hepatotoxicity. There is evidence that the INH metabolite hydrazine plays an important role in the mechanism of this toxicity. Metabolism of INH leads to the production of hydrazine via both direct and indirect pathways. In both cases, the activity of an INH amidase is required to hydrolyze an amide bond. In the present study, using a model of INH-induced hepatotoxicity in rabbits, pretreatment of rabbits with the amidase inhibitor bis-p-nitrophenyl phosphate 30 min before injection of INH inhibited the formation of INH-derived hydrazine and decreased measures of hepatocellular damage, hepatic triglyceride accumulation, and hypertriglyceridemia. Bis-p-nitrophenyl phosphate also potently inhibited the production of hydrazine from INH in in vitro microsomal incubations (IC50 2 microM). Although hepatic glutathione stores are decreased, they are not depleted in animals with INH-induced hepatotoxicity. Significant effects on hepatic microsomal cytochrome P-450 1A1/2 and cytochrome P-450 2E1 activities suggest that these isozymes may be involved in the mechanism of the toxicity. In conclusion, this study demonstrates the importance of amidase activity in this rabbit model of hepatotoxicity and provides additional evidence in support of the role of hydrazine in the mechanism of INH-induced hepatotoxicity.

Isolation of Complementary DNAs Coding for a Receptor for Activated C Kinase (RACK) from Zebrafish (Danio rerio) and Tilapia (Oreochromis niloticus): Constitutive Developmental and Tissue Expression

: We have cloned and sequenced complementary DNAs coding for a receptor for activated C kinase (RACK) from two species of teleost fishes, zebrafish (Danio rerio) and tilapia (Oreochromis niloticus). The tilapia clone is 1063 nucleotides long, and the zebrafish clone is 1069 nucleotides long. Both clones contain an open reading frame coding for the complete RACK protein of 317 amino acids. Northern hybridization analysis using these clones as probes detected a 1.2-kb band, indicating that these are nearly full-length cDNA clones. In tilapia, RACK messenger RNA was expressed in all tissues examined. In situ hybridization detected the presence of mRNA for this RACK sequence in unfertilized eggs and embryos (development up to 24 hours) from zebrafish.

Weaver cerebellar granule neurons show altered expression of NMDA receptor subunits both in vivo and in vitro

Biochemical, immunocytochemical, and molecular biological techniques were used to investigate the expression of N-methyl-D-aspartate (NMDA) receptor subunits in migration-deficient weaver mouse cerebellum in vivo and in primary cultures of the vermal weaver granule neurons with or without a rescue by verapamil. We found that both NMDAR1(zeta1) message and protein were expressed by the weaver granule neurons in situ. Immunocytochemical and biochemical analyses indicated that granule neurons of the weaver cerebellum expressed R1(zeta1) and R2A(epsilon1) subunits but showed little expression of the R2B(epsilon2) subunit. In weaver cerebellum, the R2B(epsilon2) subunit was primarily expressed in nerve fibers of the internal granule cell layer and white matter. Reverse-transcriptase-polymerase chain reaction followed by sequence analysis of the R1(zeta1) subunit indicated that the zeta1 subunit amplicons of both normal and weaver cerebella were identical, and that splice variants with exon 22 (1-2) and with or without exon 5 (a/b) or exon 21 (1-4) were detectable. The R2A(epsilon1), and R2B(epsilon2) subunits of the normal and weaver mouse cerebellum revealed no primary structural differences between the normal and weaver NMDA receptor subunits or the cloned mouse NMDA receptor subunits. In vermal cultures, normal granule neurons expressed all three NMDA receptor subunits (zeta1, epsilon1, and epsilon2), whereas the weaver neurons failed to express the epsilon2 subunit. Rescue of the weaver neurons by verapamil induced expression of the epsilon2 protein along the granule neuronal surfaces. The present results suggest that lack of the epsilon2 subunit in the weaver cerebellum may relate to the lack of functional NMDA receptors and/or to the migratory failure of the weaver granule neurons. Our data further suggest that NMDA receptor-mediated neurotoxicity is an unlikely mediator of neuronal death of the weaver granule neurons. In fact, down-regulation of the NMDA receptor expression and function may be a protective measure of the weaver granule neurons to reduce calcium entry via these receptors.

Evidence-based pharmacotherapy: review of basic concepts and applications in clinical practice

OBJECTIVE

To introduce concepts that may assist pharmacists in the use and application of scientific evidence in clinical practice. These concepts are followed by examples of clinical trials as well as case scenarios that guide the reader through solving clinical problems using the tools discussed in the article.

BACKGROUND

The introduction of evidence-based practice in the 1990s has had a positive impact on the practices of medicine and pharmacy. Part of this impact has been in the area of drug therapy. Although much literature has been published on the principles of evidence-based practice in the past few years, most of this material was intended for practicing physicians. We are not aware of any articles on the use of the evidence-based principles intended for clinical pharmacists. We are also aware that discussing all of these principles is an enormous task and thus beyond the scope of this article. Therefore, we focused this discussion on a brief summary of different study designs, factors affecting the strength of scientific evidence, and interpretation of the data. An approach in the use of these concepts is discussed through the use of case scenarios.

RECOMMENDATIONS

Clinical pharmacists must use concepts in evidence-based practice when making pharmacotherapeutic decisions.

Influences of educational interventions and adverse news about calcium-channel blockers on first-line prescribing of antihypertensive drugs to elderly people in British Columbia

BACKGROUND

The way in which dissemination of evidence changes medical practice needs to be better understood. Controversy about calcium-channel blockers (CCB) in the past 3 years has provided a natural experiment, enabling assessment of the impact of media stories, a national warning letter, a teleconference, small group workshops, and newsletters on first-line prescribing of antihypertensive drugs.

METHODS

We included all physicians (4403) in British Columbia who prescribed a thiazide diuretic, beta-blocker, inhibitor of angiotensin-converting enzyme (ACE), or CCB as the first antihypertensive agent for 36,507 residents aged 66 years and over, with no previous or concurrent sign of underlying cardiovascular disease. We used a database covering all prescriptions to elderly people to measure the change in proportion of newly treated patients who received each class of drug as first-line therapy. We used a matched cohort design for assessment of the teleconference and workshops, a randomised community design for the newsletters, and time-series analysis for the media impacts.

FINDINGS

The proportion of patients who received a CCB as first-line therapy declined gradually from 22% in early 1994 to 15% in late 1996. This proportion was not affected by two waves of adverse news about CCBs in 1995, but fell by 5% for 5 months and by 3% for 1 month after two waves in 1996. The proportion of patients who received either a CCB or an ACE inhibitor as first-line therapy, contrary to guidelines, was still 42% overall in 1996. The workshops and newsletters were followed by shifts from first-line CCB to first-line thiazide prescribing.

INTERPRETATION

Changes in prescribing practices occur gradually with the accumulation of small impacts from educational interventions and lay media attention.

The role of l-thyroxine and hepatic reductase activity in isoniazid-induced hepatotoxicity in rabbits

There is evidence that hydrazine, a metabolite of isoniazid, plays an important role in the mechanism of isoniazid-induced hepatotoxicity. Hydrazine has been reported to be metabolised by NADPH cytochrome P-450 reductase (reductase) to reactive and potentially toxic intermediates. The present study was designed, using a model of isoniazid-induced hepatotoxicity in rabbits, to determine whether or not reductase plays a role in this toxicity. Although pretreating rabbits with l-thyroxine increased hepatic reductase activity (54% greater than controls), the severity of isoniazid-induced hepatic cell damage (plasma argininosuccinic acid lyase activity) was lower in thyroxine pre-treated animals than in animals treated with isoniazid alone (31.3+/-20 vs 56.0+/-20 Takahara Units, respectively). In addition, pre-treatment with l-thyroxine completely prevented isoniazid-induced hepatic steatosis. In conclusion, contrary to our hypothesis, an increase in reductase activity achieved by pre-treatment with l-thyroxine was associated with a decrease in the severity of isoniazid-induced hepatic cell damage and steatosis in rabbits.

Laboratory investigation and comparison of Salmonella Brandenburg cases in New Zealand

An apparent increase in the incidence of S. Brandenburg in New Zealand, coupled with the possibility that the virulence of the organism may also be changing, prompted this study. Three typing methods: macro-restriction fragment length polymorphism (MRFLP) profiling using pulsed field gel electrophoresis (PFGE), plasmid profiling and antimicrobial susceptibility profiling were used to determine strain diversity amongst 115 recent and historical isolates of S. Brandenburg from both human cases and non-human sources. Antimicrobial resistance was noted only in three isolates. Plasmids of varying sizes were found in 31 isolates. MRFLP analysis resulted in 13 different patterns. Combining the three sets of typing data yielded 24 composite types. Comparison of composite type, isolation date and geographical location of case allowed the retrospective recognition of seven potential clusters during the 5-year study period. Composite types of 24 (80%) of the non-human isolates tested were indistinguishable from human isolates, suggesting that human infection may be via a number of vehicles. Although not cost-effective for routine use on all salmonella isolates, the methods used in this study are an important adjunct to serotyping for discrimination within an emerging serotype.

What is the plasma cofactor required by diuretics for direct vascular relaxant effect in vitro?

OBJECTIVE

To determine the plasma cofactor which is required by diuretics (hydrochlorothiazide, chlorthalidone, indapamide, and furosemide) for direct vasorelaxant effects in vitro.

DESIGN

A randomized, double-blind, vehicle-control design was used to avoid experimenter bias.

METHODS

We plotted concentration-response curves for responses to hydrochlorothiazide, chlorthalidone, indapamide, and furosemide of male Wistar rat aortic rings in the presence of different bath solutions containing various plasma factors.

RESULTS

Plasma was found both to make possible and facilitate the vasodilator action of the diuretics tested by an action on the membrane and to decrease the action by binding the diuretics. The diuretics retained their vasorelaxant properties in Krebs solution alone, 30 min after having been incubated in a 50:50 solution of Krebs solution and plasma for 1 h. All four diuretics exerted significant vasorelaxant actions in Krebs solution-plasma, Krebs solution-serum, and Krebs solution plus human or bovine albumin (40 g/l) media. No vasorelaxant action was found in Krebs solution alone, Krebs solution plus denatured plasma, Krebs solution plus egg albumin, and Krebs solution plus insulin.

CONCLUSION

Albumin is the main cofactor required by the diuretics tested for direct relaxant action in vitro, and these findings may explain some of the contradictory evidence concerning this action in the literature.

Birth weight and neonatal survival of harbour seal pups are positively correlated with genetic variation measured by microsatellites

We examined the relations between fitness-related traits of wild harbour seal (Phoca vitulina) pups with microsatellite heterozygosity, and with a measure of genomic diversity based on the mean squared distance between microsatellite alleles within an individual, mean d2. Birth weight was positively influenced by maternal age, pup sex, and either mean d2 or individual heterozygosity in separate multiple regression models. The association of birth weight with mean d2 was stronger than that with heterozygosity, however. The factors maternal age, pup sex, and mean d2 combined to account for 36.8% of the variation in birth weight, with mean d2 accounting for the greatest explanatory power (52.3% of the variance explained). Pups which survived until weaning had significantly higher mean d2 than pups which died, independent of birth weight. These effects are consistent with heterosis resulting from recent population mixing, and/or inbreeding depression in this population. Mean d2 thus provides (i) a better measure of individual genetic variability than heterozygosity for microsatellite data; and (ii) a convenient tool for assessing the effects of inbreeding and outbreeding in natural populations.

Male mating success in an aquatically mating pinniped, the harbour seal (Phoca vitulina), assessed by microsatellite DNA markers

Similar to many other pinniped species, harbour seals (Phoca vitulina) mate exclusively at sea. Here we present the first attempt to measure male mating success in an aquatically mating pinniped. Male mating success was estimated by paternity analysis in two cohorts of pups born at Sable Island, Nova Scotia, Canada, using microsatellite DNA markers. The genotypes of 275 pups born in 1994 and 1995 were compared to those of 90 candidate males at six microsatellite loci using a likelihood approach to resolve paternity. Paternity could be assigned for two, 22, 40 and 85 pups at confidence levels of 95, 80, 65 and 50%, respectively. Most successful males were assigned the paternity of a single offspring, suggesting a low variance in male mating success relative to most pinniped species. The proportion of paternal half sibs within cohorts and between maternally related sibs estimated by maximum likelihood were not significantly different from zero. It is thus unlikely that most offspring were sired by a small number of highly successful unsampled males, and that female harbour seals do not usually exhibit fidelity to the same male in sequential breeding seasons. A low level of polygyny in Sable Island harbour seals is consistent with predictions based on their breeding ecology, as females are highly mobile and widely dispersed in the aquatic mating environment at Sable Island.

Ulnar collateral ligament tear with concomitant extensor pollicis brevis and extensor pollicis longus disruptions: a case report

A patient with a tear of the thumb ulnar collateral ligament and simultaneous extensor pollicis brevis and extensor pollicis longus disruptions is reported. No report of a similar constellation of injuries was found in the literature.

Molecular cytogenetic analysis of heterochromatin in the chromosomes of tilapia, Oreochromis niloticus (Teleostei: Cichlidae)

The structure of the heterochromatic bands in mitotic chromosomes of the important tropical aquaculture species of tilapia, Oreochromis niloticus, was investigated by the combination of the C-banding technique, chromosomal digestion with two restriction endonucleases and fluorescence in situ hybridization (FISH) of two satellite DNAs (SATA and SATB). The tilapia chromosomes presented heterochromatic bands in the centromeres and in the short arms of almost all chromosomes that were differentially digested by the restriction endonucleases HaeIII and EcoRI. FISH of SATA showed that this satellite sequence is distributed in the centromeric region of all chromosomes of tilapia. FISH also revealed an intense hybridization signal for SATB in only one chromosome pair, but less intense signals were also present in several other pairs. The digestion of tilapia chromosomes by HaeIII and EcoRI was positively correlated with the position of SATA and SATB in chromosomes as revealed by FISH. The results obtained may be useful in future molecular and genetic studies of tilapias.

ROn-1 SINEs: a tRNA-derived, short interspersed repetitive DNA element from Oreochromis niloticus and its species-specific distribution in Old World cichlid fishes

A SINE-like repetitive element (ROn-1) has been cloned from the tilapiine cichlid fish Oreochromis niloticus. The element is 345 base pairs (bp) in length and consists of a transfer-RNA-like domain with putative RNA polymerase III recognition sequences, a tRNA-unrelated region, and a poly(A) tail. Approximately 6000 copies of ROn-1 occur in the haploid genome of O. niloticus. Southern blot analysis revealed that ROn-1 is an abundant element in the genomes of many African cichlid fishes, but absent from the genome of the Indian cichlid Etroplus.

Distinct functional stoichiometry of potassium channel beta subunits

Shaker-type potassium channels play important roles in determining the electrical excitability of cells. The native channel complex is thought to be formed by four pore-forming alpha subunits that provide four interaction sites for auxiliary modulatory Kvbeta subunits. Because Kvbeta subunits possess diverse modulatory activities including either up-regulation or down-regulation of potassium currents, differential assembly of the alpha-beta complex could give rise to diverse current properties. However, the detailed physical and functional stoichiometry of the alpha-beta complex remains unknown. Kvbeta1 subunits reduce potassium currents through inactivation, whereas Kvbeta2 subunits enhance potassium currents by inhibiting the Kvbeta1-mediated inactivation and at the same time by promoting the surface expression of certain potassium channels. In this report we show that Kvbeta1 and Kvbeta2 of the Shaker-type potassium channels display distinct functional stoichiometry to interact with the Kv1 alpha subunits, a subfamily of Shaker-type potassium channels. The interaction of Kvbeta1 subunits with alpha subunits is consistent with the alpha4betan model, where n equals 0, 1, 2, 3, or 4, depending upon the relative concentration of alpha and beta subunits. The alpha4betan stoichiometry allows for gradual changes of the Kvbeta1-mediated inactivation. In contrast, Kvbeta2 subunits self-associate to form oligomers and interact with the alpha subunits via alpha4beta4 stoichiometry, which permits effective multivalent associations with alpha subunits. Such distinct functional stoichiometry of Kvbeta1 and Kvbeta2 provides a molecular mechanism that is well suited to their contrasting activities of up-regulation or down-regulation of potassium currents.

A new genetic defect in human CYP2C19: mutation of the initiation codon is responsible for poor metabolism of S-mephenytoin

The 4'-hydroxylation of the S-enantiomer of the anticonvulsant drug mephenytoin exhibits a genetic polymorphism in humans. This polymorphism shows marked interracial heterogeneity, with the poor metabolizer (PM) phenotype representing 2 to 5% of Caucasian and 13 to 23% of Asian populations. Two defective CYP2C19 alleles, CYP2C19*2 and CYP2C19*3, have been described which account for approximately 87% of Caucasian and > 99% of Oriental PM alleles. The present study identifies a new allele (CYP2C19*4) in Caucasian PMs which contains an A-->G mutation in the initiation codon. A new polymerase chain reaction-restriction fragment length polymorphism genotyping test was developed, and the incidence of this allele was examined in a European Caucasian population which had been phenotyped for mephenytoin metabolism. One of nine putative PMs was heterozygous for CYP2C19*2/CYP2C19*4, which suggests that CYP2C19*4 represents a defective allele. Six of the seven remaining putative PMs available for genotyping were explained by CYP2C19*2. The frequency of the CYP2C19*4 allele in Caucasians was 0.6%. An additional Caucasian PM from a separate study was also heterozygous for CYP2C19*2 and CYP2C19*4. To verify that CYP2C19*4 represented a defective CYP2C19 allele, the initiation codon of the normal CYP2C19*1 cDNA was mutated to a GTG, and both cDNAs were expressed in yeast. Recombinant CYP2C19 protein was detected by Western blot analysis of colonies transformed with CYP2C19*1 cDNA, but not in those transformed with CYP2C19*4 cDNA. The two cDNAs were also used in an in vitro coupled transcription/translation assay. CYP2C19 protein was translated only from the CYP2C19*1 allele. These data indicate that CYP2C19*4 represents a new PM allele.