Hybrid zone dynamics and species replacement between Orconectes crayfishes in a northern Wisconsin lake

Hybrid zones that result in the genetic assimilation (replacement) of one species by another are underrepresented in the animal literature, most likely due to their transient nature. One such zone involves the rusty crayfish, Orconectes rusticus, and its congener O. propinquus. Orconectes rusticus was recently introduced into northern Wisconsin and Michigan lakes and streams, where it is hybridizing with and displacing resident O. propinquus. Here we report on a study investigating the dynamics of a hybrid zone between the two crayfish in Trout Lake, Wisconsin, where both the time (circa 1979) and location of the initial introduction are known. Our prediction was that hybridization should hasten the demise of O. propinquus because we expected that male O. rusticus (which are larger than congeners) would outcompete male O. propinquus for mates of both species. If hybrid progeny are unfit, then the result would be decreased reproductive output of O. propinquus females. However, we found a pattern of cytonuclear disequilibrium between allozymes and mtDNA suggesting that a majority (94.5%) of F1 hybrids resulted from matings between O. rusticus females and O. propinquus males. Also contrary to expectations, fecundity (O. rusticus and O. propinquus) and early hybrid survivorship did not differ significantly from nonhybrids. Moreover, adults of mixed ancestry were superior to both O. rusticus and O. propinquus in competition for a limiting food resource. Using a single-locus model, we estimated that hybridization increases the advance of O. rusticus genes in Trout Lake between 4.8% and 36.3% above that due to the previously documented ecological interactions. Consequently, whereas hybridization may be hastening the elimination of genetically pure O. propinquus, introgression is nevertheless slowing the loss of O. propinquus nuclear genes. Although our results suggest that O. rusticus and O. propinquus may not be true species under the biological concept, their ecological differences are of great conservation importance.     

Effect of postal prompts to patients and general practitioners on the quality of primary care after a coronary event (POST): randomised controlled trial

ObjectivesTo determine whether postal prompts to patients who have survived an acute coronary event and to their general practitioners improve secondary prevention of coronary heart disease.DesignRandomised controlled trial.Setting52 general practices in east London, 44 of which had received facilitation of local guidelines for coronary heart disease.Participants328 patients admitted to hospital for myocardial infarction or unstable angina.InterventionsPostal prompts sent 2 weeks and 3 months after discharge from hospital. The prompts contained recommendations for lowering the risk of another coronary event, including changes to lifestyle, drug treatment, and making an appointment to discuss these issues with the general practitioner or practice nurse.ResultsPrescribing of β bockers (odds ratio 1.7, 95% confidence interval 0.8 to 3.0, P>0.05) and cholesterol lowering drugs (1.7, 0.8 to 3.4, P>0.05) did not differ between intervention and control groups. A higher proportion of patients in the intervention group (64%) than in the control group (38%) had their serum cholesterol concentrations measured (2.9, 1.5 to 5.5, P<0.001). Secondary outcomes were significantly improved for consultations for coronary heart disease, the recording of risk factors, and advice given. There were no significant differences in patients’ self reported changes to lifestyle or to the belief that it is possible to modify the risk of another coronary event.ConclusionsPostal prompts to patients who had had acute coronary events and to their general practitioners in a locality where guidelines for coronary heart disease had been disseminated did not improve prescribing of effective drugs for secondary prevention or self reported changes to lifestyle. The prompts did increase consultation rates related to coronary heart disease and the recording of risk factors in the practices. Effective secondary prevention of coronary heart disease requires more than postal prompts and the dissemination of guidelines.

Key messages

• Postal prompts to patients and their general practitioners about effective secondary prevention after a myocardial infarction did not improve the prescribing of cholesterol lowering drugs and β blockers
• The prompts did improve general practice recording of cardiovascular risk factors and lifestyle advice given to patients, but they made no difference to patients’ reports of changes to lifestyle
• Other methods are needed to improve the quality of secondary prevention of coronary heart disease in general practice

     

It''s about time: the evidence for host plant-mediated selection in the apple maggot fly, Rhagoletis pomonella, and its implications for fitness trade-offs in phytophagous insects

The apple maggot fly, Rhagoletis pomonella, Walsh (Diptera: Tephritidae), provides a unique opportunity to address the issue of host-related fitness trade-offs for phytophagous insects. Rhagoletis pomonella has been controversial since the 1860's when Benjamin Walsh cited the fly's shift from hawthorn (Crataegus spp.) to apple (Malus pumila) as an example of an incipient sympatric speciation event. Allozyme and mark-release-recapture studies have subsequently confirmed the status of apple and hawthorn flies as partially reproductively isolated and genetically differentiated host races, the hypothesized initial stage in sympatric divergence. Here, we review the ecological and genetic evidence for host-plant mediated selection in R. pomonella. We reach the following three major conclusions: First, although developmental timing is not everything, it is a good deal of the story. Differences in the fruiting phenologies of apple and hawthorn trees exert different selection pressures on the diapause and eclosion time characteristics of the host races. In particular, the 3-week earlier mean fruiting phenology of apples in eastern North America appears to select for a slower rate of metabolism or deeper pupal diapause in apple than hawthorn flies. Second, host-related fitness trade-offs for R. pomonella may not be due to disruptive selection affecting any one specific life-history stage. Rather, it is the sum total of directional selection pressures acting across different life-stages that generates divergent selection on apple and hawthorn flies. For example, selection favors the alleles Me 100, Acon-2 95 and Mpi 37 (or linked genes) in the larval stage in both host races. However, these same alleles are disfavored in the pupal stage to follow, where they correlate with early adult eclosion, and by inference premature diapause termination. Because apple trees fruit an average of 3 weeks earlier than hawthorn trees, this counter-balancing selection is stronger on apple-fly pupae. The net result is that the balance of selective forces is different between apple and hawthorn flies, helping to maintain the genetic integrity of the host races in sympatry in the face of gene flow. Finally, natural R. pomonella populations harbor a good deal of genetic variation for development-related traits. This variation allows fly populations to rapidly respond to temporal vagaries in local environmental conditions across years, as well as to broad-scale geographic differences that exist across the range of the species. Perhaps most importantly, this variation gives R. pomonella the flexibility to explore and adapt to novel plants. Taken together, our results underscore how difficult it can be to document host plant-related fitness trade-offs for phytophagous insects due to the need to consider details of the entire life-cycle of a phytophagous insect. Our findings also show how reproductive isolation can arise as a by-product of host-associated adaptation in insects, a central theme for models of sympatric speciation via host shifts.     

Metalloproteases in Trypanosoma rangeli-infected Rhodnius prolixus

Protease activities in the haemolymph and fat body in a bloodsucking insect, Rhodnius prolixus, infected with Trypanosoma rangeli, were investigated. After SDS-polyacrylamide gel electrophoresis containing gelatin as substrate, analysis of zymograms performed on samples of different tissues of controls and insects inoculated or orally infected with short or long epimastigotes of T. rangeli, demonstrated distinct patterns of protease activities: (i) proteases were detected in the haemolymph of insects which were fed on, or inoculated with, short epimastigotes of T. rangeli (39 kDa and 33 kDa, respectively), but they were not observed in the fat body taken from these insects; (ii) protease was also presented in the fat bodies derived from naive insects or controls inoculated with sterile phosphate-saline buffer (49 kDa), but it was not detected in the haemolymph of these insects; (iii) no protease activity was observed in both haemolymph and fat bodies taken from insects inoculated with, or fed on, long epimastigotes of T. rangeli. Furthermore, in short epimastigotes of T. rangeli extracts, three bands of the protease activities with apparent molecular weights of 297, 198 and 95 kDa were detected while long epimastigotes preparation presented only two bands of protease activities with molecular weights of 297 and 198 kDa. The proteases from the insect infected with T. rangeli and controls belong to the class of either metalloproteases or metal-activated enzymes since they are inhibited by 1,10-phenanthroline. The significance of these proteases in the insects infected with short epimastigotes of T. rangeli is discussed in relation to the success of the establishment of infection of these parasites in its vector, R. prolixus.     

Caveolin-stabilized membrane domains as multifunctional transport and sorting devices in endocytic membrane traffic

Endocytosis comprises several routes of internalization. An outstanding question is whether the caveolar and endosomal pathways intersect. Following transport of the caveolar protein Caveolin-1 and two cargo complexes, Simian Virus 40 and Cholera toxin, in live cells, we uncovered a Rab5-dependent pathway in which caveolar vesicles are targeted to early endosomes and form distinct and stable membrane domains. In endosomes, the low pH selectively allowed the toxin to diffuse out of the caveolar domains into the surrounding membrane, while the virus remained trapped. Thus, we conclude that, unlike cyclic assembly and disassembly of coat proteins in vesicular transport, oligomeric complexes of caveolin-1 confer permanent structural stability to caveolar vesicles that transiently interact with endosomes to form subdomains and release cargo selectively by compartment-specific cues.     

Campylobacter spp., Giardia spp., Cryptosporidium spp., noroviruses, and indicator organisms in surface water in southwestern Finland, 2000-2001

A total of 139 surface water samples from seven lakes and 15 rivers in southwestern Finland were analyzed during five consecutive seasons from autumn 2000 to autumn 2001 for the presence of various enteropathogens (Campylobacter spp., Giardia spp., Cryptosporidium spp., and noroviruses) and fecal indicators (thermotolerant coliforms, Escherichia coli, Clostridium perfringens, and F-RNA bacteriophages) and for physicochemical parameters (turbidity and temperature); this was the first such systematic study. Altogether, 41.0% (57 of 139) of the samples were positive for at least one of the pathogens; 17.3% were positive for Campylobacter spp. (45.8% of the positive samples contained Campylobacter jejuni, 25.0% contained Campylobacter lari, 4.2% contained Campylobacter coli, and 25.0% contained Campylobacter isolates that were not identified), 13.7% were positive for Giardia spp., 10.1% were positive for Cryptosporidium spp., and 9.4% were positive for noroviruses (23.0% of the positive samples contained genogroup I and 77.0% contained genogroup II). The samples were positive for enteropathogens significantly (P < 0.05) less frequently during the winter season than during the other sampling seasons. No significant differences in the prevalence of enteropathogens were found when rivers and lakes were compared. The presence of thermotolerant coliforms, E. coli, and C. perfringens had significant bivariate nonparametric Spearman's rank order correlation coefficients (P < 0.001) with samples that were positive for one or more of the pathogens analyzed. The absence of these indicators in a logistic regression model was found to have significant predictive value (odds ratios, 1.15 x 10(8), 7.57, and 2.74, respectively; P < 0.05) for a sample that was negative for the pathogens analyzed. There were no significant correlations between counts or count levels for thermotolerant coliforms or E. coli or the presence of F-RNA phages and pathogens in the samples analyzed.     

Genetic polymorphism of glutathione S-transferase P1 and breast cancer risk

To evaluate the potential association between the GSTP1 genotype and the development of breast cancer, a hospital based case-control study was conducted on Korean women. The study population consisted of 171 histologically confirmed incident breast cancer cases and 171 age-matched controls with no present or previous history of cancer. PCR-RFLP was used for the GSTP1 genotyping and statistical evaluations were performed using an unconditional logistic regression model. Postmenopausal women with the GSTP1 Val allele were found to have a reduced risk of breast cancer (OR = 0.3, 95 % CI = 0.10-0.74). A significant interaction was observed between the GSTP1 genotype and alcohol consumption (p for interaction = 0.01); compared with never-drinking women with Ile/Ile genotype, ever-drinking women with the GSTP1 Val allele had almost a three-fold risk of breast cancer (OR = 2.9, 95 % CI = 1.05-7.85), whereas never-drinking women with Val allele had half this risk (OR = 0.5, 95 % CI = 0.27-0.93). Our findings suggest that the GSTP1 polymorphism influences individual susceptibility to breast cancer in the Korean women and this effect may be modified by alcohol consumption.     

A review of 35 cases of asymmetric crying facies

A review of 35 cases of asymmetric crying facies: Congenital asymmetric crying facies (ACF) is caused by congenital hypoplasia or agenesis of the depressor anguli oris muscle (DAOM) on one side of the mouth. It is well known that this anomaly is frequently associated with cardiovascular, head and neck, musculoskeletal, respiratory, gastrointestinal, central nervous system, and genitourinary anomalies. In this article we report 35 ACF patients (28 children and 7 adults) and found additional abnormalities in 16 of them (i.e. 45%). The abnormalities were cerebral and cerebellar atrophy, mega-cisterna magna, mental motor retardation, convulsions, corpus callosum dysgenesis, cranial bone defect, dermoid cyst, spina bifida occulta, hypertelorism, micrognatia, retrognatia, hemangioma on the lower lip, short frenulum, cleft palate, low-set ears, preauricular tag, mild facial hypoplasia, sternal cleft, congenital heart defect, renal hypoplasia, vesicoureteral reflux, hypertrophic osteoarthropathy, congenital joint contractures, congenital hip dislocation, polydactyly, and umbilical and inguinal hernia. Besides these, one infant was born to a diabetic mother, and had atrial septal defect and the four other children had 4p deletion, Klinefelter syndrome, isolated CD4 deficiency and Treacher-Collins like facial appearance, respectively Although many of these abnormalities were reported in association with ACF, cerebellar atrophy, sternal cleft, cranial bone defect, infant of diabetic mother, 4p deletion, Klinefelter syndrome, isolated CD4 deficiency and Treacher-Collins like facial appearance were not previously published.     

The functions of Klarsicht and nuclear lamin in developmentally regulated nuclear migrations of photoreceptor cells in the Drosophila eye

Photoreceptor nuclei in the Drosophila eye undergo developmentally regulated migrations. Nuclear migration is known to require the perinuclear protein Klarsicht, but the function of Klarsicht has been obscure. Here, we show that Klarsicht is required for connecting the microtubule organizing center (MTOC) to the nucleus. In addition, in a genetic screen for klarsicht-interacting genes, we identified Lam Dm(0), which encodes nuclear lamin. We find that, like Klarsicht, lamin is required for photoreceptor nuclear migration and for nuclear attachment to the MTOC. Moreover, perinuclear localization of Klarsicht requires lamin. We propose that nuclear migration requires linkage of the MTOC to the nucleus through an interaction between microtubules, Klarsicht, and lamin. The Klarsicht/lamin interaction provides a framework for understanding the mechanistic basis of human laminopathies.