Genetic specificity in the white pine-blister rust pathosystem

ABSTRACT Four of eight white pine species native to western North America surveyed for resistance to white pine blister rust by artificial inoculation showed classical hypersensitive reactions (HR) at frequencies ranging from very low to moderate. Mendelian segregation, indicating a single dominant allele for resistance (Cr3), was observed in southwestern white pine (Pinus strobiformis), as it was previously in sugar pine (P. lambertiana, Cr1) and western white pine (P. monticola, Cr2). HR was present at a relatively high frequency (19%) in one of five bulk seed lot sources of limber pine (P. flexilis), and was also presumed to be conditioned by a single gene locus, by analogy with the other three species. HR was not found in whitebark pine (P. albcaulis), Mexican white pine (P. ayacahuite), foxtail pine (P. balfouriana), or Great Basin bristlecone pine (P. longaeva), but population and sample sizes in these species may have been below the level of detection of alleles in low frequency. When challenged by (haploid) inocula from specific locations known to harbor virulence to Cr1 or Cr2, genotypes carrying these alleles and Cr3 reacted differentially, such that inoculum virulent to Cr1 was avirulent to Cr2, and inoculum virulent to Cr2 was avirulent to Cr1. Neither of these two inocula was capable of neutralizing Cr3. Although blister rust traditionally is considered an exotic disease in North America, these results, typical of classic gene-for-gene interactions, suggest that genetic memory of similar encounters in past epochs has been retained in this pathosystem.     

Effect of Daily Food Supplementation with Essential Fatty Acids on Canine Semen Quality

Polyunsaturated fatty acids are important membrane components that influence membrane integrity and fluidity. In the present study, the effect of oral supplementation for 60 days with essential fatty acids (omega 3, 6 and 9) and vitamin E on canine semen quality was evaluated. Sixteen dogs were selected for the experiment; eight were used as the control group and eight received the fatty acid supplemented diet for 60 days. Semen samples were taken every 15 days during the entire experimental period and were analyzed for volume (ml), motility (%), vigour (0–5), concentration (×10⁶/ml), morphology of spermatozoa (%), plasma membrane integrity (%; using the hyposmotic swelling test) and thermoresistance (motility and vigour after 4 h at 38°C). We concluded that, daily supplementation with omega 3, omega 6 and omega 9 fatty acids, together with vitamin E, for a period of 60 days, significantly increased the semen volume of the treated group after 15 days of supplementation; the vigour and concentration of spermatozoa were superior after the first month of supplementation, while the percentage of morphologically abnormal spermatozoa decreased and the cells were protected against thermal stress.     

Origin and distribution of cr2, a gene for resistance to white pine blister rust in natural populations of Western white pine

ABSTRACT The distribution and frequency of the Cr2 gene for resistance to white pine blister rust (Cronartium ribicola) in western white pine (Pinus monticola) was surveyed in natural populations of the host by inoculation of open-pollinated seedlings from 687 individual seed parents from throughout most of the species' range. Because Cr2 is dominant and results in a conspicuous hypersensitive reaction (HR) in pine needles, the phenotype can readily be detected in offspring of susceptible seed parents fertilized by unknown Cr2 donors in the ambient pollen cloud. Gametic frequencies of Cr2 were thus determined as the proportion of total challenged seedlings that were pollen receptors exhibiting the Cr2 phenotype. Zygotic frequencies, the proportion of seed parents with progeny that segregated in Mendelian ratios for the Cr2 phenotype to the total number of parents, were a complementary, though less precise, measure. Cr2 frequency was rare overall, ranging from 0.004 to 0.008 in the Sierra Nevada to about 0.001 in the central Cascade Range; it was undetectable further north in the Cascades, as well as in the Rocky Mountains and Coast Mountains of the United States and Canada. The diminishing frequency of Cr2 from the southern and central Sierra Nevada northward mirrors that of Cr1 in sugar pine (P. lambertiana) and points to this region as the origin of both genes. We rationalize that this coincidence may have resulted from protection that these genes may have conferred on both species to an endemic pine stem rust congeneric with C. ribicola (C. occidentale) in recent geologic epochs.     

Evaluation of a citrate-based anticoagulant with platelet inhibitory activity for feline blood cell Counts

Abstract: Aggregation of feline platelets in vitro results in difficulty assessing platelet number. A citrate-based anticoagulant containing the platelet inhibitors theophylline, adenosine, and dipyridamole (CTAD; Diatube-H, Becton Dickinson, Oxford, UK) has been developed for use in human platelet studies and heparin assays. To evaluate the efficacy of CTAD in reducing platelet aggregation in feline blood samples, aliquots of blood from 51 cats were anticoagulated with EDTA, CTAD, and for 12 samples, citrate solution. Samples preserved in CTAD had significantly higher (P ≤ .001) platelet counts, as determined by an impedance counter, hemacy-tometer, and smear estimation, than samples preserved in EDTA. In addition, subjective assessment of blood smears showed significantly fewer platelet aggregates (P<.001) in CTAD-treated samples compared with EDTA samples. Although values were similar, automated platelet counts and smear estimates of platelet number were significantly higher (P < .05) and platelet aggregation was significantly less (P < .05) in CTAD samples than in citrate samples. These results suggest that the platelet inhibitory activity of CTAD reduced feline platelet aggregation. Automated total WBC counts in CTAD samples were significantly lower (P<.001) than automated counts in EDTA samples but were similar to manual WBC counts in EDTA samples. Differences in both platelet and WBC counts between CTAD and EDTA or citrate samples were clinically relevant. Mean platelet volume and MCV were significantly lower (P< .05) in CTAD samples than in EDTA samples. No effect was seen on cell morphology or staining characteristics. The anticoagulant CTAD offers an advantage over both EDTA and citrate for feline hematologic analysis, by decreasing pseudothrombocytopenia and pseudoleukocytosis.     

Virulence gene distribution and dynamics of the white pine blister rust pathogen in Western north america

ABSTRACT We assayed the distribution and frequency of two genes of the blisterpathogen with specific virulence to major resistance genes in sugar pine and western white pine in inoculum from extensive parts of the hosts' ranges. The genes, vcr1 and vcr2, differentially neutralize the cognate resistance alleles Cr1 and Cr2 of the two respective hosts and are clearly marked by their interaction phenotypes. Basidiospores from each inoculum source were cast over Cr1 and Cr2 host genotypes simultaneously, and interaction phenotypes scored when developed. vcr1 was confined to sites with high concentrations of Cr1 (mostly plantations) where frequencies tended toward fixation. vcr2 showed a similar tendency, except high frequencies were occasionally observed from natural and planted stands of western white pine with very low frequencies of Cr2. Otherwise, no pattern was evident for either allele: frequencies were very erratic from site to site within short distances (<1 to 7 km) of each other and oscillated with high amplitudes at the same sites measured in consecutive years. Intense selection for virulence by Cr alleles occurs locally, but spread of vcr alleles over the landscape is mitigated by remarkably low gene flow. Absence of heterozygotes among single telia inoculum on Cr2 genotypes indicated cytoplasmic inheritance of vcr2, similar to vcr1(previously reported).     

The characterization of cycad palm toxicosis and treatment effects in 130 dogs

The purpose of this retrospective study is to characterize the clinical signs, laboratory values, treatment modalities and mortality outcomes related to cycad palm toxicosis in dogs and to identify medical interventions that potentially correlate with mortality. Dogs with confirmed cycad palm ingestion were identified by reviewing medical records from two private veterinary referral centres for key terms and phrases indicative of cycad palm toxicosis. Of 130 dogs included, 107 (82.3%) presented with clinical signs. A total of 2 (1.5%) died and 14 (10.8%) were euthanized. Diarrhea, lethargy and mortality were all associated with an elevated initial alanine transaminase (ALT) concentration. Overall mortality was 12.3%, with a significantly higher proportion of dogs with an ALT concentration <125 U/L surviving compared to dogs with an elevated ALT concentration. Treatment with activated charcoal reduced the odds of death among all dogs by 82% and was even more protective among dogs with an elevated initial ALT concentration. Among dogs that had an initial platelet count performed, the presence of thrombocytopenia (<200,000/μL) was a negative prognostic indicator and was associated with a significant increase in mortality. Given the high mortality rates reported for cycad palm toxicosis, it is imperative to identify early clinical indicators of mortality as well as treatments that reduce mortality.     

Modulation of Ovarian Function in Female Dogs Immunized with Bovine Luteinizing Hormone Receptor

Adult female dogs were immunized with 0.5 mg bovine luteinizing hormone receptor (LH-R) encapsulated in a silastic subdermal implant and subsequently with four intramuscular booster injections of 0.1 mg LH-R each. Circulating LH-R antibody was detected in the sera 3 weeks post-implant. The appearance of LH-R antibody was associated with a decline in the serum progesterone concentrations to a range of 0–0.5 ng/ml until day 365 in the immunized dogs in comparison with a range of 5–10 ng in the control animals, suggesting a lack of ovulation and corpus luteum function in immunized dogs. The immunized dogs did not show signs of `standing heat' and failed to ovulate when induced by LH-RH challenge. Serum oestradiol levels, however, remained in the range of 30–40 pg/ml in both the immunized and the control dogs. With the decline in the antibody titres, the hormonal profile and vaginal cytology returned to a fertile state and the dogs exhibited signs of `standing heat', as well as vaginal bleeding. Dogs immunized with LH-R did not show any serious metabolic, local or systemic adverse effects. The hypothalamic–pituitary gonadal axis remained intact as indicated by little difference in pituitary LH levels between control and immunized animals, and by the release of LH by LH-RH challenge. These studies demonstrate that active immunization of female dogs with LH-R could immunomodulate ovarian function to cause a reversible state of infertility. It may be postulated that, due to extensive interspecies homology, a recombinant LH receptor-based immunocontraceptive vaccine may also be effective in other vertebrates.     

Immunolocalization of Melatonin and Follicle‐Stimulating Hormone Receptors in Caprine Ovaries and their Effects During in vitro Development of Isolated Pre‐Antral Follicles

The expression of melatonin type 1 (MT1) and FSH (FSHR) receptors in caprine ovaries and the effects of these hormones on the in vitro development of isolated pre‐antral follicles were evaluated. Follicles (≤200 μm) were cultured for 12 days in α‐MEM (control) or melatonin (100 or 1000 pg/ml) or sequential melatonin medium (100 pg/ml: from day 0 to day 6; 1000 pg/ml: from day 6 to day 12; experiment 1) and in control or sequential FSH (100 ng/ml from day 0 to day 6; 500 ng/ml from day 6 to day 12) or sequential melatonin or this latter plus sequential FSH (experiment 2). MT1 and FSHR expressions were observed in granulosa cells from secondary and antral follicles. The oocytes from primordial and primary follicles also express FSHR. Sequential melatonin increased the percentage of normal follicles and oocyte recovery compared with the control or melatonin (1000 pg/ml) at day 12. In experiment 2, all the treatments increased the normal follicles and growth compared with the control. In conclusion, this study demonstrated the presence of MT1 and FSHR in caprine ovaries. The addition of increased concentrations of melatonin (sequential medium) or FSH can be used to promote the in vitro development of caprine pre‐antral follicles.     

White pine blister rust: simply inherited resistance in sugar pine

Segregation ratios of offspring from disease-free sugar pines suggest that resistance to the white pine blister rust fungus is under major gene control and simply inherited.