Diurnal Variations in Cyclic AMP and Melatonin Content of Golden Hamster Retina

Abstract: The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamster retina were studied. Both parameters showed significant diurnal variations with maximal values at night. Light exposure during the night inhibited retinal cyclic AMP and melatonin levels, whereas exposure to darkness during the day significantly increased cyclic AMP and melatonin content. Incubation with melatonin of retinas excised at different intervals indicated that the methoxyindole inhibited cyclic AMP accumulation in a time-dependent manner. The inhibitory effect of melatonin at 2400 h and at noon showed a threshold concentration of 1 and 10 pM, respectively. At 0400 h melatonin did not affect cyclic AMP accumulation. The results indicate a diurnal variability of retinal cyclic AMP and melatonin content in hamsters, mainly influenced by a photic stimulus. Cyclic AMP could be a putative second messenger for melatonin action in golden hamster retina.     

Effects of illumination and enucleation on substance-P-immunoreactive structures in subcortical visual centers of golden hamster and Wistar rat

The undecapeptide substance P is found in different entities of the visual system that control eye movement and synchronize endogenous rhythms with the light cycle (i.e., superior colliculus, suprachiasmatic nucleus, intergeniculate leaflet). Immunocytochemical methods were used to compare the reactivity to substance P in the brain of five groups of golden hamsters and two groups of Wistar rats: (1) untreated hamsters kept under 14L:10D and sacrificed at noon; (2) identically maintained animals sacrificed at midnight; (3) enucleated animals kept under control conditions; (4) hamsters kept under constant darkness; (5) hamsters kept under the same conditions as the controls, but intraventricularly injected with colchicine. The results obtained in golden hamsters of groups (1) and (3) were compared with findings in Wistar rats treated accordingly [groups (6) and (7)]. Substance P-immunoreactive perikarya were found in the suprachiasmatic nucleus and superior colliculus of hamsters and Wistar rats. Substance P-immunoreactive nerve fibers were abundant in the hypothalamic area ventral to the paraventricular nucleus, in the intergeniculate leaflet, in some thalamic nuclei, and in the superior colliculus. Immunoreactivity to substance P in the suprachiasmatic nucleus and intergeniculate leaflet did not vary among the experimental groups. However, a conspicuous decrease in reactivity to substance P was observed in the superficial layers of the superior colliculus of enucleated hamsters and rats, compared with all other groups. These results indicate that substance P immunoreactivity in the superior colliculus, but not that in the suprachiasmatic nucleus or intergeniculate leaflet, depends on the integrity of the retinal projection.     

Public Access for Pheasant Hunters: Understanding an Emerging Need

Ring-necked pheasant (Phasianus colchicus; i.e., pheasant) hunting participation is declining across North America, reflecting a larger downward trend in American hunting participation and threatening benefits to grassland conservation and rural economies. To stabilize and expand the pheasant hunting population, we must first identify factors that influence pheasant hunter participation. We used an extensive in-person hunter survey to test the hypothesis that hunter demographics interact with social-ecological traits of hunting locations to affect hunter decisions, outcomes, and perceptions. We built a series of Bayesian mixed effects models to parse variation in demographics, perceptions, and hunt outcomes of pheasant hunters interviewed at public access hunting sites across 3 regions in Nebraska, USA, that varied in pheasant abundance and proximity to urban population centers. Among pheasant hunters in Nebraska, access to private lands was negatively related to the human population density of a pheasant hunter's home ZIP code and the distance a hunter had traveled to reach a hunting location. Pheasant hunters interviewed closer to metropolitan areas tended to be more urban and travel shorter distances, and their parties were more likely to include youth but less likely to include dogs. Hunter satisfaction was positively associated with seeing and harvesting pheasants and hunting with youth. Whereas youth participation and the number of pheasants seen varied by study region, hunter satisfaction did not differ across regions, suggesting that hunters may calibrate their expectations and build their parties based on where they plan to hunt. The variation in hunter demographics across hunting locations and disconnects between social and ecological correlates of hunter satisfaction suggests that diverse pheasant hunting constituencies will be best served by diverse pheasant hunting opportunities. © 2019 The Wildlife Society.     

Sensitivity Analyses of a Population Projection Model of Ring-Necked Pheasants

Abstract A large literature exists on population dynamics of ring-necked pheasant (Phasianus colchicus) in North America, but there has not been an attempt to formulate a matrix model nor a sensitivity analysis of the relationships between vital rates and population finite growth rate (Λ) that can be used to guide management. We summarized demographic data available from a 5-year field study in Iowa, USA, collected in Kossuth County (low composition of perennial habitat) and Palo Alto County (high composition of perennial habitat) into a 2-stage (young and adult) matrix projection model. We estimated Λ₁ (the dominant eigenvalue of the deterministic matrix), the stable age distribution (ω), relative reproductive value vector (n̈), other demographic parameters, and Λ_iid, a bootstrap estimate of growth that includes interannual variation in life history parameters. We analyzed the relative importance of vital rates on population growth rate using sensitivity and elasticity of both matrix elements and lower-level parameters such as winter survival and nest success. We first characterized general life history using averaged data from both areas and all years that yielded Λ₁ = 1.086, and a stable stage distribution of. Minimum success of the initial nesting attempt (H₁) that would maintain Λ ≥ 1 under average conditions was estimated to be 42%. Changes in Λ₁ were most sensitive to survival of chicks during brood rearing (S_B), followed in importance by survival during the subsequent winter (S_W), followed by H₁. We followed the general analyses with analyses that helped us to focus on the differences in the landscapes of northwest Iowa. Λ_iid was ≥1 in only 9% of simulations of data from Kossuth whereas estimated Λ_iid was ≥1 in 88% of simulations from Palo Alto. Our analyses of the relative importance and interactions between S_B, S_W, and total recruitment (M, including H₁ and renesting), if combined with data more specific to a local area, would guide management aimed at affecting multiple life history stages whose relative importance will vary across the landscape.     

Effects of livestock exclusion on in‐stream habitat and benthic invertebrate assemblages in montane streams

1. Stream and riparian ecosystems in arid montane areas, like the interior western United States, are often just narrow mesic strands, but support diverse and productive habitats. Meadows along many such streams have long been used for rangeland grazing, and, while impacts to riparian areas are relatively well known, the effect of livestock grazing on aquatic life in streams has received less attention. 2. Attempts to link grazing impacts to disturbance have been hindered by the lack of spatial and temporal replication. In this study, we compared channel features and benthic macroinvertebrate communities (i) between 16 stream reaches on two grazed allotments and between 22 reaches on two allotments where livestock had been completely removed for 4 years, (ii) before and after the 4‐year grazing respite at a subset of eight sites and (iii) inside and outside of small‐scale fenced grazing exclosures (eight pairings; 10+ year exclosures) in the meadows of the Golden Trout Wilderness, California (U.S.A.). 3. We evaluated grazing disturbance at the reach scale in terms of the effects of livestock trampling on per cent bank erosion and found that macroinvertebrate richness metrics were negatively correlated with bank erosion, while the percentage of tolerant taxa increased. 4. All macroinvertebrate richness metrics were significantly lower in grazed areas. Bank angle, temperature, fine sediment cover and erosion were higher in grazed areas, while riparian cover was lower. Regression models identified riparian cover, in‐stream substratum, bank conditions and bankfull width‐to‐depth ratios as the most important for explaining variability in macroinvertebrate richness metrics. 5. Small‐scale grazing exclosures showed no improvements for in‐stream communities and only moderate positive effects on riparian vegetation. In contrast, metrics of macroinvertebrate richness increased significantly after a 4‐year period of no grazing. 6. The success of grazing removal reported here suggests that short‐term removal of livestock at the larger, allotment meadow spatial scale is more effective than long‐term, but small‐scale, local riparian area fencing, and yields promising results in achieving stream channel, riparian and aquatic biological recovery.     

Intercellular bridges between germ cells in the immature golden hamster testis: evidence for clonal and non-clonal mode of proliferation

Summary Intercellular bridges of prespermatogonia and of the first A-spermatogonia in the maturing testes of newborn to 17-day-old golden hamsters have been studied by electron microscopy. Incomplete cytokinesis of dividing M- and T₂-prespermatogonia and A-spermatogonia produces these bridges, which undergo different developmental fates. Bridges of the first A-spermatogonia are stable beyond subsequent mitoses of these cells; this gradually leads to the formation of bridge-connected groups of synchronously developing germ cells. Thus, the clonal mode of male germ cell proliferation is already established in this period of testis maturation. During mitoses, pre-existing bridges reversibly develop structural modifications, i.e. considerable elongation and formation of a bridge-partitioning complex. In contrast, intercellular bridges of prespermatogonia are mostly severed and become lost during subsequent mitoses of the cells involved; this results in separation of the germ cells and represents a mainly non-clonal mode of M- and T₂-prespermatogonial proliferation. Here, too, pre-existing bridges elongate and develop the bridge-partitioning complex during subsequent mitoses of the joined cells, but this is superposed and interrupted by the simultaneous process of disconnection of the bridges.Parts of this study were presented at the 85th meeting of the Anatomische Gesellschaft in Munich, April 1990     

Über zusätzliches Reizleitungsgewebe im Goldhamsterherzen

Zusammenfassung Histologisch, enzymhistochemisch und mit Hilfe formaldehyd-induzierter Fluoreszenz wird im rechten Vorhof des Goldhamsterherzens Reizleitungsgewebe nachgewiesen, das weder zum Sinus- noch zum AV-Knoten gehört. Dieses Gewebe gleicht in Struktur, Stoffwechsel, Vaskularisation und Innervation der übrigen Reizleitungsmuskulatur. Die funktionelle Bedeutung des zusätzlichen Knotengewebes wird diskutiert.

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Additional conductive tissue in the golden hamster heart

Summary In the right atrium of the heart of the golden hamster histology, enzyme histochemistry, and formaldehyde-induced fluorescence reveal conductive tissue, which does not belong to the SA or AV node. Morphology, metabolism, vascularisation, and innervation of this tissue are the same as in the other regions of the impulse conducting system. The functional significance of the additional nodal tissue is discussed.

     

A Universal Method for the Identification of Bacteria Based on General PCR Primers

The Universal Method (UM) described here will allow the detection of any bacterial rDNA leading to the identification of that bacterium. The method should allow prompt and accurate identification of bacteria. The principle of the method is simple; when a pure PCR product of the 16S gene is obtained, sequenced, and aligned against bacterial DNA data base, then the bacterium can be identified. Confirmation of identity may follow. In this work, several general 16S primers were designed, mixed and applied successfully against 101 different bacterial isolates. One mixture, the Golden mixture7 (G7) detected all tested isolates (67/67). Other golden mixtures; G11, G10, G12, and G5 were useful as well. The overall sensitivity of the UM was 100% since all 101 isolates were detected yielding intended PCR amplicons. A selected PCR band from each of 40 isolates was sequenced and the bacterium identified to species or genus level using BLAST. The results of the UM were consistent with bacterial identities as validated with other identification methods; cultural, API 20E, API 20NE, or genera and species specific PCR primers. Bacteria identified in the study, covered 34 species distributed among 24 genera. The UM should allow the identification of species, genus, novel species or genera, variations within species, and detection of bacterial DNA in otherwise sterile samples such as blood, cerebrospinal fluid, manufactured products, medical supplies, cosmetics, and other samples. Applicability of the method to identifying members of bacterial communities is discussed. The approach itself can be applied to other taxa such as protists and nematodes.     

金山绣线菊遗传转化体系的建立

以金山绣线菊愈伤组织为受体材料,采用组织培养的方法,在附加不同浓度TDZ的1／2MS培养基上诱导培养,获得再生植株。在附加0．03mg·L^-1 TDZ的培养基上获得了92．5％不定芽的再生率,且再生芽发育良好。选择抗生素筛选试验的结果表明：金山绣线菊愈伤组织对潮霉素较为敏感,在培养基中添加浓度为5～35mg·L^-1的潮霉素均对愈伤组织分化影响较大,潮霉素浓度为5mg·L^-1时,4N时间可使外植体全部褐化死亡;在培养基中添加0～100mg·L^-1的卡那霉素,不同浓度卡那霉素均对愈伤组织分化产生一定程度的影响,当卡那霉素浓度为80mg·L^-1时,愈伤组织基本不发生分化。由此确定卡那霉素为绣线菊遗传转化中适用的选择抗生素,最适选择压为80mg·L^-1。抑菌抗生素的筛选试验结果表明：200mg·L^-1的头孢霉素和200mg·L^-1。的羧苄霉素都能有效抑制农杆菌菌株LBA4404的生长,却对金山绣线菊愈伤组织的芽分化影响不大,可确定为适宜的抑菌抗生素。利用农杆菌介导法对金山绣线菊愈伤组织进行遗传转化,得到卡那霉素抗性植株164株,并初步确定预培养1d、菌液稀释10倍、侵染4min、共培养2d为金山绣线菊最优遗传转化体系,为金山绣线菊的基因工程育种奠定基础。     

血雉卵的人工孵化

2008～2010年,北京动物园在陕西洋县长青自然保护区采集血雉卵进行人工孵化研究。卵的保存及运输期为5～7d,卵保存温度17.14～18.66℃,湿度73.5%～87.1%,卵使用防震运输箱经34h运输后入孵,运输过程温度在16.38～25.95℃之间。孵化前使用碘氟稀释液擦拭卵表面。35枚受精卵中,19枚使用3台孵化机孵化,孵化温度37.4～37.5℃,使用14%～33%、40%～45%和60%～70%3个湿度梯度孵化;16枚卵使用乌鸡代亲孵化,袖珍温度记录仪测量乌鸡孵化温度在34.81～39.18℃之间,孵化环境湿度为23.4%～72.4%。记录孵化过程中的卵重量变化和孵化期。结果表明:研究期间血雉卵平均孵化率为76.5%,其中机器孵化率为84.2%,代亲孵化率为68.8%;平均孵化期为27d11h;卵失重率11.23%～16.54%,平均为13.77%±1.51%。