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Brito LF Barth AD Rawlings NC Wilde RE Crews DH Mir PS Kastelic JP 《Domestic animal endocrinology》2007,33(1):1-18
The objective of the present study was to characterize the effects of nutrition on circulating concentrations of metabolic hormones, gonadotropins, and testosterone during sexual development in bulls. Nutrition regulated the hypothalamus-pituitary-testes axis through effects on the GnRH pulse generator in the hypothalamus and through direct effects on the testes. Pituitary function (gonadotropin secretion after GnRH challenge) was not affected by nutrition. However, nutrition affected LH pulse frequency and basal LH concentration during the early gonadotropin rise (10-26 weeks of age). There were close temporal associations between changes in insulin-like growth factor-I (IGF-I) concentrations and changes in LH pulse frequency, suggesting a role for IGF-I in regulating the early gonadotropin rise in bulls. The peripubertal increase in testosterone concentration was delayed in bulls with lesser serum IGF-I concentrations (low nutrition), suggesting a role for IGF-I in regulating Leydig cell function. Serum IGF-I concentrations accounted for 72 and 67% of the variation in scrotal circumference and paired-testes volume, respectively (at any given age), indicating that IGF-I may regulate testicular growth. Bulls with a more sustained elevated LH pulse frequency during the early gonadotropin rise (high nutrition) had greater testicular mass at 70 weeks of age relative to the control group (medium nutrition), despite no differences in metabolic hormone concentrations after 26 weeks of age. Therefore, gonadotropin-independent mechanism regulating testicular growth might be dependent on previous gonadotropin milieu. 相似文献
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A single-step duplex polymerase chain reaction (PCR) technique and traditional microscopic examination of haemolymph smears were used to detect Babesia bigemina and/or Babesia bovis infection in engorged female ticks of Boophilus microplus recovered from calves raised in an endemic area of the State of Minas Gerais, Brazil. In the PCR amplification of tick-derived DNA, pairs of oligonucleotide primers specific for a 278-bp sequence from B. bigemina and for a 350-bp sequence from B. bovis were used conjointly. The microscopic examination of haemolymph revealed that 16.7% of the engorged ticks were infected with Babesia spp., although no significant differences (rho > 0.05) were found in the infection rate of ticks collected from calves of different age groups. PCR analysis showed that 77.8% of the engorged ticks whose haemolymph contained sporokinetes were infected with B. bigemina, 7.8% with B. bovis and 14.4% with both protozoan species. However, the PCR assay further revealed that, amongst the engorged female ticks whose haemolymph was apparently negative for the presence of sporokinetes, 15.6% were infected with B. bigemina, 2.2% with B. bovis and 10.0% with both species. The duplex PCR method is thus more efficient and sensitive than the microscopic assay and also permits facile identification of the protozoa species present in engorged female ticks. 相似文献
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Rúbia Monteiro de Castro Cunha Gleidice Eunice Lavalle Fernanda Camargo Nunes Ayisa Rodrigues de Oliveira Renato de Lima Santos Roberto Baracat de Araújo 《Veterinary and comparative oncology》2023,21(2):240-254
Squamous cell carcinoma (SCC) is an important malignancy in dogs, due to its incidence and clinical presentation, which can be of locally aggressive single or multiple lesions with a metastatic potential. The objective of this investigation was to evaluate SCC response to treatment, anatomopathological and immunohistochemical characteristics, disease-free interval and overall survival time. 54 dogs with histopathologically diagnosed SCC were included in this study. Their mean age was 9.16 years with a range of 1–14 years. Of the 54 animals in the study, 34 (65.4%) had white skin and white fur coats. There was a significant correlation between fur coat colour and the development of tumours in areas of sun exposure (p = .001). Animals with tumours in areas of the body exposed to the sun had longer overall survival time than animals with tumours in areas not associated with sun exposure (p = .001). Surgery combined with electrochemotherapy (ECT) yielded a survival rate 32% higher than using a surgical approach alone (HR = 0.32, p = .038, IC = 0.11–0.94). ECT, with or without surgery, had an objective response rate of 90.9%. Local lymph node and/or distant site metastasis at diagnosis, or at some point during follow-up, occurred in 34.6% (18/52) of animals. Animals with tumours in sun exposed locations had more aggressive histopathological characteristics but had longer overall survival time. This is probably due to individualised therapeutic treatment with both surgery and ECT. 相似文献
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Neil J Duncan Leonardo Ibarra-Castro & Ricardo Alvarez-Villaseñor 《Aquaculture Research》2008,39(4):427-433
Spotted rose snapper, Lutjanus guttatus (Steindachner), eggs were incubated under different photoperiods to examine the effect of photoperiod on incubation. The eggs from two fish were incubated under five artificial photoperiods: constant dark (D), constant light (L) from 06:00 hours and 6, 10 and 14 h of light from 06:00 hours. The eggs from seven other fish were incubated under a natural photoperiod. Different spawning times (21:00 – 01:00 hours) and different photoperiods combined to give the start of the dusk photoperiod change after 11–23 h of incubation. Constant light or applying the dusk photoperiod change after ≥20 h of incubation appeared to extend the hatching period. The mean hatching period for groups of eggs incubated in darkness or that received the dusk photoperiod change after ≤19 h of incubation (n=8 different groups) was 2 h 15±10 min, which was significantly lower (P<0.05) than the mean hatching period of 4 h±37 min for groups that did not receive the dusk photoperiod change or that received the dusk photoperiod change after ≥20 h of incubation (n=9 groups). However, despite these differences, the majority of the eggs hatched during a 2–3 h period from 17 to 20 h of incubation, and a sigmoid regression (r2=0.9) explained the relationship between percentage hatch and hours of incubation for all photoperiod groups. 相似文献
17.
Igo G. Guimarães Luiz E. Pezzato Margarida M. Barros Leonardo Tachibana 《Journal of the World Aquaculture Society》2008,39(6):781-789
Apparent digestibility coefficients (ADCs) provide estimates of nutrient availability in feedstuffs and can be used as a tool for selecting ingredients to compound cost‐effective diets for fish. Extrusion process is one factor that could influence ADC values. Thus, a digestibility trial was undertaken to evaluate ADC of protein, energy, and dry matter, and apparent amino acid availability (AAAA) in five cereal grain products/by‐products (corn, wheat middlings, broken rice, rice bran, and sorghum) in compounded diets for Nile tilapia. Chromic oxide was used as an external inert marker. The digestibility values of energy and dry matter in ingredients, in decreasing order, were highest for broken rice (95.34 and 96.45%), sorghum (82.37 and 87.29%), corn (67.34 and 82.21%), rice bran (57.58 and 55.59%), and wheat middlings (48.94 and 45.88%). Protein digestibility value was higher for corn (72.86%) and the lowest value was observed for sorghum (56.77%), while broken rice, wheat middlings, and rice bran presented values ranging from 63.01 to 66.88%. AAAA values were higher for corn (70.05%) and the lowest methionine and cystine availability values were recorded for wheat middlings and broken rice, respectively. Broken rice appears as one of the most indicated ingredient for using in Nile tilapia diets because of its highest values of nutrient digestibility when compared to the other energetic sources. The use of this information should aid more precise and economic diet formulation for Nile tilapia. 相似文献
18.
We describe a new manual procedure for catching and tagging fish underwater, the ‘pole-hooking’ method, and demonstrate and discuss its advantages over standard tagging techniques (i.e. hook-and-line fishing). The new technique was designed for tagging Acanthistius brasilianus [Cuvier, M., Valenciennes, L.B., 1828. Histoire Naturelle des Poissons. Museau de Histoire Naturelle, Paris], a small to medium-sized fish inhabiting rocky reefs of the Argentine coast. The pole-hooking method minimizes injuries, avoids fast depressurization of fish and allows registration of the precise location of capture and release. In addition, the equipment needed is very simple and economical. The mean number of fish tagged per minute using this methodology on shallow rocky reefs (up to 25-m depth) was similar to that obtained during hook-and-line fishing sessions (ca. one tagged fish every 3 min), given similar densities of A. brasilianus in the fished reefs. 相似文献
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