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1.
氢能作为内燃机燃料的研究   总被引:3,自引:0,他引:3  
该文论述了氢发动机运转中所存在的问题,提出了氢发动机的燃烧改进方案。研究表明,采用高压喷射、火花点火,并优化调整喷射正时和点火正时,就可控制异常燃烧,获得良好的性能  相似文献   
2.
To develop a simple procedure for estimating glomerular filtration rate (GFR) in calves, a three-sample method using iodixanol was first compared to that using the standard agent inulin. Iodixanol and inulin were co-administered intravenously to calves at 40 mg I/kg and 40 mg/kg, respectively, and blood was collected 30, 60, 120, and 180 min later. Serum iodixanol and inulin concentrations were separately determined by high performance liquid chromatography and colorimetry. Serum urea nitrogen (UN) and creatinine concentrations were also measured. GFR estimated by iodixanol was consistent with that using inulin in clinically healthy calves. Based on GFR estimations in healthy calves and those renal-loaded with iodixanol, it was found that the serum creatinine concentrations became elevated when GFR decreased to 60% of the reference value. In contrast, serum UN concentrations fluctuated widely, presumably due to extra-renal factors. When GFR was estimated using the three-sample method and compared with the single-blood-sample method, 62/69 (90%) of samples tested were within the agreement plots. The results demonstrated that the single-blood-sample method using iodixanol may be useful in monitoring GFR in calves.  相似文献   
3.
To evaluate the effects of endogenously secreted cortisol on mineral homeostasis and bone metabolism in cows, 4 ovariectomized Holstein cows were infused for 12 h with either an adrenocorticotropic hormone (ACTH) solution (0.5 mg/2 L isotonic NaCl solution per cow) or isotonic NaCl solution in a 2 × 2 crossover design. ACTH infusion stimulated cortisol secretion and increased plasma cortisol concentrations for 18 h (P < 0.001), leading to an elevated plasma glucose concentration until 36 h (P < 0.001). Plasma calcium and magnesium concentrations in ACTH-infused cows fluctuated within normal ranges, whereas hypophosphatemia was observed unequivocally. The biochemical bone resorption markers tartrate-resistant acid phosphatase 5b and hydroxyproline decreased following ACTH infusion (P < 0.001 and P = 0.003, respectively). Similarly, the bone formation marker, bone-specific alkaline phosphatase, decreased continuously until 72 h after the ACTH infusion (P < 0.001). These results demonstrate that increased secretion of cortisol via a 12-h ACTH infusion disrupted homeostasis of inorganic phosphate and suppressed bone metabolism in ovariectomized cows without involving gonadal steroid hormones.  相似文献   
4.
Arthropathy in dogs induced by ofloxacin, a quinolone antimicrobial agent, was pathophysiologically investigated. In the in vivo studies, ofloxacin was administered orally once or twice at 20 mg/kg/day to male juvenile (3-month-old, n=3) or adult (36-month-old, n=2) dogs, and the humeral and femoral heads were examined pathologically. Unlike adult dogs, fluid-filled vesicles were macroscopically observed on the articular surfaces of one juvenile dog 24 hours after a single treatment with ofloxacin. These lesions were seen in all juvenile dogs by twice dosing. Microscopically, fissures or cavity formations in the middle zone of the articular cartilage were noted only in juvenile dogs. Furthermore, the cartilage matrix from the abnormal area to the articular surface showed a decreased safranin-O staining intensity, suggesting proteoglycan depletion. Ultrastructurally, chondrocytes in the middle zone of juvenile dogs displayed dilatation of the cisternae in the rough endoplasmic reticulum as an initial hallmark. In the in vitro studies, chondrocytes isolated from the articular cartilage of naive juvenile dogs were exposed to ofloxacin at 6.3-100 microg/ml for 24 hours. Although no changes were noted in the deoxyribonucleic acid synthesis, protein synthesis, or proteoglycan release at concentrations of up to 100 microg/ml, the proteoglycan synthesis was evidently decreased in a dose-dependent manner from 12.5 microg/ml. The results obtained suggest that the inhibitory action of ofloxacin on proteoglycan syntheses in the chondrocytes may largely contribute to the early morphologic features in the articular cartilage of the juvenile dog.  相似文献   
5.
To estimate the glomerular filtration rate (GFR) in horses, an optimum dose of the nonionic contrast medium iodixanol as a tracer was assessed with blood-sample times. Iodixanol was administered intravenously at 10–40 mg I/kg to geldings and mares, and blood was collected 30, 60, 90, 120, 150, and 180 min later. Serum iodixanol concentration was determined by high-performance liquid chromatography (HPLC), and serum urea nitrogen (UN) and creatinine concentrations were also measured. The combination of 20 mg I/kg iodixanol and sampling times of 60, 90, and 120 min after injection was considered to be appropriate for practical use. In clinically healthy horses, the reference values were determined to be 1.90 ± 0.03 ml/min/kg (150.8 ± 2.94 ml/min/m2), consistent with historical data using different tracers. The result suggests that serum clearance of iodixanol is a ready-to-use tool for a screening of alterations in the equine GFR, although it is necessary to perform a more longitudinal study using horses with a variety of renal functions.  相似文献   
6.

Background

Application of a multisample method using inulin to estimate glomerular filtration rate (GFR) in cats is cumbersome.

Objectives

To establish a simplified procedure to estimate GFR in cats, a single‐blood‐sample method using inulin was compared with a conventional 3‐sample method.

Animals

Nine cats including 6 clinically healthy cats and 3 cats with spontaneous chronic kidney disease.

Methods

Retrospective study. Inulin was administered as an intravenous bolus at 50 mg/kg to cats, and blood was collected at 60, 90, and 120 minutes later for the 3‐sample method. Serum inulin concentrations were colorimetrically determined by an autoanalyzer method. The GFR in the single‐blood‐sample method was calculated from the dose injected, serum concentration, sampling time, and estimated volume of distribution on the basis of the data of the 3‐sample method.

Results

An excellent correlation was observed (r = 0.99, P = .0001) between GFR values estimated by the single‐blood‐sample and 3‐sample methods.

Conclusions and Clinical Importance

The single‐blood‐sample method using inulin provides a practicable and ethical alternative for estimating glomerular filtration rate in cats.  相似文献   
7.
A colorimetric assay used to quantify the non-ionic contrast medium iodixanol in sera was validated and compared with high-performance liquid chromatography. The application of this assay to estimate glomerular filtration rates (GFR) in cattle was examined. Serum iodixanol was de-iodinated by alkaline hydrolysis and the amount of released iodine was subsequently determined using a ceric arsenite method. There was a close correlation between the two methods using identical specimens. In clinically healthy cattle with different body weights, the reference value (166.3-178.8 mL/min/m(2)) based on body surface area was fairly stable as compared with that (2.13-3.63 mL/min/kg) based on body weight. Based on GFR data in healthy and renal-impaired cattle, when the GFR decreased to more than 60% of the reference value, serum urea nitrogen and creatinine concentrations increased. The colorimetric assay is a simple method for the estimation of GFR in cattle and requires no expensive equipment.  相似文献   
8.
To evaluate serum clearance of iodixanol, applicable to the estimation of glomerular filtration rate (GFR), clinically healthy and experimentally-induced nephropathy calves were prepared. Iodixanol was administered intravenously at 40 mg I/kg, and blood was withdrawn 60, 120, and 180 min later. Serum iodixanol concentration was determined by high-performance liquid chromatography. No statistical difference in GFR was noted between strains (Holstein vs. Japanese Black) or sexes, and the α(2)-adrenergic agonist xylazine increased GFR. In calves subjected to right renal vessel ligation, followed by a left nephrectomy, a marked reduction in GFR was observed with renal ischemic changes. These results suggest that the GFR estimation by serum iodixanol clearance is a ready-to-use tool in calf research and practice owing to the ease of monitoring serial renal function.  相似文献   
9.
Objective-To compare the use of a single-sample method involving IV administration of iodixanol with a multisample method involving inulin for the estimation of glomerular filtration rate (GFR) in cats. Animals-24 cats, including 15 healthy cats and 9 cats with naturally occurring renal diseases. Procedures-Each cat was coadministered iodixanol (a nonionic contrast medium; dose providing 40 mg of I/kg) and inulin (50 mg/kg), IV, and blood samples were collected 60, 90, and 120 minutes later. Serum iodixanol and inulin concentrations were determined by means of high-performance liquid chromatography and colorimetry, respectively. Serum urea nitrogen and creatinine concentrations were also measured. Results-Analysis of the data from healthy cats and cats with naturally occurring renal diseases revealed an excellent correlation between GFR values estimated by the multisample and single-sample methods with iodixanol. Likewise, GFR values estimated from the single-sample method with iodixanol were closely correlated with those calculated from the multisample method with inulin. Conclusions and Clinical Relevance-For estimation of GFR in cats, use of a single-sample method with iodixanol, instead of a multisample procedure, may be an expedient tool in both clinical and research settings because of its benefits to patient well-being as a result of reduced stress associated with blood sample collection.  相似文献   
10.
Dose responses of plasma calcitriol, calcium (Ca), bone metabolic markers and glomerular filtration rate (GFR) were evaluated in four nonpregnant Holstein cows treated subcutaneously with an aqueous formulation of calcitriol at four doses in a 4 × 4 Latin-square design. Calcitriol, Ca, and markers of bone metabolism were analyzed in plasma samples. GFR was measured in predose and day 5 samples. Plasma calcitriol and Ca concentrations increased dose-dependently. The calcitriol dose was positively correlated with the area under the concentration-time curve of plasma calcitriol. Bone formation markers tended to increase from day 3 onward for all doses. No significant changes in GFR were noted. Thus, exogenous calcitriol administered between 0.0625 and 0.5 μg/kg body weight elicited dose-dependent increases in both plasma calcitriol and Ca and elevated bone formation markers without affecting renal function in nonpregnant cows.  相似文献   
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