The pharmacological effects of the anesthetic alfaxalone after intramuscular administration to dogs

The pharmacological effects of the anesthetic alfaxalone were evaluated after intramuscular (IM) administration to 6 healthy beagle dogs. The dogs received three IM doses each of alfaxalone at increasing dose rates of 5 mg/kg (IM5), 7.5 mg/kg (IM7.5) and 10 mg/kg (IM10) every other day. Anesthetic effect was subjectively evaluated by using an ordinal scoring system to determine the degree of neuro-depression and the quality of anesthetic induction and recovery from anesthesia. Cardiorespiratory variables were measured using noninvasive methods. Alfaxalone administered IM produced dose-dependent neuro-depression and lateral recumbency (i.e., 36 ± 28 min, 87 ± 26 min and 115 ± 29 min after the IM5, IM7.5 and IM10 treatments, respectively). The endotracheal tube was tolerated in all dogs for 46 ± 20 and 58 ± 21 min after the IM7.5 and IM10 treatments, respectively. It was not possible to place endotracheal tubes in 5 of the 6 dogs after the IM5 treatment. Most cardiorespiratory variables remained within clinically acceptable ranges, but hypoxemia was observed by pulse oximetry for 5 to 10 min in 2 dogs receiving the IM10 treatment. Dose-dependent decreases in rectal temperature, respiratory rate and arterial blood pressure also occurred. The quality of recovery was considered satisfactory in all dogs receiving each treatment; all the dog exhibited transient muscular tremors and staggering gait. In conclusion, IM alfaxalone produced a dose-dependent anesthetic effect with relatively mild cardiorespiratory depression in dogs. However, hypoxemia may occur at higher IM doses of alfaxalone.     

Central venous blood gas and acid-base status in conscious dogs and cats

To determine the reference level of central venous oxygen saturation (ScvO₂) and clinical efficacy of central venous blood gas analysis, partial pressures of oxygen and carbon dioxide, pH, oxygen saturation, base excess (B.E.) and HCO₃ concentration were compared between simultaneously obtained central venous and arterial blood samples from conscious healthy 6 dogs and 5 cats. Comparisons between arteriovenous samples were performed by a paired t-test and Bland-Altman analysis. Between arteriovenous samples, B.E. showed good agreement, but there were significant differences in other parameters in the dogs, and no good agreement was detected in cats. The ScvO₂ in dogs and cats were 82.3 ± 3.5 and 62.4 ± 13.5%, respectively. Central venous blood gas analysis is indispensable, especially in cats.     

Simultaneous steroids measurement in dogs with hyperadrenocorticism using a column-switching liquid chromatography-tandem mass spectrometry method

We developed an analytical method using an on-line column-switching liquid chromatography with triple quadrupole mass spectrometry (LC/MS/MS) for quantifying multiple steroids in serum. Using the developed method, we evaluated the serum concentration of nine steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, 21-deoxycortisol, deoxycorticosterone, progesterone, 17α-OH-progesterone and aldosterone) in dogs with hyperadrenocorticism (HAC). Serum was mixed with stable isotope internal standards and thereafter purified by the automated column-switching system. The limit of detection ranged 2–16 pg/ml for nine steroids. In the baseline samples, five steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, and 17α-OH-progesterone) were detected in all dogs. The concentrations of cortisone, 11-deoxycortisol, and 17α-OH-progesterone in dogs with HAC (n=19) were significantly higher those in dogs without HAC (n=15, P<0.02). After the adrenocorticotropic hormone stimulation test, six steroids (cortisol, corticosterone, cortisone, 11-deoxycortisol, 17α-OH-progesterone, and deoxycorticosterone) were above the limit of quantification in all dogs. Cortisol, corticosterone, cortisone, and deoxycorticosterone concentrations of dogs with HAC were significantly higher than those of dogs without HAC (P<0.02). In addition, 11-deoxycortisol and 17α-OH-progesterone concentration was higher in dogs with HAC than in dogs without HAC (P=0.044 and P=0.048, respectively). The on-line column-switching LC/MS/MS would be feasible for measuring multiple steroids in dog serum. The results suggest that cortisone, 11-deoxycortisol, and 17α-OH-progesterone would be related to HAC. Further studies are warranted to assess the clinical feasibility of steroid profile in dogs with HAC.     

Effects of zinc on tissue uptake and toxicity of lead in Sprague Dawley rat

Lead (Pb) exposure occurs together with other metals including zinc (Zn). This study investigated the impact of Zn on Pb tissue accumulation and Pb-induced toxicities. Animals (n=6 rats per group) were exposed to lead acetate (PbAc) or a combination of PbAc and zinc acetate (ZnAc) under the following groups: control (deionized water), low PbAc [12 mg/kg PbAc (3 mg PbAc/rat/day)], low PbAc–ZnAc [12 mg/kg PbAc (3 mg PbAc/rat/day) + 0.2 mg ZnAc/rat/48 hr], high PbAc [120 mg/kg (30 mg PbAc/rat/day)], and high PbAc–ZnAc [120 mg/kg (30 mg PbAc/rat/day) + 1 mg ZnAc/rat/48 hr] for 8 weeks. A significant reduction in body weight gain was observed in the high PbAc group relative to the control group. Muscles and testes both had reduced and increased Pb uptake in low PbAc–ZnAc and high PbAc–ZnAc groups compared to PbAc only groups, respectively. Bone Pb levels in the high PbAc–ZnAc group were lower than the high PbAc group. Zinc co-administration attenuated Pb-induced inhibition of delta aminolaevulinic acid dehydratase enzyme and enhanced catalase enzyme activity at a high level of exposure. Moreover, ZnAc seems to have minimized the effects of Pb-induced mRNA dysregulation in antioxidant and antiapoptotic enzymes encoding genes. Heme oxygenase-1 was downregulated in the kidney and brain in the low PbAc group. Liver glutathione peroxidase and thioredoxin reductase-1 were downregulated in the high PbAc group. These findings suggest that zinc co-administration with lead may partially mitigate against Pb-induced toxicities.     

Spatial variations in nitrous oxide and nitric oxide emission potential on a slope of Japanese cedar (Cryptomeria japonica) forest

To quantify the spatial variation and spatial structure of nitrous oxide (N₂O) and nitric oxide (NO) emission from forest soils, we measured N₂O and NO emission rates from surface soil cores taken at 1 m intervals on a cross-line transect (65 m × 20 m) on a slope of Japanese cedar ( Cryptomeria japonica ) forest in a temperate region of central Japan and analyzed the spatial dependency of N oxide gas emissions using geostatistics. We divided N₂O emission into N₂O from denitrification and N₂O from nitrification using the acetylene inhibition method. According to the geostatistical analysis, N₂O emission rates on the slope had large spatial variation and weak spatial dependency. This weak spatial dependency was caused by the inordinately high N₂O emissions on the slope, which were derived mainly from denitrification. In contrast, NO emission rate on the slope had large spatial variation, but strong spatial dependency and a distinct spatial distribution related to slope position, that is, high in the middle of the slope and low in the shoulder and the foot of the slope. The CN ratio and water-filled pore space were the dominant factors controlling NO emission rate on a slope. Our results suggest that spatial information about topographic factors helps to improve the estimation of both N₂O emission and NO emission from forest soils.     

Urinary free metanephrines measurement in dogs with adrenal gland diseases using a new simple liquid chromatography tandem mass spectrometry method

Measurement of urinary metanephrines in spot samples is used for the diagnosis of canine pheochromocytoma (PC). We describe a simple analytical method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) for measuring free metanephrine (MN) and normetanephrine (NMN) in spot urine samples. Using the developed method, we evaluated the stability of urinary free-MN and free-NMN at various storing conditions. In addition, we assessed the feasibility of urinary free-MN and -NMN measurement for diagnosing PC. Urine samples were mixed with stable isotope internal standards and thereafter purified by ultrafiltration. The purified samples were analyzed by LC-MS/MS in the multiple reaction monitoring mode after separation on a multimode octa decyl silyl column. The coefficient of variation of free-MN and -NMN measurement was 7.6% and 5.5%, respectively. The linearity range was 0.5–10 µg/l for both analytes. Degradation was less than 10% for both analytes under any of the storage conditions. The median free-NMN ratio to creatinine of 9 PC dogs (595, range 144–47,961) was significantly higher (P<0.05) than that of 13 dogs with hypercortisolism (125, range 52–224) or 15 healthy dogs (85, range 50–117). The developed method is simple and may not require acidification of spot urine. The results of this preliminary retrospective study suggest that the measurement of urinary free metanephrines is a promising tool for diagnosing canine PC.