Effects of the calcium channel antagonist amlodipine in cats with surgically induced hypertensive renal insufficiency

OBJECTIVE: To determine whether amlodipine besylate decreases systemic arterial blood pressure (BP) and reduces the prevalence of complications in cats with induced hypertensive renal insufficiency. ANIMALS: 20 cats with partial nephrectomy. PROCEDURE: Following reduction in renal mass, 10 cats were administered 0.25 mg of amlodipine/kg, PO, q 24 h (group A). Ten cats served as a control group (group C). Systolic BP (SBP), diastolic BP (DBP), and mean BP (MBP), physical activity, and pulse rate were measured continuously for 36 days by use of radiotelemetric devices. RESULTS: Compared with values for clinically normal cats, SBP, DBP, and MBP were significantly increased in cats of group C. Cats in group A had significant reductions in SBP, DBP, and MBP, compared with values for cats in group C. Albuminuria but not urine protein-to-creatinine ratio was significantly correlated (R2 = 0.317) with SBP in hypertensive cats. Prevalence of ocular lesions attributable to systemic hypertension in group C (7 cats) was greater than that observed in group A (2). Two cats in group C were euthanatized on day 16 because of nuerologic complications attributed to systemic hypertension. One normotensive cat in group A was euthanatized because of purulent enteritis of unknown cause on day 27. CONCLUSIONS AND CLINICAL RELEVANCE: Amlodipine had an antihypertensive effect in cats with coexistent systemic hypertension and renal insufficiency. Its use may improve the prognosis for cats with systemic hypertension by decreasing the risk of ocular injury or neurologic complications induced by high BP.     

Risk factors associated with development of seizures after use of iohexol for myelography in dogs: 182 cases (1998)

OBJECTIVE: To determine prevalence of seizures after use of iohexol for myelography and identify associated risk factors in dogs. DESIGN: Retrospective study. ANIMALS: 182 dogs that received iohexol for myelography in 1998. PROCEDURE: Medical records were reviewed for age, breed, sex, weight, dose and total volume of iohexol, injection site, number of injections, lesion type and location, total duration of anesthesia, duration from time of iohexol injection to recovery, presence and number of seizures, and whether surgery followed the myelogram. RESULTS: 39 (21.4%) dogs had at least 1 generalized seizure during or after myelography. Injection site was strongly associated with prevalence of seizures, and risk of seizure was significantly higher after cerebellomedullary injections, compared with lumbar injections. Mean total volume of iohexol administered to dogs that had seizures was significantly higher, compared with that administered to dogs that did not have seizures, although dosage did not differ between groups. Weight was significantly correlated with risk of seizure, and dogs that weighed > 20 kg (44 lb) had higher prevalence of seizures than dogs that weighed < 20 kg. CONCLUSIONS AND CLINICAL RELEVANCE: It is preferential to administer iohexol via the L5-6 intervertebral space to minimize the risk of seizures. Higher prevalence of seizures in large dogs, compared with smaller dogs, may be caused by administration of larger total volumes of contrast agent per volume of CSF.     

Mercury antagonists: protection of plants against vapor injury by thiamine and other compounds

Mercury vapor-induced abscission ofColeus cuttings was prevented by Thiamine, other organo-S (Se) compounds and selenite, but not by common sugar metabolites, amino acids, non-auxin growth regulators and selenate. Protection was also afforded to other plants including ferns and gymnosperms. Thus the compounds that protect plants against Hg intoxication correspond to the Hg antagonists known in animals including man.     

Adaptive phenotypic plasticity in response to climate change in a wild bird population

Rapid climate change has been implicated as a cause of evolution in poorly adapted populations. However, phenotypic plasticity provides the potential for organisms to respond rapidly and effectively to environmental change. Using a 47-year population study of the great tit (Parus major) in the United Kingdom, we show that individual adjustment of behavior in response to the environment has enabled the population to track a rapidly changing environment very closely. Individuals were markedly invariant in their response to environmental variation, suggesting that the current response may be fixed in this population. Phenotypic plasticity can thus play a central role in tracking environmental change; understanding the limits of plasticity is an important goal for future research.     

Conservation value of variable connectivity: aquatic invertebrate assemblages of channel and floodplain habitats of a central Australian arid-zone river, Cooper Creek

Rapidly expanding water resource development in arid and semi-arid zones of Australia threatens the flow regime and ecological integrity of the few large dryland rivers and their immense floodplains. Efforts to manage and conserve the surface waters of these rivers are hampered by limited scientific data on the ecology of their flora and fauna and on their responses to the high natural variability of flow regime that typifies dryland rivers. Irregular floods connect channel and floodplain wetlands to differing degrees and for varying periods of time but the ecological significance of this connectivity is poorly understood. On Cooper Creek, a large dryland river in central Australia, we explored the degree to which assemblage composition varied with connectivity and hydrological regime. Shortly after protracted regional flooding, we sampled aquatic macroinvertebrate assemblages from the principal microhabitats in 12 channel and floodplain wetlands. Ephemeral and temporary lakes tended to have fewer taxa than semi-permanent channel or terminal lake habitats. Although hydrological connection had only recently been lost for some wetlands, there was already evidence of divergence in aquatic macroinvertebrate assemblage composition. Disruption of the natural variability in connectivity and hydrological regime by excessive water abstraction or river-flow regulation threatens the ecological integrity and aquatic macroinvertebrate biodiversity of dryland rivers. Preservation of the irregular flow regime and sporadic connectivity underpins conservation of the mosaic of floodplain wetlands that play such a crucial role in the ecosystem functioning of rivers such as Cooper Creek.     

Cross‐breeding performance of white leghorn and Australorp lines selected under continuous light for short interval between eggs: Full‐year egg production and efficiency of food utilisation

1. White Leghorn (LS) and Australorp (AS) lines selected for short oviposition interval and their control lines (LC and AC), together with three strains of Australian commercial layers, were evaluated for crossbreeding performance.

2. The estimates of selection effect on crossbreeding performance in lines LS and AS respectively were 3·5% and 15·2% for survivors’ egg number, ‐3·3% and ‐2·0% for average egg weight, and 4·3% and 7·4% for efficiency of food utilisation.

3. Compared to the commercial strains, the LS × AS cross was 13 to 15% higher for egg number, 7 to 10% lower for egg weight and 2 to 7% better for efficiency of food utilisation.

4. The LC × AC cross laid more but smaller eggs than the commerical strains. This raised the question of how effective conventional selection in the commercial nucleus flocks had been in improving egg number in the previous 10 years, a period when the control lines had been bred without deliberate selection.