It is well documented that the hormone leptin regulates energy balance via its actions in the hypothalamus. However, evidence is accumulating that leptin plays a key role in numerous CNS functions. Indeed, leptin receptors are expressed in many extrahypothalamic brain regions, with high levels found in the hippocampus and cerebellum. In the hippocampus, leptin has been shown to facilitate NMDA receptor function and modulate synaptic plasticity. A role for leptin in cerebellar function is also indicated as leptin-deficient rodents display reduced mobility that is unrelated to obesity. Here we show that leptin receptor immunolabeling can be detected in cultured cerebellar granule cells, being expressed at the somatic plasma membrane and also concentrated at synapses. Furthermore, leptin facilitated NR2B NMDA receptor-mediated Ca 2+ influx in cerebellar granule cells via a mitogen-activated protein kinase-dependent pathway. These findings provide the first direct evidence for a cellular action of leptin in cerebellar neurons. In addition, given that NMDA receptor activity in the cerebellum is crucial for normal locomotor function, these data also have important implications for the potential role of leptin in the control of movement.

The commercially available SST test and determination of serum total protein and globulin concentrations are suitable methods for assessing passive transfer status in llama and alpaca crias.

Although increased mortality has been linked to failure of passive transfer, it is clearly possible to raise crias that have low serum immunoglobulin concentrations. Llamas and alpacas do not differ significantly with respect to immunoglobulin absorption or IgG concentration in neonates. The optimal sampling time for passive transfer status is between 1 and 2 days.

Holstein steers fed protein-restricted diets were used to evaluate protein realimentation and site of serum collection on the ability of calf serum to affect proliferation, protein synthesis and degradation in L6 myoblast cell culture bioassay. In Experiment 1, five steers (average weight 227 kg) received continuous abomasal infusion of 4 L of water or casein (50% of basal dietary nitrogen intake) in a switchback design. Serum was collected 2 d before and after 1, 3, 5, 7 and 9 d of infusion. Abomasal casein infusion increased serum mitogenic activity, nitrogen retention (119%) and total post-ruminal amino acid flow (78%). In Experiment 2, serum was collected from the jugular and femoral veins and the carotid artery before and after 7 d of abomasal casein infusion. Serum from calves abomasally infused with casein increased myoblast proliferation (jugular > femoral > carotid) and protein synthesis and decreased protein degradation in cultured myotubes. The addition of test calf serum inhibited the mitogenic activity of control calf serum. Results suggest that post-ruminal amino acid flow and site of serum collection alter the ability of serum to influence cell culture bioassays.