Domestic cats and dogs are carnivores that have evolved differentially in the nutrition and metabolism of amino acids.This article highlights both proteinogenic and nonproteinogenic amino acids.Dogs inadequately synth...Domestic cats and dogs are carnivores that have evolved differentially in the nutrition and metabolism of amino acids.This article highlights both proteinogenic and nonproteinogenic amino acids.Dogs inadequately synthesize citrulline(the precursor of arginine)from glutamine,glutamate,and proline in the small intestine.Although most breeds of dogs have potential for adequately converting cysteine into taurine in the liver,a small proportion(1.3%-2.5%)of the Newfoundland dogs fed commercially available balanced diets exhibit a deficiency of taurine possibly due to gene mutations.Certain breeds of dogs(e.g.,golden retrievers)are more prone to taurine deficiency possibly due to lower hepatic activities of cysteine dioxygenase and cysteine sulfinate decarboxylase.De novo synthesis of arginine and taurine is very limited in cats.Thus,concentrations of both taurine and arginine in feline milk are the greatest among domestic mammals.Compared with dogs,cats have greater endogenous nitrogen losses and higher dietary requirements for many amino acids(e.g.,arginine,taurine,cysteine,and tyrosine),and are less sensitive to amino acid imbalances and antagonisms.Throughout adulthood,cats and dogs may lose 34%and 21%of their lean body mass,respectively.Adequate intakes of high-quality protein(i.e.,32%and 40%animal protein in diets of aging dogs and cats,respectively;dry matter basis)are recommended to alleviate aging-associated reductions in the mass and function of skeletal muscles and bones.Pet-food grade animal-sourced foodstuffs are excellent sources of both proteinogenic amino acids and taurine for cats and dogs,and can help to optimize their growth,development,and health.展开更多
Psychophysical experiments on human and animal subjects have proven that aged individuals show significantly reduced visual contrast sensitivity compared with young adults.To uncover the possible neural mechanisms,we ...Psychophysical experiments on human and animal subjects have proven that aged individuals show significantly reduced visual contrast sensitivity compared with young adults.To uncover the possible neural mechanisms,we used extracellular single-unit recording techniques to examine the response of V1（primary visual cortex） neurons as a function of visual stimulus contrast in both old and young adult cats（Felis catus）.The mean contrast sensitivity of V1 neurons to visual stimuli in old cats decreased significantly relative to young adult cats,consistent with findings reported in old primates.These results indicate that aging can affect contrast sensitivity of visual cortical cells in both primate and non-primate mammalian animals,and might contribute to the reduction of perceptual visual contrast sensitivity in aged individuals.Further,V1 cells of old cats exhibited increased responsiveness,decreased signal-to-noise ratio,and enlarged receptive field（RF） size compared with that of young adult cats,which indicated that decreased contrast sensitivity of V1 neurons accompanied a reduction of intracortical inhibition during senescence.展开更多
Previous studies have shown that visual cortical neurons in old mammals exhibit higher spontaneous activity,higher responsiveness to visual stimuli,and lower selectivity for stimulus orientations and motion directions...Previous studies have shown that visual cortical neurons in old mammals exhibit higher spontaneous activity,higher responsiveness to visual stimuli,and lower selectivity for stimulus orientations and motion directions than did neurons in young adult counterparts.However,whether the responsive difference in cortical neurons between young and old animals resulted from different effects induced by anesthetics has remained unclear.To clarify this issue,we recorded the response properties of individual neurons in the primary visual cortex of old and young adult cats while systematically varying the anesthesia level of urethane,a widely used anesthetic in physiology experiments.Our results showed that cumulatively administrating 50 mg and 100 mg of urethane upon the minimal level of urethane required to anesthetize an old or young adult cat did not significantly alter the degree of neuronal response selectivity for stimulus orientations and motion directions nor significantly change the visually-driven response and spontaneous activity of neurons in old and young adult cats.Cumulatively administrating 150 mg of urethane decreased neuronal responsiveness similarly in both age groups.Therefore,urethane appears to exert similar effects on neuronal response properties of old and young adult animals.展开更多
基金This work was supported by Texas A&M AgriLife Research(H-8200).
文摘Domestic cats and dogs are carnivores that have evolved differentially in the nutrition and metabolism of amino acids.This article highlights both proteinogenic and nonproteinogenic amino acids.Dogs inadequately synthesize citrulline(the precursor of arginine)from glutamine,glutamate,and proline in the small intestine.Although most breeds of dogs have potential for adequately converting cysteine into taurine in the liver,a small proportion(1.3%-2.5%)of the Newfoundland dogs fed commercially available balanced diets exhibit a deficiency of taurine possibly due to gene mutations.Certain breeds of dogs(e.g.,golden retrievers)are more prone to taurine deficiency possibly due to lower hepatic activities of cysteine dioxygenase and cysteine sulfinate decarboxylase.De novo synthesis of arginine and taurine is very limited in cats.Thus,concentrations of both taurine and arginine in feline milk are the greatest among domestic mammals.Compared with dogs,cats have greater endogenous nitrogen losses and higher dietary requirements for many amino acids(e.g.,arginine,taurine,cysteine,and tyrosine),and are less sensitive to amino acid imbalances and antagonisms.Throughout adulthood,cats and dogs may lose 34%and 21%of their lean body mass,respectively.Adequate intakes of high-quality protein(i.e.,32%and 40%animal protein in diets of aging dogs and cats,respectively;dry matter basis)are recommended to alleviate aging-associated reductions in the mass and function of skeletal muscles and bones.Pet-food grade animal-sourced foodstuffs are excellent sources of both proteinogenic amino acids and taurine for cats and dogs,and can help to optimize their growth,development,and health.
基金Supported by National Natural Science Foundation of China(31171082)Natural Science Foundation of Anhui Province(070413138)the Key Research Foundation of Anhui Province Education Department(KJ2009A167)
文摘Psychophysical experiments on human and animal subjects have proven that aged individuals show significantly reduced visual contrast sensitivity compared with young adults.To uncover the possible neural mechanisms,we used extracellular single-unit recording techniques to examine the response of V1（primary visual cortex） neurons as a function of visual stimulus contrast in both old and young adult cats（Felis catus）.The mean contrast sensitivity of V1 neurons to visual stimuli in old cats decreased significantly relative to young adult cats,consistent with findings reported in old primates.These results indicate that aging can affect contrast sensitivity of visual cortical cells in both primate and non-primate mammalian animals,and might contribute to the reduction of perceptual visual contrast sensitivity in aged individuals.Further,V1 cells of old cats exhibited increased responsiveness,decreased signal-to-noise ratio,and enlarged receptive field（RF） size compared with that of young adult cats,which indicated that decreased contrast sensitivity of V1 neurons accompanied a reduction of intracortical inhibition during senescence.
基金Supported by Natural Science Foundation of Anhui Province (070413138)the Key Research Foundation of Anhui Province Education Department (KJ2009A167)
文摘Previous studies have shown that visual cortical neurons in old mammals exhibit higher spontaneous activity,higher responsiveness to visual stimuli,and lower selectivity for stimulus orientations and motion directions than did neurons in young adult counterparts.However,whether the responsive difference in cortical neurons between young and old animals resulted from different effects induced by anesthetics has remained unclear.To clarify this issue,we recorded the response properties of individual neurons in the primary visual cortex of old and young adult cats while systematically varying the anesthesia level of urethane,a widely used anesthetic in physiology experiments.Our results showed that cumulatively administrating 50 mg and 100 mg of urethane upon the minimal level of urethane required to anesthetize an old or young adult cat did not significantly alter the degree of neuronal response selectivity for stimulus orientations and motion directions nor significantly change the visually-driven response and spontaneous activity of neurons in old and young adult cats.Cumulatively administrating 150 mg of urethane decreased neuronal responsiveness similarly in both age groups.Therefore,urethane appears to exert similar effects on neuronal response properties of old and young adult animals.
