Jones Donna Carlson, Bernstein Marica, German Rebecca Z
Department of Physical Medicine and Rehabilitation, The Johns Hopkins University, Baltimore, Maryland 21231, USA.
J Morphol. 2011 Apr;272(4):485-96. doi: 10.1002/jmor.10927. Epub 2011 Feb 2.
Protein malnutrition leads to growth retardation that can be reversed through catch-up growth, once normative nutrition is restored. Because growth is a dynamic process, catch-up capacity is likely influenced by the maturity of the animal and/or the duration of the insult, in addition to the type of insult experienced. We compared length of malnutrition, sexual dimorphism, body mass, and skeletal growth. Eighty Rattus norvegicus were divided into 10 treatment groups (five diets; male and female) and followed for more than 1 year. At weaning, animals were placed on either a control or low-protein isocaloric diet. Three experimental groups were switched to the control diet at 40, 60, or 90 days. Beginning with 21 days of age, animals were weighed daily and radiographed throughout the study. To determine the presence of catch-up growth, growth rates (GRs) were calculated (linear regression) for 20-day time spans before and after diet changes and compared among treatment groups. Targeted growth was measured as final size or as the coefficient of variation with age. These results show that 1) protein-restricted animals experience catch-up growth with dietary rehabilitation; 2) for females, catch-up GRs are proportional to GRs in control animals at the same age as the timing of dietary rehabilitation but not for males; and 3) targeted growth was observed in some, but not all, aspects of anatomy. The length of the tibia and humerus was indistinguishable from controls, regardless of length of malnutrition or gender, whereas the ulna and male body mass exceeded control sizes. Although most measures decreased in variation with ontogeny, the tibia failed to do so. These results support a complex biological regulation of catch-up and targeted growth. The implications for selection are that flexible and responsive developmental trajectories may have an advantage over those programed into a single size.
蛋白质营养不良会导致生长发育迟缓，一旦恢复正常营养，这种情况可通过追赶生长得以逆转。由于生长是一个动态过程，除了所经历的损伤类型外，追赶生长的能力可能还受动物成熟度和/或损伤持续时间的影响。我们比较了营养不良的时长、性别差异、体重和骨骼生长情况。80只褐家鼠被分为10个处理组（5种饮食；雄性和雌性），并跟踪观察了1年多。断奶时，将动物置于对照饮食或低蛋白等热量饮食中。三个实验组在40、60或90天时改为对照饮食。从21日龄开始，在整个研究过程中每天对动物称重并进行X光检查。为了确定是否存在追赶生长，计算了饮食改变前后20天时间段内的生长速率（线性回归），并在各处理组之间进行比较。将目标生长量测定为最终大小或随年龄变化的变异系数。这些结果表明：1）蛋白质限制的动物通过饮食康复会经历追赶生长；2）对于雌性，追赶生长速率与饮食康复时相同年龄的对照动物的生长速率成比例，但雄性并非如此；3）在某些但并非所有解剖学方面观察到了目标生长。无论营养不良的时长或性别如何，胫骨和肱骨的长度与对照无差异，而尺骨和雄性体重超过了对照大小。尽管大多数测量值随个体发育而变异减小，但胫骨并非如此。这些结果支持了追赶生长和目标生长的复杂生物学调节。其对选择的启示是，灵活且有响应性的发育轨迹可能比那些被设定为单一大小的轨迹更具优势。
