Knowledge Of Growth Dynamics Research Articles

A MODEL FOR PREDICTING DIAMETER OF 'RED SENSATION' PEARS

A MODEL FOR PREDICTING DIAMETER OF 'RED SENSATION' PEARS

Longevity and growth rate estimates for a polar dinosaur: a Pachyrhinosaurus (Dinosauria: Neoceratopsia) specimen from the North Slope of Alaska showing a complete developmental record

Our knowledge of growth dynamics in large ceratopsian dinosaurs is very poor, in part, due to the paucity of quantifiable age markers such as growth lines in their bones. We sought marker-based, osteohistological evidence for ceratopsid age structure from high Arctic paleolatitudes based on the observations that: (1) extant mammals from high latitudes better express growth lines in their hard tissues than those from lower latitudes, and (2) the occurrence of accentuated growth banding in teeth from Arctic dinosaurs. We examined the long bones in the specimens of Pachyrhinosaurus sp. from the early Maastrichtian of northern Alaska, and found conspicuous osseous banding. Histological analysis of the spacing, structure, pattern and numbers of these bands in the femur of a very large specimen suggests that they are not a taphonomic artefact, rather they appear to reflect annual growth cycling. Counts and measurements of the growth zones suggest that the animal showed rapid linear growth early in ontogeny, sexual maturity in perhaps the 9th year of life, and that it died in the 19th year of life. Our data adds to a growing body of evidence that a genetically distinct northern dinosaurian fauna existed at high paleolatitudes in Alaska during the Late Cretaceous.

Growth modelling of non-functioning pituitary adenomas in patients referred for surgery

Recent observational studies have established progression and recurrence rates of pituitary adenomas. However, it is still unknown how individual pituitary adenomas grow over years and whether growth kinetics follow a distinct growth model. The objective of this study was to define a growth model for non-functioning pituitary adenomas. Fifteen patients who had five or more serial high-quality examinations with magnetic resonance images or computerized tomography scans were identified among 216 patients with non-functioning pituitary adenomas. Tumour volumes were assessed using a stereological method based on the Cavalieri principle. Tumour growth during the observation period was analysed and different growth models were fitted to the data. Fifteen pituitary adenomas (12 recurrent tumours and 3 newly diagnosed tumours) were longitudinally observed during a median observation period of 7.4 years (range: 2.3-11.9 years). Growth kinetics could be described either by an exponential growth model (nine patients) or by a logistic model (five patients) with initial exponential growth followed by deceleration of growth. One tumour remained unchanged in size during the observation period. None of the adenomas showed accelerated growth during the observation period. Overall, the linear growth model was not suitable to describe the growth kinetics of non-functioning pituitary adenomas. Our study shows that growth of pituitary adenomas can be described by distinct growth models. Knowledge of growth dynamics has implications for clinical practice and helps to adjust scanning protocols for follow-up investigations.

A brief history of the study of human growth dynamics

SummaryHuman growth is non-linear and short term changes in height velocity cannot be used to predict future growth. This paper discusses the current knowledge of growth dynamics in the context of a historical review of the subject.