Occipital Encephalocele and Early Gestational Hyperthermia

PEDIATRICS ◽  
1981 ◽  
Vol 68 (4) ◽  
pp. 480-483
Author(s):  
Nancy L. Fisher ◽  
David W. Smith

Hyperthermia as a human teratogen has been implicated as one cause for neurulation defects. To determine whether there is an association between early maternal hyperthermia (20 to 28 days' gestation) and isolated occipital encephalocele, record reviews were conducted for the period 1969 through 1979 in three major medical centers in the Pacific Northwest. Control patients consisted of children with Down's syndrome matched for year of birth, sex, and race. Of the 17 patients ascertained with an isolated posterior encephalocele, four (24%) of the mothers gave a history of hyperthermia, due to prolonged fever of at least 1.5 C above normal thermal levels early in gestation. In the control patients and siblings of affected children, no history of maternal hyperthermia was elicited. These data are compatible with the concept that early maternal hyperthermia is one cause in the genesis of isolated occipital encephalocele.

2002 ◽  
Vol 32 (6) ◽  
pp. 1057-1070 ◽  
Author(s):  
Linda E Winter ◽  
Linda B Brubaker ◽  
Jerry F Franklin ◽  
Eric A Miller ◽  
Donald Q DeWitt

The history of canopy disturbances over the lifetime of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington was reconstructed using tree-ring records of cross-dated samples from a 3.3-ha mapped plot. The reconstruction detected pulses in which many western hemlock (Tsuga heterophylla (Raf.) Sarg.) synchronously experienced abrupt and sustained increases in ringwidth, i.e., "growth-increases", and focused on medium-sized or larger ([Formula: see text]0.8 ha) events. The results show that the stand experienced at least three canopy disturbances that each thinned, but did not clear, the canopy over areas [Formula: see text]0.8 ha, occurring approximately in the late 1500s, the 1760s, and the 1930s. None of these promoted regeneration of the shade-intolerant Douglas-fir, all of which established 1500–1521. The disturbances may have promoted regeneration of western hemlock, but their strongest effect on tree dynamics was to elicit western hemlock growth-increases. Canopy disturbances are known to create patchiness, or horizontal heterogeneity, an important characteristic of old-growth forests. This reconstructed history provides one model for restoration strategies to create horizontal heterogeneity in young Douglas-fir stands, for example, by suggesting sizes of areas to thin in variable-density thinnings.


Evolution ◽  
2005 ◽  
Vol 59 (8) ◽  
pp. 1639-1652 ◽  
Author(s):  
Brayan C. Cartens ◽  
Steven J. Brunsfeld ◽  
John R. Demboski ◽  
Jeffrey M. Good ◽  
Jack Sullivan

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