Vasa vasorum hypoperfusion is responsible for medial hypoxia and anatomic remodeling in the newborn lamb ductus arteriosus

This is a non-final version of an article published in final form in KAJINO, HIROKI ; GOLDBARG, SETH ; ROMAN, CHRISTINE ; LIU, BAO MEI ; MAURAY, FRANÇOISE ; CHEN, YAO QI ; TAKAHASHI, YASUSHI ; KOCH, CAMERON J. ; CLYMAN, RONALD I., Vasa vasorum hypoperfusion is responsible for medial hypoxia and anatomic remodeling in the newborn lamb ductus arteriosus, Pediatric research 51(2), 2002 FEB, pp. 228-235. AuthorPostnatal constriction of the full-term ductus arteriosus produces hypoxia of the muscle media. This is associated with anatomic remodeling (including smooth muscle death) that prevents subsequent reopening. We used late-gestation fetal and neonatal lambs to determine which factors are responsible for the postnatal hypoxia. Hypoxia [measured by 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide technique] and cell death (measured by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique) were observed in regions of the constricted ductus wall within 4 h after delivery. Although there was a decrease in ductus luminal flow during the first 6 h after delivery (measured by Doppler transducer), the amount of oxygen delivered to the ductus lumen (3070 ± 1880 μmol O_2 · min^ · g^) far exceeded the amount of oxygen consumed by the constricted ductus (0.052 ± 0.021 μmol O2 · min^ · g^, measured in vitro). Postnatal constriction increased the effective oxygen diffusion distance across the ductus wall to >3× the limit that can be tolerated for normal tissue homeostasis. This was owing to both an increase in the thickness of the ductus (fetus, 1.12 ± 0.20 mm; newborn, 1.60 ± 0.17 mm;p · g^; newborn, 0.21 ± 0.08 mL · min^ · g^;p < 0.01). These findings suggest that hypoxic cell death in the full-term ductus is caused primarily by changes in vasa vasorum flow and muscle media thickness and can occur before luminal flow has been eliminated. We speculate that in contrast with the full-term ductus, the preterm ductus is much less likely to develop the degree of hypoxia needed for vessel remodeling inasmuch as it only is capable of increasing its oxygen diffusion distance to 1.3× the maximally tolerated limit

Chaperone Use by Residents During Pelvic, Breast, Testicular, and Rectal Exams

We designed a questionnaire survey to study internal medicine residents' plans to use a chaperone during the pelvic, breast, rectal, and testicular examinations. We found chaperone use by male and female residents differed markedly, and neither group planned to use chaperones universally. When examining female patients, male residents overall were very likely to use a chaperone during a pelvic exam, but less likely for the breast exam and rectal exam. For the female resident, there was a significantly lower likelihood of using chaperones during the pelvic, breast, or rectal exams. There was a much lower rate of chaperone use during the sensitive portions of the male physical examination compared with the female examination, with somewhat higher use by female residents. We concluded that male and female residents differ significantly in their patterns of chaperone use. It would be valuable to develop guidelines for chaperone use to help residents understand the issues involved in the choices, and to protect the residents from the possible medico-legal consequences of forgoing chaperones

Perinatal Physiology

This chapter will discuss the mechanisms preparing the fetus to be born, the transition at birth, and the successful adaptation to the air-breathing world. This chapter will review the respiratory system including lung development, maturation, and role of surfactant system and the respiratory drive and chemoreceptor role and the circulatory system including fetal circulation and its changes at birth