PubMed · 4933577
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1970. [Minor anastomoses].. https://pubmed.ncbi.nlm.nih.gov/4933577/
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This review will discuss the use of small-angle X-ray diffraction approaches to study the organization of lipids in plasma membranes derived from two distinct mammalian cell types: arterial smooth muscle cells and ocular lens fiber cells. These studies indicate that cholesterol at an elevated concentration can self-associate and form immiscible domains in the plasma membrane, a phenomenon that contributes to both physiologic and pathologic cellular processes, depending on tissue source. In plasma membrane samples isolated from atherosclerotic smooth muscle cells, the formation of sterol-rich domains is associated with loss of normal cell function, including ion transport activity and control of cell replication. Analysis of meridional diffraction patterns from intact and reconstituted plasma membrane samples indicates the presence of an immiscible cholesterol domain with a unit cell periodicity of 34 A, consistent with a cholesterol monohydrate tail-to-tail bilayer, under disease conditions. These cholesterol domains were observed in smooth muscle cells enriched with cholesterol in vitro as well as from cells obtained ex vivo from an animal model of atherosclerosis. By contrast, well-defined cholesterol domains appear to be essential to the normal physiology of fiber cell plasma membranes of the human ocular lens. The organization of cholesterol into separate domains underlies the role of lens fiber cell plasma membranes in maintaining lens transparency. These domains may also interfere with cataractogenic aggregation of soluble lens proteins at the membrane surface. Taken together, these analyses provide examples of both physiologic and pathologic roles that sterol-rich domains may have in mammalian plasma membranes. These findings support a model of the membrane in which cholesterol aggregates into structurally distinct regions that regulate the function of the cell membrane.
It is now well known that in order to establish human hemochorial placentation and to provide a progressive increase in blood supply to the growing fetus, the uterine spiral arteries must undergo considerable alterations. This physiological modification is thought to be brought about by the interaction of invasive cytotrophoblast with the spiral artery vessel wall. Despite intensive research our understanding of the mechanisms that control human trophoblast invasion in normal, let alone abnormal pregnancy, are sill poorly understood. This is partly due to difficulties in obtaining "true" placental bed biopsies and most investigators have relied on in vitro models of trophoblast invasion. This article describes the morphological changes that occur within the placental bed throughout human pregnancy along with a review of the various studies which have attempted to sample the placental bed. Thereafter, follows a review of the evidence that invasive trophoblast can release the vasoactive agents nitric oxide and/or carbon monoxide which, in turn, could contribute to early physiological changes in spiral arteries prior to destruction of the smooth muscle within the vessel wall. Current evidence supports the idea that trophoblast-derived carbon monoxide may contribute to spiral artery modification. In contrast there is no evidence for a similar role by nitric oxide.
STUDY DESIGN: A case of arterial-esophageal fistula related to nasogastric tube placement in a 13-year-old girl after surgical correction of her progressive congenital lumbar kyphosis is presented. OBJECTIVES: This case report illustrates the importance of early recognition of "sentinel" hematemesis before massive hemorrhage, as this may allow for timely surgical intervention to prevent fatal exsanguination. The proposed pathogenesis of the arterial-esophageal fistula in the reported patient is discussed. SUMMARY OF BACKGROUND DATA: Although arterial-esophageal fistula formation has been recognized as an unusual complication of prolonged nasogastric intubation, to the authors' knowledge, this is the only case that illustrates an association of this complication with short-term nasogastric tube placement. METHODS: A 13-year-old girl was evaluated for progressive congenital lumbar kyphosis. Failure of segmentation and an anterior bar at L4-L5 was diagnosed when the patient was 7 years of age. At that time, she showed 28 degrees of kyphosis from L3 to L5. Because of her cardiopulmonary status at the time, she was deemed not to be a candidate for a corrective surgical procedure and followed conservatively until the age of 13 years. At that time, her gibbus deformity was 56 degrees from L3 to L5. She had significant ventral sagittal imbalance, which in combination with her cardiopulmonary abnormalities created difficulty with ambulation. Her preoperative neurologic examination was within normal limits. The patient had an extensive history of congenital cyanotic cardiopulmonary disease. She was born with pulmonary atresia, right-sided aortic arch with mirror image branching, a large coronary sinus type atrial septal defect, and a large ventricular septal defect. She had history of multiple surgical procedures for correction of her congenital cardiopulmonary abnormalities. The patient underwent posterior L3 and L5 wedge pedicle reduction osteotomies with posterior instrumentation and fusion from L2 to S1 using pedicle screw segmental fixation. A nasogastric tube was placed after surgery. On postoperative day 7, profuse bleeding from the patient's mouth and nose developed, which subsequently ceased. Shortly afterward, she became hypotensive and tachycardic. Upper gastrointestinal endoscopy showed a large amount of blood in her stomach without an active source. Cardiac arrest then developed, and she could not be resuscitated. The autopsy findings were consistent with an arterial-esophageal fistula. RESULTS: In the reported patient, the anomalous aortic arch system provided direct contact between the aorta and the esophagus. Dense fibrous adhesions between the aorta and esophagus resulting from multiple previous thoracic surgeries also may have facilitated the development of the fistula by the nasogastric tube in this patient. CONCLUSIONS: Patients with congenital cardiac abnormalities frequently also have congenital spinal deformities. These patients may undergo spinal correction procedures requiring nasogastric intubation. Increased awareness of arterial-esophageal fistula among the spine surgery community may enhance early recognition and treatment of this potentially lethal condition.