The physiologic impact of aortic valve stenosis is most directly reflected by an increased workload placed on the ventricle. In the pediatric population the morphology of aortic stenosis varies considerably. Fluid dynamic principles suggest that different morphologies may require the ventricle to accelerate blood to different maximal velocities for constant cardiac outputs and valve areas, resulting in different ventricular workloads. This study examined this important concept in in vitro models designed to isolate the effect of valve geometry on distal velocity, pressure gradients, and proximal work. Four stenotic valve morphologies were examined using a variable-voltage pump system. For constant orifice areas and flows, markedly different workloads were required by the pump, and this difference was reflected in direct measurements of pressure gradient and Doppler predictions of gradient. These fundamental fluid dynamic studies isolate the relationship between flow, work, and stenotic valve morphology. Different orifice geometries affect the value of the coefficient of contraction, which is reflected in different maximum velocity values for stenosis with constant anatomic areas and flows. The proximal pumping chamber must generate different levels of force to achieve these different velocities, and this variability is reflected in the clinically measured pressure gradient.

Aortic Valve↗

PubMedDate not supplied

Reduced bacterial adherence to silicone plastic neurosurgical prosthesis.

Bacteria have been shown to adhere to smooth surfaces, such as shunts, by secreting a complex polysaccharide coat called the glycocalyx. We assume that if bacterial adherence could be reduced to zero, foreign-body-related infections would be essentially eliminated. This study describes a new technique for quantitating bacterial adherence to plastic using radioactive chromium, and demonstrates that presoaking the silicone plastic surgical tubing used for ventriculoperitoneal and ventriculoatrial shunts in bacitracin A solution (50,000 units in 250 ml) reduces the adherence of Staphylococcus epidermidis by 54%. We conclude that pretreatment of a hydrocephalic shunt tubing with an aqueous bacitracin solution before its implantation may help to reduce the postoperative shunt infections due to direct contamination of the shunt at the time it is inserted.

Bacitracin↗

PubMedDate not supplied

Growth regulatory factors and carcinogenesis: the roles played by transforming growth factor beta, its receptors and signaling pathways.

It is widely recognized that growth factors play critical roles in cell proliferation and differentiation. In the early 1980s, several members of the transforming growth factor-beta (TGF-beta) superfamily were identified and subsequently shown to play important roles in many diseases, in particular cancer. Efforts to understand how TGF-beta exerts its effects led to identification of TGF-beta-receptors and several downstream signaling pathways activated by this family of growth factors. This review provides an overview of TGF-beta-receptors and its downstream signaling pathways. As part of this discussion, this review indicates that inactivation of TGF-beta-receptors or components of their signaling pathways is often a target during carcinogenesis and that mutations or altered expression at any step along this complex, growth regulatory pathway can lead to aberrant cell proliferation. Lastly, the Cancer Genome Anatomy Project is briefly discussed, in particular how it may help to identify aberrant growth factor expression during carcinogenesis and improve the diagnosis of cancer patients.

Cell Cycle↗

PubMedDate not supplied

A life cycle model of continuous clinical process innovation.

The changing healthcare environment has created a sense of urgency for continuous innovation in clinical care processes. Managers and clinicians are investing unprecedented funds and energy in the development of various clinical process innovations (CPI) such as clinical pathways, electronic workstations, and various forms of information technology. While increasing attention has been paid to the development of such initiatives, our understanding of how best to disseminate and ensure their use is limited. In this first of two articles dealing with the dissemination and use of CPI in integrated delivery systems, we present a "life cycle" model of the dissemination process and suggest opportunities for managing CPI. The management of CPI requires more than just an understanding of the factors that may facilitate or impede its implementation and use. Managers require an understanding of the actual process so that they can assess the specific implementation stage at which the organization is presently operating, and design appropriate interventions that can affect the process. A future article will identify the factors that facilitate and inhibit the process and suggest some intervention strategies.

Critical Pathways↗

PubMedDate not supplied

Solitary fibrous tumor of the meninges.

The clinical, radiologic, and pathologic features of a case of solitary fibrous tumor of the meninges at the base of the brain are reported. The tumor caused clinical symptoms in a 42-year-old Caucasian male which were indicative of compression of hypothalamus, basal ganglia, and third ventricle. Radiologically it was a large extra-axial mass isointense to brain parenchyma on precontrast T1-weighted images that filled the suprasellar cistern and deformed the left cerebral peduncle. At surgery, the tumor was firm to hard and attached to dura. Histologically the tumor was composed of spindle-cell proliferation in a collagen-rich background but exhibited regional variations. CD34 immunoreactivity was a prominent histologic finding. Ultrastructural features of meningioma, such as complex interdigitation of cell processes and intercellular specialized junctions were absent. The cells showed the typical appearances of fibroblasts with proximity of banded collagen and precollagen and cytoplasmic rough-surfaced endoplasmic reticulum. DNA ploidy analysis showed diploid DNA content. Awareness of this neoplasm may lead to increasingly frequent recognition and the current WHO classification of brain neoplasms should be modified to include this new entity.

Adult↗