New catheter design and placement technique for pulmonary arteriography

An improved catheter for pulmonary arteriography via the antecubital approach is described. The catheter has been used successfully in 56 patients.     

Radioisotope renography in spinal cord injury

Isotope renography was compared to excretory urography, voiding cystourethrography and endogenous creatinine clearances in 52 spinal cord injury patients. Renogram abnormalities were detected in 86 per cent of the cases. The most common abnormality was the delay of isotope excretion from the renal cortex and pelvis. Anticholinergic medication significantly reduced these excretion delays. A subgroup containing 22 newly injured patients was evaluated separately. Renogram abnormalities in this subgroup were associated with normal excretory urography and normal creatinine clearances. We postulate that the defect producing upper tract deterioration in spinal cord injury begins early, is obstructive to renal drainage, does not increase with time and probably requires early intervention with anticholinergic medication or transurethral sphincterotomy to prevent upper tract damage.     

Placental grading in the complicated or high-risk pregnancy.

A classification of the changes seen in the placentas of nondiabetic, non-high-risk obstetrical patients, and its relationship to fetal pulmonary maturity, has been the subject of two recent reports. Successful (100 per cent) correlation has been concluded from these studies when a Grade III placenta has been demonstrated in gestations of 33 weeks to term. To determine whether the same high degree of reliability would hold for the diabetic and high-risk obstetrical patient, 78 such patients were analyzed. All except one delivered at 33 weeks to term, and all had amniotic fluid lecithin-sphingomyelin (L/S) ratio determinations within 48 hours of sonographic placental grading and within seven days of delivery. Of the Grade III placentas (n = 13), 23 per cent had "immature" L/S ratios. However, there was no case of infantile respiratory distress syndrome (IRDS) in infants of patients with Grade III placentas. These findings suggest that placental grading may need to be part of a multifactorial assessment of fetal maturity in the diabetic or high-risk pregnancy.     

INAUGURAL ARTICLE by a Recently Elected Academy Member:Bayesian metamodeling of complex biological systems across varying representations

Comprehensive modeling of a whole cell requires an integration of vast amounts of information on various aspects of the cell and its parts. To divide and conquer this task, we introduce Bayesian metamodeling, a general approach to modeling complex systems by integrating a collection of heterogeneous input models. Each input model can in principle be based on any type of data and can describe a different aspect of the modeled system using any mathematical representation, scale, and level of granularity. These input models are 1) converted to a standardized statistical representation relying on probabilistic graphical models, 2) coupled by modeling their mutual relations with the physical world, and 3) finally harmonized with respect to each other. To illustrate Bayesian metamodeling, we provide a proof-of-principle metamodel of glucose-stimulated insulin secretion by human pancreatic β-cells. The input models include a coarse-grained spatiotemporal simulation of insulin vesicle trafficking, docking, and exocytosis; a molecular network model of glucose-stimulated insulin secretion signaling; a network model of insulin metabolism; a structural model of glucagon-like peptide-1 receptor activation; a linear model of a pancreatic cell population; and ordinary differential equations for systemic postprandial insulin response. Metamodeling benefits from decentralized computing, while often producing a more accurate, precise, and complete model that contextualizes input models as well as resolves conflicting information. We anticipate Bayesian metamodeling will facilitate collaborative science by providing a framework for sharing expertise, resources, data, and models, as exemplified by the Pancreatic β-Cell Consortium.

Cells are the basic structural and functional units of life (1). Different aspects of the cell have been studied extensively, including experimentally, computationally, and theoretically. As is the case for any model, a cell model is expected to provide more information about the cell than any of the input information used for its construction. In particular, the model should rationalize known facts and make testable predictions. We consider a desired cell model and its construction by discussing a progression from an impractical atomic model, an impractical integrative model, actual current models, and finally culminating in the modeling approach proposed here.