Development of the New Lung Allocation System in the United States

This article reviews the development of the new U.S. lung allocation system that took effect in spring 2005. In 1998, the Health Resources and Services Administration of the U.S. Department of Health and Human Services published the Organ Procurement and Transplantation Network (OPTN) Final Rule. Under the rule, which became effective in 2000, the OPTN had to demonstrate that existing allocation policies met certain conditions or change the policies to meet a range of criteria, including broader geographic sharing of organs, reducing the use of waiting time as an allocation criterion and creating equitable organ allocation systems using objective medical criteria and medical urgency to allocate donor organs for transplant. This mandate resulted in reviews of all organ allocation policies, and led to the creation of the Lung Allocation Subcommittee of the OPTN Thoracic Organ Transplantation Committee. This paper reviews the deliberations of the Subcommittee in identifying priorities for a new lung allocation system, the analyses undertaken by the OPTN and the Scientific Registry for Transplant Recipients and the evolution of a new lung allocation system that ranks candidates for lungs based on a Lung Allocation Score, incorporating waiting list and posttransplant survival probabilities.     

Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Paediatric dacryocystorhinostomy

Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease.     

Natural killer cell regulation of implantation and early lung growth of H-ras-transformed 10T1/2 fibroblasts in mice

We examined the relative role of the natural killer (NK) cell and H-ras gene in controlling metastasis formation using a novel assay for quantitating viable tumor cells entering and surviving in the lung for up to 13 days following i.v. tumor inoculation. This assay utilized the resistance to G418 sulfate conferred by transfection of the neoR gene into 10T1/2 fibroblasts along with activated H-ras. We had previously shown that the metastatic efficiency of T-24-H-ras-transformed 10T1/2 fibroblasts correlated with H-ras expression at the RNA level. In this paper we show that the NK cell could recognize H-ras-transformed fibroblasts in vivo and control experimental metastasis formation using NK-suppressed and -activated syngeneic C3H recipients. Evaluation of NK sensitivity in vitro of individual lines did not predict metastatic ability. However, NK susceptibility in vitro did inversely correlate with the ability of tumor cells to arrest and survive in the lung for the first 48 h after i.v. inoculation. Although the level of H-ras RNA correlated with the ultimate metastatic potential, it did not correlate with the initial rate of tumor cell pulmonary retention or clearing. Over the next 10 to 12 days, however, we detected a preferential survival and outgrowth of high H-ras-expressing variants, which correlated well with the ultimate metastatic ability but not NK susceptibility. These observations argue that the NK cell has its major effect early in the course of the disease, while subsequent tumor growth occurs preferentially in high H-ras-expressing cell lines.