Analyzing Panel Count Data with Informative Observation Times

In this paper, we study panel count data with informative observation times. We assume nonparametric and semiparametric proportional rate models for the underlying recurrent event process, where the form of the baseline rate function is left unspecified and a subject-specific frailty variable inflates or deflates the rate function multiplicatively. The proposed models allow the recurrent event processes and observation times to be correlated through their connections with the unobserved frailty; moreover, the distributions of both the frailty variable and observation times are considered as nuisance parameters. The baseline rate function and the regression parameters are estimated by maximizing a conditional likelihood function of observed event counts and solving estimation equations. Large sample properties of the proposed estimators are studied. Numerical studies demonstrate that the proposed estimation procedures perform well for moderate sample sizes. An application to a bladder tumor study is presented to illustrate the use of the proposed methods.

Endothelial survival factors and spatial completion, but not pericyte coverage of retinal capillaries determine vessel plasticity

Pericyte loss and capillary regression are characteristic for incipient diabetic retinopathy. Pericyte recruitment is involved in vessel maturation, and ligand-receptor systems contributing to pericyte recruitment are survival factors for endothelial cells in pericyte-free in vitro systems. We studied pericyte recruitment in relation to the susceptibility toward hyperoxia-induced vascular remodeling using the pericyte reporter X-LacZ mouse and the mouse model of retinopathy of prematurity (ROP). Pericytes were found in close proximity to vessels, both during formation of the superficial and the deep capillary layers. When exposure of mice to the ROP was delayed by 24 h, i.e., after the deep retinal layer had formed [at postnatal (p) day 8], preretinal neovascularizations were substantially diminished at p18. Mice with a delayed ROP exposure had 50% reduced avascular zones. Formation of the deep capillary layers at p8 was associated with a combined up-regulation of angiopoietin-1 and PDGF-B, while VEGF was almost unchanged during the transition from a susceptible to a resistant capillary network. Inhibition of Tie-2 function either by soluble Tie-2 or by a sulindac analog, an inhibitor of Tie-2 phosphorylation, resensitized retinal vessels to neovascularizations due to a reduction of the deep capillary network. Inhibition of Tie-2 function had no effect on pericyte recruitment. Our data indicate that the final maturation of the retinal vasculature and its resistance to regressive signals such as hyperoxia depend on the completion of the multilayer structure, in particular the deep capillary layers, and are independent of the coverage by pericytes.

Effects of various forms of calcium added to chewing gum on initial enamel carious lesions in situ

The purpose of this randomized, cross-over in situ study was to determine the effects of 4 chewing gums on artificial caries-like subsurface lesions. Two chewing gums (1 with zinc citrate and 1 without) contained dicalcium phosphate (3.9%), calcium gluconate (1.8%) and calcium lactate (0.45%), 1 chewing gum contained casein phosphopeptide-amorphous calcium phosphate nanocomplexes (0.7%), and another one contained no calcium. Fifteen subjects without current caries activity (7 male, 8 female; mean age: 27.5 +/- 2.5 years) wore removable buccal appliances in the lower jaw with 4 bovine enamel slabs with subsurface lesions. The appliances were inserted immediately before gum chewing for 20 min and then retained for an additional 20 min. This was performed 4 times per day. Every subject chewed 4 different chewing gums over 4 periods of 14 days each. During a fifth period (control) the subjects only wore the appliances without chewing gum. At completion of each period the enamel slabs were embedded, sectioned and subjected to transversal microradiography. With regard to change of mineral loss and of lesion depth no significant differences could be found between chewing gums containing calcium and calcium-free chewing gums. Moreover, the chewing gum groups and the control group did not differ significantly if adjustments were made for baseline values (p > 0.05; ANCOVA). Under the conditions of the present study it may be concluded that the use of chewing gum offers no additional remineralizing benefit to buccal tooth surfaces, even if the chewing gum contains calcium compounds.

Waiting times for cataract surgery in ten European countries: an analysis using data from the SHARE survey

AIMS: To assess waiting times for cataract surgery and their acceptance in European countries, and to find explanatory, country-specific health indicators. METHODS: Using data from the survey of health, ageing and retirement in Europe (SHARE), waiting times for cataract surgery of 245 respondents in ten countries were analysed with the help of linear regression. The influence of four country specific health indicators on waiting times was studied by multiple linear regression. The influence of waiting time and country on the wish to have surgery performed earlier was determined through logistic regression. Additional information was obtained for each country from opinion leaders in the field of cataract surgery. RESULTS: Waiting times differed significantly (p<0.001) between the ten analysed European countries. The length of wait was significantly influenced by the total expenditure on health (p<0.01) but not by the other country specific health indicators. The wish to have surgery performed earlier was determined by the length of wait (p<0.001) but not by the country where surgery was performed. CONCLUSION: The length of wait is influenced by the total expenditure on health, but not by the rate of public expenditure on health, by the physician density or by the acute bed density. The wish to have surgery performed earlier depends on the length of wait for surgery and is not influenced by the country.

Traditional Whaling Methods in Modern Times

Dr. Russell Fielding of the University of Denver discusses his study of artisanal whaling traditions throughout the Atlantic, with field sites in the Faroe Islands, Newfoundland, and the Caribbean.

Executive Reorganization: Building a State Government That Worked for People -- Tom Harrison, Diana Dowling & Sheena Wilson “In the Crucible of Change”

One of the primary accomplishments of Governor Forrest Anderson in 1969-71 was the reorganization of the Executive Branch of Montana government, something that had been attempted six different times between 1919 and 1962 as state government had grown from twenty agencies to almost 200 uncontrolled boards, bureaus and commissions. The chaotic structure of the executive branch disempowered governors of both parties and empowered the private corporations and organizations that were the power structure of Montana. With remarkable political acumen, Governor Anderson figured out how to get that near impossible job done. Central to his efforts was the creation of an Executive Reorganization Commission, including eight legislators and the Governor, the adoption of a Constitutional Amendment that limited the executive branch to no more than twenty departments under the Governor, and the timely completion of a massive research effort to delineate the actual structure of the twenty departments. That story is told in this episode by three major players in the effort, all involved directly with the Executive Reorganization Commission: Tom Harrison, Diana Dowling and Sheena Wilson. Their recollections reflect an insider’s perspective of this significant accomplishment that helped change Montana “In the Crucible of Change.” Tom Harrison is a former Republican State Representative and State Senator from Helena, who was a member of the Executive Reorganization Commission. As Majority Leader in the Montana House of Representatives in 1971, he was the primary sponsor of the House’s executive reorganization bill and helped shepherd the Senate’s version to passage. Harrison was the Republican candidate for Attorney General in 1976 after which he practiced private law for 3 more decades. He served in the Montana Army National Guard for almost 34 years, rising to the rank of Colonel in the position of Judge Advocate General. He was a founding Director of Federal Defenders of Montana (legal representation for indigents accused within the Federal Judicial System); appointed Chairman of the original Montana State Fund (workers' compensation insurance) by Gov. Stephens; served as President of the Montana Trial Lawyers Association, Helena Kiwanis Club and St. Peter's Community Hospital Foundation, as well as Chairman and Director of AAA MountainWest; and was a founder, first Chairman and Director of the Valley Bank of Helena for over 25 years. Diana Dowling was an attorney for the Executive Reorganization Commission and helped draft the legislation that was passed. She also worked for Governor Forrest Anderson and for the 1972 Constitutional Convention where she prepared and directed publication of official explanation of the new Constitution that was mailed to all Montana voters. Diana was Executive Director of the Montana Bar Association and for 20 years held various legal positions with the Montana Legislative Council. For 12 years she was a commissioner on the National Conference of Commissioners on Uniform State Laws and for 7 years was a member of Montana State Board of Bar Examiners. Diana was the first director of the Montana Lottery, an adjunct professor at both Carroll College and the UM Law School, and an administrative officer for Falcon Press Publishing Co. Diana is currently - and intends to continue being - a perpetual college student. Sheena Wilson came fresh out of the University of Montana to become a Research Assistant for the Executive Reorganization Commission. Later she worked for seven years as a field representative in Idaho and Montana for the Mountain Plains Family Education Program, for thirteen years with Congressman Pat Williams as Executive Assistant in Washington and Field Assistant here in Montana, owned and managed a Helena restaurant for seven years, worked as Executive Assistant for State Auditor John Morrison and was Deputy Chief of Staff for Governor Brian Schweitzer his full 8 years in the Governorship. Though currently “retired”, Sheena serves on the Montana Board of Investments, the Public Employees Retirement Board and the Capitol Complex Advisory Council and is a partner in a dry-land wheat farm in Teton County that was homesteaded by her great uncle.

Integrated data acquisition and processing to determine metabolite contents, relaxation times, and macromolecule baseline in single examinations of individual subjects

Absolute quantitation of clinical (1)H-MR spectra is virtually always incomplete for single subjects because the separate determination of spectrum, baseline, and transverse and longitudinal relaxation times in single subjects is prohibitively long. Integrated Processing and Acquisition of Data (IPAD) based on a combined 2-dimensional experimental and fitting strategy is suggested to substantially improve the information content from a given measurement time. A series of localized saturation-recovery spectra was recorded and combined with 2-dimensional prior-knowledge fitting to simultaneously determine metabolite T(1) (from analysis of the saturation-recovery time course), metabolite T(2) (from lineshape analysis based on metabolite and water peak shapes), macromolecular baseline (based on T(1) differences and analysis of the saturation-recovery time course), and metabolite concentrations (using prior knowledge fitting and conventional procedures of absolute standardization). The procedure was tested on metabolite solutions and applied in 25 subjects (15-78 years old). Metabolite content was comparable to previously found values. Interindividual variation was larger than intraindividual variation in repeated spectra for metabolite content as well as for some relaxation times. Relaxation times were different for various metabolite groups. Parts of the interindividual variation could be explained by significant age dependence of relaxation times.