Abstract. Objectives: To characterize the homeless adult population of an urban emergency department (ED) and study the medical, psychiatric, and social factors that contribute to homelessness. Methods: A prospective, case-control survey of all homeless adult patients presenting to an urban, tertiary care ED and a random set of non-homeless controls over an eightweek period during summer 1999. Research assistants administered a 50-item questionnaire and were trained in assessing dentition and triceps skin-fold thickness. Inclusion criteria: all homeless adults who consented to participate. Homelessness was defined as being present for any person not residing at a private address, group home, or drug treatment program. Randomly selected controls were concurrently enrolled with a 3:1 homeless:control rate. Exclusion criteria: critically ill, injured, or incapacitated patients, or patients <21 years of age. Univariate analysis with appropriate statistical tests was used. The Mantel-Haenszel test was used to adjust for population differences. Results: Two hundred fifty-two homeless subjects and 88 controls were enrolled. Data are presented for homeless vs control patients, and all p-values were <0.01. Odds ratios (ORs) with 95% confidence intervals (95% CIs) are given where appropriate: mean age (ϮSD) = 42 Ϯ 10 vs 48 Ϯ 13; male gender 95% vs 54% (OR = 17; 95% CI = 8 to 37); history of (hx) tuberculosis 49% vs 15% (OR = 2.5; 95% CI = 1.2 to 3); hx HIV infection 35% vs 13% (OR = 3.8; 95% CI = 1.8 to 8); hx penetrating trauma 62% vs 16% (OR = 8.62; 95% CI = 4.4 to 17.1); hx depression 70% vs 15% (OR = 13.4; 95% CI = 6.7 to 27); hx schizophrenia 27% vs 7% (OR = 5.1; 95% CI = 2.0 to 14); hx alcoholism 81% vs 15% (OR = 24; 95% CI = 12 to 49); significant tooth loss (>3) 43% vs 18% (OR = 3.3; 95% CI = 1.8 to 6.4); percentage of body fat 16.5% vs 19.7%; hx social isolation (no weekly social contacts) 81% vs 11% (OR = 33.3; 95% CI = 14 to 100); mean number of ED visits/year 6.0 vs 1.6. Conclusions: In the study population homelessness was associated with a history of significantly higher rates of infectious disease, ethanol and substance use, psychiatric illness, social isolation, and rates of ED utilization.

Interactions between membrane proteins and the soluble fraction are essential for signal transduction and for regulating nutrient transport. To gain insights into the membrane-based interactome, 3,852 open reading frames (ORFs) out of a target list of 8,383 representing membrane and signaling proteins from Arabidopsis thaliana were cloned into a Gateway-compatible vector. The mating-based split ubiquitin system was used to screen for potential protein–protein interactions (pPPIs) among 490 Arabidopsis ORFs. A binary robotic screen between 142 receptor-like kinases (RLKs), 72 transporters, 57 soluble protein kinases and phosphatases, 40 glycosyltransferases, 95 proteins of various functions, and 89 proteins with unknown function detected 387 out of 90,370 possible PPIs. A secondary screen confirmed 343 (of 386) pPPIs between 179 proteins, yielding a scale-free network (r2 = 0.863). Eighty of 142 transmembrane RLKs tested positive, identifying 3 homomers, 63 heteromers, and 80 pPPIs with other proteins. Thirty-one out of 142 RLK interactors (including RLKs) had previously been found to be phosphorylated; thus interactors may be substrates for respective RLKs. None of the pPPIs described here had been reported in the major interactome databases, including potential interactors of G-protein-coupled receptors, phospholipase C, and AMT ammonium transporters. Two RLKs found as putative interactors of AMT1;1 were independently confirmed using a split luciferase assay in Arabidopsis protoplasts. These RLKs may be involved in ammonium-dependent phosphorylation of the C-terminus and regulation of ammonium uptake activity. The robotic screening method established here will enable a systematic analysis of membrane protein interactions in fungi, plants and metazoa.