Clinical case management: what works, what doesn't

Often, what works best depends less on a specific model, and more on choosing the right people. Two nurses were selected to role model critical path and case management principles. These clinical care coordinators focused on all involved disciplines, cost containment and quality outcomes.

Interaction between the origin recognition complex and the replication licensing system in Xenopus

The origin recognition complex (ORC) binds to origins of replication in budding yeast. We have cloned a Xenopus homolog of the largest ORC polypeptide (XORC1). Immunodepletion of XOrc1 from Xenopus egg extracts blocks the initiation of DNA replication. We have purified Xenopus ORC, consisting of a protein complex similar to yeast ORC. In Xenopus egg extracts, ORC associates with chromatin throughout G1 and S phases. RLF-M, a component of the replication licensing system, also associates with chromatin early in the cell cycle but dissociates during S phase. We show that the assembly of RLF-M onto chromatin is dependent on the presence of chromatin-bound ORC, leading to sequential assembly of initiation proteins onto replication origins during the cell cycle.

The effect of pravastatin on coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events Trial investigators

BACKGROUND

In patients with high cholesterol levels, lowering the cholesterol level reduces the risk of coronary events, but the effect of lowering cholesterol levels in the majority of patients with coronary disease, who have average levels, is less clear.

METHODS

In a double-blind trial lasting five years we administered either 40 mg of pravastatin per day or placebo to 4159 patients (3583 men and 576 women) with myocardial infarction who had plasma total cholesterol levels below 240 mg per deciliter (mean, 209) and low-density lipoprotein (LDL) cholesterol levels of 115 to 174 mg per deciliter (mean, 139). The primary end point was a fatal coronary event or a nonfatal myocardial infarction.

RESULTS

The frequency of the primary end point was 10.2 percent in the pravastatin group and 13.2 percent in the placebo group, an absolute difference of 3 percentage points and a 24 percent reduction in risk (95 percent confidence interval, 9 to 36 percent; P = 0.003). Coronary bypass surgery was needed in 7.5 percent of the patients in the pravastatin group and 10 percent of those in the placebo group, a 26 percent reduction (P=0.005), and coronary angioplasty was needed in 8.3 percent of the pravastatin group and 10.5 percent of the placebo group, a 23 percent reduction (P=0.01). The frequency of stroke was reduced by 31 percent (P=0.03). There were no significant differences in overall mortality or mortality from noncardiovascular causes. Pravastatin lowered the rate of coronary events more among women than among men. The reduction in coronary events was also greater in patients with higher pretreatment levels of LDL cholesterol.

CONCLUSIONS

These results demonstrate that the benefit of cholesterol-lowering therapy extends to the majority of patients with coronary disease who have average cholesterol levels.

Dental caries and tooth loss in adolescents with early-onset periodontitis

The aim of this study was to assess the caries experience and tooth loss over 6 years in subjects with early-onset periodontitis as compared to their matched controls, and to describe the characteristics of teeth lost during this period. A multi-stage probability sample representing 8th to 12th grade U.S. schoolchildren were screened during the 1986/1987 school year to identify subjects with early-onset periodontitis (cases). The examination included measuring the clinical attachment level, presence of caries and dental restorations, and tooth loss. A random sample of controls without early-onset periodontitis were selected for a follow-up examination and were matched to cases on gender, race, age, and geographic location. A total of 266 subjects, with a mean age of 16 years at baseline, were examined during the 1992/1993 school year and were classified into localized (LJP) and generalized juvenile periodontitis (GJP), incidental attachment loss (IAL), and control groups. Whites had more caries experience than Blacks and Hispanics, but there were no significant differences in tooth loss between the ethnic groups. The LJP and the IAL groups, respectively, had higher and lower overall caries experience than the control group. The LJP group had a significantly higher number of missing teeth at follow-up, and exhibited more extensive tooth mortality during 6 years than the control group. The GJP group also showed more tooth loss than the control group, but the difference was not statistically significant. In the LJP, GJP, IAL, and control groups, respectively, 43%, 32%, 26%, and 18% of the subjects lost teeth over 6 years due to disease. The findings showed differences in caries activity between the early-onset periodontitis groups and a variation by race. The findings suggest that loss of periodontal support was the principal cause for tooth loss in the LJP and GJP groups, and that dental caries was the principal cause for tooth extraction in the IAL and the control groups.

Gingival state and dental calculus in early-onset periodontitis

This study was undertaken to 1) compare the prevalence of gingival inflammation and dental calculus in adolescents with early-onset periodontitis and their matched controls and 2) assess and compare the relationship between the presence of dental calculus and the extent of gingival bleeding and attachment loss in these subjects. The study group consisted of 1,285 13 to 20 year-old individuals, 651 males and 634 females, selected from a national survey of the oral health of U.S. adolescents in 1986/1987. It included 709 (55.2%) Blacks, 224 (17.4%) Hispanics, and 352 (27.4%) Whites. Eighty-nine subjects had localized or generalized juvenile periodontitis (JP), 218 had incidental attachment loss (IAL), and 978 were without clinical attachment loss (controls). The controls were matched to cases on gender, race, age, and geographic location. The subjects were examined clinically to assess the percentage of sites with gingival bleeding and supragingival calculus only and subgingival calculus with or without supragingival calculus. The IAL and JP groups had significantly more gingival bleeding and subgingival calculus than the controls. Also, the JP group had significantly higher prevalence of both conditions than the IAL group. The percentage of sites with supragingival calculus was not different between the groups, but varied by ethnicity. Hispanics with JP had the highest percentage of sites with gingival bleeding and subgingival calculus, and the lowest percentage of sites with only supragingival calculus. The results demonstrate that gingival inflammation and subgingival calculus are associated with early periodontal breakdown, and contradict earlier reports of early-onset periodontitis not being associated with these factors.

Early-onset periodontitis: progression of attachment loss during 6 years

We studied the pattern of progression of early-onset periodontitis and the change in the extent and severity of the periodontal condition in adolescents who were followed for 6 years. In a national survey of the oral health of U.S. children, 14,013 adolescents were examined clinically in 1986/1987 to assess the periodontal attachment loss of teeth. Individuals with early-onset periodontitis within this population were identified and classified into localized juvenile periodontitis (LJP), generalized juvenile periodontitis (GJP), and incidental attachment loss (IAL) groups. Ninety-one subjects, 13 to 20 years old at baseline, were examined 6 years later. They included 51 males and 40 females; and 72 Blacks, 6 Hispanics, and 13 Whites. They were clinically re-examined and then reclassified according to their periodontal status at follow-up. The severity and extent of these diseases continued to increase during the study period. In teeth that were affected at baseline, the lesions had progressed to include deeper portions of the periodontium, and more of the teeth unaffected at baseline exhibited periodontal attachment loss at follow-up, thus changing the disease characteristics and the basis for the clinical classification. Of the individuals classified with LJP at baseline, 62% continued to have LJP 6 years later and 35% developed GJP. Of those classified with GJP initially, all but two (82%) continued to have GJP at follow-up. Among the IAL group, 28% of subjects developed LJP or GJP, and 30% were reclassified in the no attachment loss group. Molars and incisors were the teeth most often affected in all three groups. The mean change in attachment loss over 6 years in the LJP, GJP, and IAL groups was 0.45, 1.12, and 0.13 mm, respectively. The present findings demonstrate the limitations of the currently used morphological criteria in the classification of early-onset periodontitis. The findings also suggest that the difference between LJP and GJP is in the number and type of teeth involved, and that the two classifications progress similarly, with some cases of LJP developing into GJP.

Cardiac and vascular responses of isolated rat tissues treated with diterpenes from Sinularia flexibilis (coelenterata: octocorallia)

The marine environment is a rich source of compounds with cardiovascular activity. This study characterizes the cardiac and vascular responses in isolated rat tissues of flexibilide, dihydroflexibilide and sinulariolide, three diterpenes isolated from the soft coral Sinularia flexibilis. On rat left ventricular papillary muscles, dihydroflexibilide and flexibilide showed similar potencies (-log EC50 = 4.69 +/- 0.05 and 4.66 +/- 0.06, respectively); the maximal response to dihydroflexibilide of 1.4 +/- 0.2 mN was 35 +/- 7% that of calcium chloride in the same muscles. All diterpenes relaxed rat thoracic aortic rings precontracted with KC1 (100 mM) with similar potencies (flexibilide, -log EC50 = 4.17 +/- 0.06). Flexibilide was further characterized and shown to increase force in isolated rat left atria by 0.8 +/- 0.5 mN at 1 x 10(-4) M, to increase rate of contraction in isolated rat right atria by 18 +/- 5 beta/min at 3 x 10(-5) M and to completely relax endothelium-denuded rat thoracic aortic rings (-log EC50 = 4.14 +/- 0.05). Toxicity as indicated by the occurrence of ectopic beats was not observed with the diterpenes at concentrations which produced complete relaxation of blood vessels, maximal positive inotropic activity and minor positive chronotropic responses. Thus, these compounds may be useful lead compounds in the search for improved treatment of cardiovascular disease, especially heart failure.

Dental caries, restoration and tooth conditions in U.S. adults, 1988-1991. Selected findings from the Third National Health and Nutrition Examination Survey

This article provides estimates of dental caries experience and selected restorative and tooth conditions among U.S. adults, obtained from Phase 1 (1988-1991) of the Third National Health and Nutrition Examination Survey. Between 1988 and 1991, 94 percent of adults in the United States showed evidence of past or present coronal caries. Based on the data collected, the authors estimate that about 40.5 percent, or 61.6 million, dentate adults had at least one tooth or tooth space that could potentially benefit from professional treatment. Minimally, it is estimated that 135.6 million tooth or tooth spaces among U.S. adults may benefit from professional treatment. These estimates supplement information available from the DMF index to provide a broader profile of the impact of dental caries on permanent tooth of U.S. adults.

Unravelling the familial tendency to aneurysmal disease: popliteal aneurysm, hypertension and fibrillin genotype

PURPOSE

To screen patients with abdominal aortic aneurysm for popliteal aneurysm and investigate cardiovascular and genetic risk factors associated with aneurysmal disease at more than one site (generalised aneurysmal disease). SUBJECTS, DESIGN AND SETTING: All patients referred to the Regional Vascular Surgical Service at Charing Cross Hospital with unruptured abdominal aortic aneurysm between 1989 and 1993 were screened for popliteal aneurysms, using ultrasonography.

MAIN OUTCOME MEASURES

Palpation of a popliteal aneurysm or ultrasonographic detection of popliteal dilatation, where the ratio maximum popliteal fossa diameter/suprageniculate popliteal diameter was > or = 1.5, in relation to cardiovascular and genetic risk factors.

RESULTS

Clinical examination detected popliteal aneurysms in only 11/232 patients (5%), but ultrasonography demonstrated the presence of popliteal aneurysm in a further 13 patients, 24/232 in total (10%). Multivariate regression identified four independent factors associated with popliteal dilatation disease: age (p = 0.046), height (p = 0.006), systolic hypertension (p = 0.037) and triglyceride concentration (p = 0.009). Generalised aneurysmal disease and systolic blood pressure were associated with polymorphic variation in the fibrillin-1 gene, but not with variations in the apolipoprotein B and type III collagen genes.

CONCLUSIONS

Few patients with abdominal aortic aneurysm (10%) also have popliteal aneurysms: the risk of popliteal dilatation increases with age, height, systolic blood pressure, triglyceride concentration and fibrillin genotype. The strong interaction between fibrillin genotype and blood pressure may contribute to the familial tendency to aortic aneurysm.

Efficient translation of the RpoS sigma factor in Salmonella typhimurium requires host factor I, an RNA-binding protein encoded by the hfq gene

The RpoS transcription factor (also called sigma Sor sigma 38) is required for the expression of a number of stationary-phase and osmotically inducible genes in Escherichia coli. RpoS is also a virulence factor for several pathogenic bacteria, including Salmonella typhimurium. The activity of RpoS is regulated in response to several different signals, at the transcriptional and translational levels as well as by proteolysis. Here we report that host factor I (HF-I), the product of the hfq gene, is required for efficient expression of rpoS in S. typhimurium. HF-I is a small, heat-stable, site-specific RNA-binding protein originally characterized for its role in replication of the RNA bacteriophage Q beta of E. coli. Its role in the uninfected bacterial cell has previously been unknown. Assays of Beta-galactosidase in strains with rpoS-lac fusions, Western blot (immunoblot) analysis, and pulse-labeling and immunoprecipitation of both fusion proteins and native RpoS show that an S. typhimurium hfq mutant has a four- to sevenfold reduction in expression of rpoS that is attributable primarily to a defect in translation. These results add a new level of complexity to the regulation of RpoS activity.

Islet cell antibodies and antibodies against glutamic acid decarboxylase in newly diagnosed adult-onset diabetes mellitus

This study aimed to determine the prevalence of antibodies against glutamic acid decarboxylase (anti-GAD) and islet cell antibodies (ICA) in relation to beta-cell function in adults newly-diagnosed with diabetes mellitus. beta-cell function was assessed in adults aged 25-70 years newly-diagnosed with diabetes mellitus (n = 84) and control subjects (n = 34) using a 1.6 MJ mixed meal test procedure. beta-cell function was evaluated by the true insulin (defined as immunoreactive insulin minus proinsulin) response to the mixed meal test. Subjects were classified on the basis of the area under the true insulin curve (normal 16830-107700 pmol min/I) and the sum of the 30 and 60 min incremental response (normal 285-3295 pmol/I). The prevalence of anti-GAD and ICA was determined using radioimmunoprecipitation and indirect immunofluorescence, respectively. Twelve (14%) of the study cohort were insulin deficient showing little or no true insulin release. Of the insulin deficient individuals, seven (58%) subjects were anti-GAD antibody positive, compared with eleven (15%) of the subjects without insulin deficiency (P < 0.001). Seven (58%) insulin deficient subjects were ICA positive, whereas only two (3%) non-insulin deficient subjects were ICA positive (P < 0.001). Eight (67%) of the insulin deficient individuals had anti-GAD or ICA, compared with twelve (17%) of those who were not insulin deficient (P < 0.001). The positive predictive values for insulin deficiency of anti-GAD and ICA were 39 and 78% respectively. The sensitivity of both antibodies for detecting insulin deficiency was 50%. The specificity for detecting insulin deficiency was 85% for anti-GAD and 97% for ICA. Positivity for both anti-GAD and ICA gave a specificity and positive predictive value for insulin deficiency of 99%, and a sensitivity of 50%. Nearly one in seven adults presenting with diabetes mellitus as a new diagnosis are insulin deficient using our criteria. Loss of beta-cell function in two thirds of individuals who are insulin deficient can be identified by anti-GAD and ICA. Early detection of these immune markers of beta-cell damage creates the potential for immune modulation to limit such damage.

Duration of protection from clinical hepatitis A disease after vaccination with VAQTA

Recent papers examining the expected persistence of anti-hepatitis A virus antibody following vaccination with inactivated hepatitis A vaccine have estimated that geometric mean antibody levels will remain above cut-off levels for 10-30 years. However, the methodology used in these papers did not take into account any estimates of variability between subjects. In this paper data from the persistence of antibody after the administration of another vaccine, VAQTA (hepatitis A vaccine, inactivated; MSD), were used to develop further models of antibody decay. Using individual subject estimates instead of group means allowed the estimation of time to negativity for various percentiles of the population (including the median), and the construction of confidence intervals on estimates of time to negativity. Data from studies of subjects who seroreverted to negativity, and subsequently received a booster dose, were also considered to show that subjects who lose detectable antibody are likely to remain protected from hepatitis A disease by persistent immune memory and rapid anamnestic response soon after exposure to hepatitis A virus. The estimates of duration of protection suggest that VAQTA will provide protection for many years, first through presence of antibody and further through an anamnestic response based on persistent immune memory.

Structural organization and mapping of the human mitochondrial glycerol phosphate dehydrogenase-encoding gene and pseudogene

Mitochondrial glycerol phosphate dehydrogenase (mtGPD) is the rate-limiting enzyme in the glycerol phosphate shuttle, which is thought to play an important role in cells that require an active glycolytic pathway. Abnormalities in mtGPD have been proposed as a potential cause for non-insulin-dependent diabetes mellitus. To facilitate genetic studies, we have isolated genomic clones containing the coding regions of the human mtGPD-encoding gene (GPDM). The gene contains 17 exons and is estimated to span more than 80 kb. All splice junctions contain GT/AG consensus sequences. Introns interrupt the sequences encoding the leader peptide, the FAD-binding site, the calcium-binding regions, and a conserved central element postulated to play a role in glycerol phosphate binding. Fluorescence in situ hybridization was used to map this gene to chromosome 2, band q24.1. A retropseudogene was identified and mapped to chromosome 17.

Self-reported changes in capillary glucose and insulin requirements during the menstrual cycle

Perimenstrual changes in glycaemic control and insulin requirements have been reported in Type 1 diabetes. A population-based sample of 124 women with Type 1 diabetes, aged 18 to 40 years, were questioned regarding perimenstrual changes in their self-monitored capillary blood glucose and insulin regimen. Sixty-one percent of women noted perimenstrual changes in capillary blood glucose. The commonest pattern was a premenstrual rise in glucose. Thirty-six percent of all study participants were making adjustments to their insulin dose in response to these changes in capillary blood glucose. There was no statistical difference in the mean glycated haemoglobin of subjects making perimenstrual adjustments in insulin (79.1 mmol mol-1 haem) compared to subjects who noted cyclical capillary glucose changes but did not adjust insulin (73.0 mmol mol-1 haem). Sixty-seven percent of subjects taking the fixed dose oestrogen/progesterone oral contraceptive pill (OCP) noted perimenstrual changes in glucose. In summary, a third of the women surveyed made perimenstrual adjustments to their insulin dose, but there was no evidence to suggest that this behaviour was associated with improved glycaemic control. Use of the fixed dose combined oral contraceptive pill did not eliminate perimenstrual changes in glucose.

Mitochondrial FAD-glycerophosphate dehydrogenase and G-protein-coupled inwardly rectifying K+ channel: No evidence for linkage in maturity-onset diabetes of the young or NIDDM

Two genes that have potentially important regulatory roles in insulin secretion are both located on chromosome 2q24.1. G-protein-coupled muscarinic potassium channel (GIRK1) is an inwardly rectifying K+ channel that helps to maintain the resting potential and excitability of cells. Mitochondrial FAD-linked glycerophosphate dehydrogenase (m-GDH) catalyzes a rate-limiting step of the glycerol phosphate shuttle in pancreatic islets. Reduced m-GDH activity has been demonstrated in islets isolated from diabetic subjects compared with islets from nondiabetic control subjects and from the diabetic GK rat. To study the relationship between these candidate genes and NIDDM, we have examined a simple tandem-repeat polymorphism (STRP) close to both the KCN J3 (GIRK1) locus and the m-GDH locus. In a linkage study of three maturity-onset diabetes of the young (MODY) pedigrees, not linked to MODY1, MODY2, or MODY3, a cumulative score of - 9.6 at a recombination fraction of theta = 0 excluded linkage. In a population-association study, no linkage disequilibrium for the STRP was found between 190 unselected NIDDM patients and 60 geographically and age-matched white nondiabetic subjects (chi2 = 1.51 on 3 df, P = 0.68). Thus, mutations involving the genes for GIRK1 or FAD-glycerophosphate dehydrogenase are unlikely to cause MODY, and a common mutation in either gene is unlikely to contribute to NIDDM in whites. These data do not exclude mutations in some families or other ethnic groups.

Neuropsychiatry of 18q- syndrome

Our understanding of neuropsychiatric abnormalities in patients with deletions of the long arm of chromosome 18 (18q- syndrome) is based mainly on sporadic case reports. We characterized the neuropsychiatric phenotype in 27 patients across a wide age range (2-47 years) with breakpoints ranging from 18q22.3-18q21.2. Adaptive behavior scores (Vineland Composite) were significantly higher in females than in males (62 +/- 5 vs. 43 +/- 3). Intelligence ranged from borderline to severely deficient (IQ, 73- < 40), with academic achievement similarly impaired. Performance in specific neuropsychological functions, including attention, novel problem solving, memory, language, visuomotor integration, and fine motor dexterity, was consistently in the moderately-to-severely impaired range. Behavioral problems were common in both sexes, including aggressivity, hyperactivity, and temper tantrums. Contrary to the few previous reports, we found no evidence of psychosis in any patients. In a subset of patients selected on the basis of no prior knowledge of behavioral problems, 1 of 16 patients (6%) had autism, as defined by the Autistic Diagnostic Interview--Revised (ADI-R) [Lord et al., 1994: J Autism Dev Disord 24:659-685]. Thus, the prevalence of autism in 18q- syndrome is probably no greater than that in other developmental disabilities with a similar level of cognitive impairment. In contrast to what has been believed since 18q- was first described 30 years ago, we found no relationship between chromosome deletion size and any measure of cognition or behavior; nor were there any correlations between any of these measures with the presence or absence of abnormalities on MRI or somatosensory-evoked potentials.

Profile of postdischarge rehospitalizations and acute care visits for seven patient groups

The study's purpose was to examine postdischarge rehospitalizations and acute care visits in seven high risk, high volume, high-cost patient groups. Subjects were drawn from an urban tertiary teaching hospital. The total sample (N = 764) consisted of seven patient groups (drawn from five randomized clinical trials): very low birthweight (VLBW) infants (n = 79); women post-unplanned cesarean birth (n = 122) and their infants (n = 123); pregnant women with diabetes (n = 55); women post-hysterectomy surgery (n = 109); and elderly with medical cardiac Diagnostic Related Groups (DRGs) (n = 142) and elderly with surgical cardiac DRGs (n = 134). The VLBW infant and pregnant diabetic groups were predominantly African American, the elderly and hysterectomy groups predominantly Caucasian, and the cesarean group almost equally distributed. The lowest rate of rehospitalization (2%) occurred in the cesarean group, the highest (35%) in the pregnant diabetics. In four groups (cesarean and infants, hysterectomy and surgical elderly), 60%-100% of the rehospitalizations occurred within 4 weeks of discharge. Subjects requiring acute care visits ranged from 13% (hysterectomy) to 82% (VLBW infants). Acute care visits demonstrated greater distribution throughout the follow-up periods but also tended to concentrate in the first 4 weeks postdischarge.

Lifestyle, environmental pollution and lung cancer in cities of Liaoning in northeastern China

Several studies were conducted in cities of Liaoning Province, one of the areas of China with heavy concentrations of industry, to investigate the effects of life-style factors and environmental pollutants on lung cancer causation. A case-control study involving 1249 lung cancer patients and 1345 population-based controls was conducted in 1985-1988 in Shenyang, the capital of Liaoning. Cigarette smoking was found to be the principal cause of lung cancer in this population, accounting for 55% of the disease in males and 37% in females. There was also a significant increase in lung cancer risk associated with an overall index of indoor air pollution due to coal-burning emission. The population attributable risk (PAR) for indoor air pollution was 13% for males and 17% for females. Risks were significantly increased for workers in the non-ferrous smelter (odds ratio (OR) = 2.6, 95% CI, 1.3-5.1), chemical and drug manufacturing (OR = 3.0, 95% CI, 1.0-8.0), and the glass and pottery industry (OR = 1.6, 95% CI, 1.0-2.5). Studies in the Anshan Iron-Steel Complex showed a significant excess of lung cancer for workers exposed to a variety of dusts. A standardized proportional mortality ratio (SPMR) study of 8887 deaths during 1980-1989 among male workers of the complex indicated a 37% excess risk of lung cancer compared to residents of the city. A nested case-control study was then conducted in that complex. A total of 610 cases of lung cancer diagnosed during 1987-1993 and 959 randomly selected controls from 196 993 active and retired employees of the complex were interviewed. Historical monitoring records for dust and benzo(a)pyrene (B(a)P) were collected from 1956-1992 to calculate cumulative exposure for each person. Results suggested that risks were increased for all occupations in which there was exposure to dusts, with the highest risks seen among coke oven workers (OR = 3.5, 95% CI, 2.0-6.4) and fire-resistant brick makers (OR = 2.9, 95% CI, 1.9-4.4). Significant dose-response patterns between cumulative total dust, cumulative total B(a)P and lung cancer risk were observed. The findings suggest that smoking and environmental pollution combine to account for elevated rates of lung cancer in cities of northeastern China.

Development of a skin model based on insoluble fibrillar collagen

A biocompatible, 3-dimensional, noncontracting, crosslinked collagen matrix was adapted to promote differentiation of epidermal keratinocytes. To produce the matrix, a 3% wt/wt dispersion of insoluble bovine collagen containing 5 mg polylysine/g collagen in 0.001 N HCl was blended, lyophilized, and crosslinked using a dehydrothermal technique. Matrices 4 cm2 and 3 mm thick were seeded with human dermal fibroblasts (1 x 10(5)/cm2). After 5 days in culture, the matrices were seeded with human epidermal keratinocytes (1 x 10(5)/cm2). The cultures were grown submerged for 1 week and raised to the liquid/air interface for 3 weeks to promote epidermal differentiation. Based on morphology and immunological staining with antibodies for human involucrin, keratin 1 (k1), filaggrin, and loricrin, the state of differentiation of the epidermal layer was nearly equivalent to that seen with cultures grown on contracted collagen lattices produced according to the methodology described in the literature and similar to the pattern produced in normal neonatal foreskin. These results demonstrate the usefulness of an in vitro skin model employing a crosslinked collagen matrix that permits the incorporation of additional covalently linked bioactive molecules during matrix formation.