Higher Urea Levels Research Articles

Treatment of hyponatraemia by urea decreases risks of brain complications in rats. Brain osmolyte contents analysis

Brain damage (myelinolysis) develops in hyponatraemia after a large increase in serum sodium regardless of the currently available methods of correction. However, a preliminary study suggests that treatment of hyponatraemia with urea limits the risks of brain lesions in rats. Benefits of sustained high blood levels of urea and mechanisms of protection remain hypothetical. In the first part of the study, hyponatraemic rats received repeated (i.p.) doses of urea (2 g/kg b.w./6 h) leading to sustained blood levels (urea+/-230 mg/dl). Neurologic outcome was compared to correction of hyponatraemia by water diuresis. In the second part of the study, we analysed the adaptative response of the brain to correction of hyponatraemia with either urea or water diuresis, by measurement of cerebral osmolyte contents. Despite a large correction of the serum sodium (mean Delta SNa=32 mEq/l/24 h), mortality rate (13%) and neurological symptoms were low in the urea-treated group contrary to control groups treated by water diuresis (mortality: 87%). This shows with stronger evidence the protective effect of urea against brain myelinolysis. In the second part, analysis of brain composition shows that, in the urea groups, 24 h after correction, intracerebral hyperionization (NaCl) was avoided and brain water contents remained normal. No significant changes of the major brain organic osmolyte composition were observed after urea administration except reaccumulation of betaine. No difference in brain composition was noted regarding concomitant plasma urea levels (>or<150 mg/dl). In rats treated by water diuresis, the brain remained also significantly depleted in organic osmolytes 24 h after correction, but contrary to administration of urea, this treatment was associated with a high mortality rate. These comparative results suggest a specific brain-protective effect of urea itself against myelinolysis.

Fertility parameters in lactating Mediterranean buffaloes fed two different diets

The aim of this study was to evaluate the effects of two different diets on fertility rate in 64 Mediterranean buffalo cows. The animals were divided in two groups: Group S (n=32) received a total mixed ration based on haysilage of Italian ryegrass (Lolium multiflorum), hay and concentrates, whereas group H (n=32) was fed only hay and concentrates. Both diets consisted of 50-55 % forages and 45-50 % concentrates and contained 0.91 MFU/kg dry matter (DM) and 16% crude protein/DM. From February until September the cows were located together with bulls and pregnancy diagnosis was performed monthly. Furthermore, blood and milk samples were monthly collected on 20 animals in each group. Statistical analysis was performed by χ2 and t Student tests. A higher fertility rate was recorded in group H vs. group S (100 vs. 78.1%, respectively; P<0.05). Furthermore, higher blood and milk urea levels were recorded in group S during the first months of the trial (respectively 10.8 vs. 9.6 mmol L-1; P<0.01 and 55.4 vs. 50.6 mg/dl; P<0.05). It can be hypothesized that the higher levels of urea in group S may have affected the reproductive performances of the animals, increasing the nitrogen concentration in the uterus.

Expression of the urease gene of Agaricus bisporus: a tool for studying fruit body formation and post-harvest development

Fruit body initials of Agaricus bisporus contain high levels of urea, which decrease in the following developmental stages until stage 4 (harvest) when urea levels increase again. At storage, the high urea content may affect the quality of the mushroom, i.e. by the formation of ammonia from urea through the action of urease (EC 3.5.1.5). Despite the abundance of urea in the edible mushroom A. bisporus, little is known about its physiological role. The urease gene of A. bisporus and its promoter region were identified and cloned. The coding part of the genomic DNA was interrupted by nine introns as confirmed by cDNA analysis. The first full homobasidiomycete urease protein sequence obtained comprised 838 amino acids (molecular mass 90,694 Da, pI 5.8). An alignment with fungal, plant and bacterial ureases revealed a high conservation. The expression of the urease gene, measured by Northern analyses, was studied both during normal development of fruit bodies and during post-harvest senescence. Expression in normal development was significantly up-regulated in developmental stages 5 and 6. During post-harvest senescence, the expression of urease was mainly observed in the stipe tissue; expression decreased on the first day and remained at a basal level through the remaining sampling period.

The determination of urea in wine – a review

The concentration of urea in wine is not routinely measured in Australian laboratories, but has been examined in studies of yeast metabolism and the formation of ethyl carbamate, a known carcinogen. For alcoholic beverages that may contain high levels of urea, steps have been taken to reduce the concentration of urea and therefore prevent ethyl carbamate production. Methods for the determination of urea in wine can be grouped into three categories that indicate how selectivity for urea is achieved; those based on colour-forming reactions, enzymatic hydrolysis and chromatographic separation. The two dominant methods used by research groups over the past fifteen years for the determination of urea in wine are based on the urea/ammonia test kit available from Boeringer Mannheim/R-Biopharm and the reaction of urea with 1-phenyl-1,2-propanedione-2-oxime; both are time-consuming and labour-intensive, but involve relatively straightforward and well-established procedures. However, other options are available that may be better suited to the desired application and the instrumentation available in any particular laboratory.

O papel da avaliação inicial simplificada no prognóstico da pancreatite aguda

OBJETIVO: Correlacionar a avaliação clínico-laboratorial inicial simplificada com a gravidade da pancreatite aguda e a presença de necrose. MÉTODO: Foi realizado um estudo retrospectivo dos pacientes com diagnóstico final de PA internados no Hospital Universitário Clementino Fraga Filho - UFRJ entre janeiro de 1990 e agosto de 2002. Foi considerado apenas o primeiro episódio de cada paciente. Os dados obtidos foram submetidos a análise estatística. Foram estudados 164 pacientes onde a idade média foi de 43,7 anos. RESULTADOS: A etiologia biliar foi a mais freqüente com 43,9% dos casos. A incidência de necrose foi de 21,3% e a mortalidade global de 23,2%. Observamos que a ausência de taquicardia na admissão estava associada à forma branda da doença, e que os níveis plasmáticos de uréia e creatinina elevados na admissão estão associados à forma grave da doença, e a hiperglicemia (121mg/dl) à necrose pancreática. CONCLUSÕES: A avaliação inicial simplificada ainda tem espaço, embora que limitado, no acompanhamento do paciente com PA.

Neonatal urinary ascites in renal candidal infection

A preterm neonate developed anuria and abdominal distension. Peritoneal fluid contained high levels of potassium, urea and creatinine with a low level of bicarbonate compared with plasma. Renal ultrasound showed dilatation of the left collecting system with echogenic material in the calyces bilaterally, which together with positive cultures of candida from blood, urine and peritoneal fluid suggested renal candidiasis with obstruction. Computed tomography (CT) showed extravasation around the right kidney on delayed post contrast films, confirming that the peritoneal fluid was urine. The patient improved rapidly after insertion of the peritoneal drain and made a full recovery with antifungal agents and a left nephrostomy. Causes of urinary ascites are discussed and characteristic biochemical features described. Ultrasound and contrast CT may be diagnostic and help to monitor progress.

ELASMOBRANCHS BALANCE UREA

![Figure][1] For most creatures, urea is a nasty toxin best got rid of, but for many elasmobranchs, it keeps them in balance with their salty environment. Yet despite this apparently amicable relationship, high tissue levels of urea still have nasty side effects on proteins. Jason Treberg in

Differentiation of human embryonic stem cells into hepatocytes in 2D and 3D culture systems in vitro

Human embryonic stem cells (hESCs) have enormous potential as a source of cells for cell replacement therapies and as a model for early human development. In this study we examined the differentiating potential of hESCs into hepatocytes in two- and three-dimensional (2D and 3D) culture systems. Embryoid bodies (EBs) were inserted into a collagen scaffold 3D culture system or cultured on collagen-coated dishes and stimulated with exogenous growth factors to induce hepatic histogenesis. Immunofluorescence analysis revealed the expression of albumin (ALB) and cytokeratin-18 (CK-18). The differentiated cells in 2D and 3D culture system displayed several characteristics of hepatocytes, including expression of transthyretin, alpha-1-antitrypsin, cytokeratin 8, 18, 19, tryptophan-2,3-dioxygenase, tyrosine aminotransferase, glucose-6-phosphatase (G6P), cytochrome P450 subunits 7a1 and secretion of alpha-fetoprotein (AFP) and ALB and production of urea. In 3D culture, ALB and G6P were detected earlier and higher levels of urea and AFP were produced, when compared with 2D culture. Electron microscopy of differentiated hESCs showed hepatocyte-like ultrastructure, including glycogon granules, well-developed Golgi apparatuses, rough and smooth endoplasmic reticuli and intercellular canaliculi. The differentiation of hESCs into hepatocyte-like cells within 3D collagen scaffolds containing exogenous growth factors, gives rise to cells displaying morphological features, gene expression patterns and metabolic activities characteristic of hepatocytes and may provide a source of differentiated cells for treatment of liver diseases.

Relationship of body condition score and blood urea and ammonia to pregnancy in Italian Mediterranean buffaloes

The relationship of body condition score (BCS) and blood urea and ammonia to pregnancy outcome was examined in Italian Mediterranean Buffalo cows mated by AI. The study was conducted on 150 buffaloes at 145 +/- 83 days in milk that were fed a diet comprising 14.8% crude protein, 0.9 milk forage units.kg-1 dry matter and a non-structural carbohydrate/crude protein ratio of 2.14. The stage of the oestrous cycle was synchronised by the Ovsynch-TAI programme and blood urea and ammonia levels were assessed on the day of AI. Energy corrected milk (ECM) production and BCS were recorded bi-weekly. The pregnancy risk was 46.7% and was slightly lower in buffaloes with BCS < 6.0 and BCS > 7.5. There were no significant differences in ECM, urea and ammonia between pregnant and non-pregnant buffaloes. However, pregnancy outcome was higher (P = 0.02) in buffaloes with blood urea < 6.83 mmol.L-1. The likelihood of pregnancy for buffaloes with low urea blood level was 2.6 greater than for high urea level and exposure to a high urea level lowered the probability of pregnancy by about 0.25. The findings indicate that buffaloes are similar to cattle and increased blood levels of urea are associated with reduced fertility when animals are mated by AI.

Mesenteric infarction: an analysis of 83 patients with prognostic studies in 44 cases undergoing a massive small-bowel resection.

A series is presented of 83 patients surgically explored for massive bowel infarction. Old men with previous heart disease and symptoms of peripheral atherosclerosis were primarily affected. Clinical presenting features were abdominal pain (100 per cent), peritonitis (57 per cent), shock (34 per cent) and hypothermia (26 per cent). A third-space syndrome with metabolic acidosis and uraemia was the most common physiological derangement. Age was the only factor that appeared to have influenced the surgeon's decision to perform massive bowel resection (71 years in non-resected versus 64 years in resected patients, P less than 0.006). The overall mortality rate was 71 per cent. Forty-four patients underwent massive bowel resection (mean length of remaining small bowel 60 +/- 40 cm) and twenty-four (54 per cent) survived the procedure. Axillary temperature was higher in survivors (36.7 degrees C versus 36.1 degrees C, P less than 0.03). Early postoperative total plasma protein and albumin concentrations were also higher in survivors (57 versus 46 g/l, P less than 0.005; 27 versus 22 g/l, P less than 0.02). Patients with previous symptoms of atherosclerotic disease and high pre-operative blood urea levels also had a bad prognosis. Survivors had a mean hospital stay of 57 days and parenteral nutrition had to be maintained for a mean of 34 days. The survival rate achieved with massive resection justifies this surgical approach in selected patients with massive bowel infarction.

The effect of body condition score on blood metabolites and hormonal profiles in ewes

The study was designed to investigate the effect of body condition score (BCS) on blood metabolites and hormones in order to assess the nutritional status and to identify which of those metabolites could be used as indicators for determining the nutritional status in ewes. Blood sampling and nitrogen balances were performed in four groups of five mature, dry and non-pregnant ewes with a different BCS namely: 1.25, 2, 3 or 4. Serum concentrations of insulin, non-esterified fatty acids, β-hydroxybutyrate, triglycerides, total lipids, albumin, globulins, total protein, urea, creatinine, insulin-like growth factor-I, and plasma glucose, glucagon, triiodothyronine, and thyroxine concentrations were determined. Results demonstrate a variation in metabolic status at the different BCSs. Undernutrition was more evident in the animals with a BCS of 1.25 but also in those with a BCS of 2. Ewes recorded lower plasma glucose, triiodothyronine and thyroxine concentrations and serum insulin, albumin, globulins, and insulin-like growth factor-I and higher serum non-esterified fatty acids, urea and creatinine. Overnutrition was obvious in ewes with a BCS of 4, reflected by high insulin, glucagon and urea levels. The BCS of 3 represented a more balanced metabolic status, as reflected by intermediate plasma glucose and glucagon, and serum insulin, albumin and globulins concentrations, and low values of urea and creatinine. The stabilization of body weight and BCS at 1.25, 2, 3 and 4 occurred at nutritional levels corresponding to 30, 60, 100 and 120% of the theoretical energy requirements for maintenance. This metabolic characterization clearly demonstrated that the BCS of ewes has a significant effect on metabolites and hormonal profiles. Ewes deal successfully with extreme nutritional conditions although a BCS of 3 appear to be ideal to assure nutritional and metabolic welfare and with a BCS below 2 or above 3 ewes seem more susceptibility to metabolic imbalances. From the variables tested as metabolic indicators glucose, non-esterified fatty acids and insulin provided the more reliable information for the diagnosis of the ewe's energy status and albumin and urea of the protein status.

Tryptic Digests of Sorghum Malt Sprouts: An Assessment of Their Usefulness as Organic Nitrogen Sources for the Yeast Saccharomyces Cerevisiae

The tryptic digests of sprouts from malts of two sorghum cultivars differed significantly in their yeast nutrient composition. While both digests contained elevated levels of Ca2+, Mg2+, and K+, the individual concentrations of the minerals varied with the sprouts' source. At 423.9 μg/g, Mg2+ levels were markedly (P < 0.001) higher in the tryptic digest of Local Red sorghum sprouts than in the Local White counterpart (287.3 μg/g), while the converse was true for Ca2+ and K+. Wide variation also occurred with respect to the nitrogen constituents. For example, the Local White sorghum sprouts digest contained considerably more ammonium, total free amino nitrogen and yeast-essential amino acids than did the Local Red counterpart. In contrast, Local Red malt sprout digest displayed significantly higher urea levels (124.7 mg/g compared with 98.94 mg/g) and superior yeast growth-promoting activity, suggesting that factors other than amino nitrogen also influenced the ability of the digests to support yeast growth. The digests of sorghum malt sprouts compared favorably with seven commercial nitrogenous bases in their ability to promote yeast growth. Results suggest that tryptic digests of sorghum malt sprouts are good alternative sources of nitrogenous and mineral nutrients for microbial cultivation.

Ruptured Abdominal Aortic Aneurysms: Factors Influencing Early Survival

In this study we aimed to define relevant prognostic predictors for the outcome of surgical treatment of ruptured abdominal aortic aneurysms. The study included 406 consecutive patients treated between January 1991 and December 2003. There were 337 (83%) male and 69 (17%) female patients aged 67 +/- 7.5 years. Fourteen (3.5%) patients had aortocaval fistula whereas 4 (0.98%) had primary aortorenteric fistula caused by aneurysm rupture into the inferior vena cava or duodenum. Reconstruction included interposition of a tube graft (215-53%), aortobiiliac bypass (134-33%), and aortobifemoral bypass (58-14.3%). Findings on admission that significantly correlated with both intraoperative (13.5%) and total operative mortality (48.3%) were systolic blood pressure <95 mmHg, low diuresis, unconsciousness, cardiac arrest, leukocytes >14 x 10(9)/L, hematocrit <0.29%, hemoglobin <100 g/L, urea> 11 mmol/L, and creatinine >180 micromol/L. Intraoperative determinants of increased mortality were aortic cross-clamping time >47 min, duration of surgery >200 min, intraoperative blood loss >3500 mL, diuresis <400 mL, arterial systolic pressure <97.5 mmHg, and the need for aortobifemoral bypass. Respiratory complications and multisystem organ failure were significantly associated with lethal outcome in the postoperative period. Surgical treatment of ruptured abdominal aortic aneurysm was life-saving in 51.7% of patients. Variables significantly associated with mortality were unconsciousness, low systolic blood pressure, cardiac arrest, low diuresis, high urea and creatinine levels, signs of blood loss, and the need for aortobifemoral reconstruction. Short aortic cross-clamping and the total operation time, low intraoperative blood loss, and well-controlled diuresis and arterial pressure during surgery have improved survival. Therapeutic efforts should concentrate on intraoperative factors that are possible to correct, leading to better survival of these patients.

Urgent Coronary Revascularization In A Familial Polycystic Kidney Disease Patient With Unstable Angina Pectoris

Familial polycystic kidney disease is a rare cause of renal insufficiency and it could be mentioned together with gastrointestinal and cardiovascular diseases such as aneurysms and diverticulosis. A congenital familial polycystic kidney disease patient with unstable angina pectoris underwent urgent coronary revascularisation operation without respecting the high levels of serum urea (125 mg/dL) and creatinine (4.8 mg/dL). We administered ultrafiltration during the cardiopulmonary bypass period and then we continued renal supplement therapy via veno-venous hemofiltration. The patient's postoperative period was uneventful and his blood urea nitrogen and creatinine levels decreased to normal levels after this therapy. We conclude that urgent coronary revascularization operations can be done safely in familial polycystic kidney disease patients with unstable angina pectoris by the using of proper renal supplement therapy methods.

Dynamics of a pasture soil microbial community after deposition of cattle urine amended with [13C]urea.

Within grazed pastures, urine patches are hot spots of nitrogen turnover, since dietary N surpluses are excreted mainly as urea in the urine. This short-term experiment investigated 13C uptake in microbial lipids after simulated deposition of cattle urine at 10.0 and 17.1 g of urea C m(-2). Confined field plots without or with cattle urine amendment were sampled after 4 and 14 days, and soil from 0- to 5-cm and 10- to 20-cm depths was analyzed for content and composition of phospholipid fatty acids (PLFAs) and for the distribution of urea-derived 13C among individual PLFAs. Carbon dioxide emissions were quantified, and the contributions derived from urea were assessed. Initial changes in PLFA composition were greater at the lower level of urea, as revealed by a principal-component analysis. At the higher urea level, osmotic stress was indicated by the dynamics of cyclopropane fatty acids and branched-chain fatty acids. Incorporation of 13C from [13C]urea was low but significant, and the largest amounts of urea-derived C were found in common fatty acids (i.e., 16:0, 16:1omega7c, and 18:1omega7) that would be consistent with growth of typical NH4(+)-oxidizing (Nitrosomonas) and NO2(-)-oxidizing (Nitrobacter) bacteria. Surprisingly, a 20 per thousand depletion of 13C in the cyclopropane fatty acid cy17:0 was observed after 4 days, which was replaced by a 10 to 20 per thousand depletion of that in cy19:0 after 14 days. Possible reasons for this pattern are discussed. Autotrophic nitrifiers could not be implicated in urea hydrolysis to any large extent, but PLFA dynamics and the incorporation of urea-derived 13C in PLFAs indicated a response of nitrifiers which differed between the two urea concentrations.

Effect of brain death on gene expression and tissue activation in human donor kidneys.

After kidney transplantation, decreased graft survival is seen in grafts from brain dead (BD) donors compared with living donors. This might result partly from a progressive nonspecific inflammation in the graft. In this study, we focused on the effects of BD on inflammatory response (adhesion molecules, leukocyte invasion, gene expression) and stress-related heat shock proteins in the human kidney. Research outcomes and clinical donor parameters were then linked to outcome data after transplantation. Kidney biopsy specimens and serum were obtained during organ retrieval from BD and living organ donor controls. Immunohistochemistry and semiquantitative reverse transcriptase-polymerase chain reaction were performed on the biopsy specimens. Clinical and laboratory parameters from BD donors were recorded and connected to outcome data of the recipients of the kidneys studied. After brain death, immunohistochemistry showed an increase of E-selectin (P<0.01) and interstitial leukocyte invasion (P<0.05) compared with controls. Also, reverse transcriptase-polymerase chain reaction showed a threefold increased heme oxygenase-1 (P<0.05) and Hsp70 (P<0.01) gene expression after BD. Levels of monocyte chemotactic protein-1 and transforming growth factor-beta were twice as high after brain death but did not reach significance. Transplantation outcome was influenced by several donor variables: positively most notably by donor treatment with desmopressin and negatively by high serum urea levels during brain death and by high intercellular adhesion molecule and vascular cell adhesion molecule expression in the kidney. Heme oxygenase-1 proved to have a protective function, but only in kidneys from living donors. The presence of interstitial leukocytes and the early adhesion molecule E-selectin in BD donor kidneys indicates an early-phase inflammatory process during organ retrieval. Elevated levels of monocyte chemotactic protein-1 and transforming growth factor-beta suggest a role for monocytes/macrophages in this phase. We suggest that BD causes a stress-related response against which protective heat shock proteins are formed in the future graft. This stress response may be too severe to be fully counteracted by elevated heat shock proteins. Which systemic and/or local factors trigger brain death-related graft injury is currently under investigation.

Ear, nose and throat manifestations in pediatric chronic renal failure patients undergoing peritoneal dialysis

Ear, Nose and Throat manifestations have been frequently observed in patients with chronic renal failure. Many factors viz. ototoxic drugs, associated conditions of renal failure such as electrolyte imbalance, alteration in blood urea etc. have been implicated for these manifestations. The present study has been conducted to evaluate ear, nose and throat manifestations in thirty pediatric patients (age group 4-16 year) of chronic renal failure undergoing peritoneal dialysis. Probable patho-physiology and treatment of ENT manifestations has been discussed. The remarkable findings in all these cases were the high blood urea level. Most of these manifestations were markedly improved by correction of the renal functions and ideal therapeutic measures.

SPECIAL COLLECTION: DOGMAS AND CONTROVERSIES IN THE HANDLING OF NITROGENOUS WASTES

Science is full of dogmas. But during the process of discovery, some dogmas face challenges, and the dogmas in nitrogen waste management are no different. As all biology students know, the dogma holds that waste proteins are broken down and excreted from the body in a variety of forms, such as

Avaliação de diferentes tipos de camas de frango, associadas à uréia, na suplementação de novilhos consumindo forragem de baixa qualidade

Utilizaram-se 12 novilhos 7/8 Holandês-Zebu em três quadrados latinos 4 x 4, constituído de três grupos de peso corporal (250, 350 e 450 kg), alojados individualmente em baias cobertas, por 60 dias (quatro períodos de 15 dias). Cada grupo de quatro animais foi alimentado, durante os quatro períodos, com capim-elefante "Napier" (Pennisetum purpureum) e suplementos constituídos por quatro tipos de cama de frango (serragem, sabugo de milho triturado, casca de café e capim-elefante "Cameroon"), uréia e concentrado à base de milho e soja (70:30%), nos níveis de 75, 12,5 e 12,5%, respectivamente. O volumoso e os suplementos foram fornecidos, separadamente, uma vez ao dia, pela manhã, e a mistura mineral e água foram fornecidas sempre à vontade. Verificou-se que a associação de elevados níveis das camas de frango e uréia teve alto efeito inibitório no consumo de suplemento, que variou de 174 a 405 g de matéria seca/animal/dia, para os suplementos contendo camas de frango constituídas de capim-elefante e serragem, respectivamente. Entretanto, os suplementos foram capazes de suprir os requerimentos nutricionais de animais com 350 kg de peso corporal e ganho de 370 g/dia em até 32, 29 e 40%, para PB, Ca e P, respectivamente, embora o consumo dos mesmos tenha sido de apenas 2,8 a 6,3% da matéria seca total. Apesar de não ter ocorrido efeito do suplemento nas variáveis ruminais e plasmáticas, foram verificadas correlações positivas entre os consumos de matéria seca e de proteína bruta no suplemento e os níveis ruminais de amônia.

Designing a Hepatocellular Microenvironment with Protein Microarraying and Poly(ethylene glycol) Photolithography

In this study, robotic protein printing was employed as a method for designing a cellular microenvironment. Protein printing proved to be an effective strategy for creating micropatterned co-cultures of primary rat hepatocytes and 3T3 fibroblasts. Collagen spots (ca. 170 microm in diameter) were printed onto amino-silane- and glutaraldehyde-modified glass slides. Groups of 15-20 hepatocytes attached to collagen regions in a highly selective manner forming cell clusters corresponding in size to the printed collagen domains. Fibroblasts, seeded onto the same surface, adhered and spread around arrays of hepatocyte islands creating a heterotypic environment. The co-cultured hepatocytes produced and maintained high levels of liver-specific biomarkers, albumin and urea, over the course of 2 weeks. In addition, protein printing was combined with poly(ethylene glycol) photolithography to define intercellular contacts within the clusters of hepatocytes residing on individual collagen islands. Glass slides, treated with 3-acryloxypropyl trichlorosilane and imprinted with 170 m diameter collagen spots, were micropatterned with a high-density array of 30 microm x 30 microm poly(ethylene glycol) (PEG) wells. As a result, discrete groups of ca. 9 PEG microwells became functionalized with the cell-adhesive ligand. When exposed to micropatterned surfaces, hepatocytes interacted exclusively with collagen-modified regions, attaching and becoming confined at a single-cell level within the hydrogel wells. Micropatterning strategies proposed here will lead to greater insights into hepatocellular behavior and will benefit the fields of hepatic tissue engineering and liver biology.