Sublimation in bright spots on (1) Ceres.

The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5-7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the 'snow line', which is the distance from the Sun at which water molecules condense.

Competition kinetics of OH radical reactions with oxygenated organic compounds in aqueous solution: rate constants and internal optical absorption effects.

Oxygenated organic compounds are omnipresent in the troposphere, due to their strong emissions from either biogenic or anthropogenic sources. Additionally, the degradation and oxidation processes of volatile organic compounds (VOCs) result in the production of oxygenated organic compounds in the troposphere. The degradation and conversion of these compounds are often initiated by radical reactions and occur in the gas phase as well as in the aqueous phase, including cloud droplets, fog, haze, rain or hygroscopic particles containing 'aerosol liquid water (ALW)'. In the present study, the temperature-dependent OH radical reactions with oxygenated organic compounds in the aqueous phase have been investigated by laser flash photolysis. To determine the rate constants, the OH radical - thiocyanate anion competition kinetics method has been used. Once the organic reactant has an absorption at the excitation wavelength of the photolysis laser, the initial OH concentration decreases. This internal absorption effect leads to an overestimated rate constant of the investigated compound. The present study considers this contribution in order to clarify the internal absorption effect of the investigated organic compounds. The following rate constants for OH radical oxidation reactions of the oxygenated organic compounds have been obtained: acetone (2-propanone) k298K = (7.6 ± 1.0) × 107 L mol-1 s-1, 1-hydroxypropan-2-one k298K = (1.1 ± 0.1) × 109 L mol-1 s-1, 1,3-dihydroxypropan-2-one k298K = (1.5 ± 0.1) × 109 L mol-1 s-1, 2,3-dihydroxypropanal k298K = (1.3 ± 0.1) × 109 L mol-1 s-1, butane-1,3-diol k298K = (2.5 ± 0.1) × 109 L mol-1 s-1, butane-2,3-diol k298K = (2.0 ± 0.1) × 109 L mol-1 s-1 and hexane-1,2-diol k298K = (4.6 ± 0.4) × 109 L mol-1 s-1. With the rate constants obtained and their T-dependencies, the source and sink processes of oxygenated organic compounds in the tropospheric aqueous phase are arrived at precisely. These findings might enhance the predictive capabilities of models such as the chemical aqueous-phase radical mechanism (CAPRAM).

Multiphase chemistry of glyoxal: revised kinetics of the alkyl radical reaction with molecular oxygen and the reaction of glyoxal with OH, NO3, and SO4- in aqueous solution.

The rate constant for the reaction of the hydrated glyoxyl radical (CH(OH)2-C(OH)2(·) with O2 has been determined as k(298) K = (1.2 ± 0.3) × 10(9) L mol(-1) s(-1) at pH 4.8. This experimental value is considerably higher than a widely used estimated value of about k = 1 × 10(6) L mol(-1) s(-1). As the aqueous phase conversion of glyoxal is of wide interest for aqSOA formation, we suggest that the newly determined rate constant should be applied in multiphase models. The formation of the dimerization product tartaric acid has as well been studied. This product is found, however in significant yields only when the oxygen content of the solution is reduced. The formation of dimers from the recombination of alkyl radicals in the atmospheric aqueous phase should hence be treated with great care. Finally, the reactions of the free radicals OH, NO3, and SO4(-) with glyoxal have been investigated and rate constants of k(298) K (OH) = (9.2 ± 0.5) × 10(8) L mol(-1) s(-1), k(298) K (SO4(-)) = (2.4 ± 0.2) × 10(7) L mol(-1) s(-1) and k(298) K (NO3) = (4.5 ± 0.3) × 10(6) L mol(-1) s(-1) were obtained.

Efficacy of bath psoralen plus ultraviolet A (PUVA) vs. system PUVA in psoriasis: a prospective, open, randomized, multicentre study.

BACKGROUND: Plaque psoriasis is an inflammatory disease affecting approximately 2% of the population. The clinical hallmarks of psoriasis are sharply demarcated, erythematous plaques with thick scales. Photochemotherapy (psoralen plus ultraviolet A, PUVA) is one of the most effective therapies of psoriasis. The photosensitizer 8-methoxypsoralen (8-MOP) can be applied either orally (system PUVA) or topically in a warm water bath (bath PUVA). OBJECTIVES: To compare bath PUVA and system PUVA in the treatment of plaque psoriasis. METHODS: This was a randomized, open, prospective, multicentre trial. We included 74 patients with moderate-to-severe plaque psoriasis during a 6-week treatment and a 4-week follow-up period. Of the patients enrolled in the study, 38 received bath PUVA and 36 system PUVA. RESULTS: Both treatment modalities significantly reduced the median Psoriasis Area and Severity Index (PASI) score in the intention-to-treat population. Within 6 weeks bath PUVA reduced the median PASI by 74% (16·4 to 4·2) while system PUVA did so by 62% (15·3 to 5·8). The difference between the two modalities was not significant with regard to treatment efficacy (P = 0·389). CONCLUSION: There is no difference between bath PUVA and system PUVA in the treatment of psoriasis.

Luminal decoration of blood vessels by activated perivasal mast cells in allergic rhinitis.

BACKGROUND: In allergic diseases, like in rhinitis, antigen challenge induces rapid degranulation of tissue resident mast cells and subsequent recruitment of leukocytes in response to soluble immunmodulators. The fate of mast cell-derived, membrane associated factors in inflamed tissue remained however unresolved. METHODS: Components of the mast cell granular membrane, including the unique marker CD63var, were examined by FACS and by confocal laser scanning microscopy in cell culture and in diseased human tissue. RESULTS: We discovered that selected mast cell membrane components appeared on the surface of distinct bystander cells. Acceptor cells did not acquire these molecules simply by uptake of soluble material or in the form of exosomes. Instead, physically stable cell-to-cell contact was required for transfer, in which a Notch2-Jagged1 interaction played a decisive role. This process is activation-dependent, unidirectional, and involves a unique membrane topology. Endothelial cells were particularly efficient acceptors. In organotypic 3D in vitro cultures we found that transferred mast cell molecules traversed an endothelial monolayer, and reappeared focally compacted on its distal surface, away from the actual contact zone. Moreover, we observed that such mast cell-derived membrane patches decorate microcapillaries in the nasal mucosa of allergic rhinitis patients. CONCLUSION: Direct membrane transfer from perivasal mast cells into nearby blood vessels constitutes a novel mechanism to modulate endothelial surface features with apparent significance in allergic diseases.

[The fate of 20 sea breams. Mycobacterium marinum infection]. / Das Schicksal von 20 Brassen. Mycobacterium-marinum-Infektion.

Cutaneous infections with Mycobacterium marinum are rare. They also are known as swimming pool or fish tank granulomas. Often the history of contact with contaminated water associated with microtrauma of the upper extremities leads to the correct diagnosis. Since chlorination of swimming pools has become standard, cases of swimming pool granuloma have become rare. Contact with fish tanks now is the most common route of infection. Positive culture of skin biopsy leads to the correct diagnosis. Moxifloxacin in combination with other antibiotics is often effective.

Aggravation of cyclophosphamide-induced acute neurological disorders under conditions of artificial acidification of chyme in rats.

The effect of artificial acidification of the intestinal content on neurological manifestations of acute severe cyclophosphamide intoxication was studied in rats. The animals were gavaged with 20 ml/kg sulfuric (0.05 M), hydrochloric, boric, or lactic acids (0.1 M) 3 h before intraperitoneal injections of the cytostatic in doses of 0, 200, 600, or 1000 mg/kg. The decrease in pH (by.0) and ammonia-producing activity of the cecal chyme developed within 3 h after administration of acids. Cyclophosphamide caused hyperammonemia; glutamine/ammonia and urea/ammonia ratios in the blood decreased. These changes augmented after administration of acids (boric acid produced maximum and lactic acid minimum effects). Acid treatment resulted in greatest elevation of ammonia level in the portal venous blood and a lesser elevation in the vena cava posterior blood. Acid treatment promoted manifestation of cyclophosphamide neurotoxic effect and animal death. Hence, acidification of the chyme inhibited the formation of ammonia in it, while ammonia release from the gastrointestinal tract into the blood increased; the treatment augmented hyperammonemia and aggravated the neurological manifestations of cyclophosphamide intoxication.

Effects on plasma corticosterone levels and brain serotonin from interference with methamphetamine-induced corticosterone release in neonatal rats.

Methamphetamine (MA) induces multiple effects in rats including alterations to corticosterone (CORT) and adrenocorticotropic hormone (ACTH). This effect is age dependent showing a U-shaped function similar to that of other stressors during the stress hyporesponsive period. Neonatal MA treatment leads to adult learning and memory impairments, but whether these are related to MA-induced CORT release is unknown. Here in, four methods were tested in neonatal rats previously established in adult rats for inhibiting stress-induced CORT release: inhibiting synthesis (metyrapone (MET) or ketoconazole (KTZ)) or surgically by adrenalectomy or adrenal autotransplantation (ADXA). Pretreatment on postnatal day 11 with MET or KTZ prior to four doses of 10 mg/kg of MA initially suppressed MA-induced increases in plasma CORT, but 24 h later, even with additional inhibitor treatment, a large CORT increase was seen which exceeded that of MA alone. Adrenalectomy blocked MA-induced increases in CORT but caused a secondary effect on brain serotonin (5-HT) and dopamine (DA), causing greater reductions than those caused by MA alone. ADXA inhibited MA-induced CORT release without causing a 24-h CORT increase and did not produce additional effects on brain 5-HT or DA. Neonatal ADXA is a new model for developmental drug or stress experiments designed to test the role of CORT in mediating early effects on later outcomes.

Increase of ammonia pool in the gastrointestinal tract of rats potentiates acute toxicity of cyclophosphamide.

For evaluation of the impact of changes of ammonia pool in the gastrointestinal tract on acute toxicity of cyclophosphamide, the dynamics of blood levels of ammonia and urea of rats was studied after intraperitoneal injection of cyclophosphamide (600 mg/kg) and clinical manifestations of intoxication and lifespan of rate were studied after cyclophosphamide injections in doses of 200, 600, 1000, and 1400 mg/kg alone or in combination with ammonium acetate. Ammonium acetate stimulated the hyperammoniemic and uremic effects of cyclophosphamide. Combined effects of the toxicants were associated with symptoms characteristic of acute poisoning with ammonium salts; these symptoms were not observed under the effect of ammonium acetate alone. Ammonium acetate stimulated the lethal effect of cyclophosphamide injected in doses of 200, 600, 1000, or 1400 mg/kg: the mean lifespan of rats decreased by 1.5, 2.1, 2.8, or 6.1 times, respectively. These data indicate that ammonia redistribution from the gastrointestinal tract into circulating blood is one of the mechanisms of thanatogenesis in acute cyclophosphamide intoxication.

Effect of hypoxia on sodium and ammonium acetate toxicity for Daphnia.

Exposure of Daphnia in degassed (boiled) culturing water (hypoxia simulation) led to solitary lethal outcomes after more than 24 h. Before this term, hypoxia had no appreciable effect on the toxicity of sodium or ammonium acetate salts. The sensitivity of daphnias to the lethal effects of the tested chemicals did not change under conditions of normal oxygenation and increased sharply (by two orders of magnitude) under conditions of hypoxia, loosing the linear relationship with toxicant concentration. Ammonium acetate toxicity more markedly increased under conditions of hypoxia than sodium acetate toxicity. These data should be taken into consideration when predicting the results of combined effects of toxicants on water ecosystems and on human organism.

Analysis of c-KIT expression and KIT gene mutation in human mucosal melanomas.

Recent data suggested an increased frequency of KIT aberrations in mucosal melanomas, whereas c-KIT in most types of cutaneous melanomas does not appear to be of pathogenetic importance. However, studies investigating the status of the KIT gene in larger, well-characterised groups of patients with mucosal melanomas are lacking. We analysed 44 archival specimens of 39 well-characterised patients with mucosal melanomas of different locations. c-KIT protein expression was determined by immunhistochemistry, KIT gene mutations were analysed by PCR amplification and DNA sequencing of exons 9, 11, 13, 17 and 18. c-KIT protein expression could be shown in 40 out of 44 (91%) tumours in at least 10% of tumour cells. DNA sequence analysis of the KIT was successfully performed in 37 patients. In 6 out of 37 patients (16%) KIT mutations were found, five in exon 11 and one in exon 18. The presence of mutations in exon 11 correlated with a significant stronger immunohistochemical expression of c-KIT protein (P=0.015). Among the six patients with mutations, in two patients the primary tumour was located in the head/neck region, in three patients in the genitourinary tract and in one patient in the anal/rectal area. In conclusion, KIT mutations can be found in a subset of patients with mucosal melanomas irrespective of the location of the primary tumour. Our data encourage therapeutic attempts with tyrosine kinase inhibitors blocking c-KIT in these patients.

Comparison of sagittal and frontal plane alignment after open- and closed-wedge osteotomy: a matched-pair analysis.

High tibial osteotomy (HTO) is a procedure for treating medial compartment osteoarthritis (OA) of the varus deformed knee. Frontal and sagittal alignment after closed- and open-wedge HTO were compared radiologically in a matched-pair study. The mean intra-operative frontal plane correction (FT axis) was +7.5 degrees for closed-wedge HTO and +8 degrees for open-wedge HTO; it increased by +0.5 degrees in closed-wedge HTO and decreased by -0.5 degrees in open-wedge HTO at last follow-up. Post-operatively, tibial slope had decreased by -0.5 degrees in closed-wedge HTO and increased significantly by +3 degrees in open-wedge HTO. Both techniques effectively and safely corrected varus deformity. A high degree of stability of the frontal plane correction was noted, however a significant change in the tibial slope after open-wedge HTO was observed post-operatively. As no loss of correction was shown, it may be related to the surgical technique rather than to the implant used.

Functional differences between Stat3alpha and Stat3beta.

Stat3beta is a short form of Stat3 that differs from the longer form (Stat3alpha) by the replacement of the C-terminal 55 amino acid residues of Stat3alpha by 7 residues specific to Stat3beta. In COS cells transfected with Stat3 expression plasmids, both Stat3alpha and Stat3beta were activated for DNA binding and transcription by the same set of growth factors and cytokines and both, when activated, formed homodimers and heterodimers with Stat1. Only Stat3beta was active in the absence of added cytokine or growth factor. Activation of each form, including constitutive activation of Stat3beta, was correlated with the phosphorylation of tyrosine 705. Activated Stat3beta in transfected COS cells was more stable and had greater DNA-binding activity than activated Stat3alpha. However, relative to DNA-binding activity, Stat3alpha showed greater transcriptional activity than Stat3beta. A mutant of Stat3alpha lacking its highly acidic C-terminal 48 amino acids had properties indistinguishable from Stat3beta. We conclude that Stat3alpha and Stat3beta have significantly different properties due to the presence or absence of the acidic C-terminal tail of Stat3alpha rather than the C-terminal sequence peculiar to Stat3beta. In addition to its effect on transcription, we speculate that the acidic tail may destabilize the active dimeric form of Stat3alpha, resulting in lower DNA-binding activity of the Y705-phosphorylated form compared to Stat3beta and in more rapid dephosphorylation.

Exotic food allergy: anaphylactic reaction to lychee.

There are very few reports on allergic reactions to lychee fruit in the literature. We describe the case of a 26-year-old man who developed pruritus, generalized urticaria, and severe angioedema of his lips and tongue with dyspnea within 15 minutes after lychee fruit intake. Although we found no lychee-specific immunoglobulin E antibodies, a basophil activation test (BAT) and a cellular antigen stimulation test (CAST) to lychee were both positive, as was a prick-to-prick test with fresh lychee fruit. The patient also suffered from an oral food allergy syndrome to parsley and was sensitized to mugwort but not to latex or profilin. BAT and CAST are helpful tools in the diagnostic workup for exotic food allergy. Mugwort is suggested as the allergen responsible for,the cross-reactivity presented by this patient, as he had no sensitization to latex or profilin.

Ecotropic viral integration site 1, a novel oncogene in prostate cancer.

Prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer in men in the western world. Mutations in tumor suppressor genes and in oncogenes are important for PCa progression, whereas the role of stem cell proteins in prostate carcinogenesis is insufficiently examined. This study investigates the role of the transcriptional regulator Ecotropic Viral Integration site 1 (EVI1), known as an essential modulator of hematopoietic and leukemic stem cell biology, in prostate carcinogenesis. We show that in healthy prostatic tissue, EVI1 expression is confined to the prostate stem cell compartment located at the basal layer, as identified by the stem cell marker CD44. Instead, in a PCa progression cohort comprising 219 samples from patients with primary PCa, lymph node and distant metastases, EVI1 protein was heterogeneously distributed within samples and high expression is associated with tumor progression (P<0.001), suggesting EVI1 induction as a driver event. Functionally, short hairpin RNA-mediated knockdown of EVI1 inhibited proliferation, cell cycle progression, migratory capacity and anchorage-independent growth of human PCa cells, while enhancing their apoptosis sensitivity. Interestingly, modulation of EVI1 expression also strongly regulated stem cell properties (including expression of the stem cell marker SOX2) and in vivo tumor initiation capacity. Further emphasizing a functional correlation between EVI1 induction and tumor progression, upregulation of EVI1 expression was noted in experimentally derived docetaxel-resistant PCa cells. Importantly, knockdown of EVI1 in these cells restored sensitivity to docetaxel, in part by downregulating anti-apoptotic BCL2. Together, these data indicate EVI1 as a novel molecular regulator of PCa progression and therapy resistance that may control prostate carcinogenesis at the stem cell level.

Phosphodiesterase 1B differentially modulates the effects of methamphetamine on locomotor activity and spatial learning through DARPP32-dependent pathways: evidence from PDE1B-DARPP32 double-knockout mice.

Mice lacking phosphodiesterase 1B (PDE1B) exhibit an exaggerated locomotor response to D-methamphetamine and increased in vitro phosphorylation of DARPP32 (dopamine- and cAMP-regulated phosphoprotein, M r 32 kDa) at Thr34 in striatal brain slices treated with the D1 receptor agonist, SKF81297. These results indicated a possible regulatory role for PDE1B in pathways involving DARPP32. Here, we generated PDE1B x DARPP32 double-knockout (double-KO) mice to test the role of PDE1B in DARPP32-dependent pathways in vivo. Analysis of the response to d-methamphetamine on locomotor activity showed that the hyperactivity experienced by PDE1B mutant mice was blocked in PDE1B-/- x DARPP32-/- double-KO mice, consistent with participation of PDE1B and DARPP32 in the same pathway. Further behavioral testing in the elevated zero-maze revealed that DARPP32-/- mice showed a less anxious phenotype that was nullified in double-mutant mice. In contrast, in the Morris water maze, double-KO mice showed deficits in spatial reversal learning not observed in either single mutant compared with wild-type mice. The data suggest a role for PDE1B in locomotor responses to psychostimulants through modulation of DARPP32-dependent pathways; however, this modulation does not necessarily impact other behaviors, such as anxiety or learning. Instead, the phenotype of double-KOs observed in these latter tasks may be mediated through independent pathways.

Effects of chronic atrial fibrillation on gap junction distribution in human and rat atria.

OBJECTIVES: To elucidate the structural basis for the electrophysiologic remodeling induced by chronic atrial fibrillation (AF), we investigated connexin40 and connexin43 (Cx40 and Cx43) expression and distribution in atria of patients with and without chronic AF and in an animal model of AF with additional electrophysiologic investigation of anisotropy (ratio of longitudinal and transverse velocities). BACKGROUND: Atrial fibrillation is a common arrhythmia that has a tendency to become persistent. Since gap junctions provide the syncytial properties of the atrium, changes in expression and distribution of intercellular connections may accompany the chronification of AF. METHODS: Atrial tissues isolated from 12 patients in normal sinus rhythm at the time of cardiac surgery and from 12 patients with chronic AF were processed for immunohistology and immunoblotting for the detection of the gap junction proteins. The functional study of the cardiac tissue anisotropy was performed in rat atria in which AF was induced by 24 h of rapid pacing (10 Hz). RESULTS: Immunoblotting revealed that AF did not induce any significant change in Cx43 content in human atria. In contrast, a 2.7-fold increase in expression of Cx40 was observed in AF. Immunohistologic analysis indicated that AF resulted in an increase in the immunostaining of both connexins at the lateral membrane of human atrial cells. A similar spatial redistribution of the Cx43 signal was seen in isolated rat atria with experimentally-induced AF. In addition, AF in rat atria resulted in decreased anisotropy with slightly enhanced transverse conduction velocity. CONCLUSIONS: This experimental study showed that AF is accompanied by spatial remodeling of gap junctions that might induce changes in the biophysical properties of the tissue.

Enhancement of Escherichia coli plasmid and chromosomal recombination by the Ref function of bacteriophage P1.

The Ref activity of phage P1 enhances recombination between two defective lacZ genes in the Escherichia coli chromosome (lac- x lac- recombination). Plasmid recombination, both lac- x lac- and tet- x tet-, was measured by transformation of recA strains, and was also assayed by measurement of beta-galactosidase. The intracellular presence of recombinant plasmids was verified directly by Southern blotting. Ref stimulated recombination of plasmids in rec+ and rec(BCD) cells by 3-6-fold, and also the low level plasmid recombination in recF cells. RecA-independent plasmid recombination, either very low level (recA cells) or high level (recB recC sbcA recA cells), was not stimulated. Ref stimulated both intramolecular and intermolecular plasmid recombination. Both normal and Ref-stimulated lac- x lac- chromosomal recombination, expected to be mostly RecBC-dependent in wild-type bacteria, were affected very little by a recF mutation. We have previously reported Ref stimulation of lac- x lac- recombination in recBC sbcB bacteria, a process known to be RecF-dependent. Chromosomal recombination processes thought to involve activated recombination substrates, e.g., Hfr conjugation, P1 transduction, were not elevated by Ref activity. We hypothesize that Ref acts by unknown mechanisms to activate plasmid and chromosomal DNA for RecA-mediated recombination, and that the structures formed are substrates for both RecF-dependent (plasmid, chromosomal) and Rec(BCD)-dependent (chromosomal) recombination pathways.

Activation of stat3 and stat1 DNA binding and transcriptional activity in human brain tumour cell lines by gp130 cytokines.

In this study we examine the activation of the latent Stat family of transcription factors by the gp130 family of cytokines in cell lines derived from human brain tumours. Of the cytokines tested, oncostatin M resulted in the most dramatic induction of Stat1 and Stat3 in all cell lines analysed, as assessed by the formation of protein/DNA complexes. Interleukin-6, leukemia inhibitory factor, and ciliary neurotrophic factor also induced Stat complexes more selectively and to a lesser magnitude than oncostatin M. The kinetics of Stat1 and Stat3 activation was rapid and transient; the nuclear accumulation of DNA binding-proficient Stat protein was detected in the nucleus within minutes of cytokine induction. The transcriptional potential of the oncostatin M-activated Stat molecules was demonstrated in two glioma cell lines (U87-MG, SNB-19) by transient transfection experiments using a Stat-responsive reporter plasmid. Oncostatin M-dependent transcription from this reporter plasmid was reduced to uninduced levels by the inclusion of a dominant-negative Stat3 molecule, demonstrating that Stat molecules were responsible for the induction. These studies demonstrate that oncostatin M is the most potent activator of Stat molecules in a variety of brain tumour-derived cell lines, an observation that could have implications affecting the balance between proliferation/apoptosis of these cells.

Migration of a human keratinocyte cell line (HACAT) to interstitial collagen type I is mediated by the alpha 2 beta 1-integrin receptor.

The migratory response of the human keratinocyte cell line HaCaT to collagen type I and the molecular mechanism underlying collagen-mediated migration have been analyzed. The migratory response of HaCaT cells to collagen type I consisted of a dose-dependent migration to insoluble step gradients of substratum-bound collagen (haptotaxis) and to gradients of soluble collagen (chemotaxis). Checkerboard analysis demonstrated a minor chemokinetic component. Denatured collagen type I was less chemoattractive than the native triple-helical form. Pre-treatment of cells with 25-250 micrograms/ml of synthetic peptides containing the fibronectin cell-recognition sequence RGD (Arg-Gly-Asp) resulted in a concentration-dependent inhibition of fibronectin-mediated chemotaxis, whereas chemotaxis to collagen was not affected. We then investigated the role of VLA/collagen-receptors for collagen type I-induced chemotaxis. Monoclonal antibody (MoAb) 5E8, which selectively blocks function of the alpha 2 subunit of the VLA-2/collagen receptor, dose-dependently inhibited the chemotactic response of HaCaT cells to collagen. This effect was specific for collagen-mediated chemotaxis because the chemotactic response to fibronectin remained unaffected. In contrast, a function blocking MoAb directed to the alpha 3 subunit of the coexpressed VLA-3 receptor, which is also capable of binding collagen, had no effect. However, function blocking MoAb directed to the beta 1-chain of integrins completely inhibited chemotaxis to collagen type I. Based on our results, we propose that the chemotactic migration of the human keratinocyte cell line (HaCaT) to collagen type I is specifically mediated by the RGD independent VLA-2/collagen receptor (alpha 2 beta 1) of the integrin family.