CD56+/CD16- Natural Killer cells expressing the inflammatory protease granzyme A are enriched in synovial fluid from patients with osteoarthritis.

OBJECTIVE: Natural killer (NK) cells have been involved in the pathology of different inflammatory and autoimmune disorders. Inflammation is an important regulator of osteoarthritis (OA), but the molecular and cellular mechanisms regulating this process are not well defined. DESIGN: To understand the role of NK cells in OA, we have compared the phenotype (CD56 subsets and perforin and granzyme expression) and cytotoxic function of NK cells in peripheral blood and synovial fluid from patients with OA undergoing total knee arthroplasty. RESULTS: In contrast to peripheral blood lymphocytes (PBLs), the majority of NK cells from the synovial fluid were CD56brightCD16(-) cells. As expected the expression of the cytolytic mediators perforin and granzyme B in CD56brightCD16(-) cells was low and correlated with a poor cytotoxic potential against K562 sensitive target cells. Surprisingly, this low cytotoxic NK cell subset expressed high levels of granzyme A (a protease recently characterized as a key modulator of inflammation in mouse models) in synovial fluid but not in peripheral blood. The presence of the CD56(+)brightCD16(-) cells expressing granzyme A correlated with increased levels of pro-inflammatory cytokines in synovial fluid from OA patients. CONCLUSION: Our results indicate that NK cells from the synovium of patients with OA, which present an immunoregulatory non-cytotoxic phenotype, show different phenotype comparing with NK cells from peripheral blood, especially expressing granzyme A, a pro-inflammatory molecule which may contribute to the establishment of chronic articular inflammation in this type of patients.

[Continuous infusion of local anesthetic at the site of the abdominal surgical wound for postoperative analgesia: a systematic review]. / Analgesia postoperatoria mediante infusión continua de anestésico local en la incisión quirúrgica tras cirugiá abdominal. Revisión sistemática de la bibliografía.

OBJECTIVES: We present a systematic review of clinical trials to evaluate the efficacy of infusing local anesthetic through a catheter placed in the abdominal surgical wound. METHODS: The Jadad (Oxford) scoring system was used to select trials. The variables considered in relation to each trial selected were as follows: type of intervention and incision; type, dose, and concentration of local anesthetic; site where the catheter was placed; rescue analgesia required; opioid use; and incidence of adverse events. RESULTS: Fifteen clinical trials with a mean Jadad score of 4.6 were selected. The 1139 patients enrolled in the trials were grouped according to catheter placement: subfascial (6 trials), subcutaneous (8 trials), and both (1 trial). Six additional unpublished trials registered at ClinicalTrials.gov were also located. CONCLUSIONS: Surgical wound analgesia is a safe technique whose effectiveness has been observed in cesarean sections and hysterectomies performed with Pfannenstiel incisions. Outcomes for other types of surgery are inconsistent. There is a lack of studies of the optimal site for catheter placement as well as of adequate anesthetic concentration and volume.

Modelling 2,4-dichlorophenol bioavailability and bioaccumulation by the freshwater fingernail clam Sphaerium corneum using artificial particles and humic acids.

The complex and variable composition of natural sediments makes it very difficult to predict the bioavailability and bioaccumulation of sediment-bound contaminants. Several approaches have been proposed to overcome this problem, including an experimental model using artificial particles with or without humic acids as a source of organic matter. For this work, we have applied this experimental model, and also a sample of a natural sediment, to investigate the uptake and bioaccumulation of 2,4-dichlorophenol (2,4-DCP) by Sphaerium corneum. Additionally, the particle-water partition coefficients (K(d)) were calculated. The results showed that the bioaccumulation of 2,4-DCP by clams did not depend solely on the levels of chemical dissolved, but also on the amount sorbed onto the particles and the characteristics and the strength of that binding. This study confirms the value of using artificial particles as a suitable experimental model for assessing the fate of sediment-bound contaminants.

Prion Function and Pathophysiology in Non-Mammalian Models.

More than thirty years have passed since the discovery of the prion protein (PrP) and its causative role in transmissible spongiform encephalopathy. Since a combination of both gain- and loss-of-function mechanisms may underlay prion pathogenesis, understanding the physiological role of PrP may give important clues about disease mechanisms. Historically, the primary strategy for prion research has involved the use of human tissue, cell cultures and mammalian animal models. Nevertheless, experimental difficulties of in vivo studies and controversial observations obtained in these systems have stimulated the search for alternative animal models. PrPC is highly conserved in mammals, and PrPC-related orthologs are expressed in zebrafish, a vertebrate model organism suitable to study the mechanisms associated with human diseases. Invertebrate models, as they do not express PrPC have served to investigate the neurotoxic mechanisms of mammalian PrP. Here we overview most recent advances in the study of PrP function in normal and pathogenic conditions based on non-mammalian studies, highlighting the contribution of zebrafish, fly and worms to our current understanding of PrP biology.

Premature loss of muscle mass and function in type 2 diabetes.

INTRODUCTION: Muscle mass and function are among the most relevant factors that contribute to an optimal quality of life, and are strong predictors of mortality in the elderly. Loss of lean tissues and deterioration of muscle function have been described as one of the many complications of type 2 diabetes mellitus (DM2), but most studies do not isolate age as an intervening factor. AIM: To study whether adult DM2 patients up to 60years of age have decreased muscle mass and function compared with healthy non-diabetic (ND) subjects of similar age. METHODOLOGY: Appendicular fat-free mass (ApFFM) by dual X-ray absorptiometry (DEXA), handgrip strength (HS), quadriceps strength (QS), 12 min walking capacity (12MW) and the Timed Up and Go test (TUG) were measured in 100 DM2 patients and 39 ND controls. Muscle quality, or the ratio between lean mass and muscle strength of upper and lower limbs, and the functional limitations associated with pain and stiffness assessed according to the Western Ontario and McMaster Universities Arthrosis Index (WOMAC) were also recorded. Specific tests were performed to rule out microvascular diabetic complications (retinal and peripheral nerves), metabolic control, kidney function and vitamin D status and examine their association with ApFFM and function. RESULTS: ApFFM was significantly higher among DM2 female patients and lower among diabetic men. However opposite results were obtained when individual values were corrected for body mass index (BMI), specifically among women, who were more likely to be obese. As for muscle strength and global functionality tests, significantly better performances in TUG, 12MW, QS and HS were observed among ND subjects of both sexes. These differences prevailed even after excluding diabetic patients with microvascular complications as well as those with more than 10years of diabetes. Muscle quality was also significantly better among ND women. Higher scores of pain and stiffness in the WOMAC scale correlated with 12MW and TUG in both groups but did not correlate with ApFFM. CONCLUSIONS: We found a clear deterioration of lean mass and muscle functions among adult DM2 patients of up to 60years old, independent of length of disease, metabolic control, vitamin D status and presence of microvascular complications and pain.

The viral capping enzyme nsP1: a novel target for the inhibition of chikungunya virus infection.

The chikungunya virus (CHIKV) has become a substantial global health threat due to its massive re-emergence, the considerable disease burden and the lack of vaccines or therapeutics. We discovered a novel class of small molecules ([1,2,3]triazolo[4,5-d]pyrimidin-7(6H)-ones) with potent in vitro activity against CHIKV isolates from different geographical regions. Drug-resistant variants were selected and these carried a P34S substitution in non-structural protein 1 (nsP1), the main enzyme involved in alphavirus RNA capping. Biochemical assays using nsP1 of the related Venezuelan equine encephalitis virus revealed that the compounds specifically inhibit the guanylylation of nsP1. This is, to the best of our knowledge, the first report demonstrating that the alphavirus capping machinery is an excellent antiviral drug target. Considering the lack of options to treat CHIKV infections, this series of compounds with their unique (alphavirus-specific) target offers promise for the development of therapy for CHIKV infections.

A novel function for the Xslug gene: control of dorsal mesendoderm development by repressing BMP-4.

The Snail family of genes comprise a group of transcription factors with characteristic zinc finger motifs. One of the members of this family is the Slug gene. Slug has been implicated in the development of neural crest in chick and Xenopus by antisense loss of function experiments. Here, we have generated functional derivatives of Xslug by constructing cDNAs that encode the Xslug protein fused with the transactivation domain of the virus-derived VP16 activator or with the repressor domain of the Drosophila Engrailed protein. Our results suggest that Xslug normally functions as a transcriptional repressor and that Xslug-VP16 behaves as a dominant negative of Xslug. In the present work, we confirm and extend previous results that suggest that Xslug has an important function in neural crest development, by controlling its own transcription. In addition we have uncovered a new function for Xslug. We show that Xslug is expressed in the dorsal mesendoderm at the beginning of gastrulation, where is it able to upregulate the expression of dorsal genes. On the other hand when Xslug is expressed outside of the organizer it represses the expression of ventral genes. Our results indicate that this effect on mesodermal patterning depends on BMP activity, showing that Xslug can directly control the transcription of BMP-4.

Epidemiologic evidence for vitamin C and vitamin E in cancer prevention.

Antioxidant nutrients have been hypothesized to be protective against cancer. Vitamin C is a major circulating water-soluble antioxidant, and vitamin E is a major lipid-soluble antioxidant. Many case-control and cohort studies have related cancer risk to estimates of nutrient intake derived from food intake reports. Diets high in fruit and vegetables, and hence high in vitamin C, have been found to be associated with lower risk for cancers of the oral cavity, esophagus, stomach, colon, and lung. Diets high in added vegetable oils, and hence high in vitamin E, have been less consistently shown to be associated with cancer protection. This may be because vitamin E offers less protection against cancer or because the estimation of vitamin E intake is less accurate than is the estimation of vitamin C intake. In contrast with the findings from epidemiologic studies based on foods, observational studies of nutrients consumed in supplements and recent experimental trials provide little support for a strong protective role for vitamins C or E against cancer. If vitamins C or E are indeed protective against cancer, that protection may derive from their consumption in complex mixtures with other nutrients and with other bioactive compounds as found in the matrix provided by whole foods.

Somatostatin attenuates ischemic intestinal injury.

Pancreatic-derived proteases play a central role in the pathogenesis of ischemic intestinal injury. We postulated that exocrine blockade by pretreatment with a long-acting somatostatin analogue, octreotide acetate, would attenuate ischemic mucosal injury. Sprague-Dawley rats received subcutaneous octreotide (10 micrograms/kg/d) for 6 days by means of surgically implanted infusion ports. In a group of sham control rats, splanchnic blood flow (portal vein Doppler measurement) and duodenal trypsin activity (p-toluene sulfonyl-L-arginine methyl ester assay) were determined. In a separate experiment, pretreated animals were subjected to 60 minutes of superior mesenteric artery ischemia alone or followed by 30 minutes of reperfusion. Gross extent of hemorrhagic necrosis and microscopic injury (rank analysis) were assessed by a blinded observer. Pretreatment with octreotide reduced intraluminal duodenal trypsin activity by 46% without affecting portal blood flow. However, octreotide pretreatment significantly attenuated the microscopic depth of injury during ischemia and the extent of gross injury during reperfusion. It appears that somatostatin may have an adjuvant role in the prevention or progression of intestinal ischemic injury.

Impact of a camp experience on phenylalanine levels, knowledge, attitudes, and health beliefs relevant to nutrition management of phenylketonuria in adolescent girls.

OBJECTIVE: To evaluate the effectiveness of an education intervention in a summer camp setting on knowledge, attitudes, and health beliefs regarding metabolic control of phenylketonuria and dietary compliance. DESIGN: An observational study of a weeklong metabolic camp for adolescent girls with phenylketonuria (PKU) who were followed up over the course of 1 year. Observations also were made in 3 subsequent years of camp. INTERVENTION: The camp experience consisted of diet and disease education, sessions on reproductive development, and recreation. Group discussions on attitudes and perceptions about PKU related to dietary compliance were held with nutritionists and a pediatric psychologist. OUTCOME MEASURES: Biochemical and psychological data were collected on the first and last days of the camp to assess short-term effects of the intervention, then at quarterly intervals during the year to determine the long-term impact of the camp. Precamp and Postcamp plasma amino acid data for the subsequent 3 years were also collected. SUBJECTS/SETTING: Analyses were based on 13 adolescent girls with PKU in the first year of a camp at Emory University in Atlanta, Ga, and compared with data from 11 additional campers enrolled the second year, 8 in the third year, and 7 in the fourth year. Mean age +/- standard deviation of first-year campers was 13 +/- 2 years, mean IQ +/- standard deviation was 98 +/- 16, and 9 of 13 girls had menstruated. STATISTICAL ANALYSES PERFORMED: Short-term effects of the intervention were computed by comparing mean levels of response from the baseline period to those from the last day of camp using t tests for dependent samples. Repeated-measures analysis of variance was used to assess the long-term effects of the camp experience over the course of a year at regular quarterly intervals. RESULTS: Short-term effects of the education intervention were significant reductions in dietary phenylalanine intake, plasma phenylalanine levels, and perceived isolation. However, these effects progressively returned to baseline levels over the course of a year. The significant short- and long-term effects of increased knowledge of diet and disease persisted throughout the study period. APPLICATIONS/CONCLUSIONS: Short-term effects of the education intervention resulted in improved metabolic control associated with improved attitudes, increased knowledge of diet and disease, increased perceived support, and decreased barriers to dietary compliance in a camp setting.

Dermatoglyphics of a high altitude Peruvian population and interpopulation comparisons.

Studies of genetic structures of Andean human populations have not been numerous, even though these studies could be used to answer questions concerning migration routes of the indigenous peoples who populated America. Such studies could provide basic genetic information and clarify uncertainties surrounding genetic relatedness of South American indigenous peoples. This present work describes, quantifies, and analyzes the digital and palmar dermatoglyphics of 120 people in the community of San Pedro de Casta, Perú. The results were then compared using distance analysis to all other Peruvian population values studied to date and other South American populations. The dermatoglyphic indicators studied were the distribution of digital pattern frequencies, the total ridge counts (TRC), the pattern intensity index (PII), the atd angle, and the a-b ridge counts. The results did not show statistically significant differences for digital patterns between hands, neither within a sex nor between sexes. The means and standard deviations of PII and TRC were 12.32 +/- 3.97 and 112.18 +/- 45.09, respectively. The means and standard deviations for the other two indicators were the following: atd angle, 94.85 degrees +/- 12.33; and a-b ridge counts, 81.57 +/- 9.06. The distance analyses results suggest the existence of two different genetic lines among high altitude populations, as well as the need for further research.

Influence of particle characteristics and organic matter content on the bioavailability and bioaccumulation of pyrene by clams.

Hydrophobic chemicals are known to associate with sediment particles including those from both suspended particulate matter and bottom deposits. The complex and variable composition of natural particles makes it very difficult therefore, to predict the bioavailability of sediment-bound contaminants. To overcome these problems we have previously devised a test system using artificial particles, with or without humic acids, for use as an experimental model of natural sediments. In the present work we have applied this experimental technique to investigate the bioavailability and bioaccumulation of pyrene by the freshwater fingernail clam Sphaerium corneum. The uptake and accumulation of pyrene in clams exposed to the chemical in the presence of a sample of natural sediment was also investigated. According to the results obtained, particle surface properties and organic matter content are the key factors for assessing the bioavailability and bioaccumulation of pyrene by clams.

Evidence of differences in the biotransformation of organic contaminants in three species of freshwater invertebrates.

Acute static bioassays were performed using three freshwater invertebrate species (the oligochaete Lumbriculus variegatus, the fingernail clam Sphaerium corneum and the larvae Chironomus riparius) exposed separately to a variety of 14C radiolabelled contaminants. The aim of this work was to investigate if the chemicals remained as parent compounds after the treatments. Chemicals used were 2,4-dichlorophenol; 2,4,5-trichlorophenol; pentachlorophenol; pyrene; Fenpropidin, and Trifluralin. Homogenates of the whole body tissue of each organism were prepared and total radioactivity was measured. Contaminants were then extracted into organic solvents and analysed by high-pressure liquid chromatography techniques. Chromatograms showed that most of the substances extracted were present as parent compounds in S. corneum and in L. variegatus. In contrast, for C. riparius a low proportion of the chemicals was recovered as parent compounds. These results suggest that different metabolic processes could take place in the different species.

Modeling pentachlorophenol bioavailability and bioaccumulation by the freshwater fingernail clam Sphaerium corneum using artificial particles and humic acids.

The uptake of anthropogenic chemicals by benthic bivalves may occur through the water phase and also by the ingestion of particles from both the suspended matter and bottom sediments. Many chemicals sorb to sediments and, subsequently, are released in the digestive tract of animals. The assessment of sediment-bound chemicals has been difficult because of the complexity of the association between these chemicals and natural particles. To simplify this complexity, we previously devised a test system using artificial particles with known chemical structures. In the present work, we improved this experimental design by adding humic materials as a source of organic matter. Bioassays were conducted by exposing the fingernail clam Sphaerium corneum to sublethal levels of pentachlorophenol (PCP) in the presence or absence of the artificial particles, treated with or without a commercial preparation of humic acids. The results showed that the bioavailability and bioaccumulation could be explained on the basis of the interactions of PCP with the active groups and/or the backbone of the resins, both in systems with or without humic acids. This model may constitute a useful approach to modeling and predicting the uptake and accumulation of chemicals bound to natural sediments.

Different volumes of injectate using electrostimulator and blinded techniques for brachial plexus block in dogs.

To compare different volumes of injectate using electrostimulator (ES)-guided and blind brachial plexus blockade (BPB) techniques in dogs. Prospective, randomised, blinded study. Fifty-eight healthy adult purpose-bred beagle dogs. Animals were randomised into 4 groups based on the volume of methylene blue 0.1 per cent administered for BPB, three using ES technique: E1 (0.2 ml/kg, n=22), E2 (0.6 ml/kg, n=22), and E3 (1.0 ml/kg, n=14), and one using blinded technique B4 (1.0 ml/kg, n=14). After euthanasia, the axillary region was dissected and nerves identified by a blinded evaluator. Success was defined as 3/4 nerves stained, or presence of dye in the tissue immediately surrounding the plexus. There were no significant differences between groups when total nerve count, adjacent staining, success rate (92.8-100 per cent), or rate of haematoma were evaluated. The musculocutaneous nerve was significantly more targeted in B4 than E1 and E2, but not E3. Electrostimulator-guided BPB using lower volumes of injectate had similar success rate as the blinded technique using higher volume, thus, lower volumes can be used without compromising success. When an ES is not available, the blind technique with 1 ml/kg is also acceptable. However, when performing an ES-guided BPB, volumes as low as 0.2 ml/kg can be used. As volume is increased, the musculocutaneous nerve becomes more likely to be targeted.

Non-thermal irreversible electroporation (N-TIRE) and adjuvant fractionated radiotherapeutic multimodal therapy for intracranial malignant glioma in a canine patient.

Non-thermal irreversible electroporation (N-TIRE) has shown promise as an ablative therapy for a variety of soft-tissue neoplasms. Here we describe the therapeutic planning aspects and first clinical application of N-TIRE for the treatment of an inoperable, spontaneous malignant intracranial glioma in a canine patient. The N-TIRE ablation was performed safely, effectively reduced the tumor volume and associated intracranial hypertension, and provided sufficient improvement in neurological function of the patient to safely undergo adjunctive fractionated radiotherapy (RT) according to current standards of care. Complete remission was achieved based on serial magnetic resonance imaging examinations of the brain, although progressive radiation encephalopathy resulted in the death of the dog 149 days after N-TIRE therapy. The length of survival of this patient was comparable to dogs with intracranial tumors treated via standard excisional surgery and adjunctive fractionated external beam RT. Our results illustrate the potential benefits of N-TIRE for in vivo ablation of undesirable brain tissue, especially when traditional methods of cytoreductive surgery are not possible or ideal, and highlight the potential radiosensitizing effects of N-TIRE on the brain.

Differential effects of paraquat on oxidative stress parameters and polyamine levels in two freshwater invertebrates.

Paraquat is still a widely used herbicide in several countries. Its toxic action on plants occurs through a one-electron reduction interfering with the photosynthesis process. By a similar reaction, the herbicide may induce peroxidation processes in non-target animal species. Furthermore, paraquat may interfere with the cellular transport of polyamines. The aim of this work was to investigate some aspects related to paraquat-induction of oxidative stress (lipoperoxidation, enzymatic activities of catalase and superoxide dismutase) and also the levels of polyamines (putrescine, spermidine and spermine) in two species of freshwater invertebrates, the oligochaete Lumbriculus variegatus and the gastropod Biomphalaria glabrata. The results showed that both organisms elicited differential responses. In addition, the data suggested that polyamines may play an important role against lipoperoxidation processes.

Role of FGF and noggin in neural crest induction.

A study of the molecules noggin and fibroblast growth factor (FGF) and its receptor in the induction of the prospective neural crest in Xenopus laevis embryos has been carried out, using the expression of the gene Xslu as a marker for the neural crest. We show that when a truncated FGF receptor (XFD) was expressed ectopically in order to block FGF signaling Xslu expression was inhibited. The effect of XFD on Xslu was specific and could be reversed by the coinjection of the wild-type FGF receptor (FGFR). Inhibition of Xslu expression by XFD is not a consequence of neural plate inhibition, as was shown by analyzing Xsox-2 expression. When ectoderm expressing XFD was transplanted into the prospective neural fold region of embryos Xslu induction was inhibited. The neural crest can also be induced by an interaction between neural plate and epidermis. As this induction is suppressed by the presence of XFD in the neural plate and not in the epidermis, it suggests that the neural crest is induced by FGF from the epidermis. However, treatment of neural plate with FGF was not able to induce Xslug expression, showing that in addition to FGF other non-FGF factors are also required. Previously we have suggested that the ectopic ventral expression of Xslu produced by overexpression of noggin mRNA resulted from an interaction of noggin with a ventral signal. Overexpression of XFD inhibits this effect, suggesting that FGF could be one component involved in this ventral signaling. Overexpression of FGFR produced a remarkable increase in the expression of Xslu in the posterior neural folds and around the blastopore. Injections in different blastomeres of the embryo suggest that the target cells of this effect are the ventral cells. Finally, we proposed a model in which the induction of the neural crests at the border of the neural plate requires functional FGF signaling, which possibly interacts with a neural inducer such as noggin.

Outcomes analysis of verbal dyspraxia in classic galactosemia.

PURPOSE: This study evaluates a genotype/phenotype relationship between developmental verbal dyspraxia (DVD) and the common, missense mutation of the galactose-1-phosphate uridyltransferase gene, Q188R, in patients with classic galactosemia (G/G). METHODS: As part of this study, we devised a questionnaire for "speech problems" to be completed by the patient\'s clinician. To validate the questionnaire and determine its accuracy in detecting DVD, we analyzed questionnaire responses for 21 patients by testing them independently and directly for DVD through a speech pathologist blinded to the patients' genotype. RESULTS: We found that the questionnaire had a sensitivity of 0.56 and a specificity of 0.75. We then calculated the prevalence of DVD for a larger set of 113 patients with G/G galactosemia whose biochemical phenotype, molecular genotypes, and clinical status were known. The prevalence of "speech problems" from raw data were 50 of 113 (44.2%). After adjusting for misclassification, 43 (38.1%) were classified as cases of DVD. Using multivariate, logistic, regression analyses we found a significant interaction between genotype and mean red blood cell (RBC) galactose-1-phosphate (Gal-1-P). When corrected, using mean RBC Gal-1-P < h 3.28 mg%, the Q188R/Q188R genotype was the best predictor of DVD. There was a significant risk (odds ratio = 9.6, p = 0.0504) of having DVD associated with homozygosity for Q188R compared with other genotypes. CONCLUSIONS: We conclude that homozygosity for Q188R mutations in the GALT gene is a significant risk factor for DVD. However, poor metabolic control obviates this relationship as indicated by RBC Gal-1-P greater than 3.28 mg%.

The inductive properties of mesoderm suggest that the neural crest cells are specified by a BMP gradient.

We have analyzed the role of mesoderm in the induction of the neural crest in Xenopus using expression of neural plate (Xsox-2) and neural crest (Xslug and ADAM). Conjugation experiments using different kinds of mesoderm together with embryonic dissection experiments suggest that the dorsolateral mesoderm is capable of specifically inducing neural crest cells. Neural crest markers can be induced in competent ectoderm at varying distances from the inducing mesoderm, with dorsal tissue inducing neural crest at a distance while dorsolateral tissue only induces neural crest directly in adjacent ectoderm. The results suggest that dorsal mesoderm has a high level of inducer and dorsolateral mesoderm has a lower level, consistent with a inductive gradient. We explored the possible role of BMP and noggin in the generation of such a hypothetical gradient and found that: (1) progressively higher levels of BMP activity are sufficient for the specification of neural plate, neural crest, and nonneural cells, respectively; (2) progressively higher levels of noggin are able to induce neural crest at greater distances from the source of inducer; and (3) modification of the levels of BMP activity causes induction of the neural crest in absence of neural plate, suggesting independent induction of these two tissues. We propose a model in which a gradient of BMP activity is established in the ectoderm by interaction between BMP in the ectoderm and BMP inhibitors in the mesoderm. Neural crest is induced when a threshold level of BMP is attained in the ectoderm. The dorsolateral mesoderm produces either BMP inhibitors or a specific neural crest inducer, with low BMP activity inducing neural plate while high BMP activity induces epidermis.