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PubMed2002

Selection of optimal process analyzers for plant-wide monitoring.

In this paper, the effect of process analyzer selection and positioning on plant-wide process monitoring is investigated. A fundamental problem in process analytical chemistry is the incomparability of different instrument characteristics. A fast but imprecise instrument is incomparable to a slow but precise instrument. Theory is developed to overcome this problem by using an abstract definition of a process analyzer. This definition allows us to put all instrument characteristics for a particular monitoring task on an equal footing. This results in a measurability factor M that expresses monitoring performance of any process measurement by combining instrument characteristics such as precision, sampling rate, grab size, response correlation, and delay time. Both the choice of location and the performance characteristics of different process analyzers can be evaluated using the measurability factor. The unifying nature of the measurability factor allows for a rational decision between completely different process analyzers and locations (Smilde et al., in this issue). The theory is illustrated and validated with an experiment. A tubular reactor for free-radical bulk polymerization of styrene is monitored by in-line short-wave near-infrared spectroscopy at different positions. Alternatively, product samples are collected for at-line near-infrared analysis. Both analyzers measure styrene monomer concentration. The analysis results are used to predict conversion as well as number and weight average molecular mass of the polystyrene reactor product. The theoretical measurability factors for this case study correspond well with the experimental findings.

Journal Article↗
PubMed2005

Molecular characterization and evolutionary study of spider tubuliform (eggcase) silk protein.

As a result of hundreds of millions of years of evolution, orb-web-weaving spiders have developed the use of seven different silks produced by different abdominal glands for various functions. Tubuliform silk (eggcase silk) is unique among these spider silks due to its high serine and very low glycine content. In addition, tubuliform silk is the only silk produced just during a short period of time, the reproductive season, in the spider's life. To understand the molecular characteristics of the proteins composing this silk, we constructed tubuliform-gland-specific cDNA libraries from three different spider families, Nephila clavipes, Argiope aurantia, and Araneus gemmoides. Sequencing of tubuliform silk cDNAs reveals the repetitive architecture of its coding sequence and novel amino acid motifs. The inferred protein, tubuliform spidroin 1 (TuSp1), contains highly homogenized repeats in all three spiders. Amino acid composition comparison of the predicted tubuliform silk protein sequence to tubuliform silk indicates that TuSp1 is the major component of tubuliform silk. Repeat unit alignment of TuSp1 among three spider species shows high sequence conservation among tubuliform silk protein orthologue groups. Sequence comparison among TuSp1 repetitive units within species suggests intragenic concerted evolution, presumably through gene conversion and unequal crossover events. Comparative analysis demonstrates that TuSp1 represents a new orthologue in the spider silk gene family.

Amino Acid Sequence↗
PubMed2002

Characterization of the major proteins of tubers of yam bean (Pachyrhizus ahipa).

Tubers of six accessions of ahipa (Pachyrhizus ahipa) contained between 0.77 and 1.34% nitrogen on a dry weight basis. This corresponds to 4.8 to 8.4% crude protein based on a nitrogen to protein conversion factor of 6.25; but detailed analysis of AC230 showed that although 93% of the total N was extracted with buffer containing 1.0 M NaCl, about a third of this was lost on dialysis. It was calculated, therefore, that salt-soluble proteins comprise about 60% of the total tuber nitrogen, with low-molecular-mass nitrogenous components comprising a further 30%. Electophoretic analysis of the salt-soluble proteins showed similar patterns of components in the six accessions, with none being present in amounts sufficiently high to suggest a role as storage proteins. Furthermore, light microscopy failed to show significant deposits of protein within the tuber cells. Five "major" protein bands, which together accounted for about 19% of the total salt-soluble protein fraction were purified and subjected to N-terminal amino acid sequencing. Comparison of these with sequences in protein databases revealed similarities to alpha-amylases, chitinases and chitin binding proteins, cysteine proteinases (including major components from P. erosus tubers), a tuberization-specific protein from potato, and proteins induced in soybean and pea by stress or the plant hormone abscisic acid, respectively. It was concluded that the primary roles of these proteins are probably in aspects of tuber metabolism and development and/or conferring protection to pests and pathogens, and that true storage proteins are not present. The absence of storage proteins is consistent with the biological role of the tubers as storage organs for carbohydrates (cf cassava tuberous roots) rather than as propagules (cf yam and potato tubers).

Amino Acid Sequence↗
PubMed2002

Aigialomycins A-E, new resorcylic macrolides from the marine mangrove fungus Aigialus parvus.

Aigialomycins A-E (2-6), new 14-membered resorcylic macrolides, were isolated together with a known hypothemycin (1) from the mangrove fungus, Aigialus parvus BCC 5311. Structures of these compounds, including absolute configuration, were elucidated by spectroscopic methods, chemical conversions, and X-ray crystallographic analysis. Hypothemycin and aigialomycin D (5) exhibited in vitro antimalarial activity with IC(50) values of 2.2 and 6.6 microg/mL, respectively, while other analogues were inactive. Cytotoxicities of these compounds were also evaluated.

Animals↗
PubMed1999

A New Insight in the Biosynthesis of Pheomelanins: Characterization of a Labile 1,4-Benzothiazine Intermediate.

It has long been known that pheomelanins, the distinctive pigments of red hair and celtic skin, arise by the oxidative cyclization of cysteinyldopas, mainly the 5-S-isomer 1, via 1,4-benzothiazines. However, the nature and reactivity of these intermediates have remained poorly defined. In an reexamination of the oxidation of 1, in aqueous buffers at physiological pHs, a hitherto unknown labile intermediate was identified and formulated as the 3-hydroxy-3,4-dihydro-1,4-benzothiazine 5 based on direct NMR analysis of the reaction mixture and conversion to the stable benzothiazines 3 and 4 under different conditions. Structure 5 was further supported by oxidation of the model compound 6 leading to the analogous more stable 2,2-dimethyldihydro-1,4-benzothiazine 9.

Journal Article↗
PubMed1999

Tamosterone Sulfates: A C-14 Epimeric Pair of Polyhydroxylated Sterols from a New Oceanapiid Sponge Genus.

Two novel, C-14 epimeric polyhydroxylated 15-keto steroid sulfates, tamosterone sulfate and 14beta-tamosterone sulfate (1 and 2), were isolated from a sponge belonging to a new genus collected in Yap, Federated States of Micronesia. Their structures were assigned by analysis of spectroscopic data and chemical conversions. 14beta-Tamosterone sulfate (2) has the rare naturally occurring C/D cis ring fusion and is the less stable epimer based on equilibration studies. Both compounds possess side-chain substitution patterns not observed previously in marine sterols.

Journal Article↗
PubMed2006

Cytotoxic hypothemycin analogues from Hypomyces subiculosus.

Three new hypothemycin analogues were isolated from the fungal strains Hypomyces subiculosus DSM 11931 and DSM 11932. The structures of these compounds were elucidated by spectroscopic methods, chemical conversion, and X-ray crystallographic analysis. One of the analogues, 4-O-demethylhypothemycin, exhibited potent and selective cytotoxic activity against cell lines with a BRAF mutation.

Antineoplastic Agents↗
PubMed1999

Stereoselective metabolism of nicotine and tobacco-specific N-nitrosamines to 4-hydroxy-4-(3-pyridyl)butanoic acid in rats.

The carcinogenic tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are believed to play a role in cancers associated with the use of tobacco products. Urinary metabolites of NNK and NNN could be used as biomarkers for an individual's ability to metabolically activate or detoxify these nitrosamines. While several metabolites of NNK can be quantified in human urine, no assay is available to determine human urinary levels of NNK and NNN metabolites resulting from the critical alpha-hydroxylation metabolic activation pathways. The major urinary metabolites resulting from alpha-hydroxylation of NNK and NNN in rodents are 4-oxo-4-(3-pyridyl)butanoic acid (keto acid) and 4-hydroxy-4-(3-pyridyl)butanoic acid (hydroxy acid). The major obstacle to the use of these metabolites as biomarkers of metabolic activation is the fact that they are also metabolites of nicotine, which is present at levels 1400-13000 times greater than those of the nitrosamines in cigarette smoke. However, the chirality of hydroxy acid could be useful in overcoming this problem. If different enantiomers of hydroxy acid were formed from nicotine versus the nitrosamines, and if the overall yield of hydroxy acid from nicotine were substantially smaller than that from the nitrosamines, then hydroxy acid might be useful as a urinary biomarker of NNK and NNN alpha-hydroxylation. To these ends, F-344 rats were administered either [5-3H]NNK, [5-3H]NNN, [5-3H]keto acid, or [2'-14C]nicotine. The levels of urinary hydroxy acid were determined by HPLC analysis. Its stereochemistry was determined by conversion to its methyl ester, reaction with (S)-(-)-alpha-methylbenzyl isocyanate, and separation and quantitation of the resulting diastereomers by HPLC. Urinary hydroxy acid accounted for 12% of the NNK dose and 31% of the NNN dose, but only 1 and 0.1% of the dose of keto acid and nicotine, respectively. Furthermore, metabolism of NNK produced mainly (S)-hydroxy acid in the urine, while metabolism of keto acid and nicotine gave predominantly (R)-hydroxy acid. Both enantiomers were present in the urine of NNN-treated rats. Therefore, in the rat, it is possible to distinguish the hydroxy acid derived from nicotine from that derived from the nitrosamines. If similar pathways occur in humans, (S)-hydroxy acid could potentially be developed as a urinary biomarker of NNK and NNN alpha-hydroxylation in smokers.

Animals↗
PubMed2004

Oral antiarrhythmic drugs in converting recent onset atrial fibrillation.

AIM: This article reviews clinical studies on oral antiarrhythmic drugs in converting recent onset atrial fibrillation. An oral loading dose of an antiarrhythmic drug for cardioversion of atrial fibrillation could be an option, due to its simplicity, both for patients admitted to outpatient departments and for episodic treatment by self administration outside the hospital. The latter treatment strategy has recently been pointed out by the American College of Cardiology, the American Heart Association and the European Society of Cardiology as the 'pill in the pocket approach'. METHODS: Articles were identified by Medline 1966 to November 2001 and Embase 1966 to November 2001. Randomized studies of oral antiarrhythmic drugs versus placebo or comparative treatment, which are written in the English language, were selected. Non-randomized or non-comparative studies were selected if the results of an analysis to identify predictors for successful conversion are described. The review of clinical trials is followed by a description of pharmacokinetic parameters of the antiarrhythmic drugs. RESULTS: Studies meeting the inclusion criteria were on propafenone, flecainide, sotalol, amiodarone, quinidine, digoxin and verapamil. Conversion rates of a single oral loading dose of 600 mg propafenone varied between 37% and 41% at 4 h after ingestion. Propafenone was more effective than quinidine, amiodarone and placebo. A single oral dose of 300 mg flecainide restored sinus rhythm in 59% and 68% of patients at 3 h. Flecainide was more effective than amiodarone and placebo. Oral sotalol, digoxin and verapamil were not effective in converting atrial fibrillation to sinus rhythm. CONCLUSION: Propafenone and flecainide are effective in converting recent onset atrial fibrillation. No serious ventricular arrhythmia, other serious proarrhythmic effects or serious non cardiac adverse events were observed. Regular supraventricular tachyarrhythmias with 1:1 AV conduction were rare and were also observed in placebo treated patients. Propafenone and flecainide are more effective in patients with atrial fibrillation of less than 24 h. The association between cardioversion and patient characteristics are not consistent between studies. The pharmacokinetics of flecainide, with lower interindividual variability of absorption kinetics, no genetically determined formation of an active metabolite and a more rapid distribution to myocardial tissue, are more favourable for episodic treatment as compared to propafenone. Both flecainide and propafenone are safe in hospitalized patients. Out of hospital self administration of antiarrhythmic drugs, also described as the 'pill in the pocket approach', could be an option for selected patients, after the treatment has proven to be safe in hospital.

Administration, Oral↗
PubMed2000

A novel natural killer cell line (KHYG-1) from a patient with aggressive natural killer cell leukemia carrying a p53 point mutation.

We present the establishment of a natural killer (NK) leukemia cell line, designated KHYG-1, from the blood of a patient with aggressive NK leukemia, which both possessed the same p53 point mutation. The immunophenotype of the primary leukemia cells was CD2+, surface CD3-, cytoplasmic CD3epsilon+, CD7+, CD8alphaalpha+, CD16+, CD56+, CD57+ and HLA-DR+. A new cell line (KHYG-1) was established by culturing peripheral leukemia cells with 100 units of recombinant interleukin (IL)-2. The KHYG-1 cells showed LGL morphology with a large nucleus, coarse chromatin, conspicuous nucleoli, and abundant basophilic cytoplasm with many azurophilic granules. The immunophenotype of KHYG-1 cells was CD1-, CD2+, surface CD3-, cytoplasmic CD3epsilon+, CD7+, CD8alphaalpha+, CD16-, CD25-, CD33+, CD34-, CD56+, CD57-, CD122+, CD132+, and TdT-. Southern blot analysis of these cells revealed a normal germline configuration for the beta, delta, and gamma chains of the T cell receptor and the immunoglobulin heavy-chain genes. Moreover, the KHYG-1 cells displayed NK cell activity and IL-2-dependent proliferation in vitro, suggesting that they are of NK cell origin. Epstein-Barr virus (EBV) DNA was not detected in KHYG-1 cells by Southern blot analysis with a terminal repeat probe from an EBV genome. A point mutation in exon 7 of the p53 gene was detected in the KHYG-1 cells by PCR/SSCP analysis, and direct sequencing revealed the conversion of C to T at nucleotide 877 in codon 248. The primary leukemia cells also carried the same point mutation. Although the precise role of the p53 point mutation in leukemogenesis remains to be clarified, the establishment of an NK leukemia cell line with a p53 point mutation could be valuable in the study of leukemogenesis.

Antigens, CD↗
PubMedDate not supplied

Downregulation of Akt1 inhibits anchorage-independent cell growth and induces apoptosis in cancer cells.

The serine/threonine kinases, Akt1/PKBalpha, Akt2/PKBbeta, and Akt3/PKBgamma, play a critical role in preventing cancer cells from undergoing apoptosis. However, the function of individual Akt isoforms in the tumorigenicity of cancer cells is still not well defined. In the current study, we used an Akt1 antisense oligonucleotide (AS) to specifically downregulate Akt1 protein in both cancer and normal cells. Our data indicate that Akt1 AS treatment inhibits the ability of MiaPaCa-2, H460, HCT-15, and HT1080 cells to grow in soft agar. The treatment also induces apoptosis in these cancer cells as demonstrated by FACS analysis and a caspase activity assay. Conversely, Akt1 AS treatment has little effect on the cell growth and survival of normal human cells including normal human fibroblast (NHF), fibroblast from muscle (FBM), and mammary gland epithelial 184B5 cells. In addition, Akt1 AS specifically sensitizes cancer cells to typical chemotherapeutic agents. Thus, Akt1 is indispensable for maintaining the tumorigenicity of cancer cells. Inhibition of Akt1 may provide a powerful sensitization agent for chemotherapy specifically in cancer cells.

Antineoplastic Agents↗
PubMed1987

Semisynthetic human [[3H2]Phe1]proinsulin.

Biosynthetic human proinsulin (obtained by recombinant DNA techniques) was used as the starting material for the preparation, by semisynthetic methods, of [3H]proinsulin with the label at the N-terminal phenylalanine residue. The labelled proinsulin was characterized by its retention time on reversed-phase h.p.l.c., by polyacrylamide-gel electrophoresis, by the time course of its enzymic conversion into insulin and by chromatographic analysis after extensive proteolytic degradation. The specific radioactivity of the product was 5 Ci/mmol. Experimental details of the preparation of human [[3H]Phe1]proinsulin, the isolation of this product by isocratic h.p.l.c. and gel filtration, and further characterization of protein intermediates have been deposited as supplement SUP 50138 (12 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on prepayment [see Biochem. J. (1987) 241, 5].

Chromatography, High Pressure Liquid↗
PubMed2001

Variability levels, population size and structure of American and European Drosophila montana populations.

The level and patterns of nucleotide diversity have been characterized for two X-linked loci, fused (fu; a region of 2362 bp) and suppressor of sable (su(s); a region of 413 bp), in one European and one American D. montana population. Sequence variation at these loci shows that the two populations are divergent, although they may not be completely isolated. Data on the level of silent site variability at su(s) (1.1% and 0.5% for the European and American populations, respectively) suggest that the effective population sizes of the two populations may be similar. At the fused locus, one European sequence was highly divergent and may have resulted from gene conversion, and was excluded from the analysis. With this sequence removed, the level of silent site variability was significantly lower in the European population (0.28%) than in the American population (2.3%), which suggests a selective sweep at or near fu in the former population.

Animals↗
PubMed2001

EVT endovascular graft for abdominal aortic aneurysm.

BACKGROUND: A variety of prostheses are now available for the endovascular treatment of abdominal aortic aneurysm (AAA). Significant advantages of the EVT device are its unibody design, secure hook attachment system and graft fabric approximating that used in conventional surgery. METHODS: Implantation of the EVT device was attempted in 60 patients who were studied prospectively with an analysis of subsequent problems encountered. RESULTS: Conversion to open repair was required in four cases (6.7%). There were nine tube grafts inserted, 13 aorto-unilateral iliac with crossover grafts and 34 aorto-bi-iliac grafts. There was one death (mortality 1.7%). Endoleaks were identified in eight patients (14%), none of which were proximal; three sealed spontaneously, two were treated with coil embolization, two are being observed and one patient had an iliac attachment converted to an open anastomosis. Access vessel problems were seen in 21 patients (35%); two-thirds were corrected at the time of initial surgery. Seven patients (12%) had primary graft limb problems identified and treated before leaving the operating room. Nine patients (16%) developed secondary graft limb problems, which were diagnosed and treated after the initial surgery. Endovascular treatment was used in eight and was successful in six with surgical revision required in two. On review of these cases to assess if the problem could have been predicted at the time of initial surgery, it was felt that more aggressive treatment of intraoperatively diagnosed graft limb stenoses, even though considered mild, may have prevented 50% of subsequent secondary graft limb occlusions. CONCLUSION: Although the EVT device has significant advantages in the endovascular management of aortic aneurysm, potential graft limb problems need to be actively identified with the majority able to be successfully managed by supplementary endovascular techniques.

Aged↗
PubMed2000

Phytochrome B binds with greater apparent affinity than phytochrome A to the basic helix-loop-helix factor PIF3 in a reaction requiring the PAS domain of PIF3.

The signaling pathways by which the phytochrome (phy) family of photoreceptors transmits sensory information to light-regulated genes remain to be fully defined. Evidence for a relatively direct pathway has been provided by the binding of one member of the family, phyB, to a promoter-element-bound, basic helix-loop-helix protein, PIF3, specifically upon light-induced conversion of the photoreceptor molecule to its biologically active conformer (Pfr). Here, we show that phyA also binds selectively and reversibly to PIF3 upon photoconversion to Pfr, but that the apparent affinity of PIF3 for phyA is 10-fold lower than for phyB. This result is consistent with previous in vivo data from PIF3-deficient Arabidopsis, indicating that PIF3 has a major role in phyB signaling, but a more minor role in phyA signaling. We also show that phyB binds stoichiometrically to PIF3 at an equimolar ratio, suggesting that the resultant complex is the unit active in transcriptional regulation at target promoters. Deletion mapping suggests that a 37-aa segment present at the N terminus of phyB, but absent from phyA, contributes strongly to the high binding affinity of phyB for PIF3. Conversely, deletion mapping and point mutation analysis of PIF3 for determinants involved in recognition of phyB indicates that the PAS domain of PIF3 is a major contributor to this interaction, but that a second determinant in the C-terminal domain is also necessary.

Arabidopsis↗
PubMed2003

Adult male rat hippocampus synthesizes estradiol from pregnenolone by cytochromes P45017alpha and P450 aromatase localized in neurons.

In adult mammalian brain, occurrence of the synthesis of estradiol from endogenous cholesterol has been doubted because of the inability to detect dehydroepiandrosterone synthase, P45017alpha. In adult male rat hippocampal formation, significant localization was demonstrated for both cytochromes P45017alpha and P450 aromatase, in pyramidal neurons in the CA1-CA3 regions, as well as in the granule cells in the dentate gyrus, by means of immunohistochemical staining of slices. Only a weak immunoreaction of these P450s was observed in astrocytes and oligodendrocytes. ImmunoGold electron microscopy revealed that P45017alpha and P450 aromatase were localized in pre- and postsynaptic compartments as well as in the endoplasmic reticulum in principal neurons. The expression of these cytochromes was further verified by using Western blot analysis and RT-PCR. Stimulation of hippocampal neurons with N-methyl-d-aspartate induced a significant net production of estradiol. Analysis of radioactive metabolites demonstrated the conversion from [(3)H]pregnenolone to [(3)H]estradiol through dehydroepiandrosterone and testosterone. This activity was abolished by the application of specific inhibitors of cytochrome P450s. Interestingly, estradiol was not significantly converted to other steroid metabolites. Taken together with our previous finding of a P450scc-containing neuronal system for pregnenolone synthesis, these results imply that 17beta-estradiol is synthesized by P45017alpha and P450 aromatase localized in hippocampal neurons from endogenous cholesterol. This synthesis may be regulated by a glutamate-mediated synaptic communication that evokes Ca(2+) signals.

Animals↗
PubMed1994

Isolation of the heme-thiolate enzyme cytochrome P-450TYR, which catalyzes the committed step in the biosynthesis of the cyanogenic glucoside dhurrin in Sorghum bicolor (L.) Moench.

The cytochrome P-450 enzyme (hemethiolate enzyme) that catalyzes the N-hydroxylation of L-tyrosine to N-hydroxytyrosine, the committed step in the biosynthesis of the cyanogenic glucoside dhurrin, has been isolated from microsomes prepared from etiolated seedlings of Sorghum bicolor (L.) Moench. The cytochrome P-450 enzyme was solubilized with the detergents Renex 690, reduced Triton X-100, and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and isolated by ion-exchange (DEAE-Sepharose) and dye (Cibacron blue and reactive red 120) column chromatography. To prevent irreversible aggregation of the cytochrome P-450 enzyme, the isolation procedure was designed without any concentration step--i.e., with dilution of the ion-exchange gel with gel filtration material. The isolated enzyme, which we designate the cytochrome P-450TYR enzyme, gives rise to the specific formation of a type I substrate binding spectrum in the presence of L-tyrosine. The microsomal preparation contains 0.2 nmol of total cytochrome P-450/mg of protein. The cytochrome P-450TYR enzyme is estimated to constitute approximately 20% of the total cytochrome P-450 content of the microsomal membranes and about 0.2% of their total protein content. The apparent molecular mass of the cytochrome P-450TYR enzyme is 57 kDa, and the N-terminal amino acid sequence is ATMEVEAAAATVLAAP. A polyclonal antibody raised against the isolated cytochrome P-450TYR enzyme is specific as monitored by Western blot analysis and inhibits the in vitro conversion of L-tyrosine to p-hydroxymandelonitrile catalyzed by the microsomal system. The cytochrome P-450TYR enzyme exhibits high substrate specificity and acts as an N-hydroxylase on a single endogenous substrate. The reported isolation procedure based on dye columns constitutes a gentle isolation method for cytochrome P-450 enzymes and is of general use as indicated by its ability to separate cytochrome P-450TYR from the cytochrome P-450 enzyme catalyzing the C-hydroxylation of p-hydroxyphenylacetonitrile and from cinnamic acid 4-hydroxylase.

Amino Acid Sequence↗
PubMed1996

armadillo, bazooka, and stardust are critical for early stages in formation of the zonula adherens and maintenance of the polarized blastoderm epithelium in Drosophila.

Cellularization of the Drosophila embryo results in the formation of a cell monolayer with many characteristics of a polarized epithelium. We have used antibodies specific to cellular junctions and nascent plasma membranes to study the formation of the zonula adherens (ZA) in relation to the establishment of basolateral membrane polarity. The same approach was then used as a test system to identify X-linked zygotically active genes required for ZA formation. We show that ZA formation begins during cellularization and that the basolateral membrane domain is established at mid-gastrulation. By creating deficiencies for defined regions of the X chromosome, we have identified genes that are required for the formation of the ZA and the generation of basolateral membrane polarity. We show that embryos mutant for both stardust (sdt) and bazooka (baz) fail to form a ZA. In addition to the failure to establish the ZA, the formation of the monolayered epithelium is disrupted after cellularization, resulting in formation of a multilayered cell sheet by mid-gastrulation. SEM analysis of mutant embryos revealed a conversion of cells exhibiting epithelial characteristics into cells exhibiting mesenchymal characteristics. To investigate how mutations that affect an integral component of the ZA itself influence ZA formation, we examined embryos with reduced maternal and zygotic supply of wild-type Arm protein. These embryos, like embryos mutant for both sdt and baz, exhibit an early disruption of ZA formation. These results suggest that early stages in the assembly of the ZA are critical for the stability of the polarized blastoderm epithelium.

Animals↗