A machine learning model for predicting the ballistic impact resistance of unidirectional fiber-reinforced composite plate.

It has been a vital issue to ensure both the accuracy and efficiency of computational models for analyzing the ballistic impact response of fiber-reinforced composite plates (FRCP). In this paper, a machine learning (ML) model is established in an effort to bridge the ballistic impact protective performance and the characteristics of microstructure for unidirectional FRCP (UD-FRCP), where the microstructure of the UD-FRCP is characterized by the two-point correlation function. The results showed that the ML model, after trained by 175 cases, could reasonably predict the ballistic impact energy absorption of the UD-FRCP with a maximum error of 13%, indicating that the model can ensure both computational accuracy and efficiency. Besides, the model's critical parameter sensitivities are investigated, and three typical ML algorithms are analyzed, showing that the gradient boosting regression algorithm has the highest accuracy among these algorithms for the ballistic impact problem of UD-FRCP. The study proposes an effective solution for the traditional difficulty of the ballistic impact simulation of composites with both high efficiency and accuracy.

Modulation of methylnitrosourea-induced breast cancer in Sprague Dawley rats by dehydroepiandrosterone: dose-dependent inhibition, effects of limited exposure, effects on peroxisomal enzymes, and lack of effects on levels of Ha-Ras mutations.

Dehydroepiandrosterone (DHEA), the major steroid precursor of androgens and estrogens produced in peripheral tissues in primates, is an effective chemopreventive agent in the N-methyl-N-nitrosourea (MNU)-induced rat mammary tumor model. Dietary DHEA (5-600 ppm; 600 mg/kg diet) was administered beginning 1 week before MNU and administered continually throughout the duration of the experiment. The highest dose of DHEA (600 ppm) significantly decreased tumor incidence from 95 to 45% and increased tumor latency and decreased tumor multiplicity from 4.1 to 0.5 tumors/rat. Lower doses of DHEA (5, 24, and 120 ppm) were also effective, decreasing tumor multiplicity by 28, 40, and 55%, respectively, increasing tumor latency in a dose-dependent manner but only minimally affecting final tumor incidence. DHEA in the diet caused a dose-dependent increase in serum levels of DHEA. The 120-ppm dietary dose of DHEA resulted in serum levels of DHEA of approximately 42 pmol/ml levels, similar to those seen in young humans. When we examined whole mounts of mammary glands derived from rats exposed to higher levels of DHEA (600 ppm), we observed a striking increase in lobular development. The doses of DHEA used in these studies (< or =600 ppm) had minimal effects on the induction of fatty acid CoA synthetase, a peroxisome-associated enzyme. In contrast, a dose of 2000 ppm substantially increased levels of peroxisome-associated fatty acid CoA synthetase. The varied and striking efficacy of DHEA was achieved in the absence of any significant effect on body weight gain in the treated rats. Furthermore, tumors from rats treated with MNU alone or rats treated with MNU plus DHEA were examined for the presence of mutations in the Ha-Ras oncogene. There was a slight decrease in the percentage of tumors bearing Ha-Ras mutations in tumors derived from MNU-control rats as contrasted with tumors from MNU-DHEA (120 and 600 ppm)-treated rats. Based on the striking chemopreventive efficacy of continual exposure to DHEA, we examined the effects of more limited exposure to DHEA. Rats were treated with DHEA for a period of 7 weeks immediately before and after MNU injection. Rats were then placed on the control diet for the ensuing 15 weeks. Even this limited exposure to DHEA for a period of 7 weeks profoundly decreased final tumor incidence and multiplicity. Additionally, we examined the effects of intermittent dosing with DHEA. Rats were treated alternatively at 3-week intervals either with diet containing DHEA or with control diet. It was found that this intermittent dosing with DHEA also substantially inhibited the formation of mammary tumors.

An uncommon phenotype of poor inducibility of CYP1A1 in human lung is not ascribable to polymorphisms in the AHR, ARNT, or CYP1A1 genes.

Cigarette smoking can induce CYP1A1 in the lung. Induction requires the aryl hydrocarbon receptor (AHR) and aryl hydrocarbon receptor nuclear translocator (ARNT) proteins. Lung samples from seven of 75 Finnish patients who smoked until the time of surgery exhibited absent or low levels of CYP1A1 protein, mRNA and enzymatic activity, suggesting that these individuals might be genetically non or poorly inducible for CYP1A1. All seven lung samples expressed normal levels of AHR mRNA and ARNT mRNA, indicating that they did not carry inactivating polymorphisms in the 5' upstream regulatory regions of these genes. Sequencing of cDNAs encompassing the complete coding regions of AHR and ARNT identified a previously known codon 554 polymorphism in AHR, which was present in the homozygous state in one individual. This polymorphism, which leads to an amino acid substitution, has previously been reported either to have no effect or to enhance CYP1A1 induction. Previously unreported silent single nucleotide polymorphisms were identified in codon 44 of AHR and codon 189 of ARNT. 1500 bp of genomic sequence from the 5' upstream regulatory sequence of the CYP1A1 gene was also sequenced in the non-inducible individuals. A nucleotide substitution polymorphism at position -459 was detected in the heterozygous state in two individuals. This polymorphic site does not reside in any known regulatory sequence. The complete CYP1A1 coding sequence and intron/exon boundaries were then sequenced. None of the non or poorly inducible individuals exhibited any polymorphisms, either homozygous or heterozygous compared to representative inducible individuals or the previously published CYP1A1 sequence. Thus, no polymorphisms in the AHR, ARNT or CYP1A1 genes were identified that could be responsible for the non/low inducibility phenotype observed.

Characterization of expression of the gene for human pterin carbinolamine dehydratase/dimerization cofactor of HNF1.

Pterin carbinolamine dehydratase/dimerization cofactor of HNF1 (PCD/DCoH) is a dual-function protein. In the cytoplasm it acts as a dehydratase in the regeneration of tetrahydrobiopterin, the cofactor for aromatic amino acid hydroxylases. In the nucleus, it functions as a dimerization cofactor of HNF1 and increases the transcriptional activity of HNF1. To deepen our understanding of this protein, we characterized its expression in human tissues and cells. Human PCD/DCoH was present predominantly in liver and kidney, with significant amounts in testis and ovary, trace amounts in lung, and undetectable levels in whole brain, heart, and spleen. It was expressed in all of the cells that were examined. Importantly, it was also present in the nucleus of HeLa cells, which lack HNF1, and in the cytoplasm of fibroblasts that have little or no tetrahydrobiopterin. The expression of human PCD/DCoH in the liver and nonhepatic cells was compared at both the mRNA and protein levels. Although the mRNA level in liver was only fourfold higher than that in keratinocytes and fibroblasts, the hepatic PCD/DCoH protein level was 20-fold higher than that in normal human epidermal keratinocytes and dermal fibroblasts. Cloning of the 5' and 3' untranslated region (UTR) of human keratinocyte PCD/DCoH revealed that it has 53 bp more of GC-rich 5' untranslated sequence than the published liver PCD/DCoH. In vitro transcription and translation analysis showed that the longer 5' UTR resulted in about a 35% decrease in translation efficiency. These data show that human PCD/DCoH is not only present in cells where tetrahydrobiopterin is synthesized or HNF1 is present but is a widely distributed protein. Its differential expression in different tissues and cells is regulated not only at the transcriptional level but also at the translational level.

Identification of hepatic nuclear factor 1 binding sites in the 5' flanking region of the human phenylalanine hydroxylase gene: implication of a dual function of phenylalanine hydroxylase stimulator in the phenylalanine hydroxylation system.

Phenylalanine hydroxylase stimulator (PHS) is a component of the phenylalanine hydroxylation system that is involved in the regeneration of the cofactor tetrahydrobiopterin. It is also identical to the dimerization cofactor of hepatocyte nuclear factor 1 (HNF1) (DCoH) that is able to enhance the transcriptional activity of HNF1. Moreover, it has the structural potential for binding macromolecules such as proteins and nucleic acids, consistent with its involvement in gene expression. We investigated whether PHS/DCoH could enhance the expression of phenylalanine hydroxylase (PAH). Cotransfection assays showed that DCoH itself could not transactivate the 9-kb human PAH 5' flanking fragment. However, this 9-kb fragment was transactivated by HNF1 in a dose-dependent manner with a maximum of nearly 8-fold activation; DCoH potentiated this transactivation by another 1.6-fold. The HNF1 binding sites were located at -3.5 kb in a region that is 77.5% identical to the mouse liver-specific hormone-inducible PAH gene enhancer. This study suggests a possible dual function of PHS in vivo in the human phenylalanine hydroxylation system: it is involved in the regeneration of the cofactor tetrahydrobiopterin and can also enhance the expression of the human PAH gene.

Human white blood cells and hair follicles are good sources of mRNA for the pterin carbinolamine dehydratase/dimerization cofactor of HNF1 for mutation detection.

Pterin carbinolamine dehydratase/dimerization cofactor of HNF1 (PCD/DCoH) is a protein that has a dual function. It is a pterin 4alpha-carbinolamine dehydratase that is involved in the regeneration of the cofactor tetrahydrobiopterin during the phenylalanine hydroxylase- catalyzed hydroxylation of phenylalanine. In addition, it is the dimerization cofactor of HNF1 that is able to activate the transcriptional activity of HNF1. Deficiencies in the gene for this dual functional protein result in hyperphenylalaninemia. Here we report for the first time that the PCD/DCoH mRNA is present in human white blood cells and hair follicles. Taking advantage of this finding, a sensitive, rapid and convenient method for screening mutations occurring in the coding region of this gene has been described.

Loss of cyp1a1 messenger rna expression due to nonsense-mediated decay.

Clones of the mouse hepatoma cell line Hepa1c1c7 (Hepa-1) with lesions in the Cyp1a1 gene were isolated previously. A subset of these clones fails to express CYP1A1 mRNA even when treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin, which induces this mRNA in wild-type Hepa-1 cells. The current investigation sought an explanation for this phenotype in one of these clones, c33. Loss of mRNA expression in c33 was shown to be caused by mutational changes in the Cyp1a1 gene rather than by its epigenetic silencing. No mutations were identified in the 5' flanking region of the Cyp1a1 gene, containing the promoter and dioxin-responsive enhancer sequences. A single nucleotide insertion occurred at nucleotide 418 in the coding region of one Cyp1a1 allele, and a single nucleotide insertion occurred at nucleotide 465 in the other allele in c33. These sequence alterations were confirmed in the genomic DNA of the clone. Both insertions generate a premature termination codon at codon 172. This termination codon occurs in a position within the intron/exon structure of the Cyp1a1 gene such that the encoded mRNA should be subject to "nonsense-mediated decay" (NMD). Inhibition of protein synthesis is known to reverse NMD. The protein synthesis inhibitors cycloheximide and puromycin fully restored CYP1A1 mRNA expression to c33 cells, supporting the notion that NMD degrades CYP1A1 mRNA in this strain. The mutations identified in the coding region of c33 provide an explanation, therefore, for its loss of both CYP1A1 enzymatic activity and inducible CYP1A1 mRNA expression.

Expression of 4alpha-carbinolamine dehydratase in human epidermal keratinocytes.

4alpha-Carbinolamine dehydratase is a bifunctional protein involved in the regeneration of tetrahydrobiopterin during the hydroxylation of the aromatic amino acids. It is also a dimerization cofactor of HNF1 and therefore is believed to function as part of the hepatic gene transcription system. In view of the recent discoveries that the distribution and developmental pattern of the dehydratase do not correlate strictly with those of the aromatic amino acid hydroxylases and HNF1, the hypothesis that the dehydratase may have other unknown functions has been put forward. In the present paper, we demonstrate unambiguously that human epidermal keratinocytes express detectable levels of this protein as indicated by enzyme assay, immunoprecipitation, Western blot, and RT-PCR. Its complete coding sequence has been cloned and was found to be identical with the human liver counterpart. The possible function of the dehydratase in skin is discussed.

Cytochrome P-450 mRNAs are modulated by dehydroepiandrosterone, nafenopin, and triiodothyronine.

Dehydroepiandrosterone (DHEA) is the only known naturally occurring compound that promotes peroxisome proliferation in rodent liver, and stimulates transcriptional induction of genes involved in lipid metabolism and peroxisomal beta-oxidation. Therefore, we examined mRNA for several such genes in rat liver, specifically acyl-CoA oxidase and the cytochromes P-450 (CYP4A1, CYP4A3, and CYP3A23), after 5 to 6 day treatments with either DHEA, or nafenopin, a known peroxisome proliferator. Acyl-CoA oxidase and CYP4A1 were induced nearly identically by DHEA and nafenopin, with induction being more pronounced in female rats. However, CYP3A23 was induced only by DHEA, suggesting an induction mechanism independent of the peroxisome proliferator activated receptor. Previously, we observed triiodothyronine (T3) suppression of peroxisome proliferator induced CYP4As and we sought to determine whether CYP3A23 might be regulated in a different manner. T3 was found to also suppress DHEA-dependent induction of CYP3A23. CYP4A2 expression in kidney was also negatively regulated by T3. To characterize a putative negative thyroid hormone response element (nTRE) in the 5' flanking region of this gene, a luciferase reporter gene containing a rat CYP4A2 flanking sequence extending to -1865 bp was transfected into HepG2 cells along with human thryroid hormone receptor expression vector. Expression of luciferase activity was unaffected by T3, suggesting the absence of a functional nTRE within this portion of CYP4A2. These data demonstrate gene regulatory activity by DHEA different from that of nafenopin, and a suppressive effect of T3, consistent with indirect regulatory mechanisms not involving an nTRE.

Binding of a burst-phase intermediate formed in the folding of denatured D-glyceraldehyde-3-phosphate dehydrogenase by chaperonin 60 and 8-anilino-1-naphthalenesulphonic acid.

Upon dilution, D-glyceraldehyde-3-phosphate dehydrogenase (GADPH) that has been fully inactivated, but only partially unfolded, in dilute guanidine hydrochloride (GuHCl) recovers activity completely. The fully unfolded enzyme, however, is re-activated only to a limited extent after dilution, and refolds rapidly in a burst phase to a partially folded intermediate characterized by increases in both the emission intensity of intrinsic fluorescence and binding to 8-anilino-1-naphthalenesulphonic acid (ANS). This intermediate aggregates with a time lag of a few minutes, and the aggregation can be suppressed completely by chaperonin 60 (GroEL). Stoichiometric analysis of the suppression of GAPDH re-activation by GroEL suggests that the tetradecameric GroEL binds to a dimeric GAPDH folding intermediate. This intermediate can be re-activated by ATP or ATP/chaperonin 10 (GroES) to an extent considerably greater than that obtained on spontaneous re-activation of the fully denatured enzyme upon dilution. Probing with a fluorescent derivative of NAD+ shows that this folding intermediate does not have a native conformation at the active site. The similar profiles of the effects of GroEL and ANS on the re-activation of GAPDH denatured by different concentrations of GuHCl suggest that GroEL and ANS recognize and bind to the same folding intermediate, which is similar to the relatively stable, partially unfolded, state of the enzyme denatured in 0.5-1.0 MGuHCl. However, the complexes of the intermediate with GroEL or ANS appear to be different, in that GroEL, but not ANS, suppresses aggregation and assists folding in the presence of ATP.