Learning Design Rules for Selective Oxidation Catalysts from High-Throughput Experimentation and Artificial Intelligence

The design of heterogeneous catalysts is challenged by the complexity of materials and processes that govern reactivity and by the fact that the number of good catalysts is very small in comparison to the number of possible materials. Here, we show how the subgroup-discovery (SGD) artificial-intelligence approach can be applied to an experimental plus theoretical data set to identify constraints on key physicochemical parameters, the so-called SG rules, which exclusively describe materials and reaction conditions with outstanding catalytic performance. By using high-throughput experimentation, 120 SiO2-supported catalysts containing ruthenium, tungsten, and phosphorus were synthesized and tested in the catalytic oxidation of propylene. As candidate descriptive parameters, the temperature and 10 parameters related to the composition and chemical nature of the catalyst materials, derived from calculated free-atom properties, were offered. The temperature, the phosphorus content, and the composition-weighted electronegativity are identified as key parameters describing high yields toward the value-added oxygenate products acrolein and acrylic acid. The SG rules not only reflect the underlying processes particularly associated with high performance but also guide the design of more complex catalysts containing up to five elements in their composition.

Deep-cavity subporphyrazines with extended π-perimeters

Unprecedentedly large subporphyrazines (SubPz) with dibenzoquinoxalino-fusion and peripheral phenyl substitution were prepared by the cyclization of perfluorated or non-fluorous polyphenyl-substituted quinoxaline dinitriles and characterized by spectroscopic techniques. The compounds suitability to act as photosensitizers was explored by wavelength-specific induction of singlet oxygen luminescence and was shown to be excellent. Determination of 1O2-quantum yields suggests that fluorine substitution enhances the photosensitization efficiencies of the SubPz. On the other hand, cyclic voltammetry reveals an increase of irreversible reductive processes in case of the fluorinated SubPz.

[Human embryonic stem cells within the context of international research activity]

Research involving pluripotent human embryonic stem cells (hESCs) is a rapidly growing field of science. Since hESCs originate from early human embryos, alternative methods for producing pluripotent cells have been developed. This article introduces some of those strategies and, in addition, covers international efforts to establish consistent international standards for cultivation, characterization and preservation of hESCs. Furthermore, global trends to form networks in the field of stem cell research as well as endeavors to harmonize ethical standards for hESC research are presented. Finally, potential applications of hESCs in the field of pharmacology/toxicology are discussed as well as recent results of animal studies using hESCs.

Constitutive NF-kappaB maintains high expression of a characteristic gene network, including CD40, CD86, and a set of antiapoptotic genes in Hodgkin/Reed-Sternberg cells

Constitutively activated nuclear factor (NF)-kappaB is observed in a variety of neoplastic diseases and is a hallmark of the malignant Hodgkin and Reed-Sternberg cells (H/RS) in Hodgkin lymphoma. Given the distinctive role of constitutive NF-kappaB for H/RS cell viability, NF-kappaB-dependent target genes were searched for by using adenoviral expression of the super-repressor IkappaBDeltaN. A surprisingly small but characteristic set of genes, including the cell-cycle regulatory protein cyclin D2, the antiapoptotic proteins Bfl-1/A1, c-IAP2, TRAF1, and Bcl-x(L), and the cell surface receptors CD86 and CD40 were identified. Thus, constitutive NF-kappaB activity maintains expression of a network of genes, which are known for frequent, marker-like expression in primary or cultured H/RS cells. Intriguingly, CD40, which is able to activate CD86 or Bcl-x(L) via NF-kappaB, is itself transcriptionally regulated by NF-kappaB through a promoter proximal binding site. NF-kappaB inhibition resulted in massive spontaneous and p53-independent apoptosis, which could be rescued by ectopic expression of Bcl-x(L), underscoring its dominant role in survival of H/RS cells. Hence, NF-kappaB controls a signaling network in H/RS cells, which promotes tumor cell growth and confers resistance to apoptosis.

System for efficient helper-dependent minimal adenovirus construction and rescue

Helper-dependent minimal adenoviral vectors deleted for all viral coding sequences are promising vectors for gene therapy. They retain only the adenovirus cis elements for replication and packaging, can accommodate up to 36 kb of foreign DNA, and exhibit prolonged transgene expression and reduced tissue toxicity as compared with first-generation adenoviral vectors. We have developed a system consisting of a set of cosmid cloning vectors (pMV and pMVX) for simple routine construction and efficient rescue of minimal adenoviral vectors. In the cloning vectors the inverted terminal repeats (ITRs) are flanked by recognition sites for the super rare-cutting endonuclease I-SceI. This allows the release of linear minimal adenovirus genomes for rescue of minimal adenovirus regardless of the sequence of the insert DNA. pMV contains a multiple cloning site for the insertion of 26 to 36 kb of therapeutic DNA. pMVX contains a noncoding human X-chromosomal DNA fragment as a vector backbone, which provides endonuclease restriction sites that allow for complete or partial replacement of the vector backbone by 1 to 26 kb of therapeutic DNA sequences, while retaining a packageable final minimal adenovirus genome size between 27 and 37.5 kb. Both vectors exist in two forms, with or without an Escherichia coli lacZ reporter gene cassette. Several minimal adenoviral vectors with insert sizes ranging from 1.5 to 16 kb were constructed with these cloning vectors. Minimal adenoviruses were efficiently rescued and amplified to high titers, using a Cre/lox-based helper system. Vectors containing the X-chromosomal backbone were stable during amplification. This simple and efficient system facilitates the construction of minimal adenoviruses and should be useful for further improvement of these new vectors.

Ovine adenovirus vectors mediate efficient gene transfer to skeletal muscle

Ovine adenovirus (OAV) vectors represent a promising tool for human gene therapy since these vectors overcome the problem of pre-existing immunity against human adenovirus vectors. In this report we investigated the in vivo characteristics of this novel vector system with respect to its potential for gene transfer into skeletal muscle. We found that moderate doses of an OAV-derived vector expressing the human alpha1-antitrypsin gene (OAVhaat) infected skeletal muscle in mice very efficiently resulting in high serum hAAT levels. The infection was restricted to skeletal muscle, but gene expression was transient and vector DNA was rapidly cleared. Vector clearance was also observed with a vector that lacked the transgene. The loss of vector DNA was accompanied by a cellular immune response in the infected muscle but was not connected with detectable expression of early or late genes of the viral backbone as analyzed by RT-PCR. A very low dose of OAVhaat (3x 10(7) infectious particles) was sufficient to produce reasonable amounts (>100 ng/ml) of serum hAAT, and this was accompanied by a weak immune response to the vector. Under these conditions, a second intramuscular injection of the same recombinant OAV vector was successful. Our study expands the known tissue tropism of OAV-derived vectors in vivo and points to the possible utility of the vector for muscle gene transfer and vaccination.

Intravenous administration of recombinant adenoviruses causes thrombocytopenia, anemia and erythroblastosis in rabbits

BACKGROUND

Recombinant adenoviruses are highly efficient gene transfer vehicles but their administration to mammals is accompanied by a strong inflammatory response. The present study reports additional side effects observed during adenoviral gene transfer studies in rabbits.

METHODS

Hematological and serological parameters, the course of viremia and the organ distribution were analyzed after in vivo administration of E1-deleted adenoviruses in rabbits.

RESULTS

The systemic administration of a therapeutic dose of 5 x 10(11) infectious particles/kg (infusion time 20 min) led to an average reduction of 80-90% in the platelet count within 48 h. Full recovery took 10-14 days. Virus administration induced a strong but transient erythroblastosis (peaking 24 h after administration) which settled 48 h later. Normochromic anemia occurred over the next 10 days with hemoglobin levels dropping by about 40% to reach the lowest level 10 days after administration and taking two months for full recovery. Dose-dependent thrombocytopenia was also found in mice, but neither erythroblastosis nor anemia was observed (in equivalent doses). The hematological findings did not improve after local injection via the portal vein. Local and systemic administration led to a comparable course of viremia. Only minor differences were found in the biodistribution of viruses between local and systemic administration. Large amounts of viral DNA and transgene expression were found in the lungs, the kidneys and the ovaries, even after local administration via the portal vein.

CONCLUSIONS

Local intravenous injection via the portal vein does not prevent systemic spread of viral vectors and the occurrence of vector-related side effects. The hematological changes observed in rabbits suggest the need for careful monitoring of hematological and rheological parameters in clinical trials.

Ovine adenovirus vectors overcome preexisting humoral immunity against human adenoviruses in vivo

Recombinant human adenoviruses (hAd) have become widely used as tools to achieve efficient gene transfer. However, successful application of hAd-derived vectors in clinical trials is limited due to immunological and potential safety problems inherent in their human origin. In this study, we describe a recombinant ovine adenovirus (OAV) as an alternative vector for gene transfer in vivo. In contrast to an hAd vector, the OAV vector was not neutralized by human sera. An OAV vector which contained the cDNA of the human alpha1-antitrypsin (hAAT) gene linked to the Rous sarcoma virus promoter was generated and administered systemically to mice. The level and duration of hAAT gene expression was similar to that achieved with an hAd counterpart in both immunocompetent and immunodeficient mice. However, the tissue distribution of the OAV vector differed from that observed for hAd vectors in that the liver was not the dominant target. Significantly, we demonstrated efficient gene transfer with the OAV vector into mice immunized with hAd vectors and vice versa. We also confirm that the immune response to a transgene product can prevent its functional expression following sequential application of a vector. Our results suggest a possible solution to endemic humoral immunity against currently used hAd vectors and should therefore have an impact on the design of improved gene therapy protocols utilizing adenovirus vectors.

Tumor cell-specific transgene expression prevents liver toxicity of the adeno-HSVtk/GCV approach

Treatment of colorectal liver metastases with the HSVtk/GCV approach and adenoviral vectors is highly toxic. We present a nontoxic alternative using the cell type-specific CEA promoter instead of the widely used hCMV immediate-early promoter to drive tk gene expression in the context of a recombinant adenovirus. Analysis of CEA promoter-dependent tk gene expression showed significant activity of this promoter in several human and rat tumor-derived cell lines but not in rat primary hepatocytes and in mouse liver, whereas the CMV promoter was highly active in all cell types and tissues investigated. CEA promoter-dependent tk gene expression was sufficient to kill 100% of cancer cells in vitro, even if less than 10% were infected by the adenoviral vector, indicating a significant bystander effect. Moreover, treatment of subcutaneous tumors in SCID mice with Ad.CEA-tk led to a several-fold reduction of tumor growth, and tail vein injection of a high dose of Ad.CEA-tk caused no side-effects in the liver. The CMV promoter was more potent than the CEA promoter in mediating GCV sensitivity to cancer cells in vitro and in vivo, but even a 20-fold reduction of the dose of Ad.CMV-tk did not prevent its liver cell toxicity after systemic application to mice and still resulted in the death of all animals within 4 days after the start of GCV treatment. These results indicate that restriction of tk gene expression to tumor cells in the liver prevents systemic toxicity. Moreover, the CEA promoter is a safe and efficient tool for tumor cell-specific expression of suicide genes in the liver.

Reactivation of the previously silenced cytomegalovirus major immediate-early promoter in the mouse liver: involvement of NFkappaB

The cytomegalovirus (CMV) major immediate-early promoter/enhancer is active in many cell culture systems and is considered to be one of the strongest promoters in vitro. However, when this promoter was used in in vivo approaches to gene therapy, it was silenced within a few weeks in several organs including the liver. In this study, we demonstrated transcriptional inactivation of the CMV promoter in mouse liver. In contrast to the CMV promoter, a hybrid promoter consisting of a minimal CMV promoter and the enhancer II of hepatitis B virus was active for at least 11 weeks in mouse liver. While investigating the reason for the shutdown of the CMV promoter, we did not find evidence for methylation of adenovirus DNA in the region of transgene insertion, but we could show that the silenced CMV promoter was reactivated after lipopolysaccharide treatment of mice or partial hepatectomy. Both stimuli are known to activate the transcription factor NFkappaB, which binds to four sites in the CMV promoter/enhancer. We show that expression from the CMV promoter in hepatocyte-derived cell lines in vitro depends on NFkappaB. In vivo experiments demonstrate that NFkappaB, which is not present in mouse hepatocytes in vivo, is activated after infection with recombinant adenoviruses and that the time course of NFkappaB activation parallels that of CMV promoter-dependent expression. Moreover, adenovirus infection of transgenic mice carrying a CMV promoter-driven lacZ gene leads to strong activation of the expression of this gene in the liver. Thus, NFkappaB is involved in the activation of the CMV promoter in the liver.

[Iodine and thyroid hormone status of mother pigs and their offspring]

The iodine concentration in the chain sow feed-->blood serum of dams-->milk-->blood serum of piglets (2 per litter) was determined in 36 litters in two experiments with different dietary iodine levels and in 16 litters in the framework of field studies in two piglet production farms in each case at weaning after four weeks lactation. In the blood serum also the concentration of thyroxine (T4) and triiodothyronine was determined. The serum concentration of iodine and T4 did not indicate dietary iodine administration (sows) or showed only a weak response (piglets). The iodine concentration of milk was very strongly affected by iodine administration and by the iodine status of sows prior to the experiments. The highest milk iodine concentration was found in the sows of piglet production farms, corresponding to the level of iodine administered. For diagnosis of the iodine supply status the iodine concentration of sow milk should be analyzed. The lower limit of milk iodine concentration is presently defined as 50 micrograms/l, and the mean of 5 random samples per sow herd should not fall below this limit. Serum concentrations of iodine and T4 may remain moderate even in case of a low iodine supply (sow serum: 30 micrograms iodine/l, 25 nmol T4/l; piglet's serum: 50 micrograms iodine/l, 55 nmol T4/l), and are unsuited for diagnosis of iodine status.

HBV-derived promoters direct liver-specific expression of an adenovirally transduced LDL receptor gene

In vivo approaches to liver gene therapy will require restriction of transgene expression to hepatocytes. Since targeting of viral vectors exclusively to the liver is not easy to achieve, use of liver-specific promoters for driving expression of therapeutic genes is an interesting alternative. We have shown previously that regulatory elements of the hepatotrophic hepatitis B virus (HBV) are strong and liver-specific in vitro and therefore might be useful in hepatic gene therapy. Here we describe recombinant adenoviruses in which the human LDL receptor gene is under the transcriptional control of the HBV core promoter, the core promoter linked directly to HBV enhancer I, or a HBV-CMV hybrid promoter, respectively. These viruses allowed for a moderate to strong expression of the LDL receptor gene in vitro in a hepatocyte-specific manner when compared with the CMV immediate-early promoter. In vivo experiments demonstrated that the promoter gave rise to an expression level comparable to that from the CMV promoter in mouse liver, but was very weak in lung and skeletal muscle. Thus, the HBV-CMV hybrid promoter is strong and hepatocyte specific both in vitro and in vivo even in the adenoviral context and would be a good choice for driving a therapeutic gene in liver gene therapy.

Gene therapy: prospects for treatment of liver disease

Gene therapy in the liver for treatment of metabolic diseases is a great challenge. The development of vectors for gene transfer to hepatocytes in vitro and to the liver in vivo has advanced very rapidly within the last few years. However, none of the existing vectors would allow for expression of therapeutic levels of a gene product for a longer period of time. Our laboratory is developing alternative strategies for gene transfer to the liver in vivo which are based on composite vectors consisting of envelopes and promoters derived from hepatitis B virus, an EBV-derived replicon, and the chromosomal protein HMG1. Hepatocyte specificity of both, binding of the particles and expression of foreign genes, was demonstrated.

Evaluation of HBV promoters for use in hepatic gene therapy

Strategies for in vivo hepatic gene therapy will require regulatory elements which allow for long-term expression of therapeutic genes and restriction of expression to hepatocytes. This study investigates the suitability of promoters derived from hepatitis B virus (HBV) for liver-specific gene expression in vectors for hepatic gene therapy. We provide three hepatocyte-specific promoters, the HBV core promoter, the HBV core promoter linked directly to the HBV enhancer I, and a hybrid promoter containing the HBV enhancer II and a basic CMV promoter, which are hepatocyte-specific and allow for increasing levels of reporter gene expression. Moreover, in long-term expression studies using our promoter constructs in the context of an EBV based expression system we found that expression from these promoters remained nearly unchanged over a period of at least two months in hepatocyte-derived cell lines.

[Spontaneous fistulae and abscesses of the upper urinary tract (author's transl)]

Spontaneous cutaneous fistulae and abscesses of the renal pelvis and ureter have become rare. Six case reports demonstrate their etiology and differential diagnostic problems. If there is no underlying urologic disease, above all no urolithiasis, other causes of fistulae and abscesses should be kept in mind, the most frequent of these being Crohn's disease.