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Biomedical subjects

E Leiter

Publications and source records attributed to E Leiter.

At least 19 recordsLinked to original sources
PubMed2004

Penicillium chrysogenum glucose oxidase -- a study on its antifungal effects.

AIMS: Purification and characterization of the high molecular mass Candida albicans-killing protein secreted by Penicillium chrysogenum. METHODS AND RESULTS: The protein was purified by a combination of ultrafiltration, chromatofocusing and gel filtration. Enzymological characteristics [relative molecular mass (M(r)) = 155 000, subunit structure alpha(2) with M(r,alpha) = 76 000, isoelectric point (pI) = 5.4] were determined using SDS-PAGE and 2D-electrophoresis. N-terminal amino acid sequencing and homology search demonstrated that the antifungal protein was the glucose oxidase (GOX) of the fungus. The enzyme was cytotoxic for a series of bacteria, yeasts and filamentous fungi. Vitamin C (1.0 mg ml(-1)) prevented oxidative cell injuries triggered by 0.004 U GOX in Emericella nidulans cultures but bovine liver catalase was ineffective even at a GOX : catalase activity ratio of 0.004 : 200 U. A secondary inhibition of growth in E. nidulans cultures by the oxygen-depleting GOX-catalase system was likely to replace the primary inhibition exerted by H(2)O(2). CONCLUSIONS: Penicillium chrysogenum GOX possesses similar enzymological features to those described earlier for other Penicillium GOXs. Its cytotoxicity was dependent on the inherent antioxidant potential of the test micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: Penicillium chrysogenum GOX may find future applications in glucose biosensor production, the disinfection of medical implants or in the food industry as an antimicrobial and/or preservative agent.

Amino Acids↗
PubMed2001

Penicillin productivity and glutathione-dependent detoxification of phenylacetic and phenoxyacetic acids in Penicillium chrysogenum.

Both toxicity and penicillin productivity of the hydroxylated derivatives of phenylacetic acid (PA) and phenoxyacetic acid (POA) were highly dependent on the position of hydroxylation on the aromatic ring in Penicillium chrysogenum. Hydroxylation at position 2 diminished penicillin production but the compounds retained most of their toxicity. On the other hand, hydroxylation at position 4 resulted in barely toxic derivatives with still significant penicillin productivity. 3-Hydroxy-PA was a weak side-chain precursor with considerably reduced toxicity. The activity of the glutathione-dependent detoxification pathway correlated well with the toxicity of the compounds but there was no correlation between acidity, toxicity and penicillin productivity.

Acetates↗
PubMed2001

Penicillin V production by Penicillium chrysogenum in the presence of Fe3+ and in low-iron culture medium.

Late-exponential-phase Penicillium chrysogenum mycelia grown in a complex medium possessed an intracellular iron concentration of 650 mumol/L (2.2 +/- 0.6 mumol per g mycelial dry mass). This iron reserve was sufficient to ensure growth and antibiotic production after transferring mycelia into a defined low-iron minimal medium. Although the addition of Fe3+ to the Fe-limited cultures increased significantly the intracellular iron levels the surplus iron did not influence the production of penicillin V. Supplements of purified major P. chrysogenum siderophores (coprogen and ferrichrome) into the fermentation media did not affect the beta-lactam production and intracellular iron level. Neither 150 nor 300 mumol/L extracellular Fe3+ concentrations disturbed the glutathione metabolism of the fungus, and increased the oxidative stress caused by 700 mmol/L H2O2. Nevertheless, when iron was applied in the FeII oxidation state the oxidative cell injuries caused by the peroxide were significantly enhanced.

Culture Media↗
PubMed2001

Searching for new-type antifungal drugs (an outline for possible new strategies).

New approaches for treatment of invasive fungal infections are necessary to cope with emerging resistant fungal pathogens of humans. In this paper, three different strategies are presented and evaluated to find new-type antifungal drugs and their targets. While experimental data obtained with potent chitinase inhibitors, e.g. allosamidin, and small-size antifungal proteins of fungal origin are encouraging more efforts are needed to verify and exploit the possible involvement of intracellular thiols, e.g. glutathione, and their metabolic enzymes in the pathogenesis of mycoses caused by dimorphic fungi. Chitinase inhibitors seem to hinder the cell separation of yeasts and the fragmentation of filamentous fungi quite effectively and, hence, they may be implicated in future therapies of systemic mycoses. In addition, small-size antifungal proteins possessing a broad inhibition spectrum may also provide us with promising new agents for the treatment of different kinds of (e.g. cutaneous) fungal infections.

Acetylglucosamine↗
PubMed2001

The glutathione metabolism of the beta-lactam producer filamentous fungus Penicillium chrysogenum.

Glutathione (gamma-L-glutamyl-L-cysteinyl-glycine; GSH) shares structural similarities with the beta-lactam biosynthetic intermediate ACV-tripeptide (delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine). Not surprisingly, GSH has been reported to inhibit the beta-lactam biosynthetic machinery quite effectively and, hence, strategies to decrease the intracellular GSH concentrations without influencing negatively the physiological status of idiophasic mycelia would attract industrial interests. Here we present a detailed map of the GSH metabolic network of P. chrysogenum and show a promising way to keep the GSH pool selectively down under penicillin producing conditions. This procedure includes a well-controlled and transient lowering of pH at the beginning of the production phase, and it relies on the GSH-dependent detoxification of the protonophore penicillin side-chain precursors phenoxyacetic acid (POA) and phenylacetic acid (PA). Encouraging preliminary fed-batch fermentation experiments have been performed to test this technological proposal. Interestingly, the mechanism of the activation of POA and PA to the appropriate CoA derivatives has remained yet to be answered but the involvement of GSH seems to be rather unlikely in this case. Our data also challenge the hypothesis that the formation of different kinds of penicillins would be an alternative to GSH-dependent detoxification processes in P. chrysogenum.

Acetates↗
PubMed2000

NOD/LtSz-Rag1null mice: an immunodeficient and radioresistant model for engraftment of human hematolymphoid cells, HIV infection, and adoptive transfer of NOD mouse diabetogenic T cells.

Development of a small animal model for the in vivo study of human immunity and infectious disease remains an important goal, particularly for investigations of HIV vaccine development. NOD/Lt mice homozygous for the severe combined immunodeficiency (Prkdcscid) mutation readily support engraftment with high levels of human hematolymphoid cells. However, NOD/LtSz-scid mice are highly radiosensitive, have short life spans, and a small number develop functional lymphocytes with age. To overcome these limitations, we have backcrossed the null allele of the recombination-activating gene (Rag1) for 10 generations onto the NOD/LtSz strain background. Mice deficient in RAG1 activity are unable to initiate V(D)J recombination in Ig and TCR genes and lack functional T and B lymphocytes. NOD/LtSz-Rag1null mice have an increased mean life span compared with NOD/LtSz-scid mice due to a later onset of lymphoma development, are radioresistant, and lack serum Ig throughout life. NOD/LtSz-Rag1null mice were devoid of mature T or B cells. Cytotoxic assays demonstrated low NK cell activity. NOD/LtSz-Rag1null mice supported high levels of engraftment with human lymphoid cells and human hemopoietic stem cells. The engrafted human T cells were readily infected with HIV. Finally, NOD/LtSz-Rag1null recipients of adoptively transferred spleen cells from diabetic NOD/Lt+/+ mice rapidly developed diabetes. These data demonstrate the advantages of NOD/LtSz-Rag1null mice as a radiation and lymphoma-resistant model for long-term analyses of engrafted human hematolymphoid cells or diabetogenic NOD lymphoid cells.

Adoptive Transfer↗
PubMed1995

Defects in the structure and expression of the genes for the T cell marker Rt6 in NZW and (NZB x NZW)F1 mice.

Rt6 is a T cell-restricted GPI-anchored membrane protein and a member of the family of mono(ADP-ribosyl)transferases. One of the two murine Rt6 genes is deleted in NZW mice. This finding is reminiscent of the deletion of one of the TCR beta genes in the same mouse strain and it is an intriguing possibility that these gene deletions arose by a common genetic mechanism. The Rt6 locus retained by the NZW mouse (designated Rt6-1) is polymorphic among inbred strains of laboratory mice. The NZW mouse shows several strain-specific restriction fragment length variants in this Rt6 locus and five amino acid substitutions occur in the predicted native Rt6 polypeptide of the NZW mouse relative to the corresponding polypeptides of NZB and BALB/c mice. Whereas transcript levels of the two Rt6 genes appear to be normal in spleen and intestine of NZB mice, the corresponding tissues of NZW mice show reduced levels of transcripts from the Rt6 locus retained in this mouse strain. Moreover, reduced levels of Rt6 mRNA also occur in spleen and intestine of (NZB x NZW)F1 hybrid animals, indicating that F1 animals have inherited a dominant factor from the genetic background of the NZW mouse, resulting in low levels of Rt6 expression. It is conceivable that the alterations in the Rt6 genes of the NZW mouse and/or the factor(s) affecting defective Rt6 expression constitute part of the genetic contribution of the NZW mouse to the autoimmune lupus-like disease in (NZB x NZW)F1 animals.(ABSTRACT TRUNCATED AT 250 WORDS)

ADP Ribose Transferases↗
PubMed1994

Structure and chromosomal location of the gene encoding mouse corticosteroid-binding globulin: strain differences in coding sequence and steroid-binding activity.

Corticosteroid-binding globulin (CBG) is a member of the serine proteinase inhibitor superfamily and is responsible for the plasma transport of glucocorticoids. The mouse Cbg gene structure has been deduced from two non-overlapping DNA fragments of a lambda EMBL-3 genomic library, as well as PCR amplification of the approx. 2 kb of genomic DNA that lies between them. Mouse Cbg comprises five exons that span a region of approx. 10.5 kb, and has been localized in tight linkage with the Aat (alpha 1-antitrypsin) and Spi (serine proteinase inhibitor) gene complex on chromosome 12, in a region syntenic with this genetic locus on human chromosome 14. Intron-specific oligodeoxyribonucleotide primers were also used to PCR-amplify Cbg coding regions from several mouse strains. No differences were found in the Cbg coding sequences of BALB/c and C57BL/6J-cpk/cpk mice, while two mutations were found within RIIIS/J Cbg that result in Lys201-->Glu and Ala357-->Thr substitutions in the mature mouse CBG polypeptide. To assess what impact these substitutions might have on the steroid-binding activity of RIIIS/J CBG, these mutations were introduced separately or together into a BALB/c mouse Cbg cDNA. Expression of these mutants in the MDCK cell line indicated that the Lys201-->Glu substitution accounts for the abnormal steroid-binding affinity of CBG in RIIIS/J mice.

Amino Acid Sequence↗
PubMed1992

Double mosaic aneuploidy: 45,X/47,XY,+8 in a male infant.

We report on a 13-month-old boy with abnormalities consistent with mosaic trisomy 8 syndrome and male genitalia with partial penoscrotal transposition without hypospadias, a retractile left testis in inguinal canal, and an absent right testis. A voiding cystourethrogram showed an outpouching close to the lower right side of the bladder (utriculum) and bilateral hydronephrosis secondary to vesicoureteral reflux. Peripheral blood karyotype was 45,X/47,XY,+8. The karyotype of cultured skin fibroblasts was 47,XY,+8 with no 45,X cells detected among 20 cells counted. Tissues removed during surgery documented a 45,X/47,XY,+8 complement in the left testicle and utriculum, but only a 45,X line among 20 cells counted from vas deferens tissue. A possible mechanism for the origin of this previously unreported mosaicism might be an abnormal zygote with a 47,XY,+8 complement with subsequent simultaneous loss of chromosome Y and 8 in a cell at a very early embryonic stage.

Aneuploidy↗
PubMed1989

Percutaneous management of postoperative lymphocele.

A case report of a pelvic lymphocele developing after lymphadenectomy for staging of prostatic carcinoma is described. This collection was successfully managed by percutaneous catheter drainage. The incidence, pathophysiology, clinical symptomatology, differential diagnosis, and treatment options of pelvic lymphocele are reviewed. We believe that percutaneous catheter drainage is currently the optimal treatment modality.

Drainage↗
PubMed1989

Bladder pheochromocytoma: evaluation with magnetic resonance imaging.

A 17-year-old black woman with a large vesical pheochromocytoma was managed successfully by hemicystectomy and ureteroneocystotomy. Preoperatively, in addition to the routine diagnostic evaluation, magnetic resonance imaging was performed. Magnetic resonance imaging proved to be an extremely useful modality to assess the integrity of the bladder wall and extent of extravesical involvement.

Adolescent↗
PubMed1989

Dramatic response of pulmonary metastasis from prostatic cancer to LH-RH agonist treatment.

A case is presented of an elderly man with stage D2 cancer of the prostate who responded dramatically to hormonal manipulation utilizing LH-RH agonist. This case has three exceptional features: absence of bone metastasis; massive pulmonary metastasis; and rectal ulceration due to prostatic neoplasm. Although any type of hormonal manipulation could have achieved the same results, the use of LH-RH agonist has distinct advantages: minimal side effects and good patient tolerance.

Adenocarcinoma↗
PubMed1987

Spontaneous retroperitoneal hemorrhage: unusual presentation of renal cancer.

Spontaneous retroperitoneal hemorrhage as the presenting sign of renal cancer is rare. A case of spontaneous retroperitoneal hemorrhage from a renal carcinoma is described and management possibilities presented. While it is true that renal angiomyolipomas are the main cause of spontaneous retroperitoneal renal bleeding, the possibility of renal cancer should be entertained more often in the differential diagnosis.

Adult↗
PubMed1986

[Interferon-alpha in the treatment of hematologic neoplasms].

This report aims to review briefly the current status of treatment of haematological malignancies with interferon-alpha (IFN-alpha). Overall hairy cell leukemia and chronic myelogenous leukemia appear to be most sensitive to IFN-alpha. We started to investigate, how interferon exerts its antileukemic activity and in which way interferon therapy can be optimized. Our preliminary results fail to support the view of interferon mediated enhancement of host responses. They rather indicate direct effects of IFN on leukemic cells in vitro. By means of IFN-dependent biological markers (e.g. beta-2-microglobulin, neopterin) clinically effective but atoxic doses of IFN-alpha could be defined for HCL and CML. In final conclusion, the recent studies on the clinical efficacy of IFN-alpha revealed its potent antitumoral effect in hematological malignancies. However, the further proof of the potential benefit of IFN treatment versus conventional therapeutic strategies remains to be elucidated.

Cell Division↗
PubMed1986

Alpha-interferon induces remission in hairy cell leukemia without enhancement of natural killing.

The number of large granular lymphocytes (LGL) and the capacity of peripheral blood mononuclear cells (PBMC) to lyse K 562 target cells in a natural killer (NK)-like fashion was evaluated in seven hairy cell leukemia (HCL) patients undergoing treatment with recombinant interferon-alpha-2 (rIFN-alpha-2). In HCL patients, whose peripheral blood showed high numbers (greater than or equal to 15 X 10(3)/microliters) of leukemic cells the number of LGL and their capacity to lyse K 562 tumor target cells were very low prior to treatment but increased significantly (p less than 0.05) following interferon (IFN) therapy. In patients with low numbers of hairy cells (HC) in their peripheral blood, both these parameters were higher and remained largely unaffected throughout IFN treatment. In vitro, HC proved to be completely insensitive to natural killing when tested against unstimulated and IFN-activated LGL from healthy donors. These results fail to support the concept of IFN-mediated enhancement of host antitumor actions, responsible for the favourable clinical results in HCL.

Adult↗
PubMed1986

Influence of ethylene-2,2'-bis (dithio)bis(ethanol) on certain human in vitro and in vivo lymphocyte functions.

The influence of in vivo or in vitro exposure of human lymphocytes to ADA 202-718 (ethylene-2,2'-bis (dithio) bis (ethanol)) was tested. Evaluated were spontaneous, lectin, or alloantigen-induced proliferation as well as the release of IFN-alpha, gamma and of neopterin. The spontaneous cell mediated lysis (NK lysis) of K 562 tumor targets was also assessed. In vitro exposure to ADA 202-718 slightly enhanced lectin and alloantigen-induced human lymphocyte proliferation. IFN-gamma release was also slightly increased. These parameters were not clearly affected by in vivo treatment with ADA 202-718. In vitro and in vivo-treatment with this drug did not affect spontaneous lymphocyte blastogenesis. Statistically significant effects, however, were seen when NK activity was assessed. Preincubation of either effector or target cells with ADA 202-718 as well as in vivo treatment caused an increase of NK lysis. When these results obtained with human cells were compared with those previously seen in a murine system, immunostimulatory activity of ADA 202-718 was more pronounced in the murine system.

Biopterins↗