PubMed Health⌕ Search

Biomedical subjects

J Uhl

Publications and source records attributed to J Uhl.

At least 19 recordsLinked to original sources
PubMed2001

Splice donor site mutation in the lysosomal neuraminidase gene causing exon skipping and complete loss of enzyme activity in a sialidosis patient.

Sialidosis is a lysosomal storage disease caused by the deficiency of alpha-N-acetylneuraminidase (NEU1; sialidase), the key enzyme for the intralysosomal catabolism of sialylated glycoconjugates. We have identified a homozygous transversion in the last intron (IVSE +1 G>C) in neu1 of a sialidosis patient. Sequencing of the truncated cDNA revealed an alternatively spliced neu1 transcript which lacks the complete sequence of exon 5. Skipping of exon 5 leads to a frameshift and results in a premature termination codon. This is the first description of an intronic point mutation causing a complete deficiency of the lysosomal neuraminidase activity.

Amino Acid Sequence↗
PubMed2001

Negative regulation of neuroblastoma cell growth by carbohydrate-dependent surface binding of galectin-1 and functional divergence from galectin-3.

The cell density-dependent growth inhibition of human SK-N-MC neuroblastoma cells is initiated by increased ganglioside sialidase activity leading to elevated cell surface presentation of ganglioside GM1, a ligand of galectin-1. We herein show that the extent of the cell surface expression of the galectin coincides with marked increases of the sialidase activity. Reverse transcriptase-polymerase chain reaction analysis excludes a regulation at the transcriptional level. Exposure of cells to purified galectin-1 reveals its carbohydrate-dependent activity to reduce cell proliferation. Assays to detect DNA fragmentation biochemically and cytometrically and to block caspases render it unlikely that galectin-1 acts as a classical proapoptotic factor on these cells. Because the chimeric galectin-3 shares binding sites and binding parameters with galectin-1 for these cells, we tested whether this galectin will elicit the same response as the homodimeric cross-linking galectin-1. Evidently, galectin-3 fails to affect cell growth by itself but interferes with galectin-1 upon coincubation. Its proteolytically truncated variant, the C-terminal lectin domain with impaired capacity to form aggregates when surface bound, has only weak binding properties. Thus, the way in which the galectin-1 interacts topologically with an apparently common set of ligands relative to galectin-3 is crucial for eliciting post-binding events. We conclude that galectin-1 is a probable effector in the sialidase-dependent growth control in this system. Moreover, the experiments with galectin-3 reveal functional divergence, most probably based on different topologies of presentation of homologous carbohydrate-binding sites.

Antigens, Differentiation↗
PubMed2001

Prenatal diagnosis and fetal pathology in a Turkish family harboring a novel nonsense mutation in the lysosomal alpha-N-acetyl-neuraminidase (sialidase) gene.

We report a Turkish family with parental consanguinity and at risk for sialidosis type II, an inherited autosomal recessive disorder caused by lysosomal alpha-N-acetyl-neuraminidase (sialidase, NEU1) deficiency. The proband was a premature male infant that presented with hydrops, hepatomegaly, respiratory distress syndrome, and anemia and that died of respiratory insufficiency 2 months after birth despite intensive care. An abnormally increased [14C]methylamine incorporation and an isolated deficiency of lysosomal alpha-N-acetyl-neuraminidase were found in cultured skin fibroblasts. A previous pregnancy of the mother terminated in a spontaneous abortion in the 13th week of gestation. A successive pregnancy showed hydrops fetalis, and an enzymatic assay of cultured amniotic fluid cells indicated a deficiency of alpha-N-acetyl-neuraminidase. Following pregnancy termination at 20 weeks gestation, light microscopy of fetal tissues revealed classic vacuolation not only in liver, bone marrow, brain, and kidney, but also in endocrine organs such as the thyroid gland, adrenal gland, hypophysis, and testes, and in the thymus. DNA analysis of the family showed that both the proband and the third sibling had a novel homozygous nonsense point mutation at nucleotide 87 in exon 1 of the alpha-N-acetyl-neuraminidase (neu1) gene causing a substitution of tryptophan at codon 29 by a termination codon (W29X). DNA sequencing of polymerase chain reaction products identified the parents as heterozygous carriers. To detect neu1 mRNA expression, a real-time reverse transcription/polymerase chain reaction was performed, and similar rates of neu1 mRNA expression were found in the fibroblasts of the fetus, the 2nd sibling, and in controls. The very early termination codon with complete loss of neuraminidase activity is probably the molecular basis of the unusually severe vacuolation pattern in this form of congenital sialidosis.

Abnormalities, Multiple↗
PubMed1999

Comparison of susceptibility testing methods with mecA gene analysis for determining oxacillin (methicillin) resistance in clinical isolates of Staphylococcus aureus and coagulase-negative Staphylococcus spp.

Ninety-nine clinical staphylococcal isolates (58 coagulase-negative Staphylococcus spp. [CoNS] and 41 Staphylococcus aureus isolates) were evaluated for susceptibility to oxacillin. The following susceptibility testing methods, media, and incubation conditions were studied: agar dilution by using Mueller-Hinton (MH) medium (Difco) supplemented with either 0, 2, or 4% NaCl and incubation at 30 or 35 degrees C in ambient air for 24 or 48 h; disk diffusion by using commercially prepared MH medium (Difco) and MH II agar (BBL) and incubation at 35 degrees C in ambient air for 24 or 48 h; and agar screen (spot or swab inoculation) by using commercially prepared agar (Remel) or MH agar (Difco) prepared in-house, each containing 4% NaCl and 6 microg of oxacillin/ml (0.6-microg/ml oxacillin was also studied with MH agar prepared in-house for the agar swab method and CoNS isolates) and incubation at 35 degrees C in ambient air for 24 or 48 h for swab inoculation and at 30 or 35 degrees C in ambient air for 24 or 48 h for spot inoculation. The results for these methods were compared to the results for mecA gene detection by a PCR method. Given the ability to support growth and the results for susceptibility testing (the breakpoint for susceptible isolates was </=2 microg/ml), the best methods for CoNS isolates were (i) agar dilution by using MH medium supplemented with 4% NaCl and incubation at 35 degrees C for 48 h (no growth failures were noted, and sensitivity was 97.6%) and (ii) agar screen (swab inoculation) by using MH medium prepared in-house supplemented with 4% NaCl and containing 0.6 microg oxacillin/ml and incubation at 35 degrees C for 48 h (one isolate that did not carry the mecA gene did not grow, and the sensitivity was 100%). All but one (agar dilution without added NaCl and incubation at 30 degrees C for 48 h) of the methods tested revealed all oxacillin-resistant S. aureus isolates, and no growth failures occurred with any method. If the breakpoint for susceptibility was lowered to </=1 microg/ml for agar dilution methods, more CoNS isolates with oxacillin resistance related to the mecA gene were detected when 0 or 2% NaCl agar supplementation was used. Only one CoNS isolate with mecA gene-associated resistance was not detected by using agar dilution and MH medium supplemented with 4% NaCl with incubation for 48 h. When the breakpoint for susceptibility was decreased 10-fold (from 6.0 to 0.6 microg of oxacillin per ml) for the agar swab screen method, fully 100% of the CoNS isolates that carried the mecA gene were identified.

Bacterial Proteins↗
PubMed1998

Orally active indole N-oxide PDE4 inhibitors.

This communication describes the synthesis and in vitro and in vivo evaluation of a novel potent series of phosphodiesterase type (IV) (PDE4) inhibitors. Several of the compounds presented possess low nanomolar IC50's for PDE4 inhibition and excellent in vivo activity for inhibition of TNF-alpha levels in LPS challenged mice (mouse endotoxemia model). Emesis studies (dog) and efficacy in a SCW arthritis model for the most potent PDE4 inhibitors are presented.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1998

The synthesis and biological evaluation of a novel series of indole PDE4 inhibitors I.

This communication describes the synthesis and in vitro evaluation of a novel potent series of phosphodiesterase type (IV) (PDE4) inhibitors. The compounds described contain an indole moiety which replaces the 'rolipram-like' 3-methoxy-4-cyclopentoxy motif. Several of the compounds presented possess low nanomolar IC50's for PDEIV inhibition. In vivo activities determined from measurement of serum TNF-alpha levels in LPS challenged mice (mouse endotoxemia model) are also reported.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1993

Hydrocortisone regulation of interleukin-6 protein production by a purified population of human peripheral blood monocytes.

The direct effect of the endogenous glucocorticoid (GC) hydrocortisone (HC) on interleukin-6 (IL-6) production was examined using purified populations of human peripheral blood monocytes (Mo). Lipopolysaccharide (LPS) induced IL-6 production by Mo in a dose-dependent fashion. IL-6 was detected in Mo supernatants as early as 2 hr after stimulation, with peak IL-6 production observed by 16 hr. Simultaneous addition of HC and LPS resulted in a significant decrease of IL-6 production 4 hr after LPS treatment, with maximum inhibition observed at 16-24 hr. An attenuation of the inhibitory effect of HC occurred with greater concentrations of LPS and with the delay of HC addition until after LPS. However, there was no correlation between the quantity of IL-6 produced by Mo and the level of HC inhibition. The inhibitory effect of HC was greater if LPS, rather than IL-1 beta, were used as a stimulus to induce IL-6 production. The EC50 of LPS-induced IL-6 production by HC was 2.0 x 10(-7) M. The inhibitory effect of HC on LPS-stimulated IL-6 production was GC specific and receptor mediated because: (i) equivalent inhibition was not observed with other endogenous steroids and (ii) equimolar amounts of the GC antagonist RU 486 blocked the GC-mediated effect.

Adult↗
PubMed1993

Intermittent versus continuous administration of 1,25-dihydroxyvitamin D3 in experimental renal hyperparathyroidism.

Conflicting results have been reported regarding the efficacy of intermittent versus continuous administration of 1,25(OH)2D3 in renal secondary hyperparathyroidism. To address this issue we examined sham-operated control rats and hyperparathyroid rats with subtotal (5/6) nephrectomy (Nx). The Nx animals (20 to 22 animals per group) were subjected to three treatment protocols: (i) solvent treatment (Nx-solvent); (ii) two i.p. injections of 35 pmol 1,25(OH)2D3 on days 0 and 4 (Nx-bolus); and (iii) continuous infusion of 70 pmol 1,25(OH)2D3 over six days via osmotic minipump (Nx-infusion). All measurements were performed six days after start of treatment. As compared to sham-operated controls, the pre-pro-PTH/beta-actin mRNA ratio was 2.04-fold higher in Nx-solvent. Both modes of administration of 1,25(OH)2D3 resulted in inhibition of PTH mRNA concentrations relative to Nx-solvent. The pre-pro-PTH/beta-actin mRNA ratio was, however, significantly lower (P < 0.05) in Nx-bolus than in Nx-infusion (Nx-bolus 1.26 higher than sham-operated controls; Nx-infusion 1.65 higher than sham-operated controls). Aminoterminal PTH (N-PTH) serum concentrations were higher in Nx-solvent (52 +/- 4 pg/ml) than in sham-operated controls (32 +/- 3 pg/ml, P < 0.01). N-PTH concentrations in Nx-bolus (38 +/- 4 pg/ml) were significantly lower than in Nx-solvent (P < 0.01) and in Nx-infusion (46 +/- 4 pg/ml, P < 0.05). Parathyroid gland weight (microgram/g body wt) was higher in Nx-solvent (1.30 +/- 0.08 pg/ml) than in sham-operated controls (0.79 +/- 0.04 pg/ml, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Direct suppression of phagocytosis by amphipathic polymeric surfactants.

Recent studies have demonstrated that phagocytosis of colloidal particles by the mononuclear phagocytes of the liver and spleen can be controlled by either coating or stabilizing particulate carriers with the amphipathic polymeric surfactants, F108 and T908. These surfactants consist of copolymers of polypropylene oxide (PPO) and polyethylene oxide (PEO) and, when adsorbed to particulate surfaces, significantly decrease sequestration of particulates by the mononuclear phagocytes (MPS) of the liver. To evaluate these observations further, murine peritoneal macrophages were incubated for varying periods with surfactant-coated and noncoated polystyrene particles (PSPs). Phagocytosis was monitored using gamma counting and quantitative fluorescence microscopy. The data show that phagocytosis is decreased when PSPs are coated with F108 and T908. In addition, suppression of phagocytic activity was observed when cells were pretreated with the surfactant and then challenged with noncoated particles. The data confirm previous observations that polymeric surfactants consisting of PEO and PPO protect particulate carriers from rapid uptake by the MPS of the liver. Further, F108 and T908 suppress phagocytosis directly without affecting the integrity, viability, or functional state of the cell.

Animals↗
PubMed1991

Modulation of synovial fibroblast plasminogen activator and plasminogen activator inhibitor production by protein kinase C.

Phorbol myristate acetate (PMA) added to human synovial fibroblast cultures caused a dose-dependent increase in the production of plasminogen activator inhibitor-type 1 (PAI-1). In addition, PMA inhibited endogenous and interleukin-1 (IL-1) induced plasminogen activator (PA) activity, while increasing mRNA PAI-1 levels. Other protein kinase C (PKC) activators, mezerein and teleocidin B4, caused similar effects. The simultaneous addition of the PKC antagonists, H-7 or staurosporine, prevented the inhibition of PA activity by PMA. This study shows that activation of PKC inhibits PA and stimulates PAI production in human synovial fibroblasts. These results suggest that activation of PKC may play an important role in regulating increased PA production associated with joint destruction in rheumatoid arthritis (RA).

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Identification of IL-1 receptors on human monocytes.

The expression and functional analysis of IL-1 beta R on human monocytes were investigated. Binding of 125I-IL-1 to human monocytes was found to be specific and saturable. Scatchard plot analysis revealed a single class of receptors with a binding constant of 600 pM and a receptor density of approximately 100 binding sites per cell. At 37 degrees C 54% of the labeled ligand was internalized over 2 h of incubation. Addition of 0.2% sodium azide to the cells reduced ligand internalization to 9% of total bound. Cross-linking studies revealed that the IL-1R in human monocytes had a Mr of 80 kDa. The addition of IL-1 to monocytes caused changes in membrane Ag expression as assessed by flow cytometric analysis. The results of this study identify IL-1 receptors on monocytes and suggest that IL-1 may act as an effector molecule for monocytes by enhancing expression of Ag correlated with cell differentiation and immune function.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Interleukin-1 mediated signal transduction associated with synovial cell activation.

The early biochemical events that link interleukin-1 (IL-1) receptor occupancy to neutral proteinase production in synovial cells were studied. Addition of human r-IL-1 to human synovial cells in culture stimulated phospholipase A2 (PLA2) activity, inositol triphosphate production and plasminogen activator (PA) activity in a dose dependent manner with similar EC50 values (0.1-0.5 nM). These results, coupled with time courses and other studies, suggest that the IL-1 modulation of PA involves both products of PLA2 and phospholipase C (PLC) activation. On the other hand, the IL-1 induction of collagenase may primarily involve PLC and protein kinase C activation.

Arthritis, Rheumatoid↗
PubMed1988

Quantitation of related proteins by Western blot analysis.

A spectrophotometric assay for quantitation of related proteins following Western blot analysis is described. Proteins were separated by polyacrylamide gel electrophoresis and electrophoretically transferred to nitrocellulose. In the system utilized in this study, immobilized interleukin-1 (IL-1) proteins were identified by ELISA reaction using a rabbit antibody specific for IL-1 beta. Subsequently, the membrane was probed with goat anti-rabbit antibody conjugated to horseradish peroxidase and IL-1 proteins were detected by incubation with 4-chloro-1-naphthol and hydrogen peroxide. The stained IL-1 bands were cut out, exposed to the peroxidase chromogenic substrate, o-phenylenediamine (OPD), and hydrogen peroxide and the rate of reaction was determined spectrophotometrically at 490 nM. A linear relationship between enzyme activity and IL-1 concentration was observed from 10 to 1000 ng/lane. Thus, this represents a sensitive and specific method for quantitating small amounts of IL-1 in complex protein mixtures.

Chromogenic Compounds↗