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Biomedical subjects

R Wolf

Publications and source records attributed to R Wolf.

At least 91 records · Page 5Linked to original sources
PubMed1997

Hepatic leukostasis and hypoxic stress in adhesion molecule-deficient mice after gut ischemia/reperfusion.

The concept that leukocyte-endothelial cell adhesion (LECA) is a major determinant of the tissue injury elicited by ischemia/reperfusion (I/R) is largely based on studies employing adhesion molecule-specific monoclonal antibodies. The objective of this study was to assess the contribution of LECA to I/R injury using mutant mice (all on a C57B1 background) that are deficient in either intracellular adhesion molecule-1, P-selectin, or CD11/CD18. The accumulation of fluorescently labeled leukocytes and the number of nonperfused sinusoids in livers of control and adhesion molecule-deficient mice were monitored by intravital microscopy for 1 h after release of the occluded (for 15 min) superior mesenteric artery. Autofluorescence of pyridine nucleotide (NADH) was measured as an indicator of mitochondrial O2 consumption and redox status. The number of stationary leukocytes in the liver after gut I/R was significantly elevated compared with baseline values in C57B1 (control) mice. Autofluorescence of NADH was also significantly increased (indicating hypoxia) after I/R in these mice, especially in the pericentral region. Intercellular adhesion molecule-1-, CD11/CD18-, and P-selectin-deficient mice all exhibited a blunted leukosequestration response to I/R and smaller increments in nonperfused sinusoids, relative to C57B1 mice. All adhesion molecule-deficient mice also exhibited an attenuated increment in NADH autofluorescence in the pericentral region, relative to control mice. These results from adhesion molecule-deficient mice provide additional support for the view that LECA is an important determinant of the liver dysfunction induced by gut I/R.

Animals↗
PubMed1997

Role of Kupffer cells in gut ischemia/reperfusion-induced hepatic microvascular dysfunction in mice.

Kupffer cells (KCs) have been implicated in the leukocyte recruitment and microvascular dysfunction associated with liver inflammation. The overall objective of this study was to assess the role of KCs in the leukocyte adhesion and oxidative stress elicited in the liver by gut ischemia/reperfusion (I/R). The accumulation of rhodamine-6G-labeled leukocytes and the number of nonperfused sinusoids (NPS) were monitored (by intravital microscopy) in mouse liver for 1 hour after a 15-minute period of normothermic intestinal ischemia. Autofluorescence of pyridine nucleotide [NAD(P)H] was measured as an index of mitochondrial O2 consumption and redox status. Leukostasis, as well as increases in NPS and NAD(P)H autofluorescence (indicating hypoxia), were observed in the liver at 60 minutes after gut I/R. Pretreatment with gadolinium chloride (GdCl3), which reduces KC function, attenuated the liver leukostasis and NPS elicited by gut I/R. The platelet activating factor (PAF) antagonist, WEB2086, and a tumor necrosis factor (TNF)-alpha-specific antibody were also effective in attenuating the gut I/R-induced leukostasis and NAD(P)H autofluorescence. The findings of this study suggest that KCs play an important role in mediating the leukocyte recruitment, impaired sinusoidal perfusion, and tissue hypoxia elicited in the liver after gut I/R. These KC-mediated responses appear to involve the participation of both PAF and TNF-alpha.

Alanine Transaminase↗
PubMed1997

Gaining more insight into the pathomechanisms of thiol-induced acantholysis.

Acantholysis is considered the initial and the main pathogenetic event of pemphigus. The first step in drug-induced acantholysis (biochemical and/or immunological) involves binding of the drug to the cell membrane and the formation of 'drug-cysteine' instead of 'cysteine-cysteine' bondings. We suggest that the reaction of D-penicillamine with cystine disulfides that results in cysteine-penicillamine disulfides is not a terminal reaction, but rather a primary initiating step of a chain reaction. It is reasonable to consider that the cysteine-penicillamine disulfide is continuing to be enzymatically reduced by various thiol reductants, in particular glutathione reductase, thereby generating a 'new' penicillamine molecule which, in turn, reacts with other cystine disulfides and does so in an unending cycle. A chain reaction is thus created in which the drug is repeatedly generated so that one molecule of the drug may attack thousands of cystine disulfide bonds. It is highly possible that normal individuals have their own endogenous means of controlling this deleterious chain reaction, whereas pemphigus-prone individuals lack the ability to stop this potentially damaging reaction. Drug-induced pemphigus should thus be added to the ever-growing list of adverse drug reactions related to pharmacogenetic disorders in drug metabolism.

Acantholysis↗
PubMed1997

The in vitro effect of hydroxychloroquine on skin morphology and transglutaminase.

BACKGROUND: Antimalarials are some of the most notorious drugs which may induce psoriasis, with 25% of all reported cases being associated with them. Antimalarials do not induce psoriasis de novo, but trigger subclinical psoriasis. In a previous report, we suggested that antimalarials exert their effect by interfering with the epidermal transglutaminase (TGase) activity. OBJECTIVE: To verify this hypothesis by examining the effect of hydroxychloroquine sulfate (HCQS) on cultured human skin and on TGase activity in vitro. MATERIALS AND METHODS: Skin samples from normal donors were cultured in the presence of HCQS for 4 days, and then processed for microscopic examination. TGase activity was assayed in the presence of HCQS and compared with blanks. RESULTS: Significant changes in epidermal morphology were seen in all explants cultured in the presence of HCQS at all concentrations employed. Areas of enhanced and irregular keratinization were observed in the upper epidermis, while a loss of cell polarity, with keratinocyte crowding and disarray, was seen in the lower epidermis. In addition, we observed intraepidermal splitting at different levels and dermo-epidermal detachments. HCQS showed a concentration-dependent inhibition of TGase activity. CONCLUSIONS: We suggest that HCQS causes an initial break in the barrier function of the epidermis by inhibiting TGase activity; this is followed by a physiologic response of the epidermis aimed at barrier restoration. This rather nonspecific stimulus to epidermal proliferation is probably sufficient to trigger psoriasis in predisposed individuals or aggravate it in psoriatic patients.

Antimalarials↗
PubMed1997

Isotopic response.

Explore the source record for details and available documents.

Herpes Zoster↗
PubMed1997

Role of nitric oxide in gut ischemia-reperfusion-induced hepatic microvascular dysfunction.

The overall objective of this study was to assess the contribution of an altered bioavailability of nitric oxide (NO) to the leukocyte adhesion and hypoxic stress elicited in the liver by gut ischemia-reperfusion (I/R). The accumulation of leukocytes, number of nonperfused sinusoids (NPS), and NADH autofluorescence were monitored (by intravital microscopy) in mouse liver after 15 min of superior mesenteric artery occlusion and 60 min of reperfusion. Leukostasis, NPS, and NADH autofluorescence (indicating hypoxia) were all increased in the liver at 60 min after gut I/R. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) exaggerated the liver leukostasis elicited by gut I/R, responses that were prevented by coadministration of L-arginine. The NO donor diethylenetriamine-NO (DETA-NO) and L-arginine were both effective in attenuating the gut I/R-induced leukostasis and increased NADH autofluorescence, whereas neither DETA nor D-arginine exerted a protective action. These findings indicate that NO is an important determinant of the liver leukostasis, impaired sinusoidal perfusion, and tissue hypoxia elicited by gut I/R.

Alanine Transaminase↗
PubMed1997

Ischemia/reperfusion-induced microvascular dysfunction: role of oxidants and lipid mediators.

The objective of this study was to define the role of oxidants and lipid mediators in the leukocyte-endothelial cell adhesion and albumin leakage elicited in rat mesenteric venules by ischemia-reperfusion (I/R). Intravital fluorescence microscopy was used to monitor leukocyte adherence and emigration, platelet-leukocyte aggregation, mast cell degranulation, and albumin leakage after release of a 20-min arterial occlusion. I/R elicited large increases in leukocyte-endothelial cell adhesion and albumin leakage. These responses were significantly attenuated in venules treated with either superoxide dismutase, oxypurinol (an inhibitor of xanthine oxidase), lodoxamide (a mast cell stabilizer), WEB-2086 (a platelet-activating factor antagonist), or SC-41930 (a leukotriene B4-receptor antagonist) but not by U-74006F (an inhibitor of lipid peroxidation). Platelet-leukocyte aggregates and mast cell degranulation induced by I/R were also attenuated by administration of either superoxide dismutase or lodoxamide. These results support the hypothesis that oxidants produced, in part, by xanthine oxidase promote the formation (by mast cells and endothelial cells) of platelet-activating factor and leukotriene B4, which recruit and activate leukocytes in postischemic venules. The adherent and emigrated leukocytes then mediate the increased albumin extravasation observed in the postcapillary venules.

Animals↗
PubMed1997

Rapid synthesis and secretion of intestinal apolipoprotein A-IV after gastric fat loading in rats.

To further investigate the possible role of apolipoprotein A-IV (apo A-IV) in the short-term control of food intake, we examined the kinetics of intestinal apo A-IV synthesis and release into lymph and plasma after intragastric delivery of physiological amounts of lipid. Within 30 min of intragastric administration of 0.1 g of triglyceride, plasma and lymph levels of apo A-IV were similar to those produced by exogenous apo A-IV that inhibit food intake. Within 15 min, 5% of gastrically delivered radioactive lipid reached the distal small bowel and cecum; by 30 min radioactivity was evenly distributed throughout the small intestine, with 10-15% of the load in the distal gut. By 30 min, synthesis of apo A-IV was significantly stimulated in proximal and distal jejunum and distal ileum and remained elevated up to 4 h after the delivery of lipid. Our results indicate that the delivery of physiological amounts of lipid into the stomach produces a significant and rapid stimulation of apo A-IV secretion into lymph and plasma, together with a rapid delivery of lipid and increases in mucosal synthesis of apo A-IV along the entire length of the small intestine. The results support a possible role for apo A-IV in the short-term control of food intake and suggest a role for the entire gut in the integrative response of apo A-IV to a fat meal.

Animals↗
PubMed1997

Antiviral therapy for recurrent herpes simplex reconsidered.

The purpose of this paper is to present our long-time concern about the safety of using antiherpetic drugs over extended periods of time as a preventive therapy for recurrent herpetic attacks. It has been shown that when herpes simplex virus (HSV) is inactivated and has thus lost its cytolytic activity by exposure to certain chemicals or ultraviolet irradiation, it can cause neoplastic changes in mammalian cells. Therefore, substances that inhibit (but not absolutely eliminate) HSV replication for prolonged periods of time might be of potential danger for the development of cancer. It becomes incumbent upon us to ask ourselves whether the prolonged inhibitory effect of prophylactic antiviral drugs might not carry with it the same risks as has been proposed for other substances known to inhibit viral replication.

Animals↗
PubMed1997

A risk-benefit assessment of mirtazapine in the treatment of depression.

Mirtazapine is the first of a new class of antidepressants, the noradrenergic and specific serotonergic antidepressants (NaSSA). Its antidepressant effect appears to be related to its dual enhancement of central noradrenergic and serotonin 5-HT1 receptor-mediated serotonergic neurotransmission. Mirtazapine possesses a number of useful pharmacokinetic characteristics such as good absorption, linear pharmacokinetics over the recommended dosage range (15 to 80 mg/day), and an elimination half-life of 20 to 40 hours, thereby allowing once-daily administration. However, since the drug is extensively metabolised by the hepatic cytochrome P450 (CYP) system and is excreted mainly in the urine, its clearance may be reduced by hepatic or renal impairment. In vitro data suggest that from a clinical point of view it is unlikely that mirtazapine would inhibit the metabolism of coadministered drugs metabolised by CYP1A2, CYP2D6 or CYP3A4. In vivo data from a study in extensive and poor metabolisers of debrisoquine indicate that strong inhibitors of CYP2D6 would have no effect on the concentration of racemic mirtazapine. In some placebo-controlled studies mirtazapine showed an early onset of antidepressant action, with significant reductions in total Hamilton Depression Rating Scale and Montgomery-Asberg Depression Rating Scale scores (relative to placebo) noted as early as 1 week after starting treatment. This therapeutic advantage was subsequently maintained during treatment, with mirtazapine proving significantly superior to placebo at treatment end-point in the majority of studies. In comparative trials, the antidepressant efficacy of mirtazapine was comparable with that of tricyclic antidepressants such as amitriptyline, clomipramine and doxepin, and in 2 studies superior to that of trazodone and fluoxetine. Mirtazapine appears to have a broad spectrum of activity, reflected in its efficacy in a variety of clinical settings. Its additional beneficial effects on the symptoms of anxiety and sleep disturbance associated with depression may reduce the need for concomitant anxiolytic and hypnotic medication seen with some antidepressants. Mirtazapine has demonstrated superior tolerability to the tricyclic antidepressants and trazodone, primarily on account of its relative absence of anticholinergic, adrenergic and serotonin-related adverse effects, in particular gastrointestinal adverse effects and sexual dysfunction. It appears that increased sedation associated with the drug is related to subtherapeutic dosages, and that it is reported in substantially fewer patients when the drug is used in appropriate dosages (> or = 15 mg as a single evening dose) from the beginning of treatment. Although 2 cases of reversible severe symptomatic neutropenia have been reported in clinical trials, there have been no additional reports of symptomatic neutropenia since the introduction of this drug to various countries in September 1994. Currently available data and initial clinical experience suggest that with its combination of dual action, simple pharmacokinetics, and clinical efficacy and tolerability, mirtazapine appears to be an important advance in the pharmacotherapy of depression.

Adult↗
PubMed1996

[Dementias--diagnosis, differential diagnosis and therapy].

The most common cause of primary (degenerative) dementia in old age is Alzheimer's disease, with vascular forms of dementia taking second place. Endocrinopathies, normal pressure hydrocephalus and space-occupying lesions are frequent causes of secondary dementia. A multitude of further, more rare clinical presentations results in a wide differential diagnostic spectrum necessitating a careful diagnostic work-up of the demential syndrome before considering treatment. This work-up must include clinical, laboratory and equipment-based investigations. The multimodal therapeutic approach to dementia covers not only the elimination of treatable underlying causal conditions and the medical treatment of cognitive symptoms and psychiatric accompanying symptoms, but also non-medicamentous aspects.

Alzheimer Disease↗
PubMed1996

Interaction of nitrogen monoxide with cytochrome P-450 monitored by surface-enhanced resonance Raman scattering.

The reaction of mammalian cytochrome P-450 2B4 with nitrogen monoxide and oxygen has been studied by surface-enhanced resonance Raman scattering (SERRS) to obtain sharp and definitive information in situ on the nature of the changes in the active site pocket. The initial reaction produces a six co-ordinate low spin haem-nitrogen monoxide adduct. A slower reaction leads to the irreversible formation of a five co-ordinate high-spin iron (III) haem with no nitrogen monoxide bound to it and to the nitration of an aromatic side chain, probably a tyrosine, in the proximity of the active site. In the presence of excess nitrogen monoxide, the second reaction is controlled by oxygen concentration. The sequence of events corresponds to the biphasic inhibition induced by NO in other cytochromes P-450 and peroxidases and is postulated to occur by the formation of a nitrating agent at the haem followed by diffusion to the tyrosine. The nitrated amino acid and the oxidation and spin state of the haem are observed easily by SERRS with low concentrations of protein making it a particularly suitable method for the investigation of reactions of NO in complex biological matrices.

Animals↗
PubMed1996

How to interpret findings on mortality of long-term lithium treated manic-depressive patients?! Critique of different methodological approaches.

Many studies have shown that patients with affective disorders have a mortality markedly higher than that of the general population. Studies of manic-depressive patients given prophylactic lithium treatment have yielded varying results. Some authors have reported mortalities which were more than four times that of the general population. Others have found mortalities which did not differ significantly from that of the general population. In order to examine these discrepancies we re-analysed the data of a previous study by IGSLI, using three different methods to calculate the Standardised Mortality Ratio (SMR). The data base was enlarged by adding mortality data from two additional centres. The results indicate that the discrepancies may result from the common use of a 'cumulative' approach which produces a distortion of the data if the treatment duration is not taken into consideration properly. An analysis which eliminates this artefact and takes the treatment duration into account ('year-by-year' approach) provides the strongest evidence that the mortality of lithium treated patients is not significantly different from that of the general population.

Adult↗
PubMed1996

The 1591C mutation in triosephosphate isomerase (TPI) deficiency. Tightly linked polymorphisms and a common haplotype in all known families.

In order to investigate the basis of the repeated occurrence of the 1591C mutation (TPI 1591C, 105 Glu-Asp) in multiple unrelated families throughout the world, we studied five microsatellite and short tandem repeat markers that lie within a 1.77 megabase region which includes the TPI gene. We also studied an intragenic polymorphic marker that lies within intron 5 of the TPI gene. This polymorphism, recently described by others, is characterized by either an A or a G at position 2262 (the A in the initiation ATG is designated as +1 for both genomic and cDNA nucleotides). With very minor exceptions, all of the known families in the world with the 1591C mutation were available for study. These included five families from the U.S., three from France, one from Greece, one (of Turkish origin) from Germany, and two from Australia. Although we did not have the opportunity to directly study five families from the U.K., key data concerning the 2262 intragenic polymorphism in these subjects were made available to us. Four of the microsatellite and short tandem repeat markers were linked, but in apparent equilibrium. In contrast, a polymorphic repeat pentamer in the CD4 gene, thought to lie telomeric to TPI, was in apparent complete linkage disequilibrium with the TPI 1591C mutation. The intragenic polymorphism was also in apparent complete linkage disequilibrium with the mutation. In unrelated persons of known phase (1591C homozygotes or normal controls), the comparative allele frequencies for the CD4 pentameric repeat were 1.0 (14/14 alleles) in homozygous TPI 1591C subjects and 0.412 (28/68 alleles) in normal subjects (p < 0.0001). Again, in persons of known phase, the comparative allele frequencies for the A form of the intragenic 2262 A or G polymorphism were 1.0 (14/14 alleles) in 1591C homozygotes and 0.130 (7/54 alleles) in normals (p < 0.0001). Haplotypes were discernible in all of the 1591C homozygotes and in several of the heterozygotes and normals. The CD4 162, TPI 2262A haplotype was found on only two of thirty-eight normal chromosomes, but was universally associated with 1591C. The data indicate that all TPI 1591C subjects are descendants of a common ancestor who probably lived in what is now England or France. The original mutation probably occurred well in excess of 1000 years ago.

Australia↗
PubMed1996

A new paradigm for operant conditioning of Drosophila melanogaster.

A freely walking single fly (Drosophila melanogaster) can be conditioned to avoid one side of a small test chamber if the chamber is heated whenever the fly enters this side. In a subsequent memory test without heat it keeps avoiding the heat-associated side. The memory mutants dunce and rutabaga successfully avoid the heated side but show no avoidance in the memory test. Wildtype flies can be trained to successively avoid alternating sides in a reversal conditioning experiment. Every single fly shows strong avoidance and a positive memory score. The new conditioning apparatus has several advantages: (1) Statistically significant learning scores can be obtained for individual flies. (2) Learning scores are obtained fully automatically without interference of the experimenter. (3) The procedure is fast, robust and requires little handling. Therefore the apparatus is suitable for largescale mutant screening. (4) Animals are not attached to a hook and thus can easily be used for breeding.

Animals↗