Search PubMed⌕ Search

Biomedical subjects

R Wolf

Publications and source records attributed to R Wolf.

At least 73 records · Page 4Linked to original sources
PubMed1999

Replacement of threonine 394 by alanine facilitates internalization and resensitization of the rat mu opioid receptor.

Signaling of G protein-coupled receptors is terminated by phosphorylation of intracellular serine and threonine residues. Resensitization of these receptors requires internalization and subsequent dephosphorylation. We have recently shown that the resensitization rate of the rat micro opioid receptor (MOR) isoforms MOR1 and MOR1B is mainly determined by the amino acid composition of their alternatively spliced C-terminal tails. Upon agonist stimulation, MOR1B passes through an accelerated cycle of receptor endocytosis and reactivation, which in turn promotes a greater resistance to agonist-induced desensitization, as compared with MOR1. Given the fact that MOR1B lacks only one putative phosphorylation site (T394 of MOR1), we replaced this threonine by an alanine and stably expressed the wild-type MOR1 and its T394A mutant in mouse neuroblastoma Neuro2a cells. We show that during prolonged [D-Ala2, MePhe4, Gly5-ol]enkephalin exposure (5 h), the T394A receptor mutant desensitized at a slower rate than MOR1. In contrast, T394A is more rapidly removed from the cell surface than MOR1, as determined by flow cytometry using epitope-tagged receptors. This fast internalization was followed by immediate resensitization of T394A during 20 min of agonist removal while the wild-type MOR1 remained inactive. Similar to MOR1B, rapid internalization and reactivation of T394A may explain its delayed desensitization. These findings suggest that T394 represents a negative regulatory signal for MOR1 internalization. Furthermore, phosphorylation of this threonine residue may influence the time course of micro opioid receptor resensitization.

Alanine↗
PubMed1999

Microvascular responses to ischemia/reperfusion in normotensive and hypertensive rats.

The objective of the present study was to determine whether long-term arterial hypertension renders the microvasculature more vulnerable to the deleterious inflammatory responses elicited by ischemia and reperfusion (I/R). Intravital fluorescence microscopy was used to monitor leukocyte adherence and emigration, platelet-leukocyte aggregation, and albumin extravasation in mesenteric postcapillary venules of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) after 10 minutes of ischemia and subsequent reperfusion. Significant and comparable increases in leukocyte adherence/emigration and the formation of platelet aggregates were elicited by I/R in both WKY and SHR. Albumin extravasation was enhanced after I/R in SHR, but not in WKY. Monoclonal antibodies directed against the adhesion glycoproteins CD18, P-selectin, or ICAM-1 showed similar patterns of protection against the I/R-induced inflammatory responses in WKY and SHR. The enhanced albumin extravasation noted in postischemic venules of SHR was prevented by immunoneutralization of either CD18 on leukocytes or ICAM-1 on endothelial cells. These results suggest that, whereas long-term arterial hypertension does not significantly modify the leukocyte and platelet recruitment normally elicited in venules by I/R, it does result in an exaggerated albumin leakage response, which is mediated by an interaction between beta(2) (CD18) integrins on leukocytes and ICAM-1 on endothelial cells.

Animals↗
PubMed1999

The back door: venous-mediated metastasis into cervical lymph nodes as an alternative metastatic pathway for oropharyngeal squamous cell carcinoma.

Circulating lymphocytes may home to lymph nodes (LNs) via paracortical postcapillary venules, high-endothelial venules (HEVs) that recognize circulating lymphocytes, enabling them to migrate into nodal cortical/paracortical regions. Our goal was to find any histologic, immunohistochemical, or in vitro evidence to support the hypothesis that squamous cell carcinoma (SCC) may gain access to LNs via an alternative venolymphatic pathway. Slides from 67 neck dissections with SCC were studied. Standard criteria for lymphatic-mediated metastasis were used; criteria for evidence ofvenolymphatic metastasis were tumor nests localized to the paracortical regions, directly contiguous to HEVs but not marginal sinuses. Cases in which LN architecture was obliterated by metastases were excluded. A modified Stamper-Woodruff assay, which assesses HEV binding, incubated cell lines from oral carcinomas and lung adenocarcinomas with fresh frozen LN sections. Double-blinded cell counts were performed by two observers and analyzed by Student's t test. Immunohistochemical examination was undertaken on 19 paraffin-embedded cases with the monoclonal antibody, MoAb CD44v6, to discover whether expression of this adhesion molecule correlated with metastatic pattern. Twenty-nine cases (66%) revealed evidence only for the LN route of metastasis; 4 cases (9%) were classified as venolymphatic metastasis; 11 cases (25%) showed evidence for both pathways. The Stamper-Woodruff assay confirmed that SCC cells preferentially bound to HEV within cervical LN sections more than did adenocarcinoma cells (P = .02). Strong staining to MoAb CD44v6 was seen in 18 (95%) of 19 SCCs with a membranous pattern. Occasionally, CD44v6 highlighted tumor emboli adjacent to HEVs, but no overall correlation could be made between CD44v6 expression and pattern of spread. Tumor metastasis via lymphatic channels is the predominant mode of metastatic spread, but the venolymphatic route is a plausible alternative pathway. The preferential attachment of SCC cells to HEVs supports this theory.

Cell Adhesion↗
PubMed1999

T-lymphocytes contribute to hepatic leukostasis and hypoxic stress induced by gut ischemia-reperfusion.

Although neutrophils have been implicated in the hepatic injury elicited by gut ischemia/reperfusion (I/R), the contribution of other leukocyte populations to this injury process remains unclear. The objective of this study was to determine whether lymphocytes contribute to gut I/R-induced microvascular dysfunction and inflammatory responses in the liver. Intravital videomicroscopy was used to monitor leukocyte recruitment, the number of nonperfused sinusoids and pyridine nucleotide (NADH) autofluorescence in livers of wild-type, SCID, and interferon-gamma (IFN-gamma) knockout mice exposed to 15 min of gut ischemia and 1 h of reperfusion. In wild-type mice, gut I/R elicited significant increases in the number of stationary leukocytes, nonperfused sinusoids, NADH autofluorescence (indicating hypoxia), and elevated plasma alanine aminotransferase (ALT) and TNF-alpha levels. All of these responses were profoundly attenuated in SCID mice, while only some of the responses (in the midzonal region) were blunted in IFN-gamma knockout mice. Reconstitution (24 h before ischemia) of the circulating lymphocyte pool with T-cell enriched splenocytes, but not T cell deficient (from nude mice), CD4+ T-cell depleted splenocytes or splenocytes derived from IFN-gamma knockout mice, allowed the SCID mice to respond to gut I/R in a manner similar to wild-type mice. Some of the responses were restored following reconstitution with CD8+ T-cell depleted splenocytes. These findings implicate CD4+ T-lymphocytes and IFN-gamma in the hepatic microvascular dysfunction and inflammatory cell accumulation elicited by gut I/R.

Animals↗
PubMed1998

Transgenic mice with increased copper/zinc-superoxide dismutase activity are resistant to hepatic leukostasis and capillary no-reflow after gut ischemia/reperfusion.

The objectives of this study were to (1) determine whether transgenic (Tg) mice overexpressing copper/zinc-superoxide dismutase (CuZn-SOD) are protected from the deleterious effects of gut ischemia/reperfusion (I/R) and (2) compare the effectiveness of Tg SOD overexpression in attenuating I/R injury to intravascularly administered CuZn-SOD or manganese (Mn)-SOD. The accumulation of fluorescently labeled leukocytes and number of nonperfused sinusoids were monitored by intravital microscopy in livers of wild-type mice (C57BL/6), CuZn-SOD Tg mice, and wild-type mice receiving either CuZn-SOD or Mn-SOD. All parameters were measured for 1 hour after release of the occluded (for 15 minutes) superior mesenteric artery. Gut I/R in wild-type mice led to an increased number of stationary leukocytes, while reducing the number of perfused sinusoids (capillary no-reflow). All of these responses were significantly blunted in CuZn-SOD Tg mice, with a corresponding attenuation of liver enzyme release into plasma. Exogenously administered SOD had little or no effect on gut I/R-induced leukostasis or capillary no-reflow in the liver. These observations suggest a role for superoxide in gut I/R-induced leukostasis and hypoxic stress in the liver. Furthermore, the findings suggest that cellular localization of SOD activity is an important determinant of the protective actions of this enzyme in experimental models of I/R injury.

Analysis of Variance↗
PubMed1998

Carboxyl-terminal splicing of the rat mu opioid receptor modulates agonist-mediated internalization and receptor resensitization.

The rat mu opioid receptor is alternatively spliced into two isoforms (MOR1 and MOR1B) which differ in length and amino acid composition at the carboxyl terminus. When stably expressed in HEK 293 cells, both splice variants bind the mu receptor agonist [D-Ala2,N-Me-Phe4,-Gly-ol5]enkephalin (DAMGO) with similar affinity and exhibit functional coupling to adenylyl cyclase with similar efficiency. However, the shorter isoform, MOR1B, desensitized at a slower rate during prolonged DAMGO exposure (4 h) but resensitized at a faster rate than MOR1 during agonist withdrawal (20 min). Immunocytochemical analysis revealed that DAMGO-induced internalization of MOR1B proceeded much faster than that of MOR1 followed by rapid recycling of the receptor to the cell surface. In addition, the greater resistance of MOR1B to homologous desensitization compared with MOR1 as well as MOR1B resensitization was abolished when receptor reactivation/recycling was blocked with monensin, an inhibitor of endosomal acidification. It is concluded that the sequence at the cytoplasmic tail of MOR1B facilitates clathrin-coated vesicle-mediated endocytosis which, in turn, promotes accelerated receptor reactivation. Taken together, our findings suggest that carboxyl-terminal splicing of the rat mu opioid receptor modulates agonist-induced internalization and receptor resensitization.

Alternative Splicing↗
PubMed1998

[Suicide in the elderly: collapse of value orientation?].

Suicide of the aged has often been understood as a careful deliberation of the quintessence of life. Nevertheless, it displays the breakdown or the entire lack of value orientation. Some gerontologists have come to terms with the fact that the ideal of value-free living results in the suicidality of the aged. Suicide seems to be a probable solution of their problems. But values regulate the social existence of humans. Accordingly, this paper considers suicide of the aged to be a result of this disorientation. Thus, it demands first of all that a rich set of values has to be developed, and secondly, that adequate resources of values have to be proposed. This can be achieved by four steps: 1) distance from the critical situation, 2) combination of interaction and mutual appreciation, 3) analyzing the reduced set of values, and 4) opening new priorities and preferences.

Aged↗
PubMed1998

[Factors affecting delayed initial diagnosis of dementing diseases].

The aim of the present study was to examine the factors responsible for an early or late date for the diagnosis of dementia. In the course of our gerontopsychiatric outpatient department concerning impaired memory ("Gedächtnissprechstunde"), we examined four patients with cognitive impairments and explored their caregivers with regard to the biographic history and the course of the patient's disease. How can we describe the time course of identification and assessment of the symptoms of dementia by caregivers and the factors which are controlling this process from its retrospectively estimated beginning to the date of the first diagnosis of dementia? Concerning the caregivers' certainty in the field of interpretation fo symptoms we could separate for the first time four consecutive stages: First, the stage of undiscovered illness; second, the stage of insecurity; third, the stage of subjective certainty; fourth, the stage of objective certainty. Our case histories revealed that the phase of disease, the insight into one's disease, and the degree of suffering by the patient on the one hand, and the medical education, the setting of social roles and the degree of suffering by the caregivers on the other hand, are possible factors which control the time interval (1.25 to 11 years) between the retrospectively estimated beginning of the disease and the date of the first diagnosis. Is there any pattern of the patient's consultations with a physician and the doctor's diagnostic answers during the time course between the retrospectively estimated beginning of the disease and the date of the first diagnosis of dementia? In spite of periodical consultations of physicians, the opportunity for an early diagnosis was not achieved. Factors which influence this diagnostic process are believed to be the status quo of professional standards of quality and the general conditions in Public Health. In two cases it took two years until the physician decided to initiate a differential diagnostic process; in another case the medical recommendation in favor of differential diagnosis was declined by the patient for more than one year. Additionally, the present case reports clearly demonstrate that coping with the disease both by the patient and the caregivers can only start when the stage of objective certainty is reached. Considering ethical issues as the principle of autonomy, this may argue for a differential diagnosis of cognitive impairment and dementia as soon as possible.

Aged↗
PubMed1998

The impact of cardiac comorbidity after carotid endarterectomy.

PURPOSE: Myocardial infarction and other comorbidities contribute to complications after carotid endarterectomy (CEA). However, because the combined stroke and death rate after CEA is less than 5%, even relatively large series have small numbers of adverse events that preclude a detailed analysis of the association between the outcome and the patient factors, such as comorbidity and age. We sought to overcome this limitation by studying patients who underwent CEA in a large random sample of Medicare beneficiaries. METHODS: We used a database that contained a 20% random sample of all Medicare beneficiaries to identify patients who underwent CEA between the years 1988 to 1990 (n = 22,165), and we followed these cases until 1992. With multivariate logistic regression and Cox proportional hazards regression models, we examined the impact of age, race, gender, geographic location, hospital characteristics, and comorbidity, including acute myocardial infarction (AMI) and congestive heart failure (CHF), on the risk of stroke and death after CEA. RESULTS: AMI and CHF had the greatest negative impact on the long-term survival rates (adjusted hazard ratio [HR]: 2.40, P < .0001, and 2.85, P < .0001, respectively). Other variables with a significant impact on the long-term survival rates were an age of >80 years (HR, 2.16; P < .0001), an acute stroke (HR, 1.51; P < .0001), diabetes mellitus (DM; HR, 1.52; P < .0001), and male sex (HR, 1.32; P < .0001). In addition, AMI, CHF, DM, and advanced age were associated with an increased risk of perioperative stroke and death. CONCLUSION: Patients with AMI, CHF, DM, and an age of >80 years have diminished perioperative and long-term survival rates after CEA. These results may alter the risk/benefit analysis for such patients, especially those with asymptomatic disease.

Age Factors↗
PubMed1998

Video-assisted thoracic surgery (VATS) lobectomy for bronchogenic carcinoma.

Video-assisted thoracic surgery (VATS) lobectomy remains controversial because surgeons have been concerned about the safety of the procedure and the adequacy of the cancer operation when it is performed for lung cancer. This review of a 4.5-year experience with 212 VATS lobectomies for primary lung cancer was undertaken to address these issues. All operations involved a standard anatomic dissection and lymph node sampling or dissection. The mean length of stay was 4.6 days. There were no serious problems of intraoperative bleeding. There was one death owing to mesenteric venous infarct. The 4.5-year survival for stage I lung cancer was 76%. The data suggest that a complete cancer operation for primary lung cancer can be safely performed with VATS, with survival that is comparable with operations performed with a thoracotomy.

Adult↗
PubMed1998

Early repeeling--a matter of time.

BACKGROUND: Repeeling after a short interval in medium-depth or deep peeling is considered by most experts as hazardous, and is generally contraindicated. Most experts recommend an interval of 6 months or more before repeating the same level of peel. The results are presented of four patients who underwent repeeling after a short interval. METHODS AND RESULTS: All four patients were dissatisfied with their first peel (medium-depth peel performed with trichoroacetic acid (TCA) 35%). Repeelings were performed using two methods: TCA 30-35% (Cases 1-3) and unoccluded Baker phenol peel (Case 4). On three occasions (Cases 1-3), the patients underwent three peelings at short intervals. All four cases gave excellent objective results. CONCLUSIONS: The risk of a second peel shortly after the first is not as high as indicated in the literature, and should not be automatically ruled out. In a selected group of patients who, for various reasons, be persuaded to wait, repeeling after a short interval (2-3 weeks) may solve certain problems and may even make the difference between an unhappy patient and a satisfied one. In performing repeeling after a short interval, one should take into consideration that the skin, particularly the keratin layer, is thinner, so that the degree of penetration of the second peel solution and the peel depth will be greater. It is possible that the scarring reported after repeeling is a result of the disregard of this important factor and, consequently, the use of too high a concentration of peel solution in the second peel procedure.

Adult↗
PubMed1998

Nitric oxide modulates gut ischemia-reperfusion-induced P-selectin expression in murine liver.

Reperfusion of ischemic intestine is associated with P-selectin-dependent adhesion of leukocytes in the liver microcirculation. The objective of this study was to define the contribution of nitric oxide (NO) to the enhanced P-selectin expression and increased leukocyte rolling elicited by gut ischemia-reperfusion (I/R). Leukocyte rolling (monitored by intravital microscopy) in the terminal hepatic venules (THV) and P-selectin expression (measured using the dual-radiolabeled monoclonal antibody technique) were determined in mice after 15 min of superior mesenteric artery occlusion and 30 min of reperfusion. After 30 min of reperfusion, P-selectin expression was significantly increased in the liver, intestine, and lung, with a corresponding increase in the number of rolling leukocytes (in THV). The NO synthase inhibitor NG-monomethyl-L-arginine exaggerated the gut I/R-induced increases in both rolling leukocytes and P-selectin expression (in liver and intestine), responses that were not detected with coadministration of L-arginine or in P-selectin-deficient mice. The NO donor diethylenetriamine/NO and L-arginine were both effective in attenuating the gut I/R-induced increases in rolling leukocytes (in THV) and P-selectin expression (in liver, intestine, and lung). These findings indicate that NO modulates gut I/R-induced recruitment of rolling leukocytes in THV via an action on P-selectin expression.

Animals↗
PubMed1998

Neuropsychiatric systemic lupus erythematosus before and after immunosuppressive treatment: a FDG PET study.

At its inception, morphological imaging, like magnetic resonance imaging (MRI), is often not useful in neuropsychiatric systemic lupus erythematosus (NPSLE), although the disease clinically shows cerebral symptoms. Functional imaging, like positron emission tomography (PET), may be a method that offers some advantages. We report a 53-year-old white man with decreased memory and visual disturbances who met four of the American Rheumatism Association (ARA) criteria for the classification of SLE. He was investigated before and after 3 months of therapy using PET and F-18-fluoro-2-deoxy-D-glucose (FDG). Treatment consisted of prednisone (25 mg/day, tapered to 10 mg/day) and cyclophosphamide (daily 100 mg for 3 weeks followed by a drug-free interval of 1 week). For the control group, 15 clinically and neurologically healthy volunteers (5 male, 10 female, aged 48 +/- 7 years) were investigated. All study participants additionally had a cranial MRI. In both controls and the SLE patient, cranial MRI was negative. However, the patient showed a significant hypometabolism in the region parieto-occipital on both sides and the parietal region on the right side before treatment. After treatment metabolism in these regions was within normal limits. Hence, FDG-PET could help to verify brain-onset of SLE earlier and may be a powerful tool for controlling SLE treatment.

Adult↗
PubMed1998

Vitamin E: the radical protector.

Since its discovery and isolation the importance of vitamin E in maintaining normal physiologic processes and its value in treating various disease states have been the subject of much controversy. It was our intention to review and highlight some of the arguments and problems regarding the usefulness of vitamin E and to try to put them into proper perspective. The major area of interest concerning vitamin E lies essentially in its role in preventing damage caused by free radicals. The latter are now known to play an important role in radiation induced carcinogenesis, photoaging and photosensitization. The chemistry of vitamin E, its physiological function as a major antioxidant and its interaction with other antioxidants are described by the sum of animal studies, in vitro research and epidemiological investigations. In preparing the current data, it appeared that despite the controversy and conflicting results the body of literature as a whole judges vitamin E to be useful as an antioxidant. Although, in principle, the use of vitamin E can be quite advantageous, the manner of its administration, especially regarding topical application, remains unclear.

Animals↗
PubMed1997

Lymphocytes mediate TNF-alpha-induced endothelial cell adhesion molecule expression: studies on SCID and RAG-1 mutant mice.

TNF-alpha is known to elicit a rapid increase in the expression of specific endothelial cell adhesion molecules (ECAMs) within different vascular beds. The aim of this study was to determine whether lymphocytes contribute to the increased ECAM expression elicited by TNF-alpha. A dual radiolabeled mAb technique was used to quantify constitutive and TNF-alpha-induced expression of ICAM-1, VCAM-1, E-selectin, and P-selectin in different vascular beds (lung, heart, stomach, mesentery, small intestine, large intestine, and muscle) in wild-type and SCID mice. In reconstitution experiments, either whole splenocytes, T cell-enriched splenocytes, or B cell-enriched splenocytes were injected into SCID mice 48 h before TNF-alpha administration. Although the constitutive expression of ECAMs differed only slightly between wild-type and SCID mice, TNF-alpha-induced ECAM expression was markedly blunted in SCID mice compared with wild-type mice. This blunted response to TNF-alpha was also demonstrated for VCAM-1 in recombination activating gene (RAG)-1 mutant mice. Reconstitution studies revealed that administration of 50 x 10(6) splenocytes in SCID mice at 48 h before cytokine treatment restored the TNF-alpha-induced expression of VCAM-1 to levels normally observed in wild-type mice. Reconstitution with T cell- but not B cell-enriched splenocytes, also restored the TNF-alpha-induced expression of VCAM-1 in SCID mice to wild-type levels. These results implicate circulating T lymphocytes as modulators of the increased ECAM expression elicited by TNF-alpha.

Animals↗
PubMed1997

Separation and quantitation of glycolipids as penetration modifiers in human skin using high-performance liquid chromatography-mass spectrometry with electrospray ionization.

An high-performance liquid chromatography-mass spectrometry method is presented for the measurement of glycolipids used as modulators of the penetration of drugs into human skin. In methanol extracts from different skin layers a detection limit of 100-400 pg/ml could be achieved. A routine analytical procedure could be set up with good quantitation reliability (relative standard deviation 6.6%).

Adjuvants, Pharmaceutic↗