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P Lemmens

Publications and source records attributed to P Lemmens.

At least 19 recordsLinked to original sources
PubMed2006

Anomalous electronic Raman scattering in NaxCoO2.yH2O.

Raman scattering experiments on NaxCoO2.yH2O single crystals show a broad electronic continuum with a pronounced peak around 100 cm(-1) and a cutoff at approximately 560 cm(-1) over a wide range of doping levels. The electronic Raman spectra in superconducting and nonsuperconducting samples are similar at room temperature, but evolve in markedly different ways with decreasing temperature. For superconducting samples, the low-energy spectral weight is depleted upon cooling below T* approximately 150 K, indicating the opening of a pseudogap that is not present in nonsuperconducting materials. Weak additional phonon modes observed below T* suggest that the pseudogap is associated with charge ordering.

Journal Article↗
PubMed2003

Sound attenuation study on the bose-Einstein condensation of magnons in TlCuCl3.

We investigate experimentally and theoretically sound attenuation in the quantum spin system TlCuCl3 in magnetic fields at low temperatures. Near the point of Bose-Einstein condensation of magnons a sharp peak in the sound attenuation is observed. The peak demonstrates a hysteresis as a function of the magnetic field pointing to a first-order contribution to the transition. The sound damping has a Drude-like form arising as a result of hard-core magnon-magnon collisions. The strength of the coupling between lattice and magnons is estimated from the experimental data. The puzzling relationship between the transition temperature and the concentration of magnons is explained by their "relativistic" dispersion.

Journal Article↗
PubMed2001

Evidence for an unconventional magnetic instability in the spin-tetrahedra system Cu(2)Te(2)O(5)Br(2).

Thermodynamic experiments as well as Raman scattering have been used to study the magnetic instabilities in the spin-tetrahedra systems Cu(2)Te(2)O(5)X(2), X = Cl and Br. While the phase transition observed in the Cl system at T(N) = 18.2 K is consistent with 3D antiferromagnetic ordering, the phase transition at T(o) = 11.4 K in the Br system has several unusual features. We propose an explanation in terms of weakly coupled tetrahedra with a singlet-triplet gap and low-lying singlets.

Journal Article↗
PubMed2001

A qualitative assessment of the neurological safety of antipsychotic drugs; an analysis of a risperidone database.

BACKGROUND: Neurological side effects of antipsychotic agents limit the use of these drugs, and development of newer antipsychotic agents has been focused on a reduced risk of extrapyramidal symptoms (EPS) as well as effective symptom control. METHODS: A qualitative analysis of EPS was performed using Extrapyramidal Symptom Rating Scale (ESRS) data from 11 double-blind risperidone trials. An ESRS factor analysis and maximum changes in ESRS scores were compared for the risperidone, haloperidol, and placebo groups. RESULTS: The factor analysis revealed five factors. Between-group comparisons showed no differences between placebo and 1 to 2 mg/day-risperidone groups. Parkinsonism, tremor, akathisia, and sialorrhea were more likely to occur with haloperidol than with placebo or risperidone at 1 to 6 mg/day. Similar results were noted by maximum changes in ESRS scores. At risperidone doses of more than 8 mg/day, acute EPS severity lay between that of the placebo and haloperidol groups. The severity of tardive dyskinesia was greater in patients receiving placebo than in those receiving either active treatment. CONCLUSIONS: As the results described above were derived from a post hoc analysis of an existing database, conclusions must remain tentative. To provide more definitive answers, EPS assessments in future studies should be refined to more accurately predict the type of EPS expected with a given agent in clinical practice.

Adolescent↗
PubMed2001

Treatment of the symptoms of schizophrenia: a combined analysis of double-blind studies comparing risperidone with haloperidol and other antipsychotic agents.

Combined data on efficacy were available from 12 double-blind short-term (maximum 8 weeks) trials comparing risperidone and other antipsychotics in patients with chronic schizophrenia. Patients received risperidone (n = 1056) or other antipsychotics (n = 703). Haloperidol (n = 473) was the most frequently prescribed other antipsychotic. Efficacy assessments include the Positive and Negative Syndrome Scale (PANSS) total, subscale (positive symptoms, negative symptoms and general psychopathology), cluster (cognitive and affective symptoms) and item (anxiety and hostility) scores. At endpoint, the mean decrease from baseline in PANSS total scores was significantly greater for patients receiving risperidone (-20.9) than other antipsychotics (-16.2; P < 0.001), or the subset receiving haloperidol (-14.3; P < 0.001). Risperidone-treated patients showed a significantly greater decrease in the positive (P < 0.01), negative (P < 0.05) and general psychopathology (P < 0.001) scores than patients receiving other antipsychotics or haloperidol. Scores for cognition, affective symptoms, anxiety and hostility each improved significantly (P < 0.05) more for patients receiving risperidone than those receiving other antipsychotics or haloperidol. Efficacy data on patients with an acute exacerbation were available from seven trials (risperidone n = 372, other antipsychotics n = 285, including haloperidol n = 120). At endpoint, the mean decrease from baseline in PANSS total scores was significantly greater for patients receiving risperidone (-24.7) than other antipsychotics (-19.8, P < 0.01) including haloperidol (-19.8, P < 0.05). Risperidone-treated patients also showed a greater decrease in positive symptom scores (-7.8) than those receiving other antipsychotics (-6.3; P < 0.01) or haloperidol (-7.1). A > or = 20% reduction in PANSS total score with risperidone, haloperidol and other antipsychotics was achieved by 65.9%, 54.3% and 54.9%, respectively; a > or = 30% PANSS reduction by 54.0%, 46.6% and 46.5% of patients, respectively; and a > or = 40% reduction by 43.8%, 33.7% and 34.4% of patients, respectively. These findings are consistent with earlier findings that show risperidone is more efficacious than haloperidol for reducing the symptoms of schizophrenia.

Antipsychotic Agents↗
PubMed2001

Experimental evaluation of a cell module for hybrid liver support.

Aim of the study was to evaluate a hybrid liver support system in a porcine model of acute liver failure, after hepatectomy. Pigs with a body weight of 70+/-18 kg underwent total hepatectomy and porto-cavo-caval shunting as well as ligation of the bile duct and the hepatic artery. Control animals were connected to the system (including capillary membrane plasma separation) containing a four compartment bioreactor with integral oxygenation and decentralized mass exchange but without liver cells. The treatment group received hybrid liver support with the same system including 370+/-42 g primary isolated porcine parenchymal liver cells in co-culture with hepatocyte nursing cells, tissue engineered to liver- like structures at high density. Treatment started after complete recovery from anesthesia and was performed continuously. A positive influence on peripheral vascular resistance and a reduced need of catecholamine dosage was observed in the treatment group. Hybrid liver support with a cell module upscaled for clinical application significantly prolonged survival time in animals after hepatectomy with the longest survival being 26 hours in the control group an 57 hours in the treatment group.

Animals↗
PubMed2000

Collective singlet excitations and evolution of raman spectral weights in the 2D spin dimer compound SrCu2(BO3)(2)

Raman light scattering of the two-dimensional quantum spin system SrCu2(BO3)(2) shows a rich structure in the magnetic excitation spectrum, including several well-defined bound state modes at low temperature, and a scattering continuum and quasielastic light scattering contributions at high temperature. The key to the understanding of the unique features of SrCu2(BO3)(2) is the presence of strong interactions between well-localized triplet excitations in the network of orthogonal spin dimers realized in this compound.

Journal Article↗
PubMed2000

Stripe conductivity in La1.775Sr0.225NiO4

We report Raman light-scattering and optical conductivity measurements on a single crystal of La1.775Sr0.225NiO4 which exhibits incommensurate charge-stripe order. The extra phonon peaks induced by stripe order can be understood in terms of the energies of phonons that occur at the charge-order wave vector Q(c). A strong Fano antiresonance for a Ni-O bond-stretching mode provides clear evidence for finite dynamical conductivity within the charge stripes.

Journal Article↗
PubMed2000

Effects of risperidone on affective symptoms in patients with schizophrenia.

The effects of risperidone on affective symptoms were determined by an analysis of pooled data from six double-blind trials of risperidone versus haloperidol in 1254 patients with chronic schizophrenia. Symptoms indicating mania were assessed by the Positive and Negative Syndrome Scale (PANSS) excitement and grandiosity items and by the excited cluster (excitement, hostility, uncooperativeness, and poor impulse control); anxious / depressive symptoms were assessed by the PANSS anxious / depressive cluster (somatic concern, anxiety, guilt feelings, and depression). Mean change scores from baseline to endpoint were compared in patients receiving risperidone, haloperidol or placebo by analysis of variance with factors for trial and baseline score included in the model. In all patients, change scores on excitement and grandiosity items and excited and anxious / depressive clusters were significantly greater for risperidone than for haloperidol or placebo. Dropouts due to inefficacy were less frequent with risperidone (5 of 59; 8%) than with haloperidol (7 of 38; 18%) or placebo (8 of 10; 80%). In patients with anxious / depressive symptoms at baseline (anxiety / depression cluster score > or = the median), anxiety / depression scores decreased significantly more with risperidone than with haloperidol, and symptom reduction occurred faster with risperidone. These results are consistent with previous reports and suggest that risperidone is more efficacious than haloperidol for affective symptoms in patients with schizophrenia.

Adolescent↗
PubMed1999

Periplakin and envoplakin are target antigens in canine and human paraneoplastic pemphigus.

BACKGROUND: On the basis of clinical and histopathologic similarities to human paraneoplastic pemphigus (PNP), we recently identified the first case of PNP in a nonhuman species, the dog. OBJECTIVE: To determine a similar pathogenesis in both species, the present study aimed to define whether common antigens are targeted in dog and man. METHODS: Canine and human PNP sera were used in parallel to immunoprecipitate 14C-labeled human keratinocyte antigens. The immunoreactive proteins were then identified by immunoprecipitation of canine keratinocyte extracts with specific antibodies to the antiplakin family members follwed by immunoblot analysis using canine and human PNP sera. RESULTS: Protein bands of 210, 190, 170, and 130 kd were identified in dogs and humans. In both species, envoplakin and periplakin were demonstrated as antigens. Anti-desmoglein 3 antibodies could not be demonstrated in canine PNP, but in human PNP. CONCLUSION: These results demonstrate that canine PNP closely correlates to the human counterpart and may therefore represent an excellent model for the human disease.

Animals↗
PubMed1999

A combined analysis of double-blind studies with risperidone vs. placebo and other antipsychotic agents: factors associated with extrapyramidal symptoms.

Combined data from double-blind risperidone studies were used to analyse the severity of extrapyramidal symptoms (EPS) associated with treatment in patients with chronic schizophrenia. Factors associated with maximum EPS severity were increasing risperidone dose (< or = 8 mg/day was similar to placebo), lower baseline EPS scores, and longer duration of psychotic symptoms, particularly in older patients. EPS severity was significantly greater in patients receiving haloperidol or other antipsychotics than in those receiving risperidone (4 to 8 mg/day) or placebo. Antiparkinsonian medications were required by significantly fewer patients treated with risperidone (4 to 8 mg/day) than by patients treated with haloperidol or other antipsychotics. Combined efficacy data showed that 4 to 8 mg/day was also the most efficacious dose range; there was no increase in efficacy with doses over 4 mg/day. Based on these data and post-marketing experience, 4 mg/day is an appropriate initial target dose for most patients with schizophrenia. Higher doses may be appropriate for patients with chronic illness, and lower doses may be appropriate for patients with a first psychotic episode or for elderly patients.

Adolescent↗
PubMed1998

Surveillance of human Yersinia enterocolitica infections in Belgium: 1967-1996.

Between 1967 and 1996, > 18,700 strains of Yersinia species, excluding Yersinia pestis, were recovered in Belgium from a variety of gastrointestinal and extraintestinal sites in patients. Full identification and serotyping were performed by the two Belgian reference laboratories. Yersinia enterocolitica serogroup O:3 predominated (79.4% of strains), followed by serogroup O:9 (11.1%). The remaining 9.5% of isolates belonged to serogroups and related species generally considered nonpathogenic. Acute enterocolitis was the most common clinical form of Y. enterocolitica infection, affecting primarily children younger than 5 years of age. Since 1967, there was a steady increase in isolations every year, with 305 cases in 1975 and up to 1,469 in 1986. From 1987 on, there was a clear decrease in the number of reported cases, although the number of participating laboratories and culture techniques remained constant. This significant decrease in the occurrence of Y. enterocolitica infections may be explained by changes in the slaughtering procedures and eating habits of the population.

Adolescent↗
PubMed1997

Antimicrobial resistance and serotypes of Shigella isolates in Kigali, Rwanda (1983 to 1993): increasing frequency of multiple resistance.

The serotype distribution and susceptibility to nine antibiotics was determined for 2491 Shigella isolates cultured in the medical laboratory of the Centre Hospitalier de Kigali, Rwanda, during 1983 to 1993. Overall, Shigella flexneri was the most frequent species, ranking before Shigella sonnei, Shigella boydii, and Shigella dysenteriae. However, the relative frequency of the different Shigella spp. showed an important variability over time. S flexneri increased from 40% in 1983 to 68% of the isolates in 1993 whereas S. dysenteriae Type 1 decreased gradually from 30 to 0.5% of the isolates in 1992. After the outbreak of severe civil unrest, which caused the displacement of many people to the capital, a new epidemic of dysentery started in the Kigali area and S. dysenteriae Type 1 accounted again for 24% of the isolates in 1993. In 1983, resistance to tetracycline, streptomycin, and sulfonamides was common among the endemic Shigella spp. Resistance to chloramphenicol was observed in 17% (30/182) of the isolates. Only 10% were resistant to ampicillin and an equal proportion to trimethoprim, whereas 5% of the isolates showed resistance to both products. By 1993, 66% (195/295) of the isolates were resistant to chloramphenicol (for comparison with 1983, p < 0.001), 70% (207/295) to ampicillin (p < 0.001), 67% to trimethoprim (p < 0.001), and 58% had combined resistance to the latter two drugs (p < 0.001). Resistance patterns differed strongly by species, S. flexneri being more frequently resistant than S. sonnei. In 1983, all S. dysenteriae Type 1 isolates were resistant to ampicillin, chloramphenicol, tetracycline, and sulfonamides. Trimethoprim resistance increased from 31% (25/80) in 1983 to 96% (26/27) of the isolates in 1986 (p < 0.001). After the introduction of nalidixic acid as an alternative for trimethoprim-sulfamethoxazole, trimethoprim resistance decreased to 87%, during 1987 to 1992, and subsequently to 68% of the isolates in 1993. However, 20% of the isolates became resistant to nalidixic acid in 1993. Ampicillin and trimethoprim-sulfamethoxazole are no longer useful for the empirical treatment of shigellosis in Rwanda.

Anti-Bacterial Agents↗
PubMed1996

Hepatitis C: indication for anti-viral therapy?

Hepatitis C infection is a frequent indication for liver transplantation. In general, recurrent graft hepatitis is assumed to be mild, but may be the cause of lethal postoperative complications in a small patient population. Out of 500 transplants in 458 patients, 123 patients were transplanted due to hepatitis C infection (26.7%) between September 1988 and April 1994. Cumulative 1- to 6-year patient survival was similar for patients transplanted due to hepatitis C (87.0%) and those transplanted for other indications (86.0%). In patients with hepatitis C virus (HCV), death, in 50% of the cases, was related to HCV recurrence and chronic rejection. Four patients (25.0%) died because of severe infection and multiple organ failure syndrome unrelated to HCV recurrence and chronic rejection. The incidence of retransplantation was similar in HCV (9.8%) and other patients (8.4%). In HCV patients, 6 of 12 retransplantations (50.0%) were performed due to HCV recurrence and chronic rejection. Of 123 HCV patients, 45 experienced histologically proven recurrent graft hepatitis between 2 weeks and 5.5 years after transplantation. The incidence of acute rejection was similar in both groups. The incidence of steroid-resistant rejection was, however, higher in HCV patients (29.3%) than in those transplanted for other indications (14.5%; P < or = 0.05). Furthermore, there was a significant association between acute rejection and the development of recurrent graft hepatitis. In conclusion, patients with hepatitis C may be transplanted with as good patient and graft survival rates as patients transplanted for other indications. However, the combination of recurrent graft hepatitis and chronic rejection remains the most limiting factor for some of these patients, which strengthens the necessity for a specific anti-viral therapy.

Graft Rejection↗
PubMed1996

Management of acute steroid-resistant rejection after liver transplantation.

Prior to the FK506 era, OKT3 was primarily used for treatment of steroid-resistant rejection. Initially FK506 has been used as a last treatment of refractory acute or chronic rejection. We provide strong evidence that the use of FK506 is more successful if rescue therapy is performed early instead of using it as the last resort. Between September 1988 and March 1995 a total of 600 liver transplantations were performed in 550 patients. Of these 550 patients, 426 received primarily cyclosporine A (CsA)-based immunosuppression. Of the 426 CsA patients, 70 (16.4%) required either FK506 (51.4%), or OKT3 rescue therapy (27.1%), or a combination of the two drugs (21.5%). The latter group of patients received first OKT3 and then FK506 rescue when OKT3 therapy failed. Treatment was initiated simultaneously (within 1 week) in 11 patients, and 4 patients received FK506 rescue later during the course of rejection. The highest success rates (88.9%) were observed in patients given FK506 rescue therapy. Retransplantation was necessary more often in patients receiving OKT3 than in those with FK506 rescue therapy (15.8% versus 5.5%, respectively). Retransplantation and death due to chronic rejection increased with the need for additional FK506 rescue therapy after OKT3 failure. This increase was most pronounced in patients receiving FK506 during the late course of rejection, reaching a failure rate of 75.0% (50. 0% of deaths were due to chronic rejection). The lowest incidence of cytomegalovirus infection and of infectious, neurologic, and renal complications was observed in the FK506 rescue group. We conclude that early FK506 rescue therapy may be the treatment of choice for acute steroid-resistant rejection.

Acute Disease↗