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Biomedical subjects

P Weiss

Publications and source records attributed to P Weiss.

At least 19 recordsLinked to original sources
PubMed1999

Immune activation and virologic response to immunization in recent HIV type 1 seroconverters.

Antigenic stimulation from invasive bacterial infections, and the vaccines designed to prevent them, may promote T cell activation and enhancement of HIV-1 replication. Changes in viral load have been correlated with antigen-specific responses. We prospectively determined the impact of immunization with 23-valent pneumococcal vaccine (PVAX) and Haemophilus influenzae type b (Hib)-modified diphtheria toxoid CRM197 (DT) vaccine on HIV-1 replication in recent HIV-1 seroconverters (n = 14; median, 5.5 months from infection; median CD4+ T cells, 535 microl), and correlated results with vaccine-related immune activation. Specific antibody responses, markers of CD4+ T cell activation (transferrin and interleukin 2 receptors), and viral burden were measured at weeks -2 (pre), 0, 1, 2, 6, and 12 after immunization. By week 2, levels of IgG had increased significantly over baseline in both HIV-1-infected patients and HIV-1-seronegative control subjects (n = 9) for each antigen (geometric mean fold rise: PVAX, 10.1 versus 5.3; Hib, 16.0 versus 11.7; and DT, 26.2 versus 24.5, respectively). Despite these vigorous responses to both polysaccharide and protein antigens, HIV-1-infected patients showed limited evidence of CD4+ T cell activation at 1 week, no consistent rise in HIV-1 burden at any point, and no decline in CD4+ T cell number over time. We conclude that recent HIV-1 seroconverters show vigorous humoral responses to vaccine antigens and limited early evidence of T cell activation, but no substantial or sustained increase in viral replication or decline in CD4+ T cell number. Thus, respiratory bacterial vaccines appear immunogenic and safe early in HIV-1 infection.

Adult↗
PubMed1999

Kinetic study of bone ingrowth and ceramic resorption associated with the implantation of different injectable calcium-phosphate bone substitutes.

This study investigated the in vivo performance of two composite injectable bone substitutes (IBS), each with different calcium-phosphate particles granulometries [40-80 (IBS 40-80) and 200-500 microm (IBS 200-500)]. These biomaterials were obtained by associating a biphasic calcium-phosphate (BCP) ceramic mineral phase with a 3% aqueous solution of a cellulosic polymer (hydroxy-propyl-methyl-cellulose). Both materials were injected for periods of 2, 3, 8, or 12 weeks into bone defects at the distal end of rabbit femurs. Quantitative results on new bone formation, BCP resorption, and staining for tartrate-resistant acid phosphatase (TRAP) activity were studied for statistical purposes. Measurements with scanning electron microscopy and image analysis showed that the final rates of newly formed bone were similar for both tested IBS after 12 weeks of implantation. Bone colonization occurred more extensively during early implantation times for IBS 40-80 than for IBS 200-500. For the latter, BCP degradation occurred regularly throughout the implantation period, whereas it was very intensive during the first 2 weeks for IBS 40-80. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than for IBS 200-500 regardless of implantation time. With the granulometry of either mineral phase, both tested IBS supported extensive bone colonization, which was greater than that previously reported for an equivalent block of macroporous BCP. The resorption-bone substitution process seemed to occur earlier and faster for IBS 40-80 than for IBS 200-500. Both tested IBS expressed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability.

Animals↗
PubMed1999

Reversible cerebral ischemia in patients with pheochromocytoma.

Cerebral ischemia and symptoms of stroke can occur as a rare manifestation in patients with pheochromocytoma. We describe a 45-year-old woman who was admitted because of a right-sided hemiparesis due to an ischemic lesion in the left hypothalamus. The clinical diagnosis of a pheochromocytoma was proven by highly elevated urinary catecholamines and confirmed histologically after operation. The successful removal of the tumor led to the almost complete recovery of the neurological deficiencies. It is of vital importance to know this atypical presentation of pheochromocytoma. The diagnosis of pheochromocytoma should be suspected in patients with focal cerebral symptoms, particularly in the presence of intermittent hypertension or other paroxysmal symptoms suggestive of pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1999

Experiences with sexual aggression within the general population in the Czech Republic.

In a representative survey of the sexual behavior of the inhabitants of the Czech Republic (862 men and 825 women older than 15), questions were included concerning experience with sexually aggressive behavior: 11.6% of women reported this kind of experience (3.4% of them more than once). The average age at the time of rape was 21.2 years. Most of these experiences occurred within marriage or a stable partnership. In only a tenth of them the perpetrator was a stranger. Only 3.4% of the offenses were reported to police. Of Czech men, 4.8% replied positively to the question whether they had ever forced a woman to have sexual contact. The most common form of these enforced contacts was vaginal coitus.

Adolescent↗
PubMed1999

A new injectable calcium phosphate biomaterial for immediate bone filling of extraction sockets: a preliminary study in dogs.

BACKGROUND: Many different bone substitutes, such as autografts, allografts or synthetic biomaterials have been proposed to restore alveolar bone loss and support efficient placement of dental implants. This experimental study evaluated the osteoconductive properties of an injectable bone substitute (IBS) composed of a polymeric carrier and a calcium phosphate mineral phase, used to fill mandibular and maxillary canine extraction sockets. METHODS: The polymer was a cellulose derivative (methyl-hydroxy-propyl-cellulose, MHPC), and the mineral phase consisted of granules of biphasic calcium phosphate (BCP) ceramics 200 to 500 microm in diameter. Mandibular and maxillary premolars extracted from 3 dogs (a total of 60 extraction sites) were immediately treated with the IBS or left unfilled as control sites. Animals were sacrificed 3 months after implantation and all extraction sockets were prepared for histological evaluation. RESULTS: Qualitative histological studies showed that the IBS was able to support the extensive apposition of well-mineralized newly formed lamellar bone over the entire socket surface and appeared to prevent alveolar ridge bone loss in treated extraction sites. Quantitative evaluation showed that the amount of newly formed bone was significantly higher in mandibular than maxillary extraction sockets for both treated and control sites. CONCLUSIONS: An injectable bone substitute composed of a polymeric carrier and calcium phosphate was effective in enhancing the bone fill of extraction sockets. This approach may prove promising for periodontal lesions. The material expressed osteoconductive capacities, and the biological properties of the mineral phase were conserved.

Animals↗
PubMed1998

In vitro evaluation of a new injectable calcium phosphate material.

The purpose of this study was to develop an injectable bone substitute (IBS) for percutaneous orthopedic surgery. The multiphasic material used was composed of a 2% aqueous solution of methylhydroxypropylcellulose (MHPC) and biphasic calcium phosphate (BCP, 60% hydroxyapatite and 40% beta-tricalcium phosphate) in which MHPC served as the carrier for 80-200 microm of BCP granules. The best BCP/polymer ratio was determined by the rheological properties and higher BCP content of the material. Steam sterilization was more effective than gamma irradiation in maintaining the stability of the mixture and conserving its physiochemical and mechanical properties. The in vitro biocompatibility of the composite was checked by direct-contact cytotoxicity and cell-proliferation assays. A preliminary in vivo test was performed in the rabbit using intraosseous implantations in the femoral epiphysis. Histological analysis was done after 1, 2, 4, and 10 weeks. Bone ingrowth into the IBS, in close association with BCP granules, was observed after 1 week and increased regularly from the surface inward at 2, 4, and 10 weeks. At the same time, smaller BCP granules (less than 80 microns in diameter) were degraded and resorbed. This injectable biomaterial proved suitable for cavity filling. The water solubility and viscosity of the polymer allow cells to recolonize, with in situ bonding of the mineral phase.

Animals↗
PubMed1998

Application of FT-IR microspectroscopy to the study of an injectable composite for bone and dental surgery.

Hydroxypropylmethylcellulose (HPMC) of high-viscosity grade is used as a ligand for a bioactive calcium phosphate ceramic (the filler) in a ready-to-use injectable sterilized biomaterial for bone and dental surgery. Application of physico-chemical methods such as XPS, NMR, or Raman spectroscopy encounters difficulties when used to study such a multiphased material. This paper reports on the application of FT-IR microspectroscopy (FT-IRM) for the investigation of inorganic and organic phases of the rough composite and separated phases obtained by mechanical or chemical extraction methods. A comparison of FT-IRM with the conventional KBr pellet method was made and indicates that the macro and micro FT-IR methods are complementary: the former revealed new chemical groups not visualized with the KBr method whereas the latter detected the major compound of the blend. FT-IR microspectroscopy was revealed to be a powerful method of analysis that is complementary to other existing spectroscopic methods. Moreover, it is expected to be a useful tool in the study of biomaterials in biological samples.

Biocompatible Materials↗
PubMed1998

Grasping an object: one movement, several components.

The visuomotor transformations for producing a grasping movement imply simultaneous control of different visual mechanisms. The object size, orientation and 3D characteristics have to be encoded for the selection of the appropriate opposition space, within which the opposition forces will be applied on the object surface. These mechanisms also have to combine with those of the transport of the hand to the object location. Finally, biomechanical constraints impose categorical visuomotor decisions for positioning the opposition space according to object changes in size, orientation and spatial location. This paper examines possible interactions between the specialized structures for visuomotor transformation and the internal model that adapts prehension to its goals.

Hand Strength↗
PubMed1998

Bilateral high-frequency stimulation of the internal globus pallidus in advanced Parkinson's disease.

We report here the results of an open prospective study in 9 patients suffering from severe Parkinson's disease with on/off fluctuations and restricted off-period mobility, who underwent bilateral implantation of stimulating electrodes in the internal pallidum. At 3-month follow-up, the total Unified Parkinson's Disease Rating Scale (UPDRS) motor score in the medication-off state was reduced from 54.1+/-14.8 to 23.9+/-11.7 (44.2%) when stimulation was turned on. Comparison of UPDRS subscores revealed significant improvements for tremor, rigidity, bradykinesia, gait and posture, and dyskinesias. The results of the clinical scoring could be confirmed by significant changes in the quantitative assessment of hand function and walking. Bilateral pallidal stimulation reduced the amount and severity of on/off fluctuations. Additional follow-up at 6 months (n=6), 9 months (n=6), and 12 months (n=4) did not show a decline in effectiveness of stimulation. There was no permanent morbidity associated with the procedure. A subtle reduction of verbal fluency, which was not evident to the patients, was the only cognitive side effect of the procedure in neuropsychological testing. Chronic bilateral high-frequency stimulation of the internal pallidum seems to be a neurologically safe and highly effective treatment for "off" symptoms, dyskinesias, and motor fluctuations in advanced stages of Parkinson's disease.

Adult↗
PubMed1998

Symmetric and asymmetric left ventricular hypertrophy in patients with end-stage renal failure on long-term hemodialysis.

BACKGROUND: Patients with end-stage renal disease on regular hemodialysis have an increased prevalence of left ventricular (LV) hypertrophy that is associated with morbidity and mortality. Asymmetric septal hypertrophy and impairment of LV outflow can occur in these patients and may contribute to adverse outcomes. More insight into the prevalence, extent, geometry, and promoting factors of LV hypertrophy is important. METHODS: An unselected group of 62 patients (31 women), aged 55 +/- 14 years, on maintenance hemodialysis was investigated by Doppler echocardiography. Eight patients with valvular heart disease were excluded from further analysis. We assessed prevalence of LV hypertrophy and asymmetric septal hypertrophy, as well as parameters of LV geometry and LV filling and outflow dynamics. RESULTS: Prevalence of LV hypertrophy was 65%. Patients were analyzed according to LV mass and geometry. Mean LV mass index was normal (105 +/- 17 g/m2) in Group 1 without LV hypertrophy (n = 19); it was markedly elevated in Group 2 (symmetric hypertrophy, n = 22) and Group 3 (asymmetric hypertrophy with systolic anterior movement of mitral valve, n = 7), and highest (191 +/- 54 g/m2) in Group 4 (asymmetric hypertrophy without systolic anterior movement of mitral valve, n = 6, p < 0.001). Age, body mass index, and duration of hypertension were associated with LV hypertrophy and asymmetric septal hypertrophy (p = 0.01). Group 3 with systolic anterior motion of mitral valve had the smallest end-diastolic LV diameters (p = 0.02); increased heart rates, and increased ejection velocities in the LV outflow tract (p = 0.03, and p = 0.005, respectively, vs. Groups 1, 2, and 4) which pointed to an impairment of LV outflow. CONCLUSIONS: Symmetric LV hypertrophy and asymmetric septal hypertrophy are frequent in patients on maintenance hemodialysis. Predictors for LV hypertrophy were age and body mass index, and, particularly for asymmetric septal hypertrophy, age and hypertension duration. Volume withdrawal during hemodialysis may lead to symptomatic hypotension due to dynamic obstruction in some patients with severe asymmetric septal hypertrophy.

Adult↗
PubMed1998

Time dependence of left ventricular recovery after delayed recanalization of an occluded infarct-related coronary artery: findings of a pilot study.

OBJECTIVES: We sought to test the hypothesis that late recanalization of infarct-related coronary arteries (IRAs) improves long-term left ventricular (LV) function. BACKGROUND: Reperfusion within 24 h of an acute myocardial infarction (MI) has been shown to improve myocardial healing and to reduce infarct expansion. Uncontrolled data suggest that there may be a time window of several weeks for such an effect. METHODS: Sixteen asymptomatic patients 10 +/- 4 days after a first Q wave anterior wall MI with persistent left anterior descending coronary artery occlusion and infarct-zone akinesia were randomized to immediate (2 weeks) or delayed (3 months) angioplasty. Repeat catheterization and cardiac magnetic resonance imaging (MRI) were performed after 3 and 12 months. RESULTS: Angiography 3 months after MI revealed that LV ejection fraction (LVEF) had increased ([mean +/- SD] 54.4 +/- 4.3% vs. 63.9 +/- 7.4%, p < 0.01) as a result of improved regional function (p < 0.01) and LV end-systolic volume had decreased (p < 0.002), whereas LV end-diastolic volume remained unchanged. With delayed angioplasty, LVEF, infarct zone wall motion and LV volumes did not improve. Cardiac MRI at baseline and at 3 and 12 months confirmed these findings and extended them up to 1 year, indicating that delayed angioplasty could no longer improve LV function because of marked LV dilation (p < 0.01). Immediate angioplasty had a high success rate, but restenosis (50%) was accompanied by new severe angina as a clinical indicator of salvaged myocardium, which did not occur after delayed angioplasty. CONCLUSIONS: This pilot study in selected patients supports the hypothesis that myocardial viability persists ("hibernation") for 2 to 3 weeks but not for 3 months after MI, during which time it may be worthwhile to restore blood flow to a large myocardial territory, even in asymptomatic patients, to improve long-term LV function.

Adult↗
PubMed1998

[Use of condoms among the population of the Czech Republic: results of a national study].

Based on an anonymous survey, using questionnaires, in a representative group of the population of the Czech Republic above 15 years of age (862 men and 857 women) the authors investigated the use of condoms at the onset of sex life and with a steady and casual sexual partner. From the results ensues that the use of condoms in our population is lower than in advanced western European countries and the USA. During the first intercourse it was used only by 19% men and 14% women, in particular those of younger age groups. In a steady partnership two thirds of the respondents have experience with a condom, however, only one fifth uses it regularly. The position is similar during intercourse also with casual sexual partners, though the respondents use it more frequently. However not even then one third of men and almost half the women do not use protection by condoms. The most important influence on the reported use of condoms is exerted by the factors of sex (men, probably to appear socially in the most favourable light report its more frequent use) and age (condoms are used more frequently by younger men and women). In the Czech population the effect of religion and education is not important in this respect.

Adolescent↗
PubMed1998

The perception of discrimination in the HIV policy among Czech gay men.

The study aimed to evaluate the perception of discrimination in the Czech national HIV policy among gay men. The anonymous questionnaires were published in the gay journal and 191 respondents filled them and returned back. Their assessment of discrimination in the HIV policy and other life activities were ranked in 5-points scale. Assumed discrimination in the HIV policy was found to be one of the lowest one. Forty-one percent of men who answered did not find any discrimination in the HIV policy at all, eleven percent of them perceived it at the highest level. The personal perception of HIV discrimination was related to the fear of discrimination in the health facilities and to the general evaluation of political change for gay life. HIV policy is generally viewed as tolerant and without discriminative approach toward vulnerable minorities. The number of negative evaluations can play important role in the obstacles of preventive programs.

Adolescent↗
PubMed1998

[Factors affecting the attitude of the Czech population towards induced abortion].

Based on an anonymous questionnaire survey of a representative population group above 15 years of age in the Czech Republic (862 men and 857 women) the authors investigated also sociodemographic factors affecting attitudes of the Czech population to induced abortions. The findings suggest that attitudes of men and women to induced abortions do not differ essentially in any of the investigated criteria. The size of domicile does not affect the attitudes substantially. The most restrictive views are expressed by respondents of the oldest age group (above 60 years) and respondents of the youngest age group (15-17 years). The liberal attitude to induced abortions increases with the educational level. Religious belief has a marked effect on restrictive attitudes to abortions, nevertheless among catholic subjects only 7% male and female respondents expressed refused induced abortions unequivocally.

Abortion, Induced↗
PubMed1997

Programming of a movement sequence in Parkinson's disease.

The execution of multiple-component movements has been shown to be impaired in Parkinson's disease patients. To determine whether this deficit is attributed to faulty motor programming, a two-segment movement was examined by studying the kinematics of the first segment when the second segment contained variable accuracy requirements. The performance of 15 Parkinson's disease patients was compared with an age-matched control group. Movement precision not only affected the kinematics of the final segment but also the kinematics of the first segment. This 'context effect' was observed in both groups. Since Parkinson's disease patients revealed similar movement patterns to those of controls, their motor programming appears to be intact. Furthermore, correlation analysis for the segment movement-times revealed subjects with high as well as low correlation indices in both groups. The correlation indices were related to the context effect only in the Parkinson's disease patients. Independent of these phenomenon. Parkinson's disease patients showed marked hesitations between the movement segments compared with controls, suggesting that they have difficulty in implementing and/or in switching between motor program steps. Impaired force control and a reduced capacity to terminate movements in Parkinson's disease are discussed as possible explanations of the deficit in motor program implementation.

Adult↗
PubMed1997

[Contraceptive behavior in the population of the Czech Republic: results of a national survey].

Based on an anonymous survey by means of questionnaires in a representative sample of the population of the Czech Republic above the age of 15 years (862 men and 857 women) the use of different types of contraception was investigated at the onset of sexual life with a steady or casual partner, as well as attitudes to contraception. From the results ensues that during the first intercourse no contraception was used by more than half the respondents, a condom was used only by 19% men and 14% women, in particular younger men and women. In a steady partnership the most frequent method of contraception is coitus interruptus, whereby about one third have experience with hormonal contraception and two thirds of the respondents have experience with condoms. Among younger age groups of men and women there are more users of hormonal contraception and condoms. The position is similar in intercourse with casual partners. Only 5% men and 4% women oppose any contraception, almost one quarter are in favour of the so-called "natural" method and almost three quarters consider it necessary. The attitudes of atheists, younger and better educated women are more liberal.

Adolescent↗