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Biomedical subjects

J Mayer

Publications and source records attributed to J Mayer.

At least 109 records · Page 6Linked to original sources
PubMed1999

[Biomaterials, human tolerance and integration].

Biomaterials and related process engineering in order to obtain optimal surface and structural biocompatibility of implants and devices are presented. Vital-avital composites for tissue engineering, cell culture models, porous ceramics and degradable polymers are introduced as examples. Emphasis is laid on the conversion of basic research results into clinical applications and on the exchange of technologies from the non-medical into the medical field and vice versa.

Animals↗
PubMed1999

Must we really fear toxicity of conventional amphotericin B in oncological patients?

Fungal infections are an important cause of morbidity and mortality in patients with malignancies. Therefore, the use of amphotericin B (AmB) is essential for these patients. Results from the literature to date show that renal toxicity is the most serious adverse effect of AmB. Renal impairment manifests as a decrease in glomerular filtration and damage to tubular function. Currently, there is no reliable method of preventing nephrotoxicity. We have observed that sodium supplementation alone may not prevent nephrotoxicity. We noted that a large decrease in serum potassium and magnesium was followed by a significant reduction in creatinine clearance and an increase in both serum urea and creatinine. Therefore, we surmised that potassium and magnesium supplements corresponding to the amounts lost by the kidneys, as well as sufficient hydration, are necessary to prevent renal function damage. We decided to test our hypothesis in 32 cancer patients. During AmB therapy, serum electrolyte concentrations and biochemical parameters of renal function and fluid balance were monitored frequently. The daily ion supplementation corresponded to the amount lost through the kidneys. The total duration of administration ranged from 4 to 39 days, with a mean of 13.7 days (median 11.0 days). The mean daily AmB dose was 0.89 mg/kg (median 0.88 mg/kg). The average diuresis was 3863 ml/day, and the median 4000 ml/day. The daily mean i.v.-administered sodium dose was 195.9 mmol, the daily mean dose of i.v. potassium was 103.7 mmol, and the daily mean dose of i.v. magnesium was 9.0 mmol. The frequency of infusion-related side-effects was only 10.0%. These reactions were treated with hydrocortisone. We observed a significant increase in potassium and magnesium lost through the kidneys, and a significant increase in fractional sodium and potassium excretion through the renal tubuli. We did not observe a significant increase in serum creatinine and ion imbalances. Interestingly, the average creatinine clearance did not decrease, but actually increased slightly, though to a statistically insignificant degree, from 1.425 ml/s at the beginning of treatment to 1.589 ml/s on the 20th day of AmB use. Sufficient hydration of patients and ion supplementation corresponding to the amount lost by the kidneys is an effective prophylaxis for prevention of AmB-induced decrease in renal function and for countering imbalances of serum electrolyte concentrations during use of AmB. The frequency of infusion-related side-effects is minimal relative to other reports.

Adult↗
PubMed1999

Aneuploidy frequencies in semen fractions from ten oligoasthenoteratozoospermic patients donating sperm for intracytoplasmic sperm injection.

OBJECTIVE: To determine aneuploidy frequencies in pellet and swim-up semen fractions from 10 infertile men with severe oligoasthenoteratozoospermia (OAT) who were donating sperm for intracytoplasmic sperm injection and to determine whether the swim-up isolation method would successfully separate aneuploid from haploid sperm. DESIGN: Prospective study. SETTING: Infertility clinic and molecular genetics laboratory. PATIENT(S): Ten patients with severe OAT. INTERVENTION(S): Cytogenetic analyses by fluorescence in situ hybridization to determine aneuploidy frequencies for chromosomes 1, 13, 18, 21, X, and Y in sperm from swim-up and pellet fractions. MAIN OUTCOME MEASURE(S): Gametic aneuploidy was scored in sperm fractions separated by the swim-up technique and clinical results after intracytoplasmic sperm injection were tabulated. RESULT(S): In all cases, chromosome aneuploidy levels in patients were significantly greater than in controls. The type and percentage of aneuploid sperm for all patients with OAT found in both swim-up and pellet fractions were not different, with the exception of diploid sperm, which remained in the pellet fraction. After ET, 2 (20%) of 10 couples achieved successful pregnancies. CONCLUSION(S): The data show significantly higher rates of diploidy, autosomal disomy and nullisomy, sex chromosome disomy and nullisomy, and total aneuploidy in sperm from all separated fractions obtained from all patients with OAT versus controls. This patient population with OAT may be at increased risk of producing aneuploid offspring.

Aneuploidy↗
PubMed1999

Embryo implantation in in vitro fertilization and intracytoplasmic sperm injection: impact of cleavage status, morphology grade, and number of embryos transferred.

OBJECTIVE: The aims of this study were to compare preimplantation embryo quality in intracytoplasmic sperm injection (ICSI) with standard IVF and to examine the impact of age and number and quality of embryos transferred on implantation and pregnancy. DESIGN: Retrospective, controlled clinical study. SETTING: Academic tertiary center. PATIENT(S): We examined 211 consecutive couples undergoing ICSI who were matched with 211 couples undergoing IVF therapy during the same time frame. INTERVENTION(S): In vitro embryo culture. MAIN OUTCOME MEASURE(S): Day 3 embryo quality as judged by the number of blastomeres and morphology scoring. RESULT(S): Patients undergoing ICSI had a significantly reduced number of embryos with good morphology and cleavage compared with IVF cases. Nevertheless, pregnancy and abortion rates were similar when adjusted by age and number of embryos transferred. Average cleavage status and age were significant predictors of implantation. Women of advanced age had significantly lower embryo cleavage and implantation rates. CONCLUSION(S): [1] The cleaving status of day 3 embryos is a valuable, although limited, indicator of implantation outcome. [2] In vitro fertilization-derived embryos had better cleavage rates and morphology scores than ICSI-derived embryos; however, the implantation potential was similar for both groups. [3] The age-related decline in implantation rate was associated with impaired embryo growth rates.

Adult↗
PubMed1999

Perifollicular blood flow Doppler indices, but not follicular pO2, pCO2, or pH, predict oocyte developmental competence in in vitro fertilization.

OBJECTIVE: To assess the relationships among perifollicular blood flow; follicular fluid pO2, pCO2, and pH; oocyte developmental capacity; preimplantation embryo quality. DESIGN: Prospective study. SETTING: Academic, tertiary care institution. PATIENT(S): Unselected, gonadotropin-stimulated IVF cycles. INTERVENTION(S): Color, pulsed Doppler analysis of perifollicular blood flow, and follicular pO2, pCO2, and pH determinations of randomly designated, mapped ovarian follicles. MAIN OUTCOME MEASURE(S): Fertilization and day 3 embryo cleavage and morphology. RESULT(S): Perifollicular vascularity indices were significantly and negatively correlated with day 3 embryo cleavage. Pulsatility index and S-D ratio also were significantly and negatively correlated with follicular pO2. The same correlation was found between resistance index and the fertilization rate of preovulatory oocytes. No relationship existed between follicular metabolic analysis and fertilization or embryo quality. The resistance index had a sensitivity of 0.57 and a specificity of 0.71 for the prediction of advanced embryo cleavage status. CONCLUSION(S): Results confirm and extend previous reports demonstrating that color, pulsed Doppler ultrasound analysis of individual preovulatory follicles during IVF therapy may provide an indirect index of the developmental competence of the corresponding oocyte. Although these methods may provide means to select embryos for transfer with the highest implantation potential, the moderate predictive power showed so far may limit their clinical applicability.

Adult↗
PubMed1999

Ifosfamide and etoposide-based chemotherapy as salvage and mobilizing regimens for poor prognosis lymphoma.

We treated 40 patients with poor prognosis lymphomas. Patients with non-Hodgkin's lymphoma (NHL, n = 14) received MINE chemotherapy (mesna, ifosfamide 1330 mg/m2 and etoposide 65 mg/m2 by i.v. infusions on days 1-3, mitoxantrone 8 mg/m2 i.v. on day 1), and those with Hodgkin's disease (HD, n = 26) received VIM chemotherapy (mesna, ifosfamide 1200 mg/m2 by i.v. infusion on days 1-5, etoposide 90 mg/m2 by i.v. infusion on days 1, 3 and 5, and methotrexate 30 mg/m2 i.v. on days 1 and 5). Chemotherapy was followed by G-CSF (10 or 16 microg/kg in two divided doses daily) to mobilize PBSC. We performed 134 aphereses (median three leukaphereses per patient) starting on either day 13 (median; VIM) or day 12 (median; MINE). The median yield was 9.9x10(6) CD34+ cells/kg and 53.2x10(4) CFU-GM/kg for VIM, and 13.5x10(6) CD34+ cells/kg and 53.4x10(4) CFU-GM/kg for MINE. Except for predictable myelosuppression, no serious toxicity was seen. Response rate using MINE was 63% (18% CR, 45% PR) and using VIM 50% (17% CR, 33% PR). We conclude that VIM and MINE are effective and well-tolerated salvage regimens in patients with lymphomas and, followed by G-CSF, they also exhibit good capacity to mobilize stem cells in a predictable time interval.

Adolescent↗
PubMed1999

Using the Hough transform for HOLZ line identification in convergent beam electron diffraction.

The Hough transform as a means for automatic line detection is applied for higher order Laue zone (HOLZ) line identification in convergent beam electron diffraction. The HOLZ line positions are commonly used to measure the strain state in the investigated material. Besides the automation, a very important aspect is the accuracy of the detected line positions. The limits are determined by the amount of noise in the pattern relative to the contrast of the HOLZ lines and the line width. Our investigations show that sub-pixel resolution can be achieved routinely. We have also developed a new strain analysis procedure in which the dynamical shift of each individual line can be taken into account using a model based on several Ewald spheres with different radii. In comparison to the effective high voltage method, finer details of the dispersion surface can be considered, which increases the accuracy of the strain analysis. A measurement of the thermal expansion of aluminium is presented as a model experiment. The lattice constants were determined with an accuracy of about 10-4.

Journal Article↗
PubMed1999

Quantitative electron spectroscopic imaging studies of microelectronic metallization layers.

The combination of focused ion beam (FIB) sample preparation and quantitative electron spectroscopic imaging is an ideal tool for the investigation of layered structures used in microelectronic metallization schemes. In the present work, Si3N4/Cu/Si3N4/SiO2/Si and Al/TiN/Ti/SiO2/Si metallization layers produced by physical vapour deposition are investigated. We apply series of energy filtered images in the low loss region for a mapping of the sample thickness which makes it possible to refine the parameters of the FIB process. We also show how series of energy filtered images in the core loss region can be used to obtain elemental distribution images and chemical bonding information on these samples on a nanometre scale. For materials with a small grain size and/or a strong variation in Bragg orientation, the intensity distribution of the elemental map is strongly influenced by the superimposed Bragg contrast. This detrimental effect can be reduced greatly by using hollow cone illumination, as is demonstrated for polycrystalline Cu. One striking feature observed in Cu layers prepared with FIB is strong, regularly arranged contrast variations caused by subsurface defects in the Cu grains. We suppose that these defects are a consequence of a strong interaction of Ga atoms from the FIB with Cu.

Journal Article↗
PubMed1999

Editorial.

Explore the source record for details and available documents.

Journal Article↗
PubMed1999

Partially degradable film/fabric composites: textile scaffolds for liver cell culture.

In this study, a composite scaffold combining textile superstructures and biomimetic glycopolymers is introduced, which may allow engineering of organotypic liver tissue in vitro. Woven poly(ethylene therephtalat) (PET) fabrics were coated on one side with a thin biodegradable polymer film (poly[D-L-lactic-co-glycolic acid] PLGA), in order to obtain a polar structure. The composite structure ensured the stability of the membrane during in vitro degradation, independently of mesh size. Matrix porosity increased when a polymer blend matrix was used. For hepatocyte culturing studies, the scaffolds were additionally coated with an artificial glycopolymer (poly[N-p-vinylbenzyl-D-lactoamide], PVLA) in order to improve cell attachment. It was observed that formation of aggregates depends on the scaffold geometry as well as on the pretreatment and medium conditions. After 4 days in culture, the pores of the fabric were filled with aggregates illustrating the possibility of immobilizing hepatocyte aggregates in well-defined spatial configurations on textile structures.

Biocompatible Materials↗
PubMed1999

[MR proton spectroscopy to monitor the concentration changes in cerebral metabolites following a TIPS placement].

BACKGROUND AND AIMS: In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowered by intrahepatic portosystemic shunting (TIPS). Although less pronounced than in surgical shunting, hepatic encephalopathy (HE) is a well-known undesired side effect. In cerebral proton MR spectroscopy (MRS), HE can be detected by a specific pattern of brain metabolite changes (increase of glutamine/glutamate (Glx) and decrease of myo-inositol (ml) and choline (Cho)). The aim of this study was to examine whether, after TIPS implantation, there is a correlation of the reduction of the portosystemic pressure gradient (PSPG) and the cerebral metabolite changes and their correspondence to the clinical status. METHODS: We examined 10 cirrhotic patients (Child B, C) before and 3-20 days after TIPS implantation. Clinical examination was performed by a senior hepatologist. Localized MR spectra were acquired in parieto-occipital gray/white matter using a short echo time (TE = 5 ms) STEAM sequence. RESULTS: After TIPS we found an increase of Glx/(Cr + PCr) of 13%-40% and a decrease of ml(Cr + PCr) of 6%-46% with a positive (Glx: r = 0.71) respectively negative (ml: r = -0.59) correlation to the reduction of the PSPG. 7/10 patients with a reduction of the PSPG of more than 9 mmHg (9-17 mmHg) showed a clinical impairment of their HE. CONCLUSIONS: Short echo time cerebral MRS allows detection of finest HE specific metabolite changes and can therefore contribute positively to an individually optimized reduction of the PSPG during TIPS implantation.

Adult↗
PubMed1999

Bone marrow processing for transplantation using the COBE spectra cell separator.

BM processing, volume reduction, and granulocyte and erythrocyte depletion are important considerations for minimizing the side effects of graft administration and bypassing ABO incompatibility in allogeneic BMT. We used the COBE Spectra cell separator for BM processing in 33 patients suffering from hematologic malignancy and solid tumor (median age 39 years). We processed 42 BM harvests with the aim of maximizing recovery of mononuclear cells (MNC). BM was collected from the posterior iliac crest under general anesthesia. The mean volume of collected BM before filtration was 1,303 ml, and the mean number of collected total nucleated cells (TNC) was 2.61 x 10(8)/kg. The BM processing resulted in a mean recovery of 35.8% (10.1%-78.3%) TNC, 22.3% (1.1%-75.7%) of granulocytes, 78.8% (34.3%-135.2%) of MNC, 77.2% (8.3%-260.0%) of CD34+ cells, and 153.3% (32.9%-464.0%) of colony-forming units (CFU-GM) in the final product. A mean of 98.2% (94.5%-99.5%) of RBC was removed, with a mean of 13.3 ml (5.1-26.2 ml) of RBC in the final product. BM processing using the COBE Spectra cell separator proved to be fast, safe, and effective. However, the reasons for the very wide range of recovery of harvested CD34+ cells and CFU-GM need to be further investigated.

Adult↗
PubMed1999

The attitudes of Australian GPs to evidence-based medicine: a focus group study.

BACKGROUND: Over the last 6 years there has been an exponential increase in the publication of medical literature on evidence-based medicine. In Australia, as in many other parts of the world, there have been calls for an increase in the practice of evidence-based medicine. In general practice, two major themes of criticism have been the lack of relevant research evidence in primary care and the failure of evidence-based medicine to take into account the complexity of the consultation. OBJECTIVE: We aimed to explore the attitudes of Australian GPs to evidence-based medicine. METHODS: We conducted a qualitative study using evidence-based guidelines as a model to explore attitudes within focus group interviews. Focus group data were analysed using grounded theory methodology. The study was set in the Australian cities Melbourne, Adelaide and Darwin. The subjects were 27 GPs in five focus groups. RESULTS: Data were used to generate a model illustrating factors affecting the consideration and use of evidence within consultations. Prior beliefs and experience had a strong influence on decision-making. Overall, the GPs had a positive attitude to evidence-based medicine and stated that this could be a helpful strategy for meeting their information needs. These needs arose during the consultation and were frequently generated by patients. The evidence-based approach was regarded as particularly useful when patients required validation of their management or had specific queries. However, the GPs also expressed some concerns, such as the application of evidence from clinical trials to individuals, and the appropriateness of using research evidence with certain patients. They also feared a move away from the 'art of medicine'. None of the GPs expressed a need for critical appraisal skills. CONCLUSIONS: The Australian GPs in this study had mixed views about the increasing profile of evidence-based medicine, and the use of this paradigm in practice. Acceptability was more likely to be influenced by relevance to general practice and local contextual and patient factors than by the strength, or critical quality of the evidence.

Adult↗
PubMed1999

Key informant surveys as a tool to implement and evaluate physical activity interventions in the community.

Key informant surveys are important tools for planning and evaluating community health programs. A survey was conducted to gather views on policies toward physical activity from four sets of key informants: physicians, church leaders, business leaders and civic leaders. Surveys were mailed to 797 key informants who were selected from 12 southeastern Missouri counties. For comparison, data from a telephone survey of 2106 persons in the general population were also analyzed. The majority (> 85%) in all four key informant groups were very supportive of required physical education in schools, but less supportive (< 69%) of government funding for places where community members can exercise. Physicians perceived community members as having somewhat greater access to places to exercise relative to the other key informant groups. Comparisons of the key informant surveys to the population survey indicated similar levels of support for physical activity policy. The information from this survey has been useful in identifying support for physical activity policy and gaining access to potential influences for community change. Since key informant research in the area of physical activity policy and cardiovascular disease prevention is sparse, there is a need for future studies.

Adult↗
PubMed1999

Systemic lymphocyte activation modulates the severity of diet-induced acute pancreatitis in mice.

To examine the role of lymphocyte activation in the development of local and systemic complications in acute pancreatitis, we compared disease severity of choline-deficient, 0.5% ethionine supplemented (CDE) diet-induced acute pancreatitis in T- and B-cell deficient SCID mice and immunocompetent C.B-17 mice. Twenty-five female SCID and 17 female C.B-17 mice were fasted for 24 h and fed a CDE diet for 72 h. Twenty SCID and 12 C.B-17 mice were bled and their organs removed for histologic evaluation. Five control animals of both kinds were fed a regular diet for 6 days. Lung, kidney, and pancreas were examined microscopically, and pancreatic damage scored. Apoptosis was detected by DNA nick-end labeling and confirmed by DNA laddering. Trypsinogen-activation peptide was measured by enzyme-linked immunosorbent assay (ELISA), and the catalytic activity of PLA2 was determined by a radiometric assay. Four-day mortality was 10% in SCID and 33% in C.B-17 mice, and 10-day mortality was 0 in SCID and 60% in C.B-17 mice. SCID mice had mild pulmonary damage, whereas pulmonary injury was severe in C.B-17 mice. Pancreatic damage was severe in both groups. Even though in situ staining of apoptotic cells was found in all pancreatitis animals, apoptosis was confirmed by DNA laddering only in C.B-17 mice. In SCID mice, apoptotic cell staining positively correlated with necrosis (r = 0.91; p < 0.001). Plasma TAP and PLA2 catalytic activity did not differ significantly between the groups. In conclusion, the absence of T and B lymphocytes prevents severe pulmonary injury resulting from acute pancreatitis but does not influence pancreatic or renal damage. Our results suggest that systemic lymphocyte activation does not affect the initiating events that trigger pancreatic injury but modulates the systemic response, in particular, pulmonary injury caused by acute pancreatitis.

Acute Disease↗
PubMed1999

Immunnohistological assessment of intestinal eosinophil activation in patients with eosinophilic gastroenteritis and inflammatory bowel disease.

OBJECTIVE: To assess the activation grade of intestinal eosinophils in patients with eosinophilic gastroenteritis (EOG), ulcerative colitis (UC), Crohn's disease (CD), and controls by immunohistochemistry. METHODS: Cecal biopsies were collected from healthy controls and from patients with EOG, CD, UC, and other noninflammatory GI diseases. Immunohistochemistry was performed in sequential sections stained with monoclonal antibodies directed against eosinophil cationic protein (ECP) or eosinophil protein X (EPX) stored in eosinophil granules (EG1) and that secreted by activated eosinophils (EG2). The ratio of EG1 to EG2-positive eosinophils expressed as percentage of lamina propria cells was calculated. ECP and EPX were measured in serum and feces. RESULTS: The percentage of EG1 and EG2-positive lamina propria cells was elevated in EOG and slightly, but not significantly, in UC. The ratio of EG1 to EG2-positive cells was decreased in CD, UC, and other patients as compared to healthy controls. Particularly low EG1 to EG2 ratios were found in EOG. Correspondingly, fecal and serum levels of ECP and EPX, respectively, were highest in patients with EOG. The EG1 to EG2 ratio was negatively correlated with fecal ECP and EPX levels. At sites of actively inflamed mucosa, the EG1 to EG2 ratio was lower than in noninflamed tissue. CONCLUSIONS: Our data strongly suggest that the EG1 to EG2 ratio may be a marker of tissue eosinophil activation. Low ratios (<1) indicate eosinophil activation, whereas ratios > or =1 are found in healthy controls. Furthermore, we show that EOG is characterized by a pronounced intestinal eosinophil accumulation and activation, whereas in CD and UC, eosinophils seem to be activated but their number is not or only slightly elevated compared to controls.

Adult↗
PubMed1999

Recommendations for toxicological investigations of drug-facilitated sexual assaults.

The recent increase in reports of drug-facilitated sexual assaults has caused alarm in the general public and prompted forensic toxicologists from across North America to address the toxicological issues surrounding this matter. The authors have developed recommendations and guidelines to inform law enforcement, medical, and scientific personnel of the requirements for performing successful toxicological examinations in cases of drug-facilitated rape.

Alcohol Drinking↗