Biomedical subjects

J Mayer

Publications and source records attributed to J Mayer.

At least 91 records · Page 5Linked to original sources

PubMed2000

Feasibility study of an online toxicological sensor based on the optical waveguide technique.

Morphological properties of the cells often change as an early response to the presence of a pharmacologically acting toxic substance [Etcheverry, S.B., Crans, D.C., Keramidas, A.D., Cortizo, A.M., Arch. Biochem. Biophys. 338 (1997) 7-14]. Recently it has been shown that living animal cell adhesion and spreading can be monitored online and quantitatively via the interaction of the cells with the evanescent electromagnetic field present at the surface of an optical waveguide [Ramsden, J.J., Li, S.Y., Heinzle, E., Prinosil, J.E. Cytometry 19 (1995) 97-102]. In the present study, optical waveguide lightmode spectroscopy (OWLS) and confocal laser scanning microscopy (CLSM), which provides information about the shape of the cells at the surface, were compared under identical experimental conditions. This allowed for the correlation between the cell-shape information from CLSM and the cell-surface interaction measurements from OWLS. The proposed design of the microsystem sensor involves the establishment of a cell layer on the surface of the waveguide and the subsequent online measurement of the morphological response of the cells to various toxic substances. In the present study, the setup was evaluated using cells from an osteoblastic MC 3T3-E1 cell line, and sodium hypochlorite was used as model toxic substance. Comparing the OWLS signal to the morphological response measured by CLSM reveals that OWLS is effective in monitoring not only cell attachment and spreading but also the cellular response to toxic compounds (i.e. by means of change in cell morphology). For the model toxin, the OWLS measurements indicate that, at concentrations above 0.01%, the cells exhibit a clearly discernable morphological effect (i.e. a decrease in average cell contact area). Thus, the potential of an on-line sensor based on OWLS to applications in toxicology, pharmacy and biocompatibility was demonstrated.

3T3 Cells↗

PubMed2000

The T-tubular network and its triads in the sole plate sarcoplasm of the motor end-plate of mammals.

The transition between the subsynaptic folds and the T-tubules demonstrated in a former paper was further investigated in the sole plate area by using the extracellular marker Lanthanum. A tubular network of the T-system of the sole plate area which is connected to the subsynaptic folds and to the t-tubular elements between the myofibrils is described for the first time. T-tubules of this network criss-cross through the sarcoplasm of the sole plate and lie in close proximity to sole plate nuclei and mitochondria. Cisterns of sarcoplasmic reticulum of the sole plate area make contact with these t-tubules forming triads. The possible physiological role of this sole plate network and its triads will be discussed with regard to a transport of substances in tubules with the dimension of nanotubes and Ca2+ activated processes in the sole plate area.

Animals↗

PubMed2000

Is the timing of implantation affected by zona pellucida micromanipulation?

PURPOSE: Our purpose was to examine the timing of implantation and early embryo development following uterine transfer of oocytes/embryos previously subjected to zona pellucida micromanipulation. METHODS: A total of 68 singleton pregnancies resulting from IVF and embryo transfer with/without micromanipulation. Patients were divided into four groups according to the type of micromanipulation technique: assisted hatching, embryo biopsy, intracytoplasmic sperm injection, and no micromanipulation (control group). Serial serum beta-hCG levels were measured between 10 and 25 days after fertilization and log-transformed. Linear regression analyses were performed and extrapolated to hCG = 10 mIU/ml (hCG10) to estimate detectable implantation. The slopes of the regression lines were used to estimate the rising speed of hCG, an indirect sign of embryo development. RESULTS: There were no significant differences among groups with respect to hCG10, the slopes or intercepts of the regression lines. CONCLUSIONS: Various oocyte/embryo microsurgical procedures used in ART involving zona pellucida manipulation do not appear to affect the timing of implantation or early embryo development.

Adult↗

PubMed2000

Treatment of hospital-acquired penumonia.

Hospital-acquired pneumonia (HAP) remains a significant cause of morbidity and attributable mortality, especially among patients undergoing mechanical ventilation. The clinical approach to this disorder continues to evolve. Although our understanding of the epidemiology, risk factors, and pathogenesis of this disorder are expanding, consensus on diagnostic, therapeutic, and preventive strategies is lacking. Although outcome is significantly improved by the rapid introduction of appropriate antimicrobial therapy, presently available diagnostic tests rarely are able to identify a specific pathogen when antimicrobial choices are made. Thus, most therapy is by necessity empirical. The American Thoracic Society (ATS) published guidelines for the empiric treatment of HAP in 1996, this article reviews the recommendations of these guidelines and, if new information is available, updates these recommendations.

Anti-Bacterial Agents↗

PubMed2000

Laboratory diagnosis of nosocomial pneumonia.

The second most common nosocomial infection in the United States is pneumonia, with the highest rates seen in patients requiring mechanical ventilation. Nosocomial pneumonia is a serious disease associated with significant morbidity and mortality; crude mortality rates have been estimated at 20% to 50%. The rapid institution of appropriate antimicrobial therapy has been shown to improve mortality in patients with ventilator associated nosocomial pneumonia. Thus, the identification of nosocomial pneumonia with a timely microbiologic diagnosis is important for the management of these patients. However, the accurate diagnosis of nosocomial pneumonia, along with identification of the responsible organism(s), can be challenging. This task becomes even more difficult in patients who are mechanically ventilated. The presence of new pulmonary infiltrates along with clinical criteria including fever, cough, and purulent secretions are neither sensitive nor specific for the diagnosis of nosocomial pneumonia. The laboratory can enhance the accuracy of pneumonia diagnosis, as well as provide the identification of an etiologic organism(s). There are, however, many challenges which confront the laboratory including: the ability to identify organisms from an extensive microbiologic spectrum; distinguishing colonization from infection of predominately gram-negative oropharyngeal flora; and providing timely results. This article reviews the various diagnostic tests available for nosocomial lung infections, and in particular, ventilator associated pneumonia including: blood cultures; pleural fluid; expectorated sputum; endotracheal aspirates; and respiratory specimens obtained by more invasive techniques using bronchoscopy and transthoracic needle aspiration. Emphasis is placed on optimal specimen collection, the processing of samples in the laboratory, and on the evaluation of potential risks and benefits associated with the varying techniques.

Bacteria, Anaerobic↗

PubMed2000

Warfarin use and fracture risk.

Two recent studies examined the association between chronic use of warfarin, a vitamin K antagonist, and fracture rate among older women. Whereas one study reported no association, the other reported a significantly higher risk for vertebral and rib fractures among warfarin users compared with nonusers. The effect of vitamin K antagonists on age-related bone loss continues to be controversial.

Animals↗

PubMed2000

Holiday weight gain: fact or fiction?

The prevalence of obesity continues to rise and controversy remains regarding the underlying specific causes of this trend. Recently, the magnitude of holiday weight gain and its contribution to annual weight gain were examined in a convenience sample of 195 adults. On average, weight gain during the 6-week winter period from Thanksgiving through New Year averaged only 0.37 kg. However, weight gain was greater among individuals who were overweight or obese, and 14% gained >2.3 kg (5 lb). In addition, among the entire population, weight gain during the 6-week holiday season explained 51% of annual weight gain. These results suggest that holiday weight gain may be an important contributor to the rising prevalence of obesity, even though absolute values for weight gain in this study were less than anticipated. Further studies using representative populations are needed to confirm these findings.

Holidays↗

PubMed2000

Inflammatory mediators in human acute pancreatitis: clinical and pathophysiological implications.

BACKGROUND: The time course and relationship between circulating and local cytokine concentrations, pancreatic inflammation, and organ dysfunction in acute pancreatitis are largely unknown. PATIENTS AND METHODS: In a prospective clinical study, we measured the proinflammatory cytokines interleukin (IL)-1 beta, IL-6 and IL-8, the anti-inflammatory cytokine IL-10, interleukin 1 beta receptor antagonist (IL-1RA), and the soluble IL-2 receptor (sIL-2R), and correlated our findings with organ and systemic complications in acute pancreatitis. In 51 patients with acute pancreatitis admitted within 72 hours after the onset of symptoms, these parameters were measured daily for seven days. In addition, 33 aspirates from ascites and the lesser sac were measured. RESULTS: Sixteen patients had mild acute pancreatitis (AP) and 35 severe AP (Atlanta classification); 18 patients developed systemic complications requiring treatment. All mediators were increased in AP. sIL-2R, IL-10, and IL-6 were significantly elevated in patients with distant organ failure. An imbalance in IL-1 beta/IL-1RA was found in severe AP and pulmonary failure. Peak serum sIL-2R predicted lethal outcome and IL-1RA was an early marker of severity. IL-6 was the best prognostic parameter for pulmonary failure. CONCLUSION: Our results suggest that local mediator release, with a probable IL-1 beta-IL-1RA imbalance in severe cases, is followed by the systemic appearance of pro- and anti-inflammatory mediators. The pattern of local and systemic mediators in complicated AP suggests a role for systemic lymphocyte activation (triggered by local release of mediators) in distant organ complications in severe AP.

Acute Disease↗

PubMed2000

MR imaging and (1)H spectroscopy of brain metabolites in hepatic encephalopathy: time-course of renormalization after liver transplantation.

PURPOSE: To evaluate changes in hydrogen 1 magnetic resonance (MR) spectroscopic findings in overt or subclinical hepatic encephalopathy (HE) after liver transplantation and to compare these changes with clinical outcomes and basal ganglia high signal intensity (BGH). MATERIALS AND METHODS: Twenty-two patients scheduled for liver transplantation and 17 healthy control subjects were examined with (1)H MR spectroscopy and standard nonenhanced MR imaging. Eight patients underwent complete MR imaging and (1)H spectroscopic examinations before liver transplantation and at 3-4-week, 12-28-week, and 10-12-month follow-up after liver transplantation. RESULTS: Before liver transplantation, typical (1)H spectroscopic changes-decreased myo-inositol (mI)/creatine (Cr) and choline (Cho)/Cr ratios and an elevated glutamine and glutamate (Glx)/Cr ratio-were found in 21 patients. Eighteen patients had BGH at T1-weighted imaging. Three to 7 months after liver transplantation, the mI/Cr and Glx/Cr ratios were within the normal range in five of eight and eight of eight patients, respectively, without any residual signs of subclinical or overt HE; however, at MR imaging, seven patients still had BGH. CONCLUSION: After successful liver transplantation, renormalization of HE-specific brain metabolite changes is detected at (1)H spectroscopy and precedes the disappearance of BGH. The neuropsychologic signs of subclinical or overt HE follow the changes seen at (1)H spectroscopy rather than those seen at MR imaging.

Adult↗

PubMed2000

Who cares? A focus group study on follow up care after discharge from hospital.

AIM: To ascertain general practitioners', patients' and hospital staff's perspectives on post discharge problems and other problems related to hospital liaison in the Darwin urban area. To identify stakeholders who have a role in addressing these problems and develop locally appropriate responses to improve post hospital discharge patient care. METHOD: A qualitative study using three focus groups was conducted with seven GPs, six ex-patients of the study hospital and 11 hospital staff. The problems and proposed strategies identified by these groups were then fed back to stakeholders for comment in order to generate recommendations to improve post discharge care. RESULTS: The main themes generated were: lack of recognition of the potential role of the GP and patient by the hospital; poor communication between the hospital, GPs and patients; and, lack of resources to improve information flow. Specifically, 'not being listened to' by hospital doctors, nurses and GPs was a major theme of the patient focus group and was equated with a 'not caring' attitude by some hospital staff and GPs. Twelve strategies were generated by the focus groups with considerable overlap of issues. The main strategies were aimed at GP liaison by providing GPs and patients with timely, adequate and comprehensible information as part of their 'duty of care'. General practitioners, however, need to provide legible, relevant and concise referral letters to facilitate this process. CONCLUSIONS: This study highlights the need for improved communication between the GP and the hospital to redress the lack of recognition of GPs. The appointment of a GP/hospital liaison officer in the study hospital could address this issue as well as others of patient empowerment and advocacy, and partnerships in health care. This project has also highlighted the importance of consulting patients and the value of their perspective to complement GP and hospital viewpoints.

Aftercare↗

PubMed2000

[Methods in optic nerve disk digital planimetry].

The authors define the term planimetry in general and planimetry of the optic disc in particular and present a brief review of the history of planimetric evaluation of the optic disc. They describe a digital analyzer of their own design, the method of examination of the optic disc and further processing and recording of data. They define the indications and contraindications of examination, summarize the asset and limitations of the method used. The authors examined so far by digital planimetry 1575 optic discs of 856 patients.

Humans↗

PubMed2000

[Effect of high-dose chemotherapy in patients with relapsing or resistant Hodgkin's disease].

The authors evaluated a group of 48 patients with relapsing or resistant Hodgkin's disease. The patients were treated by life-saving chemotherapy followed by large doses of chemotherapy and autologous transplantation of haematopoietic cells. For life-saving chemotherapy they used most frequently a combination of VIM in 40 patients and combinations of DHAP, MINE, MiniDexaBEAM. In 11 patients they changed the regime of life-saving chemotherapy because of a poor response. After completed life-saving chemotherapy 18 (37.5%) patients were in CR, 27 (56.2%) in PR and in 3 (6.3%) the disease progressed. For large dose chemotherapy the authors used BEAM in 32 patients, CBV in 2, Busulfan with Cyclophosphamide in 13 patients and Busulfan with Melfalan in one patient. After completion of large dose chemotherapy and subsequent autologous transplantation of bone marrow 31 (64.6%) patients were in CR, 8 (16.7%) in PR and the disease progressed in 9 (18.7%). In August 1999 a total of 44.9% patients in CR survive, the median period of follow up after autologous transplantation was 23 months. Life-saving chemotherapy with subsequent large dose chemotherapy led in the investigated group to induction of CR in 64.6% patients which is the basic prerequisite of long-term survival.

Adult↗

PubMed2000

[Lymphocytosis with large granular lymphocytes: case report].

Lymphoproliferative disorders of large granular lymphocytes (LGL) can arise from either CD3+ T cells or CD3- natural killer cells. Polyclonal proliferation of LG lymphocytes is called LGL lymphocytosis, monoclonal proliferation of LG lymphocytes is LGL leukaemia. Prominent clinical manifestations of LGL lymphocytosis and leukaemia are bacterial infections, splenomegaly, and may be connected with rheumatic or autoimmune disorders. Hematologic findings reveal particularly lymphocytosis, and severe neutropenia. The beta chain gene of T cell receptor rearrangement analysis is necessary for distinguishing of T LGL lymphocytosis from T LGL leukaemia. The authors report a case of young woman with T cells LGL lymphroproliferative disorder, bacterial infection, reactive lymphadenopathy, and spontaneous regression of the lymphocytosis within 6 months.

Adult↗

PubMed2000

[Will transplantation of peripheral blood stem haematopoietic cells definitively replace bone marrow transplantation?].

Findings assembled for a long time, practically from the end of the Second World War along with modern technology of genetic engineering which brought mass production of growth factors led at the beginning of the nineties of the 20th century to a rapid rise of transplantations of peripheral stem cells. Without exaggeration it may be said that the last decade of the 20th century is the decade of transplantations of peripheral stem cells. Peripheral stem cells comprise a wide range of haematopoietic cells incl. stem cells which are after a stimulus (antitumour chemotherapy or growth factors) released from bone marrow in high concentrations into the peripheral blood stream from where they can be obtained very simply by modern blood cell separators. They are suitable for autologous as well as allogenic transplantations. In autologous applications they have almost replaced bone marrow. Restoration of haematopoiesis is after their use more rapid as the transplant is richer. As regards allogenic application caution is still apparent, although even their ratio is very significant. However a higher rate of reactions of the graft to the host is feared. It seems however that this fear is not justified and that the richer transplant of peripheral stem cells can ensure a higher anti-tumourous effect of the transplantation. Peripheral stem cells are also used successfully in transplantations after so-called non-myeloablative regimes. It is beyond doubt that the use of peripheral stem cells will increase further. We may expect application of other growth factors with a higher mobilizing capacity. Peripheral stem cells will be subjected to further modifications in vitro. It will be also possible to increase their amount. A rich transplant makes it also possible to use it in transplantations from haploidentic donors. No doubt stem cell suspensions will become the objective of gene therapy.

Bone Marrow Transplantation↗

PubMed1999

Folding and association of the antibody domain CH3: prolyl isomerization preceeds dimerization.

The simplest naturally occurring model system for studying immunoglobulin folding and assembly is the non-covalent homodimer formed by the C-terminal domains (CH3) of the heavy chains of IgG. Here, we describe the structure of recombinant CH3 dimer as determined by X-ray crystallography and an analysis of the folding pathway of this protein. Under conditions where prolyl isomerization does not contribute to the folding kinetics, formation of the beta-sandwich structure is the rate-limiting step. beta-Sheet formation of CH3 is a slow process, even compared to other antibody domains, while the subsequent association of the folded monomers is fast. After long-time denaturation, the majority of the unfolded CH3 molecules reaches the native state in two serial reactions, involving the re-isomerization of the Pro35-peptide bond to the cis configuration. The species with the wrong isomer accumulate as a monomeric intermediate. Importantly, the isomerization to the correct cis configuration is the prerequisite for dimerization of the CH3 domain. In contrast, in the Fab fragment of the same antibody, prolyl isomerization occurs after dimerization demonstrating that within one protein, comprised of highly homologous domains, both the kinetics of beta-sandwich formation and the stage at which prolyl isomerization occurs during the folding process can be completely different.

Antibodies, Monoclonal↗

PubMed1999

[Diagnosis of cytomegalovirus infection with the polymerase chain reaction and antigenemia in patients after allogenic peripheral stem cell transplantation--comparison of 318 paired samples].

BACKGROUND: Cytomegalovirus (CMV) represents a serious infectious complication in patients after allogenic haematopoietic stem cell transplantation. Timely initiation of the therapy at the time of incipient active CMV infection (preemptive therapy) is an important prevention of CMV disease. It is not clear, what is the best indicator of this incipient CMV infection. METHODS AND RESULTS: The significance of the detection of incipient CMV infection by CMV-antigenaemia and DNA-viraemia was compared in this study. DNA-viraemia was detected by the non-nested polymerase chain reaction (PCR). The sensitivity of nested and non-nested PCR was also compared experimentally. We tested 318 blood samples for antigenaemia and DNA-viraemia. Six samples were significantly positive for PCR, no sample was significantly positive for antigenaemia. Timely initiation of therapy resulted in the rapid eradication of the incipient active CMV infection and clearance of DNA-viraemia. CONCLUSIONS: Non-nested PCR is a suitable and more reliable method for the monitoring of incipient active CMV infection and it is a good method for timely initiation of preemptive antiviral therapy.

Antigens, Viral↗

PubMed1999

[Kinetics of hematopoiesis after high-dose chemotherapy and autologous peripheral stem cell transplantation].

BACKGROUND: Autologous peripheral blood stem cell transplantation (APBSCT) is gradually replacing autologous bone marrow transplantation in many clinical settings. The key question is how to evaluate the quality of grafts. We analyzed the relationship between hematopoietic reconstitution and characteristics of patients and grafts. METHODS AND RESULTS: Data from 95 APBSCTs were analyzed. Peripheral stem cells were obtained after mobilization using anti-neoplastic chemotherapy followed by Neupogen (G-CSF). After high dose chemotherapy and APBSCT, patients received Leucomax (GM-CSF). Patients were reinfused with a median of 6.1 x 10(6) (range 0.83-29.3) CD34+ cells/kg, and 25.1 x 10(4) (range 1.0-167.0) CFU-GM/kg of body weight. The median time to engraftment was 12 days (both for granulocytes 1 x 10(9)/l and platelets 50 x 10(9)/l). We found a significant correlation between the number of CD34+ cells and CFU-GM reinfused and also between their respective graft sizes and time to leukocytes, platelets, and granulocytes recovery. We did not find a significant correlation between the number of mononuclear cells reinfused and any analyzed parameter (time to engraftment, age, diagnosis, number of previous chemotherapies, type of mobilization or high-dose regimen). However, administration of preparative high-dose chemotherapy consisted of busulphan and cyclophosphamide was associated with the risk of a transient secondary graft failure. CONCLUSIONS: We conclude that the content of progenitors in PBSC grafts and time to booth leukocyte and platelet recovery are best estimated by the number of CD34+ cells (not less than 1 x 10(6)/kg) and CFU-GM (not less than 1 x 10(4)/kg). The number of mononuclear cells in an autologous PBSC graft is not suitable and useful for prediction of engraftment rate. There is probably no additional benefit of reinfusion of more than 8-10 x 10(6) CD34+ cells/kg and/or 50 x 10(4) CFU-GM/kg, because hematopoietic recovery is not more rapid.

Adolescent↗

PubMed1999

Bone marrow as multidimensional orbit oscillator after autologous bone marrow transplantation.

The local renin-angiotensin system (RAS) in bone marrow is probably involved in the control of hematopoiesis. Earlier observations suggest the relationship between the frequency of sodium and potassium concentration changes in urine and bone marrow recovery after chemotherapy. The purpose of this study was to prove the relationship between sodium and potassium excretion changes in urine and granulocyte counts in peripheral blood after autologous bone marrow and peripheral blood stem cell transplantation. The correlation between amplitude maximum FFmax of F=d[Na]/d[K], where d[Na] and d[K] are changes of sodium and potassium excretions in 24 h, and granulocytes, recorded k days later, was found in 12 patients with autologous bone marrow transplantation (BMT) and/or PBSCT. In patients with successful engraftment, k ranged from 4 to 7 days. In the patient with unsuccessful BMT, k was 12 days. The results imply the interaction between systemic and bone marrow RAS.

Adolescent↗