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Biomedical subjects

C Weiss

Publications and source records attributed to C Weiss.

At least 181 records · Page 10Linked to original sources
PubMed1992

Exercise-induced symptomatic and asymptomatic myocardial ischemia in patients with severe coronary artery disease: focus on the efficacy and safety of gallopamil.

Symptomatic and asymptomatic episodes of transient myocardial ischemia are well-known risk factors in patients with coronary artery disease. In a single-blind, randomized, and placebo-controlled study, the efficacy and safety of gallopamil was studied during a 1-week treatment period in 25 patients with high-grade coronary artery stenosis and frequent, exercise-induced episodes of myocardial ischemia. Eighteen patients were men, and seven patients were women; the mean age +/- SD was 59 +/- 7 years. After a 1-week run-in period (days 1-7), all patients were treated with gallopamil 50 mg t.i.d. (days 8-14) and placebo t.i.d. (days 15-21) or vice versa. Twenty-four-hour Holter monitoring, exercise testing, and adverse effects were controlled at days 7, 14, and 21. During the run-in period, all patients suffered a mean of 5.9 +/- 2.9 episodes of transient myocardial ischemia, mean ischemic duration was 38 +/- 29 min/day. Gallopamil increased exercise tolerance from 7.9 to 9.8 min (+24%, p < 0.05) and resulted in reduction of the weekly usage of short-acting nitrates by 45% compared to placebo. During 24-h Holter monitoring, mean heart rate at the onset of ST-segment depression increased from 106 to 118 beats/min (p < 0.05). The frequency of daily ischemic episodes was reduced after gallopamil administration from 6.1 to 3.9 episodes/day (-37%, p < 0.05), the total ischemic burden decreased for symptomatic episodes by -54% (p < 0.05) and for asymptomatic episodes by 29% (p < 0.05). Gallopamil modified the circadian distribution of ischemic episodes by modifying the morning peak of transient myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

[The diagnostic imaging of complex breast nodules].

This study was aimed at determining the role of high-frequency (7.5 MHz) US combined with cytology in the diagnosis of complex breast nodules (complex cysts--cystic tumors). The study population included 60 patients presenting with complex breast nodules selected on the basis of US patterns among 3,000 cases. All patients were also submitted to US-guided fine-needle aspiration biopsy (FNAB). Cytology of nipple discharge was always performed when discharge was present (15 cases), mammography was performed in 50 cases and pneumocystography in 10. US allowed the identification of the lesion in all patients and the diagnosis of nature in 73%; with FNAB the figure reached 96.7%. Mammography identified the lesion in 95% of patients, but failed to reveal the complex nature of the nodule. In a small number of cases mammography proved to be a useful complementary tool demonstrating malignant features not recognizable on US images. On the contrary, pneumocystography yielded no further information with respect to US. Diagnostic control was obtained by means of surgery in 30 patients and of clinical-US follow-up in the extant 30 cases. On the basis of their US features the lesions were classified into two groups: I) nodules having a mainly liquid component--i.e., hemorrhagic, septic, multilocular cysts, papillary cystadenoma; II) nodules having a mainly solid component--i.e., solitary intraductal papilloma, intracystic carcinoma, mixed carcinoma, phylloid adenoma, sarcoma. As to the former group, US proved reliable in making a diagnosis in the cases with typical hemorrhagic, septic and multilocular cysts. In the atypical cases, FNAB of the solid component of the nodule was necessary to differentiate irregular clots, thick septa or inflammatory thickening from different conditions. As to the latter group, FNAB of the solid component and/or mammography proved useful in making a diagnosis, even though to this aim US revealed peculiar patterns which were highly suggestive. In our experience, combined US and FNAB are of basic importance in the diagnosis of breast lesions, thus replacing pneumocystography which has been widely employed so far. As regards mammography, its role seems limited to pointing out the peculiar characters of malignancy which could not be demonstrated otherwise.

Adult↗
PubMed1992

[Successful high-frequency current ablation of three accessory conduction pathways in a single session].

A case is presented of a 25-year-old symptomatic male with Wolff-Parkinson-White syndrome and three overt accessory atrioventricular connections which were all diagnosed and ablated during the same session. A discordant preexcitation pattern between delta wave and QRS axis was found on the surface electrocardiogram, indicating the presence of two or more accessory pathways. During atrial pacing the appearance of a changing QRS morphology and alternating delta wave suggested the presence of an additional left-sided pathway. After ablation of a right anteroseptal pathway, a second pathway was found located in the left lateral position and was successfully ablated. The final pathway became evident only after the ablation of the first two and was found to be located in a right midseptal position. This pathway was also ablated during this session. There were no complications and the patient remained asymptomatic during an 11-month follow-up.

Adult↗
PubMed1992

[Echography in gynecologic emergencies].

The authors report their experience with US in gynecologic emergencies through a retrospective study on 105 patients presenting with acute abdomen of suspected gynecologic nature. The series included 3 groups of patients: Group I: 59 patients all submitted to immediate surgery. The following pathologic conditions were observed: ectopic pregnancy (23 cases), torsion or hemorrhage from ovarian cysts (13 cases), pyosalpinx or tubo-ovarian abscess (9 cases), torsion of pedunculated uterine leiomyoma (7 cases), intraperitoneal bleeding from hemorrhagic corpus luteum (6 cases), hematocolpos and hematometra from imperforate hymen (3 cases). Two false positives, not included in this group, resulting from appendicular abscesses and misinterpreted as ovarian, were submitted to surgery in a gynecologic unit. Group II: 19 patients treated with medical therapy for the following conditions: torsion or hemorrhage from hyperstimulated ovary (10 cases), pyosalpinx or tubo-ovarian abscess (9 cases). Group III: 25 patients in whom neither US nor clinical examination revealed positive gynecologic findings. Both US and clinical follow-up were negative in these patients. The study was aimed at evaluating the role of US in identifying both lesion and peritoneal involvement, and in the diagnosis of nature. US proved a valuable tool in the first two diagnostic steps, allowing to confirm/dismiss active pathologic conditions, to indicate the medical/surgical treatment (immediate or delayed), to detect associated pathologies to study with further examinations. As for lesion nature, US alone proved poorly useful if not correlated with an accurate clinical history.

Abdomen, Acute↗
PubMed1991

Classical conditioning selectively increases AMPA receptor binding in rabbit hippocampus.

The NMDA and AMPA receptors have been shown to play critical roles in various forms of synaptic plasticity (learning and memory, long-term potentiation). The present study investigated the involvement of these two receptors in a well-characterized classical conditioning paradigm. Following classical conditioning of the rabbit nictitating membrane the binding properties of these two subclasses of excitatory amino acid transmitter receptors were analyzed in dorsal hippocampi by quantitative autoradiography. [3H] TCP and [3H] AMPA were used to identify the NMDA and AMPA receptors, respectively. The binding of [3H]TCP to the NMDA receptor remained unchanged in all the experimental groups tested. Paired presentations of the conditioned and unconditioned stimuli resulted in increased [3H] AMPA binding to the AMPA receptor in several subfields of the hippocampus, while unpaired presentations had no significant effects. The increase in binding was due to an increased affinity of the low-affinity component of the AMPA receptor. The results support the hypothesis that changes in glutamate receptors participate in the synaptic plasticity involved in certain forms of learning.

Animals↗
PubMed1991

The bradykinin receptor--a putative receptor-operated channel in PC12 cells: studies of neurotransmitter release and inositol phosphate accumulation.

Bradykinin (BK) induced [3H]norepinephrine [( 3H]NE) release and phosphatidylinositol turnover were investigated in PC12 cells. Induction of [3H]NE release by BK is mediated by activation of BK-B2-receptors, as determined using type specific BK receptor antagonists. BK induces [3H]NE release with a half maximal effective concentration of 30 +/- 0.5 nM, and reaches maximal net fractional release of 9.0 +/- 1% with 200 nM BK. The BK-induced release is Ca2+ dependent, reaching maximal release at 1.0 mM Ca2+, is pertussis toxin insensitive (1 microgram/ml), slightly increased by a dibutyryl cAMP (1 mM) and not affected by inhibitors of the cyclooxygenase or lipoxygenase pathways. Voltage-sensitive Ca2+ channel blockers, verapamil (10 microM), nifedipine (10 microM), and omega-conotoxin (CgTx 10 nM), do not block the BK-induced release. However, a considerable inhibitory effect was obtained by divalent cations Co2+ (ED50 = 0.2 mM) and Ni2+ (ED50(2)+ = 1 mM). These results indicate the involvement of a Ca2+ channel in the BK-mediated release which is different from the L- or N-type voltage sensitive calcium channels. Whereas [Ca2+]ex is essential for the BK-induction of catecholamine release, the rise in level of InsP's induced by BK in the presence or in the absence of [Ca2+]ex is similar up to concentration of 1 microM. This indicates that the rise in InsP's induced by BK is not sufficient to cause neurotransmitter release. Moreover, subsequent addition of Ca2+ to BK-stimulated cells in Ca(2+)-free medium yields no release. Hence, no activity triggered by BK alone could be further stimulated by Ca2+ for induction of release.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1991

Developmental myosin heavy chain progression in avian type IIB muscle fibres.

Myosin heavy chain species were investigated during development in avian pectoralis major muscles (type IIB fibres) by high resolution anion-exchange chromatography of the myosin head region, subfragment-1. At 15 days in ovo four distinct fast-type heavy chain species, I, II, III and IV, in order of elution, were identified. By 19 days in ovo, form IV had become predominant and remained the major species through 3-days post-hatch. This form has been named the peri-hatch form. Between 3 and 5 days post-hatch, a second massive change occurred such that by 5 days post-hatch a new species, V, apparent at 19 days in ovo in small amounts, dominated and at 8 days post-hatch was the only heavy chain species present. Form V, which corresponds to that previously identified as the post-hatch form, continued as the major species through 20 days post-hatch and was replaced slowly by the adult form. N-terminal sequencing of CNBr peptides from three subfragment-1 heavy chain species, the peri-hatch (form IV), the post-hatch (form V) and adult, revealed differences in amino acid sequence consistent with the three being products of different genes. These results confirm and extend recent reports of complexity in fast heavy chain expression prior to hatching in the chicken (Hofmann et al., 1988; Van Horn & Crow, 1989).

Amino Acid Sequence↗
PubMed1991

Methodological error and spatial variability of organ blood flow measurements using radiolabeled microspheres.

The quantitative analysis of the spatial variability of organ blood flow by means of radiolabeled microspheres (MS) requires that the methodological variability ("error") of the technique (RDmeth.) is known in each individual organ. Therefore, RDmeth. was quantified (eight to nine nuclides) in 6941 tissue samples from 13 organs of three anesthetized dogs, and the relative importance of errors originating from both the stochastic nature of MS distribution (RDtheo.) and the process of quantitation of MS radioactivity (RDcounting) was assessed under varying conditions (high/low specific MS activity (SAMS); inaccurate separation of gamma spectra; large sample size). At "minimized" methodological error (experiment 2), RDmeth. of samples trapping approximately 375 MS/nuclide was 5.8% and only slightly exceeded RDtheo. (5%). RDmeth. varied in the range 2.7-7.8% in individual organs and contributed little (3.5%) to the organs' observed spatial variability of flow. In contrast, RDmeth.--due to increased RDcounting--considerably exceeded RDtheo. when SAMS was low (experiment 3), overlap of two nuclides' main photopeaks was critical (experiment 1), or counting geometry was inappropriate (pulmonary tissue samples). At the same time, the contribution of RDmeth. to spatial flow variability rose to 7.9% (experiment 3), 26.9% (experiment 1), and 15-23% (lungs). Completely artifactual measurements, as indicated by an extremely high RDmeth. of sample flow, were rarely observed (less than 0.1%). In general, our data suggest that blood flow can be measured reproducibly and with low methodological error using up to 8 nuclides, RDmeth. does not essentially contribute to the observed spatial variability of organ blood flow, and, hence, organ flow variability may be accurately quantified using the MS technique. However, if sources of error as indicated above are present, the practice of using RDtheo. as a measure of RDmeth. (thereby neglecting RDcounting) may notably underestimate true MS error and result in an overestimation of spatial heterogeneity of organ blood flow. RDmeth., therefore, should be quantified separately in each region of interest prior to the onset of a new study.

Animals↗
PubMed1991

Decrease in soluble CD8 antigen levels in splenectomized patients as an index for reduced suppressor/cytotoxic cell activity.

To investigate the effect of splenectomy on lymphocyte subpopulations we monitored changes in serum concentrations of soluble suppressor/cytotoxic (sCD8) and soluble helper/inducer (sCD4) antigen in 11 splenectomized patients. Indications for splenectomy were hereditary spherocytosis in 2, idiopathic thrombocytopenic purpura in 2, gastric carcinoma in 4, Hodgkin's disease in 2 and pancreatitis in 1 patient. Lymphocyte subpopulations were also analyzed by means of conventional immunophenotyping with monoclonal antibodies to CD4 and CD8. We consistently found an early postoperative drop of sCD8 and sCD4 levels within the first week after splenectomy, paralleling changes in the percentages of CD4+ and CD8+ lymphocytes. While alterations of lymphocyte subsets in the peripheral blood were completely reversible and sCD4 levels returned to preoperative values, sCD8 concentrations remained suppressed even 3 months after splenectomy. SCD8 levels at the nadir and those 3 months after splenectomy were significantly lower than preoperative values (P = 0.003, P = 0.149 respectively). Since sCD8 levels reflect suppressor/cytotoxic cell activity, we suggest that suppressor cell activity is reduced in splenectomized patients.

Adult↗
PubMed1991

Effects of hyperthermia and/or hyperglycemia on pH and pO2 in well oxygenated xenotransplanted human sarcoma.

The heat-induced interdependent changes of tumor blood flow, pO2, and pH decisively influence the therapeutic effect of hyperthermia (HT). This fact has induced us to determine simultaneously the frequency distribution of local pO2 values and the intratumoral pH in a xenotransplanted human sarcoma cell line at a normal blood glucose level and under hyperglycemic conditions before, during, and after HT. Two groups, one of 10 and one of 9 congenitally athymic nude rats with a subcutaneously implanted S117 human sarcoma into the right hind paw (mean tumor volume 5.3 cm3) were treated with local waterbath HT (tumor temperature 43 degrees C, 1 hr) alone or in combination with i.p. glucose injections (6 g/kg, 2 hr before the onset of HT). Tumor oxygenation remained improved throughout HT. Tumor pH did not decrease during HT. Hyperglycemia alone elicited a decrease of intratumoral pH and pO2, probably mainly due to hemoconcentration. The additional warming of the tumors (43 degrees C) during hyperglycaemia did not further decrease pO2 and pH. Silver stained sections of the tumors showed only a few very small necrotic areas, even in tumors of volumes up to 8 cm3. Our results indicate a well oxygenated tumor. In contrast to most tumors studied so far, hyperthermia in this tumor induces not only an initial increase of oxygenation but a lasting elevation of mean tumor pO2 for the duration of HT (up to 60 min).

Animals↗
PubMed1991

Ethylene and a Wound Signal Modulate Local and Systemic Transcription of win2 Genes in Transgenic Potato Plants.

The transcriptional regulation of a win2-beta-glucuronidase gene fusion in transgenic potato (Solanum tuberosum) plants by wounding and ethylene has been analyzed. In common with other genes that are expressed in response to mechanical or chemical stress, win2 is transcribed at the site of injury and also in distant undamaged parts of the wounded plant. Similar kinetics of induction and patterns of transcription were observed in response to mechanical, wounding, elicitor, or arachidonic acid application. Experiments involving the use of chemicals that inhibited ethylene action, and those that increased ethylene production, showed that local induction of win2 transcription did not have an absolute requirement for ethylene, but ethylene was necessary for high levels of expression. In contrast, systemic expression of win2 required both a putative wound signal and ethylene. Ethylene alone had no direct effect on win2 gene expression in the absence of wounding.

Journal Article↗
PubMed1991

Isolated serum-free perfused rat kidneys release immunoreactive erythropoietin in response to hypoxia.

The renal glycoprotein hormone erythropoietin (Epo) interacts with erythrocytic progenitors to stimulate their proliferation and differentiation in the bone marrow. The renal O2-sensing mechanism in the control of the synthesis of Epo is still poorly understood. Therefore, the capacity of isolated rat kidneys to produce Epo during hypoxic and anemic perfusion was studied. The kidneys were perfused at a constant perfusion pressure of 100 mm Hg with a substrate-enriched Krebs-Henseleit solution containing 60 g/liter BSA and freshly drawn human erythrocytes. Epo was measured by RIA. When the kidneys were perfused at an arterial pO2 of 720 or 150 mm Hg (hematocrit, 5%), Epo production was very low (0.1-0.2 U/g kidney within 3 h of perfusion). When the arterial pO2 was lowered to 35 or 20 mm Hg, Epo production increased to 0.4 and 0.9 U/g kidney, respectively. The release of Epo during hypoxic perfusion (pO2 35 and 20 mm Hg) was little affected by changes in the hematocrit, i.e. the O2-carrying capacity of the perfusion medium over a wide range (0-40%). These results indicate that the production of Epo in the isolated perfused kidney depends on the availability of O2 and can be modulated by changes in the arterial pO2.

Anemia↗
PubMed1991

A local area network for medical research; planning, realization and experience.

This report focuses on the planning and realization of an interdisciplinary local area network (LAN) for medical research at the University of Heidelberg. After a detailed requirements analysis, several networks were evaluated by means of a test installation, and a cost-performance analysis was carried out. At present, the LAN connects 45 (IBM-compatible) PCs, several heterogeneous mainframes (IBM, DEC and Siemens) and provides access to the public X.25 network and to wide-area networks for research (EARN, BITNET). The network supports application software that is frequently needed in medical research (word processing, statistics, graphics, literature databases and services, etc.). Compliance with existing "official" (e.g., IEEE 802.3) and "de facto" standards (e.g., PostScript) was considered to be extremely important for the selection of both hardware and software. Customized programs were developed to improve access control, user interface and on-line help. Wide acceptance of the LAN was achieved through extensive education and maintenance facilities, e.g., teaching courses, customized manuals and a hotline service. Since requirements of clinical routine differ substantially from medical research needs, two separate networks (with a gateway in between) are proposed as a solution to optimally satisfy the users' demands.

Costs and Cost Analysis↗
PubMed1990

Divalent cations effectively replace Ca2+ and support bradykinin induced noradrenaline release.

Bradykinin (BK), a nonapeptide acting at the B2-type BK-receptor, and depolarization with high KCl (50 mM), induce catecholamine secretion in pheochromocytoma cells (PC-12). The mechanism underlying the BK-induced release, which is absolutely Ca2(+)-dependent, is not yet understood. Alkaline metals, barium (Ba2+), strontium (Sr2+) and other metal cations, manganese (Mn2+) or lanthanum (La3+), support BK-induced [3H]noradrenaline ([3H]NA) release. The extent of supporting transmitter release is dependent upon the specificity of the extracellular cation, with rank order potency of: Ba2+ greater than Sr2+ greater than Ca2+ greater than Mn2+La3+. The same rank order potency was observed for supporting both BK- and K(+)-induced release. [3H]NA release in the presence of Ba2+ or Sr2+ was much greater than in the presence of Ca2+, and unlike with Ca2+ was not saturable at the highest concentration measured. La3+ and Mn2+ were significantly less effective than Ca2+ at supporting release. These results strongly suggest that extracellular Ca2+ entry is essential for release, and that BK mediates release via a receptor-operated Ca2+ channel.

Adrenal Gland Neoplasms↗
PubMed1990

[The significance of the preoperative CEA value for the prognosis of rectal cancer].

254 patients were operated for rectal carcinoma in the period from 1980 to 1986. The number of curative procedures, recurrence rate and 5-year-survival rate were dependent on the preoperative CEA levels, which correlated with the tumour stage. Even within tumour stages with enough cases for statistical evaluation the CEA could be established as an independent prognostical variable. Within stage pT2N0M0 recurrence rate for patients with preoperative CEA level below 5 ng/ml was 29% compared to 64% in patients with higher serum levels. Median survival time for the two groups were 65 and 35 months, respectively. In stage of lymph node involvement median survival times of 46 and 25 months were observed for the groups with CEA levels above and below 5 ng/ml. The pattern of recurrence within the two stages seemed to be unaffected by the preoperative CEA level. Patients with preoperative elevated CEA represent a risk group with need of consistent postoperative follow-up and CEA controls.

Carcinoembryonic Antigen↗