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Biomedical subjects

C Konrad

Publications and source records attributed to C Konrad.

45 records · Page 3Linked to original sources
PubMed1993

[The value of Doppler imaging of the aorta, carotid artery and middle cerebral artery in obstetric diagnostics].

The relation of blood blow in the fetal aorta and carotis is a marker for the well being of the unborn child. Increase of cerebral vascularity associated with decrease of blood flow in the aorta is a sign for a fetal risk situation. It is, however, of disadvantage that the fetal carotis is often difficult to image with an wedge-shaped angle between doppler beam and vessel. We therefore included screening of an intracerebral vessel (a. cerebri media) in order to find out whether examination of this vessel, much more easier to perform, may have a similar diagnostic value or be an even more sensitive prognosticator of fetal risk than the carotis. In two hundred and forty patients in the 29th to 40th week of gestation all these three vessels were scanned with the duplex system AI 3200, Dornier company, Germany. The result was correlated to sonographic biometry, birth weight, and mode of delivery. It could be proven that when analyzing individual findings, pathology in the risk groups is much higher, whereas mean values showed less marked differences between risk and control groups. Our results suggest that the a. cerebri media is a slightly more sensitive indicator of fetal risk, since in this vessel retrograde resistance can be detected earlier and is more evident. A combination between assessment of the aorta and a cerebral vessel, is however, the method of choice in cases of pathological findings in diagnosis of fetal well being, since only examination of a peripheral and a central vessel results in an exact diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1991

Anti-CD3-enhanced interleukin-2 immunotherapy of pulmonary metastases.

UNLABELLED: A newly developed monoclonal rat IgG 2b antibody which in vitro can activate both helper and cytolytic T-lymphocytes by binding to the CD3 epsilon subunit of the T-cell receptor complex was tested alone and in combination with Interleukin-2, a growth factor for activated T-cells, for ability to reduce established pulmonary metastases in a murine model. C57BL/6 mice injected iv with a tumor cell suspension of a weakly immunogenic fibrosarcoma, MCA106, were randomly assigned to 1 of 15 treatment groups for intraperitoneal injections with YCD3 (0, 0.1, 1, 10, or 100 micrograms) on Days 3, 5, 7, 10, 12, 17, and 19 or with IL-2 (0, 1000, or 50,000 units bid) on Days 3 through 7, 10 through 12, and 17 through 19. On Day 21 all mice were sacrificed for enumeration of metastases. Pooled splenocytes of three randomly selected mice from each group were assayed for surface expressions of T-cell markers Thy-1, Ly2, and L3T4. RESULTS: High-dose IL-2 (50,000 units bid) in combination with low-dose YCD3 (1 microgram) reduced metastases 60% (P less than 0.005). YCD3 or IL-2 alone was ineffective. Combined high-dose IL-2 (50,000 units) and high-dose YCD3 (100 micrograms) resulted in 100% mortality. Phenotypically, YCD3 induced a dose-dependent depletion of T-cells from 25 to 2.4% (0.1 to 100 micrograms, respectively). These results suggest potential clinical applicability of low-dose anti-CD3 monoclonal antibody to enhance antitumor efficacy of high-dose IL-2. However, the toxicity of high-dose anti-CD3 and high-dose IL-2 cautions for care in selection of dose.

Animals↗
PubMed1990

Tamoxifen potentiates in vivo antitumor activity of interleukin-2.

Tamoxifen, an antiestrogen with efficacy in treatment of both estrogen receptor-positive and negative breast tumors, may be immunomodulatory. We tested tamoxifen's ability to augment the antitumor activity of interleukin-2 (IL-2), a lymphokine capable of expanding and activating lymphocytes, in the treatment of established pulmonary metastases of the weakly immunogenic murine fibrosarcoma MCA-106. Age-matched C57BL/6 female mice bearing pulmonary metastases induced by a tail vein injection of MCA-106 tumor suspension (5 x 10(5) cells/mouse) were treated from days 3 through 12 with intraperitoneal saline solution or IL-2 (50,000 units twice a day). Half of the mice in each group received plain and the remainder received tamoxifen-treated (2 units/ml) drinking water ad libitum for the duration of the experiment. All mice were killed on day 18 for enumeration of pulmonary metastases. Compared with saline-treated control mice, IL-2 and tamoxifen reduced metastases by 66% (p less than 0.0002) and 30% (p less than 0.005), respectively. IL-2 and tamoxifen combined reduced metastases 95% (p less than 0.0002), significantly better than did IL-2 (p less than 0.02) or tamoxifen (p less than 0.0003) alone. In vitro, tamoxifen inhibited proliferation of the weakly estrogen receptor-positive MCA-106 tumor by approximately 30%. Tamoxifen had no effect on the generation of 3-day IL-2-activated lymphocyte cytotoxicity against both natural killer-sensitive (YAC) and natural killer-resistant (MCA-106) target cells. Both YAC and MCA-106 tumor became more resistant to lysis with increased concentration of tamoxifen. This is the first demonstration of in vivo potentiation of IL-2 antitumor activity by tamoxifen and suggests its possible use clinically.

Animals↗
PubMed1978

Solubilization of a mammalian beta-adrenergic receptor.

Binding sites for iodohydroxybenzylpindolol with characteristics of a beta2-adrenergic receptor have been identified in a crude membrane fraction from guinea-pig lung. The binding sites could be solubilized by treatment of the membrane fraction with digitonin. Upon solubilization receptors retain their beta2-adrenergic type as indicated by the rank order of potencies of agonists in binding-inhibition experiments. The solubilized receptors demonstrate a marked increase in affinity for agonists compared with particulate receptors whereas antagonist affinity remains unchanged. Solubilized receptors are insensitive to divalent cations (Mg2+, Mn2+, Ca 2+) which increase the potency of agonists for particulate receptors. The effects of Mg2+ can be reversed by Gpp(NH)p in particulate preparations; Gpp(NH)p is ineffective for the solubilized preparation. These experiments establish that beta-adrenergic receptors can be solubilized even from crude mammalian membrane preparations. They also show that the mammalian beta-adrenergic receptor in situ is under constraints with respect to agonist affinity and is modulated by divalent cations and guanyl nucleotides in the intact membrane.

Adenylyl Cyclases↗
PubMed1976

Beta-adrenergic receptors in guinea-pig myocardial tissue.

Stereospecific binding sites for (-) [3H]-alprenolol, a beta-adrenergic antagonist, have been identified in guinea-pig myocardial broken cell preparations. The concentration of the sites was 0.3 pmoles per mg of protein and the dissociation constant (at 37 degrees C) 10(-8) M. A close correlation between the ability of various beta-adrenergic antagonists to compete with tracer alprenolol binding and to block the response of isoprenaline-stimulated myocardial adenylate cyclase has been found. Low affinity sites for the labelled beta-adrenergic antagonist in contrast to stereospecific sites are heat stable and do not discriminate between the (-) and the (+) forms of the beta-adrenergic antagonists. Adenylate cyclase in guinea-pig myocardial tissue is poorly stimulated by isoprenaline or 5'-guanylylimidodiphosphate. This is attributed to a high basal activity which could be lowered by a preincubation at 37 degrees C.

Adenylyl Cyclases↗
PubMedDate not supplied

Generating a learning curve for pediatric caudal epidural blocks: an empirical evaluation of technical skills in novice and experienced anesthetists.

BACKGROUND AND OBJECTIVES: Learning curves for anesthesia procedures in adult patients have been determined, but no data are available on procedures in pediatric anesthesia. The aim of this study was to assess the number of caudal blocks needed to guarantee a high success rate in performing caudal epidural analgesia in children. METHODS: At a teaching hospital, the technical skills of 7 residents in anesthesiology who performed caudal blocks were evaluated during 4 months using a standardized self-evaluation questionnaire. At the start of the study period, the residents had no prior experience in pediatric anesthesia or in performing caudal epidural blocks. All residents entered the pediatric rotation after a minimum of 1 year of training in adult general and regional anesthesia. The blocks were rated using a binary score. For comparison, the success rates of 8 experienced staff anesthesiologists were collected during the same period using the same self-evaluation questionnaire. Statistical analyses were performed by generating individual and institutional learning curves using the pooled data. The learning curves were calculated with the aid of a least-square fit model and 95% confidence intervals were estimated by a Monte Carlo procedure with a bootstrap technique. RESULTS: The success rate of residents was 80% after 32 procedures (95% confidence interval of 0.59 to 1.00). The pooled success rate of the staff anesthesiologists was 0.73 (mean) with a standard deviation of 0.45, which was not statistically different from the success rate of the residents. CONCLUSION: High success rates in performing caudal anesthesia in pediatric patients can be acquired after a limited number of cases. Success rates of residents learning this procedure are comparable to the results of staff anesthesiologists.

Anesthesia, Caudal↗