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Biomedical subjects

P Koch

Publications and source records attributed to P Koch.

At least 127 records · Page 7Linked to original sources
PubMed1991

High-dose chemoradiotherapy supported by marrow infusions for advanced neuroblastoma: a Pediatric Oncology Group study.

We conducted a pilot protocol at seven Pediatric Oncology Group (POG) institutions to examine the feasibility, toxicity, and efficacy of using a common regimen of high-dose chemoradiotherapy (HD CT/RT) supported by autologous or allogeneic marrow infusions in children with metastatic neuroblastoma (NBL) in first or second remission. During a 57-month period, we accrued 101 patients. We report here results for the 81 who completed treatment at least 2 years ago. The HD CT/RT regimen consisted of melphalan 60 mg/m2/d for three doses, and total body irradiation (TBI) either 1.5 Gy (n = 27) or 2.0 Gy (n = 54) twice daily for six doses. Twenty-three patients also received irradiation consisting of 1.2 Gy twice daily for 10 doses to persisting disease sites. Seventy-four were given autologous and seven allogeneic marrow, 64 autologous marrows being purged immunomagnetically. Fifty-four children were in first complete (CR) or partial (PR) remission and 27 in second CR or PR. As of October 1, 1990, follow-up was from 32 to 72 months. Forty-seven of these 81 children relapsed, 10 died of complications, one of unknown cause, and 23 continue in remission, including 21 of the 54 treated in first remission, and 16 who completed treatment more than 3 years ago. The 2-year actuarial event-free survival (EFS) probabilities are first CR (CR1) 32% (SE 10%), first PR (PR1) 43% (SE 9%), second CR (CR2) 33% (SE 27%), and second PR (PR2) 5% (SE 5%). Probability of EFS correlated with remission number (first better than second, P less than .001), with interval from diagnosis to HD CT/RT (greater than 9 months better than less than 9 months, P = .055), and with TBI dose (12 Gy better than 9 Gy, P = .031). These encouraging results may partly reflect selection for this treatment of patients with NBL who have a slower disease pace.

Adolescent↗
PubMed1991

Value of sonography in monitoring the therapeutic response of mediastinal lymphoma: comparison with chest radiography and CT.

The aim of this retrospective study was to assess the diagnostic value of mediastinal sonography, compared with that of chest radiographs and CT, in the follow-up of patients with mediastinal lymphomas and in the prediction of clinical outcome. The sonograms, chest radiographs, and CT scans of 40 consecutive patients with Hodgkin (n = 29) and non-Hodgkin (n = 11) lymphoma obtained before and after completion of therapy were analyzed blindly and independently by three radiologists and compared with clinical outcome. Nine patients were treated with radiotherapy, 12 with chemotherapy, and 19 with combined therapy. Therapeutic response was assessed from all available clinical and biochemical findings as well as from the combined results of all imaging studies performed on further follow-up. The sonograms showed obvious changes in the size and echogenicity of the mediastinal lymphomas that corresponded closely with the response to therapy. Sonography showed complete regression of the lymphomas in 30 patients who had complete remission. In five patients with incomplete remission, sonographic diagnoses were correct. All lymph nodes, irrespective of size, detected with sonography after a phase of complete remission indicated recurrence (five patients). Sonographic findings corresponded with those of CT in 25 (81%) of 31 cases. Clinical outcome suggested that the sonographic findings were more reliable in the five cases in which CT and sonographic findings conflicted. Chest radiographs were inadequate for monitoring the response of mediastinal lymphomas to therapy; in 17 (43%) of 40 cases, a false impression was obtained of the extent and therapeutic response of mediastinal lymphomas. The results of this study indicate that sonography is clearly superior to chest radiographs and comparable to CT for monitoring patients with mediastinal lymphomas.

Adolescent↗
PubMed1990

Treatment of refractory Hodgkin's disease with high-dose cytosine arabinoside and mitoxantrone in combination. Results of a clinical phase II study of the German Hodgkin Study Group.

In the present study, the activity and side effects of high-dose cytosine arabinoside (HD-Ara-C) in combination with mitoxantrone (mitox) (HAM) was evaluated in 32 heavily pretreated patients with refractory Hodgkin's disease. Therapy consisted of HD-Ara-C 3 g/m2 every 12 hours days 1 and 2 and mitox 10 mg/m2/d days 3 to 5. In subsequent steps, HD-Ara-C was escalated to six and eight doses for 3 and 4 days, respectively, and mitox to four doses on days 2 to 5. Thirty-two patients 17 to 55 years of age entered the study. Twenty-five cases presented with extranodal disease and disseminated organ involvement and 21 revealed systemic (B) symptoms. Eighteen patients (56%) responded with five complete and 13 partial remissions, ten patients (31%) had refractory disease, and four patients died from infections during treatment-induced cytopenia. The predominant toxicity was severe myelosuppression in all patients with major infections occurring during 55% of treatment courses. Ten of the responding 18 patients underwent subsequent autologous (n = 9) or allogeneic bone marrow transplant (BMT). Seven of these cases are currently alive at 5+ to 22+ months, six of them without evidence of disease. Among the remaining eight patients not receiving BMT, three are alive at 6+ to 19+ months from the initiation of HAM, two of them in ongoing remissions of 2+ and 5+ months' duration. Two patients died from transplant-related complications and six patients succumbed to progressive disease following relapse. The median survival for all treated patients is 6.2 months. These data indicate that HAM has a significant activity in refractory Hodgkin's disease. However, the substantial side effects and the lack of an obvious superiority to alternative, less intensive regimens limits the further application of the two-drug combination in its present form. Modifications in timing and dosage and the addition of hematopoietic growth factors will be evaluated in subsequent trials.

Adolescent↗
PubMed1990

Treatment of relapsed acute lymphocytic leukemia in adults.

Thirty-three patients with ALL/AUL in first relapse were treated with an induction of prednisone, vindesine, daunorubicin, Erwinia asparaginase, i.t. MTX (phase I), high-dose cytarabine, and etoposide (phase II). Twenty-one (64%) achieved a complete remission, one a partial remission. Side effects of induction-phase I were predominantly hematological with subsequent infections and gastrointestinal toxicity. In phase II some patients had additional cutaneous, ocular, and hepatic toxicity. The treatment efficiently induced remissions with tolerable toxicity in relapsed ALL. The disease-free survival, however, needs to be improved.

Adolescent↗
PubMed1990

An approach to differentiate between noradrenaline-elicited contractile processes in the rat isolated aorta.

The aim of the present study was to assess the different processes contributing to the contraction induced by noradrenaline (NA, 1 mumol/l) in the rat isolated aorta. Pretreatment with maximally effective concentrations of nifedipine or cromakalim reduced the NA-induced contraction to 80 +/- 3.5% or 63 +/- 2.0%, respectively, without alteration of the shape of the response. After pretreatment with Mn2+, NA caused a transient phasic contraction followed by a sustained tonic component, comparable to the response obtained in "Ca2(+)-free" medium. Ryanodine--in the presence of extracellular Ca2(+)-caused a slight increase in resting tension, but did not modify the NA-induced contraction. In "Ca2(+)-free" medium the contraction elicited by NA consisted of a transient phasic and a sustained tonic component. The amplitude of the phasic contraction decreased exponentially with the time of exposure to "Ca2(+)-free" medium. The phasic component was identified as elicited by Ca2+ released from the sarcoplasmic reticulum (SR) by means of ryanodine. If Ca2+ depleted tissues (80 min in "Ca2(+)-free" solution) were exposed to Ca2+ in the presence of Mn2+ or cromakalim, the NA-induced phasic response was inhibited, suggesting that Mn2+ and cromakalim blocked the refilling of the store. It can be concluded that activation of alpha 1-adrenoceptors in the rat aorta by NA elicits Ca2(+)-entry processes which have a different sensitivity to nifedipine, cromakalim and Mn2+. The Ca2+ released from SR contributes about 20% to the overall contractile response. Our data suggest that the depleted SR can be refilled from the extracellular space via a direct cromakalim- and Mn2(+)-sensitive pathway.

Animals↗
PubMed1990

Uncertainties in pharmacokinetic modeling for perchloroethylene. I. Comparison of model structure, parameters, and predictions for low-dose metabolism rates for models derived by different authors.

In recent years physiologically based pharmacokinetic models have come to play an increasingly important role in risk assessment for carcinogens. The hope is that they can help open the black box between external exposure and carcinogenic effects to experimental observations, and improve both high-dose to low-dose and interspecies projections of risk. However, to date, there have been only relatively preliminary efforts to assess the uncertainties in current modeling results. In this paper we compare the physiologically based pharmacokinetic models (and model predictions of risk-related overall metabolism) that have been produced by seven different sets of authors for perchloroethylene (tetrachloroethylene). The most striking conclusion from the data is that most of the differences in risk-related model predictions are attributable to the choice of the data sets used for calibrating the metabolic parameters. Second, it is clear that the bottom-line differences among the model predictions are appreciable. Overall, the ratios of low-dose human to bioassay rodent metabolism spanned a 30-fold range for the six available human/rat comparisons, and the seven predicted ratios of low-dose human to bioassay mouse metabolism spanned a 13-fold range. (The greater range for the rat/human comparison is attributable to a structural assumption by one author group of competing linear and saturable pathways, and their conclusion that the dangerous saturable pathway constitutes a minor fraction of metabolism in rats.) It is clear that there are a number of opportunities for modelers to make different choices of model structure, interpretive assumptions, and calibrating data in the process of constructing pharmacokinetic models for use in estimating "delivered" or "biologically effective" dose for carcinogenesis risk assessments. We believe that in presenting the results of such modeling studies, it is important for researchers to explore the results of alternative, reasonably likely approaches for interpreting the available data--and either show that any conclusions they make are relatively insensitive to particular interpretive choices, or to acknowledge the differences in conclusions that would result from plausible alternative views of the world.

Animals↗
PubMed1990

A continuum model of activity waves in layered neuronal networks: a neuropsychology of brainstem seizures.

We model and brainstem as two layers of respectively purely excitatory and purely inhibitory cells, with instantaneous synaptic interactions within a layer, but with a variable time delay between the layers. For appropriate values of the connection parameters, this configuration provides an attentional mechanism. As the inhibitory delay increases, input signals are, at first, increasingly amplified and confined spatially. At larger delays, the amplified activity propagates into other regions allowing for spatial summation. The temporal frequency of the amplified activity decreases with increasing delay, but its spatial frequency remains relatively constant. As the delay increases through a critical region, a new regime is reached in which highly amplified activity occurs simultaneously over large areas. This regime exhibits many properties of seizure activity.

Brain Stem↗
PubMed1990

[Femoral fractures following total hip prosthesis].

Fractures of the ipsilateral femur after hip arthroplasty are a serious problem. In most cases, minimal trauma is responsible for the fracture. Predisposing factors, such as severe osteoporosis, loosening of the stem of the prosthesis, or cortex perforations, are often found. Such fractures occurred between 1979 and 1989 in 30 patients, i.e. 2.3% of our patients who had received primary prosthesis and 2.9% of those who had undergone revision. The patients' ages at the time of fracture ranged from 41 to 88 years (mean 63 years), 33% of the patients in these group being female. The time lapse from implantation of the prosthesis to the fracture varied between 1 month and 11 years (mean 4.4 years). The fracture was at the level of the proximal trochanteric region in 3% of these patients, between the trochanteric line and the tip of the prosthesis in 20%, and below the tip of the prosthesis in 70%. Operative treatment was performed in 29 patients. Fractures were fixed with a compression plate in 19 (63%), and in 3 the plate fixation was reinforced with intramedullary cement. In 2 osteoporotic patients with supracondylar fractures the osteosynthesis ruptured and a successful revision operation with cement was performed. In 3 others internal fixation was combined with replacement of the prosthesis; 3 patients received a Wagner revision prosthesis and 1 a long-stem Protek tumor prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Treatment of low-grade non-Hodgkin's lymphoma by cytoreductive chemotherapy with prednimustine/mitoxantrone followed by interferon alpha-2b maintenance: results of a clinical phase II study.

In a clinical phase II study, the antitumor activity of the recently introduced combination of prednimustine and mitoxantrone (PmM) was evaluated in 17 patients with advanced low-grade non-Hodgkin's lymphoma after failure with or relapse after standard chemotherapy. The PmM regimen consisted of prednimustine 100 mg/m2/d orally on days 1 to 5, and mitoxantrone 8 mg/m2/d intravenously on days 1 and 2, giving a total dose of 16 mg/m2. Treatment was repeated every 4 to 6 weeks to a maximum of 6 cycles. Patients achieving complete remission (CR) or partial remission (PR) received two additional courses for consolidation, followed by interferon (IFN) alpha-2b 5 x 10(6) U subcutaneously three times a week until progression or relapse. Twelve of the 17 patients (71%) responded (CR, 4 and PR, 8). Side effects consisted mainly of neutropenia, which required dose reduction in 48% of treatment cycles. All 12 responders subsequently received IFN alpha-2b maintenance treatment. At present, remission duration ranges from 4.5+ to 17.5+ months (median 14.5 months). In comparison to unmaintained first remission prior to receiving PmM/IFN alpha-2b, a clear tendency towards a longer period of freedom from progression emerged in the 12 patients receiving IFN alpha-2b maintenance treatment during a second PR or CR. These data indicate a high antitumor activity of PmM in low-grade non-Hodgkin's lymphoma and suggest a beneficial effect of IFN alpha-2b maintenance. Present findings, however, will require confirmation in future investigations.

Adult↗
PubMed1990

Transporting bone marrow for in vitro purging before autologous reinfusion.

We describe the procedures employed for transporting bone marrow to and from a central facility. Marrow has been harvested from 80 patients with neuroblastoma, at 16 centers which are geographically dispersed throughout North America. Marrow from the outside transplant centers was packed on wet ice or cold packs in insulated containers, and transported by commercial carriers or chartered aircraft to the central processing laboratory. Post processed marrows were frozen in liquid nitrogen and returned by commercial carrier to the referring institution. In comparing transported with non-transported but similarly treated marrows, no differences were found in any of the following parameters: (1) CFU-GM recovery, (2) fraction viable cells at thawing, or (3) time to engraftment in patients. We conclude the transportation of harvested marrows to a central purging facility is safe. Based on this experience, we propose a set of standards, which, if adhered to, will insure the continued safe processing, shipping, and storage of bone marrow in all centers so engaged.

Bone Marrow Transplantation↗
PubMed1989

R 56865 differentiates between contractile agents with respect to the nifedipine-sensitive component in the isolated rat aorta.

The interaction of the benzothiazolamine R 56865 with the nifedipine-sensitive component of the serotonin (5-HT)-, angiotensin II (AII)- and arginine-vasopressin (AVP)-induced contractions was studied in the isolated rat aorta. Nifedipine caused concentration-dependently (10(-9)-10(-6) mol/l) a slight rightward shift accompanied by a limited depression of the maximum of the concentration-response curves for 5-HT-, AII- and AVP-induced contractions. R 56865 (10(-5) mol/l) antagonized the contraction elicited by 5-HT and AII in a similar manner as nifedipine. The effect of R 56865 on 5-HT- and AII-induced contractions was no longer observed after pretreatment with nifedipine. The AVP-induced contraction was not affected by R 56865 (10(-5) mol/l). As shown previously, R 56865 is a weak inhibitor of potential-operated channels but inactive on Ca2+ channels activated by NA. In conclusion, R 56865 does not only differentiate between depolarization and receptor-stimulation, but also between the activation of Ca2+ channels by different types of receptors. We propose that R 56865 may interact with Ca2+ channels at a site which plays a role in their activation.

Angiotensin II↗
PubMed1989

Effect of calmodulin antagonists on contraction and 45Ca movements in rat aorta.

To study the selectivity of calmodulin antagonists it was assumed that they should inhibit noradrenaline (NA)- and K(+)-induced contractions similarly without an accompanying inhibition of 45Ca uptake. Therefore, in isolated rat aorta the effects of W-7, calmidazolium and trifluoperazine on contraction and 45Ca uptake elicited by K+ and NA were investigated. Calmidazolium (10(-5)-10(-4) mol/l) elicited an incomplete inhibiton of K(+)- and NA-induced contraction and 45Ca uptake. Trifluoperazine inhibited the NA-induced contractions at lower concentrations (10(-8)-10(-6) mol/l) than the K(+)-induced contraction (10(-6)-10(-4) mol/l). The K(+)- and NA-induced 45Ca uptake was blocked by trifluoperazine (10(-5) mol/l). W-7 (10(-5)-10(-4) mol/l) inhibited the K(+)- and NA-induced contraction, however, in the same concentration range W-7 diminished the K(+)- and NA-induced 45Ca uptake. In conclusion, the results indicate that calmidazolium and trifluoperazine are hardly useful as calmodulin antagonists because of their additional properties, whereas W-7 seems to be the least unspecific of the calmodulin antagonists studies.

Animals↗
PubMed1989

Biological fate of sirdalud in animals and man.

1. Biotransformation and excretion of the muscle relaxant drug, sirdalud, were studied after oral doses of 14C- and 3H-sirdalud in rats, dogs, rabbits, mice and humans. Sirdalud was well absorbed and almost completely metabolized in the five species. 2. Excretion of metabolites was rapid and complete within a few days; the urine/faeces excretion ratio of the 14C label was about 70/30 in all species. Major metabolic pathways of sirdalud were oxidative degradation of the imidazoline ring and oxidation of the aromatic system. 3. A novel oxidative biotransformation pathway of the benzothiadiazole ring system of sirdalud gave a sulphone analogue of the parent drug.

Administration, Oral↗