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Biomedical subjects

D Koch

Publications and source records attributed to D Koch.

At least 55 records · Page 3Linked to original sources
PubMed1995

Relative elemental sensitivity factors in non-resonant laser-SNMS.

Using a reflectron time-of-flight mass spectrometer, the ionization process in non-resonant Laser postionization Secondary Neutral Mass Spectrometry (SNMS) has been investigated. In particular, the postionization efficiencies (PIE) achieved by multi photon and single photon absorption have been compared by ionizing ten elements sputtered from a NIST standard reference material by excimer laser radiation of 248 nm, 193 nm and 157 nm. Only in the case of single photon ionization (SPI) the measured laser intensity dependence of the PIE can be understood quantitatively in terms of corresponding theory. From the results, absolute values of the SPI cross sections have been evaluated for atoms of nine elements, which show a total variation over about two orders of magnitude. Furthermore, even in the regime of high laser intensity, where the ionization of all atoms is completely saturated, different elements have been detected with relative sensitivity factors which scatter over about one order of magnitude. This has been attributed to element dependent variations of the effective ionization volume which are caused by the different kinetic energy and angular distributions of different sputtered atoms.

Journal Article↗
PubMed1995

Structure-activity relationships in allergic contact dermatitis (I). Studies on the influence of side-chain length with derivatives of primin.

Primin (2-methoxy-6-pentyl-1,4-benzoquinone) is a naturally-occurring strong sensitizer from Primula obconica (Primulacease). To determine the effect of side-chain length on sensitizing potency, 15 analogues with linear side chains from C1 to C15 and 4 C6-analogues with branched side chains were prepared synthetically and devoted to experimental sensitization in guinea pigs. The results showed an increase of the sensitizing capacity with increasing length of the alkyl side chain from C1 to C10, reaching a maximum at C11 and C12. On further elongation, the sensitizing potency decreased beyond C13, reaching values which finally were as low as those of the C1 and C3 derivatives. The results mirror findings which formerly have been obtained with other non-quinonoid compounds like catechols, phenols, hydroquinones and gallates. In the plant kingdom, compounds approximating an "ideal allergen" consisting of a quinonoid ring with a 10 or 11 carbon-membered side chain have been identified only once: 2,3-dimethoxy-geranyl-1,4-benzoquinone, a remarkably strong sensitizer found in Wigandia caracasana (Hydrophyllaceae).

Animals↗
PubMed1994

Factors associated with the development of persistently depressed cardiac output during the first year after cardiac transplantation.

The purpose of this study was to determine factors associated with the development of a persistently depressed cardiac output during the first year after cardiac transplantation. With this aim in mind, the records of 133 consecutive patients undergoing orthotopic cardiac transplantation and surviving for > or = 1 year after transplantation were reviewed. For each patient, the mean cardiac index for each of the 3-month periods, 0-3, 4-6, 7-9, and 10-12 months after transplantation was calculated. Of the 133 patients, 19 (14%) had a mean cardiac index < 2.4 l/min/m2 during > or = 3 of these 3-month periods. The pre- and post-transplantation clinical, immunologic, and hemodynamic data of these 19 patients (study group) were compared with the remaining 114 patients (control group). Compared with the control group, the patients in the study group were older (56 +/- 5 vs. 46 +/- 15 years; p = 0.0001), more frequently had ischemic heart disease as the original diagnosis (58 vs. 37%; p < 0.05), had a lower preoperative cardiac index (1.91 +/- 0.53 vs. 2.71 +/- 1.0 l/min/m2; p = 0.0001), more frequently did not receive perioperative anti-T cell therapy (47 vs. 25%; p = 0.046), and had a greater median number of infections during the first year after transplantation (5 vs. 3; p = 0.027). However, only one factor--a low preoperative cardiac index--emerged as an independent predictor of the development of a persistently depressed cardiac index during the first year after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Phase I study of streptozocin- and carmustine-sequenced administration in patients with advanced cancer.

BACKGROUND: Fewer than 20% of patients with nonhematologic malignancies treated with chloroethylnitrosoureas (CENUs) respond, but streptozocin (STZ), which depletes O6-methylguanine-DNA-methyltransferase (MGMT), has been shown to reverse resistance to CENUs in vitro. PURPOSE: The purpose of this phase I study was to determine (a) the maximum tolerated dose (MTD) of carmustine (BCNU), a CENU, plus a fixed dose of STZ; (b) the toxic effects of the drugs; and (c) the effects on peripheral blood mononuclear cells (PBMC). METHODS: A clinical phase I study of STZ followed by BCNU was designed to simulate conditions that produce maximal sensitization of CENU-resistant HT-29 cells in vitro. Patients received a 20-minute infusion of the MTD of STZ (2 g/m2) followed 1 hour later with a 60-minute infusion of BCNU (100, 125, 137.5, or 150 mg/m2). Treatment was repeated after 6 weeks. Twenty-four patients with advanced malignancies received 32 courses of therapy (range, 1-2 courses). RESULTS: The MTD of BCNU was 125 mg/m2. The dose-limiting toxic effect was thrombocytopenia occurring about 22 days after treatment, with recovery between days 28 and 35. Transient hypophosphatemia and proteinuria were common, and serum creatinine was elevated in 9% of the courses. Two patients who received therapy died--one due to pulmonary toxic effects and one due to hepatic toxic effects. Two patients with previously untreated carcinoid achieved partial response. In three patients, MGMT levels in PBMC were more than 85% depleted after STZ administration and more than 90% depleted after BCNU infusion. CONCLUSIONS: These results show that the magnitude of MGMT depletion by STZ in PBMC is in the range necessary to produce sensitivity to CENUs in resistant cell lines but also that, when BCNU is combined with STZ, the MTD of BCNU is about 50% that of BCNU as a single agent and that platelet count suppression occurs earlier. IMPLICATIONS: We plan to conduct phase II studies of STZ plus BCNU in tumor types with low response to CENUs. One of the major goals will be to demonstrate that depletion of MGMT is greater in tumor cells than in normal cells.

Adult↗
PubMed1992

CT-guided chemical rhizotomy of the C1 root for occipital neuralgia.

Sensation in the parasagittal occipital region is usually provided by fibres from the second cervical root via the greater occipital nerve. In the case presented occipital neuralgia could be relieved only by coagulation of the C1 nerve root with 96% ethyl alcohol. Possible explanations for this observation are discussed and a technique for CT-guided treatment is described.

Cervical Atlas↗
PubMed1992

Effect of atrial natriuretic hormone on metoclopramide-induced stimulation of aldosterone.

The effect of atrial natriuretic hormone (ANH) on metoclopramide-induced stimulation of aldosterone was studied in eight healthy young men after 3 days of controlled diet (150 mEq sodium, 100 mEq potassium). Baseline values were obtained after subjects had remained sitting for 1 hour. Subjects then received 2-hour infusions of placebo, dopamine (2 micrograms/kg/min), ANH (0.6 pmol/kg/min), and ANH plus dopamine. One hour after the beginning of each infusion, a 10 mg intravenous bolus of metoclopramide was given. Prolactin levels increased 10-fold after metoclopramide with placebo infusion, and about 50% of this stimulation was abolished by preinfusion with dopamine. ANH preinfusion did not suppress prolactin release. Urinary sodium excretion increased prominently during dopamine infusion. ANH at this dose had no effect on natriuresis. The dopamine dose given had almost no effect on metoclopramide-induced aldosterone secretion, whereas ANH infusions, which resulted in approximate doubling of plasma ANH levels, suppressed aldosterone. This study supports a role of ANH in aldosterone regulation, even at nonnatriuretic doses, and suggests that ANH is acting not only through the renin-angiotensin system but under certain conditions has significant physiologic action directly on glomerulosa cells.

Adrenocorticotropic Hormone↗
PubMed1991

A phase I trial of high-dose diaziquone and autologous bone marrow transplantation: an Illinois Cancer Council study.

Diaziquone (AZQ), a synthetic quinone with demonstrated activity against acute nonlymphocytic leukemia (ANLL), primary CNS tumors, and non-Hodgkin's lymphoma (NHL), is virtually devoid of nonhematopoietic toxicity at conventional doses. As a prelude to its inclusion into bone marrow transplant (BMT) preparative regimens, a phase I study of high-dose AZQ with autologous BMT (ABMT) was performed. Patients with refractory solid tumors and lymphomas were treated with a single 24-hour infusion of AZQ at 50 to 355 mg/m2 in dose escalations of 20%. Fifty-six patients received 69 courses. Those receiving greater than 60 mg/m2 had nadir granulocyte and platelet counts less than 500/microL and 20,000/microL, respectively. Nausea, vomiting, stomatitis, and diarrhea were mild, transient, and not dose-related. Transient minimal elevations of liver function tests were seen in five patients and were also not dose-related. The maximally tolerated dose (MTD) of high-dose AZQ was found to be 245 mg/m2, with nephrotoxicity being dose-limiting. Significant azotemia was seen in four of 12 patients treated at 295 and 355 mg/m2, including fatal anuric renal failure in three of these patients. Reversible proteinuria also occurred in 24 of 26 courses above 150 mg/m2, including nephrotic range proteinuria in eight courses, all at doses of 205 to 355 mg/m2. The proteinuria was also associated with multiple proximal tubular defects including generalized aminoaciduria and proximal renal tubular acidosis. There were six early deaths including two of early renal failure (295 and 355 mg/m2), two of sepsis (205 and 245 mg/m2), one of a pulmonary embolus (85 mg/m2), and one of progressive disease (60 mg/m2). Of 50 patients who were assessable for response, there were seven responses including two of 10 with primary CNS tumors, one of 12 with malignant melanoma, one of five with non-small-cell lung carcinoma, two of two with breast carcinoma, and one of one with ovarian carcinoma. Because of its activity in ANLL and NHL and its unique toxicity spectrum, high-dose AZQ may improve the efficacy of current BMT preparative regimens without significantly increasing their nonhematopoietic toxicity.

Adolescent↗
PubMed1989

Differential effects of congenital left and right brain injury on intelligence.

IQ performance was compared in 28 prepubertal children with unilateral left vs. right hemisphere preperinatal injury. Results indicated statistically superior FSIQ and VIQ in the left-lesioned group. Findings were interpreted as consistent with the hypothesis of a left-right maturational gradient, whereby early right hemisphere damage has a more severe effect on overall intellectual functioning than early left injury. Findings also lend support for a greater crowding effect, as seen in the sparing of verbal skills, after early left hemisphere injury.

Brain Damage, Chronic↗
PubMed1986

[Significance of preoperative prognosis].

The granulocyte phagocytosis test, Karnofsky index, and ASA standard were used in the context of 287 patients for general surgery, for the purpose of retrospective elucidation of the relationship between presurgical prognostication and postsurgical complications. Sensitivity, specificity, and "predictive values" were calculated. The highest information potential in terms of prognostication was recorded from objectively measurable granulocyte phagocytosis. Presurgical prognostication was found to be of clinical relevance only to surgical problem patients.

Granulocytes↗
PubMed1985

Thalassemic children's understanding of illness: a study of cognitive and emotional factors.

A study that explored children's understanding of the body and illness was conducted with 23 thalassemic outpatients and 27 healthy controls. The findings were supportive of a developmental progression in children's understanding that is reflective of their underlying cognitive maturity. Behavioral compliance was related to psychiatric adjustment. There was a trend toward poorer psychiatric adjustment in children with impaired understanding of their illness. These findings hold implications for both educational and psychiatric intervention with this group. Optimal health care of chronically ill children requires knowledge of the developmental course and interplay of children's cognition and their familial and personal adjustment.

Adaptation, Psychological↗
PubMed1981

[Suspected "Legionnaire's disease" (author's transl)].

A 46 years old man was admitted to the medical intensive care unit on account of bronchopneumonia with high fever. Because of increasing respiratory insufficiency he was transferred to the anaesthesiological intensive care unit where he was intubated and artificially ventilated until his death 32 days later. Samples of blood, urine and cerebrospinal fluid and tracheal swabs proved sterile when cultured and serological titration methods for the presence of a variety of virus, Chlamydia and Rickettsia gave negative results. Repeated consultations with the bacteriologist finally led to the diagnosis of suspected "legionnaire's disease". Chemotherapy with a great variety of antibiotics failed to bring down the high fever. It was only after 30 days of artificial ventilation that the immuno-fluorescence test for "legionnaire's disease" showed a titre of 1:128 which, according to the literature, constitutes an indication of the presence of this rare disease. A change of antibiotic therapy to erythromycin did not prevent the fatal outcome and the patient died of hypoxic cardiovascular failure.

Anti-Bacterial Agents↗