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Biomedical subjects

M Kolb

Publications and source records attributed to M Kolb.

At least 37 records · Page 2Linked to original sources
PubMed1997

[MR angiography using Gd-DTPA in staging of abdominal aortic aneurysm: a correlation with DSA and CT].

PURPOSE: To evaluate a contrast-enhanced (CE) MRA sequence for staging AAA. METHODS: In 24 patients (male = 20, female = 4, age = 44-81 y) with known AAA the abdominal aorta and its branches including the iliac arteries were imaged, using a 3D GRE-FISP sequence (1.5 T, TR/TE/FA = 25/6/35, slab = 100-140 mm, 32 part., FOV = 440-450 mm, matrix = 256 x 256) during an i.v. infusion of 40 ml of gadopentate dimeglumine. In addition, representative axial single slices (2D breath hold FLASH-sequence. TR/TE/FA = 82/5/30) were acquired following contrast application. MR-results were correlated with i.a. DSA and CT studies. RESULTS: With CE-MRA, AAA (n = 24) and iliac aneurysms (n = 17) could be evaluated in all cases (sens. = 100%, spec. = 100%) including luminal patency and mural thrombus. 50/54 renal arteries could be identified, 4/6 accessory renal arteries (sens. = 66.6%, spec. = 100%), 8/9 renal artery stenoses > 50% (sens. = 88.8%, spec. = 89.3%), 1/1 renal artery occlusion and 7/8 iliac artery stenoses > 50% (sens. = 87.5%, spec. = 97.5%) were depicted correctly. Proximal portion of sup. mes. art. could be detected and evaluated in 21/24 cases. Quantitative determination of therapeutically relevant vascular parameters using MRA was comparable to DSA and CT. CONCLUSION: CE-MRA is a useful method for staging of AAA and may become the method of choice when ultrafast MR techniques are used.

Adult↗
PubMed1995

Impact of automation on aircrew communication and decision-making performance.

Increasing levels of automation are being introduced into the cockpit. Yet, it is difficult to predict the impact of these automatic systems on other elements of flight, such as crew communication and the ability to arrive at an effective decision. This study attempted to clarify the relation among these variables. Forty-eight pilots were assigned to two-person crews and asked to fly a simulated mission in either automated or manual conditions using a low-fidelity simulator. The scenario was designed to require crewmembers to arrive at a collective decision based on information obtained about an evolving simulated disaster. The results indicated that the introduction of automation was not associated with better performance. However, several significant differences were observed in the communications of crews flying in the automated versus manual conditions. The results are discussed in terms of their implications for communications training for advanced technology aircraft.

Adult↗
PubMed1995

Scotoma perception in white-noise-field campimetry and postchiasmal visual pathway lesions.

The authors examined 59 patients (32 women and 27 men) suffering from homonymous hemianopia by white-noise-field campimetry (Tübingen Electronic Campimeter) and by conventional perimetry (Tübingen Automatic Perimeter or Tübingen Manual Perimeter) and by computerized tomography (CT) or magnetic resonance imaging (MR). In all, 56 patients showed neuroradiologically detectable cerebral lesions, which were superimposed in a reconstructed "reference brain". Of these 56 patients, 18 were not capable of perceiving any white-noise-field scotoma, although their conventional perimetric findings showed defects. Lesions of these patients were concentrated along the optic radiation and spared the primary visual cortex. The lesions of the remaining 38 patients with scotoma detectable in both methods were accumulated in area V1, the primary visual cortex. The lesions of 6 patients, who had had persistent scotoma perception for more than 2 years, were situated at the occipital pole. The lesions of 8 patients with vanishing scotoma were concentrated in more rostral areas.

Adolescent↗
PubMed1995

Comparison of generic versus disease-specific measures of functional impairment in patients with cataract.

The increased demand for health status measures in evaluating medical interventions has increased the importance of clarifying when to use generic versus disease-specific health status measures. The authors compared the performance of a well known generic health status measure, the Sickness Impact Profile (SIP), and a disease-specific measure of functional impairment related to vision (the VF-14) in detecting functional impairment in 426 cataract patients before and at 12 months after first eye cataract surgery. Using analysis of covariance models, the associations were assessed between the SIP and VF-14 and four criterion variables--patient ratings of trouble and satisfaction with their vision and overall health, and best corrected visual acuity--after controlling for patient age and medical comorbidities. Preoperative patient ratings of trouble and satisfaction with vision were significantly associated with VF-14 scores (P < 0.001), but not with SIP scores. Preoperative visual acuity in the better eye was significantly associated with both VF-14 and SIP scores (P < 0.001). Patient general health ratings were significantly associated with SIP scores (P < 0.001), but not with VF-14 scores. Postoperative changes in patient ratings of their vision and in visual acuity were significantly associated with changes in VF-14 scores (P < 0.05), but not with changes in SIP scores. Changes in patient ratings of overall health were significantly associated with changes in SIP scores (P < 0.01), but not with changes in VF-14 scores. In patients undergoing cataract surgery, a disease-specific health status measure is more sensitive to preoperative functional impairment related to vision, and to change in functional impairment after cataract surgery, than is a generic health status measure.

Activities of Daily Living↗
PubMed1995

[Vena cava invasion in adrenal gland tumors: findings in nuclear magnetic resonance tomography].

In rare cases, large adrenal masses with a suspicion of malignancy exhibit tumor extension into the adrenal vein and inferior vena cava. When planning surgery, the relationship of the extension to the inferior vena cava is of decisive importance. We describe in two cases on the detection of a tumor thrombus in the inferior vena cava arising from a malignant adrenal mass by means of MR angiography (TOF, coronary 2D GRE images [FLASH], 3 slices acquired during 15 second apnea). The angiograms correlated well with the results of DSA venacavography and with the intraoperative findings. Thus, MRA has been demonstrated to be suitable for the certain proof of a venous tumor thrombus not only in cases of renal cell carcinomas but also in cases of malignant adrenal masses. The method should be applied whenever there is evidence of a venous involvement in the adrenal MR images.

Adenocarcinoma, Clear Cell↗
PubMed1994

Variation in ophthalmic testing before cataract surgery. Results of a national survey of ophthalmologists.

Little information is available either for the clinical value of many ophthalmic tests performed preoperatively in the evaluation of patients for cataract surgery or for variation in ophthalmologists' use of such tests. To assess variation in ophthalmologists' use of ophthalmic tests, we conducted a national survey of American Academy of Ophthalmology members. Thirty-three percent, 17%, 37%, and 19% of the respondents reported that they "frequently" or "always" perform glare testing, contrast sensitivity testing, potential acuity measurement, and specular microscopy, respectively, in patients being considered for cataract surgery who have no history of eye disease other than cataract. In contrast, 27%, 54%, 24%, and 48% of respondents reported that they never perform each of these four tests in such patients. Two ophthalmologist characteristics--a surgical volume of greater than 200 cataract extractions per year and performance of surgery in an ambulatory surgical center or private office (as opposed to a hospital)--were independently associated with an increased probability of performing each of these four tests frequently or always. Ten percent or less of the respondents reported that they frequently or always perform electroretinography, visual evoked response testing, photography of fundus or anterior segment, B-scan ultrasonography, formal color vision testing, and formal visual field testing in such patients. Thus, there is considerable variation in ophthalmologists' use of glare testing, contrast sensitivity testing, potential acuity measurement, and specular microscopy. A small percentage of ophthalmologists may be overusing several other tests in the evaluation of patients being considered for cataract surgery.

Adult↗
PubMed1992

Determinants of coronary effects of atrial natriuretic factor in dogs.

The direct vascular action of atrial natriuretic factor (ANF) is unclear. In coronary vasculature, vasodilation has been reported as well as vasoconstriction. Doses of ANF, baseline plasma ANF levels and interference with the renin-angiotensin system might account for the controversy. We tried to further analyse determinants of the effect of ANF on coronary blood flow in anaesthetized dogs. The chest was opened and the left anterior descending coronary artery cannulated and perfused at constant normal (= 76 +/- 5 mmHg, n = 10) or reduced (= 37 +/- 3 mmHg, n = 10) pressure from the femoral arteries. At normal coronary perfusion pressure, ANF (1 ng kg-1 i.c.) reduced coronary flow from 30.7 +/- 4.2 to 26.9 +/- 4.0 ml min-1 (P less than 0.05). This effect was no longer significant at reduced coronary perfusion pressure (4.9 +/- 0.8 vs. 4.6 +/- 0.7 ml min-1). ANF (1 ng kg-1 i.c.) reduced coronary blood flow in correlation with baseline plasma ANF levels (r = 0.77, P less than 0.001). However the large variability of the constrictor effect of ANF in the rather small range of baseline plasma ANF, weakens the importance of this result and suggests other additional determinants. ANF (100 ng kg-1 i.c.) significantly increased coronary blood flow by 16-23% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Synthesis of peptidyl fluoromethyl ketones and peptidyl alpha-keto esters as inhibitors of porcine pancreatic elastase, human neutrophil elastase, and rat and human neutrophil cathepsin G.

Comparison of MeO-Suc-Val-Pro-Phe-CO2Me (29) and MeO-Suc-Ala-Ala-Pro-Phe- CO2Me (25) with their corresponding trifluoromethyl ketones 9a and 9b, respectively, in rat and human neutrophil cathepsin G assays showed the alpha-keto esters to be more potent inhibitors. Likewise, Ac-Pro-Ala-Pro-Ala-CO2Me (21) was more potent than its corresponding trifluoromethyl ketone (9c) in both porcine pancreatic elastase and human neutrophil elastase assays. Within a set of Ala-Ala-Pro-Val-CF3 elastase inhibitors, the carbobenzyloxy (Cbz) N-protecting group conferred greater potency as a P5 site recognition unit for elastase than did dansyl, methoxysuccinyl, or tert-butyloxycarbonyl. Initial inhibition of elastase was greater when trifluoromethyl ketone 9f was added from a stock solution of dimethyl sulfoxide than when it had been buffer-equilibrated prior to assay, which suggests that the nonhydrated ketone is the more effective form of the inhibitor. The most potent elastase inhibitor we report is Na-(Ad-SO2)-N epsilon-(MeO-Suc)Lys-Pro-Val-CF3 (16) which has a Ki of 0.58 nM.

Amino Acid Sequence↗
PubMed1990

Percolation theory and compactibility of binary powder systems.

Defined size fractions of polyethyleneglycol powder (MW = 10,000) were mixed with defined size fractions of alpha-lactose monohydrate in order to study the effect of compaction as a function of the weight ratios of the two excipients. For a precise control of the compression cycle, tablets were compressed on a Universal Testing Machine (Zwick 1478). Tablet tensile strength sigma T was quantified as a function of compressional stress sigma c and relative density rhor r using a two-parameter model with sigma Tmax = maximal tensile strength at zero porosity and gamma = compressibility. The results have been analyzed on the basis of the percolation theory. As soon as the component with the lower mechanical stability is percolating the powder system, tablet hardness is controlled entirely by this component. The percolation threshold is a function of the geometrical arrangement of the particles in the compressed powder system. The expected two percolation thresholds can be distinguished as a function of the composition weight ratios if the particle size distributions of the two components differ enough.

Ascorbic Acid↗
PubMed1990

[Late results following meniscectomy].

In a retrospective study a total of 227 women and men between 24 and 79 years of age who had undergone meniscectomy at the State Orthopedic Clinic of Munich between 1958 and 1975 were reexamined clinically and radiologically in order to determinate late effects of surgery. Of 149 patients with an uncomplicated subtotal meniscectomy 35% showed an unsatisfactory subjective result while 62% were continuously free of symptoms regarding their operated knee. Including constitutional factors degenerative changes in the knee occurred in 50%, 34% of the total of 149 showing severe radiologic changes of grade 2 and 3. The roentgenographic changes in the knee correlated frequently with the subjective result. The frequency of degenerative arthritis in the follow-up investigation was significantly higher for patients with preoperative osteoarthritis than in those without. Some other factors seemed to have no bearing on the longterm effect of meniscectomy. The procedure of subtotal meniscectomy proved to be an important factor for degenerative arthritis. Arthroscopic and meniscus healing techniques require further examination of longterm results.

Adult↗
PubMed1989

Inhibition of mammalian spermine synthase by N-alkylated-1,3-diaminopropane derivatives in vitro and in cultured rat hepatoma cells.

A number of N-alkylated-1,3-diaminopropane derivatives [H2N-(CH2)3-NH-(CH2)nH, where n = 1-9] have been tested as potential inhibitors of partially purified rat hepatoma (HTC) cell or pure bovine spleen spermine synthase. Among the compounds described in this paper, the most potent competitive inhibitor of spermine synthase, with respect to spermidine, is N-butyl-1,3-diaminopropane with Ki values of 11.9 nM and 10.4 nM for the HTC cell and bovine spleen enzymes respectively. Inhibition of spermine synthase by this alkylated amine is selective since spermidine synthase activity is not affected up to 100 microM N-butyl-1,3-diaminopropane at a range of 5-200 microM putrescine. Added to the culture medium of growing HTC cells, N-butyl-1,3-diaminopropane causes the expected changes in the polyamine levels with a marked decrease of spermine and an increase of spermidine. Under these conditions cell growth continues unabated. Such N-alkylated-1,3-diaminopropane derivatives may have considerable potential as tools for studying the role of polyamines and in particular the functions of spermine in cell multiplication and differentiation.

Animals↗
PubMed1989

2,2-Difluoro-5-hexyne-1,4-diamine: a potent enzyme-activated inhibitor of ornithine decarboxylase.

2,2-Difluoro-5-hexyne-1,4-diamine was prepared in an eight-step sequence from ethyl 2,2-difluoro-4-pentenoate and tested as an inhibitor of mammalian ornithine decarboxylase. It produces a time-dependent inhibition of the enzyme in vitro which shows saturation kinetics, with KI = 10 microM and tau 1/2 = 2.4 min. In rats, it produces a rapid, long-lasting, and dose-dependent decrease of ornithine decarboxylase activity in the ventral prostate, testis, and thymus. In contrast with the nonfluorinated analogue 5-hexyne-1,4-diamine (Danzin et al. Biochem. Pharmacol. 1983, 32, 941), 2,2-difluoro-5-hexyne-1,4-diamine is not a substrate of mitochondrial monoamine oxidase.

Animals↗