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Biomedical subjects

J Baas

Publications and source records attributed to J Baas.

11 recordsLinked to original sources
PubMed2001

Polymorphism in pentacene.

Pentacene, C(22)H(14), crystallizes in different morphologies characterized by their d(001)-spacings of 14.1, 14.5, 15.0 and 15.4 A. We have studied the crystal structure of the 14.1 and 14.5 A d-spacing morphologies grown by vapour transport and from solution. We find a close correspondence between the 14.1 A structure reported by Holmes, Kumaraswamy, Matzeger & Vollhardt [Chem. Eur. J. (1999), 5, 3399-3412] and the 14.5 A structure reported by Campbell, Monteath Robertson & Trotter [Acta Cryst. (1961), 14, 705-711]. Single crystals commonly adopt the 14.1 A d-spacing morphology with an inversion centre on both molecules in the unit cell. Thin films grown on SiO(2) substrates above 350 K preferentially adopt the 14.5 A d-spacing morphology, with a slightly smaller unit-cell volume.

Journal Article↗
PubMed2000

Spin-singlet clusters in the ladder compound NaV2O5

The space group of alpha(')-NaV2O5 turns below T(c) = 34 K from Pmmn with all V sites equivalent, into Fmm2 with three independent vanadium sites per layer. This is incompatible with models of charge ordering into V4+ and V5+. Our structure determination indicates that the phase transition consists of a charge ordering with three distinct valence states, formally V4+, V4.5+, and V5+. The singlet formation is not associated with dimerization on the spin ladder, but with the formation of spin clusters. Finally, we ascribe the quadrupling of the c axis to the large polarizability of the V2O5 skeleton.

Journal Article↗
PubMed1995

Dynamic liver scintigraphy: a new way of measuring the function of the reticuloendothelial system of the liver.

The phagocytic function and biokinetics of the hepatic reticuloendothelial system (RES) were evaluated using a 25-nm diameter colloid (Nanocoll) and a scintillation camera technique in opossums with obstruction of the pancreatic duct (group I) and additional obstruction of the common bile duct (group II). The liver net uptake curve was analysed using natural log regression. The regression curves proved to fit very well (r > 0.93) and a parameter R was calculated to describe the curves. In group I there was a slight but significant decrease in the RES function and no morphological change in the pancreas. In group II, RES function was significantly more suppressed than in group I. The opossums developed severe haemorrhagic pancreatitis. The results show that the regression parameter R is well suited to described liver RES function, and suggest that a suppressed liver RES after biliary obstruction could be an important factor in the pathogenesis of biliary pancreatitis.

Animals↗
PubMed1994

[The reticuloendothelial system. An overview of function, pathology and recent methods of measurement].

The Reticuloendothelial System (RES) consists of cells descending from the monocytes which are able to perform phagocytosis of foreign materials and particles. 90% of the RES are located in the liver. The most important function of the RES ist phagocytosis, but it also takes part in cytotoxicity against tumor cells and has a function in the regulation of the immune system. The importance of the RES is obvious in diseases of the bile ducts. An obstruction can lead to a decrease in the function of the RES. Beside a mathematical model there are also a few experimental methods to measure the phagocytic capacity and thus the efficiency of the RES. They are based on a clearance study of the amount of particles absorbed by the RES. This study can e.g. be done with Nanocoll which has been marked with 99mTc. But instead of the bloody clearance, a scintigraphic study using a gamma camera can be performed. With that, the increase time, the liver extraction fraction and the steepness of increase can be determined. Such a test could be of clinical relevance as a parameter for the prognosis of patients with trauma, sepsis or shock. The function of the RES in the pathogenesis of the biliary pancreatitis could also be examined closer with the help of such a test. The requirements a test of the RES should meet are reproducibility, repeatability and practicability.

Animals↗
PubMed1990

Early Indium-111 antimyosin scintigraphy for assessment of regional wall motion asynergy on discharge after myocardial infarction.

To assess the relation between early Indium-111 monoclonal antimyosin antibody scintigraphy and degree of regional asynergy on discharge, 38 patients with a first acute myocardial infarct were studied (18 anterior, 20 inferoposterior infarctions). In 21 patients thrombolytic therapy was administered. On the first day of myocardial infarction, 80 MBq Indium-111 Antimyosin was injected. Planar images, anterior, lateral and left anterior oblique, were made 24 hours later. Localized myocardial uptake was present in 37/38 patients, and was evaluated for Count Density Index (count density of infarct zone/left lung count density) in the left anterior oblique images, which displayed the infarct zone well. Regional asynergy on discharge was evaluated by cross-sectional echocardiography and defined mild (hypokinesia) or severe (akinesia or dyskinesia). Count density index was significantly lower in 15 patients with mild asynergy, compared with 22 patients with severe asynergy (1.61 +/- 0.25 vs. 2.42 +/- 0.40, p less than 0.001). This difference was present in both patient groups treated with or without thrombolysis. We conclude that early count density index, reflecting the amount of local necrosis, is highly correlated to the ultimate degree of wall motion impairment.

Antibodies, Monoclonal↗
PubMed1989

Predictive value of indium-111 antimyosin uptake for improvement of left ventricular wall motion after thrombolysis in acute myocardial infarction.

In 21 patients treated with thrombolysis for acute myocardial infarction (AMI), the degree of myocardial uptake of indium-111 monoclonal antimyosin antibodies injected within 24 hours after onset of AMI was compared with the degree and extent of regional asynergy on admission and discharge, as assessed by 2-dimensional echocardiography. On the first day of AMI, 80 MBq of indium-111 antimyosin was injected and planar images were made 24 hours later. Indium-111 antimyosin uptake was evaluated for count density index (count density of infarct zone/left lung count density) in the left anterior oblique projection, in which the infarction zone was well displayed in all patients. Using 2-dimensional echocardiography, the left ventricle was divided into 13 segments and evaluated for regional asynergy, which was considered severe (akinesia or dyskinesia) or mild (hypokinesia). The extent of regional asynergy was measured by the number of asynergic segments. All 21 patients had severe regional asynergy on admission. Nine of 21 showed only mild regional asynergy on discharge and 12 of 21 had persistent severe regional asynergy in at least 1 segment. The count density index was significantly lower in patients with mild regional asynergy on discharge compared with patients with severe regional asynergy (1.63 +/- 0.27 vs 2.50 +/- 0.42, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

[Maxillofacial prosthodontics. Its possibilities and limitations].

The maxillofacial prosthodontist acts primarily as a member of the head and neck oncology team. Using special methods and techniques, and more or less specific materials, speech, chewing, swallowing and facial expression are to be regained as good as possible. Due to the complexity of several orofacial functions, surgical or prosthodontic rehabilitation cannot always be accomplished.

Dentures↗
PubMed1988

Persistent sternum synchondroses on bone scintigraphy.

This report describes the case history of two patients who showed a hyperactive midsternal area on bone scintigraphy due to a persistent sternal synchondrosis. Whereas this anatomical variant is diagnosed infrequently, midsternal hotspots can sometimes be related to arthrotic degeneration of these extra joint spaces. In the differential diagnosis of midsternal hotspots on bone scintigraphy, persistent sternum synchondroses should be considered.

Adult↗