Search PubMed⌕ Search

Biomedical subjects

W Becker

Publications and source records attributed to W Becker.

At least 307 records · Page 17Linked to original sources
PubMed1992

Calcium localization in the shell-forming tissue of the freshwater snail, Biomphalaria glabrata: a comparative study of various methods for localizing calcium.

The routes calcium might take across the mantle to the shell have been investigated with various electron-microscopical techniques in the freshwater snail Biomphalaria glabrata (Planorbidae, Basommatophora). In chemically-fixed tissue, calcium was precipitated with a tannic acid-antimonate technique in predominantly the intercellular spaces of the outer mantle epithelium and the interstitium below it. Some vacuoles of the outer mantle epithelium and one type of mucus cell in the inner mantle epithelium also contained precipitate. The presence of calcium in the precipitates was proved by electron energy loss spectroscopy combined with electron spectroscopic imaging. Incubation with lead acetate and uranyl acetate revealed binding-sites for calcium in the intercellular spaces of the epithelia interstitium and the mucus cells of the inner mantle epithelium. Precipitates were also seen after all incubations in the calcium spherites of the connective tissue. The concentrations of calcium and other elements were analysed in freeze-dried ultrathin sections of cryofixed mantle tissue by means of energy-dispersive X-ray microanalysis. Only in mitochondria of the musculature could high amounts of calcium and phosphorous be detected.

Animals↗
PubMed1992

Biomphalaria glabrata: influence of calcium, lectins, and plasma factors on in vitro phagocytic behavior of hemocytes of noninfected or Schistosoma mansoni-infected snails.

In vitro phagocytosis of erythrocytes by hemocytes of B. glabrata, intermediate host of S. mansoni, is strongly influenced by calcium, several lectins, and plasma factors. Our results indicate that two different mechanisms of non-self-recognition in B. glabrata may occur: (1) In the presence of calcium, phagocytosis occurs in noninfected and in infected snails without involvement of any other substances, and hemocytes of schistosome resistant as well as those of susceptible snails are able to recognize and phagocytose the target cells. (2) In the absence of calcium, phagocytosis occurs if bridging molecules (heterologous lectins in our assays) were present for which effector and target cells possess binding sites or if target cells were plasma coated prior to the assays. In suspensions in homologous plasma, hemocytes of both snail strains, infected or noninfected, subsequently showed phagocytic activities of about 70-80%. Preincubation of target cells in homologous plasma resulted in similar high phagocytic activities of hemocytes even in the absence of plasma during the standard assay. In these assays, a significantly higher proportion of hemocytes of resistant snails phagocytosed plasma-opsonized erythrocytes, whereas hemocytes of susceptible snails internalized less erythrocytes per cell and needed 60 min to phagocytose at percentages equivalent to that of resistant hemocytes within 10 min. Preincubation of erythrocytes in resistant plasma significantly increased the subsequent phagocytic activity of susceptible hemocytes, whereas preincubation of erythrocytes in susceptible plasma decreased the phagocytosis level of resistant hemocytes.

Animals↗
PubMed1992

Discharge patterns of levator palpebrae superioris motoneurons during vertical lid and eye movements in the monkey.

1. We recorded single-unit activity in the caudal central nucleus (CCN) of the oculomotor complex in monkeys trained to make vertical saccadic, smooth-pursuit, and fixation eye movements. We confirmed that our recordings were from motoneurons innervating the upper lid, because small lesions placed at the sites of responsive units were recovered among neurons labeled by horseradish peroxidase (HRP) injections into the levator palpebrae superioris muscle. 2. For fixations above a threshold lid position, levator motoneurons discharged at a steady rate, which increased linearly with upward lid position. The average position sensitivity during fixation was 2.9 spikes/s per deg, and the average lid motoneuron was recruited into steady firing when the eye was looking 10 degrees down. 3. During upward saccades, levator motoneurons discharged a burst of spikes that began, on average, 7.3 ms before the lid movement if the saccade started from a straight-ahead position; the lead time decreased considerably as the initial eye and lid positions shifted downward. The firing rate usually reached its peak (130-280 spikes/s) at the very onset of the burst and declined gradually during the course of the saccade. The steady rate associated with the new fixation position was reached about halfway during the saccade. All units exhibited a pause in firing during the initial half of large downward saccades; during small saccades, the pause was inconspicuous or absent. 4. During vertical sinusoidal smooth pursuit, levator motoneurons exhibited a sinusoidal modulation in firing rate, which led eye position by an average of 23 degrees at 0.3 Hz. The average velocity sensitivity calculated from such data was 0.63 spikes/s per deg/s. 5. Although they exhibit a number of qualitative similarities, the discharge patterns of levator motoneurons and superior rectus motoneurons differ in several respects. First, during a blink, when the lid undergoes a large depression but the eye exhibits only a brief transient displacement, levator motoneurons cease firing completely, whereas superior rectus motoneurons continue to discharge. Second, for all types of coordinated lid and eye movements, levator motoneurons discharge at lower firing rates than do superior rectus motoneurons. Third, during saccades, levator motoneurons have less conspicuous and shorter-lasting bursts and pauses than do motoneurons involved in rotating the eye. 6. During upward gaze, the qualitative similarity of their burst-tonic discharge patterns suggests that levator and superior rectus motoneurons receive input signals that originate from a common source, but that the signals are processed differently to deal with the different loads facing these muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

A comparison of ePTFE membranes alone or in combination with platelet-derived growth factors and insulin-like growth factor-I or demineralized freeze-dried bone in promoting bone formation around immediate extraction socket implants.

The purpose of this study was to compare bone promotion around implants which were augmented with ePTFE membranes alone or in combination with cortical demineralized freeze-dried bone (DFDB) or the combination of platelet derived growth factor-BB (PDGF) and insulin like growth factor I (PDGF/IGF-I). Membranes were placed over titanium implants which had been inserted into fresh extraction sockets with large buccal dehiscences. Twenty-four implants were placed in 4 dogs. At 18 weeks clinical bone height measurements were taken, the animals were sacrificed, and all specimens retrieved for histologic evaluation. Clinically, a significant gain in bone levels was present in both the ePTFE membrane alone group (P < 0.005) and PTFE plus PDGF/IGF-I group (P < 0.01), but not in the PTFE plus DFDB group. Results from histometric measurements revealed an approximately 2-fold increase in the percentage of implant surface in contact with bone, area of bone adjacent to the implant surface, and in the total length of the implant surface in contact with bone in the dehiscence defects treated with ePTFE plus PDGF/IGF-I compared to the defects receiving ePTFE membranes alone (each P < 0.05). The response to the DFDB was highly variable and it did not significantly improve the efficacy of the PTFE membranes for any parameter measured. The distance from the outer surface of the new bone to the implant surface was statistically significant for ePTFE membranes alone and membranes plus PDGF/IGF-I. The results demonstrated that clinically, ePTFE membranes alone or ePTFE membranes with PDGF/IGF-I were equally effective in promoting bone growth around the implants. Histologic measurements demonstrated that sites treated with ePTFE membranes plus PDGF/IGF-I had the highest bone density compared with sites which received ePTFE membranes alone or with ePTFE membranes and DFDB. The results of this study question the use of DFDB and support the use of ePTFE membranes alone or with PDG-F-BB/IGF-I as potential methods of promoting bone formation around dental implants.

Alveolar Bone Loss↗
PubMed1992

[14C]-glucose metabolism of Oncomelania snails.

To elucidate the importance of glucose metabolism in Oncomelania snails, uniformly labelled D (14C)-glucose [(U-14C)-glucose] has been used as a tracer for observing glucose uptake, incorporation into macromolecules and the activity of enzymes involved in its metabolic pathway. Radioactivity of Oncomelania increased with time of exposure (3, 6, 12 and 24 h) to [(U-14C)-glucose] solution. In snails treated with 2 ppm bromoacetamide for 24 h, the radioactivity of soft tissues was markedly less than that of normal snails. Oncomelania can synthesize glycogen from absorbed glucose, and the absorbed (U-14C)-glucose may be incorporated into nucleic acid, protein and lipid, with 14CO2 excreted as an end metabolic product. 6-phosphoglucose dehydrogenase and 6-phosphogluconate dehydrogenase activities were demonstrated by the reduction of NADP and determination of 14CO2 from (1-14C)-glucose, respectively. The results indicate that there exists a phosphopentose pathway in Oncomelania.

Acetamides↗
PubMed1992

Kinetics of 99mTc-labelled antibodies against CD4 (T-helper) lymphocytes in man.

The availability of radiolabeled anti-CD4 antibodies permitted the study of their kinetic behaviour. Four patients suffering from rheumatoid arthritis were investigated prospectively. Three of them received 250 micrograms of 99mTc-labelled anti-CD4 antibody (MAX.16H5). One patient received in vitro 99mTc-antibody-labelled lymphocytes. 4% of the activity was excreted by the kidneys. From 4 to 24 h the splenic uptake decreased from 7.5 to 4%, the liver uptake increased from 25 to 30% the bone marrow uptake remained about the same 50% and the uptake of a single diseased joint (2%) increased slightly to 2.5%. 15 to 30 min after injection of the antibody a redistribution of labelled cells or antibody from liver and spleen to the circulating blood seemed to occur. The recovery rate (0-1 h) of in vivo labelled cells amounted to 30%, that of in vitro labelled cells to 19%. One patient was examined with in vitro labelled CD4-expressing lymphocytes. There was no difference in the antibody kinetics between in vitro and in vivo labelled cells. The authors suggest that circulating CD4-lymphocytes can be labelled with monoclonal antibodies. The kinetics of these in vitro labelled cells and the injected labelled antibody itself resembles that of recirculating lymphocytes.

Antibodies, Monoclonal↗
PubMed1992

[Oxidative phosphorylation of liver mitochondria in Oncomelania snail].

Oxidative phosphorylation of liver mitochondria in Oncomelania snail was separately detected by using oxygen electrode and spectrophotometer. ADP increased oxidative reaction of liver mitochondria from 0.187 to 0.318 mumol O2/mg protein.20 min. When certain substrates of citric acid cycle were added to liver mitochondria of Oncomelania snail, we found that oxidative phosphorylation increased to 0.353-0.444 mumol O2/mg protein.20 min. ATPase was detected in the liver of Oncomelania snail. The oxidative phosphorylation of mitochondria in Oncomelania snail could be markedly inhibited by DNP and molluscicide bromoacetamide, but the latter didn't show the inhibition of ATPase. (Figs. 1,2).

2,4-Dinitrophenol↗
PubMed1992

[Indium-111 or Tc-99m-HMPAO marked granulocytes as specific markers of florid stage endocarditis--results comparing clinical, histological and scintigraphic findings in 30 patients with suspected endocarditis].

Thirty patients with clinically suspected infective endocarditis were scanned with Indium-111- or Tc-99m-HM-PAO-labeled granulocytes. The scans were correlated with the clinical course, and in 20 cases with the results from histologic examination of the valves. In six cases the scintigraphic examination gave correct positive results, in three cases false negative, in one case a false positive, and in 20 cases correct negative results. If we limit the analysis to only the histologically proven cases, our data suggest a specificity of the method of 86% and a sensitivity of about 67%.

Abscess↗
PubMed1992

[Is a TSH screening for the diagnosis or exclusion of functional thyroid autonomy meaningful?].

A normal baseline TSH serum concentration is accepted as excluding thyroid dysfunction. The present study examined the usefulness of that concentration as a screening test for functional autonomy. 310 patients were retrospectively examined. They were all clinically euthyroid and had normal peripheral thyroid hormone concentrations. The positive predictive value for the confirmation of autonomy was 55.5%, the negative predictive value for the exclusion of autonomy 87.7%, using 0.5 mU/l as a lower limit. The probability for the presence of thyroid autonomy in patients with a TSH serum concentration below 0.3 mU/l was 72.5%.

Female↗
PubMed1992

[Estimation of insulin and glucose regulation in the dairy cow using daily profiles, simple and modified glucose tolerance test].

Insulin and glucose regulation plays a central role in regulating distribution of metabolites between udder and body tissues and, consequently, in ensuring optimum adjustment between milk yield and health stability. An experimental study was conducted into four dairy cows, between 17 weeks before and 52 weeks after calving to establish six diurnal profiles for insulin and glucose concentrations in blood plasma and undertake 18 glucose tolerance tests, nine of them simple and nine modified. The three methods used in examination provided differentiated but complementary data on the glucose-insulin system of dairy cow. Flow of metabolites in the mammary gland, in early lactation, was found to be supported by low insulin concentrations in blood plasma, reduced pancreatic response to insulinogenic stimuli, and decreased responsiveness of peripheral cells to insulin. Endocrine adaptation to catabolic metabolism had its onset as early as several weeks before calving. Alterations to insulin concentrations in blood plasma as well as to pancreatic reactivity to insulinogenic stimuli and to responsiveness of peripheral cells to insulin were found to take place at various junctures. It should be proved to use the common and modified glucose tolerance test for the description of the individual metabolic type of each single dairy cow.

Animals↗
PubMed1992

Diagnostic accuracy of 99mTc-anti-CEA immunoscintigraphy in patients with liver metastases from colorectal carcinoma.

17 patients with 43 liver metastases from colorectal carcinoma were studied by immunoscintigraphy (IS) using a 99mTc-labelled monoclonal anti-CEA antibody (BW 431/26). Sensitivity and diagnostic accuracy were 21% for all liver lesions, but 47% considering the number of patients (at least one positive finding out of multiple metastases) and 77% in patients with a single metastasis. SPECT imaging did not improve sensitivity markedly in this series. There was no correlation with CEA serum levels. Liver metastases of intermediate size with moderate tumour necrosis seem to be favourable to IS. Major reason for the low sensitivity is the poor tumour-to-background ratio caused by high unspecific uptake of 99mTc-labelled antibodies in the RES of the liver. At the moment, IS seems be only a supplementary method to conventional diagnostic procedures.

Adenocarcinoma↗
PubMed1991

[Human anti-murine immunoglobulin antibodies as disturbing factors in TSH determination].

Monoclonal murine antibodies are increasingly used for immunotherapy and in vivo diagnostic procedures such as immunoscintigraphy. The therapeutic or diagnostic reagent however, is a foreign antigen, which may induce host reactivity. This may interfere with the therapeutic or diagnostic reagent in vivo, resulting in a loss of efficacy or the necessity to increase dosages. In addition, there is an important interference to in vitro immunoassays detecting specific antigens utilizing murine monoclonal antibodies. In the present study, sera of patients who had undergone a therapeutic trial using 140 mg of an anti-CD4 antibody, were investigated. Human anti-murine-immunoglobulin-antibodies (HAMA) were detected 2-3 weeks after treatment was started and reached maximal amounts of 0.8 micrograms/ml after a single and 2 micrograms/ml after a repeated treatment course. Parallely raised values of TSH were found in sera containing HAMAs of more than 0.3 micrograms/ml. Elevations of TSH levels up to 13 microU/ml were most pronounced after a repeated trial of the murine antibody and were detectable up to 20 weeks.

Antibodies, Monoclonal↗
PubMed1991

An anti-CD4 antibody for treatment of chronic inflammatory arthritis.

Monoclonal antibodies (mAb) to the CD4 surface molecule inhibit the function of CD4+ T cells in vitro and have been used for treatment of autoimmune diseases in several animal models. Recently, an anti-CD4 mAb has been described that improved the clinical situation of rheumatoid arthritis (RA) patients although no change in laboratory parameters could be observed. Here, we report on a different high-affinity anti-CD4 mAb (MAX.16H5) and its use for treatment of RA. Reduction of the Ritchie index, morning stiffness and the number of swollen joints demonstrated the clinical benefits of the therapy. In addition, laboratory parameters like ESR, CRP, and rheumatoid factor were reduced in 6/12 treatments. A rapid depletion of CD4+ T cells was observed in all patients which reached a minimum 1 hour after administration. However, efficacy of treatment did not correlate with T cell depletion. The antibody accumulates at the site of inflamed joints as detected by 99m-Tc-labelling. Affected digital joints were detected earlier by virtue of helper T cell imaging than by conventional bone scans.

Antibodies↗
PubMed1991

Human perception of horizontal trunk and head rotation in space during vestibular and neck stimulation.

The vestibular signal of head motion in space must be complemented by a neck signal of the trunk-to-head excursion in order to provide the individual with information on trunk motion in space. This consideration led us to study psychophysically the role of vestibular-neck interaction for human self-motion perception. Subjects (Ss) were presented with passive horizontal rotations of their trunk and/or head (sinusoidal rotations, f = 0.025 - 0.4 Hz) in the dark for vestibular and neck stimulation, as well as for combinations of both. Ss' perception was evaluated in terms of gain (veridical perception of stimulus magnitude, G = 1), phase, and detection threshold. (1) Perception of trunk rotation in space. During vestibular stimulation (whole-body rotation) and neck stimulation (trunk rotation with the head kept stationary) the frequency-transfer characteristics underlying this perception were very similar. The gain fell short; it was only about 0.7 at 0.4 and 0.2 Hz stimulus frequency and was further attenuated with decreasing frequency. In contrast, the phase was close to that of actual trunk position. The gain attenuation was found to be a function of the peak angular velocity of the stimulus, a fact, which we related to a 'velocity threshold' of the order of 1 deg/s. During the various vestibular-neck combinations used, Ss' perception was again erroneous, reflecting essentially the sum of its two non-ideal constituents. However, there was one noticeable exception; during the combination 'head rotation on stationary trunk', Ss veridically perceived their trunk as stationary (compatible with the notion that the sum yielded 'zero'). (2) Perception of head rotation in space. During vestibular stimulation, Ss' estimates showed the same non-ideal gain-vs.-frequency characteristics as described above for the trunk. Neck stimulation induced an illusion as if the head had been rotated in space. This neck contribution was such that, when it was combined with its vestibular counterpart during head rotation on stationary trunk, the perception became almost veridical. On closer inspection, however, this neck contribution was found to reflect the sum of two components; one was the non-ideal neck signal contributing to the perception of 'trunk in space', the other was an almost ideal neck signal of head-on-trunk rotation. (3) The results could be described by a simple model. In this model, the erroneous vestibular signal 'head in space' is primarily used to create an internal representation of 'trunk in space'.(ABSTRACT TRUNCATED AT 400 WORDS)

Head↗
PubMed1991

Sensitivity of external cuneate neurons to neck rotation in three-dimensional space.

A functionally meaningful vestibular-neck interaction, such as it has been demonstrated for postural reflexes and self-motion perception, requires the spatial and temporal response characteristics of vestibular and neck signals to be similar. We investigated the spatial coding in neurons of the external cuneate nucleus (ECN) with natural neck and vestibular stimulations, and compared them to that of neurons in the descending and medial vestibular nuclei (DVN and MVN, respectively) obtained with vestibular stimulation. Neurons were recorded extracellularly in chronically prepared cats held under light barbiturate anesthesia. Neck stimulation was performed by sinusoidally rotating the animals' trunk relative to the earth-fixed head in six different vertical planes and in the horizontal plane. Vestibular stimulation was elicited by whole-body rotations in the corresponding planes. During neck stimulation in the vertical planes, most ECN neurons showed an approximately sinusoidal discharge modulation about resting rate, which became maximal during rotation in a specific plane. Off this plane, the response declined along a cosine function and reached zero in the orthogonal plane. The majority of these ECN neurons also responded to horizontal neck rotation; the resulting "optimal" direction of rotation in three-dimensional space varied considerably among the neurons. Yet, there was a certain preference; the majority of these ECN neurons fired maximally if trunk rotation in the yaw plane stretched the neck on the ipsilateral side, if roll brought the contralateral shoulder closer to the head, and if pitch brought the back closer to the occiput. A minority of ECN neurons showed more complex response patterns which could not be described by a single, optimal direction. About one third of the neck-sensitive ECN neurons tested showed weak responses during whole body rotation, which might stem from a weak vestibular input to this nucleus. In the DVN and MVN, the optimal direction in three-dimensional space with vestibular stimulation typically had a cosine-like spatial tuning. The spatial distribution of these directions clearly differed from that of neck-sensitive neurons in the ECN. We therefore assume that a further processing of the two input signals takes place at later stages in the CNS (e.g., in the vestibulo-cerebellum) in order to yield a functionally useful vestibular-neck interaction.

Animals↗
PubMed1991

Octreotide scintigraphy localizes somatostatin receptor-positive islet cell carcinomas.

Tyr-3-Octreotide is a synthetic derivative of somatostatin and a somatostatin-receptor analogue. The iodine-123-labelled compound localizes somatostatin-receptor-positive tumours. In this paper two patients are reported in whom somatostatin receptors were demonstrated in vitro. In a 60-year-old female with an islet cell carcinoma of the pancreas, multiple liver metastases and previously unrecognized bone metastases in the right acetabulum could be diagnosed as the reason for a persistent hypoglycaemia. In a 60-year-old male an islet cell carcinoma of the pancreas was localized with 123I-Tyr-3-octreotide. The somatostatin receptors were demonstrated in vitro and the tumour was successfully treated with somatostatin. These studies demonstrate that 123I-Tyr-3-octreotide offers the possibility of localizing somatostatin-receptor-positive tumours and their metastases. Moreover the method makes it possible to determine the receptor status of a tumour in vivo.

Adenoma, Islet Cell↗
PubMed1991

Mode of action of the molluscicide bromoacetamide.

1. Uptake of bromoacetamide was found to be upgraded with exposure time (6, 12, 24 hr) and drug concentration (0.1, 0.5, 1.0 ppm). 2. Bromoacetamide was also absorbed by carp and mice, but drug concentration was markedly lower than in snails. Drug clearance from carp as well as from mice is more rapid than that of snails. 3. The ultrastructure of hepatopancreas cells are markedly influenced by bromoacetamide, including swelling of mitochondria and splitting of cristae. This finding is correlative in a decrease in action of enzymes located in mitochondria (ornithine carbamyl-transferase, citric acid synthase). 4. Oxygen uptake and glucose uptake, as well as urea excretion, are reduced and glycogen reserve are decreased.

Acetamides↗