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Biomedical subjects

U Schwarz

Publications and source records attributed to U Schwarz.

At least 73 records · Page 4Linked to original sources
PubMed1996

Do cardiac output and serum lactate levels indicate blood transfusion requirements in anemia of prematurity?

BACKGROUND: Whether and when to transfuse in anemia of prematurity is highly controversial. Some authors suggest transfusions simply if the hemoglobin (Hb) level is below a defined normal range. Others propose the use of clinical or laboratory parameters in anemic patients to decide whether to transfuse or not. HYPOTHESIS: A decreasing amount of circulating Hb should cause a compensatory increase in cardiac output (CO) and an increase in arterial serum lactate. MATERIALS AND METHODS: In 56 anemic preterm infants (not in respiratory or hemodynamic failure) we analyzed CO after the first week of life using a Doppler sonographic method. At the same time serum lactate levels, Hb levels and oxygen saturation were registered. Nineteen of these patients were given transfusion when they demonstrated clinical signs of anemia by tachycardia > 180/min, tachypnea, retractions, apneas and centralization (group 2). The remaining 37 patients were not transfused (group 1). Serum lactate, CO, heart rate (HR), oxygen delivery, respiratory rate, capillary refill and Hb were analyzed in both groups and in group 2 before and 12-24 h after transfusion. Data between groups 1 and 2 and in group 2 before and after transfusion were compared. RESULTS: In the 56 patients studied no linear correlation between Hb and CO or between Hb and serum lactate was found. Nor could any correlation be demonstrated between the other variables studied. Examining the subgroups separately, a negative linear correlation was demonstrated between serum lactate and oxygen delivery in group 2. No other significant correlations were detected. However, when the pre- and post-transfusion data were compared in group 2 (increase of Hb from 9.45 (SD 3.44) to 12.5 (SD 3.8) g/100 ml), the CO decreased from 281.3 (SD 162.6) to 224 (SD 95.7) ml/kg per min (p < 0.01) and serum lactate decreased significantly from 3.23 mmol/l (SD 2.07) before to 1.71 (SD 0.83) after transfusion. Oxygen delivery was 35.8 (+/- 0.19) ml/kg per min group 1, 27.8 (+/- 0.05) pre- and 43.4 (+/- 0.07) post-transfusion in group 2 (p < 0.01). CONCLUSIONS: CO measurements and serum lactate levels add little information to the decision-making process for blood transfusions, as neither CO nor serum lactate levels correlate with HB levels in an otherwise asymptomatic population of preterm infants. In infants where the indication for blood transfusion is made based on traditionally accepted clinical criteria, serum lactate is an additional laboratory indicator of impaired oxygenation, as it correlates significantly with oxygen delivery. A significant lower oxygen delivery in patients in whom blood transfusion is indicated and an increase in oxygen induced by transfusion demonstrate the value of these criteria in identifying preterm infants who benefit from transfusion.

Anemia, Neonatal↗
PubMed1996

Transalveolar fixation of the peri-implant soft tissue in the mandible: surgical method and clinical follow-up.

PURPOSE: Firm, immobile mucosa around endosteal implants is one prerequisite for a reliable long-term result. In the atrophic mandible, this may be achieved by a vestibuloplasty on the facial side. However, on the lingual side, the floor of the mouth is often high and the mucosa mobile, especially after unintentional detachment of the lingual flap during implant surgery. To overcome this problem, a surgical technique applying a transalveolar suture circumscribing the inserted implants was developed. PATIENTS AND METHODS: The operation was performed in six patients, and they were evaluated over a period of more than 18 months. RESULTS: There was a clinically significant increase in fixed mucosa behind the implants compared with a control group of six patients with a similar preoperative and intraoperative status. CONCLUSION: A localized lowering of the floor of the mouth limited to the peri-implant region using this technique can successfully improve the lingual mucosa around implants.

Aged↗
PubMed1996

Synergistic neurite-outgrowth promoting activity of two related axonal proteins, Bravo/Nr-CAM and G4/Ng-CAM in chicken retinal explants.

In the developing chicken retina, optic fibres migrating to the tectum express on their surfaces several cell adhesion molecules, including Bravo/Nr-CAM and G4/Nr-CAM and G4/Ng-CAM. We have previously described differential distribution along the retinotectal projection and differential modulation by environmental cues for Bravo and G4 and here we further compare the characteristics of these immunoglobulin superfamily molecules. From day 6 of embryonic development (E6) to 20 (E20), Bravo and G4 were found to coexist in the retinal optic fibre layer. However, while G4 staining was confined to that layer, as development proceeded Bravo staining spread to plexiform layers and some radial structures of the retina. G4 displayed a dose-dependent neurite-outgrowth promoting activity for E6 retinal explants, while Bravo did not support neurite growth. Surprisingly, when the retinal explants were grown on mixtures of the two molecules, a much more vigorous growth of neurites was seen, revealing a synergistic effect. We propose that Bravo and G4, as well as other axonal surface molecules, affect axonal growth in different ways when they are present in combination than when they are alone.

Animals↗
PubMed1996

Botulinum toxin in writer's cramp: objective response evaluation in 31 patients.

OBJECTIVES: To quantify the treatment effect of local botulinum toxin injections in writer's cramp a newly developed rating scale of writing performance and a computer assisted analysis of writing speed were used in 31 patients undergoing botulinum toxin therapy. METHODS: Baseline data of the writer's cramp rating scale (WCRS, see appendix) and computer based writing speed analysis were compared with those obtained at the time of subjective best response as recorded during follow up visits. RESULTS: The mean dose injected per session was 133.2 units Dysport divided between two forearm muscles. Of all 124 injection sessions during mean follow up of one year 76% produced a good improvement. The most common side effect was weakness (72% of the follow up visits). The WCRS scores as assessed by a blinded videotape review by four independent raters showed good reliability between raters and a significant improvement after treatment (P < 0.001). The speed of pen movements showed a significant (P < 0.05) increase after treatment at subjective best effect recordings and a significant correlation with WCRS subscores, documenting the validity of the scale. CONCLUSION: The present study is the first to show significant effects of botulinum toxin treatment in patients with writer's cramp on the basis of a quantifiable scale for writing performance which correlates significantly with writing speed measurements. The WCRS as employed in this study might therefore prove a useful rating instrument in other studies assessing severity and treatment response in patients with writer's cramp.

Adult↗
PubMed1996

Effect of ramipril, nifedipine, and moxonidine on glomerular morphology and podocyte structure in experimental renal failure.

BACKGROUND: Experimental renal failure causes structural alterations of the kidney. It is still unresolved how these changes are modified by antihypertensive treatment. Purpose of the study. To examine the effects of different antihypertensive agents (ramipril, nifedipine, moxonidine) mainly on glomerular geometry, cell number, cell morphology, and capillarization, in a subtotal nephrectomy model of renal failure. MATERIAL AND METHODS: Sham-operated male SD rats and subtotally nephrectomized (SNX) ad libitum-fed rats were examined. Groups of 8-10 SNX rats were left untreated or were treated with ramipril (0.5 mg/kg b.w. per day), nifedipine (20 mg/kg b.w. per day) or moxonidine (10 mg/kg b.w.per day) respectively. After perfusion fixation the kidneys were examined using stereological techniques. RESULTS: Systolic blood pressure (by tail plethysmography) was 110+/-13 mm Hg in sham-op and 119+/-9 in SNX. It was effectively and comparably reduced below normal values by ramipril (89+/-11 mmHg), nifedipine (98+/-23 mmHg) and moxonidine (92+/-11 mmHg). The glomerulosclerosis index (SI) was significantly increased in SNX versus sham-op; it was similarly decreased by ramipril and moxonidine but less so by nifedipine. Vascular damage (preglomerular vessels) was reduced by all treatments whereas tubulointerstitial damage was signficantly reduced only by ramipril and moxonidine. Mean glomerular tuft volume was increased in SNX compared to sham-op. controls and was normalized only by ramipril treatment. Glomerular cells were differentially affected the three antihypertensive agents. After subtotal nephrectomy an increase in podocyte volume and mesangial cell number per glomerulus was noted. Nifedipine, and to a lesser extent ramipril, prevented mesangial cell hyperplasia. In contrast, only the ACE inhibitor ramipril, but not nifedipine or moxonidine prevented podocyte abnormalities, particularly podocyte hypertrophy. CONCLUSIONS: (i) Despite comparable reduction in systolic blood pressure, different classes of antihypertensive agents had diverse effects on renal damage in subtotally nephrectomized rat. This observation is consistent with specific, non-hemodynamic actions of anti-hypertensives. (ii) Glomerular and tubulointerstitial damage are prevented by treatment with ACE inhibitors and antisympathotonic agents, but not with the calcium antagonist nifedipine. In contrast, renal vascular changes were also prevented by nifedipine. (iii) Only ACE inhibitors effectively inhibited podocyte hypertrophy and mesangial cell hyperplasia. Whether the superior effect of ACE inhibitors on glomerulosclerosis is related to inhibition of glomerular growth and podocyte hypertrophy as well as preservation of podocyte structure, or whether these findings are merely a passive reflection of greater efficacy, remains unresolved.

Animals↗
PubMed1996

[Use of drugs by women in the federal Saxony district based on survey data].

This study examines sex-specific differences in drug use of the Saxon population and compares them with relevant studies in the old Federal States. This study is based on data of the Drug Survey East (1992) which were secondary analyzed for Saxony. The sample population was representative for Saxon inhabitants aged 18-79 years and encompassed 765 participants interviewed by physicians about their drug use in the last 7 days. The drug exposure in women younger than 60 years is significantly higher than in men of the same age group. The difference can only partially be explained by the intake of oral contraceptives. Compared with men women take a higher number of different drugs and take more often self-acquired drugs in addition to the drugs prescribed by physicians. A comparison Saxony-Bremen shows that the intake of hormonal contraceptives, antihypertensives and betablockers in Saxon women is much higher than in women in the old Federal States, thyroid therapeutics, however, are used less often. Possible reasons for sex-specific and regional particularities in drug use are discussed.

Adolescent↗
PubMed1995

Early expression of a novel radial glia antigen in the chick embryo.

Monoclonal antibody 3CB2 recognizes an antigen expressed in discrete cell types derived from ectoderm and mesoderm. Biochemical and immunohistochemical studies indicate that the antigen recognized by the antibody is a 55 kDa cytoplasmic protein that may be an intermediate filament associated protein (IFAP). Developmental studies show that 3CB2 antigen is intensely expressed very early in the chick embryo, in the neural tube, myotomes, and in mesenchymal cells of visceral arches and the presumptive facial area. As development proceeds, antigen expression becomes restricted to astrocytes and radial glia cells throughout the brain. A detailed immunohistochemical study of the developing chick retina shows that the expression of 3CB2 antigen at embryonic day 8 (E8) is restricted to Müller cells, with the pattern of expression closely related to their degree of differentiation. We show, by immunocytochemistry labeling of entire Müller cells dissociated from retinas of E16-E20, that 3CB2 monoclonal is labeling the whole cell. 3CB2 selectively labels Müller cells in the rat and chameleon, but not their retinal horizontal cell axons. 3CB2 monoclonal is a very sensitive marker for early differentiating Müller cells. Our results provide evidence that 3CB2 antigen is a cytoskeletal component which may be involved in the morphogenesis of these cells, and also perhaps in the outgrowth of some axons.

Animals↗
PubMed1994

Site-specific labelling of the oligosaccharide chains of antibodies.

This paper presents a new method for site-specific labelling of antibodies employing enzymatic reactions without oxidizing or reducing agents. IgG was first treated with immobilized sialidase from Clostridium perfringens to cleave bound NeuAc. CMP-9-deoxy-9-salizoyl-NeuAc, an activated sialic acid analogue, was labelled with 131I via the iodogen-method in high yields (> 95%). Then the oligosaccharide chains of antibodies were labelled yield with the radioactive NeuAc analogue by transfer using alpha-2,6-sialyltransferase from rat liver in 50%.

Animals↗
PubMed1994

Human ocular responses to translation of the observer and of the scene: dependence on viewing distance.

Recent experiments on monkeys have indicated that the eye movements induced by brief translation of either the observer or the visual scene are a linear function of the inverse of the viewing distance. For the movements of the observer, the room was dark and responses were attributed to a translational vestibulo-ocular reflex (TVOR) that senses the motion through the otolith organs; for the movements of the scene, which elicit ocular following, the scene was projected and adjusted in size and speed so that the retinal stimulation was the same at all distances. The shared dependence on viewing distance was consistent with the hypothesis that the TVOR and ocular following are synergistic and share central pathways. The present experiments looked for such dependencies on viewing distance in human subjects. When briefly accelerated along the interaural axis in the dark, human subjects generated compensatory eye movements that were also a linear function of the inverse of the viewing distance to a previously fixated target. These responses, which were attributed to the TVOR, were somewhat weaker than those previously recorded from monkeys using similar methods. When human subjects faced a tangent screen onto which patterned images were projected, brief motion of those images evoked ocular following responses that showed statistically significant dependence on viewing distance only with low-speed stimuli (10 degrees/s). This dependence was at best weak and in the reverse direction of that seen with the TVOR, i.e., responses increased as viewing distance increased. We suggest that in generating an internal estimate of viewing distance subjects may have used a confounding cue in the ocular-following paradigm--the size of the projected scene--which was varied directly with the viewing distance in these experiments (in order to preserve the size of the retinal image). When movements of the subject were randomly interleaved with the movements of the scene--to encourage the expectation of ego-motion--the dependence of ocular following on viewing distance altered significantly: with higher speed stimuli (40 degrees/s) many responses (63%) now increased significantly as viewing distance decreased, though less vigorously than the TVOR. We suggest that the expectation of motion results in the subject placing greater weight on cues such as vergence and accommodation that provide veridical distance information in our experimental situation: cue selection is context specific.

Animals↗
PubMed1994

A new method for site-specific labelling of the oligosaccharide chain of antibodies: preliminary results.

There are various approaches for improving endoradiotherapy and diagnosis with monoclonal antibodies in nuclear medicine. The known methods of site-specific labelling of biomolecules based either on reactions with sulfhydryl groups or on reactions with aldehyde groups of the oligosaccharide chains effect unwanted alterations of the biomolecules. We present a new method to introduce radioactive halogens into the oligosaccharide chains of an antibody, based on the enzymatic transfer of the labelled synthetic sialic acid derivative CMP-9-deoxy-9-salizoyl-NeuAc. It was first labelled by the iodogen-method (iodine) in yields of more than 90%. Under selected conditions it was possible to obtain di- and trihalogenated products. Then the radioactive sialic acid derivatives were transferred during 90 minutes at room temperature with 2.6-sialyltransferase from rat liver into the oligosaccharide chains of antibodies. It is necessary to use neuraminidase pretreated antibodies with an increased number of binding sites for sialic acid derivatives. Yields of about 55% were obtained for the monoiodinated sialic acid derivative. With this method we present a reasonable alternative reaction of labelled compounds with biomolecules. Studies of the immunoreactivity are now in progress.

Animals↗
PubMed1993

Dopamine dependent reaction time deficits in patients with Parkinson's disease are task specific.

This study tested the hypothesis that patients with Parkinson's disease are impaired when they must rely on internal information to generate a response. Choice reaction times of control subjects and patients with Parkinson's disease, on and off their medication, were measured in tasks in which the motor demands were constant but which varied in the degree to which the stimuli held intrinsic information about the required response. A dopaminergic deficit was observed only in the tasks which employed stimuli compatible with the response and not in a task employing stimuli arbitrarily associated with the response. The data do not support the hypothesis that patients are differentially impaired in using internalized stimulus-response relationships.

Adult↗
PubMed1993

Induction of axonal growth by heterophilic interactions between the cell surface recognition proteins F11 and Nr-CAM/Bravo.

F11 and Nr-CAM/Bravo are two axon-associated glycoproteins belonging to different subgroups of the immunoglobulin superfamily. In this report we have investigated the interaction of both proteins using neurite outgrowth and binding assays. Antibody blocking experiments demonstrate that neurite extension of tectal cells on immobilized F11 is mediated by Nr-CAM/Bravo. Binding studies further reveal a direct heterophilic interaction between F11 and Nr-CAM/Bravo. This activity can be mapped to the amino-terminal second or third immunoglobulin-like domain within F11 with domain-specific monoclonal antibodies and deletion mutant proteins expressed on COS cells. Furthermore, perturbation experiments with domain-specific monoclonal antibodies demonstrate that this region is required for adhesion and neurite extension.

Animals↗
PubMed1993

Guidance and topographic stabilization of nasal chick retinal axons on target-derived components in vitro.

We studied mechanisms underlying the generation of topographic order within the developing chick retinotectal connection by combining the recently introduced stripe assay with a novel membrane protein fractionation technique. Our experiments show a preference of temporal and nasal retinal fibers for growing on cell membranes prepared from their proper target area. In addition, membrane preparations from posterior tectum were found to prolong substantially the survival of nasal neurites in vitro. We conclude that tropic as well as trophic interactions contribute to the generation of topographic maps during embryogenesis, in our case to the homing of nasal axons within the posterior tectum.

Animals↗
PubMed1993

Covert orienting of attention in macaques. I. Effects of behavioral context.

1. A task was used by Posner (1980) to measure shifts of attention that occurred covertly, in the absence of an eye movement or other orienting response. This paradigm was used here to assess the nature of covert attentional orienting in monkeys to develop an animal model for neurophysiological studies. Shifts of attention were measurable in monkeys and were consistent across a variety of experimental conditions. 2. The paradigm required that monkeys fixate and release a bar at the appearance of a target, which was preceded by a cue. Reaction times to targets that followed peripheral cues at the same location (validly cued) were significantly faster than those that followed cues in the opposite visual field (invalidly cued). This difference was defined as the validity effect, which as in humans, is used as the measure of a covert attentional shift. 3. When the proportion of validly to invalidly cued targets was decreased, no change was seen in the validity effect of the monkeys. This is in contrast to humans, for whom the ratio of validly to invalidly cued targets affected the magnitude of the validity effect. When 80% of the targets were preceded by cues at the same location, the validity effect was greatest. The effect was reversed when the proportions were reversed. From this result, it is concluded that cognitive processes can affect covert orienting to peripheral cues in humans, whereas in trained monkeys, performance was automatic. 4. To test whether cognitive influences on attention could be demonstrated in the monkey, an animal was taught to use symbolic, foveal signals to covertly direct attention. The magnitude of this validity effect was greater than that obtained with peripheral cues. 5. The effects of motivational and perceptual processes were tested. Although overall reaction times could be modified, the facilitating effects of the cues persisted. This constancy across motivational and perceptual levels supports the notion that the monkeys were performing the task in an automatic way, under the exogenous control of peripheral cues. 6. Most visual cuing has been tested with visual landmarks at the locations of cues and targets. These monkeys were trained with such landmarks, and when tested without them, the attentional effect of the cues was nearly abolished. These data suggest that local visual features can be important for covert orienting. 7. To determine the spatial extent of the effect of the cue, monkeys and humans were tested with four cue-target distances (0-60 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Diurnal variation in the elimination rate of human growth hormone (GH): the half-life of serum GH is prolonged in the evening, and affected by the source of the hormone, as well as by body size and serum estradiol.

The half-lives of endogenous and exogenous (biosynthetic monomeric) GH were compared in the morning and evening in healthy young men (n = 10). In group A, a bolus of GHRH was injected either at 0800 or at 2000 h, whereas in group B hGH was injected iv after suppression of endogenous GH by somatostatin. GH was sampled every 10 min and the t1/2 for GH was determined by deconvolution analysis (two compartments). The GH elimination half-life was shorter in the morning: for endogenous GH, t1/2 was 23 +/- 1.1 min (mean +/- SE) in the morning compared to 26 +/- 1.7 min in the evening (P < 0.02). T1/2 correlated negatively with estradiol (r = -0.78; P < 0.01) and positively with sex hormone-binding globulin (r = 0.71; P < 0.03). The half-life of exogenous 22-kilodalton GH was shorter compared to endogenous GH (P < 0.002), and diurnal variation was even more pronounced: t1/2 was 14 +/- 1.0 min in the morning and 19 +/- 1.0 min in the evening (P < 0.01). These effects were not due to differences in GH distribution volumes. The half-life of exogenous GH was significantly affected by weight (r = -0.8; P < 0.01) and height (r = 0.67; P < 0.05). We conclude that in young males, the rate of GH disappearance from the circulation depends on both diurnal mechanisms as well as the source or structural composition of the hormone. Body size and sex steroids contribute to the variability of GH clearance in healthy man.

Adult↗