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Biomedical subjects

P Neumann

Publications and source records attributed to P Neumann.

At least 91 records · Page 5Linked to original sources
PubMed1993

Autoradiographic localization of prazosin and rauwolscine binding sites in the human kidney.

In the human kidney, binding sites for the alpha 1-adrenoceptor antagonist 3H-prazosin and the alpha 2-adrenoceptor antagonist 3H-rauwolscine were localized and quantified by in vitro autoradiography. 3H-prazosin binding was found predominantly in the renal cortex. In the medulla, tubular structures were also specifically labelled. No binding sites, however, were detected in association with glomeruli or large blood vessels. 3H-rauwolscine labelled the medullary vascular bundles intensively, but no binding sites were associated with glomeruli or other cortical structures. Thus, the binding pattern for 3H-prazosin is quite similar in both human and rat renal cortex. There are, however, distinct differences between human and rat kidneys in the distribution of the alpha 2-adrenergic binding sites visualized with the antagonist 3H-rauwolscine.

Animals↗
PubMed1993

A method for studying the biomechanical load response of the (in vitro) lumbar spine under dynamic flexion-shear loads.

A method was developed to study the biomechanical response of the lumbar motion segment (Functional Spinal Unit, FSU) under a dynamic (transient) load in flexion. In order to inflict flexion-distraction types of injuries (lap seat-belt injuries) different load pulses were transferred to the specimen by means of a padded pendulum. The load response of the specimen was measured with a force and moment transducer. The flexion angulation and displacements were determined by means of high-speed photography. Two series of tests were made with ten specimens in each and with two different load pulses: one moderate load pulse (peak acceleration 5 g, rise time 30 ms, duration 150 ms) and one severe load pulse (peak acceleration 12 g, rise time 15 ms, duration 250 ms). The results showed that the moderate load pulse caused residual permanent deformations at a mean bending moment of 140 Nm and a mean shear force of 430 N at a mean flexion angulation of 14 degrees. The severe load pulse caused evident signs of failure of the segments at a mean bending moment of 185 Nm and a mean shear force of 600 N at a mean flexion angulation of 19 degrees. Significant correlations were found between the load response and the size of the specimen, as well as between the load response and the bone mineral content (BMC) in the two adjacent vertebrae. Comparisons with lumbar spine response to static flexion-shear loading indicated that the specimens could withstand higher bending moments before injury occurred during dynamic loading, but the deformations at injury tended to be smaller for dynamic loading.

Acceleration↗
PubMed1993

The ultimate flexural strength of the lumbar spine and vertebral bone mineral content.

Flexion-distraction injuries (lap seat-belt injuries resulting from car accidents) were simulated by exposing 16 lumbar functional spinal units (FSUs) to a combined quasistatic load of bending and shearing in the sagittal plane. The load response of the FSU was measured by means of a force and moment transducer. Displacements and angulations were measured and calculated by means of dial gauges and photographs taken after each loading step. The mean angulation between the vertebrae just before total rupture was 20 degrees. The ultimate values of bending moment, shear force, and bending stiffness were correlated with the bone mineral content (BMC), and so were the horizontal and vertical displacements determined around the yield point on the load-displacement curve.

Accidents, Traffic↗
PubMed1993

Structural properties of the anterior longitudinal ligament. Correlation with lumbar bone mineral content.

The relationship between the amount of bone in the lumbar spine and ligamentous properties has not been studied. This article reports the tensile structural properties of bone-ligament-bone preparations of the anterior longitudinal ligament from 15 human lumbar spine segments. Significant correlations were found between the vertebral bone mineral content expressed as BMC (g/cm) and BMA (g/cm2) and BMD (g/cm3) and the structural properties of the vertebral bone-anterior longitudinal ligament-bone complex determined at yield and failure. These findings suggest that the amount of bone tissue in the spine may be functionally related to structural properties of the spinal ligaments.

Adult↗
PubMed1992

Mechanical properties of the human lumbar anterior longitudinal ligament.

A new technique incorporating a motion analysis system and a materials testing machine was used to investigate regional differences in the tensile mechanical properties of the lumbar spine anterior longitudinal ligament (ALL). Bone-ALL-bone specimens were prepared from young human cadaveric motion segments with no disc or bony pathology. Each specimen was distracted until failure at a constant crosshead displacement rate of 2.5 mm s-1 (approximately 1.0% strain per second). Strains were evaluated from digitized video recordings of markers attached to the ALL at 12 sites along its length and width, including the ligament substance and insertions. The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51), respectively. Large and significant variations in the strains were present along the width and length of the ALL. Peak substance strains were over twofold greater than peak strains at the ligament insertion sites, whereas across the ligament width, peak strains in the outer portion of the ligament were over 40% greater than in the central region. Failure consistently occurred in the ligament mid-substance and ultimate strains at the ligament failure site averaged 12.1% (S.D. 2.3). These results indicate that the strains are highly nonuniform in the normal ALL.

Adult↗
PubMed1992

Prevalence of antibodies to Borrelia burgdorferi in serum and cerebrospinal fluid samples from patients with neurological disorders in Berlin.

Paired serum and cerebrospinal fluid (CSF) samples from 800 patients of a neurological department were tested for antibodies to Borrelia burgdorferi. A flagellum enzyme-linked immunosorbent assay was used for antibody screening. All serum/CSF pairs with any elevated antibody response were also tested by Western blotting a method for confirmation. 65 patients (8.1%) had serum IgG antibodies in ELISA and 22 of these patients (2.8%) were confirmed by Western blot. 20 patients (2.5%) had elevated antibody titres in CSF by ELISA and 12 (1.5%) reacted in the Western blot. Clinical features of Bannwarth's syndrome were present in 12 patients (1.5%) and 4 patients (0.5%) showed other manifestations of Lyme borreliosis. All patients with Bannwarth's syndrome were seropositive by both methods and 10 had elevated antibody activity in the CSF proved by the two methods. The combination of a sensitive ELISA for screening and a sensitive and specific Western blot for confirmation reduced the number of false positive results but kept its standard in detecting antibodies in patients with active disease.

Adult↗
PubMed1992

The mechanism of initial flexion-distraction injury in the lumbar spine.

The threshold for flexion-distraction injuries was determined on lumbar functional spinal units exposed to a combined flexion-shear load in the sagittal plane. The specimens could resist a bending moment of 121 Nm and a shear force of 486 N at the first sign of a permanent deformation of the osteoligamentous components, which occurred at 78% of the assumed ultimate strength of each specimen. The flexion angulation was 16 degrees. The bone mineral content determined in adjacent vertebrae by means of dual photon absorptiometry was an accurate predictor of structural properties of the entire functional spinal unit even at the first sign of a substantial structural injury and not only at ultimate failure as previously demonstrated.

Bone Density↗
PubMed1992

[Correlation between neurologic disease and Borrelia burgdorferi antibodies in 800 paired serum/cerebrospinal fluid samples].

Paired serum and cerebrospinal fluid (CSF) samples from 800 patients of a neurological clinic were tested for antibodies to Borrelia burgdorferi. A flagellum enzyme-linked immunosorbent assay was used for antibody screening. All serum/CSF pairs with any elevated antibody response were also tested by a Western blot, a method for confirmation. 65 patients (8.1%) had serum IgG antibodies on ELISA screening and 22 of these (2.8%) were confirmed by Western blot. 20 patients (2.5%) had elevated antibody titers in CSF by ELISA and 12 of these (1.5%) reacted to the Western blot. Clinical features of Bannwarth's syndrome (BS) were present in 12 patients (1.5%) and four patients (0.5%) showed other manifestations of Lyme borreliosis. All patients with Bannwarth's syndrome were positive in serum by both methods and 10 had elevated antibody activity in the CSF proven by the two methods. The combination of a sensitive ELISA for screening and a sensitive and specific Western blot for confirmation reduces the number of positive results but is sensitive in detecting active disease.

Antibodies, Bacterial↗
PubMed1992

Localization and characterization of IGF-I receptors in fetal and adult human kidneys.

Human insulin-like growth factor I (IGF-I) is a growth and differentiating factor produced by various adult and fetal tissues. In the kidney, it has been linked to the proliferative response of renal tubular and glomerular cells, following unilateral or partial nephrectomy, in acromegaly, in diabetes mellitus and in glomerulonephritis. To gain insight into the potential effects of IGF-I in human kidney, a quantitative analysis of IGF-I-binding sites was performed in fetal and adult tissue using 125I-IGF-I. The ligand consistently labelled renal cortex, medulla, and glomeruli while renal vessels were not uniformly marked. The highest affinity of binding sites was found in glomeruli (adult kidneys: Kd 24.7 +/- 5.1 pM; Bmax 5.2 +/- 0.5 fmol/mg tissue equivalent (TE); n = 4; fetal kidneys: Kd 17.0 +/- 2.5 pM; Bmax 4.5 +/- 0.7 fmol/mg TE; n = 4) and cortical tubules, while vessels and renal medulla (adult kidneys: kd 47 +/- 3.9 pM, Bmax 2.6 +/- 0.3 fmol/mg TE; n = 4; fetal kidneys: kd 41.6 +/- 9.2 pM, Bmax 3.5 +/- 0.4 fmol/mg TE; n = 3) had only about half the affinity of binding and a significantly reduced maximal capacity. The strong binding of 125I-IGF-I to glomeruli supports the view that IGF-I may be involved in modulating glomerular structure and function. Fetal renal growth may depend on the action of IGF-I on glomerular cells and tubular epithelia of the kidney.

Autoradiography↗
PubMed1991

Use of dried blood spot specimens in the detection of human immunodeficiency virus type 1 by the polymerase chain reaction.

Dried blood spots (DBSs) constitute a potentially valuable source of material for human immunodeficiency virus (HIV) serologic and molecular testing. To facilitate molecular testing, we have adapted the polymerase chain reaction (PCR) to the detection of HIV proviral DNA in DBS samples. The method is highly reproducible, with 75 microliters of whole dried blood providing sufficient DNA for duplicate testing with three primer sets. By using DBS PCR, 66 of 69 (95.6%) seropositive at-risk individuals tested positive by at least two primer sets and 85 of 85 (100%) low-risk seronegative blood donors tested negative by all three sets of primers. The frequency of HIV DNA detection in seronegative at-risk individuals was low, with only 1 of 58 (1.7%) individuals testing positive. These results show that in a clinical environment, HIV PCR analysis of DBS specimens is specific and sensitive. The method is cost effective and presents a useful alternative to the isolation of HIV from seropositive babies with an undefined infection status.

Blood↗
PubMed1990

Ultimate strength of the lumbar spine in flexion--an in vitro study.

The ultimate strength in flexion of 16 lumbar functional spinal units (FSU) was determined. The specimens were exposed to a combined static load of bending and shearing in the sagittal plane until overt rupture occurred (simulated flexion-distraction injuries). The biomechanical response of the FSU was measured with a force and moment platform. Mechanical displacement gauges were used to measure vertical displacements (flexion angulation) of the specimens. Photographs were taken after each loading step for determination of horizontal displacements and the centre of rotation. The lumbar FSU could resist a combination of bending moment and shear force of 156 Nm and 620 N respectively, before complete disruption occurred. The tension force acting on the posterior structures was 2.8 kN. The flexion angulation just before failure was 20 degrees and the anterior horizontal displacement between the upper and lower vertebrae was 9 mm. The centre of rotation was located in the posterior part of the lower vertebral body. The bone mineral content in the vertebrae appeared to be a good predictor of ultimate strength of the lumbar FSU. Knowledge of the biomechanical response of the lumbar spine under different static traumatic loads is a first step to better understand the injury mechanisms of the spine in traffic accidents.

Biomechanical Phenomena↗
PubMed1990

Intravenous streptokinase in acute myocardial infarction (I.S.A.M.): assessment of left ventricular function 1 and 7 months after infarction by radionuclide ventriculography.

I.S.A.M. was a prospective, placebo-controlled, double-blind multicentre trial of high-dose short-term intravenous streptokinase in acute myocardial infarction (AMI) within 6 h of the onset of symptoms. Determination of left ventricular ejection fraction (LVEF) by radionuclide ventriculography was performed 1 and 7 months after AMI in a subset of 192 patients at rest and, in 140 of them, also during exercise. Regional myocardial function was analysed in all 145 patients with neither a history of a previous myocardial infarction nor revascularization procedures or reinfarction within the 7-month follow-up period. One month after AMI, mean LVEF was higher in the streptokinase group in patients with anterior AMI (50 +/- 15% vs 42 +/- 16%, P = 0.013). This difference was more marked in the subgroup treated within 3 h (53 +/- 14% vs 42 +/- 15%, P = 0.004), whereas patients treated 3-6 h after the onset of symptoms did not differ from respective controls (41 +/- 16% vs 41 +/- 18%). In patients with inferior AMI, the difference in mean LVEF was small (57 +/- 11% vs 55 +/- 12%, P = 0.47). After anterior AMI benefit due to streptokinase therapy was preserved up to 7 months (52 +/- 14% vs 44 +/- 17%, P = 0.013). During exercise, the increase of mean LVEF was greater in the streptokinase group at both dates, especially 7 months after AMI (4.1 +/- 6.1% vs 1.2 +/- 6.3%, P = 0.015). In streptokinase-treated patients with anterior AMI, regional LVEF at rest was higher at both dates compared with controls, within the infarct zone as well as in remote myocardium. No treatment-control differences were demonstrable in patients with inferior AMI. During exercise, regional contractile reserve was better in the streptokinase group within the infarct zone as well as in remote myocardium, irrespective of the site of infarction. Thus, intravenous streptokinase within 3 h after the onset of AMI preserves global left ventricular function in anterior AMI over a period of at least 7 months. Intravenous streptokinase improves regional myocardial function within the infarct zone as well as in remote areas. In inferior AMI investigation solely at rest may underestimate the benefit of streptokinase therapy.

Aged↗
PubMed1990

Laboratory evidence of active HIV-1 infection in Canadians with hemophilia associated with administration of heat-treated factor VIII.

Heat-treated factor VIII has been implicated in the transmission of HIV to hemophiliacs. Previously, evidence has been limited to documenting cases of seroconversion following administration of heat-treated factor VIII. Here, we present evidence of active HIV infection, i.e., infected and not merely sensitized following factor VIII injections. Six Canadians with hemophilia had seroconverted during a longitudinal study of their HIV immune status. Two of the three patients tested by this method demonstrated HIV gag-specific sequences upon amplification by polymerase chain reaction. In addition, HIV-1 virus was isolated from peripheral blood lymphocytes of one of these two persons as shown by reverse transcriptase activity of culture supernatants as well as neutralizable p24 antigen. This, we believe, is the first evidence of active HIV infection following administration of 60 degrees C, 30 h heat-treated factor VIII.

Canada↗
PubMed1990

[The materials and border-zone micromorphology of a glass-ionomer cement cavity lining material].

The combination of various possibilities for sample preparation and investigation--the tinting penetration method, the ion beam slope cutting, the light and scanning electron microscopy--allow statements at the grind after different drying of the preparation mainly to the bond but also surface and filler shape of glass-ionomer cements. The dentine in the area of enamel-dentine-junction and of superficial root area is effectively closed by Ketac-Bond. Likewise, the bond with cover filling (Visio-Molar) can be considered without gaps except a single case. Crack propagations from the cement surface seem to related to pores and occur independently of type of drying especially in case of mechanical after treatment of already hardened cavity lining [correction of underfilling] material.

Dental Bonding↗
PubMed1989

SIMREP: a program simulating differential DNA replication.

During endoreplication, different organisms in different taxa carry out DNA syntheses without nuclear division. The result of such endocycles is either a polyploid nucleus or a polytene architecture of the chromosomes. Since not all sequences of the genome may be reduplicated simultaneously and to the same extent, endocycles provide an opportunity for primary cell differentiation at the DNA level as a result of DNA amplification or underreplication. We have designed a numerical model which simulates differential endoreplications. The program SIMREP is written in TURBO PASCAL 4.0 and can be executed on a PC/XT/AT with MS-DOS greater than or equal to 2.0. It uses diploid DNA contents derived from meiotic or mitotic nuclei together with data on amounts of DNA present after a given number of endocycles. SIMREP can be applied to genomes containing arbitrary numbers of chromosomes (maximum N = 24) to model details of their replication behaviour. It is also useful in analysing differential replication of single genes. The application of SIMREP is illustrated with two examples. (1) Female and male specific types of underreplication were found in the chironomid midge Prodiamesa olivacea. The heterosomes which appear homomorphic in metaphases were identified by their differential polytenization. (2) The Y chromosome of Drosophila nasutoides was assessed to ascertain whether its replication is regulated in parallel with, or independently from the large chromosome pair 4.

Animals↗
PubMed1987

[Diagnosis of growth hormone deficiency with the growth hormone releasing factor GRF 1-40. The potentials and limits].

Eleven patients with constitutionally delayed development, seven patients with idiopathic growth hormone deficiency and ten patients with craniopharyngeoma received growth hormone releasing factor GRF 1-40 in a dose of 1 micrograms/kg body weight as a bolus injection. In the patients with constitutionally delayed development, a mean maximum HGH value of 86.7 microU/ml was measured 30 minutes after GRF injection. Considerably higher HGH stimulation values were thus obtained after GRF than with conventional stimulation methods. In the patients with idiopathic growth hormone deficiency or craniopharyngeoma, there was mostly only a slight rise of the growth hormone level with a delayed onset. Merely two patients with craniopharyngeoma could be adequately stimulated in accordance with conventional criteria (HGH greater than 12 microU/ml), although their values also remained markedly below those of the patients with constitutionally delayed development. Both patients had somatomedin C values which were below that normal for their age; together with the delayed rise in HGH after GRF, this allowed diagnosis of growth hormone deficiency.

Adolescent↗