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Biomedical subjects

A Wichmann

Publications and source records attributed to A Wichmann.

9 recordsLinked to original sources
PubMed2002

Prosodic characteristics of skilled reading: fluency and expressiveness in 8-10-year-old readers.

Statistical methods of describing prosody were used to study fluency, expressiveness and their relationship among 8-10-year-old readers. 67 children were rated on fluency and expressiveness. The two were partially independent in the full sample: expressiveness rarely occurred without fluency, but fluency occurred without expressiveness. A balanced subsample of 24 was selected for closer instrumental and statistical analysis. There were robust relationships between fluency and measures associated with temporal organization.between expressiveness and variables associated with pitch mobility; and Interactions indicated that the relationships were not simple. Differences between groups depended on sentence content and position-expressive readers distinguished sentences more sharply according to content, and the groups diverged on some measures as the passage progressed. Also, measures associated primarily with either fluency or expression often showed secondary sensitivity to the other: temporal organization was associated with fluency, but worsened over time among inexpressive readers; and readers who were both fluent and expressive were distinctive in several respects. Some measures offer a basis for rules aimed at assigning individuals to skill categories, particularly the magnitude of pitch movements and reading time per syllable. The rules distinguish well among readers who were either at one of the extremes of skill, or fluent but inexpressive; it is harder to discriminate among the other readers (who have mixed skill patterns). The effects suggest psychological hypotheses about the underlying mechanisms.

Child↗
PubMed1996

Anaerobic metabolism in the leech (Hirudo medicinalis L.): direct and indirect calorimetry during severe hypoxia.

Anaerobic metabolism in the limnic annelid Hirudo medicinalis L. was investigated by direct and indirect calorimetry. During long-term severe hypoxia, the rate of heat dissipation was reduced up to 13% of the aerobic rate. At the same time, the rate of ATP turnover was reduced to about 30% of the aerobic rate, indicating that metabolic depression is an important mechanism to ensure survival of the leech during environmental anaerobiosis. Heat dissipation during hypoxia was monitored under two experimental conditions, favouring either concomitant hypocapnia (continuous N2 bubbling) or hypercapnia (self-induced hypoxia). The reduction in heat dissipation during hypocapnic hypoxia was less pronounced than during hypercapnic hypoxia, indicating that the different experimental conditions may influence anaerobic metabolism and the extent of metabolic depression. Biochemical analysis of known anaerobic substrates and endproducts provided the basis for indirect calorimetry during self-induced hypoxia. From changes in metabolites, the expected heat dissipation was calculated for initial (0-8 ,h) and long-term severe hypoxia (8-72 h). During the initial period, the calculated heat dissipation fully accounted for direct calorimetric determination. During long-term hypoxia, only 71% of the measured heat production could be explained from biochemical analysis of metabolites. Therefore, an additional unknown endproduct cannot be excluded, especially when anaerobic ammonia production and analysis of the carbohydrate balance are considered.

Aerobiosis↗
PubMed1989

[Kidney function in heart failure].

Congestive cardiac failure is a syndrome in which a decrease of cardiac output triggers a series of neuro-humoral compensatory mechanisms in part involving the kidney. In this response, dysfunction of atrial volume receptors as well as disturbances of the autonomic nervous system have recently been demonstrated and are held responsible for excessive stimulation of angiotensin II, followed by adverse regulatory effects. Renal hemodynamic compensation for heart failure primarily involves constriction of efferent arterioles thereby defending glomerular filtration. In this setting, the occurrence of prerenal insufficiency is indicative of a far advanced reduction in renal blood flow. Apparent diuretic resistance in the treatment of heart failure is usually caused by iatrogenic vascular compromise or by the use of a single diuretic rather than an appropriate combination. Hyponatremia, vasopressin stimulation and elevation of plasma N-epinephrine concentration have been found to be the most reliable indicators of a poor prognosis of heart failure. Atrial natriuretic peptide is stimulated in proportion to the degree of atrial distension in heart failure, however its intrarenal effects are markedly blunted or may even be absent in this particular disease.

Atrial Natriuretic Factor↗
PubMed1989

Inappropriate secretion of antidiuretic hormone, polydipsia and hypothalamic calcifications.

We studied a 41 year old patient who had pathologic fluid intake of 10 1/day together with syndrome of inappropriate antidiuretic hormone. Imaging studies revealed a lesion of the anterior wall of the third cerebral ventricle. A review of relevant literature indicated several different disturbances by which alterations of thirst, vasopressin-secretion and abnormalities of anterior third ventricle may be associated. The present case presents an unusual and potentially dangerous combination in this spectrum of changes.

Adult↗
PubMed1977

Purification of human immunoglobulin M by affinity chromatography on protamine-Sepharose.

Human IgM has been isolated from plasma by a simple procedure in high yield. The first step was adsorption to protamine-Sepharose and elution by increasing the ionic strength with NaCl. This was followed by two gel filtration steps resulting in a 98% pure IgM in about 30% yield. A somewhat modified procedure could also be used for purification of IgM from Cohn fraction II + III. The purified IgM was found to have a sedimentation constant in agreement with reported values. In immunoelectrophoresis and isoelectric focusing, purified IgM showed the same behaviour as IgM in plasma. Different fragments of IgM were tested for binding to the protamine-Sepharose adsorbent. IgM and Fab were not bound unlike (FC)5, indicating that the sites responsible for binding are located in the Fc part and that several Fc parts are necessary for sufficiently strong binding for adsorption.

Chromatography, Affinity↗
PubMed1977

[Delivery in adolescents].

The course of delivery to patients aged 16 and under during 1957 to 1961 and 1967 to 1971 is reported. The frequency of deliveries has not changed. Vaginal delivery occurred in 140 of 142 patients. The delivery of the young girls was characterized by an uncomplicated course. The incidence of breech, cesarean section and assisted deliveries was low. Neonatal complications and the perinatal mortality rate are attributed to prematurity and malformation. Prematurity might be reduced by an intensive care of pregnancy.

Adolescent↗
PubMed1976

[Pregnancy in adolescents].

The course of pregnancy to patients aged 16 and under during 1957 to 1961 and 1967 to 1973 is reported. There is an increasing number of pregnancies in these groups of adolescent girls. The frequency of delivery has not changed but the number of abortion has become more important. This fact and the complication by a substantially higher frequency of gestosis and by a tendency to premature delivery causes the pregnancy in young girls as a high risk pregnancy which needs intensive care.

Abortion, Induced↗
PubMedDate not supplied

Analysis of laser Doppler flux motion in man: comparison of autoregressive modelling and fast Fourier transformation.

In order to investigate laser Doppler (LD) flux motion in healthy subjects and patients with peripheral arterial occlusive disease (PAOD), spectrum analysis of LD signals is needed. Autoregressive analysis (AR) is presented as an alternative method of power spectrum estimation. This procedure is compared to the commonly used fast Fourier transform algorithm (FFT) by describing the analytical power of both spectra in the analysis of flux motion waves. LD signals were recorded from the forefoot of 8 healthy volunteers and 11 patients with different degrees of PAOD. The flux, concentration of moving blood cells and velocity signal was digitized and stored for off-line analysis. Special software was designed to calculate AR and FFT spectra of the LD signals and to compare the suitability of both methods for the spectral analysis of LD recordings. Additionally, three-dimensional spectrum diagrams were calculated to demonstrate time-dependent flux changes during standardized provocation maneuvers. AR facilitates the determination of frequency and amplitude of flux motion waves as compared to the FFT. Low frequency-large amplitude waves (LF waves) were detected in both groups. High frequency-small amplitude waves (HF waves), which predominantly appear in severe ischemia, were observed in 7 of the 11 patients and in 2 of the 8 controls. The spectra revealed pulsatile waves in all healthy controls, but only in 1 of the 11 patients. AR modelling allows a reliable description of important flux motion components and has considerable advantages in spectral estimation of LD signals as compared to the FFT.

Algorithms↗