Blockade der chemischen Thermogenese und Auslösung von Muskelzittern durch Adrenolytica und Ganglienblockade beim neugeborenen Meerschweinchen

Summary As has been previously shown young newborn guinea pigs do not shiver on cold exposure although oxygen consumption is considerably increased, i.e. chemical thermogenesis (non-shivering thermogenesis) is the prevailing mechanism of heat production. In the course of the first weeks of life non-shivering thermogenesis is gradually replaced by shivering thermogenesis. In the present study it has been shown that the cold-induced oxygen uptake can be reduced in guinea pigs, 0 to 2 days of age, from 69 to 38 ml/kg min by Alderlin, an adrenergic -receptor blocking agent. This effect was accompanied by an onset of shivering demonstrating that the shivering mechanism is already developed at the time of birth but is not set in function under normal conditions. Similar results have been obtained using Hexamethonium-Bromide and Dichloroisoproterenol. The elicitation of shivering following the administration of the drugs prevents the oxygen uptake from being reduced to the basal level (ca. 20 ml/kg min). When shivering was already present as in older animals (2 to 3 weeks of age) it remained uninfluenced by Alderlin (as veryfied by electromyography); the agent was thus considered suitable to block selectively chemical thermogenesis. On this basis, it was estimated from further data that the contribution of nonshivering thermogenesis to the total heat production is reduced from 91 to 26% within the first three weeks of life. Moreover, it could be shown that the shivering mechanism is less effective than chemical thermogenesis.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Morphological variability, lectin binding and Na+,K+-activated adenosine triphosphatase activity of isolated Müller (glial) cells from the rabbit retina

Rabbit retinal Müller cells were isolated by means of papaine and mechanical dissociation. These cells were shown to have a well preserved morphology and to preserve viability for many hours. Intense wheat germ agglutinin binding occurs on the photoreceptor side of Müller cells, especially in the microvillous region. Rabbit retinal Müller cells have a Na+,K+-activated adenosine triphosphatase activity in the same order of magnitude as brain astroglial cells.     

Multiplicity in polyp count and extracolonic manifestations in 40 Dutch patients with MYH associated polyposis coli (MAP)

Objective: To investigate the contribution of MYH associated polyposis coli (MAP) among polyposis families in the Netherlands, and the prevalence of colonic and extracolonic manifestations in MAP patients. Methods: 170 patients with polyposis coli, who previously tested negative for APC mutations, were screened by denaturing gradient gel electrophoresis and direct sequencing to identify MYH germline mutations. Results: Homozygous and compound heterozygous MYH mutations were identified in 40 patients (24%). No difference was found in the percentage of biallelic mutation carriers between patients with 10–99 polyps or 100–1000 polyps (29% in both groups). Colorectal cancer was found in 26 of the 40 patients with MAP (65%) within the age range 21 to 67 years (median 45). Complete endoscopic reports were available for 16 MAP patients and revealed five cases with gastro-duodenal polyps (31%), one of whom also presented with a duodenal carcinoma. Breast cancer occurred in 18% of female MAP patients, significantly more than expected from national statistics (standardised morbidity ratio = 3.75). Conclusions: Polyp numbers in MAP patients were equally associated with the attenuated and classical polyposis coli phenotypes. Two thirds of the MAP patients had colorectal cancer, 95% of whom were older than 35 years, and one third of a subset of patients had upper gastrointestinal lesions. Endoscopic screening of the whole intestine should be carried out every two years for all MAP patients, starting from age 25–30 years. The frequent occurrence of additional extraintestinal manifestations, such as breast cancer among female MAP patients, should be thoroughly investigated.     

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0°, 10°, 20°, and 30° relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%,18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determine as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes — endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.     

Listeria monocytogenes-infected human dendritic cells: uptake and host cell response

Dendritic cells (DCs) are potent antigen-presenting cells and play a crucial role in initiation and modulation of specific immune responses. Various pathogens are able to persist inside DCs. However, internalization of the gram-positive bacterium Listeria monocytogenes into human DCs has not yet been shown. In the present study, we demonstrate that human monocyte-derived immature DCs can efficiently phagocytose L. monocytogenes. This uptake is independent of listerial adhesion factors internalin A and internalin B but requires cytoskeletal motion and factors present in human plasma. A major portion of internalized bacteria is found in membrane-bound phagosomes and is rarely free in the cytosol, as shown by transmission electron microscopy and by using an L. monocytogenes strain expressing green fluorescent protein when in the host cell cytosol. The infection caused maturation of the immature DCs into mature DCs displaying high levels of CD83, CD25, major histocompatibility complex class II, and the CD86 costimulator molecule. This effect appeared to be largely mediated by listerial lipoteichoic acid. Although L. monocytogenes infection is known to induce death in other cell types, infection of human DCs was found to induce necrotic but not apoptotic death in fewer than 20% of DCs. Therefore, the ability of DCs to act as effective antigen-presenting cells for listerial immunity is probably enhanced by their resistance to cell death, as well as their ability to rapidly differentiate into mature, immunostimulatory DCs upon encountering bacteria.     

Long-term maintenance of hematopoietic stem cells does not require contact with embryo-derived stromal cells in cocultures

We recently established that two midgestation-derived stromal clones--UG26-1B6, urogenital ridge-derived, and EL08-1D2, embryonic liver-derived--support the maintenance of murine adult bone marrow and human cord blood hematopoietic repopulating stem cells (HSCs). In this study, we investigate whether direct HSC-stroma contact is required for this stem cell maintenance. Adult bone marrow ckit+ Ly-6C- side population (K6-SP) cells and stromal cells were cocultured under contact or noncontact conditions. These experiments showed that HSCs were maintained for at least 4 weeks in culture and that direct contact between HSCs and stromal cells was not required. To find out which factors might be involved in HSC maintenance, we compared the gene expression profile of EL08-1D2 and UG26-1B6 with four HSC-nonsupportive clones. We found that EL08-1D2 and UG26-1B6 both expressed 21 genes at a higher level, including the putative secreted factors fibroblast growth factor-7, insulin-like growth factor-binding proteins 3 and 4, pleiotrophin, pentaxin-related, and thrombospondin 2, whereas 11 genes, including GPX-3 and HSP27, were expressed at a lower level. In summary, we show for the first time long-term maintenance of adult bone marrow HSCs in stroma noncontact cultures and identify some secreted molecules that may be involved in this support.     

Neuronal apoptosis in the dentate gyrus in humans with subarachnoid hemorrhage and cerebral hypoxia

Apoptosis of dentate granule cells is a typical feature of several animal models of disease. In 20 autopsy cases of subarachnoid hemorrhage (SAH) and global cerebral hypoxia caused by protracted shock or respiratory failure, we evaluated by light microscopy and in situ tailing whether this pattern of neuronal damage also occurs in humans. In subarachnoid hemorrhage, 4.0/mm2 (0-13.0/mm2) apoptotic neurons were observed in the dentate gyrus, in cerebral hypoxia 3.6/mm2 (0-19.9/mm2) (p>0.05), and in 10 aged-matched control cases dying rapidly from non-neurological diseases 0/mm2 (0-0/mm2) (median [range]) (p<0.001 versus SAH and hypoxia). Neuronal apoptosis in the dentate gyrus was most frequent, when death occurred later than 24 hours and less than 11 days after disease onset. Neuronal damage in the hippocampus was always necrotic. It was more severe in hypoxia than in SAH (median neuronal damage score 3 [range: 0-3] versus 0 [0-3], p<0.001). Apoptosis appears to be the predominant mechanism of death in dentate granule cells irrespective of the underlying disease, whereas neuronal death in the hippocampus generally is of necrotic morphology.