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Biomedical subjects

N Schaad

Publications and source records attributed to N Schaad.

6 recordsLinked to original sources
PubMed1999

Hypoxic contraction of small pulmonary arteries from normal and endotoxemic rats: fundamental role of NO.

The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-micrometer outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2alpha, and exposed to either severe (bath PO2 8 +/- 3 mmHg) or milder (21 +/- 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [NG-nitro-L-arginine methyl ester (L-NAME), 10(-3) M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by L-NAME. The milder hypoxia elicited no increase in vascular tone. These results indicate an essential role of NO in the hypoxic contractions of precontracted rat SPA. The endothelium independence of HPV in arteries from LPS-treated animals appears related to the extraendothelial expression of iNOS. The severe degree of hypoxia required to elicit any contraction is consistent with a mechanism of reduced NO production caused by a limited availability of O2 as a substrate for NOS.

Animals↗
PubMed1998

Comparative distribution of nitric oxide synthase- and serotonin-containing neurons in the raphe nuclei of four mammalian species.

Monoclonal antibodies were generated against serotonin (5-HT) and the C-terminal portion of the neuronal form of nitric oxide synthase (nNOS), the enzyme producing nitric oxide in neurons. These antibodies were used to compare the distribution of 5-HT- and nNOS-containing neurons in the raphe nuclei of four animal species (rat, mouse, guinea pig, and cat). It was found that the rat was the only species in which the raphe nuclei contain a substantial number of nNOS-immunoreactive (IR) cell bodies. In this species and as observed by other authors, all mesencephalic raphe nuclei contained nNOS-IR cells, the largest group being located in the nucleus raphe dorsalis. The coexistence of nNOS and 5-HT immunoreactivities in these nuclei was visualized by double labeling. In the medulla, the nuclei raphe magnus and obscurus displayed a rather low number of nNOS-IR neurons. In the other species, nNOS-IR cell bodies were found in very low numbers, whatever raphe nucleus was considered. The rostral pole of the nucleus raphe dorsalis and the nuclei raphe magnus and obscurus contained a few nNOS-IR neurons which did not show any coincidence with the 5-HT neurons. In addition, nNOS-IR axons were rare. It is concluded that in the mouse, guinea pig, and cat the involvement of nitric oxide in functions subserved by 5-HT within the raphe nuclei might be minimal.

Animals↗
PubMed1995

Parallel nocturnal secretion of melatonin and testosterone in the plasma of normal men.

Differences and similarities in the temporal organization of hormone secretion in plasma reflect the activity of CNS pacemakers. One aspect of this activity, the temporal synchronization of the secretion of different hormones is still poorly understood. We report the analysis of melatonin and testosterone plasma concentrations during two nights in 6 normal healthy young men. Blood was collected every 20 min between 2040 and 0640. Plasma testosterone concentrations increased by 1.5- to 2-fold during the second part of the night, and melatonin by 2.5- to 4-fold. In each subject, the individual temporal pattern of melatonin was quite stable over the two nights of sampling, while testosterone profiles showed fluctuations. There was a high degree of parallelism in these two hormones nocturnal secretion. These results, together with previous studies, suggest that melatonin might entrain the nocturnal secretion of testosterone.

Activity Cycles↗
PubMed1977

[Trend scintigraphy].

Focal changes in activity concentration for given time function. The increase per time interval is calculated for each pixel and arranged into a result matrix. Areas with increasing activity are displayed in a "positive trend scintigramm", those with decreasing activity in a "negative trend scintigram", using a gray scale of color format. Statistical fluctuations are suppressed using this method; the data smoothing over the chosen time period and the fact that several individual pictures are included in the calculations provide displays with increased informational content as compared to serial imaging methods. The clinical interpretation of localized changes in activity concentration during a specific time interval is facilitated. The method is simple, can be adapted to different camera and computer systems, and requires no additional examination procedures on the patient.

Adult↗