Biomedical subjects
Publications and source records attributed to A Enjalbert.
The cells of the male rat pituitary were enzymatically dispersed with trypsin and then separated by centrifugal elutriation. The commercial equipment requires minor modifications, especially the infection system. Using a gradient of flow, enriched gonadotrop cells are obtained. The results compare favourably with those obtained by sedimentation at unit gravity.
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The correlation between venography and SGP in 41 patients was studied. Fourteen normal subjects were used as a reference. SGP was shown to be very sensitive (97.5%), including proximal and distal DVT, and highly specific (96.4%). After some recommendations for patient positioning and technical use, it will enhance both the accuracy and the reproducibility of plethysmography for evaluation of patients with suspected deep venous thrombosis.
The effect of VIP on prolactin secretion from incubated rat hemipituitaries was characterized. Under these conditions, the secretion of GH, LH, FSH, ACTH was not affected, indicating that the effect of VIP is hormone specific. The stimulation of prolactin was dose-dependent, with an apparent affinity of VIP of 10.9 +/- 3.1 nM and a maximal stimulation of 57.7 +/- 4.2%. Secretin, a structurally related peptide, was also active at higher concentrations, whereas another partial analogue, glucagon, was ineffective. Furthermore, VIP does not act through pituitary DA receptors since alpha-flupentixol, a potent dopaminergic antagonist, does not block the stimulation of prolactin secretion by VIP. In addition, stimulation by VIP and TRH was additive. Naloxone and met-enkephalin were ineffective on the VIP effect on prolactin release. In contrast, SRIF seems to inhibit the VIP stimulation of prolactin release. Our data suggest that VIP, which was found in the hypothalamo-hypophyseal blood at concentrations of the same order of magnitude as that found to stimulate PRL in vitro, could be a physiological PRF.
Arterial stenoses of moderate extent may involve modifications of the blood flow. Arterial shading is not always examined at the best incident angle to assess the extent of the stenosis. Spectral frequency analysis by Doppler examination is a good means of evaluating the effect of moderate arterial lesions. The present study was carried out with a Doppler effect having an acoustic spectrum, which is shown in a histogram having 16 frequency bands. The values were recorded on the two femoral arteries. A study was also made of 49 normal subjects so as to establish a normal envelope histogram, taking into account the following parameters: maximum peak (800 Hz), low cut-off frequency (420 Hz), high cut-off frequency (2,600 Hz); the first peak was found to be present in 81 % of the subjects (at 375 Hz) and the second peak in 75 % of the subjects (2,020 Hz). Thirteen patients with iliac lesions of different extent were included in the study; details of these lesions were established in all cases by aortography. None of the recorded frequency histograms were located within the normal envelope. Two cases of moderate iliac stenoses were noted ( Less Than 50 % of the diameter) which interfered with the histogram, even though the femoral velocity signal was normal.
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VIP stimulated prolactin secretion from incubated rat hemipituitaries. Under the same conditions, the secretion of GH, LH, FSH was not affected. The stimulation of prolactin was dose-dependent, with an apparent affinity of VIP of 10.9 +/- 3.1 nM and a maximal stimulation of 57.7 +/- 4.2%. Secretin, a structurally related peptide, was also active at higher concentrations whereas another partial analogue, glucagon, was ineffective. The effect of VIP was not blocked by alpha-flupentixol, a potent dopaminergic antagonist, at concentrations which antagonized the dopamine inhibition of prolactin secretion. Stimulation by VIP and TRH was additive. Neither Met-enkephalin nor naloxone interfered with the response to VIP. It thus seems that specific VIP receptors are present on pituitary prolactin cells. VIP, present in the mediobasal hypothalamus and detected in the hypothalamo-hypophyseal portal blood therefore is a good candidate as a physiological PRF.
Ten normal and twenty arteriosclerotic patients underwent two successive static continuous exercise tests: - 4 minutes holding of 30% maximum power - 1 minute holding of 60% maximum power. Simultaneous recordings were made of: - The Xenon 133 washout curve of the anterior tibial muscle, to assess the ischaemia induced by exercise and to measure the duration of the hyperaemic phase; - The continuous lactate level in the femoral vein, using an original electrode specific for these enzymes. The following parameters were retained; - Resting, peak and the surface of accumulation of lactate after exercise; - The appearance time and the duration of accumulation of lactate with respect to the length of the hyperaemic phase. The following conclusions are drawn: - The differences in the height of the peak of the serum lactate. The duration and the surface of accumulation of lactate were only significant in obviously arteriosclerotic patients in whom exercise had induced ischaemia. - From the dynamic point of view: the hyperaemic phase always preceded the phase of venous accumulation of lactate, in all groups, peak lactates levels always occured during the hyperaemic phase and the length of the accumulation phase was 2 to 3 times that of the hyperaemic phase; in this respect, there was a significant difference between obvious arteriosclerotic patients in whom exercise induced ischaemia, and a group of other arteriosclerotic and normal patients.
Various techniques are presently employed for noninvasive investigation of vascular function. The problem arises as the place of each method as a function of the medical surroundings and the pathological condition to be explored, and a multicentre survey was therefore conducted in 38 teams who were asked to define their activities. The most frequently used method is continuous ultrasonography (2 apparatuses per team), an 20 centres had available a mercury gauge plethysmograph. Lower limb resting pressure was measured in only 73% of centres, and an effort test conducted in 42%. Apart from medical staff, 58% of the teams included a laboratory technician, and 60.5% employed members of the nursing staff. The specialist (vascular surgeon, cardiologist...) is responsible for confirming the nature and effects of the vascular lesion, which requires the use of ultrasonography and distal pressure measurement. The laboratory for vascular exploration intervenes if surgery is contemplated or if diagnosis is not certain. Blood velocity and segment pressures are then determined. Effort and hyperemia tests can assist the decision to undertake reconstructive surgery.
In order to identify prolactin regulating factors, the effect of various neuropeptides on prolactin secretion by the adenohypophysis has been tested. 1 degree Histidyl-proline-diketopiperazine (DKP), a major degradation product of TRH in hypothalamus and pituitary, inhibited prolactin secretion from incubated hemipituitaries (Fig. 1) with an apparent affinity of 0.5 nM. Histidyl-prolineamide and histidyl-proline, other degradation products of TRH, had no effect. TSH secretion was not affected under the same conditions. 2 degrees Vasoactive intestinal peptide (VIP) stimulated prolactin secretion in vitro in a dose dependent manner. The secretion of other adenohypophyseal hormones was not affected. This effect is not mediated by a dopaminergic mechanism, since it was not blocked by neuroleptics (Table I). 3 degrees Morphinomimetic peptides had no effect on prolactin secretion in vitro, but blocked the dopamine inhibition of prolactin secretion. The effect of metenkephalin and beta-endorphin was dose dependent and was blocked by naloxone (Fig. 2 and 3). Thse results indicate that specific receptors to various neuropeptides seem to be present on prolactin cells.
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Subcellular fractionation of the mediobasal hypothalamus (MBH) and frontal cerebral cortex was performed by differential and discontinuous sucrose gradient centrifugation. Corticotropin-releasing factor (CRF) activity of the different fractions was evaluated by bioassay. Significant CRF activity was found in acidic extracts of the MBH but not of the cerebral cortex. About 80% of the MBH effect on adrenocorticotropic hormone release was recovered in the crude mitochondrial pellet (P2) which contains synaptosomes. After further fractionation, distribution of CRF activity paralleled that of lactate dehydrogenase activity, a marker of the soluble cytoplasm. It is concluded that most CRF in the MBH is located in nerve endings as already shown for several other neurohormones.
gamma-Aminobutyric acid (GABA) inhibits PRL release from incubated hemipituitaries in a dose-dependent manner. The maximum inhibition obtained with GABA is less than that obtained with dopamine. Its affinity is 100 times lower. The effect is blocked by picrotoxin but not by a dopamine inhibitor; alpha-flupentixol but not picrotoxin antagonizes dopamine inhibition. This indicates that dopamine and GABA inhibit PRL release through independent receptors. The hypothalamic extract contains sufficient GABA to inhibit PRL release in our in vitro conditions. Picrotoxin, however, does not significantly inhibit the nondopaminergic PRL-inhibiting activity of mediobasal hypothalamic extracts. Another nondopaminergic PRL-inhibiting factor, therefore, seems to be present in the hypothalamus.