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Biomedical subjects

A Leon

Publications and source records attributed to A Leon.

At least 163 records · Page 9Linked to original sources
PubMed1989

Seasonal and mood independence of low basal prolactin secretion in premenopausal women with seasonal affective disorder.

To test hypotheses of opposing roles of dopamine and serotonin in prolactin secretion in seasonal affective disorder, the authors determined basal serum prolactin concentrations for premenopausal women, eight with and 14 without seasonal affective disorder, in late afternoon during the follicular phase of the menstrual cycle (and a subgroup during the luteal phase) in winter and summer. Despite their significantly higher Hamilton depression scale scores in winter than in summer, the patients had significantly lower prolactin concentrations than the control subjects in both seasons. These results suggest that low prolactin secretion may be a trait characteristic in seasonal affective disorder.

Adult↗
PubMed1989

[Primary hyperparathyroidism: usefulness of high resolution echography in local diagnosis].

Recent reports show a better surgical outcome in primary hyperparathyroidism when an accurate preoperative localization of the lesion in available. We performed high resolution sonography in 23 consecutive patients (20 women) with biochemically proven hyperparathyroidism. Twenty two of them were operated on and their sonographic reports were compared to the surgical and pathological findings (20 adenomas, 1 carcinoma and 1 hyperplasia). One patient did not have surgery but the sonogram was compared to a Tl 201-Tc99 scintigram that suggested an adenoma. Sonography showed a single parathyroid tumor in 17 patients and failed to demonstrate a lesion in six. There were two false positives and 6 false negatives. The sensitivity was 71.5% and the positive predictive value was 88%. Three out of 6 patients with a negative sonography had an adenoma located out of reach for the method. Our results show that the high resolution sonography is a useful, non invasive method to localize abnormally enlarged parathyroid glands in hyperparathyroidism and we think it should be performed in every patient with a biochemical diagnosis of this disease.

Adult↗
PubMed1989

Efficacy of light support pantyhose.

The results of a multicenter, double-blind clinical trial indicate that the use of light support pantyhose significantly reduced the incidence of aches, swelling and fatigue in the lower legs of healthy women. A trend toward reduced foot and leg circumference was noted; however, it did not correlate significantly with subjective symptomatology.

Bandages↗
PubMed1988

GM1 ganglioside potentiates the effect of nerve growth factor in preventing vinblastine-induced sympathectomy in newborn rats.

The effects of vinblastine (VNB) and nerve growth factor (NGF) administrations were assessed on sympathetic nerve terminals by measuring the noradrenaline (NA) content in the heart, spleen and kidneys of developing animals. Six-day-old rats, treated with 0.15 mg/kg VNB on postnatal day 3 (P3) showed a dramatic decrease of NA content in all these organs. This reduction was prevented by daily administrations of NGF on P3, P4 and P5. The effectiveness of NGF in inhibiting the VNB-induced sympathectomy was related to the dose administered and to the time interval between the VNB administration and the first NGF injection given on P3. Dose-response curves to NGF (ranging from 0.01 to 0.5 mg/kg) were obtained in both heart and spleen of VNB-treated animals. Thus, this experimental paradigm provides a quantitative assessment of the NGF activity in vivo. The systemic administration of GM1 (30 mg/kg) on P3, P4 and P5, was able to potentiate the NGF activity in preventing the VNB-induced sympathectomy. This GM1 effect was more evident in the heart and may be, at least in part, attributed to increased NGF prevention of neuronal cell death due to VNB. These results suggest an in vivo interaction between exogenous GM1 and NGF and are consistent with the view that neuronal cell repair related to in vivo administration of this ganglioside may rely on its capability to modulate the activity of endogenously occurring neuronotrophic factors.

Adrenergic Fibers↗
PubMed1988

A role for gangliosides in astroglial cell differentiation in vitro.

Rat cerebral astroglial cells in culture display specific morphological and biochemical behaviors in response to exogenously added gangliosides. To examine a potential function for endogenous gangliosides in the processes of astroglial cell differentiation, we have used the B subunit of cholera toxin as a ganglioside-specific probe. The B subunit, which is multivalent and binds specifically to GM1 ganglioside on the cell surface, induced a classical star-shaped (stellate) morphology in the astroglial cells and inhibited DNA synthesis in a dose-dependent manner. The morphological response was massive and complete within 2 h, with an ED50 of 0.8 nM, and appeared to depend on the direct interaction of the B subunit with GM1 on the cell surface. A B subunit-evoked inhibition of DNA synthesis and cell division (ED50 = 0.2 nM) was observed when the cells were stimulated with defined mitogens, such as epidermal growth factor and basic fibroblast growth factor. Maximal inhibition approached 80% within 24 h. The effects of the B subunit were unrelated to increases in cAMP. These observations, taken together with previous studies, demonstrate that both endogenously occurring plasma membrane gangliosides and exogenously supplied gangliosides can influence the differentiative state (as judged by morphological and growth behaviors) of astroglial cells in vitro.

Animals↗
PubMed1988

Inhibition of DNA synthesis in C6 glioma cells following cellular incorporation of GM1 ganglioside and choleragenoid exposure.

The B subunit of cholera toxin, which is multivalent and binds specifically to GM1 ganglioside on the cell surface, has previously been used as a ganglioside-specific probe to regulate DNA synthesis in thymocytes and fibroblasts. To explore in more detail this growth-regulatory action of gangliosides, C6 glioma cells (which are GM1 ganglioside deficient) were used as a model system. When cultures of C6 cells were first treated with GM1, followed by exposure to the B subunit, proliferation was inhibited, as measured by 3H-labeled thymidine incorporation into DNA. Pretreatment of the cells with 50 microM GM1 for 15 min (followed by washing with fetal calf serum) and incubation with 1 microgram/ml of B subunit for 21 h was sufficient to reduce DNA synthesis to 15% of control values (and confirmed by autoradiographic analysis), although maximal inhibition could be achieved with as little as 30 min exposure to B, followed by washing. Furthermore, the B subunit inhibited the response of the C6 cells to basic fibroblast growth factor only following GM1 pretreatment. The B subunit-induced inhibition of DNA synthesis was specific for the ganglioside GM1, and was unrelated to increases of cyclic AMP. These results demonstrate that cell-incorporated GM1 ganglioside may act as a receptor capable of undergoing a specific ligand interaction, subsequently affecting molecular processes at the nuclear level.

Animals↗
PubMed1988

Complications of plasma exchange in the treatment of polyarteritis nodosa and Churg-Strauss angiitis and the contribution of adjuvant immunosuppressive therapy: a randomized trial in 72 patients.

We recorded side effects and other complications of 813 plasma exchanges used in early treatment of polyarteritis nodosa and Churg-Strauss angiitis in a prospective study of 72 patients (22-75 years old). All the patients were also treated with a corticosteroid (1 mg/kg/day), and half were included in a randomized trial of cyclophosphamide (2 mg/kg/day during 1 year). Centrifugation was used in 678 plasma exchange sessions (83.4%) and filtration in 128 (15.7%) (no data were available about the technique used in seven cases). The replacement fluid in 745 sessions was 4% albumin and in 115 was fresh-frozen plasma; eight patients received both (47 sessions). Two hundred and fifty-one complications were reported in 60 patients during 206 (25.3%) of the 813 completed exchanges; 47 sessions (5.8%) were temporarily stopped as a result of complications. The most common problems were technical difficulties (in 90 sessions), moderate or severe hypotension (in 52), and allergy to the replacement fluid (in 51). Hepatitis B antigen appeared in one patient. In four patients, plasma exchange was stopped permanently because of the severe side effects. No patient died during a session. Twelve of the 72 patients died during the study, six in each of the two groups. In the group treated by a combination of corticosteroid and plasma exchange, deaths were related to the deleterious effects of the disease itself and occurred after 12.8 +/- 11.1 months (1-26 months). In the group treated by the same combination plus cyclophosphamide, four of the six deaths were due to severe infections, which were related to leukopenia in three patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Pharmacokinetics of paracetamol, diclofenac and vidarabine during plasma exchange.

In order to establish guidelines for prescribing drugs in patients treated with plasma exchange (PE), we studied the pharmacokinetics of paracetamol (5 patients), diclofenac (4 patients) and vidarabine (3 patients) during one or several PE. Results were compared with those obtained without PE. Diclofenac and paracetamol were chosen because they presented different volume distribution and protein binding characteristics. Vidarabine was studied because we use it for the treatment of patients with polyarteritis nodosa related to hepatitis B virus. Diclofenac (100 mg) and paracetamol (1000 mg) were given 1 hour before PE. Samples were obtained 60 and 30 min before PE, every 15 min during PE and hourly for 2 hours after the end of PE. Vidarabine was given in continuous infusion, 15 mg/kg/d during the first week of treatment and 7.5 mg/kg/d during subsequent weeks. Samples were obtained before PE, 3 times during PE and every 30 min for 4 hours after the end of PE. Paracetamol, diclofenac, vidarabine and hypoxanthine arabinoside were assayed by high performance liquid chromatography. During each PE 60 ml/kg were removed and replaced by albumin. We found that 17% of diclofenac, 4.3% of paracetamol and 4.9% of vidarabine were removed during each session. Plasmapheresis clearance was 51% of plasma clearance for diclofenac, 15% for paracetamol and 10% for vidarabine. Drugs which are mainly removed during PE are those which are bound to proteins with a small distribution volume. Those drugs, such as diclofenac, must be administered after the end of each PE session. Drugs which present a large distribution volume and low protein binding can be given before the session. Vidarabine can be administered during PE without loss of effectiveness due to drug removal.

Acetaminophen↗
PubMed1988

Development and survival of neurons in dissociated fetal mesencephalic serum-free cell cultures: II. Modulatory effects of gangliosides.

This paper analyzes the effects of exogenously supplied GM1 on the development, i.e., specific neurotransmitter uptake capability and survival, of the dopaminergic neurons present in fetal mouse-dissociated mesencephalic cells. Exogenous GM1, but not asialo-GM1, sialic acid, or the oligosaccharide chain of GM1, enhances in a time- and concentration-dependent manner the specific 3H-dopamine uptake (increase of the apparent Vmax and decrease of the apparent Km value) and the long-term survival of the dopaminergic neurons. The GM1 effects on the behavior of the dopaminergic neurons require the presence of cell-derived neuronotrophic influences present within the culture system and are associated with an increase in the response of the cells to the trophic influences. GM1 effects are not limited to dopaminergic neurons, and depend on the stable association of the ganglioside molecule with the cells. It is suggested that GM1 is not a trophic agent per se, but rather potentiates neuronotrophic activities and/or exerts independent influences to which neurons respond only if appropriately supported.

Animals↗
PubMed1987

Voltage-dependent activation and inactivation of calcium channels in PC12 cells. Correlation with neurotransmitter release.

The existence and mechanisms of inactivation of voltage-gated Ca2+ channels are important, but still debatable, physiological problems. By using the Ca2+ indicators quin2 and fura-2, we demonstrate that in PC12 cells voltage-gated Ca2+ channels undergo inactivation dependent on both voltage and [Ca2+]i. Inactivation, however, is never complete and a small number of channels remains open during prolonged depolarization, explaining the steady state elevation of [Ca2+]i observed in cells depolarized with high KCl. A close parallel exists between Ca2+ channel inactivation and the transient nature of neurotransmitter release: secretion is rapidly stimulated during the first 30 s of depolarization, when a transient overshoot in [Ca2+]i can be demonstrated, while it is negligible during the following period, despite the persistence of an elevated [Ca2+]i; predepolarization in Ca2+-free medium and subsequent addition of Ca2+ (a condition which allows the development of the voltage inactivation) abolishes the fast phase of secretion, while not modifying the steady state [Ca2+]i eventually attained; and increases in the intracellular Ca2+ buffering decreases the amplitude of the fast secretion phase induced by KCl without altering the steady state [Ca2+]i. We suggest that localized [Ca2+]i gradients form close to the plasma membrane shortly after depolarization and that the [Ca2+]i reached in these regions is the relevant parameter in the regulation of secretion.

Adrenal Gland Neoplasms↗
PubMed1987

Selective enhancement of tubulin gene expression and increase in oligo(dT)-bound RNA in the rat brain after nigrostriatal pathway unilateral lesion and treatment with ganglioside.

Partial hemitransection of the rat nigrostriatal pathway has been applied to study changes in the expression of tubulin and actin cytoskeletal genes. RNA was isolated from ipsilateral and contralateral structures of substantia nigra and striatum tissues of lesioned or sham-operated animals by a combined proteinase K and oligo(dT)-cellulose affinity purification procedure. A significant increase in the oligo(dT)-cellulose-eluted RNA was observed in the lesioned substantia nigra and striatal tissues compared to naive controls. By 5 days, the RNA content of the lesioned nigra reached a value of 96-114.5 micrograms/mg DNA compared to 45.7-52.9 micrograms/mg DNA. Administration of GM1 gangliosides at daily intervals resulted by day 5 in a further increase (131.8-141.5 micrograms/mg DNA) in the RNA content of the lesioned but also of the sham-operated (81.9-97.8 micrograms/mg DNA) animals. By 18 hr, the lesioned nigra exhibited a four-fold increase in tubulin messenger RNA (mRNAtub) gene expression in comparison to the sham-operated animals. The substantia nigra tissue of GM1-treated animals exhibited a hybridization value for mRNAtub twice as high compared to GM1-untreated, lesioned animals. The effect of GM1 appeared selective for alpha-tubulin and beta-tubulin compared to actin transcript. The latter was also elevated in the lesioned nigra tissue above the naive or sham-operated animals. The data suggest that, after injury, cytoskeletal RNA transcripts are elevated and that GM1 may play a role in the regulation of their steady-state levels.

Animals↗
PubMed1987

Complexity of the influence of gangliosides on histamine release from human basophils and rat mast cells.

The influence of exogenous addition of gangliosides on histamine release from human basophils and rat mast cells was examined in vitro. Gangliosides dose-dependently inhibited histamine release, and this inhibition was dependent on the ganglioside sialic acid content, since GT1b, having 3 sialic acid moieties, was more potent than gangliosides with 2 moieties (GD1a and GD1b), which again were more potent inhibitors than GM1 with one moiety. Asialo-GM1 was without effect. In high concentrations the gangliosides potentiated basophil histamine release. The modulation of histamine release was reflected in the sensitivity of the cells to extracellular calcium, since inhibition of the release could be counteracted by increasing the extracellular concentration of calcium.

Animals↗
PubMed1987

Membrane sialic acid influences basophil histamine release by interfering with calcium dependence.

The influence of the cell membrane content of sialic acid on basophil histamine release was examined in vitro in allergic patients and normal controls. Enzymatical removal of sialic acid enhanced histamine release induced by allergen and anti-IgE, whereas an increase in membrane sialic acid content by insertion of sialic acid containing gangliosides into the membrane inhibited the mediator release. The reduction in membrane sialic acid content abolished the inhibitory capacity of the calcium channel antagonist nimodipine, whereas the inhibition produced by verapamil and lanthanum was not affected. This difference, together with the previous finding that alterations in membrane sialic acid content is reflected in the cell sensitivity to extracellular calcium, suggest an interaction between membrane sialic acid and the calcium channels involved in basophil histamine release.

Basophils↗
PubMed1987

An early-onset retinal dystrophy with dominant inheritance in the Abyssinian cat. Clinical and pathological findings.

The clinical and pathological features of an early-onset autosomal dominant photoreceptor degeneration in the Abyssinian cat are described. Ophthalmoscopic evidence of retinal disease at 8-12 weeks of age was always preceded by marked dilatation of the pupils, impairment of the pupillary light reflex, and nystagmus. The electroretinogram was unrecordable in all but one of the affected individuals examined. Abnormal photoreceptor development was observed by both light and electron microscopy in retinas of a 22-day-old kitten; in this individual, no outer segment material was detected, and inner segments showed impaired development which was more severe towards the posterior pole. In a 40-day-old kitten, the inner segments were relatively well-formed, whereas the outer segments, though present, showed marked disorganization and degenerative change. The retinas of older individuals showed more advanced photoreceptor degeneration, with thinning of the neural retina. This early-onset retinopathy, which may be classified as a rod-cone dysplasia, is distinct from the hereditary retinal dystrophy (progressive retinal atrophy) previously described in this breed. The gene symbol Rdy has been adopted.

Animals↗
PubMed1986

Nerve growth factor activates Thy-1 and neurofilament gene transcription in rat PC12 cells.

The effect of nerve growth factor (NGF) on the expression of neurofilament and Thy-1 genes in rat PC12 pheochromocytoma cells was examined at both the transcriptional and post-transcriptional levels. Addition of NGF to cultured PC12 cells produced increases in mRNAs corresponding to the 68 kd neurofilament protein (NF68) and the Thy-1 glycoprotein within 24 h, with maximal effects of some 90- and 45-fold stimulation (relative to beta-actin mRNA) being observed after 12 and 4 days of treatment, respectively. In addition, transcriptional run-off analyses using isolated nuclei showed that NGF treatment resulted directly in 8- and 4-fold increases in the rate of NF68 and Thy-1 gene transcription. These gene activation events were independent of overt morphological differentiation of PC12 cells occurring both under conditions permissive and non-permissive for neurite outgrowth, and once established the new molecular phenotype was dependent upon the continued presence of NGF. This is the first molecular evidence for the reversible activation of neuron-specific genes during NGF-induced differentiation in PC12 cells.

Journal Article↗