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Biomedical subjects

M Lucas

Publications and source records attributed to M Lucas.

At least 145 records · Page 8Linked to original sources
PubMed1992

Decreased protein kinase C activity is associated with programmed cell death (apoptosis) in freshly isolated rat hepatocytes.

Apoptosis of freshly isolated rat hepatocytes was induced by either the omission of fetal bovine serum in the culture medium or addition of the protein kinase C inhibitors polymyxin B or staurosporine. The time-course of DNA breakdown into oligonucleosome-sized fragments and the activity of protein kinase C was determined. Hepatocytes were found to be sensitive to bleomycin which induced a high degree of DNA breakdown even within 30 min incubation. Both staurosporine and polymyxin B induced DNA degradation in hepatocytes after three hours incubation, an effect that was partially prevented by phorbol myristate acetate (PMA). After eight hours incubation, PMA failed to counteract this action and itself produced the apoptosis of rat hepatocytes. The results suggest the involvement of protein kinase C in hepatocyte survival.

Alkaloids↗
PubMed1992

European brown hare syndrome in the U.K.; a calicivirus related to but distinct from that of viral haemorrhagic disease in rabbits.

The virus recovered from cases of European brown hare syndrome in the U.K. contains one major capsid protein of approximately 60 k molecular weight and morphologically resembles known caliciviruses. It has been compared with a European isolate of rabbit haemorrhagic disease calicivirus and, although it shows some antigenic similarity, it is not identical. In transmission and protection studies the virus from U.K. hares failed to produce disease in rabbits and did not effectively protect against subsequent challenge with the rabbit calicivirus.

Animals↗
PubMed1992

Vasoactive intestinal peptide enhances phorbol myristate acetate-induced chemiluminescence in human lymphocytes.

Phorbol-myristate-acetate (PMA) induced in lymphocytes the production or reactive oxygen intermediates in a process which was stimulated by the presence of vasoactive intestinal peptide (VIP) in a dose-dependent response at VIP concentrations in the range 10(-11)-10(-8) M. The dissociation constant for the high-affinity receptors of VIP agreed with the ID50 of the activation of adenylate cyclase, and the ID50 for the stimulation by VIP of PMA-induced chemiluminescence, which were close to 0.2 nM VIP. Forskolin produced in lymphocytes an effect quite similar to VIP. A comparison of the response to VIP and forskolin of lymphocytes and monocytes showed that, in contrast to forskolin, VIP failed to induce the above described effect in monocytes. A possible mechanism involving protein kinase C, which is activated by PMA, and an intracellular signal linked to VIP receptors is pointed out. This study further supports a role for VIP as a mediator in the neuroimmune system.

Adenylyl Cyclases↗
PubMed1992

Pancreastatin increases cytosolic Ca2+ in insulin secreting RINm5F cells.

We have investigated the effect of pancreastatin on cytosolic Ca2+ concentration in the insulin secreting cell line RINm5F. Changes in [Ca2+]i induced by pancreastatin were detected by Fluo-3 fluorescence using both flow cytometry and batch analysis measurements, and turned out to be from 90 to 315 nM equivalent to 80% of that caused by ATP, which increased [Ca2+]i from 90 nM to 400 nM. This effect of pancreastatin did not depend on extracellular calcium and was not mediated by alpha-adrenergic receptors since it was not prevented by the alpha-blocker yohimbine. It is concluded that pancreastatin has a role in the homeostasis of free cytosolic calcium in the insulin secreting cell line Rinm5F.

Adenosine Triphosphate↗
PubMed1992

Pancreastatin and its 33-49 C-terminal fragment inhibit glucagon-stimulated insulin in vivo.

1. Pancreastatin, a 49 amino acid peptide derived from chromogranin A, has been shown to have an inhibitory effect on insulin secretion in the perfused pancreas and isolated islets. 2. We have studied the effect of pancreastatin on glucagon-stimulated insulin release and the hyperglycemic of glucagon effect in vivo. 3. When administered in the mesenteric vein, pancreastatin inhibited the increase in insulin levels induced by glucagon stimulation, thereby potentiating the hyperglycemic effect of glucagon. 4. This study describes a regulatory role of pancreastatin on glucagon-induced insulin release in vivo.

Animals↗
PubMed1992

Activation of the gene encoding the glycolytic enzyme beta-enolase during early myogenesis precedes an increased expression during fetal muscle development.

We define the spatial and temporal patterns of expression of the gene encoding the glycolytic enzyme, beta-enolase, during mouse ontogenesis. Transcripts were detected by in situ hybridization using 35S labelled cRNA probes. The beta-enolase gene is expressed only in striated muscles. It is first detected in the embryo, in the cardiac tube and in newly formed myotomes. In the muscle masses of the limb, beta gene expression occurs at a low level in primary fibers, and subsequently greatly increases at a time which corresponds to the onset of innervation and secondary fiber formation. Later in development, it becomes undetectable in slow-twitch fibers. Our results demonstrate the multistep regulation of the beta-enolase gene. The regulation of this muscle-specific gene in somites is discussed in terms of the myogenic sequences of the MyoD family shown to be present when it is activated.

Animals↗
PubMed1992

RP 62203, a 5-hydroxytryptamine2 antagonist, enhances deep NREM sleep in rats.

RP 62203, a naphtosultam derivative, is an antagonist at the 5-hydroxytryptamine2 (HT2) receptor. The sleep pattern of rats treated orally with RP 62203 was studied at doses ranging from 0.5 to 4 mg/kg. Following RP 62203 administration, the duration of deep nonrapid eye movement (NREM) sleep was found to increase at the expense of wakefulness in a dose-dependent manner from 0.5 mg/kg. The 5-HT2 receptor agonist DOI and the 5-HT1a receptor agonist 8 OH-DPAT induced a dose-related increase in wakefulness; treatment with RP 62203 reversed the enhancement of wakefulness produced by DOI but not that produced by 8 OH-DPAT. These data provide further evidence for the involvement of 5-HT2 receptors in the regulation of NREM sleep in rats. RP 62203 could therefore be of clinical interest in the management of sleep disorders, particularly those developing within a psychiatric context.

Animals↗
PubMed1992

Modulation of embryonic and muscle-specific enolase gene products in the developing mouse hindlimb.

During striated muscle development, the glycolytic enzyme enolase (EC 4.2.1.11) undergoes an isozymic transition, from the embryonic alpha alpha form towards the muscle-specific forms alpha beta and beta beta. The regulation of this transition was analyzed in mouse hindlimb muscles from embryonic day 15 (E15) to the adult stage. The quantitative modulations of the levels of the transcripts and subunits of alpha and beta enolase genes were determined. The absolute amounts of alpha and beta enolase mRNAs were estimated using in vitro synthesized transcripts as calibration standards, thus allowing an evaluation of their relative contribution at each stage examined. The muscle-specific beta enolase mRNA is already present at E15. Its level then increases and, from E17, this transcript becomes predominant. This accumulation is biphasic: a steep prenatal rise, corresponding to a net increase per fiber, accompanies the formation of secondary myofibers and the development of innervation; a second rise, beginning at postnatal day 5, is temporally correlated with the definitive specialization of the myofibers. Most of the decrease in alpha mRNA level occurs postnatally. No temporal or quantitative correlation between the up-regulation of beta mRNA and the down-regulation of alpha mRNA levels is observed throughout hindlimb muscle development. Quantitative immunoblotting analyses carried out in parallel show that the enolase isozymic transition is mainly controlled at the mRNA level.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

[Collagenous colitis: clinical and histologic improvement after sulfasalazine and topical betamethasone].

We here by report a case of a 42 year-old white woman with an eight-year history of watery diarrhea where the rectal biopsies performed in endoscopically normal mucosa led to the diagnosis of collagenous colitis, characterized histologically by a thickening of the colonic subepithelial basement membrane. A brief review of the current etiopathogenic concepts of this entity is done and the importance of performing rectal biopsies in patients with unexplained diarrhea and normal appearing colon mucosa is stressed. A clinical improvement following therapy with Sulfasalazine and Beta-methasone enemas was found in this patient. We discuss the current views on the therapy and the difficulties of assessing responses to drugs in this condition.

Administration, Topical↗
PubMed1992

Educational outcome of neonatal intensive care graduates.

Studies of developmental outcome of neonatal intensive care unit graduates have generally been limited to the first 2 to 3 years of life, with outcome determined by psychometric tests. This study followed neonatal intensive care unit graduates born 1975 through 1983 (n = 457) into the public school system and compared their educational outcomes with those of newborn nursery graduates (n = 656). Outcomes were evaluated by placement in four academic categories: regular classroom, academic problems, speech/language impairment, and major impairment. Educational outcomes for children of both groups were essentially the same. Their placement in the four academic categories were equally affected by nonmedical variables, primarily income (below/above poverty level), race, and sex. Seventy percent of poverty-level children were in one of the three problem categories, compared with 40% of children above poverty level. Neither neonatal intensive care unit treatment nor low birth weight were major predictors of educational outcome. The only clear-cut neonatal intensive care unit effect occurred among children born with sensory or physical impairments. Therefore, in order to reduce poor educational outcomes, follow-up and intervention programs should be targeted primarily to children with diagnosable handicaps and from minority, low-income families.

Child↗
PubMed1991

Are 5-HT2 antagonists endowed with anxiolytic properties in rodents?

The precise role of serotonin (5-HT) in anxiety remains unclear. We report here on the effects of RP 62203, a new 5-HT2 antagonist, and ritanserin in different animal models of anxiety. In the elevated plus-maze in mice, RP 62203 increased dose-dependently the percentage of entries onto, and time spent on open arms, over the dose range 0.25-4 mg.kg-1 p.o. By contrast, ritanserin was ineffective up to the dose of 4 mg.kg-1 p.o. In addition, both compounds were tested against the anxiogenic compound FG 7142 (20 mg.kg-1, i.p.) in the plus-maze test in mice and via electrocorticographic recordings (ECoG) in rats. The anxiolytic effect of RP 62203 is antagonized by FG 7142 at a dose devoid of anxiogenic properties. A similar interaction between RP 62203 and FG 7142 is observed in ECoG studies. In contrast, ritanserin seemed to potentiate the anxiogenic and awakening activities of FG 7142. These results demonstrate that RP 62203, a selective 5-HT2 antagonist, possesses anxiolytic properties in rodents suggesting that 5-HT2 receptors are involved in the control of anxiety.

Animals↗
PubMed1991

Opposite effect of cytochalasin B on agonist-induced respiratory burst in neutrophils and monocytes.

The effects of cytochalasin B on the respiratory burst, calcium transients and cell shape change of neutrophils and monocytes has been studied. Cytochalasin B enhanced fMLP-induced respiratory burst in neutrophils whereas the opposite effect, i.e. an inhibition close to 50%, was elicited in fMLP-stimulated monocytes. The differences did not depend on calcium homeostasis. On the basis of cell shape changes, and the well known effect of cytochalasin B on actin polymerization, the opposite effects of cytochalasin B could stem from differences between both cell types concerning the pattern of cytoskeleton-membrane interaction which could affect the recruitment and assembly of membrane-bound or cytosolic components of NADPH-oxidase.

Calcium↗
PubMed1991

Induction of programmed cell death (apoptosis) in mature lymphocytes.

The apoptosis of human peripheral blood lymphocytes was analyzed by the breakdown of DNA into oligonucleosome-sized fragments. The mature lymphocytes were rendered sensitive to apoptosis by either the omission of fetal bovine serum in the culture medium or the addition of polymyxin B. In the first case it was counteracted by phorbol myristate acetate. The possible involvement of protein kinase C in cell survival is pointed out.

Blood↗
PubMed1991

Effect of tumour-promoting phorbol ester on calcium homeostasis in human platelets.

The more interesting features of the effects or PMA on [Ca2+]i and ATP release were the following: 1. preincubation with PMA inhibited thrombin-evoked calcium transients; 2. PMA stimulated slightly the release of calcium and ATP whereas inhibited calcium and ATP pools sensitive to thrombin; 3. A23187 reversed the inhibitory effect of PMA; 4. subsaturating thrombin concentrations gave results similar to PMA on thrombin-induced calcium and ATP release but not on [Ca2+]i.

Adenosine Triphosphate↗
PubMed1991

[Blood pressure with physical stress (ergometry) of 105 normotensive, borderline hypertensive and hypertensive children and adolescents].

Hypertension is one of the principal risk factors for cardiovascular diseases; its roots go back to childhood. A load study such as ergometry can help to recognise which persons are at risk. Ergometric measurements were performed by us on 105 children and adolescents, 72 of whom had borderline hypertensive or hypertensive blood pressure levels. Of these, the blood pressure rose during stress in 14%, the proportionate share being independent of the physical activity of the subjects. However, among those whose hypertension was on a borderline level, there was a disproportionately large percentage of obese subjects. These showed in addition an increase in blood pressure with increasing load and a reduced physical performance range. Obesity and lack of physical mobility had an unfavourable influence on blood pressure. Unfortunately there are no standardised rules for assessing the blood pressure during stress in children and adolescents. This would be all the more desirable since this easy examination is of prognostic value for an early discovery of manifest hypertension.

Adolescent↗