Actions of Somatostatin on Rat Neocortical Neurons in vitro

The effects of somatostatin (SS14) on neocortical neurons of the rat were investigated in an in vitro slice preparation. Intracellular recordings were performed in neurons (n=30) in layers 2 and 3 of the frontal cortex. Iontophoretically applied SS14 reduced the responses evoked by iontophoretically applied L-glutamate (GLU) and gamma-aminobutyric acid (GABA). The blocking effect of SS14 was apparent 1 - 2 min after onset of SS14 application and recovery required 2 - 3 min. The conductance increase evoked by GLU or GABA was reduced by SS14. In the majority of neurons, SS14 did not produce any measurable changes in passive membrane properties, spike threshold or on orthodromically evoked synaptic potentials. In 5 cells, SS14 induced a slight hyperpolarization (<3 mV). These results lend further support to claims that SS14 plays a neuromodulatory role in the neocortex.

Pharmacological profile of nicotinic acetylcholine receptors in the rat prefrontal cortex: an electrophysiological study in a slice preparation

The specificity of nicotinic receptors in the neocortex has been questioned previously because: (i) electrophysiological responses to nicotine could not be blocked by nicotinic antagonists, and (ii) the effect of nicotine was not mimicked by acetylcholine. In the present study, the presence of functional nicotinic receptors in rat neocortex has been assessed in a slice preparation of prefrontal cortex, using evoked field potential and unit recordings. Nicotine and the nicotinic agonists, dimethylphenylpiperazinium, cytisine, acetylthiocholine, applied by iontophoresis, produced an increase in the negative wave of field potentials, reflecting an increased excitability of cortical neurons. This effect was blocked by the selective probe for neuronal nicotinic receptors Toxin F (1.4 microM in the perfusion medium) and by dihydro-beta-erythroidine (100 microM). Alpha-bungarotoxin, the blocker of skeletal muscle acetylcholine receptor had no effect. Iontophoretically applied acetylcholine, muscarine and pilocarpine, on the other hand, produced a decrease in the field potential amplitude, which was blocked by atropine and scopolamine (1-10 microM). In the presence of eserine (10 microM), the muscarinic effect of acetylcholine was dramatically altered, leading to the development of a nicotinic response sensitive to Toxin F. Thus, the physiological activation of nicotinic receptors in rat prefrontal cortex appears to require higher concentrations of acetylcholine than do muscarinic receptors. Our results show that: (i) the rat prefrontal cortex possesses functional nicotinic receptors with a pharmacological profile clearly distinct from muscle receptors, and (ii) a nicotinic effect of acetylcholine can be revealed when its degradation by acetylcholinesterase is inhibited.

Human T lymphotropic virus I infection deregulates surface expression of the transferrin receptor

Human T-lymphotropic virus I (HTLV-I) is an etiologic agent in adult T cell leukemia. In an effort to understand the relationship between HTLV-I infection and malignant transformation, we have examined transferrin receptor expression in HTLV-I-infected cells. Transferrin receptor expression in normal T cells is tightly regulated and essential for cell proliferation. We have used matched T cell sets originating from a normal donor, consisting of tetanus toxoid-specific normal T cell clones (TM3 and TM5) and their in vitro HTLV-I-infected counterparts (TM3H and TM5H). Using these matched sets of virus-infected and normal T cells, we have determined that HTLV-I infection leads to hyperexpression of surface transferrin receptors (five- to six-fold higher than normal counterparts). Although the growth rates of the virus-infected cells did not differ significantly from their normal controls, HTLV-I-infected cells constitutively hyperexpressed surface transferrin receptors, whereas the level of surface receptor expression of normal counterpart cells varied during the cycle of antigenic stimulation. Immunoprecipitation of total (surface plus cytoplasmic) transferrin expression showed that the HTLV-I-infected cells did not possess a greater total number of transferrin receptors than their normal counterparts. This data was supported by Northern blot analysis, which showed equivalent transferrin receptor mRNA expression in HTLV-I-infected and uninfected cells. Functional analysis revealed a marked defect in 59Fe-transferrin internalization in the HTLV-I-infected cells. Furthermore, the HTLV-I-infected cells showed markedly decreased transferrin receptor phosphorylation and internalization in response to active phorbol ester. Thus the data demonstrate that in peripheral blood T cells, HTLV-I infection is accompanied by surface transferrin receptor overexpression secondary to subcellular redistribution and defective internalization.

Human T lymphotropic virus I infection deregulates surface expression of the transferrin receptor

Human T-lymphotropic virus I (HTLV-I) is an etiologic agent in adult T cell leukemia. In an effort to understand the relationship between HTLV-I infection and malignant transformation, we have examined transferrin receptor expression in HTLV-I-infected cells. Transferrin receptor expression in normal T cells is tightly regulated and essential for cell proliferation. We have used matched T cell sets originating from a normal donor, consisting of tetanus toxoid-specific normal T cell clones (TM3 and TM5) and their in vitro HTLV-I-infected counterparts (TM3H and TM5H). Using these matched sets of virus-infected and normal T cells, we have determined that HTLV-I infection leads to hyperexpression of surface transferrin receptors (five- to six-fold higher than normal counterparts). Although the growth rates of the virus-infected cells did not differ significantly from their normal controls, HTLV-I-infected cells constitutively hyperexpressed surface transferrin receptors, whereas the level of surface receptor expression of normal counterpart cells varied during the cycle of antigenic stimulation. Immunoprecipitation of total (surface plus cytoplasmic) transferrin expression showed that the HTLV-I-infected cells did not possess a greater total number of transferrin receptors than their normal counterparts. This data was supported by Northern blot analysis, which showed equivalent transferrin receptor mRNA expression in HTLV-I-infected and uninfected cells. Functional analysis revealed a marked defect in 59Fe-transferrin internalization in the HTLV-I-infected cells. Furthermore, the HTLV-I-infected cells showed markedly decreased transferrin receptor phosphorylation and internalization in response to active phorbol ester. Thus the data demonstrate that in peripheral blood T cells, HTLV-I infection is accompanied by surface transferrin receptor overexpression secondary to subcellular redistribution and defective internalization.

Chemical Waves

Spatial structures may occur in nonlinear systems far from equilibrium. Chemical waves, which are concentration variations of chemical species propagating in a system, are an example of such structures. A survey is given of some experiments on chemical waves by spectroscopic and microphotographic techniques, arranged according to different types of waves, different geometries, and various properties.

[Tobacco detoxication by acupuncture and group psychotherapy]

In the out-patient tobacco detoxication unit created, in 1977, within the pneumology department of the Hôtel-Dieu hospital, Paris, the method used is a combination of acupuncture and group psychotherapy. Its effectiveness has been evaluated, over a 2-year period, by means of a questionnaire mailed to each patient and followed, if necessary, by up to 3 reminders. A computer-assisted assessment of the data thus collected provided a follow-up of varying duration of the 555 patients concerned; 488 patients were treated, then contacted, and 371 (76 p. 100) answered the questionnaire. Weaning--defined here as complete detoxication with a 2 to 28 months follow-up when the questionnaire was filled--was obtained in 24 p. 100 of the patients who answered. Other evaluation criteria would have given figures ranging from 18 p. 100 to 58.6 p. 100. The main reason for failure mentioned by the patients was lack of will. An exhaustive study of 84 publications concerning more than 10,000 candidates to weaning showed that similar results are obtained with several types of psychotherapy, acupuncture and auriculotherapy: a success rate of about 60 p. 100 at the end of treatment, 40 p. 100 at 3 months and 30 p. 100 at 6 months and one year. The results obtained with drugs are not as good, perhaps because their use betrays a lesser desire to give up smoking.

Corticosterone reduces the excitability of hippocampal pyramidal cells in vitro

In the rat brain, the hippocampus (HC) is a major target area for corticosterone (CT). In this study, we investigated the effects of CT in the in vitro slice preparation of the rat HC. Population spikes (PS) evoked by stratum radiatum stimulation were recorded in CA1. Bath-applied CT (10(-7)-10(-5) M) induced a decrease in the PS amplitude. This effect occurred within 10-15 min after the onset of CT perfusion, reached a plateau after 20-40 min and was reversible after 20 min washout. Neither dexamethasone (10(-5) M) nor vehicle produced any significant change in PS amplitude. Paired-pulse stimulation showed that the degree of inhibition of the second PS produced by the conditioning stimulus was either unchanged or decreased by CT. In the latter case, CT also reduced the inhibitory effect of gamma-aminobutyric acid on PS and enhanced the excitatory action of the opioid peptide D-Ala2-D-Leu5-enkephalin. These results show that CT reduces the excitability of HC pyramidal cells with a time course which may be compatible with a genomic action of CT. The fact that paired-pulse inhibition was either not changed or reduced, suggests that the decrease in PS size by CT is not due to an indirect excitatory effect of CT on inhibitory interneurons. Instead, CT may hyperpolarize pyramidal cells thus lowering their excitability and depressing the interneurons involved in recurrent inhibition.

Phorbol ester-induced surface transferrin receptor modulation. No correlation with decreased cell proliferation

Both phorbol ester or diacylglycerol (DAG) reduce cell surface transferrin receptor (TFR) number in CEM cells (a human T-cell acute lymphoblastic leukemia line) and HL-60 cells (a human promyelocytic leukemia cell line). This effect occurs with a t1/2 of approx. 30 min and is mimicked by addition of phospholipase C to cell cultures. Although cell surface TFR number is reduced to 25-30% of the control level 5 h after phorbol ester administration, apparent cell proliferation (as measured by [3H]thymidine incorporation) remains unaffected. Although independent of extracellular calcium (EGTA is slightly enhancing), the phenomenon is completely blocked by 30-min pretreatment with the calcium channel blocker diltiazem. Dilitazem pretreatment, while preventing receptor redistribution, does not completely block the phorbol ester-induced increase in TFR phosphorylation thought to be associated with receptor redistribution. Thus, calcium channel blockade effectively dissociates the effects of tetradecanoylphorbol acetate (TPA) on TFR internalization and phosphorylation. Our results also demonstrate that phorbol ester-induced effects on the TFR can be mimicked by the endogenous stimulator of protein kinase C, DAG, whether added directly to cultures or produced by the cells in response to exogenous phospholipase C. Furthermore, the phenomenon of TFR redistribution here described is not associated with a decreased proliferative capacity.

Effects of dynorphin A (1-17), dynorphin A (1-13) and D-ala2-D-leu5-enkephalin on the excitability of pyramidal cells in CA1 and CA2 of the rat hippocampus in vitro

The effects of D-ala2-D-leu5-enkephalin (DADL), dynorphin (DYN) A (1-17), and DYN A (1-13) on the excitability of hippocampal (HC) pyramidal cells in CA1 and CA2 were compared in an in vitro preparation of the rat. DADL and DYN A (1-13) increased the size of the population spike (PS) evoked in CA1 and CA2 by stimulation of the stratum radiatum. Paired-pulse stimulation showed that both peptides decreased the inhibition produced by the conditioning stimulus. These effects were naloxone-reversible. DYN A (1-17) decreased the PS in CA2 and increased the inhibition evoked by the conditioning stimulus. When applied in the same concentration-range, the depressant effects of DYN A (1-17) were more pronounced in CA1 than in CA2 and not naloxone-reversible. DYN A (1-17) reduced the excitatory effects of DADL. Low concentrations of DYN A (1-17) (0.1 nM) produced, like DYN A (1-13) and DADL, an increase in the PS in CA1 in the majority of tests. The present data suggest that DYN A (1-17) shows the excitatory action of other opioids HC pyramidal cells only at low concentration.

Regulation of body temperature and nociception induced by non-noxious stress in rat

The effects of 3 different non-noxious stressors on body temperature (Tb) were investigated in the rat: (1) loose restraint in cylinders, (2) removal of the rats from cylinders, exposure to a novel environment and replacement in cylinders, a stressor called here 'novelty', and (3) gentle holding of the rats by the nape of the neck. Loose restraint and 'novelty' produced hyperthermia. On the contrary, holding induced hypothermia. Hypophysectomy (HX) reduced basal Tb, abolished restraint hyperthermia and reduced both 'novelty' hyperthermia and holding hypothermia. Dexamethasone ( DEXA ) had no effect upon either restraint or novelty hyperthermia but reduced the hypothermia. Naloxone (Nx) produced a slight fall in basal Tb accounting for its reduction of restraint and 'novelty' hyperthermias ; it did not affect holding hypothermia. The inhibitory effects of HX suggest a participation of the pituitary in the hyperthermias ; the neurointermediate lobe would be involved as the hyperthermias were not affected by DEXA , which is known to block the stress-induced release of pituitary secretions from the anterior lobe but not from the neurointermediate lobe. In contrast, substances from the anterior lobe might participate in hypothermia due to holding since it is reduced by HX and DEXA . As to the effects of Nx, endogenous opioids would not be significantly involved in the thermic effects of the stressors used in this study; they might play, if any, only a minor role in the regulation of basal Tb. These results are compared with those previously obtained on nociception using the same non-noxious stressors. It emerges that, depending on the stressor, different types of association between thermoregulation and nociception may occur, i.e. hyperthermia with analgesia, hyperthermia with hyperalgesia and hypothermia with hyperalgesia.

[Development of human resources and the Plan of Action]

This article (whose first part was published in the previous issue of Educación Médica y Salud) concludes an exhaustive review of manpower development in the Americas. This part considers the specific measures in this field enunciated in the Plan of Action; these measures pertain to four main areas: planning and programming of human resources, training in priority areas, utilization of human resources, and educational technology. The author discusses the present and future possibilities and obstacles of each of these activities and the steps to be taken to bring needs into line with real situations. It is of paramount importance that the national health authorities clearly spell out their policies for the development of human resources in the health field within the framework of general development policies. Another point to be insisted upon is the multiprofessional and multidisciplinary training of the health team and the importance of the education-service-supervision function, which usually results in permanent and continuing education, which in turn optimizes the utilization of personnel. However, none of this will be possible without an appropriate education technology with which to innovate, analyze and refine the entire education process and so meet the needs of both society and the health services.

Hyper- and hypothermia induced by non-noxious stress: effects of naloxone, diazepam and gamma-acetylenic GABA

Rats subjected to non-noxious, anxiogenic stressors were found to exhibit either hyperthermia or hypothermia depending on the nature of the stressor. The present work examines the effects of naloxone (Nx), diazepam (DZP) and gamma-acetylenic GABA (AcG), an inhibitor of GABA catabolism, on these phenomena. Nx reduced stress hyperthermia and basal temperature by similar amounts; it did not affect stress hypothermia. DZP also reduced basal Tb but was able to completely inhibit and even reverse stress hyperthermia and to reduce stress hypothermia. The effects of AcG were similar to those of DZP. In conclusion, it appears that endogenous opioids are not involved in the thermic responses to our emotional stressors whereas GABA would be an important modulator. It is suggested that DZP, through a GABAergic link might inhibit the release of hyperthermic pituitary factors from the neurointermediate lobe and of hypothermic substances from the anterior lobe.

Hyperalgesia induced by non-noxious stress in the rat

Stress-induced analgesia is well known but the reverse phenomenon is poorly documented. In this work, hyperalgesia is described following stressful but non-noxious manipulations consisting of inescapable holding or exposure to a novel environment. Hypophysectomy (HX) and dexamethasone enhanced 'holding' hyperalgesia. In contrast, 'novelty' hyperalgesia was reduced by HX and not modified by dexamethasone. So, pituitary factors may respectively compensate and take part in stress hyperalgesia. Thus pain can be modulated in opposite directions by different types of stimulation: hyperalgesia would predominate after moderate, anxiogenic stress and analgesia after noxious and/or intense stress.

Stress hyperalgesia in rats: an experimental animal model of anxiogenic hyperalgesia in human

Emotional, non-noxious stress consisting of inescapable holding or exposure to novelty were found to produce clearcut and reproducible hyperalgesia in the rat. The mechanisms of the two stress hyperalgesia appeared to be different: 1) hypophysectomy enhanced holding hyperalgesia but reduced novelty hyperalgesia, indicating that pituitary factors respectively compensate (through opioids ?) and participate (through ACTH ?) in stress hyperalgesia; 2) diazepam did not alter holding hyperalgesia but abolished novelty hyperalgesia. The two types of stress hyperalgesia might represent animal models of anxiogenic hyperalgesia observed in human: as for clinical anxieties, they are alleviated or not by diazepam.

The effect of pituitary removal on pain regulation in the rat

The effects of hypophysectomy (HX) on pain regulation in basal and in various stressful situations were investigated in the rat. Pain sensitivity was assessed by measuring the thresholds of 3 nociceptive reactions (tail withdrawal, vocalization, vocalization afterdischarge) following electrical stimulation of the tail. The completeness of HX and the integrity of hypothalamus were verified in each HX rat. (1) Baseline pain thresholds were lower in HX rats than in sham-operated animals; (2) naloxone (Nx) hyperalgesia was only slightly altered by HX; (3) different types of stress induced different types of changes in nociception i.e. analgesia or hyperalgesia. The influence of HX varied according to the stress: it increased hyperalgesia, reduced analgesia, or had no effect at all. These results indicate that in the rat: (i) the pituitary participates in the regulation of basal pain sensitivity, probably through analgesic factors; (ii) Nx hyperalgesia results essentially from an antagonism of endogenous opioids originating in the CNS and not in the pituitary; and (iii) the pain regulatory processes engaged in adaptation to stressful stimuli involve the CNS and the pituitary in variable proportions depending upon the nature of the stress.