Nailing of Layers: A Promising Way to Reinforce Concrete 3D Printing Structures.

Today, the extrusion-based 3D printing of concrete is a potential breakthrough technology for the construction industry. It is expected that 3D printing will reduce the cost of construction of civil engineering structures (removal of formwork) and lead to a significant reduction in time and improve working environment conditions. Following the use of this additive manufacturing layer-wise process, it is required to change the way concrete structures are designed and reinforced, especially for the parts of the structure under tension loads. Indeed, the extrusion-based concrete 3D printing process does not allow for the production of conventional reinforced concrete, and there is a need to develop other ways of compensating for the low mechanical performances of concrete, particularly in tension. In this study, the reinforcement of printed structures by using steel nails through the deposited layers of fresh concrete was investigated. Additionally, three-layer and 10-layer samples were reinforced with nails with varying inclination and spacing. The results show that inclined nails can be used to provide a flexural strengthening of the printing material in different directions.

[Perinatal HIV transmission prophylaxis in the Liege region]. / Prophylaxie de la transmission périnatale du HIV en région liégeoise.

In Liège, since February 1994, Protocole ACTG 076 has been followed for prevention of perinatal transmission of VIH. The pregnant women are treated by AZT during pregnancy and delivery. The newborn is also treated during 6 weeks. Following this treatment strategy, vertical transmission rate of VIH has dropped from 25.6% to 8.7%. The PCR is particulary promising for the early detection of infection in newborn, but definitive conclusion about infective status of the newborn can't be done during the first week of life. The potential role of intrapartum transmission is now under evaluation in the hope to establish the safest mode of delivery.

[Multi-disciplinary approach to adolescents with problems. The Cholet experience]. / Approche polydisciplinaire d'adolescents en difficulté. L'expérience choletaise.

The authors report their experience of management of 12-18 years adolescents in the year 1987 using a multidisciplinary approach. Eighty adolescents were hospitalized in the adolescent ward (5 beds) of a pediatric unit (38 beds; 1,691 admissions). Follow-up was carried out in a specialized out-patient clinic (SOPC) (660 patients) in a common-place apartment lent by the town-hall. A day hospital (12 beds) was reserved for those patients presenting with more important psychological problems. The causes for hospitalization (64% of females, 36% of males) consisted for 1/3 of somatic problems and for 2/3 of psychological problems, of which 40% were suicide attempts. 70% of these adolescents were met again in the SOPC (36% by a pediatrician, 29% by the pedopsychiatric team). Such a structure, open towards the outside, working in a multifocal and multidisciplinary way but with the same care team allows, in spite of some difficulties and doubts, responding to the local needs and facing a more global management and a better follow-up of adolescents with difficulties.

Excitatory amino acids: role in morphine excitation in rat periaqueductal gray.

Morphine was previously found to elicit an explosive excitatory behavior following its injection at a high dose in the rat periaqueductal gray (PAG). This non-naloxone reversible excitatory action of morphine was mimicked by the GABAA receptor antagonist, bicuculline, suggesting that morphine excitation was due in part to GABAA receptor blockade. In this paper, we report that injections of the excitatory amino acid (EAA) analogues, N-methyl-D-aspartate (NMDA), quisqualate (Q) or kainate (K) in the rat PAG resulted in similar (but not identical) behaviors. The excitatory actions of morphine or of NMDA (but not Q or K) were blocked or attenuated by the NMDA receptor antagonist, 2-amino-7-phosphonoheptanoate. These results show that both GABAA receptors as well as receptors for the EAAs may contribute to the excitatory actions of morphine in the PAG, and suggest that GABA may normally function to counterbalance a tonic excitatory influence of the EAAs.

The NMDA receptor: central role in pain inhibition in rat periaqueductal gray.

An injection of the excitatory amino acid analogue, N-methyl-D-aspartate (NMDA), in the rat periaqueductal gray resulted in potent analgesia. A prior injection of the NMDA antagonist, (-)-2-amino-7-phosphonoheptanoate (D-AP7), antagonized this action, indicating a receptor-mediated action. NMDA given with morphine potentiated the morphine analgesia while D-AP7 blocked morphine analgesia. These results delineate for the first time a functional role for the NMDA receptor in the control of pain in the mammalian central nervous system.

A dystonia-like syndrome after neuropeptide (MSH/ACTH) stimulation of the rat locus ceruleus.

The movement disorder investigated in these studies has some features in common with human idiopathic dystonia, and information obtained in these studies may be of potential clinical benefit. The present experimental results indicated that peptidergic stimulation of the LC resulted in a NE-mediated inhibition of cerebellar Purkinje cells located at terminals of the ceruleo-cerebellar pathway. However, it is not certain as to the following: (a) what receptors were stimulated by the ACTH N-terminal fragments at the LC that resulted in this disorder; (b) whether NE, released onto Purkinje cell synapses located at terminals of the ceruleo-cerebellar pathway, did indeed cause the long-term depression at Purkinje cell synapses (previously described by others) that resulted in the long duration of the movement disorder; (c) whether the inhibition of inhibitory Purkinje cells resulted in disinhibition or increased excitability of the unilateral cerebellar fastigial or interpositus nuclei, the output targets of the Purkinje cell axons, that may have been an important contributing factor to this disorder. These questions are currently being investigated.

Non-stereospecific excitatory actions of morphine may be due to GABA-A receptor blockade.

An explosive motor behavior (EMB) similar to that seen following morphine injection into the rat periaqueductal gray (PAG) was observed following an injection of GABA-A receptor antagonists into the rat PAG. In general, the potencies of certain opiates and known GABA-A antagonists in producing EMB following their injections into the PAG paralleled their potencies as GABA antagonists in a radioreceptor assay. We suggest that one of the dual actions of morphine in the CNS may be GABA blockade.

'Dystonia'-like postural asymmetry after microinjection of ACTH N-terminal fragments but not after ACTH1-39 in rat brainstem suggests role of neuropeptide mutation in genetic movement disorder.

N-terminal fragments of adrenocorticotropin (ACTH) was reported to exert potent 'dystonia'-like effects on posture and locomotion following a unilateral microinjection into the rat brainstem. The high reliability of this phenomenon provided a suitable animal model for the study of these actions. The present structure-activity study showed that ACTH1-39, in contrast to its N-terminal fragments, did not have any 'dystonic' actions, however transient or slight. Thus, the folded conformation of [1-39] in vivo may prevent its N-terminal region from interacting with those CNS sites that trigger 'dystonic' actions. These results suggest that genetically-linked human dystonia may have originated in part as a consequence of a mutation in the processing of the ACTH molecule, resulting in an aberrantly-folded conformation that allows its N-terminal region to trigger the dystonic syndrome.

Met5-enkephalin: potent contraversive rotation after microinjection in rat substantia nigra.

This study reports a novel action of Met5-enkephalin in the rat substantia nigra, i.e. potent contraversive rotation that is dose-dependent, site-specific, mimicked by morphine and blocked by naloxone. These results suggest that this pentapeptide may play an important modulatory role in the control of movement in this region of the central nervous system. Alterations in endogenous Met-enkephalin levels in the substantia nigra may be a contributive factor in Parkinson's disease, a movement disorder related to neuropathology of the substantia nigra.

Postural asymmetry and movement disorder after unilateral microinjection of adrenocorticotropin 1-24 in rat brainstem.

A unilateral microinjection of adrenocorticotropin 1-24 in the rat brainstem in the region of the locus ceruleus resulted in postural asymmetry and movement disorder that resembled human dystonia, the severity and duration (2 to 3 days) being dose-dependent. These results show for the first time that neuropeptides in the brainstem may modulate posture and movement, and they suggest that some forms of movement disorder such as dystonia may be due to a disordered regulation of postural and locomotor mechanisms by adrenocorticotropin 1-24.

Opposite temporal changes after a single central administration of B-endorphin: tolerance and sensitization.

Rats were given a single unilateral microinjection of B-endorphin in the periaqueductal gray, followed by a second microinjection of the same dose of B-endorphin in the same site a week later. A decrease in the analgesic action (i.e., tolerance) but an increase in the hyperthermic action (i.e., sensitization) was observed over this interval. These results suggest that different receptors may mediate these actions of B-endorphin. In addition, these results indicate the need for caution in repeated-measurements studies using this opiate peptide, since the assumption that such temporal effects dissipate within 3-5 days, with resulting minimal carry-over effects from the preceding treatment appears to be unjustified.

Dual actions of morphine on the central nervous system: parallel actions of beta-endorphin and ACTH.

In the studies described above, the intracerebral microinjection technique was used to study the actions of morphine at morphine-sensitive sites, the periaqueductal gray (PAG) and the midbrain reticular formation (MRF). In the PAG, morphine exerted dual actions: inhibitory and excitatory. In the MRF, morphine exerted an excitatory action only, indicating that the dual actions of morphine are dissociable and site specific. Following microinjection into the PAG, beta-endorphin exerted an inhibitory, and ACTH an excitatory, action, i.e., each duplicated one of morphine's dual actions. These results indicated that receptors for the endogenously occurring peptides, beta-endorphin and ACTH, may play a role in morphine's potent pharmacological actions. Although these studies do not shed direct light on the physiological role of these neuropeptides and their receptors, nor on their potential roles in the functional regulation of brain (especially in diseased mental states), it may be permissible to offer some speculations. We previously proposed that beta-endorphin may be an endogenous antipsychotogen, and that a deficiency in brain beta-endorphin may underlie some forms of psychopathology. In view of beta-endorphin's biosynthetic link to ACTH, and the behavioral effects of beta-endorphin (sedated immobility) that was found to be opposite in kind to those of ACTH (fearful hyperreactivity) following administration into brain, it is possible that these two neuropeptides may have regulatory roles in maintaining a functional balance in brain. (It may be speculated that these biosynthetically linked neuropeptides served survival functions of "flight" and "freeze" in our evolutionary ancestors.) An imbalance in the bioavailability of either of the two neuropeptides, e.g., a deficiency of beta-endorphin or an excess of ACTH (perhaps due to the lack of the specific enzymes that cleave these peptides from their parent prohormone) may be an etiological factor in some forms of chronic functional disorders of the brain.

Morphine and ACTH1-24: correlative behavioral excitations following micro-injections in rat periaqueductal gray.

Rats implanted with bilateral cannulas in the periaqueductal gray exhibited similar behavioral excitations following microinjections of morphine sulphate and ACTH1-24. Injections were more effective when the sites were located within rather than below the periaqueductal gray. Analgesia was observed following morphine but not ACTH microinjection. These results confirm that morphine exerts a dual action, inhibitory (i.e. analgesic) and excitatory, with ACTH mimicking only the latter action.

Excitatory and inhibitory effects of opiates in the rat vas deferens: a dual mechanism of opiate action.

Both natural (-)-morphine and its unnatural enantiomer (+)-morphine exert an excitatory action on electrically stimulated contractions of rat vas deferens. Preexposure to (-)-morphine results in cross-tolerance to the inhibitory action of beta-endorphin. (-)-Naloxone and its stereoisomer (+)-naloxone also exert an excitatory action, but only (-)-naloxone bocks the inhibtory action of beta-endorphin. Thus morphine exerts a dual action on a peripheral organ: one an inhibitory action mediated by the stereospecific endorphin receptor that is blocked stereospecifically by naloxone, the other an excitatory action mediated by a nonstereospecific receptor that is not blocked by naloxone. The opiate abstinence syndrome is seen as due to the unmasking of the excitatory action of opiates when its concomitant inhibitory influence is removed by selective blockade by naloxone or weakened by selective tolerance. The view that the rat vas deferens is devoid of morphine receptors is now seen as arising from a reverse example of morphine's dual action: the masking of the inhibitory action of morphine by its concomitant and more potent excitatory action.

Stereospecific, dose-dependent antagonism by naloxone of non-opiate behavior in mice.

When mice were placed in a novel environment, they exhibited behavioral activation, characterized by a high frequency of jumps, rearings, groomings, digging, etc. Naloxone exerted a dose-dependent antagonism of this behavior. The antagonism was stereospecfic, with the enantiomer, (+)-naloxone failing to antagonize this behavior. Morphine-injected mice showed a different behavioral syndrome, i.e., Straub tail and a compulsive, robot-like ambutation around the perimeter of the bin, with a total absence of jumps, rearings, etc. The morphine behavioral syndrome was antagonized by naloxone at 1 mg/kg, while higher naloxone doses were required to antagonize the behavioral activation in a novel environment. These results suggest that stereospecific antagonism by naloxone is a necessary but not sufficient condition for defining opiate-like action.

Test for oral and postingestional factors mediating differential acceptability of morphine, methamphetamine, and chlordiazepoxide drinking solutions.

The relative degrees to which aversive oral (presumably gustatory) and postingestional variables attenuate the voluntary drinking of morphine, methamphetamine, and chlordiazepoxide solutions by rats were assessed by comparing immediate acceptability with subsequent acceptability. Results indicated that morphine solutions (0.01--0.05%) are avoided primarily because of unpalatability, while methamphetamine (0.005--0.02%) and chlordiazepoxide solutions (0.02--0.08%) are avoided primarily because of aversive postingestional effects.