Le système nerveux sympathique est un médiateur des contraintes mécaniques dans le tissu osseuxSympathetic nervous system as transmitter of mechanical loading in bone

Sympathetic innervation has been demonstrated in bone. Adrenergic stimulation is one of the transmitters of bone loss by uncoupling between decreased bone formation and increased bone resorption.Objective. – By using a non specific antagonist of β-adrenergic pathway (propranolol per os), we hypothesized that we could rescue the uncoupling induced mechanical unloading bone loss in the rat model of tail-suspension.Materials and methods. – Twenty-two female rats Wistar, 12 week-old, have been divided into three groups: eight tail-suspended rats (SR), six tail-suspended rats treated by propranolol (SRP) and eight non suspended rats (NSR) during 30 days. Bone mineral density (BMD, g/cm²) has been measured by DXA (Hologic QDR-4500A) at D0 and D30 of the study, in the distal femoral metaphysis (DFM), the femoral diaphysis (FD), the whole body (WB, g) and body composition.Results. – Between D0 and D30, in DFM a significant variation in BMD is observed between NSR and SR (% BMD change: NSR +15.6 ± 3.1% vs. SR –1.0 ± 1.4%, P < 0.0001) and BMD rescue in SRP group (% BMD change SRP +5.3 ± 1.5% vs. SR –1.0 ± 1.4%, P = 0.03). In FD, gain of BMD is significant in NSR compared to SR (+17.5 ± 1.5% vs. +8.2 ± 2.8%, P = 0.007), and to SRP (+17.5 ± 1.5% vs + 10.1 ± 2.4%, P = 0.046). Gain in SRP group is not significant compared to SR group (P = 0.6). In WB SRP gain more BMD than NSR (+14.0 ± 1.8% vs. +5.4 ± 0.7%, P = 0.0002) and than SR (+14.0 ± 1.8% vs. +7.8 ± 1.4%, P = 0.0043). There is no difference between NSR and SR groups (P = 0.19).Conclusion. – We demonstrate that β-adrenergic pathway of sympathetic nervous system is a major transmitter pathway of mechanical loading in rat bone. A specific study is necessary to analyse a possible systemic effect of propranolol in rat bone. Propranolol could be used to prevent induced mechanical unloading bone loss as weightlessness.     

Evaluation of infectious episodes in neonates using a new procedure for the nitroblue tetrazolium test

A new procedure for the NBT slide test for peripheral blood neutrophils has been tested. 255 neonates were studied of which 63 served as control cases. Among the 114 term infants, 37 were patently infected, 30 suspicious and 47 non-infected. The latter did not significantly differ from control cases, whereas suspicious and infected infants were credited with significantly higher NBT scores.78 infants were preterm, 31 of which were patently infected, 22 suspicious and 25 non-infected. NBT scores of infected and suspicious infants were significantly higher than those of non-infected infants, but, as previously reported, scores of preterm infants were systematically and significantly lower than those of full-term infants of the same bacteriological class.Threshold values are suggested; they could represent an accurate diagnostic aid in the early differentiation of healthy infants from high-risk infants regarding bacterial infections.     

Effects in conscious dogs of ajmaline,propranolol, amiodarone and verapamil on right ventricular anodal strength-interval curves

We studied the effect of antiarrhythmic drugs on the right ventricular anodal strenth-interval curve in the conscious dog. The anodal strenth-interval curve differs from its cathodal homologue by a shorter refractory period, a higher late diastolic threshold and the existence of a dip corresponding to a period of rhythmic vulnerability. The dogs were equipped with permanent ventricular electrodes; the heart was driven at a constant frequency by left ventricular stimulation and the anodal extra-stimulus was delivered on the right ventricle. This technique allowed us to determine the variations in the effective refractory period, the interventricular conduction (IVC) and the specific curve thresholds (late diastolic threshold, LDT, minimal dip level, Sm, maximal post dip threshold, SM). Ajmaline, a quinidine-like drug, significantly increased IVC and all the thresholds. Only high doses lengthened the effective refractory period. Propranolol, a β-blocking agent significantly increased Sm. The intrinsic effect of amiodarone, a non-specific anti-adrenergic drug and a potent anti-anginal substance seemed to result in a significant increase in LDT, Sm, SM. Verapamil, a calcium antagonist only caused a significant increase in SM. Therefore, each of the four drugs studied, belonging to a different group of teh Vaughan Williams classification, acted in a different way on the anodal strengh-interval curve. This study clarified the mechanisms by which these drugs exert their antiarrhythmic effect.     

Gastric carcinoma treated by chemotherapy after resection: A controlled study

A prospective controlled study of combined chemotherapy with 5-fluorouracil, vinblastine and cyclophosphamide was conducted in 53 patients with radical resection for gastric carcinoma. The patients were divided into two groups, a control group of 26 patients and a chemotherapy group of 27 patients, that were similar in regard to age, sex, location of carcinoma, type of resection and pathologic findings. No significant differences in survival rate were observed between the control group and the chemotherapy groups.     

Neuroprotection afforded by a combination of eliprodil and a thrombolytic agent, rt-PA, in a rat thromboembolic stroke model

In the present study, we have assessed the efficacy of eliprodil, a neuroprotective agent which blocks both the modulatory polyamine site of the NMDA receptor and neuronal voltage-sensitive calcium channels, alone or in combination with the thrombolytic agent, rt-PA, in a rat embolic stroke model using a neurological score and the volume of the infarct as endpoints. Embolization was induced by intracarotid injection of an arterial blood clot. Eliprodil, administered at the dose of 1 mg/kg, iv, 10 min and 2 h 30 after embolization, reduced the neurological deficit by 54% (P<0.01) and the total volume of the brain lesion by 49%. Thrombolysis with rt-PA (2.5 mg/kg, as a 30 min iv infusion beginning 1 h after embolization) decreased the neurological deficit by 48% (P<0.05) and the size of the total infarct by 55% (P<0.05). Combined therapy greatly improved the degree of neuroprotection as assessed by neurological and histological outcomes (70% (P<0.001) and 89% (P<0.01) neuroprotection, respectively). These results demonstrate that the administration of a neuroprotective drug (eliprodil) or a thrombolytic agent (rt-PA) similarly reduce the volume of brain damage and the neurological deficit in a rat embolic stroke model. Combined cytoprotective therapy and thrombolysis markedly improved the degree of neuroprotection and may, thus, represent a valuable approach for the treatment of stroke in humans.