Maize resistance to witchweed through changes in strigolactone biosynthesis.

Maize (Zea mays) is a major staple crop in Africa, where its yield and the livelihood of millions are compromised by the parasitic witchweed Striga. Germination of Striga is induced by strigolactones exuded from maize roots into the rhizosphere. In a maize germplasm collection, we identified two strigolactones, zealactol and zealactonoic acid, which stimulate less Striga germination than the major maize strigolactone, zealactone. We then showed that a single cytochrome P450, ZmCYP706C37, catalyzes a series of oxidative steps in the maize-strigolactone biosynthetic pathway. Reduction in activity of this enzyme and two others involved in the pathway, ZmMAX1b and ZmCLAMT1, can change strigolactone composition and reduce Striga germination and infection. These results offer prospects for breeding Striga-resistant maize.

Fluoroscopic guidance of Arndt endobronchial blocker placement for single-lung ventilation in small children.

BACKGROUND: Thoracoscopic surgery may require single-lung ventilation (SLV) in infants and small children. A variety of balloon-tipped endobronchial blockers exist but the placement is technically challenging if the size of the tracheal tube does not allow the simultaneous passage of the fibreoptic scope and the endobronchial blocker. This report describes a technique for endobronchial blocker insertion using fluoroscopic guidance in children undergoing SLV. METHODS: After approval from the local Medical Ethics Committee and parental consent, 18 patients aged 2 years or younger scheduled for thoracic surgery requiring SLV were prospectively included. Following induction of anesthesia, a 5 Fr endobronchial blocker (Cook) Arndt endobronchial blocker) was inserted first into the trachea under direct laryngoscopy. Correct placement in the main bronchus was assessed by fluoroscopy and tracheal intubation next to the endobronchial blocker. Optimal position and balloon inflation was verified using a fibreoptic scope. The duration and number of insertion attempts as well as age, weight and size of the tracheal tube were recorded. RESULTS: Eighteen patients were studied. Median (range) age and weight were 12 (0.2-24) months and 11.2 (4-15) kg, respectively. SLV was successfully achieved in all patients using a 5 Fr endobronchial blocker outside a 3.5-4.5 mm ID tracheal tube within 11.2 (+/-2.2) min. No side effects were observed during the procedure. CONCLUSION: Fluoroscopic-guided insertion of extraluminal endobronchial blocker is an effective and reliable tool to place Arndt endobronchial blockers in small children.

Congenital myopathy with central cores and fingerprint bodies in association with malignant hyperthermia susceptibility.

A 26-year-old man had proximal weakness in the shoulder and the pelvic girdle since infancy. His sister, aged 16 years, presented a similar phenotype with more pronounced pelvic weakness. His muscle biopsy showed dense non-reducing inclusions which had a lamellar pattern at the ultrastructural level. These structures showed the typical features of fingerprint inclusions which were widely distributed in the fibers. Several central cores and other structural changes such as Z-line streaming were also observed. In view of the central cores, the male patient was investigated for malignant hyperthermia susceptibility. After exposure to halothane or caffeine, unusual intense contractures were observed on fiber preparations. The coexistence of central cores associated with fingerprint inclusions is suggestive of mixed congenital myopathy, which is in our case associated with malignant hyperthermia susceptibility.

In vitro human masseter muscle hypersensitivity: a possible explanation for increase in masseter tone.

To determine whether a difference in fiber-type caffeine and Ca2+ sensitivities exists between human masseter and vastus lateralis skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers from 13 masseter and 18 vastus lateralis muscles. Caffeine sensitivity was defined as the threshold concentration inducing > 10% of the maximal tension obtained after the fiber was loaded with a 1.6 x 10(-2) mM Ca2+ solution for 30 s. Significant difference in the mean caffeine sensitivity was found between type I masseter fibers [2.57 +/- 1.32 (SD) mM] vs. type I (6.02 +/- 1.74 mM) and type II vastus lateralis fibers (11.25 +/- 3.13 mM). Maximal Ca(2+)-activated force per cross-sectional area was significantly different between masseter and vastus lateralis fibers. However, the Ca2+ concentration corresponding to half-maximal tension (pCa50) was not significantly different between type I masseter (pCa50 5.9 +/- 0.02) and type I vastus lateralis muscle (pCa50 6.01 +/- 0.08). These results suggest that the increase in caffeine sensitivity of masseter muscle reflects the presence of a low reactivity threshold of the sarcoplasmic reticulum.

Malignant hyperthermia susceptibility: anaesthetic implications and risk stratification.

Malignant hyperthermia (MH) is a rare autosomal dominant trait that predisposes individuals to great danger when exposed to certain anaesthetic triggering agents, such as potent volatile anaesthetics and succinylcholine. Sudden hypermetabolic reaction occurs in skeletal muscle, leading to hyperthermia and massive rhabdomyolysis. Precautions must be taken before the anaesthesia of MH-susceptible patients. No triggering agents should be administered, central body temperature and ETCO2 should be carefully monitored, and dantrolene must be immediately available. In addition, the anaesthesia machine should be carefully washed to remove traces of halogenated agents, and the use of fresh disposable anaesthetic circuits is recommended. Early diagnosis of the syndrome by alert, informed anaesthesiologists, and the immediate administration of dantrolene and other supportive measures, has reduced mortality. Patients with MH susceptibility should be instructed to alert the anaesthesiologist about their condition whenever anaesthesia is needed. Although people diagnosed with MH susceptibility should not change their lifestyle in general, military service is limited.

Shortening velocity of skeletal muscle from humans with malignant hyperthermia susceptibility: effects of halothane.

The aim of this investigation was to assess the effect of halothane on the velocity of shortening and lengthening of muscle from normal subjects and from patients with malignant hyperthermia susceptibility. Strips were mounted horizontally at optimal length in normal Krebs-Ringer's solution and mechanical parameters were obtained before and after exposure to 3 vol.% halothane. The maximun shortening velocity at zero load (V(max)) was determined by using Hill's characteristic equation. The contraction and relaxation indices were measured under isotonic and isometric conditions: maximum shortening and lengthening velocities (maxV(c) and maxV(r), respectively); isometric peak twitch tension; peak of the positive (+dP/dt(max)) and negative (-dP/dt(max)) twitch tension derivative; ratio R1=maxV(c)/maxV(r) and ratio R2=(+dP/dt(max))/(-dP/dt(max)). In normal muscle, halothane markedly increased V(max), maxV(c) and peak twitch tension by 30+/-10%, 30+/-5% and 40+/-15%, respectively. The maxV(r) values increased concomitantly with the maxV(c) values, such that no change in the ratio R1 was observed. Both +dP/dt(max) and -dP/dt(max) increased such that the ratio R2 did not vary. In malignant hyperthermia susceptibility muscle, halothane induced a significant decrease in V(max) (-30+/-10%) and maxV(r) (-45+/-15%) without changing maxV(c). The decrease in maxV(r) was greater than that of maxV(c), such that the ratio R1 increased significantly. Peak twitch tension and +dP/dt(max) remained unchanged whereas -dP/dt(max) decreased significantly; the ratio R2 increased by 40+/-10%. These results suggest that halothane alters the contractile properties of malignant hyperthermia susceptibility muscle.

Effects of halothane on mechanical response of skeletal muscle from malignant hyperthermia susceptible patients.

The purpose of this investigation was to compare the effects of halothane on malignant hyperthermia (MH) and normal isolated muscle bundle performance during isometric contraction and relaxation phases. Mechanical parameters were measured: peak tension (PT), time to peak tension (TPT) and positive peak of isometric tension derivative (+dP/dtmax) characterized the contraction phase. Half-relaxation time (RT1/2) and negative peak of isometric tension derivative (-dP/dtmax) characterized the relaxation phase. The ratio R = (+dP/dtmax)/(-dP/dtmax) was used to study the coupling between contraction and relaxation under isometric condition. In normal muscle, halothane increased PT by nearly 40% without altering TPT. The +dP/dtmax value increased concomitantly with the -dP/dtmax values, thus no changes in R was observed. In MH muscle, PT was first potentiated (0.5-1.0 vol% halothane) and then depressed (2.0-3.0 vol% halothane). TPT and +dP/dtmax were not altered whereas RT1/2 increased progressively with concomitant decrease in -dP/dtmax, thus R increased by nearly 40%. The amplitude of MH muscle contracture with stepwise concentrations of halothane was correlated with the increase of RT1/2 and R, and the decrease of -dP/dtmax. These results suggest that halothane alters the relaxation phase more than the contraction phase in MH human skeletal muscle compared to normal muscle.

Hip-flexed postures do not affect local anaesthetic spread following induction of epidural analgesia for labour.

Hip-flexed postures enlarging the pelvic diameter are used to improve the obstetric course of labour. Although most investigations show that lateral and sitting positions do not affect the spread of epidural analgesia, the effect of recently introduced hip-flexed postures has yet to be confirmed. This prospective randomised study included 93 parturients. Ropivacaine 0.1% 12 mL plus sufentanil 0.5 micrograms/mL was administered epidurally over a period of 6 min in one of four postures: sitting, right hip-flexed left lateral position, left hip-flexed right lateral position and supine 30 degrees lateral tilt as a control group. Left and right cephalad and sacral epidural spread were measured every 2 min over a period of 30 min. Pain relief, motor blockade and maternal and fetal side effects were noted. The total epidural spread was 15+/-0.3 dermatomes and the upper level of thermo-algesic blockade T7-T8 (range T3 to T10) in all groups. There were no differences between groups in left or right total spread or upper level of epidural blockade, time to maximal block or pain relief. There was no motor block nor any maternal or fetal side effects. The power of the study (1 - beta) was 93%. We conclude that, for the three hip-flexed postures tested, position does not influence local anaesthetic spread or symmetry of thermo-algesic blockade after induction of obstetric epidural analgesia.

Parturition and angioneurotic oedema.

Angioneurotic oedema is a rare disease caused by Cl esterase inhibitor deficiency. Hereditary angioneurotic oedema includes type I (quantitative and functional) deficiency and type 11 (functional) deficiency. Its prophylactic treatment during pregnancy, based on danazol therapy if the fetus is male, may avoid acute attacks of generalized or laryngeal oedema. It must be instituted before delivery and carried into the postpartum period. If the fetus is female, epsilon aminocaproic acid may be used. The acquired form of angioneurotic oedema can be due to antibodies to C1 esterase inhibitor. A prophylactic therapy is not well established, but high doses of corticosteroids are recommended. Operative delivery is best avoided when possible. Regional analgesia is indicated for labour or caesarean section to prevent pain and stress and to avoid the difficulties associated with laryngeal oedema and tracheal intubation. In the treatment of an acute attack, Cl esterase inhibitor concentrates (1500 units) may be given i.v. We present two cases, one of hereditary and one of acquired angioneurotic oedema, both presenting during pregnancy and both delivered vaginally under epidural analgesia with successful outcome.

[Gamstorp's disease and pregnancy. A case report]. / Maladie de Gamstorp et grossesse. A propos d'un cas.

Gamstorp's disease or hyperkaliemic periodic paralysis is a rare pathology leading to spells of generalized hypotonia due to hyperkaliema. It is hard to say how far pregnancy affects the course of the disease and what is the impact of the disease on pregnancy. We report a case of Gamstorp's disease during pregnancy and we insist on the fact that because it can be crippling during its acute phases, close surveillance is needed during pregnancy. Screening for malignant hyperthermia should be carried out. During labour, kaliemia level should be monitored repeatedly and the expulsion phase kept as short as possible if necessary by forceps delivery.

[Cerebral tumors and pregnancy. Apropos of 8 cases]. / Tumeurs cérébrales et grossesse. A propos de huit cas.

Pregnancy is an aggravating factor for brain tumours on which it acts by three mechanism: acceleration of tumour growth, increase of peritumoral oedema and the immunotolerance to foreign tissue antigens that is proper to pregnancy. Histologically, the brain tumour most frequently encountered is glioma, usually revealed during the third trimester. Brain tumours is pregnant women have no special clinical features, and their diagnosis rests on computerized tomography or nuclear magnetic resonance completed, if required, by stereotactic biopsy. Following a review of the literature, the authors present an updated description of the neurological and obstetrical actions to be taken, illustrated by a report of eight personal cases. The indications for surgery depend on the site and histological nature of the tumour. As regards obstetrical measures, induced therapeutic abortion and caesarean section, no longer routinely performed, are now being replaced by vaginal delivery with systematic instrumental extraction. In both mother and foetus the prognosis has improved over the last ten year, but it remains very sombre.

[Cerebral aneurysms and pregnancy: 4 cases]. / Anévrysmes cérébraux et grossesse: 4 cas.

Haemorrhagic cerebral accidents are the commonest neurosurgical diagnoses made in pregnancy. The state of pregnancy makes it more likely that an arterial or an arteriovenous aneurysm will rupture and this is the principal cause of most haemorrhages. They occur more often in primiparae in the third trimester of pregnancy. The clinical picture is classical. The conformation of the diagnosis is made by scanning and angiography. The main differential diagnosis is eclampsia. Neurosurgical treatment should be carried out immediately whenever possible in order to avoid the two great risks that follow, namely recurrence of haemorrhage and secondly ischaemia. As far as the obstetric side is concerned, Caesarean section would only be indicated if: the clinical state of the mother is severe with coma and brain stem damage when the child is viable, if there is symptomatic vascular malformation diagnosed at term, if there is haemorrhagic arteriovenous malformation which is highly liable to occur and cannot be operated on without risks for the child if viable, if, finally, the interval between the surgical treatment of the condition and labour is less than 8 days. In all other cases a vaginal delivery is preferable under epidural anaesthetic which should be given if medical induction is carried out, and where instrumental delivery is being carried out systematically, unless radical treatment is being performed. The prognosis which is, in spite of all steps that may be taken, poor, depends on the initial neurosurgical stage and the nature of the causes of lesion and the possibilities of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

[Mild hypothermia and cerebral protection]. / Hypothermie modérée et protection cérébrale.

To define the part played by mild-to-moderate hypothermia in neuroprotection, it is necessary to take into account the thermoregulatory responses that occur in the normal human as the change in central temperature exceeds 0.2 degrees C. The mechanisms induced by cold are cutaneous vasoconstriction and shivering. They must be suppressed before starting controlled hypothermia. In these conditions, controlled moderate hypothermia between 32 and 35 degrees C does not seem to have deleterious side-effects, especially on coagulation. Caution is needed with the analysis of the numerous papers reporting experiments concerning the effects of moderate hypothermia in animals with induced cerebral ischaemia because of significant differences in the study designs. These differences concern mainly the time of onset of hypothermia, viz before or after ischaemia, the fact that the ischaemia is either global or focal, that it is caused by vascular occlusion posttraumatic or initiated by hypo or hyperglycemia. Some differences are also existing in the criteria used to appreciate the neuronal damage, as well as in the level of temperature and the site where it is measured. The mechanism of neuroprotection from moderate hypothermia seems to be not only a decrease in cerebral metabolism, but also involves a specific action on some intra-cellular events such as the blocking of the release of glutamate and of lipid peroxydation in brain tissue. An indirect proof of the neuroprotective effect of moderate hypothermia is the increase in the neuronal damage induced by moderate hyperthermia. It is conceivable that moderate hypothermia could exert a better neuroprotective effect than the drugs having this reputation, such as barbiturates, isoflurane and propofol.(ABSTRACT TRUNCATED AT 250 WORDS)

[Central core disease associated with malignant hyperthermia sensitivity]. / Myopathie à axe central (central core disease) associée à une sensibilité à l'hyperthermie maligne.

The authors report the case of a 57-year old woman who was susceptible to malignant hyperthermia (MH) and also had central core disease (CCD) of muscle. The latter was asymptomatic and was discovered when muscle biopsy was performed for in vitro tests of susceptibility to malignant hyperthermia. This case was compared with the 117 cases of CCD and 33 cases of CCD associated with MH published in the literature. Anaesthesia-induced MH is lethal in 80 per cent of the cases without treatment and in 20 per cent with treatment. CCD and MH are both transmitted as autosomal dominant traits. Susceptibility to MH is a functional abnormality of unknown mechanism. CCD is a disease of muscle fibre structure. One may hope that molecular studies and genetic probes will show whether or not these two diseases are transmitted by genes that are similar but distinct and independent.

[Screening tests for malignant hyperthermia susceptibility]. / Tests de dépistage de la sensibilité à l'hyperthermie maligne.

The ideal screening test for malignant hyperthermia susceptibility (MHS) has yet to be discovered. It should be simple noninvasive, yet totally specific and sensitive. Until such an ideal test becomes available, allowing simple routine preoperative screening, tests should only be used in certain specific situations. These include: patients in whom a clinical crisis was suspected; the members of the family of a subject labeled MHS because of a fatal, or otherwise, crisis, or in whom tests were positive; patients with other pathological conditions which could be linked to malignant hyperthermia (MH) (some myopathies, effort or stress MH, neuroleptic malignant syndrome). The various tests proposed in the literature aim at revealing MHN subjects, using or not a triggering agent, halothane most often. However, detecting these abnormalities sometimes gives greater insight into the physiopathology of MH than in the detection of an individual patient's susceptibility. The tests have been classified as in vivo, electrophysiological, blood, and in vitro muscle biochemical, morphological, and pharmacological tests. The discovery of new tests gives renewed hope: CPK levels, platelet tests, calcium sarcoplasmic reticular reuptake, lymphocyte Quin 2 test, nuclear magnetic resonance spectroscopy. However, experts worldwide agree that the only reference test to this day remains the in vitro halothane caffeine contracture tests. These tests have shown their reliability; they must be performed on muscle strips obtained from surgically removed muscle biopsies, by laboratories used to this technique and who have at their disposal a sufficiently large group of MHS subjects with a clear-cut clinical crisis, as well as controls. The patients must therefore travel to these laboratories. The design of common protocols for European laboratories on one hand, and the North American laboratories on the other, is a good guarantee of the reliability of these tests.

[Calcium inhibitors and anesthesia]. / Inhibiteurs calciques et anesthésie.

Calcium blockers (CB) are routinely used. This could lead to possible interference with anaesthetic drugs. CB prevent calcium from entering the cell by inhibiting the slow voltage-dependent calcium channels. They act mostly on heart and smooth muscle. Of all the possible indications, the three that are confirmed are coronary heart disease, arterial hypertension and supraventricular rhythm disturbances. Most of the work published and the cases reported concerns interactions between CB and halogenated anaesthetic agents; the latter's actions on the heart depend on cellular calcium exchange. Also, the cardiovascular effects of these anaesthetics are similar to that of CB. Experimentally, halothane and enflurane have direct cardiac inhibitory effects similar to verapamil and diltiazem, whereas isoflurane's properties seem closer to the dihydropyridines (nifedipine and nicardipine). Giving verapamil or diltiazem increases the number of sino-atrial and atrio-ventricular blocks when using a halogenated agent. Clinically, interpreting the effects of CB during anaesthetic induction is difficult because of the pathology (coronary heart disease, cardiac failure), the other drugs (beta-blockers and nitrates) and the type of anaesthesia (emergency or elective). Interactions can give rise to anything from a severe cardiovascular collapse, requiring catecholamines, to a mild fall in blood pressure which responds well to plasma expansion, or even no effect on blood pressure. Rebound is seen on stopping CB in patients with coronary heart disease or arterial hypertension; stopping them before surgery does not therefore seem justified. However, extreme care must be taken when using halogenated agents for patients under treatment with CB and/or beta-blockers. A wary anaesthetist will be able to adapt the technique to the patient. It has been suggested that CB could be used to treat preoperatively myocardial ischaemia (diltiazem), hypertensive crises (nifedipine, nicardipine) and ventricular rhythm disturbances (verapamil); this must be done with caution, the patient being closely monitored (haemodynamic and electrocardiographic monitoring). Postoperatively, intranasal nifedipine, continuous intravenous nicardipine or diltiazem have been used to treat increases in arterial blood pressure during recovery and to adapt the cardiovascular system to the increased metabolic needs. Here again, close patient monitoring is essential. In any case, treatment with CB which has been stopped should be started up again as soon as possible.

[Malignant hyperthermia: new developments in diagnosis and clinical management]. / Hyperthermie maligne: nouveautés diagnostiques et cliniques.

OBJECTIVE: To analyse the current knowledge concerning anaesthetic malignant hyperthermia. DATA SOURCES: References were obtained from computerized bibliographic research (Medline), recent review articles, the library of the service and personal files. DATA SYNTHESIS: Knowledge to possess, about the diagnosis and treatment of the acute hyperthermia crises and about "safe-anaesthesia" for malignant hyperthermia susceptible patients, are explained. The pathophysiology chapter give information about the calcium's transport and the defect existing in MH. Molecular genetics of MH find linkage to the region encoding the RyR1. The profile of hyperthermia episodes has changed over time due to the endtidal carbon dioxide-monitoring. Clinical aspects of MH are exposed. The treatment of the acute hyperthermia crises consist mainly to stop all triggering agents instantly and infuse dantrolene sodium. The gold standard for the diagnosis of malignant hyperthermia susceptibility relies on the in vitro contracture test (halothane and caffeine). Associated to genetic studies, it could lead to an non-invasive screening of the MH susceptibility. A protocol for "safe-anaesthesia" is proposed. Some syndromes with features similar to those of MH should be known (central core disease and exertionnal rhabdomyolysis).

[Target-controlled infusion with propofol for neuro-anesthesia]. / Le propofol et l'AIVOC en neuro-anesthésie.

Propofol is an intravenous anaesthetic agent, which presents interesting features for its use in neuro-anaesthesia: it is a powerful hypnotic that does not increase the intracranial pressure. The delay of recovery is short even after several hours of continuous infusion. This is essential for a fast neurologic examination. Continuous infusion should be preferred to bolus in order to prevent hypotension and decrease of the cerebral perfusion pressure. Target-controlled infusion models based on effect site concentrations are now available through several softwares. This technique appears especially useful for awake craniotomy and functional neurosurgery. The level of consciousness is easily fixed between deep anaesthesia and light sedation permitting to ask the patient to move following orders. A sedation controlled by the patient himself is even possible.

[Anesthesia for arthroscopy of the knee: propofol versus thiopental and halothane]. / Anesthésie pour arthroscopie du genou: propofol versus thiopental et halothane.

Sixty ASA I or II patients, who underwent general anaesthesia for arthroscopy of the knee, were separated into two groups. Induction was performed either with thiopentone 7 mg . kg-1 (group I) or with propofol 2.5 mg . kg-1 (group II). All patients were intubated and ventilated. Dextromoramide was used as analgesic. Maintenance of anaesthesia was obtained with halothane inhalation (group I) or by continuous automatic injection of propofol at a dose of 9 mg . kg-1 . h-1 (group II). Induction and maintenance were satisfactory in both groups. Pulse rate was stable at induction and intubation for the propofol group, whereas it increased at both stages of anaesthesia with thiopentone; it fell moderately in both groups afterwards. Systolic and diastolic blood pressures dropped more in the propofol group after induction, with a maximum decrease of 20%. Recovery was significantly more rapid and comfortable with propofol than with thiopentone.

[Examination of the family of a patient susceptible to anesthetic malignant hyperthermia]. / Exploration de la famille d'un sujet sensible à l'hyperthermie maligne anesthésique.

The familial nature of anaesthetic malignant hyperthermia must lead to the search for susceptibility in other members of the family of a sensitive subject. According to the literature, only in vitro studies of contraction characteristics of biopsied skeletal muscle fibres exposed to caffeine or halothane are of predictive value. Four members of the family of a patient who died as a result of malignant hyperthermia were investigated. The results expressed in accordance with the criteria defined by the European group on malignant hyperthermia, coupled with a histoenzymatic study, defined three of the subjects as HMN (negative) and one subject as HM (c) (equivocal or intermediate).