Prenatal exome sequencing: A useful tool for the fetal neurologist

Prenatal exome sequencing (pES) is a promising tool for diagnosing genetic disorders when structural anomalies are detected on prenatal ultrasound. The aim of this study was to investigate the diagnostic yield and clinical impact of pES as an additional modality for fetal neurologists who counsel parents in case of congenital anomalies of the central nervous system (CNS). We assessed 20 pregnancies of 19 couples who were consecutively referred to the fetal neurologist for CNS anomalies. pES had a diagnostic yield of 53% (10/19) with most diagnosed pregnancies having agenesis or hypoplasia of the corpus callosum (7/10). Overall clinical impact was 63% (12/19), of which the pES result aided parental decision making in 55% of cases (6/11), guided perinatal management in 75% of cases (3/4), and was helpful in approving a late termination of pregnancy request in 75% of cases (3/4). Our data suggest that pES had a high diagnostic yield when CNS anomalies are present, although this study is limited by its small sample size. Moreover, pES had substantial clinical impact, which warrants implementation of pES in the routine care of the fetal neurologist in close collaboration with gynecologists and clinical geneticists.     

Metabolic effects of very low calorie weight reduction diets.

A randomized comparison trial of two very low calorie weight reduction diets was carried out for 5 or 8 wk in 17 healthy obese women. One diet provided 1.5 g protein/kg ideal body weight; the other provided 0.8 g protein/kg ideal body weight plus 0.7 g carbohydrate/kg ideal body weight. The diets were isocaloric (500 kcal). Amino acid metabolism was studied by means of tracer infusions of L-[1-13C]leucine and L-[15N]alanine. After 3 wk of adaptation to the diets, nitrogen balance was zero for the 1.5 g protein diet but -2 g N/d for the 0.8 g protein diet. Postabsorptive plasma leucine and alanine flux decreased from base line by an equal extent with both diets by approximately 20 and 40%, respectively. It was concluded that protein intakes at the level of the recommended dietary allowance (0.8 g/kg) are not compatible with nitrogen equilibrium when the energy intake is severely restricted, and that nitrogen balance is improved by increasing the protein intake above that level. Basal rates of whole body nitrogen turnover are relatively well maintained, compared with total fasting, at both protein intakes. However, turnover in the peripheral compartment, as evidenced by alanine flux, may be markedly diminished with either diet.     

Presynaptic dopaminergic activity of phencyclidine in rat caudate

This study tested the hypothesis that phencyclidine (PCP) is an indirect dopamine (DA) agonist in the caudate nucleus. Single caudate neurons in rats anesthetized with urethane were recorded extracellularly with multibarrel micropipettes. Effects of drug solutions, applied by pressure microejection, were measured as changes in spontaneous and evoked neuronal activity. Caudate neurons were classified according to their latency-to-discharge in response to supramaximal cortical stimulation. PCP inhibited the spontaneous activity of 92% of neurons with latencies less than 13 msec, while DA inhibited 87%. Both drugs inhibited evoked activity significantly less than spontaneous activity (P less than .01). Neurons with latencies greater than 13 msec were excited by DA significantly more often (45%) than by PCP (13%; P less than .05). Receptor stereospecificity is suggested by the finding that the (+)-isomer of the 3-methyl piperidine derivative of PCP was significantly more potent than the (-)-isomer for inhibition of spontaneous activity. Mg++, which blocks presynaptic release of neurotransmitter, significantly antagonized inhibitory effects of PCP on spontaneous activity, which suggests a presynaptic effect of PCP. DA, which acts postsynaptically, was much less affected by Mg++. The potency of PCP was significantly less in rats treated with reserpine or 6-hydroxydopamine than in control rats, suggesting the endogenous DA is required for the action of PCP. Fluphenazine and (+)-butaclamol, potent DA-receptor antagonists, blocked the effect of PCP, but (-)-butaclamol did not. These results support the hypothesis that PCP facilitates release and/or inhibits reuptake of DA in nerve terminals and thereby acts as an indirect DA agonist in the caudate. However, there may be a subpopulation of caudate neurons in which PCP acts by a nondopaminergic mechanism.     

Electrophysiological evidence for presynaptic actions of phencyclidine on noradrenergic transmission in rat cerebellum

The actions of the psychotomimetic drug phencyclidine (PCP) were studied using Purkinje neurons in the cerebellum of urethane-anesthetized rats. PCP, applied by micropressure ejection through multibarreled micropipettes, depressed the spontaneous activity of these neurons as recorded by extracellular electrophysiological techniques. This depressant effect was blocked by neuroleptic drugs and lithium, both of which also block the depressant effects of norepinephrine, but not those of gamma-aminobutyric acid. PCP-elicited depressions could not be obtained in rats in which the cerebellar noradrenergic terminals had been lesioned selectively by pretreatment with the neurotoxin 6-hydroxydopamine. However, PCP was still an effective depressant in animals after destruction of non-noradrenergic intrinsic excitatory and inhibitory interneurons which synapse on the Purkinje cell by neonatal X-irradiation. Further treatment of the X-irradiated animal with 6-hydroxy-dopamine resulted in Purkinje neurons which were not responsive to PCP. Administration of magnesium ions, which reduces the release of neurotransmitters from afferent terminals, also blocked the depressant effects of PCP. The results of this study suggest that PCP acts in the cerebellum by a presynaptic mechanism involving the release of norepinephrine from intact, functioning noradrenergic terminals.     

Severe road traffic injuries in Kenya, quality of care and access

Background

Road traffic injuries (RTI) are on increase in developing countries. Health care facilities are poorly equipped to provide the needed services.

Objective

Determine access and quality of care for RTI casualties in Kenya.

Design

Cross-sectional survey

Setting

53 large and medium size private, faith-based and public hospitals.

Participants

In-patient road traffic crash casualties and health personnel in the selected hospitals were interviewed on availability of emergency care and resources. Onsite verification of status was undertaken.

Results

Out of 310 RTI casualties interviewed, 72.3%, 15.6% and 12.2% were in public, faith-based and private hospitals, respectively. Peak age of the injured was 15–49 years. First aid was availed to 16.0% of casualties. Unknown persons transported 76.5% of the injured. Police and ambulance vehicles transported 6.1% and 1.4%, respectively. 51.9% reached health facilities within 30 minutes of crash and medical care provided to 66.2% within one hour. 40.8% of recipient facilities were adequately prepared for RTI emergencies.

Conclusions

Most RTI casualties were young and from poor backgrounds. Training of motorists and general public in first aid should be considered in RTI control initiatives. Availability of basic trauma care medical supplies in public health facilities was highly deficient.     

Methadone metabolism and clearance are induced by nelfinavir despite inhibition of cytochrome P4503A (CYP3A) activity

Background

Methadone plasma concentrations are decreased by nelfinavir. Methadone clearance and the drug interactions have been attributed to CYP3A4, but actual mechanisms of methadone clearance and the nelfinavir interaction are unknown. We assessed nelfinavir effects on methadone pharmacokinetics and pharmacodynamics, intestinal and hepatic CYP3A4/5 activity, and intestinal P-glycoprotein transport activity. CYP3A4/5 and transporters were assessed using alfentanil and fexofenadine, respectively.

Methods

Twelve healthy HIV-negative volunteers underwent a sequential crossover. On three consecutive days they received oral alfentanil plus fexofenadine, intravenous alfentanil, and intravenous plus oral methadone. This was repeated after nelfinavir. Plasma and urine analytes were measured by mass spectrometry. Opioid effects were measured by pupil diameter change (miosis).

Results

Nelfinavir decreased intravenous and oral methadone plasma concentrations 40–50%. Systemic clearance, hepatic clearance, and hepatic extraction all increased 1.6- and 2-fold, respectively, for R- and S-methadone; apparent oral clearance increased 1.7- and 1.9-fold. Nelfinavir stereoselectively increased (S > R) methadone metabolism and metabolite formation clearance, and methadone renal clearance. Methadone bioavailability and P-glycoprotein activity were minimally affected. Nelfinavir decreased alfentanil systemic and apparent oral clearances 50 and 76%, respectively. Nelfinavir appeared to shift the methadone plasma concentration–effect (miosis) curve leftward and upward.

Conclusions

Nelfinavir induced methadone clearance by increasing renal clearance, and more so by stereoselectively increasing hepatic metabolism, extraction and clearance. Induction occurred despite 50% inhibition of hepatic CYP3A4/5 activity and more than 75% inhibition of first-pass CYP3A4/5 activity, suggesting little or no role for CYP3A in clinical methadone disposition. Nelfinavir may alter methadone pharmacodynamics, increasing clinical effects.     

Contribution of itraconazole metabolites to inhibition of CYP3A4 in vivo

Itraconazole (ITZ) is metabolized in vitro to three inhibitory metabolites: hydroxy-itraconazole (OH-ITZ), keto-itraconazole (keto-ITZ), and N-desalkyl-itraconazole (ND-ITZ). The goal of this study was to determine the contribution of these metabolites to drug-drug interactions caused by ITZ. Six healthy volunteers received 100 mg ITZ orally for 7 days, and pharmacokinetic analysis was conducted at days 1 and 7 of the study. The extent of CYP3A4 inhibition by ITZ and its metabolites was predicted using this data. ITZ, OH-ITZ, keto-ITZ, and ND-ITZ were detected in plasma samples of all volunteers. A 3.9-fold decrease in the hepatic intrinsic clearance of a CYP3A4 substrate was predicted using the average unbound steady-state concentrations (C(ss,ave,u)) and liver microsomal inhibition constants for ITZ, OH-ITZ, keto-ITZ, and ND-ITZ. Accounting for circulating metabolites of ITZ significantly improved the in vitro to in vivo extrapolation of CYP3A4 inhibition compared to a consideration of ITZ exposure alone.     

Interventional radiology and the care of the pediatric oncology patient

Interventional radiology has become increasingly involved in the diagnosis and management of the pediatric oncology patient. Percutaneous biopsy and needle aspiration can be performed for solid and liquid lesions with image guidance, both for the primary diagnosis and for management of sequelae of cancer therapy. Therapeutic options also can be performed with image guidance, including radiofrequency ablation and transarterial chemoembolization. When surgical resection is required, image guided tumor localization can be used to aid in identifying small lesions.