A STUDY OF THE PLASMA CONCENTRATIONS OF LORAZEPAM IN MOTHER AND NEONATE

A standard dose to lorazepam 2.5 mg was given i.v. to two groupsof mothers: (a) before surgical induction of labour and (b)at the beginning of the second stage of labour. A group of non-pregnantwomen was sudied as control. Plasma concentrations of lorazepamwere measured by gas-liquid chromatography, in the mothers beforedelivery, and in the mother and neonate at delivery and 24 and48 h thereafter. Concentrations at delivery in the neonateswere similar to those in the mothers in group (a), but significantlyless in group (b). Fetal concentration rarely exceeded thatin the mother. Measurements after delivery indicated that theneonates were able to metabolize lorazepam at the same rateas the mothers. Of the 22 neonates studied only one had an Apgarscore of less than 8 at 5 min and this score was 10 at 10 min.     

CHRONIC EXPERIMENTAL ALLERGIC NEURITIS IN LEWIS RATS

An experimental chronic relapsing demyelinating neuropathy was produced by immunizing adult Lewis rats with bovine myelin in low (2.5 mg) and high (5 mg) doses, with and without Mycobacterium tuberculosis in the adjuvant. Each regime produced a similar disease course: acute severe hind limb weakness was followed by apparent recovery and then reappearance of mild neurological deficit with occasional spontaneous exacerbations. The partially recovered animals were relatively resistant to reimmunization with myelin. Immunization of four-week-old rats with myelin in complete adjuvant produced disease with a similar course. Subsequent immunization of these juvenile rats with adjuvant alone precipitated exacerbations. In the late stages, the prominent changes in peripheral nerves and nerve roots were axon loss, axonal regeneration and remyelination while inflammatory cell infiltration was confined to occasional foci. Onion bulb formation was extremely common in the dorsal root ganglia and affected in particular the nerve fibres close to the dorsal root ganglion cells. The cells forming the onion bulbs resembled the satellite cells surrounding the axon hillocks. Onion bulb formation also occurred in the portion of the ventral roots adjacent to the dorsal root ganglion but was rare elsewhere. Immunocytochemistry revealed only occasional lymphocyte infiltration but there was increased Class I and Class II MHC antigen expression throughout the peripheral nervous system. The results are relevant to the interpretation of biopsies from patients with chronic demyelinating neuropathy of possible inflammatory or autoimmune origin.     

False positive gel-acetylcholinesterase results in blood-stained amniotic fluids

Summary. The effect of blood contamination on the gel-acetylcholinesterase (AChE) test used in the diagnosis of fetal open neural-tube defects was studied with amniotic fluid samples artificially contaminated with fetal or maternal blood in concentrations covering a range exceeding that usually found in clinical practice. Amniotic fluid samples contaminated with maternal blood gave negative gel-AChE results at all concentrations. Contamination with fetal blood yielded positive results if the erythrocyte concentration was greater than about 60 × 10⁶ cells/ml. Thus contamination of amniotic fluid with blood is only likely to cause false positive gel-AChE results if this critical concentration is exceeded. Such samples will occur only rarely in clinical practice but when they do the diagnosis should be made with caution.     

INFLUENCE OF SAMPLE SITE ON BLOOD CONCENTRATIONS OF ICI 35 868

Simultaneous blood samples from an artery, a peripheral veinand a central vein were analysed for ICI 35 868 concentrationsfollowing an induction dose of 2.0 mg kg^–1 administeredi.v. over 60 s, to five patients before cardiac surgery. Upto 60 s after the end of the administration of the drug therewere wide differences in drug concentration between the samplingsites. Thus, any attempt to correlate effect with blood concentrationover this early period would be problematic. From 60 s therewere no significant differences in drug concentration betweenthe three sites. Thus, as long as the mixing period is allowedfor, peripheral venous sampling provides an acceptable alternativeto arterial puncture in studies to correlate drug effect andconcentration and for pharmacokinetic investigations.     

On the early-stage diametral tensile strength of dental amalgam

It was investigated whether theoretical doubts against the diametral tensile strength test applied to a material such as dental amalgam in the early stage of hardening have practical consequences. The diametral tensile strength values were compared with compressive strengths. The same conclusions may be drawn independent of whether a compressive or a diametral test is used.