2ZD, 2Department of Biochemistry and 3Department of Pharmacology, Marischal College, University of Aberdeen AB9 lAS 1 The localisation and distribution of cytochrome P-450 in human tissues has been studied by immunocytochemistry using a monoclonal antibody to a major form of human hepatic cytochrome P-450, P-45OhA7, which is closely related to cytochromes P-450 HLp and P-45ONF. 2 Strong immunoreactivity was identified in hepatocytes, columnar absorptive epithelial cells of the small intestine, polymorphonuclear leucocytes and their precursors in the bone marrow, and in mast cells.3 Weak immunoreactivity was present in the proximal tubules of the kidney, pancreatic acini, gall bladder epithelium, squamous epithelium and sebaceous glands of the skin, interstitial cells of the testis and luteal cells of the ovary. 4 Immunoreactivity could not be demonstrated in the adrenal gland, placenta, colonic epithelium and alveolar type II cells and Clara cells of the lung.

SUMMARYTwo indices of motor unit recruitment, the ramp-force and repetitive-discharge thresholds, were compared in the first dorsal interosseus muscle of ten young and twelve elderly subjects. The purpose was to determine the effect of age on the relationship between the two recruitment thresholds and the spike-triggered average force of motor units. Each subject performed three tasks requiring isometric abduction of the left index finger: a maximum voluntary contraction (MVC), a ramp-and-hold contraction, and a repetitive-discharge task. The elderly subjects used coactivation of the antagonist muscle (second palmar interosseus) more frequently than the young subjects during the ramp-and-hold contraction. Many elderly subjects expressed difficulty with the controlled ramp-down phase of the ramp-and-hold contraction and preferred a coactivation strategy to a derecruitment strategy for this task. There were no differences due to age or gender in the ramp-force thresholds between the various groups. However, the normalized repetitivedischarge threshold was significantly less for the younger subjects and for the male subjects. Nonetheless, the two recruitment thresholds were able to predict the spike-triggered average force with similar success for both the young and the elderly subjects. These data suggest that the recruitment threshold of a motor unit in first dorsal interosseus was characterized equally well by either the ramp-force or repetitive-discharge measurement for both young and elderly subjects but that coactivation was used more frequently by the elderly subjects during the ramp-and-hold task.

Haemolytic uraemic syndrome secondary to infection with neuraminidase producing Streptococcus pneumoniae is well recognised, but was previously considered to be rare. This case report describes the course of a 9-month-old male with pneumococcal pneumonia, T activation and haemolytic uraemic syndrome. The clinical features of three other cases treated in Southeast Queensland in the past 2 years and 12 previously reported cases are summarised. The widespread availability of rapid diagnostic testing for this entity should allow for increased recognition, enabling appropriate use of low plasma volume blood products with improved patient outcome.

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Objective Five studies are described to determine whether there is an outermost lining of surface-active phospholipid (SAPL) adsorbed to the peritoneum and to quantify its ability to act as a release (antistick) agent and boundary lubricant by standard tests. Methods Using a hydrophobic probe (phosphin E), epifluorescence microscopy was used to demonstrate an outermost lining of oligolamellar SAPL by spectral analysis of the emitted light, a finding consistent with the appreciable hydrophobicity demonstrated on canine peritoneal mesothelium and its virtual elimination by incubation with bile salt. Good release and excellent lubricating capabilities of human peritoneal SAPL have been quantified as the release factor and coefficient of friction, respectively, by standard tests from the physical sciences. Results A well-defined outermost layer was clearly visible on peritoneal mesothelium whose color spectrum was identical to that produced by pure phosphatidylcholine ultrasonicated into its oligolamellar state. Further evidence for a SAPL lining was demonstrated by a parietal contact angle of 43° (47° visceral) on this surface and its virtual elimination by incubation with dilute bile salt. Human SAPL from continuous ambulatory peritoneal dialysis (CAPD) effluent proved an effective release agent, reducing adhesion by 67%, and an excellent lubricant as quantified by a coefficient of friction of 0.091 under load (1.9 kg/cm2). Conclusions The good release and excellent lubricating properties of SAPL adsorbed to mesothelial surfaces are highly desirable in reducing wear and exfoliation of epithelial cells. In spanning epithelial cells, the same lining might also serve to render tight junctions tight and reduce macromolecular escape while compatible with many aspects of CAPD, including lipid permeability and conflicting results obtained from administering exogenous SAPL.

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Flounder Platichthys flesus from a pollution gradient in the Forth estuary, Scotland, were analysed for specific cytochrome P-450 and metal-binding protein induction as an indication of sublethal impact of organic xenobiotics and Group IIB metals respectively. Hepatic ethoxyresorufin Odeethylase (EROD) activity in fish from a reference site was around 9 nmol (g liver)-' min-l and increased up to 9-fold in the area near discharges from a major petrochemical complex. Hepatic metallothionein (MT) content rose from 20 pg (g liver)-' at the uppermost site by ca 19-fold near the petrochemical complex. The study further demonstrates the validity of biochemical measurements for the assessment of pollutant impact in an estuarine environment.

Atlantic menhaden, Brevoortia tyrannus, spawn on the continental shelf off North Carolina in the late fall and winter. Larvae are transported shoreward where they enter and migrate up estuaries to the juvenile habitat. In this paper, we synthesize behavioural and sensory physiological studies of the ontogeny of biological rhythms, responses to temperature, salinity and light, and swimbladder inflation and deflation of this species, to develop descriptive models of larval behaviour in ocean and estuarine areas that contribute to horizontal transport. Young (postyoke sac, <9 mm total length, TL) larvae occur primarily offshore, have an endogenous rhythm in nocturnal diel vertical migration, and are predicted to remain at depths above the pycnocline, if present, due to responses to light, temperature and salinity. They ascend in response to a salinity increase and temperature decrease, which frequently occur at the pycnocline. Intermediate age (9–17 mm TL) and older (18–27 mm TL) larvae are found in inshore and estuarine areas. They have an endogenous activity rhythm that suggests they will remain at moderate depths during the day in the ocean. At sunset, they swim up to surface to engulf air to fill their swimbladders and then sink due to inactivity and negative buoyancy. Thus, at night the majority of larvae are deeper than during the day. The swimbladder is deflated at sunrise in response to light and larvae are predicted to swim up to their daytime depth. They have the same responses to a temperature decrease and salinity increase as younger larvae, which should keep them above a pycnocline. The ascent to fill the swimbladder is not impeded by responses to temperature or salinity change. Chemical cues in ocean and estuarine waters induce different behavioural responses. Larvae use selective tidal stream transport for up‐estuary movement in which they are in the water column on rising tides at night and not abundant at other times. Larvae lack an endogenous tidal rhythm in vertical migration upon entering an estuary, and swimming during the day is reduced by light. The ascent into the water column during flood tides may be cued by the rate of increase in salinity at this time. Collectively, these behaviours contribute to feeding, predator avoidance and transport from the spawning area to the juvenile habitat.