John R. McLean

The Effects of Restricted Preview on Driver Steering Control and Performance

Driver steering control and performance were studied for straight-lane driving under conditions of restricted far-sight distance. The far-sight distance necessary for the driver to adequately align the car was found to be 70 ft. and was independent of vehicle speeds of 20 and 30 m.p.h. With far-sight distances beyond 70 ft., there was no improvement in driver steering performance. Spectral analysis of steering wheel angle showed peaks in the frequency range 0.1 to 0.3 Hz. The value of the peak frequency was affected by allowed preview time, where preview time was far-sight distance divided by vehicle speed. Cross-correlation analysis suggested that the peaks were associated with the drivers control of vehicle heading angle. Higher frequency peaks were observed in the range 0.35 to 0.6 Hz. These peaks were more likely to occur under conditions of severely reduced preview.

Noradrenaline uptake by non-innervated smooth muscle

1 Uptake of noradrenaline (NA) into the non‐innervated smooth muscle cells of the human umbilical artery and the chick amnion has been studied with the fluorescence histochemical technique for localizing monoamines. Comparison has been made with uptake into sympathetically innervated smooth muscle of the rabbit ear artery. 2 Accumulation of NA within non‐innervated smooth muscle cells is observed histochemically after exposure to much lower concentrations of NA (10−7 g/ml) than in sympathetically innervated smooth muscle cells, where accumulation occurs with NA (10−5 g/ml). 3 In contrast to innervated smooth muscle, uptake of NA (10−4 g/ml) by non‐innervated smooth muscle is characterized by lack of inhibition by phenoxybenzamine, normetanephrine and cold, although some inhibition is apparent at lower NA concentrations. Retention of NA during prolonged washing in NA‐free Krebs demonstrates that it is strongly bound within the non‐innervated smooth muscle cells, particularly in the nucleus. 4 After inhibition of catechol‐O‐methyl transferase, the accumulation of NA in innervated smooth muscle closely resembles that in non‐innervated smooth muscle.

STEERING REVERSALS AS A MEASURE OF DRIVER PERFORMANCE AND STEERING TASK DIFFICULTY

A review is made of past work in which steering reversal rates were used as a measure of driver performance. The data from two previously reported experiments carried out in a controlled situation, are used to compare steering reversal rates with other performance measures. It is shown that, while steering reversal rates correlate with other measures of control frequency, they do not necessarily correlate with measures of absolute steering performance. This result is consistent with the view that frequency characteristics provide a measure of steering task difficulty rather than steering performance. It is shown that, when considering steering task difficulty, care must be taken to differentiate between the difficulty imposed by the task constraints and the factors which affect the drivers ability to maintain a level of performance commensurate with those constraints.

HISTOCHEMICAL LOCALIZATION OF CATECHOLAMINES IN THE URINARY BLADDER OF THE TOAD (BUFO MARINUS)

Fluorescent histochemical localization of monoamines in whole mounts of the bladder of the toad (Bufo marinus) revealed bundles of fluorescent nerves containing predominantly adrenaline. These formed a wide meshed net work about arteries but not veins. A small proportion of muscle bundles was supplied by fine varicose fluorescent nerves. Loading with adrenaline or noradrenaline increased the intensity of the fluorescence in the nerves, but produced no appreciable increase in the number of muscle bundles supplied by fluorescent nerves. Large, brilliantly fluorescent cells containing a primary monoamine were located along nerve bundles. Chronic reserpine treatment abolished the fluorescence in nerves but not in these cells. Ganglion cells showed no specific fluorescence, nor did fluorescent terminals impinge on them, but many ganglion cells contained autofluorescent granules. The significance of the presence and localization of catecholamines in the toad bladder is discussed in relation to the pharmacology of the organ and to histochemical investigations of the innervation in other vertebrate bladders.

Analysis of Drivers' Control Movements

Driver control movements were studied in two simple steering tasks: driving along a straight lane and on a circular path. In both cases drivers were found to make most of their control movements within a fairly small frequency range. Spectral analysis shows peaks in spectral density in the range 0.15 to 0.3 Hz. for the circular course and 0.1 to 0.2 Hz. for most cases on the straight course. In a number of trials, secondary peaks occurred in the region 0.35 to 0.6 Hz. An attempt is made to explain these results in terms of the information being used by the driver to steer the car. In the circular-course experiment each driver drove the vehicle with three different steering ratios. Change of steering ratio did not show any consistent effect on the form of the spectrum of steering-wheel angle.

Catecholamine-containing neurons and lymphoid cells in a lacrimal gland of the pigeon

The Harderian gland of birds, a major lacrimal gland, contains a large population of lymphoid cells that produce IgA, a significant component of tears. Using histochemical techniques, we have examined the innervation of the gland. There was an extensive acetylcholine-esterase positive fiber network throughout the gland. However, catecholamine positive fibers were seen mainly associated with peripheral blood vessels and the lymphoid cell population which contained autofluorescent plasma cells. Ultrastructural examination showed that vesicle filled nerve varicosities were often seen near plasma cells and that some of these varicosities reacted positively for catecholamines. These anatomical data suggest that the lymphoid cell population may be affected by the autonomic nervous system.

The distribution of cholinergic and adrenergic nerve fibres in the retractor penis and vas deferens of the dog

SummarySections of the retractor penis and vas deferens of the dog have been examined to reveal the histochemical localization of noradrenaline (NA) and acetylcholinesterase (AChE) in the intrinsic nerve fibres. Pine varicose nerves containing NA were abundant along the entire length of the retractor penis muscle, while fine fibres exhibiting high AChE activity were restricted almost entirely to the anterior half of the muscle. In the testicular end of the vas deferens, a dense plexus of noradrenergic nerves was found at the base of the mucosal epithelial cells and other NA-containing nerves were scattered relatively sparsely through the muscle coats. In contrast, at the urethral end, the smooth muscle coats contained a far more dense population of NA-containing nerves, and there was no evidence of a submucosal nerve plexus. Fibres exhibiting high AChE activity were also found throughout the muscle coats, but no concentration of staining fibres was observed in the submucosa at the testicular end of the organ. It is concluded that the smooth muscle of both the retractor penis and the vas deferens of the dog may receive innervation from separate adrenergic and cholinergic fibres. Appreciable levels of AChE do not appear to be associated with adrenergic axons in this species.

Non-adrenergic, non-cholinergic neurons innervating the guinea-pig trachea are located in the oesophagus : evidence from retrograde neuronal tracing

The possibility that non-adrenergic, non-cholinergic (NANC) neurons innervating the guinea-pig trachea may be located within the oesophagus has been investigated using an in vitro retrograde tracing technique. The cervical trachea and oesophagus were excised from guinea-pigs and Dil was applied to a 5 mm region of the trachealis muscle. These preparations were maintained in organotypic culture for 3 days and processed for immunohistochemistry. A mean of 44 (4 neural cell bodies in the oesophageal myenteric plexus were found to be labelled by Dil. The vast majority of these neurons contained nitric oxide synthase, vasoactive intestinal polypeptide and neuropeptide Y. It is suggested that the population of neurons identified in this study are postganglionic parasympathetic neurons mediating NANC relaxation of the trachealis muscle in this species.

Axoplasmic flow of adrenaline and monoamine oxidase in amphibian sympathetic nerves.

SummaryThe accumulation of both A and MAO proximal to a ligature on toad spinal nerves has been shown to occur at a slower rate than in mammals. As in mammals, there are two components of axonal transport in amphibian nerves, with the accumulation of A reaching a peak at between 4 and 7 days (cf. 2–4 days for NA in mammals), while MAO accumulation does not reach its maximum before 9 days (cf. 7 days in mammals). No accumulation occurs after sympathectomy, providing evidence for localization of MAO within amphibian sympathetic adrenergic nerves. Distal accumulation of MAO occurs in toad sympathetic nerves; this has not been reported to occur in mammalian nerves. Distal accumulation reaches a peak at 2–4 days, which suggests either a fast retrograde flow of MAO or that induction of MAO is occurring. These results are discussed in relation to differences between mammalian and amphibian sympathetic nerves and to the events occurring following ligation of these nerves.

Extraneuronal effects of 6-hydroxydopamine

SummaryThe effects of various concentrations of 6-hydroxydopamine (6OHDA) on rat adrenocortical cells in tissue culture were studied with phase contrast and electron microscopy. With 40 mg/l of 6-OHDA the first signs of alteration as revealed by microcinematography appeared in isolated cortical cells as early as 15 min after addition of the drug. There was a cessation of movement of cell organelles and an immobilisation of membrane undulations followed by the development of dark inclusion bodies. The cells underwent increasing shrinkage and collapsed by 11/2 h. Chromaffin cells were not affected until 45 min after exposure to the drug and neurons were the most resistant population. However 61/2 h after application of the drug most cells in the culture were dead. 6-OHDA applied in different doses and to adrenal expiants did not alter the sequence of events. Ultrastructurally cortex cells underwent damage along two lines: they either showed lytic changes or developed various types of dense bodies before reaching the lytic stage.Treatment of cortical cells with 40 mg/l 5-or 6-OHDA followed by exposure to buffered 2% glyoxylic acid and heat did not produce a fluorescence within the cells. Microspectrofluorimetry on amine models with noradrenaline, 5- and 6-OHDA revealed that neither 5-nor 6-OHDA are capable to form a fluorophore with glyoxylic acid.