Monitoring of hospital water supplies for Legionella.

In order to determine the value of regular surveillance for Legionella in the prevention of hospital-acquired (nosocomial) legionellosis, water samples were obtained over a three-year period from 17 hospitals located in England and Scotland. Prior to the study, all of the hospitals had in operation defined protocols and maintenance schedules which followed national guidelines for the prevention of legionellosis in health care premises. Six samples, from key locations in the water system of each hospital, were taken at six-monthly intervals.

An uncrossed tectopontine pathway mediates ipsiversive circling.

Stimulation of the superior colliculus (SC) of rodents, following knife cuts to the predorsal bundle decussation, evokes ipsiversive circling along with "cringing" or avoidance responses. A major uncut SC output is the uncrossed tectopontine pathway that projects heavily to the ventrolateral pons (VLP). Stimulation of this pathway in the VLP also evokes ipsiversive circling, but the circling is smoother, lacks the avoidance components, and begins with a shorter latency than SC circling.

Electrically evoked turning: asymmetric and symmetric collision between anteromedial cortex and striatum.

Electrical stimulation of the anteromedial cortex (AMC) or striatum of rats evoked contraversive eye, head and body movements. In these experiments we test which neurons and which pathways are responsible for the turning by delivering conditioning (C) pulses to one site and test (T) pulses to the second site, and measuring the frequency of pulse pairs required to evoke a full turn in 10 s. Decreases in the required frequency were usually found at C-T intervals from 0.

Duration of visible persistence in relation to stimulus complexity.

Visible persistence refers to the phenomenal impression that a stimulus is still present after its offset. A dispute exists whether visible persistence is due to temporal sluggishness in the visual pathway (neural hypothesis) or whether it is a byproduct of information-extraction processes under cognitive control (process hypothesis). This was investigated by manipulating stimulus complexity in five temporal integration experiments and one recognition memory experiment.

Biopsychosocial aspects of chronic fatigue syndrome (myalgic encephalomyelitis).

Fifteen patients, with a primary complaint of chronic fatigue, were referred to a physician by their general practitioners. Psychological distress, measured by simple psychiatric rating scales was common, but specific psychiatric diagnoses, derived from a comprehensive diagnostic interview, occurred less frequently. One questionnaire (Montgomery-Asberg depression rating scale) found emotional distress in 93%, but the diagnostic instrument (Present State Examination) suggested depressive syndromes in only two patients (13%).

"Temporal summation decay" in hypothalamic self-stimulation: threshold changes at long intrapair intervals due to axonal subnormal periods.

Rats were trained to bar press for trains of conditioning (C) and test (T) pulses delivered via lateral hypothalamic electrodes. As intrapair (C-T) intervals increased from 10 ms to 100 ms, the frequency of pulses required for self-stimulation increased, similar to results of Smith and Coons (1970). This effect was observed only for electrode placements where self-stimulation was obtained at frequencies below 16 Hz and currents of 600 microA and higher.

Differential effects of atropine, procaine and dopamine in the rat ventral tegmentum on lateral hypothalamic rewarding brain stimulation.

Microinjections of the muscarinic antagonist, atropine, of dopamine, or of the local anesthetic, procaine, in the ventral tegmentum elevated frequency thresholds for lateral hypothalamic self-stimulation. The largest and most robust effects were observed following atropine (30 or 60 micrograms) microinjections. The most sensitive sites for the atropine effect were near dopamine cells.

Double-pulse stimulation of startle-like responses in rats: refractory periods and temporal summation.

A startle-like response was evoked by electrical stimulation with one pulse in several brainstem sites of the primary acoustic startle circuit. If a second pulse was delivered 0.4-10 ms after the first pulse, a stronger response or a decreased current threshold resulted.

Two substrates for medial forebrain bundle self-stimulation: myelinated axons and dopamine axons.

The directly activated substrates for medial forebrain bundle (MFB) self-stimulation are primarily low threshold, myelinated axons with absolute refractory periods of 0.4 to 1.2 msec, conduction velocities of 1 to 8 m/sec and current-distance constants of 1000 to 3000 microA/mm2.

Cholinergic antagonists in ventral tegmentum elevate thresholds for lateral hypothalamic and brainstem self-stimulation.

Frequency thresholds for lateral hypothalamic self-stimulation are elevated following microinjections of atropine into ventral tegmentum (73). Many self-stimulation sites in brainstem are situated near cholinergic cell groups and axons, and ventral tegmentum receives cholinergic afferents terminals. To test the hypothesis that ventral tegmental muscarinic receptors are involved in lateral hypothalamic and brainstem self-stimulation, stimulating electrodes were placed in lateral hypothalamus and dorsal tegmentum near the midbrain-pons border, and cannulae were implanted in ventral tegmentum.

Turning responses evoked by stimulation of visuomotor pathways.

Lateral eye, head, and body movements are produced by electrical stimulation of many brain regions from frontal cortex to pons. A new collision method shows that at least 5 separate axon bundles mediate stimulation-elicited lateral head and body movements in rats. One bundle passes between the rostromedial tegmentum and medial pons, with conduction velocities of 0.

Excitability properties of medial forebrain bundle axons of A9 and A10 dopamine cells.

A9 and A10 units identified as dopaminergic were recorded with extracellular micropipettes. The units were antidromically activated by electrical stimulation at the level of the preoptic area. The absolute refractory periods ranged from 1.

Contraversive circling elicited from the internal capsule and substantia nigra: evidence for a continuous axon bundle mediating circling.

Electrical stimulation of many brain sites (e.g., anteromedial cortex, internal capsule, substantia nigra, superior colliculus, rostro-medial tegmentum, and medial pons) evokes circling.

Circling elicited from the anteromedial cortex and medial pons: refractory periods and summation.

Contraversive circling is evoked by stimulating the anteromedial cortex (AMC) of rats, and ipsiversive circling is evoked by stimulating the medial pons (PONS). During AMC circling, lateral and vertical head movements and vibrissae movements were exhibited. During PONS circling, although lateral head movements were exhibited, vertical head movements and vibrissae movements were not exhibited.

Two converging brainstem pathways mediating circling behavior.

Ipsiversive circling results from stimulation of the rostromedial tegmentum (RMT) or medial pons (PONS), and contraversive circling results from stimulation of the superior colliculus (SC). To determine whether these sites are functionally connected, the collision method of Shizgal, Bielajew, Corbett, Skelton and Yeomans (1980) was used in rats. Pairs of stimulation pulses were presented to two sites, and the degree of collision between stimulation-evoked action potentials was assessed by measuring the frequency required for circling at short and long intrapair conditioning-testing (C-T) intervals.

Sensory registration and informational persistence.

The traditional view of iconic memory as a precategorical, high-capacity, quickly decaying visible memory has recently come under attack (e.g., Coltheart, 1980).

Current-distance relations of axons mediating circling elicited by midbrain stimulation.

Stimulation of mediocaudal midbrain in rats produces ipsiversive circling due to the stimulation of longitudinal axons. The refractory periods of these axons were measured by delivering trains of conditioning and testing pulses via a single electrode at various conditioning-testing (C-T) intervals. As C-T interval increased from 0.

Behaviorally measured refractory periods are lengthened by reducing electrode tip exposure or raising current.

Small tip exposures and high currents allow the stimulation of high-threshold axons. These studies were conducted to measure the effects of current and tip surface area on stimulation parameters required to produce a constant rate of self-stimulation of lateral hypothalamic sites, or of circling when stimulating medial brain stem sites. Thresholds for circling decreased when tip surface area was decreased to 0.

Longitudinal brainstem axons mediating circling: behavioral measurement of conduction velocity distributions.

Current applied near the midline brainstem elicits rapid ipsiversive circling. Pontine and midbrain sites were stimulated concurrently with paired pulses and the number of pulse pairs required to produce 3 complete circles in 10 s was measured at various intrapair (C-T) intervals. The same results were obtained when C pulses were presented via the midbrain electrode and T pulses via the pontine electrode, or vice versa: as C-T interval increased from 0.