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Biomedical subjects

G Leng

Publications and source records attributed to G Leng.

170 records · Page 10Linked to original sources
PubMed1980

Rat supraoptic neurones: the effects of locally applied hypertonic saline.

1. Extracellular action potentials were recorded from supraoptic neurones in lactating, urethane-anaesthetized rats. A microtap was used to apply a very small volume (about 10(-7) ml.) of hypertonic saline (1-4 M-NaCl) to the immediate neighbourhood of these units over about 1 min.2. Twenty-five of twenty-seven supraoptic neurones were excited by this local osmotic stimulus. The response of individual units was reversible and repeatable. Microtap applications of isotonic saline to supraoptic neurones were without observed effect.3. Continuously firing supraoptic neurones responded to hypertonic saline with a smooth acceleration in firing rate. Phasic neurones showed an increase in the over-all level of activity, and in particular, a prolongation of the active phases. Slow, irregularly firing cells responded either with a smooth acceleration in firing rate, or with phasic behaviour.4. The response to local hypertonic saline appears to be reasonably specific to the supraoptic nucleus. Of thirty-five neurones recorded close to the supraoptic nucleus but which were not antidromically activated from stimulation of the neural stalk, only nine responded to the local application of hypertonic saline.5. Similarities between the manner of response of supraoptic neurones to local application of hypertonic saline and the manner of their response to systemic increases in the osmotic pressure of blood plasma support the hypothesis that supraoptic neurones are osmosensitive.

Action Potentials↗
PubMed1979

Effects of increased potassium in scala tympani on auditory nerve sensitivity.

Raising the K+ concentration in scala tympani of the guinea-pig cochlea generally caused a substantial increase in the spontaneous firing rate of single auditory nerve fibres. This effect was not accompanied by any observed reduction in the threshold sensitivity of these fibres. These findings cast doubt on current theories of cochlear transduction.

Action Potentials↗
PubMed1979

Action of putative neurotransmitters in the guinea pig cochlea.

Scala tympani of the guinea pig was perfused with artificial perilymph containing putative transmitter substances. Single auditory nerve fibre activity was recorded during these perfusions and the responses of these fibres were studied using computer-controlled routine. Acetylcholine significantly inhibited tone-induced responses of a large proportion of the fibres tested. Glutamate appeared to be a potent depolarising agent when applied in concentrations between 2 and 10 mM. Noradrenaline did not affect tone-induced activity, but inhibited the spontaneous activity of some fibres. The results support the view that acetylcholine is the transmitter at synapses of the olivocochlear bundle, and that glutamate may be involved in the afferent synapse. The data do not support the hypothesis that noradrenaline is the afferent transmitter.

Acetylcholine↗
PubMedDate not supplied

'Real' epidemiology of varicose veins and chronic venous diseases: the San Valentino Vascular Screening Project.

The aim of this study was to evaluate the prevalence and incidence of venous diseases and the role of concomitant/risk factors for varicose veins (VV) or chronic venous insufficiency (CVI). The study was based in San Valentino in Central Italy and was a real whole-population study. The study included 30,000 subjects in eight villages/towns evaluated with clinical assessment and duplex scanning. The global prevalence of VV was 7%; for CVI, the prevalence was 0.86% with 0.48% of ulcers. Incidence (new cases per year) was 0.22% for VV and 0.18% for CVI; 34% of patients with venous disease had never been seen or evaluated. The distribution of VV and CVI in comparison with duplex-detected incompetence (DI) indicates that 12% of subjects had only VV (no DI), 2% had DI but no VV, 7.5% had DI associated with VV, 2% apparent CVI without DI, 3% DI only (without CVI), and 1.6% both CVI and DI. VV associated with DI are rapidly progressive and CVI associated with DI often progresses to ulceration (22% in 6 years). VV without significant DI (3%) and venous dilatation without DI tend to remain at the same stage without progression for a lengthy time. New cases per year appear to have a greater increase in the working population (particularly CVI) possibly as a consequence of trauma during the working period. In older age (>80 years), the incidence of CVI tends to decrease. Ulcers increase in number with age. Only 22% of ulcers can be defined as venous (due to venous hypertension, increased ambulatory venous pressure, shorter refilling time, obstruction and DI). Medical advice for VV or CVI is requested in 164 subjects of 1,000 in the population. In 39 of 1,000, there is a problem but no medical advice is requested and in only 61 of 1,000, the venous problem is real. In VV in 78% of limbs, there is only reflux, in 8% only obstruction, and in 14% both. In CVI, 58% of limbs have reflux, 23% obstruction, and 19% both. In conclusion, VV and CVI are more common with increasing age. The increase with age is linear. There was no important difference between males and females. These results are the basis for future real, whole population studies to evaluate VV and CVI.

Adolescent↗
PubMedDate not supplied

The effect of potassium on the activity of auditory nerve fibres of the guinea pig cochlea.

Scala tympani of the guinea pig cochlea was perfused with solutions having an increased potassium concentration. The response characteristics of single auditory nerve fibres in both normal and kanamycin-damaged cochleas were studied using computer controlled routines. The results indicate that these perfusions caused a marked increase in the spontaneous firing rate of auditory nerve fibres, without loss of threshold sensitivity. Current theories of cochlear transduction support the view that the potassium concentration difference across the reticular plate is fundamental to the sensitivity of the cochlea. The results presented here do not support this view.

Acoustic Stimulation↗