SUMMARY1. Action potentials were recorded from single afferent units of the superior laryngeal nerves in neonatal and adult sheep, cats and monkeys when liquids were passed over the laryngeal mucosa. 2. Two types of mucosal receptors, sensitive to water but not to isotonic saline, were found in each species from birth. The most common type of unit responded after a short latency ( < 1 sec), discharged maximally in the first 1-3 see and became inactive when the stimulus was withdrawn. The other type responded only after several seconds, the discharges gradually increasing in frequency and continuing after removal of the stimulus.3. Reproducible responses were elicited by tactile stimulation of the laryngeal mucosa over the receptive field of each of the long-latency units. Fewer than 50 % of the short-latency units were excited, the remainder responding only unreproducibly to firm pressure.4. Short-latency, but not long-latency, units responded to milks, gastric contents, saliva and isotonic solutions of sugars.5. The responses of long-latency units to water were often modified by, but rarely dependent on, reflexly evoked activity in laryngeal muscles.6. The conduction velocities of afferent fibres of water sensitive units ranged from 22 to 49 m/sec, and differed little from those of water-insensitive laryngeal mechanoreceptors.7. Histological examination of the laryngeal mucosa showed that taste buds were present in lambs from birth whereas they developed post-natally in kittens and monkeys. The evidence suggests that taste buds were not associated with watersensitive units.

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SUMMARY1. Direct simultaneous recordings from chronically implanted electrodes in different parts of the diaphragm were made in young lambs in which laryngeal adductor (thyroarytenoideus) and intercostal electromyograms, airflow, tracheal pressure and electrocorticogram and electro-oculograms for behavioural state were also recorded.2. An asynchrony of diaphragmatic contraction occurred which was dependent on sleep state. The vertebral portion showed maximal post-inspiratory activity while the lateral paratendinous portion usually terminated abruptly with end-inspiration, reciprocating closely with the onset of expiratory laryngeal adductor activity during quiet sleep. The contraction of the sternal portion was similar to the vertebral portion. In active (rapid eye movement) sleep there was no expiratory laryngeal constriction and post-inspiratory activity occurred in all portions of the diaphragm. During the characteristic bursts of rapid breathing in active sleep all post-inspiratory activity disappeared and the diaphragm contracted synchronously.3. General anaesthesia (Halothane/N20 or Nembutal) abolished expiratory laryngeal adductor activity and the discharge pattern became similar in all parts of the diaphragm.4. Intrathoracic vagotomy of Xylocaine blockade below the recurrent laryngeal nerves abolished post'inspiratory activity in all parts of the diaphragm, in contrast to the effect on expiratory laryngeal adductor activity which increased.5. Sustained 'tonic' electromyographic activity was often recorded from the costa and to a lesser extent the paratendinous portion of the diaphragm. This activity related to adjacent intercostal activity:ipsilateral intercostal blockade with local anaesthetic (Xylocaine 1 %) abolished both the intercostal and the 'tonic' activity of the costal margins of the diaphragm. Conversely ipsilateral phrenic nerve blockade abolished all but the 'tonic' activity which related to intercostal activity.6. Interpretation of the respiratory activity of the diaphragm could not be made adequately from conventionally placed electrodes (i.e. costal, sternal slip or surface) during spontaneous breathing in unanaesthetized lambs. Simultaneous recordings showed that while expiratory flow and duration were actively controlled by expiratory * To whom requests for reprints should be addressed. t Present address:

Respiration, sinus nerve chemoreceptor discharge, and carotid arterial pH were monitored in cats. Chemoreceptor discharge frequency showed oscillations that had a respiratory period when averaged over many respiratory cycles. These oscillations disappeared when pH oscillations of respiratory period were eliminated from the carotid arterial blood. The maximum sinus nerve discharge was associated with the most acid point of the recorded pH oscillation. Briefly increasing PCO2 by giving CO2-rich saline into the aortic root resulted in brief reduction in carotid arterial pH, and when this reduction occurred during inspiration tidal volume increased, even with a pH change no larger than the pH oscillations. However, increased chemoreceptor discharge could only be demonstrated when each pH change had twice the amplitude of the pH oscillations. Injections of fixed acid mixed with free carbonic anhydrase transiently increased chemoreceptor frequency, whereas injections of fixed acid alone had no effect. The carotid body is therefore sensitive to small rapid changes in arterial PCO2, and the pH electrode record indicates the size of the stimulus except when fixed acid changes are produced too closely upstream.

Growth and bone histoiogy in experimental uremia Material and Methods: Male Spra e-Dawley rats were subjected to subtotal nephrectomy stage procedure with irradiation of rest parenchyma) reducing GFR(CCR) 4 weeks p.0. to 19.8% of shamop, pairfed controls.Serum (creatinine, urea, electrolytes) and urine (elec trolytes, protein, CAMP, aminoacids) chemistry, fecal fat and nitrogen, body wei ht, body length, tibia geometry, tibia histology fv.Kossa stain) and total body fat were measured. Results and conc1usions:Longitudinal growth in uremic rats was reduced with respect to ad lib. fed control rats, but identical with respect to pairfed control rats. The reduction of longitudinal growth is entirely accounted for by reduced calorie and protein intake in uremia (U),although rickets (histology) and 20 hyperparathyroidism (histology, urinary CAMP) are present in the U skeleton. In spite of their identical length, weight was less in U rats than in control rats. This difference is not accounted for by difference of intracellular water (measured as difference organ dry weight -organ wet weight) or extracellular water (measured as 82 Brspace). It may point to a disturbance of protein synthesis in U. HBpital OEBROUSSE -LYONCongenital r i c k e t s a premature i n f a n t : evolution of serum parathyroid hormone (iPTH) and plasma 25 hydroxycholecalciferol (25 OH CCI ( I n t r . by R. FRANCOIS)A small-for-date premature i n f a n t [gest.age =34 weeks, birthweight 1100g) had t y p i c a l X-Rays a s p e c t of r i c k e t s a t b i r t h .A t t h e age of 4 days, low serum Ca= 8 , 2 mg/100 m l , low serum P = 8,4/100 rnl and high serum a l k a l i n e phosphatase (A.P.) 323 I U / m l (,< 2001 were found. Very high l e v e l of serum iPTH was found a t 17 days of age : 295 plEq/ml ( N ( 5 0 ) . Evidence of maternal vitamin 0 d e f i c i e n c y was shown by low plasma 25 OH CC : 1.1 ng/ml (N 13 c 4 ) .Ca i n f u s i o n (15 mg/kg/3h) r e s u l t e d i n marked decrease i n iPTH (280 t o 84 plEq/mll. A t t h e age of 30 days, a d m i n i s t r a t i o n of v i t amin O2 (2400 u/day) f o r 10 days induced some healing of X-Ray aspect : A.P. remained high : 400 I U / m l ; plasma 25 OH CC was normal 10,2 ng/ml and serum iPTH decreased t o 115 plEq/ml. A t t h e age of 40 days, o r a l a d m i n i s t r a t i o n of 25 O H CC (15 pg/24h) was given f o r on a week : it r e s u l t e d i n a r i s e of 25 OH CC t o 64.5 ng/ml with minor change of serum iPTH (94 plEq/ml). This d a t a show t h a t :11 a secondary hyperparathyroidism i s present i n con g e n i t a l r i c k e t s 21 i t i s normally depressed by calcium-infusion 3) i n view of t h e r e c e n t demonstration t h a t 1-25 OH CC may be an important f a c t o r of r e g u l a t i o n of PTH s e c r e t i o n ( 0 . S. CHERTON e t a l l . S.C.I. 56, 668, 19751, t h e absence of iPTH normalization i n our case, i n s p i t e of nigh plasma 25 UH CC suggests $ reduced a c t i v a t i o n of 25 OH CC. N.MATSANIOTIS,T.KARPATHIOS*~ F.MAOUNIS*, P.N~COLAIDOU*,C.THEODORIDIS . 1st...