The complete nucleotide sequence of wheat germ phenylalanine transfer RNA (tRNA(Phe)) is presented. This RNA, which is an acceptable substrate for yeast phenylalanine tRNA synthetase, has a structure very similar to that of yeast tRNA(Phe). Only 16 of the 76 nucleotides are different, and all but two of the nucleotide changes are located in regions that are doublestranded in the cloverleaf model. The two changes in single-stranded regions involve minor modifications of the same nucleotide. The dihydrouridine loop and its supporting stem are completely free of nucleotide changes.

Amino Acid Sequence↗

PubMed1969

Evaporative water loss in the new-born baby.

1. Measurements of total evaporative water loss (EWL) were made on sixty-three premature and full-term babies 0-65 days after birth within a closed Perspex chamber under varied environmental conditions by measuring the flow and absolute humidity of air entering and leaving the chamber. Control experiments suggested that the method underestimated loss by about 5%. Measurements of O(2) consumption were made concurrently by recording the volume change of the closed gas circuit.2. The total basal EWL averaged 10.8 g H(2)O/m(2).hr in infants 2-10 days old when ambient water vapour pressure (P(H2O)) was 18 mm Hg; basal EWL was correlated with basal metabolic rate at all ages studied and evaporative heat loss accounted for approximately 23% of basal heat production.3. Respiratory water loss was measured by detecting the water added to air at 33 degrees C passed across the face of eight infants in a trunk plethysmograph. Respiratory water loss was inversely related to the water vapour content of the inspired air; gas appeared to leave the nose approximately 95% sat. at 35.6 degrees C.4. Measurements of total EWL were obtained when humidity was varied and skin loss was calculated by subtracting estimated respiratory loss from total loss; changing P(H2O) from 7 to 25 mm Hg appeared to decrease basal skin water loss by only 1.5 g/m(2).hr.5. No consistent changes in EWL were obtained when environmental temperature (T(E)) was varied between 28 and 34 degrees C. Active sweating occurred in infants 0-10 days old born within 3 weeks of term when T(E) exceeded 34-35 degrees C and rectal temperature (T(R)) rose above 37.2 degrees C. The threshold rectal temperature at which sweating was detected fell significantly in the first 10 days of life; EWL increased two to fourfold when T(R) rose to between 37.5 and 37.8 degrees C.6. In infants of less than 215 days post-conceptual age (term approximately 268 days) EWL increased less than 50% at T(R) 37.7-37.8 degrees C; it is concluded that the sweating mechanism is defective in these infants.

Basal Metabolism↗

PubMed1969

The response of the sweat glands of the newborn baby to thermal stimuli and to intradermal acetylcholine.

1. Measurements of evaporative sweat loss were made on fifty-six premature and full-term babies 1-67 days after birth with an infra-red analyser and a ventilated capsule placed on the thigh. Measurements were also made of total evaporative water loss while in a closed metabolic chamber and of the regional distribution of sweating with starch-iodine paper.2. No sweating to thermal stimuli could be detected in infants of less than 210 days post-conceptual age, even when rectal temperature rose as high as 37.8 degrees C. In older infants sweat was detected first on the forehead and temple, later on the chest, and usually by 240-260 days post-conceptual age on the legs (term approximately 268 days). Generalized sweating on the limbs appeared at an earlier post-conceptual age in the more prematurely born infants.3. The response of sweat glands on the thigh to an intradermal injection of 2 mug acetylcholine (ACh) was tested. No sweat response was detected in infants under 225 days post-conceptual age, while all infants born within 2 weeks of term responded. The response was often augmented after 2-5 tests at 5-10 min intervals; all the eight infants born within 2 weeks of term who were examined twice in the first 2 weeks of life showed a greater response on the second occasion.4. An average of 414 active sweat glands/cm(2) were detected on the thigh in eight babies 7-10 days old born within 2 weeks of term. This was 6(1/2) times the number found in adults. The mean peak sweat rate to chemical stimulation was however only 2.4 nl./gland.min, which was 3 times lower than the maximum rate recorded in adults.5. In five infants with congenital defects of the brain and complete absence of temperature control there was no sweat response to thermal or direct chemical stimulation of the glands.6. Functional maturation appears to depend on intact central innervation and is marginally hastened by post-natal factors. Immaturity of the sweat glands can account for the lack of any response to thermal stimuli in premature babies, but not for the modest thermal response obtained in babies at term.

Acetylcholine↗

PubMed1969