The nature of the 5''-linked 5'' nucleotide sequence at the 5'' end of rabbit globin messenger ribonucleic acid.

Poly(A)-containing messenger RNA isolated from rabbit reticulocytes as estimated by periodate oxidation and condensation with [3H]isoniazid has two oxidizable end groups per molecule of mol. wt. 220000. When the mRNA is subjected to stepwise degradation by beta-elimination, only one oxidizable end-group is found. This indicates that one of the 2',3' hydroxyl end-groups is linked through the normal 3'--5' phosphodiester bond, but that the other is linked in such a way that after stepwise degradation no new 2',3 hydroxyl group is revealed. This structure could be a 5'-linked 5'-phospho di- or tri-ester. On digestion with ribonuclease the isoniazid-labelled RNA produced oligonucleotide hydrazones consistent with a poly(A) sequence at the 3' end plus fragments that are not found after stepwise degradation. These fragments have a charge of --6 and --8 from pancreatic ribonuclease or --7 from ribonuclease T1 digestion. These charges are changed to --3.4 and --4.1 after pancreatic ribonuclease, ribonuclease T2 and alkaline phosphatase digestion. methyl-3H-labelled-poly(A)-containing RNA isolated from late erythroid cells contain a methyl-labelled fragment resistant to endonuclease and phosphodiesterase II digestion. After digestion with phosphodiesterase I this fragment produces methyl-3 H-labelled nucleotides with the electrophoretic mobility of pm7G and pAm. It is concluded that globin mRNA has the 5' sequences m7G(5')ppp'AmpYpGp ... and m7G(5')pppAmpApGpYp.     

Release of gastrin by vagal stimulation in the acid secretory response to food.

Gastric pouches were constructed in 8 dogs; in 4 they were of denervated type and in 4 the innervation was intact. An oesophageal fistula was then prepared in each dog. The acid secretory response to oral, tube and sham feeding was determined before and after denervation of the pyloric antrum. The results support the view that vagal release of gastrin makes a relatively small contribution to the total acid secretory response to food.     

Cryopreservation of human granulocytes.

Granulocyte preservation was undertaken using hydroxyethylstarch for both sedimentation of red cells and cryopreservation of buffy coat white cells from CPD whole blood. Buffy coats were mixed with HES to a final concentration of 4% (w/v) and hematocrit of 30%, and sedimented in inverted plastic syringes. The leukocyte enriched (100–500×) supernatant was frozen at 2.0 °C/min to ?80 °C (and stored frozen up to 3 months). Alternatively, sedimented leukocytes were frozen after a slow addition of 10% DMSO to 5%. Tubes were thawed at 37 °C, and DMSO was removed by dilution with Hank's solution containing CPD and centrifugation. The pellets of granulocytes were resuspended in Normosol.Buffy coat from 10 units yielded 60 ± 9.7% of the available whole blood leukocytes, of which 43 ± 14% were recovered after sedimentation in HES. Freezing in DMSO yielded all, 101% of the prefrozen leukocytes. Postthawed viability of granulocytes was estimated morphologically and by their ability to inhibit the rate of growth of E. coli. Complete inhibition was observed at a ratio of one E. coli to one granulocyte. Postthawed granulocytes were characterized by high myeloperoxidase activity and exclusion of trypan blue. Approximately 25% of the total available granulocytes in CPD whole blood were recovered.     

Control of protein synthesis in reticulocyte lysates: the effect of nucleotide triphosphates on formation of the translational repressor.

High concentrations (1–2mM) of GTP completely prevented the decline in protein synthesis which occurs in a reticulocyte lysate incubated in the absence of haemin. The effect of GTP was diminished by raising the concentration of ATP. When formation of the haemin-controlled translational repressor was studied as a partial reaction using post-ribosomal supernatant, it was found that GTP acted by blocking repressor formation, whilst ATP was found to stimulate this process.     

Thermoregulatory, metabolic, and cardiovascular response of rats to microwaves.

This study was undertaken to determine the effects of 2,450-MHz microwave irradiation on thermoregulation, metabolism, and cardiovascular function of rats. Young adult male animals (430 g) were exposed for 30 min to 2,450-MHz microwaves in a cavity at absorbed dose rates of 0, 4.5, 6.5, or 11.1 mW/G. For animals of the size used in this study, these dose rates represent absorption of energy at the rate of 27.7, 40.1, and 68.2 cal/min, respectively. For a period of 5 h following exposure, measurements were made of colonic temperature, skin temperature, oxygen consumption, carbon dioxide production, respiratory quotient, and heart rate. Rats that received 27.7 cal/min for 30 min exhibited an initial transient increase in colonic and skin temperatures but no alterations in other functions. The group irradiated at 40.1 cal/min had greater elevations in colonic and skin temperatures immediately after exposure, followed by overcompensation and lower than normal colonic temperatures for about 3 h. The metabolic rate was depressed in this group for 3 h. Bradycardia developed within 20 min after exposure and persisted for about 3 h. The group of rats that received 68.2 cal/min for 30 min had responses similar to those of the 40.1 cal/min group, but the changes were more severe and lasted longer. In addition, a number of transient abnormalities were noted in the ECG tracings of rats that had received the highest dose, including irregular rhythms and incomplete heart block. The physiological changes observed in this study can be attributed to the heating induced by irradiation.     

The effects of diet, lipolysis and limb ischaemia on the distribution of plasma tryptophan in the rat.

A non-linear relationship between the plasma non-esterified fatty acid concentration and the percentage of free plasma tryptophan was found in rats in different nutritional states, although non-esterified fatty acids are not the only factors determining the percentage of free tryptophan. This relationship was not seen in rats injured by limb ischaemia. The effect of drugs causing rapid increases in the plasma non-esterified fatty acid concentration was also studied. Isoprenaline decreased the total plasma tryptophan concentration. Dichloroisoprenaline caused a sustained increase in the plasma non-esterified fatty acid concentration which was accompanied by an increase in the concentration of free plasma tryptophan and followed by a fall in the concentration of total tryptophan. The loss of tryptophan from the plasma was attributed to an altered distribution of tryptophan in the extracellular space rather than to increased metabolism. This interpretation was supported by determinations of the irreversible disposal rate of plasma tryptophan which in uninjured rats was unaffected by the concentration of free plasma tryptophan. In the injured rats this rate was unaltered during limb ischaemia but was decreased after removal of the tourniquets; increased competition for tissue entry by other neutral amino acids and the fall in body temperature could be factors in this fall.