PubMed Health⌕ Search

Biomedical subjects

A G Morton

Publications and source records attributed to A G Morton.

At least 19 recordsLinked to original sources
PubMed1989

Cerebellar abiotrophy in crossbred cattle.

Cerebellar abiotrophy affected 9 of 74 calves sired by a Poll Hereford bull over 2 successive calving seasons. The disease was characterised by episodes of recumbency and ataxia, with hypermetria and wide base stance. Clinical signs commenced between birth and 8 months of age. Two calves which were affected first at 8 months of age recovered clinically 9 months later. Histological lesions were found in the cerebellar cortex of 7 calves and consisted of segmental degeneration and loss of Purkinje cells, and axonal swellings. The clinical signs and pathological findings were consistent with bovine familial convulsions and ataxia, which has not been described previously in Australia. The clinical signs were not attributable to the lesions observed in the cerebellum and an underlying electrophysiological abnormality is proposed. The aetiology of the condition is probably genetic and appears to have a multifactorial basis.

Animals↗
PubMed1988

General method for quantifying base adducts in specific mammalian genes.

A general method has been developed to measure the formation and removal of DNA adducts in defined sequences of mammalian genomes. Adducted genomic DNA is digested with an appropriate restriction enzyme, treated with Escherichia coli UvrABC excision nuclease (ABC excinuclease), subjected to alkaline gel electrophoresis, and probed for specific sequences by Southern hybridization. The ABC excinuclease incises DNA containing bulky adducts and thus reduces the intensity of the full-length fragments in Southern hybridization in proportion to the number of adducts present in the probed sequence. This method is similar to that developed by Bohr et al. [Bohr, V. A., Smith, C. A., Okumoto, D. S. & Hanawalt, P. C. (1985) Cell 40, 359-369] for quantifying pyrimidine dimers by using T4 endonuclease V. Because of the wide substrate range of ABC exinuclease, however, our method can be used to quantify a large variety of DNA adducts in specific genomic sequences.

4-Nitroquinoline-1-oxide↗
PubMed1980

The regulation of iron release from the perfused rat liver.

Factors affecting iron efflux from the isolated perfused rat liver were studied following the intravenous administration of transferrin-(59)Fe or transferrin-(55)Fe administered to the rat from 1.5 h to 3.5 d before perfusion of the liver. The liver was perfused with rat red cells suspended either in rat plasma or Eagle's Basal Medium (EBM). The mean rate of efflux into a plasma pool containing normal iron and transferrin concentrations was 0.9% of the initial hepatic radioactive iron pool per hour. In EBM the average rate of efflux was 0.1%/h and this could be increased to the rate observed with plasma by the addition of apotransferrin. The rate of iron release from the liver in the presence of apotransferrin or other chelators was inversely proportional to the time of prelabelling. Maximal release rates were observed in livers perfused within 5 h of administering transferrin-(59)Fe to the rat. The effect of apotransferrin on efflux into EBM was concentration dependent. However, the maximum release of liver iron by apotransferrin occurred at physiological apotransferrin concentrations and addition of apotransferrin to plasma produced no increase in the rate of iron efflux. The stimulation of iron release in EBM caused by apotransferrin could be reversed by reducing the unsaturated iron binding capacity of the perfusate, either by addition of iron or removal of apotransferrin. However, increasing the iron concentration in the perfusate by the addition of iron-saturated transferrin without any reduction in the unsaturated iron binding capacity additionally increased iron release into plasma and EBM. This presumably reflects the exchange of plasma transferrin-(56)Fe for liver (59)Fe. Hence iron release measured in these studies represent the sum of two processes-net release of (59)Fe induced by apotransferrin and iron exchange between plasma and liver iron pools. Apotransferrin and desferrioxamine were equally effective, per unit iron binding capacity, in mobilizing liver iron, and may compete for the same parenchymal iron pool. This suggests that mobilization of iron by apotransferrin may depend solely on its ability to chelate ferric iron and not on a more specific ferroxidase activity or interaction with membrane receptors.

Animals↗
PubMed1978

The control of hepatic iron uptake: correlation with transferring synthesis.

The control of hepatic iron uptake was studied in the perfused liver isolated from rats subjected to nutritional iron deficiency. The total hepatic iron uptake and incorporation into ferritin was found to be higher in iron deficiency and during the 48 h of oral refeeding with iron than in the normal state. Specific incorporation of iron into feritin from a perfusate of normal transferrin iron saturation was enhanced in nutritional iron deficiency as compared to controls after 5 h of perfusion but not after 1 h, suggesting that increased uptake of iron from the perfusate may play a role in stimulating hepatic ferritin synthesis and assembly. This promotion of uptake into ferritin was inhibited by cycloheximide suggesting that enhanced incorporation of iron is dependent upon de novo synthesis of apoferritin. In control, nutritionally iron deficient and iron-refed rats there was a significant, direct correlation between the transferrin-iron saturation of the perfusate at physiological transferrin concentrations and total hepatic iron uptake after 5 h perfusion. A significant positive correlation was found between the hepatic total and ferritin iron uptake and the transferrin synthetic rate measured in the same liver. It is proposed that in the liver the negative feedback of iron supply on transferrin synthesis may be linked with a positive feedback on ferritin synthesis. The time-course of these reciprocal responses suggests a role for hepatic ferritin and/or a component of the non-haem, non-ferritin iron pool in the regulation of transferrin synthesis.

Animals↗
PubMed1978

Adenosine triphosphate in the bovine chromaffin granule.

1. pH and potential gradients are generated across the membranes of chromaffin granule 'ghost' by incubating them with MgATP: the inside of the 'ghosts' is positive and acid with respect to the incubation medium. 2. The pH gradient is partially dissipated by inclusion of a substrate for the catecholamine pump, or a mitochondrial uncoupling agent, but is enhanced by reserpine. 3. An imposed pH gradient leads to amine uptake by the 'ghosts': a potential gradient leads to ATP uptake. Studies with inhibitors confirm that amine accumulation by chromaffin granules is dependent on the former, and that ATP uptake results from ATPase-induced potential difference generation. 4. ATP has two known roles in chromaffin granule structure: the first is as a substrate for a membrane-bound proton-translocating ATPase; the second is as a component of the intragranular catecholamine storage complex.

Adenosine Triphosphate↗
PubMed1977

The role of iron in the regulation of hepatic transferrin synthesis.

The role of iron supply in the regulation of hepatic transferrin synthesis by the isolated perfused rat liver was studied using nutritional iron deficiency as the experimental model. The increased transferrin release encountered in iron deficiency could be equated with enhanced de novo synthesis as evidenced by the inhibitory effects of cycloheximide and measurements of intrahepatic protein pools before and after perfusion. Refeeding with iron, sufficient to restore plasma iron and hepatic ferritin iron but before correction of anaemia, promoted a reduction towards normal in the transferrin synthetic rate. This effect was not produced by transfusional correction of the anaemia, suggesting a specific response to iron supply. Phenobarbitone treatment, which produced a marked fall in hepatic ferritin iron concentration but no change in haemoglobin or plasma iron concentrations, promoted a specific enhancement of transferrin synthesis in both control and iron deficient livers. The concentration of liver iron stores appears to be a major regulatory factor in the control of hepatic transferrin synthesis.

Animals↗