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Biomedical subjects

D Gifford

Publications and source records attributed to D Gifford.

29 records · Page 2Linked to original sources
PubMed1983

Modulation of latent protein phosphatase activity from vascular smooth muscle by histone-H1 and polylysine.

An apparently latent phosphatase which migrated as a protein of Mr 130,000 during sucrose density centrifugation, and a spontaneously active phosphatase (Mr 68,000) were isolated from bovine aortic smooth muscle. Basal phosphorylase phosphatase activity of the latent preparations was stimulated 12 fold by low concentrations of lysine-rich histone-H1 (30 micrograms/ml) and 6 fold by polylysine (Mr 17,000; 12 micrograms/ml), whereas the spontaneously active enzyme was only slightly affected. The enzymatic activity of the spontaneously active preparation was completely destroyed by beta-mercaptoethanol. In contrast, the apparently latent enzyme was converted to a more active form of lower molecular weight (Mr 86,000) following treatment with beta-mercaptoethanol and this form of the enzyme was still stimulateable by histone-H1. These findings show that the aortic spontaneous and apparently latent phosphatase actives are ascribable to separate enzymes and they suggest that the activity of latent phosphatase in living cells may be modulated by cationic proteins such as histones or similar effector molecules.

Animals↗
PubMed1983

An aortic spontaneously active phosphatase dephosphorylates myosin and inhibits actin-myosin interaction.

Actin-myosin interaction in aortic actomyosin reportedly requires phosphorylation of the 20,000 dalton myosin light chains. A spontaneously active phosphatase which dephosphorylates phosphorylase a and isolated phosphorylated cardiac myosin light chains was extracted from bovine aortic smooth muscle. This enzyme, when added to aortic native actomyosin (a) significantly suppressed phosphorylation of the light chains of the native hexameric smooth muscle myosin, (b) accelerated the rate and increased the magnitude of myosin light chain dephosphorylation in actomyosin that had been prephosphorylated, and (c) markedly attenuated the rate of actin-myosin interaction. These results support the hypothesis that myosin phosphorylation and subsequent actin-myosin interactions (contractility) in vascular smooth muscle may be modulated by spontaneously active aortic phosphatase.

Actins↗
PubMed1983

Spontaneously active and ATPMg-dependent protein phosphatase activity in vascular smooth muscle.

A spontaneously active (Mr greater than 350,000) and an ATPMg-dependent phosphatase (Mr congruent to 140,000) were identified in bovine aortic smooth muscle. The spontaneously active phosphatase was effective in dephosphorylating both phosphorylase a (240nmol32P/min/mg) and phosphorylated myosin light chains (1000nmol32P/min/mg). In contrast, the ATPMg-dependent phosphatase was only effective in dephosphorylating phosphorylase a (400nmol32P/min/mg). Phosphorylase phosphatase activity of the ATPMg-dependent enzyme was suppressed by the well-characterized modulator protein (inhibitor-2), whereas the activity of the spontaneously active enzyme was unaffected. The aortic spontaneously active phosphatase did not convert to an ATPMg-dependent form when it was stored at 4 degrees or incubated at 30 degrees C in either the presence or absence of modulator protein. These findings suggest that spontaneous and ATPMg-dependent phosphatase activities described in these studies are probably ascribable to different enzymes. Since both phosphorylase and myosin light chains are phosphorylated when smooth muscle contracts these phosphatases may participate in coordinating arterial contractility and metabolism.

Adenosine Triphosphate↗
PubMed1983

Properties and function of phosphatases from vascular smooth muscle.

Myosin light chain phosphatase (MLCP) activity was present in extracts from a wide variety of mammalian tissues. A partially purified preparation of bovine aortic MLCP also showed activity against phosphorylase a and p-nitrophenyl phosphate (PNP). Whether these three activities are ascribable to a single multifunctional phosphatase or to three distinct phosphatases is unknown. The three phosphatase activities coelute during gel filtration both before and after treatment with ethanol showing exclusion volumes corresponding to 240,000 and 35,000 daltons, respectively. This indicates that the enzyme is dissociable into a smaller catalytic subunit. The widespread occurrence of MLCP activity and the close parallel among MLCP, phosphorylase a phosphatase, and PNP phosphatase activities suggest that the enzyme (or enzymes) may participate in physiological processes in addition to dephosphorylation of phosphorylated myosin light chains.

Animals↗
PubMed1979

Insulin binding and degradation by muscles from streptozotocin-diabetic rats.

Insulin degradtion by muscle was examined in normal, streptozotocin-induced diabetic rats, and diabetic rats treated with insulin. Insulin degradation by the 100,000 X g supernatant fractions was identical in all three groups, but insulin metabolism by the intact epitrochlaris muscle was significantly increased in diabetic animals. Insulin treatment of the diabetic animals partially restored the activity toward normal. Specific binding of 125l-insulin to the intact muscles was also increased in the diabetic animals. Streptozotocin diabetes, therefore, increased the binding and degradation of insulin by intact muscle but did not alter the insulin degradation by the total soluble intracellular degradative activity.

Animals↗
PubMed1975

A new design policy for protective barriers in departments of x-ray diagnosis.

In order to calculate the thicknesses of protective barriers requried in departments of radiodiagnosis for walls, floors, ceilings, protective screens, etc., it is necessary to make an assessment of work load and occupancy factor in each direction. In order to ensure that barriers are safe, it is customary to assume that all the radiological procedures are carried out at the greatest kVp value used in the room in question, and to look up the necessary thicknesses from prepared tables. In fact, only a small fraction of work load is carried out at the highest kilovoltage, and also it is found that a considerable fraction of the total work load is directed downwards. A computer program has been written to use data available from comprehensive analyses of work load broken down into suitable kVp intervals. As the cost of providing the necessary protective barriers can be anything from a few hundred pounds to several thousand pounds, the use of exact values for work load separated into kVp ranges for each direction can lead to substantial savings in cost amounting to hundreds of pounds per room whilst still satisfying the requirements of the Code of Practice for the Protection of Persons against Ionizing Radiations arising from Medical and Dental Use (HMSO, 1972). Departmental surveys were carried out to establish the distribution of work load in kVp and direction, and also to ascertain dosage levels to the staff and within existing rooms. The results show that in practice the doses are such that the reduced barriers found by the method described would be entirely satisfactory.

Computers↗
PubMedDate not supplied

Comorbidity and drug use in cognitively impaired elderly living in long-term care.

Cognitive impairment is associated with an increased mortality in older people. The prevalence and impact of comorbidity on functional status and mortality of demented patients has not been fully elucidated. Using a population-based data set, we describe the prevalence of cognitive impairment, functional status, principal comorbid conditions and 1-year survival for over 300,000 patients admitted to the nursing homes in five US states. Sixty-one percent of patients have some level of cognitive impairment, and this correlates with the degree of physical frailty. Severer cognitive impairment is associated with a higher mortality rate. Yet, patients with cognitive impairment appear to have fewer comorbid conditions and are less likely to receive medications and special treatments than residents with normal cognitive status. Additional studies are needed to understand whether demented patients may paradoxically be considered healthier or, instead, are only neglected.

Aged↗