Biomedical subjects

J Preston

Publications and source records attributed to J Preston.

At least 55 records · Page 3Linked to original sources

PubMed1988

Comparative separation of human plasma proteins on polysulphated chromatographic media.

Polysulphated chromatographic media, particularly Heparin Sepharose, are generally used to purify a variety of different plasma proteins. Heparin Sepharose, dextran sulphate Sepharose and sulphated dextran are compared with two recently available sulphated cellulose chromatographic media. The potential influence of structural features of different polysaccharides on the interaction with selected plasma proteins has been evaluated with the particular objective of developing an alternative medium for the preparation of specific therapeutic factor concentrates. The studies indicate that the degree of sulphation of the matrix is an important but not a critical determinant for resolution of factors IX and X. Despite large differences in the carbohydrate structure of the matrices, the new sulphated cellulose gel 5.2 had a total protein capacity and specific binding profile comparable to Heparin Sepharose. The sulphated cellulose which is competitively priced, and has excellent stability, is a potential alternative to Heparin Sepharose especially for larger scale industrial processing of factor IX concentrate.

Blood Proteins↗

PubMed1988

Community care for 20 psychiatrically disabled older men.

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Activities of Daily Living↗

PubMed1987

High extracellular Ca2+ and Mg2+ stimulate accumulation of inositol phosphates in bovine parathyroid cells.

We examined the effects of the divalent cations Ca2+ and Mg2+ on inositol phosphate accumulation in bovine parathyroid cells prelabelled with [3H]inositol to determine whether the high extracellular Ca2+ and Mg2+-evoked transients in cytosolic Ca2+ in these cells might result from increases in cellular IP3 levels. In the presence of Li+, both Ca2+ and Mg2+ produced rapid, 2-6-fold increases in IP3 and IP2 and a linear increase in IP of 6-8-fold at 30 min. Smaller (1.5-2-fold) increases in IP2 and IP3 were evident within 7.5-15 s upon exposure to high (3 mM) Ca2+ in the absence of Li+. The relative potencies of Ca2+ and Mg2+ (Ca2+ 3-fold more potent than Mg2+) in elevating inositol phosphates were similar to those for their effects in inhibiting PTH release. Fluoride (5 and 10 mM) also produced similar increases in inositol phosphate accumulation, presumably through activation of phospholipase C by a guanine nucleotide (G) protein-dependent process. Thus, high extracellular Ca2+ and Mg2+-induced spikes in cytosolic Ca2+ in bovine parathyroid cells may be mediated by increases in IP3, perhaps through a receptor-mediated process linked to phospholipase C by a G-protein.

Animals↗

PubMed1987

Temporal characteristics of the speech of normal elderly adults.

A number of physical and psychological changes occur as a result of the normal aging process. These changes often result in an increase in the time subjects require to perform various motor (and sensory) tasks. Although the effects of aging upon a variety of behaviors have been quite well documented, considerably less information is available concerning how normal aging may affect speech production. The present study examined temporal characteristics of the speech of 10 normal, elderly adults and 10 young adults who produced a variety of words and sentences at both normal and fast speaking rates. Acoustic analyses indicated that the elderly adults' segment, syllable, and sentence durations were 20 to 25% longer than those of the young adults at both the normal and the fast rates of speech. In addition to comparisons that were made between these two groups of subjects, comparisons were also made with durations of the speech of young children studied in previous research. It was observed that the elderly subjects tended to produce durations comparable to those of 6- and 7-year-old children.

Adult↗

PubMed1987

Permeabilization reveals classical stimulus-secretion coupling in bovine parathyroid cells.

Unlike most secretory cells, high extracellular Ca2+ inhibits, rather than stimulates, PTH release from parathyroid cells. To gain more direct access to the potentially unique secretory apparatus of this cell type, we developed techniques for permeabilizing parathyroid cells using electroshock. Exposure of dispersed bovine parathyroid cells to five 2-kV discharges results in more than 90% uptake of trypan blue and rapid loss of intracellular 86Rb, documenting permeabilization of the plasma membrane. Unlike intact parathyroid cells, a high Ca2+ concentration increases PTH release 2.8-fold from permeabilized cells, with half-maximal and maximal stimulation at 10(-5) and 4 X 10(-4) M Ca2+, respectively, a pattern similar to classical stimulus-secretion coupling. Moreover, PTH release was low at Ca2+ concentrations equivalent to those in intact cells at low extracellular Ca2+ levels (approximately 2 X 10(-7) M). Cellular mechanisms other than changes in the cytosolic Ca2+ concentration per se, therefore, presumably mediate low Ca2+-stimulated PTH release in the intact cell. Diacylglycerol and protein kinase C may play a role in this process, since dioctanoylglycerol (10(-4) M) and 12-O-tetradecanoyl phorbol 13-acetate (10(-6) M) each enhance PTH release from permeabilized cells 2- to 4-fold at a Ca2+ concentration (approximately 2 X 10(-7) M) equivalent to that present in the intact cell at low extracellular Ca2+ concentrations.

Animals↗

PubMed1986

Guanine nucleotides are potent secretagogues in permeabilized parathyroid cells.

We studied the effects of GTP and its' analogues on PTH release in permeabilized parathyroid cells to assess their role in mediating the unusual inverse relationship between Ca2+ and PTH release in intact parathyroid cells. Both 10-5 M GppNHp and GTP gamma S, nonhydrolysable analogues of GTP, produce up to an 8-fold enhancement of PTH release, which is dose-dependent. This effect is specific for GTP analogues as we could not mimic it with other nucleotides. 10(-3) M GDP beta S, a nonhydrolysable GDP analogue, completely abolishes GppNHp-stimulated hormone release, providing further support for mediation of this effect by a guanine-nucleotide regulatory protein. In GppNHp-stimulated cells, PTH release is maximal at free [Ca2+] less than 200 nM and progressively decreases as the free [Ca2+] increases from 300 nM to 100 microM. These results suggest the presence of a guanine-nucleotide binding protein in the parathyroid cell that may play an important role in the regulation of PTH secretion by Ca2+ and perhaps other secretagogues.

Animals↗

PubMed1984

Marital therapy for the elderly.

Little attention has been paid to marital therapy for the elderly in spite of its relevance to morale and emotional problems. Physical illness is of particular significance in altering the dynamics of the marital relationship. Retirement and financial problems, as well as changes in sexual activity and gender roles, are also important. However, radical changes in patterns of behaviour cannot be expected. Therapeutic techniques must be altered for this age group, and the therapist must be active, giving and concretely helpful. As with therapy for younger couples, children may need to be involved in the therapy sessions. Family physicians should be a main source of help for marital problems among the elderly. However, because problems related to countertransference must be faced, working with the elderly will not be for everyone.

Aged↗

PubMed1983