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Biomedical subjects

I C Jones

Publications and source records attributed to I C Jones.

At least 19 recordsLinked to original sources
PubMed1998

Springboard oscillation during hurdle flight.

The relative influences of board-tip rebound and fulcrum setting upon vertical board-tip oscillation during hurdle flight were investigated to gain insight into the mechanism by which highly skilled divers are able to make effective contact with the springboard. Data were collected on running dives executed by 3-m finalists at the 1995 World Diving Cup (men), the 1996 Olympic Games (women) and the 1996 US Junior Olympics (boys and girls). Analysis of the vertical board-tip patterns of motion during hurdle flight revealed substantial deviations from a regular damped oscillation, particularly during the first excursion above the horizontal. The latter was characterized by two peaks, the first resulting from upward momentum and the second due to the board's colliding with the fulcrum. A regression analysis of the senior divers' data indicated that 83.7% of the variance in hurdle flight time could be accounted for by the maximum height reached by the board-tip and only 3.6% by fulcrum setting. We conclude that, among senior divers, rebound of the springboard was the dominant factor influencing the length of time required for the board to complete its characteristic 2.25 and 2.50 cycles before take-off.

Biomechanical Phenomena↗
PubMed1998

Incidence of peripheral neuropathy in the contralateral limb of persons with unilateral amputation due to diabetes.

Eighty persons with first-time, nontraumatic amputation, mean age 66.7 yrs +/- 12.6 (1 SD) were examined to determine the extent of peripheral neuropathy (PN) present in the intact limb. Thirty-eight (47.5%) of the subjects had confirmed diabetes mellitus (DM); in those subjects, vibration sense (73.3%), temperature sense (42.1%), and nociception (71.1%) were decreased or absent in the intact limb. The prevalence of sensory impairment was significantly less in nondiabetic subjects in whom vibration sense 46.5% (p < 0.02), temperature sense 16.3% (p < 0.01), and nociception 32.6% (p < 0.02) were decreased or absent. Using a scale that stages the severity of PN, a significant difference (p < 0.001) in the distribution was found between these two groups. Only one person with known DM had no evidence of PN. Twenty-eight out of 42 nondiabetic subjects had evidence of PN. Eighty percent of all subjects had PN. This study confirms the significant potential for PN in persons with DM and presents new evidence of a significant incidence of neuropathy in nondiabetic individuals with amputation. The finding of unexpected peripheral nerve compromise is an important consideration in the treatment of persons with peripheral vascular disease who are at risk for amputation and for persons with amputation who depend on the intact limb for stability and ambulation.

Aged↗
PubMed1995

Medical problems affecting musicians.

The physical demands of performing on musical instruments can cause pain, sensory loss, and lack of coordination. Five cases illustrate common problems. Knowledge of the interaction between the technique of playing the instrument and the particular musician can help physicians diagnose and resolve problems.

Adolescent↗
PubMed1986

The X zone of the mouse adrenal cortex of the Swiss albino strain.

The adrenal gland of the Swiss albino strain was investigated with particular reference to the X zone. The degeneration of the X zone in the male occurred concomitant with puberty. The unmated female possessed an X zone which gradually degenerated with age. First pregnancy gave a rapid disappearance of the zone. Gonadectomy preserved the X zone in both sexes, to decline with age. Hypophysectomy produced the classical sequelae, but injecting equine luteinizing hormone preserved the X zone. The X zone and its homologous/analogous representatives in various eutherian species differ from the pattern given in a common laboratory mouse. The difficulties are discussed.

Adrenal Cortex↗
PubMed1984

Phosphatidic acid regulates the activity of the channel-forming ionophores alamethicin, melittin, and nystatin: a 1H-NMR study using phospholipid membranes.

The regulation of ion channels by phosphatidic acid (a proposed active metabolite in the phosphatidylinositol effect) was investigated using 1H-NMR spectroscopy and small unilamellar phospholipid vesicles. Transport across egg-yolk phosphatidylcholine (egg PC) and dipalmitoyl phosphatidylcholine (DPPC) vesicular membranes in the presence of the channel-forming ionophores alamethicin, melittin, and nystatin was monitored using the lanthanide probe ion Pr3+. In the absence of the ionophores, phosphatidic acid (PA) alone was found to have no ionophore properties, but in the presence of the ionophores the incorporation of 3 mol % phosphatidic acid in the bilayer markedly increased the rate of transport using melittin and nystatin, but decreased the rate using alamethicin, independent of the type of phosphatidylcholine used. The presence of PA in the bilayer also stimulated the production of lytic type channels, the extent of which were both ionophore- and lipid-dependent. These results are discussed in terms of possible molecular interactions between the PA, the individual ionophores, and type of lipid used.

Alamethicin↗
PubMed1983

A 1H-NMR investigation of the effects of ethanol and general anaesthetics on ion channels and membrane fusion using unilamellar phospholipid membranes.

Using 1H-NMR of small unilamellar vesicles in the presence of the lanthanide probe ion Pr3+, the effects of ethanol, diethyl ether and chloroform on various mechanisms of channel-mediated transport were studied. The mechanisms include channel formation by the polypeptide Alamethicin 30 and vesicular lysis at the gel to liquid-crystal phase transition of the lipid. Channel stabilisation and membrane fusion induced by sub-critical micelle concentrations of Triton X-100 were also investigated. The observation that ethanol and diethyl ether increase membrane permeability and fusion while chloroform inhibits them suggests a common locus of action on the properties and structure of channel-associated water. This conclusion is discussed in terms of current theories of general anaesthesia.

Anesthetics↗
PubMed1977

Time course of lithium-induced alterations in renal and endocrine function in normal and Brattleboro rats with hypothalamic diabetes insipidus.

1. A lithium chloride (1.1 g/kg) supplemented diet was given to Long Evans (LE) and Brattleboro (DI) rats to investigate its actions in the presence (LE) and absence (DI) of vasopressin. 2. During the first 24 h, Li-supplemented LE rats displayed an initial water deficit (drinking less than renal output), increased plasma antidiuretic (ADH) titres and slightly increased plasma renin activities (PRA) and plasma osmolarities. Such changes were qualitatively similar to those seen in rats fed a normal diet, but deprived of water for 24 hours. After 12 days, the Li-supplemented rats had elevated plasma ADH titres, but reduced pituitary oxytocic and antidiuretic activities. 3. The urinary losses of Na, K and Cl exceeded dietary intakes in LE rats on the introduction of the Li-supplement, and the urinary osmolarity fell by 50%. Electrolyte balances were gradually re-established, although drinking and urine production increased in parallel to reach twice the control values by day 12 of the supplement. 4. Aldosterone and corticosterone secretory rates and their peripheral plasma concentrations were unchanged both after 24 h and 28 days of the Li-supplement. 5. Li elicited no water deficit or saluresis in DI rats, and although the polyuria and polydipsia were exacerbated, urinary osmolarity did not change over the 12 day observation period. 6. Li increased Ca excretion in both rat types; after 12 days the PRA of DI but not LE animals were increased. 7. It is concluded that the overall renal actions of Li are tempered by vasopressin rather than adrenocorticosteroids.

Adrenal Cortex↗
PubMed1976

Effects of adrenalectomy and hypophysectomy on water and electrolyte metabolism in male and female rats with inherited hypothalamic diabetes insipidus (Brattleboro strain).

Observations on water and electrolyte metabolism after hypophysectomy or adrenalectomy, in male and female rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain) are confirmed and extended. The diabetic (homozygous, DI) state relative to the non-diabetic (heterozygous, non-DI) state was characterized by (1) water intake of 55-120% body weight; (2) copious urine hypo-osmotic to plasma; (3) greater excretory rates of total solute, Na, Ca and Mg; (4) similar plasma composition except that in male DI rats, K concentration was less, and in female DI rats osmolarity was higher; (5) glomerular filtration rates (GFR) were similar with close correlations between: food and water intakes, water intake and output, urinary Na and K, Na and Cl, K and Cl, and Ca and Mg; (6) both female DI and non-DI rats had lower urinary Na:K ratios and lower plasma Na concentrations than males; (7) female DI rats excreted relatively larger amounts of K and Cl, and had higher plasma Ca concentrations than other groups. Hypophysectomized DI rats had decreased water intake and urine output, decreased solute excretion, decreased loss of osmotically free water, lower excretory rates of Na, K and Cl, and increased urinary osmolarity and K concentrations. Hypophysectomized non-DI rats had increased urinary excretory rates, decreased solute excretion (by 60-70%), decreased osmotically free water absorption, decreased urinary osmolarity, Na and K concentrations, and increased excretory rates of Ca and Mg. Hypophysectomized DI and non-DI rats had increased plasma osmolarity and Na concentration. Plasma renin activities (PRA) were higher in DI than in non-DI rats with female values lower than those of males; values for both sexes of DI and non-DI rats were reduced after hypophysectomy. Adrenalectomized DI rats had about a 50% reduction in water intake, urine output and free water clearance, increased urinary concentration of electrolytes and total solute by day 4 after operation; their Na balance (dietary:urine) did not change significantly in contrast to adrenalectomized non-DI rats in which a greater percentage of dietary Na appeared in the urine. GFR was similarly reduced in adrenalectomized DI and non-DI rats. Plasma osmolarity increased in adrenalectomized male DI, decreased in female DI and non-DI, and did not change in male non-DI rats. Plasma K concentrations increased after adrenalectomy in all groups, only non-DI rats had a significantly decreased plasma Na concentration. There was no sex difference in pituitary oxytocic activity but it was consistently reduced in DI rats; there was little change after adrenalectomy in male DI and non-DI rats; but there was an increase in DI and non-DI females. Pituitaries of DI rats had no measurable ADH activity (except the inherent activity of oxytocin). Pituitary ADH values for male and female non-DI rats were similar and were unaffected by adrenalectomy.

Adrenal Glands↗