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Biomedical subjects

D Jones

Publications and source records attributed to D Jones.

At least 793 records · Page 44Linked to original sources
PubMed1975

Ferritin and intestinal iron absorption: pancreatic enzymes and free iron.

Rat intestinal mucosa gave low yields of ferritin purified by standard procedures. The resulting ferritin had less protein relative to iron and migrated faster electrophoretically than ferritin from other rat tissues. Pancreatic duct ligation reduced these differences, suggesting digestive enzyme attack during ferritin isolation. Even in ligated rats, ferritin accounted for only 5-10% of mucosal iron. However, shortly after giving 59FeCl3 orally, 50% of mucosal radioactivity occurred in cell sap, about equally distributed between ferritin and low-molecular-weight (chelated?) iron. No other cell sap components were 59Fe labeled. Iron may thus be transported as a chelate with which ferritin is in rapid equilibrium. Mucosal ferritin content increased with age and iron treatment and decreased with iron deficiency. The iron-deficient rats showed accelerated 59Fe uptake into blood with little mucosal retention. One day after administering parenteral iron to deficient rats, 59Fe transfer to blood became retarded but 59Fe now accumulated excessively in the mucosa, suggesting that iron status affects transport more rapidly at the serosal than at the mucosal cell surface. A scheme for control of iron absorption is presented.

Age Factors↗
PubMed1975

Wall stress and patterns of hypertrophy in the human left ventricle.

It is generally recognized that chronic left ventricular (LV) pressure overload results primarily in wall thickening and concentric hypertrophy, while chronic LV volume overload is characterized by chamber enlargement and an eccentric pattern of hypertrophy. To assess the potential role of the hemodynamic factors which might account for these different patterns of hypertrophy, we measured LV wall stresses throughout the cardiac cycle in 30 patients studied at the time of cardiac catheterization. The study group consisted of 6 subjects with LV pressure overload, 18 with LV volume overload, and 6 with no evidence of heart disease (control). LV pressure, meridional wall stress (sigman), wall thickness (h), and radius (R) were measured in each patient throughout the cardiac cycle. For patients with pressure overload, LV peak systolic and end diastolic pressures were significantly increased (220 plus or minus 6/23 plus or minus 3 mm Hg) compared to control (117 plus or minus 7/10 plus or minus 1 mm Hg, P less than 0.01 for each). However, peak systolic and end diastolic (sigman) were normal (161 plus or minus 24/23 plus or minus 3 times 10-3 dyn/cm-2) compared to control (151 plus or minus 14/17 plus or minus 2 times 10-3 dyn/cm-2, NS), reflecting the fact that the pressure overload was exactly counterbalanced by increased wall thickness (1.5 plus or minus 0.1 cm for pressure overload vs. 0.8 plus or minus 0.1 cm for control, P less than 0.01). For patients with volume overload, peak systolic (sigman) was not significantly different from control, but end diastolic (sigmam) was consistently higher than normal (41 plus or minus 3 times 10-3 dyn/cm-2 for volume overload, 17 plus or minus 2 times 10-3 dyn/cm-2 for control, P less than 0.01). LV pressure overload was associated with concentric hypertrophy, and an increased value for the ratio of wall thickness to radius (h/R ratio). In contrast, LV volume overload was associated with eccentric hypertrophy, and a normal h/R ratio. These data suggest the hypothesis that hypertrophy develops to normalize systolic but not diastolic wall stress. We propose that increased systolic tension development by myocardial fibers results in fiber thickening just sufficient to return the systolic stress (force per unit cross-sectional area) to normal. In contrast, increased resting or diastolic tension appears to result in gradual fiber elongation or lengthening which improves efficiency of the ventricular chamber but cannot normalize the diastolic wall stress.

Adolescent↗
PubMed1975

Cardiac pacemaker induced ventricular fibrillation during surgical diathermy.

Two demand pacemakers were observed to repeatedly fibrillate the heart during clinical surgery employing diathermy. Marked hypotension associated with a rapid, irregular venticular action was observed in another patient who had a fixed rate pacemaker implanted. Pacemakers were tested with function generators over a range of frequencies and some increased their rate to between 200-600 impulse/min. Animal experiments confirmed that, contrary to manufacturers advice, surgical diathermy produces myocardial fibrillation in the presence of some pacemakers. Mechanisms of these effects and their clinical significance are discussed.

Aged↗
PubMed1975

Physical complaints of patients with sickle cell trait.

Prospective and retrospective experience with physical complaints of 112 oral contraceptive and 67 intrauterine device Black family planning patients with sickle cell trait was evaluated by comparing their cumulative complaint rates with a randomly selected control group of non-sickle cell trait family planning patients having the same method, age and parity distribution as the sickle cell trait patients. Physical complaints considered are: dysmenorrhea, mental depression, vaginal discharge, fatigue, headaches, and nausea-vomiting. No evidence of a significant difference at level .05 is found between cumulative complaint rates of sickle cell trait and control patients for either oral or intrauterine device users for any of the complaint types. Further clinical research may be desirable in this area for dysmenorrhea and mental depression.

Anemia, Sickle Cell↗
PubMed1975

Capillary muscle blood flow in human sepsis.

Tissue perfusion was determined by cardiac index (Cl) and skeletal muscle capillary blood flow (MBF), and arteriovenous oxygen difference (AVD) and oxygen uptake were compared in seven patients with severe spesis and eight nonseptic patients. Skeletal capillary muscle blood flow also was measured before and after a 2 day fast in 14 normal volunteers. In both septic and nonseptic patients, MBF varied directly with Cl. The average muscle blood flow was greater in septic than in nonseptic patients and, in addition, was greater per unit Cl. AVD in septic patients was narrower than in nonseptic patients. Septic patients with an AVD of less than 4 ml. of O2 had markedly higher MBF and Cl than did septic patients with an AVD greater than 4 ml. of O2. Fasting normal volunteers who, like the septic patients, would be catabolic had a significant increase in MBF during the fast. Although peripheral shunts are not ruled out ans an explanation of the hyperdynamic circulation in sepsis, the evidence is against their existence, at least in skeletal muscle, since capillary flow increases in direct proportion to cardiac output. If capillary flow is increased in fact in sepsis, then flow like blood pressure becomes less of a critical factor in explaining the demise of the septic patient. It might be postulated that the increased capillary flow seen in sepsis is secondary to the mobilization of amino acids from the body cell mass for gluconeogenesis and energy.

Adult↗
PubMed1974

Co-operative action by endo- and exo-beta-(1 leads to 3)-glucanases from parasitic fungi in the degradation of cell-wall glucans of Sclerotinia sclerotiorum (Lib.) de Bary.

1. Two fungi, Coniothyrium minitans Campbell and Trichoderma viride Pers. ex Fr., were grown on autoclaved crushed sclerotia of the species Sclerotinia sclerotiorum, which they parasitize. 2. In vitro the crude culture filtrates would lyse walls isolated from hyphal cells or the inner pseudoparenchymatous cells of the sclerotia, in which a branched beta-(1-->3)-beta-(1-->6)-glucan, sclerotan, is a major constituent. 3. Chromatographic fractionation of the enzymes in each culture filtrate revealed the presence of several laminarinases, the most active being an exo-beta-(1-->3)-glucanase, known from previous studies to attack sclerotan. Acting alone this brought about a limited degradation of the glucan, but the addition of fractions containing an endo-beta-(1-->3)-glucanase led to almost complete breakdown. A similar synergism between the two enzymes was found in their lytic action on cell walls. 4. When acting alone the endo-beta-(1-->3)-glucanase had a restricted action, the products including a trisaccharide, tentatively identified as 6(2)-beta-glucosyl-laminaribiose. 5. These results are discussed in relation to the structure of the cell walls and of their glucan constituents.

Ascomycota↗