Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The magnitude and distribution of mechanical stresses acting on the closed cusps of porcine bioprosthetic valves (PBVs) were estimated using a finite element model. The effects of leaflet stiffening, focal calcium and focal thinning on leaflet stresses were determined. In a normal closed PBV leaflet, stresses increased as pressure was increased. At a pressure of 80 mm Hg, the maximal normal principal stresses were 11 g/mm2 near the center of the leaflet and increased to 19 g/mm2 at a pressure of 160 mm Hg. These observations suggest that the closed valve in the mitral position would experience higher mechanical stresses than the closed valve in the aortic position. Tissue stiffening increased stresses throughout the leaflet and introduced a site of stress concentration near the center of the leaflet. At a pressure of 80 mm Hg, the maximal principal normal stress increased 55% when the leaflet was stiff in comparison to the normal leaflet. Focal calcium and focal thinning caused marked gradients of stress between the sites of calcium or thinning and the immediate surrounding tissue. The magnitude of these stress gradients increased with increasing pressure. These sites of mechanical stress concentration or stress gradients appear to be compatible with sites of leaflet calcification or disruption. Such stresses may contribute to spontaneous degeneration of PBVs.
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PMID:Estimation of mechanical stresses on closed cusps of porcine bioprosthetic valves: effects of stiffening, focal calcium and focal thinning. 398 72

Digitised M-mode echocardiography was used to study the changes in left ventricular diastolic function over a 3-year period in 11 patients with hypertrophic cardiomyopathy an 14 normals. Compared to normal, in hypertrophic cardiomyopathy, isovolumic relaxation was prolonged (P less than 0.001) and mitral valve opening delayed relative to minimum dimension (P less than 0.001). There was a wide range of values for the peak rates of dimension increase and wall thinning, and although the means were normal, 6 and 8 patients respectively were outside the normal range. There were no significant mean changes in function during the 3.4 +/- 0.3 years of follow-up, but, in 3 patients, marked alterations in relaxation were observed. They showed a gross reduction in the delay in mitral valve opening (125 to 55 125 to 35 and 110 to 75 msec). There was little overall change in isovolumic relaxation in two, but in one patient it reduced from 95 to 50 msec. In most patients with hypertrophic cardiomyopathy, relaxation and diastolic function appear to remain stable over a period of 3 years, and none had an apparent deterioration. Some patients may have an apparently spontaneous "improvement" in function similar in extent to that described due to the therapeutic action of calcium antagonists.
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PMID:Longitudinal changes in left ventricular diastolic function in hypertrophic cardiomyopathy. 404 Apr 99

Thinning of the egg shell is produced by p-p'-DDT and DDE in several species of birds. A study was made of the effect of DDE administered in vitro and in vivo on the Ca2+ binding and Ca2+-Mg2+-activated ATPase of a homogenate of the egg shell gland of ducks (Anas platyrhynchos var.). The concentration of Ca2+ was 1 X 10(-4) M and that of MgATP 1 X 10(-3) M. In vitro, DDE in concentrations of 2-16 micrograms/ml of incubation medium inhibited the Ca2+-Mg2+-activated ATPase in a concentration-dependent manner, whereas Mg2+-activated ATPase was not affected by these concentrations. The Ca2+ binding by the homogenate was reduced by DDE in the same concentrations. The sodium azide sensitive Ca2+ binding was most sensitive. In vivo, DDE administered in a concentration of 40 mg/kg dry weight of the food for 45 days reduced the egg shell index by 18% in comparison to controls. After 45 days of treatment the DDE concentrations in the egg shell gland mucosa was 1.20 +/- 0.16 micrograms/g of wet weight, while no DDE was detected in the controls. The Ca2+-Mg2+-activated ATPase was reduced by 32%, whereas the Mg2+-ATPase was not changed. The Ca2+ binding by the homogenate was reduced by 29%, the sodium azide sensitive part being most vulnerable, DDE increased the total Ca content of the egg shell gland mucosa by 44%. Since Ca is transported against a concentration gradient between blood plasma, and the lumen of the shell gland, it is suggested that DDE, by inhibiting the Ca2+-Mg2+-activated ATPase, decreased the Ca translocation over the egg shell gland mucosa.
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PMID:Effect of p-p'-DDE administered in vivo and in vitro on Ca2+ binding and Ca2+-Mg2+-ATPase activity in egg shell gland mucose of ducks. 612 33

The pesticide p-p'-DDT and its persistent metabolite p-p'-DDE cause thinning of the eggshells in several species of birds. In earlier investigations on ducks this thinning was found to be associated with a reduction of the ATP-dependent Ca2+ binding to a homogenate of the shell gland mucosal cells by DDE. The activity of a Ca2+-Mg2+-activated ATPase in the homogenate was also decreased on administration of DDE in vivo. We have therefore investigated the in vitro effects of some other chlorinated hydrocarbon pesticides of ecotoxicological interest on the ATP-dependent Ca2+ binding and the Ca2+-Mg2+-activated ATPase activity in a homogenate of the eggshell gland mucosa of the hen and determined the molar concentrations that produced 50% inhibition (=IC50). Several of the investigated compounds, namely toxaphene, chlordane, p-p'-DDD, o-p'-DDE, p-p'-DDT, methoxychlor and PCB (Arochlor 1242), had a similar IC50 to inhibit the Ca2+ binding as p-p'-DDE. Lindane, p-p'-DDA and biphenyl had an IC50 3.3-4 times higher and that of 2.4 D was 13.5 times higher than that of p-p'-DDE. When the IC50 of some of the compounds (p-p'-DDE, PCB, toxaphene, Lindane) was determined that decreased the Ca2+-Mg2+-activated ATPase of the homogenate it was found to be only 18 to 29 per cent of that needed to inhibit the Ca2+ binding by the homogenate. It is therefore probable that some other effect than inhibition of this enzyme is also involved in the Ca2+-binding process and affected by the compounds.
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PMID:The inhibitory effect of some chlorinated hydrocarbon pesticides on the ATP-dependent Ca2+ binding of the particulate fraction of the eggshell gland mucosa cells. 613 49

Women with primary biliary cirrhosis malabsorb calcium, phosphate and vitamin D, and develop accelerated cortical bone thinning. We have assessed the value of parenteral vitamin D, oral hydroxyapatite (HA), and calcium gluconate (CG) in the treatment of cortical bone thinning in primary biliary cirrhosis. Sixty-four postmenopausal women with primary biliary cirrhosis were assigned randomly into three groups: one group receiving no mineral supplements (control), one group receiving HA, and one group receiving CG. All patients received parenteral vitamin D2 (100,000 IU monthly). Eleven patients withdrew from the study and 10 withdrew due to poor compliance (six HA, four CG). Over a 14-month follow-up period, none of the groups showed a significant change in serum calcium or inorganic phosphate levels. Pre- and posttreatment hand radiographs were used to assess changes in metacarpal cortical thickness using the technique of caliper radiogrammetry. Cortical bone loss occurred in the control group (p less than 0.01). The HA group showed a significant gain in cortical bone thickness (p less than 0.01), while no significant change occurred in the CG group. This study indicated that vitamin D2 does not halt metacarpal cortical bone thinning in primary biliary cirrhosis. The addition of CG prevents bone thinning, and HA promotes positive cortical bone balance.
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PMID:Vitamin D, hydroxyapatite, and calcium gluconate in treatment of cortical bone thinning in postmenopausal women with primary biliary cirrhosis. 628 35

Congenital angular deformity of the tibia (CADT) is one of the classic inborn errors. The treatment of the disease is very difficult because of insufficient clinical and experimental data and lack of complete experimental model of the disease. The present study is designed to establish a new experimental model of CADT. In vivo experiment: Only one injection of ethane-1-hydroxy-1,1-diphosphonate (EHDP) (4 X 10(-2)-4 X 10(-1) mumol/g egg wt.) was given into the yolk sac of fertile white leghorn egg at 8 days of incubation. The skeletal deformities of the chick embryos were examined during the period of EHDP-administration until hatching. Furthermore, the effect of EHDP was compared with that of its analogs (dichloromethylene diphosphonate: Cl2MDP and inorganic pyrophosphate: PPi) in a similar manner. In vitro experiment: Tibiae from 9-day-old chick embryos were cultured at 37 degrees C for 6 days by roller-tube method in the medium containing EHDP, Cl2MDP or PPi at concentrations of 4-400 microM to measure dry weight and calcium content of the tibiae. The results are summarized as follows. Angular deformity of the tibia in chick embryo was produced in vivo specifically by EHDP-administration compared to its analogs. There existed the critical stage of bone development and the critical dose of EHDP-administration to induce angular deformity of the tibia. The incidence and the severity of the tibial bowing depended on the dose of EHDP-administration. The thinning of periosteal bone collar and retardation of primary bone marrow formation were observed in EHDP-administered tibia. According to 3H-thymidine autoradiographic study, EHDP inhibited DNA synthesis of osteoblast by about 58% after 2 days of administration. The DNA synthesis of chondrocyte was also inhibited by about 20% after 2 days of EHDP-administration. EHDP had a more inhibitory effect on calcification of chick embryonic tibiae than Cl2MDP and PPi at concentration of 40 microM without influencing the dry weight of tibiae in vitro. This new experimental model of CADT offers a significant possibility to elucidate the etiology of this disease.
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PMID:[Congenital angular deformity of the tibia in chick embryo induced by ethane-1-hydroxy-1, 1-diphosphonate (EHDP)]. 644 26

In a strain of ducks sensitive to the eggshell-thinning effect of p-p'-DDE, administration of 40 mg kg of the compound in the food for 45 days reduced the eggshell index (EI) by 13% and the content of calcium in the fluid of the shell gland forming an eggshell by 36%, and raised the calcium content of the shell gland mucosa by 19%, compared with the control values. DDE inhibited the translocation (secretion) of calcium between the gland mucosa and the uterine cavity. The ATP-dependent binding of Ca2+ to the subcellular fractions of the gland mucosa was reduced in DDE-treated ducks. The Ca2+ binding to a microsomal subfraction (FI) rich in fragments of the plasma membrane was reduced by 16%, whereas that to a subfraction FIII which bound Ca2+ at a very high rate was reduced by 36%. The latter may contain calcium-secreting granules of the gland. In the mitochondrial fraction the Ca2+ binding was reduced by 35%. In the domestic fowl DDE did not lower EI or interfered with the translocation of calcium between the shell gland mucosa and uterine cavity. DDE administration increased the Ca2+ binding to FI by 26%; the binding to other subfractions was not changed significantly. DDE may interfere with the stimulus-secretion mechanism of the eggshell gland in ducks through its effect on Ca2+ binding.
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PMID:Comparison of the effect of DDE on the Ca metabolism of the eggshell gland and its subcellular fractions of the duck and the domestic fowl. 646 84

The formation of two spherical model membranes at the tips of two syringes has allowed us to study the role of gangliosides in membrane adhesion and look for changes in conductance between two such membranes during the process of adhesion. Membranes were formed in aqueous 100 mM NaCl, 10 mM KCl, 1 mM CaCl2 from 1% (w/v) egg phosphatidylcholine in n-decane, with or without mixed bovine brain gangliosides. After thinning to the 'black' bilayer state, two membranes were moved into contact. With gangliosides, the contact area and conductance increased colinearly with time over a 5 to 20 min period of adhesion. The role of electrostatic bridging by calcium was investigated. In the absence of calcium or in the presence of 2 mM EDTA, adhesion proceeded after a longer lag time at about one-half the normal rate. As the ganglioside concentration was increased from 0 to 15 mol%, the electrical conductance of individual membranes decreased 3-fold from 48 +/- 30 nS/cm2 to 17 +/- 13 nS/cm2. The conductance was pH dependent with a minimum at neutral values. At neutral pH, when two membranes containing 4.1 mol% gangliosides adhered, the region of adhesion had a specific conductance three times that of the nonadhering regions of membranes. Without gangliosides, the specific conductance of the contact region was the same as that of non-adhering regions of the membrane. These data suggest that mixed gangliosides can mediate an adhesion-dependent increase in conductance.
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PMID:Role of gangliosides in adhesion and conductance changes in large spherical model membranes. 647 10

The diastolic portion of the cardiac cycle can be divided into sequential phases: isovolumic ventricular relaxation; rapid ventricular filling; slow, or passive, ventricular filling; and atrial contraction. Contraction and relaxation are to some extent interrelated; however, relaxation is not simply a passive reversal of events during systole. Rather, relaxation is an energy-consuming process which involves dissociation of calcium from the actin-myosin-complex and reuptake of calcium by the sarcoplasmic reticulum. Left ventricular diastolic function is determined by the interrelationship of several/factors, including some intrinsic to the left ventricular chamber (completeness of left ventricular relaxation, time course of left ventricular contraction, and elastic and viscous properties of the myocardium) and others extrinsic to the left ventricle (pericardial and pleural pressure, right ventricular contraction, and coronary perfusion pressure). Acute ischemia alters diastolic left ventricular function by: slowing isovolumic relaxation, delaying left ventricular filling and altering passive elastic properties of the myocardium. Slowing of isovolumic relaxation is measured as a fall in the maximal rate of left ventricular pressure decline (peak negative dP/dt) and as an increase in the time constant (T) of left ventricular pressure fall. Delayed left ventricular filling is manifested regionally as a reduced rate of septal and posterior wall thinning (by echocardiography) and globally as a reduced rate of chamber filling (by gated radionuclide angiography).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Hemodynamics in ischemia: diastolic phase]. 652 97

The growth and differentiation of epidermal cells in vitro show a marked dependence on the calcium concentration of the medium. In this study the effect of experimentally produced hyper- and hypocalcaemia on the rat epidermis in vivo has been investigated. Hypercalcaemia, induced by injections of calcium chloride, produced a decrease in epidermal labelling index and some epidermal thinning. On the other hand hypocalcaemia, induced by calcitonin, failed to lead to changes in these measurements. The diurnal variation in epidermal labelling index and serum calcium levels was also measured. Whilst the labelling index decreased considerably over the period 09.00 hours to 18.00 hours, no significant changes were observed in serum calcium. These results suggest that while, under certain circumstances in vivo, the epidermal cell shows the same sensitivity to calcium as it does in vitro, calcium is not a major regulator of epidermopoiesis.
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PMID:The effect of serum calcium levels on the rate of epidermal renewal in the rat. 654 May 96


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