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P T Cheng

Publications and source records attributed to P T Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effects of pyrophosphatase on dissolution of calcium pyrophosphate dihydrate crystals.

Understanding the dissolution mechanisms involved in calcium pyrophosphate dihydrate (CPPD) crystals may prove important for the development of therapy for CPPD arthropathy. We demonstrate that yeast pyrophosphatase effectively dissolved CPPD crystals in solutions. Maximum enzymatic dissolution of CPPD crystals was achieved at neutral pH and when the enzyme had access to the crystal surface. The enzymatic dissolution of CPPD crystals was highly dependent on ambient [Mg++] and [Ca++]. The stimulating effects of Mg++ on crystal dissolution in the presence of the enzyme is due to stimulation of pyrophosphatase activity and to enhanced direct release of pyrophosphate ions from the crystal surface. The inhibiting effect of Ca++ on crystal dissolution by the enzyme is mainly due to the suppression of pyrophosphatase activity.

Calcium↗
PubMed1991

Aneurysmal subarachnoid hemorrhage. Report of 219 cases in Chang Gung Memorial Hospital.

Two hundred and nineteen cases with aneurysmal subarachnoid hemorrhage treated at Chang Gung Memorial Hospital from January 1986 to December 1989 were studied. Their ages ranged from 19 to 76, with a mean of 55 +/- 16 years. About one third of the cases occurred in the age group of 50 to 59 years. Females were predominant with a female to male ratio of 2:1, but there was a male predominance below age 40. The most common site of aneurysm was the anterior communicating artery. Rebleeding, delayed vasospasm with cerebral infarction, and hydrocephalus were the main causes of death or disability. The mean follow-up of 6 months for the whole group showed a 59% favorable outcome, 13% severe disability and a 28% mortality. For those 166 patients who underwent surgical treatment, there was 8% mortality.

Adult↗
PubMed1990

Effects of fluoride on rat cancellous bone.

Female Wistar rats were divided into four groups each fed ad libitum regular rodent chow and fluoridated water at four levels (0, 2, 4, 6 mmol/l) for 3 months. There were significant differences in ash weights between control and fluoridated vertebrae (P less than 0.01). Intact bone fluoride (F) values observed were: 0.04 +/- 0.01% fat-free dry weight (ffdw) for control vertebrae and 0.22-0.34 +/- 0.03% ffdw for fluoridated vertebrae. Deproteinized fluoridated vertebral bone had significantly lower specific surface area (SSA) (from 100 +/- 19 m2/g, P less than 0.01, down to 80 +/- 20 m2/g, P less than 0.001) than the control group (120 +/- 10 m2/g); a finding in support of our hypothesis that more of the bone mineral units in fluoridated bone are older (hence denser) than in normal bone. Static morphometric analysis of toluidine blue-stained sections of the femoral metaphyses showed that both cancellous bone volume/tissue volume (Cn-BV/TV) and trabecular thickness (Tb.Th) increased linearly with NaF dosage (R = 0.99 and 0.97, respectively); with Cn-BV/TV increasing from 21 +/- 7 to 33 +/- 6% (P less than 0.01) and Tb.Th from 76 +/- 8 to 98 +/- 9 microns (P less than 0.01). Similar Cn-BV/TV results were also obtained from von Kossa-stained sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Field dependence of 19F NMR in rat bone powders.

The 19F NMR properties of fluoridated rat bone powder samples have been studied in several external magnetic fields. The results show a characteristic field dependence, related to the strength of chemical shift interactions compared to dipole-dipole interactions. While the free induction decay shape is relatively insensitive to the 19F bone mineral concentration, the spin-lattice relaxation time decreases with increasing 19F concentration. Multi-exponential spin-lattice relaxation processes indicate that there are at least two chemically inequivalent incorporation sites for fluorine in bone mineral. Evidence for clustering of 19F fluoride impurities in bone mineral is seen in Hahn echo experiments. Sample preparation and handling methods are shown to affect the values of some of the observed NMR parameters.

Animals↗
PubMed1988

Inhibition of calcium pyrophosphate dihydrate crystal formation: effects of carboxylate ions.

Proteoglycans are recognized to inhibit calcium pyrophosphate dihydrate (CPPD) crystal formation but the mechanisms are not known. To study the role of carboxylate (-CO2-) ligands, the possible inhibitor effects of sodium acetate, sodium D-glucuronate, disodium malate, and trisodium citrate were studied using solution mixtures containing [Ca2+] = 1.5 mM, [Mg2+] = 0.5 mM, [PPi] = 0.1 mM, [Pi] = 0.1 mM, [Na+] = 140 mM, 37 degrees C, pH 7.4 with or without 9.5 +/- 0.5 mg CPPD (seed) crystals. These studies showed that monocarboxylates (acetate, glucuronate) have little inhibitive effect. Progressively greater inhibition was found with dicarboxylate (malate) and tricarboxylate (citrate) indicating that the arrangement of carboxylate (and sulfate) ligands on proteoglycan is more important than the inhibitory effect of individual ligands.

Calcium↗
PubMed1988

Fluoride reduces the rate of dissolution of bone.

Recently, fluoride has been used in the treatment of osteoporosis in an attempt to rebuild bone lost due to this disease. Fluoride has been shown to have a profound effect on osteoblasts and bone formation. Studies have shown that synthetic fluorapatite is more stable and less soluble than hydroxyapatite. This study was designed to determine the dissolution properties of bones from rats fed a normal diet versus rats fed a high fluoride diet. Intact and deproteinized bones were dissolved in buffered solutions, containing physiological amounts of inorganic Ca and P, at pH 3.4, 4.4 and 5.4. The data demonstrate that fluoridated bones dissolve slower than normal bones, deproteinized bones dissolve faster than intact bones and that the initial rate of dissolution of fluoridated bone is always significantly lower than that of normal bone. This may help to explain the reduced rate of osteoclastic resorption in patients undergoing fluoride therapy.

Animals↗
PubMed1988

Ferrous [Fe++] but not ferric [Fe] ions inhibit de novo formation of calcium pyrophosphate dihydrate crystals: possible relationships to chondrocalcinosis and hemochromatosis.

To determine the physical-chemical effects of [Fe++] and [Fe ] on calcium pyrophosphate dihydrate (CPPD) crystal formation de novo, we studied CPPD crystal formation in an established model aqueous solution mixture system using physiological concentrations of Na+, Mg++, Ca++, C1-. We found that [Fe++] greater than 1 microM or [Fe ] greater than or equal to 100 microM inhibits CPPD crystal formation under conditions of [Ca++] = 1.5 mM, [Pi] = 0.1 mM, and [PPi] = 0.1 mM that simulate CPPD formation in vivo. These experiments suggest that at biological concentrations, Fe++ acts to inhibit CPPD formation but that [Fe++] depletion therapy by removal of inhibition effects may facilitate CPPD crystal formation in articular tissues.

Calcium Pyrophosphate↗
PubMed1988

Calcium pyrophosphate crystal deposition in hyaline cartilage. Ultrastructural analysis and implications for pathogenesis.

Using transmission electron microscopy, selected area electron diffraction, and micro x-ray diffraction techniques, we studied calcium pyrophosphate dihydrate (CPPD) deposits from 23 patients with chondrocalcinosis affecting the femoral head to delineate the cellular and matrix environment in which CPPD crystals form, to determine the sequence of crystal deposition, and to address the question of coexistent calcium apatite crystal deposition. We found 2 types of CPPD crystal deposits with few transitional forms. First, small collections of crystals were seen at the border of the territorial matrix at the articular and subarticular poles of the chondron. CPPD crystal deposits were unassociated with collagen or matrix vesicles. Second, and more frequently, large collections of randomly arranged crystals (agglomerates) were observed, the smallest replacing the chondrocyte and adjacent pericellular matrix. Chondrocytes adjacent to crystal deposits were intact. Coexistent apatite crystal deposition was demonstrated in only 2 of 23 cartilages ultrastructurally examined, providing evidence that mixed crystal deposits are possible but not common in CPPD crystal arthropathy.

Aged↗
PubMed1988

Effects of magnesium on calcium phosphate formation.

All biological calcium phosphates form in various neutral aqueous solutions containing [CaCl2] = 1 or 3 mM, [MgCl2] = 0-9 mM, [Na2HPO4] = 0.1-90 mM and NaCl (total 300 mosM) kept quiescently at 37 degrees C for 21 days. In all solutions containing 1 mM Ca and in solutions with [Ca] = 3 mM and [PO4] less than 10 mM, heterogeneous nucleation of octa-calcium phosphate (for Mg/Ca less than or equal to 1) or brushite (for Mg/Ca greater than 1) was observed; the former transforming to apatite with time. In contrast, homogeneous nucleation of an unstable amorphous calcium magnesium phosphate occurred in solutions with [Ca] = 3 mM and [PO4] greater than or equal to 10 mM, transforming to apatite, to brushite, and to whitlockite (and newberyite) depending on Mg/Ca and [PO4] values.

Apatites↗
PubMed1988

Pathologic calcium phosphate deposition in model systems.

Pathologic calcium phosphate deposition occurs mainly in tissues exposed to highly supersaturated body fluids such as urine and saliva. In vitro models employed to study pathologic calcification include aqueous solutions and hydrogels. Results from studies on de novo formation of various biologic calcium phosphates in aqueous solutions resembling various body fluids have been rewarding. Among others, the de novo results have shown that the formation conditions for each calcium phosphate crystal phase are quite different and are pH dependent, and yet all phases including brushite can form in neutral solutions. This is an important finding because when coupled to the facts that all calcium phosphates including brushite are more soluble in acidic solutions than in neutral ones and that, except in extreme cases of hypercalciuria and/or hyperphosphaturia, body fluid Ca and Pi are not very high, it suggests that in most cases pathologic calcification occurs in alkaline or near neutral milieus. HAP is ubiquitous because it is the most insoluble calcium phosphate crystal phase in alkaline or slightly acidic fluids. In fluids close to neutrality, whitlockite is the next favored, provided that the fluid Mg:Ca ration is neither too low nor too high. Although OCP is only slightly more soluble than whitlockite in near neutral milieus, it is favored only by low fluid Ca:Pi and Mg:Ca ratios and transforms easily to HAP. Except in very acidic milieus, brushite is the most soluble biologic calcium phosphate. Its formation is favored by acidic body fluids with high Ca x Pi or by neutral or slightly alkaline ones with very low Ca:Pi ratio or high Mg:Ca ratio.

Body Fluids↗
PubMed1988

Crystal associated diseases: role of scanning electron microscopy in diagnosis.

As crystals are important etiologic agents for disease, their accurate identification in tissues and body fluids is of utmost importance. This paper surveys the roles of crystals in disease process and outlines current analytical techniques for crystal detection and identification in bone tissues. The value of multiple correlated techniques is demonstrated including scanning electron microscopy, x-ray energy spectroscopy and powder diffraction analysis. The current feasibility of utilizing intermediate voltage scanning transmission analytical electron microscopy to integrate these analytical techniques on the same tissue sample is emphasized.

Body Fluids↗
PubMed1987

Effect of synthetic calcium pyrophosphate and hydroxyapatite crystals on the interaction of human blood mononuclear cells with chondrocytes, synovial cells, and fibroblasts.

Synthetic calcium pyrophosphate dihydrate crystals and, to a lesser extent, synthetic hydroxyapatite crystals increased the amount of interleukin-1/mononuclear cell factor released by human blood monocytes, as measured by collagenase and prostaglandin E2 production by rabbit chondrocytes, human dermal fibroblasts, and adherent rheumatoid synovial cells. The same crystals also directly induced collagenase and prostaglandin E2 secretion by rabbit chondrocytes, and potentiated the action of interleukin-1/mononuclear cell factor on chondrocytes. These mechanisms may be important in the pathogenesis of the destructive arthropathies associated with these crystals.

Animals↗
PubMed1987

Formation of octacalcium phosphate and subsequent transformation to hydroxyapatite at low supersaturation: a model for cartilage calcification.

By means of X-ray powder diffraction (XRD), octacalcium phosphate (OCP, Ca8H2(PO4)6 X 5H2O, Ca/P = 1.33) has been shown to be a metastable precursor of hydroxyapatite (HA, Ca10(PO4)6(OH)2, Ca/P = 1.67) during de novo HA formation in aqueous solutions containing [CaCl2] = 1.0-2.0 mM and [Na2HPO4] less than or equal to 3 mM, kept at 37 degrees C, 300 mosM and stirred gently at 150 rpm. At the precipitation boundary with initial pH = 7.4, OCP is stable for at least 24 hours when [Ca] = 1.0 mM, and is less stable when [Ca] = 2.0 mM, transforming into a mixture of OCP and HA within 24 hours. Almost complete transformation to HA within 24 hours takes place with high [Ca] and high [Pi]. Statistical analysis of the pH 7.4 precipitation boundary data supports the XRD findings: although [Ca][Pi] values vary significantly (P less than 0.001) with [Ca] (2.70 +/- 0.05 mM2 for [Ca] = 1.0 mM and 2.00 +/- 0.10 mM2 for [Ca] = 2.0 mM), [Ca]1.33[Pi] values do not vary with [Ca] suggesting that the initial precipitation process is 6(1.33 Ca + Pi)----OCP. With initial pH = 7.6, a different precipitation boundary with lower [Ca][Pi] values has been determined. These findings strongly support the fact that rat epiphyseal cartilage fluid which has [CaUF][PiUF] = 2.6 mM2 (UF = ultrafiltrate) and pH 7.6 [2] should be able to support de novo calcification.

Calcification, Physiologic↗
PubMed1987

Effect of glycosaminoglycans on calcium pyrophosphate crystal formation in collagen gels.

Formation of calcium pyrophosphate dihydrate (CPPD) crystals in native collagen gels represent an in vitro model system for the study of pathological cartilage calcification. The conditions under which CPPD forms in collagen gels have been determined. At low Ca X pyrophosphate product, CPPD forms directly. At high Ca X pyrophosphate product, CPPD forms via the amorphous intermediate calcium magnesium pyrophosphate (CMPP). Chondroitin sulfate (CS) inhibits formation of CPPD by both pathways, but apparently by different mechanisms. Direct CPPD formation is inhibited with low potency by CS, apparently by binding of Ca2+ ions. Indirect formation of CPPD is inhibited with high potency by CS, apparently by stabilization of the CMPP intermediate. Comparison of the inhibition of direct CPPD formation by the two glycosaminoglycan species occurring in cartilage proteoglycan showed that CS is a more potent inhibitor than keratan sulfate (KS), in agreement with the greater Ca2+-binding affinity of CS. The increase in KS/CS ration which occurs in human hyaline cartilage with aging may facilitate deposition of CPPD crystals by decreasing the exclusion of pyrophosphate anions.

Calcium Pyrophosphate↗
PubMed1987

Fictitious calculi and human calculi with foreign nuclei.

The correlative approach employing polarized light microscopy, x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and energy dispersive x-ray microanalysis proves to be very useful in identifying fictitious calculi and genuine human calculi with foreign body nuclei. The common artifacts as reported in the literature and observed also by us were minerals, vegetable and plant seeds, cereals, sand grains and sea shell fragments. Two interesting cases involving foreign body nuclei have been reported: one urinary calculus containing a piece of plastic-coated titanium foil in the center; one nasal calculus with a nut as a nucleus. Another common cause for foreign body nucleation is iatrogenic: intrauterine devices, catheters, suture materials and even surgical staples have been reported in the literature to be potent nidi for calculus formation. These cases remind us of the important fact that our body fluids are supersaturated with respect to calcium phosphates and occasionally to other compounds. Hydroxyapatite crystals are readily nucleated by foreign bodies. Whitlockite is involved if the fluid Mg/Ca ratio is in a suitable range, brushite if the fluid is acidic and struvite if there is urea-splitting infection. In urine and other fluids, calcium oxalate and uric acid crystals contribute to the calculus growth.

Calculi↗
PubMed1986

Rhesus monkeys (Macaca mulatta) as a model for calcium pyrophosphate dihydrate crystal deposition disease.

Calcium pyrophosphate dihydrate crystal deposition disease (CPDD) was recognized in 4 of 30 free-ranging rhesus macaques. By means of tissue radiography, focal radiodensities were noted in lumbar intervertebral discs, menisci, and articular cartilage. Crystal deposits were identified as calcium pyrophosphate dihydrate (Ca2P2O7 X 2H2O) by means of X-ray diffraction. The pathogenesis of calcium pyrophosphate dihydrate arthropathy in man remains elusive. However, with the recognition of this arthritis in a well defined population of aged nonhuman primates, a model now exists to facilitate the study of this disease.

Animals↗