Magnesium is an essential microelement which is not harmful to human body. As a light-weight metal with properties similar to natural bone, magnesium material possesses the characteristics of its degradability, little biotoxicity, as well as its regulatory strength and controllable degradation-speed. After the tissue has healed sufficiently, the burden of a second surgical procedure can be avoided. Therefore, there is need of investigation on the possible use of magnesium and its alloys as medical biomaterials, and the study of its bioactivity is the foundation of further application. This article reviews the bioactivity of magnesium and its alloys.
Absorbable Implants ; Alloys ; chemistry ; metabolism ; Biocompatible Materials ; chemistry ; Bone Substitutes ; chemistry ; metabolism ; Humans ; Magnesium ; chemistry ; metabolism ; Prostheses and Implants

Magnesium is a macroelement which is indispensable to human bodies. As a lightweight metal with high specific strength and favorable biocompatibility, magnesium and its alloys have been introduced in the field of biomedical materials research and have a broad application prospect. It is possible to develop new type of biodegradable medical magnesium alloys by use of the poor corrosion resistance of magnesium. Bioabsorbable magnesium stents implanted in vivo could mechanically support the vessel in a short term, effectly prevent the acute coronary occlusion and in-stent restenosis, and then be gradully biodegraded and completely absorbed in a long term. Osteoconductive bioactivity in magnesium-based alloys could promote the apposition growth of bone tissue. This paper reviews the progress of magnesium and its alloys applied in bone tissue and cardiovascular stents, and the prospect of the future research of magnesium-based biomaterials is discussed.
Absorbable Implants ; Alloys ; chemistry ; metabolism ; Biocompatible Materials ; chemistry ; Bone Substitutes ; chemistry ; metabolism ; Humans ; Magnesium ; chemistry ; metabolism ; Stents

OBJECTIVETo investigate the tissue toxicity and degradation of ZK60 magnesium alloy with micro-arc oxidation coatings (MAO-ZK60), in order to discuss the possibility of its potential application for orthopedic implantation.

METHODSEighteen Sprague-Dawley rats were randomized equally to three groups of A, B, C. MAO-ZK60 sticks were implanted in the femoral condyles of rats in group A (experimental group). Sticks of ZK60 magnesium alloy without any surface treatment (ZK60) were implanted in the femoral condyles of rats in group B (control group). The poly L-lactic acid (PLLA) sticks were implanted in the femoral condyles of rats in group C (control group). The changes of blood bio-chemical indexes of different groups were observed and compared. All the rats were sacrificed at 12 weeks and histological observation of liver and kidney were carried out to evaluate the hepatic and renal toxicity. Micro-CT was used to evaluate the degradation of the implants and to observe the bone-implant interface. GEHC MicroView software was operated to calculate the volume variation of magnesium alloy.

RESULTSThere was no apparent biochemical index change with time in each group, and there was no significant change among each group. No significant pathology change of liver and kidney was detected among three groups. By using a micro-CT, a gap was found on the bone-implant interface at 4 weeks after implantation in group A, which decreased gradually at 8 weeks after implantation and continued to decrease at 12 weeks after implantation. A good combination between bone and implant formed at 12 weeks after implantation. Group A has less change of volume with time than group B (P < 0.05).

CONCLUSIONZK60 magnesium alloy with micro-arc oxidation coatings is safe in vivo. It has higher corrosion resistance than ZK60 magnesium alloy without any surface treatment.

Alloys ; chemistry ; metabolism ; toxicity ; Animals ; Magnesium ; chemistry ; Male ; Rats ; Rats, Sprague-Dawley

AIMTo study the effects of sodium magnesium fructose diphosphate (SMFD) on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome, so as to explore the protective mechanisms of SMFD on cerebral ischemia.

METHODSThe synaptosomes from normal rat brain were prepared by phase partition and cultured with oxygen-glucose deprivation to establish ischemic synaptosome model. The intrasynaptosomal free calcium concentration and nitric oxide synthase activity were detected separately after the synaptosomes were co-incubated with SMFD (1.3 mmol.L-1) or fructose-1, 6-diphosphate (FDP, 4.0 mmol.L-1) for 60 min.

RESULTSSMFD decreased the free calcium concentration and reduced the activity of nitric oxide synthase (NOS) of ischemic synaptosomes. Its effects were more powerful than those of FDP.

CONCLUSIONSMFD may protect neurons from ischemic injury by preventing intracellular Ca2+ overload and inhibiting the activity of nitric oxide synthase.

Animals ; Brain Ischemia ; enzymology ; metabolism ; Calcium ; metabolism ; Chelating Agents ; pharmacology ; Fructosediphosphates ; pharmacology ; Magnesium ; chemistry ; Male ; Nitric Oxide Synthase ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Sodium ; chemistry ; Synaptosomes ; metabolism

OBJECTIVETo study the level of brain-derived neurotrophic factor (BDNF) in the microenvironment of the neuron-astrocyte co-culture system by Mg2+-free-induced seizure-like discharge and analyze the source of BDNF.

METHODSHippocampal neurons (N) of fetal rats and astrocytes (AST) of neonatal rats were purified and divided into four groups, included control N (Con N) group, Mg2+-free treated N (Mg2+-free N) group, control N+AST co-culture (Con N+AST) group and Mg2+-free treated N+AST co-culture (Mg2+-free N+AST) group. The Mg2+-free treated groups were exposed to Mg2+-free media for 3 hrs to induce a repeated spontaneous seizure-like discharge. The level of BDNF in each group at different time points was measured using ELISA.

RESULTSThe cellular morphous of AST changed in the Mg2+-free N+AST group at 48 hrs. Neuronal epileptiform activity was observed in the Mg2+-free media at 3 hrs, and continued to exist until the microenvironment returned to normal for 72 hrs. The BDNF level increased at 24 hrs and 48 hrs in the Con N+AST group compared with the control N group (P<0.05). Compared with Con N+AST group, BDNF level increased at 12, 24 and 48 hrs in the Mg2+-free N+AST group, especially at 12 and 24 hrs (P<0.01). There were no significant differences in the level of BDNF between the Con and Mg2+-free N groups. Compared with Mg2+-free N group, BDNF level increased at 24 hrs in the Mg2+-free N+AST group (P<0.05).

CONCLUSIONSThe results of the experiment suggest that BDNF in the Con N+AST group might be excreted from both N and AST, but chiefly from N. Activated AST may be the main source for increasing BDNF in the Mg2+-free N+AST group.

Animals ; Astrocytes ; chemistry ; Brain-Derived Neurotrophic Factor ; analysis ; Cellular Microenvironment ; Coculture Techniques ; Female ; Hippocampus ; chemistry ; Magnesium Deficiency ; metabolism ; Male ; Neurons ; chemistry ; Rats ; Rats, Wistar ; Seizures ; metabolism

The ionized calcium level in blood is known to be falsely decreased when self-prepared liquid heparin anticoagulant is used, due to dilution and binding effects. The effect of liquid heparin on the determination of ionized magnesium is not as well understood. We compared the effect of liquid sodium heparin on the determination of ionized calcium and magnesium in 44 clinical samples using two types of user-prepared heparin syringes which differed in the amount of residual heparin from the BD Preset(TM) reference syringe. With the type 1 syringe, the liquid heparin was expelled once or twice such that some heparin could be left in the dead space at the syringe hub, while the liquid sodium heparin was thoroughly expelled from the type 2 syringe. The ionized magnesium levels obtained with the type 1 syringe were significantly lower than the reference value (by 0.068 mmol/L) (p < 0.0001), while the value obtained with the type 2 syringe differed less from the reference, by only 0.014 mmol/L (p < 0.0001). The heparin binding effect resulted in more negative bias in ionized magnesium (-0.026 +/- 0.032 mmol/L) than in ionized calcium (-0.009 +/- 0.042 mmol/L, p < 0.0001). In conclusion, we recommend using lyophilized, calcium-balanced, heparinized syringes for the determination of ionized magnesium and ionized calcium due to the increased negative bias in ionized magnesium determinations. When user-prepared syringes are used, the thorough evacuation of heparin solution should be strictly prescribed.
Syringes ; Protein Binding ; Magnesium/*chemistry/metabolism ; Ions ; Humans ; Heparin/administration & dosage/*therapeutic use ; Calcium/*metabolism ; Blood Specimen Collection/*methods ; Blood Chemical Analysis/*methods ; Anticoagulants/therapeutic use

Little is known about hair mineral status in fibromyalgia patients. This study evaluated the characteristics of hair minerals in female patients with fibromyalgia compared with a healthy reference group. Forty-four female patients diagnosed with fibromyalgia according to the American College of Rheumatology criteria were enrolled as the case group. Age- and body mass index-matched data were obtained from 122 control subjects enrolled during visit for a regular health check-up. Hair minerals were analyzed and compared between the two groups. The mean age was 43.7 yr. General characteristics were not different between the two groups. Fibromyalgia patients showed a significantly lower level of calcium (775 microg/g vs 1,093 microg/g), magnesium (52 microg/g vs 72 microg/g), iron (5.9 microg/g vs 7.1 microg/g), copper (28.3 microg/g vs 40.2 microg/g) and manganese (140 ng/g vs 190 ng/g). Calcium, magnesium, iron, and manganese were loaded in the same factor using factor analysis; the mean of this factor was significantly lower in fibromyalgia group in multivariate analysis with adjustment for potential confounders. In conclusion, the concentrations of calcium, magnesium, iron, and manganese in the hair of female patients with fibromyalgia are lower than of controls, even after adjustment of potential confounders.
Adult ; Body Height ; Body Mass Index ; Calcium/analysis ; Female ; Fibromyalgia/*metabolism ; Hair/*chemistry ; Humans ; Iron/analysis ; Magnesium/analysis ; Manganese/analysis ; Metals/*analysis ; Middle Aged

Vitamin K2 is widely used for the treatment of osteoporosis in Japan. To understand the effects of vitamin K2 on bone mass and bone metabolism, we reviewed its effects on the development of osteopenia in rats, which characterizes models of osteoporosis. Vitamin K2 was found to attenuate the increase in bone resorption and/or maintain bone formation, reduce bone loss, protect against the loss of trabecular bone mass and its connectivity, and prevent the decrease in strength of the long bone in ovariectomized rats. However, combined treatment of bisphosphonates and vitamin K2 had an additive effect in preventing the deterioration of the trabecular bone architecture in ovariectomized rats, while the combined treatment of raloxifene and vitamin K2 improved the bone strength of the femoral neck. The use of vitamin K2 alone suppressed the increase in trabecular bone turnover and endocortical bone resorption, which attenuated the development of cancellous and cortical osteopenia in orchidectomized rats. In addition, vitamin K2 inhibited the decrease in bone formation in prednisolone-treated rats, thereby preventing cancellous and cortical osteopenia. In sciatic neurectomized rats, vitamin K2 suppressed endocortical bone resorption and stimulated bone formation, delaying the reduction of the trabecular thickness and retarding the development of cortical osteopenia. Vitamin K2 also prevented the acceleration of bone resorption and the reduction in bone formation in tail-suspended rats, which counteracted cancellous bone loss. Concomitant use of vitamin K2 with a bisphosphonate ameliorated the suppression of bone formation and more effectively prevented cancellous bone loss in tail-suspended rats. Vitamin K2 stimulated renal calcium reabsorption, retarded the increase in serum parathyroid hormone levels, and attenuated cortical bone loss primarily by suppressing bone resorption in calcium-deficient rats while maintaining the strength of the long bone in rats with magnesium deficiency. These findings suggest that vitamin K2 may not only stimulate bone formation, but may also suppress bone resorption. Thus, vitamin K2 could regulate bone metabolism in rats, which represented the various models of osteoporosis. However, the effects of vitamin K2 on bone mass and bone metabolism seem to be modest.
Vitamin K 2/chemistry/metabolism/*pharmacology ; Tomography, X-Ray Computed ; Tibia/pathology ; Rats ; Osteoporosis/*drug therapy/*prevention & control ; Male ; Magnesium Deficiency/diagnosis ; Magnesium/metabolism ; Homeostasis ; Female ; *Disease Models, Animal ; Diphosphonates ; Calcium/metabolism ; Bone and Bones/*drug effects/metabolism ; Bone Resorption ; Bone Diseases, Metabolic/*metabolism ; Animals

OBJECTIVETo study the effect of different extracts of Alisma orientalis on urinary calcium oxalate stone formation in rats and to identify the effective constituents.

METHODDifferent extracts were administered through a stomach tube to rats of different groups with renal calcium oxalate stones induced by ethylene glycol (EG) and ammonium chloride (AC).

RESULTIn the rats administered with ethyl acetate elution of ethyl acetate extract, blood Cr, BUN, renal tissue calcium content, urinary calcium excretion and crystals deposition in renal tissue were significantly lower than those of the stone formation group.

CONCLUSIONThe ethyl acetate elution of ethyl acetate fraction extract of Alisma orientalis can significantly inhibit urinary calcium oxalate stone formation in rats and be the most effective constituent of Alisma orientalis.

Alisma ; chemistry ; Ammonium Chloride ; Animals ; Blood Urea Nitrogen ; Calcium ; metabolism ; Calcium Oxalate ; urine ; Creatinine ; blood ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Ethylene Glycol ; Kidney ; metabolism ; Kidney Calculi ; chemically induced ; metabolism ; prevention & control ; Magnesium ; metabolism ; urine ; Male ; Rats ; Rats, Wistar

Human NUDT16 (hNUDT16) is a decapping enzyme initially identified as the human homolog to the Xenopus laevis X29. As a metalloenzyme, hNUDT16 relies on divalent cations for its cap-hydrolysis activity to remove m⁷GDP and m²²⁷GDP from RNAs. Metal also determines substrate specificity of the enzyme. So far, only U8 small nucleolar RNA (snoRNA) has been identified as the substrate of hNUDT16 in the presence of Mg²(+). Here we demonstrate that besides U8, hNUDT16 can also actively cleave the m⁷GDP cap from mRNAs in the presence of Mg²(+) or Mn²(+). We further show that hNUDT16 does not preferentially recognize U8 or mRNA substrates by our cross-inhibition and quantitative decapping assays. In addition, our mutagenesis analysis identifies several key residues involved in hydrolysis and confirms the key role of the REXXEE motif in catalysis. Finally an investigation into the subcellular localization of hNUDT16 revealed its abundance in both cytoplasm and nucleus. These findings extend the substrate spectrum of hNUDT16 beyond snoRNAs to also include mRNA, demonstrating the pleiotropic decapping activity of hNUDT16.
Amino Acid Motifs ; Biocatalysis ; Cell Nucleus ; enzymology ; Consensus Sequence ; Cytoplasm ; enzymology ; metabolism ; Guanosine Diphosphate ; metabolism ; Histidine ; metabolism ; Humans ; Hydrolysis ; Luciferases ; genetics ; Magnesium ; metabolism ; Manganese ; metabolism ; Mutagenesis ; Mutation ; Pyrophosphatases ; antagonists & inhibitors ; chemistry ; genetics ; metabolism ; RNA Caps ; chemistry ; metabolism ; pharmacology ; RNA, Small Nucleolar ; chemistry ; metabolism ; pharmacology