Joint toxicity of cadmium (II) and microplastic leachates on wheat seed germination and seedling growth.

Cadmium (Cd) pollution ranks first in soils (7.0%) and microplastics usually have a significant adsorption capacity for it, which could pose potential threats to agricultural production and human health. However, the joint toxicity of Cd and microplastics on crop growth remains largely unknown. In this study, the toxic effects of Cd2+ and two kinds of microplastic leachates, polyvinyl chloride (PVC) and low-density polyethylene (LDPE), on wheat seed germination and seedlings' growth were explored under single and combined conditions. The results showed that Cd2+ solution and two kinds of microplastic leachates stimulated the wheat seed germination process but inhibited the germination rate by 0-8.6%. The combined treatments promoted wheat seed germination but inhibited the seedlings' growth to different degrees. Specifically, the combination of 2.0 mg L-1 Cd2+ and 1.0 mgC L-1 PVC promoted both seed germination and seedlings' growth, but they synergistically increased the antioxidant enzyme activity of seedlings. The toxicity of the PVC leachate to wheat seedlings was stronger than LDPE leachate. The addition of Cd2+ could alleviate the toxicity of PVC leachate on seedlings, and reduce the toxicity of LDPE leachate on seedlings under the same concentration class combinations but aggravated stress under different concentration classes, consistent with the effect on seedlings' growth. Overall, Cd2+, PVC, and LDPE leachates have toxic effects on wheat growth, whether treated under single or combined treatments. This study has important implications for the joint toxicity of Cd2+ solution and microplastic leachates in agriculture.

[The actuality and trend of biomaterial effectiveness and safety evaluation].

The evaluation of biomaterial effectiveness and safety is a key step before the biomaterial approaches to clinics. In recent years, lots of new biomaterials with different composition, shape, implant site and use have been coming out and in need of more special, sensitive and systematic evaluation methods. With the development of immunology, microdetective technique, inbred strain mammal and other connective branches, there are many chances for the consummation and integration of biomaterial evaluation system. The three-"R" principle (replace, refine, reduce), that is, developing in vitro experiments, using sensitive, special and advanced evaluation methods, improving and reducing the member of experimental animals, as well as the fundamental rule, that is, establishing an evaluation system covering three levels (molecule, cell and body) will guide the research of biomaterial evaluation to more promising development.

[Advances and prospective application of stem cell technique in stomatology].

In this paper the background and advances of stem cell technique in stomatology were reviewed, especially the lately research of repair of maxillofacial defects with bone marrow stem cells, repair or reconstitution of teeth with dental pulp stem cells and repair of other tissues such as parotid with embryonic stem cell. Stem cell technique provides a new choice and extensive prospect of application for stomatology, therefore, deserves further research.

[Application of enzyme histochemistry in evaluation of in vitro and in vivo biocompatibility of HA/TCP].

In order to explore the possibility of applying enzyme histochemistry in biocompatibility evaluation, we investigated the effect of biomaterials on the activities of intracellular enzymes in this experiment. It was found that there was no obvious difference in morphology between osteoblasts co-cultured with HA/TCP and with Ti-alloy. However, transient down-regulation of NADH, SDH, LDH and CCO of the osteoblasts co-cultured with HA/TCP was detected by enzyme histochemistry, but these enzymes of osteoblasts the co-cultured with Ti-alloy were not down-regulated. It was indicated that something extracted from HA/TCP injured the co-cultured osteoblasts slightly. Similar early acute inflammatory reactions were observed after HA/TCP and Ti-alloy were separately implanted into the dorsal muscle of rabbit. There was also no obvious difference between the tissue response to HA/TCP and that to Ti-alloy. Activities of enzymes in tissues around implanted materials were down-regulated at the early injury period and recovered gradually within 30 days post-operation. But the mild toxicity of extracts from HA/TCP was demonstrated by the fact that the recovery period of HA/TCP group was longer than that of Ti-alloy group. It was proved that enzyme histochemistry is more sensitive than tissue morphology analysis in detecting the cell or tissue responses to biomaterials. Therefore, it is possible to use enzyme histochemistry in biocompatibility evaluation.

[Osteogenesis of HA/TCP biphasic ceramics implanted into muscle: a long-term study].

New bone formation in long-term intramuscle implant of Ca-P biomaterial was investigated in this experiment. After implanting into dog dorsal muscle for 15 months, a thin fibrous membrane that wrapped HA/TCP implant was still observed obviously. Three types of tissues, i.e. mesenchymal tissue, bone and bone marrow, regularly distributed in different pores of implant. Nearly all the pores of implants were occupied by bone. Bone in the pores located in the central region of implant was matured lamellar bone characterized by obvious lacuna and rich bone marrow. However, bone in the peripheral pores was immature woven bone without bone marrow formation. Furthermore, mesenchymal tissues only exist in the peripheral pores and usually were connected with immature woven bone. It was demonstrated that porous HA/TCP has bone inductivity and it could induce new bone formation at non-osseous site. Well-regulated distribution of mesenchymal tissue, bone and bone marrow in the pores suggest bone morphogenesis in the implant must obey a specific space-time program.

A modified splint tubing technique for heterotopic heart transplantation in mouse.

BACKGROUND: The complexity of surgical procedure in mouse heterotopic heart transplantation (HHT) has prevented its widespread use. The present study reported a modified technique - splint tubing technique (STT) based on cuff technique (CT). MATERIALS AND METHODS: C57BL/10 and BALB/c mice were performed in syngeneic and allogeneic HHT using STT and CT. The main improvement is that the recipient external jugular vein and common carotid artery were independently opened a mouth and inserted a cannula to avoid the difficult operations of sleeved and everted tube. Graft function was assessed by pulse palpation, echocardiography and histopathologic examination. RESULTS: Ten syngeneic and thirty allogeneic HHT using STT were performed with six graft losses. Ten allogeneic HHT using CT were carried out with two graft losses. Technically successful syngeneic grafts have survived to the pre-specified 30days endpoint with strong contraction. STT significantly shortened operation time compared with CT (32.33±4.21min vs 45.15±4.89min, P<0.05). No significant difference was observed in survival time between two methods. CONCLUSION: STT is easily learned. It reduces the operation difficulty and makes the operation possible for the beginner to master this skill within 1-2weeks. Shorter operation time leads higher operative success rate.

A long-term evaluation of osteoinductive HA/beta-TCP ceramics in vivo: 4.5 years study in pigs.

It has been proved that some material-dependent calcium phosphate ceramics have intrinsic potentials to induce osteogenesis. But there is little literature concerning about the tissue response in long-term. The aim of this study is to evaluate the safety of the osteoinductive biocreamics and the stability of the newly formed bone after long-term tissue response. Porous calcium phosphate ceramics rods which contain hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) were implanted in the dorsal muscles of Banna Minipig Inbreding Line. After 4.5 years, all the implanted rods with surrounding tissues were harvested and stained with hematoxylin and eosin for histological observation. The 7 months' rods were also harvested as short-term comparison. The histological results showed that compared with the short-term rods, amount of bone tissue formed after 4.5 years. And the newly formed bone in this bioceramics neither disappeared nor gave rise to uncontrolled growth. The bone growth in this bioceramics seemed to be self-confined. The surrounding soft tissues were normal and no tumor cell was found. We conclude that instead of disappearing or giving rise to out of control, the induced bone tissue trends to be further matured. And this bioceramics thus might have potentials in future clinical use.

[Influence of dosage on cell biocompatibility of hydroxyapatite/tricalcium phosphate].

OBJECTIVE: To investigate the influence of different dose levels of hydroxyapatite/tricalcium phosphate (HA/TCP) on the proliferation and alkaline phosphatase (ALP) activity of rabbit osteoblasts. METHODS: Three different dose levels of HA/TCP (10%, 40%, 70%) were co-cultivated with rabbit osteoblasts respectively. The proliferation and ALP expression capacity of osteoblasts were examined with MTT method and enzyme histochemistry once every 24 hours until 5 days. Three control groups of other materials were treated and examined in the same way: rabbit osteoblasts as normal control; polyvinylchloride as positive control; titanium alloy as negative control. RESULTS: There was remarkable time-effect relationship in the proliferation of osteoblasts. Ten percent HA/TCP did not affect osteoblasts growth while 40% HA/TCP could slow the cell growth rate down though time-effect relationship still existed. The proliferation of osteoblasts stagnated when co-cultivated with 70% HA/TCP. On the other hand, 10% HA/TCP could cause reversible damage on ALP activity of osteoblasts, whereas when the dose was 40%, and the cultivation lasted 6 days the damage was irreversible. Three different dose levels of titanium alloy (10%, 40%, 70%) had no effect on the proliferation or ALP activity of osteoblasts. CONCLUSION: Dosage is an important factor affecting the biocompatibility evaluation of biomaterial. It suggests that dose choosing should be more specified upon each individual biomaterial. It also indicates that ALP may be a good supplementary index of the cell compatibility of material.