Mechanobiological model of bone remodeling based on stress state at cellular and molecular level / 医用生物力学

Objective To develop a mechanobiological model of bone remodeling based on stress state at cellular and molecular level. Methods Through analysis of bone remodeling process and mechanical stimulus from an engineering perspective, as well as absorption from the idea of mechanical strength design theory, the equivalent stress as the mechanical stimulus and the appropriate calculation formula of mechanical stimulus based on stress state were selected to propose a mechanobiological model of bone remodeling based on stress state at the cellular and molecular level. The model was then used to simulate bone remodeling of alveolar bone in orthodontics. Results The reduction of the vascular porosity and increase of bone mass appeared in tensile stress area, while vascular porosity increased and bone mass reduced in compression stress area, which was consistent with the features of alveolar bone. Conclusions The mechanobiological model of bone remodeling based on stress state at cellular and molecular level considered the effect of stress state on failure forms of bone tissues, embodied bone remodeling as a cellular automaton optimization process under mechanical stimulus, which would contribute to investigating effects of stress state on bone remodeling at the cellular and molecular level. The study is a supplement and improvement of bone remodeling theory and will provide theoretical guidance for treatment of orthodontics.

Mechanostat of bone remodelling under dynamic loads / 医用生物力学

Objective To discuss the mechanostat of bone remodeling under dynamic loads. Methods By analysis on mechanostat of bone remodeling and absorption from the idea of mechanical fatigue strength theory, the mechanostat of bone remodeling under dynamic loads was developed. Damage was selected as the mechanical stimulus under dynamic loads and the model of bone remodeling under dynamic loads was proposed. Physical exercise for prevention and treatment of osteoporosis was simulated to analyze the biomechanical phenomenon why the osteogenesis effect under dynamic loads seems better than that under static loads. Results The biomechanical phenomenon as mentioned above was reasonably explained. An increase of 10%-30% in physical exercise could cause an increase of 3.13%-8.61% in bone mineral density. Conclusions The mechanostat of bone remodeling under dynamic loads will provide theoretical guidance for using mechanical vibration to treat or prevent diseases related to bone metabolism, which is the supplement and improvement for mechanostat of bone remodeling.

Relationship between bronchoalveolar lavage mycoplasma load and clinical characteristics in children with Mycoplasma pneumoniae pneumonia / 中华儿科杂志

<p><b>OBJECTIVE</b>Mycoplasma pneumoniae (MP) is an important pathogen for community-acquired pneumonia in children. MP infection was considered to be self-limited, but many severe refractory MP pneumonia cases have been reported in recent years. The reason for variation in severity of MP pneumonia remains unclear. MP virulence including drug-resistance and host immunologic function are important influencing factors. The present study aimed to clarify relationship between local MP load and severity of MP pneumonia.</p><p><b>METHOD</b>MP DNA was quantitatively detected by fluorescent real-time PCR in bronchoalveolar lavage fluid (BALF) from 77 children with MP pneumonia. They were classified into groups of low MP load ( < 10(3)/ml, n = 14) , moderate MP load (10(3)-10(6)/ml, n = 22) and high MP load ( > 10(6)/ml, n = 41) . Clinical symptoms, main laboratory and imaging results of children among the three groups were compared.</p><p><b>RESULT</b>When compared with low load group and moderate load group, high load group had longer fever duration (7 d, 10 d vs. 12 d) , longer time to normalization of temperature with macrolide administration (4 d, 8 d vs. 10 d) , more patients with high fever (50.0%, 68.2% vs. 87.8%) and longer duration of fever than 10 d (35.7%, 50.0% vs. 73.2%).Statistically significant difference existed in CRP among the three groups (1.0 mg/L, 11.5 mg/L, 34 mg/L). Large field of consolidation or atelectasis were found in 58.5% of high load patients, much higher than 22.7% in moderate load and 14.3% in low load patients. Bilateral or massive pleural effusion was not found in low load group, while in moderate load and high load group, they were 13.6% and 24.4%. However, no significant difference was found in symptoms and main laboratory and imaging results among different age groups in high load patients.</p><p><b>CONCLUSION</b>There is a close relationship between MP load in BALF and clinical characteristics in children with MP pneumonia. Those with high MP load have a more severe process.</p>

Mixed infections in children with Mycoplasma pneumoniae pneumonia / 中华儿科杂志

<p><b>OBJECTIVE</b>To investigate the incidence and clinical features of mixed infections in children with Mycoplasma pneumoniae (MP) pneumonia.</p><p><b>METHOD</b>A total of 201 cases diagnosed as MP pneumonia were investigated for mixed infections by sputum bacterial culture, respiratory virus antigen detection and serum Chlamydia pneumoniae antibody test. For those with the indications for bronchoscopy, we also did bronchoalveolar lavage and lavage bacterial culture.</p><p><b>RESULT</b>A high incidence (103/201, 51.2%) of mixed infections in children with MP pneumonia was revealed. The most frequent co-infected pathogen was Chlamydia pneumoniae (52, 25.9%), followed by viruses (29, 14.4%), and bacteria (22, 10.9%). Among viruses, respiratory syncytial virus was the most common (17, 8.5%), followed by adenovirus (6, 3.0%), parainfluenza virus type III (4, 2.0%) and influenza virus type B (2, 1.0%). Sputum bacterial culture was positive in 14/201 (7.0%) cases, Streptococcus pneumonia being most common (6, 3.0%). BALF culture yielded positive results in 11.6% (8/69), Streptococcus pneumonia was also common (5, 7.3%). Among 29 cases with MP and virus coinfection, 26 were younger than 3 years (89.7%), while for MP and Chlamydia pneumoniae coinfection, most of them were older than 3 years (40/52, 76.9%). Compared with non-mixed infections, those with mixed infections had longer fever duration (24.5% and 40.8% longer than 10 d), more frequently developed pleural effusion (11.2%, 23.3%) and large area of shadow in chest imaging (35.7%, 51.5%). White blood cell [(14.28 ± 4.99) × 10(9)/L], C-reactive protein (CRP) [69(32.5 - 99.5) mg/L] and neutrophil ratio in BALF [0.86 (0.63 - 0.91)] were much higher in children with mixed bacterial infections than that in non-mixed infections [(9.06 ± 3.47) × 10(9)/L, 3 (0 - 31.0) mg/L, 0.44 (0.03 - 0.88)]. But no significant difference was found in peripheral blood neutrophil proportion between mixed bacterial infections (0.38 ± 0.25) and non-mixed infections (0.51 ± 0.19).</p><p><b>CONCLUSION</b>More than half of cases with MP pneumonia had mixed infections, most commonly caused by Chlamydia pneumonia followed by viruses. The incidence of mixed infections with bacteria was low. Mixed infections with virus were more common in young children, while mixed infection with Chlamydia pneumoniae was more common in older ones. Bacterial infections should be paid more attention, especially those caused by Streptococcus pneumoniae, for those with high peripheral white blood cell counts, high CRP levels and high proportion of neutrophils in BALF.</p>

Genotyping of Mycoplasma pneumoniae in nasopharyngeal aspirate from children with pneumonia in Zhejiang Province / 中华儿科杂志

<p><b>OBJECTIVE</b>The P1 protein of Mycoplasma pneumoniae (MP) plays an important role in the pathogenesis of MP pneumonia. It mediates the attachment of the pathogen to host cells and elicits a strong humoral immune response during infection. In early studies, only two types of MP P1 genes were assumed to exist. Later, eight subtypes of MP P1 genes and some variations of P1 gene were reported. However, there are no related reports in China until now. This study aimed to understand epidemiology of MP subtype in Zhejiang province, China, as well as the relationship between MP subtype and clinical severity of MP pneumonia.</p><p><b>METHOD</b>Clinical samples were collected by nasopharyngeal aspiration from children with MP pneumonia hospitalized in the Children's Hospital of Zhejiang University School of Medicine from February to December in 2009. P1 gene fragment was amplified by using PCR method (with primers of ADH1/ADH2 and ADH3/ADH4, respectively). Then ADH1/ADH2-generated fragments were digested with HaeIII, HpaII, Sau3A, and the ADH3/ADH4-generated fragments digested with HaeIII, Sau3A, HhaI, RsaI. The MP P1 subtypes were determined based on resulting fragments. Part of samples were selected for sequencing. The clinical data of different MP subtype pneumonia were compared.</p><p><b>RESULT</b>A total of 300 hospitalized children with MP pneumonia were enrolled in this study. All the samples produced specific bands for MP P1 gene after PCR with primers of ADH1/ADH2 and ADH3/ADH4 respectively. By restrictive fragment length polymorphism analysis, 297 clinical specimens showed the characteristic band patterns for P1 type 1 identical to Mp129, and only 3 clinical specimens showed the characteristic band pattern for P1 type 2 identical to MP-FH. All P1 type 1 and P1 type 2 showed the same subtype bands respectively, as subtype 1b and 2a. After sequencing, one synonymous point mutation in P1 type 1 was identified relative to the MP129 P1 sequence at nucleotide position (nt) 208(G→A). Three cases with P1 type 2 MP pneumonia were found to have liver damage, and longer hospital stay and fever duration than P1 type 1, but no statistically significant difference was found.</p><p><b>CONCLUSION</b>Clinical samples can be used directly for genotyping of MP. The dominating type of MP in Zhejiang Province was P1 type 1 subtype 1b. But whether there was any relationship between MP subtype and clinical severity remains to be clarified.</p>