Has breeding altered the light environment, photosynthetic apparatus, and photosynthetic capacity of wheat leaves?

Whether photosynthesis has improved with increasing yield in major crops remains controversial. Research in this area has often neglected to account for differences in light intensity experienced by cultivars released in different years. Light intensity is expected to be positively associated with photosynthetic capacity and the resistance of the photosynthetic apparatus to high light but negatively associated with light-utilization efficiency under low light. Here, we analyzed the light environment, photosynthetic activity, and protein components of leaves of 26 winter wheat cultivars released during the past 60 years in China. Over time, light levels on flag leaves significantly decreased due to architectural changes, but photosynthetic rates under high or low light and the resistance of the photosynthetic apparatus to high light remained steady, contrary to expectations. We propose that the difference between the actual and expected trends is due to breeding. Specifically, breeding has optimized photosynthetic performance under high light rather than low light. Moreover, breeding selectivity altered the stoichiometry of several proteins related to dynamic photosynthesis, canopy light distribution, and photoprotection. These results indicate that breeding has significantly altered the photosynthetic mechanism in wheat and its response to the light environment. These changes likely have helped increase wheat yields.

PD-1/PD-L1 inhibitor monotherapy in recurrent or metastatic squamous cell carcinoma of the head and neck: a meta-analysis.

PURPOSE: To evaluate the efficacy and safety of programmed cell death-1/programmed cell death-ligand 1 inhibitor monotherapy compared to the standard of care in the first-line setting for recurrent or metastatic head and neck squamous cell carcinoma. MATERIALS AND METHODS: The PubMed, Embase, and Cochrane Library databases were searched for relevant randomized controlled trials. The clinical outcomes of overall survival, progression-free survival, objective response rates, and grade 3 or higher adverse events were analyzed using Stata SE 15 software with a significance level set to 0.05. RESULTS: We identified four randomized controlled trials (1 nivolumab, 2 pembrolizumab, and 1 durvalumab), including a total of 2474 patients. The results of the meta-analysis showed pooled hazard ratios of overall and progression-free survival for programmed cell death-1/programmed cell death-ligand 1 inhibitor monotherapy of 0.82 (95% CI: 0.73-0.91, p < 0.001) and 0.96 (95%CI: 0.84-1.07, p < 0.001) and pooled odds ratios of objective response rates and grade 3 or higher adverse events of 1.04 (95%CI: 0.46-2.37; p = 0.926) and 0.28 (95%CI: 0.22-0.35, p < 0.001), respectively. Subgroup analysis showed that inhibitors for both programmed cell death-1 (nivolumab and pembrolizumab) and programmed cell death-ligand 1 (durvalumab) were associated with significantly longer overall survival (HR = 0.80, 95% CI: 0.70-0.90, p < 0.001 and HR = 0.88, 95%CI: 0.70-1.06, p < 0.001, respectively). CONCLUSIONS: Programmed cell death-1/programmed cell death-ligand 1 inhibitor monotherapy showed more clinical benefit versus the standard of care in patients with recurrent or metastatic head and neck squamous cell carcinoma, with an acceptable safety profile.

Photoprotection by mitochondrial alternative pathway is enhanced at heat but disabled at chilling.

The mitochondrial alternative pathway (AP) represents an important photoprotective mechanism for the chloroplast, but the temperature sensitivity of its photoprotective role is unknown. In this study, using the aox1a Arabidopsis mutant, the photoprotective role of the AP was verified under various temperatures, and the mechanism underlying the temperature sensitivity of the AP's photoprotective role was clarified. It was observed that the photoprotective role of the AP increased with rising temperature but was absent at low temperature. The photoprotective role of the AP was severely reduced under non-photorespiratory conditions. Disturbance of the AP inhibited the conversion of glycine to serine in mitochondria, which may restrain upstream photorespiratory metabolism and aggravate photoinhibition. With rising temperatures, photorespiration accelerated and the restraint of photorespiration caused by disturbance of the AP also increased, determining the temperature sensitivity of the AP's photoprotective role. We also verified that not only the AP but also the cytochrome pathway in mitochondria contributes to photoprotection by maintaining photorespiration.

Chronic stress induces wide-spread hyperalgesia: The involvement of spinal CCK1 receptors.

Chronic primary pain (CPP) occurs in the absence of tissue injury and includes temporomandibular disorders (TMD), fibromyalgia syndrome (FMS) and irritable bowel syndrome (IBS). CPP is commonly considered a stress-related chronic pain and often presents as wide-spread pain or comorbid pain conditions in different regions of the body. However, whether prolonged stress can directly result in the development of CPP comorbidity remains unclear. In the present study, we adapted a 21 day heterotypic stress paradigm in mice and examined whether chronic stress induced wide-spread hyperalgesia, modeling comorbid CPP in the clinic. We found that chronic stress induced anxiety- and depression-like behaviors, and resulted in long-lasting wide-spread hyperalgesia over several body regions such as the orofacial area, hindpaw, thigh, upper back and abdomen in female mice. We further found that the expression of cholecystokinin (CCK)1 receptors was significantly increased in the L4-L5 spinal dorsal horn of the female mice after 14 and 21 day heterotypic stress compared with the control animals. Intrathecal injection of the CCK1 receptor antagonist CR-1505 blocked pain hypersensitivity in the subcervical body including the upper back, thigh, hindpaw and abdomen. These findings suggest that the upregulation of spinal CCK1 receptors after chronic stress contributes to the central mechanisms underlying the development of wide-spread hyperalgesia, and may provide a potential and novel central target for clinical treatment of CPP.

Case series: O-arm navigation assisted by the Wiltse approach improves the accuracy of pedicle screw placement in ankylosing spondylitis combined with thoracolumbar fractures.

Here we assessed the accuracy of O-arm navigation assisted by Wiltse approach to improve based pedicle screw insertion in ankylosing spondylitis combined with thoracolumbar fractures. We then compared it with the freehand pedicle screw insertion technique. The study sample included 32 patients with ankylosing spondylitis combined with thoracolumbar fractures. Pedicle screw reduction and internal fixation was performed under an O-arm navigation system assisted by a Wiltse approach-combined osteotomy ("navigation group," n = 17) and posterior pedicle screw reduction and internal fixation was performed using freehand technique combined osteotomy ("freehand group," n = 15). We then compared the operation time and bleeding volume between the 2 groups. The visual analog scale (VAS) and Oswestry disability index (ODI) were then used to evaluate the clinical efficacy and the kyphosis Cobb angle was used to evaluate the radiological efficacy before operation, 3 days after operation and after the last follow-up. All complications were noted when detected. Finally, classification of screw positions as proposed by Neo et al was used to evaluate the relationship of the position between the screw, the bone cortex, and the incidence of screw penetration. All patients were followed up for 18 to 36 months (i.e., 24.2 ±â€…3.5 months). The operation time and intraoperative bleeding volume of the navigation group were significantly shorter (lower) than those of the freehand group (P < .05). In addition, Both groups showed significantly decreased VAS, ODI, and Cobb angle 3 days after the operation and at the last follow-up when compared to values recorded pre-operation. However, we found no significant difference in VAS, ODI, and Cobb angle between the 2 groups (P > .05). We identified no complications (e.g., infection, VTE/PE, or nerve injury). Moreover, the pedicle screw placement position of the navigation group was better than that of the freehand group (P < .05), and the screw cortical penetration rate was lower than the freehand group (P < .05). During the process of posterior pedicle screw placement, O-arm navigation assisted by the Wiltse approach can significantly reduce operation time, minimize the amount of bleeding volume, and enhance the accuracy of pedicle screw implantation.

Efficacy and safety of weekly versus triweekly cisplatin concurrent with radiotherapy in nasopharyngeal carcinoma: A meta-analysis.

BACKGROUND: Cisplatin-based concurrent chemoradiotherapy is a standard of care for locally advanced nasopharyngeal carcinoma (NPC), and weekly and triweekly cisplatin are both alternative regimens based on the results of squamous cell carcinoma of the head and neck. However, there is a lack of direct evidence on the efficacy and safety of weekly versus triweekly cisplatin concurrent with radiotherapy in NPC alone. This meta-analysis aimed to identify which regimen is more superior between weekly and triweekly cisplatin in patients with NPC treated with concurrent chemoradiotherapy. METHODS: The PubMed, Embase, and Cochrane Library were searched for eligible literatures. Clinical outcome measures including 1-year overall survival (OS), 3-year OS, 5-year OS, 5-year loco-regional failure-free survival, 5-year distant metastasis-free survial and the most common 3 grade or higher acute toxicities (hematological toxicity, mucositis and nausea and vomiting) were analyzed by RevMan 5.4 software; significance level was 0.05. RESULTS: Seven clinical controlled studies with 1795 patients were included in the meta-analysis. There were no significant differences between weekly and triweekly cisplatin in 1-year OS, 3-year OS, 5-year OS, 5-year loco-regional failure-free survival, and 5-year distant metastasis-free survial) (all P > .05). Grade 3 or higher mucositis and nausea and vomiting showed similar between the 2 arms. However, grade 3 or higher hematological toxicity of weekly cisplatin was significantly higher than that of triweekly cisplatin (1.55; 95% CI, 1.22-1.98, P = .0004). CONCLUSIONS: Weekly cisplatin resulted in similar survival benifit as triweekly cisplatin, but with higher hematological toxicity.

The unsaturation of phosphatidylglycerol in thylakoid membrane alleviates PSII photoinhibition under chilling stress.

Over-expression of chloroplast glycerol-3-phosphate acyltransferase gene (LeGPAT) in tomato increased cis-unsaturated fatty acid content in phosphatidylglycerol (PG) of the thylakoid membrane. Under chilling stress, the oxygen evolving activity, the maximal photochemical efficiency of PSII (F (v)/F (m)), and superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities decreased less in sense lines than in antisense lines compared to wild-type (WT) plants. Consistently, the relative electric conductivity, O⁻2and H(2)O(2) contents in sense lines were lower than those of WT and antisense lines. The antisense lines with low level of unsaturated fatty acids in PG were extremely susceptible to photoinhibition of PSII and had a significant reduction in the D1 protein content of PSII reaction center under chilling stress. However, in the presence of streptomycin (SM), the degradation of D1 protein was faster in sense lines than in WT and antisense plants. These results suggested that, under chilling stress conditions, increasing cis-unsaturated fatty acids in PG through over-expression of LeGPAT can alleviate PSII photoinhibition by accelerating the repair of D1 protein and improving the activities of antioxidant enzymes in chloroplasts.

Overexpression and suppression of violaxanthin de-epoxidase affects the sensitivity of photosystem II photoinhibition to high light and chilling stress in transgenic tobacco.

Tobacco (Nicotiana tabacum) transformed with the sense and antisense constructs of tomato (Lycopersicon esculentum) violaxanthin de-epoxidase gene (LeVDE) was obtained under the control of the cauliflower mosaic virus 35S promoter (35S-CaMV). Reverse transcription-polymerase chain reaction and western blot analysis demonstrated that the exogenous gene was integrated into the tobacco genome. Wild type (WT), the sense-transgenic line T(1)-24(+) and the antisense-transgenic line T(1)-17(-) were used for physiological measurement. The ratio of (A+Z)/(V+A+Z) and non-photochemical quenching in WT were lower than that in sense plants and higher than that in antisense ones under high light and chilling stress with low irradiance. The maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm) and the net photosynthetic rate (Pn) in the sense line decreased less, while Fv/Fm and Pn in the antisense line decreased most obviously among all lines. These results suggest that the expression of the violaxanthin de-epoxidase gene in transgenic plants affects the sensitivity of PSII photoinhibition to high light and chilling stress.

Overexpression of sweet pepper glycerol-3-phosphate acyltransferase gene enhanced thermotolerance of photosynthetic apparatus in transgenic tobacco.

In order to investigate the relationship between the lipid composition in thylakoid membrane and thermostability of photosynthetic apparatus, tobacco transformed with sweet pepper sense glycerol-3-phosphate acyltransferase (GPAT) gene were used to analyze the lipid composition in thylakoid membrane, the net photosynthetic rate and chlorophyll fluorescence parameters under high temperature stress. The results showed that the saturated extent of monogalactosyldiacylglycerol (MGDG), sulfoquinovosyldiacylglycerol, digalactosyldiacylglycerol and phosphatidylglycerol in thylakoid membrane of transgenic tobacco T(1) lines increased generally. Particularly, the saturated extent in MGDG increased obviously by 16.2% and 12.0% in T(1)-2 and T(1)-1, respectively. With stress temperature elevating, the maximum efficiency of photosystem II (PSII) photochemistry (Fv/Fm), actual photochemical efficiency of PSII in the light (Phi(PSII)) and net photosynthetic rate (Pn) of the two lines and wild type tobacco plants decreased gradually, but those parameters decreased much less in transgenic plants. Even though the recovery process appeared differently in the donor and acceptor side of PSII in transgenic tobacco compared with wild-type plants, the entire capability of PSII recovered faster in transgenic tobacco, which was shown in the parameters of PI, Fv/Fm and Phi(PSII), as a result, the recovery of Pn was accelerated. Conclusively, we proposed that the increase in saturated extent of thylakoid membrane lipids in transgenic plants enhanced the stability of photosynthetic apparatus under high temperature stress.

[Effect observation of percutaneous pedicle screw fixation combined with percutaneous vertebroplasty for the treatment of osteoporotic thoracolumbar fractures].

OBJECTIVE: To evaluate the clinical effects of percutaneous pedicle screw fixation(PPSF) combined with percutaneous vertebroplasty(PVP) for the treatment of osteoporotic thoracolumbar fractures. METHODS: The clinical data of 94 patients with osteoporotic thoracolumbar fractures treated from January 2014 to December 2015 were retrospectively analyzed. There were 31 males and 63 females, aged from 65 to 70 years old with an average of 67.2 years. Fracture level was T11 on 15 cases, T12 on 32 cases, L1 on 29 cases and L2 on 18 cases. The patients were divided into two groups according to different therapeutic methods. Percutaneous pedicle screw fixation combined with percutaneous vertebroplasty were applied in 43 patients(group A) and percutaneous vertebroplasty was applied to 51 patients(group B). Operation time, intraoperative blood loss, bone cement volume, postoperative in-bed time were recorded; preoperatively, 3 d, 1 year after the operation, the ratios of anterior border heights, sagittal Cobb angles, visual analogue scale(VAS) scores were compared between two groups. The condition of postoperative complication in two groups was analyzed. RESULTS: All the patients were followed up for 12 to 24 months with an average of 18.5 months. Operation time of group A [(96.2±28.7) min] was longer than that of group B [(31.8±10.6) min]. Intraoperative blood loss of group A[(62.2±25.5) ml] was more than that of group B [(25.4±10.9) ml]. Bone cement volume of group A [(5.5±0.5) ml] was larger than that of group B [(4.9±1.1) ml]. Postoperative in-bed time of group A[(5.1±1.8) d] was longer than that of group B[(1.8±0.7) d]. There were significant differences in operation time, intraoperative blood loss, bone cement volume, postoperative in-bed time between two groups(P<0.05). Three days, 12 months after the operation, the ratios of anterior border heights and Cobb angles in two groups were significantly improved. At final follow-up, the ratio of anterior border height and Cobb angle of group A[(85.6±3.5)%, (11.9±5.3)°] were better than of group B[(84.2±4.5)%, (15.3±3.4)°](P<0.05). Three cases in group B had re-collapse of cemented vertebral bodies. Postoperative at 3 d, 1 year, VAS score of all patients had significantly decreased(P<0.05), and there was no significant difference between two groups(P>0.05). CONCLUSIONS: Compared to simple PVP, PPSF combined with PVP in treating osteoporotic thoracolumbar fracture can obtain stronger vertebral strength and stiffness, furthermore to improve vertebral reduced effect, keeping vertebral heights, and preventing vertebral re-collapse.

Mechanisms by which Bisphenol A affect the photosynthetic apparatus in cucumber (Cucumis sativus L.) leaves.

Bisphenol A (BPA), a widely distributed pollutant, suppresses photosynthesis in leaves. In previous studies on higher plants, the plants were treated by BPA through irrigation to root. This method cannot distinguish whether the BPA directly suppresses photosynthesis in leaves, or indirectly influences photosynthesis through affecting the function of root. Here, only the leaves but not the roots of cucumber were infiltrated with BPA solution. The photosystem II and I (PSII, PSI) were insensitive to BPA under darkness. BPA aggravated the PSII but not the PSI photoinhibition under light. BPA also inhibited CO2 assimilation, and the effect of BPA on PSII photoinhibition disappeared when the CO2 assimilation was blocked. The H2O2 accumulated in BPA-treated leaves under light. And the BPA-caused PSII photoinhibition was prevented under low (2%) O2. We also proved that the BPA-caused PSII photoinhibition depend on the turnover of D1 protein. In conclusion, this study proved that BPA could directly suppress photosynthesis in leaves, however, BPA does not damage PSII directly, but inhibits CO2 assimilation and over-reduces the electron transport chain under light, which increases the production of reactive oxygen species (H2O2), the over-accumulated ROS inhibits the turnover of D1 protein and consequently aggravates PSII photoinhibition.

The efficacy of N-acetylcysteine plus sodium bicarbonate in the prevention of contrast-induced nephropathy after cardiac catheterization and percutaneous coronary intervention: A meta-analysis of randomized controlled trials.

BACKGROUND: The efficacy of combining use of N-acetylcysteine (NAC) and sodium bicarbonate (SOB) in the prevention of contrast-induced nephropathy (CIN) after cardiac catheterization and percutaneous coronary intervention (PCI) is unclear. METHODS: All relevant studies that compared the effect of combining the use of NAC and SOB with individual use on CIN in patients undergoing cardiac catheterization and PCI were identified by searching the databases including Pubmed, Embase, Cochrane Library, and Web of Science without time and language limitation. Only randomized controlled trials (RCTs) with full-text published were considered. RESULTS: Sixteen RCTs involving 4432 cases were included into this meta-analysis. The results showed there were no additional benefit in reduction of CIN in COM group (COM versus NAC: RR 0.85, 95% CI 0.70-1.03, P=0.103; COM versus SOB: RR 0.91, 95% CI 0.71-1.16, P=0.449), even in patients with diabetes mellitus (COM versus NAC: RR 1.11, 95% CI 0.71-1.75, P=0.646; COM versus SOB: RR 1.06, 95% CI 0.45-2.47, P=0.893), undergoing PCI procedure (COM versus NAC: RR0.76, 95% CI 0.39-1.47, P=0.411; COM versus SOB: RR0.96, 95% CI 0.65-1.40, P=0.814), or with baseline renal dysfunction (COM versus NAC: RR 0.89, 95% CI 0.70-1.14, P=0.366; COM versus SOB: RR 0.95, 95% CI 0.67-1.36, P=0.788). CONCLUSIONS: The present study demonstrated combining use of NAC and SOB was not significantly superior to individual use method in the prevention of CIN after cardiac catheterization and PCI.

Effect of Pioglitazone in Preventing In-Stent Restenosis after Percutaneous Coronary Intervention in Patients with Type 2 Diabetes: A Meta-Analysis.

BACKGROUND: The benefits of pioglitazone in patients with type 2 diabetes mellitus (T2DM) after percutaneous coronary intervention (PCI) is unclear. OBJECTIVES: To evaluate the effect of pioglitazone on prevention of in-stent restenosis (ISR) in patients with T2DM after PCI. METHODS: All full-text published relevant studies compared the effect of pioglitazone with control group (placebo or no pioglitazone treatment) on ISR in patients with T2DM after PCI were identified by searching the databases including PubMed, EMBASE, Cochrane Library and ISI Web of Science through October 2015. The endpoints were defined as the rate of ISR, late lumen loss, in-stent neointimal volume, target lesion revascularization (TLR) and major adverse cardiac events (MACE). RESULTS: Six studies (5 RCTs and 1 retrospective study), comprising 503 patients, were included into this meta-analysis. In the pioglitazone group, as compared with the control group, the risk ratio for ISR was 0.48 (I2 = 14.5%, P = 0.322; 95%CI 0.35 to 0.68, P<0.001), the risk ratio for TLR was 0.58 (I2 = 6.0%, P = 0.363; 95%CI 0.38 to 0.87, P = 0.009). The result showed there was no association between the use of pioglitazone and the events of MACE (I2 = 36.7%, P = 0.209; RR 0.56, 95%CI 0.30 to 1.05, P = 0.071). For the considerable heterogeneity, further analysis was not suitable for the endpoints of late lumen loss (I2 = 81.9%, P<0.001) and neointimal volume (I2 = 75.9%, P = 0.016). CONCLUSIONS: The treatment of pioglitazone was associated with a reduction in ISR and TLR in T2DM patients suffering from PCI, except the incidence of MACE.

Overexpression of tomato enhancer of SOS3-1 (LeENH1) in tobacco enhanced salinity tolerance by excluding Na+ from the cytosol.

The salt overly sensitive pathway has an important function in plant salinity tolerance. The enhancer of SOS3-1 (ENH1) participates in a new salinity stress pathway with SOS2 but without SOS3. To investigate the physiological effects and functional mechanism of ENH1 under salt stress, ENH1 was isolated from tomato and overexpressed in tobacco. Under salt stress, the sprouting percentage, fresh weight, and dry weight of transgenic plants were higher than those of wild-type (WT) plants. Under salt stress, the chlorophyll content, net photosynthetic rate, and maximal photochemical efficiency of PSII in transgenic plants decreased more slowly than those in WT plants. The overexpression of LeENH1 in tobacco excluded Na(+) from the cytosol and retained high K(+) levels in the cytosol to reestablish ion homeostasis. Higher thylakoid-bound ascorbate peroxidase activity and lower reactive oxygen species levels were found in transgenic plants under salt stress.

Overexpression of glycerol-3-phosphate acyltransferase gene improves chilling tolerance in tomato.

A tomato (Lycopersicon esculentum Mill.) glycerol-3-phosphate acyltransferase gene (LeGPAT) was isolated. The deduced amino acid sequence revealed that LeGPAT contained four acyltransferase domains, showing high identities with GPAT in other plant species. A GFP fusion protein of LeGPAT was targeted to chloroplast in cowpea mesophyll protoplast. RNA gel blot showed that the mRNA accumulation of LeGPAT in the wild type (WT) was induced by chilling temperature. Higher expression levels were observed when tomato leaves were exposed to 4 degrees C for 4 h. RNA gel and western blot analysis confirmed that the sense gene LeGPAT was transferred into the tomato genome and overexpressed under the control of 35S-CaMV. Although tomato is classified as a chilling-sensitive plant, LeGPAT exhibited selectivity to 18:1 over 16:0. Overexpression of LeGPAT increased total activity of LeGPAT and cis-unsaturated fatty acids in PG in thylakoid membrane. Chilling treatment induced less ion leakage from the transgenic plants than from the WT. The photosynthetic rate and the maximal photochemical efficiency of PS II (Fv/Fm) in transgenic plants decreased more slowly during chilling stress and recovered faster than in WT under optimal conditions. The oxidizable P700 in both WT and transgenic plants decreased obviously at chilling temperature under low irradiance, but the oxidizable P700 recovered faster in transgenic plants than in the WT. These results indicate that overexpression of LeGPAT increased the levels of PG cis-unsaturated fatty acids in thylakoid membrane, which was beneficial for the recovery of chilling-induced PS I photoinhibition in tomato.

The function of chloroplastic NAD(P)H dehydrogenase in tobacco during chilling stress under low irradiance.

The function of chloroplastic NAD(P)H dehydrogenase (NDH) was examined by comparing a tobacco transformant (DeltandhB) in which the ndhB gene had been disrupted with its wild type, upon exposure to chilling temperature (4 degrees C) under low irradiance (100 micro mol m(-2) s(-1) PFD). During the chilling stress, the maximum photochemical efficiency of PSII (F(v)/F(m)) decreased markedly in both the wild type and DeltandhB. However, both F(v)/F(m) and P700(+), as well as the PSII-driven electron transport rate (ETR), in DeltandhB were lower than that in the wild type, implying that NDH-dependent cyclic electron flow around PSI functioned to protect the photosynthetic apparatus from chilling stress under low irradiance. Under the stress, non-photochemical quenching (NPQ), particularly the fast relaxing NPQ component (qf) and the de-epoxidized ratio of the xanthophyll cycle pigments, (A+Z)/(V+A+Z), were distinguishable in DeltandhB from those in the wild type. The lower NPQ in DeltandhB might be related to an inefficient proton gradient across thylakoid membranes (DeltapH) because of lacking an NDH-dependent cyclic electron flow around PSI at chilling temperature under low irradiance.

[Role of recombinant human bone morphogenetic protein 2/collagen as an onlay bone graft on adult rat calvarial bone].

OBJECTIVE: To evaluate the bone regenerative potential of recombinant human bone morphogenetic protein 2(rhBMP-2)/collagen on adult rat calvarial bone. METHODS: A tight subperiosteal pocket was produced under both sides of the temporal muscle in rats. rhBMP-2/collagen was implanted in one side and collagen alone was implanted in the other side as control. The rats were sacrificed 2, 4 and 8 weeks after operation. The specimen was harvested and examined histologically. For morphometric analysis, the thickness of the temporal bone of both sides was measured and compared. RESULTS: The rhBMP-2/collagen onlay implant resulted in active bone formation and the augmented bone was connected directly with the original bone, whereas the collagen alone resulted in neither bone nor cartilage production. The ossification process in the rhBMP-2/collagen occurred directly through bone formation, similar to intramembranous ossification. CONCLUSION: rhBMP-2/collagen is an effective material as a biological onlay implant.