Gorham-Stout disease(GSD) is a rare osteolytic disorder characterized by spontaneous and progressive osteolysis, along with abnormal angiogenesis and lymphangiogenesis, with no new bone formation. We present a case of a 15-year-old female admitted due to " recurrent right leg pain for 5 years, 11 months after undergoing right femoral fracture surgery". Through comprehensive integration of the patient's clinical phenotype, laboratory tests, imaging findings, pathological examinations, and molecular biological test results, GSD was considered highly likely. A multidisciplinary treatment approach was conducted, including a combination of zoledronic acid and sirolimus to inhibit osteolysis, along with rehabilitation training and orthopedic intervention, providing a personalized and comprehensive treatment strategy.

ObjectiveTo investigate microbial contamination status and distribution characteristics in laboratory animal barrier facilities, so as to provide a scientific basis for environmental quality control in barrier facilities. MethodsIn accordance with the national standard "Laboratory Animals—Environment and Housing Facilities" and the "Standard Operating Procedures" of the barrier facility, bacterial monitoring was performed on samples of air-settling bacteria, materials, and personnel gloves in the single-corridor barrier facility of the Animal Core Facility, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences (CEMCS). The monitoring data from January 2020 to December 2024 were collected, organized and statistically analyzed, and partial samples were subjected to species identification using PCR and sequencing methods. ResultsA total of 7 898 samples were collected from 2020 to 2024, including 3 175 air-settling bacteria samples, 3 353 material samples, and 1 370 glove samples. The overall compliance rate was 95.7% (7 559/7 898), among which the compliance rate of air-settling bacteria was 97.1% (3 084/3 175), that of materials was 93.2% (3 125/3 353), and that of personnel gloves was 98.5% (1 350/1 370). Over the five years, the compliance rates of all three types of monitored samples were above 90%. There were statistically significant differences in the compliance rates of air-settling bacteria and material samples among different quarters (P<0.05). Further investigation was conducted on samples collected from January to March 2024, and 190 bacterial strains were obtained through isolation and culture, including 126 strains from air-settling bacteria, 52 strains from materials, and 12 strains from personnel gloves. The strains were identified by PCR amplification and sequencing, and the 190 bacterial strains belonged to 9 genera and 20 species. Gram-positive bacteria accounted for the majority, with Staphylococcus as the dominant genus, accounting for 77.9% (148/190). ConclusionMicroorganisms carried by air, materials, and personnel gloves in barrier facilities are mainly Gram-positive bacteria. Regular monitoring of air-settling bacteria, materials, and personnel gloves in barrier facilities enables timely detection and control of potential risks during husbandry management and facility operation, which is of great significance for maintaining the sound operation of the barrier facility system and ensuring the quality of animal experiments.

OBJECTIVE: Chromosome conformation-based karyotype analysis (C-MoKa) technology was used to test a couple who had experienced multiple adverse pregnancies in order to provide them with genetic counseling and reproductive guidance. METHODS: A couple presented at the Reproductive Medicine Center of the First Hospital of Lanzhou University in 2023 was selected as the study subject. Through C-MoKa testing, copy number variation sequencing (CNV-seq), and preimplantation genetic testing for aneuploidy (PGT-A), it was found that the couple's repeatedly miscarried fetuses and abnormal embryos exhibited highly similar chromosomal structural abnormalities. Using C-MoKa, the potential genetic abnormalities in both partners were traced, and reproductive guidance was provided based on the result. This study was approved by the Medical Ethics Committee of the Hospital (Ethics No.: LDYYSZLLKH2025-09). RESULTS: CNV-seq analysis of the couple's miscarriage fetal chorionic villi showed del(18)(q21.2q23)(28.90 Mb) and dup(13)(q31.2q34)(26.26 Mb). Chromosomal karyotyping analysis of both partners showed no abnormality. From 2024 to 2025, the couple underwent three rounds of PGT-A assisted reproduction. The first embryo test showed del(13)(q31.2q34)(26.77 Mb) and dup(18)(q21.2q23)(29.08 Mb). The second embryo test showed dup(13)(q31.2q34)(26.26 Mb) and del(18)(q21.2q23)(28.90 Mb). And the third embryo test results showed complex chromosomal abnormalities. In 2025, after genetic counseling, the couple had opted C-MoKa test, which has detected no abnormality in the wife, but a balanced 46,XY,t(13;18)(q31.2;q21.2) translocation in the husband. CONCLUSION As a high-throughput sequencing method based on the three-dimensional conformation of chromatin, C-MoKa has the advantages of high resolution and high accuracy, and can accurately detect balanced translocations with similar banding patterns. It has therefore offered a powerful new tool for chromosomal analysis.
Female ; Humans ; Male ; Pregnancy ; Abortion, Habitual/genetics* ; DNA Copy Number Variations ; Karyotyping/methods* ; Preimplantation Diagnosis ; Translocation, Genetic

ObjectiveTo investigate the regulatory effects of Huanglian Jiedutang （HLJDT） on immune cell migration， blood-brain barrier protection， and cellular functional recovery in a model of ischemic stroke. MethodsA transient middle cerebral artery occlusion （tMCAO） model was established in mice to induce ischemic stroke. Cerebral blood flow and neurological function were evaluated using laser speckle imaging and neurological deficit scoring. Histopathological damage in brain tissues was assessed by hematoxylin-eosin （HE） and Nissl staining. Mice were divided into a sham group， a model group， an HLJDT group， and a Ginkgo biloba extract （GBE） group. After one week of acclimatization， intragastric administration was initiated. The sham and model groups received normal saline， the HLJDT group received HLJDT at 1.82 g·kg^-¹， and the GBE group received GBE at 0.432 g·kg^-¹. Administration was continued for 5 consecutive days， and the tMCAO model was established after the final dose on day 6. Single-cell RNA sequencing was performed on brain tissues and peripheral immune cells. UMAP and odds ratio （OR） indices were used to analyze cell distribution. Differential expression analysis was conducted to evaluate the effects of HLJDT on endothelial cells， pericytes， and macrophages， combined with CellChat and decoupler to analyze cell-cell communication and transcription factor regulation. Finally， PCR and ELISA were used to validate the mRNA and protein expression of relevant genes. ResultsCompared with the sham group， the model group showed significantly increased neurological deficit scores （P<0.01） and significantly decreased cerebral blood flow （P<0.01）， accompanied by cortical structural disorder， aggravated cytoplasmic vacuolization， and increased numbers of Nissl bodies. Compared with the model group， both the HLJDT and GBE groups exhibited significantly reduced neurological deficit scores （P<0.01） and markedly improved cerebral blood flow （P<0.01）， along with amelioration of cortical structural disorder， alleviated cytoplasmic vacuolization， and reduced numbers of Nissl bodies. Single-cell analysis showed that HLJDT protected endothelial cells and pericytes by preventing their reduction， restored the expression of functional genes in these cells （e.g.， PECAM1 and NOS3）， and downregulated the expression of chemokines and adhesion-related factors （e.g.， CCL2 and CXCL2）. In macrophages， HLJDT reduced their recruitment to the central nervous system and downregulated the expression of chemokine receptors and inflammatory factors （e.g.， IL-6， CCR2， and CXCR2）. Cell-cell communication analysis further indicated that HLJDT， through the above mechanisms， alleviated damage to pericytes and endothelial cells， reduced their recruitment of macrophages， and decreased ligand-receptor interactions in chemokine signaling pathways （including CCL， CXCL， and CSF3） between pericytes/endothelial cells and macrophages， thereby preventing secondary injury. Compared with the sham group， the model group showed significantly upregulated mRNA expression levels of IL-1β， IL-6， TNF-α， CCL2， CXCL2， and CSF3 （P<0.01）， while mRNA expression levels of endothelial- and pericyte function-related genes （RGS5， PECAM1， VEGFB， and NOS3） were significantly downregulated （P<0.01）. In contrast， compared with the model group， the HLJDT and GBE groups exhibited significantly decreased mRNA expression levels of IL-1β， IL-6， TNF-α， CCL2， CXCL2， and CSF3 （P<0.01）， and significantly increased expression of RGS5， PECAM1， VEGFB， and NOS3 （P<0.01）. At the protein level， compared with the sham group， the model group showed significantly increased expression of IL-1β， IL-6， and TNF-α （P<0.01）， whereas these protein levels were significantly reduced in the HLJDT and GBE groups compared with the model group （P<0.01）. ConclusionHLJDT reduces neuronal damage in ischemic stroke by protecting endothelial cells and pericytes， while inhibiting their interaction with macrophages， thereby mitigating secondary injury in the central nervous system.

ObjectiveTo investigate the effects of prostaglandin E₂ （PGE₂） microinjection into the median preoptic nucleus （MnPO） on core body temperature in female mice， and to clarify its underlying mechanism. MethodsMicroinjection cannula were implanted into the MnPO of female mice using stereotaxic surgery.Subsequently， a multi-channel temperature acquisition system was used to simultaneously monitor rectal and brown adipose tissue （BAT） temperatures before and after intra-MnPO injections of different reagents.To investigate the thermoregulatory effects of the microinjection of PGE₂ into the MnPO， 12 female C57BL/6 mice were randomly divided into a saline group （n=6） and a PGE₂ group （n=6）， which were injected with 0.1 μL saline and PGE₂ （2.8 mmol/L）， respectively.To determine whether E-series prostaglandin receptor （EP）1， EP3， and EP4 receptors mediate the thermoregulatory effects of PGE₂， 15 female C57BL/6 mice were randomly divided into 3 groups （n=5 per group）.Mice in each group first received an injection of 0.1 μL PGE2 （2.8 mmol/L） into the MnPO. After their body temperature returned to baseline levels， they were subsequently injected with a mixture of either EP1， EP3 or EP4 antagonist （ant） （20 mmol/L） + PGE2 （2.8 mmol/L）. ResultsCompared with baseline level， the rectal temperature （P<0.01） and BAT temperature （P<0.001） of female mice both increased significantly after microinjection of PGE₂ into the MnPO.Compared with the saline group， the increases in rectal temperature （P<0.001） and BAT temperature （P<0.000 1） were significantly greater in the PGE₂ group of mice.Furthermore， following the injection of PGE₂ into MnPO， the increase in BAT temperature was found to be significantly greater than that in rectal temperature in mice （P<0.001）.Compared to the administration of PGE₂ alone， co-injection of an EP3 ant + PGE₂ into the MnPO of mice resulted in a significantly smaller increase in both rectal temperature （P<0.001） and BAT temperature （P<0.001）.In contrast， the increases in rectal and BAT temperatures following MnPO injection of either EP1 ant + PGE₂ or EP4 ant + PGE₂ were not statistically significant （P>0.05）. ConclusionInjection of PGE₂ into the MnPO elevates BAT and core body temperature in female mice via the EP3 receptor.

ObjectiveTo evaluate the therapeutic effects of Huanglian Jiedutang on cerebral infarction injury in a mouse model of middle cerebral artery occlusion （MCAO） and to explore its mechanism of action on oligodendrocytes， particularly its potential in myelin repair. MethodsMultiple experimental approaches were used to evaluate cerebral ischemic injury and the effects of drug intervention. Laser speckle imaging was used to detect changes in cerebral blood flow， 2，3，5-Triphenyltetrazolium chloride （TTC） staining was used to measure infarct volume， and neurological function was scored according to the Zea-Longa criteria. Brain tissues were routinely embedded in paraffin and subjected to HE and Nissl staining to observe tissue structure and neuronal damage. Animals were divided into a sham group （n=24）， model group （n=24）， Huanglian Jiedutang group （n=24）， and Ginkgo biloba extract （GBE） group （n=18）. After 1 week of acclimatization， intragastric administration was initiated. The sham and model groups received normal saline， the Huanglian Jiedutang group was administered 1.82 g·kg^-1， and the GBE group was administered 0.432 g·kg^-1 after preparation as a 2.16 g·L^-1 solution. All groups were treated for 5 consecutive days at a dose of 0.2 mL·（10 g）^-¹·d^-¹. The MCAO model was established after the final administration on day 6. Single-cell RNA sequencing was used to analyze brain tissue cellular composition and changes in oligodendrocyte subpopulations. Distinct subpopulations were identified by Uniform manifold approximation and projection （UMAP） dimensionality reduction and unsupervised clustering， and marker gene expression was analyzed. Pathway enrichment and causal inference were further performed using IPA. Finally， real-time quantitative PCR was used to verify mRNA expression changes of myelin-related genes. ResultsCompared with the sham group， the model group showed significantly increased neurological function scores （P<0.01）， significantly impaired blood flow （P<0.01）， significantly enlarged cerebral infarct area （P<0.01）， and pathological changes including disordered cortical structural arrangement， aggravated cytoplasmic vacuolization， and increased Nissl bodies. Compared with the model group， the Huanglian Jiedutang and GBE groups showed significantly decreased neurological function scores （P<0.01）， markedly restored blood flow levels （P<0.01）， significantly reduced cerebral infarct area （P<0.01）， and improvement in cortical structural disorder， alleviation of cytoplasmic vacuolization， and a reduction in Nissl bodies. Single-cell data showed that a myelin-associated oligodendrocyte （Mye-OL） subpopulation existed among oligodendrocytes， which was closely related to myelin generation. Compared with the sham group， the number of Mye-OL cells decreased in the model group. Compared with the model group， the number of Mye-OL cells increased in the Huanglian Jiedutang group. This subpopulation promoted the expression of myelin-related genes， including MOG， MBP， and MAG， via transcription factors such as OLIG1， OLIG2， NKX2-2， and SOX10， thereby regulating myelin generation， restoring cognition， and exerting therapeutic effects on acute cerebral infarction. Compared with the sham group， the mRNA expression levels of OLIG1， OLIG2， NKX2-2， and SOX10 were significantly downregulated in the model group （P<0.01）， and the mRNA expression levels of myelin-related genes， including MOG， MBP， and MAG， were also significantly downregulated （P<0.01）. In contrast， compared with the model group， the Huanglian Jiedutang and GBE groups showed significantly upregulated mRNA expression levels of OLIG1， OLIG2， NKX2-2， and SOX10 （P<0.01）， and significantly upregulated mRNA expression levels of myelin-related genes， including MOG， MBP， and MAG （P<0.01）. ConclusionHuanglian Jiedutang exerts therapeutic effects on acute cerebral infarction by regulating the OLIG1/2-NKX2-2-SOX10 signaling pathway to promote myelin generation by Mye-OL cells.

ObjectiveTo investigate the characteristics of metabolic reprogramming during cerebral ischemia-reperfusion injury using single-cell transcriptome sequencing， analyze the heterogeneity of microglial populations， and evaluate the interventional effects of Huanglian Jiedutang on metabolic abnormalities and neuroinflammation. MethodsA transient middle cerebral artery occlusion （tMCAO） model was used to establish ischemic stroke in mice. Local cerebral blood flow changes were monitored by laser speckle imaging. Neurological impairment was evaluated using the Zea-Longa score， and histopathological damage in brain tissue was observed by HE and Nissl staining. Animals were divided into a sham group， model group， Huanglian Jiedutang group， and Ginkgo biloba extract （GBE） group. After 1 week of acclimatization， intragastric administration was initiated. The sham and model groups received normal saline， the Huanglian Jiedutang group was administered 1.82 g·kg^-1， and the GBE group was administered 0.432 g·kg^-1 after preparation as a 2.16 mg/mL solution. All groups were treated for 5 consecutive days （0.2 mL/10 g/day）， and the tMCAO model was established on day 6 after the final administration. At the molecular level， single-cell RNA sequencing was performed on ischemic hemisphere tissue. Non-negative matrix factorization （NMF） was used to cluster microglial subpopulations， combined with differential expression analysis， metabolic reprogramming assessment， and inflammatory factor correlation analysis to elucidate their functional characteristics in ischemia-reperfusion injury. Transcription factor enrichment analysis was further conducted to identify key regulatory nodes. Finally， PCR was used to detect mRNA expression changes of relevant genes to validate the single-cell sequencing results. ResultsCompared with the sham group， the model group showed increased neurological function scores （P<0.01）， decreased blood flow levels （P<0.01）， disordered cortical structure， increased cytoplasmic vacuolization， and increased Nissl bodies. Compared with the model group， the Huanglian Jiedutang and GBE groups showed decreased neurological function scores （P<0.01）， increased blood flow levels （P<0.01）， alleviated cortical structural disorder， reduced cytoplasmic vacuolization， and decreased Nissl bodies. Single-cell analysis showed that microglia could be divided into five subpopulations. Among them， clusters 3 and 5 exhibited significant pro-inflammatory phenotypes， with marked activation of hypoxia and NF-κB signaling pathways， and were identified as pro-inflammatory subpopulations. Clusters 1 and 2 were enriched in Wnt/β-catenin and transforming growth factor（TGF）-β signaling pathways and exhibited prominent anti-inflammatory and reparative characteristics. Meanwhile， glycolysis-related genes， such as HK2， PFKP， and LDHA， were significantly upregulated in the pro-inflammatory subpopulations. Correlation analysis showed that the expression levels of inflammatory molecules were positively correlated with glycolysis-related gene expression levels， whereas the expression levels of reparative and anti-inflammatory molecules were negatively correlated with glycolysis-related gene expression levels， indicating that microglia rely on the glycolytic pathway for energy acquisition under ischemic conditions. Further single-cell transcriptome analysis revealed that Huanglian Jiedutang effectively downregulated key genes driving metabolic reprogramming （such as HK2， PFKP， and LDHA）， significantly reduced the proportion of microglial subpopulations accompanied by glycolytic reprogramming， and inhibited their transformation toward a damage phenotype， thereby reducing inflammatory injury. Meanwhile， compared with the sham group， the mRNA expression levels of interleukin （IL）-1β， IL-6， tumor necrosis factor（TNF）-α， CCL2， CXCL2， and CSF3 were significantly upregulated （P<0.01） in the model group， whereas the mRNA expression levels of endothelial- and pericyte-related functional genes， including RGS5， PECAM1， VEGFB， and NOS3， were significantly downregulated （P<0.01）. In contrast， compared with the model group， the Huanglian Jiedutang and GBE groups showed significantly decreased mRNA expression levels of IL-1β， IL-6， TNF-α， CCL2， CXCL2， and CSF3 （P<0.01）， and significantly increased mRNA expression levels of endothelial- and pericyte-related functional genes， including RGS5， PECAM1， VEGFB， and NOS3 （P<0.01）. ConclusionHuanglian Jiedutang exerts neuroprotective effects by regulating the metabolic reprogramming state of microglia and modulating their inflammatory levels， thereby inhibiting neuroinflammatory injury.

Objective: To compare the Reveos automated blood processing system with the current method, and to evaluate the feasibility and validity of using the Reveos system for blood component preparation. Methods: Forty units of 400 mL whole blood samples were divided into two groups: 2C group (for two-component preparation) and 3C group (for three-component preparation). Each group was further divided into a Reveos subgroup and a control subgroup. Blood components were prepared using the Reveos system and the current centrifugation method respectively. The 2C group yielded suspended red blood cells and plasma, while the 3C group yielded suspended red blood cells, plasma, and platelets. Key quality indicators for red blood cells, plasma, and platelets were measured before and after separation. Inter-group differences were analyzed using SPSS 25.0. Results: The trend of changes in the main performance indicators of red blood cells, plasma, and platelets before and after separation was generally consistent between the Reveos group and the control group, with no significant differences for most performance indicators. The Reveos system outperformed the current method in several aspects: in the 3C group, the hematocrit (Hct) was significantly higher in the Reveos group than in the control group [(62.82%±1.64%) vs (53.62%±3.04)%, P<0.001]; the white blood cell count in red blood cell suspensions was significantly lower than that in the control group [(3.37±1.42)×10 /L vs (8.42±2.30)×10 /L, P<0.001]; plasma yield was 27.5% higher than that in the control group [(183.90±17.37) mL vs (144.28±20.53) mL, P<0.001]; and the platelet activation rate was significantly lower than that in the control group [(21.97±14.25)% vs (34.73±11.92)%, P=0.044]. Conclusion: The Reveos system demonstrates good consistency with the current method in preparing blood components, and outperforms the current method in terms of leukocyte reduction and red blood cell concentration.

The pathogenesis of metabolic dysfunction-associated steatotic liver disease （MASLD） is fundamentally rooted in spleen deficiency and is closely associated with phlegm turbidity， damp-heat and blood stasis. Clinically， liver constraint with spleen deficiency and internal retention of damp turbidity represent the predominant traditional Chinese medicine （TCM） syndrome patterns. Researches have indicated intrinsic connections between the syndrome patterns and biological indicators such as gut microbiota and metabolic profiles. Regarding treatment， classical famous formulas， modern empirical formulas， and newly developed TCM drugs show positive effects in regulating glucose and lipid metabolism， improving insulin resistance， and alleviating metabolic inflammation， exhibiting multi-target mechanisms of action； acupuncture and other external therapies also provide adjunctive value. Nevertheless， current researches still have limitations such as the lack of high-quality clinical evidence and insufficient systematic elucidation of the uncerlying mechanisms. Future efforts should focus on conducting high-quality TCM clinical trials with hard endpoint outcomes such as hepatic histology outcomes， and utilizing modern technologies like multi-omics to elucidate TCM's mechanisms of action， thereby advancing the position of TCM as a first-line therapeutic strategy for MASLD.

ObjectiveTo investigate the gene expression sequence and molecular mechanisms in the local microenvironment during the subacute to chronic phases (1-28 days) in mouse models of spinal cord compression injury and hemisection spinal cord injury, thereby revealing the molecular characteristics of spinal cord repair and providing a theoretical basis for selecting therapeutic targets for spinal cord injury. MethodsThirty-six 8-9-week-old SPF-grade ICR mice were randomly divided into three groups (n=12 per group): sham-operated control (CTR) group, hemisection spinal cord injury (HSCI) group, and spinal cord compression injury (SCC) group. Mice in the CTR group underwent the same surgical preparation and anesthesia, followed by a dorsal midline incision at the T₉-T₁₀ segment. After layer-by-layer dissection and removal of the corresponding lamina, the spinal cord dura mater was fully exposed and kept intact. The cord was exposed to air for 10 minutes (matching the duration of the compression injury group), during which any instrument contact with the cord was avoided. The incision was then irrigated and sutured. The HSCI group underwent a 70% transection of the T₉ spinal cord segment using micro-instruments to establish a hemisection spinal cord injury model. The SCC group underwent sustained compression of the T₁₀ spinal cord segment for 10 minutes using a self-made compressor (a 30 g solid small iron bar) to establish a spinal cord compression injury model. Motor function recovery was assessed using the modified Basso-Beattie-Bresnahan (BBB) score on postoperative days 1, 3, 7, 14, 21, and 28. On days 7 and 14 post-operation, mice were anesthetized, and the injured spinal cord segments were harvested. The evolution of specific molecular networks in the spinal cord injury mouse models was analyzed via RNA sequencing (RNA-Seq) and enrichment analysis, and the expression of key genes was verified using real time fluorogenic quantitative PCR. ResultsBBB scores indicated that motor function recovery in the SCC group was significantly better than that in the HSCI group, with BBB scores showing a continuously increasing trend and remaining higher than those in the HSCI group over the 4-week period (P <0.001). Gene ontology （GO)and Kyoto Encyclopedia of Genes and Genomes （KEGG） enrichment analyses based on RNA-Seq differentially expressed genes revealed that, compared to the CTR group, genes related to the extracellular matrix were significantly up-regulated (P<0.05), while genes related to axon guidance were significantly down-regulated (P <0.05) in the SCC group on day 7 post-operation. On day 21, genes involved in immune regulation and the retinol signaling pathway were significantly activated in the SCC group (P<0.05). In contrast, in the HSCI group, genes associated with inflammation and immune response were significantly up-regulated (P<0.001), while genes related to neuronal differentiation and synapse formation were significantly down-regulated (P <0.001) on day 7. On day 21, genes related to cell-matrix junctions and N-methyl-D-aspartate receptors were significantly up-regulated (P<0.001) in the HSCI group. Furthermore, compared to the SCC group, the HSCI group exhibited different pathway enrichment characteristics in GO and KEGG analyses on days 7 and 21 post-injury. On day 7, genes involved in the NOD-like receptor signaling pathway and the complement and coagulation cascades were significantly up-regulated in the HSCI group (P<0.001). On day 21, genes related to the extracellular matrix-receptor interaction and the neuroactive ligand-receptor interaction pathways were significantly activated (P<0.001). Finally, real time fluorogenic quantitative PCR validation results were highly consistent with the RNA-Seq results, further confirming the differential expression trends of key genes between the SCC and HSCI groups. ConclusionThe SCC and HSCI injury models may drive distinct repair pathways: the preservation of some axons in the SCC model predisposes it toward tissue repair, whereas the HSCI model requires the coordination of more complex molecular networks to achieve a new equilibrium. This finding further deepens the understanding of the heterogeneous regulatory mechanisms underlying spinal cord injury.