Prolonged efficacy of cefazolin in intraosseous regional prophylaxis for total knee arthroplasty: a rabbit model study.

BACKGROUND: A novel approach known as intraosseous regional administration (IORA) has emerged as a technique for delivering prophylactic antibiotics, and it results in higher tissue concentrations around the knee. It is hypothesized that IORA of cefazolin for antibiotic prophylaxis during total knee arthroplasty will result in sustained effective levels for a longer duration. The aim of the current study was to investigate temporal changes in peri-knee cefazolin blood concentrations after IORA of cefazolin. METHODS: Twelve rabbits were randomly divided into two groups, with six rabbits in each group. In control group a single intravenous bolus injection of cefazolin (10 mL, 100 mg) was administered into the marginal ear vein. In experimental groupexperimental group the same dose of cefazolin was injected into the left tibial marrow cavity after tourniquet inflation at the base of the left thigh. Blood samples were collected periodically at different timepoints, and cefazolin concentrations were determined. RESULTS: The intraosseous treatment resulted in significant differences in plasma cefazolin concentrations at all timepoints. Experimental group exhibited higher plasma cefazolin concentrations than control group. CONCLUSIONS: Cefazolin in intraosseous regional prophylaxis exhibits effectiveness in intraoperative antibiotic prophylaxis by maintaining concentrations above the minimum inhibitory concentration for extended durations, rather than relying solely on high concentrations.

s

Recently, the bilayer perovskite nickelate La_{3}Ni_{2}O_{7} has been reported to show evidence of high-temperature superconductivity (SC) under a moderate pressure of about 14 GPa. To investigate the superconducting mechanism, pairing symmetry, and the role of apical-oxygen deficiencies in this material, we perform a random-phase approximation based study on a bilayer model consisting of the d_{x^{2}-y^{2}} and d_{3z^{2}-r^{2}} orbitals of Ni atoms in both the pristine crystal and the crystal with apical-oxygen deficiencies. Our analysis reveals an s^{±}-wave pairing symmetry driven by spin fluctuations. The crucial role of pressure lies in that it induces the emergence of the γ pocket, which is involved in the strongest Fermi-surface nesting. We further found the emergence of local moments in the vicinity of apical-oxygen deficiencies, which significantly suppresses the T_{c}. Therefore, it is possible to significantly enhance the T_{c} by eliminating oxygen deficiencies during the synthesis of the samples.

Correlation between characteristics of intracranial atherosclerotic plaques and ischemic stroke in high-resolution vascular wall MRI.

BACKGROUND: Intracranial atherosclerotic stenosis is a major cause of ischemic stroke, accounting for 30% of ischemic strokes in Asian populations. PURPOSE: To investigate the relationship between the degree of arterial stenosis and enhancement grade of intracranial atherosclerotic disease (ICAD), the plaque characteristics in different remodeling patterns, and its potential impact. MATERIAL AND METHODS: A total of 210 patients diagnosed with ICAD were enrolled in this retrospective study. Patients were divided into the middle cerebral artery (MCA) group (101 cases), posterior cerebral artery (PCA) group (14 cases), basilar artery (BA) group (71 cases), and intracranial segment of vertebral artery (VA) group (90 cases) according to the difference of diseased vessels. Data on presence or absence of ischemic infarction, intracranial vascular position of lesions, plaque characteristics, ICAD enhancement grade, remodeling index, and degree of arterial stenosis were collected for analysis. RESULTS: The incidence of ischemic infarction in enhancement grade 2 was significantly higher than that in enhancement grade 1 in MCA group (P = 0.019). Enhancement grade 2 of ICAD was an independent risk factor for the development of ischemic infarction (odds ratio = 4.60; 95% confidence interval: 1.91-11.03; P = 0.001). There was no significant statistical difference in infarct rate between different remodeling modalities (P>0.05). CONCLUSION: Enhancement grade of ICAD is significantly associated with the degree of stenosis and the occurrence of ischemic stroke, which varies in different intracranial vessels. The pattern of vascular remodeling varies among different intracranial vessels, and the pattern of vascular remodeling has a significant impact on plaque characteristics.

A Study on the Persistent Trigeminal Artery and Its Classification Based on Magnetic Resonance Angiograph Images.

BACKGROUND: The persistent trigeminal artery (PTA) is the most common remnant of primitive circulation, communicating the developing carotid and vertebrobasilar junction. PURPOSE: This study aimed to evaluate the implementation of magnetic resonance angiography for the detection of PTA and to reclassify the variations based on Weon typing. Moreover, the correlation of various Weon types with the posterior cerebral artery (PCA), Willis ring, basilar artery (BA) dysplasia, and the relationship between PTA and arteriosclerosis were analyzed. METHODS: From November 2017 to October 2019, a total of 48,184 patients underwent magnetic resonance angiography examination in our hospital, and 79 patients were diagnosed with PTA. Of these, 70 patients with complete radiological and clinical information were included in this study. RESULTS: Among the 70 patients with complete data, 27 were classified as Weon type I (38.6%), 7 as type II (10%), 14 as type III (20%), 8 as type IV (11.4%), and 3 as type V (4.3%: type Va, 1 case; type Vb, 2 cases). The remaining 11 cases were PCA with mixed blood supply, so the new type VI was divided into 3 subtypes: type VIa, type VIb, and type VIc, and each subtype of type V was further refined into 4 subtypes. There were 32 cases of PTA with BA dysplasia, including 14 with type I (51.9%), 5 with type II (71.4%), 2 with type III (14.3%), 5 with type IV (62.5%), and 6 with type VI (54.5%). Cerebral infarction was found in 55 cases (78.6%) of PTA, among which 11 had a cerebral infarction in the posterior circulation blood supply area. There were 46 cases (65.7%) accompanied by intracranial arteriosclerosis, and in 6 cases, arteriosclerosis mainly occurred in the posterior circulation. CONCLUSIONS: We redefined the classification of PTA based on Weon typing for a better understanding of clinical symptoms and surgical risks. Moreover, PTA was correlated with the fetal origin of PCA, BA dysplasia, and posterior circulation arteriosclerosis. These factors may increase the incidence of cerebral infarction in the posterior circulation blood supply area.

HR-MRI findings of intracranial artery stenosis and distribution of atherosclerotic plaques caused by different etiologies.

OBJECTIVE: To investigate the etiology of intracranial artery stenosis and the distribution characteristics of intracranial artery atherosclerotic stenosis using high-resolution magnetic resonance imaging (HR-MRI). METHODS: A total of 262 patients with intracranial artery stenosis that underwent HR-MRI from November 2019 to December 2020 were retrospectively enrolled. The etiology of intracranial anterior and posterior circulation artery stenosis was analyzed, and the relationship between the location of plaques and the distribution characteristics of plaques and the occurrence of ischemic stroke was summarized. RESULTS: A total of 276 plaques were identified with HR-MRI. There were 101 cases (36.59%) in the middle cerebral artery (MCA), 14 cases (5.07%) in the posterior cerebral artery (PCA), 90 cases (32.62%) in vertebral artery (VA), and 71 cases (25.72%) in the basilar artery (BA). The infarct rate of ventral and superior wall MCA plaques was higher than that of dorsal and inferior wall (63.33% vs 31.25% P = 0.021) (100.00% vs 50% P = 0.022). MCA with plaques throughout the course had the greatest degree of stenosis (P < 0.001). Sphenoid segment (M1) of MCA was most susceptible (85 cases, 84.16%), MCA plaques were most common in the proximal M1 segment (35 cases, 34.65%), and most BA plaques were found in the distal segment (28 cases, 39.44%). PCA plaques were most frequently involved in traffic anterior segment (P1) (7 cases, 50.00%). CONCLUSION: HR-MRI could provide accurate imaging reference for clinical evaluation of intracranial arterial stenosis and formulation of treatment plans. The intracranial arterial plates mostly appeared in the middle cerebral artery and vertebral artery. Middle cerebral arteries with atherosclerotic plaques are more likely to narrow.

Kohn-Luttinger Mechanism Driven Exotic Topological Superconductivity on the Penrose Lattice.

The Kohn-Luttinger mechanism for unconventional superconductivity (SC) driven by weak repulsive electron-electron interactions on a periodic lattice is generalized to the quasicrystal (QC) via a real-space perturbative approach. The repulsive Hubbard model on the Penrose lattice is studied as an example, on which a classification of the pairing symmetries is performed and a pairing phase diagram is obtained. Two remarkable properties of these pairing states are revealed, due to the combination of the presence of the point-group symmetry and the lack of translation symmetry on this lattice. First, the spin and spacial angular momenta of a Cooper pair is decorrelated: for each pairing symmetry, both spin-singlet and spin-triplet pairings are possible even in the weak-pairing limit. Second, the pairing states belonging to the 2D irreducible representations of the D_{5} point group can be time-reversal-symmetry-breaking topological SCs carrying spontaneous bulk super current and spontaneous vortices. These two remarkable properties are general for the SCs on all QCs, and are rare on periodic lattices. Our work starts the new area of unconventional SCs driven by repulsive interactions on the QC.

The Modulation of Trehalose Metabolism by 20-Hydroxyecdysone in Antheraea pernyi (Lepidoptera: Saturniidae) During its Diapause Termination and Post-Termination Period.

Trehalose plays a crucial role in the diapause process of many insects, serving as an energy source and a stress protectant. Trehalose accumulation has been reported in diapause pupae of Antheraea pernyi; however, trehalose metabolic regulatory mechanisms associated with diapause termination remain unclear. Here, we showed that the enhanced trehalose catabolism was associated with an increase in endogenous 20-hydroxyecdysone (20E) in hemolymph of A. pernyi pupae during their diapause termination and posttermination period. Injection of 20E increased the mRNA level of trehalase 1A (ApTre-1A) and trehalase 2 (ApTre-2) of A. pernyi diapause pupae in a dose-dependent manner but did not affect the mRNA level of trehalase 1B (ApTre-1B). Meanwhile, exogenous 20E increased the enzyme activities of soluble and membrane-bound trehalase, leading to a decline in hemolymph trehalose. Conversely, the expression of ApTre-1A and ApTre-2 were down-regulated after the ecdysone receptor gene (ApEcRB1) was silenced by RNA interference or by injection of an ecdysone receptor antagonist cucurbitacin B (CucB), which inhibits the 20E pathway. Moreover, CucB treatment delayed adult emergence, which suggests that ApEcRB1 might be involved in regulating pupal-adult development of A. pernyi by mediating ApTre-1A and ApTre-2 expressions. This study provides an overview of the changes in the expression and activity of different trehalase enzymes in A. pernyi in response to 20E, confirming the important role of 20E in controlling trehalose catabolism during A. pernyi diapause termination and posttermination period.

Value of flaccid penile ultrasound in screening for arteriogenic impotence: a preliminary prospective study.

BACKGROUND: This prospective study is to evaluate the potential value of sonographic measurements in the flaccid penis for the screening of arteriogenic impotence. METHODS: A consecutive series of 260 Chinese males consulting for sexual dysfunction and 54 controls underwent sonographic examination. The sonographic parameters were correlated with the clinical gold standards, including the international index of erectile function (IIEF) and penile erectile hardness grading scale (EHGS). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the receiver operating characteristic curve (AUROC) of flaccid peak systolic velocity (PSV) in predicting patients with normal function were analyzed. RESULTS: The mean cavernous PSV of both sides in the patients with sexual dysfunction ranged from 7.76 to 11.12 cm/sec with a stepwise increase in IIEF and EHGS grading scale (P < .05). The cutoff value of flaccid PSV for the differential diagnosis of grade 4 of IIEF-5 or EHGS was 8.20-8.90 cm/sec, with an AUROC of 0.657-0.724, specificity of 82.96-86.84% and PPV of 95.20-96.60%, respectively. CONCLUSIONS: This simple flaccid PSV measurement is a specific tool for screening arteriogenic impotence.

Causal effect of air pollution on the risk of cardiovascular and metabolic diseases and potential mediation by gut microbiota.

BACKGROUND: Epidemiological studies have explored the relationship between air pollution and cardiovascular and metabolic diseases (CVMDs). Accumulating evidence has indicated that gut microbiota deeply affects the risk of CVMDs. However, the findings are controversial and the causality remains uncertain. To evaluate whether there is the causal association of four air pollutants with 19 CVMDs and the potential effect of gut microbiota on these relationships. METHODS: Genetic instruments for particulate matter (PM) with aerodynamic diameter < 2.5 µm (PM2.5), <10 µm (PM10), PM2.5 absorbance, nitrogen oxides (NOx) and 211 gut microbiomes were screened. Univariable Mendelian randomization (UVMR) was used to estimate the causal effect of air pollutants on CVMDs in multiple MR methods. Additionally, to account for the phenotypic correlation among pollutant, the adjusted model was constructed using multivariable Mendelian randomization (MVMR) analysis to strength the reliability of the predicted associations. Finally, gut microbiome was assessed for the mediated effect on the associations of identified pollutants with CVMDs. RESULTS: Causal relationships between NOx and angina, heart failure and hypercholesterolemia were observed in UVMR. After adjustment for air pollutants in MVMR models, the genetic correlations between PM2.5 and hypertension, type 2 diabetes mellitus (T2DM) and obesity remained significant and robust. In addition, genus-ruminococcaceae-UCG003 mediated 7.8 % of PM2.5-effect on T2DM. CONCLUSIONS: This study firstly provided the genetic evidence linking air pollution to CVMDs and gut microbiota may mediate the association of PM2.5 with T2DM. Our findings highlight the significance of air quality in CVMDs risks and suggest the potential of modulating intestinal microbiota as novel therapeutic targets between air pollution and CVMDs.

Charge-4e superconductivity and chiral metal in 45°-twisted bilayer cuprates and related bilayers.

The material realization of charge-4e/6e superconductivity (SC) is a big challenge. Here, we propose to realize charge-4e SC in maximally-twisted homobilayers, such as 45∘-twisted bilayer cuprates and 30∘-twisted bilayer graphene, referred to as twist-bilayer quasicrystals (TB-QC). When each monolayer hosts a pairing state with the largest pairing angular momentum, previous studies have found that the second-order interlayer Josephson coupling would drive chiral topological SC (TSC) in the TB-QC. Here we propose that, above the Tc of the chiral TSC, either charge-4e SC or chiral metal can arise as vestigial phases, depending on the ordering of the total- and relative-pairing-phase fields of the two layers. Based on a thorough symmetry analysis to get the low-energy effective Hamiltonian, we conduct a combined renormalization-group and Monte-Carlo study and obtain the phase diagram, which includes the charge-4e SC and chiral metal phases.

Arthritis of the hip caused by arteriovenous malformations: A case report.

BACKGROUND Arthritis of the hip caused by arteriovenous malformations (AVMs) has been rarely reported. Therefore, total hip replacement (THR) in patients with AVM-induced arthritis of the hip is challenging. CASE SUMMARY We report a 44-year-old woman with aggravated right hip pain during the past decade. The patient presented with severe pain and a functional disorder of the right hip. X-ray examination revealed severely narrowed right hip joint space and abnormal trabecular bone loss in the femoral neck and trochanter area. Doppler ultrasound, magnetic resonance imaging and computed tomography angiography revealed AVMs surrounding the right hip, along with erosion. To ensure the safety of THR, we performed vascular embolization and temporary balloon occlusion of the iliac artery three times during the operation. However, serious hemorrhage occurred, which was rescued by the multimodality blood conservation strategy. THR was successfully performed, and the patient was discharged 8 d later for rehabilitation. Postoperative pathological examination showed osteonecrosis of the femoral head with malformed thick-walled vessels and focal granulomatous inflammation of the surrounding soft tissues. The Harris Hip Scale score increased from 31 to 82 at 3 mo of follow-up. The patient was followed up for 1 year, and all her clinical symptoms were significantly alleviated. CONCLUSION Arthritis of the hip caused by AVMs is rare in clinical practice. The activity and function of the involved hip joint can be effectively treated with THR after comprehensive imaging and multidisciplinary consultation.

Revision Total Hip Arthroplasty with Severe Acetabular Defect: A Preliminary Exploration and Attempt of Robotic-Assisted Technology.

BACKGROUND: Robotic-assisted technology may be useful in hip revision cases with acetabular defects. However, data on the use of robotic-assisted technology for such complex diseases is lacking. CASE PRESENTATION: This case study described the adoption of MAKO robotic-assisted treatment of revision total hip arthroplasty (THA) combined with severe acetabular defect (Paprosky type IIIB). Robotic-assisted technology accurately achieved preoperative planning; the acetabular component and augment were placed in the original position and angle as planned. Robotic-assisted acetabular reaming was successful in a single pass, preserving the remaining acetabular bone mass very well with no procedure-related complications. The Harris Hip Score (HHS) at 6 months postoperatively was 84 and the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index was 24. CONCLUSION: Robotic-assisted technology can help in the accurate reconstruction of acetabular defect in complex hip revision surgery.

Surgical treatment of delayed cervical infection and incomplete quadriplegia with fish-bone ingestion: A case report.

BACKGROUND: The most commonly ingested foreign body in Asians is fish bone. The vast majority of patients have obvious symptoms and can be timely diagnosed and treated. Cases of pyogenic cervical spondylitis and diskitis with retropharyngeal and epidural abscess resulting in incomplete quadriplegia due to foreign body ingestion have been rarely reported. The absence of pharyngeal or esophageal discomfort and negative computed tomography (CT) findings of fish bone have not been reported. We report the case of an elderly female patient with delayed cervical infection and incomplete quadriplegia who had a history of fish bone ingestion. CASE SUMMARY: A 73-year-old woman presented with right neck pain and weakness of four limbs for a week, and had a history of fish bone ingestion and negative findings on laryngoscopic examination one month previously. She did not complain of any pharyngeal or esophageal discomfort. Cervical magnetic resonance imaging showed C4/C5 spondylitis and diskitis along with retropharyngeal and ventral epidural abscesses. No sign of fish bone was detected on lateral cervical radiography and CT scans. The muscle strength of the patient's right lower limb receded to grade 1 and other limbs to grade 2 suddenly on the 10th day of hospitalization. Emergency surgery was performed to drain the abscess and decompress the spinal cord by removing the anterior inflammatory necrotic tissue. Simultaneously, flexible esophagogastroduodenoscopy was carried out and a hole in the posterior pharyngeal wall was found. The motor weakness of the right lower limb improved to grade 3 and the other limbs to grade 4 within 2 d postoperatively. CONCLUSION: This rare case highlights the awareness of the posterior pharyngeal or esophageal wall perforation in patients with cervical pyogenic spondylitis along with a history of fish bone ingestion, even though local discomfort symptoms are absent and the radiological examinations are negative.

Insulin-Like Peptide and FoxO Mediate the Trehalose Catabolism Enhancement during the Diapause Termination Period in the Chinese Oak Silkworm (Antheraea pernyi).

In insects, trehalose accumulation is associated with the insulin/insulin-like growth factor signalling (IIS) pathway. However, whether insulin-like peptide is involved in the regulation of the trehalose metabolism during diapause termination remains largely unknown. This study assessed whether insulin-like peptide (ApILP) enhances the trehalose catabolism in the pupae of Antheraeapernyi during their diapause termination process. Injection of 10 µg of bovine insulin triggered diapause termination and synchronous adult eclosion in diapausing pupae. Moreover, treatment with bovine insulin increased the expression of trehalase 1A (ApTre-1A) and trehalase 2 (ApTre-2), as well as the activity of soluble and membrane-bound trehalase, resulting in a decline in trehalose levels in the haemolymph. Silencing ApILP via RNA interference significantly suppressed the expression of ApTre-1A and ApTre-2, thus leading to an increase in the trehalose concentration during diapause termination. However, neither injection with bovine insulin nor ApILP knockdown directly affected trehalase 1B (ApTre-1B) expression. Moreover, overexpression of the transcription factor forkhead box O (ApFoxO) induced an increase in trehalose levels during diapause termination; however, depletion of ApFoxO accelerated the breakdown of trehalose in diapausing pupae by increasing the expression of ApTre-1A and ApTre-2. The results of this study help to understand the contributions of ApILP and ApFoxO to the trehalose metabolism during diapause termination.

Sesquiterpenoids from Inula lineariifolia inhibit nitric oxide production.

Fourteen sesquiterpenoids including six new analogues (1-6) were isolated from the aerial parts of Inula lineariifolia.. The structures of the new sesquiterpenoids were determined by spectroscopic data analysis, and the structures of 1 and 6 were confirmed by single-crystal X-ray diffraction data and the modified Mosher method. All 14 compounds were examined for the inhibition of LPS-induced nitric oxide production in RAW264.7 macrophages. Compounds 6, 13, and 14 were found to inhibit nitric oxide production potently, with IC(50) values of 0.11, 0.25, and 0.10 microM, respectively.

Vitiligo in North-Eastern China: An association between mucosal and acrofacial lesions.

Vitiligo is a mucocutaneous pigmentary disorder with worldwide distribution. Little is known about the clinical profile of vitiligo in North-eastern China. Accordingly, we reviewed 692 vitiligo out-patients from seven government hospitals in North-eastern China via a questionnaire in a multi-centre study conducted between June 2007 and June 2008, and hence characterized the epidemiology of vitiligo in North-eastern China. The mean +/- standard deviation age of onset was 23.69 +/- 13.83 years (range < 1-77 years). No gender preponderance was seen. The back was the most common site of involvement (39.6%). Vitiligo vulgaris was the predominant form (53.5%). Mucosal lesions were associated with lesions on the feet (odds ratio (OR) = 3.177, p < 0.001), hands (OR = 2.228, p < 0.01), face (OR = 2.028, p < 0.05) and neck (OR = 0.454, p < 0.05); but were not associated with chest, abdomen, waist, arms, legs or scalp lesions. Mucosal vitiligo is probably a special form of acrofacial vitiligo.

[Transcription regulation by histone-modifying enzymes].

During gene transcription, it needs to recruit many histone-modifying enzymes to modify histone. These chemical modification contains methylation, acetylation, phosphorylation, ubiquitylation, sumoylation of histone and so on. Most of histone-modifying enzymes can form a complex with various transcriptional factors, they can change the interaction between histone and DNA, which regulate gene transcription. This review is focused on recent findings regarding the composition, the structure and the function of the histone-modifying enzyme complexes.

Giant monostotic osteofibrous dysplasia of the ilium: A case report and review of literature.

BACKGROUND: Osteofibrous dysplasia (OFD) is a developmental skeletal disorder, and cases with a giant affected area in the pelvis are rare. CASE SUMMARY: In this case report, a 48-year-old man presented with a large tumor in the right iliac region that turned out to be OFD. The patient had rebound tenderness in his right hip. After radiography examination, magnetic resonance imaging examinations and some physical examination, extensive bone destruction in the right ilium was confirmed. Moreover, changes in bone mineral density and peripheral cortical bone sclerosis with surrounding soft tissue swelling were observed. Thus, this patient was considered to have giant monostotic OFD of the ilium. The tumor-related area was removed completely by surgery, and the remaining cavity was filled by artificial bones from the opposite ilium. According to the results of follow-up, the patient had normal flexion and extension activities of the right hip joint, and there was no evidence of recurrence of the tumor. CONCLUSION: Suture of iliopsoas and gluteus medius muscle following focus curettage and bone grafting is a promising and effective method to treat giant OFD of the ilium. It is a feasible way to fill a large cavity after removing a lesion like the one is this case.

Establishment of embryonic shoot-root axis is involved in auxin and cytokinin response during Arabidopsis somatic embryogenesis.

Auxin and cytokinin signaling participates in regulating a large spectrum of developmental and physiological processes in plants. The shoots and roots of plants have specific and sometimes even contrary responses to these hormones. Recent studies have clearly shown that establishing the spatiotemporal distribution of auxin and cytokinin response signals is central for the control of shoot apical meristem (SAM) induction in cultured tissues. However, little is known about the role of these hormones in root apical meristem (RAM) initiation. Here, we found that the expression patterns of several regulatory genes critical for RAM formation were correlated with the establishment of the embryonic root meristem during somatic embryogenesis in Arabidopsis. Interestingly, the early expression of the WUS-RELATED HOMEOBOX 5 (WOX5) and WUSCHEL genes was induced and was nearly overlapped within the embryonic callus when somatic embryos (SEs) could not be identified morphologically. Their correct expression was essential for RAM and SAM initiation and embryonic shoot-root axis establishment. Furthermore, we analyzed the auxin and cytokinin response during SE initiation. Notably, cytokinin response signals were detected in specific regions that were correlated with induced WOX5 expression and subsequent SE formation. Overexpression of the ARABIDOPSIS RESPONSE REGULATOR genes ARR7 and ARR15 (feedback repressors of cytokinin signaling), disturbed RAM initiation and SE induction. These results provide new information on auxin and cytokinin-regulated apical-basal polarity formation of shoot-root axis during somatic embryogenesis.

Auxin-cytokinin interaction regulates meristem development.

Plant hormones regulate many aspects of plant growth and development. Both auxin and cytokinin have been known for a long time to act either synergistically or antagonistically to control several significant developmental processes, such as the formation and maintenance of meristem. Over the past few years, exciting progress has been made to reveal the molecular mechanisms underlying the auxin-cytokinin action and interaction. In this review, we shall briefly discuss the major progress made in auxin and cytokinin biosynthesis, auxin transport, and auxin and cytokinin signaling. The frameworks for the complicated interaction of these two hormones in the control of shoot apical meristem and root apical meristem formation as well as their roles in in vitro organ regeneration are the major focus of this review.