N-acetylserotonin alleviates retinal ischemia-reperfusion injury via HMGB1/RAGE/NF-κB pathway in rats

AIM

To observe the effects of N-acetylserotonin (NAS) administration on retinal ischemia-reperfusion (RIR) injury in rats and explore the underlying mechanisms involving the high mobility group box 1 (HMGB1)/receptor for advanced glycation end-products (RAGE)/nuclear factor-kappa B (NF-κB) signaling pathway.

METHODS

A rat model of RIR was developed by increasing the pressure of the anterior chamber of the eye. Eighty male Sprague Dawley were randomly divided into five groups: sham group (n=8), RIR group (n=28), RIR+NAS group (n=28), RIR+FPS-ZM1 group (n=8) and RIR+NAS+ FPS-ZM1 group (n=8). The therapeutic effects of NAS were examined by hematoxylin-eosin (H&E) staining, and retinal ganglion cells (RGCs) counting. The expression of interleukin 1 beta (IL-1β), HMGB1, RAGE, and nod-like receptor 3 (NLRP3) proteins and the phosphorylation of nuclear factor-kappa B (p-NF-κB) were analyzed by immunohistochemistry staining and Western blot analysis. The expression of HMGB1 protein was also detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

H&E staining results showed that NAS significantly reduced retinal edema and increased the number of RGCs in RIR rats. With NAS therapy, the HMGB1 and RAGE expression decreased significantly, and the activation of the NF-κB/NLRP3 pathway was antagonized along with the inhibition of p-NF-κB and NLRP3 protein expression. Additionally, NAS exhibited an anti-inflammatory effect by reducing IL-1β expression. The inhibitory of RAGE binding to HMGB1 by RAGE inhibitor FPS-ZM1 led to a significant decrease of p-NF-κB and NLRP3 expression, so as to the IL-1β expression and retinal edema, accompanied by an increase of RGCs in RIR rats.

CONCLUSION

NAS may exhibit a neuroprotective effect against RIR via the HMGB1/RAGE/NF-κB signaling pathway, which may be a useful therapeutic target for retinal disease.

In Situ Photoisomerization of an Azobenzene-Based Triple Helicate with a Prolonged Thermal Relaxation Time

The phosphate-coordination triple helicates A2 L3 (A=anion) with azobenzene-spaced bis-bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise "disassembly-isomerization-reassembly" process. This is enabled by the structural self-adaptability of the "aniono" assembly arising from multiple relatively weak and flexible hydrogen bonds between the phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of the isomerized azobenzene unit is significantly decreased (up to 20-fold) for the triple helicates compared to the free ligands. Moreover, the binding of chiral guest cations inside the cavity of the Z-isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light-activated chiroptical materials.

[Expression and significance of immune checkpoint B7-homolog 4 in endometrial cancer]

Objective: To investigate the expression of B7 homolog 4 (B7-H4) and its clinical significance in endometrial cancer. Methods: A total of 833 patients with endometrial cancer admitted to Peking Union Medical College Hospital, Chinese Academy of Medical Sciences from 2009 to 2019, were enrolled. The expression of B7-H4, mismatch repair (MMR), p53, programmed cell death ligand 1 (PD-L1) protein, and CD₈⁺ T lymphocyte density in endometrial cancer tissues were detected by the EnVision two-step method of immunohistochemical staining. First-generation sequencing (Sanger method) was used to determine molecular subtyping of endometrial cancer. The χ² test was used to compare the differences in positive expression rate of B7-H4 protein in endometrial cancer tissues with different clinicopathological features and molecular subtyping, PD-L1 protein expression, and CD₈⁺ T lymphocyte density. Survival analyses [including recurrence-free survival (RFS) and disease-specific survival (DSS)] were performed for 664 patients with follow-up time≥3 months, with a median follow-up time of 31 months (range: 4-121 months), and the Cox proportional hazards regression model was used to analyze the relevant factors affecting the prognosis of patients with endometrial cancer. Results: (1) The median age of 833 patients was 58 years (range: 25-88 years); pathological type: 595 with endometrioid carcinoma, 238 with non-endometrioid carcinoma; surgical-pathological staging: 542 cases at stage Ⅰ, 38 cases at stage Ⅱ, 173 cases at stage Ⅲ, and 45 cases at stage Ⅳ. Molecular subtyping was performed in 590 patients, including 50 with POLE mutation, 163 with mismatch repair defect (MMR-d) type, 246 with nospecific molecular change (NSMP) type, and 131 with p53 mutation subtype. (2) B7-H4 protein was expressed with brownish-yellow stainind in the cell membrane and cytoplasm of endometrial carcinoma, and the positivity rate of B7-H4 protein was 71.5% (596/833). The positivity rates of B7-H4 protein among patients with different age, surgical-pathological stage, tumor grade, pathological type, depth of muscular invasion, presence or absence of lymphovascular space invasion, and molecular subtype were significantly different (all P<0.05). The positivity rates of B7-H4 protein among patients with different PD-L1 protein expression and CD₈⁺ T lymphocyte density were not significantly different (P>0.05). The 5-year RFS (83.9%) and DSS (87.3%) of B7-H4 protein-positive patients had an increasing trend compared with the 5-year RFS (77.2%) and DSS (78.1%) of B7-H4 protein-negative patients, but there were not statistically significant differences (P=0.053, P=0.083). (3) Univariate analysis showed that the 5-year RFS and DSS of patients with different age, tumor grade, surgical-pathological stage, pathological type, depth of muscular invasion, lymphovascular space invasion, and molecular subtype were significantly different (all P<0.01). There were no significant differences in 5-year RFS (P=0.184, P=0.113) and DSS (P=0.549, P=0.247) among patients with different CD₈⁺ T lymphocyte density and PD-L1 protein expression. Further analysis according to molecular subtype, the results of CD₈⁺ T lymphocyte density and PD-L1 protein expression showed that the 5-year RFS and DSS of B7-H4 protein-positive patients were higher than those of B7-H4 protein-negative patients with NSMP subtype, low density of CD₈⁺ T lymphocyte and PD-L1 protein-negative endometrial carcinoma (all P<0.05), however, there was no significant difference in 5-year DSS between B7-H4 protein-positive patients and B7-H4 protein-negative patients with PD-L1 protein-negative endometrial cancer (P=0.060). Multivariate analysis showed that positive expression of B7-H4 protein was an independent factor for 5-year RFS (HR=0.27, 95%CI: 0.09-0.78, P=0.016) and DSS (HR=0.16, 95%CI: 0.05-0.58, P=0.005) in patients with NSMP subtype endometrial carcinoma. In patients with low-density CD₈⁺ T lymphocytes endometrial cancer, positive expression of B7-H4 protein was an independent factor for 5-year RFS (HR=0.45, 95%CI: 0.26-0.80, P=0.006), but it was not an independent factor for 5-year DSS. In patients with PD-L1 protein-negative endometrial cancer, B7-H4 protein was not an independent factor for 5-year RFS. Conclusion: B7-H4 protein expressed highly in endometrial carcinoma tissues, and its high expression is closely related to clinicopathological features, molecular subtype of p53 mutant and NSMP, and the favorable prognosis of patients with low density of CD₈⁺ T lymphocyte immunophenotype endometrial carcinoma.

Recognition-guided sulfate extraction and transport using tripodal hexaurea receptors

Hexaurea-based receptors enable highly efficient sulfate extraction (over 97%) via liquid–liquid extraction, and a controllable release of the bound sulfate is achieved by acidifying the solution, as demonstrated in the U-tube experiment.

Reducing lipofuscin accumulation and cardiomyocytic senescence of aging heart by enhancing autophagy

Cardiomyocytes are particularly prone to lipofuscin accumulation. In the aging heart, lipofuscin accumulation is augmented. This study examined distribution of lipofuscin and senescent cardiomyocytes and evaluated improvement of lipofuscin accumulation and cardiomyocytic senescence of the aging heart after treatment with rapamycin. The results of Schmorl staining, Sudan black staining and autofluorescence detection showed that there was more lipofuscin in the myocardium of the ventricles especially in the left ventricle. The conductive tissue contained less lipofuscin than the myocardium. In the aged hearts, lipofuscin accumulation and senescent cardiomyocytes were increased, and the level of autophagy was reduced. In double staining of Sudan black B and senescence-associated β-galactosidase, 10%-20% lipofuscin-loaded cardiomyocytes became senescent. All senescent cardiomyocytes contained lipofuscin deposits. After enhancing autophagy with feed of rapamycin for six months, lipofuscin accumulation and senescence of cardiomyocytes were improved in old rats. Colocalization of autophagic structure and lipofuscin as well as electron micrographs showed that some lipofuscin-loaded lysosomes were sequestrated by autophagic structures. This study suggests that rapamycin-enhanced autopahgy is effective for reducing lipofuscinogenesis and promoting degradation of lipofuscin. Therefore, enhancing autophagy is a novel therapy for alleviating lipofuscin accumulation and myocardial senescence.

[Feasibility study of blood oxygen level-dependent magnetic resonance imaging in evaluating the response of metastatic lymph nodes of rabbit VX2 tumor to radiotherapy]

Objective: To investigate the feasibility of blood oxygen level-dependent magnetic resonance imaging (MRI) in evaluating the response of metastatic lymph nodes of rabbit VX2 tumor to radiotherapy. Methods: Twenty-eight healthy New Zealand white rabbits which were provided by the Laboratory Animal Center of Soochow University, male or female, 2 to 3 months, weighing 2 to 3 kg, were used to establish the animal model of VX2 tumor popliteal fossa metastatic lymph node, and then were divided into either the radiotherapy group (n=16) or the control group (n=12). The radiotherapy group received a 20 Gy radiotherapy per rabbit, the control group received sham radiotherapy. All rabbits underwent MRI scan on four time points, including before (0 day), 3rd, 7th and 14th days after radiotherapy. The two parameters of size and R(2*) value (s(-1)) of lymph node were measured. At each time point,two rabbits in each group were sacrificed randomly to resect lymph nodes for pathological examination, and two parameters of microvessel density (MVD, strip/HP) and apoptosis index (AI, %) were analyzed. The parameters among the four time points in each group or between the two groups were compared. The correlation of lymph node size and R(2*) value with MVD or AI was analyzed, respectively. Results: A significant size difference was neither between the two groups or among the each time points in each group (P>0.05). The R(2*) of lymph node in the radiotherapy group was (29.6±1.7),(36.8±2.6),(44.8±5.8) and (57.7±6.2) s(-1) at the time points of 0, 3, 7 and 14 days, respectively, showing a gradual increase trend; MVD was (52.3±2.5),(41.0±3.6),(34.0±3.6) and (22.7±2.5) strip/HP respectively, showing a decreasing trend; AI was 12.8%±0.5%,14.9%±0.6%,20.6%±0.5% and 27.5%±0.7% respectively, showing a gradual increase trend (all P<0.05). In the control group, both R(2*) value and AI among the four time points did not change statistically (all P>0.05), but MVD showed a gradual increase trend,(50.0±3.0),(53.0±1.7),(60.3±2.5) and (70.0±2.0) strip/HP, respectively, P<0.05. There were significant differences in R(2*) and MVD at 3, 7 and 14 days, in AI at 7 and 14 days between the two groups (all P<0.05). There was a linear correlation of R(2*) value, but not of size, with MVD and AI (r=-0.87 and 0.94, respectively). Conclusion: Blood oxygen level-dependent MRI can indirectly reflect the hypoxic status of metastatic lymph nodes after radiotherapy, and has potential value in evaluating the response of metastatic lymph nodes to radiotherapy.

Clinical usefulness of two-phase 18F-sodium-fluoride (18F-NaF) bone PET/CT for evaluating treatment response of bone metastases from breast cancer: Case report

We report the case of a breast cancer patient in whom a two-phase ¹⁸F-sodium-fluoride (¹⁸F-NaF) bone PET/CT was useful for detecting hidden bone metastases and assessing treatment response. The patient underwent a two-phase bone PET/CT to evaluate a newly developed lesion found on bone scintigraphy following surgery. In the perfusion and bone phase PET/CT images, focally increased perfusion and bony uptake were found in the sacrum and L5 vertebra, suggesting bone metastases of breast cancer. Therefore, the patient subsequently underwent palliative treatment. In another twoPET/CT studies (each including two-phase bone images) performed after 3and 6months of follow-up, the perfusion phase images showed an improvement of the lesion uptake more clearly than in the bone phase images in the visual and semi-quantitative analyses, and thus the perfusion phase images were more useful for clarifying the treatment response earlier than the bone phase images. This is the first case showing the clinical usefulness of ¹⁸F-NaF bone PET/CT with the perfusion imaging technique for evaluating bone metastases and the therapeutic response of metastatic bone lesions.

[Effect of snow sports on knee cartilage maturation in children and adolescent with MRI quantitative analysis Zhang]

Objective: To evaluate the effect of snow sports to the knee cartilage maturation of children and adolescent with quantitative analysis of 3.0 T MRI. Methods: Twenty children and adolescent who underwent snow sports training more than 6 months (11 males and 9 females) were recruited and named with sports group, and twenty children and adolescent who live regularly without any exercise (10 males and 10 females) were recruited as control group from June 2014 to June 2015.Each group was divided into subgroups according to their gender.Both groups were scanned by 3.0 T MR.According to the loading features of knee articular cartilage in snow sports, medial femoral condyle, lateral femoral condyle, medial tibial condyle and lateral tibial condyle were divided into subareas.T₂ values and cartilage thickness were measured in all areas. Results: The median ages of the sports group and control group were 14.2 and 13.6 years old, which showed no statistical difference between two groups.The BMI of the sports group and control group were 18.3 and 17.9 kg/m^2, which showed no statistical difference between two groups.Both in sports group and control group, the thickness and T₂ values of all areas showed significant differences between man and women in each group (all P<0.05). The cartilage thickness of sports group was higher than control group (P<0.05). The T₂ values showed no statistical difference in anterior central, posterior central of femoral condyles and anterior, central areas of tibial condyles between sports group and control group(P≥0.05). The T₂ values of anterior part of posterior femur and posterior areas of tibial condyle in sports group was higher than control group (P≥0.05). Conclusion: Gender difference may be an important effect factor of cartilage thickness. Scientific snow sports training maybe has positive influence for cartilage maturation of children and adolescent.

Late paradoxical lymph node enlargement during and after anti-tuberculosis treatment in non-HIV-infected patients

SETTINGS

A tertiary referral centre in South Korea.

OBJECTIVE

To investigate the incidence, clinical characteristics and outcomes of late paradoxical response (>4 months after the initiation of anti-tuberculosis treatment) during and after anti-tuberculosis treatment in non-human immunodeficiency virus (HIV) infected patients with lymph node tuberculosis (TB).

DESIGN

We retrospectively reviewed the medical records of non-HIV-infected patients with lymph node TB between 1997 and 2007, and prospectively enrolled patients with newly diagnosed lymph node TB between 2008 and 2013.

RESULTS

Of 467 patients with confirmed and probable lymph node TB, 83 (18%) displayed a paradoxical response: 57 of these (69%) were classified as early and 26 (31%) as late paradoxical response. Patients with late paradoxical response (median 12 months) received more prolonged anti-tuberculosis treatment than those with early (median 9 months, P < 0.001) or no paradoxical response (median 9 months, P < 0.001). The frequency of post-treatment lymph node enlargement increased progressively from those without any paradoxical response (6%), through those with an early response (12%) to those with a late response (23%).

CONCLUSIONS

Paradoxical response presents late in about one third of non-HIV-infected patients with lymph node TB who experience a response. Although anti-tuberculosis treatment is commonly prolonged in patients with late paradoxical response, post-treatment lymph node enlargement is more frequent in these patients.

[Correlation between susceptibility weighted imaging manifestation and serum cystatin C for delayed graft function]

OBJECTIVE

To explore the correlation between susceptibility weighted imaging (SWI) manifestation and serum cystatin C level for delayed graft function (DGF).

METHODS

The conventional MRI, SWI and serum cystatin C of 27 cases with DGF in nephrotransplantation center in Third Affiliated Hospital of Suzhou University from September 2014 and August 2015 were retrospectively analyzed.By contrasting conventional MRI images of transplanted kidney in DGF, the imaging manifestations of benign tumors such as cysts and angiomyolipomas were excluded on SWI images, and then making the renal cortex as the reference, if the abnormal signal lesions were found in the transplanted kidney, the location and signal intensity would be analyzed. The differences in serum cystatin C level between DGF groups without and with abnormal signal lesions were compared by using independent-sample t-test.The correlation between SWI manifestation and serum cystatin C level for DGF was assessed with Spearman rank correlation analysis.

RESULTS

A total of 15 cases were found without abnormal signal lesions and the average value of their serum cystatin C level was (2.92±0.44) mg/L.A total of 12 cases were found with abnormal low signal lesions located at junctional zone between cortex and medulla, and the average value of their serum cystatin C level was (6.91±0.96) mg/L. The differences in serum cystatin C level between the two DGF groups were statistically significant (t=-4.040, P=0.000). There was a positive correlation between the abnormal low signal lesions on SWI and serum cystatin C level (r=0.660, P=0.000).

CONCLUSION

The status of renal function impairment could be reflected by being with or without abnormal signal lesions on SWI. A relatively big renal function impairment may be predicted by the appearance of abnormal low signal lesions at junctional zone between cortex and medulla on SWI.

Effect of N-acetylserotonin on hepatocyte apoptosis after liver ischemia-reperfusion injury in rats

AIM: To investigate the effect of N-acetylserotonin (NAS) on hepatocyte apoptosis after liver ischemia-reperfusion (I/R) injury in rats.

METHODS: Adult male SD rats weighting 200-250 g were used. The afferent vessels of the left and median lobes were occluded by a microvascular bulldog clamp and then reperfused after 60 min with or without NAS. The morphologic changes and hepatocyte apoptosis were evaluated by hematoxylin-eosin (HE) staining and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining, respectively. The expression of Bcl-2, Bax and activated Caspase3 was evaluated by immunohistochemistry.

RESULTS: The hepatocytes exhibited marked ballooning hydropic degeneration and focal necrosis in the I/R group. NAS pretreatment rescued the morphological damage. Compared with the sham operation group, the expression of cleaved Caspase3, Bcl-2 and Bax in the liver tissue was increased, and the ratio of Bcl-2/Bax was decreased in the I/R group (P < 0.01). The apoptosis index (AI) and expression of cleaved Caspase3 and Bax were decreased in the NAS intervention group compared with the I/R group (P < 0.01), and the expression of Bcl-2 and Bcl-2/Bax ratio were increased (P < 0.01).

CONCLUSION: NAS could attenuate hepatocyte apoptosis after liver I/R injury via mechanisms possibly associated with induction of Bcl-2 protein expression and inhibition of Bax protein expression in hepatocytes.

Chlamydial infection during trachoma monitoring: are the most difficult-to-reach children more likely to be infected?

OBJECTIVES

During mass antibiotic distributions for trachoma, certain individuals are difficult to locate and go untreated. These untreated individuals may serve as a source of community reinfection. The importance of this difficult-to-locate, untreated population is unclear. We sought to determine whether individuals who are difficult to locate were more likely to be infected with ocular chlamydia than those who were easier to locate.

METHODS

We monitored 12 Ethiopian communities 1 year after a third annual mass azithromycin treatment for trachoma. Conjunctival swabbing for chlamydial RNA was performed in a random sample of children from each community. If insufficient numbers of children were enrolled on the first monitoring day, we returned on subsequent days.

RESULTS

Of the 12 communities, 10 required more than one monitoring day. On average, 16.1% (95% CI 7.9-30.0) of children were enrolled after the initial day. Evidence of chlamydia was found in 7.1% (95% CI 2.7-17.4) of 0- to 9-year-old children. No ocular swabs collected after the initial day were positive for chlamydial RNA. Children examined after the initial monitoring day were significantly less likely to have ocular chlamydial infection than children seen on the initial day; Mantel-Haenszel common OR = 0 (95% CI 0-0.77).

CONCLUSIONS

In a setting of repeated annual mass azithromycin treatments, after approximately 80% of individuals have been located in a community, extra efforts to find absent individuals may not yield significantly more cases of ocular chlamydia.

Heterogeneous expression of Wnt signal molecules in parental HepG2 cells and HepG2 colony-forming cells

AIM: To investigate the heterogeneous expression of Wnt signal molecules in HepG2 cells with different proliferative ability.

METHODS: The soft agar colony formation assay was used to separate HepG2 colony-forming cells. The mRNA expression and protein expression and distribution of β-catenin and COX-2 in parental HepG2 cells and HepG2 colony-forming cells were detected by RT-PCR, Western blotting and immunochemistry, respectively.

RESULTS: The expression levels of β-catenin mRNA and protein in HepG2 colony-forming cells were significantly higher than those in parental HepG2 cells (0.905 vs 0.549; 1.021 vs 0.700; both P < 0.05). β-catenin was mainly localized in the cytoplasm in parental HepG2 cells and in the nucleus in HepG2 colony-forming cells. The expression levels of COX-2 mRNA and protein in parental HepG2 cells were significantly higher than those in HepG2 colony-forming cells (0.857 vs 0.527; 0.731 vs 0.434; both P < 0.05). Immunochemistry analysis showed that most HepG2 cells were positive for COX-2.

CONCLUSION: β-catenin and COX-2 may be closely related to the degree of differentiation of hepatocellular carcinoma. The expression patterns of β-catenin and COX-2 in parental HepG2 cells and HepG2 colony-forming cells imply that HepG2 colony-forming cells have the characteristics of liver cancer stem cells.

Comparison of colony-forming capacity of HepG2 cells in different soft agar systems

AIM: To determine the optimal cell density and agar concentration for separation of cell clones and thereby provide a reference for screening of tumor stem cells.

METHODS: HepG2 cells were mixed with 10 g/L agarose and inoculated in 2 g/L (group A) and 3 g/L (group B) soft agar at different densities. After 14 d of culture, the number of cell clones was counted and the rate of colony formation was calculated.

RESULTS: The number of clones formed in group A was significantly higher than that in group B (t = 4.36, P < 0.05). The rates of colony formation observed in both group A and group B increased with the increase in cell density that varied between 100 and 500 cells per well. In contrast, the rate of colony formation decreased with the increase in cell density that varied between 600 and 1000 cells per well.

CONCLUSION: The optimal concentration of agar in the upper layer for colony formation is 3 g/L, with 10% agarose as a stock agar. The maximum rate of colony formation is achieved when cells are inoculated at a density of 500 cells per well.

Morphological characteristics of human embryonic hepatic stem cells

AIM: To observe the morphological features, temporal-spatial distribution and differentiation of hepatic stem cells in the early stage of human embryonic livers.

METHODS: Paraffin sections were prepared from human embryos of 3 to 12 wk by routine method. Immunohistochemical staining was used to observe the development of human embryonic livers and hepatic stem cells as well as the expression of α-fetoprotein (AFP), c-Met and cytokeratin 19 (CK19) under light microscope.

RESULTS: Liver buds came into being in wk 3, hepatic cords formed in wk 4, and primal hepatic sinusoids were found in wk 5. The hepatic cells of the 3-5 wk displayed the typical features of immature cells: small size, a round or ovoid nuclei with dark color, scant cytoplasm with slight blue and a high ratio of nuclei to cytoplasm. Moreover, they were positive for AFP and c-Met. At 6 wk, a part of hepatocytes, whose numbers increased as the growth of the embryos, became larger with nuclei of slight color, which were negative for AFP and c-Met. At 10-12 wk, the AFP- and c-Met-positive cells were mainly found at the periportal region. The CK19-positive reaction began to appear in some hepatocytes which were similar to the AFP- and c-Met-positive cells at 7 wk. At 10-11 wk, the reaction was confined at the hepatocytes adjacent to the portal region, ductal plate and biliary epithelial cells. At 12 wk, the positive reaction was only found at the ductal plate and biliary epithelial cells. Furthermore, all the cells were positive for AFP, c-Met and CK19 at this time.

CONCLUSION: Hepatocytes of 3-5 wk, phenotyped AFP⁺/c-Met⁺, are homogenous and belong to the hepatic stem cells. At 6 wk, the hepatic stem cells begin to differentiate to hepatocyte system, and then to cholangiocyte system in the next week. Like oval cells in the adult liver, the hepatic stem cells mainly locate at the periportal region at 10-12 wk. The cells characterized by AFP⁺/c-Met⁺/CK19⁺ belong to the progenitor cells of biliary epithelial cells.

Effects of random potential on transport

The effects of random potential on the transport of two systems, which are the motion of motor proteins along a biopolymer and the thermally assisted vortex diffusion in layered high-Tc superconductors, are investigated, respectively. It is found that the effects of the random potential on the transport process as the amplitude of random potential increased are much more remarkable than those as the correlation length of random potential increased. The amplitude and the correlation length of random potential play opposing roles in the transport of the systems.

Biomechanical properties and a kinetic simulation model of the smooth muscle I2 in the buccal mass of Aplysia

The muscle I2 is a smooth muscle from the buccal mass of the marine mollusc Aplysia californica whose neural control, in vivo kinematics, and behavioral role have been extensively analyzed. In this study, we measured the activation and contractile dynamics of the muscle in order to construct a Hill-type kinetic model of the muscle. This is the first study to our knowledge, of Aplysia muscle contractile dynamics. The isometric force-frequency relationship of I2 had a frequency threshold of about 6-8 Hz, and its force output saturated at 20-25 Hz, properties that match the high frequency (20 Hz) bursts generated by the B31/B32 neurons that innervate it. Peak isometric force was generated at about 118% of the in situ relaxed length. These results and I2's estimated in vivo kinematics suggest that it generates maximum force at the onset of protraction. The muscle tension during iso-velocity lengthening and shortening was an asymmetric function of velocity. Short range stiffness and yielding responses were observed in lengthening, whereas muscle tension decreased smoothly in shortening. These visco-elastic properties suggest that the I2 muscle can serve to brake forceful retraction movements. A Hill-type model, parameterized from the measurements, captured many of the mechanical properties of I2. Our results provide a quantitative understanding of the biomechanical significance of the muscle's neural control and provide a basis for simulation studies of the control of feeding behavior.

Isolation and characterization of a cDNA encoding the cysteine proteinase inhibitor, induced upon flower maturation in carnation using suppression subtractive hybridization

The suppression subtractive hybridization (SSH) method was used to isolate differentially expressed genes during carnation flower maturation. Five cDNA clones, designated as carnation flower maturation-induced (CFMI), were verified as flower maturation-induced cDNAs. Sequence analysis of five CFMI (CFMI-5, CFMI-6, CFMI-7, CFMI-9, and CFMI-10) clones revealed that one of the clones, CFMI-5, showed high sequence similarity to the cysteine proteinase inhibitor gene, predicted to be involved in flower maturation. The full length cDNA clone CFMI-5 was 531 nucleotides (nts) long and consisted of an open reading frame of 294 nucleotides, encoding a 98 amino acid protein, 12 nucleotides of 5'-untranslated region and 3'-untranslated region (225 nts) with a poly(A)+ tail. The predicted CFMI-5 amino acid sequence had a conserved sequence Gln-Val-Val-Ala-Gly, which corresponds to the active site of proteinase inhibition. Northern blot analysis revealed tissue-specific expression of CFMI-5 transcripts, as the transcripts were expressed preferentially in petals and styles. A PCR-based cDNA subtraction method, termed suppression subtractive hybridization, was identified as a rapid method to screen differentially expressed genes in a short time.

A nonisometric kinetic model for smooth muscle

We have modeled the nonisometric contractile dynamics of smooth muscle by modifying a four-state model of actin and myosin bonds originally proposed by Hai and Murphy to simulate the isometric contractions of vertebrate smooth muscle. The model includes a latch bridge, which cycles more slowly than regular cross bridges. We generalized this model to represent the calcium-regulated processes of vertebrate and invertebrate smooth muscles. We added length dynamics by assuming length-dependent bonding and unbonding rates for the cross bridges. The calculation of the cross-bridge length distribution was simplified by assuming a Gaussian distribution, as first done by Zahalak for skeletal muscle. To test the performance of this model, we simulated isometric and nonisometric responses of different kinds of smooth muscle, including vascular smooth muscle, airway smooth muscle, molluscan catch muscle (anterior byssus retractor muscle), and Aplysia I(2) muscle. The model captures the economical force maintenance property at the later stages of isometric muscle contraction and responses to imposed lengthening and shortening movements.

Interactive program for spectral and area analysis of compound action potentials of A-fiber and C-fiber

An interactive program was described to correct the baseline wandering of the compound action potentials (CAPs) of C-fiber, to calculate the area and the peak amplitude of CAPs, and to analyze their spectral distribution. Using this program, we found the optimal bandpass of the filter for recording CAPs to be from 10 Hz to 3 kHz.

Canine intervertebral disks: correlation of anatomy and MR imaging

Because the structure, maturation, and degeneration of canine intervertebral disks resemble those of humans, the authors developed a model of acute intervertebral disk degeneration in dogs. Herniated disks of 18 dogs were examined with magnetic resonance (MR) imaging and then sectioned with a freezing microtome. On the basis of their morphologic appearance in the freezing microtome sections, most of the lumbar intervertebral disks could be categorized as one of six types. Each type has characteristic features and a distinctive appearance on MR images. Findings of this study--including decreased signal intensity from the intervertebral disk, altered signal intensity in contiguous bone marrow, bulging of the anulus fibrosus, herniation of the nucleus pulposus, and contrast enhancement after intravenous administration of gadolinium diethylenetriaminepentaacetic acid (DTPA)--resemble observations from human clinical studies. Classification of degenerating disks and identification of MR imaging characteristics of each type may improve the interpretation of MR images and recognition of early disk degeneration in humans.