Influence of Proteolytic Cleavage of ENaC's Gamma Subunit upon Na+ and K+ Handling

The ENaC γ subunit is essential for homeostasis of Na+, K+, and body fluid. Dual γ subunit cleavage before and after a short inhibitory tract allows dissociation of this tract, increasing channel open probability (PO), in vitro. Cleavage proximal to the tract occurs at a furin recognition sequence (143RKRR146, in the mouse γ subunit). Loss of furin-mediated cleavage prevents in vitro activation of the channel by proteolysis at distal sites. We hypothesized that 143RKRR146 mutation to 143QQQQ146 (γQ4) in 129/Sv mice would reduce ENaC PO, impair flow-stimulated flux of Na+ (JNa) and K+ (JK) in perfused collecting ducts, reduce colonic amiloride-sensitive short circuit current (ISC), and impair Na+, K+, and body fluid homeostasis. Immunoblot of γQ4/Q4 mouse kidney lysates confirmed loss of a band consistent in size with the furin-cleaved proteolytic fragment. However, γQ4/Q4 male mice on a low Na+ diet did not exhibit altered ENaC PO or flow-induced JNa, though flow-induced JK modestly decreased. Colonic amiloride-sensitive ISC in γQ4/Q4 mice was not altered. γQ4/Q4 males, but not females, exhibited mildly impaired fluid volume conservation when challenged with a low Na+ diet. Blood Na+ and K+ were unchanged on a regular, low Na+, or high K+ diet. These findings suggest that biochemical evidence of γ subunit cleavage should be used in isolation to evaluate ENaC activity. Further, factors independent of γ subunit cleavage modulate channel PO and the influence of ENaC on Na+, K+, and fluid volume homeostasis in 129/Sv mice, in vivo.

Proteolytic Cleavage of the ENaC γ Subunit - Impact Upon Na + and K + Handling

The ENaC gamma subunit is essential for homeostasis of Na + , K + , and body fluid. Dual subunit cleavage before and after a short inhibitory tract allows dissociation of this tract, increasing channel open probability (P O ), in vitro . Cleavage proximal to the tract occurs at a furin recognition sequence ( 143 RKRR 146 in mouse). Loss of furin-mediated cleavage prevents in vitro activation of the channel by proteolysis at distal sites. We hypothesized that 143 RKRR 146 mutation to 143 QQQQ 146 ( Q4 ) in 129/Sv mice would reduce ENaC P O , impair flow-stimulated flux of Na + (J Na ) and K + (J K ) in perfused collecting ducts, reduce colonic amiloride-sensitive short circuit current (I SC ), and impair Na + , K + , and body fluid homeostasis. Immunoblot of Q4/Q4 mouse kidney lysates confirmed loss of a band consistent in size with the furin-cleaved proteolytic fragment. However, Q4/Q4 male mice on a low Na + diet did not exhibit altered ENaC P O or flow-induced J Na , though flow-induced J K modestly decreased. Colonic amiloride-sensitive I SC in Q4/Q4 mice was not altered. Q4/Q4 males, but not females, exhibited mildly impaired fluid volume conservation when challenged with a low Na + diet. Blood Na + and K + were unchanged on a regular, low Na + , or high K + diet. These findings suggest that biochemical evidence of gamma subunit cleavage should not be used in isolation to evaluate ENaC activity. Further, factors independent of gamma subunit cleavage modulate channel P O and the influence of ENaC on Na + , K + , and fluid volume homeostasis in 129/Sv mice, in vivo .

Construction of multifunctional porcine acellular dermal matrix hydrogel blended with vancomycin for hemorrhage control, antibacterial action, and tissue repair in infected trauma wounds

Prevention of bacterial infection and reduction of hemorrhage, the primary challenges posed by trauma before hospitalization, are essential steps in prolonging the patient's life until they have been transported to a trauma center. Extracellular matrix (ECM) hydrogel is a promising biocompatible material for accelerating wound closure. However, due to the lack of antibacterial properties, this hydrogel is difficult to be applied to acute contaminated wounds. This study formulates an injectable dermal extracellular matrix hydrogel (porcine acellular dermal matrix (ADM)) as a scaffold for skin defect repair. The hydrogel combines vancomycin, an antimicrobial agent for inducing hemostasis, expediting antimicrobial activity, and promoting tissue repair. The hydrogel possesses a porous structure beneficial for the adsorption of vancomycin. The antimicrobial agent can be timely released from the hydrogel within an hour, which is less than the time taken by bacteria to infest an injury, with a cumulative release rate of approximately 80%, and thus enables a relatively fast bactericidal effect. The cytotoxicity investigation demonstrates the biocompatibility of the ADM hydrogel. Dynamic coagulation experiments reveal accelerated blood coagulation by the hydrogel. In vivo antibacterial and hemostatic experiments on a rat model indicate the healing of infected tissue and effective control of hemorrhaging by the hydrogel. Therefore, the vancomycin-loaded ADM hydrogel will be a viable biomaterial for controlling hemorrhage and preventing bacterial infections in trauma patients.

Study of charged particle activation analysis (II): Determination of boron concentration in human blood samples

Boron Neutron Capture Therapy (BNCT) is a radiotherapy for the treatment of intractable cancer. In BNCT precise determination of ¹⁰B concentration in whole blood sample before neutron irradiation of the patient, as well as accurate neutron dosimetry, is crucial for control of the neutron irradiation time. For this purpose ICP-AES and neutron induced prompt γ-ray analysis are generally used. In Ibaraki Neutron Medical Research Center (iNMRC), an intense proton beam will be accelerated up to 8 MeV, which can also be used for Charged Particle Activation Analysis (CPAA). Thus, in this study, we apply the CPAA utilizing the proton beam to non-destructive and accurate determination of ¹⁰B concentration in whole blood sample. A CPAA experiment is performed by utilizing an 8 MeV proton beam from the tandem accelerator of Nuclear Science Research Institute in Japan Atomic Energy Agency. The 478 keV γ-ray of ⁷Be produced by the ¹⁰B(p, α)⁷Be reaction is used to quantify the ¹⁰B in human blood. The 478 keV γ-ray intensity is normalized by the intensities of the 847 keV and 1238 keV γ-rays of ⁵⁶Co originating from Fe in blood. The normalization methods were found to be linear in the range of 3.27 μg ¹⁰B/g to 322 μg ¹⁰B/g with correlation coefficients of better than 0.9999.

SHH E176/E177-Zn2+ conformation is required for signaling at endogenous sites

Sonic hedgehog (SHH) is a master developmental regulator. In 1995, the SHH crystal structure predicted that SHH-E176 (human)/E177 (mouse) regulates signaling through a Zn²⁺-dependent mechanism. While Zn²⁺ is known to be required for SHH protein stability, a regulatory role for SHH-E176 or Zn²⁺ has not been described. Here, we show that SHH-E176/177 modulates Zn²⁺-dependent cross-linking in vitro and is required for endogenous signaling, in vivo. While ectopically expressed SHH-E176A is highly active, mice expressing SHH-E177A at endogenous sites (Shh^E177A/-) are morphologically indistinguishable from mice lacking SHH (Shh^-/-), with patterning defects in both embryonic spinal cord and forebrain. SHH-E177A distribution along the embryonic spinal cord ventricle is unaltered, suggesting that E177 does not control long-range transport. While SHH-E177A association with cilia basal bodies increases in embryonic ventral spinal cord, diffusely distributed SHH-E177A is not detected. Together, these results reveal a novel role for E177-Zn²⁺ in regulating SHH signaling that may involve critical, cilia basal-body localized changes in cross-linking and/or conformation.

[Analysis of the survival of 123 patients with intrahepatic cholangiocarcinoma after surgical resection]

OBJECTIVE

To investigate the prognostic factors for patients with intrahepatic cholangiocarcinoma after surgical resection.

METHODS

The clinicopathological and follow-up data of 123 patients with intrahepatic cholangiocarcinoma who underwent surgical resection in Cancer Hospital, Chinese Academy of Medical Sciences between January 1999 and June 2015 were collected and reviewed, and their survival and prognosis were analyzed with the Kaplan-Meier method and Cox regression model.

RESULTS

The median follow-up time was 22 months and median recurrence-free survival time was 8.97 months. The 1-, 2- and 3-year recurrence rates were 58.6%, 68.9% and 76.5%, respectively. Cox multivariate regression analysis showed that preoperative rise in CEA, lymph node metastasis, multiple lesions, extrahepatic invasion, and combination of tumor necrosis were significant adverse prognostic factors affecting the postoperative recurrence-free survival in patients with intrahepatic cholangiocarcinoma after surgical resection (P<0.05 for all). The median overall survival time was 21.17 months, and the 1-, 3- and 5-year overall survival rates were 76.6%, 33.2% and 26.1%, respectively. The Cox multivariate regression analysis showed that preoperative rise in CEA, lymph node metastasis, multiple lesions, and extrahepatic invasion were significant adverse prognostic factors affecting the postoperative overall survival in patients with intrahepatic cholangiocarcinoma after surgical resection(P<0.05 for all).

CONCLUSION

Preoperative rise in CEA, lymph node metastasis, multiple lesions and extrahepatic invasion are significant adverse prognostic factors for patients with intrahepatic cholangiocarcinoma after surgical resection.

[Influence of BMP-7 on chondrocyte secretion and expression of Col-II,AGG and Sox9 mRNA in porous tantalum-chondrocyte composites in vitro]

OBJECTIVE

To study the influence of bone morphogenetic protein-7 (BMP-7) on chondrocyte secretion and expression of type II collagen (Col-II), aggrecan (AGG) and SRY-related high mobility group-box gene 9 (Sox9) mRNA in porous tantalum-chondrocyte composites.

METHODS

The articular chondrocytes were isolated from 3-week-old New Zealand immature rabbits and identified. The 2nd generation of chondrocytes with 1×10(6)/mL inoculate concentration was seeded in porous tantalum and divided into 4 groups, and control group (tantalum/chondrocyte), 50 μg/L BMP-7 group (50 μg/L BMP-7/tantalum/chondrocyte), 100 μg/L BMP-7 group (100 μg/L BMP-7/tantalum/chondrocyte), and 200 μg/L BMP-7 group (200 μg/L BMP-7/tantalum/chondrocyte). The proliferation of chondrocytes was measured by CCK-8 assay. The chondrocyte growth and morphology were observed by scanning electron microscopy (SEM). The synthesis of glycosaminoglycan (GAG) in chondrocytes was tested by dimethyl methylene blue (DMMB) colorimetric quantification method. Col-II, AGG and Sox9 mRNA in chondrocytes were detected by real-time PCR.

RESULTS

The chondrocytes were spindle-shaped in 24 hours of primary cell culture and most cells became polygonal shaped in 4 days. The chondrocytes were affirmed by alcian blue, safranin O and Col-II immunocytochemistry staining. The result of CCK-8 assay showed that the level of cell proliferation in 100 μg/L BMP-7 groups were higher than those in the other groups (P<0.05). The chondrocytes implanted into porous tantalum scaffolds with BMP-7 had better functions, by which cytoplasmic processes developed and extended to the surface and inner of porous tantalum by SEM observation. DMMB quantitative determination of GAG showed that GAG amount of chondrocytes in 100 μg/L BMP-7 groups was significantly higher than those in the other groups (P<0.05). The expressions of Col-II, AGG and Sox9 mRNA in chondrocytes were up-regulated in the experimental groups, compared with the control group and the best effect appeared when concentration of BMP-7 was 200 μg/L. (P<0.05).

CONCLUSION

BMP-7/tantalum/chondrocytes composites enhanced in vitro chondrocyte proliferation and extracellular matrix greatly, and can promote chondrogenic gene expression.

Fluxes, variability and sources of cadmium, lead, arsenic and mercury in dry atmospheric depositions in urban, suburban and rural areas

In China's largest city, Shanghai, dry deposition fluxes of Cd, Pb, As and Hg were 137, 19354, 2897 and 9.4 μgm(-2)a(-1), respectively in an urban area, intermediate in a suburban area, and 51.7, 5311, 1703 and 7.3 μgm(-2)a(-1), respectively in a rural area. Enrichment factors were Cd>Pb>As>Hg. Seasonal variations of metals differed: Pb and As were dominated by fossil fuel combustion, Cd was related to industrial pollution, and natural source controlled Hg levels.

Effect of dasatinib against thyroid cancer cell lines in vitro and a xenograft model in vivo

Tyrosine kinase inhibitors (TKIs) have emerged as a promising class of agents against thyroid cancer. The aim of the present study was to investigate the in vitro and in vivo activity of dasatinib against a panel of thyroid cancer cell lines and explore possible mechanisms of action, using various assays and western blotting. Our results showed that dasatinib exhibits prominent cytostatic activity both in vitro and in vivo against thyroid cancer cell lines with RET/PTC rearrangement (BHP2-7) and KRAS mutation (Cal62). Although dasatinib has primarily been described as an ABL/SRCfamily kinase inhibitor, the cytostatic activity observed in the present study is mediated by several off-target effects of dasatinib, some of which have not previously been reported. These effects include a reduction in phospho-FAK, FAK, RAS, Caveolin and SYK protein levels and an increase in β-catenin protein expression, which leads to the induction of senescence, an increase in the adhesiveness of the cells, a decrease in reactive oxygen species level, and changes in the expression profile of molecules involved in cellular adhesion such as integrins. Therefore, we propose that dasatinib is an effective therapeutic agent for certain patients with thyroid cancer, and these candidate patients may be identifiable on the basis of standard genotypic analyses.

Balanced Shh signaling is required for proper formation and maintenance of dorsal telencephalic midline structures

BACKGROUND

The rostral telencephalic dorsal midline is an organizing center critical for the formation of the future cortex and hippocampus. While the intersection of WNTs, BMPs, and FGFs establishes boundaries within this critical center, a direct role of Shh signaling in this region remains controversial. In this paper we show that both increased and decreased Shh signaling directly affects boundary formation within the telencephalic dorsal midline.

RESULTS

Viral over-expression of Shh in the embryonic telencephalon prevents formation of the cortical hem and choroid plexus, while expanding the roof plate. In a transgenic model where cholesterol-lacking ShhN is expressed from one allele (ShhN/+), genes expressed in all three domains, cortical hem, choroid plexus and roof plate expand. In Gli1/2 -/- mutant brains, where Shh signaling is reduced, the roof plate expands, again at the expense of cortical hem and plexus. Cell autonomous activation of Shh signaling in the dorsal midline through Gdf7-driven activated Smoothened expression results in expansion of the Wnt3a-expressing cortical hem into the plexus domain. In addition, developmental stage determines dorsal midline responsiveness to Shh.

CONCLUSIONS

Together, these data demonstrate that balanced Shh signaling is critical for maintaining regional boundaries within the dorsal midline telencephalic organizing center.

Comprehensive assessment of toxic metals in urban and suburban street deposited sediments (SDSs) in the biggest metropolitan area of China

A set of toxic metals, i.e. As, Hg, Pb, Cd, Cu, Zn, Ni and Cr, in urban and suburban SDSs were investigated comparatively in the biggest metropolitan area of China, Shanghai. Results showed that all of the metals except As were accumulated greatly, much higher than background values. Geo-accumulation index indicated that metal contamination in urban SDSs was generally heavier than that in suburban SDSs. Potential ecological risk index demonstrated that overall risks caused by metals were considerable. Cd contributed 52% to the overall risk. Multivariate statistical analysis revealed that in urban SDSs, Zn, Ni, Cd, Pb, Cu and Cr were related to traffic and industry; coal combustion led to elevated levels of Hg; soil parent materials controlled As contents. In suburban SDSs, Pb, Cu, As and Cd largely originated from traffic pollution; Zn, Ni and Cr were associated with industrial contaminants; Hg was mainly from domestic solid waste.

Synergistic antileukemic effects between ABT-869 and chemotherapy involve downregulation of cell cycle-regulated genes and c-Mos-mediated MAPK pathway

Internal tandem duplications (ITDs) of fms-like tyrosine kinase 3 (FLT3) receptor play an important role in the pathogenesis of acute myeloid leukemia (AML) and represent an attractive therapeutic target. ABT-869 has demonstrated potent effects in AML cells with FLT3-ITDs. Here, we provide further evidence that ABT-869 treatment significantly downregulates cyclins D and E but increases the expression of p21 and p27. ABT-869 induces apoptosis through downregulation of Bcl-xL and upregulation of BAK, BID and BAD. We also evaluate the combinations of ABT-869 and chemotherapy. ABT-869 demonstrates significant sequence-dependent synergism with cytarabine and doxorubicin in cell lines and primary leukemia samples. The optimal combination was validated in MV4-11 xenografts. Low-density array analysis revealed the synergistic interaction involved in downregulation of cell cycle and mitogen-activated protein kinase pathway genes. CCND1 and c-Mos were the most significantly inhibited targets on both transcriptional and translational levels. Treatment with short hairpin RNAs targeting either CCND1 or c-Mos further sensitized MV4-11 cells to ABT-869. These findings suggest that specific pathway genes were further targeted by adding chemotherapy and support the rationale of combination therapy. Thus, a clinical trial using sequence-dependent combination therapy with ABT-869 in AML is warranted.

The Evf-2 noncoding RNA is transcribed from the Dlx-5/6 ultraconserved region and functions as a Dlx-2 transcriptional coactivator

The identification of ultraconserved noncoding sequences in vertebrates has been associated with developmental regulators and DNA-binding proteins. One of the first of these was identified in the intergenic region between the Dlx-5 and Dlx-6 genes, members of the Dlx/dll homeodomain-containing protein family. In previous experiments, we showed that Sonic hedgehog treatment of forebrain neural explants results in the activation of Dlx-2 and the novel noncoding RNA (ncRNA), Evf-1. In this report, we show that the Dlx-5/6 ultraconserved region is transcribed to generate an alternatively spliced form of Evf-1, the ncRNA Evf-2. Evf-2 specifically cooperates with Dlx-2 to increase the transcriptional activity of the Dlx-5/6 enhancer in a target and homeodomain-specific manner. A stable complex containing the Evf-2 ncRNA and the Dlx-2 protein forms in vivo, suggesting that the Evf-2 ncRNA activates transcriptional activity by directly influencing Dlx-2 activity. These experiments identify a novel mechanism whereby transcription is controlled by the cooperative actions of an ncRNA and a homeodomain protein. The possibility that a subset of vertebrate ultraconserved regions may function at both the DNA and RNA level to control key developmental regulators may explain why ultraconserved sequences exhibit 90% or more conservation even after 450 million years of vertebrate evolution.

Gene structure and expression of the targeting subunit, RGL, of the muscle-specific glycogen-associated type 1 protein phosphatase, PP1G

The type I phosphatase associated with glycogen, PP1G, plays an important role in glycogen metabolism. PP1G is targeted to glycogen by the R(GL) subunit, which regulates the function of the enzyme. We report the cloning and characterization of the gene as well as the pattern of expression of the R(GL) subunit from mouse. The gene covers more than 37 kb, is composed of four exons and three introns, and codes for a 1089 residue polypeptide with a calculated molecular weight of 121,000. The amino acid sequence has 60% identity with the human and rabbit R(GL). The 5' flanking region of the gene contains a TATA box, c-Myc sites, and a potential cAMP-responsive element. Muscle specific motifs, such as MyoD and MEF-2, were also found. The A-T rich 3'-UTR contained several polyadenylation signals, two associated with poly(A) down-stream consensus motifs. ARE elements, which regulate mRNA stability, were dispersed throughout the 3'-UTR. Northern analysis of poly(A) mRNA from various murine tissues indicates a major transcript of 7.5 kb in skeletal muscle and heart. Western analysis demonstrates that R(GL) protein is present in skeletal and cardiac muscle from mouse, rat, and rabbit but not in L6 myoblasts, L6 myotubes, 3T3 L1 fibroblasts, 3T3 L1 or rat primary adipocytes, confirming that expression of the gene is specific to striated muscle. Analysis of skeletal muscle from rats made diabetic by streptozotocin treatment reveals that the level of R(GL) protein is the same as in control animals, indicating that expression is not regulated by insulin.

M-Ras/R-Ras3, a transforming ras protein regulated by Sos1, GRF1, and p120 Ras GTPase-activating protein, interacts with the putative Ras effector AF6

M-Ras is a Ras-related protein that shares approximately 55% identity with K-Ras and TC21. The M-Ras message was widely expressed but was most predominant in ovary and brain. Similarly to Ha-Ras, expression of mutationally activated M-Ras in NIH 3T3 mouse fibroblasts or C2 myoblasts resulted in cellular transformation or inhibition of differentiation, respectively. M-Ras only weakly activated extracellular signal-regulated kinase 2 (ERK2), but it cooperated with Raf, Rac, and Rho to induce transforming foci in NIH 3T3 cells, suggesting that M-Ras signaled via alternate pathways to these effectors. Although the mitogen-activated protein kinase/ERK kinase inhibitor, PD98059, blocked M-Ras-induced transformation, M-Ras was more effective than an activated mitogen-activated protein kinase/ERK kinase mutant at inducing focus formation. These data indicate that multiple pathways must contribute to M-Ras-induced transformation. M-Ras interacted poorly in a yeast two-hybrid assay with multiple Ras effectors, including c-Raf-1, A-Raf, B-Raf, phosphoinositol-3 kinase delta, RalGDS, and Rin1. Although M-Ras coimmunoprecipitated with AF6, a putative regulator of cell junction formation, overexpression of AF6 did not contribute to fibroblast transformation, suggesting the possibility of novel effector proteins. The M-Ras GTP/GDP cycle was sensitive to the Ras GEFs, Sos1, and GRF1 and to p120 Ras GAP. Together, these findings suggest that while M-Ras is regulated by similar upstream stimuli to Ha-Ras, novel targets may be responsible for its effects on cellular transformation and differentiation.

Electrophoresis of creatine kinase isoforms: a highly sensitive fluorescence scanning method

OBJECTIVE

To develop an agarose electrophoretic method for creatine kinase (CK) isoforms, using highly sensitive fluorescence scanning.

METHODS

A discontinuous buffer system was used. Electrophoresis on agarose gel was performed under constant current and low voltage. CK isoforms were separated within 30 minutes and detected by fluorescence scanning.

RESULTS

There were no significant differences when the activities of CK-MM were between 853.0 U/L and 14.0 U/L and those of CK-MB between 152.0 U/L and 2.4 U/L. The detection limits of stain method for CK-MM and CK-MB isoforms were 36.0 U/L and 12.3 U/L, respectively; while those of fluorescence method were 12.0 U/L and 2.1 U/L. The experimental results showed good precision for CK-MM isoforms, as well for CK-MB isoforms and isoenzymes.

CONCLUSION

An agarose electrophoretic method has been developed to measure CK isoenzymes and isoforms clinically. This method is rapid, simple, sensitive, highly reproducible and inexpensive. It is suitable for general laboratories.

DNA damage in rat brain cells after in vivo exposure to 2450 MHz electromagnetic radiation and various methods of euthanasia

The present study was done to confirm the reported observation that low-intensity acute exposure to 2450 MHz radiation causes DNA single-strand breaks (Lai and Singh, Bioelectromagnetics 16, 207-210, 1995). Male Sprague-Dawley rats weighing approximately 250 g were irradiated with 2450 MHz continuous-wave (CW) microwaves for 2 h at a specific absorption rate of 1.2 W/kg in a cylindrical waveguide system (Guy et al., Radio Sci. 14, 63-74, 1979). There was no associated rise in the core body temperature of the rats. After the irradiation or sham treatments, rats were euthanized by either CO2 asphyxia or decapitation by guillotine (eight pairs of animals per euthanasia group). After euthanasia the brains were removed and immediately immersed in cold Ames medium and the cells of the cerebral cortex and the hippocampus were dissociated separately and subjected to the alkaline comet assay. Irrespective of whether the rats were euthanized by CO2 asphyxia or decapitated by guillotine, no significant differences were observed between either the comet length or the normalized comet moment of cells from either the cerebral cortex or the hippocampus of sham-treated rats and those from the irradiated rats. However, the data for the rats asphyxiated with CO2 showed more intrinsic DNA damage and more experiment-to-experiment variation than did the data for rats euthanized by guillotine. Therefore, the guillotine method of euthanasia is the most appropriate in studies relating to DNA damage. Furthermore, we did not confirm the observation that DNA damage is produced in cells of the rat cerebral cortex or the hippocampus after a 2-h exposure to 2450 MHz CW microwaves or at 4 h after the exposure.

Detection of DNA damage by the alkaline comet assay after exposure to low-dose gamma radiation

The alkaline comet assay as described by Olive et al. (Exp. Cell Res. 198, 259-267, 1992) was used to detect DNA damage in cells exposed to low doses (0-5 cGy) of gamma radiation. Experiments were performed using lymphocytes isolated from whole blood of rats. The comet parameters, normalized comet moment and comet length, described by Kent et al. (Int. J. Radiat. Biol. 67, 655-660, 1995), were used as measurements of DNA damage. It was observed that the alkaline comet assay can detect DNA damage at doses as low as 0.6 cGy. The results of the experiments using low-dose gamma radiation are comparable with published results obtained using the alkaline comet assay according to the method of Singh et al. (Int. J. Radiat. Biol. 66, 23-28, 1994). Based on this observation and analysis of results published previously, we conclude that the version of the alkaline comet assay described by Olive et al. is as sensitive as other modifications of the comet assay reported in literature for the detection of DNA damage in cells exposed to low doses of ionizing radiation.

Enhanced expression of transforming growth factor-beta type I and type II receptors in wound granulation tissue and hypertrophic scar

In the present study we have analyzed and compared, by immunohistochemistry and in situ hybridization, the expression pattern of the R4/ALK5 transforming growth factor (TGF)-beta type I receptor (RI) and the TGF-beta type II receptor (RII) in normal human skin, in wounded skin at various stages during the transition of wound granulation tissue to scar, and in long-persisting post-burn hypertrophic scars. In normal human skin, expression of RI and RII was clearly visible in the epidermis, in epidermal appendages, and in vascular cells, although only a small number of dermal fibroblasts revealed detectable levels of TGF-beta receptor expression. In contrast, granulation tissue fibroblasts showed strong expression of both TGF-beta receptor types, although in normal-healing excisional wounds their density decreased during granulation tissue remodeling. However, in post-burn hypertrophic scars, RI- and RII-overexpressing fibroblasts were found in high densities up to 20 months after injury. From these findings we suggest that the repair process of deep wounds involves the transformation of a subset of fibroblastic cells toward an increased TGF-beta responsiveness and a transient accumulation of these cells at the wound site. In addition, our study provides evidence that excessive scarring is associated with a failure to eliminate TGF-beta receptor-overexpressing fibroblasts during granulation tissue remodeling, which leads to a persistent autocrine, positive feedback loop that results in over-production of matrix proteins and subsequent fibrosis.

Studies on the creatine kinase MM isoforms of normal and Duchenne muscular dystrophic patients

OBJECTIVE

To study the changes of creatine kinase MM (CK-MM) isoforms in Duchenne muscular dystrophy (DMD) patients.

METHODS

Serum samples from 49 DMD patients and 40 control subjects were collected for CK-MM isoforms measurement. CK-MM isoforms were separated within 30 minutes by electrophoresis on agarose gel with a discontinuous buffer system at constant current of 30 mA and low voltage of 200-300 V, then measured by fluorescence scanning.

RESULTS

Significant differences of MM2/MM1 ratio were found between DMD patients and control subjects (P < 0.05) as well as among the three different age groups of DMD patients (P < 0.05).

CONCLUSIONS

CK-MM isoforms may present useful information for the early diagnosis and evaluation of DMD and the ratio of MM2/MM1 can be considered as a specific indicator of the degree of seriousness for DMD patients.