[The beginnings and evolution of a pancreatic surgeon: a technical morphological analysis in first 5 years].

Objective: To explore the development of the pancreatic surgeon technique in a high-volume center. Methods: A total of 284 cases receiving pancreatic surgery by a single surgeon from June 2015 to December 2020 were retrospectively included in this study. The clinical characteristics and perioperative medical history were extracted from the medical record system of Zhongshan Hospital,Fudan University. Among these patients,there were 140 males and 144 females with an age (M (IQR)) of 61.0 (16.8) years(range: 15 to 85 years). The "back-to-back" pancreatic- jejunal anastomosis procedure was used to anastomose the end of the pancreas stump and the jejunal wall. Thirty days after discharge,the patients were followed by outpatient follow-up or telephone interviews. The difference between categorical variables was analyzed by the Chi-square test or the CMH chi-square test. The statistical differences for the quantitative data were analyzed using one-way analysis of variance or Kruskal-Wallis H test and further analyzed using the LSD test or the Nemenyi test,respectively. Results: Intraoperative blood loss in pancreaticoduodenectomy between 2015 and 2020 were 300,100(100),100(100),100(0),100(200) and 150 (200) ml,respectively. Intraoperative blood loss in distal pancreatectomy was 250 (375),100 (50),50 (65), 50 (80),50 (50),and 50 (100) ml,respectively. Intraoperative blood loss did not show statistical differences in the same operative procedure between each year. The operative time for pancreaticoduodenectomy was respectively 4.5,5.0(2.0),5.5(0.8),5.0(1.3),5.0(3.3) and 5.0(1.0) hours in each year from 2015 to 2020,no statistical differences were found between each group. The operating time of the distal pancreatectomy was 3.8 (0.9),3.0 (1.5),3.0 (1.8),2.0 (1.1),2.0 (1.5) and 3.0(2.0) hours in each year,the operating time was obviously shorter in 2018 compared to 2015 (P=0.026) and 2020 (P=0.041). The median hospital stay in 2020 for distal pancreatectomy was 3 days shorter than that in 2019. The overall incidence of postoperative pancreatic fistula gradually decreased,with a incident rate of 50.0%,36.8%,31.0%,25.9%,21.1% and 14.8% in each year. During this period,in a total of 3,6,4,2,0 and 20 cases received laparoscopic operations in each year. The incidence of clinically relevant pancreatic fistula (grade B and C) gradually decreased,the incident rates were 0,4.8%,7.1%,3.4%,4.3% and 1.4%,respectively. Two cases had postoperative abdominal bleeding and received unscheduled reoperation. The overall rate of unscheduled reoperation was 0.7%. A patient died within 30 days after the operation and the overall perioperative mortality was 0.4%. Conclusion: The surgical training of a high-volume center can ensure a high starting point in the initial stage and steady progress of pancreatic surgeons,to ensure the safety of pancreatic surgery.

[High-throughput texture analysis in the distinction of single metastatic brain tumors from high-grade gliomas].

Objective: To explore the feasibility of high-throughput texture analysis in the distinction of single brain metastases (SBM) from high-grade gliomas (HGG) and validate the established model. Methods: A total of 86 patients who were histologically diagnosed with SBM or HGG were retrospectively collected, including 43 patients with SBM and 43 with HGG. All of patients were performed preoperative conventional head magnetic resonance imaging (MRI) scans. A total of 236 fluid-attenuated inversion recovery (FLALR) images containing the information of tumors were selected from the MRI images and each image was considered as an object. The training set had 200 images, including 106 from SBM group and 94 from HGG group, whereas the validation set had 36 images, including 19 from SBM group and 17 from HGG. After images preprocessing, images segmentation, features extraction, and features selection, a radiomic diagnostic model was finally established using the training set. The diagnostic performance of the diagnostic model was evaluated using a receiver operating characteristic (ROC) curve. Hierarchical clustering analysis was used to evaluate the quality of the extracted feature data and the classification effect of the model. The model was further validated using the independent validation set. Results: A total of 629 features were extracted and quantified from each sample, and 41 features were selected to establish feature subsets and the diagnostic model. The classification decision function of the model is f(x)=sign■ and the kernel function of the model is K(x, x(i))=exp■. In the training set, the diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive value were 0.845, 0.849, 0.840, 0.857 and 0.832, respectively. The area under the ROC curve reached to 0.939. Similar results were obtained in the validation set. Conclusion: The high-throughput texture analysis shows high accuracy in differentiating SBM from HGG.

A literature review of antithrombotic and anticoagulating agents on sexual function.

Although millions of people receive antithrombotic agents (ATAs) or anticoagulating agents (ACAs) for vascular prophylaxis daily, the negative impact of these agents on sexual function has not been systematically studied. Therefore, a literature search was conducted to determine the effects of the marketed ATAs and ACAs on sexual function. In regard to men, the results show that thienopyridine derivatives increase the risk of erectile dysfunction (ED) and decrease libido and sexual function. The relationship between aspirin use and ED is inconsistent, ranging from a moderate risk to beneficial effects. Nonetheless, aspirin appears to result in a lower risk for ED than does clopidogrel, and seems to benefit patients with lithium-induced ED. Coumarin can cause vasculogenic priapism. In regard to women, only a single report of genital haemorrhage was found. Available data exclusively focus on male subjects. Taken together, ATAs and ACAs can disturb sexual function in different aspects in men. Newer thienopyridine derivatives, such as prasugrel or ticagrelor, may be used as a substitute for clopidogrel when sexual dysfunction occurs. Priapism and genital haemorrhage were found to be uncommon but serious complications of ACA treatment. Additional studies examining the effects of ATAs and ACAs on sexual function are needed, especially in woman and elderly.

[Clinical value of classified detection of circulating tumor cells in peripheral blood of NSCLC patients].

OBJECTIVE: To investigate the clinical value of detection of circulating tumor cells (CTCs) classified by epithelial cell adhesion molecule (EpCAM) in peripheral blood of patients with non-small cell lung cancer (NSCLC). METHODS: Peripheral blood samples (7.5 ml each time) were collected from 47 NSCLC patients. Among them, blood samples were collected at the end of each therapy-cycle in three patients for longitudinal monitoring of CTCs. CTCs were enriched by the depletion of leucocytes using a magnetic bead separation technique, stained with EpCAM, cytokeratin 7/8 and their isotypic control antibodies, respectively, and then identified and counted by multi-parameter flow cytometry. RESULTS: In the blood samples from 47 patients, EpCAM-positive CTCs were detected in 64.3%(9/14), 40.0%(4/10) and 43.5%(10/23) of patients in stages Ⅰ-Ⅱ, Ⅲ and Ⅳ, respectively. EpCAM-negative CTCs were detected in 78.6%(11/14), 90.0%(9/10) and 91.3%(21/23) of patients in stage Ⅰ-Ⅱ, Ⅲ, and Ⅳ, respectively. The total detection rates of EpCAM-positive and EpCAM-negative CTCs were 48.9%(23/47) and 87.2%(41/47), respectively, showing a statistically significant difference between them (P<0.001). According to the stage of the cancer, there was a significant difference between the detection rates of the two types of CTCs in patients of stage Ⅳ(P=0.001), but not in stage Ⅰ-Ⅱ and Ⅲ (P>0.05). The number of EpCAM-negative CTCs was significantly higher than that of EpCAM-positive CTCs in all stages (P<0.05). The frequency of patients with the percentage of EpCAM-negative CTCs >90% was significantly higher in stage Ⅳ patients than that in stage Ⅰ-Ⅱ cases (P=0.030), while the frequency of patients with the percentage of EpCAM-negative CTCs between 50%~90% was significantly lower in the stage Ⅳ than that in the stage Ⅰ-Ⅱ patients (P=0.001). The treatment of most patients with EpCAM-negative CTCs >50% showed to be ineffective (P=0.033). CONCLUSION: Detection of CTCs classified by EpCAM in peripheral blood is helpful in evaluating the distant metastasis and treatment effectiveness of NSCLC patients.

Seasonal variation and source apportionment of organic tracers in PM10 in Chengdu, China.

Organic compound tracers including n-alkanes, triterpane, sterane, polycyclic aromatic hydrocarbons (PAHs) and dicarboxylic acids of airborne particulate matter (PM10) were characterized for samples collected at five sites from July 2010 to March 2011 using GC/MS. Spatial and temporal variations of these organic tracers in PM10 were studied, and their sources were then identified respectively. Average daily concentrations of PM10 varied in different seasons with the trend of PM10 in winter (0.133 mg/m(3)) > autumn (0.120 mg/m(3)) > spring (0.103 mg/m(3)) > summer (0.098 mg/m(3)). Daily concentrations of n-alkanes (C11-C36) ranged from 12.11 to 163.58 ng/m(3) with a mean of 61.99 ng/m(3). The C max and CPI index of n-alkanes indicated that vehicle emissions were the major source in winter, while the contributions of high plant wax emissions became significant in other seasons. It was discovered that the main sources of triterpenoid and steranes were gasoline and diesel engine emissions. Concentrations of ∑15PAHs in PM10 also varied (12.25-58.56 ng/m(3)) in different seasons, and chrysene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi) perylene and fluoranthene were the dominant components. In the four seasons, the concentration of ∑15PAHs was relatively higher at the northern site because of traffic congestion. The main source of airborne PAHs was traffic emissions and coal combustion. Average daily concentrations of dicarboxylic acids (C4-C10) in PM10 ranged from 12.11 to 163.58 ng/m(3), of which azeleic acid was the major compound (0.49-52.04 ng/m(3), average 14.93 ng/m(3)), followed by succinic acid (0.56-19.08 ng/m(3), average 6.84 ng/m(3)). The ratio of C6/C9 showed that the major source in winter was biological, while the contributions of emissions from anthropogenic activities were much higher in summer.

Long-distance measurement-device-independent quantum key distribution with coherent-state superpositions.

Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method that gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long-distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.

Effects of curcumin on hippocampal expression of NgR and axonal regeneration in Aß-induced cognitive disorder rats.

Curcumin has been widely used for the prevention and treatment of Alzheimer's disease (AD), but its mechanism is still not clear. Inhibitory factors of axonal regeneration have been shown to cause a series of pathophysiological changes in the early period of AD. In this study, the co-receptor (Nogo receptor; NgR) of three axonal growth-inhibitory proteins was examined, and effects of curcumin on spatial learning and memory abilities and hippocampal axonal growth were investigated in amyloid ß-protein (Aß)1-40-induced AD rats. Results showed that the expression of NgR in the AD group significantly increased and the number of axonal protein-positive fibers significantly reduced. The spatial learning and memory abilities of AD rats were significantly improved in the curcumin group. Furthermore, hippocampal expressions of NgR mRNA and protein decreased, and the expression of axonal protein significantly increased. There was a negative correlation between the expression of NgR and axonal growth. Together, these results suggested that curcumin could improve the spatial learning and memory abilities of AD rats. The mechanism might be related with its lowering of hippocampal NgR expression and promoting axonal regeneration.

Nummular headache after trans-sphenoidal surgery: a referred pain-based headache syndrome.

Nummular headache (NH) is a newly categorized primary headache characterized by a consistent location, shape and size of painful area in each attack. The etiopathogenesis is entirely unknown. Currently, the peripheral theory of epicranial neuralgia is accepted more widely than the central theory but it cannot fully explain the clinical picture. We report a patient who suffered from a relapsing and remitting course of NH at the high parietal area and vertex shortly after resection for pituitary prolactinoma via a trans-sphenoidal approach. There was no focal trophic change or paresthesia but a mild allodynia in the painful area. The patient did not exhibit trigeminal sensory disorder or cranial trauma thoroughly. The pain responded well to gabapentin. Therefore, physicians should be aware of postoperative NH, which is amenable to treatment. The findings in our patient support a dual mechanism of NH and suggest that central NH is a form of referred pain.

[Evaluation of effects of comprehensive intervention based on key persons on AIDS-related high-risk behaviors in male sex workers in entertainment venues].

Objective: To evaluate the effect of comprehensive intervention model based on key persons in entertainment venues on the incidence of AIDS-related high-risk behaviors in male sex workers (MSW). Data from this study thus can be used to provide compelling evidence for the wider implementation of the intervention model. Methods: In this randomized controlled trial, MSW were recruited and followed-up from May to December, 2021 in entertainment venues in Wuxi, Jiangsu Province, with an estimated sample size of 320. The MSW in the intervention group were provided with comprehensive interventions via key persons in entertainment venues compared with the control group receiving routine interventions. The effect of the intervention model was assessed by comparing the behavioral differences between these two groups and in the intervention group before and after intervention. Results: A total of 330 MSW were recruited at baseline survey, in which 168 were divided into intervention group and 162 into control group. There was no significant difference in socio-demographic characteristics between two groups (all P>0.05). After intervention for 6 months, the rate of consistent condom use in commercial homosexual activities in the intervention group was 79.5% (101/127), higher than 63.2% (74/117) in the control group, and in the intervention group, 90.1% (73/81) of MSW used condom consistently in heterosexual activities, higher than in the control group (59.6%, 59/99) . Compared with 30.8% (36/117) of MSW with drug abuse history in the control group, a lower proportion of 9.4% (12/127) was observed in the intervention group. Differences in all of aforementioned variables were significant (all P<0.05). After intervention, the incidence of group sex was 3.9% (5/127) in the intervention group and 9.4% (11/117) in the control group, the incidence of anal sex post-alcohol consumption was 40.2% (51/127) in the intervention group and 32.5% (38/117) in control group, the differences were not significant (all P>0.05). Conclusions: The intervention model based on key persons in entertainment venues could promote consistent condom use in MSW in both commercial homosexual and heterosexual activities and help them reduce drug abuse, but had no significant effect on decreasing group sex and anal sex after alcohol consumption. It is crucial to improve the intervention model according to the specific characteristics of MSW in order to enhance the effects of comprehensive intervention.

Acute isolated orchalgia as the initial symptom in thoracic cord disorder: 2 case report and literature review.

INTRODUCTION: Orchalgia is a common andrological disorder and usually results from pathognomonic change of testes and regional structures. However, responsible cause is still unknown in more than one-fourth of patients. METHODS: We report two men who initially suffered an acute, isolated orchalgia and posteriorly complicated with paraparesis. They had previous history of prostate cancer and cervical myelitis. The urological examination was negative in both of them. Finally, prostate cancer metastasis and recurrent myelitis at T2/3 level was identified, respectively. Although their orchalgia progressively subsided, their urological, sexual and neurological dysfunction persisted. CONCLUSIONS: In the literature, the responsible pathology of spinal orchalgia was exclusively found below T10 level, frequently delaying affirmative diagnosis. Therefore, a thorough evaluation of spinal cord above T10 level should be alerted for idiopathic orchalgia with a pre-existing history or risk of spinal cord disorder and a negative urological examination.

Actin monomer binding proteins.

Small actin monomer binding proteins are essential components of the actin polymerization machinery. Originally thought of as passive buffers that prevent polymerization of actin monomers, recent discoveries elucidate how some actin monomer binding proteins can promote as well as inhibit polymerization, and how they cooperate to regulate actin assembly.

[Isolation and characterization of twenty-one polymorphic microsatellite loci in the Tibetan macaque (Macaca thibetana)].

Twenty-one microsatellite loci were isolated from AC-enriched library of Tibetan macaque (Macaca thibetana). The number of alleles at the 21 microsatellite loci ranged from 8 to 15, with an average of 12.2 per locus. Polymorphism information content (PIC) ranged from 0.805 to 0.910 with an average of 0.873. The observed and expected heterozygosities ranged from 0.208 to 0.792 and from 0.843 to 0.938, respectively. These microsatellite loci will be useful for future studies that relate to the genetic diversity and population structure of Tibetan macaque.

Reversibility of gelsolin/actin interaction in macrophages. Evidence of Ca2+-dependent and Ca2+-independent pathways.

We have developed an immunoadsorption technique for quantitating EGTA-resistant gelsolin/actin complexes in macrophages extracted with Triton X-100. We report here that the proportion of gelsolin complexed irreversibly to actin is low in freshly harvested macrophages. The amount of the EGTA-resistant complex increases spontaneously during incubation of the cells in suspension at 37 degrees C, or after exposure to the Ca2+ ionophore ionomycin. On the other hand, exposure of suspended cells to the chemotactic oligopeptide, FMLP, or plating of the cells onto tissue culture dishes causes the EGTA-resistant complex to dissociate rapidly. Plating even prevents Ca2+ ionomycin-treated cells with elevated intracellular Ca2+ from inducing this complex. Therefore, our results suggest that macrophages possess a mechanism, not directly involving Ca2+, for dissociating actin/gelsolin EGTA-resistant complexes. This mechanism may be a Ca2+-independent signal for leukocyte activation.

[HIV infection and associated factors of male sex workers among men who have sex with men].

Objective: This study aimed to discover the HIV infection and associated factors among male sex workers (MSW) who provide sexual services for men. Data from this study thus can be used to provide evidence for designing related intervention programs. Methods: In this observational study, MSW were recruited from May to July, 2019 in KTV venues in Wuxi, China. A questionnaire was used to collect information with blood sample collected and tested for HIV and syphilis. EpiData 3.0 and SPSS 17.0 software were used to clean up data and statistical analysis. Results: A number of 500 MSW were involved including 243 (48.6%) heterosexual and 257 (51.4%) homosexual MSW. The overall HIV prevalence was 5.4%(27/500) among all the MSW. there were significant differences between the HIV prevalence rates, the heterosexual MSW (3.3%, 8/243) and the homosexual MSW (7.4%, 19/257)(χ(2)=4.112, P=0.043). In the past 3 months, 28.0% (72/257) of the homosexual MSW mainly engaged in receptive anal sex which was higher than 11.5%(28/243) of the heterosexual MSW. Compared to 15.6% (40/257) of the homosexual MSW who engaged in heterosexual behavior, a higher proportion of 98.4% (239/243) was noticed among the heterosexual MSW. Higher percentage (44.9%, 109/243) appeared among the heterosexual MSW who had not been tested for HIV than the homosexual MSW (20.6%, 53/257). Results from logistic regression multivariate analysis showed that age ≥30 (aOR=7.54, 95%CI: 2.53-37.11), having unprotected anal sexual practice (aOR=3.76, 95%CI:1.15-12.23), having anal sex after drinking alcohol (aOR=10.91, 95%CI: 2.29-51.87) and syphilis tested positive (aOR=8.23, 95%CI:1.29-52.51) were risk factors associated with HIV infection among the heterosexual MSW. Having unprotected anal sexual behavior (aOR=2.94, 95%CI: 1.17-7.37), having group anal sex (aOR=4.08, 95%CI:1.05-15.81), without record on HIV testing (aOR=6.58, 95%CI: 2.01-18.06) and syphilis tested positive (aOR=4.55, 95%CI: 1.15-18.06) were risk factors associated with HIV among the homosexual MSW. Conclusions: High HIV prevalence was discovered among both heterosexual and homosexual MSW in Wuxi, China. Differences in sexual behaviors between these two groups should be considered when designing targeted HIV intervention programs for these populations.

[Study on HIV testing behavior among men who have sex with men based on structural equation model].

Objective: To analyze HIV testing behaviors and associated factors in men who have sex with men (MSM) and provide evidence for making intervention on promoting HIV testing. Methods: Our observational study was conducted between April and June, 2018 in Wuxi, Jiangsu province in MSM. A self-completed questionnaire was used to collect the information about their socio-demographic characteristics, sexual behaviors, acceptance of intervention services, psychological status and HIV testing behaviors. Structural equation model (SEM) was chosen to fit data and the model was modified to analyze the relationships between variables. Results: A total of 410 MSM were enrolled in our study, among whom 72.9%(299/410) were aware of the necessity of HIV testing and 69.0%(283/410) reported having HIV tests in the last year. A modified structural equation model presented good fitting results with fitting index of root mean square error of approximation (RMSEA)was 0.065, normed fit index (NFI) was 0.946, relative fit index (RFI) was 0.922, Tucker-Lewis index (TLI) was 0.968 and comparative fit index (CFI) was 0.952. Results of SEM showed that intervention service was the factor with the largest standardized total effect value of 0.57 associated with HIV testing behaviors among MSM. Among intervention services, HIV testing reminding had the biggest factor loading of 0.88. Psychological status scores played a negative role in HIV testing behaviors among MSM with the path coefficient value of -0.33. Conclusions: The awareness and testing rate of HIV among MSM population need to be further improved. While effective measures are implemented to promote HIV testing among MSM, more attention should be paid to the mental health problems of MSM.

Genomic organization and biosynthesis of secreted and cytoplasmic forms of gelsolin.

Gelsolin is an actin regulatory protein which is unique among vertebrates in that it is found as both an intrinsic cytoplasmic protein and as a secreted plasma protein. We demonstrate that plasma and cytoplasmic gelsolins are derived by alternative transcriptional initiation sites and message processing from a single gene 70 kb long, containing at least 14 exons. Their message and amino acid sequences are identical except at the 5' end/NH2 termini. The cytoplasmic-specific 5' sequence is derived from two exons that encode untranslated sequence, while the plasma message-specific 5' sequence is derived from a single exon that encodes untranslated sequence, the signal peptide, and the first 21 residues of the plasma protein. The two transcriptional initiation sites are separated by greater than or equal to 32 kb. Biosynthetic and RNase protection studies indicate that a number of cell types make both plasma and cytoplasmic gelsolin in widely varying amounts and ratios.

Identification of a polyphosphoinositide-modulated domain in gelsolin which binds to the sides of actin filaments.

Gelsolin is a Ca2+- and polyphosphoinositide-modulated actin-binding protein which severs actin filaments, nucleates actin assembly, and caps the "barbed" end of actin filaments. Proteolytic cleavage analysis of human plasma gelsolin has shown that the NH2-terminal half of the molecule severs actin filaments almost as effectively as native gelsolin in a Ca2+-insensitive but polyphosphoinositide-inhibited manner. Further proteolysis of the NH2-terminal half generates two unique fragments (CT14N and CT28N), which have minimal severing activity. Under physiological salt conditions, CT14N binds monomeric actin coupled to Sepharose but CT28N does not. In this paper, we show that CT28N binds stoichiometrically and with high affinity to actin subunits in filaments, suggesting that it preferentially recognizes the conformation of polymerized actin. Analysis of the binding data shows that actin filaments have one class of CT28N binding sites with Kd = 2.0 X 10(-7) M, which saturates at a CT28N/actin subunit ratio of 0.8. Binding of CT28N to actin filaments is inhibited by phosphatidylinositol 4,5-bisphosphate micelles. In contrast, neither CT14N nor another actin-binding domain located in the COOH-terminal half of gelsolin form stable stoichiometric complexes with actin along the filaments, and their binding to actin monomers is not inhibited by PIP2. Based on these observations, we propose that CT28N is the polyphosphoinositide-regulated actin-binding domain which allows gelsolin to bind to actin subunits within a filament before serving.

Identification of gelsolin, a Ca2+-dependent regulatory protein of actin gel-sol transformation, and its intracellular distribution in a variety of cells and tissues.

Antiserum prepared against gelsolin, a major Ca2+-dependent regulatory protein of actin gel-sol transformation in rabbit lung macrophages, was used to detect the presence of proteins immunologically related to gelsolin in a variety of cells and tissues. Cell extracts were electrophoresed on polyacrylamide gels, and replicas of the gels on cellulose nitrate paper were stained by an indirect immunohistochemical technique. A single band of crossreactive material which comigrates with macrophage gelsolin is found in at least nine different kinds of cells and tissues derived from rabbits and humans and in four lines of cultured cells from humans and rats. Gelsolin was also identified in human serum and plasma, raising the possibility that it may contribute to the clearance of actin from the circulatory system. Using this antiserum, we demonstrated, by indirect immunofluorescent staining of acetone-fixed macrophages and polymorphonuclear leukocytes, that gelsolin resides in the cortical cytoplasm and that during phagocytosis it is concentrated in pseudopodia engulfing particles to be ingested, an area of the cytoplasm actively engaged in movement. In longitudinal cryostat sections of contracted rabbit skeletal muscle, antigelsolin staining was associated with the I-band of the myofibril, suggesting that it may be involved, by an as yet undefined mechanism, in skeletal muscle function. In rabbit intestinal epithelial cells, gelsolin was associated with the cytoplasm and the terminal web region of the brush border, a localization distinct from that previously reported for villin, a structurally and functionally similar protein isolated from the brush borders of chicken intestinal epithelial cells. In conclusion, our findings support the idea that gelsolin is involved in the regulation of movement and suggest that gelsolin-mediated Ca2+-regulation of actin cytoskeletal structure, first characterized in macrophages, may be of general importance.

The actin filament-severing domain of plasma gelsolin.

Gelsolin, a multifunctional actin-modulating protein, has two actin-binding sites which may interact cooperatively. Native gelsolin requires micromolar Ca2+ for optimal binding of actin to both sites, and for expression of its actin filament-severing function. Recent work has shown that an NH2-terminal chymotryptic 17-kD fragment of human plasma gelsolin contains one of the actin-binding sites, and that this fragment binds to and severs actin filaments weakly irrespective of whether Ca2+ is present. The other binding site is Ca2+ sensitive, and is found in a chymotryptic peptide derived from the COOH-terminal two-thirds of plasma gelsolin; this fragment does not sever F-actin or accelerate the polymerization of actin. This paper documents that larger thermolysin-derived fragments encompassing the NH2-terminal half of gelsolin sever actin filaments as effectively as native plasma gelsolin, although in a Ca2+-insensitive manner. This result indicates that the NH2-terminal half of gelsolin is the actin-severing domain. The stringent Ca2+ requirement for actin severing found in intact gelsolin is not due to a direct effect of Ca2+ on the severing domain, but indirectly through an effect on domains in the COOH-terminal half of the molecule to allow exposure of both actin-binding sites.