EGF receptor signaling stimulates SRC kinase phosphorylation of clathrin, influencing clathrin redistribution and EGF uptake

Epidermal growth factor (EGF) binding to its receptor causes rapid phosphorylation of the clathrin heavy chain at tyrosine 1477, which lies in a domain controlling clathrin assembly. EGF-mediated clathrin phosphorylation is followed by clathrin redistribution to the cell periphery and is the product of downstream activation of SRC kinase by EGF receptor (EGFR) signaling. In cells lacking SRC kinase, or cells treated with a specific SRC family kinase inhibitor, EGF stimulation of clathrin phosphorylation and redistribution does not occur, and EGF endocytosis is delayed. These observations demonstrate a role for SRC kinase in modification and recruitment of clathrin during ligand-induced EGFR endocytosis and thereby define a novel effector mechanism for regulation of endocytosis by receptor signaling.

High glucose-induced apoptosis in human endothelial cells is mediated by sequential activations of c-Jun NH(2)-terminal kinase and caspase-3

BACKGROUND

Diabetes mellitus causes multiple cardiovascular complications. High glucose can induce reactive oxygen species and apoptosis in endothelial cells. Little is known about the molecular mechanisms in high glucose-induced endothelial cell apoptosis.

METHODS AND RESULTS

We elucidated the signaling pathway of high glucose-induced apoptosis in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with media containing 5.5, 19, or 33 mmol/L of glucose in the presence or absence of an antioxidant, ascorbic acid. The level of intracellular H(2)O(2) was measured by flow cytometry. For detection of apoptosis, the cell death detection ELISA assay and the morphological Hoechst staining were used. High glucose was capable of inducing the activity of c-Jun NH(2)-terminal kinase (JNK) but not extracellular signal-regulated kinase 1/2 or p38 mitogen-activated protein kinase during the treatment periods, as evidenced by immunocomplex kinase assay. Moreover, we found that the interleukin 1beta-converting enzyme (ICE)/CED-3 family protease (caspase-3) became activated in high glucose-induced apoptosis. Caspase-3/CPP32-specific inhibitor, Ac-DEVD-CHO, could inhibit high glucose-induced apoptosis. Furthermore, we found that JNK1 specific antisense oligonucleotide could suppress caspase-3 activity but not affect H(2)O(2) generation and could block apoptosis induced by high glucose. Also, H(2)O(2) generation, JNK activity, caspase-3 activity, and the subsequent apoptosis induced by high glucose could be suppressed by ascorbic acid.

CONCLUSIONS

The present study indicates that reactive oxygen species induced by high glucose may be involved in JNK activation, which in turn triggers the caspase-3 that facilitates the apoptosis in HUVECs.

Arthroscopically assisted rotator cuff repair: correlation of functional results with integrity of the cuff

Thirty-three patients (35 full-thickness rotator cuff tears) who underwent arthroscopically assisted mini open repair between June 1987 and January 1990 were evaluated for shoulder function and cuff integrity. The study population was composed of 19 women and 14 men with an average age of 63 years (range 35-76) and an average follow-up of 3.7 years (range 2.5-5.1). Functional results were obtained using the UCLA Shoulder Rating Scale. Integrity of the rotator cuff was established by shoulder arthrography at a minimum 2 years postoperatively. UCLA Shoulder Rating Scale showed 86% good/excellent results with 92% patient satisfaction. The shoulder arthrography showed 12 (34%) full-thickness tears, seven (20%) partial tears, and 16 (46%) no tears. The size of the arthrographic defect correlated well with the size of the intraoperative tear. Seventy percent of the large tears had follow-up full-thickness defects and 80% of the small tears had no defect. Eighty percent and 88% good/excellent functional results were achieved in patients with full-thickness defects and no defects, respectively, without significant differences. The size of the tear at the time of the repair is a major determinant of the integrity of the cuff after repair. The integrity of the cuff at follow-up does not determine the functional outcome of the operated shoulder.

Interactions between HIV1 Nef and vacuolar ATPase facilitate the internalization of CD4

CD4 is the primary receptor for the human immunodeficiency virus (HIV). Nef is an accessory protein of HIV that decreases the expression of CD4 on the surface of infected cells. In this study, we identified the Nef binding protein 1 (NBP1), which interacts specifically with Nef in vitro and in vivo. Since it shares sequence similarity with the catalytic subunit of the vacuolar ATPase (V-ATPase) and complements the loss of this VMA13 gene in yeast, NBP1 is the human homolog of Vma13p. Direct interactions between Nef and NBP1 were correlated with the ability of Nef to internalize CD4. The expression of the antisense NBP1 abrogated these effects. We conclude that NBP1 helps to connect Nef with the endocytic pathway.

Primary immunolocalization of estrogen and progesterone target cells in the human anterior cruciate ligament

To identify estrogen and progesterone target cells in the human anterior cruciate ligament immunohistochemical localization of both estrogen and progesterone receptors was performed in 17 specimens of human anterior cruciate ligament. All ligament specimens were obtained at surgery. Thirteen specimens were from women, and four were from men: the average age was 57 years (range, 18-78 years). Eleven specimens (from nine women and two men) came from total knee replacements for osteoarthritis of the knee: three (from two women and one man), from reconstructions of the anterior cruciate ligament: two (both from women), from medial meniscectomies; and one (from a man), from an amputation secondary to chondrosarcoma of the pelvis. An immunoperoxidase method using monoclonal antibodies to the estrogen and progesterone receptors was employed to identify estrogen and progesterone target cells in the anterior cruciate ligament. Staining of both receptors was demonstrable in 14 specimens and in the remaining three specimens less than 15% of the cells were stained. Both estrogen and progesterone receptors were localized to synoviocytes in the synovial lining, fibroblasts in the anterior cruciate ligament stroma and cells in the blood vessel walls of the ligament. This demonstration of receptors for estrogen and progesterone in the cells of anterior cruciate ligament suggests that female sex hormones may have an effect on its structure and composition.

Estrogen affects the cellular metabolism of the anterior cruciate ligament. A potential explanation for female athletic injury

Investigations from this laboratory have established the presence of estrogen receptors in the human anterior cruciate ligament. This study further investigates the effects of 17 beta-estradiol on the cellular proliferation and collagen synthesis of fibroblasts derived from the rabbit anterior cruciate ligament. Fibroblast proliferation and collagen synthesis in response to near log concentrations of 17 beta-estradiol (at 0.0029, 0.025, 0.25, 2.5, and 25 ng/ml) were assessed by measuring [3H]thymidine and [14C]hydroxyproline incorporation, respectively. Collagen synthesis was significantly reduced with increasing local estradiol concentration (P < 0.001). Declining collagen synthesis was first noted at a 17 beta-estradiol concentration of 0.025 ng/ml. Within normal physiologic levels of estrogen (0.025 to 0.25 ng/ml), collagen synthesis was reduced by more than 40% of control, and at pharmacologic levels of 2.5 and 25 ng/ml, by more than 50% of control. A significant reduction of fibroblast proliferation was also observed with increasing estradiol concentrations (P = 0.023). Clinically, alterations in anterior cruciate ligament cellular metabolism caused by estrogen fluctuations may change the composition of the ligament, rendering it more susceptible to injury.

Amino acid sequence and domain structure of entactin. Homology with epidermal growth factor precursor and low density lipoprotein receptor

Entactin (nidogen), a 150-kD sulfated glycoprotein, is a major component of basement membranes and forms a highly stable noncovalent complex with laminin. The complete amino acid sequence of mouse entactin has been derived from sequencing of cDNA clones. The 5.9-kb cDNA contains a 3,735-bp open reading frame followed by a 3'-untranslated region of 2.2 kb. The open reading frame encodes a 1,245-residue polypeptide with an unglycosylated Mr of 136,500, a 28-residue signal peptide, two Asn-linked glycosylation sites, and two potential Ca2+-binding sites. Analysis of the deduced amino acid sequence predicts that the molecule consists of two globular domains of 70 and 36 kD separated by a cysteine-rich domain of 28 kD. The COOH-terminal globular domain shows homology to the EGF precursor and the low density lipoprotein receptor. Entactin contains six EGF-type cysteine-rich repeat units and one copy of a cysteine-repeat motif found in thyroglobulin. The Arg-Gly-Asp cell recognition sequence is present in one of the EGF-type repeats, and a synthetic peptide from the putative cell-binding site of entactin was found to promote the attachment of mouse mammary tumor cells.

Inhibition of hepatitis B virus by a novel L-nucleoside, 2'-fluoro-5-methyl-beta-L-arabinofuranosyl uracil

2'-Fluoro-5-methyl-beta-L-arabinofuranosyl uracil (L-FMAU) was discovered to have potent antiviral activity against hepatitis B virus (HBV). L-FMAU was more potent than its D-enantiomer and produced dose-dependent inhibition of the viral DNA replication in 2.2.15 cells (human HepG2 cells with the HBV genome), with a 50% inhibitory concentration of 0.1 microM. There was no inhibitory effect on HBV transcription or protein synthesis. In the 2.2.15 cell system, L-FMAU did not show any toxicity up to 200 microM, whereas the D-enantiomer was toxic, with a 50% inhibitory concentration of 50 microM. Repeated treatments of HepG2 cells with L-FMAU at a 1 microM concentration for 9 days did not result in any decrease in the total mitochondrial DNA content, suggesting that a mode of toxicity similar to that produced by 2',3'-dideoxycytidine is unlikely. Also at concentrations as high as 200 microM, L-FMAU did not adversely affect mitochondrial function as determined by lactic acid production by L-FMAU-treated hepatoma cells. L-FMAU was metabolized in the cells to its mono-, di-, and triphosphates, A dose-dependent inhibition of HBV DNA synthesis by L-FMAU triphosphate was observed in the DNA polymerase assays with isolated HBV particles, suggesting that the mode of action of this compound could involve viral polymerase. However, L-FMAU was not incorporated into the cellular DNA. Considering the potent inhibition of the viral DNA synthesis and the nontoxicity of L-FMAU towards the host DNA synthetic machinery, this compound should be further explored for development as asn anti-HBV drug.

Regulation of clathrin assembly and trimerization defined using recombinant triskelion hubs

Clathrin polymerization into a polyhedral vesicle coat drives receptor sorting at cellular membranes during endocytosis and organelle biogenesis. To study clathrin self-assembly, we expressed the C-terminal third of the clathrin heavy chain in bacteria. The recombinant fragment trimerized, bound clathrin light chains, and morphologically resembled the hub domain of the triskelion-shaped clathrin molecule. Self-assembly of recombinant hubs demonstrated a regulatory role for clathrin light chains and for the distal portions of triskelion legs in clathrin coat formation. Deletion mutagenesis of the hub localized a domain mediating light chain binding and clathrin self-assembly and mapped a transferable trimerization domain. These studies define molecular interactions controlling clathrin self-assembly and establish a recombinant system for future analysis.

Morphology and matrix composition during early tendon to bone healing

This study outlines the early morphologic phenomenon of tendon to bone healing in the rabbit model. Twelve skeletally mature, male New Zealand White rabbits received transplantation of the hallucis longus tendon into a 2-mm calcaneal bone tunnel. The morphologic characteristics of the healing tendon to bone interface were evaluated at 1, 2, 4, and 6 weeks after surgery by the use of conventional histology and immunohistochemical localization of collagen Types I, II, and III. Histologic analysis illustrated progressive maturation and reorganization of the tendon to bone interface with subsequent development of tissue collagen fiber continuity between the tendon and bone. Initially, diffuse immunolocalization of all three collagen types was observed within the scar tissue filling the space between the tendon and bone. During a 6-week period, reorganization of the scar tissue into an interface occurred, similar to an indirect insertion. Although a definitive fibrocartilage region did not form, Type II collagen was localized at the remodeling insertion site throughout the first 6 weeks of repair. In addition, Type III collagen fibers, resembling Sharpey's fibers, were noted to span this interface. The characterization of the insertion between tendon and bone is important to the understanding of healing in commonly used orthopaedic grafting procedures, such as anterior cruciate ligament reconstructions.

Long-term effects of fetal ethanol exposure on pituitary-adrenal response to stress

Pregnant female rats were fed either a 5.0-5.5% w/v ethanol-containing liquid diet ad lib or pair-fed the isocaloric control diet during gestation weeks 2 and 3. At 75-105 days of age, female offspring of the ethanol-treated dams showed significantly greater corticosterone responses than pair-fed- or normally-derived offspring to the stress of cardiac puncture or of noise and shaking, while pituitary-adrenal responses to exposure to a novel environment, cold or 2-3 days of fasting were normal. Adrenal sensitivity to ACTH in dexamethasone-suppressed adult offspring was unaffected by the prenatal treatment. The results demonstrate that fetal ethanol exposure enhances adult pituitary-adrenal responses to certain stressors, including alcohol as demonstrated previously, and suggest that the long-term effects may be mediated by developmental actions of alcohol on central neural mechanisms involved in the regulation of this neuroendocrine system.

Clathrin self-assembly is mediated by a tandemly repeated superhelix

Clathrin is a triskelion-shaped cytoplasmic protein that polymerizes into a polyhedral lattice on intracellular membranes to form protein-coated membrane vesicles. Lattice formation induces the sorting of membrane proteins during endocytosis and organelle biogenesis by interacting with membrane-associated adaptor molecules. The clathrin triskelion is a trimer of heavy-chain subunits (1,675 residues), each binding a single light-chain subunit, in the hub domain (residues 1,074-1,675). Light chains negatively modulate polymerization so that intracellular clathrin assembly is adaptor-dependent. Here we report the atomic structure, to 2.6 A resolution, of hub residues 1,210-1,516 involved in mediating spontaneous clathrin heavy-chain polymerization and light-chain association. The hub fragment folds into an elongated coil of alpha-helices, and alignment analyses reveal a 145-residue motif that is repeated seven times along the filamentous leg and appears in other proteins involved in vacuolar protein sorting. The resulting model provides a three-dimensional framework for understanding clathrin heavy-chain self-assembly, light-chain binding and trimerization.

Characteristics of Vibrio parahaemolyticus O3:K6 from Asia

A variety of serovars of the food-borne pathogen Vibrio parahaemolyticus normally cause infection. Since 1996, the O3:K6 strains of this pathogen have caused pandemics in many Asian countries, including Taiwan. For a better understanding of these pandemic strains, the recently isolated clinical O3:K6 strains from India, Japan, Korea, and Taiwan were examined in terms of pulsed-field gel electrophoresis (PFGE) typing and other biological characteristics. After PFGE and cluster analysis, all the O3:K6 strains were grouped into two unrelated groups. The recently isolated O3:K6 strains were all in one group, consisting of eight closely related patterns, with I1(81%) and I5(13%) being the most frequent patterns. Pattern I1 was the major one for strains from Japan, Korea, and Taiwan. All recently isolated O3:K6 strains carried the thermostable direct hemolysin (tdh) gene. No significant difference was observed between recently isolated O3:K6 strains and either non-O3:K6 reference strains or old O3:K6 strains isolated before 1996 with respect to antibiotic susceptibility, the level of thermostable direct hemolysin, and the susceptibility to environmental stresses. Results in this study confirmed that the recently isolated O3:K6 strains of V. parahaemolyticus are genetically close to each other, while the other biological traits examined were usually strain dependent, and no unique trait was found in the recently isolated O3:K6 strains.

A dominant-negative clathrin mutant differentially affects trafficking of molecules with distinct sorting motifs in the class II major histocompatibility complex (MHC) pathway

The role of clathrin in intracellular sorting was investigated by expression of a dominant-negative mutant form of clathrin, termed the hub fragment. Hub inhibition of clathrin-mediated membrane transport was established by demonstrating a block of transferrin internalization and an alteration in the intracellular distribution of the cation-independent mannose-6-phosphate receptor. Hubs had no effect on uptake of FITC-dextran, adaptor distribution, organelle integrity in the secretory pathway, or cell surface expression of constitutively secreted molecules. Hub expression blocked lysosomal delivery of chimeric molecules containing either the tyrosine-based sorting signal of H2M or the dileucine-based sorting signal of CD3gamma, confirming a role for clathrin-coated vesicles (CCVs) in recognizing these signals and sorting them to the endocytic pathway. Hub expression was then used to probe the role of CCVs in targeting native molecules bearing these sorting signals in the context of HLA-DM and the invariant chain (I chain) complexed to HLA-DR. The distribution of these molecules was differentially affected. Accumulation of hubs before expression of the DM dimer blocked DM export from the TGN, whereas hubs had no effect on direct targeting of the DR-I chain complex from the TGN to the endocytic pathway. However, concurrent expression of hubs, such that hubs were building to inhibitory concentrations during DM or DR-I chain expression, caused cell surface accumulation of both complexes. These observations suggest that both DM and DR-I chain are directly transported to the endocytic pathway from the TGN, DM in CCVs, and DR-I chain independent of CCVs. Subsequently, both complexes can appear at the cell surface from where they are both internalized by CCVs. Differential packaging in CCVs in the TGN, mediated by tyrosine- and dileucine-based sorting signals, could be a mechanism for functional segregation of DM from DR-I chain until their intended rendezvous in late endocytic compartments.

Combined effects of estrogen and progesterone on the anterior cruciate ligament

Previous studies from the authors' laboratory have established the presence of estrogen and progesterone receptors in the human anterior cruciate ligament. The purpose of the current study was to investigate the combined effects of 1beta-estradiol and progesterone on cell proliferation and procollagen synthesis of the human anterior cruciate ligament fibroblasts. Fibroblast proliferation and procollagen synthesis in response to logarithmic concentrations of 17beta-estradiol (0.0025 ng/mL, 0.025 ng/mL, 0.25 ng/mL) and progesterone (1 ng/mL, 10 ng/mL, 100 ng/mL) were assessed with the measurement of 3H-thymidine incorporation and Types I and III procollagen specific equilibrium radioimmunoassays. On Days 1, 3, and 5 there was a dose dependent decrease in the fibroblast proliferation and procollagen Type I synthesis with increasing estradiol concentrations. The effect was attenuated with increasing progesterone concentrations. Controlling for estrogen levels, a dose dependent increase in fibroblast proliferation and procollagen Type I synthesis was observed with increasing progesterone concentrations. The effect was more pronounced at lower concentrations of estrogen, suggesting estrogen levels were the dominant factor. The effects of estrogen and progesterone became less apparent by Day 7. No significant differences in Type III procollagen synthesis were seen with varying estradiol concentrations at any of the designated times. These early physiologic changes in fibroblast proliferation and Type I procollagen synthesis may provide a biologic explanation for the increased anterior cruciate ligament injury rate observed in female athletes, suggesting the acute cyclical hormonal variations in the female athlete during menstruation predispose her to ligamentous injury.

Comparison of open and arthroscopically assisted rotator cuff repairs

Open rotator cuff repair has shown reliable results in terms of pain relief and improved shoulder function. Recently, however, arthroscopically assisted rotator cuff repair has shown promising preliminary results. We compared the results of these two procedures with regard to pain, function, range of motion, strength, patient satisfaction, and return to previous activity. Thirty-seven rotator cuff repairs were evaluated in 36 patients with a minimum followup of 2 years. The open repair group comprised 20 shoulders with an average followup of 3.3 years; the arthroscopically assisted repair group comprised 17 shoulders with an average followup of 3.2 years. Overall, the open repair group had 80% good-to-excellent results and 88% patient satisfaction, and the arthroscopically assisted repair group had 85% good-to-excellent results and 92% patient satisfaction. Shoulder flexion and abduction strength, the size of the tear repaired, and the functional outcome did not differ significantly between the two groups. In general, however, small and moderate-sized tears (< 3 cm) had better functional outcome with arthroscopically assisted repair. The arthroscopically assisted repair group was hospitalized 1.2 days less and returned to previous activity an average of 1 month earlier. In the surgical treatment of symptomatic complete rotator cuff tears, arthroscopically assisted rotator cuff repair is as effective as open repair.

Electron solvation in two dimensions

Ultrafast two-photon photoemission has been used to study electron solvation at two-dimensional metal/polar-adsorbate interfaces. The molecular motion that causes the excess electron solvation is manifested as a dynamic shift in the electronic energy. Although the initially excited electron is delocalized in the plane of the interface, interactions with the adsorbate can lead to its localization. A method for determining the spatial extent of the localized electron in the plane of the interface has been developed. This spatial extent was measured to be on the order of a single adsorbate molecule.

Fetal exposure to ethanol enhances pituitary-adrenal and temperature responses to ethanol in adult rats

Long lasting effects of perinatal ethanol exposure were studied in adult rats who were the offspring of dams fed a 5.0% w/v ethanol-containing liquid diet ad libitum or pair-fed the isocaloric control diet during gestation weeks 2 and 3 or during postnatal week 1. Fetal exposure to ethanol reduced body weight of pups at birth unless the ethanol diet was supplemented with casein; neonatal exposure to the ethanol or pair-fed diets, casein supplemented or not, reduced pup weights until day 21 postnatally when weights of all fetally or neonatally exposed pups were normal. Between 52 and 120 days of age females were tested for pituitary-adrenal and temperature responses to a challenge dose of ethanol. Prenatally ethanol-exposed rats showed significantly higher plasma corticosterone titers and developed a greater hypothermia in response to an intraperitoneal injection of ethanol (0.75--1.5 g/kg) than did pair-fed controls. Similar responses enhancement did not occur in the postnatally ethanol-exposed rats. Temporal patterns of blood ethanol levels after an intraperitoneal injection of ethanol (1.5 g/kg) were similar in prenatally ethanol-exposed females and their pair-fed controls. The data indicate that exposure to ethanol in utero exerts persistent effects on the offspring, rendering them more responsive to the hypothermic and pituitary-adrenal activating effects of alcohol as adults.

Comparison of lateral ankle ligamentous reconstruction procedures

The static restraints of various surgical procedures for chronic lateral ankle instability were compared. Forty cadaveric ankles were divided equally into the following five groups: 1) ankles with intact anterior talofibular and calcaneofibular ligaments, 2) ankles with incised anterior talofibular and calcaneofibular ligaments, 3) ankles with Chrisman-Snook procedure, 4) ankles with Watson-Jones procedure, or 5) ankles with modified Broström procedure. All ankles were placed in a mechanical apparatus for anterior drawer stress and inversion stress tests. After each application of force, a radiograph of the ankle joint was taken, and the anterior talar displacement and the talar tilt angle were measured. All procedures reduced anterior drawer and talar tilt when compared with the ankles with incised anterior talofibular and calcaneofibular ligaments. Significant differences were found among the groups for both inversion and anterior drawer stress at all forces, except for the third and fourth groups. The modified Broström group had the least amount of anterior talar displacement and talar tilt angle at all forces. There were no significant differences between the Watson-Jones and the Chrisman-Snook procedures in anterior talar displacement and talar tilt. The modified Broström procedure produced a greater mechanical restraint than either of the other procedures.

A prospective evaluation of a new physical examination in predicting glenoid labral tears

We studied 62 patients (40 men and 22 women) with an average age of 28 years over a 28-month period who presented with shoulder pain that was refractory to 3 months of conservative management. Patients with a prior glenohumeral dislocation or a rotator cuff tear were excluded. The "crank" test was performed with the arm elevated to 160 degrees in the scapular plane of the body, loaded axially along the humerus, and with maximal internal and external rotation. Although similar tests have been described, the crank test is a new examination previously unreported. Half of the patients (31) had a positive crank test. Arthroscopy performed on all 62 patients revealed glenoid labral tears in 32 patients. Two patients who had positive crank tests did not have labral tears but had partial-thickness, articular-side rotator cuff tears. The sensitivity of the crank test was 91%, the specificity was 93%, the positive predictive value was 94%, and the negative predictive value was 90%. With these data, the crank test fulfills the criteria as a single physical examination test that is highly accurate for the preoperative diagnosis of glenoid labral tears. Accordingly, expensive imaging modalities currently used in this patient population may be employed less in the future.

Diagnosis of anterolateral ankle impingement. Comparison between magnetic resonance imaging and clinical examination

We reviewed 22 patients who had arthroscopic evaluations and preoperative magnetic resonance imaging studies of their ankles because of chronic anterolateral ankle pain after sprains. The ability of surgeons to use the initial clinical examination to predict arthroscopically confirmed anterolateral ankle impingement was compared with the ability to predict this condition using preoperative magnetic resonance imaging. The patient population consisted of 15 men and 7 women who had an average age of 28 years. Five patients (23%) were intercollegiate athletes and 17 patients (77%) were recreational athletes. All patients reported previous traumas to the involved ankles, and all were seen with chronic ankle pain. Clinical examinations were used to assess ankle pain, swelling, range of motion, and stability. Anterolateral ankle impingement was confirmed in 18 patients (82%) with arthroscopic examination. Clinical examinations had a sensitivity of 94% and a specificity of 75% for predicting impingement, and magnetic resonance imaging had a sensitivity of 39% and a specificity of 50%. The results of this study suggest that preoperative magnetic resonance imaging examination is not beneficial or cost-effective in the diagnosis of anterolateral ankle impingement; furthermore, its use may cause further delay in treatment.

Effect of estrogen on cellular metabolism of the human anterior cruciate ligament

Previous studies from this laboratory have established the presence of estrogen receptors in the human anterior cruciate ligament. The purpose of this study was to investigate the effects of 17 beta-estradiol on cell proliferation and procollagen levels, as an indicator of collagen synthesis, in the human anterior cruciate ligament fibroblasts. Fibroblast proliferation and procollagen synthesis in response to near log concentrations of 17 beta-estradiol (at 0.0029 ng/mL, 0.025 ng/mL, 0.25 ng/mL, 2.5 ng/mL, and 25 ng/mL) were assessed with the measurement of 3H-thymidine incorporation and Types 1 and 3 procollagen specific equilibrium radioimmunoassays. On Days 1 and 3, there was a dose dependent decrease in the proliferation of anterior cruciate ligament fibroblasts with increasing estradiol concentrations. This dose dependent effect of decreased fibroblast proliferation with increasing estradiol concentrations became less apparent at 7, 10, and 14 days. On Days 1 and 3, procollagen synthesis decreased in a dose dependent manner with increasing estradiol concentrations. On Days 7, 10, and 14, this dose dependent effect was attenuated. No significant differences in Type 3 procollagen synthesis by anterior cruciate ligament fibroblasts were observed with varying estradiol concentrations at any of the designated points. These early physiologic changes in fibroblast proliferation and Type I procollagen synthesis may provide a biologic explanation for the increased anterior cruciate ligament injury rate observed in female athletes, suggesting that it is the acute cyclic variations in the female athlete who is menstruating that predisposes her to ligamentous injury.