Depolarization-induced slow current in cerebellar Purkinje cells does not require metabotropic glutamate receptor 1

Activation of cerebellar Purkinje cells by either brief depolarizing steps or bursts of climbing fiber synaptic activation evokes a slow inward current, which we have previously called depolarization-induced slow current or DISC. DISC is triggered by Ca influx via voltage-sensitive Ca channels and is attenuated by inhibitors of vacuolar ATPase or vesicle fusion. This led us to suggest that DISC required vesicular release of glutamate from the somatodendritic region of Purkinje cells. Furthermore, we found that DISC was attenuated by the mGluR1 antagonist 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), indicating that DISC required autocrine activation of metabotropic glutamate receptor 1 (mGluR1). Here, we have revisited the role of mGluR1 and found that it is, in fact, not required for DISC. CPCCOEt, but not three other specific mGluR1 antagonists (JNJ16259685, alpha-amino-5-carboxy-3-methyl-2-thiopheneacetic acid (3-MATIDA), Bay 36-7620), attenuated DISC, even though all four of these drugs produced near-complete blockade of current evoked by puffs of the exogenous mGluR1/5 agonist DHPG. Cerebellar slices derived from mGluR1 null mice showed substantial DISC that was still attenuated by CPCCOEt. mGluR5 is functionally similar to mGluR1, but is not expressed at high levels in cerebellar Purkinje cells. 2-Methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP), an mGluR5 antagonist, did not attenuate DISC, and DISC was still present in Purkinje cells derived from mGluR1/mGluR5 double null mice. Thus, neither mGluR1 nor mGluR5 is required for DISC in cerebellar Purkinje cells.

A case of disseminated Nocardia farcinica diagnosed through DNA sequencing in a kidney transplantation patient

Nocardia is a rare gram-positive bacteria causing opportunistic infection, and belongs to the aerobic Actinomycetes group. As the mortality in the immunocompromised patients with nocardiosis is high, early diagnosis and treatment is very important. However, clinical manifestations of infection caused by Nocardia are very variable and early diagnosis is limited by the difficulty in obtaining specimens and its isolation. Rapid diagnosis of Nocardia infection may allow for earlier effective therapy, thus improving patient outcome. We report a case of Nocardia farcinica diagnosed by DNA sequencing through blood culture in a renal transplant recipient with severe pneumonia and multiple brain abscesses.

Oesophageal strictures caused by the ingestion of corrosive agents: effectiveness of balloon dilatation in children

AIM

To evaluate the safety and clinical effectiveness of balloon dilatation in children for oesophageal strictures caused by the ingestion of corrosive agents.

MATERIALS AND METHODS

The study comprised 11 children (median age 6 years; range 1-14 years) with oesophageal strictures caused by corrosive agents, who underwent a total of 36 balloon dilatation sessions. The technical and clinical success, recurrence of dysphagia, complications, and primary and secondary patency rates were retrospectively evaluated.

RESULTS

Technical success was achieved in 91% of patients and in 97% of balloon dilatation sessions. Clinical success (defined as improved food intake and reduced dysphagia within 1 month of the first balloon dilatation session) was achieved in 64% of patients (7/11). During the mean 35-month follow-up period (range 1-89 months), 10 (91%) patients experienced recurrence. Oesophageal rupture (types 1 or 2) occurred in 45% of patients and in 31% of balloon dilatation sessions. Primary patency rates at 6 months and 1, 2, 3, 4, and 5 years were 36, 27, 14, 14, 14, and 14%, respectively. Secondary patency rates at 6 months and 1, 2, 3, 4, and 5 years were 82, 82, 82, 56, 42, and 42%, respectively. The secondary patency rate was higher than the primary patency rate (p<0.05).

CONCLUSION

The present study examined oesophageal balloon dilatation for paediatric oesophageal strictures caused by the ingestion of corrosive agents. Although the technical success rate was high and there were no deaths, the clinical success rate was low owing to a high recurrence rate. However, repeated balloon dilatations resulted in an acceptable secondary patency rate.

Management of airway involvement of oesophageal cancer using covered retrievable nitinol stents

AIM

To assess the efficacy and safety of covered retrievable nitinol stents in oesophageal cancer patients with airway involvement.

MATERIALS AND METHODS

Under fluoroscopic guidance, covered retrievable nitinol airway stents were placed in 23 oesophageal cancer patients with airway stricture and/or oesophagorespiratory fistula (ERF) over a long period of 12 years. Six patients only had aspiration by ERF and three patients had both airway stricture and asymptomatic ERF. Technical aspects, dyspnoea improvement, and/or resolution of ERF symptoms, complications, reinterventions, and survival data were evaluated.

RESULTS

A total of 27 airway stents (14 tracheal, 11 bronchial, and two hinged) were placed successfully in 23 patients with airway stricture or ERF. Dyspnoea score decreased significantly after stent placement (p<0.001). ERF were sealed off in all nine patients. Complications included stent migration or expectoration (n=4), haemoptysis (n=2), sputum retention (n=7), and tumour overgrowth (n=1). All three migrated stents were easily removed. Twenty-one patients died, with the median survival period of 76 days (range 2-197 days).

CONCLUSION

Placement of covered retrievable expandable nitinol stents was safe and effective for the palliative treatment of airway strictures and/or ERF, with a reasonable range of complications, in patients with advanced oesophageal cancer.

Impact of helical computed tomography in clinically evident appendicitis

OBJECTIVES

To determine the utility of multidetector computed tomography (MDCT) in patients with clinically evident acute appendicitis and to compare the test characteristics of overall clinical impression, Alvarado scores, and MDCT in suspected appendicitis.

METHODS

A prospective observational cohort study was conducted in two urban emergency departments (ED). Consecutive patients with suspected acute appendicitis were clinically evaluated by an emergency physician who was asked to determine whether appendicitis was clinically evident or not. Elements of the Alvarado scores were collected and all patients then underwent MDCT and a decision to operate, observe, or discharge the patients was made by a surgeon. The final diagnosis was based on surgical pathology or clinical follow-up. The test characteristics of clinical impression, Alvarado scores and MDCT were then calculated and the rates at which acute appendicitis was falsely diagnosed based on clinical impression and MDCT were compared using McNemar's test.

RESULTS

Of 157 study patients, 71 were considered to have clinically evident appendicitis before MDCT and 91 had findings of acute appendicitis on MDCT. 19 of the 71 patients with clinically evident appendicitis did not have appendicitis. 14 of 52 patients with an Alvarado score > or = 8 also did not have appendicitis. Three of 91 patients with acute appendicitis based on MDCT did not have appendicitis. The specificities of clinical impression and Alvarado score > or = 8 were 71.6% and 79.1%, respectively, and these were significantly lower than that of MDCT (95.5%, p<0.05).

CONCLUSION

The performance of abdominal MDCT in patients with a high degree of clinical suspicion for acute appendicitis reduces the number of false positives and has the potential to reduce negative appendectomies.

Fluoroscopically guided percutaneous jejunostomy: outcomes in 25 consecutive patients

AIM

To assess the feasibility and safety of fluoroscopically guided percutaneous jejunostomy.

MATERIAL AND METHODS

Between May 1999 and August 2006 percutaneous jejunostomy was attempted in 25 patients. A 5 F vascular catheter (n=20) or a 7.5 F multifunctional coil catheter (n=5) was used to insufflate the jejunum. The distended jejunum was punctured using a 17 G needle (n=19) or a 21 G Chiba needle (n=6) with the inserted catheter as a target. A 12 or 14 F loop feeding tube was inserted after serial dilations. The technical success, complications, 30-day mortality, and in-dwelling period of the feeding tube placement were evaluated.

RESULTS

The technical success rate was 92% (23/25). Technical failures (n=2) resulted from the inability to insufflate the jejunum secondary to failure to pass the catheter through a malignant stricture at the oesophagojejunostomy site and thus subsequent puncture of the undistended jejunum failed, or failure to introduce the Neff catheter into the jejunum. Pericatheter leakage with pneumoperitoneum was a complication in three patients (12%) and was treated conservatively. The 30-day mortality was 13% (3/23); however, there was no evidence that these deaths were attributed to the procedure. Except for four patients who were lost to follow-up and two failed cases, 15 of the 19 jejunostomy catheters were removed because of patient death (n=12) or completion of treatment (n=3), with a mean and median in-dwelling period of 231 and 87 days, respectively.

CONCLUSIONS

Fluoroscopically guided percutaneous jejunostomy is a feasible procedure with a high technical success and a low complication rate. In addition to a 17 G needle, a 21 G needle can safely be used to puncture the jejunum.

Paroxysmal stabbing headache in the multiple dermatomes of the head and neck: a variant of primary stabbing headache or occipital neuralgia?

A paroxysmal stabbing or icepick-like headache in the multiple nerve dermatomes, especially involving both trigeminal and cervical nerves, has not been fully explained or classified by the International Classification of Headache Disorder, 2(nd) Edition (ICHD-II). Of patients with acute-onset paroxysmal stabbing headache who had visited the Hallym University Medical Center during the last four years, 28 subjects with a repeated stabbing headache involving multiple dermatomes at the initial presentation or during the course were prospectively enrolled. All patients were neurologically and otologically symptom free. A coincidental involvement of both trigeminal and cervical nerve dermatomes included seven cases. Six cases involved initially the trigeminal and then cervical nerve dermatomes. Five cases showed an involvement of the cervical and then trigeminal nerve dermatomes. The remaining patients involved multiple cervical nerve branches (the lesser occipital, greater occipital and greater auricular). Pain lasted very shortly and a previous history of headache with the same nature was reported in 13 cases. Preceding symptom of an infection and physical and/or mental stress were manifested in seven and six subjects, respectively. All patients showed a self-limited benign course and completely recovered within a few hours to 30 days. Interestingly, a seasonal gradient in occurrence of a stabbing headache was found in this study. A paroxysmal stabbing headache manifested on multiple dermatomes can be explained by the characteristics of pain referral, and may be considered to be a variant of primary stabbing headache or occipital neuralgia.

A dual-design expandable colorectal stent for malignant colorectal obstruction: results of a multicenter study

BACKGROUND AND STUDY AIMS

It is known that metal stent placement is safe, easy, and effective for the treatment of malignant colorectal obstruction, but these stents are associated with delayed complications of tumor ingrowth and stent migration. The aim of this study was to prospectively investigate the technical feasibility, clinical effectiveness, and safety of a dual-design colorectal stent (consisting of an outer stent and an inner bare nitinol stent) in patients with malignant colorectal obstruction.

PATIENTS AND METHODS

Placement of the dual stent using a 4.5-mm stent delivery system was attempted in 151 patients with malignant colorectal obstruction, either before surgery (n = 50) or for palliation (n = 101). Multivariate logistic regression analysis was used to identify risk factors associated with complications.

RESULTS

Stent placement was technically successful in 145/151 patients (96%). Of the patients who had a technically successful placement, bowel obstruction resolved within 2 days after stent placement in 48/50 (96%) of the patients in the bridge-to-surgery group and in 87/95 (92%) of the patients in the palliative group. Perforation occurred in 16 patients, incomplete stent expansion in eight patients, stent migration in four patients, tumor overgrowth in five patients, severe rectal pain in five patients, and bleeding in eight patients. Complete obstruction was the only significant risk factor for perforation (odds ratio 6.88, 95% CI 2.04-23.17, P = 0.002). In the palliative group, the median survival was 152.0 days and the mean survival was 263.8 days.

CONCLUSIONS

The dual stent with a 4.5-mm stent delivery system is easy to insert, safe, and reasonably effective for the palliative treatment of malignant colorectal obstruction. However, a great deal of care is needed in its deployment because of the high rate of perforation.

Prevalence of non-tuberculous mycobacteria in a hospital environment

In recent years, non-tuberculous mycobacteria (NTM) have emerged as an important cause of opportunistic nosocomial infections but there is little known about the isolation and identification of NTM in Korea. The aim of this study was to assess the prevalence of NTM in the hospital environment and identify the species. A total of 150 samples were collected from different parts of the hospital. NTM were isolated and identified by restriction fragment length polymorphism analysis of the gene encoding rpoB and partial sequencing analysis of hsp65 and rpoB. In this study, 60 strains of NTM were isolated from 50 of the 150 samples. Half of the tap water samples (50 of 100) were positive for mycobacteria. An estimated 73.3% of the isolates were saprophytic, 21.7% were potentially pathogenic and 5% were unidentified. The presence of NTM in hospital tap water is not uncommon. Such water isolates might cause true nosocomial infection in immunocompromised patients, in addition to the risk of false-positive culture results.

Microinvasive ductal carcinoma arising within a fibroadenoma: A case report

Fibroadenomas are among the most common benign breast tumors in which carcinomas rarely develop. We report the imaging findings of a microinvasive ductal carcinoma arising within a fibroadenoma in a 51-year-old woman. This mass showed coarse heterogeneous microcalcifications within a circumscribed mass on mammography, a heterogeneous hypoechoic mass on ultrasound, and an early enhancing mass on magnetic resonance imaging. Although a fibroadenoma in an older woman appears benign-looking, the presence of any unusual signs should raise concerns about malignancy.

A case of successful embolotherapy for gastric ulcer bleeding from the intercostal artery after oesophagectomy and gastric reconstruction

We report a successful treatment with coil embolisation of an intercostal artery for ulcer bleeding in a gastric tube in a 70-year-old man who underwent a total oesophagectomy and gastric tube reconstruction for oesophageal cancer. This case teaches us to search aberrant feeding vessels when active bleeding is suspected in reconstructed gastric tube in the patient with oesophagectomy and oesophagogastrostomy.

Deep tracheal laceration after balloon dilation for benign tracheobronchial stenosis: case reports of two patients

We report two cases of deep tracheal laceration in female patients after balloon dilation for benign tracheobronchial stenosis. Immediate post-procedure bronchoscopy and CT including 3D reconstructions showed deep lacerations in the posterior tracheal wall. Clinically, the patients' dyspnoea subsided and there has been no recurrence during follow-up after balloon dilation. On the follow-up 3D-reconstructed CT scans obtained 2 months and 8 months following balloon dilation, respectively, the lacerations had healed completely and there was considerable improvement in lumen size.

Value of repeat ultrasound-guided fine-needle aspiration in nodules with benign cytological diagnosis

PURPOSE

To assess the value of repeat ultrasound-guided fine-needle aspiration (US-FNA) in nodules with benign cytological diagnosis.

MATERIAL AND METHODS

One-hundred-and-eighty-seven patients undergoing repeat US-FNA were included after a benign cytological diagnosis had been made by the initial US-FNA. They were divided into a re-aspiration group, who underwent repeat US-FNA within 6 months for a discordant pathological and clinico-radiological result, and a follow-up aspiration group, who underwent repeat US-FNA after 6 months without any clinical or radiological suspicion. The cancer rate in each group and the US findings of the later-diagnosed malignant nodules were assessed.

RESULTS

Nine malignancies were verified in the 187 cases (4.8%) by repeat US-FNA or surgery. In 44 patients in the re-aspiration group, 6 malignancies were identified (13.6%), compared with 3 malignancies in the 143 patients in the follow-up aspiration group (2.1%) (P<0.05). The later-diagnosed malignant nodules were an average of 1.0 cm in diameter; 66.7% were round; 66.7% were circumscribed; 100% were solid; 88.9% were hypoechoic; and 55.6% contained calcifications on US.

CONCLUSION

The follow-up of nodules with benign cytological diagnosis without clinicoradiological suspicion of malignancy is warranted using imaging surveillance rather than repeated US-FNA.

Malignant esophageal-tracheobronchial strictures: parallel placement of covered retrievable expandable nitinol stents

PURPOSE

To assess the safety and clinical effectiveness of the parallel placement of covered retrievable expandable metallic stents in the palliative treatment of malignant esophageal and tracheobronchial strictures.

MATERIAL AND METHODS

Under fluoroscopic guidance, parallel stents were placed in 12 symptomatic patients with both malignant esophageal and tracheobronchial strictures. Seven of these 12 patients also had an esophagorespiratory fistula (ERF) and one patient had an esophagocutaneous fistula. Technical success, clinical improvement, complications, and survival rates were evaluated.

RESULTS

A total of 28 esophageal and airway stents were successfully placed. The grade of dysphagia and dyspnea score significantly decreased after stent placement (P=0.002 and 0.003, respectively). ERF and esophagocutaneous fistula were sealed off in all eight patients after esophageal stent placement; however, the esophagocutaneous fistula reopened 1 month later. Complications included stent migration or expectoration (n=3), tracheal compression by the esophageal stent (n=3), new fistula development due to covering membrane degradation of the esophageal stent (n=1), and symptomatic sputum retention (n=1). Stent removal was easily performed for two stents; one migrated stent and the other with covering membrane degradation. All 12 patients died within the mean survival period of 72.50 days (range 7-375 days).

CONCLUSION

Parallel placement of covered retrievable expandable metallic stents is safe and effective for the palliative treatment of malignant esophageal and tracheobronchial strictures.

Chimerism and mosaicism are important causes of ABO phenotype and genotype discrepancies

Discrepancies between blood group genotype and RBC phenotype are important to recognize when implementing DNA-based blood grouping techniques. This report describes two such cases involving the ABO blood group in the Korean population. Propositus #1 was a 22-year-old healthy man undergoing pretransfusion testing for minor surgery. Propositus #2 was a 23- year-old male blood donor. RBCs from both propositi were determined to be group AB and demonstrated unusual agglutination patterns on forward typing, which were inconsistent with their ABO genotype determined by allele-specific (AS) PCR. RBCs from propositus #1 demonstrated mixed field agglutination with both anti-A and -B, while RBCs from propositus #2 demonstrated mixed field only with anti-A reagents. Both had B/O genotypes by AS-PCR. Cloning and sequencing of ABO exons 6 and 7 revealed three alleles in both propositi: propositus #1: A102/B101/O04; propositus #2: A102/B101/O01. A panel of nine short-tandem repeat (STR) loci was tested on DNA extracted from blood, buccal mucosal cells, and hair from the propositi and on DNA isolated from their parents' blood. In all tissues tested from propositus #1, three loci demonstrated a double paternal and a single maternal DNA contribution, indicating that he was a chimera or a mosaic; in those from propositus # 2, one STR locus demonstrated a double paternal DNA contribution, indicating that he was a tetragametic chimera. Chimerism and mosaicism are uncommon but important causes of ABO genotype and phenotype discrepancies. The evaluation of patients and donors with unusual or unexpected serology in pretransfusion testing and consensus ABO alleles may include the evaluation of STR loci to detect these phenomena.

The genetic and phenotypic basis of blood group A subtypes in Koreans

A serological and genetic study of Korean blood donors with phenotypic group A subtypes was performed. There were 176 donors with phenotypic A subtypes identified. Exons 6 and 7 from 57 representative donors were sequenced. The A(var) allele (784 G > A) was cloned and sequenced, and a family study demonstrating its inheritance and unusual serological characteristics was performed. The A102 allele was the most frequently identified allele in phenotypically A2 (58%, 11/19) and A2B (68%, 17/25) donors. Anti-A1 was rarely present amongst A2 and A2B donors. The family study revealed that the A(var) allele was expressed as phenotype A(weak)B in A(var)/B heterozygote members, but as phenotype O in A(var)/O heterozygotes. The most frequent allele in Korean donors with the A2 phenotype differs from its Caucasian counterpart, as does the frequency of anti-A1. The A(var) allele demonstrates allelic enhancement in A(var)/B heterozygotes.

Usefulness of the carina as a radiographic landmark for central venous catheter placement in paediatric patients † †Presented, in part, at the 2005 Annual Meeting of European Society of Anaesthesiologists, Vienna, Austria

BACKGROUND

Several reports have proposed radiographic landmarks for the proper positioning of central venous catheters (CVC). The carina is one of the proposed landmarks in adults. Here, we evaluate the possibility of using the carina as a radiographic landmark for the identification of proper positioning of the CVC tip in paediatric patients.

METHODS

We studied 57 right internal jugular vein catheterizations in infants and children undergoing surgery for the treatment of congenital heart disease. After placing the CVC tip at the junction of the superior vena cava and the right atrium (SVC-RA junction) via intraoperative transoesophageal echocardiography, and by taking postoperative anterior-posterior chest radiographs, we measured the longitudinal distance from the carina to the SVC-RA junction, using the Picture Archiving and Communicating System.

RESULTS

The average distance between the carina and the SVC-RA junction was 1.5 cm (95% CI 1.3-1.8 cm). No catheter tip was above the carina. Although there was no particular relationship between this distance and the patient's age, height, or weight, the distance between the carina and the SVC-RA junction tended to be more variable in younger and smaller children.

CONCLUSIONS

The carina can be used as a radiographic landmark for the proper CVC tip placement in paediatric patients. If the tip of the CVC is not distal to the carina the chances are minute that it is in the right atrium.

Identification and characterization of the peroxiredoxin gene family in chickens

Peroxiredoxin (PRX) is a crucial antioxidant protein that protects against endogenously produced peroxides in prokaryotes to eukaryotes. To date, 6 different isoforms have been identified in mammals. In this study, we describe the first members of the PRX protein family to be characterized in Chicken. Through bioinformatics analysis, we observed that at least 4 different classes of PRX protein have been evolutionarily conserved in chickens. Furthermore, in vitro functional assays of the candidate chicken PRX proteins demonstrated that they had levels of antioxidant activity similar to those of the mammalian enzymes. The expression patterns of the PRX transcript in several chicken tissues were not tissue specific, suggesting that they might play an essential role as a housekeeping gene in all tissues to protect against oxidative damage. In conclusion, the sequences of the putative members of this functional gene family in chickens could be effectively retrieved in silico through bioinformatics analysis, and the functionality of their gene products evaluated by in vitro comparative assay.

A set of testis-specific novel genes collected from a collection of Korean Native Chicken ESTs

We report a set of testis-specific novel genes by comparing the The Institute for Genomic Research (TIGR) chicken gene index with the 13,132 expressed sequence tag (EST) collection from Korean Native Chicken (KNC). A total of 553 novel transcripts have resulted after comparison of our EST contigs and singlets against the chicken gene index and chicken genome sequences. Interestingly, 76% of the new genes were from testis-specific EST contigs or singlet and analysis of exon/intron structure showed that a significant number of the contigs have intronless coding regions. A large portion of the testis-specific transcripts have intronless coding region indicating that the testis-specific expression pattern is related to a group of single exon genes in the chicken. The chicken EST data that are described in this paper have been submitted to the NCBI dbEST under accession numbers CO759017-CO764274, CO765331-CO768903 and CO769672-CO773972.

Analysis of testis-specific transcripts in the chicken

Sequences of candidate chicken testis-specific genes were analysed in order to develop a resource for functional genomic studies of the testis and male germ cells. Tentative consensus sequences (TC) containing expressed sequence tags expressed in testis libraries were selected from the TIGR Gallus gallus Gene Index, resulting in 292 TC. The transcriptional expression of these genes were evaluated in several chicken tissues, including testis and ovary. One hundred ten of the 292 TC were expressed in a testis-specific manner. Annotation of the TC using the Gene Ontology database terms showed that the proportion of testis-specific TC that were classified as having catalytic activity (within the molecular function branch) was higher than the proportion of total chicken TC classified in the same way. Our results may facilitate the investigation of testis-specific genes and their functional analysis in the chicken, as well as in other avian species.

Feasibility study on the removal of nitrous compounds with a hollow-fiber membrane biofilm reactor

The objective of this study was to develop an integrated nitrogen treatment system using autotrophic organisms. A treatment system consists of an aerobic hollow-fiber membrane biofilm reactor (HfMBR) and anaerobic HfMBR. In the aerobic HfMBR, a mixture gas of air and O2 was supplied through the fibers for nitrification. Denitrification occurred in the anaerobic HfMBR using H2 as the electron donor. The treatment system was continuously operated for 190 days. NH4-N removal efficiencies ranging from 95% to 97% were achieved at NH4-N concentrations of influent ranging from 50 to 100 mg N/L. When glucose was added to the influent, the simultaneous nitrification and denitrification occurred in the aerobic HfMBR, and nitrogen removal rates were changed according to the COD/NH4-N ratio of influent. In the anaerobic HfMBR, autotrophic denitrification using H2 occurred and the removal rates achieved in this study were 23-58 mg N/m2 d. In this study, the achieved removal efficiency was lower than other study findings; however, the result suggested that this hybrid HfMBR system can be used effectively for nitrogen removal in oligotrophic water.

Scaling of F-actin network rheology to probe single filament elasticity and dynamics

The linear and nonlinear viscoelastic response of networks of cross-linked and bundled cytoskeletal filaments demonstrates remarkable scaling with both frequency and applied prestress, which helps elucidate the origins of the viscoelasticity. The frequency dependence of the shear modulus reflects the underlying single-filament relaxation dynamics for 0.1-10 rad/sec. Moreover, the nonlinear strain stiffening of such networks exhibits a universal form as a function of prestress; this is quantitatively explained by the full force-extension relation of single semiflexible filaments.