Etiology-Specific Mineralization Patterns in Patients with Labyrinthitis Ossificans.

BACKGROUND AND PURPOSE: Our aim was to identify whether specific patterns of ossification in labyrinthitis ossificans are associated with the known risk factors. Labyrinthitis ossificans has been described as sequela of prior temporal bone trauma, prior infection, and other disorders including sickle cell disease. Specific patterns of mineralization in the membranous labyrinth associated with these risk factors has not been previously described. MATERIALS AND METHODS: This was a retrospective study evaluating temporal bone CT scans at our institution from November 2005 to May 2018 in patients with labyrinthitis ossificans. Membranous labyrinthine structures evaluated for ossification included the following: basal, middle, and apical cochlear turns; lateral, posterior, and superior semicircular canals; and the vestibule for both ears in all patients. These structures were assigned a severity score, 0-4, based on degree of mineralization. Clinical records were reviewed for potential labyrinthitis ossificans risk factors. Basic descriptive statistics and a mixed model were used to correlate the degree and patterns of ossification with clinical history. RESULTS: Forty-four patients (58 ears) with labyrinthitis ossificans were identified and evaluated. The most common risk factors were chronic otomastoiditis (n = 18), temporal bone surgery (n = 9), temporal bone trauma (n = 6), sickle cell disease (n = 5), and meningitis (n = 4). For all etiologies, the semicircular canals were most severely affected, and the vestibule was the least. In patients with prior temporal bone surgery, significantly greater mineralization was seen in the basal turn of the cochlea (P = .027), the vestibule (P = .001), and semicircular canals (P < .001-.008). No significant pattern was identified in patients with meningitis, sickle cell disease, or trauma. CONCLUSIONS: Significant patterns of mineralization in labyrinthitis ossificans were observed in patients with prior temporal bone surgery. For all etiologies, the semicircular canals were most severely affected. No significant mineralization pattern was observed in patients with chronic otomastoiditis, meningitis, sickle cell disease, or prior temporal bone trauma.

Structure and dynamics of NBD1 from CFTR characterized using crystallography and hydrogen/deuterium exchange mass spectrometry.

The DeltaF508 mutation in nucleotide-binding domain 1 (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) is the predominant cause of cystic fibrosis. Previous biophysical studies on human F508 and DeltaF508 domains showed only local structural changes restricted to residues 509-511 and only minor differences in folding rate and stability. These results were remarkable because DeltaF508 was widely assumed to perturb domain folding based on the fact that it prevents trafficking of CFTR out of the endoplasmic reticulum. However, the previously reported crystal structures did not come from matched F508 and DeltaF508 constructs, and the DeltaF508 structure contained additional mutations that were required to obtain sufficient protein solubility. In this article, we present additional biophysical studies of NBD1 designed to address these ambiguities. Mass spectral measurements of backbone amide (1)H/(2)H exchange rates in matched F508 and DeltaF508 constructs reveal that DeltaF508 increases backbone dynamics at residues 509-511 and the adjacent protein segments but not elsewhere in NBD1. These measurements also confirm a high level of flexibility in the protein segments exhibiting variable conformations in the crystal structures. We additionally present crystal structures of a broader set of human NBD1 constructs, including one harboring the native F508 residue and others harboring the DeltaF508 mutation in the presence of fewer and different solubilizing mutations. The only consistent conformational difference is observed at residues 509-511. The side chain of residue V510 in this loop is mostly buried in all non-DeltaF508 structures but completely solvent exposed in all DeltaF508 structures. These results reinforce the importance of the perturbation DeltaF508 causes in the surface topography of NBD1 in a region likely to mediate contact with the transmembrane domains of CFTR. However, they also suggest that increased exposure of the 509-511 loop and increased dynamics in its vicinity could promote aggregation in vitro and aberrant intermolecular interactions that impede trafficking in vivo.

Binding affinities and geometries of various metal ligands in peptide deformylase inhibitors.

Removal of the N-terminal formyl group from newly synthesized proteins by the enzyme peptide deformylase (PDF) is essential for normal growth of bacteria but not higher organisms. Recently, PDF has been explored as a target for novel antibiotics. Screening a collection of natural products for antimicrobial activity identified actinonin and two matlystatin analogs as potent PDF inhibitors. A number of synthetic analogs of these natural products were prepared and their inhibitory potency determined. Previous work has shown that PDF is an iron metalloproteinase also containing a catalytic glutamic acid residue. Ligation of the ferrous cation is an essential feature of potent inhibitors. The structures of actinonin, a matlystatin analog and a synthetic inhibitor complexed with PDF were determined by crystallography. A quantum mechanics/molecular mechanics (QM/MM) method was used to reproduce the geometry of known complexes, to predict the protonation state in the active site and to predict the geometry of additional complexes. The requirement for protonation of the active site glutamate anion is an important factor in understanding the potency of inhibitors with acidic iron-ligating groups such as hydroxamate and carboxylate. Even though potent inhibitors of PDF have been discovered, their bacteriostatic mechanism of action and the rapid development of resistance in vitro may limit their potential as antibacterial drugs.

Polyunsaturated fatty acids and cardiovascular risk: interference at the level of gene expression.

Long-chain polyunsaturated fatty acids (PUFA) are important structural components of the cell membrane as well as precursors of highly active lipid mediators, the eicosanoids. In addition, they have been identified as novel intracellular signaling molecules which either directly or indirectly through the modulation of other signaling pathways activate transcription factors and gene expression. With regard to cardiovascular risk and diseases, effects of PUFA have been observed on genes whose products regulate either metabolic processes, especially fatty acid metabolism, or are involved in inflammatory and mitogenic processes of vascular cells. Often, the effects of n-3 and n-6 PUFA on the expression of both types of genes are antagonistic indicating a balancing role of n-3 and n-6 PUFA in cell metabolism and function already at the level of gene expression.

Peptidic inhibitors of the hepatitis C virus serine protease within non-structural protein 3.

New treatments for HCV (Hepatitis C virus) infections are likely to arise from inhibition of the essential, virally-encoded enzymes. These targets include the serine protease required for processing of the HCV polyprotein. The protease constitutes one functional domain of the bifunctional HCV NS3 (non-structural protein 3). Here, insights regarding the NS3 structure and recently synthesized NS3 inhibitors are reviewed. Interestingly, many NS3 protease inhibitors have taken advantage of an unusual product inhibition by N-terminal products of cleavage at the polyprotein processing sites.

Jugulotympanic paragangliomas.

Jugulotympanic paragangliomas are the most common tumors of the middle ear and temporal bone. Although these larger tumors can prove to be formidable, the advent of microscopic and skull base surgical techniques has greatly enhanced the ability to treat and manage these tumors.

Intracranial surgery: to shave or not to shave?

OBJECTIVE: In an effort to improve patient confidentiality as well as cosmesis, the authors have stopped shaving for all intracranial procedures. The objective was to determine whether this lack of shaving increased the postoperative infection rate. DESIGN: A retrospective study was performed comparing all intracranial surgical procedures performed in the last 2(1/2) years, when hair was not shaved, with the infection rate in patients who did have their hair shaved in the preceding 3(1/2) years. SETTING: An academic tertiary care referral center. PATIENTS: Every patient (children and adults) who underwent an intracranial procedure by the skull base surgery team was included. Similar patient demographics were used for the hair-shaved group. INTERVENTION(S): Intracranial procedures consisted of acoustic tumor removal, vestibular nerve sections, skull base surgery procedures, vascular decompressions, and craniotomies for benign and malignant tumors. MAIN OUTCOME MEASURES: The most essential criterion was to determine whether postoperative wound infection developed in a patient. This was documented as either minor (stitch abscess or wound dehiscence), moderate (wound breakdown requiring inpatient or outpatient therapy, such as oral or intravenous antibiotics), or severe (significant wound breakdown that required hospitalization, with surgical debridement and antibiotics). RESULTS: In all, 150 patients were not shaved for their intracranial procedures; postoperative wound infections developed in 11 (7%). The infections were minor (6), moderate (5), and severe (0). By comparison, 100 patients undergoing intracranial procedures had their hair shaved. In this group, the number of infections noted was 6 (6%). Their categorization into mild, moderate, and severe was 4, 2, and 0, respectively. Statistical analysis did not reveal any significant difference between the two infection rates. CONCLUSIONS: The rate of postoperative wound infection was statistically no greater when the hair was shaved than when it was not. Thus, for patient confidentiality as well as patient esteem, we recommend not shaving hair for intracranial procedures.

Design, high-level expression, purification and characterization of soluble fragments of the hepatitis C virus NS3 RNA helicase suitable for NMR-based drug discovery methods and mechanistic studies.

RNA helicases represent a family of enzymes that unwind double-stranded (ds) RNA in a nucleoside triphosphate (NTP)-dependent fashion and which are required in all aspects of cellular RNA metabolism and processing. The hepatitis C virus (HCV) non-structural 3 (NS3) protein possesses a serine protease activity in the N-terminal one-third, whereas RNA-stimulated NTPase and helicase activities reside in the C-terminal portion of the 631 amino acid residue bifunctional enzyme. The HCV NS3 RNA helicase is of key importance in the life cycle of HCV, which makes it a target for the development of therapeutics. However, neither the precise mechanism nor the substrate structure has been defined for this enzyme. For nuclear magnetic resonance (NMR)-based drug discovery methods and for mechanistic studies we engineered, prepared and characterized various truncated constructs of the 451-residue HCV NS3 RNA helicase. Our goal was to produce smaller fragments of the enzyme, which would be amenable to solution NMR techniques while retaining their native NTP and/or nucleic acid binding sites. Solution conditions were optimized to obtain high-quality heteronuclear NMR spectra of nitrogen-15 isotope-labeled constructs, which are typical of well-folded monomeric proteins. Moreover, NMR binding studies and functional data directly support the correct folding of these fragments.

Transient increase of monocyte adhesion after a single dose of simvastatin.

Beneficial effects of HMG-CoA reductase inhibitors, such as simvastatin have been attributed to lipid lowering and cholesterol-independent mechanisms, for example a reduction of monocyte adhesion to endothelium. However, little is known about acute effects of statin intake. In an attempt to test for short-term effects of drug intake, we found that the adhesion of blood monocytes isolated from healthy volunteers or mildly hypercholesterolemic patients was increased after intake of simvastatin but not placebo at 0.5 h and declined to baseline levels at 3 h. Blood cholesterol levels were unaltered and the observed effects did not correlate with systemic concentrations of the pro-drug nor the active drug concentration in the peripheral circulation. In conclusion, the transient increase in adhesiveness of monocytes may be due to direct and/or enterohepatic metabolites of simvastatin, demonstrating the necessity of drug metabolism for exerting the beneficial effects of long-term treatment.

Potassium recycling pathways in the human cochlea.

OBJECTIVES/HYPOTHESIS: Potential pathways for recycling potassium (K+) used in the maintenance of inner ear electrochemical gradients have been elucidated in animal models. However, little is known about K+ transport in the human cochlea. This study was designed to characterize putative K+ recycling pathways in the human ear and to determine whether observations from animal models can be extrapolated to humans. STUDY DESIGN: A prospective laboratory study using an immunohistochemical approach to analyze the distribution of key ion transport mediators in the human cochlea. METHODS: Human temporal bones were fixed in situ within 1 to 6 hours of death and subsequently harvested at autopsy. Decalcification was accomplished with the aid of microwaving. Immunohistochemical staining was then performed to define the presence and cell type-specific distribution of Na,K-ATPase, sodium-potassium-chloride cotransporter (NKCC), and carbonic anhydrase (CA) in the inner ear. RESULTS: Staining patterns visualized in the human cochlea closely paralleled those seen in other species. Anti-Na,K-ATPase stained strongly the basolateral plasma membrane of strial marginal cells and nerve endings underlying hair cells. This antibody also localized Na,K-ATPase to type II, type IV, and type V fibrocytes in the spiral ligament and in limbal fibrocytes. NKCC was present in the basolateral membrane of strial marginal cells as well as in type II, type V, and limbal fibrocytes. Immunoreactive carbonic anhydrase was present in type I and type III fibrocytes and in epithelial cells lining Reissner's membrane and the spiral prominence. CONCLUSIONS: The distribution of several major ion transport proteins in the human cochlea is similar but not identical to that described in various rodent models. These results support the presence of a complex system for recycling and regulating K+ homeostasis in the human cochlea, similar to that described in other mammalian species.

Purification of a bacterially expressed herpes simplex virus type 1 origin binding protein for use in posttranslational processing studies.

The origin binding protein (OBP) encoded by the UL9 open reading frame of herpes simplex virus type 1 (HSV-1) plays an essential role in productive infection by promoting the initiation of viral DNA synthesis. In this study, OBP was inducibly expressed in Escherichia coli and purified to homogeneity using a two-step chromatographic separation procedure. The properties of this recombinant OBP (rOBP) were found to be indistinguishable from those of the virus-encoded protein. Since rOBP was synthesized in bacterial cells, it lacked the posttranslational processing which normally occurs in OBP produced in HSV-1-infected mammalian cells and could therefore be exploited in experiments which addressed the effects of protein modification on OBP function. As an initial study, the impact of phosphorylation on enzymatic activity was examined using rOBP which had been treated with a panel of purified cellular kinases. rOBP was found to act as a substrate for nearly all of the kinases tested in (32)P-labeled phosphate transfer assays. However, only phosphorylation by protein kinase A (PKA, or cAMP-dependent protein kinase) was shown to significantly alter the enzymatic properties of rOBP, as it increased by five- to eightfold the ATPase activity associated with this protein. Activation of this critical viral DNA replication enzyme by a cAMP-dependent kinase such as PKA may be of some relevance in the natural course of HSV-1 infections, since reactivation of latent virus is thought to involve both signal transduction events and the induction of viral DNA synthesis. Thus, the expression and purification strategy outlined in this work provides an economical source of unmodified HSV-1 OBP that should prove useful in future in vitro studies.

Identification and characterization of a benzothiophene inhibitor of herpes simplex virus type 1 replication which acts at the immediate early stage of infection.

Analysis of a large compound library in a high throughput virus infection assay screen identified the benzothiophene PD146626 as a potent and specific inhibitor of herpes simplex virus type 1 (HSV-1) replication. PD146626 possessed an EC(50) and EC(90) against HSV-1 of 0.1 and 1 microM, respectively, and mediated no detectable cytotoxicity in cells at concentrations up to 1 microM. Western blot analyses and time of addition experiments demonstrated that in the presence of PD146626 HSV-1 underwent a specific block in viral gene expression at the immediate early stage. However, several observations indicated that a cellular function rather than a viral immediate early transactivator protein represented the molecular target for PD146626, including the lack of resistance of VP16 and ICP0 mutant viruses to the compound, the inability to select resistant strains of HSV-1 following exhaustive serial passaging of virus in the presence of the compound, and the sensitivity of human cytomegalovirus, which lacks VP16 and ICP0 homologs, to the compound. Moreover, kinetic studies suggested an unusual pattern of responsiveness of the host cell to PD146626, in that the compound could induce an extended antiviral state in cells after only a brief exposure. Together these results suggest that PD146626 targets a novel cellular function that is critical for the expression of HSV-1 immediate early genes but not host cell genes.

A colorimetric assay for high-throughput screening of inhibitors of herpes simplex virus type 1 alkaline nuclease.

Herpes simplex virus type 1 (HSV-1) encodes a deoxyribonuclease that is frequently referred to as alkaline nuclease (AN) because of its elevated pH optimum. Studies with recombinant viruses which contain deletions in the HSV-1 gene encoding AN have indicated that this enzyme is required for efficient virus replication and therefore represents a potential target for novel antiviral therapies. A simple colorimetric assay for deoxyribonuclease activity employing a DNA-methyl green substrate was adapted for use in a high-throughput screen to identify small molecule inhibitors of this enzyme. This screen identified 1,2-benzoisothiazolin-3-one as a specific inhibitor of AN, since it exhibited activity against AN but was completely inactive against bovine pancreatic DNaseI. Subsequent studies revealed that this compound most likely inhibited AN by forming disulfide linkages with one or more exposed cysteine residues on the surface of the enzyme and that AN was sensitive to sulfhydryl-group-modifying reagents in general. These results demonstrated the utility of this DNA-methyl green substrate-based assay in both the rapid identification and the characterization of novel small molecule inhibitors of the AN encoded by HSV-1 and other herpesviruses.

Microwave decalcification of human temporal bones.

OBJECTIVES/HYPOTHESIS: Morphological and immunohistochemical studies of human temporal bones are challenging as a result of difficulties in obtaining reliably fixed specimens and the lengthy time required for decalcification, typically 4 to 7 months. A novel method of processing human temporal bones using a microwave oven to accelerate decalcification is described. This procedure provides a rapid means of decalcifying temporal bones with good preservation of tissue morphology and antigenicity. METHODS: Human temporal bone specimens obtained at autopsy (n = 12, from specimens aged 43-91 y) were fixed within 6.5 hours of death by transtympanic perilymphatic perfusion of the inner ear. Decalcification was carried out using ethylenediaminetetra-acetic acid (EDTA) in a microwave oven and required only 3 to 6 weeks. Specimens were then dehydrated, embedded in paraffin, sectioned, and mounted on slides for morphological and immunohistochemical evaluation. RESULTS: Microscopic examination revealed no obvious artifacts attributable to the microwave decalcification process. The quality of morphological preservation was largely dependent on the postmortem fixation interval and adequacy of perilymphatic perfusion. Immunohistochemical analysis demonstrated strong positive staining for the enzyme Na,K-ATPase, an integral membrane protein. CONCLUSIONS: This study demonstrates that microwave decalcification provides an efficient and reliable means of processing human temporal bones for histological and histochemical examination. Decalcification time is significantly reduced with no apparent adverse effects on structural preservation or antigenicity.

Association of myocardial infarction with mononuclear cell expression of the cytomegalovirus chemokine receptor US28 in patients with NIDDM.

BACKGROUND: Infectious agents have been linked to atherosclerosis and its acute manifestations; however, little is known about their influence in the context of established risk factors. OBJECTIVE: To elucidate the role of the cytomegalovirus (CMV)-encoded chemokine receptor US28 in myocardial infarction (MI) afflicting patients with or without type II diabetes mellitus (NIDDM) on a molecular level. PATIENTS AND METHODS: In a group of patients (n=112) with a high prevalence of NIDDM and coronary artery disease, CMV serology was performed, and mRNA expression of US28 and immediate early 1 gene as markers of CMV reactivation were analyzed in peripheral mononuclear blood cells by a nested reverse transcription-polymerase chain reaction. Moreover, transendothelial chemotaxis assays using mononuclear cells transfected with or without US28 were performed in vitro. RESULTS: While the incidence of smoking was higher in nondiabetic patients with MI than in those without MI, significant differences in other risk factors, such as cholesterol, low density lipoprotein, fibrinogen, blood pressure, and Chlamydia pneumoniae immunoglobulin G or CMV immunoglobulin G titres, were not observed. In contrast, the levels of C-reactive protein reflecting inflammation or infection were raised in NIDDM patients with or without MI. Notably, mRNA expression of intermediate early 1 gene and US28 indicative of CMV reactivation was detected in a small subset (four of 21) of NIDDM patients with MI but not in those without MI (P<0.03). Transfection of US28 in mononuclear cells conferred transendothelial chemotaxis to monocyte chemokines, inferring a mechanism for deleterious effects of CMV under permissive conditions. CONCLUSIONS: Results show that MI was associated with mononuclear expression of CMV genes such as functional chemokine receptor US28 in a subset of patients with NIDDM, inferring that this association may predispose to MI. Ongoing infection or inflammation in NIDDM patients as shown by increased C-reactive protein may account for susceptibility to CMV reactivation and MI.

Cross-reactivity of the anti-PML antibody PG-M3 with the herpes simplex virus type 1 immediate early protein ICP4.

The PML protein is one of the components of ND10, nuclear matrix-associated structures which undergo rapid disintegration at the onset of herpes simplex virus type 1 (HSV-1) infection. This disruption event has been frequently visualized in immunofluorescence assays using the anti-PML mouse monoclonal antibody PG-M3. This antibody was surprisingly found to also stain nuclear virus replication compartments when employed at higher concentrations. This was shown to be due to an unexpected cross-reactivity of the PG-M3 antibody with the HSV-1 immediate early protein ICP4, a known component of replication compartments. The sequences of ICP4 recognized by PG-M3 were found to map to the extreme amino-terminal end of the protein, which includes a 21 amino acid segment that is partially homologous to the peptide of PML that was used to make PG-M3. These results suggest that PG-M3 may no longer represent an appropriate antibody for use in visualizing the fate of PML and ND10 during HSV-1 infection.

Cyclic AMP blocks bacterial lipopolysaccharide-induced myosin light chain phosphorylation in endothelial cells through inhibition of Rho/Rho kinase signaling.

During Gram-negative sepsis bacterial LPS induces endothelial cell contraction, actin reorganization, and loss of endothelial integrity by an unknown signal mechanism. In this study, we provide evidence that LPS-stimulation of endothelial cells (HUVEC) decreases myosin light chain (MLC) phosphatase, resulting in an increase in MLC phosphorylation followed by cell contraction. All of these LPS effects could be blocked by the Rho-GTPase inhibitor C3 transferase from Clostridium botulinum or the Rho kinase inhibitor Y-27632. These data suggest that LPS induces MLC phosphorylation via Rho/Rho kinase-mediated inhibition of MLC phosphatase in HUVEC. Furthermore, we observed that cAMP-elevating drugs, known to exert a vasoprotective function, mimicked the effects of C3 transferase and Y-27632, i.e., inhibited LPS-induced MLC phosphatase inactivation and MLC phosphorylation. cAMP elevation did not inhibit myosin phosphorylation induced by constitutively active V14Rho or the MLC phosphatase inhibitor calyculin and did not induce phosphorylation of RhoA in HUVEC, indicating inhibition of an upstream regulator of Rho/Rho kinase. Taken together, Rho/Rho kinase appears to be a central target for inflammatory mediators causing endothelial cell contraction such as bacterial toxins, but also for vasoprotective molecules elevating intracellular cAMP.