Single-stranded DNA aptamer RT1t49 inhibits RT polymerase and RNase H functions of HIV type 1, HIV type 2, and SIVCPZ RTs

Natural and selected resistance of HIV-1 to current anti-HIV drugs continues to pose serious problems to the development of HIV-1 antivirals. The viral reverse transcriptase (RT) is a proven therapeutic target. Single-stranded RNA and DNA (ssRNA and ssDNA) aptamers have been selected that specifically and potently inhibit RT function. In particular, the ssDNA aptamer RT1t49 was previously selected to recognize the RT from a subtype B strain of HIV-1 and binds with a reported K(d) of 4 nM. In the present work, we show that RT1t49 inhibits recombinant RT cloned from diverse branches of the primate lentiviral family. Aptamer concentrations required for half-maximal inhibition of all HIV-1, HIV-2, and SIV(CPZ) RTs assayed were in the low-to mid-nanomolar range for both polymerase and RNase H activities. Using pre-steady-state and order-of-addition kinetic analyses, we also established that this ssDNA aptamer competes with primer-template for access to RT, and that addition of a nucleoside analog RT inhibitor (NRTI) to the in vitro reaction enhanced the overall effectiveness of both drugs, while nonnucleoside analog RT inhibitors (NNRTIs) exhibited simple additivity. This is the first demonstration of universal inhibition of HIV and SIV(cpz) RTs by a nucleic acid aptamer and supports previous reports suggesting that resistance to RT1t49 may be exceptionally infrequent.

Cross-clade inhibition of recombinant human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus SIVcpz reverse transcriptases by RNA pseudoknot aptamers

Reverse transcriptase (RT) remains a primary target in therapies directed at human immunodeficiency virus type 1 (HIV-1). RNA aptamers that bind RT from HIV-1 subtype B have been shown to protect human cells from infection and to reduce viral infectivity, but little is known about the sensitivity of the inhibition to amino sequence variations of the RT target. Therefore, we assembled a panel of 10 recombinant RTs from phylogenetically diverse lentiviral isolates (including strains of HIV-1, simian immunodeficiency virus SIVcpz, and HIV-2). After validating the panel by measuring enzymatic activities and inhibition by small-molecule drugs, dose-response curves for each enzyme were established for four pseudoknot RNA aptamers representing two structural subfamilies. All four aptamers potently inhibited RTs from multiple HIV-1 subtypes. For aptamers carrying family 1 pseudoknots, natural resistance was essentially all-or-none and correlated with the identity of the amino acid at position 277. In contrast, natural resistance to aptamers carrying the family 2 pseudoknots was much more heterogeneous, both in degree (gradation of 50% inhibitory concentrations) and in distribution across clades. Site-directed and subunit-specific mutagenesis identified a common R/K polymorphism within the p66 subunit as a primary determinant of resistance to family 1, but not family 2, pseudoknot aptamers. RNA structural diversity therefore translates into a nonoverlapping spectrum of mutations that confer resistance, likely due to differences in atomic-level contacts with RT.

Catalytic core of alphavirus nonstructural protein nsP4 possesses terminal adenylyltransferase activity

The RNA-dependent RNA polymerase nsP4 is an integral part of the alphavirus replication complex. To define the role of nsP4 in viral RNA replication and for a structure-function analysis, we expressed Sindbis virus nsP4 in Escherichia coli. The core catalytic domain of nsP4 (Delta97nsP4, a deletion of the N-terminal 97 amino acids), which consists of the predicted polymerase domain containing the GDD amino acid motif required for viral RNA synthesis, was stable against proteolytic degradation during expression. Therefore, the recombinant core domain and selected mutants were expressed and purified to homogeneity. We determined that Delta97nsP4 possesses terminal adenylyltransferase (TATase) activity, as it specifically catalyzed the addition of adenine to the 3' end of an acceptor RNA in the presence of divalent cations. Furthermore, Delta97nsP4 is unable to transfer other nucleotides (UTP, CTP, GTP, and dATP) to the acceptor RNA in the absence or presence of other nucleotides. Delta97nsP4 possessing a GDD-to-GAA mutation completely inactivates the enzymatic activity. However, a GDD-to-SNN mutation did not inactivate the enzyme but reduced its activity to approximately 45% of that of the wild type in the presence of Mg(2+). Investigation of the TATase of the GDD-to-SNN mutant revealed that it had TATase equivalent to that of the wild type in the presence of Mn(2+). Identification of Delta97nsP4 TATase activity suggests a novel function of the alphavirus RNA-dependent RNA polymerase in the maintenance and repair of the poly(A) tail, an element required for replication of the viral genome.

Template requirements for recognition and copying by Sindbis virus RNA-dependent RNA polymerase

The Sindbis virus (SIN) nonstructural protein nsP4 possesses the RNA-dependent RNA polymerase activity required for the replication of the SIN genome and transcription of a subgenomic mRNA during infection. Isolation of this protein from other viral components of the RNA synthetic complex allowed the characterization of template requirements for nsP4-mediated genome replication. The major findings of this study are: (i) in the absence of other viral proteins nsP4 is capable of copying SIN plus- and minus-strand templates, but does not transcribe subgenomic RNA; (ii) mutations in the 3' conserved sequence element and poly(A) tail of the plus-strand template prevent nsP4-mediated de novo initiation of minus-strand RNA synthesis; (iii) nsP4-dependent terminal addition of nucleotides occurs on template RNA possessing certain mutations in the 3'CSE and polyadenylate tail ; (iv) nsP4 is capable of minus-strand synthesis independent of the sequence at the 5' end of the template; (v) an A-U rich sequence in the 3'CSE represents a binding site for a replicase component, probably nsP4; (vi) plus-strand genomic RNA synthesis is dependent on the 3' end of the minus-strand template. These studies begin to define the specific interactions with the viral RNA templates mediated by individual components of the viral replication complex and suggest a model for ternary complex formation during the initiation of minus-strand RNA synthesis.

The role of the 3' terminus of the Sindbis virus genome in minus-strand initiation site selection

Genome replication of plus-strand RNA viruses begins with the generation of a minus-strand copy of the genome. Minus-strand synthesis must initiate at or close to the 3' end of the genome and progress to processive elongation to yield the appropriate template for genomic RNA synthesis. The Sindbis virus genome possesses a 3' polyadenylate tail preceded by a 19 nucleotide conserved sequence element (3' CSE). Analyses of in vitro and in vivo synthesized minus-strand RNA presented in this manuscript identify the cytidylate residue immediately preceding the poly (A) tail as the predominant wild-type initiation site. Mutations in the poly (A) tail and the 3' CSE caused the initiation site to shift to the poly (A) tail. Analysis of the products of non-wild-type initiation events demonstrated that they are not productively elongated. This study indicates that full-length minus-strand RNA synthesis is dependent upon initiation occurring at the appropriate site and suggests a mechanism for selection and maintenance of the wt 3' CSE and poly (A) tail.

Requirements at the 3' end of the sindbis virus genome for efficient synthesis of minus-strand RNA

The 3'-untranslated region of the Sindbis virus genome is 0.3 kb in length with a 19-nucleotide conserved sequence element (3' CSE) immediately preceding the 3'-poly(A) tail. The 3' CSE and poly(A) tail have been assumed to constitute the core promoter for minus-strand RNA synthesis during genome replication; however, their involvement in this process has not been formally demonstrated. Utilizing both in vitro and in vivo analyses, we have examined the role of these elements in the initiation of minus-strand RNA synthesis. The major findings of this study with regard to efficient minus-strand RNA synthesis are the following: (i) the wild-type 3' CSE and the poly(A) tail are required, (ii) the poly(A) tail must be a minimum of 11 to 12 residues in length and immediately follow the 3' CSE, (iii) deletion or substitution of the 3' 13 nucleotides of the 3' CSE severely inhibits minus-strand RNA synthesis, (iv) templates possessing non-wild-type 3' sequences previously demonstrated to support virus replication do not program efficient RNA synthesis, and (v) insertion of uridylate residues between the poly(A) tail and a non-wild-type 3' sequence can restore promoter function to a limited extent. This study shows that the optimal structure of the 3' component of the minus-strand promoter is the wild-type 3' CSE followed a poly(A) tail of at least 11 residues. Our findings also show that insertion of nontemplated bases can restore function to an inactive promoter.

Protein and lipid sources affect cholesterol concentrations of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone)

Two experiments were conducted to evaluate the effects of protein and lipid sources on cholesterol, AA, and fatty acid content, and on biological performance of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone). In Exp. 1, seven isonitrogenous and isocaloric diets were prepared using fish meal; soybean meal; casein; fish meal + soybean meal; fish meal + casein; soybean meal + casein; and fish meal + soybean meal + casein. In Exp. 2, seven isonitrogenous and isocaloric diets were prepared using fish oil; soy oil; poultry fat; fish oil + soy oil; fish oil + poultry fat; soy oil + poultry fat; and fish oil + soy oil + poultry fat. Nine shrimp (average BW 570 mg) were stocked per 60-L tank, with three tanks per diet in each experiment. Shrimp were fed to apparent satiation twice daily for 28 d. Protein sources affected shrimp cholesterol, feed consumption, feed efficiency, protein consumption, protein efficiency ratio, and crude body fat (P < or = 0.05), but not weight gain, survival, hepatosomatic index, body protein, ash, and AA composition. Body (without hepatopancreas) cholesterol concentrations were the highest in shrimp fed the diet containing fish meal (0.81%), lowest for those fed the casein diet (0.64%), and intermediate in the other dietary treatment groups (range 0.71 to 0.74%). Lipid source also affected shrimp body cholesterol, body fatty acid profiles, and fatty acid profiles in the hepatopancreas (P < or = 0.05), but not growth performance, body protein, fat, ash, and cholesterol concentrations in the hepatopancreas. Shrimp fed the fish oil diet had the highest body cholesterol (0.75%), whereas those fed the soy oil or poultry fat diets were lowest (0.66 and 0.65%, respectively). Results indicate that by replacing fish meal and fish oil with soybean meal and soy oil, shrimp growth performance is not affected, but body cholesterol concentration is reduced.

The pathology of phosphorus deficiency in fish--a review

Phosphorus (P) is an essential component of fish diets. Its deficiency affects not only hard tissues, where it is responsible for rickets, leading to skeletal malformation, but also influences various aspects of intermediary metabolism, and thus growth and feed conversion. Therefore, optimizing the dietary inclusion level is critical at all times. As the aquaculture industry has expanded, so the effects of P in farm effluents, derived from metabolic and uneaten food sources, have also become recognized. Diets are increasingly formulated on a basis that will not only provide adequate P for fish needs, but also endeavour to ensure minimal acceptable P levels in effluents at the same time. Many variables influence P requirements and P availability in fish diets, so it is inadvisable to feed diets formulated to an assumed minimum dietary requirement level, irrespective of the advantages that such a formulation may provide to environmental impact.

Hepatitis C virus RNA synthesis in a cell-free system isolated from replicon-containing hepatoma cells

A number of hepatitis C virus (HCV) proteins, including NS5B, the RNA-dependent RNA polymerase, were detected in membrane fractions from Huh7 cells containing autonomously replicating HCV RNA replicons. These membrane fractions were used in a cell-free system for the analysis of HCV RNA replication. Initial characterization revealed a reaction in which the production of replicon RNA increased over time at temperatures ranging from 25 to 40 degrees C. Heparin sensitivity and nucleotide starvation experiments suggested that de novo initiation was occurring in this system. Both Mn2+ and Mg2+ cations could be used in the reaction; however, concentrations of Mn2+ greater than 1 mM were inhibitory. Compounds shown to inhibit recombinant NS3 and NS5B activity in vitro were found to inhibit RNA synthesis in the cell-free system. This system should be useful for biochemical analysis of HCV RNA synthesis by a multisubunit membrane-associated replicase and for evaluating potential antiviral agents identified in biochemical or cell-based screens.

DrosophilaAmphiphysin is implicated in protein localization and membrane morphogenesis but not in synaptic vesicle endocytosis

Amphiphysin family members are implicated in synaptic vesicle endocytosis, actin localization and one isoform is an autoantigen in neurological autoimmune disorder; however, there has been no genetic analysis of Amphiphysin function in higher eukaryotes. We show that Drosophila Amphiphysin is localized to actin-rich membrane domains in many cell types, including apical epithelial membranes, the intricately folded apical rhabdomere membranes of photoreceptor neurons and the postsynaptic density of glutamatergic neuromuscular junctions. Flies that lack all Amphiphysin function are viable, lack any observable endocytic defects, but have abnormal localization of the postsynaptic proteins Discs large, Lethal giant larvae and Scribble, altered synaptic physiology, and behavioral defects. Misexpression of Amphiphysin outside its normal membrane domain in photoreceptor neurons results in striking morphological defects. The strong misexpression phenotype coupled with the mild mutant and lack of phenotypes suggests that Amphiphysin acts redundantly with other proteins to organize specialized membrane domains within a diverse array of cell types.

Soluble guanylate cyclase is required during development for visual system function in Drosophila

A requirement for nitric oxide (NO) in visual system development has been demonstrated in many model systems, but the role of potential downstream effector molecules has not been established. Developing Drosophila photoreceptors express an NO-sensitive soluble guanylate cyclase (sGC), whereas the optic lobe targets express NO synthase. Both of these molecules are expressed after photoreceptor outgrowth to the optic lobe, when retinal growth cones are actively selecting their postsynaptic partners. We have previously shown that inhibition of the NO-cGMP pathway in vitro leads to overgrowth of retinal axons. Here we examined flies mutant for the alpha subunit gene of the Drosophila sGC (Gcalpha1). This mutation severely reduced but did not abolish GCalpha1 protein levels and NO-stimulated sGC activity in the developing photoreceptors. Although few mutant individuals possessed a disorganized retinal projection pattern, pharmacological NOS inhibition during metamorphosis increased this disorganization in mutants to a greater degree than in the wild type. Adult mutants lacked phototactic behavior, and the off-transient component of electroretinograms was frequently absent or greatly reduced in amplitude. Normal phototaxis and off-transient amplitude were restored by heat shock-mediated Gcalpha1 expression applied during metamorphosis but not in the adult. We propose that diminished sGC activity in the visual system during development causes inappropriate or inadequate formation of first-order retinal synapses, leading to defects in visual system function and visually mediated behavior.

Diagnosis and treatment of piriformis syndrome

Piriformis syndrome remains a controversial diagnosis, despite its having first been described over 60 years ago. The controversy stems from several factors: variable and sometimes unclear cause, similarity to other more easily recognizable causes of sciatica, lack of consistent objective diagnostic findings, and relative rarity. Nevertheless, it is reasonable to infer that sciatic pain may be caused by compression anywhere along its length, from the spinal root level to the popliteal fossa, as is peripheral nerve entrapment elsewhere in the body. Pathologic changes at the greater sciatic notch may well be the source of sciatic pain and should be considered by the clinician. The diagnosis of piriformis syndrome remains one of exclusion, however, and in patients who present with sciatica, more common causes such as lumbar disease should be investigated and ruled out first. After excluding the most common causes of sciatica, physicians can use the criteria described here to investigate the possibility of piriformis syndrome. If properly diagnosed, it can often be treated effectively with either surgical or nonsurgical means.

Epidural fibrosis and the failed back surgery syndrome: history and physical findings

Patients who present with recurrent symptoms after surgical intervention aimed at correcting their lumbosacral disease pose a therapeutic challenge. A heterogeneous group of factors may underlie symptom recurrence and formulation of a therapeutic strategy depends on an accurate diagnosis of the patient's underlying problem. In this review, the authors discuss the relevant historical and physical findings in patients with epidural fibrosis and the failed back surgery syndrome.

An unusual multiple drug intoxication case involving citalopram

A 47-year-old male with a history of drug abuse and suicide attempts was found dead at home. The death scene investigation showed evidence of cocaine abuse and multiple drug ingestion. Citralopram, a new selective serotonin reuptake inhibitor, cocaine, oxycodone, promethazine, propoxyphene, and norpropoxyphene were identified and quantitated in the postmortem samples by gas chromatography-mass spectrometry. The concentration of citalopram in the femoral blood was 0.88 mg/L. The heart blood concentration was 1.16 mg/L. Femoral blood concentrations of the other drugs were as follows: cocaine, 0.03 mg/L; oxycodone, 0.06 mg/L; promethazine, 0.02 mg/L; propoxyphene, 0.02 mg/L; and norpropoxyphene, 0.07 mg/L. Other tissue samples were also analyzed. The concentrations of cocaine, oxycodone, promethazine, and propoxyphene in the blood, liver, brain, and gastric contents did not suggest an intentional overdose. However, the possibility of multiple drug interactions including citalopram was evident. In this case, the citalopram concentrations were consistent with those reported in fatal cases involving multiple drug use. Citalopram was present in urine at a concentration of 0.9 mg/L.

A molecular pathway for light-dependent photoreceptor apoptosis in Drosophila

Light-induced photoreceptor apoptosis occurs in many forms of inherited retinal degeneration resulting in blindness in both vertebrates and invertebrates. Though mutations in several photoreceptor signaling proteins have been implicated in triggering this process, the molecular events relating light activation of rhodopsin to photoreceptor death are yet unclear. Here, we uncover a pathway by which activation of rhodopsin in Drosophila mediates apoptosis through a G protein-independent mechanism. This process involves the formation of membrane complexes of phosphorylated, activated rhodopsin and its inhibitory protein arrestin, and subsequent clathrin-dependent endocytosis of these complexes into a cytoplasmic compartment. Together, these data define the proapoptotic molecules in Drosophila photoreceptors and indicate a novel signaling pathway for light-activated rhodopsin molecules in control of photoreceptor viability.

Genetically similar transduction mechanisms for touch and hearing in Drosophila

To test the effects of mechanosensory mutations on hearing in Drosophila, we have recorded sound-evoked potentials originating from ciliated sensory neurons in Johnston's organ, the chordotonal organ that is the sensory element of the fly's antennal ear. Electrodes inserted close to the antennal nerve were used to record extracellular compound potentials evoked by near-field sound stimuli. Sound-evoked potentials are absent in atonal mutant flies, which lack Johnston's organ. Mutations in many genes involved in mechanotransduction by tactile bristles also eliminate or reduce the Johnston's organ response, indicating that related transduction mechanisms operate in each type of mechanosensory organ. In addition, the sound-evoked response is affected by two mutations that do not affect bristle mechanotransduction, beethoven (btv) and touch-insensitive-larvaB (tilB). btv shows defects in the ciliary dilation, an elaboration of the axoneme that is characteristic of chordotonal cilia. tilB, which also causes male sterility, shows structural defects in sperm flagellar axonemes. This suggests that in addition to the shared transduction mechanism, axonemal integrity and possibly ciliary motility are required for signal amplification or transduction by chordotonal sensory neurons.

The Cys(3)-His(1) motif of the respiratory syncytial virus M2-1 protein is essential for protein function

The M2 gene of respiratory syncytial (RS) virus has two open reading frames (ORFs). ORF1 encodes a 22-kDa protein termed M2-1. The M2-1 protein contains a Cys(3)-His(1) motif (C-X(7)-C-X(5)-C-X(3)-H) near the amino terminus. This motif is conserved in all human, bovine, and ovine strains of RS virus. A similar motif found in the mammalian transcription factor Nup475 has been shown to bind zinc. The M2-1 protein of human RS virus functions as a transcription factor which increases polymerase processivity, and it enhances readthrough of intergenic junctions during RS virus transcription, thereby acting as a transcription antiterminator. The M2-1 protein also interacts with the nucleocapsid protein. We examined the effects of mutations of cysteine and histidine residues predicted to coordinate zinc in the Cys(3)-His(1) motif on transcription antitermination and N protein binding. We found that mutating the predicted zinc-coordinating residues, the cysteine residues at amino acid positions 7 and 15 and the histidine residue at position 25, prevented M2-1 from enhancing transcriptional readthrough. In contrast, mutations of amino acids within this motif not predicted to coordinate zinc had no effect. Mutations of the predicted zinc-coordinating residues in the Cys(3)-His(1) motif also prevented M2-1 from interacting with the nucleocapsid protein. One mutation of a noncoordinating residue in the motif which did not affect readthrough during transcription, E10G, prevented interaction with the nucleocapsid protein. This suggests that M2-1 does not require interaction with the nucleocapsid protein in order to function during transcription. Analysis of the M2-1 protein in reducing sodium dodecyl sulfate-polyacrylamide gels revealed two major forms distinguished by their mobilities. The slower migrating form was shown to be phosphorylated, whereas the faster migrating form was not. Mutations in the Cys(3)-His(1) motif caused a change in distribution of the M2-1 protein from the slower to the faster migrating form. The data presented here show that the Cys(3)-His(1) motif of M2-1 is essential for maintaining the functional integrity of the protein.

A new approach to estimating the minimum dietary requirement of phosphorus for large rainbow trout based on nonfecal excretions of phosphorus and nitrogen

A new method was developed to estimate the minimum dietary requirement of phosphorus (P) for large fish for which conventional methods are not suitable. The method is based upon nonfecal (mainly urinary) excretion of inorganic P and total nitrogen from fish placed in a metabolic tank. In the first experiment, small and large rainbow trout (body wt 203 and 400 g, respectively) and, in the second experiment, P-sufficient, P-deficient and starved rainbow trout (different in diet history; body wt 349-390 g) were fed a constant amount (standard feeding rate) of semipurified diets with incremental P concentrations once daily at 15 degrees C. In all cases, there was no measurable excretion of P when dietary P concentration was low; however, beyond a specific dietary concentration, excretion of P increased rapidly. The point where the fish started to excrete P was assumed to be the minimum dietary requirement. By d 3 of consuming the experimental diets, the response of the fish to dietary P concentration stabilized, and excretion of P remained constant within dietary treatment groups for the subsequent sampling days (d 6, 9 and 12). The minimum dietary requirement of available P for fish having body wt of 203 and 400 g was estimated to be 6.62 and 5.54 g/kg dry diet, respectively, and that for P-sufficient, P-deficient and starved fish was estimated to be 4.06, 5.83 and 4.72 g/kg dry diet, respectively, when feed efficiency is 1.

Phosphatase activity in rat adipocytes: effects of insulin and insulin resistance

Insulin regulates the activity of both protein kinases and phosphatases. Little is known concerning the subcellular effects of insulin on phosphatase activity and how it is affected by insulin resistance. The purpose of this study was to determine insulin-stimulated subcellular changes in phosphatase activity and how they are affected by insulin resistance. We used an in vitro fatty acid (palmitate) induced insulin resistance model, differential centrifugation to fractionate rat adipocytes, and a malachite green phosphatase assay using peptide substrates to measure enzyme activity. Overall, insulin alone had no effect on adipocyte tyrosine phosphatase activity; however, subcellularly, insulin increased plasma membrane adipocyte tyrosine phosphatase activity 78 +/- 26% (n = 4, P < 0.007), and decreased high-density microsome adipocyte tyrosine phosphatase activity 42 +/- 13% (n = 4, P < 0.005). Although insulin resistance induced specific changes in basal tyrosine phosphatase activity, insulin-stimulated changes were not significantly altered by insulin resistance. Insulin-stimulated overall serine/threonine phosphatase activity by 16 +/- 5% (n = 4, P < 0.005), which was blocked in insulin resistance. Subcellularly, insulin increased plasma membrane and crude nuclear fraction serine/threonine phosphatase activities by 59 +/- 19% (n = 4, P < 0. 005) and 21 +/- 7% (n = 4, P < 0.007), respectively. This increase in plasma membrane fractions was inhibited 23 +/- 7% (n = 4, P < 0. 05) by palmitate. Furthermore, insulin increased cytosolic protein phosphatase-1 (PP-1) activity 160 +/- 50% (n = 3, P < 0.015), and palmitate did not significantly reduce this activity. However, palmitate did reduce insulin-treated low-density microsome protein phosphatase-1 activity by 28 +/- 6% (n = 3, P < 0.04). Insulin completely inhibited protein phosphatase-2A activity in the cytosol and increased crude nuclear fraction protein phosphatase-2A activity 70 +/- 29% (n = 3, P < 0.038). Thus, the major effects of insulin on phosphatase activity in adipocytes are to increase plasma membrane tyrosine and serine/threonine phosphatase, crude nuclear fraction protein phosphatase-2A, and cytosolic protein phosphatase-1 activities, while inhibiting cytosolic protein phosphatase-2A. Insulin resistance was characterized by reduced insulin-stimulated serine/threonine phosphatase activity in the plasma membrane and low-density microsomes. Specific changes in phosphatase activity may be related to the development of insulin resistance.

Evaluation of a fully automated high-performance liquid chromatography assay for hemoglobin A1c

INTRODUCTION

Measurement of hemoglobin A1c (HbA1c) is used as an objective measure of long-term blood glucose control in diabetic patients. Recent improvements in automation combined with new recommendations for precision and accuracy have caused us to reevaluate our methods for measuring HbA1c.

OBJECTIVE

We evaluated a newly automated high-performance liquid chromatography (HPLC) instrument for measurement of HbA1c (Tosoh A1c 2.2 Plus Glycohemoglobin Analyzer, Tosoh Medics, Foster City, Calif) and compared the results obtained by HPLC to those obtained with an immunoassay (Hitachi 911, Boehringer Mannheim Corporation, Indianapolis, Ind).

RESULTS

The Tosoh analyzer was found to be linear in a range of 5.3% to 17% and had a throughput of 20 samples per hour. HbA1c results for 102 patient samples by the 2 techniques showed good correlation, with a slope of 0.87 and an intercept at 1.27% +/- 0.15%. Both the total and within-run coefficients of variation were consistently lower for the HPLC method compared with the immunoassay method. The HPLC method produces a chromatogram that shows the different hemoglobin fractions, allowing identification of abnormal hemoglobin variants. In heterozygous individuals, HbA1c measurements are made with no interference from the hemoglobin variant. In the case of homozygous or doubly heterozygous hemoglobin variants, the Tosoh HPLC identifies the hemoglobin variants as such and correctly does not report a HbA1c value in the presence of a markedly decreased amount of hemoglobin A.

CONCLUSIONS

The Tosoh HPLC provides adequate throughput and improved precision, and the method is traceable to the Diabetes Control and Complications Trial.

Anterior cervical discectomy for one- and two-level cervical disc disease: the controversy surrounding the question of whether to fuse, plate, or both

Since the introduction of anterior approaches to the cervical spine for the surgical treatment of degenerative disc disease, controversies have developed regarding the necessity of fusion following anterior cervical discectomy, the use of allografts instead of autologous bone for fusion, and, recently, the employment of anterior cervical plating systems in addition to fusion for uncomplicated disc disease. We reviewed seven clinical papers dealing with these issues; these articles surveyed a total of 1153 patients. Several observations can be made from these reviews. First, there is little or no difference in clinical outcome following single-level anterior discectomy, whether a fusion is performed or not, regardless of whether the operation was for soft discs or osteophytes. Second, most patients who underwent two-level discectomies had outcomes comparable to patients who underwent surgery at one level, regardless of whether they were fused or not. Data from four prospective randomized clinical studies in addition to multiple non-randomized or retrospective studies support these conclusions. Although the incidence of complications such as persistent postoperative posterior cervical and shoulder pain and kyphotic deformities is higher in unfused patients (and is quite significant in some series), the advantages conferred by interbody fusion such as biomechanical stability, decreased incidence of kyphotic deformity, and decreased pain are offset by graft and donor-site morbidity. Specific indications for fusion include multi-level discectomies, significant straightening of the cervical spine, failed prior fusions, and trauma. It has been demonstrated that comparable fusion rates can be achieved with allografts rather than harvested autologous bone. The advantages of autografts over allografts are relatively slight in most patients who undergo anterior fusion for one- or two-level disc disease, although patients with impaired healing, significant osteopenia, or concomitant microvascular disease, such as chronic smokers, may benefit from autologous bone. The use of allografts avoids donor-site morbidity in patients without these problems. Anterior cervical plates are useful for cases of instability requiring fusion (such as trauma); these implants may decrease reoperation rates and the incidence of delayed instability in select cases. However, the cost-effectiveness of their generalized use for uncomplicated cervical disc disease has not been demonstrated. In conclusion, a general statement regarding the optimal surgical treatment for cervical disc herniations using anterior approaches is difficult to make with this limited review. Surgeons' experience and familiarity with a particular approach are probably the most important factors in ensuring successful outcomes.

Diverse gene junctions of respiratory syncytial virus modulate the efficiency of transcription termination and respond differently to M2-mediated antitermination

The ability of the diverse gene junctions of respiratory syncytial (RS) virus to signal the termination of transcription was analyzed. Nine dicistronic subgenomic replicons of RS virus were constructed; each contained one of the RS virus gene junctions in its natural upstream and downstream sequence context. The RNA synthesis activities of these subgenomic replicons were analyzed in the absence and presence of the M2 protein, which we showed previously to function as a transcription antiterminator. Our data showed that the efficiency with which the polymerase terminated transcription was affected by the gene junction that it encountered. The M2 protein significantly decreased the efficiency of the termination of transcription, resulting in increased levels of readthrough transcription at all the gene junctions. The diverse gene junctions fell into three broad groups with respect to their ability to signal transcription termination. One group of gene junctions (NS1/NS2, NS2/N, M2/L, and L/trailer) showed inefficient termination in the absence or the presence of the M2 protein. A second group of gene junctions (N/P, P/M, M/SH, SH/G, and G/F) terminated transcription efficiently. The SH/G gene junction terminated transcription with the greatest efficiency and produced low levels of readthrough transcripts in the absence or the presence of the M2 protein, correlating with the absence of SH/G polycistronic transcripts in RS virus-infected cells. The F/M2 gene junction was particularly sensitive to the M2 protein: it efficiently signaled termination in the absence of the M2 protein but produced high levels of readthrough transcripts in the presence of the M2 protein. This result suggests that the M2 protein may regulate its own production by negative feedback. The data presented here show that the different gene junctions of RS virus do modulate RS virus transcription termination. The M2 protein reduced termination at all gene junctions. The magnitude of antitermination due to the M2 protein, however, varied at the different gene junctions. The data presented here indicate that the mechanism for the regulation of RS virus gene expression is more complex than was previously appreciated.