Hepatic myelopathy after splenorenal shunting: report of one case and review of the literature

Hepatic myelopathy is a rare complication of cirrhosis, usually associated with surgical or spontaneous porto-systemic shunts. Its pathophysiology is unknown. It is characterized by a motor involvement of the lower limbs without clinical sensory abnormality, leading to spastic paraparesis. These neurological features are related to a symmetric loss of myelin in the lateral corticospinal tracts. Usefulness of liver transplantation in this setting is not yet determined. We describe here the case of a 29-year-old male who presented with progressive spastic paraparesis of the lower limbs 3 years after a spleno-renal shunt.

Childhood experiences and adult behavior in a group of women with pain accounted for by psychological factors and a group recovered from major depression

OBJECTIVE

In this study twenty-four women with pain accounted for by psychological factors (DSM-IV, 307.80) and twenty-four with major depression diagnosed according to DSM-III-R were compared to study the relationship between pain and depression.

METHOD

They were examined by a semi-structured, tape-recorded interview to study their childhood experiences and adult behavior. The interviews were rated by two independent and blind raters. Interrater correlation (Cohen-Kappa) varied between good and close agreement.

RESULTS

Of childhood experiences, "brutality between parents," "brutality toward child," and "sexual abuse" were often found in both groups and were more strongly represented in these than in comparison groups of former studies. As adults, the pain group had experienced more serious illness (p = 0.037) and surgery (p = 0.014). The depression group more often had a history of depression (15/24 vs. 4/24; p = 0.001). The pain group spoke negatively of its physicians (p = 0.001), was more hostile during the interview (p = 0.041), was less convinced of the benefit of the hospital stay (p = 0.029), felt less self-responsible, and was more pessimistic (p = 0.013). The pain patients also provoked negative emotions in the raters, whereas the latter's reaction to the depression group was compassion and interest (p = 0.0005) (Pearson's chi2 and Fisher's exact tests).

CONCLUSIONS

The results show that negative childhood experiences are prominent and similar in patients with pain accounted for by psychological factors and in patients after major depression. Adult behavior, however, is very different.

Persistence of botulinum neurotoxin A demonstrated by sequential administration of serotypes A and E in rat EDL muscle

Botulinum neurotoxin serotypes A (BoNT/A) and E (BoNT/E) inhibit neurotransmitter release from peripheral cholinergic nerve terminals by cleaving different sites on SNAP-25, a protein involved in synaptic vesicle docking and exocytosis. Since recovery from BoNT/A is protracted, but reversal of BoNT/E intoxication is relatively rapid, it was of interest to determine whether sequential exposure to BoNT/A and BoNT/E could provide insight into the factors responsible for persistence of BoNT action. Extensor digitorum longus (EDL) muscles from rats were injected locally with 5 mouse LD(50) units of BoNT/A or 20 mouse LD(50) units of BoNT/E; these doses were selected to produce total paralysis of EDL muscles within 48 hr. Additional groups of rats were injected sequentially with either BoNT/A followed 48 h later by BoNT/E or with BoNT/E followed 48 h later by BoNT/A. Muscle tensions were elicited in situ in response to supramaximal stimulation of the peroneal nerve to monitor recovery from BoNT intoxication. Tensions returned to 53% and 94% of control, respectively, 7 and 15 days after injection of BoNT/E. In contrast, tensions in muscles injected with BoNT/A returned to only 2% and 12% of control at these time points. Preparations injected sequentially with BoNT/A followed by BoNT/E or with BoNT/E followed by BoNT/A exhibited slow recovery times resembling those recorded in the presence of BoNT/A alone. Pronounced atrophy of the EDL muscle was observed in rats injected with BoNT/A or in those receiving serotype combinations in either sequence, whereas no loss of muscle mass was observed in animals treated with BoNT/E alone. Data suggesting that BoNT/E can enter BoNT/A-treated preparations was obtained by findings that 3,4-diaminopyridine, which readily reversed muscle paralysis after BoNT/A exposure, lost this ability within 1 h of BoNT/E addition. Evidence that BoNT/E was able to cleave SNAP-25 at its characteristic site during sequential neurotoxin exposure was demonstrated by western blot analysis of cultured primary cortical neurons. Since the sequential exposure studies indicate that recovery from BoNT intoxication is lengthened by exposure to serotype A, but not shortened by exposure to serotype E, the duration of BoNT/A intoxication appears to be determined predominantly by the intracellular stability of catalytically active BoNT/A light chain.

Long-term terlipressin administration improves renal function in cirrhotic patients with type 1 hepatorenal syndrome: a pilot study

BACKGROUND

Hepatorenal syndrome (HRS) is a severe complication of liver cirrhosis. Recently, ornipressin, a potent splanchnic vasoconstrictor, was reported to improve renal function in patients with HRS. However, this treatment is associated with a high incidence of vascular complications. Terlipressin is thought to be as effective as ornipressin with less systemic complications.

AIMS

To evaluate the effectiveness and safety of terlipressin administration in cirrhotic patients with type 1 HRS.

PATIENTS

Twelve consecutive patients fulfilling HRS criteria of the International Ascites Club were included in the study. Median plasma creatinine and sodium, urine volume and sodium before treatment were 3.4 mg% (2.5-4.0); 127 mEq/l (124-130), 500 ml/24 h (100-1031) and 7 mEq/24 h (1-17).

METHODS

Terlipressin was administered i.v. 2 mg bid in 8 patients and tid in 4 others for at least one week and up to 2 months.

RESULTS

After one week of treatment median plasma creatinine decreased to 1.8 mg% (1.3-2.1) together with an increase in urine volume, sodium excretion, creatinine and free-water clearance. Three patients underwent successful liver transplantation with a near normal renal function after 34, 36 and 111 days. The 9 other patients died during follow-up (4 from sepsis, 2 from digestive bleeding and 3 from liver failure). No ischaemic complications were encountered during the treatment.

CONCLUSIONS

Long-term terlipressin administration is safe and effective to control type 1 HRS. However, it does not cure the underlying disease and therefore, may only be considered as a bridge to a definitive treatment as liver transplantation.

Cefdinir vs. amoxicillin/clavulanic acid in the treatment of suppurative acute otitis media in children

An investigator-blinded, randomized, multicenter study was conducted to compare the efficacy and safety of cefdinir and amoxicillin/ clavulanate (amoxicillin/CA) in the treatment of pediatric patients with acute suppurative otitis media. Patients 6 months to 12 years of age were randomized in a 1:1:1 ratio to receive cefdinir 14 mg/kg once-daily, cefdinir 7 mg/kg b.i.d., or amoxicillin/CA 13.3 mg/kg t.i.d. Test-of-cure was determined 11 to 16 days posttherapy. Of the 752 patients who entered the study, 665 (88%) completed treatment and 595 (79%) were evaluable. Response rates in the three treatment groups were similar. Overall rates of adverse events were statistically lower in the cefdinir once-daily group than in the amoxicillin/CA group. Diarrhea was the most common adverse event in all treatment groups. Cefdinir given either once-daily or twice-daily is a safe and effective treatment for pediatric patients with acute suppurative otitis media.

Preparation, characterization, and the crystal structure of the inhibitor ZK-807834 (CI-1031) complexed with factor Xa

Factor Xa plays a critical role in the formation of blood clots. This serine protease catalyzes the conversion of prothrombin to thrombin, the first joint step that links the intrinsic and extrinsic coagulation pathways. There is considerable interest in the development of factor Xa inhibitors for the intervention in thrombic diseases. This paper presents the structure of the inhibitor ZK-807834, also known as CI-1031, bound to factor Xa and provides the details of the protein purification and crystallization. Results from mass spectrometry indicate that the factor Xa underwent autolysis during crystallization and the first EGF-like domain was cleaved from the protein. The crystal structure of the complex shows that the amidine of ZK-807834 forms a salt bridge with Asp189 in the S1 pocket and the basic imidazoline fits snugly into the S4 site. The central pyridine ring provides a fairly rigid linker between these groups. This rigidity helps minimize entropic losses during binding. In addition, the structure reveals new interactions that were not found in the previous factor Xa/inhibitor complexes. ZK-807834 forms a strong hydrogen bond between an ionized 2-hydroxy group and Ser195 of factor Xa. There is also an aromatic ring-stacking interaction between the inhibitor and Trp215 in the S4 pocket. These interactions contribute to both the potency of this compound (K(I) = 0.11 nM) and the >2500-fold selectivity against homologous serine proteases such as trypsin.

Bone metastases from thyroid carcinoma: a histopathologic study with clinical correlates

CONTEXT

Only limited information exists on the pathologic aspects of thyroid carcinomas with bone metastases, most large studies having concentrated mainly on their clinical features.

OBJECTIVE

To study in detail the morphologic features of thyroid carcinomas with skeletal metastases.

DESIGN

Seventy-nine cases of thyroid carcinoma with bone metastases treated at Memorial Sloan-Kettering Cancer Center, New York, NY, between 1964 and 1998 were investigated, with emphasis on the pathology of the primary and/or metastatic tumors and comparison of the morphologic features of the tumors at both the sites, wherever possible. The tumors were also compared for various clinical parameters.

RESULTS

The cohort consisted of 22 papillary, 17 follicular, 16 insular, 10 anaplastic, 9 Hürthle cell, and 5 medullary carcinomas. Of these cases, 68% had poorly differentiated or undifferentiated features in the primary and/or metastatic tumors. The metastatic tumors were better differentiated than the primary in one third of the cases (6 of 18). Only one case showed a less differentiated metastasis. The overall 5- and 10-year survival probabilities after the bone metastases were 29% and 13%, respectively (Kaplan-Meier method). Although both the tumor type and differentiation seemed to affect survivals after bone metastasis (P =.007 and.012, respectively) (log-rank test), this was primarily due to the much worse prognosis in the cases of anaplastic and medullary carcinoma. Cases of Hürthle cell carcinoma showed the longest median survival. There was no significant difference in survival among patients up to or older than 45 years at the time of metastases (P =.31).

CONCLUSIONS

Most thyroid carcinomas with bone metastases are of papillary type, and most have poorly differentiated or undifferentiated features. The influence of the microscopic tumor type and tumor differentiation on survival after bone metastasis primarily appears to be due to the much worse prognosis among anaplastic and medullary carcinomas. Age at diagnosis of bone metastases does not influence survivals.

Antagonism of botulinum toxin A-mediated muscle paralysis by 3, 4-diaminopyridine delivered via osmotic minipumps

The ability of 3,4-diaminopyridine (3,4-DAP) to antagonize muscle paralysis following local injection of botulinum neurotoxin A (BoNT/A) complex was evaluated in the in situ rat extensor digitorum longus (EDL) preparation. The minipumps were implanted 6 h prior to BoNT/A administration and delivered their contents over a 7-day period producing a steady plasma 3,4-DAP concentration of 27-29 microM. In the absence of 3,4-DAP, a local injection of five mouse LD(50) units of BoNT/A led to total paralysis of EDL muscles within 24 h of application. Recovery from paralysis was slow, remaining at <30% of control 14 days after toxin injection. 3,4-DAP delivery by osmotic minipumps antagonized the actions of BoNT/A on neuromuscular transmission. Seven days after the onset of 3,4-DAP infusion, indirectly elicited twitch and tetanic tensions in BoNT/A-injected EDL muscles were 72.4 and 46.9% of control, respectively. In the absence of 3,4-DAP, twitch and tetanic tensions were only 5.4 and 15. 1% of control. The benefits conferred by 3,4-DAP treatment were not maintained after minipumps were removed. Seven days after cessation of 3,4-DAP infusion, twitch and tetanic tensions were not significantly different from those observed in muscles receiving BoNT/A alone. It is concluded that 3,4-DAP may be useful for treatment of BoNT/A-induced muscle paralysis, but sustained delivery of the drug would be required for the entire period of BoNT intoxication to maintain muscle function.

Sex differences in thermoregulation after acute and chronic morphine administration in mice

Sex differences in thermoregulation have been reported following acute morphine administration in rats only. This study assessed whether male and female mice also differ in thermoregulatory responses following acute and chronic morphine administration. Females displayed significantly higher baseline colorectal temperature and greater morphine (24mg/kg, s.c.) hypothermia (2. 5-fold) on day 1. Two additional days of morphine treatment did not alter baseline temperature readings on Day 4 in either sex, but significantly reduced the morphine hypothermia relative to Day 1 in a sex-dependent manner. Whereas the morphine hypothermia was completely abolished in males, significant hypothermia was still observed in females. Acute and chronic saline injections had no effect on colorectal temperature. The data demonstrate sex differences in the thermoregulatory responses to acute and chronic morphine administration in mice.

Surface composition of spray-dried particles of bovine serum albumin/trehalose/surfactant

PURPOSE

To characterize via electron spectroscopy for chemical analysis (ESCA) the surface of spray-dried particles of trehalose plus a protein (bovine serum albumin). Additionally, to show how and why the addition of a surfactant reduces protein adsorption, and by this mechanism could reduce protein instability during spray-drying.

METHODS

Aqueous solutions of trehalose plus bovine serum albumin (bSA) were spray-dried with increasing concentrations of surfactant. The surface composition of the dried particles was examined using ESCA.

RESULTS

The presence of bSA, trehalose, and surfactant could be detected quantitatively in the particle surface. In the absence of surfactant the bSA had a large surface excess concentration (determined via its N atoms). Increasing concentration of polysorbate 80 reduced the surface excess of bSA in a concentration-dependent manner. At high polysorbate 80 concentration (5 mg/ml) the bSA could no longer be detected in solid surface. Using sodium dodecyl sulfate it was shown that the reduction in surface concentration of the protein is accompanied by a simultaneous increase in surface concentration of the surfactant. Neither surfactant fully covers the surface at the point of complete protein exclusion.

CONCLUSIONS

ESCA provides a direct, quantitative measure of the surface composition of spray-dried trehalose/protein/surfactant particles. Surfactant reduces protein adsorption at the water/air-interface. This appears to be a result of complex formation with the surfactant within the bulk spray solution.

Modified genetic algorithm resolves ambiguous NOE restraints and reduces unsightly NOE violations

In an ideal world, every NOE cross peak would have a unique assignment. However, the interpretation of NOE peaks is frequently complicated by overlapping resonances. In theory, ambiguous assignments could be resolved by performing separate structure calculations with each possible interpretation. Unfortunately, this would require an astronomical amount of computing time. A modified genetic algorithm has been developed that efficiently resolves hundreds of ambiguous restraints in parallel. Each NOE assignment becomes a gene that can be passed on to a new generation. New individuals are constructed by making a constraint lists from a subset of the genes. The constraint lists are then tested for self-consistency by using molecular dynamics to generate new structures for each list. To a first-degree approximation, there is enough information retained in each list to determine the global fold of the protein. Self-consistent constraint lists receive higher scores and their genes (or NOEs) stand a better chance of surviving into the next generation. The process selects NOEs that are consistent with the global fold. Under normal conditions, the program converges in 3 to 8 generations using 70 structures per generation. The final constraints are self-consistent and contain almost no residual NOE violations.

Bone metastases from thyroid carcinoma: clinical characteristics and prognostic variables in one hundred forty-six patients

To describe the clinical characteristics and define the indicators that best predict survival in patients with bone metastases from thyroid carcinomas. We collected data from medical records of 146 patients with documented bone metastases from thyroid carcinoma seen at our medical center over a 38-year period. Univariate and multivariate analyses of prognostic indicators for survival were performed. Bone metastases were present at the initial diagnosis in 47% of patients. Vertebrae (29%), pelvis (22%), ribs (17%), and femur (11%) were the most common sites of metastases. Multiple lesions were present in 53% of the cases. The overall 10-year survival rate from the time of diagnosis of thyroid cancer was 35%, and from diagnosis of initial bone metastasis was 13%. By univariate analysis from the time of the initial bone metastasis, radioiodine uptake by skeletal metastases, the absence of nonosseous metastases and treatment with radioiodine were significant prognostic factors. By multivariate analysis, radioiodine uptake by skeletal metastases and the absence of nonosseous metastases were independent favorable prognostic variables for survival. In a subgroup of patients in which histologic specimens were available and were reviewed, Hurthle cell carcinoma was the most favorable histologic subtype for survival with the undifferentiated subtype being the worst. The spread of thyroid carcinoma to bone is more common in patients over 45 years of age, is usually symptomatic, and is often multicentric. Overall survival is best in those whose lesions concentrate radioactive iodine and those who have no nonosseous metastases.

Allosteric inhibitors of inducible nitric oxide synthase dimerization discovered via combinatorial chemistry

Potent and selective inhibitors of inducible nitric oxide synthase (iNOS) (EC ) were identified in an encoded combinatorial chemical library that blocked human iNOS dimerization, and thereby NO production. In a cell-based iNOS assay (A-172 astrocytoma cells) the inhibitors had low-nanomolar IC(50) values and thus were >1,000-fold more potent than the substrate-based direct iNOS inhibitors 1400W and N-methyl-l-arginine. Biochemical studies confirmed that inhibitors caused accumulation of iNOS monomers in mouse macrophage RAW 264.7 cells. High affinity (K(d) approximately 3 nM) of inhibitors for isolated iNOS monomers was confirmed by using a radioligand binding assay. Inhibitors were >1,000-fold selective for iNOS versus endothelial NOS dimerization in a cell-based assay. The crystal structure of inhibitor bound to the monomeric iNOS oxygenase domain revealed inhibitor-heme coordination and substantial perturbation of the substrate binding site and the dimerization interface, indicating that this small molecule acts by allosterically disrupting protein-protein interactions at the dimer interface. These results provide a mechanism-based approach to highly selective iNOS inhibition. Inhibitors were active in vivo, with ED(50) values of <2 mg/kg in a rat model of endotoxin-induced systemic iNOS induction. Thus, this class of dimerization inhibitors has broad therapeutic potential in iNOS-mediated pathologies.

The role of technical assistance in the replication of effective HIV interventions

This article examines the role of technical assistance (TA) in supporting the replication of proven HIV interventions. A case study of the replication of the VOICES/VOCES intervention elucidates the level and types of TA provided to support new users through the adoption process. TA included help in garnering administrative support, identifying target audiences, recruiting groups for sessions, maintaining fidelity to the intervention's core elements, tailoring the intervention to meet clients' needs, strengthening staff members' facilitation skills, troubleshooting challenges, and devising strategies to sustain the intervention. Two to four hours per month of TA were provided to each agency adopting the intervention, at an estimated monthly cost of $206 to $412. Findings illustrate how TA supports replication by establishing a conversation between the researcher TA providers experienced with the intervention and new users. This communication helps preserve key program elements and contributes to ongoing refinement of the intervention.

Evaluation of phosphoramidon and three synthetic phosphonates for inhibition of botulinum neurotoxin B catalytic activity

Three putative metalloprotease inhibitors were synthesized and tested for their ability to inhibit the catalytic activity of botulinum neurotoxin B light chain (BoNT/B LC). The compounds were designed to emulate the naturally occurring metalloprotease inhibitor phosphoramidon, which has been reported to be a weak antagonist of BoNT/B action. All three analogs contained the dipeptide Phe-Glu in place of Leu-Trp of phosphoramidon and possessed a phenyl, ethyl or methyl group in place of the rhamnose sugar of the parent compound. The inhibitors were evaluated in a cell-free assay based on the detection of a fluorescent product following cleavage of a 50-mer synaptobrevin peptide ([Pya(88)] S 39-88) by BoNT/B LC. This peptide corresponds to the hydrophilic core of synaptobrevin-2 and contains a fluorescent analog L-pyrenylalanine (Pya) in place of Tyr(88). Cleavage of [Pya(88)] S 39-88 by BoNT/B LC gives rise to fragments of 38 and 12 amino acid residues. Quantification of BoNT/B-mediated substrate cleavage was achieved by separating the 12-mer fragment (FETSAAKLKRK-Pya) that contains the C-terminal fluorophore and measuring fluorescence at 377 nm. The results indicate that the phenyl-substituted synthetic compound ICD 2821 was slightly more active than phosphoramidon, but analogs with methyl or ethyl substitutions were relatively inactive. These findings suggest that phosphonate monoesters may be useful for providing insights into the structural requirement of BoNT/B protease inhibitors.

Self-assembly of DNA-streptavidin nanostructures and their use as reagents in immuno-PCR

The self-assembly of bis-biotinylated double-stranded DNA and the tetravalent biotin-binding protein streptavidin (STV) have been studied by non-denaturing gel electrophoresis and atomic force microscopy (AFM). The rapid self-assembly reproducibly generated populations of individual oligomeric complexes. Most strikingly, the oligomers predominantly contained bivalent STV molecules bridging two adjacent DNA fragments to form linear nanostructures. Trivalent STV branch points occurred with a lower frequency and the presence of tetravalent STV was scarce. However, valency distribution, size and the exchange dynamics of the supramolecular aggregates were highly sensitive to stoichiometric variations in the relative molar coupling ratio of bis-biotinylated DNA and STV. The largest aggregates were obtained from equimolar amounts while excess STV led to the formation of smaller oligomers appearing as fingerprint-like band patterns in electrophoresis. Excess DNA, however, induces a complete breakdown of the oligomers, likely a consequence of the instability of STV conjugates containing more than two biotinylated DNA fragments. It was demonstrated that the oligomers can further be functionalized, for instance by the coupling of biotinylated immunoglobulins. Both pure and also antibody-modified DNA-STV oligomers were used as reagents in immuno-PCR (IPCR), a highly sensitive detection method for proteins and other antigens. Employment of the supramolecular reagents led to an approximately 100-fold enhanced sensitivity compared to the conventional IPCR procedure.

Peptides that mimic the carboxy-terminal domain of SNAP-25 block acetylcholine release at an Aplysia synapse

Botulinum neurotoxin serotypes A and E (BoNT/A and BoNT/E) block neurotransmitter release, presumably by cleaving SNAP-25, a protein involved in docking of synaptic vesicles with the presynaptic plasma membrane. Three excitation-secretion uncoupling peptides (ESUPs), which mimic the carboxy-terminal domain of SNAP-25 and span or adjoin the cleavage sites for BoNT/A and BoNT/E, also inhibit transmitter release from permeabilized bovine chromaffin cells. In this study, these peptides were tested for effects on acetylcholine (ACh) release at an identified cholinergic synapse in isolated buccal ganglia of Aplysia californica. The presynaptic neuron was stimulated electrically to elicit action potentials. The postsynaptic neuron was voltage-clamped, and evoked inhibitory postsynaptic currents (IPSCs) were recorded. The ESUPs were pressure-injected into the presynaptic neuron, and their effects on the amplitude of the IPSCs were studied. Acetylcholine release from presynaptic cells, as measured by IPSC amplitudes, was gradually inhibited by the ESUPs. All three peptides caused ca. 40% reduction in IPSC amplitude in 2 h. Random-sequence peptides of the same amino acid composition had no effect. Injection of BoNT/E, in contrast, caused ca. 50% reduction in IPSC amplitude in 30 min and almost complete inhibition in 2 h. These results are the first demonstration that ESUPs block neuronal cholinergic synaptic transmission. They are consistent with the concept that ESUPs compete with the intact SNAP-25 for binding with other fusion proteins, thus inhibiting stimulus-evoked exocytosis of neurotransmitter.

Rapid microplate assay for monitoring botulinum neurotoxin B catalytic activity

The binding activity of a rabbit polyclonal antiserum raised against a 51-residue peptide (P51) homologous to human VAMP2 (residues 44-94) was examined. Human VAMP2 is an 18-kDa protein located on the external membrane of small synaptic vesicles and is targeted by four of the seven botulinum neurotoxin (BoNT) serotypes (B, D, F and G). The antiserum, designated anti-P51, recognized P51 but exhibited little cross-reactivity with the two cleavage products that result from BoNT/B-mediated proteolysis of P51. The larger of these fragments, designated as P33 (residues 44-76), exhibited a weak but measurable interaction with the antiserum. The smaller cleavage product, designated as P18 (residues 77-94), was not recognized by the antiserum. Anti-P51 was used to monitor BoNT/B light chain (LC)-mediated cleavage of P51 using an indirect ELISA. The serine protease inhibitor phenylmethylsulfonyl fluoride did not inhibit BoNT/B activity, but the zinc chelator N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) and the elastase inhibitor 7- N -phenylcarbamoylamino-4-chloro-3-propyloxyisocoumarin (ICD 1578) produced complete blockade of BoNT/B LC action. Under ideal conditions, it will be possible to evaluate up to seven candidate anti-BoNT/B drugs in triplicate at four concentrations using a single 96-well microtiter plate. These findings indicate that the ELISA will be suitable for rapid screening of BoNT/B inhibitors.

Mechanism of action of sodium cyanide on rat diaphragm muscle

The effects of sodium cyanide (NaCN) were investigated on the contractile and electrophysiological properties of rat diaphragm muscles in vitro. Sodium cyanide (0.1-1.0 mM) produced an initial potentiation of directly elicited twitch tensions, followed by a slow progressive depression. The potentiation and depression were both dependent on the NaCN concentration and stimulation frequency. Muscles exposed to NaCN exhibited marked reductions of creatine phosphate concentration, but ATP levels were not significantly lowered. Sodium cyanide had no effect on the resting potential, input resistance or action potential, indicating that the toxicity of the metabolic inhibitor is not mediated by alterations of membrane excitability or passive electrical properties. Sodium cyanide reduced the amplitude of contractures elicited by 70 mM K(2)SO(4), suggesting that the actions of NaCN cannot be explained by a failure of action potentials to propagate across the muscle surface or within t-tubular membranes. Sodium cyanide suppressed the first phase of the caffeine contracture, an observation consistent with an impaired release of, or reduced sensitivity to, sarcoplasmic reticular Ca(2+), but did not alter the amplitude of the second phase, which represents rigor following ATP depletion. These results, in conjunction with those of previous studies, suggest that the depression in muscle tension following exposure to NaCN may result from alterations in Ca(2+) homeostasis, intracellular acidosis or from accumulation of one or more products of phosphocreatine breakdown.

The safety profile and antiviral activity of the combination of stavudine, didanosine, and nelfinavir in patients with HIV infection

We assessed the safety profile, tolerability, and antiviral effect of 12 weeks of triple combination therapy with stavudine (d4T), didanosine (ddI), and nelfinavir in patients who had not previously received therapy with d4T, ddI, or a protease inhibitor. We also assessed the effect of the buffered tablet formulation of ddI on the pharmacokinetics of nelfinavir. The study had a single-arm, open-label design and enrolled patients aged > or =18 years who had HIV infection and > or =10,000 plasma HIV RNA copies/mL. Patients received the full recommended doses of oral d4T, ddI, and nelfinavir. Efficacy was assessed in terms of change from baseline in plasma HIV RNA and CD4+ cell counts, as well as in terms of the proportion of patients achieving HIV RNA levels <400 copies/mL. The first 10 patients enrolled in the study were included in a substudy to determine the effects of the buffered tablet formulation of ddI on the pharmacokinetic profile of nelfinavir. A dose of ddI was given 1 hour before nelfinavir, after which the maximum plasma concentration (Cmax), time to Cmax (Tmax), and area under the concentration-time curve (AUC) of nelfinavir were determined. A total of 22 patients entered the trial, of whom 1 (5%) had AIDS, 12 (55%) had symptomatic HIV infection, and 9 (41%) were asymptomatic. The median baseline CD4+ cell count was 315 cells/microL (range, 70-709 cells/microL), and the median plasma viral load was 4.8 log10 copies/mL (range, 4.0-5.6 log10 copies/mL). ddI had no clinically significant effects on the plasma pharmacokinetics of nelfinavir. At the end of 12 weeks of treatment, the mean (+/- SE) decrease in plasma viral load was 1.36+/-0.24 log10 copies/mL, and 8 of 16 patients (50%) achieved plasma HIV RNA levels <400 copies/mL; the mean (+/- SE) increase in CD4+ cell count was 111.4+/-31.7 cells/microL. Patients who were judged to be compliant with antiretroviral therapy (ie, who missed <7 days of all 3 study drugs during 12 weeks of treatment) experienced mean decreases in viral load exceeding 2.0 log10 copies/mL, and 6 of 7 patients achieved HIV RNA levels <400 copies/mL after 12 weeks of therapy. Although 95% of patients reported an adverse event of grade 1 or higher, only 1 patient experienced a grade 3 or 4 adverse event (maculopapular rash) related to nelfinavir. As reflected in the Cmax, Tmax, and AUC, administration of ddI 1 hour before nelfinavir did not influence the pharmacokinetic profile of the protease inhibitor. Triple drug therapy with d4T, ddI, and nelfinavir was well tolerated and associated with few clinically significant toxicities. This treatment resulted in substantial reductions in viral load and improvements in CD4+ cell count over 12 weeks.