Improving plastic degrading enzymes via directed evolution

Plastic degrading enzymes have immense potential for use in industrial applications. Protein engineering efforts over the last decade have resulted in considerable enhancement of many properties of these enzymes. Directed evolution, a protein engineering approach that mimics the natural process of evolution in a laboratory, has been particularly useful in overcoming some of the challenges of structure-based protein engineering. For example, directed evolution has been used to improve the catalytic activity and thermostability of polyethylene terephthalate (PET)-degrading enzymes, although its use for the improvement of other desirable properties, such as solvent tolerance, has been less studied. In this review, we aim to identify some of the knowledge gaps and current challenges, and highlight recent studies related to the directed evolution of plastic-degrading enzymes.

Multiple classes and isoforms of the RNA polymerase recycling motor protein HelD

Efficient control of transcription is essential in all organisms. In bacteria, where DNA replication and transcription occur simultaneously, the replication machinery is at risk of colliding with highly abundant transcription complexes. This can be exacerbated by the fact that transcription complexes pause frequently. When pauses are long-lasting, the stalled complexes must be removed to prevent collisions with either another transcription complex or the replication machinery. HelD is a protein that represents a new class of ATP-dependent motor proteins distantly related to helicases. It was first identified in the model Gram-positive bacterium Bacillus subtilis and is involved in removing and recycling stalled transcription complexes. To date, two classes of HelD have been identified: one in the low G+C and the other in the high G+C Gram-positive bacteria. In this work, we have undertaken the first comprehensive investigation of the phylogenetic diversity of HelD proteins. We show that genes in certain bacterial classes have been inherited by horizontal gene transfer, many organisms contain multiple expressed isoforms of HelD, some of which are associated with antibiotic resistance, and that there is a third class of HelD protein found in Gram-negative bacteria. In summary, HelD proteins represent an important new class of transcription factors associated with genome maintenance and antibiotic resistance that are conserved across the Eubacterial kingdom.

Glycoengineering design options for IgG1 in CHO cells using precise gene editing

Precise gene editing technologies are providing new opportunities to stably engineer host cells for recombinant production of therapeutic glycoproteins with different glycan structures. The glycosylation of recombinant therapeutics has long been a focus for both quality and consistency of products and for optimizing and improving pharmacokinetic properties as well as bioactivity. Structures of glycans on therapeutic glycoproteins are important for circulation, biodistribution and bioactivity. In particular, the latter has been demonstrated for therapeutic IgG1 antibodies where the core α1,6Fucose on the conserved N-glycan at Asn297 have remarkable dampening effects on antibody effector functions. We previously explored precise gene engineering and design options for N-glycosylation in CHO cells, and here we focus on engineering options possible for N-glycans on human IgG1. We demonstrate stable precise gene engineering of rather homogenous biantennary N-glycans with and without galactose (G0F, G2F) as well as the α2,6-linked monosialylated (G2FS1) glycoform. We were unable to introduce substantial disialylated glycoforms. Instead we engineered a novel monoantennary homogeneous N-glycan design with complete α2,6-linked sialic acid capping. All N-glycoforms may be engineered with and without core α1,6Fucose. The stably engineered design options enable production of human IgG antibodies with an array of distinct glycoforms for testing and selection of optimal design for different therapeutic applications.

Primary tumor location and bevacizumab effectiveness in patients with metastatic colorectal cancer

BACKGROUND

There is an unmet need for predictive markers for the antiangiogenic agent bevacizumab in metastatic colorectal cancer (mCRC). We aimed to assess whether the location of the primary tumor is associated with bevacizumab effectiveness when combined with capecitabine and oxaliplatin (CAPEOX) in the first-line treatment of patients with mCRC.

PATIENTS AND METHODS

A cohort of 667 consecutive patients with mCRC from the general community treated from 2006 to 2011 with CAPEOX and bevacizumab as standard first-line therapy was compared with a cohort of 213 patients treated with CAPEOX from 2003 to 2006, before bevacizumab was approved. Main outcome measures were progression-free survival (PFS) and overall survival (OS). Differences in outcome were tested using Kaplan-Meier curves and log-rank tests, and multivariate analyses were carried out using Cox Proportional Hazards models.

RESULTS

Patients treated with CAPEOX and bevacizumab with primary tumors originating in the sigmoid colon and rectum had a significantly better outcome than patients with primary tumors originating from the cecum to the descending colon, both for PFS (median PFS 9.3 versus 7.2 months; hazard ratio (HR) 0.68, 95% confidence interval (CI) 0.56-0.82) and for OS (median OS 23.5 versus 13.0 months; HR 0.47, 95% CI 0.38-0.57). This difference was confirmed in multivariate analyses after adjustment for other potentially prognostic factors. For patients treated with CAPEOX, there was no association between primary tumor location and outcome, neither in unadjusted nor adjusted analyses.

CONCLUSIONS

The addition of bevacizumab to CAPEOX in first-line treatment of patients with mCRC may primarily benefit patients with primary tumors originating in the rectum and sigmoid colon. This hypothesis needs to be validated in data from completed randomized trials.

CLINICALTRIALSGOV IDENTIFICATION NUMBER

NCT00212615.

NS11394 [3'-[5-(1-hydroxy-1-methyl-ethyl)-benzoimidazol-1-yl]-biphenyl-2-carbonitrile], a unique subtype-selective GABAA receptor positive allosteric modulator: in vitro actions, pharmacokinetic properties and in vivo anxiolytic efficacy

The novel positive allosteric modulator NS11394 [3'-[5-(1-hydroxy-1-methyl-ethyl)-benzoimidazol-1-yl]-biphenyl-2-carbonitrile] possesses a functional selectivity profile at GABA(A) receptors of alpha(5) > alpha(3) > alpha(2) > alpha(1) based on oocyte electrophysiology with human GABA(A) receptors. Compared with other subtype-selective ligands, NS11394 is unique in having superior efficacy at GABA(A)-alpha(3) receptors while maintaining low efficacy at GABA(A)-alpha(1) receptors. NS11394 has an excellent pharmacokinetic profile, which correlates with pharmacodynamic endpoints (CNS receptor occupancy), yielding a high level of confidence in deriving in vivo conclusions anchored to an in vitro selectivity profile and allowing for translation to higher species. Specifically, we show that NS11394 is potent and highly effective in rodent anxiety models. The anxiolytic efficacy of NS11394 is most probably mediated through its high efficacy at GABA(A)-alpha(3) receptors, although a contributory role of GABA(A)-alpha(2) receptors cannot be excluded. Compared with benzodiazepines, NS11394 has a significantly reduced side effect profile in rat (sedation, ataxia, and ethanol interaction) and mouse (sedation), even at full CNS receptor occupancy. We attribute this benign side effect profile to very low efficacy of NS11394 at GABA(A)-alpha(1) receptors and an overall partial agonist profile across receptor subtypes. However, NS11394 impairs memory in both rats and mice, which is possibly attributable to its efficacy at GABA(A)-alpha(5) receptors, albeit activity at this receptor might be relevant to its antinociceptive effects (J Pharmacol Exp Ther 327:doi;10.1124/jpet.108.144, 2008). In conclusion, NS11394 has a unique subtype-selective GABA(A) receptor profile and represents an excellent pharmacological tool to further our understanding on the relative contributions of GABA(A) receptor subtypes in various therapeutic areas.

Comparison of the novel subtype-selective GABAA receptor-positive allosteric modulator NS11394 [3'-[5-(1-hydroxy-1-methyl-ethyl)-benzoimidazol-1-yl]-biphenyl-2-carbonitrile] with diazepam, zolpidem, bretazenil, and gaboxadol in rat models of inflammatory and neuropathic pain

Spinal administration of GABA(A) receptor modulators, such as the benzodiazepine drug diazepam, partially alleviates neuropathic hypersensitivity that manifests as spontaneous pain, allodynia, and hyperalgesia. However, benzodiazepines are hindered by sedative impairments and other side effect issues occurring mainly as a consequence of binding to GABA(A) receptors containing the alpha(1) subunit. Here, we report on the novel subtype-selective GABA(A) receptor-positive modulator NS11394 [3'-[5-(1-hydroxy-1-methyl-ethyl)-benzoimidazol-1-yl]-biphenyl-2-carbonitrile], which possesses a functional efficacy selectivity profile of alpha(5) > alpha(3) > alpha(2) > alpha(1) at GABA(A) alpha subunit-containing receptors. Oral administration of NS11394 (1-30 mg/kg) to rats attenuated spontaneous nociceptive behaviors in response to hindpaw injection of formalin and capsaicin, effects that were blocked by the benzodiazepine site antagonist flumazenil. Ongoing inflammatory nociception, observed as hindpaw weight-bearing deficits after Freund's adjuvant injection, was also completely reversed by NS11394. Likewise, hindpaw mechanical allodynia was fully reversed by NS11394 in two rat models of peripheral neuropathic pain. Importantly, NS11394-mediated antinociception occurred at doses 20 to 40-fold lower than those inducing minor sedative or ataxic impairments. In contrast, putative antinociception associated with administration of either diazepam, zolpidem, or gaboxadol only occurred at doses producing intolerable side effects, whereas bretazenil was completely inactive despite minor influences on motoric function. In electrophysiological studies, NS11394 selectively attenuated spinal nociceptive reflexes and C-fiber-mediated wind-up in vitro pointing to involvement of a spinal site of action. The robust therapeutic window seen with NS11394 in animals suggests that compounds with this in vitro selectivity profile could have potential benefit in clinical treatment of pain in humans.

Do antihistamines have a role in asthma therapy?

The coexistence of allergic rhinitis with asthma is widely recognized by clinicians. Histamine, a common mediator for both diseases, has a substantial role in the pathophysiology of asthma through its ability to produce smooth muscle contraction and promote vascular permeability. Because antihistamines often are administered to manage allergic rhinitis symptoms, the effects of antihistamines in asthma should be evaluated. The usefulness of first-generation antihistamines is limited by their side-effect profile, namely sedation and cognitive impairment. Second-generation antihistamines have only a modest effect in attenuating bronchospasm induced by histamine, cold air, exercise, and allergen bronchoprovocation, suggesting that second-generation antihistamines do not have a direct role as a single agent for treating asthma. Studies have shown that controlling allergic rhinitis with antihistamines has a small, indirect effect in improving asthma symptoms. Future work should be directed at improving the potency of antihistamines and defining their antiinflammatory activity.

K+ supplementation increases muscle [Na+-K+-ATPase] and improves extrarenal K+ homeostasis in rats

Effects of K+ supplementation (approximately 200 mmol KCl/100 g chow) on plasma K+, K+ content, and Na+-K+-adeonsinetriphosphatase (ATPase) concentration ([Na+-K+-ATPase]) in skeletal muscles as well as on extrarenal K+ clearance were evaluated in rats. After 2 days of K+ supplementation, hyperkalemia prevailed (K+-supplemented vs. weight-matched control animals) [5.1 +/- 0.2 (SE) vs. 3.2 +/- 0.1 mmol/l, P < 0.05, n = 5-6], and after 4 days a significant increase in K+ content was observed in gastrocnemius muscle (104 +/- 2 vs. 97 +/- 1 micromol/g wet wt, P < 0.05, n = 5-6). After 7 days of K+ supplementation, a significant increase in [3H] ouabain binding site concentration (344 +/- 5 vs. 239 +/- 8 pmol/g wet wt, P < 0.05, n = 4) was observed in gastrocnemius muscle. After 2 wk, increases in plasma K+, K+ content, and [3H]ouabain binding site concentration in gastrocnemius muscle amounted to 40, 8, and 68% (P < 0.05) above values observed in weight-matched control animals, respectively. The latter change was confirmed by K+-dependent p-nitrophenyl phosphatase activity measurements. Fasting for 1 day reduced plasma K+ and K+ content in gastrocnemius muscle in rats that had been K+ supplemented for 2 wk by 3.1 +/- 0.3 mmol/l (P < 0.05, n = 5) and 15 +/- 2 micromol/g wet wt (P < 0.05, n = 5), respectively. After induction of anesthesia, arterial plasma K+ was measured during intravenous KCl infusion (0.75 mmol KCl x 100 g body wt(-1) x h(-1)). The K+-supplemented fasted group demonstrated a 42% (P < 0.05) lower plasma K+ rise, associated with a significantly higher increase in K+ content in gastrocnemius muscle of 7 micromol/g wet wt (P < 0.05, n = 5) compared with their control animals. In conclusion, K+ supplementation increases plasma K+, K+ content, and [Na+-K+-ATPase] in skeletal muscles and improves extrarenal K+ clearance capacity.

Reduced concentration of myocardial Na+,K(+)-ATPase in human aortic valve disease as well as of Na+,K(+)- and Ca(2+)-ATPase in rodents with hypertrophy

Myocardial Na+,K(+)-ATPase was studied in patients with aortic valve disease, and myocardial Na+,K(+)- and Ca(2+)-ATPase were assessed in spontaneously hypertensive rats (SHR) and hereditary cardiomyopathic hamsters using methods ensuring high enzyme recovery. Na+,K(+)-ATPase was quantified by [3H]ouabain binding to intact myocardial biopsies from patients with aortic valve disease. Aortic stenosis, regurgitation and a combination hereof were compared with normal human heart and were associated with reductions of left ventricular [3H]ouabain binding site concentration (pmol/g wet weight) of 56, 46 and 60%, respectively (p < 0.01). Na+,K(+)- and Ca(2+)-ATPases were quantified by K(+)- and Ca(2+)-dependent p-nitrophenyl phosphatase (pNPPase) activity determinations in crude myocardial homogenates from SHR and hereditary cardiomyopathic hamsters. When SHR were compared to age-matched Wistar Kyoto (WKY) rats an increase in heart-body weight ratio of 75% (p < 0.001) was associated with reductions of K(+)- and Ca(2+)-dependent pNPPase activities (mumol/min/g wet weight) of 42 (p < 0.01) and 27% (p < 0.05), respectively. When hereditary cardiomyopathic hamsters were compared to age-matched Syrian hamsters an increase in heart-body weight ratio of 69% (p < 0.001) was found to be associated with reductions in K(+)- and Ca(2+)-dependent pNPPase activities of 50 (p < 0.001) and 26% (p = 0.05), respectively. The reductions in Na+,K(+)- and Ca(2+)-ATPases were selective in relation to overall protein content and were not merely the outcome of increased myocardial mass relative to Na+,K(+)- and Ca(2+)-pumps. In conclusion, myocardial hypertrophy is in patients associated with reduced Na+,K(+)-ATPase concentration and in rodents with reduced Na+,K(+)- and Ca(2+)-ATPase concentrations. This may be of importance for development of heart failure and arrhythmia in hypertrophic heart disease.

Antileukotriene therapy for asthma

The role of leukotrienes (LTs) in asthma is reviewed, and research to develop anti-LT agents for this condition is described. Greater understanding of the role played by inflammatory cells and their mediators in the pathophysiology of asthma has shifted the emphasis of research from the bronchoconstriction component of the disease to the inflammatory one. LTs are believed to play a key role in the complex interplay of inflammatory cells that occurs in asthma. Inhibiting the production of LTs or blocking their receptor sites may decrease the inflammatory response and thereby provide a useful therapeutic modality. Three approaches have been used in attempts to affect the activity of LTs: inhibition of 5-lipoxygenase, inhibition of 5-lipoxygenase-activating protein, and LTD4-receptor antagonism. Investigational agents that have undergone clinical trials include zileuton (a 5-lipoxygenase inhibitor), MK-591 (a 5-lipoxygenase-activating protein inhibitor), and zafirlukast, pranlukast, and verlukast (three LT-receptor antagonists). Many studies suggest that these orally administered agents are effective, particularly with respect to the early asthmatic response to allergens and other challenges, and have a low adverse-effect profile; the reaction of greatest concern is elevation of liver enzymes, especially with zileuton. Larger trials conducted over longer periods, as well as comparative trials, will be necessary to delineate the ultimate role of these agents in asthma therapy. Because of the complexity of the inflammatory process in asthma, anti-LT agents are likely to become part of multidrug regimens. Using drugs to interfere with leukotrienes may prove beneficial in the treatment of asthma.

[Endometrial resection. Peroperative complications and postoperative course]

The effectiveness of transcervical resection of the uterine endometrium was assessed in 106 consecutive women admitted for surgical treatment for menstrual disorders, suitable for treatment with endometrial resection. No hormonal pretreatment was given. Amenorrhoea occurred in about 25%; 80% were satisfied after the initial treatment and 86% were satisfied if the procedure was repeated after at least one year postoperatively. The results were the same in 34 (32%) who had fibroids or polyps in the uterine cavity. No serious operative or postoperative complications appeared. Seven patients (6.6%) required temporary tamponade to control bleeding. It is concluded that endometrial resection is an advance in the management of menstrual disorders. The satisfaction in the patients is high and the complication rate low.

Reduction of cerebral cortical [3H]ouabain binding site (Na+,K(+)-ATPase) density in dementia as evaluated in fresh human cerebral cortical biopsies

Na+,K(+)-ATPase density in human cerebral cortex was for the first time studied by vanadate facilitated [3H]ouabain binding to intact samples. Fresh human cerebral cortical biopsies were obtained as a result of diagnostic frontal lobe biopsy from patients with normal pressure hydrocephalus (NPH) syndrome and associated dementia. For control measurements post-mortem samples were obtained from patients without clinically observed dementia. [3H]ouabain binding kinetics were evaluated: when incubating samples in 1 microM [3H]ouabain binding equilibrium was obtained after 6 h of incubation, non-specific uptake and retention amounted to only 2.3% of total uptake and retention of [3H]ouabain and release of specifically bound [3H]ouabain during washout in the cold occurred only slowly (T1/2 = 37 h). Evaluation of receptor affinity for ouabain was in agreement with a heterogeneous population of [3H]ouabain binding sites. [3H]Ouabain binding was significantly reduced after frozen storage of samples before measurements. Post-mortem degradation of cerebral [3H]ouabain binding sites occurred only slowly (T1/2 = 75 h). No significant variation in [3H]ouabain binding site density was observed between the cerebral lobes with occipital, parietal and temporal values (means +/- S.E.M., n = 5) amounting to 10281 +/- 649, 11267 +/- 1011 and 9263 +/- 615 pmol/g wet wt., respectively. [3H]Ouabain binding measured in frontal cortical samples gave values of (means +/- S.E.M., n = 5) 4274 +/- 1020 and 11397 +/- 976 pmol/g wet wt. delta % = 62; P < 0.05) in patients with dementia and controls, respectively. Human cerebral cortical capacity for active K+ uptake was around 37- and 16-fold greater than in skeletal muscular and myocardial tissue, respectively.

A novel breath actuated device (Autohaler) consistently actuates during the early phase of inspiration

OBJECTIVE

To establish and quantify the point during inspiration that the Autohaler (AH) inhalation system releases a metered dose of aerosol (placebo). The second objective was to determine if the Autohaler system actuates consistently, regardless of the canister life.

DESIGN

Double-blind, randomized, two-period crossover, one-day trial.

SETTING

Community based allergy and asthma clinic.

PARTICIPANTS

Twelve patients with mild to moderate asthma.

RESULTS

Mean verbal training time for the AH which included the patient demonstrating their ability to correctly use the AH was approximately 6 minutes. The mean time for actuation for the AH early in its canister life ("new canister") was 195 msec compared to 205 msec for the AH late in its canister life ("old canister") (p = 0.589). This represented the early part of inspiration as patients had a mean inspiratory duration of 2231 msec for the "new" AH and 2343 msec for the "old" AH. The mean percentage of inspiration time required to actuate the "new" AH was 8.92% compared to 8.82% for the "old" AH. Patients rated the system as easier to much easier to use compared with their current standard press and breathe inhaler.

CONCLUSIONS

The AH consistently actuates early during inspiration, which is considered the optimal time for drug delivery, regardless of the canister life.

Quantification in crude homogenates of rat myocardial Na+, K(+)- and Ca(2+)-ATPase by K+ and Ca(2+)-dependent pNPPase. Age-dependent changes

Assays for complete quantification of Na+, K(+)- and Ca(2+)-ATPase in crude homogenates of rat ventricular myocardium by determination of K(+)- and Ca(2+)-dependent p-nitrophenyl phosphatase (pNPPase) activities were evaluated and optimized. Using these assays the total K(+)- and Ca(2+)-dependent pNPPase activities in ventricular myocardium of 11-12 week-old rats were found to be 2.98 +/- 0.10 and 0.29 +/- 0.02 mumol x min-1 x g-1 wet wt. (mean +/- SEM) (n = 5), respectively. Coefficient of variance of interindividual determinations was 7 and 12%, respectively. The total Na+, K(+)- and Ca(2+)-ATPase concentrations were estimated to 2 and 10 nmol x g-1 wet wt., respectively. Evaluation of a putative developmental variation revealed a biphasic age-related change in the rat myocardial Ca(2+)-dependent pNPPase activity with an increase from birth to around the third week of life followed by a decrease. By contrast, the K(+)-dependent pNPPase activity of the rat myocardium showed a decrease from birth to adulthood. It was excluded that the changes were simple outcome of variations in water and protein content of myocardium. Expressed per heart, the K(+)- and Ca(2+)-dependent pNPPase activity gradually increased to a plateau. The present assay for Na+, K(+)-ATPase quantification has the advantage over [3H] ouabain binding of being applicable on the ouabain-resistant rat myocardium, and is more simple and rapid than measurements of K(+)-dependent 3-O-methylfluorescein phosphatase (3-O-MFPase) in crude tissue homogenates. Furthermore, with few modifications the pNPPase assay allows quantification of Ca(2+)-ATPase on crude myocardial homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of conventional press-and-breathe metered-dose inhaler technique in 501 patients

Conventional press-and-breathe metered dose inhalers (MDIs) are widely prescribed but are often difficult for many patients to properly use. A total of 501 patients from different medical specialties were enrolled in this study, which evaluated how the patients used their MDIs. Using a conservative method (minimum number of errors) of determining errors, we found that 388 (77.5%) of the patients made at least one error when demonstrating how they use their MDI for two observers. Using a liberal (maximum number of errors) method of analysis, we found that 447 (89.2%) of the patients made at least one error. There was no difference in errors made stratified by patient gender, patient age, or the medical specialty that treated the patient's pulmonary disease. The two most common errors made by patients were failure to breathe out to functional residual capacity before actuation (225 by minimum method, 280 by maximum method) and not actuating the canister at the start of inhalation (207 by minimum method, 323 by maximum method). Of the patients with improper timing of actuation, the majority (121 patients by minimum method and 187 patients by maximum method) actuated the canister early. In this large patient sample, regardless of which medical specialty provided the treatment, the majority of the patients evaluated had less than optimal MDI technique. Routine assessment of MDI technique should be instituted as standard practice care.

Reduced 3H-ouabain binding site (Na,K-ATPase) concentration in ventricular myocardium of dogs with tachycardia induced heart failure

The present study evaluates 3H-ouabain binding site (Na,K-ATPase) concentration in left ventricular myocardium of dogs with heart failure induced by tachycardia as a result of ventricular pacing. Samples of left ventricle were obtained from 10 dogs exposed to pacing of 240 beats/min for 3 to 4 weeks and eight sham-operated controls. Na,K-ATPase was quantified using vanadate facilitated 3H-ouabain binding to intact samples. At time of sacrifice paced dogs showed clinical signs of heart failure, a significant 257% increase in left ventricular end diastolic pressure and a significant 46% decrease in left ventricular dP/dt compared with control. There was no significant change in left ventricular mass. 3H-ouabain binding concentration was significantly reduced by 16%. Evaluation of 3H-ouabain binding kinetics revealed no significant difference between myocardium from paced and control dogs: Equilibrium binding conditions were at the various concentrations used obtained after similar incubation time; nonspecific uptake and retention of 3H-ouabain was 0.9-0.8% of total uptake and retention obtained in the standard assay; apparent dissociation constant (KD) was 6.5 x 10(-8)-6.6 x 10(-8) mol/l; loss of specifically bound 3H-ouabain during washout at 0 degrees C occurred with a half-life time (T1/2) of 120 and 121 h. Hence, total 3H-ouabain binding site concentration in left ventricular myocardium was (mean +/- SEM) 1110 +/- 56 and 1317 +/- 68 pmol/g wet weight, 8.54 +/- 0.43 and 10.05 +/- 0.52 pmol/mg protein, and the total amount of 3H-ouabain binding sites in the entire left ventricle 121 +/- 6 and 162 +/- 8 nmol in paced (n = 10) and control (n = 8) dogs (p < 0.05), respectively. In conclusion, the present study reports a significant reduction in left ventricular myocardium 3H-ouabain binding site concentration in tachycardia induced heart failure. This observation supports the concept of a relationship between Na,K-ATPase concentration and contractile capacity and may be of pathophysiological importance in tachycardia and heart failure.

Administration errors with a conventional metered dose inhaler versus a novel breath actuated device

Metered dose inhalers are difficult for patients to use. A device that eliminates coordination and timing of actuation may simplify the use of metered dose inhalers. This trial compared (1) number of errors made and (2) specific errors made between the conventional press and breathe metered dose inhaler (MDI) and the novel breath actuated Autohaler inhalation device in 24 subjects. We studied the use of each device in 12 patients trained and experienced in using an MDI and in 12 volunteers who had never been exposed to any inhalation device. We observed that even experienced patients continue to have difficulty with the coordination and timing of metered dose inhalers. The volunteer group had equal difficulty with both devices but it appeared that it was easier for them to learn how to use the breath actuated device than the MDI.

Leukotriene-receptor antagonists and 5-lipoxygenase inhibitors in asthma

OBJECTIVE

To familiarize readers with a potentially new class of compounds for treating asthma. Background information on leukotrienes is provided in addition to an in-depth review of pertinent clinical trials.

DATA SOURCES

Information was obtained from controlled clinical trials, abstracts, and review articles identified through a MEDLINE search of English-language articles.

STUDY SELECTION

Emphasis was placed on early clinical trials that showed some benefit with these compounds as well as more recent studies using newer agents that produced more promising results.

DATA EXTRACTION

Information regarding leukotriene biochemistry was extracted from basic science research and data from human studies were evaluated by the authors according to patient selection, study design, methodology, and therapeutic response.

DATA SYNTHESIS

Leukotrienes have a pathophysiologic role in asthma. Two distinct but pharmacologically similar classes of leukotriene inhibitors are currently being clinically evaluated. These are leukotriene receptor antagonists and 5-lipoxygenase inhibitors. Early clinical trials with these agents yielded unfavorable results primarily because of lack of drug potency and selectivity, poor patient tolerance, and possibly the route of administration. Subsequent studies with more potent and selective agents have further implicated leukotrienes as biochemical mediators in asthma and, consequently, have shown promising clinical outcomes with respect to pulmonary function testing and patient tolerance.

CONCLUSIONS

Advancements in the pathogenesis of asthma are beginning to define a role for the leukotrienes. Although more studies are needed to assess the efficacy of leukotriene inhibitors, recent clinical trials using leukotriene-receptor antagonists and 5-lipoxygenase inhibitors indicate a potential for the expansion of therapeutic regimens currently used in the treatment of asthma.

Quantification of rat cerebral cortex Na+,K(+)-ATPase: effect of age and potassium depletion

Na+,K(+)-ATPase concentration in rat cerebral cortex was studied by vanadate-facilitated [3H]ouabain binding to intact samples and by K(+)-dependent 3-O-methylfluorescein phosphatase activity determinations in crude homogenates. Methodological errors of both methods were evaluated. [3H]Ouabain binding to cerebral cortex obtained from 12-week-old rats measured incubating samples in buffer containing [3H]ouabain, and ouabain at a final concentration of 1 x 10(-6) mol/L gave a value of 11,351 +/- 177 (n = 5) pmol/g wet weight (mean +/- SEM) without any significant variation between the lobes. Evaluation of affinity for ouabain was in agreement with a heterogeneous population of [3H]ouabain binding sites. K(+)-dependent 3-O-methylfluorescein phosphatase activity in crude cerebral homogenates of age-matched rats was 7.24 +/- 0.14 (n = 5) mumol/min/g wet weight, corresponding to a Na+,K(+)-ATPase concentration of 12,209 +/- 236 pmol/g wet weight. It was concluded that the present methods were suitable for quantitative studies of cerebral cortex Na+,K(+)-ATPase. The concentration of rat cerebral cortex Na+,K(+)-ATPase showed approximately 10-fold increase within the first 4 weeks of life to reach a plateau of approximately 11,000-12,000 pmol/g wet weight, indicating a larger synthesis of Na+,K+ pumps than tissue mass in rat cerebral cortex during the first 4 weeks of development. K+ depletion induced by K(+)-deficient fodder for 2 weeks resulted in a slight tendency toward a reduction in K+ content (6%, p > 0.5) and Na+,K(+)-ATPase concentration (3%, p > 0.4) in cerebral cortex, whereas soleus muscle K+ content and Na+,K(+)-ATPase concentration were decreased by 30 (p < 0.02) and 32% (p < 0.001), respectively. Hence, during K+ depletion, cerebral cortex can maintain almost normal K+ homeostasis, whereas K+ as well as Na+,K+ pumps are lost from skeletal muscles.

[Induction of labor when a large fetus is suspected]

The courses of 945 deliveries in which the infant weighed greater than or equal to 3,800 g are reviewed retrospectively with comparison between the deliveries which began spontaneously and the induced deliveries. In the deliveries which were induced on account of a suspected large foetus, the frequency of emergency Cesarean section was tripled and the frequency of vacuum extraction was doubled. Significantly more infants had Apgar scores of less than 7 after one minute than in the deliveries which began spontaneously. It is concluded that induction of labour is not indicated in cases where a large foetus is suspected.

Sensitivity of FEV1 response following one and two inhalations of albuterol: a pilot study

Eleven patients entered a pilot study designed to evaluate the proportion of eligible responders following a single inhalation of albuterol aerosol, the degree of response, and the sensitivity to distinguish between one and two inhalations based on FEV1 response. Each patient received a single inhalation at 0 and 60 minutes. FEV1 was measured 30 and 60 minutes after each inhalation. Most patients (82%) responded to a single inhalation and the majority (73%) were capable of further response after two inhalations. This study design was able to distinguish FEV1 responses to one and two inhalations of albuterol and provide upward and downward sensitivity sufficient to detect major differences in products.

Diabetes decreases Na+-K+ pump concentration in skeletal muscles, heart ventricular muscle, and peripheral nerves of rat

Na+-K+-ATPase or the Na+-K+ pump is essential for some specific properties of muscle and nerve tissue such as contractility and excitability. Previous studies have shown conflicting variations in Na+-K+-ATPase activity or Na+-K+ pump concentration of muscle cells in experimental diabetes. Our study demonstrates that early untreated diabetes in rats induced by injection of streptozocin is associated with decreases in [3H]ouabain binding-site concentration of 24-48% in various skeletal muscles and 16% in peripheral nerves as well as a decrease in K+-dependent 3-O-methylfluorescein phosphatase activity of 21% in the heart ventricle. These effects could be prevented by insulin treatment. They probably represent a decrease in the concentration of Na+-K+ pumps. There was no evidence for more than one population of Na+-K+ pumps in intact samples of skeletal muscle and nerves from normal, diabetic, and insulin-treated animals. The decrease in Na+-K+ pump concentration in nerve cells may be due to atrophy of the axons. In skeletal muscles, myocardium, and peripheral nerves, the observed decrease in Na+-K+ pump concentration may be important for the pathophysiology of diabetes. We emphasize that quantification of Na+-K+-ATPase or the Na+-K+ pump in muscle and nerve tissue from diabetic animals should preferably be performed with either intact samples or crude homogenates of whole tissue.

Heart Na,K-ATPase activity in cardiomyopathic hamsters as estimated from K-dependent 3-O-MFPase activity in crude homogenates

The hamster hereditary cardiomyopathy provides a unique model for the study of membrane abnormalities during chronic congestive heart failure. It is associated with intracellular calcium accumulation, mitochondrial calcification and cell necrosis. Previous studies have shown a decrease in Na,K-ATPase activity purified from ventricle sarcolemma. The present study demonstrates a decrease in K-dependent 3-O-methylfluorescein phosphatase (3-O-MFPase) activity from 1.93 to 1.30 mumol/g wet wt. or 33% in crude homogenates from the left ventricle of 7-months-old cardiomyopathic hamsters as compared to control animals. This represents an equivalent decrease in Na, K-ATPase activity. The values are several times higher than previously published for membrane fractions of myocardium from the hamster. Concomitantly, there was an increase in intracellular Na-concentration of the myocardium of 42% whereas the K-concentration was unchanged. The decrease in Na,K-pump concentration may be of importance for the increase in intracellular sodium and ensuing calcifying necrosis observed in the myocardium of cardiomyopathic hamsters. It is emphasized that quantification of the Na,K-ATPase or Na,K-pump should preferably be performed using crude homogenates.

Responsiveness of the renin-aldosterone system during exercise in young patients with essential hypertension

The effect of exercise of gradually increased intensity, i.e. 75 W for 20 min followed by 100 W for 20 min, on plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) was studied in young patients with essential hypertension and normotensive control subjects. During exercise without previous sodium loading PRC and PAC increased to the same degree in both hypertensives and normotensives during light exercise; PRC increased further significantly in the normotensives (63 to 72 microIU/ml (medians), P less than 0.01) but not in the hypertensives (46 to 51 microIU/ml) during heavy exercise. PRC and PAC were significantly correlated during both 75 W (rho = 0.633, P less than 0.05) and 100 W (rho = 0.635, P less than 0.05) exercise in the normotensives, but not in the hypertensives. During exercise after loading with 500 ml sodium chloride (0.85 mol/l) PRC and PAC increased in both hypertensives (28 to 42 microIU/ml, P less than 0.01; 0.11 to 0.53 nmol/l, P less than 0.01) and normotensives (22 to 33 microIU/ml, P less than 0.02; 0.12 to 0.34 nmol/l, P less than 0.01), although to a considerably lower degree than without previous loading. PRC and PAC were, however, significantly higher in the hypertensive than in the normotensive group after exercise. It is suggested that the responsiveness of the renin-aldosterone system is abnormal during exercise in young patients with mild essential hypertension, both without and with previous intravenous sodium loading.

Effects of exercise on urinary excretion of albumin and beta 2-microglobulin in young patients with mild essential hypertension without treatment and during long-term propranolol treatment

The effect of exercise on the urinary excretion of albumin, beta 2-microglobulin, renal plasma flow (RPF) and glomerular filtration rate (GFR) was studied in two groups of young patients with mild essential hypertension, one comprising nine untreated patients (1) and one comprising eight patients treated with propranolol (2), and in a group comprising ten normotensive healthy control subjects (3). The urinary excretion of albumin and beta 2-microglobulin, RPF and GFR were measured during four consecutive periods: a control period of 40 min; two exercise periods of 20 min each, with a load of 75 W and 100 W, respectively; and a control period. During exercise group 1 showed an increase in albumin excretion and a decrease in beta 2-microglobulin excretion, while group 2 showed an increase in albumin excretion during heavy exercise only and unchanged beta 2-microglobulin excretion, and group 3 showed unchanged albumin and beta 2-microglobulin excretion. RPF and GFR were reduced during exercise in all groups, most markedly in the hypertensive groups. During both exercise loads albumin excretion was higher and RPF was lower in group 1 than in 3. In group 2 albumin excretion was lower than in 1 during the light exercise load, whereas RPF and GFR were lower during both exercise loads. It is concluded that young patients with mild essential hypertension have both an abnormally high albumin excretion and an abnormally low RPF during exercise. During propranolol therapy urinary albumin excretion was partly normal. The changes in albumin excretion suggest glomerular leakage.

Comparison of the effects of propranolol and labetalol on renal haemodynamics at rest and during exercise in essential hypertension

The effect of exercise on renal haemodynamics was examined in young patients with mild essential hypertension. Four groups of subjects were studied: 13 normotensive, healthy control subjects, and 15 untreated, 11 propranolol-treated, and 6 labetalol-treated patients. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured during four consecutive periods, a pre-exercise control period, two exercise periods with loads of 450 kpm/min and 600 kpm/min, respectively, and a post-exercise control period. In the untreated patients RPF and GFR were lower during exercise than in the normotensive control subjects, whereas no significant differences were found at rest. In the propranolol-treated patients the reduction in RPF and GFR during exercise was more pronounced than in the untreated hypertensives. In the labetalol-treated patients however, RPF and GFR were reduced only to the same degree as in the untreated hypertensives. The reduced renal blood flow in propranolol-treated patients may be attributed to a compensatory increase in sympathetic activity caused by an impaired cardiac response to exercise. The lack of reduction in renal blood flow during labetalol therapy could partly be related to alpha-adrenergic blockade in the renal vascular bed induced by labetalol, and partly to the smaller reduction in cardiac output during labetalol than during propranolol therapy.

Ultrasonographic study on changes in axial eye dimensions after encircling procedure in retinal detachment surgery

The pre- and postoperative results of ultrasonographic measurements on the axial ocular components in 10 phakic eyes with retinal detachment treated with encircling silicone rubber band are presented. A significant increase (P less than 0.001) in axial eye length from 0.62 to 1.24 mm (average: 0.98 mm) was found. The elongation of the eye was caused by a corresponding increase in the length of the vitreous cavity. No significant changes were found in the anterior segment of the eyes. These data demonstrate that the postoperative refractive change in a myopic direction, which an encircling procedure with moderate indentation often produces, is caused by an axial elongation of the eye.

Axial length of the emmetropic eye and its relation to the head size

The results of the ultrasonographic measurements of the ocular components in 40 emmetropic eyes from men of nearly the same age are presented and the possible relation between the axial eye length and the head size is discussed. A significant correlation was found between the axial eye length and the head circumference (P less than 0.001), between the axial eye length and the head length (P less than 0.01) and between the axial eye length and the head breadth (P less than 0.02). A significant correlation was also found between the axial eye length and the height of the subjects (P less than 0.01). It is suggested that such a correlation can explain not only the wide individual range of axial eye lengths in emmetropic eyes, but also the existing difference in axial eye length between the sexes. The mean eye length was 23.82 mm in 40 men and 23.02 mm in 10 women; both sexes were of the same age (20-30 years).