Complete genome sequences of new divergent potato virus X isolates and discrimination between strains in a mixed infection using small RNAs sequencing approach

Potato virus X (PVX; genus Potexvirus, family Alphaflexiviridae, order Tymovirales) is one of the most widespread and intensively studied viruses of potato. However, little is known about its diversity in its likely center of radiation, the Andean region of South America. To fill this gap, the strategy of Illumina deep sequencing of small RNAs was used to obtain complete or near complete genome sequence of PVX from 5 symptomatically infected greenhouse and 3 field samples (Solanum tuberosum) from Peru. PVX sequences determined in this study were assigned into three different phylogenetic groups of isolates. Notably, a complete genome sequence of a representative of a new PVX phylogenetic lineage was obtained, which shows a high level of sequence dissimilarity to other completely sequenced isolates (∼17%). The new PVX genotype was detected in greenhouse and field samples. One of the field samples was infected with the mixture of two PVX strains, which were efficiently discriminated using small RNA sequencing approach. The study confirms the utility of small RNAs deep sequencing for successful viral strain differentiation and discovery of new viral strains and indicates a high diversity of PVX in the Andean region of South America, a pattern which may be expected also for other potato pathogens.

Phase II trial of docetaxel and vinorelbine in patients with advanced non-small-cell lung cancer

PURPOSE

Docetaxel and vinorelbine are active agents in advanced non-small-cell lung cancer (NSCLC) and demonstrate preclinical synergism perhaps, in part, through their inactivation of the proto-oncogene bcl-2. We show that docetaxel (60 mg/m(2)) and vinorelbine (45 mg/m(2)) can be safely combined when given on an every 2-week schedule with filgrastim, with encouraging antitumor activity observed.

PATIENTS AND METHODS

Thirty-five chemotherapy naïve patients with advanced NSCLC received vinorelbine as an intravenous push immediately followed by docetaxel as a 1-hour intravenous infusion once every 2 weeks. Prophylactic corticosteroids, ciprofloxacin, and filgrastim were used.

RESULTS

We delivered median doses of 450 mg/m(2) of vinorelbine and 600 mg/m(2) of docetaxel. The major objective response rate was 51% (95% confidence interval [CI], 34% to 68%). With a median follow-up of 14 months, the predicted median survival time was 14 months, and the 1-year survival rate was 60% (95% CI, 44% to 80%). Febrile neutropenia occurred in five patients and five (1.3%) of 384 treatments. No dose-limiting neurotoxicity occurred. Symptomatic onycholysis and excessive lacrimation were observed after several months or more of therapy.

CONCLUSION

Docetaxel 60 mg/m(2) and vinorelbine 45 mg/m(2), both given every 2 weeks, is a highly active combination for the treatment of advanced NSCLC. Filgrastim largely obviates neutropenic fever and allows for the single-agent dose-intensity of both drugs to be delivered. The occurrence of certain late toxicities can limit use in some cases and suggests that the combination could also be beneficial in settings requiring briefer, fixed periods of treatment, such as in induction or postoperative therapy.

Phase I trial of docetaxel and vinorelbine in patients with advanced nonsmall cell lung carcinoma

BACKGROUND

With preclinical evidence of synergy, this dose-finding trial examining the combination of docetaxel and vinorelbine given with prophylactic filgrastim for the treatment of patients with nonsmall cell lung carcinoma was undertaken.

METHODS

Twenty-seven patients with advanced nonsmall cell lung carcinoma received vinorelbine as an intravenous push immediately followed by docetaxel as a 1-hour intravenous infusion once every 2 weeks at 1 of 7 different dose levels. Vinorelbine was escalated from 15 mg/m(2) (Level I) to 45 mg/m(2) (Level VII) and docetaxel was increased from 50 mg/m(2) (Level I) to 60 mg/m(2) (Level VII). Prophylactic corticosteroids and filgrastim were employed prospectively.

RESULTS

After completion of dose Level VII, accrual was terminated because Phase II dose intensity of both agents had been reached and further escalation was believed to be unsafe. At dose Level VII, one episode of first-cycle febrile neutropenia and a death after three treatment cycles due to Haemophilus influenzae sepsis (Grade 5 toxicity according to the Common Toxicity Criteria of the National Cancer Institute) without neutropenia were noted. In all, 209 treatment cycles were administered and febrile neutropenia was observed in only 4 of these treatments (1.9%). Bacteremia occurred in three patients (four episodes) in the absence of neutropenia. Symptomatic onycholysis was observed in three patients. Clinically significant peripheral neuropathy and fluid retention were rare. Confirmed partial responses were noted in 10 patients for a response rate of 37% (95% confidence interval, 20-57%).

CONCLUSIONS

Docetaxel at a dose of 60 mg/m(2) and vinorelbine at a dose of 45 mg/m(2), both given every 2 weeks, can be combined safely to achieve Phase II dose intensity of both agents. An ongoing Phase II trial will define the activity of this treatment combination.

Does rib cage-abdominal paradox signify respiratory muscle fatigue?

Studies suggesting that abnormal motion of the rib cage (RC) and abdomen (Ab) may indicate respiratory muscle fatigue have not separated the influence of respiratory load from that of fatigue in its pathogenesis. We hypothesized that abnormalities on RC-Ab motion are primarily related to increased load rather than fatigue. We tested this hypothesis in subjects breathing against resistive loads while maintaining 30 and 60% of maximum mouth pressure (Pmmax). RC-Ab asynchrony and paradox and the degree of variation in compartmental contribution to tidal volume were measured by inductive plethysmography and quantitated by the Konno-Mead method of analysis. Comparing measurements of base line and 30 and 60% of Pmmax indicated that the degree of asynchrony, paradox, and variation in compartmental contribution were significantly related to the level of the load; significant abnormalities were observed at even 30% of Pmmax, a target pressure that can be sustained indefinitely. In another group of subjects, fatigue was induced by sustaining 60% of Pmmax to the limits of tolerance. Indexes of abnormal RC-Ab motion increased from base line during the 1st min of loaded breathing but displayed no progression from the beginning to the end of the fatigue run. Immediately on discontinuation of the load, the indexes returned to levels similar to base line despite persistence of the fatigue state. These results in healthy subjects breathing against severe resistances indicate that RC-Ab asynchrony and paradox and variation in compartmental contribution to tidal volume are predominantly due to increases in respiratory load rather than muscle fatigue.

Konno-Mead analysis of ribcage-abdominal motion during successful and unsuccessful trials of weaning from mechanical ventilation

Respiratory muscle fatigue is considered a common cause of weaning failure but its detection is hampered by the lack of a satisfactory diagnostic test. Abdominal paradox has been proposed as a valuable clinical index of fatigue and thus its presence may lead to curtailment of weaning trials. However, sensitivity and specificity of this sign as a predictor of weaning outcome is unknown. We hypothesize that abnormal ribcage-abdominal (RC-Ab) motion is a common finding in the early stages of weaning and its presence does not inevitably imply an unsuccessful weaning outcome. We tested this hypothesis in patients undergoing a weaning trial: one group had a successful weaning outcome and were extubated (n = 10) and the other group failed the trial (n = 7). Normal RC-Ab motion was separately characterized in 17 healthy subjects. Employing a calibrated respiratory inductive plethysmograph, quantitative assessment of asynchrony and paradox was obtained by computing several indices from series of breaths at fixed time periods using the Konno-Mead method of analysis. During the weaning trial, both groups of patients displayed significant increases in asynchrony and Ab paradox compared to normal values. As a group, patients who failed the trial displayed significantly greater asynchrony and paradox of the RC and Ab than patients with a successful outcome. However, there was considerable overlap between the individual patients in the 2 study groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Accuracy of the respiratory inductive plethysmograph during loaded breathing

Indirect methods of measuring ventilation, such as the respiratory inductive plethysmograph (RIP), operate on the assumption that the respiratory system possesses two degrees of freedom of motion: the rib cage and abdomen. Accurate measurements have been obtained in many patients with pulmonary disease who possess additional degrees of freedom. Since calibration and validation of the RIP was carried out during quiet breathing in these patients, the amount of asynchronous or paradoxic breathing was presumably similar during the calibration and validation runs. Conversely, accuracy might be lost if following the initial calibration procedure the magnitude of chest wall distortion increased during subsequent validation runs. We calibrated the RIP during quiet breathing and examined its accuracy while subsequently breathing against resistive loads that required the generation of 20-80% of the subject's maximum inspiratory mouth pressure (Pmmax). We compared the relative accuracy of three commonly employed calibration methods: isovolume technique, least-squares technique, and single position loop-area technique. Up to 60% of Pmmax, 89% of the RIP values with the least-squares technique were within +/- 10% of simultaneous spirometric (SP) measurements and 100% were within +/- 20% of SP, compared with 63 and 91%, respectively, for the loop-area technique and 19 and 54%, respectively, for the isovolume technique. At 70 and 80% of Pmmax accuracy deteriorated. Accuracy of respiratory timing was judged in terms of fractional inspiratory time (TI/TT).(ABSTRACT TRUNCATED AT 250 WORDS)

The pattern of breathing during successful and unsuccessful trials of weaning from mechanical ventilation

We prospectively examined the pattern of breathing in patients being weaned from mechanical ventilation: one group (n = 10) underwent a successful weaning trial and were extubated, whereas another group (n = 7) developed respiratory failure and required the reinstitution of mechanical ventilation. During the period of ventilator support, minute ventilation (VI), tidal volume (VT), and respiratory frequency (f) were similar in the 2 groups. After discontinuation of the ventilator, VI remained similar in the 2 groups, but VT was lower and f was higher in the patients who failed the trial compared with those who were successful, 194 +/- 23 and 398 +/- 56 ml (p less than 0.001), respectively, and 32.3 +/- 2.3 and 20.9 +/- 2.8 breaths/min (p less than 0.001), respectively. The failure group displayed a significant increase in PaCO2 (p less than 0.005) during spontaneous breathing, without a concomitant increase in the alveolar-arterial PO2 difference. Eighty-one percent of the variance in PaCO2 was accounted for by the pattern of rapid, shallow breathing. During weaning, resting respiratory drive (reflected by mean inspiratory flow, VT/TI) and fractional inspiratory time (TI/Ttot) were similar in the 2 groups. The patients in the failure group showed significant increases in VT/TI, 265 +/- 27 to 328 +/- 32 ml/s (p less than 0.01), and VI, 5.82 +/- 0.53 to 7.32 +/- 0.52 L/min (p less than 0.01), from the beginning to the end of the weaning trial; VT and f showed no further change.(ABSTRACT TRUNCATED AT 250 WORDS)

Breathing pattern and metabolic behavior during anticipation of exercise

The mechanisms responsible for the marked increase in ventilation at the onset of exercise are incompletely defined. A conditioned response to exercise anticipation has been suggested as an influencing factor, but systematic measurements have not been made during the transition from rest to the time when exercise is anticipated but has not yet commenced. We tested the hypothesis that cortical activity associated with the anticipation of exercise causes hyperpnea, which is at least partly responsible for the increased ventilation at the onset of exercise. To assess the influence of continuous cortical activity in the absence of exercise anticipation the subjects performed mental arithmetic tasks. Fifteen subjects performed the two experiments in a random order. Ventilation was measured noninvasively using a calibrated respiratory inductive plethysmograph and end-tidal CO2 concentration (FETCO2) was monitored at the nasal vestibule. Both exercise anticipation and mental arithmetic caused an increase in minute ventilation (VI) (P less than 0.01) and mean inspiratory flow (VT/TI, P less than 0.01), which reflects respiratory center drive, although the derivation differed in that the former was volume based, whereas the latter was due to alteration in timing. Despite the increase in VI, FETCO2 remained constant in both instances. In a complementary study the constant FETCO2 in the face of increased VI was shown to be due to increased CO2 output. The results show that the mere anticipation of exercise causes an increase in ventilation. The mechanism responsible for this hyperpnea cannot be due solely to respiratory center activation because of the constancy of FETCO2 and the associated alterations in cardiac and metabolic behavior.

Separation of factors responsible for change in breathing pattern induced by instrumentation

Employment of mouthpiece and noseclips (MP + NC) has repeatedly been shown to increase tidal volume (VT), but its effect on respiratory frequency (f) and its subsets is controversial. The mechanisms accounting for this alteration in breathing pattern are poorly understood and may include stimulation of oral or nasal sensory receptors or alteration in the route of breathing. In this study we demonstrated that use of a MP + NC, compared with nonobtrusive measurement with a calibrated respiratory inductive plethysmograph, alters the majority of the volume and time indexes of breathing pattern, with increases in minute ventilation (P less than 0.01), VT (P less than 0.001), inspiratory time (TI, P less than 0.05), expiratory time (TE, P less than 0.05), mean inspiratory flow (P less than 0.05), and mean expiratory flow (P less than 0.05) and a decrease in f(P less than 0.05). Separating the potential mechanisms we found that when the respiratory route was not altered, independent oral stimulation (using an occluded MP) or nasal stimulation (by applying paper clips to the alae nasi) did not change the breathing pattern. In contrast, obligatory oral breathing without additional stimulation of the oral or nasal sensory receptors caused increases in VT (P less than 0.05), TI (P less than 0.05), and TE (P less than 0.01) and a fall in f(P less than 0.05). Heating and humidifying the inspired air did not prevent the alteration in breathing pattern with a MP. Thus change in the respiratory route is the major determinant of the alteration in breathing pattern with a MP + NC.(ABSTRACT TRUNCATED AT 250 WORDS)