Enzyme intermediates captured "on the fly" by mix-and-inject serial crystallography

BACKGROUND

Ever since the first atomic structure of an enzyme was solved, the discovery of the mechanism and dynamics of reactions catalyzed by biomolecules has been the key goal for the understanding of the molecular processes that drive life on earth. Despite a large number of successful methods for trapping reaction intermediates, the direct observation of an ongoing reaction has been possible only in rare and exceptional cases.

RESULTS

Here, we demonstrate a general method for capturing enzyme catalysis "in action" by mix-and-inject serial crystallography (MISC). Specifically, we follow the catalytic reaction of the Mycobacterium tuberculosis β-lactamase with the third-generation antibiotic ceftriaxone by time-resolved serial femtosecond crystallography. The results reveal, in near atomic detail, antibiotic cleavage and inactivation from 30 ms to 2 s.

CONCLUSIONS

MISC is a versatile and generally applicable method to investigate reactions of biological macromolecules, some of which are of immense biological significance and might be, in addition, important targets for structure-based drug design. With megahertz X-ray pulse rates expected at the Linac Coherent Light Source II and the European X-ray free-electron laser, multiple, finely spaced time delays can be collected rapidly, allowing a comprehensive description of biomolecular reactions in terms of structure and kinetics from the same set of X-ray data.

Wait times for diagnosis and treatment of lung cancer: a single-centre experience

Background

Multiple clinical practice guidelines recommend rapid evaluation of patients with suspected lung cancer. It is uncertain whether delays in diagnosis and management have a negative effect on outcomes.

Methods

This retrospective study included 551 patients diagnosed with lung cancer through the diagnostic assessment program at the Institut universitaire de cardiologie et de pneumologie de Québec between September 2013 and March 2015. Median wait times between initial referral, diagnosis, and first treatment were calculated and compared with recommended targets. Analyses were performed to evaluate for specific factors associated with longer wait times and for the effect of delays on the outcomes of progression-free survival (pfs), relapse-free survival (rfs) after primary surgical resection, and overall survival (os).

Results

Most patients were investigated and treated within recommended targets. Of the entire cohort, 379 patients were treated at our institution. Of those 379 patients, 311 (82%) were treated within recommended targets. In comparing patients within and outside target times, the only statistically significant difference was found in the distribution of treatment modalities: patients meeting targets were more likely to be treated with surgery or chemotherapy rather than with radiation. The pfs on first treatment modality was influenced by clinical stage, but not by time to therapy [hazard ratio (hr): 1.10; p = 0.65]. The os for the entire cohort was also influenced by stage, but not by delays (hr: 1.04; p = 0.87). For the 209 patients treated by surgery with curative intent, a significant reduction in rfs was associated with male sex and TNM stage, but not with delays (hr: 1.11; p = 0.83). The os after primary surgical resection was also associated with TNM stage, but not with delays (hr: 1.82; p = 0.43).

Conclusions

Recommended targets for wait times in the investigation and treatment of lung cancer can be achieved within a diagnostic assessment program. Compared with radiation treatment, treatment with surgery or chemotherapy is more likely to be completed within targets. Delays in investigation and treatment do not appear to negatively affect the clinical outcomes of os, rfs, and pfs. Prospective studies are needed to evaluate whether efficient work-up and treatment influence other important variables, such as quality of life, cost of care, and access to therapies while performance status is adequate.

[Not Available]

Les professionnels de la santé sont directement interpellés par le défi du système de santé québécois et canadien. La diversité et la force du leadership infirmier agissent comme un véritable levier dans la transformation du système. Cet article fait valoir l’engagement des infirmières autour du projet proposé par l’Ordre des infirmières et infirmiers du Québec (OIIQ), à la fois mobilisateur et facilitateur du changement. Fortement inspirées par l’approche LEADS du Collège canadien des leaders en santé (CCLS)1, les auteures ajoutent d’autres marqueurs cruciaux propres au leadership clinique infirmier, réunis sous l’acronyme de LEADERS. La présentation de résultats auprès des personnes soignées, de leur famille, des équipes de soins et des établissements, renforce la marque distinctive de ce leadership exercé sur le terrain. Des témoignages glanés auprès de leaders soutiennent la place déterminante de l’infirmière dans le réseau de la santé. Pour façonner l’avenir, les auteures misent sur les forces du leadership clinique.

Structural enzymology using X-ray free electron lasers

Mix-and-inject serial crystallography (MISC) is a technique designed to image enzyme catalyzed reactions in which small protein crystals are mixed with a substrate just prior to being probed by an X-ray pulse. This approach offers several advantages over flow cell studies. It provides (i) room temperature structures at near atomic resolution, (ii) time resolution ranging from microseconds to seconds, and (iii) convenient reaction initiation. It outruns radiation damage by using femtosecond X-ray pulses allowing damage and chemistry to be separated. Here, we demonstrate that MISC is feasible at an X-ray free electron laser by studying the reaction of M. tuberculosis ß-lactamase microcrystals with ceftriaxone antibiotic solution. Electron density maps of the apo-ß-lactamase and of the ceftriaxone bound form were obtained at 2.8 Å and 2.4 Å resolution, respectively. These results pave the way to study cyclic and non-cyclic reactions and represent a new field of time-resolved structural dynamics for numerous substrate-triggered biological reactions.

Presence of Illicit Drugs and Pharmaceutical Residues in the Wastewaters of an Eastern Canadian City

Not available

Management and outcomes of localized esophageal and gastroesophageal junction cancer in older patients

BACKGROUND

Older patients are commonly excluded from clinical trials in esophageal and gastroesophageal junction (gej) cancer. High-level evidence to guide management in this group is lacking. In the present study, we compared outcomes and described tolerance for curative- and noncurative-intent treatments among patients 70 years of age and older.

METHODS

We retrospectively reviewed all patients 70 years of age and older diagnosed with localized esophageal and gej cancer at our centre between 2005 and 2012.

RESULTS

The 74 patients identified had a median age of 77 years. Of those patients, 62% received curative-intent treatment, consisting mostly of concomitant chemoradiation therapy (n = 43, 93%). Median overall survival for patients receiving curative-intent treatment was 18.6 months [95% confidence interval (ci): 13.0 to 28.0 months], with 23% being long-term survivors (95% ci: 11.3% to 36.7%). In contrast, patients receiving noncurative-intent treatment had a median overall survival of 8.8 months (95% ci: 6.7 to 11.9 months), with none being long-term survivors (p < 0.0001). Improvement of dysphagia was seen after curative (81%) or palliative radiotherapy (78%) in symptomatic patients, and toxicities were manageable. The odds of not receiving curative treatment was higher by a factor of 8.5 among patients 80 years of age or older compared with those 70-79 years of age (95% ci: 2.5 to 28.7).

CONCLUSIONS

In managing older patients with esophageal and gej cancer, curative-intent treatment (compared with noncurative-intent treatment) leads to a significant survival benefit with a reasonable toxicity profile. Informed counselling of patients and their families about a curative treatment approach and efforts to increase awareness among oncology care providers are suggested.

Pericardiocentesis versus pericardiotomy for malignant pericardial effusion: a retrospective comparison

BACKGROUND

Treatment of malignant pericardial effusion remains controversial, because no randomized controlled trials have been conducted to determine the best approach, and results of retrospective studies have been inconsistent. The objective of the present study was to compare pericardiocentesis and pericardiotomy with respect to efficacy for preventing recurrence, and to determine, for those two procedures, diagnostic yields, complication rates, and effects on survival. We also aimed to identify clinical and procedural factors that could predict effusion recurrence.

METHODS

We retrospectively assessed 61 patients who underwent a procedure for treatment of a malignant pericardial effusion at the Institut universitaire de cardiologie et de pneumologie de Québec between February 2004 and September 2013.

RESULTS

Pericardiocentesis was performed in 42 patients, and pericardiotomy, in 19 patients. The effusion recurrence rate was significantly higher in patients treated with pericardiocentesis than with pericardiotomy (31.0% vs. 5.3%, p = 0.046). The diagnostic yield of the procedures was not significantly different (92.9% vs. 86.7%, p = 0.6). The overall rate of complications was similar in the two groups, as was the median overall survival (2.4 months vs. 2.6 months, p = 0.5). In univariate analyses, the procedure type was the only predictor of recurrence that approached statistical significance. Age, sex, type of cancer, presence of effusion at the time of cancer diagnosis, prior chest irradiation, tamponade upon presentation, and total volume of fluid removed did not influence the recurrence rate.

CONCLUSIONS

Compared with pericardiocentesis, pericardiotomy had higher success rate in preventing recurrence of malignant pericardial effusion, with similar diagnostic yields, complication rates, and overall survival.

The interaction role of obesity and pubertal timing on the psychosocial adjustment of adolescent girls: longitudinal data

OBJECTIVE

The objective of the study was to verify the hypothesis that obesity is associated with pubertal timing, as both factors interact to predict psychosocial adjustment problems in girls.

SUBJECTS

We selected 811 girls who had participated in a longitudinal study on a representative sample of French Canadian children from 1986 to 1997.

METHOD

Only data collected between 1993 and 1996 were analyzed. We classified the participants into three weight categories (normal, overweight, and obese) and pubertal timing (early, on-time, or late-maturing) and compared their internalized and externalized problem behavior and conflict as well as their socioeconomic status.

RESULT

We found that (1) early and late-maturing girls are more at risk of being overweight during the whole period of pubertal development as demonstrated by the increasing rate of obesity in these two groups between 11 and 13 y old, and (2) there was an interaction effect between pubertal timing and obesity in predicting problem behavior and conflict. Overweight and obese girls who developed faster or slower than their peers displayed more adjustment problems at 11 and 12 y old. At 13 y old, obesity predicted adjustment problems separately without regard to pubertal timing. Our results suggest that puberty timing is a risk factor for obesity and that both pubertal timing and being overweight predict adjustment problems during all the courses of pubertal development, supporting partially our hypothesis.

CONCLUSION

Programs and interventions must take into account these two factors and adolescents should be monitored throughout all the periods of pubertal development.

Tremor-related activity of neurons in the 'motor' thalamus: changes in firing rate and pattern in the MPTP vervet model of parkinsonism

The pathophysiology of parkinsonian tremor remains a matter of debate with two opposing hypotheses proposing a peripheral and a central origin, respectively. A central origin of tremor could arise either from a rhythmic activity of the internal segment of the globus pallidus (GPi) or from a structure such as the thalamus, outside the basal ganglia. In this study, single-unit recordings were performed in three 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys within the GPi and within three territories of the motor thalamus (delimited by their afferent inputs from the GPi, the substantia nigra and the cerebellum, respectively). For each recorded neuron, we compared the variations in firing rate and pattern in tremor and no tremor periods. Tremor either occurred spontaneously or was induced by external stimulation. When the animals entered into a tremor period we observed: (i) an increase in the mean firing rate in about half of the recorded neurons of the motor thalamus; and (ii), a change from an irregular to a rhythmic discharge within the range of tremor frequency (5-7 Hz) in about 10% of the recorded neurons of the motor thalamus (pallidal and cerebellar territories) and the GPi. Most of the thalamic neurons that exhibited a rhythmic discharge during tremor were found to be sensitive to external stimulation. Because the changes in firing rate occurred predominantly in the motor thalamus and not in the GPi, and because a fast rhythmic discharge of 10-15 Hz was frequently observed in the GPi and not in the motor thalamus, we conclude that thalamic activity is not a simple reproduction of basal ganglia output. Moreover, we suggest that thalamic processing of basal ganglia outputs could participate in the genesis of tremor, and that this thalamic processing could be influenced by sensory inputs and/or changes in attentional level elicited by external stimulation.

Nondetection of the S antigen due to the presence of sodium hypochlorite

Low concentrations of sodium hypochlorite (chlorine bleach) are known to destroy S antigen on intact fresh red blood cells (RBCs). Sodium hypochlorite is commonly used as a disinfectant. We report nondetection of the S antigen in tube and microplate saline indirect antiglobulin testing (SIAT) with a lot of commercial saline utilized in our donor screening and reference laboratories. Known S+s+ RBCs were found to be nonreactive with anti-S by SIAT in our reference laboratory. Our investigation demonstrated the presence of chlorine in the commercial saline. The saline lot was used for several days of donor screening and recall of FFP and platelet concentrates was initiated. Two lots of saline were recalled from blood banks across North America.

[Experimental models of Parkinson's disease]

Parkinson's disease is a neurodegenerative condition who is related to a large loss of nigral dopaminergic neurons leading to a depletion of dopamine in the striatum. Experimental research is required in order to increase our knowledge on the cellular mechanism and functional consequences of this degenerative process. These models allow investigations of new therapeutics in order to improve the treatment of patients or to test new drugs able to protect any remaining dopaminergic neurons. It is relatively easy to obtain animal models of this disease since the target structure and the neuronal population are clearly defined. Two neurotoxic compounds are available for inducing animal models of Parkinson's disease, 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). A new one, rotenone, requires further investigations. Each of the neurotoxic compounds requires a specific protocol which can be used either with rodents or non-human primates. Progressive lesioning, using MPTP on green african monkeys (Cercopithecus aethiops sabaeus) provides the most reliable model of the idiopathic disease.

Examining the specificity of practice hypothesis: is learning modality specific?

The specificity of practice hypothesis was examined using a tracking task. In Experiment 1, visual or auditory feedback about performance was provided. Vision was more useful than audition early in acquisition. Performance gains found in acquisition were maintained during retention, but learning was specific only if the acquisition modality was visual. Specificity did not increase with the amount of practice. In Experiment 2, visual and auditory information were combined. Again, the specificity of practice hypothesis was supported. Also, instructing participants to attend to one information source allowed us to demonstrate that information can be explicitly or implicitly processed. Further, specificity effects may occur because of different rates of development for error detection and correction processes.

Behavioral reactions reflecting differential reward expectations in monkeys

Learning theory emphasizes the importance of expectations in the control of instrumental action. This study investigated the variation of behavioral reactions toward different rewards as an expression of differential expectations of outcomes in primates. We employed several versions of two basic behavioral paradigms, the spatial delayed response task and the delayed reaction task. These tasks are commonly used in neurobiological studies of working memory, movement preparation, and event expectation involving the frontal cortex and basal ganglia. An initial visual instruction stimulus indicated to the animal which one of several food or liquid rewards would be delivered after each correct behavioral response, or whether or not a reward could be obtained. We measured the reaction times of the operantly conditioned arm movement necessary for obtaining the reward, and the durations of anticipatory licking prior to liquid reward delivery as a Pavlovian conditioned response. The results showed that both measures varied depending on the reward predicted by the initial instruction. Arm movements were performed with significantly shorter reaction times for foods or liquids that were more preferred by the animal than for less preferred ones. Still larger differences were observed between rewarded and unrewarded trials. An interesting effect was found in unrewarded trials, in which reaction times were significantly shorter when a highly preferred reward was delivered in the alternative rewarded trials of the same trial block as compared to a less preferred reward. Anticipatory licks preceding the reward were significantly longer when highly preferred rather than less preferred rewards, or no rewards, were predicted. These results demonstrate that behavioral reactions preceding rewards may vary depending on the predicted future reward and suggest that monkeys differentially expect particular outcomes in the presently investigated tasks.