Identification of cancer stem cells and a strategy for their elimination

It has been established previously that up to 40% of mouse CD34⁺ hematopoietic stem cells are capable of internalizing exogenous dsDNA fragments both in vivo and ex vivo. Importantly, when mice are treated with a combination of cyclophosphamide and dsDNA, the repair of interstrand crosslinks in hematopoietic progenitors is attenuated, and their pluripotency is altered. Here we show for the first time that among various actively proliferating mammalian cell populations there are subpopulations capable of internalizing dsDNA fragments. In the context of cancer, such dsDNA-internalizing cell subpopulations display cancer stem cell-like phenotype. Furthermore, using Krebs-2 ascites cells as a model, we found that upon combined treatment with cyclophosphamide and dsDNA, engrafted material loses its tumor-initiating properties which we attribute to the elimination of tumor-initiating stem cell subpopulation or loss of its tumorigenic potential.     

Self-directed practice schedule enhances learning of suturing skills

Background

Most preoperative surgical training programs experience challenges with the availability of expert surgeons to teach trainees. Some research suggests that trainees may benefit from being allowed to actively shape their learning environments, which could alleviate some of the time and resource pressures in surgical training. The purpose of this study was to investigate the effects of self-directed or prescribed practice schedules (random or blocked) on learning suturing skills.

Methods

Participants watched an instructional video for simple interrupted, vertical mattress and horizontal mattress suturing then completed a pretest to assess baseline skills. Participants were assigned to 1 of 4 practice groups: self-directed practice schedule, prescribed blocked practice schedule, prescribed random practice schedule or matched to the self-directed group (control). Practice of the skill was followed by a delayed (1 h) posttest. Improvement from pretest to posttest was determined based on differences in performance time and expert-based assessments.

Results

Analyses revealed a significant effect of group for difference in performance time of the simple interrupted suture. Random practice did not show the expected advantage for skill learning, but there was an advantage of self-directed practice.

Conclusion

Self-directed practice schedules may be desirable for optimal learning of simple technical skills, even when expert instruction is available. Instructors must also take into account the interaction between task difficulty and conditions of practice to develop ideal training environments.     

Postoperative complications of laparoscopic adjustable gastric banding

Background: The primary aim was to determine the rate and nature of late postoperative complications in relation to the type of band used and the route through which it encircled the stomach in a retrospective review of postoperative complications that necessitated reoperation in 500 consecutive cases of laparoscopic adjustable gastric banding (LAGB) conducted over the past 48 months. Methods: The four study groups were: (A) Lap‐Band^® perigastric route, 186 cases; (B) Lap‐Band^® pars flaccida route 73 cases; (C) SAGB perigastric 70 cases, and (D) SAGB pars flaccida, 171 cases. There were 414 women and 86 men. The mean age was 39.2 ± 11.0 years (17–68). The mean weight was 126 kg, and mean BMI was 43.4 kg/m² prior to operation. Results: There were 32 cases of slippage (17%) in group A and five cases (7%) in Group B (P < 0.05). In group C there were 15 cases (21%) of slippage and in group D six cases (3%) (P < 0.05). There were no significant differences between Groups A and C or Groups B and D. Except for one case of band erosion in Group C, erosion, tube disconnection and aneurysmatic balloon dilatation occurred only in groups A and B. Band erosion occurred in 2% each in groups A and B, tube disconnection in 3% and 4%, respectively, and balloon dilatation in 2% in each of groups A and B. Conclusions: Slippage was primarily route dependent. Erosion, tube disconnection and aneurysmatic dilatation of the balloon were encountered almost exclusively in the high‐pressure system. We conclude that the pars flaccida route with the low‐pressure system is more effective in reducing the rate of complications necessitating reoperation.     

Effects of voice harmonic complexity on ERP responses to pitch-shifted auditory feedback

Objective

The present study investigated the neural mechanisms of voice pitch control for different levels of harmonic complexity in the auditory feedback.

Methods

Event-related potentials (ERPs) were recorded in response to +200 cents pitch perturbations in the auditory feedback of self-produced natural human vocalizations, complex and pure tone stimuli during active vocalization and passive listening conditions.

Results

During active vocal production, ERP amplitudes were largest in response to pitch shifts in the natural voice, moderately large for non-voice complex stimuli and smallest for the pure tones. However, during passive listening, neural responses were equally large for pitch shifts in voice and non-voice complex stimuli but still larger than that for pure tones.

Conclusions

These findings suggest that pitch change detection is facilitated for spectrally rich sounds such as natural human voice and non-voice complex stimuli compared with pure tones. Vocalization-induced increase in neural responses for voice feedback suggests that sensory processing of naturally-produced complex sounds such as human voice is enhanced by means of motor-driven mechanisms (e.g. efference copies) during vocal production.

Significance

This enhancement may enable the audio-vocal system to more effectively detect and correct for vocal errors in the feedback of natural human vocalizations to maintain an intended vocal output for speaking.     

The Ongoing Revolution of MALDI-TOF Mass Spectrometry for Microbiology Reaches Tropical Africa

Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) represents a revolution in routine pathogen identification in clinical microbiology laboratories. A MALDI-TOF MS was introduced to tropical Africa in the clinical microbiology laboratory of the Hôpital Principal de Dakar (Senegal) and used for routine pathogen identification. Using MS, 2,429 bacteria and fungi isolated from patients were directly assayed, leading to the identification of 2,082 bacteria (85.7%) and 206 fungi (8.5%) at the species level, 109 bacteria (4.5%) at the genus level, and 16 bacteria (0.75%) at the family level. Sixteen isolates remained unidentified (0.75%). Escherichia coli was the most prevalent species (25.8%) followed by Klebsiella pneumoniae (14.8%), Streptococcus agalactiae (6.2%), Acinetobacter baumannii (6.1%), Pseudomonas aeruginosa (5.9%), and Staphylococcus aureus (5.9%). MALDI-TOF MS has also enabled the detection of rare bacteria and fungi. MALDI-TOF MS is a powerful tool for the identification of bacterial and fungal species involved in infectious diseases in tropical Africa.