二尖瓣病变伴左房血栓的外科治疗

本文报道了18例风湿性心脏病伴有左房血栓病人的手术治疗,其中瓣膜置换者5例,二尖瓣直视成形者13例。死亡4例中1例死于脑栓塞。血栓形成和房颤有直接关系。左房血栓术前诊断主要依靠心脏B超,血栓治疗以手术清除为主。为预防术后再发,应纠正房颤及适当应用抗凝血药物。     

Dual Ca2+ modulation of glycinergic synaptic currents in rodent hypoglossal motoneurones

Glycinergic synapses are implicated in the coordination of reflex responses, sensory signal processing and pain sensation. Their activity is pre- and postsynaptically regulated, although mechanisms are poorly understood. Using patch-clamp recording and Ca²⁺ imaging in hypoglossal motoneurones from rat and mouse brainstem slices, we address here the role of cytoplasmic Ca²⁺ (Ca_i) in glycinergic synapse modulation. Ca²⁺ influx through voltage-gated or NMDA receptor channels caused powerful transient inhibition of glycinergic IPSCs. This effect was accompanied by an increase in both the failure rate and paired-pulse ratio, as well as a decrease in the frequency of mIPSCs, suggesting a presynaptic mechanism of depression. Inhibition was reduced by the cannabinoid receptor antagonist SR141716A and occluded by the agonist WIN55,212-2, indicating involvement of endocannabinoid retrograde signalling. Conversely, in the presence of SR141716A, glycinergic IPSCs were potentiated postsynaptically by glutamate or NMDA, displaying a Ca²⁺-dependent increase in amplitude and decay prolongation. Both presynaptic inhibition and postsynaptic potentiation were completely prevented by strong Ca_i buffering (20 m m BAPTA). Our findings demonstrate two independent mechanisms by which Ca²⁺ modulates glycinergic synaptic transmission: (i) presynaptic inhibition of glycine release and (ii) postsynaptic potentiation of GlyR-mediated responses. This dual Ca²⁺-induced regulation might be important for feedback control of neurotransmission in a variety of glycinergic networks in mammalian nervous systems.     

Modified oxygen mask to induce target levels of hyperoxia and hypercarbia during radiotherapy: A more effective alternative to carbogen

Purpose: Carbogen has long been under investigation as an adjuvant to radiotherapy of tumors. A major factor confounding its evaluation is its inconsistency in raising blood partial pressure of CO₂ (pCO₂). We investigated whether a new partial rebreathing method would provide better control of pCO₂ than carbogen.

Methods and materials: We compared the efficacy of each method in 10 healthy volunteers. Volunteers breathed 1.5, 3 and 5% carbogen in 5-min stages via the usual non-rebreathing circuit. All the volunteers then breathed 100% O₂ through a commercial sequential gas delivery (SGD) circuit modified by attaching a reservoir to its exhalation port. Hypercarbia was induced by step reductions in oxygen flow to the SGD circuit. We monitored minute ventilation and end-tidal pCO₂ (ETpCO₂) as a surrogate for its arterial value.

Results: Inhalation of 1.5 and 3% carbogen did not increase ETpCO₂ from baseline (40 ± 1.5 mmHg); 5% carbogen increased ETpCO₂ to 45 ± 1.6 mmHg (p < 0.001). With the SGD circuit, reducing O₂ flow to 4.3 ± 0.7 l/min increased ETpCO₂ in all subjects from 41 ± 2.0 mmHg (baseline) to 46 ± 2.1 mmHg (p < 0.001). Voluntary hyperventilation reduced ETpCO₂ with 5% carbogen but not with SGD (p = 0.379).

Conclusions: We confirm previous observations that carbogen inhalation does not result in a predictable rise in ETpCO₂ and suggest that a precise and stable target ETpCO₂ can instead be induced by simply controlling O₂ flow into a modified SGD circuit. We hoped that the reliable control of pCO₂ will enable studies that address first, the efficacy of raising ETpCO₂ on specific tumor blood flow, and eventually, its benefit as an adjuvant to radiotherapy.     

Aetiology,timing and clinical predictors of early vs. late readmission following index hospitalization for acute heart failure: insights from ASCEND‐HF

Aims

Patients hospitalized for heart failure (HF) are at high risk for 30‐day readmission. This study sought to examine the timings and causes of readmission within 30 days of an HF hospitalization.

Methods and results

Timing and cause of readmission in the ASCEND‐HF (Acute Study of Clinical Effectiveness of Nesiritide and Decompensated Heart Failure) trial were assessed. Early and late readmissions were defined as admissions occurring within 0–7 days and 8–30 days post‐discharge, respectively. Patients who died in hospital or remained hospitalized at day 30 post‐randomization were excluded. Patients were compared by timing and cause of readmission. Logistic and Cox proportional hazards regression analyses were used to identify independent risk factors for early vs. late readmission and associations with 180‐day outcomes. Of the 6584 patients (92%) in the ASCEND‐HF population included in this analysis, 751 patients (11%) were readmitted within 30 days for any cause. Overall, 54% of readmissions were for non‐HF causes. The median time to rehospitalization was 11 days (interquartile range: 6–18 days) and 33% of rehospitalizations occurred by day 7. Rehospitalization within 30 days was independently associated with increased risk for 180‐day all‐cause death [hazard ratio (HR) 2.38, 95% confidence interval (CI) 1.93–2.94; P < 0.001]. Risk for 180‐day all‐cause death did not differ according to early vs. late readmission (HR 0.99, 95% CI 0.67–1.45; P = 0.94).

Conclusions

In this hospitalized HF trial population, a significant majority of 30‐day readmissions were for non‐HF causes and one‐third of readmissions occurred in the first 7 days. Early and late readmissions within the 30‐day timeframe were associated with similarly increased risk for death. Continued efforts to optimize multidisciplinary transitional care are warranted to improve rates of early readmission.

     

Three-dimensional imaging improves surgical skill performance in a laparoscopic test model for both experienced and novice laparoscopic surgeons

Study objective

The objective of this study was to evaluate and compare the impact of three-dimensional (3D) imaging system on the performance of basic laparoscopic tasks in a test model by novice and experienced surgeons.

Design

Three tasks were performed in a test model by 30 surgeons, 15 experienced surgeons, and 15 with minimal laparoscopic experience. The tasks were performed using 2D and 3D vision systems.

Design classification

Canadian Task Force II-1.

Subjects

Fifteen experienced laparoscopic surgeons and fifteen novices with minimal laparoscopic experience.

Measurements

Performance times were recorded using both two-dimensional and 3D imaging system for each task.

Main results

Performance time for all skills was significantly (P < 0.02) shorter when using 3D imaging system. Performance times were reduced by 18–31 % using 3D imaging for all participants. Experienced surgeons performed the tasks faster and showed similar improvement while using 3D imaging system.

Conclusion

3D vision systems allow for significant improvement in performance times of basic laparoscopic tasks in a test model for both inexperienced and advanced laparoscopic surgeons. Experienced surgeons benefit as much as novices from 3D imaging system. This benefit should be weighed against the disadvantages of the 3D vision systems, mainly cost, decreased light, eye strain, headaches, and shorter focal lengths.     

The contribution of calcium/calmodulin-dependent protein-kinase II (CaMKII) to short-term plasticity at the neuromuscular junction

Calcium/calmodulin-dependent protein-kinase II (CaMKII) is a ubiquitous intracellular enzyme, which is implicated in learning and memory mechanisms in the central nervous system, however its contribution to peripheral cholinergic neurotransmission is not well characterized. This study evaluated the impact of CaMKII on the function of frog neuromuscular synapse using electrophysiological recordings. Application of the selective CaMKII inhibitor KN-93 (5 μM) did not significantly alter the parameters of evoked and spontaneous quantal acetylcholine release under low-frequency stimulation (0.03 Hz). KN-93, on the other hand, produced pronounced changes in short-term synaptic plasticity: particularly, KN-93 inhibits the second component of paired-pulse facilitation (interpulse intervals of 100 ms and longer) and strengthens the depression of synaptic transmission under high-frequency stimulation (50 Hz). These results imply that CaMKII plays an important role in presynaptic functions at the frog neuromuscular junction, and potentiates quantal acetylcholine release under high-frequency activity.     

Suppression of facilitative glucose transporter 1 mRNA can suppress tumor growth

We attempted to suppress glucose transporter 1 (GLUT1) expression by transfecting MKN45 cells with cDNA for antisense GLUT1. Glucose transport was significantly decreased in cells with antisense GLUT1 compared with wild-type cells or cells with vector alone. Suppression of GLUT1 mRNA resulted in a decreased number of cells in the S phase. This was accompanied by overexpression of p21 protein. Tumorigenicity in the nude mice injected with antisense GLUT1 expressing cells was significantly slower than in those with wild-type MKN45 cells. These results suggest that antisense GLUT1 mRNA inhibits tumor growth through a G(1) arrest and that expression of antisense GLUT1 mRNA via gene therapy can be used as a tool in the treatment of cancer.