Magnetic resonance elastography of the lung: technical feasibility.

Magnetic resonance elastography (MRE) is a phase-contrast technique that can spatially map shear stiffness within tissue-like materials. To date, however, MRE of the lung has been too technically challenging-primarily because of signal-to-noise ratio (SNR) limitations and phase instability. We describe an approach in which shear wave propagation is not encoded into the phase of the MR signal of a material, but rather from the signal arising from a polarized noble gas encapsulated within. To determine the feasibility of the approach, three experiments were performed. First, to establish whether shear wave propagation within lung parenchyma can be visualized with phase-contrast MR techniques, MRE was performed on excised porcine lungs inflated with room air. Second, a phantom consisting of open-cell foam filled with thermally polarized (3)He gas was imaged with MRE to determine whether shear wave propagation can be encoded by the gas. Third, preliminary evidence of the feasibility of MRE in vivo was obtained by using a longitudinal driver on the chest of a normal volunteer to generate shear waves in the lung. The results suggest that MRE in combination with hyperpolarized noble gases is potentially useful for noninvasively assessing the regional elastic properties of lung parenchyma, and merits further investigation.     

Comparison of seizure detection algorithms in continuously monitored pediatric patients.

SUMMARY: Robust, automated seizure detection has long been an important goal in epilepsy research because of both the possibilities for portable intervention devices and the potential to provide prompter, more efficient treatment while in clinic. The authors present results on how well four seizure detection algorithms (based on principal eigenvalue [EI], total power, Kolmogorov entropy [KE], and correlation dimension) discriminated between ictal and interictal EEG and electrocorticoencephalography (ECoG) from four patients (aged 13 months to 21 years). Test data consisted of 46 to 78 hours of continuously acquired EEG/ECoG for each patient (245 hours total), and the detectors' accuracy was checked against seizures found by a board-certified neurologist and an experienced registered EEG technician. The results were patient-specific: no algorithm performed well on a 13-month-old patient, and no algorithm consistently performed best on the other three patients. One of the metrics (EI) supported the existence of a postictal period of 5 to 15 minutes in the three oldest patients, but no strong evidence of a preictal anticipation was found. Two metrics (EI and KE) cycled continuously with a period of several hours in a 21-year-old patient, highlighting the importance of continuous analysis to differentiate background cycling from anticipation.     

1,6—二磷酸果糖对手术后应激病人应用全肠外营养支持效果的影响

本文在胃癌行全胃或胃大部切除术引起的中等程度应激病人，随机分组对比观察了全肠外营养或ＴＰＮ加用１，６－二磷酸果糖的效果。结果显示，与单纯ＴＰＮ相比，ＴＰＮ加用ＦＤＰ后血清皮质醇和胰高血糖素等应激激素水平有所下降，尿中３－甲基组氨酸排出减少，累积氮平衡增加。     

A mechanical study of six digital pulley reconstruction techniques: Part II. Strength of individual reconstructions

A laboratory study was done on fresh-frozen human cadaver limbs, using six types of pulley reconstructions about the flexor tendons of the fingers. The reconstructions used were those described by (1) Bunnell, (2) Karev, (3) Weilby, and (4) Lister, and two types developed by us that have not been previously described. The pulleys were tested at constant strain rate to failure with the peak force recorded as the breaking strength. A total of 385 reconstructed pulleys were tested and the results were analyzed statistically. A new "loop and one half" pulley reconstruction was significantly stronger than the other five reconstructions (p less than 0.01) with an average load to failure of 22.5 kilograms-force. The other pulley reconstructions varied in average breaking strength from 2.8 kilograms-force to 18.4 kilograms-force.     

Contributions of ion conductances to the onset responses of octopus cells in the ventral cochlear nucleus: simulation results

The onset response pattern displayed by octopus cells has been attributed to intrinsic membrane properties, low membrane impedance, and/or synaptic inputs. Although the importance of a low membrane impedance generally is acknowledged as an essential component, views differ on the role that ion channels play in producing the onset response. In this study, we use a computer model to investigate the contributions of ion channels to the responses of octopus cells. Simulations using current ramps indicate that, during the "ramp-up" stage, the membrane depolarizes, activating a low-threshold K(+) channel, K(LT), which increases membrane conductance and dynamically increases the current required to evoke an action potential. As a result, the model is sensitive to the rate that membrane potential changes when initiating an action potential. Results obtained when experimentally recorded spike trains of auditory-nerve fibers served as model inputs (simulating acoustic stimulation) demonstrate that a model with K(LT) conductance as the dominant conductance produces realistic onset response patterns. Systematically replacing the K(LT) conductance by a h-type conductance (which corresponds to a hyperpolarization-activated inward rectifier current, I(h)) or by a leakage conductance reduces the model's sensitivity to rate of change in membrane potential, and the model's response to "acoustic stimulation" becomes more chopper-like. Increasing the h-type conductance while maintaining a large K(LT) conductance causes an increase in threshold to both current steps and acoustic stimulation but does not significantly affect the model's sensitivity to rate of change in membrane potential and the onset response pattern under acoustic stimulation. These findings support the idea that K(LT), which is activated during depolarization, is the primary membrane conductance determining the response properties of octopus cells, and its dynamic role cannot be provided by a static membrane conductance. On the other hand, I(h), which is activated during hyperpolarization, does not play a large role in the basic onset response pattern but may regulate response threshold through its contribution to the membrane conductance.     

Changes in food intake and activity after quitting smoking

Quitting smoking often results in weight gain. The causes of the gain are not known. The present study evaluated changes in calories, total sugars, sucrose, fat, protein, and nonsugar carbohydrates as well as changes in activity levels after quitting smoking. Ninety-five subjects were randomly assigned to either early (Week 2) or late (Week 6) quit dates. Subjects were assessed on weight, food intake, activity levels, and smoking levels at baseline, at Weeks 4 and 8, and at Weeks 12 and 26 postquit. The results indicated significant increases in calories, sucrose, and fats 2 weeks after the quit date. Changes for total sugars were less consistent. Activity levels did not change significantly. Early caloric increases predicted weight gain at 26 weeks for abstinent women. No relation was found for abstinent men, but interpretation of this finding is weakened by a small subsample size. Abstinent subjects gained over 9 lb by 26 weeks postquit. Despite this gain, Week 26 results showed that caloric intake for abstinent women was approximately equal to that observed at baseline, whereas that for abstinent men had dropped significantly.     

The effect of protein malnutrition on the IgA immune response in mice.

The influence of protein malnutrition on the IgA immune response was determined in BALB/c mice fed isocaloric diets containing 20% (control), 4%, or 2% protein. We describe here a severely protein-deficient state (6 weeks on a 2% protein diet) and a moderately malnourished state (6-8 weeks on a 4% protein diet). The total IgA concentration in intestinal washes, as determined by radial immunodiffusion, was reduced at 6 and 8 weeks in the 4% diet group and at 6 weeks in the 2% diet group, compared to the controls. Serum IgA levels were significantly elevated in both the 2% and 4% diet-fed groups at all time intervals. The IgA anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) response generated after oral immunization with SRBC did not differ between the control and the 4% diet group at any time interval, yet the IgA PFC/spleen response was significantly reduced in the 2% diet group at all time intervals studied. However, the IgA PFC/10(6) spleen cells was reduced only with the 2% protein diet group at 6 weeks. Severely protein-deficient mice replenished with the control diet for 3 weeks showed a recovery to values similar to the 8-week control group of both the IgA PFC response and the total IgA concentration in intestinal washes. These results suggest that protein deprivation leads to a reversible reduction in the IgA response to antigens encountered at the intestinal mucosa.     

Osteoclasts contain macrophage and megakaryocyte antigens

The origin and mechanism of formation of the osteoclast remains controversial. Although it is known to be derived from a circulating mononuclear percursor, the identity of this cell is unknown. Using a panel of monoclonal antibodies raised against macrophage and other marrow-derived cells, we determined the immunocytochemical staining of human osteoclasts in both fetal bone metaphyseal imprints and frozen sections. Osteoclasts and marrow mononuclear cells were stained by three broad spectrum antimacrophage antibodies, EBM-11, Y182a and BM2. T310, an antibody which stains macrophages and T helper cells, and C17, an antimegakaryocyte antibody, also stained osteoclasts. EBM-11, Y182a and BM2 also stained megakaryocytes in bone imprints as well as normal bone marrow smears. The presence of macrophage-associated antigens in osteoclasts, megakaryocytes and bone marrow mononuclear cells indicates that they are phenotypically similar to macrophages.