Spinal Motion and Muscle Activity during Active Trunk Movements – Comparing Sheep and Humans Adopting Upright and Quadrupedal Postures

Sheep are used as models for the human spine, yet comparative in vivo data necessary for validation is limited. The purpose of this study was therefore to compare spinal motion and trunk muscle activity during active trunk movements in sheep and humans. Three-dimensional kinematic data as well as surface electromyography (sEMG) of spinal flexion and extension was compared in twenty-four humans in upright (UR) and 4-point kneeling (KN) postures and in 17 Austrian mountain sheep. Kinematic markers were attached over the sacrum, posterior iliac spines, and spinous and transverse processes of T5, T8, T11, L2 and L5 in humans and over the sacrum, tuber sacrale, T5, T8, T12, L3 and L7 in sheep. The activity of erector spinae (ES), rectus abdominis (RA), obliquus externus (OE), and obliquus internus (OI) were collected. Maximum sEMG (MOE) was identified for each muscle and trial, and reported as a percentage (MOE%) of the overall maximally observed sEMG from all trials. Spinal range of motion was significantly smaller in sheep compared to humans (UR / KN) during flexion (sheep: 6–11°; humans 12–34°) and extension (sheep: 4°; humans: 11–17°). During extension, MOE% of ES was greater in sheep (median: 77.37%) than UR humans (24.89%), and MOE% of OE and OI was greater in sheep (OE 76.20%; OI 67.31%) than KN humans (OE 21.45%; OI 19.34%), while MOE% of RA was lower in sheep (21.71%) than UR humans (82.69%). During flexion, MOE% of RA was greater in sheep (83.09%) than humans (KN 47.42%; UR 41.38%), and MOE% of ES in sheep (45.73%) was greater than KN humans (14.45%), but smaller than UR humans (72.36%). The differences in human and sheep spinal motion and muscle activity suggest that caution is warranted when ovine data are used to infer human spine biomechanics.     

Pore-forming Activity of the Escherichia coli Type III Secretion System Protein EspD

Enterohemorrhagic Escherichia coli is a causative agent of gastrointestinal and diarrheal diseases. Pathogenesis associated with enterohemorrhagic E. coli involves direct delivery of virulence factors from the bacteria into epithelial cell cytosol via a syringe-like organelle known as the type III secretion system. The type III secretion system protein EspD is a critical factor required for formation of a translocation pore on the host cell membrane. Here, we show that recombinant EspD spontaneously integrates into large unilamellar vesicle (LUV) lipid bilayers; however, pore formation required incorporation of anionic phospholipids such as phosphatidylserine and an acidic pH. Leakage assays performed with fluorescent dextrans confirmed that EspD formed a structure with an inner diameter of ∼2.5 nm. Protease mapping indicated that the two transmembrane helical hairpin of EspD penetrated the lipid layer positioning the N- and C-terminal domains on the extralumenal surface of LUVs. Finally, a combination of glutaraldehyde cross-linking and rate zonal centrifugation suggested that EspD in LUV membranes forms an ∼280–320-kDa oligomeric structure consisting of ∼6–7 subunits.     

Climatic sensitivity of species’ vegetative and reproductive phenology in a Hawaiian montane wet forest

Understanding how tropical tree phenology (i.e., the timing and amount of seed and leaf production) responds to climate is vital for predicting how climate change may alter ecological functioning of tropical forests. We examined the effects of temperature, rainfall, and photosynthetically active radiation (PAR) on seed phenology of four dominant species and community-level leaf phenology in a montane wet forest on the island of Hawaiʻi using monthly data collected over ~ 6 years. We expected that species phenologies would be better explained by variation in temperature and PAR than rainfall because rainfall at this site is not limiting. The best-fit model for all four species included temperature, rainfall, and PAR. For three species, including two foundational species of Hawaiian forests (Acacia koa and Metrosideros polymorpha), seed production declined with increasing maximum temperatures and increased with rainfall. Relationships with PAR were the most variable across all four species. Community-level leaf litterfall decreased with minimum temperatures, increased with rainfall, and showed a peak at PAR of ~ 400 μmol/m²s⁻¹. There was considerable variation in monthly seed and leaf production not explained by climatic factors, and there was some evidence for a mediating effect of daylength. Thus, the impact of future climate change on this forest will depend on how climate change interacts with other factors such as daylength, biotic, and/or evolutionary constraints. Our results nonetheless provide insight into how climate change may affect different species in unique ways with potential consequences for shifts in species distributions and community composition.     

Taste systems of the petrosal ganglion of the rat glossopharyngeal nerve

Single unit recordings were taken from sensory ganglion cellsin the petrosal ganglion (PG) of the glossopharyngeal nerveof the rat. These taste units were examined with respect tospontaneous and evoked discharge patterns and responsivenessto a wide variety of chemical compounds, most of natural occurrence.Spontaneous activity patterns, with few exceptions, tended tobe extremely irregular with both bursting (clusters of 2–3spikes) and grouping (large groups of spikes as in evoked discharges).Most interspike interval histograms of spontaneous activitywere multimodal, similar to rat geniculate ganglion (GG) units.Evoked discharges usually displayed grouping of spikes, andlong latencies of onset and persistence of discharge after rinsewere sometimes seen. Little response was shown to nucleotidesor salts. Units responsive to amino acids tended to show largedischarge to only one or two amino acids; and the most responsiveamino acid usually varied from cell to cell. Units responsiveto alkaloids only responded to a few alkaloids with atropineand quinine being the most stimulatory. Units responsive toacids only discharged to a few of the acids tested and oftenacids of low pH elicited no discharge. Saccharin activated unitsresponsive to both sugar and alkaloids. A few units highly responsiveto both sugar and alkaloids were seen. The units were placedinto four clusters on the basis of chemicals activating themand certain neurophysiological characteristics: PG salt units,PG acid units and, tentatively, amino acid (sugar) units andX (alkaloid and alkaloid plus) units. The PG salt units didnot show the exclusive sensitivity to sodium and lithium compoundsas did the GG salt units. The PG acid units could also be differentiatedfrom the GG acid units. The petrosal amino acid and X units,on the other hand, could not be differentiated from similarunits in the rat GG.     

Effects of yohimbine and desipramine on cardiac noradrenaline release and ventricular arrhythmias during acute coronary artery occlusion and reperfusion in anesthetized dogs

Effects of yohimbine (YHMB, an alpha 2-antagonist) and desipramine (DMI, a neuronal uptake inhibitor) were compared on cardiac noradrenaline (NA) release either upon left ansa subclavia nerve stimulation during acute occlusion of the left anterior descending coronary artery (LAD) or upon subsequent LAD reperfusion without stimulation in anesthetized dogs. In control dogs, before LAD occlusion, coronary sinus (CS) NA output increased from 5.4 +/- 1.0 to 26.8 +/- 4.0 ng/min (p less than 0.05) upon stimulation (2 Hz, 30 s). The response to stimulation remained unchanged 25 min after LAD occlusion. During reperfusion 60 min after occlusion, the output of CS-NA and lactate increased from 6.1 +/- 0.8 to 51.3 +/- 19.4 ng/min (p less than 0.05) and from 2.7 +/- 0.5 to 6.7 +/- 1.3 mg/min (p less than 0.05), respectively. In dogs treated with YHMB, the stimulation-induced increase in NA output was potentiated at least fourfold (p less than 0.05) either before or during LAD occlusion, but not during reperfusion. In dogs receiving DMI, stimulation-induced CS-NA output was enhanced to a similar extent (approximately twofold, p less than 0.05) either before or during occlusion, while reperfusion-induced NA output was markedly potentiated by approximately ninefold (p less than 0.05). Maximum dP/dt of left ventricular pressure remained unchanged upon reperfusion in all groups. The total arrhythmic ratio in the drug-treated groups did not significantly differ from the ratio in control dogs upon either stimulation or reperfusion. The data suggest that an abrupt increase in NA output upon reperfusion may result from a washout of NA locally accumulated in the ischemic and (or) peri-ischemic region during the preceding occlusion period, and that NA thus released does not have substantial hemodynamic effects. The results indicate that in the presence of YHMB or DMI, the potentiated increase in NA release in response to either nerve stimulation during LAD occlusion or to reperfusion without stimulation did not aggravate ventricular arrhythmia, most probably owing to the antiarrhythmic properties of these substances.