Evolution of bioengineering at UCSD: opening new vistas

Before this, the field of bioengineering refers to biomedical engineering of prosthetic devices in physiology. In addition to exciting applications of engineering principles, UCSD Department of Bioengineering began to extend the notion of engineering models of physiological systems to physiological processes. This led to a conceptual shift in the discipline and contributed to the areas of tissue and physiological process engineering. In 1988, Dr. Shu Chien and Richard Skalak joined UCSD to begin research and education on cellular and molecular bioengineering, especially, mechanobiology. Dr. Fung and Dr. Skalak initiated the new field of tissue engineering. These two decades of evolution of bioengineering and its growth across the country was spearheaded by the Whitaker Foundation, whose leitmotif was the building of bioand biomedical engineering across the country. We have garnered other accomplishments in the following fields: regenerative medicine; bioinspired artificial extracellular matrices; flexible bioelectronics and tatoos; cells show how to synchronize biological clocks; and systems medicine.     

Phyto- and necromass above and below ground in a fen

Few investigations deal with the subterranean phytomass in fens (minerotrophic peatlands), their results differing widely. This study was carried out in a "rich fen" in central Sweden, and involved excavation of peat monoliths, depth-sectioning and hand-sorting as to species, type of organ, and living or dead condition. The below-ground living phytomass was large, over 4 kg m⁻² in each of two sample plots, being no <97–96% in the dominants, Carex limosa and C. lasiocarpa , 89% on average in Menyanthes trifoliata , and c. 93% for all species. Carex limosa had its rhizome maximum slightly higher than C. lasiocarpa , but a greater part of its roots penetrated deeper. For Menyanthes , also net annual production above and below ground was estimated. The subterranean phytomass decreased with depth, but living roots were found even at 42 cm. The recognizable necromass did not decrease with depth. These recent constituents would render a very unequal age to the peat. The imbalance between the small green aerial phytomass and the much greater subterranean phytomass was emphasized. It could be related to a relatively very great translocation of photosynthates from above to below ground, and/or to longevity of below-ground organs, the latter at least in Menyanthes.     

Effects of foundation species above and below tree line

The facilitative effects of “foundation species” on community diversity and composition in alpine systems can be strong, but the strength of these effects often varies along gradients that occur above tree line. Here, we explore the effects of foundation species above and below tree line, a globally consistent and often abrupt climatic and ecological transition. The experiment was developed in Northern Rocky Mountains of Wyoming and Montana, USA, in vegetation with similar herbaceous physiognomies without trees, but containing dominant foundation species with “cushion” morphologies. In these systems, we compared the diversity and structure of plant communities occurring within these foundation species to that in the open at three sites below tree line and three sites above tree line. Above tree line, 69–94% of all species were significantly spatially associated with foundation species, whereas below tree line, 29–62% of the species were associated with foundation species. Similar patterns were observed in species accumulation curves with foundation species affecting the accumulation of species by +17 to +47% above tree line vs. –27 to +24% below tree line. Our results were consistent with the idea that facilitative interactions are more common with greater abiotic stress. However, our results also suggest the possibility that the climatic transition representing tree line might also represent a threshold, rather than a simple linear response, in how foundation species affect community diversity. A much larger sample size is warranted to thoroughly test such thresholds, but the fundamental ecological and physiological transition that plants experience at the climate of the tree line may also be reflected in small-scale species interactions that organize communities.     

Conceptualization of above and below relationships by an insect

Relational rules such as 'same' or 'different' are mastered by humans and non-human primates and are considered as abstract conceptual thinking as they require relational learning beyond perceptual generalization. Here, we investigated whether an insect, the honeybee (Apis mellifera), can form a conceptual representation of an above/below spatial relationship. In experiment 1, bees were trained with differential conditioning to choose a variable target located above or below a black bar that acted as constant referent throughout the experiment. In experiment 2, two visual stimuli were aligned vertically, one being the referent, which was kept constant throughout the experiment, and the other the target, which was variable. In both experiments, the distance between the target and the referent, and their location within the visual field was systematically varied. In both cases, bees succeeded in transferring the learned concept to novel stimuli, preserving the trained spatial relation, thus showing an ability to manipulate this relational concept independently of the physical nature of the stimuli. Absolute location of the referent into the visual field was not a low-level cue used by the bees to solve the task. The honeybee is thus capable of conceptual learning despite having a miniature brain, showing that such elaborated learning form is not a prerogative of vertebrates.     

Man and Sea in the Mesolithic: Coastal Settlement above and below Present Sea Level

Man and Sea in the Mesolithic: Coastal Settlement above and below Present Sea Level. Anders Fischer. ed. Oxbow Monograph, 53. Oakville, CT. David Brown Book Company, 1995. 440 pp.     

Deception above, deception below: linking pollination and mycorrhizal biology of orchids

Several key characteristics of the species-rich orchid familyare due to its symbiotic relationships with pollinators andmycorrhizal fungi. The majority of species are insect pollinatedand show strong adaptations for outcrossing, such as pollinationby food- and sexual-deception, and all orchids are reliant onmycorrhizal fungi for successful seedling establishment. Recentstudies of orchid pollination biology have shed light on thebarriers to reproductive isolation important to diversificationin different groups of deceptive orchids. Molecular identificationof orchid mycorrhizal fungi has revealed high fungal specificityin orchids that obtain organic nutrients from fungi as adults.Both pollinator and fungal specificity have been proposed asdrivers of orchid diversification. Recent findings in orchidpollination and mycorrhizal biology are reviewed and it is shownthat both associations are likely to affect orchid distributionand population structure. Integrating studies of these symbioseswill shed light on the unparalleled diversification of the orchidfamily. Key words: Mutualism, myco-heterotrophy, pollinator limitation, speciation Received 5 October 2007; Revised 12 December 2007 Accepted 21 December 2007     

Correction to: Freshwater fish functional and taxonomic diversity above and below Niagara Falls

Environmental Biology of Fishes -     

Plasma acid-base regulation above and below ventilatory threshold in late gestation.

Stewart's physicochemical approach was used to study the effects of pregnancy on acid-base regulation in arterialized blood. Responses of 15 healthy pregnant women (PG; gestational age, 37.1 +/- 0.2 wk) were compared with those of 15 nonpregnant controls (CG) at rest and during cycling at 70 and 110% of the ventilatory threshold (T(vent)). Hydrogen ion concentration ([H(+)]) was lower in the PG vs. CG at rest and during exercise (P < 0.05 at rest and 70% T(vent)). Exercise-induced changes in [H(+)] were similar between groups. Lower resting [H(+)] values in the PG vs. CG resulted from lower values for arterialized PCO(2) (Pa(CO(2))) and total weak acid ([A](tot)), which were partly offset by a lower strong-ion difference ([SID]). Reductions in [A](tot) and [SID] at rest were primarily the result of reductions in albumin [Alb] and sodium [Na(+)], respectively. In the transition from rest to 70% T(vent), small increases in Pa(CO(2)) and [A](tot) contributed to moderate increases in [H(+)] in both groups, however [SID] increased in the PG and decreased in the CG (P < 0.05 between groups). In the transition from rest to 110% T(vent), decreases in [SID] made a significantly greater contribution to changes in [H(+)] in the CG vs. PG. Exercise-induced increases in [H(+)] are similar in the pregnant vs. nonpregnant state, but there is a reduced contribution of [SID] both above and below T(vent) during pregnancy.     

Freshwater fish functional and taxonomic diversity above and below Niagara Falls

The Niagara River, which connects two Great Lakes (Erie and Ontario) and forms a border between Canada and the United States, has experienced decades of abiotic and biotic disturbance as well as long-term restoration efforts. Given the iconic riverscape and importance as a binational fisheries resource, a biodiversity assessment of the mainstem Niagara River fish assemblage is overdue. Here, fish assemblage and habitat data from a standardized boat electrofishing program of the Niagara River were combined with species trait data related to substrate associations, diet preferences, reproductive strategies, and body size to quantify biodiversity patterns among river sections (sites above and below Niagara Falls), seasons (spring, summer, fall), and years (2015–2017). Sixty-five species were captured representing a variety of trait combinations. Significant differences in functional dispersion and divergence (i.e., functional diversity) were observed between river sections, seasons, and (or) years. The fish community captured in the lower river in spring 2015 had both the highest average functional dispersion (2.08?±?0.32 SD) and divergence (0.88?±?0.04 SD) compared to the other seasonal sampling efforts, but relatively few fishes were captured (n?=?686). Although non-native fishes represented a small portion of the catch over the 3 years (8.6% of catch), the seasonal presence (spring and fall) of mostly introduced large-bodied salmonids expanded functional trait space in the lower river during these periods. The importance of rare species on functional diversity metrics suggests further insight on local species detection probabilities is needed to understand if differences in functional diversity reflect ecological patterns or are driven by sampling design.

     

Physiology of the esophageal pressure transition zone: separate contraction waves above and below

Manometrically measured peristaltic pressure amplitude displays a well-defined trough in the upper esophagus. Whereas this manometric "transition zone" (TZ) has been associated with striated-to-smooth muscle fiber transition, the underlying physiology of the TZ and its role in bolus transport are unclear. A computer model study of bolus retention in the TZ showed discoordinated distinct contraction waves above and below. Our aim was to test the hypothesis that distinct upper/lower contraction waves above/below the manometric TZ are normal physiology and to quantify space-time coordination between tone and bolus transport through the TZ. Eighteen normal barium swallows were analyzed in 6 subjects with concurrent 21-channel high-resolution manometry and digital fluoroscopy. From manometry, the TZ center (nadir pressure amplitude) and the upper/lower margins of the pressure trough were objectively quantified. Using fluoroscopy, we quantified space-time trajectories of the bolus tail and bolus tail pressures and maximum intraluminal pressures proximal to the tail with their space-time trajectories. In every swallow, the bolus tail followed distinct trajectories above/below the TZ, separated by a well-defined spatial "jump" that terminated an upper contraction wave and initiated a lower contraction wave (3.32 +/- 1.63 cm, P = 0.0004). An "indentation wave" always formed within the TZ distal to the upper wave, increasing in amplitude until the lower wave was initiated. As the upper contraction wave tail entered the TZ, it slowed and the tail pressure reduced rapidly, while indentation wave pressure increased to normal tail pressure values at the initiation of the lower wave. The TZ was a special zone of segmental contraction. The TZ is, physiologically, the transition from an upper contraction wave originating in the proximal striated esophagus to a lower contraction wave that moves into the distal smooth muscle esophagus. Complete bolus transport requires coordination of upper/lower waves and sufficient segmental squeeze to fully clear the bolus from the TZ during the transition period.     

Diffusion of short chain alcohols from amorphous maltose-water mixtures above and below their glass transition temperature

The apparent diffusion coefficient for short chain alcohols in undercooled maltose-water mixtures close to the calorimetric glass transition temperature, Tg, was measured by following desorption using headspace gas chromatography. The plasticising effect of the alcohols on Tg was characterised using differential scanning calorimetry. The initial appearance of alcohol in the headspace showed a linear dependence on the square root of time, allowing it to be modelled as a Fickian diffusive process. The diffusion coefficient decreased with increasing molecular size of alcohol and proximity to Tg. Close to the glass transition the variation of diffusion coefficient with temperature and composition does not follow that of viscosity and, for ethanol, divergence was observed at Tg/T> 0.88.     

The CNS lesion scar: new vistas on an old regeneration barrier

The endothelins (ETs) are regulatory peptides, distributed in many organ systems and with potent physiological effects. ETs represent the most powerful vasoconstrictive substances known today. They also act as growth factors and seem to be involved in fetal development. Much data support a pathophysiological role for ETs, especially in diseases of the vascular system, such as hypertension, preeclampsia, ischemic heart disease, subarachnoidal haemorrhage, and cerebral ischemia. The development of drugs affecting ET-receptors and the biosynthesis of ETs presently attract great interest for the establishment of new treatments of diseases in which ETs are involved. Hopefully, the elaboration of more specific ET-receptor ligands will fulfill some of these expectations.