Bone Load Estimation for the Proximal Femur Using Single Energy Quantitative CT Data

A density-based load estimation method was applied to determine femoral load patterns. Two-dimensional finite element models were constructed using single energy quantitative computed tomography (QCT) data from two femora. Basic load cases included parabolic pressure joint loads and constant tractions on the greater trochanter. An optimization procedure adjusted magnitudes of the basic load cases, such that the applied mechanical stimulus approached the ideal stimulus throughout each model. Dominant estimated load directions were generally consistent with published experimental data for gait. Other estimated loads suggested that loads at extreme joint orientations may be important to maintenance of bone structure. Remodeling simulations with the estimated loads produced density distributions qualitatively similar to the QCT data sets. Average nodal density errors between QCT data and predictions were 0.24 g/cm(3) and 0.28 g/cm(3). The results indicate that density-based load estimation could improve understanding of loading patterns on bones.     

Determination of the Length of the Vegetative and Pre-floral Stages in the Day-Neutral Plant Helianthus annuus by Chilling Pulses

Helianthus annuus seedlings grown in an 18 h day at 28 ?C wereexposed to one 6 d chilling pulse of 12 ?C, at spaced timesduring the first 21 d from sowing. At 2 d intervals, the terminalbuds of 5 plants were dissected to determine leaf number andto score the vegetative or flowering state of the shoot apex.It was found that, while the rate of leaf initiation was reducedequally by each chilling pulse, pulses commencing on days 9or 12 reduced the total leaf number from 30 to 26, while pulsesapplied earlier had little effect. This variation is interpretedin terms of the time available for leaf production. The apicesof control plants commenced the visible transition to flowering16 d after sowing. Chilling pulses applied from days 3 or 6delayed this transition by about 5 d, whereas later pulses causedonly a 1•5 d delay. In a second experiment, where the chillingwas reduced to 2 d duration, it was again found that chillingdelayed flowering during the first 8 d and was progressivelyless effective when applied later. From this variation in temperaturesensitivity it is proposed that chilling sunflower plants immediatelyafter sowing delays flowering by extending the vegetative phaseof growth and so delaying the attainment of a ‘ripenessto flower’ state that appears to coincide with the expansionof the first pair of leaves. From day 8 onwards processes leadingto flowering that are relatively temperature insensitive apparentlybecome dominant in the apex and result in visible signs of flowering8 d later, although during this transitional stage leaf primordiacontinue to be initiated on the flanks of the apex.     

Functional Anatomy of the Association Between Motor Units and Muscle Receptors

Muscle spindles and tendon organs occur in most somatic musclesof the mammal and are particularly concentrated in muscles subservingfine movements, including postural muscles and small musclesof the distal extremities. In those mixed muscles in which thedifferent fiber and motor unit types are "compartmentalized,"the spindles, and perhaps tendon organs also, are virtuallylimited to those compartments predominated by "oxidative" musclefibers. These morphological observations based on a broad arrayof muscles in many species, complement electrophysiologicalstudies which have emphasized that (1) the "oxidative" motorunits have low reflex thresholds and (2) segmental proprioceptivereflexes may be primarily concerned with the control of finelygraded contractions. Consideration of the functional anatomyof the association between motor units and muscle receptorssuggests the need for detailed structural-functional analysesof those muscles with specializations in architecture, fiber-typecomposition and distribution, and in the number and distributionof their muscle spindles and tendon organs. An electrophysiologicalanalysis of the relationship between the spinal cord and suchmuscles might also reveal certain strategies and mechanismsunderlying segmental motor control which are either absent orobscured in the analysis of that select number of "homogenously-mixed"muscles conventionally used in the study of the mammalian segmentalmotor control system.     

Thermogenesis of three species of Arum from Crete

Inflorescences of arum lilies have a three-part spadix with a scent-producing, sterile appendix above two bands of fertile male and female florets. The appendix and male florets are thermogenic, but with different temporal patterns. Heat-production was measured in Arum concinnatum , A. creticum and A. idaeum . The male florets of A. concinnatum showed a 3 d continuous episode of thermogenesis with three waves, and the appendix warmed in a single, 6 h episode. Maximum fresh-mass-specific CO₂ production rate was 0.17  µ mol s⁻¹ g⁻¹ to achieve a 10.9 °C temperature elevation by the appendix, and 0.92  µ mol s⁻¹ g⁻¹ to achieve a 4.8 °C elevation by male florets. Reversible, physiological temperature regulation was not evident in either tissue. Respiration increased with tissue temperatures with Q₁₀ values of 1.8–3.9, rather than less than 1.0 as occurs in thermoregulatory flowers. Experimental step changes in temperature of appendix and male floret tissues also failed to show thermoregulatory responses. The patterns of thermogenesis therefore appear to be fixed by the temporal sequence of blooming. Thermogenesis in the alpine species, A. creticum and A. idaeum , was significantly lower than in the lowland A. concinnatum , possibly related to difficulty in raising floral temperature in their cold and windy habitat.     

Systematic revision of Nearctic species of Achalcus Loew (Diptera: Dolichopodidae) with comments on their phylogeny, ecology and zoogeography

The species of the genus Achalcus Loew from the Nearctic Region are revised and a key to males and females is provided. Achalcus utahensis (Harmston & Miller) and A. oregonensis (Harmston & Miller) are redescribed, and A. californicus sp.n., A. dytei sp.n. and A. similis sp.n. are described. Together with eight of the nine known Palaearctic species of the genus, they represent a monophyletic species group, which is characterized by the presence of five pairs of dorsocentral bristles and the incorporation of the epandrial setae onto the shaft of the epandrial lobe. Like their Palaearctic congeners, most Nearctic species occur in damp habitats, such as coastal forests and riparian vegetation. Most specimens were collected in the Pacific coastal states from British Columbia to California, but one species occurs in Utah, and one of six species which were not described because males are lacking, was discovered in Ontario.     

Effects of H-Y Antigen on Morphologic and Endocrine Differentiation of Gonads in Mammals

The effects of H-Y antigen, released in a soluble state by male human Burkitt lymphomas and mouse teratomas, were studied in the fetal gonads from 13 to 21-day-old rats and 98-day-old calves, using histologic techniques, radioimmunoassays for testosterone, and bioassays for Müllerian-inhibiting substance (MIS). Whereas no effect was detected in the younger gonads, some structural changes were observed in bovine and 21-day-old rat ovaries when cultured for 5 days with Daudi and male teratoma supernatants, but there was no synthesis of testosterone or MIS. These observations raise questions concerning the critial period of sensitively to H-Y antigen of female gonads, and the dissociation between morphologic and biochemical events.     

Assessment of genetic and pheromonal diversity of the Cydia strobilella species complex (Lepidoptera: Tortricidae)

Combining pheromone trapping and genetic analyses can be useful when trying to resolve complexes of closely related insect taxa that are difficult to distinguish based on morphological characters. Nearctic and Palearctic populations of the spruce seed moth, Cydia strobilella L., have been considered taxonomically synonymous since 1983, but more recent work revealing distinct sex pheromones for Canadian and Swedish moths suggest that populations in the two regions belong to different species. In order to test this hypothesis, we performed field trapping using different pheromone lures at ten sites in North America, Europe and Asia, and reconstructed phylogenetic relationships among trapped moths using mitochondrial (cytochrome oxidase subunit I) and nuclear (elongation factor 1 alpha) DNA sequence data. Trapping data and tree topologies for both genes revealed distinct pherotypes in North America and Eurasia. A genetically distinct population from China was investigated further with respect to its sex pheromone. Electrophysiological data indicated that Chinese females produce a deviant ratio of the sex pheromone components (dienic acetates) compared to Swedish females. However, trapping experiments in both areas revealed a similar broad response profile in males to a wide range of acetate ratios, and these populations should be considered taxonomically synonymous. A previous suggestion of an agonistic effect on the attraction of C. strobilella males in Sweden when adding the corresponding alcohols to the binary acetate blend was also tested in Sweden as well as in China, with no observed effect on attraction of males. In conclusion, our study demonstrates the great potential of using pheromone trapping as a tool for identification and delimitation of taxa within cryptic species complexes. Based on our data, Nearctic and Palearctic populations of C. strobilella should be considered different species, and C. youngana Kearfott stat. rev. is resurrected here as valid name for North American populations, which was the case before the revision in 1983.     

New species of the genus Plesiolacerta (Squamata: Lacertidae) from the upper Oligocene (MP28) of Southern Germany and a revision of the type species Plesiolacerta lydekkeri

Abstract: The lacertid material from the locality of Herrlingen 8 (upper Oligocene, MP28) is described as a new species of the genus Plesiolacerta. The material is disarticulated and comprises isolated elements including parietal, frontal, maxilla and dentary. It can be assigned to a single species on the basis of the external surface ornamentation. This morphology is typical for the genus Plesiolacerta, but the material differs in detail from the type species P. lydekkeri. The most significant feature of the new species is that the occipital scute of the parietal bone is narrow, rectangular in shape and anteroposteriorly short. Hitherto, the last occurrence of this genus was in the lower Oligocene. This material represents the first evidence of the existence of this genus in the upper Oligocene. Therefore, our knowledge of its evolution is expanded by providing new data on its spatial and temporal ranges and morphology. This taxon has a much longer history than we thought. In addition, the Eocene species, P. lydekkeri, is reviewed here. P. lydekkeri shares the most lacertid synapomorphies and, given our present knowledge, Plesiolacerta is a taxon very close to or possibly within crown Lacertidae. The frontal and postorbitofrontal of Plesiolacerta are described for the first time. In view of the primitive morphology and early occurrence of Plesiolacerta, it seems that the feature of a longer anterior region of the frontal could be considered as a plesiomorphic feature within lacertid lizards, and the condition in Timon (approximately the same length) as derived.     

Regulation and acclimation of leaf gas exchange in a piñon–juniper woodland exposed to three different precipitation regimes

Leaf gas‐exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas‐exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon–juniper Pinus edulis–Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (?45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas‐exchange rates under well‐watered conditions, leaf‐specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade‐off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA.