The lumbosacral transition: morphologic variations and their functional significance

The articular facet of a superior articular process of the sacrum is directed backward, inward, and upward with marked variations. 4 angles characterize the orientation of this facet: a) The relative angle of tilt: i.e. the angle between the articular facet and the upper end-plate of the sacrum, measured in a sagittal plane. b) The absolute angle of tilt: i.e. the angle between the articular facet and the horizontal plane, measured in a sagittal plane. c) The tilted part-angle of opening: i.e. the angle between the articular facet and the sagittal plane, measured in a plane parallel to the upper end-plate of the sacrum. d) The horizontal part-angle of opening: i.e. the angle between the articular facet and the sagittal plane, measured in a horizontal plane. These 4 angles are determined by characteristic straights within the articular facet and certain reference planes (upper end-plate of the sacrum, horizontal plane, sagittal plane). Only 2 intersecting straights suffice for an adequate determination of a geometrical plane; therefore, if we know the relative angle of tilt and the tilted part-angle of opening, we are able to construct or to calculate the absolute angle of tilt as well as the horizontal part-angle of opening by using the range of inclination of the sacrum. The shape as well as the orientation of the articular facets at the superior articular processes of the sacrum do not depend on the inclination of the pelvis nor on the inclination of the sacrum nor on the range of the lumbosacral angle. Only the absolute angle of tilt shows a reference to the inclination of the sacrum because the relative angle of tilt shows a certain constancy. The orientation of the articular facets is slightly influenced by static moments, but considerably determined by dynamical requirements. At spines with irregular numbers of praesacral vertebrae, the orientation of the lumbosacral articular facets do not differ from the orientation of these facets at spines with the regular number of 24 praesacral vertebrae. This, however, does not prove right at spines, that have a lumbosacral "transitional vertebra". Such lumbosacral transitional vertebrae detract much from the stability of the lumbosacral region of the spine.     

Primate play vocalizations and their functional significance

It is well known that, among mammals, specific play vocalizations are produced exclusively by certain nonhuman primate species. In order to investigate the functional significance of these calls, we examined their phyletic distribution among New World and Old World monkeys. The results indicate that such calls are produced by species in which allomothering behaviour occurs. We propose a functional explanation of play vocalizations according to which they serve as a possible source of information for maternal retrieval of infants whenever necessary.     

Inter- and intragenus structural variations in caliciviruses and their functional implications

The family Caliciviridae is divided into four genera and consists of single-stranded RNA viruses with hosts ranging from humans to a wide variety of animals. Human caliciviruses are the major cause of outbreaks of acute nonbacterial gastroenteritis, whereas animal caliciviruses cause various host-dependent illnesses with a documented potential for zoonoses. To investigate inter- and intragenus structural variations and to provide a better understanding of the structural basis of host specificity and strain diversity, we performed structural studies of the recombinant capsid of Grimsby virus, the recombinant capsid of Parkville virus, and San Miguel sea lion virus serotype 4 (SMSV4), which are representative of the genera Norovirus (genogroup 2), Sapovirus, and Vesivirus, respectively. A comparative analysis of these structures was performed with that of the recombinant capsid of Norwalk virus, a prototype member of Norovirus genogroup 1. Although these capsids share a common architectural framework of 90 dimers of the capsid protein arranged on a T=3 icosahedral lattice with a modular domain organization of the subunit consisting of a shell (S) domain and a protrusion (P) domain, they exhibit distinct differences. The distally located P2 subdomain of P shows the most prominent differences both in shape and in size, in accordance with the observed sequence variability. Another major difference is in the relative orientation between the S and P domains, particularly between those of noroviruses and other caliciviruses. Despite being a human pathogen, the Parkville virus capsid shows more structural similarity to SMSV4, an animal calicivirus, suggesting a closer relationship between sapoviruses and animal caliciviruses. These comparative structural studies of caliciviruses provide a functional rationale for the unique modular domain organization of the capsid protein with an embedded flexibility reminiscent of an antibody structure. The highly conserved S domain functions to provide an icosahedral scaffold; the hypervariable P2 subdomain may function as a replaceable module to confer host specificity and strain diversity; and the P1 subdomain, located between S and P2, provides additional fine-tuning to position the P2 subdomain.     

Evolutionary trends and their functional significance in chasmopine trilobites

In response to environmental pressures, speciation within the Chasmopinae involved the attempt to minimise the anterior blind spot. This was attempted in four different ways: by positioning the eyes progressively closer to the glabella, in the Chasmops-Toxochasmops lineage; on the sides of the cephalon, in Bolbochasmops and Rollmops; by elevating and reducing the size of the eyes, in Scopelochasmops ; and by the development of very large eyes in species of Chasmops and Toxochasmops. Development of different eye morphologies resulted in complementary cephalic morphological changes, involving frontal lobe convexity, position and orientation of glabellar furrows, size of hypostome and overall cephalic shape. The strong selection pressure acting on eye form in order to minimise the anterior blind spot suggests that the Chasmopinae may have led a predatory mode of life.     

Seasonal variations in the cambial anatomy of Tectona grandis (Verbenaceae)

A study of seasonal activity of the cambium in Tectona grandis L. f. has shown that the activity initiates in the first week of June, reaches a peak in July and then slowly declines. The length of fusiform cambial initials undergo considerable variations during the activity and dormancy of the cambium. The initiation of cambial activity is closely associated with the opening of the dormant foliar buds in the first week of May. Cambium is more active with high numbers of immature xylem and phloem elements from July to September when the trees are with mature foliage and flowers and dormant from January to April when leaves dry and defoliation takes place. The differentiation of xylem and phloem starts simultaneously and the number of their immature elements reach the maximum in July.     

The structure and functional significance of variations in the connective tissue within muscle

The amount of intramuscular connective tissue (IMCT) and its morphological distribution is highly variable between muscles of differing function. The functional roles of this component of muscle have been poorly understood, but a picture is gradually emerging of the central role this component has in growth, transmission of mechanical signals to muscle cells and co-ordination of forces between fibres within a muscle. The aim of this review is to highlight recent advances that begin to show the functional significance of some of the variability in IMCT. IMCT has a number of clearly defined roles. It patterns muscle development and innervation, and mechanically integrates the tissue. In developing muscles, proliferation and growth of muscle cells is stimulated and guided by cell-matrix interactions. Recent work has shown that the topography of collagen fibres is an important signal. The timing and rates of expression of connective tissue proteins also show differences between muscles. Discussion of mechanical roles for IMCT has traditionally been limited to the passive elastic response of muscle. However, it is now clear that IMCT provides a matrix to integrate the contractile function of the whole tissue. Mechanical forces are co-ordinated and passed between adjacent muscle cells via cell-matrix interactions and the endomysial connective tissue that links the cells together. An emerging concept is that division of a muscle into fascicles by the perimysial connective tissue is related to the need to accommodate shear strains as muscles change shape during contraction and extension.     

叶脉网络功能性状及其生态学意义

叶脉网络结构是叶脉系统在叶片里的分布和排列样式。早期叶脉网络结构研究主要集中在其分类学意义上; 近年来叶脉网络功能性状及其在植物水分利用上的意义已成为植物生态学研究的热点。该文介绍了叶脉网络功能性状的指标体系(包括叶脉密度、叶脉直径、叶脉之间的距离、叶脉闭合度等), 综述了叶脉网络功能性状与叶脉系统功能(包括水分、养分和光合产物等物质运输、机械支撑和虫害防御等)的关系, 叶脉网络功能性状与叶片其他功能性状(包括比叶重、叶寿命、光合速率、叶片大小、气孔密度等)的协同变异和权衡关系, 以及叶脉网络功能性状随环境因子(包括水分、温度、光照等)的变化规律等方面的最新研究进展。此外, 叶脉网络功能性状的研究成果也被应用于古环境重建、城市交通规划、流域规划及全球变化研究中。由于叶脉网络功能性状是环境因子与系统发育共同作用的结果, 未来开展分子—叶片—植物—生态系统等多尺度的叶脉网络功能性状研究, 理清叶脉网络功能性状与气孔失水—茎干导水—根系吸水等植物水分利用的关系, 将为预测植物及生态系统对全球变化的响应提供新的启示。     

Luteolin and daphnetin derivatives in the juncaceae and their systematic significance

During a chemosystematic survey of 38 representative species of the Juncaceae for leaf and stem flavonoids, the 5-methyl ether of luteolin was discovered for the first time in plants. It occurs both free and as the 7-glucoside; its identity was confirmed by synthesis. Flavone sulphates were also found in the family and the 7-glucosidesulphates of luteolin and chrysoeriol were characterised for the first time. 7,3′,4′-Trihydroxyflavone and its 7-glucoside, not previously reported in the monocotyledons, were found in three species. The presence of luteolin 5-methyl ether or its glucoside in 70% of the species surveyed serves to distinguish the Juncaceae from the morphologically related Centrolepidaceae, Restionaceae and Thurniaceae. Flavone C-glycosides, common in grasses and sedges, were found only in Prionium, a genus which on anatomical grounds is anomalous in the Juncaceae. Among other phenolics detected during the survey, the uncommon 7,8-dihydroxycoumarin, daphnetin, was identified in Juncus effusus and its 8-methyl ether in four Luzula species. Taken together, these chemical findings show that the Juncaceae are very distinctive in their phenolic pattern and confirm the correctness of assigning them an isolated position in a separate order, the Juncales. The results indicate that the Juncaceae are chemically specialized, in spite of the facts that the family has been regarded as ancestral to the Cyperaceae and Gramineae and that they have been assigned a low advancement index by Sporne.     

New pedal remains of Megaladapis and their functional significance

New remains of Megaladapis from the caves within the Ankarana Range of northern Madagascar and the cave site of Ankilitelo near Toliara in southwestern Madagascar add considerably to the present sample of pedal remains for this genus. Here we describe and analyze the new pedal material and discuss the function of the Megaladapis foot in terms of positional behavior and substrate use. The northern specimens belong to the M. madagascariensis/M. grandidieri group in terms of size and morphology, whereas the new southwestern fossils are assigned to M. madagascariensis. The new specimens demonstrate that the small and intermediate sized M. madagascariensis and M. grandidieri were very similar in anatomy and inferred locomotor function, findings that also support the prior suggestion that they belong to a single widespread subgenus (Megaladapis). The new fossils provide the first examples of many pedal elements and present the first opportunity to analyze the whole pedal complex from associated remains. The foot of Megaladapis is distinctive among primates in numerous features. Intrinsic proportions of the hindlimb indicate that the foot is relatively longer than that of any other primate. The first complete calcanei reveal a large and highly modified hindfoot. The calcaneus is reduced distally, indicating an emphasis on climbing over leaping or quadrupedal walking and running. Proximally, a large, medially directed calcaneal tuberosity suggests both a strong inversion component to plantarflexion and a well-developed abductor mechanism and recalls the calcaneal morphology of the larger lorisines in some respects. Talar shape is consistent with considerable tibial rotation during plantarflexion and dorsiflexion. The subtalar joint is designed to emphasize supination/pronation and medial/lateral rotation over proximodistal translation. The distal tarsals are extremely reduced in length, and they form a high transverse arch and a serial tarsus; this configuration promotes inversion/eversion at the transverse tarsal joint. The phalanges are long and moderately curved, and the hallux is very long, robust, and abducted. Pedal morphology suggests that Megaladapis (subgenus Megaladapis) was well adapted to exploit an arboreal environment. The grasping mechanism of Megaladapis is an extreme modification of the prosimian condition, emphasizing a highly inverted set, mobility in rotation, and a powerful abduction/flexion type grasp using large hallux and the lateral abductor musculature. Such a mechanism insures a secure grasp regardless of the position of the hindlimb or the substrate. These pedal design features contrast with the grasping strategy seen in highly arboreal palaeopropithecids (or “sloth lemurs”), a group that reduces and modifies the hindfoot, culminating in Palaeopropithecus, and emphasizes extrinsic digital flexors in a more hook-like mechanism. Much less is known of M. (Peloriadapis) edwardsi. The larger body size, more gorilla-like talar articular morphology, and anatomy of the proximal fifth metatarsal suggest that this species may have been more terrestrial than the smaller forms, but other aspects of pedal morphology suggest it also exploited arboreal habitats.     

γ—氨基丁酸受体的反应动力学及其功能意义

γ－氨基丁酸（ＧＡＢＡ）受体的反应动力学（激活,失敏和失活）是否在快速抑制性突触传递中起作用及怎样发挥作用是一个重要问题。随着分子生物学的发展,膜片钳技术及快速施药系统的应用,对ＧＡＢＡ受体的反应动力学的结构基础,单通道水平的发生机制及其人功能意义等开始形成较全面的认识,揭示了其反应动力学在调节抑制性突触后电流（ＩＰＳＣ）中的关键作用及在快速抑制性突触传递中的重要意义。     

Contractile properties of intercostal muscles and their functional significance

To have some insight into the functional coupling between the parasternal intercostals (PS) and the diaphragm (DPM), we have examined the isometric contractile properties of bundles from canine PS and DPM muscles. Bundles of external (EXT) and internal (INT) interosseous intercostals were studied for comparison. In addition we have related sonometrically measured length of the intercostals in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We found that 1) intercostal twitch speed is significantly faster than DPM, thus displacing their relative force-frequency curve to the right of that of the DPM; 2) the ascending limb of the active length-tension curve of all intercostals lies below the DPM curve; i.e., at 85% Lo, PS force is 46% of maximal force (Po), whereas DPM force is still 87% Po; 3) for any given length change beyond Lo, all intercostals generate greater passive tension than the DPM; 4) Po is greater for the intercostals than the DPM; and 5) at supine FRC, both EXT and INT in dogs are nearly operating at Lo, whereas the PS are operating at a length greater than Lo. We conclude that 1) PS produce less force than DPM during breathing efforts involving low- (10-20 Hz) stimulation frequencies, but they generate more force than DPM when high- (greater than 50 Hz) stimulation frequencies are required; and 2) the pressure-generating ability of the PS is better preserved than that of the DPM with increases in lung volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic variations in human fetal globin gene microsatellites and their functional relevance

Short tandem repeats are abundantly present within the genome. They are commonly used as polymorphic markers but their potential functional role is poorly documented. Several of these microsatellites have been described within the β-globin locus and some could be involved in controlling gene expression. Our purpose was to investigate the extent and significance of the (TG)n(CG)m dinucleotide repeat polymorphisms in the two γ-globin gene IVS2s. Two groups of subjects were studied: a group of 63 β-thalassaemic patients presenting either with a severe Cooley’s anaemia (n = 50) or with thalassaemia intermedia (TI, n = 13), and a control group of 60 unrelated healthy individuals. A high heterogeneity of the polymorphic repeats was demonstrated, extending the range of the published alleles from 13 to 22 and allowing a first attempt at making a phenotype/genotype correlation. One specific allele, (TG)₁₃ in the Aγ-gene, was highly enriched in the TI patients (46.1% vs 2.9% of the Cooley’s anaemia cases, P < 0.0002, and 23.3% in the normal controls, P < 0.008) and preferentially observed in TI patients with a high haemoglobin F (Hb F). Transient transfection assays in K562 cells, with the growth hormone gene as a reporter, showed a positive regulatory action mediated by a (TG)₁₃-containing 243 nt IVS2 fragment. Finally, a first set of mobility shift experiments with erythroid (K562 and MEL) and nonerythroid (HeLa) cell lines showed binding of erythroid component(s) in this DNA region and the binding pattern was modified upon induction of MEL cells by DMSO. Thus, our in vivo and in vitro data raise the question of a possible contribution of the γ-gene IVS2s polymorphic microsatellites to the variable Hb F synthesis in the major haemoglobinopathies: a well known, puzzling and still unanswered question. Received: 22 April 1998 / Accepted: 15 December 1998     

Differential localization of arabinan and galactan side chains of rhamnogalacturonan 1 in cambial derivatives

 The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen (Populus tremula L. × P. tremuloides Michx.) using biochemical and immunocytochemical methods. Comparisons were also made between active and resting tissues. Active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. Use of antibodies raised against arabinan side chains of rhamnogalacturonan 1 (LM6), as well as biochemical analysis, revealed an obvious decrease from the cortex to the differentiating xylem. Galactan side chains, detected with LM5 antibodies, were present mainly in the cambial zone and enlarging xylem cells. In contrast, they were totally absent from sieve-tube cell walls. Image analysis of LM5 immunogold labelling in the cambial zone showed a clustered distribution of galactan epitopes in the radial walls, a distribution which might result from the association of two different periodic processes, namely the exocytosis of galactan and wall expansion. Cessation of cambial activity was characterized by cell wall thickening accompanied by a sharp decrease in the relative amount of pectin and a lowering of the degree of methylesterification. The data provide evidence that the walls of phloem and xylem cells differ in their pectin composition even at a very early stage of commitment. These differences offer useful tools for identifying the initial cells among their immediate neighbours. Received: 12 June 1999 / Accepted: 20 October 1999