Xeromorphic Leaves of Hakea suaveolens R. Br. IV. Ontogeny, Structure and Function of the Sclereids

1990 ◽  
Vol 38 (1) ◽  
pp. 25 ◽  
Author(s):  
HS Heide-Jorgensen
Keyword(s):  
Structure And Function ◽  
Point Of View ◽  
Cross Sectional ◽  
Palisade Tissue ◽  
Cell Layers ◽  
Functional Point ◽  
Palisade Cells ◽  
And Function ◽  
Shade Leaves ◽  
Sun Leaves

Osteosclereids in the leaves of Hakea suaveolens are investigated from a developmental, structural and functional point of view. The sclereid initial cell is located outermost in a boundary parenchyma comprising 1-3 cell layers next to the palisade tissue. Boundary parenchyma cells, including sclereid initial cells, are the first cells to accumulate starch. Acid phosphatase was localised during development of sclereids and palisade cells. The outer ramifications of the sclereid form a pseudohypodermis, and the inner ramifications penetrate 1-3 cell layers inwards, making contact with specialised cells (tracheoids) of the vein endings and with fibres. The sclereids do not become lignified in the outer ramifications, and they remain alive as long as the leaf itself. Water pathways were localised by addition of the fluorochrome berberine sulfate to the transpiration stream. It is concluded that, besides giving mechanical strength, the sclereids are also important as vein extensions and that, like bundle sheath extensions, they conduct water to the epidermis and directly to both palisade layers. The percentage of the cross-sectional leaf area occupied by lignified water-conducting cells, including sclereids, is higher than in many other cylindrical, xeromorphic leaves. There are about 200 sclereids per square millimetre of palisade tissue in sun leaves, but the number falls in shade leaves and after fertilisation with nitrate and phosphate.

scholarly journals Lower leg muscle structure and function are altered in long-distance runners with medial tibial stress syndrome: a case control study

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Joshua Mattock ◽  
Julie R. Steele ◽  
Karen J. Mickle
Keyword(s):  
Lower Leg ◽  
Structure And Function ◽  
Flexor Hallucis Longus ◽  
Plantar Flexor ◽  
Distance Runners ◽  
Long Distance ◽  
Cross Sectional ◽  
Muscle Structure ◽  
Leg Muscle ◽  
And Function

Abstract Background Medial tibial stress syndrome (MTSS) is a common lower leg injury experienced by runners. Although numerous risk factors are reported in the literature, many are non-modifiable and management of the injury remains difficult. Lower leg muscle structure and function are modifiable characteristics that influence tibial loading during foot-ground contact. Therefore, this study aimed to determine whether long-distance runners with MTSS displayed differences in in vivo lower leg muscle structure and function than matched asymptomatic runners. Methods Lower leg structure was assessed using ultrasound and a measure of lower leg circumference to quantify muscle cross-sectional area, thickness and lean lower leg girth. Lower leg function was assessed using a hand-held dynamometer to quantify maximal voluntary isometric contraction strength and a single leg heel raise protocol was used to measure ankle plantar flexor endurance. Outcome variables were compared between the limbs of long-distance runners suffering MTSS (n = 20) and matched asymptomatic controls (n = 20). Means, standard deviations, 95 % confidence intervals, mean differences and Cohen’s d values were calculated for each variable for the MTSS symptomatic and control limbs. Results MTSS symptomatic limbs displayed a significantly smaller flexor hallucis longus cross-sectional area, a smaller soleus thickness but a larger lateral gastrocnemius thickness than the control limbs. However, there was no statistical difference in lean lower leg girth. Compared to the matched control limbs, MTSS symptomatic limbs displayed deficits in maximal voluntary isometric contraction strength of the flexor hallucis longus, soleus, tibialis anterior and peroneal muscles, and reduced ankle plantar flexor endurance capacity. Conclusions Differences in lower leg muscle structure and function likely render MTSS symptomatic individuals less able to withstand the negative tibial bending moment generated during midstance, potentially contributing to the development of MTSS. The clinical implications of these findings suggest that rehabilitation protocols for MTSS symptomatic individuals should aim to improve strength of the flexor hallucis longus, soleus, tibialis anterior and peroneal muscles along with ankle plantar flexor endurance. However, the cross-sectional study design prevents us determining whether between group differences were a cause or effect of MTSS. Therefore, future prospective studies are required to substantiate the study findings.

Structure and Function of Three Suberized Cell Layers

Plant Roots ◽  
2013 ◽  
pp. 5-1-5-20 ◽  
Author(s):  
Chris Meyer ◽  
Carol Peterson
Keyword(s):  
Structure And Function ◽  
Cell Layers ◽  
And Function

scholarly journals Fin ray patterns at the fin-to-limb transition

2019 ◽  
Vol 117 (3) ◽  
pp. 1612-1620 ◽  
Author(s):  
Thomas A. Stewart ◽  
Justin B. Lemberg ◽  
Natalia K. Taft ◽  
Ihna Yoo ◽  
Edward B. Daeschler ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Structure And Function ◽  
Crown Group ◽  
Cross Sectional ◽  
Pectoral Fins ◽  
The Third ◽  
Fin Ray ◽  
Fin Rays ◽  
And Function ◽  
Ray Patterns

The fin-to-limb transition was marked by the origin of digits and the loss of dermal fin rays. Paleontological research into this transformation has focused on the evolution of the endoskeleton, with little attention paid to fin ray structure and function. To address this knowledge gap, we study the dermal rays of the pectoral fins of 3 key tetrapodomorph taxa—Sauripterus taylori (Rhizodontida), Eusthenopteron foordi (Tristichopteridae), and Tiktaalik roseae (Elpistostegalia)—using computed tomography. These data show several trends in the lineage leading to digited forms, including the consolidation of fin rays (e.g., reduced segmentation and branching), reduction of the fin web, and unexpectedly, the evolution of asymmetry between dorsal and ventral hemitrichia. In Eusthenopteron, dorsal rays cover the preaxial endoskeleton slightly more than ventral rays. In Tiktaalik, dorsal rays fully cover the third and fourth mesomeres, while ventral rays are restricted distal to these elements, suggesting the presence of ventralized musculature at the fin tip analogous to a fleshy “palm.” Asymmetry is also observed in cross-sectional areas of dorsal and ventral rays. Eusthenopteron dorsal rays are slightly larger than ventral rays; by contrast, Tiktaalik dorsal rays can be several times larger than ventral rays, and degree of asymmetry appears to be greater at larger sizes. Analysis of extant osteichthyans suggests that cross-sectional asymmetry in the dermal rays of paired fins is plesiomorphic to crown group osteichthyans. The evolution of dermal rays in crownward stem tetrapods reflects adaptation for a fin-supported elevated posture and resistance to substrate-based loading prior to the origin of digits.

scholarly journals Muscles of mice deficient in α-sarcoglycan maintain large masses and near control force values throughout the life span

2005 ◽  
Vol 22 (2) ◽  
pp. 244-256 ◽  
Author(s):  
Christina M. Consolino ◽  
Franck Duclos ◽  
Jane Lee ◽  
Roger A. Williamson ◽  
Kevin P. Campbell ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Life Span ◽  
Structure And Function ◽  
Null Mouse ◽  
Control Force ◽  
Wild Type ◽  
Cross Sectional ◽  
Muscle Structure ◽  
And Function

α-Sarcoglycan-deficient ( Sgca-null) mice provide potential for elucidating the pathogenesis of limb girdle muscular dystrophy type 2D (LGMD 2D) as well as for studying the effectiveness of therapeutic strategies. Skeletal muscles of Sgca-null mice demonstrate an early onset of extensive fiber necrosis, degeneration, and regeneration, but the progression of the pathology and the effects on muscle structure and function throughout the life span are not known. Thus the phenotypic accuracy of the Sgca-null mouse as a model of LGMD 2D has not been fully established. To investigate skeletal muscle structure and function in the absence of α-sarcoglycan throughout the life span, we analyzed extensor digitorum longus and soleus muscles of male and female Sgca-null and wild-type mice at 3, 6, 12, and 18 mo of age. Maximum isometric forces and powers were measured in vitro at 25°C. Also determined were individual myofiber cross-sectional areas and numbers, water content, and the proportion of the cross section occupied by connective tissue. Muscle masses were 40–100% larger for Sgca-null compared with age- and gender-matched wild-type mice, with the majority of the increased muscle mass for Sgca-null mice attributable to greater connective tissue and water contents. Although the greater mass of muscles in Sgca-null mice was primarily noncontractile material, absolute forces and powers were maintained near control levels at all ages, indicating a successful adaptation to the deficiency in α-sarcoglycan not observed at any age in LGMD 2D patients.

scholarly journals Interactive effects of denervation and malnutrition on diaphragm structure and function

1996 ◽  
Vol 81 (5) ◽  
pp. 2165-2172 ◽  
Author(s):  
Michael I. Lewis ◽  
Thomas J. Lorusso ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Fiber Type ◽  
Structure And Function ◽  
Interactive Effects ◽  
Diaphragm Muscle ◽  
Fiber Types ◽  
Specific Force ◽  
Cross Sectional ◽  
Total Cross Sectional Area ◽  
Generating Capacity ◽  
And Function

Lewis, Michael I., Thomas J. Lorusso, Wen-Zhi Zhan, and Gary C. Sieck. Interactive effects of denervation and malnutrition on diaphragm structure and function. J. Appl. Physiol. 81(5): 2165–2172, 1996.—The purpose of this study was to examine the interactive effects of unilateral denervation (DN) and prolonged malnutrition (MN) on the structure and function of the diaphragm muscle (Dia). Four groups of rats were studied: control (Con), MN, DN, and DN-MN. MN began 2 wk after DN and lasted 4 wk. In both the DN and DN-MN groups, the relative loss in Dia weight exceeded the relative change in body weight. Compared with the Con group, Dia specific force was reduced by ∼40% in both the DN and DN-MN groups but was unaffected in the MN group. Dia fatigue resistance improved in all experimental groups but to a greater extent in the DN and DN-MN groups. In both the DN and DN-MN groups, ∼50% of Dia fibers were classified as type IIc, whereas fiber type proportions did not change in the MN group. In the DN group, only type IIb/x fibers atrophied, whereas all fiber types atrophied in the MN and DN-MN groups. We conclude that in the DN-MN group the reduction in specific force combined with the reduction in total cross-sectional area of the muscle significantly curtails Dia force-generating capacity.

scholarly journals Brain structure of perinatally HIV-infected patients on long-term treatment

2019 ◽  
Vol 9 (5) ◽  
pp. 433-442 ◽  
Author(s):  
Malon Van den Hof ◽  
Anne Marleen ter Haar ◽  
Matthan W.A. Caan ◽  
Rene Spijker ◽  
Johanna H. van der Lee ◽  
...  
Keyword(s):  
Brain Structure ◽  
Diffusion Tensor ◽  
Structure And Function ◽  
Resonance Spectroscopy ◽  
Cross Sectional ◽  
Long Term Treatment ◽  
Brain Structure And Function ◽  
And Function ◽  
Hiv Negative

ObjectiveWe aim to give an overview of the available evidence on brain structure and function in PHIV-infected patients (PHIV+) using long-term combination antiretroviral therapy (cART) and how differences change over time.MethodsWe conducted an electronic search using MEDLINE, Embase, and PsycINFO. We used the following selection criteria: cohort and cross-sectional studies that reported on brain imaging differences between PHIV+ of all ages who used cART for at least six months before neuroimaging and HIV-negative controls. Two reviewers independently selected studies, performed data extraction, and assessed quality of studies.ResultsAfter screening 1500 abstracts and 343 full-text articles, we identified 19 eligible articles. All included studies had a cross-sectional design and used MRI with different modalities: structural MRI (n = 7), diffusion tensor imaging (DTI) (n = 6), magnetic resonance spectroscopy (n = 5), arterial spin labeling (n = 1), and resting-state functional neuroimaging (n = 1). Studies showed considerable methodological limitations and heterogeneity, preventing us to perform meta-analyses. DTI data on white matter microstructure suggested poorer directional diffusion in cART-treated PHIV+ compared with controls. Other modalities were inconclusive.ConclusionEvidence may suggest brain structure and function differences in the population of PHIV+ on long-term cART compared with the HIV-negative population. Because of a small study population, and considerable heterogeneity and methodological limitations, the extent of brain structure and function differences on neuroimaging between groups remains unknown.

scholarly journals Abdominal fat distribution and its relationship to brain changes: the differential effects of age on cerebellar structure and function: a cross-sectional, exploratory study

BMJ Open ◽  
2013 ◽  
Vol 3 (1) ◽  
pp. e001915 ◽  
Author(s):  
Matthias Raschpichler ◽  
Kees Straatman ◽  
Matthias Leopold Schroeter ◽  
Katrin Arelin ◽  
Haiko Schlögl ◽  
...  
Keyword(s):  
Exploratory Study ◽  
Fat Distribution ◽  
Abdominal Fat ◽  
Structure And Function ◽  
Cross Sectional ◽  
Differential Effects ◽  
Brain Changes ◽  
And Function
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