We define generalized hyperbolic Kähler spaces as a particular case of Eisenhart's generalized Riemannian spaces, with some additional conditions related to the almost product structure. Since a ...generalized hyperbolic Kähler space is equipped with a non-symmetric basic tensor, it admits five linearly independent curvature tensors. Some properties of these curvature tensors as well as those of the corresponding Ricci tensors are established. Also, we consider holomorphically projective mappings, as well as equitorsion holomorphically projective mappings between generalized hyperbolic Kähler spaces and find some invariant geometric objects with respect to these mappings.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Long-term potentiation (LTP) in the rat hippocampus is the most extensively studied cellular model for learning and memory. Induction of classical LTP involves an NMDA-receptor- and calcium-dependent ...increase in functional synaptic AMPA receptors, mediated by enhanced recycling of internalized AMPA receptors back to the postsynaptic membrane. Here we report a physiologically relevant NMDA-receptor-independent mechanism that drives increased AMPA receptor recycling and LTP. This pathway requires the metabotropic action of kainate receptors and activation of G protein, protein kinase C and phospholipase C. Like classical LTP, kainate-receptor-dependent LTP recruits recycling endosomes to spines, enhances synaptic recycling of AMPA receptors to increase their surface expression and elicits structural changes in spines, including increased growth and maturation. These data reveal a new and, to our knowledge, previously unsuspected role for postsynaptic kainate receptors in the induction of functional and structural plasticity in the hippocampus.
Muscarinic receptor activation facilitates the induction of synaptic plasticity and enhances cognitive function. However, the specific muscarinic receptor subtype involved and the critical ...intracellular signaling pathways engaged have remained controversial. Here, we show that the recently discovered highly selective allosteric M1receptor agonist 77-LH-28-1 facilitates long-term potentiation (LTP) induced by theta burst stimulation at Schaffer collateral synapses in the hippocampus. Similarly, release of acetylcholine by stimulation of cholinergic fibers facilitates LTP via activation of M1receptors. N-methyl-D-aspartate receptor (NMDAR) opening during theta burst stimulation was enhanced by M1receptor activation, indicating this is the mechanism for LTP facilitation. M1receptors were found to enhance NMDAR activation by inhibiting SK channels that otherwise act to hyperpolarize postsynaptic spines and inhibit NMDAR opening. Thus, we describe a mechanism where M1receptor activation inhibits SK channels, allowing enhanced NMDAR activity and leading to a facilitation of LTP induction in the hippocampus.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We consider canonical F-planar mappings of spaces with affine connection onto 3-symmetric spaces. The main equations for the mappings have been obtained as a closed system of PDEs of Cauchy type in ...covariant derivatives. We have found the maximum numbers of essential parameters which the general solution of the system depends on.
The purpose of the present study was (i) to explore the reliability of the most commonly used countermovement jump (CMJ) metrics, and (ii) to reduce a large pool of metrics with acceptable levels of ...reliability via principal component analysis to the significant factors capable of providing distinctive aspects of CMJ performance. Seventy-nine physically active participants (thirty-seven females and forty-two males) performed three maximal CMJs while standing on a force platform. Each participant visited the laboratory on two occasions, separated by 24-48 h. The most reliable variables were performance variables (CV = 4.2-11.1%), followed by kinetic variables (CV = 1.6-93.4%), and finally kinematic variables (CV = 1.9-37.4%). From the 45 CMJ computed metrics, only 24 demonstrated acceptable levels of reliability (CV ≤ 10%). These variables were included in the principal component analysis and loaded a total of four factors, explaining 91% of the CMJ variance: performance component (variables responsible for overall jump performance), eccentric component (variables related to the breaking phase), concentric component (variables related to the upward phase), and jump strategy component (variables influencing the jumping style). Overall, the findings revealed important implications for sports scientists and practitioners regarding the CMJ-derived metrics that should be considered to gain a comprehensive insight into the biomechanical parameters related to CMJ performance.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Activation of muscarinic acetylcholine receptors (mAChR) facilitates the induction of synaptic plasticity and enhances cognitive function. In the hippocampus, M(1) mAChR on CA1 pyramidal cells ...inhibit both small conductance Ca(2+)-activated KCa2 potassium channels and voltage-activated Kv7 potassium channels. Inhibition of KCa2 channels facilitates long-term potentiation (LTP) by enhancing Ca(2+)calcium influx through postsynaptic NMDA receptors (NMDAR). Inhibition of Kv7 channels is also reported to facilitate LTP but the mechanism of action is unclear. Here, we show that inhibition of Kv7 channels with XE-991 facilitated LTP induced by theta burst pairing at Schaffer collateral commissural synapses in rat hippocampal slices. Similarly, negating Kv7 channel conductance using dynamic clamp methodologies also facilitated LTP. Negation of Kv7 channels by XE-991 or dynamic clamp did not enhance synaptic NMDAR activation in response to theta burst synaptic stimulation. Instead, Kv7 channel inhibition increased the amplitude and duration of the after-depolarisation following a burst of action potentials. Furthermore, the effects of XE-991 were reversed by re-introducing a Kv7-like conductance with dynamic clamp. These data reveal that Kv7 channel inhibition promotes NMDAR opening during LTP induction by enhancing depolarisation during and after bursts of postsynaptic action potentials. Thus, during the induction of LTP M(1) mAChRs enhance NMDAR opening by two distinct mechanisms namely inhibition of KCa2 and Kv7 channels.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Free weight training vs. elastic band training Vojinovic, Andrija; Janicijevic, Danica; Petrovic, Milos R. ...
Kinesiology (Zagreb, Croatia),
06/2023, Volume:
55, Issue:
1
Journal Article, Paper
Peer reviewed
Open access
The aim of this study was to assess the effectiveness of two resistance training (RT) programs (free weight FW and elastic band EB) on velocity variables (handball throwing velocity HTV and maximal ...theoretical velocity
V
0) using load-velocity (L-V) relationship modelling.
Both programs lasted 6 weeks and consisted of performing bench press and overarm dumbbell pull-over using free weights (FW group) or elastic bands (EB group). Nineteen male sports science students were randomly assigned to EB (n=10) or FW group (n=9).
Both RT programs increased HTV and
V
0, although the increment was greater in the FW (>2 m
·
s-1) compared to the EB group (<1 m
·
s-1). RT programs had selective effects on the strength variables being FW more effective in increasing 1-repetition maximum, while EB in increasing maximal isometric force. Very large correlations were observed between two-point (L-V relationship modelled through two pairs of L and V data) and multiple-point methods (L-V relationship modelled through six pairs of L and V data) (
V
0:
r=
0.96; HTV:
r=
0.93). All coefficients of variation showed high validity both for
V
0 and HTV (≤6.2%). Altogether, FW training should be used for increasing the velocity of the throwing performance, while the two-point method for following training-induced changes.
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DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We relax the conditions related to the almost product structure and in such a
way introduce a wider class of generalized para-K?hler spaces. Some
properties of the curvature tensors as well as those ...of the corresponding
Ricci tensors of these spaces are pointed out. We consider holomorphically
projective mappings between generalized para-K?hler spaces in Eisenhart?s
sense. Also, we examine some invariant geometric objects with respect to
equitorsion holomorphically projective mappings. These geometric objects
reduce to the para-holomorphic projective curvature tensor in case of
holomorphically projective mappings between usual para-K?hler spaces.
nema
Background:
Force-velocity (F-V) relationship models gained popularity as a tool for muscle mechanical assessment. However, it is not clear whether the validity of the F-V relationship parameters ...(maximal theoretical force F0, velocity V0 and power Pmax) is affected using different load types: gravitational (W, rubber bands pulling the barbell downward), inertial (I, rubber bands pulling the barbell, which is equalized to the weight of the added plates upward), and combined (W + I, weight of the plates).
Hypothesis:
Load type would affect both the magnitude and validity of F-V relationship parameters. The highest magnitude and validity was expected for F0 using a W, for V0 using an I, and for Pmax using a W + I load.
Study Design:
Cross-sectional.
Level of Evidence:
Level 3.
Methods:
A total of 13 resistance-trained men (body mass, 87.7 ± 11.2 kg and body height, 183.9 ± 6.4 cm) performed bench press (BP) throws (BPTs) using 3 types of loads against 30 to 80 kg. The validity of F-V relationship parameters was explored with respect to the tests used traditionally for force (maximal voluntary contraction and 1-repetition maximum 1RM), velocity (maximal velocity achieved during almost unloaded tasks), and power (BPT against the 50%1RM and medicine ball throws) assessment.
Results:
The W + I loading promoted the highest values of F0 and Pmax, while the highest magnitude of V0 was promoted by the I loading. The validity was acceptable for F0 obtained using the 3 loading conditions with respect to the BP 1RM (r range, 0.30-0.83), and V0 obtained using the I loading with respect to the stick throw (r = 0.54).
Conclusion:
The magnitude of the F-V relationship parameters is affected by load type, but their validity with respect to standardized tests is comparable, with the exception of the higher validity of V0 when obtained using the I loading.
Clinical Relevance:
Any load type can be used for assessing F0, while I load should be selected when assessing V0.
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FSPLJ, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
We deal with almost geodesic lines of manifolds with non-symmetric linear connection. Also, we consider special almost geodesic mappings of the second type between Eisenhart’s generalized Riemannian ...spaces as well as between generalized classical (elliptic) and hyperbolic Kähler spaces. These mappings are generalizations of holomorphically projective mappings between generalized classical and hyperbolic Kähler spaces. We prove some existence theorems for special almost geodesic mappings of the second type between generalized Riemannian spaces as well as between generalized classical and hyperbolic Kähler spaces. Finally, we find some invariant geometric objects with respect to these mappings.
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