PMID- 15298914
OWN - NLM
STAT- MEDLINE
DCOM- 20050217
LR  - 20231103
IS  - 0006-3495 (Print)
IS  - 1542-0086 (Electronic)
IS  - 0006-3495 (Linking)
VI  - 87
IP  - 2
DP  - 2004 Aug
TI  - Ca-activation and stretch-activation in insect flight muscle.
PG  - 1101-11
AB  - Asynchronous insect flight muscle is specialized for myogenic oscillatory work, 
      but can also produce isometric tetanic contraction. In skinned insect flight 
      muscle fibers from Lethocerus, with sarcomere length monitored by a striation 
      follower, we determined the relation between isometric force (F(0)) at serial 
      increments of [Ca(2+)] and the additional active force recruited at each [Ca(2+)] 
      by a stretch of approximately 12 nm per half-sarcomere (F(SA)). The isometric 
      force-pCa relation shows that 1.5-2 units of pCa are necessary to raise isometric 
      force from its threshold (pCa approximately 6.5) to its maximum (F(0,max)). The 
      amplitude of F(SA) depends only on the preceding baseline level of isometric 
      force, which must reach at least 0.05 F(0,max) to enable stretch-activation. 
      F(SA) rises very steeply to its maximum as F(0) reaches approximately 0.2 
      F(0,max), then decreases as F(0) increases so as to produce a constant sum (F(0) 
      + F(SA)) = F(max). Thus Ca- and stretch-activation are complementary pathways 
      that trigger a common process of cross-bridge attachment and force production. We 
      suggest that stretch-induced distortion of attached cross-bridges relieves the 
      steric blocking by tropomyosin of additional binding sites on actin, thereby 
      enabling maximum force even at low [Ca(2+)].
FAU - Linari, Marco
AU  - Linari M
AD  - Laboratorio di Fisiologia, Dipartimento di Biologia Animale e Genetica, 
      Universita degli Studi di Firenze and Istituto Nazionale di Fisica della Materia, 
      Firenze, Italy.
FAU - Reedy, Michael K
AU  - Reedy MK
FAU - Reedy, Mary C
AU  - Reedy MC
FAU - Lombardi, Vincenzo
AU  - Lombardi V
FAU - Piazzesi, Gabriella
AU  - Piazzesi G
LA  - eng
GR  - AM 14317/AM/NIADDK NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Biophys J
JT  - Biophysical journal
JID - 0370626
RN  - I38ZP9992A (Magnesium)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Animals
MH  - Calcium/*pharmacology
MH  - Cells, Cultured
MH  - Dose-Response Relationship, Drug
MH  - Flight, Animal/*physiology
MH  - Heteroptera/drug effects/*physiology
MH  - Isometric Contraction/drug effects/*physiology
MH  - Magnesium/pharmacology
MH  - Mechanotransduction, Cellular/drug effects/*physiology
MH  - Muscle Fibers, Skeletal/drug effects/*physiology
MH  - Muscle, Skeletal/drug effects/*physiology
MH  - Physical Stimulation/methods
MH  - Stress, Mechanical
PMC - PMC1304450
EDAT- 2004/08/10 05:00
MHDA- 2005/02/18 09:00
PMCR- 2005/08/01
CRDT- 2004/08/10 05:00
PHST- 2004/08/10 05:00 [pubmed]
PHST- 2005/02/18 09:00 [medline]
PHST- 2004/08/10 05:00 [entrez]
PHST- 2005/08/01 00:00 [pmc-release]
AID - S0006-3495(04)73591-2 [pii]
AID - 37374 [pii]
AID - 10.1529/biophysj.103.037374 [doi]
PST - ppublish
SO  - Biophys J. 2004 Aug;87(2):1101-11. doi: 10.1529/biophysj.103.037374.