Ca2+ regulation of vascular smooth muscle

Regulation of intracellular free Ca2+ concentrations in vascular smooth muscle is accomplished mainly by Ca2+ channels and ATP-dependent Ca2+ pumps in the plasmalemma and sarcoplasmic reticulum (SR). Ca2+ entry through the plasmalemma is apparently mediated by four different pathways: leak; receptor-operated Ca2+ channels; potential sensitive Ca2+ channels; and stretch-activated channels. The agonist releasable intracellular Ca2+ store appears to be identical with the SR. Evidence for the involvement of Ca2+-induced Ca2+ release and inositol-1,4,5-trisphosphate in the release of SR Ca2+ is discussed. Smooth muscle contractions induced by certain agonists may be further enhanced by inhibition of Ca2+ uptake by the SR and of active Ca2+ extrusion across the plasmalemma. At the moment it is not clear from a consideration of the Ca2+ regulatory mechanisms present in vascular smooth muscle how dietary Ca2+ affects vascular tone. The increased Ca2+ permeation through smooth muscle cell membranes of resistance arteries taken from spontaneously hypertensive rats may be relevant to this problem.     

The effect of vasoactive intestinal polypeptide on the urinary bladder and taenia coli of the guinea pig.

The effect of vasoactive intestinal polypeptide (VIP) on the contractile activity of the urinary bladder and taenia coli of the guinea pig has been investigated. In the urinary bladder VIP caused a weak contraction and a small potentiation of the nerve-induced contraction. In the taenia coli VIP caused a small relaxation and had no effect on the nerve-induced relaxation of the preparation. The present experiments provide no evidence that VIP fulfills a role as a neurotransmitter in the urinary bladder or taenia coli, but it could be a modulator of transmitter action in the urinary bladder.     

Reflex ovulation in light-induced persistent estrus (LLPE) rats: Role of sensory stimuli and the adrenals

Penile intromissions have been thought to be the primary stimulus for reflex ovulation in light-induced persistent estrus (LLPE) rats, even though other stimuli also trigger reflex ovulation. To clarify the nature of these noncoital stimuli, intact (nonadrenalectomized) LLPE rats were briefly exposed to a variety of environmental stimuli, other than intromissions, and checked for ova 19–22 hr later. Summary of results (number of rats ovulating/number of rats tested): (A₁) home cage ($\text{3}\text{10}$); (B₁) home cage + vaginal taping ($\text{2}\text{9}$); (C₁) home cage + male-soiled bedding ($\text{15}\text{28}$); (D₁) novel cage ($\text{2}\text{11}$); (E₁) novel cage + vaginal taping ($\text{2}\text{11}$); (F₁) novel cage + vaginal taping + male-soiled bedding ($\text{9}\text{19}$); (G₁) novel cage + vaginal taping + male-soiled bedding + male mounts without intromissions ($\text{14}\text{26}$). The percentage of LLPE rats that ovulated in the last-mentioned test condition was related to the degree of proceptivity/receptivity of the LLPE females. Eight of eight proceptive LLPE females ovulated, but only $\text{6}\text{18}$ nonproceptive females ovulated. To account for reflex ovulation in the absence of intromission it has been suggested that adrenal progesterone (P) stimulates release of an ovulatory quota of luteinizing hormone. This study demonstrates no significant differences in percentage of LLPE females ovulating in corresponding groups of adrenalectomized (ADX) and adrenal-intact females. Summary of results: A₂ = $\text{0}\text{6}$, B₂ = $\text{5}\text{15}$, C₂ = $\text{4}\text{16}$, D₂ = $\text{2}\text{14}$, E₂ = $\text{5}\text{13}$, F₂ = $\text{7}\text{19}$, G₂ = $\text{10}\text{21}$. Conclusion: (a) Exposure to a factor in male-soiled bedding induces reflex ovulation in a significant proportion of adrenal-intact LLPE animals while exposure to a novel cage and/or vaginal taping does not, (b) penile intromissions are not the primary stimulus for reflex ovulation in intact proceptive LLPE rats, and (c) adrenal P is not required for reflex ovulation after tests with noncoital stimuli.     

Chinanteco management ofAechmea Magdalenae: Implications for the use of TEK and TRM in management plans

The importance of incorporating traditional ecological knowledge (TEK) and traditional resource management (TRM) into resource management plans is increasingly recognized, but little quantitative data exists on the ecological and economic implications of these systems. We quantitatively evaluate the TEK and TRM associated with the nontimber forest species, Aechmea magdalenae, in indigenous Chinanteco communities in Mexico. Two TRM systems forA. magdalenae are described and their effects on growth rates of individuals and populations are measured. Simulations using matrix population models combined with yield experiments reveal that one management system is higher yielding and less costly than the other. Thinning and transplanting are two of the most important management practices that enable populations to withstand higher rates of harvest than those predicted in a management plan that was not based on TRM. Quantitative evaluation of Chinanteco TEK is used to discuss how it may be best combined with science in management plans for nontimber forest species.