Differences in automaticity between Purkinje strands from right and left dog ventricle

1980 ◽  
Vol 239 (2) ◽  
pp. H247-H251
Author(s):  
J. Reiser ◽  
G. J. Anderson
Keyword(s):  
Intrinsic Rate ◽  
Adrenergic Blockade ◽  
Adrenergic Stimulation ◽  
Purkinje Fibers ◽  
Chronotropic Response ◽  
Cycle Lengths ◽  
Left And Right ◽  
Ventricular Conduction

Previous in situ studies have implicated differences in the pacemaker rates between the left and right ventricular conduction system. Our studies were conducted to characterize automaticity in peripheral right and left canine Purkinje fibers in vitro. Standard microelectrode techniques were utilized. In paired right (RPF) and left (LPF) canine Purkinje fibers, control intrinsic rate (IR) was found to be higher in LPF (24.8 +/- 1.7 beats/min) than in RPF (11.5 +/- 1.5 beats/min, P less than 0.01). Following overdrive stimulation at various cycle lengths, LPF consistently showed earlier escape beats. In low K0+ (1.35 mM), IR increased comparably in both RPF and LPF. However, high K0+ (5.4 mM) resulted in a greater reducton of the IR in RPF (-78%) than in LPF (-58%). After epinephrine (10(-6) M) the IR of LPF > RPF although the chronotropic response was more pronounced in RPF. Adrenergic stimulation preceded by beta-adrenergic blockade did not produce significant differences in the intrinsic rate between RPF and LPF. These findings indicate that automaticity in right and left Purkinje strands is functionally dissimilar.

Mechanisms of airway hypercontractility in basenji-greyhound dogs

1987 ◽  
Vol 63 (5) ◽  
pp. 2008-2014 ◽  
Author(s):  
T. M. Murphy ◽  
N. M. Munoz ◽  
C. A. Hirshman ◽  
J. S. Blake ◽  
A. R. Leff
Keyword(s):  
Maximal Response ◽  
Adrenergic Blockade ◽  
Vagus Nerves ◽  
Response Curves ◽  
Bronchial Smooth Muscle ◽  
Muscarinic Response ◽  
Contractile Forces ◽  
Stimulation Of

The comparative effects of contractile agonists and physiological stimulation of the tracheal and bronchial smooth muscle (BSM) response were studied isometrically in situ in five Basenji-greyhound (BG) and six mongrel dogs. Frequency-response curves generated by bilateral stimulation of the vagus nerves (0–20 Hz, 15–20 V, 2-ms duration) elicited greater maximal contraction in mongrel trachea (36.8 +/- 8.1 vs. 26.9 +/- 4.0 g/cm; P less than 0.02) and exhibited greater responsiveness in mongrel BSM (half-maximal response to electrical stimulation 3.0 +/- 1.1 vs. 7.0 +/- 0.5 Hz; P less than 0.05) compared with BG dogs. However, muscarinic sensitivity to intravenous methacholine (MCh) was substantially greater in BG dogs; MCh caused contraction greater than 1.5 g/cm at a mean dose of 3.0 X 10(-10) mol/kg for BG dogs compared with 5.1 X 10(-9) mol/kg for mongrel controls (P less than 0.03, Mann-Whitney rank-sum test). In contrast to the muscarinic response, the contractile response elicited by intravenous norepinephrine after beta-adrenergic blockade was similar in trachea and bronchus for both mongrel and BG dogs. Our data confirm previous in vitro demonstration of tracheal hyporesponsiveness in BG dogs and demonstrate that the contraction resulting from efferent parasympathetic stimulation is less in the BG than mongrel dogs. However, postsynaptic muscarinic responsiveness of BG BSM is substantially increased. We conclude that a component of airway responsiveness in BG dogs depends directly on contractile forces generated postsynaptically that are nongeometry dependent, postjunctional, and agonist specific.

Endogenous modulation of alpha-adrenergic contraction in canine tracheal muscle

1986 ◽  
Vol 61 (2) ◽  
pp. 464-471 ◽  
Author(s):  
J. Tallet ◽  
N. M. Munoz ◽  
R. Fried ◽  
A. R. Leff
Keyword(s):  
Contractile Response ◽  
Time Dependent ◽  
Adrenergic Blockade ◽  
Adrenergic Agonists ◽  
Adrenergic Stimulation ◽  
Resting Tension ◽  
Tension Time ◽  
Passive Stretch ◽  
First Time

We studied the effect of passive stretch on the contraction of canine tracheal smooth muscle (TSM) to alpha-adrenergic agonists and acetylcholine (ACh) in 211 epithelium-free TSM strips from 42 dogs in vitro. Passive stretch at a resting tension of 100 g/cm2 caused a time-dependent decrease in the contractile response to alpha-adrenergic agonists after beta-adrenergic blockade with propranolol. Initial contraction elicited by 10(-3) M phenylephrine (PE) and clonidine (CLO) decreased at 2 h by 31 and 100%, respectively. Decrease in alpha-adrenergic contractility did not result from tachyphylaxis; no contraction was elicited by PE or CLO given for the first time after 4-h passive stretch at 100 g/cm2. The TSM response to ACh was unchanged over the same time in the same strips. When TSM strips were incubated at zero resting tension for 6 h, some attenuation of the alpha-adrenergic contractile still occurred but was not substantial. Similarly, when strips were incubated with 10(-6) M indomethacin (INDO) or 10(-5) M mefenamic acid (MEF) at 100 g/cm2 resting tension, time-dependent attenuation of the response to PE and CLO was reduced for at least 6 h, and initial contraction elicited by PE was augmented. Response of TSM to ACh was not affected by prostaglandin synthetase inhibition with INDO. We conclude that passive stretch of canine TSM in vitro leads to decreased responsiveness to alpha-adrenergic stimulation that can be prevented with INDO or MEF. These data are consistent with the synthesis of an inhibitory eicosanoid in epithelium-free canine TSM that may be activated by mechanical deformation of the muscle.

Physiological antagonism caused by adrenergic stimulation of canine tracheal muscle

1986 ◽  
Vol 60 (1) ◽  
pp. 216-224 ◽  
Author(s):  
A. R. Leff ◽  
J. Tallet ◽  
N. M. Munoz ◽  
N. Shoulberg
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Contraction ◽  
Tracheal Smooth Muscle ◽  
Adrenergic Blockade ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Beta Adrenoceptor ◽  
Response Characteristics ◽  
Stimulation Of

We studied the simultaneous alpha- and beta-adrenergic response characteristics of canine tracheal smooth muscle in 398 strips from 67 dogs in vitro. Experiments were performed to determine the effects of beta-adrenergic blockade on the expression of the alpha-adrenoceptor contractile responses elicited by norepinephrine (NE), phenylephrine (PE), and clonidine (CLO). Maximal active tension caused by NE increased from 39.1 +/- 27.0 to 241 +/- 75.0 g/cm2 as the concentration of propranolol (PROP) was increased from 10(-6) to 10(-4) M. Augmentation of tracheal smooth muscle contraction caused by PE and CLO was also observed with progressive beta-adrenoceptor blockade; contraction to NE, PE, and CLO was blocked selectively with 3 X 10(-5) M phentolamine (PA) and phenoxybenzamine (PBZ). The beta-adrenergic relaxing properties of the same three agonists were also studied. After alpha-adrenergic blockade with PA or PBZ, all three agonists caused relaxation (NE greater than CLO greater than PE) of methacholine-induced contraction of tracheal smooth muscle that was reversed selectively with PROP. We demonstrate that NE, PE, and CLO cause simultaneous stimulation of both the alpha- and beta-adrenergic receptors in tracheal smooth muscle; the net response elicited is the result of adrenergic physiological antagonism and depends on the relative degree of alpha- and/or beta-adrenoceptor blockade.

Dispersed rat parotid acinar cells. I. Morphological and functional characterization

1975 ◽  
Vol 229 (3) ◽  
pp. 553-559 ◽  
Author(s):  
JA Mangos ◽  
NR McSherry ◽  
F Butcher ◽  
K Irwin ◽  
T Barber
Keyword(s):  
Functional Characterization ◽  
Acinar Cells ◽  
Spherical Shape ◽  
Cell Physiology ◽  
Adrenergic Stimulation ◽  
Membrane Function ◽  
Physiology And Biochemistry ◽  
Rat Parotid

Morphologically and functionally intact acinar cells have been obtained from the rat parotid gland through enzymatic dispersion with pure collagenase, hyaluronidase, and trypsin as well as mild mechanical forces. Cell yields of 30-50% of the original tissue weight with over 95% acinar cells were accomplished. The cells in suspension assumed a more or less spherical shape but the intracellular polarity of organelle distribution was maintained. The cells in suspension at 37 degrees C maintained stable monovalent cationic composition but lost potassium and gained sodium rapidly upon exposure to ouabain, 10(-5) M. The intracellular amylase concentration and the patterns of secretion of amylase and of synthesis of cyclic AMP by the cells in response to adrenergic stimulation with epinephrine or isoproterenol were comparable to those of the intact gland in situ. In addition, the cells showed good O2 consumption and maintained it constant for periods up to 8 h. These cells could be used as experimental tools for in vitro studies of receptor physiology and biochemistry, cell membrane function, cellular secretory mechanisms, and other parameters of exocrine gland cell physiology.

Fluid-phase endocytosis by in situ cardiac myocytes of rat atria

1993 ◽  
Vol 265 (4) ◽  
pp. C986-C996 ◽  
Author(s):  
E. Page ◽  
J. Upshaw-Earley ◽  
G. E. Goings ◽  
D. A. Hanck
Keyword(s):  
Cardiac Myocytes ◽  
Secretory Granules ◽  
Fluid Phase ◽  
Membrane Receptors ◽  
Adrenergic Stimulation ◽  
Experimental Conditions ◽  
Adult Rat ◽  
Fluid Phase Endocytosis

Fluid-phase endocytosis (FPE) associated with recycling of fused plasmalemma-secretory granules or membranes and/or membrane receptors by in situ cardiac myocytes was studied at 37 degrees C in vitro noncontracting adult rat atrial preparations. Measurements included 1) the volume (VS*) of the compartment consisting of presumptive endocytotic vesicles and the endosomes or lysosomes transiently in continuity with them (S*), which internalizes [14C]-sucrose but is inaccessible to simultaneously measured [methoxy-3H]inulin, 2) the kinetics of [14C]sucrose efflux from S*, and 3) morphometry to quantify interstitial space and non-heart muscle cells. Vs* (0.39 +/- 0.04 ml/g dry atrium for unstretched atria at 37 degrees C) was 1) variable over a 3.7-fold range under various experimental conditions, 2) significantly increased by neomycin or by lowering the temperature to 18 degrees C, and 3) significantly decreased by alpha 1-adrenergic stimulation. Analysis of sucrose efflux kinetics confirmed the presence of an intramyocytic sucrose-containing compartment. A smaller inulin-inaccessible sucrose space (S*) was also present in right ventricle. Thus, during FPE, vesicles and endosomes initially containing high (extracellular) Ca2+ and Cl- concentrations continually enter, circulate within, and undergo exocytosis from myocardial cells.

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

In Situ Localization of PPAR Gamma and Uncoupling Protein in Mouse Embryo Sections Using Digoxigenin-Labeled Riboprobes

1996 ◽  
Vol 54 ◽  
pp. 32-33
Author(s):  
C. Jennermann ◽  
S. A. Kliewer ◽  
D. C. Morris
Keyword(s):  
Alkaline Phosphatase ◽  
Room Temperature ◽  
Uncoupling Protein ◽  
Ppar Gamma ◽  
Nuclear Hormone Receptor ◽  
Full Length ◽  
Northern Analysis ◽  
Peroxisome Proliferator

Peroxisome proliferator-activated receptor gamma (PPARg) is a member of the nuclear hormone receptor superfamily and has been shown in vitro to regulate genes involved in lipid metabolism and adipocyte differentiation. By Northern analysis, we and other researchers have shown that expression of this receptor predominates in adipose tissue in adult mice, and appears first in whole-embryo mRNA at 13.5 days postconception. In situ hybridization was used to find out in which developing tissues PPARg is specifically expressed.Digoxigenin-labeled riboprobes were generated using the Genius™ 4 RNA Labeling Kit from Boehringer Mannheim. Full length PPAR gamma, obtained by PCR from mouse liver cDNA, was inserted into pBluescript SK and used as template for the transcription reaction. Probes of average size 200 base pairs were made by partial alkaline hydrolysis of the full length transcripts. The in situ hybridization assays were performed as described previously with some modifications. Frozen sections (10 μm thick) of day 18 mouse embryos were cut, fixed with 4% paraformaldehyde and acetylated with 0.25% acetic anhydride in 1.0M triethanolamine buffer. The sections were incubated for 2 hours at room temperature in pre-hybridization buffer, and were then hybridized with a probe concentration of 200μg per ml at 70° C, overnight in a humidified chamber. Following stringent washes in SSC buffers, the immunological detection steps were performed at room temperature. The alkaline phosphatase labeled, anti-digoxigenin antibody and detection buffers were purchased from Boehringer Mannheim. The sections were treated with a blocking buffer for one hour and incubated with antibody solution at a 1:5000 dilution for 2 hours, both at room temperature. Colored precipitate was formed by exposure to the alkaline phosphatase substrate nitrobluetetrazoliumchloride/ bromo-chloroindlylphosphate.

CONSERVATION OF RARE SPECIES PLANTS AND LICHENS IN SITU WITH PLANNED ANTHROPOGENIC ACTIVITIES: BASIC APPROACHES AND IMPLEMENTATION PRINCIPLES

2018 ◽  
Vol 12 (7-8) ◽  
pp. 38-45
Author(s):  
A. N. EFREMOV ◽  
N. V. PLIKINA ◽  
T. ABELI
Keyword(s):  
Rare Species ◽  
Technology Implementation ◽  
Technology Development ◽  
Anthropogenic Activities ◽  
Natural Habitat ◽  
Local Population ◽  
Main Stage ◽  
Social Risks

Rare species are most vulnerable to man-made impacts, due to their biological characteristics or natural resource management. As a rule, the economic impact is associated with the destruction and damage of individual organisms, the destruction or alienation of habitats. Unfortunately, the conservation of habitat integrity is an important protection strategy, which is not always achievable in the implementation of industrial and infrastructural projects. The aim of the publication is to summarize the experience in the field of protection of rare species in the natural habitat (in situ), to evaluate and analyze the possibility of using existing methods in design and survey activities. In this regard, the main methodological approaches to the protection of rare species in the natural habitat (in situ) during the proposed economic activity were reflected. The algorithm suggested by the authors for implementing the in situ project should include a preparatory stage (initial data collection, preliminary risk assessments, technology development, obtaining permitting documentation), the main stage, the content of which is determined by the selected technology and a long monitoring stage, which makes it possible to assess the effectiveness of the taken measures. Among the main risks of in situ technology implementation, the following can be noted: the limited resources of the population that do not allow for the implementation of the procedure without prior reproduction of individuals in situ (in vitro); limited knowledge of the biology of the species; the possibility of invasion; the possibility of crossing for closely related species that сo-exist in the same habitat; social risks and consequences, target species or population may be important for the local population; financial risks during the recovery of the population. The available experience makes it possible to consider the approach to the conservation of rare species in situ as the best available technology that contributes to reducing negative environmental risks.

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