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1.
J Dairy Sci ; 101(5): 4667-4675, 2018 May.
Article in English | MEDLINE | ID: mdl-29501334

ABSTRACT

The objective of this study was to evaluate the efficacy of a commercial vacuum fly trap (CowVac, Spalding Laboratories, Reno, NV) in on-farm organic dairy production systems to control horn flies, stable flies, and face flies. As cows walk through the trap, flies are brushed off the face, flank, and back with hanging flaps and blown off the belly, udder, and legs from one side, and then vacuumed from the air into a chamber from vacuum inlets opposite the blower and above the cow. The study included 8 organic dairy farms during the summer of 2015 in Minnesota, and herds ranged from 30 to 350 cows in size. The farms were divided into pairs by location; during the first period of the summer (June to July), the trap was set up on 1 farm, whereas during the second period of the summer (August to September) the trap was sent to its paired farm. Farms were visited once per week to collect and count flies from the trap as well as count and record flies on cows. Bulk tank milk, fat, and protein production and somatic cell count were collected on farms during the entire study period. Data were analyzed using the GLM procedure of SAS (version 9.3, SAS Institute Inc., Cary, NC). Independent variables for analyses were the fixed effects of farm, trap presence, housing scenario, and summer period. Horn fly numbers on cows were lower by 44% on farm in the presence of a trap (11.4 vs. 20.5 flies/cow-side) compared with the absence of a trap. Stable fly (5.4 vs. 7.1 flies/leg) and face fly (1.0 vs. 1.0 flies/cow) numbers were similar on farm whether the trap was present or absent on farms, respectively. Milk production was similar for farms with the trap (15.5 kg/d) compared to without (15.3 kg/d) the trap. Bulk tank milk, milk components, and somatic cell count were statistically similar in the presence and absence of the trap, so potential benefits of the trap for those measures were not evident at low fly populations observed during the study. The presence of a trap on farm reduced horn fly population growth rates (-1.01 vs. 1.00 flies/d) compared with the absence of a trap. Cows on farms with no housing (100% pasture) tended to have reduced horn fly numbers (11.7 vs. 28.3 flies/cow-side) in the presence of a trap compared with the absence of a trap on farm. Cows on farms with housing had similar horn fly numbers (11.2 vs. 14.8 flies/cow-side) in the presence of a trap compared with the absence of a trap on farm. In summary, these results indicate the trap was effective in reducing horn fly numbers on cows and reduced horn fly growth rates during the pasture season in organic dairy production systems, but benefits in improved milk production were not evident likely because of relatively low fly populations.


Subject(s)
Cattle/microbiology , Diptera/growth & development , Insect Control/methods , Animals , Cattle/metabolism , Cattle/parasitology , Dairying , Female , Insect Control/instrumentation , Male , Milk/metabolism , Minnesota , Organic Agriculture , Seasons , Vacuum
2.
J Dairy Sci ; 100(4): 3318-3325, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28161184

ABSTRACT

Heifer calves (n = 102) were used to evaluate the effect of once- or twice-daily feeding on growth, behavior, and economics of calves in an organic group management system. Calves were assigned to replicate feeding groups of 10 in superhutches by birth order, during 2 seasons from September to December 2013 and March to May 2014 at the University of Minnesota West Central Research and Outreach Center, Morris. Calves in groups were the experimental unit. Breed groups of calves were Holsteins (n = 26), crossbreds (n = 45) including combinations Holsteins, Montbéliarde, and Viking Red (selected for high production), and crossbreds (n = 31) including combinations of Holsteins, Jersey, Normande, and Viking Red (selected for robustness). Treatment groups were once-daily feeding (1×) or twice-daily feeding (2×). Calves in both groups were fed 6 L per calf/daily of organic milk with 13% total solids and then weaned at 60 d when the group consumption averaged 0.91 kg/d of starter per calf. Body weight and hip height were recorded at birth, once a week, at weaning, and at 90 and 120 d of age. Hobo Pendant G loggers (Onset Computer Corp., Bourne, MA) were applied to the right rear leg of calves to measure total lying and standing time. Data were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Independent variables for analyses were the fixed effects of birth weight (co-variable), season of birth, and treatment group, along with replicate as a random effect. No significant differences were found between feeding groups for body weight, weight gain, average daily gain, hip height, or heart girth. For calves in 1× and 2× groups, respectively, weaning group performance was as follows: gain per day was 0.79 and 0.81 kg, weaning weight was 92.7 and 93.3 kg, and weaning hip height was 95.2 and 95.3 cm. Daily gain to 90 d was 0.85 and 0.85 kg, and daily gain to 120 d was 0.85 and 0.83 kg for 1× and 2× calves, respectively. For lying time, calves in groups 1× (988 min/d) and 2× (995 min/d) did not differ. During the evening hours, 2× calves had lesser lying times (34 min/h for 1×; 28 min/h for 2×) because they were fed at 1800 h every evening. The average cost per kilogram of gain for the 2× ($4.03/kg) calves was greater than that for the 1× ($3.56/kg) calves. In summary, group-fed calves fed once a day in an organic production system had similar average daily gains and body dimensions compared with calves fed twice a day. Our results indicated that there is no need for twice-daily milk feeding under the conditions of the present study.


Subject(s)
Animal Feed , Diet/veterinary , Animals , Cattle , Female , Milk , Weaning , Weight Gain
3.
Basic Res Cardiol ; 106(6): 953-66, 2011 Nov.
Article in English | MEDLINE | ID: mdl-21681579

ABSTRACT

In rat atrial myocytes GIRK (Kir3) channels can be activated by acetylcholine and adenosine via M(2) and A(1) receptors coupled to Pertussis-toxin-sensitive G proteins, such as M(2)R or A(1)R. Owing to the lower density of A(1)R, the amplitude of current activated by a saturating concentration (10 µM) of Ado (I(K(Ado))) amounts to about 40% of maximum I(K(ACh)). Adenovirus-driven overexpression of A(1)R results in an increase in I(K(Ado)). In a fraction of A(1)R-overexpressing cells, both ACh and Ado failed to activate GIRK channels. These cells had a large constitutive Ba(2+)-sensitive inward rectifying background K(+) current, which was insensitive to the GIRK channel inhibitor tertiapin (200 nM), suggesting this current component to be carried by I(K1) (Kir) channels. This effect of A(1)R overexpression was reduced by treatment (48 h) with the A(1)R antagonist DPCPX. siRNA-mediated knockdown of Kir2.1, simultaneously with A(1)R overexpression, substantially reduced I(K1). The mechanisms underlying the upregulation of functional I(K1) channels involve activation of the phosphatidylinositol 3-kinase (Pi3K)/Akt (protein kinase B) pathway. Kir2.1 transcripts are not increased in myocytes overexpressing A(1)R. These data demonstrate that manipulation of the expression level of a G protein-coupled receptor has unpredictable effects on functional expression of proteins that are supposed to be unrelated to the pathway controlled by that GPCR.


Subject(s)
G Protein-Coupled Inwardly-Rectifying Potassium Channels/metabolism , Heart Atria/metabolism , Myocytes, Cardiac/metabolism , Receptor, Adenosine A1/biosynthesis , Signal Transduction/physiology , Animals , Female , Gene Knockdown Techniques , Male , Organ Culture Techniques , Patch-Clamp Techniques , RNA Interference , Rats , Rats, Inbred WKY , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Transduction, Genetic , Up-Regulation
4.
J Biol Chem ; 276(40): 37347-54, 2001 Oct 05.
Article in English | MEDLINE | ID: mdl-11495921

ABSTRACT

G protein-activated inwardly rectifying K(+) (GIRK) channels, expressed in atrial myocytes, various neurons, and endocrine cells, represent the paradigmatic target of beta gamma subunits released from activated heterotrimeric G proteins. These channels contribute to physiological slowing of cardiac frequency and synaptic inhibition. They are activated by beta gamma dimers released upon stimulation of receptors coupled to pertussis toxin-sensitive G proteins (G(i/o)), whereas beta gamma released from G(s) do not converge on the channel subunits. This is in conflict with the finding that dimeric combinations of various beta and gamma subunits can activate GIRK channels with little specificity. In the present study, we have overexpressed the major subtypes of cardiac beta-adrenergic receptors (beta(1)-AR and beta(2)-AR) in atrial myocytes by transient transfection. Whereas in native cells beta-adrenergic stimulation with isoproterenol failed to induce measurable GIRK current, robust currents were recorded from myocytes overexpressing either beta(1)-AR or beta(2)-AR. Whereas the beta(2)-AR-induced current showed the same sensitivity to pertussis toxin as the current evoked by the endogenous G(i/o)-coupled muscarinic M(2) receptor, isoproterenol-activated currents were insensitive to pertussis toxin treatment in beta(1)-AR-overexpressing myocytes. In contrast to a recent publication (Leaney, J. L., Milligan, G., and Tinker, A. (2000) J. Biol. Chem. 275, 921-929), sizable GIRK currents could also be activated by isoproterenol when the signaling pathway was reconstituted by transient transfection in two different standard cell lines (Chinese hamster ovary and HEK293). These results demonstrate that specificity of receptor-G protein signaling can be disrupted by overexpression of receptors. Moreover, the alpha subunit of heterotrimeric G proteins does not confer specificity to G beta gamma-mediated signaling.


Subject(s)
Heart Atria/metabolism , Myocardium/metabolism , Potassium Channels, Inwardly Rectifying , Potassium Channels/physiology , Receptors, Adrenergic, beta-1/metabolism , Receptors, Adrenergic, beta-2/metabolism , Animals , Atrial Function , Electrophysiology , Female , GTP-Binding Protein alpha Subunits, Gi-Go/metabolism , GTP-Binding Protein alpha Subunits, Gs/metabolism , Male , Potassium Channels/metabolism , Rats , Rats, Inbred WKY , Transfection
5.
J Biol Chem ; 276(31): 28873-80, 2001 Aug 03.
Article in English | MEDLINE | ID: mdl-11384974

ABSTRACT

K(+) channels composed of G-protein-coupled inwardly rectifying K(+) channel (GIRK) (Kir3.0) subunits are expressed in cardiac, neuronal, and various endocrine tissues. They are involved in inhibiting excitability and contribute to regulating important physiological functions such as cardiac frequency and secretion of hormones. The functional cardiac (K((ACh))) channel activated by G(i)/G(o)-coupled receptors such as muscarinic M(2) or purinergic A(1) receptors is supposed to be composed of the subunits GIRK1 and GIRK4 in a heterotetrameric (2:2) fashion. In the present study, we have manipulated the subunit composition of the K((ACh)) channels in cultured atrial myocytes from hearts of adult rats by transient transfection of vectors encoding for GIRK1 or GIRK4 subunits or GIRK4 concatemeric constructs and investigated the effects on properties of macroscopic I(K(ACh)). Transfection with a GIRK1 vector did not cause any measurable effect on properties of I(K(ACh)), whereas transfection with a GIRK4 vector resulted in a complete loss in desensitization, a reduction of inward rectification, and a slowing of activation. Transfection of myocytes with a construct encoding for a concatemeric GIRK4(2) subunit had similar effects on desensitization and inward rectification. Following transfection of a tetrameric construct (GIRK4(4)), these changes in properties of I(K(ACh)) were still observed but were less pronounced. Heterologous expression in Chinese hamster ovary cells and human embryonic kidney 293 cells of monomeric, dimeric, and tetrameric GIRK4 resulted in robust currents activated by co-expressed A(1) and M(2) receptors, respectively. These data provide strong evidence that homomeric GIRK4 complexes form functional G(beta)gamma gated ion channels and that kinetic properties of GIRK channels, such as activation rate, desensitization, and inward rectification, depend on subunit composition.


Subject(s)
Heart/physiology , Myocardium/metabolism , Potassium Channels, Inwardly Rectifying , Potassium Channels/physiology , Acetylcholine/pharmacology , Amino Acid Sequence , Animals , Antibodies , CHO Cells , Cell Line , Cell Membrane/drug effects , Cell Membrane/physiology , Cricetinae , Dimerization , Epitopes/chemistry , G Protein-Coupled Inwardly-Rectifying Potassium Channels , Heart Atria , Humans , In Vitro Techniques , Membrane Potentials/drug effects , Membrane Potentials/physiology , Molecular Sequence Data , Patch-Clamp Techniques , Potassium Channels/chemistry , Potassium Channels/genetics , Protein Subunits , Rats , Rats, Inbred WKY , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Transfection
6.
J Biol Chem ; 276(8): 5650-8, 2001 Feb 23.
Article in English | MEDLINE | ID: mdl-11104770

ABSTRACT

G protein-gated inwardly rectifier K+ current in atrial myocytes (I(K(ACh))) upon stimulation with acetylcholine (ACh) shows a fast desensitizing component (t(1/2) approximately 5 s). After washout of ACh, I(K(ACh)) recovers from fast desensitization within < 30 s. A recent hypothesis suggests that fast desensitization is caused by depletion of phosphatidylinositol 4,5-bisphosphate (PtIns(4,5)P(2)), resulting from costimulation of phospholipase C (PLC)-coupled M3 receptors (M3AChR). The effects of stimulating two established PLC-coupled receptors, alpha-adrenergic and endothelin (ET(A)), on I(K(ACh)) were studied in rat atrial myocytes. Stimulation of these receptors caused activation of I(K(ACh)) and inhibition of the M2AChR-activated current. In myocytes loaded with GTPgammaS (guanosine 5'-3-O-(thio)triphosphate), causing stable activation of I(K(ACh)), inhibition via alpha-agonists and ET-1 was studied in isolation. Stimulation of either type of receptor under this condition, via G(q/11), caused a slow inhibition (t(1/2) approximately 50 s) by about 70%. No comparable effect on GTPgammaS-activated I(K(ACh)) was induced by ACh, suggesting that PLC-coupled M3AChRs are not functionally expressed in rat myocytes, which was supported by the finding that M3AChR transcripts were not detected by reverse transcriptase-polymerase chain reaction in identified atrial myocytes. Supplementing the pipette solution with PtIns(4,5)P(2) significantly reduced inhibition of I(K(ACh)) but had no effect on fast desensitization. From these data it is concluded that stimulation of PLC-coupled receptors causes slow inhibition of I(K(ACh)) by depletion of PtIns(4,5)P(2), whereas fast desensitization of I(K(ACh)) is not related to PtIns(4,5)P(2) depletion. As muscarinic stimulation by ACh does not exert inhibition of I(K(ACh)) comparable to stimulation of alpha(1)- and ET(A) receptors, expression of functional PLC-coupled muscarinic receptors in rat atrial myocytes is unlikely.


Subject(s)
GTP-Binding Proteins/metabolism , Heart Atria/metabolism , Phosphatidylinositol 4,5-Diphosphate/metabolism , Potassium Channels, Inwardly Rectifying , Potassium Channels/metabolism , Receptors, Cell Surface/metabolism , Type C Phospholipases/metabolism , Acetylcholine/pharmacology , Electric Conductivity , Endothelin-1/metabolism , Guanosine 5'-O-(3-Thiotriphosphate)/metabolism , Heart Atria/cytology , Ion Channel Gating , Muscarinic Antagonists/pharmacology , Phenylephrine/pharmacology , Piperidines/pharmacology , Receptors, Endothelin/metabolism , Receptors, Muscarinic/metabolism
7.
Circ Res ; 86(6): 643-8, 2000 Mar 31.
Article in English | MEDLINE | ID: mdl-10746999

ABSTRACT

In adult rat atrial myocytes, muscarinic acetylcholine (ACh)-sensitive K(+) current activated by a saturating concentration of adenosine (I(K(ACh),(Ado))) via A(1) receptors (A(1)Rs) amounts to only 30% of the current activated by a saturating concentration of ACh (I(K(ACh),(ACh))) via muscarinic M(2) receptors. The half-time of activation of I(K(ACh),(Ado)) on a rapid exposure to agonist was approximately 4-fold longer than that of I(K(ACh),(ACh)). Furthermore, I(K(ACh),(Ado)) never showed fast desensitization. To study the importance of receptor density for A(1)R-I(K(ACh),(Ado)) signaling, adult atrial myocytes in vitro were transfected with cDNA encoding for rat brain A(1)R and enhanced green fluorescent protein (EGFP) as a reporter. Whole-cell current was measured on days 3 and 4 after transfection. Time-matched cells transfected with only the EGFP vector served as controls. In approximately 30% of EGFP-positive cells (group I), the density of I(K(ACh),(Ado)) was increased by 72%, and its half-time of activation was reduced. Density and kinetic properties of I(K(ACh),(ACh)) were not affected in this fraction. In approximately 70% of transfection-positive myocytes (group II), the density of I(K(ACh),(ACh)) was significantly reduced, its activation was slowed, and the fast desensitizing component was lost. Adenosine-induced currents were larger in group II than in group I, their activation rate was further increased, and a fast desensitizing component developed. These data indicate that in native myocytes the amplitude and activation kinetics of I(K(ACh),(Ado)) are limited by the expression of A(1)R. Overexpression of A(1)R negatively interferes with signal transduction via the muscarinic M(2) receptor-linked pathway, which might reflect a competition of receptors with a common pool of G proteins. Negative interference of an overexpressed receptor with physiological regulation of a target protein by a different receptor should be considered in attempts to use receptor overexpression for gene therapy.


Subject(s)
Acetylcholine/physiology , Myocardium/metabolism , Potassium Channels/physiology , Receptors, Muscarinic/physiology , Receptors, Purinergic P1/metabolism , Acetylcholine/pharmacology , Adenosine/pharmacology , Animals , Electric Conductivity , Female , Heart Atria , Male , Myocardium/cytology , Potassium Channels/drug effects , Rats , Rats, Inbred WKY , Receptor, Muscarinic M2 , Transfection
8.
FEBS Lett ; 451(3): 279-83, 1999 May 28.
Article in English | MEDLINE | ID: mdl-10371205

ABSTRACT

K+ channels composed of GIRK subunits are predominantly expressed in the heart and various regions of the brain. They are activated by betagamma-subunits released from pertussis toxin-sensitive G-proteins coupled to different seven-helix receptors. In rat atrial myocytes, activation of K(ACh) channels is strictly limited to receptors coupled to pertussis toxin-sensitive G-proteins. Upon treatment of myocytes with antisense oligodesoxynucleotides against GRK2, a receptor kinase with Gbetagamma binding sites, in a fraction of cells, K(ACh) channels can be activated by beta-adrenergic receptors. Sensitivity to beta-agonist is insensitive to pertussis toxin treatment. These findings demonstrate a potential role of Gbetagamma binding proteins for target selectivity of G-protein-coupled receptors.


Subject(s)
Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors , Cyclic AMP-Dependent Protein Kinases/genetics , Heart Atria/metabolism , Oligonucleotides, Antisense/pharmacology , Potassium Channels/metabolism , Receptors, Adrenergic, beta/metabolism , Signal Transduction/drug effects , Animals , Cells, Cultured , Cyclic AMP-Dependent Protein Kinases/metabolism , Ion Channel Gating/genetics , Oligonucleotides, Antisense/genetics , Potassium Channels/genetics , Rats , Rats, Inbred WKY , Receptors, Adrenergic, beta/genetics , Signal Transduction/genetics , beta-Adrenergic Receptor Kinases
9.
FEBS Lett ; 439(1-2): 115-20, 1998 Nov 13.
Article in English | MEDLINE | ID: mdl-9849890

ABSTRACT

Muscarinic K+ channels (IK(ACh)) in native atrial myocytes are activated by betagamma subunits of pertussis toxin (Ptx)-sensitive heterotrimeric G proteins coupled to different receptors. betagamma subunits of Ptx-insensitive Gs, coupled to beta-adrenergic receptors, do not activate native IK(ACh). In atrial myocytes from adult rats transfected with rat brain beta1 subunit IK(ACh) can be activated by stimulation of beta-adrenergic receptors using isoprenaline. This effect is insensitive to Ptx. These findings demonstrate for the first time promiscuous (Ptx-insensitive) coupling of Gsbetagamma to GIRK channels in their native environment.


Subject(s)
GTP-Binding Proteins/physiology , Myocardium/metabolism , Potassium Channels/physiology , Receptors, Adrenergic, beta/physiology , Animals , Atrial Function/physiology , Cells, Cultured , Female , GTP-Binding Proteins/metabolism , Heart/physiology , Male , Membrane Potentials , Potassium Channels/metabolism , Rats , Rats, Wistar , Receptors, Adrenergic, beta/metabolism
10.
J Physiol ; 512 ( Pt 2): 407-20, 1998 Oct 15.
Article in English | MEDLINE | ID: mdl-9763631

ABSTRACT

1. The effects of diadenosine polyphosphates (APnA, where n = 4-6) were studied on beating frequency of perfused guinea-pig hearts and on muscarinic K+ current (IK(ACh)) and ATP-regulated K+ current (IK(ATP)) in atrial myocytes from guinea-pig hearts using whole-cell voltage clamp. 2. Bradycardia induced by APnA in perfused hearts was completely inhibited by 8-cyclopentyl- 1,3-dipropylxanthine (CPX, 20 microM), a selective antagonist at A1 adenosine receptors, and was augmented by dipyridamole (Dipy), an inhibitor of cellular adenosine (Ado) uptake. 3. Whereas exposure of atrial myocytes to Ado (100 microM) within about 1 s induced a significant whole-cell IK(ACh), APnA up to 1 mM applied for some tens of seconds failed to activate IK(ACh). If present for periods > 2 min, APnA caused inhibition of agonist-evoked IK(ACh) and activation of a weakly inward rectifying K+ current, which was identified as IK(ATP) by its sensitivity to glibenclamide and its current-voltage curve. 4. The actions of extracellular APnA on IK(ACh) and IK(ATP) were mimicked by intracellular loading of compounds via the patch clamp pipette and by intracellular loading of AMP. 5. The results from isolated myocytes exclude APnA acting as A1 agonists. It is suggested that myocytes can take up APnA, which are degraded to AMP. In the presence of ATP, AMP is converted to ADP, a physiological activator of ATP-regulated K+ channels, by adenylate kinase. A similar mechanism resulting in a reduction of the [GTP]/[GDP] ratio might be responsible for inhibition of IK(ACh). 6. In the perfused heart and other multicellular cardiac preparations the actions of APnA are mediated by Ado via A1 receptors. It is suggested that APnA in multicellular cardiac tissue are hydrolysed by an ectohydrolase to yield AMP which is converted to Ado by ectonucleotidases.


Subject(s)
Acetylcholine/physiology , Adenine Nucleotides/pharmacology , Adenosine Triphosphate/physiology , Myocardium/metabolism , Potassium Channels/metabolism , Animals , Chromatography, High Pressure Liquid , Electric Stimulation , Electrophysiology , Guinea Pigs , Heart Atria/cytology , Heart Atria/metabolism , In Vitro Techniques , Membrane Potentials/physiology , Myocardium/cytology , Patch-Clamp Techniques , Potassium Channels/drug effects
11.
Neuroscience ; 87(1): 109-21, 1998 Nov.
Article in English | MEDLINE | ID: mdl-9722145

ABSTRACT

Neurons growing out from cultivated fetal medullary slices that exhibited spontaneous electrical activity after blockade of synaptic transmission were investigated by the patch-clamp technique for their response to decreases in the extracellular pH. Increases in the [H+], induced by increases in pCO2, resulted in a decrease in spike frequency associated with a decrease in the rate of depolarization preceding each action potential. The type of ion channel, contributing to interspike depolarization, and which may therefore be the site of CO2/H+ action, was identified by application of agents that inhibited the hyperpolarization-activated cation, IH, channel (Cs+ and ZD7288). Application of Cs+ and ZD7288 slightly hyperpolarized the cell membrane, decreased the interspike slope and inhibited CO2/H+-induced modulations of spike frequency in one group of CO2-inhibited medullary neurons, suggesting that IH contributes to spontaneous neuronal activity and to CO2/H+-sensitivity. CO2/H+ effects on IH were further confirmed in voltage-clamp experiments. Increasing the bath CO2 from 2% to 9% reduced the IH amplitude, shifted the mean EH from -54 to -60 mV, lengthened the voltage-dependent delay of current activation and increased the time-constants of activation at all potentials studied. It is concluded that depolarizing inward currents through IH channels participate in the gradual ramp-like change in membrane potential which depolarizes the cell up to the threshold of Na+ spike generation. CO2/H+-induced inhibition of IH reduces the contribution of this ion current to the interspike depolarization and accounts for the CO2/H+-induced decrease in spike frequency in one type of CO2/H+-inhibited medullary cells.


Subject(s)
Carbon Dioxide/pharmacology , Ion Channels/physiology , Medulla Oblongata/physiology , Nerve Tissue Proteins/physiology , Action Potentials/drug effects , Action Potentials/physiology , Animals , Cells, Cultured , Cesium/pharmacology , Chemoreceptor Cells/drug effects , Chemoreceptor Cells/physiology , Cyclic Nucleotide-Gated Cation Channels , Hydrogen-Ion Concentration , Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels , In Vitro Techniques , Ion Channels/antagonists & inhibitors , Medulla Oblongata/cytology , Medulla Oblongata/drug effects , Medulla Oblongata/embryology , Neural Inhibition/drug effects , Neural Inhibition/physiology , Neurons/drug effects , Neurons/physiology , Patch-Clamp Techniques , Potassium Channels , Pyrimidines/pharmacology , Rats , Rats, Sprague-Dawley
12.
J Neurophysiol ; 79(6): 2885-94, 1998 Jun.
Article in English | MEDLINE | ID: mdl-9636094

ABSTRACT

Neurons in fetal rat medullary slices that exhibited spontaneous electrical activity after blockade of synaptic transmission were investigated for their response to decreases in extracellular pH. Increases in [H+] (induced either by fixed acid or increases in PCO2) induced a significant increase in the frequency of action potentials, associated with a membrane depolarization, and/or increases in the slope of the interspike depolarization. In addition, CO2/H+ prolonged the repolarizing phase of action potentials and reduced the afterhyperpolarization, suggesting that K+ channels were the primary site of CO2/H+ action. The type of K+ channel that was modulated by CO2/H+ was identified by application of agents that inhibited Ca2+-activated K+ channels either directly (tetraethylammonium chloride, TEA) or indirectly (Cd2+ ions) by inhibiting Ca2+ influx. CO2/H+ effects on neuronal activity were abolished after application of these blockers. The contribution of Ca2+-activated K+ channels to H+ sensitivity of these neurons was confirmed further in voltage-clamp experiments in which outward rectifying I-V curves were recorded that revealed a zero current potential of -70 mV. CO2/H+ induced a prominent reduction in outward currents and shifted the zero current potential to more positive membrane potentials (mean -63 mV). The CO2/H+-sensitive current reversed at -72 mV and was blocked by external application of TEA. It is concluded that CO2/H+ exerts its stimulatory effects on fetal medullary neurons by inhibition of Ca2+-activated K+ channels, either directly or indirectly, by blocking voltage-dependent Ca2+ channels, which in turn results in a reduction of K+ efflux and in cell depolarization.


Subject(s)
Calcium/physiology , Medulla Oblongata/cytology , Medulla Oblongata/physiology , Neurons/drug effects , Neurons/metabolism , Potassium Channels/drug effects , Potassium Channels/physiology , Animals , Carbon Dioxide/pharmacology , Electric Stimulation , Electrophysiology , Female , Fetus/physiology , Hydrogen-Ion Concentration , Medulla Oblongata/drug effects , Membrane Potentials/drug effects , Membrane Potentials/physiology , Organ Culture Techniques , Patch-Clamp Techniques , Pregnancy , Rats , Rats, Sprague-Dawley , Stimulation, Chemical , Tetraethylammonium/pharmacology
13.
Respir Physiol ; 111(2): 137-51, 1998 Feb.
Article in English | MEDLINE | ID: mdl-9574866

ABSTRACT

Medullary slices of the fetal rat at gestational day 16 were cultivated (organotypic culture) for up to 20 days and current clamp experiments were performed on outgrowing neurons. CO2-sensitivity was tested by changing the P(CO2) in the bath solution (equilibrating CO2 fraction from 0.02 to 0.09). Two groups of CO2-sensitive neurons were found; one with and the other without intrinsic CO2-chemosensitivity. Neurons with intrinsic CO2-sensitivity maintained their spontaneous activity and chemosensitivity after blockade of synaptic transmission. These neurons exhibited action potentials that were preceeded by a spontaneous interspike depolarization and followed by an afterhyperpolarization (beating neurons). Increasing P(CO2) either decreased (inhibited neurons, n = 55) or increased the spike frequency of these neurons (stimulated neurons, n = 31). The reduced activity of CO2-inhibited neurons was associated with membrane hyperpolarization and/or decreases in the slope of interspike depolarization. In contrast CO2-stimulated neurons were depolarized and the slope of their interspike depolarization was augmented during acidosis. In addition, we demonstrated a strong voltage dependence of CO2-induced effects on membrane potential and spike frequency. Neurons with non-beating activity did not show a spontaneous interspike depolarization and their spike generation and CO2-sensitivity appeared to be entirely produced through synaptic inputs. The CO2-mediated changes in electrical properties of these neurons closely resemble those of various CNS neurons, including respiratory neurons, in whole animal or neonatal brainstem-spinal cord preparations.


Subject(s)
Carbon Dioxide/pharmacology , Medulla Oblongata/drug effects , Medulla Oblongata/physiology , Action Potentials/drug effects , Action Potentials/physiology , Animals , Culture Techniques , Drug Resistance , Electrophysiology , Female , Fetus/drug effects , Fetus/physiology , Medulla Oblongata/cytology , Neurons/drug effects , Neurons/physiology , Patch-Clamp Techniques , Pregnancy , Rats , Rats, Sprague-Dawley , Respiratory Mechanics/drug effects , Respiratory Mechanics/physiology , Synaptic Transmission/drug effects , Synaptic Transmission/physiology
15.
Monatsschr Kinderheilkd ; 129(6): 324-7, 1981 Jun.
Article in German | MEDLINE | ID: mdl-6114410

ABSTRACT

Basic principles of the antibiotic therapy of urinary tract infections in children are discussed with reference to the literature and own recent publications. In the field of pediatrics there seems to be no justification for a short-term therapy of so-called uncomplicated urinary tract infections as for example cystourethritis as has been propagated for adults because of the lack of reliable criteria to differentiate between infections of the upper or lower urinary tract. Only exception to this is the long-known cystourethritis of the young girl without previous renal disease. For some patients there is no doubt the chance of a spontaneous recovery from an acute pyelonephritis; nevertheless, each urinary tract infection in children should be treated properly since there is always the chance that an acute infections becomes chronic due to a therapy which was unspecific, too short, and without later check-ups. There is no alternative to the individually planned prophylaxis of reinfection in chronic pyelonephritis, including regular check-ups over a long period.


Subject(s)
Urinary Tract Infections/drug therapy , Age Factors , Child , Child, Preschool , Chronic Disease , Female , Humans , Nitrofurantoin/therapeutic use , Pyelonephritis/drug therapy , Pyelonephritis/prevention & control , Sulfamethoxazole/therapeutic use , Trimethoprim/therapeutic use
17.
Infection ; 7 Suppl 2: S231-5, 1979.
Article in German | MEDLINE | ID: mdl-108223

ABSTRACT

In 1960 there were two outbreaks of mostly severe diarrhoea due to pseudomonas aeruginosa in the special nursery for premature infants and sick newborns of the Universitäts-Kinderklinik Münster/Westf. resp. Kinderklinik Offenbach/Main. In both cases a single strain of Ps. aeruginosa was isolated from patients with diarrhoea and symptom-free children. The clinical picture ranges from mild diarrhoea to severe enteritis with septicemia. The source of the strain found in the first outbreak was not identified. In the second case the causative strain could be isolated from the faeces of two nurses and also from various objects in the environment. Systemic antibiotic treatment is necessary in all cases, especially in premature infants, which were much more susceptible to serious infection than normal infants. Symptom-free children may be a potential danger because they can become carriers of the pathogenic organism in the nursery. After antibiotic treatment superinfections with Ps. aeruginosa should be recognised as a danger of faecal carriage. The problem of enteritis due to the so called facultative-pathogenic bacteria will be discussed. The best way to get clear information seemed to be by using the quantitative bacteriological analysis of faeces. In all cases of diarrhoea due to Ps. aeruginosa, systemic antibiotic therapy is indicated without any exception in spite of the potential danger of septicemia.


Subject(s)
Enteritis/microbiology , Infant, Newborn, Diseases/microbiology , Infant, Premature, Diseases/microbiology , Pseudomonas aeruginosa/pathogenicity , Cross Infection/microbiology , Diarrhea, Infantile/microbiology , Feces/microbiology , Humans , Infant, Newborn , Infant, Premature , Pseudomonas Infections/microbiology , Sepsis/microbiology
19.
Med Klin ; 72(18): 806-8, 1977 May 06.
Article in German | MEDLINE | ID: mdl-865382

ABSTRACT

Between 8. 1. 1976 and 10. 8. 1976 16 new or premature born children got a gastroenteritis due to salmonella panama. All these children were together in one pediatric ward of the hospital. Most of them came directly for the labour ward or from the newborn-ward. They had antibiotic therapy due to the indication of the mother or the child. It was impossible to fine the source of the salmonella infection, therefore, finally the ward was closed. After radical desinfection new patients came to the ward. Again they were infected with salmonella panama. Now it became clear that contaminated milk (Humanan-Heilnahrung) was the source of infections. Most papers mention a mild benign course of the infections. In contrary we could see severe conditions dependent on the pre-damage of the child or his reduced immunity. The minimal number of germs of dietic food products needs to be examinated.


Subject(s)
Cross Infection/diagnosis , Salmonella Infections/diagnosis , Enteritis/diagnosis , Food Microbiology , Humans , Infant , Infant Food , Infant, Newborn , Infant, Newborn, Diseases/diagnosis , Infant, Premature, Diseases/diagnosis
20.
Dtsch Med Wochenschr ; 100(52): 2636-41, 1975 Dec 26.
Article in German | MEDLINE | ID: mdl-1106977

ABSTRACT

Within 4 years 1400 children were investigated for urinary-tract infection in a long-term study. Children with manifest infection were treated and followed-up. In 59 children with chronic pyelonephritis 159 recurrences were observed: 146 were reinfections (change of organism) and 13 relapses (organism unchanged). Serotyping of 0-antigens showed differences between children with chronic pyelonephritis and children with a single exacerbation within the observation period. Reinfection with resistant bacteria mainly occurred shortly after cessation of therapy.


Subject(s)
Urinary Tract Infections/diagnosis , Antigens, Bacterial , Child , Chronic Disease , Escherichia coli Infections/diagnosis , Follow-Up Studies , Humans , Pyelonephritis/diagnosis , Recurrence , Serotyping
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