Effects of food deprivation on midbrain 5-HT1A autoreceptors in Lewis and SHR rats

Food deprivation stimulates the activity of the hypothalamo-pituitary-adrenal axis and brain serotonin (5-hydroxytryptamine, 5-HT) synthesis. Because midbrain somato-dendritic 5-HT1A autoreceptors may obey homologous and heterologous (e.g. by glucocorticoids) down-regulation, we have analyzed whether 24 hr of fasting affects midbrain 5-HT1A receptor binding and sensitivity in Lewis and SHR rats (i.e. strains that differ in behavioral/neuroendocrine responses to stressors). Fasting affected neither [3H]8-hydroxy-2-(di-N-propylamino)tetralin ([3H]8-OH-DPAT) binding at 5-HT1A autoreceptors nor 8-OH-DPAT-induced inhibition of midbrain 5-HT synthesis (an index of 5-HT1A autoreceptor sensitivity). Because fasting increased 5-HT precursor (tryptophan) levels to similar extents in the midbrains of saline- and 8-OH-DPAT-treated rats, we conclude that food deprivation does not affect 5-HT1A autoreceptors. In turn, our results suggest that the differential effects of 5-HT1A receptor agonists on food intake, in fed and fasted rats may be independent from 5-HT1A autoreceptors.

Administration of AVP to the area postrema alters response of NTS neurons to afferent inputs

This study was designed to determine if arginine vasopressin (AVP) facilitates the response of nucleus of the solitary tract (NTS) neurons to baroreceptor input. In anesthetized sinoaortic-denervated vagotomized rabbits, AVP was intravenously infused (15 microg x kg(-1) x min(-1), 1 min) or microinjected into the area postrema (AP; 1 ng/nl, 10 nl). Extracellular recordings of evoked NTS neuronal responses to electrical stimulation of the aortic depressor nerve (ADN) or vagus nerve (1 Hz, 2-20 V, 0.05-0.6 ms) were evaluated before and after AVP administration. In neurons receiving input from the ADN (n = 19), 58% of them increased their responses after AVP (40.3 +/- 5.0 to 71.5 +/- 4,8%, P < 0.001). Similarly, in neurons activated by vagal stimulation (n = 22), 55% of them were facilitated during AVP administration (59.7 +/- 12.8 to 90.8 +/- 10.7%, P < 0.01). This action of AVP was independent of the mode of AVP administration, since either microinjection or venous infusion was effective in augmenting responses of NTS neurons to aortic/vagal stimulation. In an additional 37 spontaneous NTS neurons, AVP showed no effect on the mean baseline firing rate (8.9 +/- 1.3 vs. 9.6 +/- 1.3 spikes/s, P > 0.05), but increased neuronal activity in 54% of neurons (6.9 +/- 1.3 vs. 13.1 +/- 1.7 spikes/s, P < 0.01). In two rabbits pretreated with vasopressin antagonist (15 microg/kg iv), AVP failed to produce facilitatory effects (n = 8). The results of this study provide evidence in support of the hypothesis that circulating peptides modulate the arterial baroreflex via activation of neurons in the AP.

Modification of feed intake response to a beta 2-agonist by bovine somatotropin in lactating or dry dairy cows

The aim of this experiment was to show whether growth hormone could increase the effect of the beta 2-adrenergic agonist clenbuterol on feed intake. Two groups of Holstein cows [lactating (n = 4) and dry (n = 4)] were used to rule out the possible effects of increased energy requirements on feed intake. Treatments were administered according to a crossover experimental design with two 13-d periods and an 8-d readjustment interval. Treatments consisted of daily injections of 40 mg of bST or a placebo. Moreover, clenbuterol (3.16 micrograms/kg of BW) or saline challenges were infused intravenously for 4 h either on d 8 or on d 11 of each period. The cows were offered a dehydrated total mixed diet for ad libitum intake for 4 h twice daily. For both groups of cows, clenbuterol reduced DMI on the experimental day only, and bST intensified the effects of clenbuterol on DMI, causing a sharper decrease in DMI over 2 d. This enhancement of clenbuterol activity modified certain metabolic parameters including higher lipid mobilization during infusion and higher glycogenolysis. For dry cows, the initial rate of eating was reduced under bST treatment alone. During early lactation, bST, either by itself or through increased beta 2-adrenergic stimulation may restrict the development of intake by dairy cows over a few weeks.

Interactions between vasopressin and baroreflex control of the sympathetic nervous system

1. In addition to its effects at the renal tubules to influence water retention and at vascular smooth muscle to cause vasoconstriction, the hormone arginine vasopressin also appears to modulate cardiovascular reflex control of the sympathetic nervous system. Infusion or endogenous release of vasopressin results in enhanced baroreflex sympatho-inhibitory responses compared with other pressor agents. In addition, when changes in arterial pressure are imposed on an elevated background level of circulating vasopressin, due either to infusion or endogenous release, the arterial baroreflex response is shifted to lower pressures, and the maximum sympatho-excitation to a decrease in pressure is reduced. 2. Evidence suggests that vasopressin may influence cardiovascular reflex function at multiple sites. Nevertheless, the primary site involved in the effects of circulating vasopressin on baroreflex function appears to be in the central nervous system, specifically in the area postrema. Lesion of the area postrema abolishes the ability of circulating vasopressin to modulate arterial baroreflex and cardiopulmonary reflex function and electrical or chemical stimulation of this circumventricular organ mimics the effects of vasopressin. In addition, vasopressin has been shown to influence the activity of area postrema neurons in vivo and in vitro. Although not all studies agree, the effects of the area postrema and vasopressin on cardiovascular reflex function appear to be dependent on afferent input from peripheral baroreceptors. 3. Most evidence suggests that vasopressin exerts its effects on baroreflex function through a V1 vasopressin receptor mechanism. Systemic administration or microinjection into the area postrema of a specific V1 receptor antagonist abolishes the action of arginine vasopressin on arterial baroreflex and cardiopulmonary reflex control of the sympathetic nervous system. 4. The ability of vasopressin and the area postrema to influence baroreflex function appears to be dependent on an alpha 2-adrenoceptor mechanism at the level of the nucleus tractus solitarius (NTS). Blockade of alpha 2-adrenoceptors in the NTS abolishes the effects of vasopressin and the area postrema on the sympathetic nervous system. Facilitation of NTS processing of baroreceptor afferent inputs by the area postrema could contribute to the enhanced sympatho-inhibition and shift of the baroreflex curve to lower pressures during elevations in circulating vasopressin.

Subcellular mechanisms of angiotensin II and arginine vasopressin activation of area postrema neurons

Angiotensin II (ANG II) and arginine vasopressin (AVP) act on area postrema (AP) neurons to modulate the baroreflex. Because activation of AP neurons by either ANG II or AVP increases intracellular free Ca2+ concentrations ([Ca2+]i), the goal of this study was to analyze the factors affecting the [Ca2+]i responses to ANG II and AVP. Neurons were recovered from 14- to 16-day old rats and studied after 8-14 days in culture by use of the microscopic digital image analysis for fura 2-loaded cells. The effects of ANG II (100 nM) and AVP (100 nM) on [Ca2+]i were determined in normal (2 mM) and low (< 10 nM) extracellular Ca2+ concentrations. In 143 of 240 neurons, ANG II increased [Ca2+]i 4.65-fold after 20 s, and a similar response was observed in the absence of extracellular Ca2+ (3.65-fold after 20 s). After 60 s of observation, steady-state levels of increased [Ca2+]i were still present under both conditions. Pretreatment with AT1 antagonist or pertussis toxin abolished the response to ANG II. AVP also increased [Ca2+]i (3.6-fold at peak, 20 s) in normal and low extracellular Ca2+. Pretreatment with AVP V1 antagonist or pertussis toxin abolished the response to AVP. This study indicates that ANG II-induced increases in [Ca2+]i are independent of extracellular Ca2+ concentrations and involve the activation of AT1 receptors and a pertussis toxin-sensitive G protein. Although AVP affects a fewer number of AP neurons, the mechanisms of activation are also independent of extracellular Ca2+ concentration and are mediated by a pertussis toxin-sensitive G protein.

Synaptic connections and interactions between area postrema and nucleus tractus solitarius

The purpose of this study was to examine whether there are separate excitatory and inhibitory pathways from the area postrema (AP) to the nucleus tractus solitarius (NTS) and to examine the synaptic interactions between inputs from the AP and solitary tract (ST) on the NTS neurons. The following observations were made: (1) the predominant projections from the AP to the NTS were excitatory. Among the cells that had AP input, 90% of the cells (43/48) were excited by AP stimulation while 10% (5/48) of the cells were inhibited; (2) inputs from the AP and ST mainly summated occlusively on the NTS neurons, but at near threshold of discharge, the input from one source could facilitate the generation of action potentials induced by the other; and (3) single conditioning stimulation of the AP did not significantly inhibit the NTS neuronal response to ST stimulation, but stimulation of the AP with a train of high frequency stimuli inhibited the response of NTS neurons to ST stimulation and inhibited the evoked response to AP stimulation. The results of this study may help in the understanding of the modulatory role of the AP in the baroreflex and the integration process in the NTS.

Construction and characterization of an azurin analog for the purple copper site in cytochrome c oxidase

A protein analog of a purple copper center has been constructed from a recombinant blue copper protein (Pseudomonas aeruginosa azurin) by replacing the loop containing the three ligands to the blue copper center with the corresponding loop of the CuA center in cytochrome c oxidase (COX) from Paracoccus denitrificans. The electronic absorption in the UV and visible region (UV-vis) and electron paramagnetic resonance (EPR) spectra of this analog are remarkably similar to those of the native CuA center in COX from Paracoccus denitrificans. The above spectra can be obtained upon addition of a mixture of Cu2+ and Cu+. Addition of Cu2+ only results in a UV-vis spectrum consisting of absorptions from both a purple copper center and a blue copper center. This spectrum can be converted to the spectrum of a pure purple copper by a prolonged incubation in the air, or by addition of excess ascorbate. The azurin mutant reported here is an example of an engineered purple copper center with the A480/A530 ratio greater than 1 and with no detectable hyperfines, similar to those of the CuA sites in COX of bovine heart and of Paracoccus denitrificans.

Chronic neurosteroid treatment attenuates single cell GABAA response and its potentiation by modulators in cortical neurons

In previous studies we have observed that chronic neurosteroid 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha) treatment produced downregulation of the GABAA receptors, heterologous uncoupling, and decreased heterologous efficacy at the GABAA receptor complex in cultured mammalian cortical neurons. In this study, using whole cell recording, we examined the consequence of chronic 5 alpha 3 alpha (1 microM; 5 days) treatment on GABA-induced currents in isolated cortical neurons. We observed that the GABA current was decreased by 78% after 5 days treatment of cortical cells with 1 microM 5 alpha 3 alpha. We also observed decreased pentobarbital, and 5 alpha 3 alpha potentiation of GABA currents after chronic 5 alpha 3 alpha treatment. These findings support the notion that GABA response, and its potentiation by pentobarbital, and neurosteroid, 5 alpha 3 alpha, are attenuated after chronic 5 alpha 3 alpha treatment.

Area postrema voltage-activated calcium currents

1. Calcium currents in rabbit area postrema neurons were studied with the perforated patch-clamp technique. Experimental conditions eliminated Na+ and K+ currents and identified both low- and high-threshold voltage-activated calcium currents. 2. Low-threshold, T-type calcium currents were observed in 64% of the area postrema neurons recorded. This current activated near -60 mV and had an average peak amplitude of -36.2 +/- 5 pA (mean +/- SE) at -40 mV. This current began rapid inactivation near -95 mV, reached half-maximal inactivation at -71 mV and was totally inactivated by -40 mV. 3. A high-threshold transient current was recorded in all area postrema neurons, which consisted of both a transient and sustained component. This current was present at voltages greater than -40 mV and the transient component of this current was responsible for the majority of the total Ca2+ current. 4. Nickel ions (10 microM) effectively reduced both the T-type current and the high-threshold current. Cadmium ions (100 microM) effectively reduced the high-threshold current while having insignificant effects on the low-threshold current. 5. Application of the dihydropyridine antagonist nimodipine (1-10 microM) had no effect on either the low- or high-threshold voltage-activated calcium Ca2+ in area postrema neurons. In addition, application of omega-conotoxin-GVIA (2-10 microM) was also without effect on either the low- or high-threshold voltage-activated Ca2+ current, suggesting that area postrema neurons possess neither L- or N-type voltage-activated Ca2+ currents. 6. Application of omega-conotoxin MVIIC (10 microM) significantly inhibited the peak high-threshold Ca2+ current by 65.4% suggesting that area postrema neurons do possess a omega-conotoxin MVIIC-sensitive high-threshold Ca2+ channel. 7. Arg-vasopressin (150 nM) significantly increased the transient component of the high-threshold Ca2+ current but had little effect on either the low-threshold or the high-threshold sustained component.

Changes in sexual function after radiotherapy treatment of prostate cancer

OBJECTIVE

To assess sexual function before and after definitive irradiation for the treatment of cancer of the prostate.

PATIENTS AND METHODS

The study comprised 67 patients (mean age 68 years) treated in five radiotherapy departments and assessed with repeated questionnaires about their libido, arousal, frequency and quality of intercourse, and sexual satisfaction. Interviews were obtained before radiotherapy and at the end of the first year after treatment. Sixty-three patients were married and 50 had a sexually effective partner. Forty-six patients presented with another pathology or medical treatment capable of inducing sexual dysfunction. Before radiotherapy, 40 patients were sexually active, with good to acceptable intercourse.

RESULTS

Between 10 and 24 months after the end of radiotherapy, no disease progression was observed and prostate-specific antigen levels remained high in only two patients. Sexual function was preserved in 67% of patients but only 50% observed no change. The functional prognosis seemed to be related to the initial frequency and quality of intercourse; more than three times per month, the prognosis remained good, under three per month, it was poor. The patient's age was a predictive factor for the frequency of intercourse.

CONCLUSION

Several causes of impairment of sexual function may be associated and can change over a long time. A longer survey should be conducted to analyse the organic response to radiation.

Membrane properties of area postrema neurons

Intrinsic membrane properties, voltage-dependent sodium and voltage-dependent potassium currents of area postrema neurons in culture have been characterized with respect to their voltage dependence, time dependence and sensitivity to specific blocking agents. The area postrema is a hindbrain circumventricular organ which is known to have an important role in the central regulation of cardiovascular function. This study is the first to describe the biophysical properties of ion channels present in rat area postrema neurons. Recordings in current-clamp mode revealed a mean resting membrane potential of -55.0 +/- 1.6 (n = 24) mV and an input resistance of 213.6 +/- 23 M omega. For the 24 neurons tested, the evoked action potential had a mean threshold of 38.8 +/- 2 mV and a mean amplitude of 107.3 +/- 15 mV. Our results show that the area postrema possesses only one principle sodium current which is completely abolished by 5 microM tetrodotoxin (TTX) (n = 28). This current activated near -50 mV and reached peak amplitude at -30 mV. The area postrema does not possess a TTX insensitive sodium current. The area postrema has at least two types of potassium currents. All area postrema neurons studied with tetraethylamonium (TEA) (n = 40) showed the presence of a slowly activating outward current which was present at voltages greater than -40 mV and was blocked by 10 mM TEA. In addition, 75% of the neurons studied (n = 30/40) also showed a rapidly inactivating, 4-AP sensitive IA type current which activated near -30 mV. Angiotensin II attenuated both the peak and the steady-state potassium currents, suggesting that angiotensin II may modulate area postrema activity by inhibiting voltage-gated potassium channels.

Metabotropic glutamate receptor inhibition of visceral afferent potassium currents

The effects of metabotropic glutamate receptor activation (mGluR) on voltage-gated potassium currents have been characterized in visceral sensory afferent neurons. L-Glutamate is known to be a primary neurotransmitter in visceral afferents which terminate at the level of the nucleus of the solitary tract (NTS). Synaptic communication between these afferents and the NTS has been shown to involve both postsynaptic ionotropic and presynaptic metabotropic glutamate receptor activation. The purpose of the present study was to determine the effects of mGluR activation on voltage-gated potassium currents in visceral sensory neurons. Application of mGluR agonist t-ACPD inhibited both the peak and the steady state voltage-gated potassium current in 39 out of 56 visceral afferent neurons tested (70%) by 22.0 +/- 3 and 22.8 +/- 2%, respectively. Voltage and pharmacological protocols were utilized to isolate the potassium current affected by mGluR activation. Increasing the holding potential from -100 mV to -30 mV only partially attenuated the inhibitory effects of t-ACPD (decreased effect by 11%), suggesting that t-ACPD modulates both a voltage insensitive and a voltage-sensitive potassium current. In addition, 4-aminopyridine (5 microM) was applied to eliminate the 4-AP sensitive transient current. Also, this protocol only partially attenuated the inhibitory effects of t-ACPD (decreased effect by 6.3%), suggesting that mGluR activation inhibits both a 4-AP-sensitive and 4-AP-insensitive potassium current in visceral afferent neurons. Results from this study suggest that mGluRs may regulate visceral sensory afferent neuronal activity through inhibition of voltage-gated potassium channels.

Intra-operative radiotherapy in soft tissue sarcomas

We treated 31 soft tissue sarcoma bearing patients with intraoperative radiation therapy (IORT) with ages ranging from 26 to 71: first curative intent treatment, 16 patients; and recurrent tumors, 15 patients. The tumor site was the pelvis and the retroperitoneal spaces in 13 patients and the limbs or the trunk in 18 patients. The histological type was: malignant histiocytofibroma, 14 patients; liposarcomas, 10 patients; malignant schwanoma, 1 patient; leiomyosarcoma, 2 patients; hemangiopericytoma, 1 patient; embryonic rhabdomyosarcoma, 2 patients; and synovialosarcoma, 1 patient. All the patients were diagnosed without any distant metastatic evolution at the moment of the treatment. All the patients except one underwent a complete surgical excision without any gross residual disease and received an intraoperative radiation single dose of 10 Gy in one case, 12.5 Gy in one case, 13 Gy in one case, 15 Gy in 17 cases, 18 Gy in three cases, 20 Gy in seven cases and 25 Gy in one case. Thereafter the treatment was completed by a postoperative X-ray dose of 45-50 Gy in 4.5-5 weeks for 16 patients. Local control (LC) was obtained in 27 out of 31 patients (87%), with a minimal follow-up duration of 2 years. Eleven out of 31 patients died: seven with local control (one from an intercurrent disease, six from distant metastasis) and four with local failure inside the IORT fields. Twenty patients are alive with no evolutive disease in 19 cases and with a distant metastasis in one case.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamate metabotropic receptor inhibition of voltage-gated calcium currents in visceral sensory neurons

1. Metabotropic glutamate receptors (mGluRs) have been suggested to modulate neurotransmission of glutamatergic pathways via autoreceptive action. Visceral sensory afferents and baroreceptor afferents in particular are thought to utilize L-glutamate (L-glu) as a primary neurotransmitter. The purpose of this study was to investigate whether visceral sensory afferents possess a mGluR and determine the effect of mGluR activation on voltage-gated calcium currents in these neurons. 2. Activation of mGluRs by the selective agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD) reversibly suppressed the voltage-gated calcium currents in visceral sensory afferents of the nodose ganglion. Concentrations of t-ACPD ranging from 50 to 1,000 microM consistently decreased the evoked calcium current with a maximum suppression of the peak current of 25-30%. This response was repeatable and reversible within a given cell. 3. Metabotropic GluR activation selectively decreased the high-threshold calcium current evoked from step potentials greater than -30 mV and had no effect on the low-threshold calcium current. The inhibitory effects of t-ACPD on the high-threshold channel was partially blocked by omega-conotoxin (omega-CTx-GVIA) suggesting that at least part of the effects of mGluR inhibition of the voltage-gated calcium current is because of a modulation of the omega-CTx-GVIA sensitive high-threshold current. 4. Finally, the inhibitory effects of quisqualate (quis) on the high-threshold calcium current were blocked by pretreatment of the neurons with pertussis toxin (PTX). These results suggest that visceral sensory afferents do possess a PTX-sensitive mGluR and activation of this receptor results in the inhibition of a omega-CTx-GVIA sensitive high-threshold calcium channel.

Stimulation of area postrema by vasopressin and angiotensin II modulates neuronal activity in the nucleus tractus solitarius

There is an abundance of evidence suggesting that the area postrema (AP) is involved in the central actions of arginine-vasopressin (AVP) and angiotensin II (Ang II) on cardiovascular regulation. Furthermore, recent studies have shown that activation of the AP facilitates the response of nucleus tractus solitarius (NTS) neurons to tractus stimulation. In the present study, using the perfused rabbit brain slice preparation, we examined the response of NTS neurons when AVP and Ang II were microinjected onto the AP. Spontaneous or solitary tract stimulation-induced neuronal activity was recorded extracellularly from the medial NTS before, during and after AVP or Ang II application. An increase or decrease in activity by more than 30% of the baseline value was considered excitatory or inhibitory. The effects of AVP were studied in 57 NTS cells, 14 of which were spontaneously active and 43 were driven by tract stimulation. Of the cells with evoked activity, 49% were excited, 19% were inhibited, and 32% did not respond. The percentage of cells responding to AVP was similar in spontaneously active cells. The effects of Ang II were tested in 85 cells including 54 with evoked activity and 31 with spontaneous activity. In NTS cells with evoked activity, AP application of Ang II caused inhibition in 37%, excitation in 7%, while 56% did not respond. The proportion of cells responding to Ang II was similar in spontaneously active cells. These results suggest that AVP may act on the AP to increase the excitatory response of NTS neurons while the actions of Ang II result in an inhibitory influence.

A- and C-type rat nodose sensory neurons: model interpretations of dynamic discharge characteristics

1. Neurons of the nodose ganglia provide the sole connection between many types of visceral sensory inputs and the central nervous system. Electrophysiological studies of isolated nodose neurons provide a practical means of measuring individual cell membrane currents and assessing their putative contributions to the overall response properties of the neuron and its terminations. Here, we present a comprehensive mathematical model of an isolated nodose sensory neuron that is based upon numerical fits to quantitative voltage- and current-clamp data recorded in our laboratory. Model development was accomplished using an iterative process of electrophysiological recordings, nonlinear parameter estimation, and computer simulation. This work is part of an integrative effort aimed at identifying and characterizing the fundamental ionic mechanisms participating in the afferent neuronal limb of the baroreceptor reflex. 2. The neuronal model consists of two parts: a Hodgkin-Huxley-type membrane model coupled to a lumped fluid compartment model that describes Ca2+ ion concentration dynamics within the intracellular and external perineuronal media. Calcium buffering via a calmodulin-type buffer is provided within the intracellular compartment. 3. The complete model accurately reproduces whole-cell voltage-clamp recordings of the major ion channel currents observed in enzymatically dispersed nodose sensory neurons. Specifically, two Na+ currents exhibiting fast (INaf) and slow tetrodotoxin (TTX)-insensitive (INas) kinetics; low- and high-threshold Ca2+ currents exhibiting transient (ICa,t) and long-lasting (ICa,n) dynamics, respectively; and outward K+ currents consisting of a delayed-rectifier current (IK), a transient outward current (I(t)) and a Ca(2+)-activated K+ current (IK,Ca). 4. Whole-cell current-clamp recordings of somatic action-potential dynamics were performed on enzymatically dispersed nodose neurons using the perforated patch-clamp technique. Stimulus protocols consisted of both short (< or = 2.0 ms) and long (> or = 200 ms) duration current pulses over a wide range of membrane holding potentials. These studies clearly revealed two populations of nodose neurons, often termed A- and C-type cells, which exhibit markedly different action-potential signatures and stimulus response properties. 5. Using a single set of equations, the model accurately reproduces the electrical behavior of both A- and C-type nodose neurons in response to a wide variety of stimulus conditions and membrane holding potentials. The structure of the model, as well as the majority of its parameters are the same for both A- and C-type implementations.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of exercise on the oral consumption of morphine and methadone in rats

Endogenous opioid peptides have been hypothesised to play a regulatory role in exogenous opiate agonist dependence. It was hypothesised that exercised rats would demonstrate increased beta-endorphin (beta EP) levels and decreased exogenous opiate intake. After providing morphine or methadone as their sole liquid, drug preference levels were determined by amounts of exogenous opiate consumed when rats were offered a choice between drugged and nondrugged solutions. Treatment animals were exercised in a treadmill and were found to consume significantly less exogenous opiate than control animals. Plasma, pituitary, and whole brain beta EP levels were nonsignificantly higher in exercised animals. Differences were observed in the drug ingestion patterns of morphine- and methadone-exposed rats.

Calcium-activated potassium channels in rat visceral sensory afferents

The purpose of the present study was to describe, at the single-channel level, the activity of a calcium-sensitive potassium channel in rat visceral-sensory neurons which has been suggested to be involved in sensory neuron excitability. Single-channel recordings in the inside-out configuration identified a 220 pS conductance calcium-activated potassium channel (KCa). From a -20 mV holding potential, increasing [Ca2+]i from 0.01 microM to 1.0 microM increased the open probability of this channel 92% (from 0.12 to 0.23). However, from a +20 mV holding potential, increasing [Ca2+]i from 0.01 to 1.0 microM increased the open probability by 326% (from 0.15 to 0.64). In addition, this large conductance KCa channel was blocked by TEA (1.0 microM) and charybdotoxin (40 microM) when applied to the external surface. These results are the first to characterize a large conductance KCa channel in the sensory afferent neurons of the rat nodose ganglia and should further expand the understanding of the ionic currents involved in the regulation of sensory afferent neuronal activity.

An intermediate conductance calcium-activated potassium channel in rat visceral sensory afferent neurons

Whole-cell and single channel recordings were used to characterize an intermediate conductance calcium-activated potassium (KCa) channel in sensory neurons of the nodose ganglion. From a -80 mV holding potential, the total outward current in these neurons was increased when extracellular calcium was raised from 0.02 to 5 mM. This calcium-evoked outward current was not blocked by either charybdotoxin (50 nM) or apamine (40 nM). In the inside-out patch configuration, the current-voltage relationship for this channel was linear between -60 and +60 mV in symmetrical 145 mM potassium aspartate (KAsp) and possessed a conductance of approximately 60 picosiemens (pS). Increasing [Ca2+]i from 0.01 microM to 1.0 microM markedly increased the cumulative open probability of this channel and the effect of increasing [Ca2+]i on these channels was not voltage dependent. In the outside-out patch configuration, neither tetraethylammonioum (TEA), (1 mM), apamine (40 nM) or charybdotoxin (ChTx) (50 nM) had any effect on the activity of this channel. These results provide new evidence for the existence of pharmacologically distinct intermediate conductance KCa channel in sensory afferent neurons.

Molecular maturation of cell adhesion systems during mouse early development

During cleavage, the mouse embryo expresses a variety of cell adhesion systems on its cell surfaces. We have reviewed biogenetic and assembly criteria for the formation of the uvomorulin/catenin, tight junction and desmosome adhesion systems as the trophectoderm differentiates. Each system reveals different mechanisms regulating molecular maturation. Adhesion processes contribute to the generation of distinct tissues in the blastocyst by modifying the expression pattern of blastomeres entering the non-epithelial inner cell mass lineage. Cell adhesion also influences the spatial organisation, but rarely the timing of expression, of proteins involved in trophectoderm differentiation.

Biogenesis of structural intercellular junctions during cleavage in the mouse embryo

The preimplantation embryo differentiates the trophectoderm epithelium which, from the 32-cell stage, generates the blastocoel of the blastocyst and, after implantation, gives rise to most extraembryonic lineages of the conceptus. Trophectoderm differentiation begins at compaction (8-cell stage) when cell-cell adhesion, mediated by uvomorulin, and epithelial cell polarisation first occur. Here, we review our work on the biogenesis of tight junctions and desmosomes during epithelial differentiation. Tight junction construction begins at compaction and appears to be a gradual process, both at morphological and molecular levels. This maturation pattern may be due in part to sequential expression of tight junction constituents from the embryonic genome. Tight junction formation is dependent upon uvomorulin adhesion but can be inhibited by different means without apparently disturbing cell adhesion or polarisation. Cell interactions appear to regulate tight junction tissue specificity, in part by controlling the level of synthesis of constituents. Desmosome formation begins at the 32-cell stage, particularly as the embryo initiates blastocoel accumulation, and, in contrast with tight junction formation, does not appear to be a gradual process. Thus, nascent desmosomes appear mature in terms of their molecular composition. Desmosomal proteins are synthesised well in advance of desmosome formation but the synthesis of the principal glycoprotein components begins at the blastocyst stage and may regulate the timing of junction assembly. Implications of these differing patterns of biogenesis for the embryo are discussed.

Open half-pin insertion for distal radial fractures

Twenty-two patients with unstable distal radial fractures were treated with external fixation using the open technique for half-pin insertion. Of the final study group of 19 patients, 7 (37%) demonstrated early pin-tract drainage, which resolved within 2 weeks after insertion. No pin loosening, pin change, pin breakage, infection, dorsal sensory nerve entrapment or irritation, tendon injury, or additional radial fracture occurred. Wrist range of motion in flexion/extension was 51/47 degrees, and the grip strength ratio (injured versus non-injured side) was approximately 61% on follow-up (average, 8 months). The open technique has proved efficacious in reducing complications associated with external fixation.

Characteristics and zona binding ability of FRESH and cooled domestic cat epididymal spermatozoa

Maintenance of genetic diversity within endangered species is important for ensuring healthy populations. Because unexpected deaths can occur, it would be advantageous to salvage gametes to effect posthumous participation in species reproduction. Using the domestic cat as a model for nondomestic felids, this investigation was undertaken to determine epididymal sperm cell characteristics, capacitation timing and the effects of storage temperature on fertilizing ability. In Study 1, the timing of capacitation was evaluated by examining zona attachment of spermatozoa to in vitro matured oocytes at 30-min intervals for 5 h. In Study 2, the ability of freshly collected (FRESH) and overnight cooled (COOL) epididymal spermatozoa to undergo capacitation and nuclear decondensation was evaluated using the zona attachment and zona-free hamster ova penetration assays. From Study 1, mean characteristics (n=29) for epididymal sperm cell motility and progressive status were 51.9% and 3.1+/-0.1, respectively, with a concentration of 80.3 x 10(6) spermatozoa/ml and 51% morphologically normal cells. Zona attachment (n >/= 25 ova/time interval) by sperm cells occurred at each time interval, but both the mean number of attached sperm cells/zona and the percentage of zonae with attached spermatozoa reached maximum values at 240 min (12.0+/-2.1 and 89.7%, respectively; P<0.05). In Study 2, overnight cooling did not affect progressive status of motility (3.3+/-0.1) or the percentage of morphologically normal spermatozoa (53.2+/-4.4) compared with that of FRESH (2.9+/-0.1, 50.7+/-3.2%) samples; however, motility was 14% lower (P<0.05) in the COOL vs FRESH group. Hamster ova penetration and the mean number of sperm cells attached/zona were greater in the COOL (28%, 18.6+/-5.7) than in the FRESH (5%, 7.4+/-2.0) group (P<0.05). However, it is speculated that the increased sperm-zonae interaction may have been the result of acrosomal damage. Nevertheless, these data demonstrate that domestic cat epididymal sperm cells have the ability to capacitate and undergo the first stages of fertilization.

Association of silicosis, lung dysfunction, and emphysema in gold miners

BACKGROUND

In an earlier study of gold miners men with silicosis were found to have abnormal lung function, including airflow obstruction and reduced diffusing capacity. In a follow up study a sample of these men was examined by computed tomography to determine whether emphysema accounted for these abnormalities, which are associated with silicosis in this working population.

METHODS

A sample of 70 men from a cohort of older gold miners with and without silicosis who had worked underground for a mean period of 29 years was examined by computed tomography to determine whether each man had emphysema. In addition, each man had lung function tests and routine chest radiography (125 kV).

RESULTS

A total of 48 men had emphysema on examination by computed tomography. On the basis of the results in a chest radiograph 55 of the men had silicosis. Emphysema was related to silicosis, being present in five of the 15 men without silicosis and in 43 of the 55 with silicosis. Diffuse emphysema was apparent in two men without silicosis (14%) and in 25 men with silicosis (45%). The proportion of men with diffuse emphysema increased from 14% in those with International Labour Organisation category 0 nodule profusion to 46% in those with category 1, 48% in those with category 2, and 67% in those with category 3. Emphysema was also related to smoking: eight of the 18 who had never smoked and 40 of the 52 smokers had emphysema. All of those who had never smoked and had emphysema had silicosis with category 2/2 or greater nodule profusion. Lung function tests showed changes associated with silicosis that could be explained by the associated emphysema.

CONCLUSIONS

In this population emphysema occurred in association with silicosis and accounted for the abnormalities in lung function associated with silicosis.