Extrinsic Stimulation Research Articles

1,25-Dihydroxycholecalciferol modulates 3H-thymidine incorporation in FRTL5 cells.

1,25-dihydroxycholecalciferol (1,25(OH)2D3) possesses proliferation and differentiation modulating effects in many cell types in vitro. We studied the effect of 1,25(OH)2D3 on 3H-thymidine incorporation in FRTL5 cells, a cultured rat thyroid follicular cell line. 1,25(OH)2D3 alone at 10(-11) and 10(-9) M exerted no effect on 3H-thymidine incorporation. However, at 10(-7) M, 1,25(OH)2D3 slightly enhanced 3H-thymidine incorporation. In the presence of 5% calf serum, 1,25(OH)2D3 increased 3H-thymidine incorporation induced by calf serum in a dose-dependent manner. 1,25(OH)2D3 also enhanced 3H-thymidine incorporation induced by PMA, an extrinsic stimulator of protein kinase C, without directly affecting PMA-induced protein kinase C translocation. In contrast to the stimulatory effects of 1,25(OH)2D3 on the calf serum and PMA-induced 3H-thymidine incorporation, 1,25(OH)2D3 inhibited the increase in 3H-thymidine incorporation induced by TSH in a dose-dependent manner. This effect of 1,25(OH)2D3 on TSH-induced 3H-thymidine incorporation may be, in part, due to post-cAMP pathways since 1,25(OH)2D3 also inhibited the increase in 3H-thymidine incorporation induced by Bu2cAMP without affecting the TSH-induced increase in cAMP. The stimulatory effect of insulin on 3H-thymidine incorporation, a cAMP-independent process, was also inhibited by 1,25(OH)2D3. We conclude that 1,25(OH)2D3 affects 3H-thymidine incorporation in FRTL5 cells raising the possibility of a physiologic role for 1,25(OH)2D3 in the growth and function of thyroid follicular cells.

Occupational or extrinsic stimulation factors and initial signs of progressive systemic sclerosis.

Forty-eight patients with progressive systemic sclerosis (PSS) (man-woman ratio, 7:41) were studied, and detailed questionnaires were used to clarify the relationship between occupational stresses and the initial signs of PSS. All of the patients were right-handed. Raynaud sign was seen in 37 of the 48 patients (77.1%) as the predominant initial sign of PSS, and it first was noticed on the right index and middle fingers. Three sets of extrinsic aggravating factors, vibration stress, fine hand work with mental stress, and exposure to cold, were believed to be related closely to the development of the initial signs because the initial signs appeared after long-term exposure to the extrinsic factors.

Visually Evoked Potentials in Response to Rotating Plane-Polarized Blue Light

Visually evoked cortical potentials closely related to the appearance and disappearance of Haidinger's brushes were obtained in response to onset and offset of rotation of plane-polarized blue light. The method provides a means of investigating macular function in man; it is fairly independent of ocular opacities and relates, for the first time, entoptic phenomena to those evoked by extrinsic light stimulation.

Some membrane properties of the circular muscle of chicken rectum and its non-adrenergic non-cholinergic innervation.

1. Membrane properties and innervation of the circular muscle of chicken rectum were investigated by recording intracellularly electrotonic potentials evoked by passing current, and excitatory and inhibitory junction potentials (EJPs and IJPs) evoked by electrical stimulation of the extrinsic or intrinsic nerves. 2. The membrane potential was -55 +/- 0.6 mV (n = 95). Action potentials of long duration (1.2-4.0 s) discharged spontaneously, or were generated when the membrane depolarization due to either electrotonic potential or EJP reached the threshold. The drug D600 blocked the generation of action potentials. 3. Electrotonic potentials spread fairly well in the longitudinal direction of the muscle fibres but not in the transverse direction. The longitudinal space constant was 1.7 +/- 0.2 mm (n = 10) and the membrane time constant was 205 +/- 21 ms (n = 10). 4. Field stimulation of intramural nerves evoked an EJP followed by a long-lasting IJP (3-12 s in total duration) in most cells, and an EJP alone or an IJP alone in a small number of cells. The EJP and IJP were preserved in the simultaneous presence of atropine and guanethidine, but abolished with tetrodotoxin. 5. Stimulation of Remak's nerve trunk or its branches produced EJPs which were atropine resistant and guanethidine resistant just like the EJP elicited by intramural nerve stimulation. The extrinsic nerve stimulation was ineffective in eliciting IJPs. 6. The EJP amplitude declined in a linear manner as the distance from the stimulating site of intramural nerves was increased. The decline was much greater along the transverse axis than the longitudinal axis of circular muscle fibres. 7. The reversal potential for the EJP was estimated by extrapolation to be about - 15.3 +/- 0.3 mV (n = 7). 8. Apamin did not inhibit the IJP. During the hyperpolarization of a single IJP or summed IJPs, electrotonic potentials remained unchanged or slightly decreased in amplitude.

Unfamiliar environments impair information processing as measured by behavioral and cardiac orienting responses to auditory stimuli in preweanling and adult rats.

Placing animals in an unfamiliar environment triggers at least two major reactions: (1) a heightened state of arousal, fear, or distress and (2) a sharp increase in information processing as the animal attempts to learn about its new environment. These changes could have a profound effect on the way in which the animal reacts to the types of extraneous innocuous stimuli typically used to study learning and memory. For example, an increase in arousal or fear could either (1) make the animal more "attentive" to stimulus change resulting in a larger orienting response, or (2) produce a shift from orienting to defensive responding. Conversely, processing of the new stimuli present in the unfamiliar environment may make the animal less responsive to additional extrinsic stimulation. These possibilities were examined experimentally using both autonomic and behavioral measures of orienting and defensive responses. The results demonstrated that animals fail to exhibit either an orienting response or a defensive response to a novel auditory stimulus when they are first placed in an unfamiliar environment. With continued exposure to the test environment the orienting response appears and then shows a time-dependent increase in magnitude. This pattern of results was obtained in both preweaning and young adult rats. On the basis of additional research and analysis, it was concluded that a limitation in information processing capacity was the primary reason for the failure of the orienting response to occur when an animal is first placed in an unfamiliar test chamber.

Accessory cell neoplasia as a result of the breakdown of immunological regulation?

We have previously shown that the injection of spleen cells from old individual donors into young syngeneic recipients has two unexpected consequences (1). Firstly, in most recipients there is a gradual increase in the proportion of donor T cells and, secondly, the majority of the recipients develop tumours. These also derive from the donor inoculum. According to the classification of Dunn (2) they are type B reticulum cell neoplasms (RCN-B). The tumour cells have neither T nor B cell characteristics, most constitutively express class-II antigens, and those that have so far been tested function as accessory cells in in vitro assays (3–5). We have therefore suggested that they are the neoplastic counterpart of normal lymphoid dendritic cells (6). In the present paper the relationship between the two consequences of the injection of old cells is explored, and a hypothesis proposed to account for the finding that similar tumours, also of donor origin, can be induced in recipients of young syngeneic lymphocytes if they are subjected to repeated extrinsic antigenic stimulation.

Role of HLA class II and cytokine expression in rheumatoid arthritis.

HLA class II expression is notable in rheumatoid arthritis. We have investigated the mechanism of HLA class II regulation in the joints and found local synthesis, as judged by mRNA levels to be high. The role of antigen presentation in maintaining class II mRNA was explored, and blocking presentation by using monoclonal antibodies to HLA class II inhibited synthesis of mRNA for HLA-DR alpha chain. HLA class II expression is maintained by cytokines and so cytokine production in rheumatoid joints was investigated. It was chosen to use mRNA analysis by slot blotting as a screening assay, and the expression of many cytokines was detected. Levels of these were maintained in culture in the absence of extrinsic stimulation.

Gastrointestinal motility in relation to spontaneous meal occurrence in domestic fowls

The relationship between gastrointestinal (GI) motility and spontaneous feeding activity was investigated in five immature domestic hens, by recording simultaneously their feeding and contractions of the gizzard and duodenum. Different parameters of GI motility were interrelated, and gizzard contraction frequency (GCF) was used as an overall index of motility. Significant ( P < 0.05) changes in GCF relative to mealtimes varied between individual birds and between different meal length classes. The most consistent change was a rapid increase in GCF at the start of meals, followed by a decline which usually commenced before the end of long meals, but after the end of shorter ones. The increase in GCF commenced before the start of meals in one bird which had longer inter-meal intervals than the rest. There were no consistent changes in GCF at the ends of intervals or meals that might suggest a causal association between motility and hunger and satiety. It is suggested that the observed variation in GI motility may be accounted for mainly by variation in extrinsic stimulation from the vagus nerve.

Is co-transmission involved in the excitatory responses of the rat anococcygeus muscle?

1 Electrical and mechanical responses to field (transmural) and extrinsic nerve stimulation were recorded simultaneously in the rat anococcygeus muscle. Membrane potential changes recorded intracellularly following either method of stimulation were indistinguishable. Single stimuli usually produced a slow depolarization; trains of pulses produced a fast excitatory junction potential (e.j.p.) initially, followed by a slow depolarization similar to that produced by single pulses. The fast e.j.ps, the slow depolarizations and the accompanying contractions were abolished by the alpha-adrenoceptor antagonists, phentolamine (1 X 10(-6)M) or prazosin (1 X 10(-7)M) and by tetrodotoxin (TTX, 1 X 10(-6)M) but unaffected by alpha, beta-methylene adenosine triphosphate (alpha, beta-MeATP, 1(-10) X 10(-6)M), an agent known to desensitize purinoceptors. 2 Application of noradrenaline (NA, 1 X 10(-8)-1 X 10(-6)M), by pressure ejection from a micropipette, depolarized the membrane and produced a localized contraction, both of which were abolished by phentolamine (1 X 10(-6)M) or prazosin (1 X 10(-7)M). 3 Application of adenosine-5'-triphosphate (ATP, 1 X 10(-4)-1 X 10(-3)M), by pressure ejection from a micropipette, produced a small membrane depolarization and localized contraction which were unaffected by phentolamine (1 X 10(-6)M) or prazosin (1 X 10(-7)M) but abolished by alpha, beta-MeATP (1 X 10(-6)M). 4 The results show that, in the rat annococcygeus muscle, (1) field or extrinsic nerve stimulation released only one excitatory transmitter, namely NA, although receptors for both NA and ATP were present on the muscle, (2) alpha, beta-MeATP was selective for purinoceptors and (3) there was no evidence for excitatory co-transmission in this tissue.

Steroidogenic and morphological characteristics of granulosa and thecal compartments of the differentiating rabbit corpus luteum in culture.

On the day after ovulation, the thecal tissue and associated mural granulosa lutein cells of the rabbit corpus luteum were separated from the granulosa lutein 'core' by dissection and these tissues were cultured separately or together (whole corpus luteum) in defined medium for 10 days on stainless-steel grids. The medium was changed completely every 24 h. Replicate tissues were cultured with testosterone (10 ng/ml), but no other hormones were added to the medium. Progesterone production increased during the first 2 days of culture for whole corpus luteum, granulosa lutein cells and the thecal compartment which also included granulosa lutein cells. After 3 days, the production of progesterone declined gradually, but was still detectable on Day 10. The production of the metabolite, 20 alpha-dihydroprogesterone, by whole corpus luteum was equal to or greater than that of progesterone. Without the addition of testosterone, the granulosa lutein cells produced little (10 pg/culture) oestradiol during 1 day of culture, but the thecal compartment and whole corpus luteum each produced about 100 pg/culture on Day 1 and declining quantities over the next 2 days. In the presence of testosterone added to the medium, the formation of oestradiol was greatly increased for all tissues for 5-6 days of culture, after which time oestradiol was no longer detectable with or without testosterone in medium. Transmission electron microscopy of cells after 10-12 days of culture revealed fine structure that is characteristic of luteal cells, including abundant smooth endoplasmic reticulum, lipid droplets, and junctions between the luteal cells. The corpus luteum in culture resembles the corpus luteum in situ in that steroidogenesis and differentiation can proceed for a period after ovulation without extrinsic hormonal stimulation.

Afferent influences on brain stem auditory nuclei of the chicken: effects of conductive and sensorineural hearing loss on n. magnocellularis.

Nucleus magnocellularis is the avian homologue of the spherical cell region of the mammalian anteroventral cochlear nucleus. Its primary excitatory synaptic input is from large end bulbs of Held from the eighth nerve ganglion cells. We have examined the effects of three peripheral manipulations--middle ear ossicle (columella) removal (monaural and binaural), columella removal and oval window puncture (monaural), and monaural earplug--on cross-sectional cell area ("cell size") of second-order auditory neurons in n. magnocellularis of the chicken. Manipulations were performed between embryonic day 19 and posthatch day 4. Survival time was varied from 2 to 60 days. Air conduction and bone conduction thresholds were determined to assess for conductive and sensorineural hearing loss associated with each of these manipulations. Hair cell counts were made from basilar papillae of each experimental group. We found that a columella removal alone, which produced a 50-55-dB purely conductive hearing loss, was not associated with changes in cell size of n. magnocellularis neurons. Similarly, chronic monaural earplugging did not affect the cross-sectional area of these second-order auditory neurons. Conversely, a combined columella removal and oval window puncture, which produced a mixed hearing loss with a 15-40-dB sensorineural component was associated with an 18-20% reduction in n. magnocellularis cell area. Hair cell counts for experimental ears were not significantly different from control ears. These results, in conjunction with measurements of multiunit activity recorded in n. magnocellularis, suggest that manipulations which markedly attenuate extrinsic auditory stimulation, but do not result in chronic change in the average activity levels, also do not influence the size of n. magnocellularis cell bodies. On the other hand, a manipulation which influences overall activity levels, but does not result in degeneration of receptor cells, resulted in marked changes in n. magnocellularis cell size.

Some characteristics of transmission from non-adrenergic, non-cholinergic excitatory nerves to the smooth muscle of the chicken

Non-adrenergic, non-cholinergic excitatory junction potentials (e.j.p.s) were recorded from the longitudinal muscle cells of the chicken rectum following stimulation of the nerve of Remak and field stimulation of intramural nerves. The amplitude of e.j.p.s was a direct function of the stimulus intensity. When peak depolarization of an e.j.p. reached threshold, a muscle action potential was evoked. When the extrinsic nerve was stimulated with a given stimulus intensity, the e.j.p.s recorded from different cells showed little change in amplitude and time-course, reached their peaks in 74 ms and declined to half their amplitudes in 230 ms. These corresponding values for the e.j.p.s in response to field stimulation were 51 ms and 159 ms respectively, but became larger as the microelectrode was moved away from the stimulating site. The amplitude became smaller also and the distance at which the e.j.p. declined to half its control amplitude was 4.3 mm. The time constant for the exponential decay phase of the e.j.p. was the same as the time constant for the muscle membrane. Facilitation of e.j.p. amplitude occurred during repetitive nerve stimulation; however, the facilitation was accompanied frequently by an initial depression phase during extrinsic nerve stimulation.

Characterization of human lymphocytes which proliferate "spontaneously" in vitro.

Human peripheral blood lymphocytes proliferate "spontaneously" in vitro following the reduction in the proportion of monocytes in culture. This cell proliferation, which takes place in the absence of any extrinsic antigenic stimulation, was found to reside in a small fraction of a non-T non-B cell population which was also Fc receptor-negative. Concomitant with the in vitro proliferation of the monocyte-depleted cells, an increase in the proportion of E rosette-forming cells was observed. Hence, in addition to the regulation of spontaneous proliferation of lymphocytes, it is suggested that monocytes may also be involved in the regulation of the proportion of T cells or in expression of the E-rosetting marker.

The electrical responses of the rabbit rectococcygeus following extrinsic parasympathetic nerve stimulation.

1. The responses of the rabbit rectococcygeus muscle to stimulation of the extrinsic pelvic nerves have been investigated using intracellular micro-electrode recording techniques. 2. Submaximal pelvic nerve stimulation evoked a depolarization (e.j.p.) which was graded with stimulus strength and abolished by atropine (10(-6) g/ml.) and tetrodotoxin (TTX). 3. Single supramaximal stimuli evoked action potentials associated with muscle contraction. 4. In the presence of atropine, to abolish the e.j.p.s, supramaximal stimulation of the pelvic nerves evoked hyperpolarizations (i.j.p.s) which were graded with stimulus strength and abolished by TTX. 5. The transmitter responsible for the i.j.p.s is unknown. Phentolamine (10(-5) g/ml.) and propranolol (3 x 10(-5) g/ml.) in concentrations which block respectively alpha and beta adrenoceptors and the adrenergic neurone blocking agent guanethidine (10(-6) g/ml.) were ineffective in blocking the inhibitory response. 6. It is concluded that stimulation of the pelvic nerves to the rectococcygeus releases two transmitters, acetylcholine, responsible for the e.j.p. (and muscle contraction) and a non-adrenergic non-cholinergic transmitter which is the basis for the mechanical relaxation.

The effects of periarterial nerve activation on coronary vessel tone in an isolated and perfused slab of beef ventricle

The direct effects of extrinsic nerve stimulation on coronary artery tone are unclear because of the complications arising from alterations in myocardial dynamics which themselves alter flow. An isolated and perfused nonbeating slab of beef ventricle was utilized in the present experiments to eliminate secondary complications and the efects of periarterial nerve activation on coronary perfusion pressure were examined. It was found that stimulation induced vasoconstrictor responses which were enhanced by physostigmine, a cholinesterase inhibitor, and blocked by atropine. These responses were duplicated by exogenous acetylcholine both in the perfused preparation and in isolated strips of coronary artery. Although added noradrenaline gave vasodilatation, no response attributable to the release of noradrenaline from nerves was obtained. It is concluded that the coronary vasculature of the beef receives a cholinergic innervation and that its activation, especially under conditions of reduced transmitter degradation, may induce considerable coronary vessel constriction.

An investigation of the role of ganglia in the innervation of the rat anococcygeus muscle: an electrical and mechanical study.

1 A preparation is described which allows the rat anococcygeus muscle to be stimulated via its two extrinsic nerves. Each nerve contains both excitatory and inhibitory fibres. A ganglionated nerve plexus lies on the surface of the muscle. 2 The possibility that at least part of the excitatory pathway was interrupted as a ganglion synapse lying in one of the nodes of plexus close to the muscle was suggested by the observations that (a) the excitatory response to extrinsic nerve stimulation was reduced by the nicotinic antagonists tubocurarine (0.13 to 0.26 mM) and dihydro beta-erythroidine (0.1 to 0.14 mM). (b) Fibres from one extrinsic nerve were shown to synapse on a ganglion cell from which intracellular recordings were made while the output from this ganglion cell was traced microscopically to the muscle. 3 Intracellular recording from ganglion cells in this plexus indicated that cholinergic synaptic transmission occurred in these ganglia. Tubocurarine (0.13 mM) and hexamethonium (1.3 mM) reversibly abolished intracellularly-recorded synaptic potentials. 4 Hexamethonium (0.1 to 1 mM) initially enhanced the motor response to nerve stimulation and raised muscle tone, probably by an action involving pre- and postsynaptic sites. Subsequently, hexamethonium inhibited the response to extrinsic nerve stimulation presumably by an effect at ganglia lying along the excitatory pathway. Hexamethonium enhanced, without subsequently inhibiting, the response to exogenously added noradrenaline in both untreated and 6-hydroxydopamine-treated rats. These results suggest that the initial enhancement produced by hexamethonium involved sites at postganglionic nerve endings and on smooth muscle receptors. 5 Inhibitory responses were obtained following extrinsic nerve stimulation when the tone of the muscle was raised and the excitatory response abolished by either guanethidine (3 micron) alone or by carbachol (10 micron) followed by phentolamine (3 micron). The inhibitory response was not reduced by hexamethonium (up to 2.8 mM) tubocurarine (up to 1.3 mM) or by atropine (up to 1 micron).

Luteinizing hormone requirements for ovulation in the pentobarbital-treated proestrous rat.

The LH requirements for ovulation in the pentobarbital-blocked proestrous CD rat have been studied by increasing serum gonadotropin levels through electrical stimulation of the brain and subsequently comparing the effects of timed hypophysectomy on ovulation and serum LH concentrations. The arcuate nucleus (ARC) or the medial preoptic area (POA) was stimulated unilaterally for 45 min with matched pairs of biphasic rectangular pulses through a coaxial platinum electrode. Serum LH was significantly elevated above basal values at the end of stimulation, but not in sham-stimulated controls. The results of both hormone measurement and hypophysectomy showed that the pituitary continued to release LH after extrinsic stimulation of the hypothalamus had ceased. Animals did not ovulate if they had been hypophysectomized at the end of the 45 min stimulation whereas nearly all ovulated if hypophysectomy was delayed for an additional 20 min. Some evidence suggested that the pituitary could be removed earlier without affecting ovulation if the rate of LH release was increased. The minimum peak LH concentration measured in rats that subsequently ovulated fully was 187 ng/ml, substantially lower than concentrations ordinarily attained in the spontaneous proestrous surge. When serum LH was insufficiently high to cause follicle rupture, there was nevertheless the resumption of meiosis and luteinization of the large ovarian follicles. Attempts were made to restore ovulability in animals presumed to have released a subovulatory quota of gonadotropin. Ovulation was obtained when such animals, prepared by hypophysectomy after the 45 min stimulation, had been bilaterally nephrectomized prior to stimulation. However, multiple injections of progesterone after hypophysectomy were without effect. The results are discussed in relation to variables that affect minimum requirements of LH for ovulation.

Arousal from sleep: The effects of the rise-time of auditory stimuli

The present research involves the methodological strategy of investigating sleep by determining an individual’s reaction to extrinsic stimulation. Particularly, the investigation was concerned with whether or not the onset character of an auditory stimulus was an important parameter in precipitating changes in the pattern of electroencephalographic activity occurring during sleep. The results indicated that stimulus onset is an important parameter but only during sleep characterized by slow-wave electroencephalographic activity. In this respect, the effects of stimulus onset are similar to the effects of psychological loudness. The results are also discussed in relation to the effects of stimulus onset when awake individuals are exposed to auditory stimuli, and, again similar to psychological loudness, the data from awake individuals is not predictive of an individual’s reaction during sleep.

The effect of chronic protein malnutrition on trans-callosal evoked responses in the rat.

Studies were carried out on the trans-callosal evoked response in rats born of dams fed either a low (8%) or normal (25%) protein diet beginning 5 weeks prior to mating and throughout gestation and lactation. After weaning, pups were fed the same diets as their mothers. Bipolar (surface vs depth) stainless steel stimulating and recording electrodes were positioned at corresponding loci in the right and left sensorimotor cortices. Trans-callosal evoked responses were measured under urethane anesthesia using twice-threshold bipolar pulses of .1 msec duration at ages 13, 21, and 60-66 days. Evoked response latency was significantly greater in malnourished animals at 13 days of age, whereas at adulthood no latency differences were seen. Poststimulation excitability (15-100 msec range) was not significantly affected by the dietary treatment. These results are interpreted as corroborating previous reports on rats undernourished during development using sensory evoked potentials. By avoiding the use of extrinsic sensory stimulation, the present study demonstrates a dietary effect upon ontogeny of cortical evoked potentials independent of any possible effect on sensory receptor mechanisms.

Idiopathic (Asymptomatic) Monoclonal Gammopathies

Asymptomatic forms of monoclonal gammopathies (MG) are recognized with increasing frequency; their recognition and differentiation from the symptomatic forms of MG appear imperative, since the therapeutic approaches are different. Available clinical and laboratory indexes lack specificity required for useful and practical discrimination; presently, we must still rely on the timecourse monitoring of such laboratory values as hemoglobin levels, M-protein concentrations, and presence of Bence Jones proteins. Elucidation of histocompatibility A and W antigenic profiles, as well as the functions and kinetics of B-lymphocytes from such patients, appear most promising. Evidence of the causative role of extrinsic and intrinsic antigenic stimulation in MG production is increasing; segregation into two distinct concentration ranges of M-proteins in the asymptomatic and symptomatic groups suggests two control levels of the expression of immune response (Ir) genes, due to partial or complete derepression of the latent Ir gene function, reflecting "partial" (asymptomatic, benign MG) and "complete" (symptomatic, malignant MG) monoclonal immune responders.