[Development of parenting behavior scale for caregivers of children aged 2 to 6 years and analysis for its reliability and validity]

To develop a caregiver parenting behavior scale for children aged 2 to 6 years, and to verify its reliability and validity. This study recruited 1 350 caregivers of children aged 2 to 6 years. The item discrimination analysis and exploratory factor analysis were used to analyze the structure, dimensions and items of the scale. Homogeneity reliability, split-half reliability and test-retest reliability were used to analyze the reliability of the scale. Content validity and construct validity were used to analyze the validity of the scale. The results showed that the final scale contained 7 dimensions and 45 items. Cronbach's α coefficient of the total scale was 0.945; the coefficient of split half was 0.899; the test-retest reliability analysis showed that the correlation coefficients between the two tests were 0.893 (total score), 0.854 (social), 0.832 (language), 0.871 (gross motor), 0.893 (fine motor), 0.862 (cognitive), 0.832 (self-care), and 0.872 (sensory). The content validity analysis was carried out by two rounds of expert argumentation using Delphi expert consultation method. The Kendall coefficient of the items score in two rounds of Delphi expert consultation was 0.813 (P<0.01). The structure validity analysis showed that there were significant correlations between each dimension and the total scale, also between each dimension of the scale, and the extracted average variance values of each dimension was greater than the correlation coefficients between this dimension and other dimensions. In conclusion, the reliability and validity of the scale are qualified. It can be used as a tool to evaluate and guide the parenting behavior of caregivers of children aged 2 to 6 years.

[Tear film stability after trabeculectomy and its relationship with bleb morphology]

Objective: To investigate the tear film stability after trabeculectomy and its relationship with bleb morphology using Optical Quality Analysis System Ⅱ (OQAS Ⅱ). Methods: A cross-sectional study. Glaucoma patients undergoing trabeculectomy in the Eye Hospital of Wenzhou Medical University from November 2011 to November 2016 were invited by telephone to perform optical quality, bleb photography, and break-up time examinations, and history of surgeries and medications was collected. Bleb morphology was graded according to the Indiana bleb appearance grading scale. The tear film stability was the average objective scatter index value measured using OQAS Ⅱ for 10 seconds after blinking minus the baseline objective scatter index. The higher the tear film stability value, the worse the stability. The difference in the tear film stability between the surgical eyes and non-surgical eyes was compared by the Mann-Whitney U test, and the relationships between the optical quality, bleb height, extent and vascularity were compared by the Kruskal-Wallis H test. Results: Sixty-three patients (76 eyes) were enrolled in the study, including 55 surgical eyes and 21 non-surgical eyes. The mean follow-up time was (39.6±26.2) months.In the surgical and non-surgical eyes, the M(Q(R)) of tear film stability was 0.46 (0.86) and 0.23 (0.41), respectively. The tear film stability in the surgical eyes was reduced compared to the non-surgical eyes (P=0.044). The trabeculectomy group was divided into three subgroups according to the height of the filtering bleb: H0 (17 eyes), H1 (24 eyes) and H2-3 (14 eyes). The M(Q(R)) of tear film stability in the three subgroups was 0.40(0.68), 0.70(1.02) and 0.40(1.24), respectively, with no statistically significant difference detected (P=0.481). According to the bleb extent, the surgical group was divided into two subgroups: E0-1 (36 eyes) and E2-3 (19 eyes). The M(Q(R)) of optical quality in the two subgroups was 0.63 (0.78) and 0.26(1.17), respectively, with no significant difference detected (P=0.261). According to the degree of bleb vascularity, the surgical group was divided into three subgroups: V0 (25 eyes), V1 (14 eyes), and V2-3 (16 eyes). The M(Q(R)) of optical quality in the three subgroups was 0.39 (0.69), 0.55 (1.18) and 0.63 (1.24), respectively, with no significant difference (P=0.401). Conclusion: Although tear film stability decrease after trabeculectomy, the decrease is not associated with the bleb morphology. (Chin J Ophthalmol, 2019, 55:214-219).

[Epidemiologic survey on the prevalence and distribution of infants' common gastrointestinal symptoms in 7 cities in China: a population-based study]

Objective: Regurgitation, infantile colic, and functional constipation are common gastrointestinal symptoms in childhood, the aim of this study was to explore the prevalence and distribution of these symptoms in China. Methods: A screening program in infants aged 0 to 3 years selected through stratified cluster random sampling was carried out in 7 cities in China. Questionnaires were filled, and then diagnosis were made according to Rome Ⅳ criteria. Areas, (urban-rural), age and gender distribution of prevalence of childhood common gastrointestinal symptoms were analyzed. Results: Totally, 20 932 effective questionnaires were returned. The total number of infants aged 0 to 1 years was 10 193. Regurgitation was diagnosed in 1 960 infants, with the prevalence of 19.2%, among infants aged 0 to 3 months that had highest prevalence (29.8%). The prevalence decreased with age, and differences among different age groups showed significant. For infantile colic, 4 470 infants aged 0 to 5 months were analyzed and the prevalence of infantile colic was 7.3%. The prevalence of infantile colic was the highest in infants aged 1 to 2 months (10.0%). Age specific difference was significant. Of all the infants, functional constipation was diagnosed in 1 755 infants with the prevalence of 8.4%, and the lowest prevalence was found in infants aged 0 to 3 months (6.2%), and the highest prevalence was in infants aged 30 to 36 months (10.0%). The differences in different age group were significant. Conclusion: Symptoms of regurgitation, infantile colic, and functional constipation are common in infants in China, with age specific difference in prevalence of the symptoms.

Amphetamine normalizes the electrical activity of dopamine neurons in the ventral tegmental area following prenatal ethanol exposure

Prenatal ethanol exposure has been shown to produce a persistent reduction in the spontaneous activity of ventral tegmental area (VTA) dopamine (DA) neurons and in DA neurotransmission. Amphetamine-like stimulants are effective in treating attention deficit/hyperactivity disorder (ADHD), which is a major symptom in fetal alcohol syndrome. Because there is a link between reduced DA neurotransmission and ADHD, we investigated the possibility that amphetamine could restore the spontaneous activity of VTA DA neurons. Pregnant rats were administered 0 or 6 g/kg/day ethanol via intragastric intubation during gestation days 8 to 20. The spontaneous activity of VTA neurons was studied in 6- to 8-week-old male offspring using extracellular single-unit recording in unanesthetized (paralyzed, locally anesthetized) or chloral hydrate-anesthetized rats. Prenatal ethanol exposure reduced the number of spontaneously active DA neurons without changing the firing rate or firing pattern in both groups of animals. Acute amphetamine administration (2 mg/kg, i.v.) increased the number of spontaneously active DA neurons after prenatal ethanol exposure. Because amphetamine inhibited DA neuron firing rate in ethanol-exposed animals, it is possible that amphetamine restored the number of spontaneously active neurons by alleviating the depolarization block. These results show that the reduction in the number of spontaneously active DA neurons resulting from prenatal ethanol exposure is not confounded by using general anesthesia. Furthermore, acute amphetamine treatment can normalize the activity of DA neurons after prenatal ethanol exposure. This mechanism may contribute to the therapeutic effects of amphetamine-like stimulants in attention problems observed in children with fetal alcohol syndrome.

Prenatal ethanol reduces the activity of adult midbrain dopamine neurons

BACKGROUND

Prenatal ethanol exposure has been demonstrated to reduce dopamine (DA) neurotransmission in the forebrain area, which could be contributed by altered electrical activity in midbrain DA neurons. This hypothesis was tested in the present study.

METHODS

The effects of prenatal ethanol exposure on the spontaneous activity of DA neurons in the substantia nigra and ventral tegmental area were investigated with extracellular single-unit recording techniques in adult male rats. Pregnant rats were administered single daily doses of 0, 3, or 5 g/kg ethanol via intragastric intubation from gestation day 8 through 20. An additional control group did not receive the intubation procedure.

RESULTS

Prenatal ethanol treatment significantly reduced the number of spontaneously active DA neurons in the substantia nigra and ventral tegmental area in 3- to 5-month-old male offspring. The firing rate and firing pattern of the remaining spontaneously active DA neurons were not altered. There were no differences in the spontaneous activity of DA neurons between the nonintubated and 0 g/kg control groups, indicating possible intubation-induced stress did not influence the activity of DA neurons in adult offspring. Similar prenatal ethanol effects were also determined from older animals (14-16 months old), suggesting that the reduction in the spontaneous activity of DA neurons is a persistent phenomenon in adulthood after prenatal ethanol exposure. Furthermore, the reduction in the number of spontaneously active DA neurons was not the result of a loss in DA neurons per se, as revealed by the results of tyrosine hydroxylase immunohistochemistry. The prenatal ethanol exposure-induced reduction in DA neuronal activity may result from depolarization inactivation, because systemically administered apomorphine (20 microg) increased the spontaneous activity of DA neurons.

CONCLUSIONS

Prenatal ethanol exposure induced a long-lasting reduction in the activity of midbrain DA neurons in adult animals. The effect was not the result of cell loss but possible changes in the electrical properties of DA neurons. The decreased electrical activity in midbrain DA neurons could contribute to the prenatal ethanol exposure-induced reduction in DA content and metabolites observed in previous studies and the attention/hyperactivity problems reported in children with fetal alcohol effects/fetal alcohol syndrome.

5-Hydroxytryptamine2 receptor facilitates GABAergic neurotransmission in rat hippocampus

5-Hydroxytryptamine (5-HT; serotonin) administration enhances GABAergic synaptic activity recorded in pyramidal neurons of the CA1 region of hippocampus. Previous studies have attributed this effect to the activation of HT-5(3) receptors located on GABAergic interneurons. During unrelated experiments, we noticed that under our recording conditions, 5-HT can still increase GABAergic synaptic activity after the complete blockade of 5-HT3 receptors. This indicated the involvement of an additional 5-HT receptor subtype. Therefore, we reinvestigated the effects of 5-HT on GABAergic synaptic activity recorded in pyramidal cells of the CA1 region. The ability of 5-HT to increase GABAergic synaptic activity in the presence of 5-HT3 receptor blockade was mimicked by the selective 5-HT2 agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane and blocked by the selective 5-HT2 antagonist ketanserin. This indicated that the additional 5-HT receptor belongs to 5-HT2 receptor family. 5-HT2 receptor activation resulted in an increase in the frequency of spontaneous inhibitory postsynaptic currents as well as a shift in their amplitude distribution toward larger sizes. These effects were absent in the presence of tetrodotoxin. We interpret these results to indicate that 5-HT2 receptors activate GABAergic interneurons in the slice, leading to an increase in GABAergic synaptic activity onto pyramidal cells of the CA1 region.

The effects of chronic amphetamine treatment on prenatal ethanol-induced changes in dopamine receptor function: electrophysiological findings

The sensitivity of dopamine (DA) receptors in the mesoaccumbens DA system was investigated with extracellular recording and microiontophoresis techniques in adult rats that received prenatal ethanol exposure and chronic postnatal amphetamine treatment. Pregnant rats were fed with a liquid diet containing 0 or 35% ethanol-derived calories from gestation day 6 to 20. An ad libitum group received laboratory chow and water. Offspring were injected with amphetamine (2 mg/kg/day s.c.) or saline from postnatal day 22 to 10- to 12-months of age. Electrophysiological recording procedures were performed 16 to 24 hr after the last amphetamine injection. A supersensitivity of somatodendritic DA autoreceptors in the ventral tegmental area was observed in animals exposed prenatally to ethanol. This prenatal ethanol exposure-induced supersensitivity was not observed after postnatal amphetamine treatment. In control animals, postnatal amphetamine treatment did not affect the sensitivity of somatodendritic DA autoreceptors. The sensitivity of D-1 DA receptors in the nucleus accumbens was reduced by prenatal ethanol exposure. Postnatal amphetamine treatment reduced D-1 DA receptor sensitivity in control animals, but not in animals exposed prenatally to ethanol. Neither prenatal ethanol treatment nor postnatal amphetamine treatment altered the sensitivity of D-2 DA receptors in the nucleus accumbens. There were no differences between the ad libitum and 0% ethanol-derived calorie groups, indicating undernutrition did not affect DA receptor function. These results show that prenatal ethanol exposure altered DA receptor function in the mesoaccumbens DA system in adult animals. Furthermore, postnatal amphetamine treatment was able to eliminate the supersensitivity of somatodendritic DA autoreceptors in prenatal ethanol-exposed animals.

Brain-derived neurotrophic factor increases the electrical activity of pars compacta dopamine neurons in vivo

Chronic infusions of brain-derived neurotrophic factor (BDNF) immediately above the substantia nigra augment spontaneous locomotion, rotational behavior, and striatal dopamine (DA) turnover, indicating that BDNF increases functions of the nigrostriatal DA system. Because the function of the nigrostriatal DA system is related to the electrical activity of DA neurons, we investigated the effect of BDNF on the electrical activity of DA neurons in the substantia nigra pars compacta in vivo. Chronic supranigral infusions of BDNF (12 micrograms/day), nerve growth factor (11 micrograms/day), or phosphate-buffered saline were started 2 weeks before the electrophysiological recordings. BDNF increased the number of spontaneously active DA neurons by 65-98%, increased the average firing rage by 32%, and increased the number of action potentials contained within bursts. Neither nerve growth factor nor phosphate-buffered saline infusions altered any of these properties relative to unoperated animals. In addition, extremely fast-firing DA neurons (> 10 spikes per sec) were commonly found only in the BDNF-infused animals. These results demonstrate neurotrophin effects on the electrical activity of intact central nervous system neurons in vivo and suggest that the increases in locomotor behavior and striatal dopamine turnover obtained during supranigral BDNF infusions may result from increases in the electrical activity of DA neurons.

Dopamine neuron membrane physiology: characterization of the transient outward current (IA) and demonstration of a common signal transduction pathway for IA and IK

Dopamine neurons derived from the mesencephalon of embryonic rats were maintained in primary culture, identified and studied with whole-cell patch recording techniques. These neurons demonstrated a rapidly activating and inactivating voltage-dependent outward current which required the presence of K+ ions. This current was termed IA because of its transient nature. It was elicited by step depolarizations from holding potentials more negative than -50 mV and exhibited steady-state inactivation at a membrane potential more positive than -40 mV and half-maximal inactivation observed at -65 mV. This current rapidly achieved peak activation in less than 8 msec and decayed with a time constant (tau) of 58 +/- 5 msec. This current was observed in the presence of tetraethylammonium but was readily blocked by 4-aminopyridine (2-4 mM). This current was also observed to be modulated by stimulation of D2 dopamine receptors (DA autoreceptors) located on the dopamine neurons. Thus, both DA and the D2 receptor agonist quinpirole enhanced the peak IA observed, while the partial D1 receptor agonist SKF 38393 was without effect. The enhancement of IA was confirmed to be due to the activation of D2 receptors as the effects of either DA or quinpirole were blocked by the D2 receptor antagonists eticlopride and sulpiride, but not by the D1 receptor antagonist SCH 23390. Since we have previously demonstrated that the IK present in these cells is also enhanced by D2 receptor stimulation, we investigated the signal transduction pathways involved in coupling DA autoreceptors to both IA and IK. The response of both these potassium currents to DA autoreceptor stimulation was completely abolished by the preincubation of cultures with pertussis toxin, indicating the possible involvement of the G proteins Gi and G(o). In an attempt to further characterize which G protein may be involved, additional experiments were performed. The ability of DA autoreceptor stimulation to augment both currents was also blocked completely when G protein activation was prevented by the intracellular application of GDP beta S (100 microM). In contrast, irreversible activation of G proteins by intracellular application of the nonhydrolyzable GTP analog GTP gamma S (100 microM) mimicked the effects of DA autoreceptor stimulation on both IA and IK. In addition, the intracellular application of a polyclonal antibody that was selective for the alpha-subunit of G(o) completely abolished the DA autoreceptor modulation of both currents while preimmune serum was without effect.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of in utero ethanol administration on the electrophysiological activity of rat nigrostriatal dopaminergic neurons

Iontophoresis and single-unit extracellular recording techniques were utilized to study the effects of in utero ethanol administration on nigrostriatal dopaminergic (NSDA) neurons in adult rats. Pregnant Sprague-Dawley rats consumed an ethanol-containing liquid diet providing 0%, 17.5%, or 35% ethanol-derived calories (EDC) from gestation day 8 until parturition. A separate group was fed standard rat chow as an ad lib, diet control. The dose-response curves of intravenously administered apomorphine on the spontaneous activity of NSDA neurons were shifted to the right in animals exposed to a liquid diet containing 17.5% or 35% EDC compared to 0% EDC or ad lib. control groups. The responsiveness of NSDA neurons to microiontophoretic application of the D-2 DA receptor agonist, quinpirole, was not altered following in utero ethanol exposure. These results suggest that in utero ethanol exposure may produce a down-regulation in the function of DA receptors distinct from the somatodendritic impulse-regulating D-2 autoreceptors. The firing pattern of NSDA neurons was also found to be altered after in utero ethanol exposure. There was a dissociation between the firing rate and burst activity in neurons that displayed burst-firing patterns in animals with in utero ethanol exposure. These observations agree with biochemical and behavioral studies that in utero ethanol exposure produces a long-lasting effect on the development of electrophysiological and pharmacological characteristics of midbrain DA systems in adulthood.

Acute withdrawal after repeated ethanol treatment reduces the number of spontaneously active dopaminergic neurons in the ventral tegmental area

The effect of acute withdrawal, after repeated ethanol administration, on the electrophysiological activity of dopamine (DA) neurons in the ventral tegmental area was studied. Male rats received a 10-day treatment of ethanol at 4 g/kg, twice daily via intragastric intubation. In animals treated with ethanol, the number of spontaneously active DA neurons, determined with the cells-per-track population sampling technique, was significantly reduced (ethanol group = 0.70 +/- 0.10; control group = 1.49 +/- 0.18). I.V. apomorphine (20-64 micrograms/kg) reversed the reduced number of spontaneously active DA neurons (1.30 +/- 0.14) to near control levels. 'Silent' DA neurons could also be induced to fire by microiontophoretic application of GABA. These results suggest that the reduction in the number of spontaneously active DA neurons was due to the induction of tonic depolarization-inactivation on these neurons.

Microiontophoretic studies of the effects of D-1 and D-2 receptor agonists on type I caudate nucleus neurons: Lack of synergistic interaction

Several lines of evidence have suggested there may be a physiologically relevant form of synergistic interaction between D-1 and D-2 dopamine (DA) receptors located on postsynaptic neurons in the forebrain that receive a dopaminergic innervation. Because of the theoretical importance of such an interaction with respect to understanding the normal physiology of dopaminergic systems, we evaluated effects of D-1 and D-2 selective agonists, applied microiontophoretically, on the spontaneous electrical activity of a single, identifiable subpopulation of neurons within the caudate nucleus, the type I striatal neuron, in locally anesthetized, gallamine-paralyzed rats. It was observed that the D-2 receptor agonist quinpirole (QUIN) produced biphasic effects on cell firing rate. Low ejection currents significantly increased firing rate, while higher currents produced an inhibition. Similar effects were observed for the D-1 agonists SKF 38393; however, the overall excitations observed at low ejection currents were far less than those observed for QUIN. When these two agonists were applied concurrently, a simple additive effect (but not synergism) was always observed. The acute reduction of striatal levels of DA, by as much as 84% (with pretreatment with alpha-methyl-p-tyrosine, AMPT), did not alter the responsiveness of type I striatal neurons to the DA receptor agonists applied alone or in combination. These observed effects were not altered either by chloral hydrate anesthesia (in which glutamate-driven activity was studied) or by a more severe depletion of striatal DA levels (98% depletion produced by combined pretreatment with AMPT and reserpine).

Effect of recombinant porcine somatotropin and dietary protein on pancreatic digestive enzymes in the pig

This study was conducted to determine the effect of daily recombinant porcine somatotropin (rpST) injection (0 or 120 micrograms/kg BW) and dietary CP level of the feed (14 or 26% CP) on pancreatic characteristics of growing pigs. Daily injection of rpST did not affect pancreatic weight (P = .885) but did decrease pancreatic amylase content (P = .005). The ratios of amylase:protein and amylase:trypsin were also lowered by daily rpST injection (P = .002 and P = .0002, respectively). There were protein x rpST and protein x rpST x sex interactions for the ratio of amylase:chymotrypsin. The CP content of the diet had a greater effect than the injection of rpST on pancreatic characteristics. Pigs consuming the 26% CP diet had significantly higher pancreatic weight (P = .003) and greater total pancreatic chymotrypsin (P = .006) than pigs consuming the 14% CP diet. The ratios of trypsin and chymotrypsin to DNA were also higher in pigs fed the 26% CP diet (P = .007 and P = .005, respectively). These responses were not influenced by sex. Recombinant porcine somatotropin seemed to have a slight effect on porcine pancreatic characteristics; however, dietary protein had a greater effect on pancreatic characteristics in market-weight hogs.

Disappearance of acetic acid from the bovine reticulorumen at basal and elevated concentrations of acetic acid

Disappearance of acetic acid was quantified to determine whether removal of this acid from the reticulorumen is altered when ruminal acetic acid concentrations are elevated. Ruminally fistulated beef steers (n = 3 per experiment; BW = 320 +/- 9 kg) were fed eight times daily a 46% corn-based concentrate:54% mixed hay diet to meet maintenance energy requirements (3.5 kg of DM/d). In situ production of acetic acid, determined by pulsed-continuous infusion of [1-14C]acetic acid, was 530 mmol/h (CV = 12%). Disappearance from the reticulorumen (i.e., presumed absorption) was 460 mmol/h (CV = 2%) or 87% (CV = 2%) of ruminal production. Variation is described within an operational steady state. Acetic acid concentrations were increased by continuous infusion of unlabeled acetic acid into the reticulorumen. Ruminal disappearance (mmol/h) increased when this simulated production was elevated up to and exceeding in situ rates reported previously (530 to 2,700 mmol/h). These data suggest that two-thirds to three-fourths of ruminal acetate production disappeared across the reticuloruminal wall when concentration was elevated; the complement exited from the rumen with the liquid phase. The reticulorumen has an additional capacity to remove acetic acid; however, it does so with an apparent reduced efficiency at higher production rates. Liquid out-flow may affect the efficiency of reticuloruminal disappearance. Sites distal to the rumen become quantitatively important when ruminal acetic acid concentrations are increased.

Pilocarpine and digestive efficiency in beef cattle fed a high-concentrate diet

The effect of pilocarpine HCl, a parasympathetic muscarinic agonist, on digestive characteristics was evaluated in growing beef steers fed a high-grain diet. Oral doses of 0, 2 or 4 mg/kg BW were administered daily to each of eight steers immediately prior to offering an 88% concentrate: 12% hay diet in this three-period crossover design (19 d/period). Treatments did not improve digestibilities of dry matter, organic matter and nitrogen, ruminal liquid volume and fractional dilution rate, body weight gain or feed efficiency. Although daily voluntary feed intake was not altered by treatment (P = .25), there was a dose-dependent slowing of the rate at which feed was consumed (P less than .01). Also, ruminal fluid pH was increased with increasing dose (5.36, 5.55 and 6.11 respectively; P = .10). These observations indicate that the digestive improvements due to pilocarpine reported to occur in mature, nongrowing cattle consuming a high-forage diet are not observed in growing steers fed a production-type diet.

Propionic acid disappearance from the foregut and small intestine of the beef steer

Studies were conducted to determine the disappearance of propionic acid from the rumen and across the small intestine. Four crossbred beef steers, fitted with ruminal, duodenal and ileal cannulas, were given pulsed-continuous infusions of a nonabsorbable liquid phase marker (CrEDTA) and buffered propionic acid to achieve ruminal propionate productions (RPP) of 142 (basal), 567 and 997 mmol/h. Liquid flows from the rumen, and at the duodenum and ileum (2.75, 3.57 and .92 liters/h, respectively) were not affected by RPP (P greater than .23), although significant differences existed between sites (P = .001), reflecting a net addition of liquid between the rumen and duodenum and a net removal of liquid within the small intestine. Propionate disappearance from the rumen was 40 to 57% irrespective of RPP, with the complement passing from the rumen. Of the propionate that exited the rumen, 93 to 97% disappeared prior to entering the duodenum. Overall removal of RPP prior to the duodenum was 97 to 99% irrespective of RPP. Passage of propionic acid at the duodenum and at the ileum did not differ (P greater than .76) across all RPP, and the overall mean passages did not differ from zero (P greater than .34); similar results were observed for other VFA. These observations indicate that essentially all RPP is removed prior to entering the small intestine. Additionally, net propionate disappearance across the small intestine was undetectable and likely biologically irrelevant. Therefore, VFA absorption does not appear to be a limiting biological process in the beef steer.

Disappearance and passage of propionic acid from the rumen of the beef steer

Studies were conducted to define steady state pH, propionic acid concentrations and fluid turnover in the rumen of steers fed every 3 h and to determine whether rates of ruminal propionic acid disappearance were linearly related to their in situ production rates. Ruminally fistulated beef steers (326 +/- 11 kg; n = 3) were fed eight times daily a 54% mixed hay: 46% corn-based concentrate diet to meet maintenance energy requirements. Maximal acceptable variations from the mean at steady state conditions of pH, propionic acid concentrations and specific activity, and liquid flow (Cr marker concentrations) were defined as 4%, 20%, 30% and 10%, respectively, across 4 h of observation. In situ production of propionic acid, determined by pulse-continuous infusion of 1-14C-propionic acid, was 142 mmol/h (CV = 8.4%). The ruminal half-life of propionic acid was estimated to be 1.5 h and the liquid flow rate was 3.8 liters/h. Propionic acid production rates subsequently were elevated by continuous intraruminal infusion of buffered propionic acid. Irrespective of production (basal and infusion) rate, approximately 66% disappeared (i.e., presumed absorption) and 34% passed from the rumen to the lower tract in the liquid phase. Ruminal disappearance of propionate was linearly related with its production rate, and propionate concentrations and production rates also were linearly related. Liquid passage was linearly related to production rate, but there was insufficient evidence to conclude that fractional dilution rate or ruminal volume were similarly related. When ruminal production of propionic acid is elevated, the rumen has additional absolute capacity to remove propionate, but the fractional removal appears to be constant. The digestive tract distal to the rumen is likely an important site of propionate absorption in cattle when propionate production is high.

Statistical analysis of dose-response curves in extracellular electrophysiological studies of single neurons

The application of polynomial regression and the analysis of covariance (ANCOVA) to dose-response (DR) data derived from extracellular electrophysiological studies of midbrain dopamine neurons and noradrenergic locus coeruleus neurons in vivo is demonstrated and discussed. Third-order polynomial regression was found to be a better method for estimating ED50 values than probit analysis of linear regression. ANCOVA provides a more powerful statistical method than ANOVA for detecting significant differences in ED50 values or DR curves when a confounding variable such as basal discharge rate is present. The methods of analysis presented herein should be useful in the analysis of other types of neurons in electrophysiological studies.