Prestimulus EEG influence on late ERP components

Ten healthy volunteers were submitted to an auditory oddball event related potentials (ERP) paradigm. Single trial 500 ms poststimulus ERPs (Pz, Cz, Fz--linked earlobes) along with the correspondent 1000 ms prestimulus EEG (O1-Cz) were stored. EEG epochs were submitted to spectral analysis and a slow wave index (SWI = delta + theta/total) was computed. Three selective ERP averages corresponding to low, medium and high SWI were computed. N2 latency was longer and P3a amplitude was lower in high SWI averages as compared to low SWI averages.     

Effect of indomethacin on cyclic AMP phosphodiesterase activity in myometrium from pregnant rhesus monkeys

Our results indicate that indomethacin inhibits cyclic AMP phosphodiesterase in the myometrium of the pregnant rhesus monkey under in vitro as well as in vivo conditions. Kinetic data on extracts of myometrium from pregnant rhesus monkeys indicated two cyclic AMP phosphodiesterase activities. The apparent K_m value for the high affinity enzyme averaged 3.9 μM and for the low affinity enzyme 23 μM; the V_max values averaged 0.56 and 1.4 nmoles cyclic AMP hydrolized per mg protein min^?1 respectively. When indomethacin was added to the myometrial extracts, the activity of the high K_m phosphodiesterase was competitively inhibited, with an average K_i of 200 μM; the low K_m enzyme was noncompetitively inhibited with an average K_i of 110 μM. Experiments on myometrial slices demonstrated that 10 μM indomethacin potentiated the effect of PGE₁ and epinephrine on cyclic AMP levels, presumably by inhibiting the phosphodiesterase activity. The uterine relaxing effect of indomethacin is generally attributed to the inhibition of prostaglandin synthetase activity. However, treatment of pregnant rhesus monkeys with therapeutic doses of indomethacin resulted in a significant inhibition of myometrial cyclic AMP phosphodiesterase activity in association with uterine relaxation and prolongation of gestation.     

Effects of Power Frequency Electromagnetic Fields on Growth of Germinating Vicia faba L., the Broad Bean

Experimental investigations were carried out to evaluate the effect of continuous and delayed exposure of power frequency electromagnetic fields at 5, 50 and 100 μT on germinating Vicia faba seedlings as a model system. These studies included physical parameters (length and girth of primary roots, number as well as length of lateral roots and imbibition), major biochemical constituents (total sugar, protein, and fat) and activities of important housekeeping enzymes (amylases, proteases, and lipase) at 2, 4, and 8 days of growth. Also, mitotic index and rate of DNA synthesis were studied at day 8 of growth. There was no significant change in physical parameters and major biochemical constituents between control and experimental groups. Also, the comparison between the control and experimental group of seeds showed that α-amylase activity significantly decreased at 5, 50 and 100 μT on day 2 and 4 of growth. β-amylase and protease (37^○C & 50^○C) showed a significant decrease in activity on day 2 and 4 of growth at 100 μT, whereas activity of lipase significantly decreased only on day 2 of growth at 100 μT. At day 8 of growth, all enzyme activities reverted back to the same as control. Also, there was a significant increase in mitotic index as well as ³H-thymidine uptake at 100 μT delayed exposure on day 8. The present study suggests that exposure to power frequency electromagnetic fields up to 100 μT on germinating seedlings does not cause any permanent damage since the initial alteration under the magnetic fields in some important housekeeping enzymes involved in the onset of seed germination were returened to control values on day 8 of growth. Also, the growth of the germinated seedlings was found to be enhanced by the application of power frequency magnetic fields (100 μT) as evidenced by mitotic index and ³H-thymidine uptake.     

Giemsa-based cytological assessment of area,shape and nucleus:cytoplasm ratio of goblet cells of rabbit bulbar conjunctiva

Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm² (average 193 ± 50 μm²). The area could be predicted reliably from the longest and shortest dimensions (r² = 0.903). The areas of goblet cell nuclei were 15–58 μm² (average 33 ± μm²) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation.     

Pre-stimulus spectral EEG patterns and the visual evoked response

The relationship between the latencies and amplitudes of the N1 and P2 components of the visual evoked potential (VEP) and the psychophysiological state of the brain immediately preceding the time of the stimulus has been investigated in 7 male subjects. Power spectral measures in the delta, theta, alpha and beta bands of the 1 sec pre-stimulus EEG were used to assess the brain state, and low intensity flashes, delivered randomly between 2 and 6 whole seconds, were used as the stimuli. Trials were ranked separately according to the relative amounts of pre-stimulus power in each EEG band and were partitioned into groups by an equal pre-stimulus spectral power criterion. Averaged EPs were computed from these groups and multiple regression analysis was used to relate pre-stimulus spectral power values to EP features. Five of the 7 subjects displayed consistent increases in N1-P2 amplitude as a function of increasing pre-stimulus relative alpha power. The between-subjects effect of pre-stimulus EEG on N1 latency was small, but was moderate for P2 latency (both significant). Both N1 and P2 latency were found to decrease with increasing amounts of pre-stimulus relative delta and theta power.     

Electrical characteristics of the apical and basal-lateral membranes in the turtle bladder epithelial cell layer

(1) The active transport of Na⁺ across the turtle bladder epithelial cell layer consists of a passive entry step through a Na⁺-selective path in the apical membrane and an active extrusion step through Na⁺ pump-containing path in the basal-lateral membrane together with some back-leakage through the paracellular spaces and tight junctions between the epithelial cells. This hypothesis has now been verified qualitatively and to some extent, quantitatively by the use of an intracellularly-located microelectrode in conjunction with a conventional assembly of extracellularly-located macroelectrodes mainly in short-circuited bladders bathed by Na⁺-rich Ringer media. Under these conditions, the intracellular potential (V_sc) averaged 38.4 mV with the cell electronegative; the fractional resistance of the apical membrane ($\text{?R}{}_{\mathrm{<mtext>a</mtext>}}$) averaged 0.55; while the concomitant transepithelial parameters, short circuiting current (I_sc) and electrical conductance (G_t), average 68.6 μA/cm² and 0.98 mS/cm², respectively. (2) The relation between these parameters and the transepithelial flow of Na⁺ (orI_sc) is evoked by blocking Na⁺ entry into the cell (by the mucosal addition of amiloride or removal of mucosal Na⁺). Amiloride-induced blockade of the Na⁺ entry step results in a rapid hyperpolarization of the cell interior during which V_sc = —79.1 mV and $\text{?R}{}_{\mathrm{<mtext>a</mtext>}}\text{= 0.92}$. I_sc and G_t (equivalent to the shunt conductance under these conditions) averaged 5 μA/cm² and 0.35 mS/cm², respectively. The entire process is reversible on re-admission of Na⁺ entry into the cell. (3) A slow depolarization of the cell interior in the period of blocked transapical Na⁺ entry is opposite to that expected from an electroneutral Na⁺-K⁺ exchanging pump; but instead is the predictable response of an electrogenic Na⁺ pump in parallel with a passive K⁺-selective conductance in the basal-lateral membrane. (4) The electrogenicity concept is substantiated after pretreatment of the bladder with serosal ouabain, which changes the response of V_sc to amiloride (from the aforementioned biphasic response) to a step-function response, attributable mainly to the development of a slowly dissipating K⁺ diffusion potential across the basallateral membrane. (5) Under open-circuit conditions, the electronegativity of cell to mucosa (V_a) is a linear inverse function of the electropositivity of serosa to mucosa (V_t). For V_t ? 100 mV, V_a is positive; and for V_t between ?30 and 90 mV, V_a is negative.     

The Inhibition of Clostridium chauvoei (Jakari strain) Neuraminidase Activity by Methanolic Extracts of the Stem Barks of Tamarindus indicus and Combretum fragrans

The inhibition of neuraminidase from Clostridium chauvoei (jakari strain) with partially purified methanolic extracts of some plants used in Ethnopharmacological practice was evaluated. Extracts of two medicinal plants, Tamarindus indicus and Combretum fragrans at 100–1000 μg/ml, both significantly reduced the activity of the enzyme in a dose-dependent fashion (P < 0.001).

The estimated IC₅₀ values for Tamarindus indicus and Combretum fragrans were 100 and 150 μ/ml respectively. Initial velocity studies conducted, using fetuin as substrate revealed a non-competitive inhibition with the V_max significantly altered from 500 μmole min^?1 mg^?1 to 240μmole min^?1 mg^?1 and 340 μmole min^?1 mg^?1 in the presence of Tamarindus indicus and Combretum fragrans respectively. The K_M remained unchanged at 0.42 mM. The computed Index of physiological efficiency was reduced from 1.19 min^?1 to 0.57 min^?1 and 0.75 min^?1 with Tamarindus indicus and Combretum fragrans as inhibitors respectively.     

Activation of the human red cell calcium ATPase by calcium pretreatment

Some kinetic parameters of the human red cell Ca²⁺-ATPase were studied on calmodulin-free membrane fragments following preincubation at 37°C. After 30 min treatment with EGTA(1 mm) plus dithioerythritol (1 mm), a V _max of about 0.4 μmol P_i/mg × hr and a K _s of 0.3 μm Ca²⁺ were found. When Mg²⁺ (10 mm) or Ca²⁺(10 μm) were also added during preincubation, V _maxbut not Kwas altered. Ca²⁺ was more effective than Mg²⁺, thus increasing V _max to about 1.3 μmol P_i/mg × hr. The presence of both Ca²⁺ and Mg²⁺ during pretreatment decreasedKto 0.15 μm, while having no apparent effect on V _max. Conversely, addition of ATP (2 mm) with either Ca²⁺ or Ca²⁺ plus Mg²⁺increased V_max without affecting K. Preincubation with Ca²⁺ for periods longer than 30 min further increased V_maxand reduced Kto levels as low as found with calmodulin treatment. The Ca²⁺ activation was not prevented by adding proteinase inhibitors (iodoacetamide, 10 mm; leupeptin, 200 μm; pepstatinA, 100 μm; phenylmethanesulfonyl fluoride, 100 μm). The electrophoretic pattern of membranes preincubated with or without Mg²⁺, Ca²⁺ or Ca²⁺ plus Mg²⁺ did not differ significantly from each other. Moreover, immunodetection of Ca²⁺-ATPase by means of polyclonal antibodiesrevealed no mobility change after the various treatments. The above stimulation was not altered by neomycin (200 μm), washing with EGTA (5 mm) or by both incubating and washing with delipidized serum albumin (1 mg/ml), or omitting dithioerythritol from the preincubation medium. On the other hand, the activation elicited by Ca²⁺ plus ATP in the presence of Mg²⁺ was reduced 25–30% by acridine orange (100 μm), compound 48/80 (100 μm) or leupeptin (200 μm) but not by dithio-bis-nitrobenzoic acid (1 mm). The fluorescence depolarization of 1,6-diphenyl-and l-(4-trimethylammonium phenyl)-6-phenyl 1,3,5-hexatriene incorporated into membrane fragments was not affected after preincubating under the different conditions. The results show that proteolysis, fatty acid production, an increased phospholipid metabolism or alteration of membrane fluidity are not involved in the Ca²⁺ effect. Ca²⁺ preincubation may stimulate the Ca²⁺-ATPase activity by stabilizing or promoting the E₁ conformation.     

Enzymatic production of α-dehydrobiotin from biotin

The enzymatic production of α-dehydrobiotin (α-DHB), an antibiotic, from biotinyl-CoA using acyl-CoA oxidase and from biotin using a coupling system of biotinyl-CoA synthetase and acyl-CoA oxidase was developed. Acyl-CoA oxidase was found to show activity for biotinyl-CoA. K_m and V_max values of acyl-CoA oxidase for biotinyl-CoA were 75 μM and 3.92 μmol min⁻¹ mg⁻¹, respectively. Optimum reaction conditions for the α-DHB production from biotin were examined. The maximum production of α-DHB (4.29 μmol ml⁻¹) was obtained, when the reaction was carried out at 30°C for 36 h in a mixture consisting of 100 mM potassium phosphate buffer (pH 8.0), 20 mM biotin, 20 mM ATP, 60 mM CoA, 20 mM MgCl₂, 2 units of biotinyl-CoA synthetase, 90 units of acyl-CoA oxidase and 25 units of catalase in a total volume of 0.6 ml under aerobic conditions. The product was purified from 14 ml of the reaction mixture and 10 mg of crystals with white needle form were obtained. From NMR, mass spectra and other physical analyses, this compound was identified as (+)-trans-α-DHB.     

Functional dissociation of ongoing oscillatory brain states

The state of a neural assembly preceding an incoming stimulus is assumed to modulate the processing of subsequently presented stimuli. The nature of this state can differ with respect to the frequency of ongoing oscillatory activity. Oscillatory brain activity of specific frequency range such as alpha (8-12 Hz) and gamma (above 30 Hz) band oscillations are hypothesized to play a functional role in cognitive processing. Therefore, a selective modulation of this prestimulus activity could clarify the functional role of these prestimulus fluctuations. For this purpose, we adopted a novel non-invasive brain-computer-interface (BCI) strategy to selectively increase alpha or gamma band activity in the occipital cortex combined with an adaptive presentation of visual stimuli within specific brain states. During training, oscillatory brain activity was estimated online and fed back to the participants to enable a deliberate modulation of alpha or gamma band oscillations. Results revealed that volunteers selectively increased alpha and gamma frequency oscillations with a high level of specificity regarding frequency range and localization. At testing, alpha or gamma band activity was classified online and at defined levels of activity, visual objects embedded in noise were presented instantly and had to be detected by the volunteer. In experiment I, the effect of two levels of prestimulus gamma band activity on visual processing was examined. During phases of increased gamma band activity significantly more visual objects were detected. In experiment II, the effect was compared against increased levels of alpha band activity. An improvement of visual processing was only observed for enhanced gamma band activity. Both experiments demonstrate the specific functional role of prestimulus gamma band oscillations for perceptual processing. We propose that the BCI method permits the selective modulation of oscillatory activity and the direct assessment of behavioral consequences to test for functional dissociations of different oscillatory brain states.     

The electrical changes accompanying fertilization and cortical vesicle secretion in the medaka egg

The electrical properties of the egg of the medaka, Oryzias latipes, were studied before, during, and after fertilization. The resting potential of the unfertilized egg averaged ?39 ± 9 mV in Yamamoto's Ringers (Y. Ringers), but 20% of the values were between ?50 and ?60 mV. Fertilization triggers a small depolarization of 4 ± 3 mV in 10% Y. Ringers with an average duration of 20 ± 10 sec. The amplitude of this depolarization is independent of [Na⁺]_o, [Ca²⁺]_o, and [Cl^?]_o, so it appears to be due to a nonspecific leak triggered by sperm-egg fusion. The depolarization is followed by a longer hyperpolarizing phase with an average amplitude of 31 ± 12 mV. Recovery from this hyperpolarization has a fast phase lasting 155 ± 18 sec, followed by a slower phase which reaches a steady average membrane potential of ?19 ± 1 mV by 9 min after fertilization. The membrane resistance falls 10-fold during the first 2 min after fertilization, from 40 (1520 kΩ-cm²) to 3 MΩ. This is largely due to an increase in the K⁺ conductance. At the peak of the hyperpolarization, the membrane potential exhibits a 28 mV/decade [K⁺]_o dependence and a 6 mV/decade [Na⁺]_o dependence. The membrane resistance slowly recovers over the next 8 min to a value about 30% larger than before fertilization. The relation of current vs voltage was linear before, during, and after fertilization and indicated a reversal potential of ?98 ± 20 mV for the hyperpolarization peak. The egg's capacitance averaged 0.04 ± 0.01 μF (0.9 μF/cm²) before fertilization and approximately doubles within 90 sec after fertilization. It then decreases over a 9-min period, reaching a value 25% smaller than before fertilization.     

Event related desynchronization: use as a neurophysiologic marker is restricted

The present research aims to show that the occurrence of alpha blocking or event-related desynchronization (ERD) strongly depends on the amplitude and also on the phase angle of alpha activity at the stimulus onset. Simple visual stimulation was presented to 17 healthy subjects during EEG recording. An O₂ electrode was used for analysis with a 32 channel EEG sampling system. We used a segmentation of raw data in order to obtain the evoked potential. Prestimulus and poststimulus activities were filtered in the alpha (8–13 Hz) frequency band. Later, four different events (blocked, time-locked, phase-locked, and eliminated) were separately averaged. Phase-locked sweeps were determined by application of inter-trial coherence analysis. The evaluation of the data shows that “time-locked and phase-locked sweeps” were the dominating pattern and not “the blocked pattern”, which occurred only when the prestimulus alpha was high. In the analyses of EEG-EP sweeps, only 22 % of epochs showed (ERD). The ANOVA revealed significant differences between four different alpha responses (F(3,48) = 11.175; p < 0.001). Furthermore, alpha oscillations in time-locked responses were significantly higher than blocked (p < 0.0001). The analyses clearly demonstrate that important precaution is needed when using the ERD as a cognitive or pathological marker.     

3β-Hydroxysteroid dehydrogenaseΔ5−4isomerase activity in the rhesus monkey placenta and fetal adrenal,testis and ovary during late gestation

3β-Hydroxysteroid $\text{dehydrogenase}\text{Δ}{}^{\mathrm{5?4}}\text{isomerase}$ (3β-HSDH) was measured in the rhesus monkey ($\text{Macaca mulatta}$) placenta, fetal adrenal (whole organ minus medulla), testis and ovary during late gestation (Days 145–162). Activities were evaluated from the conversion of [³H]-pregnenolone to [³H]progesterone. The maximum enzyme velocity (V_m) in adrenal microsomes (100,000 g pellet) was significantly higher (146 nmoles progesterone/h x mg^?1protein) than in microsomes from the other tissues. Testicular V_m was greater than either ovarian or placental V_m which were not different from one another (11.5 versus 1.9, 1.2 nmoles progesterone/h x mg^?1protein, respectively). Apparent Michaelis-Menten constants in the adrenal, placenta, testis and ovary averaged 1.8,2.5,0.27 and 0.16 μM, respectively. In some cases, substrate inhibition was noted. Estimated dissociation constants for pregnenolone were 2.3 μM (adrenal), 2.1 μM (placenta), 0.74 μM (testis) and 0.13 μM (ovary). 3β-HSDH was less active in a crude mitochondrial preparation from the fetal adrenal (10,000 g pellet) than in microsomes, whereas activity in the placenta and testis appeared to be equally distributed between mitochrondria and microsomes.Rate measurements were consistent with the apparent potentials of these organs to synthesize their characteristic hormones. Thus, 3β-HSDH activity may be an important rate determining step in hormone synthesis. The importance of substrate inhibition in progesterone formation remains to be assessed.     

Steady-state gradient in calcium ion activity across the intercellular bridges connecting oocytes and nurse cells in Hyalophora cecropia

Intracellular activities of K⁺, H⁺, Mg²⁺, Ca²⁺, and Cl^?, measured with ion selective microelectrodes in the oocyte and the nurse cells in ovarian follicles of Hyalophora cecropia, indicated that a Ca²⁺ current is a key component of the electrical potential that is maintained across the intercellular bridges connecting these two cells. In vitellogenic follicles, Ca²⁺ activity averaged 650 nM in the oocyte and 190 nM in the nurse cells, whereas activities of the other ions studied differed between these cells by no more than 6%. Incubation in 200 μM ammonium vanadate caused a reversal of electrical potential from 8.3 mV, nurse cell negative, to 3.0 mV, oocyte negative, and at the same time the Ca²⁺ gradient was reversed: activities rose to an average 3.0 μM in the nurse cells and 1.6 μM in the oocyte, whereas transbridge ratios of the other cations remained at 0–3%. In immature follicles that had not yet initiated their transbridge potentials, Ca²⁺ activities averaged ～? 2 μM in both oocyte and nurse cells. The results suggest that vitellogenic follicles possess a vanadatesensitive Ca²⁺ extrusion mechanism that is more powerful in the nurse cells than in the oocyte. © 1994 Wiley-Liss, Inc.     

An altered fibronectin matrix induces anoikis of human squamous cell carcinoma cells by suppressing integrin alpha v levels and phosphorylation of FAK and ERK

Fibronectin regulates many cellular processes, including migration, proliferation, differentiation, and survival. Previously, we showed that squamous cell carcinoma (SCC) cell aggregates escape suspension-induced, p53-mediated anoikis by engaging in fibronectin-mediated survival signals through focal adhesion kinase (FAK). Here we report that an altered matrix, consisting of a mutated, nonfunctional high-affinity heparin-binding domain and the V region of fibronectin (V⁺H⁻), induced anoikis in human SCC cells; this response was blocked by inhibitors of caspase-8 and caspase-3. Anoikis was mediated by downregulation of integrin alpha v in a panel of SCC cells and was shown to be proteasome-dependent. Overexpression of integrin alpha v or FAK inhibited the increase in caspase-3 activation and apoptosis, whereas suppression of alpha v or FAK triggered a further significant increase in apoptosis, indicating that the apoptosis was mediated by suppression of integrin alpha v levels and dephosphorylation of FAK. Treatment with V⁺H⁻ decreased the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, and direct activation of ERK by constitutively active MEK1, an ERK kinase, increased ERK1 and ERK2 phosphorylation and inhibited the increase in apoptosis induced by V⁺H⁻. ERK acted downstream from alpha v and FAK signals, since alpha v and FAK overexpression inhibited both the decrease in ERK phosphorylation and the increase in anoikis triggered by V⁺H⁻. These findings provide evidence that mutations in the high-affinity heparin-binding domain in association with the V region of fibronectin, or altered fibronectin matrices, induce anoikis in human SCC cells by modulating integrin alpha v-mediated phosphorylation of FAK and ERK.     

Leb-active glycolipid in human plasma: Measurement by radioimmunoassay

A radioimmunoassay that measures Le^b-active glycolipids in human plasma has been developed using antiserum from a goat immunized with a Le^b blood group hapten, lacto-N-difucohexaose I, conjugated to polylysine. Binding by the antiserum of lacto-N-difucohexaose I conjugated to ¹²⁵I-labeled bovine serum albumin is specifically inhibited by Le^b-active ceramide hexasaccharide. Plasma levels of the glycolipid are quantitated by comparing the inhibitory activity of plasma with that of the purified Le^b-active glycolipid. Plasma samples from 35 blood group O Le(a ? b +) individuals contain Le^b-active ceramide hexasaccharide at an average concentration of 0.9 μg/ml (range: 0.2 to 2.5 μg/ml); no Le^b-active glycolipid (less than 0.02 μg/ml) could be detected in plasma from blood group O Le(a + b?) or O Le(a? b?) individuals. Plasma from A₁ Le(a ? b+) individuals contains less Le^b-active glycolipid than plasma from A₂ Le(a? b+) individuals: its level in 19 samples of A, Le(a? b+) plasma averages 0.2 μg/ml (range: 0.1 to 0.45 μg/ml), and its level in 9 samples of A₂ Le(a? b+) plasma averages 1.1 μg/ml (range 0.8 to 1.3 μg/ml). About one-third of the total Le^b-active glycolipid in whole blood is associated with erythrocytes and the rest is found in plasma.     

Short and middle latency vestibular evoked responses to acceleration in man

We have succeeded in recording short and middle latency vestibular evoked responses in human subjects. The head was held rigidly in a special, patented head holder, constructed individually for each subject, which gripped the teeth of the upper jaw. The stimulus consisted of 2/sec steps of angular acceleration impulses produced by a special motor with intensities of about 10,000°/sec² and with a rise time of 1–2 msec. The electrical activity was recorded as the potential difference between special forehead and mastoid electrodes having a large, secure contact area with the skin. The activity was digitally filtered and averaged in 2 separate channels by means of a Microshev 2000 evoked response system. The short latency responses, with peaks at about 3.5 msec (forehead positive), 6.0 msec (forehead negative) and 8.4 msec (forehead positive; bandpass: 200–2000 Hz; average of 1024 trials), had amplitudes of about 0.5 μV. The middle latency responses had peaks at about 8.8 msec (forehead positive), 18.8 msec (forehead negative) and 26.8 msec (forehead positive; 30–300 Hz; N = 128 trials), with larger amplitudes (about 15 μV). These responses were consistently recorded in the same subject at different times and were similar in different normal subjects. Strenuous control experiments were conducted in order to ensure that these responses are not artefacts due to the movement of conducting media (head, electrodes and leads) in the electromagnetic field of the motor and are elicited by activation of normal labyrinths. Among other controls, they were not present in a cadaver, in patients with bilateral absence of nystagmus to caloric stimuli and in conducting volumes the size of the human head. They were also not masked by white noise.     

Auditory evoked potentials in the West Indian manatee (Sirenia:Trichechus manatus)

Summary Potentials evoked by clicks and tone pips were recorded by fine wires inserted extracranially in four West Indian manatees (Trichechus manatus) in air. Sounds were delivered via padded ear phones.Averaging a few thousand trials at 20/s reveals early peaks at N5.4 (vertex negativity to a frontal reference, at 5.4 ms), P7.6, N8.8, P9.5 — probably equivalent to waves IV and VII of the typical mammalian auditory brainstem response (ABR). Averaging 100 trials at <4/s suffices to reveal a complex sequence of later peaks including N25, P80, N150 and P190; consistent smaller peaks are visible when several hundred trials are averaged.Using tone pips with a rise and fall time of 2–5 ms the carrier frequency becomes important. Evoked potential wave forms are not the same at different frequencies, bringing out the fact that frequency is not a scalar that can be compensated for by intensity. Therefore the method was not used to obtain audiograms; however the largest EPs occur in the range of 1–1.5 kHz. EPs are found up to 35 kHz; almost no evoked potential is discernible at 40 kHz but the undistorted intensity available was limited. This is in reasonable agreement with the theoretical expectation for the upper limit of behavioral hearing from Heffner and Masterton based on head size and aquatic medium.Among several ear phone placements, that over the external auditory meatus was the most effective, but only slightly so. The external canal is presumably fluid or tissue filled and sound enters over a large area.Comparing data for two species on the most effective range of frequencies and the power spectra of their vocalizations,T. manatus is lower thanT. inunguis in both respects.The results show the utility and limitations of the method of recording extracranial evoked potentials to sounds, especially for large and valuable animals under makeshift conditions.Abbreviations ABR auditory brainstem response - AEP averaged evoked potentials - EMG electromyogram - F frontal sinuses - V vertex     

Running average analysis of clinical trial ambulatory blood pressure data

A method is presented for analyzing ambulatory blood pressure monitoring (ABPM) time series data obtained from well-controlled clinical trials. The method uses running averages based on fixed time-of-day intervals (rather than a fixed number of neighboring measurements). These "interval running averages" effectively estimate average blood pressure during the specified time intervals, adjusting for unequal spacing between measurements, embedded missing data, varying measurement times-of-day, and doses of study medication taken during ABP monitoring. Blood pressure changes from baseline may be computed using the interval running averages in order to separate treatment effects from patients' normal daily blood pressure cycles. To ensure valid estimation of treatment effects over time, study medication dosing times should be rigorously controlled in the trial design and conduct. Interval running average curves may be presented graphically, and from them summary statistics may be computed for purposes of statistical analysis. By allowing for the inherent complications of ABP data collection, the effect of antihypertensive treatment in well-controlled clinical trials can be discerned.