Rapid and sensitive assay of dobutamine in plasma by high-performance liquid chromatography and electrochemical detection.

A sensitive and specific high-performance liquid chromatographic method with electrochemical detection was developed for measuring dobutamine in human plasma samples. Following an external standard method, 0.1 ml of EDTA-glutathione plasma was diluted on ice with 0.

Inhibition of vasopressin and aldosterone release by atrial natriuretic peptide in conscious rabbits.

To elucidate the regulatory role of atrial natriuretic factor (ANF) on vasopressin (AVP) and aldosterone release in conscious rabbits, ANF was administered systematically at a rate of 15 pmol min-1 (kg body wt)-1 for 15 min in two series of experimental animals in which AVP and/or aldosterone production was stimulated. In euhydrated rabbits (series I), systemic administration of angiotensin II (Ang II) (10 pmol min-1 (kg body wt)-1, 15 min) stimulated aldosterone release threefold from basal plasma concentrations (140 pg ml-1). The co-application of ANF inhibited the Ang II-induced release of aldosterone without influencing the non-stimulated AVP system.

Modulation of kidney function in conscious Pekin ducks by atrial natriuretic factor.

The influence of avian atrial natriuretic factor (ANF) on renal function was examined in conscious saltwater-acclimated Pekin ducks undergoing a steady state diuresis maintained by iv infused isotonic avian Krebs-Ringer solution at a rate of 1.0 ml/min. Synthetic chicken ANF (chANF) was applied iv at doses of 10, 50, and 90 ng/min.

Differential effects of mild hypoglycemia on proximal and distal retinal structures in man as revealed by electroretinography.

We investigated the effect of blood glucose concentration on the human visual system. Blood sugar levels were modified by intravenous infusion with insulin or glucose. Luminance electroretinograms (L-ERG) were elicited with colored flashes, and pattern ERGs (P-ERG) evoked by checkerboard reversal stimuli were obtained simultaneously with cortical visually evoked potential (VEP).

Nutrient and shunt flow responses to vidian nerve stimulation in nasal and facial tissues of the dog.

The potency of parasympathetic vasomotor efferent nerves in controlling blood flow of the face and nose was indicated by the following features attributed to the maxillary artery and their vascular compartments in dogs. Electrical stimulation of the vidian nerve induced a frequency-dependent increase in maxillary flow, which was due to a significant decrease in resistance to flow in nutrient and shunt vessels. Pronounced increases in perfusion rates mainly occurred in evaporative tissues of the nose, in particular the naso-maxilloturbinates and alar fold during vidian nerve stimulation, while those, for example, of the skin remained unchanged.

Effects of dopaminergic and noradrenergic mechanisms on the neuronal activity of the isolated pineal organ of the trout, Oncorhynchus mykiss.

The effects of exogenous applied catecholamines on the neuronal activity of ganglion cells of the luminance type (achromatic cells) were investigated in the photosensitive pineal organ of the trout, Oncorhynchus mykiss. Extracellular recordings were performed on neurons of the superfused isolated pineal organ. Addition of dopamine to the superfusion medium increased the spontaneous activity of more than 60% of the achromatic neurons (n = 25).

Scotopic versus photopic pattern onset-offset electroretinograms.

We investigated the contribution of rods and cones to the human pattern electroretinogram to onset and offset checkerboards of different spatial frequency and wavelength in a 39 degrees x 39 degrees field. Under strictly scotopic conditions, there was a negative potential at onset and a positive potential at offset, whereas under photopic conditions, there was a positive potential at onset and a negative/positive potential at offset. Thus, the waveform to pattern onset (offset) was that of the luminance electroretinogram to decreasing (increasing) luminances.

Amplification and sequencing of mRNA encoding acidic fibroblast growth factor (aFGF) from porcine heart.

Progredient stenosis of coronary arteries can induce angiogenic processes, which are probably regulated by polypeptide growth factors like aFGF. Using applications of reverse transcription-polymerase chain reaction, we amplified and sequenced an mRNA encoding aFGF in the porcine myocardium. A DNA fragment of expected size encoding aFGF was amplified with human and bovine aFGF specific oligonucleotide primers in porcine heart.

Action of gamma-aminobutyric acid (GABA) in the isolated photosensory pineal organ.

The effect of GABA (gamma-aminobutyric acid), its agonists (muscimol, baclofen) and antagonist (bicuculline) on pineal ganglion cells of the luminosity type were studied in the isolated, superfused pineal organ of the rainbow trout, Oncorhynchus mykiss. Extracellular recordings revealed that GABA added through the superfusion medium caused a clear alteration of the activity of projecting neurons, which transmit luminosity responses to the brain. Spontaneous discharges of ganglion cells were predominantly suppressed by GABA (33 neurons out of 48), but 10 neurons were clearly excited.

Absence of xanthine oxidoreductase activity in human myocardium.

Study Objective: The aim was to examine whether or not xanthine oxidase activity may be a significant source of oxygen derived free radicals in the human heart.

Design: Xanthine oxidoreductase activity of human myocardium was assayed in vitro. In addition, tests were performed to assess whether or not endogenous inhibitors of the enzyme were present in myocardial homogenates.

Contrast and stereoscopic visual stimuli yield lateralized scalp potential fields associated with different neural generators.

The use of dynamic random-dot stereograms (RDS) allows to investigate evoked potential components generated exclusively by cortical structures. We analyzed the scalp distribution of stereoscopically evoked or contrast evoked potential field by recording electrical brain activity in 20 channels simultaneously from an electrode array covering the occipital scalp areas. Evoked brain activity was obtained from 13 healthy adults with dynamic RDS stimuli presented as a stereoscopic checkerboard pattern in the center, or in the right or left visual half-field.

Impairment of the myocardial ultrastructure and changes of the cytoskeleton in dilated cardiomyopathy.

This study was designed to determine the morphological correlate of chronic heart failure. Myocardial tissue from eight patients undergoing transplantation surgery because of end-stage dilated cardiomyopathy was investigated by electron microscopy and immunocytochemistry using monoclonal antibodies against elements of the cytoskeleton: desmin, tubulin, vinculin, and vimentin. The tissue showed hypertrophy, atrophy of myocytes, and an increased amount of fibrosis.

Spatial frequency of the human short-wavelength-sensitive (blue) cone mechanism. Psychophysical studies and pattern-reversal visual evoked potentials.

The interactions of spatial and chromatic processing of the short-wavelength-sensitive cone mechanism were studied in humans with patterned (checkerboard) stimuli of various spatial frequency (10, 22, 44, and 85 min of are respectively), under steady exposure to yellow light (575 nm, 390 cd/m2). Psychophysical studies and pattern-reversal visual evoked potentials were employed. Parameters of the transient pattern-reversal visual evoked potentials (pattern reversal rate of 2.

Atrial natriuretic factor controls salt gland secretion in the Pekin duck (Anas platyrhynchos) through interaction with high affinity receptors.

Marine birds possess supraorbital salt-secreting glands in addition to the kidneys as osmoregulatory organs to excrete a strongly hypertonic salt solution of mainly NaCl. Atrial natriuretic factor (ANF)-like peptides could be demonstrated immunocytochemically in duck atria, but not in the salt glands. To elucidate the putative role of bird-specific ANF (cANF) in the control of salt gland function, conscious saltwater-acclimated Pekin ducks received 15 pmol/min.

Retinal origin of VECP delays as revealed by simultaneously recorded ERG to patterned stimuli.

Electroretinal and electrocortical potentials evoked by reversing checkerboards (PERG, PVECP) were simultaneously recorded in diseases of the central retina (10 patients) and in tumor-related optic nerve disorders (11 patients) exhibiting comparable P-100 delays in the PVECP. Retinal diseases showed a peak-time delay both in the PERG and in the PVECP, while optic nerve disorders revealed no delay in the PERG. Thus, simultaneous recording of PERG and PVECP may differentiate retinal from postretinal disorders of the visual system.

Maternal vitamin A restriction alters biochemical development of the brain in rats.

The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 micrograms retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine, respectively.

Characterization of the light response in the pineal gland of intact and sympathectomized rats.

Electrophysiological recordings were performed in the pineal gland of pigmented rats BD9 to investigate the possible contribution of a direct neural connection of the gland with the central nervous system in the transmission of photic information. Extracellular potentials were recorded during brief photic stimulation of the eyes before and after bilateral sympathectomy. Two types of responses could be distinguished in intact as well as in sympathectomized rats: spontaneously active units which were unresponsive to light flashes and units responding to photic stimulation with ON and ON/OFF discharges.

Global field power and topographic similarity.

Multichannel recordings are commonly presented as topographic maps series displaying the change of the potential distribution over time. When reviewing a sequence of potential maps it becomes obvious that there are epochs with only little activity (few field lines; small extrema values) while at other times the fields display high peaks and deep troughs with steep gradients. The measure of global field power (GFP) corresponds to the spatial standard deviation, and it quantifies the amount of activity at each time point in the field considering the data from all recording electrodes simultaneously resulting in a reference-independent descriptor of the potential field.

Spatial selectivity of pattern electroretinogram components.

Pattern electroretinograms were recorded to checkerboard stimuli of various check size to both onset-offset pattern and pattern reversal under most similar conditions of contrast and luminance. With onset-offset pattern the amplitude of the p-q and q-r components of the onset response showed a peak for checks of about 20 min of arc (spatial tuning), whereas the offset response was spatially nonselective at high contrast regardless of the luminance level. With pattern reversal the potentials were similar to those after algebraic summation of onset and offset responses both in waveform and check size of peak amplitude at 50 min of arc.

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.

Hemiretinal stimuli elicit different amplitudes in the pattern electroretinogram.

Pattern electroretinograms were elicited in 13 normal eyes by half-field checkerboard stimulation of nasal-temporal and upper-lower retinal areas. With nasal-temporal visual half-field stimulation the p-q component amplitude of the nasal hemiretina was significantly larger than that of the temporal hemiretina. With upper-lower visual half-field stimulation the amplitude was significantly larger for the upper than for the lower hemiretina.

Pattern electroretinogram peak times as a clinical means of discriminating retinal from optic nerve disease.

Fifty-two patients with unilateral or bilateral retinal or optic nerve disease exhibited abnormal peak times and/or amplitudes in the pattern electroretinogram. While this abnormality in patients with optic nerve diseases was confined to an amplitude reduction, 40% of the eyes with retinal diseases exhibited additionally a peak time delay of the p and/or q component. We conclude that recording of pattern electroretinogram peak times provides an additional means to distinguish retinal from optic nerve diseases.

Electrophysiology and perimetry in acute retrobulbar neuritis.

Eighteen patients with acute retrobulbar neuritis were examined by visual field analysis and electroophthalmological recordings. The visual fields were measured to 30 degrees with the automatic perimeter Octopus 201. The pattern-evoked cortical potential showed an increased P-100 latency followed by a decrease in 12 patients during the first two weeks of the disease.

The anti-arrhythmic effects of myocardial ischaemia. Relation to reperfusion arrhythmias?

Ventricular tachycardia was induced in the intact non-ischaemic pig heart by intramyocardial or intracoronary infusions of noradrenaline or N6, O2'-dibutyryl-cAMP. The chemically induced tachycardia was consistently stopped within 10 to 30 s by occluding the coronary artery supplying the infusion area. This ischaemic effect was readily reversed by coronary reperfusion, with ventricular tachycardia resuming within seconds after release of the occlusion.

Data reduction of multichannel fields: global field power and principal component analysis.

Electroencephalographic data recorded for topographical analysis constitute multidimensional observations, and the present paper illustrates methods of data analysis of multichannel recordings where components of evoked brain activity are identified quantitatively. The computation of potential field strength (Global Field Power, GFP) is used for component latency determination. Multivariate statistical methods like Principal Component Analysis (PCA) may be applied to the topographical distribution of potential values.