Dopamine beta-hydroxylase immunoreactivity in human cerebrospinal fluid: properties, relationship to central noradrenergic neuronal activity and variation in Parkinson's disease and congenital dopamine beta-hydroxylase deficiency

1. Dopamine beta-hydroxylase is stored and released with catecholamines by exocytosis from secretory vesicles in noradrenergic neurons and chromaffin cells. Although dopamine beta-hydroxylase enzymic activity is measurable in cerebrospinal fluid, such activity is unstable, and its relationship to central noradrenergic neuronal activity in humans is not clearly established. To explore the significance of cerebrospinal fluid dopamine beta-hydroxylase, we applied a homologous human dopamine beta-hydroxylase radioimmunoassay to cerebrospinal fluid, in order to characterize the properties and stability of cerebrospinal fluid dopamine beta-hydroxylase, as well as its relationship to central noradrenergic neuronal activity and its variation in disease states such as hypertension, renal failure, Parkinsonism and congenital dopamine beta-hydroxylase deficiency. 2. Authentic, physically stable dopamine beta-hydroxylase immunoreactivity was present in normal human cerebrospinal fluid at a concentration of 31.3 +/- 1.4 ng/ml (range: 18.5-52.5 ng/ml), but at a 283 +/- 27-fold lower concentration than that found in plasma. Cerebrospinal fluid and plasma dopamine beta-hydroxylase concentrations were correlated (r = 0.67, P = 0.001). Some degree of local central nervous system control of cerebrospinal fluid dopamine beta-hydroxylase was suggested by incomplete correlation with plasma dopamine beta-hydroxylase (with an especially marked dissociation in renal disease) as well as the lack of a ventricular/lumbar cerebrospinal dopamine beta-hydroxylase concentration gradient. 3. Cerebrospinal fluid dopamine beta-hydroxylase was not changed by the central alpha 2-agonist clonidine at a dose that diminished cerebrospinal fluid noradrenaline, nor did cerebrospinal fluid dopamine beta-hydroxylase correspond between subjects to cerebrospinal fluid concentrations of noradrenaline or methoxyhydroxyphenylglycol; thus, cerebrospinal fluid dopamine beta-hydroxylase concentration was not closely linked either pharmacologically or biochemically to central noradrenergic neuronal activity. 4. Cerebrospinal fluid dopamine beta-hydroxylase was not changed in essential hypertension. In Parkinson's disease, cerebrospinal fluid dopamine beta-hydroxylase was markedly diminished (16.3 +/- 2.9 versus 31.3 +/- 1.4 ng/ml, P < 0.001) and rose by 58 +/- 21% (P = 0.02) after adrenal-to-caudate chromaffin cell autografts. In congenital dopamine beta-hydroxylase deficiency, lack of detectable dopamine beta-hydroxylase immunoreactivity in cerebrospinal fluid or plasma suggests absent enzyme (rather than a catalytically defective enzyme) as the origin of the disorder. 5. We conclude that cerebrospinal fluid dopamine beta-hydroxylase immunoreactivity, while not closely linked to central noradrenergic neuronal activity, is at least in part derived from the central nervous system, and that its measurement may be useful in both the diagnosis and treatment of neurological disease.

Inhibition by ethanol of the cardiovascular effects of glutamate in the nucleus of the solitary tract

This study investigates whether ethanol affects the cardiovascular changes evoked by the excitatory amino acid glutamate in the nucleus of the solitary tract (NTS). Male Sprague-Dawley rats were anesthetized with urethane and instrumented for microinjection of drugs into the NTS. In 28 animals, an initial dose-response curve for glutamate (37, 74, and 148 pmol/60 nL) was obtained. In eight animals (control group), the dose-response curve was unchanged when it was tested after microinjection of 60 nL of saline into the NTS. In contrast, the prior intra-NTS administration of ethanol (25 or 50 mM) consistently inhibited the hypotensive and bradycardic effects of glutamate. The specificity of this inhibitory response was corroborated by the inability of intra-NTS administrations of ethanol (50 mM) to affect the hypotensive and bradycardic responses to nicotine (922 pmol. 1.84 nmol, and 3.96 nmol). These results indicate that the cardiovascular effects of glutamate can be antagonized by ethanol in the NTS. This inhibitory effect, in turn, may provide a basis for the hypertensinogenic action of ethanol in humans.

Genetics and molecular biology of hypotension

Major strides in the molecular biology of essential hypertension are currently underway. This has tended to obscure the fact that a number of inherited disorders associated with low blood pressure exist and that these diseases may have milder and underrecognized phenotypes that contribute importantly to blood pressure variation in the general population. This review highlights some of the gene products that, if abnormal, could cause hypotension in some individuals. Diseases due to abnormalities in the catecholamine enzymes are discussed in detail. It is likely that genetic abnormalities with hypotensive phenotypes will be as interesting and diverse as those that give rise to hypertensive disorders.

Rapid isolation of nuclei from carrot suspension culture cells using a BioNebulizer

The BioNebulizer is an instrument that breaks cells and large molecules using the shearing forces created by laminar flow of high-pressure gas in the microcapillary channels generated by the instrument. Within 4 min, 90% of the carrot suspension culture cells that passed through the nebulizer were broken. Cytosol and organelles were released from the broken cells leaving cell wall ghosts. Nuclei were further purified by means of a discontinuous Percoll gradient. This method yielded an average of 2 x 10(5) nuclei from 2 g of suspension culture cells (approximately 2 x 10(6) cells). The isolated nuclei actively incorporated [8,5'-3H]-GTP into RNA.

Ligaments of the lumbosacral spine and their role in possible extraforaminal spinal nerve entrapment and tethering

The extraforaminal ligaments of the lumbosacral spine were studied in 34 cadavers. The corporotransverse ligament attached to the body and transverse process of the same vertebra. The ligament may entrap the exiting nerve root below it in rotary subluxation or in complete disk space loss. The lumbosacral ligament extends from the transverse process of L5 and the L5-S1 disk to the sacral ala, forming the roof of the lumbosacral tunnel through which the L5 spinal nerve passes. This may be the site of extraforaminal entrapment if lateral disk herniations, osteophytes, or tumor metastasis are also present. The nerve suspensory ligament attaches to the nerve sheath and to the disk and is felt to be significant as a vehicle for mechanoreception.

The diagnosis and treatment of baroreflex failure

BACKGROUND

Baroreflexes originate in the great vessels of the neck and thorax and prevent arterial pressure from rising or falling excessively.

METHODS

This study was undertaken to clarify the cause, clinical spectrum, and therapy of this disorder. We studied 11 patients with baroreflex failure presenting as severe, labile hypertension and hypotension, often with headache, diaphoresis, and emotional instability, and characterized by the failure of exogenous vasoactive substances to alter heart rate. Each underwent hemodynamic monitoring and biochemical, physiologic, and pharmacologic testing.

RESULTS

The patients' maximal systolic blood pressures ranged from 164 to 280 mm Hg, and their minimal systolic pressures ranged from 58 to 96 mm Hg. Plasma norepinephrine and epinephrine concentrations were sometimes many times normal during blood-pressure surges. All the patients had excessive pressor and tachycardia responses to the mental-arithmetic and cold pressor tests and marked hypersensitivity to clonidine. The underlying causes of baroreflex failure included the familial paraganglioma syndrome, neck surgery or radiation therapy for pharyngeal carcinoma, bilateral lesions of the nucleus tractus solitarii, and surgical section of the glossopharyngeal nerves; in two patients the cause was unknown. Therapy with clonidine reduced the frequency of attacks by 81 percent and attenuated the elevated blood pressure and heart rate in the attacks that occurred.

CONCLUSIONS

The syndrome of baroreflex failure should be considered in patients with otherwise unexplained labile hypertension. Clonidine attenuates the pressor and tachycardic surges in baroreflex failure.

Autonomic neuropharmacology

In the past year, improvements have occurred in our understanding of the pathophysiology and management of autonomic disorders and syncope. There has also been improved understanding of the autonomic role in the physiology of weightlessness.

Cochlear nerve fiber responses to amplitude-modulated stimuli: variations with spontaneous rate and other response characteristics

1. Single-fiber responses to sinusoidally amplitude-modulated (AM) tones were recorded from the cochlear nerves of anesthetized guinea pigs. Stimuli were presented at the fiber's characteristic frequency (CF) and covered the intensity range between the fiber's minimum rate threshold and 90-100 dB SPL in 5- or 6-dB steps. The amount of modulation in each fiber's response and the average rate of the responses were quantified. The observed response modulation was compared with the modulation to be expected on the assumption that the instantaneous discharge rates varied with intensity in the same way that the average rates did (i.e., as predicted from each fiber's average-rate vs. level function). 2. The difference between the observed and expected response modulation varied widely across fibers. In most fibers' the responses to a limited range of stimulus intensities (typically between 20 and 30 dB above the fiber's rate threshold) were modulated far more than expected on the basis of their average rates, with responses to stimuli either above or below this range differing progressively less from expectation. Little or no response modulation was observed above approximately 70 dB SPL in these fibers. Other fibers exhibited response modulation that exceeded the expected modulation by smaller amounts, but maintained this modulation to much higher sound pressure levels. 3. The discrepancy between the observed and expected responses to AM stimuli also varied with the frequency of modulation (fm) within individual fibers. The discrepancies were least pronounced at low fms (e.g., 10 Hz) but became progressively larger as fm was increased to between 50 and 320 Hz (subject to the inter-fiber variations described in 2, above). 4. The AM response characteristics varied systematically with the fiber's spontaneous rate and other response characteristics (e.g., rate threshold, CF rate vs. level function type, and rapid adaptation characteristics). In particular, the most sensitive, high spontaneous rate fibers had responses that adapted rapidly after the onset of a stimulus, and showed the greatest enhancement of AM-related information at low-to-moderate stimulus intensities. However, these fibers appeared incapable of encoding AM-related information at high intensities, since their response rates "saturated" and their AM response enhancements diminished around 30 dB above threshold. In contrast, the less sensitive (i.e., higher threshold), lower spontaneous rate fibers showed less evidence of rapid adaptation near the onsets of their response, and lesser enhancements of the modulated responses predicted from their average-rate versus level functions.(ABSTRACT TRUNCATED AT 400 WORDS)

Classification of autonomic disorders

Recent advances in our understanding of the pathophysiology of cardiovascular regulation and the metabolism of catecholamines have enabled us to develop an improved system of classification of autonomic disorders. Patients with autonomic impairment, clinically unassociated with other neurological abnormalities, are considered to have the Bradbury-Eggleston syndrome (idiopathic orthostatic hypotension, pure autonomic failure). Individuals whose autonomic failure is accompanied by degeneration in other neurological systems are classified as having the Shy-Drager syndrome (multiple system atrophy with autonomic failure). Patients in whom a deficiency of the enzyme dopamine-beta-hydroxylase is present from birth have many features suggestive of the Bradbury-Eggleston syndrome but manifest normal sweating and biochemically have an elevated plasma and urinary dopamine level. Recognition of these individuals is of particular importance because they are uniquely responsive to treatment with oral dihydroxyphenylserine (L-DOPS). A fourth disorder is baroreflex failure; this disorder is usually due to surgery, trauma, radiation or other injury to the ninth or tenth cranial nerves or the medullary nuclei which their fibers innervate. Patients with baroreflex failure have oscillations between hypertension and hypotension, but these alterations are poorly correlated with posture. Very high levels of plasma norepinephrine are found during the hypertensive phase of baroreflex failure. Baroreflex failure is generally responsive to treatment with clonidine. In conclusion, the diagnosis and therapy of autonomic disorders has improved due to the more precise taxonomy now current.

Effects of nicotine on brain stem mechanisms of cardiovascular control

The role of the central nervous system in the pressor effect of nicotine is not well understood. In this study, we evaluated the cardiovascular effects of nicotine in the lower brainstem of normotensive and hypertensive rats. Microinjection of nicotine (0.012-3696 pmol/60 nl) into the nucleus of the solitary tract and area postrema of Sprague-Dawley (SD), Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) decreased blood pressure and heart rate. In contrast, administration of similar doses of nicotine within the rostral ventrolateral medulla (RVLM) evoked a long-lasting pressor and tachycardic effect. This pressor effect was completely abolished by prior microinjection of hexamethonium. In SHR the depressor and bradycardic responses in the nucleus of the solitary tract and area postrema were similar to those of normotensive animals. The pressor effect in the RVLM, however, was more pronounced in the SHR than in WKY or SD rats. In additional experiments, the changes produced by intra-RVLM administration of nicotine on renal sympathetic nerve activity, blood pressure and heart rate were evaluated before and after equidepressor intravenous doses of either clonidine, labetalol or prazosin. The prior administration of labetalol antagonized the pressor effect of nicotine in the three strains of rats (SHR, 82 +/- 6%; SD, 96 +/- 4%; WKY, 83 +/- 9%). Prazosin inhibited the nicotine pressor response by 69% in SHR, by 44% in SD and by 70% in WKY. Clonidine had no effect on nicotine response in the three groups of rats. In conclusion, nicotine administration within the RVLM increases renal sympathetic nerve activity and blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intra-cochlear perfusion of salicylates on cochlear microphonic and other auditory responses in the guinea pig

The ototoxic action of salicylate was investigated in the guinea pig by perfusion of both salicylate and bromosalicylate through scala tympani. The results qualitatively confirmed experiments using intravenous administration in cats (Stypulkowski, 1990), showing dose-dependent elevations in compound action potential (CAP) thresholds, increases in cochlear microphonics (CM) and level-dependent reductions in 2f1-f2 acoustic distortion products. The endocochlear potential was not significantly affected and iontophoretic injection of salicylate into scala media had no measurable effect on CAP thresholds, consistent with an action on the basolateral walls of the hair cells. Perfusion with indomethacin produced effects similar to those of the salicylates, but at non-physiological doses. Together with the great effectiveness of 5-bromosalicylate, this suggests that salicylate does not act by inhibiting prostaglandin synthesis. The results are qualitatively consistent with the proposition that salicylates act on the basolateral walls of the outer hair cells. However, the magnitude of the CM increases, particularly at high drug concentrations, and the fact that salicylate reduced, but did not eliminate the effects of olivocochlear efferent stimulation on CM amplitude indicate that a simple explanation for salicylate effects based solely on a conductance increase in the outer hair cell membranes may be inadequate.

Tissue destruction with focused ultrasound in vivo

The management of some tumours presents a difficult surgical problem. Focused ultrasound surgery is a technique which provides the possibility of destroying, non-invasively, a selected volume of tissue at depth within an organ such as the liver whilst sparing overlying tissues. For the safe and effective use of this technique, it is essential to understand the way in which such a focused ultrasound surgery beam interacts with normal and malignant tissue and to study the histological response of different tissues to the ultrasonic insult. In this paper the histology of lesions in normal rat liver, as viewed by light and electron microscopy, is described.

A Na pump inhibitor from bovine posterior pituitary: purification, structure determination and its cardiovascular effect in rat

We examined the hypothesis that hypothalamo-hypophysial tissue contains an endogenous Na pump inhibitor. From bovine posterior pituitary, we purified a substance which inhibits Rb uptake by human erythrocytes. This inhibitory activity was found in the eluate of 10% acetonitrile from a C18 flash column and purified by subsequent three steps of reversed-phase high-performance liquid chromatography (HPLC). Sequence analysis revealed that this substance was identical to joining peptide, one of the major products of proopiomelanocortin (POMC). This peptide had hypertensive and tachycardiac effects in spontaneously hypertensive rats (SHR) after central administration, with weak Na,K-ATPase inhibitory activity (IC50 = 0.5 mM).

Ultrastructural localization of bcl-2 protein

Previous cell subfractionation studies have indicated that bcl-2 is an inner mitochondrial membrane protein. We have sought to determine the ultrastructural localization of bcl-2 protein in lymphoma and breast carcinoma cell lines and biopsy material known to overexpress bcl-2 using immunoelectron microscopy. To avoid the possibility of processing artifacts, samples were prepared by three different methods: progressive lowering of temperature, cryosectioning, and freeze-substitution. In all instances the labeling of bcl-2 protein was relatively weak but the distribution the same. In both lymphoma and breast carcinoma tissues, bcl-2 protein was detected on the periphery of mitochondria: little labeling of either the mitochondrial matrix or cristae could be detected. Labeling was also detected on the perinuclear membrane and throughout the cytoplasm, as also indicated by confocal microscopy. These data therefore indicate that bcl-2 protein can be detected at several intracellular sites and that at the likely functional destination, the mitochondria, there appears to be, contrary to expectations, a preferential association with the outer membrane.

Synthesis and deposition of glycosaminoglycans in the murine hemopoietic stromal line S17: modulators of the hemopoietic microenvironment

The murine hemopoietic stromal cell line S17 can support either myelopoiesis or lymphopoiesis depending on the culture conditions (i.e., the presence of steroid or mercaptoethanol). The glycosaminoglycans are important components of the extracellular matrix, which influence hemopoietic cell proliferation. Accordingly, glycosaminoglycans have been compared under different growth conditions. Under myeloid conditions (with steroid) a higher proportion of the sulfated glycosaminoglycans was incorporated into the cell layer and the extracellular matrix was increased, whereas synthesis was reduced under lymphoid conditions (with mercaptoethanol). The inclusion of steroid or mercaptoethanol did not alter the nature of the heparan sulfate synthesized as shown by DEAE anion-exchange chromatography, cleavage with specific enzymes and resolution of the digestion products by gel electrophoresis (oligomapping), and glycosaminoglycan size. The major species of sulfated proteoglycan synthesized under the different growth conditions (200 and 110 kd for the culture supernatant and 110, 71, and 38 kd for the cell layer) were shown to be very similar by polyacrylamide gel electrophoresis. Although no qualitative difference was found biochemically between the major glycosaminoglycans/proteoglycans, scanning electron microscopy revealed major differences in the pattern of deposition of the glycosaminoglycans. Under myeloid conditions, a rich fibrous matrix covered the cell layer, whereas under lymphoid conditions glycosaminoglycan was sparsely deposited. The arrangement of the extracellular matrix may have important consequences for myelo- and lymphopoiesis.

Time-course and extent of retinal ganglion cell death following ablation of the superior colliculus in neonatal rats

This study has examined the deleterious effect of superior colliculus (SC) ablation on the viability of identified retinotectally projecting ganglion cells in the neonatal rat retina. The time-course and extent of lesion-induced retinal ganglion cell (rgc) death has been determined and an estimate obtained for the rate of clearance of individual dying neurons. In order to demonstrate the projection of rgcs to the SC and the subsequent death of these same neurons after SC lesions, the fluorescent dye diamidino yellow (DY) was injected into the left SC of anesthetized 2 day old Wistar rats (P2: day of birth = P0). DY retrogradely labels the nuclei of tectally projecting rgcs; if these identified rgcs subsequently die, their DY-labelled nuclei become pyknotic and can be visualized in retinal wholemounts. At P4 the rats were again anesthetized and the injected area, seen as a yellow patch in the SC, was removed by aspiration. Rats were perfused 2 to 336 hours after the lesion and retinal wholemounts of the right eye were prepared. Control rats received only DY injections and were perfused at times corresponding to the lesioned animals. In three sham-operated rats; the injected SC was reexposed at P4 but the tectal tissue was not removed. In each of the 42 rats that were analyzed, about 10% of the retina containing retrogradely labelled rgcs was counted; the number of pyknotic versus normally labelled rgcs was determined and changes in normal cell density were also assessed. Pyknotic rates in control and sham-operated rats were similar (average 0.8%, n = 11). In SC-lesioned rats, the proportion of pyknotic DY-labelled rgcs increased to about 2.5% 4 to 8 hours postlesion (PL); the peak period of death occurred at 23 hours PL (8.0%). The amount of pyknosis decreased thereafter and most dying cells had been eliminated by 50 hours PL. Phagocytosis of dying cells was a common feature of retinae in SC lesioned rats. In the long-term (336 hours) rats, counts of normal DY-labelled rgcs in corresponding regions of control and lesioned rats revealed an average decrease in rgc density of 47.3% after P4 tectal ablation. Calculations suggest a clearance time of about 3 hours for dying neonatal rgcs.

Electron microscopic immunocytochemistry of GAP-43 within proximal and chronically denervated distal stumps of transected peripheral nerve

Growth-associated protein, GAP-43 was initially described as a neuron-specific molecule thought to play a critical role in axonal growth and regeneration. However, it is also expressed in vitro in certain CNS glia, Schwann cell precursors and non-myelinating Schwann cells. In this paper, we report the subcellular localization of GAP-43 in vivo in chronically-denervated Schwann cells in the distal stumps of previously transected rat sciatic nerve. We have used a progressive lowering of temperature method combined with the non-polar acrylic resin Lowicryl HM20 and a post-embedding labelling regime to visualize the distribution of GAP-43, S-100 (marker for Schwann cells), RT97 and NF68 (markers for different subunits of the neurofilament molecule). We report that (1) the smallest calibre regrowing axons were GAP-43-positive, sometimes NF68-positive but always RT97-negative; (2) regenerating myelinated axons and larger unmyelinated axons (> 0.7 microns diameter) were NF68-positive, RT97-positive but GAP-43-negative; (3) cytoplasmic processes within Schwann cell basal lamina tubes in the distal stumps were S-100-positive, GAP-43-positive but RT97- and NF68-negative. The similar localization of GAP-43 within regrowing axons and denervated Schwann cells suggests that GAP-43 may function similarly in both situations, and may thus be involved in motility and/or elongation of axons and Schwann cells during regeneration.

Histological and angiographic effects of a pulsed holmium:YAG laser in normal and atherosclerotic human coronary arteries and aorta

OBJECTIVE

The aims were (1) To determine the histological and angiographic effects of holmium:YAG laser energy delivered through clinical multifibre laser catheters on fresh cadaveric coronary arteries; and (2) to relate the placement of optical fibres in the catheter to patterns of tissue ablation in cadaveric aorta.

METHODS

Eight fresh cadaveric hearts and segments of aorta were used. Hearts were mounted on a new pressure perfusion device. The laser catheter was delivered over a guidewire in the lumen until it met an area of resistance. The coronary artery lumen was perfused at approximately 100 mm Hg mean pressure. These arterial areas were identified on angiography, marked, and then exposed to laser energy in the range 600-3000 mJ.mm-2. Normal and atherosclerotic areas of fresh cadaveric aortic strips were exposed to increasing laser energies using either constant or increasing fluence. Coronary arteries were pressure perfused with formalin for 18-24 h at 100 mm Hg mean pressure, and aortic strips were immersed in 5% formalin. Light and scanning electron microscopy studies were carried out.

RESULTS

There were no perforations or dissections by angiography in the fresh coronary arteries. One of 15 normal coronary artery segments and 10 of 16 of the pressure perfused, fixed, atherosclerotic coronary artery segments showed thermal changes associated with atherosclerotic plaque ablation. In aortic tissue, thermal effects extended 0 to 0.6 mm lateral to the ablated crater. Acoustic effects were seen only in the aortic strips after ablation at fluences > 1000 mJ.mm-2. The "dead spaces" around the optical fibres in the catheter resulted in significant amounts of coagulated tissue fragments remaining in the crater.

CONCLUSIONS

Holmium:YAG laser energy delivered through multifibre catheters ablated atherosclerotic tissue in coronary arteries with minimal damage to the normal walls. The cadaveric coronary artery perfusion apparatus is useful for assessing catheter delivery and mobility and the effects of laser energy on the coaxially orientated normal and atherosclerotic coronary arterial wall.