Changes in aqueductal CSF stroke volume in shunted patients with idiopathic normal-pressure hydrocephalus.

BACKGROUND AND PURPOSE: Aqueductal CSF stroke volume (ACSV) measured by phase-contrast MR imaging is a tool for selection of surgical patients with idiopathic normal-pressure hydrocephalus (iNPH). The aim of the present study was to investigate whether there is a relationship between clinical outcome and changes in ACSV in patients with iNPH who have been shunted. MATERIALS AND METHODS: Sixty-five shunted patients with iNPH underwent clinical evaluation and ACSV measurements 7-30 days before and 1, 3, 6, and 12 months after surgery. RESULTS: Two patients were excluded from the study for the occurrence of a perioperative complication. In a group of 35 clinically improved patients, the mean preoperative ACSV (157.01 microL) decreased to 18% one month after ventriculoperitoneal shunt (VPS) and < or =49% at 12 months post-VPS. In a group of 15 unimproved patients, the lower mean preoperative ACSV (84.2 microL) decreased to 14.3% one month post-VPS and < or =34% at 12 months post-VPS. In the other 8 improved patients who developed a subdural fluid collection (SDFC), ACSV values decreased by 43%-75% in the 3 months post-VPS. A postoperative ACSV increase was noted in 6 patients with a shunt system malfunction. One patient experienced both SDCF and shunt malfunction. CONCLUSIONS: ACSV decreases in all patients in whom the VPS system works properly, with the rate of ACSV decrease being higher in the patients who show clinical improvement. Postoperative ACSV increase suggests shunt malfunction. A precipitous drop of ACSV values after VPS may be the consequence of increased drainage and herald the occurrence of SDFC.

Changes in aqueductal CSF stroke volume and progression of symptoms in patients with unshunted idiopathic normal pressure hydrocephalus.

BACKGROUND AND PURPOSE: Idiopathic normal pressure hydrocephalus (iNPH) represents a diagnostic challenge, given its variable presentation and progression. Stroke volume (SV), defined as the mean volume of CSF passing through the aqueduct during both systole and diastole, greater than or equal to 42 muL, serves as a selection criterion for patients with good probabilities of improvement after ventriculoperitoneal shunt surgery (VPS). In this study, we evaluated the changes in SV during the progression of clinical symptoms in patients with suspected NPH. MATERIALS AND METHODS: Nine patients who presented with clinical and radiologic evidence of NPH, but refused treatment with VPS, were evaluated every 6 months for up to 2 years for progression in their clinical symptoms and changes in their SV, as measured by phase-contrast cine MR imaging (PCCMR). RESULTS: SV seems to increase between the onset of the symptoms and the following 18 to 20 months, then seems to plateau, followed in the next 18 to 20 months by a slight decline, and finally to a more precipitous drop in the next 12 months. During this time, however, the patient's clinical symptoms progressively worsen. CONCLUSION: Patients with a low SV have not necessarily had brain atrophy and can show, in the following months, a progressive increase in SV, which qualifies them as good candidates for VPS. The progressive reduction of the SV in untreated patients with worsening clinical symptoms may be a sign of a progressive cerebral ischemic injury, which renders the NPH irreversible.

Extra-arachnoidal cranio-cervical decompression for syringomyelia associated with Chiari I malformation in adults: technique assessment.

BACKGROUND: The osteo-dural decompression of the cerebellar tonsils at the cranio-cervical junction is generally considered the most effective treatment for syringomyelia-Chiari I complex. However much controversy concerning a great number of surgical adjuvants to the standard bony decompression is still present. In this work an extra-arachnoidal cranio-cervical decompression (CCD) without duroplasty is described and the surgical results are reported. METHOD: Between 2000 and 2005, 24 adult patients underwent surgery for symptomatic syringomyelia-Chiari I complex not associated with hydrocephalus. In all cases, the surgical procedure consisted of a limited suboccipital craniectomy and laminectomy of C1 (when necessary C2 as well) followed by dural opening leaving the arachnoid membrane intact. The dura mater is left open and stitched laterally to the muscles. FINDINGS: With a mean clinical long term follow-up of 44 months (range, 12-78 mo), neurological disturbances improved in 21 of 24 patients (87.5%) as result of extra-arachnoidal CCD. The postoperative complications occurred when the arachnoid was accidentally violated (4 cases, 16.6%). The complications included aseptic meningitis (one patient), nucal pseudomeningocele (two patients) and postoperative hydrocephalus requiring a ventriculoperitoneal shunt (one patient). Finally, one patient received an additional C2 laminectomy in order to obtain symptoms improvement and syrinx shrinkage. Postoperative MRI studies demonstrated that the syrinx decreased in size or collapsed in 20 patients (83.3%) and stabilized in 4 (16.7%). CONCLUSIONS: The extra-arachnoidal CCD is a safe and effective treatment for syringomyelia associated with Chiari I malformation in adults without intraoperative evidence of adhesive arachnoiditis. However a larger number of patients and longer follow-up will be necessary to determine the efficacy of extra-arachnoidal CCD.

Effect of prolonged moderate and severe energy restriction and refeeding on plasma leptin concentrations in obese women.

BACKGROUND: Plasma leptin in humans is subject to both long- and short-term regulation; it correlates with indexes of body fat that can only change slowly. However, short-term fasting causes large and rapid decreases. OBJECTIVE: We tested the interactions between energy intake and fat loss on plasma leptin during prolonged moderate and severe energy restriction, with a view to understanding mechanisms of control. DESIGN: Postabsorptive leptin was measured with an enzyme-linked immunosorbent assay specific for the human peptide in 21 obese women aged 41 +/- 3 y (weight: 102 +/- 4 kg; 48 +/- 1% body fat) after 1 wk of a weight-maintaining diet and then weekly for 4 wk during a total fast (group 1); a 1.9-MJ/d all-protein, very-low-energy diet (VLED) (group 2); or a low-energy, balanced-deficit diet (BDD) providing 50% of maintenance energy (group 3). In groups 1 and 2, leptin was also measured after 1 wk of refeeding with a diet equivalent to the BDD. RESULTS: Mean leptin decreased markedly by up to 66% (P < 0.001) at week 1 of energy restriction and then gradually thereafter. The change in leptin per kilogram fat mass correlated with that in glucose concentrations [r = 0.538 (P = 0.012) at week 1 and r = 0.447 (P = 0.042) at week 4] but not with that in fat mass. During refeeding postfasting, leptin increased (P = 0.008), despite an ongoing loss of fat mass and correlated positively with changes in resting energy expenditure. At times with comparable cumulative energy restriction and fat loss between diets, the percentage change in leptin paralleled that in glucose. CONCLUSIONS: In obesity, changes in energy intake over days to weeks are a primary modulator of plasma leptin concentrations that are related to the change in glycemia and are able to override the regulatory influence of fat mass.

Metabolic, gastrointestinal, and CNS neuropeptide effects of brain leptin administration in the rat.

To investigate whether brain leptin involves neuropeptidergic pathways influencing ingestion, metabolism, and gastrointestinal functioning, leptin (3.5 micrograms) was infused daily into the third cerebral ventricular of rats for 3 days. To distinguish between direct leptin effects and those secondary to leptin-induced anorexia, we studied vehicle-infused rats with food available ad libitum and those that were pair-fed to leptin-treated animals. Although body weight was comparably reduced (-8%) and plasma glycerol was comparably increased (142 and 17%, respectively) in leptin-treated and pair-fed animals relative to controls, increases in plasma fatty acids and ketones were only detected (132 and 234%, respectively) in pair-fed rats. Resting energy expenditure (-15%) and gastrointestinal fill (-50%) were reduced by pair-feeding relative to the ad libitum group, but they were not reduced by leptin treatment. Relative to controls, leptin increased hypothalamic mRNA for corticotropin-releasing hormone (CRH; 61%) and for proopiomelanocortin (POMC; 31%) but did not reduce mRNA for neuropeptide Y. These results suggest that CNS leptin prevents metabolic/gastrointestinal responses to caloric restriction by activating hypothalamic CRH- and POMC-containing pathways and raise the possibility that these peripheral responses to CNS leptin administration contribute to leptin's anorexigenic action.

Regulation of average 24h human plasma leptin level; the influence of exercise and physiological changes in energy balance.

OBJECTIVE: The effects of short-term moderate physiological changes in energy flux and energy balance, by exercise and over- or underfeeding, on a 24h plasma leptin profile, were investigated. DESIGN: Subjects were studied over 24h in four randomized conditions: no exercise/energy balance (energy intake (EI)=energy expenditure (EE)=11.8+/-0.8 MJ); exercise/energy balance (EI=EE=15.1+/-0.6 MJ); exercise/negative energy balance (EI=11.8+/-0.8 MJ, EE=15.1+/-0.8 MJ); exercise/positive energy balance (El=18.6+/-0.7 MJ, EE=15.1+/-0.6 MJ). SUBJECTS: Eight healthy, lean men (age: 23.5+/-7.0y, body fat 14.1+/-5.4%, body mass index (BMI): 21.4+/-2.3 kg/m2). MEASUREMENTS: Blood was sampled every hour during the daytime (09.00-23.00h) and every two hours during the night (01.00-09.00h) for analysis of plasma leptin, insulin, glucose, FFA and catecholamines. RESULTS: Plasma leptin levels were highest around 01.00h (mean+/-s.e.m. 4.9+/-2.0 ng/ml) and lowest around 11.00 h. (2.3+/-0.7 ng/ml). An increased 24h EE, induced by exercise under conditions of energy balance, significantly decreased the peak and average 24h plasma leptin concentration. A positive energy balance, by overfeeding, resulted in a significantly higher amplitude of the 24h plasma leptin curve, compared to a condition of energy balance. CONCLUSION: Exercise decreases peak and average 24h plasma leptin concentration and a moderately positive energy balance increases the amplitude of the 24h plasma leptin profile. These effects are not acute, but are manifest within 24h. The variations of average 24h FFA and average 24h glucose concentrations almost fully explained the variation in average 24h leptin concentration across trials.

High expression of leptin by human bone marrow adipocytes in primary culture.

Adipocytes participate in the microenvironment of the bone marrow (BM), but their exact role remains to be determined. It has recently been shown that leptin, a hormone secreted from extramedullary adipocytes, could be involved in hematopoiesis. Therefore we have developed a primary culture system of human BM adipocytes to characterize their differentiation and determine whether leptin is also secreted from these adipocytes. BM cells were cultured with fetal calf and horse sera. In the presence of dexamethasone, cells with vesicles containing lipids appeared within 15 days. They expressed glycerol phosphate dehydrogenase activity and a lipolytic activity in response to isoproterenol, but expressed neither the adrenergic beta3 receptor nor the mitochondrial uncoupling protein UCP1. The addition of insulin alone to the culture media did not promote adipocyte differentiation. Leptin was expressed and secreted at high levels during adipocyte differentiation. Acute exposure of differentiated adipocytes to insulin had little effect on leptin expression whereas forskolin strongly inhibited it. These results show that although human BM adipocytes differ from extramedullary adipose tissues in their sensitivity to different effectors, they are a secondary source of leptin production. They suggest that BM adipocytes could contribute to hematopoiesis via the secretion of leptin in the vicinity of hematopoietic stem cells.

Central leptin stimulates corticosterone secretion at the onset of the dark phase.

Leptin, a hormone secreted by adipose tissue in proportion to body adiposity, is proposed to be involved in the central nervous regulation of food intake and body weight. In addition, evidence is emerging that leptin regulates neuroendocrine and metabolic functions as well, presumably via its action in the central nervous system (CNS). To investigate this regulatory effect of leptin, we infused 3.5 microg of human leptin directly into the third cerebral ventricle (i3vt) of lean male Long-Evans rats, 90 min before the onset of their dark phase. Before and after infusion, blood samples were withdrawn through indwelling catheters for assessment of hormonal (plasma corticosterone, insulin, leptin), autonomic (plasma norepinephrine, epinephrine), and metabolic (plasma glucose) parameters. I3vt leptin caused an increase in plasma corticosterone and plasma leptin levels relative to the control condition. The effects of i3vt leptin on corticosterone secretion became particularly apparent after the onset of the dark phase. The results of the present study indicate that i3vt leptin stimulates the hypothalamo-pituitary-adrenal (HPA) axis, particularly when rats normally encounter their largest meals. These results are consistent with the possibility that high circulating leptin levels may underlie the increased activity of the HPA axis that is generally characteristic of human obesity and most animal models of obesity.

Insulin normalization as an approach to the pharmacological treatment of obesity.

Hyperinsulinemia and exaggerated insulin response to glucose are among the hallmarks of obesity. However, the role of hyperinsulinemia in the etiology and maintenance of obesity has been controversial. If hyperinsulinemia plays a critical role as proposed, then its reversal may have therapeutic potential. To test this hypothesis, the activity of Ro 23-7637, (4-(2,2-diphenylethenyl)-1-[1-oxo-9-(3-pyridinyl) nonyl]piperidine), which partially normalizes plasma insulin by an action on pancreatic islets from obese rats, was assessed. When islets were cultured for 2 days with 10 microM Ro 23-7637, a significant reduction in the exaggerated glucose-induced insulin secretion was observed. When islets from lean rats were exposed to Ro 23-7637, no reduction in insulin secretion was observed. The effects of oral administration of Ro 23-7637 were assessed in Zucker and diet-induced obese rats in doses ranging from 5 to 90 mg/kg/day. Dose-related reductions were observed in: 1) glucose-induced insulin secretion; 2) basal insulin concentration; 3) daily food intake; and 4) bodyweight gain. In diet-induced obese rats, selective mobilization of fat, maintenance of body protein, and decreased energetic efficiency were also observed. An association between the partial normalization of glucose-induced insulin responses and reductions of basal insulin, reduced rates of body weight gain or body weight loss and decreased food intake was observed in obese rats. Therefore, these studies indicate that Ro 23-7637 is an orally active, efficacious antiobesity agent.

Structure, localization, and action of buccalin B: a bioactive peptide from Aplysia.

The cholinergic motor neurons for the accessory radula closer (ARC) contain several neuropeptides that affect muscle contractions. In the present study, we have purified and sequenced a sixth ARC neuropeptide, using a combination of high pressure liquid chromatography and bioassays. This neuropeptide, Gly-Leu-Asp-Arg-Tyr-Gly-Phe-Val-Gly-Gly-Leu-amide, has been named buccalin B (BUCb) because it is significantly homologous to the previously characterized neuropeptide buccalin A. BUCb was found to be two-three times more potent than buccalin A in depressing motor neuron induced contractions.

Structure, bioactivity, and cellular localization of myomodulin B: a novel Aplysia peptide.

Important insights into mechanisms by which neuromuscular activity can be modulated have been gained by the study of experimentally advantageous preparations such as the ARC neuromuscular system of Aplysia. Previous studies have indicated that one source of modulatory input to the ARC muscle is its own two motor neurons, B15 and B16. Both of these neurons synthesize multiple peptide cotransmitters in addition to their primary neurotransmitter acetylcholine (ACh). Peptides present in the ARC motor neurons include SCPA, SCPB, buccalin A and B, and myomodulin A. We have now purified a novel neuropeptide, myomodulin B, which is structurally similar to myomodulin A. Myomodulin B is present in two identified Aplysia neurons that contain myomodulin A; the ARC motor neuron B16 and the abdominal neuron L10. Ratios of myomodulin A to myomodulin B are approximately 6:1 in both cells. Like myomodulin A, myomodulin B potentiates ARC neuromuscular activity; it acts postsynaptically, and increases the size and relaxation rate of muscle contractions elicited either by motor neuron stimulation or by direct application of ACh to the ARC. When myomodulin A is applied to the ARC in high doses (e.g., at about 10(-7) M), it decreases the size of motor neuron-elicited muscle contractions. This inhibitory effect is never seen with myomodulin B. Thus, despite the structural similarity between the two myomodulins, there exists what may be an important difference in their bioactivity.

Buccalin is present in the cholinergic motor neuron B16 of Aplysia and it depresses accessory radula closer muscle contractions evoked by stimulation of B16.

The accessory radula closer (ARC) buccal muscle motor neuron B16 is buccalin-immunoreactive and it synthesizes a peptide with chromatographic properties identical to those of buccalin. Terminal varicosities in the ARC muscle are buccalin-immunoreactive, and buccalin reduces muscle contractions evoked by stimulation of neuron B16, probably by a presynaptic action.

Release of peptide cotransmitters from a cholinergic motor neuron under physiological conditions.

In previous studies, we demonstrated that B15, one of the two cholinergic motor neurons of the accessory radula closer muscle of Aplysia, synthesizes two peptides, small cardioactive peptides A and B (SCPA and SCPB), that, when exogenously applied, increase the size and relaxation rate of muscle contractions elicited by motor neuron stimulation. In the present experiments, we obtained evidence that the SCPs are released under physiological conditions. Specifically, we characterized firing patterns of motor neuron B15 during normal behavior, simulated them in vitro, and demonstrated that this type of neuronal activity produces decreases in SCP levels in neuronal processes and terminals. We also obtained evidence that suggests that enough SCP is released under physiological conditions to modulate neuromuscular activity in the accessory radula closer. We demonstrated that physiological activity of neuron B15 produces significant increases in muscle cAMP levels. Furthermore, increases in the size and relaxation rate of muscle contractions can be produced by changes in stimulation parameters that are also likely to maximize effects of released endogenous SCPA and SCPB.

Purification and sequencing of neuropeptides contained in neuron R15 of Aplysia californica.

R15 is a large identified neuron present in the abdominal ganglion of the mollusc Aplysia. Previous studies have indicated that this neuron may play a role in water balance and possibly renovascular functions. A peptidic factor contained in the neuron R15 has been shown to increase the water content of Aplysia. To determine the structure of the peptides contained in R15, we purified the extracts of 820 R15 cells by means of two steps of reverse-phase HPLC. The purification yielded a number of peptides, only one of which, R15 alpha 1, resulted in water uptake when injected into animals. Determination of the amino acid content and sequence analysis of the R15 alpha 1 peptide demonstrated that this peptide contains 38 residues, including two cysteines. The peptide failed to react with iodoacetate, indicating that the two cysteines are connected by a disulfide bridge. To confirm the assigned structure, the peptide was synthesized with a disulfide bridge. The chromatographic properties and bioactivity of the synthetic material were identical to those of the native peptide. Several other R15 peptides were inactive in the bioassay for water uptake. The sequence of one of these peptides (R15 beta) was determined, and it was established that the peptide contains 28 residues. Amino acid analysis of three other peaks was performed. One of these peaks contained a peptide (R15 beta f) whose amino acid composition suggests that it is a fragment of the R15 beta peptide. The other two peaks contained peptides with identical amino acid compositions, suggesting that they are variants of a single peptide (R15 gamma). The amino acid sequences of all the peptides identified in neuron R15 correspond to stretches of a polyprotein encoded by a recently sequenced R15 cDNA.

Structure and action of buccalin: a modulatory neuropeptide localized to an identified small cardioactive peptide-containing cholinergic motor neuron of Aplysia californica.

A model system that consists of a muscle utilized in biting, the accessory radula closer (ARC), and the two cholinergic motor neurons innervating this muscle, neurons B15 and B16, has been used to study the expression of food-induced arousal in the marine mollusk Aplysia. The ARC muscle receives modulatory input from an extrinsic source, the serotonergic metacerebral cells, which partially accounts for the progressive increase in the strength of biting seen in aroused animals. Another source of modulation may arise from the ARC motor neurons themselves, which synthesize neuropeptides that can potentiate ARC contractions. Neuron B15 synthesizes the two homologous peptides, small cardioactive peptides A and B, whereas neuron B16 synthesizes the structurally unrelated peptide myomodulin. Here we report the purification and sequencing of a neuropeptide termed buccalin and show that it is colocalized with the small cardioactive peptides to neuron B15. Buccalin is also bioactive at the ARC neuromuscular junction but, in contrast to the small cardioactive peptides, when exogenously applied, it decreases rather than increases the size of muscle contractions elicited by firing of the motor neurons. Also unlike the small cardioactive peptides, which exert postsynaptic actions, buccalin seems to act only presynaptically. It has no effect on muscle relaxation rate and decreases motor neuron-elicited excitatory junction potentials in the ARC without affecting contractions produced by direct application of acetylcholine to the muscle. Neuron B15, therefore, appears to contain three modulatory neurotransmitters, two of which may act postsynaptically on the muscle to potentiate the action of the primary neurotransmitter acetylcholine and one of which may act presynaptically on nerve terminals to inhibit acetylcholine release.

Myomodulin: a bioactive neuropeptide present in an identified cholinergic buccal motor neuron of Aplysia.

When Aplysia are initially exposed to food stimuli, their biting responses show progressive increases in speed and strength. The accessory radula closer (ARC) buccal muscles have been used to study this phenomenon, and it has been shown that changes in ARC muscle contraction are partially due to activity of a serotonergic neuron that modulates this muscle, by both a direct action and an action on two ARC motor neurons (B15 and B16). The motor neurons use acetylcholine as their excitatory transmitter, but they also contain bioactive peptides that can potentiate muscle contractions when they are exogenously applied. Motor neuron B15 contains the structurally related small cardioactive peptides A and B, whereas motor neuron B16 contains a different peptide--termed myomodulin. In the present study we determined the full amino acid sequence of myomodulin. Myomodulin is present in the ARC muscle, and exogenous application of the peptide potentiates ARC muscle contractions in a manner similar to the potentiation by small cardioactive peptides A and B. The structure of myomodulin, however, bears little resemblance to the small cardioactive peptides. Thus it appears that ARC muscle contractions may be regulated by at least three distinct classes of neuromodulators: serotonin, the small cardioactive peptides, and myomodulin.

Multiple neuropeptides in cholinergic motor neurons of Aplysia: evidence for modulation intrinsic to the motor circuit.

Changes in Aplysia biting responses during food arousal are partially mediated by the serotonergic metacerebral cells (MCCs). The MCCs potentiate contractions of a muscle utilized in biting, the accessory radula closer (ARCM), when contractions are elicited by stimulation of either of the two cholinergic motor neurons B15 or B16 that innervate the muscle. We have now shown that ARCM contractions may also be potentiated by peptide cotransmitters in the ARCM motor neurons. We found that motor neuron B15 contains small cardioactive peptides A and B (SCPA and SCPB)--i.e., whole B15 neurons were bioactive on the SCP-sensitive Helix heart, as were reverse-phase HPLC fractions of B15 neurons that eluted like synthetic SCPA and SCPB. Furthermore, [35S]methionine-labeled B15 peptides precisely coeluted with synthetic SCPA and SCPB. SCPB-like immunoreactivity was associated with dense-core vesicles in the soma of B15 and in neuritic varicosities and terminals in the ARCM. B16 motor neurons did not contain SCPA or SCPB but contained an unidentified bioactive peptide. RP-HPLC of [35S]methionine-labeled B16s resulted in one major peak of radioactivity that did not coelute with either SCP and which, when subject to Edman degradation, yielded [35S]methionine in positions where there is no methionine in the SCPs. Exogenously applied B16 peptide potentiated ARCM contractions elicited by stimulation of B15 or B16 neurons. Thus, in this system there appear to be two types of modulation; one type arises from the MCCs and is extrinsic to the motor system, whereas the second type arises from the motor neurons themselves and hence is intrinsic.