Effects of an intraoperative infusion of 4% succinylated gelatine (Gelofusine(R)) and 6% hydroxyethyl starch (Voluven(R)) on blood volume.

BACKGROUND: This study aims to study changes in blood volume after 1 litre infusions of Gelofusine(®) [4% succinylated gelatine in 0.7% saline, weight-average molecular weight (MWw) 30 kDa] and Voluven(®) (6% hydroxyethyl starch in 0.9% saline, MWw 130 kDa) in the presence of increased capillary permeability. METHODS: In this randomized double-blind study, adults undergoing laparoscopic cholecystectomy received 1 litre of Gelofusine(®) (n=12) or Voluven(®) (n=13) over 1 h at the induction of anaesthesia. No other fluids were given. Haematocrit, serum electrolytes, and osmolality were measured before infusion and hourly thereafter for 4 h. Changes in blood volume were calculated from changes in haematocrit. The urinary albumin:creatinine ratio (ACR) was measured before and after operation. RESULTS: Baseline parameters before the two infusions were similar (P>0.050). The urinary ACR increased significantly after operation after Gelofusine(®) (P=0.011) and Voluven(®) (P=0.002), indicating increased capillary permeability. Voluven(®) produced a greater increase in serum chloride concentration (P=0.028) and a larger decrease in strong ion difference (P=0.009) than Gelofusine(®). There were no significant differences in changes in haematocrit (P=0.523) and blood volume (P=0.404) over the study period when the two infusions were compared, nor were there any differences in serum sodium, potassium, bicarbonate, and albumin concentrations (P>0.050). Urine output, sodium concentration, and osmolality were similar after the two infusions (P>0.050). CONCLUSIONS: The blood volume-expanding effects of the two colloids were not significantly different, despite the increase in postoperative urinary ACR and the 100 kDa difference in MWw.

Body mass influences cortical bone mass independent of leptin signaling.

Obesity in humans is associated with increased bone mass. Leptin, a hormone produced by fat cells, functions as a sentinel of energy balance, and may mediate the putative positive effects of body mass on bone. We performed studies in male C57Bl/6 wild type (WT) and leptin-deficient ob/ob mice to determine whether body mass gain induced by high fat intake increases bone mass and, if so, whether this requires central leptin signaling. The relationship between body mass and bone mass and architecture was evaluated in 9-week-old and 24-week-old WT mice fed a regular mouse diet. Femora and lumbar vertebrae were analyzed by micro computed tomography. In subsequent studies, slowly and rapidly growing ob/ob mice were injected in the hypothalamus with a recombinant adeno-associated virus containing the leptin gene (rAAV-lep) or a control vector, rAAV-GFP (green fluorescent protein). The mice were maintained on a regular control diet for 5 or 7 weeks and then subdivided into groups and either continued on the control diet or fed a high fat diet (45% of kcal from fat) for 8 weeks. In the WT mice, femoral and vertebral bone mass was positively correlated with body mass (Pearson's r=0.65-0.88 depending on endpoint). rAAV-lep therapy dramatically decreased body mass (-61%) but increased femur length. However, in the distal femur and lumbar vertebra, rAAV-lep therapy reduced cancellous bone volume/tissue volume, trabecular number and trabecular thickness, and increased trabecular spacing. The high fat diet increased body mass, irrespective of vector treatment. Total femur bone volume, length, cross-sectional volume, and cortical volume and thickness were increased in mice with increased body mass, independent of rAAV treatment. In the distal femur, increased body mass had no effect on cancellous architecture and there were no vector x body mass interactions. In WT mice, increased body mass resulted in increased (+33%) vertebral cancellous bone volume/tissue volume. Increased body mass had minimal independent effect on cancellous vertebral bone mass in ob/ob mice. Taken together, these findings suggest that increased body mass has a positive effect on femur cortical bone mass that is independent of leptin signaling.

Aquatic environmental effects monitoring guidance for environmental assessment practitioners.

The Canadian Environmental Assessment Act (CEAA) defines the federal environmental assessment (EA) process for evaluating the likelihood that development projects (e.g., roads, buildings, factories) will have impacts on the environment. Environmental effects monitoring (EEM) programs for mining and pulp and paper mills under the Federal Fisheries Act, define the process that is to be used to evaluate existing effects caused by liquid effluents discharged by operating facilities. The EA process occurs before a project is approved, and involves predicting whether the project is going to cause significant environmental impacts. The EEM process occurs after a project is operational, and involves determining whether an existing project has had or is continuing to have significant impacts on the environment. Ideally, the processes are complimentary, with the EA process identifying environmental attributes considered important, and the EEM process demonstrating whether predicted or unpredicted impacts occurred. The two processes are usually done in isolation so potential synergies are lost. The point of this manuscript is to justify bridging the two processes. We use the aquatic environment as the example, and briefly describe the EEM process, aquatic environment indicators, experimental designs, and typical environmental thresholds, to illustrate how the EEM and EA processes link.

Effects of metal mining effluent on Atlantic salmon (Salmo salar) and slimy sculpin (Cottus cognatus): using artificial streams to assess existing effects and predict future consequences.

In the summer of 2000, the effects of metal mine discharge on fish growth and exercise performance were assessed at a Zn-Pb-Cu mine in New Brunswick, Canada. Juvenile Atlantic salmon (Salmo salar) were exposed to 0%, 20%, and 80% treated metal mine effluent in a mobile, fish-only artificial stream system. Fish were fed commercial salmon pellets throughout the study. Young-of-the-year slimy sculpins (Cottus cognatus) were exposed to the same treatments in a multitrophic level, modular artificial stream system or mesocosm, in which the fish were dependent on seeded algae and invertebrates for nutrition. Treatment concentrations were chosen to represent existing discharge dilutions (80%) and a scenario of reduced effluent discharge (20%) as predicted upon mine closure (scheduled for 2008). Al, Ba, B, Fe, Mn, Sr, Tl, Ti, and Zn increased in a concentration-dependent fashion across the three treatments. Salmon body burdens of Ba, Cd, Li, Cu, Mn, Se, Sr, and Zn were increased in the 80% treatment, while Tl increased across all treatment levels. Mortalities and depressions in growth in both fish species paralleled treatment concentrations (80%>20%>0%). Salmon liver weight was significantly greater in fish exposed to 20% and 80% effluent in a concentration-dependent fashion. Exercise performance in fish, as assessed by the ability to recover from forced exercise, showed little effect of treatment. The contamination of the receiving environment by mine discharges has led to loss of fish, making it impossible to study the system in situ. However, the use of the artificial stream systems enabled us to assess effects of present conditions on fish, as well as the potential impacts of mine reclamation. The 20% discharge predicted following mine reclamation is potentially favourable for the reinstitution of native fishes into the system.

Evidence for the existence of distinct central appetite, energy expenditure, and ghrelin stimulation pathways as revealed by hypothalamic site-specific leptin gene therapy.

To identify the specific hypothalamic sites in which leptin acts to decrease energy intake and/or increase energy expenditure, recombinant adeno-associated virus vector-encoding leptin was microinjected bilaterally into one of four hypothalamic sites in female rats. Leptin transgene expression in the ventromedial nucleus and paraventricular nucleus induced comparable decreases in daily food intake (FI; 18-20%) and body weight (BW; 26-29%), accompanied by drastic reductions in serum leptin (81-97%), insulin (92-93%), free fatty acids (35-36%), and normoglycemia. Leptin transgene expression in the arcuate nucleus (ARC) decreased BW gain (21%) and FI (11%) to a lesser range, but the metabolic hormones were suppressed to the same extent. Leptin transgene expression in the medial preoptic area (MPOA) decreased BW and metabolic hormones without decreasing FI. Finally, leptin transgene expression in all four sites augmented serum ghrelin and thermogenic energy expenditure, as shown by uncoupling protein-1 mRNA expression in brown adipose tissue. Proopiomelanocortin gene expression in the ARC was up-regulated by leptin expression in all four sites, but neuropeptide Y gene expression in the ARC was suppressed by leptin transgene expression in the ARC but not in the MPOA. Thus, whereas leptin expression in the paraventricular nucleus, ventromedial nucleus, or ARC suppresses adiposity and insulin by decreasing energy intake and increasing energy expenditure, in the MPOA it suppresses these variables by increasing energy expenditure alone.

Peri-operative fluid and electrolyte management: a survey of consultant surgeons in the UK.

BACKGROUND: Current peri-operative fluid and electrolyte management in the UK may be suboptimal. We assessed the attitudes of consultant surgeons to fluid and electrolyte prescribing and gathered suggestions for improvement in education on the subject. METHODS: A postal questionnaire survey was sent to 1091 Fellows of the Association of Surgeons of Great Britain and Ireland. Of the 730 (67%) replies, 20 were invalid or incomplete, and 710 (65%) questionnaires were analysed. Outcome measures included provision of guidelines and teaching to junior staff on fluid and electrolyte prescribing, appropriateness of fluid management and suggestions to improve standards. RESULTS: Junior staff were given written guidelines in 22% of instances. Only 16% of respondents felt that their preregistration house officers (PRHOs) were adequately trained in the subject before joining the firm; 15% also stated that PRHOs did not receive much training on their firm. 65% felt that fluid balance charts were accurately maintained, nursing shortages being the commonest reason for inaccuracies. Only 30% felt that postoperative patients were receiving appropriate amounts of water, sodium and potassium. Respondents who had been consultants for > 5 years were more likely to prefer erring on the side of under-replacement of fluid than those who were consultants for 5 years (63% versus 47%, P < 0.0005). Suggestions for improvement in education included problem-oriented ward rounds, written guidelines, and discussion of patient scenarios. CONCLUSIONS: Consultant surgeons feel that present practice in peri-operative fluid management is unsatisfactory. Higher standards within clinical governance and risk management may be achieved by focused practical training combined with formal written guidelines.

Audit of acute pancreatitis management: a tale of two hospitals.

BACKGROUND: A case note audit of existing practices in the management of acute pancreatitis (AP) at a district general hospital (DGH) and a teaching hospital was undertaken to determine if practices were in accordance with published UK guidelines. METHODS: Casenotes of all adults admitted with AP over a period of one year at the two hospitals were reviewed. RESULTS: Ninety-five patients were treated for AP at the teaching hospital and 52 at the DGH. The age, sex and aetiological distributions at the two hospitals were similar. Fifteen (15.8%) patients at the teaching hospital and eight (15.3%) at the DGH had severe AP. Four patients died at each hospital. Prognostic Glasgow criteria tests (excluding LDH) were completed within 48 hours in 43% patients at the teaching hospital and 48% at the DGH. Five of the twenty-five cholecystectomies at the teaching hospital and 4/18 at the DGH were performed within four weeks after admission with AP. CONCLUSION: Audit of current practice has highlighted deficiencies at many levels compared with current evidence-based guidelines, although this has not resulted in unexpected mortality. It remains to be seen whether new measures to aid compliance with guidelines will result in improvement in morbidity and mortality.

Identification and treatment of a waste stream at a bleached-kraft pulp mill that depresses a sex steroid in the mummichog (Fundulus heteroclitus).

Changes to indicators of reproductive performance have been documented in fish exposed to some bleached kraft pulp mill effluents (BKPMEs). However, responses are not consistent across mill types or processes. It is not clear where the sources of the effects are within mills, what the causative compounds are, or what process changes are effective to remove these sources. Our previous studies suggested that condensates were a source of compounds that reduced plasma testosterone in the mummichog (Fundulus heteroclitus). Results also suggested that reverse osmosis (RO) treatment of condensates removed this source. The objective of this study was to use a toxicity identification evaluation approach and expose mummichog to various waste streams in the laboratory to identify the effluent source that depressed plasma testosterone in the mummichog and the effects of RO treatment. In 7- and 21-d exposures, mummichog were exposed to dilutions of RO feed condensate, RO permeate, combined mill effluent (CME), and final effluent. Results confirmed that condensates depressed plasma testosterone in mummichog. Chemical characterization of the condensate indicated that plant phytosterols were likely not the responsible compounds. Results also confirmed that RO treatment removed the potential of the condensates to depress plasma testosterone in mummichog at environmentally relevant concentrations of final mill effluent (1%).

Problems with solutions: drowning in the brine of an inadequate knowledge base.

BACKGROUND & AIMS: We undertook a telephone questionnaire to determine current fluid prescribing practices and relevant knowledge among surgical preregistration house officers (PRHOs) and senior house officers (SHOs) working in 25 British hospitals. METHODS: One hundred PRHOs were surveyed within 10 days of starting their first job (Group A). Fifty other PRHOs were surveyed 6-8 weeks after starting their first job(Group B) along with 50 surgical SHOs (Group C). Outcome measures included responsibility for prescribing, knowledge of the composition of common intravenous fluids and the principles governing their use. RESULTS: PRHOs were responsible for prescribing in 89% of instances. Only 56% of respondents stated that fluid balance charts were checked on morning ward rounds. Less than half were aware of the sodium content of 0.9% saline or the daily sodium requirement. Although potassium supplements were usually correct, 25% of respondents prescribed two or more litres of 0.9% saline per day, which is far in excess of normal requirements. Although SHOs were more confident (P<0.0001), there was no significant difference between the three groups for most responses. CONCLUSIONS: Inadequate knowledge and suboptimal prescribing of fluid and electrolytes is common. Undergraduate and postgraduate training in this basic patient management skill needs improvement, with particular emphasis on the practical aspects.

A GABA-neuropeptide Y (NPY) interplay in LH release.

Neuropeptide Y (NPY) stimulates and gamma-amino butyric acid (GABA) inhibits LH release in the rat. Since a sub-population of NPY-producing neurons in the arcuate nucleus (ARC) of the hypothalamus co-express GABA, the possibility of an interplay between NPY and GABA in the release of LH was investigated in two ways. First by employing light and electron microscopic double staining for NPY and GABA, using pre and post-immunolabeling on rat brain sections, we detected GABA in NPY immunoreactive axon terminals in the MPOA, one of the primary sites of action of these neurotransmitters/neuromodulators in the regulation of LH release. These morphological findings raised the possibility that inhibitory GABA co-released with NPY may act to restrain the excitatory effects of NPY on LH release. Muscimol (MUS, 0.44 or 1.76 nmol/rat), a GABA(A) receptor agonist, administered intracerebroventricularly (icv), alone failed to affect LH release, but NPY (0.47 nmol/rat icv) alone stimulated LH release in ovarian steroid-primed ovariectomized rats. On the other hand, administration of MUS blocked the NPY-induced stimulation of LH release in a dose-dependent manner. Similarly, administration of MUS abolished the excitatory effects on LH release of 1229U91, a selective NPY Y4 receptor agonist. These results support the possibility that in the event of co-release of these neurotransmitters/neuromodulators, GABA may act to restrain stimulation of LH release by NPY during the basal episodic and cyclic release of LH in vivo.

The mPVN mediates blockade of NPY-induced feeding by a Y5 receptor antagonist: a c-FOS analysis.

To identify the site(s) of NPY Y5 receptor (Y5R) mediation of NPY-induced feeding, we employed c-Fos immunostaining and a selective Y5R antagonist (Y5R-A), CGP71683A, in adult male rats. Intracerebroventricular (icv) administration of NPY stimulated feeding and c-Fos-like immunoreactivity (FLI) in the dorsomedial hypothalamus, supraoptic nucleus and the two subdivision of the hypothalamic paraventricular nucleus (pPVN), the parvocellular (pPVN), and magnocellular (mPVN). Y5R-A on its own, injected either intraperitoneally or icv, neither affected feeding nor FLI in hypothalamic sites. However, Y5R-A pretreatment suppressed NPY-induced food intake and FLI selectively in the mPVN. Taken together with our previous similar finding of Y1R involvement, these results suggest that NPY receptor sites concerned with feeding behavior reside selectively in the mPVN and Y1 and Y5 receptors are either coexpressed or expressed separately in those target neurons that promote appetitive drive.

Evidence of NPY Y5 receptor involvement in food intake elicited by orexin A in sated rats.

Intracerebroventricular (icv) injections of orexin A stimulate feeding in sated rats. Since neuropeptide Y is a potent orexigenic peptide and orexin-containing neurons are morphologically linked with NPY-producing neurons in the hypothalamus, we evaluated the functional relationship between the two orexigenic peptides. The results show that whereas it was ineffective on its own, a selective NPY Y5 receptor antagonist, injected icv 15 min. before orexin A significantly suppressed orexin A-induced feeding. Since previous investigations demonstrated that an NPY Y1 receptor antagonist also inhibits feeding induced by orexin A, the current results further underscore the existence of a functional link between orexin and NPY producing neurons as the orexin network appears to be capable of influencing NPYergic signaling through Y1 and Y5 receptors to stimulate feeding.

Regulation of leptin secretion: effects of aging on daily patterns of serum leptin and food consumption.

We have investigated the effects of age on the daily rise in serum leptin levels during the dark-phase of the light-dark cycle. The results show that in young 7-week-old rats, serum leptin levels increase significantly at 2300 h from the levels at 1500 h in association with increased food consumption. However, in middle-aged rats 25 weeks old, the dark-phase increase in serum leptin is absent despite retention of the daily dark-phase increase in food consumption. When compared to our earlier published results, these finding show that the loss of dark-phase rise in serum leptin occurred despite the daily increase in adipocyte leptin gene expression. These results are in accord with the view that the daily pattern in serum leptin is unlikely to be a contributor to the daily patterning of food consumption.

Melanocortin signaling is decreased during neurotoxin-induced transient hyperphagia and increased body-weight gain.

Hypothalamic neuropeptides play critical roles in the regulation of feeding behavior and body weight (BW). Disruption of signaling in the ventromedial nucleus by microinjection of the neurotoxin, colchicine (COL), produces transient hyperphagia with corresponding BW gain lasting for 4 days. Because the melanocortin system exerts an inhibitory control on food intake, we hypothesized that hyperphagia in COL-treated rats is due to decreased melanocortin-induced restraint on feeding. Melanocortin restraint is exerted through alpha-melanocortin-stimulating hormone derived from proopiomelanocortin (POMC) and is antagonized by agouti-related peptide produced in neurons located in the arcuate nucleus (ARC). COL (4 microg/0.5 microl saline) or saline was microinjected bilaterally into the ventromedial nucleus of adult male rats. In conjunction with BW gain, blood leptin levels were elevated, whereas POMC mRNA in the ARC was significantly decreased in COL-injected rats. Levels of alpha-melanocortin-stimulating hormone were also decreased in the micropunched paraventricular nucleus, dorsomedial nucleus, and perifornical hypothalamus, sites implicated in the control of food intake. That diminution in melanocortin signaling underlies hyperphagia was supported by the observation that intracerebroventricular injection of the MC3/MC4 melanocortin receptor agonist, MTII, prevented the hyperphagia and BW gain. Surprisingly, however, mRNA levels of the orexigenic peptide agouti-related peptide in the ARC were decreased perhaps due to the action of elevated leptin. These results show that transient hyperphagia and BW gain induced by disruption of signaling in the ventromedial nucleus results from two neurochemical rearrangements: development of leptin resistance in POMC neurons and diminution in melanocortin signaling as reflected by decreased POMC gene expression in the ARC and decreased availability of alpha-melanocortin-stimulating hormone for release in feeding relevant sites.

A 'palliative' resection which became potentially curative.

We report a very unusual case of a woman with rectal cancer, who, at operation, appeared to have peritoneal metastases. An anterior resection was carried out, and subsequent histology showed the rectal tumour to be a well-differentiated Dukes' B adenocarcinoma, which had been completely excised. The apparent 'metastases' were found to be schistosomal granulomas and there was also a schistosomal granuloma within the tumour.

Hypothalamic galanin is up-regulated during hyperphagia and increased body weight gain induced by disruption of signaling in the ventromedial nucleus.

Disruption of signaling in the ventromedial nucleus (VMN) by colchicine (COL) produces transient (4 days) hyperphagia and weight gain. Microinjection of galanin into various hypothalamic sites stimulates feeding, so we tested the hypothesis that galanin is up-regulated in COL-treated rats by analyzing galanin concentrations in micropunched hypothalamic sites. Galanin was increased in the paraventricular nucleus on Days 1 through 4 after COL-injection. Galanin was also elevated in three other hypothalamic sites, the dorsomedial nucleus, lateral hypothalamic area, and perifornical hypothalamus, on Days 2-4 and in the lateral preoptic area, on Day 1 only. In the median eminence-arcuate nucleus and amygdala an initial decrease on Day 1 was followed by a then progressive increase through Day 4. These increases occurred despite marked elevations in blood insulin and leptin, hormones known to suppress hypothalamic galanin. When COL- or saline-treated rats were injected intracerebroventricularly with galanin, it stimulated feeding further in the hyperphagic COL-treated rats, but the relative response over basal consumption was similar in both COL-treated and control rats. These results in VMN disrupted rats suggest that neurochemical rearrangements, including increased availability of galanin, may contribute to the hyperphagia and increased weight gain; additionally, it seems that neurons in the VMN normally exert a restraint on galanin signaling.

Effects of centrally administered antisense oligodeoxynucleotides on feeding behavior and hormone secretion.

The effects of neurotransmitters and neuromodulators can be interrupted by either blockade or diminution in the amount of release by curtailing the availability of the neuropeptides in the nerve terminals. Theoretically, antisense oligodeoxynucleotides decrease the availability of signals by blocking the transcription process, thus offering an opportunity to dissect the relative roles of neurotransmitters that elicit similar biological responses. Both NPY and GAL stimulate feeding and LHRH secretion, but antisense oligodeoxynucleotides behaved differently in interrupting these two responses. Centrally administered antisense oligodeoxynucleotides were effective in blocking the stimulatory effects of NPY on LH release, thereby demonstrating that neuronal permeability, degradation, and toxicity of oligodeoxynucleotides are not limiting factors. Thus, for short-term studies the unmodified phosphodiester sequences can be successfully used. Because the attempts to block the behavioral effects of NPY yielded equivocal results, it is clear that newly synthesized NPY, critical for LH release, is relatively insignificant for feeding. Blockade of behavioral effects requires a longer period of effectiveness of oligodeoxynucleotides necessitating that the rate of oligodeoxynucleotide degradation be retarded. Effective protection from degradation in vivo can be achieved by phosphorothioating one or two terminal bases. This modification, unlike the earlier practice of phosphorothioate protection of each base, causes no toxicity and is well tolerated after central administration. Adequate controls, including vehicle and similarly modified missense or scrambled sequences, are essential to confirm specificity and to exclude toxicity. The site of administration is another important factor to be considered in the experimental design. Whereas i.c.v. injections (lateral ventricle, or IIIrd ventricle) have been largely effective in allowing access to multiple hypothalamic sites, direct injection into relevant hypothalamic nuclei may provide surgical precision to effect concentrated blockade at the site of synthesis. Earlier studies with centrally administered oligodeoxynucleotides were plagued by these limitations, resulting in inconsistent and equivocal results. However, more recent investigations, designed with these caveats in mind, have successfully used antisense oligodeoxynucleotides as exemplified by the studies to establish the role of the Y5R subtype in transducing the orexigenic NPY signal.

Food intake elicited by central administration of orexins/hypocretins: identification of hypothalamic sites of action.

Orexin A and B, a recently identified pair of neuropeptides, are produced in perikarya located in the lateral and perifornical hypothalamus (LH and PFH). Immunoreactive fibers from these neurons innervate several nuclei in the hypothalamus. Orexin A and orexin B stimulate feeding when administered intracerebroventricularly to rats. To identify the specific sites of orexin action, orexin A and B were microinjected into a number of hypothalamic and extrahypothalamic sites in rats. Orexin A was found to enhance food intake when injected into four hypothalamic sites, the paraventricular nucleus (PVN), the dorsomedial nucleus (DMN), LH and the perifornical area, but was ineffective in the arcuate nucleus (ARC), the ventromedial nucleus (VMN), and the preoptic area (POA) as well as the central nucleus of the amygdala (CeA) and nucleus of the tractus solitarius (NTS). Orexin B was not effective at any site tested. These findings demonstrate that orexin A receptive sites for stimulation of food intake exist primarily in a narrow band of neural tissue within the hypothalamus that is known to be involved in control of energy homeostasis.

Comparing the hypothalamic and extrahypothalamic actions of endogenous hyperleptinemia.

To determine whether the depletion of body fat caused by adenovirus-induced hyperleptinemia is mediated via the hypothalamus, we used as a "bioassay" for hypothalamic leptin activity the hypothalamic expression of a leptin-regulated peptide, cocaine- and amphetamine-regulated transcript (CART). The validation of this strategy was supported by the demonstration that CART mRNA was profoundly reduced in obese rats with impaired leptin action, whether because of ablation of the ventromedial hypothalamus (VMH) or a loss-of-function mutation in the leptin receptor, as in Zucker diabetic fatty rats. We compared leptin activity in normal rats made hyperleptinemic by adenovirus-leptin treatment (43 +/- 9 ng/ml, cerebrospinal fluid leptin 100 pg/ml) with normal rats made hyperleptinemic by a 60% fat intake (19 +/- 4 ng/ml, cerebrospinal fluid leptin 69 +/- 22 pg/ml). CART was increased 5-fold in the former and 2-fold in the latter, yet in adenovirus-induced hyperleptinemia, body fat had disappeared, whereas in high-fat-fed rats, body fat was abundant. Treatment of the high-fat-fed rats with adenovirus-leptin further increased their hyperleptinemia to 56 +/- 6 ng/ml without changing CART mRNA or food intake, indicating that leptin action on hypothalamus had not been increased. Nevertheless, their body fat declined 36%, suggesting that an extrahypothalamic mechanism was responsible. We conclude that in diet-induced obesity body-fat depletion by leptin requires supraphysiologic plasma concentrations that exceed the leptin-transport capacity across the blood-brain barrier.