Euglycemic hyperinsulinemia, but not lipid infusion, decreases circulating ghrelin levels in humans

The orexigenic and anabolic gastric hormone ghrelin is secreted in response to acute and chronic energy requirements. While pre-prandial increases and post-prandial decreases of plasma ghrelin levels in rodents and humans seem to indicate a role for the novel peptide hormone as an afferent meal initiator or "hunger hormone", the precise mechanisms which are suppressing ghrelin secretion in response to caloric intake remain largely unknown. We show here that human ghrelin levels decrease by almost 50% under hyperinsulinemic euglycemic clamp conditions (no.=4, p=0.001), revealing physiologically relevant increases of insulin levels as an independent determinant of circulating ghrelin levels. In a second study, 3-4-fold increased plasma free fatty acid levels, as another metabolic candidate for the modulation of circulating ghrelin concentrations, were generated by constant lipid infusion, but failed to change plasma ghrelin. Simultaneous elevation of free fatty acids and insulin again markedly decreased ghrelin concentration (no.=4, p=0.01). Insulin induced suppression of circulating ghrelin levels (or the lack thereof) could be a mechanism with relevance for the understanding of the (patho-) physiology of meal initiation and termination, the pathogenesis of the metabolic syndrome and for the development of respective therapeutic perspectives.

Effects of duodenal fat, protein or mixed-nutrient infusions on epigastric sensations during sustained gastric distension in healthy humans

Duodenal fat modulates sensory and motor responses to gastric distension and raises plasma cholecystokinin compared with glucose. The effects of protein (also releasing cholecystokinin), or mixed nutrients (with a balanced macronutrient composition), on gastrointestinal sensations in relation to gastric relaxation and plasma cholecystokinin concentrations are not known. The aim of this study was therefore to compare the effects of duodenal infusion of fat, protein or mixed nutrients during sustained gastric distension (mimicking the intragastric presence of food) on these parameters. In 10 healthy subjects, gastric distension to fullness was maintained for 90 min, while gastric volume, sensations and plasma cholecystokinin were monitored during duodenal infusion of isotonic saline or nutrients (2 kcal min-1). During saline infusion, all parameters remained unchanged for 90 min. Initially, only lipid increased plasma cholecystokinin, gastric volume and scores for sensations. Cholecystokinin and gastric volume responses to protein and mixed nutrients were delayed and not associated with significant changes in sensations. In conclusion, the intensity of gastrointestinal sensations is related to, but not entirely explained by, the magnitude in intragastric volume and plasma cholecystokinin changes. Our results offer new insights into the role of dietary nutrient composition in gastrointestinal sensations, and may have implications for the dietary management of digestive symptoms.

[Arterial aneurysm within a tumor in a pediatric patient]

A middle cerebral artery aneurysm, completely enclosed in a large frontotemporal anaplastic astrocytoma, is demonstrated in a 11-month-old girl admitted for intracranial hypertension. Clipping of the aneurysm along with radical resection was successfully performed. Five years later, follow-up neurological examination is normal, aneurysm occlusion and no evidence of tumor recurrence are demonstrated by angiogram and MRI. The association of brain tumor and aneurysm is discussed, and documented with the only two cases of a neoplasm surrounding on aneurysm reported in the literature.

Weight gain decreases elevated plasma ghrelin concentrations of patients with anorexia nervosa

OBJECTIVE

Ghrelin is a new gastric hormone that has been identified as an endogenous ligand for the growth hormone (GH) secretagogue receptor subtype 1a (GHS-R1a). Ghrelin administration however not only stimulates GH secretion but also induces adiposity in rodents by increasing food intake and decreasing fat utilization. We hypothesized that impaired ghrelin secretion in anorexia nervosa may be involved in the pathogenesis of this eating disorder. To examine this hypothesis and to further investigate the role for ghrelin in regulating energy homeostasis, we analyzed circulating ghrelin levels in patients with anorexia nervosa and examined possible correlations with clinical parameters before and after weight gain.

METHODS

Plasma ghrelin levels were measured in overnight fasting plasma samples from 36 female patients with anorexia nervosa (age: 25.0+/-1.2 years, BMI: 15.2+/-0.2 kg/m(2)) before and after weight gain following psychotherapeutic treatment intervention in a psychosomatic institution. Plasma ghrelin levels were also measured in fasting plasma samples from 24 age-matched female controls (31+/-1.4 years, BMI: 22.9+/-0.45 kg/m(2)). For quantification of ghrelin levels a commercially available radioimmunoassay (Phoenix Pharmaceuticals, USA) was used.

RESULTS

Fasting plasma ghrelin levels in anorectic patients were significantly higher (1057+/-95 pg/ml) than in normal age-matched female controls (514+/-63 pg/ml n=24, P=0.02). Therapeutic intervention in a psychosomatic institution caused an BMI increase of 14% (P<0.001) leading to a significant decrease in circulating ghrelin levels of 25%, (P=0.001). A significant negative correlation between Deltaghrelin and DeltaBMI was observed (correlation coefficient: -0.47, P=0.005, n=36).

CONCLUSION

We show for the first time that fasting plasma levels of the novel appetite-modulating hormone ghrelin are elevated in anorexia nervosa and return to normal levels after partial weight recovery. These observations suggest the possible existence of ghrelin resistance in cachectic states such as caused by eating disorders. Future studies are necessary to investigate putative mechanisms of ghrelin resistance such as a possible impairment of intracellular ghrelin receptor signaling in pathophysiological states presenting with cachexia.

The tobacco plasma membrane aquaporin NtAQP1

This paper gives a summary of a project to characterize a tobacco aquaporin. The cDNA and gene, including the 5' upstream region, for the tobacco aquaporin NtAQP1 has been isolated and the encoded protein characterized. The significance of promoter regions for an abscisic acid- and gibberellic acid-induced gene expression could be restricted to a region between -1450 and -1112 upstream of the transcription start point by transient transformation of a bicistronic vector into tobacco protoplasts. NtAQP1 expression in tobacco plants was found to be elevated in flowers, stems and roots. In roots, the protein was detected close to xylem vessels in pitch-like structures. Studies with a NtAQP1-GFP fusion indicated a plasma membrane location. For a functional analysis, the cDNA was expressed in Xenopus oocytes. NtAQP1 was found to be a heavy metal-insensitive aquaporin with additional permeability for glycerol. Mutation of a threonine at position 233 to a cysteine transformed NtAQP1 into a heavy metal-sensitive aquaporin.

Fat digestion modulates gastrointestinal sensations induced by gastric distention and duodenal lipid in humans

BACKGROUND AND AIMS

It is unclear whether fat digestion is required for the induction of gastrointestinal sensations and whether different fats have different effects. We investigated the effect of fat digestion and of medium-chain triglycerides (MCTs; C < 12) and long-chain triglycerides (LCTs; C > 16) on gastrointestinal sensations.

METHODS

In a double-blind study, 15 healthy subjects were studied on 5 occasions during which LCT or MCT emulsions (2 kcal/min), with or without 120 mg tetrahydrolipstatin (THL, lipase inhibitor), or sucrose polyester (SPE, nondigestible fat) were infused intraduodenally in randomized order. After 30 minutes, the proximal stomach was distended in 1 mm Hg steps/min. Intensity of gastrointestinal sensations (on a 0-10 visual analog scale), plasma cholecystokinin (CCK) levels, and gastric volumes were assessed throughout.

RESULTS

LCT and MCT increased gastric volume at baseline pressure compared with SPE, and LCT more than MCT. THL entirely abolished this effect (volumes [mL]: LCT, 213 +/- 19; LCT-THL, 39 +/- 3; MCT, 155 +/- 12; MCT-THL, 43 +/- 5; SPE, 44 +/- 5). Only LCT increased plasma CCK levels (pmol/L per 30 minutes: LCT, 21 +/- 2; LCT-THL, 9 +/- 1; MCT, 9 +/- 1; MCT-THL, 11 +/- 1; SPE, 9 +/- 1). During distentions, intragastric volumes were greater during infusion of LCT and MCT than during the respective THL conditions or SPE, but plasma CCK levels did not change. The intensity of sensations increased (hunger decreased) more with LCT than with MCT. During infusion of THL or SPE, the effects were smaller than during LCT or MCT.

CONCLUSIONS

Fat digestion is required for the modulation of gastrointestinal sensations during gastric distention. The effects of fat depend on the fatty acid chain length and are not entirely explained by release of CCK.

Role of duodenal lipid and cholecystokinin A receptors in the pathophysiology of functional dyspepsia

BACKGROUND/AIMS

We aimed to evaluate the role of fat and cholecystokinin (CCK) in the pathophysiology of functional dyspepsia (FD) by investigating symptoms and plasma CCK levels following increasing doses of duodenal lipid during gastric distension, and the effect of CCK-A receptor blockade.

SUBJECTS/METHODS

In study A, six FD patients were studied on three occasions during duodenal infusion of saline or lipid (1.1 (L-1) or 2 kcal/min (L-2)) and proximal gastric distensions. Six healthy subjects were also studied as controls during L-2 only. In study B, the effect of the CCK-A antagonist dexloxiglumide (5 mg/kg/h) on L-2 induced symptoms was studied in 12 FD patients. Changes in gastric volume at minimal distending pressure and plasma CCK (study A) were assessed, gastric distensions were performed using a barostat, and dyspeptic symptoms were monitored.

RESULTS

Lipid increased gastric volume compared with saline (DeltaV (ml): saline 15 (20), L-1 122 (42), L-2 114 (28)) in patients and even more so in controls (221 (37); p<0.05). During distensions, symptoms were greater during L-2 than during saline or L-1, and greater in patients than in controls, while gastric compliance was smaller in patients than in controls (p<0.05). Lipid increased plasma CCK levels in patients and controls (p>0.05). Dexloxiglumide abolished the increase in gastric volume (DeltaV (ml): dexloxiglumide 17 (9), placebo 186 (49)) and dyspeptic symptoms (sum of scores: dexloxiglumide 24 (7), placebo 44 (19)) during duodenal lipid infusion. Dexloxiglumide also reduced gastric compliance (ml/mm Hg: dexloxiglumide 51 (7), placebo 72 (11)) and symptoms (sum of scores: dexloxiglumide 101 (17), placebo 154 (21)) during gastric distension.

CONCLUSION

CCK-A receptors are involved in the generation of dyspeptic symptoms by duodenal lipid during gastric distension.

[Evidence of Cryptococcus neoformans in domestic and sports pigeons in Thyringia]

19 strains of Cryptococcus neoformans var. neoformans were isolated from 17 (= 40.5%) of 42 investigated pigeon breeder flocks in Thuringia.

[Mycoses in fish]

Over 4 years 1.241 fish were examined mycologically. In 182 (14.7%) of them positive results were obtained. Most of the isolates belonged to the following genera: Cladosporium, Saprolegnia, Candida and Penicillium. Fungal infections were correlated with findings of Saprolegnia, Branchiomyces, Pythium, Ichtyophonus and sometimes Cladosporium. Most fungal isolates were etiologically irrelevant for diseases or death.

Pavlovian conditioning of taste aversion using a motion sickness paradigm

OBJECTIVE

Pavlovian conditioning of taste aversion has rarely been investigated in healthy humans using motion sickness as the unconditioned stimulus (US).

METHODS

Ninety subjects were pretested for susceptibility to illusory motion (vection) in a rotating drum. Thirty-two subjects susceptible to pseudomotion were assigned randomly to two groups and received either water 1 hour before rotation and a novel taste (elderberry juice, conditioned stimulus, [CS]) immediately before rotation in a rotating chair (conditioning group), or the sequence of water and juice was reversed (control group). During the test session 1 week later, all subjects were exposed to water 1 hour before and juice immediately before rotation. The amount of liquids ingested, nausea ratings, rotation tolerance, and blood levels of hormones (ACTH, ADH, PP) were evaluated.

RESULTS

Subjects in the conditioning group developed taste aversion toward the novel taste, but not subjects in the control group. Postrotation nausea rating was affected marginally by conditioning, but rotation tolerance was not changed by conditioning. ACTH and ADH but not PP levels increased with rotation, but were unaffected by conditioning.

CONCLUSIONS

Pavlovian conditioning of behavioral, but not of endocrine, indicators was effective in susceptible subjects using a rotating chair as US and a single CS-US pairing.

Cell-specific expression of the mercury-insensitive plasma-membrane aquaporin NtAQP1 from Nicotiana tabacum

The aquaporin NtAQP1 from Nicotiana tabacum L. is insensitive to heavy-metal ions. In addition to water, the transport of urea or glycerol is facilitated by this plasma-membrane-located water channel. Northern hybridization and whole-mount in situ hybridization revealed a high steady-state level of NtAQP1-RNA in roots, a decreased content in shoots and a low content in leaves. By immunolocalization with an antibody targeted to the N-terminus of the aquaporin, the localization of NtAQP1-protein at sites of expected high water transport rates from and to the apoplast or symplast could be demonstrated. The specific pattern of NtAQP1 distribution in petioles strongly indicates a transcellular movement of water.

Engineered acid-stabile human interferon gamma

Loss of anti-viral potency upon pH2-treatment is an inherent feature of interferon (IFN)-gamma. The phenomenon seems to be caused by dissociation of IFN-gamma homodimer into subunits upon acidification and subsequent self-association of monomers into aggregates with reduced activity after neutralization. We demonstrated that acid-stability could be engineered into human IFN-gamma without affecting its specific activity. An artificial intra-monomer disulphide bond E7C/S69C stabilizes the dimeric form of the cytokine, which retained its full bioactivity after exposure to pH2. Acidification did not modify the antigenic structure of IFN-gamma as proved by a panel of mouse anti-human IFNgamma antibodies.

Relationship between increasing duodenal lipid doses, gastric perception, and plasma hormone levels in humans

Duodenal lipid causes gastric relaxation, CCK secretion, and nausea. Vasopressin has been implicated in motion sickness-related nausea. We hypothesized that increasing doses of lipid enhance gastric relaxation and CCK-vasopressin secretion, resulting in a dose-related exacerbation of nausea. Nine healthy subjects received isotonic saline or lipid (1, 2, or 3 kcal/min, L1, L2, L3) duodenally. Changes in gastric volume, sensations, and plasma hormone levels were assessed during infusions and isobaric gastric distensions. Lipid infusions increased gastric volume, plasma CCK (but not vasopressin) levels, and gastric compliance during distensions, compared with saline. Plasma CCK levels were related to the dose of lipid administered [CCK levels at 30 min (pmol/l), saline: 1.1 +/- 0.2, L1: 1.8 +/- 0.2, L2: 3.0 +/- 0.2, L3: 4.3 +/- 0.6]. During distensions, nausea increased in intensity with increasing doses of lipid [score (where 0 is no sensation and 100 is strongest sensation), saline: 7 +/- 4, L1: 19 +/- 7, L2: 44 +/- 7, L3: 66 +/- 8]; however, no further rise in plasma CCK occurred. Because neither lipid nor distension alone induced significant nausea, we conclude that the interaction between these stimuli together with a modulation by CCK is responsible for the effects observed. Vasopressin is not involved in lipid- and distension-induced nausea.

Accuracy of 13C-urea breath test in clinical use for diagnosis of Helicobacter pylori infection

The 13C-urea breath test (UBT) is a noninvasive test for diagnosis of Helicobacter pylori infection of gastric mucosa. The aim of this prospective study was to assess the accuracy of a simple UBT in clinical routine use.

METHODS

The study population comprised of 100 patients (49 f, 51 m) requiring diagnostic upper GI endoscopy. One biopsy specimen was taken from the gastric antrum, body and fundus, respectively, for standard histological examination and one additional specimen from each location was transformed into transport medium for cultivation of H. pylori. After vaccination of the culture plates the biopsies were tested for urease activity (UAT). After recovery from endoscopy the patients had to pass an one liter endexspiratory breath sample before and 15 min after drinking 200 ml orange juice, pH 3.6, containing 75 mg of 13C-urea. 13CO2 was measured in the breath samples using isotope-selective nondispersive infrared spectrometry.

RESULTS

Defining gold standard groups with all biopsy tests (from antrum and corpus) positive or negative the 13CO2 delta over baseline (DOB) cut-off level of UBT was set at 6.5/1000 in order to best discriminate positive from negative patients (ROC analysis). UBT was positive in 37% of all subjects. Taken UAT and histological examination together (positive when both tests were positive) UBT displayed a sensitivity of 92%, a specificity of 94%, a positive predictive value of 89%, and a negative predictive value of 94%. When including the results of culture sensitivity and negative predictive value reached almost 100%. The mean of the 13CO2-DOB values from H. pylori-positive duodenal or gastric ulcer patients did not differ from controls (H. pylori-positive patients without lesions). The 13CO2-DOB values of the ulcer group were correlated significantly with the active inflammatory component of gastritis in antrum, corpus, and fundus.

CONCLUSION

UBT with this setup detects H. pylori infection in clinical routine use with high accuracy. The increase of exhaled 13CO2 does not predict ulcer disease but reflects the degree of active inflammation of gastric mucosa.

The Nicotiana tabacum plasma membrane aquaporin NtAQP1 is mercury-insensitive and permeable for glycerol

A new aquaporin from Nicotiana tabacum (cv. Samsun) was characterized. It shares sequence homology to the Arabidopsis thaliana PIP1 protein family. By two-phase partitioning and immunoblot analysis, plasma membrane localization could be demonstrated. The corresponding mRNA is highly abundant in roots and flowers, while it is rarely expressed in leaves and stems. Functional expression in Xenopus oocytes revealed that NtAQP1 can mediate glycerol transport in addition to water flow. However, NtAQP1 is impermeable for Na+, K+ and Cl- ions. The water permeability and selectivity could not be modulated by addition of mercurials or the activity of cAMP-dependent protein kinases.

Interferon-gamma variants with deletions in the AB surface loop--flexibility is a critical point for receptor binding

The receptor-binding AB loop of recombinant human interferon-gamma (IFN-gamma) has multiple contacts with the extracellular part of the IFN-gamma receptor a chain (IFN-gammaRalpha). We explored the possible length of truncated AB loops and their conformations by molecular modelling. Deletions of two amino acids at the tip of the loop were tolerated in the model without van der Waals collisions of the AB loop with helix F. Based on these modelling results, two deletion mutants were constructed by overlap-extension PCR mutagenesis: des-(A23, D24)-IFN-gamma and des-(N25, G26)-IFN-gamma. Both mutations were tolerated by the folding pattern of recombinant human IFN-gamma, as proved by CD spectroscopy. The stability of both mutants against cosolvent-induced unfolding was equal to that of wild-type IFN-gamma. In contrast to the biophysical similarities of wild-type and mutant IFN-gamma proteins, the biological activities of both mutants dropped significantly. Antiviral activity and human leucocyte antigen (HLA)-DR induction of des-(N25, G26)-IFN-gamma was 10% that of wild-type activity. des-(A23, D24)-IFN-gamma had only 1% remaining activity. Receptor-binding experiments confirmed that both deletions had a negative influence on the affinity of recombinant human IFN-gamma to its cellular receptor. We conclude from this combined molecular modelling and mutagenesis experiments, that the reduced flexibility of the truncated AB loop abrogates the possibility of the formation of a 3(10) helix in the receptor-bound state as observed in the X-ray structure of the IFN-gammaRalpha-IFN-gamma complex.

Myelography with a dimeric (iodixanol) and a monomeric (iohexol) contrast medium: a clinical multicentre comparative study

The purpose of this study was to evaluate and compare the radiographic efficacy and safety of iodixanol (Visipaque; 270 and 320 mg I/ml) and iohexol (Omnipaque; 300 mg I/ml) in myelography. The study was randomized, double-blind and comparative including 398 patients from five European university clinics. The radiographic visualisation was evaluated as poor, good or excellent. Adverse events were recorded by interviewing the patients after the myelography, and each patient was given a questionnaire to be returned after 1 week. In cervical myelography with cervical puncture more films with excellent quality was obtained after iodixanol 320 mgI/ml compared with iohexol 300 mgI/ml (p = 0.009). Also in lumbar myelography iodixanol 320 mgI/ml compared favourably with iohexol 300 mgI/ml (p = 0.006). The most frequent adverse event was headache, which occurred in 5-35 % of patients during the first 24 h and in 19-61 % within the first 7 days, depending on the centre. There was no difference in frequency and severity of the adverse effects between the contrast media.

The response of peritoneal macrophages after implantation of several ceramics as measured by the change of ectoenzyme activity

The bioactive calcium phosphate ceramics with various calcium: phosphorus ratios: Ca/P = 1.67 (hydroxyapatite, HA), Ca/P = 1.6 and Ca/P = 1.5 (tricalcium phosphate, beta-TCP), the bioinert aluminium oxide ceramic (Al2O3) and the toxic calcium oxide ceramic (CaO) have been investigated with respect to their ability to activate peritoneal macrophages of NMRI-mice and with respect to their influence on the extracellular nucleotide degradation of these macrophages. Two weeks after the intraperitoneal injection of a suspension of ceramic particles in an isotone salt solution (phosphate-buffered saline = PBS), we observed that the peritoneal macrophages were only slightly activated into the responsive state, independent of the type of ceramic. 5'Nucleotidase (5'N) ectoenzyme hydrolyses adenosine monophosphate (AMP) and a decrease of its activity is a general biochemical marker of activated macrophages. This ectoenzyme activity was slightly reduced after ceramic implantation. The lacking rise of the extracellular diadenosine tetraphosphate (Ap4A)-catabolism by the macrophage ectoenzyme alkaline phosphodiesterase I (APD) demonstrated that the peritoneal macrophages did not completely reach the responsive state. After the implantation of calcium phosphate ceramics the extracellular adenosine triphosphate (ATP)-reduction was slightly diminished. After the implantation of tricalcium phosphate ceramic about 30% more peritoneal exsudate cells (PEC) were obtained from the peritoneal cavity than after injections of pure PBS (used as non-inflammatory control). Similar to the phenomena following the injection of thioglycollate (Tg, inflammation producing control agent) a slightly but not significantly increased proportion of pseudopodia-building cells was observed after the implantation of the ceramic with Ca/P = 1.6.

Spinal ischaemia after surgery for abdominal infrarenal aortic aneurysm. Diagnosis with nuclear magnetic resonance

A 76-year-old man underwent surgery for an infrarenal aortic aneurysm reaching 6 cm in maximal transverse diameter. The aorta was crossclamped below the level of the renal arteries. A tube graft was interposed and tend between the infrarenal aorta and the aortic bifurcation. Due to leakage on the suture line two consecutive episodes of crossclamping for a total duration of 40 min. were required. No hypotension was noted during or after the procedure. After operation, the patient complained of difficulties to move both legs and neurologic examination demonstrated paraparesis, with mild sensory deficit. Faecal and urinary incontinences were also noted and urodynamic testing demonstrated sphincterovesical palsy. Nuclear magnetic resonance imaging detected an ischaemic zone in the spinal cord at the level of T11. Faecal incontinence and motor deficit partially resolved but no bladder function recovery was observed. Spinal ischaemia is a rare complication after abdominal aortic surgery. Several risk factors have been suggested which include level and duration of the aortic crossclamping, possible interruption of the spinal cord blood supply via the greater medullary artery (the so-called artery of Adamkiewicz), presence of intra- or postoperative episodes of hypotension, atheromatous embolization, underlying occlusive arteriosclerosis of spinal arteries, and respect or not of the hypogastric circulation. In our case, the duration of the crossclamping and interruption of the blood flow in lumbar arteries probably supplying the distal spinal cord were likely contributive factors.