Meal sugar-protein balance determines postprandial FGF21 response in humans

Biological mechanisms to promote dietary balance remain unclear. Fibroblast growth factor 21 (FGF21) has been suggested to contribute to such potential regulation considering that FGF21 1) is genetically associated with carbohydrate/sugar and protein intake in opposite directions, 2) is secreted after sugar ingestion and protein restriction, and 3) pharmacologically reduces sugar and increases protein intake in rodents. To gain insight of the nature of this potential regulation, we aimed to study macronutrient interactions in the secretory regulation of FGF21 in healthy humans. We conducted a randomized, double-blinded, crossover meal study (NCT05061485), wherein healthy volunteers consumed a sucrose drink, a sucrose + protein drink, and a sucrose + fat drink (matched sucrose content), and compared postprandial FGF21 responses between the three macronutrient combinations. Protein suppressed the sucrose-induced FGF21 secretion [incremental area under the curve (iAUC) for sucrose 484 ± 127 vs. sucrose + protein -35 ± 49 pg/mL × h, P < 0.001]. The same could not be demonstrated for fat (iAUC 319 ± 102 pg/mL × h, P = 203 for sucrose + fat vs. sucrose). We found no indications that regulators of glycemic homeostasis could explain this effect. This indicates that FGF21 responds to disproportionate intake of sucrose relative to protein acutely within a meal, and that protein outweighs sucrose in FGF21 regulation. Together with previous findings, our results suggests that FGF21 might act to promote macronutrient balance and sufficient protein intake.NEW & NOTEWORTHY Here we test the interactions between sugar, protein, and fat in human FGF21 regulation and demonstrate that protein, but not fat, suppresses sugar-induced FGF21 secretion. This indicates that protein outweighs the effects of sugar in the secretory regulation of FGF21, and could suggest that the nutrient-specific appetite-regulatory actions of FGF21 might prioritize ensuring sufficient protein intake over limiting sugar intake.

Plasma FGF21 concentrations are regulated by glucose independently of insulin and GLP-1 in lean, healthy humans

BACKGROUND

Fibroblast growth factor 21 (FGF21) treatment improves metabolic homeostasis in diverse species, including humans. Physiologically, plasma FGF21 levels increase modestly after glucose ingestion, but it is unclear whether this is mediated by glucose itself or due to a secondary effect of postprandial endocrine responses. A refined understanding of the mechanisms that control FGF21 release in humans may accelerate the development of small-molecule FGF21 secretagogues to treat metabolic disease. This study aimed to determine whether FGF21 secretion is stimulated by elevations in plasma glucose, insulin, or glucagon-like peptide-1 (GLP-1) in humans.

METHODS

Three groups of ten healthy participants were included in a parallel-group observational study. Group A underwent a hyperglycemic infusion; Group B underwent a 40 mU/m²/min hyperinsulinemic euglycemic clamp; Group C underwent two pancreatic clamps (to suppress endogenous insulin secretion) with euglycemic and hyperglycemic stages with an infusion of either saline or 0.5 pmol/kg/min GLP-1. Plasma FGF21 concentrations were measured at baseline and during each clamp stage by ELISA.

RESULTS

Plasma FGF21 was unaltered during hyperglycemic infusion and hyperinsulinemic euglycemic clamps, compared to baseline. FGF21 was, however, increased by hyperglycemia under pancreatic clamp conditions (P < 0.05), while GLP-1 infusion under pancreatic clamp conditions did not change circulating FGF21 levels.

CONCLUSION

Increases in plasma FGF21 are likely driven directly by changes in plasma glucose independent of changes in insulin or GLP-1 secretion. Ecologically valid postprandial investigations are now needed to confirm our observations from basic science infusion models.

Does FGF21 Mediate the Potential Decrease in Sweet Food Intake and Preference Following Bariatric Surgery?

The liver-derived hormone fibroblast growth factor 21 (FGF21) has recently been linked to preference for sweet-tasting food. We hypothesized, that surgery-induced changes in FGF21 could mediate the reduction in sweet food intake and preference following bariatric surgery. Forty participants (35 females) with severe obesity (BMI ≥ 35 kg/m²) scheduled for roux-en-y gastric bypass (n = 30) or sleeve gastrectomy (n = 10) were included. Pre- and postprandial responses of intact plasma FGF21 as well as intake of sweet-tasting food assessed at a buffet meal test, the hedonic evaluation of sweet taste assessed using an apple juice with added sucrose and visual analog scales, and sweet taste sensitivity were assessed before and 6 months after bariatric surgery. In a cross-sectional analysis pre-surgery, pre- and postprandial intact FGF21 levels were negatively associated with the hedonic evaluation of a high-sucrose juice sample (p = 0.03 and p = 0.02). However, no changes in pre- (p = 0.24) or postprandial intact FGF21 levels were found 6 months after surgery (p = 0.11), and individual pre- to postoperative changes in pre- and postprandial intact FGF21 levels were not found to be associated with changes in intake of sweet foods, the hedonic evaluation of sweet taste or sweet taste sensitivity (all p ≥ 0.10). In conclusion, we were not able to show an effect of bariatric surgery on circulating FGF21, and individual postoperative changes in FGF21 were not found to mediate an effect of surgery on sweet food intake and preference.

Transient postprandial increase in intact circulating fibroblast growth factor-21 levels after Roux-en-Y gastric bypass: a randomized controlled clinical trial

Background

Despite a consistent link between obesity and increased circulating levels of fibroblast growth factor-21 (FGF21), the effect of weight-loss interventions on FGF21 is not clear. We aimed to determine the short- and long-term effects of Roux-en-Y gastric bypass (RYGB) on intact plasma FGF21 levels and to test the hypothesis that RYGB, but not diet-induced weight loss, increases fasting and postprandial responses of FGF21.

Method

Twenty-eight participants with obesity followed a low-calorie diet for 11 weeks. The 28 participants were randomized to undergo RYGB surgery at week 8 (RYGB group, n = 14), or to a control group scheduled for surgery at week 12 (n = 14). Fasting levels of intact, biologically active FGF21 (amino acids 1-181) and its postprandial responses to a mixed meal were assessed at week 7 and 11, and 78 weeks (18 months) after RYGB.

Results

At week 11 (3 weeks after RYGB), postprandial responses of intact FGF21 were enhanced in participants undergoing surgery at week 8 (change from week 7 to 11: P = 0.02), whereas no change was found in non-operated control participants in similar negative energy balance (change from week 7 to 11: P = 0.81). However, no between-group difference was found (P = 0.27 for the group-week-time interaction). Fasting, as well as postprandial responses in intact FGF21, were unchanged 18 months after RYGB when both the RYGB and control group were collapsed together (change from week 7 to 78 weeks after RYGB: P = 0.17).

Conclusion

Postprandial intact FGF21 levels were enhanced acutely after RYGB whereas no signs of sustained changes were found 18 months after surgery. When comparing the acute effect of RYGB with controls in similar negative energy balance, we failed to detect any significant differences between groups, probably due to the small sample size and large inter-individual variations, especially in response to surgery.

Factors Associated with Favorable Changes in Food Preferences After Bariatric Surgery

PURPOSE

Bariatric surgery may shift food preferences towards less energy-dense foods. Eating behavior is multifactorial, and the mechanisms driving changes in food preferences could be a combination of a physiological response to surgery and social and psychological factors. This exploratory study aimed to identify potential factors explaining the variation in changes in food preferences after bariatric surgery.

MATERIALS AND METHODS

Physiological, social, and psychological data were collected before, 6 weeks or 6 months after surgery. All variables were analyzed in combination using LASSO regression to explain the variation in changes in energy density at an ad libitum buffet meal 6 months after bariatric surgery (n=39).

RESULTS

The following factors explained 69% of the variation in changes in food preferences after surgery and were associated with more favorable changes in food preferences (i.e., a larger decrease in energy density): female gender, increased secretion of glicentin, a larger decrease in the hedonic rating of sweet and fat and a fatty cocoa drink, a lower number of recent life crises, a low degree of social eating pressure, fulfilling the diagnostic criteria for binge eating disorder, less effort needed to obtain preoperative weight loss, a smaller household composition, a lower degree of self-efficacy and a higher degree of depression, nutritional regime competence, and psychosocial risk level.

CONCLUSION

Factors explaining the variation in altered food preferences after bariatric surgery not only include a physiological response to surgery but also social and psychological factors.

Oxyntomodulin and Glicentin May Predict the Effect of Bariatric Surgery on Food Preferences and Weight Loss

BACKGROUND

Alterations in several gastrointestinal hormones are implicated in the postoperative suppression of food intake leading to weight loss after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). The aim was to evaluate changes in responses of gastrointestinal hormones after RYGB and SG and the associations of these changes with weight loss, energy intake, and food preferences.

METHODS

Forty-two subjects with severe obesity were included (32 RYGB; 10 SG). Postprandial responses of glicentin, oxyntomodulin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and ghrelin were measured before and 6 months after surgery. Energy intake and energy density were assessed before and 6 months after surgery using a buffet meal test and weight loss was assessed 18 months after surgery.

RESULTS

Postprandial concentrations of glicentin, oxyntomodulin, GLP-1, and ghrelin differed between RYGB and SG (all P ≤ .02). Enhanced responses of glicentin and oxyntomodulin predicted a greater weight loss (both P < .01) and were associated with a larger decrease in energy density (P ≤ .04). No associations were found for GLP-1, PYY, and ghrelin, and changes were not associated with changes in energy intake. When combing all hormones, 60%, 19%, and 33% of the variations in weight loss, energy intake, and energy density, respectively, could be explained.

CONCLUSION

Postprandial responses of gastrointestinal hormones differed between RYGB and SG. Enhanced responses of glicentin and oxyntomodulin predicted a better weight loss and were associated with a decreased preference for energy-dense foods. Replication of these results could imply an opportunity to identify patients in need of additional support after surgical treatments of obesity.

Bariatric Surgery Leads to Short-Term Effects on Sweet Taste Sensitivity and Hedonic Evaluation of Fatty Food Stimuli

OBJECTIVE

The aim of this study was to investigate the effect of bariatric surgery on sweet taste sensitivity and the hedonic evaluation of sweet, savory, and fatty food stimuli as well as associations with weight loss and food preferences assessed at a buffet meal test.

METHODS

The detection and recognition threshold for sweet taste and the hedonic rating of sweet, savory, and fatty food stimuli were assessed before and after a preoperative diet-induced weight loss and 6 weeks, 6 months, and 18 months after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) (n = 29).

RESULTS

The detection threshold for sweet taste decreased after the diet-induced weight loss and 6 weeks after RYGB (both P ≤ 0.03). The hedonic rating of high-fat food stimuli decreased 6 weeks after RYGB and SG (all P ≤ 0.02). Changes in the hedonic rating of high-fat food stimuli were associated with increased preferences for high-fat foods at the buffet meal (P = 0.03) and tended to be associated with weight loss (P = 0.05). No changes were detected for sweet and savory food stimuli.

CONCLUSIONS

RYGB increased sweet taste sensitivity; however, this effect was already seen after the diet-induced weight-loss. RYGB and SG decreased the hedonic evaluation of high-fat food stimuli, but this effect did not translate into decreased preferences for high-fat food.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Food Preferences and Potential Mechanisms Involved

PURPOSE OF REVIEW

Bariatric surgery leads to a substantial decrease in energy intake. It is unclear whether this decrease in energy intake is simply due to eating smaller portions of the same food items or a shift in food preference towards less energy-dense foods. This review evaluates the existing literature on changes in food preferences after bariatric surgery and the potential mechanisms involved.

RECENT FINDINGS

Changes in food preferences have been reported; however, the evidence is mainly based on indirect measurements, such as self-reporting. When changes in food preferences are directly assessed, results contradict previous findings, indicating that results based on self-reporting must be interpreted with caution as they do not necessarily reflect actual behaviour. However, it seems that there could be inter-individual differences in the response to surgery. Future studies investigating changes in food preferences should not only focus on direct measured of behaviour but should also consider the heterogeneity of the response after bariatric surgery.

Effects of RYGB on energy expenditure, appetite and glycaemic control: a randomized controlled clinical trial

OBJECTIVES

Increased energy expenditure (EE) has been proposed as an important mechanism for weight loss following Roux-en-Y gastric bypass (RYGB). However, this has never been investigated in a controlled setting independent of changes in energy balance. Similarly, only few studies have investigated the effect of RYGB on glycaemic control per se. Here, we investigated the effect of RYGB on EE, appetite, glycaemic control and specific signalling molecules compared with a control group in comparable negative energy balance.

SUBJECTS/METHODS

Obese normal glucose-tolerant participants were randomized to receive RYGB after 8 (n=14) or 12 weeks (n=14). The protocol included a visit at week 0 and three visits (weeks 7, 11 and 78) where 24-h EE, appetite and blood parameters were assessed. Participants followed a low-calorie diet from weeks 0-11, with those operated at week 12 serving as a control group for those operated at week 8.

RESULTS

Compared with controls, RYGB-operated participants had lower body composition-adjusted 24-h EE and basal EE 3 weeks postoperatively (both P<0.05) but EE parameters at week 78 were not different from preoperative values (week 7). Surgery changed the postprandial response of glucagon-like peptide-1 (GLP-1), peptide YY3-36 (PYY), ghrelin, cholecystokinin, fibroblast growth factor-19 and bile acids (all P<0.05). Particularly, increases in GLP-1, PYY and decreases in ghrelin were associated with decreased appetite. None of HOMA-IR (homeostasis model assessment-estimated insulin resistance), Matsuda index, the insulinogenic index, the disposition index and fasting hepatic insulin clearance were different between the groups, but RYGB operated had lower fasting glucose (P<0.05) and the postprandial glucose profile was shifted to the left (P<0.01).

CONCLUSIONS

Our data do not support that EE is increased after RYGB. More likely, RYGB promotes weight loss by reducing appetite, partly mediated by changes in gastrointestinal hormone secretion. Furthermore, we found that the early changes in glycaemic control after RYGB is to a large extent mediated by caloric restriction.

No effect of high-dose atorvastatin on leukotriene B₄ formation from neutrophils in patients treated with coronary bypass surgery: a randomized placebo-controlled double-blinded trial with a crossover design

Inflammation plays a pivotal role in the pathophysiology of cardiovascular disease, (CVD) and leukotrienes may play a role in atherogenesis. Statins reduce mortality from CVD by reducing LDL cholesterol and potentially by other (pleiotropic) mechanisms. The aim of this study was to investigate if atorvastatin exerts an anti-inflammatory effect by reducing leukotriene B₄ (LTB₄) formation from stimulated neutrophils in patients treated with coronary artery bypass grafting. The study was a randomized, placebo-controlled, double-blinded crossover study. Patients (n=80) were allocated to 80 mg atorvastatin or placebo for 6 weeks before crossing over to the opposite treatment for another 6 weeks. There was no significant correlation between baseline LDL cholesterol levels on formation of LTB₄, and atorvastatin had no effect on LTB₄ formation. Hence, this study does not support any effect of atorvastatin on LTB₄ formation as part of the explanation for its beneficial effect on CVD.

X-ray tomography using the full complex index of refraction

We report on x-ray tomography using the full complex index of refraction recorded with a grating-based x-ray phase-contrast setup. Combining simultaneous absorption and phase-contrast information, the distribution of the full complex index of refraction is determined and depicted in a bivariate graph. A simple multivariable threshold segmentation can be applied offering higher accuracy than with a single-variable threshold segmentation as well as new possibilities for the partial volume analysis and edge detection. It is particularly beneficial for low-contrast systems. In this paper, this concept is demonstrated by experimental results.

The effect of low-dose marine n-3 fatty acids on the biosynthesis of pro-inflammatory 5-lipoxygenase pathway metabolites in overweight subjects: a randomized controlled trial

INTRODUCTION

Marine n-3 polyunsaturated fatty acids (PUFA) have a variety of anti-inflammatory properties. This study evaluated the effect of n-3 PUFA in a low, but recommended cardioprotective dosage on the formation of 5-lipoxygenase pathway metabolites in overweight subjects.

MATERIALS AND METHODS

Fifty subjects were randomized to 1.1g of n-3 PUFA or olive oil for 6 weeks.

RESULTS

Leukotriene B(4) formation decreased by 14% in the n-3 PUFA group which proved to be significant within the group (p=0.005) but not between groups (p=0.25). The formation of 5-hydroxyeicosatetraenoic acid (5-HETE) did not differ significantly between the groups. In the n-3 PUFA group, both 5-hydroxyeicosapentaenoic (5-HEPE) acid and leukotriene B(5) increased significantly compared to the control group (p<0.001).

CONCLUSION

In conclusion, we did not observe any significant net anti-inflammatory effect on the 5-lipoxygenase pathway from a daily supplement of 1.1g marine n-3 PUFA for 6 weeks.

C-terminal modification of osteopontin inhibits interaction with the αVβ3-integrin

Osteopontin (OPN) is a multifunctional phosphorylated protein containing the integrin binding sequence Arg-Gly-Asp through which it interacts with several integrin receptors, such as the α(V)β(3)-integrin. OPN exists in many different isoforms differing in phosphorylation status that are likely to interact differently with integrins. The C-terminal region of OPN is particularly well conserved among mammalian species, which suggests an important functional role of this region. In this study, we show that modification of the extreme C terminus of OPN plays an important regulatory role for the interaction with the α(V)β(3)-integrin. It is demonstrated that highly phosphorylated OPN has a much reduced capability to promote cell adhesion via the α(V)β(3)-integrin compared with lesser phosphorylated forms. The cell attachment promoted by highly phosphorylated OPN could be greatly increased by both dephosphorylation and proteolytic removal of the C terminus. Using recombinantly expressed OPN containing a tag in the N or C terminus, it is shown that a modification in the C-terminal part significantly reduces the adhesion of cells to OPN via the α(V)β(3)-integrin, whereas modification of the N terminus does not influence the binding. The inhibited binding of the α(V)β(3)-integrin to OPN could be restored by proteolytic removal of the C terminus by thrombin and plasmin. These data illustrate a novel mechanism regulating the interaction of OPN and the α(V)β(3)-integrin by modification of the highly conserved C-terminal region of the protein.

Long-term delivery of nerve growth factor by encapsulated cell biodelivery in the Göttingen minipig basal forebrain

Nerve growth factor (NGF) prevents cholinergic degeneration in Alzheimer's disease (AD) and improves memory in AD animal models. In humans, the safe delivery of therapeutic doses of NGF is challenging. For clinical use, we have therefore developed an encapsulated cell (EC) biodelivery device, capable of local delivery of NGF. The clinical device, named NsG0202, houses an NGF-secreting cell line (NGC-0295), which is derived from a human retinal pigment epithelial (RPE) cell line, stably genetically modified to secrete NGF. Bioactivity and correct processing of NGF was confirmed in vitro. NsG0202 devices were implanted in the basal forebrain of Göttingen minipigs and the function and retrievability were evaluated after 7 weeks, 6 and 12 months. All devices were implanted and retrieved without associated complications. They were physically intact and contained a high number of viable and NGF-producing NGC-0295 cells after explantation. Increased NGF levels were detected in tissue surrounding the devices. The implants were well tolerated as determined by histopathological brain tissue analysis, blood analysis, and general health status of the pigs. The NsG0202 device represents a promising approach for treating the cognitive decline in AD patients.

Molecular interactions between barley and oat beta-glucans and phenolic derivatives

Equilibrium dialysis, molecular modeling, and multivariate data analysis were used to investigate the nature of the molecular interactions between 21 vanillin-inspired phenolic derivatives, 4 bile salts, and 2 commercially available beta-glucan preparations, Glucagel and PromOat, from barley and oats. The two beta-glucan products showed very similar binding properties. It was demonstrated that the two beta-glucan products are able to absorb most phenolic derivatives at a level corresponding to the absorption of bile salts. Glucosides of the phenolic compounds showed poor or no absorption. The four phenolic derivatives that showed strongest retention in the dialysis assay shared the presence of a hydroxyl group in para-position to a CHO group. However, other compounds with the same structural feature but possessing a different set of additional functional groups showed less retention. Principal component analysis (PCA) and partial least-squares regression (PLS) calculations using a multitude of diverse descriptors related to electronic, geometrical, constitutional, hybrid, and topological features of the phenolic compounds showed a marked distinction between aglycon, glucosides, and bile salt retention. These analyses did not offer additional information with respect to the mode of interaction of the individual phenolics with the beta-glucans. When the barley beta-glucan was subjected to enzyme degradation, the ability to bind some but not all of the phenolic derivatives was lost. It is concluded that the binding must be dependent on multiple characteristics that are not captured by a single molecular descriptor.

Modelling patient flows as an aid to decision making for critical care capacities and organisation

Using real data from a number of hospitals, we predicted the patient flows following a capacity or organisational change. Clinically recognisable patient groups obtained through classification and regression tree analysis were used to tune a simulation model for the flow of patients in critical care units. A tuned model which accurately reflected the base case of the flow of patients was used to predict alterations in service provision in a number of scenarios which included increases in bed numbers, alterations in patients' lengths of stay, fewer delayed discharges, caring for long stay patients outside the formal intensive care unit and amalgamating small units. Where available the predictions' accuracy was checked by comparison with real hospital data collected after an actual capacity change. The model takes variability and uncertainty properly into account and it provides the necessary information for making better decisions about critical care capacity and organisation.

Chronic subthalamic high-frequency deep brain stimulation in Parkinson's disease ? a histopathological study

This study describes the pathological findings in the brain of a patient with Parkinson's disease (PD) treated with bilateral subthalamic high-frequency deep brain stimulation (STN DBS) for 29 months prior to death. After routine neuropathological examination, tissue blocks containing the electrode tracts, the subthalamic nucleus (STN), the substantia nigra and the pre-frontal cortex were paraffin embedded and cut into 5-microm-thick serial sections and stained with several conventional staining methods and immunohistochemistry. Bilateral nigral depigmentation, cell loss and Lewy body formation confirmed the diagnosis of PD. Microscopic evaluation furthermore confirmed the location of the electrodes in the STN. The electrode tracts were surrounded by a 150-microm-wide glial fibrillary acidic protein (GFAP)-positive capsule consisting of a thin collagen layer lining the lumen of the tract, whilst an area with few cells and axons constituted the capsule wall towards the surrounding normal brain tissue. The brain tissue appeared normal outside the capsule boundaries with no difference in areas of stimulation compared with areas of no stimulation. Our results correspond with previous studies performed after fewer months of STN DBS and indicate mild histopathological changes in the vicinity of the electrode tract, appearing to result from the electrode placement and not from the electrical stimulation.

SorCS3 does not require propeptide cleavage to bind nerve growth factor

The functional properties of the Vps10p-domain receptor SorCS3 are undescribed. Here, we examine its processing and sorting in cellular transfectants, and analyze the binding of potential ligands to the purified receptor. We show that SorCS3 is synthesized as a proprotein and converted to its mature form by N-terminal propeptide cleavage in distal Golgi compartments. The propeptide is not a requirement for normal processing of the receptor and does not prevent ligands from binding to the SorCS3 precursor form. Expression of wt and chimeric receptors further suggests that SorCS3 predominates on the plasma membrane, exhibits slow internalization and does not engage in intracellular trafficking. SorCS3 emerges as a new neurotrophin binding Vps10p-domain receptor functionally distinct from its relatives Sortilin and SorLA.

Routine X-ray control of upper central venous lines: Is it necessary?

BACKGROUND

Insertion of central venous catheters (CVCs) is a procedure associated with a varying risk of complications, depending on the setting and the skill of the clinician who undertakes the procedure. The aim of this study was to monitor the complication rate of CVC insertion and evaluate the value of routine chest X-ray control.

METHODS

Anesthesiologists at eight hospitals filled in a questionnaire immediately after insertion of a CVC. The post-procedural clinical evaluation, including expected complications, was compared to actual radiological findings. Chest X-ray was ordered by the anesthesiologist, and described by staff radiologists.

RESULTS

The clinicians had from 2 months to 30 years of experience as anesthesiologists, and trainees inserted 34% and specialists 66% of the catheters, using landmark techniques. Over a period of 2 months, 473 CVC-insertion procedures were included in the investigation. Two patients (0.4%) had a pneumothorax: one was among the 11 cases in which the clinician suspected complications after the procedure, and another was found in a high-risk patient 13 h after CVC insertion. Both patients were treated successfully with chest tubes. The favorite approach was right vena jugularis interna with 324 (69%) catheters; of these patients one had a pneumothorax, catheter-tip placement was correctly predicted in 317 (97%), and no catheters were repositioned.

CONCLUSION

In the hands of trained clinicians, insertion of CVCs is a safe procedure. We found no value of routine X-ray control and omission of routine chest X-ray must be considered.

Post-traumatic stress disorder and emotional distress in persons with spinal cord lesion

STUDY DESIGN

Questionnaire.

OBJECTIVE

To evaluate the prevalence of post-traumatic stress disorder (PTSD) and emotional distress in persons with recent onset of spinal cord lesion.

SETTING

Denmark.

METHODS

A total of 69 patients with paraplegia or tetraplegia from two rehabilitation centres in Denmark filled in the questionnaire. PTSD and emotional distress were assessed using the Harvard Trauma Questionnaire and the Medical-Based Emotional Distress Scale, 83 days on average after the spinal cord lesion. The level of neurological lesion and completeness were recorded adhering to the International Standards for Neurological Classification of Spinal Cord Injury.

RESULTS

The prevalence of PTSD was 20%. Patients with PTSD experienced significantly more symptoms of depression and more emotional distress than patients without PTSD. Age and neurological level were related to PTSD in patients with traumatic injuries, but not in patients with nontraumatic lesions.

CONCLUSIONS

Persons with a recent onset of spinal cord lesions are at increased risk of having PTSD, and comorbidities such as depression and other symptoms of emotional distress.

Mathematical modelling and simulation for planning critical care capacity

Using average number of patients expected in a year, average length of stay and a target occupancy level to calculate the number of critical care beds needed is mathematically incorrect because of nonlinearity and variability in the factors that control length of stay. For a target occupancy in excess of 80%, this simple calculation will typically underestimate the number of beds required. More seriously, it provides no quantitative guidance information about other aspects of critical care demand such as the numbers of emergency patients transferred, deferral rates for elective patients and overall utilisation. The combination of appropriately analysing raw data and detailed mathematical modelling provides a much better method for estimating numbers of beds required. We describe this modelling approach together with evidence of its performance.

Cubilin dysfunction causes abnormal metabolism of the steroid hormone 25(OH) vitamin D(3)

Steroid hormones are central regulators of a variety of biological processes. According to the free hormone hypothesis, steroids enter target cells by passive diffusion. However, recently we demonstrated that 25(OH) vitamin D(3) complexed to its plasma carrier, the vitamin D-binding protein, enters renal proximal tubules by receptor-mediated endocytosis. Knockout mice lacking the endocytic receptor megalin lose 25(OH) vitamin D(3) in the urine and develop bone disease. Here, we report that cubilin, a membrane-associated protein colocalizing with megalin, facilitates the endocytic process by sequestering steroid-carrier complexes on the cellular surface before megalin-mediated internalization of the cubilin-bound ligand. Dogs with an inherited disorder affecting cubilin biosynthesis exhibit abnormal vitamin D metabolism. Similarly, human patients with mutations causing cubilin dysfunction exhibit urinary excretion of 25(OH) vitamin D(3). This observation identifies spontaneous mutations in an endocytic receptor pathway affecting cellular uptake and metabolism of a steroid hormone.

[Is visual assessment of MRI adequate in the investigation of patients with temporal lobe epilepsy? Evaluation of the diagnostic accuracy of the visual assessment of MRI in mesial temporal sclerosis]

INTRODUCTION

Is visual assessment of MRI adequate in patients with temporal lobe epilepsy? Visual versus quantitative MRI assessment of mesial temporal sclerosis (hippocampal gliosis (HG) and hippocampal atrophy (HA)).

MATERIAL AND METHODS

The MRIs of 25 patients with temporal lobe epilepsy were assessed visually by three radiologists with different levels of neuroradiological MRI experience (expert, trained, and inexperienced). Diagnosis obtained earlier by T2-relaxometry and volume measurements were considered to be the gold standard.

RESULTS

The diagnostic accuracy of visual assessment was high for unilateral HA, but low for bilateral HA and unilateral and bilateral HG, and it was not better for the expert eye than for the inexperienced. Interobserver agreement on the visual diagnosis of HG and HA (Cohen's Kappa coefficient): 0.49 (HG) and 0.84 (HA). Intraobserver reliability for the expert/trained/inexperienced observer for visual diagnosis (Kappa): 0.83/0.64/0.47 (HG) and 0.88/0.69/0.73 (HA).

DISCUSSION

Reproducibility and diagnostic accuracy of visual assessment varied unacceptably from the quantitative MRI-based diagnosis. Quantitative measurements are recommended in patients suspected of MTS.

Maxi K+ channels co-localised with CFTR in the apical membrane of an exocrine gland acinus: possible involvement in secretion

The primary secretion formed in various exocrine glands has a [K+] 2-5 times that of plasma. In this study we measured the transepithelial flux of 36Cl-, 22Na+ and 42K+ across the frog skin and applied the single-channel patch-clamp technique to the apical membrane of frog skin gland acini to investigate the pathway taken by K+ secreted by the glands. Transepithelial K+ secretion was active and was driven by a larger force than the secretion of Na+. When driving Na+ through the epithelium by clamping the transepithelial potential to 100 mV (apical solution reference), blockers of cellular secretion (apical 5-nitro-2-(3-phenylpropylamino)benzoate or basolateral quinine or furosemide) decreased K+ secretion but left Na+ secretion unaffected. We conclude that K+ follows a transcellular pathway across the epithelium. Patch-clamp analysis of the apical membrane of microdissected gland acini revealed a population of voltage- and calcium-activated K+ channels of the maxi K+ type. In cell-attached patches these channels were activated by membrane potential depolarisation or exposure to prostaglandin E2 and had a permeability of 3.6 +/- 0.3 x 10(-13) cm3 s-1, giving a calculated conductance of 170 pS with 125 mM K+ on both sides of the membrane. In inside-out patches the channels were activated by increasing intracellular [Ca2+] from 10(-7) to 10(-6) M and were blocked by Ba2+ added to the cytoplasmic side. Exposure of inside-out patches containing the maxi K+ channel to ATP on the inside activated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels, confirming that both channels are co-localised to the apical membrane. We interpret these findings in terms of a model where transepithelial NaCl secretion can be supported in part by an apical K+ conductance.

Comparison of several one-step home urinary luteinizing hormone detection test kits to OvuQuick

OBJECTIVE

To compare clinical accuracy and ease of use for several of the new rapid one-step home urinary LH detection kits compared with the preexisting OvuQuick brand LH detection kit (designated as the standard).

DESIGN

Prospective cohort study.

SETTING

University-based infertility clinic.

PATIENT(S)

All women undergoing intrauterine inseminations at the clinic, regardless of infertility diagnosis, were offered enrollment during a 28-month study period.

INTERVENTION(S)

Each participant was supplied three one-step test kits (OvuQuick One-Step, ClearPlan Easy, and SureStep) in addition to a multistep OvuQuick test kit and instructed to run the tests in parallel on the same urine sample and to record the results. Urine testing was performed every 12 hours, beginning 3 days before the anticipated onset of an LH surge, and continued with the one-step kits every 12 hours for 48 hours after the surge was first detected by OvuQuick. Subjects also completed questionnaires evaluating the use of each test kit.

MAIN OUTCOME MEASURE(S)

Correlation of LH surge detection by one-step kits in comparison to surge detection by OvuQuick. Satisfaction and ease of use questionnaires.

RESULT(S)

Sixty-three volunteers returned useable data, from which 81 evaluable cycles were analyzed. The majority of patients found the newer one-step kits to be easier to use and less time consuming than OvuQuick. The three one-step kits detected the LH surge within +/- one testing period (+/-12 hours) of detection by OvuQuick 68%-84% of the time. OvuQuick One-Step, with modified instructions allowing for an equal color intensity in the test and reference areas, had the highest correlation with OvuQuick (84%). However, with a study power (alpha = 0.05, beta = 0.10) sufficient to detect a 10% difference between Ovuquick and each one-step kit, all one-step kits were statistically equivalent to each other. There was no cycle in which a one-step kit detected a positive LH surge but OvuQuick did not.

CONCLUSION(S)

One-step urinary LH kits are easier for patients to use than a multistep home urinary LH kit and have reasonable correlation with the multistep kit when used clinically for timing artificial inseminations.

Activation and functional characterization of the mosaic receptor SorLA/LR11

We previously isolated and sequenced the approximately 250-kDa type 1 receptor sorLA/LR11, a mosaic protein with elements characterizing the Vps10p domain receptor family as well as the low density lipoprotein receptor family. The N terminus of the Vps10p domain comprises a consensus sequence for cleavage by furin ((50)RRKR(53)) that precedes a truncation found in sorLA isolated from human brain. Here we show that sorLA, like sortilin-1/neurotensin receptor-3, whose lumenal domain consists of a Vps10p domain only, is synthesized as a proreceptor that is cleaved by furin in late Golgi compartments. We show that the truncation conditions the Vps10p domain for propeptide inhibitable binding of neuropeptides and the receptor-associated protein. We further demonstrate that avid binding of the receptor-associated protein, apolipoprotein E, and lipoprotein lipase not inhibited by propeptide occurs to sites located in other lumenal domains. In transfected cells, about 10% of full-length sorLA were expressed on the cell surface capable of mediating endocytosis. However, the major pool of receptors was found in late Golgi compartments, suggesting possible interaction with newly synthesized ligands. The results show that sorLA, following activation by truncation, binds multiple ligands and may mediate both endocytosis and sorting.

Ca2+ binding to alpha-synuclein regulates ligand binding and oligomerization

alpha-Synuclein is a protein normally involved in presynaptic vesicle homeostasis. It participates in the development of Parkinson's disease, in which the nerve cell lesions, Lewy bodies, accumulate alpha-synuclein filaments. The synaptic neurotransmitter release is primarily dependent on Ca(2+)-regulated processes. A microdialysis technique was applied showing that alpha-synuclein binds Ca(2+) with an IC(50) of about 2-300 microm and in a reaction uninhibited by a 50-fold excess of Mg(2+). The Ca(2+)-binding site consists of a novel C-terminally localized acidic 32-amino acid domain also present in the homologue beta-synuclein, as shown by Ca(2+) binding to truncated recombinant and synthetic alpha-synuclein peptides. Ca(2+) binding affects the functional properties of alpha-synuclein. First, the ligand binding of (125)I-labeled bovine microtubule-associated protein 1A is stimulated by Ca(2+) ions in the 1-500 microm range and is dependent on an intact Ca(2+) binding site in alpha-synuclein. Second, the Ca(2+) binding stimulates the proportion of (125)I-alpha-synuclein-containing oligomers. This suggests that Ca(2+) ions may both participate in normal alpha-synuclein functions in the nerve terminal and exercise pathological effects involved in the formation of Lewy bodies.

Pharmacological properties of the mouse neurotensin receptor 3. Maintenance of cell surface receptor during internalization of neurotensin

We recently reported the molecular identification of a new type of receptor for the neuropeptide neurotensin (NT), the neurotensin receptor 3 (NTR3), identical to sortilin, which binds receptor-associated protein. Here, we demonstrate that the cloned mouse NTR3 is expressed on the plasma membrane of transfected COS-7 cells. The mouse NTR3 is detectable by photoaffinity labeling and immunoblotting at the cell surface as a 100 kDa N-glycosylated protein. Biochemical analysis and confocal microscopic imaging clearly indicate that NT is efficiently internalized after binding to NTR3, and that despite this internalization, the amount of receptor present on the cell surface is maintained.

Microtubule-associated protein 1B is a component of cortical Lewy bodies and binds alpha-synuclein filaments

Lewy bodies, neuropathological hallmarks of Parkinson's disease and dementia with Lewy bodies, comprise alpha-synuclein filaments and other less defined proteins. Characterization of Lewy body proteins that interact with alpha-synuclein may provide insight into the mechanism of Lewy body formation. Double immunofluorescence labeling and confocal microscopy revealed approximately 80% of cortical Lewy bodies contained microtubule-associated protein 1B (MAP-1B) that overlapped with alpha-synuclein. Lewy bodies were isolated using an immunomagnetic technique from brain tissue of patients dying with dementia with Lewy bodies. Lewy body proteins were resolved by polyacrylamide gel electrophoresis. Immunoblotting confirmed the presence of MAP-1B and alpha-synuclein in purified Lewy bodies. Direct binding studies revealed a high affinity interaction (IC(50) approximately 20 nm) between MAP-1B and alpha-synuclein. The MAP-1B-binding sites were mapped to the last 45 amino acids of the alpha-synuclein C terminus. MAP-1B also bound in vitro assembled alpha-synuclein fibrils. Thus, MAP-1B may be involved in the pathogenesis of Lewy bodies via its interaction with monomeric and fibrillar alpha-synuclein.

Effects of atmospheric conditions, NaCl and pH on growth and interactions between moulds and yeasts related to blue cheese production

The starter culture Penicillium roqueforti, undesired cultures Penicillium caseifulvum and Geotrichum candidum and the potential starter culture Debaryomyces hansenii were examined for their growth and interactions at environmental conditions similar to the Danish blue cheese Danablu. The combined effect of low oxygen (0.3%) and high level of carbon dioxide (25%) at 4% NaCl w/v (a(w) 0.97) and pH 4.5 and 6.5 on radial growth was examined on a cheese medium at 10 degrees C. P. roqueforti and G. candidum were well adapted to growth at low levels of oxygen and high levels of carbon dioxide but G. candidum was not able to grow in the presence of 4% NaCl (w/v). Growth of P. caseifulvum was strongly inhibited at atmospheric conditions comprising 25% carbon dioxide, especially in combination with 0.3% oxygen. Generally D. hansenii showed strong growth at all environmental conditions examined, except at 0.3% oxygen combined with 25% carbon dioxide and 4% NaCl (w/v). Growth and sporulation of P. roqueforti was highly affected in the presence of G. candidum at 25% carbon dioxide irrespective of levels of oxygen and NaCl in the cheese media. P. caseifulvum caused a pronounced inhibitory effect towards growth of P. roqueforti and D. hansenii at 21% oxygen. D. hansenii caused weak inhibition of P. roqueforti at 21% oxygen, while positive interactions between the two species were indicated at 25% carbon dioxide and 0.3% oxygen.

Effect of alpha1-adrenergic stimulation of Cl- secretion and signal transduction in exocrine glands (Rana esculenta)

In the present work, the effect of stimulation of alpha-adrenergic receptors on Cl- secretion via exocrine frog skin glands was investigated. The alpha-adrenergic stimulation was performed by addition of the adrenergic agonist noradrenaline in the presence of the beta-adrenergic antagonist propranolol. In the presence of propranolol, noradrenaline had no effect on the cellular cAMP content. The Cl- secretion was measured as the amiloride-insensitive short circuit current (ISC). Addition of noradrenaline induced a biphasic increase in the ISC. The increase in ISC coincided with an increase in the net 36Cl- secretion. The noradrenaline-induced increase in ISC was dose-dependent with an EC50 of 13 +/- 0.3 microM. Epifluorescence microscopic measurements of isolated, fura-2-loaded frog skin gland acini were used to characterize the intracellular calcium ([Ca2+]i) response. Application of noradrenaline induced a biphasic [Ca2+]i response, which was dose-dependent with an EC50 of 11 +/- 6 microM. The Ca2+ plateau unlike the peak-response was sensitive to removal of Ca2+ from the extracellular medium. The noradrenaline-induced increase in the Cl- secretion as well as in [Ca2+]i was sensitive to the alpha1-adrenergic antagonist prazosine. Ryanodine and caffeine had no effect on [Ca2+]i indicating that the release was independent of ryanodine-sensitive Ca2+ stores. Noradrenaline mediated a significant increase in the cellular inositol 1,4,5-trisphosphate (IP3) content suggesting that the signal transduction pathway leading to the noradrenaline-induced increase in Ca2+ involved IP3 and a release of Ca2+ from IP3-sensitive stores.

Contribution of the carboxy-terminal domain of lipoprotein lipase to interaction with heparin and lipoproteins

The C-terminal domain of lipoprotein lipase (LPL) is involved in several important interactions. To assess its contribution to the binding ability of full-length LPL we have determined kinetic constants using biosensor technique. The affinity of the C-terminal domain for heparin was about 500-fold lower than that of full-length LPL (K(d) = 1.3 microM compared to 3.1 nM). Replacement of Lys403, Arg405 and Lys407 by Ala abolished the heparin affinity, whereas replacement of Arg420 and Lys422 had little effect. The C-terminal domain increased binding of chylomicrons and VLDL to immobilized heparin relatively well, but was less than 10% efficient in binding of LDL compared to full-length LPL. Deletion of residues 390-393 (WSDW) did not change the affinity to heparin and only slightly decreased the affinity to lipoproteins. We conclude that the C-terminal folding domain contributes only moderately to the heparin affinity of full-length LPL, whereas the domain appears important for tethering triglyceride-rich lipoproteins to heparin-bound LPL.

Trichosanthin interacts with and enters cells via LDL receptor family members

The type-I ribosome-inactivating protein trichosanthin displays selective cytotoxicity, suggesting specific mechanisms for entry into cells. Here we show that trichosanthin binds specifically to the endocytic receptors LRP and megalin, and that binding as well as uptake into cells is inhibited by the receptor-associated protein (RAP). The results suggest that the known abortifacient and renotoxic actions of trichosanthin are caused by LRP-mediated uptake in trophoblasts and megalin-mediated uptake in proximal tubule epithelial cells, respectively.

Effect of carbachol and prostaglandin E2 on chloride secretion and signal transduction in the exocrine glands of frog skin (Rana esculenta)

Carbachol (CCH) increased the short-circuit current across frog skin glands in a biphasic manner, which coincided with an increase in the transepithelial Cl- net flux. CCH also induced a biphasic increase in [Ca2+]i. Both these responses were mediated via muscarinic receptors. The plateau phase of the CCH-induced Cl- secretion was modestly inhibited by indomethacin and unaffected by tetrodotoxin or tetrodotoxin plus indomethacin, indicating that CCH can increase Cl- secretion directly via receptors on the secretory cells. Prostaglandin E2 (PGE2) increased secretion and cAMP production, indicating expression of EP2 and/or EP4 receptors. PGE2 failed to increase [Ca2+]i ruling out involvement of EP1 receptors. The secretory response to CCH was potentiated by prestimulation with PGE2, and it was investigated whether this potentiation is caused by interaction at the level of the messengers involved. Stimulation by CCH plus PGE2 failed to stimulate cAMP production further than PGE2 alone. Addition of PGE2 during the CCH-elevated [Ca2+]i plateau phase in most cases reduced the level of [Ca2+]i. These data show that the synergy between CCH and PGE2 is not based on interactions at the intracellular messenger level.

Increased mortality associated with growth hormone treatment in critically ill adults

BACKGROUND

The administration of growth hormone can attenuate the catabolic response to injury, surgery, and sepsis. However, the effect of high doses of growth hormone on the length of stay in intensive care and in the hospital, the duration of mechanical ventilation, and the outcome in critically ill adults who are hospitalized for long periods is not known.

METHODS

We carried out two prospective, multicenter, double-blind, randomized, placebo-controlled trials in parallel involving 247 Finnish patients and 285 patients in other European countries who had been in an intensive care unit for 5 to 7 days and who were expected to require intensive care for at least 10 days. The patients had had cardiac surgery, abdominal surgery, multiple trauma, or acute respiratory failure. The patients received either growth hormone (mean [+/-SD] daily dose, 0.10 +/- 0.02 mg per kilogram of body weight) or placebo until discharge from intensive care or for a maximum of 21 days.

RESULTS

The in-hospital mortality rate was higher in the patients who received growth hormone than in those who did not (P<0.001 for both studies). In the Finnish study, the mortality rate was 39 percent in the growth hormone group, as compared with 20 percent in the placebo group. The respective rates in the multinational study were 44 percent and 18 percent. The relative risk of death for patients receiving growth hormone was 1.9 (95 percent confidence interval, 1.3 to 2.9) in the Finnish study and 2.4 (95 percent confidence interval, 1.6 to 3.5) in the multinational study. Among the survivors, the length of stay in intensive care and in the hospital and the duration of mechanical ventilation were prolonged in the growth hormone group.

CONCLUSIONS

In patients with prolonged critical illness, high doses of growth hormone are associated with increased morbidity and mortality.

alpha-synuclein binds to Tau and stimulates the protein kinase A-catalyzed tau phosphorylation of serine residues 262 and 356

alpha-Synuclein has been implicated in the pathogenesis of several neurodegenerative disorders based on the direct linking of missense mutations in alpha-synuclein to autosomal dominant Parkinson's disease and its presence in Lewy-like lesions. To gain insight into alpha-synuclein functions, we have investigated whether it binds neuronal proteins and modulates their functional state. The microtubule-associated protein tau was identified as a ligand by alpha-synuclein affinity chromatography of human brain cytosol. Direct binding assays using (125)I-labeled human tau40 demonstrated a reversible binding with a IC(50) about 50 pM. The interacting domains were localized to the C terminus of alpha-synuclein and the microtubule binding region of tau as determined by protein fragmentation and the use of recombinant peptides. High concentrations of tubulin inhibited the binding between tau and alpha-synuclein. Functionally, alpha-synuclein stimulated the protein kinase A-catalyzed phosphorylation of tau serine residues 262 and 356 as determined using a phospho-epitope-specific antibody. We propose that alpha-synuclein modulates the phosphorylation of soluble axonal tau and thereby indirectly affects the stability of axonal microtubules.

Sortilin/neurotensin receptor-3 binds and mediates degradation of lipoprotein lipase

Lipoprotein lipase and the receptor-associated protein (RAP) bind to overlapping sites on the low density lipoprotein receptor-related protein/alpha2-macroglobulin receptor (LRP). We have investigated if lipoprotein lipase interacts with the RAP binding but structurally distinct receptor sortilin/neurotensin receptor-3. We show, by chemical cross-linking and surface plasmon resonance analysis, that soluble sortilin binds lipoprotein lipase with an affinity similar to that of LRP. The binding was inhibited by heparin and RAP and by the newly discovered sortilin ligand neurotensin. In 35S-labeled 3T3-L1 adipocytes treated with the cross-linker dithiobis(succinimidyl propionate), lipoprotein lipase-containing complexes were isolated by anti-sortilin antibodies. To elucidate function in cells, sortilin-negative Chinese hamster ovary cells were transfected with full-length sortilin and shown to express about 8% of the receptors on the cell surface. These cells degraded 125I-labeled lipoprotein lipase much faster than the wild-type cells. The degradation was inhibited by unlabeled lipoprotein lipase, indicating a saturable pathway, and by RAP and heparin. Moreover, inhibition by the weak base chloroquine suggested that degradation occurs in an acidic vesicle compartment. The results demonstrate that sortilin is a multifunctional receptor that binds lipoprotein lipase and, when expressed on the cell surface, mediates its endocytosis and degradation.

Propeptide cleavage conditions sortilin/neurotensin receptor-3 for ligand binding

We recently reported the isolation and sequencing of sortilin, a new putative sorting receptor that binds receptor-associated protein (RAP). The luminal N-terminus of sortilin comprises a consensus sequence for cleavage by furin, R41WRR44, which precedes a truncation originally found in sortilin isolated from human brain. We now show that the truncation results from cellular processing. Sortilin is synthesized as a proform which, in late Golgi compartments, is converted to the mature receptor by furin-mediated cleavage of a 44 residue N-terminal propeptide. We further demonstrate that the propeptide exhibits pH-dependent high affinity binding to fully processed sortilin, that the binding is competed for by RAP and the newly discovered sortilin ligand neurotensin, and that prevention of propeptide cleavage essentially prevents binding of RAP and neurotensin. The findings evidence that the propeptide sterically hinders ligands from gaining access to overlapping binding sites in prosortilin, and that cleavage and release of the propeptide preconditions sortilin for full functional activity. Although proteolytic processing is involved in the maturation of several receptors, the described exposure of previously concealed ligand-binding sites after furin-mediated cleavage of propeptide represents a novel mechanism in receptor activation.

Binding of alpha-synuclein to brain vesicles is abolished by familial Parkinson's disease mutation

The presynaptic protein alpha-synuclein has been implicated in the pathogenesis of Parkinson's disease. First, two missense mutations A30P and A53T cause inheritable early onset Parkinson's disease in some families. Secondly, alpha-synuclein is present in Lewy bodies of affected nerve cells in the predominant sporadic type of Parkinson's disease as well as in dementia with Lewy bodies. We demonstrate in the rat optic system that a portion of alpha-synuclein is carried by the vesicle-moving fast component of axonal transport and that it binds to rat brain vesicles through its amino-terminal repeat region. We find alpha-synuclein with the A30P mutation of familial Parkinson's disease devoid of vesicle-binding activity and propose that mutant alpha-synuclein may accumulate, leading to assembly into Lewy body filaments.

Colony interaction and secondary metabolite production of cheese-related fungi in dual culture

Interactions between fungi used as starter cultures (Penicillium roqueforti, Penicillium camemberti, Penicillium nalgiovense, and Geotrichum candidum) and fungal contaminants associated with cheese were investigated on agar medium at two temperatures, 18 and 25 degrees C. Mutual inhibition on contact was the most common interaction observed. The only other interaction observed was inhibition of the contaminant, while the starter continued to grow, especially in dual cultures involving G. candidum as the starter culture. Dual cultures involving G. candidum showed inhibition of production of the mycotoxins mycophenolic acid, roquefortin C, chaetoglobosin A, and cyclopiazonic acid produced by the contaminants. An unknown metabolite was detected in considerably larger quantity in dual cultures involving G. candidum compared to detection in single cultures. There was no correlation between detection of this metabolite and the observed interactions. The results show that G. candidum plays a major role in interactions between fungi on cheese.

Protection by fungal starters against growth and secondary metabolite production of fungal spoilers of cheese

The influence of fungal starter cultures on growth and secondary metabolite production of fungal contaminants associated with cheese was studied on laboratory media and Camembert cheese. Isolates of the species Penicillium nalgiovense, P. camemberti, P. roqueforti and Geotrichum candidum were used as fungal starters. The species P. commune, P. caseifulvum, P. verrucosum, P. discolor, P. solitum, P. coprophilum and Aspergillus versicolor were selected as contaminants. The fungal starters showed different competitive ability on laboratory media and Camembert cheese. The presence of the Penicillium species, especially P. nalgiovense, showed an inhibitory effect on the growth of the fungal contaminants on laboratory media. G. candidum caused a significant inhibition of the fungal contaminants on Camembert cheese. The results indicate that G. candidum plays an important role in competition with undesirable microorganisms in mould fermented cheeses. Among the starters, P. nalgiovense caused the largest reduction in secondary metabolite production of the fungal contaminants on the laboratory medium. On Camembert cheese no significant changes in metabolite production of the fungal contaminants was observed in the presence of the starters.

The carboxy-terminal domain of the receptor-associated protein binds to the Vps10p domain of sortilin

Binding of the receptor-associated protein (RAP) to the newly identified putative sorting receptor, sortilin, was analyzed by surface plasmon resonance analysis of recombinant RAP and sortilin domains and compared with binding to megalin and low density lipoprotein receptor-related protein (LRP). The data show that the RAP-binding site in sortilin is localized in the cysteine-rich lumenal part homologous to yeast vacuolar protein-sorting 10 protein (Vps10p), and the sortilin-binding site in RAP is localized in the carboxy-terminal domain III of the three homologous domains in RAP. Whereas sortilin bound only RAP domain III, megalin and LRP bound all RAP domains with the functional affinity order: domain III >domain I > domain II.

The basolateral Ca2+-dependent K+ channel in rat colonic crypt cells

Previous studies have indicated that a 16-pS K+ channel (KCca) in the basolateral membrane is responsible for the acetylcholine-induced whole-cell K+ conductance in these cells. In the present study we have examined this channel in excised inside-out patches of the basolateral membrane. Over a wide voltage range this channel showed inward rectification. The Ca2+ sensitivity was very marked, with a Hill coefficient of three and with half-maximal activation at 330 nmol/l. After several minutes most channels showed a slow run-down. Channel activity could be refreshed by addition of ATP (1 mmol/l) to the bath solution. The non-metabolizable derivative 5'-adenylylimidodiphosphate (AMP-PNP) had no such effect. In contrast, it inhibited channel activity by some 50%. ATP and its derivatives had no effect on the Ca2+ sensitivity. Channels activated by ATP were subsequently studied in the presence of alkaline (10 kU/l) or acidic (1 kU/l) phosphatase. Both phosphatases reduced channel activity significantly. These data suggest that the 16-pS K+ channel is directly controlled by cytosolic Ca2+. This regulatory step is probably distal to an activation produced by protein-kinase-C-dependent phosphorylation. As is the case for several other K+ channels, high concentrations of non-metabolizable ATP analogues inhibit this channel.

Binding of Abeta to alpha- and beta-synucleins: identification of segments in alpha-synuclein/NAC precursor that bind Abeta and NAC

NAC, a 35-residue peptide derived from the neuronal protein alpha-synuclein/NAC precursor, is tightly associated with Abeta fibrils in Alzheimer's disease amyloid, and alpha-synuclein has recently been shown to bind Abeta in vitro. We have studied the interaction between Abeta and synucleins, aiming at determining segments in alpha-synuclein that can account for the binding, as well as identifying a possible interaction between Abeta and the beta-type synuclein. We report that Abeta binds to native and recombinant alpha-synuclein, and to beta-synuclein in an SDS-sensitive interaction (IC50 approx. 20 microM), as determined by chemical cross-linking and solid-phase binding assays. alpha-Synuclein and beta-synuclein were found to stimulate Abeta-aggregation in vitro to the same extent. The synucleins also displayed Abeta-inhibitable binding of NAC and they were capable of forming dimers. Using proteolytic fragmentation of alpha-synuclein and cross-linking to 125I-Abeta, we identified two consecutive binding domains (residues 1-56 and 57-97) by Edman degradation and mass spectrometric analysis, and a synthetic peptide comprising residues 32-57 possessed Abeta-binding activity. To test further the possible significance in pathology, alpha-synuclein was biotinylated and shown to bind specifically to amyloid plaques in a brain with Alzheimer's disease. It is proposed that the multiple Abeta-binding sites in alpha-synuclein are involved in the development of amyloid plaques.