Human eating: evidence for a physiological basis using a modified paradigm

The aim of these studies was to determine if meal requests and changes in hunger ratings in humans were related to spontaneous changes in blood glucose concentration. In our first study, 18 healthy subjects were acutely isolated from food ant time cues. Blood glucose was continuously monitored online and visual analog ratings of hunger were obtained following an overnight fast. Spoken meal requests, if they occurred, were also recorded. In 83% of the subjects, both the perception and behavioral expression of hunger, as assessed by changes in hunger ratings and meal requests, were preceded by, and correlated with, brief, transient declines in blood glucose (nadir: -10% at 27 min). The pattern, magnitude and time course of these declines was similar to those observed in rats. This significant association, between increased expression of hunger and declines in blood glucose, is being tested in a second, ongoing study using acute insulin infusions to mimic spontaneous transient declines in blood glucose. Each subject was studied twice: either insulin or saline was infused while hunger ratings were obtained. Preliminary results in five subjects indicate that hunger ratings increased after insulin-induced transient declines in blood glucose. No change in hunger ratings occurred when blood glucose concentration was stable. These results suggest that this temporal pattern of blood glucose reflects an antecedent physiological event or provides a signal related to the expression of hunger in humans. Further understanding of human eating may result from investigation of the complex interaction of physiological and other factors in an experimental setting that allows the expression the behavior under study.

Liquid secondary ion mass spectrometry of methyl glycosides of oligosaccharides using matrices containing carboxamides

Intense cluster ions corresponding to proton-bound hetero-dimers of an amide molecule and an oligosaccharide molecule are observed in the liquid secondary ion mass spectra of methyl glycosides of oligoxylans if a solution of an aliphatic carboxamide in glycerol is used as the liquid matrix. These cluster ions are particularly abundant and persist for a long period if urea (U) or thiourea (TU) is used as the matrix additive. In these cases, cluster ions containing more than one molecule of U or TU and two oligosaccharide molecules are also observed. The intense signal due to the proton-bound hetero-dimer between U or TU and the oligosaccharide can be used with advantage for a molecular weight determination. The bonding interactions between a protonated saccharide molecule and a molecule U or TU in the proton-bound hetero-dimers are so strong that the urea molecules remain attached to the fragment ions during the decay of metastable cluster ions and even during collision-induced dissociation. Thus, the mass-analysed ion kinetic energy spectra of these proton-bound hetero-dimers are dominated by abundant cluster ions [Bn+U] and [Ym+U] arising from cleavage of the glycosidic bonds within the oligosaccharides. The collisionally-activated mass spectra of the proton-bound hetero-dimers additionally contain peaks of the free ions Bn and Ym. Therefore, these spectra clearly reflect the arrangement of the monosaccharide residues in the oligosaccharide and can be used conveniently for structural analysis.

Weighing the options: criteria for evaluating weight-management programs. The Committee to Develop Criteria for Evaluating the Outcomes of Approaches to Prevent and Treat Obesity

The United States is experiencing an epidemic of obesity among both adults and children. Approximately 35 percent of women and 31 percent of men age 20 and older are considered obese, as are about one-quarter of children and adolescents. While government health goals for the year 2000 call for no more than 20 percent of adults and 15 percent of adolescents to be obese, the prevalence of this often disabling disease is increasing rather than decreasing. Obesity, of course, is not increasing because people are consciously trying to gain weight. In fact, tens of millions of people in this country are dieting at any one time; they and many others are struggling to manage their weight to improve their appearance, feel better, and be healthier. Many programs and services exist to help individuals achieve weight control. But the limited studies paint a grim picture: those who complete weight-loss programs lose approximately 10 percent of their body weight, only to regain two-thirds of it back within 1 year and almost all of it back within 5 years. These figures point to the fact that obesity is one of the most pervasive public health problems in this country, a complex, multifactorial disease of appetite regulation and energy metabolism involving genetics, physiology, biochemistry, and the neurosciences, as well as environmental, psychosocial, and cultural factors. Unfortunately, the lay public and health-care providers, as well as insurance companies, often view it simply as a problem of willful misconduct--eating too much and exercising too little. Obesity is a remarkable disease in terms of the effort required by an individual for its management and the extent of discrimination its victims suffer. While people often wish to lose weight for the sake of their appearance, public health concerns about obesity relate to this disease's link to numerous chronic diseases that can lead to premature illness and death. The scientific evidence summarized in Chapter 2 suggests strongly that obese individuals who lose even relatively small amounts of weight are likely to decrease their blood pressure (and thereby the risk of hypertension), reduce abnormally high levels of blood glucose (associated with diabetes), bring blood concentrations of cholesterol and triglycerides (associated with cardiovascular disease) down to more desirable levels, reduce sleep apnea, decrease their risk of osteoarthritis of the weight-bearing joints and depression, and increase self-esteem. In many cases, the obese person who loses weight finds that an accompanying comorbidity is improved, its progression is slowed, or the symptoms disappear. Healthy weights are generally associated with a body mass index (BMI; a measure of whether weight is appropriate for height, measured in kg/m2) of 19-25 in those 19-34 years of age and 21-27 in those 35 years of age and older. Beyond these ranges, health risks increase as BMI increases. Health risks also increase with excess abdominal/visceral fat (as estimated by a waist-hip ratio [WHR] > 1.0 for males and > 0.8 for females), high blood pressure (> 140/90), dyslipidemias (total cholesterol and triglyceride concentrations of > 200 and > 225 mg/dl, respectively), non-insulin-dependent diabetes mellitus, and a family history of premature death due to cardiovascular disease (e.g., parent, grandparent, sibling, uncle, or aunt dying before age 50). Weight loss usually improves the management of obesity-related comorbidities or decreases the risks of their development. The high prevalence of obesity in the United States together with its link to numerous chronic diseases leads to the conclusion that this disease is responsible for a substantial proportion of total health-care costs. We estimate that today's health-care costs of obesity exceed $70 billion per year.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of diadenosine polyphosphates, ATP and angiotensin II on membrane voltage and membrane conductances of rat mesangial cells

Diadenosine polyphosphates have been shown to influence renal perfusion pressure. As mesangial cells may contribute to these effects we investigated the effects of diadenosine triphosphate (Ap3A), diadenosine tetraphosphate (Ap4A), diadenosine pentaphosphate (Ap5A) and diadenosine hexaphosphate (Ap6A) on membrane voltage (Vm) and membrane conductance (gm) in mesangial cells (MC) of normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats in primary and long-term culture. We applied the patch-clamp technique in the fast-whole-cell configuration to measure Vm and gm. To compare the effects of diadenosine polyphosphates with hitherto known agonists we also tested adenosine 5´-triphosphate (ATP) and angiotensin II (Ang II). As there was no significant difference in the Vm values in MC of WKY (-42 +/- 1 mV, n = 70) and SHR rats (-45 +/- 2 mV, n = 99) as well as in the agonist-induced changes of Vm, all data were pooled. The Vm of all the cells was -44 +/- 1 mV (n = 169) and gm was 15.9 +/- 1.8 nS (n = 141). Ion-exchange experiments showed the presence of a K+ and a non-selective cation conductance in resting MC whereas a Cl- conductance or a Na+-selective conductance could not be observed. Ap3A, Ap4A, Ap5A, AP6A and ATP each at a concentration of 5 micromol/l, led to a significant depolarization of Vm by 5 +/- 2 mV (n = 14), 7 +/- 1 mV (n = 25), 3 +/- 1 mV (n = 23), 2 +/- 1 mV (n = 16), and 14 +/- 2 mV (n = 23), respectively. For Ap4A, the most potent diadenosine polyphosphate, we determined the half-maximally effective concentration (EC50) as 6 micromol/l (n = 5-25), for ATP as 2 micromol/l (n = 9-37), and for Ang II as 8 nmol/l (n = 6-18). Ap4A 100 micromol/l increased gm significantly by 55 +/- 20% (n = 16), 100 micromol/l ATP by 135 +/- 60% (n = 18). The diadenosine polyphosphates examined were able to depolarize Vm (Ang II > ATP > Ap4A > Ap3A > Ap5A > Ap6A) by activation of a Cl- conductance and a non-selective cation conductance, as do ATP or Ang II.

Non-involvement of the redox site of NMDA receptors in bidirectional synaptic plasticity in the CA1 area of the rat hippocampus in vitro

We have examined the effects of the redox reagent 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) on synaptic potentials recorded extracellularly from the CA1 area in hippocampal slices following low frequency stimulation (LFS) and tetanic stimulation (TS). Application of DTNB (200 microM) neither changed synaptic responses, nor prevented the expression of TS-induced long-term potentiation of synaptic responses and their depotentiation by LFS. Conversely, in naive slices, LFS still induced long-term depression of synaptic responses following application of DTNB. This depression could be subsequently reversed with a TS. It is concluded that the redox state of N-methyl-D-aspartate receptors does not affect the expression of long-term potentiation and depression of synaptic responses.

Illusory contours activate specific regions in human visual cortex: evidence from functional magnetic resonance imaging

The neural basis for perceptual grouping operations in the human visual system, including the processes which generate illusory contours, is fundamental to understanding human vision. We have employed functional magnetic resonance imaging to investigate these processes noninvasively. Images were acquired on a GE Signa 1.5T scanner equipped for echo planar imaging with an in-plane resolution of 1.5 x 1.5 mm and slice thicknesses of 3.0 or 5.0 mm. Visual stimuli included nonaligned inducers (pacmen) that created no perceptual contours, similar inducers at the corners of a Kanizsa square that created illusory contours, and a real square formed by continuous contours. Multiple contiguous axial slices were acquired during baseline, visual stimulation, and poststimulation periods. Activated regions were identified by a multistage statistical analysis of the activation for each volume element sampled and were compared across conditions. Specific brain regions were activated in extrastriate cortex when the illusory contours were perceived but not during conditions when the illusory contours were absent. These unique regions were found primarily in the right hemisphere for all four subjects and demonstrate that specific brain regions are activated during the kind of perceptual grouping operations involved in illusory contour perception.

Autonomic nervous system activity in weight gain and weight loss

Studies in both animals and humans indicate that the autonomic nervous system (ANS) responds to changes in systemic energy balance. In the present study, ANS response to weight change was examined by sequential blockade of cardiac autonomic innervation with parasympathetic (atropine) and sympathetic (esmolol) blockers. Change in heart period (interbeat interval) from baseline after atropine defined the amount of parasympathetic control (PC), and the subsequent change after esmolol defined the amount of sympathetic control (SC). In nonobese subjects, weight gain to 10% above initial body weight resulted in a decrease in PC and an increase in SC, and conversely, weight loss to 10% below initial weight resulted in an increase in PC and a decrease in SC. In obese subjects, weight loss resulted in the same pattern of changes in PC and SC. The major changes were in the parasympathetic arm of the ANS. These findings support the hypothesis that the ANS acts to oppose weight change.

Role and benefits of carbohydrate in the diet: key issues for future dietary guidelines

There is now widespread advocacy for a reduction in fat intake. Furthermore, there is little evidence that an increase in protein intake would be advisable. Therefore, a greater proportion of carbohydrate energy in the diet has become a central tenet of current dietary advice. A careful examination of the benefits of a "high"-carbohydrate diet must therefore occupy our attention. Three aspects of the role of carbohydrate in the diet will be considered: 1) the role of carbohydrate in the control of food intake in humans, 2) the effect of carbohydrate on energy metabolism as measured by long-term feeding experiments in small numbers of human subjects, and 3) whether a large carbohydrate intake leads to increased lipogenesis in humans.

Changes in energy expenditure resulting from altered body weight

BACKGROUND

No current treatment for obesity reliably sustains weight loss, perhaps because compensatory metabolic processes resist the maintenance of the altered body weight. We examined the effects of experimental perturbations of body weight on energy expenditure to determine whether they lead to metabolic changes and whether obese subjects and those who have never been obese respond similarly.

METHODS

We repeatedly measured 24-hour total energy expenditure, resting and nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. The subjects were studied at their usual body weight and after losing 10 to 20 percent of their body weight by underfeeding or gaining 10 percent by overfeeding.

RESULTS

Maintenance of a body weight at a level 10 percent or more below the initial weight was associated with a mean (+/- SD) reduction in total energy expenditure of 6 +/- 3 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 5 kcal per kilogram per day in the obese subjects (P < 0.001). Resting energy expenditure and nonresting energy expenditure each decreased 3 to 4 kcal per kilogram of fat-free mass per day in both groups of subjects. Maintenance of body weight at a level 10 percent above the usual weight was associated with an increase in total energy expenditure of 9 +/- 7 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 4 kcal per kilogram per day in the obese subjects (P < 0.001). The thermic effect of feeding and nonresting energy expenditure increased by approximately 1 to 2 and 8 to 9 kcal per kilogram of fat-free mass per day, respectively, after weight gain. These changes in energy expenditure were not related to the degree of adiposity or the sex of the subjects.

CONCLUSIONS

Maintenance of a reduced or elevated body weight is associated with compensatory changes in energy expenditure, which oppose the maintenance of a body weight that is different from the usual weight. These compensatory changes may account for the poor long-term efficacy of treatments for obesity.

Analyzing correlations of three types in selected lines of Drosophila melanogaster that have evolved stable extreme geotactic performance

The behavior-genetic analysis of Drosophila melanogaster with geotactic performance as the phenotype is an ideal model system with which to investigate the complex relations between heredity and behavior. As part of a long-term, 38-year study, we report 4 experiments that identify and analyze trait correlations in the selected high- and low-geotaxis lines. We performed F2 correlational analyses and backcrosses to examine 3 types of correlations: (a) genotype-genotype (alcohol dehydrogenase [Adh]-amylase [Amy]), (b) genotype-phenotype (Adh and Amy-geotaxis), and (c) phenotype-phenotype (mate preference-geotaxis). Only the Adh-geotaxis correlation survived meiosis and reappeared in the F2 generation, which indicates a genotype-phenotype correlation, whereas the others did not. The importance of hybrid correlational analysis to the behavior-genetic analysis of a species is discussed.

The reaction of D-glucose with aminoguanidine

The reaction of D-glucose with aminoguanidine was examined at pH 7.0 and 37 degrees C (phosphate buffer). Under these conditions, the reaction requires ca. 42 days for 50% of the sugar to react, as measured by the disappearance of D-glucose, and at 60 degrees C all the aminoguanidine had reacted within 72 h. The initial product, a beta-D-glucopyranosyl aminoguanidine (1) was obtained in the crystalline state as the trifluoroacetate salt. Data collected on this compound suggests that, in solution, it is largely a glycosylamine in the beta pyranose form. Acetylation gave a crystalline heptaacetate (2), which, in solution (as evidenced by NMR spectroscopy) exists in two different conformational forms. The crystal structure of the heptaacetate also includes two conformers. Both crystallographically independent molecules are in the normal beta pyranose form, with the acetylated guanyl residue occupying different spatial positions relative to the ring.

Family support and other social factors precipitating suicidal ideation

To examine the effects of family support and demographics on suicidal behavior, 385 subjects completed a demographic questionnaire and a Suicidal Ideation Questionnaire (SIQ). Sixteen percent described themselves as "serious" ideators, while 59% were seen as ideators, numbers consistent with past suicide research. Multiple regression analyses revealed that the type of caregiver a person reported having while growing up accounted for a significant amount of the variance on ideator status. Serious ideators were more common among single parent households. Although many demographic variables were assessed, only the primary caregiver a person had as a child impacted their status as a suicidal ideator. This suggests that suicidal behaviors may occur due to a complex interaction between social factors and childhood care. The influence of living in a single-parent home may contribute to whether or not a person considers suicide.

The future for treatment by bone marrow transplantation for adrenoleukodystrophy, metachromatic leukodystrophy, globoid cell leukodystrophy and Hurler syndrome

Within the past decade, bone marrow transplantation has been applied to over 200 patients worldwide with the intention of treating storage diseases. Bone marrow transplantation has provided a method for treatment of adrenoleukodystrophy, metachromatic leukodystrophy, globoid cell leukodystrophy and Hurler syndrome. After engraftment, significant improvement in the clinical course of each of these diseases occurs. Survival data of engrafted patients are superior to those of non-transplanted. Engraftment and the resulting enzymatic reconstitution are concordant. Outcomes based on neuropsychological tests indicate continued maintenance and in some cases increase in cognitive function. Magnetic resonance imaging as well as spectroscopic examinations of the brain provide further evidence that positive changes occur in the central nervous system following long-term engraftment. A better quality of life follows engraftment. Greater gains from use of bone marrow transplantation for these particular storage diseases will occur in the future. Earlier diagnosis will allow bone marrow transplantation in the presymptomatic stage at a younger age, providing an enhancement of positive effects noted from such treatment. At the same time, advances in bone marrow technology will serve to reduce the risk factors involved with the bone marrow transplantation process itself. These two factors taken together will be more than additive in providing benefits from use of bone marrow transplantation.

Strategies for school-based response to loss: proactive training and postvention consultation

The suicide of a student or staff member is one of the most difficult crisis confronting a high school. This article describes the first year of a school-based postvention program to train and consult with crisis personnel in a structured response to this crisis. Responding to Loss (RTL) is one program offered by Community Action for Youth Survival, a project of the Ronald McDonald Children's Charities. Serving a contiguous three county urban area, this program integrates public health, epidemiological, psychiatric, and prevention paradigms to provide a comprehensive approach to the aftermath of adolescent suicide. RTL provides an interdisciplinary model for comprehensive, school-based postvention programs based on the guidelines developed by the Centers for Disease Control and national and local psychological autopsy data. It highlights the significance of responding to increased rates of suicide in minority youth, suicide witnessed by peers, and suicide victims who have dropped out of school. Organizational issues, such as systematic school entry, development of a computerized school database, proactive training, and collaboration with the offices of medical examiners and coroners, are described. Initial evaluation data from year 1 indicate significant gains in participants' knowledge and skills, as well as a high rate of consumer satisfaction.

K+ channels in the basolateral membrane of rat cortical collecting duct are regulated by a cGMP-dependent protein kinase

The basolateral membrane of the rat cortical collecting duct (CCD) principal cell is K+ conductive. Recently, two different K+ channels have been described, namely a small- and an intermediate-conductance K+ channel (s-K+ and i-K+) which most likely are responsible for the macroscopic K+ conductance. K+ channel activity was investigated at the single-channel level using the patch-clamp technique. Patch-clamp recordings were obtained from enzymatically isolated CCD segments and freshly isolated CCD cells using conventional cell-free, cell-attached, cell-attached-nystatin and slow-whole-cell methods. Both K+ channels showed rundown behaviour after excision. In an excised inside-out oriented membrane, K+ channels could be activated by simultaneous addition of 0.1 mmol/l (cyclic guanosine monophosphate (cGMP) and 0.1 mmol/l MgATP to the bath. The i-K+ was activated in 13 out of 45, the s-K+ in 15 out of 45, cases. No activation of either channel was observed with cGMP alone (0.1 mmol/l), MgATP alone (0.1 mmol/l), cGMP and guanosine triphosphate (GTP) (0.1 mmol/l each) or cyclic adenosine monophosphate (cAMP) and MgATP (0.1 mmol/l each) n = 15, 11, 7, 8, respectively). The activated s-K+ could be blocked by KT 5823 (n = 8), a specific inhibitor of a cGMP-dependent protein kinase (PKG). An inhibition of the activated i-K+ was seen in seven cases. The membrane potential hyperpolarized significantly after application of dibutyryl-cGMP (0.1 mmol/l, n = 6) or nitroprusside (10 mumol/l, n = 5), which is known to liberate NO and thus increase the intracellular cGMP level.(ABSTRACT TRUNCATED AT 250 WORDS)

pH dependence of K+ conductances of rat cortical collecting duct principal cells

The K+ channels of the principal cells of rat cortical collecting duct (CCD) are pH sensitive in excised membranes. K+ secretion is decreased with increased H+ secretion during acidosis. We examined whether the pH sensitivity of these K+ channels is present also in the intact cell and thus could explain the coupling between K+ and H+ secretion. Membrane voltages (Vm), whole-cell conductances (gc), and single-channel currents of K+ channels were recorded from freshly isolated CCD cells or isolated CCD segments with the patch-clamp method. Intracellular pH (pHi) was measured using the pH-sensitive fluorescent dye 2'-7'-bis(carboxyethyl)-5-6-carboxyfluorescein (BCECF). Acetate (20 mmol/l) had no effect on Vm, gc, or the activity of the K+ channels in these cells. Acetate, however, acidified pHi slightly by 0.17 +/- 0.04 pH units (n = 19). Vm depolarized by 12 +/- 3 mV (n = 26) and by 23 +/- 2 mV (n = 66) and gc decreased by 26 +/- 5% (n = 13) and by 55 +/- 5% (n = 12) with 3-5 or 8-10% CO2, respectively. The same CO2 concentrations decreased pHi by 0.49 +/- 0.07 (n = 15) and 0.73 +/- 0.11 pH units (n = 12), respectively. Open probability (Po) of all four K+ channels in the intact rat CCD cells was reversibly inhibited by 8-10% CO2. pHi increased with the addition of 20 mmol/l NH4+/NH3 by a maximum of 0.64 +/- 0.08 pH units (n = 33) and acidified transiently by 0.37 +/- 0.05 pH units (n = 33) upon NH4+/NH3 removal. In the presence of NH4+/NH3 Vm depolarized by 16 +/- 2 mV (n = 66) and gc decreased by 26 +/- 7% (n = 16). The activity of all four K+ channels was also strongly inhibited in the presence of NH4+/NH3. The effect of NH4+/NH3 on Vm and gc was markedly increased when the pH of the NH4+/NH3-containing solution was set to 8.5 or 9.2. From these data we conclude that cellular acidification in rat CCD principal cells down-regulates K+ conductances, thus reduces K+ secretion by direct inhibition of K+ channel activity. This pH dependence is present in all four K+ channels of the rat CCD. The inhibition of K+ channels by NH4+/NH3 is independent of changes in pHi and rather involves an effect of NH3.

Hollow glass waveguides for broadband infrared transmission

Broadband hollow glass waveguides have been fabricated with losses as low as 0.15 dB/m at 10.6 microm. We make these hollow glass waveguides by coating the inside of polyimide-coated silica-glass tubing with a metallic layer followed by a thin dielectric coating of a metal halide. The bore sizes of the guides range from 320 to 700 microm, and we have made lengths as long as 3 m. The bending radii of the waveguides are less than 5 cm for bore sizes less than 500 microm. We have used these waveguides to deliver greater than 80 W of CO(2) laser power and 5 W of Er:YAG laser power. The hollow glass guides are inexpensive, robust, and quite flexible and therefore a good infrared fiber for power and sensor applications.

Histamine receptor antagonists and lipid stability in total nutrient admixtures

Drug stability and compatibility studies should be performed for all medications added to total nutrient admixtures (TNAs) before administration to patients. The stability of TNA components will vary depending on product selection and final concentrations. This variability prohibits generalizing published study results generically to TNAs containing untested products or combinations. Histamine receptor antagonists (H2RAs) are commonly administered by continuous infusion via nutrient solutions. When the delivery vehicle is a TNA, comparative stability and compatibility studies performed under similar test conditions are lacking. The stability of marketed parenteral H2RAs and of the investigational H2RA, nizatidine was analyzed in TNA solutions containing either Liposyn II or Intralipid at differing concentrations. All H2RAs remained at more than 90% of initial concentration at 24 hours. After 48 hours, only ranitidine concentrations fell to less than 90% in all study solutions. Each TNA containing an H2RA was within pH stability ranges for lipid products, and no change in particle size was detected during the 48-hour period. This is the first report determining H2RA compatibility and stability in TNA solutions with both 3% and 5% Intralipid and Liposyn II and using similar methodology for all standard H2RA concentrations. Results suggest that these drugs are stable for 24 hours in TNAs containing either lipid product. Beyond this time, administration of ranitidine may be unreliable because of poor stability under the conditions tested.

Analysing ion channels with hidden Markov models

Ion channel current amplitudes (mu) and open probabilities (Po) have been analysed so far by defining a 50% threshold to distinguish between open and closed states of the channels. With this standard method (SM) it is very difficult or even impossible to analyse channels of different size in one membrane patch correctly. A stochastical model, named the hidden Markov model (HMM), separates between observation noise and the stochastic process of opening and closing of ion channels. The HMM allows the independent analysis of mu, Po, and mean dwell times (tau) of different channels in one membrane patch, without defining threshold levels. Using this method errors in the analysis are not summarized like in the SM because all different analysing procedures (e.g. filtering, setting of threshold, fitting processes) are done in one step. Two different K+ channels in excised basolateral membranes of the cortical collecting duct of rat (CCD) were analysed by the SM and the HMM. The mu value of the intermediate-conductance K+ channel (i-K+) was 3.9 +/- 0.1 pA (SM) and 3.8 +/- 0.2 pA (HMM) for 11 observations. The Po value of this channel was 10.2 +/- 4.2% (SM) and 10.1 +/- 4.0% (HMM). The mean tau values were 5.4 +/- 0.6 ms for the open state and 9.6 +/- 2.2 ms and 145 +/- 21 ms for the closed states (SM) and 7.8 +/- 1.1 ms, 7.7 +/- 0.9 ms and 148 +/- 24 ms (HMM), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of postoperative nausea and vomiting in the surgical setting

Postoperative nausea and vomiting is one of the most common complications of inpatient and day case surgical procedures. In a climate where total cost of an illness is becoming increasingly important, postoperative nausea and vomiting is a major contributor to direct and indirect costs for both the hospital and patient. In patient terms, the impact of increased recovery room stays and extra nursing time required by PONV patients has been estimated to range from 96-576 more surgical procedures which may be performed in an 'average' day case surgery centre. Postoperative nausea and vomiting is perceived by patients to account for equal or more debilitation than surgery itself and may cause them to lose wages due to absence from work. Reducing the incidence of nausea and vomiting and its associated problems may therefore provide opportunities to improve patient care, decrease the size of waiting lists and improve utilisation of scarce healthcare resources.

K+ channels in the basolateral membrane of rat cortical collecting duct

Impalement studies in isolated perfused cortical collecting ducts (CCD) of rats have shown that the basolateral membrane possesses a K+ conductive pathway. In the present study this pathway was investigated at the single-channel level using the patch-clamp technique. Patch-clamp recordings were obtained from enzymatically isolated CCD segments and freshly isolated CCD cells with the conventional cell-free, cell-attached and the cell-attached nystatin method. Two K+ channels were found which were highly active on the cell with a conductance of 67 +/- 5 pS (n = 18) and 148 +/- 4 pS (n = 21) with 145 mmol/l K+ in the pipette. In excised patches the first channel had a conductance of 28 +/- 2 pS (n = 15), whereas the second one had a conductance of 85 +/- 1 pS (n = 53) at 0 mV clamp voltage with 145 mmol/l K+ on one side and 3.6 mmol/l K+ on the other side of the membrane. So far it has not been possible to characterize the smaller channel further. Excised, and with symmetrical K+ concentrations of 145 mmol/l, the intermediate channel had a linear conductance of 198 +/- 19 pS (n = 5). After excision in the inside-out configuration the open probability (Po) of this channel was low (0.18 +/- 0.05, n = 13) whereas in the outside-out configuration this channel had a threefold higher Po (0.57 +/- 0.04, n = 12). Several inhibitors were tested in excised membranes. Ba2+ (1 mmol/l), tetraethylammonium (TEA+, 10 mmol/l) and verapamil (0.1 mmol/l) all blocked this channel reversibly.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro lipid synthesis in human adipose tissue from three abdominal sites

The association between abdominal deposition of adipose tissue and morbidities accompanying obesity may be related to high rates of free fatty acid release from enlarged intra-abdominal stores. To investigate cellular mechanisms that might contribute to enlargement of intra-abdominal adipocytes, lipolysis, triacylglycerol (TG), and diacylglycerol (DG) synthesis from [14C]glucose was measured in abdominal subcutaneous, omental, and mesenteric adipose tissue from severely obese women and men. Subcutaneous adipose tissue from women showed the highest rates of TG synthesis compared with the intra-abdominal site, or any site in men. isoproterenol stimulated TG synthesis more in intra-abdominal than subcutaneous adipose tissue. In the basal state, intra-abdominal adipose tissue from both men and women showed rates of [14C]DG accumulation approximately 50% total [14C]acylglyceride accumulation, whereas, in subcutaneous adipose tissue, [14C]DG accumulation was approximately 25% of total. Basal lipolysis was lower in intra-abdominal than subcutaneous adipocytes. Stimulation of lipolysis reduced [14C]DG accumulation more in intra-abdominal than subcutaneous adipose tissue. Low rates of acylglyceride synthesis in intra-abdominal adipocytes may prevent accumulation of large intra-abdominal fat stores in women.

Venovenous compares favorably with venoarterial access for extracorporeal membrane oxygenation in neonatal respiratory failure

Traditional extracorporeal membrane oxygenation via the venoarterial route requires cannulation and ligation of the internal jugular vein and common carotid artery. Concerns about ligation of the common carotid artery prompted development of a 14F double-lumen internal jugular vein cannula for venovenous oxygenation for neonates with respiratory failure. We retrospectively compared 22 patients supported by venovenous bypass and 20 patients supported with traditional venoarterial bypass. The two groups of patients were selected to be comparable in terms of diagnosis and severity of respiratory insufficiency. The diagnoses in both groups were limited to meconium aspiration syndrome or persistent pulmonary hypertension of the newborn. The average oxygenation indexes in the two groups were similar (46.6 venovenous, 47.2 venoarterial, p = not significant). Venovenous access allowed flow rates of more than 100 ml/kg per minute, which were adequate for gas exchange support. One patient required conversion from venovenous to venoarterial bypass because of hemodynamic instability. The average time of bypass support was 115 hours (range 24 to 338 hours) for venovenous bypass and 134 hours (range 47 to 361 hours) for venoarterial bypass (p < 0.05). The time to extubation after decannulation from extracorporeal membrane oxygenation was 133 hours (range 38 to 720 hours) for venovenous support and 100 hours (range 27 to 192 hours) for venoarterial support (p = not significant). One patient supported with venoarterial bypass had an intracranial hemorrhage. There were no documented neurologic injuries in the patients managed with venovenous bypass. There were no deaths in either group. Venovenous extracorporeal membrane oxygenation through a double-lumen cannula can adequately provide respiratory support for neonates with pulmonary failure and effectively avoids ligation of the common carotid artery.

Determination of linkage positions in peracetylated (methyl) xylo-oligosaccharides with fast atom bombardment mass spectrometry

Distinction between the linkage types 1-->2, 1-->3 and 1-->4 of xylobioses can be achieved on the basis of the unimolecular decomposition spectra of the oxonium ions of the per-O-acetylated methyl glycosides. The spectra of the oxonium ions of various unbranched xylotri-, tetra- and pentaoses allow determination of the linkage position between the xylose residues. This indicates that in unbranched peracetylated xylo-oligosaccharides the linkage between the xylose residues at the non-reducing end can be determined.

Lack of beta 3-adrenergic effect on lipolysis in human subcutaneous adipose tissue

Human adipocytes are responsive to both alpha- (antilipolytic) and beta-(lipolytic) actions of catecholamine agonists. These effects are mediated by G proteins which interact with adenylcyclase beta 1- and beta 2-adrenoreceptor (AR) subtypes are identified in human adipose tissue. The existence of a third beta-adrenergic (beta 3) receptor has been recently proposed. The beta 3-AR has been reported to mediate catecholamine-induced cAMP accumulation and to be more responsive in this regard than either the beta 1- or the beta 2-AR. To examine the possibility that a beta 3-AR plays a significant role in the control of catecholamine-stimulated lipolysis in human adipose tissue, we used a sensitive in vitro measure of lipolysis. Abdominal and gluteal sc adipose tissue samples from 14 adults were incubated with isoproterenol, a nonspecific beta-AR agonist which activates adenylyl cyclase via all three beta-AR subtypes, in the presence of varying concentrations of a beta-AR antagonist, alprenolol, which blocks the beta 1- and beta 2-AR, but not the beta 3-AR. In tissue from both abdominal and gluteal sites, alprenolol (10(-3) M) completely abolished the lipolytic response to isoproterenol (10(-6) M). Alprenolol (10(-3) M) alone reduced basal lipolysis by 10.2 +/- 2.2% (SEM) in abdominal tissue (P < 0.01), and 7.1 +/- 2.7% in gluteal tissue (P < 0.05). In the presence of alprenolol (10(-3) M), isoproterenol (10(-6) M) had no demonstrable lipolytic effect. The probability of incorrect acceptance of the null hypothesis that isoproterenol had no effect on lipolysis in alprenolol-blocked tissue is P beta < 0.05 for both depots. As an additional control, pooled inguinal adipose tissue from adult male Sprague-Dawley rats was incubated with the same concentrations of alprenolol. Rat adipose tissue has been previously shown to express the beta 3-adrenoreceptor and lipolysis was increased in rat adipose tissue in the presence of alprenolol 10(-4) M and 10(-5) M. We conclude that beta 3-ARs, if present in human adipocyte plasma membranes, do not significantly affect rates of lipolysis.

Ondansetron: a cost-effective advance in anti-emetic therapy

A cost-effectiveness analysis is one form of full economic evaluation where drug acquisition costs and the costs that are incurred as a result of using a particular treatment are assessed together with clinical efficacy. This paper reviews two such studies. One of the studies was a prospective randomised cost-effectiveness study which compared ondansetron (8 mg i.v. 0, 4 and 8 h following chemotherapy) with metoclopramide (3 mg/kg i.v. followed by an infusion of 0.5 mg/kg/h for 8 h) over the first 24 h following chemotherapy in hospitalised patients receiving highly emetogenic chemotherapy. This study showed that the cost per successfully treated patient (defined in this study as having < or = 1 emetic episode and no adverse events) for these 2 treatments were approximately equal: ondansetron pounds 95 and metoclopramide pounds 92. The second study was an economic evaluation based on data collected over a 5-day period following cyclophosphamide-based chemotherapy given on an outpatient basis for the treatment of breast cancer. Patients received an intravenous dose of 16 mg dexamethasone with either 8 mg ondansetron or 60 mg metoclopramide intravenously before chemotherapy followed by oral dosing with 8 mg ondansetron or 20 mg metoclopramide 3 times daily for 5 days. The costs per successfully treated patient (defined in this study as no vomiting or retching episodes and no anti-emetic-related adverse events during the 5-day period) were comparable: ondansetron pounds 184 and metoclopramide pounds 160. A recent study has established that ondansetron (8 mg) given orally twice daily is as effective as the same dose given 3 times a day. A sensitivity analysis using the cost of an ondansetron twice daily regimen showed that ondansetron is more cost-effective than metoclopramide (pounds 133 vs. pounds 160). These cost effectiveness studies have shown that ondansetron is at least as cost-effective as metoclopramide and simplified ondansetron dosing schedules render ondansetron more cost-effective. These full economic evaluations illustrate that drug acquisition costs can be a misleading guide to the economic impact of antiemetics.

Cation specificity and pharmacological properties of the Ca(2+)-dependent K+ channel of rat cortical collecting ducts

The luminal membrane of principal cells of rat cortical collecting duct (CCD) is dominated by a K+ conductance. Two different K+ channels are described for this membrane. K+ secretion probably occurs via a small-conductance Ca(2+)-independent channel. The function of the second, large-conductance Ca(2+)-dependent channel is unclear. This study examines properties of this channel to allow a comparison of this K+ channel with the macroscopic K+ conductance of the CCD and with similar K+ channels from other preparations. The channel is poorly active on the cell. It has a conductance of 263 +/- 11 pS (n = 36, symmetrical K+ concentrations) and of 139 +/- 3 pS (n = 91) with 145 mmol/l K+ on one side and 3.6 mmol/l K+ on the other side of the membrane. Its open probability is high after excision (0.71 +/- 0.03, n = 85). The channel flickers rapidly between open and closed states. Its permeability in the cell-free configuration was 7.0 +/- 0.2 x 10(-13) cm3/s (n = 85). It is inhibited by several typical blockers of K+ channels such as Ba2+, tetraethylammonium, quinine, and quinidine and high concentrations of Mg2+. The Ca2+ antagonist verapamil and diltiazem also inhibit this K+ channel. As is typical for the maxi K+ channel, it is inhibited by charybdotoxin but not by apamin. The selectivity of this large-conductance K+ channel demonstrates significant differences between the permeability sequence (pK > pRb > pNH4 > pCs = pLi = pNa = pcholine = 0) and the conductance sequence (gK > gNH4 > gRb > gLi = gcholine > gCs = gNa = 0). The only other cations that are significantly conducted by this channel besides K+ (gK at Vc = infinity is 279 +/- 8 pS, n = 88) re NH+4 (gNH4 = 127 +/- 22 pS, n = 10) and Rb+ (gRb = 36 +/- 5 pS, n = 6). The K+ currents through this channel are reduced by high concentrations of choline+, Cs+, Rb+, and NH+4. These properties and the dependence of this channel on Ca2+ and voltage classify it as a "maxi" K+ channel. A possible physiological function of this channel is discussed in the accompanying paper.

Regulation and possible physiological role of the Ca(2+)-dependent K+ channel of cortical collecting ducts of the rat

In the luminal membrane of rat cortical collecting duct (CCD) a big Ca(2+)-dependent and a small Ca(2+)-independent K+ channel have been described. Whereas the latter most likely is responsible for the K+ secretion in this nephron segment, the function of the large-conductance K+ channel is unknown. The regulation of this channel and its possible physiological role were examined with the conventional cell-free and the cell-attached nystatin patch-clamp techniques. Patch-clamp recordings were obtained from the luminal membrane of isolated perfused CCD segments and from freshly isolated CCD cells. Intracellular calcium was measured using the calcium-sensitive dye fura-2. The large-conductance K+ channel was strongly voltage- and calcium-dependent. At 3 mumol/l cytosolic Ca2+ activity it was half-maximally activated. At 1 mmol/l it was neither regulated by cytosolic pH nor by ATP. At 1 mumol/l Ca2+ activity the open probability (Po) of this channel was pH-dependent. At pH 7.0 Po was decreased to 4 +/- 2% (n = 9) and at pH 8.5 it was increased to 425 +/- 52% (n = 9) of the control. At this low Ca2+ activity the Po of the channel was reduced by 1 mmol/l ATP to 8 +/- 4% (n = 6). Cell swelling activated the large-conductance K+ channel (n = 14) and hyperpolarized the membrane potential of the cells by 9 +/- 1 mV (n = 23). Intracellular Ca2+ activity increased after hypotonic stress. This increase depended on the extracellular Ca2+ activity.(ABSTRACT TRUNCATED AT 250 WORDS)

The Zucker fatty (fa) gene is not a mutation of corticotropin-releasing factor

Corticotropin-releasing factor (CRF) appears to regulate several physiological systems that display prominent abnormalities in Zucker fatty (fa/fa) rats, including the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and feeding behavior. Moreover, central administration of CRF ameliorates the obese phenotype. In light of these observations, the gene for CRF is a plausible candidate for the defective gene in the Zucker fatty rat. We report here the use of molecular genetic linkage analysis to test the hypothesis that fa is a mutant allele of the CRF gene. A restriction fragment length polymorphism for CRF between Zucker (13M) and Brown Norway (BN) DNA allowed us to examine segregation of 13M and BN CRF alleles relative to fa in 58 obese (fa/fa) F2 progeny of a 13MBN fa/+F1 intercross. If fa = CRF, all animals homozygous for the fatty mutation should be homozygous for the 13M CRF allele. However, only 10/58 fa/fa animals were homozygous for the 13M CRF allele, indicating that fa and CRF are not allelic. Thus, although CRF may be important in the physiology of Zucker rat obesity, fa is not a CRF mutation. Using a mouse C57BL/6J Spretus F1 x C57BL DBA/2J F1 intercross, we were able to demonstrate that the mouse CRF gene is linked to the carbonic anhydrase II (Car-2) gene on mouse chromosome 3, in a region of synteny-homology with rat chromosome 2. Thus the rat CRF gene is probably located on chromosome 2.

A molecular genetic method for genotyping fatty (fa/fa) rats

After three decades of physiological research, the precise nature of the genetic lesion in Zucker fatty (fa/fa) rats remains unknown. Several methods have been used to identify preobese rats to detect the earliest phenotypic effects of the fa mutation. Most of these methods have used phenotypic characteristics that are not reliable until the second week of life, when increased adiposity is already evident. We have used a restriction fragment length polymorphism (RFLP) for a human genomic DNA probe (VC85) that is tightly linked to the fa locus on rat chromosome 5 to genotype the F2 progeny of a Zucker (13M) x Brown Norway (BN) fa/+ F1 intercross. Sixty-four rats, comprising five litters, were killed at 5-6 wk of age. DNA was isolated either from tail at age 4-7 days (36 rats) or from organs at the time of death (28 rats). Adiposity was scored using inguinal fat pad weight as a percentage of body weight. RFLP analysis was > 99% accurate in identifying obese (fa/fa) rats. This molecular genetic method can be used to genotype fatty rats from an appropriate genetic cross at any age, even prenatally. Moreover, this method can distinguish heterozygous from homozygous littermates, enabling an analysis of gene dosage effects.

The reaction of some dicarbonyl sugars with aminoguanidine

The reactions of aminoguanidine (guanylhydrazine) with 3-deoxy-D-erythro-hexos-2-ulose (1a), 3-deoxy-D-glycero-pentose-2-ulose (1b), D-erythro-hexos-2-ulose (1c), and D-glycero-pentose-2-ulose (1d) were examined at 37 degrees at a solution pH of 7.0 (phosphate buffer). For 1a and 1b, two major products were observed and shown respectively to be the 5- and 6-substituted 3-amino-1,2,4-triazine derivatives. The ratios of the products were independent of the amount of aminoguanidine present or the order of mixing the reagents prior to the experiments. For 1c and 1d, only the 5-substituted triazine derivatives were formed. No evidence for hydrazone or bishydrazone formation was observed.

Effects of systemic growth hormone (GH) administration on regional adipose tissue in children with non-GH-deficient short stature

Chronic administration of exogenous GH to GH-deficient children is associated with a selective depletion of the abdominal sc fat depot and a resultant relative increase in gluteal, relative to abdominal, adipocyte lipid content. In GH-deficient children, the degree of this change in relative lipid content per adipocyte appears to be correlated with decreases in sensitivity of abdominal subcutaneous fat to the antilipolytic action of insulin. We studied abdominal and gluteal sc adipose tissue from 10 children with short stature (height less than 5% ile, growth velocity less than 5 cm/yr, bone age delayed at least 2 yr), who were not GH deficient based upon provocative testing (non-GH-deficient short stature) 1) before beginning and 2) after 3 months of therapy with exogenous GH (Humatrope, 0.1 mg/kg sc 3 times/week). In abdominal and gluteal adipocytes, we measured lipid content, rates of reesterification of fatty acids released by ongoing lipolysis and rates of in vitro lipolysis and lipogenesis in response to insulin, adenosine, and various adrenoreceptor agonists. These biochemical measures were correlated with measures of statural growth and adipose tissue distribution in each subject. We found that GH therapy was associated with a significant reduction in abdominal adipocyte size (0.48 microgram +/- 0.08 lipid per cell prior to therapy vs. 0.43 microgram +/- 0.08 lipid per cell after therapy, P less than 0.05) and a significant increase in responsiveness of gluteal sc adipose tissue to the lipogenic actions of insulin. The significant correlations of changes in abdominal adipocyte volume with changes in regional adipose tissue insulin sensitivity that were noted in GH-deficient children were not noted in this subject population, perhaps due to effects of endogenous GH on pretreatment insulin responsiveness of adipose tissue. These data reaffirm that GH has site-specific effects on regional adipose tissue depots.

Selection for conditionability in Drosophila melanogaster

Successful bidirectional selective breeding of Drosophila melanogaster for excitatory conditionability is reported, using the reliable measures of individual differences (first described by Holliday & Hirsch, 1984, 1986a, 1986b) to test 1,324 animals. Bidirectional selective breeding for good and poor conditioning has produced, respectively, one population in which the percentage of animals showing good conditioning has increased over 25 generations from 19% to 77% and another in which it has decreased over 23 generations to 0%-4%. No increase in a measure of sensitization induced by an unconditioned stimulus (the central excitatory state) accompanied the increase in the percentage of good conditioners in the population selected for good conditioning, whose level of conditioned responding exceeds that of the sensitization measure.

Energy intake required to maintain body weight is not affected by wide variation in diet composition

Diets rich in fat may promote obesity by leading to a greater deposition of adipose-tissue triglycerides than do isoenergetic diets with less fat. This possibility was examined by a retrospective analysis of the energy needs of 16 human subjects (13 adults, 3 children) fed liquid diets of precisely known composition with widely varied fat content, for 15-56 d (33 +/- 2 d, mean +/- SE). Subjects lived in a metabolic ward and received fluid formulas with different fat and carbohydrate content, physical activity was kept constant, and precise data were available on energy intake and daily body weight. Isoenergetic formulas contained various percentages of carbohydrate as cerelose (low, 15%; intermediate, 40% or 45%; high, 75%, 80%, or 85%), a constant 15% of energy as protein (as milk protein), and the balance of energy as fat (as corn oil). Even with extreme changes in the fat-carbohydrate ratio (fat energy varied from 0% to 70% of total intake), there was no detectable evidence of significant variation in energy need as a function of percentage fat intake.

A center-of-mass computation describes the precision of random dot displacement discrimination

We test three specific models of how the human visual system computes a just-noticeable-difference (jnd) in spatial separation. The strategies employed by these three models range from strictly local to global, and use a new discrimination task that measures the precision with which displacements of random dots in random dot arrays can be detected. Fits of these models to the data convincingly exclude the two most local models where the displacement discrimination is based on either point-to-point or bin-to-bin measurements of local dot positions. However, the data are consistent with a model where displacement discrimination is based on a globally computed center-of-mass parameter. This finding enlarges current views of what determines the precision of spatial discrimination to include the effects of stimulus complexity (number of dots) and multiplicity (number of dots displaced).