bluuebunny/crossref_metadata_2025 huggingface dataset:
Chest Radiograph Scores in Preterm Infants: Interobserver Agreement and Relation to Respiratory Function
Authors: Snepvangers Yvonne , Burger Huibert , de Winter Peter , Arets Bert , Beek Eric , van der Ent Cornelis
Published: April 2004

To evaluate scoring systems for chest radiographs, we determined interobserver agreement and relation to the lung function during the 1st week of life in ventilated preterm infants. Three independent observers examined chest radiographs by applying radiological scores according to Lischka, Yuksel, Greenough, Toce, and Giedion on postnatal days 2 and 7. Kappa statistics was used to assess the interobserver agreement. By means of regression analysis, mean scores and individual radiological scores of the three observers were studied in relation to ventilation and oxygenation indices and respiratory system resistance and compliance. Forty-eight radiographs were evaluated on day 2 and 17 radiographs on day 7. All scoring systems showed kappa values equal to or <0.5. Regression analysis revealed no significant associations between radiological scores and ventilator requirements or respiratory mechanics. We conclude that in ventilated preterm infants radiological scoring systems showed a poor interobserver agreement and that they were not related to the actual respiratory function.
Recognition of Facial Expressions of Emotion by Patients with Dementia of the Alzheimer Type
Authors: Burnham Helen , Hogervorst Eva
Published: April 2004

Bilateral amygdala damage has been linked with an inability to recognise facial expressions of emotion, particularly the expression of fear. Patients with Alzheimer’s disease (AD) suffer from atrophy of the amygdala at an early stage of the disease. It was therefore predicted that AD patients would have more difficulty in two tasks of processing facial expressions of emotion. Thirteen patients diagnosed with probable AD referred to the Oxford Project to Investigate Memory and Ageing (OPTIMA) and 13 age-matched controls enrolled in the programme participated in the study. Participants were shown two tasks, one involved recognising and labelling a target expression, the other matching a target expression with one of four others. The results showed that compared with the controls, the patients were not impaired in recognising any facial expressions of emotion in the labelling task, but were impaired in matching three facial expressions of emotion in the second task. It was speculated that the impairment in the matching task could have been a result of visuospatial dysfunction rather than one of processing emotions.
Who Participates in Psychosocial Interventions for Caregivers of Patients with Dementia?
Authors: Wettstein Albert , Schmid Regula , König Markus
Published: April 2004

Objective: The purpose of the present study is to evaluate if the participants in psychosocial interventions for dementia caregivers are representative of the whole population of dementia patients or if some socioeconomic groups are over- or underrepresented. Design: The demographic and socioeconomic characteristics of the 128 participants of a randomized controlled study on the effects of caregiver education were compared with those of all the elderly residents of the City of Zurich (n = 64,856, elderly group), of all demented patients entering a City of Zurich nursing home in a 6-month period (n = 218, NH entry group) and of all demented inhabitants evaluated during a 20-month follow-up at a community memory clinic (n = 187, memory group). Methods: Data on income and wealth were derived from official tax records. The characteristics of the different groups were compared by χ2 or t tests. Results: As expected in a study on caregiver education, the demented patients were younger, more often male and married than all other study groups (p < 0.01). The participants in the psychosocial intervention had significantly (p < 0.01) higher education than all other groups; this effect is caused in part by the higher proportion of males. The NH entry group was less well educated than the elderly group (p < 0.05). The intervention group had a higher income and was wealthier than the three other groups (p < 0.01), but there was no significant difference with respect to the wealth of the memory group. The 25% poorest of the elderly group made up only about 10% of the participants in the intervention group. However, the 25% richest of the elderly group made up 42% of the intervention group. The method of recruitment for the psychosocial intervention (by media, referral of physicians and by a memory clinic) was not significantly related to any of the demographic or socioeconomic parameters. Conclusion: The lower socioeconomic strata are clearly underrepresented in psychosocial interventions.
ImmunoDip®: An Improved Screening Method for Microalbuminuria
Authors: Davidson Mayer B. , Bazargan Mohsen , Bakris George , Peters Harmel Anne , Campese Vito , Basta Emad
Published: April 2004

Background: It is important to test for microalbuminuria in patients with diabetes, hypertension and possible insulin resistance syndrome. Current screening methods are suboptimal. This study evaluates a new office screening test for microalbuminuria that utilizes a monoclonal antibody against human serum albumin (ImmunoDip®). Methods: 182 urine samples were collected from patients attending diabetes, nephrology or hypertension clinics. The ImmunoDip® screening test was carried out in the 182 samples after which albumin and creatinine concentrations were measured quantitatively in a reference laboratory. Results: Screening the 182 patient samples with ImmunoDip® and designating an albumin:creatinine ratio of ≧30 µg/mg as positive yielded a sensitivity of 96%, a specificity of 80%, a positive predictive value (PPV) of 66% and a negative predictive value (NPV) of 98%. The reduced specificity and PPV were not due to an intrinsic inaccuracy with ImmunoDip® screening of these samples, but rather was shown to be due to the discordance between the accepted upper limits of normal for the albumin:creatinine ratio (30 µg/mg) and the albumin concentration (20 mg/l), the latter corresponding to a ratio of 20 µg/mg. In 35 samples with albumin concentrations of 20–50 mg/l, ImmunoDip® screening yielded only one false negative (FN) result. Conclusions: ImmunoDip® is an excellent screening tool for microalbuminuria.
Anatomy and Neurocontrol of the Pelvic Floor
Authors: Vodušek David B.
Published: April 2004

Neural control of pelvic organs is affected by a unique coordination of somatic and autonomic motor nervous systems. Sensory information and feedback is supplied by both visceral and somatic sensory fibers. The anatomical features of the pelvic floor and perineal muscles, and their innervation are described. Altogether more detailed information is known in humans on the peripheral innervation as compared to the central nervous system centers and connections of pelvic organ neurocontrol. Controversies in regional neuroanatomy are explained. Reports on individual variability and asymmetry – the former particularly with methods revealing structures, and the latter with functional methods – are interesting but need further validation.
Functional Asymmetry of Pelvic Floor Innervation and Its Role in the Pathogenesis of Fecal Incontinence
Authors: Enck Paul , Hinninghofen Heidemarie , Wietek Beate , Becker Horst D.
Published: April 2004

While the regular and symmetric innervation of the pelvic floor has been regarded as ‘established’ for many years, recent data indicate that asymmetry of innervation of the sphincters may exists and may contribute to the occurrence and severity of incontinence symptoms in case of pelvic floor trauma. Methods: A systematic review of published papers on asymmetry of sphincter innervation was performed including studies in healthy volunteers and patients with incontinence. 234 consecutive patients with fecal incontinence were investigated by means of side-separated mass surface EMG from the left and right side anal canal, these data were correlated to clinical and anamnestic findings. Results: The literature survey indicates that asymmetry of sphincter innervation exists in a subgroup of healthy male and female volunteers, and may be a risk factor to become incontinent in case of trauma. Patients with incontinence in whom asymmetry of sphincter innervation could be shown more frequently reported a history of pelvic floor trauma during childbirth. Childbirth per se but not the number of deliveries predicted sphincter asymmetry. Asymmetrically innervated sphincters show a compromised sphincter function in routine anorectal manometry. Conclusion: Assessment of sphincter innervation asymmetry may be of value in clinical routine testing of patients with incontinence. However, a new technology is needed to replace mass surface EMG by multi-electrode arrays on a sphincter probe. This is one of the goals of the EU-sponsored research project OASIS.
Multichannel Surface EMG for the Non-Invasive Assessment of the Anal Sphincter Muscle
Authors: Merletti R. , Bottin A. , Cescon C. , Farina D. , Gazzoni M. , Martina S. , Mesin L. , Pozzo M. , Rainoldi A. , Enck P.
Published: April 2004

Background/Aims: This work focuses on recording, processing and interpretation of multichannel surface EMG detected from the external anal sphincter muscle. The aim is to describe the information that can be extracted from signals recorded with such a technique. Methods: The recording of many signals from different locations on a muscle allows the extraction of additional information on muscle physiology and anatomy with respect to that obtained by classic bipolar recordings. Multichannel EMG methods have been recently developed for the assessment of the external anal sphincter. An anal probe was used in this study to record signals at different depths within the anal canal during contractions at different effort levels. The plug is 150 mm in length and 14 mm in diameter, holding a circumferential array of 16 equally spaced silver bar electrodes, located at a distance of 20 mm from the probe tip and aligned with the probe axis. Results: Information about localization of the innervation zone, fiber length, EMG amplitude, muscle fiber conduction velocity and single motor unit analysis can be obtained from the signals recorded with the circumferential array by means of innovative signal processing techniques. Conclusions: The type of information extracted from multichannel surface EMG signals cannot be obtained with other currently available techniques. The technological innovation described in this work is promising for a further insight into the investigation of pelvic floor pathologies and rehabilitation treatments.
Innervation Zones of the External Anal Sphincter in Healthy Male and Female Subjects
Authors: Enck P. , Franz H. , Azpiroz F. , Fernandez-Fraga X. , Hinninghofen H. , Kaske-Bretag K. , Bottin A. , Martina S. , Merletti R.
Published: April 2004

Objectives: The objective of this work was to investigate the distribution of the innervation zones of the motor units that make up the external anal sphincter (EAS) in healthy males and females. Methods: A cylindrical probe carrying a circumferential array of 16 electrodes was used to detect the generation, propagation and extinction of individual motor unit action potentials (MUAPs) at 1, 2, and 3 cm depth from the orifice of the anal canal during maximal voluntary contractions of the EAS. Fifteen healthy males and 37 healthy nulliparous females were investigated. Results: IZs could be detected in all males and in 34 out of 37 females. In the males, the IZs are scattered in the right and left hemisphincter at each of the three levels and their distribution is not affected by depth. In the females, the distribution is also concentrated in the right and left hemisphincter at depth 1 cm but is more uniform at depth 2 cm and more concentrated in the dorsal and ventral regions at depth 3 cm. ANOVA shows a statistically significant dependence of the IZ distribution on depth only in females and not in males. Conclusions: It is concluded that (a) IZs of the EAS can indeed be detected with a circumferential array placed at different depths along the anal canal; (b) large individual variability is observed, and (c) IZs show similar distribution at the three depth levels in males and different distributions in females.
The Heart Rate Response to Exercise Is Blunted in Patients with Sleep-Related Breathing Disorder
Authors: Grote Ludger , Hedner Jan , Peter Jörg Hermann
Published: April 2004

Background: This study addressed the hypothesis that cardiovascular reactivity during graded bicycle exercise is influenced by a coexisting sleep-related breathing disorder (SRBD). Methods: Blood pressure and heart rate were assessed at rest and during graded exercise (110 W and maximal load) in 1,149 patients of a Sleep Disorders Center. The degree of SRBD, and potential confounders, including blood gases and pulmonary function, were determined. Results: Maximal exercise capacity tended to decrease with SRBD activity (p = 0.07). The heart rate reactivity was blunted and reduced by –0.07 and –0.09 beats/min for every SRBD unit at 110 W (p < 0.001) and at maximal load (p < 0.001), respectively. Systolic and diastolic blood pressure reactivity at maximal load were positively associated with SRBD severity. These associations were independent of possible confounders. Conclusion: SRBD is associated with reduced physical working capacity and a modified hemodynamic response to exercise.
Uteroplacental Hemodynamics during Early Human Pregnancy: A Longitudinal Study
Authors: Mäkikallio K. , Tekay A. , Jouppila P.
Published: April 2004

Background: To determine normal physiologic changes in the uteroplacental hemodynamics during early placental development in the first trimester of pregnancy. Methods: Sixteen normal singleton pregnancies were included in this longitudinal study. Transvaginal Doppler ultrasonographic examinations of uterine, arcuate, radial and spiral arteries were performed at the 5th, 7th, 8th and 10th completed gestational weeks. Peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV) and the pulsatility index (PI) were measured. Results: Uterine artery PSV, TAMXV and PI remained unchanged from the 5th to the 8th week of gestation. From the 8th to the 10th week, PSV (p = 0.02) and TAMXV (p = 0.005) increased and PI decreased (p = 0.006). Changes in the arcuate arteries were similar to those in uterine arteries. No significant changes in PSV, TAMXV or PI of the radial artery were noticed. Spiral artery PSV (p = 0.02) and TAMXV (p = 0.02) increased from the 5th to the 7th week. Thereafter they remained unchanged. Spiral artery PI decreased from the 5th to the 10th week, (p = 0.004). Throughout the study period, the PSV, TAMXV and PI values were significantly higher in the uterine artery than in the arcuate artery, and in the arcuate artery compared with the radial artery. At the 5th gestational week, no differences in PSV and TAMXV were found between radial and spiral arteries. From the 7th gestational week onwards, PSV and TAMXV were significantly lower in the radial artery than in the spiral artery. However, the PI values in the radial artery were significantly higher compared with those in the spiral artery during the whole study period. Conclusions: Spiral artery impedance decreases and blood flow velocities increase as early as between the 5th and the 7th weeks of gestation. During that period, the uterine and arcuate artery hemodynamics remain unchanged. In the uterine and arcuate arteries, decreases in impedance and increases in absolute velocities are detected after the 8th week of gestation. This delay between the changes in the spiral and uterine arteries may represent the magnitude of the increase of placental volume and spiral arterial involvement which is needed to affect uterine hemodynamics.
Are Depressive Persons Capable of Describing Changes in Their Reactions without Being Able to Explain Them?
Authors: Leibetseder Max , Kamolz Thomas
Published: April 2004

Background: Many studies on the autobiographical memory and the explanation of reasons for success and failure proved that persons suffering from major depression tend to overgeneralize. This study examines the hypothesis that changes of reactions caused by a depressive disorder can be described by the affected persons but not explained. Sample and Methods: Persons suffering from major depression and persons with posttraumatic stress disorder or disturbance of accommodation with depressive mood (= reactive form of a depressive disorder) were presented with a list of modalities (behaviour, emotional and physical reactions) characteristic for depression. They were asked to identify modalities applicable to them and to describe and explain them. Their responses were analysed using a content analysis and assigned to the categories description and explanation. Results: Persons with a major depression tended to use explanations or evaluations rather than descriptions for their depression-related modalities. Those persons suffering from a reactive form of depressive disorder tended to prefer evaluations. Conclusion: These results support the assumption that states of depression cause general descriptions of depression-relevant behaviour. The specific characteristics that have been perceived confirm the general concepts, which however make the patient prone to the respective selective perceptions. Persons suffering from a reactive form of depressive mood cannot be assumed to have this tendency of self-affirmation. Their depressive state may be maintained by perseverating general pessimistic schemes. Limitations: It must however be conceded that it was not possible to control the physical comorbidity methodically and to take its effects into consideration, even though only persons without serious illnesses were included in the samples. This study did not verify whether other clinical groups, like patients suffering from anxiety, show the same patterns of explaining and describing their problems. It should furthermore be reviewed how other actions, e.g. positive ones, are represented by depressive persons.
Internalizing and Externalizing Conditions in Adolescent Anorexia
Authors: Muratori Filippo , Viglione Valentina , Maestro Sandra , Picchi Lara
Published: April 2004

Objective: To identify the prevalence of internalizing and externalizing conditions in referred anorexic adolescents. Method: Child Behavior CheckList (CBCL) and Youth Self Report (YSR) were used to assess psychopathology: (a) in the global sample (43 adolescents); (b) in different subtypes of anorexia; (c) considering the timing of admission after the onset of the disease. Results: A high percentage of patients were found in the internalizing clinical range both at CBCL and YSR. Higher mean values were found in full syndromes both at CBCL and YSR, and in the binge-eating subtype only at the YSR. Subjects arrived within the first year of illness showed a less severe psychopathology. Conclusions: Adolescents with anorexia have high rates of internalizing psychopathology. The less severe psychopathology in adolescents arrived within the first year of illness shed light on discontinuity between anorexia and internalizing condition. On the basis of the psychopathological severity, three types of adolescent anorexia are proposed which could be of interest for therapeutic decisions.
Iron Metabolism and the IRE/IRP Regulatory System: An Update
Authors: PANTOPOULOS KOSTAS
Published: April 2004

Abstract: Cellular iron homeostasis is accomplished by the coordinated regulated expression of the transferrin receptor and ferritin, which mediate iron uptake and storage, respectively. The mechanism is posttranscriptional and involves two cytoplasmic iron regulatory proteins, IRP1 and IRP2. Under conditions of iron starvation, IRPs stabilize the transferrin receptor and inhibit the translation of ferritin mRNAs by binding to “iron responsive elements” (IREs) within their untranslated regions. The IRE/IRP system also controls the expression of additional IRE‐containing mRNAs, encoding proteins of iron and energy metabolism. The activities of IRP1 and IRP2 are regulated by distinct posttranslational mechanisms in response to cellular iron levels. Thus, in iron‐replete cells, IRP1 assembles a cubane iron‐sulfur cluster, which prevents IRE binding, while IRP2 undergoes proteasomal degradation. IRP1 and IRP2 also respond, albeit differentially, to iron‐independent signals, such as hydrogen peroxide, hypoxia, or nitric oxide. Basic principles of the IRE/IRP system and recent advances in understanding the regulation and the function of IRP1 and IRP2 are discussed.
Heme Oxygenase‐1: Transducer of Pathological Brain Iron Sequestration under Oxidative Stress
Authors: SCHIPPER HYMAN M.
Published: April 2004

Abstract: Mechanisms responsible for the pathological deposition of redox‐active brain iron in human neurological disorders remain incompletely understood. Heme oxygenase‐1 (HO‐1) is a 32‐kDa stress protein that degrades heme to biliverdin, free iron, and carbon monoxide. In this chapter, we review evidence that (1) HO‐1 is overexpressed in CNS tissues affected by Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and other degenerative and nondegenerative CNS diseases; (2) the pro‐oxidant effects of dopamine, hydrogen peroxide, b‐amyloid, and proinflammatory cytokines stimulate HO‐1 expression in some of these conditions; and (3) upregulation of HO‐1 in astrocytes exacerbates intracellular oxidative stress and promotes sequestration of nontransferrin‐derived iron by the mitochondrial compartment. A model is presented implicating glial HO‐1 induction as a “final common pathway” leading to pathological iron sequestration and mitochondrial insufficiency in a host of human CNS disorders.
Nutritional Iron Deprivation Attenuates Kainate‐Induced Neurotoxicity in Rats: Implications for Involvement of Iron in Neurodegeneration
Authors: SHOHAM S , YOUDIM M B H
Published: April 2004

Abstract: There is evidence suggesting that oxidative stress contributes to kainate neurotoxicity. Since iron promotes oxidative stress, the present study explores how change in nutritional iron content modulates kainate‐induced neurotoxicity. Rats received an iron‐deficient diet (ID) from 22 days of age for 4 weeks. One control group received the same diet supplemented with iron and another control group received standard rodent diet. Cellular damage after subcutaneous kainate (10 mg/kg) was assessed by silver impregnation and gliosis by staining microglia. ID reduced cellular damage in piriform and entorhinal cortex, in thalamus, and in hippocampal layers CA1‐3. ID also attenuated gliosis, except in the hippocampal CA1 layer. Given involvement of zinc in hippocampal neurotransmission and in oxidative stress, we tested for a possible interaction of nutritional iron with nutritional zinc. Rats were made iron‐deficient and then assigned to supplementation with iron, zinc, or iron + zinc. Controls were continued on ID diet. After 2 weeks, rats were treated with kainate. Iron supplementation abolished the protective effect of ID in piriform and entorhinal cortex. In hippocampal CA1 and dorsal thalamus, neither iron nor zinc supplementation alone abolished the protective effect of ID against cellular damage. Iron + zinc supplementation abolished ID protection in dorsal thalamus, but not in reuniens nucleus. Kainate‐induced gliosis in CA1 remained unaffected by nutritional treatments. Thus, in piriform and entorhinal cortex, nutritional iron has a major impact on cellular damage and gliosis. In hippocampal CA1, gliosis may associate with synaptic plasticity not modulated by nutritional iron, while cellular damage is sensitive to nutritional iron and zinc.
Manganese Neurotoxicity
Authors: DOBSON ALLISON W. , ERIKSON KEITH M. , ASCHNER MICHAEL
Published: April 2004

Abstract: Manganese is an essential trace element and it is required for many ubiquitous enzymatic reactions. While manganese deficiency rarely occurs in humans, manganese toxicity is known to occur in certain occupational settings through inhalation of manganese‐containing dust. The brain is particularly susceptible to this excess manganese, and accumulation there can cause a neurodegenerative disorder known as manganism. Characteristics of this disease are described as Parkinson‐like symptoms. The similarities between the two disorders can be partially explained by the fact that the basal ganglia accumulate most of the excess manganese compared with other brain regions in manganism, and dysfunction in the basal ganglia is also the etiology of Parkinson's disease. It has been proposed that populations already at heightened risk for neurodegeneration may also be more susceptible to manganese neurotoxicity, which highlights the importance of investigating the human health effects of using the controversial compound, methylcyclopentadienyl manganese tricarbonyl (MMT), in gasoline to increase octane. The mechanisms by which increased manganese levels can cause neuronal dysfunction and death are yet to be elucidated. However, oxidative stress generated through mitochondrial perturbation may be a key event in the demise of the affected central nervous system cells. Our studies with primary astrocyte cultures have revealed that they are a critical component in the battery of defenses against manganese‐induced neurotoxicity. Additionally, evidence for the role of oxidative stress in the progression of manganism is reviewed here.
Divalent Metal Transporter 1 in Lead and Cadmium Transport
Authors: BRESSLER JOSEPH P. , OLIVI LUISA , CHEONG JAE HOON , KIM YONGBAE , BANNONA DESMOND
Published: April 2004

Abstract: The effect of exposure to cadmium (Cd) and lead (Pb) on human health has been recognized for many years and recent information suggests that minimal exposure levels are themselves too high. Common scenarios for Pb exposure include occupational, residential, and/or behavioral (hand‐to‐mouth activity) settings. The main source of Cd exposure for nonsmokers is dietary, through plants or animals that accumulate the metal. Specific cellular importers for Pb and Cd are unlikely as these metals are nonessential and toxic. Accordingly, in the intestine, the operational mechanism is assumed to be inadvertent uptake through pathways intended for essential nutrients such as iron. Results from experimental and epidemiological studies indicated that diets low in iron (Fe) result in increased absorption of Pb and Cd, suggesting common molecular mechanisms of Cd and Pb transport. Indeed, recent mechanistic studies found that the intestinal transporter for nonheme iron, divalent metal transporter 1 (DMT1), mediates the transport of Pb and Cd. DMT1 is regulated, in part, by dietary iron, and chemical species of Cd and Pb that are transported by DMT1 would be made available through digestion and are also found in plasma. Accordingly, the involvement of DMT1 in metal uptake offers a mechanistic explanation for why an iron‐deficient diet is a risk factor for Pb and Cd poisoning. It also suggests that diets rich in iron‐containing food could be protective against heavy metal poisoning.
The role of muscarinic receptors and intracellular Ca2+ in the spectral reflectivity changes of squid iridophores
Authors: Mäthger Lydia M. , Collins Toby F. T. , Lima Pedro A.
Published: April 2004

In this paper we describe changes in spectral reflectivity of the light reflectors (iridophores) of the squid Alloteuthis subulata. The spectral changes that can be seen in living squid, can also be brought about by superfusing whole skin preparations with acetylcholine (ACh) (20 μmol l-1) and muscarine (30 μmol l-1) but not nicotine (up to 50 mmol l-1), suggesting that cholinergic muscarinic receptors are involved. Changing the osmolarity of the external solution had no effect on spectral reflectivity. To study the iridophores at the cellular level,iridophores were isolated enzymatically. Lucifer Yellow filled the iridophores uniformly, showing cellular individuality. Isolated iridophore cells were loaded with Fura-2 AM and cytoplasmic Ca2+ was recorded ratiometrically. Intracellular Ca2+ (resting concentration at 66.16 nmol l-1) increased transiently after addition of ACh (50 μmol l-1), muscarine (25 μmol l-1), but not nicotine (up to 5 mmol l-1). Ca2+ also increased when superfused with potassium chloride (10 mmol l-1) and caffeine (2.5 mmol l-1). Hypo- and hyperosmotic solutions had no effects on the cytoplasmic Ca2+. By presenting direct evidence that iridophores are polarised cellular structures containing Ca2+ stores and that they are activated via cholinergic muscarinic receptors, we demonstrate that Ca2+ is involved in the reflectivity changes of the iridophores of A. subulata. Specimens were prepared for transmission electron microscopy. It was found that the orientations of the plates with respect to the skin surface are in good agreement with the expected orientations based on the prediction that the iridophores act as multilayer reflectors.
The transepithelial voltage of the isolated anterior stomach of mosquito larvae (Aedes aegypti): pharmacological characterization of the serotonin-stimulated cells
Authors: Onken H. , Moffett S. B. , Moffett D. F.
Published: April 2004

The lumen-negative transepithelial voltage (Vte) of the isolated and perfused anterior stomach of mosquito larvae (Aedes aegypti) was studied with a `semi-open' preparation in which one end of the gut was ligated onto a perfusion pipette and the other end remained open to the bath. All experiments were performed with serotonin-stimulated preparations. Vte was abolished after addition of 2.5 mmol l-1 dinitrophenol and depended on the presence of Cl-. Na+ substitution experiments showed that a major part of Vte depended on the presence of this cation in the hemolymph side of the epithelium. Addition of 10 μmol l-1concanamycin (78±6% inhibition) or 2.5 mmol l-1 ouabain(15±2% inhibition) to the bath partially inhibited Vte. DPC (0.5 mmol l-1) or DIDS (0.1 mmol l-1) reduced Vte when applied to the hemolymph side of the epithelium (to 49±8% or 78±3% of the control,respectively). When present on both sides of the epithelium, these inhibitors caused further Vte reductions (to 23±4% or 35±4% of the control, respectively). Hemolymph-side furosemide (0.1 mmol l-1) or BaCl2 (5 mmol l-1) reduced Vte by 13±3% or 23±4% of the control,respectively. When applied to the hemolymph side of the epithelium, amiloride(0.2 mmol l-1) significantly decreased Vte by 35±6% of the control, whereas the drug caused no further effect when it was subsequently also applied to the luminal side of the epithelium. The above results are the basis for an extended model for the cellular mechanisms of NaHCO3 secretion/HCl absorption involved in alkalization of the anterior stomach of mosquito larvae.
The regulation and importance of glucose uptake in the isolated Atlantic cod heart: rate-limiting steps and effects of hypoxia
Authors: Clow Kathy A. , Rodnick Kenneth J. , MacCormack Tyson J. , Driedzic William R.
Published: April 2004

This study investigated the regulation of glucose uptake in Atlantic cod(Gadus morhua) hearts. Isolated hearts were perfused with or without glucose in the medium, under either normoxic or severely hypoxic conditions. Working at basal levels, hearts did not require extracellular glucose to maintain power under aerobic conditions. However, cardiac performance was significantly reduced without exogenous glucose under oxygen-limiting conditions. The addition of the glucose transporter inhibitor cytochalasin B caused hypoxic hearts to fail early, and hearts perfused with a glucose analogue, 2-deoxyglucose (2-DG), increased glucose uptake 3-fold under hypoxia. The uptake of 2-DG was only partially inhibited when cytochalasin B was added to the medium. Isolated ventricle strips were also incubated in the presence of 2-DG and the extracellular marker mannitol. Glucose uptake(glucose transport plus intracellular phosphorylation) was assessed by measuring the initial rate of 2-deoxyglucose-6-phosphate (2-DG-6-P)accumulation. At 1 mmol l-1 2-DG, the rate of 2-DG uptake remained linear for 60 min, and 2-DG-6-P, but not free 2-DG, accumulation was increased. The fact that intracellular 2-DG did not increase indicates that glucose transport is the rate-limiting step for glucose utilization in non-stimulated cardiac tissue. Replacement of Na+ by choline in the incubation medium did not affect 2-DG uptake, providing evidence that Na+-coupled glucose transport is absent in cod cardiac tissue. Similar to cytochalasin B, glucose uptake was also inhibited by phloridzin,suggesting that facilitated, carrier-mediated glucose transport occurs in cod hearts. Under the conditions employed in these experiments, it is clear that(1) activation of glucose transport is required to support hypoxic performance, (2) the rate-limiting step for glucose utilization is glucose transport rather than glucose phosphorylation, (3) 2-DG uptake accurately reflects glucose transport activity and (4) glucose uptake in cod hearts does not involve an Na+-dependent mechanism.
Surface pauses in relation to dive duration in imperial cormorants; how much time for a breather?
Authors: Wilson Rory P. , Quintana Flavio
Published: April 2004

Air-breathing animals diving to forage can optimize time underwater by diving with just enough oxygen for the projected performance underwater. By so doing they surface with minimal body oxygen levels, which leads to maximal rates of oxygen uptake. We examined whether imperial cormorants Phalacrocorax atriceps adhere to this by examining dive:pause ratios in birds diving for extended, continuous periods to constant depths, assuming that the oxygen used underwater was exactly replenished by the periods at the surface. Examination of the cumulative time spent in surface pauses relative to the cumulative time spent in diving showed that surface pauses increase according to a power curve function of time spent in the dive or water depth. In a simplistic model we considered the rate at which birds expended energy underwater to be constant and that the rate of oxygen replenishment during the surface pause was directly proportional to the oxygen deficit. We then worked out values for the rate constant for the surface pause before using this constant to examine bird body oxygen levels immediately pre- and post dive. The model predicted that imperial cormorants do not submerge with just enough oxygen to cover their projected dive performance but rather dive with substantial reserves, although these reserves decrease with increasing dive depth/duration. We speculate that these oxygen reserves may be used to enhance bird survival when rare events, such as the appearance of predators or discovery of large prey requiring extended handling time, occur. The form of the oxygen saturation curve over time at the surface means that the time costs for maintaining constant oxygen reserves become particularly onerous for long,deep dives, so the observed decrease in reserves with increasing dive duration is expected in animals benefiting by optimizing for time.
The hydrodynamics of eel swimming
Authors: Tytell Eric D. , Lauder George V.
Published: April 2004

Eels undulate a larger portion of their bodies while swimming than many other fishes, but the hydrodynamic consequences of this swimming mode are poorly understood. In this study, we examine in detail the hydrodynamics of American eels (Anguilla rostrata) swimming steadily at 1.4 Ls-1 and compare them with previous results from other fishes. We performed high-resolution particle image velocimetry (PIV) to quantify the wake structure, measure the swimming efficiency, and force and power output. The wake consists of jets of fluid that point almost directly laterally,separated by an unstable shear layer that rolls up into two or more vortices over time. Previously, the wake of swimming eels was hypothesized to consist of unlinked vortex rings, resulting from a phase offset between vorticity distributed along the body and vorticity shed at the tail. Our high-resolution flow data suggest that the body anterior to the tail tip produces relatively low vorticity, and instead the wake structure results from the instability of the shear layers separating the lateral jets, reflecting pulses of high vorticity shed at the tail tip. We compare the wake structure to large-amplitude elongated body theory and to a previous computational fluid dynamic model and note several discrepancies between the models and the measured values. The wake of steadily swimming eels differs substantially in structure from the wake of previously studied carangiform fishes in that it lacks any significant downstream flow, previously interpreted as signifying thrust. We infer that the lack of downstream flow results from a spatial and temporal balance of momentum removal (drag) and thrust generated along the body, due to the relatively uniform shape of eels. Carangiform swimmers typically have a narrow caudal peduncle, which probably allows them to separate thrust from drag both spatially and temporally. Eels seem to lack this separation, which may explain why they produce a wake with little downstream momentum while carangiform swimmers produce a wake with a clear thrust signature.
Thermolimit respirometry: an objective assessment of critical thermal maxima in two sympatric desert harvester ants,Pogonomyrmex rugosusandP. californicus
Authors: Lighton John R. B. , Turner Robbin J.
Published: April 2004

The critical thermal maxima (CTmax) of two sympatric,diurnal, thermophilic harvester ants from the Mojave Desert, USA(Pogonomyrmex rugosus and P. californicus) were measured by ramping their temperature upwards at a rate of 0.25°C min-1during flow-through respirometry with optical activity detection. Rates of CO2 emission(V̇CO2) increased exponentially to plateau values that were twice as high in P. californicus as P. rugosus on a mass-specific basis. V̇CO2 then fell sharply, during which gross motor activity (measured optically) and spiracular control (measured from V̇CO2 variation)abruptly ceased, yielding two independent measures of CTmax. As determined by loss of muscular coordination, the CTmax of Pogonomyrmex rugosus was 51.57±0.38°C (mean ± s.d., while that of Pogonomyrmex californicus was 51.74±0.25°C. As determined by loss of spiracular control, the CTmax of Pogonomyrmex rugosus was 51.59±0.35°C, while that of Pogonomyrmex californicus was 51.78±0.37°C. In each species a pronounced post-mortal peak of V̇CO2 was observed. The major ecological and behavioral differences of the two species are not reflected in their CTmax values, which do not differ significantly. `Thermolimit respirometry' allows CTmax to be estimated objectively with coefficients of variation (s.d./mean) <1%, lending confidence to comparisons between species or treatment groups.
Control of planula migration by LWamide and RFamide neuropeptides inHydractinia echinata
Authors: Katsukura Yuki , Ando Hiroshi , David Charles N. , Grimmelikhuijzen Cornelis J. P. , Sugiyama Tsutomu
Published: April 2004

Planula larvae of Hydractinia echinata (Cnidaria) settled on a substratum migrate toward light. We observed that planula migration is not a continuous process. Instead, it consists of repeating cycles of active migration (about 8 min on average) and inactive resting periods (about 26 min on average). This pattern of periodic migration is regulated by LWamide and RFamide neuropeptides. LWamide (10-8 mol l-1)stimulates migration primarily by making the active periods longer, whereas RFamide (10-7 mol l-1) inhibits migration by blocking the initiation and also shortening the length of the active periods. Since sensory neurons containing LWamides and RFamides are present in planula larvae, it appears likely that planula migration is regulated by the release of endogenous neuropeptides in response to environmental cues.
Molecular adsorption of n‐alkyl amines, carboxylic acids, and amides onto well‐defined, polar organic surfaces
Authors: Lee Seok‐Won , Laibinis Paul E.
Published: April 2004

This paper details the formation of oriented monolayer films by the solution‐phase adsorption of n‐alkyl‐chained adsorbates (CH3(CH2)n‐1Y) onto the polar surfaces of terminally‐substituted self‐assembled monolayers (SAMs; Au/S(CH2)mX). The polar tail groups (X and Y) of the adsorbate and SAM included amine, carboxylic acid, and amide groups, and the formation of the adsorbed monomolecular films on the SAMs relied on non‐covalent interactions between X and Y. Highly organized monomolecular adlayers could be produced on the SAM surface that were as densely packed as the underlying alkanethiolate SAMs comprising the first layer. The quality of the adsorbed monolayers was related to the identities of the tail groups X and Y.
Isolation of directed evolution mutants of chloroperoxidase resistant to suicide inactivation by primary olefins
Authors: Rai Gyan P. , Zong Qin , Hager Lowell P.
Published: April 2004

Wild‐type chloroperoxidase catalyzes the efficient chiral epoxidation of secondary olefins but is rapidly inactivated in a mechanism‐based suicide reaction when incubated with hydrogen peroxide and primary olefins. Directed evolution mutants of chloroperoxidase have now been isolated that are resistant to suicidal inactivation. Plasmid vectors containing error‐prone copies of the chloroperoxidase gene and a hygromycin B resistance marker gene have been used to transform Caldariomyces fumago spheroplasts and produce mutant libraries. The mutant library clones were screened for their ability to resist mechanism‐based inactivation by allylbenzene. Four generations of PCR‐based random mutagenesis and screening yielded mutants that were completely resistant to the suicide‐inactivation reaction. Rather surprisingly, the fourth generation mutant developed enhanced epoxidation activity in addition to resistance to allylbenzene inactivation. These initial results suggest that the directed evolution technique can be used to produce chloroperoxidase variants that can further exploit the potential of chloroperoxidase for the synthesis of chiral intermediates.
Cyclodextrin‐based carbohydrate clusters by amide bond formation
Authors: Fulton David A. , Pease Anthony R. , Stoddart J. Fraser
Published: April 2004

Per‐6‐amino‐2,3‐dimethyl‐ß‐cyclodextrin was prepared very efficiently as its hydrochloride salt from native ß‐cyclodextrin in four steps and 89% overall yield. O‐Acetyl‐protected ß‐D‐thioglucose and ß‐D‐thiolactose derivatives, containing short spacer arms terminated with carboxylic acid functions, were prepared by the BF3·OEt2‐catalyzed thioglycosylation of ß‐D‐glucose pentaacetate and ß‐lactose octaacetate with 3‐mercaptopropionic acid, respectively. Utilizing amide bond formation as the key step, these thio‐ß‐D‐glucosyl and lactosyl derivatives were coupled to per‐6‐amino‐2,3‐dimethyl‐ß‐cyclodextrin to afford, after deprotection, perfunctionalized ß‐cyclodextrin‐based clusters containing seven thio‐ß‐D‐glucosyl and seven ß‐lactosyl appendages, respectively. Molecular modeling of both these ß‐cyclodextrin‐based clusters revealed the glucose and lactose clusters to be approximately 23 Å and 27 Å in diameter, respectively, and approximately 19 Å in height in both cases. The association constants for the complexation of the anti‐inflammatory drug naproxen by ß‐cyclodextrin, per‐2,3‐dimethyl‐ß‐cyclodextrin, and the lactose cluster of ß‐cyclodextrin in 0.01 M phosphate buffered saline solution (pH 7.4) were found by UV‐vis spectrophotometric titration to be 374 ± 75 M−1, 351 ± 70 M−1, and 165 ± 33 M−1, respectively.
Catalytic Behavior of Bis(Pyrrolide‐Imine) and Bis(Phenoxy‐Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1‐Hexene, or Norbornene
Authors: Yoshida Yasunori , Nakano Takashi , Tanaka Hidetsugu , Fujita Terunori
Published: April 2004

This contribution reports the catalytic behavior of bis(pyrrolide‐imine)Ti complexes 1 and 2, [2‐(RNCH)‐C4H3N]2TiCl2 (1, R = Ph; 2, R = cyclohexyl), and bis(phenoxy‐imine)Ti complex 3, [2‐(Ph‐NCH)‐3‐t Bu‐C6H3O]2TiCl2 for the copolymerization of ethylene with propylene, 1‐hexene, or norbornene. An inspection of the X‐ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide‐imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy‐imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3. Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1‐hexene and incorporated higher amounts of propylene (1; 30.5 mol%, 2; 23.4 mol%) and 1‐hexene (1; 1.9 mol%, 2; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1‐hexene; 0.4 mol%). The incorporation levels of propylene and 1‐hexene displayed by complexes 1 and 2 were lower than those for Cp2TiCl2 (propylene; 41.6 mol%, 1‐hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents (1; 32.0 mol%, 2; 26.5 mol%) than Cp2TiCl2 (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp2TiCl2 and provided a copolymer with extremely narrow molecular weight distribution (Mw/Mn 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation.
Stepwise synthesis of cellodextrins assisted by a mutant cellulase
Authors: Fort Sébastien , Christiansen Lars , Schülein Martin , Cottaz Sylvain , Drigueza Hugues
Published: April 2004

A 4II‐protected α‐cellobiosyl fluoride is an efficient donor for the enzymatic stepwise condensations onto methyl ß‐D‐glycoside acceptors. These reactions, catalyzed by the Cel7B E197A glycosynthase from Humicola insolens, gave cellodextrins from degree of polymerization 3 to 6 in high yields.
Interaction of heparin with Ca2+: A model study with a synthetic heparin‐like hexasaccharide
Authors: Angulo Jesús , De Paz José‐Luis , Nieto Pedro M. , Martín‐Lomas Manuel
Published: April 2004

The binding of Ca2+ to synthetic hexasaccharide 1, containing the structural motifs of the regular region of heparin, has been investigated using NMR spectroscopy and molecular modeling. The NMR data of the calcium salt of 1 indicate the existence of specific Ca2+ binding, and molecular modeling results predict three different types of binding sites with different negative potential and preorganized geometry. The presence of Ca2+ does not seem to affect the overall helical structure of hexasaccharide 1, although it seems to have a marked influence on the flexibility of the oligosaccharide backbone.
Hydrolysis of chlorpyrifos in aqueous and colloidal systems
Authors: Wu Jigang , Laird David A.
Published: April 2004

Hydrolysis of chlorpyrifos [O,O‐diethyl O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate] to TCP (3,5,6‐trichloro‐2‐pyridinol) is an important degradation process influencing the fate of chlorpyrifos in aquatic environments. The effects of water chemistry and suspended colloids (smectites, humic acid, and river sediment) on the hydrolysis of chlorpyrifos were investigated in this study. Chlorpyrifos was incubated in various aqueous and colloidal systems at 23 ± 2 °C for up to 100 days, and aqueous phase concentrations of chlorpyrifos and TCP were determined using solid phase extraction‐high performance liquid chromatography (SPE‐HPLC). Chlorpyrifos degraded in the aqueous solutions with half‐lives ranging from 27 to 158 days, depending on the initial concentration of chlorpyrifos and the chemistry of the aqueous solutions. The rate of degradation was slower in systems containing low concentrations of suspended colloids (1 g L−1 in 0.01 M CaCl2) than in the control (0.01 M CaCl2, with no colloids), and negligible hydrolysis of chlorpyrifos was found for concentrated colloidal systems (20 g L−1 in 0.01 M CaCl2). Total recoveries of chlorpyrifos for the concentrated colloidal systems ranged from 78% to 97%, with a tendency to decrease with incubation time. The study indicates that the formation of chlorpyrifos‐colloid complexes inhibits the hydrolysis of chlorpyrifos in aqueous systems and that chlorpyrifos‐colloid complexes may act as a buffer by slowly releasing chlorpyrifos to the aqueous phase.