bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of system compliance on collapse of triaxial sand samples
Authors: Gajo A
Published: April 2004

The observed occurrences of dynamic instability of triaxial samples of loose sand presented in the literature are considered in relation to the existence of energetically possible departure paths involving homogeneous deformations. The existence of energetically possible departure paths is investigated under small strain conditions through the sign of the second-order variation in the total energy of the whole mechanical system, comprising both the sample and the loading devices, thus taking the influence of system compliance into account. The SevernTrent sand model is used to evaluate the second-order deformation work of the sample and no ad hoc assumption is found necessary to improve the model's response. The evolution of elastic anisotropy is measured and taken into account, revealing negligible effects. The theoretical findings prove consistent with experiments and highlight the important part played by the compliance of the loading apparatus, which can deeply affect the onset of dynamic instability, as further confirmed by new experimental evidence. Key words: sand, elastic anisotropy, constitutive modelling, mechanical stability, system compliance.
Evaluation of horizontal homogeneity of geomaterials with the distance analysis of surface waves
Authors: Phillips Christopher , Cascante Giovanni , Hutchinson D Jean
Published: April 2004

A new approach to surface wave analysis, termed the distance analysis of surface waves (DASW) method, is presented. The method examines the phase of surface waves with respect to distance to determine horizontal homogeneity of a medium. The method is verified theoretically and numerically with finite-difference simulations. Several cases are examined, including a half-space, a half-space comprised of two distinct mediums, a medium with a linear variation of elastic properties, and a half-space containing a rectangular void. The use of complementary information in the time domain, frequency domain, and frequencywavenumber domain is presented as a useful technique for the understanding of wave propagation in complex geological settings. The DASW method accurately identifies horizontal changes in medium properties. Therefore, the method evaluates the condition of horizontal homogeneity, which is necessary for the use of the spectral analysis of surface waves (SASW) method, and complements the information commonly obtained using the SASW method.Key words: surface waves, horizontal homogeneity, phase velocity, wave propagation simulations, finite-difference modeling, frequency domain analysis, fk plots.
Clinical and Angiographic Features in Nasal Branch Retinal Vein Occlusion
Authors: Battaglia Parodi Maurizio , Iacono Pierluigi , Di Crecchio Lorenzo , Sanguinetti Giorgia , Ravalico Giuseppe
Published: April 2004

Purpose: To analyse the epidemiological and clinical characteristics of nasal branch retinal vein occlusion (NBRVO). Methods: Patients affected by branch retinal vein occlusion observed in the out-patient departments of the Eye Clinic of Trieste between January 1995 and January 1999 were enrolled. Results: Out of 144 patients with branch retinal vein occlusion, 128 (88.9%) were affected by temporal branch retinal vein occlusion (TBRVO), and 16 patients were affected by NBRVO (11.1%). The two groups did not differ as far as systemic hypertension, diabetes mellitus, glaucoma and ischaemic heart disease were regarded. NBRVO cases were characterized by better visual acuity and greater figures of capillary non-perfusion, retinal neovascularization and vitreous haemorrhage. Conclusions: NBRVO, even though infrequent, shares the same epidemiological characteristics as TBRVO. The higher prevalence of ischaemic cases in the NBRVO group could depend on a bias during the enrolment of patients, because especially symptomatic patients may have been examined in our out-patient departments. The relatively high percentage of epiretinal membrane formation after laser photocoagulation suggests particular caution, especially in cases presenting with vitreous haemorrhage.
A Contribution to the Surgery of the Trachomatous Entropion and Trichiasis
Authors: Bujger Zdenko , Cerovski Branimir , Kovacevic Suzana , Nasic Mirjana , Pokupec Rajko , Tojagic Miljenka
Published: April 2004

Although the WHO document WHO/PBL/93.29 recommends the bilamellar tarsal rotation operation for trachomatous entropion, we will describe another operation that has proved to be very reliable. It is a combined method, consisting of the modified tarsal wedge resection and the eversion splinting–grey line incision. A possible additional correction of the grey line incision on the first postoperative day improves the results. A total of 708 eyes with moderate trachomatous entropion and major trichiasis underwent this surgery, but only 508 of these were followed up during a 6-month period. The rate of failed operations, which consisted of incomplete closure of the lids or more than two inverted lashes remaining, was 6.9%.
Correlation between the Perceptual Rating of Speech in Dutch Patients with Velopharyngeal Insufficiency and Composite Measures Derived from Mean Nasalance Scores
Authors: Keuning Kornelis H.D.M. , Wieneke George H. , Dejonckere Philippe H.
Published: April 2004

Objective: To evaluate the potential clinical use of composite measures derived from mean nasalance scores. Procedure: Speech samples with a normal distribution of phonemes (normal text, NT) and speech samples free of nasal consonants (denasal text, DT) of 43 patients with perceived hypernasality were used. The overall grade of severity, hyperrhinophonia, audible nasal emission, misarticulations associated with velopharyngeal insufficiency and intelligibility were perceptually rated on separate visual analog scales. Mean nasalance scores were computed by the Nasometer for the same speech samples on which the perceptual ratings were performed. From the mean nasalance scores computed for the NT and DT passages the difference and the quotient were calculated. The advantage could be that the derived measures provide some normalization with regard to the performance of the individual speaker. Spearman correlation coefficients were computed between these composite measures and the perceptually rated parameters. The results were compared with the correlation coefficients between the mean nasalance scores and the ratings. Setting: The Institute of Phoniatrics, Utrecht University Hospital, The Netherlands. Results: The correlations between the composite measures and the perceptual ratings were generally lower than the correlations between mean nasalance scores and the ratings. Conclusion: Normalization of the nasalance scores did not enhance the correlation with the perceptual ratings in this study.
Shower PUVA: A Novel Variant of Photochemotherapy
Authors: Sánchez Ruderisch H. , Aryee-Boi J. , Schwarz C. , Radenhausen M. , Tebbe B.
Published: April 2004

Shower PUVA is a new variant of photochemotherapy suitable for therapy of various skin disorders. Psoralen, e.g. trioxsalen-containing water recirculates in a closed shower system and wets the skin continuously. After showering, whole-body UVA irradiation (320–400 nm) is performed. In order to prove the equal distribution of photosensitivity in vivo minimal phototoxic dose (MPD) was determined in different skin areas of healthy individuals. Additionally, we investigated the accumulation of trioxsalen in psoriasis lesions under the conditions described by quantifying psoralen in scales collected after showering. In a randomized study 20 healthy volunteers (skin type I–III) took showers for 5 and 10 min in trioxsalen (0.27 mg/l)-containing water at 37°C. Immediately afterwards, MPD was tested on the inside of the upper arms and on the buttocks by using a polychromator light source (315–400 nm). The applied UVA doses were 0.06–0.75 J/cm2 with steps of 0.125 J/cm2. MPD was evaluated after 72 h. Equal distribution of photosensitivity was defined as equal MPD on the insides of the upper arm and the buttocks (±0.125 J/cm2). Skin scales of 21 patients with psoriasis were collected by scratching after showering with trioxsalen-containing water (0.27 mg/l) for 5 min. For quantification of trioxsalen in the scales HPLC was performed. An equal distribution of photosensitivity was achieved in 70% (14/20) cases after 10-min showering in trioxsalen-containing water. Showering for 5 min only revealed a 30% (6/20) rate of equal distributed photosensitivity. After 10-min shower time MPD was 0.325 J/cm2 (median; range: 0.06–0.625 J/cm2). The average amount of trioxsalen found in the scales was 2.03 ng/mg scales (range: 0.38–7.2 ng/mg). For shower PUVA using trioxsalen, 10 min shower time is recommended to achieve sufficient distribution of photosensitivity on the skin. Clinical efficacy of shower PUVA can be explained by skin accumulation of trioxsalen which enters from the aqueous phase into the upper skin layers in detectable amounts. This is the first report demonstrating the efficacy of shower PUVA which in short shower time allows an uptake of psoralen by the skin.
Mismatch Negativity Brain Response as an Index of Speech Perception Recovery in Cochlear-Implant Recipients
Authors: Lonka Eila , Kujala Teija , Lehtokoski Anne , Johansson Reijo , Rimmanen Satu , Alho Kimmo , Näätänen Risto
Published: April 2004

Speech-discrimination performance and the mismatch negativity (MMN) response elicited by vowel changes were used to track vowel-perception improvement of 5 adult cochlear-implant (CI) recipients. The MMN was recorded several times during the first 3 years after CI activation. Artefacts, presumably caused by CI, contaminated most of the brain responses until 1 year after CI activation. We found that speech discrimination improved over time and the MMN, observed in all patients after 2.5 years of CI use, was first seen for the larger vowel difference and later for the smaller one.
Immunohistochemical Detection of Estrogen Receptor Alpha in Pituitary Adenomas and Its Correlation with Cellular Replication
Authors: Pereira-Lima Julia F.S. , Marroni Caroline P. , Pizarro Cristina B. , Barbosa-Coutinho Ligia M. , Ferreira Nelson P. , Oliveira Miriam C.
Published: April 2004

With the aim of evaluating the relationship between pituitary tumorigenesis and the presence of estrogen receptor-α (ERα) by immunohistochemistry (IH) and their relevance to patients’ clinical presentation, hormonal phenotypes of adenomas, preoperative neuroimaging findings, and the index of cellular replication MIB-1, a study was conducted with material from 91 women and 67 men with pituitary adenomas. The patients had acromegaly (29.7%), Cushing’s disease (14.6%), hyperprolactinemic syndrome (20.9%), and clinically nonfunctioning tumors (34.8%). Of the patients, 14.6% had microadenomas, 52.5% had macroadenomas with or without suprasellar growth, 28.5% had invasive macroadenomas and in 4.4% the adenoma was not visualized. IH showed that 43 were positive for growth hormone (GH), 16 for corticotropin (ACTH), 18 for prolactin (PRL), 18 for PRL+GH, 6 for luteinizing hormone (LH) and follicle-stimulating hormone (FSH), 15 had a plurihormonal reaction, and 42 had nonfunctioning adenomas. The presence of ERα was positive in 9/158 adenomas with a median value for the percentage of labeled cells of 42.89%, and in 6/16 controls (autopsy samples) with a median value for the percentage of labeled cells of 0.024%. ERα was significantly more prevalent in controls than in patients with adenomas (37.5 versus5.7%; p = 0.001); however, the mean ERα concentration in adenomas was significantly greater than in controls (42.89 versus 0.024%; p < 0.001). No significant difference in the concentration of ERα was found across the clinical presentations, hormonal phenotypes or findings of preoperative CT. Among the ERα-positive adenomas, ERα values were significantly greater in invasive macroadenomas (80%) than in microadenomas (3.33%). MIB-1 values did not differ significantly between ERα-positive and -negative adenomas, nor did the correlation between ERα values and the MIB-1 index attain significance in the total sample, even when only ERα-positive adenomas and positive MIB-1 indexes were considered. It was concluded that, when present in pituitary tumors, ERα exhibits a high concentration, and is more common in nonfunctioning and invasive adenomas, but absent in ACTH-secreting ones.
Obesity and Plasma Concentrations of Alpha-Tocopherol and Beta-Carotene in Epileptic Girls Treated with Valproate
Authors: Verrotti Alberto , Greco Rita , Latini Giuseppe , De Simone Michele , Chiarelli Francesco
Published: April 2004

To investigate whether epileptic patients who become obese after valproic acid (VPA) therapy can have a high risk of atherosclerosis related to the oxidation of low-density lipoprotein, we prospectively studied the plasma concentrations of lipid-soluble antioxidant vitamins in a group of 20 epileptic girls and 20 controls. After 1 year of VPA treatment, epileptic patients who gained weight had decreased plasma concentrations of α-tocopherol and α- and β-carotene, the main lipid-soluble antioxidants. Moreover, 5 patients who gained weight were reevaluated 6 months after withdrawal from VPA therapy and showed normal body mass indices and normalized plasma levels of antioxidants. In conclusion, the data suggest that epileptic patients who gain weight after VPA therapy have reduced plasma concentrations of antioxidant vitamins and that these reductions are reversible after VPA withdrawal.
Determination of Nontoxic Concentrations of Piperacillin/Tazobactam for Intravitreal Application
Authors: Özkiriş Abdullah , Evereklioglu Cem , Kontaş Olgun , Öztürk Öner Ayşe , Erkiliç Kuddusi
Published: April 2004

Background: To investigate the highest nontoxic intravitreal dose of piperacillin/tazobactam in rabbits. Material and Methods: Forty New Zealand white albino rabbits were used in this study. The rabbits were divided into four equal groups (10 rabbits in each) and the right eyes were treated with 0.1 ml intravitreal injections of 1,000 µg piperacillin/tazobactam in group 1, 500 µg in group 2, 250 µg in group 3, and 100 µg in group 4. The left eyes served as controls and were injected with 0.1 ml of saline solution. Ganzfeld electroretinogram (ERG) was performed on all eyes before and after 4 weeks of intravitreal injections. Then, the rabbits were killed and the eyes were enucleated for histopathological evaluation of the retina. Retinal sections were evaluated by morphometric analyses on cell counts of ganglion cell layer and thickness of the various retinal layers. Results: Baseline ERGs were similar among the groups (p > 0.05). After 4 weeks of injection, there were a reduction of the b-wave amplitude and extension of the b-wave implicit time in photopic and scotopic ERGs in group 1 and group 2 when compared with controls (for each, p < 0.001). Intravitreal injection of 100 and 250 µg piperacillin/tazobactam did not cause any deterioration of the b-wave of ERGs throughout the follow-up period of 4 weeks (for each, p > 0.05). After morphometric analysis of retinal sections in all groups, there were no statistically significant differences in the mean number of surviving ganglion cells, thickness of the whole retina and the inner plexiform layer compared with controls (p > 0.05). Conclusion: 250 µg/0.1 ml piperacillin/tazobactam is the highest nontoxic dose to the normal retinas of adult albino rabbits as intravitreal injection. Piperacillin/tazobactam may be a new, potentially important drug in the treatment of endophthalmitis as it has a broad antimicrobial spectrum.
Corneal Concentrations following Systemic Administration of Amphotericin B and Its Lipid Preparations in a Rabbit Model
Authors: Goldblum David , Rohrer Kaspar , Frueh Beatrice E. , Theurillat Regula , Thormann Wolfgang , Zimmerli Stefan
Published: April 2004

Background: Amphotericin B (AmB) and various lipid formulations of AmB are available for the treatment of fungal infections of the eye. Currently, the recommended route of administration for the treatment of fungal keratitis is by topical application. Nevertheless, because of the risk of a difficult to treat exogenous fungal endophthalmitis, a combined topical and systemic treatment is frequently given when treating deep fungal keratitis. To date, little is known about the pure corneal availability of these drugs following systemic treatment. In this study, the corneal concentration following 7 daily doses of parenteral AmB lipid complex (ABLC) or liposomal AmB (L-AmB) was compared to that of AmB deoxycholate (D-AmB) in a rabbit model. Methods: Following induction of uveitis in one rabbit eye by intravitreal injection of endotoxin, daily doses of D-AmB (1 mg/kg), ABLC (5 mg/kg) or L-AmB (5 mg/kg) were given intravenously on 7 consecutive days. Five or more rabbits per treatment were used. AmB concentrations were determined by high-performance liquid chromatography (HPLC) in corneas collected at autopsy 24 h after the 7th and final dose. Data were analyzed using the Mann-Whitney U test. Results: After 7 days of treatment, mean corneal concentrations of AmB in the inflamed eyes were significantly higher (2.38 ± 1.47 µg/g; p < 0.01) following treatment with L-AmB compared with ABLC (<0.1 µg/g) and D-AmB (0.46 ± 0.2 µg/g). No AmB could be detected in the corneas of the non-inflamed eyes. Conclusion: In our rabbit model, AmB penetration into the cornea was significantly higher after systemic administration of L-AmB compared with conventional D-AmB or ABLC.
Pulmonary Stretch Receptor Activity during Partial Liquid Ventilation in Cats with Healthy Lungs
Authors: Rieger-Fackeldey Esther , Sindelar Richard , Jonzon Anders , Schulze Andreas , Sedin Gunnar
Published: April 2004

Aim: To study whether pulmonary stretch receptor (PSR) activity in mechanically ventilated young cats with healthy lungs during partial liquid ventilation (PLV) is different from that during gas ventilation (GV). Methods: In 10 young cats (4.4 ± 0.4 months, 2.3 ± 0.3 kg; mean ± SD), PSR instantaneous impulse frequency (PSR fimp) was recorded from single fibres in the vagal nerve during GV and PLV with perfluorocarbon (30 ml/kg) at increasing positive inspiratory pressures (PIP; 1.2, 1.8, 2.2 and 2.7 kPa), and at a positive end-expiratory pressure of 0.5 kPa. Results: All PSRs studied during GV maintained their phasic character with increased impulse frequency during inspiration during PLV. Peak PSRfimp was lower at PIP 1.2 kPa (p < 0.05) and at PIP 2.7 kPa (p = 0.10) during PLV than during GV, giving a lower number of PSR impulses at these two settings during PLV (p < 0.05). Conclusion: The phasic character of PSR activity is similar during GV and PLV. PSR activity is not higher during PLV than during GV in cats with healthy lungs, indicating no extensive stretching of the lung during PLV.
Flutamide Suppresses Adrenal Steroidogenesis but Has No Effect on Insulin Resistance and Secretion and Lipid Levels in Overweight Women with Polycystic Ovary Syndrome
Authors: Vrbíková J. , Hill M. , Dvořáková K. , Stanická S. , Vondra K. , Stárka L.
Published: April 2004

The authors evaluate the effects of 2 months of treatment with 250 mg flutamide daily on adrenal steroidogenesis (ACTH test) and metabolic parameters (lipids, insulin resistance) in 12 PCOS women aged 33.8 ± 7.5 years and with a BMI of 33.6 ± 4.2 kg/m2. Significant decreases in basal DHEA-S (p < 0.0001), DHEA (p < 0.01) and androstenedione (p < 0.05), in the ACTH-stimulated levels of DHEA-S (p < 0.0001), testosterone (p < 0.05) and in ACTH-stimulated 17β-hydroxysteroid dehydrogenase activity (p < 0.01) were observed. No significant change in basal blood glucose, insulin, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides or in insulin resistance, as estimated by the insulin tolerance test, was found. Flutamide is effective in reducing adrenal androgen production in overweight women, but has no effect on lipid spectrum or on insulin resistance.
Treatment of Endometrial Hyperplasia with a Danazol-Releasing Intrauterine Device: A Prospective Study
Authors: Tamaoka Yukoku , Orikasa Hideki , Sumi Yukari , Sakakura Keiichi , Kamei Kiyoshi , Nagatani Midori , Ezawa Sachiko
Published: April 2004

The purpose of the present study was to assess the effect of a danazol-releasing intrauterine device (D-IUD) in the treatment of endometrial hyperplasia. Twenty patients with endometrial hyperplasia including 14 with simple endometrial hyperplasia and 2 with complex endometrial hyperplasia (group A), and 4 with atypical endometrial hyperplasia (group B) were enrolled in the prospective study between August 1999 and December 2003. During and just after the treatment, improvement was seen in all patients. Simple or complex endometrial hyperplasia (group A) demonstrated regression to a normal secretory endometrium (38% of group A), pseudodecidual stromal change (31%) and glandular atrophy (25%), and miscellaneous change (inflammation, necrosis, etc.) (38%). Atypical hyperplasia (group B) demonstrated regression to a normal secretory endometrium (25% of group B), pseudodecidual stromal change (75%), glandular atrophy (50%) and miscellaneous change (granulation) (25%). In group A, 2 women conceived after completion of the treatment. The recurrence rate in patients with endometrial hyperplasia (groups A and B) in the follow- up was 20% and acceptable as compared with other studies. The pretreatment menstrual interval patterns of the patients were maintained peri- and post-treatment. These data indicate that D-IUD therapy might be a novel and effective method for the treatment of endometrial hyperplasia.
Spectrum of Acute Coronary Syndromes: History and Clinical Presentation in Relation to Sex and Age
Authors: Perers Elisabeth , Caidahl Kenneth , Herlitz Johan , Sjölin Margaretha , Karlson Björn W. , Karlsson Thomas , Hartford Marianne
Published: April 2004

Objectives: To study sex-based differences in the clinical presentation in relation to age and type of acute coronary syndrome (ACS) in patients under 80 years of age. Methods: The study includes 1,744 consecutive patients with the full spectrum of ACS (ST elevation myocardial infarction (MI), non-ST elevation MI, and unstable angina of high- and low-risk types) admitted to the coronary care unit in a university hospital. Results: The women were older than the men and were as likely to present with ST elevation MI. They had lower rates of prior MI and prior coronary artery bypass surgery than men but similar rates of percutaneous coronary interventions. Further, women were less likely to have a short delay before admission to hospital and they were attended to less rapidly in the emergency department. The prevalence of risk factors, prior cardiovascular disease and ongoing treatment with cardiovascular drugs were strongly associated with less severe type of ACS with no significant sex interaction. Presentation with non-ST elevation MI was significantly associated with older age while the opposite was true for unstable low-risk angina. ECG signs of acute ischemia were not associated with age. Significant interactions between age and sex were observed for the prevalence of treatment with diuretics as well as hypotension at presentation, both more prevalent among women than men below 65 years of age. Conclusions: Women are struck by ACS at a higher age than men, are less likely to present early for hospital care, and at younger age women are more likely to present with hypotension. There is a striking difference in risk factors and previous history depending on type of ACS in both sexes.
Rheumatic Fever: From Sore Throat to Autoimmune Heart Lesions
Authors: Guilherme Luiza , Kalil Jorge
Published: April 2004

Molecular mimicry between streptococci and heart components has been proposed as the triggering factor leading to autoimmunity in rheumatic heart disease (RHD). In this review, we present data from cellular autoimmune responses, focusing on the interactions between HLA class II molecules, streptococcal peptides and heart tissue proteins and T-cell receptor (TCR) usage. HLA-DR7DR53 associated with DQ molecules seem to be related with the development of valvular lesions in severe RHD patients. DR7DR53 molecules were also involved in the recognition of an immunodominant M5 peptide in these patients. T cells infiltrating RHD hearts displayed several oligoclonal expansions. Intralesional T-cell clones presenting identical TCR-BVBJ AVAJ and -CDR3 sequences were able to recognize several antigens with little or low homology, showing an intramolecular degenerate pattern of antigen recognition. Peripheral blood mononuclear cells of rheumatic fever (RF) patients produced proinflammatory cytokines, and intralesional mononuclear cells from severe RHD patients produced predominantly Th1-type cytokines. These results illustrate the complex mechanisms leading to heart tissue damage in RF/RHD patients.
Changes in Peak Respiratory Flow and Quality of Life during Nebivolol Therapy
Authors: Zuber Michel , Erne Paul
Published: April 2004

Background: Nebivolol is a highly cardioselective β1-adrenoceptor antagonist with proven efficacy and safety in the treatment of hypertension. This study aimed to specifically address the effects of nebivolol on lung function and quality of life in patients suffering from mild to moderate hypertension. Objectives: The study assessed the effects of nebivolol, taken alone or in combination with other antihypertensives for 12 weeks, on peak respiratory flow, libido, general health, and physical condition. The effects on blood pressure and heart rate were also determined. Methods: A total of 367 patients suffering from mild to moderate hypertension were enrolled in 93 private general practices. Changes in peak respiratory flow, blood pressure, and heart rate were recorded after 4 and 12 weeks. A questionnaire on items of sexual function, physical energy, and general health elicited the patients’ perception of their quality of life. Safety was assessed on the basis of adverse events. Results: After 4 and 12 weeks, peak respiratory flow was significantly increased in patients receiving nebivolol alone (p < 0.01). Diastolic blood pressure (p < 0.01), systolic blood pressure (p < 0.01), and heart rate (p < 0.01) were significantly lowered during treatment. Moreover, nebivolol treatment (alone or in combination with other antihypertensives) statistically significantly improved libido, breathlessness, and energy level (p < 0.05). Conclusion: The favourable effect on peak respiratory flow, coupled with an improved quality of life, renders this cardioselective β1-blocker useful in the treatment of essential hypertension in the general practice setting.
Successful Pregnancies in 2 Infertile Patients with Endometrial Adenocarcinoma
Authors: Nakao Yoshifumi , Nomiyama Mari , Kojima Kayoko , Matsumoto Yumi , Yamasaki Fumio , Iwasaka Tsuyoshi
Published: April 2004

Two infertile patients with well-differentiated endometrial adenocarcinoma succeeded in having their own babies with assisted reproductive technology following treatment with a high dose of medroxyprogesterone acetate and repeated endometrial curettages. Their follow-up pathological examinations revealed no evidence of recurrent disease. Consequently, conservative treatment may be indicated in patients with well-differentiated endometrial adenocarcinoma at an early stage who desire to preserve their fertility.
Iron, Atherosclerosis, and Neurodegeneration: A Key Role for Cholesterol in Promoting Iron‐Dependent Oxidative Damage?
Authors: ONG WEI‐YI , HALLIWELL BARRY
Published: April 2004

Abstract: This article reviews the roles and interactions of iron, atherosclerosis, and neurodegeneration. It highlights the importance of cholesterol in promoting iron‐dependent oxidative damage. An intriguing possibility is that hypercholesterolemia can increase brain iron load and both the aggregation of beta‐amyloid and the ability of iron on plaques to catalyze oxidative damage. This could explain why hypercholesterolemia is a risk factor for Alzheimer's disease. Further work is necessary to study the mechanism of increased iron transport across the blood brain barrier in atherosclerosis.
Oxidative Basis of Manganese Neurotoxicity
Authors: HAMAI DIEM , BONDY STEPHEN C.
Published: April 2004

Abstract: Exposure to excessive levels of manganese, an essential trace element, can evoke severe psychiatric and extrapyramidal motor dysfunction closely resembling Parkinson's disease. The clinical manifestations of manganese toxicity arise from focal injury to the basal ganglia. This region, characterized by intense consumption of oxygen and significant dopamine content, can incur mitochondrial dysfunction, depletion of levels of peroxidase and catalase, and catecholamine biochemical imbalances following manganese exposure. The site specificity of the pathology and the nature of the cellular damage caused by manganese have been attributed to its capacity to produce cytotoxic levels of free radicals. However, support for such a pro‐oxidant role for manganese has been largely limited to inferences drawn from histopathological observations. More recently, research efforts into the molecular details of manganese toxicity have provided evidence of an etiological relationship between oxidative stress and manganese‐related neurodegeneration. This review focuses on studies that evaluate the redox chemistry of manganese during the neurodegenerative process and its molecular consequences.
Aceruloplasminemia: An Inherited Neurodegenerative Disease with Impairment of Iron Homeostasis
Authors: XU XUEYING , PIN SOKHON , GATHINJI MURAYA , FUCHS RALPH , HARRIS Z LEAH
Published: April 2004

Abstract: In 1987, Miyajima et al. first characterized an autosomal recessive, adult‐onset neurodegenerative disorder resembling Parkinson's disease associated with near‐absent circulating serum ceruloplasmin levels. Coined “familial apoceruloplasmin deficiency”, they described a patient with a presenting triad of diabetes mellitus, retinal degeneration, and neurodegeneration with blepharospasm. Neuropathological evaluation revealed abundant iron deposition in selected neurons of the basal ganglia and substantia nigra with associated neuronal dropout and spongioform degeneration without evidence of reactive gliosis. Subsequently, mutations in the ceruloplasmin gene have been determined to result in the excessive iron accumulation seen in the pancreas, retina, and brain. Elevated serum ferritin suggests a systemic iron overload syndrome, yet affected patients had low transferrin saturation and a mild anemia. This new disease, “aceruloplasminemia”, reveals a role for ceruloplasmin as an essential ferroxidase critical for iron homeostasis. This multicopper oxidase promotes efficient iron efflux such that individuals lacking ceruloplasmin develop a presumed oxidative injury secondary to iron accumulation and significant neuronal damage. Aceruloplasminemic mice provide a valuable model to further study the mechanisms by which ceruloplasmin regulates iron trafficking and the role of iron in oxidative injury. Despite the dependence of ceruloplasmin on copper for its function, aceruloplasminemia represents an iron storage disease and not a defect in copper metabolism. However, recent evidence in Saccharomyces cerevisiae indicates that Fet3, the yeast homologue of ceruloplasmin, functions as an essential cuprous oxidase. Further investigation into the mechanisms by which ceruloplasmin regulates iron and copper homeostasis will provide valuable insight into the pathogenesis of metallo‐mediated diseases and elucidate mechanisms for transition metal (copper, iron) neuropathology.
Temperature induces gonadal maturation and affects electrophysiological sexual maturity indicators inBrachyhypopomus pinnicaudatusfrom a temperate climate
Authors: Quintana Laura , Silva Ana , Berois Nibia , Macadar Omar
Published: April 2004

In contrast to most of the previous studies in gymnotiform reproduction,which have been conducted in the tropical region, this study examines a gymnotid from the temperate region in both the natural habitat and the laboratory. The gonadal histology of Brachyhypopomus pinnicaudatus is described for the first time. The male had a paired, lobular testis of the unrestricted spermatogonial type, and females a paired saccular cystovary. Analysis of gonads and their annual cycle enabled us to confirm the breeding season and to conclude that this species is a multiple spawner. Water temperature and photoperiod showed the expected annual cycles for the region. High temperature and a 14 h:10 h L:D photoperiod in the natural habitat coincided with (1) mature gonadal stages, (2) electrophysiological sexual dimorphism: males present a lengthened negative phase in their electric organ discharge (EOD) and (3) decreased temperature sensitivity of the EOD: the waveform does not change when temperature increases above 20°C. Acclimation to sustained high temperature (30 days, 28°C, 12 h:12 h L:D,low conductivity) induced gonad maturation along with EOD dimorphism. Our data show that high environmental temperature is enough to trigger sexual maturity in Brachyhypopomus pinnicaudatus from a temperate climate.
Escape behavior and escape circuit activation in juvenile crayfish during prey–predator interactions
Authors: Herberholz Jens , Sen Marjorie M. , Edwards Donald H.
Published: April 2004

The neural systems that control escape behavior have been studied intensively in several animals, including mollusks, fish and crayfish. Surprisingly little is known, however, about the activation and the utilization of escape circuits during prey–predator interactions. To complement the physiological and anatomical studies with a necessary behavioral equivalent, we investigated encounters between juvenile crayfish and large dragonfly nymphs in freely behaving animals using a combination of high-speed video-recordings and measurements of electric field potentials. During attacks, dragonfly nymphs rapidly extended their labium, equipped with short, sharp palps, to capture small crayfish. Crayfish responded to the tactile stimulus by activating neural escape circuits to generate tail-flips directed away from the predator. Tail-flips were the sole defense mechanism in response to an attack and every single strike was answered by tail-flip escape behavior. Crayfish used all three known types of escape tail-flips during the interactions with the dragonfly nymphs. Tail-flips generated by activity in the giant neurons were predominantly observed to trigger the initial escape responses to an attack, but non-giant mediated tail-flips were often generated to attempt escape after capture. Attacks to the front of the crayfish triggered tail-flips mediated either by the medial giant neuron or by non-giant circuitry, whereas attacks to the rear always elicited tail-flips mediated by the lateral giant neuron. Overall, tail flipping was found to be a successful behavior in preventing predation, and only a small percentage of crayfish were killed and consumed.
Thermodynamics of organic compound transfer from the gas phase to environmentally important sorbents
Authors: Borisover Mikhail , Graber Ellen R.
Published: April 2004

Linear Free Energy Relationships (LFERs) based on distribution coefficients between the aqueous phase and the sorbent are often unsuccessful for interpreting sorption mechanisms in environmentally important sorbents because they comprise contributions not only from solute interactions with the sorbent, but also from hydration of the solute in bulk water. To avoid this problem, we suggest an approach for studying interactions between organic sorbates and environmentally important sorbents using a thermodynamic cycle to eliminate interactions between the solute and bulk water. In this approach, aqueous distribution coefficients are converted to gas phase distribution coefficients that are related to the free energy of transfer from the gas phase to the hydrated sorbent, and include contributions from all interactions occurring during the transfer. Gas phase distribution coefficients are compared for different compounds with similar molar refraction values to give insights into the nature of specific and nonspecific interactions of organic molecules with environmental sorbents. This methodology is illustrated for sorption of organic molecules in soil organic carbon and at mineral surfaces, and examples of insights obtainable from this methodology are given.
Volatile organic compound emissions from terrestrial ecosystems: A primary biological control over atmospheric chemistry
Authors: Monson Russell K.
Published: April 2004

Plants produce a variety of non‐methane volatile organic compounds (NMVOCs) that react with photochemical components of the atmosphere and influence the production of atmospheric oxidants. In this review, the case is made that biogenic NMVOC emissions exert one of the primary controls over regional and global atmospheric chemistry. The diversity of biogenic, reactive organic compounds capable of fueling atmospheric chemistry is immense, including terpenes, alcohols, aldehydes, ketones, and organic acids. Considerable effort has been devoted to the design of models capable of predicting NMVOC emission rates, and thus driving atmospheric chemistry models. Over the past decade, however, what once seemed like promising conceptual connections of NMVOC emissions to fundamental biochemical processes such as photosynthesis, have not been realized; this has delayed the development of mechanistic NMVOC emissions models. Future progress in this area will require new subcellular experimental systems, and the biochemical insight that will accompany these investigations. The past use of existing coupled biogenic emission—photochemistry models at the global scale, even with their mechanistic limitations, has revealed the potential for NMVOC emissions from terrestrial ecosystems to cause reductions in tropospheric hydroxyl radical concentration and increases in the concentration and lifetime of radiatively important trace gases such as methane and ozone.
Structure of self‐assembled monolayers of semifluorinated alkanethiols on gold and silver substrates
Authors: Frey S. , Heister K. , Zharnikov M. , Grunze M. , Tamada K. , Colorado R. , Graupe M. , Shmakova O. E. , Lee T. R.
Published: April 2004

Self‐assembled monolayers (SAMs) formed from semifluorinated alkanethiols (SFATs) CF3(CF2)9(CH2)nSH (F10HnSH: n = 2, 11, and 17) on poly‐crystalline Au and Ag were characterized by X‐ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and near edge X‐ray absorption fine structure spectroscopy. SFATs were found to form highly ordered and densely packed SAMs on both substrates. The molecules are strongly bonded to the substrates via their sulfur head groups, in the same manner as conventional alkanethiol (AT) SAMs. The hydrocarbon (except for n = 2) and fluorocarbon parts of the adsorbed SFATs retain the expected planar zigzag and helical conformations of the respective bulk materials. The orientation of the fluorocarbon chains does not depend on the substrate. These entities are almost perpendicular to the substrate in F10H2S/Au and F10H2S/Ag and become slightly more tilted in SFAT SAMs with longer hydrocarbon moieties. However, the alkyl parts of the SFAT films exhibit tilt and twist angles that are similar to those of normal alkanethiol films on Ag and Au substrates despite the reduced packing density in the SFAT films as compared to normal AT SAMs. We suggest that the substrate‐related differences in tilt and twist angles for both systems are associated with the different character of the head‐group‐substrate bonding on Au and Ag.
Detection of time‐resolved photoionization currents from pesticide‐contaminated vegetation
Authors: Kadosh Michal , Gridin Vladimir V. , Schechter Israel
Published: April 2004

Multiphoton‐ionization fast‐conductance (MPI‐FC) was directly applied for detection of photoionization currents originated from pesticide traces irradiated by UV‐laser. The principal methodology required for direct screening of pesticide traces deposited on various vegetational specimens was addressed. This approach was exemplified with 1,2,3,4,5,6‐hexachlorocyclohexane and 3‐amino‐1,2,4‐triazole, which are frequently found in agriculture‐related industries. The range of pesticide concentrations covered was from 0.001 ng/mL to 1 mg/mL, and all measurements were carried out under ambient conditions. Our target vegetation substrates were sampled from the outdoors: grass, plant, and/or tree leaves. Neither material purification nor laborious extraction routines were utilized; thus employing MPI‐FC for in situ/on‐line monitoring of pesticide‐contaminated vegetation is feasible.
Synthesis, characterization, and magnetic properties of α‐MnS nanocrystals
Authors: Kan Shihai , Felner Israel , Banin Uri
Published: April 2004

MnS nanocrystals have been prepared by a colloidal synthesis route through the reaction of MnCl2 and S[Si(CH3)3]2 in trioctylphosphineoxide. The nanocrystals were characterized using X‐ray diffraction and transmission electron microscopy. The magnetic properties were studied with SQUID magnetometry. X‐ray diffraction shows that the nanocrystals are of the thermodynamically stable α‐MnS (alabandite) structure. Size control was achieved by changing the concentration of the precursors. Nanocrystal sizes were measured by transmission electron microscopy, and three samples of average diameters 20, 40, and 80 nm were obtained, with narrow size distribution (σ˜9%). The zero field cooled magnetization curves for the 80‐, 40‐, and 20‐nm samples showed a cusp at 116 K, 97 K, and 50 K respectively, all smaller than the antiferromagnetic transition temperature, TN = 130 K, of bulk α‐MnS. Below TN the magnetization exhibits a paramagnetic behavior unlike typical antiferromagnetic materials. These results indicate that there is a mixture of paramagnetic and antiferromagnetic phases in the nanocrystals. The size dependence shows a general trend of decrease of TN with reduced particle size, indicating size dependent magnetic ordering.
Quantum‐mechanical reaction rate constants from centroid molecular dynamics simulations: Barrier crossing in an asymmetrical double‐well
Authors: Navrotskaya Irina , Shi Qiang , Geva Eitan
Published: April 2004

Quantum‐mechanical reaction rate constants were calculated from centroid molecular dynamics (CMD) simulations, for the case of barrier crossing in an asymmetrical double‐well potential bilinearly coupled to a harmonic bath. The calculation is based on a recently proposed formulation of the reaction rate constant in terms of the position—flux correlation function, which can be approximated via CMD in a well‐defined manner. The predictions of CMD and various simplified versions of it are compared to exact results, which were obtained via the quasi‐adiabatic propagator path integral (QUAPI) method, and/or path integral quantum transition state theory (PI‐QTST). The predictions based on CMD are found to be in good agreement with both.
Semiconductor nanorods: Cu, Zn, and Cd chalcogenides
Authors: Govindaraj A. , Leonard Deepak F. , Gunari N. A. , Rao C.N.R.
Published: April 2004

Semiconductor nanorods have been synthesized by the use of surfactants. The nanorods of CuS, ZnS, CdS, CuSe, ZnSe, and CdSe have diameters in the 5–150 nm range and exhibit high aspect ratios, with lengths of up to several microns. By using a high surfactant concentration, nanotube‐like structures of CdS and CdSe with high aspect ratios are obtained. All the chalcogenide nanostructures possess hexagonal structures, independent of the structures of the stable phases of the materials.
Self‐assembled monolayers of metallosalophenes on gold
Authors: Beulen Marcel W. J. , Van Veggel Frank C. J. M. , Reinhoudt David N.
Published: April 2004

Salophene complexes of transition metals exhibit a reversible electrochemistry. We have synthesized salophene complexes with sulfur‐containing sub‐stituents aimed at the formation of self‐assembled monolayers on a gold surface. Such monolayers have interesting cation complexating properties. The monolayers were fully characterized by wettability studies, grazing‐angle Fourier transform infrared spectroscopy (FT‐IRS), X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS), and electrochemical capacitance measurements. These measurements indicate liquid‐like monolayers. Cation complexation could be monitored indirectly by electrochemical impedance spectroscopy measurements, showing responses for Na+ and K+. This complexation behavior of the metallosalophene monolayers could not be studied directly by electrochemistry of the metallosalophene either due to electrochemical instability of the monolayer or a smeared redox response.
Polystyrene‐Supported 2‐Arylindenyl Zirconocene Catalysts for Propylene Polymerization
Authors: Diehl Stephen C. , Waymouth Robert M.
Published: April 2004

Mono‐ and bis 2‐arylindenyl zirconocene/methylalumoxane (MAO) catalysts are prepared on a crosslinked polystyrene resin using gel‐phase organic reactions. The 2‐arylindene ligands are bonded to the polystyrene backbone through a disiloxane linkage, and the zirconocene is prepared directly on the support in high yield. These supported 2‐arylindenylzirconocenes in the presence of MAO show high activity and yield polypropylenes with microstructures similar to those produced by the analogous solution‐phase catalysts.
A mild route to α‐alkoxyacetylenes mediated by lewis acids and synthetic routes to 10‐, 11‐, and 12‐membered ring enediyne carbocycles
Authors: Comanita Bogdan M. , Heuft Matthew A. , Rietveld Tanya , Fallis Alex G.
Published: April 2004

The condensation of silyl substituted acetylenes with dimethoxy acetals via a modified “Mukaiyama‐type reaction” to afford α‐alkoxyacetylenes is described. These propargylic ethers 17–21 were synthesized from the reaction of aluminum or zinc acetylides with acetals mediated by Lewis acids. In appropriate cases, when a second acetal was present in the initial acyclic product (24), a subsequent intramolecular acetal‐ene (Prins) cyclization ensued to afford the silylalkylidenealkoxycyclopentane (25). Enediyne species were unreactive under these conditions, even in an intramolecular case. Routes to 11‐ and 12‐membered carbocyclic enediyne compounds (43, 44) were developed via an intramolecular pinacol coupling of the dialdehydes 39 with sammarium diodide/HMPA. The requisite double bond was introduced using the thiocarbonate expulsion method with trimethyl phosphite. A route to the highly substituted 10‐membered ring enediyne 50 is also described based on the use of an isopropylidene acetal tether control group to facilitate an intramolecular chromium (II)/nickel (II)‐mediated coupling of the iodoacetylene aldehyde 49.
Thermal resonant tunneling rates by a generalized flux averaging method
Authors: Caspary Maytal , Berman Lihu , Peskin Uri
Published: April 2004

The calculation of the thermal rate constant as a time integral over flux‐flux correlation functions is a challenging task when the potential energy along the reaction coordinate cannot be associated with a distinctive single barrier. In the case of resonant tunneling through a double barrier potential, the calculations may become formidable due to the population of long‐lived resonance states and the corresponding long time‐decay of the flux‐flux correlation functions. The flux averaging method was introduced recently in order to circumvent this problem in cases where the long time dynamics is due to a single resonance state with the longest lifetime in the system. In this work we generalize the method for calculations of thermal resonant‐tunneling rates in systems of many resonances, where the long time‐decay is accompanied by an internal dynamics within the quasi‐bound system. This extra complication is handled by additional averaging of flux‐flux correlation funcation over the time period of the internal dynamics. The result is an exact expression for the rate constant in terms of a linear combination of time integrals over flux‐flux correlation functions, which reaches its asymptotic time limit in a short (direct scattering) time, regardless of the long time‐decay of the flux‐flux correlation functions. This is derived for an analytic model system, and demonstrated in a numerical simulation of resonant tunneling through a double barrier potential.