bluuebunny/crossref_metadata_2025 huggingface dataset:
Accommodation dynamics as a function of age
Authors: Heron G. , Charman W. N. , Gray L. S.
Published: March 2003

Abstract Experiments are described in which the dynamic accommodation response to a stimulus whose vergence was varying sinusoidally with time between 1.33 and 2.38 D was measured as a function of frequency for 19 subjects, with ages distributed between 18 and 49 years. Response to abrupt stimulus change between the same levels was also measured. The results showed that at any age, for the sinusoidal stimuli, gain fell with frequency and phase lag increased: at fixed frequency, gain fell with age and phase lag increased. Neither reaction nor response times for step stimuli changed with age. Analysis of the sinusoidal data suggests the possible existence of a cut‐off frequency of about 2 Hz, which varies little with age and above which the system cannot respond. The phase data is compatible with the existence of a frequency‐independent time delay, which increases with age from about 0.17 s at 20 years to 0.48 s at 40 years. The results are discussed in terms of current knowledge of the factors contributing to the development of presbyopia.
Objective predictors of subjective visual function for different age‐related cataract morphologies
Authors: Hakim‐Banan N. , Horgan S. E. , Hull C. C.
Published: March 2003

Purpose:  To find objective chart tests that give a measure of visual function in the different age‐related cataract morphological groups and can be applied in a clinical setting.

Methods:  Subjects with age‐related cataract (N = 33) were recruited to the study from both private optometric practice and a hospital eye department. All subjects underwent LOCS III grading of their cataract and had their functional vision assessed using the VF‐14 questionnaire. High (96%) and low (16%) contrast logMAR visual acuity were measured together with Pelli–Robson contrast sensitivity. A stepwise linear regression was then performed on the data to find significant predictors for VF‐14 in the three age‐related cataract morphological groups as well as in a mixed group.

Results:  Low contrast logMAR visual acuity was a significant predictor of VF‐14 in the cortical (p = 0.014) and nuclear (p = 0.024) subgroups. For the mixed morphological group both high and low contrast visual acuity were significant predictors (p < 0.03). There were only three subjects with pure posterior subcapsular cataract and so no meaningful analysis could be performed.

Conclusions:  Low contrast logMAR visual acuity may be a better predictor of visual function in cortical and nuclear cataract compared with high contrast logMAR visual acuity or Pelli–Robson contrast sensitivity.
Oculomotor adaptations produced by virtual reality environments
Authors: Stanger S. , Gray L. S. , Mon‐Williams M.
Published: March 2003

Purpose:  Virtual reality (VR) displays require a static accommodation response to be maintained despite continual variation in vergence. The aim of this experiment was to establish the effect of VR stimulation upon the tonic elements of the accommodation and vergence controllers.

Methods:  Twenty subjects (mean age 22.0 ± 4.5 years) participated with informed consent in the experiment. The subjects were emmetropic and free of all ocular or systemic disease. Tonic accommodation (TA) was measured in darkness using the Shin‐Nippon SRW‐5000 (Tokyo, Japan) infrared autorefractor which takes a measure of the accommodative state every 1 s. Readings were taken over a period of 3 min and an average TA value was calculated when the accommodative state had reached a stable level. Tonic vergence (TV) was measured in darkness continuously for 3 min using an EyeTrace 300X (Iota AB, Sundvall, Sweden) infrared limbal eyetracker and an average TV value was calculated when the traces had reached a stable level. Subjects were then immersed in a VR environment, for 30 min, generated using SimulEyes field‐sequential shutter goggles controlled by a Dell XPS R450 PC (Bracknell, UK). The VR display required a constant accommodation response of 3D, while the vergence response typically varied between 0 and 5 MA. Following immersion, measurements of TA and TV were repeated.

Results:  A significant relationship (y = 1.13x − 0.71, R = 0.85, p = 0.001) was found between the initial TV level and the shift induced by the VR environment such that negative TV positions shifted in the positive direction and vice‐versa. No significant change in TA was observed.

Conclusions:  The VR environment produced substantial adaptation of TV. These findings suggest that the vergence controller acts to shift vergence bias in order to reduce stimuli conflicts with accommodation found in VR environments. This enables subjects to maintain a stable accommodation response despite continual changes in the vergence position.
Temporal integration of astigmatic blur information
Authors: Potter J. A. , Strang N. C. , Whitaker D.
Published: March 2003

Purpose:  The accommodation response has recently been shown to improve visual acuity (VA) in the presence of astigmatism in some individuals. This improvement could potentially result from the accommodation system exhibiting a cyclic tracking response. This type of response would allow the integration of target features over time, resulting in an improvement in VA. In this study we measure VA in simulated astigmatic blur conditions, with the magnitude of astigmatic blur being temporally modulated over a range of astigmatic blur intervals. Improvement of VA with increased range of astigmatic blur would support the integration of visual information over time hypothesis.

Methods:  Three fully corrected subjects participated in a 3‐Alternative Force Choice method of constant stimuli paradigm where they were asked to identify one of three randomly chosen letters (K, R or X). The stimuli (Arial, font size 18) were subjected to varying amounts of Gaussian blur along the horizontal and vertical meridian and presented at a distance of 1.3 m. On any trial, the stimuli were randomly presented to the subjects at one of six astigmatic blur intervals. Each blur interval revolved at a temporal frequency of 2 Hz around the circle of least confusion with the smallest interval presenting the stimuli at the circle of least confusion and the largest oscillating the stimuli across the full interval, i.e. from the most horizontally to vertically blurred meridian.

Results:  From the resulting psychometric functions it was shown that all subjects exhibit a progressive improvement in letter recognition with increasing astigmatic blur interval.

Conclusions:  The improvement of VA with increased astigmatic blur interval strengthens the hypothesis that visual information can be integrated over a period of time.
Stimulus size and the variability of the threshold response in the central and peripheral visual field
Authors: Kim L. S. , Wild J. M.
Published: March 2003

Purpose:  The investigation of the peripheral visual field has shown considerable interest for the investigation of field loss attributed to anticonvulsant therapy. The purpose was to determine the within‐visit between‐subject, the between‐visit between‐subject, and the between‐location variability of the threshold response in the normal eye with increase in stimulus eccentricity out to 60° as a function of stimulus size.

Methods:  Forty‐eight normal subjects attended for a total of three visits (mean age = 49.5 years, SD = 18.9, range 22–84 years). At the first visit, one randomly assigned eye of each subject was examined with the Humphrey Field Analyzer 750 (Carl Zeiss, Jena, Germany) and the Full Threshold algorithm using Programs 30–2 and 60–4 and stimulus sizes III and V. The combination of stimulus size and of program, and the order of the combination within‐ and between‐sessions, were randomized for each subject. The results of the first visit were considered as a familiarization period and were discarded. The protocol at the second and third visits was identical to that at the first visit for each subject.

Results:  The ratio of the SD of the group mean sensitivity was determined at each stimulus location for stimulus size III compared with stimulus size V for Programs 30–2 and 60–4 at visit 3. The SDs were greater than unity for Program 30–2 (p < 0.0001) and for Program 60–4 (p < 0.0001) indicating greater variability for the size III stimulus. The SDs were also greater than unity for the central inner zone (p < 0.0001), central outer zone (p < 0.0001) and peripheral inner zone (p < 0.0001). The ratios in the peripheral outer zone were not quite greater than unity (p = 0.054). The ratios increased with increase in eccentricity by up to 2.7 times between 15° and 30° eccentricity and by up to 2.7 times between 30° and 60° eccentricity. The group mean ratio did not vary significantly between the two visits for Program 30–2 stimulus size III (p = 0.563), Program 60–4 stimulus size III (p = 0.935) and for Program 60–4 stimulus size V (p = 0.005). However, the group mean SD was lower at visit 3 compared with visit 2 for Program 30–2 stimulus size V (p = 0.0004). The SDs associated with the extreme peripheral locations in the superior and nasal fields were smaller for stimulus size III because the threshold was frequently attenuated by lid and facial contour.

Conclusions:  Considerably narrower confidence limits for normality for the peripheral regions of Program 30–2 and for 60–4 are demonstrated with the use of Goldmann size V.
Induced irregular astigmatism in hypermetropic PRK and LASIK: a bilateral cohort study
Authors: Sciscio A. , Hull C. C. , Stephenson C. G. , O'Brart D. P. S. , Marshall J.
Published: March 2003

Purpose:  To determine if there was a difference in irregular astigmatism following hypermetropic correction with Photorefractive Keratectomy (PRK) and Laser In Situ Keratomileusis (LASIK) by Fourier analysis of corneal topographical data.

Methods:  Thirty‐six eyes of 18 patients affected by hypermetropia were enrolled as part of a prospective study in which one eye was treated with PRK and the other with LASIK. In the eyes that underwent LASIK the flap was cut on a nasal hinge with a LSK one microkeratome. The laser system was a Summit SVS Apex Plus with an optical zone of 6.5 mm and a blending zone of 1.5 mm. Corneal topographical data was acquired with a TMS‐1 pre‐operatively and at 1, 3, 6 and 12 months post‐operatively. The dioptric files for each time point were converted into ASCII format and subsequently analysed with purpose written software to extract the Fourier harmonics. This permitted the objective analysis of the irregular astigmatism, equivalent spherical component and regular astigmatism.

Results:  The irregular astigmatism increased in both groups post‐operatively, reached a peak at 3 months and then reduced over the next 9 months. There was no statistically significant difference between the two groups at any time point (p < 0.05 all cases). At 12 months the irregular astigmatism values for both groups remained above their pre‐operative levels.

Conclusion:  The irregular astigmatism analysed in this study showed no statistically significant difference between the PRK and the LASIK group throughout the follow‐up period. It appears that, from a corneal topographical point of view, the two procedures induce an equal amount of irregular astigmatism.
Chromatic and achromatic loss of sensitivity in glaucoma
Authors: Pacheco‐Cutillas M. , Barbur J. L. , Edgar D. F.
Published: March 2003

Purpose:  Loss of both chromatic and achromatic sensitivity in glaucoma has been shown, however, the relative loss is unknown. We aim to quantify and establish which of these systems is affected most in glaucoma.

Methods:  Earlier experiments have shown that thresholds for detection of coherent motion of colour‐defined, spatially structured stimuli are not affected by dynamic luminance contrast noise. We used these results to design stimuli conditions that isolate chromatic and achromatic mechanisms. We studied 13 subjects with Primary Open Angle Glaucoma (POAG) with mean age of 70 years, 17 control subjects with a mean age of 68 years and 13 young normal subjects with a mean age of 31 years. Contrast thresholds were measured using a 4‐alternative, forced‐choice procedure involving discrimination of motion direction. Achromatic and chromatic sensitivities were measured, the latter along the tritan and protan confusion axes, foveally and at 8° eccentricity.

Results:  There were statistically significant differences between the three subject groups. Comparison of the control and POAG groups revealed a loss of sensitivity in the POAG group. Achromatic sensitivity thresholds increased 1.4‐fold (both at the fovea and at 8°), whereas chromatic thresholds increased 1.8‐ (B/Y) and 1.5‐fold (R/G) at the fovea and 2.0‐ (B/Y) and 1.6‐fold (R/G) at 8°. Comparison of the control and young groups reflected the ageing effects. Achromatic sensitivity showed 1.5‐fold reduction (both fovea and 8°), but the chromatic loss was more severe: 3.5‐ (B/Y) and 3.0‐fold (R/G) at the fovea, and 3.6‐ (B/Y) and 3.2‐fold (R/G) at 8°.

Conclusions:  The results confirm that the B/Y channel is most affected in glaucoma, but both chromatic and achromatic mechanisms are affected by ageing and glaucoma.
Dietary Considerations in HIV and AIDS
Authors: Woods Margo N. , Gorbach Sherwood L.
Published: March 2003

Abstract Nutritional evaluation and counseling are important aspects of the overall care of patients with HIV and AIDS. While certain groups of patients, such as those with opportunistic infection and significant weight loss, malabsorption, or any medical condition affecting dietary intake or metabolism, should be referred to a physician nutrition specialist or registered dietician for evaluation and treatment, general nutritional care of other patients may be effectively accomplished in the setting of the primary care or infectious disease clinic. This article presents evidence from observational trials concerning the energy and protein needs of patients with HIV and AIDS, outlines the roles of various micronutrients in immune functioning, and summarizes data from observational studies concerning relationships between HIV infection and micronutrient status. The possible role of dietary and supplemental omega three fatty acids in AIDS is discussed as well. Provisional recommendations for levels of energy, protein, and micronutrient intakes based on epidemiological data and risk of toxicity are given, and tables of high energy and protein snacks and foods high in various micronutrients are supplied to assist clinical implementation of these recommendations.
Alcohol's Effect on the Development and Progression of Cancer
Authors: Homann Nils , Seitz Helmut K.
Published: March 2003

In industrialized countries, alcohol intake is the major cause of cancer of the esophagus, oral cavity, and pharynx. It is also one of the most important risk factors for laryngeal and hepatocellular cancer. Epidemiologic studies are presently investigating a link between alcohol and an increased risk for breast, left‐sided colon, and rectal cancers. Experimental studies have elucidated some of the mechanisms behind these findings. Alcohol‐associated malnutrition and the fundamental changes of alcohol in the metabolism of other nutrients may explain a part of alcohol‐associated carcinogenesis. Alcohol per se is not carcinogenic but its first metabolite, acetaldehyde, is teratogenic, mutagenic, and carcinogenic. Genetic linkage studies suggest that certain polymorphisms and/or mutations in the genes coding for enzymes responsible for acetaldehyde accumulation and detoxification, namely alcohol dehydrogenases and aldehyde dehydrogenases, are associated with an increased cancer risk. These experiments suggest that the major carcinogenic action of alcohol is likely produced by acetaldehyde. Other pathomechanisms of alcohol are being studied as well. Alcohol and alcoholism also influence the treatment of cancer, as alcoholics are at a greater risk of perioperative morbidity and surgical complications.
The Oral Effects of Osteoporosis
Authors: Krall Elizabeth A.
Published: March 2003

A majority of elderly persons have lost one or more teeth, a condition that adversely affects the ability to maintain an adequate nutritional intake. Presence of a systemic disease, such as osteoporosis, is one of several factors thought to lead to tooth loss in older adults. Many studies with elderly populations have shown associations between low bone mineral density and number of missing teeth, increased levels of alveolar bone loss, and clinical measures of periodontal disease. However, the clinical significance of systemic bone loss density in contributing to the loss of oral bone and teeth is unknown. Future studies will determine if nutritional interventions could play a role in preventing tooth loss. Until there is more evidence, patients should follow the current recommendations for calcium and vitamin D intakes to ensure overall health.
Evaluation and Treatment of Low Bone Density in Anorexia Nervosa
Authors: Misra Madhusmita , Klibanski Anne
Published: March 2003

The prevalence of anorexia nervosa has increased in recent years, and a large proportion of adults as well as adolescents with this disorder have low bone density and, therefore, an increased risk of fractures. Anorexia nervosa often begins during adolescence, when peak bone mass is accumulated, resulting in significant deficits in bone mass accrual. Therefore, it is important to determine bone mineral density in adolescent and adult women who have this disorder, and to improve or at least stabilize bone metabolism in those with low bone mass. To do this, it is necessary to understand the mechanisms underlying low bone density in anorexia nervosa. This article discusses current concepts related to bone loss associated with anorexia nervosa, including how to prevent it.
Establishing an Effective Framework for Physical Activity Counseling in Primary Care Settings
Authors: Blackburn, MALD David G.
Published: March 2003

This article examines the role of the primary care physician in providing physical activity counseling and proposes a framework for maximizing the effectiveness of this activity. Many studies have been conducted to evaluate the effectiveness of physical activity counseling in the primary care setting. Unfortunately, the results of most of these studies have not been encouraging as there has not been compelling evidence that brief physical activity counseling for the general population results in long‐term changes in physical activity behaviors. In contrast, the evidence of health improvements in patients who are successful in achieving levels of physical activity consistent with the Surgeon General's recommendations is compelling and should serve as the source of motivation as we seek more effective paradigms for physical activity counseling. The PACE (Patient‐Centered Assessment and Counseling for Exercise and Nutrition) Program is presented as an evidenced‐based and effective framework for effective physical activity counseling. By adopting a patient‐centered approach to counseling and by tailoring the message to the readiness of the patient to take action, it is possible to engage in physical activity counseling in a cost‐ and time‐effective manner. This article provides specific counseling strategies for addressing patients at various stages of readiness to engage in behavior change regarding physical activity.
Apoptosis in regenerating and denervated, nonregenerating urodele forelimbs
Authors: Mescher Anthony L , White Gary W , Brokaw James J
Published: March 2003

Denervated limbs of larval salamanders fail to regenerate if amputated and, unlike adult limbs, undergo regression. The cellular basis of the tissue loss is poorly understood. We used TUNEL staining of larval axolotl limbs fixed and sectioned at intervals after bilateral amputation and unilateral denervation to investigate the role of apoptosis during normal limb regeneration and denervated limb regression. In the first week after amputation a small percentage of apoptotic cells was found in both innervated and denervated limbs. During the second week the apoptotic index remained low in the mitotically active mesenchymal cells of the regenerating limbs, but increased twofold in the nondividing, dedifferentiated cells of the regressing limbs. TUNEL‐positive cells resembling apoptotic bodies were restricted primarily to the dedifferentiated area beneath the wound epithelium, but were also present within the wound epithelium itself. Macrophages were identified immunohistochemically and were also found in increased numbers in distal areas of the denervated regressing limbs. The results suggest a role for apoptosis in the early phase of normal regeneration and indicate that denervated limb regression involves an increased rate of apoptosis and removal of apoptotic bodies by macrophages and the wound epithelium.

(WOUND REP REG 2000;8:110–116)
In‐vivo particle mediated delivery of mRNA to mammalian tissues: ballistic and biologic effects
Authors: Sohn Richard L. , Murray Mary T. , Schwarz Karl , Nyitray Joseph , Purray Praveen , Franko Alexander P. , Palmer Kenneth C. , Diebel Lawrence N. , Dulchavsky Scott A.
Published: March 2003

Biolistic transmission of mRNA provides transient gene therapy to in vivo organs. This study documents particle mediated mRNA transmission to a solid organ and wound healing model using the mRNA of Green Fluorescent Protein to determine optimal delivery parameters. Renal function, bullet penetration, cellular injury, and Green Fluorescent Protein synthesis were quantified. Chimeric human epidermal growth factor‐FLAG epitope cDNA or mRNA was transmitted to wounds in normal or steroid treated animals. Wound bursting strength, human epidermal growth factor‐FLAG, and collagen synthesis were determined. Injury and bullet penetration correlated with the delivery velocity and bullet size. Optimal delivery parameters were established which provided widespread Green Fluorescent Protein synthesis. Human epidermal growth factor‐FLAG treatment significantly increased collagen content and wound breaking strength in normal and steroid treated animals. FLAG protein synthesis was evident in mRNA treated fascia following treatment. We found the gene gun provides a novel method for efficient, in vivo delivery of mRNA‐based therapeutic strategies to mammalian organs with minimal histologic damage allowing transient expression of protein in in vivo target tissues. Co‐delivery of Green Fluorescent Protein mRNA may provide a useful positive control to determine effective transmission. Biolistic transmission of human epidermal growth factor‐FLAG mRNA provides increased tissue epidermal growth factor levels and accelerates wound healing in normal and steroid exposed animals.
Allogeneic fibroblasts in dermal substitutes induce inflammation and scar formation
Authors: Lamme Evert N. , Van Leeuwen Rene T. J. , Mekkes Jan R. , Middelkoop Esther
Published: March 2003

In the present study, we compared the use of autologous versus allogeneic fibroblasts in dermal skin substitutes in a porcine wound model. The allogeneic fibroblast populations were isolated from female and a male pig (allo‐1, ‐ 2 and ‐ 3) and the controls, autologous fibroblasts, from female graft‐recipient pigs (control). The histocompatibility of the three donor pigs with the recipient pigs was determined with a mixed lymphocyte reaction. In two pigs, full‐thickness wounds were treated with the fibroblast‐seeded dermal substitutes (n=5 per animal) and immediately overgrafted with meshed split‐skin autografts. After 6 weeks, wound contraction was measured by planimetry and scar formation was scored. At 2, 4, and 6 weeks biopsies were taken and evaluated for the presence of inflammatory reactions, myofibroblasts, and scar formation. The mixed lymphocyte reaction of both recipient pigs showed the highest responses on peripheral blood mononuclear cells of the allo‐3 donor pig, and was low or negative for allo‐1 and allo‐2. In all “allogeneic” wounds, more inflammatory cells were observed over time along with inflammatory foci consisting of a mix of lymphocytes and granulomatous cells. After 4 weeks, myofibroblasts were absent in the control wounds, whereas in “allogeneic” wounds, myofibroblasts colocalized with inflammation foci. The final scar tissue of the “allogeneic” wounds showed granulating areas with thin, immature collagen bundles. In contrast, the control wounds showed a dermal tissue with mature collagen bundles organized randomly like in normal skin. The wounds treated with allo‐3 fibroblasts showed in both pigs a significant increase in scar formation and wound contraction when compared with control wounds. In conclusion, for optimal restoration of dermal skin function with minimal scar formation, skin substitutes containing autologous fibroblasts are preferred over skin substitutes with allogeneic fibroblasts. (WOUND REP REG 2002;10:)
Significance of cell cycle for wound stratification in clinical trials: analysis of a pressure ulcer clinical trial utilizing cyclin D/cdk4
Authors: Vande Berg Jerry S. , Rose Michael A. , Payne Wyatt G. , Haywood‐Reid Patricia L. , Robson Martin C.
Published: March 2003

During the past 5 years, progress in the treatment of pressure ulcers appears to have reached a plateau. Several factors in the design of recent clinical studies may have contributed to this situation. These factors include the criteria chosen for patient selection, small sample size, and lack of a concisely defined final clinical outcome. Hunt noted that wound stratification according to a patient's physiological characteristics may be a key to quantifying differences among clinical treatments.1To address this issue, we examined the expression of cyclin D/cdk4 in pressure ulcer fibroblasts taken from tissues during a recent clinical trial. The treatment groups included patients treated with the following regimens: placebo, granulocyte macrophage‐colony stimulating factor alone, basic fibroblast growth factor alone, or granulocyte macrophage‐colony stimulating factor and basic fibroblast growth factor given in sequence.2 Immunocytochemical colocalization of cyclin D and cdk4 showed that, before the initial treatment began, patients were distributed disproportionately among treatment subgroups in regards to the initial expression of these markers. For example, we found that compared with other subgroups, ulcer fibroblasts in the basic fibroblast growth factor treatment group showed a much lower expression of cyclin D/cdk4 at day 0. However, this group exhibited higher levels of expression of this complex after 35 days of treatment. This study shows that measurement of cyclin D/cdk4 expression permits more accurate stratification of patients within treatment subgroups, measurement of a cell's ability to detect the presence of functional cytokines, identification of area(s) of failure within the G1 of the cell cycle, and a basis for critical evaluation of various treatments. (WOUND REP REG 2003;11:11–18)
Complex microstructures preserved in rocks with a simple matrix: significance for deformation and metamorphic processes
Authors: Bell  , Hickey
Published: March 2003

Schists from the foothills of the Central Sierra Nevada contain one dominant matrix foliation and yet four phases of growth of both cordierite and andalusite porphyroblasts can be distinguished. These occurred early during four separate deformation events that formed successive steep and shallow foliations. A fifth deformation event pre‐dates the growth of all porphyroblasts studied. The multiple phases of porphyroblast growth allow correlation of structures across and along the region. A repeated pattern of deformation, in terms of the curvature of earlier foliations against the overprinting one, allows samples containing porphyroblasts with simpler inclusion trail geometries to be interpreted with confidence. The large‐scale fold structures in this region formed before or during the second of the five deformation events recorded by the porphyroblasts. However, the matrix foliation is predominantly a product of the fourth deformation, which has commonly reactivated or re‐used older foliations, and is dominated by east‐side‐up shear. The intervening third deformation produced locally intense foliations and was accompanied by top‐to‐the‐east shear. The very weak fifth deformation produced weak crenulations with subhorizontal axial planes and was coaxial. Multiple phases of episodic but synchronous growth of cordierite and andalusite were produced by the KFMASH univariant equilibrium Ms+Chl+Qtz=And+Crd+Bt+H2O. The rocks crossed this reaction at a pressure just below the intersection with the KFMASH divariant equilibrium Ms+Chl+Qtz=Crd+Bt+H2O; the latter being overstepped in favour of the former as there is no evidence for cordierite growth prior to andalusite in these rocks. Subsequent multiple episodes of synchronous growth of cordierite and andalusite indicate that the possible variation in P–T  during subsequent deformations was not large. This requires the high‐amplitude macroscopic fold to form prior to porphyroblast growth and then be simply tightened and modified by the younger deformations.
Petrological characterization and tectonic significance of retrogressed garnet peridotites, Raobazhai area, North Dabie Complex, east‐central China
Authors: Tsai  , Liou  , Ernst
Published: March 2003

The Raobazhai ultramafic body of the North Dabie Complex is re‐interpreted as a mantle‐derived peridotitic slice enclosed in, and isofacially metamorphosed with, surrounding granulite‐to‐amphibolite facies gneisses. The ultramafic sheet consists mainly of metaharzburgite, but includes subunits of metadunite and mylonitic lherzolite. The rocks contain spinel but neither garnet nor plagioclase. However, in the mylonitic lherzolite, fine‐grained intergrowths of spinel, orthopyroxene and clinopyroxene outline domains resembling the habit of garnet in two dimensions; broad‐beam microprobe analyses imply pseudomorphs after a pyropic garnet precursor. The mineral assemblage of the metadunite and metaharzburgite is: olivine (Fo92)+orthopyroxene (En92)+tremolitic‐to‐magnesiohornblende+Mg–Al‐chromite, indicating amphibolite facies recrystallization. The mineral assemblage of the mylonitic lherzolite is: olivine (Fo90)+orthopyroxene (En90)+clinopyroxene+Cr‐bearing spinel+pargasitic amphibole, indicative of granulite‐to‐amphibolite facies metamorphism. Phase equilibria and geothermometric estimations show that the Raobazhai meta‐ultramafics have undergone at least three stages of recrystallization: (I) 950–990 °C, (II) 750–860 °C, and (III) 670–720 °C, assuming equilibrium in the spinel peridotite stability field (c. 6–15 kbar), although an early, high‐pressure stage (≥18 kbar) is probable, based on the inferred garnet pseudomorphs. Petrochemical and geothermobarometric data suggest that the ultramafic slice represents a fragment of the mantle wedge, tectonically incorporated into subducted continental crust and re‐equilibrated at granulite‐to‐amphibolite facies conditions while being exhumed to shallow levels.
Early Tertiary fluid flow and pressure–temperature conditions in the Shimanto accretionary complex of south‐west Japan: constraints from fluid inclusions
Authors: Lewis  , Byrne  , Pasteris  , London  , Morgan Vi
Published: March 2003

The pressure and temperature history of the Tertiary Shimanto belt of south‐west Japan has been elucidated by analysing fluids trapped in quartz crystals which grew syn‐kinematically along late‐stage brittle faults. The samples come from three areas that span the Paleogene exposures on the Muroto Peninsula of Shikoku Island. Applying microthermometric and laser Raman microsampling techniques to coeval water‐rich and carbonic fluid inclusions, we have constrained the pressure and temperature conditions that accompanied a widespread and kinematically distinct phase of deformation. The results suggest elevated geothermal gradients during late‐stage deformation, conditions that are in disaccord with previous plate reconstructions that have depicted old, thermally mature Pacific crust subducting beneath Eurasia during the early to middle Tertiary. These conditions can most easily be accounted for by including an additional plate boundary in the western Pacific during Paleogene time. Plate reconstructions that include the Kula plate in this region are therefore consistent with our findings. In addition, our results provide clues to the conditions that likely accompany seismogenic deformation at active convergent plate boundaries.
K‐rich fluid metasomatism at high‐pressure metamorphic conditions: Lawsonite decomposition in rodingitized ultramafite of the Maksyutovo Complex, Southern Urals (Russia)
Authors: Schulte B. , Sindern S.
Published: March 2003

Fine grained rodingite‐like rocks containing epidote, clinozoisite, garnet, chlorite, phengite and titanite occur within antigorite serpentinite boudins from the high‐pressure metamorphic Maksyutovo Complex in the Southern Urals. Pseudomorphs after lawsonite, resorption of garnet by chlorite and phengite and stoichiometry suggest the reaction lawsonite + garnet + K‐bearing fluid → clinozoisite + chlorite + phengite, and define a relic assemblage of lawsonite + garnet + chlorite + titanite ± epidote as well as a later post‐lawsonite assemblage of clinozoisite + phengite + chlorite + titanite. The reaction lawsonite + titanite → clinozoisite + rutile + pyrophyllite + H2O delimits the maximum stability of former lawsonite + titanite to pressures >13 kbar. P–T conditions of 18–21 kbar/520–540 °C result, if the average chlorite, Mg‐rich garnet rim and average epidote compositions are used as equilibrium compositions of the former lawsonite assemblage. These estimates indicate a similar depth of formation but lower temperatures to those recorded in nearby eclogites. The metamorphic conditions of the lawsonite assemblage are considerably higher than previously suggested and, together with published structural data, support a model in which a normal fault within the Maksyutovo complex acted as the major transport plane of eclogite exhumation.

The maximum Si content of phengite and minimum Fe content in clinozoisite constrain the metamorphic conditions of the later pseudomorph assemblage to be >4.5 kbar and <440 °C. Rb–Sr isotopic dating of the pseudomorph assemblage results in a formation age of 339 ± 6 and 338 ± 5 Ma, respectively. These results support the recent exhumation models for this complex.
ACID‐BASE IN RENAL FAILURE: What Have Isotope Studies in Humans Told Us About the Nutritional Effects of Acidosis in Dialysis?
Authors: Louden Jonathan D. , Roberts Russell G. , Goodship Timothy H. J.
Published: March 2003

In order to understand how acidosis might predispose to loss of lean body mass it is important to recognise that body protein is in a dynamic state with a daily turnover of approximately 300 g of protein in a 60 kg man. This is significantly greater than the daily protein intake at a level of 1 g · kg‐1· day‐1. Loss of lean body mass occurs when the balance between whole body protein synthesis and breakdown is negative. Measurement of whole body protein turnover is possible using either boluses or primed constant infusions of isotopically labelled amino acids. Previously, a variety of in vitro and in vivo animal studies have shown that acidosis increases protein degradation and amino acid oxidation. Several research groups including our own have used amino acid tracer techniques to examine whether protein degradation is increased in vivo in human subjects with acidosis and chronic renal failure. The results from these studies have shown a remarkable concordance with increased protein degradation in all groups of patients studied. However, the results for protein synthesis have been more difficult to interpret, with only a few studies directly measuring the effects of acidosis on amino acid incorporation into protein.
Are Parathyroidectomies Still Appropriate in Chronic Dialysis Patients?
Authors: Cunningham John
Published: March 2003

The uremic milieu generates chronic stimulatory input to the parathyroid glands, which is mediated principally by low calcium, high phosphate and low calcitriol, and results in increased parathyroid hormone (PTH) synthesis and release and an increase in parathyroid mitotic activity with the development of monoclonal areas of nodular hyperplasia. Such glands do not fully express the machinery required to mediate the suppressive inputs to the parathyroids; the extracellular calcium receptor (CaR) and the vitamin D receptor (VDR) are both downregulated. In most of these patients ablation, by parathyroidectomy or ethanol injection, provides the only means of correcting the hyperparathyroidism; apoptosis in parathyroid cells is negligible and clinically irrelevant. In practice, surgery is often delayed by a doomed and ultimately futile attempt to effect control by medical means. Better predictors of the likely success or failure of optimal non surgical management are needed. Gland size exceeding 1 cm3 and elevated PTH despite hypercalcemia (implying loss of suppressibility by calcium), in the presence of good phosphate control and adequate calcitriol provision point strongly to eventual failure of medical treatment and the need for parathyroid ablation. Parathyroidectomy, usually subtotal, remains the standard management, with ultrasound guided injection of ethanol or calcitriol showing promise in some centers. The above scenario is unlikely to be changed greatly by the new emerging vitamin D metabolites, but calcimimetic agents may well increase the scope of non surgical management.
Improvement in Hemodialysis Vascular Access Outcomes in a Dedicated Access Center
Authors: Arnold W. Perry
Published: March 2003

There are more than 300,000 end‐stage renal disease (ESRD) patients in the United States, with those on hemodialysis requiring vascular access for dialysis treatment. According to the 1999 annual report of the U.S. Renal Data System (USRDS), the leading cause of morbidity in this patient population is related to vascular access placement and the resultant complications. Vascular access procedures account for more than 10% of the annual ESRD budget and are conservatively estimated at $1 billion annually. The impact of dysfunctional vascular access on physician time, health care resources, and patient quality of life is profound. In 1997 I opened a freestanding, dedicated access center for the diagnosis and treatment of access‐related disorders. This article summarizes the experience of this center. In our freestanding dialysis access center, a large referral base has been established consisting of 30 dialysis centers with approximately 2000 patients. During the 27 months from October 1997 to December 1999, 1087 patients were treated. These patients received 2862 access procedures (2.6 procedures/patient). Annualized, this gives a dysfunction rate of 1.15 episodes/patient/year at risk. Endovascular declotting procedures were performed 1282 times (45%) with a success rate (defined as one uneventful hemodialysis following the procedure) of 93% (1187/1282). Prospective angiography followed by percutaneous transluminal angioplasty was performed 703 times (24%). This procedure was successful 695 times for a success rate of 99%. There were 644 (23%) catheter procedures performed consisting of catheter placements, catheter exchanges through new or old tracts, and catheter removals. The success rate for catheter procedures was 99.1%. Complication rates were extremely low, both for major and minor complications, exceeding all published standards. Hemodialysis vascular access can be optimized in a freestanding, focused, outcomes‐driven outpatient access center. Outcomes can meet or exceed the National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF‐DOQI) guidelines for vascular access while at the same time providing the patient with an outpatient procedure and the referring dialysis unit and nephrologist with an efficient, effective mode of patient care.
Modalities for the Removal of β2‐Microglobulin from Blood
Authors: Ameer Guillermo A.
Published: March 2003

The long‐term accumulation of β2‐microglobulin (β2M) in patients with kidney failure results in a debilitating condition referred to as dialysis‐related amyloidosis (DRA). There have been few methods specifically designed to remove the large quantities of β2M that are produced by the body. This article briefly reviews current modalities and concepts for the removal of β2M from blood. The various approaches are classified according to the mechanism of β2M clearance. The potential application of immunoadsorption, a biologically specific approach to remove macromolecules, in the treatment and understanding of DRA is discussed.
Dynamic of β2‐Microglobulin Fibril Formation and Reabsorption: The Role of Proteolysis
Authors: Bellotti Vittorio , Gallieni Maurizio , Giorgetti Sofia , Brancaccio Diego
Published: March 2003

Dialysis‐related amyloidosis (DRA) is caused by the deposition, in target tissues, of β2‐microglobulin (β2M) in fibrillar conformation. Several reports indicate that fibrillar β2M is chemically heterogeneous and such heterogeneity is partially related to the presence of truncated species of the protein. In association with the full‐length species, a β2M isoform lacking six N‐terminal residues is present in all the samples of our collection of ex vivo fibrils. The pattern of proteolytic cleavage in amyloidosis and in other diseases is completely different, as demonstrated by the absence in fibrillar β2M of the cleavage at lysine 58, which is contrary to that described in rheumatoid arthritis and other diseases. The role of limited proteolysis of β2M in the pathogenesis of the disease is uncertain. However, we have shown that the apparently minor modification of the intact protein, such as the removal of N‐terminal hexapeptide, is capable of dramatically affecting its stability, protection from proteolytic digestion, and enhance its capacity to make in vitro amyloid fibrils. The structure, folding dynamic, and function of the truncated species of β2M, peculiar of DRA, could shed new light on the mechanism of β2M fibril formation and reabsorption.
Dialysis‐Related Amyloidosis: History and Clinical Manifestations
Authors: Danesh Farhad , Ho Louisa T.
Published: March 2003

Dialysis‐related amyloidosis (DRA) or β2‐microglobulin amyloidosis (Aβ2M) is a unique type of amyloidosis that has been described in individuals with both long‐standing chronic renal disease and end‐stage renal disease (ESRD). It has been associated with serious complications that significantly add to the morbidity of long‐term dialysis patients. The deposition of β2M in amyloid fibrils in various joint and osteoarticular surfaces leads to the clinical complaints and findings typical of this disorder. However, a visceral form with systemic organ involvement has also been described. Despite advances in the understanding of this disorder and in the delivery of dialysis, the ability to alter the incidence of DRA and its course remains uncertain.
Protein Intake in Patients with Renal Failure: Comments on the Current NKF‐DOQI Guidelines for Nutrition in Chronic Renal Failure
Authors: Lim Victoria S. , Flanigan Michael J.
Published: March 2003

The National Kidney Foundation Clinical Practice Dialysis Outcomes Quality Initiative (DOQI) guidelines recently recommended dietary protein intake for patients with chronic renal failure as follows: predialysis patients should receive 0.60 g/kg/day of protein and increase intake to 0.75 g/kg/day for subjects who cannot follow such a diet. For stable maintenance hemodialysis patients, the recommended protein intake is 1.2 g/kg/day, and for chronic peritoneal dialysis patients, 1.2–1.3 g/kg/day. We differ with these recommendations and believe that a dietary protein intake of 0.8 g/kg/day is appropriate for the predialysis population; an intake of 0.9–1.0 g/kg/day and 1.0–1.1 g/kg/day for maintenance hemodialysis patients and peritoneal dialysis patients, respectively, should be adequate. The rationale and the evidence supporting our arguments are outlined and discussed.
Continuous Flow Peritoneal Dialysis: Is There a Need for it?
Authors: Ronco Claudio
Published: March 2003

Automated peritoneal dialysis (APD) is the fastest growing technique of peritoneal dialysis. However, recently APD has displayed some limitations imposed by the characteristics of the technique and by the characteristics of the peritoneal membrane of some patients. In general, the advent of a new technique such as continuous flow peritoneal dialysis (CFPD) should be seen as a benefit for several patients based on different considerations: CFPD is a high‐efficiency technique which could overcome some of the limitations imposed by other techniques in terms of adequacy targets and performance. CFPD may become a useful tool to keep patients on PD who would otherwise be transferred to hemodialysis. CFPD may present advantages in terms of biocompatibility and also in terms of the possible modulation of the peritoneal solution to patient needs. Recent developments in technology seem to have made CFPD easily feasible and well tolerated. A new era of PD is probably beginning and CFPD will definitely represent one of the key issues in the future of PD.
Do AV Fistulas Contribute to Cardiac Mortality in Hemodialysis Patients?
Authors: Dikow Ralf , Schwenger Vedat , Zeier Martin , Ritz Eberhard
Published: March 2003

Potential fistula‐related problems which may impact on patient survival include high fistula flow with hyperkinetic circulation and cardiac failure, low fistula flow with the risks of underdialysis and fistula thrombosis, vascular access infection with local or systemic manifestations, and possibly induction and maintenance of a microinflammatory state (at least for synthetic grafts). All these complications are much more common with prosthetic grafts than with native arteriovenous (AV) fistulas. Fistula flow should be monitored (e.g., by duplex sonography) to guarantee adequate flow and permit preemptive intervention to avoid fistula thrombosis.
Imaging in the Dialysis Patient: Image‐Guided Peritoneal Access and Management of Complications in Peritoneal Dialysis
Authors: Taylor Paul M.
Published: March 2003

The principal complications of continuous ambulatory peritoneal dialysis (CAPD), namely malposition of the dialysis catheter, peritonitis, exit site infection, leakage of dialysis fluid, sclerosing peritonitis, and renal cysts and tumors, are considered in this article. The techniques that are used to reposition displaced dialysis catheters and extend the duration of dialysis are described. The role of imaging in establishing the diagnosis of peritonitis is relatively small. However, both computed tomography (CT) and ultrasound may be used to identify loculation of fluid and localized sites of sepsis, and permit percutaneous drainage. Ultrasonography of the catheter track through the percutaneous tissues allows identification of pericatheter collections in patients with exit‐site infection. The technique of CT peritoneography is helpful in establishing sites of dialysis fluid leakage. These commonly occur at the site of entry of the dialysis catheter, through abdominal incisions, or along the patent tunica vaginalis into the scrotum. The appearances on CT of sclerosing peritonitis reflect pathologic changes and are characterized by the presence of peritoneal thickening and calcification. Bowel obstruction, which may develop in sclerosing peritonitis, can be identified on abdominal radiographs or barium studies of the gastrointestinal tract. Acquired renal cystic disease and renal carcinomas occur in a significant proportion of patients undergoing CAPD. Ultrasound is the investigation of first choice in the identification and clarification of the pathology (cystic or solid) of suspected renal masses.