Formation of internal stress fields in rails during long-term operation

The structure and the internal stress fields in R65 rails withdrawn from operation because of side wear after long-term operation are studied and estimated. A high scalar dislocation density (higher by a factor of 1.5–2), the fragmentation of cementite lamellae, and the precipitation of carbide particles are detected in the layers adjacent to the roll surface. The stresses at the boundaries of the particles with the ferrite matrix can exceed the ultimate strength of the steel.     

Identification and structural influence of a differentially modified N-terminal methionine in human S100b

The calcium-binding protein S100b is a homodimer comprised of two identical 91-residue beta-subunits. Recombinant S100b is a heterogeneous protein, although the basis of this heterogeneity has not been established. We have used mass spectrometry and NMR spectroscopy to determine that heterogeneity in S100b arises from a mixture of formyl-S100b and desformyl-S100b when expressed in Escherichia coli. Reversed-phase HPLC purification of these two forms of S100b has allowed the differences in N-terminal composition to be used as a probe for tertiary contacts in the protein. The presence or absence of the N-terminal formyl group affected the chemical shifts of sequence neighboring residues and those in the linker of the protein (residues 40-43), indicating that these two regions are close in space.     

Structural changes in a railway wheel rim during operation

The structural changes in the near-surface layers of a railway wheel rim are studied during operation in rolling stock. The standard operating conditions of rail transport are shown to be characterized by alternating impact loading; regular braking; and, hence, periods of rapid heating of the surface layers in wheels that are replaced by intense heat removal after the end of braking of rolling stock. In this case, the heating of wheels is sufficient for the beginning of phase transformations, which result in softening, embrittlement, and strain aging of the near-surface layer metal.     

Mild memory deficits differentially affect 6-year changes in compensatory strategy use.

The authors examined memory compensation techniques used by older adults from 2 memory status groups, not impaired control (NIC) and mild memory deficit (MMD), both at baseline and across a 6-year (3-wave) interval. The groups were derived from a parent sample of 55- to 85-year-old adults from the Victoria Longitudinal Study (NIC baseline, n = 276; memory > parent sample mean; MMD baseline, n = 79; memory > 1 standard deviation below parent sample mean). Multilevel modeling was used to test 3 research questions concerning differences in initial use of, and 6-year changes and variability in, memory compensation. Initial group differences were observed for both a memory compensation technique and a general compensation indicator. Significant differences in 6-year change patterns were observed for 2 memory compensation techniques (recruitment of human memory assistance, investment of extra effort in memory tasks). Interactions of group status and wave showed that older adults with MMD declined in their use of memory compensation strategies, whereas initially NIC older adults increased their use of compensatory techniques over the 6 years. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term ovarian and gonadotropin changes in mice exposed to 4-vinylcyclohexene

This study investigated the relationships between 4-vinylcyclohexene-induced follicular destruction, plasma FSH levels, and the development of ovarian preneoplastic changes. Female, 28-day-old, B6C3F1 mice were administered VCH (800 mg/kg/day, ip) or sesame seed oil, ip daily for 30 days. At 30, 60, 120, 240, and 360 days following the beginning of treatment, groups were killed, their ovaries were harvested, and plasma was collected for measurement of FSH. Ovarian weight was less and oocytes contained in preantral follicles were significantly fewer than controls at all time points. Plasma FSH concentrations in VCH-treated animals were increased significantly above controls at 240 d and 360 d. Histologically, there was oocyte loss at all times, whereas at 240 and 360 days, small to medium, irregularly shaped foci of hypertrophic cells were present. In addition, at 360 days 80% of the VCH-treated mice had a 1- to 2-mm, blood-filled cystic structure present in one or both ovaries. These studies indicate that VCH-induced oocyte destruction and follicle loss are associated with increases in plasma FSH, are associated with ovarian failure at 360 days, and are temporally related to ovarian cellular hypertrophy and the formation of blood-filled cystic ovarian structures. These events are possibly related to ovarian neoplasms produced by long-term exposure to VCH.     

100 years radical abdominal operation of cervix carcinoma: in memory of Wertheim's predecessors

1895 was a crucial year in the course of the development of abdominal radical surgery for effective treatment of cervical cancer. In March of 1895, Ries presented the rationale of modern radical hysterectomy and was the first to call for systematic removal of pelvic lymph nodes. Independently, Clark in Baltimore, Rumpf in Berlin, and Latzko in Vienna performed the first radical hysterectomies. This article is dedicated to the memory of the contributions by these four pioneers of surgical gynecology presented in 1895.     

The influence of tempering temperature on small fatigue crack behavior monitored with surface acoustic waves in quenched and tempered 4140 steel

Small surface fatigue crack growth in specially designed cantilevered bending samples of high-purity 4140 steel quenched and tempered to various strength levels was investigated. Tempering temperatures of 200 °C, 400 °C, 550 °C, and 700 °C were used to produce a range of yield strengths and microstructures. Crack propagation and crack closure were monitored with a surface acoustic wave ultrasonic technique. The small crack results were compared to those of long cracks in compact tension samples. Small cracks in the 200 °C and 400 °C tempers grew at ΔK levels above their long crack thresholds. Small cracks in the 550 °C tempers grew at ΔK levels slightly below the long crack threshold. The surface cracks in the 700 °C temper grew well below the long crack threshold showing the “small crack effect.” Small crack growth occurred in a very narrowda/dN- ΔK scatter band showing much less variation with microstructure than the long crack data. The differences between the long and small crack data were due to the high, relatively similar closure values for the small cracks and the variation of long crack growth with microstructure. Formerly Graduate Research Assistant, Department of Materials Science and Engineering, Stanford University, Stanford, CA.     

Long-term changes in excitability induced by protein kinase C activation in Aplysia sensory neurons

Protein kinases A (PKA) and C (PKC) play a central role as intracellular transducers during simple forms of learning in Aplysia. These two proteins seem to cooperate in mediating the different forms of plasticity underlying behavioral modifications of defensive reflexes in a state- and time-dependent manner. Although short- and long-term changes in the synaptic efficacy of the connections between mechanosensory neurons and motoneurons of the reflex have been well characterized, there is also a distinct intermediate phase of plasticity that is not as well understood. Biochemical and physiological experiments have suggested a role for PKC in the induction and expression of this form of facilitation. In this report, we demonstrate that PKC activation can induce both intermediate- and long-term changes in the excitability of sensory neurons (SNs). Short application of 4beta-phorbol ester 12,13-dibutyrate (PDBU), a potent activator of PKC, produced a long-lasting increase in the number of spikes fired by SNs in response to depolarizing current pulses. This effect was observed in isolated cell culture and in the intact ganglion; it was blocked by a selective PKC inhibitor (chelerythrine). Interestingly, the increase in excitability measured at an intermediate-term time point (3 h) after treatment was independent of protein synthesis, while it was disrupted at the long-term (24 h) time point by the general protein synthesis inhibitor, anisomycin. In addition to suggesting that PKC as well as PKA are involved in long-lasting excitability changes, these findings support the idea that memory formation involves multiple stages that are mechanistically distinct at the biochemical level.     

SR 48692, a non-peptide neurotensin receptor antagonist differentially affects neurotensin-induced behaviour and changes in dopaminergic transmission

Unilateral microinjection of neurotensin in the ventral tegmental area of the rat (2.5 micrograms/0.5 microliter) produced behavioural excitation illustrated by contralateral circling. Given orally, SR 48692, a selective and potent non-peptide neurotensin receptor antagonist, significantly reduced these rotations with a triphasic dose-effect relationship. Inhibition occurred at 0.12 mg/kg; further increases in dose up to 2.5 mg/kg produced no significant antagonism, then at doses > or = 5 mg/kg, a second phase of antagonism was observed. Bilateral injection of neurotensin (0.5 microgram each side) into the nucleus accumbens antagonized the increase in locomotor activity following intraperitoneal injection of amphetamine. Given orally, SR 48692 reduced dose-dependently (0.1-1 mg/kg) these intra-accumbens neurotensin effects. Using high pressure liquid chromatography with electrochemical detection, we showed that microgram amounts of neurotensin injected into the ventral tegmental area increased dihydroxyphenylacetate/dopamine ratios in the nucleus accumbens. Using in vivo voltammetry techniques, we found that the injection of nanogram and picogram amounts of neurotensin in the ventral tegmental area stimulated dopamine efflux in the nucleus accumbens. None of these biochemical changes were affected by SR 48692 (0.1-10 mg/kg). These results indicate complex interactions between neurotensin and the mesolimbic dopamine system. More particularly, the differential ability of SR 48692 to affect neurotensin-evoked behavioural versus biochemical changes supports the concept of neurotensin receptor heterogeneity.     

Long-term sealing efficacy of four root surface sealing materials used in endodontic leakage studies

Fifty extracted human maxillary anterior teeth were biomechanically instrumented and divided into five equal groups, four experimental and a control. The teeth in the experimental groups had their root surface coated with one of four sealants; epoxy, casting resin, sticky wax, or nail polish. The roots of the remaining teeth were not coated and served as controls. All of the teeth were mounted in the caps of scintillation vials. Five microliters of [3H]uridine were deposited in the root canal space and disintegration counts were obtained over time periods of 1, 4, 8, 12, and 36 wk. At the conclusion of the experiment, sticky wax was demonstrated to provide a superior seal (p < 0.0001).     

Isoforms p69 and p100 of 2'',5''-oligoadenylate synthetase induced differentially by interferons in vivo and in vitro

There is no better place to test life-saving resuscitation interventions than in the prehospital setting. Patients rarely survive cardiac arrest if resuscitation techniques have failed before leaving the scene. Also, paramedics are usually very experienced in key initial resuscitative techniques, and they routinely operate under strict paramilitary protocol, resulting in better study compliance. In addition, the large study populations that are derived from emergency medical services (EMS) systems lead to faster study completion and statistically stronger data. Most important, by reinforcing standardized care, rigidly scrutinized trials improve patient care, regardless of the effect of the study intervention. The success of productive EMS research centers requires routine communication between hospital and EMS administrators and their medical directors, designation of mutually acceptable data collectors who guarantee confidentiality, reciprocal exchange of study data provided as educational seminars to the hospitals, commitments to support the budget requests of an EMS program and appropriate system modifications, inclusion of EMS personnel in study design from the very beginning, prospective education of the medical community and media before protocol implementation, an authoritative grassroots medical director, and a paramedic supervisor system.     

Developmentally regulated changes in the cell surface architecture of Leishmania parasites

The cell surface of Leishmania parasites is coated by a highly unusual glycocalyx which varies markedly during the parasite life cycle. The predominant molecule on the extracellular promastigote (sandfly) stage is a complex lipophosphoglycan (LPG), which together with a number of GPI-anchored proteins and a family of low molecular weight glycoinositolphospholipids (GIPLs), forms a morphologically distinct protective coat over the plasma membrane. The structure of the LPG has been shown to vary in different species and during promastigote development in the sandfly. This polymorphism is thought to be important in allowing Leishmania parasites to colonize a range of insect hosts, and in facilitating the regulated migration of promastigotes along the sandfly alimentary canal. Stage-specific changes in LPG are also involved in preadapting promastigotes to life in the mammalian host. This complex glycocalyx coat is absent from the amastigote stage that proliferates in the phagolysosomes of mammalian macrophages, as the expression of both the LPG and GPI-anchored proteins is massively down-regulated. Instead, the plasma membrane of amastigotes is coated by a densely packed layer of parasite-derived GIPLs and host-derived glycosphingolipids. We propose that the down-regulation of the promastigote macromolecules and the acquisition of host glycolipids by amastigotes represents an important strategy to avoid detection by specific and non-specific components of the immune system.     

Long-term alcohol self-administration and alcohol withdrawal differentially modulate microtubule-associated protein 2 (MAP2) gene expression in the rat brain

Chronic alcohol intoxication is known to produce neuronal degeneration in the central and peripheral nervous system of experimental animals and of humans. It is suggested that various components of the cytoskeleton undergo profound changes following chronic alcohol use and misuse. Here we studied the expression of the neuronal cytoskeletal microtubule-associated protein 2 (MAP2) following long-term alcohol consumption and subsequent alcohol withdrawal. Alcohol-preferring AA (Alko Alkohol) rats with a high voluntary alcohol consumption for a period of 16 months were compared with age-matched control rats without prior experience with alcohol. For comparison, in a second experiment, heterogeneous Wistar rats that also had voluntary access to alcohol for 8 months were examined following alcohol consumption and withdrawal. In situ hybridization and subsequent dot blot and Northern blot analysis for further quantification revealed that chronically alcoholized animals exhibit markedly decreased MAP2 mRNA levels in several parts of the extrapyramidal system (mainly in the caudate putamen, the substantia nigra pars compacta and the globus pallidus), the mesolimbic system, in several hypothalamic nuclei and in the nucleus inferior colliculus. Other areas such as the hippocampus, frontoparietal cortex and cerebellum were less affected by chronic alcohol intake, however, in these regions the MAP2 mRNA levels were increased during alcohol withdrawal. These results suggest that long-term alcohol self-administration affects central neurons involved in motor control via the influence on the integrity of the cytoskeleton and may thus induce motor dysfunction.