Characterizing fretting particles by analysis of SEM images

Detailed surface characteristics of the particles produced during fretting may well be significant in determining their biological effects. Apart from a broad size determination very few attempts have been made at devising means of describing profile textures of particles. An approach is presented for describing the nature of particle shape and surface texture, as detected on the particle profile. Careful processing and analysis of the digitised image enabled both the sizes of micro-projections and their relative numbers to be determined. Such processing of images of a large number of particles generated a considerable amount of data. An artificial neural network was used to categorise the data and to compare the nature of fretting particles generated by titanium, titanium-molybdenum and stainless steel. Although showing a tendency towards a spherical form, all three metals produced different results, with titanium showing the greatest diversity of textures and sizes, steel the least.

Prevention of severe ovarian hyperstimulation syndrome in IVF with or without ICSI and embryo transfer: a modified 'coasting' strategy based on ultrasound for identification of high-risk patients

Ovarian hyperstimulation syndrome (OHSS) can be a severe and potentially life-threatening complication of ovarian stimulation for IVF. Coasting or withholding gonadotrophin stimulation relies on frequent estimation of serum oestradiol to identify patients at risk. A modified coasting protocol was developed in which identification of patients at risk of severe OHSS was based on ultrasound monitoring. Serum oestradiol concentrations were measured only in patients with >20 follicles on ultrasound (high risk). If serum oestradiol concentrations were <3000 pmol/l, the gonadotrophin dose was maintained; if concentrations were >/=3000 pmol/l but <13200 pmol/l and >/=25% of the follicles had a diameter of >/=13 mm, the gonadotrophin dose was halved; and if serum oestradiol concentrations were >/=13 200 pmol/l and >/=25% of the follicles had a diameter of >/=15 mm, patients were coasted. In the latter group, human chorionic gonadotrophin (HCG) 10000 IU was administered when at least three follicles had a diameter of >/=18 mm and serum oestradiol concentrations were <10000 pmol/l. Over a 10 month period, serum oestradiol concentrations were measured in 123 out of 580 cycles (24%) and in 50 cycles, gonadotrophins were withheld. Overall, moderate OHSS occurred in three patients (0.7%) and severe OHSS in one patient (0.2%). The pregnancy rates in the cycles where the gonadotrophin dose was reduced or withheld were 39.6 and 40% per cycle respectively; corresponding implantation rates were 30.7 and 25.6%. It is concluded that the modified coasting strategy is associated with a low risk of moderate and severe OHSS to a minimum without compromising pregnancy rates. Identification of patients at risk by ultrasound reduces the number of serum oestradiol measurements and thus inconvenience to patients as well as costs and workload.

Does laparoscopic ovarian diathermy affect the outcome of IVF-embryo transfer in women with polycystic ovarian syndrome? A retrospective comparative study

Controlled ovarian stimulation for IVF and embryo transfer and outcome parameters were compared retrospectively in 31 women with clomiphene-resistant polycystic ovarian syndrome (PCOS). Of these women, 15 had previously undergone laparoscopic ovarian diathermy before IVF (group A, total 22 cycles) and 16 had not had surgical treatment (group B, total 24 cycles). No statistically significant differences were observed in the number of oocytes retrieved, although the number of embryos available for transfer was significantly higher in group B (7.1 +/- 3.8 versus 4.6 +/- 2.7, P < 0.01). The clinical pregnancy rate per embryo transfer appeared to be higher in group B (63.2 versus 41.2%), as did the miscarriage rate (66.7 versus 28.6%), giving an apparent improved ongoing pregnancy rate per embryo transfer in group A (29.4 versus 10.5%), but this was not statistically significantly different. The incidence of severe ovarian hyperstimulation syndrome (OHSS) was apparently higher in group B (4.2 versus 0%), but this difference was not statistically significant. No cases of severe OHSS were seen in group A. Ovarian diathermy does not appear to have a deleterious effect on controlled ovarian stimulation, and the outcome of IVF-embryo transfer may be beneficial in decreasing the risk of severe OHSS and improving the ongoing clinical pregnancy rate.

Loss of genomic methylation causes p53-dependent apoptosis and epigenetic deregulation

Cytosine methylation of mammalian DNA is essential for the proper epigenetic regulation of gene expression and maintenance of genomic integrity. To define the mechanism through which demethylated cells die, and to establish a paradigm for identifying genes regulated by DNA methylation, we have generated mice with a conditional allele for the maintenance DNA methyltransferase gene Dnmt1. Cre-mediated deletion of Dnmt1 causes demethylation of cultured fibroblasts and a uniform p53-dependent cell death. Mutational inactivation of Trp53 partially rescues the demethylated fibroblasts for up to five population doublings in culture. Oligonucleotide microarray analysis showed that up to 10% of genes are aberrantly expressed in demethylated fibroblasts. Our results demonstrate that loss of Dnmt1 causes cell-type-specific changes in gene expression that impinge on several pathways, including expression of imprinted genes, cell-cycle control, growth factor/receptor signal transduction and mobilization of retroelements.

Patients with diagnosed diabetes mellitus can be accurately identified in an Indian Health Service patient registration database

OBJECTIVE

The computerized patient registration databases maintained by the Indian Health Service (IHS) represent a potentially important source of data about the epidemic of diabetes among American Indian and Alaskan Native people. The purpose of this study is to determine the accuracy of this data source, and to identify the optimal search criteria to identify patients with a diagnosis of diabetes in an IHS patient registration database.

METHODS

The authors compared the results of a series of computerized searches to a "gold standard" sample of 465 manually reviewed charts from a large IHS facility.

RESULTS

Among patients ages 15 years and older, the best criterion for identifying patients diagnosed with diabetes was the presence of at least one purpose of visit narrative identified by a 250.00 to 250.93 ICD-9 code. The presence of a single computerized code for diabetes identified patients with diagnosed diabetes with a sensitivity of 92% (95% confidence interval [CI] 81, 97), a specificity of 99% (95% CI 98, 99), and a calculated positive predictive value of 94% (95% CI 85, 99). In a separate chart review of 462 charts of patients who had at least one 250.00 to 250.93 ICD-9 code recorded in the database, 435 had a diagnosis of diabetes for an observed positive predictive value of 94%. Because the prevalence of diabetes varies by age of the patient, the positive predictive value of the ability to identify patients with diabetes also varies by age.

CONCLUSION

A computerized search of an IHS patient database can identify patients with a diagnosis of diabetes with an accuracy that is similar to the reported accuracy from other health care system databases.

Correlation between the immune responses to collagens type I, III, IV and V and Klebsiella pneumoniae in patients with Crohn's disease and ankylosing spondylitis

BACKGROUND

Increased levels of collagen types I, III and V are found in strictures of patients with Crohn's disease (CD) compared with normal gut tissue. Type IV collagen is present in the basement membranes, basal lamina, retina and cornea. Elevated levels of antibody to Klebsiella pneumoniae are found in both active CD and active ankylosing spondylitis (AS) patients compared with healthy controls.

METHODS

Reactivities for immunoglobulin class-specific antibodies (IgM, IgG and IgA) against collagen types I, III, IV, V and whole K. pneumoniae were measured by ELISA in nine patients with early CD and 10 with late CD from King's College Hospital and 12 late CD patients and 36 HLA-B27-positive AS patients from Middlesex Hospital and was compared with values for 26 healthy controls from the Blood Transfusion Service in London.

RESULTS

Levels of class-specific IgM, IgG and IgA antibodies to collagen types I, III, IV, V and K. pneumoniae were significantly elevated in early and late CD patients compared with healthy controls (P<0.001). Levels of IgM, IgG antibody to the four collagen types and K. pneumoniae were also significantly elevated (P<0.001) in AS patients compared with healthy controls. In addition, the level of IgA antibody to K. pneumoniae was elevated in AS patients (P<0.001). Furthermore, a positive correlation between antibody levels to collagen types I, III, IV and K. pneumoniae was demonstrated in both early and late CD patients and in those with AS, whilst a positive correlation to type V was found in early CD.

CONCLUSION

The role of K. pneumoniae and anti-collagen antibodies in the aetiopathogenesis of CD and AS requires further study.

Genetic diversity in Proteus mirabilis isolates found in the urinary tract of rheumatoid arthritis patients

OBJECTIVE

Elevated levels of anti-Proteus antibodies but not antibodies to E. coli have been reported in patients with rheumatoid arthritis (RA). The suggestion has been made that P. mirabilis may have a role in the aetiopathogenesis of rheumatoid arthritis. The aim of this study was to determine whether there are differences at the genetic level inisolates of P. mirabilis obtained from controls and RA patients.

METHODS

A blind study was performed whereby P. mirabilis isolates obtained from urinary cultures of RA patients and controls were analysed using RAPD PCR. Isolates were then grouped on the basis of their DNA band profile after agarose gel electrophoresis, thereby allowing the composition of the Proteus population in the urinary tract to be analysed at the genetic level.

RESULTS

Fourteen different DNA band profiles were obtained from the 93 isolates tested: 70% of these isolates fell into only five of the 14 groups and approximately 25% of all isolates fell into one group. No differences were observed in the frequency of isolates from either control or RA subjects.

CONCLUSIONS

There is genetic diversity in P. mirabilis populations found in the urinary tract, but there are no differences in the frequency of these bacteria between RA patients and controls.

Tris(2-methylphenyl)phosphonium tetrachloroborate

The title compound, C(21)H(22)P(+).BCl(4)(-), is the first structurally characterized example of the [HP(o-tolyl)(3)](+) cation, presented here with BCl(4)(-) as the counter-ion. The cation has a near-tetrahedral P atom and the BCl(4)(-) anion is near-tetrahedral at boron. There are no unusually short cation-anion contacts.

Complications of ocular paintball injuries in children

PURPOSE

To evaluate the ocular complications of paintball injuries in children.

METHODS

The clinical course of four children with traumatic ocular paintball injuries was evaluated. All patients underwent a complete ocular examination. Their age, injuries sustained, surgical procedure(s) performed, presence of protective eyewear at the time of injury, and final visual outcome was assessed. The presence of directly related anterior and posterior segment abnormalities were also evaluated.

RESULTS

Four boys sustained traumatic paintball injuries. Average patient age was 11.25 years (range: 10-12 years). None of the children were wearing ocular or facial protection at the time of the initial injury. All patients had hyphema and traumatic cataract, and some form of retinal pathology (vitreous hemorrhage, epiretinal membrane, retinal hemorrhage, and choroidal rupture). One child had a partial-thickness corneal laceration that did not require surgical intervention. All other patients underwent ophthalmic surgery. Final visual acuity was 20/30 or better in two patients, and 20/100 or worse in the others. The cause of decreased visual acuity in these children was directly related to macular pathology.

CONCLUSION

Ocular injuries resulting from paintball impact are often severe and usually occur when the participants are not wearing eye protection or this protection becomes dislodged. Treatment of these injuries is sometimes limited to an attempt to salvage what remains of useful vision. Unfortunately, most of these sports-related injuries could have been prevented if patients wore adequate eye protection when involved in this sport.

The nurse's role in misoprostol induction: a proposed protocol

The use of misoprostol (PGE 1) for induction of labor has been studied in the United States since 1993. The current medical literature contains studies of this non-FDA-approved indication for misoprostol. The data reveal that misoprostol is as effective or more effective in inducing labor as are oxytocin and prostaglandin E2 (PGE 2), with less cost. Nurses need to understand the physiology of prostaglandins and management of misoprostol in labor. Nurses often must assess the safety of mother and fetus during a misoprostol induction without a protocol based on research findings. This article presents a sample protocol.

Role of SRP19 in assembly of the Archaeoglobus fulgidus signal recognition particle

Previous studies have shown that SRP19 promotes association of the highly conserved signal peptide-binding protein, SRP54, with the signal recognition particle (SRP) RNA in both archaeal and eukaryotic model systems. In vitro characterization of this process is now reported using recombinantly expressed components of SRP from the hyperthermophilic, sulfate-reducing archaeon Archaeoglobus fulgidis. A combination of native gel mobility shift, filter binding, and Ni-NTA agarose bead binding assays were used to determine the binding constants for binary and ternary complexes of SRP proteins and SRP RNA. Archaeal SRP54, unlike eukaryotic homologues, has significant intrinsic affinity for 7S RNA (K(D) approximately 15 nM), making it possible to directly compare particles formed in the presence and absence of SRP19 and thereby assess the precise role of SRP19 in the assembly process. Chemical modification studies using hydroxyl radicals and DEPC identify nonoverlapping primary binding sites for SRP19 and SRP54 corresponding to the tips of helix 6 and helix 8 (SRP19) and the distal loop and asymmetric bulge of helix 8 (SRP54). SRP19 additionally induces conformational changes concentrated in the proximal asymmetric bulge of helix 8. Selected nucleotides in this bulge become modified as a result of SRP19 binding but are subsequently protected from modification by formation of the complete complex with SRP54. Together these results suggest a model for assembly in which bridging the ends of helix 6 and helix 8 by SRP19 induces a long-range structural change to present the proximal bulge in a conformation compatible with high-affinity SRP54 binding.

Effect of chronic fluoride exposure in uremic rats

This study was conducted to test the hypothesis that the margin of safe fluoride exposure is narrowed in rats that are physiologically compromised by renal dysfunction. The study objective was to determine whether increases in fluoride retention and tissue fluoride levels in rats with surgically induced renal insufficiency result in toxic fluoride effects not ordinarily observed in healthy animals. Uremic and sham-operated control rats received 0 microg/ml, 5 (0.26 mmol/l), 15 (0.79), or 50 microg/ml (2.63 mmol/l) of fluoride in their drinking water for 3 or 6 months. Fluoride retention was monitored, and, following euthanasia, tissue fluoride and biochemical markers of tissue function were analyzed. Selected tissues were saved for histology, and bone marrow cells were harvested for determining the frequency of sister chromatid exchange, a marker of genetic damage. In spite of significantly higher levels of fluoride in the tissues of the animals with renal insufficiency, there were no clinically adverse, fluoride-induced, extraskeletal physiological, biochemical, or genetic effects of chronic exposure to common levels of fluoride in these rats.

Differential cytokeratin and glycoconjugate expression by the surface and crypt epithelia of human palatine tonsils

Human palatine tonsils are clinically important due to their susceptibility to tonsillitis and association with other local and systemic diseases. Paradoxically, the tonsils function as antigen sampling sites of the mucosal immune system and, consequently, the tonsil epithelia perform both protective and antigen sampling roles. These epithelia are divided into stratified squamous epithelium overlying the tonsil surface and crypt epithelium lining the tonsil crypts, the latter of which includes reticular areas which are infiltrated by lymphocytes and are responsible for antigen sampling. In this study we characterised cytokeratin and glycoconjugate expression by healthy epithelia of human palatine tonsils. We identified pan-epithelial tonsil markers and also demonstrated that the surface and reticular crypt epithelia are differentiated by the expression of multiple cytokeratins. The latter finding supports the hypothesis that these epithelia undergo alternate differentiation pathways and possess different functional roles. In addition, we identified cell subpopulations in the tonsil epithelia which may represent distinct cell subtypes including specialised antigen sampling cells. These findings establish a basis for future studies to investigate histochemical changes in tonsil epithelia that are associated with or predispose to local and/or systemic disease.

Molecular mimicry between HLA-DR alleles associated with rheumatoid arthritis and Proteus mirabilis as the Aetiological basis for autoimmunity

Molecular mimicry is one of the pathological mechanisms proposed to explain the association between microorganisms and autoimmune diseases. This review deals with the association between bacteria and rheumatic diseases with a special emphasis on rheumatoid arthritis where upper urinary tract infection by Proteus mirabilis is the possible cause of this severe, arthritic condition. Prospective trials involving anti-Proteus therapy should be carried out.

New world views: preparing physicians in training for global health work

BACKGROUND AND OBJECTIVES

To determine the impact of international health experiences on physicians in training, we studied 60 US medical students who participated in an International Health Fellowship Program (IHFP).

METHODS

In 1995 and 1996, US medical students were selected to participate in the IHFP, which included training at three US medical schools and at seven medical schools in developing countries. The program included a 2-week preparatory course at a US school and a 6- to 8-week field experience. Evaluative data were collected prior to the course, after the course, after the field experience, and 1-2 years later.

RESULTS

A total of 60 students were selected from 145 applicants. At the end of the fellowship, a majority of participants noted that the exposure affected them in the following ways: changed world views; increased cultural sensitivity; enhanced community, social, and public health awareness; enhanced clinical and communication skills; more appropriate resource utilization; changes in career plans; and a greater understanding of the challenges of working in areas with scarce resources. After the international field experience, students more strongly agreed with the importance of oral rehydration, communication skills, and patient education. According to student self-assessments, the IHFP significantly improved core medical skills. Ninety-six percent of participants recommended international health experiences for other students.

CONCLUSIONS

This study of IHFP fellows demonstrates multiple significant impacts of international health experiences on US medical students in training. The knowledge, attitudes, and skills gained through international health experiences are important for medical practice in the United States and abroad. Given the high interest of medical students in international health and the potential for positive educational impacts, medical schools should increase the availability of high-quality international experiences.

2.8 A crystal structure of the malachite green aptamer

Previous in vitro selection experiments identified an RNA aptamer that recognizes the chromophore malachite green (MG) with a high level of affinity, and which undergoes site-specific cleavage following laser irradiation. To understand the mechanism by which this RNA folds to recognize specifically its ligand and the structural basis for chromophore-assisted laser inactivation, we have determined the 2.8 A crystal structure of the aptamer bound to tetramethylrosamine (TMR), a high-affinity MG analog. The ligand-binding site is defined by an asymmetric internal loop, flanked by a pair of helices. A U-turn and several non-canonical base interactions stabilize the folding of loop nucleotides around the TMR. The aptamer utilizes several tiers of stacked nucleotides arranged in pairs, triples, and a novel base quadruple to effectively encapsulate the ligand. Even in the absence of specific stabilizing hydrogen bonds, discrimination between related fluorophores and chromophores is possible due to tight packing in the RNA binding pocket, which severely limits the size and shape of recognized ligands. The site of laser-induced cleavage lies relatively far from the bound TMR ( approximately 15 A). The unusual backbone conformation of the cleavage site nucleotide and its high level of solvent accessibility may combine to allow preferential reaction with freely diffusing hydroxyl radicals generated at the bound ligand. Several observations, however, favor alternative mechanisms for cleavage, such as conformational changes in the aptamer or long-range electron transfer between the bound ligand and the cleavage site nucleotide.

Leucovorin and fluorouracil with or without oxaliplatin as first-line treatment in advanced colorectal cancer

PURPOSE

In a previous study of treatment for advanced colorectal cancer, the LV5FU2 regimen, comprising leucovorin (LV) plus bolus and infusional fluorouracil (5FU) every 2 weeks, was superior to the standard North Central Cancer Treatment Group/Mayo Clinic 5-day bolus 5FU/LV regimen. This phase III study investigated the effect of combining oxaliplatin with LV5FU2, with progression-free survival as the primary end point.

PATIENTS AND METHODS

Four hundred twenty previously untreated patients with measurable disease were randomized to receive a 2-hour infusion of LV (200 mg/m(2)/d) followed by a 5FU bolus (400 mg/m(2)/d) and 22-hour infusion (600 mg/m(2)/d) for 2 consecutive days every 2 weeks, either alone or together with oxaliplatin 85 mg/m(2) as a 2-hour infusion on day 1.

RESULTS

Patients allocated to oxaliplatin plus LV5FU2 had significantly longer progression-free survival (median, 9.0 v 6.2 months; P =.0003) and better response rate (50.7% v 22.3%; P =.0001) when compared with the control arm. The improvement in overall survival did not reach significance (median, 16.2 v 14.7 months; P =. 12). LV5FU2 plus oxaliplatin gave higher frequencies of National Cancer Institute common toxicity criteria grade 3/4 neutropenia (41. 7% v 5.3% of patients), grade 3/4 diarrhea (11.9% v 5.3%), and grade 3 neurosensory toxicity (18.2% v 0%), but this did not result in impairment of quality of life (QoL). Survival without disease progression or deterioration in global health status was longer in patients allocated to oxaliplatin treatment (P =.004).

CONCLUSION

The LV5FU2-oxaliplatin combination seems beneficial as first-line therapy in advanced colorectal cancer, demonstrating a prolonged progression-free survival with acceptable tolerability and maintenance of QoL.

A water channel in the core of the vitamin B(12) RNA aptamer

BACKGROUND

The 3.0 A crystal structure of the vitamin B(12) RNA aptamer revealed an unusual tertiary structure that is rich in novel RNA structural motifs. Important details of the interactions that stabilize noncanonical base pairing and the role of solvent in the structure were not apparent owing to the limited resolution.

RESULTS

The structure of the vitamin B(12) RNA aptamer in complex with its ligand has been determined at 2.3 A resolution by X-ray crystallography. The crystallographic asymmetric unit contains five independent copies of the aptamer-vitamin B(12) complex, making it possible to accurately define well-conserved features. The core of the aptamer contains an unusual water-filled channel that is buried between the three strands of an RNA triplex. Well-ordered water molecules positioned within this channel form bridging hydrogen bonds and stabilize planar base triples that otherwise lack significant direct base-base contacts. The water channel terminates at the interface between the RNA and the bound ligand, leaving a pair of water molecules appropriately positioned to hydrogen bond with the highly polarized cyanide nitrogen of vitamin B(12). Analysis of the general solvation patterns for each nucleotide suggests that water molecules are not precisely positioned, as observed in previous RNA duplex structures, but instead might adjust in response to the varying local environment. Unusual intermolecular base pairing contributes to the formation of three different dimerization contacts that drive formation of the crystal lattice.

CONCLUSIONS

The structure demonstrates the important role of water molecules and noncanonical base pairing in driving the formation of RNA tertiary structure and facilitating specific interactions of RNAs with other molecules.