Divergent members of a single autoreactive B cell clone retain specificity for apoptotic blebs

Specificity for double-stranded DNA can arise due to somatic mutations within one of the branches of an autoreactive B cell clone. However, it is not known whether a different autospecificity predates anti-dsDNA and whether separate offshoots of an expanding B cell clone retain or evolve alternative specificities. We compared 3H9, an anti-dsDNA IgG, to 4H8 and 1A11, antibodies produced by hybridomas representing an alternative branch of the 3H9 B cell clone. All three IgG bound chromatin in ELISA and apoptotic cells in confocal microscopy, yet only 3H9 bound dsDNA, as measured by plasmon resonance. Moreover, we demonstrate that despite the unique specificity of 3H9 for dsDNA, all three clone members exhibited indistinguishable binding to chromatin. The binding to chromatin and apoptotic cells was unaffected by N-linked glycosylation in L chain CDR1, a modification that results from a replacement of serine 26 with asparagine in 4H8 and 1A11. These data provide the first evidence that specificity for nucleosome epitopes on apoptotic cells provides the initial positive stimulus for somatic variants that comprise a B cell clone, including those that subsequently acquire specificity for dsDNA. Conversely, selection of autoreactive B cells for binding to apoptotic cells leads to clonal expansion, antibody diversification, and the development of linked sets of anti-nuclear autoantibodies.     

Is there higher percentage of undetected osteopenia and osteoporosis among patients with ulcerative colitis in Saudi Arabia?

Detection of prevalence and development of osteopenia or osteoporosis in patients with inflammatory bowel disease using only bone mineral density could be inappropriate to detect all individuals at risk for osteoporosis. Numerous patients could remain undetected by using only bone mineral density as a screening method, especially in patients with ulcerative colitis. Therefore, trabecular bone score should be used as a complementary method.     

Potential beneficial effects of low molecular weight heparin on cognitive impairment in elderly patients on haemodialysis

Vascular cognitive impairment or mixed vascular cognitive impairment and Alzheimer's disease (AD) appear to be much more common in elderly patients than AD alone. Furthermore, vascular dementia (VaD) and AD are more prevalent in elderly patients receiving haemodialysis (HD), leading to a loss of independence and a poor quality of life. Hypotensive episodes in patients receiving HD contribute to vascular changes in the brain, with consequent progression of VaD and AD. The use of the lowest individually optimized bolus dose of low molecular weight heparin (LMWH) during HD, with fewer hypotensive episodes during and between HD procedures, may exert a sparing effect on changes in microvascular circulation and decrease the incidence of VaD and AD. We believe that long-term use of LMWH, with its direct effect on amyloid β protein (Aβ) in the blood and on Aβ accumulation in the brain and indirect effects on prevention of complement activation, may delay the progression of cognitive impairment in patients receiving HD. There is a need for a robustly designed, prospective trial to evaluate the effects of long-term treatment with LMWH on mild cognitive impairment, VaD and AD in elderly patients receiving maintenance HD.     

Synthesis,characterization and conformational transition in poly(cyclohexylmethyl methacrylate)

Poly(cyclohexylmethyl methacrylate), (poly[1-(cyclohexylmethoxycarbonyl)-1-methylethylene]) was prepared and characterized by osmometric and viscometric measurements. The temperature dependences of the viscosity data and of the refractive index increment of the polymer were investigated in isobutyl methyl ketone solution. A discontinuity of the intrinsic viscosity [η] was observed over the temperature range 5°C – 10°C. Also sharp changes of the unperturbed dimensions parameter K_? and the thermodynamic parameter B from the Stockmayer-Fixman plot were observed in the same temperature range. Similar discontinuities occur with the refractive index increments dn/dc. This phenomenon can be accounted for by assuming conformational changes of the chain in the chosen solvent at a specific temperature range. The results are compared with that obtained in poly(cyclohexyl methacrylate). The influence of the spacer group ? CH₂? in the conformational behaviour of poly(cyclohexylmethyl methacrylate) is analyzed.     

Glucocorticoid receptors in ageing rats

The role of the glucocorticoid receptor (GR) in senescence was studied in rats of increasing age. Statistically significant changes in the number of GRs from rat liver were detected, whereas the affinity for the ligand triamcinolone acetonide (TA) did not change with increasing age, and was in the range of 1–2 nM. In all cases the number of receptors was lower in rats treated with hormone in vivo relative to untreated animals. In addition, we have found changes in GR activation, as measured by the binding to DNA cellulose in the mentioned age groups. Furthermore, expression of the glucocorticoid hormone (GH)-inducible gene, tyrosine amino transferase (TAT) also showed age-related alterations. We conclude that receptor function shows oscillatory changes during ageing. In addition, response to GH generally declines towards the older age. This specific periodicity in functional characteristics of the GR may reconcile conflicting results about the receptor number and properties during the ageing process, and marks particular age at which individual organism shows the highest or the lowest sensitivity to the actions of GH.     

Replication error-positive samples found in pheochromocytomas

Adenomatous polyposis coli, (APC) and E-cadherin (CDH1) tumor suppressor genes were investigated in human pheochromocytoma. Both genes are components of adherens junctions, but are also involved in wnt signalling in which one of the target molecules is c-myc protein. MATERIALS AND METHODS: Fifteen sporadic pheochromocytomas were tested for gene instability by PCR/loss of heterozygosity. Detection of c-myc protein was performed using immunohistochemistry. RESULTS: One sample with allelic imbalance of the APC gene and one with allelic imbalance of the CDH1 gene were found. Interestingly, another type of genomic instability was detected--replication error-positive samples (RER+). Four out of 13 heterozygous samples were RER-positive (30.8%). The instability is the result of impaired cellular mismatch repair. Immunohistochemistry showed increased levels of c-myc in comparison to normal adrenal tissue. CONCLUSION: Our results suggest that microsatellite genetic instabilities of the E-cadherin gene have a role in pheochromocytoma development and progression. Detected instability indicates that mismatch repair may be targeted in pheochromocytoma. Increased expression of c-myc protein as well as allelic imbalances of APC and CDH 1 genes suggest that the wnt signalling pathway may have a role in this malignancy.     

Conformational transition in poly[4-(1,1,3,3-tetramethylbutyl)phenyl methacrylate] and poly(4-tert-butylphenyl methacrylate) in dilute solutions

Temperature dependence of viscosity data and refractive index increment was investigated on two polymers: poly[4-(1,1,3,3-tetramethylbutyl)phenyl methacrylate] ( 1a ) and poly(4-tert-butylphenyl methacrylate) ( 1b ) in dilute solution. A discontinuity in intrinsic viscosity was observed over a narrow temperature range. From this behaviour it was possible to visualize sharp changes of unperturbed dimensions (K_θ) and thermodynamic parameters (B). This phenomenon can be accounted for by assuming conformational changes of the chain in the chosen solvent in a specific temperature range. These changes can be also observed by discontinuities in refractive index increments dn/dc. In the case of 1b the conformational change disappears on addition of a polar solvent (CHCl₃).     

Cancer incidences in the digestive tube: is cobalamin a small intestine cytoprotector?

Malignancies are common in the digestive tube, although with unequal distribution among segments. The aim of this paper was to compare available interpretations of the low cancer incidence in the small bowel and high in the large bowel. Supposed mechanisms include relatively small bacterial population, large secretion of liquid and rapid transit in the small bowel. Small bowel mucosa is the main absorptive part of the digestive tube with absorption rates for various nutrients so high that they can even be considered as clearances from the intestinal content. Consequently, these nutrients are not present in the large bowel. An alternative explanation is that an absorbable protective substance from the intraluminal content, might protect the mucosa from malignant transformations. It can be speculated that if there are any cytoprotective substances in the digested food their effect would be expressed mostly in the absorptive small intestine, leaving the large bowel mucosa unprotected. Vitamin B12 might be a possible candidate for this role. Cobalamin molecules are initially bound to haptocorrin (Hc) in the stomach, but in the small intestine B12 is transferred to intrinsic factor (IF) after the action of pancreatic trypsin on Hc. Cobalamin-IF complexes are absorbed in the terminal ileum leaving only a small fraction of B12 to enter the large bowel. We have tried to summarize available data regarding cancer incidences in digestive tube, segmental length and transit times of tube content. Cancer density is calculated as incidence per length and transit speed as length per transit time. Cancer incidences for seven intestinal segments were considered low if they were below one case per 100 000 inhabitants annually, while the low cancer density meant less than six cases per 100 000 inhabitants per metre. For instance, transverse colon was considered as a high cancer incidence place (2.15 cases), with low cancer density (4.3 cases/m). Transit speed more than 0.3 metre/hour was associated with low cancer incidences (accuracy 0.85) and low cancer density segments (accuracy 1.00). Cobalamin availability showed similar distribution, available in low incidence segments and unavailable in high incidence segments. Experimental studies are needed to quantify B12 availability in the large bowel and to determine whether small amounts of B12-IF or, perhaps, B12-haptocorrin complexes are absorbed by the small bowel mucosa. Without that, no cytoprotective effects of B12 in the digestive tube can be expected.     

A calcium homeostasis model: orchestration of fast acting PTH and calcitonin with slow calcitriol

Calcitriol is in plasma bound to transcalciferin and this results in a long calcitriol half-life in plasma (5-12h). Abundance of bound calcitriol molecules prevents the exact and quick control of its effects and makes it an inert regulator with a time lag between the changes of calcitriol synthesis and its effect on peripheral tissues. The added regulatory inertia is here defined as: calcitriol(bound)/calcitriol(free) and it approaches value of 99. Estrogens increase transcalciferin levels. It is possible that the estrogen-induced increase in the total calcitriol plasma pool makes calcitriol effects even more inert, augmenting and prolonging the calcitriol effects and thus improving calcium balance in women. Since calcitriol synthesis in kidneys depends on the PTH level, it can be assumed that the size of the total calcitriol pool in plasma reflects more the average PTH secretion during previous hours, than the high or low peaks of PTH secretion in the same period. In other words, one or more PTH tides of short duration are followed with a late calcitriol tide that lasts for hours, and even longer lasting rise in calcitriol effects. Bone integrity depends also on the cortisol level. A possible speculation is that the main result of all profound bone effect of hypecortisolemia, might be reduction of the bone amino acids uptake, thus allowing redistribution of available proteins. Both PTH and calcitriol prevent dangerous hypocalcemia. PTH is quick in mobilizing bone calcium, while calcitriol tends to increase absorption of dietary calcium. In case of low or no dietary calcium, calcitriol mobilizes bone calcium and thus increase PTH initiated demineralization. In the case of calcium abundance, increased plasma calcium reduces PTH levels. Calcitriol plasma level (reflecting previous PTH surges) can induce both calcium absorption and bone demineralization. This two-blade action is tuned by calcitonin that reduces osteoclastic bone resorption, allowing bone deposition of abundant calcium. An overnight fast with a reduced absorption of dietary calcium, might decrease plasma calcium below the regulatory set point, inducing an increase in PTH secretion. Increased average nighttime PTH secretion induces more calcitriol to be synthesized in kidneys. The resultant late calcitriol morning and daytime tide would stimulate calcium absorption from gut, or from bone, depending on the availability of dietary calcium. Due to the described time lag in calcitriol effects, increased calcium absorption might continue during daytime, regardless of the plasma calcium level. If plasma calcium is above the set point, calcitonin will allow excess calcium to deposit in bones. A speculation based on this model is that it might be more efficient to avoid calcium rich food for dinner or supper, and to administer calcium supplementation in the morning, during the calcitriol tide.     

Does breast biopsy marker cost and availability influence utilisation in radiology practice?

Introduction

Breast Screen Australia and Breast Screen Aotearoa guidelines recommend breast biopsy marker (BBM) use in indicated patients. This study aims to evaluate whether BBM cost and availability impacts BBM utilisation.

Methods

An online survey was disseminated to radiologists who identified ‘breast imaging’ as their area of practice in the Royal Australian and New Zealand College of Radiologists (RANZCR) customer relationship management system. Survey questions addressed participant demographics and factors relating to BBM use.

Results

Most (92%, 245/266) participants report that BBMs are routinely available at their place of practice. Those employed in private practice were more likely to report that BBMs are not routinely available. 22% (58/266) of radiologists report that BBM cost influences choice of biopsy type (core biopsy vs fine needle aspirate), this finding was more frequent in those employed in private practice. 47% of respondents report that the cost of BBMs is passed on to the patient, with all these respondents employed in a private or mixed private/public setting. Half the respondents (133/266) reported that their decision to use BBMs would be influenced by the availability of insurance coverage to cover BBM costs.

Conclusions

Results suggest that BBM cost and availability influences both choice of biopsy type (core biopsy vs FNA) and choice to use a BBM. Radiologists working in private practice or mixed private/public practice report that BBMs are less likely to be available for use, and that BBM cost is more likely passed to the patient; possibly disadvantaging patients who present to private radiology providers with imaging findings or conditions that would indicate BBM insertion under current national guidelines.