Biomineralisation by earthworms: an investigation into the stability and distribution of amorphous calcium carbonate

Background Many biominerals form from amorphous calcium carbonate (ACC), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete calcium carbonate granules which contain highly stable ACC. We analysed the milky fluid from which granules form and solid granules for amino acid (by liquid chromatography) and functional group (by Fourier transform infrared (FTIR) spectroscopy) compositions. Granule elemental composition was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and electron microprobe analysis (EMPA). Mass of ACC present in solid granules was quantified using FTIR and compared to granule elemental and amino acid compositions. Bulk analysis of granules was of powdered bulk material. Spatially resolved analysis was of thin sections of granules using synchrotron-based μ-FTIR and EMPA electron microprobe analysis. Results The milky fluid from which granules form is amino acid-rich (≤ 136 ± 3 nmol mg−1 (n = 3; ± std dev) per individual amino acid); the CaCO3 phase present is ACC. Even four years after production, granules contain ACC. No correlation exists between mass of ACC present and granule elemental composition. Granule amino acid concentrations correlate well with ACC content (r ≥ 0.7, p ≤ 0.05) consistent with a role for amino acids (or the proteins they make up) in ACC stabilisation. Intra-granule variation in ACC (RSD = 16%) and amino acid concentration (RSD = 22–35%) was high for granules produced by the same earthworm. Maps of ACC distribution produced using synchrotron-based μ-FTIR mapping of granule thin sections and the relative intensity of the ν2: ν4 peak ratio, cluster analysis and component regression using ACC and calcite standards showed similar spatial distributions of likely ACC-rich and calcite-rich areas. We could not identify organic peaks in the μ-FTIR spectra and thus could not determine whether ACC-rich domains also had relatively high amino acid concentrations. No correlation exists between ACC distribution and elemental concentrations determined by EMPA. Conclusions ACC present in earthworm CaCO3 granules is highly stable. Our results suggest a role for amino acids (or proteins) in this stability. We see no evidence for stabilisation of ACC by incorporation of inorganic components

Relapse after withdrawal from anti-TNF therapy for inflammatory bowel disease: an observational study, plus systematic review and meta-analysis.

Infliximab and adalimumab have established roles in inflammatory bowel disease (IBD) therapy. UK regulators mandate reassessment after 12 months' anti-TNF therapy for IBD, with consideration of treatment withdrawal. There is a need for more data to establish the relapse rates following treatment cessation.This article is freely available via Open Access. Click on the 'Additional Link' above to access the full-text from the publisher's site.Publishe

Excessive leukotriene B4 in nucleus tractus solitarii is prohypertensive in spontaneously hypertensive rats

Inflammation within the brainstem microvasculature has been associated with chronic cardiovascular diseases. We found that the expression of several enzymes involved in arachidonic acid (AA) - leukotriene B4 (LTB4) production was altered in NTS of SHR. LTB4 produced from AA by 5-lipoxygenase (5LOX) is a potent chemoattractant of leukocytes. Leukotriene B4-12-hydroxydehydrogenase (LTB4-12-HD), which degrades leukotriene B4 (LTB4), was down-regulated compared to Wistar-Kyoto rats (WKY). Quantitative RT-PCR revealed that LTB4-12-HD was reduced by 63 and 58% in the NTS of adult SHR and pre-hypertensive (PH) SHR respectively, compared to age-matched WKY rats (n=6). 5LOX gene expression was up-regulated in the NTS of SHR (~50%; n=6). LTB4 levels were increased in the NTS of the SHR (17%; n=10, p<0.05). LTB4 receptors BLT1 (but not BLT2), were expressed on astroglia in the NTS but not neurons or vessels. Microinjection of LTB4 into the NTS of WKY rats increased both leukocyte adherence and arterial pressure for over 4 days (peak: +15 mmHg; P<0.01). In contrast, blockade of NTS BLT1 receptors lowered blood pressure in the SHR (peak: -13 mmHg; P<0.05) but not WKY rats. Thus, excessive amounts of LTB4 in NTS of SHR possibly as a result of up-regulation of 5LOX and down regulation of LTB412-HD, can induce inflammation. Since blockade of NTS BLT1 receptors lowered arterial pressure in the SHR their endogenous activity may contribute to the hypertensive state of this rodent model. Thus, inflammatory reactions in the brainstem are causally associated with neurogenic hypertension

Hypertension is critically dependent on the carotid body input in the spontaneously hypertensive rat

The peripheral chemoreflex is known to be enhanced in individuals with hypertension. In pre-hypertensive (PH) and adult spontaneously hypertensive rats (SHRs) carotid body type I (glomus) cells exhibit hypersensitivity to chemosensory stimuli and elevated sympathoexcitatory responses to peripheral chemoreceptor stimulation. Herein, we eliminated carotid body inputs in both PH-SHRs and SHRs to test the hypothesis that heightened peripheral chemoreceptor activity contributes to both the development and maintenance of hypertension. The carotid sinus nerves were surgically denervated under general anaesthesia in 4- and 12-week-old SHRs. Control groups comprised sham-operated SHRs and aged-matched sham-operated and carotid sinus nerve denervated Wistar rats. Arterial blood pressure was recorded chronically in conscious, freely moving animals. Successful carotid sinus nerve denervation (CSD) was confirmed by testing respiratory responses to hypoxia (10% O(2)) or cardiovascular responses to i.v. injection of sodium cyanide. In the SHR, CSD reduced both the development of hypertension and its maintenance (P < 0.05) and was associated with a reduction in sympathetic vasomotor tone (as revealed by frequency domain analysis and reduced arterial pressure responses to administration of hexamethonium; P < 0.05 vs. sham-operated SHR) and an improvement in baroreflex sensitivity. No effect on blood pressure was observed in sham-operated SHRs or Wistar rats. In conclusion, carotid sinus nerve inputs from the carotid body are, in part, responsible for elevated sympathetic tone and critical for the genesis of hypertension in the developing SHR and its maintenance in later life

Hypertension is critically dependent on the carotid body input in the spontaneously hypertensive rat

The peripheral chemoreflex is known to be enhanced in individuals with hypertension. In pre-hypertensive (PH) and adult spontaneously hypertensive rats (SHRs) carotid body type I (glomus) cells exhibit hypersensitivity to chemosensory stimuli and elevated sympathoexcitatory responses to peripheral chemoreceptor stimulation. Herein, we eliminated carotid body inputs in both PH-SHRs and SHRs to test the hypothesis that heightened peripheral chemoreceptor activity contributes to both the development and maintenance of hypertension. The carotid sinus nerves were surgically denervated under general anaesthesia in 4- and 12-week-old SHRs. Control groups comprised sham-operated SHRs and aged-matched sham-operated and carotid sinus nerve denervated Wistar rats. Arterial blood pressure was recorded chronically in conscious, freely moving animals. Successful carotid sinus nerve denervation (CSD) was confirmed by testing respiratory responses to hypoxia (10% O(2)) or cardiovascular responses to i.v. injection of sodium cyanide. In the SHR, CSD reduced both the development of hypertension and its maintenance (P < 0.05) and was associated with a reduction in sympathetic vasomotor tone (as revealed by frequency domain analysis and reduced arterial pressure responses to administration of hexamethonium; P < 0.05 vs. sham-operated SHR) and an improvement in baroreflex sensitivity. No effect on blood pressure was observed in sham-operated SHRs or Wistar rats. In conclusion, carotid sinus nerve inputs from the carotid body are, in part, responsible for elevated sympathetic tone and critical for the genesis of hypertension in the developing SHR and its maintenance in later life