Ethnic differences in calcium, phosphate and bone metabolism.

The prevalence of osteoporosis and the incidence of age-related fragility fracture vary by ethnicity. There is greater than 10-fold variation in fracture probabilities between countries across the world. Mineral and bone metabolism are intimately interlinked, and both are known to exhibit patterns of daily variation, known as the diurnal rhythm (DR). Ethnic differences are described for Ca and P metabolism. The importance of these differences is described in detail between select ethnic groups, within the USA between African-Americans and White-Americans, between the Gambia and the UK and between China and the UK. Dietary Ca intake is higher in White-Americans compared with African-Americans, and is higher in White-British compared with Gambian and Chinese adults. Differences are observed also for plasma 25-hydroxy vitamin D, related to lifestyle differences, skin pigmentation and skin exposure to UVB-containing sunshine. Higher plasma 1,25-dihydroxy vitamin D and parathyroid hormone are observed in African-American compared with White-American adults. Plasma parathyroid hormone is also higher in Gambian adults and, in winter, in Chinese compared with White-British adults. There may be ethnic differences in the bone resorptive effects of parathyroid hormone, with a relative skeletal resistance to parathyroid hormone observed in some, but not all ethnic groups. Renal mineral excretion is also influenced by ethnicity; urinary Ca (uCa) and urinary P (uP) excretions are lower in African-Americans compared with White-Americans, and in Gambians compared with their White-British counterparts. Little is known about ethnic differences in the DR of Ca and P metabolism, but differences may be expected due to known differences in lifestyle factors, such as dietary intake and sleep/wake pattern. The ethnic-specific DR of Ca and P metabolism may influence the net balance of Ca and P conservation and bone remodelling. These ethnic differences in Ca, P and the bone metabolism may be important factors in the variation in skeletal health.

Developmental changes in hypothalamic Kiss1 expression during activation of the pulsatile release of luteinising hormone in maturing ewe lambs.

Onset of puberty is characterised by a marked increase in the frequency of release of gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH). The Kiss1 gene plays a critical role in pubertal development, and its product, kisspeptin, stimulates GnRH and LH release. In the present study, we tested the hypothesis that Kiss1 gene expression in the preoptic area (POA) and hypothalamus increases during maturation of the reproductive neuroendocrine axis in association with increased LH pulsatility. Ovariectomised, oestradiol-replaced lambs were euthanised at 25, 30 and 35 weeks of age. Blood samples were collected before euthanasia to characterise the pattern of LH release. Kiss1 mRNA was detected in coronal sections of the POA and hypothalamus and Kiss1-expressing cells were identified on the basis of silver grain density. The mean number of Kiss1-expressing cells in the POA/periventricular (PeV) areas increased from 25 to 30 weeks of age. No further increase at 35 weeks of age was observed, and the changes in Kiss1 expression in the POA/PeV were independent of changes in LH pulse frequency. The mean number of Kiss1-expressing cells in the arcuate (ARC) nucleus did not differ among age groups, although it was greater in the middle ARC of lambs exhibiting increased frequency of LH release. The density of silver grains per cell did not differ among groups in any of the areas studied. The results obtained indicate that the Kiss1 gene is activated in the POA/PeV and ARC of ewe lambs during juvenile development, and that kisspeptin neurones in the middle ARC, in particular, are involved in the acceleration of pulsatile LH release during maturation of the reproductive neuroendocrine axis in ewe lambs.

Favorable effect of immunomodulator therapy on bone mineral density in multiple sclerosis.

BACKGROUND: Osteoporosis is a complication of multiple sclerosis (MS), especially if corticosteroid therapy is given. Little is known about the effect on bone of immunomodulatory therapy (IMT) for MS. AIM: We sought to evaluate bone mass in patients with MS on IMT. METHODS: We measured bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) in 37 patients with MS who received IMT. Different IMTs were administered: interferon beta-1a in 70%, interferon beta-1b in 27% and Glatiramer in 3%. High-dose pulse corticosteroid therapy (intravenous methylprednisolone 500 mg) was given to 81% ranging from 1 to 17 courses. RESULTS: Both mean BMD Z-score at spine of 0.53 (CI, 0.15-0.92; P = 0.0084) and mean BMD Z-score at femur of 0.72 (CI, 0.42-1.01; P < 0.0001) were significantly greater than zero. CONCLUSIONS: IMT may have a favorable effect on bone in patients with MS even in the presence of pulse steroid therapy.

Myocardial protection using an omega-3 fatty acid infusion: quantification and mechanism of action.

OBJECTIVES: Omega-3 fatty acids exhibit anti-inflammatory, antithrombotic, and antiarrhythmic properties. We investigated the extent and underlying mechanism of protection conferred by a pre-emptive omega-3 infusion in a model of regional cardiac ischemia-reperfusion injury. METHODS: New-Zealand White rabbits received either the omega-3 infusion or a control infusion of 0.9% saline (n = 14 in each group). The large marginal branch of the left coronary artery was occluded for 30 minutes, cardiac function was assessed during 3 hours of reperfusion, and infarct size was measured. Pretreatment-induced alterations in myocardial membrane fatty acid composition and intramyocardial heat shock protein 72 were additionally assessed (n = 5 in each group). Serum markers of myocardial membrane oxidative stress, malonaldehyde and 8-isoprostane, were also determined. Results are expressed as means +/- standard error of the mean and significance was tested with analysis of variance. RESULTS: Pretreatment increased myocardial membrane omega-3 fatty acid content 5-fold, from 0.94% +/- 0.07% in controls to 5.38% +/- 0.44% in the omega-3 group (P < .01), and it produced a 225% elevation of levels of heat shock protein 72 (P = .019) before ischemia-reperfusion. This was associated with a 40% reduction in infarct size (P < .01). Whereas the reperfusion-induced rise in malonaldehyde levels was higher with omega-3 pretreatment, 10.2 +/-1.5 micromol/L versus 6.1 +/- 0.7 micromol/L in controls (P = .04), 8-isoprostanes showed a 9-fold reduction, 679 +/- 190 pg/mL in controls vs 74 +/- 45 pg/mL in the omega-3 group (P = .0077). CONCLUSIONS: A pre-emptive omega-3 infusion significantly reduces infarct size through the dual mechanisms of upregulation of heat shock protein 72, a key preconditioning protein, and a dramatic increase in the omega-3 content of myocardial membranes, which appears to facilitate a shift in oxidant ischemia-reperfusion injury. Further study to optimally shorten the pretreatment regimen for this potentially acceptable infusion will now be pursued.

Physiological tests to predict long-term outcome of total abdominal colectomy for intractable constipation.

OBJECTIVE: Total abdominal colectomy (TAC) for intractable constipation has a variable reported success rate that decreases to 50% beyond 2 yr. We hypothesize that this inconsistent outcome can be explained by a more extensive intestinal involvement in some patients. DESIGN: A consecutive sample of patients with intractable constipation had preoperative evaluations that included both upper and lower GI studies. Stool frequency, constipation, diarrhea, abdominal pain, and laxative or enema requirements were compared before and after operation. The study took place in an academic referral center and included 37 consecutive referred patients with severe intractable constipation and colonic dysmotility documented by radiopaque marker studies. INTERVENTIONS: TAC, with ileoproctostomy in 34 patients and ileostomy in three. MAIN OUTCOME MEASURES: Patients with motility abnormalities only of the lower GI tract were diagnosed as having colonic inertia (CI). Those with motility disorders of both the upper and the lower GI tracts were considered to have generalized intestinal dysmotility (GID) with colon predominance. RESULTS: Twenty-one patients had CI, and 16 had GID. Ninety percent of CI patients undergoing TAC had a successful outcome with a mean of 23 bowel movements (BMs)/wk at a mean follow-up of 7.5 yr. Although 88% of GID patients had initial improvement, with a mean of 19 BMs/wk at 6 months, only 13% had prolonged relief. After 2 yr, nine of the GID patients had recurrent constipation, and three had severe diarrhea. CONCLUSIONS: This study has identified two distinct types of colonic dysmotility, CI and GID. It has demonstrated the long-term success of TAC for CI and the importance of upper GI physiological studies to identify colon-predominant GID, which has a poor long-term response to TAC.

Unusual structure of the exopolysaccharide of Rhizobium leguminosarum bv. viciae strain 248.

The exopolysaccharide from R. leguminosarum bv. viciae strain 248 differs from those of other Rhizobium strains with similar symbiotic behavior. 13C-N.m.r. spectroscopy of fragments generated by partial hydrolysis, together with methylation analysis and 13C-n.m.r. spectroscopy of the enzymically depolymerised exopolysaccharide, indicated the following nonasaccharide repeating-unit: [formula: see text] The locations of the acetyl and 3-hydroxybutanoyl substituents in the exopolysaccharide are assigned provisionally. R. leguminosarum bv. viciae strain 248, cured of its Sym plasmid pRL1JI, synthesised an exopolysaccharide in which the sites and degree of substitution were unchanged. A Tn5 mutant, derived from strain 248 and unable to induce nodules, synthesised small amounts of EPS that lacked galactose.

Induction of pathogenic-like responses in the legume Macroptilium atropurpureum by a transposon-induced mutant of the fast-growing, broad-host-range Rhizobium strain NGR234.

Mutant strain ANU2861, a transposon Tn5 mutant of the fast-growing, broad-host-range Rhizobium strain ANU280 (NGR234 Smr Rfr) overproduces polysaccharide, is an ade auxotroph, and induces poorly developed nodules on Leucaena leucocephala and Lablab purpureus (H.C. Chen, M. Batley, J.W. Redmond, and B.G. Rolfe, J. Plant Physiol. 120:331-349, 1985). Strain ANU2861 cannot form nodules on Macroptilium atropurpureum Urb. (siratro) or on Desmodium intortum and D. uncinatum and the nonlegume Parasponia. The parent strain, ANU280, effectively nodulates all these legume species except Parasponia, on which it forms ineffective nodules. Ultrastructural examination of infection sites on the legume siratro showed that mutant strain ANU2861 caused root hair curling (Hac+ phenotype), some cortical cell division (Noi+), but no infection threads (Inf-). Localized cellular responses, known to occur in phytopathological interactions, were observed in electron micrographs of the epidermal tissue at or near the infection zone after inoculation with strain ANU2861 but not the wild-type parental strain. These include (i) the rapid (within 20 h) accumulation of osmiophilic droplets attached to membranes at potential sites of strain ANU2861 penetration and (after 48 h) in the epidermal cells in the immediate region of the curled root hairs, and (ii) localized cell death of the epidermal cells. In addition, strain ANU2861 can initiate a systemic response in split-root siratro plants which prevents the successful nodulation of strain ANU280. A 6.3-kilobase fragment of wild-type genomic DNA, which includes the site of Tn5 insertion in strain ANU2861, was cloned and introduced to strain ANU2861. All the phenotypic defects of the mutant strain were corrected by the introduction of this DNA fragment. This indicates that the original Tn5 insertion is responsible for the phenotype.

Identification of a nodD-dependent locus in the Rhizobium strain NGR234 activated by phenolic factors secreted by soybeans and other legumes.

Transfer of the strain NGR234nodD 1 gene into the narrow host range R. trifolii strain ANU843 on either a 6.7-kb HindIII or 17-kb XhoI fragment broadens the host range of this bacterium to include the tropical legumes Vigna unguiculata, Glycine ussuriensis, Leucaena leucocephala, and siratro (Macroptilium atropurpureum). Contrary to previous data (Bassam et al. 1986), mutagenesis of the 17-kb XhoI fragment with a mini-Mu lac transposon (Mu dII1734) showed that a functional nodD 1 gene was essential for extended host range. Gene expression studies using both Mu dII1734 fusions and a promoter-cloning vector indicated that several loci, including the nodD 1 gene, are constitutively expressed. No evidence was found for regulation of the strain NGR234 nodD 1 gene by its product. Another locus nod-81, was induced only in the presence of exudates from various plant species, including soybean (Glycine max). Whereas the expression of nod-81 was dependent on the presence of a functional nodD 1 gene product, a regulatory nod-box DNA sequence was not detected 5' to this gene by using available oligonucleotide hybridization probes. The nod-81 locus was induced by genistein, daidzein, naringenin, and coumestrol from both cotyledon and root tissue of freshly germinated soybean seedlings. A broad spectrum of commercially available phenolic compounds stimulated induction of the nod-81 locus, including some that antagonize nod gene induction in other Rhizobium species. The nodD 1 gene product from strain NGR234 was shown to determine the spectrum of compounds that induce nod-81 expression.

Nuclear magnetic resonance spectra of lipoteichoic acid.

Lipoteichoic acid acids with a range of chemical compositions have been studied using 1H; 13C- and 31P-nuclear magnetic resonance. Proton spectroscopy provided a rapid method for demonstrating whether alanine in a sample is covalently bound to the polyglycerophosphate chains and for monitoring hydrolysis of alanine. The nature of sugar substituents can be determined, with some limitations, from the 13C spectra, and the proportions of glycerol residues substituted by alanine and sugar can be measured. The 31P spectra of lipoteichoic acid provided information about both the degree of substitution and the distribution of the substituent along the polyglycerophosphate chain, except when the substituent was galactose. The polyglycerophosphate chains were shown to undergo rapid internal rotation and no evidence for tertiary structure was found either in the presence or absence of magnesium ions. Magnesium ions exchange rapidly between the bound and free state and the binding constant to lipoteichoic acid of 64 M-1 is typical for monophosphates in aqueous solution. There was no evidence that alanine substitution affects the binding constant for magnesium ions.