Author Correction: The solute carrier SLC9C1 is a Na+/H+-exchanger gated by an S4-type voltage-sensor and cyclic-nucleotide binding.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The solute carrier SLC9C1 is a Na+/H+-exchanger gated by an S4-type voltage-sensor and cyclic-nucleotide binding.

Voltage-sensing (VSD) and cyclic nucleotide-binding domains (CNBD) gate ion channels for rapid electrical signaling. By contrast, solute carriers (SLCs) that passively redistribute substrates are gated by their substrates themselves. Here, we study the orphan sperm-specific solute carriers SLC9C1 that feature a unique tripartite structure: an exchanger domain, a VSD, and a CNBD. Voltage-clamp fluorimetry shows that SLC9C1 is a genuine Na+/H+ exchanger gated by voltage. The cellular messenger cAMP shifts the voltage range of activation. Mutations in the transport domain, the VSD, or the CNBD strongly affect Na+/H+ exchange, voltage gating, or cAMP sensitivity, respectively. Our results establish SLC9C1 as a phylogenetic chimaera that combines the ion-exchange mechanism of solute carriers with the gating mechanism of ion channels. Classic SLCs slowly readjust changes in the intra- and extracellular milieu, whereas voltage gating endows the Na+/H+ exchanger with the ability to produce a rapid pH response that enables downstream signaling events.

Historical pollution of seldom monitored trace elements in Sweden--Part A: sediment properties and chronological indicators.

Sediment cores from four small oligotrophic boreal lakes, with minor acidification, in remote regions of central Sweden were used for historical interpretation of their metal content, with focus on Cu, Cd, Pb and Zn in Lake Stensjön, which has the longest sediment record (at least two centuries according to (210)Pb dating). Comparison is made with the other three lakes. Major and trace elements in lake water, porewater and the acid-leached (HNO(3)) solid sediment phase was analysed with ICP-MS. In addition, general lake water chemistry, TOC and principal anions were measured in the aqueous phases. Redistribution processes were interpreted from geochemical modelling. The solid/solution distribution of pe/pH sensitive elements, indicates a minor diagenetic redistribution and the concentration profiles are therefore suitable for chronological evaluation. The ratios of Al, Ti, Sc and V, indicated a qualitative shift of sedimenting material a century ago, which did not have any impact on the retention of trace elements. Lead had a concentration profile, supported by the (206)Pb/(207)Pb ratio, where it was possible to distinguish preindustrial conditions, early industrialisation in Europe, industrialisation in Sweden, and the use of leaded petrol after the Second World War. Cadmium showed a similar concentration pattern. The zinc profile resembled that of cadmium, but with less enrichment. Local lithogenic sources are believed to be quantitatively important. The solid/solution distribution (K(d)) was independent of depth for all four elements. The sediment concentrations of copper and zinc are not related to early industrialisation but its concentration has doubled since the Second World War.

Historical pollution of seldom monitored trace elements in Sweden--Part B: sediment analysis of silver, antimony, thallium and indium.

Sediment cores from four boreal and remote lakes in a south to north transect in central Sweden were analysed for acid leachable silver, antimony, thallium and indium in the solid sediment phase and the corresponding porewater. Dating of the cores was made by their content of acid leachable lead and the (206)Pb/(207)Pb ratio, in one lake also by (210)Pb. The impact of diagenesis on element redistribution in the sediments was included and found to be minor except for thallium. The results show lowered concentrations towards the north and most intense accumulation after the Second World War, which is taken as evidence for atmospheric deposition being the primary source. Indium has declining concentrations in recent strata while silver and antimony increase. Thallium has lowered acid-leachable concentrations in recent strata. For all metals the impact of domestic industrialisation as well as the early industrialisation of central Europe is discernible. Only thallium appears to reach a geological background at depths that correspond to the late 18th century. For the other metals elevated levels are concluded.

Sediment reference concentrations of seldom monitored trace elements (Ag, Be, In, Ga, Sb, Tl) in four Swedish boreal lakes--comparison with commonly monitored elements.

This paper presents reference and recent acid-leachable concentrations of some seldom monitored trace elements (SMTE; Ag, Be, Ga, In, Sb and Tl) in sediments from four boreal oligotrophic lakes in a south to north transect in Sweden. For comparison commonly monitored trace elements (As, Cd, Co, Cr, Cu, Ni, Pb and Zn) are included as well as those of relevance for redistribution processes (Al, Ca, Fe, Mg and Mn). Pore water pH and the corresponding solid/solution distribution coefficients (Kd) indicated that redistribution of the elements due to acidification is minor. The depth of impact was defined as the level in the sediment where the mean values became constant on successive exclusion of metal concentrations in overlying strata. Reference concentrations were calculated below the depth of impact. The present concentration changes are estimated by the ratio between the average concentration above the depth of impact and the reference concentration. Reference concentration ranges for the SMT-elements are (mg/kg, dry wt.): Ag 0.16-0.66; Be 1.6-3.7; Ga 2.0-5.1; In 0.05-0.22; Sb 0.05-0.11 and Tl 0.17-0.70. The concentration ratios for these elements ranged in the two most southern lakes from 1.5 to 4.5 and in the two northern ones from 0.6 to 1.6. A high correlation between Kd for the SMT-elements, and iron, except for Sb and Tl, infer that the biogeochemistry of iron is quantitatively important for the accumulation of these elements. The reference concentration ranges for the commonly monitored trace elements are (mg/kg, dry wt.): As 7.0-29.6; Cd 0.33-0.98; Co 5.7-23.8; Cr 15.2-26.1; Cu 27.6-58.4; Ni 5.4-20.8; Pb 44-96. The corresponding concentration ratios were 1.2-18 (second highest 3.9) in the two most southern lakes and 0.8-1.6 in the two northern ones. Declining ratios were found from south to north, most obvious for cobalt and zinc. The copper ratios did not show a regional pattern, partly because of the impact from old mine waste. Increased concentrations of Ag, Be, Ga, In, Sb and Tl in recent sediments up to 4.5 times the reference levels in combination with the geographical pattern infer an elevated loading of these elements.

Structural basis of pyrimidine specificity in the MS2 RNA hairpin-coat-protein complex.

We have determined the X-ray structures of six MS2 RNA hairpin-coat-protein complexes having five different substitutions at the hairpin loop base -5. This is a uracil in the wild-type hairpin and contacts the coat protein both by stacking on to a tyrosine side chain and by hydrogen bonding to an asparagine side chain. The RNA consensus sequence derived from coat protein binding studies with natural sequence variants suggested that the -5 base needs to be a pyrimidine for strong binding. The five -5 substituents used in this study were 5-bromouracil, pyrimidin-2-one, 2-thiouracil, adenine, and guanine. The structure of the 5-bromouracil complex was determined to 2.2 A resolution, which is the highest to date for any MS2 RNA-protein complex. All the complexes presented here show very similar conformations, despite variation in affinity in solution. The results suggest that the stacking of the -5 base on to the tyrosine side chain is the most important driving force for complex formation. A number of hydrogen bonds that are present in the wild-type complex are not crucial for binding, as they are missing in one or more of the complexes. The results also reveal the flexibility of this RNA-protein interface, with respect to functional group variation, and may be generally applicable to other RNA-protein complexes.

Deletion of a single hydrogen bonding atom from the MS2 RNA operator leads to dramatic rearrangements at the RNA-coat protein interface.

The MS2 coat protein binds specifically to an RNA hairpin formed within the viral genome. By soaking different RNA fragments into crystals of MS2 coat protein capsids it is possible to determine the X-ray structure of the RNA-protein complexes formed. Here we present the structure to 2.85 A resolution of a complex between a chemically modified RNA hairpin variant and the MS2 coat protein. This RNA variant has a substitution at the -5 base position, which has been shown previously to be pyrimidine-specific and is a uracil in the wild-type RNA. The modified RNA hairpin contains a pyridin-4-one base (4one) at this position that lacks the exocyclic 2-oxygen eliminating the possibility of forming a hydrogen bond to asparagine A87 in the protein. The 4one complex structure shows an unprecedented major conformational change in the loop region of the RNA, whereas there is almost no change in the conformation of the protein.

Crystallographic studies of RNA hairpins in complexes with recombinant MS2 capsids: implications for binding requirements.

The coat protein of bacteriophage MS2 is known to bind specifically to an RNA hairpin formed within the MS2 genome. Structurally this hairpin is built up by an RNA double helix interrupted by one unpaired nucleotide and closed by a four-nucleotide loop. We have performed crystallographic studies of complexes between MS2 coat protein capsids and four RNA hairpin variants in order to evaluate the minimal requirements for tight binding to the coat protein and to obtain more information about the three-dimensional structure of these hairpins. An RNA fragment including the four loop nucleotides and a two-base-pair stem but without the unpaired nucleotide is sufficient for binding to the coat protein shell under the conditions used in this study. In contrast, an RNA fragment containing a stem with the unpaired nucleotide but missing the loop nucleotides does not bind to the protein shell.

A 12-residue-long polyleucine tail is sufficient to anchor synaptobrevin to the endoplasmic reticulum membrane.

Synaptobrevin is a tail-anchored protein with a hydrophobic C-terminal transmembrane segment that inserts into the endoplasmic reticulum membrane independently of the SRP/Sec61p pathway. Here, we show that idealized hydrophobic segments composed of 11-17 leucines and 1 valine function as insertion signals in vitro, whereas shorter segments do not. These results suggest that there are no specific requirements beyond overall hydrophobicity for C-terminal endoplasmic reticulum insertion signals.

Effect of milk and fermented milk on iron absorption in ileostomy subjects.

This study was undertaken to determine whether milk with its high calcium content adversely affects the absorption of nonheme iron from the diet as greatly as single-meal studies indicate. Nine ileostomy subjects ate a low-fiber, low-phytate diet for 8 consecutive weeks. During the first and eight weeks they drank a 250-mL soft drink with three main meals and an evening snack each day (0.16 g Ca/d). During the two intervening 3-wk periods, they drank the same amount of low-fat milk or fermented low-fat milk (Verum; Hälsofil, Norrmejerier, Umeä, Sweden) according to a formally randomized crossover design (1.4 g Ca/d). During the last 2 d in each of the four periods, apparent iron absorption (balance) from a test diet together with that period's beverage was measured and the plasma ferritin concentration was determined. There was no decrease in apparent iron absorption during the milk diet periods.

Effects of low-fat milk and fermented low-fat milk on cholesterol absorption and excretion in ileostomy subjects.

OBJECTIVE: To study small bowel cholesterol absorption and sterol excretion in order to explain possible serum cholesterol-lowering mechanisms of low-fat milk products. DESIGN: Two 24-h sterol balance studies with 1 litre of low-fat milk or one litre of fermented milk, in random order, added to a controlled diet. [3H]Cholesterol absorption was measured during each period. The results were compared to those on two 24-h periods with isocaloric amounts of lemonade given to the same basic diet, before and after the study. One litre of the two milk products was also consumed in addition to their normal diets in a cross-over design of 3 weeks and with run-in and run-out periods of 2 weeks each with 1000 ml of lemonade preceding the balance studies: SETTING: Outpatient clinic, where the subjects were eating their meals during the day and ileostomy bags collected. SUBJECTS: Nine ileostomy subjects, who have earlier participated in similar studies, volunteered for the study. All subjects completed the study. RESULTS: Cholesterol absorption was highest (66%) in the lemonade period, intermediate in the low-fat milk period (61%) and lowest in the fermented low-fat period (55%) (P < 0.05 for differences). Net cholesterol excretion (excretion minus intake) and calculated endogenous cholesterol excretion were significantly (P < 0.05 for differences) higher in the low-fat milk period than in the lemonade period and the fermented low-fat milk period. No significant change in serum cholesterol was, however, seen after 3 weeks on each milk regimen. CONCLUSION: Assimilation of cholesterol by microorganisms could possibly explain the reduced uptake of cholesterol with fermented milk. The mechanism behind the increased endogenous cholesterol excretion, induced by low-fat milk, is unclear.

Effects of active addition of bacterial cultures in fermented milk to patients with chronic bowel discomfort following irradiation.

Radiotherapy is a cornerstone in the treatment of malignancies in the pelvis. Consequently, there is usually exposure of the intestine and especially the lower colon and rectum, with ensuing disturbances in bowel habits at different times following radiotherapy. The main problem is diarrhoea associated with lactose intolerance, bile salt absorption and fat malabsorption. Bacterial contamination has also been described. In the present study we have evaluated the influence of the active administration of specific bacterial cultures in fermented milk, which inhibit the growth of potentially pathogenic micro-organisms, to 40 consecutive patients with chronic alteration in their bowel habits caused by previous radiotherapy of pelvic malignancies. The results suggest that intake of fermented milk products could be of value in decreasing chronic bowel discomfort following radiotherapy of pelvic malignancies. However, a more extensive study is warranted in order to very the significance of the results and to find the optimal product.

Is penicillin the appropriate treatment for recurrent tonsillopharyngitis? Results from a comparative randomized blind study of cefuroxime axetil and phenoxymethylpenicillin in children. The Swedish Study Group.

The efficacy of cefuroxime axetil compared with phenoxymethylpenicillin (PcV) was studied in group A beta-haemolytic streptococci (GAS) culture-proven tonsillitis in children aged 3-12 years with a history of at least 1 episode of tonsillopharyngitis requiring antibiotic therapy during the previous 3 months. This was a comparative, randomized, investigator-blind, multicentre study. A total of 236 children received either cefuroxime axetil suspension or PcV syrup. Inclusion criteria were a positive, rapid, group A strep test verified by bacteriological culture and clinical signs and symptoms of tonsillopharyngitis. Cefuroxime axetil treatment gave a significantly higher bacteriological eradication rate and clinical cure rate than PcV. At day 2-5 post treatment the eradication rates were 99/114 (87%) for cefuroxime axetil vs 61/109 (56%) for PcV (p < 0.001). The clinical cure rates were 98/114 (86%) and 73/109 (67%) respectively (p < 0.01). Up to 21-28 days post-treatment, 9/114 (8%) cefuroxime axetil patients and 37/109 (34%) PcV patients were treatment failures or had recurrence/reinfection of GAS tonsillopharyngitis (p < 0.001). More than 90% of the patients who experienced bacteriological treatment failure at either the first or second follow-up had the same serotype isolated pre- and post-treatment. During the study period, 21/114 (18%) patients in the cefuroxime axetil group and 50/109 (46%) patients in the PcV group received additional antibiotics (p < 0.001). No serious adverse events were noted and the mild adverse events were equally distributed among the patients in the 2 study groups: 15% for cefuroxime axetil and 14% for PcV.

Alpha-streptococci as supplementary treatment of recurrent streptococcal tonsillitis: a randomized placebo-controlled study.

Recurrences are a common finding after antibiotic treatment of acute group A streptococcal tonsillitis. This has been attributed to several factors, among others a disturbed normal throat flora and especially a lack of alpha-streptococci. It thus seems logical in patients with recurrent streptococcal tonsillitis, to restore the normal alpha-streptococcal flora by reimplantation of alpha-streptococci. This was performed in a double blinded, randomized, placebo-controlled study. 36 patients with recurrent streptococcal group A tonsillitis were treated with antibiotics followed by either placebo (19 patients) or a pool of 4 selected alpha-streptococcal strains (17 patients) with good interfering activity against clinical isolates of beta-streptococci. No patient recurred during the first 2 months of follow-up in the alpha-treated group, but 7 in those treated with antibiotics and placebo. After 3 months 1 in the patient group treated with antibiotics and alpha-streptococci and 11 in the placebo-treated group recurred. These results are statistically highly significant and show that recolonisation with alpha-streptococci seems to offer a new way to lower the rate of recurrence in streptococcal throat infections.

Interfering alpha-streptococci as a protection against recurrent streptococcal tonsillitis in children.

Recurrent streptococcal tonsillitis/pharyngitis is a great problem, especially in certain epidemiological situations. Patients treated with antibiotics often have a disturbed normal throat flora and may lack, e.g., alpha-streptococci known in vitro to have an interfering activity against group A streptococci. Thirty-one patients with recurrent streptococcal tonsillitis were given antibiotics for 10 days. At the end of this treatment they were sprayed in their mouths with four selected alpha-streptococcal strains known to have strong growth inhibiting activity in vitro against most beta-streptococci group A. The follow-up period after this colonization was 3 months. After alpha-streptococcal treatment, none of the patients attracted a new tonsillitis during the follow-up period while 8% of the controls had a second tonsillitis. Treatment of streptococcal tonsillitis/pharyngitis with antibiotics followed by recolonization with alpha-streptococci seems to hinder further recurrences.

Influence of phenoxymethylpenicillin on the vaginal ecosystem.

The effects of phenoxymethylpenicillin on the bacterial flora of the vagina were investigated in 6 women who fulfilled the criteria of 'normality': predominance of lactobacilli, and absence of Enterobacteriaceae and fungi. Fourteen healthy women were enrolled and followed longitudinally; 8 of these were subsequently excluded because of divergence from normality. Following penicillin treatment, Gram-negative rods appeared in 4 of the remaining 6 women, and in 1 subject heavy growth of Candida albicans resulted. In 5 of the women there was no change in the lactobacillus count and a rise in pH was found in 4 subjects. In 1 woman, lactobacilli disappeared completely and were replaced by Escherichia coli. Concomitantly, high concentrations of endotoxins were found in the vaginal fluid. Treatment with penicillin may interfere with the normal vaginal bacterial flora and provide an environment favorable for Enterobacteriaceae and fungi.