Replication of the linear chromosomal DNA from the centrally located oriC of Streptomyces ambofaciens revealed by PFGE gene dosage analysis

From a cosmid clone of Streptomyces ambofaciens containing the dnaA and gyrAB genes, a 2.7-kb self-replicating DNA fragment containing the chromosome replication origin oriC was isolated. This cosmid was previously maped physically to a region near the middle of the 8-Mb linear chromosomal DNA. A pulsed-field gel electrophoresis time-course analysis revealed that sequences flanking oriC were overrepresented relative to the rest of the chromosomal DNA during rapid growth, indicating that this origin is active. In addition, the terminal regions of the chromosomal DNA showed a slight overrepresentation at the onset of stationary phase.

Evidence for the absolute conformational specificity of the intestinal H+/peptide symporter, PEPT1

This study was initiated to determine whether the intestinal H+/peptide symporter PEPT1 differentiates between the peptide bond conformers of substrates. We synthesized a modified dipeptide where the peptide bond is replaced by the isosteric thioxo peptide bond. The Ala-Pro derivative Ala-psi[CS-N]-Pro exists as a mixture of cis and trans conformation in aqueous solution and is characterized by a low cis/trans isomerization rate. The compound was recognized by PEPT1 with high affinity. The Ki value of Ala-psi[CS-N]-Pro for the inhibition of the uptake of radiolabeled glycylsarcosine in Caco-2 cells was 0.30 +/- 0.02 mM, determined in solution with 96% trans conformation. In contrast, the Ki value was 0.51 +/- 0.02 mM when uptake media with 62% trans conformer were used. We conclude that only the trans conformer interacts with the transport system. From our data, a significant affinity of the cis conformer at PEPT1 cannot be derived. In a second approach, conformer-specific uptake of Ala-psi[CS-N]-Pro was studied by analyzing the intracellular content of Caco-2 cells following transport as well as the composition of the extracellular medium using capillary electrophoresis. The percentage of trans conformer that was 62% in the uptake medium increased to 92% inside the cells. This is the first direct evidence that an H+/peptide cotransport system selectively binds and transports the trans conformer of a peptide derivative.

Giant cephalhaematoma in a 17-year-old boy with Ehlers-Danlos syndrome

We report a case of giant cephalhaematoma in a 17-year-old boy with Ehlers-Danlos syndrome. This haematoma occurred after a minor head injury. It increased in size, immediately after needle aspiration and was responsible for considerable blood loss. Possible physiopathological mechanisms and treatment modalities are discussed.

Analytical validation of the BEM--application of the BEM to the electrocardiographic forward and inverse problem

The objective of this study is to analytically validate a boundary element (BE) formulation for the relationship between the transmembrane potential on the heart's surface and the potential on the body surface applying a concentric spherical test geometry. The relative difference (reldif) between the potential on the outer sphere of the test geometry computed analytically and numerically is determined by 3.59% for the coarse discretization (48 BEs) and by 0.46% in the case of the finer subdivision (192 BEs). In the inverse problem, the transmembrane potential on the inner sphere is estimated numerically from the electric potential on the outer sphere by using a minimum-norm least-square approach. The relative differences found are 20.2% when no measurement noise is added and 26.4% in the presence of 2% additional Gaussian noise. The BE formulation is also applied to real world data for solving the electrocardiographic inverse problem. A normal volunteer's inhomogeneous thorax (outer thorax surface, surfaces of the lungs, epicardial heart surface) is modelled by 424 BEs. The same inverse method is then applied in order to reconstruct the transmembrane potential on the epicardium from the measured body surface potential (BSP) data during normal ventricular depolarisation.

Separation of cis/trans conformers of human and salmon calcitonin by low temperature capillary electrophoresis

Conformer-specific recognition of peptides and proteins has often been proved with the aid of indirect methods. Here we provide an analytical approach for a direct investigation of separated isomers. Cis/trans conformers of the peptide hormones human (hCT) and salmon (sCT) calcitonin exhibit different migration properties in capillary zone electrophoresis at subambient temperatures. Calcitonin consists of 32 amino acids with two proline residues incorporated. It is the longest unstructured peptide for which a conformer separation by capillary electrophoresis has yet been achieved. Lowering the temperature yielded a splitting into two and three peaks for sCT and hCT, respectively, in acidic buffer. The peak ratios of 66:34 for sCT and 71:23 for hCT are in good agreement with the conformer distribution previously reported from nuclear magnetic resonance (NMR) studies. The addition of different organic modifiers (5-20% v/v) to the running buffer does not improve the separation. The observed merging of conformer peaks in buffer containing 20% v/v 2,2,2-trifluoroethanol (TFE) is attributed to structure formation.

Consanguinity in question in two patients with congenital adrenal hyperplasia who bear an identical first and last name--second look

Two patients with identical first and last name, both suffering from Congenital Adrenal Hyperplasia due to 21-hydroxylase deficiency, were investigated in our endocrine outpatient unit. The families of the two girls did not know of each other's existence. Although paternal ancestors were identified up to the 11th and 9th previous generations, respectively, and a common area of origin, roughly 50 km apart, in the northwestern part of the Czech Republic (formerly Austrian Silesia) was established, no common ancestor was found. The patients' respective paternal CYP 21B allele was identical. However, by means of analysis of class I-and class II-HLA regions in both patients and their respective parents no common paternal haplotype was established. In order to still postulate consanguinity by the same paternal haplotype it is necessary to assume that two recombinations in the HLA region must have occurred. The probability that these two events have taken place within the past 11 generations is 0.11%.

Double-blind trial of omeprazole and amoxicillin in the cure of Helicobacter pylori infection in gastric ulcer patients. The Ulcer Study Group, Germany

BACKGROUND

Our aim was to investigate the efficacy of omeprazole and amoxicillin in curing Helicobacter pylori infection in gastric ulcer patients.

METHODS

In a double-blind trial 185 H. pylori-positive gastric ulcer patients were prospectively randomized to receive 40 mg omeprazole twice daily and either 750 mg amoxicillin three times daily or 750 mg amoxicillin placebo three times daily on days 1-14, followed by 20 mg omeprazole daily on days 15-56.

RESULTS

Twenty-seven patients were excluded because of lack of compliance or missed follow-up examinations; one patient receiving amoxicillin discontinued treatment owing to side effects. On an intention-to-treat basis, omeprazole/amoxicillin led to cure of H. pylori infection in 67.1% (47 of 70) of patients not using non-steroidal anti-inflammatory drugs (NSAIDs)/aspirin (ASA) and in 46.7% (14 of 30) of those taking NSAIDs/ASA (P < 0.05). With the omeprazole/placebo regimen, H. pylori infection was cured in 8.8% (no NSAIDs), and 0% (NSAIDs).

CONCLUSIONS

The use of NSAIDs/ASA may limit the efficacy of omeprazole/amoxicillin in curing H. pylori infection in gastric ulcer patients.

Buprenorphine maintenance in pregnant opiate addicts

Opioid maintenance agents such as methadone and slow-release morphine have provided beneficial effects in pregnant opioid-dependent women in both themselves and their child. However, one of the major drawbacks involved with these agents is that they cause an increase in the severity of neonatal abstinence syndrome (NAS) when compared to mothers using heroin. Consequently, a trial was performed to investigate the effects of buprenorphine use during pregnancy. A total of nine pregnant opioid-dependent women were transferred from either a mean daily dose of 39.7 mg methadone or 400 mg slow-release morphine to a mean daily dose of 8.1 mg buprenorphine. The buprenorphine-maintained patients were integrated into an already established outpatient maintenance treatment programme covering all aspects of prenatal and perinatal care. Results demonstrated that buprenorphine administration in opioid-dependent pregnant patients is efficacious and well tolerated. Babies born to buprenorphine-maintained patients had birthweight and Apgar scores within the normal range (2,500-4,500 g and 9-10, respectively) and no evidence of opioid-related NAS was observed. The results from this preliminary study indicate the potential for buprenorphine maintenance therapy in pregnant addicts, although further research is required to confirm this hypothesis.

Comparison of buprenorphine and methadone maintenance in opiate addicts

As a maintenance agent for opioid dependency, buprenorphine offers advantages such as a lower level of dependence and minimal withdrawal symptoms, due to its partial agonist properties at the micro-opioid receptor. Previous studies have shown 8 mg sublingual buprenorphine to be equivalent to 60 mg oral methadone in terms of retention rate and opioid-negative urine levels. In a 24-week, ongoing European study, 34 opioid-dependent subjects were assessed; 16 receiving buprenorphine and 18 methadone. A free dosing schedule was used with no upper limit for methadone dosing but with a maximum buprenorphine dose of 8 mg. Screening prior to the study excluded subjects with polysubstance dependence, somatic disease and/or HIV infection. Primary outcome measures were abstinence from other drugs, for which subjects provided weekly urine samples for analysis of opioids, cocaine and benzodiazepines, and retention in treatment. Patients in the buprenorphine group provided a greater proportion of negative urine samples, in particular cocaine-negative samples, compared with the methadone group, although this was not statistically significant. Retention in the buprenorphine group was significantly lower than in the methadone group, suggesting that the 8 mg buprenorphine limit may have biased the results in favour of methadone, and that this dose may have been too low for those subjects with high levels of dependence. However, buprenorphine is clearly effective in the more motivated subjects and further investigation in this subgroup is recommended.

The unified biosocial model of personality in schizophrenia families and controls

This report describes the application of a unified biosocial model of personality developed by C.R. Cloninger to a sample of families identified through a proband with schizophrenia and a sample of controls. Families of schizophrenic patients were ascertained in USA and Austria. We could detect differences between females and males in their response to positive reinforcement (Reward Dependence) and differences between young and old people with respect to the response to new and/or exciting situations (Novelty Seeking). In general, results obtained for individuals from schizophrenia families and controls were similar. These results are not substantially influenced by psychiatric disorders in individuals. Psychiatric diagnosis may have an influence on the third dimension of Cloninger's model, designated Harm Avoidance. Analysis showed that patients with a diagnosis of schizophrenia or from the schizophrenia spectrum try harder to avoid punishment or aversive stimuli than family members with another psychiatric disorder or without a psychiatric diagnosis as well as controls. The results are promising and further research is needed to evaluate the structure of the proposed personality model in families and the relationship of personality to psychiatric status.

Sequence-specific and phosphorylation-dependent proline isomerization: a potential mitotic regulatory mechanism

Pin1 is an essential and conserved mitotic peptidyl-prolyl isomerase (PPIase) that is distinct from members of two other families of conventional PPIases, cyclophilins and FKBPs (FK-506 binding proteins). In response to their phosphorylation during mitosis, Pin1 binds and regulates members of a highly conserved set of proteins that overlaps with antigens recognized by the mitosis-specific monoclonal antibody MPM-2. Pin1 is here shown to be a phosphorylation-dependent PPIase that specifically recognizes the phosphoserine-proline or phosphothreonine-proline bonds present in mitotic phosphoproteins. Both Pin1 and MPM-2 selected similar phosphorylated serine-proline-containing peptides, providing the basis for the specific interaction between Pin1 and MPM-2 antigens. Pin1 preferentially isomerized proline residues preceded by phosphorylated serine or threonine with up to 1300-fold selectivity compared with unphosphorylated peptides. Pin1 may thus regulate mitotic progression by catalyzing sequence-specific and phosphorylation-dependent proline isomerization.

Ro 25-6981, a highly potent and selective blocker of N-methyl-D-aspartate receptors containing the NR2B subunit. Characterization in vitro

The interaction of Ro 25-6981 with N-methyl-D-aspartate (NMDA) receptors was characterized by a variety of different tests in vitro. Ro 25-6981 inhibited 3H-MK-801 binding to rat forebrain membranes in a biphasic manner with IC50 values of 0.003 microM and 149 microM for high- (about 60%) and low-affinity sites, respectively. NMDA receptor subtypes expressed in Xenopus oocytes were blocked with IC50 values of 0.009 microM and 52 microM for the subunit combinations NR1C & NR2B and NR1C & NR2A, respectively, which indicated a >5000-fold selectivity. Like ifenprodil, Ro 25-6981 blocked NMDA receptor subtypes in an activity-dependent manner. Ro 25-6981 protected cultured cortical neurons against glutamate toxicity (16 h exposure to 300 microM glutamate) and combined oxygen and glucose deprivation (60 min followed by 20 h recovery) with IC50 values of 0.4 microM and 0.04 microM, respectively. Ro 25-6981 was more potent than ifenprodil in all of these tests. It showed no protection against kainate toxicity (exposure to 500 microM for 20 h) and only weak activity in blocking Na+ and Ca++ channels, activated by exposure of cortical neurons to veratridine (10 microM) and potassium (50 mM), respectively. These findings demonstrate that Ro 25-6981 is a highly selective, activity-dependent blocker of NMDA receptors that contain the NR2B subunit.

Intramolecular assistance of cis/trans isomerization of the histidine-proline moiety

Peptidyl-prolyl cis/trans isomerization is a slow conformational interconversion in the polypeptide backbone that is frequently rate-limiting in refolding of proteins and is thought to play a role in cellular restructuring of proteins. In order to probe the influence of positively charged amino acids located in sequence segments adjacent to proline, the rotational barriers of Arg-Pro- and His-Pro-containing peptides were determined by isomer-specific proteolysis and dynamic NMR spectroscopy for Suc-Ala-His-Pro-Phe-NH-Np, Ac-Ala-Arg-Pro-Ala-Lys-NH2, Ac-Ala-His-Pro-Ala-Lys-NH2, angiotensin III, thyrotropin-releasing hormone (TRH), and [His(3-Me)2]TRH in aqueous solution. In contrast to the guanidinium group of arginine, the protonated side chain of histidine preceding proline led to an acceleration of the prolyl isomerization up to 10-fold relative to the unprotonated state. Both arginine and histidine residues succeeding proline in an amino acid sequence proved to be ineffective. Under basic and acidic conditions the kinetic solvent deuterium isotope effects Kc-->tH20/Kc-->tD20 for angiotensin III were 1.0 +/- 0.1 and 2.0 +/- 0.1, respectively. The results are interpreted in terms of intramolecular general acid catalysis of prolyl bond rotation by the imidazolium group that is without precedent in intermolecular catalysis.

Catalysis of protein folding by parvulin

Recently a new family of prolyl isomerases was discovered, which is unrelated with the cyclophilins or the FK-506 binding proteins. Parvulin, the smallest member of this new family, is a protein with only 92 residues, but parvulin-like domains occur in several large proteins that are apparently involved in protein folding or activation processes. We show here that, in addition to its activity in assays with proline-containing tetrapeptides, parvulin catalyzes the proline-limited folding of a variant of ribonuclease T1 with a kcat/Km value of 30,000 M-1 s-1. This value is much smaller than the kcat/Km value of 1.1x10(7) M-1 s-1 determined for the parvulin-catalyzed prolyl isomerization in the tetrapeptide succinyl-Ala-Leu-Pro-Phe-4-nitroanilide. Parvulin itself unfolds and refolds reversibly in a simple two-state reaction with a Gibbs free energy of stabilization of 28 kJ/mol at 10 degrees C. Most of the unfolded parvulin molecules refold in a slow reaction that involves prolyl isomerization and is catalyzed by cyclophilin, another prolyl isomerase. Moreover, parvulin accelerates its own refolding in an autocatalytic fashion, and the rate of refolding increases tenfold when the concentration of parvulin is increased from 0.5 to 3.0 microM. Apparently, small single-domain prolyl isomerases catalyze prolyl isomerization much better in short peptides than in protein folding reactions, presumably because the prolyl bonds are less accessible in refolding protein chains. It is possible that the additional domains of the large prolyl isomerases improve the affinity for protein substrates.

A protease-free assay for peptidyl prolyl cis/trans isomerases using standard peptide substrates

Peptidyl prolyl cis/trans isomerases (PPIases) are ubiquitous and abundant enzymes catalyzing peptide bond cis/trans isomerization adjacent to proline in peptides and proteins. An uncoupled protease-free assay of PPIase activity has been developed using the standard tetrapeptide substrates of the proteolytically coupled test system. Differences in the UV/vis absorption spectra of cis and trans conformations of Suc-Ala-Xaa-Pro-Phe-(Y-) anilide (Xaa = Ala, Leu, Phe; Y = 4-nitro, 2,4-difluoro) were exploited to monitor the time course of the cis/trans isomerization subsequent to a solvent jump from 0.47 M LiCl/trifluoroethanol into aqueous solution. The utility of the assay has been demonstrated by the determination of the Michaelis-Menten constants of cytosolic cyclophilin (Cyp18) and of the proteolytically sensitive FK506-binding protein-like PPIase SlyD from Escherichia coli. Furthermore, similar inhibition constants were estimated for the reversible inhibition of human Cyp18 by cyclosporin A (CsA) with both the proteolytically coupled and the novel uncoupled PPIase assay.

Genetic instability and its possible evolutionary implications on the chromosomal structure of Streptomyces

Recent progress in the understanding of the chromosomal rearrangements in Streptomyces has allowed us to envisage the possible involvement of genetic instability in the evolution of the chromosomal structure. The characterization of recombinational events in the terminal parts of the S ambofaciens chromosome, as well as the observation by other groups that linear plasmids and chromosomes are able to interact, would provide an explanation for the very high levels of polymorphism seen in the terminal inverted repeats of different strains of Streptomyces.

A time-resolved FTIR difference study of the plastoquinone QA and redox-active tyrosine YZ interactions in photosystem II

In this paper, we present the first time-dependent measurements of flash-induced infrared difference spectra of photosystem II (PSII) using Fourier transform infrared (FTIR) spectroscopy. With this experimental approach, we were able to obtain the YZoxQA-/YZQA vibrational difference spectrum of Tris-washed, PSII-enriched samples in the absence of hydroxylamine at room temperature (16 +/- 2 degrees C), with a spectral resolution of 4 cm-1 and a temporal resolution of 50 ms. In order to determine the dominant species in the FTIR spectrum at a particular point in time after an excitation flash, the decay kinetics of YZox and QA- were independently monitored by EPR and chlorophyll a fluorescence, respectively, under the same experimental conditions. These measurements confirmed that the addition of DCMU to Tris-washed PSII samples does not significantly affect the YZox decay, but does substantially slow down the QA- decay. By making use of the difference in the decay kinetics using DCMU, the QA-/QA signals could be separated from the YZox/YZ signals and a pure QA-/QA difference spectrum obtained. By comparison of the YZoxQA-/YZQA difference spectrum with the pure QA-/QA difference spectrum, a large differential band at 1706/1699 cm-1 could be identified and associated with YZ oxidation. In contrast, an intense band at 1478 cm-1, whose DCMU-sensitive decay follows the QA- decay based on the chlorophyll a fluorescence measurements, was present in all of the time-resolved spectra. Since no significant reversible Chl+ radicals could be detected by the EPR measurements under our experimental conditions, we confirm that this band most likely arises only from the semiquinone anion QA- [Berthomieu, C., Nabedryk, E., Mäntele, W., & Breton, J. (1990) FEBS Lett. 269, 363-367].

Modular structure of the trigger factor required for high activity in protein folding

The Escherichia coli trigger factor is a peptidyl-prolyl cis/trans isomerase (PPIase) which catalyzes proline-limited protein folding extremely well. It has been found associated with nascent protein chains as well as with the chaperone GroEL. The trigger factor utilizes protein regions outside the central catalytic domain for catalyzing refolding of unfolded proteins efficiently. Here we produced several fragments which encompass individual domains or combinations of the middle FKBP-like domain (M) with the N-terminal (N) and C-terminal (C) regions, respectively. These fragments appear to be stably folded. They show ordered structure and cooperative urea-induced unfolding transitions, and the far-UV CD spectrum of the intact trigger factor is well represented by the sum of the spectra of the fragments. This suggests that the native trigger factor shows a modular structure, which is composed of three fairly independent folding units. In the intact protein there is a slight mutual stabilization of these units. The high enzymatic activity in protein folding could not be restored by fusing alternatively the N or the C-terminal regions to the catalytic domain (in NM and MC constructs, respectively). Surprisingly, the high folding activity of the intact trigger factor has been regained partially by functional complementation of the overlapping NM and MC constructs.

Localized facial flushing in infancy. Auriculotemporal nerve (Frey) syndrome

BACKGROUND

Patients with auriculotemporal nerve syndrome (Frey syndrome) have facial flushing, sweating, or both localized to the distribution of the auriculotemporal nerve that occurs in response to gustatory stimuli. In adults, the syndrome usually results from surgical injury or trauma to the parotid gland. The condition is rare in infants, but usually manifests during infancy with the introduction of solid food, thus leading to the misdiagnosis of food allergy by physicians unfamiliar with the syndrome.

OBSERVATIONS

We describe 8 children with auriculotemporal nerve syndrome who manifested with flushing only. The reaction was erroneously attributed to food allergy in most cases. Six of the 8 patients were delivered with forceps assistance. The remaining 2 patients, with disease onset during the first 3 months of life, had bilateral involvement without known trauma.

CONCLUSIONS

Auriculotemporal nerve syndrome may manifest during infancy as flushing with eating food. In contrast to the syndrome in adults, gustatory sweating is rarely associated. The known use of forceps to assist in the delivery of at least 14 of the 28 previously reported pediatric cases and in 6 of our 8 patients suggests that trauma to the parotid region may be responsible for the condition in most infants, as it is in adults. Auriculotemporal nerve syndrome in infancy should be recognized as a benign condition that often resolves spontaneously. Treatment is ineffective and unnecessary.

Conformational state of a 25-mer peptide from the cyclophilin-binding loop of the HIV type 1 capsid protein

Recently a 25-residue part of Gag polyprotein from HIV type 1 (HIV-1) was reported to bind to the cytosolic 18 kDa cyclophilin (Cyp18) with an IC50 value of 180 microM. This peptide corresponds to the Cyp18-binding domain of HIV-1 Gag. A replacement of Gly with Ala in the cyclophilin-binding loop of HIV-1 Gag polyprotein results in the prevention of the packaging of Cyp18 into virions. We found only two conformers of this peptide among 16 possible expected conformers, owing to cis/trans isomerization of four peptidyl-prolyl bonds. Although this finding implicates the existence of a stabilizing structure, we were not able to detect secondary structure formation by 1H-NMR and CD spectroscopy. We characterized the peptide as a substrate for Cyp18 by two-dimensional exchange 1H-NMR spectroscopy. Surprisingly, we found similar binding characteristics for a peptide corresponding to 25-mer peptide containing the above-mentioned Gly to Ala substitution.