Influence of purinoceptor antagonism on diadenosine pentaphosphate-induced hypotension in anesthetized rats

Diadenosine polyphosphates (ApnA; n = 3-6) are potent vasoactive agents in isolated vessels. Information on effects of ApnA in vivo is still limited despite the fact that these compounds are starting to be used in humans. This study was designed to compare the effects of ApnA and their possible metabolites on blood pressure in vivo and to functionally identify purinoceptors involved in their action. All four ApnA and their degradation products induced a sustained drop of mean arterial blood pressure during i.v. infusion, which was fully reversible. The rank order of potency was Ap4A > or = Ap6A > Ap5A = Ap3A = ATP = ADP > AMP > or = adenosine, suggesting that the hypotensive effect is predominantly evoked by the original dinucleotides and not by their degradation products. The hypotensive effect of Ap5A was reduced by the P2X and P2Y(1) purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, the A(1) purinoceptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, and the A(2) purinoceptor antagonist 3, 7-dimethyl-1-propargylxanthine. The hypertensive effect by the prototype P2X receptor agonist alphabeta-methylene ATP was inhibited by pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, too. Purinoceptor antagonists reduced the maximal effects of the agonists indicating a noncompetitive inhibition. In summary, the reported vasocontractile effect of ApnA seems to be limited to isolated preparations under resting tone conditions; however, the systemic cardiovascular effects of all four ApnA are hypotensive, also making them candidates for blood pressure reduction in humans. These effects are fast in onset and easily reversible. Activation of different purinoceptors in the vasculature (most probably P2Y(1) and A(2) receptors) contributes to the Ap5A-induced decrease of mean arterial blood pressure.

Diadenosine polyphosphates cause contraction and relaxation in isolated rat resistance arteries

The effects of diadenosine polyphosphates (APnA; n = 3-6) and adenine nucleotides on contractile reactivity of isolated rat mesenteric resistance arteries (MrA) and superior epigastric arteries (SEA), which display a dense and sparse autonomic innervation, respectively, were evaluated. All agonists examined, except adenosine and AMP, induced contractions. The rank order of potency was similar in both arteries: alpha,beta-methylene ATP (alpha,beta-meATP) > AP5A > AP6A > AP4A > ATP > ADP > AP3A. Contractions were stable during several minutes in SEA but highly transient in MrA. They were reduced after exposure to 10 microM alpha,beta-meATP and by 10 microM of the P2X antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid. During phenylephrine (10 microM)-induced contractions, the agonists induced a further contraction in SEA. In MrA, however, further contraction was followed by marked relaxation. The rank order of relaxing potency was comparable to that of the contractile potency of agonists. Also, the relaxing effects of APnA were blunted by 10 microM pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid and after exposure to alpha,beta-meATP. In vitro and in vivo sympathectomy with 6-hydroxydopamine and removal of the endothelium did not modify the effects of APnA in MrA. Thus, the contractile effects of APnA in resistance arteries 1) are due to a P2X purinoceptor-mediated stimulation of the smooth muscle; 2) depend on the length of the phosphate chain; and 3) are followed by endothelium-independent relaxing effects in MrA but not SEA, which may involve receptors that are similar to those mediating contraction. The regional heterogeneity of APnA effects cannot be attributed to a direct neurogenic influence.

Regulation of the renal basolateral transport system for organic anions by calcium channel blockers

Calcium channel blockers have been reported to exert multiple effects on renal tubular function. Therefore, the effects of the calcium channel blockers nifedipine and verapamil on the cellular uptake of tritiated para -aminohippuric acid (PAH) into microdissected non-perfused rabbit kidney S2 proximal tubule segments were investigated to study a possible influence of calcium channel blockers on renal PAH transport. Since the tubules were entirely collapsed, the accumulated radioactivity overwhelmingly reflects the transport across the basolateral membrane. Tubular PAH accumulation was increased by 1 and 10 microm verapamil, and by 1 microm nifedipine, but it was unaffected by lower or higher concentrations of these calcium channel blockers. The increase in PAH accumulation caused by 1 microm nifedipine or 10 microm verapamil was independent from changes in intracellular Ca(2+) and inhibited by staurosporine (1 and 10 n m) a potent inhibitor of protein kinase C (PKC). Our results indicate that the calcium channel blockers nifedipine and verapamil increase the transport of organic anions across the basolateral membrane of proximal tubules, probably by an activation of PKC. Furthermore, the increased tubular PAH transport may disturb the estimation of the renal PAH-clearance.

Vertex epidural hematoma: surgical versus conservative management: two case reports and review of the literature

OBJECTIVE AND IMPORTANCE

Vertex epidural hematomas may be underestimated or overlooked altogether when computed tomographic scans alone are used for diagnosis. Such hematomas can be resolved with active intervention and sometimes with conservative treatment.

CLINICAL PRESENTATION

Two cases of successfully treated vertex epidural hematomas, in a 33-year-old man who presented with seizures and an 11-year-old girl who presented with headache and vomiting, are described. Both hematomas were traumatic in origin and were associated with cranial fractures. In each, coronal images (computed tomographic or magnetic resonance imaging scans) showed the extent of the hematoma much more clearly than did axial images.

INTERVENTION

One case was treated surgically and the other conservatively.

CONCLUSION

Magnetic resonance imaging is not usually indicated for trauma patients, but it is an appropriate diagnostic modality for these rare lesions, to supplement standard axial computed tomographic scans. Because vertex epidural hematomas may resolve spontaneously with time, conservative treatment should be considered on a case-by-case basis.

Kidney transplantation improves baroreceptor sensitivity

Kidney transplant recipients as well as patients on hemodialysis frequently share an increased risk of cardiovascular diseases. Besides other factors, modulations in central neural blood pressure regulation have to be considered as a pathogenetic factor. In this study, baroreceptor function as a possible modulator of blood pressure and the activity of the generating components of the sympathetic nervous system were estimated in 20 kidney transplant recipients, 20 normotensive patients on hemodialysis and 20 age-matched volunteers using the sequence analysis technique and Fast Fourier Transformation (FFT). No blood pressure differences could be measured (83.7+/-2.5 vs. 82.5+/-3.8 vs. 79.2+/-2.4 mm Hg). Pulse interval-blood pressure sequences and the slope of delta pulse interval/delta mean arterial blood pressure of these sequences, representing baroreceptor sensitivity, did not differ between kidney transplant recipients and controls (11.2+/-1.4 vs. 13.4+/-1.3 ms/mm Hg), whereas in hemodialysis patients a reduced baroreceptor sensitivity (5.2+/-1.2 ms/mm Hg) was detected. The 66-129 mHz component (Mayer waves) of heart rate and blood pressure spectrum in normals (650+/-57 and 630+/-70 modulus) significantly (p<0.05) exceeded its equivalent in kidney transplant recipients (430+/-32 and 452+/-27 modulus) and patients on hemodialysis (375+/-38 and 394+/-40 modulus). In conclusion, our study provided evidence that both in kidney transplant and dialysis patients a decreased activity of the generating compounds of the sympathetic nervous system can be detected as compared to healthy volunteers. In contrast to hemodialysis patients, the baroreceptor sensitivity is unaffected in kidney transplant recipients and may, therefore, not contribute to the development of cardiovascular diseases.

Short-term and long-term hemodynamic and clinical effects of metoprolol alone and combined with amlodipine in patients with chronic heart failure

BACKGROUND

Initiation of beta-blocker therapy is often limited by worsening congestive heart failure, which may manifest as worsening hemodynamics. Deleterious hemodynamic effects might be mitigated with the vasodilation of combined calcium channel/beta-blocker therapy.

METHODS AND RESULTS

This prospective, randomized study assessed the safety and efficacy of metoprolol alone or combined with amlodipine on hemodynamic parameters at baseline, 2 hours after the first dose of study medication, and after 12 weeks of therapy in patients receiving background triple therapy for mild to severe heart failure. Functional, exercise, and hormonal status were assessed at baseline and end of study. Twenty-nine patients (mean age 50 +/- 12.1 years) were enrolled; 21 completed 12 weeks of treatment. Mean ejection fraction at baseline was 13.4% +/- 5.7%; 79% of patients had heart failure classified as New York Heart Association class III, and 66% had heart failure of idiopathic origin. Heart rate and blood pressure did not change with short-term therapy in either group. The first dose of both regimens produced significant increases in systemic vascular resistance and significant decreases in cardiac output and index and stroke volume and stroke work indexes; combination therapy acutely yielded small but statistically significant increases in pulmonary artery, pulmonary capillary wedge, and right atrial pressures. Long-term therapy with both regimens produced significant decreases in heart rate, systemic vascular resistance, and pulmonary capillary wedge pressure and significant increases in cardiac output and index and stroke volume and stroke work indexes. Combination therapy produced significant long-term decreases in blood pressure.

CONCLUSIONS

There was no further measurable benefit with the addition of amlodipine to metoprolol compared with the effects of metoprolol alone. Therapy with metoprolol alone and the combination of metoprolol and amlodipine was well tolerated in patients with mild to severe heart failure, as evidenced by a lack of adverse effects on hemodynamic parameters over the short term and clinical and hemodynamic improvement with long-term treatment.

Peptidomimetic compounds that inhibit antigen presentation by autoimmune disease-associated class II major histocompatibility molecules

We have identified a heptapeptide with high affinity to rheumatoid arthritis-associated class II major histocompatibility (MHC) molecules. Using a model of its interaction with the class II binding site, a variety of mimetic substitutions were introduced into the peptide. Several unnatural amino acids and dipeptide mimetics were found to be appropriate substituents and could be combined into compounds with binding affinities comparable to that of the original peptide. Compounds were designed that were several hundred-fold to more than a thousand-fold more potent than the original peptide in inhibiting T-cell responses to processed protein antigens presented by the target MHC molecules. Peptidomimetic compounds of this type could find therapeutic use as MHC-selective antagonists of antigen presentation in the treatment of autoimmune diseases.

Effects of moxonidine and clonidine on potassium excretion in Sprague-Dawley rats

Recently we demonstrated that clonidine and moxonidine exert specific action on fractional fluid and Na+ excretion in anaesthetised Sprague-Dawley rats. Classically, most of the diuretics used induce an increased K+ excretion, at least in part due to Na+ load in the distal tubule and exchange of Na+ by K+. Therefore, we studied the effects of moxonidine and clonidine on K+ excretion in anaesthetised Sprague-Dawley rats. Moxonidine (0.25 and 0.5 mg kg-1 body wt. i.v.) increased transiently K+ (1.0 +/- 0.3 -1.9 +/- 0.4 and 0.9 +/- 0.2 -2.9 +0.7 micromol min-1 100 g body wt.) and Na+ (1.4 +/- 1.0 -6. 9 +/- 3.1 and 0.8 +/- 0.36 -6.6 +/- 1.5 micromol min-1100 g body wt.) excretion. Clonidine (0.25 mg kg-1) caused a more pronounced increase in K+ (1.0 +/- 0.1 -2.7 +/- 0.4 micromol min-1 100 g body wt.) and Na+ (0.6 +/- 0.3 -9.5 +/- 0.4 micromol min-1 100 g body wt.) excretion, whereas the higher dose of 0.5 mg kg-1 body wt. had less effect as compared to moxonidine (K+: 0.8 +/- 0.1 -1.7 +/- 0.2 micromol min-1 100 g body wt., Na+: 0.3 +/- 0.1 -3.4 +/- 1.0 micromol min-1 100 g body wt.). The increased electrolyte excretion returned (similar to moxonidine) to baseline levels within 20 min after injection of the drugs. Antagonists such as idazoxan and yohimbine did not change K+ and Na+ excretion by their own. Both, the non-selective imidazoline/alpha2-adrenoceptor antagonist idazoxan and the pure alpha2-adrenoceptor antagonist yohimbine attenuated the moxonidin-induced effects on K+ and Na+ excretion. This could be also observed with clonidine and simultaneous injection of these two antagonists. Our results demonstrate that moxonidine and clonidine also increase renal K+ excretion in this animal model. K+and Na+ excretion show a parallel behaviour, indicating that the increased K+ excretion is mainly due to Na+ load in the tubular system.

Resting diastolic function and left ventricular mass are related to exercise capacity in hypertensive men but not in women

We evaluated the impact of diastolic function and gender on exercise capacity in sedentary, untreated hypertensive subjects (34 men, 23 women) using echocardiography and a bicycle ergometry with measurement of oxygen consumption (VO2). In men, peak (A) mitral inflow velocity and left ventricular (LV) mass were inversely related to peak VO2 (r = -0.64) and maximal workload (r = -0.57) and were the sole independent determinants of exercise capacity. In women, there was no relationship between any echocardiographic measure and exercise capacity. Thus, LV mass and Doppler-determined diastolic function predict maximal VO2 in hypertensive men but not in women. This finding may be related to gender differences in the contribution of diastolic filling to exercise capacity or may reflect limitations of resting Doppler echocardiography to predict exercise diastolic filling in hypertensive women.

Activation of Na+, H+ exchanger produces vasoconstriction of renal resistance vessels

To evaluate the influence of the sodium/proton exchanger (Na+,H+ exchanger) on the constriction of rat resistance vessels and on the iliac artery, the isometric vasoconstrictions of renal resistance vessels and strips from iliac artery derived from Wistar-Kyoto rats were measured using a vessel myograph. The Na+,H+ exchanger was activated by intracellular acidification using propionic acid. Cytosolic pH (pHi) and cytosolic free sodium concentration ([Na+]i) in vascular smooth muscle cells were measured using the fluorescent dye technique. The activation of the Na+,H+ exchanger increased the [Na+]i by 12.4 +/- 1.3 mmol/L (n = 8). The activation of the Na+,H+ exchanger caused a contractile response of the renal resistance vessels (increase of tension, 1.5 +/- 0.1 x 10(-3) N; n = 13) and of the rat iliac artery (increase of tension, 7.5 +/- 0.8 x 10(-3) N; n = 5). The contractile response after activation of the Na+,H+ exchanger was significantly inhibited in the absence of external sodium or in the presence of amiloride, confirming the involvement of the Na+,H+ exchanger. The contractile response after activation of the Na+,H+ exchanger was significantly reduced in the absence of external calcium, after inhibition of calcium channels by nifedipine, and in the presence of an intracellular calcium antagonist 8-(diethylamino-)-octyl-3,4,5-trimethoxybenzoate (TMB-8), indicating that the activation of the Na+,H+ exchanger consecutively caused transplasma membrane calcium influx. On the other hand, the inhibition of the Na+,Ca2+ exchanger by NiCl2 significantly increased the vasoconstriction of renal resistance vessels after activation of the Na+,H+ exchanger. The activation of the Na+,H+ exchanger produces vasoconstriction by an increased cytosolic sodium concentration, inhibition of the Na+,Ca2+ exchanger, and activation of transplasma membrane calcium influx through potential dependent calcium channels.

Continuous solar UV monitoring in Germany

Early in 1993, the Federal Office for Radiation Protection (BfS, Salzgitter) together with the Federal Environmental Office (UBA, Berlin) established an overall UV monitoring network for the continuous measurement of spectrally resolved UV radiation. Every 6 min the solar UV spectrum is measured by a Bentham DM 150 double monochromator system in a wavelength ranging from 290 to 450 nm. Every night, UV data are automatically transferred via modem to the reference station in Munich where they are quality controlled and then stored in a host computer. Human health assessment of the exposure is documented in 1/2 h MED (minimal erythemal dose) values. The selected sites of Zingst (1 m, 54 degrees N, Baltic Sea), Offenbach (110 m, 50 degrees N, Rhine rift valley), Schauinsland (1205 m, 48 degrees N, Black Forest) and Neuherberg (493 m, 48 degrees N, Munich) provide a good overview of the UV radiation situation in Germany and therefore an ideal supplement to more detailed biological effect research, especially of comparison measurements with biosensors under environmental conditions. Preliminary investigations have already been started.

From genetic to structural characterization of a new class of RNA-binding domain within the SacY/BglG family of antiterminator proteins

SacY is the prototype of a family of regulatory proteins able to prevent transcription termination. It interacts with a 29 nucleotide RNA sequence able to fold into a stem-loop structure and partially overlapping with a terminator sequence located in the 5' leader mRNA region of the gene it controls. We show here that the N-terminal fragment of SacY, SacY(1-55), and the corresponding fragments of other members of the family have antiterminator activities with efficiency and specificity identical to those of the full-length proteins. In vitro, this activity correlates with the specific affinity of SacY(1-55) for its RNA target. UV melting experiments demonstrate that SacY(1-55) binding stabilizes the RNA target structure. The NMR solution structure of SacY(1-55) is very similar to that obtained in the crystal (van Tilbeurgh et al., 1997): the peptide is folded as a symmetrical dimer without any structural homology with other RNA-binding domains yet characterized. According to a preliminary NMR analysis of the SacY(1-55)-RNA complex, the protein dimer is not disrupted upon RNA binding and several residues implicated in RNA recognition are located at the edge of the dimer interface. This suggests a new mode of protein-RNA interaction.

Catabolite repression resistance of gnt operon expression in Bacillus subtilis conferred by mutation of His-15, the site of phosphoenolpyruvate-dependent phosphorylation of the phosphocarrier protein HPr

Carbon catabolite repression of the gnt operon of Bacillus subtilis is mediated by the catabolite control protein CcpA and by HPr, a phosphocarrier protein of the phosphotransferase system. ATP-dependent phosphorylation of HPr at Ser-46 is required for carbon catabolite repression as ptsH1 mutants in which Ser-46 of HPr is replaced with an unphosphorylatable alanyl residue are resistant to carbon catabolite repression. We here demonstrate that mutation of His-15 of HPr, the site of phosphoenolpyruvate-dependent phosphorylation, also prevents carbon catabolite repression of the gnt operon. A strain which expressed two mutant HPrs (one in which Ser-46 is replaced by Ala [S46A HPr] and one in which His-15 is replaced by Ala [H15A HPr]) on the chromosome was barely sensitive to carbon catabolite repression, although the H15A mutant HPr can be phosphorylated at Ser-46 by the ATP-dependent HPr kinase in vitro and in vivo. The S46D mutant HPr which structurally resembles seryl-phosphorylated HPr has a repressive effect on gnt expression even in the absence of a repressing sugar. By contrast, the doubly mutated H15E,S46D HPr, which resembles the doubly phosphorylated HPr because of the negative charges introduced by the mutations at both phosphorylation sites, had no such effect. In vitro assays substantiated these findings and demonstrated that in contrast to the wild-type seryl-phosphorylated HPr and the S46D mutant HPr, seryl-phosphorylated H15A mutant HPr and H15E,S46D doubly mutated HPr did not interact with CcpA. These results suggest that His-15 of HPr is important for carbon catabolite repression and that either mutation or phosphorylation at His-15 can prevent carbon catabolite repression.

Cortexillins, major determinants of cell shape and size, are actin-bundling proteins with a parallel coiled-coil tail

Cortexillins I and II of D. discoideum constitute a novel subfamily of proteins with actin-binding sites of the alpha-actinin/spectrin type. The C-terminal halves of these dimeric proteins contain a heptad repeat domain by which the two subunits are joined to form a two-stranded, parallel coiled coil, giving rise to a 19 nm tail. The N-terminal domains that encompass a consensus actin-binding sequence are folded into globular heads. Cortexillin-linked actin filaments form preferentially anti-parallel bundles that associate into meshworks. Both cortexillins are enriched in the cortex of locomoting cells, primarily at the anterior and posterior ends. Elimination of the two isoforms by gene disruption gives rise to large, flattened cells with rugged boundaries, portions of which are often connected by thin cytoplasmic bridges. The double-mutant cells are multinucleate owing to a severe impairment of cytokinesis.

Safety and efficacy of beta blockade in patients with chronic congestive heart failure awaiting transplantation

BACKGROUND

Donor availability remains a limiting factor for heart transplantation while transplant waiting time entails significant morbidity and mortality. This study was designed to assess the efficacy and safety of long-term beta blockade as optimization of therapy in patients with severe congestive heart failure already receiving digoxin, diuretics, and converting enzyme inhibitors awaiting transplantation.

METHODS

The beta-1 antagonist metoprolol was given to 19 patients with moderate to severe congestive heart failure. Hemodynamic, clinical, and neurohormonal measurements were obtained before drug therapy and after 3 months of treatment. Patients initially received 6.25 mg of metoprolol orally twice daily which was increased to a target dose of 50 mg twice daily over several weeks.

RESULTS

Metoprolol produced significant clinical, exercise, and hemodynamic benefits. Long-term therapy was associated with improvements in New York Heart Association class, ejection fraction, 6-minute walk, and peak maximal oxygen consumption. There were significant decreases in heart rate, pulmonary arterial systolic pressure, and left ventricular filling pressure with significant increases in stroke volume index and stroke work index. Four patients were removed from the transplant list after improving to New York Heart Association I. Only one patient required hospitalization during the first 6 months of therapy. There were no deaths caused by progressive heart failure; however, one patient died suddenly.

CONCLUSIONS

Beta blockade with metoprolol can be safely administered to patients awaiting heart transplantation producing clinical, exercise, and hemodynamic improvements. Thus, beta blockade may prove to be a safe and cost-effective bridge to transplantation.

New beta-glucoside (bgl) genes in Bacillus subtilis: the bglP gene product has both transport and regulatory functions similar to those of BglF, its Escherichia coli homolog

The Bacillus subtilis sacY and sacT genes encode antiterminator proteins, similar to the Escherichia coli bglG gene product and required for transcription of sucrose metabolism genes. A Tn10 insertion into bglP (formerly sytA) has been previously identified as restoring sucrose utilization to a strain with deletions of both sacY and sacT. The nucleotide sequence of bglP showed a high degree of homology with the E. coli bglF gene (BglF is a beta-glucoside permease of the phosphotransferase system and also acts as a negative regulator of the BglG antiterminator). Complementation studies of an E. coli strain with a deletion of the bgl operon showed that BglP was a functional beta-glucoside permease. In B. subtilis, bglP complemented in trans both the bglP::Tn10 original insertion and a phenotypically similar bglP deletion. Disruption of licT abolished the suppressor phenotype in a bglP mutant. LicT is a recently identified third B. subtilis antiterminator of the BglG/SacY family. These observations indicated that BglP was also a negative regulator of LicT. Both LicT and BglP seem to be involved in the induction by beta-glucosides of an operon containing at least two genes, bglP itself and bglH, encoding a phospho-beta-glucosidase. Other beta-glucoside genes homologous to bglP and bglH have been recently described in B. subtilis. Thus, B. subtilis possesses several sets of beta-glucoside genes, like E. coli, but these genes do not appear to be cryptic.

[The importance of roentgenological and scintigraphic studies in patients with and without thigh pain following cementless PCA hip endoprosthesis]

Persisting postoperative thigh pain is a common problem in cementless total hip prostheses occurring in a rate of about 15-20% of the patients. The reason for that phenomenon has not become clear so far. In a clinical, radiological and scintigraphic study 70 patients with 81 PCA cementless total hips were randomized in groups with (n = 34) and without significant thigh pain (n = 36). All patients underwent clinical examination including a standardized questionnaire, x-ray and 3-phase bone scintigraphy. Quantitative assessment of Tc-99m-MDP uptake was made. In the group of patients with persisting thigh pain the scintigraphic analysis showed an significantly increased uptake at the tip and the medial and lateral femur. These findings could not be correlated with clinical loosening of the prosthesis. Slight or moderate uptake in the area of the greater and lesser trochanter as well as the tip was a common finding in PCA prosthesis in all patients. In the radiological analysis no difference between both groups was evident. The study showed that patients with thigh pain after cementless PCA total hip prosthesis have specific regions of significantly increased uptake in scintigraphic examination (tip, medial and lateral femur), which cannot be correllated with clinically or radiologically signs of loosening. The morphologic reasons for the thigh pain remain unclear.

Loss of protein kinase-catalyzed phosphorylation of HPr, a phosphocarrier protein of the phosphotransferase system, by mutation of the ptsH gene confers catabolite repression resistance to several catabolic genes of Bacillus subtilis

In gram-positive bacteria, HPr, a phosphocarrier protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), is phosphorylated by an ATP-dependent, metabolite-activated protein kinase on seryl residue 46. In a Bacillus subtilis mutant strain in which Ser-46 of HPr was replaced with a nonphosphorylatable alanyl residue (ptsH1 mutation), synthesis of gluconate kinase, glucitol dehydrogenase, mannitol-1-P dehydrogenase and the mannitol-specific PTS permease was completely relieved from repression by glucose, fructose, or mannitol, whereas synthesis of inositol dehydrogenase was partially relieved from catabolite repression and synthesis of alpha-glucosidase and glycerol kinase was still subject to catabolite repression. When the S46A mutation in HPr was reverted to give S46 wild-type HPr, expression of gluconate kinase and glucitol dehydrogenase regained full sensitivity to repression by PTS sugars. These results suggest that phosphorylation of HPr at Ser-46 is directly or indirectly involved in catabolite repression. A strain deleted for the ptsGHI genes was transformed with plasmids expressing either the wild-type ptsH gene or various S46 mutant ptsH genes (S46A or S46D). Expression of the gene encoding S46D HPr, having a structure similar to that of P-ser-HPr according to nuclear magnetic resonance data, caused significant reduction of gluconate kinase activity, whereas expression of the genes encoding wild-type or S46A HPr had no effect on this enzyme activity. When the promoterless lacZ gene was put under the control of the gnt promoter and was subsequently incorporated into the amyE gene on the B. subtilis chromosome, expression of beta-galactosidase was inducible by gluconate and repressed by glucose. However, we observed no repression of beta-galactosidase activity in a strain carrying the ptsH1 mutation. Additionally, we investigated a ccpA mutant strain and observed that all of the enzymes which we found to be relieved from carbon catabolite repression in the ptsH1 mutant strain were also insensitive to catabolite repression in the ccpA mutant. Enzymes that were repressed in the ptsH1 mutant were also repressed in the ccpA mutant.

Plasmids designed to alter the antibiotic resistance expressed by insertion mutations in Bacillus subtilis, through in vivo recombination

Numerous insertion mutations conferring resistance to antibiotics are available in Bacillus subtilis. However, many of them have been constructed in vitro by inserting genes from the Staphylococcus aureus plasmids, pC194 or pE194, conferring resistance to chloramphenicol (Cm) or erythromycin (Er). Others are insertions of the Enterococcus faecalis Tn917 transposon conferring resistance to Er. This paucity of resistance markers has been limiting the possibilities of constructing and studying mutants carrying two or more of these mutations in the past. We constructed plasmids which can be used to change the antibiotic resistance expressed by preexisting chromosomal insertions, through transformation and homologous recombination. These vectors replace the pre-existing resistance to Cm or Er with new resistances to neomycin (Nm), phleomycin (Pm), spectinomycin (Sp) or tetracycline (Tc).

Cloning, sequencing, and disruption of a levanase gene of Bacillus polymyxa CF43

The Bacillus polymyxa CF43 lelA gene, expressing both sucrose and fructan hydrolase activities, was isolated from a genomic library of B. polymyxa screened in Bacillus subtilis. The gene was detected as expressing sucrose hydrolase activity; B. subtilis transformants did not secrete the lelA gene product (LelA) into the extracellular medium. A 1.7-kb DNA fragment sufficient for lelA expression in Escherichia coli was sequenced. It contains a 548-codon open reading frame. The deduced amino acid sequence shows 54% identity with mature B. subtilis levanase and is similar to other fructanases and sucrases (beta-D-fructosyltransferases). Multiple-sequence alignment of 14 of these proteins revealed several previously unreported features. LelA appears to be a 512-amino-acid polypeptide containing no canonical signal peptide. The hydrolytic activities of LelA on sucrose, levan, and inulin were compared with those of B. subtilis levanase and sucrase, confirming that LelA is indeed a fructanase. The lelA gene in the chromosome of B. polymyxa was disrupted with a chloramphenicol resistance gene (cat) by "inter-gramic" conjugation: the lelA::cat insertion on a mobilizable plasmid was transferred from an E. coli transformant to B. polymyxa CF43, and B. polymyxa transconjugants containing the lelA::cat construct replacing the wild-type lelA gene in their chromosomes were selected directly. The growth of the mutant strain on levan, inulin, and sucrose was not affected.

Easy cloning of mini-Tn10 insertions from the Bacillus subtilis chromosome

Delivery vectors for mini-Tn10 transposons function in Bacillus subtilis (M. A. Petit, C. Bruand, L. Janniére, and S. D. Ehrlich, J. Bacteriol. 172:6736-6740, 1990). Using this system, we identified a new gene (sytA) whose inactivation affected regulation of genes of sucrose metabolism. For cloning the sytA::Tn10 insertion in Escherichia coli, we developed a methodology similar to that commonly used for B. subtilis Tn917 insertions. We constructed a plasmid which can be used to insert (by in vivo recombination) a ColE1 origin linked to a spectinomycin resistance gene (ori-spc element) into mini-Tn10 transposons inserted into the B. subtilis chromosome. DNA extracted from a sytA::Tn10::ori-spc transformant was cut with restriction enzymes that do not cut into the Tn10::ori-spc sequence; plasmids containing the sytA::Tn10 insertion were cloned by self-ligation, followed by transformation of E. coli. To obtain the wild-type sytA region, one of these plasmids was ligated with an E. coli-B. subtilis shuttle vector conferring erythromycin resistance, and the hybrid was used to transform the wild-type B. subtilis strain. Erythromycin-resistant transformants, detected as spectinomycin sensitive, resulted from conversion of the insertion mutation by the resident wild-type locus. The shuttle plasmid containing the wild-type locus could then be recovered in E. coli.

Mice lacking the tumour necrosis factor receptor 1 are resistant to TNF-mediated toxicity but highly susceptible to infection by Listeria monocytogenes

Tumour necrosis factor (TNF), jointly referring to TNF alpha and TNF beta, is a central mediator of immune and inflammatory responses; its activities are mediated by two distinct receptors, TNFR1 (p55) and TNFR2 (p75) (reviewed in refs 1-3). The cytoplasmic domains of the TNFRs are unrelated, suggesting that they link to different intracellular signalling pathways. Although most TNF responses have been assigned to one or the other of the TNF receptors (mostly TNFR1), there is no generally accepted model for the physiological role of the two receptor types. To investigate the role of TNFR1 in beneficial and detrimental activities of TNF, we generated TNFR1-deficient mice by gene targeting. We report here that mice homozygous for a disrupted Tnfr1 allele (Tnfr1(0)) are resistant to the lethal effect of low doses of lipopolysaccharide after sensitization with D-galactosamine, but remain sensitive to high doses of lipopolysaccharide. The increased susceptibility of Tnfr1(0)/Tnfr1(0) mutant mice to infection with the facultative intracellular bacterium Listeria monocytogenes indicates an essential role of TNF in nonspecific immunity.

Targeted disruption of the MHC class II Aa gene in C57BL/6 mice

The MHC class II gene Aa was disrupted by targeted mutation in embryonic stem (ES) cells derived from C57BL/6 mice to prevent expression of MHC class II molecules. Contrary to previous reports, the effect of the null-mutation on T cell development was investigated in C57BL/6 mice, which provide a defined genetic background. The complete lack of cell surface expression of MHC class II molecules in B6-Aa0/Aa0 homozygous mutant mice was directly demonstrated by cytofluorometric analysis using anti-Ab and anti-Ia specific mAbs. Development of CD4+CD8- T cells in the thymus was largely absent except for a small population of thymocytes expressing high levels of CD4 together with low amounts of CD8. The majority of these cells express the TCR at high density. Although mature CD4+CD8- T cells were undetectable in the thymus, some T cells with a CD4+CD8-TCRhigh phenotype were found in lymph nodes and spleen. Peripheral T cells from the mutant mice can be polyclonally activated in vitro with the mitogen concanavalin A. However, they could not be stimulated with staphylococcal enterotoxin B in autologous lymphocyte reactions, thereby demonstrating the absence of MHC class II expression in these mice. Peripheral B cells in B6-Aa0/Aa0 mutants were functional and responded to the T cell independent antigen levan by the production of antigen-specific IgM antibodies similar to wild-type cells. The B6-Aa0/Aa0 mutant mice described in this study represent an important tool to investigate the involvement of MHC class II molecules in lymphocyte maturation and the immune response.

[The value of bone scintigraphy in thigh pain following cementless hip prosthesis]

Persisting postoperative pain of the thigh is a common problem of cementless hip endoprostheses occurring in about 15-20% of the patients. We performed a comparative study including patients with (n = 40) and without (n = 45) pain of the thigh. 85 cementless porous-coated anatomic (PCA) hip endoprostheses in 74 patients were examined. All patients underwent clinical examination including a standardized questionnaire, x-ray, and 3-phase bone scintigraphy. Slight or moderate 99mTc-MDP uptake in the area of the greater and lesser trochanter as well as at the tip was a common finding in PCA prostheses in patients without pain and was not a sign of loosening of the hip. Radiologically, there was no difference between patients with and without pain. However, persisting pain of the thigh in patients with PCA prosthesis corresponded with an increased uptake at the tip and the medial and lateral femur, not being a sign of loosening even in this group. The special biomechanical conditions of cementless prostheses causing inhomogeneous intraosseous stress distribution are supposed to be the reason for that.

Genomic organization and promoter function of the murine tumor necrosis factor receptor beta gene

Using the tumor necrosis factor receptor beta (TNFR beta) cDNA as a probe, overlapping clones from a genomic phage library were isolated which encompass the murine TNF receptor beta gene. Analysis of the gene led to the identification of 10 exons, most of which were concentrated in two clusters. The boundaries of the exons do not match protein domains or characteristic motifs of the extracellular region of the TNFR beta. The 5'-flanking region of the gene shows a high density of G and C nucleotides with a strong overrepresentation of CpG dinucleotides. Most of the analyzed CpG were found to be nonmethylated, suggesting that this region is an HTF island. We revealed at least three transcriptional start sites which is likely due to the absence of classical TATA and CAAT sequences from the putative promoter region. CAT assays confirmed promoter activity of the 5'-flanking sequences. Surprisingly, some successively shortened promoter constructs displayed higher relative promoter activity than a full length clone. Preliminary experiments indicate that the promoter region of the TNFR beta gene does not respond to a variety of cytokines. In summary, the structural and functional analysis suggest that the TNFR beta expression is directed by a non-inducible housekeeping-type promoter.

Aussagefähigkeit der Skelettszintigraphie bei Oberschenkelschmerz nach zementlosem Hüftgelenkersatz

Der persistierende postoperative Oberschenkelschmerz tritt als besonderes Problem der zementlosen Hüftendoprothetik bei ca. 15-20% der Patienten auf. In einer vergleichenden Studie wurde bei insgesamt 40 PCA-Prothesen (Porous-Coated Anatomie) mit Oberschenkelschmerzen sowie bei beschwerdefreien Patienten mit insgesamt 45 PCA-Prothesen eine klinische Untersuchung des Hüftgelenkes, eine Röntgenuntersuchung und eine 3-Phasen-Skelettszintigraphie durchgeführt. Die Auswertung der szintigraphischen Spätaufnahmen zeigte, daß eine geringe bis mäßige Mehranreicherung im Bereich des kleinen und großen Trochanters sowie der Prothesenspitze bei zementlosen PCA-Prothesen als normal anzusehen ist. Die Mehranreicherung ist bei beschwerdefreien Patienten nicht als Anzeichen einer Lockerung zu bewerten. Radiologisch unterscheiden sich die Patientengruppen mit und ohne Oberschenkelschmerz nicht voneinander. Die Oberschenkelbeschwerden bei zementloser PCA-Hüftprothese korrelieren mit einer Zunahme der Mehranreicherung im Bereich der Prothesenspitze sowie des medialen und lateralen Schaftes, deren Ursache in der besonderen Biomechanik der zementlosen Prothesen mit inhomogener intraossärer Streßverteilung gesehen werden kann.

Functional expression of a human TCR beta gene in transgenic mice

A functionally rearranged TCR beta (Tcrb) gene was isolated from a cloned human T helper cell recognizing the CS.T3 epitope of Plasmodium falciparum with HLA-DR2. Transgenic mice were generated by co-injection of the human gene together with the mouse Tcrb enhancer. Analysis of transgenic mice shows that the functional Tcrb gene of xenogenic, i.e. human, origin exerts allelic exclusion of endogenous Tcrb genes. Cytofluorometric analysis revealed expression of the human TCR beta chain on virtually all thymocytes and peripheral T cells together with endogenous TCR beta chains and CD3 components. No surface expression of mouse TCR beta chain or rearrangement of endogenous Tcr genes was detectable. Expression of the hybrid receptor causes a reduction in the number of thymocytes and a bias for CD4+CD8- T cells in the thymus as compared with non-transgenic littermates. Peripheral transgenic T cells mount a normal proliferative response against allogeneic targets in mixed lymphocyte reactions. These results show that a hybrid mouse/human TCR is able to pass positive and negative selection in the thymus, and is functional in transgenic mice.

Specificity determinants and structural features in the RNA target of the bacterial antiterminator proteins of the BglG/SacY family

Induction of the Bacillus subtilis sacB gene and sacPA operon and Escherichia coli bgl operon is mediated by structurally homologous antiterminators encoded by the sacY, sacT, and bglG genes, respectively. When activated, these proteins prevent early transcription termination at terminators located in the leader regions of the three operons. BglG was previously shown to bind in vitro to an imperfectly palindromic 29-nucleotide RNA sequence located upstream of the terminator and partially overlapping with it [Houman, F., Diaz-Torres, M.R. & Wright, A. (1990) Cell 62, 1153-1163]. Similar motifs, here termed ribonucleic antiterminators (RATs), strongly conserved in sequence and in position, are found in the leader of both sacB and sacPA. Mutations were created in sacB RAT and tested in B. subtilis; this showed that sacB RAT is the target for SacY-mediated induction of sacB and that a stem-loop structure in the mRNA is required for regulatory function. Mutations increasing the similarity of the sacB RAT with those of sacPA or bgl rendered sacB inducible by SacT or BglG, respectively; most of these changes did not strongly affect induction by SacY, suggesting that the nucleotides at these variable positions act as negative specificity determinants.

Transcription of the Bacillus subtilis sacX and sacY genes, encoding regulators of sucrose metabolism, is both inducible by sucrose and controlled by the DegS-DegU signalling system

The adjacent sacX and sacY genes are involved in sucrose induction of the Bacillus subtilis sacB gene by an antitermination mechanism. sacB, encoding the exoenzyme levansucrase, is also subject to regulation by the DegS-DegU signalling system. Using sacXY'-lacZ and sacX'-lacZ fusions, we show that the transcription of the sacX and sacY genes is both inducible by sucrose and regulated by DegU. sacX and sacY appear to constitute an operon, since the deletion of the sacX leader region abolished the expression of a sacXY'-lacZ fusion. The degU-dependent promoter was located by deletion analysis and reverse transcriptase mapping 300 nucleotides upstream from the sacX initiator codon. Sucrose induction of the sacX'-lacZ fusion requires either SacY or the homologous SacT antiterminator, which is involved in sucrose induction of the intracellular sucrase gene (sacPA operon). Sequence analysis of the sacX leader region revealed (20 nucleotides downstream from the transcription start site) a putative binding site for these regulators; however, no structure resembling a rho-independent terminator could be found overlapping this site, unlike the situation for sacPA and sacB. Deletion of a segment of the leader region located 100 nucleotides downstream from this site led to constitutive expression of the sacXY'-lacZ and sacX'-lacZ fusions. These results suggest that the mechanism of sucrose induction of sacXY is different from that of sacPA and sacB.

Expression of a transgenic T cell receptor beta chain enhances collagen-induced arthritis

SWR/J transgenic (tg) mice were generated expressing the TCR beta chain derived from an anticollagen type II (CII) arthritogenic T cell clone. The SWR/J strain was selected because it is resistant to collagen-induced arthritis (CIA) and lacks the V beta gene segment used by the T cell clone. Expression of the tg beta chain on all thymocytes and peripheral lymph node T cells led to a more efficient anti-CII immune response, but did not confer CIA susceptibility to SWR/J mice. Nevertheless, this tg beta chain enhanced predisposition to CIA as (DBA/1 x SWR) F1 beta tg mice were more susceptible than normal F1 littermates. Our results demonstrate that the expression of the tg beta chain contributes to CIA susceptibility, but by itself it is not sufficient to overcome CIA resistance in the SWR/J strain.

A degU-containing SP beta prophage complements superactivator mutations affecting the Bacillus subtilis degSU operon

The Bacillus subtilis degSU two-gene operon encodes a two-component regulatory system which positively controls expression of a variety of genes encoding degradative enzymes. Point superactivator mutations in either degS or degU increase the production of these enzymes. A specialized transducing SP beta phage which partially complements several of these mutations was isolated from a phage library of the B. subtilis chromosome. This phage was shown to contain the degU (wild-type) gene. This unexpected co-dominance is discussed.

Allelic exclusion of a T cell receptor-beta minilocus

A TCR-beta minilocus in germline configuration (beta M) has previously been shown to undergo rearrangement and expression in transgenic mice. To study allelic exclusion of TCR miniloci, several beta M transgenic mouse lines were generated and crossed with mice transgenic for a functionally rearranged TCR V beta 2 gene (beta R). PCR analysis of beta M beta R double transgenic mice revealed almost complete suppression of endogenous TCR V beta gene rearrangements, but blockage of minilocus V beta rearrangements was achieved with only one of five minilocus transgenic lines. This result cannot be explained by copy number or arrangement of the multiple miniloci integrated. It appears that the minilocus is not autonomously regulated which suggests that sequences flanking the integration sites influence accessibility of the minilocus for rearrangement and allelic exclusion. However, although productively rearranged genes were formed in double transgenic mice, surface expression of minilocus-encoded beta chains was not detected. This indicates that allelic exclusion may operate at a level after gene rearrangement.

Allelic exclusion of a T cell receptor-beta minilocus

A TCR-beta minilocus in germline configuration (beta M) has previously been shown to undergo rearrangement and expression in transgenic mice. To study allelic exclusion of TCR miniloci, several beta M transgenic mouse lines were generated and crossed with mice transgenic for a functionally rearranged TCR V beta 2 gene (beta R). PCR analysis of beta M beta R double transgenic mice revealed almost complete suppression of endogenous TCR V beta gene rearrangements, but blockage of minilocus V beta rearrangements was achieved with only one of five minilocus transgenic lines. This result cannot be explained by copy number or arrangement of the multiple miniloci integrated. It appears that the minilocus is not autonomously regulated which suggests that sequences flanking the integration sites influence accessibility of the minilocus for rearrangement and allelic exclusion. However, although productively rearranged genes were formed in double transgenic mice, surface expression of minilocus-encoded beta chains was not detected. This indicates that allelic exclusion may operate at a level after gene rearrangement.

Allelic exclusion at DNA rearrangement level is required to prevent coexpression of two distinct T cell receptor beta genes

In mice double transgenic for functionally rearranged T cell receptor (TCR) V beta 2 and V beta 8.2 genes we found that most T lymphocytes express both TCR beta chains simultaneously. These T cells show no abnormality in thymic selection in vivo and their TCRs are capable of transducing activation signals in vitro. These results indicate that multispecific T cells may appear in the periphery if allelic exclusion of TCR beta genes is not established at the level of gene rearrangement.

The T-cell-receptor repertoire in the synovial fluid of a patient with rheumatoid arthritis is polyclonal

We have analyzed the T-cell-receptor repertoire expressed in the synovial fluid of a patient with rheumatoid arthritis by using an inverse polymerase chain reaction. Total RNA was isolated from Ficoll-purified mononuclear cells and converted into circularized double-stranded cDNA. Specific amplification of alpha- and beta-chain variable regions (V alpha and V beta) was achieved with inverted alpha- and beta-chain constant region (C alpha and C beta) primer pairs, and the amplification products were cloned into phage vectors. A total of 78 alpha and 76 beta clones were sequenced, and 67 and 72 productively rearranged alpha and beta genes were identified, respectively. Thirty-one V alpha, 33 alpha-chain joining region (J alpha), 29 V beta, and 12 beta-chain joining region (J beta) gene segments were found in the productively rearranged clones, indicating that the T-cell repertoire expressed in the synovial fluid of this RA patient is highly heterogenous and polyclonal. Comparison of peripheral blood and synovial fluid repertoires showed that the most abundant V beta sequences, V beta 2.1 and V beta 3.1, were enriched in the inflamed joint by a factor of 2 to 3. It is possible that T cells expressing these V beta gene segments, which recognize bacterial superantigens, play a role in the disease.

Tumor necrosis factor: receptors and inhibitors

Tumor necrosis factor (TNF) is a highly potent pleiotropic response modifier in inflammatory and immunologic host defense reactions. It can also be toxic to cells and elicit toxic systemic reactions, as evinced by certain pathophysiologic conditions that are initiated or aggravated by an excess of TNF. The cellular mechanisms for transducing TNF signals are complex. There are two forms of TNF, alpha and beta, and two distinct TNF receptors. Many cells express both receptor types simultaneously, even though neither membrane receptor can distinguish between TNF-alpha and TNF-beta. The effects of TNF are inhibited by binding proteins that are truncated fragments of the extracellular domains of the TNF receptors. The mechanisms by which these components of the TNF signal transmission pathways interact to mediate the pleiotropic effects of TNF remain unclear.

Construction of a derivative of Tn917 containing an outward-directed promoter and its use in Bacillus subtilis

Engineered variants of the transposon Tn917 have been widely used to obtain insertion mutations and transcriptional fusions in Bacillus subtilis and other Gram-positive bacteria. We have developed a novel Tn917-based methodology useful for isolation and characterization of mutants resulting from gene over-expression. A Tn917 variant was constructed which contains a strong out-facing promoter near one end, able to promote transcription of genes in the vicinity of its insertion target. This transposon, designated Tn917PF1, was tested in model conditions. Three Tn917PF1 mutants of B. subtilis, with phenotypes presumed to result from gene over-expression, were analysed. Their phenotypes were shown to be due to transcription from the transposon promoter. In one mutant the promoter activated a deg gene, probably degQ. The other two contained different insertions decryptifying a B. subtilis gene encoding beta-galactosidase.

Dual effect of a Tn917 insertion into the Bacillus subtilis sacX gene

The most common effect of transposon insertion is the inactivation of genes. However, in some cases, transposons can activate in cis the expression of genes in the neighbourhood of their integration site. We previously described an insertion of the transposon Tn917 into the Bacillus subtilis sacXY locus. sacX and sacY encode respectively a negative and a positive regulator involved in induction by sucrose of the exoenzyme levansucrase. Data in this paper show that the Tn917 insertion had two effects: it inactivated sacX and it increased the transcription of sacY. The latter effect involved one or several elements internal to the transposon.

Model reference adaptive control with constraints for postoperative blood pressure management

This paper presents an approach for adaptive control of blood pressure using sodium nitroprusside. A modified stochastic model reference adaptive control algorithm with a time varying reference model is developed and used for this purpose. An automatic adjustment of the reference model is proposed in order to optimize the performance of the closed loop system while meeting clinical constraints imposed on the infusion rate and the mean arterial pressure. Extensive computer simulations show the robustness of the proposed controller in the presence of relatively high noise levels, over the full range of plant parameters and for large parameter variations.

Structure of the murine mb-1 gene encoding a putative sIgM-associated molecule

Genomic DNA clones containing the B cell-specific murine mb-1 gene were isolated and a 5.6-kb BamH I fragment was characterized. It is 5629 bp long and contains five exons: an exon containing the 5' untranslated and the coding sequence of the signal peptide, an exon of 294 bp, which contains most of the extracellular sequence of the MB-1 protein, a 119-bp long exon coding mainly for the transmembrane portion, and two exons of 69 bp and 427 bp encoding the cytoplasmic domain and the 3'-untranslated region, respectively. The mb-1 gene does not contain a "TATA box" found in many eukaryotic promoters. The 5'-flanking region has sequence stretches homologous to IgVH 5'-promoter regions and a bcl 2 intron sequence. It contains the decanucleotide sequence (ATGGCAAATA) almost identical to the octamer motif of IgVH promoters. A B cell-specific DNase I-hypersensitive site was found in the 3'-flanking region indicating that this region might be involved in B cell-specific expression of mb-1. Southern blot analysis of genomic liver DNA with the cloned mb-1 cDNA suggests the existence of another mb-1-related gene segment.

Structure of the murine mb-1 gene encoding a putative sIgM-associated molecule

Genomic DNA clones containing the B cell-specific murine mb-1 gene were isolated and a 5.6-kb BamH I fragment was characterized. It is 5629 bp long and contains five exons: an exon containing the 5' untranslated and the coding sequence of the signal peptide, an exon of 294 bp, which contains most of the extracellular sequence of the MB-1 protein, a 119-bp long exon coding mainly for the transmembrane portion, and two exons of 69 bp and 427 bp encoding the cytoplasmic domain and the 3'-untranslated region, respectively. The mb-1 gene does not contain a "TATA box" found in many eukaryotic promoters. The 5'-flanking region has sequence stretches homologous to IgVH 5'-promoter regions and a bcl 2 intron sequence. It contains the decanucleotide sequence (ATGGCAAATA) almost identical to the octamer motif of IgVH promoters. A B cell-specific DNase I-hypersensitive site was found in the 3'-flanking region indicating that this region might be involved in B cell-specific expression of mb-1. Southern blot analysis of genomic liver DNA with the cloned mb-1 cDNA suggests the existence of another mb-1-related gene segment.

Expression of levansucrase-beta-galactosidase hybrids inhibits secretion and is lethal in Bacillus subtilis

The lacZ gene of Escherichia coli was fused to several positions downstream from the 5' end of the Bacillus subtilis sacB gene, which encodes levansucrase (LS), a sucrose-inducible extracellular enzyme. Effects of hybrid protein expression in B. subtilis were studied. Several fusions were tested, and two significantly interfered with growth of cells and with LS secretion when induced with sucrose. Chromosomal amplification of the fusions, leading to strong expression of the hybrid proteins, completely blocked LS secretion and was lethal for B. subtilis when expression was induced.

Nucleotide sequence of the sacS locus of Bacillus subtilis reveals the presence of two regulatory genes

The nucleotide sequence of 3 kb of Bacillus subtilis chromosomal DNA, including sacS, reveals that the regulatory locus for levansucrase synthesis consists of two genes, sacX and sacY. The sacX gene product is remarkably similar to sucrose-specific enzyme II of the B. subtilis phosphoenolpyruvate-dependent phosphotransferase system. The product of sacY is similar, both in amino acid sequence and most probably in its function, to BglG, an Escherichia coli transcriptional antitermination factor.

T-cell specific rearrangement of T-cell receptor beta transgenes in mice

To study rearrangement of T cell receptor (TCR) genes, transgenic mice were generated with a TCR beta minilocus in germline configuration, containing three V beta, two D beta, fourteen J beta and two C beta gene segments and the TCR beta enhancer. Using the polymerase chain reaction as an analytical tool both partial DJ as well as complete VDJ rearrangements were seen, indicating that the minilocus contained all sequence elements required for rearrangment. Rearrangements of minilocus gene segments were restricted to T cells in the thymus and the periphery and did not occur in B cells. V beta 8.3 and V beta 5 sequences encoded by the minilocus were expressed on the surface of peripheral T cells at high frequencies. Transgenic mice with TCR minilocus genes will be a useful system to identify DNA sequence elements required for regulation of rearrangement in vivo.