Nucleotide sequence and genome organization of grapevine leafroll-associated virus-2 are similar to beet yellows virus, the closterovirus type member

The entire genome of grapevine leafroll-associated closterovirus-2 (GLRaV-2), except the exact 5' terminus, was cloned and sequenced. The sequence encompasses nine open reading frames (ORFs) which include, in the 5' to 3' direction, an incomplete ORF1a encoding a putative viral polyprotein and eight ORFs that encode proteins of 52 kDa (ORF1b), 6 kDa (ORF2), 65 kDa (ORF3), 63 kDa (ORF4), 25 kDa (ORF5), 22 kDa (ORF6), 19 kDa (ORF7) and 24 kDa (ORF8) respectively, and 216 nucleotides of the 3' untranslated region. An incomplete ORF1a potentially encoded a large polyprotein containing the conserved domains characteristic of a papain-like protease, methyltransferase and helicase. ORF1b potentially encoded a putative RNA-dependent RNA polymerase. The expression of ORF1b may be via a +1 ribosomal frameshift mechanism, similar to other closteroviruses. A unique gene array, which is conserved in other closteroviruses, was also identified in GLRaV-2; it includes genes encoding a 6 kDa small hydrophobic protein, 65 kDa heat shock protein 70, 63 kDa protein of function unknown, 25 kDa coat protein duplicate and 22 kDa coat protein. Identification of ORF6 (22 kDa) as the coat protein gene was further confirmed by in vivo expression in E. coli and immunoblotting. Phylogenetic analysis comparing different genes of GLRaV-2 with those of other closteroviruses demonstrated a close relationship with beet yellows virus (BYV), beet yellow stunt virus and citrus tristeza virus. GLRaV-2 is the only closterovirus, so far, that matches the genome organization of the type member of the group, BYV, and thus can be unambiguously classified as a definitive member of the genus Closterovirus.

Surgical repair of patients with tetralogy of Fallot and unilateral absence of pulmonary artery

BACKGROUND; Patients with tetralogy of Fallot and unilateral absence of pulmonary artery are a high-risk group for whom there is no consensus on the correct approach to medical management. The purpose of this report is to review a 29-year experience in the treatment of those patients.

METHODS

Between May 1966 and February 1995, 2,511 patients underwent correction of tetralogy of Fallot in our department, 24 of those patients with unilateral absence of pulmonary artery (20 had absence of the left pulmonary artery, 4 had absence of the right pulmonary artery). Valved conduits were used in 9 patients, right ventricular patches were used in 4 patients, and transannular patches with a monocusp that was made of the patient's pericardium were used in 11 patients.

RESULTS

There were two operative deaths; both were in patients with hypoplasia of the left ventricle. All survivors had good early and late results.

CONCLUSIONS

A right ventricular patch should be used in patients with tetralogy of Fallot and infundibular stenosis; a transannular patch with a monocusp should be used in patients with tetralogy of Fallot and stenosis of the left or right pulmonary artery's origin as well as the pulmonary trunk. A homograft valved conduit is suitable for patients with anomalous coronary artery or pulmonary atresia.

The coat protein gene of grapevine leafroll associated closterovirus-3: cloning, nucleotide sequencing and expression in transgenic plants

A lambda ZAP II cDNA library was constructed by cloning cDNA prepared from a high molecular weight double-stranded RNA (dsRNA, ca. 18 kb) isolated from grapevine leafroll associated closterovirus-3 (GLRaV-3) infected tissues. This cDNA library was immuno-screened with GLRaV-3 coat protein specific polyclonal and monoclonal antibodies and three immuno-positive clones were identified. Analysis of nucleotide sequences from these clones revealed an open reading frame (ORF) which was truncated at the 3' end; the remainder of this ORF was obtained by sequencing a fourth clone that overlapped with one of the immunopositive clones. A total of 2028 bp was sequenced. The putative GLRaV-3 coat protein ORF, 939 bp, encodes a protein (referred to as p35) with a calculated M(r) of 34866. Multiple alignment of the p35 amino acid sequence with coat protein sequences from other closteroviruses revealed that the consensus amino acid residues (R and D) of filamentous plant viruses are preserved in the expected locations. The GLRaV-3 coat protein gene was then engineered for sense and antisense expression in transgenic plants. Transgenic Nicotiana benthamiana plants that contain the sense GLRaV-3 coat protein gene produced a 35 kDa protein that reacted with GLRaV-3 antibody in Western blot.

Evidence for a loop-like insertion mechanism of pro-Omp A into the inner membrane of Escherichia coli

We have studied the insertion of pro-OmpA into the Escherichia coli membrane in vivo using various mutants that have either alterations in the amino-terminal parts of the signal peptide or in the mature region that flanks the signal peptide. A pro-OmpA mutant with an amino terminal extension of 142 residues derived from ribulokinase (AraB) was analysed for its membrane insertion. The AraB portion, which includes a cluster of seven charged residues close to the signal sequence, did not interfere with the Sec components and allowed efficient export of OmpA. During translocation the AraB portion remained in the cytoplasm. Further mutants of OmpA were constructed in the carboxy-terminal region flanking the signal sequence. Pro-OmpA does not translocate across the membrane when a charge cluster, comprised of Lys-Arg-Arg-Glu-Arg, is introduced after positions 5, 11 or 15 of the mature region, but is translocated when the cluster is introduced after position 22. This defines a region of about 20 residues in the mature part of pro-OmpA that is crucial for membrane insertion. These results suggest that in the case of the Sec-dependent pro-OmpA, as with the Sec-independent M13 procoat, the precursor assumes a loop-like structure involving the signal peptide and the early part of the mature region, leaving the amino terminus of the signal peptide at the cytoplasmic face.

Cardiac function and histological changes after non-dynamic cardiomyoplasty and preliminary study of dynamic cardiomyoplasty

By means of histological method and ultrasound cardiographic (UCG) examination, the left-right ratio of transectional area of muscle fiber of latissimus dorsi muscle (LDM) after non-dynamic cardiomyoplasty was 77.4 +/- 11.7% in Group I (3 weeks after operation), and 78.4 +/- 11.6% atrophy and hyperplasia of LDM, but the basical structure was retained. The ejection fraction (EF) decreased significantly after operation (P < 0.05), but the difference between two groups was non- significant. Also, dynamic cardiomyoplasty was performed on a sheep. UCG showed the increased cardiac systolic function after operation. ATPase, succinodehydrogenase (SDH) and PAS examination implied the strengthening of fatigue-resistant ability in skeletal muscles after long-term electrical stimulation. So cardiomyoplasty is suggested to be a supplementary measure in treating end-stage heart failure.

[Surgical treatment of congenital mitral valve insufficiency (CMVI)]

This paper reported surgical treatment on 154 patients with CMVI. Of them, pure CMVI only existed in 23 cases, the associated anomalies in 131 cases. Surgical repair of mitral valve were performed in 144 cases, replacement of valve were done in 10 cases. Surgical repair included plication of the commissure in 125 cases, closure of the fenestration of the large leaflet in 1 case, partial resection of the small leaflet with approximation and valve ring annuloplasty in 3 cases, shortening of elongated chordae taeniae in large leaflet in 4 cases, respectively. The smallest age within all patients undergoing mitral replacement was 3 years. There were 1 early and late death, respectively, in this group. However, reoperation were performed in 2 cases for unsatisfactory repair and 1 case for failure of prosthetic valve. The results showed that echocardiography is a simple and effective tool in preoperative diagnosis and making selection of operative indication, finally, leading to proper repair of associated anomalies. Surgical repair on cases of CMVI should be the first choice, and proper procedure should be selected according to the type of mitral valve deformity. The results were satisfactory even without artificial valve ring. Valve replacement was considered to be essential on severe patients and unsatisfactory repair. On children, slight large valve with double leaflets was preferable.

Charged residues render pro-OmpA potential dependent for initiation of membrane translocation

We have examined the effects of positively and negatively charged residues on the translocation of outer membrane protein A precursor (pro-OmpA) across the bacterial inner membrane. Pro-OmpA does not translocate across the membrane when 2 positively charged residues are inserted immediately after the leader peptide, whereas it does insert when 2 neutral or negatively charged residues are introduced. Using a cell-free translocation system, we show that the membrane potential stimulated the rate of initial insertion of pro-OmpA with negatively charged residues, inhibited pro-OmpA with positively charged residues, and had no effect on neutral pro-OmpA. Thus, acidic residues render pro-OmpA potential-dependent for loop formation, which then initiates the translocation process.

MRI-T2 values in the differentiation of recurrence and fibrosis after radiation of nasopharyngeal carcinoma

The possibility of T2 values in the differentiation of local recurrence and irradiation fibrosis was studied prospectively in 36 patients with nasopharyngeal carcinoma (NPC) after radiotherapy. All the patients had a soft-tissue mass in the nasopharynx demonstrated by CT. Fourteen patients had tumor recurrence, 20 radiation fibrosis, 1 postradiation edema, and 1 inflammatory change. The control group consisted of 8 patients with untreated NPC. It was found that T2 was longer in patients with tumor than in patients with radiation fibrosis. We conclude that MRI may be used as a noninvasive method for differentiating radiation fibrosis from local recurrent NPC, but the prolonged T2 value of tumor is not specific and may be seen in radiation edema and infection.

MRI differentiation of recurrent nasopharyngeal carcinoma from postradiation fibrosis

A prospective study was performed to determine the usefulness of magnetic imaging (MRI) in differentiating local recurrence versus post-irradiation fibrosis in 72 patients after radiotherapy of nasopharyngeal carcinoma (NPC). All patients had a soft-tissue mass in the nasopharynx demonstrated by computed tomography. A total of 29 patients had tumor recurrence; 40 patients had only radiation fibrosis; 1 patient had postradiation edema and 2 patients had inflammatory changes. Based on the differences in signal intensity on T2-weighted images, MRI may be promising as a noninvasive method for differentiating radiation fibrosis from local recurrent NPC. However, the signal intensity pattern of the tumor is not specific and may be seen in radiation edema and infection.

Mapping of catalytically important domains in Escherichia coli leader peptidase

Leader peptidase (Lep) is a central component of the secretory machinery of Escherichia coli, where it serves to remove signal peptides from secretory proteins. It spans the inner membrane twice with a large C-terminal domain protruding into the periplasmic space. To investigate the importance of the different structural domains for the catalytic activity, we have studied the effects of a large panel of Lep mutants on the processing of signal peptides, both in vivo and in vitro. Our data suggest that the first transmembrane and cytoplasmic regions are not directly involved in catalysis, but that the second transmembrane region and the region immediately following it may be in contact with the signal peptide and/or located spatially close to the active site of Lep.

Efficient translocation of positively charged residues of M13 procoat protein across the membrane excludes electrophoresis as the primary force for membrane insertion

The coat protein of bacteriophage M13 is inserted into the Escherichia coli plasma membrane as a precursor protein, termed procoat, with a typical leader peptide of 23 amino acid residues. Its membrane insertion requires the electrochemical potential but not the cellular components SecA and SecY. Since the electrochemical gradients result in the periplasmic side of the membrane being positively charged, the membrane potential could contribute to the transfer of the negatively charged central region of procoat across the membrane. Here we demonstrate that the central domain following the leader peptide can be translocated across the membrane even when the net charge of the region is changed from -3 to +3. This rules out an electrophoresis-like insertion mechanism for procoat. We also show that the sec independence of procoat insertion is linked to the presence of the second apolar domain. The deletion of most of the second apolar domain from a procoat fusion protein results in sec dependent membrane insertion of the hybrid protein. Moreover, like other proteins that require the sec genes, translocation of this sec dependent procoat protein is inhibited when positively charged residues are introduced after the leader peptide. Loop models involving one or two hydrophobic regions are presented that account for the differences in tolerance of positively charged residues.

Both a short hydrophobic domain and a carboxyl-terminal hydrophilic region are important for signal function in the Escherichia coli leader peptidase

Leader peptidase, typical of inner membrane proteins of Escherichia coli, does not have an amino-terminal leader sequence. This protein contains an internal signal peptide, residues 51-83, which is essential for assembly and remains as a membrane anchor domain. We have employed site-directed mutagenesis techniques to either delete residues within this domain or substitute a charged amino acid for one of these residues to determine the important properties of the internal signal. The deletion analysis showed that a very small apolar domain, residues 70-76, is essential for assembly, whereas residues that flank it are dispensable for its function. However, point mutations with charged amino acid residues within the polar sequence (residues 77-82) slow or abolish leader peptidase membrane assembly. Thus, a polar region, Arg-Ser-Phe-Ile-Tyr-Glu, is important for the signal peptide function of leader peptidase, unlike other signals identified thus far.