GreA-induced transcript cleavage is accompanied by reverse translocation to a different transcription complex conformation

GreA- and GreB-induced transcript cleavage drives reverse translocation of Escherichia coli RNA polymerase on a DNA template in the absence of NTPs (Feng, G.-H., Lee, D. N., Wang, D., Chan, C. L., and Landick, R. (1994) J. Biol. Chem. 269, 22282-22294, accompanying report). During transcript elongation, the sizes of the DNA footprint and the single-stranded transcription bubble vary markedly among transcription complexes halted at different template positions. To test whether transcription complex intermediates formed during transcript cleavage-induced reverse translocation also display heterogeneous conformations at different template positions, we examined the structures of two different transcription complexes before and after GreA treatment. Transcription complexes halted at position +16 after initiation at the T7 A1 promoter or paused at the trpL pause site exhibited strong blocks to transcript cleavage after removal of 6 to 10 nucleotides. In both cases, the down-stream contact between RNA polymerase and DNA moved little during transcript cleavage, thereby increasing its distance from the active site, whereas the upstream DNA contact and the borders of the transcription bubble moved in approximate register with the transcript 3'-end. The backward movements of halted E. coli RNA polymerase are similar to a recently postulated model for discontinuous translocation during transcription, but differ from those reported for arrested RNA polymerase II transcription complexes.

[Clinicopathological analysis of rhabdomyosarcoma of the ocular adenexa]

12 cases including 11 males and 1 female of rhabdomyosarcoma of ocular adenexa were analysed. The average age of the patients was 4.2 years. 9 cases of lesion were located in the orbit, 2 in the eyelid and 1 in conjunctiva. Pathologically 8 cases were embryonal forms, 2 alveolar, 2 polymorphic. Immunohistochemical studies were performed in 8 cases, which showed desmin positive. Myoglobin presented strong or weak positive in 5 cases, suspicious positive in 3 cases. The clinical manifestation, prognosis and treatment were briefly discussed.

[Experimental study and clinical application of end-to-side (transverse incision) anastomosis between small arteries]

The results of end to side anastomoses with longitudinal or transverse incision on the transverse limb were investigated. The anastomosis of the superficial epigastric artery to the femoral artery in rabbits served as the experimental model. The results demonstrated that the microartery end to side anastomosis with transverse arteriotomy is a more preferable anastomosis style with higher patency, easier arteriotomy and suturing, and it effectively prevents anastomotic stoma spasm or stenosis, and in accord with vascular physiological function. It is worthy to be recommended. The clinical successful cases are also reported.

The mutL repair gene of Escherichia coli K-12 forms a superoperon with a gene encoding a new cell-wall amidase

We report a molecular genetic analysis of the region immediately upstream from the Escherichia coli mutL DNA repair gene at 94.8 min. An open reading frame ending 9 bp upstream from the start of mutL corresponds to a 48 kDa polypeptide detected previously in minicells. The predicted amino acid sequence of this 48 kDa polypeptide shows homology to the major N-acetylmuramoyl-L-alanine amidase autolysin of Bacillus subtilis, a known amidase of Bacillus licheniformis, and the product of a Salmonella typhimurium gene that maps near 50 min. Insertions in this upstream gene, which we named amiB, or in mutL did not affect cell shape or viability; however, overexpression of the AmiB polypeptide caused cell lysis, hypersensitivity to osmotic shock and treatment with water, and temporary autolysis by low levels of antibiotics, which are all consistent with AmiB acting as a cell-wall hydrolase. Analysis of chromosomal transcription demonstrated that amiB forms a complex operon with mutL and two additional upstream genes. mutL transcripts also originated from an internal promoter, designated PmutL, located in amiB 312 bp upstream from the translational start of mutL. Together, these results suggest that E. coli contains a second amidase possibly involved in cell-wall hydrolysis, septation, or recycling, and that transcription of this amidase is directly linked to a gene central for DNA repair.

[Pathologic, electron microscopic and experimental examination of band keratopathy]

One hundred and thirteen cases previously diagnosed as band keratopathy were reexamined by light microscopy and histochemistry, 10 cases of which were studied by TEM and 2 cases were studied by SEM. We find that the calcium deposition initially occur as fine calcific particles within the cytoplasm of epithelic cells and in the basal membrane and bowman's layer, which aggregated to form calcific spherules and large calcific masses extracellularly. When 3 normal corneal tissues were frozen and cultured, the calcium deposition occur in the superficial layer of bowman's membrane and in the stromal lamellae, Authors suggest that the degeneration and calcific abnormal metabolism of the cell caused by various factors is the main pathogenesis that leads to the calcific deposit. The evaporation and constructive destruction of the corneal surface in the interpiperbral area inhibits the formation of the lacrimal membrane and results in deposition of calcium salts in the superficial tissue of exposed cornea in a band configuration. The combination of glycosaminoglycan with calcium salts is the dynamics of aggregation of the fine calcific particles to form the calcific spherules and calcific masses.

The natural history of dry type of age-related macular degeneration

To study the natural history of dry type of age-related macular degeneration (AMD) and search for a sensitive method for detecting the development of the disease, the fundus fluorescein angiography, visual acuity, electroretinogram and FM 100-hue test were used to examine 75 eyes, 147 eyes, 73 eyes, and 94 eyes respectively. These examinations were taken at least twice during the follow-up periods. The average age was 63.2 years (50-80 years). The average follow-up was 29.8 months with a range of 3-74 months. It was shown tht there were not any statistically significant difference in the macular lesions and electroretinogram between the initial examinations and after follow-up (P > 0.05). 91.14% of the eyes maintained good visual acuity during the follow-up. Subretinal neovascularization developed only in one of the eyes. The total error score of FM 100-hue test had a statistically significant difference between the initial test and the test taken two years afterwards (P < 0.01). It was suggested that most of the dry type of AMD had a favorable prognosis and that color visual test was a sensitive method for monitoring the development of dry type of AMD.

Dynamic investigation on chromosome aberration of a human retinoblastoma cell line So-Rb50

G-banding and karyotype analyses of cells in seventeen passages of SO-Rb50 during a long period of culture for about four years were performed. Three chromosome markers 13q14-, 1p36+ and 12p13+ were found. Cells possessed 13q14- reduced to zero after the 200th passage while 1p+ and 12p+ cells increased to 100% after 30 and 200 passages respectively. Abnormal chromosomes, ring chromosomes, chromosome radiuses and double minutes were also observed. These chromosomal changes were more often seen before the 200th passage. The significance of these changes are discussed.

Inhibition of brain protein kinase C subtypes by lead

Protein kinase C (PKC) is an important enzyme in mediating cellular signal transduction and neuronal plasticity. Extremely low concentrations (picomolar range) of Pb++ have been reported to activate partially purified PKC from rat brain (Markovac and Goldstein, 1988). However, the lead activation of PKC at such low concentrations is still a matter of discussion (Simons, 1989). To clarify this point, we have examined the lead effect on highly purified PKC subtypes. Pb++ was found to be a potent inhibitor for all three PKC subtypes (types I, II and III) with IC50 of 2 to 10 microM. Characterization of this lead inhibition of PKC suggests that 1) the inhibition is not due to the competition with Ca++, 2) the site of action of lead is on the catalytic domain of PKC, 3) the inhibition is not dependent on the mode of activation (phosphatidylserine/diacylglycerol vs. cis-unsaturated fatty acid) and 4) the inhibition is totally reversible.

Cystic acoustic schwannomas: MR characteristics

PURPOSE

To evaluate the spectrum of MR characteristics of cystic acoustic schwannoma and to investigate its incidence.

METHODS

We retrospectively reviewed the MR findings and clinical records of 16 patients with cystic acoustic schwannomas. In addition, the MR examinations of 411 consecutive patients referred for clinical suspicion of acoustic schwannomas were reviewed retrospectively to assess the incidence of acoustic schwannomas with cystic lesions arising from the internal auditory canal.

RESULTS

Of the 16 acoustic schwannomas with MR evidence of intramural cysts, 11 tumors had single small cysts, and five had multiple intramural cysts of variable size. Intramural cysts in 11 of the 16 tumors exhibited higher signal intensity than that of cerebrospinal fluid; the remainder were isointense to cerebrospinal fluid on both T1- and T2-weighted images. All intramural cysts showed circumferential enhancement after contrast administration. Nine of the 16 cystic acoustic schwannomas also had MR evidence of extramural/arachnoid cysts. Six of the extramural/arachnoid cysts had epicenters away from the dural interface, and the other three cysts were broadly based against the dura. The incidence of cystic acoustic schwannomas was 11.3% and association with extramural/arachnoid cysts 7.5%.

CONCLUSION

Our series suggests that cystic changes in acoustic schwannomas and the association with extramural/arachnoid cysts are not as rare as previously reported by other diagnostic methods. The high signal intensity of intramural cysts is probably related to necrotic material, blood, or colloid-rich fluid. The difference in the MR characteristics of extramural/arachnoid cysts associated with acoustic schwannomas and those of typical arachnoid cysts not associated with neoplasia may be related to higher protein and/or colloid contents secreted by the tumor. Most extramural/arachnoid cysts had epicenters between the tumor and brain, suggesting that the most likely mechanism of formation is peritumoral adhesions. It creates a pseudo-duplication caused by the trapping of fluid between the leptomeninges and the mass, resulting in an acquired type of arachnoid cyst.

[Choroidal malignant melanoma (clinical and pathologic studies of 42 cases)]

Clinical and pathologic studies of 42 cases of choroidal malignant melanoma are reported. We discussed: (1) The diagnosis of early stage cases and later cases with complication. (2) The prognosis is related to the size of tumor, the skill level of surgery, and whether tumor cell invades the superficial sclera of venous duct.

[Glycosaminoglycans associate with corneal transparency]

Keratoplasty specimens form 12 patients with macular corneal dystrophy, 1 patient with systemic glycosaminoglycan stored disease and 12 cases of normal cornea were studied by electron-histochemistry. The results showed that the normal cornea contains chondroitin sulfate in the basement membrane and bowman's membrane, Keratan sulfate and chondroitin sulfate between the collagen fibrils of strome, heparan sulfate on the cell membranes of various cells, and hyaluronic acid on the surface of endothelial cell. The chondroitin sulfate of the stroma of macular corneal dystrophy increases, but the keratan sulfate is absent. The keratocytes and endothelial cells of macular corneal dystrophy synthesize fibrillogranular material and abnormal glycosaminoglycan. The heparan sulfate is stored in the cytoplasm of corneal epithelial cell and keratocyte of systemic glycosaminoglycan stored disease and absent on the membrane of involved cells. The authors suggest that glycosaminoglycan play important role in maintaining corneal transparency and the changes of distribution, character and quantity of glycosaminoglycan in the cornea cause corneal opaqueness.

[Selection of optimum technological conditions for vinegar-processing of fresh rhizoma Corydalis]

The Total alkaloid contents of chloroform extracts and aqueous decoctions of different vinegar-processed samples of fresh Rhizoma Corydalis were determined and compared using orthogonal experimental design. Two optimum schemes suggested by the results are 1. If aqueous decoction is wanted, the fresh tuber Corydalis should be scalded by hot edible vinegar till the liquid has permeated to its center; 2. If total alkaloid extract is required for making Chinese traditional patent medicine, the fresh Rhizoma should be slightly scalded with edible vinegar which has been diluted with an equal volume of water.

[Results of percutaneous transluminal angioplasty]

Percutaneous transluminal angioplasty (PTA) can be subdivided into three epochs: 1. from its inception by Dotter and Judkins up to the first coronary artery stenosis dilatation with the Grüntzig balloon catheter system; 2. from the introduction of coronary stenosis dilatation by Grüntzig up to its unequivocal acceptance; 3. the period of influence of low-risk coronary dilatation on peripheral angioplasty and the search for techniques to compliment or obviate the need for balloon dilatation. The Grüntzig double-lumen balloon catheter system contributed to the lower rate of complications and higher success rate. The clinical acceptance appeared greater for the coronary arteries since, in contrast to the peripheral vascular system, the indication for treatment is established by the physician performing the dilatation. PTA implies percutaneous puncture of a vessel with Seldinger technique and introduction of devices such as guidewires, Dotter or Grüntzig catheters among others, catheters with fiberglass for laser conduction and instruments for fractionating, drilling and cutting. The goal of PTA is to completely or partially eliminate, without surgery, intraluminal vascular narrowing in the presence of peripheral arterial disease in stage II, III or IV. Prerequisite to the use of PTA are: 1. adequate fluoroscopic and angiographic facilities; 2. adequate instrumentation; 3. experience with at least 200 procedures; 4. knowledge of the pathophysiology and adjunctive treatment; 5. knowledge of the treatment of complications; 6. cooperation with a vascular surgery service. A number of factors may influence the results of treatment. Adjunctive medical treatment: the use of platelet aggregation inhibitors and heparin influences the rate of early rethrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)