Cleavage and recognition pattern of a double-strand-specific endonuclease (I-creI) encoded by the chloroplast 23S rRNA intron of Chlamydomonas reinhardtii

Several group-I introns have been shown to specifically invade intron-minus alleles of the genes that contain them. This type of intron mobility is referred to as 'intron homing', and depends on restriction endonucleases (ENases) encoded by the mobile introns. The ENase cleaves the intron-minus allele near the site of intron insertion, thereby initiating gene conversion. The 23S (LSU) rRNA-encoding gene (LSU) of the chloroplast genome of Chlamydomonas reinhardtii contains a self-splicing group-I intron (CrLSU) that has a free-standing open reading frame (ORF) of 163 codons. Translation of CrLSU intron RNA in cell-free systems produces a polypeptide of approx. 18 kDa, the size expected for correct translation of the ORF. The in vitro-synthesized 18-kDa protein cleaves plasmid DNA that contains a portion of LSU where the intron normally resides, but lacking the intron itself. Cleavage by the intron-encoded enzyme (I-CreI) occurs 5 bp and 1 bp 3' to the intron insertion site (in the 3'-exon) in the top (/) and bottom (,) strands, respectively, resulting in 4-nt single-stranded overhangs with 3'-OH termini. We also show that the recognition sequence of I-CreI spans the cleavage site and is 24 bp in length (5'-CAAAACGTC,GTGA/GACAGTTTGGT).

The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions

Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gp120 and gp41, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.

Overlap syndrome of progressive systemic sclerosis and polymyositis: report of 40 cases

Forty cases of overlap syndrome of progressive systemic sclerosis and polymyositis (OS PSS-PM) are reported in this paper. All of these cases had manifestations of both PSS and PM as well as Raynaud's phenomenon. The sclerodermatous skin changes were diffused over the whole body in most cases. All cases had muscular weakness, elevated skeletal muscle enzyme levels and muscle damage as seen on the electromyogram. Histopathologic changes showed characteristics of myositis. There was noticeable systemic involvement, especially with the digestive and circulatory systems. Serologic examination frequently revealed autoantibodies. The patients responded well to traditional Chinese medicines and corticosteroids.

Cytogenetic studies on peripheral lymphocytes of members from two multiple familial polyposis coli families

Cytogenetic studies were carried out on peripheral lymphocytes of 30 members from two typical familial polyposis coli (FPC) families. It was found that, under low folic acid culture conditions, the chromosome aberration rate of FPC family members (10%) was much higher than that of the control group (2.3%). No significant difference in SCE was found between the two groups. We suggest that the chromosome aberration rate under certain conditions may be used as a parameter for the early detection of FPC in certain FPC families. The analysis of fragile sites sensitive to low folic acid in FPC family members revealed that besides the significant increase of 3p14, which is frequently seen in tumor patients, other unique sites (1p22, 1p32 and 6q21) were also present in most of the FPC patients. Fragile sites 1p22, 1p32 and 6q21 are located near certain well known oncogene loci; thus, they may have something to do with the pathogenesis of FPC. The actual relationship between these fragile sites and FPC remains to be elucidated.

[Progressive systemic sclerosis and polymyositis overlap syndrome: a report of 40 cases]

We studied 40 patients who had clinical features of both typical progressive systemic sclerosis (PSS) and polymyositis (PM). The indurated skin extended over the metacarpophalangeal joints in all patients. The sclerotic changes, diffuse in type, involved the whole body, including the face, neck, extremities and trunk in most cases. All showed Raynaud's phenomenon. All patients had muscle weakness, elevated skeletal muscle enzymes and myogenic disorders in electromyograms, and biopsy of muscles showed myositic changes. The symptoms involved multiple systems, particularly the gastrointestinal and circulatory systems, presenting features of both PSS and PM. Serologic examinations often revealed auto-antibodies in these patients. Treatment with small doses of corticosteroid and traditional chinese medicines usually had good results. We found that either PSS or PM might appear first, or they might appear simultaneously. It is our opinion that as long as we keep alert and carefully observe the features and their development, we can easily diagnose the disease early.

Human immunodeficiency virus vpr gene encodes a virion-associated protein

The vpr gene of human immunodeficiency virus type 1 (HIV-1) is one of the seven accessory genes that are believed to have roles in the virus replication cycle. We report here the detection of a 13 kD vpr protein in sucrose gradient-purified HIV-1. This protein was not detected in cells infected with a virus having a truncated vpr gene that lacks the potential to encode for 26 C-terminal amino acid residues. These findings raise the possibility that virion-associated vpr proteins may be involved in the early life cycle of HIV-1 replication and suggest that the C-terminal region of the vpr gene is essential for its expression.

Theoretical investigation of a phased-array hyperthermia system with movable apertures

A four-applicator phased-array hyperthermia system with movable apertures (MA) is compared with an eight-applicator annular phased-array hyperthermia system with fixed apertures (AA) in terms of the HEP (hyperthermia equipment performance) values, based on two-dimensional models and the bioheat transfer equation. A hybrid element method is used to calculate the zeta-directed two-dimensional electric field with the inhomogeneities in tissue properties taken into account. The amplitudes and phases of each applicator are then optimized with the objective of uniform power deposition in the tumour and no power deposited in normal tissues. The temperature distributions under different blood flow conditions are obtained by solving the bioheat transfer equation using the finite element method. It is found that among the seven patient models studied, the MA and AA in general perform equally well when the tumour has zero blood flow, or equally poorly when the tumour has a blood flow larger than 5 ml/100 g per min. The performance of AA is often significantly better than that of MA when the tumour blood flow is 2.7 ml/100 g per min. The effects of different weighting functions are evaluated. We show that even if uniform absorbed power density (ARD = absorption rate density) could be achieved in the tumour volume with zero ARD in normal tissue the entire tumour would still not be brought to 43 degrees C or greater. However, it is found that the performance of uniform ARD in the tumour is on average far better than either the AA or MA, and choosing the uniform ARD as the objective function improved 35% of the cases for AA and 16% for MA. The optimization formula includes a weighting function that can be varied for different tissues. By decreasing the weights in regions of high blood flow the HEP values can sometimes be improved quite noticeably. Finally, the importance of the locations of applicators is studied. The results obtained indicate that the applicators should be placed about 5 cm or more away from the patient body (assuming water is the coupling medium) to ensure good HEP ratings.

[Clinical analysis of 60 cases of scleredema]

Clinical analysis of 60 cases of scleredema is reported with emphasis on clinical manifestations, microcirculatory changes, histopathological and ultrastructural observations. It is noted that the prognosis of scleredema may not always be good, and severe cases may lose their working capacity or even die. Attention should be paid to proper treatment of scleredema and long term follow-up is indicated to observe its course, outcome and pattern of evolution.

[Studies on stimulating circulation to end stasis in scleroderma]

Of 725 cases of scleroderma, 265 were of systemic type (the sex ratio being 1M:6F) and 460 of circumscribed type (the sex ratio being 1M:9F). The patients were divided into three groups and treated with three different stimulating circulation to end stasis (SCES) prescriptions. Satisfactory therapeutic effects were obtained in all. According to the clinical practice and laboratory findings, although SCES therapy exerted manifold actions on the disease, it not only softened the indurated connective tissues, tonified the body and improved the symptoms, but also improved laboratory indexes as follows: nailfold bed capillary, parameter of the peripheral blood stream in patients, content of urinary 2-ketol, 17-KS, free corten, serum joint-hexose, amino-hexose and histopathology including ultrastructure of the skin. The main effect was the improvement of circulation, especially the microcirculation and regulation of the metabolism of the connective tissues. Great attention should be paid to the drug's function of softening the indurated connected tissues. For further investigation, the authors have stressed three important points: screening of clinical symptoms and signs, examination of blood circulatory disturbances, and examination of pathological changes of the connective tissue. The necessity of developing new criteria for judging the therapeutic effects was emphasized.