Using a TRAPS upstream transmission detector to verify multileaf collimator positions during dynamic radiotherapy delivery.

With the advancement of high-precision radiotherapy and the increasing use of higher intensity beams, the risk to the patient increases should the radiotherapy machine malfunction. Hence more accurate treatment verification is required. In this paper we provide a solution for real-time monitoring of X-ray beams from radiotherapy linear accelerators using monolithic active pixel sensors. We show that leaf errors can be detected with high precision in static fields and IMRT step and shoot, and accurate leaf tracking is possible in Volumetric Modulated Arc Therapy. The prototype MAPS detector meets the criteria of 1% attenuation acceptable for clinical use.

Effects of cyclic bending and physiological solution on plasma-sprayed hydroxylapatite coatings of varying crystallinity.

This study investigated the effects of cyclic bending stress levels and testing in simulated physiological solutions or air on the integrity of plasma-sprayed hydroxylapatite (HA) coatings of two different crystallinities. Hydroxylapatite-coated commercially pure (CP) Ti rods were evaluated by immersion testing in Hank's Balanced Salt Solution (HBSS) and by rotating bending in air and HBSS. Static immersion testing of nonstressed specimens resulted in significant microcracking of coating surfaces after 42 days. Specimens cyclically tested at bending stresses above the yield strength of Ti experienced low cycle fatigue failure of the Ti substrates prior to spallation of the HA coatings. Coatings tested at 1 x 10(6) cycles with interface bending stresses of 180 MPa displayed increased surface microcracking, but no bulk coating spallation. Coatings cycled in HBSS displayed greater amounts of microcracking and surface alteration than samples cycled in air. There was no apparent relation between HA crystallinity and mechanical integrity under cyclic bending stresses.

Evidence for cooperation between murine leukemia virus Env molecules in mixed oligomers.

A retroviral Env molecule consists of a surface glycoprotein (SU) complexed with a transmembrane protein (TM). In turn, these complexes are grouped into oligomers on the surfaces of the cell and of the virion. In the case of murine leukemia viruses (MuLVs), the SU moieties are polymorphic, with SU proteins of different viral isolates directed towards different cell surface receptors. During maturation of the released virus particle, the 16 C-terminal residues of TM (the R peptide or p2E) are removed from the protein by the viral protease; this cleavage is believed to activate the membrane-fusing potential of MuLV Env. We have tested the possibility that different MuLV Env proteins in the same cell can interact with each other, both physically and functionally, in mixed oligomers. We found that coexpressed Env molecules can be precipitated out of cell lysates by antiserum which reacts with only one of them. Furthermore, they can evidently cooperate with each other: if one Env species lacks the R peptide, then it can apparently induce fusion if the SU protein of the other Env species encounters its cognate receptor on the surface of another cell. This functional interaction between different Env molecules has a number of implications with respect to the mechanism of induction of membrane fusion, for the genetic analysis of Env function, and for the design of targeted retroviral vectors for gene therapy.

Modulation of bacteriophage T4 capsid size.

Bacteriophage T4 capsid assembly requires the vertex protein (gp24). Mutations that bypass this requirement are found in gene 23, which produces the major capsid protein (gp23). The latter were used to study the role of gp24 in head length control. We found that gp24 is no longer present in the capsids of several gp24 bypass mutants. We measured the capsid lengths of several of these bypass mutants, because gp24 had been reported to be implicated in head length control. One bypass mutant (reported in 1977) produced 40-60% short headed ("petite") phage in the presence of wild-type amounts of gp24. The bypass mutations, when combined with amber mutations in gene 24, produced normal size heads in either suppressor or nonsuppressor host bacteria. When several known bypass mutations were back-crossed with wild-type phage, one-third of the byp/24wt mutants isolated produced large amounts of petite phage, indicating that the ability to produce petite phage is a general property of the bypass mutations. Sequencing several of these bypass mutants showed that those that produced petite phage contained at least one additional missense mutation in gene 23. This suggests that gp24 itself has no direct role in head length regulation, but that in the presence of bypass 24 mutations and certain easily acquired gene 23 mutations (called trb) the gp23-gp24 interactions can modulate head length.

High level production of potyvirus-like particles in insect cells infected with recombinant baculovirus.

The full length gene for the coat protein (CP) of the potyvirus, Johnsongrass mosaic virus, was incorporated into recombinant baculovirus and expressed in insect cells. Western blot and Coomassie-stained polyacrylamide gel electrophoresis analysis of infected insect cells demonstrated that CP was produced in large quantity. Electron microscopic examination of these cells showed the presence of numerous potyvirus-like particles in the cytoplasm. Morphologically the particles resembled potyvirus particles assembled in vitro in the absence of viral RNA and those found in Escherichia coli expressing the recombinant CP gene.

Production of an enzymatically inactive analog of phospholipase D from Corynebacterium pseudotuberculosis.

The gene pld, encoding the phospholipase D (PLD) of Corynebacterium pseudotuberculosis, was mutagenized using formic acid and then expressed in Escherichia coli. Mutagenesis was targeted at the coding region of pld, so as to produce only one or a limited number of point mutations. Transformants were screened for the enzymatic and immunological properties of their PLD products. One clone was found to produce a protein which was enzymatically inactive, but which was comparable to the wild-type PLD in size and antigenicity. The sequence of the pld mutant revealed a single base change. As a consequence, the codon for His20 was converted to Tyr. These results suggest that His20 forms part of the active site of the PLD molecule. If this protein is immunogenic in sheep, it would form the basis of a genetically inactivated vaccine.

Extensive polymorphism of the BoLA-DRB3 gene distinguished by PCR-RFLP.

A polymerase chain reaction (PCR)-based method is described for typing of alleles of the bovine lymphocyte antigen (BoLA)-DRB3 gene. A total of 30 DRB3 alleles were distinguished by digestion of PCR amplification products of BoLA-DRB3 exon 2 with RsaI, BstYI and HaeIII (PCR-RFLP). All restriction fragment patterns, with the exception of one HaeIII pattern, were consistent with restriction sites that were found among 14 previously sequenced DRB3 alleles. The PCR-RFLP typing method was evaluated on 168 genomic DNA samples collected from animals of 10 cattle breeds, 48 of which were typed in the Fourth International BoLA Workshop for BoLA-DRB and -DQ by conventional restriction fragment length polymorphism (RFLP) analysis using heterologous and homologous DNA probes. Thirty-one DRB/DQ haplotypes containing 23 DRB3 alleles were identified among the 48 workshop animals analysed. Using PCR-RFLP, 11 DRB3 alleles were identified in 18 workshop animals for which DRB RFLPs were not informative. PCR-RFLP typing of additional animals revealed five new DRB3 alleles, of which three contained a putatively located three basepair deletion in the identical position as found for the sequenced allele DRB*2A. PCR-RFLP was shown to be a rapid and sensitive method for the detection of polymorphism in a functionally relevant domain of the BoLA-DRB3 gene and should be useful for studying the evolution of DRB polymorphism in cattle and other Bovidae.

Immunisation against ovine caseous lymphadenitis: correlation between Corynebacterium pseudotuberculosis toxoid content and protective efficacy in combined clostridial-corynebacterial vaccines.

Groups of sheep were dosed with vaccines containing Corynebacterium pseudotuberculosis toxoid combined in varying amounts with 5 clostridial antigens. Resistance of the sheep to infection with C pseudotuberculosis was tested at 1, 6 and 12 months after vaccination by infection with pus from ovine lymph glands actively infected with C pseudotuberculosis. The outcome was assessed 3 months after challenge by slaughter and inspection of the sheep for caseous lymphadenitis lesions. Protection was demonstrated by a significant reduction in the proportion of immunised sheep exhibiting lesions compared with control sheep, and by fewer abscesses in affected immunised sheep than in affected control sheep. A positive correlation was found between amount of C pseudotuberculosis toxoid administered and degree of protection obtained. Chromatographically-purified toxoid induced essentially the same protection, suggesting that anti-toxic immunity is the major factor in protection.

FP/MIS: a management information system for a community family planning clinic.

The management information system (FP/MIS) used by the Howard University Center for Family Planning Services, which operates community family planning clinics in Washington, D.C. is described. The system was developed to satisfy program objectives in patient management, program planning and evaluation, resource management, federal reporting systems and clinical, epidemiological and health services research. The data collection forms used in the system and the output from the four data display groups--patient profile, resource management, quality of care and epidemiology-are described along with examples of their use.

PIP: The Howard University Center for Family Planning Services (HUCFPS) was established in June 1970 with the stated goals of promoting maternal and child health and disseminating family planning information and supplies within the community target area in the District of Columbia. The management information system (FP/MIS) used by the Center was developed to facilitate program objectives, program planning and evaluation and to meet federal reporting requirements. Development of the FP/MIS is described. The input and encounter forms are described and pictured. Uses made of the collected data are outlined. Patient profiles, resource management, quality of care, and epidemiological assessments can be made from the data.