Phase-stepped fringe projection by rotation about the camera's perspective center.

A technique to produce phase steps in a fringe projection system for shape measurement is presented. Phase steps are produced by introducing relative rotation between the object and the fringe projection probe (comprising a projector and camera) about the camera's perspective center. Relative motion of the object in the camera image can be compensated, because it is independent of the distance of the object from the camera, whilst the phase of the projected fringes is stepped due to the motion of the projector with respect to the object. The technique was validated with a static fringe projection system by moving an object on a coordinate measuring machine (CMM). The alternative approach, of rotating a lightweight and robust CMM-mounted fringe projection probe, is discussed. An experimental accuracy of approximately 1.5% of the projected fringe pitch was achieved, limited by the standard phase-stepping algorithms used rather than by the accuracy of the phase steps produced by the new technique.

Genomic instability and catalase gene amplification induced by chronic exposure to oxidative stress.

Chronic exposure (>200 days) of HA1 fibroblasts to increasing concentrations of H2O2 or O2 results in the development of a stable oxidative stress-resistant phenotype characterized by increased cellular antioxidant levels, particularly catalase (D. R. Spitz et al, Arch. Biochem. Biophys., 279: 249-260, 1990; D. R. Spitz et al., Arch. Biochem. Biophys., 292: 221-227, 1992; S. J. Sullivan et al., Am. J. Physiol. (Lung Cell. Mol. Physiol.), 262: L748-L756, 1992). Acutely stressed cells failed to develop a stably resistant phenotype or increased catalase activity, suggesting that chronic exposure is required for the development of this phenotype. This study investigates the mechanism underlying increased catalase activity in the H2O2- and O2-resistant cell lines. In H2O2- and O2-resistant cells, catalase activity was found to be 20-30-fold higher than that in the parental HA1 cells and correlated with increased immunoreactive catalase protein and steady-state catalase mRNA levels. Resistant cell lines also demonstrated a 4-6-fold increase in catalase gene copy number by Southern blot analysis, which is indicative of gene amplification. Chromosome banding and in situ hybridization studies identified a single amplified catalase gene site located on a rearranged chromosome with banding similarities to Z-4 in the hamster fibroblast karyotype. Simultaneous in situ hybridization with a Z-4-specific adenine phosphoribosyltransferase (APRT) gene revealed that the amplified catalase genes were located proximate to APRT on the same chromosome in all resistant cells. In contrast, HA1 cells contained only single copies of the catalase gene that were not located on APRT-containing chromosomes, indicating that amplification is associated with a chromosomal rearrangement possibly involving Z-4. The fact that chronic exposure of HA1 cells to either HO2 or 95% O2 resulted in gene amplification suggests that gene amplification represents a generalized response to oxidative stress, contributing to the development of resistant phenotypes. These results support the hypothesis that chronic exposure to endogenous metabolic or exogenous environmental oxidative stress represents an important factor contributing to gene amplification and genomic instability.

Construction of a pilot human YAC library in a recombination-defective yeast strain.

Using high-molecular-weight DNA fragments from a human lymphoblastoid cell line, a pilot collection of 2500 YACs was constructed in YKK115, a recombination-deficient strain of Saccharomyces cerevisiae carrying mutations in both the rad51 and rad52 genes. Analysis of 520 clones from the current library by pulsed-field gel electrophoresis revealed more than 97% single YACs with an insert size averaging 340 kb. Fluorescent in situ hybridization (FISH) performed with 37 clones on metaphase chromosomes suggested a high proportion mapping at centromeric (7) or telomeric (4) locations. The results are consistent with the stabilization of YACs in strains disarmed in recombination functions [Kohno, K., Oshiro, T., Kishine, H., Wada, M., Takeda, H., Ihara, N., Imamoto, F., Kano, Y. and Schlessinger, D. (1997) Human YACs unstable in a rad52 single mutant strain become stable in rad51rad52 double mutant. Gene, 000, 000-000 (GENE 10429)], and further suggest that the YACs may include regions that have been difficult to clone in other strains.

Cloning and chromosomal localization of the gene coding for human protein kinase CK1.

A cDNA clone coding for human protein kinase CK1 (casein kinase 1) has been isolated and sequenced demonstrating that it corresponds to a homolog of the CK1 alpha form found in bovine brain. The derived amino acid sequence of the human CK1 alpha is identical to the bovine counterpart except that it contains 12 extra amino acids at the carboxyl end. Using this cDNA sequence and PCR amplification, YAC genomic clones that contain this human CK1 alpha sequence have been isolated. These YACs have been used for fluorescent in situ hybridization in order to localize the human CK1 alpha gene to chromosome 13q13.

Amplification and altered expression of the hsc70/U14 snoRNA gene in a heat resistant Chinese hamster cell line.

We have recently demonstrated that the heat resistant phenotype of the HR-1 variant isolated from HA-1 Chinese hamster fibroblasts after a series of heat shocks is associated with the increased expression of Hsc70, the constitutive form of Hsp70 (Laszlo and Li 1985). Here, we report the cloning and characterization of the Chinese hamster hsc70 gene and its organization and expression in wild type HA-1 and permanently heat resistant HR-1 cells. DNA sequencing revealed that the structure and nucleotide sequence of the hamster hsc70 gene is highly homologous to the human and rat genes coding for Hsc70. Three of the eight introns of the hamster hsc70 gene encode U14 small nucleolar RNAs, as has been demonstrated in other species. Although putative transcriptional elements, including a TATA box, two inverted CAT boxes, and two sets of heat shock elements (HSEs) are completely conserved in the human and hamster hsc70 genes, the regulation of expression of the hamster hsc70 gene is different from that reported for its human counterpart in that the mRNA coding for Hsc70 increases at least 10-fold after a mild heat shock in Chinese hamster cells while no induction of Hsc70 by heat shock has been reported in human cell lines. In situ hybridization revealed a complex chromosomal rearrangement in HR-1 cells which results in the 4- to 5-fold amplification of the hsc70 gene as indicated by genomic Southern blots. In association with this amplification of the hsc70 gene, the levels of Hsc70 mRNA and U14 snoRNA are increased in the HR-1 cells under both normal growing conditions and after heat shock. Thus, the elevated expression of both Hsc70 and U14 snoRNA might play a role in the heat resistant phenotype of the HR-1 cells. This is the first report of the amplification of a heat shock gene and the possible induction of gene amplification by heat shock.

Problems and pitfalls in assessing human T-lymphocyte mutant frequencies.

The measurement of 6-thioguanine-resistant frequencies in human T-lymphocytes has been used to quantitate the in vivo HPRT mutant frequency. The data so far indicate a large variability in normal healthy individuals. The reliability with which wells are identified for clonal growth in the assay was investigated using 5 different methods of scoring: visual scoring, uptake of [3H]thymidine (either by cut off point or by statistical analysis), cell count and cytogenetic analysis. None of these methods presented a viable means of scoring the assay. An examination of the statistical precision of the assay under the limitations imposed by the experimental conditions leads to the conclusion that there is a large inherent error associated with the estimated mutant frequencies. Analysis of the T-lymphocyte subpopulations by cell surface monoclonal antibodies also leads us to believe that the observed mutant frequencies may not be representative of the true in vivo mutant frequencies. If the assay is to be used as a sensitive screen for individual or population exposure to possible mutagens, a closer understanding of the biology of the assay is indicated, and a comprehensive reevaluation of the methodology required. The utility of the system for studying qualitative aspects of human mutagenesis is not in doubt.

Cutaneous neuro-endocrine (Merkel cell) carcinoma.

Two cases of neuro-endocrine (Merkel cell) tumours of the skin are reported. There was evidence of distant relapse in both patients who eventually succumbed to the disease. The wide range of clinical and radiological manifestations of this rare tumour are discussed and the literature reviewed.

Inguinal and iliac lymph node involvement in germ cell tumours of the testis: implications for radiological investigation and for therapy.

The clinical details of 1191 patients with primary germ cell tumours of the testis seen at the Royal Marsden Hospital between 1977 and 1989 were reviewed in order to determine the incidence of inguinal or iliac node metastases. This was detected in 22 patients, 11 with inguinal and 11 with iliac lymphadenopathy. Seven of these patients had a history of maldescent and orchidopexy, and one patient had congenitally fused testes. Of the remaining 14 patients, eight had bulky para-aortic lymphadenopathy (5 cm or greater in diameter), one had histological evidence of breach of the tunica vaginalis by tumour, and in five patients no predisposing factors were identified. Eight patients had a seminoma, 11 a non-seminoma, and two a combined tumour. Inguinal or iliac nodes were significantly more common in the group of patients defined by bulky para-aortic disease or a history of maldescent and orchidopexy (15/267) than those without either factor (7/924, P less than 0.0004). Patients with a history of maldescent, congenital anomalies of the genitourinary system, or with bulky para-aortic disease, should routinely have the pelvis and inguinal regions included in a staging or follow-up CT scan. These factors should also influence the extent of the radiation field or of surgical dissection when these modalities are employed.

Deep venous thrombosis of the upper extremity--a case report.

This report describes a case of deep venous thrombosis (DVT) of the upper extremity following a routine blood donation by a regular donor. This cause of an upper limb DVT has not been previously reported. A review of the literature follows.

Epidermoid tumour of the cerebellopontine angle: diagnosis by MRI.

Epidermoids are the third most common cerebellopontine angle tumour, and their diagnosis in the last two decades has been largely obtained using computed tomography (CT). More recently magnetic resonance imaging (MRI) has become a valuable diagnostic tool, and the signal characteristics and enhancement pattern of an epidermoid following intravenous gadolinium with MRI is presented and the literature reviewed.

Spontaneous subclavian vein thrombosis.

A young man presented with swelling of his right arm and engorgement of the superficial veins over the shoulder. Bilateral upper limb venography was performed and confirmed the presence of thrombus in the right subclavian vein. Deep venous thrombosis (DVT) of the upper extremity is an unusual thrombotic event with a reported incidence of 1-2% of all cases of venous occlusion. Review of the literature reveals a number of diverse aetiologies, and no agreement regarding the best terminology for the subgroups of this disorder.

MRI diagnosis of accessory soleus muscle strain.

An accessory soleus muscle is a rare anatomical variant. Clinical awareness of this entity and the appropriate use of magnetic resonance imaging (MRI) can yield a definitive diagnosis in those patients with symptomatic accessory muscles. A case is presented in which the unique sensitivity of MRI in the evaluation of exertional muscle injuries proved useful in the detection of an accessory soleus muscle strain.

Magnetic resonance imaging in sports medicine--an overview.

As more Britons become health conscious and are involved in a variety of sporting events, sports-related injuries are a daily occurrence. Although evaluation of bony abnormalities resulting from acute and chronic sports injury by conventional radiography and bone scintigraphy has been satisfactory, the assessment of soft tissue and tendinous injury is more difficult and imprecise. Due to its superior contrast sensitivity and multiplanar imaging capability, magnetic resonance imaging has already shown great promise in delineating soft-tissue and tendinous abnormalities. In addition, marrow pathology is exquisitely displayed.

Magnetic resonance imaging in the diagnosis of sacral stress fracture.

Low back and buttock pain in athletes can be a source of frustration for the athlete and a diagnostic dilemma for the doctor. Sacral stress fractures have been increasingly recognised as a potential cause of these symptoms. As plain radiographs are often normal and the radiation load of an isotope bone scan is substantial, the alternative use of magnetic resonance imaging in the diagnosis of a sacral stress fracture is highlighted in this case report.

Extrachromosomal maintenance and amplification of yeast artificial chromosome DNA in mouse cells.

Linear and circular forms of a 660-kb yeast artificial chromosome (YAC) containing the human hypoxanthine phosphoribosyltransferase gene were introduced into mouse L A-9 cells by fusion with yeast spheroplasts, and in situ hybridization was used to determine the location and fate of the yeast- and YAC-derived DNA in 25 fusion cell lines. Human and yeast DNAs were observed as extrachromosomal DNA molecules, present at least 27 cell divisions after fusion, in half the cell lines. The extrachromosomal molecules replicate extrachromosomally but segregate poorly like plasmids that contain an autonomously replicating sequence element in yeast. This system may allow analysis of DNA requirements for replication and segregation in mammalian cells. The extrachromosomal elements resemble double minutes (DMs), and in five cell lines human and yeast DNAs were present as very large integrated blocks of DNA resembling homogeneously staining regions (HSRs). Thus, the fusion cell lines contain the two characteristic forms of amplified DNA observed in cancer cell lines, DMs and HSRs, indicating that these can be formed from fragments of DNA introduced by cell fusion.