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Biomedical subjects

B Patterson

Publications and source records attributed to B Patterson.

At least 19 recordsLinked to original sources
PubMed1999

Cis-regulatory elements of the mitotic regulator, string/Cdc25.

Mitosis in most Drosophila cells is triggered by brief bursts of transcription of string (stg), a Cdc25-type phosphatase that activates the mitotic kinase, Cdk1 (Cdc2). To understand how string transcription is regulated, we analyzed the expression of string-lacZ reporter genes covering approximately 40 kb of the string locus. We also tested protein coding fragments of the string locus of 6 kb to 31.6 kb for their ability to complement loss of string function in embryos and imaginal discs. A plethora of cis-acting elements spread over >30 kb control string transcription in different cells and tissue types. Regulatory elements specific to subsets of epidermal cells, mesoderm, trachea and nurse cells were identified, but the majority of the string locus appears to be devoted to controlling cell proliferation during neurogenesis. Consistent with this, compact promotor-proximal sequences are sufficient for string function during imaginal disc growth, but additional distal elements are required for the development of neural structures in the eye, wing, leg and notum. We suggest that, during evolution, cell-type-specific control elements were acquired by a simple growth-regulated promoter as a means of coordinating cell division with developmental processes, particularly neurogenesis.

Animals↗
PubMed1998

Accelerated radiation therapy for primary lymphoma of the brain.

BACKGROUND AND PURPOSE: We report the results of a pilot study of the use of accelerated radiation therapy for 10 patients with primary lymphoma of the brain. MATERIALS AND METHODS: There were five females and five males with a median age of 60 years (range 31-77 years) and a median Karnofsky performance status of 60 (range 30-90). Nine patients underwent biopsies only and one patient underwent a partial resection. The radiation therapy consisted of 50 Gy in 25 fractions over 13 consecutive days to the whole brain including all meningeal surfaces. Two fractions were delivered daily with a minimum interval of 6 h between fractions. Treatment was delivered daily right through the weekend with no treatment interruptions. RESULTS: To date nine patients have died. The median survival was 17 months. Seven patients have demonstrated definite evidence of recurrence (six in the brain and one with positive CSF cytology only). There have been two autopsies, one of which demonstrated diffusely recurrent tumor and the other showing residual disease and radiation demyelination and small areas of necrosis in the pons which undoubtedly was the cause of death at 5 months. One patient alive and free of recurrence at 69 months has bilateral radiation retinopathy and an undiagnosed degenerative neurologic condition. CONCLUSION: We conclude that this accelerated schedule of radiation therapy is ineffective in improving survival in primary lymphoma of the brain and is associated with unacceptable increased toxicity.

Adult↗
PubMed1998

Intragenic suppressors of Dictyostelium myosin G680 mutants demarcate discrete structural elements. Implications for conformational states of the motor.

We are using intragenic suppression to generate inferences about currently inaccessible conformations of the molecular motor myosin. We identified 19 unique suppressors of Dictyostelium G680A and G680V mutants and find that they are structurally and chemically restricted, suggestive of specific, compensatory mechanisms of action. Suppressors cluster in two adjacent elements of the myosin structure, one of which is dominated by substitutions that increase the volume of hydrophobic residues. The suppressors outline a general model for the mechanism of suppression of the G680A and G680V alterations. Secondary phenotypes conferred by suppressors independent of the G680 changes demonstrate that they will be useful substrates for biochemical and genetic characterization.

Animals↗
PubMed1997

Cold-sensitive mutants G680V and G691C of Dictyostelium myosin II confer dramatically different biochemical defects.

Cold-sensitive myosin mutants represent powerful tools for dissecting discrete deficiencies in myosin function. Biochemical characterization of two such mutants, G680V and G691C, has allowed us to identify separate facets of myosin motor function perturbed by each alteration. Compared with wild type, the G680V myosin exhibits a substantially enhanced affinity for several nucleotides, decreased ATPase activity, and overoccupancy or creation of a novel strongly actin-binding state. The properties of the novel strong binding state are consistent with a partial arrest or pausing at the onset of the mechanical stroke. The G691C mutant, on the other hand, exhibits an elevated basal ATPase indicative of premature phosphate release. By releasing phosphate without a requirement for actin binding, the G691C can bypass the part of the cycle involving the mechanical stroke. The two mutants, despite having alterations in glycine residues separated by only 11 residues, have dramatically different consequences on the mechanochemical cycle.

Actins↗
PubMed1997

Requirement for the transcription factor LSIRF/IRF4 for mature B and T lymphocyte function.

Lymphocyte-specific interferon regulatory factor (LSIRF) (now called IRF4) is a transcription factor expressed only in lymphocytes. Mice deficient in IRF4 showed normal distribution of B and T lymphocyes at 4 to 5 weeks of age but developed progressive generalized lymphadenopathy. IRF4-deficient mice exhibited a profound reduction in serum immunoglobulin concentrations and did not mount detectable antibody responses. T lymphocyte function was also impaired in vivo; these mice could not generate cytotoxic or antitumor responses. Thus, IRF4 is essential for the function and homeostasis of both mature B and mature T lymphocytes.

Animals↗
PubMed1997

Primary lymphoma of brain: results of management of a modern cohort with radiation therapy.

PURPOSE: To assess the outcome and prognostic factors for patients with primary lymphoma of brain managed with radiation therapy between 1979 and 1988. METHODS AND MATERIALS: A retrospective review was undertaken of 49 patients referred to Princess Margaret Hospital. There were 25 males and 24 females. Median age was 60 years, with a range of 17-80 years. Tumors were located supratentorially in 35, infratentorially in 10, and both in 4 patients. Single masses were demonstrated on CT brain in 36, and multiple lesions in 13 patients. Cranial irradiation was given in 48, and 11 patients received chemotherapy. All patients in this series were immunocompetent. RESULTS: Over a follow-up range of 3-11 years of surviving patients, with a median of 6 years, 40/49 patients have died. Overall median survival was 1.4 years (17 months) and 5-year actuarial survival was 26%. Statistical analysis revealed the following significant factors: Karnofsky performance status (KPS), age, and distribution pattern of disease on presenting CT brain. Five-year actuarial survival for patients with a KPS > 60 or <60 was 56% and 10%, respectively (P = 0.01); for patients with age < 60 or >60, 5-year actuarial survival was 42% and 9%, respectively (P = 0.03); for patients with solitary or multiple lesions, 5-year actuarial survival was 30% and 15%, respectively (P = 0.04). CONCLUSIONS: We conclude that Karnofsky performance status, age, and distribution pattern on pretreatment CT of brain are significant prognostic factors in primary lymphoma of brain, and that new approaches need to be developed for these patients.

Adolescent↗
PubMed1996

Shiga-like toxin purges human lymphoma from bone marrow of severe combined immunodeficient mice.

Shiga-like toxin-1 (SLT-1) is a bacterial toxin that kills cells by inhibiting protein synthesis. SLT-1 is composed of one cytotoxic A-subunit and five B-subunits that bind to CD77, a cell-surface glycolipid. In the human hematopoietic system, CD77 expression is restricted to a subset of activated B cells and derived cancers. Here we report that SLT-1 treatment of murine bone marrow ex vivo effectively cures severe combined immunodeficient mice of a human B-cell lymphoma xenograft while sparing normal hematopoietic precursor cells. Flow cytometry results using fluorescein isothiocyanate-labeled SLT-1 B-subunit show the high prevalence of expression of SLT-1 receptors (CD77) in human non-Hodgkin's lymphomas, especially follicular lymphomas. These results suggest the use of SLT-1 for the purging of human bone marrow before autologous bone marrow transplant in the case of CD77+ B-cell lymphomas as just one of many possible uses.

Animals↗
PubMed1996

Investigation of tick-borne viruses as pathogens of humans in South Africa and evidence of Dugbe virus infection in a patient with prolonged thrombocytopenia.

In the course of investigating suspected cases of viral haemorrhagic fever in South Africa patients were encountered who had been bitten by ticks, but who lacked evidence of infection with Crimean-Congo haemorrhagic fever (CCHF) virus or non-viral tick-borne agents. Cattle sera were tested by enzyme-linked immunoassay to determine whether tick-borne viruses other than CCHF occur in the country. The prevalence of antibody in cattle sera was 905/2116 (42.8%) for CCHF virus, 70/1358 (5.2%) for Dugbe, 21/1358 (1.5%) for louping ill, 6/450 (1.3%) for West Nile, 7/1358 (0.5%) for Nairobi sheep disease, 3/625 (0.5%) for Kadam and 2/450 (0.4%) for Chenuda. No reactions were recorded with Hazara, Bahig, Bhanja, Thogoto and Dhori viruses. The CCHF findings confirmed previous observations that the virus is widely prevalent within the distribution range of ticks of the genus Hyalomma, while antibody activity to Dugbe antigen was detected only within the distribution range of the tick Amblyomma hebraeum. Cross-reactivity for the nairoviruses, Hazara, Nairobi sheep disease and Dugbe, was detected in serum samples from 3/72 human patients with confirmed CCHF infection, and serum from 1/162 other patients reacted monospecifically with Dugbe antigen. The latter patient suffered from febrile illness with prolonged thrombocytopenia.

Animals↗
PubMed1996

Cold-sensitive mutations of Dictyostelium myosin heavy chain highlight functional domains of the myosin motor.

Dictyostelium provides a powerful environment for characterization of myosin II function. It provides well-established biochemical methods for in vitro analysis of myosin's properties as well as an array of molecular genetic tools. The absence of myosin function results in an array of phenotypes that can be used to genetically manipulate myosin function. We have previously reported methods for the isolation and identification of rapid-effect cold-sensitive myosin II mutations in Dictyostelium. Here, we report the development and utilization of a rapid method for localizing these point mutations. We have also sequenced 19 mutants. The mutations show distinct clustering with respect to three-dimensional location and biochemically characterized functional domains of the protein. We conclude that these mutants represent powerful tools for understanding the mechanisms driving this protein motor.

Amino Acid Sequence↗
PubMed1996

Head circumference measurements in children with autism.

To assess head circumference in children with autism, 148 charts were retrospectively reviewed. All of the children met the Diagnostic and Statistical Manual of Mental Disorders (DSM-III or DSM-III-R) criteria for autism and had no known underlying condition that might affect head circumference. In addition, data were collected regarding height, weight, brain imaging, cognitive development, adaptive behavior, and language. The children were divided into two groups: those with head circumference at or above the 98th percentile (Group 1) and those with head circumference below the 98th percentile (Group 2). Group 1 consisted of 27 (18.2%) of the children. Height measurements were significantly higher in Group 1 as compared with Group 2 (P = .0006) as were weight measurements (P = .0003). Group 1 had a significantly lower percentage of females (P = .04) and lower adaptive behavior scores (P = .0067) than Group 2. Routine brain imaging studies could not explain the macrocephaly in Group 1. The etiology of large head circumference and increased growth indices in children with autism is unclear.

Autistic Disorder↗
PubMed1995

Lack of detection of enteroviral RNA or bacterial DNA in magnetic resonance imaging-directed muscle biopsies from twenty children with active untreated juvenile dermatomyositis.

OBJECTIVE: To investigate for the presence of increased titers of circulating antibody to putative infectious agents and for detectable viral RNA or bacterial DNA in children with active recent-onset juvenile dermatomyositis (DM). METHODS: Magnetic resonance imaging-directed muscle biopsies were performed in 20 children with active, untreated, recent-onset juvenile DM and in age-matched children with neurologic disease. Sera were tested for complement-fixing antibody to Coxsackievirus B (CVB), influenza A and B, parainfluenza 1 and 3, Mycoplasma pneumoniae, mumps, respiratory syncytial virus, and Reovirus; and by immunofluorescence for IgG antibody to Toxoplasma gondii cytomegalovirus and IgM antibody to Epstein-Barr virus. Muscle from juvenile DM patients and control children, CD-1 Swiss mice with and without CVB1 infection, and viral stock positive for CVB1-6 were tested using reverse-transcriptase polymerase chain reaction with 5 primer sets, 4 probes (1 Coxsackievirus, 3 Enterovirus), and universal primers for DNA. RESULTS: No increased antibody, viral RNA, or bacterial DNA was present in the juvenile DM patients or the control children. CONCLUSION: Juvenile DM may be triggered by unidentified agent(s) in the genetically susceptible host.

Adolescent↗
PubMed1995

A novel positive selection for identifying cold-sensitive myosin II mutants in Dictyostelium.

We developed a positive selection for myosin heavy chain mutants in Dictyostelium. This selection is based on the fact that brief exposure to azide causes wild-type cells to release from the substrate, whereas myosin null cells remain adherent. This procedure assays myosin function on a time scale of minutes and has therefore allowed us to select rapid-onset cold-sensitive mutants after random chemical mutagenesis of Dictyostelium cells. We developed a rapid technique for determining which mutations lie in sequences of the myosin gene that encode the head (motor) domain and localized 27 of 34 mutants to this domain. We recovered the appropriate sequences from five of the mutants and demonstrated that they retain their cold-sensitive properties when expressed from extrachromosomal plasmids.

Animals↗
PubMed1995

Highly purified quiescent human peripheral blood CD4+ T cells are infectible by human immunodeficiency virus but do not release virus after activation.

Previous studies have suggested that resting CD4+ lymphocytes can be infected by human immunodeficiency virus (HIV), but viral production is inhibited. If these cells are activated, progeny virions are released. The present data indicate that CD4+ lymphocytes in the G0/G1 stage of the cell cycle which have been highly purified to remove macrophages and activated HLA-DR+ cells can also be infected by HIV. However, our findings differ from those of earlier reports since in this study, infected quiescent CD4+ cells cannot be activated to produce virus after virus inoculation. PCR analyses indicate that reverse transcription in these CD4+ cells is arrested at a very early step in proviral DNA formation (U3-R region). They do not show any evidence of longer DNA transcripts (e.g., U3-gag). When these quiescent infected CD4+ lymphocytes are activated by exposure to mitogens and macrophages and then reinoculated with HIV, the replication of virus takes place. Resting CD4+ lymphocytes are also resistant to infection when they are cocultured with HIV-infected macrophages. Only activated CD4+ cells are susceptible to cell-to-cell transmission. These observations suggest that in vivo tissue macrophages, susceptible to HIV replication, are the major cells initially productively infected by the virus. Then these cells can transfer HIV to activated CD4+ lymphocytes with resultant virus production. The presence of arrested reverse transcription in quiescent cells raises questions about the cellular factors required to permit production of longer HIV proviral DNA copies. Because they can be reinfected once they have been activated, these infected quiescent cells could be a source of recombinant viruses in the host.

CD4-Positive T-Lymphocytes↗
PubMed1995

Direct evidence using in situ polymerase chain reaction that the endothelial cell and T-lymphocyte harbor latent murine cytomegalovirus.

The latent viral genome, harbored indefinitely, threatens reactivation from its remote location. Although polymerase chain reaction (PCR) has detected the organs responsible for latency, it is not known whether latent cytomegalovirus (CMV) infection is maintained within organ-specific cells or ubiquitous elements such as macrophages, endothelial cells, or perhaps others. PCR lacks correlation with tissue structure. However, PCR-based in situ hybridization maintains cellular architecture while allowing the identification of the latently infected cells. Murine CMV (MCMV) nucleic acid sequences in organs of latently infected Balb/C mice were amplified by PCR incorporating digoxigenin-11-dUTP, holding the product DNA in situ (appropriate controls analyzed in parallel). Product DNA was then hybridized in situ with a biotinylated oligonucleotide probe for detection via streptavidin-alkaline phosphatase and light microscopy. Immunohistochemistry verified the positive cell types. Using this technique, we have shown directly in multiple organs of latently infected Balb/C mice including kidney (5/5), liver (5/5), and spleen (5/5) that the endothelial cell and/or T-lymphocyte harbor latent MCMV, whereas in uninfected animals, MCMV DNA was not detected. PCR-based in situ hybridization allows detection of the specific cell(s) harboring latent MCMV DNA while allowing conservation of cellular architecture.

Animals↗
PubMed1994

Renal epithelial cells rapidly bind and internalize calcium oxalate monohydrate crystals.

Renal tubular fluid is supersaturated with calcium and oxalate ions, which can nucleate to form crystals of calcium oxalate monohydrate (COM), the most abundant constituent of kidney stones. However, the mechanisms by which nascent crystals are retained in the nephron and then grow into kidney stones are unclear. An interaction of COM crystals with the surface of renal epithelial cells could be a critical initiating event in nephrolithiasis. To investigate this possibility we used cultures of monkey kidney epithelial cells (BSC-1 line) as a model system and found that [14C]COM crystals bound to the cell surface within seconds. Scanning electron microscopy revealed that crystals bind first to apical microvilli, which subsequently migrate over the crystalline surface. When visualized by transmission electron microscopy, intracellular crystals were located within vesicles. Cytoskeletal responses to crystal uptake were sought by immunofluorescence microscopy, which revealed concentration of F-actin at sites of crystal contact as well as a generalized reorganization of the intermediate filament network containing cytokeratin 8. Uptake of COM crystals did not adversely affect renal epithelial cell growth, and internalized crystals were apparently distributed to daughter cells during division. Rapid adherence of COM crystals to the apical surface of tubular epithelial cells could promote crystal retention in the kidney. Elucidation of factors that regulate this process may provide insight into the pathogenesis of nephrolithiasis.

Animals↗
PubMed1994

Immature human cord blood progenitors engraft and proliferate to high levels in severe combined immunodeficient mice.

Unseparated or Ficoll-Hypaque (Pharmacia, Piscataway, NJ)--fractionated human cord blood cells were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice. High levels of multilineage engraftment, including myeloid and lymphoid lineages, were obtained with 80% of the donor samples as assessed by DNA analysis, fluorescence-activated cell sorting (FACS), and morphology. In contrast to previous and concurrent studies with adult human bone marrow (BM), treatment with human cytokines was not required to establish high-level human cell engraftment, suggesting that neonatal cells either respond differently to the murine microenvironment or they provide their own cytokines in a paracrine fashion. Committed and multipotential myelo-erythroid progenitors were detected using in vitro colony assays and FACS analysis of the murine BM showed the presence of immature CD34+ cells. In addition, human hematopoiesis was maintained for at least 14 weeks providing further evidence that immature hematopoietic precursors had engrafted the murine BM. This in vivo model for human cord blood-derived hematopoiesis will be useful to gain new insights into the biology of neonatal hematopoietic cells and to evaluate their role in gene therapy. There is growing evidence that there are ontogeny-related changes in immature human hematopoietic cells, and therefore, the animal models we have developed for adult and neonatal human hematopoiesis provide useful tools to evaluate these changes in vivo.

Animals↗