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Biomedical subjects

M Potter

Publications and source records attributed to M Potter.

At least 109 records · Page 6Linked to original sources
PubMed1994

Identification of two genes on chromosome 4 that determine resistance to plasmacytoma induction in mice.

BALB/cAn mice are highly susceptible to the induction of plasmacytomas (PCTs) by the i.p. injection of paraffin oils, whereas DBA/2 mice are solidly resistant. To search for genes that control the dominant resistant phenotype of DBA/2, BALB/c.DBA/2 (C.D2) congenic strains were constructed, and the susceptibility and resistance to PCT development were determined. PCT formation takes place over an extended period of 365 days but begins morphologically in focal proliferations of atypical plasma cells (foci) in the reactive oil granuloma that forms on mesenteric surfaces. Cells from some of these foci spread to other locations in oil granuloma tissue, forming new foci. Mice that develop six or more foci appear to be progressing towards eventual overgrowth and replacement of all peritoneal tissues with PCT cells. From Days 100 to 250, between 28 and 56% of PCT-susceptible BALB/cAn mice had 6 or more foci, whereas less than 5% of resistant DBA/2, BALB/c x DBA/2 F1 (hereafter called CD2F1), C57BL/6, and BALB/cJ mice had 6 or more foci. Four CD2 congenic strains carrying D2 alleles of genes on chromosomes other than chromosome 4 were highly susceptible. Between 0 and 20% of the mice in C.D2-Chr 4 congenic strains C.D2-MIA, C.D2-TF3, C.D2-Fv-1n/n, C.D2-Pnd7, C.D2-Lgm-1A, C.D2-Lgm-1B, C.D2-Lgm-1C, and C.D2-Lgm-1H developed 6 or more foci from 125 to 260 days, indicating resistance. The segments of DBA/2 chromosome 4 chromatin in C.D2-Fv-1n/n and C.D2-Pnd7 were discontinuous with those in C.D2-TF3, C.D2-Lgm-1A, C.D2-Lgm-1B, C.D2-Lgm-1C, and C.D2-Lgm-1H, indicating there are at least two genes (Pctr1 and Pctr2) in the distal half of this chromosome that confer resistance. Pctr1 is located between Ifa and D4Rck41, and Pctr2 is between Tnfr-1 and Pkcz. Each locus acting alone distinctly conferred a partial resistant phenotype. Pctr1 and Pctr2 did not appear to prevent the formation of clonal foci but did appear to limit the ability of the plasma cells in foci to acquire greater autonomy; thus, these genes affect tumor progression.

Animals↗
PubMed1994

PCR assessment of bone marrow status in 'isolated' extramedullary relapse of childhood B-precursor acute lymphoblastic leukaemia.

Approximately one-third of first relapses of childhood ALL occur at an extramedullary site without morphological evidence of bone marrow disease. However, the high incidence of subsequent medullary relapse in these cases strongly suggests that leukaemia is present at submicroscopic levels at the time of 'isolated' relapse. PCR analysis of immunoglobulin heavy chain (IgH) and T-cell receptor (TCR) gene rearrangements now allows detection of leukaemia at levels as low as 0.001%. We have therefore used this technique to reassess bone marrow status at morphologically isolated relapse in 13 children with B-lineage ALL (11 with off-treatment relapses, two on treatment). In 12 of these 13 patients marrow disease was detectable by PCR at the time of this relapse--in all cases at levels below the threshold of light microscopy. Where relapse occurred off-therapy this indicated re-emergence of disease. since MRD has never been detected by PCR at this stage in patients remaining in long-term remission. In both patients who relapsed on-therapy the level of MRD at the time of relapse represented an increase on that seen in their previous marrow sample. We conclude that re-emerging bone marrow disease can be detected in most cases of 'isolated' relapse when investigated by this highly sensitive technique. Our findings at a molecular level confirm a long-held clinical suspicion and indicate that full systemic re-induction as well as local therapy is obligatory for these children.

Adolescent↗
PubMed1994

Construction of a series of congenic mice with recombinant chromosome 1 regions surrounding the genetic loci for resistance to intracellular parasites (Ity, Lsh, and Bcg), DNA repair responses (Rep-1), and the cytoskeletal protein villin (Vil).

The interval of mouse chromosome 1 extending from Idh-1 to Pep-3 harbors the natural resistance gene Ity/Lsh/Bcg; it controls the outcome of infection with Salmonella typhimurium, Leishmania donovani, and several Mycobacterium species. This region also contains a DNA repair gene, Rep-1, which determines the rapidity with which double-strand breaks in chromatin are repaired. BALB/cAnPt and DBA/2N mice differ in their phenotypic expression of these genes. To generate appropriate strains of mice for the study of these genes, a series of 10 C.D2 congenic strains recombinant across a 28-centimorgan interval of mouse chromosome 1 extending from Idh-1 to Pep-3 were derived from crosses of the C.D2-Idh-1 Pep-3 congenic strain back to BALB/cAn. Analyses of these recombinant strains will allow the correlation of biological-immunological phenotypes with defined genetic regions.

Animals↗
PubMed1994

Construction of a BALB/c congenic mouse, C.C3H-Lpsd, that expresses the Lpsd allele: analysis of chromosome 4 markers surrounding the Lps gene.

Development of a congenic BALB/c mouse strain that contains a segment of chromosome 4 including the Lpsd allele of the lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ strain is presented. On the basis of LPS-induced spleen cell mitogenesis, macrophage tumor necrosis factor secretion, and tyrosine phosphorylation in vitro and lethality in galactosamine-sensitized mice in vivo, the C.C3H-Lpsd strain provides a model of LPS hyporesponsiveness that is comparable to that of the parental C3H/HeJ strain. Analysis of markers in this region indicates that length of the donor fragment is approximately 5.5 centimorgans. Thus, the C.C3H-Lpsd strain provides an important genetic tool for analysis of markers in this region and for examining functional effects of Lpsd expression on the BALB/c background.

Alleles↗
PubMed1994

DNA repair defects associated with chromosomal translocation breaksite regions.

Using an assay that measures the removal of UV-induced pyrimidine dimers in specific DNA sequences, we have found that the Pvt-1, immunoglobulin H-C alpha (IgH-C alpha), and IgL-kappa loci are poorly repaired in normal B lymphoblasts from plasmacytoma-susceptible BALB/cAnPt mice. Breaksites in these genes are associated with the chromosomal translocations that are found in > 95% of BALB/cAnPt plasmacytomas. In contrast to those from BALB/cAnPt mice, B lymphoblasts from plasmacytoma-resistant DBA/2N mice rapidly repair Pvt-1, IgH-C alpha, and IgL-kappa. Further, (BALB/cAnPt x DBA/2N)F1 hybrids, which are resistant to plasmacytoma development, carry an efficient (DBA/2N-like) repair phenotype. Analysis of allele-specific repair in the IgH-C alpha locus indicates that efficient repair is controlled by dominant, trans-acting factors. In the F1 heterozygotes, these factors promote efficient repair of BALB/cAnPt IgH-C alpha gene sequences. The same sequences are poorly repaired in the BALB/cAnPt parental strain. Analysis of the strand specificity of repair indicates that both strand-selective and nonselective forms of repair determine repair efficiency at the gene level in nonimmortalized murine B lymphoblasts.

Animals↗
PubMed1994

A novel c-myc-activating reciprocal T(12;15) chromosomal translocation juxtaposes S alpha to Pvt-1 in a mouse plasmacytoma.

Oil-induced murine plasmacytomas typically carry c-myc-activating non-random reciprocal chromosomal translocations that take the form of either a T(12;15) that fuses the c-myc proto-oncogene to an immunoglobulin heavy chain switch region or a T(6;15) that juxtaposes the Pvt-1 locus, located 220 kb 3' of c-myc, to the immunoglobulin light china locus, C kappa. In this report we show that the plasmacytoma ABPC 60 harbors a novel c-myc-activating T(12;15) in which the chromosome 15 breakpoint occurs in the Pvt-1 region, resulting in the head-to-tail juxtaposition of the Pvt-1 major breakpoint cluster to the IgA switch region. Restriction mapping and nucleotide sequencing of this atypical translocation indicate that a paracentric inversion in chromosome 12 must have preceeded the translocation. This is the first example of a T(12;15) with a break 3' of the c-myc gene. The rearrangement places the 3' C alpha enhancer (3' alpha E) greater than 200 kb downstream of the c-myc promoters, however c-myc mRNA levels are similar to those observed in plasmacytomas with typical T(12;15)s that translocate 3' alpha E much closer (15-25 kb) and upstream of c-myc. The up regulation of c-myc that results from this rearrangement is thought to be brought about by the interaction of the c-myc promoters with the IgA enhancer element that has been strategically relocated into the Pvt-1 region.

Animals↗
PubMed1993

Detection of recombinations between c-myc and immunoglobulin switch alpha in murine plasma cell tumors and preneoplastic lesions by polymerase chain reaction.

Virtually all murine plasmacytomas carry chromosomal translocations that activate c-myc. The predominant (approximately 90%) c-myc-activating chromosomal translocation in pristane (2,6,10,14-tetramethylpentadecane)-induced plasmacytomas in BALB/c mice is a reciprocal translocation t(12;15) in which an immunoglobulin heavy-chain switch sequence is joined to the 5' region of c-myc. The most common switch region involved is S alpha. We developed a direct PCR method to screen for recombinations between c-myc and S alpha. The critical step in establishing the method was the cloning and sequencing of the 5' flank of C alpha, a region with a reduced number of switch repeats that is much more favorable for designing specific PCR primers than the highly repetitive S alpha region. In applying this PCR method, we detected translocation-specific junction fragments in transplanted (10/16, 63%) and primary (5/15, 33%) plasmacytomas. Moreover, the sensitivity of a nested version of that technique allowed us to discern rare t(12;15)s in BALB/c mice in the preneoplastic stage of plasmacytoma-genesis (8/20 mice, 40%) as early as 30 days after administration of pristane. We conclude that t(12;15) is the probable primary, if not initiating, oncogenic step in plasmacytomagenesis.

Animals↗
PubMed1993

In vitro culture of primary plasmacytomas requires stromal cell feeder layers.

Attempts to grow primary murine plasmacytomas in vitro have, to date, been largely unsuccessful. In this study, we demonstrate that long-term in vitro growth of primary plasmacytomas is accomplished by using feeder layers composed of stromal cells from the initial site of plasmacytomagenesis. The early neoplastic lines established in this manner are dependent on physical contact with the stromal layer, which is mediated in part by CD44, for growth and survival. The stromal cells provide at least two stimuli for the plasma cells, one being interleukin 6 and the second, of unknown nature, resulting from direct physical interaction that cannot be replaced by soluble factors. These plasma cell lines have been passaged for as long as 20 months yet still maintain characteristics associated with primary plasmacytomas as they will grow in vivo only in pristane-primed animals, indicating a continued dependence on the pristane-induced microenvironment characteristic of early-stage tumors. The ability to grow primary plasmacytomas in culture and maintain their "primary" properties provides a model system for detailed analysis of early events in plasma cell tumor progression involving neoplastic cells completely dependent on physical contact with a stromal feeder layer for survival and expansion.

Animals↗
PubMed1993

Epidemiological investigation of risk factors for campylobacter colonization in Norwegian broiler flocks.

An epidemiological investigation was conducted to identify risk factors related to hygiene and husbandry practices which determine the introduction of Campylobacter spp. into broiler chicken flocks. All 176 broiler farms in an area in southeastern Norway participated in the study. Each farm was represented by one flock selected at random during a one-year period. The flocks were examined for campylobacter colonization at slaughter, and the flock managers were subsequently interviewed about hygiene and husbandry practices. Campylobacter spp. were recovered from 32 (18%) of the flocks. The proportion of colonized flocks varied geographically and seasonally with a peak in the autumn. The following variables were found to be independently associated with an increased risk of campylobacter colonization using logistic regression analysis: (i) feeding the broilers undisinfected water (odds ratio (OR) = 3.42, P = 0.045), (ii) tending other poultry prior to entering the broiler house (OR = 6.43, P = 0.007), (iii) tending pigs before entering the house (OR = 4.86, P = 0.037), (iv) geographic region (Hedmark versus Ostfold county) (OR = 2.91, P = 0.023, (v) season (autumn versus other seasons) (OR = 3.43; P = 0.008). Presence of rats on the farm was associated with an increased risk, but this factor did not reach statistical significance (OR = 3.96, P = 0.083). Preventive measures should include disinfection of drinking water and strict hygienic routines when the farm workers enter the rearing room. The results indicate that disinfection of drinking water is the preventive measure most likely to have the greatest impact on the prevalence of campylobacter among broiler chicken flocks in the study area (population attributable fraction = 0.53).

Animal Husbandry↗
PubMed1993

A phase I study of intravenous bryostatin 1 in patients with advanced cancer.

Bryostatin 1 is a novel antitumour agent derived from Bugula neritina of the marine phylum Ectoprocta. Nineteen patients with advanced solid tumours were entered into a phase I study to evaluate the toxicity and biological effects of bryostatin 1. Bryostatin 1 was given as a one hour intravenous infusion at the beginning of each 2 week treatment cycle. A maximum of three treatment cycles were given. Doses were escalated in steps from 5 to 65 micrograms m-2 in successive patient groups. The maximum tolerated dose was 50 micrograms m-2. Myalgia was the dose limiting toxicity and was of WHO grade 3 in all three patients treated at 65 micrograms m-2. Flu-like symptoms were common but were of maximum WHO grade 2. Hypotension, of maximum WHO grade 1, occurred in six patients treated at doses up to and including 20 micrograms m-2 and may not have been attributable to treatment with bryostatin 1. Cellulitis and thrombophlebitis occurred at the bryostatin 1 infusion site of patients treated at all dose levels up to 50 micrograms m-2, attributable to the 60% ethanol diluent in the bryostatin 1 infusion. Subsequent patients treated at 50 and 65 micrograms m-2 received treatment with an intravenous normal saline flush and they did not develop these complications. Significant decreases of the platelet count and total leucocyte, neutrophil and lymphocyte counts were seen in the first 24 h after treatment at the dose of 65 micrograms m-2. Immediate decreases in haemoglobin of up to 1.9g dl-1 were also noted in patients treated with 65 micrograms m-2, in the absence of clinical evidence of bleeding or haemodynamic compromise. No effect was observed on the incidence of haemopoietic progenitor cells in the marrow. Some patients' neutrophils demonstrated enhanced superoxide radical formation in response to in vitro stimulation with opsonised zymosan (a bacterial polysaccharide) but in the absence of this additional stimulus, no bryostatin 1 effect was observed. Lymphocyte natural killing activity was decreased 2 h after treatment with bryostatin 1, but the effect was not consistently seen 24 h or 7 days later. With the dose schedule examined no antitumour effects were observed. We recommend that bryostatin 1 is used at a dose of 35 to 50 micrograms m-2 two weekly in phase II studies in patients with malignancies including lymphoma, leukaemia, melanoma or hypernephroma, for which pre-clinical investigations suggest antitumour activity.

Adult↗
PubMed1993

Genetic control of Leishmania major infection in congenic, recombinant inbred and F2 populations of mice.

The outcome of subcutaneous infection with L. major NIH 173 was evaluated in a series of recombinant inbred and congenic strains, as well as F2 progeny generated from a genetic linkage testing stock carrying the visible markers Ra, Os, and Pt. The disease parameters monitored were the incidence of open or necrotic lesions and footpad depths of infected feet, and the incidence and number of amastigotes in livers following infection. Regions of mouse chromosomes 2, 4, 7, 8, 12 and 15 were excluded from linkage to a gene (Scl-1) involved in the susceptibility of inbred strains of mice to cutaneous infection with L. major NIH 173 by F2 and congenic strain analyses. Strain distribution patterns generated for Scl-1 in the CXB and CXS recombinant inbred strains suggested linkage to the distal end of mouse Chromosome 11.

Animals↗
PubMed1993

Lymphocyte transformation responses to phytohaemagglutinin and pokeweed mitogen in patients at differing stages of HIV infection: are they worth measuring?

AIMS: To determine whether the routine measurement of lymphocyte transformation responses to mitogenic stimuli provide any information additional to that available from routine T cell CD4 and CD8 analysis in patients with HIV infection. METHODS: The case records of 197 immunologically investigated HIV seropositive patients were reviewed. The influence of disease stage on T lymphocyte subsets and lymphocyte transformation responses (LyTR) to phytohaemagglutinin (PHA) and Pokeweed mitogen was assessed. RESULTS: The median CD3 and CD4 counts and LyTR to PHA and Pokeweed mitogen were highest in patients with persistent generalised lymphadenopathy (PGL) and decreased progressively in the order: asymptomatic patients, those with ARC, those with AIDS. LyTR to PHA was preserved in over 70% of all patients, but the response to Pokeweed mitogen was depressed in 8% of patients with PGL, 34% of asymptomatic patients, 68% of those with ARC and 78% of those with AIDS. Subnormal values of both CD4 + T cells and LyTR to Pokeweed mitogen were more common in patients with ARC and AIDS (68%) than in those who were asymptomatic or had PGL (20%). CONCLUSIONS: CD4 T cell analysis and LyTR to Pokeweed mitogen, but not to PHA, both correlate with disease states in patients with HIV infection.

AIDS-Related Complex↗
PubMed1993

Diversion from custody. I: Psychiatric assessment at the magistrates' court.

The homeless mentally disordered defendant facing minor charges poses considerable problems regarding appropriate disposal. Psychiatric assessment may be required in order to facilitate the court's decision, but this is often available only after remand in custody. A psychiatric assessment service based at two inner-London magistrates' courts is described. Over 18 months, 201 defendants were referred. They were predominantly male, single, and of no fixed abode, suffering from serious psychiatric disorder; these defendants had often received previous in-patient treatment, frequently as detained patients. They typically were recidivists charged with minor offences. Following initial assessment, 25% were admitted to hospital, 50% were released, and 25% returned to custody. The Crown Prosecution Service discontinued 29% of cases. For those admitted directly to hospital, the mean (s.d.) time from arrest to hospital admission was 5.8 (6.8) days, significantly quicker than with prison-based assessments.

Adolescent↗
PubMed1993

Diversion from custody. II: Effect on hospital and prison resources.

Two hundred and one referrals to a psychiatric assessment scheme based at two inner-London magistrates' courts were followed up to assess the effect of the scheme on hospital and prison resources. Of the 65 hospital admissions, 50 (77%) derived some or marked benefit from psychiatric treatment. Those who did badly were more likely to be of no fixed abode, and had higher rates of criminality and previous compulsory admission to hospital. Absconding was the largest management problem; 30 (46%) of those admitted did so. Twelve months after admission, all patients except one had been discharged; 10 (15%) had been readmitted to hospital. The scheme generated an extra 21 (64%) hospital admissions per annum from the two courts, compared with the three years before its introduction. The saving in remand time to the prison was approximately double the increased admission time to hospital. However, the overall effect of early diversion on hospital and prison resources was small.

Adolescent↗
PubMed1993

Retroviral enhancer insertion 5' of c-myc in two translocation-negative mouse plasmacytomas upregulates c-myc expression to different extents.

Essentially all murine plasmacytomas have deregulated c-myc expression that is typically brought about by chromosomal translocations between the c-myc/Pvt-1 locus and one of the immunoglobulin loci. ABPC 22 and RFPC 2782 are BALB/c plasmacytomas that lack chromosomal translocations yet have Southern blot evidence of c-myc gene rearrangements. In this report we show that proviral integrations 5' of the c-myc gene can deregulate c-myc expression in mouse plasmacytomas. Analysis of DNA sequences 5' of the c-myc genes from both tumors demonstrated that rearrangements were caused by retroviral integrations 5' of c-myc exon 1. The proviral insertion in RFPC 2782 was associated with a high steady-state c-myc mRNA level comparable to that seen in plasmacytomas with typical translocations. An analogous proviral insertion in ABPC 22 was associated with a c-myc RNA level that was only 38% of that of RFPC 2782. Nuclear run-on studies of c-myc transcription showed that ABPC 22 has both a lower rate of transcription and a greater degree of transcriptional attenuation than RFPC 2782. DNA sequencing of the long terminal repeat of each tumor provirus showed that the ABPC 22 provirus harbors a deletion of one of the two direct repeats in the viral enhancer, whereas both repeats are present in the RFPC 2782 provirus. These data indicate that maximum LTR enhancer effectiveness in plasmacytomas in vivo requires the presence of both LTR direct repeats. The documentation of the low level of steady-state c-myc mRNA in ABPC 22 supports the notion that deregulated c-myc expression, even at low steady state levels, is effective in supporting the development of plasmacytomas.

Animals↗
PubMed1992

Pathogenetic mechanisms in B-cell non-Hodgkin's lymphomas in humans.

A very large proportion of non-Hodgkin's lymphoma in the United States are of B-cell origin. This group of tumors includes a variety of different pathological and clinical types. Chromosomal rearrangements play an important role in the pathogenesis of many of these tumors. In B-cells these translocation processes appear to develop as illegitimate products of physiological V-(D)-J or heavy chain switch rearrangements. The biology of the well-known chromosomal translocations is discussed. Additional biological factors in lymphomagenesis (aging, immunodeficiency, role of antigenic stimulation, and genetically determined susceptibility) are discussed.

Humans↗