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E H Brown

Publications and source records attributed to E H Brown.

At least 19 recordsLinked to original sources
PubMed2001

Feasibility of surveillance of changes in human fertility and semen quality.

There is concern that male fertility is declining, but this is difficult to study because few men volunteer for studies of semen quality, and recruitment bias may over-represent the subfertile. The Human Reproduction Programme of the World Health Organization developed a protocol for multicentre studies of fertility involving a questionnaire for pregnant women to obtain time to pregnancy (TTP): the number of menstrual cycles taken to conceive. Male characteristics and semen quality will be determined in a subset of the partners. Our aim was to validate the TTP questionnaire, and to examine potential recruitment bias and feasibility of conducting large-scale surveillance of fertility. The questionnaire was administered to 120 pregnant women (16-32 weeks). Validation included internal reliability by consistency of responses, test-re-test reliability by repeat administration (20 women) and accuracy by comparison of gestational age from first antenatal ultrasound and menstrual dates. Internal reliability was high. Agreement between categorical responses on re-testing was very good (k > 0.8). In both the re-test and gestational age analysis, differences in TTP of 1 cycle were found (standard deviation <0.25 cycles). In this small pilot study there was no evidence of recruitment bias. Response rates indicate the feasibility of surveillance of fertility in large maternity centres.

Adult↗
PubMed2000

Feasibility of surveillance of changes in human fertility and semen quality.

To show that male fertility is declining is not simple. Few men volunteer and recruitment bias may lead to over-representation of the subfertile. Semen analysis has errors arising from counting and poorly standardized criteria, which may be overcome by automation. Time to pregnancy (TTP)-the number of menstrual cycles taken to conceive-measures fertility and allows male recruitment bias to be estimated. We review automated measurement of sperm concentration, motility and morphology and present a preliminary report on a study to assess a retrospective TTP questionnaire, recruitment bias and feasibility for large-scale surveillance of fertility.

Feasibility Studies↗
PubMed1999

Comparative effect of ALA derivatives on protoporphyrin IX production in human and rat skin organ cultures.

Samples of human and rat skin in short-term organ culture exposed to ALA or a range of hydrophobic derivatives were examined for their effect on the accumulation of protoporphyrin IX (PpIX) measured using fluorescence spectroscopy. With the exception of carbobenzoyloxy-D-phenylalanyl-5-ALA-ethyl ester the data presented indicate that, in normal tissues, ALA derivatives generate protoporphyrin IX more slowly than ALA, suggesting that they are less rapidly taken up and/or converted to free ALA. However, the resultant depot effect may lead to the enhanced accumulation of porphyrin over long exposure periods, particularly in the case of ALA-methyl ester or ALA-hexyl ester, depending on the applied concentration and the exposed tissue. Addition of the iron chelator, CP94, greatly increased PpIX accumulation in human skin exposed to ALA, ALA-methyl ester and ALA-hexyl ester. The effect in rat skin was less marked.

Aminolevulinic Acid↗
PubMed1990

The emergence of bacterial resistance in hospitals--a need for continuous surveillance.

The antibiotic sensitivities of a total of 220,000 isolates from 44 hospitals collected over 2.5 years were monitored by computer. Gram-negative organisms account for 63% of the total, the most common being Escherichia coli (43%). Staphylococcus aureus was the most frequently isolated Gram-positive organism (44%). The organism most commonly isolated from blood was E. coli; this organism was susceptible to ceftazidime (100%), ampicillin (47%), gentamicin (99%) and co-trimoxazole (85%). The organism most frequently isolated from sputum was Haemophilus influenzae; this organism was susceptible to ceftazidime (99%), cefuroxime (99%), ampicillin (89%) and erythromycin (78%). A 15-fold increase in the use of ceftazidime over the past 4 years has not been accompanied by increased resistance in common pathogens. Analysis shows that the susceptibility of E. coli and Pseudomonas aeruginosa to ceftazidime has remained constant throughout the duration of this survey. The data collected from this type of survey can be used to determine local trends in antibiotic susceptibility and hence aid the rational use of antibiotics in hospitals.

Anti-Bacterial Agents↗
PubMed1990

A three year survey of clinical isolates in the United Kingdom and their antimicrobial susceptibility.

A United Kingdom national survey of clinical isolates and their antimicrobial susceptibility was performed, with 61 participating hospital laboratories, between 1986 and 1989. Each centre used Microbe Base, a commercial suite of micro-computer programs which can record and analyse antimicrobial susceptibility data Informative on 366,853 bacterial isolates and their antimicrobial susceptibility was received from hospital and domiciliary specimens; Candida spp. accounted for a further 9121 isolates. The sites of origin were urine 51%, skin and soft tissue 21%, lower respiratory tract 8%, genital tract 7%, ear, nose and throat 6%, eye 3%, blood 1.5% and faeces 1%. Gram-negative bacteria accounted for 242,307 isolates, the main species were Escherichia coli 48%, Proteus spp. 9%, Pseudomonas spp. 7%, Haemophilus influenzae 6% and Klebsiella spp. 4%. Gram-positive bacteria numbered 124,546 with a predominance of Staphylococcus aureus 42%, beta-haemolytic streptococci 20%, Enterococcus spp. 12%, coagulase negative staphylococci 10% and Streptococcus pneumoniae 5%. All pneumococci were sensitive to penicillin, and methicillin resistant in Staph. aureus was only 2%. Twelve per cent of H. influenzae strains were resistant to ampicillin. There were no significant levels of gentamicin resistance in Gram-negative bacilli.

Drug Resistance, Microbial↗
PubMed1988

Replication program of active and inactive multigene families in mammalian cells.

In a comprehensive study, the temporal replication of tissue-specific genes and flanking sequences was compared in nine cell lines exhibiting different tissue-specific functions. Some of the rules we have determined for the replication of these tissue specific genes include the following. (i) Actively transcribed genes usually replicate during the first quarter of the S phase. (ii) Some immunoglobulin genes replicate during the first half of S phase even when no transcriptional activity is detected but appear to replicate even earlier in cell lines where they are transcribed. (iii) Nontranscribed genes can replicate during any interval of S phase. (iv) Multigene families arranged in clusters of 250 kilobases or less define a temporal compartment comprising approximately one-quarter of S phase. While these rules, and others that are discussed, apply to the tissue-specific genes studied here, all tissue-specific genes may not follow this pattern. In addition, housekeeping genes did not follow some of these rules. These results provide the first molecular evidence that the coordinate timing of replication of contiguous sequences within a multigene family is a general property of the mammalian genome. The relationship between replication very early during S phase and the transcriptional activity within a chromosomal domain is discussed.

Animals↗
PubMed1987

Rate of replication of the murine immunoglobulin heavy-chain locus: evidence that the region is part of a single replicon.

We measured the temporal order of replication of EcoRI segments from the murine immunoglobulin heavy-chain constant region (IgCH) gene cluster, including the joining (J) and diversity (D) loci and encompassing approximately 300 kilobases. The relative concentrations of EcoRI segments in bromouracil-labeled DNA that replicated during selected intervals of the S phase in Friend virus-transformed murine erythroleukemia (MEL) cells were measured. From these results, we calculated the nuclear DNA content (C value; the haploid DNA content of a cell in the G1 phase of the cell cycle) at the time each segment replicated during the S phase. We observed that IgCH genes replicate in the following order: alpha, epsilon, gamma 2a, gamma 2b, gamma 1, gamma 3, delta, and mu, followed by the J and D segments. The C value at which each segment replicates increased as a linear function of its distance from C alpha. The average rate of DNA replication in the IgCH gene cluster was determined from these data to be 1.7 to 1.9 kilobases/min, similar to the rate measured for mammalian replicons by autoradiography and electron microscopy (for a review, see H. J. Edenberg and J. A. Huberman, Annu. Rev. Genet. 9:245-284, 1975, and R. G. Martin, Adv. Cancer Res. 34:1-55, 1981). Similar results were obtained with other murine non-B cell lines, including a fibroblast cell line (L60T) and a hepatoma cell line (Hepa 1.6). In contrast, we observed that IgCh segments in a B-cell plasmacytoma (MPC11) and two Abelson murine leukemia virus-transformed pre-B cell lines (22D6 and 300-19O) replicated as early as (300-19P) or earlier than (MPC11 and 22D6) C alpha in MEL cells. Unlike MEL cells, however, all of the IgCH segments in a given B cell line replicated at very similar times during the S phase, so that a temporal directionality in the replication of the IgCH gene cluster was not apparent from these data. These results provide evidence that in murine non-B cells the IgCH, J, and D loci are part of a single replicon.

Abelson murine leukemia virus↗
PubMed1985

Rat cells infected with anemia-inducing Friend leukemia virus contain integrated replication-competent but not defective proviral genomes.

The integrated proviral DNA in five murine cell lines transformed by the anemic strain of Friend leukemia virus (FLV-A) was examined by Southern hybridization to a cloned Friend virus (F-MuLV) probe. Kpn I fragments 9 kilobases (kb) and 5.7 kb long were observed for each cell line. However, the number of copies of each fragment in the cell genome varied according to the cell type. As compared to the adherent epithelioid cell lines, the anchorage-independent erythroleukemic cell lines contained more copies of the 5.7-kb fragment than of the 9-kb fragment, suggesting that the former may be biologically significant and perhaps related to the growth of erythroid cells. The presence of Kpn I fragments of the same sizes, albeit in fewer copies, in normal mouse spleen DNA made it difficult to distinguish exogenous virus from endogenous viral sequences. Therefore, rat 3Y1 cells, which contained no murine endogenous viruses, were infected with FLV-A stock virus prepared directly from the spleens of leukemic mice. Only the 9-kb Kpn I fragment, representing replication-competent Friend virus component, was detected in the infected rat cell DNA. No hybridization was observed to a 0.6-kb fragment of the spleen focus-forming virus env gene that is specific for xenotropic and dual-tropic mink cell focus-forming viruses. Since the virus synthesized by the infected rat cells was leukemogenic in adult mice, these data suggest that the wild-type FLV-A is replicative and fully pathogenic in the absence of other competent virus components.

Animals↗
PubMed1983

Changes in the levels of viral and cellular gene-transcripts in the cell cycle of SV40 transformed mouse cells.

We have analyzed the regulation of transcription of integrated SV40 DNA and of five cellular genes during the cell cycle of two lines of SV40 transformed mouse 3T3 cells. These cells (ts SV3T3) are temperature sensitive for the expression of the transformed phenotype and at the nonpermissive temperature (39 degrees C) become arrested in G1 at low serum concentrations. SV40 specific RNAs are not detected either in the nuclear or in the cytoplasmic poly(A+)RNA of quiescent cells, suggesting control at the level of transcription. After serum stimulation, however, viral transcription increases and reaches its maximum during S-phase. The expression of a group of selected housekeeping genes has received parallel analysis to determine whether other cellular genes, beside the integrated SV40, are shut off in G1 arrested cells or are expressed in restricted periods of the cell cycle. We have found that, while the mRNAs for collagen, adenosinphosphoribosiltransferase (APRT) and the mouse major histocompatibility complex (H2) are present throughout the cell cycle, the genes coding for the multifunctional protein CAD and dehydrofolate reductase are cell-cycle regulated.

Adenine Phosphoribosyltransferase↗
PubMed1982

Induction of sister chromatid exchange by polyoma large viral tumor antigen in transformed rat fibroblasts.

The frequency of sister chromatid exchange (SCE) was determined in rat fibroblasts transformed by wild-type polyoma virus or by a mutant temperature sensitive for viral large tumor antigen function (ts-a). Elevated SCE frequencies were observed in two wild-type transformed cell lines growing at 37 degrees and in four ts-a-transformed lines upon growth at the permissive temperature for large viral tumor antigen (33 degrees). The increase in SCE frequency in ts-a-transformed cells at 33 degrees was reversed by growth at 39 degrees (nonpermissive for T-antigen function). An increase in SCE at 33 degrees was not observed in untransformed cells or in a ts-a-transformed cell line which makes a defective large viral tumor antigen. These results suggest that large viral tumor antigen can induce SCEs. Since large viral tumor antigen is also responsible for amplification of integrated viral DNA sequences (4), we tried to correlate this phenomenon with the increased SCE frequency. However, increasing SCE artificially by growing cells in the presence of 12-O-tetradecanoylphorbol-13-acetate did not result in amplification of integrated viral DNA in the absence of large viral tumor antigen function. Thus, there is no simple causal relationship between increased SCE and amplification.

Animals↗
PubMed1981

alpha-Globulin sequences are located in a region of early-replicating DNA in murine erythroleukemia cells.

The time of replication in the S phase of regions of the mouse genome including the alpha-globin genes was determined in the murine erythroleukemia cell line transformed by Friend virus. Cells grown for short times in the presence of BrdUrd were fractionated into synchronous populations by centrifugal elutriation. The DNA was cleaved by restriction endonucleases, and fragments containing bromouracil (BrU-DNA) were isolated in density gradients of Cs2SO4. BrU-DNA fractions replicated during selected S-phase intervals were subjected to electrophoresis in agarose gels, transferred to diazobenzyloxymethyl-paper, and hybridized to an alpha-globin probe. Reconstruction experiments using a cloned mouse EcoRI fragment including one alpha-globin gene demonstrated that the extent of hybridization provides an accurate measurement that the extent of hybridization provides an accurate measurement of the concentrations of specific fragments in a DNA sample. The alpha-globin fragments were detected primarily in the BrU-DNA replicated during early S phase (approximately the first quarter of S). This result was confirmed in other synchrony experiments and by Cot analysis. (Cot is the initial concentration of DNA in mol of nucleotide per liter multiplied by the time in sec.) The temporal replication of mouse satellite sequences, already known from previous studies, was used as an internal control for cell synchrony. To show that the globin sequences were not lost from the cells in late S phase during isolation of the DNA, we quantitated th alpha-globin fragments in BrU-DNA prepared from a mixture of cells in early and late S phase. The results demonstrate that the alpha-globin gene regions in these cells are replicated during early S phase.

Animals↗
PubMed1979

Perturbation of growth and differentiation of Friend murine erythroleukemia cells by 5-bromodeoxyuridine incorporation in early S phase.

Cultured Friend murine erythroleukemia cells (Friend cells) are induced to undergo erythroid differentiation when grown in the presence of dimethylsulfoxide (DMSO) and other compounds. The effects of unifilar substitution of bromouracil (BU) for thymidine in the DNA (BU-DNA) of Friend cells were examined. Cells were grown in the presence of 5-bromodeoxy-uridine (BrdU) for one generation, then centrifuged and resuspended in medium containing DMSO without BrdU. These cells exhibited a delay in the appearance of heme-producing, benzidine-reative (B+) cells and a decreased rate of cell proliferation in comparison to the control not containing BU-DNA. A transient inhibition of entry into S phase was observed when control cells or cells containing BU-DNA were grown in the presence of DMSO) for 10 to 20 hours. This transient inhibition was increased in the BrdU culture. Thus BU-substitution in Friend cells alters other cellular functions in addition to erythroid differentiation. The rate of increase in the percent of cells committed to differentiate (those forming B+ colonies in plasma clots) was similar in the BrdU and control cultures until 40 to 50 hours. After this time, a delay in the appearance of committed cells was observed in the BrdU culture. The effect of BrdU on the appearance of B+ cells was more pronounced and occurred earlier than its effect on the rate of commitment. Therefore, the delay in the appearance of B+ cells in the BrdU culture was due primarily to perturbation of post-commitment events such as the accumulation of hemoglobin. We also examined the effect on growth and differentiation after BrdU was incorporated during different intervals of S phase in cells synchronized by centrifugal elutriation or by double thymidine block and hydroxyurea treatment. The delay in the appearance of B+ cells and inhibition of cell proliferation were only observed when BrdU was incorporated in the first half of S phase. BrdU (10 muM) had no effect on growth or differentiation when present during late S or G1 and G2. These results, using two very different methods to achieve cell synchrony, indicate that the effects of BrdU on growth and differentiation described above are due to its incorporation into DNA sequences replicating during early S.

Animals↗