Does a bloody tap prevent postdural puncture headache?
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Blood Patch, Epidural↗
Biomedical subjects
J Holland
Publications and source records attributed to J Holland.
Genetic bottlenecks and population passages cause profound fitness differences in RNA viruses.
Repeated clone-to-clone (genetic bottleneck) passages of an RNA phage and vesicular stomatitis virus have been shown previously to result in loss of fitness due to Muller's ratchet. We now demonstrate that Muller's ratchet also operates when genetic bottleneck passages are carried out at 37 rather than 32 degrees C. Thus, these fitness losses do not depend on growth of temperature-sensitive (ts) mutants at lowered temperatures. We also demonstrate that during repeated genetic bottleneck passages, accumulation of deleterious mutations does occur in a stepwise (ratchet-like) manner as originally proposed by Muller. One selected clone which had undergone significant loss of fitness after only 20 genetic bottleneck passages was passaged again in clone-to-clone series. Additional large losses of fitness were observed in five of nine independent bottleneck series; the relative fitnesses of the other four series remained close to the starting fitness. In sharp contrast, when the same selected clone was transferred 20 more times as large populations (10(5) to 10(6) PFU transferred at each passage), significant increases in fitness were observed in all eight passage series. Finally, we selected several clones which had undergone extreme losses of fitness during 20 bottleneck passages. When these low-fitness clones were passaged many times as large virus populations, they always regained very high relative fitness. We conclude that transfer of large populations of RNA viruses regularly selects those genomes within the quasispecies population which have the highest relative fitness, whereas bottleneck transfers have a high probability of leading to loss of fitness by random isolation of genomes carrying debilitating mutations. Both phenomena arise from, and underscore, the extreme mutability and variability of RNA viruses.
Cell Line↗
Many-trillionfold amplification of single RNA virus particles fails to overcome the Muller's ratchet effect.
We showed earlier that transfers of large populations of RNA viruses lead to fitness gains and that repeated genetic bottleneck transfers result in fitness losses due to Muller's ratchet. In the present study, we examined the effects of genetic bottleneck passages intervening between population passages, a process akin to some natural viral transmissions, using vesicular stomatitis virus as a model. Our findings show that the pronounced fitness increases that occur during two successive population passages cannot overcome the fitness decreases caused by a single intervening genetic bottleneck passage. The implications for natural transmissions of RNA viruses are discussed.
Genetic Variation↗
Psychological aspects of the Canadian randomized controlled trial of human growth hormone and low-dose ethinyl oestradiol in children with Turner syndrome. The Canadian Growth Hormone Advisory Group.
Preliminary results are presented after 2 years of the Canadian long-term multicentre study on the impact of hormone therapy on the final height, sexual development and psychological status of girls with Turner syndrome. Girls entering the study were randomized either to be treated with recombinant human growth hormone or to act as controls. Both groups received oestrogen replacement therapy in the same dose and format at the age of 13 years. However, for the purposes of the psychological study at this time, children receiving oestrogen were excluded from analysis. Girls treated with GH for a period of 2 years showed a significant increase in growth rate, which declined with continued treatment, while the growth rate in the control group remained constant throughout. There was a correlation between the higher growth rate and the girls' perceptions of themselves as more intelligent, more attractive, having more friends, greater popularity and experiencing less teasing than the untreated group. Growth rate was not correlated with family or school functioning.
Analysis of Variance↗
Isolation of cDNA clones mapping around DXS178: a search for human X-linked agammaglobulinaemia gene using yeast artificial chromosomes, cosmids and direct cDNA selection.
X-linked agammaglobulinaemia (XLA) was previously mapped using genetic linkage analysis to Xq22. No recombinants have been found so far between the XLA locus and DXS178 in over 30 informative meioses. Two overlapping yeast artificial chromosomes (YACs), which cover a region of approximately 1000 kb around DXS178 and form part of a larger YAC contig, were hybridised to an ordered cosmid library constructed from a human fibroblast cell line with karyotype 49,XXXXX. Positive cosmids were gridded in high density arrays onto nylon filters and rescreened with a series of YACs, YAC end probes and additional markers from the region to assign cosmids into intervals. A 640 kb-YAC hybridising to p212 (DXS178) was used for direct selection of PCR-amplified cDNA from two cDNA libraries. To identify the cosmids containing transcribed sequences the enriched cDNA from each library was radiolabelled and hybridised back to positive clones which mapped to the region of interest. These clones were then hybridised to the subcloned enriched cDNA sublibraries. Candidate cDNA clones were isolated, grouped within the region of interest and their position was confirmed by mapping back to the cosmids.
Agammaglobulinemia↗
Rapid fitness losses in mammalian RNA virus clones due to Muller's ratchet.
Muller's ratchet is an important concept in population genetics. It predicts that when mutation rates are high and a significant proportion of mutations are deleterious, a kind of irreversible ratchet mechanism will gradually decrease the mean fitness of small populations of asexual organisms. In contrast, sexual recombination may stop or reverse this mutational ratchet by recombinational repair of genetic damage. Experimental support for Muller's ratchet has previously been obtained in protozoa and in a tripartite RNA bacteriophage. We now show clear evidence that Muller's ratchet can operate on a nonsegmented nonrecombining pathogenic RNA virus of animals and humans. We did genetic bottleneck passages (plaque-to-plaque transfers) of vesicular somatitis virus (VSV) and then quantitated relative fitness of the bottleneck clones by allowing direct replication competition in mixed infections in cell culture. We document variable fitness drops (some severe) following only 20 plaque-to-plaque transfers of VSV. In some clones no fitness changes (or only insignificant changes) were observed. Surprisingly, the most regular and severe fitness losses occurred during virus passages on a new host cell type. These results again demonstrate the extreme genetic and biological variability of RNA virus populations. Muller's ratchet could have significant implications for variability of disease severity during virus outbreaks, since genetic bottlenecks must often occur during respiratory droplet transmissions and during spread of low-yield RNA viruses from one body site to another (as with human immunodeficiency virus). Likewise, the lower-probability generation of increased-fitness clones during repeated genetic bottleneck transfers of RNA viruses in nature might also affect disease pathogenesis in infected individuals and in host populations. Whenever genetic bottlenecks of RNA viruses occur, enhanced biological differences among viral subpopulations may result.
Animals↗
Plasmacytoma. Treatment results and conversion to myeloma.
Forty-six cases of solitary plasmacytoma were reviewed for response to radiation and progression to multiple myeloma. Cases were classified as solitary plasmacytomas of bone (SPB) (32 cases) or extramedullary plasmacytomas (EP) (14 cases). There was an overall 93% response rate of the tumor to radiation therapy: 62% had a complete response after radiation therapy, whereas 31% had a partial response. Conversion to multiple myeloma was influenced by the type of plasmacytoma; 53% of the patients with SPB converting to myeloma versus 36% of the patients with EP. Time from diagnosis to conversion for patients with SPB showed no evidence of plateau, with conversion continuing to occur even after 17 years. The median survival time for patients after conversion to myeloma was 14.5 months and was not affected by time to conversion. Serum protein level, presence of monoclonal gammopathy, and size of primary lesion were of some prognostic significance in predicting conversion to myeloma. Adjuvant chemotherapy did not affect the incidence of conversion but did appear to delay conversion to myeloma. Seven patients in whom multiple sequential solitary plasmacytomas developed formed a distinct subset, with a median time to a second plasmacytoma of 63 months. In three of these patients, conversion to myeloma occurred subsequently. This study supports the idea of EP having a lower incidence of conversion to myeloma and a different natural history from SPB, with SPB likely to be multiple myeloma in evolution.
Adult↗
A model for counseling the medically ill: the Linda Pollin Foundation approach. Introduction.
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Adaptation, Psychological↗
The development and application of automated gridding for efficient screening of yeast and bacterial ordered libraries.
An automated gridding procedure for the inoculation of yeast and bacterial clones in high-density arrays has been developed. A 96-pin inoculating tool compatible with the standard microtiter plate format and an eight-position tablet have been designed to fit the Biomek 1000 programmable robotic workstation (Beckman Instruments). The system is used to inoculate six copies of 80 x 120-mm filters representing a total of approximately 20,000 individual clones in approximately 3 h. High-density arrays of yeast artificial chromosome (YAC) and cosmid clones have been used for rapid large-scale hybridization screens of ordered libraries. In addition, an improved PCR library screening strategy has been developed using strips cut from the high-density arrays to prepare row and column DNA pools for PCR analysis. This strategy eliminates the final hybridization step and allows identification of a single clone by PCR in 2 days. The development of automated gridding technology will have a significant impact on the establishment of fully versatile screening of ordered library resources for genomic studies.
Animals↗
Risk, power and the possibility of pleasure: young women and safer sex.
This paper draws on the work of the Women Risk and AIDS Project (WRAP) which was undertaken by the authors working collectively. It reports on data from a sociological study of the sexual beliefs and practices of two samples each of 75 young women between 16 and 21 in the cities of London and Manchester in the UK. The period of data collection was 1988-1990. The paper sets out the methods used by the WRAP team and locates this research process within wider debates about feminist theory and methodology. There then follows a discussion of the main research findings--relating to the respondents sexual practice--which are then illustrated in some detail in relation to the themes of 'risk and trust' and 'power and empowerment'. Based on these findings conclusions are drawn about the need for a gendered dimension in the development of policy and practice for HIV and AIDS prevention.
Adolescent↗
Tn916 insertion mutagenesis in Escherichia coli and Haemophilus influenzae type b following conjugative transfer.
Transposon Tn916 was shown to be capable of direct conjugative transfer in broth and membrane matings between strains of Escherichia coli K12 and between E. coli K12 and Haemophilus influenzae type b. Only Tn916 was transferred, but Tn916 donor ability was not itself inheritable by the recipients and seemed to be associated with the presence of Tn916 on a non-conjugative pBR322-derived vector in the original donor strain. Transfer of Tn916 by conjugation was found to be an efficient method for producing insertion mutations in the chromosome of recipient cells. Although such insertions were unstable when the cells were grown under non-selective conditions, it was possible to show that over 40% of the isolated Tn916 insertions in the chromosome of E. coli K12 were in gene(s) concerned with histidine biosynthesis, implying that there is a partial hot-spot for Tn916 insertion on the E. coli K12 chromosome. When a strain of H. influenzae type b was used as a recipient, out of approximately 1500 transconjugants tested, two mutants were isolated with insertions in genes controlling the expression of iron-regulated transferrin-binding proteins. These mutants constitutively produced major 76 kDa and minor 90 kDa proteins which bound transferrin, even when grown under iron-sufficient conditions. Tn916 insertion mutagenesis, following transfer by conjugation, is a convenient method for isolating mutations in genes concerned with iron acquisition by this important human pathogen.
Bacteriological Techniques↗
Evidence for in vivo expression of transferrin-binding proteins in Haemophilus influenzae type b.
Haemophilus influenzae type b acquires transferrin-bound iron via a siderophore-independent mechanism involving direct contact between the human iron-binding glycoprotein and the bacterial cell surface. Evidence has accumulated to show that the transferrin receptor consists of at least two iron-regulated outer membrane transferrin-binding proteins (TBPs), of which one has a molecular mass of around 100 kDa (TBP1) and the other has a molecular mass of 60 to 90 kDa (TBP2). In H. influenzae type b strain Eagan, proteins of 76, 90, and 107 kDa appear to be involved in transferrin binding. To determine whether these TBPs are expressed during growth in vivo, strain Eagan was recovered without subculture from the intraperitoneal cavities of infected infant rats. By using a dot blot assay, outer membranes prepared from these in vivo-grown bacteria, unlike those grown in iron-sufficient broth, bound human transferrin and produced the 76-, 90-, and 107-kDa TBPs. Immunoblotting experiments using convalescent sera from infected rats also revealed the presence of antibodies to the 76- and 90-kDa strain Eagan TBPs. In addition, convalescent sera from three of four patients recovering from H. influenzae type b meningitis contained antibodies to the 90- and 105-kDa TBPs of the corresponding infecting strain. Furthermore, fresh clinical isolates of H. influenzae type b recovered from blood and cerebrospinal fluid showed constitutive expression of the TBPs, which became iron regulated only after prolonged in vitro subculture on iron-sufficient medium. This contrasted with the laboratory-adapted Eagan strain, in which the TBPs remained iron regulated even after animal passage. These findings indicate that the H. influenzae type b transferrin receptor is expressed during experimental animal and human infections.
Animals↗
Dietitians view the horizon.
In honor of the American Dietetic Association's landmark 75th anniversary, FM asked ADA members representing six market sectors to share their perspectives on the opportunities & challenges for dietitians in the '90s. An exciting era lies ahead.
Administrative Personnel↗
Multicentre study of the treatment of primary liver cancer in Africa with two anthracycline drugs.
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Africa↗
Molecular heterogeneity of the fragile X syndrome.
The fragile X syndrome is an X-linked disorder which has been shown to be associated with the length variation of a DNA fragment containing a CGG trinucleotide repeat element at or close to the fragile site. Phenotypically normal carriers of the disorder generally have a smaller length variation than affected individuals. We have cloned the region in cosmids and defined the area containing the amplified sequence. We have used probes from the region to analyse the mutation in families. We show that the mutation evolves in different ways in different individuals of the same family. In addition we show that not all fragile X positive individuals show this amplification of DNA sequence even though they show expression of the fragile site at levels greater than 25%. One patient has alterations in the region adjacent to the CGG repeat elements. Three patients in fragile X families have the normal fragment with amplification in a small population of their cells. These observations indicate that there is molecular heterogeneity in the fragile X syndrome and that the DNA fragment length variation is not the only sequence responsible for the expression of the fragile site or the disease phenotype.
Base Sequence↗
Isolation and characterisation of Haemophilus influenzae type b mutants defective in transferrin-binding and iron assimilation.
The quinone antibiotic streptonigrin was used to select mutants of Haemophilus influenzae type b defective in human transferrin binding. Compared with the parent wild-type strain (JKP1), mutant JKP5 was unable to bind transferrin whilst mutant JKP4 showed reduced binding. JKP5 appeared to lack an approximately 72 kDa transferrin-binding protein. Unlike JKP1, neither JKP4 nor JKP5 were able to acquire iron from human transferrin but their ability to use a variety of other iron and haem compounds as iron sources was unaffected. Such mutants should prove useful in further elucidating the mechanism of transferrin iron-acquisition and its contribution to the virulence of H. influenzae.
Carrier Proteins↗
Red blood cell NMR proton relaxation times in ill and recovered patients with unipolar and bipolar affective disorders.
Red blood cell NMR relaxation times T1 and T2 and water content were measured in ill and recovered patients with mania, unipolar depressed phase, bipolar depressed phase and control subjects. The results suggest that relaxation times are elevated in ill bipolar manic and ill unipolar depressed patients but are normal in both groups in the recovered phase and in ill bipolar depressed patients. Relaxation times therefore seem to be state-dependent but behave differently in unipolar and bipolar patients.
Bipolar Disorder↗
Hexamethylmelamine for the treatment of ovarian cancer--the Mount Sinai experience.
Two regimens were tested, CHAP I and CHAP II, the latter, a hexamethylmelamine dosage-intensive regimen, first as second line (salvage) therapy and then as primary therapy. Both produced the most successful results achieved in the Mount Sinai series up to the time of their introduction, when compared to their predecessor regimens: CAP, AP and P. In an overall interim comparison, CHAP II was significantly superior to historical AP and CAP as primary therapy, as was CHAP I vs. AP in several important subgroups compared as part of a randomized trial. CHAP II overall progression-free survival was improved in spite of added new sensitive test methods. Salvage therapy also improved markedly with the addition of intensive hexamethylmelamine. Several biological and treatment characteristics strongly influenced outcome, especially young age and adding hexamethylmelamine. Other possible factors included: poor tumor grade, poor performance status, and extent of surgical debulking, even to intermediate residual, 2-6 cm size [CHAP II only]; extensive (optimum) surgery [CHAP I only]. The hexamethylmelamine-containing regimens interact favorably with some of these factors, better than did the preceding regimens. Five-year follow-up analyses weakened slightly for extensive surgery, intermediate size and poorly differentiated tumors. It confirmed and strengthened several findings favoring CHAP I & II, the hexamethylmelamine-containing regimens.
Altretamine↗