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Biomedical subjects

J A Mills

Publications and source records attributed to J A Mills.

At least 19 recordsLinked to original sources
PubMed1992

Spontaneous insertion of an IS1-like element into the virF gene is responsible for avirulence in opaque colonial variants of Shigella flexneri 2a.

Colonial variation of Shigella flexneri serotype 2a from the translucent (2457T) to the opaque form (2457O) occurs spontaneously once in 10(4) cell divisions, with concomitant loss of ipa gene expression and virulence. The appearance of 2457O was associated with the insertional inactivation of virF, an invasion plasmid-encoded positive regulator of ipa gene expression. Plasmid pWR110, a Tn5-tagged invasion plasmid that restores the invasive phenotype to plasmid-cured Shigella derivatives, was conjugally transferred into 2457O. Synthesis of the invasion-associated IpaB and IpaC polypeptides, normally present on the surface of virulent shigellae, and the invasive phenotype were restored in 2457O(pWR110) transconjugants. Plasmid DNA restriction endonuclease patterns of 2457T and 2457O, along with hybridization analysis, showed that a SalI fragment carrying the virF gene in 2457O had increased in size relative to its counterpart in 2457T. Analysis of virF DNA sequences amplified by the polymerase chain reaction revealed that the virF sequence from 2457O was 780 bp larger than that amplified from 2457T. Moreover, the virF sequence amplified from 2457O hybridized to an IS1 DNA probe whereas the amplified 2457T virF sequence did not. DNA sequence analysis mapped the insertion element, designated IS1SFO, within an A.T-rich region of the virF open reading frame and identified a 9-bp virF target sequence that was duplicated at the insertion site of IS1SFO. The DNA sequence of IS1SFO was greater than 99% homologous to IS1F. Plasmid pWR600, carrying a 1,260-bp HpaII fragment encoding a wild-type virF gene, was able to restore the virulent phenotype and translucent colonial morphology to nine independently isolated 2457O hosts.

Bacterial Proteins↗
PubMed1991

Effects of in-vitro exposure to HCG on subsequent HCG-responsiveness of human granulosa cells obtained following treatment with GnRH analogue and gonadotrophins: an in-vitro model for luteal phase support.

The pregnancy rate in patients undergoing assisted conception treatment following pituitary desensitization with GnRH analogue and ovarian stimulation with gonadotrophins has been reported to be higher when ovarian function is supported in the luteal phase by exogenous human chorionic gonadotrophin (HCG). In the present study, we have examined the effects of culturing monolayers of granulosa cells, collected from such patients at oocyte retrieval, for various time intervals in the presence or absence of HCG on their subsequent ability to secrete progesterone (P4) either spontaneously or in response to further challenge with HCG. When cultured in the absence of HCG, granulosa cells demonstrated a rapid decline in both the spontaneous P4 secretion rate and the ability to secrete P4 in response to HCG. Maintenance in the presence of HCG inhibited the rapid decline in ability to secrete P4 spontaneously and also significantly enhanced the ability to respond to subsequent HCG stimulation. These results suggest that HCG support in the luteal phase in GnRH analogue-treated patients may have a cellular basis for its action both in maintenance of P4 secretion and also in rendering the corpus luteum more sensitive to rescue by conceptus-derived HCG.

Buserelin↗
PubMed1990

The American College of Rheumatology 1990 criteria for the classification of Henoch-Schönlein purpura.

Criteria for identifying Henoch-Schönlein Purpura (HSP) and distinguishing HSP from other forms of systemic arteritis were developed by comparing the manifestations in 85 patients who had HSP with those of 722 control patients with other forms of vasculitis. By the traditional format of choosing different combinations of candidate criteria and comparing the combinations for their ability to separate HSP cases from controls, 4 criteria were identified: age less than or equal to 20 years at disease onset, palpable purpura, acute abdominal pain, and biopsy showing granulocytes in the walls of small arterioles or venules. The presence of any 2 or more of these criteria distinguish HSP from other forms of vasculitis with a sensitivity of 87.1% and a specificity of 87.7%. The criteria selected by a classification tree method were similar: palpable purpura, age less than or equal to 20 years at disease onset, biopsy showing granulocytes around arterioles or venules, and gastrointestinal bleeding. These were able to distinguish HSP from other forms of vasculitis with a sensitivity of 89.4% and a specificity of 88.1%.

Adolescent↗
PubMed1990

Molecular characterization of a trans-acting, positive effector (ipaR) of invasion plasmid antigen synthesis in Shigella flexneri serotype 5.

A trans-acting, positive effector of invasion plasmid antigen (Ipa) synthesis has been identified and mapped on the pWR100 invasion plasmid of Shigella flexneri serotype 5 (strain M90T-W). Recombinant plasmids carrying this regulatory gene, designated ipaR, were found to restore full virulence to a non-invasive ipaR::Tn5 insertion mutant [M90T-W(pHS1042)] that had lost the ability to synthesize four Ipa antigens (IpaA, 70 kDa; IpaB, 62 kDa; IpaC, 42 kDa; and IpaD, 37 kDa). Genetic mapping of the ipaR gene positioned the locus on a 2.6 kb PstI-AccI fragment contained within a larger 8.0 kb EcoRI molecule that also encoded IpaD, IpaA, and two small proteins (27 kDa and 28 kDa). The trans regulatory effect of the ipaR product on ipaB, ipaC, ipaD, and ipaA expression was demonstrated by transforming compatible ipaBC, ipaDA, ipaR and ipaDAR plasmid recombinants, in various combinations, into M90T-A3, an isogenic invasion plasmid mutant of M90T-W that contained a deletion of the pWR100 ipaBCDA and ipaR loci; such transformants produced wild type levels of the IpaB, IpaC, IpaD and IpaA antigens only in the presence of IpaR+ plasmids. DNA sequence analysis of the ipaR region established that the intiation codon for ipaR is 459 bp from the 3'-end of the ipaA gene and that ipaR encodes a 309 amino acid residue protein. An interesting feature of the IpaR polypeptide was its strong sequence homology with the bacteriophage P1 partition protein ParB, consisting of a 42.8% amino acid identity over a 278 residue section of the aligned proteins.

Amino Acid Sequence↗
PubMed1990

Clinical and biochemical pregnancy in two respective recipients without ovarian function following gamete intrafallopian transfers using oocytes from a single donor.

Infertility resulting from premature ovarian failure in two independent patients was treated using a combination of steroid replacement, oocyte donation and gamete intrafallopian transfer (GIFT). Following ovarian stimulation four oocytes were retrieved from a volunteer donor undergoing simultaneous laparoscopic sterilisation. Two oocytes were subsequently replaced into each recipient's fallopian tube together with capacitated sperm from their respective husbands. In one recipient (Turner's syndrome) an intrauterine sac with fetal heart present was observed by ultrasound six weeks post GIFT whereas in the second recipient (premature menopause) plasma beta-hCG reached a peak value of 954mIU/ml eighteen days after GIFT before decreasing rapidly in the absence of ultrasound evidence of pregnancy. Intramuscular administration of progesterone appeared to be necessary during the post-GIFT period for maintenance of pregnancy. The above treatment was carried out on a predominantly out-patient basis in a small assisted conception unit based in a teaching hospital.

Adult↗
PubMed1989

Hallux varus.

We reviewed 12 patients with congenital hallux varus who had had operations on 20 feet to enable them to wear normal shoes and to improve the appearance. After an average follow-up of 12.7 years the results of soft tissue procedures were satisfactory in 12 of 17 feet. Arthrodesis of the first metatarsophalangeal joint, performed primarily in one foot and secondarily in two others was also satisfactory, but metatarsal osteotomy in two feet gave unsatisfactory results leading to local amputation. The unsatisfactory results were generally due to the appearance of shortness of the first metatarsal and rarely because of symptoms or recurrent deformity.

Child↗
PubMed1988

Shigella flexneri invasion plasmid antigens B and C: epitope location and characterization with monoclonal antibodies.

Invasion plasmid antigens B (IpaB) and C (IpaC) are associated with the ability of shigellae to invade cultured mammalian cells. Monoclonal antibodies against IpaB and IpaC polypeptides were produced and used in a whole-cell enzyme-linked immunosorbent assay to show that both IpaB and IpaC polypeptides were exposed on the surface of virulent shigellae. Moreover, these surface epitopes were shown to be highly conserved among different serotypes of Shigella spp. and enteroinvasive Escherichia coli. Cross-reactive epitopes were not found on noninvasive Shigella strains or on other enteric bacteria including Salmonella, Yersinia, Campylobacter, Vibrio, and Aeromonas spp. and various pathogenic strains of E. coli. The monoclonal antibodies were used in competitive binding assays to define three unique epitopes of the IpaB polypeptide and four unique epitopes of the IpaC polypeptide. Epitope locations and their corresponding DNA-encoding regions were defined by examining the IpaB and IpaC products expressed by lambda gt11 recombinants and by constructing a genetic map of the insert DNAs of these recombinants. Three IpaB epitopes (2F1, 1H4, 4C8) were found to be encoded on three contiguous DNA regions comprising a 700-base-pair (bp) segment that corresponded to the amino-terminal end of the IpaB polypeptide. Similarly, a 640-bp DNA segment that corresponded to the amino-terminal end of the IpaC polypeptide was found to encode three clustered IpaC epitopes (5H1, 9B6, 5B1). Approximately 50 bp downstream from this region a fourth IpaC epitope-encoding region (2G2) was found. The effect of the monoclonal antibodies on plaque formation by virulent Shigella flexneri on a monolayer of cultured mammalian cells (a sensitive measure of invasiveness) was determined. Only the IpaB-specific monoclonal antibody 2F1 was able to reduce the plaque-forming capacity by greater than 50%, suggesting that this epitope of the IpaB polypeptide is involved in the invasion process.

Antibodies, Bacterial↗
PubMed1988

Use of disposable ear canal electrodes in auditory brainstem response testing.

In this study a disposable ear canal electrode and stimulus delivery system (the Enhancer l) was evaluated for its clinical utility and the observed enhancement of the auditory brainstem response Wave I with its use. Data were collected from normally and abnormally hearing subjects, with both the conventional forehead-to-mastoid electrode array and the forehead-to-ear canal electrode arrangement provided by the Enhancer I ear canal electrode setup. For the normally hearing group, simultaneous acquisition of forehead-to-ipsilateral ear canal and forehead-to-ipsilateral mastoid electrode linkages was obtained. For the abnormally hearing subjects, a comparison was made between the Enhancer I system and the conventional forehead-to-mastoid electrode configuration used with a TDH-49 transducer for click delivery. Our findings indicate that Wave I was enhanced substantially when using the disposable ear canal electrode compared with the more conventional forehead-to-mastoid electrode configuration for both normally and abnormally hearing subjects. The Enhancer I electrode evaluated in this study proved to be painless for the subjects and extremely easy to use, requiring no more time in subject preparation than the more common surface recording electrode application.

Adult↗
PubMed1987

Thomas Brown on the philosophy and psychology of perception.

Thomas Brown's theory of perception is set in its philosophical context, and the influence of George Berkeley, David Hume, and Thomas Reid on Brown is discussed. Destutt de Tracy, who appears to have been an unacknowledged source for Brown's ideas, is also discussed. Brown's theory of perception is elaborated, and he is categorized both as a sense-datum theorist and as a phenomenalist.

History, 18th Century↗
PubMed1987

Effects of high-dose and multiple-dose gonadotropin stimulation on mouse oocyte quality as assessed by preimplantation development following in vitro fertilization.

The effects of increasing the level of ovarian stimulation on preimplantation embryonic development were assessed using a mouse in vitro fertilization system. When F1 hybrid (C57BL/6 X CBA/Ca) mice received a single injection of 5 IU pregnant mare's serum gonadotropin (PMSG) followed 60 hr later by 5 IU human chorionic gonadotropin (hCG) approximately 50% of the resultant postovulatory oocytes developed to the blastocyst stage following in vitro fertilization. Increasing the single dose of PMSG to 10 or 15 IU resulted in significant reductions in the frequency of development to the blastocyst stage. When one or two additional doses of 5 IU PMSG were administered 24 and 48 hr after an initial injection of 5 IU, lower frequencies of oocytes with the potential for full preimplantation development were again observed. This reduction in gamete quality was significantly greater when the final dose of PMSG was administered only 12 hr prior to hCG. The results suggest that excessive gonadotropin stimulation may compromise the quality of the preimplantation embryos obtained following in vitro fertilization and that the timing of gonadotropin administration may also be critical.

Animals↗
PubMed1987

Preimplantation development following in vitro fertilization of mouse oocytes: effects of timing of superovulation and preincubation in vitro.

The early embryonic development of in vitro fertilized oocytes was assessed following superovulation in F1 hybrid (C57BL/6 X CBA/Ca) mice. Decreasing the time interval between the administration of constant doses of pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) resulted in decreases in the frequency of development to the blastocyst stage but had no significant effect on development to the two-cell stage. Preincubation of postovulatory oocytes in vitro prior to insemination did not compensate for the reduced preovulatory development in vivo but resulted in decreases in the frequency of development to the blastocyst stage. The results indicate that inadequate preovulatory development of superovulated mouse oocytes can adversely affect the preimplantation development of in vitro fertilized embryos in the absence of a visible inhibitory effect on development to the two-cell stage and also that preincubation of postovulatory oocytes in vitro prior to fertilization reduces subsequent developmental capacity.

Animals↗