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Biomedical subjects

B Mason

Publications and source records attributed to B Mason.

At least 37 records · Page 2Linked to original sources
PubMed1994

Isolation and characterization of a cDNA encoding the zebra finch myelin proteolipid protein.

A cDNA was isolated from a zebra finch telencephalon cDNA library that encodes the myelin proteolipid protein. The clone was 2874 nucleotides long containing an open reading frame of 831 nucleotides that encoded a 277 amino acid myelin proteolipid protein. The 5'- and 3' untranslated regions were 112 and 1931 nucleotides, respectively. In Northern blots the clone hybridized to 3 bands of 3.5, 2.4 and 1.5 Kb in mouse brain RNA, but to only a single band of 3.0 kb in zebra finch brain RNA, suggesting the lack of alternative polyadenylation sites within the 3' untranslated region of the zebra finch PLP mRNAs. There was a small degree of homology between the zebra finch and chicken PLP 5' untranslated regions, but relatively little homology of the 5' untranslated regions of the zebra finch PLP cDNA clone with the homologous regions of PLP cDNAs of many mammalian species. Except for a small stretch of considerable homology, there was little overall homology with the 3' untranslated regions of mammalian PLP mRNAs. Approximately 10% (i.e. 28) of the amino acids in the zebra finch PLP differed from mammalian PLP, with most of these changes located within exon 3. There were 16 amino acid changes between zebra finch and chicken, suggesting that greater sequence variation in PLP structure is tolerated among avian species than among mammalian species.

Amino Acid Sequence↗
PubMed1994

Magnesium sulfate versus phenytoin for seizure prevention in amygdala-kindled rats.

OBJECTIVE: Magnesium sulfate is widely used for seizure prophylaxis in preeclampsia-eclampsia. However, its anticonvulsant effects in other types of seizures have not been proved. Diphenylhydantoin has been widely characterized as the "gold standard" of anticonvulsants. In this study we compared the anticonvulsant effects of therapeutic blood levels of magnesium sulfate and phenytoin in seizures generated in amygdala-kindled rats. STUDY DESIGN: Eighteen male rats had a bipolar electrode stereotaxically implanted into the central nucleus of the amygdala. After recovery an electrical seizure threshold was determined for each rat. Rats were stimulated twice daily at their seizure thresholds (i.e., kindling) until three consecutive generalized tonic-clonic seizures occurred. Kindled rats randomly received one of the following intravenous injections in a volume of 1.5 ml/kg: saline solution, magnesium sulfate (30, 60, or 90 mg/kg), or phenytoin (12.5, 25, or 50 mg/kg). Fifteen minutes after injection rats were stimulated at their seizure thresholds, and electrical and behavioral seizure activity was assessed. Statistical comparisons were made by analysis of variance and post hoc comparisons when appropriate. RESULTS: Magnesium sulfate had no effect on any of the seizure parameters assessed. Phenytoin significantly reduced seizure duration (p < 0.01), duration of postictal depression (p < 0.01), and behavioral seizure stage (p < 0.01). CONCLUSION: Amygdala-kindled seizures are more potently inhibited by phenytoin than by magnesium sulfate.

Amygdala↗
PubMed1994

General professional training in public health medicine--the Leicestershire Senior House Officer scheme.

BACKGROUND: This study investigates the subsequent careers of the Senior House Officers (SHOs) who have passed through the Leicestershire SHO training scheme in public health medicine since its inception in 1981 and their views of the scheme. METHODS: Postal questionnaires were sent to past and current SHOs, using addresses compiled from personnel records, the Medical Directory and the General Medical Council Medical Register. One reminder letter was sent to non-responders. RESULTS: Of the 21 past SHOs, one is now a consultant and four are currently trainees in public health medicine. Other past SHOs have followed diverse careers but the largest group are now in general practice. The four past SHOs who are now trainees in public health gained no further clinical experience before obtaining registrar or lecturer posts. All past SHOs responded favourably when asked about the benefits of the scheme regardless of their subsequent career choice. CONCLUSION: The continuing need for high-calibre recruits to the specialty and the favourable response from past SHO trainees suggests that this scheme, and no doubt other similar schemes, should be making their benefits known to a wider audience.

Career Choice↗
PubMed1993

Brain-derived neurotrophic factor expression after long-term potentiation.

Long-term potentiation (LTP) of perforant-path dentate granule cell synapses, in awake rats, was followed by a time-dependent expression of brain-derived neurotrophic factor (BDNF) mRNA in dentate granule cells. This BDNF expression was blocked by the N-methyl-D-aspartate (NMDA) antagonist dizocilpine maleate (MK-801), which also blocked LTP induction, and by sodium pentobarbital, which shortens LTP persistence. These results suggest that BDNF may participate in the NMDA-receptor mediated cascade of events that result in LTP stabilization.

Animals↗
PubMed1993

Endocrinology of in-vitro fertilization pregnancies during the first trimester.

The endocrine function of the corpus luteum and placenta and the inter-relationships between ovarian steroids and the placental proteins in pregnancies achieved following ovarian stimulation, in-vitro fertilization and embryo transfer (IVF-ET) have been investigated. The serum concentrations of human chorionic gonadotrophin (HCG), Schwangerschaft protein-1 (SP-1), pregnancy-associated plasma protein A (PAPP-A), progesterone and oestradiol were measured at weekly intervals between the 4th (ET plus 2 weeks) and 14th week of gestation in 86 pregnancies. The mean concentrations of the placental proteins and oestradiol were significantly higher in twin than in singleton pregnancies from as early as 5 weeks gestation, but the mean concentrations of progesterone were significantly higher only at the end of the first trimester. Ranking, as demonstrated by the presence of statistically significant correlations between serum levels of each substance analysed in week 13 with those of preceding weeks, was established for progesterone and SP-1 from the 5th week, for oestradiol and PAPP-A from the 7th week and for HCG from the 8th week of gestation. The presence of statistically significant correlations between each substance analysed suggests that the placenta becomes the dominant source of oestradiol from 8 weeks gestation and of progesterone not until 12 weeks gestation, and that the placental synthesis of HCG, SP-1, PAPP-A, oestradiol and progesterone appear to be linked. There were no statistically significant correlations between the serum concentrations of HCG and either progesterone or oestradiol until the production of each had become predominantly placental.

Adult↗
PubMed1993

Histocompatibility and liver transplantation.

BACKGROUND: The role of histocompatibility between donor and recipient in liver transplant rejection is unclear because of a paucity of data. The influence of human leukocyte antigen (HLA) type on immunologic graft loss was examined for primary liver transplantations performed at this center. METHODS: Immunologic graft loss included patient death or retransplantation as a result of rejection or impending graft loss caused by either late hepatic artery thrombosis or severe, unremitting rejection requiring FK 506 rescue therapy. HLA A, B, and DR matching was available on 205 donor-recipient combinations, and an additional 31 patients had A and B matching only. RESULTS: A mismatch of class I antigens (HLA A and B) was predictive of immunologic graft loss (p = 0.018). DR mismatch did not correlate with graft loss. When the A and B loci were analyzed separately, an A mismatch correlated significantly with immunologic graft loss (p = 0.02), in contrast to a B mismatch (p = 0.17). Better matching significantly improved patient survival (p = 0.02) and overall graft survival (p = 0.009). CONCLUSIONS: The beneficial effect of HLA class I antigen compatibility on liver transplantation outcome is in contrast to pancreatic and kidney transplantation in which class II antigen matching but not class I matching is beneficial. Immunologic mechanisms of hepatic allograft rejection may differ from those involved in kidney transplant rejection.

Forecasting↗
PubMed1992

Cumulative conception and livebirth rates after in-vitro fertilisation.

Cumulative conception and livebirth rates related to age and cause of infertility provide the most useful estimate of success after in-vitro fertilisation (IVF), but limited data are available. It is also uncertain whether the probability of pregnancy, livebirth, and pregnancy failure changes with repeated treatment cycles. To assess the effects of patients' age and cause of infertility on these outcomes, we studied the results of 5055 consecutive IVF cycles (773 clinical pregnancies, 518 livebirths) undertaken on 2735 patients in a single IVF unit. Cumulative conception and livebirth rates were analysed by the life-table approach and differences in rates between age-groups and between causes of infertility were measured by the log-rank test and logistic regression modelling. Both conception and livebirth rates per cycle declined with age (p less than 0.001), and cumulative conception and livebirth rates after five treatment cycles were about 54% and 45%, respectively, at 20-34 years, compared with 38.7% and 28.9% at 35-39 years and 20.2% and 14.4% at greater than or equal to 40 years. The two rates were significantly different between causal groups (p less than 0.001 and p = 0.02, respectively) and were lowest in patients with male infertility or multiple infertility factors. The pregnancy failure rate was higher (p = 0.006) in women over the age of 34 years and there was a significant decline in the chances of pregnancy and livebirth per cycle with successive treatment cycles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Obstetric outcome of in vitro fertilization pregnancies compared with normally conceived pregnancies.

OBJECTIVE: To compare the obstetric outcome of in vitro fertilization pregnancies with normally conceived pregnancies. STUDY DESIGN: The obstetric outcome of in vitro fertilization pregnancies achieved in 763 British residents at two in vitro fertilization clinics resulting in the births of 961 babies were compared by means of the relative risk statistic with a control group of naturally conceived primiparous pregnancies matched by maternal age and multiplicity of pregnancy. RESULTS: Twenty-five percent of in vitro fertilization pregnancies were multiple pregnancies. The incidence of singleton term breech presentation was similar to that among controls. As compared with controls there was an increased incidence among in vitro fertilization pregnancies of vaginal bleeding and hypertension requiring hospitalization (p less than 0.001) and cesarean births (p less than 0.001) and, among in vitro fertilization singleton pregnancies, an increased incidence of intrauterine growth retardation (p less than 0.05), placenta previa (p less than 0.05), and preterm delivery (p less than 0.001). The congenital malformation, stillbirth, and perinatal mortality rates were comparable with maternal age-standardized national rates. CONCLUSIONS: Although the majority of in vitro fertilization pregnancies have a satisfactory obstetric outcome, there are a number of increased obstetric risks that may reflect the history of infertility, the relatively high incidence of poor obstetric history, and the lower threshold for obstetric intervention in in vitro fertilization patients.

Adult↗
PubMed1992

The routine use of gonadotropin-releasing hormone agonists for all patients undergoing in vitro fertilization. Is there any medical advantage? A prospective randomized study.

OBJECTIVE: To determine if the routine use of gonadotropin-releasing hormone agonists (GnRH-a) for all patients undergoing in vitro fertilization (IVF) produces any significant medical advantage. DESIGN: Prospective randomized study. PATIENTS: Three hundred eight patients having their first ever IVF attempt. INTERVENTIONS: Patients were randomly divided into four groups and received either human menopausal gonadotropin (hMG) alone for ovarian simulation (group A, n = 81); clomiphene citrate and hMG (group B, n = 77); a 3-day ultrashort course of GnRH-a and hMG (group C, n = 74); or pituitary desensitization with GnRH-a followed by hMG (group D, n = 76). RESULTS: The indications for IVF and mean age of all four groups of patients were comparable. There was a significant difference in the number of embryos cleaved and transferred among the groups, but there were no significant differences in the cancellation rate, mean number of oocytes collected or fertilized, and number of cases of failed fertilization. There were also no significant differences in the pregnancy and live birth rates per cycle commenced or per embryo transfer. CONCLUSION: The routine use of GnRH-a for all patients undergoing IVF has practical but no significant medical advantages.

Abortion, Spontaneous↗
PubMed1991

Immunochemical analysis of a recombinant, genetically engineered, secreted HLA-A2/Q10b fusion protein.

We engineered a fusion gene which encodes the alpha 1 and alpha 2 domains of HLA-A2 with the alpha 3 and truncated transmembrane domains of the murine class I-like protein Q10b, and transferred it into mouse L cells along with the gene for human beta 2-microglobulin (beta 2m). The secreted rA2/Q10b gene product consisted of a single heavy chain of molecular weight 42 kd that was noncovalently associated with the human beta 2m light chain. Native detergent-solubilized HLA-A2 and secreted rA2/Q10b proteins were found to be similar by: (a) the binding to mouse monoclonal anti-HLA antibodies in an ELISA; (b) the blocking of lysis of HLA-A2+ cells by human anti-HLA-A2,-B17, anti-HLA-A2,9,28, and anti-HLA-A2,28 cross-reactive group (CREG) antisera in a complement-dependent cytotoxicity assay; and (c) the ability when coupled to Sepharose to selectively purify HLA-A2,9,28 and HLA-A2,28 CREG-specific antibodies. Mouse L cells expressing rA2/Q10b produced as much as 2.5 micrograms protein per 10(6) cells/day, or 50- to 100-fold more antigen on a per cell basis than the level of HLA-A2 expressed by B-lymphoblastoid cell line or spleen cells. Thus rA2/Q10b represents a viable alternative to detergent-solubilized HLA-A2 for purification of anti-HLA-A2 antibodies and analysis of anti-HLA-A2 immune responses.

Animals↗
PubMed1991

An investigation of the safety of the blood reinfusion step used with tunneled venous access devices in children with cancer.

Infection has been identified as the most serious potential complication of the indwelling catheter. As a result, the primary nursing goal using the catheters is to prevent infection. Nurses must frequently manipulate the catheters when securing blood specimens and are concerned that this manipulation may serve as a source of infection for the immunocompromised pediatric oncology patient. One particular step in catheter manipulation during blood sampling is blood reinfusion, ie, residual blood in the catheter is withdrawn and set aside while a second sample is collected for laboratory analysis but is subsequently returned to the patient through the catheter. The purpose of this study was to examine this nursing procedure for its potential of contaminating the blood sample that was to be reinfused, or for the potential of reinfusing a sample that contained preexisting pathogens independent of the procedure itself. An experimental design was used with 21 patients randomly assigned to an experimental group (unclean procedure to exaggerate the potential to incur pathogens during the process), and 21 randomly assigned to a control group (usual clean procedure followed with the reinfusion sample). The usual blood sampling procedure was altered for all participants as the typical amount of blood that normally constitutes the reinsertion sample was not reinserted, but was instead used to complete certain microbial analyses. Of the 42 participants, 17 were male and 25 were female; 35 were white and seven were black; 22 were diagnosed with leukemias and 20 with solid tumors. The age range for participants was 2 to 20 years (mean = 9.4 years, SD = 4.8).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Hygienic hand disinfection tests in three laboratories.

A comparative study was made in three laboratories of a test for hygienic hand disinfection. Staphylococcus aureus was applied to the fingertips of a total of 74 volunteers (49 female and 25 male) and the effect of washing with three chlorhexidine preparations and one non-medicated soap was assessed after one and five applications. Fingertip inoculation is convenient and is a realistic representation of the in-use situation. Although significant differences were obtained between log10 reductions in test organisms using the same formulation in different centres, and different periods in the same centre, the maximum differences after a single application of a preparation were small, e.g. between centres 0.39 and between periods in the same centre 0.55, and after multiple applications the maximum difference between centres was 0.42 and between periods in the same centre it was 0.51. The differences between preparations were similar in all centres. This test compares well with other similar tests and products can be placed in rank order of effectiveness. It is concluded that this test, if carried out under the controlled conditions described, is sufficiently reproducible between laboratories and repeatable within laboratories to be used as a standard test.

Chlorhexidine↗
PubMed1990

Influence of superovulation on endometrial and embryonic development.

The authors have studied the temporal relationship between follicular rupture and endometrial development in 13 women during a natural ovarian cycle (length 25 to 35 days), and subsequently after standard treatment with clomiphene citrate, human menopausal gonadotropin and human chorionic gonadotropin (hCG) to induce multiple folliculogenesis for oocyte recovery, in vitro fertilization, and embryo freezing (cycle length 23 to 27 days). An endometrial biopsy was taken during both cycles 1.5 to 2.0 days after the oocytes had been released or removed. The samples were examined by light and transmission electron microscopy. Samples of peripheral blood were taken at defined times for hormone analysis. After treatment 11 subjects (85%) had advanced morphological development of the endometrium (8 women by 3 to 4 days, 3 women by 1 to 2 days). The concentrations of plasma estradiol (E2) and progesterone (P) on the days of follicular rupture and endometrial biopsy were significantly raised in the treatment cycles. The concentration of total urinary estrogens on the day of hCG administration and the mean change in the concentration of plasma E2 (treatment/control) on the days of endometrial biopsy were positively correlated with the extent of endometrial advancement. In addition, the mean change in the concentration of plasma P (treatment/control) was markedly increased on the days of follicular rupture and endometrial biopsy in those subjects with an advanced endometrium. Embryonic development was not so obviously related to the extent of superovulation. Asynchronous endometrial and embryonic development may therefore contribute to the low pregnancy rate in these patients.

Adult↗