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Biomedical subjects

J H Ford

Publications and source records attributed to J H Ford.

At least 19 recordsLinked to original sources
PubMed1996

The human glycine receptor beta subunit: primary structure, functional characterisation and chromosomal localisation of the human and murine genes.

The inhibitory glycine receptor (GlyR) is a pentameric receptor comprised of alpha and beta subunits, of which the beta subunit has not been characterised in humans. A 2106 bp cDNA, isolated from a human hippocampal cDNA library, contained an open reading frame of 497 amino acids which encodes the beta subunit of the human GlyR. The mature human GlyR beta polypeptide displays 99% amino acid identity with the rat GlyR beta subunit and 48% identity with the human GlyR alpha 1 subunit. Neither [3H]strychnine binding nor glycine-gated currents were detected when the human GlyR beta subunit cDNA was expressed in the human embryonic kidney 293 cell line. However, co-expression of the beta subunit cDNA with the alpha 1 subunit cDNA resulted in expression of functional GlyRs which showed a 4-fold reduction in the EC50 values when compared to alpha 1 homomeric GlyRs. Glycine-gated currents of alpha 1/beta GlyRs were 17-fold less sensitive than homomeric alpha 1 GlyRs to the antagonists picrotoxin, picrotoxinin and picrotin, providing clear evidence that heteromeric alpha 1/beta GlyRs were expressed. The beta subunit appears to play a structural rather than ligand binding role in GlyR function. Fluorescence in situ hybridisation was used to localise the gene encoding the human GlyR beta subunit (GLRB) to chromosome 4q32, a position syntenic with mouse chromosome 3. In situ hybridisation using the human GlyR beta subunit cDNA showed that the murine GlyR beta subunit gene (Glrb) maps to the spastic (spa) locus on mouse chromosome 3 at bands E3-F1. This is consistent with the recent finding that a mutation in the murine GlyR beta subunit causes the spa phenotype. It also raises the possibility that mutations in the human beta subunit gene may cause inherited disorders of the startle response.

Amino Acid Sequence↗
PubMed1995

Pregnancy and lifestyle study: the long-term use of the contraceptive pill and the risk of age-related miscarriage.

Maternal ageing is a very important factor in aneuploidy. It is associated with an increased risk of a liveborn trisomy, especially Down's syndrome, and with a dramatic increase in trisomic conceptions, the majority of which miscarry. A total of 585 volunteer couples who were planning pregnancies participated in a prospective study of reproduction. The couples answered extensive questionnaires and early pregnancy tests (day 28) were conducted each month. The number of years of contraceptive pill use was correlated with pregnancy outcome. Lowered rates of miscarriage were found with increased years of pill use. The cut-off point for this positive effect appeared to be 9 years. Use of oral contraceptives for > or = 9 years was associated with a spontaneous abortion rate of 11.3%, which is about half the rate (23%) which was found in couples who had not used the pill. However, the effect of pill taking was correlated with female age, and when age was examined as an independent factor, the reduction in miscarriage was only statistically significant in women > 30 years old, where the rate of abortion reduced from 28 to 7%. Because age-related aneuploidy in humans probably occurs as a direct or an indirect result of follicle depletion, it is proposed that the long-term use of the oral contraceptive pill protects against abortion due to aneuploidy by preserving the number of follicles.

Abortion, Spontaneous↗
PubMed1994

Insertional mutagenesis inducing hypomyelination in transgenic mice.

Investigations of myelin disorders, in particular multiple sclerosis (MS), have concentrated on immunemediated damage to formed myelin, while there has been less emphasis on the molecular genetics of myelin formation. We have generated a transgenic mouse mutant (designated 2-50) which carries an insertional mutation in a locus regulating myelination. These mice carry a transgene comprising 1.3 Kb of the mouse myelin basic protein (MBP) promoter conjugated to a fragment containing exons 2 and 3 of the human c-myc gene. Positive mice show a significant reduction in myelin compared to controls and a shivering phenotype. Unlike other myelin mutants, all 2-50 mice lose the shivering phenotype and breed normally. Expression of c-myc is detectable in only 65% of transgene-carrying mice, and when present occurs at extremely low levels. This shows that the phenotype is caused by insertional inactivation of a gene necessary for myelination rather than ectopic expression of the transgene. The transgene was found by in situ hybridization to be inserted into a single site which is very distally located on chromosome 9. The 2-50 mice represent a unique model which will be ideal for investigating the molecular basis of myelin assembly and for developing gene therapy to promote remyelination in conditions such as MS.

Animals↗
PubMed1994

A fluorescent in situ hybridization analysis of the chromosome constitution of ejaculated sperm in a 47,XYY male.

Two semen samples from a 47,XXY male were examined using chromosome-specific DNA probes and fluorescent in situ hybridization (FISH) to determine the distribution of sex chromosomes and an autosome (chromosome 17) in the sperm. A motile population of sperm was also prepared from one sample using the swim-up technique to compare the motile and total sperm populations. Chromosomes were localized using single FISH and a biotinylated chromosome 17 probe (TR17), or double FISH using a biotinylated X chromosome probe (TRX) and a digoxigenin-labelled Y chromosome probe (HRY). Labelling efficiencies were 95-98%. Ploidy levels were estimated by measurement against a microscope eye-piece graticule. The overall ratio of X- to Y-bearing sperm was 47% to 48.4% in the neat samples, and 48.4% to 45.3% in the swim-up fraction. Neither of the ratios was significantly different from 1:1. The frequencies of monosomic and disomic (but otherwise haploid sperm) were not different from the frequencies we observed in normal donors. In contrast, the frequencies of both diploid and tetraploid cells were increased in the neat samples of the XYY male. In the swim-up fractions, however, none of these parameters differed from those of ten normal semen donors. These results support the hypothesis that the extra Y chromosome in XYY men is eliminated during spermatogenesis.

Adult↗
PubMed1993

Simultaneous detection of X- and Y-bearing human sperm by double fluorescence in situ hybridization.

Double fluorescence in situ hybridization (FISH) was used to detect sex chromosomes in decondensed human sperm nuclei. Biotinylated X chromosome specific (TRX) and digoxigenin-labeled Y chromosome specific (HRY) probes were simultaneously hybridized to sperm preparations from 12 normal healthy donors. After the hybridization, the probes were detected immunocytochemically, using two different and independent affinity systems. Ninety-six percent of the 12,636 sperm showed fluorescent labeling, of which 47.4% were haploid X and 46.8% were haploid Y. A frequency of 0.46% of XX-bearing sperm (0.28% disomic, 0.18% diploid) and 0.38% YY-bearing sperm (0.21% disomic, 0.17% diploid) was found. The overall proportions of X- and Y-bearing sperm in the ejaculates were 47.9% and 47.2%, respectively, which was not significantly different from the expected 50:50 ratio. In addition 0.21% of cells appeared to be haploid XY-bearing sperm, 0.62% were diploid XY-bearing cells, and 0.05% of cells were considered to be tetraploid cells. The application of double FISH to human sperm using X-chromosome and Y-chromosome probes has allowed a more accurate assessment of the sex chromosal complements in sperm than single FISH method and quinacrine staining for Y-bodies.

Adult↗
PubMed1993

Detection of X- and Y-bearing human spermatozoa after motile sperm isolation by swim-up.

OBJECTIVE: To assess the ratio of X- to Y-bearing human spermatozoa in motile fractions isolated by the swim-up technique. DESIGN: The proportions of X- and Y-bearing sperm were determined in neat semen samples (control) and in motile fractions isolated from the same samples by swim-up. X- and Y-bearing sperm were simultaneously identified using chromosome-specific DNA probes and double fluorescence in situ hybridization. SETTING: Hospital-based university department. PARTICIPANTS: Ten healthy donors with normal semen characteristics. MAIN OUTCOME MEASURES: The distribution of haploid cells (X or Y), normal size cells with two sex chromosome (XX, YY, or XY), and large cells containing two (XX, YY, or XY) or four (XXYY) sex chromosomes were measured in neat semen samples and in motile fractions prepared by swim-up. RESULTS: Overall, 95% of sperm in the neat semen and swim-up fractions were labeled with the probes. The ratios of X- to Y-bearing sperm were 47.3:46.9 (neat semen) and 48.4:47.1 (swim-up fractions), which were not significantly different from a 1:1 ratio. The frequencies of sperm with normal size nuclei and two sex chromosomes (XX, YY, or XY) in the swim-up fractions were not significantly different from the controls, but there was a significant reduction in the proportion of cells with large nuclei and two (XX, YY, or XY) or four (XXYY) sex chromosomes in the swim-up fractions. CONCLUSIONS: The swim-up technique does not selectively enrich either X- or Y-bearing sperm. Because the isolation of motile spermatozoa is an important procedure for routine IUI, IVF-ET, and GIFT, the results of this study are important reassurance that the sex ratio is not altered by this method of sperm preparation.

Cell Nucleus↗
PubMed1992

Detection of chromosome 17- and X-bearing human spermatozoa using fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) with DNA probes specific to chromosomes 17 and the X has been applied to human ejaculated sperm. After sperm nuclei were decondensed with EDTA and DTT, biotinylated alpha satellite DNA probes TR17 and TRX were separately used on preparations from thirteen healthy donors. After hybridization 96% of sperm were labelled with the TR17 probe and 48% of sperm were labelled with the TRX probe. Frequencies of 0.33% disomic 17 and 0.29% disomic X sperm were found. The frequencies of diploid sperm were assessed as 0.37% using the TR17 probe and 0.20% using the TRX probe which labelled only one half of the sperm; after correcting the result from the X-probe to 0.40% the two frequencies are very similar.

Aneuploidy↗
PubMed1992

Chromosome errors at mitotic anaphase.

Errors in mitotic divisions were assayed using various satellite DNAs as probes, hybridized in situ, to show that they included nondisjunction, chromosome and chromatid lagging, chromatid malsegregation, and monopolar segregations. The total rates of error were 1.7, 1.1, and 0.6% for chromosomes X, 17, and 18, respectively. Lagging was the most common error for all chromosomes and chromatid malsegregation, a source of 3:1 segregations occurred at about the same frequency as nondisjunction. In some cells, lagging of both X chromatids occurred and there were several cells where both X chromosomes showed errors in segregation. The disjunction of chromosomes was shown to be independent of their segregation and is speculated to involve a different mechanism.

Anaphase↗
PubMed1992

Localization by in situ hybridization of a type I keratin intermediate filament gene (Krt-1.14) to band D of mouse chromosome 11.

A probe from the 3' noncoding region of a murine type I keratin intermediate filament (IF) gene (Krt-1.14) localizes to band D of murine Chromosome 11 using in situ hybridization. This localization provides a physical confirmation of the assignment of the type I keratin genes by linkage analysis in the mouse. It also demonstrates that the Krt-1.14 genes are at a single locality in the mouse in contrast to the two locations on the short and long arms of chromosome 17 in humans.

Animals↗
PubMed1991

Centralized telemetry monitoring: implementation and management.

Baptist Memorial Hospital in Memphis, Tennessee has implemented a newly designed cardiac arrhythmia monitoring system. Management engineers worked closely with nurses and physicians in the design process which led to development and implementation of a centralized telemetry monitoring system. Changes in the work distribution, improvement of the work environment, efficient use of nursing personnel and upgrades of monitoring equipment are several of the objectives addressed by this new centralized monitoring system. The backbone of the centralized telemetry monitoring system is an effective communication system that fully addresses staff needs during emergency situations. This paper presents the communication system features as well as the operational, functional and technical considerations necessary to support a centralized telemetry monitoring system. Some topics covered in detail include communication system selection, staff scheduling, selection, training, and supervision of staff members, ergonomic workstation design parameters and centralized telemetry monitoring system benefits. One benefit observed was that an additional 35 minutes per nurse per shift was made available to provide additional patient care activities.

Arrhythmias, Cardiac↗
PubMed1990

Novel translocations in acute nonlymphocytic leukemia. Two cases involving chromosome 21, band q22.

We present two cases in which translocations involving 21q22 were found at presentation in acute nonlymphocytic leukemia (ANLL). The first of these translocations, t(3;21)(q26-q27;q22), is previously unknown in ANLL, but appears indistinguishable from that reportedly associated with Philadelphia-positive chronic myelogenous leukemia. The second case involves t(15;21)(q21-q22;q22), a translocation previously undescribed in ANLL. Both of these exchanges involve 21q22 plus another chromosome region associated with leukemogenesis. We attempted to interrelate these cytogenetic data with the oncogenic significance of 21q22.

Chromosome Banding↗