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Biomedical subjects

C J Hamilton

Publications and source records attributed to C J Hamilton.

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

Transport systems for the critically ill: focuses for development.

There is a worldwide increase in the transportation of critically ill patient which reflects the increasing technological specialisation and centralisation of services. In the United Kingdom (UK) a minimum of 10,000 patients with life-threatening illnesses are transported between hospitals each year (Wright, McDonald & Rogers 1988). Transport programmes are generally being more carefully assessed, and application of past experience can make them safer for patients and personnel and most cost-effective (Purdie, Ridley & Wallace 1990). This applies to both primary (movement of a patient from the community to hospital) and secondary transport (movement of a patient between hospitals). These processes are as active in the UK as in other countries with developed systems of medical care. This paper will focus on two important areas, which are relevant to how transport facilities may be expanded for the best overall advantage. These areas are the means of transport and the transporting team. The discussion is supported by a literature review. It became apparent on preparing this paper that much of the transport literature from other countries, whilst helpful, is not directly applicable to the UK.

Cost-Benefit Analysis↗
PubMed1994

Seasonality in the results of in-vitro fertilization.

Seasonal variation has been found in various reproductive outcomes. As known causes for reducing the rate of success of in-vitro fertilization (IVF) cannot explain all the variation in IVF results, we studied whether the season had any additional explanatory power. The study population consisted of 1126 women who were treated for the first time with IVF at the University Hospital in Nijmegen, The Netherlands, between 1987 and 1993. Only first IVF cycles were analysed. After adjusting for confounding by the age of the woman, type of infertility, indication for IVF and year of aspiration, some seasonal variation was observed in the fertilization rate, embryo quality, pregnancy rate and birth rate.

Adult↗
PubMed1993

The value of luteal support with progesterone in gonadotropin-induced cycles.

OBJECTIVE: To evaluate the effect of luteal support with vaginal P suppositories in hMG- and hCG-induced cycles. DESIGN: Between March 1988 and February 1989 patients did not receive luteal support, while between March 1989 and January 1990 P was given routinely in the luteal phase. Induction protocol and patient selection remained otherwise unchanged. SETTING: Infertility clinic of a tertiary care hospital. PATIENTS: Twenty-seven patients with hypogonadotropic amenorrhea (World Health Organization [WHO] group I) (11 women with luteal support, 16 women without) and 102 patients with euprolactinemic clomiphene citrate (CC)-resistant anovulation (WHO group II) (52 women with luteal support, 50 women without). INTERVENTION: Vaginal P suppositories 200 mg/d in the luteal support group. MAIN OUTCOME MEASURES: Pregnancy rate (PR), pregnancy outcome. RESULTS: The overall PR in 118 cycles with luteal support was 26.3% whereas 10.4% pregnancies were achieved in 115 cycles of the control group. The influence of luteal support was more pronounced in patients with CC-resistant anovulation (25.2% versus 6.9%) than in patients with hypogonadotropic amenorrhea (33.3% versus 21.4%, not significant). The abortion rate was not significantly changed. CONCLUSION: Luteal support with P increases the PR after hMG and hCG induction. The need for supplementary P seems to be related to the underlying cause of ovarian disturbance.

Abortion, Spontaneous↗
PubMed1993

Different follicle stimulating hormone/luteinizing hormone ratios for ovarian stimulation.

The aim of the present study was to investigate whether reducing the amount of luteinizing hormone (LH) in gonadotrophic preparations impairs follicular growth in in-vitro fertilization (IVF) cycles during suppression of endogenous LH levels. A selected group of 20 IVF patients was randomly divided into two groups. One group was treated with Org 31338 [follicle stimulating hormone (FSH)/LH 3:1], the other group with Metrodin (purified FSH), both during pituitary down-regulation with buserelin. A fixed daily dose of 150 IU FSH i.m. was given. Serum concentrations of FSH, LH, oestradiol and progesterone were determined frequently and serial ultrasound examinations were performed. Multiple follicular growth with concomitant rise of oestradiol levels was observed in all cycles. The duration of the stimulation phase was shorter in the group treated with Org 31338 than in the group treated with Metrodin. The number of follicles and oocytes and the fertilization rate was larger and the mean embryo quality was higher in the Org 31338 group, but the differences did not reach statistical significance. No significant differences were found in hormonal values. In women with normal endocrine profiles, lowering of the LH activity in gonadotrophic preparations during gonadotrophin-releasing hormone agonist treatment results in adequate ovarian stimulation. However, a preparation with some LH needed a shorter stimulation than a purified FSH preparation. Whether the other beneficial effects of Org 31338 also occur in a larger population needs further investigation.

Adult↗
PubMed1993

Percoll semen preparation enhances human oocyte fertilization in male-factor infertility as shown by a randomized cross-over study.

The aim of this study was to compare two methods of semen preparation: multiple tube swim-up and Percoll separation, using a randomized cross-over clinical study, in which sperm parameters, oocyte fertilization rates, embryo quality and cell stage were analysed. Overall, there was no difference between the two preparation methods in the normozoospermic cycles. In the male-factor cycles, Percoll extracted a higher total number of spermatozoa (P = 0.02), increased the concentration of motile spermatozoa (P = 0.02), increased the total number of motile spermatozoa per sample (P = 0.02), and enhanced the recovery rate of motile spermatozoa (P = 0.04) compared to swim-up. There was a significant improvement in fertilization rates (P = 0.0006), in the percentage of embryos over 2-cell stage on day of transfer (P = 0.004), and in the number of replaced embryos per transfer (P = 0.01) in the Percoll as compared to swim-up cycles. There was no significant difference in embryo quality. We conclude, therefore, that in advanced reproductive procedures where sperm dysfunction exists, semen preparation with Percoll should replace the swim-up technique.

Female↗
PubMed1992

Polymer membranes in clinical sensor applications. I. An overview of membrane function.

Polymer membranes are used in a wide variety of molecular sensing devices many of which are of potential clinical interest. The role of the polymer and the physical properties required of it are, however, rarely clearly defined. An extensive review is presented of the range of polymers whose use as membranes is described in the sensor literature. This forms the basis of an overview of membrane function in potentiometric amperometric and fibre optic sensors. In particular, the interaction of permeability, permselectivity and transmembrane potential is highlighted, together with the role of polymer membranes as matrices for the immobilization of reactive chemical and biological agents.

Biocompatible Materials↗
PubMed1992

Polymer membranes in clinical sensor applications. II. The design and fabrication of permselective hydrogels for electrochemical devices.

Hydrogels, particularly the tough, low water content materials, have potential advantages in the field of clinical biosensors because of their established use as medical polymers. The factors that control transport behaviour in these polymers are discussed with particular reference to ion selectivity. The nature of the transport behaviour in relation to coated wire electrode performance is presented and an extension of these permselectivity studies to the fabrication of miniaturized devices, such as ISFETs, is described. Linear soluble hydrogel polymers, coated on to sensor substrates, may be converted to insoluble membranes using solid photosensitive aromatic monomers, such as N-vinyl carbazole. Photolithographic patterning is achieved using a UV source together with appropriate masking, followed by an oxygen plasma etch process. Gas plasma etching, which selectively removes uncross-linked (masked) areas forms the basis of an all dry, low-temperature patterning process capable of giving micrometre-scale resolution. This novel photographic process, which does not damage or extract enzymes or ionophores, can advantageously be extended to the fabrication of poly(vinylchloride)-based membranes.

Biocompatible Materials↗
PubMed1992

Polymer membranes in clinical sensor applications. III. Hydrogels as reactive matrix membranes in fibre optic sensors.

The potential of hydrogel copolymer membranes in clinical sensors, based on fibre optics, is addressed. The particular properties of the membranes of relevance in this application are the ease of refractive index modulation and the potential of the hydrogel to act as a permselective barrier in which a colorimetric agent may be immobilized. The results presented illustrate the complexity of colorimetric and refractive index effects together with their dependence on pH and tonicity for hydrogels of a given composition range. The incorporation of an acryloyl-functionalized reagent (bromopyrogallol red) is used to illustrate the way in which a working pH sensor based on these combined properties may be designed and fabricated.

Biocompatible Materials↗
PubMed1991

Prediction of successful embryo implantation by measuring interleukin-1-alpha and immunosuppressive factor(s) in preimplantation embryo culture fluid.

To find a better predictor of pregnancy after in vitro fertilization (IVF), supernatant fluids from embryo culture media were analyzed after 24 hours and 48 hours for the presence of interleukin-1-alpha (IL-1), interleukin-2, and the percent of immunosuppression. The measurements were performed on 108 consecutive IVF cycles between June 1989 and October 1989. The IL-1 level +/- SD in the 24-hour aliquots of the supernatant of embryo culture fluid was 66.2 +/- 10.2 pg/mL in all viable pregnancy cycles and 35.4 +/- 9.01 pg/mL in unsuccessful cycles. The percent of immunosuppression after 24 hours was 22.06% +/- 4.5% in viable pregnancy cycles and 7.3 +/- 5.5% in unsuccessful cycles. The percent of immunosuppression 48 hours after ovum pick-up was generally decreased in all embryo culture fluid, showing 17.5% +/- 4.4% in viable pregnancy cycles and 3.8% +/- 3.6% in unsuccessful cycles. Interleukin-1 levels in the 48-hour aliquots were moderately decreased, being 39.0 +/- 6.3 pg/mL in viable pregnancy cycles and 34.3 +/- 4.7 pg/mL in the unsuccessful cycles. In 24 hours, embryo culture aliquots IL-1 level greater than 60 pg/mL was seen in 17 of 21 (80.9%) pregnancy cycles, and the combined data of IL-1 level greater than 60 pg/mL and/or greater than 20 percent of immunosuppression predicted 21 of 21 (100%) pregnancy cycles.

Culture Techniques↗
PubMed1991

Artificial endometrial stimulation for frozen embryo replacement.

In this study, 18 cycles initiated for the transfer of cryopreserved embryos. Endometrium was prepared using a uniform protocol of exogenous E and P. This approach eliminated cycle cancellations caused by ovulatory dysfunction and gave complete cycle control. Fourteen cycles had embryo division and replacement resulting in three pregnancies. In these conception cycles, E was discontinued at 12 days and P at 26 days after ET. One aborted at 6 weeks gestation, whereas the other two pregnancies progressed uneventfully into the third trimester.

Abortion, Spontaneous↗
PubMed1989

Longitudinal ultrasonographic study of the ovarian suppressive activity of a low-dose triphasic oral contraceptive during correct and incorrect pill intake.

A longitudinal study was conducted to evaluate the ability of a low-dose triphasic oral contraceptive to suppress ovulation as documented by frequent ultrasonographic scanning and progesterone determinations, even in the event of a missed pill. The extent of follicular growth and maturation, the incidence of escape ovulation, and the effect of correct and incorrect pill intake were assessed in 30 evaluable women during two consecutive spontaneous menstrual cycles. After the first cycle, 11 of 30 women (36.6%) had follicle-like structures of at least 10 mm in diameter. Ten of 11 structures gradually disappeared during the second cycle, with one persistent structure remaining through the second cycle. Seven of 30 women (23%) developed follicle-like structures during the second cycle. Of these, one woman had a probable ovulation, and another had an elevated progesterone level without follicle rupture, suggesting the luteinized unruptured follicle syndrome. Both of these women missed a pill on day 1 of the second cycle. In all cases cervical scores indicating hostility were noted. Thus, although suppression of ovarian activity may have been incomplete when oral contraceptives were incorrectly taken, secondary mechanisms of contraception remained operant. When they were correctly taken, low-dose triphasic oral contraception consistently prevented ovulation.

Adult↗
PubMed1989

Synthetic hydrogels. VI. Hydrogel composites as wound dressings and implant materials.

An overview is presented of the use of hydrogel composites as biomaterials. These range from laminates or coatings (in which a homogeneous hydrogel is used in conjunction with a more mechanically stable substrate), through blends of hydrogels with synthetic hydrophobic polymers, to the use of two-component systems in which water enhances the compatibility of two structurally different polymers. Although synthetic hydrogels provide an ideal basis for materials of these types, naturally occurring hydrophilic polymers with their unique properties have a major contribution to make. It is in the clinical and patent literature, rather than journals dealing with polymers per se, that the vast majority of examples of the use of hydrogel composites are found. This review collects and comments on examples based on synthetic developments in this field during the last decade, particularly in relation to the development of wound dressings and implant materials.

Bandages↗
PubMed1987

The reliability of ovulation prediction by a single ultrasonographic follicle measurement.

Since ultrasonographic ovulation detection has been introduced many authors have speculated about the ovulation predictive value of this new technique. Reliable studies in this respect, however, are lacking. The present study describes ultrasonographic data of 158 spontaneously ovulating, infertile patients. Each patient contributed only one cycle to the study. To construct individual follicle growth curves serial follicular measurements were performed. A wide range existed in mean maximum diameters of the preovulatory follicles. Furthermore, the slopes of the follicle growth curves, as well as the durations of the follicle growth phases showed considerable variations. The intrinsic variability in the various characteristics of follicle growth makes a single measurement as accurate as serial measurements in predicting ovulation. A formula has been devised by means of the data of the first 100 women, which correlates follicular diameter with the time interval to ovulation. The formula was developed based on one randomly selected measurement per patient. The validity of the formula has been tested in 58 additional women, also contributing one measurement each. According to this validation the adequacy of the prediction rule was demonstrated. Ultrasound appeared to be a less sensitive method for prediction of ovulation than has been speculated by some investigators. It is, however, an improvement, compared to the prediction of ovulation based upon the length of the previous menstrual cycles. A single follicle measurement may therefore be helpful in timing post-coital tests or artificial inseminations, in addition to being an adjuvant to more reliable methods.

Female↗
PubMed1987

Ovulatory disturbances in patients with luteal insufficiency.

In order to study ovulatory disturbances in patients with luteal insufficiency we evaluated 210 cycles of 170 women from infertile couples by ultrasonographic follicle measurements and hormonal determinations. Only cycles with evidence of luteinization were included into the study. Mid-luteal progesterone (P) levels were determined in relation to the ultrasonographic ovulation time or, where the follicle failed to rupture, in relation to the LH peak. In spontaneous cycles with a mid-luteal P level below 32 nmol/l (10 ng/ml) a luteinized unruptured follicle (LUF) was found in 71.1% of cycles, whereas in spontaneous cycles with a mid-luteal P level above 32 nmol/l only 7.9% cycles exhibited a failure of the follicle to rupture. The same phenomenon was encountered in cycles in which agents had been given to induce ovulation. The incidence of LUF cycles in an average infertility population could be calculated to be as high as 50% if the mid-luteal P level is below 32 nmol/l and as low as 4% if the mid-luteal P level is above 32 nmol/l. The geometric mean mid-luteal P level in spontaneous LUF cycles was 32.5 nmol/l, compared to 55.2 nmol/l in spontaneous ovulatory cycles (P less than 0.001). We conclude that in patients with luteal insufficiency a high incidence is found of a failure of the follicle to rupture. The entrapment of the oocyte in the unruptured follicle constitutes an important cause of infertility in these patients.

Female↗
PubMed1986

Ovulatory disorders and inflammatory adnexal damage: a neglected cause of the failure of fertility microsurgery.

Failure of reconstructive tubal surgery is usually attributed to pre-existing endosalpingeal damage, recurrent adhesion formation or progressive inflammatory disease. We studied ovarian follicle development and ovulation by ultrasound in 25 infertile patients with laparoscopically proven sequelae of pelvic inflammatory disease. Failure of the follicle to rupture was seen in 13, although luteinization occurred. The mean mid-luteal progesterone concentration in cycles with an unruptured follicle was significantly lower than the concentrations both in ovulatory cycles in the same patients and in a comparison group of 45 normally ovulating women (P less than 0.01). Microsurgical adhesiolysis did not seem to influence the occurrence of the ovulation disorder.

Adult↗