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Biomedical subjects

R J Hart

Publications and source records attributed to R J Hart.

At least 19 recordsLinked to original sources
PubMed2006

Discovery of a 25-cm asteroid clast in the giant Morokweng impact crater, South Africa.

Meteorites provide a sample of Solar System bodies and so constrain the types of objects that have collided with Earth over time. Meteorites analysed to date, however, are unlikely to be representative of the entire population and it is also possible that changes in their nature have occurred with time. Large objects are widely believed to be completely melted or vaporized during high-angle impact with the Earth. Consequently, identification of large impactors relies on indirect chemical tracers, notably the platinum-group elements. Here we report the discovery of a large (25-cm), unaltered, fossil meteorite, and several smaller fragments within the impact melt of the giant (> 70 km diameter), 145-Myr-old Morokweng crater, South Africa. The large fragment (clast) resembles an LL6 chondrite breccia, but contains anomalously iron-rich silicates, Fe-Ni sulphides, and no troilite or metal. It has chondritic chromium isotope ratios and identical platinum-group element ratios to the bulk impact melt. These features allow the unambiguous characterization of an impactor at a large crater. Furthermore, the unusual composition of the meteorite suggests that the Morokweng asteroid incorporated part of the LL chondrite parent body not represented by objects at present reaching the Earth.

Journal Article↗
PubMed2005

Excisional surgery versus ablative surgery for ovarian endometriomata.

BACKGROUND: Endometriomata are endometriotic deposits within the ovary. The surgical management of these blood filled cysts is controversial. The laparoscopic approach to the management of endometriomata is favoured for as it offers the advantage of a shorter hospital stay, faster patient recovery and decreased hospital costs. Currently the commonest procedures for the treatment of ovarian endometriomata are either excision of the cyst capsule or drainage and electrocoagulation of the cyst wall. OBJECTIVES: The objective of this review was to determine the most effective technique of treating an ovarian endometrioma; either excision of the cyst capsule or drainage and electrocoagulation of the cyst wall, with regard to relief of pain, recurrence of the endometrioma, recurrence of symptoms and the subsequent spontaneous pregnancy rate. SEARCH STRATEGY: The reviewers searched the Cochrane Menstrual Disorders and Subfertility Group specialised register of trials (searched 15 Nov 2004), the Cochrane Register of Controlled Trials (The Cochrane Library, Issue 4, 2004), MEDLINE (1966-Nov 2004), EMBASE (1980- Nov 2004) and reference lists of articles, the handsearching of relevant journals and conference proceedings and by contacting leaders in the field of endoscopic surgery throughout the world. SELECTION CRITERIA: Randomised controlled trials of excision of the cyst capsule versus drainage and electrocoagulation of the cyst in the management of ovarian endometriomata. DATA COLLECTION AND ANALYSIS: Reviewers assessed eligibility and trial quality. MAIN RESULTS: No randomised studies of the management of endometriomata by laparotomy were found. Two randomised studies of the laparoscopic management of ovarian endometriomata of greater than 3cm in size were included. Laparoscopic excision of the cyst wall of the endometrioma was associated with a reduced rate of recurrence of the endometrioma (OR 0.41 CI 0.18-0.93), reduced requirement for further surgery (OR 0.21 CI 0.05-0.79), reduced recurrence rate of the symptoms of dysmenorrhoea (OR 0.15 CI 0.06-0.38), dyspareunia OR 0.08 CI 0.01-0.51) and non-menstrual pelvic pain (OR 0.10 CI 0.02-0.56). It was also associated with a subsequent increased rate of spontaneous pregnancy women who had documented prior sub-fertility (OR 5.21 CI 2.04-13.29). AUTHORS' CONCLUSIONS: There is some evidence that excisional surgery for endometriomata provides for a more favourable outcome than drainage and ablation, with regard to the recurrence of the endometrioma, recurrence of symptoms and subsequent spontaneous pregnancy in women who were previously subfertile. Consequently this approach should be the favoured surgical approach. However we found no data as to the effect of either approach in women who subsequently undergo assisted reproductive techniques.

Drainage↗
PubMed2001

Birth of the Kaapvaal tectosphere 3.08 billion years ago.

The crustal remnants of Earth's Archean continents have been shielded from mantle convection by thick roots of ancient mantle lithosphere. The precise time of crust-root coupling (tectosphere birth) is poorly known but is needed to test competing theories of continental plate genesis. Our mapping and geochronology of an impact-generated section through the Mesoarchean crust of the Kaapvaal craton indicates tectosphere birth at 3.08 +/- 0.01 billion years ago, roughly 0.12 billion years after crust assembly. Growth of the southern African mantle root by subduction processes occurred within about 0.2 billion years. The assembly of crust before mantle may be common to the tectosphere.

Journal Article↗
PubMed1999

The cost of a hysterectomy in a UK hospital.

Vaginal hysterectomy has been demonstrated to be the cheapest route to perform a hysterectomy but no detailed costing has been performed in the United Kingdom. In this study the costs incurred by a UK teaching hospital for 30 women aged between 40 and 50 years of age undergoing either abdominal (AH), laparoscopically assisted vaginal hysterectomy (LH) were compared with vaginal hysterectomy (VH). VH was significantly the cheapest procedure (993.00 Pounds, 95th Cl 883.20 Pounds to 1124.80 Pounds) and there was a tendency for LH (1148.00 Pounds, 95th Cl 1006.80 Pounds to 1289.20 Pounds) to be less expensive than AH (1340.00 Pounds, 95th CI 1080.80 Pounds to 1595.20 Pounds); this difference may be reversed if disposable laparoscopic instruments were to be used for LH. Our study agrees with data from other countries showing that VH is the cheapest type of hysterectomy. With the added benefits of shorter hospital stay, convalescence and return to work, effort should be directed towards increasing the proportion of hysterectomies performed vaginally in the UK.

Journal Article↗
PubMed1999

Simple technique for rectus sheath closure after laparoscopic surgery using straight needles, with review of the literature.

The increasing use of laparoscopic surgery with more complicated procedures means that the use of multiple and larger ports is becoming commonplace. One well-known risk associated with the use of ports more than 10 mm in diameter is the development of an incisional hernia unless the deep fascia is closed adequately. This complication is estimated to follow 3% of major laparoscopic procedures. Closure of trocar incisions is therefore recommended for large sites. We have developed a closure technique using standard sutures with straight needles, a 5-mm laparoscopic grasper, and a 4-mm hysteroscope which we have found simple and fast, with the added advantage of low cost.

Fasciotomy↗
PubMed1998

The "remote control" laparoscopic bag: a simple technique to remove intra-abdominal specimens.

BACKGROUND: To facilitate extraction and avoid intra-abdominal spillage during laparoscopic removal of adnexal masses, various designs and sizes of endopouches (bags) have been used. We describe a simple technique using a special laparoscopic bag that requires no additional instruments to hold, open, or close the bag. TECHNIQUE: The laparoscopic bag can be prepared from the sterile wrapping of disposable surgical items (eg, suction tubing) and two long sutures. The bag is introduced through the cannula of the laparoscope and is unfurled. By manipulation of the two long sutures threaded through the neck of the bag, the surgeon can easily open and close it. EXPERIENCE: We have performed this procedure "in vitro" on many occasions to ensure that the drawstring technique works. The laparoscopic bag has been used successfully in three patients undergoing oophorectomy and salpingo-oophorectomy. Our experience shows that this type of laparoscopic bag is easy to use and safe, reduces operative time, and is cost effective. Because the bag can be large, operating inside the bag is also possible. CONCLUSION: Our drawstring design allows easy manipulation of a laparoscopic bag to facilitate its opening and closure.

Equipment Design↗
PubMed1989

Bacterial contamination of intraocular and extraocular fluids during extracapsular cataract extraction.

Fluid aspirated from the anterior chamber and fluid drained from the conjunctival sac during 101 extracapsular cataract operations was examined for bacterial contamination. Bacteria were grown by enrichment culture from the conjunctival sac of 90 eyes and from the anterior chamber aspirate of 29 eyes. Conjunctival fluid, stained with fluorescein, was demonstrated to flow into the anterior chamber during the aspiration stage of extracapsular cataract extraction and during intraocular lens implantation. It is suggested that this fluid from the conjunctival sac, contaminated with bacteria, routinely enters the anterior chamber during extracapsular cataract extraction and is the likely source of some cases of post-operative endophthalmitis.

Anterior Chamber↗
PubMed1989

[Echocardiographic diagnosis of acute graft rejection in heart transplant patients under cyclosporin therapy].

Though endomyocardial biopsy has remained the gold standard for diagnosing acute cardiac rejection (AR), this invasive method does not provide adequate means for close monitoring of the rejection process. In order to assess the usefulness of M-Mode- and two-dimensional (2D) echocardiography for the noninvasive diagnosis of AR in heart transplant recipients on cyclosporin, 45 patients (mean age 40.6 +/- 8.8 years, 19.9 +/- 14.4 months postoperatively) were evaluated prospectively. Mean observation time was 9.1 +/- 4.8 months. Echocardiographic examination techniques were strictly standardized; besides measurements of left (LV) and right ventricular (RV) diastolic wall thickness and of the isovolumic relaxation time, computerized frame-by-frame-analysis was applied to LV short axis cross sections for the determination of diastolic cavity cross-sectional area and extent and mean velocity of systolic and diastolic area change. To account for technical and biological variability, 95%-confidence limits were calculated for each parameter from two rejection-free examinations, allowing identification of significant changes during AR. In this study, 36 biopsy-proven AR occurred in 19 patients. Compared to control values, mean heart rate increased from 86.2 +/- 10.2 to 94.6 +/- 15.1 b/min (p less than 0.05), diastolic septal + posterior wall thickness from 21.2 +/- 4.1 to 24.9 +/- 6.2 mm (p less than 0.001) and RV free wall thickness from 6.3 +/- 1.1 to 8.9 +/- 1.8 mm (p less than 0.001). Isovolumic relaxation time decreased from 73.2 +/- 14.4 to 54.8 +/- 16.6 ms (p less than 0.001), diastolic cross-sectional area from 12.8 +/- 2.0 to 11.1 +/- 2.2 cm2 (p less than 0.05), relative area change from 65.8 +/- 9.8 to 49.1 +/- 14.4% (p less than 0.001) and systolic and diastolic area change velocities from 28.1 +/- 7.8 and 41.8 +/- 8.5 cm2/s to 18.9 +/- 5.6 and 28.6 +/- 9.2 cm2/s, respectively (p less than 0.001). Though significant changes occurred during AR, most measurements remained within the normal range. Thus, in individual patients, AR could only be suspected in comparison to the control measurements. None of the examined parameters allowed to establish the diagnosis of AR in all instances. However, when the measurements of all parameters were considered together, 35 of the 36 AR diagnosed by biopsy could also be identified by echocardiography, including all requiring intensified immunosuppressive therapy. Mild AR was not always detected, and the differential diagnosis between LV hypertrophy and AR required an endomyocardial biopsy in some instances.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1988

Campylobacter and Salmonella contamination of unpasteurized cows' milk on sale to the public.

Campylobacters and salmonellas were isolated respectively from 6 and 0.2% of samples of unpasteurized cow's milk on sale to the public. There was a significant association between the presence of Escherichia coli and that of Campylobacter jejuni. The mean E. coli count was also higher in campylobacter-positive samples. Enumeration of E. coli would seem to have value as an indicator of faecal contamination and thus potential hazard in raw milk.

Animals↗
PubMed1986

The effects of precocene treatment on egg wax production in Gené's organ and egg viability in the cattle tick Boophilus microplus (Acarina Ixodidae): an ultrastructural study.

Wax synthesis by Gené's organ, the egg waxing organ of ticks, is by precocene treatment of engorged female Boophilus microplus, resulting in desiccated nonviable eggs due to the absence of a waterproofing wax layer. Electron microscopy shows that precocene has a destructive effect on the glandular cells of Gené's organ. The precocene also inhibited in vitro wax synthesis by the gland cells, indicating a selective cytotoxic effect. Oogenesis and oviposition were otherwise unaffected, also suggesting that precocene affects the gland cells directly, rather than indirectly by antagonism of juvenile hormone.

Administration, Topical↗
PubMed1985

Relevance and utility of courses in medical ethics. A survey of physicians' perceptions.

In the last decade the teaching of medical ethics has become almost universal in American medical schools. Its effectiveness is, however, just beginning to be evaluated. A stratified random sample of 3,000 practicing physicians who were graduated between 1974 and 1978 was surveyed to evaluate their perceptions of the utility and relevance of medical ethics teaching. Those who had courses in medical ethics perceived it to be of substantial benefit in confronting the actual ethical issues they encountered in daily practice. They favored the continuation and expansion of the teaching of medical ethics and had suggestions for its improvement. Data were also obtained on the relative frequency of specific ethical issues in practices and on the relative influence of home, personal values, medical education, medical practice, and ethics courses on respondents' approaches to ethical issues.

Attitude of Health Personnel↗
PubMed1985

Rubella encephalopathy.

Rubella is a rare cause of acute neurological symptoms with only a few reported cases. We describe a case which was diagnostically confusing initially because results of examination of blood and cerebrospinal fluid suggested bacterial meningitis.

Child↗
PubMed1985

A study of workload units in five microbiology laboratories.

A study of a modified Canadian unit system of measuring laboratory workload was undertaken in five joint Public Health Laboratory Service and hospital microbiology laboratories. Ten percent of the specimens received over six months were sampled, the number of units expended on each was recorded, and the results were analysed on a central computer. The process of gathering information in the absence of laboratory computers was time consuming and, despite careful planning, differences were found in the recording practices of the laboratories. The analysis of results did not lead to major changes in data gathering techniques because the same information about laboratory workload could be obtained by collecting numbers of clearly defined specimens. Analysis of workload units could be useful for particular purposes, such as comparing differences between laboratories using different techniques for the same investigation or assessing the possible benefits of automation. It must be appreciated, however, that workload units are measures of quantity not of laboratory performance.

Blood↗
PubMed1984

Ultrastructure of the accessory glands of gene's organ in the cattle tick, Boophilus.

The organization and ultrastructure of the accessory glands of the cattle tick, Boophilus microplus, are described. The glands consist of two groups of acinar cells situated on either side of Gene's organ. A single acinus consists of from eight to 12 cells and each cell is connected via an individual duct to pores on the dorsal surface of the mouthparts. The position of these pores is such that the secretion of the accessory glands is incorporated into the egg wax during oviposition. Each gland cell has striking quantities of smooth endoplasmic reticulum and numerous Golgi dictyosomes and appears to produce a secretion that is lipoidal in nature. Each cell secretes into its own individual lumen and is connected to a cuticular pore by a duct cell.

Animals↗