The contribution of twins to perinatal mortality in Jamaica

Summary. The Jamaican Perinatal Mortality Survey collected data that have been used in this paper to estimate: (1) the rate of multiple deliveries on the island; (2) the way in which this varies with demographic features; and (3) the causes of perinatal mortality among twins on the island.
The survey consisted of two phases: a study of all births in the months of September and October 1986 (the cohort months) and a study of all perinatal deaths in the 12 months from 1 September 1986 to 31 August 1987.
Among the 10408 pregnancies in the cohort months, 99(1.0%) were multiple pregnancies. The twinning rate showed statistically significant trends with maternal age and parity but no association with social factors.
Among the 2020 perinatal deaths occurring in the 12-month period, 173 (8.6%) were twins, with particularly high contribution to the Wigglesworth group 'deaths from immaturity'. Mortality rate of twins was significantly lower if mothers resided in areas where there were good obstetric and paediatric facilities.     

Assessment of risk of perinatal death in Jamaica

Summary. Data from the Jamaican Perinatal Mortality Survey had been used to create a statistical model using logistic regression.¹ From this a simple additive scoring system to predict perinatal death was devised and tested on the 2 cohort months of the study.
The score had a theoretical range of 0–28 points, with the higher the score, the greater the likelihood of a perinatal death. For a cut-point of 7, sensitivity was 43% and specificity 84%. A cut-point of 8 resulted in 27% sensitivity and 94% specificity. Higher cut-points resulted in much reduced sensitivity but enhanced specificity (e.g. cut-point 10: 11% sensitivity, 99% specificity).
However, it is likely that these estimates are optimistically high, and to achieve unbiased estimates of sensitivity and specificity the score needs to be tested on a sample of the population from which it was not derived before implementation takes place. Meanwhile, the cut-off level for implementation will depend on appropriate resources available.     

Antenatal and perinatal care in Jamaica: do they reduce perinatal death rates?

Summary. Information concerning 9919 singleton pregnancies delivered in Jamaica in the 2-month period of September and October 1986 and surviving the early neonatal period were compared with 1847 singleton perinatal deaths occurring in the 12-month period from 1 September 1986 to 31 August 1987, classified according to the Wigglesworth schema.
Logistic regression was used to assess features of antenatal and intrapartum care that were associated with the different groups of perinatal death after taking account of environmental, maternal and medical factors.
In Jamaica, 67% of all mothers took iron during pregnancy. These mothers appeared to have a lower risk of perinatal death. This does not appear to be an artefact related to the gestation at which the mother delivers, and was particularly associated with antepartum fetal deaths.
Commencement of antenatal care in the first trimester appeared to reduce the risk of all perinatal deaths, and for intrapartum asphyxia in particular. It is speculated that the mechanism may involve early detection and treatment of anaemia and syphilis.
Quality of perinatal care available in the area of residence, as measured by the presence of consultant obstetricians and a paediatric consultant unit, is shown to be significantly related to a reduction in deaths from intrapartum asphyxia, but it appeared not to be related to antepartum fetal deaths.     

Comparison of the Amplicor HIV-1 monitor test and the nucleic acid sequence-based amplification assay for quantitation of human immunodeficiency virus RNA in plasma, serum, and plasma subjected to freeze-thaw cycles.

The Amplicor HIV-1 Monitor test was compared to the nucleic acid sequence-based amplification (Nasba) assay system for the quantitation of human immunodeficiency virus (HIV) RNA in three different types of clinical samples: plasma, serum, and plasma subjected to freeze-and-thaw cycles. Each assay detected HIV RNA in the same 73 (90%) of 81 samples tested, and the quantitative results obtained with the two assays were significantly correlated. Both assays detected higher RNA levels in patients with CD4+ cell counts lower than 200 cells/mm3 than in patients with CD4+ cell counts higher than 200 cells/mm3. In addition, RNA levels in plasma higher than 5 logs predicted higher numbers of clinical events than did RNA levels in plasma lower than 5 logs. Quantitation of HIV RNA in paired plasma and serum samples showed lower HIV RNA content in serum than in the paired plasma sample, with mean differences between HIV RNA contents of plasma and serum of 0.54 and 0.28 log RNA copy/ml by the Nasba assay and the Amplicor HIV-1 Monitor assay, respectively. No significant loss of HIV RNA was detected with either assay in plasma samples subjected to multiple freeze-and-thaw cycles. These studies demonstrate that the Nasba and Amplicor assays perform similarly with plasma and serum samples. Further, the results indicate that freeze-and-thaw cycles do not result in significant loss of detectable HIV RNA.     

Hemodynamic Parameters Influencing Clinical Performance of Novacor Left Ventricular Assist System

The interrelationships between hemodynamic variables including right ventricular (RV) performance with filling/ejection dynamics of the Novacor left ventricular assist system (LVAS) were determined in 10 of 11 patients who received LVAS as a bridge to heart transplant. Nine were successfully transplanted. Data were obtained intraoperatively, at periodic intervals up to 48 h postimplant and at explant. The hypotheses investigated included (a) RV performance influences LVAS filling characteristics and (b) LVAS pump output is influenced by systemic vascular resistance (SVR). During the period of LVAS support (2-126 days), pumping characteristics included a mean filling volume of 51 ml (range, 24-70), residual volume of 4.9 ml (range, 1-18), pump rate of 113/min (range, 63-175), and pump output of 5.81/min (range, 2.8-8.2). Multiple regression analysis identified pulmonary vascular resistance (PVR), RV stroke work index (RVSWI), and pulmonary capillary wedge pressure, but not RV ejection fraction, pulmonary artery pressure, or central venous pressure (CVP) as the most important correlates with LVAS filling volume (p less than 0.001, R2 = 0.6). In addition, LVAS pump output was influenced mainly by RVSWI, PVR, and SVR (p less than 0.001, R2 = 0.7). It was concluded that LVAS performance is highly dependent on RV function and systemic/pulmonary vascular resistances.     

Cytomegalovirus infection in immunocompromised guinea pigs: a model for testing antiviral agents in vivo

An experimental model for testing antiviral agents against severe cytomegalovirus (CMV) infection in immunocompromised hosts was developed. The model consisted of cyclophosphamide (Cy) treatment of CMV-infected guinea pigs to simulate CMV infection in immunodeficient individuals. Of the 3 Cy regimens tested, a single 300 mg/kg dose administered one day after virus inoculation resulted in the most severe CMV infection considering mortality rates, mean day of death and loss of body weight. Evaluation of responses to both T and B cell mitogens suggested that the severe and lethal CMV infection resulted from the combined immunosuppressive effect of Cy and CMV. The nucleoside analog [9-(1-3-dihydroxy-2-propoxymethyl)guanine (DHPG) was used to assess the usefulness of the CMV-infected immunocompromised host model. DHPG (100 mg/kg/day for 8 days) prevented death but did not reduce virus infectivity titers in blood of Cy-treated, CMV-infected guinea pigs. This model of CMV infection in immunocompromised guinea pig is a relevant and convenient experimental tool for the assessment of candidate anti-CMV agents under well-defined experimental conditions, such as appropriate CMV inoculum and Cy regimen.     

Buthionine sulfoximine-mediated depletion of glutathione in intracranial human glioma-derived xenografts

D-54 MG, a human glioma-derived continuous cell line growing as subcutaneous or intracranial xenografts in athymic mice, was found to be sensitive to the effects of D,L-buthionine-(SR)-sulfoximine, a selective inhibitor of gamma-glutamylcysteine synthetase. Intraperitoneal administration of one dose of buthionine sulfoximine (BSO, 5 mmol/kg) resulted in depletion of total intracellular glutathione to 57 and 47% of control 12 hr, and 73 and 23% of control 24 hr, after BSO in subcutaneous and intracranial xenografts respectively. Concurrent measurement of total glutathione in the contralateral (non-tumor-containing) cerebral hemisphere in mice bearing intracranial D-54 xenografts demonstrated insignificant depletion of glutathione. Multiple doses of BSO, at 12-hr intervals, resulted in further depletion to 27% (s.c.) and 16.5% (i.c.) of control 12 hr following the final dose of BSO. Quantitative analysis of BSO delivery to xenograft and contralateral brain tissue revealed transfer constants, K1, of 15.8-24.1 x 10(-3) and 2.4 x 10(-3) ml.g-1.min-1 for xenograft and "normal" brain respectively. This highly selective depletion of glutathione in neoplastic tissue versus surrounding non-neoplastic host tissue may have therapeutic implications for the rational use of chemotherapeutic and radiotherapeutic intervention.     

The next decade in external dosimetry

In recent years, a number of external dosimetry problems have been solved. However, changes in standards and legal concepts relating to the application of dosimetry results will require further enhancements in measurement techniques and philosophy in the next 10 y. The introduction of effective dose equivalent and the legal use of probability of causation will require that much greater attention be given to determination of weighted organ dose from external exposure. An imminent change--an increase in the fast neutron quality factor--will require a new round of technology development in a field that has just received a decade of close scrutiny. For the future, we must take advantage of developments in microelectronics. The use of random access memory (RAM) and metal-on-silicon (MOS) devices as detector elements, particularly for neutron dosimetry, has exciting possibilities that are just beginning to be explored. Advances in microcircuitry are leading, and will continue to lead, in the development of a new generation of small, rugged and "smart" radiation survey instruments that will make the most of detector data. It has become possible with very compact instruments to obtain energy spectra, linear-energy-transfer (LET) spectra, and quality factors in addition to the usual integrated dosimetric quantities: exposure, absorbed dose, and dose equivalent. These instruments will be reliable and easy to use. The user will be able to select the level of sophistication that is required for any specific application. Moreover, since the processing algorithms can be changed, changes in conversion factors can be accommodated with relative ease. During the next decade, the use of computers will continue to grow in value to the health physicist. Personal computers and codes designed for dosimetry applications will become prominent, providing the health physicist with the ability to perform sophisticated data reduction, spectra unfolding and even radiation modeling and transport calculations on the desk top. In the far term, the use of computers could extend to the development of sophisticated tracking systems that would follow and record the workers' movements throughout a radiation area. These data, together with information from area monitors, air samplers and personnel dosimeters, could be used to develop truly integrated dose estimates, including reconstruction of organ doses.     

Propagation of alloreactive lymphocytes from histologically negative endomyocardial biopsies from heart transplant patients. Association with subsequent histological evidence of allograft rejection

Endomyocardial biopsies from heart transplant patients were cultured in vitro in the presence of Interleukin-2 and irradiated feeder cells to propagate graft-infiltrating lymphocytes. A correlation was seen between the frequency of lymphocyte growth and the degree of cellular infiltration of the biopsies. In this study, 43 of 113 (38%) histologically negative biopsies obtained from 55 patients during the first month post-transplant yielded lymphocyte cultures. The cumulative incidence of subsequent histological rejection was considerably higher in patients with such "grower" biopsies than in patients with "nongrower" biopsies. In the grower group, we were able to obtain data on alloreactivity of 32 lymphocyte cultures assayed by primed lymphocyte testing (PLT). The presence of donor-specific PLT reactivity in the cultured lymphocytes was associated with an additional risk for subsequent histological rejection. These findings suggest that the in vitro culturing of histologically negative endomyocardial biopsies will identify patients at increased risk for developing heart transplant rejection.