Mortality and morbidity from malaria among children in a rural area of The Gambia, West Africa

Mortality and morbidity from malaria were measured among 3000 children under the age of 7 years in a rural area of The Gambia, West Africa. Using a post-mortem questionnaire technique, malaria was identified as the probable cause of 4% of infant deaths and of 25% of deaths in children aged 1 to 4 years. The malaria mortality rate was 6.3 per 1000 per year in infants and 10.7 per 1000 per year in children aged 1 to 4 years. Morbidity surveys suggested that children under the age of 7 years experienced about one clinical episode of malaria per year. Calculation of attributable fractions showed that malaria may be responsible for about 40% of episodes of fever in children. Although the overall level of parasitaemia showed little seasonal variation, the clinical impact of malaria was highly seasonal; all malaria deaths and a high proportion of febrile episodes were recorded during a limited period at the end of the rainy season.

Attributable fraction estimates and case definitions for malaria in endemic areas

Asymptomatic carriage of malaria parasites occurs frequently in endemic areas and the detection of parasites in a blood film from a febrile individual does not necessarily indicate clinical malaria. In areas of low and moderate endemicity the parasite prevalence in fever cases can be compared with that in community controls to estimate the fraction of cases which are attributable to malaria. In areas of very high transmission such estimates of the attributable fraction may be imprecise because very few individuals are without parasites. Furthermore, non-malarial fevers appear to suppress low levels of parasitaemia resulting in biased estimates of the attributable fraction. Alternative estimation techniques were therefore explored using data collected during 1989-1991 from a highly endemic area of Tanzania, where over 80 per cent of young children are parasitaemic. Logistic regression methods which model fever risk as a continuous function of parasite density give more precise estimates than simple analyses of parasite prevalence and overcome problems of bias caused by the effects of non-malarial fevers. Such models can be used to estimate the probability that any individual episode is malaria-attributable and can be extended to allow for covariates. A case definition for symptomatic malaria that is used widely in endemic areas requires fever together with a parasite density above a specific cutoff. The choice of a cutoff value can be assisted by using the probabilities derived from the logistic model to estimate the sensitivity and specificity of the case definition.

Interpreter use and satisfaction with interpersonal aspects of care for Spanish-speaking patients

OBJECTIVES

Many patients have limited English proficiency and require an interpreter. The authors evaluated the effect of current interpreting practices on Spanish-speaking patients' satisfaction with the patient-provider relationship.

METHODS

A cross-sectional survey was conducted of 457 patients seen in a public hospital emergency department. Measures were satisfaction with the provider's friendliness, respectfulness, concern, ability to make the patient comfortable, and time spent for the exam.

RESULTS

A total of 237 patients communicated adequately with their provider without the use of an interpreter (group 1), 120 patients communicated through an interpreter (88% of whom were ad hoc interpreters; group 2), and 100 patients communicated directly with the provider but said an interpreter should have been called (group 3). Compared with patients in group 1, patients who communicated through an interpreter (group 2) rated their provider as less friendly, less respectful, less concerned for the patient as a person, and less likely to make the patient comfortable. Patients who said an interpreter should have been called (group 3) had the lowest satisfaction ratings; compared with group 2, they were less satisfied with their provider's friendliness, concern for the patient as a person, efforts to make the patient comfortable, and amount of time spent.

CONCLUSIONS

Patients who communicated through an interpreter or who did not have an interpreter when they thought one was necessary were less satisfied with the patient-provider relationship. Further efforts are needed to ensure interpreter availability and proper interpretation technique.

Control of sexually transmitted diseases for HIV-1 prevention: understanding the implications of the Mwanza and Rakai trials

Two randomised controlled trials of sexually transmitted disease (STD) treatment for the prevention of HIV-1 Infection, in Mwanza, Tanzania, and Rakai, Uganda, unexpectedly produced contrasting results. A decrease in population HIV-1 incidence was associated with improved STD case management in Mwanza, but was not associated with STD mass treatment in Rakai. Some reductions in curable STDs were seen in both studies. These trials tested different interventions in different HIV-1 epidemic settings and used different evaluation methods; the divergent results may be complementary rather than contradictory. Possible explanations include: differences in stage of the HIV-1 epidemic, which can influence exposure to HIV-1 and the distribution of viral load in the infected population; potential differences in the prevalence of Incurable STDs (such as genital herpes); perhaps greater Importance of symptomatic than symptomless STDs for HIV-1 transmission; and possibly greater effectiveness of continuously available services than of intermittent mass treatment to control rapid STD reinfection. Implications of the trials for policy and future research agenda are discussed.

Excess incidence of squamous cell esophageal cancer among US Black men: role of social class and other risk factors

Data from a population-based case-control study were used to evaluate the relation between social class factors and squamous cell esophageal cancer and the extent to which alcohol, tobacco, diet, and low income contribute to the higher incidence among Black men than among White men in the United States. A total of 347 male cases (119 White, 228 Black) and 1,354 male controls (743 White, 611 Black) were selected from three US geographic areas (Atlanta, Georgia, Detroit, Michigan, and New Jersey). Cases were residents of the study areas aged 30-79 years who had been diagnosed with histologically confirmed esophageal cancer between 1986 and 1989. The adjusted odds ratios for subjects with annual incomes less than $10,000 versus incomes of $25,000 or more were 4.3 (95% confidence interval: 2.1, 8.7) for Whites and 8.0 (95% confidence interval: 4.3, 15.0) for Blacks. The combination of all four major risk factors-low income, moderate/heavy alcohol intake, tobacco use, and infrequent consumption of raw fruits and vegetables-accounted for almost all of the squamous cell esophageal cancers in Whites (98%) and Blacks (99%) and for 99% of the excess incidence among Black men. Thus, lifestyle modifications, especially a lowered intake of alcoholic beverages, would markedly decrease the incidence of squamous cell esophageal cancer in both racial groups and would narrow the racial disparity in risk. Further studies on the determinants of social class may help to identify a new set of exposures for this tumor that are amenable to intervention.

Trial of an attenuated bovine rotavirus vaccine (RIT 4237) in Gambian infants

A randomised, controlled trial of bovine rotavirus vaccine was undertaken in Gambian infants. Three doses were administered, from the age of ten weeks, concurrently with oral or killed polio vaccine. Prevaccination rotavirus neutralising antibody levels were high. 84/185 infants (45%) showed an increase in neutralising antibody titre after receiving rotavirus vaccine, compared with 20/91 (22%) unvaccinated infants. Clinical rotavirus infection was detected in 24/78 (31%) children in the rotavirus/oral polio group, 34/83 (41%) children in the placebo/oral polio group, and 23/92 (25%) children in the rotavirus/killed polio group, giving an overall vaccine efficacy of 33% (95% CI 4-53%). RIT 4237 did not appear to reduce the severity of clinical infections. Most cases (92%) were caused by rotaviruses with short RNA electropherotypes. Serological responses to rotavirus vaccination appeared unaffected by the concurrent administration of oral polio vaccine. Lower types 1 and 3 polio antibody levels were found in children who received oral polio and rotavirus vaccines but the differences were not statistically significant.

Effects of the N-methyl-D-aspartate receptor blocker MK-801 on neurologic function after experimental brain injury

Pharmacologic inhibition of excitatory amino acid (EAA) neurotransmission attenuates cell death in models of global and focal ischemia and hypoglycemia and improves neurologic outcome after experimental traumatic spinal cord injury. The present study examined the effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor blocker MK-801 on cardiovascular and neurologic function after experimental fluid-percussion (FP) brain injury in the rat. Animals received either an intravenous bolus of MK-801 (1 mg/kg) or saline (equal volume) 15 min prior to FP brain injury or 15 min following FP brain injury. MK-801 pretreatment significantly improved postinjury cardiovascular variables and attenuated postinjury neurologic dysfunction. Postinjury treatment with MK-801 also significantly improved cardiovascular variables, but had little effect on postinjury neurologic scores. These results suggest that EAA neurotransmitters may be involved in the pathophysiological sequelae of traumatic brain injury and that noncompetitive blockade of the NMDA receptor prior to brain injury may reduce EAA-induced damage and limit neurologic dysfunction.

Effect of noncompetitive blockade of N-methyl-D-aspartate receptors on the neurochemical sequelae of experimental brain injury

Pharmacological inhibition of excitatory neurotransmission attenuates cell death in models of global and focal ischemia and hypoglycemia, and improves neurological outcome after experimental spinal cord injury. The present study examined the effects of the noncompetitive N-methyl-D-aspartate receptor blocker MK-801 on neurochemical sequelae following experimental fluid-percussion brain injury in the rat. Fifteen minutes after fluid-percussion brain injury (2.8 atmospheres), animals received either MK-801 (1 mg/kg, i.v.) or saline. MK-801 treatment significantly attenuated the development of focal brain edema at the site of injury 48 h after brain injury, significantly reduced the increase in tissue sodium, and prevented the localized decline in total tissue magnesium that was observed in injured tissue of saline-treated animals. Using phosphorus nuclear magnetic resonance spectroscopy, we also observed that MK-801 treatment improved brain metabolic status and promoted a significant recovery of intracellular free magnesium concentrations that fell precipitously after brain injury. These results suggest that excitatory amino acid neurotransmitters may be involved in the pathophysiological sequelae of traumatic brain injury and that noncompetitive N-methyl-D-aspartate receptor antagonists may effectively attenuate some of the potentially deleterious neurochemical sequelae of brain injury.

Alternatives to randomisation in the evaluation of public health interventions: design challenges and solutions

BACKGROUND

There has been a recent increase in interest in alternatives to randomisation in the evaluation of public health interventions. We aim to describe specific scenarios in which randomised trials may not be possible and describe, exemplify and assess alternative strategies.

METHODS

Non-systematic exploratory review.

RESULTS

In many scenarios barriers are surmountable so that randomised trials (including stepped-wedge and crossover trials) are possible. It is possible to rank alternative designs but context will also determine which choices are preferable. Evidence from non-randomised designs is more convincing when confounders are well-understood, measured and controlled; there is evidence for causal pathways linking intervention and outcomes and/or against other pathways explaining outcomes; and effect sizes are large.

CONCLUSION

Non-randomised trials might provide adequate evidence to inform decisions when interventions are demonstrably feasible and acceptable, and where evidence suggests there is little potential for harm, but caution that such designs may not provide adequate evidence when intervention feasibility or acceptability is doubtful, and where existing evidence suggests benefits may be marginal and/or harms possible.

Antibody to herpes simplex virus type 2 as a marker of sexual risk behavior in rural Tanzania

A serosurvey was conducted in a random sample of 259 women and 231 men in 12 rural communities in Mwanza Region, Tanzania, using a type-specific ELISA for Herpes simplex virus type 2 (HSV-2) infection. Seroprevalence rose steeply with age to approximately 75% in women >=25 years old and 60% in men >=30. After adjusting for age and residence, HSV-2 prevalence was higher in women who were married, in a polygamous marriage, Treponema pallidum hemagglutination assay (TPHA)-positive, had more lifetime sex partners, or who had not traveled. Prevalence was higher in men who were married, had lived elsewhere, had more lifetime partners, had used condoms, or were TPHA-positive. HSV-2 infection was significantly associated with recent history of genital ulcer. The association between HSV-2 infection and lifetime sex partners was strongest in those <25 years old in both sexes. This association supports the use of HSV-2 serology as a marker of risk behavior in this population, particularly among young people.

Cost-effectiveness of improved treatment services for sexually transmitted diseases in preventing HIV-1 infection in Mwanza Region, Tanzania

BACKGROUND

A community-randomised trial was undertaken to assess the impact, cost, and cost-effectiveness of averting HIV-1 infection through improved management of sexually transmitted diseases (STDs) by primary-health-care workers in Mwanza Region, Tanzania.

METHODS

The impact of improved treatment services for STDs on HIV-1 incidence was assessed by comparison of six intervention communities with six matched communities. We followed up a random cohort of 12,537 adults aged 15-54 years for 2 years to record incidence of HIV-1 infection. The total and incremental costs of the intervention were estimated (ingredients approach) and used to calculate the total cost per case treated, the incremental cost per HIV-1 infection averted, and the incremental cost per disability-adjusted life-year (DALY) saved.

FINDINGS

During 2 years of follow-up, 11,632 cases of STDs were treated in the intervention health units. The baseline prevalence of HIV-1 infection was 4%. The incidence of HIV-1 infection during the 2 years was 1.16% in the intervention communities and 1.86% in the comparison communities. An estimated 252 HIV-1 infections were averted each year. The total annual cost of the intervention was US$59,060 (1993 prices), equivalent to $0.39 per head of population served. The cost for STD case treated was $10.15, of which the drug cost was $2.11. The incremental annual cost of the intervention was $54,839, equivalent to $217.62 per HIV-1 infection averted and $10.33 per DALY saved (based on Tanzanian life expectancy) or $9.45 per DALY saved (based on the assumptions of the World Development Report). In a sensitivity analysis of factors influencing cost-effectiveness, cost per DALY saved ranged from $2.51 to $47.86.

INTERPRETATION

Improved management of STDs in rural health units reduced the incidence of HIV-1 infection in the general population by about 40%. The estimated cost-effectiveness of this intervention ($10 per DALY) compares favourably with that of, for example, childhood immunisation programmes ($12-17 per DALY). Cost-effectiveness should be further improved when the intervention is applied on a larger scale. Resources should be made available for this highly cost-effective HIV control strategy.

Adsorption of NOM onto Activated Carbon: Effect of Surface Charge, Ionic Strength, and Pore Volume Distribution

Adsorption of natural organic matter (NOM) onto seven activated carbons with a wide range of surface properties was studied at high and low ionic strength over a range of pH values. From adsorption isotherm studies it was found that, for six of seven carbons, at low surface concentrations, increased ionic strength decreased NOM adsorption. As the surface concentration increased, the adsorption isotherms converged and intersected, after which the addition of salt resulted in increased adsorption. This "crossover point" marked a change in the adsorption mechanism from the "screening reduced" to the "screening enhanced" adsorption regimes. The adsorption mechanisms are extremely complicated and appear attributable to various factors, including electrostatic forces, pore volume distribution, and chemical interactions between the NOM and the surface functionalities on the carbon surfaces. Copyright 1999 Academic Press.

Sexual behaviour patterns and other risk factors for HIV infection in rural Tanzania: a case-control study

OBJECTIVE

To examine the association between HIV infection and patterns of sexual behaviour and other risk factors in a rural Tanzanian population in a case-control study, nested within a randomized trial of improved sexually transmitted disease treatment.

METHODS

All HIV-positive patients from the baseline survey of the randomized trial were eligible as cases. Cases (n = 338) and controls (a random sample of one in eight HIV-negative persons; n = 1078) were interviewed about risk factors for HIV infection using a structured questionnaire.

RESULTS

A significantly higher HIV prevalence was found among men and women not currently employed in farming [men: odds ratio (OR), 2.08; women: OR, 3.65], women who had travelled (OR, 3.27), educated women (OR, 4.51), and widowed/ divorced people compared with those currently married (men: OR, 3.10; women: OR, 3.54). Two spouse-related factors were significantly associated with HIV, even after adjustment for the sexual behaviour of the index case: HIV was more prevalent in men with younger spouses (P = 0.020 for trend) and in women married to men currently employed in manual work, office work or business (OR, 2.20). In women only, blood transfusions were associated with a higher HIV prevalence (OR, 2.40), but only a small population attributable fraction (4%). There was an increased HIV prevalence associated with increasing numbers of injections. Reported number of lifetime sexual partners was significantly associated with HIV infection (women: OR, 7.33 if > or = 10 lifetime partners compared with < or = 1; men: OR, 4.35 for > or = 50 compared with < or = 1). After adjustment for confounders, male circumcision was associated with a lower HIV prevalence (OR, 0.65; P = 0.11).

CONCLUSIONS

In these rural communities, many HIV infections occur through sexual transmission. Some people are at high risk of HIV infection through large numbers of sex partners, whereas some are at risk through their spouse or regular partner. The role of circumcision in HIV transmission is unclear. Commercial sex seems to play a negligible role in HIV transmission in these communities. Our results confirm marked heterogeneity in HIV risk, indicating the scope for risk reduction strategies.

Is antenatal syphilis screening still cost effective in sub-Saharan Africa

OBJECTIVES

To estimate the cost effectiveness of on-site antenatal syphilis screening and treatment in Mwanza, Tanzania. To compare this intervention with other antenatal and child health interventions, specifically the prevention of mother to child transmission of HIV (PMTCT).

METHODS

The economic costs of adding the intervention to routine antenatal care were assessed. Cost effectiveness (CE) ratios of the intervention were obtained for low birth weight (LBW) live births and stillbirths averted and cost per DALY saved. Cost per DALY saved was also estimated for previous CE studies of syphilis screening. The CE of the intervention at different syphilis prevalence rates was modelled.

RESULTS

The economic cost of the intervention is $1.44 per woman screened, $20 per woman treated, and $187 per adverse birth outcome averted. The cost per DALY saved is $110 with LBW as the only adverse outcome. When including stillbirth, this estimate improves 10-fold to $10.56 per DALY saved. The cost per DALY saved from all syphilis screening studies ranged from $3.97 to $18.73.

CONCLUSIONS

Syphilis screening is shown to be at least as cost effective as PMTCT and more cost effective than many widely implemented interventions. There is urgent need for scaling up syphilis screening and treatment in high prevalence areas. The CE of screening interventions is highly dependent on disease prevalence. In combination, PMTCT and syphilis screening and treatment interventions may achieve economies of scope and thus improved efficiency.

Amino acid sequence of the sex steroid binding protein of human blood plasma

The amino acid sequence of the sex steroid binding protein (SBP) from human plasma has been determined. The SBP subunit consists of a 373-residue polypeptide chain containing two disulfide bonds and three oligosaccharide chains. The sequence was solved primarily by analysis of peptides derived by cleavage at either lysyl or methionyl residues. In our preparations, approximately half of the protein molecules have the amino-terminal sequence Arg-Pro-Val-Leu-Pro; the other half lack Arg-Pro and begin with the valine. Preparations of Hammond et al. [Hammond, G. L., Robinson, P. A., Sugino, H., Ward, D. N., & Finne, J. (1986) J. Steroid Biochem. 24, 815] have an additional leucine at the amino terminus, making a total of 373 residues in the chain. Oligosaccharide chains are placed at Thr-7 and at Asn residues 351 and 367. The two disulfide bonds connect Cys-164 to Cys-188 and Cys-333 to Cys-361. The reported heterogeneity of preparations of the molecule may result in part from the amino-terminal microheterogeneity, in part from variations in the oligosaccharide moieties, and possibly in part from rearrangements involving cyclic imide formation in two Asn-Gly sequences. Certain hydrophobic segments are suggested as possible components of the steroid-binding sites. The protein shows no homology either with the cDNA-derived sequences of the estrogen and glucocorticoid receptors found by others to be homologous with each other or with any other protein sequence in the 1986 data base.

Deaths in infancy and early childhood in a well-vaccinated, rural, West African population

A survey of deaths in children under the age of 7 years was made over a 1-year period in a rural area of The Gambia with few facilities for curative medicine but with a good record of infant immunizations. One hundred and eighty-four deaths were investigated. Only 12% of deaths occurred in a hospital or health centre but an attempt was made to establish a cause of death by interviewing the family of each dead child and by examining any health records that were available. The infant mortality rate was 142 per 1000 live births and the child mortality rate (death in children aged 1-4 years) 43 per 1000 per year. Acute respiratory infections, malaria and chronic diarrhoea with marasmus were the most frequent causes of death after the 1st month of life. Few children died of diseases that could have been prevented by routine immunizations. An effective immunization programme has probably had some effect on deaths in infancy and early childhood but it will be necessary to find ways of preventing deaths from malaria, acute respiratory infections and chronic diarrhoea/marasmus at the primary health care level if infant and childhood mortality are to be reduced further in rural areas of The Gambia.

Risk factors for pulmonary mycobacterial disease in South African gold miners. A case-control study

Pulmonary mycobacterial disease is common in miners. Risk factors for nontuberculous pulmonary mycobacterial (NTM) disease and tuberculosis (TB) in gold miners were identified in a retrospective case-control study that included 206 NTM patients and 381 TB patients of known human immunodeficiency virus (HIV) status diagnosed between 1993 and 1996. A total of 180 HIV-tested trauma/surgical inpatients were selected as control patients. Both HIV infection (odds ratio [OR] 3.6 for NTM and 4.5 for TB patients) and higher grades of silicosis (OR 5.0 for NTM and 4.9 for TB patients) were significantly more common in NTM and TB patients than in control patients. HIV prevalence rose in the control and both case groups during the study period. The overall HIV prevalence was 13.1% in NTM patients, 14.2% in TB patients, and 5.6% in control patients. Previous TB (OR 9.6), premorbid focal radiological scarring (OR 7.4) and a dusty job at diagnosis (OR 2.4) were additional significant risk factors for NTM disease. These findings suggest that the historically high incidence of NTM disease in miners is largely attributable to chronic chest disease from silica dust inhalation and prior TB. HIV infection has recently become an additional risk factor for mycobacterial disease in miners and is likely to become increasingly important as the HIV epidemic progresses.

Improved treatment services significantly reduce the prevalence of sexually transmitted diseases in rural Tanzania: results of a randomized controlled trial

OBJECTIVE

To evaluate the impact of improved case management for sexually transmitted diseases (STD) at the primary health care level on the incidence and prevalence of STD.

DESIGN

Community-randomized controlled trial.

SETTING

Mwanza region, Tanzania.

SUBJECTS

A random cohort of about 1000 adults aged 15-54 years from each of 12 communities, in six matched pairs. One member of each pair was assigned at random to receive the intervention, and the others served as a comparison community. This cohort was surveyed at baseline and at follow-up 2 years later. About 100 antenatal clinic attenders were also studied in each community on two occasions: the first shortly after the implementation of the intervention, and the second approximately 1 year later.

INTERVENTION

Improved services were established for the management of STD, using the syndromic approach, in rural health units.

RESULTS

A total of 12,534 individuals were enrolled in the cohort study, of whom 8844 (71%) were seen again 2 years later. The prevalence of serological syphilis (rapid plasma reagin titre > or = 1:8, Treponema pallidum haemagglutinin assay positive) was 6.2% in both intervention and comparison communities at baseline. At follow-up it was 5.0% in the intervention community and 7.0% in the comparison community [adjusted relative risk (RR), 0.71; 95% confidence interval (CI), 0.54-0.93; P < 0.02]. The prevalence of urethritis in males did not differ significantly between intervention and comparison groups at follow-up, but the prevalence of symptomatic urethritis was reduced by about 50% (adjusted RR, 0.51; 95% CI, 0.24-1.10; P = 0.08). There was no significant difference between the groups in the incidence of self-reported STD symptoms over the last year of the follow-up period, or in the prevalence of any STD in antenatal clinic attenders.

CONCLUSION

The reduction in HIV incidence previously reported in this intervention study can be attributed to a reduction in the duration, and hence the prevalence of symptomatic STD.

Vascular abnormalities in non-insulin-dependent diabetes mellitus identified by arterial waveform analysis

PURPOSE

The arterial pressure waveform is derived from the complex interaction of the left ventricular stroke volume and the physical properties of the arterial circulation. Widespread abnormalities in the physical characteristics of the arterial vessels associated with diabetes mellitus can produce consistent changes in the shape of the pressure pulse waveform, providing information about arterial structure and tone that can be quantitated by pulse contour analysis.

PATIENTS AND METHODS

We analyzed intraarterial brachial artery waveforms in 28 patients with non-insulin-dependent diabetes mellitus and 22 control subjects matched for age and sex. A computer-based assessment of the diastolic pressure decay and a modified Windkessel model of the circulation were employed to quantify changes in arterial waveform morphology in terms of the large-artery compliance (C1), the oscillatory diastolic waveform (C2), inertance, and systemic resistance.

RESULTS

No differences were found in heart rate, mean arterial pressure, cardiac output, or stroke volume between groups. The mean oscillary arterial compliance estimate was significantly reduced in diabetic subjects versus controls: 0.02 (95% confidence interval [CI], 0.01 to 0.03) mL/mm Hg versus 0.08 (95% CI, 0.04 to 0.12) mL/mm Hg (p < 0.001). Oscillatory compliance values were uniformly reduced in the diabetic subjects regardless of the presence or absence of physical complications of the disease. No differences in large-artery compliance, inertance, or systemic resistance were found between groups. No positive correlations were found between indices of glycemic control, the known duration of diabetes, and any of the hemodynamic variables.

CONCLUSIONS

Quantitative changes in the arterial pressure pulse waveform, reflected by a reduced oscillatory compliance estimate, were found in patients with non-insulin-dependent diabetes mellitus. This estimate appears to act as an early marker for the vascular abnormalities associated with diabetes before complications of the disease become clinically apparent. By contrast, no changes in large-artery compliance were found in this patient population free from clinically obvious macrovascular disease.

Medroxyprogesterone acetate and homozygous sickle-cell disease

The haematological and clinical effects of medroxyprogesterone acetate in homozygous sickle-cell (SS) disease were assessed in a 2-year controlled crossover trial completed by 23 patients. Haematological indices remained steady during the placebo phase, but during the medroxyprogesterone-acetate phase fetal haemoglobin, total haemoglobin, red-cell mass, and red-cell survival rose significantly, and reticulocytes, irreversibly-sickled-cell counts, and total bilirubin fell significantly. Painful crises were significantly less frequent during the medroxyprogesterone-acetate than the placebo phase. These results are compatible with an inhibition of in-vivo sickling in patients with SS disease during medroxyprogesterone-acetate treatment. The mechanisms of such an effect require further study.

Mortality among workers exposed to ethylene oxide

BACKGROUND

Ethylene oxide is a sterilant gas that causes leukemia and other cancers in animals. Studies in Sweden have shown an excess of leukemia and stomach cancer in humans exposed to ethylene oxide, but other studies have generally failed to confirm these findings.

METHODS

We conducted a study of mortality in 18,254 U.S. workers exposed to ethylene oxide at 14 plants producing sterilized medical supplies and spices. The subjects averaged 4.9 years of exposure to the gas and 16 years of follow-up. The exposure levels in recent years averaged 4.3 ppm (eight-hour time-weighted adjusted exposure) for sterilizer operators and 2.0 ppm for other workers. The levels in earlier years are likely to have been several times higher. Mortality in this cohort was compared with that in the general U.S. population.

RESULTS

Overall there was no significant increase in mortality from any cause in the study cohort. The standardized mortality ratios (SMRs) were 0.97 for leukemia (95 percent confidence interval, 0.52 to 1.67; 13 deaths observed), 1.06 for all hematopoietic cancers (95 percent confidence interval, 0.75 to 1.47; 36 deaths), and 0.94 for stomach cancer (95 percent confidence interval, 0.45 to 1.70; 11 deaths). Analyses according to job category and according to the duration of exposure showed no excess in cancers, as compared with the rate in the general population, but there was a significant trend toward increased mortality with increasing lengths of time since the first exposure for all hematopoietic cancers. The rate of death from hematopoietic cancer (especially non-Hodgkin's lymphoma) was significantly increased among men (SMR, 1.55; 27 deaths). Mortality from leukemia in recent years (1985 through 1987) was significantly increased among men (SMR, 3.45; 5 deaths).

CONCLUSIONS

For the entire cohort, there was no increase in mortality from hematopoietic cancer. There was a slight but significant increase among men, however. Among men and women combined, there was a trend toward an increased risk of death from hematopoietic cancer with increasing lengths of time since the first exposure to ethylene oxide.

Degrading chloroplast mRNA: the role of polyadenylation

Chloroplast development involves changes in the stability of specific plastid mRNAs. To understand how the half-lives of these mRNAs are modified, several laboratories are investigating how plastid mRNAs are degraded. This has led to the isolation of a high-molecular-weight complex that contains an endoribonuclease and a 3'-5' exoribonuclease, and the discovery that efficient mRNA degradation requires polyadenylation. These findings are similar to recent discoveries in Escherichia coli. However, an important difference between the two systems is that chloroplast mRNA degradation involves nuclear-encoded proteins. Modification of these proteins could provide the mechanism for altering plastid-mRNA half-lives in response to developmental stimuli.