Genital chlamydial infection: a role for social scientists

Potential sociomedical research contributions to the understanding of genital chlamydial infections are outlined in a six-part sociomedical 'checklist'. Sociomedical research focuses on human behavior and its social, economic, cultural, and psychological determinants. Thus, the author urges sociomedical researchers--primarily medical sociologists, medical anthropologists, social psychologists, and public health economists--to explore the cultural, socioeconomic, and behavioral factors contributing to the current 'epidemic' of genital chlamydial infection, a sexually transmitted disease (STD) that is found worldwide and has now supplanted gonorrhea as the most common STD in the industrialized nations. Control of this STD is particularly important because of its grave consequences for women's and maternal/child health; these include ectopic pregnancy, infertility, and neonatal morbidity. Before effective prevention and control programs can be realized, however, beliefs and behaviors surrounding such areas as sexuality, fertility, contraception, STDs, hygiene, and health care must be discerned for widely based populations in both industrialized and nonindustrialized nations.

The impact of zoonotic diseases transmitted by pets on human health and the economy

In the context of all causes of human morbidity and mortality, or even within the context of all infectious diseases affecting the public health, pet-associated zoonotic infections are of moderate importance. The data documented in Table 1, however, indicate that they do exact significant human health and economic costs. If complete data were available for all of the infections shown in Table 1, the costs would be considerably higher. Moreover, most of these diseases are preventable through educating the public, particularly pet owners, of the zoonotic potential of these diseases, so that they may take precautions to minimize the risks leading to infection. These measures include appropriate health care of pets to eliminate infectious agents, reducing the number of uncontrolled, ownerless pets as well as unwanted or poorly supervised pets, preventing pets from soiling public places with their feces, excluding animals from areas where children play, enforcing leash laws, and promoting responsible pet ownership. Veterinarians, physicians, and public health agencies can aid in these efforts; ultimately, however, the responsibility lies with the pet owner.

Toxoplasmosis

Infection with T. gondii can have devastating effects on the development of the unborn human fetus. As veterinarians or physicians, we should be able to accurately assess the true risk of exposure of a person to meat-borne tissue cysts or to oocysts based on the age, health, roaming and feeding habits of their cats, and the occupational or recreational activities of the individual. When time precludes an in-depth discussion of preventive measures to decrease exposure to the parasite, the whole client education program can be neatly summarized in the admonition, "When pregnant, wash your hands thoroughly before eating or touching your face, and cook your meat thoroughly." In this way, the risk of exposure to toxoplasmosis and all other meat- or soil-borne diseases is greatly reduced.

Physical activity and its relationship to blood pressure in school children

The present report analyzes the relationship between physical activity and blood pressure in 1341 school children aged 7-14 years (girls = 598, boys = 743) participating in a screening for cardiovascular risk factors that took place in the suburban area of Naples. During the baseline examination, systolic (SBP) and diastolic (DBP) blood pressure, height, weight, and resting pulse rate (PR) were measured. The Harvard-Modified Step Test was also performed in order to score both a crude recovery index (RI) and an index corrected for the initial resting pulse rate (RI-PR) used as measures of the level of habitual physical activity. Significant differences have been found between the quartiles of distribution of both the crude recovery index and the corrected index in girls and boys with regard to systolic blood pressure but not diastolic. In both sexes, better responders to the Harvard-Modified Step Test showed on the average lower systolic blood pressure than poorer responders. In boys, the inverse association between systolic blood pressure and the recovery index was independent of the effect of age, body mass index, height, and resting pulse rate, while in girls the same association did not reach statistical significance. Our results support the hypothesis that systolic blood pressure is independently related to the level of habitual physical activity in children.

Reye's syndrome: current concepts

Despite greater than 23 years of study, an incomplete understanding of the etiology, epidemiology and pathogenesis of Reye's syndrome persists. Better understanding of the disease has been hampered by the lack of a good animal model on which hypotheses of its pathogenesis could be tested. Human studies indicate that a primary mitochondrial injury may lead to complex metabolic disturbances that produce the observed pathophysiology. Specific directions regarding avenues for future research should pursue two lines: a good animal model still needs to be developed in which the biochemical and morphologic alterations identified in Reye's syndrome are duplicated. This model should include an antecedent viral illness but may not require aspirin exposure as an essential ingredient. With the identification of a satisfactory model, specific questions about the roles of environmental toxins or medications may be answered. Study of noncomatose cases of Reye's syndrome should continue. The specific emphasis should be to delineate what factors (NH3, free fatty acids and dicarboxylic acids) may be implicated in the pathogenesis of the CNS disease with the hopes of devising strategies for more effective treatment of encephalopathy and its attendant morbidity and mortality.

Eating patterns in childhood and adult health

This paper first reviews the evidence that the pathogenesis of many diseases which present in adult life begin in childhood, and that intervention in childhood may delay their onset. The diseases discussed include ischaemic heart disease, malignancy, cerebrovascular accidents, hypertension and obesity. The factors determining food habits are described and the possibilities of influencing food preferences and eating patterns in childhood are explored.

Risk factors for complex partial seizures: a population-based case-control study

This investigation is to our knowledge the first population-based case-control study of risk factors for complex partial seizures (CPS). Included in the study were all patients with onset of complex partial seizures before age 35, who were residents of Rochester, Minnesota, at the time of diagnosis between 1935 and 1979, and who were also born in Rochester (n = 82). Two control subjects were matched to each patient, and for both patients and control subjects, the unique records-linkage system for residents of Rochester was used to obtain information about possible risk factors. A history of epilepsy or febrile seizures in the mother, febrile seizures, neonatal convulsions, cerebral palsy, head trauma, and viral encephalitis were significantly more common in patients than in control subjects (p less than 0.05). None of the prenatal or perinatal factors investigated were found to be associated with complex partial seizures, except for being small for gestational age at birth. This factor lost significance after adjustment for cerebral palsy.

Risk of osteoporotic fractures in women with breast cancer: a population-based cohort study

A population-based study was undertaken to assess the risk of osteoporotic fractures in an inception cohort of breast cancer patients and an age-matched cohort of women from the community. Prior to the index date, 9.4% of cases and 12.3% of controls (p = 0.30) had one or more osteoporotic fractures. After the index date, these proportions were 16.2 and 20.0% (p = 0.28), but follow-up was shorter for cases due to reduced survival. When duration of follow-up was accounted for in a person-years analysis, the relative risk of any fracture was 1.0 and for any osteoporotic fracture was 0.9 (95% C.I. 0.7-1.2). After adjusting for other factors in a proportional hazards model, the relative risk of any osteoporotic fracture in breast cancer cases compared to controls was 0.9. Despite contentions that breast cancer patients have more often been exposed to estrogenic factors, we found little to suggest that such women are substantially protected from osteoporotic fractures.

Multifocal retinitis in New Zealand sheep dogs

Thirty-nine percent of 1,448 working sheep dogs were affected with varying degrees of multifocal retinal disease on ophthalmoscopic examination. Lesions consisted of localized areas of hyperreflexia in the tapetal fundus, often associated with hyperpigmentation. Severely affected animals had widespread hyperreflexia with retinal vascular attenuation. Only 6% of 125 New Zealand dogs raised in urban environment were similarly affected. Both eyes of 70 dogs from New Zealand were examined histologically. Forty-seven of 70 dogs had ocular inflammatory disease. Ten other dogs had noninflammatory eye disease, and 13 dogs had normal eyes. Histologically, eyes with inflammatory disease were divided into three categories: Dogs 3 years of age or less with active inflammatory disease of the retina, uvea, and vitreous. Four dogs in this group had migrating nematode larvae identified morphologically as genus Toxocara. Diffuse retinitis and retinal atrophy in conjunction with localized retinal necrosis and choroidal fibrosis. Dogs in this category were severely, clinically affected. Chronic, low-grade retinitis with variable retinal atrophy. Most dogs in this category were over 3 years of age, and many were visually functional. The existence of a definable spectrum of morphological changes associated with inflammation, suggests that Toxocara sp. ocular larva migrans may be the cause of a highly prevalent, potentially blinding syndrome of working sheep dogs in New Zealand.

HLA antigens in patients with various courses after hepatitis B virus infection

The course after hepatitis B virus infection seems to be determined by the host's immune response, which in turn may be regulated by the major histocompatibility complex. In order to find a possible relationship between the course of disease and the phenotype frequency of HLA determinants, we studied 396 Dutch subjects of northern European local race. Six groups of individuals with various courses after hepatitis B virus infection were compared to healthy controls. The hepatitis B patients were grouped according to standard criteria: 47 had recovered from acute symptomatic hepatitis B virus infection; 60 had recovered from asymptomatic hepatitis B virus infection; 26 were asymptomatic hepatitis B surface antigen carriers; 16 had chronic persistent hepatitis B; 37 had chronic active hepatitis B, and 10 had chronic active hepatitis after elimination of hepatitis B antigens. Twenty-nine Class I and 13 Class II HLA antigens were assayed by standard microlymphocytotoxicity tests. The phenotype frequency of the Class II antigen DQw1 appeared to be significantly lower in patients with chronic active hepatitis B virus infection. Some other HLA specificities showed deviations from control values, but they were not statistically significant after correction for the number of antigens tested. In conclusion, we have found no evidence that the elimination of hepatitis B virus is related to HLA phenotype. DQw1, however, may affect the morphologic type of chronic hepatitis B infection, since its presence may protect against chronic active hepatitis.

Human toxocariasis. Review with report of a probable case

A 23-year-old woman with fever, myalgias, stridor, pelvic cramping, lower abdominal pain, and profound eosinophilia was presumed to have toxocariasis. An enzyme-linked immunosorbent assay titer of 1:64 and an elevated IgE level supported the diagnosis. The patient became asymptomatic without treatment, and the eosinophil count returned to normal over several months. A stool sample from her dog was found to contain Toxocara canis ova, but the patient had no history of geophagia. Presumably, she acquired infection by hand-to-mouth transmission of infectious ova after handling the dog. Toxocariasis from this type of transmission is usually not seen in an adult, but it does occur, as this case demonstrates. Thus, the primary care physician should consider toxocariasis in any patient with a suggestive clinical picture and eosinophilia.

A population-based study of multiple sclerosis in twins

Results from studies of twin concordance in multiple sclerosis have not conclusively differentiated between environmental and genetic factors that determine susceptibility to the disease. Published studies that have been based on case finding by public appeal have been characterized by difficulties in ascertainment. The data reported here are from a large population-based study of multiple sclerosis in twins, in which ascertainment has been relatively unbiased and the cooperation of patients nearly complete. A total of 5463 patients attending 10 multiple sclerosis clinics across Canada were surveyed. Twenty-seven monozygotic and 43 dizygotic twin pairs were identified, and the diagnosis of multiple sclerosis was verified by examination and laboratory investigation. Seven of 27 monozygotic pairs (25.9 percent) and 1 of 43 dizygotic pairs (2.3 percent) were concordant for multiple sclerosis. The concordance rate for 4582 nontwin siblings of patients at two multiple sclerosis clinics was 1.9 percent, closely paralleling the concordance rate in dizygotic twins. To the extent that the difference in concordance rates between monozygotic and dizygotic twins indicates genetic susceptibility, the results of this study show a major genetic component in susceptibility to multiple sclerosis.

Early oral contraceptive use and breast cancer: theoretical effects of latency

Many cancers and other chronic diseases are associated with a long delay between exposure to a putative risk factor and subsequent diagnosis. This presents well recognised problems in the elucidation of suspected risk factors by epidemiological methods. In this paper we discuss the interpretation in epidemiological studies of the effect of a possible risk factor when population exposure is recent and rapidly changing. An important contemporary example concerns the study of early oral contraceptive (OC) use in relation to the subsequent risk of breast cancer. Computer simulations reported here indicate that plausible delays in the manifestation of any effect on breast cancer incidence make it difficult to exclude early OC use as a risk factor for breast cancer, even when large well conducted epidemiological studies show no apparent increased risk. Methods for detecting a 'latent' effect are discussed.

Characterization of cytotoxic steroids in human faeces and their putative role in the etiology of human colonic cancer

It has been shown previously that chemically induced nuclear abeerrations in the murine colon are correlated with the carcinogenicity of the respective chemicals. Consequently, the nuclear aberration assay was utilized for the identification of putatife carcinogens in human faeces. Human fecal samples were fractionated by several chromatographic methods, and the assay led to the isolation of two substances. A combination of spectroscopic (mass, nuclear magnetic resonance, ultraviolet, and infrared) and chromatographic (HPLC and GLC) methods showed that they are 5-alpha- cholestan-3-one (I) and cholest-4-en-3-one (II). A number of C-27-C-30 steroids isolated from closely related fractions of feces were inactive in this assay. Thus I and II could play a role in etiology of large bowel cancer in humans.

An epidemic of cirrhosis in Danish women revisited

Between 1944 and 1947 the mortality statistics for the Danish population show an epidemic increase of liver diseases: subacute necrosis and cirrhosis. The epidemic only affected female mortality rates. Mortality due to cirrhosis remained at a higher rate for women than men until 1970 as a result of an excess mortality in the cohort of women who in 1945 were over the age of 45. Up to 1981 this group showed an excess of 4,000 fatalities. A reevaluation of medico-statistical data shows that the disease cannot be explained by the epidemic hepatitis occurring in 1942-1944 or by increased consumption of alcohol. Possible causes could be pharmaceutical products or additives, perhaps hormone preparations.

Effect of blind passage and multiple sampling on recovery of Chlamydia trachomatis from urogenital specimens

Detection of chlamydial infections depends on the sensitivity of the techniques used. Variables include the number of body sites sampled, the number of samples obtained, and the number of passages in tissue culture. To assess these factors, microdilution plate cultures with a single blind passage were performed on specimens from 10,291 men and women attending a sexually transmitted disease clinic. Overall, 21% of the men and 30% of the women were culture positive. However, 18% of endocervical, 28% of female urethral, and 29% of male urethral cultures that were positive became so only after a single passage. Of culture-positive women, 23% were positive at the urethra only. Pooled urethral and endocervical specimens were positive more often than an endocervical specimen alone but less often than separately cultured endocervical and urethral specimens. A total of 221 specimens from 92 men and 66 women were subjected to five serial blind passages. Of 83 positive specimens, 29 (35%) were positive only after two or more passages. A total of 37 (46%) women were culture-positive, but only 12 (33%) of those who were positive and had an endocervical culture would have been detected by a single endocervical culture that was not passaged. The sensitivity of chlamydial culture is substantially less than 100% but can be improved by culturing samples from both the urethra and endocervix in women and by serial passage in tissue culture.

On the spatial spread of rabies among foxes

We present a simple model for the spatial spread of rabies among foxes and use it to quantify its progress in England if rabies were introduced. The model is based on the known ecology of fox behaviour and on the assumption that the main vector for the spread of the disease is the rabid fox. Known data and facts are used to determine real parameter values involved in the model. We calculate the speed of propagation of the epizootic front, the threshold for the existence of an epidemic, the period and distance apart of the subsequent cyclical epidemics which follow the main front, and finally we quantify a means for control of the spatial spread of the disease. By way of illustration we use the model to determine the progress of rabies up through the southern part of England if it were introduced near Southampton. Estimates for the current fox density in England were used in the simulations. These suggest that the disease would reach Manchester within about 3.5 years, moving at speeds as high as 100 km per year in the central region. The model further indicates that although it might seem that the disease had disappeared after the wave had passed it would reappear in the south of England after just over 6 years and at periodic times after that. We consider the possibility of stopping the spread of the disease by creating a rabies 'break' ahead of the front through vaccination to reduce the population to a level below the threshold for an epidemic to exist. Based on parameter values relevant to England, we estimate its minimum width to be about 15 km. The model suggests that vaccination has considerable advantages over severe culling.

Binding of oestradiol to blood proteins and aetiology of breast cancer

A prospective study of 5,000 women has shown that, compared to controls, those who subsequently developed breast cancer had a higher proportion of their blood oestradiol in the non-protein-bound and albumin-bound fractions (the bio-available fraction) and a lower proportion in the sex-hormone-bound fraction. The increased proportion of bio-available oestradiol was partly due to a lower concentration of sex-hormone-binding globulin. Weight was excluded as a confounding factor.

Menopausal oestrogens and breast cancer risk: an expanded case-control study

A study among 1960 post-menopausal breast cancer cases and 2258 controls identified through a nation-wide screening program enabled evaluation of effects of oestrogen use on breast cancer risk. Ever use was not associated with increased risk (RR = 1.0), but a significant trend was observed with increasing years of use, with users of 20 or more years being at a 50% excess risk. Elevations associated with long-term use were apparent across all menopause subgroups (natural, ovaries retained, ovaries removed). Hormones exerted particularly adverse effects in those initiating use subsequent to a diagnosis of benign breast disease, particularly long-term users (RR = 3.0, 95% CI 1.6-5.5). There was also some indication that effects predominated among the lower stage tumours, an observation similar to that observed for endometrial cancer. These findings support a role for oestrogens in the aetiology of breast cancer, although risk appears to be enhanced only after extended periods of use, and not to the extent observed for other hormonally-sensitive tumours.

Epidemiologic study of Holstein dairy cow performance and reproduction near a high-voltage direct-current powerline

The development and operation of a high-voltage direct-current (HVDC) transmission line in rural Minnesota generated public concern over potential adverse effects to nearby residents and their livestock. Electrical environmental parameters near an HVDC line decline rapidly with distance, but effects on ambient space charge have been detected out to 1 mile. Previous studies of powerline effects on livestock have involved the more common alternating-current (HVAC) lines, which create a different electrical environment. To identify potential adverse effects of HVDC line operation on livestock, case-control and cohort study methods were used to examine various indices of Holstein performance in relation to distance from the line and the onset of line operation. It was believed that these indices would reflect changes in physiologic function or overt health effects that might arise from the HVDC environment. High-quality performance data from existing Dairy Herd Improvement Association (DHIA) records were obtained for 97% of qualifying herds located within 10 miles of the line. The large number of animals and years of observation provided high statistical power to detect even small systematic changes in performance. No significant differences in milk production or reproductive capacity were associated with presumed exposure to the HVDC environment. The absence of measurable effects in a large "sentinel" animal population may have implications for the assessment of human health risks related to HVDC transmission lines.

Risk factors for bladder cancer in a cohort exposed to aromatic amines

Occupational and nonoccupational risk factors for bladder cancer were analyzed in a cohort of 1385 workers with known exposure to a potent bladder carcinogen, beta-naphthylamine. Bladder cancer was approximately seven times (95% confidence interval [CI] = 3.9, 12.4) more likely in exposed rather than nonexposed individuals, yet, otherwise, the groups were generally similar in other exogenous or hereditary risk factors. A total of 13 cases of bladder cancer were identified. After the first year of a screening program involving 380 members of the cohort, 9 of the 13 cases of bladder cancer and 36 persons with atypical bladder cytology, histology, or pathology were compared with 335 noncases for distributions of different variables. Occupational variables were significant in a multivariate model that controlled for age, cigarette smoking history, and source of drinking water. The estimated odds ratio for the association for bladder cancer and the duration of employment, when controlling of these other variables, is 4.3 (95% CI = 1.8, 10.3). In addition to the occupational factors, age was significant in the multivariate analysis. Other potential risk factors, such as consumption of coffee or artificial sweeteners, use of phenacetin, or decreased use of vitamin A were not found to be significantly different in cases and noncases.

Very low birth-weight (less than 1,500 g) and previous induced abortion: Victoria 1982-1983

In Victoria, previous termination of pregnancy is a risk factor for giving birth to a very low birth-weight infant (less than 1,500 g)--the risk of giving birth to an infant less than 1,000 g is increased more than 2.5-fold by a prior induced abortion and more than 3.5-fold by 2 or more prior abortions. However, more than 97% of women with a prior termination gave birth to infants weighing more than 1,500 g. Subsequent very preterm delivery appears to be a real but rare complication of induced abortion, responsible for about 9% of very low birth-weight infants in 1982-1983.

Immune response of athymic and euthymic germfree mice to Campylobacter spp

Pure cultures of several Campylobacter spp. induced a specific humoral immune response after they colonized and infected gnotobiotic mice; however, Campylobacter-immune mouse serum was not bactericidal (in vitro), manifested a weak agglutination reaction (in vitro), and showed specificity (strain 45100-immune mouse sera) for the homologous (infecting) Campylobacter strain, but was not able to passively protect germfree athymic (nu/nu) BALB/c mice against Campylobacter infection and diarrhea. Active immunization of germfree nu/nu mice with Formalin-killed C. jejuni also did not protect the gnotobiotic mice from Campylobacter infection and diarrhea. It appears from the results of our initial gnotobiotic studies that antibodies in serum against the infecting strain of C. jejuni may not play an essential role in resistance to Campylobacter disease in mice.

Assessing the health effects of potential exposure to PCBs, dioxins, and furans from electrical transformer fires: the Binghamton State Office Building medical surveillance program

A medical surveillance program has been established for 482 persons who were potentially exposed to polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans from an electrical transformer fire in a Binghamton, NY office building in 1981. Blood samples were analyzed for serum concentrations of PCBs and for biochemical and hematologic parameters at the time of the fire and 9 to 12 mo later. Firefighters and individuals who were in the building for 25 hr or more were also asked about post-fire symptomatology and examined after 1 yr for disorders of the skin, eyes, liver, and neurologic system. The results indicated that reported exposure was positively related to mean serum PCB levels (p = .004). The means and individual values, however, were within the range reported by other studies of persons with no unusual exposures. Significant correlations were observed between serum PCB concentrations and levels of liver enzymes and lipids, but mean levels of these biochemical parameters were not associated with reported exposure after adjustment for relevant covariables. Approximately one-half of those examined had skin lesions, but no cases of chloracne were detected, and there was no clinical evidence of any other exposure-related systemic disorder. The data suggest that exposure to contaminants from the building did not result in substantial absorption or cause any major short-term health effects.

Effects of vitamins C and E on N-nitroso compound formation, carcinogenesis, and cancer

The properties of N-nitroso compounds (NNC) and of vitamins C and E are briefly described. The author reviews the ability of vitamins C and E to inhibit NNC formation in chemical systems, in nitrite-preserved meat, in experimental animals and in humans. Dietary vitamins C and E both produced 30% to 60% inhibitions in most carcinogenesis experiments employing preformed carcinogens. Vitamin C reversed transformation in an in vitro system. Carcinogenicity tests of the vitamins are reviewed (vitamin C can promote bladder carcinogenesis). Intake of fresh fruits and vegetables (which contain vitamin C) is negatively correlated with cancer of the stomach, esophagus, larynx, mouth and cervix. For gastric and esophageal cancer, there is evidence that this association is due to an inhibition of in vivo NNC formation. Vitamin C is apparently not a useful treatment for cancer. The author supports the recommendation that fresh fruit and vegetable intake be increased to lower the risk of cancer.

Some trends in medical populations genetics

Five topics concerning medical population genetics have been selected for discussion: in the field of population cytogenetics, the frequency of chromosomal aberrations and the roles of mutation and selection in the maintenance of balanced rearrangements are studied; the long term genetic effects of treatment and prevention of genetic diseases are reviewed; the relationships between malaria and the sickle-cell trait are discussed; some recent works concerning human DNA polymorphisms in the field of population genetics are presented, and finally, some methods of genetic epidemiology are described.

Nutrition education of the cancer patient and family. Myths and realities

Common myths about nutrition education and care of cancer patients are debunked and realities are discussed. First, frequently held misconceptions of nonspecialized health professionals are considered. These include the myths that diet change in the population will be rapid now that dietary guidelines to prevent cancer have been issued; nutrition education is best relegated to the dietitian for cancer patients; patients do not need nutritional advice until treatment is actually in progress, and then only rarely while they are hospitalized; nutrition education needs taper off once consolidation or intermittent therapy begins and cease entirely with survival of 5 or more years; and nutrition education of the family usually can be ignored. Next, common myths which many patients and their families subscribe to are discussed. These myths include the following: by following the cancer prevention dietary guidelines, protection against cancer is guaranteed; if only the victim had eaten differently, the cancer never would have developed; cancer prevention dietary guidelines also should be followed in the nutritional support of cancer patients; cancer patients can rely on their appetites and hidden hungers to stay in good nutritional balance; special diets can cure cancer; all cancer anorexia can now be reversed by following proper diet; children who have cancer should neither be fed nor can they eat diets similar to those fed to other children at that age; special nutritional support measures such as tube feeding and total parenteral nutrition are only useful for those younger than 65 years; and there is no sense in paying attention to the nutrition of cancer patients in hospices because they are going to die anyway. It is concluded that nutrition education can enhance quality of life, for the patient and his family, throughout his illness and after his recovery.

What causes childhood leukaemia? Some beliefs of parents of affected children

The theories of parents about the cause of their children's leukaemia have been documented in the course of a case-control study. From a sample of 175 children who were diagnosed as having acute lymphoblastic leukaemia, 91.4% of their parents put forward their theories. Some of these theories were related clearly to material that had been published and therefore had some scientific validity. Other theories often had no apparent scientific basis. Persons who are involved in the care of children with leukaemia should be aware of the wide variety of theories that are held by their parents so that they may provide counselling which could be of help in the relief of feelings of anxiety or guilt among the parents. Parents should always be afforded the opportunity to put forward their own theories so that they may be discussed on a rational basis. It is conceivable that some parents might put forward new hypotheses about leukaemogenesis that could be tested scientifically.

HLA-A,B and DR matching in corneal transplantation

One hundred eighty-five consecutive corneal transplants were performed in recipients selected on the basis of the best available HLA-A,B and DR match. Endothelial rejection-free transplant survival in this group was compared to a retrospective historical control group of 199 consecutive transplants performed in recipients selected on the basis of age and longest wait criteria. The two groups were comparable with regards to primary diagnosis, preoperative corneal vascularization, donor and recipient age, and operative techniques. Thirty-eight transplants in the study group and 28 transplants in the control group were at high risk for endothelial transplant rejection. At 12 months, the estimated rejection-free survival (Kaplan-Meier method) of the high-risk study group transplants was 87% compared to 74% for the high-risk historical control group and transplants. This difference did not reach the significant level of 0.05 with the log-rank test. The 12-month estimated rejection-free survival of low-risk study group and historical control group transplants were similar. In the study group, the 12-month estimated rejection-free survival of well-matched transplants was 95% compared to 83% for poorly matched transplants (log rank, P less than 0.02). These findings suggest that a relationship exists between HLA-A,B and DR compatibility of donor and recipient and the corneal rejection-free transplant survival.

Improved biochemical screening procedure for small clinical laboratories for vero (Shiga-like)-toxin-producing strains of Escherichia coli O157:H7

Of 327 sorbitol-negative fecal isolates of Escherichia coli, 37 O157:H7 Vero (Shiga-like)-toxin-producing strains were identified. The specificity of the basic sorbitol screen was improved from 11.3 to 33.6% by the exclusion of organisms with negative ornithine and lysine decarboxylase reactions.

Oral immunization and protection of raccoons (Procyon lotor) with a vaccinia-rabies glycoprotein recombinant virus vaccine

Animal rabies control has been frustrated by the existence of multiple wildlife reservoirs and the lack of efficacious oral vaccines. In this investigation, raccoons fed a vaccinia-rabies glycoprotein recombinant virus in a sponge bait developed rabies virus-neutralizing antibody (0.6-54.0 units) and resisted street rabies virus infection 28 and 205 days after feeding. Additional raccoons immunized by oral infusion with attenuated antigenic variants of rabies virus strains CVS-11 and ERA failed to develop rabies virus-neutralizing antibody. This work demonstrates the feasibility of a recombinant virus vaccine containing the rabies glycoprotein gene for immunization of raccoons, and possibly other wildlife, to obtain long-term protection against rabies.

Influence of iron on growth, morphology, outer membrane protein composition, and synthesis of siderophores in Campylobacter jejuni

Three human isolates of Campylobacter jejuni were grown in a biphasic culture medium with and without the addition of a synthetic chelator to induce iron limitation. Cells grown in low-iron medium exhibited slower growth rates and altered cellular morphology. Increased numbers of longer, more filamentous forms were seen in Gram-stained smears. Three proteins, with apparent Mrs of 82,000, 76,000, and 74,000, were consistently present in the outer membrane of cells grown in low-iron medium. At least one of these proteins (76,000 to 74,000) was exposed on the cell surface. A bioassay was used to look for the production of siderophores by these and other strains of C. jejuni. Seven of 26 strains tested produced detectable amounts of siderophores. Growing strains at 42 degrees C failed to suppress siderophore synthesis or to alter the outer membrane protein profiles of iron-starved cells. The ability of three strains to utilize exogenously supplied siderophores for growth in low-iron medium was also examined. All three strains were able to utilize enterochelin and ferrichrome, but none utilized aerobactin, rhodotorulic acid, or desferrioxamine B. The effect of iron on the virulence of C. jejuni for 11-day-old chicken embryos inoculated via the chorioallantoic membrane was also determined.

Do learning handicaps and headache cluster?

Children who are brought to medical attention because of frequently recurring or disabling headaches appear to have an increased prevalence of learning handicaps. Some of this increase might reflect Berkson's principle--the selection bias of an overrepresentation of patients with two disorders. Consideration is given to five models that show a relationship between learning handicap and headache. Two of the models are dismissed as too simple. Studies are needed to determine whether learning handicap and headache are indeed associated, and, if so, how. Clinicians are advised not to wait until these studies have been completed before implementing therapeutic programs that might prove helpful to those children with both headache and learning handicap.

Squamous cell carcinoma of bladder: an increased incidence in blacks

In a ten-year review of bladder cancer cases at the University Hospital, Cincinnati, Ohio, there was an apparent increased incidence of squamous cell histology in black patients. We report the findings of our local study as well as the results of our literature search on bladder cancer histology in racial subgroups. Squamous cell carcinoma represents 10 to 15 per cent of bladder cancer cases in blacks and approximately 5 per cent of bladder cancer cases in whites.

The chicken embryo as a model for campylobacter invasion: comparative virulence of human isolates of Campylobacter jejuni and Campylobacter coli

Eleven-day-old chicken embryos were used to compare the relative virulence of minimally passaged human isolates of Campylobacter jejuni and Campylobacter coli. Graded doses of bacteria were inoculated onto the chorioallantoic membrane, and 50% lethal doses were calculated at 72 h postinfection. Strains varied markedly in their ability to invade the chorioallantoic membrane and kill the embryos. The 50% lethal doses varied by about 6 logs for 25 strains of C. jejuni, and by 2 logs for 5 strains of C. coli. Although both outbred and inbred embryos were employed in the study, the latter were found to be more susceptible to infection with most strains. All isolates were screened for plasmid DNA, but there was no apparent relationship between plasmid content and virulence of strains for the embryos. Neither could virulence be associated with the production of siderophores by the strains. The ability of selected strains of C. jejuni to invade the liver of embryos was also studied. The number of campylobacters culturable from the liver was found to be inversely related to the 50% lethal dose of the strain. By inoculating 11-day-old embryos intravenously, it was possible to demonstrate that a strain of C. jejuni which was poorly virulent after chorioallantoic inoculation was relatively noninvasive. Invasiveness alone, however, could not fully account for the lethality of two highly virulent strains of C. jejuni administered by the intravenous route. Finally, there was no correlation between motility and virulence in this model system.

Evidence of an immunopathogenic basis for central nervous system disease in primary Sjögren's syndrome

The pathogenesis of central nervous system complications in primary Sjögren's syndrome (CNS-SS) is unknown. In order to determine whether patients with active CNS-SS have cerebrospinal fluid (CSF) abnormalities indicative of CNS inflammation, CSF analyses from 30 patients with active CNS-SS (SSA) were contrasted with those from 20 SS patients without CNS involvement (SSI) and 20 patients with systemic lupus erythematosus and active CNS disease (SLEA). Elevations of total protein concentration, IgG concentration, IgG to total protein ratio, and IgG index were observed in patients with SSA, but not in those with SSI. Agarose gel electrophoresis results were abnormal, with 1 or more bands, in 25 of 29 SSA patients (86%), but in only 3 of 18 SSI patients (17%). Similar, but less striking, CSF abnormalities were seen in a minority of SLEA patients. Fifteen SSA patients (50%) had transient, mild-to-moderate CSF pleocytosis, while only 1 SSI patient and 2 SLEA patients had similar findings. Cytologic findings were abnormal in 18 SSA patients (60%); these included atypical mononuclear cells, lymphoblastoid cells, and plasma cells. The presence of immunocompetent cells and evidence for the intrathecal synthesis of IgG within the CSF of SSA, but not SSI, patients provide diagnostic parameters which are indicative of active disease and which can be monitored serially during therapy.

Comparison of HLA-Dw1 and -Dw2 positive adherent cells in antigen presentation to heterozygous T-cell lines: a low rubella antigen-specific response associated with HLA-Dw2

T-cell lines specific for purified tuberculin (PPD), rubella, and herpes simplex virus (HSV) antigens were established from two Dw1/w2 heterozygous subjects. Fresh peripheral blood monocytes from healthy individuals with shared and non-shared D-antigens were used as presenting cells and the T-cell lines as responders in lymphocyte blast transformation assays with specific antigens. An HLA-restricted reaction was seen with all the antigens, although the PPD- and HSV-specific cell lines reacted stronger than rubella-specific lines when the specific antigens were presented by monocytes not sharing the D-antigens. A significantly lower response was seen when rubella antigen was presented by Dw2 positive monocytes as compared to response promoted by Dw1 positive monocytes (p less than 0.0001, Mann-Whitney U-test), whereas no such difference was seen in responses to PPD or herpes simplex antigen.