Developmental regulation of polysialic acid synthesis in mouse directed by two polysialyltransferases, PST and STX

Polysialic acid is a developmentally regulated carbohydrate attached to the neural cell adhesion molecule, N-CAM, and abundant in embryonic tissues. There is increasing evidence that polysialic acid reduces N-CAM adhesion, thereby promoting neurite outgrowth and cellular mobility. It has been shown that two enzymes, polysialyltransferase, PST, and sialyltransferase X, STX, form polysialic acid on N-CAM. However, it is not known how these two enzymes contribute to polysialylation. In order to determine how the expression of PST and STX leads to polysialic acid synthesis during mouse development, the expression of PST and STX transcripts were evaluated by Northern blot analysis, competitive reverse transcription-polymerase chain reaction and in situ hybridization, and those results were correlated to the expression of polysialic acid. The results obtained by these analyses demonstrated that both PST and STX transcripts were barely detected at embryonic day 8 (E8) but increased after E9. PST and STX transcripts were present in substantial quantity between E11 and E15, coinciding with the period when maximum synthesis of polysialic acid is required. Ten days after birth, the level of STX transcript declined substantially, whereas the level of PST transcript only gradually declined and persisted in the adult brain. These results, taken together, strongly suggest that PST and STX coordinately synthesize polysialic acid during development. At the same time, they are expressed differentially in tissue-specific and cell-type-specific manners, suggesting that PST and STX may have distinct roles in development and organogenesis.

[A simple method for determining the presence of Toxoplasma gondii (Eucoccidia: Sarcocystidae) in meat]

Presence of T. gondii in meat from several sources was determined by traditional methods and by a new simplified method in which animals are fed meat directly without any previous treatment with artificial gastric fluid. Tissues are ground and the animals ingest them naturally. Determination of Toxoplasma in lungs or brain (as well as by specific antibody test), showed no statistically significant differences between both methods.

Fractionation of feline bone marrow with the soybean agglutinin lectin yields populations enriched for erythroid and myeloid elements: transplantation of soybean agglutinin-negative cells into lethally irradiated recipients

Feline bone marrow cells treated with the soybean agglutinin (SBA) lectin are separated into two populations, the agglutinated SBA(+) fraction containing predominantly cells of myeloid origin and the nonagglutinated SBA(-) fraction consisting of cells primarily of the erythroid lineage. FACScan analyses revealed a clear distinction of the cells based on their light scattering properties, i.e., large cells and cells with high granularity were found in the SBA(+) fraction, whereas cells having a low forward light scatter and side light scatter were found in the SBA(-) fraction. Colony-forming assays showed colony-forming unit-granulocyte/monocyte (CFU-GM) cells to have a strong affinity for SBA because these were found almost entirely in the SBA(+) fraction; in contrast, burst-forming unit-erythroid (BFU-E)-forming cells were concentrated in the SBA(-) fraction. When the marrow was fractionated by counterflow centrifugal elutriation (CCE), a differential binding to SBA among the CFU-GM forming cells was found. The SBA(-) fractions of cells collected at 21 and 25 ml/min contained primarily BFU-E forming cells, similar to that observed with whole marrow; the later CCE fractions, those collected at 32 ml/min and the rotor off fraction, when treated with SBA showed a small but significant number of CFU-GM cells in the SBA(-) fraction. T lymphocytes were found predominantly in the SBA(+) fractions of whole bone marrow and the CCE fractions. Successful autologous marrow transplants were performed with the early CCE SBA(-) fractions. The latter cells were used for our initial transplant attempts because ongoing studies in our laboratory had shown these cells to be free of any viral-containing cells when the marrow had been obtained from animals infected with the feline immunodeficiency virus. In summary, although SBA treatment of feline marrow yields a marked separation of CFU-GM and BFU-E progenitors, select CCE SBA(-) fractions contain stem cells capable of providing hematopoietic reconstitution of lethally irradiated animals.

Renal 99Tc(m)-DMSA SPET and planar imaging: are they really the same?

Previous studies have suggested that more defects are detected on SPET than on planar DMSA images. The aim of this study was to evaluate differences between planar and SPET imaging. Sixty-four kidneys from pyelonephritic patients were studied using both techniques. An automated algorithm for reorientation and centring of the SPET images was used to minimize inter-observer variability. Reduced uptake and contour defects showed different localization on planar and SPET imaging. Coincidence of defects on both types of image was low. We also noted a dependence on defect frequency content for detectability. Image contrast played a noticeable role in the detection of defects. Differences in contrast between SPET and planar images may be responsible for the variable success in the detection of defects. Contour defects are seen more frequently on tomographic slices, whereas reduced uptake defects are seen more frequently on planar images. A difference is also noted between the cortical and calyceal zones for differently contrasted lesions. SPET and planar DMSA images can potentially provide a different diagnosis of renal lesions.

Seroprevalence of hepatitis B virus among school-age children in the Stann Creek District of Belize, Central America

Adults in the Stann Creek District of Belize have a high prevalence of hepatitis B virus (HBV) infection, but the age of onset of these infections is unclear. We conducted a seroprevalence study of hepatitis B markers among Stann Creek school-age children to provide information for planning a hepatitis B vaccine program. The overall prevalence in 587 students was high for antibody to hepatitis B core antigen (anti-HBc) (43.3%) and hepatitis B surface antigen (HBsAg) (7.7%). There was marked variation of anti-HBc by school and by the predominant ethnic groups attending those schools. Maya had the highest prevalence (76%), followed by Mestizo (50%), Garifuna (37%), and Creole (25%). Children less than nine years of age attending the rural primary schools (mostly Mayan and Mestizo) had significantly higher prevalence of anti-HBc than did children attending the urban primary school (mostly Garifuna and Creole) (P < 0.05). Anti-HBc was found in 42% and 36% of students at the two high schools. Of the five schools tested, only at the urban primary school did anti-HBc positivity increase with age. Based on an analysis of the cost of serologic screening before immunization compared with mass vaccination, preimmunization serologic screening resulted in vaccine program cost savings in four of the five schools. Because most children in the rural areas contract hepatitis B before entering school, immunization against HBV should be integrated into the routine infant immunization program.

[Seasonality of parasites and intestinal bacteria in vegetables that are consumed raw in Costa Rica]

In Costa Rica, a total of 640 samples from eight different vegetables used for raw consumption, were analyzed for the presence of intestinal parasites and fecal coliforms. Eighty samples of each vegetable were analyzed, forty during the dry season and forty in the rainy. A greater, but unsignificant (p > 0.05) level of fecal coliforms was found during the dry season. Levels of Escherichia coli, were higher (p < 0.05) during the dry season in lettuce (Latuca sativa) and cilantro (Coleandrum sativum) leaves. Cysts of Endolimax nana, Entamoeba coli, Entamoeba histolytica, Giardia intestinalis and Cryptosporidium sp. were found in all vegetables. The greater percentage of positive samples was found during the dry season, although these relation was only corroborated (p < 0.05) in radish (Raphanus sativus) and cilantro leaves. Only lettuce and cilantro levels showed a positive linear correlation (p < 0.05) between occurrences of intestinal parasites and fecal coliforms.

Seroepidemiology of toxoplasmosis in humans: possible transmission routes in Costa Rica

A serological survey with immunofluorescence techniques to detect toxoplasma antibodies was done on a sample of 1234 Costa Ricans. The overall prevalence was 76%; it increased from 60% in donors aged 1-4 years to 90% in those over 25 years. No significant difference was found in seropositivity between males (42.8%) and females (57.2%) and between donors from urban and rural (LPI) areas. Consumption of raw meat, especially prepared meat, was significantly correlated with antibody prevalence, but cat contact was not, indicating a possible change in the usual pattern of transmission described for the country. Nevertheless, our data suggest that infectious cat feces play an important role in the transmission of toxoplasmosis.

[Susceptibility of Sigmodon hispidus (Rodentia: Cricetidae) to Toxoplasma gondii (Eucoccidia: Sarcocystidae)]

Sigmodon hispidus, a cotton rat, was inoculated with tachyzoites or oocysts of Costa Rican strains of Toxoplasma gondii to demonstrate the resistance to this parasite, as compared with mice, hamster and white rat infection. Susceptibility to tachyzoite inoculation was higher in this animal than in white rats but lower than in the other animals. Independent to the Toxoplasma strain studied, oocyst infection was less lethal for S. hispidus when compared with mice and hamsters; the results were similar to those observed for white rats. There is a probable participation of this wild animal in the natural Toxoplasma life cycle.

An automatic technique for micro-drilling a stapedotomy in the flexible stapes footplate

This paper describes a technique for controlling the drill bit breakthrough during low-speed micro-drilling of a flexible bone element. The research reported focuses on the penetration of the stapes footplate at the boundary of the middle and inner ear where there is a need to minimize the penetration of the drill bit through the medial surface. The bone is of unknown thickness and compliance, and the efficiency of cutting is variable between specimens. An automated system is presented that is able to determine these unknowns, to detect the onset of breakthrough and to control drill protrusion beyond the medial surface. The methods used to determine and control the level of protrusion on breakthrough are described. It is reported that the drill bit protrusion beyond the medial surface is achieved to within 0.02 mm of the ideal position.

Randomized comparison of 5 and 10 microgram doses of two recombinant hepatitis B vaccines

The high cost of hepatitis B vaccines remains an obstacle to their use. Since the recommended adult dose of Recombivax HB (MSD) is 10 micrograms and that of Engerix B (SKB) is 20 micrograms, we sought to determine if 10 microgram doses of each vaccine are equally immunogenic. Further, since 5 microgram doses of Recombivax are routinely used in those < or = 29 years of age in the US military, we sought to compare this dose with 5 microgram doses of Engerix B. Lower doses of Engerix would result in vaccine cost savings.

METHODS

members of the Belize Defence Force who were > or = 18 years of age (median 24) without detectable anti-HBc were randomly assigned to receive Recombivax, 5 or 10 micrograms, or ENgerix, 5 or 10 micrograms IM at 0, 1, and 6 months. Randomization was weighted toward Engerix.

RESULTS

after 3 doses, geometric mean concentrations (GMC) of anti-HBs were highest among those receiving Recombivax 10 micrograms (n=22) or 5 micrograms (n=46) with GMC anti-HBs of 744 and 570 mIU ml-1, respectively. Similar proportions in the two groups developed > or = 10 mIU m-1 anti-HBs (100 and 98%). Among the 91 people who received Engerix 10 micrograms, the GMC anti-HBs was 325 mIU ml-1 and 91% developed > or = 10 mIU ml-1. The 87 people who received Engerix 5 micrograms had the lowest GMC, 177 mIU ml-1 (p < 0.05 compared with either Recombivax group). Only 86% attained > or = 10 mIU ml-1 anti-HBs (p > 0.05 compared with other regimens). The proportion attaining > or = 100 mIU ml-1 was lower in the 5 microgram Engerix group (63%) compared with 80% in the 5 microgram or 95% in the 10 microgram Recombivax groups (p < 0.05).

CONCLUSIONS

Engerix administered in 5 microgram doses is less immunogenic than 5 or 10 microgram doses of Recombivax. In healthy populations < 30 years of age, regimens of half the recommended adult dose (5 micrograms of Recombivax or 10 micrograms of Engerix) are highly immunogenic and may result in significant vaccine cost savings.

Prevalence of hepatitis B virus among health care workers in Belize, Central America

A seroprevalence survey of hepatitis B virus (HBV) markers was conducted among health care workers in Belize to help determine the epidemiology of hepatitis B and to determine if screening before immunization might lower vaccine costs. Of the 330 workers tested, 94 (29%) were positive for antibody to HBV core antigen (anti-HBc) and three (1%) had HBV surface antigen. The presence of anti-HBc increased significantly with age from 12% in those 18-24 years old to 52% in those > or = 50 years old. The rate was 17% of 48 men compared with 30% of 282 women (P = 0.05). Rates increased with years of medical service and were higher among nurses (69 of 228; 30%) and nonprofessional staff (15 of 44; 34%) than among physicians (0 of 20). The presence of anti-HBc also differed significantly among ethnic groups: Mestizo, 4%; Creole, 33% and Garifuna, 57%. Rates differed by district ranging from 3% in a northern district (mostly Mestizo) to 67% in a southern district (mostly Garifuna). Parental exposure to hepatitis B through needle stick injuries and blood transfusions was not associated with anti-HBc. Multiple logistic regression analysis confirmed ethnicity, district of residence, and age as the best predictors of anti-HBc in health care workers. Cost analysis suggests that because of regional differences in exposure, testing of health care workers for anti-HBc in the Belize and Stann Creek districts in southern Belize before hepatitis B immunization would result in vaccine program cost savings.

Major birth defects at King Fahd Hofuf Hospital: Prevalence, risk factors and outcome

We analyzed the medical records of all live birth infants (LBs) born with major birth defects (MBDs) at King Fahd Hofuf Hospital (KFHH) during a three-year period. Our objectives were to determine defect prevalence rate, patterns, geographic differences, associated maternal and infant risk factors, and the contribution of the defects to mortality in our Neonatal Intensive Care Unit (NICU). Out of 30,159 infants born alive during the study period, 687 (2.27%) had one or more MBDs. Systems most commonly affected were the cardiac (20.8%), musculoskeletal (18.7%), and central nervous (18.3%) systems. We observed higher rates/1000 LBs of life-threatening CNS and cardiac defects and diaphragmatic hernia than rates reported from other countries. Rate of defects/1000 LBs increased from 0.79% in the birth-weight group >/=4000 g to 15.2% in the birth-weight category <1500 g. Fifty-six infants with MBDs were born to diabetic mothers; diabetes was the only identified maternal disease associated with birth defects. Diabetic mothers and those of infants with chromosomal anomalies had higher means of age and parity than the control mothers ( 33.5 yrs (SD 5.2), 31.4 yrs (7.5), and 8.8 (3.8), 7.39 (3.8), for age and parity of diabetic and chromosomal anomalies respectively vs. 26.8 yrs (6.4) and 5.2 (3.7) in the controls, P<0.01). Out of the 687 infants, 254 (36.97%) died; and MBDs were the most common disease- specific cause of death in our NICU throughout the study period.

Determination of Toxoplasma gondii in several organs of cattle by carbon immunoassay (CIA) testing

Samples of muscle, heart, liver and lung were tested for the presence of Toxoplasma gondii using mice as a biologic detector and the carbon immunoassay (CIA) for immunological diagnosis. In positive tissues the percentage of samples positive ranged from 10 to 50% which indicates the importance of cattle in the epidemiology of Toxoplasma in Costa Rica. We discuss these findings in relation to the transmission of the parasite in Costa Rica.

Epidemic optic neuropathy in Cuba. Eye findings

OBJECTIVE

To characterize and establish a clinical definition of the optic neuropathy that appeared in epidemic form in Cuba in 1992 and 1993.

METHODS

At the invitation of the Cuban Ministry of Health, Havana, members of ORBIS International and the Pan American Health Organization, assembled teams that traveled to Cuba in May 1993. We were initially briefed by Cuban national experts in the areas of virology, nutrition, toxicology, ophthalmology, neurology, and public health. We then examined 20 patients on our own. Thirteen of these patients underwent a comprehensive neuro-ophthalmologic examination, including neurologic examination, ophthalmologic examination, visual fields, optic nerve function studies, contrast sensitivity studies, and funduscopy. We returned 4 months later to perform an additional 12 comprehensive neuro-ophthalmologic and follow-up examinations.

RESULTS

Only seven of the 13 patients who were alleged to have the optic form of the epidemic and who were rigorously and systematically examined on the first visit demonstrated a bilateral optic neuropathy. These seven patients had several features that included decreased visual acuity, poor color vision, central scotomas, decreased contrast sensitivity, saccadic eye movements, and most prominent and distinctive of all, nerve fiber layer wedge defects of the papillomacular bundle. Our clinical definition was then implemented by the Cuban ophthalmologists and epidemiologists. On returning 4 months later, we found that all newly presented patients were correctly diagnosed to have the epidemic disease. With the new case definition and the application of a few simple psychophysical tests, the false-positive rate of diagnosis became much lower. After vitamin therapy, we reexamined the patients seen on our initial visit, and all showed marked improvement.

CONCLUSIONS

The Cuban epidemic was characterized by an optic neuropathy with features that were similar to those of tobacco/alcohol amblyopia and Leber's optic atrophy. Recent political, economic, and social changes in Cuba may have contributed to the nutritional and/or toxic compromise of mitochondrial function of an acquired nature, which led to selective retinal ganglion cell damage. We have termed this condition Cuban epidemic optic neuropathy.

Seroepidemiology of Toxoplasma gondii (Apicomplexa) in meat producing animals in Costa Rica

A serologic screening for Toxoplasma gondii antibodies by IgG indirect fluorescent antibodies test (IgG-IFAT) was carried among 496 swine and 601 cattle serum samples from throughout Costa Rica, to study the possible role of their meat in the transmission of the parasite. The overall prevalence of antibodies was 34.4% in cattle and 43.8% in swine. No significant differences were found in the antibody prevalence between males and females in both animal groups, which acquire the infection early in their lives. Swine did not present significant differences between age groups. In cattle there was a high percent of seropositivity between the first and third years of age. The provinces that showed a greater number of seropositive animals were Limón and Puntarenas for both animals, and Guanacaste for cattle.

The prevalence of hepatitis A, B and C infection among different ethnic groups in Belize

Little is known about the prevalence of infection with hepatitis viruses in Belize, Central America. We conducted a serologic survey among members of the Belize Defence Force (BDF), which is composed of the five major ethnic groups in Belize, to estimate prevalence rates of hepatitis A, B, and C among military-aged men and women in Belize. Of approximately 600 men and women in the BDF, 492 (82%) completed a questionnaire and blood collection. Antibody to hepatitis A was found in 94%, with similar rates by age, sex, rank, and ethnicity. Antibody to hepatitis B core antigen (anti-HBc) was found in 31%. Rates of anti-HBc varied significantly among the ethnic groups with the lowest rates in Mestizo (5%) and Mayan Indians (9%), and significantly higher rates among Creoles (30%) and Garifuna (56%). Rates increased with increasing age from 28% in those 18-24 years old to 35% in those > or = 35 years old (P = 0.07, by chi-square test for trend). Hepatitis B surface antigen was found in 21 (4%) overall. Antibody to hepatitis C was found in two (0.4%). In this young healthy population, exposure to hepatitis A before the age of 18 is almost universal, while exposure to hepatitis B is related to age and ethnic origin.

Natural and induced blood dissemination of Toxoplasma gondii: experimental model in white mice and hamsters

Blood inoculation in mice showed that Toxoplasma organisms circulate in blood after 1 h of oocyst infection. Parasites were detected up to 15 days later and then disappeared from the bloodstream concomitantly with cyst formation in the brain, probably due to antibody presence. Immunosuppression caused by cortisone acetate treatment induced Toxoplasma bloodstream invasion in chronically infected mice and hamsters, causing death in some. Natural dissemination is discussed in relation with congenital toxoplasmosis. Induced immunosuppressive effect is compared with that produced by natural diseases such as Hodgkin, lymphoma, AIDS and others.

Specificity of the carbon immunoassay (CIA) test for the diagnosis of Toxoplasma infections

A rapid and low cost procedure, the carbon immunoassay (CIA) test, was evaluated for the diagnosis of Toxoplasma gondii infections. Using a closely related parasite (Besnoitia jellisoni) as antigen, and homologous or heterologous immune sera, it was demonstrated by light and electron microscopy that CIA is a very reliable and specific test. As it is neither expensive nor time-consuming, it can be recommended for general and routine laboratory use.