Colonization levels of Streptococcus mutans between mother and infant: a postnatal prospective cohort study.

OBJECTIVE: To investigate the possible association between maternal S. mutans levels and those of the infant during the period between birth and 5 months and evaluate possible risk factors in the S mutans colonization. STUDY DESIGN: A prospective cohort study was carried out comprising 62 infants and their mothers, selected at the time of childbirth. For each infant, a sample swab was taken at 0, 15, 30, 90, and 150 days postpartum; on the same days, a sample was obtained from the mothers. TYCSB medium was employed for identifying the microorganism, which was later confirmed by Gram staining, the catalase activity test, and the API strep test. RESULTS: The final total sample consisted of 60 infants, from which S. mutans was detected in only 2 (3%) at the 150th day of oral sample collection. Of the sample of 60 mothers, 54 exhibited colonization levels. CONCLUSIONS: In the studied sample pairs up to 150 days, it was not possible to demonstrate the presence of a direct relationship between maternal S. mutans oral levels.

[Hereditary sensory and autonomic neuropathy type II A: early neurological and skeletal findings]. / Neuropatía sensitiva autonómica hereditaria tipo IIA: manifestaciones neurológicas y esqueléticas tempranas.

The hereditary sensory and autonomic neuropathies are genetic disorders characterized by the loss of sensation including pain, tactile and temperature. Its clinical and molecular features vary widely; the symptoms may begin from birth or be noticed in the first or second decade, with different types of complications of trauma to the extremities such as ulcers, mutilations and acral amputations. They are classified into six groups from I to VI, determined by the abnormality in eleven genes leading to phenotypic variations in the age of onset and the presence or absence of dysautonomia signs. With the exception of type I, all are autosomal recessive. The type II of these neuropathies is characterized by insensitivity to pain, heat and proprioception. We describe three members of a Mexican family with WNK1 gene mutation that caused hereditary neuropathy IIA.

Isolation and characterization of mammalian cell lines carrying suppressible mutations.

To obtain animal cell lines carrying nonsense mutations and the corresponding suppressors, we used a "supersuppressor" selection strategy on the CHO cell line. The wild-type strain is resistant to the aminopterin present in HAT medium (i.e., it is HATr) because it contains the enzymes hypoxanthine-guanine phosphoribosyl transferase (HPRT) and thymidine kinase (TK), whereas both HPRT- mutants - selected by their resistance to 6-thioguanine (TGr) - and TK- mutants - selected by their resistance to 5-bromodeoxyuridine (BrdUrdr) - are HATs. Therefore, from HPRT- TK- double nonsense mutants, whose phenotype would be TGr BrdUrdr (HATs), simultaneous HPRT+ TK+ double phenotypic revertants could be obtained by selecting HATr (TGs BrdUrds) variants carrying the corresponding nonsense supersuppressors. Through ethylmethane sulfonate (EMS) mutagenesis of the CHO cell line we obtained 65 TGr variants, 53 of which were HATs and the rest HATr. Among 36 TGr (HATs) variants tested, 23 did not revert to HATr, 4 reverted spontaneously and with EMS, and 9 reverted only with EMS. Some of the latter were probably HPRT- nonsense mutants because they were very stringent (had less than 2% of wild-type [3H]hypoxanthine incorporation and HPRT enzyme activity), and did not complement genetically. The introduction of a second marker (BrdUrdr) in 7 of these strains allowed us to isolate 29 TGr BrdUrdr (HATs) double drug-resistant lines. Through one-step mutagenesis and selection in HAT medium, from two double resistant strains we could isolate HATr (TGs BrdUrds) wild-type phenotypic revertants, each of which probably carries suppressible HPRT and TK nonsense (or missense) alleles and the corresponding supersuppressor. Our strategy could now be extended to obtain variants carrying suppressors in other cell lines.

Exposure to arsenic and lead and neuropsychological development in Mexican children.

This cross-sectional study examined the effects of chronic exposure to lead (Pb), arsenic (AS) and undernutrition on the neuropsychological development of children. Two populations chronically exposed to either high (41 children) or low (39 children) levels of As and Pb were analyzed using the Wechsler Intelligence Scale for Children, Revised Version, for México (WISC-RM). Geometric means of urinary arsenic (AsU) and lead in blood (PbB) were 62.9+/-0.03 (microgAs/g creatinine) and 8.9+/-0.03 (microg/dl) for the exposed group and 40.2+/-0.03 (microgAs/g creatinine) and 9.7+/-0.02 (microg/dl) for the reference group. The height for age index (HAI) was used as an indicator of chronic malnutrition and sociodemographic information was obtained with a questionnaire. Lead and arsenic were measured by atomic absorption spectrophotometry. Data on full, verbal, and performance intelligence quotients (IQ) scores, long-term memory, linguistic abstraction, attention span, and visuospatial organization were obtained through the WISC-RM. After controlling for significant potential confounders verbal IQ (P<0.01) decreased with increasing concentrations of AsU. The HAI correlated positively with full-scale and performance IQ (P<0.01). Higher levels of AsU were significantly related to poorer performance on WISC-RM factors examining long-term memory and linguistic abstraction, while lower scores in WISC-RM factors measuring attention were obtained at increasing values of PbB. Our results suggest that exposure to As and chronic malnutrition could have an influence on verbal abilities and long-term memory, while Pb exposure could affect the attention process even at low levels.