Multiple left-right asymmetry defects in Shh(-/-) mutant mice unveil a convergence of the shh and retinoic acid pathways in the control of Lefty-1.
(41/1527)
Asymmetric expression of Sonic hedgehog (Shh) in Hensen's node of the chicken embryo plays a key role in the genetic cascade that controls left-right asymmetry, but its involvement in left-right specification in other vertebrates remains unclear. We show that mouse embryos lacking Shh display a variety of laterality defects, including pulmonary left isomerism, alterations of heart looping, and randomization of axial turning. Expression of the left-specific gene Lefty-1 is absent in Shh(-/-) embryos, suggesting that the observed laterality defects could be the result of the lack of Lefty-1. We also demonstrate that retinoic acid (RA) controls Lefty-1 expression in a pathway downstream or parallel to Shh. Further, we provide evidence that RA controls left-right development across vertebrate species. Thus, the roles of Shh and RA in left-right specification indeed are conserved among vertebrates, and the Shh and RA pathways converge in the control of Lefty-1. (+info)
Magnetic resonance imaging. Application to family practice.
(42/1527)
OBJECTIVE: To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. QUALITY OF EVIDENCE: Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. MAIN MESSAGE: For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. CONCLUSIONS: With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients. (+info)
Multivitamin supplementation and risk of birth defects.
(43/1527)
It is widely accepted that supplementation with folic acid, a B vitamin, reduces the risk of neural tube defects (NTDs). This case-control study tested the hypothesis that multivitamins reduce risks of selected birth defects other than NTDs. Infants with and without birth defects and aborted fetuses with birth defects were ascertained in the greater metropolitan areas of Boston, Philadelphia, and Toronto during 1993-1996. Mothers were interviewed within 6 months after delivery about a variety of factors, including details on vitamin use. Eight case groups were included: cleft lip with or without cleft palate, cleft palate only, conotruncal defects, ventricular septal defects, urinary tract defects, limb reduction defects, congenital hydrocephaly, and pyloric stenosis (n's ranged from 31 to 186). Controls were 521 infants without birth defects (nonmalformed controls) and 442 infants with defects other than those of the cases (malformed controls). Daily multivitamin supplementation was evaluated according to gestational timing categories, including periconceptional use (28 days before through 28 days after the last menstrual period). Odds ratios (ORs) below 1.0 were observed for all case groups except cardiac defects, regardless of control type. For periconceptional use, ORs with 95% confidence intervals that excluded 1.0 were estimated for limb reduction defects using both nonmalformed controls (OR = 0.3) and malformed controls (OR = 0.2) and for urinary tract defects using both nonmalformed controls (OR = 0.6) and malformed controls (OR = 0.5). Statistically significant ORs for use that began after the periconceptional period were observed for cleft palate only and urinary tract defects. These data support the hypothesis that periconceptional vitamin supplementation may extend benefits beyond a reduction in NTD risk. However, other than folic acid's protecting against NTDs, it is not clear what nutrient or combination of nutrients might affect risk of other specific defects. (+info)
Prenatal diagnosis and selective abortion: a challenge to practice and policy.
(44/1527)
Professionals should reexamine negative assumptions about the quality of life with prenatally detectable impairments and should reform clinical practice and public policy to improve informed decision making and genuine reproductive choice. Current data on children and families affected by disabilities indicate that disability does not preclude a satisfying life. Many problems attributed to the existence of a disability actually stem from inadequate social arrangements that public health professionals should work to change. This article assumes a pro-choice perspective but suggests that unreflective uses of prenatal testing could diminish, rather than expand, women's choices. This critique challenges the view of disability that lies behind the social endorsement of such testing and the conviction that women will or should end their pregnancies if they discover that the fetus has a disabling trait. (+info)
Ethnicity, bioethics, and prenatal diagnosis: the amniocentesis decisions of Mexican-origin women and their partners.
(45/1527)
Bioethical standards and counseling techniques that regulate prenatal diagnosis in the United States were developed at a time when the principal constituency for fetal testing was a self-selected group of White, well-informed, middle-class women. The routine use of alpha-fetoprotein (AFP) testing, which has become widespread since the mid-1980s, introduced new constituencies to prenatal diagnosis. These new constituencies include ethnic minority women, who, with the exception of women from certain Asian groups, refuse amniocentesis at significantly higher rates than others. This study examines the considerations taken into account by a group of Mexican-origin women who had screened positive for AFP and were deciding whether to undergo amniocentesis. We reviewed 379 charts and interviewed 147 women and 120 partners to test a number of factors that might explain why some women accept amniocentesis and some refuse. A woman's attitudes toward doctors, medicine, and prenatal care and her assessment of the risk and uncertainty associated with the procedure were found to be most significant. Case summaries demonstrate the indeterminacy of the decision-making process. We concluded that established bioethical principles and counseling techniques need to be more sensitive to the way ethnic minority clients make their amniocentesis choices. (+info)
What is the leading cause of infant mortality? A note on the interpretation of official statistics.
(46/1527)
OBJECTIVES: According to vital statistics reports, congenital malformation is the leading cause of infant death in the United States and accounts for a much greater proportion of infant mortality than does premature birth. The purpose of this study was to examine the potential underestimation of prematurity-related mortality in current vital statistics reports. METHODS: National mortality data from 1985, 1991, and 1996 were analyzed. RESULTS: The official statistics significantly understate the role of prematurity-related mortality. An alternative etiology-based classification designates prematurity as the underlying cause in approximately one third of all infant deaths. CONCLUSIONS: Although no single scheme is suitable for every objective, analysts and policymakers should recognize the degree to which technical classification practices can influence the apparent importance of various causes of death. (+info)
Failure to pass meconium: diagnosing neonatal intestinal obstruction.
(47/1527)
Timely passage of the first stool is a hallmark of the well-being of the newborn infant. Failure of a full-term newborn to pass meconium in the first 24 hours may signal intestinal obstruction. Lower intestinal obstruction may be associated with disorders such as Hirschsprung's disease, anorectal malformations, meconium plug syndrome, small left colon syndrome, hypoganglionosis, neuronal intestinal dysplasia and megacystis-microcolon-intestinal hypoperistalsis syndrome. Radiologic studies are usually required to make the diagnosis. In addition, specific tests such as pelvic magnetic resonance imaging, anorectal manometry and rectal biopsy are helpful in the evaluation of newborns with failure to pass meconium. (+info)
Role of rubella in congenital malformations in India.
(48/1527)
In the present study rubella HI antibodies were determined in cases of congenital malformation and bad obstetric history to determine the role of rubella in such cases in India, as it has been reported to be rare in Japan in contrast to Western countries. The incidence of antibodies was statistically significant in cases of congenital eye, C.N.S., visceral and miscellaneous malformations and cases of spontaneous abortion and still-birth compared with controls of matching age groups. This is further supported by the demonstration of IgM antibodies in seven cases of congenital malformations and ten cases of spontaneous abortion. Our findings show that congenital rubella is not rare in India. (+info)