Twinning and anencephaly

The literature on anencephaly in twins ascertained in series has been reviewed and some hitherto unpublished data presented. 1. Anencephaly rates in opposite-sexed twin pairs seem not to differ appreciably from those in related singleton births. 2. There is good evidence that the incidence of anencephaly is higher in same-sexed twin pairs than in opposite-sexed pairs. One would infer that anencephaly is commoner in MZ than DZ pairs: this inference is supported by some data on anencephaly in twins of which the zygosity has been diagnosed. It is estimated that members of MZ twin pairs are about 1 2/3 times as likely to be anencephalic as are other individuals. 3. Concordance rates are not low, as is sometimes suggested, but are of the same order as recurrence rates. 4. It seems likely that concordance rates are higher in same-sexed than in opposite-sexed pairs. This would be expected because of the sex-preferential nature of the condition, and the hypothesized higher incidence rates in MZ pairs.     

Twinning in niobium,a continuous nucleation theory

The energy required to form a twin in niobium (columbium) has been experimentally determined to be of the order 10⁹ erg/cm³. This high energy has been explained in terms of a continuous nucleation theory which also accounts for the observed morphology of twins in bcc transition metals and the heat evolved in the process.     

Basic principles of cancer genetics

All cancer can be described as genetic, that is, due to altered DNA. Many of these mutations will be accumulated during the normal division of cells. However, some people may inherit abnormal genes, which predispose those individuals to high risk of certain malignancies. These individuals can sometimes be identified as having a family history of affected individuals, some of which might have early age of onset or multiple malignancies. Specific genes have been identified as being associated with certain of these malignancies. The hereditary cancers include (but are not limited to) ovary, breast, colon, endometrium, and to a lesser extent, prostate, skin and pancreas. Some of these cancer predisposing genes are highly penetrant with up to 80 to 90 percent of gene carriers developing the associated malignancy within a 70 year life expectancy. Molecular testing for the presence of cancer predisposing genes is available for many of the hereditary syndromes. While there currently is no way to correct a mutant gene, early detection and some techniques of chemoprevention are of clinical value. People who fear that they are at high risk only learn that they are not, can benefit from the relief of anxiety through the genetic counseling process.     

The genetics of colorectal cancer

This article reviews the genetic alterations that are thought to play a role in the development of sporadic and hereditary forms of colorectal cancer. It also highlights their potential utility in clinical practice, especially in the field of presymptomatic diagnostic testing for hereditary forms of colorectal cancer.     

Molecular genetics of breast cancer

During 1994, 129 specimens of chub (Leuciscus cephalus L.) from two localities, polluted--Bolelouc, 80th river kilometer, near the city of Olomouc, and unpolluted--Brodské, 225th river kilometer, near the Lanzhot on the Morava river, were examined for metazoan parasites. Altogether 38 metazoan parasite species including helminths, leeches and glochidia belonging to 14 genera were found, 34 in the case of unpolluted locality (Brodské) and 28 in the polluted one (Bolelouc). In both localities, 24 parasite species (Dactylogyrus folkmanovae, D. naviculoides, D. prostae, D. vistulae, D. vranoviensis, Gyrodactylus carassii, G. gasterostei, G. gracilihamatus, G. scardiniensis, G. vimbi, Gyrodactylus sp., Paradiplozoon ergensi, P. homoion, P. megan, Paradiplozoon sp., Caryophyllaeus brachycollis, Diplostomum spathaceum--larval stage, Philometra abdominalis, Acanthocephalus anguillae, Pomphorhynchus laevis and Glochidium sp.) were found, 10 (D. crucifer, D. nanoides, G. hemibarbi, G. lamberti, G. leucisci, G. lomi, P. rutili, C. fennica, A. imitans, S. bramae) were identified solely in the unpolluted locality Brodské and 4 (D. fallax, G. laevis, P. ovata, G. kearni) parasite species were found only in the polluted locality Bolelouc. Differences in parasite species richness, the level of dominance, the structure of core and in satellite species were observed. Current methods of statistical evaluation were used.     

Familial adenomatous polyposis-associated thyroid cancer: a clinical, pathological, and molecular genetics study

The par genes are required to establish polarity in the Caenorhabditis elegans embryo. Mutations in two of these genes, par-3 and par-6, exhibit similar phenotypes. A third gene, pkc-3, gives a similar phenotype when the protein is depleted by RNA interference. PAR-3 and PKC-3 protein are colocalized to the anterior periphery of asymmetrically dividing cells of the germline lineage and the peripheral localizations of both proteins depends upon the activity of par-6. Here we report the molecular cloning of par-6 and the immunolocalization of PAR-6 protein. We found that par-6 encodes a PDZ-domain-containing protein and has homologues in mammals and flies. Moreover, we discovered that PAR-6 colocalizes with PAR-3 and that par-3 and pkc-3 activity are required for the peripheral localization of PAR-6. The localization of both PAR-3 and PAR-6 proteins is affected identically by mutations in the par-2, par-4 and par-5 genes. The co-dependence of PAR-3, PAR-6 and PKC-3 for peripheral localization and the overlap in their distributions lead us to propose that they act in a protein complex.     

Environment-Assisted Cracking of Twinning Induced Plasticity (TWIP) Steel: Role of pH and Twinning

This article presents the study of the environment-assisted cracking (EAC) of twinning induced plasticity (TWIP) steels that possess remarkable combination of strength and ductility. EAC of a high-manganese TWIP steel was investigated, using aqueous solutions of different pH, which provided a mechanistic insight into the combined role of the localized deformation due to twinning and the electrochemical characteristic of the steel. Slow strain rate testing in inert environment as well as in acidic, neutral and alkaline solutions, and the fractography of the failed specimens have suggested a profound role of twinning in EAC crack propagation.     

Molecular genetics of small bowel cancer

Streptococcus adjacens has never previously been reported as an etiologic organism of infective endocarditis in Taiwan. We describe a case of severe native valve endocarditis caused by S. adjacens, involving the mitral valve, the aortic valve, and the left atrium, in a 29-year-old woman with nephrotic syndrome on steroid therapy. Blood cultures yielded gram-positive cocci that grew poorly on blood agar but strongly on chocolate agar. Despite aggressive antibiotic treatment, the patients continued to have high fever and progressive congestive heart failure, which necessitated surgical intervention. Symptoms were alleviated after surgery; teicoplanin was continued for 4 weeks and the patient remained symptom-free at the 6 month follow up. To our knowledge, this is the first reported case of bacterial endocarditis involving the left atrium without preexisting myxoma.     

The molecular genetics of pancreatic cancer

Exaggerated blood pressure (BP) response to exercise in normotensive subjects is considered as a predictor of future hypertension. The aim of the study was to find out whether elevated BP response to exercise is associated with any other haemodynamic, metabolic or hormonal abnormalities. Abnormal BP response to exercise, i.e. systolic BP (SBP) > 200 mmHg at 150 W or lower workload, was found in 37 out of 180 normotensive, male students, aged 20-24 years. Fifteen students with elevated exercise BP (group E) volunteered for further examinations. Their resting and ambulatory BP showed high normal values. Eight of them had a family history of hypertension. Four subjects met the criteria of cardiac hypertrophy. Significant correlations were found between exercise SBP and left ventricular mass index, average 24 h and daytime SBP recordings. In comparison with normal subjects of the same age (group N, n = 13), those from group E did not differ in body mass index, plasma lipid profile, fasting glucose, insulin and catecholamine (CA) concentrations, but had increased erythrocyte sodium content, slightly elevated plasma renin activity and cortisol level. During exercise, E subjects showed greater cardiac output (CO) increases with normal heart rate, total peripheral resistance (TPR) and plasma CA. There were no significant differences between groups in haemodynamic and plasma CA responses to posture change from supine to standing. Glucose ingestion (75 g) caused smaller increases in CO and smaller decreases in TPR in E than in N subjects without differences in BP, blood glucose plasma insulin and CA. It is concluded that young normotensive men with exaggerated BP response to exercise show some other characteristics that may be considered as markers of predisposition to hypertension or factors promoting the development of hypertension.     

Clinical and research issues in breast cancer genetics

Breast cancer is the most common form of cancer in women in the U.S. The risk factors for developing breast cancer include increasing age, a family history of breast cancer, and the lack of a child by age 30. A substantial fraction of breast cancer, however, occurs in women who have no identifiable risk factors. The diagnosis, pathology, treatment, and presymptomatic testing of cancer susceptibility genes are reviewed. Syndromes with an associated risk of breast cancer are described, such as hereditary breast-ovarian cancer syndrome, Li-Fraumeni syndrome, ataxia telangiectasia, and Cowden's disease. With the localization of the BRCA1 gene to chromosome 17q21 and the BRCA2 gene to chromosome 13q12, issues surrounding breast cancer susceptibility genetic testing are assuming an ever greater measure of importance. The sensitivity and specificity for molecular testing of cancer susceptibility genes, however, have not been well defined. The progress in presymptomatic genetic testing is further hampered by various factors such as the technical difficulty in distinguishing mutations from polymorphisms, the number of different mutations identified thus far and the possibility of false positive and false negative results. Laboratory quality assurance/quality control issues are of paramount importance to avoid misleading interpretations. Many issues surrounding genetic screening and testing, such as insurance and employment discrimination, privacy, and informed consent, are under active debate, and guidelines and standards are under active development. It is therefore important to proceed with caution, so that irreversible harm resulting from data misinterpretation can be avoided.     

Ovarian cancer: an update on genetics and therapy

This article reviews the important aspects of the management of both early and advanced ovarian cancer with a particular emphasis on genetic predisposition and recent and anticipated advances in treatment.     

Earnings, education, genetics, and environment

A major and well-recognized difficulty in estimating the effects of education on earnings is that the more educated are likely to be more able, irrespective of education. If ability also determines earnings and is not controlled, ordinary least squares will yield biased estimates of the education coefficient. In this study, we use data on identical twins to control for differences in ability that arise from genetic endowments and family environment. Not controlling for genetics and family environment may cause a large bias, up to two-thirds of the noncontrolled coefficient.