TAP genes and immunity

The transporter associated with antigen processing (TAP) is a member of the ATP-binding cassette transporter family that specializes in delivering cytosolic peptides to class I molecules in the endoplasmic reticulum. The TAP is a major target of genetic alteration in tumours and disruption by viral inhibitors. In some species, TAP genes have co-evolved with MHC class I molecules to deliver peptides that are customised for particular alleles. In humans, MHC class I polymorphism determines the level of tapasin-mediated association with TAP and subsequent peptide optimisation within the peptide-loading complex (PLC). MHC class I molecules that still load peptides without complexing to the TAP might be more resistant to viral interference of the PLC and less sensitive to competition for TAP by other class I allotypes.     

Tumor genes and their proteins in cytologic and surgical specimens: Relevance and detection systems

Oncogenesis is the consequence of a series of genetic alterations that allow unrestrained cellular growth, tissue invasion, and eventual metastases. Tumor-related genes can be classified into functional categories. Proto-oncogenes/oncogenes have a stimulatory role in cell growth, and the inactivation of cancer-suppressor genes/antioncogenes results in the loss of cell cycle regulation. More recently, three other groups of tumor-related genes have been recognized. They include the antiapoptosis genes which protect from programmed cell death, the antimetastasis genes, and multidrug resistance genes. Besides aiding in tumor diagnosis, the detection of such tumor-associated genes and their products allows the identification of individuals with an inherited predisposition to neoplastic growths, and the overexpression of many of these oncogene products has been shown to be a potential marker of tumor behavior and a predictor of treatment outcome and response. The ability to utilize DNA and RNA probes for nucleic acid hybridization and polymerase chain reaction procedures in cell and tissue preparations of solid tumors and lymphoid proliferations expands and complements the information provided by immunohistochemical techniques. These probes allow direct visualization and correlation of specific genes and their protein products with cytomorphologic features, and form a powerful addition to the armamentarium of the cytopathologist and surgical pathologist. © 1995 Wiley-Liss, Inc.     

A reciprocal translocation (X;11) in a female with gonadal dysgenesis

A 24-year-old female patient was referred for evaluation of primary amenorrhea. Endocrine studies showed elevated gonadotropins, consistent with gonadal failure. At laparoscopy, a normal nulligravid uterus, normal fallopian tubes, and bilateral streak gonads were observed. Histologic studies showed that the left gonad consisted entirely of fibrous tissue, confirming the presence of streak gonads. Chromosome banding studies of peripheral blood and cultures of tissue from the left gonad demonstrated a 46,X,rcp(X;11)(q22;q13) karyotype. A review of reports of X-autosome reciprocal translocations indicated that abnormal gonadal development is associated with break-points in the mid-region of the long arm of the X chromosome.     

Perceived access to health care and its influence on the prevalence of behavioral risks among urban African Americans

INTRODUCTION: Individuals who have difficulty gaining access to health care may delay seeking and obtaining treatment, underutilize preventive health care services, and may have a high prevalence of chronic disease risks. This report examines participant perception of the level of difficulty encountered when obtaining medical care and its influence on the prevalence of chronic disease behavioral risks among urban African Americans. RESULTS: We found a significantly higher prevalence of current cigarette smoking and alcohol consumption among African Americans who reported that they experienced difficulty in obtaining medical care than among those who did not. Compared to those who experienced no difficulty obtaining care, participants who perceived a high level of difficulty in obtaining care were less likely to have had a physical exam in the past year and to have seen the same doctor when services were obtained. CONCLUSION: The perception of a high level of difficulty obtaining health care may be associated with a higher prevalence of behavioral risks for chronic disease. The limited data suggest a need to more closely examine the perception of health care accessibility and its relationship to health services utilization and the prevalence of chronic disease behavioral risks.     

Quality assurance in screening strategies

The pre-requisites for successful screening programmes include understanding and acceptance of the necessity for tests with achieved high coverage of those at risk for the disease, provision of screening tests, provision of facilities for treatment of abnormalities, and acceptance by women of the necessity for further investigation of abnormalities, all requiring attention to quality assurance. Screening programmes for cancer of the cervix have been very effective in many developed countries but in very few developing countries. In general, the failures in developing countries can be directly related to failure to achieve adequate quality in one or other component of a programme. Some of these failures occur at the level of the laboratory, but in several Latin American countries, there are superb laboratories, but overall the programme has failed to achieve the expected impact. In some countries this has led to alternatives to the cytology smear being evaluated, without recognition that it is not the test that has failed, but another essential component of an effective programme. The solution is attention to management and organisation at all levels, with quality assurance at each. This is required at the level of: definition of the target population, identification of the individual women in the target population, recruitment of the at risk woman to screening, administration of the screening test, laboratory examination of the test, communication of results from the laboratory to the woman and her physician, ensuring the woman attends for investigation and management of abnormal screening tests, ensuring adequate therapy of lesions identified by the diagnostic process, ensuring adequate follow-up of treated women, ensuring women with negative screening tests return for re-screening at the appropriate intervals, and monitoring and evaluation of the programme.     

Comparison of Discrete Cardiovascular Fitness Groups on Plasma Catecholamine and Selected Behavioral Responses to Psychological Stress

Discrete cardiovascular fitness groups consisting of high-fit (n=10) and low-fit (n=9) men performed a well-learned vigilance task and their self-report, performance, and plasma catecholamine responses were compared. No significant differences were observed between the fitness groups on self-report or psychomotor performance responses to the vigilance task. However, the low-fit group took significantly longer than high-fit subjects to complete the first of three sets of anagrams administered immediately after the vigilance task. Plasma norepinephrine but not epinephrine response was greater in the low-fit group compared to their high-fit counterparts. The findings indicate that enhanced cardiovascular fitness may be characterized by an attenuated plasma norepinephrine response to a vigilance task with sustained cognitive performance subsequent to the task.     

Potential modifier role of the R618Q variant of proalpha2(I)collagen in type I collagen fibrillogenesis: in vitro assembly analysis

An arginine to glutamine substitution in the triple helix of proalpha2(I)collagen (R618Q) was first reported in a patient with a variant of Marfan syndrome and later identified in conjunction with a second mutation in a patient with osteogenesis imperfecta (OI). The presence of the R618Q proalpha2(I)collagen allele in unaffected or mildly affected family members suggests that the R618Q allele is either a non-affecting polymorphism or a potential genetic modifier. Conservation of arginine618 across species and fibrillar collagen types suggests it is functionally significant. To investigate the functional significance of the R618Q proalpha2(I)collagen allele, we isolated type I collagen from cultured dermal fibroblasts of control and two unrelated individuals heterozygous for the R618Q proalpha2(I)collagen allele and evaluated helical stability and fibrillar assembly. Type I collagen thermal stability analyzed by protease susceptibility and CD spectroscopy demonstrated no statistical difference between control and R618Q containing collagen molecules. In vitro fibril assembly analyses demonstrated that R618Q containing collagen exhibits rapid fibrillar growth with minimal fibril nucleation phase. Further, electron microscopy demonstrated that the diameter of assembled R618Q containing collagen fibrils was approximately 20% of control collagen fibrils. These findings suggest the R618Q variant does not impact triple helical stability but has a role in collagen fibril assembly, supporting the hypothesis that the R618Q proalpha2(I)collagen variant is a modifier of connective tissue structure/function and is potentially involved in disease pathogenesis.