Exposure and dose in panoramic radiology

Panoramic radiology entrance skin exposure (ESE) was measured for a Siemens Orthopantomograph 10 E using a thimble chamber and TLDs. Thimble chamber measurements are shown to be inaccurate for the moving, narrow beam panoramic scan geometry due to partial volume and partial charged-particle equilibrium effects. For 75 KVp, 8 mA panoramic scans the TLD measured beam central ray ESE on the scan central plane (patient midsagittal plane) was an approximately constant 20 mR for the first 7.5 cm from the entrance slit. A theoretical model of central plane ESE for a fixed rotation center agrees very well with the TLD measurements and is consistent with all of the known ESE (and dose) properties near rotation centers. Head phantom skin dose measurements demonstrate the dependence of skin dose on exact equipment mode of use and patient anatomy. Central plane, beam central ray ESE is judged to be a convenient, universal measure of panoramic radiology radiation output.

Radiation exposure during skeletal traction treatment of pediatric femoral fractures

Radiation-exposure data during femoral fracture management has not been previously reported. We report a retrospective analysis of radiation exposure in 45 patients aged 5-12 years (average, 8.3) with isolated femoral shaft fractures treated by 90/90 degrees femoral skeletal traction. Group I had 32 patients aged 5-9 years (average, 7.3), and group II had 13 patients of an average age of 10.7 years. Total average radiation dose before casting was 0.699 rads and was independent of age and gender. In addition to potential complications of tractions and increased hospital stay with attendant fiscal and psychosocial burdens, radiation exposure with this type of management, in this series, was significant.

Diffraction effects in hydrophone measurements

Theoretical and experimental methodology are presented for accurately determining the effective radii of unfocused, circular plane piston transducers as well as using tone burst hydrophone measurements to verify steady-state theoretical calculations. Experiments using two specially fabricated unfocused, composite piezoelectric transducers demonstrate the validity of the methodology. For spherically focused circular transducers, a simple model is used to estimate the transient diffraction encountered in co-axial flat hydrophone measurements.

Issues involving biomarkers in the study of the genetics of human cancer

The investigation of hereditary factors in human cancer was suggested from kindreds that exhibited aggregations of cancer consistent with Mendelian inheritance. A subset of cancer that exhibits strong familial tendencies is due to single genes that 'cause' cancer; more commonly, hereditary factors may influence tumorigenesis in a stepwise probabilistic rather than deterministic manner through a variety of mechanisms, e.g. influencing the disposition of carcinogens. The roles of both common susceptibility genes and rare 'familial' cancer genes are receiving increasing attention in the general population. Population-based studies designed to examine more common genetic variants differ from linkage-based studies. Candidate susceptibility genes may be studied by phenotype or genotype approaches, and the relative advantages and disadvantages of each approach are considered. The issue of gene-environment interaction, implicit in the concept of susceptibility genes, is considered. The influence of genetic factors on individual and attributable risk is addressed.

Caffeine dependence in schoolchildren?

Schoolchildren (N = 289) kept a log and calculated their habitual caffeine consumption (principally in soft drinks). On 2 successive days, they completed a 20-item checklist adapted from the Profile of Moods Scale. On Day 2, they abstained from caffeine. Complete data were obtained for 175 children. A low-consumption group (10 mg or less daily) was compared with a high-consumption group (50 mg or more daily). The high-consumption group reported more stimulation than did the low-consumption group on Day 1 and more dysphoric symptoms during abstinence on Day 2. The results of this open-label pilot trial suggest that a large-scale double-blind placebo-controlled trial would be worthwhile.

Migration, fertility, and state policy in Hubei Province, China

Despite China's one-child family planning policy, the nation experienced a slight rise in the birth rate in the mid-1980s. Many observers attributed this rise to the heightened fertility of those rural-to-urban migrants who moved without a change in registration (temporary migrants), presumably to avoid the surveillance of family planning programs at origin and destination. Using a sequential logit analysis with life-history data from a 1988 survey of Hubei Province, we test this possibility by comparing nonmigrants, permanent migrants, and temporary migrants. While changing family planning policies have a strong impact on timing of first birth and on the likelihood of higher-order births, migrants generally do not have more children than nonmigrants. In fact, migration tends to lower the propensity to have a child. More specifically, the fertility of temporary migrants does not differ significantly from that of other women.

A peptide derived from an extracellular domain selectively inhibits receptor internalization: target sequences on insulin and insulin-like growth factor 1 receptors

Certain peptides derived from the alpha1 domain of the major histocompatibility class I antigen complex (MHC-I) inhibit receptor internalization, increasing the steady-state number of active receptors on the cell surface and thereby enhancing the sensitivity to hormones and other agonists. These peptides self-assemble, and they also bind to MHC-I at the same site from which they are derived, suggesting that they could bind to receptor sites with significant sequence similarity. Receptors affected by MHC-I peptides do, indeed, have such sequence similarity, as illustrated here by insulin receptor (IR) and insulin-like growth factor-1 receptor. A synthetic peptide with sequence identical to a certain extracellular receptor domain binds to that receptor in a ligand-dependent manner and inhibits receptor internalization. Moreover, each such peptide is selective for its cognate receptor. An antibody to the IR peptide not only binds to IR and competes with the peptide but also inhibits insulin-dependent internalization of IR. These observations, and binding studies with deletion mutants of IR, indicate that the sequence QILKELEESSF encoded by exon 10 plays a key role in IR internalization. Our results illustrate a principle for identifying receptor-specific sites of importance for receptor internalization, and for enhancing sensitivity to hormones and other agonists.

Lack of phospholipase A2 mutations in neuroblastoma, melanoma and colon-cancer cell lines

A candidate murine tumor-suppressor gene, Mom1, has been identified as the secretory phospholipase A2 (GDB nomenclature: PLA2G2A) gene. Evidence suggests that PLA2G2A functions as a tumor-suppressor because mice lacking PLA2G2A expression demonstrate increased colonic polyposis. The human homologue of PLA2G2A has been mapped to chromosome 1p36, a region frequently implicated in the pathogenesis of neuroblastoma, colon cancer and melanoma. We identified 2 alterations in the PLA2G2A gene in a single neuroblastoma cell line out of 20 examined; however, we found no mutations in 24 melanoma cell lines, 12 lymphoblastoid cell lines from patients having chromosome 1-linked familial melanoma and 10 colon cancer cell lines. Secretory phospholipase A2 is unlikely to play a significant role in the pathogenesis of these tumors.

Characterization of a YAC contig containing the NBCCS locus and a novel Kruppel-type zinc finger sequence on chromosome segment 9q22.3

Gorlin's syndrome or nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by a familial or hereditary predisposition to basal cell carcinomas (generally multiple and of early onset), odontogenic keratocysts (jaw cysts), palmar and plantar pits, a wide variety of developmental defects, as well as cancers such as medulloblastomas and ovarian fibromas. The gene for NBCCS has been mapped to human chromosome region 9q22.1-q31 by linkage analysis and by cytogenetic evidence of deletions in this region in patients with the syndrome. This is supported by loss of heterozygosity in tumors of polymorphic marker loci flanked by D9S197 and D9S180. We have utilized sequence tagged site (STS) mapping and somatic cell hybrid panel analysis to construct two overlapping yeast artificial chromosome (YAC) contigs spanning this region of the genome. We used the YAC contigs to identify a new zinc finger gene containing a highly informative microsatellite locus.

Imaging of pelvic postpartum complications

Differentiation between endometritis and RPOC in febrile postpartum patients is commonly requested by clinicians. Sonography is the screening technique of choice to assess the endometrial contents. For cases in which the retained placenta is calcified or still has demonstrable blood flow, a specific diagnosis of RPOC can be made. In more complicated cases, a CT scan or an MR image may be requested. In addition to evaluating the uterus and any intra- or extrauterine fluid collections, attention must be paid to the ovarian veins to exclude the diagnosis of ovarian vein thrombosis.

Molecular analysis of chromosome 9q deletions in two Gorlin syndrome patients

Gorlin syndrome is an autosomal dominant disorder characterized by multiple basal cell carcinomas, medulloblastomas, ovarian fibromas, and a variety of developmental defects. All affected individuals share certain key features, but there is significant phenotypic variability within and among kindreds with respect to malformations. The gene (NBCCS) maps to chromosome 9q22, and allelic loss at this location is common in tumors from Gorlin syndrome patients. Two recessive cancer-predisposition syndromes, xeroderma pigmentosum group A (XPAC) and Fanconi anemia group C (FACC), map to the NBCCS region; and unusual, dominant mutations in these genes have been proposed as the cause of Gorlin syndrome. This study presents cytogenetic and molecular characterization of germ-line deletions in one patient with a chromosome 9q22 deletion and in a second patient with a deletion of 9q22-q3l. Both have typical features of Gorlin syndrome plus additional findings, including mental retardation, conductive hearing loss, and failure to thrive. That Gorlin syndrome can be caused by null mutations (deletions) rather than by activating mutations has several implications. First, in conjunction with previous analyses of allelic loss in tumors, this study provides evidence that associated neoplasms arise with homozygous inactivation of the gene. In addition, dominant mutations of the XPAC and FACC1 genes can be ruled out as the cause of Gorlin syndrome, since the two patients described have null mutations. Finally, phenotypic features that show variable expression must be influenced by genetic background, epigenetic effects, somatic mutations, or environmental factors, since these two patients with identical alterations (deletions) of the Gorlin syndrome gene have somewhat different manifestations of Gorlin syndrome.

Increased urinary nitrite excretion in children with minimal change nephrotic syndrome

OBJECTIVE

We tested the hypothesis that nitric oxide synthesis by the kidney is increased in children with primary nephrotic syndrome.

METHODS

We examined the urinary excretion of nitrite, a stable metabolite of nitric oxide, using the Griess reaction, in children with nephrotic syndrome.

RESULTS

In comparison with healthy children, patients with minimal change nephrotic syndrome had increased urinary nitrite excretion regardless of whether the disease was in relapse or remission (p < 0.025). In contrast, urinary nitrite excretion was similar in control subjects and patients with focal segmental glomerulosclerosis or IgA nephropathy.

CONCLUSION

These findings indicate that measurement of urinary nitrite excretion may be a useful test to help discriminate between minimal change nephrotic syndrome and focal segmental glomerulosclerosis in children with idiopathic nephrotic syndrome.

Heroin addicts and methadone treatment in Albuquerque: a 22-year follow-up

All heroin addicts who registered for methadone treatment in Albuquerque in 1969-1971, 1019 in all, were the subjects of this follow-up study, conducted in 1991-1993. The cohort was almost entirely of Hispanic (Chicano) ethnicity, 86% male, with median age 27 at entry. We located 776, dead or alive, and we were able to interview 243 concerning many aspects of their lives. At least one-third of the original group had died during the 22-year period, representing standard mortality ratios 4.0 for males and 6.8 for females. Drug overdose, violence, alcohol, or suicide accounted for nearly all deaths of which the causes were known. Despite the availability of treatment, including methadone maintenance, both heroin use and criminality continued at a high rate. Of the 428 known survivors, 48% were currently enrolled in a methadone program after 22 years. They were using significantly less heroin, alcohol, and other drugs (except nicotine) than those not on methadone. Similar beneficial effects of methadone maintenance were reported retrospectively at interview. Our findings offer an insight into heroin addiction as a chronic lifelong relapsing disease with a high fatality rate.

What does it mean to be a cancer gene carrier? Problems in establishing causality from the molecular genetics of cancer

This article addresses the following question: What does it mean to be a cancer gene carrier? The existence of families prone to cancer has prompted an intense search for predisposing heritable gene mutations. Genes that impart susceptibility to colorectal, breast, and ovarian cancers have been recently identified. It is doubtful, however, that the action of a single mutant gene totally accounts for the development of malignant disease. The mutant gene likely causes cancer in these family members only in conjunction with other genes, environmental factors, or both. Furthermore, although an individual carrier of a mutant gene within a cancer-prone family has an increased risk of malignancy, nutritional, pharmacologic, or other interventions may still confer protection. Extrapolations from cancer-prone families to the general population are even more problematic. The excess risk of malignancy among carriers of mutant genes who are not members of cancer-prone families is unknown. Large-scale epidemiologic studies are needed to determine the magnitude (or even the existence) of such excess risk.

Training pediatric residents to prevent tobacco use

OBJECTIVE

To assess the effectiveness and acceptability of incorporating the National Cancer Institute (NCI) Guide to Preventing Tobacco Use During Childhood and Adolescence into pediatric training.

DESIGN

Preintervention and postintervention self-reported surveys for residents receiving training and postintervention baseline surveys for those residents not receiving training. Measures include: (1) a self-reported knowledge, attitude, and behavior survey of residents; and (2) physician behavior reports from parent exit interviews.

SETTING

A hospital-based pediatric residency program and continuity clinic.

SUBJECTS

Pediatric residents and parents of pediatric patients seen for well child examinations.

INTERVENTIONS

Structured NCI smoking cessation curriculum modified for delivery during scheduled teaching activities.

RESULTS

The NCI training was acceptable and perceived as important by residents. Many did not recall receiving the materials or training. Trained residents who remembered the intervention improved their smoking cessation counseling effectiveness. Most patients' parents think it appropriate for physicians to ask; however, most reported not having been asked about smoking or environmental smoke exposure.

CONCLUSIONS

For residents to learn effective prevention counseling strategies, systematic, reinforced preventive educational curricula must become an institutionalized part of residency training.

Cancer genes: single and susceptibility: exposing the difference

'Single' genes, necessary and sufficient to cause cancer, are contrasted with 'susceptibility' genes that are neither, but may act in the presence of specific environmental exposures to alter the chances of cancer in the host. The former are rare, are of high absolute and relative risks, have minimal dependence on exposures and therefore have low population attributable risks. A small number of such genes are well established in the literature and typically exhibit familial aggregations of disease that serve as a starting point for genetic studies. 'Susceptibility' genes, as typified by the pharmacogenetic model, are common, have low relative and absolute risk, are strongly dependent upon exposure, and may have potentially high population attributable risks. Mechanistic and epidemiologic data are suggestive but currently fall short of confirmation for these associations. Familial aggregation is not a prominent feature and epidemiological study designs with careful exposure assessment is the investigative method of choice. Both approaches require interdisciplinary expertise and benefit from advances in molecular biology.

Somatostatin levels during infancy, pregnancy, and lactation: a review

This paper reviews research on somatostatin (SS) levels during infancy, pregnancy, and lactation. Neonates have elevated levels of circulating SS, which reach a peak at the age of 3 months and then decrease gradually, but remain elevated during the first years of life. SS response to feeding is not well developed in newborns. Elevated levels are also found during pregnancy, especially during the late phases. Influence of sucking on maternal SS plasma levels is varied and could be related to vagal stimulation. pH levels, and basal SS levels. SS has been found in high concentrations in maternal milk. Milk-borne SS appears to be protected from proteolysis by milk components, but apparently SS is not absorbed in its intact form through the duodenal wall and its effects could be indirect. More research is needed to determine the regulating role of milk-borne SS and the contribution of SS to development.

Romanticism and self-esteem among pregnant adolescents, adolescent mothers, and nonpregnant, nonparenting teens

Feelings of romanticism and self-esteem among pregnant adolescents, adolescent mothers, and a control group of nonpregnant, nonparenting adolescents were investigated. The Bachman Self-Esteem Scale (Bachman, O'Malley, & Johnston, 1978) and the Dean Romanticism Scale (Dean, 1961) were distributed to 649 U.S. female adolescents--255 pregnant adolescents, 121 adolescent mothers, and 273 teenagers in the control group. For romanticism, the results indicated a significant main effect for group (pregnant teens, teen mothers, and a control group consisting of nonpregnant, nonparenting teenagers) and ethnicity (White, Hispanic, African American, and Asian) but not for age (13 to 15 years and 16 to 19 years). The pregnant teens and teen mothers thus had a higher degree of romanticism than the control group did. For self-esteem, there was a significant main effect for race, but not for group or for age. This main effect was qualified by a significant interaction between ethnicity and age.

Regulation of receptor internalization by the major histocompatibility complex class I molecule

We showed previously that peptides derived from the alpha 1 domain of the major histocompatibility complex class I protein (MHC-I) inhibit internalization of some receptors, thereby increasing the steady-state number of active receptors on the cell surface. In consequence, sensitivity to hormone (e.g., insulin) is enhanced, transport (e.g., of glucose by GLUT-4) is increased, and carrier proteins (e.g., transferrin) operate less efficiently. Now we report that a bioactive peptide (but not closely related inactive ones) binds to MHC-I on the cell surface, not in the groove but apparently to the alpha 1 helix. The binding is saturable, and the number of peptide binding sites on the cell surface approximately equals the number of MHC-I molecules. Antibodies to MHC-I inhibit peptide binding. Most significant, antibodies to MHC-I mimic the effect of a bioactive peptide, inhibiting receptor internalization. These results indicate that MHC-I participates in the regulation of cell surface receptor activity.