Prognostic factors and secondary malignancies in childhood medulloblastoma

PURPOSE

Little is known of the outcome of long-term survivors of childhood medulloblastoma, one of the most common pediatric malignancies. To determine the potential for secondary malignancies, a retrospective outcome evaluation in 88 consecutive cases of childhood medulloblastoma was performed.

PATIENTS AND METHODS

The records of all patients with childhood medulloblastoma diagnosed at Children's National Medical Center in Washington, DC from 1969 through 1997 were reviewed.

RESULTS

The median follow-up time was 92 months (range 6-257 months). Overall survival was 59% at 5 years and 52% at 10 years. Univariate analysis showed that age at diagnosis, extent of surgical resection, presence of metastatic disease (M stage), ventriculoperitoneal shunt placement within 30 days from diagnosis, posterior fossa radiation therapy dose, and adjuvant chemotherapy significantly affected survival. Although based on small numbers, the risk of second neoplasms was significantly increased in this cohort. Multiple basal cell carcinomas developed in the areas of radiation therapy in two patients; these patients also had nevoid basal cell carcinoma syndrome (NBCCS) diagnosed. One other patient died of glioblastoma multiforme 8 years after treatment of medulloblastoma. A meningioma developed in another patient 10 years after radiation therapy.

CONCLUSION

As survival of medulloblastoma patients improves, increased surveillance regarding secondary malignancies is required, especially because radiation-induced tumors may occur many years after treatment. These two cases of NBCCS also illustrate the importance of considering the concomitant diagnosis of NBCCS in young patients with medulloblastoma. In those patients, alternative therapy should be considered to minimize radiation therapy-related sequelae.

Allelic loss on chromosome bands 13q11-q13 in esophageal squamous cell carcinoma

Allelic loss on chromosome 13 occurs frequently in esophageal squamous cell carcinoma. However, studies of the two known tumor suppressor genes located on 13q, RB1 and BRCA2, have shown few mutations, suggesting that other genes are likely to be involved in the development of this tumor type. To identify a minimal deletion interval, we first analyzed 42 microsatellite markers spanning chromosome bands 13q11-q13 in 56 esophageal squamous cell carcinoma patients, including 34 with a family history of upper gastrointestinal cancer and 22 without a family history of cancer. Lifestyle risk factors and clinical/pathologic characteristics were also collected. Two commonly deleted regions were identified: one was located on band 13q12.11, between markers D13S787 and D13S221; the other was located on bands 13q12.3-q13.1 from markers D13S267 to D13S219. We observed higher allelic loss frequencies for eight of the microsatellite markers in those patients with a family history of upper gastrointestinal cancer compared to patients without such a history. This study suggests that one or more unidentified tumor suppressor genes are located on chromosome arm 13q that play a role in the development of esophageal squamous cell carcinoma.

A common founder for the V126D CDKN2A mutation in seven North American melanoma-prone families

One of the most common melanoma-related CDKN2A mutations reported in North America is the V126D mutation. We examined nine markers surrounding CDKN2A in three American and four Canadian families carrying the V126D mutation. All seven families had a haplotype consistent with a common ancestor/founder for this mutation. In addition, the mutation appears to have originated 34-52 generations ago (1-LOD-unit support interval 13-98 generations).

Frequent inactivation of the TP53 gene in esophageal squamous cell carcinoma from a high-risk population in China

Esophageal squamous cell carcinoma (ESCC) is one of the most common fatal cancers worldwide, and north central China has some of the highest rates in the world. Previous studies from tumors in this area of China have shown high frequencies of allelic loss on chromosome 17p13-11, which includes the region where the TP53 gene is found. We examined 56 ESCC patients using single-strand conformation polymorphism and DNA sequencing to assess the frequency and spectrum of TP53 mutation and the association between allelic loss at microsatellite marker TP53 and TP53 mutations. Ninety-six % of cases were found to have at least one genetic alteration, including TP53 mutation (77%), allelic loss within the TP53 gene (73%), and/or loss of heterozygosity at the TP53 microsatellite marker (80%); 75% had two or more such alterations, including 59% with both a point mutation and an intragenic allelic loss ("two hits"). The majority of mutations observed were in exon 5, where the most common type of nucleotide substitution was a G:C-->A:T or C:G-->T:A transition, including half that occurred at CpG sites. Allelic loss was most commonly found in exon 4 but was very common in exon 5 as well. Taken together, the multiple genetic alterations of TP53 in this population at high risk for ESCC indicate that there is a very high degree of genetic instability in these tumors, that TP53 is a primary target for inactivation, and that this tumor suppressor gene plays a critical role in the carcinogenesis process for ESCC.

Counter-matching in studies of gene-environment interaction: efficiency and feasibility

The interest in studying gene-environment interaction is increasing for complex diseases. However, most methods of detecting gene-environment interactions may not be appropriate for the study of interactions involving rare genes (G:) or uncommon environmental exposures (E:), because of poor statistical power. To increase this power, the authors propose the counter-matching design. This design increases the number of subjects with the rare factor without increasing the number of measurements that must be performed. In this paper, the efficiency and feasibility (required sample sizes) of counter-matching designs are evaluated and discussed. Counter-matching on both G: and E: appears to be the most efficient design for detecting gene-environment interaction. The sensitivity and specificity of the surrogate measures, the frequencies of G: and E:, and, to a lesser extent, the value of the interaction effect are the most important parameters for determining efficiency. Feasibility is also more dependent on the exposure frequencies and the interaction effect than on the main effects of G: and E: Although the efficiency of counter-matching is greatest when the risk factors are very rare, the study of such rare factors is not realistic unless one is interested in very strong interaction effects. Nevertheless, counter-matching appears to be more appropriate than most traditional epidemiologic methods for the study of interactions involving rare factors.

Chordoma: incidence and survival patterns in the United States, 1973-1995

BACKGROUND

Chordoma, a rare tumor arising from notochordal remnants, has been described to date only by single-institution case series or small population-based surveys.

METHODS

We used data from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute, 1973-1995, to calculate age-adjusted incidence and survival rates for 400 cases of microscopically confirmed chordoma and to derive information regarding case distribution and risk of second cancer.

RESULTS

The age-adjusted chordoma incidence rate (IR) of 0.08 per 100,000 was age-dependent, more common in males (IR 0.10) than females (IR 0.06) and rare among patients aged <40 years and blacks. Within the axial skeleton 32% of cases were cranial, 32.8% spinal and 29.2% sacral. Young age (<26 years; p = 0.0001) and female sex (p = 0.037) were associated with greater likelihood of cranial presentation. There was no overall increased risk for second primary cancers after chordoma. Median survival was 6.29 years; 5- and 10-year relative survival rates were 67.6% and 39.9%, respectively. Comparison with other bone sarcomas revealed racial disparities in incidence for the two developmental tumors, chordoma and Ewing's sarcoma.

CONCLUSIONS

This study provides new data regarding incidence and survival patterns of chordoma in the US. Additional epidemiologic studies are required to elucidate the genetic and environmental determinants underlying this rare, distinctive neoplasm.

High frequency allelic loss on chromosome 17p13.3-p11.1 in esophageal squamous cell carcinomas from a high incidence area in northern China

Allelic loss on chromosome 17p has been reported frequently in esophageal squamous cell carcinoma (ESCC) and generally encompasses the p53 locus at 17p13.1. However, a good correlation between allelic loss on 17p and mutation of p53 has not been found. This suggests the possibility that unknown tumor suppressor genes near p53 may be involved in the development of ESCC. To evaluate this possibility, we analyzed 30 microsatellite markers covering the entire short arm of chromosome 17 in 56 ESCC patients from a high risk population in northern China, including 34 with a family history of upper gastrointestinal (UGI) cancer and 22 without a family history of any cancer. Cancer lifestyle risk factors and clinical/pathological characteristics were also collected. We found frequent allelic loss (>/=65%) at 28 of the 30 markers evaluated in these ESCC patients. The highest frequencies of allelic loss (> or =80%) were found in three smaller regions: deletion region I located at 17p13.3-p13.2 (between D17S849 and D17S1828); deletion region II located at 17p13.2-p13.1 (between D13S938 and TP53); deletion region III located at 17p13.1-p12 (between D17S804 and D17S799). A number of genes have already been identified in these deleted regions, including: OVCA1, OVCA2 and HIC-1 in deletion region I; p53 in deletion region II; ZNF18, ZNF29, ALDH3 and ALDH10 in deletion region III. These results will help us direct future testing of candidate genes and narrow the search region for major new tumor suppressor genes that may play a role in the pathogenesis of ESCC.

Gene-covariate interaction between dysplastic nevi and the CDKN2A gene in American melanoma-prone families

The CDKN2A gene has been implicated in cutaneous malignant melanoma pathogenesis. Although CDKN2A mutations confer substantial risk for melanoma, clinicoepidemiological covariates including dysplastic nevi (DN), total nevi, and solar injury also enhance melanoma risk. To examine the relationship between CDKN2A and these three risk factors, we conducted combined segregation/linkage analysis using the class D regressive logistic model, as implemented in the computer program REGRESS. Genetic and covariate data were collected on 20 American melanoma-prone families, 13 of which had cosegregating CDKN2A mutations. Two types of analyses were conducted. The missing-indicator method used a missing-value indicator, set to 1 for unknown and 0 for known covariate status, and a second variable set to 1 for exposed and 0 for unexposed or unknown. The second method, complete-cases method, coded subjects with missing covariates as unknown for the affection status. The results for both analyses were very similar. Overall, there was a significant improvement in the likelihood when DN, total nevi or both covariates were added to the base model, which included dominant transmission of the CDKN2A gene and a linear increase of risk with the logarithm of age on the logit scale. In contrast, inclusion of solar injury did not significantly improve the likelihood for the base model. Significant evidence for a gene-covariate interaction was detected between DN and CDKN2A when DN was the only covariate in the model (missing-indicator method or complete-cases method) or when both DN and total nevi were in the model (complete-cases method only). Interestingly, in both methods, the odds ratio (OR) for DN was greater in subjects without mutations (OR, 20.1; 95% confidence interval, 4.8-92.8) versus those with CDKN2A mutations (OR, 3.3; 95% confidence interval, 1.1-10.0; complete-cases method). The CDKN2A-DN interaction illustrates the complex etiology of melanoma and needs to be confirmed in a larger sample of families.

Detection of interaction involving identified genes: available study designs

Advances in molecular genetic techniques have led to an increased ability to examine gene-environment interactions. Studies to detect gene-environment interactions are motivated by different situations, including 1) most identified cancer genes having associated lifetime risks less than 100% (i.e., incomplete penetrance), 2) hereditary factors that control the metabolism of carcinogens that may modulate risk of disease as hypothesized in pharmacogenetics, and 3) inconsistent associations across studies between a cancer and a suspected risk factor. The above situations and others have led to increased study of interaction between genetic and environmental factors. Less studied so far, but with increased potential for the future, is interaction between identified genes. Gene-gene interaction studies would also be motivated by the situations described above. Approaches to detect gene-environment and gene-gene interactions are reviewed. Available risk estimates, required types of subjects, and feasibility of the proposed study designs are discussed; efficiency and power for interaction assessment are summarized where available. In general, most designs allow for estimating risk associated with a genetic factor, environmental factor, and interaction effect. Although power and efficiency for detecting interactions have been assessed for specific situations in some of the methods, further investigations are needed to define the efficiency spectra of each design.

Haplotype analysis of two recurrent CDKN2A mutations in 10 melanoma families: evidence for common founders and independent mutations

Germ-line mutations in CDKN2A have been shown to predispose to cutaneous malignant melanoma. We have identified 2 new melanoma kindreds which carry a duplication of a 24bp repeat present in the 5' region of CDKN2A previously identified in melanoma families from Australia and the United States. This mutation has now been reported in 5 melanoma families from 3 continents: Europe, North America, and Australasia. The M53I mutation in exon 2 of CDKN2A has also been documented in 5 melanoma families from Australia and North America. The aim of this study was to determine whether the occurrence of the mutations in these families from geographically diverse populations represented mutation hotspots within CDKN2A or were due to common ancestors. Haplotypes of 11 microsatellite markers flanking CDKN2A were constructed in 5 families carrying the M53I mutation and 5 families carrying the 24bp duplication. There were some differences in the segregating haplotypes due primarily to recombinations and mutations within the short tandem-repeat markers; however, the data provide evidence to indicate that there were at least 3 independent 24bp duplication events and possibly only 1 original M53I mutation. This is the first study to date which indicates common founders in melanoma families from different continents.

Genotype-phenotype relationships in U.S. melanoma-prone families with CDKN2A and CDK4 mutations

BACKGROUND

Two genes have been implicated in the development of cutaneous malignant melanoma (CMM). CDK4 (the gene encoding cyclin-dependent kinase 4, an oncogene) has exhibited germline mutations found in only three melanoma-prone families to date. CDKN2A is a tumor suppressor gene that encodes p16 (which inhibits activity of the cyclin D1-CDK4 complex) with germline mutations detected in 10%-25% of melanoma-prone families, some of whom are also prone to pancreatic cancer.

METHODS

We compared 104 CMM patients from 17 CDKN2A families and 12 CMM case subjects from two CDK4 families. We used nonparametric statistics to test for differences in median age at first CMM diagnosis, numbers of CMMs, and numbers of nevi. The three recurrent mutations were haplotyped. All P values were two-sided.

RESULTS

The median age at CMM diagnosis (P =.70) and the median numbers of CMMs (P =.73) did not differ between CMM case subjects from CDKN2A versus CDK4 families. Assessment of CMM case subjects from CDKN2A families with and without pancreatic cancer revealed no statistically significant differences in median age at diagnosis (P =.80) or in tumor number (P =.24). There was, however, a statistically significant difference in age-adjusted median numbers of nevi (P =.004), and CMM case subjects from CDKN2A families without pancreatic cancer had greater numbers of nevi. Recurrent CDKN2A mutations were a change from valine to aspartic acid at codon 126 (n = 3) and from glycine to tryptophan at codon 101 (n = 3). Six CDKN2A families had pancreatic cancer. Both CDK4 families carried a mutation resulting in an arginine-to-cysteine substitution at codon 24. Analyses of recurrent CDKN2A and CDK4 mutations suggested common haplotypes.

CONCLUSIONS

The recurrent CDKN2A mutations were observed in families with and without pancreatic cancer, which suggests that other factors may be involved in the development of pancreatic cancer. Despite hypothetical differences in the mechanisms of action between CDKN2A and CDK4, clinical factors were indistinguishable between CMM case subjects from CDKN2A versus CDK4 families.

Patterning the heart's left-right axis: from zebrafish to man

Normal left-right asymmetry is highly conserved among vertebrates. Errors in the proper patterning of this axis are believed to lead to congenital anomalies of the heart and abdominal viscera, often with profound clinical consequences. We review briefly the nature of potential signals and signaling sources that lead to the break in left-right symmetry. The evidence suggests that left-right reversal, or homogenization, of these signals may lead to different consequences, and we explain some malpositions and malalignments of the atria, ventricles, and/or outflow tract that are seen in a variety of congenital cardiac diseases. We speculate that there are units of organ assembly responsive to laterality signals, and these units may be driven independently. One crucial source of signals appears to be the notochord and floorplate. In order to examine the clinical relationship of these midline structures to putative disorders of laterality, we review all patients with disturbances of normal laterality seen at the Massachusetts General Hospital over the past 20 years. We find a significant association between laterality defects and anomalies of the spine and other midline structures.

Sib-pair linkage analyses of nuclear family data: quantitative versus dichotomous disease classification

Model-free sib-pair linkage analysis was used to screen 367 highly polymorphic markers for evidence of linkage to a disease, defined either quantitatively (Q1) or dichotomously (AF). Five individual replicates, plus a case family data set containing all families in these replicates with at least one individual with AF, were analyzed. Sib-pair linkage results for Q1 and AF varied considerably among the five replicates and did not consistently detect any of the three underlying major loci, MG1, MG2, and MG3. For the pooled case families, linkage analyses of Q1, but not AF, detected the flanking markers for MG1 and MG2 at the 0.05 and 0.01 levels, respectively. Overall, type 1 error rates were not elevated. The ability to analyze the disease quantitatively (Q1) and construct a data set more appropriate for linkage analysis (case families) enhanced the power to detect at least some of the major loci underlying the disease.

Detecting gene-environment interactions using a case-control design

We assessed the sample size required for detecting gene-environment (G x E) interactions in a case-control study of complex diseases. The results suggest that large numbers of cases and controls will be required to detect G x E interaction for some odds ratio and exposure frequency combinations. These and other results suggest that alternative study designs may be needed to detect G x E interaction particularly with rare genes or uncommon environmental exposures.

Mutation screening of the CDKN2A promoter in melanoma families

Germline mutations of CDKN2A, at 9p21, are responsible for predisposition to melanoma in some families. However, evidence of linkage to 9p21 has been demonstrated in a significant proportion of kindreds with no detectable mutations in CDKN2A. It is possible that mutations in noncoding regions may be responsible for predisposition to melanoma in these families. We have analyzed approximately 1 kb of the CDKN2A promoter upstream of the start codon in an attempt to identify causal mutations in 107 melanoma families. Four sequence variants were detected. Two of these (A-191G and A-493T) did not segregate with disease and were present in a control population at a comparable frequency, indicating that they are unlikely to predispose to melanoma. The A-493T variant appeared to be in linkage disequilibrium with the previously described CDKN2A polymorphism Ala148Thr. The variant G-735A was detected in the control population, but segregation of this variant with melanoma within families could not be discounted. The fourth variant (G-34T), located in the 5' UTR, creates an aberrant initiation codon. This variant appeared to segregate with melanoma and was not detected in a control population. G-34T has recently been identified in a subset of Canadian melanoma families and was concluded to be associated with predisposition to melanoma. The creation of an aberrant initiation site in the 5' UTR may have an important role in carcinogenesis in a small percentage of families; however, mutations in the CDKN2A promoter appear to have a limited role in predisposition to melanoma.

Intracranial calcifications in childhood medulloblastoma: relation to nevoid basal cell carcinoma syndrome

BACKGROUND AND PURPOSE

Medulloblastoma is one of the most common posterior fossa tumors to occur in children. Our purpose was to document the frequency, location, and time of occurrence of intracranial calcifications in cranial CT studies of children with medulloblastoma.

METHODS

We retrospectively reviewed cranial CT studies of 56 patients diagnosed with medulloblastoma from 1983 through 1997 for the presence of intracranial calcifications. The findings were compared with 159 cranial CT studies of patients who were evaluated in the emergency department (control group). Thirty-two patients with medulloblastoma without shunts were compared with 118 patients from the control group without shunts. Similarly, 24 patients with medulloblastoma with shunts were compared with 41 patients from the control group with shunts.

RESULTS

Overall, three (9%) patients with medulloblastoma without shunts, four (16%) patients with medulloblastoma with shunts, and four (10%) patients from the control group with shunts had falx calcification. Only the two children carrying the diagnoses of medulloblastoma and nevoid basal cell carcinoma syndrome, however, had calcification of the falx cerebri shown on the cranial CT scans obtained during the peridiagnostic period. Both were diagnosed with medulloblastoma before the age of 3 years and later developed jaw cysts and multiple basal cell carcinomas in the radiation field.

CONCLUSION

Previous studies have shown that falx calcification is a major component of nevoid basal cell carcinoma syndrome. Our two cases illustrate the importance of considering the diagnosis of nevoid basal cell carcinoma syndrome when falx calcification is present in young patients with medulloblastoma. If the concomitant diagnosis of nevoid basal cell carcinoma syndrome is made, alternative types of therapy should be sought to minimize radiation therapy sequelae.

Lack of germline CDK6 mutations in familial melanoma

Germline mutations in genes encoding several components of the retinoblastoma pathway have been linked with inherited predisposition to melanoma. Most commonly, such mutations involve CDKN2A, a cyclin-dependent kinase inhibitor of two kinases, CDK4 and CDK6, which phosphorylate the retinoblastoma protein (pRB) and thereby promote passage through the G1/S cell-cycle restriction point. Less frequently, germline mutations in the CDK4 gene have also been linked with an increased risk of melanoma. Despite the sequence and functional homology between CDK4 and CDK6, the role of germline mutations in CDK6 in melanoma predisposition is unknown. We detected no CDK6 mutations within the p16 (CDKN2A) binding domain in index cases from 60 melanoma-prone kindreds that lacked germline mutations in the coding regions of either CDKN2A or within the entire CDK4 coding region. We conclude that germline mutations in CDK6 do not make a significant contribution to melanoma predisposition.

Extracardiac anomalies in the heterotaxy syndromes with focus on anomalies of midline-associated structures

The extracardiac defects in patients with heterotaxy have not been examined as extensively as cardiac defects. We found a high incidence of midline-associated defects in 160 autopsied cases of heterotaxy (asplenia, polysplenia, or single right-sided spleen). Fifty-two percent of patients with left-sided polysplenia had a midline-associated defect, as did 45% of those with asplenia. Most common were musculoskeletal or genitourinary anomalies, as well as cleft palate. Fused adrenal glands and anal stenosis or atresia occurred exclusively among patients with asplenia. A midline anomaly was twice as likely to be detected on complete autopsy than from clinical findings alone. Linkage studies should take into account that affected subjects may have isolated subclinical midline defects. The high incidence of midline-associated defects supports the theory that the midline plays a critical role in establishing left-right asymmetry in the body. Comparison of these defects with mouse models of laterality defects suggests that mutations that disrupt the transforming growth factor beta pathway may result in heterotaxy.

Identification of novel regions of allelic loss from a genomewide scan of esophageal squamous-cell carcinoma in a high-risk Chinese population

Esophageal cancer is one of the most common fatal cancers worldwide. Deletions of genomic regions are thought to be important in esophageal carcinogenesis. We conducted a genomewide scan for regions of allelic loss using microdissected DNA from 11 esophageal squamous-cell carcinoma patients with a family history of upper gastrointestinal tract cancer from a high-risk region in north central China. Allelic patterns of 366 fluorescently labeled microsatellite markers distributed at 10-cM intervals over the 22 autosomal chromosomes were examined. We identified 14 regions with very high frequency (>/= 75%) loss of heterozygosity (LOH), including broad regions encompassing whole chromosome arms (on 3p, 5q, 9p, 9q, and 13q), regions of intermediate size (on 2q, 4p, 11p, and 15q), and more discrete regions identified by very high frequency LOH for a single marker (on 4q, 6q, 8p, 14q, and 17p). Among these 14 regions were 7 not previously described in esophageal squamous-cell carcinoma as having very high frequency LOH (on 2q, 4p, 4q, 6q, 8p, 14q, and 15q). The very high frequency LOH regions identified here may point to major susceptibility genes, including potential tumor suppressor genes and inherited gene loci, which will assist in understanding the molecular events involved in esophageal carcinogenesis and may help in the development of markers for genetic susceptibility testing and screening for the early detection of this cancer. Genes Chromosomes Cancer 27:217-228, 2000. Published 2000 Wiley-Liss, Inc.

Identification of novel regions of allelic loss from a genomewide scan of esophageal squamous-cell carcinoma in a high-risk Chinese population

Esophageal cancer is one of the most common fatal cancers worldwide. Deletions of genomic regions are thought to be important in esophageal carcinogenesis. We conducted a genomewide scan for regions of allelic loss using microdissected DNA from 11 esophageal squamous-cell carcinoma patients with a family history of upper gastrointestinal tract cancer from a high-risk region in north central China. Allelic patterns of 366 fluorescently labeled microsatellite markers distributed at 10-cM intervals over the 22 autosomal chromosomes were examined. We identified 14 regions with very high frequency (>/= 75%) loss of heterozygosity (LOH), including broad regions encompassing whole chromosome arms (on 3p, 5q, 9p, 9q, and 13q), regions of intermediate size (on 2q, 4p, 11p, and 15q), and more discrete regions identified by very high frequency LOH for a single marker (on 4q, 6q, 8p, 14q, and 17p). Among these 14 regions were 7 not previously described in esophageal squamous-cell carcinoma as having very high frequency LOH (on 2q, 4p, 4q, 6q, 8p, 14q, and 15q). The very high frequency LOH regions identified here may point to major susceptibility genes, including potential tumor suppressor genes and inherited gene loci, which will assist in understanding the molecular events involved in esophageal carcinogenesis and may help in the development of markers for genetic susceptibility testing and screening for the early detection of this cancer. Genes Chromosomes Cancer 27:217-228, 2000. Published 2000 Wiley-Liss, Inc.

A genome-wide search for loci contributing to smoking and alcoholism

Using the Collaborative Study on the Genetics of Alcoholism (COGA) data, we performed a sib-pair linkage analysis of two smoking-related traits and one alcoholism phenotype. The first trait, EVRNVR, was a dichotomous one we constructed based on epidemiological definitions of smoking. The second trait, PKYRS, used the quantitative pack-year history provided, and the third trait was the COGA alcoholism classification, ALDX1. There was some evidence for linkage of the EVRNVR trait to regions-on chromosomes 6, 9, and 14. Smaller numbers of loci provided nominal evidence for linkage to PKYRS, although some candidate gene regions were identified. The number of loci identified using EVRNVR suggests that a threshold-based phenotype may better identify loci affecting smoking history. Approximately one-third of the loci that showed evidence for linkage to EVRNVR at a nominal significance level (p < 0.01) also showed evidence for linkage to ALDX1. Some of these regions may represent loci increasing vulnerability to both smoking and alcoholism.

Sib-pair linkage analyses of alcoholism: dichotomous and quantitative measures

We hypothesized that a quantitative alcoholism trait would have greater power than the Collaborative Study on the Genetics of Alcoholism (COGA) dichotomous alcoholism traits, ALDX1 and ALDX2, to detect putative alcoholism loci. To test this, we performed nonparametric sib-pair linkage analysis to screen 285 polymorphic autosomal markers for evidence of linkage to ALDX1, ALDX2, and a quantitative trait, QUANT, defined from the 11 COGA latent class variables. We also examined the effects on the analyses of including covariates (sex, age, and pack-years of smoking) and of transforming QUANT (log and square root). ALDX1 and ALDX2 showed the greatest evidence for linkage to markers on chromosome 1, by both the affected sib-pair and the Haseman-Elston tests. Regions of interest were also identified on chromosomes 4, 8, 16, and 17. QUANT showed little evidence for linkage to any chromosomal region, having no more significant results than were expected by chance. Including covariates or transforming QUANT had little effect on the analyses. A quantitative trait based on all 37 latent class variables, with each variable appropriately weighted, may have had more power than QUANT to detect genomic regions of relevance to alcoholism.

Effects of fire fighting uniform (modern, modified modern, and traditional) design changes on exercise duration in New York City Firefighters

Fire departments have replaced traditional uniforms with modern, more thermal protective gear. Although the new uniforms afford superior burn protection, they may reduce work time. Our purpose was to determine if exercise time was (1) reduced by wearing the modern versus traditional uniform, and (2) increased by a design change to a modified modern uniform (T-shirt and short pants rather than a shirt and long pants under the outer uniform). Male firefighters (n = 23; age 27 to 59) performed a maximum exercise test in gym clothes (maximal oxygen consumption = 46 +/- 9 ml/kg/min) and then returned on separate days to exercise using a moderately high intensity, constant work rate treadmill protocol while wearing fire fighting breathing apparatus and each of three uniforms. Firefighters exceeded anaerobic threshold by 1 minute and eventually reached or exceeded maximum heart rate and maximal oxygen consumption. Exercise time in modern (15 +/- 3 min) was significantly less than in traditional (18 +/- 5 min) uniform. Exercise time in modified modern (17 +/- 5 min) was significantly greater than in modern and not significantly different than in traditional uniforms. The rate of change in oxygen consumption and water loss were significantly affected by uniform type, with faster rates in modern compared with modified modern or traditional uniforms. These findings show the impact that design changes have on energy demands and exercise duration.