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Biomedical subjects

B K Hecht

Publications and source records attributed to B K Hecht.

At least 19 recordsLinked to original sources
PubMed1998

The journal "impact factor": a misnamed, misleading, misused measure.

The Institute for Scientific Information (ISI), a database publishing company that publishes Current Contents and Science Citation Index, has devised and promulgated what it terms the journal "impact factor." ISI describes this factor as a "measure of the frequency with which the 'average article' in a journal has been cited in a particular year." The factor is a ratio between citations and recent citable published items calculated by dividing the number of all current citations of items published in a journal during the preceding 2 years by the number of articles published in those 2 years by that journal. What, if anything, is wrong with the "impact factor"? There is absolutely nothing incorrect with the calculation of the ratio itself. However, the "impact factor" is misnamed and misleading. Being misnamed and misleading, the "impact factor" has been misused. It is being held out as a measure of the importance of a specific journal article and the journal in which the article appeared. By extension, the "impact factor" is also being misused to gauge the relative importance of individual researchers, research programs, and even the institution hosting the research. We recommend that the term "impact factor" be abolished and that this measure be renamed in keeping with its actual role, that merely of a time-specific "citation rate index" and nothing more. What is currently called the "impact factor" should not be misused to evaluate journals or to validate the scientific relevance of a particular researcher or research program, especially in decisions regarding employment, funding, and tenure.

Bibliometrics↗
PubMed1997

Mapping FRA11A, a folate-sensitive fragile site in human chromosome band 11q13.3.

FRA11A, a rare folate-sensitive fragile site assigned to 11q13.3, lies in an area of genomic instability associated with several diseases and amplification events. To map FRA11A, we used fluorescence in situ hybridization with yeast artificial chromosome and cosmid probes on metaphase chromosomes of patients expressing the fragile site. FRA11A was found situated centromeric to ACTN3 and telomeric to D11S913, these markers being within an interval of approximately 1 Mb in the 11q13.3 region.

Cells, Cultured↗
PubMed1997

BCL3 rearrangements and t(14;19) in chronic lymphocytic leukemia and other B-cell malignancies: a molecular and cytogenetic study.

The t(14;19)(q32.3;q13.1) is a recurring translocation found in the neoplastic cells of some patients with chronic lymphocytic leukemia (CLL) or other B-lymphocytic neoplasms. We previously cloned the translocation breakpoint junctions present in the leukemic cells from three such patients and identified a gene, BCL3, whose transcription is increased as a result of the translocation. In the present paper, we describe three additional patients with the t(14;19), one with lymphoma and two with CLL, and report the cloning and sequencing of the breakpoint junction in one of these patients as well as in a previously reported patient. We and others have found that the breakpoints on chromosome 14, with one exception, fall within the switch region upstream of the immunoglobulin heavy chain C alpha 1 or C alpha 2 sequences. Several of the breaks within chromosome 19 fall immediately upstream of the BCL3 gene, but several others are more than 16 kb 5' of the gene. Most patients with CLL and the t(14;19) also show trisomy 12.

Adult↗
PubMed1995

Cytogenetics of malignant gliomas: I. The autosomes with reference to rearrangements.

Autosomal chromosome abnormalities are far from always detectable and, when detected, far from fully consistent in malignant gliomas. In 15 of 41 malignant gliomas, we found autosomal chromosome aberrations ranging from solitary trisomy to a wildly abnormal polyploid complement. The sequence of chromosome events appears to proceed from the normal to the near-diploid state (via structural and numerical changes) to near-tetraploidy (via polyploidization), and finally toward near-triploidy (via chromosome loss and additional rearrangements). Characteristic chromosome changes of trisomy 7 and monosomy 10 were repeatedly found, usually together in the same cell clones. In only one case was trisomy 7 an isolated change. We observed structural rearrangements of chromosomes 7 and 10 which may be of some use in mapping specific genes duplicated or deleted by the whole-chromosome changes of chromosomes 7 and 10. Nonrandom structural changes of other autosomes, including chromosomes 1, 5, and 11, fit with the model of malignant glioma as a process involving multiple genes. An unusual concentration of breakpoints in 12q13, juxtaposing it to at least five other regions, reflects the presence of genetic information in 12q13 important to the development of malignant gliomas.

Adult↗
PubMed1995

Cytogenetics of malignant gliomas. II. The sex chromosomes with reference to X isodisomy and the role of numerical X/Y changes.

Sex chromosomal monosomy with total loss of an X or Y is frequently observed in malignant gliomas. Beyond that, not much is known about the behavior of the sex chromosomes in these tumors. We noted loss of the X from 3 of 13 gliomas from women (23%) compared to loss of the Y from 16 of 28 gliomas from men (57%). There were two structural rearrangements of the Y (an inversion and a translocation with chromosome 4). Most unexpectedly, clones with sex chromosome reversal were encountered in 3 cases. These XX clones in gliomas from men are perforce the consequence of Y loss coupled with X isodisomy, a nonrandom sequence of sex chromosome changes. We examined the company kept by numerical X and Y changes in clones and found that clones with numerical sex chromosome changes had fewer autosomal abnormalities, reflecting a distinct tendency to clonal separation of sex chromosome from autosomal abnormalities. We conclude that the sex chromosome changes are not a necessary part of the neoplastic process in malignant gliomas but that they must be of biologic significance to the brain since they are highly nonrandom in frequency, type, and sequence in brain cells.

Adult↗
PubMed1995

Chromosomes in gliomatosis cerebri.

Gliomatosis cerebri is a rare brain tumor which histologically resembles a diffuse cerebral astrocytoma. It can simultaneously infiltrate multiple sites in the cerebrum, cerebellum, brainstem, and spinal cord. This remarkable diffuseness has led to the idea that gliomatosis cerebri does not derive from a solitary focus but must arise from a broad field of glial cells. We studied the chromosomes from gliomatosis cerebri in a 12-year-old boy by conventional cytogenetics and fluorescence in situ hybridization (FISH). Aside from normal cells, we found a majority of cells with the karyotype 44,XY,del(6)(q25),del(14)(q21), der(15;21)(q10;q10),add(18)(q22),del(19)(p12),add(20)(p13),-21. A smaller proportion of cells had 88 chromosomes with a doubling of this abnormal karyotype. These findings are consistent with a clonal neoplasm stemming from a single cell. The chromosome changes we observed, with the possible exception of the chromosome 6 deletion, did not resemble those frequently found in astrocytomas. Gliomatosis cerebri may therefore belong to a separate category of brain tumors.

Brain Neoplasms↗
PubMed1993

Prenatal detection of de novo paracentric inversion 46, XX inv (14) (q22q32.1) in a normal child: report and review of the literature.

We present prenatal diagnosis and follow-up examination of an individual with a de novo paracentric inversion of the long are of chromosome 14. A literature search documented 19 other cases of paracentric inversion of 14q. The outcome of each of these cases is specified together with that of this current case. Four of the 20 cases, all XY, manifested significant abnormalities with mental retardation and microcephaly present in 3 of the 4 cases; 15% (2/13) of familial cases had abnormalities and 40% (2/5) of de novo cases had abnormalities.

Adult↗
PubMed1993

Direct molecular diagnosis of myotonic dystrophy.

Myotonic dystrophy (DM) arises from an unstable trinucleotide (CTGn) repeat sequence within the DM locus at 19q13.3. Twenty-three myotonic dystrophy families containing 205 persons with no symptoms, minimal manifestations, classic DM or congenital DM were investigated to validate the application of the pM10M6 probe to direct molecular diagnosis. Affected family members had been diagnosed clinically and the unaffected family members had been assigned carrier probabilities close to either zero or 100%, using closely linked flanking markers. Southern analysis identified all 89 DM gene carriers as having expansions of the unstable element. PstI detected all small expansions of the repeat sequence as easily seen discrete bands; but large expansions were usually seen as diffuse smears, sometimes difficult to distinguish from lane background. EcoRI concentrated these diffuse smears, associated with somatic instability, into discrete bands which were easy to detect; but it did not resolve the smaller expansions present in 9 (10%) of the DM carriers. It is essential that PstI and EcoRI gels are run in parallel to detect all DM gene carriers. The extent of expansion of CTG correlated with age of onset and disease severity. Biopsies of various fetal tissues from two terminated pregnancies confirmed the diagnosis obtained by CVS and revealed no heterogeneity between tissues at this developmental stage. Further expansion occurred during the culture of CVS cells, indicating that direct prenatal diagnosis needs to be carried out on CVS tissue rather than on cultured cells. The intergenerational change of the repeat sequence from DM parent to DM offspring showed a significant parental sex difference for those parents with large expansions. Contraction of the unstable element was observed in the three males carrying the largest expansions and could explain why congenital DM is exclusively of maternal origin.

Female↗
PubMed1992

X;6 translocation in a child with congenital acute lymphocytic leukemia.

A case of congenital acute lymphoblastic leukemia (ALL) displayed an X;6 translocation. This is the third reported case of ALL with an X;6 translocation. In addition, two of the three ALL cases occurred during infancy, at ages 2 months and newborn, and both translocations involved the band q15-16 region of chromosome 6. Anomalies of the long arm of chromosome 6, mainly interstitial and terminal deletions, have been reported as a recurrent karyotypic event in a significant number of ALL cases. The molecular basis and propensity of an X;6 rearrangement in this case of congenital ALL is unclear and merits further investigation. The similarities in this case and the other infant ALL case cited suggest that an X;6 rearrangement with a breakpoint in bands q15-16 of chromosome 6 is characteristic of a form of congenital ALL.

Bone Marrow↗