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D R Jacobson

Publications and source records attributed to D R Jacobson.

At least 19 recordsLinked to original sources
PubMed1995

Detection of K-ras oncogene mutations in bronchoalveolar lavage fluid for lung cancer diagnosis.

BACKGROUND: Lung cancer is the leading cause of cancer deaths in the United States. A long-standing goal of cancer researchers has been to develop tests that would facilitate earlier diagnosis and treatment of lung cancer and thereby decrease mortality from this disease. Because cancer results from the accumulation of a variety of genetic events (e.g., mutations, rearrangements, and deletions) in genes controlling cell growth and differentiation, these changes might serve as diagnostically useful molecular markers. Activation of the K-ras oncogene by point mutations in codon 12, which occurs in many cases of lung adenocarcinoma, may serve as one such clinically useful molecular marker. For detection of K-ras point mutations in bronchoalveolar lavage fluid, in which small numbers of malignant cells are mixed with a population of predominantly genetically normal cells, the sensitivity of commonly used assays for ras mutations risks false-negative results. PURPOSE: By applying a highly sensitive assay, we investigated whether detection of K-ras codon 12 mutations in samples of bronchoalveolar lavage fluid could be clinically useful in diagnosing lung cancer. METHODS: We developed a highly sensitive assay for detecting K-ras codon 12 mutations based on an enriched polymerase chain reaction (PCR) technique. This technique was applied to 87 specimens of bronchoalveolar lavage fluid specimens that were obtained from 86 patients, and associated tumor biopsy specimens obtained from 35 of these patients who underwent diagnostic bronchoscopy for clinically suspected lung cancer. Statistical comparisons were performed by using the two-tailed Fisher's exact test [corrected]. RESULTS: Of 52 patients with confirmed lung cancer, samples of bronchoalveolar lavage fluid from 16 patients contained K-ras codon 12 mutations, including 14 (56%) of 25 patients with lung adenocarcinomas, one (33%) of three with bronchoalveolar carcinomas, one (20%) of five with large-cell carcinomas, and none of the 14 with squamous cell carcinomas. Mutations were detected in four additional cases in which cancer was suspected but had not been histologically confirmed. Tissue samples from 35 of the patients all yielded the identical K-ras codon 12 genotype found in the corresponding samples of bronchoalveolar lavage fluid. No mutation was found in any sample from 30 patients with diagnoses other than non-small-cell lung cancer. Thus, for those cases in which tissue was available and tested, the sensitivity and specificity of detecting K-ras mutations in bronchoalveolar lavage fluid for diagnosing K-ras mutation-positive lung cancer were both 100%. For nine patients, K-ras mutations were detected in bronchoalveolar lavage fluid obtained during otherwise nondiagnostic bronchoscopies. CONCLUSIONS: Our data demonstrate that sensitive detection of K-ras codon 12 mutations can serve as an important adjunct to cytology in the diagnosis of lung cancer. IMPLICATIONS: Detection of these mutations could lead to earlier cancer diagnosis and less need for invasive diagnostic procedures.

Bronchoalveolar Lavage Fluid↗
PubMed1995

Increased prevalence of K-ras oncogene mutations in lung adenocarcinoma.

Reported estimates of ras mutation prevalence in lung adenocarcinoma of 15-24% may be underestimates because of the insensitivity of the assays used. We have devised a rapid, non-radioactive assay for ras mutations, which detects 1 mutant allele/10(3) normal alleles and have used it to study DNA isolated from 53 lung tumor samples (including 28 adenocarcinomas) previously analyzed by PCR/allele specific oligonucleotide hybridization, which is less sensitive. We detected mutations in 13 of 28 samples, including 7 not detected by PCR/allele specific oligonucleotide hybridization. We also found ras mutations in 14 of 25 previously unstudied samples (56%). Our results indicate that the prevalence of K-ras codon 12 mutations in lung adenocarcinoma is higher than previously reported; thus, ras mutations may be more clinically useful as molecular markers for lung cancer than has been appreciated.

Adenocarcinoma↗
PubMed1995

Transthyretin Ser 6 gene frequency in individuals without amyloidosis.

Transthyretin (TTR) Ser 6 was originally described in a Scottish kindred without amyloidosis. This variant, arising from a G-->A transition in codon 6 that destroys an MspI site and creates a BsrI site, was present in none of 50 controls, and was therefore thought to be rare. This variant has subsequently been found in a normal human cDNA liver library and in two unrelated patients with familial amyloidosis and other TTR variants, raising the question whether it is actually a common polymorphism. To address this question, we performed PCR and restriction digestion of 574 DNA samples from people without evidence of amyloidosis or a known family history of amyloidosis. The TTR Ser 6 allele frequency was 33/558 (.060) in Caucasians (including 8/192 (.04) in North American Ashkenazic Jews, 16/218 (.07) in North American non-Jews, and 9/148 (.06) in Portuguese), 3(242 (.01) in African Americans, 0/140 in Africans, and 0/208 in Asians. These data are most suggestive of a single Caucasian founder and the known 25% admixture of "Caucasian" genes in the African-American population. Alternatively, as this variant arose from a transition at a CG dinucleotide "hot spot," it may have arisen on multiple occasions. These data indicate that TTR Ser 6 is a common non-amyloidogenic population polymorphism in Caucasians.

Amyloidosis↗
PubMed1995

Variable-mode helical CT: imaging protocols.

Helical CT provides a rapidly acquired, accurately registered, two-dimensional data set during the phase of maximum vascular and parenchymal enhancement. The z-axis can be covered by using either a single acquisition, single breath-hold technique or by using multiple helical groups with intergroup delays for the patient's breathing. The latter approach, called variable-mode helical CT, allows large z-axis coverage of more than one anatomic region during injection of a single bolus of contrast material. We discuss helical scanning protocols, both single-acquisition and variable-mode, that we have developed for detection of disease involving major blood vessels (pulmonary arteries and aorta), perivascular tissue planes (neck, thorax, and pelvis), and abdominal viscera (liver, pancreas, and kidneys).

Humans↗
PubMed1995

Amyloid fibril composition and transthyretin gene structure in senile systemic amyloidosis.

BACKGROUND: In many different forms of amyloidosis, transthyretin (TTR) comprises the major amyloid fibril protein. In the familial forms, various TTR mutations are linked to disease. This study was designed to characterize the components of the TTR-derived amyloid fibril protein in senile systemic amyloidosis and to determine whether any mutation in the TTR gene was present. EXPERIMENTAL DESIGN: Heart tissues from two patients with advanced senile systemic amyloidosis were studied. Amyloid fibrils were extracted and the amyloid fibril protein purified. The relationship between full-length and fragmented TTR and the amino acid sequence of the TTR were determined. The TTR gene was studied by single-strand conformation polymorphism analysis or direct sequencing. RESULTS: In both cases, the amyloid deposits contained full-length TTR and a complex mixture of TTR fragments. The fragments, most of which had their N-termini at positions 46-52, predominated. No amino acid substitution was identified. The N-terminal fragment (1-45) was not identified in either patient. In each case, the four exons of the TTR gene were of normal sequence. CONCLUSIONS: In familial amyloidosis resulting from deposition of TTR Met 30 (Swedish-type familial amyloidosis), full-length TTR molecules (some mutant) usually predominate, and TTR fragments lacking three of the eight beta-strands (nonmutant) form a major part of the fibril in senile systemic amyloidosis. This may indicate a difference in the fibrillogenesis between these two forms of TTR-derived amyloidosis. We propose that the name senile systemic amyloidosis be used only for normal-sequence TTR amyloidosis occurring in advanced age.

Aged↗
PubMed1994

A double-variant transthyretin allele (Ser 6, Ile 33) in the Israeli patient "SKO" with familial amyloidotic polyneuropathy.

Transthyretin (TTR) isolated from amyloid fibrils from an Israeli patient ("SKO") with familial amyloidotic polyneuropathy has been studied by two groups of investigators. Originally, a position 49 Thr-->Gly substitution was reported; subsequently, a position 33 Phe-->Ile substitution was found instead. We have studied DNA from this patient by single strand conformation polymorphism analysis, restriction analysis, and DNA sequencing. On one allele, exon 2 contained both a T-->A transversion at the first position of codon 33, encoding the previously described Phe-->Ile substitution, and a G-->A transition at the first position of codon 6, encoding a Gly-->Ser substitution. The originally reported position 49 mutation was not encoded in the genomic DNA. This is the first report of a TTR double-variant allele in a patient with TTR amyloidosis.

Alleles↗
PubMed1994

A highly sensitive assay for mutant ras genes and its application to the study of presentation and relapse genotypes in acute leukemia.

Most studies of ras oncogene activation use assays for ras mutations based on the polymerase chain reaction (PCR) of DNA segments containing ras exons 1 and 2, followed by allele-specific oligonucleotide (ASO) hybridization or direct sequencing, which require that to be detectable, a mutation must be present in at least 3-25% of ras alleles. Thus, studies of tissues in which only a fraction of cells contains a ras mutation risk false negative results. To minimize this risk, we have developed a highly sensitive, non-radioactive assay for ras mutations. Ras genes were PCR-amplified using mismatched primers, to introduce restriction sites into products derived from normal alleles. Repeated restriction digestion and PCR enriched for mutant alleles, visualized by agarose gel electrophoresis. Serially diluted DNA samples containing ras mutations demonstrated detection of 1 mutant/10(6) normal alleles (four orders of magnitude more sensitive than PCR/ASO hybridization). This assay was applied to DNA from four patients with relapsed acute leukemia in whom ras mutations present at diagnosis were not detectable by PCR/ASO hybridization at relapse. In one case, the mutation present at diagnosis was demonstrated at relapse. In the others, loss of the mutation was confirmed, at a greatly increased sensitivity. This method is widely applicable to detection of mutant ras alleles admixed with larger numbers of normal alleles.

Alleles↗
PubMed1992

Transthyretin Pro55, a variant associated with early-onset, aggressive, diffuse amyloidosis with cardiac and neurologic involvement.

Mutations in the protein transthyretin cause amyloidosis involving the heart, peripheral nerves, and other organs. A family from West Virginia developed an unusually aggressive form of widespread transthyretin amyloidosis. Single-strand conformation polymorphism analysis revealed a variant in the transthyretin gene, which was found on sequencing to be a T----C transversion at position 2 of codon 55, corresponding to a Leu----Pro substitution. The variant sequence was confirmed by restriction analysis and polymerase chain reaction (PCR)-primer introduced restriction analysis.

Amyloidosis↗
PubMed1992

Radiographic exposure calculator and mammographic dose calculator.

A set of dose calculators has been designed to facilitate quick and easy calculation of surface exposure (or skin dose) for routine radiography and average glandular dose in mammographic studies. Acceptance by technologists has been good, and in two inspections by the Joint Commission for Accreditation of Health Care Organizations, the calculators were deemed adequate to satisfy the diagnostic radiology standards that doses be monitored.

Humans↗
PubMed1992

A specific test for transthyretin 122 (Val----Ile), based on PCR-primer-introduced restriction analysis (PCR-PIRA): confirmation of the gene frequency in blacks.

The variant transthyretin (TTR) allele, TTR (122 Val----Ile), associated with cardiac amyloidosis in blacks, is caused by a G----A transition which destroys a MaeIII site. This variant has previously been detected by PCR around codon 122, followed by MaeIII digestion, but this test is not specific: any of 12 mutations in the MaeIII recognition site, each of which yields a different amino acid change, would also destroy this site. A modification of PCR, termed "PCR-primer-introduced restriction analysis," was used to introduce a new FokI site into the PCR products derived from the variant (122 Ile) but not wild-type (122 Val) allele. This test demonstrated that each of six previously identified MaeIII(-) alleles had lost its MaeIII site because of a G----A transition encoding TTR (122 Val----Ile), confirming that the same TTR variant was present both in 4/177 healthy black individuals and as a homozygous variant in an individual with cardiac amyloidosis.

Alleles↗
PubMed1991

Frequency and genetic background of the position 122 (Val----Ile) variant transthyretin gene in the black population.

Transthyretin (TTR) (122 Val----Ile), caused by a point mutation which destroys a MaeIII restriction site, is associated with cardiac amyloidosis in black individuals. To estimate the frequency of the MaeIII(-) gene in the black population without overt cardiac disease, DNA from 177 black individuals without amyloidosis was amplified by the PCR around TTR codon 122 and was digested with MaeIII. The MaeIII(-) gene frequency was 4/354 (1.1%; 95% confidence interval 0.32%2.7%), suggesting that the variant is relatively common in blacks. HLA genotype testing did not suggest that the TTR (122 Val----Ile) heterozygotes were of a closely related genetic background.

Amino Acid Sequence↗