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Biomedical subjects

C A Weber

Publications and source records attributed to C A Weber.

At least 37 records · Page 2Linked to original sources
PubMed1994

Trichothiodystrophy: clinical spectrum, central nervous system imaging, and biochemical characterization of two siblings.

Trichothiodystrophy (TTD), an autosomal recessive disorder characterized by sulfur-deficient brittle hair, identifies a group of genetic disorders with an altered synthesis of high-sulfur matrix proteins and a defect in excision repair of ultraviolet damage in fibroblasts of most TTD patients. In contrast to patients with xeroderma pigmentosum (XP), TTD patients do not have an increased frequency of skin cancers. TTD patients may be grouped into four categories: 1) those without photosensitivity and without a defect in excision repair of UV damage; 2) those without photosensitivity and with an excision-repair defect in the same gene as in XP-D (complementation group D); 3) those with photosensitivity and with the XP-D repair defect; 4) those with photosensitivity and with a repair defect distinct from that in XP-D. We present a brother and sister in the third category of TTD. Clinically, the patients have brittle hair, short stature, ichthyosis, photosensitivity, nail and dental dysplasias, cataracts, mental retardation, and pyramidal tract abnormalities. Diagnosis was made by hair mount, which shows the characteristic banding pattern with polarizing microscopy, and by hair amino acid analysis, which demonstrated decreased high-sulfur matrix proteins. Fibroblasts cultured from skin biopsies had a marked DNA excision repair defect similar to the repair defect seen in XP-D. We have documented a unique dysmyelinating disorder on magnetic resonance imaging of the brain that might explain their mental retardation, marked hyperactivity, and neurologic deficits. Following the discovery that the human excision repair cross complementing rodent ultraviolet group 2 (ERCC2) gene is able to correct the ultraviolet sensitivity of XP-D cell strains, the ERCC2 cDNA from previous TTD patients was sequenced and shows frameshifts, deletions and point mutations in the ERCC2 gene. Molecular analysis of our patients is in progress. Molecular analysis of the defects in ERCC2 in clinically distinct patients with XP,XP/Cockayne's syndrome, and TTD may provide insight into the molecular mechanisms of these genetically related but clinically distinct disorders.

Brain↗
PubMed1992

A Rorschach study of attachment and anxiety in inpatient conduct-disordered and dysthymic adolescents.

We investigated the constructs of attachment and anxiety in inpatient conduct-disordered and dysthymic adolescents. Texture, diffuse shading, and pure human content (Exner, 1986) Rorschach indices were compared between 48 subjects who met the criteria for conduct disorder and 30 subjects who met the criteria for dysthymia, according to the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev. [DSM-III-R]; American Psychiatric Association, 1987). We also compared mild, moderate, and severe conduct-disorder groups on the three selected Rorschach variables and investigated certain family characteristics for the two groups. We found a lower frequency of texture and pure human content responses in conduct-disordered subjects and a greater frequency of diffuse shading responses in the dysthymic subjects. The conduct-disordered subjects also came from homes in which the mother figure was significantly less present. Our psychometric findings of lessened attachment and diminished anxiety in the conduct-disordered adolescents are similar to adult psychopaths. We urge that an attachment or socialization disturbance criterion be reintroduced into the forthcoming DSM-IV conduct-disorder diagnosis.

Adolescent↗
PubMed1990

ERCC2: cDNA cloning and molecular characterization of a human nucleotide excision repair gene with high homology to yeast RAD3.

Human ERCC2 genomic clones give efficient, stable correction of the nucleotide excision repair defect in UV5 Chinese hamster ovary cells. One clone having a breakpoint just 5' of classical promoter elements corrects only transiently, implicating further flanking sequences in stable gene expression. The nucleotide sequences of a cDNA clone and genomic flanking regions were determined. The ERCC2 translated amino acid sequence has 52% identity (73% homology) with the yeast nucleotide excision repair protein RAD3. RAD3 is essential for cell viability and encodes a protein that is a single-stranded DNA dependent ATPase and an ATP dependent helicase. The similarity of ERCC2 and RAD3 suggests a role for ERCC2 in both cell viability and DNA repair and provides the first insight into the biochemical function of a mammalian nucleotide excision repair gene.

Amino Acid Sequence↗
PubMed1990

Cyclobutane-pyrimidine dimer excision in UV-sensitive CHO mutants and the effect of the human ERCC2 repair gene.

Using a radiochromatographic assay, we have examined cis-syn cyclobutane-pyrimidine dimer removal after ultraviolet irradiation in cell lines representative of the first 6 complementation groups of Chinese hamster ovary DNA nucleotide excision repair mutants. AA8, the CHO cell line from which these mutants were derived, consistently showed normal dimer excision for a rodent cell. The mutants uniformly exhibited no significant dimer excision within the limits of determination. Additionally, V-H1, a mutant belonging to complementation group 2 and derived from V79 hamster cells, exhibited no dimer excision. Two UV5 derived transformants that carry the complementing human ERCC2 repair gene showed a capacity for dimer excision comparable to the AA8 wild-type cells.

Animals↗
PubMed1990

Depletion of tissue glutathione with diethyl maleate enhances hyperbaric oxygen toxicity.

Rats exposed to hyperbaric hyperoxia experience severe central nervous system and lung toxicity. Exogenous glutathione administration has been shown to protect rats from the effects of hyperbaric hyperoxia. To explore the hypothesis that decreases in tissue glutathione (GSH) could increase the susceptibility of rats to hyperbaric hyperoxia, we administered diethyl maleate (DEM) (a compound that conjugates with GSH and rapidly lowers tissue levels) and measured tissue GSH levels. DEM administration decreased plasma GSH by 86%, liver GSH by 82%, and brain GSH by 45% between 2 and 4 h after injection with values returning to normal by 24 h. We then treated rats with DEM or saline and began exposure at 2 h after treatment to 100% oxygen at 4 ATA. Time-to-convulsion and time-to-death were recorded. Rats that received DEM 2 h before exposure seized earlier and died earlier than controls. Intraperitoneal administration of GSH to DEM-treated rats abolished the enhanced toxicity occurring during a hyperbaric hyperoxic exposure. DEM appears to increase the toxicity of rats exposed to hyperbaric hyperoxia by lowering tissue GSH levels, and replenishment of lung and brain GSH by exogenous administration reverses these effects.

Animals↗
PubMed1990

A long-range restriction map of the human chromosome 19q13 region: close physical linkage between CKMM and the ERCC1 and ERCC2 genes.

We report on the physical ordering of genes in a relatively small area of chromosome 19, segment q13, containing the locus for myotonic dystrophy (DM), the most frequent heritable muscular dystrophy of adulthood in man. DNAs from somatic cell hybrids with der 19q products that carry a breakpoint across the muscle-specific creatine kinase (CKMM) gene were analyzed by Southern blotting using probes for CKMM, APOC2, and the repair genes ERCC1 and ERCC2. Results were combined with data from CHEF and field inversion-gel-electrophoresis separation of large-sized DNA restriction fragments to establish a map localizing both DNA-repair genes and the CKMM gene within the same 250 kb of DNA, the order being cen-CKMM-ERCC2-ERCC1-ter, with APOC2 being at more than 260 kb proximal to CKMM. Transcriptional start sites of the CKMM and DNA-repair genes are all on the telomeric side of the genes. Our results provide a framework for the construction of a larger physical map of the area, which will facilitate the search for the DM gene.

Animals↗
PubMed1989

Complementation of repair gene mutations on the hemizygous chromosome 9 in CHO: a third repair gene on human chromosome 19.

A human DNA repair gene, ERCC2 (Excision Repair Cross Complementing 2), was assigned to human chromosome 19 using hybrid clone panels in two different procedures. One set of cell hybrids was constructed by selecting for functional complementation of the DNA repair defect in mutant CHO UV5 after fusion with human lymphocytes. In the second analysis, DNAs from an independent hybrid panel were digested with restriction enzymes and analyzed by Southern blot hybridization using DNA probes for the three DNA repair genes that are located on human chromosome 19: ERCC1, ERCC2, and X-Ray Repair Cross Complementing 1 (XRCC1). The results from hybrids retaining different portions of this chromosome showed that ERCC2 is distal to XRCC1 and in the same region of the chromosome 19 long arm (q13.2-q13.3) as ERCC1, but on different MluI macrorestriction fragments. Similar experiments using a hybrid clone panel containing segregating Chinese hamster chromosomes revealed the hamster homologs of the three repair genes to be part of a highly conserved linkage group on Chinese hamster chromosome number 9. The known hemizygosity of hamster chromosome 9 in CHO cells can account for the high frequency at which genetically recessive mutations are recovered in these three genes in CHO cells. Thus, the conservation of linkage of the repair genes explains the seemingly disproportionate number of repair genes identified on human chromosome 19.

Animals↗
PubMed1989

Hypermagnesemia. A potential complication during treatment of theophylline intoxication with oral activated charcoal and magnesium-containing cathartics.

Toxic reaction to theophylline compounds is common. Oral activated charcoal (OAC) is a widely accepted mode of therapy for management of moderate to severe cases of theophylline toxicity. Magnesium-containing cathartics are generally recommended in conjunction with OAC in the treatment of drug or toxin ingestions. We report two cases of hypermagnesemia complicating the treatment of theophylline toxicity with OAC and magnesium citrate. In both patients, the hypermagnesemia contributed significantly to morbidity or mortality. In light of these cases and after review of the literature, we suggest that sorbitol be considered the cathartic agent of choice in the treatment of theophylline toxicity with OAC.

Aged↗
PubMed1989

Utility of the Wang 18-gauge transbronchial histology needle in the staging of bronchogenic carcinoma.

Use of the Wang 18-gauge histology needle in TBNA was employed as a staging procedure in 29 patients with bronchogenic carcinoma and mediastinal adenopathy demonstrated on chest CT. Twenty patients had malignant aspirates; 12 had both histologic and cytologic specimens demonstrating malignancy; six patients had malignant histologic specimens; two had cancerous cytologic specimens as their only evidence of mediastinal disease. Of the nine negative aspirates, four were true negative at surgery. Five patients had false-negative aspirates. Overall sensitivity of the Wang 18-gauge histology needle in the mediastinal staging of patients with bronchogenic carcinoma was 80 percent. When patients with small cell carcinoma were excluded, sensitivity was 82 percent. The enhanced yield of the 18-gauge histology needle warrants its use in mediastinal staging of bronchogenic carcinoma. We conclude that all patients with bronchogenic carcinoma and mediastinal adenopathy demonstrated on chest CT accessible via TBNA should undergo histology needle aspiration as an initial staging procedure.

Biopsy, Needle↗
PubMed1988

Molecular cloning and biological characterization of a human gene, ERCC2, that corrects the nucleotide excision repair defect in CHO UV5 cells.

The UV-sensitive Chinese hamster ovary (CHO) cell line UV5, which is defective in the incision step of nucleotide excision repair, was used to identify and clone a complementing human gene, ERCC2, and to study the repair process. Genomic DNA from a human-hamster hybrid cell line was sheared and cotransferred with pSV2gpt plasmid DNA into UV5 cells to obtain five primary transformants. Transfer of sheared DNA from one primary transformant resulted in a secondary transformant expressing both gpt and ERCC2. The human repair gene was identified with a probe for Alu-family repetitive sequences. For most primary, secondary, and cosmid transformants, survival after UV exposure showed a return to wild-type levels of resistance. The levels of UV-induced mutation at the aprt locus for secondary and cosmid transformants varied from 50 to 130% of the wild-type level. Measurements of the initial rate of UV-induced strand incision by alkaline elution indicated that, whereas the UV5 rate was 3% of the wild-type level, rates of cosmid-transformed lines were similar to that of the wild type, and the secondary transformant rate was about 165% of the wild-type rate. Analysis of overlapping cosmids determined that ERCC2 is between 15.5 and 20 kilobases and identified a closely linked gpt gene. Cosmids were obtained with functional copies of both ERCC2 and gpt. ERCC2 corrects only the first of the five CHO complementation groups of incision-defective mutants.

Animals↗
PubMed1987

Recent progress with the DNA repair mutants of Chinese hamster ovary cells.

Repair-deficient mutants of Chinese hamster ovary (CHO) cells are being used to identify human genes that correct the repair defects and to study mechanisms of DNA repair and mutagenesis. Five independent tertiary DNA transformants were obtained from the EM9 mutant, which is noted for its very high sister-chromatid exchange frequencies. In these clones a human DNA sequence was identified that correlated with the resistance of the cells to chlorodeoxyuridine (CldUrd). After EcoRI digestion, Southern transfer, and hybridization of transformant DNAs with the BLUR-8 Alu family sequence, a common fragment of 25-30 kilobases (kb) was present. Since the DNA molecules used to produce these transformants were sheared to less than 50 kb in size, the correcting gene should be small enough to clone in a cosmid vector. Using drug-resistance markers to select for hybrids after fusion, we have done complementation experiments with ultraviolet light (u.v.)-sensitive mutants and have identified a sixth complementation group, line UV61. Additionally, CHO mutants UV27-1 and MMC-2, isolated in other laboratories, were found to belong to UV group 3, which is represented by line UV24. To study the behaviour of transfected DNA molecules in repair-deficient cells, we treated plasmid pSV2gpt with either u.v. radiation or cis-diamminedichloroplatinum(II) (cis-DDP) and introduced the damaged DNA into normal CHO cells (AA8) and mutants UV4 and UV5. Unrepaired damage to the plasmid was indicated by loss of colony-forming ability of the transfected cells in selective medium containing mycophenolic acid. With u.v. damage, the differential survival of the cell lines was similar to that seen when whole cells are treated with u.v. However, with cis-DDP damage, mutant UV4 did not exhibit the extreme hypersensitivity (50-fold) that occurs when cells are treated. This result suggests that UV4 cells may be able to repair cross-links in transfected DNA.

Animals↗
PubMed1987

Comparative effects of hypertension and nicotine on injury-induced myointimal thickening.

Although hypertension has been shown to increase myointimal thickening after arterial injury, a similar effect of nicotine has not been demonstrated. To compare the influence of nicotine with the known effect of hypertension, a standard balloon catheter injury was created in the aortas of four groups of experimental animals. A preliminary group (P) (n = 11) consisted of adult Wistar Kyoto rats used to determine the degree of denudation and the time course of arterial healing; group I (n = 10) consisted of adult Wistar Kyoto rats; group II (n = 13) consisted of spontaneously hypertensive rats; and group III (n = 16) consisted of Wistar Kyoto rats fed nicotine. Endothelial denudation was achieved after an identical injury with an aortic balloon catheter; completeness of denudation was confirmed in group P with Evans blue stain. Injured vessels were fixed by perfusion at 2- and 9-week intervals. Intima to media (I/M) ratios were measured at 82 points per animal by use of light microscopy. Computer-assisted statistical analysis was performed with the t test and Wilcoxon nonpaired rank sum test. Serum nicotine levels were maintained in group III at 73.3 +/- 36.7 ng/ml, which is comparable to levels in human smokers. There were no significant differences in I/M ratios between any of the groups at 2 weeks. At 9 weeks both groups II and III had significantly higher I/M ratios than did control subjects (p = 0.039). The nicotine-treated group had greater myointimal thickening than did the hypertensive animals (p = 0.02). Since there was no hypertension or tachycardia in nicotine-treated rats, we postulate that our data reflects the desquamating effect of nicotine.

Animals↗
PubMed1986

DNA repair genes of mammalian cells.

In the Chinese hamster ovary (CHO) cell line, various mutations affecting DNA repair have been obtained. Mutants that belong to 5 genetic complementation groups for ultraviolet (UV) sensitivity and resemble the cells from individuals having the cancer-prone genetic disorder xeroderma pigmentosum (XP) were previously identified. Each mutant is defective in the incision step of nucleotide excision repair and hypersensitive to bulky DNA lesions. These UV mutants can be divided into two subgroups; only Groups 2 and 4 are extremely sensitive to mitomycin C and other DNA cross-linking agents. The clear-cut phenotypes of the CHO mutants have allowed us to construct hybrid cells by fusion with human lymphocytes and thereby identify which human chromosomes carry genes that correct the CHO mutations. The first two mutations analyzed, UV20 (excision-repair deficient; UV Group 2) and EM9, which has a very high frequency of sister chromatid exchange (SCE), are both corrected by chromosome 19. Efforts are underway to isolate complementing repair genes by DNA-mediated gene transfer. The human gene that corrects mutant EM9 and the hamster gene that corrects UV135 (UV Group 5) have been introduced by cotransfer of genomic DNA and the dominant selectable marker gpt (guanine phosphoribosyltransferase) gene. In each case, the DNA repair function was co-selected based on resistance to 5-chlorodeoxyuridine (CldUrd) or repeated UV irradiation, respectively. The presence of a functional human repair gene in the EM9 transformants is shown by the presence of common human DNA sequences on some fragments produced by restriction enzyme cleavage. In UV135, transfer of a repair gene is indicated by a colony distribution containing "jackpots" and by instability of the resistant phenotype.

Animals↗