Biomedical subjects

H Schuster

Publications and source records attributed to H Schuster.

At least 109 records · Page 6Linked to original sources

PubMed1992

Familial defective apolipoprotein B-100: a common cause of primary hypercholesterolemia.

Familial defective apolipoprotein B-100 (FDB) is a recently identified dominantly inherited genetic disorder characterized by a decreased binding of low density lipoprotein (LDL) to the LDL receptor due to defective apo B-100. FDB is caused by a G to A mutation at nucleotide 10,708 in exon 26 of the apo B gene creating a substitution of glutamine for arginine in the codon for amino acid 3500. The arginine (3500)----glutamine mutation has been observed in several populations in North America and Europe with a similar frequency of approximately 1/500 to 1/700. Haplotype analysis has demonstrated that the arginine(3500)----glutamine mutation occurs on the same chromosomal background. The fact that all individuals with FDB are of Caucasian extraction implies that the mutation has its origin in this population. The arginine(3500)----glutamine mutation has a profound impact of varying strength on the plasma LDL cholesterol level, leading to heterogeneous clinical expression comparable to "classic" familial hypercholesterolemia (FH) caused by a defective LDL receptor: tendon xanthoma, premature atherosclerosis and arcus lipoides. The present data suggest that the combination of these clinical features is no longer appropriate for the diagnosis of LDL-receptor-defective FH, but may be a common feature of a defective LDL receptor pathway originating either from defective LDL receptors or from malfunctioning ligand apo B-100.

Apolipoprotein B-100↗

PubMed1992

Allele-specific and asymmetric polymerase chain reaction amplification in combination: a one step polymerase chain reaction protocol for rapid diagnosis of familial defective apolipoprotein B-100.

We have combined the asymmetric polymerase chain reaction (PCR) with allele-specific PCR to detect a single point mutation. A set of two priming oligonucleotides and a third allele-specific primer were used to identify heterozygotes for a G to A mutation at nucleotide 10,708 in the apolipoprotein B (apo B) gene. The system requires neither restriction enzyme digestion nor allele-specific oligonucleotides as conventionally applied for allele-specific hybridization of slot blots. This method clearly allows for the detection of the mutant allele by inspection, after agarose gel electrophoresis of a single PCR reaction. DNA from 40 patients with familial defective apo B-100 due to the G to A mutation at nucleotide 10,708 in the apo B gene and their normal relatives was analyzed. Complete agreement with allele-specific hybridization of slot blots confirms supposition that the system is effective to screen a larger population.

Alleles↗

PubMed1992

Familial defective apolipoprotein B100: clinical characteristics of 54 cases.

Familial defective apolipoprotein B100 (FDB) is a recently identified dominantly inherited genetic disorder, which is characterized by a decreased affinity of low density lipoprotein (LDL) for the LDL receptor. FDB is caused by a G to A mutation at nucleotide 10 708 in exon 26 of the apo B gene creating a substitution of glutamine for arginine in the codon for amino acid 3500. To determine the consequences of the arginine(3500)----glutamine mutation on plasma lipid levels and other clinical features, we have investigated 54 FDB heterozygotes from Germany (24 men, 30 women, mean age 37.2 (4-73) years). The average total cholesterol level in plasma was 308 mg/dl (average LDL-cholesterol 242 mg/dl), which was 116 mg/dl (120 mg/dl) above the 50th percentile of the age and sex-matched controls reported in the LRC population studies (Lipid Research Clinics' Program 1980). Tendon xanthoma and arcus lipoides were present in 25.9% and 22.2% of the patients, respectively. Plaques in the carotid arteries, determined by duplex scanning, were present in 38.9%, and coronary artery disease was present in 22.2%. This study shows that the combination of tendon xanthoma, arcus lipoides and premature atherosclerosis is no longer totally appropriate for the diagnosis of familial hypercholesterolemia (FH). It rather seems that these features are characteristic of a defective LDL receptor pathway, which could be caused by a defective LDL receptor or a defective ligand apo B100. The distinction between FH and FDB may have therapeutic implications, because certain lipid lowering drugs act by stimulation of the LDL receptor, which has a normal function in FDB.

Adolescent↗

PubMed1992

Transcriptional control via translational repression by c4 antisense RNA of bacteriophages P1 and P7.

The c4 repressors of bacteriophages P1 and P7 are antisense RNAs that inhibit antirepressor synthesis. This antisense inhibition is unusual in that the c4 repressor and the repressed genes orfx and ant are cotranscribed in that order from the same promoter, and c4 RNA is processed from a precursor RNA. Here, we show that c4 RNA directly represses translation of orfx, a small open reading frame, to which ant is translationally coupled. This translational repression blocks ant transcription via a rho-dependent terminator. Thus, c4 RNA controls expression of the ant gene by a novel indirect mechanism combining translational repression, translational coupling, and rho-dependent termination.

Bacteriophages↗

PubMed1992

Screening for the apolipoprotein B-100 arginine3500-->glutamine mutation in patients with type III hyperlipoproteinemia.

Forty-three patients with clinically and biochemically unequivocally defined type III hyperlipoproteinemia (HLP) were screened for the presence of the apolipoprotein (apo) B-100 arginine3500-->glutamine mutation. This receptor-binding defective apolipoprotein B variant is the cause of familial defective apo B-100 (FDB), an autosomal dominantly inherited disease, which leads to increased plasma cholesterol levels and premature atherosclerosis. Neither patient expressed FDB. It is concluded that the gene defect responsible for FDB is not involved in the pathogenesis of type III HLP.

Adult↗

PubMed1992

Expression of oat phyA cDNA in the moss Ceratodon purpureus.

The possibility of transforming Ceratodon purpureus protoplasts by PEG-mediated direct DNA uptake was tested. Transformation with a plasmid carrying a kanamycin-resistance gene resulted in kanamycin-resistant colonies of C. purpureus protonemata. A full-length cDNA clone coding for oat phyA phytochrome was isolated. The clone HM4.1 which is 3.7-kb long exhibits about 99% nucleotide sequence identity to the known phytochrome clone AP3. The expression of HM4.1 in C. purpureus protonemata was tested. A construct with the 35S-promotor and the structural gene of HM4.1 was cotransformed with the plasmid containing the kanamycin-resistance. Kanamycin-resistant colonies were tested for the presence of HM4.1 sequences in a genomic Southern experiment. Two out of 19 kanamycin-resistant colonies reacted positively with a HM4.1 specific probe. The expression of phyA in the positive colonies was examined with monoclonal antibodies specific for oat phytochrome. The Western blot experiment with protein extracts of the two positive colonies grown in the dark revealed clear signals at 124-kDa which were not detected in control plants. These data demonstrate the possibility of expressing oat phyA-apoprotein in C. purpureus protonemata. The transgenic moss protonemata did not show phenotypical alterations in response to the foreign phytochrome polypeptide; it is not known at the moment if the tetrapyrole chromophore is attached to the oat polypeptide in the protonemata or not.

Base Sequence↗

PubMed1992

Diagnosis of familial hypercholesterolemia using DNA haplotype analysis in three large families with two hyperlipidemic parents.

Since the cloning of the human LDL receptor (LDLR) gene, familial hypercholesterolemia (FH) can be diagnosed by recombinant DNA technology either using restriction enzyme mapping to detect major rearrangements of the gene or using restriction fragment length polymorphisms (RFLPs) and linkage analysis in family studies. Genotypes and haplotypes of four RFLPs (StuI, ApaII 5', PvuII, NcoI) were used to study the inheritance of the detective LDLR gene in three families. Diagnosis of FH based on the lipid levels alone was not possible because in these kindreds both parents exhibit elevated lipid levels. However, in two families using haplotype analysis, elevated cholesterol levels in certain relatives could be attributed to the inheritance of a defective LDRL gene and thereby distinguished from hypercholesterolemia due to familial combined hyperlipidemia. In the third family where both hypercholesterolemic parents carried a defective LDLR gene, a case of homozygous FH could be excluded in a child by demonstrating the inheritance of a normal LDLR gene.

Adult↗

PubMed1991

Identification of a 76-year-old patient with compound heterozygous familial hypercholesterolemia by haplotype analysis of the LDL receptor gene.

In a large family with clinical characteristics of heterozygous familial hypercholesterolemia (FH) seven restriction fragment length polymorphisms (RFLP) were used to determine low-density-lipoprotein receptor (LDLR) gene haplotypes. Following the inheritance of the LDL receptor genes characterized by their seven RFLP haplotypes, two different alleles were found to cosegregate with elevated cholesterol levels within this family. In a 76-year-old man both alleles identified as defective were present, thus classifying this individual as heterozygous compound for FH. In five heterozygous family members one allele was associated with 38% higher cholesterol levels when compared to the other mutant allele in two heterozygous family members. Cosegregation of hypercholesterolemia with the apolipoprotein B (apoB) gene and apolipoprotein E (apoE) gene was excluded by genotyping all individuals for the apoB XbaI RFLP and apoE polymorphisms. These findings are consistent with variable phenotypic expression of the mutant LDLR gene alleles.

Aged↗

PubMed1991

Identification of a silent point mutation in the LDL-receptor gene by direct DNA sequencing.

To study the allelic variation at the human LDL-receptor gene locus in a number of individuals with familial hypercholesterolemia, a protocol was applied for direct sequence analysis of genomic DNA. The asymmetric polymerase chain reaction (PCR) was used to synthesize single-stranded DNA. Sequencing was carried out with modified T7 DNA polymerase (Sequenase version 2.0, United States Biochemical) after purification of the amplification product with a glass powder adhesion method. The method is sensitive enough to identify the heterozygous state of allelic variation and bypasses cumbersome cloning and subcloning procedures. Here we report the occurrence of a guaninine-to-adenine change in the codon for amino acid 655. However, the glycine residue is not replaced by the base change at this position, and the mutation observed here does not represent the underlying genetic defect of the LDL-receptor defect in this individual. Preliminary data suggest that this mutation represents a rare genetic variation.

Amino Acid Sequence↗

PubMed1991

Identification of a heterozygous compound individual with familial hypercholesterolemia and familial defective apolipoprotein B-100.

Familial defective apolipoprotein B-100 (FDB) is a recently identified dominantly inherited genetic disorder, which leads to increased serum levels of low density lipoprotein (LDL) cholesterol with reduced affinity for the LDL receptor. This genetic disorder is characterized by defective binding of the apolipoprotein B-100 (apo B-100), which is virtually the sole protein constituent of LDL, to the LDL receptor. The defective binding results from a G to A mutation at amino acid 10,708 in exon 26 of the apolipoprotein B (apo B) gene creating a substitution of glutamine for arginine in the codon for amino acid 3500. It is postulated that FDB can exhibit the same clinical features as familial hypercholesterolemia (FH) caused by a defective LDL receptor. The purpose of this paper is to report on an individual with a defective LDL and a defective LDL receptor. The clinical features of this individual were the same as in the family members with either defective LDL or a defective LDL receptor: premature arcus lipoides, tendon xanthomata, and premature atherosclerosis. Although the clinical features were present to the same degree as in individuals with either defect the prognosis and treatment of such an individual could be different.

Adolescent↗

PubMed1991

Detection of the G to A mitochondrial DNA mutation at position 11778 in German families with Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral (usually permanent) loss of central vision, caused by neuroretinal degeneration. The maternal inheritance is explained by the mitochondrial origin of the disease. Recently, a single mitochondrial DNA (mtDNA) mutation, a G to A substitution at position 11778 that converts a highly conserved arginine to histidine, has been associated with LHON. The mutation eliminates an SfaNI restriction enzyme recognition site and thus provides a method for detection of the mutation by amplification, enzyme digestion and agarose gel electropheresis of polymerase chain reaction (PCR) products. Leukocyte mtDNA from 7 German families with LHON, diagnosed by clinical criteria, was tested for the presence of the G to A mutation at bp 11778. The mtDNa mutation, detected as a loss of the SfaNI site, was seen in one family. The G to A mtDNA mutation is the only known gene alteration associated with LHON so far. It has been identified in patients of different ethnic origin and recent reports strongly support the hypothesis that it represents the most frequent cause of LHON. Identification of the mtDNA replacement mutation using PCR and restriction enzyme digestion requires only a small amount of blood and can be performed rapidly. This method is thus a useful tool in the diagnosis of LHON.

Adenine↗

PubMed1991

Atypical vertebral artery in a patient with an intra-and extraspinal cervical neurenteric cyst.

A 15 year old girl experienced Horner's syndrome on the right side, paraesthesia of the right arm and meningitis. CT and MRI showed a cystic lesion on the right side of the cervical spine at C3/C4 which descended with an extraspinal portion down to C6. Histology revealed a complex neurenteric cyst. The ipsilateral vertebral artery showed an atypical course. This abnormal artery besides a partial fusion of the vertebrae C2/C3/C4 suggest a complex malformation at the site of the cyst. Disturbed developmental relationships in this case indicate that pathological blood vessels may represent a risk factor in the surgical treatment of neurenteric cysts.

Adolescent↗

PubMed1991

Familial defective apolipoprotein B-100: haplotype analysis of the arginine(3500)----glutamine mutation.

Familial defective apolipoprotein B-100 (FDB) is a recently identified, dominantly inherited genetic disorder, which leads to an increased serum level of low density lipoprotein (LDL) cholesterol with reduced affinity for the LDL receptor. It is postulated that this disorder results from a G to A mutation at nucleotide 10,708 in exon 26 of the apo B gene creating a substitution of glutamine for arginine in the codon for amino acid 3500. To investigate whether recurrent mutation has contributed to the high frequency of FDB, we have conducted a haplotype analysis in previously reported and newly detected FDB heterozygotes in Germany. 5 FDB families and 6 unrelated FDB heterozygotes were genotypes at 4 polymorphic sites in the 3' end of the apo B gene. These sites consisted of the diallelic markers XbaI, MspI, EcoRI and the hypervariable region (3'HVR). In 5 FDB families and 1 unrelated FDB heterozygote the arginine(3500)----glutamine mutation could be unambiguously assigned to the haplotype XbaI-/MspI+/EcoRI-/3'HVR48, in the other 5 FDB unrelated heterozygotes this finding was consistent with the combination of the genotype. The existence of the arginine(3500)----glutamine mutation on the same and supposedly rare allele suggests that the mutant alleles are identical by descent in our population. The fact that the same mutant allele was identified in North America and Austria suggests a common European origin of the arginine(3500)----glutamine mutation.

Adult↗

PubMed1991

Use of DNA haplotype analysis in diagnosis of familial hypercholesterolaemia in 31 German families.

In the majority of patients, familial hypercholesterolaemia (FH) is caused by different mutations affecting the well defined low density lipoprotein receptor (LDLR) gene. However, 3% of patients in Munich with a clinical diagnosis of FH have a particular mutation in the apolipoprotein B gene causing familial defective apolipoprotein B-100 (FDB). To date none of the LDLR mutations causing FH in German patients has been identified and it is therefore not yet possible to use DNA technology for direct diagnosis. However, indirect molecular diagnosis based on genetic linkage of common restriction fragment length polymorphisms (RFLPs) of the LDLR gene can be used for diagnosis in family studies. Patients with FDB were excluded from this study. Genotypes and haplotypes of four RFLPs (StuI, ApalI 5', PvuII, and NcoI) were determined in a total of 164 independent alleles from 31 pedigrees that included 222 subjects. Allele frequencies and four RFLP haplotype distribution did not differ significantly from those reported in other populations. The applicability of DNA diagnosis in our lipid clinic is comparable with the estimation from calculations on frequencies and heterozygosities of RFLPs, as predicted using these four RFLPs before. On the basis of cosegregation of haplotypes and normo- or hypercholesterolaemia in one or more sibs or offspring, defective and normal LDLR gene alleles could be distinguished in 42 of 58 heterozygous FH patients who were heterozygous for at least one RFLP. In 97 of 134 (72%) children of these 42 subjects, diagnosis of FH could be carried out unambiguously.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

A bacteriophage P1-encoded modulator protein affects the P1 c1 repression system.

Bacteriophage P1 encodes a tripartite immunity system composed of the immC, immI, and immT region. Their basic genetic elements are the c1 repressor of lytic functions, the c4 repressor which negatively regulates antirepressor synthesis, and the bof gene, respectively. The function of the latter will be described here. We have cloned and sequenced the bof gene from P1 wild type and a P1 bof amber mutant. Based on the position of a TAG codon of the bof amber mutant the bof wild type gene was localized. It starts with a TTG codon, comprises 82 codons, and is preceded by a promoter structure. The bof protein (Mr = 7500) was overproduced in Escherichia coli from a bof recombinant plasmid and was purified to near homogeneity. The N-terminal amino acids predicted from the DNA sequence of the bof gene were confirmed by sequence analysis of the bof protein. Using a DNA mobility shift assay, we show that bof protein enhances the binding of c1 repressor to the operator of the c1 gene. In accordance with this result, in transformants of Escherichia coli, containing both a bof- and a c1-encoding plasmid, c1 expression is down-regulated. We conclude that bof acts as a modulator protein in the repression of a multitude of c1-controlled operators in the P1 genome.

Base Sequence↗

PubMed1990

The c1 repressor inactivator protein coi of bacteriophage P1. Cloning and expression of coi and its interference with c1 repressor function.

The immC region of bacteriophage P1 contains the c1 repressor gene and its upstream region with four c1-controlled operators and four open reading frames. A c1 inactivator gene, coi, was defined by mutations in immC that suppress the virulence of the P1virC mutation. The exact location of the coi gene was not known (Scott, J.R. (1980) Curr. Top. Microbiol. Immunol. 90, 49-65). When a variety of P1 immC fragments were inserted into an expression vector, a gene product was inducible for the open reading frame 4 only. We identify this product as the c1 inactivator protein, coi by the following criteria: (a) expression of coi from a recombinant plasmid induces the P1 prophage and inhibits lysogenization of sensitive bacteria by P1; (b) all c1-controlled operator-promoter elements tested in vivo are derepressed by coi; (c) a partially purified coi protein (apparent molecular weight = 4800) interacts with c1 repressor and inhibits its binding to the operator in vitro. Based on these results we refine a model for the regulation of those genes and elements within immC which participate in the decision of P1 to enter the lytic or lysogenic pathway.

Base Sequence↗

PubMed1990

The c4 repressors of bacteriophages P1 and P7 are antisense RNAs.

The c4 repressors of P1 and P7 inhibit antirepressor synthesis and are solely responsible for heteroimmunity of the phages. We show that c4 is a new type of antisense RNA acting on a target, ant mRNA, that is transcribed from the same promoter. Interaction depends on complementarity of two pairs of short sequences encompassing the ribosome binding site involved in ant expression. We demonstrate that heteroimmunity of P1 and P7 is due to just two substitutions in each of the complementary sequences of c4 and ant mRNA. Based on P1-P7 sequence comparison and a mutant analysis, we propose a secondary structure model for c4 RNA, with the complementary regions in loops as important sites for antisense control.

Base Sequence↗

PubMed1990

A cellular automation model of excitable media including curvature and dispersion.

Excitable media are spatially distributed systems characterized by their ability to propagate signals undamped over long distances. Wave propagation in excitable media has been modeled extensively both by continuous partial differential equations and by discrete cellular automata. Cellular automata are desirable because of their intuitive appeal and efficient digital implementation, but until now they have not served as reliable models because they have lacked two essential properties of excitable media. First, traveling waves show dispersion, that is, the speed of wave propagation into a recovering region depends on the time elapsed since the preceding wave passed through that region. Second, wave speed depends on wave front curvature: curved waves travel with normal velocities noticeably different from the plane-wave velocity. These deficiencies of cellular automation models are remedied by revising the classical rules of the excitation and recovery processes. The revised model shows curvature and dispersion effects comparable to those of continuous models, it predicts rotating spiral wave solutions in quantitative accord with the theory of continuous excitable media, and it is parameterized so that the spatial step size of the automation can be adjusted for finer resolution of traveling waves.

Animals↗