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J L Weber

Publications and source records attributed to J L Weber.

At least 163 records · Page 9Linked to original sources
PubMed1990

Linkage mapping of the highly informative DNA marker D21S156 to human chromosome 21 using a polymorphic GT dinucleotide repeat.

A (GT)n repeat within the anonymous DNA sequence D21S156 was shown to be highly polymorphic in DNA from members of the 40 CEPH families. At least 12 alleles of this locus were recognized by electrophoresis on polyacrylamide gels of DNA amplified by the polymerase chain reaction (PCR) using primers flanking the (GT)n repeat. The polymorphism information content was 0.82. PCR amplification of DNA from somatic cell hybrid lines mapped D21S156 to human chromosome 21 and linkage analysis localized this marker close to the loci ETS2, D21S3, and HMG14 on chromosomal band 21q22.3. This polymorphism is highly informative and can serve as an anchor locus for human chromosome 21.

Alleles↗
PubMed1990

Human DNA polymorphisms and methods of analysis.

The current predominant method of analyzing base substitution polymorphisms, RFLP analysis, is likely to be gradually supplanted by methods based on PCR because of the improved sensitivity and genotyping rate. The most promising PCR methods for analysis appear to be allele-specific PCR and single-stranded conformational analysis. The single-stranded conformation approach has already been applied to the scanning of cystic fibrosis exons for new mutations. Linkage mapping projects that cover large segments of the human genome will probably rely, in the coming years, primarily on tandem repeat polymorphisms, particularly microsatellite polymorphisms. Microsatellite polymorphisms have at least a fourfold advantage over base substitution RFLPs because they are twice as informative and can be typed at at least twice the rate. The facioscapulohumeral muscular dystrophy gene was recently mapped in just 6 weeks using microsatellite polymorphisms. Because of the informativeness handicap, it will be difficult for base substitution polymorphisms to overtake tandem repeat markers for large-scale linkage mapping. Methods that allow base substitution polymorphisms to be typed at two or three times the rate of microsatellite markers would have to be developed. Most of the other applications of DNA polymorphisms described in the introduction are also increasingly likely to rely on highly informative tandem repeat markers in the future. Methods for analysis will probably be based on PCR. It is easy to envisage, for example, an automated method for large-scale DNA fingerprinting of individuals based upon a standard set of highly informative, dependable microsatellite polymorphisms. Methods for analyzing base substitution polymorphisms will continue to be important for the diagnostic detection of disease-gene alleles.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA↗
PubMed1989

MINIMAC: a totally numeric 15 channel implanted stimulator.

After CHORIMAC-8 and CHORIMAC-12 a new multichannel cochlear implant is presented, characterized by its totally numeric sound signal processing. Owing to FFT the whole speech information is cut into 15 channels, then sequentially transmitted to an implanted receptor and electrode bearer. This digital processing provides the new system with several advantages: 1. miniaturization of outside emitter end implanted receiver; 2. compatibility of this new emitter with the 12 channel receivers implanted in the last 10 years; 3. increasing the number of stimulating electrodes from 12 to 15; 4. simple emitter programming with an IBM-PC; 5. option to postoperatively program the number (1 to 15) and the value (80 to 3,800 Hz) of the peak filters, and the amplification (6, 10, 18 dB) of each electrode. The next implanted device will have: a. constant current; b. programming of a particular current value for each electrode; and c. stimulation of the cochlear nerve through an extra cochlear electrode bearer, allowing deep implantation without deafness.

Cochlear Implants↗
PubMed1989

Ultraviolet irradiation for hepatic rickets.

An infant with chronic cytomegalovirus hepatitis and a child with atypical Alagille's syndrome had vitamin D deficiency rickets due to malabsorption. Both received ultraviolet irradiation. This treatment corrected biochemical abnormalities and healed the rickets. In the infant use of a sunlamp at home maintained normal 25 hydroxy-vitamin D for over a year. Our study shows that ultraviolet irradiation is an effective treatment of hepatobiliary rickets.

Child↗
PubMed1989

Abundant class of human DNA polymorphisms which can be typed using the polymerase chain reaction.

Interspersed DNA elements of the form (dC-dA)n.(dG-dT)n constitute one of the most abundant human repetitive DNA families. We report that specific human (dC-dA)n.(dG-dT)n blocks are polymorphic in length among individuals and therefore represent a vast new pool of potential genetic markers. Comparison of sequences from the literature for (dC-dA)n.(dG-dT)n blocks cloned two or more times revealed length polymorphisms in seven of eight cases. Variations in the lengths of 10 (dC-dA)n.(dG-dT)n blocks were directly demonstrated by amplifying the DNA within and immediately flanking the repeat blocks by using the polymerase chain reaction and then resolving the amplified DNA on polyacrylamide DNA sequencing gels. Use of the polymerase chain reaction to detect DNA polymorphisms offers improved sensitivity and speed compared with standard blotting and hybridization.

Alleles↗
PubMed1988

Primary structure of a Plasmodium falciparum malaria antigen located at the merozoite surface and within the parasitophorous vacuole.

DNA encoding an antigen of 101,000 apparent molecular weight from the human malaria parasite Plasmodium falciparum was cloned and sequenced. Genomic DNA from the Camp strain covering the complete coding region along with cDNA from the FCR3 strain covering 81% of the coding region were obtained. The cloned DNA specified a full-length protein of 743 amino acids which included two tandemly repeated regions, one near the amino terminus containing eight hexapeptide repeats of sequence TVNDEDED, and the second near the carboxyl terminus containing primarily KE and KEE repeats. The latter repeated region is encoded by a 174-base stretch of mRNA containing only a single pyrimidine. Except for a putative leader sequence located at the amino terminus of the protein, the protein is hydrophilic and highly charged with a calculated isoelectric point of 5.6. Sequences from the Camp and FCR3 strains are very close and are also nearly identical to the partial cDNA sequence of the acidic basic repeated antigen (ABRA) protein from the FC27 strain (Stahl, H.D., Bianco, A.E., Crewther, R.F., Anders, R.F., Kyne, A.P., Coppel, R. L., Mitchell, G.F., Kemp, D.J., and Brown, G.V. (1986) Mol. Biol. Med. 3, 351-368). ABRA was previously shown to be located at the merozoite surface and in the parasitophorous vacuole. Because of its location and because it becomes complexed to merozoites when schizonts rupture in the presence of immune serum, ABRA is a candidate component of a malaria vaccine.

Amino Acid Sequence↗
PubMed1988

Plasmodium falciparum: mapping genes to nine parasite chromosomes.

Using pulsed field gel electrophoresis with pulse time of 120 sec, eight chromosomal DNA molecules from clone 7G8 of the Plasmodium falciparum Brazilian isolate IMTM22 were resolved. A ninth chromosomal molecule which did not enter the gel was identified at the slot by hybridization to two DNA probes and by restriction enzyme analysis. Thirteen parasite DNA sequences were mapped to the nine chromosomes, with at least one sequence mapped to each chromosome. The restriction enzyme NotI appeared to produce only one cut in the entire IMTM22 genome.

Animals↗
PubMed1988

Interspersed repetitive DNA from Plasmodium falciparum.

An interspersed repetitive DNA element from the Camp strain of the human malaria parasite Plasmodium falciparum was cloned and sequenced. The element is repeated at least 11 times in the genome, is a minimum of 2.0 kilobases long and maps to eight or more different parasite chromosomes. The cloned DNA includes a 1.0 kilobase open reading frame. RNA complementary to the repetitive element is found within blood stage forms of the parasite, but only in the most mature forms. Searches of DNA and protein sequence databases for homology to the element were unsuccessful. Sizes of restriction enzyme fragments which hybridize to the element show considerable variation between strains, indicating that the repeat family represented by this element could be transposable.

Amino Acid Sequence↗
PubMed1988

The introduction of biologically active foreign genes into human respiratory epithelial cells using electroporation.

A simple method for introducing genes into respiratory epithelial cells would assist molecular studies of a variety of pulmonary disorders. Several different techniques for introducing foreign DNA into cells have been described but have either not been useful for respiratory epithelial cells or are difficult and cumbersome to perform. Electroporation is a simple technique that consists of exposing a cell-DNA suspension to an electric shock. Although it has been used to introduce genes into a variety of cell types, it has not previously been applied to respiratory epithelial cells. Human nasal epithelial cells were transfected with the plasmid pRSVCAT, which is an expression vector containing the origin of replication of pBR322 coupled to the Rous sarcoma virus (RSV) long terminal repeat (LTR) region driving the coding sequence for the chloramphenicol acetyltransferase (CAT) gene. The CAT gene is useful for determining optimal conditions for electroporation since it is not normally present in eukaryotic cells, and CAT activity correlates with the level of CAT mRNA; this provides a measure of expression of introduced foreign genes. Successful expression of the CAT gene was demonstrated by electroporation, whereas calcium phosphate transfection resulted in very low CAT activity. Optimal conditions for electroporation of respiratory epithelial cells were determined. Electroporating nasal epithelial cells using 500 volts, a DNA concentration of 10 micrograms/ml, and a sucrose buffer yielded the highest CAT activity, which peaked at 48 h after electroporation.

Avian Sarcoma Viruses↗
PubMed1988

[The monochannel Monomac and multichannel Minimac cochlear implants].

Monomac monochannel and Minimac multichannel cochlear implants bring to the remaining hearing fibers sound information that is previously converted into adequate electric signals. Both function at constant currents. The Monomac monocanal system possesses only one electrode implanted either inside or outside the cochlea and sends off sound of basic laryngeal rythm to all the nervous fibers. The Minimac is entirely numerical and sends off the whole of the sound information by splitting it into 15 frequency tracks, to 15 electrodes inserted within the scala tympani by means of an electrode-holder. Programming allows for selecting specific values from each frequency track and thus regulating the needed compression individually. Both these implants (Monomac and Minimac) work no conflictlessly but complementarily to each other because they answer different, well-defined clinical needs.

Cochlear Implants↗
PubMed1987

Efficacy of murine malaria sporozoite vaccines: implications for human vaccine development.

As part of a study of potential vaccines against malaria, the protective efficacy of sporozoite subunit vaccines was determined by using the Plasmodium berghei murine malaria model. Mice were immunized with recombinant DNA-produced or synthetic peptide-carrier subunit vaccines derived from the repetitive epitopes of the Plasmodium berghei circumsporozoite gene, or with radiation-attenuated sporozoites. Immunization with subunit vaccines elicited humoral responses that were equivalent to or greater than those elicited by irradiated sporozoites, yet the protection against sporozoite challenge induced by either of the subunit vaccines was far less than that achieved by immunization with attenuated sporozoites. Passive and adoptive transfer studies demonstrated that subunit vaccines elicited predominantly antibody-mediated protection that was easily overcome whereas irradiated sporozoites induced potent cell-mediated immunity that protected against high challenge doses of sporozoites. These studies indicate that new strategies designed to induce cellular immunity will be required for efficacious sporozoite vaccines.

Animals↗
PubMed1987

Plasmodium berghei: cloning of the circumsporozoite protein gene.

A DNA fragment encoding the carboxy terminal 80% of the Plasmodium berghei circumsporozoite protein was selected from a genomic DNA expression library. Sequencing revealed that the P. berghei circumsporozoite protein was similar in overall structure to circumsporozoite proteins from other malaria species, although the central repeat region was unique in comprising two different blocks of tandem peptide repeats: 11 eight amino acid repeats with predominant sequence DPAPPNAN were followed by 16 two amino repeats, predominantly PQ. The P. berghei circumsporozoite protein exhibited limited, but about equal amino acid homology to circumsporozoite proteins from P. knowlesi, P. vivax, and P. falciparum, indicating that P. berghei is not closely related to any of these other malaria species. Cloning of the P. berghei circumsporozoite protein gene will allow direct testing of sporozoite vaccines in mice.

Amino Acid Sequence↗
PubMed1987

Analysis of sequences from the extremely A + T-rich genome of Plasmodium falciparum.

The genome of the human malaria parasite Plasmodium falciparum has an A + T content of about 82%, higher than any other organism whose DNA has been characterized. Computer analysis of 36 kb of available nucleotide sequences from this species showed that the coding regions, with an A + T content of 69.0%, are flanked by more A + T-rich regions of 86.0% A + T. Within the coding sequences, the A/T ratio was 1.68 in the mRNA sense strand, and overall A + T content in the three codon positions increased in the order 1st-2nd-3rd position. Codons with T or especially A in the third position were strongly preferred. Codon usage among individual parasite genes was very similar compared to genes from other species. Dinucleotide frequencies for the parasite DNA were close to those expected for a random sequence with the known base composition, except that the CpG frequency in the coding sequences was low.

Adenine↗
PubMed1987

Morbidity after percutaneous liver biopsy.

The safety of percutaneous liver biopsy with a 1.2 mm Menghini needle in infants aged one year or less was investigated. One hundred and eighty four procedures performed from 1975 to 1985 were reviewed. There were no deaths or major complications within 48 hours associated with the procedure. In five instances specific complications occurred: a drop in haemoglobin concentration (three), transient hypotension (one), and haematoma at the biopsy site (one). The result of liver biopsy was diagnostic in 83% of cases, compatible with unspecified metabolic disease in 8%, and normal or not diagnostic in 9%. This study suggests that percutaneous liver biopsy can be performed with relative safety in small infants if coagulation is normal and there are no major contraindications, and the results yield important diagnostic information which cannot be obtained using less invasive procedures.

Biopsy, Needle↗
PubMed1986

Variation in the gene encoding a major merozoite surface antigen of the human malaria parasite Plasmodium falciparum.

Plasmodium falciparum merozoites have a variable surface protein of about 195,000 molecular weight which may be involved in strain-specific immunity. We have cloned and sequenced a major portion of the gene encoding this antigen from the CAMP strain and have located sites of preferred mung bean nuclease cleavage around the gene. These sites depend on reaction conditions, but at 40% formamide and 2 units of mung bean nuclease per microgram DNA, the intact gene was excised from the chromosome. Comparison of the CAMP strain gene with the same gene from other strains of P. falciparum by matching available DNA sequences and by DNA hybridization revealed five regions of homology separated by divergent segments. Two of the variable regions encoded three amino acid repeats, predominantly Ser-Gly-Thr and Thr-Glu-Glu. Implications of these findings on the function of the antigen, and possible mechanisms for generation of variants are discussed.

Amino Acid Sequence↗
PubMed1986

Adenocarcinoma of the pancreas in a neonate managed by pancreatoduodenectomy.

A 3-week-old infant presenting with jaundice and an abdominal mass was found to have juvenile adenocarcinoma of the pancreas (pancreatoblastoma). A pancreatoduodenectomy was performed, and the child is alive, well, and free of disease at age 4 years. The operative management and surgical technique are discussed.

Adenocarcinoma↗