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Biomedical subjects

D Levanon

Publications and source records attributed to D Levanon.

At least 55 records · Page 3Linked to original sources
PubMed1989

The primary structure of human liver type phosphofructokinase and its comparison with other types of PFK.

The complete mRNA sequence of the human liver-type phosphofructokinase (hPFKL) was determined. The sequence included 55 nucleotides of 5' and 515 of 3' noncoding regions, as well as 2,337 nucleotides encoding the 779 amino acids of the hPFKL. Extensive similarity (approximately 90%) in the coding region was observed between the hPFKL and the mouse PFKL, whereas the degree of similarity between different types of PFK, i.e., hPFKL and human muscle-type PFK (hPFKM), was merely 68%. Nevertheless, striking similarity between these different types of PFK was noticed when the amino acid residues creating the various active sites of the enzyme were compared. Human PFK L- and M-specific probes were constructed and used to quantitate the mRNA levels in fetal and adult brains and fetal liver. It was found that while relative amount of PFKL mRNA in adult brain was one-fourth of that detected in fetal brain the level of PFKM mRNA in adult brain was slightly higher than in fetal tissue, suggesting that PFK expression might be controlled at the transcriptional level.

Amino Acid Sequence↗
PubMed1989

Permeability of blood vessels in experimental gliomas: uptake of 99mTc-glucoheptonate and alteration in blood-brain barrier as determined by cytochemistry and electron microscopy.

Experimental gliomas were induced in rats by prenatal exposure to ethyl nitrosourea. Changes in the blood-brain barrier were determined by the uptake of a water-soluble compound, 99mTc-glucoheptonate. Increased uptake of 99mTc-glucoheptonate was measured in intact tumors and in various sectors of dissected tumors. The extent of 99mTc-glucoheptonate uptake greatly varied among different tumors and among different sectors of the same tumor. Ultrastructural and cytochemical analysis of the capillary endothelial wall revealed major alterations in tight junctions, which became permeable to horseradish peroxidase. In brain tissue around the tumors, uptake of 99mTc-glucoheptonate and ultrastructure of tight junctions were comparable to normal brain capillaries. The results of the present study indicate that altered endothelial tight junctions may provide the main route of transport of 99mTc-glucoheptonate through the endothelial wall.

Animals↗
PubMed1987

Construction of a cDNA clone containing the entire coding region of the human liver-type phosphofructokinase.

Genomic fragments containing coding sequences of the human liver phosphofructokinase (PFKL) were used to screen cDNA libraries and several clones corresponding to PFKL were isolated. Three overlapping cDNA clones spanning the entire coding region were stitched together yielding the plasmid pG-cPFKL3.0 containing a 3Kb PFKL cDNA down stream of the T7 promoter. To assess its coding capacity pG-cPFKL3.0 was transcribed by T7 RNA polymerase and the RNA product was used to program an in vitro translation system. An 80KDa polypeptide which co-migrated with an in vivo labeled PFKL and was recognized by anti PFKL antibodies was synthesized. These results show that the cDNA clone pG-cPFKL3.0 contains the entire coding region of the human PFKL.

Cloning, Molecular↗
PubMed1987

Scanning Electron Microscope Studies of Interactions between Agaricus bisporus (Lang) Sing Hyphae and Bacteria in Casing Soil.

Relationships between the hyphae of Agaricus bisporus (Lang) Sing and bacteria from the mushroom bed casing layer were examined with a scanning electron microscope. Hyphae growing in the casing layer differed morphologically from compost-grown hyphae. Whereas the compost contained thin single hyphae surrounded by calcium oxalate crystals, the casing layer contained mainly wide hyphae or mycelial strands without crystals. The bacterial population in the hyphal environment consisted of several types, some attached to the hyphae with filamentlike structures. This attachment may be important in stimulation of pinhead initiation.

Journal Article↗
PubMed1986

Genomic clones of the human liver-type phosphofructokinase.

Genomic clones of human liver phosphofructokinase (PFK) were isolated by screening a gene bank enriched for chromosome 21 sequences with two synthetic oligonucleotide probes designed from peptide sequences of purified human liver PFK. A 3.3 Kb fragment derived from the genomic clones was sub-cloned and designated to pG-PFKL 3.3. It hybridized with a 3.5 Kb mRNA on Northern blots and was able to enrich selectively for liver PFK mRNA by hybrid-selection. These results demonstrated that the isolated clones contain sequences homologous to human PFKL mRNA. When hybridized to genomic DNA blots pG-PFKL 3.3 reacted with the same 3.3 Kb BamHI fragment in both human DNA and DNA of the mouse/human hybrid line WA17 which contains human chromosome 21 as the only human chromosome. These data confirm the assignment of the PFKL gene to chromosome 21.

Animals↗
PubMed1986

Horseradish peroxidase as a cytochemical marker of blood-brain barrier integrity in oxygen toxicity in the central nervous system.

The ultrastructural integrity of endothelial tight junctions in cerebral microvessels of the rat exposed to hyperbaric oxygen was examined to find whether or not there are alterations of the blood-brain barrier in the initial phase of central nervous system oxygen toxicity. Rats were pre-implanted with cortical electrodes for continuous EEG and provided with two polyethylene cannulae inserted into the common carotid artery. HRP was administered to unanesthetized rats through a cannula directed into the brain, before the onset of O2 pressurization. As soon as the early electrical discharges of oxygen toxicity were recorded (20 to 30 min), the animal was killed by injection with saturated KCl into the heart. Examination of small blood vessels in both LM and EM did not support the possibility that the blood-brain barrier is altered prior to the first electrical discharge appearing in central nervous system oxygen toxicity.

Animals↗
PubMed1986

The relationship of eel Anguilla anguilla (L.) body size, lipid, protein, glucose, ash, moisture composition and enzyme activity (aldolase).

Body composition: protein, lipid, ash, moisture; and enzyme activity (aldolase) were studied in European eels (Anguilla anguilla) of various sizes. The fish were brought to the laboratory as glass eels (0.35 g) and maintained under controlled conditions (23 degrees C) for one year. After one year of growth, various sizes (between 9 and 420 g) were found. Significant correlation coefficients of the equation W = a ln C + b (where W = body weight, in g; C = composition, % or activity, u; and a,b are constants) were found among the composition parameters: protein, lipid, glucose and aldolase. Relative amounts of protein, glucose, moisture, ash and aldolase activity were found to decrease with an increase in the weight of eels, but the percentage of fat was higher in large eels than in small ones.

Anguilla↗
PubMed1986

Collagen fiber alignment in the human preauricular dermis before and after rhytidectomy--a scanning electron microscopy study.

The microarchitecture of collagen fibers in preauricular dermis specimens that were obtained during two-phase rhytidectomy were visualized and recorded using the scanning electron microscope. Examination of photomicrographs revealed that both spatial arrangement and degree of convolution of the collagen fibers were completely different in the specimens of the two phases. The results are interpreted in terms of the viscoelastic properties of the skin.

Collagen↗
PubMed1985

Architecture and anatomy of the chromosomal locus in human chromosome 21 encoding the Cu/Zn superoxide dismutase.

The SOD-1 gene on chromosome 21 and approximately 100 kb of chromosomal DNA from the 21q22 region have been isolated and characterized. The gene which is present as a single copy per haploid genome spans 11 kb of chromosomal DNA. Heteroduplex analysis and DNA sequencing reveals five rather small exons and four introns that interrupt the coding region. The donor sequence at the first intron contains an unusual variant dinucleotide 5'-G-C, rather than the highly conserved 5'-GT. The unusual splice junction is functional in vivo since it was detected in both alleles of the SOD-1 gene, which were defined by differences in the length of restriction endonuclease fragments (RFLPs) that hybridize to the cDNA probe. Genomic blots of human DNA isolated from cells trisomic for chromosome 21 (Down's syndrome patients) show the normal pattern of bands. At the 5' end of gene there are the 'TATA' and 'CAT' promoter sequences as well as four copies of the -GGCGGG- hexanucleotide. Two of these -GC- elements are contained within a 13 nucleotide inverted repeat that could form a stem-loop structure with stability of -33 kcal. The 3'-non coding region of the gene contains five short open reading-frames starting with ATG and terminating with stop codons.

Bacteriophage lambda↗
PubMed1984

Human Cu/Zn superoxide dismutase gene: molecular characterization of its two mRNA species.

Two cytoplasmic superoxide dismutase (SOD-1) mRNAs of about 0.7 and 0.9 kilobases (Kb.) were previously found in a variety of human cells. The two SOD-1 mRNAs are transcribed from the same gene and the major 0.7 Kb. species is approximately four times more abundant than the minor 0.9 Kb. mRNA. These two mRNAs differ in the length of their 3'-untranslated region and both have multiple 5'-ends. The longer transcript contains 222 additional nucleotides beyond the 3'-polyadenylated terminus of the short mRNA. S1 nuclease mapping and sequence analysis showed that these extra 222 nucleotides are specified by sequences contiguous to those shared by the two SOD-1 mRNAs. The 5'-termini of the two SOD-1 mRNAs were identified and mapped by both primer extension and S1 mapping. The majority of SOD-1 mRNA molecules (90-95%) have a 5'-start site located 23 base pairs (b.p.) downstream of the hexanucleotide -TATAAA-. The rest of the SOD-1 mRNA molecules have 5'-termini 30, 50 and 65 b.p. upstream from the major start region.

Base Sequence↗
PubMed1984

Pseudoexfoliation: epidemiology, clinical and scanning electron microscopic study.

The prevalence of pseudoexfoliation among patients of Sephardic origin was more than twice the expected when compared with the ethnic distribution of the population consulting the Rambam Medical Center eye clinic. A strong association between brown irises and pseudoexfoliation was noted. No uniform scanning electron microscope pattern was seen of the pseudoexfoliation.

Aged↗
PubMed1968

Macrophage cultures: an extracellular esterase.

An enzyme having esterase activity accumulates in the culture media of mouse peritoneal mononuclear leukocytes during differentiation of the cells into macrophages. It has a pH optimum of 6.5 and shows aryl esterase characteristics. The esterase differs from another macrophage hydrolase, acid phosphatase, in its mainly extracellular distribution.

Acid Phosphatase↗
PubMedDate not supplied

Evaluation of microvilli in gluten-sensitive enteropathy by means of scanning and transmission electron microscopy.

Biopsies from jejunum of nonceliac patients and patients with active celiac disease were studied and compared by means of transmission (TEM) and scanning (SEM) electron microscopy. Fracturing of dried specimens enabled the visualization of the epithelial microvilli with SEM. Alteration in microvillous appearance in celiac patients, as determined by TEM, could also be clearly detected in SEM images. The SEM preparation is easier to accomplish and less time-consuming compared to the TEM. This may be an advantage for clinical assessment of jejunal biopsies in syndromes in which early detection of alterations in microvilli in the epithelial mucosa is of diagnostic value.

Biopsy↗
PubMedDate not supplied

Influence of patient age on photorefractive keratectomy for myopia.

BACKGROUND: To determine whether the outcomes of photorefractive keratectomy (PRK) for myopia are age-dependent. METHODS: The influence of age on PRK outcomes was analyzed for one eye of each of 72 patients divided into two groups: 39 patients (18 to 26 years) and 33 patients (35 to 54 years). The influence of the amount of preoperative myopia (low myopia less than -4.00 diopters (D); moderate to high myopia -4.00 or more D) was also evaluated. All patients were followed for at least 1 year, and all underwent cycloplegic refractions. RESULTS: One year after PRK, the average refraction was -0.15 D in the younger group and +0.38 D in the older group. The achieved refraction was higher than the attempted by +1.00 D or more only in eyes with moderate to high myopia (-4.00 to -10.00 D); 11.54% (3 eyes) of the younger group and in 34.78% (8 eyes) of the older group. CONCLUSIONS: After PRK for myopia, patients between the ages of 35 and 54, with moderate to high myopia, obtained more refractive change with the same intended dioptric correction compared to younger patients with moderate to high myopia. Attempted correction should be adjusted according to age and amount of myopia.

Accommodation, Ocular↗