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Biomedical subjects

M Franko

Publications and source records attributed to M Franko.

15 recordsLinked to original sources
PubMed2001

Effect of organic solvents in the on-line thermal lens spectrometric detection of chromium(III) and chromium(VI) after ion chromatographic separation.

The effect of methanol, acetone and acetonitrile on the sensitivity, selectivity and the detection limits (LODs) of the determination of chromium species by ion chromatography was investigated. A collinear dual-beam thermal lens spectrometer was used for the direct detection of chromium complexes [pre-column derivatized Cr(III)-pyridine-2,6-dicarboxylic acid, and post-column derivatized Cr(VI)-1,5-diphenylcarbazide] following the ion chromatographic separation on a Dionex HPIC-CS5A solvent compatible column. Different amounts of organic solvents were added directly to the eluent (up to 30%) and to the post-column reagent (up to 60%) to improve the thermooptical properties of the solvents. Consequently, the sensitivity of the technique was increased by a factor of 2-3 and LODs of 0.1 and 10 microg dm(-3) were achieved for Cr(VI) and Cr(III), respectively, when the eluent reaching the detector contained 30% of acetonitrile. The addition of organic solvents also resulted in significant changes in retention times, which improved the Cr(III)/Cr(VI) separation.

Chromatography, Liquid↗
PubMed2001

Transport of human immunodeficiency virus type 1 pseudoviruses across the blood-brain barrier: role of envelope proteins and adsorptive endocytosis.

Blood-borne human immunodeficiency virus type 1 (HIV-1) crosses the blood-brain barrier (BBB) to induce brain dysfunction. How HIV-1 crosses the BBB is unclear. Most work has focused on the ability of infected immune cells to cross the BBB, with less attention devoted to the study of free virus. Since the HIV-1 coat glycoprotein gp120 can cross the BBB, we postulated that gp120 might be key in determining whether free virus can cross the BBB. We used radioactive virions which do (Env+) or do not (Env-) bear the envelope proteins to characterize the ability of HIV-1 to be taken up by the murine BBB. In vivo and in vitro studies showed that the envelope proteins are key to the uptake of free virus and that uptake was enhanced by wheat germ agglutinin, strongly suggesting that the envelope proteins induce viral adsorptive endocytosis and transcytosis in brain endothelia. Capillary depletion showed that Env+ virus completely crossed the vascular BBB to enter the parenchyma of the brain. Virus also entered the cerebrospinal fluid, suggesting passage across the choroid plexus as well. About 0.22% of the intravenously injected dose was taken up per g of brain. In vitro studies showed that postinternalization membrane cohesion (membrane binding not reversed with acid wash or cell lysis) was a regulated event. Intact virus was recovered from the brain endothelial cytosol and was effluxed from the endothelial cells. These results show that free HIV-1 can cross the BBB by an event related to adsorptive endocytosis and mediated by the envelope proteins.

Animals↗
PubMed2001

Molecular cloning, expression, and regulation of hippocampal amyloid precursor protein of senescence accelerated mouse (SAMP8).

Alzheimer's disease (AD) is associated with increased expression of amyloid precursor protein (APP) with a consequent deposition of amyloid beta peptide (Abeta) which forms characteristic senile plaques. We have noticed that the senescence accelerated mouse (SAMP8), a strain of mouse that exhibits age-dependent defects such as loss of memory and retention at an early age of 8-12 months, also produces increased amounts of APP and Abeta similar to those observed in Alzheimer's disease (AD). In order to investigate if this is due to mutations in APP similar to those observed in AD, and to develop molecular probes that regulate its expression, APP cDNA was cloned from the hippocampus of 8-month-old SAMP8 mouse. The nucleotide sequence is 99.7% homologous with that of mouse and rat, 88.7% with monkey, and 89.2% with human homologues. At the amino acid level, the homology was 99.2% and 97.6% with rodent and primate sequences, respectively. A single amino acid substitution of Alanine instead of Valine at position 300 was unique to SAMP8 mouse APP. However, no mutations similar to those reported in human familial AD were observed. When the cDNA was expressed in HeLa cells, glycosylated mature APP could be detected by immunoblotting technique. The expression could be regulated in a time- and concentration-dependent manner by using an antisense oligonucleotide specific to APP mRNA. Such regulation of APP expression may have a therapeutic application in vivo.

Aging↗
PubMed2000

Site-directed antisense oligonucleotide decreases the expression of amyloid precursor protein and reverses deficits in learning and memory in aged SAMP8 mice.

beta amyloid protein (Abeta) is a 40-43 amino acid peptide derived from amyloid precursor protein (APP). Abeta has been implicated as a cause of Alzheimer's disease (AD). Mice with spontaneous or transgenic overexpression of APP show the histologic hallmarks of AD and have impairments in learning and memory. We tested whether antisense phosphorothiolated oligonucleotides (AO) directed at the Abeta region of the APP gene given with or without antibody directed at Abeta could reverse the elevated protein levels of APP and the behavioral impairments seen in SAMP8 mice, a strain which spontaneously overexpresses APP. We found that intracerebroventricular (ICV) administration of antibody with either of two AOs directed at the midregion of Abeta improved acquisition and retention in a footshock avoidance paradigm, whereas two AOs directed more toward the C-terminal, a random AO, and vehicle were without effect. Three injections of the more potent AO given without antibody reduced APP protein levels by 43-68% in the amygdala, septum, and hippocampus. These results show that AO directed at the Abeta region of APP can reduce APP levels in the brain and reverse deficits in learning and memory.

Age Factors↗
PubMed1999

Determination of organophosphate and carbamate pesticides in spiked samples of tap water and fruit juices by a biosensor with photothermal detection.

The determination of organophosphate (paraoxon, chlorpyrifos, diazinon) and carbamate (carbaryl, carbofuran) pesticides in spiked drinking water and fruit juices was carried out using a photothermal biosensor. The biosensor consists of a cartridge containing immobilised enzyme acetylcholinesterase (AChE) placed in a flow-injection analysis (FIA) manifold and a photothermal detector based on thermal lens spectrometry. With this approach, 0.2 ng/ml of paraoxon can be detected in less than 15 min. Limits of detection for other organophosphate (chlorpyrifos, diazinon) and carbamate (carbaryl, carbofuran) pesticides varied, depending on their antiacetylcholinesterase (AntiAChE) toxicity, from 1 ng/ml to 4 microg/ml. The biosensor was used for the direct detection of pesticides in spiked tap water and fruit juices without any pretreatment steps. In these cases, the LOD3sigma of 1.5, 2.8 and 4 ng/ml paraoxon in tap water, orange juice and apple juice were obtained, respectively.

Beverages↗
PubMed1999

Ultrasensitive determination of beta-carotene in fish oil-based supplementary drugs by HPLC-TLS.

This research study demonstrates that thermal lens spectrometry (TLS) combined with efficient isocratic HPLC separation provides an excellent analytical means to profile and quantify carotenes in fish body oils and possibly also in vegetable oils. In particular, a highly sensitive, selective, simple and rapid method for the determination of ultratraces of beta-carotene in fish oil-based supplementary drugs has been proposed. The analyte could be determined reliably and precisely in the presence of a complex matrix including other fat-soluble vitamins (A, D and E), polyunsaturated fatty acids, sterols and other pigments by matrix-matched calibration in cod liver oil. The suitability of the method is also evidenced by favourable analytical figures of merit for beta-carotene such as a linearity range of 1-120 ng ml(-1), LOD of 0.58 ng ml(-1), recovery of 101.4+/-3.3% and measurement repeatability of 4.1%.

Antioxidants↗
PubMed1998

Determination of trans-beta-carotene and other carotenoids in blood plasma using high-performance liquid chromatography and thermal lens detection.

Thermal lens spectrometry (TLS) was applied for the detection of beta-cryptoxanthin, alpha-carotene, trans-beta-carotene, and lycopen in blood plasma. This combined high-performance liquid chromatography-TLS (HPLC-TLS) method was validated by comparison with HPLC-UV-Vis analysis of blood plasma under identical chromatographic conditions and by comparing the results obtained from an independent, standard HPLC procedure for determination of carotenoids in blood plasma samples. The results demonstrated good agreement with the target values for carotenoids in an in-laboratory control sample and confirmed the accuracy of the HPLC-TLS technique. Limits of detection for blood plasma samples were 70 pg/ml for beta-cryptoxanthin, 85 pg/ml for alpha-carotene, 100 pg/ml for trans-beta-carotene, and 120 pg/ml for lycopen. This represents a 100-fold improvement compared to the HPLC analysis with UV-Vis detection.

Carotenoids↗
PubMed1986

Diagnosis of Creutzfeldt-Jakob disease by Western blot identification of marker protein in human brain tissue.

We tested purified preparations of brain tissue from 39 patients with Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, or kuru, and from 32 patients with a variety of nonspongiform degenerative diseases, with the use of Western blots against an antiserum to a similarly purified fraction made from scrapie-infected hamster brain. Positive reactions occurred in 81 percent of the 31 specimens from the patients with Creutzfeldt-Jakob disease (and in all of the 7 specimens that were stored frozen for less than one year), in 3 of the 4 specimens from the patients with kuru, in 3 of the 4 specimens from the patients with Gerstmann-Sträussler-Scheinker syndrome, and in none of the specimens from the patients with other neurologic degenerative disorders, including familial or sporadic Alzheimer's disease; dementia associated with myoclonus, motor neuron disease, or parkinsonism; and acquired-immunodeficiency-syndrome encephalopathy. Immunologic testing has thus begun to provide a useful and rapid adjunct to neuropathological examinations and animal-transmission experiments for the diagnosis of the spongiform encephalopathies.

Animals↗
PubMed1985

Effect of iso-propyl-thio-beta-D-galactoside concentration on the level of lac-operon induction in steady state Escherichia coli.

In steady state E. coli cells growing at their maximal rate in broth, maximum induction of beta-galactosidase occurs at 0.10 mM isopropyl-thio-beta-D-galactoside (IPTG). Although induction of lac is near zero in steady state cells that are growing in 0.01 mM IPTG, induction at mildly subdued levels persists down to at least 0.001 mM in post-steady state cultures. Meanwhile, thiogalactoside transacetylase remains uninduced over the full range in which the cells are in steady state.

Acetyltransferases↗
PubMed1982

Experimental scrapie in golden Syrian hamsters: temporal comparison of in vitro cell-fusing activity with brain infectivity and histopathological changes.

Golden Syrain hamsters were inoculated intracerebrally with the hamster-adapted 263K strain of scrapie virus, and the evolution of in vitro cell fusing activity induced by brain suspensions was compared with brain infectivity titers and histological changes. Cell-fusing activity abruptly appeared 4 weeks after inoculation, 1 week before the earliest detectable histopathological changes, at an infectivity level of 7.6 log 50% lethal doses per g of brain. Cell-fusing activity was sustained throughout the remaining 4 weeks of the incubation period and the subsequent 1- to 3-week stage of clinical illness but did not increase with the logarithmic progression of infectivity, which reached a level of 11 log 50% lethal doses per g in the agonal stage of disease. Gliosis was most sensitively detected by a monoclonal antibody reacting with astrocyte intermediate filaments in an indirect immunofluorescence test, anticipating histological recognition of gliosis and spongiform change by 1 to 2 weeks. In vitro cell-fusing activity is thus one of the earliest known biological markers (apart from infectivity itself) of experimental scrapie infection.

Animals↗
PubMedDate not supplied

Chromium-induced micronuclei in fish.

An investigation of the cytogenetic effects of chromium (Cr(VI) and Cr(III)) in Prussian carp (Carassius auratus gibelio) was made. For detecting cytogenetic damage, micronuclei induction in fish erythrocyte cells was employed. Fish were investigated 100 m above and 400 m below the discharge of leather waste products into the river Ljubljanica, and by exposing fish to three doses of chromium (Cr(VI) and Cr(III)) in the laboratory. The exposure of fish to various concentration levels (sub-lethal) of chromium under laboratory and field conditions caused an increase in the frequency of micronuclei compared with the control groups.

Animals↗