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Biomedical subjects

J Lechner

Publications and source records attributed to J Lechner.

At least 37 records · Page 2Linked to original sources
PubMed1996

Thallium and cadmium in recent snow and firn layers in the Canadian Arctic by atomic fluorescence and absorption spectrometries.

Compared to the Antarctic and Greenland, the Canadian Arctic has seen extremely few trace metal studies on snow and ice. Surface, subsurface and depth samples of snow and firns were collected from the Agassiz Ice Cap, Ellesmere Island, Canada using clean room practices. Results for Tl (directly determined by LEAFS) and Cd (determined by GFAAS) are reported. To our knowledge, the thallium depth profile presented here is the first one so far reported for both polar systems, Greenland or other places. Tl concentrations peak in the winter-spring periods, when the Arctic atmosphere is loaded with foreign pollutants and suspended particulates which sometime severely reduce the visibility, creating a phenomenon commonly known as the Arctic haze. These results are in general accordance with the historical Arctic air pollution and acidity/conductivity data on ice cores. Surface concentrations of Tl range from 0.3 to 0.9 pg/g, which is a few times higher than those found in Antarctica. Cadmium shows seasonal characteristics similar to Tl although there is not a definite correlation between the two. However, there could be two predominant origins of metals which were deposited in the snow: Eurasian origin in January-April corresponding to high level metals (main deposition), and a less definite origin in May-December corresponding to low level metals.

Journal Article↗
PubMed1996

LEAFS determination and concentration of metals in Great Lakes ecosystem.

A Laser-Excited Atomic Fluorescence Spectrometric (LEAFS) method for Tl determination has been extended to investigate the direct determination (without preconcentration nor acid digestion) of total Pb, for which the method validation was successfully achieved by using a standard reference material as well as many spike recoveries of digested and undigested unfiltered water samples. The method was applied to study total and dissolved Pb in many water columns collected from different stations in Lake Ontario. Dissolved Pb was found to be about twice as much as dissolved Tl, and total Pb about seven times higher than total Tl. Seventy five percent of Pb is in particulate form versus 11% for Tl. Also, a simple cold dissolution procedure using HNO(3) and HF (not a hot acid digestion) is proposed to "liquefy" sediments in a form suitable for LEAFS analysis and was used to analyze a sediment core, where pore water samples were also collected. The interaction dynamics of Tl within the natural environment of a water/pore water/sediment system from Lake Erie was assessed. The calculations of fluxes suggest a strong similarity between Tl and Cd geochemical transport. The paper also presents for the first time a genuine sediment pore water profile of Tl concentration, which ranged from sub- to 40 ng/l and which was directly determined by LEAFS.

Journal Article↗
PubMed1996

Examination of p53 alterations and cytokeratin expression in sputa collected from patients prior to histological diagnosis of squamous cell carcinoma.

Mutations in the p53 gene are detected in greater than 50% of squamous cell carcinomas of the lung and to a lesser extent in adenocarcinomas. The p53 protein is also overexpressed in a relatively high percentage of preinvasive lesions of the bronchial epithelium. However, unlike tumor tissue, immunoreactivity does not necessarily imply that cells in preinvasive lesions carry a mutant p53 allele. In some cases, overexpression may result from a cellular checkpoint reaction to a toxic or mutagenic substance such as exposure to tobacco smoke. In any case, p53 overexpression in preinvasive lesions may serve as a biomarker for high risk assessment of lung cancer and other tumors in the aerodigestive tract. A study was designed to retrospectively analyze p53 overexpression in cells from sputum samples collected prior to histological tumor diagnosis. The rationale was based on the observation that both preinvasive and tumor cells from the bronchial epithelium are exfoliated into the airways and can be detected based on morphology in sputa. Two sets of cases were chosen: 1) patients whose first primary tumor was a squamous cell carcinoma containing a mutant p53 allele with overexpression observed in most of the tumor cells; and 2) patients whose squamous cell tumor did not contain a mutant p53 allele. Cells which stained positive for p53 expression were observed in sputum samples collected from all six patients whose tumors were positive for a mutant p53 allele. Also p53 positive cells were detected on sputum slides for two of the five cases where the tumor DNA did not contain a mutation and/or tumor cells which overexpress p53 were not detected in tissue sections. Although cells which stained positive for p53 were present in sputum from patients whose tumors contained a missense mutation, the presence of p53 overexpression was not specific for tumors which contain an altered p53 allele since overexpression was detected in sputum cells from patients whose tumor DNA did not contain a p53 mutation and/or tumor cells which stained positive for p53 were not observed in tissue sections. However, the p53 positive cells in sputa collected from the latter group of patients could have been exfoliated from other lesions which contained a mutant p53 allele. The accumulation of p53 in some sputum cells was concomitant with expression of simple epithelial type cytokeratins (CK) 8 and 18 or at least one of the other cytokeratins detected by a broad spectrum (PAN) CK antibody mixture. These data imply that most of the sputum cells which overexpress p53 are epithelial cells. Moreover, our results are consistent, at least in part, with other observations that cells which overexpress p53 in dyplasias and hyperplasias express CK 8, 18. We will continue to explore the possibility that expression of cytokeratins 8, 18 and/or other cytokeratins in conjunction with p53 overexpression and/or morphological criteria could define a new class of atypical cells which are predisposed to cancer development.

Alleles↗
PubMed1995

Helicobacter-like organisms: histopathological examination of gastric biopsies from dogs and cats.

Gastric biopsies from the fundic gland region of 122 dogs and 127 cats were subjected to histopathological examination. The aim of the study was to determine infection rates and degrees of colonization by Helicobacter-like organisms (HLOs), and to ascertain their possible relationship to histopathological changes. In all, 82% of the dogs and 76% of the cats had an HLO infection. The most striking histopathological changes were glandular degeneration with accumulation of lymphocytes and neutrophilic granulocytes (dogs, 21%; cats, 39%), fibrosis of the lamina propria mucosae (dogs, 41%; cats, 58%), oedema in the lamina propria mucosae (dogs, 54%; cats, 23%), lymphoid follicles (dogs, 17%; cats, 19%) and lymphoplasmacytic infiltrates. A relation between the degree of colonization by HLOs and the extent of histopathological changes could only be discovered in the cats. It was not possible to ascertain whether these bacteria, irrespective of the degree of colonization, were responsible for the histopathological changes in the dogs.

Animals↗
PubMed1994

A zinc finger protein, essential for chromosome segregation, constitutes a putative DNA binding subunit of the Saccharomyces cerevisiae kinetochore complex, Cbf3.

A multisubunit protein complex, Cbf3, is a component of the Saccharomyces cerevisiae kinetochore. Cbf3 was recently shown to be essential for chromosome segregation in vivo and for movement of centromere DNA (CEN) along microtubules in vitro. Cbf3 contains three proteins, Cbf3a, Cbf3b and Cbf3c. Here the characterization of Cbf3b is described. Cbf3b contains an N-terminal Zn2Cys6 type zinc finger domain, a C-terminal acidic domain and a putative coiled coil dimerization domain. Cbf3b is essential for growth. Mutations within the zinc finger domain result in cells that exhibit a G2-M cell cycle delay and increased chromosome loss in each mitotic cell division. Therefore, Cbf3b has an essential function in chromosome segregation and the zinc finger domain executes part of this function presumably by providing the specific interaction between Cbf3 and CEN. Finally, data are provided to show that Cbf3c is encoded by CTF13, a gene that had been cloned recently by complementing a temperature sensitive mutant that exhibits chromosome loss as a result of a defective centromere.

Amino Acid Sequence↗
PubMed1994

A new familial glomerulonephropathy in Bernese mountain dogs.

Between 1989 and 1992, 22 Bernese mountain dogs (18 females and four males) aged between two and seven years, which had been suffering for some weeks from weight loss, anorexia, apathy, vomiting, polydipsia and polyuria, were examined. All of them had high blood urea nitrogen and serum creatinine concentrations, and many had hyperphosphataemia, hypercholesterolaemia, hypoproteinaemia and nonregenerative anaemia. All the dogs had very high protein: creatinine ratios in the urine, and macroproteinuria was identified by sodium dodecyl sulphate gel electrophoresis. The immunofluorescent titres against Borrelia burgdorferi, measured in 19 of the dogs, ranged between 256 and 32,768. In all cases, membrano-proliferative glomerulonephritis with concomitant interstitial nephritis was diagnosed. From an analysis of the dogs' pedigree it was concluded that the glomerulonephritis of these Bernese mountain dogs was inherited as an autosomal recessive trait and that its expression was influenced by a second gene locus with a sex-linked dominance exchange.

Animals↗
PubMed1993

Brainstem peptidergic neurons projecting to the medial and lateral thalamus and zona incerta in the rat.

The presence of neuropeptides in brainstem neurons that project to the medial and lateral thalamus and zona incerta has been studied in the rat. Brainstem neurons were retrogradely labeled from the medial and lateral thalamus and the zona incerta by colloidal gold-WGA-HRP and, after silver intensification of the retrograde label, their content of immunoreactivity for nine different neuropeptides was determined after colchicine administration. The medial thalamus and zona incerta both received a large peptidergic input and the lateral thalamus a smaller input from neurons in several brainstem nuclei. These were principally from the locus coeruleus, parabrachial nucleus, the dorsal raphe and the dorsal tegmentum. The principal input to the medial thalamus arose from neurotensin, neuropeptide Y and galanin neurons in the locus coeruleus, neurotensin neurons in the dorsal tegmentum, dynorphin neurons in the parabrachial nucleus and dorsal tegmentum, galanin neurons in the dorsal raphe, substance P neurons in the lateral and dorsal periaqueductal grey and calcitonin gene-related peptide neurons in the nucleus paragigantocellularis. The principal peptidergic input to the zona incerta was from dynorphin neurons in the nucleus of the solitary tract, bombesin neurons in the lateral reticular nucleus, calcitonin gene-related peptide and cholecystokinin neurons in the dorsal tegmentum, substance P, bombesin and galanin neurons in the locus coeruleus, dynorphin and substance P neurons in the lateral periaqueductal grey and cholecystokinin neurons in the substantia nigra, ventral tegmental nucleus and raphe linearis. The principal peptidergic input to the lateral thalamus came from calcitonin gene-related peptide and cholecystokinin neurons in the dorsal tegmentum, calcitonin gene-related peptide and galanin neurons in the locus coeruleus; substance P, neuropeptide Y, galanin and calcitonin gene-related peptide neurons in the dorsal raphe, substance P neurons in the lateral periaqueductal gray, galanin neurons in the nucleus interpedunculus and cholecystokinin neurons in the raphe linearis. In all these cases, from 25% to virtually all of the projection neurons in the brainstem nucleus could contain immunoreactivity to the neuropeptide. A lesser, but significant peptidergic input to the thalamus and zona incerta also arose from the trigeminal nucleus, the substantia nigra, the nucleus of the solitary tract, the lateral reticular nucleus, the interpeduncular nucleus, the raphe linearis, the paragigantocellularis, the inferior olive and ventral tegmental area. Overall, the neuropeptides most frequently present in the projection neurons were substance P, calcitonin gene-related peptide, galanin and cholecystokinin. Bombesin, neuropeptide Y, neurotensin and dynorphin were less common; and enkephalin was present in only a small percentage of projection neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Isolation and characterization of a gene (CBF2) specifying a protein component of the budding yeast kinetochore.

We have cloned and determined the nucleotide sequence of the gene (CBF2) specifying the large (110 kD) subunit of the 240-kD multisubunit yeast centromere binding factor CBF3, which binds selectively in vitro to yeast centromere DNA and contains a minus end-directed microtubule motor activity. The deduced amino acid sequence of CBF2p shows no sequence homologies with known molecular motors, although a consensus nucleotide binding site is present. The CBF2 gene is essential for viability of yeast and is identical to NDC10, in which a conditional mutation leads to a defect in chromosome segregation (Goh, P.-Y., and J. V. Kilmartin, in this issue of The Journal of Cell Biology). The combined in vitro and in vivo evidence indicate that CBF2p is a key component of the budding yeast kinetochore.

Amino Acid Sequence↗
PubMed1993

Invasive tumors derived from xenotransplanted, immortalized human cells after in vivo exposure to chemical carcinogens.

Several chemicals that are found in cigarette smoke or diesel oil engine exhausts, such as benzo[a]pyrene (B[a]P) and 1,6-dinitropyrene (DNP) are carcinogenic in experimental animal models. In the present study, we have exposed in vivo the xenotransplanted immortalized human bronchial epithelial cell line BEAS-2B to the ultimate carcinogen of B[a]P, benzo[a]pyrene diolepoxide (BPDE), to DNP or to the benzo[e]pyrene, a less active compound that has tumor-promoting abilities in mouse skin carcinogenesis bioassays. All three compounds were administered using slow-release beeswax pellets. After a 6 month exposure, BPDE produced two tumors in seven transplants, four tumors were seen in 10 transplants treated with DNP and one tumor was observed in five tracheal grafts exposed to B[a]P. All the neoplasms were well-differentiated invasive adenocarcinomas. Tracheal transplants exposed to beeswax without carcinogen did not show any evidence of neoplastic growth, and their luminal surfaces were lined by a single or double layer of cuboidal cells. All lines derived from the adenocarcinomas showed increased in vitro resistance to serum-induced terminal differentiation, gelatinolytic activity, s.c. tumorigenicity and invasive growth in an in vivo assay. When these cell lines were compared with previously described tumor cell lines derived from xenotransplants exposed to cigarette smoke condensate, it became clear that the latter exhibited a more aggressive invasive behavior. Nevertheless treatment with the three chemicals gave rise to tumor cell lines that exhibited a similar invasive behavior in vivo, and were able to penetrate early into the wall of the tracheal transplants in which they were seeded. These data indicate that this system based on xenotransplanted bronchial epithelial cells is a very relevant model to identify human carcinogens and to study mechanisms of bronchogenic cancer pathogenesis.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1993

[Surgical treatment of Galeazzi fracture].

In this study 20 patients with Galeazzi fractures were studied. In 19 patients the Galeazzi fracture was reset using the osteosynthetic procedure and one had conservative treatment alone. Open repositioning is apparently unavoidable. The fracture should be treated with dynamic compression plates (DCP) using 6-8 holes. It is also still open to question as to whether a prolonged healing process can be avoided. A revision of the wrist should only be done if the stability after osteosynthesis is not guaranteed or if repositioning is not satisfactory. Post-operative immobilization proved to be of no value. Although with improved operative techniques the prognosis is not bad, subluxation persists.

Adolescent↗
PubMed1993

[Propofol--a short-term narcotic--tested in gastroduodenoscopy in the cat].

The injection anaesthetic propofol (Disoprivan) was used in 85 cats for performing gastroduodenoscopy. Anaesthesia and feasibility for executing endoscopy were evaluated. Two cats suffered from a transient (30 sec) respiratory arrest. In any other cases stable cardiovascular and acceptable respiratory conditions were observed. The endoscopy was easy to perform and no emesis was induced. Anaesthesia of the cat with propofol can be very well controlled. It is characterised by gentle induction and a recovery free from excitation.

Anesthesia↗
PubMed1991

A 240 kd multisubunit protein complex, CBF3, is a major component of the budding yeast centromere.

A key protein component (CBF3) of the budding yeast (S. cerevisiae) centromere/kinetochore has been purified and characterized. CBF3 is a 240 kd multisubunit protein complex that binds specifically to the yeast wild-type centromere DNA (CEN), but not to nonfunctional CEN DNA containing a single base substitution in the critical CDEIII consensus sequence. When purified by affinity chromatography, CBF3 contains three protein components: CBF3A (110 kd), CBF3B (64 kd), and CBF3C (58 kd). Highly purified CBF3 requires the presence of a separate assembly factor or chaperone activity to bind to CEN DNA. Treatment with phosphatase inactivates CBF3, indicating that at least one of the CBF3 subunits must be phosphorylated for DNA binding to occur. A 56 bp region including the 26 bp CDEIII consensus is protected from DNAase I cleavage in the CBF3-CEN DNA complex.

Base Sequence↗
PubMed1991

[Fulminant malignant hyperthermia during the 6th general anesthesia using volatile anesthetics].

We report on the fulminant crisis of malignant hyperthermia occurring in a 30-year-old female during kidney transplantation. In the past, she had been anaesthetised repeatedly without complications. Anaesthesia was induced with thiopental and vecuronium and continued with isoflurane/N2O/O2. After an initially normal course of anaesthesia, the patient developed symptoms of a fulminant malignant hyperthermia (MH) including excessive increase in end expiratory CO2, hyperkalaemia, tachycardia and hyperpyrexia. The patient was saved by the timely administration of dantrolene. A surgical revision required the next day because of bleeding was done under dantrolene cover and took an uncomplicated course. The patient was extubated 7.5 hours after the second intervention and transferred to a normal ward after 4 days. A subsequently performed in vitro contracture test clearly revealed susceptibility to malignant hyperthermia.

Adult↗
PubMed1991

[Cystocentesis in dogs and cats].

The technique of cystocentesis in dogs and cats was studied. The indications and contraindications of this method are discussed, using illustrations.

Animals↗