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Biomedical subjects

M Exner

Publications and source records attributed to M Exner.

At least 127 records · Page 7Linked to original sources
PubMed1993

NHE3: a Na+/H+ exchanger isoform of renal brush border.

Na+/H+ exchangers in the brush-border (luminal, apical) membrane of renal proximal tubules are responsible for active, transcellular reabsorption of NaHCO3 and NaCl. Although well characterized kinetically, the protein that mediates Na+/H+ exchange in the renal brush border has not been identified. Several Na+/H+ exchanger genes, including NHE1, NHE2, NHE3, and NHE4, are expressed in the kidney. To identify the NHE3 gene product and to determine its cellular and subcellular localization in the rabbit kidney, an NHE3-isoform-specific antibody was prepared. Guinea pigs were immunized with purified fusion protein containing the carboxy-terminal 40 amino acids of NHE3 (fpNHE3-C40). After affinity purification, immune sera demonstrated specific reactivity to the NHE3 sequence within the fusion protein as well as to an 80-kDa polypeptide expressed in NHE3-transfected LAP1 cells. Western blot analysis showed that anti-fpNHE3-C40 specifically reacted with an 80-kDa protein that is relatively enriched in renal brush-border membrane compared with basolateral membrane. Immunocytochemical studies confirmed that the Na+/H+ exchanger isoform NHE3 is expressed along the microvillar membrane of the brush border of proximal tubule cells in the rabbit kidney.

Animals↗
PubMed1993

Behaviour in the novel environment predicts responsiveness to d-amphetamine in the rat: a multivariate approach.

The behaviour of rats in a novel environment was studied using a rapid time-sampling observation procedure followed by a principal component analysis (PCA) of the data. This approach revealed that novel environment behaviour can be described by two factors or principal components. The first factor comprised rearing, sniffing-up, ambulation and locomotion (photocell counts), and was termed "Escape". The second factor, which had high positive loadings of sniffing-down and locomotion and a high negative loading of immobility, was termed "Exploration". The scores of individual rats on the "Escape" factor predicted the stimulatory effect of acutely administered d-amphetamine (1.5mg/kg) on unconditioned behaviour. "Escape" high responders (HRs) showed more behavioural stimulation than "Escape" low responders (LRs). However, the locomotor stimulatory response of both groups increased after long-term, periodic administration of d-amphetamine and drug discrimination training, such that the level of drug-induced locomotor activity was now equivalent for the two groups. The same rats were tested twice with various doses of d-amphetamine after being trained to discriminate this drug (0.5mg/kg) from saline. "Escape" HRs were less sensitive than "Escape" LRs to the discriminative effects of 0.125-0.25mg/kg d-amphetamine. In contrast to these findings, "Exploration" HRs and LRs were not different on any of the dependent measures described above. These results are discussed in relation to the possibility that "Escape" factor scores are an indication of an animal's responsivity to novelty-induced stress. If this is the case, then animals which are more susceptible to the effects of novelty stress are more sensitive to the locomotor stimulating effects of acute d-amphetamine, but less sensitive to the cueing properties of low doses of this drug.

Journal Article↗
PubMed1992

Immunocytochemical characterization of Na(+)-H+ exchanger isoform NHE-1 in rabbit kidney.

We have recently isolated cDNAs encoding a Na(+)-H+ exchanger isoform, referred to as NHE-1, from rabbit kidney and LLC-PK1 cells. To identify the NHE-1 protein and to establish its cellular and subcellular localization in the rabbit kidney, we prepared antibodies to a NHE-1 fusion protein. cDNA encoding the COOH-terminal 41 amino acids of NHE-1 was subcloned into a maltose-binding protein vector and the purified fusion protein (FP347A) used to immunize guinea pigs. To identify the NHE-1 protein, we performed Western blot analysis against membrane fractions prepared from rabbit renal cortex. Anti-FP347A antibody specifically reacted with a polypeptide with an apparent molecular mass of 100-110 kDa that was enriched in basolateral membrane fractions. When indirect immunofluorescence was performed on semithin (0.5 micron) cryosections of paraformaldehyde-lysine-periodate-fixed rabbit kidney, anti-FP347A specifically stained the basolateral plasma membrane of cells of the proximal tubule, thick ascending limb, and distal convoluted tubule. Anti-FP347A similarly stained connecting tubule cells and principal cells. No staining was detected on the apical membrane of any cells of the rabbit nephron. We conclude that NHE-1 is a 100- to 110-kDa protein expressed on the basolateral membrane of multiple nephron segments.

Animals↗
PubMed1992

Agonist and antagonist activity of low efficacy D2 dopamine receptor agonists in rats discriminating d-amphetamine from saline.

The ability of the low efficacy D2 agonists preclamol and SDZ 208-911 to both antagonise, and substitute for, the d-amphetamine discriminative cue was investigated in rats trained to discriminate d-amphetamine (0.5mg/kg) from saline. All doses of preclamol (2.0-16.0mg/kg) and SDZ 208-911 (0.125-1.0mg/kg) only partially antagonised d-amphetamine discrimination. In contrast, the lower efficacy D2 agonist SDZ 208-912 completely blocked the cueing properties of d-amphetamine. Preclamol (4.0 and 16.0mg/kg) and SDZ 208-911 (1.0mg/kg) also partially substituted for d-amphetamine. In an additional study, the former drug enhanced the discriminative effects of a low dose of d-amphetamine (0.125mg/kg), whilst antagonising the effects of the training dose. Preclamol also partially antagonised the ability of the selective D2 agonist quinpirole (0.125mg/kg) to substitute for d-amphetamine. In contrast to the drug discrimination findings, preclamol completely antagonised the locomotor hyperactivity induced by acute d-amphetamine, in animals which had received the same long-term d-amphetamine treatment as the drug discrimination rats. The present findings reveal that preclamol and SDZ 208-911 can exert both agonist and antagonist activity in animals trained to discriminate d-amphetamine from saline. This partial agonist profile is probably due to the low efficacy D2 agonists interacting with a postsynaptic D2 receptor population possessing a higher response capability than those D2 receptors mediating d-amphetamine-induced locomotor hyperactivity.

Journal Article↗
PubMed1992

[Case study of a Legionella epidemic in a rehabilitation clinic].

A series of nosocomial Legionella infections in a rehabilitation center is reported. In a three months period a total of 10 pneumonias with 3 deaths occurred (8 patients, 1 companion, 1 staff member). Serologic analysis proved additional Legionella infections within the nursing staff. The warm-water system was proved to be the source of infection by isolating Legionella pneumophila serogroup 1 subtype Pontiac both in warm-water and patients samples. The air conditioning system could not be ruled out as another (secondary) route of exposure because of shortcomings in construction. Conclusions about prevention and the course of the disease are discussed and standards for warm-water and air conditioning systems are proposed.

Adult↗
PubMed1991

Role of dopamine D1 and D2 receptors in mediating the d-amphetamine discriminative cue.

The role of D1 and D2 dopamine (DA) receptors in mediating the discriminative cue produced by d-amphetamine (0.5 mg/kg) in rats has been assessed by using compounds which exert strong selectivity for each of these DA receptor subtypes. The D2 agonists quinpirole and RU 24213 substituted completely for d-amphetamine, while the D1 agonists SKF 38393 and SKF 81297 failed to exert such effects. On the other hand, the D2 antagonists raclopride and YM 09151-2, and D1 antagonists SCH 23390 and SKF 83566, all completely blocked d-amphetamine discrimination. The D2 antagonists produced more pronounced inhibitory effects on response rate than did D1 antagonists. Quinpirole substitution for d-amphetamine was blocked by YM 09151-2, but not by SCH 23390, while the locomotor stimulatory effect of quinpirole was inhibited by both drugs. The present findings confirm that D2 receptors play a primary role in the d-amphetamine discriminative cue, while the precise role of D1 receptors remains to be disclosed.

Animals↗
PubMed1991

[Detection methods and occurrence of Cryptosporidium sp. in selected surface waters].

Cryptosporidium, a small coccidian parasite, is accepted as an important cause of severe diarrheal illness in man and animals; in immunocompromised persons illness may be life-threatening. Cryptosporidium is transmitted by oocysts, passed in the faeces. These oocysts are remarkable resistant to common disinfectants and they can survive for several months. Person-to-person, animal-to-person and faecal contaminations of the environment are proven routes of transmission. Also waterborne disease outbreaks caused by Cryptosporidium are well documented. This paper represents a modification of a method for the detection of Cryptosporidium in water, developed by Musial et al. and Rose et al. The method includes steps for filtration, elution, centrifugation, flotation and microscopic detection of Cryptosporidium oocysts in sediments using an indirect immunofluorescence technique and a native contrast-technique. With this modified method efficiency of recovery ranged from 8.1% to 27.1%. In addition, selected surface waters in Northrhine-Westphalia were examined. The finding of Cryptosporidium oocysts in 7 of 9 water samples (78%) demonstrates the occurrence of Cryptosporidium oocysts in surface waters in Western-Germany. These results suggest that more detailed studies are needed to assess the risk of this new pathogen in water, especially in removal and disinfection in water treatment plants.

Animals↗
PubMed1991

[Cryptosporidiosis--characterization of new infection with special reference to water as a source of infection].

Within the past few years, microorganisms of the Genus Cryptosporidium have been recognized as an important pathogen to humans. A possible mode of transmission is represented by the presence of Cryptosporidium-oocysts in water. Meanwhile several outbreaks of diarrheal illness caused by the contamination of drinking water by Cryoptosporidium have been documented; an infection can be life-threatening for immunosuppressed patients. This article reviews the organism causing Cryptosporidiosis, his ecology, the clinical feature, the sources of infection and the epidemiology. The remarkable resistance of the oocysts to disinfectants, such like chlorine, their survival for a long time and the low infectious dose shows evidently that the conservative guidelines in treatment and quality control of drinking water should be discussed newly.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Determining guidelines for metals in children's playgrounds in North Rhine-Westphalia].

In 1990, the State of North-Rhine-Westphalia established an ordinance on the quality of playground soil and sand. This ordinance includes guideline values for toxic metals (arsenic, lead, cadmium, chromium) in playground soil not covered by vegetation and quality standards for sand to be applied on playgrounds. Additionally guideline values were set for mercury, nickel and thallium. The guideline values include two categories: guideline value I represents the upper limits (95-percentiles) of the background levels of toxic metals generally found in upper soil layers in the State of North-Rhine-Westphalia. Guideline values II ("action levels") were selected on the basis of toxicological considerations. In cases where concentrations of metals above these guideline values are detected, immediate actions (urgent redevelopment measures) are required. Quality standards for playground sand were established to ensure that only noncontaminated sand is applied for playgrounds.

Child↗
PubMed1990

[Cryptosporidiosis. Characterization of a new infection with special regard to water as the source of infection].

Within the past few years, microorganisms of the Genus Cryptosporidium have been recognized as an important pathogen to humans. A possible mode of transmission is represented by the presence of Cryptosporidium-oocysts in water. Meanwhile several outbreaks of diarrheal illness caused by the contamination of drinking water by Cryptosporidium have been documented; an infection can be life-threatening for immunosuppressed patients. This article reviews the organism causing Cryptosporidiosis, his ecology, the clinical feature, the sources of infection and the epidemiology. The remarkable resistance of the oocysts to disinfectants, such like chlorine, their survival for a long time and the low infectious dose shows evidently that the conservative guidelines in treatment and quality control of drinking water should be discussed newly.

Animals↗
PubMed1990

[Hygienic measures in endoscopy].

Risks of infection associated with endoscopy, sources of infection, relevant microorganisms (P. aeruginosa, Serratia, HIV, HB, Cryptosporidiosis), disinfection procedures and the steps of disinfection procedures and reasons for failing of disinfection procedures are discussed. Channel systems and rinsing solutions are relevant but until today underestimated sources of infection. In detail the contamination of the channel system in endoscopes, problems of good disinfection and the significance of mechanical cleaning are described. In cases of Pseudomonas aeruginosa infections after endoscopy an immediate investigation of the contamination of the endoscope and of rinsing solutions is necessary. Automatic disinfection systems are requested, because with such systems a higher security for patient and personal is achievable. A regular control of the efficacy of the disinfection process by a competent Hygiene-Institute is recommended.

Cross Infection↗