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Biomedical subjects

A Schober

Publications and source records attributed to A Schober.

At least 55 records · Page 3Linked to original sources
PubMed1993

Accurate high-speed liquid handling of very small biological samples.

Molecular biology techniques require the accurate pipetting of buffers and solutions with volumes in the microliter range. Traditionally, hand-held pipetting devices are used to fulfill these requirements, but many laboratories have also introduced robotic workstations for the handling of liquids. Piston-operated pumps are commonly used in manually as well as automatically operated pipettors. These devices cannot meet the demands for extremely accurate pipetting of very small volumes at the high speed that would be necessary for certain applications (e.g., in sequencing projects with high throughput). In this paper we describe a technique for the accurate microdispensation of biochemically relevant solutions and suspensions with the aid of a piezoelectric transducer. It is suitable for liquids of a viscosity between 0.5 and 500 milliPascals. The obtainable drop sizes range from 5 picoliters to a few nanoliters with up to 10,000 drops per second. Liquids can be dispensed in single or accumulated drops to handle a wide volume range. The system proved to be excellently suitable for the handling of biological samples. It did not show any detectable negative impact on the biological function of dissolved or suspended molecules or particles.

Base Sequence↗
PubMed1991

Morphology of neurons in the rat basal forebrain nuclei: comparison between NADPH-diaphorase histochemistry and immunohistochemistry of glutamic acid decarboxylase, choline acetyltransferase, somatostatin and parvalbumin.

Transversal sections through the basal forebrain of 11 adult male rats were immunostained for glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), somatostatin (SOM) and parvalbumin (PARV). Immunohistochemistry of ChAT, PARV, and SOM was combined with histochemistry of NADPH-diaphorase (NADPH-d) to obtain information on the colocalization of various neuroactive substances and this enzyme and to facilitate the recognition of morphological details of double-stained neurons. The distribution patterns of GAD- and PARV-immunoreactive cells were only in part congruent in basal forebrain nuclei in the rat. In the medial septal nucleus (MS) and the vertical limb of the diagonal band (vDB) PARV-immunopositive neurons were homogeneously scattered inside the nucleus, whereas the GAD-immunoreactive cells were much more numerous in the lateral part of this nuclear complex. In the horizontal limb of the diagonal band (hDB) and the nucleus preopticus magnocellularis (NPM), where GAD-immunoreactive cells occurred in high number, only very few cells contained PARV-immunoreaction product. In the substantia innominata-nucleus basalis Meynert complex (SI-NB) and in the ventral pallidum (VP) the neuropil was heavily stained with the GAD-immunoreaction product. The number of GAD-positive cells appeared low in the SI-NB, but much higher in the VP. In this nucleus GAD- and PARV-immunoreactive cells seem to be identical. PARV-positive neurons are very sparse in the SI-NB. Double-staining of PARV-immunoreactivity and NADPH-d was not registered. These nuclei were the only ones in which some cells with SOM-like immunoreactivity were observed. Among ChAT-positive neurons those double-stained with NADPH-d occurred in moderate number, but with obvious regional differences. In MS-vDB and the marginal zone of hDB the two neuron groups were intermingled, but only in the innermost part of the hDB ChAT-single-immunostained cells form aggregates, which were also typical of the zone in the SI-NB that surrounds and infiltrates the globus pallidus (GP). Double-labelled cells were more frequent in the lateral aspect of the NPM and SI-NB. Cells single-stained for NADPH-d were frequent in the MS-vDB along the border toward the lateral septal nuclei, but low in number in the NPM, VP and SI-NB. The functional aspects of the occurrence of GAD-immunoreactive cell aggregates in the lateral preoptic area (LP) and the lateral hypothalamic area (LH) were discussed with special regards to extrinsic GABAergic input in the dorsal SI-NB.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

The cholinergic nuclei of the basal forebrain of the hamster (Mesocricetus auratus): a combined Golgi- and AChE-topochemical investigation.

The cholinergic basal forebrain nuclear complex of the golden hamster was investigated Golgi-architectonically and AChE-topochemically using enzymehistochemical and immunohistochemical methods. We demonstrated 12 different classes of neurons in the whole basal forebrain complex with the Golgi-Kopsch-technique. The classical anatomical subdivision of the septal-region into nucleus medialis septi and nucleus tractus diagonalis has not been confirmed by results elaborated with this method. We found at least one class of neurons with varicose dendrites in every part of the cholinergic basal forebrain complex. The varicosities reacted positively for AChE. This morphological feature might be characteristic for cholinergic neurons in the nuclei of the basal forebrain complex.

Acetylcholinesterase↗
PubMed1984

[Effect of a weak magnetic field on the course of an acute inflammation in the rat].

To determine the influence of weak magnetic field on the development of inflammations, a non-specific acute inflammation was induced in rats by subcutaneous injection of sterile SEPHADEX-gel in the lower dorsal quadrants. The magnetic field applied had a strength of 10 Gauss (equivalent to 20 times the magnetic field of the earth), rectangular curve and a frequency of 10 Hz. Following a field exposure of 2 and 3 days, cytological and biochemical analyses of the blood and inflammatory exudate were performed. Parameters were leucocytes and proteins in the blood and in the focus of inflammation as well as blood electrolytes. The protein values in the focus of inflammation of the control animals remained unchanged on the second and third day whereas in the animals exposed to the magnetic field, they increased from the second to the third day. In the blood similar effects could be seen, but they were not as pronounced. We conclude from these data that the magnetic field causes an increased exudation of serum proteins in the focus of inflammation. The cellular component remains unchanged.

Acute Disease↗
PubMed1982

[Electrolytic changes in the white mouse under the influence of weak magnetic fields].

On female white mice, the influence of weak magnetic fields on their electrolyte balance has been tested. Three types of magnetic fields, namely of a 50 HZ sinusoidal, a 50 Hz rectangular and a 10 Hz rectangular field have been applied, the latter mainly because of its similarity to some biologic rhythms and because some technical environments also tend to produce similar type of fields. The changes of electrolyte balance mentioned above were measured after one and seven days of exposure of the animals to those fields. The 50 Hz sinusoidal and 50 Hz rectangular type of the field shows - with the exception of Ca++ - no significant changes in the animals electrolyte balance, neither after one more after seven days. Ca++ levels however were in both cases significantly lower in test animals then in controls. A one days exposure to a 10 Hz rectangular field significantly lowers the Na+ and increases K+ levels. Almost reversed results are obtained after seven days, probably indicating overcompensation, after recovery. Since Na+ in liver homogenates after one days exposure is also low, we tend to hold the opinion that it must be excreted. Therefore it should be of some interest to check the balance of those hormones (e.g. angiotensin, vasopressin) which are closely connected with the above mentioned measured effects.

Animals↗
PubMed1981

Solid-phase radioimmunoassay for detection of alcoholic hyalin antigen (AHAg) and antibody (anti-AH).

Alcoholic hyalin (AH) was isolated and purified from post-mortem livers of patients with alcoholic hepatitis. Antibodies against AH (anti-AH) were raised in guinea-pigs. Their specificity was demonstrated by immunofluorescence and by immunoabsorption. The antisera were positive in immunofluorescence and complement fixation up to serum dilutions of 1:320 and 1:32 respectively. In order to achieve a higher sensitivity a solid-phase radioimmunoassay (SP-RIA) was established for detection of alcoholic hyalin antigen (AHAg) and anti-AH. Anti-AH could thus be measured up to a 10(5) serum dilution. Using a blocking test, solubilized AH at protein concentrations as low as 80 to 160 ng/ml could be detected. With this SP-RIA, neither AHAg nor anti-AH was found in the sera of 32 patients with histologically proven alcoholic hepatitis. The sera were likewise negative by indirect immunofluorescence, complement fixation and immune adherence haemagglutination test.

Antibodies↗
PubMed1978

[Asymptomatic chronic-persisting hepatitis B in a young child as source of infection of hepatitis B within a family (author's transl)].

Five members of an eight-member family fell ill with an acute icteric hepatitis B of the same subtype within eleven months. In all probability the source of the infection was a just over one-year-old fostered child with asymptomatic chronic persisting hepatitis B and signs of massive viraemia (usually high HBs antigen concentration, high virus-specific DNA-polymerase activity and positive HBe antigen test). No relation could be demonstrated between HLA constellation and illness in the family members. Since no specific treatment is available, the only possible prophylactic measure is to isolate the child in the present environment, to avoid further cases of the disease.

Acute Disease↗
PubMed1975

Direct solid-phase radioimmunoassay (dSP-RIA) for detection of antibody to hepatitis B surface (HBs) antigen.

Using direct solid-phase radioimmunoassay (dSP-RIA) which was shown to be specific and about 10000 times more sensitive than immunodiffusion and even 10 times more sensitive than the radioimmunoprecipitation test used by us before, anti-HBs was detected in 90% of hepatitis B convalescents who were followed up for a one year observation period and who had eliminated HBs antigen from their sera (60/68). In 13% of these patients (8/60 anti-HBs was only temporarily detectable. In 50% of all patients who developed antibody within a two to twelve months observation period (n = 151), anti-HBs appeared within three to four months after height of disease. In 16.5% of patients with HBs antigen negative hepatitis (32/193) anti-HBs was observed to develop during convalescence indicating a type B infection despite a negative finding for HBs antigen in the acute stage of disease. Using dSP-RIA anti-HBs was found in 5.5% of voluntary blood donors (n = 1036), in 20.2% of hospitalized patients without clinical hepatitis (n = 252), and in 30.6% of hospital staff (n = 304). Anti-HBs increases with age: in 14 year olds we found 0.5%, in 60 year olds, 14%. The fact that at least 70% of the anti-HBs positive normal persons and medical staff groups had no history of hepatitis illustrates the frequency and importance of subclinical hepatitis B infections.

Adolescent↗