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Biomedical subjects

H Mohr

Publications and source records attributed to H Mohr.

At least 73 records · Page 4Linked to original sources
PubMed1986

Differentiation between primary and recurrent cytomegalovirus infections.

Two blocking tests were applied simultaneously to detect antibodies to cytomegalovirus (CMV) in human serum specimens. Two different peroxidase-labelled tracers were prepared from human sera taken either early during a primary CMV infection or late after recurrent infection. Sera of acute primary CMV cases effectively competed with the labelled antibodies of the "early" tracer but a rather weak inhibition was observed with the "late" tracer. Sera of cases with recurrent infection strongly inhibited both tracers. Immunoblot experiments were carried out to explain the mechanism of this differential inhibition.

Acute Disease↗
PubMed1986

Calcium ionophore A 23 187 in the presence of phorbol ester PMA: a potent inducer of interleukin 2 and interferon-gamma synthesis by human blood cells.

Cultures of human blood mononuclear cells incubated with the calcium ionophore A 23 187 in the presence of the tumor promoter phorbol 12-myristate-13-acetate (PMA) produced 5-10 times more of the lymphokines interleukin 2 (IL 2) and interferon-gamma (IFN-gamma) than cultures which were stimulated with other combinations of inducing agents and PMA. Especially at low protein concentrations, the amount of ionophore which is necessary to induce maximal quantities of both lymphokines was determined by the protein content of the culture medium. The synthesis of the two lymphokines was inhibited by low doses of Mn++ which competes with Ca++ for binding to the ionophore. This suggests the importance of Ca++ in the induction process. The synthesis rates of IL 2 were maximal 10-12 h, and those of IFN-gamma 20-40 h after induction. Maximal titers of IL 2 were detected 48 h after the addition of A 23187 and PMA to the cultures, and the highest IFN-gamma levels 12-24 h later.

Calcimycin↗
PubMed1985

Structures of the major carbohydrates of natural human interleukin-2.

Purified human interleukin-2 secreted by peripheral blood lymphocytes from healthy donors was found to exist in several forms. These forms were (partially) resolved by reversed-phase high-performance liquid chromatography and sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Two major polypeptide species (interleukin-2 N1 and N2, 16.5 kDa) were shown to be glycosylated on the basis of [3H]galactose/[3H]glucosamine incorporation and determination of amino sugars after acid hydrolysis. A third component (interleukin-2 M, 14.5 kDa) represents a nonglycosylated form. The amino acid composition and the NH2-terminal sequence of both forms are consistent with the data deduced from the cDNA coding for interleukin-2 after removal of a leader peptide of 20 amino acids. Carbohydrates are O-linked to the IL-2 protein via threonine-3 of the polypeptide chain. The oligosaccharides were released by reductive beta-elimination and were purified by gel filtration and high-performance liquid chromatography. Applying methylation analysis, exoglycosidase digestion and fast atom bombardment mass spectrometry the following major carbohydrate structures were identified: N1, NeuAc(alpha 2-3)Gal(beta 1-3)GalNAc-ol; and N2, NeuAc(alpha 2-3)Gal(beta 1-3)[NeuAc(alpha 2-6)]GalNAc-ol.

Amino Acid Sequence↗
PubMed1985

Simple detection of antibodies to different viruses using rheumatoid factor and enzyme-labelled antigen (ELA).

A new one-step method was developed to detect IgG antibodies to different virus antigens. Human serum specimens were mixed with different enzyme-labelled antigen (ELA) preparations in microtitre plates coated with rheumatoid factor (RF). During the incubation in the wells of microtitre plates immune complexes form which are specifically bound to the RF on the solid phase. The test detects antibody to cytomegalovirus (CMV) and West-Nile virus with a high sensitivity and specificity.

Antibodies, Viral↗
PubMed1985

Mode of coaction between blue/UV light and light absorbed by phytochrome in light-mediated anthocyanin formation in the milo (Sorghum vulgare Pers.) seedling.

Anthocyanin formation in milo (Sorghum vulgare Pers.) seedlings (coleoptile, mesocotyl, taproot) occurs only in white light and blue/UV light (BL/UV), while red light (RL) and far-RL are totally ineffective. However, after a BL/UV pretreatment, the participation of phytochrome can be demonstrated. With a short-wavelength light source [peak emission in longwave UV (UV-A)], the mode of coaction between BL/UV and light absorbed by phytochrome (RL) was studied with the following principal results. (i) As soon as the seedling becomes competent to respond to UV-A (with regard to anthocyanin formation), the involvement of phytochrome can be detected. (ii) A 5-min pulse of UV-A has a strong effect on the anthocyanin synthesis in the milo mesocotyl. This effect is fully reversible if a long-wavelength far-RL pulse (RG9 light) is given immediately after the UV-A light pulse. (iii) When seedlings treated with 5 min of UV-A and 5 min of RG9 light are kept in darkness for 3 hr and then transferred to RL, anthocyanin appears. (iv) In continuous UV-A treatment, anthocyanin accumulation starts after a lag phase of 3.5 hr (25 degrees C). A RL pretreatment prior to the onset of UV-A treatment strongly increases anthocyanin accumulation in UV-A, though the lag phase is not affected. Moreover, a RL pretreatment does not affect the time course for escape from reversibility in UV-A. It is concluded from these data that BL/UV cannot mediate induction of anthocyanin synthesis in the absence of P(fr), the active form of phytochrome that absorbs maximally in the far-red. Rather, the action of BL/UV must be considered to establish responsiveness of the anthocyanin-producing mechanism to P(fr). P(fr) operates in this system via two different channels. As the effector of the terminal response, it sets in motion the signal-response chain that eventually leads to the appearance of anthocyanin. This is a slow process with a lag phase of the order of 3.5 hr. The second function of P(fr) is to determine the responsiveness to the effector P(fr) in mediating anthocyanin synthesis. This is a very fast and highly sensitive phytochrome action that can be detected readily within 1 min. However, as long as the plant has not received BL/UV, the strong effect of RL on the effectiveness of P(fr) remains cryptic. The effect of a RL pretreatment and the effect of a UV-A pretreatment on responsiveness towards P(fr) (or, effectiveness of P(fr)) were found to be totally independent of each other, even though it is the UV-A that permits operation of P(fr).

Journal Article↗
PubMed1984

Interferon-alpha yields from Sendai virus-induced human leukocyte cultures are enhanced by lowering the incubation temperature.

Increased yields of Sendai virus-induced human leukocyte interferon (IFN-alpha) were obtained by lowering the incubation temperature from the initial 37 degrees C within 1 to 6 h after the addition of virus. Maximal stimulation was found when this was done 2 to 4 h after induction and when the lowered temperature was between 29 and 32 degrees C. Compared to cultures kept at 37 degrees C throughout, the resulting IFN-alpha yields were enhanced by 2.5- to 3-fold. This was mainly due to prolonged synthesis of IFN-alpha, which could be observed up to 20 h after induction, whereas in cultures kept at 37 degrees C the production of IFN-alpha had practically ceased approx. 10 h after the addition of virus.

Cells, Cultured↗
PubMed1982

Phytochrome action on chlorophyll synthesis-a study of the escape from photoreversibility.

A brief red light pretreatment (pulse), operating through phytochrome, stimulates the synthesis of chlorophyll a and b in Sorghum vulgare shoots that are placed in continuous saturating white light. The red light effect is fully reversible by a far-red (756 nanometers) light pulse for 45 minutes. Thereafter, escape from reversibility is fast, being completed within 2 hours. It is shown here that physiologically active phytochrome (Pfr) is required continuously during these first 45 minutes if the onset of the loss of photoreversibility is to begin 45 minutes after the red light treatment. Thus, the initial action of Pfr consists of two distinct processes: the first process is to overcome the lag prior to escape from photoreversibility; the second process is the actual stimulation of chlorophyll synthesis by Pfr. The duration of the lag prior to escape from photoreversibility depends on the level of Pfr established by the light pulse. The duration increases with increasing Pfr levels from nondetectable to 45 minutes. Above approximately 15% Pfr (Pfr/P(lot) approximately 0.15), the duration of the lag prior to escape from photoreversibility remains constant at 45 minutes.

Journal Article↗
PubMed1980

Different handling of parathyrin by basal-lateral and brush-border membranes of the bovine kidney cortex.

The two parts of the bovine kidney cortex plasma membrane, the basal-lateral and the brush-border membrane, were simultaneously prepared from the same organ. Both types of membrane bound parathyrin, but only from the basal-lateral fraction was the hormone displaceable by its bioactive N-terminal fragment. In parallel, parathyrin-stimulated adenylate cyclase was predominantly found in basal-lateral membranes. The hormone was fragmented by both membrane types. Basal-lateral membranes generated fragments with a rather uniform size distribution (somewhat smaller than the intact peptide) and apparently preferred the hormone itself as a substrate. In contrast, the fragments produced by brush-border membranes were numberous small peptides.

Adenylyl Cyclases↗
PubMed1980

Human parathyroid hormone: antibody characterization.

PTH antibodies were raised in two sheep (S 469 and S 478) by immunizing with porcine and bovine parathyroid extracts. Both antisera were characterized with various PTH preparations and fragments. Both antisera cross react with human, bovine and porcine PTH, one antiserum also binds rat PTH. Region specificity could be attributed to the mid region of the PTH molecule with particularly high affinities of both antisera for the fragment 44-68 hPTH. S 478 has similarly high affinity for intact hormone (affinity constants 0.6 x 10(13) l/mol), while S 469 has much higher affinity for the 44-68 fragment (affinity constant 0.84 x 10(13) l/mol) than for intact hormone. The antibodies are useful not only for clinical radioimmunoassay, but also for experimental work. They have been distributed to many laboratories.

Animals↗
PubMed1980

Parathyroid hormone fragments in secretory granules of human parathyroid adenomata.

The composition of human parathyroid hormone immunoreactivity in the secretory granule fraction of parathyroid hormone adenomata was investigated. Granular extracts were separated by gel filtration and the eluates assayed by radioimmunoassay and sequence specific immunoradiometric assays detecting aminoterminal and carboxyterminal activity. About half of the extracted adenomata contained fragments besides intact hormone. The fragment composition varied from adenoma to adenoma.

Adenoma↗
PubMed1980

Adsorption of parathyrin: pitfall for solid phase assays using radiolabelled antibodies?

The physicochemical behaviour of parathyrin on surfaces was investigated. Parathyrin is bound to the wall of polyethylene, polypropylene and flint glass tubes. This adsorptive binding of the hormone, detected by labelled antibodies, is a time-dependent process which is complete within one hour. The addition of plasma decreases but does not prevent adsorption. Coating of the tubes with an anti-N-regional or anti-C-regional antiserum decreases the sensitivity of the detection of 1-34, 53-84 and 1-84 intact parathyrin, when performed in buffer. In the presence of plasma the increase of radiolabelled antibody detecting the parathyrin was more pronounced when tubes were precoated with an anti-parathyrin antibody. The sensitivity of the 1-84 parathyrin assay was also reduced when incubation was carried out in the presence of high concentrations of parathyrin-fragments, calcitonin, somatostatin or bovine serum albumin. Assay specificity seems to be related to the specificity of the labelled antibody for the respective hormonal fragment, not to that of the antibody used for coating the tubes. This investigation illustrates the necessity for the careful control of parathyrin assay conditions, e. g. non-specific binding of native parathyrin and radiolabelled tracers to laboratory reaction vessels.

Adsorption↗
PubMed1978

Alamethicin biosynthesis: acetylation of the amino terminus and attachment of phenylalaninol.

Alamethicin synthetase was extracted from the fungus Trichoderma viride at the end of its exponential growth phase. It is multienzyme complex with a molecular weight of approx. 480 000. The biosynthesis of alamethicin is initiated on the synthetase by acetylation of thiolester-bound aminoisobutyric acid, which remains enzyme bound. Acetyl-CoA serves as the acetate donor. Of the alamethicin constituents, glycine, alanine and valine are also acetylated when incubated alone. This acetylation is prevented by added aminoisobutyric acid, which indicates that the site on alamethicin synthetase catalyzing the acetylation has a preference for aminoisobutyric acid. Alamethicin formation on the synthetase is terminated by linkage of phenylalaninol to the carboxyl terminus of the peptide. It is unlikely that the amino alcohol is a degradation product of alamethicin or that it had been split off from the synthetase complex. Thus it is probably the reaction product of a separate enzyme system.

Acetylation↗