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E Mayer

Publications and source records attributed to E Mayer.

At least 199 records · Page 11Linked to original sources
PubMed1984

Interlaboratory comparison of 25-hydroxyvitamin D determination.

This interlaboratory study on determination of 25-hydroxyvitamin D (25-OH-D) in serum involved 15 laboratories in eight European countries. All could distinguish between normal (50 +/- 31 nmol/L, mean +/- SD) and grossly increased concentrations, but for eight laboratories the results for serum samples with low and normal 25-OH-D content overlapped. In general, values were well reproducible, but interlaboratory variation in 25-OH-D measurement was large, 24,25(OH)2D3 interfering in most of the assays. We present evidence in favor of chromatography before assay, as opposed to nonchromatographic methods. Liquid chromatography with ultraviolet detection for quantifying 25-OH-D2 and 25-OH-D3 appears to be an appropriate reference method, whereas competitive protein binding assay is the method of choice for routine determinations. Control sera with subnormal, normal, and above-normal concentrations of 25-OH-D3 are needed for use in standardization of 25-OH-D assays.

25-Hydroxyvitamin D 2↗
PubMed1983

Isolation and identification of 1,25-dihydroxy-24-oxo-vitamin D3 and 1,23,25-trihydroxy-24-oxo-vitamin D3. New metabolites of vitamin D3 produced by a C-24 oxidation pathway of metabolism for 1,25-dihydroxyvitamin D3 present in intestine and kidney.

Two new vitamin D metabolites were isolated in pure form from separate incubations of homogenates of chick small intestinal mucosa or rat kidney employing either 1 alpha,25-dihydroxyvitamin D3 (28 microM) or 1 alpha,24R,25-trihydroxyvitamin D3 as substrate (0.17-1.3 microM). The newly characterized compounds and the amounts isolated in pure form from separate isolations are, respectively: 1 alpha,25-dihydroxy-24-oxo-vitamin D3 (1,25(OH)2-24-oxo-D3), 147 micrograms from kidney and 4.2 and 40 micrograms from intestine; 1 alpha,23,25-trihydroxy-24-oxo-vitamin D3 (1,23,25(OH)3-24-oxo-D3), 155 micrograms from kidney and 5.9 and 34 micrograms from intestine. Their structures were identified after extensive high pressure liquid chromatography by means of ultraviolet absorption spectrometry, mass spectrometry of the free compounds and their trimethylsilylated derivatives, proton nuclear magnetic resonance spectrometry, specific chemical reduction of the 24-oxo functionality with sodium borohydride, as well as direct comparison with synthetic 1,25(OH)2-24-oxo-D3. These structural assignments for both compounds correct previous determinations which had been proposed (Ohnuma, N., Kruse, J. R., Popjak, G., and Norman, A. W. (1982) J. Biol. Chem. 257, 5097-5102). The activity of the C-24 oxidation pathway used for the production of the 1,25(OH)2-24-oxo-D3 and 1,23,25(OH)3-24-oxo-D3 can be enhanced 10-fold by prior priming of the chicks or rats with a single intravenous dose of 1,25(OH)2D3 (1-12 nmol/100 g body weight); the induction of the enzyme activity is maximal by 3-6 h and returns to basal levels within 12 h. Further, 1,25(OH)2D3, 1,24,25(OH)3D3, and 1,25(OH)2-24-oxo-D3 all were found to be capable of serving as a precursor with chick intestine and rat kidney homogenates of 1,23,25(OH)3-24-oxo-D3. Collectively these results suggest the existence of a C-24 oxidation pathway for metabolism of 1,25(OH)2D3 by the target intestinal mucosa and kidney to 1,23,25(OH)3-24-oxo-D3. The pathway may play an important role in controlling the tissue levels of this hormonally active form of vitamin D3.

Animals↗
PubMed1983

Biological activity assessment of the vitamin D metabolites 1,25-dihydroxy-24-oxo-vitamin D3 and 1,23,25-trihydroxy-24-oxo-vitamin D3.

Two new metabolites of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], namely 1,25(OH)2-24-oxo-vitamin D3 and 1,23,25(OH)3-24-oxo-vitamin D3, have been prepared in vitro using chick intestinal mucosal homogenates. To investigate the binding of 1,25(OH)2-[23-3H]-24-oxo-D3 and 1,23,25(OH)3-[23-3H]-24-oxo-D3 to the chick intestinal receptor we have isolated both metabolites in radioactive form using an incubation system containing 1,25(OH)2-[23,24-3H))-D3 with a specific radioactivity of 5.6 Ci/mmol. Both metabolites were highly purified by using Sephadex LH-20 chromatography followed by high-pressure liquid chromatography (HPLC). Sucrose density gradient sedimentation analysis showed specific binding of both tritium-labeled metabolites to the chick intestinal cytosol receptor. Experiments were carried out to determine the relative effectiveness of binding to the chick intestinal mucosa receptor for 1,25(OH)2D3. The results are expressed as relative competitive index (RCI), where the RCI is defined as 100 for 1,25(OH)2D3. Whereas the RCI obtained for 1,25(OH)2-24-oxo-D3 was 98 +/- 2 (SE), the RCI for 1,23,25(OH)3-24-oxo-D3 was only 28 +/- 6 (SE). Also, the biological activity of both new metabolites was assessed in vivo in the chick. In our assay for intestinal calcium absorption, 1,25(OH)2-24-oxo-D3 was active at a dose level of 1.63 and 4.88 nmol/bird (at 14 h), whereas 1,23,25(OH)3-24-oxo-D3 showed only weak biological activity in this system. In our assay for bone calcium mobilization, administration of both new metabolites showed modest activity at the 4.88-nmol dose level, which was reduced at the 1.63-nmol dose level. The results indicate that biological activity declines as 1,25(OH)2D3 is metabolized to 1,24R,25(OH)3D3, 1,25(OH)2-24-oxo-D3, and then 1,23,25(OH)3-24-oxo-D3.

Animals↗
PubMed1983

23,25-Dihydroxy-24-oxovitamin D3: a metabolite of vitamin D3 made in the kidney.

Kidney homogenates of rats produced a new metabolite of 25-hydroxyvitamin D3 which has been isolated in pure form after five column chromatographic steps. It was identified as 23,25-dihydroxy-24-oxovitamin D3 by means of ultraviolet and infrared absorption spectrophotometry, mass spectrometry, and proton nuclear magnetic resonance spectrometry. The stereochemistry at the C-23 position is as yet unknown. 25-Hydroxy-24-oxovitamin D3, which also has been isolated in pure form from this system, was found to be the precursor of the new metabolite in vitro. The production of the new metabolite was induced by two different methods: (a) perfusion of the kidneys with 1,25-dihydroxyvitamin D3 contained in the perfusate and (b) injection of 1,25-dihydroxyvitamin D3 in the intact animal. 23,25-Dihydroxy-24-oxovitamin D3 was not biologically active in an assay for intestinal calcium transport and bone calcium mobilization in the vitamin D deficient chick at a dose level of 5.3 nmol. A metabolic pathway is proposed to describe the results; it leads from 25-hydroxyvitamin D3 leads to 24(R),25-dihydroxyvitamin D3 leads to 25-hydroxy-24-oxovitamin D3 leads to 23,25-dihydroxy-24-oxovitamin D3.

Animals↗
PubMed1983

Immune reactions in infective endocarditis. II. Relevance of circulating immune complexes, serum inhibition factors, lymphocytotoxic reactions, and antibody-dependent cellular cytotoxicity against cardiac target cells.

Circulating immune complexes (IC) were detected in 35 out of 41 patients (85%) with infective endocarditis of known bacterial origin in contrast to only 9 out of 20 patients (45%) with endocarditis but negative blood cultures (p less than 0.05). Peak IC levels of 33.25 +/- 24.33 micrograms/ml in the early period fell significantly to 8.38 +/- 13.37 micrograms/ml after antibiotic treatment (p less than 0.001). High levels of IC coincided with relative hypocomplementemia. Erythrocyturia was observed in 51 of 58 IC-positive patients demonstrating peripheral sequelae of circulating IC. Incidence and concentrations of IC correlated neither with the mere presence of the rheumatoid factor nor with the titers of antimyolemmal antibodies, nor with antibody mediated cytolysis in the presence of complement. Serum inhibition factors (SIF) and E-rosette inhibitory factors (RIF) were not demonstrated, indicating that IC in endocarditis do not suppress phytohemagglutinin-induced lymphocyte proliferation or the E-rosetting of T cells. Significant lymphocytotoxicity against heterologous cardiac target cells without serum (LC) could be demonstrated in 11 out of 23 patients (48%) with endocarditis as compared to its absence in controls (n = 33, p less than 0.01). In assays of antibody-dependent cellular cytotoxicity (ADCC), either enhancement or blocking of lymphocytotoxicity by autologous serum or both was observed. The modulation of lymphocytotoxicity was most likely due to antimyolemmal antibodies, to IC, or to both, although effects of other serum factors cannot be ruled out completely.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1983

Observations on some environmental factors connected with fertility in heat stressed cows.

A field study was performed using 15 Kibutz dairy herds, in which 4195 cows situated in northern Israel were milked to determine the influence of climatological factors and nutritional regimes on the conception rate during the summer period (July-September). The Overall Conception Rate (OCR) during summer was 28.2% (17.3-41.9%) compared to 40% in the spring (May-June). The conception rate from first inseminations (CRl) was 31.3% during summer and 45.3% during spring. The OCR of the nullipara heifers in the same herds was 59.2% in summer and 60.4% in spring. The OCR in summer was negatively correlated with the minimum temperature (r=-0.53), the relative humidity at 0800 hrs. (r=-0.47), and the relative humidity at 1400 hrs (r=-0.49), whereas the CRl during summer was negatively correlated only with the minimum temperature (r=-0.51). In 12 (13) feeding groups of cows examined in 6 herds, no correlation was found between rectal temperatures and the actual milk productions of the cows. In 14 (15) herds, the milk production in summer was lower than in spring; the decrease varied from 0.9%-18.2% (average 7.8%). A highly significant negative correlation was found between the OCR and the various parameters of protein intake: grams of crude protein/cow/day, grams of crude protein/kg FCM/day, and percentage of protein from total dry matter. Particularly high correlations were found between the OCR and the average amounts of protein/kg FCM/day in milk of all cows (r=-0.84).

Journal Article↗
PubMed1983

Regulation of vitamin D metabolism in normal human pregnancy.

The increasing serum concentrations of various hormones (PTH, PRL, estrogens, and human placental lactogen) are hypothesized to regulate 1,25-dihydroxyvitamin D [1,25(OH)2D] and possibly 24,25-dihydroxyvitamin D [24,25(OH)2D] production during pregnancy. We examined the correlation between the serum levels of 1,25(OH)2D and the pregnancy-related hormones in 25 normal pregnant women, followed throughout gestation and postpartum. Maternal serum levels of 1,25(OH)2D were high during the first trimester (mean +/- SE, 74 +/- 8 pg/ml), remained high until the time of delivery (95 +/- 14 pg/ml), and then fell to almost normal levels (50 +/- 9 pg/ml) on the third postpartum day. The serum levels of 1,25(OH)2D do not correlate with the serum levels of any of the aforementioned hormones. The increase in serum 1,25(OH)2D in pregnancy has been postulated to be related to the stressed calcium homeostatic mechanisms known to occur in the mother. In twin pregnancy, this maternal calcium homeostatic mechanism(s) conceivably may be stressed to a greater extent. However, serum 1,25(OH)2D levels, measured in 27 women with a twin pregnancy in both the second and third trimesters as well as at delivery, did not differ from the levels observed in women with a singleton pregnancy. There were no significant changes in the serum levels of 24,24(OH)2D or 25-hydroxyvitamin D as pregnancy progressed. However, serum 24,25(OH)2D correlated significantly with both serum 1,25(OH)2D (r - 0.51; p less than 0.001, n = 83) and serum 25-hydroxyvitamin D (r = 0.37; P less than 0.001, n = 94). In conclusion, serum levels of 1,25(OH)2D rise early in the first trimester of pregnancy, fall acutely to normal levels soon after delivery, and are similar in singleton and twin pregnancies. The changes in the serum levels of 1,25(OH)2D do not relate to the changes in the serum levels of any of the pregnancy-related hormones.

24,25-Dihydroxyvitamin D 3↗
PubMed1981

[Abnormality of the palmaris longus muscle].

A compression syndrome of the median nerve in the forearm of a 16-years-old girl was caused by an atypical distal belly of the palmaris longus muscle with a tumorlike appearance. Special swimming training with so called "paddles" is thought to be the reason for the enlargement of this muscle.

Adolescent↗
PubMed1980

Factors affecting the differential counting of human lymphocyte subpopulations in blood smears.

We have previously used the antibody-mediated binding of bacteria to identify Ig-bearing cells and the natural binding of bacteria to identify several lymphocyte subpopulations. By using bacteria this identification can be carried out in conventional blood smears since bacteria are small and easily distinguished from all blood elements. To develop a standardized method for identification of lymphocyte subpopulations that may become useful in clinical laboratories, we investigated here several parameters that might affect the safety and accuracy of the test, and that might simplify the procedure. We found that: (1) the rosettes formed between bacteria and lymphocytes cannot be disrupted by vigorous handling; (2) the ability fo form rosettes is a stable property of the bacterial strains; (3) for optimal results the blood sample must not be stored for more than 4 hr at 25 degrees C and the entire procedure must be performed in medium supplemented with 6% bovine serum albumin; (4) a large excess of anti-Ig antibody is required for the optimal coating of bacteria to detect Ig-bearing cells; (5) both the antibody-coated bacteria and formaldehyde-fixed bacteria can be stored at 4 degrees C or at -20 degrees C for at least 6 months; (6) the buffy coat from the blood sample can be used instead of the whole blood to reduce the time required for reading the smears; and (7) some of the pathogenic bacteria can be killed by autoclaving without modifying their binding properties. A complete and simple method which uses the bacterial adherence for the identification of lymphocyte subpopulations in blood smears is presented.

Antibodies, Anti-Idiotypic↗
PubMed1979

Effects of alcohol on the pyloric sphincter.

The effects of an intoxicating dose of alcohol (79 g of 100 proof alcohol) on pyloric sphincter function were studied in 12 normal subjects using an infused manometric system. Alcohol had no effect on resting pyloric sphincter pressure. Intraduodenal administration of olive oil and hypertonic amino acids increased pyloric sphincter pressure significantly to 10.8 +/- 1.4 and 10.2 +/- 2.0 mm Hg, respectively. These responses were not affected by the administration of alcohol. In contrast, alcohol decreased the pyloric pressure response to duodenal acidification from 12.0 +/- 2.1 to 8.0 +/- 1.3 mm Hg (P less than 0.05). These results suggest that an intoxicating dose of alcohol may interfere with the normal function of the pyloric sphincter.

Adult↗
PubMed1979

Ribosome biosynthesis is not necessary for initiation of DNA replication.

Synthesis of mature 28-S ribosomal RNA and 60-S ribosomal subunits is inhibited in baby hamster kidney (BHK) cell line ts 422E at non-permissive temperature (39 degrees C). This leads to a 66% decrease of total ribosomes per cell, a marked imbalance between the large and small ribosomal subunits in the cytoplasm and a decrease of cells per dish after prolonged culture at 30 degrees C. However, inhibition of ribosome synthesis does not affect progression of cells through the G1 period of the cell division cycle, the length of the pre-replicative period, and the rate of entry of cells into S phase. In contrast to culture at non-permissive temperature, culture of BHK ts 422E cells in the presence of 0.04 micrograms/ml actinomycin D at 33 degrees C inhibits markedly the entry into S period. It is concluded that low doses of actinomycin D exert their inhibitory effect on cell growth by preventing maturation and transport of mRNA rather than by interfering with ribosome synthesis. Microfluorometric analysis revealed only slight differences in the distribution of BHK ts 422E cells in G1, S and G2 phases of the cycle either when cultured at 33 degrees C or at 39 degrees C. When too few ribosomes per cell are produced in BHK ts 422E cells at 39 degrees C, cells do not seem to be arrested reversibly at a specific point of the cell cycle but rather to die at random.

Animals↗
PubMed1978

Rapid isolation and identification of group B streptococci from selective broth medium by slide co-agglutination test.

Direct identification of group B streptococci from a selective broth medium was performed with the Phadebact streptococcus test to determine the feasibility of this technique for early detection of streptococcal colonization. Of 124 clinical isolates, 122 (98.4%) were correctly identified in less than 24 h from the selective broth medium, whereas standard cultures from blood agar plates identified, after 48 h, only 66 (53.2%). The presence of group B streptococci in mixed cultures was always detected by the Phadebact test, and no false-positive co-agglutination tests were observed in 372 cultures from which organisms other than group B streptococci were isolated.

Adult↗