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M Vollmer

Publications and source records attributed to M Vollmer.

At least 55 records · Page 3Linked to original sources
PubMed1996

Comparison of the pharmacodynamic effects of deflazacort and prednisolone in healthy subjects.

OBJECTIVE: Deflazacort, a synthetic oxazoline derivative of prednisolone, has been suggested as having major advantages over other glucocorticoids, as it is claimed to cause fewer adverse effects at equivalent antiinflammatory potency. The assumed equipotency ratio of deflazacort versus other glucocorticoids is critical for this assumption. METHODS: In a randomized cross-over study we compared the acute effects of deflazacort and prednisolone on serum cortisol, osteocalcin, insulin and blood cells (eosinophils and lymphocytes) in normal subjects. On seven occasions separated by a wash out period > or = 1 week all participants received placebo, prednisolone (8 mg, 20 mg, 40 mg) and deflazacort (12 mg, 30 mg, 60 mg). The medication was given orally at 20.00 h as a single dose. Blood was collected at 8.00 h before and after each medication. Log (dose) response relationships were calculated and were used to compare the drugs. RESULTS: The following equipotent dose ratios (mg deflazacort: mg prednisolone) were found: osteocalcin suppression 1.54, cortisol suppression 2.27, suppression of eosinophils 1.14 and lymphocytes 2.77. As parallelism between regression curves was rejected, equipotency could not be calculated for insulin. In 3 subjects even the highest dose of deflazacort failed to suppress serum cortisol. CONCLUSION: Our study highlights the difficulties of establishing equipotency ratios for glucocorticoids. It casts doubts on the generally assumed equipotency dose ratio of deflazacort vs prednisolone, as both for cortisol and lymphocytes the 95% CI was > 1.2. Thus, reduced adverse effects during deflazacort therapy may be a consequence of lower effective glucocorticoid dosage.

Adult↗
PubMed1995

[Effect duration and treatment effectiveness of salmeterol, fenoterol and salbutamol in severe forms of respiratory tract obstruction].

Duration and intensity of bronchodilator action of 0.2 mg Fenoterol, 0.2 mg Salbutamol, and 0.05 mg Salmeterol were investigated in 15 subjects with COPD over a period of 12 hours. Airway resistance and FEV1 were measured and subjective side effects noted. Salbutamol MDI was used as rescue medication. Airway resistance and FEV1 demonstrated significant bronchodilation with all bronchodilator drugs after 15 min and maximum bronchodilation between 1 and 2 hrs. After 3 to 5 hrs. bronchodilator effects of fenoterol and salbutamol are lost by at least 50%, whereas this effect is only seen after 8 to 9.5 hrs. with salmeterol. There were considerable individual differences of the efficacy of all three drugs. However, salmeterol was equally efficaceous, compared to fenoterol and salbutamol, but its duration was at least twice as long. Consequently, rescue medication was used in only about 50% of the cases. Side effects of all substances were comparable. From these data it may be concluded that the efficacy of beta2-adrenergic agonists is comparable, irrespective of the duration of action of a single administration, if repeated administrations are used with short acting substances. In addition, this study confirmed that in individual patients a) the response to beta2-adrenergic agonists is variable and b) that different lung function parameters such as airway resistance and FEV1 may give different results.

Adult↗
PubMed1995

[Responder and non-responder in the bronchodilator test?].

In 15 patients with chronic airflow obstruction 0.2 mg salbutamol was administered to determine reversibility within 15 minutes ("test effect"). Subsequently, maximum 24-hour effects of three beta 2-agonists (fenoterol 0.2 mg, salbutamol 0.2 mg, salmeterol 0.05 mg, each by MDI) were determined in random order ("best effect"). Airways obstruction was measured by FEV1, MEF50, MEF25, airway resistance Raw and thoracic gas volume TGV. "Best effects" were compared with "test effects". As a whole test effects were significantly smaller than best effects, often not reaching a 15% change, normally achieved during the 24-hour observation. Significant correlations existed between FEV1 and the corresponding values of Raw, MEF50 and MEF25, although there were considerable individual differences between test results. The reduction of TGV after a beta 2-agonist was significantly related to TGV-baseline values. We conclude in line with other authors that tests of acute reversibility of airways obstruction cannot reliably differentiate between "responders" and "non-responders" and that such tests may mislead if used for the differentiation of asthma and COPD.

Administration, Inhalation↗
PubMed1994

Structural requirements for peptides that stimulate a subset of gamma delta T cells.

Hybridomas representing the V gamma 1-positive subset of murine gamma delta T cells secrete lymphokines in response to synthetic peptides representing a short segment of the mycobacterial 60-kDa heat shock protein (HSP-60). Here we show the TCR dependency of this response by transfection of productively rearranged TCR genes derived from an HSP-60 reactive gamma delta T cell hybridoma. We also have defined structural requirements for the stimulatory peptide. The smallest HSP-60 peptide capable of stimulating these hybridomas is seven amino acids long, representing positions 181-187, and having the sequence FGLQLEL. Amino acid-substituted derivatives of this peptide, and another containing the same core, p180-190, revealed amino acids essential for stimulatory activity. Phenylalanine in position 181 and leucine in position 183 seem to be required for stimulation of all HSP-60 reactive cells, whereas others are only required by some. Clonal differences in the responses to these peptides provide indirect evidence for cognate TCR-peptide interactions. The smallest stimulatory peptide, p181-187, represents an area not well conserved among HSP-60 molecules of other species, and stimulates a mycobacteria-specific response unlike the earlier observed cross-reactive responses of the same hybridomas with longer HSP-60 peptides derived from mycobacteria and other species (our manuscript in preparation). We propose that the TCR-dependent multiclonal gamma delta T cell response to HSP-60 peptides and derivatives, which in some ways resembles superantigen responses and in other ways resembles responses to conventional Ag, may be a separate, third type of Ag response by T cells.

Amino Acid Sequence↗
PubMed1994

Response of a murine epidermal V gamma 1/V delta 6-TCR+ hybridoma to heat shock protein HSP-60.

In the epidermis, the major population of T lymphocytes expresses a T-cell receptor (TCR) with V gamma 5 and V delta 1 variable regions, which is unique to this tissue. Roberts et al and Ezquerra et al, also describe a minor population of gamma delta-TCR+ cells in the epidermis that expresses a V gamma 1/V delta 6 TCR. These cells are different from other epidermal T cells in that they "spontaneously" produce cytokines, a result thought to be due to autoreactivity. Over the past 5 years, our laboratory has produced V gamma 1/V delta 6+ T-cell hybridomas from many tissue sources. These spontaneously produce cytokines but also are activated by heat shock protein (HSP-60)-derived peptides. Ezquerra et al report that none of their V gamma 1/V delta 6+ epidermal T-cell lines derived from C3H/HeN mice respond to HSP-60. Of the 99 gamma delta-TCR+ hybridomas we have produced from epidermal T cells of C57BL/6 mice, only one expressed the V gamma 1/V delta 6 TCR. This hybridoma, 70BET-2.12, not only spontaneously produces cytokines, but, unlike the V gamma 1/V delta 6-TCR+ epidermal T cells of Ezquerra et al, it also responds to the whole HSP-60 protein and a 17-mer HSP-60 peptide from M. leprae, producing increased levels of interleukin-2 of up to approximately ten-fold above the spontaneous level. This shows that V gamma 1/V delta 6-TCR+ epidermal T cells can respond to HSP-60. To confirm that 70BET-2.12 expresses TCR genes similar to those of cells that have HSP-60 reactivity, V gamma 1-C gamma 4 and V delta 6-C delta cDNA were produced from RNA isolated from this hybridoma, amplified by the polymerase chain reaction, and sequenced. The gamma and delta TCR gene sequences were similar but not identical to previously published sequences of HSP-60-reactive cells from lymphoid and other organs. No explanation can be found for the discrepancy between our findings and those of others at the level of TCR expression such that other strain-specific factors might be responsible for HSP-60 reactivity.

Animals↗
PubMed1993

An unstructured mRNA region and a 5' hairpin represent important elements of the E. coli translation initiation signal determined by using the bacteriophage T7 gene 1 translation start site.

Gene 1 of bacteriophage T7 early region--the RNA polymerase gene--is very actively translated during the infectious cycle of this phage. A 29 base pair fragment of its ribosome binding site containing the initiation triplet, the Shine-Dalgarno sequence (S-D), 10 nucleotides (nt) upstream and 6 nt downstream of these central elements was cloned into a vector to control the expression of the mouse dihydrofolate reductase gene (dhfr). Although all essential parts of this translation initiation region (TIR) should be present, this fragment showed only very low activity. Computer analysis revealed a potentially inhibitory hairpin binding the S-D sequence into its stem base paired to vector-derived upstream sequences. Mutational alterations demonstrated that this hairpin was not responsible for the low activity. However, addition of 21 nt of the T7 gene 1 upstream sequence to the 29 base pair fragment were capable of increasing the translational efficiency by one order of magnitude. Computer analysis of this sequence, including nucleotide shuffling, revealed that it contains a highly unstructured region lacking mRNA secondary structures but with a hairpin at its 5' end, here formed solely by T7 sequences. There was not much difference in activity whether the mRNA included or lacked vector-derived sequences upstream of the hairpin. Such highly unstructured mRNA regions were found in all very efficiently expressed T7 genes without any obvious sequence homologies. The delta G values of these regions were higher, i.e. potential secondary structural elements were fewer, than in TIR of genes from E. coli. This is likely due to the fact that T7 as a lytic phage is relying for successful infection on much stronger signals which a cell cannot afford because of the indispensable balanced equilibria of its interdependent biochemical processes. When the 5' ends of efficient T7 gene mRNA are formed by the action of RNase III they generally start with an unstructured region. Efficiently expressed T7 genes within a polycistronic mRNA, however, always contain a hairpin preceding the structure free sequence. We suggest that the formation of this 5' hairpin is releasing enough energy to keep the unstructured regions free of secondary RNA structures for sufficient time to give ribosomes and factors a good chance for binding to the TIR. In addition, sequences further downstream of the start codon give rise to an additional increase in efficiency of the TIR by almost two orders of magnitude.

Bacteriophage T7↗
PubMed1993

Evidence that murine V gamma 5 and V gamma 6 gamma delta-TCR+ lymphocytes are derived from a common distinct lineage.

Murine V gamma 5 and V gamma 6+ T lymphocytes develop sequentially in the thymus during fetal and newborn life, giving rise to intraepithelial lymphocytes of the epidermis and female reproductive tract. In analyzing a panel of gamma delta T cell hybridomas derived from various tissues, we found that all V gamma 6+ cells tested (n = 25) expressed V gamma 5-C gamma 1 mRNA, whereas none of a panel of V gamma 6- cells analyzed (n = 33) expressed this mRNA. V gamma 6 mRNA was rare in V gamma 5+ cells (1 of 9), and absent in all other gamma delta T cells (n = 10). These findings suggest that most, if not all, V gamma 6-TCR+ lymphocytes arise from precursor cells that have previously rearranged the V gamma 5 gene, and indicate that V gamma 5 and V gamma 6+ lymphocytes belong to a common, distinct lineage that does not give rise to other gamma delta T cells.

Animals↗
PubMed1993

In vivo response of murine gamma delta T cells to a heat shock protein-derived peptide.

Recent results suggested that a large subset of heat shock protein HSP-60 reactive peripheral lymphoid gamma delta T cells preexists in normal adult mice, all members of which respond to a single segment of this common HSP. However, the experimental evidence supporting this idea involved in vitro peptide responses of gamma delta T-cell hybridomas generated from unprimed spleen cells. Here, we report an attempt to elicit a gamma delta T-cell response in vivo by stimulation of adult C57BL/10 mice with HSP-60 or an HSP-60-derived peptide fragment comprising amino acids 180-196 of mycobacterial HSP-60. Whereas no gamma delta T-cell response was detectable in mice injected with the intact protein, stimulation with the peptide altered the reactive gamma delta T-cell population in vivo. These changes were detected among hybridomas generated with cells restimulated in vitro and included a large increase in hybridizable gamma delta T cells, a nearly maximal increase in the relative frequency of HSP-60-reactive cells, and structural changes in expressed T-cell receptors of HSP-60-reactive cells. Interestingly, we failed to elicit a detectable alpha beta T-cell response to the particular peptide stimulatory for gamma delta T cells, although at least three other HSP-60 epitopes were recognized. Our data show that normal gamma delta T cells can respond in vivo to small peptide antigens. The gamma delta T-cell response to the HSP-60-derived peptide studied here is apparently independent of antigen-specific alpha beta T-cell reactivity.

Animals↗