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Biomedical subjects

J Franke

Publications and source records attributed to J Franke.

At least 127 records · Page 7Linked to original sources
PubMed1989

The cyclic nucleotide phosphodiesterase gene of Dictyostelium discoideum utilizes alternate promoters and splicing for the synthesis of multiple mRNAs.

The cyclic nucleotide phosphodiesterase (phosphodiesterase) gene plays essential roles in the development of Dictyostelium discoideum during cellular aggregation and postaggregation morphogenesis. Genomic clones spanning the gene were isolated and used to determine the sequence and structure of the phosphodiesterase gene. We found an unusually complex organization for a gene of D. discoideum. Two transcripts of 2.4 and 1.9 kilobases (kb) were synthesized from start sites separated by 1.1 kb. A developmentally regulated promoter was utilized for the 2.4-kb mRNA, and a constitutive promoter regulated synthesis of the 1.9-kb transcript. The gene was found to be divided into four exons that are alternately spliced to give rise to the two mRNAs. The precursor of the 2.4-kb mRNA contained a 2.3-kb intron, whereas the precursor of the constitutive transcript was synthesized with a 1.7-kb intron. The two transcripts contained identical protein-coding regions and 400-nucleotide 3' untranslated sequences. The 2.4-kb developmentally regulated mRNA was distinguished by a long 5' untranslated leader of 666 nucleotides. The complex structure of the gene may allow multiple levels of control of the expression of the phosphodiesterase during development.

Base Sequence↗
PubMed1988

The cyclic nucleotide phosphodiesterase of Dictyostelium discoideum: the structure of the gene and its regulation and role in development.

The cyclic nucleotide phosphodiesterase (phosphodiesterase) of Dictyostelium discoideum plays an essential role in development by hydrolyzing the cAMP used as a chemoattractant by aggregating cells. We have studied the biochemistry of the phosphodiesterase and a functionally related protein, the phosphodiesterase inhibitor protein, and have cloned the cognate genes. A 1.8-kb and a 2.2-kb mRNA are transcribed from the single-phosphodiesterase gene. The 2.2-kb mRNA comprises the majority of the phosphodiesterase mRNA found in differentiating cells and is transcribed only during development from a promoter at least 2.5 kb upstream of the translational start site. The 1.8-kb phosphodiesterase mRNA is detected at all stages of growth and development, is present at lower levels than the developmentally induced mRNA, and is transcribed from a site proximal to the protein-coding region. The phosphodiesterase gene contains a minimum of three exons, and a 2.3-kb intron, the longest yet reported for this organism. We have shown that the pdsA gene and four fgd genes affect the accumulation of the phosphodiesterase mRNAs, and we believe that these loci represent a significant portion of the genes regulating expression of the phosphodiesterase. The phosphodiesterase gene was introduced into cells by transformation and used as a tool to explore the effects of cAMP on the terminal stages of development. In cells expressing high levels of phosphodiesterase activity, final morphogenesis cannot be completed, and differentiated spore and stalk cells do not form. We interpret these results to support the hypothesis that cAMP plays an essential role in organizing cell movements in late development as well as in controlling the aggregation of cells in the initial phase of the developmental program.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Disruption of Dictyostelium discoideum morphogenesis by overproduction of cAMP phosphodiesterase.

The development and cellular differentiation of Dictyostelium discoideum are disrupted in transformants secreting high levels of the cyclic nucleotide phosphodiesterase. The aggregation of these cells in the early stage of development proceeds rapidly and without the formation of organized streams. The later stages of development, in which differentiation into stalk and spore cells normally takes place, are completely blocked so that the transformants remain in spherical clusters of undifferentiated cells that do not elaborate the tip structure that regulates morphogenesis. These effects are due to overproduction of extracellular phosphodiesterase and demonstrate the role of cAMP during the aggregation phase of development as well as in the control of differentiation and pattern formation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Fluoride and osteoporosis.

After a review of the historical background and the first studies with fluoride therapy for osteoporosis the author presents his own studies of more than 100 cases of industrial fluorosis. It is followed by instructions how to perform the fluoride therapy: indications, contra-indications, dosage, controls and additional therapy. Since 1969 we treated 158 patients suffering from primary and secondary osteoporosis with 3 different sodium fluoride preparations (pure sodium fluoride powder, Ossin, Koreberon). Clinically and subjectively, 80.4% recovered or became symptom-free. In 53.8% (with Koreberon in 64%), we detected radiologically distinct reossification in the spine after 23 +/- 12 months, in a further 26.6% the reossification was questionable and only 4.4% showed further fractures. In summary, we found about 20% of fast-responders (reossification after 13.2 months, high alkaline phosphatase), 60% of responders and 20% of non-responders. The strengthening effect of the sodium fluoride therapy becomes especially evident if considering the spontaneous fracture rate. Side effects were: gastrointestinal disturbances (34%), gastric ulcers (4.4%), stress fractures (6.9%), very common arthralgies (34%), and sometimes overdosages (fluorosis). Only if therapy is controlled most intensively will the greatest effectiveness be obtained.

Bone and Bones↗
PubMed1987

The expression of two transcripts of the phosphodiesterase gene during the development of Dictyostelium discoideum.

One of the earliest events in the development of Dictyostelium discoideum is the induction of the cyclic nucleotide phosphodiesterase gene. During vegetative growth a small amount of secreted phosphodiesterase is synthesized. The phosphodiesterase transcript which is responsible for the vegetative enzyme has a size of 1800 nucleotides. Soon after starvation begins a more abundant mRNA with a size of 2200 nucleotides is synthesized by the developing cells. The induction of the 2200-nucleotide mRNA is dependent on protein synthesis and takes place under all regimens of growth and starvation. When growth is in axenic medium and development is in phosphate buffer, the appearance of the larger transcript is very rapid, occurring within 30 min after the onset of starvation. The initial burst of phosphodiesterase mRNA synthesis is followed by a decline in mRNA abundance unless the cells are stimulated by cAMP. When cells are grown on bacteria and development takes place on filter paper, the larger transcript appears after 4 hr, reaches a peak at 10-12 hr of development, and then slowly disappears. When prestalk and prespore cells from migrating slugs are separated, a small amount of transcript can be found only in the prestalk cells. A series of mutants blocked early in development make very little phosphodiesterase transcript or are otherwise abnormal in expression of the phosphodiesterase mRNA. Together these mutants define five independent genetic loci which affect the accumulation of the phosphodiesterase mRNA. These are the pdsA, fgdA, fgdC, fgdD, and fgdE genes.

Cell Aggregation↗
PubMed1987

Bronchial and vascular effects of Paf in the rat isolated lung are completely blocked by WEB 2086, a novel specific Paf antagonist.

1 The effect of the platelet-activating factor (Paf) antagonist, WEB 2086, on Paf-induced increase of pulmonary artery perfusion pressure (Pp), bronchial inflation pressure (Pi) and wet-to-dry lung weight ratios (W/D) was investigated in the rat isolated lung. 2 Lungs were perfused with Krebs-Ringer solution (KRS) as controls or with KRS containing WEB 2086 (0.1, 1.0, 10.0 or 100 micrograms ml-1) and then injected with a bolus of 20 micrograms Paf. 3 A dose-related inhibition of the Paf-induced increase of Pp, Pi and W/D was observed, being almost maximal for the 10.0 micrograms ml-1 and complete for the 100 micrograms ml-1 doses of WEB 2086 when compared to controls. 4 It is concluded that WEB 2086 is a highly effective and specific Paf antagonist in the pulmonary vasculature and bronchial tract.

Animals↗
PubMed1987

The Ilizarov distractor for the correction of relapsed or neglected clubfoot.

The correction of a relapsed or neglected clubfoot by an external distractor is an alternative to a major operation which may involve triple arthrodesis and is often associated with skin problems. We report the use of the Ilizarov method to treat nine severely deformed feet, with satisfactory results in terms of function and appearance. The distractor enables treatment to be applied before maturity and avoids the shortening of the foot that results from wedge osteotomies. We discuss the indications, technique, complications and results of the method.

Adolescent↗
PubMed1986

Molecular cloning and developmental expression of the cyclic nucleotide phosphodiesterase gene of Dictyostelium discoideum.

The cyclic nucleotide phosphodiesterase of Dictyostelium discoideum functions to maintain the responsiveness of cells to the chemoattractant cAMP during the aggregation phase of development. We have prepared a cDNA library and have isolated clones which contain a portion of the 5' untranslated region and the entire coding and 3' untranslated portions of the cyclic nucleotide phosphodiesterase gene. The primary structure of the extracellular cyclic nucleotide phosphodiesterase precursor has been deduced from the nucleotide sequence. The molecule is composed of 452 amino acids and was calculated to have a molecular mass of 51,078 daltons. Forty-nine amino-terminal residues which contain a hydrophobic leader sequence are not present in the mature extracellular enzyme. Four potential asparagine-linked glycosylation sites were found within the phosphodiesterase. An amino acid sequence homology search revealed no closely related proteins. Phosphodiesterase mRNA levels are low in growing cells and first increase soon after the onset of development. The amount of transcript then decreases before rising in abundance to maximum levels during the terminal stages of cell aggregation and apical tip formation. During formation of the fruiting body, levels of phosphodiesterase mRNA decrease. Exposure of cells to cAMP increases the amount of phosphodiesterase mRNA. Increases of mRNA abundance are correlated with increases in enzyme activity, suggesting regulation at the level of transcription.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Detection and developmental regulation of the mRNA for the regulatory subunit of the cAMP-dependent protein kinase of D. discoideum by cell-free translation.

cAMP is an important effector of the development of Dictyostelium discoideum amoebae and could exert its effects on gene expression through the cytosolic cAMP-dependent protein kinase (cAK). Antibodies, specific for the regulatory subunit (R) of the cAK, were used to investigate the developmental regulation of the corresponding mRNA (R-mRNA) by in vitro translation and immunoprecipitation. Under such conditions, a single polypeptide of the same mol. wt. as R (42 kd) is detected, showing that the protein is not synthesized as a large precursor. The level of the R-mRNA, which is low in vegetative cells, increases 10- to 20-fold during the first hours of development. Its expression is stimulated by the treatment of AX3 cells with cAMP either added to a concentration of 1 mM or given as 0.1 microM pulses every 5 min, whereas such treatments have little or no effect in cells of strain AX2. The R-mRNA remains highly expressed (0.01-0.03% of translatable mRNA) throughout post-aggregative development; it is not affected by mechanical disaggregation of the multicellular organism. The parallel developmental time courses of the translatable R-mRNA and the R protein produced in vivo suggest that the expression of this polypeptide is regulated at the level of mRNA synthesis.

Carrier Proteins↗
PubMed1986

Isolation of a cDNA encoding a portion of the cyclic nucleotide phosphodiesterase of Dictyostelium discoideum.

The cyclic nucleotide phosphodiesterase (phosphodiesterase) of Dictyostelium discoideum is one of a group of developmentally regulated proteins which enable cells to aggregate by chemotaxis during the early stages of development. We report the identification and DNA sequence of a cDNA clone encoding the amino-terminal region of the phosphodiesterase. The clone, pPD-3, was selected from a cDNA library created by priming first strand synthesis using a set of oligonucleotides with sequences predicted from the amino-terminal amino acid sequence of purified phosphodiesterase. The DNA sequence of pPD-3 encodes perfectly the available phosphodiesterase amino acid sequence, and pPD-3 selects an mRNA which can be translated into material recognized by phosphodiesterase antisera. The nucleotide sequence of pPD-3 indicates there are 49 amino acids, which contain a segment possessing the characteristics of a signal peptide, that separate the amino-terminal residue identified in the purified protein from the methionine codon at which translation originates. DNA blot analysis demonstrates that the phosphodiesterase gene exists as a single copy in the nuclear genome. Analysis of RNA indicates that the phosphodiesterase transcript is 2.1 kb long, which is approximately 0.8 kb more than the minimum required to encode this protein.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Secreted adenylate cyclase of Bordetella pertussis: calmodulin requirements and partial purification of two forms.

The extracellular adenylate cyclase of Bordetella pertussis was partially purified and found to contain high- and low-molecular-weight species. The high-molecular-weight form had a variable molecular weight with a peak at about 700,000. The smaller species had a molecular weight of 60 to 70,000 as determined by gel filtration. The low-molecular-weight form could be derived from the high-molecular-weight species. The high-molecular-weight complex purified from the cellular supernatant was highly stimulated by calmodulin, while the low-molecular-weight enzyme was much less stimulated. Active enzyme could be recovered from sodium dodecyl sulfate (SDS) gels at positions corresponding to molecular weights of about 50,000 and 65,000. Active low-molecular-weight enzyme recovered from SDS gels migrated with a molecular weight of about 50,000, which coincides with a coomassie blue-stained band. However, when both high- and low-molecular weight preparations were analyzed in 8 M urea isoelectrofocusing gels, the enzyme activity recovered did not comigrate with stained protein bands. The enzyme recovered from denaturing isoelectrofocusing or SDS gels was activated by calmodulin, indicating a direct interaction of calmodulin and enzyme. The high-molecular-weight form of the enzyme showed increasing activity with calmodulin concentrations ranging from 0.1 to 500 nM, while the low-molecular-weight form was fully activated by calmodulin at 20 nM. Adenylate cyclase on the surface of living cells was activated by calmodulin in a manner which resembled that found for the high-molecular-weight form.

Adenylyl Cyclases↗