Biomedical subjects

J Hirschberg

Publications and source records attributed to J Hirschberg.

At least 19 recordsLinked to original sources

PubMed1996

Cloning and characterization of the cDNA for lycopene beta-cyclase from tomato reveals decrease in its expression during fruit ripening.

The cDNA which encodes lycopene cyclase, CrtL, was cloned from tomato (Lycopersicon esculentum cv. VF36) and tobacco (Nicotiana tabacum cv. Samsun NN) and functionally expressed in Escherichia coli. This enzyme converts lycopene to beta-carotene by catalyzing the formation of two beta-rings at each end of the linear carotene. The enzyme interacts with half of the carotenoid molecule and requires a double bond at the C-7,8 (or C-7,8') position. Inhibition in E. coli indicated that lycopene cyclase is the target site for the inhibitor MPTA, 2-(4-methylphenoxy)tri-ethylamine hydrochloride. The primary structure of lycopene cyclase in higher plants is significantly conserved with the enzyme from cyanobacteria but different from that of the non-photosynthetic bacteria Erwinia. mRNA of CrtL and Pds, which encodes phytoene desaturase, was measured in leaves, flowers and ripening fruits of tomato. In contrast to genes which encode enzymes of early steps in the carotenoid biosynthesis pathway, whose transcription increases during the 'breaker' stage of fruit ripening, the level of CrtL mRNA decreases at this stage. Hence, the accumulation of lycopene in tomato fruits is apparently due to a down-regulation of the lycopene cyclase gene that occurs at the breaker stage of fruit development. This conclusion supports the hypothesis that transcriptional regulation of gene expression is a predominant mechanism of regulating carotenogenesis.

Amino Acid Sequence↗

PubMed1995

[Surgical management of voice and speech disoreders in childhood. Phonosurgery].

By phonosurgery is meant the sum total of operative techniques that are aimed primarily or solely at the improvement of voice or speech. The different methods of phonosurgery can be used first of all for reducing or ceasing the pathological change of the voice quality, the dysphony and the rhinophony. The techniques recommended for the improvement in dysphony are: direct surgeries on the vocal cords (extirpation methods, intracordal injections) and indirect interventions affecting the cartilaginous frame of the larynx; some neurosurgical methods (nerve-to-nerve anastomosis) are curiosities and the larynx transplantation may show only the future trends. The surgical correction of the hyperrhinophony due to velopharyngeal insufficiency constitutes the other main group of phonosurgery. The velopharyngoplasty (flap surgery) is the most common technique among them. The author categorizes the surgical indications and methods (mostly concerning children) on the basis of his 38 years experience. Removal of vocal cord nodules was performed in 7% of 1740 children with dysphony. The importance of the complex treatment in these cases (speech therapy, medicines, psychotherapy) is stressed. Endolaryngeal interventions (implantation, cutting of a membrane or scars) may only be considered in children when voice problems exist alone without respiratory difficulties. The author has carried out 1000 velopharyngoplasties because of severe hypernasality with different etiology. Anatomical healing was good in 98% of the cases with no mortality; the hyperrhinophony disappeared in 90% of the patients. The ideal age for operation is 4 1/2-5 years. Team work and a competent postoperative logopedic treatment are essential to obtain good results.

Age Factors↗

PubMed1995

Cloning and expression in Escherichia coli of the gene encoding beta-C-4-oxygenase, that converts beta-carotene to the ketocarotenoid canthaxanthin in Haematococcus pluvialis.

In the green alga Haematococcus pluvialis the ketocarotenoid astaxanthin accumulates under stress conditions. Astaxanthin is a red carotenoid pigment which possess antioxidative activity. We have cloned the gene for beta-C-4 oxygenase (beta-carotene ketolase) from the green algae H. pluvialis. The cloning method took advantage of a strain of E. coli which was genetically engineered to produce beta-carotene. An expression cDNA library of H. pluvialis was transfected to cells of this strain and visually screened for brown-red pigmented colonies. One colony out of 100,000 transformants showed color change due to accumulation of canthaxanthin. The cDNA clone in this transformant colony encodes the enzyme beta-C-4 oxygenase that catalyzes the conversion of beta carotene to canthaxanthin via echinenone. This enzyme does not convert zeaxanthin to astaxanthin. It is concluded that in H. pluvialis astaxanthin is synthesized via canthaxanthin and therefore an additional enzyme is predicted, which converts canthaxanthin to astaxanthin.

Bacterial Proteins↗

PubMed1995

An unusual organization of the genes encoding cytochrome b559 in Chlamydomonas reinhardtii: psbE and psbF genes are separately transcribed from different regions of the plastid chromosome.

The psbE and psbF genes encode the apoproteins of cytochrome b559, an essential component of the pigment protein complex photosystem II. Together with psbL and psbJ, these genes constitute a single operon in all photosynthetic organisms examined thus far. We have cloned and sequenced the psbE and psbF genes of the Chlamydomonas reinhardtii plastid genome. The predicted amino-terminal domains of both polypeptides are more basic than those of other organisms, and the sequence of the psbE gene product indicates a departure from the 'positive-inside' rule for the insertion of proteins in the thylakoid membrane. Northern blot analysis demonstrated that psbE is transcribed into a 0.3 kb mRNA, while transcription of psbF and psbL genes results in a 0.9 kb transcript. The splitting of the psbEFLJ operon into separate transcription units suggests a unique mechanism of regulation of expression of these genes in C. reinhardtii.

Amino Acid Sequence↗

PubMed1995

Voice disorders in children.

The pediatric otolaryngologist has an especially important role in the differential diagnosis and treatment of two voice disorders; these are the voice quality problems (dysphony) and the resonance problems (rhinophony). The first step in the examination is to preclude the organic causes. The functional dysphonia is mostly related to voice abuse/misuse, but may be present on a psychosomatic basis; environmental factors can also play a role in the etiology and the personality structure has been found to be very relevant. The perceptual evaluation of voice is of obvious importance. Endoscopy with a transnasal flexible scope makes it possible, in practically all cases, to identify the morphodynamic changes. Stroboscopy and phonetography can be carried out only in older children, sometimes a 'trial treatment' is of valuable help. The therapy can be divided into five groups (counselling, voice re-education, drug treatment, psychotherapy, surgery), but should be always individual. An open question: how to choose the preferable treatment of vocal nodules: surgery, conservative or wait-and-see? According to a detailed survey in Kurume University Hospital the following can be stated: if the patient is in trouble due to hoarseness, and immediate improvement of his voice is necessary, surgery should be indicated; if they need the improvement but do not need it urgently, voice therapy is recommended; without motivation vocal hygiene is proposed. No matter what treatment patients receive, their voices improve in the majority after puberty, but 15% of the patients do not show any improvement. In cases of hoarseness due to long-term postintubational glottic lesions logopedic treatment is the only therapeutic possibility. The delay of speech development of tracheotomized children can and should be avoided by applying proper cannula technique and by logopedic training. The physiological nasality which depends upon the undisturbed activity of the velopharyngeal closure, can become pathologic in four forms: closed, open, mixed and alternating nasality (rhinophonolalia). In the diagnosis of hyperrhinophony due to VPI X-ray procedures, supplemented with nasendoscopy, proved to be the most informative methods, the etiology (neuromyogen processes) may be revealed by electrophysiological methods; the voice and speech can be assessed and visualized by nasometry, but the detailed speech evaluation is indispensable. The basic possibilities of treatment are as follows: speech therapy, surgery, speech bulb, electrotherapy and medicines. The basis of operative treatment is flap surgery. The anatomical result of 1000 (velo) pharyngoplasties carried out in Madarász and Heim Pál Children's Hospital (Budapest) is good in 98%, the hyperrhinophony ceased or became minimal in 90% after surgery. The ideal age for operation is 4.5 years.

Adolescent↗

PubMed1995

Metabolism of cyclic carotenoids: a model for the alteration of this biosynthetic pathway in Capsicum annuum chromoplasts.

The biosynthetic pathway of cyclic carotenoid is known to be quantitatively and qualitatively different in the non-green plastids of Capsicum annuum fruits compared with chloroplasts. Here, the cloning is described of a novel cDNA from this organism, which encodes an enzyme catalyzing the cyclization of lycopene to beta-carotene when expressed in Escherichia coli. The corresponding gene is constitutively expressed during fruit development. Significant amino acid sequence identity was observed between this enzyme and capsanthin/capsorubin synthase which is involved in the synthesis of the species-specific red carotenoids of C. annuum fruits. The latter enzyme was found also to possess a lycopene beta-cyclase activity when expressed in E. coli. A model is proposed for the origin of the capsanthin/capsorubin synthase gene and the role of this enzyme, together with the newly cloned lycopene cyclase, in the specific re-channeling of linear carotenoids into beta-cyclic carotenoids in C. annuum ripening fruits.

Amino Acid Sequence↗

PubMed1994

Cloning and characterization of the gene for phytoene desaturase (Pds) from tomato (Lycopersicon esculentum).

The gene Pds encodes phytoene desaturase, a key enzyme in carotenoid biosynthesis that converts phytoene to zeta-carotene. We have cloned and analyzed the genomic DNA sequence of Pds from tomato. In tomato Pds is comprised of 15 exons that, together with the introns occupy over 8 kb. A putative promoter sequence has been identified by comparison with the cDNA sequence of Pds. A consensus nucleotide sequence around intron splicing sites in tomato genes was determined by compiling data on 137 introns in 34 genes. This consensus sequence generally agrees with the consensus sequence of other higher plants with only minor differences that are unique to tomato.

Amino Acid Sequence↗

PubMed1994

Molecular structure and enzymatic function of lycopene cyclase from the cyanobacterium Synechococcus sp strain PCC7942.

A gene encoding the enzyme lycopene cyclase in the cyanobacterium Synechococcus sp strain PCC7942 was mapped by genetic complementation, cloned, and sequenced. This gene, which we have named crtL, was expressed in strains of Escherichia coli that were genetically engineered to accumulate the carotenoid precursors lycopene, neurosporene, and zeta-carotene. The crtL gene product converts the acyclic hydrocarbon lycopene into the bicyclic beta-carotene, an essential component of the photosynthetic apparatus in oxygen-evolving organisms and a source of vitamin A in human and animal nutrition. The enzyme also converts neurosporene to the monocyclic beta-zeacarotene but does not cyclize zeta-carotene, indicating that desaturation of the 7-8 or 7'-8' carbon-carbon bond is required for cyclization. The bleaching herbicide 2-(4-methylphenoxy)triethylamine hydrochloride (MPTA) effectively inhibits both cyclization reactions. A mutation that confers resistance to MPTA in Synechococcus sp PCC7942 was identified as a point mutation in the promoter region of crtL. The deduced amino acid sequence of lycopene cyclase specifies a polypeptide of 411 amino acids with a molecular weight of 46,125 and a pI of 6.0. An amino acid sequence motif indicative of FAD utilization is located at the N terminus of the polypeptide. DNA gel blot hybridization analysis indicated a single copy of crtL in Synechococcus sp PCC7942. Other than the FAD binding motif, the predicted amino acid sequence of the cyanobacterial lycopene cyclase bears little resemblance to the two known lycopene cyclase enzymes from nonphotosynthetic bacteria. Preliminary results from DNA gel blot hybridization experiments suggest that, like two earlier genes in the pathway, the Synechococcus gene encoding lycopene cyclase is homologous to plant and algal genes encoding this enzyme.

Amino Acid Sequence↗

PubMed1994

A new dual chamber single lead system.

A DDD pacing system normally requires the introduction and positioning of two separate electrode leads. A VDD system may use a single lead with a ventricular electrode at the tip and at least one atrial ring electrode. The disadvantage of VDD systems is that the full range of DDD stimulation and detection alternatives is not available. The present animal study was made to evaluate a new single lead design with the distal electrode placed in the atrium and the proximal ring electrode in the right ventricle. This design permits the full range of DDD options including atrial stimulation. Acute stimulation thresholds and sensing amplitudes were stable and comparable to conventional DDD systems. Long-term studies are on-going.

Animals↗

PubMed1994

A corpus-based study of repair cues in spontaneous speech.

The occurrence of disfluencies in fully natural speech poses difficult challenges for spoken language understanding systems. For example, although self-repairs occur in about 10% of spontaneous utterances, they are often unmodeled in speech recognition systems. This is partly due to the fact that little is known about the extent to which cues in the speech signal may facilitate automatic repair processing. In this paper, acoustic and prosodic cues to self-repairs are identified, based on an analysis of a corpus taken from the ARPA Air Travel Information System database, and methods are proposed for exploiting these cues for repair detection, especially the task of modeling word fragments, and repair correction. The relative contributions of these speech-based cues, as well as other text-based repair cues, are examined in a statistical model of repair site detection that achieves a precision rate of 91% and recall of 86% on a prosodically labeled corpus of repair utterances.

Artificial Intelligence↗

PubMed1993

Molecular and biochemical characterization of herbicide-resistant mutants of cyanobacteria reveals that phytoene desaturation is a rate-limiting step in carotenoid biosynthesis.

Mutant strains of the cyanobacterium Synechococcus sp. PCC 7942 that are resistant to the herbicides norflurazon and fluridone were analyzed. These herbicides inhibit phytoene desaturase, a key enzyme in the carotenoid biosynthetic pathway. In three mutants the phenotype was related to specific point mutations in pds, the gene encoding phytoene desaturase. Since the resistance was manifested in a cell-free carotenogenic assay, it is evident that the predicted amino acid changes in the target protein alter the enzyme-herbicide interactions. In addition, the mutations also reduced the in vitro activity of phytoene desaturase. Increased levels of the substrate phytoene, accompanied by a reduction in colored carotenoids, were detected in cells of each of the mutant strains. A correlation was established between the degree of increase in the steady-state levels of phytoene and the extent of reduction in total carotenoid content in the cells. These two phenomena in turn are correlated with the rate of enzymatic activity of phytoene desaturase that was measured in vitro. Hence we deduce that phytoene desaturation is a rate-limiting step in carotenogenesis in cyanobacteria. Support for this conclusion is obtained from analysis of cells of an additional mutant strain, which overexpress phytoene desaturase due to a deletion mutation in the promoter region of pds. Cells of this mutant contained more colored carotenoids than the wild-type and were resistant to herbicides that inhibit phytoene desaturase.

Amino Acid Sequence↗

PubMed1993

Cloning and functional expression in Escherichia coli of a cyanobacterial gene for lycopene cyclase, the enzyme that catalyzes the biosynthesis of beta-carotene.

Carotenoids with cyclic end groups are essential components of the photosynthetic membrane in all known oxygenic photosynthetic organisms. These yellow pigments serve the vital role of protecting against potentially lethal photo-oxidative damage. Many of the enzymes and genes of the carotenoid biosynthetic pathway in cyanobacteria, algae and plants remain to be isolated or identified. We have cloned a cyanobacterial gene encoding lycopene cyclase, an enzyme that converts the acyclic carotenoid lycopene to the bicyclic molecule beta-carotene. The gene was identified through the use of an experimental herbicide, 2-(4-methylphenoxy)triethylamine hydrochloride (MPTA), that prevents the cyclization of lycopene in plants and cyanobacteria. Chemically-induced mutants of the cyanobacterium Synechococcus sp. PCC7942 were selected for resistance to MPTA, and a mutation responsible for this resistance was mapped to a genomic DNA region of 200 bp by genetic complementation of the resistance in wild-type cells. A 1.5 kb genomic DNA fragment containing this MPTA-resistance mutation was expressed in a lycopene-accumulating strain of Escherichia coli. The conversion of lycopene to beta-carotene in these cells demonstrated that this fragment encodes the enzyme lycopene cyclase. The results indicate that a single gene product, designated lcy, catalyzes both of the cyclization reactions that are required to produce beta-carotene from lycopene, and prove that this enzyme is a target site of the herbicide MPTA. The cloned cyanobacterial lcy gene hybridized well with genomic DNA from eukaryotic algae, thus it will enable the identification and cloning of homologous genes for lycopene cyclase in algae and plants.

Carotenoids↗

PubMed1993

[Snoring and obstructive sleep apnea in childhood].

In this paper the development of the diagnostic procedure of sleep apnoe syndrome is summarized and a survey of the pathophysiology and possible causes of this illness is given as well as two groups of patients children with hypertrophic tonsils and adenoids and tightenings after pharyngo-plastic operations where this disorder was observed are demonstrated. Detailed description is given of the examinations used as well as of the possibilities of treatment.

Age Factors↗

PubMed1993

[Hearing loss resulting from purulent meningitis in the light of adjuvant dexamethasone therapy].

Results of objective audiometry of 109 infants and children after purulent meningitis are presented. Among them 17 patients got dexamethasone as a supportive therapy. There was no statistically significant difference in hearing loss between the dexamethasone-treated and the control group. (41 vs 43% sensorineural hearing loss respectively). Authors do not contraindicate the dexamethasone therapy in purulent meningitis because of its harmlessness and useful effect to the course of the disease but further investigations are needed for avoidance of hearing loss following meningitis.

Chemotherapy, Adjuvant↗

PubMed1993

Transitory evoked otoacoustic emission (TEOAE) in a child with profound hearing loss.

The case of a 3-month-old, prematurely born boy with auditory brainstem response (ABR), verified profound hearing loss and normal transitory evoked otoacoustic emission is presented. Isolated retrocochlear deafness which did not influence TEOAE is hypothesised as a possible cause. The critical evaluation of results when using TEOAE as a screening method is suggested.

Deafness↗

PubMed1992

Thermoluminescence and flash-induced oxygen yield in herbicide resistant mutants of the D1 protein in Synechococcus PCC7942.

Several strains of Synechococcus PCC7942 carrying point mutations in the gene psbA were studied by thermoluminescence and polarographic measurement of flash-induced oxygen yield. The following results were obtained: (a) Replacement of Ser-264 in D1 by Ala (mutant Di1) or Gly (mutant G264) resulting in DCMU and atrazine resistance leads to a downshift of the thermoluminescence (TL) B-band peak temperature from 40 degrees C in wild-type thylakoids to about 30 degrees C. In dark adapted samples of both mutants the TL and oxygen yield pattern induced by a train of single turnover flashes were strongly damped indicative of a high miss factor. (b) In contrast to Ser-264 mutants, replacement of Phe-255 in D1 by Tyr (mutant Tyr5) induced strong resistance to atrazine but not to DCMU and did not affect the peak termperature of the B-band and the flash-induced TL and oxygen yield patterns. In this respect mutant Tyr5 resembles the wild type. (c) No significant differences have been found between strains with single site mutations in psbAI and normal psbAII/psbAIII genes, and strains with same mutations in psbAI but additional deletion of psbAII and psbAIII. Obviously in strains were psbAI is present, PS II complexes containing gene products of psbAII and psbAIII are not assembled in detectable amounts. (d) Strains with double mutations at positions 264 and 255 display a downshift of the B-band peak temperature. Their oscillatory patterns of B-band intensity and oxygen yield are highly damped. This behaviour is similar to strains D1 and G264 which are modified at position 264 only. We extend reports on additivity of mutation effects on herbicide binding to binding of QB. (e) Mutations at the QB site not only influence the binding of QB and herbicides but also change the thermoluminescence quantum yield and the lifetimes of the redox states S2 and S3 of the water oxidase. This finding might indicate long ranging effects on Photosystem II exerted by structural modifications of the QB site. From these data we conclude that Ser-264 is essential for binding of atrazine, DCMU and QB, whereas Phe-255 is involved in atrazine binding and its substitution by Tyr does not markedly affect QB or DCMU binding in Synechococcus PCC7942.

Atrazine↗

PubMed1992

A single polypeptide catalyzing the conversion of phytoene to zeta-carotene is transcriptionally regulated during tomato fruit ripening.

The cDNA of the gene pds from tomato, encoding the carotenoid biosynthesis enzyme phytoene desaturase, was cloned, and its nucleotide sequence was determined. Cells of Escherichia coli that expressed the tomato pds gene could convert phytoene to zeta-carotene. This result suggests that one polypeptide, the product of the pds gene, can carry out phytoene desaturation in the carotenoid biosynthetic pathway. Transcripts of the pds gene accumulate in orange tomato fruit, indicating transcriptional control of pds expression during fruit ripening. The deduced amino acid sequence of phytoene desaturase indicates that this enzyme in tomato contains 583 amino acids that are highly conserved with respect to the homologous enzymes in cyanobacteria and algae. The deduced amino acid sequences of the phytoene desaturases from other microorganisms (purple bacteria and fungi) appear to be evolutionarily unrelated to those from green photosynthetic organisms.

Amino Acid Sequence↗

PubMed1992

Molecular cloning and expression in Escherichia coli of a cyanobacterial gene coding for phytoene synthase, a carotenoid biosynthesis enzyme.

The first committed step in the biosynthetic pathway of carotenoids in plants and algae is the conversion of geranylgeranyl pyrophosphate (GGPP) to prephytoene pyrophosphate (PPPP), which is converted to phytoene. We have cloned the gene pys that encodes the enzyme phytoene synthase in the cyanobacterium Synechococcus PCC7942. The co-expression of pys in cells of Escherichia coli together with the gene crtE from Erwinia uredovora, which encodes geranylgeranyl pyrophosphate synthase, resulted in accumulation of phytoene. This result indicates that phytoene synthase is a single polypeptide enzyme that catalyzes the 2-step reaction from GGPP to phytoene. The deduced amino acid sequence of pys is highly conserved with that of pTOM5, a tomato cDNA that is differentially expressed during fruit ripening. These findings suggest that pTOM5 encodes phytoene synthase in tomato.

Alkyl and Aryl Transferases↗