Observation of differences between low-energy electron- and positron-diffraction structural determinations of the cleavage faces of CdSe.
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Journal Article↗
Biomedical subjects
A Kahn
Publications and source records attributed to A Kahn.
The brain-specific gene for rat aldolase C possesses an unusual housekeeping-type promoter.
A DNA fragment encompassing the first exon and about 750 bp of the 5'-flanking sequence has been isolated and sequenced. The gene has multiple start sites of transcription which are dispersed over about 200 bp. The promoter lacks TATA and CAAT boxes and is very G + C-rich, with putative binding sites for the transcriptional factors Sp1 and AP2. Similar features are shared with two other brain-specific genes encoding thy-1 antigen and gamma-enolase. The existence of a conserved block of similarity upstream of the human and rat aldolase C genes suggests that this region could be involved in tissue-specific expression whose mechanism seem to be, at least in part, transcriptional.
Animals↗
Transfection of hepatic genes into adult rat hepatocytes in primary culture and their tissue-specific expression.
We describe in this paper a method for studying transient gene expression in a primary culture of adult rat hepatocytes. After isolation by collagenase perfusion, hepatocytes in a monolayer were transfected with foreign DNA by the calcium phosphate precipitation technique during the first 24 hours after plating. When they were transfected with a plasmid containing the gene for chloramphenicol acetyltransferase driven by the early promoter of simian virus 40, hepatocytes reproducibly expressed high levels of chloramphenicol acetyltransferase (CAT); this transient expression was much higher than that obtained with the rat hepatoma cell line H4II. Different medium conditions have been tested; an optimal level of CAT activity can be obtained using a serum-free, hormonally defined medium. Using these techniques, we have investigated the expression of liver-specific genes transferred into hepatocytes. We show that the L-pyruvate kinase promoter is active in these hepatocytes while it is silent in fibroblasts. Moreover, the use of serum-free medium may allow investigation of the role of hormones and nutrients in cells which respond normally to these effectors.
Animals↗
Stiles and Kahn reply.
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Journal Article↗
Expression of MyoD1 coincides with terminal differentiation in determined but inducible muscle cells.
We have examined the expression of MyoD1, a potential determination factor of myogenic cells, in permissive and inducible C2 myoblasts. These two types of myoblasts exhibit distinct requirements to undergo terminal differentiation. Unlike permissive cells, inducible cells fail to differentiate in the presence of growth medium plus fetal calf serum and require insulin to undergo terminal differentiation. We show that while expression of MyoD1 is constitutive in permissive cells, no trace of MyoD1 transcripts is found in inducible cells at the myoblast stage. In these cells, however, expression of MyoD1 accompanies differentiation. This indicates that MyoD1 may not be required for the maintenance of the myoblast phenotype, and could act as an effector of terminal differentiation in already determined muscle cells. Our results provide new evidence that permissive and inducible cells represent two distinct stages of the progression of determined muscle cells toward terminal differentiation.
Autoradiography↗
Illegitimate transcription: transcription of any gene in any cell type.
Using in vitro amplification of cDNA by the polymerase chain reaction, we have detected spliced transcripts of various tissue-specific genes (genes for anti-Müllerian hormone, beta-globin, aldolase A, and factor VIIIc) in human nonspecific cells, such as fibroblasts, hepatoma cells, and lymphoblasts. In rats, erythroid- and liver-type pyruvate kinase transcripts were also detected in brain, lung, and muscle. The abundance of these "illegitimate" transcripts is very low; yet, their existence and the possibility of amplifying them by the cDNA polymerase chain reaction provide a powerful tool to analyze pathological transcripts of any tissue-specific gene by using any accessible cell.
Animals↗
Sleep pattern alterations and brief airway obstructions in overweight infants.
The sleep characteristics of 10 overweight infants were monitored polysomnographically and compared with those of 10 age- and sex-matched control infants with no weight excess. The infants were selected from a well-babies clinic. Infants were assigned to the weight excess group if their weight was greater than 120% of ideal weight/height for age. There were six boys and four girls in both groups, with a median age of 23.5 weeks in the weight excess group and 22.0 weeks in the control group. The infants with weight excess spent significantly less time sleeping in non-rapid-eye-movement (NREM) sleep stage 3-4 and more time in indeterminate sleep than their matched controls. The infants with weight excess had also significantly more gross body movements and more sleep stage shifts than the control infants. Brief airway obstructions were found significantly more frequently in the weight excess group than in the control group. Seven overweight infants showed a total of 74 brief airway obstructions; 41 occurred in NREM sleep stage 1 or 2 and 14 in rapid-eye-movement (REM) sleep. The median duration of the obstructive episodes was 8 s (range 3-13 s). Of the 10 control subjects, only 2 had one obstructive episode each, lasting 3 and 4 s and occurring during REM sleep. Only one mixed apnea of 6.5 s was recorded in a 39-week-old overweight boy. The obstructive episodes were accompanied by a median fall in heart rate of 9% (range 0-51%) and by a median fall in oxygen saturation of 0.9% (range 0-10%).(ABSTRACT TRUNCATED AT 250 WORDS)
Airway Obstruction↗
Results of a multicenter outpatient burn study on the safety and efficacy of Dimac-SSD, a new delivery system for silver sulfadiazine.
Dimac with silver sulfadiazine (Dimac-SSD), a new silver sulfadiazine delivery system, was evaluated prospectively in a multicenter study for the treatment of outpatient burn injuries. The goal of this study was to evaluate the effect of Dimac-SSD on the microbiology of the burn wounds and to quantitate its clinical safety and efficacy. A total of 197 patients were evaluated. Eight (4%) of these patients did not complete the study. Six patients withdrew because of local discomfort caused by the Dimac-SSD and two patients were terminated because of technical problems. The mean +/- SD duration of treatment with Dimac-SSD was 12 +/- 8.5 days, during which time the mean number of dressing changes was 2.9 per patient. During treatment with Dimac-SSD, the burn wound bacterial flora remained stable and overgrowth with Pseudomonas species or Gram-negative bacilli did not occur. Only four (2%) patients developed clinical infections; thus the Dimac-SSD appeared to have good antimicrobial effectiveness. This dressing was not associated with any organ system or metabolic side-effects and patient discomfort during application and removal was minimal. Thus this new delivery system for silver sulfadiazine was associated with excellent wound healing, a low incidence of wound infections, reduced frequency for dressing changes, and excellent patient compliance.
Acrylates↗
Analysis by cell-free transcription of the liver-specific pyruvate kinase gene promoter.
A DNA fragment spanning nucleotides -183 to -4 with respect to the cap site of the rat L-type pyruvate kinase (L-PK) gene contains at least four binding sites for putative transcriptional factors: hepatocyte nuclear factor 1 (HNF1), liver factor A1 (LF-A1), nuclear factor 1 (NF1), and major late transcription factor (MLTF). This fragment was used to direct transcription of a reporter sequence (a G-free cassette) in cell extracts. This L-PK promoter was active in liver nuclear extracts, but not in extracts from nonhepatic tissues. A reduction of 50% of the activity was obtained with a deleted L-PK promoter containing only the HNF1-binding site. In contrast, deletion of the HNF1-binding site inactivated the promoter by more than 90%. These results were confirmed by titration experiments with synthetic oligonucleotides. Titration of HNF1 resulted in an 85% decrease of transcriptional activity, while titration of LF-A1 resulted in only a 40% decrease. The influence of NF1 and MLTF seemed to be marginal in this system. The proximal 5'-flanking sequence of the L-PK gene therefore appears to function in vitro as an efficient liver-specific promoter which requires the binding of the liver factor HNF1 and which is also stimulated by the binding of another liver-specific factor, LF-A1.
Animals↗
Variable modes of proopiomelanocortin gene transcription in human tumors.
We studied the mechanism of POMC gene expression in human nonpituitary tumors that is responsible for the ectopic ACTH syndrome. All tumors contained a 1200-nucleotide (nt) POMC mRNA species identical to that in normal and tumoral pituitaries. In two of six nonpituitary tumors, equivalent amounts of a larger, ca. 1450-nt POMC mRNA species were also present. S1 mapping studies with probes encompassing the three exons of the gene revealed that this larger POMC mRNA species was 5' extended; the other regions were identical to that in the 1200-nt POMC mRNA. In order to analyze the 5'-end of the larger POMC mRNA species, a genomic clone starting at 3.0 kilobases upstream from the usual (pituitary) cap site was obtained, and single-stranded DNA probes were used for S1 mapping studies. They showed several upstream start sites of transcription located at -369, -217, and -108. Analysis of the human genomic sequence showed TATA and GC box-like motifs preceding the -369 and -217 sites and a GC-rich region preceding the -108 site. S1 mapping with a DNA probe, encompassing exon 1 and 93 nt of its 5'-flanking region, allowed quantitative determinations, which showed that the 5'-extended POMC mRNA species accounted for variable proportions of the overall POMC transcripts in different tissues: 0.3% or less in two normal pituitaries, 0.5-3% in five tumoral pituitaries, and up to 35% and 40% in two of six nonpituitary tumors. These results show that variable modes of human POMC gene expression are induced by upstream promotors whose relative activities appear increased in some nonpituitary tumors.(ABSTRACT TRUNCATED AT 250 WORDS)
ACTH Syndrome, Ectopic↗
Pro-opiomelanocortin gene expression in human phaeochromocytomas.
Phaeochromocytoma is an occasional cause of the ectopic ACTH syndrome. The mechanisms of proopiomelanocortin (POMC) gene expression were analysed in 11 human tumours not associated with Cushing's syndrome, by detecting and characterizing the POMC mRNA. A DNA probe corresponding to most of the protein-coding region of the third exon was used in Northern blot studies of total and poly(A)+ RNA. All tumours contained a short (800 bases) mRNA species different from the 1200 base mRNA species of the human pituitary. This short mRNA was also present in the normal adrenal, where S1 mapping showed that it resulted from transcription initiation within the third exon. However, in two tumours, equivalent amounts of the 1200 base mRNA were also present, and in one of them a third POMC mRNA of approximately 1450 bases was detected. These data show that POMC gene expression occurs in all phaeochromocytomas. It is suggested that excess production of the 1200 bases (or the larger, 1450 base) mRNA in some tumours may be responsible for the rare occurrence of the ectopic ACTH syndrome.
ACTH Syndrome, Ectopic↗
Identification of major Trypanosoma cruzi antigenic determinants in chronic Chagas' heart disease.
To identify Trypanosoma cruzi target antigens in overt Chagas' heart disease, a parasite lambda gt11 cDNA library was screened with the serum of a patient with a severe chagasic heart involvement (JL). Using a phage dot array immunoassay, 5 highly antigenic clones, JL1, JL5, JL7, JL8, and JL9, were probed with sera from clinically characterized T. cruzi infected subjects. The correlation of cloned T. cruzi antigen recognition with the clinical status of the subjects led to the identification of a recombinant antigen, JL5, that reacted predominantly with sera from patients with Chagas' heart disease. The antigenic determinant of the JL5 recombinant was a small 35 amino acid peptide. The nucleotide and the deduced amino acid sequence, together with other experimental data, allowed identification as the C-terminal portion of a T. cruzi P ribosomal protein. The C-terminal undecapeptide in JL5, EDDDMGFGLFD, was highly homologous to the same region of the human P protein SD(D/E)DMGFGLFD. The latter sequence has been identified as the P protein epitope in systemic lupus erythematosus (SLE). Positive SLE sera reacted with the JL5 recombinant phage, suggesting that the T. cruzi P protein might induce antibodies with a similar specificity to that of P antibodies in SLE.
Adult↗
Long-term development of children monitored as infants for an apparent life-threatening event during sleep: a 10-year follow-up study.
The outcomes of 26 children who had an apparent life-threatening event during sleep and who were monitored at home were evaluated. In a preliminary study that was first reported when the children had a mean age of 2.7 years, only minor behavioral difficulties were seen. The children of this earlier study were characterized by more aggressive behavior, which was tentatively related to parental anxiety. The same children were retested at a mean age of 7 years (range 6 to 10 years), together with sex-, age-, and social class-matched control children. No significant differences were found in their clinical daytime and nighttime behavior or in IQ tests, although in some of the psychodevelopmental tests minor signs of anxiety were revealed. In conclusion, infants with an apparent life-threatening event who underwent continued cardiopulmonary home monitoring develop normally during preadolescence. A prolonged follow-up of the children during adolescence is needed to evaluate later school performance.
Anxiety↗
Milk intolerance in children with persistent sleeplessness: a prospective double-blind crossover evaluation.
From July 1986 to July 1988, 146 children less than 5 years of age were referred by their physicians to our university sleep clinic for continual waking and crying during sleep hours. For 85 children (58.2%), the sleeplessness was attributed to inappropriate sleep habits. For 17 children (11.6%), no explanation was found for the sleep difficulties in spite of an extensive workup. Their median age at referral was 13.5 months (range 2.5 to 29 months). Their persistent sleeplessness was tentatively attributed to an undiagnosed intolerance to cow's milk. Cow's milk was excluded from their diet. In 15 children sleep normalized after 5 weeks (range 4 to 6 weeks). As seen from the parents' logs, the median time needed by the children to fall asleep decreased from 15 minutes (range 15 to 60 minutes) to 10 minutes (range 10 to 15 minutes, P = .001). The number of complete arousals decreased from 5 (range 1 to 12) to less than 1 per night (range 0 to 2) (P = .001). Total sleep time per 24 hours increased from 5.5 hours (range 3 to 8.5 hours) to 13.0 hours (range 10 to 14.5 hours, P = .001). Sleep normalized in one child who continued to receive no cow's milk only after the hydrolyzed hypoallergenic diet was discontinued. In every child, a double-blind crossover challenge was conducted involving a control diet containing no cow's milk and a diet containing cow's milk. The challenge induced the reappearance of insomnia and agitated behavior in all except one child. The child's initial sleep difficulties were retrospectively attributed to inappropriate sleep habits.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Sleep problems in healthy preadolescents.
Few data currently exist concerning the sleep problems of preadolescents. A parent report questionnaire concerning sleep habits and problems was developed. The questionnaires were completed by the parents of 1000 unscreened elementary school children attending the third, fourth, and fifth grades. The schools were randomly selected from an urban area. Of the 1000 questionnaires, 972 were completed and could be used for statistical analysis. Among the parents, 24% reported sleeping poorly and 12% regularly relied on sedatives to induce sleep. Sleep difficulties lasting more than 6 months were present in 43% of the children. In 14% (132 of 972), sleep latency was longer than 30 minutes, and more than one complete arousal occurred during the night at least two nights per week. The following variables were seen among the poor sleepers: lower parental educational and professional status, parents who were more likely to be divorced or separated, and more noise or light in the rooms were they slept. They also presented a higher incidence of somnambulism, somniloquia, and night fears (nightmares and night terrors) than the children who slept well. Boys who slept poorly were significantly more likely to have insomniac fathers (P less than .010). Regular use of sedatives was described in 4% (5 of 132) of the children who slept poorly. Among the "poor sleepers," 21% (33 of 132) had failed 1 or more years at school. School achievement difficulties were encountered significantly more often among the poor sleepers than among the children without sleep problems (P = .001). Of the families with children suffering from sleep problems, 28% expressed a desire for counseling.(ABSTRACT TRUNCATED AT 250 WORDS)
Belgium↗
Transcription of the dystrophin gene in human muscle and non-muscle tissue.
The gene that is defective in patients with Duchenne and Becker muscular dystrophy consists of about 60 short exons scattered along a gigantic DNA region that spans some 2 megabase pairs. The encoded protein, dystrophin, was recently characterized as a component of muscle intracellular membranes of low abundance. The dystrophin messenger RNA is difficult to study in both normal and pathological tissue specimens because it is large (14 kilobases) and scarce (0.01-0.001% of total muscle mRNA). We report here that efficient in vitro co-amplifications of the mRNAs of the dystrophin gene and of a reporter gene, aldolase A, by the polymerase chain reaction procedure enables us to obtain a quantitative estimate of the dystrophin gene transcript. A processed, transcribed segment was thus detected in 13 different human tissues. It ranged from 0.02-0.12% of total mRNA in skeletal muscle to 25,000 times less in lymphoblastoid cells.
Brain Chemistry↗
The 'CC.Ar.GG' box. A protein-binding site common to transcription-regulatory regions of the cardiac actin, c-fos and interleukin-2 receptor genes.
We have previously suggested that a repeated sequence motif in the upstream region of the human cardiac actin gene 'CC.Ar.GG', where Ar is an (A + T)-rich six-base-pair-sequence, may be important in the muscle-specific expression of this gene [Minty, A. & Kedes, L. (1986) Mol. Cell Biol. 6, 2125-2136]. Here we show that this sequence binds a nuclear protein, and that binding is abolished by mutating either the CC and GG dinucleotides or the (A + T)-rich centre. Mutation of the CC and GG nucleotides also abolishes the transcription-stimulating activity of this sequence on the cardiac actin promoter. A similar sequence has been implicated in the serum-response of the c-fos gene [Treisman, R. (1986) Cell 46, 567-574]. We show that this c-fos 'CC.Ar.GG' sequence competes with the cardiac actin sequence for factor binding. Our results suggest that the minimum sequence requirements for binding of the serum response factor may correspond to the 'CC.Ar.GG' box sequence. Using this criterion, we predict and confirm the existence of such a binding site in a regulatory region of the interleukin-2 receptor gene. It appears therefore that interactions between 'CC.Ar.GG' boxes and similar proteic factors could be involved in the control of different genes responding to different stimuli, e.g. muscle differentiation (cardiac actin gene) or growth stimulation (c-fos, cytoskeletal actin or interleukin-2 receptor genes).
Actins↗
Correlation between EF pinning and development of metallic character in Ag overlayers on GaAs(110).
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