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Biomedical subjects

C Carlson

Publications and source records attributed to C Carlson.

At least 55 records · Page 3Linked to original sources
PubMed1989

Analysis of heterogeneous fluorescence photobleaching by video kinetics imaging: the method of cumulants.

The method of cumulants has been applied to digital video fluorescence microscopy. The method is used to reconstruct the distribution of fluorescent molecules before the initiation of fluorescence photobleaching, and to characterize heterogeneous photobleaching by imaging one or more of the cumulants of the bleaching decay rate. Using the pipelined pixel processor of the image analysis system for the bulk of the calculations, rather than the general-purpose host-computer CPU, the video kinetics imaging can be performed in near real-time. The method is applied to chick embryo myotubes labelled with fluorescein-conjugated alpha-bungarotoxin. The pre-bleach fluorescence distribution is derived, and the image of fluorescein fluorescence is separated from glutaraldehyde-induced autofluorescence on the basis of the spatially resolved average photobleaching decay rate.

Animals↗
PubMed1989

Protein-DNA interactions at steroid hormone regulated genes.

This work summarizes binding data that were obtained with partially purified glucocorticoid and progesterone receptors, as well as with a crude nuclear protein extract, to DNA sequences in and around hormonally regulated genes. The sequence recognition by the glucocorticoid receptor at the different defined glucocorticoid regulatory elements (GRE) is discussed and a consensus sequence formulated. A three dimensional representation gives an impression of the mode of interaction between the protein and the double helix of DNA. In the promoters of mouse mammary tomour virus (MTV) and chicken lysozyme overlapping binding sites for both, glucocorticoid and progestine-receptors are found that are responsible for the hormonal inducibility of the genes. In crude extract from rat liver nuclei, a nonhistone protein is found that specifically binds to sequences on the MTV-LTR region overlapping the GRE. The possible implication of this protein in hormonal regulation of transcription is discussed.

Animals↗
PubMed1986

Established cell lines from nonmammalian vertebrates: models for DNA repair studies.

Several established cell lines from different classes of vertebrates were assayed for the presence of O6-methylguanine acceptor protein. This protein is instrumental in removing adducts from DNA caused by exposure to alkylating agents. Cultured cells had levels of acceptor protein activity within the range found in fresh tissues from animals in the same class. We suggest that cells from lower vertebrates are satisfactory in vitro models for studies of this DNA repair function.

Amphibians↗
PubMed1986

Computer-aided three-dimensional reconstruction of nematode embryos from EM serial sections.

Embryos of the nematode Caenorhabditis elegans were serially sectioned and photographed in the electron microscope (EM). The micrographs were used to produce three-dimensional (3D) reconstructions. Size and position of each nucleus were entered into a computer, displayed as spheres, and were color-coded to indicate lineage membership. Location in space and position in the cell cycle are generally adequate criteria to identify cells. The reconstructions allow visualization of lineage-related topographic patterns and ultrastructural analysis of differently determined cells.

Animals↗
PubMed1986

Presence of O6-methylguanine acceptor protein in the tissues of different classes of vertebrates and invertebrates.

We have measured the ability of extracts of tissues from several species of mammals, birds, reptiles, amphibia and fish to demethylate adducts of O6-methylguanine in exogenous DNA by transfer of the methyl group to an acceptor protein. Our study also encompassed tissues from a smaller number of invertebrates, from arthropods, molluscs and annelids. The vertebrate tissues used were liver, brain, spleen and kidney. In the case of the invertebrates we sampled liver, neural tissue, gonads, digestive tract and hepatopancreas. There was no consistent change in the amount of acceptor activity per unit of protein or DNA going from cold-blooded to warm-blooded vertebrates. Liver invariably had the highest amount; this finding was not unexpected since metabolic processes in the liver are high, and good cellular protective mechanism important. Inter-class comparisons within the vertebrates are highly speculative, and hindered by the fact that there is little information on carcinogenesis in animals other than rodents and humans. O6-methylguanine acceptor activity was found in all the invertebrate tissues tested. The amounts were variable, 0.003-0.0051 fmol/micrograms cellular DNA, but the values fell within the range of those found in the tissues of vertebrates.

Amphibians↗
PubMed1986

Molecular model of the interaction between the glucocorticoid receptor and the regulatory elements of inducible genes.

Binding sites for the glucocorticoid receptor in an ecdysone-inducible gene from Drosophila melanogaster and in the chicken vitellogenin gene are described. A comparison with other binding sites for the glucocorticoid receptor, which have been analyzed by methylation protection experiments, shows they can be classified into three groups. The first group exhibits two blocks of contact points in two subsequent turns of the DNA helix, and includes only functional regulatory elements. The second group shows an identical contact with the hexanucleotide 5'-TGTYCT-3', but only half the contact points in the other turn of the helix, whereas the third group of sites exhibits only the contact points within the conserved hexanucleotide. An analysis of the hydrogen-bonding potential of the DNA base pairs along the major groove of 10 binding sites shows a very well-conserved pattern and a twofold rotational symmetry, suggesting that the array of hydrogen bonds may be a relevant aspect of sequence recognition by hormone receptors. A representation of the binding sites and contact points by computer graphics suggests the interaction of a receptor dimer, in a head-to-head arrangement, with two subsequent turns of the B-DNA helix within the glucocorticoid regulatory elements.

Animals↗
PubMed1985

The relationship of the nonstress test to gestational age.

Five hundred ninety-three nonstress tests were performed on 41 obstetric patients, at gestational ages ranging from 20 to 40 weeks. Diagnoses included 10 cases of prematurity, six cases of diabetes mellitus, five cases of collagen-vascular disease, five cases of poor obstetric history, three cases of cardiac arrhythmia, and one case each of asthma, polyhydramnios, leukemia, nonimmune fetal hydrops; and eight volunteers were without high-risk factors. All neonates had a 5-minute Apgar score greater than 8; 29 neonates weighed greater than or equal to 2500 gm, 12 weighed less than 2500 gm, and four weighed less than 1500 gm. One neonate died of prematurity, and one was small for gestational age. There were no congenital anomalies. There was a significant difference in the number of reactive nonstress tests and nonreactive nonstress tests between the 20- to 24-week, 24- to 28-week, 28- to 32-week, and 32- to 36-week gestational age groups. The increased incidence of nonreactive nonstress tests at earlier gestational ages may have clinical implications.

Adult↗
PubMed1985

Levels of O6-methylguanine acceptor protein in tissues of rats and their relationship to carcinogenicity and aging.

N-nitroso compounds react with cellular DNA to produce various damaging adducts, one of the more important being O6-alkylguanine. DNA restoration is accomplished by transfer of the alkyl group to a cysteine residue of an acceptor protein. The levels of acceptor activity were compared in several tissues from well-fed and dietary-restricted inbred SD rats 30-1,194 days of age. Striking and consistent differences were found in the levels of acceptor activity in different tissues from both groups; these levels corresponded to their sensitivity to tumorigenesis by alkylating agents. Acceptor activity levels were highest in the liver and somewhat less in the spleen; there were significantly lower levels in brain and kidney. The random loss with time in the integrity of DNA may cause alterations in cellular function or limit cellular proliferation, thus leading to senescence and death. DNA repair processes may alter the rate of accumulation of damage, thereby affecting potential longevity. There were no significant age-associated changes in the ability of cells from either dietary group to remove DNA adducts and there was no evidence of alterations in the acceptor protein with age that would compromise its functional activity.

Aging↗
PubMed1980

Host defenses in acute pelvic inflammatory disease. I. Bacterial clearance in the murine uterus and oviduct.

Bacterial clearance in the uterine horn and oviduct as a host defense in acute pelvic inflammatory disease was studied in 8- to 12-week-old virgin Balb/c mice. Quantitative cultures of organ homogenates were determined at various intervals following intrauterine injection of a standard inoculum of E. coli by micropuncture technique. The effect of uterine horn ligation and of estrus cycle of inoculated mice was evaluated also. Mean bacterial counts in the uterine horn were significantly higher than in the contiguous oviduct (p less than 0.005), suggesting a barrier function of the uterotubal junction for bacterial passage into the oviduct. Our data suggest a protective role for the uterotubal junction, and demonstrate the influence of uterine obstruction and estrus cycle on bacterial clearance of the oviduct.

Animals↗
PubMed1980

Brainstem auditory evoked potentials in postconcussion dizziness.

Twenty-seven patients with postconcussion dizziness following minor injury to the head or neck had brainstem auditory evoked potential studies from one day to eight months (median, 37 days) following injury. All patients were normal on clinical examination at the time of study. Three patients had one or more interpeak latencies prolonged beyond the 99% tolerance limit for normal control subjects. The group mean 1-3, 2-3, and 1-5 interpeak latencies were significantly prolonged. These findings indicate that minor head or neck injury with associated subjective symptomatology may be accompanied by objectively demonstrable brainstem dysfunction.

Adult↗
PubMed1978

Comparison of the effect of the beta1-blocking drugs atenolol and metoprolol on bronchial asthma.

Twenty patients with severe or medium severe asthma were given atenolol (Atenol ICI-Pharma) and/or metoprolol (Seloken Hässle) for tachycardia, hyperkinetic tremor, arterial hypertension or symptoms of angina pectoris. These cardioselective beta-blocking drugs caused only a very slight decrease in PF values. There was no difference between atenolol and metoprolol as regards the PF values. A 24 hourly dose of 100 mg atenolol caused a distinct fall in diastolic fall in diastolic pressure as compared with the same amount of metoprolol. Both these two beta1-blockers moderated the tachycardia which occurs in asthma; atenolol in this dose had a slightly stronger action. The subjective condition of five patients with severe or medium severe asthma was considerably relieved by atenolol and/or metoprolol. The relief manifested as a lessening of dyspnoea and improvement of the general status. No essential change was observed in the PF values despite the subjective effects. The most noteworthy change was the amelioration of tachycardia which had continued longer than expected in these patients. The heart rate dropped from 140-120/min to 90-70/min and dyspnoea was relieved at the same time.

Adult↗