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Biomedical subjects

A Olson

Publications and source records attributed to A Olson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Structure and organization of two closely related low-temperature-induced dhn/lea/rab-like genes in Arabidopsis thaliana L. Heynh.

We have isolated a 7 kb EcoRI genomic fragment from Arabidopsis thaliana which contains, in a tandem arrangement, two closely related dhn/lea/rab-like genes, lti29 (formerly named lti45) and cor47, corresponding to previously isolated cDNA clones. Both transcripts have been shown to accumulate in response to low temperature (LT), abscisic acid (ABA) and dehydration. Alignment of the amino acid sequences of the deduced polypeptides showed that they are 67% identical. The calculated molecular masses of the two polypeptides were 29 kDa for LTI29 and 30 kDa for COR47. Both polypeptides contain one conserved serine-stretch and three lysine-rich repeats characteristic of DHN/LEA/RAB-like proteins. In addition, both LTI29 and COR47 harbour and N-terminal acidic repeat only found in a few members amongst the DHN/LEA/RAB proteins. The close distance between the two genes (separated by 2.7 kb) and their tandem organization in the A. thaliana genome as well as the overall homology at the nucleotide sequence level of the coding region suggest that the two genes have evolved through a duplication event. This seems to be a common feature among A. thaliana LT-responsive genes.

Amino Acid Sequence↗
PubMed1994

Non-spatial extinction following lesions of the parietal lobe in humans.

Efficient behaviour in the visual environment requires selection between stimuli competing for control of action. Many current models of selection are spatial: relevant objects are chosen by attending to their locations. The unilateral stimulus extinction observed following lesions of the parietal lobe provides evidence for spatial selection. Such patients may identify a single stimulus presented in their contralesional field, but can fail to detect the same stimulus when a competing stimulus is shown simultaneously on the ipsilesional side. Here we demonstrate that extinction need not be spatial in nature, but may be determined by characteristics of the objects to be selected. In two patients with parietal lobe lesions and poor spatial localization, pictures extinguished words and closed shapes extinguished open shapes. This object-based extinction indicates the existence of biases within non-spatial selection mechanisms which are independent of biases produced by spatial selection mechanisms. We suggest that selection of objects for action requires that the 'winners' produced by the independent competitive biases for selection are bound together within distinct neural areas concerned with object properties and space.

Brain Diseases↗
PubMed1994

Characterization and differential expression of dhn/lea/rab-like genes during cold acclimation and drought stress in Arabidopsis thaliana.

We have characterized cDNAs for two new dhn/lea/rab (dehydrin, late embryogenesis-abundant, responsive to ABA)-related genes from Arabidopsis thaliana. The two genes were strongly induced in plants exposed to low temperature (4 degrees C) and were accordingly designated lti45 and lti30 (low temperature-induced). The lti45 gene product contains the conserved serine stretch and three lysine-rich repeats characteristic of DHN/LEA/RAB proteins and is very similar to another low temperature-responsive protein of A. thaliana, COR47 [17]. Both proteins have the same repeat structure and an overall amino acid identity of 64%. This structural similarity of the proteins and the tandem array of the genes suggest that this gene pair arose through a duplication. The other polypeptide, LTI30, consists of several lysine-rich repeats, a structure found in CAP85, a low temperature- and water stress-responsive protein in spinach [41] and similar proteins found in wheat [20]. The expression pattern of the five dhn/lea/rab-related genes (cor47, dhnX, lti30, lti45 and rab18) identified so far in A. thaliana, was characterized in plants exposed to low temperature, drought and abscisic acid (ABA). Expression of both lti30 and lti45 was mainly responsive to low temperature similar to cor47. The lti45 and lti30 genes show only a weak response to ABA in contrast to cor47, which is moderately induced by this hormone. The three genes were also induced in severely water-stressed plants although the expression of lti30 and lti45 was rather low. In contrast to these mainly low temperature-induced genes, the expression of rab18 was strongly induced both in water-stressed and ABA-treated plants but was only slightly responsive to cold. The dhnX gene showed a very different expression pattern. It was not induced with any of the treatments tested but exhibited a significant constitutive expression. The low-temperature induction of the genes in the first group, lti30 and lti45, is ABA-independent, deduced from experiments with the ABA-deficient (aba-1) and ABA-insensitive (abil) mutants of A. thaliana, whereas the induction of rab18 is ABA-mediated. The expression of dhnX was not significantly affected in the ABA mutants.

Abscisic Acid↗
PubMed1994

Efficacy of anterior gastric fundoplication in the treatment of gastroesophageal reflux in infants and children.

Anterior gastric fundoplication (AGF) has been performed at the University of Michigan since 1988. To objectively evaluate the long-term efficacy of the AGF, the authors performed a study of children who had undergone AGF between June 1988 and June 1990 (n = 46). Six of them died of unrelated causes. Twenty-two consented to follow-up evaluation that included parental interview, physical examination, upper gastrointestinal series (UGI), 24-hour esophageal pH probe monitoring (EpH), and a liquid-phase gastric emptying study. Twenty patients (74%) remained asymptomatic, and only one child required reoperation. Four asymptomatic patients exhibited gastroesophageal reflux (GER) by UGI, and three others by EpH. Three children were noted to have delayed gastric emptying. These results compare favorably with data previously reported from this institution of a 5-year follow-up of children after Nissen fundoplication. There is a trend toward improved efficacy (87% v 74%; P = .12), decreased reoperation rate (4% v 14%; P = .11), and less severe complications. The present study shows that AGF is effective treatment for GER when evaluated by objective studies and is comparable in therapeutic efficacy and safety to the Nissen fundoplication.

Adolescent↗
PubMed1993

Diffusion coefficient of cyclic GMP in salamander rod outer segments estimated with two fluorescent probes.

Experiments have demonstrated that single photoisomerizations in amphibian and primate rods can cause the suppression of 3-5% of the dark circulating current at the response peak (Baylor, D. A., T. D. Lamb, and K. W. Yau. 1979. J. Physiol. (Lond.). 288:613-634; Baylor, D. A., B. J. Nunn, and J. L. Schnapf. 1984. J. Physiol. (Lond.). 357:575-607). These results indicate that the change in [cGMP] effected by a single isomerization must spread longitudinally over at least the corresponding fractional length of the outer segment. The effective longitudinal diffusion coefficient, Dx, of cGMP is thus an important determinant of rod sensitivity. We report here measurements of the effective longitudinal diffusion coefficients, Dx, of two fluorescently labeled molecules: 5/6-carboxyfluorescein and 8-(fluoresceinyl)thioguanosine 3',5'-cyclic monophosphate, introduced into detached outer segments via whole-cell patch electrodes. For these compounds, the average time for equilibration of the entire outer segment with the patch pipette was approximately 6 min. Fluorescence images of rods were analyzed with a one-dimensional diffusion model that included limitations on transfer between the electrode and outer segment and the effects of intracellular binding of the dyes. The analyses yielded estimates of Dx of 1.9 and 1.0 microns 2.s-1 for the two dyes. It is shown that these results place an upper limit on Dx for cGMP of 11 microns2.s-1. The actual value of Dx for cGMP in the rod will depend on the degree of intracellular binding of cGMP. Estimates of the effective buffering power for cGMP in the rod at rest range from two to six (Lamb and Pugh, 1992; Cote and Brunnock, 1993). When combined with these estimates, our results predict that for cGMP itself, Dx falls within the range of 1.4-5.5 microns 2.s-1.

Ambystoma↗
PubMed1993

Women, obesity, and the results of medical management.

Women represent more than 75% of the individuals who receive obesity treatment; suprisingly, the numbers of morbidly obese white men and women are approximately equal. Surgical and nonsurgical medical treatments are successful in promoting weight loss; however, maintaining the weight loss is a continuing problem. Weight loss provides many benefits but can lead to undesirable consequences (eg, gallstones and nutrient deficiencies). Long-term success can be accomplished only if the weight loss is permanent; weight cycling increases the health risks associated with obesity. Caution should be exercised in choosing a treatment for obesity so that weight loss is not accomplished at the expense of the health of the individual.

Female↗
PubMed1991

Contamination and radiation exposure from 201Tl in patients undergoing dialysis after a nuclear medicine study.

Our institution is a major kidney research and transplant center. Hemodialysis patients that are scheduled for renal transplant are given a 201Tl stress test. Possible radiation exposure and contamination are of concern to attending personnel. We investigated this situation and found measurable activity in the effluent of patients receiving dialysis but no significant contamination of equipment. We determined that dialysis personnel received minimal radiation exposure.

Equipment Contamination↗
PubMed1989

Deficient neurogenic innervation of the myenteric plexus with normal submucous plexus involving the entire small and large bowel.

A newborn presented with a picture of intestinal obstruction. Multiple biopsies of the small and large bowel showed an unusual neurogenic innervation. The myenteric plexus of Auerbach was severely depleted of ganglion cells and nerve fibers, while the submucous plexus of Meissner was normally innervated. An ileostomy failed to function and extended trial with experimental smooth muscle stimulant (Cisapride) was equally ineffective. The patient was finally treated by a myectomy from the duodenum to the descending colon with a sigmoid colostomy. This procedure, coupled with a Nissen fundoplication, stopped the vomiting and allowed normal defecation through the colostomy. The patient is presently taking increasing increments of oral fluids with a concomitant decrease in the volume of parenteral nutrition. The myectomy initiated marked hypertrophy of the muscularis mucosa. Could this muscular hypertrophy account for the improvement in bowel function? Possible etiology will be discussed. We caution that rectal submucosal suction biopsy alone may be misleading if normal ganglion cells and nerve fibers are found, yet the patient's clinical symptoms fail to improve. A full thickness bowel wall biopsy is then recommended.

Ganglia, Parasympathetic↗
PubMed1989

Preclinical studies on deoxycoformycin and deoxyadenosine as pharmacologic T cell purging tools.

Deoxycoformycin (dCf) is a potent toxin to T lymphocytes in human peripheral blood and bone marrow. In the presence of deoxyadenosine (dAdo), dCf inhibits T cell function as measured by DNA synthesis induced by stimuli in the rank order of mixed lymphocyte culture greater than murine monoclonal antibody OKT3 greater than phytohemagglutinin. Approximately two logs of human bone marrow T cells were removed by 24 h of incubation with dCf and dAdo at doses that preserved colony-forming ability of the treated marrow. A semi-closed system of isolating mononuclear cells in large volumes using density gradient centrifugation was developed. Using this system, it was found that dCf and dAdo could remove about two logs of T lymphocytes after 24 h of incubation when the cells were incubated in large volumes at a relatively high concentration (10(7) cells/ml). This system appears well suited for purging T lymphocytes from human bone marrow before clinical transplantation.

Adenosine Deaminase Inhibitors↗
PubMed1988

Myoplasmic binding of fura-2 investigated by steady-state fluorescence and absorbance measurements.

Binding of the fluorescent Ca2+ indicator dye fura-2 by intracellular constituents has been investigated by steady-state optical measurements. Fura-2's (a) fluorescence intensity, (b) fluorescence emission anisotropy, (c) fluorescence emission spectrum, and (d) absorbance spectra were measured in glass capillary tubes containing solutions of purified myoplasmic proteins; properties b and c were also measured in frog skeletal muscle fibers microinjected with fura-2. The results indicate that more than half, and possibly as much as 85%, of fura-2 molecules in myoplasm are in a protein-bound form, and that the binding changes many properties of the dye. For example, in vitro characterization of the Ca2+-dye reaction indicates that when fura-2 is bound to aldolase (a large and abundant myoplasmic protein), the dissociation constant of the dye for Ca2+ is three- to fourfold larger than that measured in the absence of protein. The problems raised by intracellular binding of fura-2 to cytoplasmic proteins may well apply to cells other than skeletal muscle fibers.

Action Potentials↗
PubMed1982

Immunogenic structure of the influenza virus hemagglutinin.

We chemically synthesized 20 peptides corresponding to 75% of the HA1 molecule of the influenza virus. Antibodies to the majority (18) of these peptides were capable of reacting with the hemagglutinin molecule. These 18 peptides are not confined to the known antigenic determinants of the hemagglutinin molecule, but rather are scattered throughout its three-dimensional structure. In contrast, antibody raised to intact hemagglutinin did not react with any of the 20 peptides. Taken together these results suggest that the immunogenicity of an intact protein molecule is not the sum of the immunogenicity of its pieces.

Amino Acid Sequence↗