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Biomedical subjects

K Pedersen

Publications and source records attributed to K Pedersen.

At least 145 records · Page 8Linked to original sources
PubMed1987

Self-assessment of hearing problems in an elderly population. A longitudinal study.

As part of a large population study, 386 randomly selected probands 70 years of age, representative of the population of an industrialized Swedish city, were questioned regarding hearing difficulties in different social conditions. The same questions were presented to the participants of that study, at the age of 75 and 79 years. The results showed that of the 70-year-old persons, more than 95% had quite a good estimate of their hearing capacity. The subjective hearing problems increased with increasing age. However, at the age of 79 years, 86% still had no hearing problems or had only slight or moderate difficulties. The males reported that they had more hearing problems than the females. The prevalence of irritating tinnitus was about the same for males as for the females (8%). The number of probands with severe tinnitus was constant throughout the investigated period. It is suggested that hearing difficulties experienced when talking to only one person can be used to estimate the need for hearing amplification. A comparison between two cohorts with an age difference of 5 years was made. In a difficult listening situation at the age of 70 years, the hearing of subjects born in 1906-07 was reportedly worse than that of these born in 1901-02.

Aged↗
PubMed1987

Routine synthesis of carbon-11-carboxyl-labeled L-dopa.

Carbon-11-carboxyl-labeled L-dopa has been synthesized by the modified Bucherer-Strecker method. The reaction mixture was first purified by chiral HPLC followed by deprotection using hydriodic acid. The entire procedure was performed in a remotely operated system which gave the product in 28% radiochemical yield (decay corrected) in an overall synthesis time of 55-60 min.

Carbon Radioisotopes↗
PubMed1986

Sequence analysis and characterization of a maize gene encoding a high-sulfur zein protein of Mr 15,000.

We have isolated a gene coding for a sulfur-rich zein protein from a maize genomic library. The nucleotide sequence of this gene predicts a protein composed of 180 amino acids, including a 20-amino acid signal peptide. As is true of other zeins, there are no intervening sequences in the gene. Comparison of the nucleotide sequence of this gene with that of a homologous cDNA clone revealed only a single difference resulting in a valine/alanine substitution. The Mr 15,000 zein contains no repetitive nucleotide sequences and shows no homology with genes encoding the Mr 22,000 and 19,000 zeins. Circular dichroism analysis of the Mr 15,000 zein protein revealed that it is composed primarily of beta and turn structures. This gene has a short region of nucleotide sequence homology to the cysteine-rich domain of the Mr 27,000 zein, as well as the cysteine-containing barley B-hordein.

Amino Acid Sequence↗
PubMed1986

Effects of presbycusis and other types of hearing loss on auditory brainstem responses.

Auditory brainstem responses were studied in 373 healthy individuals of various ages and with sensorineural hearing loss of differing degrees. 209 subjects were elderly and had a hearing loss which included a component of presbycusis. The remainder were young or middle-aged with cochlear hearing loss. Altogether 606 ears were tested. The old individuals had generally longer ABR wave latencies than the young subjects. The I-V interpeak latency (IPL) was also prolonged in the older age groups compared with the group of younger individuals, except for subjects with pronounced hearing loss. The results of the study indicate that an age-related dysfunction of the auditory pathway in the brainstem can be present in presbycusis.

Adult↗
PubMed1985

Brain-stem auditory evoked potentials in different age groups.

Brain-stem auditory potential (BAEP) latencies were measured from individuals with normal or nearly normal hearing. Different age groups were studied separately. Males have 0.1-0.2 msec longer latencies of waves III and V and longer I-V IPLs than females in all age groups. The latencies of waves I, III and V increase 0.1-0.2 msec with increasing age, but the I-V IPL was the same in all age groups. The recognizability was very good for waves I, III and V and fairly good for waves II and IV. There was no interaural time difference.

Adolescent↗
PubMed1984

Auditory brain stem responses in patients with vertigo.

Sixty-two patients with vertigo were examined with ABR. Eight of the 30 patients with vestibular neuronitis had abnormal ABR indicating brain stem dysfunction. Most of the patients with abnormal ABR showed continued ABR abnormality after recovery from the disease. Only one patient with epidemic vertigo had abnormal ABR, the remaining 15 patients had no signs of brain stem involvement. All 16 patients with benign positional vertigo had normal ABR.

Acute Disease↗
PubMed1982

A structural model for maize zein proteins.

With the knowledge of the amino acid sequences of two maize zein proteins (apparent molecular weights of 19,000 and 22,000), a structural model is proposed for their molecular conformation. The circular dichroic spectrum taken in the 190-240 nm range for a zein protein mixture in methanol solution showed the zein secondary structure to be largely helical. The polar, hydrophobic, and turn characteristics of the zein residues, as well as the homologous repeat units in their primary sequences, suggested a structure with nine adjacent, topologically antiparallel helices clustered within a distorted cylinder. Polar residues distributed along the helical surfaces allowed intra- and intermolecular hydrogen bonding such that the zein molecules could be arranged in planes. The proposed glutamine-rich turns located between the helices and at the cylindrical caps would favor side chain interactions resulting in stacking of the molecular planes. Physical properties observed for the zein proteins are explained by the model.

Amino Acid Sequence↗
PubMed1982

Cloning and sequence analysis reveal structural variation among related zein genes in maize.

We have isolated a gene encoding one of the 19,000 dalton zein proteins from a maize genomic library constructed in Charon 4A. This gene occurs on a 7.7 kb Eco RI fragment, and based on Southern hybridization analysis, represents one of several homologous sequences present in the maize genome. The nucleotide sequence of the gene predicts a protein composed of 235 amino acids, including a signal peptide of 21 amino acids. There are no intervening sequences in the gene. By comparing the nucleotide sequence of this gene with that of a homologous cDNA clone, we have identified a basis for microheterogeneity within the gene family. The 5' nucleotide sequences of the genomic and cDNA clones are identical, but they differ in the center of the protein, where repeated amino acid sequences occur. A nucleotide sequence encoding a conserved peptide of 20 amino acids is repeated nine times in the center of both of these clones.

Base Sequence↗
PubMed1982

Method for studying microbial biofilms in flowing-water systems.

A method for the study of microbial biofilms in flowing-water systems was developed with special reference to the flow conditions in electrochemical concentration cells. Seawater was circulated in a semiclosed flow system through biofilm reactors (3 cm s) with microscope cover slips arranged in lamellar piles parallel with the flow. At fixed time intervals cover slips with their biofilm were removed from the pile, stained with crystal violet, and mounted on microscope slides. The absorbances of the slides were measured at 590 nm and plotted against time to give microbial biofilm development. From calibration experiments a staining time of 1 min and a rinse time of 10 min in a tap water flow (3 cm s) were considered sufficient. When an analysis of variance was performed on biofilm development data, 78% of the total variance was found to be due to random natural effects; the rest could be explained by experimental effects. The absorbance values correlated well with protein N, dry weight, and organic weight in two biofilm experiments, one with a biofilm with a high (75%) and one with a low ( approximately 25%, normal) inorganic content. Comparisons of regression lines revealed that the absorbance of the stained biofilms was an estimate closely related to biofilm dry weight.

Journal Article↗
PubMed1982

Factors regulating microbial biofilm development in a system with slowly flowing seawater.

Microbial biofilm development was followed under growth conditions similar to those of a projected salinity power plant. Microscope glass cover slips were piled in biofilm reactors to imitate the membrane stacks in such a plant. A staining technique closely correlating absorbance values with biofilm dry weight was used for the study. Generally, the biofilms consisted of solitary and filamentous bacteria which were evenly distributed with considerable amounts of various protozoa and entrapped debris of organic origin. Protozoa predation was shown to decrease the amount of biofilm produced. The biofilm development lag phase was longer at lower temperatures. The subsequent growth phase was approximately arithmetic until stationary phase appeared. Adaptation of a hyperbolic saturation function gave curves that agreed well with the logarithm of the amount of biofilm as a function of time. Increased flow velocity, temperature, and nutrient concentration increased the biofilm production rate. An exponential relationship was shown between biofilm production rate and flow velocity within the range of 0 to 15 cm s. Intervals in which the biofilms were exposed to fresh water decreased the biofilm production rate more than four times. If the cover slips were inoculated with untreated seawater for 24 h, subsequent UV treatment had an insignificant effect on the biofilm formation.

Journal Article↗