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K Kivirikko

Publications and source records attributed to K Kivirikko.

10 recordsLinked to original sources
PubMed1998

Substrate specificity of human prolyl-4-hydroxylase.

Proline analogs (3-F, 3-Cl, 3-Br, 3,3-cyclopropyl, 3,3-methylene, 3-Me, and 4-Me) were synthesized, incorporated into CbzGlyPheXGlyOEt, and tested as substrate analogues/mechanistic probes for the human prolyl-4-hydroxylase catalyzed hydroxylation reaction. With the exception of the 3-fluoroproline containing peptide, none of these peptides were substrates for the enzyme.

Humans↗
PubMed1998

Characterization of recombinant type II collagen: arthritogenicity and tolerogenicity in DBA/1 mice.

Recombinant human type II collagen (rhCII) was produced using both the HT1080 mammalian cell expression system (rhCIIht) and a baculovirus expression system (rhCIIbac). The biosynthesis of CII requires extensive post-translational modifications, such as the hydroxylation of prolyl and lysyl residues and glycosylation of hydroxylysyl residues. Amino acid analyses indicated that the rhCIIbac was adequately hydroxylated at prolyl residues but underhydroxylated at lysyl residues and underglycosylated compared with tissue-derived hCII, while rhCIIht was hyperhydroxylated and hyperglycosylated at lysyl residues. When the murine collagen-induced arthritis (CIA) model was used to investigate the immunological properties of the two forms of recombinant CII, each induced a high incidence of arthritis following immunization of susceptible mice when emulsified with complete Freund's adjuvant (CFA). However, the severity of the arthritis, as assessed by the number of affected limbs, was significantly higher in mice immunized with rhCIIht than in mice immunized with rhCIIbac. These data indicate that the degree of hydroxylysine glycosylation may play a role in the induction of the arthritogenic response to CII. Each of the recombinant collagens was comparable to tissue-derived hCII in their ability to induce tolerance and suppress arthritis when given as intravenous or oral tolerogens. Taken together, our data suggest that recombinant CII can be prepared in adequate amounts for therapeutic uses and that the material is immunologically comparable to tissue-derived hCII when used to induce tolerance.

Administration, Oral↗
PubMed1997

The order and transcriptional orientation of the human COL13A1 and P4HA genes on chromosome 10 long arm determined by high-resolution FISH.

The genes for type XIII collagen (COL13A1) and prolyl 4-hydroxylase (P4HA) were previously assigned to human chromosome 10q by radioactive in situ hybridization. Here we have applied fluorescence in situ hybridization combined with targets representing different levels of resolution to determine, first, the order of these genes along chromosome 10; second, their transcriptional orientation; and third, the distance between these genes. The order along the chromosome was determined to be centromere-COL13A1-P4HA-telomere using mechanically stretched chromosomes. By combining the data from stretched chromosomes and interphase nuclei, we found that the transcriptional orientation were tail to tail (COL13A1 3'-3' P4HA). The distance between these genes was measured by fiber FISH to be approximately 550 kb.

Centromere↗
PubMed1996

Multiple-unit responses to pitch changes in rabbits.

Multiple-unit activity (MUA) was recorded from the hippocampus (Hc), the visual cortex (VCx) and the cerebellar cortex (CerCx) in rabbits when pitch deviant tones were presented in a series of standard tones (oddball situation) and when standard tones were absent (deviant-alone situation). Significant MMN-like responses (deviant responses minus standard responses in the oddball situation) occurred in Hc, reflecting a MUA increase to the standards and its decrease to the deviants. In accordance with parallel ERPs reported earlier, the MMN-like responses reflected responses only to different presentation frequencies of stimuli. Non-selectivity in the pitch of such responses in VCx and a lack of an effect of the different stimulus repetition frequencies on responses in CerCx resulted in absent MMN-like responses in both of these locations.

Animals↗
PubMed1996

ERPs to pitch changes: a result of reduced responses to standard tones in rabbits.

Event-related potentials (ERPs) were recorded in rabbits when pitch deviant tones occurred in a series of standard tones (oddball situation). In control recordings, the deviant tones were presented without the standard tones (deviant-alone situation). In the oddball situation, significant difference ERPs (deviant ERPs-standard ERPs) could be found in the hippocampal and cerebellar recordings but not in the visual cortex. All the ERPs to the deviant stimuli observed in the oddball situation were also present in the deviant-alone situation. The difference ERPs were therefore based on reduced responses to the standards. The results are discussed in the context of a mismatch negativity (MMN) in humans.

Acoustic Stimulation↗
PubMed1995

Hippocampal event-related potentials to pitch deviances in an auditory oddball situation in the cat: experiment I.

Hippocampal event-related potentials (ERP) in the areas CA1, CA3, and dentate fascia (Df) were recorded in cats during an oddball situation when pitch deviant tones occurred in a series of standard tones. When difference waves were calculated by subtracting ERPs to the standard tones from those to the deviant tones, no clear N40d, corresponding to a cat analogue of the human mismatch negativity (MMN) observed in earlier studies, could be detected. Instead, a prominent later negativity (N130d) was observed. A possible extra-hippocampal source of the process reflected by the MMN-like negativity, and a relation between an orienting response (OR) and the N130d are discussed.

Acoustic Stimulation↗
PubMed1995

Behavioral and hippocampal evoked responses in an auditory oddball situation when an unconditioned stimulus is paired with deviant tones in the cat: experiment II.

Event-related potentials (ERP) in the areas CA1, CA3 and dentate fascia (Df) of the hippocampal formation were recorded during an oddball situation in the cat. A rewarding electrical stimulation of the lateral hypothalamus (US) was paired with deviant tones (2500 Hz) that occurred randomly in a series of the standard tones (2000 Hz) given to the left ear. In addition to developing orienting head movements to the side of the deviant tones, an increase in the amplitude of parallel hippocampal ERPs was observed. Both the behavioral and neural responses appeared not until a 50 ms latency range. Furthermore, time-amplitude characteristics of the ERPs corresponded to time-acceleration characteristics of the conditioned orienting head movements. The results are discussed in the context of a cat analogue of the human mismatch negativity (MMN) and a role of the hippocampal formation to model and predict the conditioned behavioral orienting responses.

Acoustic Stimulation↗