RESUMEN
Objective: To investigate the presence of exacerbating factors of persistent perceptual-postural dizziness (PPPD) in patients with vestibular symptoms during the early period after vestibular symptoms onset, and to examine possible predictive factors for developing PPPD later. Methods: One hundred and fifty-five consecutive patients with vestibular symptoms who presented less than 90 days from the onset were included in this study. They filled out the Niigata PPPD Questionnaire (NPQ) that consists of 12 questions on the exacerbating factors of PPPD. The NPQ scores of patients who developed PPPD were compared with those of patients who did not develop PPPD during the follow-up. Results: Seventy-eight of the155 patients (50.3%) showed positive NPQ scores (≥27 points). High NPQ scores were found in patients diagnosed with psychogenic dizziness and vestibular neuritis. During the follow up for an average of 543.3 days after the initial presentation, eight patients (10.3%) developed PPPD. Seven of these eight patients (87.6%) showed positive NPQ scores and all of them had all three exacerbating factors of PPPD at their initial presentation. The NPQ scores of the patients who developed PPPD (40.6 ± 11.6) were significantly higher than those of the patients who did not develop PPPD (26.4 ± 18.3; p <.05). Conclusion: Approximately a half of the patients with vestibular symptoms had exacerbating factors of PPPD in the early stages of the disease. Patients who develop PPPD are likely to have its exacerbating factors in the initial stages after presentation. Level of Evidence: 3.
RESUMEN
We have cloned four cDNAs encoding astacin-like squid metalloproteases (ALSMs)-I and -II from the Japanese common squid and ALSMs-I and -III from the spear squid. Analysis of the deduced amino acid sequences revealed that ALSMs possess a signal peptide and a pro-sequence followed by an astacin-like catalytic domain and an MAM (meprin, A5 protein, receptor protein-tyrosine phosphatase mu) domain. Phylogenetic analysis revealed that ALSM corresponds to a new cluster of astacins. To analyze the function of the MAM domain, wild-type ALSM and an MAM-truncated mutant were expressed in a baculovirus expression system. The expressed protein encoding full-length ALSM hydrolyzed myosin heavy chain as effectively as native ALSM, whereas the MAM-truncated mutant possessed no protease activity, suggesting that the MAM domain contributes to substrate recognition. ALSM has been isolated from squid liver and mantle muscle. However, analysis with a specific antibody generated against ALSM indicated the presence of ALSM in a wide variety of tissues. ALSM was located in the extracellular matrix of mantle muscle cells. Thus, ALSM is a secreted protease, as are other members of the astacin family. The extracellular localization raises the possibility of substrates other than myosin. The physiological role of ALSM remains unknown, at this time.