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C Fermin

Publications and source records attributed to C Fermin.

8 recordsLinked to original sources
PubMed1996

Shape deformation of the organ of Corti associated with length changes of outer hair cell.

Cochlear outer hair cells (OHC) are commonly assumed to function as mechanical effectors as well as sensory receptors in the organ of Corti (OC) of the inner ear. OHC in vitro and in organ explants exhibit mechanical responses to electrical, chemical or mechanical stimulation which may represent an aspect of their effector process that is expected in vivo. A detailed description, however, of an OHC effector operation in situ is still missing. Specifically, little is known as to how OHC movements influence the geometry of the OC in situ. Previous work has demonstrated that the motility of isolated OHCs in response to electrical stimulation and to K(+)-gluconate is probably under voltage control and causes depolarisation (shortening) and hyperpolarization (elongation). This work was undertaken to investigate if the movements that were observed in isolated OHC, and which are induced by ionic stimulation, could change the geometry of the OC. A synchronized depolarization of OHC was induced in guinea pig cochleae by exposing the entire OC to artificial endolymph (K+). Subsequent morphometry of mid-modiolar sections from these cochleae revealed that the distance between the basilar membrane (BM) and the reticular lamina (RL) had decreased considerably. Furthermore, in the three upper turns OHC had significantly shortened in all rows. The results suggest that OHC can change their length in the organ of Corti (OC) thus deforming the geometry of the OC. The experiments reveal a tonic force generation within the OC that may change the position of RL and/or BM, contribute to damping, modulate the BM-RL-distance and control the operating points of RL and sensory hair bundles. Thus, the results suggest active self-adjustments of cochlear mechanics by slow OHC length changes. Such mechanical adjustments have recently been postulated to correspond to timing elements of animal communication, speech or music.

Animals↗
PubMed1995

Interleukin-3 or erythropoietin induced nuclear localization of protein kinase C beta isoforms in hematopoietic target cells.

Protein kinase C (PKC) has been implicated in the signal transduction pathways for the biological effect of both interleukin-3 (IL-3) and erythropoietin (EPO) in hematopoietic target cells. The goal of this study was to identify specific classical isoforms of PKC and their localization in hematopoietic cells in response to the growth factors, IL-3 or EPO. In addition to murine fetal liver cells as a source of normal erythroid progenitor cells, we have utilized the B6SUt.EP cell line, a non-transformed hematopoietic cell line that requires IL-3 for proliferation, but for which EPO can substitute as a growth factor. With polyclonal antibodies prepared against peptide sequences specific for the alpha, beta I, beta II and gamma isoforms of PKC, we have identified beta I and beta II as the predominant nuclear isoforms in target cells that proliferate in response to IL-3 or EPO.

Animals↗
PubMed1995

Dormant microbes in interstitial cystitis.

Interstitial cystitis (IC) is an inflammatory disease of the urinary bladder that has no known etiology. A microbial association with this disease has not been supported since routine cultures of urine from IC patients are usually negative. However, we have demonstrated the presence of bacterial 16S rRNA genes in bladder biopsies from 29% of patients with IC, but not from control patients with other urological diseases. The ability to identify the presence of bacterial DNA in these patients was accomplished using a sensitive and specific nested PCR method capable of amplifying 16S rRNA genes from a wide variety of bacterial genera. Cloning and sequencing of 16S rRNA gene fragments amplified from bladder tissue of IC patients showed that these genes were derived from genera representing Gram-negative bacteria. In addition to the molecular data, a novel finding of 0.22 micron. filterable forms has been isolated in culture from the biopsy tissue of 14 of 14 IC patients and from 1 of 15 controls. The forms contain nucleic acids and resemble cell wall-deficient bacteria in gross morphology; however, their swirled myelin-like ultrastructure is unusual and suggests a heretofore unclassified microbe. These results demonstrate for the first time an association of Gram-negative bacterial DNA and filterable forms with affected bladder tissue from patients with IC.

Bacteria↗
PubMed1994

Transitory endolymph leakage induced hearing loss and tinnitus: depolarization, biphasic shortening and loss of electromotility of outer hair cells.

There are types of deafness and tinnitus in which ruptures or massive changes in the ionic permeability of the membranes lining the endolymphatic space [e.g., of the reticular lamina (RL)] are believed to allow potassium-rich endolymph to deluge the low [K+] perilymphatic fluid (e.g., in the small spaces of Nuel). This would result in a K+ intoxication of sensory and neural structures. Acute attacks of Ménière's disease have been suggested to be an important example for this event. The present study investigated the effects of transiently elevated [K+] due to the addition of artificial endolymph to the basolateral cell surface of outer hair cells (OHC) in replicating endolymph-induced K+ intoxication of the perilymph in the small spaces of Nuel. The influence of K+ intoxication of the basolateral OHC cell surface on the transduction was then examined. Intoxication resulted in an inhibition of the physiological repolarizing K+ efflux from hair cells. This induced unwanted depolarizations of the hair cells, interfering with mechanoelectrical transduction. A pathological longitudinal OHC shortening was also found, with subsequent compression of the organ of Corti possibly influencing the micromechanics of the mechanically active OHC. Both micromechanical and electrophysiological alterations are proposed to contribute to endolymph leakage induced attacks of deafness and possibly also to tinnitus. Moreover, repeated or long-lasting K+ intoxications of OHC resulted in a chronic and complete loss of OHC motility. This is suggested to be a pathophysiological basis in some patients with chronic hearing loss resulting from Ménière's syndrome.

Action Potentials↗
PubMed1993

Effects of microgravity on vestibular ontogeny: direct physiological and anatomical measurements following space flight (STS-29).

Does space flight change gravity receptor development? The present study measured vestibular form and function in birds flown as embryos for 5 days in earth orbit (STS-29). No major changes in vestibular gross morphology were found. Vestibular response mean amplitudes and latencies were unaffected by space flight. However, the results of measuring vestibular thresholds were mixed and abnormal responses in 3 of the 8 flight animals raise important questions.

Action Potentials↗
PubMed1990

Enhanced expression of the beta II subspecies of protein kinase C in differentiating erythroleukemia cells.

Polyclonal antipeptide antibodies which recognize selected isozymes (alpha, beta I, beta II, and gamma) of the protein kinase C family were used to identify specific subspecies in undifferentiated Friend erythroleukemia cells and in cells triggered to differentiate with hexamethylene bisacetamide. The beta II isozyme of protein kinase C was the primary isozyme expressed and its abundance was significantly increased (P less than 0.05) in differentiated cells. Differences in immunostaining between control and experimental groups were objectively quantitated by determining percentage transmission of light through cells based on color threshold rather than gray intensity levels. Staining was localized to the cytoplasm predominantly in differentiated cells, whereas nuclei stained more intensely in undifferentiated cells. These results provide immunocytochemical evidence to support the hypothesis that changes in the expression of the beta II subspecies of protein kinase C are essential to the programmed maturation of differentiating Friend erythroleukemia cells.

Animals↗