Biomedical subjects

C L Franklin

Publications and source records attributed to C L Franklin.

59 records · Page 4Linked to original sources

PubMed1993

In vitro model of adhesion and invasion by Bacillus piliformis.

An in vitro model of Bacillus piliformis infection was developed to investigate the mechanisms of adhesion and internalization of this obligate intracellular bacterium. Adhesion and internalization events were examined by electron microscopic evaluation of infected Caco-2 cell monolayers. A few bacteria were identified in apical surface invaginations and in vacuoles subjacent to the apical surface, whereas the majority of bacteria were observed free within the cytoplasm, suggesting that B. piliformis entered epithelial cells via a phagocytic process and rapidly escaped the phagosome. To confirm that host cell phagocytosis was involved in entry of B. piliformis into mammalian cells, Intestine 407 cells were treated with the phagocytic inhibitor cytochalasin D, infected with B. piliformis, and evaluated for bacterial internalization by double-fluorescence labeling. The results showed decreased intracellular bacteria, suggesting that internalization was dependent on host cell microfilament function. To examine the role of B. piliformis in internalization, growth of live and Formalin-killed bacteria was compared. Dead bacteria were not internalized, suggesting that B. piliformis actively participates in internalization. B. piliformis appears to enter host cells by a bacterially directed phagocytic process. The in vitro system described should prove invaluable in further investigations of B. piliformis pathogenic mechanisms.

Actin Cytoskeleton↗

PubMed1991

Treatment of Trichophyton mentagrophytes infection in rabbits.

Copper sulfate and a metastabilized chlorous acid/chlorine dioxide (MECA) compound were evaluated for efficacy in treating Trichophyton mentagrophytes infection in rabbits. Forty rabbits naturally infected with T mentagrophytes were allotted to 5 treatment groups: nontreated control, sham dip, 1% copper sulfate dip, MECA dip, and MECA spray. Results of lesion culture, regression of gross lesions, and histopathologic findings were documented. Copper sulfate and MECA were effective in treating clinical dermatophytosis and in decreasing T mentagrophytes carrier status in rabbits.

Administration, Topical↗

PubMed1991

Developmental expression of excitatory amino acid responses in cerebellar Purkinje neurons in culture.

We have examined the developmental expression of excitatory amino acid responses in cerebellar Purkinje neurons using a culture model system, extracellular recording techniques and micropressure application of agonists. In mature cultured Purkinje neurons, glutamate (Glu) and the selective receptor agonists quisqualate (Quis) and kainate (KA) elicited multiphasic responses with both excitatory and inhibitory phases. N-methyl-D-aspartate was ineffective. The agonist responses were characterized by an initial excitatory period, a period of burst activity and an inhibitory period. Glu, Quis and KA differed in the ability to evoke the 3 response components. Quis was the most potent agonist and the most effective in producing burst activity and an inhibitory period. Immature Purkinje neurons without visible dendritic structure also exhibit prolonged multiphasic responses when tested with the 3 agonists. However, response components were generally less robust than in mature neurons. Developmental changes in response properties were observed for all agonists, but the developmental changes in total response duration and the duration of the inhibitory period observed for the Quis response were not observed for the Glu or KA responses. These data can be explained by the presence of multiple excitatory amino acid receptor subtypes in both mature and immature Purkinje neurons.

Amino Acids↗

PubMed1987

Acute ethanol alters the firing pattern and glutamate response of cerebellar Purkinje neurons in culture.

Modified explant cultures derived from the cortical region of fetal rat cerebellum, and extracellular recording techniques were used to examine the sensitivity and response of cerebellar neurons, isolated from extracerebellar afferent input, to acute ethanol (EtOH) exposure. Recordings were made from Purkinje neurons (PNs) and granule cells maintained in culture for several weeks, with the emphasis on the PN. Both the PNs and granule cells exhibited spontaneous activity in culture, but, unlike the PNs, not all of the granule cells were spontaneously active. The majority of PNs studied exhibited a high frequency, regular simple spike firing pattern, previously shown to be endogenously generated by voltage-sensitive mechanisms intrinsic to the PN. The granule cells exhibited slow, irregular patterns of activity. EtOH at doses as low as 22 mM (100 mg%), a concentration that reflects blood levels during EtOH intoxication, altered the spontaneous activity of both neuronal types, demonstrating that EtOH has direct actions on cerebellar neurons. In the PNs, acute EtOH (20-80 mM) produced an increase in the regularity of the spontaneous activity and either a transient increase or no change in firing rate. Acute EtOH also significantly altered the response of PNs to the excitatory transmitter glutamate. In the granule cells, acute EtOH altered firing pattern with small and variable effects on firing rate. These data demonstrate that there are multiple sites of EtOH action in the cerebellum and that changes in PN activity with acute EtOH exposure may occur via direct actions on the PN and indirect actions via synaptically connected cerebellar neurons. The demonstration of EtOH-sensitive sites intrinsic to the cerebellum suggests that EtOH actions at these sites contribute to alterations in PN activity that occur in vivo after acute EtOH exposure.

Action Potentials↗

PubMed1987

Morphological and physiological differentiation of Purkinje neurons in cultures of rat cerebellum.

During ontogeny, vertebrate CNS neurons differentiate from relatively simple stem cells to complex units that express unique morphological and electrophysiological characteristics. We have examined several aspects of this developmental process in an identified CNS neuronal type, the Purkinje neuron (PN) of the cerebellum. Our approach has included the use of a tissue culture preparation and immunohistochemical and electrophysiological techniques. Using immunohistochemical techniques, we have identified immature PNs in culture and examined their morphological and synaptic development. These studies have shown that PNs undergo extensive morphological and synaptic development in culture, the morphological characteristics of the immature PNs in culture and the developmental sequence and time course are reflective of that described for PNs in vivo, synapse formation is initiated at an early stage of PN development in culture and proceeds concurrently with the morphological development, and the main period of synapse formation is associated with the main period of dendritic development, reflecting the preferential location of synaptic sites at the dendritic region of mature PN. Using electrophysiological techniques, we have examined the physiological development of PNs in culture and have correlated the stages in physiological, morphological, and synaptic development. Results from these studies show the following. Mature PNs in culture exhibit complex electrophysiological properties, including the ability to generate 2 types of spike events, simple and complex spikes, and endogenously generated activity. Expression of electrophysiological properties begins at an early stage in PN development, when the PNs consist of little more than a soma with a few fine perisomatic processes. The earliest physiological characteristics to be expressed by the PN include sensitivity to transmitters, the ability to respond to synaptic input, and the ability to generate simple spikes. Synaptic input produces spontaneous activity in young PNs, but the patterns of activity change during development as mechanisms underlying endogenously generated activity and complex spike generation are expressed, and synapse formation proceeds.(ABSTRACT TRUNCATED AT 400 WORDS)

4-Aminopyridine↗