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Biomedical subjects

R Chase

Publications and source records attributed to R Chase.

At least 55 records · Page 3Linked to original sources
PubMed1986

In vitro activity of ketoconazole against herpes simplex virus.

The effects of ketoconazole alone and in combination with acyclovir and adenine arabinoside upon the replication of herpes simplex virus types 1 and 2 (HSV-1 and -2) were investigated by using a yield reduction assay. Ketoconazole demonstrated antiviral activity against HSV-1 and -2 and synergistic antiviral activity when it was combined with acyclovir. Combinations of ketoconazole with adenine arabinoside resulted in either interference or indifference. The effects of ketoconazole upon the protein synthesis of HSV-2-infected cells were also determined in an effort to define the mechanism of action for the antiviral activity of ketoconazole. There was no reduction of HSV proteins when compared with acyclovir. These findings suggest that further investigations of the use of ketoconazole for the treatment of HSV infections are warranted.

Acyclovir↗
PubMed1985

Quantification of ultrastructural symmetry at molluscan chemical synapses.

Two criteria were developed to identify symmetrical synapses in the tentacle ganglion of the snail Achatina fulica. First, the concentration of electron lucent vesicles within 20 nm of one membrane had to be less than three times the concentration at the opposed membrane. Second, paramembranous densities had to be present in both cells, as unanimously judged by three independent observers. Nine synapses (27% of sample) satisfied both criteria. It is suggested that these synapses transmit chemically in two directions.

Animals↗
PubMed1985

Developmental changes in the passive membrane properties of an identified molluscan neuron.

We have studied developmentally the electrotonic fate of synaptic potentials in an identified giant neuron of the Pulmonate mollusc Achatina fulica. Our experimental preparation enabled us to sample spontaneously occurring excitatory postsynaptic potentials (EPSPs) from embryogenesis onward, while concomitantly analyzing the postsynaptic membrane properties. We observe non-monotonic changes in the electrotonic attenuation of synaptic inputs which invade the somata. Our data suggest that non-monotonic changes in the specific membrane resistance can account for these observations.

Animals↗
PubMed1985

Responses to odors mapped in snail tentacle and brain by [14C]-2-deoxyglucose autoradiography.

The method of 2-deoxyglucose (2-DG) autoradiography has been widely used to map functional neuronal systems in vertebrates, but in invertebrate species, where morphological dimensions favor its use, the applications have been minimal. This study uses [14C]-2-DG to map the olfactory system of a terrestrial snail, Achatina fulica. The olfactory organ in the snail's tentacles bears a striking resemblance to the vertebrate olfactory mucosa. There are also complex neural structures in the tentacle and brain that are devoted to subsequent processing. These facts make the molluscan olfactory system a suitable complement to the traditional vertebrate and insect models in olfaction. The experiments utilized intact snails in which one tentacle was exposed to a controlled odor environment while the contralateral tentacle was held in a retracted position. The dose of [14C]-2-DG (2 microCi/gm) was injected into the hemocele. Tissue processing involved freeze-substitution with acetone, dry sectioning, and the preparation of liquid film autoradiographs. Optical density measurements permitted quantitative comparisons between experimental conditions. The natural odors of conspecific snails and of carrots elicited significantly more uptake of 2-DG in the exposed tentacle than in the unexposed tentacle and, in the exposed tentacle, significantly more label over the axons of the primary sensory neurons than was elicited by exposure to clean air. Amyl acetate and octanol were less effective. A small number of superficially placed sensory neurons were labeled in all stimulus conditions, including clean air, and may represent the mechanosensors. Stimulus-dependent labeling in the brain was limited to the procerebrum and included both neuropilar and cellular parts. In contrast to vertebrate and insect olfactory systems, there was no evidence of spatial coding for odor quality.

1-Octanol↗
PubMed1984

Cerebrospinal fluid glucose and leukocyte responses in experimental meningitis.

The fall in cerebrospinal fluid (CSF) glucose and CSF leukocyte response was studied in cats with experimental meningitis. Klebsiella pneumoniae or Streptococcus pneumoniae were injected intracisternally, and the latter organisms were incubated with CSF in vitro. When 10(6)-10(9)K. pneumoniae were incubated with 4 ml of CSF, the time time necessary for the glucose to decrease to less than 10 mg/dl ranged from 6.5 to 2.5 h, at a rate proportional to the size of the inoculum. When the same numbers of bacteria were injected intracisternally, the time ranged from 9 to 3 h, and the CSF leukocyte response did not exceed 1200 WBC/mm3. At this time, only minimal histological changes in brain and choroid plexus were seen. Twenty hours after intrathecal K. pneumoniae, large numbers of leukocytes (up to 4 X 10(4)/mm3) were recovered from the CSF. Regardless of the number of leukocytes, however, hypoglycorrhachia occurred when the CSF contained more than 10(7) bacteria/ml. At this interval, large numbers of leukocytes were seen invading the stroma of the choroid plexus, leptomeninges and perivascular spaces. When 10(8) S. pneumoniae were injected intracisternally, CSF glucose concentration decreased as rapidly as with K. pneumoniae. The spinal fluid leukocyte response to S. pneumoniae was, however, greater than that to K. pneumoniae. These results suggest that under the conditions of these studies, hypoglycorrhachia of bacterial meningitis is the result of metabolism of the bacteria with little contribution from the leukocytes.

Animals↗
PubMed1983

Ontogenesis and characteristics of epidermal growth factor receptors in human placenta.

Epidermal growth factor promotes growth in many cell types. The role of epidermal growth factor during gestation and fetal development is unknown. This study investigates the presence and binding characteristics of epidermal growth factor receptors in placentas throughout gestation. Cell membrane preparations were obtained from first-, second-, and third-trimester placentas and hydatidiform moles. Specific epidermal growth factor receptors were observed as early as 6 weeks of gestation. Throughout gestation, Scatchard analysis of epidermal growth factor binding was curvilinear, and dissociation studies were consistent with site-to-site interaction with negative cooperativity. Affinity constants at high (Ke = 9.9 +/- 0.79 X 10(9) L/mol) and low (Kf = 3.0 +/- 0.25 X 10(9) L/mol) receptor occupancy were unchanged throughout normal gestation. However, the number of receptors per milligram of protein significantly increased with advancing normal gestation (correlation coefficient, r = 0.81). In hydatidiform moles, the number of receptors was reduced when compared to that of normal tissue of similar gestational age. Our study provides a quantitative basis for further evaluation of epidermal growth factor as a possible factor in embryogenesis and fetal development.

Cell Membrane↗
PubMed1983

Neuronal elements in snail tentacles as revealed by horseradish peroxidase backfilling.

The snail tentacle ganglion is a prominent structure that innervates an epithelial pad sensitive to wind and odors. Its neural composition, and that of the sensory pad, was studied in the terrestrial snail Achatina fulica by applying horseradish peroxidase to the distal end of the cut tentactle nerve. Five types of neurons were labelled by the procedure: receptors, located in the subepithelial region; three kinds of interneurons, located in the ganglion and its digitlike extensions; and a bipolar neuron, located in the dermo-muscular wall of the tentacle. In contrast to earlier descriptions based on silver stains, the present results demonstrate the presence of neurons of large size (soma diameters up to 46 microns). Also, contrary to earlier interpretations, the results indicate that all five identified cell types send axons directly to the CNS.

Animals↗
PubMed1983

Morphology and odor sensitivity of regenerated snail tentacles.

This study examined certain structural and functional aspects of the olfactory system in regenerated posterior tentacles of the terrestrial snail Achatina fulica. Regeneration of the epithelial sensory pad occurs with accurate size regulation. All five neuronal cell types which are normally revealed by horseradish peroxidase backfilling are also regenerated. The sensory cells attain normal numbers at about 20 weeks postlesion. The organization of neuronal elements within the tentacle is chaotic, however, at early stages of regeneration. Even later, the digitlike extensions of the ganglion, which are characteristic of intact tentacles, fail to appear. The recovery of odor sensitivity was evaluated using a tentacular olfactormeter and a behavioral assay that involved locomotor orientation towards the odor stimulus. Thresholds and concentration-dependent response rates were equivalent for regenerated and intact tentacles, tested in the same animals, at 10 weeks post-lesion.

Animals↗
PubMed1982

Identification of Epstein-Barr virus strain differences with monoclonal antibody to a membrane glycoprotein.

Two monoclonal antibodies directed against Epstein--Barr virus (EBV)-induced membrane antigens (MA) were isolated in this study. On of the monoclonal antibodies, designated 2F5.6, was an IgG2 which, as detected by membrane and fixed cell immunofluorescence, reacted with MA-positive lymphoblastoid cell lines that produced transforming EBV but not with the MA-positive P3HR-1 cell line that produced the lytic, nontransforming strain of this virus. This antibody precipitated the Mr 320,000/350,000 glycoprotein from B-95 virus infected cultures and the Mr 300,000 and 220,000/250,000 glycoproteins from Raji cells superinfected with P3HR-1 virus but did not precipitate any of these EBV-specific glycoproteins from the P3HR-1 cell line. In contrast, the second monoclonal antibody, IgM designated B10.3, reacted with all virus-producing cell lines including the P3HR-1 cell line. The identity of the glycoprotein that serves as the target for this antibody is still unknown. Neither antibody had neutralizing activity against the B-95 or P3HR-1 strain of EBV. These results indicated that the 2F5.6 monoclonal antibody was directed against an antigenic determinant on the major membrane glycoprotein which is common to transforming strains of EBV but absent from the lytic P3HR-1 stain whereas the B10.3 monoclonal antibody was directed against a group-specific EBV-induced membrane determinant.

Antibodies, Monoclonal↗
PubMed1982

Purification and biologic characterization of a major Epstein Barr virus-induced membrane glycoprotein.

The Epstein Barr virus membrane antigen (MA) complex is composed of three major high m.w. glycoproteins designated gp 300/350, gp 200/250, and gp 85/90. In the experiments reported in this paper, the gp 300/350 glycoprotein was purified from MA-positive extracts prepared from the B-95-8 cell line. This was accomplished by tandem combination of ion-exchange and lectin chromatography. It was routinely possible to purify this glycoprotein 400- 600-fold by this procedure. Sera from animals immunized with gp 300/350 purified by this approach neutralized EBV infectivity and mediated antibody-dependent cellular cytotoxicity (ADCC) demonstrating that both of these important antigenic determinants were expressed on this glycoprotein. The presence of an ADCC determinant on this molecule was further substantiated by the finding that monoclonal antibody to gp 300/350 blocked ADCC mediated by a human ADCC antibody-positive reference serum.

Animals↗
PubMed1977

Homologous neurosecretory cell groups in the land snail Achatina fulica and the sea slug Aplysia californica.

The right parietal ganglion of the African snail Achatina fulica contains an identifiable cluster of 20-40 white cells with somatic diameters of 80-110 mu. Cobalt chloride injection into these cells revealed an axon projection in the right parietal nerve as well as apparent terminations in the capsule. The cells contain an abundance of electron dense granules 1000-2000 A in diameter which are formed in the Golgi apparatus. The granules stain with Gomori's chrome hematoxylin and paraldehyde fuchsin methods. While most cluster cells showed no "spontaneous" electrical activity, there was a correlation for the active cells between rate of activity and intensity of cell whiteness. These and other data suggest that the cluster cells are neurosecretory. A claim of homology with the "rostral white cells", R3-R13, in the parieto-visceral ganglion of Aplysia is based on a similarity of morphological and electrophysiological features, together with analogous locations in the respective ganglia. It is concluded that the right parietal ganglion of Achatina is homologous with the right half of the parieto-visceral ganglion of Aplysia.

Action Potentials↗