Biomedical subjects

C R Parks

Publications and source records attributed to C R Parks.

At least 19 recordsLinked to original sources

PubMed2000

Glutamatergic drugs exacerbate symptomatic behavior in a transgenic model of comorbid Tourette's syndrome and obsessive-compulsive disorder.

We previously created a transgenic mouse model of comorbid Tourette's syndrome and obsessive-compulsive disorder (TS+OCD), by expressing a neuropotentiating cholera toxin (CT) transgene in a subset of dopamine D1 receptor-expressing (D1+) neurons thought to induce cortical and amygdalar glutamate output. To test glutamate's role in the TS+OCD-like disorder of these transgenic mice (D1CT-7 line), the effects of glutamate receptor-binding drugs on their behavior were examined. MK-801, a non-competitive NMDA receptor antagonist that indirectly stimulates cortical-limbic glutamate output, aggravated a transgene-dependent abnormal behavior (repetitive climbing and leaping) in the D1CT-7 mice at doses insufficient to induce stereotypies, and more readily induced stereotypies and limbic seizure behaviors at high doses. NBQX, a seizure-inhibiting AMPA receptor antagonist, reduced only the MK-801-dependent stereotypic and limbic seizure behavior of D1CT-7 mice, but not their transgene-dependent behaviors. These data imply that TS+OCD-like behavior is mediated by cortical-limbic glutamate, but that AMPA glutamate receptors are not an essential part of this behavioral circuit. Our findings lead to the prediction that the symptoms of human Tourette's syndrome and obsessive-compulsive disorder are elicited by excessive forebrain glutamate output.

Animals↗

PubMed2000

Phylogeny and biogeography of Juglans (Juglandaceae) based on matK and ITS sequence data.

We investigated phylogenetic and biogeographic relationships within Juglans (walnuts), a Tertiary disjunct genus, using 15 species of Juglans and related (Juglandaceae) outgroups. The relationships were analyzed using nucleotide sequences of the chloroplast gene matK and its flanking spacers and of the internal transcribed spacers (ITS) and 5.8S gene of the nuclear ribosomal DNA. The DNA sequences provided 246 informative characters for parsimony analysis. ITS data supported as monophyletic groups the four generic sections, Cardiocaryon, Dioscaryon, Rhysocaryon, and Trachycaryon. Within Rhysocaryon, the temperate black walnuts and the tropical black walnuts were supported as monophyletic groups. When the two data sets were combined, J. cinerea was nested within Cardiocaryon. Combined analysis with published nuclear DNA restriction site data placed J. cinerea in a monophyletic group with Cardiocaryon. These analyses consistently supported Juglans as a monophyletic group and as the sister group to the genus Pterocarya. The results of this work are consistent with the known geological history of Juglans. The fossil record suggests that the butternuts had evolved by the early Oligocene in North America. The presence of butternuts in Eurasia could be the result of migration from North America to Eurasia during the warming trend of the mid Oligocene.

Journal Article↗

PubMed1984

Distorted segregation and linkage of alcohol dehydrogenase genes in Camellia japonica L. (Theaceae).

Alcohol dehydrogenase isozymes in Camellia japonica are encoded by two genes, Adh-1 and Adh-2. Both loci are expressed in seeds, and their products randomly associate into intragenic and intergenic dimers. Electrophoresis of leaf extracts reveals only the products of Adh-2. Formal genetic analysis indicated that the two Adh loci are tightly linked (combined estimate of r = 0.004). Most segregations fit expected Mendelian ratios, but in some families distorted segregation was observed at Adh-1, Adh-2, or both loci. The deficient progeny class varied across families, and in two apparent back-crosses three rather than two phenotypic classes were recovered. The mechanism underlying these distortions is not known, but evidence is presented that suggests that the phenomenon is genic or segmental in nature. Plausible hypotheses include linkage of the Adh structural genes with a gametophytic self-incompatibility locus, translocation heterozygosity involving the segment bearing Adh-1 and Adh-2, or a combination of these two mechanisms.

Alcohol Dehydrogenase↗

PubMed1979

Use of an inclined footrest for panoramic dental radiography.

An inclined footrest was evaluated as a positioning aid for dental panoramic radiography. Experimental and control groups of students were examined by a conventional panoramic technique, with and without the addition of an inclined footrest. All radiographs obtained were evaluated for six parameters in a single-blind fashion by three dentists. Results indicated that the inclined footrest reduced spinal-shadow artifacts and improved over-all image quality.

Adult↗

PubMed1978

Xeroradiography of dental structures. II. Image analysis.

Xeroradiography provides an attractive, convenient, low-radiation-dose alternative to conventional intraoral film radiography. In this study the image properties of the two techniques were compared quantitatively and qualitatively. Over all, image quality was very similar, but xeroradiography delivered radiation doses seven to fourteen times less than conventional film radiography.

Models, Anatomic↗

PubMed1978

Use of intraoral cassettes for dental xeroradiography.

Before clinical trials of intraoral xeroradiography are begun, we felt the need to evaluate the clinical acceptability of the thicker, more rigid xerographic cassettes. We stimulated these cassettes by fastening rigid acrylic plates of appropriate thickness to conventional film packets and then conducted parallel evaluations of simulated cassettes and conventional film packets, using thirty volunteer patients. We found no difference in anatomic placement, operator acceptance, and patient acceptance between the "cassettes" and film packets. The increased thickness and rigidity of intraoral xerographic cassettes should not prove disadvantageous to in vivo intraoral xeroradiography.

Adolescent↗

PubMed1977

Ventilatory response in the fetal lamb following peripheral chemodenervation.

Carotid infusions of sodium cyanide solution and perfusions of hypoxemic or hypercapnic fetal blood were done before and after peripheral chemoreceptor denervation. Step changes in PaO2 ranged from -11 to -22 Torr; step changes in PaCO2 ranged from +17 to +42 Torr. The cyanide dose was 0.2 mg/kg per loop system. Control perfusions consisted of 25 ml of fetal blood without changes in pH and blood gases. A ventilatory response occurred in the majority of all experimental perfusions regardless of innervation status of the peripheral chemoreceptors. No response occurred with control perfusions. There was a marked variability in the time of onset of ventilatory activity with a delay of greater than 10 s occurring following most perfusions. These studies demonstrate that the fetus has an attenuated ventilatory response to chemical stimuli and that hypoxia stimulates ventilation in the absence of peripheral chemoreceptors.

Animals↗

PubMed1974