PubMed Health⌕ Search

Biomedical subjects

R L Carroll

Publications and source records attributed to R L Carroll.

10 recordsLinked to original sources
PubMed1999

Homology among divergent Paleozoic tetrapod clades.

A stringent definition of homology is necessary to establish phylogenetic relationships among Paleozoic amphibians. Many derived characters exhibited by divergent clades of Carboniferous lepospondyls resemble those achieved convergently among Cenozoic squamates that have elongate bodies and reduced limbs, and by lineages of modern amphibians that have undergone miniaturization. Incongruent character distribution, poorly resolved cladograms and functionally improbable character transformations determined by phylogenetic analysis suggest that convergence was also common among Paleozoic amphibians with a skull length under 3 cm, including lepospondyls, early amniotes and the putative ancestors of modern amphibians. For this reason, it is injudicious to equate apparent synapomorphy (perceived common presence of a particular derived character in two putative sister-taxa) with strict homology of phylogenetic origin. Identification of homology by the similarity of structure, anatomical position and pattern of development is insufficient to establish the synapomorphy of bone and limb loss or precocial ossification of vertebral centra, which are common among small Paleozoic amphibians. The only way in which synapomorphies can be established definitively is through the discovery and recognition of the trait in question in basal members of each of the clades under study, and in their immediate common ancestors.

Amphibians↗
PubMed1996

Photodynamic therapy (PDT) and photodiagnosis (PD) using endogenous photosensitization induced by 5-aminolevulinic acid (ALA): current clinical and development status.

Exogenous provision of 5-aminolevulinic acid (ALA) to many tissues results in the accumulation of sufficient quantities of the endogenous photosensitizer protoporphyrin IX (PpIX) via the heme biosynthetic pathway, to produce a photodynamic effect when exposed to activating light. Therefore, ALA may be considered the only current photodynamic therapy (PDT) agent in clinical development that is a biochemical precursor of a photosensitizer. Topical ALA application, followed by exposure to activating light (ALA PDT), has been reported effective for the treatment of a variety of dermatologic diseases including cutaneous superficial and nodular basal cell carcinoma, Bowen's disease, actinic (solar) keratoses, and T cell lymphoma. Local internal application of ALA has also been used for selective endometrial ablation in animal model systems and, in human clinical studies, it has shown selective formation of PpIX within the endometrium. PpIX induced by ALA application has also been used as a fluorescence detection marker for photodiagnosis (PD) of cancer and dysplastic conditions of the urinary bladder and other organs. Systemic, oral administration of ALA has been used for ALA PDT of superficial head and neck cancer, various gastrointestinal cancers, and the condition known as Barrett's esophagus. This paper reviews the current clinical and development status of ALA PDT and PD.

Aminolevulinic Acid↗
PubMed1980

Congenital nystagmus among the Red-skins of the Highlands of Papua New Guinea.

Sixty-four people with pigmentary anomalies of the skin were examined in the Eastern Highlands of New Guinea. Thirty-one had a bronze-red skin colour which appears to be unique to New Guinea. Eighteen of the Red-skins had congenital nystagmus which was not associated with impairment of visual acuity. The fundi were normal. The pigmentary anomaly is recessively inherited, and the gene responsible for the nystagmus appears to be associated with those controlling skin colour. The condition appears to be a unique form of albinism and confers no disadvantage on those who have it.

Adolescent↗
PubMed1967

Romeriscus, the oldest known reptile.

The description of Romeriscus, a new genus of limnoscelid reptile, is based on a partial skeleton from the Early Pennsylvanian (Westphalian A) of Nova Scotia. Although it is the earliest and most primitive reptile yet known, it is probably already too late and too specialized to be ancestral to the more advanced Carboniferous and Permian captorhinomorphs and pelycosaurs.

Animals↗
PubMedDate not supplied

Vertebral development and amphibian evolution.

Amphibians provide an unparalleled opportunity to integrate studies of development and evolution through the investigation of the fossil record of larval stages. The pattern of vertebral development in modern frogs strongly resembles that of Paleozoic labyrinthodonts in the great delay in the ossification of the vertebrae, with the centra forming much later than the neural arches. Slow ossification of the trunk vertebrae in frogs and the absence of ossification in the tail facilitate the rapid loss of the tail during metamorphosis, and may reflect retention of the pattern in their specific Paleozoic ancestors. Salamanders and caecilians ossify their centra at a much earlier stage than frogs, which resembles the condition in Paleozoic lepospondyls. The clearly distinct patterns and rates of vertebral development may indicate phylogenetic separation between the ultimate ancestors of frogs and those of salamanders and caecilians within the early radiation of ancestral tetrapods. This divergence may date from the Lower Carboniferous. Comparison with the molecular regulation of vertebral development described in modern mammals and birds suggests that the rapid chondrification of the centra in salamanders relative to that of frogs may result from the earlier migration of sclerotomal cells expressing Pax1 to the area surrounding the notochord.

Amphibians↗
PubMedDate not supplied

Adductor spastic dysphonia: heterogeneity of physiologic and phonatory characteristics.

Physiologic and phonatory characteristics of 23 subjects with adductor spastic dysphonia were studied, including examination of the laryngeal appearance by fiberoptic nasoendoscopy, neurologic examination, and measurement of phonatory airflow and speaking fundamental frequency. These characteristics displayed considerable heterogeneity among the subjects investigated. Three patterns of laryngeal appearance during phonation were observed: vocal fold adduction, associated ventricular fold constriction, and approximation of the laryngeal inlet. Eight of 13 subjects demonstrated some neurologic abnormality. For the majority of subjects, the airflow demonstrated marked variability during sustained phonation; for different subjects, this variability was observed to be associated with either an oscillatory or irregular airflow pattern. The modal speaking fundamental frequency for the women and men with adductor spastic dysphonia was not significantly different from that for age- and sex-matched controls.

Adult↗