PubMed Health⌕ Search

Biomedical subjects

J A Leonard

Publications and source records attributed to J A Leonard.

At least 19 recordsLinked to original sources
PubMed2003

Widespread occurrence of a domestic dog mitochondrial DNA haplotype in southeastern US coyotes.

Sequence analysis of the mitochondrial DNA control region from 112 southeastern US coyotes (Canis latrans) revealed 12 individuals with a haplotype closely related to those in domestic dogs. Phylogenetic analyses grouped this new haplotype in the dog/grey wolf (Canis familiaris/Canis lupus) clade with 98% bootstrap support. These results demonstrate that a male coyote hybridized with a female dog, and female hybrid offspring successfully integrated into the coyote population. The widespread distribution of this haplotype from Florida to West Virginia suggests that the hybridization event occurred long ago before the southeastern USA was colonized by coyotes. However, it could have occurred in the southeastern USA before the main front of coyotes arrived in the area between male coyotes released for sport and a local domestic dog. The introgression of domestic dog genes into the southeastern coyote population does not appear to have substantially affected the coyote's genetic, morphological, or behavioural integrity. However, our results suggest that, contrary to previous reports, hybridization can occur between domestic and wild canids, even when the latter is relatively abundant. Therefore, hybridization may be a greater threat to the persistence of wild canid populations than previously thought.

Animals↗
PubMed2001

Widespread origins of domestic horse lineages.

Domestication entails control of wild species and is generally regarded as a complex process confined to a restricted area and culture. Previous DNA sequence analyses of several domestic species have suggested only a limited number of origination events. We analyzed mitochondrial DNA (mtDNA) control region sequences of 191 domestic horses and found a high diversity of matrilines. Sequence analysis of equids from archaeological sites and late Pleistocene deposits showed that this diversity was not due to an accelerated mutation rate or an ancient domestication event. Consequently, high mtDNA sequence diversity of horses implies an unprecedented and widespread integration of matrilines and an extensive utilization and taming of wild horses. However, genetic variation at nuclear markers is partitioned among horse breeds and may reflect sex-biased dispersal and breeding.

Alleles↗
PubMed2001

Examining monophyly in a large radiation of Madagascan butterflies (Lepidoptera: Satyrinae: Mycalesina) based on mitochondrial DNA data.

The satyrine butterfly subtribe Mycalesina has undergone one of the more spectacular evolutionary radiations of butterflies in the Old World tropics. Perhaps the most phenotypically pronounced diversification of the group has occurred in the Malagasy region, where 68 currently recognized species are divided among five genera. Here, we report the results of phylogenetic analyses of sequence data from the cytochrome c oxidase II and cytochrome b mitochondrial genes, for a total of 54 mycalesine taxa, mostly from Madagascar. These molecular data complement an existing data set based on male morphological characters. The molecular results support the suggestion from morphology that three of the five Malagasy genera are paraphyletic and support the monophyly of at least three major morphological clades. Novel hypotheses of terminal taxon pairs are generated by the molecular data. Dense taxon sampling appears to be crucial for elucidating phylogenetic relationships within this large radiation. A potentially complex scenario for the origin of Malagasy mycalesines is proposed.

Animals↗
PubMed2000

Population genetics of ice age brown bears.

The Pleistocene was a dynamic period for Holarctic mammal species, complicated by episodes of glaciation, local extinctions, and intercontinental migration. The genetic consequences of these events are difficult to resolve from the study of present-day populations. To provide a direct view of population genetics in the late Pleistocene, we measured mitochondrial DNA sequence variation in seven permafrost-preserved brown bear (Ursus arctos) specimens, dated from 14,000 to 42,000 years ago. Approximately 36,000 years ago, the Beringian brown bear population had a higher genetic diversity than any extant North American population, but by 15,000 years ago genetic diversity appears similar to the modern day. The older, genetically diverse, Beringian population contained sequences from three clades now restricted to local regions within North America, indicating that current phylogeographic patterns may provide misleading data for evolutionary studies and conservation management. The late Pleistocene phylogeographic data also indicate possible colonization routes to areas south of the Cordilleran ice sheet.

Alaska↗
PubMed1998

A genetic record of population isolation in pocket gophers during Holocene climatic change.

A long-standing question in Quaternary paleontology is whether climate-induced, population-level phenotypic change is a result of large-scale migration or evolution in isolation. To directly measure genetic variation through time, ancient DNA and morphologic variation was measured over 2,400 years in a Holocene sequence of pocket gophers (Thomomys talpoides) from Lamar Cave, Yellowstone National Park, Wyoming. Ancient specimens and modern samples collected near Lamar Cave share mitochondrial cytochrome b sequences that are absent from adjacent localities, suggesting that the population was isolated for the entire period. In contrast, diastemal length, a morphologic character correlated with body size and nutritional level, changed predictably in response to climatic change. Our results demonstrate that small mammal populations can experience the long-term isolation assumed by many theoretical models of microevolutionary change.

Biological Evolution↗
PubMed1998

Conservation genetics of the endangered Pampas deer (Ozotoceros bezoarticus).

The Pampas deer (Ozotoceros bezoarticus L. 1758) is the most endangered neotropical cervid, and in the past occupied a wide range of open habitats including grassland, pampas, savanna, and cerrado (Brazil) from 5 degrees to 41 degrees S. To better understand the effect of habitat fragmentation on gene flow and genetic variation, and to uncover genetic units for conservation, we examined DNA sequences from the mitochondrial control region of 54 individuals from six localities distributed throughout the present geographical range of the Pampas deer. Our results suggest that the control region of the Pampas deer is one of the most polymorphic of any mammal. This remarkably high variability probably reflects large historic population sizes of millions of individuals in contrast to numbers of fewer than 80,000 today. Gene flow between populations is generally close to one migrant per generation and, with the exception of two populations from Argentina, all populations are significantly differentiated. The degree of gene flow was correlated with geographical distance between populations, a result consistent with limited dispersal being the primary determinant of genetic differentiation between populations. The molecular genetic results provide a mandate for habitat restoration and reintroduction of Pampas deer so that levels of genetic variation can be preserved and historic patterns of abundance can be reconstructed. However, the source of individuals for reintroduction generally should be from populations geographically closest to those now in danger of extinction.

Animals↗
PubMed1996

Use of bivalved ankle-foot orthosis in neuropathic foot and ankle lesions.

The neuropathic foot is a common complication of diabetes mellitus and is associated with development of chronic ulcers and Charcot joints. Treatment of these complications presents a complex management task. This report presents long-term follow-up data on 16 patients with neuropathic changes who were treated with a total contact, laminated, bivalved, rocker-bottom-soled ankle-foot orthosis (TCAFO). Of the 16 patients, 6 were treated for Charcot changes only, 10 were treated for ulcers, and 2 of the 10 had ulcers bilaterally. Eight of the 12 ulcers (67%) healed in an average of 10 months (range 1-24 mo), 1 patient required amputation, and 2 patients who had complete healing, 5 have resumed wearing TCAFOs secondary to recurrent ulcers. Three of the 5 patients with Charcot changes no longer use the orthosis and have had negative bone scans after an average of 20.7 months (range 12-28 mo). In this retrospective uncontrolled study, the TCAFO proved to be a safe, functional, and cost-effective therapy for complications of the neuropathic foot.

Adult↗
PubMed1992

Long thoracic neuropathy from athletic activity.

Four cases of long thoracic mononeuropathy associated with sports participation are presented. Each patient developed shoulder pain or dysfunction after an acute event or vigorous activity, and demonstrated scapular winging consistent with serratus anterior weakness. The diagnosis was confirmed with electromyography in each case. It is suggested that the athletic activity caused a stretch injury to the long thoracic nerve. Conservative management, consisting of range of motion exercises for the shoulder and strengthening of the serratus anterior muscle, resulted in a favorable outcome in all patients.

Adolescent↗
PubMed1989

Prosthetics, orthotics, and assistive devices. 1. General concepts.

This self-directed learning module highlights the general concepts and new advances in the area of orthotics and prosthetics. This general overview is part of the chapter on prosthetics, orthotics, and assistive devices for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. This section contains essential information on spinal, lower and upper limb orthotics, lower and upper limb prosthetics, juvenile prosthetics, kinesiology, motion analysis, and assistive devices such as canes and crutches. This article establishes a foundation on which the second, third, and fourth articles of this chapter will build. The three articles to follow review newer developments in specialized seating and assistive devices, prosthetics, and the orthotic management of selected disorders.

Adult↗
PubMed1989

Prosthetics, orthotics, and assistive devices. 2. Specialized seating and assistive devices.

This self-directed learning module discusses topics in specialized seating, mobility devices, augmented communication, and adaptive equipment. Development, perceptual-motor, and cognitive factors are addressed in regard to appropriate prescription, training, and follow-up. It is part of the chapter on prosthetics, orthotics, and assistive devices for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation.

Adult↗
PubMed1989

Prosthetics, orthotics, and assistive devices. 3. Prosthetics.

This self-directed learning module highlights new advances in prosthetics. It is part of the chapter on prosthetics, orthotics, and assistive devices for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. This section contains information regarding conventional and myoelectric upper limb prosthetics, above-knee (AK) socket designs and materials, and foot and ankle systems. New advances that are covered in this section include the narrow medial-lateral AK socket, the flexible AK socket, and new prosthetic foot and ankle systems. Proper understanding and clinical application of this technology is essential for the optimal prosthetic rehabilitation of the amputee.

Artificial Limbs↗
PubMed1989

Prosthetics, orthotics, and assistive devices. 4. Orthotic management of selected disorders.

This self-directed learning module presents core information and new advances in the orthotic management of problems of the runner and of patients with neurovascular foot ulcers or arthritis. Additional topics covered include a comprehensive approach to positioning and splinting for burns and tone-reducing orthoses for spasticity management. It is part of the chapter on prosthetics, orthotics, and assistive devices for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation.

Adult↗
PubMed1989

Injection-related ulnar neuropathy.

Two previously healthy people sustained mild ulnar mononeuropathies at the level of the upper arm after injections by the same nurse. In both, the nurse was attempting to inject into the middle deltoid; the ulnar nerve was presumably reached by standing at the patient's side and injecting "sidearm" into the upper arm. These cases point out the careful attention to local anatomy required for those administering injections, and the importance of proper positioning.

Action Potentials↗
PubMed1986

Acoustic myography as a control signal for an externally powered prosthesis.

Contracting skeletal muscle produces sounds that are easily recorded with a standard microphone. The recording of these sounds is known as acoustic myography, or AMG. As a control signal for an externally powered prosthesis, some advantages of AMG over surface EMG are: there is no need for direct skin contact; the AMG signal is unaffected by changes in skin impedence; AMG intensity is high enough to produce a 50 mV output from a standard microphone, requiring less amplification and electrical shielding; the AMG signal is qualitatively less sensitive to placement on the muscle than EMG. Disadvantages, such as the susceptibility of AMG to interference by extraneous environmental noise, are relatively easy to overcome. To demonstrate this, we have constructed a myoacoustically controlled prosthetic hand, whose tristate control via a single microphone (vs differential control) proves its feasibility in the more difficult case. The control circuitry for this device costs less than $50. The existing device utilizes a free-standing hand; a prosthetic shell which will allow comparison of AMG vs EMG control is currently being designed. The two patients who have tried it have learned to open and close the hand reliably after only three minutes of practice. Protocols are being established for functional assessment of AMG control.

Acoustics↗
PubMed1985

Posterior interosseous palsy after dental treatment: case report.

Unilateral posterior interosseous nerve palsy occurred in a woman after deep palpation by her dentist during treatment for temporomandibular joint (TMJ) syndrome. Weakness of wrist and finger extension was noticed by the patient after the dentist used techniques of "applied kinesiology," including "pressure-point palpation." Electromyography confirmed the localization. This case exemplifies nerve damage caused by unorthodox treatment directed at the musculoskeletal system.

Arm↗
PubMed1980

Dantrolene sodium suspension in treatment of spastic cerebral palsy.

A double-blind study was carried out on 20 children with spasticity secondary to cerebral palsy, in order to compare the effects of dantrolene sodium suspension and a placebo. The drug was found to be physiologically active in reducing the force of muscle contraction, but objective functional improvement, as measured by multiple performance tests, was irregular and probably not significant.

Activities of Daily Living↗