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Biomedical subjects

W D Clark

Publications and source records attributed to W D Clark.

At least 19 recordsLinked to original sources
PubMed1995

The effects of continuously or diurnally fed melatonin on broiler performance and health.

An experiment was designed to investigate the effects of dietary melatonin (MEL) on the performance and health of broiler chicks. Chicks raised under constant lighting were fed practical broiler diets in mash form containing 0, 20, or 40 ppm MEL from 0 to 3 wk. A fourth treatment (0 ppm MEL: 6h/d; 20 ppm MEL: 18 h/d) was used to mimic a diurnal light:dark cycle. Commercial broiler grower diets without MEL supplementation were fed from 3 to 6 wk of age. A small dose-related decrease was observed in weight gain (0 to 14 d) and feed consumption (0 to 21 d) due to continuous feeding of MEL. Continuously fed MEL also improved feed efficiency in the first 3 wk vs the control (0 ppm). Growth and feed consumption from 0 to 21 d were not affected by the diurnally fed diet when compared with the control treatment. No effects were found for mortality. However, the incidence of sudden death syndrome (SDS) was numerically less for the diurnal (3.56%) and 40 ppm (3.76%) diets from 0 to 42 d than for the control treatment 5.56%. Skeletal disease was generally unaffected, with the exception of the incidence of crooked toes at 42 d (0 ppm MEL: 8.67% vs diurnal: 4.89%). Dietary MEL fed either continuously or in a diurnal pattern had a minor effect on the performance and health of broiler chickens.

Animals↗
PubMed1992

Relative rates of nucleotide substitution at the rbcL locus of monocotyledonous plants.

We subjected 35 rbcL nucleotide sequences from monocotyledonous taxa to maximum likelihood relative rate tests and estimated relative differences in rates of nucleotide substitution between groups of sequences without relying on knowledge of divergence times between taxa. Rate tests revealed that there is a hierarchy of substitution rate at the rbcL locus within the monocots. Among the taxa analyzed the grasses have the most rapid substitution rate; they are followed in rate by the Orchidales, the Liliales, the Bromeliales, and the Arecales. The overall substitution rate for the rbcL locus of grasses is over 5 times the substitution rate in the rbcL of the palms. The substitution rate at the third codon positions in the rbcL of the grasses is over 8 times the third position rate in the palms. The pattern of rate variation is consistent with the generation-time-effect hypothesis. Heterogenous rates of substitution have important implications for phylogenetic reconstruction.

Genes, Plant↗
PubMed1989

Teaching indirect mirror laryngoscopy.

Indirect mirror laryngoscopy is difficult to learn. An anatomic model of the oropharynx and larynx is described here. This model is used to familiarize medical students with the component skills of mirror laryngoscopy. The students progress to competency at mirror laryngoscopy on patients more quickly after initial use of this model.

Laryngoscopy↗
PubMed1988

Surgical care of submental gunshot wounds.

The care of patients with self-inflicted facial gunshot wounds is complex and challenging. The magnitude and self-inflicted nature of the injuries naturally give rise to questions about potential for successful rehabilitation. The surgical care and rehabilitation of ten such patients are described. The initial grotesque disfiguration belies the reasonable chances for functional restoration. Patients in this series who completed reconstruction swallow well enough to maintain body weight, speak understandably, breathe without tracheostomy, and have an appearance sufficiently normal that they can interact socially without embarrassment. Guidelines are proposed for multidisciplinary medical care leading to satisfactory functional, aesthetic, social, and psychiatric rehabilitation.

Adult↗
PubMed1987

Parotid lipoblastoma in an infant.

We report a case of 'matured' lipoblastoma occurring within the parotid gland of a 7-month-old male. This benign fatty tumor is considered to represent localized continuation of fetal fat development into the post-birth period. At least 7 cases have been reported in the head and neck region, but this is the first known occurrence within a salivary gland.

Humans↗
PubMed1987

Tumoral calcinosis in the neck.

Tumoral calcinosis manifests soft-tissue calcification, usually near major joints. It variably includes hyperphosphatemia, elevated 1,25-dihydroxycalciferol, and an affected sibling. Serum calcium, alkaline phosphatase, and parathyroid hormone are normal. Tumoral calcinosis of the head and neck is very rare, but this diagnosis should be considered when x-ray film of a poorly defined mass shows irregular soft-tissue calcification.

Adult↗
PubMed1986

Invasive papillomatosis and squamous carcinoma complicating juvenile laryngeal papillomatosis.

Juvenile laryngeal papillomatosis (JLP), usually a benign, self-limited disease, occasionally has a highly aggressive course characterized by extension of neoplastic cells into the tracheobronchial tree, lung, and soft tissues. Less frequently, squamous carcinoma has arisen in JLP, most commonly following radiation therapy. Rarely, carcinoma has occurred without previous irradiation, but distant metastases do not generally occur. We describe a 14-year-old boy, with a particularly aggressive form of JLP, who developed invasion of the lungs, intrapulmonary lymph nodes, and arteries by cytologically benign neoplastic tissue. He also developed a metastasizing squamous carcinoma of the lung and humoral hypercalcemia of malignancy. A discussion of the implications of the case and a review of the current literature are provided.

Adolescent↗
PubMed1986

Lethal enhancement of therapeutic doses of acetaminophen by alcohol.

A 47-year-old man undergoing supervised alcohol detoxification developed severe liver disease after receiving small doses of acetaminophen. Autopsy revealed extensive hepatic necrosis. Proposed mechanisms for alcohol potentiation of acetaminophen hepatotoxicity are described. We feel acetaminophen should not be routinely used for patients with active alcoholism unless its safety can be established.

Acetaminophen↗
PubMed1986

Epithelial-myoepithelial carcinoma of the parotid gland.

The EME carcinoma of intercalated duct origin is now recognized as a distinct salivary gland malignancy. A case has been reported that typifies clinical and pathologic features. Both the surgeon and pathologist should learn not only to recognize its dual cellular characteristics, but also to be aware of the potential destructive nature and possibility for metastases with this tumor.

Adenoma↗
PubMed1986

Phytate phosphorus intake and disappearance in the gastrointestinal tract of high producing dairy cows.

Thirty Holstein cows were fed diets of 50% grain and 50% corn silage (dry matter basis) through the first 18 wk of lactation. Grain mixes were supplemented with inorganic calcium sources (aragonite, calcite flour, or albacar) to provide .6 or .9% dietary calcium (dry matter basis). Phytate phosphorus intake averaged 38.3 and 42.6 g/d in digestion trials conducted during wk 4 and 10 of lactation, respectively. Even though large quantities of feed and significant amounts of grain were consumed, 98% of dietary phytate phosphorus was hydrolyzed to inorganic phosphorus. Neither calcium source nor calcium quantity affected the hydrolysis of phytate phosphorus.

Animals↗