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Biomedical subjects

P R Morrison

Publications and source records attributed to P R Morrison.

7 recordsLinked to original sources
PubMed1992

Pulse duration effects on cutaneous pigment.

Melanin, an endogenous chromophore in pigment containing cells in skin, is being specifically altered by lasers using the principle of selective photothermolysis (SPT). This implies that a combination of specific laser parameters of wavelength, pulse duration, spotsize, and energy density are required to confine the delivered laser energy to the targeted cells alone. Because the bulk of cutaneous pigment is localized to epidermal basal cells, pigmentary incontinence has been found to occur in skin exposed to laser irradiation. This study demonstrates that pulse duration or exposure time of the laser affect the severity of pigmentary incontinence induced. Pigment granules are more abundant, aggregated, and located deeper in the dermis following exposure to 500 nsec pulse duration than 100 nsec at a wavelength of 504 nm. This relationship appears to be independent of the laser energy density used.

Animals↗
PubMed1992

Altered actin and myosin expression in muscle during exposure to microgravity.

The mechanism for cardiovascular deconditioning and skeletal muscle atrophy during microgravity is not known. The purpose of the present study was to determine whether a decrease in contractile protein gene expression in the muscle of rats occurred after 14 days of microgravity. No differences existed in the profile of myosin protein isoforms or beta-myosin heavy chain mRNA in hearts between the flight and synchronous control groups. On the other hand, differences in the expression of beta-myosin heavy chain mRNA relative to the 18S and 28S rRNA in the heart between flight and synchronous control groups were noted with a covariance mapping analysis. Both the vastus intermedius and lateral gastrocnemius muscles exhibited significant (P less than 0.05) decreases in skeletal alpha-actin mRNA per unit of extractable RNA in the flight group compared with the synchronous control group. However, no significant difference for skeletal alpha-actin mRNA occurred in the triceps brachii muscle between these groups. Cytochrome c mRNA per unit of extractable RNA decreased (P less than 0.05) only in the vastus intermedius but not in the lateral gastrocnemius or triceps brachii muscles. In summary, changes in the pretranslational regulation of contractile protein gene expression occur in both heart and skeletal muscle after 14 days of microgravity.

Actins↗
PubMed1991

Cytochrome c mRNA levels decrease in senescent rat heart.

The concentration of mitochondria decreases in the heart as rodents age from maturity to senescence. The reason for this change is not known. One purpose of the present study was to determine if cytochrome c mRNA, representative of proteins of the inner mitochondrial membrane, decreased in the hearts of Fischer 344 rats as they aged from 12 to 24 months. Twenty-two percent less cytochrome c mRNA existed per given quantity of extracted RNA from the heart in 24-month-old rats as compared with the 12-month-old group. No change in the quantities of cardiac alpha-actin mRNA, Ca2+/calmodulin protein kinase II mRNA or 18S rRNA was noted between 12- and 24-month-old hearts. Thus, the decrease in cytochrome c mRNA suggests that decreases in mRNAs for proteins of the inner mitochondrial membrane could play some role in the diminished concentration of mitochondria that exists in the senescent heart.

Actins↗
PubMed1978

Amino acid differences between major and minor hemoglobins from lemmings (Lemmus and Dicrostonyx).

1. Dual hemoglobins were isolated from both Lemmus and Discrostonyx, two genera of microtine rodents of the tribe Lemmini. 2. The dual hemoglobins result from dual alpha-chains and the charge difference Asp----Ala at position alpha 5. 3. The beta-chains of Dicrostonyx and Lemmus hemoglobins differ in charge by Ala----Asp at beta 125. 4. Cladograms are presented for the hemoglobin chains of microtine rodents.

Amino Acid Sequence↗
PubMed1975

Gluconeogenesis in arctic ground squirrels between periods of hibernation.

The hibernation season in the arctic ground squirrel (Citellus undulatus) is broken into 8- to 18- day cycles by short homeothermal periods during which the carboydrate reserves depleted during hibernation are replenished. This study follows a number of metabolities in tissues and body fluids to assess the sources for reconstitution of the glucose reserves: lactate, urea, ammonia, free fatty acid, glycerol, triglyceride, and glucose in plasma; glycogen in liver and muscle; and urea and ammonia nitrogen in urine. Fat is the major energy source during both homeothermal and heterothermal periods, the contribution from glucose being limited to glycolysis. Reconstitution of glycogen is accomplished prior to reentry through maximal use of substrates from all sources including glycolysis, fat, and protein metabolism. Of the new gluconeogenic substrate, one-fourth is supplied from protein and three-fourths from fat.

Ammonia↗
PubMed1975

Impairment of metabolic capability in feral house mice by Klossiella muris invection.

Kidney infection by Klossiella muris in highland house mice from Peru was associated with lowered metabolic capability (57%) and endurance time (25%) at maximum metabolic rate. Administration of coccidiostatic preparations improved the metabolic capability from 7.8 to 10.5 cc 0-2 g hr and the endurance from 2.8 to longer than 10 min. Their colony-reared offspring, which were free from parasites, sustained maximum metabolic rates of 13.8 cc 0-2/g hr also for longer than 10 min. This rate was slightly higher than the values found in both healthy lowland controls: feral house mice from Arkansas and laboratory white mice [lab: HA(ICR)]. Although clinically inapparent under oridinary conditions, the effects of K muris infection were easily demonstrated at high metabolic loads stimulated by cold. Thus emphasizing the importance of such performance tests in assessing the status of experimental subjects.

Animals↗