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Biomedical subjects

C Palmer

Publications and source records attributed to C Palmer.

16 recordsLinked to original sources
PubMed1992

Allopurinol preserves cerebral energy metabolism during perinatal hypoxia-ischemia: a 31P NMR study in unanesthetized immature rats.

The effects of high dose allopurinol (ALLOP) pretreatment on the cerebral energy metabolism of unanesthetized 7-day-postnatal rats during exposure to 3 h of cerebral hypoxia-ischemia were serially quantitated using non-invasive 31P NMR spectroscopy. Adenosine triphosphate, integrated over the last 2 h of hypoxia and expressed as a fraction of baseline, was 0.73 +/- 0.16 with ALLOP pretreatment (200 mg/kg s.c.) compared to 0.52 +/- 0.05 for saline pretreatment (P = 0.001). Inorganic phosphate/phosphocreatine (Pi/PCr), integrated over the same time interval, was 2.63 +/- 1.23 relative to baseline with ALLOP versus 5.13 +/- 1.45 for saline-treated pups (P less than 0.0005). We suggest that the neuroprotection achieved with high dose ALLOP pretreatment may be attributed in part to preservation of energy metabolites.

Adenosine Triphosphate↗
PubMed1992

Growth kinetics and chemoprevention of aberrant crypts in the rat colon.

Single and multiple colonic crypts exhibiting dysplasia that are detectable in situ by staining of rat colon with methylene blue are called aberrant crypts (AC) and may serve as an intermediate marker for colon cancer. In a characterization study, we have established the kinetics of AC growth and development over a period of 20 d following injection of rats with the carcinogen azoxymethane (AOM). AC are not present at 5 d post-injection, but are a constant feature at 10 d and thereafter. Multiple AC, presumably clonal, begin to evolve at 10 d and are consistent by 20 d, forming incipient microadenomata. We have examined 20 candidate chemopreventive agents for inhibition of AC. All agents were given in AIN-76 diet, at two dose levels, with injections of AOM. AC were measured after 5 weeks of growth. Among the most active AC-inhibiting agents were BHA, DFMO, quercetin, diallyl sulfide, 18 beta-glycyrrhetinic acid, and ascorbyl palmitate. In a post-initiation study, the differentiating agent sodium butyrate was ineffective, but piroxicam was highly effective in modulating AC growth. Further, piroxicam inhibited AC development at all stages of growth from single to polycryptal clusters of AC. The AC assay shows marked sensitivity and specificity for screening agents for chemoprevention of colon cancer.

Animals↗
PubMed1992

Are we making any progress?

This report offers a limited view, by example, of dentistry's multifaceted interactions with several agencies on selected issues. It is intended to be neither comprehensive nor predictive.

American Dental Association↗
PubMed1992

The effect of a progesterone/estradiol ear implant on the performance of young beef steers.

A progesterone/estradiol ear implant was tested over a 84 d feedlot period on 96 young Bonsmara steers which were randomly allocated to implant and control groups. Animals were adapted over 5 d to a complete feed formulated to South African feedlot standards. Health aberrations were observed and feed intake, mass gain and slaughter data were recorded. The implant group elicited a 23.2 kg gain per animal (P less than 0.01). Mean treatment feed intakes varied marginally but the implant group showed a 14.91% feed to gain improvement over controls. Warm carcass dressing percentage showed an overall improvement of 4.96% for both groups. Bloat incidence was calculated at 0.98% over 8,064 cattle feedlot days. Mortality was 2.08% and 12 animals were considered to be chronic bloaters. This may have been due to the high proportion of fine particles in the diet. A composite feed sample revealed that 62.48% consisted of particle lengths of 0.5-4mm. The effect of this on ruminal health is briefly discussed. It is concluded that the progesterone/estradiol implant provided greater mass gain and improved feed to gain ratios for treated steers over a control group.

Animal Feed↗
PubMed1991

Investigations in the amplitude of sounded piano tones.

The relationship between final hammer velocity and maximum amplitude of radiated piano sound was investigated. Piano tones with varying hammer velocities were produced by a computer-monitored acoustic piano containing optical sensors and solenoids, and the sounded tones were recorded and digitized for analysis. Maximum amplitudes over the duration of the sounded tones were linearly proportional to piano hammer velocities for a range of frequencies and hammer velocities. Changes in room acoustics did not alter the linear relationship. Measurements of maximum amplitudes of individual tones and combined tones (dyads) also indicated a linear relationship between the sum of the maximum amplitudes of the individual tones and the maximum amplitude of the dyads. These findings indicate that the principle of superposition holds for peak amplitudes of sounded piano tones. Findings are discussed with regard to production and perception of musical dynamics.

Computer Graphics↗
PubMed1991

Nutritional support in treatment of oral carcinomas.

Two young adults, one lean and one obese, with squamous cell carcinomas of the oral cavity received aggressive antitumor therapies with comprehensive nutritional support in an effort to minimize the secondary malnutrition that often accompanies cancer treatments.

Adult↗
PubMed1979

Interpositus and fastigial unit activity during sleep and waking in the cat.

Fine wire microelectrodes were used to record single unit activity from two of the intracerebellar nuclei, the interpositus and fastigius, during the sleep-waking cycle. The mean rates, interspike interval distributions and patterns of firing as revealed by autocorrelograms, were investigated. For each stage of the sleep-waking cycle and for as many units as possible the constancy of these measures was examined throughout several sleep cycles. Twenty-four interpositus units were recorded throughout at least one complete sleep-waking cycle. The firing rate of these units in paradoxical sleep without REM was equal to that in quiet wakefulness and greater than that occurring during slow wave sleep. The highest firing rates occurred during REM periods. Some interpositus units were found to have apparent eye movement related activity during REM periods but there was no correlation with waking eye movements. Eleven fastigial units were investigated throughout the sleep-waking cycle. At least half of these units were found to have rhythmic bursting activity during paradoxical sleep which did not appear to be tightly linked with REM periods. Fastigial and interpositus units were found to have slow shifts in their 'background' level of firing which occurred independently of the sleep-waking cycle. The results of these experiments are discussed in relation to the known inputs to the nuclei and in relation to previous studies on other groups of neurons during sleep and waking.

Animals↗
PubMed1978

B-cell leukemia-lymphoma with striking resemblance to Burkitt lymphoma in a 70-year-old woman.

A 70-year-old woman developed acute leukemia and a serum IgM spike. She entered complete remission with an adriamycin, vincristine, cytosine arabinoside, and prednisone combination. Bone marrow remission was maintained with intermittent cytosine arabinoside; however, she developed large skin nodules which partly remitted following adriamycin, vincristine, cyclophosphamide, and prednisone combination. They very rapidly recurred, and she died soon after. Autopsy revealed extensive tumor in the abdomen, pelvis, and thoracic cavity, but no bone marrow involvement. Histology revealed a "starry sky" appearance. Cytology showed undifferentiated cells with vacuolated cytoplasm resembling Burkitt lymphoma cells. Peroxidase and esterase stains were negative. There was strong pyroninophilia and the periodic acid-Schiff reaction showed granular activity in the cytoplasm. Electron microscopic appearances also resembled Burkitt lymphoma. Cytogenetic studies were normal, with no Ph1 chromosome. Immunofluorescence demonstrated surface IgM and a little IgA. 3H-thymidine incorporation was high, indicating rapid growth. Dibutyral cyclic adenosine monophosphate (cAMP) stimulated growth, which was further evidence of the lymphoid origin of the tumor. The close resemblance of this tumor to Burkitt lymphoma emphasizes the difficulties in systematically classifying the lymphomas.

Acute Disease↗
PubMed1976

Scanning electron microscopy of cell surfaces following removal of extracellular material.

The application of scanning electron microscopy to the study of cell surfaces is limited in intact tissues, because extracellular material may often obscure the details of nonluminal surfaces. To remove connective tissue elements we have treated human skin and both kidney, and an autonomic ganglion of the rat with hydrochloric acid and collagenase. Regional variations in the basal surface of the nephron are noted following removal of the basement membrane. The basilar interdigitations of the cells of the proximal tubule appeared as parallel ridges encircling the tubule. Ridges on the parietal epithelium of Bowman's capsule were randomly arranged and alternated with smooth surfaces. The dermal surface of the human epidermis has an alveolar or honeycomb appearance due to the elevation of the epidermal ridges and numerous pits for the dermal pegs. At higher magnifications the basal surface of cells of the stratum germinativum possessed numerous and irregular projections. Neurons with their processes are evident in the autonomic ganglion. The soma of the neurons are enclosed by flattened satellite cells. Irregular spaces between opposed satellite cells are interpreted as regions for the passage of processes related to the ganglion cells. Nodes of Ranvier were clearly seen along nerve fibers. Some pitting of the nerve fibers was also noted. The HCl-collagenase method has the advantage of the removal of collagen and basement membrane while preserving the structural integrity of the cell surface.

Animals↗
PubMed1975

Holoprosencephaly: birth data, benetic and demographic analyses of 30 families.

Thirty families were studied to determine genetic and evnironmental factors involved in holoprosencephaly. Those with chromosomal abnormalities were excluded. Many factors appear to cluster in proband families, such as mental retardation, mental illness, endocrine disorders, increased twinning and poverty level socioeconomic status. The empiric recurrence risk was 6%. Among 7 with lobar holoprosencephaly, there were 3 females and 4 males, while there were 19 females and 6 males with alobar holoprosencephaly.

Abnormalities, Severe Teratoid↗
PubMedDate not supplied

31P NMR spectroscopy of perinatal hypoxic-ischemic brain damage: a model to evaluate neuroprotective drugs in immature rats.

Cerebral energy metabolism can be measured non-invasively in unanesthetized neonatal rats with 31P NMR spectroscopy. Using this technique, serial changes in high energy phosphates were determined from the right cerebral hemispheres of 7 day postnatal rat pups during a hypoxic-ischemic insult known to produce focal brain injury. During 3 h of hypoxia-ischemia the concentration of ATP dropped to 33 +/- 8% of prehypoxic (baseline) levels, phosphocreatine (PCr)/Pi decreased from 1.5 +/- 0.51 to 0.16 +/- 0.06, while pH decreased nominally by 0.2 units. After 2.5 h of recovery in air, ATP returned to 75 +/- 10% of baseline levels, PCr/Pi rose to 1.1 +/- 0.28, and pH returned to its normal value of 7.16 +/- 0.06. This model was used to test the efficacy of the adenosine deaminase inhibitor, 2-deoxycoformycin (DCF) as a potential neuroprotective drug. The data for the drug- and saline-treated populations were analyzed by integrating ATP and Pi/PCr levels over specific time intervals, expressing it relative to baseline levels, and modeling it with cubic splines. Pretreatment with 500 micrograms/kg DCF shows a small, but statistically significant, preservation of both ATP and phosphorylation potential during hypoxia and initial recovery. Brain water content (edema) at 42 h recovery was apparently associated with both mean ATP and mean Pi/PCr in the last 2 h of hypoxia-ischemia. When ATP fell below 70% of baseline, brain edema was evident at 42 h of recovery. This methodology is suitable for extension to human infants.

Adenosine Triphosphate↗
PubMedDate not supplied

A microwire technique for recording single neurons in unrestrained animals.

A technique is described in which bundles of 25 mu dia. insulated wires can be stereotaxically implanted for single unit recording in the brain. With this method extremely stable recordings can be obtained lasting many hours and sometimes days. The unit activity recorded with these electrodes has been found comparable with that recorded from rigid etched microelectrodes in conscious animals. The fine wire electrodes have also been found to be durable for at least a month when chronically implanted in cats. The electrode assembly is easy to construct and the electrodes are easily implanted in any region of the brain.

Animals↗