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Biomedical subjects

E R Allen

Publications and source records attributed to E R Allen.

At least 37 records · Page 2Linked to original sources
PubMed1976

Ultrastructure of the salivary bladder of the nine-banded armadillo.

The nine-banded armadillo possesses a salivary bladder which is a dilated portion of the main duct of the submandibular gland at its origin. The wall of the bladder is composed of an epithelium, a submucosa and a thick coat of skeletal muscle. The ultrastructure of the epithelium reveals that it is complex and consists of three cell types: 1) principal cells, 2) light cells, and 3) basal cells. The general organization of the epithelium suggests that it is a transporting type of epithelium such as that found in the amphibian and reptilian and reptilian urinary bladders and the mammalian gall bladder. The submucosa is composed primarily of densely-packed collagen fibers. The skeletal muscle is very vascular and richly innervated.

Animals↗
PubMed1972

The sulfur cycle.

Even granting our uncertainties about parts of our model of the sulfur cycle, we can draw some conclusions from it: 1) Man is now contributing about one half as much as nature to the total atmospheric burden of sulfur compounds, but by A.D. 2000 he will be contributing about as much, and in the Northern Hemisphere alone he will be more than matching nature. 2) In industrialized regions he is overwhelming natural processes, and the removal processes are slow enough (several days, at least) so that the increased concentration is marked for hundreds to thousands of kilometers downwind. 3) Our main areas of uncertainty, and ones that demand immediate attention because of their importance to the regional air pollution question, are: (i) the rates of conversion of H(2)S and SO(2) to sulfate particles in polluted as well as unpolluted atmospheres; (ii) the efficiency of removal of sulfur compounds by precipitation in polluted air. And for a better understanding of the global model we need to know: (i) the amount of biogenic H(2)S that enters the atmosphere over the continents and coastal areas; (ii) means of distinguishing man-made and biogenic contributions to excess sulfate in air and precipitation; (iii) the volcanic production of sulfur compounds, and their influence on the particle concentration in the stratosphere; (iv) the large-scale atmospheric circulation patterns that exchange air between stratosphere and troposphere (although absolute amounts of sulfate particles involved are small relative to the lower tropospheric burden); (v) the role of the oceans as sources or sinks for SO(2).

Air Pollution↗
PubMedDate not supplied

Solubility and cation exchange in phosphate rock and saturated clinoptilolite mixtures.

Mixtures of zeolite and phosphate rock (PR) have the potential to provide slow-release fertilization of plants in synthetic soils by dissolution and ion-exchange reactions. This study was conducted to examine solubility and cation-exchange relationships in mixtures of PR and NH4- and K-saturated clinoptilolite (Cp). Batch-equilibration experiments were designed to investigate the effect of PR source, the proportion of exchangeable K and NH4, and the Cp to PR ratio on solution N, P, K, and Ca concentrations. The dissolution and cation-exchange reactions that occurred after mixing NH4- and K-saturated Cp with PR increased the solubility of the PR and simultaneously released NH4 and K into solution. The more reactive North Carolina (NC) PR rendered higher solution concentrations of NH4 and K when mixed with Cp than did Tennessee (TN) PR. Solution P concentrations for the Cp-NC PR mixture and the Cp-TN PR mixture were similar. Solution concentrations of N, P, K, and Ca and the ratios of these nutrients in solution varied predictably with the type of PR, the Cp/PR ratio, and the proportions of exchangeable K and NH4 on the Cp. Our research indicated that slow-release fertilization using Cp/PR media may provide adequate levels of N, P, and K to support plant growth. Solution Ca concentrations were lower than optimum for plant growth.

Calcium↗