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Biomedical subjects

J R Allen

Publications and source records attributed to J R Allen.

At least 253 records · Page 14Linked to original sources
PubMed1975

Distribution and metabolism of 3H-2,5,2',5'-tetrachlorobiphenyl in rats.

Distribution and metabolism of an isomeric polychlorinated biphenyl were determined in rats. Over 70% of a single dose of 3H-2,5,2',5'-tetrachlorobiphenyl was excreted in the feces and another 13% in the urine during a 14-day period. Adipose tissue, blood, skin, and liver were found to contain low levels of the compound. Over 90% of the excreted tritiated compound was found to be metabolized, the major metabolite being identified as 3-OH-2,5,2',5'-tetrachlorobiphenyl. All of the unmetabolized 2,5,2',5'-tetrachlorobiphenyl was eliminated by the alimentary route.

Adipose Tissue↗
PubMed1975

Urinary metabolites of 2, 5, 2', 5'-tetrachlorobiphenyl in the nonhuman primate.

The metabolism of 2, 5, 2', 5'-tetrachlorobiphenyl (TCB) in nonhuman primates was found to be different from that previously reported in lower species. Monohydroxy TCB (I), the only metabolite in the ether extracts of rat urine, is a minor metabolite in the urine of nonhuman primates. The two major metabolites identified in the urine were dihydroxy TCB (II) and trans-3,4-dihydro-3,4-dihydroxy TCB (III). A second minor metabolite was identified as hydroxy-3,4-dihydro-3,4-dihydroxy TCB (IV). None of the above mentioned metabolites have been reported in primates and only I and III have been identified in lower animals. It is concluded that a likely mechanism for metabolism of TCB in primates is through arene oxide intermediates. This observation is of particular importance in that these types of intermediates are known to alkylate cellular components causing carcinogenic, mutagenic, necrogenic and teratogenic effects.

Animals↗
PubMed1975

Optometric manpower resources--1973. Part II.

The Optometric Manpower Resources Project, funded under government contract since June of 1971, has completed its 1973 national census of licensed optometric manpower in the United States. The first article in this series of three reported on the distribution of optometrists by census region and the current ratio of practicing optometrists to civilian population. This second article reports on the principal forms of employment of active optometrists, the distribution of number of years in practice and practice size. The data indicate that there has been a shift away from self-employment (88% in 1968, 77% in 1973) into more varied forms of salaried employment, especially among those in practice fewer than ten years. Practice size is shown to peak at between fifteen and twenty-four years in practice with a median of approximately 5,400 patients.

Female↗
PubMed1975

Optometric manpower resources--1973. Part III.

The Optometric Manpower Resources Project, funded under government contract since June of 1971, has completed its 1973 national census of licensed optometric manpower in the United States. The first article in this series of three reported on the distribution of optometrists by census region and the current ratios of practicing optometrists to civilian population. The second article reported on the principal forms of employment of active optometrists, the number of years in practice and practice size. This third article reports on the age and sex distributions of licensed optometrists, their racial/ethnic composition, their pattern of specialization, and the schools/colleges of optometry from which they graduated. The data indicate that almost 50% of active optometrists were over 50 years of age. Approximately 90% of male optometrists and only 58.5% of female optometrists were active. The data also indicate that one-third of all optometrists active in 1973 graduated from four schools/colleges of optometry.

Age Factors↗
PubMed1975

Dehydroretronecine-induced rhabdomyosarcomas in rats.

Two groups of rat were given s.c. injections of either monocrotaline or its major detectable metabolite, dehydroretronecine, biweekly for 1 year. Tissues obtained from partial hepatectomies performed at 4 months on a portion of these animals showed that both compounds caused a decided inhibition of mitotic division in regenerating liver. Rhabdomyosarcomas developed at the site of dehydroretronecine injection in 51.6% of the rats and in 3.3% of the monocrotaline-treated rats. Metastatic lesions were recorded in 8.3% of these animals. In addition to the above, 10% of the monocrotaline-treated rats developed other tumors that included myelogenous leukemias, hepatocellular carcinomas, and pulmonary adenomas. These data indicate that either monocrotaline or its metabolite dehydroretronecine are capable of causing neoplastic transformations in the tissues of experimental animals.

Animals↗
PubMed1975

Growth and development of the fetal Rhesus monkey. VI. Morphometric analysis of the developing lung.

Groups of fetal monkeys were studied at 50, 75, 100, 125 and 150 days gestational age, and postnatal monkeys were studied at 175 days gestational age and in adult life (full term gestation is 168 plus or minus 4 days). The ratios between the various tissues of which lung is composed were determined by light and electronmicroscopy. Characteristic changes in ratios were noted at each developmental age. Primitive bronchioles increased from 50 to 75 days, decreased as permanent bronchioles, alveolar ducts and alveoli developed, and were absent after 150 days. Mesenchymal tissue decreased progressively from 50 to 150 days. Alveoli were present at 100 days gestational age; alveolar lumens accounted for approximately 1/2 the volume of peripheral lung by 150 days, and 2/3 the volume of lung in adult animals. By 150 days alveolar epithelial cells could be identified as Type I (membranous) or Type II (granular) on the basis of the characteristic cytoplasmic lamellar inclusion bodies of the latter. The ratios of the Type II/Type I cells were .21-.23 at 150 and 175 days, and fell to approximately half that value in adult lungs.

Animals↗
PubMed1975

Binding of tritiated dehydroretronecine to macromolecules.

In vivo and in vitro experiments have shown that the pyrrolizidine alkaloid metabolite dehydroretronecine binds readily to macromolecules. In the in vivo experiment there was a preferential binding of dehydroretronecine to the gastric mucosa. Further extraction of the mucosa revealed a large percentage of the 3H was bound to the protein fraction and to a much lesser extent to DNA and RNA. The influence of pH on the binding of dehydroretronecine was substantiated in the in vitro experiment. Dehydroretronecine bound to calf thymus DNA and bovine serum albumin most readily under acidic conditions. These data suggest a direct correlation of the levels of dehydroretronecine binding to cellular macromolecules with the lesions that develop in affected organs.

Animals↗
PubMed1974

Pathobiological and behavioral effects of lead intoxication in the infant rhesus monkey.

When infant rhesus monkeys were exposed to lead via the addition of lead acetate (0.5-9 mg/kg body weight) to their formula or by the consumption of lead particles from lead-based surrogate mothers, they developed symptoms of lead intoxication within 6 weeks. Seizures, muscular tremors, and altered social interaction were the predominant changes. Visual impairment was also apparent in the more severely affected animals. In the animals showing obvious symptoms lead levels varied between 300 to 500 mug/100 ml of blood. Even in those animals having blood lead levels below 100 mug, hyperactivity and insomnia were observed. When the exposure to lead was eliminated, seizures subsided and visual impairment was reduced; however, the abnormal social interaction persisted. These animals also experienced a gradual decline in hematocrit and hemoglobin values during the period of examination. Liver and kidney biopsies obtained from these lead-exposed animals revealed characteristic intranuclear inclusions.When adolescent and adult monkeys were exposed to doses of lead acetate similar to those employed in the infant experiments, lead levels in excess of 200 mug/100 ml of blood were recorded. However, there were no obvious behavioral abnormalities observed. There were, however, numerous lead inclusion bodies in kidney biopsy specimens from these animals. These data suggest that, like man, the infant nonhuman primate is much more susceptible to lead intoxication than is the adult. The clinical and behavioral changes recorded in these infant rhesus monkeys suggest their use as an experimental model to evaluate lead intoxication.

Administration, Oral↗