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Biomedical subjects

T E Johnson

Publications and source records attributed to T E Johnson.

At least 127 records · Page 7Linked to original sources

Ganglioglioma of the optic nerve.

We examined a 15-year-old boy who had a ganglioglioma involving the left optic nerve, which caused proptosis, decreased vision, and optic atrophy. Computed tomography demonstrated an intraconal mass along the course of the orbital portion of the optic nerve. The only evidence of systemic neurofibromatosis was axillary freckling. The patient underwent a combined medial and lateral orbitotomy and excision of the tumor. Histologic examination demonstrated a mass composed of neurons and glial cells characteristic of ganglioglioma. After a one-year follow-up period, we have found no evidence of recurrence.

Adolescent↗

Long-lived lines of Caenorhabditis elegans can be used to establish predictive biomarkers of aging.

Long-lived recombinant inbred lines, some of which have mean and maximum life spans up to 70% longer than wild type, were used in these analyses. Longer life results from a slower exponential rate of increase in mortality. General motor activity decreases with chronological age in all genotypes; this decay in general motor activity is a biomarker of aging in that it is a predictor of maximum life span. The aging process has also been dissected into component processes. The length of development and the length of reproduction are unrelated to increased life span; lengthened life is due entirely to an increase in post-reproductive life span. Development, reproduction, and life span are each under independent genetic control. General motor activity and life span share at least one common rate-determining genetic component.

Aging↗

Aneurysmal bone cyst of the orbit.

Proptosis of the left eye had developed in a 42-year-old woman for 2 months' duration. Roentgenogram studies showed a mass in the roof of the left orbit and bone erosion. An excisional biopsy confirmed the presence of an aneurysmal bone cyst. To the authors' knowledge, the patient is the oldest reported patient who has this uncommon orbital lesion.

Adult↗

A mutation in the age-1 gene in Caenorhabditis elegans lengthens life and reduces hermaphrodite fertility.

age-1(hx546) is a recessive mutant allele in Caenorhabditis elegans that results in an increase in mean life span averaging 40% and in maximal life span averaging 60% at 20 degrees; at 25 degrees age-1(hx546) averages a 65% increase in mean life span (25.3 days vs. 15.0 days) and a 110% increase in maximum life span (46.2 days vs. 22.0 days for wild-type hermaphrodites). Mutant males also show extended life spans. age-1(hx546) is associated with a 75% decrease in hermaphrodite self-fertility as compared to the age-1+ allele at 20 degrees. Using two novel strategies for following the segregation of age-1, we present evidence that longer life results from a mutation in a single gene that increases the probability of survival at all chronological ages. The long-life and reduced-fertility phenotypes cosegregate and are tightly linked to fer-15, a locus on linkage group II. age-1(hx546) does not affect the timing of larval molts, the length of embryogenesis, food uptake, movement, or behavior in any way tested. Although age-1(hx546) lowers hermaphrodite self-fertility, it does not markedly affect the length of the reproductive period with all the increase in life expectancy due to an increase in the length of postreproductive life. In so far as we are aware, this mutant in age-1 is the only instance of a well-characterized genetic locus in which the mutant form results in lengthened fife. It is likely that the action of age-1 in lengthening life results not from eliminating a programmed aging function but rather from reduced hermaphrodite self-fertility or from some other unknown metabolic or physiologic alteration.

Alleles↗

Three mutants that extend both mean and maximum life span of the nematode, Caenorhabditis elegans, define the age-1 gene.

Long-lived mutants in the nematode Caenorhabditis elegans have been studied to determine if the mutations responsible for extended life were allelic. Three of four mutant strains studied (MK31, MK542, MK546) contain recessive mutations that significantly lengthen life; MK542 and MK546 consistently fail to complement the long life phenotype of age-1 and are therefore allelic. MK31, although longer lived than wild type, is equivocal, in some cases failing to complement age-1 but not in others. All three long-lived strains have reduced hermaphrodite self-fertility and also fail to complement for this presumed pleiotropic effect of the age-1 mutation. Each of these three strains also contains an independent mutation at unc-31 IV. Since the mutants were isolated in the same mutant hunt (Klass, 1983) using protocols that did not guarantee independence, the mutations cannot be assumed to be independently isolated.

Aging↗

Radiation effects on life span in Caenorhabditis elegans.

Wild-type and radiation-sensitive (Rad) mutants of Caenorhabditis elegans were irradiated using a 137Cs source (2.7 krads/min.) at several developmental stages and subsequently monitored for life span. Acute doses of radiation ranged from 1 krad to 300 krads. All stages required doses above 100 krads to reduce mean life span. Dauers and third stage larvae were more sensitive, and 8-day-old adults were the most resistant. Occasional statistically significant but nonrepeatable increases in survival were observed after intermediate levels of irradiation (10-30 krads). Unirradiated rad-4 and rad-7 had life spans similar to wild-type; all others had a significant reduction in survival. The mutants were about as sensitive as wild-type to the effects of ionizing radiation including occasional moderate life span extensions at intermediate doses. We conclude that the moderate life span extensions sometimes observed after irradiation are likely to be mediated by a means other than the induction of DNA repair enzymes.

Animals↗

Aging can be genetically dissected into component processes using long-lived lines of Caenorhabditis elegans.

The aging process has been dissected by analysis of genetic variants of the nematode Caenorhabditis elegans. Long-lived recombinant inbred lines were generated; some of these lines have mean and maximum life spans up to 70% longer than wild type. Longer life results from a slowing of the characteristic exponential increase in mortality rate that is typical of aging populations in all species. The length of developmental periods and the length of the reproductive period are unrelated to increased life span. Lengthened life is due entirely to an increase in postreproductive life span. Development, reproduction, and life span are each under independent genetic control. General motor activity decays linearly with chronological age in all genotypes. The decay in general motor activity is correlated with and a predictor of life span, suggesting that both share at least one common rate-determining component.

Aging↗

Caenorhabditis elegans DNA does not contain 5-methylcytosine at any time during development or aging.

DNA, isolated from age-synchronous senescent populations of Caenorhabditis elegans has been quantitatively and qualitatively analyzed for the presence of 5-methylcytosine. High performance liquid chromatography on two wild-type and several mutant strains of C. elegans failed to detect any 5-methylcytosine. The restriction endonuclease isoschizomers, HpaII and MspI, were used to digest genomic DNA after CsCl purification and failed to detect any 5' cytosine methylation at any age. We conclude that C. elegans does not contain detectable (0.01 mole percent) levels of 5-methylcytosine.

5-Methylcytosine↗

Optic nerve sheath and retinal hemorrhages associated with the shaken baby syndrome.

A 13-month-old child with the pathognomonic findings of the shaken baby syndrome died secondary to cerebellar herniation. Pathologic examination disclosed extensive intraocular, optic nerve sheath, and intracranial hemorrhages, despite a paucity of external signs of trauma. Many of the hemorrhages were old, suggesting that the child had experienced multiple episodes of trauma. Hemorrhages of the optic nerve sheaths have not been previously reported with the shaken baby syndrome but probably accompany this condition frequently. Our patient's ocular hemorrhages may have resulted from a sudden rise in intracranial pressure.

Child Abuse↗

Mitigating circumstance information, censure, and aggression.

One hundred men received one of two levels of mitigating circumstance information either before or after being insulted or not insulted by a co-worker. Participants were then provided with an opportunity ostensibly to deliver aversive noise to the co-worker under either high or low social censure conditions. Physiological data and self-report measures revealed that participants who learned of mitigating circumstance information before being provoked exhibited smaller increases in physiological arousal and reported less annoyance than did those who learned of mitigating circumstance information after insult. Aggression data showed that angered participants evaluated their provoker more favorably and retaliated less when they learned of mitigation before rather than after being insulted. These findings supported attribution theory assumptions that mitigating circumstance information known before the provoking incident influences the individual's interpretation of harm, thereby reducing anger and the instigation to aggression. The reduced impact of information on aggression that is acquired after provocation may reflect the provoked individual's shift of attention from cues surrounding harm to a consideration of inhibitory factors for aggression.

Adult↗

Programmed aging or error catastrophe? An examination by two-dimensional polyacrylamide gel electrophoresis.

We have examined newly synthesized proteins in the young adult and in older populations of the nematode Caenorhabditis elegans using two-dimensional polyacrylamide gel electrophoresis (2D PAGE). A temperature-sensitive mutant strain, DH26, with a mean life span of about 15 days, under our conditions, was used to block progeny development. Nematodes of several different ages were pulse-labeled for 5 h, in vivo, with 35S-labeled E. coli, A subsequent 30-min chase with unlabeled E. coli served to rid the worms of endogenous labeled E. coli proteins. We resolve 700 or more proteins by 2D PAGE polyacrylamide gel electrophoresis of extracts of young nematodes. The patterns of these proteins are highly reproducible in comparisons of independent repeats of identical experiments. No new major proteins are synthesized at any time during the adult phase (4-22 days) nor are any of the most abundant proteins not made during this period. At our level of detectability (estimated as a satellite spot containing 4% of the amount of label in a major spot) we see no misincorporation of radioactive amino acids into newly synthesized proteins. These data are inconsistent with predictions by any one of several, so called, "error catastrophe" models of senescence and also show that modulation of the highest abundancy classes of proteins are also not involved in senescence.

Aging↗

The assessment of two methods for removing eye movement artefact from the EEG.

A quantitative assessment of both computerised correlation and analogue techniques for the removal of eye movement artefact from the electroencephalogram was undertaken. In both methods a fraction of the measured EOGs was subtracted from the measured EEG to leave the corrected EEG. In the correlation method the correction factors were computed from the cross-correlations of the EOGs and measured EEGs. In the analogue method the fraction subtracted was derived using a potential divider arrangement. The relative effectiveness of the two methods was determined by comparing the autocorrelation functions of the corrected EEGs at a lag of 2 sec. It was found that the computerised correlation technique was superior. A 3-channel EOG correlation correction procedure was found adequate in which two horizontal and one vertical EOGs were used. The analogue technique was very time consuming and possibly erroneous.

Electroencephalography↗

Arresting development arrests aging in the nematode Caenorhabditis elegans.

Larval development of the nematode, Caenorhabditis elegans, can be arrested by either of two different treatment: (1) complete starvation, or (2) growth in a partially defined culture medium (axenic medium) of strains adapted to bacterial growth. The developmental arrest is complete under total starvation and the starved populations live about 10 days. The developmental block is incomplete in axenic medium; most animals mature but maturation takes 10 times longer than normal. If developmentally arrested cultures are returned to growth on E. coli, both the completely starved and the axenically arrested cultures mature at normal rates. Life-span is prolonged by 1 day for each day of complete starvation; life-span is prolonged by 0.7 days for each day of axenic arrest. These results suggest that aging and development are closely coupled in this system. The results are discussed in terms of previous observations on nutritional deprivation in other invertebrates and caloric restriction in mammals and are interpreted in light of theoretical models of senescence.

Aging↗

The uptake of plutonium-238, 239, 240, americium-241, strontium-90 and caesium-137 into potatoes.

Transfer factors have been measured for 239 Pu + 240 Pu, 241 Am, 90 Sr and 137 Cs into potatoes grown in a blend of soil which included silt polluted with radioactive waste discharged into the Irish Sea. The experiment has been carried out over four seasons and attempts to assess the radiological consequences to the consumer which would arise if potatoes were to be grown in land heavily contaminated with the silt. During the course of the experiment plutonium and americium became less available for uptake, 90 Sr became slightly more available and 137 Cs remained nearly constant in its availability. The values of the transfer factors are among the lowest reported for these radionuclides into potatoes.

Americium↗