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Biomedical subjects

A G Morris

Publications and source records attributed to A G Morris.

106 records · Page 6Linked to original sources
PubMed1978

Induction of infectious virus DNA and virus particles by mitomycin C in SV40-transformed mouse cells.

A line of SV40-transformed mouse cells (SV/3T3-4E) was isolated and four clones were derived from this line. Spontaneous production of small amounts of infectious SV40 DNA was detected in the parental line and in three out of the four clones tested, although no synthesis of virions could be demonstrated. The yields of SV40 DNA were significantly enhanced following treatment of these cells with mitomycin C and infectious virus particles became detectable occasionally.

Cell Line↗
PubMed1978

Parent education in well-baby care: a new role for the occupational therapist.

Children who grow up without adequate stimulation often develop learning problems that require intensive treatment to permit them to perform at their optimum level. Many times they do not have the opportunity to make up for the experiences missed and become school drop-outs. Remedial services are time-consuming for children and wasteful of public funds, whereas preventive services enable children to achieve their intellectual potential. Occupational therapists can make an important contribution to ambulatory pediatrics because of their background in physical and mental development, as well as their expertise in planning and carrying out treatment programs. They could put these skills to good use in the pediatric clinic playroom by screening children who presentdevelopmental lags and who could then be referred for additional testing and evaluation. The playroom could extend its role to provide needed services: a base for a cognitively oriented educational program for parents of infants and toddlers; recreation activities for waiting children and their siblings; and early detection of developmental and/or emotional problems.

Adult↗
PubMed1977

Simian virus 40-Chinese hamster kidney cell interaction. III. Characteristics of chemical induction in a clone of virogenic transformed cells.

A number of chemical and physical agents were screened to determine their effectiveness in inducing simian virus (SV40) production in a virogenic clone of SV40-transformed Chinese hamster cells. Mitomycin C (MC) was the most effective inducing agent, and MC induction was further characterized. It was found that levels of infectious SV40 DNA were increased above control levels as early as 6 h after addition of MC to the culture medium and reached maximum levels by 48 h. Virus capsid (V) antigen and virions followed with a lag of about 24 h. V antigen production was sensitive to hydroxyurea, suggesting a dependence on virus DNA synthesis. The proportion of virus-producing cells (infectious centres) and the virus burst per cell were both stimulated by MC. Studies of 3H-thmidine incorporation demonstrated that the rate of SV40 DNA synthesis was maximal at 48 h post-induction, at which time cellular DNA synthesis was almost abolished. Caffeine, at doses not toxic to non-induced cells, strongly inhibited SV40production in both non-induced and induced cells, suggesting some role for DNA repair mechanisms.

Animals↗
PubMed1977

Simian virus 40-Chinese hamster kidney cell interaction. IV. Enhanced virus replication in infected cells upon treatment with mitomycin C.

Chinese hamster kidney cells are semi-permissive to simian virus 40 (SV40). Exposure to mitomycin C (MC) of Chinese hamster kidney cells infected with SV40 DNA enhanced the yield of infectious virus 10- to 100-fold. This stimulation occurred whether the treatment was performed before or after infection. A simultaneous increase in the number of V antigen-synthesizing cells and virus-producing cells, as well as the virus burst size, was observed upon MC pretreatment, whereas the proportion of T antigen-synthesizing cells remained unchanged. MC pretreatment clearly stimulated virus DNA replication in SV40 virus-infected cells. Cells treated with MC exhibited an unbalanced growth pattern, with continuing protein synthesis in the absence of cell division and a markedly reduced ability to replicate the cellular DNA. These results suggest that MC enhances the permissiveness of Chinese hamster kidney cells by inducing the synthesis of a specific cellular factor(s) required for SV40 reproduction in Chinese hamster kidney cells.

Animals↗
PubMed1976

Simian virus 40-chinese hamster kidney cell interaction. II. The semipermissivity of the cell system.

Throughout in vitro passages, Chinese hamster kidney (CHK) cells progressively lost susceptibility to SV 40 virus infection while remaining continuously susceptible to viral DNA infection. Upon infection with SV 40 virus or viral DNA, the CHK cell line supported viral DNA and virus replication at a low level. SV 40 transformed CHK cell lines spontaneously produced small amounts of viral DNA and virions. The percentage of virus-producing cells was low. Various clones derived from each of these lines behaved as the parental cell population, leading to the conclusion that each CHK cell, whether transformed or not with SV 40, is potentially permissive for this virus.

Animals↗
PubMed1976

Educational intervention for preschool children in a pediatric clinic.

A parent education program aimed at promoting cognitive development in 2- and 3-year-olds was instituted in both a pediatric clinic of a general hospital and a child health station in the community. Parent participants were asked to work at home daily with their children using age-graded play materials supplied by the program. They were tutored individually, in the clinic playroom, by bilingual playroom assistants using role-playing techniques. One hundred fifty children completed the program out of a total of 468. Subjects were tested before and after training on the Cattell: Stanford-Binet and showed a positive gain in performance. Parents reported that their program experiences made them aware of their ability to teach their children. This was reflected in their changing view of the children's activities which were previously seen as aimless and "bad" and were now viewed as constructive and amenable to modification by the parents.

Child Development↗
PubMed1975

Simian virus 40-chinese hamster kidney cell interaction. I. Relationship of chromosome changes to transformation.

After approximately 20 in vitro passages, Chinese hamster kidney (CHK) cell cultures transformed upon exposure to different strains of SV 40 can show a diploid modal chromosome number of 22 with chromosome counts exclusively or essentially in the diploid range (20-25). In primary culture and at the 5th-7th subculture, tumors produced in nude mice by such cells can display a diploid modal value of 22 chromosomes. Numerical chromosome variations and karyotype abnormalities observed in CHK cells transformed upon infection with SV 40, are apparently indistinguishable from those that can be observed in uninfected CHK cells undergoing "spontaneous"-transformation. These results indicate that polyploidization is not a necessary step either in the process of transformation or in that of tumorigenic conversion with SV 40.

Animals↗
PubMed1975

The induction of SV40-transformed chinese hamster and mouse kidney cells by mitomycin C.

The induction by mitomycin C (MC) of SV40 production in three lines of semi- or nonpermissive SV40-transformed cells is described. The production of virions by a line of semipermissive, virus-shedding Chinese hamster kidney cells is increased 1,000-fold by MC treatment; the proportion of infectious centers and V-antigen-containing cells is increased to a lesser degree, suggesting that both the burst per cell and the number of virus-producing cells are increased. MC treatment induces the production of small amounts of infectious DNA and virions in one line of nonpermissive mouse kidney cells, and infectious DNA apparently alone in another.

Animals↗