PubMed Health⌕ Search

Biomedical subjects

J P Carroll

Publications and source records attributed to J P Carroll.

16 recordsLinked to original sources
PubMed1999

Radiation-resistant and radiation-sensitive forms of host resistance to polyomavirus.

Newborn mice of several inbred strains develop few or no tumors following inoculation with highly tumorigenic strains of polyomavirus. Here we show that such resistant strains can be divided into two groups based on the responses of adult mice to radiation followed by virus inoculation. Most strains show a radiation-sensitive form of resistance (Rr-s) and develop tumors following radiation and virus challenge. This type of resistance has previously been recognized as immunological, based on T-cell responses against virus-encoded neoantigen(s) expressed in tumor cells. Other strains exhibit a radiation-resistant form of resistance (Rr-r) and fail to develop tumors when treated in the same manner. Three additional properties of Rr-r mice distinguish them from Rr-s mice: (i) survival of newborns following inoculation with a highly virulent and usually lethal strain of virus, (ii) resistance to virus spread in newborns inoculated with either tumorigenic or virulent virus strains, and (iii) dominant or semidominant transmission of resistance in crosses with a highly susceptible strain. The Rr-r phenotype reflects a constitutive nonimmunological type of resistance that is targeted to the virus and blocks its dissemination.

Animals↗
PubMed1995

Susceptibility to tumors induced by polyoma virus is conferred by an endogenous mouse mammary tumor virus superantigen.

A dominant gene carried in certain inbred mouse strains confers susceptibility to tumors induced by polyoma virus. This gene, designated Pyvs, was defined in crosses between the highly susceptible C3H/BiDa strain and the highly resistant but H-2k-identical C57BR/cdJ strain. The resistance of C57BR/cdJ mice is overcome by irradiation, indicating an immunological basis. In F1 x C57BR/cdJ backcross mice, tumor susceptibility cosegregates with Mtv-7, a mouse mammary tumor provirus carried by the C3H/BiDa strain. This suggests that Pyvs might encode the Mtv-7 superantigen (SAG) and abrogate polyoma tumor immunosurveillance through elimination of T cells bearing specific V beta domains. DNA typing of 110 backcross mice showed no evidence of recombination between Pyvs and Mtv-7. Strongly biased usage of V beta 6 by polyoma virus-specific CD8+ cytotoxic T lymphocytes in C57BR/cdJ mice implicates T cells bearing this Mtv-7 SAG-reactive V beta domain as critical anti-polyoma tumor effector cells in vivo. These results indicate identity between Pyvs and Mtv-7 sag, and demonstrate a novel mechanism of inherited susceptibility to virus-induced tumors based on effects of an endogenous superantigen on the host's T cell repertoire.

Animals↗
PubMed1994

A method to describe corneal topography.

Most commercially available corneal topographers produce color-coded maps of the cornea. Although these maps are clinically useful, more precise quantitative methods for the analysis of corneal topographic data are needed. The purpose of this work is to apply a method, known as an expansion in a complete set of functions, to this problem. This method leads to a set of parameters which are a direct extension of the common clinical method of describing corneal topography in terms of the corneal sphere power, cylinder power, and cylinder axis. To illustrate this approach, data were gathered on three subjects with the TMS corneal topographer and the parameters were estimated using linear regression procedures.

Astigmatism↗
PubMed1993

Pyvs: a dominantly acting gene in C3H/BiDa mice conferring susceptibility to tumor induction by polyoma virus.

Results in a previous report established the presence of dominant genetic factor(s) in C3H/BiDa mice which contributed to the unusually high susceptibility of this strain to polyoma virus-induced tumors (Freund et al. (1992) Virology 191, 724-731). Here we show that C57BR/cdJ mice, while identical to C3H/BiDa at the H-2 locus, are almost completely lacking in susceptibility. Analysis of crosses between these two H-2k strains has shown that susceptibility is due to a single dominant autosomal gene, designated Pyvs. On an H-2k background, Pyvs acts in a highly penetrant manner to confer susceptibility to induction of a broad range of tumors by the virus. Analysis of F1 mice between C3H/BiDa and the highly resistant C57BL/6 (H-2b) strain shows that Pyvs can partially overcome the immunologically mediated resistance associated with an H-2b haplotype. Pyvs does not encode cell receptors for the virus, nor does it affect levels of virus replication or anti-viral humoral responses in the host. Studies with early passage embryo fibroblasts in culture show that Pyvs does not affect intracellular events essential for either productive infection or cell transformation by the virus. Pyvs thus determines a generalized susceptibility of the host to polyoma-induced tumors but apparently does not act at the level of target cells for tumor induction.

3T3 Cells↗
PubMed1992

Changes in frequency, morphology, and behavior of tumors induced in mice by a polyoma virus mutant with a specifically altered oncogene.

Alterations in the tumor-inducing ability of a polyoma virus mutant encoding a partially defective middle T oncogene have been investigated. The mutant middle T associates with and activates the tyrosine protein kinase pp60c-src normally but does not promote binding of a second enzyme, phosphatidyl-inositol 3-kinase. Compared with the wild type virus, this mutant shows an altered and reduced ability to induce tumors after inoculation into newborn mice, as judged by the following criteria: lower frequency of tumors, reduced morbidity and increased survival times of host mice, changes in the spectrum of tumor types, and altered morphologic properties of tumors at several target organ sites. These results indicate an important role of changes in 3-phosphoinositide metabolism in induction of a variety of tumors in this experimental system.

Animals↗
PubMed1982

Component and correlation ametropia.

The average axial length for eyes grouped according to refractive error must vary as a function of refractive error. In fact, this change in the average axial length can account almost totally for the change in refractive error. This finding is incompatible with the usual interpretation of correlation ametropia. When the categorization of eyes is based on axial length rather than on refractive error, then a more statistically meaningful division of eyes into component and correlation categories is achieved.

Analysis of Variance↗
PubMed1982

Control theory approach to accommodation and vergence.

A control theory model that treats the accommodative system and the vergence system each as negative feedback systems is investigated. The effects of accommodative vergence and vergence accommodation are included. The controllers in this model are assumed to be linear time-invariant operators. Only time-independent stimuli are considered. If vergence accommodation is neglected, the model is consistent with classical graphical analysis. By including vergence accommodation, several important changes occur. Disparity vergence is not, in general, equal to the dissociated phoria. The shape of the zone of single, clear, binocular vision is changed. Instabilities in the system arise.

Accommodation, Ocular↗
PubMed1981

Regression curves for the optical parameters of the eye.

Based on the data collected by Stenstrom (1948), the regression curves involving refractive error and axial length are examined. The regression of refractive error on axial length is shown to be nonlinear; it curves upward at low axial lengths and downward at high axial lengths. It is shown that this curve can be partially accounted for by the lack of compensating corneal changes for extreme values of the axial length. On the other hand, the regression of axial length on refractive error, is shown to be approximately linear. The slope of this regression is related to a formula derived from geometrical optics.

Cornea↗
PubMed1981

Depth of field for the presbyope.

As a general rule the near addition (add) for a presbyope is selected so that the range of clear vision is dioptrically and not linearly balanced. Implicit in such thinking is the assumption that the dioptric and linear range of clear vision cannot be simultaneously balanced. Assuming that the range of clear vision for the absolute presbyope is due to depth of field and assuming also that the blur circle theory adequately describes the limits of depth of field, I will show that the dioptric and linear range of clear vision can indeed be simultaneously balanced. The results are independent of the actual position of the reference plane from which the measurements are made.

Accommodation, Ocular↗
PubMed1980

Geometrical optics and the statistical analysis of refractive error.

Relationships among statistical quantities used in the analysis of refractive error are derived from geometrical optics principles. The accuracy of these results are verified using the data of Sorsby et al. As an application of these results, it is shown that there is difficulty in accounting for leptokurtosis of refractive error in terms of correlation among the optical parameters of the eye. Also, it is shown that the distribution of the optical parameters of the eye cannot be a joint-normal distribution.

Humans↗
PubMed1980

Apodization model of the Stiles-Crawford effect.

Several implication of Metcalf's apodization model of the Stiles-Crawford effect are presented in this paper. Metcalf showed that there should be a slight smearing of the point-spread function due to the Stiles-Crawford effect. It will be shown that this smearing is approximately equal to the size of a foveal cone. As an abvious consequence of this smearing, there is a decrement in the dodulation transfer function for high spatial frequecies. But unexpectedly, there is an increment in the MTF for low spatial frequencies.

Humans↗
PubMed1976

Blurred imagery and the cylinder sine-squared law.

The sine-squared law is shown to describe changes in spherical power which either minimize the blur or maximize the visibility of gratings oriented at various angles to the principal meridians of an astigmatic eye. These results help justify the use of the sine-squared law in applications such as meridional refraction. This derivation and its interpretation is quite different from the usual approach which emphasizes the meridional changes in curvature of a toric surface.

Astigmatism↗
PubMedDate not supplied

Nonstationary properties of postural sway.

Postural sway during quite stance is usually assumed to be a stationary stochastic process. We tested this assumption by investigating the time invariance of the average value and variance of the postural sway of three subjects. The sway was measured with a force plate under three conditions: subject standing on two feet with eyes open; subject standing on two feet with eyes closed; and subject standing on one foot with eyes open. Data were collected in 1 min runs. More than 50 min of data were collected for each subject under each test condition. The data were averaged across all runs for each subject and condition. Trends were found to be present in the data. In addition, there were initial transient increases in the second-order moments about the trends. The transient changes in first- and second-order moments usually disappeared during the first 20 s. In light of these findings, we can reject the hypothesis that postural sway is a stationary process. The results imply that the usual methods to parameterize postural sway have to be either changed or reinterpreted.

Adult↗