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Biomedical subjects

C Knutson

Publications and source records attributed to C Knutson.

9 recordsLinked to original sources
PubMed2006

Nonlinear domain-wall velocity enhancement by spin-polarized electric current.

The interaction between a dc spin-polarized electric current and a magnetic domain wall in a Permalloy nanowire was studied by high-bandwidth scanning Kerr polarimetry. The full functional dependence of wall velocity on electric current and magnetic field is presented. With the pinning potential nulled by a field, current-induced velocity enhancements exceeded 35 m/s at a current density of approximately 6 x 10(11) A/m(2). This large enhancement, more than 10 times that found in pinning-dominated experiments, results in part from an interaction that is nonlinear in current and independent of current direction.

Journal Article↗
PubMed1998

Child and adolescent traumatic brain injury: correlates of injury severity.

A record review focused on children and adolescents, with a history of traumatic brain injury, who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. Significant correlates of severity of injury in the cognitive, education and communication domains of functioning included Performance IQ but not Verbal IQ nor standardized ratings of language or learning disability. Current organic personality syndrome (OPS) but not attention deficit hyperactivity disorder or oppositional defiant disorder/conduct disorder diagnostic status was significantly related to severity. In conclusion, the findings in this referred sample are similar to prospective studies indicating that Performance IQ appears sensitive in reflecting brain damage. The finding linking OPS to severity of injury is not surprising. This is because OPS is a diagnosis which is dependent on the clinician's judgment of the likelihood that the organic factor is etiologically related to a defined behavioural syndrome. The diagnosis therefore requires a clinical judgment that the threshold of severity of a presumed organic etiological factor has been reached.

Adolescent↗
PubMed1998

Child and adolescent traumatic brain injury: correlates of disruptive behaviour disorders.

A record review focused on children and adolescents, with a history of traumatic brain injury (TBI), who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. Correlates of post-injury oppositional defiant disorder/conduct disorder (ODD/CD) and post-injury attention deficit hyperactivity disorder (AHD) were investigated. Subjects who developed ODD/CD following TBI, when compared to subjects without a lifetime history of the disorder, had significantly more impaired family functioning, showed a trend toward a greater family history of alcohol dependence/abuse and suffered a milder TBI. In contrast, there were no variables which discriminated between subjects who developed ADHD following injury and those with no lifetime history of ADHD. It is difficult to determine whether ODD, CD and ADHD occurring after TBI in the patient is related to the TBI, directly or indirectly. Appropriate clinical assessment requires consideration of the important mediating role of family functioning, severity of injury and family psychiatric history.

Adolescent↗
PubMed1997

Child and adolescent traumatic brain injury: psychiatric findings from a paediatric outpatient specialty clinic.

A record review focused on children and adolescents, with a history of traumatic brain injury, who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. The development of a 'novel' psychiatric disorder (not present before injury) occurred in 76% (38/50) of the cohort and was correlated significantly with family psychiatric history and family function, but not with severity of injury, preinjury psychiatric status, intellectual/educational functioning, or socioeconomic status. Psychiatric consultation is often necessary in this paediatric population even though much of the psychopathology, particularly following mild injury, may not be directly related to brain trauma.

Adolescent↗
PubMed1993

Tetrasomy 9p: tissue-limited idic(9p) in a child with mild manifestations and a normal CVS result. Report and review.

Supernumerary isochromosomes resulting in autosomal tetrasomy are rare and have been described only for 12p, 18p, and 9p. Nineteen previous cases of tetrasomy 9p have been reported, and in 6 cases, tissue-specific mosaicism was implied with the i(9p) cell line present exclusively or predominantly in blood. We report on an infant who had apparently normal chromosomes (46,XY) on CVS. He was referred for genetic evaluation because of mild developmental delay and minor anomalies. In 75% of blood cells he had an extra isodicentric 9p chromosome (pter-->q12-->pter). The interpretation of tetrasomy 9p was confirmed by elevated GALT activity. No tetrasomy 9p cells were seen in 100 skin fibroblasts. This case demonstrates the tissue specific mosaicism in tetrasomy 9p which rendered the anomaly undetectable by CVS. It also demonstrates the mild end of the clinical spectrum associated with tetrasomy 9p.

Chromosome Aberrations↗
PubMed1989

Utilization of amniocentesis and chorionic villus sampling by South Carolina women 35 years of age and older.

An increase in utilization of prenatal diagnosis was observed from 1985 to 1986 in South Carolina. The overall rate of 39.9% for 1986 is comparable with other areas of the U.S. Utilization was correlated with geographic residence, race, and referral source. While there was considerable variation in prenatal diagnostic test utilization between counties in South Carolina, overall utilization rates were reasonably high and continued to increase from 1985 to 1986. It will be interesting to see what effect CVS has on overall utilization rates as this new procedure becomes more established throughout the state.

Adult↗
PubMed1985

Immunological aspects of type 1 and 2 diabetes mellitus.

IDDM occurs predominantly among individuals being class II antigen HLA-DR 3 and/or 4 positive, while NIDDM is not associated with HLA-D. Although the HLA-DR 3 or 4 specificities are prerequisites for IDDM to develop, their high frequencies (about 60%) in the background population preclude tissue typing as a predictive test, underlined by the observation that less than 50% of monozygotic twins are concordant for IDDM. The presence of a number of immune abnormalities argues that the causes of IDDM may be sought in an altered immune reaction against antigens present in the pancreatic B cells and/or in the environment. The majority of IDDM patients of short duration show both cellular and humoral autoimmunity against the pancreatic B cells. Similar phenomena may be observed in patients initially diagnosed as NIDDM and treated with oral hypoglycemic agents. It has been speculated that these patients have a retarded form of IDDM. It is possible that the combination of specific Class II antigen molecule(s) and an invading antigen (virus, bacterium, chemical etc.) presented to the immune system triggers the formation of effector cells such as B lymphocytes and cytotoxic T lymphocytes which also cross-react with the pancreatic B cells. Multiple exposures to this or related antigens throughout several years may eventually lead a sufficient loss of pancreatic B cells to cause insulin dependence.

Antibody Formation↗