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Biomedical subjects

Andrew M Johnson

Publications and source records attributed to Andrew M Johnson.

12 recordsLinked to original sources
PubMed2007

Natural course of fever during influenza virus infection in children.

During the 2001-2002 epidemic of influenza virus A/H1N1, A/H3N2, and B, the authors obtained detailed profiles of fever from 118 infected children. The only treatment given was acetaminophen for temperatures greater than 39.0 degrees C. Fever was most prominent in A/H3N2 and young children. Secondary fever was observed frequently at 72 to 132 hours in all types. The duration of fever was associated negatively with the age of the child and positively with the maximal temperature. The information will be no longer available in current era of oseltamivir therapy.

Acetaminophen↗
PubMed2005

Nerve growth factor increases connexin43 phosphorylation and gap junctional intercellular communication.

The function of gap junctions is regulated by the phosphorylation state of their connexin subunits. Numerous growth factors are known to regulate connexin phosphorylation; however, the effect of nerve growth factor on gap junction function is not understood. The phosphorylation of connexin subunits is a key event during many aspects of the lifecycle of a connexin, including open/close states, assembly/trafficking, and degradation, and thus affects the functionality of the channel. PC12 cells infected with connexin43 (Cx43) retrovirus were used as a neuronal model to characterize the signal transduction pathways activated by nerve growth factor (NGF) that potentially affect the functional state of Cx43. Immunoblot analysis demonstrated that Cx43 and the mitogen-activated protein kinase (MAPK), ERK-1/2, were phosphorylated in response to TrkA activation via NGF and that phosphorylation could be prevented by treatment with the MEK-1/2 inhibitor U0126. The effects of NGF on gap junction intercellular communication were examined by monitoring fluorescence recovery after photobleaching PC12-Cx43 cells preloaded with calcein. Fluorescence recovery in the photobleached area increased after NGF treatment and decreased when pretreated with the MEK-1/2 inhibitor U0126. These data are the first to show a direct signaling link between neurotrophins and the phosphorylation of connexin proteins through the MAPK pathway resulting in increased gap junctional intercellular communication. Neurotrophic regulation of connexin activity provides a novel mechanism of regulating intercellular communication between neurons during nervous system development and repair.

Animals↗
PubMed2005

Evaluating clinical rating scales for evidence-based dermatology: some basic concepts.

Evidence-based dermatology has necessitated the development of rating scales that measure multidimensional and abstract constructs, such as quality of life. This article discusses some basic psychometric concepts, such as reliability, validity, standardization, and measurement precision, which need to be considered when choosing a clinical rating instrument. Also discussed is the impact of these parameters on increasing the statistical power of a clinical trial.

Dermatology↗
PubMed2005

Memory perception and strategy use in Parkinson's disease.

Although there is growing support for the existence of memory deficits within Parkinson's disease (PD), little has been done to evaluate the extent to which PD patients demonstrate differences in their use of metacognitive strategies. In the present study, 79 PD patients (46 men and 33 women) and 49 age-matched healthy participants (19 men and 30 women) were compared on a metamemory questionnaire. PD patients reported significantly less strategy-use than age-matched controls, particularly with regards to external memory strategies (such as making lists). This suggests that auxiliary treatments such as memory strategy training might be effective in this population.

Adaptation, Psychological↗
PubMed2004

Screening for Parkinson's disease with response time batteries: a pilot study.

BACKGROUND: Although significant response time deficits (both reaction time and movement time) have been identified in numerous studies of patients with Parkinson's disease (PD), few attempts have been made to evaluate the use of these measures in screening for PD. METHODS: Receiver operator characteristic curves were used to identify cutoff scores for a unit-weighted composite of two choice response tasks in a sample of 40 patients and 40 healthy participants. These scores were then cross-validated in an independent sample of 20 patients and 20 healthy participants. RESULTS: The unit-weighted movement time composite demonstrated high sensitivity (90%) and specificity (90%) in the identification of PD. Movement time was also significantly correlated (r = 0.59, p < 0.025) with the motor score of the Unified Parkinson's Disease Rating Scale (UPDRS). CONCLUSIONS: Measures of chronometric speed, assessed without the use of biomechanically complex movements, have a potential role in screening for PD. Furthermore, the significant correlation between movement time and UPDRS motor score suggests that movement time may be useful in the quantification of PD severity.

Aged↗
PubMed2004

Visual inspection time in Parkinson's disease: deficits in early stages of cognitive processing.

Inspection time (IT) is a simple information processing paradigm dependent on a participant's ability to identify physical properties of a stimulus presented for a specified time interval. In contrast with reaction time (RT) studies, the dependent variable of interest in IT is not related to the motoric speed with which the individual is able to respond, but rather the minimum presentation time necessary for participants to reliably identify physical properties of the stimulus. It is well documented that individuals with Parkinson's disease (PD) experience significant impairment on tests of simple RT, but it is unclear whether such deficits can be interpreted as 'pure' slowness of information processing, or a delay in the selection and output of a motor response. In the first experiment described here, a sample of 'optimally medicated' PD patients was compared with an age-matched control group, on an IT task. Results of this experiment suggested that individuals with PD required significantly longer stimulus presentation times than healthy participants. The second experiment compared a sample of PD patients (tested both "ON" and "OFF" their typical dopaminergic medications), with an age-matched control group, on the same test of IT. Results again indicated a significant IT deficit in participants with PD, and suggested that these deficits do not significantly resolve with levodopa treatment. Overall, the results of these two experiments suggest that information processing deficits associated with PD are distinct from motor impairment. These findings are further discussed in terms of existing neurochemical models of information processing ability.

Adult↗
PubMed2004

Sex difference in brain nerve conduction velocity in normal humans.

Nerve conduction velocity (NCV), the speed at which impulses travel along nerves, has been extensively determined in human peripheral nerves because of its clinical utility. In contrast, almost no studies have been made of human brain NCV. We determined brain NCVs in the visual nerve pathway for 185 male and 200 female university students ages 18-25 years. In each of three independent test conditions, we found that the mean NCV of male students is about 4% faster than in females (P < or = 0.0001 for each condition). These male students also have a shorter reaction time in each of seven different RT tests than do females, even though, on the null hypothesis of equal NCVs, we would expect males to have longer RT times because of their greater physical size. Four of these comparisons are significant at or below the 0.001 level. These males also increase their NCVs with increasing age, in contrast to females. These sex differences in NCV parallel reported sex differences in age changes in white matter in the brain. These age changes may largely explain these NCV differences.

Adolescent↗
PubMed2004

A behavior genetic investigation of the relationship between leadership and personality.

Phenotypic research on leadership style has long considered the importance of individual differences in personality when identifying the behaviors associated with good leaders. Although leadership and many personality traits have been separately shown to be heritable, these constructs have not been examined with genetically informative data to identify common sources of heritability in the two domains. A logical extension to current research, therefore, is to examine the extent to which factors of personality are predictive of leadership dimensions and the extent to which unique genetic contributions to the relationship between personality and leadership style may be identified. Adult twin pairs (183 MZ and 64 same-sex DZ) completed the Multifactor Leadership Questionnaire (MLQ) and the Personality Research Form (PRF). Univariate analyses indicated that both leadership factors (transformational and transactional leadership) and all five of the "Big Five" factors (openness, conscientiousness, extraversion, disagreeableness, and neuroticism) were best fit by genetic models. Multivariate genetic analyses suggest that transformational leadership shows a statistically significant positive genetic correlation with conscientiousness, extraversion, and openness to experience. Transactional leadership shows a significant negative genetic correlation with conscientiousness and extraversion, and a significant positive genetic correlation with disagreeableness. These results underscore the importance of conscientiousness and extraversion in predicting leadership style, and illustrate important differences between transformational and transactional leaders.

Adult↗
PubMed2003

A role of the basal ganglia in movement: the effect of precues on discrete bi-directional movements in Parkinson's disease.

The effect of a precue on improving movement initiation (i.e., reaction time; RT) is well understood, whereas its influence on movement execution (i.e., movement time; MT) has rarely been examined. The current study investigated the influence of a directional precue (i.e., left vs. right) on the RT and MT of simple and discrete bi-directional movements in a large sample of Parkinson's disease patients and healthy control participants. Both patients and controls were tested twice, with testing sessions separated by 2 hours. Patients were tested first following an overnight levodopa withdrawal and again after they had taken their medication. Both patients and controls demonstrated a significant RT improvement when information was provided in advance. MT in both healthy participants and medicated patients was, however, slower with the provision of advance information, while unmedicated patients showed no significant MT effects. These results suggest that while the basal ganglia may not be involved in motor program selection, they may dynamically modulate movement execution.

Adult↗
PubMed2002

Sublingual atropine for sialorrhea secondary to parkinsonism: a pilot study.

Sialorrhea is a relatively common symptom in idiopathic Parkinson's disease and related conditions for which most of the accepted treatments are either highly invasive or may cause substantial systemic side effects. This study describes an open-label pilot study of sublingual atropine drops for the treatment of sialorrhea in 7 patients (6 with Parkinson's disease, 1 with progressive supranuclear palsy). Participants demonstrated statistically significant declines in saliva production, both objectively and subjectively. Self-reported drooling severity showed a significant decline between baseline and 180 minutes, t(6) = 3.240 P < 0.025 (eta(2) = 0.636), and between baseline and 1 week, t(6) = 4.583 P < 0.005 (eta(2) = 0.778). Objectively measured saliva production decreased significantly between baseline and the 1-week follow-up, t(6) = 2.711 P < 0.05 (eta(2) = 0.551). Delirium occurred in 1 patient (concurrent with a urinary tract infection), and 2 patients experienced worsening of hallucinations (active hallucinosis was concealed by both individuals to allow participation in the trial). The remaining trial participants did not experience any anticholinergic side effects. This trial shows that, in selected patient populations, sublingual atropine is a simple and inexpensive treatment for sialorrhea associated with parkinsonism.

Administration, Sublingual↗