Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain

Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy

UDP-glucuronosyltransferase and sulfotransferase polymorphisms, sex hormone concentrations, and tumor receptor status in breast cancer patients

INTRODUCTION: UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes are involved in removing sex hormones from circulation. Polymorphic variation in five UGT and SULT genes – UGT1A1 ((TA)(6)/(TA)(7)), UGT2B4 (Asp(458)Glu), UGT2B7 (His(268)Tyr), UGT2B15 (Asp(85)Tyr), and SULT1A1 (Arg(213)His) – may be associated with circulating sex hormone concentrations, or the risk of an estrogen receptor-negative (ER(-)) or progesterone receptor-negative (PR(-)) tumor. METHODS: Logistic regression analysis was used to estimate the odds ratios of an ER(- )or PR(- )tumor associated with polymorphisms in the genes listed above for 163 breast cancer patients from a population-based cohort study of women in western Washington. Adjusted geometric mean estradiol, estrone, and testosterone concentrations were calculated within each UGT and SULT genotype for a subpopulation of postmenopausal breast cancer patients not on hormone therapy 2–3 years after diagnosis (n = 89). RESULTS: The variant allele of UGT1A1 was associated with reduced risk of an ER(- )tumor (P for trend = 0.03), and variants of UGT2B15 and SULT1A1 were associated with non-statistically significant risk reductions. There was some indication that plasma estradiol and testosterone concentrations varied by UGT2B15 and SULT1A1 genotypes; women with the UGT2B15 Asp/Tyr and Tyr/Tyr genotypes had higher concentrations of estradiol than women with the Asp/Asp genotype (P = 0.004). Compared with women with the SULT1A1 Arg/Arg and Arg/His genotypes, women with the His/His genotype had elevated concentrations of testosterone (P = 0.003). CONCLUSIONS: The risk of ER(- )breast cancer tumors may vary by UGT or SULT genotype. Further, plasma estradiol and testosterone concentrations in breast cancer patients may differ depending on some UGT and SULT genotypes

Stimulus frequency processing in awake rat barrel cortex.

In awake rats, we examined the relationship between neural spiking activity in primary somatic sensory cortex and the frequency of whisker stimulation. Neural responses were recorded extracellularly in barrel cortex while single whiskers were deflected with 0.5-18 air puffs per second (apps), a range that includes the whisk rates observed when rats explore their environment and discriminate surfaces with their whiskers. Twenty-nine neurons in layers III and IV were isolated in three rats (23 in barrel columns and 6 in septum columns). At < or = 9 apps, cortical neurons responded with one to two spikes per stimulus, whereas at > 9 apps, the response efficacy was reduced to only 0.2-0.4 spikes per stimulus. Several mechanisms are discussed that could account for the decrement in responsiveness. Despite this adaptation, neural spike rates increased in direct proportion with stimulus frequency when cast on logarithmic scales. At > 9 apps, however, this relationship deteriorated in barrel columns in which the response approximately halved. In contrast, septum column cells continued to increase their spike rates linearly up to 18 apps, although they responded at lower magnitude than the barrel column cells. Our findings suggest that septum column neurons are potential candidates to encode stimulus frequency using spike rate across the entire frequency range relevant to rats' whisking behavior

Electrophysiological evidence for an L-shaped interhemispheric connection in the cat

Transcallosal potentials evoked by electrical stimulation with rectangular pulses of 1 ms, 5 c/s and variable intensity were recorded from the cortical surface in cats anesthetized with ketamine hydrochloride. Sites of stimulation and recording were selected by means of a cartesian map of most of the neocortex. In addition to the well known transcallosal projection pattern it was found that stimulation of a restricted posterior area evokes low voltage potentials over the contralateral symmetric area while high voltage potentials are recorded from a few sites located at the ipsilateral anterior cortex and from the area symmetric as to the latter. This L-shaped transcallosal connection may be involved in complex cortical processes and is compatible with effective results of partial anterior callosotomies in patients with multifocal epilepsy and frontal bisynchronism