Altered kinetics and benzodiazepine sensitivity of a GABA(A) receptor subunit mutation [gamma(2)(R43Q)] found in human epilepsy

The gamma-aminobutyric acid type A (GABA(A)) receptor mediates fast inhibitory synaptic transmission in the CNS. Dysfunction of the GABA(A) receptor would be expected to cause neuronal hyperexcitability, a phenomenon linked with epileptogenesis. We have investigated the functional consequences of an arginine-to-glutamine mutation at position 43 within the GABA(A) gamma(2)-subunit found in a family with childhood absence epilepsy and febrile seizures. Rapid-application experiments performed on receptors expressed in HEK-293 cells demonstrated that the mutation slows GABA(A) receptor deactivation and increases the rate of desensitization, resulting in an accumulation of desensitized receptors during repeated, short applications. In Xenopus laevis oocytes, two-electrode voltage-clamp analysis of steady-state currents obtained from alpha(1)beta(2)gamma(2) or alpha(1)beta(2)gamma(2)(R43Q) receptors did not reveal any differences in GABA sensitivity. However, differences in the benzodiazepine pharmacology of mutant receptors were apparent. Mutant receptors expressed in oocytes displayed reduced sensitivity to diazepam and flunitrazepam but not the imiclazopyricline zolpidem. These results provide evidence of impaired GABA(A) receptor function that could decrease the efficacy of transmission at inhibitory synapses, possibly generating a hyperexcitable neuronal state in thalamocortical networks of epileptic patients possessing the mutant subunit.

Human response to environmental noise: The role of perceived control

Negative impacts of noise exposure on health and performance may result in part from learned helplessness, the syndrome of deficits typically produced by exposure to uncontrollable events. People may perceive environmental noise to be uncontrollable, and several effects of noise exposure appear to parallel learned helplessness deficits. In the present socioacoustic survey (N = 1,015), perceived control over aircraft noise correlated negatively with some effects of noise (though not others). Furthermore, these effects were better predicted by perceived control than by noise level. These observational data support the claim that learned helplessness contributes to the effects of noise exposure.

Identification of cellular changes associated with increased production of human growth hormone in a recombinant Chinese hamster ovary cell line

A proteomics approach was used to identify the proteins potentially implicated in the cellular response concomitant with elevated production levels of human growth hormone in a recombinant Chinese hamster ovary (CHO) cell line following exposure to 0.5 mM butyrate and 80 muM zinc sulphate in the production media. This involved incorporation of two-dimensional (2-D) gel electrophoresis and protein identification by a combination of N-terminal sequencing, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry, amino acid analysis and cross species database matching. From these identifications a CHO 2-D reference,map and annotated database have been established. Metabolic labelling and subsequent autoradiography showed the induction of a number of cellular proteins in response to the media additives butyrate and zinc sulphate. These were identified as GRP75, enolase and thioredoxin. The chaperone proteins GRP78, HSP90, GRP94 and HSP70 were not up-regulated under these conditions.

Finite-difference time-domain-based studies of MRI pulsed field gradient-induced eddy currents inside the human body

In modern magnetic resonance imaging (MRI), patients are exposed to strong, rapidly switching magnetic gradient fields that, in extreme cases, may be able to elicit nerve stimulation. This paper presents theoretical investigations into the spatial distribution of induced current inside human tissues caused by pulsed z-gradient fields. A variety of gradient waveforms have been studied. The simulations are based on a new, high-definition, finite-difference time-domain method and a realistic inhomogeneous 10-mm resolution human body model with appropriate tissue parameters. it was found that the eddy current densities are affected not only by the pulse sequences but by many parameters such as the position of the body inside the gradient set, the local biological material properties and the geometry of the body. The discussion contains a comparison of these results with previous results found in the literature. This study and the new methods presented herein will help to further investigate the biological effects caused by the switched gradient fields in a MRI scan. (C) 2002 Wiley Periodicals, Inc.

Identification of novel "pathologs" (human disease-related gene candidates) from the RIKEN full-length mouse cDNA data set

The majority of common diseases such as cancer, allergy, diabetes, or heart disease are characterized by complex genetic traits, in which genetic and environmental components contribute to disease susceptibility. Our knowledge of the genetic factors underlying most of such diseases is limited. A major goal in the post-genomic era is to identify and characterize disease susceptibility genes and to use this knowledge for disease treatment and prevention. More than 500 genes are conserved across the invertebrate and vertebrate genomes. Because of gene conservation, various organisms including yeast, fruitfly, zebrafish, rat, and mouse have been used as genetic models.

The human organization of time: Temporal realities and experience (Book)

Reviews the book "The Human Organization of Time: Temporal Realities and Experience," by Allen C. Bluedorn.

The force-velocity relationship of the human soleus muscle during submaximal voluntary lengthening actions

In experiments on isolated animal muscle, the force produced during active lengthening contractions can be up to twice the isometric force, whereas in human experiments lengthening force shows only modest, if any, increase in force. The presence of synergist and antagonist muscle activation associated with human experiments in situ may partly account for the difference between animal and human studies. Therefore, this study aimed to quantify the force-velocity relationship of the human soleus muscle and assess the likelihood that co-activation of antagonist muscles was responsible for the inhibition of torque during submaximal voluntary plantar flexor efforts. Seven subjects performed submaximal voluntary lengthening, shortening(at angular, velocities of +5, -5, +15, -15 and +30, and -30degrees s(-1)) and isometric plantar flexor efforts against an ankle torque motor. Angle-specific (90degrees) measures of plantar flexor torque plus surface and intramuscular electromyography from soleus, medial gastrocnemius and tibialis anterior were made. The level of activation (30% of maximal voluntary isometric effort) was maintained by providing direct visual feedback of the soleus electromyogram to the subject. In an attempt to isolate the contribution of soleus to the resultant plantar flexion torque, activation of the synergist and antagonist muscles were minimised by: (1) flexing the knee of the test limb, thereby minimising the activation of gastrocnemius, and (2) applying an anaesthetic block to the common peroneal nerve to eliminate activation of the primary antagonist muscle, tibialis anterior and the synergist muscles, peroneus longus and peroneus brevis. Plantar flexion torque decreased significantly (P<0.05) after blocking the common peroneal nerve which was likely due to abolishing activation of the peroneal muscles which are synergists for plantar flexion. When normalised to the corresponding isometric value, the force-velocity relationship between pre- and post-block conditions was not different. In both conditions, plantar flexion torques during shortening actions were significantly less than the isometric torque and decreased at faster velocities. During lengthening actions, however, plantar flexion torques were not significantly different from isometric regardless of angular velocity. It was concluded that the apparent inhibition of lengthening torques during voluntary activation is not due to co-activation of antagonist muscles. Results are presented as mean (SEM).

Purification of recombinant human growth hormone from CHO cell culture supernatant by Gradiflow preparative electrophoresis technology

Purification of recombinant human growth hormone (rhGH) from Chinese hamster ovary (CHO) cell culture supernatant by Gradiflow large-scale electrophoresis is described. Production of rhGH in CHO cells is an alternative to production in Escherichia coli, with the advantage that rhGH is secreted into protein-free production media, facilitating a more simple purification and avoiding resolubilization of inclusion bodies and protein refolding. As an alternative to conventional chromatography, rhGH was purified in a one-step procedure using Gradiflow technology. Clarified culture supernatant containing rhGH was passed through a Gradiflow BF200 and separations were performed over 60 min using three different buffers of varying pH. Using a 50 mM Tris/Hepes buffer at pH 7.5 together with a 50 kDa separation membrane, rhGH was purified to approximately 98% purity with a yield of 90%. This study demonstrates the ability of Gradiflow preparative electrophoresis technology to purify rhGH from mammalian cell culture supernatant in a one-step process with high purity and yield. As the Gradiflow is directly scalable, this study also illustrates the potential for the inclusion of the Gradiflow into bioprocesses for the production of clinical grade rhGH and other therapeutic proteins. (C) 2003 Elsevier Science (USA). All rights reserved.

Localization of a brain sulfotransferase, SULT4A1, in the human and rat brain: An immunohistochemical study

Cytosolic sulfotransferases are believed to play a role in the neuromodulation of certain neurotransmitters and drugs. To date, four cytosolic sulfotransferases have been shown to be expressed in human brain. Recently, a novel human brain sulfotransferase has been identified and characterized, although its role and localization in the brain are unknown. Here we present the first immunohistochemical (IHC) localization of SULT4A1 in human brain using an affinity-purified polyclonal antibody raised against recombinant human SULT4A1. These results are supported and supplemented by the IHC localization of SULT4A1 in rat brain. In both human and rat brains, strong reactivity was found in several brain regions, including cerebral cortex, cerebellum, pituitary, and brainstem. Specific signal was entirely absent on sections for which preimmune serum from the corresponding animal, processed in the same way as the postimmune serum, was used in the primary screen. The findings from this study may assist in determining the physiological role of this SULT isoform.