Vitamin D and bone metabolism in Graves' disease: a prospective study.

PURPOSE: Vitamin D and osteoporosis in Graves' disease (GD) have been examined in cross-sectional studies with divergent results. Here, we prospectively studied vitamin D metabolism and bone health in patients with newly diagnosed GD. METHODS: Thirty consecutive patients with de novo overt thyrotoxicosis diagnosed with GD were included. At diagnosis, none of the patients were treated with vitamin D or anti-osteoporotic drugs. All patients were initially treated with antithyroid drugs. Blood samplings were taken at baseline and at 6 weeks, 3, 6, 12 and 24 months after treatment start. Serum levels of 25OHD3, 1,25OH2D3, calcium, parathyroid hormone (PTH), and C-terminal telopeptides of Type I collagen (CTX-I) were analysed. Bone mineral density (BMD) was measured at baseline, and 1 and 2 years after treatment initiation. RESULTS: At diagnosis, patients with GD did not have vitamin D deficiency. There were no significant correlations between levels of 25OHD3 and thyrotoxicosis. Upon treatment of the thyrotoxicosis, serum calcium fell transiently, and PTH and 1,25OH2D3 increased. 25OHD3 fell within the normal range and stabilised at 6 months. CTX-I fell over 12 months, BMD increased significantly up to 2 years, p = 0.002, < 0.001 and 0.005 in the spine, left total hip and left femoral neck, respectively. CONCLUSIONS: The present data underline that thyrotoxicosis has a negative impact on bone health and demonstrate fine-tuned dynamics in bone and vitamin D metabolism. Upon treatment, bone health improved over a follow-up period of 24 months despite rising PTH. Increased conversion of 25OHD3 to 1,25OH2D3 occurs during treatment of GD.

Radial Two-Dimensional Ion Crystals in a Linear Paul Trap.

We experimentally study two-dimensional (2D) Coulomb crystals in the "radial-2D" phase of a linear Paul trap. This phase is identified by a 2D ion lattice aligned entirely with the radial plane and is created by imposing a large ratio of axial to radial trapping potentials. Using arrays of up to 19 ^{171}Yb^{+} ions, we demonstrate that the structural phase boundaries of such crystals are well described by the pseudopotential approximation, despite the time-dependent ion positions driven by intrinsic micromotion. We further observe that micromotion-induced heating of the radial-2D crystal is confined to the radial plane. Finally, we verify that the transverse motional modes, which are used in most ion-trap quantum simulation schemes, are well-predictable numerically and remain decoupled and cold in this geometry. Our results establish radial-2D ion crystals as a robust experimental platform for realizing a variety of theoretical proposals in quantum simulation and computation.

PTSD in women is associated with a block in conversion of progesterone to the GABAergic neurosteroids allopregnanolone and pregnanolone measured in plasma.

There is a need to identify new and more effective treatments for posttraumatic stress disorder (PTSD). Allopregnanolone and its stereoisomer pregnanolone (together termed ALLO) are metabolites of progesterone that positively and allosterically modulate GABA effects at GABAA receptors, thereby reducing anxiety and depression. Previous research revealed that women with PTSD had low cerebrospinal fluid (CSF) ALLO levels and a low ratio of ALLO to the allopregnanolone precursor 5α-DHP, consistent with deficient activity of the ALLO synthetic enzyme 3α-hydroxysteroid dehydrogenase (3α-HSD). The current study examined ALLO and the ratio of ALLO to 5α-DHP in plasma at rest and in response to psychophysiological stressors in trauma-exposed, medication-free women with and without PTSD. Participants were examined twice in random order during the early follicular phase (eFP) and mid-luteal phase (mLP) of the menstrual cycle. Plasma neurosteroids were measured using gas chromatography-mass spectrometry. Results indicate that the ALLO to 5α-DHP ratio in plasma increases between the eFP and mLP. In addition, women with PTSD have a lower ratio of ALLO to 5α-DHP than trauma-exposed healthy women, as well as blunted increases in this ratio in response to a moderately stressful laboratory procedure, i.e., differential fear conditioning, across the menstrual cycle. Clinically feasible testing for 3α-HSD dysfunction is critical to translating this line of research into clinical care. Measurement of this ratio in plasma could facilitate patient stratification in clinical treatment trials, as well as precision medicine targeting of treatments that address ALLO synthesis deficits in women with PTSD.

Simvastatin-doped pre-mixed calcium phosphate cement inhibits osteoclast differentiation and resorption.

Simvastatin, a cholesterol lowering drug, has been shown to have positive effects on fracture healing and bone regeneration based on its dual effect; bone anabolic and anti-resorptive. In this study the focus has been on the anti-resorptive effect of the drug and its impact on the degradation of acidic calcium phosphate cement. The drug was added to the pre-mixed acidic cement in three different doses (0.1, 0.25 and 0.5 mg/g cement) and the release was measured. Furthermore the effect of the loaded cements on osteoclast differentiation and resorption was evaluated by TRAP activity, number of multinucleated cells, gene expression and calcium ion concentration in vitro using murine bone marrow macrophages. The simvastatin did not affect the cell proliferation while it clearly inhibited osteoclastic differentiation at all three doses as shown by TRAP staining, TRAP activity and gene expression. Consistent with these results, simvastatin also impaired resorption of cements by osteoclasts as indicated by reduced calcium ion concentrations. In conclusion, our findings suggest that simvastatin-doped pre-mixed acidic calcium phosphate cement inhibits the osteoclastic mediated resorption of the cement thus slowing down the degradation rate. In addition with simvastatin's bone anabolic effect it makes the cement-drug combination a promising bone graft material, especially useful for sites with compromised bone formation.

Resorption of monetite calcium phosphate cement by mouse bone marrow derived osteoclasts.

Recently the interest for monetite based biomaterials as bone grafts has increased; since in vivo studies have demonstrated that they are degradable, osteoconductive and improve bone healing. So far osteoclastic resorption of monetite has received little attention. The current study focuses on the osteoclastic resorption of monetite cement using primary mouse bone marrow macrophages, which have the potential to differentiate into resorbing osteoclasts when treated with receptor activator NF-κB ligand (RANKL). The osteoclast viability and differentiation were analysed on monetite cement and compared to cortical bovine bone discs. After seven days live/dead stain results showed no significant difference in viability between the two materials. However, the differentiation was significantly higher on the bone discs, as shown by tartrate resistant acid phosphatase (TRAP) activity and Cathepsin K gene expression. Moreover monetite samples with differentiated osteoclasts had a 1.4 fold elevated calcium ion concentration in their culture media compared to monetite samples with undifferentiated cells. This indicates active resorption of monetite in the presence of osteoclasts. In conclusion, this study suggests that osteoclasts have a crucial role in the resorption of monetite based biomaterials. It also provides a useful model for studying in vitro resorption of acidic calcium phosphate cements by primary murine cells.

The spatial rotator.

This paper presents a new local volume estimator, the spatial rotator, which is based on measurements on a virtual 3D probe, using computer assisted microscopy. The basic design of the probe builds upon the rotator principle which requires only a few manual intersection markings, thus making the spatial rotator fast to use. Since a 3D probe is involved, it is expected that the spatial rotator will be more efficient than the the nucleator and the planar rotator, which are based on measurements in a single plane. An extensive simulation study shows that the spatial rotator may be more efficient than the traditional local volume estimators. Furthermore, the spatial rotator can be seen as a further development of the Cavalieri estimator, which does not require randomization of sectioning or viewing direction. The tissue may thus be sectioned in any arbitrary direction, making it easy to identify the specific tissue region under study. In order to use the spatial rotator in practice, however, it is necessary to be able to identify intersection points between cell boundaries and test rays in a series of parallel focal planes, also at the peripheral parts of the cell boundaries. In cases where over- and underprojection phenomena are not negligible, they should therefore be corrected for if the spatial rotator is to be applied. If such a correction is not possible, it is needed to avoid these phenomena by using microscopy with increased resolution in the focal plane.

Sensitivity of the acoustic waveguide biosensor to protein binding as a function of the waveguide properties.

The aim of this work is to study the effect of operating frequency, piezoelectric substrate and waveguide layer thickness on the sensitivity of the acoustic waveguide sensor during the specific binding of an antibody by a protein. Shear horizontal (SH) wave devices consisting of (a) a LiTaO3 substrate operating at 104 MHz, (b) a quartz substrate operating at 108 MHz and (c) a quartz substrate operating at 155 MHz were coated with a photoresist polymer layer in order to produce acoustic waveguide devices supporting a Love wave. The effect of the thickness of the polymer layer on the Love wave was assessed by measuring the amplitude and phase of the wave before and after coating. The sensitivity of the above three biosensors was compared during the detection of the specific binding of different concentrations of Immunoglobulin G in the range of 0.7-667 nM to a protein A modified surface. Results indicate that the thickness of the polymer guiding layer is critical for obtaining the maximum sensitivity for a given geometry but a trade-off has to be made between the theoretically determined optimum thickness for waveguiding and the device insertion loss. It was also found that increasing the frequency of operation results in a further increase in the device sensitivity to protein detection.

The socially-isolated mouse: a model to study the putative role of allopregnanolone and 5alpha-dihydroprogesterone in psychiatric disorders.

Allopregnanolone (3alpha,5alpha-TH PROG) and 5alpha-dihydroprogesterone (5alpha-DH PROG), the two most important neuroactive steroids synthesized in the brain, potently modulate neuronal activity by allosterically regulating GABA action at GABA(A) receptors or by changing specific GABA(A) receptor subunit gene expression, respectively. We recently reported [Proc. Natl. Acad. Sci. USA 95 (1998) 3239] that in patients with severe depression there is a decrease in the CSF levels of 3alpha,5alpha-TH PROG, which is normalized by treatment with drugs (i.e. fluoxetine) that improve psychopathology. The mechanism by which fluoxetine and other selective serotonin reuptake inhibitors normalize 3alpha,5alpha-TH PROG CSF levels appears to involve a direct stimulation of 3alpha-hydroxysteroidoxidoreductase (3alpha-HSD), an enzyme that catalyses the reduction of 5alpha-DH PROG into 3alpha,5alpha-TH PROG. Here, we propose the use of socially-isolated mice that have a downregulation of 3alpha,5alpha-TH PROG and of 5alpha-DH PROG expression to establish a model to study the behavioral consequences of this deficiency. After 4-6 weeks of isolation, these mice exhibit increased anxiety and aggressive behavior and also a decreased response to the administration of GABA-mimetic drugs. In these mice, the decrease in 3alpha,5alpha-TH PROG is selectively normalized by the use of fluoxetine in doses that reduce behavioral abnormalities. In addition, the expression of 5alpha-reductase Type I mRNA and protein was lower in socially-isolated mice than that in group-housed mice whereas 3alpha-HSD mRNA expression remained unchanged. The results of these studies may enable us to design drugs that specifically affect neurosteroidogenic enzymatic activities and may provide an efficacious treatment for the psychopathologies associated with psychiatric disorders.

Increased pituitary and adrenal reactivity in premenopausal women with posttraumatic stress disorder.

BACKGROUND: Limited studies of hypothalamic-pituitary-adrenal axis regulation in posttraumatic stress disorder have been performed in premenopausal women. We therefore undertook a study of hypothalamic-pituitary-adrenal axis regulation in this population. METHODS: Outpatient posttraumatic stress disorder subjects were compared with healthy, age- and weight-matched nontraumatized subjects. Subjects were free from psychotropic medications, alcohol and other illicit substances for at least 4 weeks before study. Menstrual cycle phase was determined by monitoring the LH surge and plasma progesterone levels. Corticotropin releasing factor and adrenocorticotropin stimulation tests, as well as 24-hour urinary-free cortisol measurements were performed. RESULTS: Corticotropin releasing factor test: Baseline adrenocorticotropic hormone and cortisol levels did not differ between the 12 PTSD and 11 comparison subjects, but the posttraumatic stress disorder group had greater adrenocorticotropic hormone and cortisol responses to corticotropin releasing factor, as well as a later cortisol peak. Adrenocorticotropic hormone test: Baseline cortisol levels did not differ between the 10 posttraumatic stress disorder subjects and seven controls, but the posttraumatic stress disorder group showed greater cortisol responses to adrenocorticotropic hormone. Peak cortisol responses to corticotropin releasing factor and adrenocorticotropic hormone were correlated with each other and with 24-hour urinary-free cortisol excretion. CONCLUSIONS: Pituitary and adrenal hyperreactivity to exogenous corticotropin releasing factor and adrenocorticotropic hormone is demonstrated in premenopausal women with chronic posttraumatic stress disorder. Cortisol hyperreactivity thus may play a role in the pathophysiology of posttraumatic stress disorder in women.

Light-dependent gene expression for proteins in the respiratory chain of potato leaves.

Expression of genes for respiratory chain dehydrogenases was investigated in potato (Solanum tuberosum L. cv. Desiree) leaves. The recently characterized nda1 and ndb1 genes, homologues to genes encoding the non-proton pumping respiratory chain NADH-dehydrogenases of Escherichia coli and yeast, were compared to genes encoding catalytic subunits of the proton-pumping NADH dehydrogenase (complex I). As leaves develop from young to mature, the nda1 transcript level increases, accompanied by an elevation in immunodetected NDA protein and internal rotenone-insensitive NADH oxidation. The other investigated transcripts, proteins and NAD(P)H oxidation activities were essentially unchanged. A variation in transcript level, specific for nda1, is seen at different times of the day with highest expression in the morning. This variation also influences the apparent developmental induction. Further, the nda1 mRNA in leaves specifically and completely disappears during dark treatment, with a rapid re-induction when plants are returned to light. Corresponding immunodetected NDA protein is specifically decreased in mitochondria isolated from dark-treated plants, accompanied by a lower capacity for internal rotenone-insensitive NADH oxidation. Complete light dependence and diurnal changes in expression have previously not been reported for genes encoding respiratory chain proteins. Qualitatively similar to NDA, the alternative oxidase showed developmental induction and light dependence. In addition to the specific change in nda1, a general, slower down-regulation in darkness was seen for the other NAD(P)H dehydrogenase genes. The nda1 expression during development, and in response to light, indicates a specific role of the encoded enzyme in the photosynthetically associated mitochondrial metabolism.

Relationship among plasma cortisol, catecholamines, neuropeptide Y, and human performance during exposure to uncontrollable stress.

OBJECTIVE: Although many people are exposed to trauma, only some individuals develop posttraumatic stress disorder; most do not. It is possible that humans differ in the degree to which stress induces neurobiological perturbations of their threat response systems, which may result in a differential capacity to cope with aversive experiences. This study explored the idea that differences in the neurobiological responses of individuals exposed to threat are significantly related to psychological and behavioral indices. METHODS: Individual differences in neurohormonal, psychological, and performance indices among 44 healthy subjects enrolled in US Army survival school were investigated. Subjects were examined before, during, and after exposure to uncontrollable stress. RESULTS: Stress-induced release of cortisol, neuropeptide Y, and norepinephrine were positively correlated; cortisol release during stress accounted for 42% of the variance in neuropeptide Y release during stress. Cortisol also accounted for 22% of the variance in psychological symptoms of dissociation and 31% of the variance in military performance during stress. CONCLUSIONS: Because dissociation, abnormalities in the hypothalamic-pituitary-adrenocortical axis, and catecholamine functioning have all been implicated in the development of stress disorders such as posttraumatic stress disorder, these data suggest that some biological differences may exist before index trauma exposure and before the development of stress-related illness. The data also imply a relationship among specific neurobiological factors and psychological dissociation. In addition, the data provide clues about the way in which individuals' psychobiological responses to threat differ from one another.

Clinical and functional correlates of posttraumatic stress disorder in urban adolescent girls at a primary care clinic.

OBJECTIVE: To identify clinical and functional correlates of posttraumatic stress disorder (PTSD) in trauma-exposed urban adolescent girls. METHOD: Ninety female adolescents aged 12 to 21 years (mean 17.3 years) who presented for routine medical care at an adolescent primary care clinic were assessed with self-report questionnaires and interviews for trauma exposure, posttraumatic stress symptoms, other psychopathology, and psychosocial, family, and school function. RESULTS: Ninety-two percent (n = 83) endorsed at least one trauma. Witnessing community violence (85.6%) and hearing about a homicide (67.8%) were the most common traumatic events endorsed. Twelve (14.4%) and 10 (11.6%) traumatized girls met DSM-IV symptom criteria for full and partial PTSD, respectively. Compared with traumatized girls without PTSD, girls with PTSD were significantly more depressed, used more cigarettes and marijuana, and were more likely to have failed a school grade, been suspended from school, or been arrested. CONCLUSIONS: Urban adolescent girls are exposed to multiple types of trauma. Whereas most develop at least one posttraumatic stress symptom, girls who meet full symptom criteria for PTSD show evidence of other psychopathology, increased cigarette and marijuana use, and poorer school performance. Further research is needed to identify and treat inner-city girls with PTSD.

Plasma neuropeptide-Y concentrations in humans exposed to military survival training.

BACKGROUND: Neuropeptide-Y (NPY) is present in extensive neuronal systems of the brain and is present in high concentrations in cell bodies and terminals in the amygdala. Preclinical studies have shown that injections of NPY into the central nucleus of the amygdala function as a central anxiolytic and buffer against the effects of stress. The objective of this study was to assess plasma NPY immunoreactivity in healthy soldiers participating in high intensity military training at the U.S. Army survival school. The Army survival school provides a means of observing individuals under high levels of physical, environmental, and psychological stress, and consequently is considered a reasonable analogue to stress incurred as a result of war or other catastrophic experiences. METHODS: Plasma levels of NPY were assessed at baseline (prior to initiation of training), and 24 hours after the conclusion of survival training in 49 subjects, and at baseline and during the Prisoner of War (P.O.W.) experience (immediately after exposure to a military interrogation) in 21 additional subjects. RESULTS: Plasma NPY levels were significantly increased compared to baseline following interrogations and were significantly higher in Special Forces soldiers, compared to non-Special Forces soldiers. NPY elicited by interrogation stress was significantly correlated to the subjects' behavior during interrogations and tended to be negatively correlated to symptoms of reported dissociation. Twenty-four hours after the conclusion of survival training, NPY had returned to baseline in Special Forces soldiers, but remained significantly lower than baseline values in non-Special Forces soldiers. NPY was positively correlated with both cortisol and behavioral performance under stress. NPY was negatively related to psychological symptoms of dissociation. CONCLUSIONS: These results provide evidence that uncontrollable stress significantly increases plasma NPY in humans, and when extended, produces a significant depletion of plasma NPY. Stress-induced alterations of plasma NPY were significantly different in Special Forces soldiers compared to non-Special Forces soldiers. These data support the idea that NPY may be involved in the enhanced stress resilience seen in humans.

Low baseline and yohimbine-stimulated plasma neuropeptide Y (NPY) levels in combat-related PTSD.

BACKGROUND: Consistent with many studies demonstrating enhanced reactivity of the sympathetic nervous system in posttraumatic stress disorder (PTSD), the administration of yohimbine, a noradrenergic alpha(2)-antagonist, has been shown to increase core symptoms of PTSD and to induce greater increases in plasma 3-methyl-4-hydroxy-phenyl-glycol (MHPG) in subjects with PTSD compared with healthy control subjects. In turn, neuropeptide Y (NPY) has been shown to inhibit the release of norepinephrine from sympathetic noradrenergic neurons. METHODS: In the following study, plasma NPY responses to yohimbine and placebo were measured in a subgroup of 18 subjects with PTSD and 8 healthy control subjects who participated in the previous study of the effect of yohimbine on plasma MHPG. RESULTS: The PTSD subjects had lower baseline plasma NPY and blunted yohimbine-stimulated increases in plasma NPY compared with the healthy control subjects. Within the PTSD group, baseline plasma NPY levels correlated negatively with combat exposure scale scores, baseline PTSD and panic symptoms, and yohimbine-stimulated increases in MHPG and systolic blood pressure. CONCLUSIONS: This study suggests that combat stress-induced decreases in plasma NPY may mediate, in part, the noradrenergic system hyperreactivity observed in combat-related PTSD. The persistence of this decrease in plasma NPY may contribute to symptoms of hyperarousal and the expression of exaggerated alarm reactions, anxiety reactions, or both in combat veterans with PTSD long after war.

Homologues of yeast and bacterial rotenone-insensitive NADH dehydrogenases in higher eukaryotes: two enzymes are present in potato mitochondria.

Two different cDNAs, homologous to genes for rotenone-insensitive NADH dehydrogenases of bacteria and yeast, were isolated from potato. The encoded proteins, called NDA and NDB, have calculated molecular masses of 55 and 65 kDa, respectively. The N-terminal parts show similarity to mitochondrial targeting peptides and the polypeptides are in vitro imported into potato mitochondria. Import processing to a smaller polypeptide is seen for the NDA but not the NDB protein. After import, NDA is intramitochondrially sorted to the matrix side of the inner membrane, whereas NDB becomes exposed to the intermembrane space. Imported proteins are associated to membranes upon digitonin permeabilization. On expression in Escherichia coli, NDB is released from the bacterial membrane in the absence of divalent cations whereas detergents are necessary for solubilization of NDA. Both deduced amino-acid sequences contain the dual motifs for nucleotide binding with the characteristics of the core criteria, similar to the bacterial homologues. Unique among NADH dehydro- genases, the NDB amino-acid sequence contains a non-conserved insert, which is similar to EF-hand motifs for calcium binding. Phylogenetic analyses group the rotenone-insensitive NADH dehydrogenases largely by species, but suggest ancient gene duplications.

Two separate transhydrogenase activities are present in plant mitochondria.

Inside-out submitochondrial particles from both potato tubers and pea leaves catalyze the transfer of hydride equivalents from NADPH to NAD(+) as monitored with a substrate-regenerating system. The NAD(+) analogue acetylpyridine adenine dinucleotide is also reduced by NADPH and incomplete inhibition by the complex I inhibitor diphenyleneiodonium (DPI) indicates that two enzymes are involved in this reaction. Gel-filtration chromatography of solubilized mitochondrial membrane complexes confirms that the DPI-sensitive TH activity is due to NADH-ubiquinone oxidoreductase (EC 1.6.5.3, complex I), whereas the DPI-insensitive activity is due to a separate enzyme eluting around 220 kDa. The DPI-insensitive TH activity is specific for the 4B proton on NADH, whereas there is no indication of a 4A-specific activity characteristic of a mammalian-type energy-linked TH. The DPI-insensitive TH may be similar to the soluble type of transhydrogenase found in, e.g., Pseudomonas. The presence of non-energy-linked TH activities directly coupling the matrix NAD(H) and NADP(H) pools will have important consequences for the regulation of NADP-linked processes in plant mitochondria.

Role of norepinephrine in the pathophysiology and treatment of posttraumatic stress disorder.

This review focuses on the role of norepinephrine (NE) in traumatic stress. The review is divided into three sections. The first section, "Norepinephrine and Arousal," describes preclinical studies related to norepinephrine's role in arousal, orienting to novel stimuli, selective attention and vigilance. It also contains a brief discussion of NE and its relationship to fear-provoking stimuli followed by preclinical and clinical studies that demonstrate heightened noradrenergic neuronal reactivity, increased alpha 2 receptor sensitivity and exaggerated arousal in organisms that have been exposed to chronic uncontrollable stress. The second section, "Norepinephrine and Memory," describes preclinical and clinical studies related to norepinephrine's role in enhanced encoding of memory for arousing and aversive events and in subsequent re-experiencing symptoms such as, intrusive memories and nightmares. The third section, "Norepinephrine and Pharmacologic Treatment," briefly discusses the use of adrenergic blockers, clonidine and propranol, as well as tricyclic and MAO inhibitors, for the treatment of PTSD. Finally, we attempt to synthesize trauma-related preclinical and clinical studies of norepinephrine. We do this, in part, by focusing on a series of yohimbine studies in subjects with PTSD because data from these studies allow for a discussion that brings together preclinical and clinical findings relevant to trauma-related alterations in arousal and memory.

The role of mesoprefrontal dopamine neurons in the acquisition and expression of conditioned fear in the rat.

The mesoprefrontal dopamine neurons are sensitive to physical, pharmacological and psychological stressors. In this report, the role of these neurons in the response to classical fear conditioning was investigated. 6-Hydroxydopamine lesions to the medial prefrontal cortex reduced dopamine levels to about 13% of controls but did not alter behavior during the acquisition of fear conditioning. As expected, conditioned fear increased dopamine metabolism (3,4-dihydroxyphenylacetic acid/dopamine ratio) in the nucleus accumbens in sham-lesion rats. The medial prefrontal 6-hydroxydopamine lesions did not alter this effect. During the expression, however, lesioned rats demonstrated a delayed extinction of the conditioned response without an overall increase in the initial conditioned response. This effect was consistent in rats receiving 6-hydroxydopamine lesions before or after the acquisition period. The calculated rates of extinction showed that the 6-hydroxydopamine lesioned rats had a reduced rate of extinction, but not acquisition, of fear conditioning. The results presented in this manuscript indicate that the mesoprefrontal dopamine neurons are involved in co-ordinating the normal extinction of a fear response but do not alter the acquisition of fearful behaviors. These data are consistent with the conclusion that the mesoprefrontal dopamine neurons are involved in maintaining the animal's response adaptability with regards to stress-related changes in the external environment.

Plasma neuropeptide Y (NPY) increases in humans in response to the alpha 2 antagonist yohimbine.

Previous studies have shown that the intravenous administration of yohimbine, an alpha 2 antagonist, increases norepinephrine turnover and has related anxiogenic effects in humans. We herein report that yohimbine also increases plasma neuropeptide Y (NPY) in healthy human subjects. This finding is consistent with previous reports in animals, but contrasts with a previously reported study in humans. NPY is a 36 amino acid peptide neurotransmitter located in sympathetic and nonsympathetic nerve fibers, as well as in brain structures such as the locus coeruleus, where it is colocalized with norepinephrine. NPY has been shown to inhibit locus coeruleus neuronal firing, decrease norepinephrine release, and increase postsynaptic noradrenergic signal transduction. When administered centrally, NPY also has anxiolytic properties. This study therefore suggests that yohimbine challenge may be useful in assessing NPY and noradrenergic system interactions in neuropsychiatric disorders such as panic disorder or post traumatic stress disorder in which noradrenergic system dysfunction has been observed.

Molecular characterisation of the 76 kDa iron-sulphur protein subunit of potato mitochondrial complex I.

Genes encoding subunits of complex I (EC 1.6.5.3) of the mitochondrial respiratory chain vary in their locations between the mitochondrial and nuclear genomes in different organisms, whereas genes for a homologous multisubunit complex in chloroplasts have to date only been found on the plastid genome. In potato (Solanum tuberosum L.), the gene coding for the mitochondrial 76 kDa iron-sulphur protein is identified in the nuclear genome. The gene is transcribed into polyadenylated mRNA which is most abundant in flowers, and more frequent in tubers than in leaves. The amino acid sequence is well conserved relative to the nuclear-encoded 75 kDa and 78 kDa subunits of Bos taurus and Neurospora crassa, respectively, and to the Paracoccus denitrificans homologue, most prominently in the region presumed to carry the iron-sulphur clusters. Polyclonal antibodies directed against the 78 kDa complex I subunit of N. crassa recognise the 76 kDa polypeptide in potato mitochondrial complex I, and additionally a polypeptide of 75 kDa in solubilised stroma thylakoids from spinach chloroplasts. The 32 amino acid residues long presequence of the potato mitochondrial 76 kDa complex I subunit targets the precursor polypeptide into isolated potato mitochondria but not into isolated chloroplasts. These results suggest that chloroplast stroma thylakoids contain a protein similar in size and antigenicity to, but genetically distinct from, the mitochondrial subunit.