Synthesis of 2-hydroxy-3-alkyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one via molybdenum hexacarbonyl mediated CO gas- and ligand free carbonylative reactions

Carbon monoxide gas and ligand-free condition were developed for the synthesis of 2-hydroxy-3-alkyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one via catalytic carbonylation with Mo(CO)₆ as an efficient carbonylating agent for the novel MCR reaction.

Inactivity produces increases in neurotransmitter release and synapse size

When hippocampal synapses in culture are pharmacologically silenced for several days, synaptic strength increases. The structural correlate of this change in strength is an increase in the size of the synapses, with all synaptic components--active zone, postsynaptic density, and bouton--becoming larger. Further, the number of docked vesicles and the total number of vesicles per synapse increases, although the number of docked vesicles per area of active zone is unchanged. In parallel with these anatomical changes, the physiologically measured size of the readily releasable pool (RRP) and the release probability are increased. Ultrastructural analysis of individual synapses in which the RRP was previously measured reveals that, within measurement error, the same number of vesicles are docked as are estimated to be in the RRP.

Visualizing postendocytic traffic of synaptic vesicles at hippocampal synapses

We have investigated mechanisms in postendocytic processing of synaptic vesicles at hippocampal synapses, using synaptobrevin/vesicle-associated membrane protein (VAMP) tagged with variants of the green fluorescent protein. Following exocytosis, VAMP is retrieved at synaptic and adjoining axonal regions. Retrieved VAMP-containing vesicles return to synaptic vesicle clusters at a rate slower than endocytosis. Vesicles containing a different protein, synaptophysin, recluster at a similar rate, suggesting common vesicular intermediates for the two proteins. Activity prolongs the time taken by endocytosed vesicles to return to synapses. Exogenous calcium buffers slow endocytosis but have no additional effect on the time course of reclustering. In contrast, the protein kinase inhibitor staurosporine does not affect endocytosis but slows reclustering. Finally, since VAMP can move freely on surface membranes, sustained synaptic activity leads to mixing of this vesicular component between adjacent synapses.

Synaptic plasticity: rush hour traffic in the AMPA lanes

Recent experiments indicate that modification of synaptic strength may involve rapid regulation of vesicular traffic on the postsynaptic side of the synapse. The specific vesicular trafficking route taken by postsynaptic receptors appears to depend on the stimulus.

Synaptic interactions mediating synchrony and oscillations in primate sensorimotor cortex

The appearance of oscillatory modes of 'gamma' activity in many cortical areas of different species has generated interest in understanding their underlying mechanisms and possible functions. This paper reviews evidence from studies on primate motor cortex showing that oscillatory activity entrains many neurons during periods of exploratory manipulative behavior. These oscillatory episodes synchronize widely spread neurons in sensorimotor cortex bilaterally, including descending corticospinal neurons, as evidenced by correlated modulations in EMG activity. The resulting neural synchronization involves task-related and -unrelated neurons similarly, suggesting that it is more likely to play some global role in attention than mediating any obvious interactions involved in coordinating movements. Intracellular recordings have elucidated the strength and types of synaptic interactions between motor cortical neurons that are involved in both normal and oscillatory activity. Spike-triggered averages (STAs) of intracellular membrane potentials have revealed serial connections in the form of unitary excitatory and inhibitory post-synaptic potentials (EPSPs and IPSPs). More commonly, STAs showed large synchronous excitatory or inhibitory potentials (ASEPs and ASIPs) beginning before the trigger spike and composed of multiple unitary events. ASEPs involved synchronous activity in a larger and more widespread group of presynaptic neurons than ASIPs. During oscillatory episodes synchronized excitatory and inhibitory synaptic potentials occurred in varying proportions. EPSPs evoked by stimulating neighboring cortical sites during the depolarizing phase of spontaneous oscillations showed evidence of transient potentiation. These observations are consistent with several functional hypotheses, but fit best with a possible role in attention or arousal.

Dynamics of dendritic calcium transients evoked by quantal release at excitatory hippocampal synapses

Synaptic N-methyl-D-aspartate (NMDA) receptors detect coincident pre- and postsynaptic activity and play a critical role in triggering changes in synaptic strength at central synapses. Despite intensive study of synaptic plasticity, relatively little is known about the magnitude and duration of calcium accumulation caused by unitary events at individual synapses. We used fluorescence imaging to detect NMDA receptor-mediated miniature synaptic calcium transients (MSCTs) caused by spontaneous release of synaptic vesicles in dendrites of cultured hippocampal neurons. MSCTs originated focally in dendritic regions <1 microm in length and decayed with a time constant of 0.35 +/- 0.03 s. Multiple occurrences of MSCTs recorded at single sites had fluctuating amplitudes, with a coefficient of variation of 0.34. From the reduction in the spatial spread of MSCTs with decreasing concentration of indicator dye, we estimated that the dominant endogenous calcium buffer in dendrites is relatively immobile (diffusion coefficient between 10 and 50 microm(2)/s). We conclude that calcium rise caused by spontaneous quantal synaptic NMDA receptor activation (i) is variable, (ii) lasts for a time period briefer than previous measurements indicate, and (iii) is confined by endogenous calcium buffers to local dendritic regions even when synapses are not on spines.

Reversal of synaptic vesicle docking at central synapses

We used quantitative fluorescence imaging of vesicles labeled with membrane-soluble dyes to determine rates of undocking and spontaneous exocytosis of vesicles docked to the active zone of hippocampal synapses in culture. Individual vesicles undock about once per two minutes and spontaneously exocytose about once per eight minutes. Thus, not only does undocking occur, but it is over threefold faster than spontaneous fusion.

Optical detection of synaptic vesicle exocytosis and endocytosis

Recent advances in optical methods have catalyzed a detailed study of individual visualized synapses in several model systems. Quantal events at small central synapses, as well as single granule exocytosis in secretory cells, have been detected using quantitative fluorescence imaging. Sensitive detection of exocytosis and endocytosis at individual synapses has advanced our knowledge of synaptic vesicle trafficking.

Synaptic plasticity: step-wise strengthening

Recent studies suggest that the strength of synapses in the brain may change in a step-wise manner, rather than continuously.

Synaptic vesicles retain their identity through the endocytic cycle

After fusion of synaptic vesicles with presynaptic membrane and secretion of the contents of the vesicles into the synaptic cleft (a process known as exocytosis), the vesicular membrane is retrieved by endocytosis (internalization) for re-use. Several issues regarding endocytosis at central synapses are unresolved, including the location of membrane retrieval (relative to the active zone, where exocytosis occurs), the time course of various endocytic steps, and the recycling path taken by newly endocytosed membranes. The classical model of synaptic-vesicle recycling, proposed by analogy to other cellular endocytic pathways, involves retrieval of the membrane, fusion of the membrane with endosome-like compartments and, finally, budding of new synaptic vesicles from endosomes, although the endosomal station may not be obligatory. Here we test the classical model by using the fluorescent membrane dye FM1-43 with quantitative fluorescence microscopy. We find that the amount of dye per vesicle taken up by endocytosis equals the amount of dye a vesicle releases on exocytosis; therefore, we conclude that the internalized vesicles do not, as the classical picture suggests, communicate with intermediate endosome-like compartments during the recycling process.

Synaptic plasticity: neighborhood influences

Recent studies indicate that, when the strengths of specific synapses are modified by activity, changes in strengths also occur at neighboring synapses; this neighborhood influence has important implications for how synaptic modifications implement learning and memory.

Heterogeneous release properties of visualized individual hippocampal synapses

We have used endocytotic uptake of the styryl dye FM1-43 at synaptic terminals (Betz and Bewick, 1992) to study properties of individual synapses formed by axons of single hippocampal neurons in tissue culture. The distribution of values for probability of evoked transmitter release p estimated by dye uptake is continuous, with a preponderance of low p synapses and a broad spread of probabilities. We have validated this method by demonstrating that the optically estimated distribution of p at autapses in single-neuron microislands predicts, with no free parameters, the rate of blocking of NMDA responses by the noncompetitive antagonist MK-801 at the same synapses. Different synapses made by a single axon exhibited varying amounts of paired-pulse modulation; synapses with low p tended to be facilitated more than those with high p. The increment in release probability produced by increasing external calcium ion concentration also depended on a synapse's initial p value. The size of the recycling pool of vesicles was strongly correlated with p as well, suggesting that synapses with higher release probabilities had more vesicles. Finally, p values of neighboring synapses were correlated, indicating local interactions in the dendrite or axon, or both.

Oscillatory activity in sensorimotor cortex of awake monkeys: synchronization of local field potentials and relation to behavior

1. Oscillations of 20-40 Hz were observed in local field potentials (LFPs) and unit activity in sensorimotor cortices of three awake monkeys while the monkeys performed trained wrist movements and untrained exploratory arm movements. The mean frequency of LFP oscillations was 25.9 +/- 1.4 (SD) Hz and the number of cycles of oscillations per episode was variable, with a mean of 4.2 +/- 0.5 (mean +/- SE). 2. Oscillatory episodes occurred most often when the monkeys retrieved raisins from a Klüver board (0.59 +/- 0.23 episodes per s, mean +/- SD) or from unseen locations with the use of somatosensory feedback (0.62 +/- 0.12 episodes per s); they occurred less often when the monkeys performed repetitive wrist flexion and extension movements (0.22 +/- 0.04 episodes per s) or sat quietly at rest (0.23 +/- 0.17 episodes per s). 3. The amplitude of LFP oscillations increased with depth in cortex, reaching a maximum between 1 and 2 mm. LFP oscillations at the surface of the cortex were 180 degrees out of phase with oscillations in the deep cortical layers. The phase shift (with respect to the deep layers) decreased with depth in the cortex and disappeared at depths of > 1 mm. 4. LFPs were recorded simultaneously at multiple sites in the sensorimotor cortex when monkeys retrieved raisins from a Klüver board or from unseen locations. Cross-correlation of LFPs recorded at different sites indicated that oscillations in the 20- to 40-Hz range could become synchronized at sites separated by up to > or = 14 mm in the precentral cortex. 5. The probability of occurrence of significant correlations between LFP oscillations at paired sites and the average correlation amplitude decreased with increasing horizontal separation of sites in precentral cortex. The phase shift between LFP oscillations recorded at paired sites did not change significantly with increasing horizontal separation. 6. For paired sites in precentral cortex, the average strength of correlations and the proportion of oscillations that were significantly correlated were greater during exploratory behaviors such as retrieving raisins from slots of the Klüver board than during periods of rest or overtrained wrist movements. 7. Oscillations could become synchronized with small phase shifts (0.5 +/- 1.6 ms) between pre- and postcentral cortical sites. Average strength and probability of occurrence of significant correlations between pre- and postcentral LFPs increased during exploratory behaviors. 8. Oscillations occurred simultaneously in the left and right motor cortex and could become synchronized with negligible phase shifts when the monkey performed bimanual manipulations. However, synchronization occurred as often and as strongly for unimanual as for bimanual manipulations. 9. These results indicate that episodes of 20- to 40-Hz oscillations occur often and become synchronized over a large cortical area during exploratory forelimb movements. However, they have no reliable relation to particular components of the movement and therefore seem unlikely to be involved directly in movement execution; instead, they may represent a neural correlate of attention during demanding sensorimotor behaviors.

Synchronization of neurons during local field potential oscillations in sensorimotor cortex of awake monkeys

1. The neural activity associated with 20- to 40-Hz oscillations in sensorimotor cortex of awake monkeys was investigated by recording action potentials of single and multiple units. At a given site, activity of many units became synchronized with local field potential (LFP) oscillations. Cycle-triggered histograms (CTHs) of unit spikes aligned on cycles of LFP oscillations indicated that about two thirds of the recorded units (n = 268) were entrained with LFP oscillations. On average, units had the highest probability of spiking 2.7 ms before peak LFP negativity, corresponding to a -27.6 degrees phase shift relative to the negative peak of the LFP. 2. The average relative modulation amplitude (RMA), defined as the ratio of amplitude of oscillatory component of CTH and the baseline multiplied by 100, was 45 +/- 27% (mean +/- SD). The RMAs of single units did not differ significantly from those of multiple units. 3. Phase shifts and RMAs did not vary systematically with the cortical depth of recorded units. 4. Autocorrelation histograms (ACHs) of entrained units exhibited clear 20- to 40-Hz periodicity if they were compiled with spikes that occurred during oscillatory episodes in LFPs. ACHs of spikes outside oscillatory episodes usually did not show periodicity. Global ACHs of all spikes typically showed weak or no evidence of periodic activity. 5. Cross-correlation histograms (CCHs) between pairs of units complied with all spikes, whether they occurred during or outside LFP oscillations, seldom revealed significant features (19 of 134 pairs or 14%). However, CCHs compiled with spikes that occurred during oscillatory episodes (OS-CCHs) had significant features in 67 of 134 pairs recorded ipsilaterally; in these 67 cases, units at both sites showed modulation in CTHs. 6. The latencies of the OS-CCH peaks (taking the medial unit as reference) were normally distributed about a mean of -0.5 +/- 13 ms. Normalized peak height of CCHs (peak/baseline x 100) was, on average, 14.3 +/- 11.2%. Peak latency and normalized peak amplitude did not change significantly with horizontal separation of recorded precentral pairs up to 14 mm. 7. Units in the left and right hemispheres could become synchronized during oscillations. Significant features in OS-CCH were detected in 22 of 42 pairs of units recorded bilaterally. The average peak latency was 0.2 +/- 8.0 ms and the average normalized peak amplitude was 10 +/- 8%. These parameters did not differ significantly from those for ipsilateral OS-CCHs. 8. Oscillations tended to affect both the temporal structure and net rate of unit firing. For each unit, the firing rate was clamped to a narrow range of frequencies during oscillatory episodes. The coefficient of variation (SD/mean) of firing rates was significantly reduced during oscillatory episodes compared with prior rates (P < 0.001, paired t-test). However, the overall mean firing rate of each unit during all oscillatory episodes did not differ from its average rate immediately before the episodes. Thus oscillatory episodes tended to clamp mean firing rates to the cells' average rates outside episodes. 9. The strength of synchronization between units during oscillatory episodes was unrelated to their involvement in the task. For pairs of precentral units recorded ipsilaterally, the probability of occurrence of significant features in the OS-CCH was slightly larger when both units of the pair were task related (33 of 56 pairs or 59%) than when only one unit was task related (20 of 39 pairs or 51%) or neither unit was task related (7 of 16 or 44%). However, these differences were not statistically significant. The magnitude of the correlation peak and the latency to peak were also not significantly different for the three cases. 10. These results suggest that units across wide regions can become transiently synchronized specifically during LFP oscillations, even if their spikes are uncorrelated during nonoscillatory periods.

Coherent 25- to 35-Hz oscillations in the sensorimotor cortex of awake behaving monkeys

Synchronous 25- to 35-Hz oscillations were observed in local field potentials and unit activity in sensorimotor cortex of awake rhesus monkeys. The oscillatory episodes occurred often when the monkeys retrieved raisins from a Klüver board or from unseen locations using somatosensory feedback; they occurred less often during performance of repetitive wrist flexion and extension movements. The amplitude, duration, and frequency of oscillations were not directly related to movement parameters in behaviors studied so far. The occurrence of the oscillations was not consistently related to bursts of activity in forearm muscles, but cycle-triggered averages of electromyograms revealed synchronous modulation in flexor and extensor muscles. The phase of the oscillations changed continuously from the surface to the deeper layers of the cortex, reversing their polarity completely at depths exceeding 800 microns. The oscillations could become synchronized over a distance of 14 mm mediolaterally in precentral cortex. Coherent oscillations could also occur at pre- and postcentral sites separated by an estimated tangential intracortical distance of 20 mm. Activity of single units was commonly seen to burst in synchrony with field potential oscillations. These findings suggest that such oscillations may facilitate interactions between cells during exploratory and manipulative movements, requiring attention to sensorimotor integration.

Antihepatotoxic activity of eclipta alba, tephrosia purpurea and boerhaavia diffusa

Alcoholic and chloroform extracts of E. albaT. purpurea and B. diffusa were screened for antihepatotoxic activity. The extracts were given after the liver was damaged with CCl4. Liver function was assessed based on liver to boy weight ratio, pentobarbitone sleep time, serum levels of transaminase (SGPT, SGOT), alkaline phosphatase (SALP) and bilirubin. Alcoholic extract of E. alba was found to have good antihepatotoxic activity.

Hepatic apo B-100 lipoproteins and plasma LDL heterogeneity in African green monkeys

The contribution of hepatic apolipoprotein (apo) B-100 lipoproteins to plasma low-density lipoprotein (LDL) metabolic heterogeneity was examined in African green monkeys. Hepatic 3H-labeled very low-density lipoproteins (VLDL) (d less than 1.006, where d is density in g/ml) or hepatic 131I-labeled LDL (1.030 less than d less than 1.063) were isolated from perfused livers and injected simultaneously with autologous plasma 125I-LDL into African green monkeys. Serial blood samples were taken, and the distribution of radioactivity among various subfractions of apo B-100 lipoproteins was determined using density-gradient ultracentrifugation. Compartmental models were developed to describe simultaneously the kinetics of hepatic lipoproteins and plasma LDL. In five of seven studies, the metabolic behavior of LDL derived from radiolabeled hepatic lipoprotein precursors differed from the metabolic behavior of radiolabeled autologous plasma LDL. These differences could be described by different models supporting two hypotheses with different physiological interpretations: 1) lipoproteins of donor and recipient animals are kinetically distinct, and/or 2) plasma LDL derived from various potential sources are kinetically distinct. Compartmental modeling was used to test these hypotheses, which were not accessible to testing by conventional experimental methodologies. The kinetic analyses of these studies suggest that plasma LDL may be derived from a variety of precursors, including hepatic VLDL and hepatic LDL, with each source giving rise to metabolically distinct plasma LDL.

Metabolic regulation of apoproteins of high-density lipoproteins by estrogen and progesterone in the baboon (Papio sp)

To determine the metabolic regulation of the apoproteins of high-density lipoproteins (HDL) by estrogen and progesterone, 12 ovariectomized and hysterectomized baboons were fed a high cholesterol, high fat diet and were divided into four groups. One of these groups was the untreated control and the remaining three groups were treated with estrogen, progesterone, or a combination of both. After 10 months of treatment, there were significant differences in HDL apolipoprotein (apo) A-I and apo A-II levels in these groups. The apo A-I level was highest in baboons treated with the combination therapy, followed by those treated with estrogen. Baboons treated with progesterone and those in the control group had similar levels of apo A-I. Baboons treated with both estrogen and progesterone and estrogen alone had significantly higher levels of apo A-I than those in the control or progesterone group. Baboons treated with hormones had higher apo A-II levels than controls, and those treated with the combination therapy had the highest level. Metabolic studies suggested that both estrogen and progesterone increased apo A-I and apo A-II production. Progesterone also increased the fractional catabolic rate of apo A-I, but not of apo A-II. On the other hand, estrogen did not affect the fractional catabolic rate of either apo A-I or apo A-II. Thus, increased apo A-I content of HDL in baboons treated with both estrogen and progesterone or estrogen alone appears to be due to increased apo A-I synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of larger high density lipoproteins accumulating in some families of baboons fed a high cholesterol and high saturated fat diet

Progeny of certain baboon sires accumulate lipoproteins in high density lipoprotein-1 (HDL1) when challenged with a high cholesterol, high saturated fat diet. These studies were conducted to determine the apoprotein composition and metabolic fate of HDL1 in the plasma. HDL1 particles containing apoA-I with and without apoE were detected. The majority of particles, however, contained apoA-I without any detectable apoE. To determine the metabolic fate of HDL1 in plasma, HDL1 labeled with iodinated apoA-I from animals with high levels of HDL1 and iodinated apoA-I-labeled autologous HDL were coinjected into both high and low HDL1 animals. The data for the decay of radioactivity in HDL1 and HDL were analyzed by multicompartment modelling. The radioactivity from HDL1 was cleared from the plasma either via direct removal (9.1 +/- 4.7% in low and 21.7 +/- 8.3% in high HDL1 animals) or via its conversion to HDL. A large proportion of radioactivity from HDL1 was rapidly transferred to HDL directly or metabolized via an intermediate compartment. Most of the radioactivity from apoE-poor HDL1, however, was transferred to HDL. Both high and low HDL1 animals catabolized HDL1 and HDL similarly. Low HDL1 animals transferred HDL1 radioactivity to HDL much faster. No detectable radioactivity from HDL was transferred to HDL1. Thus, HDL1 that accumulates in high HDL1 animals is mainly a precursor for HDL. Our hypothesis is that this accumulation of HDL1 is due to the slower cholesteryl ester transfer from HDL to lower density lipoproteins, thus affecting reverse cholesterol transport in high HDL1 baboons.

Psychiatric morbidity and the menopause

A sample consisting of Menopausal, pre menopausal and post menopausal women in the age range of 36 to 50 years was studied using a two stage screening procedure for identifying and assessing psychiatric morbidity. The screening device, General Health questionnaire (GHQ) identified 21 of the 105 women studied as 'possible cases'. On further interviews using standard psychiatric interview (SPI) a higher proportion of menopausal women were found to be psychiatrically ill. The predominant symptom in the Menopausal group was depression. Both menopausal women and women who had undergone hysterectomy (surgical menopause) received higher mean ratings on SPI. The inter-rater reliability of SPI was found to be high and was comparable to those reported by original authors.

Personality and the nature of suicidal attempts

In a comparative study (Vinoda, 1966) of personality characteristics of 50 female attempted suicides and an individually matched group of 50 psychiatric controls and 50 normals, it was observed that the attempted suicides differed from the psychiatric and normal controls on measures of hostility, guilt, rigidity and neuroticism. Attempted suicides (AS) were significantly more hostile and rigid than both psychiatric controls (PC) and normal controls (NC), and they were significantly more personally ill (neurotic) than normal controls but not more than psychiatric controls. On the basis of previous researches it was hypothesized that the group of attempted suicides would be more hysteroid in their personality and intropunitive in the direction of their punitiveness than the control groups. The first study (Vinoda, 1966) did not reveal such differences. The scrutiny of results showed that there were more or less equal numbers of hysteroid and obsessoid personalities among attempted suicides and similarly a more or less equal number of persons who were intropunitive or extrapunitive in the direction of their aggression. This led the author to hypothesize that these variables might be more related to the nature of suicidal attempts in terms of seriousness of the attempts made.