Inducing Mechanical Stimuli to Tissues Grown on a Magnetic Gel Allows Deconvoluting the Forces Leading to Traumatic Brain Injury.

Traumatic brain injury (TBI), which is characterized by damage to the brain resulting from a sudden traumatic event, is a major cause of death and disability worldwide. It has short- and long-term effects, including neuroinflammation, cognitive deficits, and depression. TBI consists of multiple steps that may sometimes have opposing effects or mechanisms, making it challenging to investigate and translate new knowledge into effective therapies. In order to better understand and address the underlying mechanisms of TBI, we have developed an in vitro platform that allows dynamic simulation of TBI conditions by applying external magnetic forces to induce acceleration and deceleration injury, which is often observed in human TBI. Endothelial and neuron-like cells were successfully grown on magnetic gels and applied to the platform. Both cell types showed an instant response to the TBI model, but the endothelial cells were able to recover quickly-in contrast to the neuron-like cells. In conclusion, the presented in vitro model mimics the mechanical processes of acceleration/deceleration injury involved in TBI and will be a valuable resource for further research on brain injury.

A Platform for Assessing Cellular Contractile Function Based on Magnetic Manipulation of Magnetoresponsive Hydrogel Films.

Despite significant advancements in in vitro cardiac modeling approaches, researchers still lack the capacity to obtain in vitro measurements of a key indicator of cardiac function: contractility, or stroke volume under specific loading conditions-defined as the pressures to which the heart is subjected prior to and during contraction. This work puts forward a platform that creates this capability, by providing a means of dynamically controlling loading conditions in vitro. This dynamic tissue loading platform consists of a thin magnetoresponsive hydrogel cantilever on which 2D engineered myocardial tissue is cultured. Exposing the cantilever to an external magnetic field-generated by positioning magnets at a controlled distance from the cantilever-causes the hydrogel film to stretch, creating tissue load. Next, cell contraction is induced through electrical stimulation, and the force of the contraction is recorded, by measuring the cantilever's deflection. Force-length-based measurements of contractility are then derived, comparable to clinical measurements. In an illustrative application, the platform is used to measure contractility both in untreated myocardial tissue and in tissue exposed to an inotropic agent. Clear differences are observed between conditions, suggesting that the proposed platform has significant potential to provide clinically relevant measurements of contractility.

Improved design for a highly efficient pulsed-valve supersonic source with extended operating frequency range.

We present a new design for a pulsed supersonic-beam source, inspired by the Even-Lavie valve, which is about four times more energy efficient than its predecessor and can run at more than double the repetition rate without experiencing resonances. Its characteristics make it a better candidate as a source for cryogenic-related experiments as well as spectroscopy with rapidly pulsed lasers. The new design is also simpler to build and is more robust, making it accessible to a larger portion of the scientific community.

Vortex beams of atoms and molecules.

Angular momentum plays a central role in quantum mechanics, recurring in every length scale from the microscopic interactions of light and matter to the macroscopic behavior of superfluids. Vortex beams, carrying intrinsic orbital angular momentum (OAM), are now regularly generated with elementary particles such as photons and electrons. Thus far, the creation of a vortex beam of a nonelementary particle has never been demonstrated experimentally. We present vortex beams of atoms and molecules, formed by diffracting supersonic beams of helium atoms and dimers off transmission gratings. This method is general and could be applied to most atomic and molecular gases. Our results may open new frontiers in atomic physics, using the additional degree of freedom of OAM to probe collisions and alter fundamental interactions.

An outbreak of leptospirosis among Israeli troops near the Jordan River.

An outbreak of leptospirosis that involved 7 of a team of 27 Israeli troops occurred following a military exercise in northern Israel near the Jordan River. The organism implicated in the outbreak was Leptospira interrogans serovar Hardjo. The clinical course was uncomplicated and all patients fully recovered. There were no cases of asymptomatic infection. Military personnel should be recognized as having an occupational risk for contracting leptospirosis, especially when military activity takes place near natural water sources inhabited by cattle, taking into account the local epidemiology of this disease. Moreover, outbreaks among military personnel may serve as a sentinel for leptospiral illness in areas in which civilian exposure takes place, such as the Jordan River, which is an important site that involves immersion in the context of both pilgrimage and civilian recreational activities."Bathe and you will become clean. So he went down and immersed himself seven times in the Jordan, as Elisha had told him to do. And his flesh became clean once more like the flesh of a small child."II Kings 5:14.

Basic fibroblast growth factor selectively amplifies the functional state of neurons producing neuropeptide Y but not somatostatin in cultures of fetal brain cells: evidence for a cooperative interaction with insulin-like growth factor-I.

The role of basic fibroblast growth factor (bFGF) in regulating the functional state of neuropeptide Y (NPY) neurons in the brain was investigated, using aggregate cultures, derived from 17-day-old fetal rat cortex maintained for 16 days in serum-free medium, as a model. The criterion for the functional state was NPY production in response to a 24-h exposure to forskolin + phorbol 12-myristate 13-acetate (For + PMA). bFGF (0.1 nM) induced a approximately 2-fold increase in NPY production under basal conditions as well as after For + PMA (p < 0.001 vs control). To address the possibility that bFGF may interact with other growth factors, we assessed the effect of bFGF in the presence of long R3-insulin-like growth factor-I (l-IGF-I; 1 nM) and found that NPY production in response to For + PMA was even greater than with bFGF alone (2-fold; p < 0.001); even though l-IGF-I by itself was ineffective; suggesting that bFGF is the driving force of this amplification. To assess the selectivity of this process, we evaluated SRIF production in response to For + PMA and found that it was not amplified by bFGF, l-IGF-I, or bFGF + l-IGF-I. These results are consistent with bFGF selectively amplifying the functional state of the cAMP and protein kinase C (PKC) pathways leading to increased NPY-production, with cooperative interaction(s) between bFGF and IGF-I, and with a role for bFGF and IGF-I in the developmental expression/survival of the NPY neurons.

Forskolin and phorbol ester stimulation of neuropeptide Y (NPY) production and secretion by aggregating fetal brain cells in culture: evidence for regulation of NPY biosynthesis at transcriptional and posttranscriptional levels.

Using fetal brain cells in culture, we have previously shown that activation of the cAMP pathway by forskolin induces the production and secretion of neuropeptide Y (NPY). In this study we wished to ascertain 1) if activation of the protein kinase C pathway induces NPY production and/or secretion and if there is synergism between the pathways, and 2) the role of protein/RNA synthesis and influx of extracellular calcium. Aggregates, formed from dissociated cells obtained from the hypothalamus-olfactory tubercle area of 17-day-old rat fetuses, were cultured in serum-free medium for 12 days. The NPY content of aggregates incubated for 24 h with solvent (control) was 4.4 ng/flask, and the medium content was 7.6 ng. Forskolin (10 microM) or phorbol 12-myristate 13-acetate (PMA; 20 nM) marginally affected aggregate content, but each increased medium content 2- to 3-fold; forskolin and PMA were additive. When cycloheximide (75 microM) was included along with forskolin, PMA, or forskolin plus PMA for a period of 10 h, the increase in NPY medium content was abolished. Actinomycin D (Act-D; 5 micrograms/ml) inhibited the response to each secretagogue in a time-dependent manner. When Act-D was included along with forskolin, PMA, or forskolin plus PMA for a total period of 12 or 24 h, the 12 h increase in content was not affected, whereas the 24 h increase was abolished. When the presence of Act-D was limited to 0-24, 6-24, or 12-24 h, and forskolin plus PMA were included for the entire 24-h period, the increase in NPY content was inhibited by 94%, 57%, and 12%, respectively. Verapamil (100 microM) totally inhibited the 24 h response to forskolin and partially (40-50%) inhibited the response to PMA or forskolin plus PMA. In none of these conditions was the inhibition of the increase in medium NPY content accompanied by an increase in aggregate content, nor was the NPY content of aggregate/medium of control cultures affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence that copper-amino acid complexes are potent stimulators of the release of luteinizing hormone-releasing hormone from isolated hypothalamic granules.

Chelated copper has been previously shown to stimulate the release of LHRH from isolated hypothalamic granules. In this study, we evaluated the chelator specificity, the kinetic constants, and the characteristics of copper interaction with LHRH granules. LHRH granules were isolated from the median eminence area of adult male rats and then incubated in a buffered medium at 37 C. Release of LHRH into the incubation medium was assessed by RIA of LHRH remaining in the granules after incubation. It was found that CuHistidine (CuHis) as well as CuCysteine markedly stimulated LHRH release from the isolated granules, release being 56% and 63%, respectively, of the total LHRH content of granules incubated in buffer alone. In contrast, neither CuGly-His-Lys nor CuBSA stimulated LHRH release. The CuHis-stimulated release of LHRH was a saturable function of the concentration of CuHis. The Michaelis-Menten constants of this release process were estimated; the apparent Km for copper was found to be 4 microM, and the maximal velocity was 65% of the granule content of LHRH released in 5 min. In addition, we noted that CuHis-stimulated release of LHRH, assessed 6 min after CuHis, was completely abolished when dithiothreitol (DTT) was added immediately after CuHis, partially abolished when added 1 or 2 min after CuHis, and not affected at all when added 3 min after CuHis. This time course of DTT inhibition of LHRH release suggests that a period of 2-3 min of copper interaction with the granules is required for the 6-min manifestation of copper action. Furthermore, this DTT-inhibitable interaction of copper did not occur when granules were incubated at 4 C. In summary the findings that copper, chelated to putative circulating chelators, markedly stimulates LHRH release and that the apparent Km of 4 microM for copper in this process is within the concentration range for the physiological action of copper support the proposal that blood-borne copper can interact rapidly with the LHRH granule in an energy-requiring fashion and that, consequent to this interaction, LHRH release occurs.

Progesterone augments copper-prostaglandin E2 stimulation of the release of gonadotropin-releasing hormone from explants of the median eminence of immature female rats: an estrogen-dependent process.

We have previously shown that extracellular copper (Cu) amplifies prostaglandin E2 (PGE2) stimulation of LHRH release from explants of the median eminence area (MEA) of adult male rats, and that amplification is a post-PGE2 receptor event involving the adenylate cyclase system. We addressed the question: Is the process of Cu-amplified PGE2 stimulation of LHRH release regulated by ovarian steroids and, if so, is the regulatory steroid estrogen and/or progesterone? Immature female rats (30-32 days old) were ovariectomized and 6 days later treated with a combination of these steroids: E, sc implant of 17 beta-estradiol in a Silastic capsule for 3 days; EEi, E plus im injection of 17 beta-estradiol (2 micrograms/rat) 24 h before killing; and P, either im injection of 0.08 mg/kg progesterone 1 h before killing or 10(-9) M P included in the incubation buffer starting 1 h before Cu/PGE2 exposure. Controls were treated with the vehicle. MEAs were incubated for 5 min with 150 microM Cu, for 15 min with 10 microM PGE2, and then for 45 min with buffer (Cu/PGE2); LHRH release into the medium was measured by RIA. Cu/PGE2-stimulated LHRH release from MEA of intact rats was about 10 times greater than basal release. Ovariectomy led to a 50% reduction in Cu/PGE2-stimulated release [sham, 20.6 +/- 2.0 (mean +/- SE); ovariectomized, 9.4 +/- 1.8], pg/30 mm/MEA; and neither E, EEi, nor P significantly altered this response. In contrast, administration of P to either E- or EEi-primed rats augmented Cu/PGE2 stimulation of LHRH release 3.5-fold (E vs. EP or EEi vs. EEiP); however, P did not augment stimulation of LHRH release by Cu alone or PGE2 alone. Also, inclusion of P in the incubation buffer was as effective as in vivo P in augmenting Cu/PGE2 stimulation of LHRH release from the MEA of EEi-primed rats. On the other hand, in vitro P by itself did not alter LHRH release. These effects of P on the response of the MEA to Cu/PGE2 were not accompanied by a significant increase in the MEA content of LHRH. The process of Cu/PGE2 stimulation of LHRH release is regulated by ovarian steroids, so that ovariectomy leads to a marked reduction of the response of the MEA to Cu/PGE2, and P augments this response in an estrogen-dependent manner. Moreover, it is the secretory process elicited by the combined effects of Cu and PGE2 that is augmented by P.(ABSTRACT TRUNCATED AT 400 WORDS)

The maturational process of gonadotropin-releasing hormone neurons in the male rat: a role for the adrenal gland in the increase in secretory function.

The aim of this study was to define the maturational process of the LHRH neuron in the male rat and the role of the adrenal and testis. Maturing (7-week-old) and adult (12-week-old) male rats were adrenalectomized (ADX), castrated (TX), or ADX and TX; controls were sham operated. Two weeks later, LHRH release from explants of the median eminence area (MEA), MEA LHRH content, and serum testosterone (T) were determined. MEA were incubated for 5 min with 150 microM copper and then for 15 min with 10 microM prostaglandin E2 (Cu/PGE2). LHRH release in response to Cu/PGE2 increased 3-fold between 7 and 9 weeks of age [from 10.4 +/- 1.8 to 29.2 +/- 2.1 pg/15 min.MEA (mean +/- SE)], and there was no further increase thereafter. ADX, TX, or ADX plus TX of 7-week-old rats prevented the increase in Cu/PGE2-stimulated release. In contrast, ADX of 12-week-old rats did not alter LHRH release, whereas TX or ADX plus TX drastically reduced it (75%). The MEA content increased gradually between 7 and 14 weeks of age (from 2.0 +/- 0.2 to 3.0 +/- 0.3 ng). ADX of either 7- or 12-week-old rats did not alter LHRH content, whereas TX or ADX plus TX reduced it to 1.3 ng in both age groups. Serum T increased 6.7-fold between 7 and 9 weeks of age (from 1.06 +/- 0.42 to 6.70 +/- 0.57 ng/ml), and there was no further increase thereafter. ADX of 7-week-old rats did not alter serum T, whereas ADX of 12-week-old rats reduced serum T to 0.62 +/- 0.15 ng/ml. Serum T was undetectable in TX or ADX plus TX rats of both age groups. In summary, maturation of the male reproductive system is associated with a moderate increase in LHRH content of the median eminence and marked increases in the secretory function of the LHRH neuron and in serum T; the testis is essential for these maturational increases. In addition to the testis, the adrenal is necessary for the maturational increase in the secretory function of the LHRH neuron, but not for the increase in LHRH content or that in serum T. It is proposed that dissociable mechanisms regulate LHRH secretion and content in the maturing male, and that T and a substance of adrenal origin (steroid?) are required for the maturational increase in secretory function of the LHRH neuron.

Copper stimulates the release of luteinizing hormone releasing hormone from isolated hypothalamic granules.

Copper, administered to female rabbits, stimulates LHRH release into the hypophyseal portal blood (5) and induces ovulation (1-3). To gain further understanding of the mechanism of action of copper, in this study we addressed the question: Does copper, in the form of CuATP, stimulate LHRH release from isolated hypothalamic granules? Isolated hypothalamic granules, obtained from adult male rats, were incubated under in vitro conditions in the absence (control) or presence of CuATP (0.1 - 2.5 mM). In the presence of CuATP, we noted that LHRH release was stimulated, and the magnitude of stimulation was a saturable function of the concentration of copper, being maximal at 2.5 mM. In addition, we compared the effects of a series of divalent cations (Cu, Zn, Mg, Ca, Fe, Ba, Sr, Mn; 2.5 mM each) on LHRH release and found that copper stimulated release seventeenfold, zinc--sixfold, and the other divalent cations--twofold or less. Thus, copper appears to be a unique releaser of LHRH, and it may act at the level of the LHRH granule.

A correlation between the ligand specificity for 67copper uptake and for copper-prostaglandin E2 stimulation of the release of gonadotropin-releasing hormone from median eminence explants.

We have previously shown that copper (Cu) leads to a 3- to 4-fold amplification of prostaglandin E2 (PGE2) stimulation of LHRH release from explants of the median eminence area (MEA), that this amplification is a saturable function of [Cu], and that complexed Cu but not ionic Cu is the active form of the metal. This implicates a ligand-specific site in Cu action. In this study we address the following questions. Is there a ligand specificity for Cu amplification of PGE2 stimulation of LHRH release, and if so, does it correlate with the ligand specificity for Cu uptake? MEAs of 1-month-old female rats were incubated for 5 min with 150 microM Cu solution and then for 15 min with 10 microM PGE2 (Cu/PGE2); LHRH released into the medium was evaluated by RIA. To assess Cu uptake, MEAs were incubated with 100 microM67 Cu solution for 15 min, and 67Cu accumulation by the MEA was evaluated. The Cu was complexed to one of the following ligands: histamine, His, Cys, Thr, Gly, glutathione, Gly-His-Lys, or albumin. There was a high degree of correlation (r = 0.943) between the ligand specificity for Cu/PGE2 stimulation of LHRH release (Cu action) and 67Cu uptake. Complexation of ionic Cu with His facilitated Cu action and 67Cu uptake 3-fold each, and this was completely prevented by the inclusion of His in a 100-fold excess over the concentration of the Cu/His complex. Histamine, the amino acids, and the peptides facilitated Cu action and 67Cu uptake, whereas albumin did not do so. Of these facilitatory ligands, histamine and His were the most effective and Gly-His-Lys was the least effective. In summary, both 67Cu uptake and Cu action are ligand-dependent and ligand-specific; the Cu interactive sites have a common recognition for the Cu-ligand complex and for the ligand itself; and the ligand specificity for 67Cu uptake and for Cu action are highly correlated. These results are consistent with the ligand specificity for Cu uptake being the primary determinant of the ligand specificity for Cu/PGE2 stimulation of LHRH release.

Extracellular calcium is required for copper-amplified prostaglandin E2 stimulation of the release of gonadotropin-releasing hormone from median eminence explants.

Prostaglandin E2 (PGE2) is known to stimulate the release of LHRH from hypothalamic tissue incubated under in vitro conditions. We have previously shown that a short preincubation of explants of the median eminence area with copper(II) [Cu(II)] complexed to histidine (CuHis) markedly amplifies PGE2 stimulation of LHRH release. In this study, we wished to ascertain if Cu-amplified PGE2 stimulation of LHRH release is dependent on influx of extracellular calcium (Ca) and, if so, whether it is the copper and/or PGE2 action that is Ca dependent. Median eminence area explants were incubated for 5 min with 200 microM CuHis, then for 15 min with 10 microM PGE2, and finally for 45 min in buffer (Cu/PGE2). Controls were incubated with CuHis or PGE2. In the presence of Ca (1.8 mM), Cu/PGE2 stimulation of LHRH release reached a peak value within 15 min of exposure to PGE2 (accelerated phase), after which the rate of release declined, with a half-life of about 20 min (decelerated phase). In the absence of Ca, Cu/PGE2 stimulation of LHRH release was inhibited by 70% during the accelerated phase, and it was completely inhibited during the decelerated phase. When incubation was carried out in the presence of Ca and 100 microM verapamil, Cu/PGE2 stimulation of LHRH release was similar to that seen in the absence of extracellular Ca. When Ca was omitted from the incubation medium during the exposure to CuHis but was included during and after the exposure to PGE2, the response to PGE2 was fully restored. In addition, we evaluated the extracellular Ca requirement for stimulation of LHRH release by PGE2 alone (without pretreatment with CuHis) and found that release was inhibited by 65% in the absence of Ca. These results indicate that the process of PGE2 stimulation of LHRH release is partially dependent on extracellular Ca, that the process of Cu-amplified PGE2 stimulation of release is highly dependent on influx of extracellular Ca, and that PGE2 action, but not Cu action, is dependent on Ca influx. Since cAMP has been implicated in Ca2+-dependent secretion in other cells, we propose that Cu amplifies the functional state of a postreceptor component involved in the Ca-cAMP secretory pathway stimulated by PGE2.

Evidence that a short-lived effect of copper leads to amplification of prostaglandin E2 stimulation of the release of gonadotropin-releasing hormone from median eminence explants.

We have previously shown that copper (Cu) amplifies prostaglandin E2 (PGE2) stimulation of LHRH release from explants of the median eminence area (MEA) incubated under in vitro conditions. In this study, we have carried out an extensive comparative study of the kinetics of the process of PGE2 stimulation and C alpha-amplified PGE2 (Cu/PGE2) stimulation of LHRH release. MEA explains obtained from adult male rats were incubated under in vitro conditions, and LHRH released into the medium was assayed by RIA. Kinetic parameters were established by varying the time of exposure of the MEA to Cu or PGE2 and the dose of Cu or PGE2. Cu action requires a minimal 5-min period of exposure of the MEA, is rapidly manifested (less than 5 min after transfer of Cu-free medium), and is reversible (half-life, 10-15 min). Cu amplification of PGE2 action is a saturable function of the concentration of both Cu and PGE2; half-saturation and saturation were achieved with 120 and 200 microM copper, respectively, and with 0.6 and 10 microM PGE2, respectively. A 5-min exposure of Cu-treated MEA to PGE2 has the following time course of PGE2 action: the maximal rate of LHRH release is attained within 5 min; release is maintained at the maximal rate for another 5 min and then declines. Importantly, this decline is not prevented by a longer (15-min) exposure of the MEA to PGE2, indicating desensitization to PGE2 action. When MEA treated with Cu (5 min) and PGE2 (15 min) is allowed to recover for 45 min in buffer, the tissue regains its responsiveness to PGE2. All of the kinetic parameters of the process induced by PGE2 alone are similar to those described above for Cu/PGE2, except that the magnitude of the maximal rate of PGE2-stimulated release is 4- to 6-fold lower and that release is maintained at this rate for about 45 min. We also examined the PG structure specificity for stimulation of LHRH release and found that PGD2 by itself or after Cu pretreatment is much less effective than PGE2 in stimulating LHRH release. In summary, Cu amplification of PGE2 stimulation of LHRH release from LHRH neuronal terminals (i.e. MEA explants) involves rapid activation of a short-lived component.(ABSTRACT TRUNCATED AT 400 WORDS)

Disproportionate accumulation of immunoreactive corticotropin, melanotropin, and lipotropin in the brain of the maturing rat.

The accumulation of immunoreactive ACTH (ACTHi), alpha MSH (alpha MSHi), and gamma-lipotropin (gamma LPHi) as a function of age (10-120 days) was determined in three regions of the brain of male rats: the medial basal hypothalamus (MBH), the preoptic anterior hypothalamus (POA), and the thalamus. In each region of the brain, the concentrations of ACTHi, alpha MSHi, and gamma LPHi increased with age. In the MBH, the increase occurred in such a manner that the molar ratio of alpha MSHi to ACTHi remained constant regardless of the age of the animals. In contrast, in the POA and thalamus, the increase occurred disproportionately in favor of alpha MSHi, and thus the molar ratio of alpha MSHi to ACTHi was 3 times higher in the adult (120 days old) than in the young (10 or 21 days old) animals. Nevertheless, the ratio of (ACTHi plus alpha MSHi) to gamma LPHi was constant at a level of about 2 regardless of the age of the animal or the region of the brain. Extracts of the MBH or POA were fractionated on columns of Sephadex G-75 superfine. The gel filtration profiles of ACTHi were indicative of the presence of five molecular weight forms of ACTH: greater than 40K, 30-40K, 20-30K, 5.7K, and 4.5K. We tentatively identified greater than 40K ACTH as a large form of proopiocortin, 30-40K ACTH as proopiocortin, 20-30K ACTH as ACTH biosynthetic intermediate, 5.7K as glycosylated ACTH(1-39), and 4.5K ACTH as ACTH-(1-39). Regardless of the age of the animals, the fractional amount of 30-40K ACTH the age of the animals, the fractional amount of 30-40K ACTH was high in the MBH compared to that in the POA. Moreover, the small fractional amount of 30-40K ACTH in the POA was associated with a large fractional amount of small molecular weight forms of ACTHi. However, the predominant form of ACTHi in the POA changed with age: 20-30K ACTH was the major form in the young, whereas 4.5K ACTH was the major form in the adult. These results support the proposal that the production of proopiocortin increases with age, and there is enhanced processing of proopiocortin to ACTH-(1-39) and alpha MSH in the brain of the maturing rat.

A role for extracellular copper in modulating prostaglandin E2 (PGE2) action: facilitation of PGE2 stimulation of the release of gonadotropin-releasing hormone (LHRH) from median eminence explants.

Copper is present in high concentrations in axonal terminals of hypothalamic neurons (1). We have previously postulated that copper is released from axonal terminals of hypothalamic neurons (2). In this study, we addressed the question: Does extracellular copper facilitate PGE2 action, specifically, the stimulation of LHRH release? The median eminence area (MEA) of male rats was incubated under in vitro conditions, and LHRH release into the medium was quantified by RIA. When MEA were incubated for 5 min with 100 microM copper and then for 15 min with 50 microM PGE2 (Cu/PGE2), Cu/PGE2-stimulated release of LHRH was significantly (P less than 0.001) greater (2 times) than the sum of copper- and PGE2-stimulated release. When MEA were first incubated for 15 min with PGE2 and then for 5 min with copper (PGE2/Cu), PGE2/Cu-stimulated release equalled the sum of PGE2- and copper-stimulated release of LHRH. Thus, copper facilitates PGE2 stimulation of LHRH release from the MEA, and the characteristics of this facilitation are consistent with an enhancement of PGE2 binding to its receptor. These results support the proposition that extracellular copper can serve as a modulator of PGE2 action.

Ontogeny of the subcellular compartmentalization of thyrotropin releasing hormone and luteinizing hormone releasing hormone in the rat hypothalamus.

The 900 x g supernatant fluid prepared from hypothalamic homogenates from male and female rats (ranging in age from -1 to 120 days) was fractionated by means of continuous sucrose density gradient centrifugation. Thyrotropin releasing hormone (TRH) and LH releasing hormone (LHRH) in the gradient fractions were quantified by radioimmunoassay. In adult hypothalamic homogenates, TRH and LHRH were associated with two populations of particles distinguishable by their sedimentation properties. Each peptide was in turn distributed in two subpopulations of parties differing in size but similar in density. The distribution of each peptide within its subpopulations of particles was found to be a function of age. In hypothalami of 22-day-old fetuses, TRH was associated almost entirely with the subpopulation of small particles. However, in the neonates, an age-dependent increase in the fractional amount of the TRH confined to the subpopulation of large particles was observed. By the 7th day of age, the peptide was equally distributed in the two subpopulations. The buoyant density of the 1-day-old neonatal particles and that of the adult small and large particles containing TRH was similar. The ontogeny of the subcellular compartmentalization of LHRH differed appreciably from that of TRH. LHRH was barely detectable in hypothalami of 22-day-old neonates. Nevertheless, at this age, the peptide was confined primarily to the subpopulation of large particles, and a similar compartmentalization was noted in hypothalami of 5- and 7-day-old neonates. However, in hypothalami of 14-day-old males and 21-day-old females, association of LHRH with the subpopulation of small particles was evident. It is concluded that 1) the nature of the hypothalamic subcellular compartmentalization of TRH and LHRH is age dependent, 2) the compartmentalization of each peptide in neonatal hypothalami differs from that in the adults, and 3) the development of the mature profile of subcellular compartmentalization of TRH and LHRH proceeds asynchronously.

Studies on the subsynaptosomal localization of luteinizing hormone-releasing hormone and thyrotropin-releasing hormone in the rat hypothalamus.

In the current investigation, subcellular particles (synaptosomes) of hypothalamic homogenates were isolated by differential centrifugation and discontinuous sucrose density gradient fractionation and found to be rich in LHRH, TRH, and the neuronal marker, norepinephrine (NE). Of the total quantity of LHRH, TRH, or NE in the nuclei-free homogenate, 52-65% was recovered in synaptosomes, whereas the cytosol, myelin/microsomes, and mitochondria contained only 1-12%. To determine the subsynaptosomal localization of LHRH and TRH, purified synaptosomes were lysed and the resulting suspensions were fractionated on discontinuous sucrose density gradients. LHRH (30-40%) was found to be localized primarily in subsynaptosomal particles which banded at sucrose densities between 0.6-1.0 M. Electron micorscopic analysis of these particles revealed the presence of dense-cored granules (70-80 nm diameter) and synaptosomal membrane remnants. Norepinephrine was found in two pools within the isolated nerve endings: 15-25% of synaptosomal NE was associated with the synaptic vesicles (45-55-nm diameter); about 40% was in the cytosol. TRH was present primarily as a soluble component of the nerve ending. No apparent association of TRH with dense-cored granules was demonstrable in this study; however, there may be some TRH in synaptic vesicles.

Dexamethasone-induced accumulation of neuropeptide-Y by aggregating fetal brain cells in culture: a process dependent on the developmental age of the aggregates.

Neuropeptide-Y (NPY) and glucocorticoid receptors are coexpressed in many neurons in the brain. We addressed the question: Do glucocorticoids regulate the accumulation and/or secretion of immunoreactive (IR) NPY by fetal rat brain cells in culture, and if so, is the effect developmental stage dependent? Aggregates, formed from dissociated cells obtained from the hypothalamus-olfactory tubercle of 17-day-old fetuses, were cultured in serum-free medium for 23 days. On day 23, the aggregate NPY content was 6 ng/flask, and secretion (last 2 days) was approximately 12 ng/24 h. Exposure to dexamethasone (Dex; 20 nM) between days 0-23 led to a 1.9-fold increase in the aggregate content of NPY, whereas NPY secretion was not altered. When Dex exposure was limited to days 12-23, 16-23, 19-23, or 21-23, only a 12- to 23-day exposure induced NPY accumulation, and it was as effective as a 0- to 23-day exposure. The Dex-induced increase in NPY content was evident after a lag period of 4 days or more. When Dex exposure occurred on days 0-12, the aggregate NPY content on day 12 or 23 was not altered. None of these treatments altered the aggregate/medium content of immunoreactive somatostatin (SRIF) or the response to a 48-h exposure to forskolin (10 microM). Dex induction of NPY accumulation was a saturable function of the Dex concentration (maximal at 20 nM), and it was completely inhibited by RU486, a glucocorticoid/progesterone receptor antagonist; neither progesterone, 17 beta-estradiol, nor testosterone altered aggregate/medium NPY contents. Protein/DNA contents of the aggregates were either unaffected or slightly reduced by Dex. Thus, 1) Dex stimulates the accumulation of immunoreactive NPY, but not SRIF, by cultured fetal brain cells; 2) this effect requires a continuous 8-12 days of exposure to Dex during a late developmental stage in culture; 3) Dex does not potentiate or attenuate forskolin action on the NPY neuron; and 4) Dex action appears to be mediated by the glucocorticoid receptor. These results are consistent with glucocorticoid induction of production and/or decreased intracellular degradation of NPY, and with glucocorticoids regulating the NPY neuron in the perinatal brain in a developmental age-dependent manner.

Expression of steroid metabolizing enzymes by aggregating fetal brain cells in culture: a model for developmental regulation of the progesterone 5 alpha-reductase pathway.

In this study, we established an in vitro model system for the study of developmental regulation of steroid enzyme expression in the perinatal brain. Single cell suspensions were prepared from the hypothalamic-olfactory tubercle region of 18-day-old rat fetuses, and aggregates were formed by incubation under constant rotation. On day 0, 3, 6, or 12 of culture, aggregates were incubated for 4 or 20 h with 3H-progesterone (P4) and the profile of 3H-steroids in the medium analyzed. Five major metabolites were formed from 3H-P4: 5 alpha-pregnan-3, 20-dione (DHP), 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH-DHP), 3 beta-hydroxy-5 alpha-pregnan-20-one (3 beta-OH-DHP), and two unidentified polar substances designated A and B. Progressively with aggregate-age in culture, there was a decrease in the relative amounts of 3H-P4 recovered in the medium and a sequential increase in DHP, 3 beta-OH-DHP, 3 alpha-OH-DHP, A and B. Aggregates maintained in a chemically defined, serum-free medium metabolized P4 at an accelerated rate compared to those maintained in serum. An inhibitor of the enzyme 5 alpha-reductase completely inhibited P4 metabolism, indicating that 5 alpha-reduction is the primary step in this pathway. Thus, the aggregates express three key enzymes in P4 metabolism: 5 alpha-reductase, 3 alpha- and 3 beta-hydroxysteroid oxidoreductases and the operation of this pathway is proposed: P4----DHP----3 alpha-OH-DHP + 3 beta-OH-DHP; A and B are derived from one or more of the latter three. Hence, this culture system can serve as a model to study regulatory processes in the developing steroidogenic brain.