Microtubule-Targeting Combined with HDAC Inhibition Is a Novel Therapeutic Strategy for Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine gliomas (DIPG) are an incurable childhood brain cancer for which novel treatments are needed. DIPGs are characterized by a mutation in the H3 histone (H3K27M), resulting in loss of H3K27 methylation and global gene dysregulation. TRX-E-009-1 is a novel anticancer agent with preclinical activity demonstrated against a range of cancers. We examined the antitumor activity of TRX-E-009-1 against DIPG neurosphere cultures and observed tumor-specific activity with IC50s ranging from 20 to 100 nmol/L, whereas no activity was observed against normal human astrocyte cells. TRX-E-009-1 exerted its anti-proliferative effect through the induction of apoptotic pathways, with marked increases in cleaved caspase 3 and cleaved PARP levels, while also restoring histone H3K27me3 methylation. Co-administration of TRX-E-009-1 and the histone deacetylase (HDAC) inhibitor SAHA extended survival in DIPG orthotopic animal models. This antitumor effect was further enhanced with irradiation. Our findings indicate that TRX-E-009-1, combined with HDAC inhibition, represents a novel, potent therapy for children with DIPG.

A novel design of low-cost hearing aid devices using an efficient lifting filter bank with a modified variable filter

OBJECTIVES

In recent years, audio signal processing begins its outbreak on a global scale, which has altered the global market and has rapidly extended out as a fundamental design in various industries. Lifting based method is frequently implemented in many applications such as image processing and audio processing because it has some advantages that faster implementation with minimum computational cost.

METHODS

In this proposed work, a Novel Lifting based Filter Bank (NLFB) is proposed using a modified variable filter aimed at digital hearing aid devices. This filter bank design has some mandatory constraints, such as hardware complexity, power consumption, and delay. The proposed method is designed with four lifting steps such as split, predict, update and merge to make the perfect reconstruction in analysis and decomposition in synthesis bank. The performance analysis of the proposed method is discussed in this article.

RESULTS

The proposed method consumes less power, up to 45mW, and a minimum delay between 85ns and 91.1ns when compared to traditional methods.

CONCLUSION

The proposed design output consumes 32 % of minimum hardware components, 12% of low power compared to interpolated filter bank and 6% of delay is reduced using Modified Variable Filter (MVFB).

Efficient phyto-synthesis and structural characterization of rutile TiO2 nanoparticles using Annona squamosa peel extract

In the present study, the biosynthesis of rutile TiO(2) nanoparticles (TiO(2) NPs) was achieved by a novel, biodegradable and convenient procedure using fruit peel Annona squamosa aqueous extract. This is the first report on the new, simple, rapid, eco-friendly and cheaper methods for the synthesis of rutile TiO(2) NPs at lower temperature using agricultural waste. Rutile TiO(2) NPs were characterized by UV, XRD, SEM, TEM and EDS studies. The UV-Vis spectrophotometer results were promising and showed a rapid production of TiO(2) NPs with a surface plasmon resonance occurring at 284 nm. The formation of the TiO(2) NPs as observed from the XRD spectrum is confirmed to be TiO(2) particles in the rutile form as evidenced by the peaks at 2θ=27.42°, 36.10°, 41.30° and 54.33° when compared with the literature. The TEM images showed polydisperse nanoparticles with spherical shapes and size 23±2 nm ranges.

Synthesis, spectral characterization and larvicidal activity of acridin-1(2H)-one analogues

Acridin-1(2H)-one analogue of 7-chloro-3,4-dihydro-9-phenyl-2-[(pyridine-2yl) methylene] acridin-1(2H)-one, 5 was prepared by using 7-chloro-3,4-dihydro-9-phenylacridin-1(2H)-one, 3 and picolinaldehyde, 4 in the presence of KOH at room temperature. These compounds were characterized by analytical and spectral analyses. The purpose of the present study was to assess the efficacy of larvicidal and repellent activity of synthesized 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues such as compounds 3 and 5 against the early fourth instar larvae of filariasis vector, Culex quinquefasciatus and Japanese encephalitis vector, Culex gelidus (Diptera: Culicidae). The compound exhibited high larvicidal effects at 50mg/L against both the mosquitoes with LC(50) values of 25.02 mg/L (r(2)=0.998) and 26.40 mg/L (r(2)=0.988) against C. quinquefasciatus and C. gelidus, respectively. The 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues that are reported for the first time to our best of knowledge can be better explored for the control of mosquito population. This is an ideal ecofriendly approach for the control of Japanese encephalitis vectors, C. quinquefasciatus and C. gelidus.

Fungus-mediated biosynthesis and characterization of TiO₂ nanoparticles and their activity against pathogenic bacteria

In the present study, the biosynthesis of TiO(2) nanoparticles (TiO(2) NPs) was achieved by a novel, biodegradable and convenient procedure using Aspergillus flavus as a reducing and capping agent. Research on new, simple, rapid, eco-friendly and cheaper methods has been initiated. TiO(2) NPs were characterized by FTIR, XRD, AFM, SEM and TEM studies. The X-ray diffraction showed the presence of increased amount of TiO(2) NPs which can state by the presence of peaks at rutile peaks at 100, 002, 100 and anatase forms at 101 respectively. SEM observations revealed that synthesized TiO(2) NPs were spherical, oval in shape; individual nanoparticles as well as a few aggregate having the size of 62-74 nm. AFM shows crystallization temperature was seen on the roughness of the surface of TiO(2). The Minimum inhibitory concentration value for the synthesized TiO(2) NPs was found to be 40 μg ml(-1) for Escherichia coli, which was corresponding to the value of well diffusion test. This is the first report on antimicrobial activity of fungus-mediated synthesized TiO(2) NPs, which was proved to be a good novel antibacterial material.

Efficacy of indigenous plant extracts on the malaria vector Anopheles subpictus Grassi (Diptera: Culicidae)

BACKGROUND & OBJECTIVES

Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of plant origin may serve as suitable alternative biocontrol techniques in the future. The purpose of the present study was to assess the ethyl acetate, acetone and methanol extracts of Andrographis paniculata, Eclipta prostrata and Tagetes erecta leaves tested for oviposition-deterrent, ovicidal and repellent activities against malaria vector, Anopheles subpictus Grassi (Diptera: Culicidae).

METHODS

The dried leaves of the three plants were powdered mechanically and extracted with ethyl acetate, acetone and methanol. One gram of crude extract was first dissolved in 100 ml of acetone (stock solution). From the stock solution, test solution concentrations of 31.21- 499.42 mg/l for oviposition- deterrence assay and repellency and 15.60 - 998.85 mg/l were used in ovicidal assay. The percentage oviposition- deterrence, hatching rate of eggs and protection time were calculated. One-way analysis of variance was used for the multiple concentration tests and for per cent mortality to determine significant treatment differences.

RESULTS

The percentage of effective oviposition repellency was highest at 499.42 mg/l and the lowest at 31.21 mg/l in ethyl acetate, acetone and methanol extracts of A. paniculata, E. prostrata and T. erecta. The oviposition activity index (OAI) value of ethyl acetate, acetone and methanol extracts of A. paniculata, E. prostrata and T. erecta at 499.42 mg/l were -0.91, -0.93, -0.84, -0.84, -0.87, -0.82, -0.87, -0.89 and -0.87, respectively. Mortality (no egg hatchability) was 100 per cent with ethyl acetate and methanol extracts of A. paniculata, E. prostrata and T. erecta at 998.85 mg/l. The maximum adult repellent activity was observed at 499.42 mg/l in ethyl acetate extracts of A. paniculata, E. prostrata and methanol extracts of T. erecta, and the mean complete protection time ranged from 120 to 150 min with the different extracts tested.

INTERPRETATION & CONCLUSIONS

The acetone extract of A. paniculata, methanol extract of E. prostrata and T. erecta showed good oviposition-deterrent, ovicidal and repellent activities respectively. These results suggest that the leaf extracts of A. paniculata, E. prostrata and T. erecta may have the potential to be used as an ideal eco-friendly approach for the control of the An. subpictus.

Larvicidal activity of medicinal plant extracts against Anopheles subpictus & Culex tritaeniorhynchus

BACKGROUND & OBJECTIVES

Mosquitoes transmit serious human diseases, causing millions of deaths every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. Plants may be alternative sources of mosquito control agents. The present study assessed the role of larvicidal activities of hexane, chloroform, ethyl acetate, acetone, and methanol dried leaf and bark extracts of Annona squamosa L., Chrysanthemum indicum L., and Tridax procumbens L. against the fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae).

METHODS

Larvicidal activities of three medicinal plant extracts were studied in the range of 4.69 to 1000 mg/l in the laboratory bioassays against early 4 th instar larvae of An. subpictus and Cx. tritaeniorhynchus. The mortality data were subjected to probit analysis to determine the lethal concentrations (LC50 and LC90) to kill 50 and 90 per cent of the treated larvae of the respective species.

RESULTS

All plant extracts showed moderate effects after 24 h of exposure; however, the highest toxic effect of bark methanol extract of A. squamosa, leaf ethyl acetate extract of C. indicum and leaf acetone extract of T. procumbens against the larvae of An. subpictus (LC 50 = 93.80, 39.98 and 51.57 mg/l) and bark methanol extract of A. squamosa, leaf methanol extract of C. indicum and leaf ethyl acetate extract of T. procumbens against the larvae of Cx. tritaeniorhynchus (LC50 =104.94, 42.29 and 69.16 mg/l) respectively.

INTERPRETATION & CONCLUSIONS

Our data suggest that the bark ethyl acetate and methanol extract of A. squamosa, leaf ethyl acetate and methanol extract of C. indicum, acetone and ethyl acetate extract of T. procumbens have the potential to be used as an ecofriendly approach for the control of the An. subpictus, and Cx. tritaeniorhynchus.

Studies on effects of indigenous plant extracts on malarial vector, Anopheles subpictus Grassi (Diptera:Culicidae)

Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The present investigations were made to evaluate the repellent, ovicidal and oviposition-deterrent potential of leaf hexane and chloroform extracts of Aegle marmelos, Andrographis lineata, Andrographis paniculata, Cocculus hirsutus, Eclipta prostrata and Tagetes erecta against Anopheles subpictus Grassi (Diptera:Culicidae). The hexane extract of A. lineata was more effective in exhibiting the repellent action against the mosquito as compared with A. marmelos extract. Complete protections for 150 min were found in hexane extract of A. lineata at 500 ppm against An. subpictus bites. Mean percent hatchability of the ovicidal activity was observed 24 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. No hatchability was observed with hexane and chloroform extracts of A. lineata, A. paniculata and hexane extract of T. erecta were exerted at 1,000 ppm. The percentage of effective oviposition repellency of 93.07, 93.95, 98.03, 90.43, 92.63, 81.53, 94.81, 97.50, 97.26, 92.22, 82.85 and 72.77 at 500 ppm and the lowest repellency of 62.03, 53.64, 73.47, 59.05, 57.95, 48.17, 62.22, 72.99, 75.48, 67.77, 40.57 and 52.11 at 31.25 ppm in hexane and chloroform extracts of A. marmelos, A. lineata, A. paniculata, C. hirsutus, E. prostrata and T. erecta, respectively. The oviposition activity index (OAI) values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. These results clearly reveal that the hexane extract of A. lineata, served as a potential repellent, ovicidal and oviposition- deterrent against An. subpictus.

Larvicidal efficacy of medicinal plant extracts against Anopheles stephensi and Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes transmit serious human diseases, causing millions of deaths every year. Natural products of plant origin with insecticidal properties have been used in recent years for control of a variety of pest insects and vectors. The present study was based on assessments of the larvicidal activity to determine the efficacies of hexane, chloroform, ethyl acetate, acetone and methanol extracts of ten medicinal plants tested against fourth instar larvae of malaria vector, Anopheles stephensi Liston and lymphatic filariasis vector, Culex quinquefasciatus Say (Diptera: Culicidae). The larvicidal activity was assessed by the procedure of WHO with some modification. The highest larval mortality was found in leaf acetone of Adhatoda vasica, bark ethyl acetate of Annona squamosa, methanol leaf and flower of Cassia auriculata, leaf ethyl acetate of Hydrocotyle javanica, methanol leaf and seed of Solanum torvum and leaf hexane extracts of Vitex negundo against the fourth instar larvae of An. stephensi and Cx. quinquefasciatus. The calculated LC90 for acetone, ethyl acetate, methanol and hexane extracts of dried leaf and bark of A. vasica, A. squamosa, S. torvum, and V. negundo were in the range of 70.38-210.68 ppm. Our results suggest that the leaf methanol extract of S.torvum and bark ethyl acetate extract of A. squamosa from Southern India have the potential for use to control mosquitoes. Therefore, this study provides the larvicidal activity against An. stephensi and Cx. quinquefasciatus of plant extracts.

Testosterone increases and estradiol decreases middle cerebral artery occlusion lesion size in male rats

This study was undertaken to determine the effects of estrogen and testosterone on cerebral ischemic lesion size induced by middle cerebral artery (MCA) occlusion in male rats. Rats were gonadectomized and treated with testosterone, estrogen, or testosterone plus estrogen filled Silastic pellets. The animals were divided into 6 groups: intact, intact + estrogen (E2), castrate, castrate + testosterone (T), castrate + E2, and castrate + T + E2. One week after treatment, cerebral ischemia was induced by MCA occlusion for 40 min, followed by reperfusion. After 24 h, rats were sacrificed and slices were then stained to assess lesion size. The presence of testosterone increased and the removal of testosterone decreased lesion size. A strong positive correlation (r2 = 0.922) between plasma testosterone concentrations and ischemic lesion size was observed. Estradiol treatment reduced ischemic area. In summary, the present study provides evidence that testosterone exacerbates and estrogens ameliorate ischemic brain damage in an animal model of cerebral ischemia.

Hypoglycemia-induced seizures reduce cyclic AMP response element binding protein levels in the rat hippocampus

Cyclic AMP response element binding protein (CREB) is a transcription factor that has been implicated in the activation of protein synthesis required for long-term memory. Since memory deficits are manifest following seizure, we undertook the present study to investigate the effects of hypoglycemia-induced seizure on CREB-immunoreactive neurons in several brain regions. We induced generalized seizures in male Long Evans rats (n=5) by injecting them with insulin (30 IU/kg, i.p). Animals were recovered by administration of 3 ml of 30% glucose within 5 min of the occurrence of seizure. Control animals (n=3) were injected with saline instead of insulin. All animals were perfused 90 min after recovery and the brains processed for CREB immunohistochemistry. Cell counts were determined for CREB-positive neurons using a computer-assisted program. When compared to control animals there was a 50% decrease (P<0.0001) in CREB-positive neurons in the CA1 region of the experimental animals. In the CA3 and dentate gyrus there was a 36% (P<0.001) and 25% decrease (P<0.001), respectively. Given the importance of hippocampus in memory-related processes and evidence that CREB is critical for memory formation, it is possible that seizures interfere with memory by disrupting CREB-dependent transcription.

Effects of gender and estradiol treatment on focal brain ischemia

The present studies were undertaken to investigate the effects of gender and estrogen treatment on focal cerebral ischemia in male and female rats. Focal ischemia was created by inserting a 3-0 surgical suture through the left cervical internal carotid artery to obstruct the blood flow into the middle cerebral artery (MCA). The MCA was reperfused by removing the suture in 40 min. All rats were sacrificed for measurement of infarct area after 24 h. In the first study, mortalities from MAC occlusion were 12.5% (2/16) each for intact male rats and intact female rats, and 23.5% (4/17) for ovariectomized (OVX) female rats. The coronal infarct area (mean+/-S. E.M.) was 9.5+/-1.0% for intact female rats, 16.6+/-1.6% for intact male rats (p=0.0001 vs. intact female rats), and 16.0+/-1.4% for OVX female rats (p=0.0002 vs. intact female rats). In a second experiment, OVX-female rats were administrated either 17beta-estradiol (E2) or its vehicle, hydroxypropyl-beta-cyclodextrin (HPCD), at 40 min after the onset of MCA occlusion. Mortalities were 40% (4/10) for vehicle treated OVX rats and 0% for E2 treated OVX rats. The coronal infarct area (mean+/-S.E.M.) was 19.3+/-1.8% for vehicle treated rats vs. 8.0+/-1. 2% for E2 treated rats (p<0.01). Serum estrogen levels for vehicle treated OVX rats were 14.5+/-1.2% pg/ml vs. 142.7+/-23.6 pg/ml for E2 treated OVX rats (p<0.01). These results strongly suggest that the level of circulating estrogens play an important role in protecting brain tissues against ischemia induced by MCA occlusion.

17beta-estradiol attenuates CREB decline in the rat hippocampus following seizure

Cyclic AMP response element-binding protein (CREB) is a transcription factor that has been implicated in the activation of a number of genes. We reported that CREB levels decline following a severe hypoglycemic episode in the hippocampus and cortex in the male rat brain. The present experiment was undertaken to investigate whether 17beta-estradiol prevents the decline in CREB-immunoreactive cells following seizure in female rats. Rats were divided into four groups: ovariectomized (OVX), ovariectomized and insulin-treated (OVX-I), estrogen-replaced (E2), and estrogen-replaced and insulin-treated (E2-I). Generalized seizures were induced by injections with insulin (12.5 IU/kg, intraperitoneally) and animals were recovered by administration of glucose within 5 min of the occurrence of seizure. Control animals were injected with saline instead of insulin. All animals were perfused 90 min after recovery and the brains were processed for CREB immunoreactivity. CREB-positive neurons were counted using a computer-assisted program. Insulin treatment of OVX rats caused a significant decline in CREB-positive neurons in the CA1, CA3, and dentate gyrus compared to OVX rats. Estrogen treatment of OVX rats significantly increased CREB-positive neurons in the CA1 and dentate gyrus and attenuated the insulin-induced decline of CREB-positive neurons in all three regions compared to OVX rats. In conclusion, estrogens appear to induce CREB expression and attenuate its decline in the hippocampus following a severe hypoglycemic episode.

Estrogens may reduce mortality and ischemic damage caused by middle cerebral artery occlusion in the female rat

The present study was undertaken to determine if estrogens protect female rats from the neurodegenerative effects of middle cerebral artery (MCA) occlusion. The rats were ovariectomized and 7 or 8 days later various estrogen preparations were administered before or after MCA occlusion. Pretreatment with 17beta-estradiol (17beta-E2) or a brain-targeted 17beta-E2 chemical delivery system (CDS) decreased mortality from 65% in ovariectomized rats to 22% in 17beta-E2-treated and 16% in 17beta-E2 CDS-treated rats. This marked reduction in mortality was accompanied by a reduction in the ischemic area of the brain from 25.6+/-5.7% in the ovariectomized rats to 9.8+/-4% and 9.1+/-4.2% in the 17beta-E2-implanted and the 17beta-E2 CDS-treated rats, respectively. Similarly, pretreatment with the presumed inactive estrogen, 17alpha-estradiol, reduced mortality from 36 to 0% and reduced the ischemic area by 55 to 81%. When administered 40 or 90 minutes after MCA occlusion, 17beta-E2 CDS reduced the area of ischemia by 45 to 90% or 31%, respectively. In summary, the present study provides the first evidence that estrogens exert neuroprotective effects in an animal model of ischemia and suggests that estrogens may be a useful therapy to protect neurons against the neurodegenerative effects of stroke.

Role of estrogen replacement therapy in memory enhancement and the prevention of neuronal loss associated with Alzheimer's disease

Recent evidence supports a role for estrogens in both normal neural development and neuronal maintenance throughout life. Women spend 25-33% of their life in an estrogen-deprived state and retrospective studies have shown an inverse correlation between dose and duration of estrogen replacement therapy (ERT) and incidence of Alzheimer's disease (AD), suggesting a role for estrogen in the prevention and/or treatment of neurodegenerative diseases. To explore these observations further, an animal model was developed using ovariectomy (OVX) and ovariectomy with estradiol replacement (E2) in female Sprague-Dawley rats to mimic postmenopausal changes. Using an active-avoidance paradigm and a spatial memory task, the effects of estrogen deprivation were tested on memory-related behaviors. OVX caused a decline in avoidance behavior, and estrogen replacement normalized the response. In the Morris water task of spatial memory, OVX animals showed normal spatial learning but were deficient in spatial memory, an effect that was prevented by estrogen treatment. Together these data indicate that OVX in rats results in an estrogen-reversible impairment of learning/memory behavior. Because a plethora of information has been generated that links decline in memory-related behavior to dysfunction of cholinergic neurons, the effects of estrogens on cholinergic neurons were tested. We demonstrated that OVX causes a decrease in high affinity choline uptake and choline acetyltransferase activity in the hippocampus and frontal cortex; ERT reverses this effect. Further, we showed that estrogens promote the expression of mRNA for brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), 2 neurotrophic substances that have been shown to ameliorate the effects of age and injury on cholinergic neurons. Tissue culture models were used to evaluate whether estrogen treatment increases the survival of neurons when exposed to a variety of insults. 17-beta-Estradiol (beta-E2) protects cells from the neurotoxic effects of serum deprivation and hypoglycemia in human neuroblastoma cell lines. We have also observed that 17-alpha-estradiol (alpha-E2), a weak estrogen, shows neuroprotective efficacy in the SK-N-SH cell line at concentrations equivalent to beta-E2. Finally, we have observed that tamoxifen, a classic estrogen antagonist, blocks only one-third of the neuroprotective effects of either alpha-E2 or beta-E2. Collectively, these results indicate that estrogen is behaviorally active in tests of learning/ memory; activates basal forebrain cholinergic neurons and neurotrophin expression; and is neuroprotective for human neuronal cultures. We conclude that estrogen may be a useful therapy for AD and other neurodegenerative diseases.

17 beta-estradiol attenuates fimbrial lesion-induced decline of ChAT-immunoreactive neurons in the rat medial septum

We investigated the neuroprotective effects of 17 beta-estradiol (E2) on medial septal cholinergic neurons following partial unilateral lesion of the fimbriafornix. Adult female rats were ovariectomized (OVX) and, 5 days later, treated with a single intravenous (iv) injection of an estradiol (E2)-chemical delivery system (E2-CDS) or its vehicle hydroxypropyl-beta-cyclodextrin (HPCD). All rats were subjected to partial unilateral electrolytic fimbrial lesion the following day. At 20 days postlesion, brain slices from treated animals were assessed for choline acetyltransferase (ChAT) by immunohistochemistry. Animals treated with HPCD or E2-CDS showed a 44 or 4% decrease, respectively, in ChAT-positive neurons on the lesioned side compared to the nonlesioned side of the medial septum. In a second study using the same lesioning procedure, adult OVX rats received either a subcutaneous E2 pellet implant (n = 6), or, 5 days postovariectomy, a single iv injection of E2-CDS (n = 8) or HPCD (n = 6). Animals treated with HPCD showed a 55% decrease in ChAT-positive neurons on the lesioned side compared to the nonlesioned side of the medial septum. By contrast, rats treated with E2-CDS or E2 pellet had a 14 or 13% decrease, respectively, in ChAT-positive neurons. Interestingly, E2 treatment substantially decreased ChAT-positive neurons on the nonlesioned side of the medial septum in comparison to control animals. The present study suggests that cholinergic neurons in the medial septum are protected from lesion-induced degeneration by treatments which increase brain E2 levels. Thus, E2 may play a neuroprotective role in the basal forebrain cholinergic system.

Relationship between cAMP production and protein secretion in rat submandibular acini: evidence for loss of reserve capacity with age

We assessed isoproterenol and forskolin-stimulated cAMP production and protein secretion in submandibular salivary glands from young (4-7 mo) and old (25 mo) male F-344 rats. In senescent acini, the maximum amount of cAMP produced was three-fold less and the protein secreted was one-third less in response to the highest dose of isoproterenol (100 microM). Following isoproterenol stimulation, the young acini were more sensitive than the old for protein secretion than for cAMP production. Post-receptor stimulation (by forskolin) of cAMP production and protein secretion were less in the senescent rats. This report demonstrates the validity of an in vitro model for simultaneous assessment of biochemical and functional correlates. Furthermore, the observations suggest that both receptor and post-receptor stimulation of cAMP production and protein secretion diminish with age. Moreover, there is a reserve capacity for cAMP production with respect to protein secretion in the young that is diminished or even absent in the old rats.

Desipramine desensitizes beta-adrenergic signal transduction in salivary glands: differential regulation with age

We previously reported that the tricyclic antidepressant, desipramine desensitizes beta-adrenergic signal transduction in parotid and submandibular salivary glands. To determine the consequences of repeated desipramine administration on beta-adrenergic signal transduction in salivary glands from aged rats and whether the recovery after drug withdrawal is impaired, we assessed the effects of 28-day desipramine administration and the reversibility of this treatment following a 15-day washout period on beta-adrenoceptors and adenylyl cyclase activity in parotid and submandibular glands from F-344 rats of 6, 12 and 24 months of age. beta-Adrenoceptors were also assessed in the cerebral cortex. Desipramine administration down-regulated receptor number and attenuated isoproterenol-stimulated adenylyl cyclase activity in all three ages of rats. However, the reduction in isoproterenol-stimulated adenylyl cyclase activity was greater than the loss of receptor number. Desipramine administration attenuated the efficacy of NaF-stimulated activity with no change in forskolin-stimulated adenylyl cyclase activity. These data suggest that in addition to desensitizing beta-adrenergic-mediated signal transduction, desipramine impaired G-protein-mediated adenylyl cyclase stimulation. The recovery from desipramine desensitization was age dependent. beta-Adrenoceptor density recovered more slowly in the cerebral cortex and the submandibular gland in 24-month-old rats than in 6-month-old rats. In contrast, in 12-month-old rats, there was a receptor up-regulation and adenylyl cyclase supersensitivity. These data indicate that the capacity for receptor modulation is age dependent and suggest that desipramine treatment may down-regulate stimulatory G protein.

In vivo mitogenic effects of estradiol on colon cancers: role of gastrin and gastrin receptors

We have previously reported mitogenic effects of gastrin on a mouse colon cancer (MC-26) cell line in vivo. The present studies were undertaken to determine if gonadal hormones can influence the mitogenic response of MC-26 cells to gastrin. The female gonadal hormone, estradiol (E2), was determined to be as mitogenic as pentagastrin (PG) for the growth of MC-26 tumors in mice; the mitogenic effects of E2 and PG were not additive. Female gonadal hormones were furthermore as effective as PG in maximally up-regulating gastrin receptor (GR) concentrations on MC-26 tumor membranes, which was confirmed in autoradiographic studies. Since PG and E2 had similar and non-additive trophic effects it was hypothesized that gastrin may be mediating the trophic effects of E2. Serum gastrin concentrations were significantly increased in E2 treated ovariectomized mice that correlated with an increase in tumor weights; E2 however was ineffective in stimulating the release of gastrin from perfused rat stomachs indicating that the increase in serum gastrin concentration on long-term treatment with E2 was mediated by some other mechanism. Saturable high-affinity E2 binding sites were not measured in MC-26 cells and tumors, supporting the possibility that mitogenic effects of E2 were probably mediated via indirect mechanisms. In summary our results indicate that both E2 and PG are equally mitogenic for colon cancer cells in vivo which may explain the sex- and age-related discrepancy in the incidence of human colon cancers.

Desipramine desensitizes beta-adrenergic signal transduction in rat salivary glands

The consequences of the tricyclic antidepressant drugs include sedation, orthostatic hypotension and salivary dysfunction. It was reported that administration of desipramine resulted in a decrease in the concentration of secreted salivary protein. Tricyclic antidepressants may indirectly alter salivary function as a result of their action on the central nervous system to decrease adrenergic neural transmission or, alternately, may act directly on salivary glands to modulate beta-adrenergic signal transduction. To investigate the latter possibility, the effects of administration of desipramine (DMI) for 28 days was assessed on beta-adrenergic and post-receptor signal transduction in the parotid and submandibular glands of the rat and the reversibility of this treatment following a washout period of 15 days. Both glands demonstrated desensitization of the isoproterenol-stimulated activity, and in the parotid gland treatment with DMI decreased the post-receptor signal transduction as well. The washout period of 15 days completely reversed the desensitization in the parotid gland and partially reversed the effects in the submandibular gland. These data suggest that desipramine-induced attenuation of beta-adrenergic signal transduction is not limited to the brain and that these direct effects on salivary glands may explain the salivary dysfunction observed after administration of desipramine.

Estradiol is trophic for colon cancer in mice: effect on ornithine decarboxylase and c-myc messenger RNA

The mitogenic role of estradiol on the growth of colon cancer was examined in mice. Sham-operated or ovariectomized mice were injected with cancer cells and received estradiol treatment. Tumor growth was noted: tumor weights were higher in female than male mice. The growth of the tumors was least in ovariectomized mice and highest in estradiol-treated ovariectomized mice. Tumor messenger RNA (mRNA) levels for ornithine decarboxylase (ODC) and proto-oncogenes c-myc, c-fos, and H-ras were examined. Two transcripts (2.2 and 2.7 kilobase pairs) of ODC were observed. The steady-state mRNA levels for ODC paralleled the changes observed in the weight of the tumors in all groups of animals. Less dramatic changes were observed in c-myc mRNA levels. No significant differences were observed in the mRNA levels for H-ras and c-fos. It thus appears likely that an increase in the ODC mRNA levels and, to a lesser extent, an increase in c-myc mRNA levels may be some of the important mechanisms by which estradiol mediates its growth effects on colon cancer cells in vivo.

Beta-adrenergic signal transduction in aging parotid and submandibular salivary glands

This study assessed agonist- and post-receptor-stimulated adenylate cyclase (AC) activity in parotid and submandibular salivary glands from female F-344 rats of 3, 12, and 24 months of age. Isoproterenol-stimulated dose-response activation of adenylate cyclase was unchanged between 3 and 12 months but decreased at 24 months (p less than .05). Forskolin-stimulated AC activity, representing catalytic unit activity, was decreased at 24 months in the parotid (p less than .05) and at 12 months (p less than .05) and 24 months (p less than .01) in the submandibular gland. Beta-adrenergic signal transduction in salivary glands stimulates the secretion of salivary proteins that have important functions in the maintenance of oral health.

Dopamine receptor modulation by conformationally constrained analogues of Pro-Leu-Gly-NH2

Two series of conformationally constrained analogues of Pro-Leu-Gly-NH2 (PLG) have been synthesized. In one series of analogues, the Leu-Gly-NH2 dipeptide segment of PLG was replaced with the gamma-lactam residues 3(S)- and 3(R)-amino-2-oxopyrrolidineacetamide and the delta-lactam residue 3(S)-amino-2-oxopiperidineacetamide. The corresponding gamma-lactam analogues of less than Glu-Leu-Gly-NH2 were also synthesized. In a second series of analogues, the glycinamide residue of PLG was replaced with the 2-ketopiperazine, 3(S)-amino-2-pyrrolidone, and 3(S)-amino-2-piperidone residues. The above analogues were tested for their ability to enhance the binding of the dopamine receptor agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (ADTN) to striatal dopamine receptors. Of the conformationally constrained analogues of PLG synthesized in this study, only the gamma-lactam analogue 3(R)-(N-L-prolylamino)-2-oxo-1-pyrrolidineacetamide (3) was found to possess significant activity. This analogue was 10,000 times more active than PLG, under preincubation conditions. It significantly enhanced the binding of ADTN at concentrations of 10(-9) and 10(-10) M.

17 beta Estradiol-induced increase in brain dopamine D-2 receptor: antagonism by MIF-1

Animal behavioral and neurochemical studies implicate dopaminergic systems in the neurological sequelae induced by estrogen. In the present study, we demonstrated for the first time that MIF-1, a neuropeptide unrelated to classical dopamine agonists, when given prior to, concurrently with, and after 17 beta-estradiol, antagonized significantly the estrogen-induced increase in the density of dopamine D-2 receptor both in the striatum and the mesolimbic area of male rat brain. The current findings have implications for the prophylactic and therapeutic potential for MIF-1 in extrapyramidal motor disorders caused by estrogen imbalance in humans.

Down-regulation of haloperidol-induced striatal dopamine receptor supersensitivity by active analogues of L-prolyl-L-leucyl-glycinamide (PLG)

Tardive dyskinesia, a clinical syndrome, is one of the major side effects of protracted treatment with neuroleptics in schizophrenic patients. Functional supersensitivity of striatal dopamine receptors is believed to contribute to the pathogenesis of schizophrenia and tardive dyskinesia. In a rodent model of neuroleptic-induced dopamine receptor supersensitivity, we investigated the efficacy of structurally modified analogues of PLG to down-regulate the striatal dopamine receptor supersensitivity as determined by alterations in [3H]spiroperidol binding to striatal membranes in vitro. The PLG analogue, L-prolyl-L-leucyl-(+)-thiazolidine-2-carboxamide-HCl, when given at the dose of 10 mg/kg IP for 5 days prior to haloperidol (3 mg/kg IP 21 days) significantly prevented the up-regulation of striatal dopamine receptor supersensitivity, thus demonstrating a prophylactic effect. Two other analogues, L-prolyl-L-leucyl-5-aminomethyltetrazole and L-prolyl-L-leucyl-glycine-dimethylamide at a dose of 10 mg/kg IP when given concurrently with haloperidol for 21 days, suppressed the development of dopamine receptor supersensitivity. None of the analogues tested in the post-haloperidol session reversed the haloperidol-induced increase in the density of striatal dopamine receptors. Active PLG analogues hold promise as potential therapeutic agents for the amelioration of tardive dyskinesia.

L-prolyl-L-leucyl-glycinamide analogues--a new class of peptide antihypertensives

Accumulating evidence suggests that there is an increase in the density (maximum binding sites) of striatal dopamine receptors in the central nervous system of spontaneously hypertensive rats (SHR). A tripeptide of hypothalamic origin, PLG (L-Prolyl-L-Leucyl-Glycinamide) has been found to have modulatory effect on the dopamine receptors in the central nervous system of rats. Two analogues of PLG with cyclic amino-acid residues, L-Prolyl-L-Leucyl-(-)-thiazolidine-2-carboxamide and L-Prolyl-L-Leucyl-(+)-thiazolidine-2-carboxamide, have shown antihypertensive effect at the established phase of hypertension in 16-week old SHRs at a dose of 35 mg/kg per day per 7 days i.p. It was also observed from studies of radioligand [3H]-spiroperidol binding that the laevo-isomer of the PLG analogue has down-regulated the up-regulated dopamine receptors. Our findings confirm the role of central dopaminergic pathways in the pathogenesis of hypertension in SHR.

Characterization of high-affinity dopamine D2 receptors and modulation of affinity states by guanine nucleotides in cholate-solubilized bovine striatal preparations

3,4-Dihydroxyphenylethylamine (dopamine) D2 receptors, solubilized from bovine striatal membranes using a cholic acid-NaCl combination, exhibited the typical pharmacological characteristics of both agonist and antagonist binding. The rank order potency of the agonists and antagonists to displace [3H]spiroperidol binding was the same as that observed with membrane-bound receptors. Computer-assisted analysis of the [3H]spiroperidol/agonist competition curves revealed the retention of high- and low-affinity states of the D2 receptor in the solubilized preparations and the proportions of receptor subpopulations in the two affinity states were similar to those reported in membrane. Guanine nucleotide almost completely converted the high-affinity sites to low-affinity sites for the agonists. The binding of the high-affinity agonist [3H]N-n-propylnorapomorphine ([3H]NPA) was clearly demonstrated in the solubilized preparations for the first time. Addition of guanylyl-imidodiphosphate completely abolished the [3H]NPA binding. When the solubilized receptors were subjected to diethylaminoethyl-Sephacel chromatography, the dopaminergic binding sites eluted in two distinct peaks, showing six- to sevenfold purification of the receptors in the major peak. Binding studies performed on both peaks indicated that the receptor subpopulation present in the first peak may have a larger proportion of high-affinity binding sites than the second peak. The solubilized preparation also showed high-affinity binding of [35S]guanosine-5'-(gamma-thio)triphosphate, a result suggesting the presence of guanine nucleotide binding sites, which may interact with the solubilized D2 receptors. These data are consistent with the retention of the D2 receptor-guanine nucleotide regulatory protein complex in the solubilized preparations and should provide a suitable model system to study the receptor-effector interactions.

Dopamine receptor modulation by Pro-Leu-Gly-NH2 analogues possessing cyclic amino acid residues at the C-terminal position

The synthesis of several analogues of L-prolyl-L-leucylglycinamide (PLG) was carried out in which the glycinamide residue was replaced with the following cyclic amino acid residues: L- and D-prolinamide, (+)- and (-)-thiazolidine-2-carboxamide, L- and D-3,4-dehydroprolinamide, L-azetidine-2-carboxamide, L-piperidine-2-carboxamide, and L-thiazolidine-4-carboxamide to give PLG analogues 2-10, respectively. The ability of these analogues to enhance the binding of the dopamine agonist ADTN (2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene) to dopamine receptors was determined by using bovine brain tissue. All of the PLG analogues synthesized in this study enhanced the binding of ADTN to central dopamine receptors. The percent enhancement of ADTN binding produced by analogues 2,3, and 7-10 at various concentrations was comparable to the percent enhancement produced by PLG. The PLG analogues Pro-Leu-(+)-thiazolidine-2-carboxamide (4), Pro-Leu-(-)-thiazolidine-2-carboxamide (5), and Pro-Leu-L-3,4-dehydroprolinamide (6), however, produced significantly greater enhancement (2-3-fold) in ADTN binding than did PLG.

Synthesis of Pro-Leu-Gly-NH2 analogues modified at the prolyl residue and evaluation of their effects on the receptor binding activity of the central dopamine receptor agonist, ADTN

Several analogues of L-prolyl-L-leucylglycinamide (PLG) were synthesized wherein the prolyl residue was replaced with other heterocyclic amino acid residues. Among the analogues synthesized were D-Pro-Leu-Gly-NH2 (2), less than Glu-Leu-Gly-NH2 (3), Thz-Leu-Gly-NH2 (4), Pip-Leu-Gly-NH2 (5), Aze-Leu-Gly-NH2 (6), L-delta 3,4-Pro-Leu-Gly-NH2 (7), and D-delta 3,4-Pro-Leu-Gly-NH2 (8). These analogues were tested for their ability to enhance the binding of the agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene to central dopamine receptors. Analogues 2, 3, and 5-7 showed activity comparable to that of PLG, while the tripeptides 4 and 8 were found to be inactive. The results show that the N-terminal prolyl residue of PLG is not an essential requirement for this tripeptide's ability to modulate dopamine receptors.

Mesolimbic and striatal dopamine receptor supersensitivity: prophylactic and reversal effects of L-prolyl-L-leucyl-glycinamide (PLG)

Functional supersensitivity of mesolimbic and striatal dopamine receptors has been suggested to contribute to the pathogenesis of schizophrenia and tardive dyskinesia. Using the rodent model of chronic administration of the neuroleptic haloperidol, we investigated the possible desensitizing effects of a tripeptide structurally unrelated to dopamine agonists, L-prolyl-L-leucyl-glycinamide (PLG) on mesolimbic and striatal dopaminergic receptor supersensitivity. Administration of PLG either prior to or after chronic haloperidol, inhibited the supersensitivity of dopamine receptors. The results have implications for pharmacological intervention in preventing tardive dyskinesia and relapse psychosis of schizophrenia.

Differential changes in central serotonin and dopamine receptors in spontaneous hypertensive rats

Functional significance of central dopaminergic and serotonergic mechanism in relation to the pathogenesis of hypertension, was assessed in the brain of hypertensive rat (SHR) models. In the mesolimbic area, dopamine receptors were found to be significantly enhanced in the SHR as compared with the normotensive control, whereas serotonin receptors in the hippocampus and frontal cortex were not significantly altered in the SHR. Our results, coupled with our previous finding on the enhanced 3H-spiroperidol binding in the striatum support the hypothesis that supersensitivity of central dopamine receptors may contribute towards the development of hypertension.