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In insects, lipid transfer to the tissues is mediated by lipophorin, the major circulating lipoprotein, mainly through a nonendocytic pathway involving docking receptors. Currently, the role of such receptors in lipid metabolism remains poorly understood. In this work, we performed a histological characterization of the fat body of the Chagas' disease vector, Panstrongylus megistus (Burmeister), subjected to different nutritional conditions. In addition, we addressed the role of the β-chain of ATP synthase (β-ATPase) in the process of lipid transfer from lipophorin to the fat body. Fifth-instar nymphs in either fasting or fed condition were employed in the assays. Histological examination revealed that the fat body was composed by diverse trophocyte phenotypes. In the fasting condition, the cells were smaller and presented a homogeneous cytoplasmic content. The fat body of fed insects increased in size mainly due to the enlargement of lipid stores. In this condition, trophocytes contained abundant lipid droplets, and the rough endoplasmic reticulum was highly developed and mitochondria appeared elongated. Immunofluorescence assays showed that the β-ATPase, a putative lipophorin receptor, was located on the surface of fat body cells colocalizing partially with lipophorin, which suggests their interaction. No changes in β-ATPase expression were found in fasting and fed insects. Blocking the lipophorin-β-ATPase interaction impaired the lipophorin-mediated lipid transfer to the fat body. The results showed that the nutritional status of the insect influenced the morphohistological features of the tissue. Besides, these findings suggest that β-ATPase functions as a lipophorin docking receptor in the fat body., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America.)

DmCatD, a cathepsin D-like peptidase of the hematophagous insect Dipetalogaster maxima, is synthesized by the fat body and the ovary and functions as yolk protein precursor. Functionally, DmCatD is involved in vitellin proteolysis. In this work, we purified and sequenced DmCatD, performed bioinformatic analyses and investigated the events involved in its targeting and storage in developing oocytes. By ion exchange and gel filtration chromatography, DmCatD was purified from egg homogenates and its identity was confirmed by mass spectrometry. Approximately 73% of the full-length transcript was sequenced. The phylogeny indicated that DmCatD has features which suggest its distancing from "classical" cathepsins D. Bioinformatic analyses using a chimeric construct were employed to predict post-translational modifications. Structural modeling showed that DmCatD exhibited the expected folding for this type of enzyme, and an active site with conserved architecture. The interaction between DmCatD and lipophorin in the hemolymph was demonstrated by co-immunoprecipitation. Colocalization of both proteins in developing oocyte membranes and yolk bodies was detected by immunofluorescence. Docking assays favoring the interaction DmCatD-lipophorin were carried out after modeling lipophorin of a related triatomine species. Our results suggest that lipophorin acts as a carrier for DmCatD to facilitate its further internalization by the oocytes. The mechanisms involved in the uptake of peptidases within the oocytes of insects have not been reported. This is the first experimental work supporting the interaction between cathepsin D and lipophorin in an insect species, enabling us to propose a pathway for its targeting and storage in developing oocytes., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Lipophorin is the main lipoprotein in the hemolymph of insects. During vitellogenesis, lipophorin delivers its hydrophobic cargo to developing oocytes by its binding to non-endocytic receptors at the plasma membrane of the cells. In some species however, lipophorin may also be internalized to some extent, thus maximizing the storage of lipid resources in growing oocytes. The ectopic β chain of ATP synthase (β-ATPase) was recently described as a putative non-endocytic lipophorin receptor in the anterior midgut of the hematophagous insect Panstrongylus megistus. In the present work, females of this species at the vitellogenic stage of the reproductive cycle were employed to investigate the role of β-ATPase in the transfer of lipids to the ovarian tissue. Subcellular fractionation and western blot revealed the presence of β-ATPase in the microsomal membranes of the ovarian tissue, suggesting its localization in the plasma membrane. Immunofluorescence assays showed partial co-localization of β-ATPase and lipophorin in the membrane of oocytes as well as in the basal domain of the follicular epithelial cells. Ligand blotting and co-immunoprecipitation approaches confirmed the interaction between lipophorin and β-ATPase. In vivo experiments with an anti-β-ATPase antibody injected to block such an interaction demonstrated that the antibody significantly impaired the transfer of fatty acids from lipophorin to the oocyte. However, the endocytic pathway of lipophorin was not affected. On the other hand, partial inhibition of ATP synthase activity did not modify the transfer of lipids from lipophorin to oocytes. When the assays were performed at 4°C to diminish endocytosis, the results showed that the antibody interfered with lipophorin binding to the oocyte plasma membrane as well as with the transfer of fatty acids from the lipoprotein to the oocyte. The findings strongly support that β-ATPase plays a role as a docking lipophorin receptor at the ovary of P. megistus, similarly to its function in the midgut of such a vector. In addition, the role of β-ATPase as a docking receptor seems to be independent of the enzymatic ATP synthase activity., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: Triatoma infestans is the main vector of Chagas'disease in Southern Cone countries. In triatomines, symptoms suggesting neurotoxicity were observed after treatment with Jaburetox (Jbtx), the entomotoxic peptide obtained from jackbean urease. Here, we study its effect in the central nervous system (CNS) of this species., Methods: Immunohistochemistry, Western blots, immunoprecipitation, two-dimensional electrophoresis, tandem mass spectrometry and enzymatic assays were performed., Results: Anti-Jbtx antibody labeled somata of the antennal lobe only in Jbtx-treated insects. Western blot assays of nervous tissue using the same antibody reacted with a 61kDa protein band only in peptide-injected insects. Combination of immunoprecipitation, two-dimensional electrophoresis and tandem mass spectrometry identified UDP-N-acetylglucosamine pyrophosphorylase (UDP-GlcNAcP) as a molecular target for Jbtx. The activity of UDP-GlcNAcP increased significantly in the CNS of Jbtx-treated insects. The effect of Jbtx on the activity of nitric oxide synthase (NOS) and NO production was investigated as NO is a recognized messenger molecule in the CNS of T. infestans. NOS activity and NO levels decreased significantly in CNS homogenates of Jbtx-treated insects., Conclusions: UDP-GlcNAcP is a molecular target of Jbtx. Jbtx impaired the activity of T. infestans nitrergic system, which may be related with early behavioral effects., General Significance: We report that the CNS of Triatoma infestans is a target for the entomotoxic peptide and propose that a specific area of the brain is involved. Besides potentially providing tools for control strategies of Chagas' disease vectors our data may be relevant in various fields of research as insect physiology, neurobiology and protein function., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this work we have analyzed the involvement of cell death pathways during the process of follicular atresia in the hematophagous insect vector Dipetalogaster maxima. Standardized insect rearing conditions were established to induce a gradual follicular degeneration stage by depriving females of blood meal during post-vitellogenesis. We first characterized the morpho-histological and ultrastructural changes of the ovarian tissue at early and late follicular atresia by light and transmission electron microscopy. Apoptosis was investigated by DAPI nuclear staining, TUNEL labeling and the detection of active caspase-3 by immunofluorescence. Autophagy was assessed by the measurement of acid phosphatase activity in ovarian homogenates and monitored by the detection of the specific marker of autophagic compartments, LC3. High levels of acid phosphatase activity were detected at all atretic stages. However, follicular cells of follicles undergoing incipient degeneration in early atresia exhibited features of apoptosis such as chromatin condensation, DNA fragmentation and the presence of active caspase-3. The ultrastructural findings and the increased levels of LC3-II found at late follicular atresia supported the relevance of autophagy at this atretic stage, although the extent of autophagosome formation demonstrated that this cell death pathway also occurred at early atresia. In late atresia, follicular cells also displayed more drastic changes compatible with necrosis. Taken together, results showed that apoptosis, autophagy and necrosis were operative during follicular atresia in D. maxima. Moreover, it was shown that the relevance of these cell death mechanisms correlates with the time elapsed since the onset of the degenerative process., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The tribe Emphorini is a group of pollen-collecting solitary bees with a geographical distribution restricted to the western hemisphere. Most of the Emphorini bees collect Page 10 linepollen from a few specific plant families and display specialized behaviors for constructing their nests. Insect sensilla are the basic structural and functional units of cuticle receptors, serving mainly mechano- and chemo-receptor functions. The external morphology of the antennal sensilla has been well characterized in species of different families of Apoidea, however there is scarce information about this issue in solitary bees of the family Apidae. For a better understanding of the association between the external sensory system and several types of behaviors which emerged along the evolutionary history of bees, it is important to characterize the antennal receptors in several representative species of this tribe. The distribution of the antennal sensilla on the dorsal flagella of 18 taxa was studied in insects of both sexes, using light and scanning electron microscopy. There were six types of sensilla and setae on the antennae, which were identified as sensilla placodea, trichodea, basiconica, coeloconica, coelocapitular and ampullacea. The sensilla trichodea were classified into subtypes, A, B, C-D. Sensilla subtype A were the most abundant sensilla and were distributed over the entire antennae, while sensilla placodea and sensilla trichodea type B, showed a restricted distribution on specific areas of the flagella. We have recognized four patterns of spatial distribution of setae on dorsal flagella. Species having setae on the distal part of the flagellomeres tended to contain a low density of sensilla trichodea type A. Females showed a higher number of sensilla subtypes B and C-D than males; instead sensilla trichodea A were more abundant in males. No significant difference was found in the number of sensilla placodea, ampullacea, coeloconica and coelocapitular. Sensilla basiconica were found only in females. Our results showed that gustative and tactile sensilla were more abundant in female bees, as well as, olfactory receptors predominate in the antennal system of males. The possible coevolution of flagellar sensilla in males and females of solitary bees is discussed in light of previous reports. Patterns of distribution of setae determine the relative abundance of the types of sensilla in the flagellum., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In this work, we have explored the biochemical changes characterizing the transition from vitellogenesis to follicular atresia, employing the hematophagous insect vector Dipetalogaster maxima as a model. Standardized insect rearing conditions were established to induce a gradual follicular degeneration stage by depriving females of blood meal during post-vitellogenesis. For the studies, hemolymph and ovaries were sampled at representative days of pre-vitellogenesis, vitellogenesis and early and late follicular atresia. When examined by scanning electron microscopy, ovarioles at the initial stage of atresia were small but still showed some degree of asynchronism, a feature that was lost in an advanced degeneration state. At late follicular atresia, in vivo uptake assays of fluorescently labeled vitellogenin (Vg-FITC) showed loss of competitiveness of oocytes to uptake vitellogenin. Circulating vitellogenin levels in atresia were significantly higher than those registered at pre-vitellogenesis, most likely to maintain appropriate conditions for another gonotrophic cycle if a second blood meal is available. Follicular atresia was also characterized by partial proteolysis of vitellin, which was evidenced in ovarian homogenates by western blot. When the activity of ovarian peptidases upon hemoglobin (a non-specific substrate) was tested, higher activities were detected at early and late atresia whereas the lowest activity was found at vitellogenesis. The activity upon hemoglobin was significantly inhibited by pepstatin A (an aspartic peptidase inhibitor), and was not affected by E64 (a cysteine peptidase inhibitor) at any tested conditions. The use of specific fluorogenic substrates demonstrated that ovarian homogenates at early follicular atresia displayed high cathepsin D-like activity, whereas no activity of either, cathepsin B or L was detected. Mass spectrometry analysis of the digestion products of the substrate Abz-AIAFFSRQ-EDDnp further confirmed the presence of a cathepsin D-like peptidase in ovarian tissue. In the context of our findings, the early activation of cathepsin D-like peptidase could be relevant in promoting yolk protein recycling and/or enhancing follicle removal., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The distribution of corazonin in the central nervous system of the heteropteran insect Triatoma infestans was studied by immunohistochemistry. The presence of corazonin isoforms was investigated using MALDI-TOF mass spectrometry in samples containing the brain, the subesophageal ganglion, the corpora cardiaca-corpus allatum complex and the anterior part of the aorta. Several groups of immunopositive perikarya were detected in the brain, the subesophageal ganglion and the thoracic ganglia. Regarding the brain, three clusters were observed in the protocerebrum. One of these clusters was formed by somata located near the entrance of the ocellar nerves whose fibers supplied the aorta and the corpora cardiaca. The remaining groups of the protocerebrum were located in the lateral soma cortex and at the boundary of the protocerebrum with the optic lobe. The optic lobe housed immunoreactive somata in the medial soma layer of the lobula and at the level of the first optic chiasma. The neuropils of the deutocerebrum and the tritocerebrum were immunostained, but no immunoreactive perikarya were detected. In the subesophageal ganglion, immunostained somata were found in the soma layers of the mandibular and labial neuromeres, whereas in the mesothoracic ganglionic mass, they were observed in the mesothoracic, metathoracic and abdominal neuromeres. Immunostained neurites were also found in the esophageal wall. The distribution pattern of corazonin like immunoreactivity in the central nervous system of this species suggests that corazonin may act as a neurohormone. Mass spectrometric analysis revealed that [Arg(7)]-corazonin was the only isoform of the neuropeptide present in T. infestans tissue samples., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The distribution of cholecystokinin-like immunoreactivity was studied in the central nervous system of the heteropteran insect Triatoma infestans using high-sensitivity immunocytochemistry. In the protocerebrum, CCK-IR somata were observed in the anteromedial, anterolateral and posterior cell-body layers. The neuropils displayed different densities of immunoreactive neurites. Few immunoreactive somata were found in the optic lobe in both the medial and lateral soma rinds, as well as in the proximal optic lobe. Immunoreactive fibers were present in the medulla and lobula neuropils. The sensory deutocerebrum contained a higher number of immunopositive perikarya than the antennal mechanosensory and motor center. The antennal lobe glomeruli displayed a moderate density of immunoreactive fibers. With regard to the subesophageal ganglion, numerous CCK-IR somata were found close to the root of the mandibular nerve; others were present in the soma rind of the remaining neuromeres. CCK-IR perikarya were present in both thoracic ganglia, with the abdominal neuromeres containing the highest number of positive somata. The neuropils of both ganglia showed moderate densities of immunopositive processes. The distribution of CCK-LI in somata and neuropils of central nervous system of T. infestans is widespread suggesting that a CCK-like peptide may act mainly as a neuromodulator in the integration of information from distinct sensory receptors.

The biochemical characterization of nitric oxide synthase (NOS) and its distribution in the central nervous system (CNS) were studied in the heteropteran bug Triatoma infestans. NOS-like immunoreactivity was found in the brain, subesophageal ganglion, and thoracic ganglia by using immunocytochemistry. In the protocerebrum, NOS-immunoreactive (IR) somata were detected in the anterior, lateral, and posterior soma rinds. In the optic lobe, numerous immunostained somata were observed at the level of the first optic chiasma, around the lobula, and in the proximal optic lobe. In the deutocerebrum, NOS-IR perikarya were mainly observed in the lateral soma rind, surrounding the sensory glomeruli, and a few cell bodies were seen in association with the antennal mechanosensory and motor neuropil. No immunostaining could be detected in the antennal nerve. The subesophageal and prothoracic ganglia contained scattered immunostained cell bodies. NOS-IR somata were present in all the neuromeres of the posterior ganglion. Western blotting showed that a universal NOS antiserum recognized a band at 134 kDa, in agreement with the expected molecular weight of the protein. Analysis of the kinetics of nitric oxide production revealed a fully active enzyme in tissue samples of the CNS of T. infestans.

The distribution of FMRFamide (FMRFa)-like immunoreactivity (LI) was studied in the brain and subesophageal ganglion of Triatoma infestans, the insect vector of Chagas' disease. The neuropeptide displayed a widespread distribution with immunostained somata in the optic lobe, in the anterior, lateral, and posterior soma rinds of the protocerebrum, and around the antennal sensory and mechanosensory and motor neuropils of the deutocerebrum. FMRFa-immunoreactive profiles of the subesophageal ganglion were seen in the mandibular, maxillary, and labial neuromeres. Immunostained neurites were detected in the medulla and lobula of the optic lobe, the lateral protocerebral neuropil, the median bundle, the calyces and the stalk of the mushroom bodies, and the central body. In the deutocerebrum, the sensory glomeruli showed a higher density of immunoreactive processes than the mechanosensory and motor neuropil, whereas the neuropils of each neuromere of the subesophageal ganglion displayed a moderate density of immunoreactive neurites. Colocalization of FMRFa-LI and crustacean pigment-dispersing hormone-LI was found in perikarya of the proximal optic lobe, the lobula, the sensory deutocerebrum, and the labial neuromere of the subesophageal ganglion. The distribution pattern of small cardioactive peptide B (SCP(B))-LI was also widespread, with immunolabeled somata surrounding every neuropil region of the brain and subesophageal ganglion, except for the optic lobe. FMRFa- and SCP(B)-LIs showed extensive colocalization in the brain of this triatomine species. The presence of immunolabeled perikarya displaying either FMRFa- or SCP(B)-LI confirmed that each antisera identified different peptide molecules. The distribution of FMRFa immunostaining in T. infestans raises the possibility that FMRFa plays a role in the regulation of circadian rhythmicity. The finding of immunolabeling in neurosecretory somata of the protocerebrum suggests that this neuropeptide may also act as a neurohormone.

The distribution of serotonin was studied in the Triatoma infestans central nervous system by using immunocytochemistry. Serotonin immunoreactive cell bodies and fibers were observed in the brain, subesophageal ganglion, and thoracic ganglia. In the brain, serotonin-like immunoreactivity was detected in a limited number of somata, which gave rise to an extensive network of labeled neurites in patterned as well as in nonglomerular neuropils. Immunolabeled perikarya were observed in the optic lobe and in the anteromedial and caudolateral soma rinds of the protocerebrum. Deutocerebral immunoreactive somata were mainly found in the medial layer surrounding the antennal lobe glomeruli, as well as in relationship to the antennal mechanosensory and motor center. The subesophageal ganglion contained serotonin immunoreactive perikarya of variable sizes and moderate to low density of positive fibers. In the prothoracic ganglion, immunoreactive somata were detected near the cephalic connectives as well as in its caudal end. Serotonin immunoreactive somata and fibers were observed in the posterior ganglion of the thorax, with the abdominal neuromeres harboring the highest number of immunolabeled perikarya. These results show that there is a widespread unique serotonergic system in the CNS of Triatoma infestans and suggest that the indolamine could act as a neuromodulator or as a neurohormone., (Copyright 2004 Wiley-Liss, Inc.)

The distributions of neuropeptide Y (NPY) -like immunoreactivity (LI) and that of its Y1 receptor (Y1), as well as their coexistence with cholecystokinin (CCK) -LI, were studied in the central nervous system of Triatoma infestans by using immunohistochemistry. NPY-immunoreactive (IR) cell bodies and fibers were observed in the brain, subesophageal ganglion, and thoracic ganglia. NPY-IR somata were seen in the optic lobe and the anteromedial and caudolateral soma rinds of the protocerebrum. Immunostained cell bodies were also found in the lateral edge of the antennal lobe glomeruli as well as in the caudal part of the antennal mechanosensory and motor center. The subesophageal ganglion harbored few NPY-IR perikarya and fibers in the three neuromeres. Positive somata of the prothoracic ganglion were detected near both the cephalic and posterior connectives as well as by the root of prothoracic nerve I, whereas in the posterior ganglion, they were seen by the roots of mesothoracic and abdominal nerves. Coexpression of NPY-LI and CCK-LI was seen in cell bodies of the protocerebrum, the subesophageal and posterior ganglia. Protocerebral Y1-IR cell groups were detected in the anterolateral and posteromedial soma rinds and at the level of the lamina ganglionaris and the external optic chiasma. Numerous positive perikarya surrounded the antennal lobe glomeruli as well as the antennal mechanosensory and motor center. Other immunostained cell bodies were seen in the posterior edge of the esophageal canal and by the roots of the mandibular and the maxillary nerves. Y1-IR cell bodies of the prothoracic ganglion were found near the roots of prothoracic nerves I-II, whereas in the posterior ganglion, they were located mainly in the abdominal neuromeres. Coexpression of Y1-LI and CCK-LI were detected in several brain areas as well as in the metathoracic and abdominal neuromeres of the posterior ganglion. When assessed by immunoblotting, Y1 antibodies detected two protein bands between 34 and 46 kDa. Analysis of the distribution patterns of NPY-LI and Y1-LI suggest that peptide and receptor are mainly involved in the processing of information coming from sensory receptors., (Copyright 2003 Wiley-Liss, Inc.)

The effects of the alpha-2 adrenoceptor agonist clonidine (CLO) on the growth hormone (GH) regulatory neuronal systems, growth hormone-releasing hormone (GHRH) and somatostatin (SS), were studied in adult male rats given a single or a short-term administration (1, 3 and 6 days) of the drug. Acute administration of CLO significantly decreased hypothalamic GHRH content [leaving unaltered GHRH messenger RNA (mRNA) levels] and increased plasma GH levels; hypothalamic SS content/mRNA levels and pituitary GH content/mRNA levels remained unchanged. In 1- and 3-day CLO-treated rats, by contrast, decreased hypothalamic GHRH content was coupled with a significant reduction in GHRH mRNA levels. In these rats, pituitary GH content and mRNA levels were also significantly increased, whereas hypothalamic SS content and mRNA levels remained unaltered. In 6-day CLO-treated rats, hypothalamic GHRH content and mRNA levels were still significantly reduced, plasma GH levels were increased, but to a lesser extent than in 1- and 3-day CLO-treated rats, and pituitary GH content and mRNA reverted to control levels. Hypothalamic SS content and mRNA levels remained unaltered. These results indicate that 1) functional activation of alpha-2 adrenergic receptors by CLO increases GHRH release from the hypothalamus, 2) CLO, via GHRH, increases GH secretion and biosynthesis, which in turn feeds back in the hypothalamus to reduce GHRH biosynthesis, and 3) reduction of hypothalamic GH-stimulatory activity tones down the initial pituitary somatotropic hyperfunction. Unaltered hypothalamic SS content and mRNA levels in all CLO-treated rats suggests that the somatostatinergic system is less sensitive than the GHRH system to changes in circulating GH levels.

Immunohistochemistry was used to establish the presence of nitric oxide synthase (NOS) in the central nervous system of Triatoma infestans which is the main vector for Chagas' disease in Argentina and neighbouring countries. In addition, we have investigated the presence of cholecystokinin (CCK) and studied the possible coexistence of these molecules. The results show NOS-like immunoreactivity (LI) in neurones of the soma rind of the protocerebrum, the optic lobe and in the lateral part of the sensory deutocerebrum with a few cells in the suboesophageal and the prothoracic ganglia. The distribution of CCK-LI was similar to that of NOS-LI and in several areas both molecules coexisted in neurones and fibres. The results suggest that nitric oxide may act as a neurotransmitter in the brain of insects.

We have studied in old dogs the effects of short-term administration of growth hormone (GH)-releasing hormone (GHRH) alone or co-administered with clonidine (CLO), an alpha 2-adrenergic agonist, on the GH secretory pattern (cluster analysis), and GH responsiveness to an acute GHRH or GHRH + CLO challenge and plasma somatomedin C (SMC) levels. Dogs were given either GHRH alone twice daily for 10 days (treatment 1) or combined GHRH + CLO both given twice daily (treatment 2) or GHRH + CLO given once daily (treatment 3). Animals were sampled from 09.00 to 15.00 h, at 10-min intervals, both before and 14 h after treatments. At the end of the 6-hour sampling period, dogs were challenged with simultaneous administration of GHRH and CLO, while they were tested with GHRH alone on the morning of the following day. In dogs undergoing treatment 1, acute administration of GHRH or GHRH + CLO elicited mean GH peak responses higher than before treatment, but none of the GH secretory indices were modified during the 6-hour sampling period, except for the increase in mean GH peak amplitude. In dogs undergoing treatment 2, acute administration of GHRH elicited a mean GH peak response higher than that before treatment, whereas administration of GHRH + CLO induced a mean GH peak response not different from that elicited by GHRH + CLO before treatment or by GHRH alone after treatment. However, this treatment significantly augmented the frequency of spontaneous bursts of GH secretion, the mean GH peak amplitude and the total peak area.(ABSTRACT TRUNCATED AT 250 WORDS)

Recently, we have reported in immature female rats that short-term blockade of glutamate receptors of the N-methyl-D-aspartic acid (NMDA) subtype by the noncompetitive antagonist MK-801 induced a reduction of growth rate, basal and stimulated growth hormone (GH) release and plasma somatomedin C levels. In the present study, we investigated in immature male rats the mechanism(s) through which agonists and antagonists of glutamate receptors affect GH secretion. In 21-day-old male rats, administration of MK-801 (0.2 mg/kg i.p.b.i.d.) for 10 days induced a significant impairment of growth rate, which was unrelated to a significant reduction of food intake. GH secretion from anterior pituitary fragments of MK-801-treated rats was not significantly reduced under basal conditions but was significantly less under stimulation by 40 mM K+. Incubation of dispersed pituitary cells of 31-day-old rats with N-methyl-aspartic acid (1 and 100 microM), alone or associated with MK-801 (1 microM) did not change GH secretion. Semi quantitative densitometric analysis of hypothalami of MK-801-treated rats evidenced a clearcut decrease in the intensity of GHRH-like immuno-reactivity (LI) staining in the median eminence (ME), whereas no difference was observed in the ME-somatostatin (SS)-LI. Finally, GHRH mRNA but not SS-mRNA, evaluated by slot-blot hybridization, was reduced in the hypothalamus of MK-801-treated rats. These and our previous data would demonstrate that NMDA glutamate receptors play an important role in the neuroendocrine control of GH secretion in the rat, and suggest an action mediated by GHRH-secreting neurons.

The release of prolactin (PRL) and growth hormone (GH) of pituitary grafts and in situ glands was investigated using perifusion techniques. Whole pituitary or anterior lobe grafts were used. The grafts or the in situ glands were incubated alone in a chamber. The hypophysis of dioestrous-1 glands were used as controls. Both types of grafts released PRL an GH to the medium, being the PRL release of the anterior lobe graft higher than that of the whole pituitary graft. The in situ pituitary glands of grafted animals released less PRL than the control dioestrous glands. Also, the in situ glands of whole pituitary grafted animals released less PRL than the hypophysis of animals which bore grafts of only the anterior lobe. No difference in GH secretion, either by the graft or by the in situ gland was observed when whole pituitary or anterior grafts were used. These results provide a further support to the hypothesis that a pituitary graft under the kidney capsule exerts profound modifications in the function of the in situ hypophysis. The presence of the neurointermediate lobe (NIL) in the graft is modulatory to the release of PRL.

The morphology of the papilla palatina, the nasopalatine ducts and the taste buds situated within these ducts was studied in pups and adult rats using light and electron microscopy. During development, the papilla palatina grew in width and depth, becoming a protuberance in weanlings and adults. The nasopalatine ducts enlarged and two folds of the lateral walls of the ducts differentiated, reducing the width of the tubes in the region of the oral openings. Taste buds appeared postnatally. Light, dark, and perigemmal cells were found in all stages studied, but light cells were scarce up to 8 days of age. The taste pore appeared between 11 and 13 days of age; it lacked electron-dense material of cellular origin. Synaptic-like images could be found only in relation to dark cells. The papilla palatina, the nasopalatine ducts and the taste buds were fully developed by the 3rd week of life.