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W H Yu

Publications and source records attributed to W H Yu.

At least 37 records · Page 2Linked to original sources
PubMed2001

Three distinct types of GnRH receptor characterized in the bullfrog.

It has been proposed recently that two types of GnRH receptors (GnRHR) exist in a particular species. Here we present data demonstrating that at least three types of GnRHR are expressed in a single diploid species, the bullfrog. Three different cDNAs, encoding distinct types of bullfrog GnRHR (bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3), were isolated from pituitary and hindbrain of the bullfrog. BfGnRHR-1 mRNA was expressed predominantly in pituitary, whereas bfGnRHR-2 and -3 mRNAs were expressed in brain. The bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3 proteins have an amino acid identity of approximately 30% to approximately 35% with mammalian GnRHRs and approximately 40% to approximately 50% with nonmammalian GnRHRs. Interestingly, bfGnRHR-2 has an 85% amino acid homology with Xenopus GnRHR. Less than 53% amino acid identity was observed among the three bfGnRHRs. All isolated cDNAs encode functional receptors because their transient expression in COS-7 cells resulted in a ligand-dependent increase in inositol phosphate production. Notably, all three receptors exhibited a differential ligand selectivity. For all receptors, cGnRH-II has a higher potency than mGnRH. In addition, salmon GnRH also has a strikingly high potency to stimulate all three receptors. In conclusion, we demonstrated the presence of three GnRHRs in the bullfrog. Their expression in pituitary and brain suggests that bfGnRHRs play an important role in the regulation of reproductive functions in the bullfrog.

Amino Acid Sequence↗
PubMed2001

Androgen receptors in cranial nerve motor nuclei of male and female rats.

This study compared AR proteins in four cranial nerve motor nuclei among male and female rats that were intact, gonadectomized, or gonadectomized and given TP by immunohistochemistry. AR-immunoreactive (ir) neurons were found, in descending order of abundance, in the nucleus ambiguus, hypoglossal nucleus, and the facial and trigeminal motor nuclei of both males and females of intact and gonadectomized plus TP rats. Virtually every neuron of the nucleus ambiguus was AR-ir. In contrast, AR-ir neurons were either restricted to a specific area of the hypoglossal nucleus, or randomly distributed in the facial and trigeminal motor nuclei. The predominant AR-ir site shifted from cell nuclei to the cytoplasm, depending upon the presence or absence of ligand. Sex differences in the amount and staining intensity of AR-ir neurons were discernable in all four motor nuclei of intact rats, and these differences were maintained in gonadectomized plus TP rats, with the exception of the nucleus ambiguus. The immunostaining results were complemented by results from AR binding studies. Cytosolic AR binding values for the hypoglossal and facial motor nuclei of females were only approximately 50% of those of males despite the absence of a sex difference in neuron number. These results indicate that intrinsic sex differences in AR levels and androgenic regulation of AR exist in cranial nerve motor nuclei, and that there are differences in the abundance and distribution pattern of AR responsive neurons in cranial nerve motor nuclei. These results are consistent with the idea that sex differences in AR could account for sex differences observed in nerve regeneration and neuron loss following cranial nerve injury.

Animals↗
PubMed2001

Lamprey gonadotropin-releasing hormone-III selectively releases follicle stimulating hormone in the bovine.

Recent studies have shown that lamprey gonadotropin-releasing hormone (l-GnRH) is localized in the mammalian brain, and that l-GnRH-III, can selectively induce FSH secretion in the rat both in vivo and in vitro. Consequently, the purpose of this study was to determine if l-GnRH-III could elicit selective FSH release in cattle and compare this response with that to mammalian luteinizing hormone releasing hormone (m-LHRH). Cattle were chosen as the animal model because previous studies have demonstrated that FSH and LH are secreted by separate gonadotropes in that species. For these studies, crossbred cycling heifers were implanted with jugular cannulae and l-GnRH-III was infused either between Days 9-14 or on Day 20 of the estrous cycle. Blood samples were collected both before and following peptide infusion. Our results demonstrate that during Days 9-14 of the estrous cycle (luteal phase), when progesterone levels averaged between 4 and 5 ng/ml, a dose of 0.25 mg of l-GnRH-III induced the release of FSH (P < 0.05), but not LH. A 0.5 mg dose of l-GnRH-III caused a greater release of FSH (P < 0.01), but still did not induce LH release. Higher doses of the peptide were capable of significantly releasing both gonadotropins. Importantly, during the luteal phase, doses of 0.5 and 2 mg of m-LHRH were ineffective in stimulating FSH, but did elicit marked increases (P < 0.001) in LH. Again, progesterone levels averaged 4-5 pg/ml. In order to assess gonadotropin releasing ability of l-GnRH-III at a different phase of the estrous cycle, some animals were administered the peptide on Day 20, when progesterone levels were below 1.0 pg/ml. At this time, the l-GnRH-III induced the release of LH (P < 0.01), but not FSH. Overall, our results demonstrate that l-GnRH-III can selectively induce FSH in cattle during the luteal phase, whereas m-LHRH was ineffective in that regard. Furthermore, the fact that l-GnRH-III can selectively stimulate FSH when serum progesterone is high, and LH when serum progesterone is low, suggests its actions are under strong control of this steroid. We suggest the FSH releasing capacity of l-GnRH-III in cattle could render this peptide useful for enhancement of reproductive efficiency in this species.

Animals↗
PubMed2001

Lipopolysaccharide-induced tumor necrosis factor-alpha release is controlled by the central nervous system.

OBJECTIVE: Lipopolysaccharide (LPS) injection in mammals orchestrates the release of many proinflammatory and anti-inflammatory cytokines. Intravenous administration of 0.2 mg/kg of LPS into unanesthetized rats with indwelling jugular catheters provoked a rapid, 50-fold increase in plasma tumor necrosis factor (TNF)-alpha within 30 min, which declined by 60% by 120 min. To test our hypothesis that such a rapid increase of TNF-alpha would be either neurally or hormonally controlled, the effect on TNF-alpha release of anesthesia (ketamine/acepromazine/xylazine) and catecholaminergic agonists and antagonists, either alone or in the presence of LPS, was determined. METHODS: Rats bearing indwelling external jugular catheters were injected with the test drug or saline after removal of 0.6 ml of blood (-10 min). At time zero, LPS or saline was administered. Thereafter, blood samples were drawn at 15, 30, 120, 240 and 360 min. TNF-alpha was measured by immunoassay. RESULTS: Among all the drugs tested, only propranolol increased plasma TNF-alpha. Anesthesia significantly blunted the LPS-induced TNF-alpha peak by 50%. Isoproterenol, a beta-adrenergic agonist, also blocked LPS-induced TNF-alpha release by 70% at 30 min and 90% at 120 min. On the contrary, propranolol, a beta-receptor blocker, induced a highly significant 3-fold increase in plasma TNF-alpha concentrations at 30 min and augmented the response to LPS 2-fold after endotoxin injection. Phentolamine, an alpha-receptor blocker, decreased the LPS-induced TNF-alpha release by 57% at 30 min. Similarly, alpha-bromoergocryptine, a dopamine D2 receptor agonist, decreased the LPS-induced TNF-alpha peak by 70% at 30 min and 50% at 120 min. CONCLUSIONS: We conclude that TNF-alpha is at least in part neurally controlled since the anesthetic blocked its response to LPS. The fact that isoproterenol decreased the LPS-induced TNF-alpha release, whereas propranolol augmented basal and LPS-induced release suggests that the sympathetic nervous system inhibits basal and LPS-stimulated TNF-alpha release via beta-adrenergic receptors. Since phentolamine blocked LPS-induced release, this release may be induced, in part at least, by LPS-stimulated adrenergic drive acting on alpha-adrenergic receptors. The suppressive action of bromoergocryptine, a dopamine D2 receptor agonist, on LPS-induced TNF-alpha release may be mediated in part by suppression of prolactin release, which triggers TNF-alpha release.

Adrenergic alpha-Antagonists↗
PubMed2001

Comparisons of the effects of anesthesia and stress on release of tumor necrosis factor-alpha, leptin, and nitric oxide in adult male rats.

Bacterial lipopolysaccharide (LPS) stimulates massive release of tumor necrosis factor-alpha (TNF-alpha) together with nitric oxide (NO) and a lessor release of leptin. We hypothesized that other types of stress such as that of surgery might also release these cytokines and NO. Adult male rats were anesthetized with ketamine/acepromazine/xylazine anesthesia (90 + 2 + 6 mg/ml, respectively) and an external jugular catheter was inserted for removal of blood samples (0.6 ml) at various times postoperatively. Plasma TNF-alpha was almost undetectable in decapitated rats and was near zero immediately following the placement of the jugular catheter (time zero [t0]). As the rats awakened from anesthesia, there was a rise in TNF-alpha at 30 min that peaked at 2 hr with a 400-fold increase and then precipitously declined 40-fold to a level still greater than zero at 3 hr. At 6 hr on the following morning, TNF-alpha values were near zero, but following connection of tubing and withdrawal of the initial blood sample, there was a 100-fold increase 1 hr later, followed by a decline over the next 3 hr. In contrast, plasma [NO/NO2] from decapitated rats was 117 microM. Values at tO were decreased and plummeted 4-fold within 30 min, then rose slightly in the ensuing 3 hr. At 6 hr on the next day [NO3/NO2] values were lower than at tO and declined gradually during the next 4 hr. Leptin gradually declined from pre-operative concentrations, reaching a minimum at 3 hr and its concentration was unaffected by the bleeding stress of the second day. We conclude that release of TNF-alpha, [NO3/NO2], and leptin are neurally controlled since plasma levels of all three declined as a result of anesthesia. TNF-alpha secretion was remarkably stress responsive, whereas NO release appeared to be suppressed by the combined operative and bleeding stress, and leptin was stress unresponsive.

Acepromazine↗
PubMed2000

TIMP-3 binds to sulfated glycosaminoglycans of the extracellular matrix.

Of the four known tissue inhibitors of metalloproteinases (TIMPs), TIMP-3 is distinguished by its tighter binding to the extracellular matrix. The present results show that glycosaminoglycans such as heparin, heparan sulfate, chondroitin sulfates A, B, and C, and sulfated compounds such as suramin and pentosan efficiently extract TIMP-3 from the postpartum rat uterus. Enzymatic treatment by heparinase III or chondroitinase ABC also releases TIMP-3, but neither one alone gives complete release. Confocal microscopy shows colocalization of heparan sulfate and TIMP-3 in the endometrium subjacent to the lumen of the uterus. Immunostaining of TIMP-3 is lost upon digestion of tissue sections with heparinase III and chondroitinase ABC. The N-terminal domain of human TIMP-3 was expressed and found to bind to heparin with affinity similar to that of full-length mouse TIMP-3. The A and B beta-strands of the N-terminal domain of TIMP-3 contain two potential heparin-binding sequences rich in lysine and arginine; these strands should form a double track on the outer surface of TIMP-3. Synthetic peptides corresponding to segments of these two strands compete for heparin in the DNase II binding assay. TIMP-3 binding may be important for the cellular regulation of activity of the matrix metalloproteinases.

Alkylation↗
PubMed2000

Non-replicating Epstein-Barr virus-based plasmids extend gene expression and can improve gene therapy in vivo.

To date, no gene transfer vector has produced prolonged gene expression following a single intravenous injection and then efficiently re-expressed the delivered gene following repeated systemic injection into immunocompetent hosts. To overcome these limitations, a gene therapy regimen using non-replicating Epstein-Barr virus (EBV)-based expression plasmids was developed. One plasmid contains the FR (EBV family of repeats) sequence and the expressed gene. The other encodes Epstein-Barr nuclear antigen 1 (EBNA-1), but lacks FR. Although unable to replicate in mice, intravenous co-injection of EBV-based plasmids in cationic liposome-DNA complexes (CLDCs) substantially prolonged luciferase gene expression. The use of a two-vector system limited host exposure to the EBNA-1 gene product. Furthermore, this EBV-based vector system could be intravenously re-injected multiple times into immunocompetent mice without loss of transfection efficiency. Use of this vector system significantly improved the therapeutic efficacy of the biologically important human granulocyte colony-stimulating factor gene. Delivery of the human granulocyte colony-stimulating factor gene in EBV-based plasmids increased circulating white blood counts for at least 2 months following a single CLDC-based intravenous co-injection. Conversely, white blood counts were never elevated following injection of CLDCs lacking EBV-derived elements. Thus, this EBV-based plasmid vector system both markedly prolongs gene expression at therapeutic levels and efficiently and repeatedly re-transfects immunocompetent hosts. These properties of EBV-based plasmid vectors appear to be due, at least in part, to the documented abilities of the EBNA-1 protein both to retain FR-containing DNA intracellularly and within the nucleus and to block anti-EBNA-1 cytotoxic T cell responses.

Animals↗
PubMed2000

Ascorbic acid acts as an inhibitory transmitter in the hypothalamus to inhibit stimulated luteinizing hormone-releasing hormone release by scavenging nitric oxide.

Because ascorbic acid (AA) is concentrated in synaptic vesicles containing glutamic acid, we hypothesized that AA might act as a neurotransmitter. Because AA is an antioxidant, it might therefore inhibit nitric oxidergic (NOergic) activation of luteinizing hormone-releasing hormone (LH-RH) release from medial basal hypothalamic explants by chemically reducing NO. Cell membrane depolarization induced by increased potassium concentration [K(+)] increased medium concentrations of both AA and LH-RH. An inhibitor of NO synthase (NOS), N(G)-monomethyl-l-arginine (NMMA), prevented the increase in medium concentrations of AA and LH-RH induced by high [K(+)], suggesting that NO mediates release of both AA and LH-RH. Calcium-free medium blocked not only the increase in AA in the medium but also the release of LH-RH. Sodium nitroprusside, which releases NO, stimulated LH-RH release and decreased the concentration of AA in the incubation medium, presumably because the NO released oxidized AA to dehydro-AA. AA (10(-5) to 10(-3) M) had no effect on basal LH-RH release but completely blocked high [K(+)]- and nitroprusside-induced LH-RH release. N-Methyl-d-aspartic acid (NMDA), which mimics the action of the excitatory amino acid neurotransmitter glutamic acid, releases LH-RH by releasing NO. AA (10(-5) to 10(-3) M) inhibited the LH-RH-releasing action of NMDA. AA may be an inhibitory neurotransmitter that blocks NOergic stimulation of LH-RH release by chemically reducing the NO released by the NOergic neurons.

Animals↗
PubMed2000

Heparan sulfate proteoglycans as extracellular docking molecules for matrilysin (matrix metalloproteinase 7).

Many matrix metalloproteinases (MMPs) are tightly bound to tissues; matrilysin (MMP-7), although the smallest of the MMPs, is one of the most tightly bound. The most likely docking molecules for MMP-7 are heparan sulfate proteoglycans on or around epithelial cells and in the underlying basement membrane. This is established by extraction experiments and confocal microscopy. The enzyme is extracted from homogenates of postpartum rat uterus by heparin/heparan sulfate and by heparinase III treatment. The enzyme is colocalized with heparan sulfate in the apical region of uterine glandular epithelial cells and can be released by heparinase digestion. Heparan sulfate and MMP-7 are expressed at similar stages of the rat estrous cycle. The strength of heparin binding by recombinant rat proMMP-7 was examined by affinity chromatography, affinity coelectrophoresis, and homogeneous enzyme-based binding assay; the K(D) is 5-10 nM. Zymographic measurement of MMP-7 activity is greatly enhanced by heparin. Two putative heparin-binding peptides have been identified near the C- and N-terminal regions of proMMP-7; however, molecular modeling suggests a more extensive binding track or cradle crossing multiple peptide strands. Evidence is also found for the binding of MMP-2, -9, and -13. Binding of MMP-7 and other MMPs to heparan sulfate in the extracellular space could prevent loss of secreted enzyme, provide a reservoir of latent enzyme, and facilitate cellular sensing and regulation of enzyme levels. Binding to the cell surface could position the enzyme for directed proteolytic attack, for activation of or by other MMPs and for regulation of other cell surface proteins. Dislodging MMPs by treatment with compounds such as heparin might be beneficial in attenuating excessive tissue breakdown such as occurs in cancer metastasis, arthritis, and angiogenesis.

Animals↗
PubMed2000

Short-term enzyme replacement in the murine model of Sanfilippo syndrome type B.

The Sanfilippo syndrome type B (MPS III B) is an autosomal recessive disease caused by deficiency of alpha-N-acetylglucosaminidase (EC 3. 2.1.50), one of the lysosomal enzymes required for the degradation of heparan sulfate. The disease is characterized by profound neurodegeneration but relatively mild somatic manifestations, and is usually fatal in the second decade. A mouse model had been generated by disruption of the Naglu gene in order to facilitate the study of pathogenesis and the development of therapy for this currently untreatable disease. Recombinant human alpha-N-acetylglucosaminidase (rhNAGLU) was prepared from secretions of Lec1 mutant Chinese hamster ovary cells. The enzyme, which has only unphosphorylated high-mannose carbohydrate chains, was endocytosed by mouse peritoneal macrophages via mannose receptors, with half-maximal uptake at ca. 10(-7) M. When administered intravenously to 3 month-old mice, rhNAGLU was taken up avidly by liver and spleen but marginally if at all by thymus, lung, kidney, heart, and brain (in order of diminishing uptake). The half-life of the enzyme was 2.5 days in liver and spleen. Immunohistochemistry and electron microscopy showed that only macrophages were involved in enzyme uptake and correction in these two organs, yet the storage of glycosaminoglycan was reduced to almost normal levels. The results show that the macrophage-targeted rhNAGLU can substantially reduce the body burden of glycosaminoglycan storage in the mouse model of Sanfilippo syndrome III B.

Acetylglucosaminidase↗
PubMed2000

The similarity of FSH-releasing factor to lamprey gonadotropin-releasing hormone III (l-GnRH-III).

To validate further the existence of a specific hypothalamic follicle stimulating hormone releasing factor (FSHRF), stalk-median eminence (SME) fragments from sheep and whole hypothalami from male rats were purified by gel filtration on Sephadex G-25, and the gonadotropin-releasing activity on hemipituitaries of rats incubated in vitro was determined by bioassay and compared with the radioimmunoassayable luteinizing hormone releasing hormone (LHRH) and lamprey gonadotropin releasing hormone (l-GnRH) activities in the fractions. The FSH-releasing fractions eluted in the same sequence of tubes from the Sephadex column found earlier by in vivo bioassay and were clearly separated from the immunoassayable and bioassayable LHRH. The radioimmunoassay (RIA) for l-GnRH recognized equally l-GnRH-I and -III but had negligible cross-reactivity with LHRH. Fractionation of rat hypothalamic extract by gel filtration on Sephadex G-25 revealed three peaks of l-GnRH determined by RIA, all of which eluted prior to the peak of LHRH. Only the second peak had FSH-releasing but not LH-releasing activity. To determine if this FSH-releasing activity was caused by the presence of l-GnRH in the fraction, the pituitaries were incubated with normal rabbit serum or the l-GnRH antiserum (1:1000), and the effect on the FSH- and LH-releasing activity of the FSH-releasing fraction and the LH-releasing activity of LHRH was determined. The antiserum had no effect on basal release of either FSH or LH but eliminated the FSH-releasing activity of the active fraction without altering the LH-releasing activity of LHRH. Since l-GnRH-I has little activity to release FSH or LH, and its activity is nonselective, whereas previous experiments have shown that l-GnRH-III highly selectively releases FSH with a potency equal to that of LHRH to release LH, the results support the hypothesis that the FSH-releasing activity observed in these experiments was caused by l-GnRH-III or a closely related peptide.

Animals↗
PubMed2000

The possible role of prolactin in the circadian rhythm of leptin secretion in male rats.

In humans there is a circadian rhythm of leptin concentrations in plasma with a minimum in the early morning and a maximum in the middle of the night. By taking blood samples from adult male rats every 3 hr for 24 hr, we determined that a circadian rhythm of plasma leptin concentrations also occurs in the rat with a peak at 0130h and a minimum at 0730h. To determine if this rhythm is controlled by nocturnally released hormones, we evaluated the effect of hormones known to be released at night in humans, some of which are also known to be released at night in rats. In humans, prolactin (PRL), growth hormone (GH), and melatonin are known to be released at night, and adrenocorticotropic hormone (ACTH) release is inhibited. In these experiments, conscious rats were injected intravenously with 0.5 ml diluent or the substance to be evaluated just after removal of the first blood sample (0.3 ml), and additional blood samples (0.3 ml) were drawn every 10 min thereafter for 2 hr. The injection of highly purified sheep PRL (500 microg) produced a rapid increase in plasma leptin that persisted for the duration of the experiment. Lower doses were ineffective. To determine the effect of blockade of PRL secretion on leptin secretion, alpha bromoergocryptine (1.5 mg), a dopamine-2-receptor agonist that rapidly inhibits PRL release, was injected. It produced a rapid decline in plasma leptin within 10 min, and the decline persisted for 120 min. The minimal effective dose of GH to lower plasma leptin was 1 mg/rat. Insulin-like growth factor (IGF-1) (10 microg), but not IGF-2 (10 microg), also significantly decreased plasma leptin. Melatonin, known to be nocturnally released in humans and rats, was injected at a dose of 1 mg/rat during daytime (1100h) or nighttime (2300h). It did not alter leptin release significantly. Dexamethasone (DEX), a potent glucocorticoid, was ineffective at a 0. 1-mg dose but produced a delayed, significant increase in leptin, manifest 100-120 min after injection of a 1 mg dose. Since glucocorticoids decrease at night in humans at the time of the maximum plasma concentrations of leptin, we hypothesize that this increase in leptin from a relatively high dose of DEX would mimic the response to the release of corticosterone following stress in the rat and that glucocorticoids are not responsible for the circadian rhythm of leptin concentration. Therefore, we conclude that an increase in PRL secretion during the night may be responsible, at least in part, for the nocturnal elevation of leptin concentrations observed in rats and humans.

Animals↗
PubMed2000

The mechanism of action of cytokines to control the release of hypothalamic and pituitary hormones in infection.

During infection, bacterial and viral products, such as bacterial lipopolysaccharide (LPS), cause the release of cytokines from immune cells. These cytokines can reach the brain by several routes. Furthermore, cytokines, such as interleukin-1 (IL-1), are induced in neurons within the brain by systemic injection of LPS. These cytokines determine the pattern of hypothalamic-pituitary secretion that characterizes infection. IL-2, by stimulation of cholinergic neurons, activates neural nitric oxide synthase (nNOS). The nitric oxide (NO) released diffuses into corticotropin-releasing hormone (CRH)-secreting neurons and releases CRH. IL-2 also acts in the pituitary to stimulate adrenocorticotropic hormone (ACTH) secretion. On the other hand, IL-1 alpha blocks the NO-induced release of luteinizing hormone-releasing hormone (LHRH) from LHRH neurons, thereby blocking pulsatile LH but not follicle-stimulating hormone (FSH) release and also inhibiting sex behavior that is induced by LHRH. IL-1 alpha and granulocyte macrophage colony-stimulating factor (GMCSF) block the response of the LHRH terminals to NO. The mechanism of action of GMCSF to inhibit LHRH release is as follows. It acts on its receptors on gamma-aminobutyric acid (GABA)ergic neurons to stimulate GABA release. GABA acts on GABAa receptors on the LHRH neuronal terminal to block NOergic stimulation of LHRH release. IL-1 alpha inhibits growth hormone (GH) release by inhibiting GH-releasing hormone (GHRH) release, which is mediated by NO, and stimulating somatostatin release, also mediated by NO. IL-1 alpha-induced stimulation of PRL release is also mediated by intrahypothlamic action of NO, which inhibits release of the PRL-inhibiting hormone dopamine. The actions of NO are brought about by its combined activation of guanylate cyclase-liberating cyclic guanosine monophosphate (cGMP) and activation of cyclooxygenase (COX) and lipoxygenase (LOX) with liberation of prostaglandin E2 and leukotrienes, respectively. Thus, NO plays a key role in inducing the changes in release of hypothalamic peptides induced in infection by cytokines. Cytokines, such as IL-1 beta, also act in the anterior pituitary gland, at least in part via induction of inducible NOS. The NO produced inhibits release of ACTH. The adipocyte hormone leptin, a member of the cytokine family, has largely opposite actions to those of the proinflammatory cytokines, stimulating the release of FSHRF and LHRH from the hypothalamus and FSH and LH from the pituitary directly by NO.

Adjuvants, Immunologic↗
PubMed2000

Induction of pulmonary matrilysin expression by combustion and ambient air particles.

The molecular mechanism(s) by which chemically complex air pollution particles mediate their adverse health effects is not known. We have examined the ability of combustion and ambient air particles to induce pulmonary matrilysin expression due to the well-documented role of matrix metalloproteinases in tissue injury and repair responses. Rats were exposed to saline, residual oil fly ash (2.5 mg/rat), or ambient air particles (2.5 mg/rat) via intratracheal instillation and examined 3-72 h after exposure. Saline-exposed animals had low levels of matrilysin mRNA, whereas the animals exposed to either complex particle showed an early induction of pulmonary matrilysin gene expression as well as of the 19-kDa activated form of matrilysin. Immunocytochemistry and in situ hybridization analyses identified the alveolar macrophages and monocytes as primary sources of air pollution particle-induced matrilysin expression. Matrilysin gene induction and protein activation by combustion and ambient air particles correlated with the early histopathological changes produced by these particles. These results demonstrate the ability of combustion and ambient air particles to induce pulmonary matrilysin expression and suggest a role for this matrix metalloproteinase in the initiation of lung injury produced by these particles.

Air Pollutants↗
PubMed2000

Lipopolysaccharide-induced leptin release is not mediated by nitric oxide, but is blocked by dexamethasone.

The adipocyte hormone, leptin, has homology with tumor necrosis factor-alpha (TNF-alpha) and the leptin receptor (OB-Rb) has homology with the interleukin(IL)-6 receptor. Lipopolysaccharide (LPS) from gram-negative bacteria stimulates the release of many pro-inflammatory cytokines, such as TNF-alpha, IL-1 and IL-6, among others. To test the hypothesis that LPS would also stimulate the release of leptin, LPS (0.6 mg/kg) was injected intravenously into conscious male rats bearing external jugular venous catheters. Vehicle (0.9% NaCl) was injected into control animals. Blood samples (0.3 ml) were drawn immediately before injection and every 10 min afterwards for 120 min. Plasma leptin concentrations increased gradually in the LPS-treated rats, reaching a peak at 120 min of nearly twice the starting level. To determine if this release was mediated by nitric oxide (NO), nitroarginine methyl ester (NAME), an inhibitor of NO synthase, was injected at doses of 11 or 23 mg/kg (i. v.). The lower dose decreased plasma leptin slightly, whereas the higher dose of NAME increased plasma leptin at 110 min but had no effect on LPS-induced leptin release. On the other hand, dexamethasone (DEX) (0.85 mg/kg), a synthetic glucocorticoid, injected 15 min before LPS, decreased LPS-induced leptin release by 80% (p < 0.001). The results indicate that LPS is a stimulant of leptin release, that NO has little control over basal or LPS-induced leptin release, but that glucocorticoids, epitomized by DEX, largely block LPS-induced leptin release. Increased release of leptin during infection may contribute to the decreased feeding, altered hormonal release and metabolic changes that occur during infection.

Animals↗
PubMed1999

Mouse model of Sanfilippo syndrome type B produced by targeted disruption of the gene encoding alpha-N-acetylglucosaminidase.

The Sanfilippo syndrome type B is an autosomal recessive disorder caused by mutation in the gene (NAGLU) encoding alpha-N-acetylglucosaminidase, a lysosomal enzyme required for the stepwise degradation of heparan sulfate. The most serious manifestations are profound mental retardation, intractable behavior problems, and death in the second decade. To generate a model for studies of pathophysiology and of potential therapy, we disrupted exon 6 of Naglu, the homologous mouse gene. Naglu-/- mice were healthy and fertile while young and could survive for 8-12 mo. They were totally deficient in alpha-N-acetylglucosaminidase and had massive accumulation of heparan sulfate in liver and kidney as well as secondary changes in activity of several other lysosomal enzymes in liver and brain and elevation of gangliosides G(M2) and G(M3) in brain. Vacuolation was seen in many cells, including macrophages, epithelial cells, and neurons, and became more prominent with age. Although most vacuoles contained finely granular material characteristic of glycosaminoglycan accumulation, large pleiomorphic inclusions were seen in some neurons and pericytes in the brain. Abnormal hypoactive behavior was manifested by 4.5-mo-old Naglu-/- mice in an open field test; the hyperactivity that is characteristic of affected children was not observed even in younger mice. In a Pavlovian fear conditioning test, the 4.5-mo-old mutant mice showed normal response to context, indicating intact hippocampal-dependent learning, but reduced response to a conditioning tone, perhaps attributable to hearing impairment. The phenotype of the alpha-N-acetylglucosaminidase-deficient mice is sufficiently similar to that of patients with the Sanfilippo syndrome type B to make these mice a good model for study of pathophysiology and for development of therapy.

Acetylglucosaminidase↗
PubMed1999

Localization of immunoreactive lamprey gonadotropin-releasing hormone in the rat brain.

A highly specific antiserum against lamprey gonadotropin-releasing hormone (GnRH) was used to localize 1-GnRH in areas of the rat brain associated with reproductive function. Immunoreactive 1-GnRH-like neurons were observed in the ventromedial preoptic area (POA), the region of the diagonal band of Broca and the organum vasculosum lamina terminalis, with fiber projections to the rostral wall of the third ventricle and the organum vasculosum lamina terminalis. Another population of 1-GnRH-like neurons was localized in the dorsomedial and lateral POA, with nerve fibers projecting caudally and ventrally to terminate in the external layer of the median eminence. Other fibers apparently projected caudally and circumventrically to terminate around the cerebral aqueduct in the mid-brain central gray. By using a highly specific antiserum directed against mammalian luteinizing hormone-releasing hormone (m-LHRH), the localization of the LHRH neuronal system was compared to that of the 1-GnRH system. There were no LHRH neurons in the dorsomedial or the lateral region of the POA that contained the 1-GnRH neurons. As expected, there was a large population of LHRH neurons in the ventromedial POA associated with the diagonal band of Broca and organum vasculosum lamina terminalis. In both of these regions, there were many more LHRH neurons than 1-GnRH neurons and the LHRH neurons extended more dorsally and laterally than the 1-GnRH neurons. The LHRH neurons seemed to project to the median eminence in the same areas as those that were innervated by the 1-GnRH neurons. Absorption studies indicated that 1-GnRH cell bodies were eliminated by adding 1 microg of either 1-GnRH-I or 1-GnRH-III, but not m-LHRH to the antiserum before use. Fibers were largely eliminated by the addition of 1 microg 1-GnRH-III to the antiserum. No chicken GnRH-II neurons or nerve fibers could be visualized by immunostaining. Because the antiserum recognized GnRH-I and GnRH-III equally, we have visualized an 1-GnRH system in rat brain. The results are consistent with the presence of either one or both of these peptides within the rat hypothalamus. Because 1-GnRH-I has only weak nonselective gonadotropin-releasing activity, whereas 1-GnRH-III is a highly selective releaser of follicle-stimulating hormone, and because 1-GnRH neurons are located in areas known to control follicle-stimulating hormone release selectively, our results support the hypothesis that 1-GnRH-III, or a closely related peptide, may be mammalian follicle-stimulating hormone-releasing factor.

Animals↗