[Clinical and epidemiological characteristics of patients with paracoccidioidomycosis diagnosed in a hospital of Resistencia, Chaco]

In order to describe the clinical and epidemiological characteristics of paracoccidioidomycosis, a descriptive study of all the cases diagnosed by the Clinical Microbiology Service at Dr. Julio C. Perrando hospital in the city of Resistencia (Chaco Province, Argentina) was conducted. Between 2011 and 2014, 46 cases were detected. In the period 2013-2014, an almost 4-fold increase in the incidence rate was detected. The chronic form of the disease was predominant with an average age of 53 years. Serological tests in 39 out of 46 patients were performed. In 15 of 39 patients, serological tests were the only diagnostic tool while in 4 patients with a microbiological diagnosis serological tests were non-reactive. In patients from endemic areas with non-specific infectious syndrome it is important to include paracoccidioidomycosis in the differential diagnosis and to apply all available diagnostic tools to reach a timely diagnosis and to reduce the long-term sequelae and their socio-economic impact.

La investigación al alcance de los profesionales de Osakidetza: Programa de Investigación en Atención Primaria de Salud

Objetivo

Describir el proceso y resultados del Programa de Investigación en Atención Primaria de Salud 2010-2011, organizado por la Unidad de Investigación de Atención Primaria de Bizkaia.

Diseño

Estudio descriptivo.

Emplazamiento

Atención primaria del servicio público de salud Osakidetza.

Participantes

Un total de 107 profesionales que solicitaron participar entre los 4.338 médicos/as, enfermeros/as y personal administrativo a los que se difundió el programa.

Mediciones principales

Nivel de participación, clasificación de los temas de investigación, valoración del programa por los participantes, financiación de los proyectos generados y costes del programa.

Resultados

La proporción de profesionales que solicitaron participar en el programa fue de un 2,47%; IC 95% 2,41-2,88%. Se seleccionaron 28 de ellos y lo finalizaron 19. Los temas a investigar están mayoritariamente relacionados con los problemas de salud crónicos más frecuentes (32%) y la prevención y promoción de la salud (18%). Más del 90% de los participantes evaluó como buena o excelente la calidad del programa y la mitad lo consideró difícil o muy difícil. Se generaron 18 proyectos nuevos, de los que 12 obtuvieron financiación, con 16 ayudas, 10 del Departamento de Sanidad del Gobierno Vasco, 4 del Instituto de Salud Carlos III y 2 del Instituto Kronikgune, captando 500.000 € para dichos proyectos. Los costes totales del programa ascendieron a 198.327 €.

Conclusiones

Esta experiencia puede servir para otros interesados en el fomento de la investigación en atención primaria de salud (APS), ya que el programa ha logrado sus objetivos, es útil y productivo.

The burden of mental disorders in primary care

OBJECTIVES

To describe and compare the prevalence of mental disorders across primary care populations, and estimate their impact on quality of life.

METHODS

Cross-sectional multilevel analysis of a systematic sample of 2539 attendees to eight primary care centres in different regions of Spain, assessed with the WHO Composite International Diagnostic Interview (CIDI 1.1), the Short Form Health Survey (SF-36) quality of life questionnaire and the SF-6D utility index.

RESULTS

The 12-month prevalence of any mental disorder was 23% (95% confidence interval: 21-24%), 10% had mood, 9% anxiety, 5% organic, 4% somatoform, and 1% alcohol use disorders, with a significant between-centre variability (P<0.001). People with mental disorders had one standard deviation lower mental quality of life than the general population. We estimated that 1831 quality-adjusted life-years (QALYs) are lost annually per 100,000 patients due to mental disorders, without considering mortality. Mood disorders have the worst impact with an annual loss of 1124 QALYs per 100,000 patients, excluding mortality (95% confidence interval: 912-1351).

CONCLUSIONS

Prevalence rates were similar to those obtained in international studies using the same diagnostic instrument and, given the significant between-centre variability found, it is recommended that mental health statistics be considered at small area level. Mental disorders, and especially mood disorders, are associated with very poor quality of life and higher scores on disability indexes than other common chronic conditions.

Venom of the crotaline snake Atropoides nummifer (jumping viper) from Guatemala and Honduras: comparative toxicological characterization, isolation of a myotoxic phospholipase A(2) homologue and neutralization by two antivenoms

A comparative study was performed on the venoms of the crotaline snake Atropoides nummifer from Guatemala and Honduras. SDS-polyacrylamide gel electrophoresis, under reducing conditions, revealed a highly similar pattern of these venoms, and between them and the venom of the same species from Costa Rica. Similar patterns were also observed in ion-exchange chromatography on CM-Shephadex C-25, in which a highly basic myotoxic fraction was present. This fraction was devoid of phospholipase A(2) activity and strongly reacted, by enzyme-immunoassay, with an antiserum against Bothrops asper myotoxin II, a Lys-49 phospholipase A(2) homologue. A basic myotoxin of 16 kDa was isolated to homogeneity from the venom of A. nummifer from Honduras, showing amino acid composition and N-terminal sequence similar to those of Lys-49 phospholipase A(2) variants previously isolated from other crotaline snake venoms. Guatemalan and Honduran A. nummifer venoms have a qualitatively similar toxicological profile, characterized by: lethal; hemorrhagic; myotoxic; edema-forming; coagulant; and defibrinating activities, although there were significant quantitative variations in some of these activities between the two venoms. Neutralization of toxic activities by two commercially-available antivenoms in the region was studied. Polyvalent antivenom produced by Instituto Clodomiro Picado was effective in the neutralization of: lethal; hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, but ineffective against edema-forming activity. On the other hand, MYN polyvalent antivenom neutralized: hemorrhagic; myotoxic; coagulant; defibrinating; and phospholipase A(2) activities, albeit with a lower potency than Instituto Clodomiro Picado antivenom. MYN antivenom failed to neutralize lethal and edema-forming activities of A. nummifer venoms.

The venom of Bothrops asper from Guatemala: toxic activities and neutralization by antivenoms

Bothrops asper is responsible for approximately half of the snakebite envenomations in Central America. Despite its medical relevance, only the venom of Costa Rican populations of this species has been studied to some detail, and there is very little information on intraspecies variability in venom composition and toxicity. Venom of B. asper from Guatemala was analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis, and its basic pharmacological activities were investigated with standard laboratory assays. Venom has lethal, hemorrhagic, myotoxic, edema-forming, coagulant, defibrinating and phospholipase A(2) activities, showing a similar toxicological profile to the one previously described for B. asper from Costa Rica. In addition, polyvalent antivenoms produced in Mexico and Costa Rica, and currently used in Guatemala, were tested for their ability to neutralize venom's toxic activities. Both antivenoms were effective against all effects studied, although the Costa Rican product showed higher potency against most activities tested and higher antibody titer against venom components, as determined by enzyme immunoassay. It is suggested that different dosage regimes should be considered when using these antivenoms in B. asper envenomations in Guatemala.

N-glycosylated variants of growth hormone in human pituitary extracts

This study was designed to investigate the existence, in human pituitary extracts, of growth hormone (GH) variants not encoded by the hGH-N gene. Using anion exchange-fast protein liquid chromatography followed by SDS-PAGE, we isolated several basic forms of pituitary GH. Incubation of these basic forms with endoglycosidase F/N-glycosidase F revealed that two of them (about 34 and 12 kD) were N-glycosylated. In contrast, no changes were found when samples were incubated with the O-linked glycosylation-specific O-glycosidase. Since the GH-N molecule lacks consensus sequences for N-linked glycosylation, our findings suggest that GH genes other than hGH-N are expressed in the human pituitary gland.

Cardiotrophin-1 requires LIFRbeta to promote survival of mouse motoneurons purified by a novel technique

The cytokines ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) signal through a receptor complex formed between two transmembrane proteins, gp130 and LIFRbeta. In addition, CNTF also uses a ligand-binding component which is anchored to the cell membrane. In the case of cardiotrophin-1 (CT-1), LIFRbeta is also required in cardiomyocytes, but this has not been proven in neurons, and published data suggest that motoneurons may use a different receptor complex. We used Lifrbeta knockout mice to assess the requirement for this receptor component in the signal transduction of CT-1 in motoneurons. To study purified motoneurons from such mutants, we have developed a method allowing for isolation of highly purified mouse motoneurons. This protocol is based on the immunoaffinity purification of motoneurons using antibodies against the extracellular domain of the neurotrophin receptor, p75, followed by cell sorting using magnetic microbeads. We show that CNTF, LIF, and CT-1 are unable to promote the survival of motoneurons derived from homozygous Lifrbeta-/- mutant embryos. Thus, LIFRbeta is absolutely required to transduce the CT-1 survival signal in motoneurons.

Neurons derived in vitro from ES cells express homeoproteins characteristic of motoneurons and interneurons

We have characterized different neuronal subpopulations derived from in vitro differentiation of embryonic stem (ES) cells using as markers the expression of several homeodomain transcription factors. Following treatment of embryo-like aggregates with retinoic acid (RA), Pax-6, a protein expressed by ventral central nervous system (CNS) progenitors is induced. In contrast, Pax-7 expressed in vivo by dorsal CNS progenitors, and erbB3, a gene expressed by neural crest cells and its derivatives, are almost undetectable. CNS neuronal subpopulations generated expressed combinations of markers characteristic of somatic motoneurons (Islet-1/2, Lim-3, and HB-9), cranial motoneurons (Islet-1/2 and Phox2b) and interneurons (Lim-1/2 or EN1). Molecular characterization of neuron subtypes generated from ES cells should considerably facilitate the identification of new genes expressed by restricted neuronal cell lineages.

Pattern of presentation of the human growth hormone variant (hGH-V) gene in the normal population

The human growth hormone variant (hGH-V) gene is a member of the GH gene family, expressed by the syncytiotrophoblast. Although its physiological role is poorly understood, certain data suggest that it may be involved in the control of fetal growth and development. As a first step to asses its physiological relevance, we investigated its degree of polymorphism in the normal population. Genetic studies have been difficult to carry out due to the high sequence identity among GH-family members. We overcame this problem by selectively amplifying a fragment of the hGH-V gene by PCR. DSCP analysis of the amplimers revealed a heterozygous pattern in one of the 64 subjects studied. Investigation of the subject's relatives showed a similar pattern in his father. In all, our results indicate that the hGH-V gene is highly conserved in the normal population.

Role of neurotrophic factors in motoneuron development

More than 10 factors from different gene families are now known to enhance motoneuron survival, and to be expressed in a manner consistent with a role in regulating motoneuron numbers during development. We provide evidence that: a) different factors may act on different sub-populations of motoneurons; b) different factors may act in synergy on a given motoneuron. Thus, the functional diversity of motoneurons, and the cellular complexity of their environment, may be reflected in the mechanisms that have evolved to keep them alive.

Synergistic effects of schwann- and muscle-derived factors on motoneuron survival involve GDNF and cardiotrophin-1 (CT-1)

The survival of central neurons depends on multiple neurotrophic factors produced by different cell types. We demonstrate that media conditioned by muscle and Schwann cell lines show strong synergistic effects on survival of purified embryonic day 14.5 rat motoneurons in culture. Different lines of evidence implicate glial cell line-derived neurotrophic factor (GDNF) and cardiotrophin-1 (CT-1) in this synergy. Their expression in the environment of the motoneuron is compartmentalized: gdnf transcripts are expressed principally in Schwann cell lines, whereas ct-1 mRNA is present in myotubes. Blocking antibodies to GDNF inhibit the trophic activity of Schwann cell line-conditioned media by 75%, whereas CT-1 antibodies diminish the myotube-derived activity by 46%. CT-1 and GDNF act synergistically to enhance motoneuron survival in vitro. In vivo, individual motoneurons coexpress both GDNF and CT-1 receptor components. GDNF and CT-1, therefore, are major components of the trophic support provided by the Schwann and muscle cells, respectively. The possibility that they act together on individual motoneurons suggests that the motoneuron must integrate distinct signals from different cellular partners when deciding whether to die or to survive.

Hepatocyte growth factor (HGF/SF) is a muscle-derived survival factor for a subpopulation of embryonic motoneurons

Muscle-derived factors are known to be important for the survival of developing spinal motoneurons, but the molecules involved have not been characterized. Hepatocyte growth factor/scatter factor (HGF/SF) plays an important role in muscle development and motoneuron axon outgrowth. We show that HGF/SF has potent neurotrophic activity (EC50=2 pM) for a subpopulation (40%) of purified embryonic rat motoneurons. Moreover, HGF/SF is an essential component of muscle-derived support for motoneurons, since blocking antibodies to HGF/SF specifically inhibited 65% of the trophic activity of media conditioned by C2/C7 skeletal myotubes, but did not inhibit the trophic activity secreted by Schwann cell lines. High levels of expression of the HGF/SF receptor c-Met in the spinal cord are restricted to subsets of motoneurons, mainly in limb-innervating segments. Consistent with this distribution, cultured motoneurons from limb-innervating brachial and lumbar segments showed a more potent response to HGF/SF than did thoracic motoneurons. By the end of the period of motoneuron cell death, levels of c-Met mRNA in motoneurons were markedly reduced, suggesting that the effects of HGF/SF may be limited to the period of motoneuron cell death. HGF/SF may play an important role during motoneuron development as a muscle-derived survival factor for a subpopulation of limb-innervating motoneurons.

Expression of the human growth hormone normal gene (hGH-N) in proliferating and differentiated HL-60 cells

The possibility that human leukemic cells could synthesize growth hormone (GH) was investigated in the HL-60 cell line. Western blot analysis of protein extracts obtained from these cells revealed the existence of a major immunoreactive GH (irGH) band, with an approximate molecular weight of 22 kDa, together with lower amounts of 20- and 44-kDa bands. Stimulating proliferating HL-60 cells with KCl clearly increased GH concentration in the incubation medium as compared to basal values. RT-PCR amplification of HL-60 RNA and restriction assay of the amplimers demonstrated that those proteins were the result of the expression of the GH-N (normal) gene in this cell line. These results were confirmed by Northern blot, which also showed that the rate of GH-N gene expression was clearly dependent upon the proliferative state of the cells: while GH transcripts were easily detectable in actively proliferating cells, only minute amounts were observed when cells were induced to differentiate with dimethyl sulphoxide (DMSO). Similar differences were observed by Western blot. In all, these findings demonstrate that HL-60 cells are capable to produce and secrete a GH identical to pituitary GH. Interestingly, the rate of synthesis of the hormone dramatically increases when cells are actively proliferating. Therefore, it is likely that locally produced GH might be involved in the control of leukemic cell proliferation. Further studies are now in course to establish whether this mechanism occurs via an autocrine and/or paracrine way.

Cardiotrophin-1, a cytokine present in embryonic muscle, supports long-term survival of spinal motoneurons

The muscle-derived factors required for survival of embryonic motoneurons are not clearly identified. Cardiotrophin-1 (CT-1), a cytokine related to ciliary neurotrophic factor (CNTF), is expressed at high levels in embryonic limb bud and is secreted by differentiated myotubes. In vitro, CT-1 kept 43% of purified E14 rat motoneurons alive for 2 weeks (EC50 = 20 pM). In vivo, CT-1 protected neonatal sciatic motoneurons against the effects of axotomy. CT-1 action on motoneurons was inhibited by phosphatidylinositol-specific phospholipase C (PIPLC), suggesting that CT-1 may act through a GPI-linked component. Since no binding of CT-1 to CNTFR alpha was detected, CT-1 may use a novel cytokine receptor alpha subunit. CT-1 may be important in normal motoneuron development and as a potential tool for slowing motoneuron degeneration in human diseases.

Use of chimeric F3-NCAM molecules to explore the properties of VASE exon in modulating polysialylation and neurite outgrowth

Differential splicing of VASE exon in the fourth immunoglobulin (Ig) domain and attachment to the fifth Ig domain of alpha 2-8 linked sialic acid (PSA) both dramatically change, in opposite manner, Neural Cell Adhesion Molecule (NCAM) functional properties. Reciprocal patterns of VASE and PSA expression suggest that they might be mutually exclusive. Here, we tested whether informations conferring polysialylation reside in NCAM-Ig domains 4 and 5 and the influence of the VASE exon encoded sequence on this process. We also examined if the VASE sequence was still able to inhibit neurite outgrowth when presented out of its normal NCAM context. Constructs have been prepared encoding NCAM-Ig domains 4 (with or without the VASE exon) and 5 fused to the F3 molecule. Stable clones expressing the chimeric molecules or wild type F3 were then obtained in the AtT-20 cell line. Although the chimeric molecules were expressed on the cell surface none of them was bearing PSA. Thus, polysialylation cannot be conferred to proteins by addition of the NCAM-Ig domains 4 and 5 modular motif and in this molecular context, the VASE sequence is not influencing the process. These chimeric molecules, either expressed at the surface of RIN or COS cells or presented as soluble forms, were examined for their effect on neurite outgrowth. In all cases, the length of neurites of sensory neurons was significantly reduced when grown in presence of the VASE containing chimera by comparison with the chimera without VASE or wild type F3. When neurons from NCAM knock-out mice were used for the assay, the VASE inhibition could not be detected. Thus VASE is able to act as a modular motif and NCAM expressed on neurons participates in transducing its effect.

Regulation of hypothalamic somatostatin by glucocorticoids

Glucocorticoids (GCs) play a key role in the physiology of the hypothalamic-somatotroph axis, since these steroids enhance growth hormone (GH) gene transcription and increase GHRH receptor synthesis. However, GC excess inhibits normal growth in all species studied. This is mainly due to the impaired GH secretion observed during hypercortisolism, a situation in which GH responses to a number of stimuli, including GHRH, are blunted. The inhibitory effect of GCs on GH secretion seems to be dependent on enhanced hypothalamic SS secretion. Since SS release is stimulated by beta-adrenergic agonism we tested the possibility that GC inhibition of GH secretion would depend on increased beta-adrenoceptor activity in SS-producing neurons. The experimental design consisted in evaluating the GH response to GHRH in normal subjects after having induced hypercortisolism, with DEX, and blocking beta-adrenoceptors with propranolol (PRO). Moreover, to investigate the specificity of this mechanism, GHRH-induced GH release was tested after inducing hypercortisolism and enhancing alpha 2-adrenergic or muscarinic cholinergic tone, by giving clonidine (CLO) or pyridostigmine (PD), respectively. As expected, nocturnal DEX administration inhibited the GH response to GHRH. In this situation of hypercortisolism, both PRO and CLO, but not PD, were able to reverse the inhibitory effect of DEX on GHRH-elicited release. However, the potentiating effect of these drugs on the GHRH-induced GH secretion was only observed for PRO. These data confirm that GC excess inhibits GH release by increasing hypothalamic SS secretion, and that the mechanism is mediated by GC-induced enhanced beta-adrenergic responsiveness. Therefore, the defective GHRH secretion observed in chronic hypercortisolism must be a consequence of the continuous blockade that SS excess exerts on GHRH-producing neurons. Our postulate agrees with other data in the literature showing that GCs modulate the secretion of some hypothalamic peptides by changing the responsiveness of the producing neurons from alpha 2-adrenoceptors to that of beta-adrenoceptors.

Clonidine potentiates the growth hormone response to a growth hormone releasing hormone challenge in hypothalamic growth hormone releasing hormone deficient rats

This study was designed to further investigate our postulate regarding the inhibitory role played by central alpha 2-adrenergic pathways on hypothalamic somatostatin (SS) release in rats. The growth hormone (GH) responses to exogenous GH-releasing factor (GRF; 3 micrograms/kg i.v.) or clonidine (CLO; 100 micrograms/kg i.v.), either given alone or in combination, were tested in 3-month-old male rats made GH-releasing hormone (GH-RH) deficient neonatally by administration of monosodium glutamate (MSG; 4 mg/g body weight s.c.). To prevent the presumable decrease in the pituitary GH content in these animals from leading to an erroneous interpretation of the results obtained, half of these rats were given GRF (MSG-GRF rats; 30 micrograms/kg s.c.) for 3 days immediately prior to GH testing. The other half of MSG-treated and non MSG-treated rats received saline during these days (MSG-S and controls, respectively). To establish the efficiency of GRF priming, the pituitary GH content was measured in other MSG-GRF, MSG-S, and control animals. The mean (+/- SEM) GH peaks in response to GRF challenge were significantly higher in controls than in MSG-GRF rats (125.2 +/- 28.5 vs. 67.5 +/- 19.4 micrograms/l; p < 0.05), while no significant GRF-induced GH release was observed in the MSG-S group. Most likely these results are related to the different pituitary GH content, significantly (p < 0.01) higher in controls than in MSG-GRF rats, and in the latter higher than in MSG-S animals (p < 0.05). CLO administration did not evoke a significant GH release in MSG rats, whether primed with GRF or not.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA sequences that act as high affinity targets for the vitamin D3 receptor in the absence of the retinoid X receptor

DNA binding site discrimination within a subgroup of nuclear receptors, including the human vitamin D3 receptor (hVDR), appears to be influenced primarily by spacing and orientation differences of response element half-sites, since many receptors recognize and bind to the same hexameric half-site sequence, AGGTCA. Small sequence differences within half-sites, however, may also play an important role in distinguishing between different receptor complexes. Several laboratories have reported that the AGGTCA element in a direct repeat (DR) configuration appears to be a high affinity recognition site for only nuclear receptor-9 retinoid X receptor (RXR) heterodimers. However, we have previously shown that a closely related, but distinct, element (AGTTCA; essentially the mouse osteopontin [Spp-1] vitamin D response element) acts as a high affinity target for purified hVDR in the absence of RXR. This suggests that some half-site sequences could be targets for hVDR alone while others serve as recognition elements for hVDR-RXR complexes. In this report, we test this hypothesis by selecting, using purified hVDR only, for high affinity receptor binding sites in a complex DNA mixture which should by chance contain such sequences. We find that the purified receptor selects a heptameric sequence resembling a half-site of the osteopontin vitamin D response element, consistent with osteopontin-like sequences acting as high affinity targets for hVDR in the absence of RXR. We directly test this by comparing the in vitro DNA binding activity of purified hVDR to DR+3 elements comprised of osteopontin-like AGTTCA or AGGTCA half-sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Diurnal rhythm of the in vivo acetate metabolism to CO2 and nonsaponifiable lipids by neonatal chick

The in vivo incorporation of acetate into nonsaponifiable lipids was studied in different tissues from 14-day-old chick. Total nonsaponifiable lipids (nmol/30 min/g tissue) were mainly synthesized in testicles and liver. The in vivo CO2 production from acetate by 1-day-old chick did not exhibit diurnal variations. However, in 14-day-old chick, a maximal value was observed in the middle of the light period, while a minimal value was found 9 h after the start of the dark period. No significant diurnal differences were detected in the in vivo acetate incorporation into nonsaponifiable lipids by liver and duodenal mucosa from 1-day-old chick. Nevertheless, a clear diurnal rhythm was found in liver and duodenal mucosa from 14-day-old chick, but not in brain and kidney from animals of the same age. Distribution of radioactivity from (1-14C)acetate among the different constituents of the nonsaponifiable fraction has been also studied at 3-h intervals. Cholesterol was the major sterol formed from acetate by chick liver at any time of day. In duodenal mucosa and kidney, maximal values in the percentage of cholesterol synthesized were observed during the light period.

Clonidine potentiates the growth hormone (GH) response to GH-releasing hormone in norepinephrine synthesis-inhibited rats: evidence for an alpha-2-adrenergic control of hypothalamic release of somatostatin

The aim of this study was to investigate whether central alpha 2-adrenergic pathways act, in rats, by inhibiting somatostatin (SS) release, as it has been postulated to occur in other species. The growth hormone (GH) responses to GH-releasing hormone (GRF, 3 micrograms/kg i.v.) or clonidine (CLO, 100 micrograms/kg, i.v.), either given alone or in combination, were tested in male rats in which norepinephrine synthesis had been previously blocked with the dopamine-beta-hydroxylase inhibitor diethyldithio-carbamate (DDTC, 400 mg/kg i.p.). These experiments were also carried out in a control group of animals that had been given placebo (P) instead of DDTC. The GH responses to GRF in the presence of anti-SS serum given to other P and DDTC rats, allowed us to assess whether DDTC treatment had induced increased SS secretion. GH tests were carried out during spontaneous (P) or pharmacologically induced (DDTC) trough periods. Therefore, the mean (+/- SEM) GRF-induced GH peak was similarly low in both groups of rats (P: 66.5 +/- 16.6 micrograms/l; DDTC: 58 +/- 14 micrograms/l). The administration of anti-SS serum significantly (p < 0.01) increased these responses (P: 413 +/- 22; DDTC: 695 +/- 36; p < 0.01 vs. P). CLO administration elicited a maximal GH peak significantly higher (p < 0.05) in P (20.5 +/- 3) than in DDTC rats (4.1 +/- 2); however, the former was significantly lower than GH responses to GRF.(ABSTRACT TRUNCATED AT 250 WORDS)

Delineation of a DNA recognition element for the vitamin D3 receptor by binding site selection

The vitamin D3 receptor is a ligand-inducible transcriptional regulatory protein. The receptor modulates the transcription of target genes by binding directly to specific DNA sites, termed vitamin D response elements; these sites vary considerably in their homologies to each other. In order to approach the question of what sequences can constitute high affinity recognition elements for the vitamin D3 receptor, we have selected for such sites in vitro by mixing overexpressed and purified vitamin D3 receptor DNA binding domain with an oligonucleotide duplex pool containing a completely randomized central region flanked by primer-annealing sites. Following multiple rounds of immunoprecipitation and amplification by PCR to enrich for high affinity sites, individual clones were sequenced and found to contain nearly identical hexameric sequences, yielding a consensus 5'-AGGGGG-3'. This sequence is similar to some known vitamin D3 receptor binding sites, such as osteocalcin, but quite divergent from others. This suggests that the vitamin D3 receptor may be able to selectively recognize at least two classes of sequence elements.

A comparative study of the in vitro and in vivo formation of lanosterol derivatives from acetate by different chick tissues

The optimal conditions for the synthesis of lanosterol derivatives, previously demonstrated as inhibitors of cholesterogenesis, have been studied in 14-day-old chicks using acetate as precursor. In experiments carried out in vitro, the relative percentage of lanosterol derivatives in the total nonsaponifiable fraction was practically similar in each tissue at any incubation time considered (15-120 min). This percentage was higher in kidney and duodenal mucosa than in liver. The percentage of lanosterol derivatives was constant at any acetate concentration assayed (1-12 mM) in liver and duodenal mucosa, while in kidney this percentage increased at high acetate concentration (8-12 mM). In experiments carried out in vivo, the relative percentage of lanosterol derivatives was lower than that found in each tissue in the in vitro conditions. This behaviour was opposed to the acetate incorporation into cholesterol in the same experimental conditions. No significant differences were observed in the in vivo acetate incorporation into lanosterol derivatives by chick brain at different times of day. However, in duodenal mucosa and kidney maximal values were found during the dark period, on the contrary to that previously observed in the percentage of cholesterol. Our results demonstrated that kidney and duodenal mucosa were the chick tissues in which the higher percentage of lanosterol derivatives was accumulated.

Glucocorticoids may inhibit growth hormone release by enhancing beta-adrenergic responsiveness in hypothalamic somatostatin neurons

The aim of this study was to investigate the mechanisms by which glucocorticoids inhibit GH secretion in man. In 10 normal volunteers subjects we compared the pattern of GHRH-induced GH release to that elicited by similar challenge given 60 min after a pretreatment with drugs affecting adrenergic and muscarinic cholinergic neurotransmission, both in basal situations and after having induced hypercortisolism. In a first study (P), synthetic GHRH [GRF-(1-29); 1 microgram/kg, i.v.] was administered 60 min after giving placebo. In other experiments, the administration of propranolol (PRO; 40 mg, orally), or clonidine (CLO; 0.300 mg, orally), or pyridostigmine (PD; 120 mg, orally) was followed by GHRH administration 60 min later. These experiments were repeated after giving a nocturnal dose of dexamethasone (DEX; 8 mg, orally at 2300 h). The administration of DEX significantly (P < 0.05) blunted the GH response to GHRH (peaks: 10.7 +/- 3.9 vs. 20.3 +/- 5.5 micrograms/L; DEX vs. P study, respectively). Conversely, either beta-adrenergic blockade (PRO), or alpha 2-adrenergic agonism (CLO), or the enhancement of muscarinic cholinergic tone (PD) significantly increased the GH response to GHRH (peaks: 43 +/- 4.6, 55.6 +/- 5.6 and 51.2 +/- 7, micrograms/L; PRO, CLO, and PD, respectively; P < 0.01 vs. P study). After nocturnal DEX administration, both PRO and CLO, but not PD, were able to reverse the inhibitory effect of DEX on GHRH-elicited GH release (peaks: 39 +/- 5.5, 25.9 +/- 3.9 and 12.9 +/- 3.1, micrograms/L; DEX + PRO, DEX + CLO, and DEX + PD, respectively). However, whereas the potentiating effect of PRO on GHRH-elicited GH release was still observed under hypercortisolism, it was lacking for both CLO and PD when these drugs were given in this situation. These data suggest that the inhibitory effect of glucocorticoid excess on GH release is due to increased hypothalamic somatostatin secretion which appears to be dependent on DEX-induced enhanced beta-adrenergic responsiveness. Moreover, the data further support a major role of hypothalamic alpha 2-adrenergic and beta-adrenergic activities in GH neuroregulation in man.

Studies on alpha 2-adrenergic modulation of hypothalamic somatostatin secretion in rats

This study was undertaken to investigate whether or not alpha 2-adrenergic pathways would negatively modulate the hypothalamic somatostatin release in rats. To induce pharmacological changes in SS release, three groups of male Sprague-Dawley rats (n = 30/group) were separately anesthetized by ip administration of urethan (which increases SS tone; 1.2 g/kg), pentothal (which impairs SS release; 30 mg/kg), or ketamine (which does not affect spontaneous SS secretion; 40 mg/kg). Ten rats from each group were challenged with GRF (2 micrograms/kg iv), clonidine (40 micrograms/kg iv), or GRF plus clonidine. Administration of clonidine markedly increased the GH responsiveness to GRF in rats anesthetized with urethane or ketamine. In contrast, the GH response to GRF was not modified by clonidine in rats anesthetized with pentothal. These results show that alpha 2-adrenergic stimulation only modifies the GRF-induced GH rise when SS release is high. Therefore, in rats, central alpha 2-adrenergic pathways appear to play a main inhibitory effect on hypothalamic SS secretion.

Clonidine pretreatment modifies the growth hormone secretory pattern induced by short-term continuous GRF infusion in normal man

OBJECTIVE

The aim of this study was to investigate the effect of a single dose of clonidine on the pattern of GH release in response to a 10-hour continuous GRF infusion in normal man.

DESIGN

Plasma GH was analysed in samples withdrawn at 20-minute intervals, from 0900 to 1900 h, according to the following protocols: in a control study, a placebo was given at 1000 h; in other experiments, clonidine (300 micrograms, orally) was given at 1000 h, alone or together with a continuous intravenous infusion of GRF 1-29 (0.3 micrograms/kg/h) starting at this time. In another experiment, the continuous infusion of GRF 1-29 was preceded by placebo administration at 1000 h.

PATIENTS

Eight normal volunteers (four women and four men), aged 19-24 years were studied.

MEASUREMENTS

Plasma GH levels were measured by RIA. Analysis of the pattern of GH secretion was performed using cluster analysis.

RESULTS

Clonidine induced a slight but significant increase in plasma GH values, peaking 60 to 120 minutes later; however, no significant changes were observed in indices of total and pulsatile GH release for the whole sampling period in this study. Continuous GRF administration led to increased episodic GH secretion, by augmenting GH peak amplitude, although peak frequency was not modified. An increase in interpulse GH values was also observed during GRF infusion. Pretreatment with clonidine clearly changed the pattern of GH release during GRF infusion: the amount of GH secreted was significantly higher, the number of GH peaks significantly increased, and almost all the GH was secreted within them.

CONCLUSIONS

These data concord with our previous demonstration that clonidine disrupts the hypothalamic-somatotroph rhythm by inhibiting the hypothalamic release of somatostatin. Given that clonidine pretreatment induced a more physiological episodic pattern of GRF-induced GH release, the possibility of combining clonidine and GRF therapy for short stature in children is envisaged.

Evidence that alpha 2-adrenergic pathways play a major role in growth hormone (GH) neuroregulation: alpha 2-adrenergic agonism counteracts the inhibitory effect of muscarinic cholinergic receptor blockade on the GH response to GH-releasing hormone, while alpha 2-adrenergic blockade diminishes the potentiating effect of increased cholinergic tone on such stimulation in normal men

The aim of this study was to investigate the interrelationships between alpha 2-adrenergic and cholinergic pathways in the control of hypothalamic somatostatin (SRIF) secretion in humans. In eight normal volunteers subjects we compared the pattern of GHRH-induced GH release to that elicited by similar challenge given 60 min after a pretreatment with drugs affecting alpha 2-adrenergic and muscarinic cholinergic neurotransmission. In a control study, synthetic GHRH [GRF-(1-29); 1 microgram/kg, iv] was administered 60 min after giving placebo. In other experiments, the administration of atropine (1 mg, im), or clonidine (0.300 mg, orally), or atropine plus clonidine, or pyridostigmine (120 mg, orally), or yohimbine (30 mg, orally), or pyridostigmine plus yohimbine, at 0 min was followed by GHRH administration 60 min later. The administration of both clonidine and pyridostigmine significantly (P less than 0.01) enhanced the GH responses to GHRH compared to those elicited by this challenge when given after placebo. Conversely, atropine pretreatment significantly (P less than 0.01) blocked the GH response to GHRH challenge, whereas yohimbine did not significantly affect it. When atropine and clonidine were given together, the inhibitory effect of the former was overcame and mean GHRH-elicited GH peak response was significantly (P less than 0.05) higher than that in the control study. In contrast, pretreatment with yohimbine significantly (P less than 0.05) blunted the pyridostigmine-induced enhancement of GHRH-elicited GH release. These data confirm our previous postulate suggesting that the stimulatory effect of clonidine on GH release is mainly exerted by inhibiting the hypothalamic SRIF release. Moreover, the effect of cholinergic neurons on SRIF release seems to be, at least in part, dependent on alpha 2-adrenergic pathways. Based on these data, it can be proposed that the alpha 2-adrenergic system plays a major role in the control of hypothalamic SRIF release, and hence in GH neuroregulation, whereas the muscarinic cholinergic system would participate in such regulation by modulating the functional activity of the former.

Degenerative and regenerative changes in murine skeletal muscle after injection of venom from the snake Bothrops asper: a histochemical and immunocytochemical study

The degenerative and regenerative changes in murine skeletal muscle after injection of Bothrops asper venom were studied by histological, lectin histochemical and immunocytochemical techniques. According to our observations, the process was divided into four main stages: (a) During the first 3 days prominent degenerative events took place in skeletal muscle fibres, capillaries, arteries, veins and intramuscular nerves. An inflammatory infiltrate was abundant after the first day and removal of necrotic material was well advanced by the third day. (b) Muscle regeneration was evident by the fourth day. From 4 to 6 days there were two populations of regenerating muscle fibres, one of apparently normal fibres located in areas where capillary vessels were abundant, and another population of groups of regenerative fibres showing signs of degeneration. This second type of fibre was predominant in areas where the number of capillaries was greatly reduced. (c) One and 2 weeks after envenomation areas of small regenerative fibres of normal morphology and areas of degenerating regenerative fibres were observed. The latter were abundant in regions of dense fibrotic tissue and scarce capillaries. (d) Finally, at 4 and 8 weeks after envenomation there were both areas of fibrosis and areas where regenerating muscle fibres predominated. However, the diameter of these fibres was abnormally small, an indication that they may have been atrophic fibres. It is suggested that muscle regeneration is partially impaired after myonecrosis induced by Bothrops asper venom, probably due to the damage induced by this venom on muscle microvasculature and nerves.

Role of central dopaminergic pathways in the neural control of growth hormone secretion in normal men: studies with metoclopramide

The aim of this study was to gain further insight into the role that central dopaminergic pathways play in GH neuroregulation in man. Our experimental hypothesis was based on the possibility that most of the controversies on DA role could be due to the fact that the hypothalamic somatotroph rhythm (HSR) was not taken into account when interpreting the GH responses after pharmacological manipulations on dopaminergic pathways. In 10 normal subjects we monitored the effect of central dopaminergic blockade, achieved with metoclopramide (MCP; 10 mg, i.v. bolus), on the pattern of spontaneous GH secretion and the GH responses to a GHRH challenge (GRF1-29, 1 microgram/kg, i.v. bolus) administered together with MCP or 60 min after this drug was given. The study of HSR was made according to our previous postulate. Our results indicate that MCP administration, either prior to or together with the GHRH bolus, significantly increased GHRH-induced GH release during a refractory HSR phase; but not when the GHRH challenge took place during a spontaneous secretory phase. The strong relationship between pre-GHRH plasma GH values and GHRH-elicited GH peaks was lost when MCP was given. These data indicate that MCP was able to disrupt the intrinsic HSR by inhibiting the hypothalamic release of somatostatin (SS). While a main conclusion would be that central DA is a secretagogue for SS secretion, our results also suggest that this role could be dependent on its effects on the adrenergic inputs to SS neurons.

The role of sexual steroids in the modulation of growth hormone (GH) secretion in humans

Sex steroids contribute to modulate GH secretion in man. However, both the exact locus and mechanism by which their actions are exerted still remain not clearly understood. We undertook a number of studies designed to ascertain: (1) whether or not sudden or chronic changes in circulating gonadal steroids may affect GH secretion in normal adults; and (2) the reason(s) for gender-related dimorphic pattern of GH release. The pituitary reserve of GH, as evaluated by means of a GHRH challenge, was similar in women with anorexia nervosa and in normally menstruating women. Estrogenic receptor blockade with tamoxifen (TMX) did not significantly change GHRH-induced GH response in these normal women. Therefore, acute or chronic hypoestrogenism apparently had no important effects at level of somatotrophs. In another group of normal women we tested the possibility that changes in circulating estrogens might induce changes in the hypothalamic-somatotroph rhythm (HSR). GHRH challenges were performed throughout a menstrual cycle, and again after having achieved functional ovarian blockade with a GnRH agonist treatment. Short-term ovarian blockade did not significantly affect the parameters of GH response to GHRH, although it was accompanied by an increase in the number of women in a refractory HSR phase at testing. This suggested a low potentiating effect on the basic pattern of somatostatin (SS) release occurring as a consequence of the decrease in circulating estrogens. In normal men, neither the GH response to GHRH nor the HSR were affected by functional testicular blockade (after GnRH agonist treatment). However, the administration of testosterone enanthate (250 mg) to another group of men increased both the GHRH-induced GH release and the number of subjects in a spontaneous secretory HSR phase at testing; these were reversed by estrogenic receptor blockade with TMS. In another group of normal men, the fraction of GH secreted in pulses (FGHP) during a nocturnal sampling period was significantly decreased by testicular blockade. Other parameters of GH secretion,such as the number of GH pulses and their mean amplitude (A), and the mean plasma GH concentration (MCGH), showed a slight, although not significant, decrease following the lack of androgens. The administration of testosterone enanthate (500 mg) reversed these parameters to values similar to those in the basal study. Interestingly, when tamoxifen was given after testosterone enanthate, A, MCGH and FGHP increased to values significantly higher than in any other experimental condition in that study.(ABSTRACT TRUNCATED AT 400 WORDS)

Synergistic effect of growth hormone-releasing hormone (GHRH) and clonidine in stimulating GH release in young and old dogs

The effect of acute administration of growth hormone-releasing hormone (GHRH), clonidine (CLO), an alleged GHRH releaser, or GHRH and clonidine given simultaneously was studied in young and old dogs. Simultaneous administration of CLO induced in young dogs an additive effect on GH release and potentiated in old dogs the GHRH-induced GH release, with the GH response being clearly higher than the sum of the GH responses to GHRH or CLO alone. These data suggest that CLO promotes GH release in the dog also by inhibition of somatostatin release.

Alpha 2-adrenergic agonism enhances the growth hormone (GH) response to GH-releasing hormone through an inhibition of hypothalamic somatostatin release in normal men

The purpose of this study was to investigate the precise mechanism by which central alpha 2-adrenergic pathways modulate GH secretion in humans. In 10 normal subjects we compared the pattern of clonidine-induced GH release to that elicited by GH-releasing hormone (GHRH) given at a time of presumably similar responsiveness of the somatotrope. We also evaluated the effect of stimulation by GHRH (either endogenous, by administration of clonidine, or exogenous) on the GH response to a further exogenous GHRH stimulation. In 2 experiments the administration of clonidine (0.150 mg, orally) at 0 or 60 min was followed by a GHRH [GRF-(1-29); 1 micrograms/kg, iv] challenge at 180 min. In other experiments subjects received on separate occasions placebo or clonidine at 0 min, followed by GHRH at 60 min and again at 180 min. In a further experiment the administration of clonidine at 0 min was followed by 2 GHRH challenges (60 and 180 min later). The administration of clonidine 60 or 120 min, but not 180 min, before the GHRH bolus significantly (P less than 0.01) increased the GH responses to this challenge compared to those elicited by GHRH when given after placebo in a period of a similar somatotrope responsiveness. These, in turn, were significantly (P less than 0.05) higher than those elicited by clonidine alone. The close relationship between pre-GHRH plasma GH values and GHRH-elicited GH peaks, not observed for clonidine, was lost after pretreatment with this drug. These data indicate that clonidine was able to disrupt the intrinsic hypothalamic-somatotroph rhythm, suggesting that alpha 2-adrenergic pathways have a major inhibitory effect on somatostatin release. Our data also indicate that GH responses to a GHRH bolus administered 120 min after a prior GHRH challenge are dependent on two parameters: the intrinsic hypothalamic-somatotroph rhythm at the time of the second GHRH bolus, and the magnitude of GH secretion elicited by the previous somatotroph stimulation. In summary, alpha 2-adrenergic agonism appears to act primarily in GH control by inhibiting the hypothalamic release of somatostatin, rather than by stimulating GHRH secretion.

Down-regulation of alpha 2-adrenoceptors involved in growth hormone control in the hypothalamus of infant rats receiving short-term clonidine administration

In infant rats short-term administration of the alpha 2-adrenoceptor agonist, clonidine (CLO), induces refractoriness to the growth hormone (GH)-releasing effect of an acute CLO challenge. CLO reportedly stimulates GH release via increased release of GH-releasing hormone (GHRH) from the hypothalamus. Based on these premises, in this study we investigated the possibility that repeated CLO administration may induce down-regulation of hypothalamic alpha 2-adrenoceptors, involved in GH control, thus prohibiting the GH-releasing effect of the drug. alpha 2-Adrenoceptor binding was determined in different brain regions of 10-day-old rats pretreated for 5 days with CLO (150 micrograms/kg, b.i.d.) and killed 14 h after last CLO administration. [3H]p-Aminoclonidine [( 3H]PAC) was used as the specific ligand of alpha 2-adrenoceptors. Treatment with CLO decreased by about 30% the maximum number of binding sites (Bmax) in areas of the mediobasal hypothalamus (MBH) involved in the stimulatory control of GH secretion, i.e. nucleus periventricularis arcuatus, nucleus ventromedialis hypothalami and nucleus lateralis hypothalami. Reduction of Bmax for [3H]PAC binding was observed also in the nucleus periventricularis hypothalami, an area involved in the inhibitory control of GH secretion and, among extrahypothalamic areas, only in the cortex piriformis. In no brain areas was the affinity constant (Kd) for [3H]PAC binding significantly changed after CLO pretreatment. Binding studies performed with a specific ligand of alpha 1-adrenoceptors, [3H]prazosin, showed that the effect of CLO was specific since no changes in the Bmax or Kd were present in either hypothalamic or extrahypothalamic regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in myofibrillar components after skeletal muscle necrosis induced by a myotoxin isolated from the venom of the snake Bothrops asper

The effects of a myotoxic phospholipase A2 isolated from the venom of the crotaline snake Bothrops asper on skeletal muscle myofibrils were studied by histological, ultrastructural, immunohistochemical, and biochemical parameters. Myotoxin induced a rapid and prominent muscle necrosis after intramuscular injection in mice. In this process, myofibrils were affected and three main changes were observed: (A) Initially, they were hypercontracted, eventually forming "clumped," dense masses which alternated with spaces devoid of myofilaments in the cytoplasm. This initial stage is probably due to hypercontraction resulting from a calcium influx after toxin-induced sarcolemmal damage. (B) A second change occurred between 3 and 6 hr, when the clumped or hypercontracted pattern changed to a "hyaline" pattern in which myofilaments were relaxed and had a more uniform distribution in the cellular space. Although there was not a widespread degradation of myofibrillar components at this stage, desmin started to be lost in samples obtained as early as 15 min after toxin injection, and alpha-actinin was almost absent by 7 hr. Thus, it is proposed that this shift may be due to a selective proteolytic degradation of structurally relevant components, particularly alpha-actinin. As a consequence, the mechanical integration of myofilaments is impaired, precluding hypercontraction. (C) Finally, at later time periods (24, 48, and 72 hr), there was widespread degradation of myofibrillar proteins, probably caused by proteases derived from inflammatory cells such as neutrophils and macrophages, whose numbers in necrotic muscle increased markedly at these time periods.

Reasons for the variability in growth hormone (GH) responses to GHRH challenge: the endogenous hypothalamic-somatotroph rhythm (HSR)

The aims of this study were: (1) to test the possibility that pre-GHRH plasma GH values could reflect the functional status of the hypothalamic-somatotroph rhythm (HSR) at testing, and thus explain if it is responsible for the marked variability in GH responsiveness to GHRH challenge and (2) to see if exogenous somatostatin (SS) could disrupt this endogenous HSR and thus make the GH responses homogeneous. (1) Two to 14 GHRH acute tests (GRF-29, 1 micrograms/kg, i.v. bolus) were performed in 12 normal men and 10 normal women at the same time (0830 h) at random intervals (2 to 60 days). Blood samples to measure plasma GH were drawn at 15 min intervals before and after GHRH challenge. Given that the increments in pre-GHRH plasma GH values (I = value at 0 min minus value at -15 min) were highly correlated with either GHRH-elicited peaks of GH (men, r = 0.81; women; r = 0.69; P less than 0.0001) or the rise in GH after the challenge (r = 0.685; P less than 0.0001, in the total of tests performed), three theoretical HSR phases were proposed: (A) I greater than or equal to 0.4 microgram/l Secretory Phase; (B) I less than or equal to 0, (from GH at -15 min greater than or equal to 1.5 microgram/l), Secretion Plateau; (C) I less than or equal to 0, (from GH at -15 min less than or equal to 1.5 microgram/l), Refractory Phase. Individually, 91% of the men and 86% of the women showed a constant HSR phase when tested at the same time of day independently of the intervals between tests. GH responses (peaks, mean +/- SEM, g/l) in Phase A (women, 51.5 +/- 4.1; men, 31.4 +/- 3.2) were significantly higher (P less than 0.01) than those in Phase B (women, 22.6 +/- 1.8; men, 19.7 +/- 1.5), and these than those in Phase C (women, 9.2 +/- 1.5; men, 6.2 +/- 0.5). The great dispersion observed when GH peaks were analysed as a whole disappeared (except in Phase A in women) when they were evaluated according to the HSR Phase at testing. (2) In seven men and eight women 7 min after stopping an infusion of SS (250 micrograms/h for 3 h) a new GHRH test was performed. Plasma GH variations prior to SS infusion expressed the previous HSR Phase, while the GHRH-elicited peak of GH established the Phase at the moment of testing.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone (GH) responsiveness to GHRH in normal adults is not affected by short-term gonadal blockade

The effects of changes in circulating gonadal steroids on GH secretion elicited by GHRH challenge (1 microgram/kg) in normal adults volunteers (aged 18-24 years), were evaluated in 10 women and 10 men before and after gonadal blockade was achieved by a GnRH agonist (1500 micrograms/day by nasal spray for 40 days). To see if the effect of testosterone on GH secretion was dependent on its aromatization to estradiol (E2), GHRH tests were performed in 7 normal men prior to administration of testosterone enanthate (250 mg im), 8 days after this treatment had began, and again after E2 receptor blockade with tamoxifen (30 mg for 2 days plus 10 mg on the third day 2 h before the GHRH test, po) administered 8 days after testosterone enanthate. The study of the functional status of the somatotropes at the time of GHRH testing was made according to our previous postulate. Short-term gonadal blockade did not affect the parameters of GH response to GHRH in neither women nor men. Thus, the functional blockade of the gonads may be advisable as an adjunct therapy in the treatment of hypothalamic GH-deficiency during the peripubertal stage. In the other group of men, administration of testosterone enanthate significantly increased GHRH-elicited GH release, but this was reverted after E2 receptor blockade. Since the hypothalamic-somatotrope rhythm was altered by both these pharmacological manipulations, it appears that testosterone acts on GH release mainly at the suprapituitary level, and that this action is secondary to its aromatization to E2.

Age-related changes in the mevalonate metabolism in vivo in chick kidneys

The mevalonate incorporation in vivo into total nonsaponifiable lipids by chick kidneys drastically increased after hatching, reaching similar levels to those previously observed in liver. Cholesterol was the major sterol formed from mevalonate from 11 days onward, while a fraction of polar nonsaponifiable lipid(s) was observed as the major compound(s) synthesized at 5-8 days. Relative percentages of squalene, squalene oxide(s) and lanosterol synthesized from mevalonate also increased between 11-18 days after hatching. Results in this paper demonstrate for the first time the accumulation of a fraction of nonsaponifiable lipid(s) identified as lanosterol derivatives and cholesterol precursors formed by kidneys from [5-14C]mevalonate in experiments carried out in vivo, as well as their evolution during postnatal period.

Regulation of hepatic cholesterogenesis by polar steroids accumulated after cholesterol feeding

The incorporation of mevalonate into nonsaponifiable lipids by chick liver in vivo strongly increased between 1-18 days after hatching. Cholesterol feeding (2%) inhibited this. Synthesis of cholesterol was strongly inhibited, whereas the intermediates isolated by TLC accumulated. Most of the polar nonsaponifiable lipids that accumulated in liver 90 minutes after mevalonate administration to 18-day-old cholesterol-fed chicks were identified as lanosterol derivatives. 3-Hydroxy-3-methylglutaryl-CoA reductase activity, as well as acetate and mevalonate incorporation into nonsaponifiable lipids, was inhibited by the presence of these compounds. To our knowledge, this is the first report of such inhibition; this confirms the physiological function of polar steroids in the regulation of cholesterogenesis in vivo.

Studies on the diurnal rhythm of mevalonate metabolism by sterol and nonsterol pathways and of mevalonate-activating enzymes

Both in vivo and in vitro incorporation of mevalonic acid into nonsaponifiable lipids by 17-day-old chick liver and kidney did not show diurnal rhythm. Using 14CO2 production from MVA as an index of the shunt pathway not leading to sterols, we have demonstrated for the first time that there is no diurnal rhythm in this pathway. No significant differences were found in the specific activities of mevalonate kinase, mevalonate-5-phosphate kinase and mevalonate-5-pyrophosphate decarboxylase from chick liver and kidney throughout a period of 24 hr, using [1-14C]mevalonate as substrate. The absence of diurnal rhythm in the decarboxylase activity was corroborated by further experiments carried out using [2-14C]mevalonate-5-pyrophosphate as specific substrate of this enzyme.

Squalene, lanosterol and cholesterol synthesis from acetate in neonatal chick tissues

Acetate incorporation into squalene, lanosterol and cholesterol by liver and kidney slices and intestinal mucosa scrapes from neonatal chick was studied. Contrary to what is observed when using mevalonate as substrate, cholesterol was the main nonsaponifiable synthesized from acetate in all the conditions assayed. Low percentages of squalene and lanosterol were synthesized by liver and kidney slices, while in intestinal mucosa squalene was practically undetectable. The highest percentage of radioactivity in cholesterol was found in liver, followed by intestinal mucosa and kidney. Relative percentages of squalene, lanosterol and cholesterol were practically similar in each tissue at any incubation time and acetate concentration considered. Only in kidney these percentages, especially in the case of squalene, seemed to decrease at higher acetate concentrations (8-12 mM).

Effect of dietary cholesterol on mevalonate metabolism by sterol and nonsterol pathways

Results in the present communication demonstrate for the first time that the shunt pathway of mevalonate not leading to sterols is regulated by cholesterol feeding in a reverse fashion to the sterol pathway. Mevalonate incorporation into nonsaponifiable lipids by liver slices was inhibited by cholesterol feeding while the shunt pathway was clearly enhanced. Moreover, inhibition of renal sterologenesis by dietary cholesterol is also reported. These changes in the mevalonate metabolism are closely correlated with the increase observed in the esterified cholesterol content in neonatal chick liver and kidneys after 10 days of 2% cholesterol supplementation of the diet.

Postnatal development of the sterol and nonsterol mevalonate metabolism in chick liver and kidneys. Effect of cholesterol feeding

The effect of 2% cholesterol feeding on changes throughout postnatal development of total, free, and esterified cholesterol in neonatal chick liver and kidneys was studied. The increase observed in the hepatic cholesterol content after supplementation of the diet with 2% cholesterol was mainly due to the accumulation of esterified cholesterol. Small but significant differences were also found in the esterified cholesterol content in kidneys between control and cholesterol-fed animals. In normally fed chicks, the hepatic percentage of squalene synthesized from mevalonate decreased during the first days of independent life while cholesterol percentage increased. On the contrary, the percentage of squalene recovered in kidneys immediately after hatching was minimal, increasing during postnatal development. Addition of 2% cholesterol to the diet produced a clear inhibition in the mevalonate incorporation into nonsaponifiable lipids by liver slices, especially from 4 days onwards. This inhibition was particularly clear in the percentage of cholesterol synthesized. Mevalonate incorporation by kidney slices was higher than in liver, although cholesterol supplementation had little influence on the percentage of each nonsaponifiable lipid formed. In normally fed chicks, kidneys metabolized mevalonate by the shunt pathway not leading to sterols at a rate more than 50 times that of liver. Cholesterol feeding produced a clear enhancement of the hepatic shunt pathway while in kidneys it had practically no effect.

The in vivo incorporation of acetate into different non-saponifiable lipids by neonatal chick tissues

The in vivo incorporation of [l-14C]acetate into non-saponifiable lipids was higher in neonatal chick liver than in intestinal mucosa, brain and kidneys, and proportional to the amount of substrate injected (2-20 mumole). 14CO2 expired in the breath was also proportional to the dose of acetate. Radioactivity from [l-14C]acetate accumulated by liver was maximal 30 min after the injection of acetate and decreased afterwards. Acetate was mainly incorporated into cholesterol by all the tissues assayed, although small percentages of lanosterol and squalene were obtained in liver. In this tissue, distribution of radioactivity was practically independent from the dose of substrate injected while in intestinal mucosa, brain and kidneys the percentage of cholesterol increased with this dose. The time course of the in vivo formation of different non-saponifiable lipids by neonatal chick tissues was also studied. More than 90% of radioactivity in this fraction obtained 15 min after the acetate injection was recovered as cholesterol in liver and kidneys, while in brain and intestinal mucosa this percentage was about 50% at this time, increasing afterwards. A high percentage of lanosterol was found in brain and intestinal mucosa 15 min after the injection of acetate.

Incorporation of mevalonate into squalene, lanosterol and cholesterol by different neonatal chick tissues

The role of neonatal chick liver and kidneys in the incorporation of mevalonic acid into squalene, lanosterol and cholesterol was studied. Differences between the synthesizing ability of these and other tissues and the influence of the in vivo or in vitro conditions were also examined. In the in vivo experiments, distribution of radioactivity among the nonsaponifiable lipids was not dependent of the doses of mevalonic acid injected. About 80-95% of radioactivity was recovered as cholesterol in liver and brain, whereas in kidneys this percentage was only about 35%. Squalene and lanosterol were formed by kidneys in a high percentage, higher than in liver and other tissues. 12 hr after mevalonate injection, the percentage of cholesterol formed by kidneys increased until more than 50%. In the in vitro experiments carried out in the presence of 0.045-4.0 mM mevalonate, cholesterol was also the main nonsaponifiable identified, but in a lesser percentage than in vivo. In the same conditions, the incorporation of mevalonic acid by kidneys was maximal into squalene. After in vitro incubations for 2 hr, the percentage of cholesterol in kidneys also increased.

Studies of the in vivo metabolism of mevalonic acid in the neonatal chick

After 4 hr of the intraperitoneal injection of different doses of (R)-[5-14C]mevalonic acid (MVA), its incorporation into nonsaponifiable and saponifiable lipids was maximal in neonatal chick kidneys and liver, and minimal in brain, spinal cord and skin. Using 14CO2 production from [5-14C]MVA as an index of the shunt pathway not leading to sterols, we have demonstrated for the first time that about 11% of MVA was in vivo metabolized by this pathway in nonmammalian species. Kidneys presented the maximal ability to incorporate MVA into nonsaponifiable and saponifiable lipids at any time considered (15-750 min). The percentage of radioactivity recovered as saponifiable lipids in liver and kidney decreased after 12 hr the injection of MVA. Although the absolute amounts of 14C incorporated in both derivatives were much less in brain, spinal cord and skin than in liver and kidneys, the relative percentages found in the saponifiable fraction were clearly higher in the former tissues, especially in the spinal cord.

The in vitro metabolism of mevalonate by sterol and nonsterol pathways in neonatal chick

1. Incorporation of mevalonate into nonsaponifiable lipids by neonatal chick liver and kidney slices was studied as a function of weight of tissue and incubation time. In the same conditions, more nonsaponifiable lipids were produced in kidney than in liver. 2. CO2 production from mevalonate increased with the weight of tissue and with the incubation time. Over 80% of CO2 produced from mevalonate resulted from the shunt pathway in kidney, while in liver this route was quantitatively insignificant. 3. 2-14C from mevalonate was also incorporated into saponifiable (acidic) fraction by kidney slices. 4. Incorporation into nonsaponifiable lipids and total CO2 increased with the concentration of mevalonate. This increase was more pronounced in kidney than in liver especially at low mevalonate concentrations. In the presence of 0.1-8.0 mM mevalonate over 80% of the CO2 produced from this substrate resulted from the shunt pathway, while liver was practically ineffective whatever be the concentration of mevalonate. 5. The percentage of mevalonate metabolized in the kidney by shunt pathway increased with the incubation time and reached over 15% in the presence of 0.1-8.0 mM mevalonate.

A comparative study of cholesterogenic activities from acetate of neonatal chick liver, kidney and intestinal mucosa

1. Acetate incorporation into nonsaponifiable lipids by liver and kidney slices and intestinal mucosa scrapes from neonatal chick was linear up to 100-150 mg of tissue. CO2 production from [1-14C]acetate was also studied as a function of weight of tissues. 2. Rate of acetate incorporation by the three mentioned tissues was essentially linear with respect to the incubation time assayed (0-120 min), CO2 production was also linear up to 60 min in kidney and 120 min in liver and intestinal mucosa. 3. In the conditions assayed the formation of nonsaponifiable lipids by liver slices reached constant values at acetate concentration of approximately 6 mM, while acetate incorporation by kidney and intestinal mucosa in the same conditions increased in nearly linear relationship to the concentration of available substrate. 4. Using the optimal assay conditions, acetate incorporation into nonsaponifiable lipids was maximal in neonatal chick liver, whereas kidney and intestinal mucosa only showed about 10% of the hepatic cholesterogenic activity. The percentage of acetate utilization for cholesterogenesis was also maximal in neonatal liver (about 10%). In the intestinal mucosa this percentage was also important (2-3%) being minimal in kidney slices (0.3%).