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Biomedical subjects

D Valle

Publications and source records attributed to D Valle.

At least 55 records · Page 3Linked to original sources
PubMed1999

Anopheles albitarsis eggs: ultrastructural analysis of chorion layers after permeabilization.

Construction of transgenic Anopheles mosquitoes refractory to Plasmodium requires knowledge of mosquito developmental biology. In order to study Anopheles embryology the removal or, alternatively, the permeabilization of the melanized and sclerotized egg chorion were attempted. The protocol classically used for chorion removal of Drosophila eggs was applied, with partial efficacy, to Anopheles albitarsis, a neotropical malaria vector. Each step was monitored by scanning electron microscopy and the results suggest differences in chorion composition between the two taxa. As an alternative to chorion removal, mosquito eggs were permeabilized with benserazide, an inhibitor of Dopa Decarboxylase, one of the enzymes needed for mosquito eggshell sclerotization. Embryo morphology and viability were not affected by this treatment. Permeabilization of the egg chorion allowed the ultrastructural observation of an internal homogeneous endochorion and an external compound exochorion, the latter consisting of a basal lamellar layer and protruding tubercles.

Journal Article↗
PubMed1999

Mutations in the gene encoding 3 beta-hydroxysteroid-delta 8, delta 7-isomerase cause X-linked dominant Conradi-Hünermann syndrome.

X-linked dominant Conradi-Hünermann syndrome (CDPX2; MIM 302960) is one of a group of disorders with aberrant punctate calcification in cartilage, or chondrodysplasia punctata (CDP). This is most prominent around the vertebral column, pelvis and long bones in CPDX2. Additionally, CDPX2 patients may have asymmetric rhizomesomelia, sectorial cataracts, patchy alopecia, ichthyosis and atrophoderma. The phenotype in CDPX2 females ranges from stillborn to mildly affected individuals identified in adulthood. CDPX2 is presumed lethal in males, although a few affected males have been reported. We found increased 8(9)-cholestenol and 8-dehydrocholesterol in tissue samples from seven female probands with CDPX2 (ref. 4). This pattern of accumulated cholesterol intermediates suggested a deficiency of 3beta-hydroxysteroid-delta8,delta7-isomerase (sterol-delta8-isomerase), which catalyses an intermediate step in the conversion of lanosterol to cholesterol. A candidate gene encoding a sterol-delta8-isomerase (EBP) has been identified and mapped to Xp11.22-p11.23 (refs 5,6). Using SSCP analysis and sequencing of genomic DNA, we found EBP mutations in all probands. We confirmed the functional significance of two missense alleles by expressing them in a sterol-delta8-isomerase-deficient yeast strain. Our results indicate that defects in sterol-delta8-isomerase cause CDPX2 and suggest a role for sterols in bone development.

Adolescent↗
PubMed1999

Hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome is caused by mutations in a gene encoding a mitochondrial ornithine transporter.

Neurospora crassa ARG13 and Saccharomyces cerevisiae ARG11 encode mitochondrial carrier family (MCF) proteins that transport ornithine across the mitochondrial inner membrane. We used their sequences to identify EST candidates that partially encode orthologous mammalian transporters. We thereby identified such a gene (ORNT1) that maps to 13q14 and whose expression, similar to that of other urea cycle (UC) components, was high in liver and varied with changes in dietary protein. ORNT1 expression restores ornithine metabolism in fibroblasts from patients with hyperammonaemia-hyperornithinaemia-homocitrullinuria (HHH) syndrome. In a survey of 11 HHH probands, we identified 3 ORNT1 mutant alleles that account for 21 of 22 possible mutant ORNT1 genes in our patients: F188delta, which is common in French-Canadian HHH patients and encodes an unstable protein; E180K, which encodes a stable, properly targeted protein that is inactive; and a 13q14 microdeletion. Our results show that ORNT1 encodes the mitochondrial ornithine transporter involved in UC function and is defective in HHH syndrome.

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

Hypothalamic derangement in traumatized patients: growth hormone (GH) and prolactin response to thyrotrophin-releasing hormone and GH-releasing hormone.

OBJECTIVE: To study the impact of severe head injury on both basal pituitary hormone secretion and the response to exogenous synthetic hypothalamic releasing factors (TRH and GHRH) in order to evaluate sequential changes in the central control of hypophyseal secretion in the days following head injury. DESIGN: Prospective clinical study PATIENTS: 21 comatose male patients with head injuries, each intubated and ventilated, intensively monitored and having no previous endocrine problems. MEASUREMENTS: AND RESULTS The GH and PRL responses to TRH (200 microg iv), and the GH and PRL responses to GHRH (50 microg iv) were evaluated, respectively, on the days 1 and 16 and on days 2, 7and 15 after admission. Daily blood samples were also collected for GH, PRL, TSH, T3 and T4 evaluation. In the basal samples taken on days 2, 7 and 15, IGF-I and cortisol were also determined. Nitrogen balance was assessed daily. On the day 1, TRH increased GH levels from 9.8 +/- 2.2 to 22.4 +/- 6.5 mU/l but failed to induce GH release on day 16. The PRL response to TRH was normal. The GH peak response to GHRH was normal on the day 2 (35.7 +/- 13.9 mU/l), but was increased on days 7 and 15 (68.3 +/- 10.7 mU/l on day 7; 73.8 +/- 9.2 mU/l on day 15, P < 0.01 vs. day 2). We found a significant PRL response to GHRH during the whole period of observation. In the daily evaluation, nitrogen balance was negative in all patients from the day 1 to 5. On average, all patients reached a positive nitrogen balance on the day 8. Compared to the day 2, a statistical increase in IGF-I concentration was observed on days 7 and 15. CONCLUSIONS: The evaluation of pituitary dynamics in the acute phase of a severe injury demonstrates an alteration of GH and PRL secretion, which correlate with the aminergic and/or peptidergic derangements. Taken together, our data suggest augmented tone of both GHRH and somatostatin in the very acute phase, while an imbalance of releasing factors is hypothesized in the following days. The metabolic consequences of this neuroendocrine pattern could be advantageous in the rapid recovery from the cascade of events produced by the trauma, as documented by the increase in IGF-1 levels and the positive nitrogen balance.

Accidents, Traffic↗
PubMed1999

Plasma leptin levels after biliopancreatic diversion: dissociation with body mass index.

Human obesity is associated with increased leptin levels, related to body composition and fat mass (FM). Insulin has been suggested to be a regulator of in vivo leptin secretion. To further investigate the relationships between insulin and leptin levels in human obesity, we have studied 10 obese females, aged 26-57 yr [body mass index (BMI), 42.9+/-6.3], successfully treated by biliopancreatic (BPD) diversion, in an early postoperative period (2 months after surgery, post-BPD I; BMI, 37.2+/-7.5) and a late postoperative period (16-24 months after surgery; BMI, 27.6+/-3.96). Fourteen normal female subjects (18-59 yr; BMI, 27.9+/-1.4 kg/m2) were studied as controls. In pre-BPD obese subjects, leptin levels were higher than those in controls (60.5+/-18.8 vs. 28.7+/-4.8 ng/mL; P<0.001). BMI and insulin levels were also significantly greater (P<0.0001 and P<0.03, respectively). After surgery, the three parameters considered significantly decreased (P = 0.0007 for BMI, P<0.0001 for leptin, and P = 0.038 for insulin, using Friedman's test for repeated data). Concerning the correlation between leptin and FM in our patients, control subjects and pre-BPD subjects confirmed the correlation found in the general population (r = 0.78; P<0.01). On the contrary, post-BPD patients at 2 months lay outside the general correlation between FM and leptin; in fact, patients with low leptin levels still had a high FM. Moreover, in the post-BPD patients there was no longer a significant correlation between FM and leptin. Concerning the correlation between insulin and leptin levels, a significant correlation was present in control subjects and pre-BPD patients (r = 0.46; P<0.05). Using correlation analysis for repeated measures in surgically treated obese patients, a significant correlation within the subjects was present (r = 0.91; P<0.0001). After operation, BMI and leptin levels had a different pattern of decrease; leptin decreased rapidly, without correlation with BMI, indicating that body composition is not the only factor regulating leptin levels. The consistent correlation with insulin levels suggests an important interaction between these two hormones in post-BPD obese subjects.

Adult↗
PubMed1999

Head versus trunk patterning in the Drosophila embryo; collier requirement for formation of the intercalary segment.

Whereas the segmental nature of the insect head is well established, relatively little is known about the genetic and molecular mechanisms governing this process. In this paper, we report the phenotypic analysis of mutations in collier (col), which encodes the Drosophila member of the COE family of HLH transcription factors and is activated at the blastoderm stage in a region overlapping a parasegment (PS0: posterior intercalary and anterior mandibular segments) and a mitotic domain, MD2. col mutant embryos specifically lack intercalary ectodermal structures. col activity is required for intercalary-segment expression both of the segment polarity genes hedgehog, engrailed, and wingless, and of the segment identity gene cap and collar. The parasegmental register of col activation is controlled by the combined activities of the head-gap genes buttonhead and empty spiracles and the pair-rule gene even skipped; it therefore integrates inputs from both the head and trunk segmentation systems, which were previously considered as being essentially independent. After gastrulation, positive autoregulation of col is limited to cells of anterior PS0. Conversely, heat-pulse induced ubiquitous expression of Col leads to disruption of the head skeleton. Together, these results indicate that col is required for establishment of the PS(-1)/PS0 parasegmental border and formation of the intercalary segment. Our data support neither a simple combinatorial model for segmental patterning of the head nor a direct activation of segment polarity gene expression by head-gap genes, but rather argue for the existence of parasegment-specific second order regulators acting in the head, at a level similar to that of pair-rule genes in the trunk.

Amino Acid Sequence↗
PubMed1998

Expression of PEX11beta mediates peroxisome proliferation in the absence of extracellular stimuli.

Mammalian cells typically contain hundreds of peroxisomes but can increase peroxisome abundance further in response to extracellular stimuli. We report here the identification and characterization of two novel human peroxisomal membrane proteins, PEX11alpha and PEX11beta. Overexpression of the human PEX11beta gene alone was sufficient to induce peroxisome proliferation, demonstrating that proliferation can occur in the absence of extracellular stimuli and may be mediated by a single gene. Time course studies indicated that PEX11beta induces peroxisome proliferation through a multistep process involving peroxisome elongation and segregation of PEX11beta from other peroxisomal membrane proteins, followed by peroxisome division. Overexpression of PEX11alpha also induced peroxisome proliferation but at a much lower frequency than PEX11beta in our experimental system. The patterns of PEX11alpha and PEX11beta expression were examined in the rat, the animal in which peroxisome proliferation has been examined most extensively. Levels of PEX11beta mRNA were similar in all tissues examined and were unaffected by peroxisome-proliferating agents. Conversely, PEX11alpha mRNA levels varied widely among different tissues, were highest in tissues that are sensitive to peroxisome-proliferating agents, and were induced more than 10-fold in response to the peroxisome proliferators clofibrate and di(2-ethylhexyl) phthalate. Taken together, these data implicate PEX11beta in the constitutive control of peroxisome abundance and suggest that PEX11alpha may regulate peroxisome abundance in response to extracellular stimuli.

Amino Acid Sequence↗
PubMed1998

Identification and characterization of the human ortholog of rat STXBP1, a protein implicated in vesicle trafficking and neurotransmitter release.

In a screen designed to identify genes expressed preferentially in retina, we identified a cDNA encoding the human ortholog of rat STXBP1 (n-Sec1, Munc-18-1, rbSec1), a protein implicated in vesicle trafficking and neurotransmitter release. This protein also has similarity to Drosophila Rop (65% aa identity) and Caenorhabditis elegans UNC-18 (58% aa identity). The major human cDNA encodes a protein of 594 amino acids which has 100 % amino acid identity with its rat and murine counterparts. Additionally, there is an alternative splice form in humans, arising from the inclusion of an additional exon, which encodes a protein of 603 amino acids and is also 100% identical to the corresponding rat isoform. We found expression of the shorter cDNA in all tissues and cell lines we examined with highest levels in retina and cerebellum. By RT-PCR analysis, we found expression of the longer cDNA in neural tissues only. We mapped the structural gene to 9q34.1, a region without obvious candidate phenotypes. However, due to its evolutionary conservation and abundant expression in retina and brain, STXBP1 should be considered a candidate gene for retinal and/or neural disorders mapping to 9q34.1.

Amino Acid Sequence↗
PubMed1998

Molecular analysis of the third component of canine complement (C3) and identification of the mutation responsible for hereditary canine C3 deficiency.

Genetically determined deficiency of the third component of complement (C3) in the dog is characterized by a predisposition to recurrent bacterial infections and to type 1 membranoproliferative glomerulonephritis. The current studies were undertaken to characterize the cDNA for wild-type canine C3 and identify the molecular basis for hereditary canine C3 deficiency. Amplification, cloning, and sequence analysis indicated that canine C3 is highly conserved in comparison with human, mouse, and guinea pig C3. Southern blot analysis failed to show any gross deletions or rearrangements of DNA from C3-deficient animals. Northern blot analysis indicated that the livers of these animals contain markedly reduced quantities of a normal length C3 mRNA. The full-length 5.1-kb canine C3 cDNA was amplified in overlapping PCR fragments. Sequence analysis of these fragments has shown a deletion of a cytosine at position 2136 (codon 712), leading to a frameshift that generates a stop codon 11 amino acids downstream. The deletion has been confirmed in genomic DNA, and its inheritance has been demonstrated by allele-specific oligonucleotide hybridization.

Amino Acid Sequence↗
PubMed1998

Genomic organization of the 70-kDa peroxisomal membrane protein gene (PXMP1).

The 70-kDa peroxisomal membrane protein (PMP70) is a member of a family of half-ATP-binding cassette (ABC) transporter proteins located in the human peroxisomal membrane. Other members include the PMP70-related peroxisomal membrane protein, the adrenoleukodystrophy protein (ALDP), and the adrenoleukodystrophy-related protein. The functions of ABC transporters in the peroxisomal membrane are poorly understood. Evidence from yeast and human mutants suggests that they are involved in the peroxisomal import of fatty acids and/or fatty acyl-CoAs into the organelle. We report the cloning and characterization of the human PMP70 structural gene (gene symbol: PXMP1) localized on human chromosome 1p21-p22. PXMP1 is approximately 65 kb in length, contains 23 exons, and is quite different in structure from the gene (ALD) that encodes the related protein, ALDP. We also analyzed the 5' flanking region of the human PXMP1 gene and the corresponding region of murine Pxmp-1. Both promoters have features of housekeeping genes, including a high GC content and multiple consensus Sp1 binding sequences. In more than 3 kb of Pxmp-1 5' flanking sequence we did not identify a consensus peroxisomal proliferator responsive element.

ATP-Binding Cassette Transporters↗
PubMed1998

Delta3,5-delta2,4-dienoyl-CoA isomerase from rat liver. Molecular characterization.

rECH1, a recently identified rat cDNA (FitzPatrick, D. R., Germain-Lee, E., and Valle, D. (1995) Genomics 27, 457-466) encodes a polypeptide belonging to the hydratase/isomerase superfamily. We modeled the structure of rECH1 based on rat mitochondrial 2-enoyl-CoA hydratase 1. The model predicts that rECH1p has the hydratase fold in the core domain and two domains for interaction with other subunits. When we incubated 3,5,8,11, 14-eicosapentaenoyl-CoA with purified rECH1p, the spectral data suggested a switching of the double bonds from the Delta3-Delta5 to the Delta2-Delta4 positions. This was confirmed by demonstrating that the product was a valid substrate for 2,4-dienoyl-CoA reductase. These results indicate that rECH1p is Delta3,5-Delta2,4-dienoyl-CoA isomerase. Subcellular fractionation and immunoelectron microscopy using antibodies to a synthetic polypeptide derived from the C terminus of rECH1p showed that rECH1p is located in the matrix of both mitochondria and peroxisomes in rat liver. Consistent with these observations, the 36,000-Da rECH1p has a potential N-terminal mitochondrial targeting signal as well as a C-terminal peroxisomal targeting signal type 1. Transport of the protein into the mitochondria with cleavage of the targeting signal results in a mature mitochondrial form with a molecular mass of 32,000 Da; transport to peroxisomes yields a protein of 36,000 Da.

Amino Acid Sequence↗
PubMed1998

Evaluation of the vascular pattern of hepatocellular carcinoma with dynamic computed tomography and its use in identifying optimal temporal windows for helical computed tomography.

The aim of this work was to study the vascularization of hepatocellular carcinoma (HCC) by means of dynamic CT and to demonstrate the existence of optimal temporal windows for visualization of HCC in order to develop new protocols for helical CT of the liver. We studied, by means of dynamic CT, 42 histologically proved HCCs in 30 patients after injecting contrast medium (100 ml, 3 ml/s). We performed a time-density analysis of the aorta, liver, portal vein, spleen and lesion. We identified three temporal curves of attenuation of the neoplastic tissue. Curve 1 was three-phasic: hyperattenuation, isoattenuation and hypoattenuation; curve 2 was two-phasic: hyperattenuation and isoattenuation; curve 3 was two-phasic: isoattenuation and hypoattenuation. Thirty-two lesions were homogeneous (curve 1 in 22 cases, 68.7 %; curve 2 in 7 cases, 21.8 %; curve 3 in 3 cases, 9.4 %), whereas 10 lesions were non-homogeneous. Two optimal temporal windows were identified: the first, with predominantly hyperattenuating lesions (range 29-65 s, 90.4 % sensitivity); the second, with predominantly hypoattenuating lesions (range 132.1-360 s, 76.1 %). There is an interposed time range of reduced visualization (range 62-127 s, 54.7 %) in which lesions are isoattenuating. Combined CT study during the first and second temporal windows improves the detection of HCCs especially for homogeneous and small lesions. The intermediate isoattenuation time range does not increase lesion detection rate.

Aged↗
PubMed1998

Restoration of PEX2 peroxisome assembly defects by overexpression of PMP70.

The mutant Chinese hamster ovary (CHO) cell line Z78/C has defective peroxisome assembly due to a missense mutation in PEX2, the gene which encodes the 35 kDa peroxisomal integral membrane protein. In humans, PEX2 mutations are responsible for complementation group 10 of the human peroxisome biogenesis disorders (PBD), a genetically heterogeneous group of lethal, autosomal recessive diseases including the Zellweger syndrome and related phenotypes. To develop additional cellular models for Zellweger syndrome, we produced a series of new mutant CHO cell clones in the same complementation group as Z78/C (Z2, Z7, Z22, and Z105). As expected, expression of human PEX2 restores peroxisomal biogenesis in all of these clones. Surprisingly, expression of the human 70 kDa peroxisomal membrane protein (PMP70) also restores peroxisome biogenesis in these same CHO cell clones. We confirmed this effect of PMP70 expression on peroxisome biogenesis by determining the subcellular latency of catalase, the immunohistochemical localization of catalase and the beta-oxidation of very long chain fatty acids (VLCFA). By contrast, expression of a mutant allele of PMP70 identified in a patient with Zellweger syndrome did not restore peroxisome biogenesis in the PEX2-deficient CHO cell clones. Our results indicate that overexpression of PMP70 suppresses the phenotype of PEX2 gene mutations. These observations suggest a functional interaction between PEX2 and PMP70 in the peroxisome membrane.

ATP-Binding Cassette Transporters↗
PubMed1998

Evaluation of pre- and postprandial growth hormone (GH)-releasing hormone-induced GH response in subjects with persistent body weight normalisation after biliopancreatic diversion.

BACKGROUND: Obesity is characterised by growth hormone (GH) abnormalities, including a blunted response to stimulation and a 'paradoxical' increase after meals. The blunted GH release is reversed by a surgical intestinal bypass procedure. However, this does not mean that normal GH dynamics have been restored. The present study assessed whether post-surgical weight reduction in obese patients normalised the modulation of GH release produced by metabolic fuels. SUBJECTS: Ten obese female subjects, aged 23-54 y, were studied before and after biliopancreatic diversion (BPD). All patients, after surgery, had experienced a significant reduction in body weight (mean body mass index (BMI) 25.78 +/- 1.01 kg/m2 vs 44.68 +/- 1.73 kg/m2). Two groups were also studied as controls: Ten normal body weight female subjects and ten patients suffering from anorexia nervosa (AN, mean BMI 17.46 +/- 1.12 kg/m2). MEASUREMENTS: We have studied the GH response to a GH releasing hormone (GHRH) bolus (1 microg/kg i.v., at 13.00 h) before and after a standard meal. RESULTS: In post-BPD subjects, the GH response to GHRH in the fasting state, was clearly augmented in comparison with the pre-BPD values (peak values 18.06 +/- 4.56 vs 3.24 +/- 0.68 microg/L). In post-BPD subjects the postprandial GH response was further augmented in comparison with the fasting test (peak 30.12 +/- 4.99 microg/L, P < 0.05). This pattern was similar to that observed in anorexic patients. CONCLUSION: The surgical procedure restores a normal GH response to GHRH in the fasting state, but the 'paradoxical' GH response after meals remains present, suggesting a persistent GH derangement in such patients, which is not related to body weight per se. The surgical procedure makes obese patients similar to anorexics, in the relationships between metabolic fuels and GH secretion. The persistence of the GH postprandial response to GHRH in post-BPD subjects suggests a role for metabolic fuels in the regulation of somatostatin (SRIF) secretion.

Adult↗
PubMed1998

Identification of PEX10, the gene defective in complementation group 7 of the peroxisome-biogenesis disorders.

The peroxisome-biogenesis disorders (PBDs) are a group of genetically heterogeneous, lethal diseases that are characterized by neuronal, hepatic, and renal abnormalities; severe mental retardation; and, in their most severe form, death within the 1st year of life. Cells from all PBD patients exhibit decreased import of one or more classes of peroxisome matrix proteins, a phenotype shared by yeast pex mutants. We identified the human orthologue of yeast PEX10 and observed that its expression rescues peroxisomal matrix-protein import in PBD patients' fibroblasts from complementation group 7 (CG7). In addition, we detected mutations on both copies of PEX10 in two unrelated CG7 patients. A Zellweger syndrome patient, PBD100, was homozygous for a splice donor-site mutation that results in exon skipping and loss of 407 bp from the PEX10 open reading frame. A more mildly affected neonatal adrenoleukodystrophy patient was a compound heterozygote for a missense mutation in the PEX10 zinc-binding domain, H290Q, and for a nonsense mutation, R125ter. Although all three mutations attenuate PEX10 activity, the two alleles detected in the mildly affected patient, PBD052, encode partially functional PEX10 proteins. PEX10-deficient PBD100 cells contain many peroxisomes and import peroxisomal membrane proteins but do not import peroxisomal matrix proteins, indicating that loss of PEX10 has its most pronounced effect on peroxisomal matrix-protein import.

Adrenoleukodystrophy↗