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Biomedical subjects

R Dominguez

Publications and source records attributed to R Dominguez.

At least 19 recordsLinked to original sources
PubMed1998

The effect of 10 : 1 compression and soft copy interpretation on the chest radiographs of premature neonates with reference to their possible application in teleradiology.

The aim of the study was to assess the potential application of teleradiology in the neonatal intensive care unit (NICU) by ascertaining whether any decrease in conspicuity of anatomic detail or interventional devices in the chest radiographs of premature infants is caused by picture archiving and communication system (PACS)-based soft copy interpretation of 10 : 1 compressed images. One hundred digital chest radiographs of low-birthweight infants were obtained in the NICU using a storage phosphor system. Laser-printed images were interpreted and the data set for each radiograph was then irreversibly compressed by a 10 : 1 ratio. Four radiologists with extensive PACS experience used a five-point grading system to score laser-printed hard copy images for the visibility of six parameters of anatomic landmarks and interventional devices in the chest. Compressed soft copy images displayed on 2K PACS workstation were subsequently scored using the same approach. Statistical manipulation demonstrated no loss of anatomic detail in five of the six parameters scored, with minimal difference in one landmark, the retrocardiac lung assessment. While further study is required to assess the clinical impact of the variance noted when evaluating lung parameters, the preservation or improvement of information in the remaining parameters following irreversible compression and soft copy interpretation is promising for the potential use of teleradiology in this population.

Data Interpretation, Statistical↗
PubMed1997

Structures of four Ca2+-bound troponin C at 2.0 A resolution: further insights into the Ca2+-switch in the calmodulin superfamily.

BACKGROUND: In contrast to Ca2+4-bound calmodulin (CaM), which has evolved to bind to many target sequences and thus regulate the function of a variety of enzymes, troponin C (TnC) is a bistable switch which controls contraction in striated muscles. The specific target of TnC is troponin I (TnI), the inhibitory subunit of the troponin complex on the thin filaments of muscle. To date, only the crystal structure of Ca2+2-bound TnC (i.e. in the 'off' state) had been determined, which together with the structure of Ca2+4-bound CaM formed the basis for the so-called 'HMJ' model of the conformational changes in TnC upon Ca2+ binding. NMR spectroscopic studies of Ca2+4-bound TnC (i.e. in the 'on' state) have recently been carried out, but the detailed conformational changes that take place upon switching from the off to the on state have not yet been described. RESULTS: We have determined the crystal structures of two forms of expressed rabbit Ca2+4-bound TnC to 2.0 A resolution. The structures show that the conformation of the N-terminal lobe (N lobe) is similar to that predicted by the HMJ model. Our results also reveal, in detail, the residues involved in binding of Ca2+ in the regulatory N lobe of the molecule. We show that the central helix, which links the N and C lobes of TnC, is better stabilized in the Ca2+2-bound than in the Ca2+4-bound state of the molecule. Comparison of the crystal structures of the off and on states of TnC reveals the specific linkages in the molecule that change in the transition from off to on state upon Ca2+-binding. Small sequence differences are also shown to account for large functional differences between CaM and TnC. CONCLUSIONS: The two lobes of TnC are designed to respond to Ca2+-binding quite differently, although the structures with bound Ca2+ are very similar. A small number of differences in the sequences of these two lobes accounts for the fact that the C lobe is stabilized only in the open (Ca2+-bound) state, whereas the N lobe can switch between two stable states. This difference accounts for the Ca2+-dependent and Ca2+-independent interactions of the N and C lobe. The C lobe of TnC is always linked to TnI, whereas the N lobe can maintain its regulatory role - binding strongly to TnI at critical levels of Ca2+ - and in contrast, forming a stable closed conformation in the absence of Ca2+.

Animals↗
PubMed1997

The effect of lossy discrete cosine transform compression on subtle bone fractures.

Extensive research efforts have been devoted to the feasibility of picture archiving and communication systems (PACS) in recent years. The advantages of PACS are numerous but mainly include reduced cost and improvement in the operational efficiency of a PACS-based radiology department. In digital radiography, images are viewed either in hard-copy or soft-copy format. Usually, these images are subsequently compressed and archived for future evaluation. There are various methods used in image compression. In this study, computed radiography images showing subtle pediatric bone fractures were compressed with the lossy method of image compression after they had been initially evaluated on workstation monitors. These studies were subsequently evaluated by observers, who were unaware of the interpretations of these images before compression, to determine if they could detect similar abnormalities. Our conclusion is that there is no difference in the interpretation of soft-copy computed radiographic images before or after lossy 10:1 compression in studies of subtle pediatric bone fractures. This is a US government work. There are no restrictions on its use.

Analysis of Variance↗
PubMed1997

A polysomnographic comparison of veterans with combat-related PTSD, depressed men, and non-ill controls.

Post-traumatic stress disorder (PTSD) overlaps major depression (MD) clinically, but differs with respect to treatment response and some biological markers. Sleep disturbances represent core features of PTSD and are also common in MD. Rapid eye movement sleep (REM) has been postulated to be involved in the pathophysiology of PTSD, and REM abnormalities occur in MD. Twenty-five patients with combat-related PTSD, 16 men with a principal diagnosis of MD, and 10 asymptomatic male controls were compared by polysomnography (PSG) under medication and substance-free conditions. Data were obtained from recordings made after an accommodation night. One subject from each group was excluded for significant apnea or limb movements. Sleep efficiency was decreased in the PTSD group compared to the MD and control groups. REM density was comparably increased in PTSD and MD groups, while the amount of REM sleep was reduced in PTSD compared to MD groups. These sleep measures were not significantly associated with co-morbid depression, substance-use disorder histories, or subclinical sleep apnea or limb movements within the PTSD group. These findings support sleep maintenance being impaired in chronic PTSD patients. Increased REM density in PTSD patients was replicated and was comparable to increases in the MD group. Divergence of REM time between these clinical groups suggests the possibility of different underlying mechanisms.

Adult↗
PubMed1997

Synthesis, affinity at 5-HT2A, 5-HT2B and 5-HT2C serotonin receptors and structure-activity relationships of a series of cyproheptadine analogues.

Cyproheptadine is a drug that shows high affinity for type 2 (5-HT2) receptors. We studied a series of compounds obtained by modification of the tricyclic system of Cyp (dibenzocycloheptadiene): 2f (thioxanthene), 2g (xanthene), 2h (dihydrodibenzocycloheptadiene), 2j (diphenyl), 2i (fluorene), and 3b (phenylmethyl). Their activities at the rat cerebral cortex 5-HT2A receptor were (pKi +/- S.E.M.): 8.80 +/- 0.11 (Cyp), 8.60 +/- 0.07 (2f), 8.40 +/- 0.02 (2g), 8.05 +/- 0.03 (2h), 7.87 +/- 0.12 (2j), 6.70 +/- 0.02 (2i) and 6.45 +/- 0.02 (3b); those at the rat stomach fundus 5-HT2B receptor (pA2 +/- S.E.M.) were: 9.14 +/- 0.25 (Cyp), 8.49 +/- 0.07 (2f), 7.58 +/- 0.58 (2g), 7.02 +/- 0.14 (2h), 6.07 +/- 0.20 (2j), and undetectable (2i, 3b): and those at the pig choroidal plexus 5-HT2C receptor (pKi +/- S.E.M.) were: 8.71 +/- 0.08 (Cyp), 8.68 +/- 0.01 (2f), 8.58 +/- 0.20 (2g), 7.95 +/- 0.05 (2h), 7.57 +/- 0.04 (2j), 6.98 +/- 0.04 (2i) and 6.63 +/- 0.20 (3b). The slopes did not differ significantly from unity. The compounds exhibited the same order of activities at every type of receptor, and the most active molecules presented certain steric (butterfly conformation of the tricyclic system) and electrostatic (proton affinity on the top of the central rings) patterns. It is concluded that the activity of cyproheptadine derivatives at 5-HT2 receptors is related to these molecular features, which make feasible a common disposition to interact with all three 5-HT2 subtypes.

Animals↗
PubMed1996

The crystal structure of endoglucanase CelA, a family 8 glycosyl hydrolase from Clostridium thermocellum.

BACKGROUND: Cellulases, which catalyze the hydrolysis of glycosidic bonds in cellulose, can be classified into several different protein families. Endoglucanase CelA is a member of glycosyl hydrolase family 8, a family for which no structural information was previously available. RESULTS: The crystal structure of CelA was determined by multiple isomorphous replacement and refined to 1.65 A resolution. The protein folds into a regular (alpha/alpha)6 barrel formed by six inner and six outer alpha helices. Cello-oligosaccharides bind to an acidic cleft containing at least five D-glucosyl-binding subsites (A-E) such that the scissile glycosidic linkage lies between subsites C and D. The strictly conserved residue Glu95, which occupies the center of the substrate-binding cleft and is hydrogen bonded to the glycosidic oxygen, has been assigned the catalytic role of proton donor. CONCLUSIONS: The present analysis provides a basis for modeling homologous family 8 cellulases. The architecture of the active-site cleft, presenting at least five glucosyl-binding subsites, explains why family 8 cellulases cleave cello-oligosaccharide polymers that are at least five D-glycosyl subunits long. Furthermore, the structure of CelA allows comparison with (alpha/alpha)6 barrel glycosidases that are not related in sequence, suggesting a possible, albeit distant, evolutionary relationship between different families of glycosyl hydrolases.

Binding Sites↗
PubMed1995

Differential effects of unilateral lesions in the medial amygdala on spontaneous and induced ovulation.

The possible existence of asymmetry in the control of ovulation by the medial amygdala was explored. Unilateral lesions of the medial amygdala were performed on each day of the estrous cycle. The estral index diminished in almost all animals with a lesion in the right side of medial amygdala. Lesions of the right medial amygdala, when performed on diestrus-1, resulted in a significant decrease in the number of rats ovulating compared to controls (4/8 vs. 8/8, p < 0.05). In ovulating animals a significant reduction in the number of ova shed by the left ovary was found (2.2 +/- 0.8 vs. 6.3 +/- 0.8, p < 0.05). Lesions of the stria terminalis performed on diestrus-1 did not affect ovulation. In a second experiment, administration of GnRH did not restore ovulation in rats with lesions of the right medial amygdala. However, sequential injections of PMSG-hCG did result in ovulation by all members of a group of lesioned animals. In this last condition a significant decrease in the number of ova shed by the right ovary was found compared to animals in the lesion-only condition (1.5 +/- 0.5 vs. 6.0 +/- 1.5, p < 0.05). These data suggest that control of ovulation by the medial amygdala is asymmetric and varies during the estrous cycle.

Amygdala↗
PubMed1995

In vitro lead cation-hyaluronic acid interaction.

It is the purpose of this investigation to study the in vitro spontaneous interaction lead-hyaluronic acid using the equilibrium dialysis technique. The following working conditions were used: membrane retention capacity starting from 12000 D; solvent was an aqueous buffer solution (pH 7.4); relation of internal-external volume of 0.5 : 25 mL: dialysis time 24 hours; lead concentration in dialyzing solution 4 micrograms/mL (always outside the bag); temperature 4 degrees C; concentrations of hyaluronic acid 0.3, 1.2, 2.1 and 3.0 mg/mL; concentration of plasma proteins 1.5 mg/mL; lead was determined in the internal solution of the bag, and was measured quantitatively by atomic absorption spectrometry. Testing separately hyaluronic acid and plasma proteins both types of marcromolecules turned out to bind lead. As the concentration of hyaluronic acid increases, the amount of lead retained increases as well, although this relation is only approximately linear. At the normal concentrations of plasma proteins and hyaluronic acid in synovial fluid, the proteins solution bound more lead than hyaluronic acid solution 16.2 +/- 2.1 and 5.7 +/- 0.4 micrograms/mL respectively (P < 0.0001). What these data show ist that both, hyaluronic acid and proteins are involved in the in vitro lead retention. The effect of both ligands must be synergistic, because when the two molecules are present, a higher amount of lead is retained compared to the amount bound separately, suggesting that lead can replace calcium by complexation with mucopolysaccharides; this explains the lead accumulation in synovial fluid since this fluid is rich in hyaluronic acid and proteins.

Cations↗
PubMed1995

A common protein fold and similar active site in two distinct families of beta-glycanases.

The structure of Clostridium thermocellum endoglucanase CelC, a member of the largest cellulase family (family A), has been determined at 2.15 A resolution. The protein folds into an (alpha/beta)8 barrel, with a deep active-site cleft generated by the insertion of a helical subdomain. The structure of the catalytic core of xylanase XynZ, which belongs to xylanase family F, has been determined at 1.4 A resolution. In spite of significant differences in substrate specificity and structure (including the absence of the helical subdomain), the general polypeptide folding pattern, architecture of the active site and catalytic mechanism of XynZ and CelC are similar, suggesting a common evolutionary origin.

Amino Acid Sequence↗
PubMed1995

Crossed cerebellar atrophy in children: a neurologic sequela of extreme prematurity.

Unilateral atrophy of a cerebellar hemisphere occurring as a sequela of ischemic or destructive injury of the contralateral cerebral hemisphere is uncommon in children. We reviewed our experience with this phenomenon and found an unexpected association with extreme prematurity and a complicated perinatal course with a poor subsequent neurologic outcome. We retrospectively identified eight children, aged 8 months to 13 years, in whom cerebellar atrophy associated with cerebral injury was diagnosed on MR or CT, and reviewed their past medical history, neurologic findings, and neuroimaging studies. Seven patients were born extremely premature, EGA 25-28 weeks, and had severe perinatal intracranial hemorrhage. Neurologic problems include severe developmental delay in seven, spastic paresis in six, and seizures in five. Neuroimaging showed severe unilateral holohemispheric atrophy in four, bilateral asymmetric holohemispheric atrophy in two, and left temporoparietal atrophy in one. Cerebellar atrophy was unilateral in five and bilateral but asymmetric in two. Gliosis of the atrophic cerebellum occurred in one patient. Sequential neuroimaging in one patient showed evolution of crossed cerebellar atrophy at 8 months of age. The final patient, a term infant, had an idiopathic perinatal left cerebral infarct. In our experience, crossed cerebellar atrophy was an uncommon manifestation of extreme prematurity complicated by severe intracranial hemorrhage and/or ischemic necrosis of white matter. The cerebellar atrophy is most often a secondary degenerative phenomenon rather than a result of direct cerebellar injury.

Atrophy↗
PubMed1994

Characterization of two crystal forms of Clostridium thermocellum endoglucanase CelC.

Endoglucanase CelC from Clostridium thermocellum expressed in Escherichia coli has been crystallized in two different crystal forms by the hanging drop method. Crystals of form I were grown with polyethylene glycol as a precipitant. They are orthorhombic, space group P2(1)2(1)2(1), with cell dimensions a = 51.4 A, b = 84.3 A, and c = 87.5 A. Crystals of form II, obtained in ammonium sulfate solutions, belong to the tetragonal space group P4(1)2(1)2 (or P4(3)2(1)2) with cell dimensions of a = b = 130.7 A and c = 69.6 A. Diffraction data to 2.8 A resolution were observed for both crystal forms with a rotating anode generator. Preliminary oscillation images of the orthorhombic form I crystals using a synchrotron radiation source show diffraction to 2.2 A resolution, indicating that these crystals are suitable for high resolution crystallographic analysis.

Cellulase↗
PubMed1994

Gorham's disease or vanishing bone disease: plain film, CT, and MRI findings of two cases.

Gorham's disease may develop in any region of the skeleton, but shows a predilection for the bones of the shoulders and pelvic girdles. Less frequently, the disease may involve the spine, and it is the proximity to the spinal cord which may worsen the patient's outcome. We report the clinical outcomes of two children with typical, yet differently localized involvement, and also review the plain film, CT and MRI findings.

Cervical Vertebrae↗
PubMed1994

Pulsatile versus continuous oxytocin infusion for the oxytocin challenge test.

In a prospective study, 140 patients had an oxytocin challenge test with either a continuous or a pulsed infusion (one minute of infusion in every five minutes). Both infusion regimens had similar success rates in terms of uterine contractions (97.1 vs 98.6%). The potency ratio (pulsed versus continuous infusion) was significant at 2.7 (1.27 to 5.2), which means that more uterine activity was induced with each mU of oxytocin with pulsatile than with continuous administration. The total amount of oxytocin required to obtain three good contractions in 10 minutes was about 40% less with pulsed administration than with continuous infusion, but the test took 40 minutes longer with the pulsed than with the continuous infusion (P < 0.01).

Adult↗
PubMed1994

Different effects of unilateral and bilateral lesions of the dorsal raphe nucleus on puberty and first ovulation.

The effects of unilateral and bilateral electrolytic lesions of the dorsal raphe nuclei (DRN) of 30-day-old rats, on the spontaneous and induced ovulation, were analyzed. The bilateral lesion and the lesion on the right side of the DRN delayed the age of first vaginal estrous. None of the animals with bilateral lesion on the DRN ovulated on the day of first estrous (0/8 vs. 12/15, p < 0.05). The ovulation rate in animals with unilateral lesion on the DRN was similar to sham-operated animals, but the number of ova shed by ovulating animals increased in the ovary ipsilateral to the lesion (lesion on right DRN, right ovary: 6.5 +/- 0.5 vs. 4.5 +/- 0.4; lesion on left DRN, left ovary: 6.4 +/- 0.3 vs. 4.2 +/- 0.4, p < 0.05). By the injection of human chorionic gonadotropin, ovulation was restored in rats with a bilateral lesion on the DRN (3/5 vs. 0/8, p < 0.05). The present results suggest that serotoninergic input to the hypothalamus, arising from the DRN, exerts a facilitatory influences on the control of luteinizing hormone release. To explain the increase in the number of ova shed by the left and right ovary, observed in rats with an ipsilateral lesion, we suggest the existence of a neural connection between the DRN and the ovary.

Animals↗
PubMed1994

[Larsen syndrome: multicenter study of 12 new cases. Diagnosis, planning and results of treatment].

Larsen's syndrome is characterized by the association of congenital knee, hip and elbow dislocations, characteristic facial abnormalities, joint hyperlaxity, and other inconstant malformations. A review is made after description of 12 new cases from a multicenter study. A partial modification of diagnostic criteria is proposed, based on the analysis of the frequency and localization of the deformities. Radiological aspects, surgical indications, clinical evolution, complications and late results are presented, with emphasis on lower extremity problems. Good clinical results are more remarkable in the children treated early. Periodic follow-up is obligatory for good therapeutic results.

Abnormalities, Multiple↗
PubMed1993

Caudal duplication syndrome.

OBJECTIVE: To present the clinical and roentgenographic features of caudal duplication syndrome. DESIGN: Retrospective review of the medical records and all available imaging studies. SETTING: Two university-affiliated teaching hospitals. PARTICIPANTS: Six children with multiple anomalies and duplications of distal organs derived from the hindgut, neural tube, and adjacent mesoderm. INTERVENTIONS: None. RESULTS: Spinal anomalies (myelomeningocele in two patients, sacral duplication in three, diplomyelia in two, and hemivertebrae in one) were present in all our patients. Duplications or anomalies of the external genitalia and/or the lower urinary and reproductive structures were also seen in all our patients. Ventral herniation (in one patient), intestinal obstructions (in one patient), and bowel duplications (in two patients) were the most common gastrointestinal abnormalities. CONCLUSIONS: We believe that the above constellation of abnormalities resulted from an insult to the caudal cell mass and hindgut at approximately the 23rd through the 25th day of gestation. We propose the term caudal duplication syndrome to describe the association between gastrointestinal, genitourinary, and distal neural tube malformations.

Abnormalities, Multiple↗
PubMed1992

Congenital primary cerebral angiosarcoma: CT, US, and MR findings.

Congenital primary intracranial angiosarcoma (CAS) is an exceptionally rare tumor. To our knowledge the imaging features of intracranial angiosarcomas have only been briefly mentioned in the neuropathologic literature. To our knowledge, only one case of CAS has been reported. We present a case of a pathologically proven CAS found in a neonate.

Brain Neoplasms↗