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Biomedical subjects

M Madrid

Publications and source records attributed to M Madrid.

At least 19 recordsLinked to original sources
PubMed2006

Treatment of cerebral aneurysms with hydrogel-coated platinum coils (HydroCoil): early single-center experience.

PURPOSE: The authors report their experience using HydroCoils in the treatment of cerebral aneurysms. METHODS: We performed a retrospective review of the first 100 nonrandomized patients (104 coiled saccular cerebral aneurysms) treated with HydroCoils during a 27-month period. RESULTS: The average percentage of HydroCoil by length detached in treated aneurysms was 45.5% (range, 9.9-100%). Immediate postprocedure angiography demonstrated complete aneurysm occlusion in 34%, neck remnant in 35%, and incomplete occlusion in 32%. Immediate procedure-related morbidity and mortality rates were 5.8% and 0%, respectively. Angiographic follow-up was obtained in 51% (51/100 patients; 53/104 aneurysms; average, 10.3 months; range, 0-31 months). In these 53 angiographically followed aneurysms, the overall recanalization rate was 21%: no recanalization occurred in 23 aneurysms with small size (<10 mm)/small neck (<4 mm) (S/S); 4 recanalizations occurred in 7 aneurysms with small size/wide neck (>4 mm) (S/W); 6 recanalizations (27%) occurred in 22 large (L) aneurysms (>10-25 mm, 70% angiographic follow-up); and 1 giant (G) (>25 mm) aneurysm recanalized. A large proportion of aneurysms that were not initially completely occluded were completely occluded on follow-up (15/43 [35%]). Clinical follow-up was obtained in 73 patients (73%; average, 5.3 months; range, 0-24 months): 93% of these patients were neurologically improved or unchanged. Three patients rehemorrhaged and 3 patients with unruptured aneurysms developed delayed hydrocephalus. CONCLUSIONS: The overall safety profile of HydroCoils appears acceptable. Preliminary midterm observations suggest less coil compaction/aneurysm recanalization in large aneurysms. However, HydroCoil-related delayed hydrocephalus is a concern.

Adolescent↗
PubMed2001

Molecular dynamics of HIV-1 reverse transcriptase indicates increased flexibility upon DNA binding.

HIV-1 reverse transcriptase (RT) is one of the main targets for drugs used in the treatment of AIDS, among them, the non-nucleoside RT inhibitors (NNRTIs). The flexibility of RT unliganded and complexed to double-stranded DNA (RT/dsDNA), in water, has been studied by means of molecular dynamics. The simulations show that RT flexibility depends on its ligation state. The RT/dsDNA trajectories show larger fluctuations in the atomic positions than uncomplexed RT, particularly at the tips of the p66 fingers and thumb subdomains. This increased flexibility is consistent with the ability of the p66 fingers of the RT/dsDNA complex to close down after the binding of a deoxynucleoside triphosphate (dNTP) molecule, as observed in the crystal structures of RT/dsDNA bound to dNTP. The two complexation states present different patterns of concerted motions, indicating that the bound dsDNA alters RT flexibility. The motions of amino acid residues that form the non-nucleoside RT inhibitor binding pocket upon complexation with a NNRTI are anticorrelated with the p66 fingers (in RT/dsDNA) and correlated to the RNase H subdomain (unliganded RT). These concerted motions indicate that binding of a NNRTI could alter the flexibility of the subdomains whose motions are correlated to those of the binding pocket.

Binding Sites↗
PubMed2001

Perfusion brain scintigraphy studies in infants and children with malformations of the vein of Galen.

Cerebral perfusion brain scintigraphy obtained in six unselected patients (age newborn to 14 years) from among 50 children with vein of Galen malformations was used in conjunction with magnetic resonance imaging to determine the basis of the neurological and cognitive abnormalities in patients with vein of Galen malformations (VGMs). Five had a hemiparesis - persistent, transient, or alternating. Four were developmentally delayed. Two had so far been cognitively normal and acquired a neurological deficit, following an embolization procedure. The school age patient had a nonverbal learning disability. Three had epilepsy and/or an abnormal electroencephalogram. Magnetic resonance imaging documented only the VGM, hydrocephalus and atrophy; one child with perinatal asphyxia had periventricular leukomalacia. Perfusion brain scintigraphy was normal in two (a normal infant, and a toddler with a hemiparesis and aphasia). Abnormal findings included: left parietal hypoperfusion, fronto-temporal atrophy, patchy flow; left fronto-temporal hypoperfusion, left hemiatrophy, bilateral medial temporal hypoperfusion, right cerebellar hypoperfusion; right temporal hypoperfusion, patchy flow; right hemiatrophy, occipital hypoperfusion. Perfusion brain scintigraphy findings correlated better with focal neurological and cognitive defects than did magnetic resonance imaging.

Adolescent↗
PubMed1999

Major subdomain rearrangement in HIV-1 reverse transcriptase simulated by molecular dynamics.

We have performed eight 1-ns in vacuo molecular dynamics simulations of HIV-1 reverse transcriptase (RT). Starting with the p66 thumb subdomain in an upright configuration, the p66 thumb moved down over the palm during six of the eight trajectories, in excellent agreement with the crystallographic structure of unliganded RT. The large rearrangement of the p66 thumb subdomain, its tip moving approximately 30 A, occurs during the first 30-200 ps. This approach may allow a detailed study of the processes involved in biologically significant conformational changes in macromolecules.

Crystallography, X-Ray↗
PubMed1998

[Cyclosporosis. Report of a clinical case in Concepción, Chile].

Cyclospora cayetanensis is a newly recognized parasite widely distributed throughout the world, and isolated from children, immunocompetent adults and HIV infected individuals. The clinical manifestations of the infection are watery prolonged diarrhea, anorexia, fatigue, nausea, bloating and weight loss. In immunocompetent individuals, diarrhea is usually self limited but may last several weeks. In immunocompromised hosts it is prolonged, severe and can be associated with biliary tract involvement. We report a 50 years old female that, five days after returning from Cuba, presented with low grade fever, anorexia, fatigue, explosive diarrhea and weight loss. Physical examination was normal. A stool specimen contained many organisms with morphological features of Cyclospora caetanensis. The diagnosis was confirmed at the Centers for Disease Control (Atlanta Ga).

Animals↗
PubMed1996

Occipital arteriovenous malformations: visual disturbances and presentation.

BACKGROUND: Occipital arteriovenous malformations (AVMs) cause a variety of visual disturbances and headaches. Early diagnosis may lead to treatment that reduces the risk of hemorrhages, visual field loss and other neurologic deficits, and death. METHODS: We reviewed the records of the 70 patients with occipital AVMs referred to New York University Medical Center to investigate the mode of presentation and the outcome of treatment. RESULTS: Sixty-eight patients presented with one or more symptoms, including homonymous visual disturbances in 39, headache in 39, seizures in 20, and hemorrhage in twenty-six. Visual field loss was more common (p = 0.0007) and more severe (p = 0.0002) in patients who bled than in those with unruptured AVMs (16/44). The frequency of visual field loss was not associated with calcarine artery supply to the AVM. Prior to treatment, the fields improved in five patients with visual loss associated with a hemorrhage. Forty-six patients were treated with embolization, surgery, radiosurgery, or a combination of therapies. The AVM was eliminated in 19 of 20 patients (nine with preoperative partial embolization) treated with surgery versus in 4 of 27 patients treated only with embolization. There were two AVM-associated deaths, two subarachnoid hemorrhages, and four new neurologic deficits after treatment. Visual fields were worse in 15 patients, unchanged in 22, and improved in eight. CONCLUSIONS: Whereas some features of headache and visual symptoms are similar for occipital AVMs and migraine, the two disorders are usually distinguishable. Visual field improvement can spontaneously occur in patients who have had loss secondary to an intracerebral bleed. Treatment with embolization or surgery, particularly with surgical excision of the AVM, can result in new or worse visual field loss.

Adolescent↗
PubMed1996

[Hospital nursing conducted according to Rogers' theory. The participating process of human field patterning in a clinical environment].

The participating process of human field patterning in an acute-care environment Scientific story-telling is the basis of this article, which describes the care of a patient within the conceptual framework of Martha Rogers. Dr. Mary Madrid, a nurse at New York University Hospital and a student of Rogers, describes the continuous process of intentional pattern changes of the human energy field. The human energy field finds itself in an ongoing, mutual and integral process with the environmental energy field. Madrid elucidates in this way that the human energy field is integral to a continuous, mutual process of becoming and enfolding with the universe. The theory of Barrett, derived from Rogers' "Science of unitary human beings" is applied. Furthermore, nursing interventions congruent with Rogers' system are being described. These are therapeutic touch, guided visualisation, music therapy as well as breathing and relaxation exercises. This scientific story of Madrid is an excellent example of Rogers' science-based nursing.

Acquired Immunodeficiency Syndrome↗
PubMed1995

A novel low oxygen affinity recombinant hemoglobin (alpha96val--> Trp): switching quaternary structure without changing the ligation state.

Using our Escherichia coli expression plasmid (pHE2) in which synthetic human alpha and beta-globin genes are coexpressed with the E. coli methionine aminopeptidase gene under the control of separate tac promoters, we have constructed a new artificial hemoglobin in which the valine residue at position 96 of the alpha chain, located in the alpha 1 beta 2 subunit interface, has been replaced by a tryptophan residue using site-directed mutagenesis. We have determined the oxygen-binding properties of this recombinant hemoglobin, r Hb (alpha 96Val-->Trp), and have used proton nuclear magnetic resonance spectroscopy to investigate its tertiary structure around the heme group and the quaternary structure in the alpha 1 beta 2 subunit interface. This artificial hemoglobin shows a low oxygen affinity, but high cooperativity in oxygen binding, and exhibits no unusual subunit dissociation when ligated. Molecular dynamics simulations suggest that the unique oxygen-binding property of r Hb (alpha 96Val-->Trp) may be due to an extra hydrogen bond between alpha 96Trp and beta 99Asp in the alpha 1 beta 2 subunit interface in the deoxy form. Despite the replacement of a small amino acid residue, valine, by a large tryptophan residue in the alpha 1 beta 2 subunit interface, this artificial hemoglobin shows very similar tertiary structure around the heme pockets and quaternary structure in the alpha 1 beta 2 subunit interface compared to those of human normal adult hemoglobin. Another unique feature of this artificial hemoglobin is that the ligated form, e.g. carbonmonoxy form, of this hemoglobin in the oxy-quaternary structure can be converted to the deoxy-like quaternary structure by the addition of an allosteric effector, inositol hexaphosphate, as well as by lowering the temperature in the absence of inositol hexaphosphate, without changing its ligation state. Thus, this recombinant hemoglobin can be used to gain new insights regarding the nature of subunit interactions in the alpha 1 beta 2 interface and the molecular basis for the allosteric mechanism of hemoglobin.

Base Sequence↗
PubMed1995

Deep central arteriovenous malformations of the brain: the role of endovascular treatment.

Cerebral deep central arteriovenous malformations (AVMs) are uncommon lesions associated with considerable difficulty in treatment. The authors report a series of 14 deep central AVMs treated by endovascular methods and examine the present role of endovascular treatment. This treatment used alone resulted in complete obliteration of AVMs in approximately 15% of case and reduction in 50% to a size permitting treatment by means of radiosurgery. Reversal of previous neurological signs and symptoms occurred in 35.7% of embolized patients. Overall, nearly 80% of patients had either complete obliteration of the lesion, reduction to a size allowing radiosurgical treatment, or reversal of previous neurological deficits. There were treatment complications in 14.3% of the cases. Endovascular treatment methods may make a significant contribution to the therapy of AVMs that have a particularly poor course and are difficult to treat by other means.

Adult↗
PubMed1994

Restoring allosterism with compensatory mutations in hemoglobin.

Abnormal human hemoglobins (HBs) with amino acid substitutions in the alpha 1 beta 2 interface have very high oxygen affinity and greatly reduced cooperativity in O2 binding compared to normal human Hb. In such abnormal Hbs with mutations at position beta 99, the intersubunit hydrogen bonds between Asp-beta 99 and Tyr-alpha 42 and between Asp-beta 99 and Asn-alpha 97 are broken, thus destabilizing the deoxyquaternary structure of these Hbs. A molecular dynamics method has been used to design compensatory amino acid substitutions in these Hbs that can restore their allosteric properties. We have designed a compensatory mutation in a naturally occurring mutant Hb, Hb Kempsey (Asp-beta 99-->Asn), and have produced it using our Escherichia coli expression plasmid pHE2. We have determined the O2 binding properties of this recombinant double mutant Hb, Hb(Asp-beta 99-->Asn and Tyr-alpha 42-->Asp) and have used 1H NMR spectroscopy to investigate the tertiary structures around the heme groups and the quaternary structure in the alpha 1 beta 2 subunit interface. Our results clearly show that the Tyr-alpha 42-->Asp replacement can substantially compensate for the functional defect of Hb Kempsey caused by the Asp-beta 99-->Asn substitution. The structural and functional information derived from this recombinant Hb provides insights into the structural basis of allosterism and the design of compensatory amino acid substitutions to restore the functional properties of other abnormal HBs associated with hemoglobinopathies.

Allosteric Regulation↗
PubMed1993

Reconstruction of the ligated external carotid artery for embolization of cervicofacial arteriovenous malformations.

PURPOSE: Until recently, the accepted management of life-threatening complications of unresectable cervicofacial arteriovenous malformations (AVMs) has been ligation of the major feeding vessels, usually the branches or the main trunk of the external carotid artery. Rapid enlargement of collateral vessels around the ligature is usually associated with an early return of symptoms. Percutaneous transcatheter embolization of the nidus of the arteriovenous malformation is now the preferred treatment for symptomatic AVMs that cannot be excised. Previous ligation of the main feeding vessels prevents catheter access and embolization therapy of the lesion. The purpose of this report is to describe our experience with the treatment of patients with symptomatic unresectable cervicofacial AVMs and previous external carotid artery ligation. METHODS: Six patients with symptoms from cervicofacial arteriovenous malformations required surgical reconstruction of their previously ligated external carotid artery with the anticipation of catheter embolization therapy to the branch vessels feeding the malformation. Saphenous vein was used in five reconstructions; a polytetrafluoroethylene graft was used in one. RESULTS: After successful arterial reconstruction, massive swelling of the tongue and perioral tissue developed in two patients, which necessitated tracheostomy in one patient; and embolization therapy before extubation could be safely performed in the other patient. In all, four patients underwent successful embolization therapy. One refused subsequent treatment. In one patient with severe epistaxis, external carotid artery revascularization led to the healing of the nasal ulcers without need for embolization therapy. CONCLUSIONS: For patients with previous ligations of the external carotid artery and symptomatic AVMs, revascularization of the external carotid artery is an important step in treatment. The surgery must be carefully coordinated with the interventional radiologist for possible emergency postoperative embolization therapy. External carotid artery ligation only complicates the treatment of patients with cervicofacial AVMs, and should no longer be used in the treatment of these individuals.

Adult↗
PubMed1993

Recent improvement in outcome using transcatheter embolization techniques for neonatal aneurysmal malformations of the vein of Galen.

Vein of Galen malformations may present as congestive heart failure in the neonate and are usually fatal if untreated. Early studies using transcatheter embolization techniques, in a series of 22 patients, had a 50% mortality rate and a 37% incidence of severe mental retardation in survivors. Modifications of embolization techniques and neonatal care have improved the outlook in a more recent series of 11 patients. The diagnosis was established within 3 days of life in 91% of the cases. No mortality occurred, and 6 of the patients were functionally normal at up to 30 months' follow-up. Although two patients had severe neurologic deficits and/or a seizure disorder, only one case was possibly temporally associated with the embolization procedure. Some developmental delay was noted in one other patient. These improvements result, in part, from modifications of the treatment protocol, including earlier diagnosis, avoidance of digoxin, improvement in the application of newer microcatheters and acrylic polymers (n-butylcyanoacrylate), avoidance of overly aggressive neurosurgical procedures, and the use of stable central vascular access for total parenteral nutrition accompanying other general improvements in neonatal care.

Catheterization↗
PubMed1992

Refined solution structure and ligand-binding properties of PDC-109 domain b. A collagen-binding type II domain.

We have determined, via 1H-n.m.r., the solution conformation of the collagen-binding b-domain of the bovine seminal fluid protein PDC-109 (PDC-109/b). The structure determination is based on 341 interproton distance estimates and 42 dihedral angle estimates: a set of 24 initial structures were computed; 12 using the variable target function program DIANA, and 12 using the metric matrix program DISGEO. These structures were optimized by restrained energy minimization and dynamic simulated annealing using the CHARMM and X-PLOR programs. The average pairwise root-mean-square difference (r.m.s.d) between the optimized DIANA (DISGEO) structures is 0.71 A (0.82 A) for the backbone atoms, and 1.73 A (2.03 A) for all atoms. Both sets of structures exhibit the same global fold, secondary structure and placement of most non-polar side-chains. Two central antiparallel beta-sheets, which lie roughly perpendicular to each other, and two irregular loops support a large, partially exposed, hydrophobic surface that defines a putative binding site. A test of a hybrid relaxation matrix-based distance refinement protocol (MIDGE program) was performed using a normalized 250 millisecond NOESY spectrum. The resulting distances were input to the molecular mechanics/dynamics procedures mentioned above in order to optimize the DIANA structures. Our results indicate that relaxation matrix refinement of distances is most useful when used conservatively for identifying underestimated distance constraints. 1H-n.m.r. monitored ligand titration experiments revealed definite, albeit weak, binding interactions for phenethylamine and leucine analogs (Ka less than or equal to 25 M-1). Residues perturbed by ligand binding include Tyr7, Trp26, Tyr33, Asp34 and Trp39. These results suggest that PDC-109/b may recognize specific leucine and/or isoleucine-containing sequences within collagen.

Amino Acid Sequence↗
PubMed1991

Neonatal vein of Galen malformations: experience in developing a multidisciplinary approach using an embolization treatment protocol.

A multidisciplinary team approach using a staged transcatheter embolization and neurosurgical protocol was applied to 22 patients with neonatal presentation of vein of Galen malformations over a 12 year period. Aggressive medical therapy was combined with interventions including: ventricular shunting, transcatheter embolization, retrograde transtorcular embolization, and neurosurgical obliteration. There was a high frequency of high output cardiac failure, multiple organ system dysfunction, seizures, hydrocephalus, visual, developmental and neurological disability. Of the first 11 patients, five survived; four with seizures and three with marked retardation. Of the last 11 patients, six survived; five with seizures but only one with retardation. Despite persistently high morbidity and mortality, our continuously evolving protocol offers these otherwise hopeless patients some chance of survival.

Cerebral Veins↗
PubMed1991

Management of facial arteriovenous malformations.

Today's management of vascular anomalies requires that the nurse be a vital element in the recovery process. Understanding the role of embolization in managing vascular lesions and keeping informed about the newest developments in this fast changing field enables the nurse to better help the patient toward a successful outcome.

Adolescent↗